Large diameter pipe cap

 The large variations of caps, are the so-called ellipsoidal or dished heads. There are used to close pipes of large diameters, and are similar to those used for constructing vessels.

large-diameter-pipe-cap
Large diameter pipe cap

WELD PREPARATION
Contents [hide]

1 WELD PREPARATION
2 STANDARD:
3 SURFACE TREATMENT:
4 KEYWORD:
5 COMMON SHAPES:
6 SIZE
For wall thickness less than 3 mm, the caps are supplied with plain weld ends. Larger thicknesses are supplied with the weld bevel of 37 ½°±2 ½°.

STANDARD:
ANSI B16.9 / 16.28, ASTM A53/A106, API 5L, ASME B36.10M—1996, DIN2605 / 2615 / 2616, JIS P2311/2312

A234-WPB-Large-Diameter-Pipe-Cap
A234 WPB Large Diameter Pipe Cap

SURFACE TREATMENT:
Transparent oil, rust-proof black oil or hot galvanized.

Special design available All the production process are made according to ISO9001:2000 strictly.

KEYWORD:
cap,Seamless cap,Steel cap,Carbon Steel Seamless cap,pipe cap,cap end

Based on different materials, pipe caps include carbon steel cap, stainless steel cap, and alloy steel cap etc.
Depending on their construction, pipe caps contain threaded cap, tapered cap and anti-roll cap etc.

COMMON SHAPES:
Pipe caps can be in various shapes. Some of the common shapes are hemispherical, oval, square, rectangular, U shape and I shape.

SIZEcaps
Pipe cap: 1/2″-60″, DN15-DN1500

Wall Thickness:
sch10, sch20, sch30, std, sch40, sch60, xs, sch80, sch100, sch120, sch140, sch160, xxs, sch5s, sch20s, sch40s, sch80s
Max. wall thickness: 200mm

Materials
Carbon steel: ASTM/ASME A234 WPB-WPC
Alloy steel: ASTM/ASME A234 WP 1-WP 12-WP 11-WP 22-WP 5-WP 91-WP 911
Stainless steel: ASTM/ASME A403 WP 304-304L-304H-304LN-304N
ASTM/ASME A403 WP 316-316L-316H-316LN-316N-316Ti
ASTM/ASME A403 WP 321-321H ASTM/ASME A403 WP 347-347H
Low temperature steel: ASTM/ASME A402 WPL 3-WPL 6
High performance steel: ASTM/ASME A860 WPHY 42-46-52-60-65-70

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The Types of Pipe Flanges

 Pipe flanges connect pipes, valves, pumps and other equipment in a piping

system. Flanges are usually welded or screwed into the systems and then joined

with bolts. The eight types of pipe flanges are available in round, square and

rectangular shapes.

Blind Flanges

A blind, or blanking, flange is a round

plate with no center hold (but with bolt holes) that closes the ends of piping

systems.

Lap Joint Flanges

Piping fitted with lapped pipe or with

lap joint stub ends often use lap joint flanges. Also, systems frequently taken

apart for inspection and cleaning often use lap joint flanges.

Orifice Flanges

Orifice meters that measure the flow rate

of either gases or liquids use orifice flanges.

Reducing Flanges

When a change in diameter is required in

a piping system, reducing flanges are used. A reducing flange has a specified

diameter with a bore of a different, smaller diameter.

Slip-On Flanges

Slip-on flanges slide over the end of a

pipe and are then welded into place. These flanges work well for low-pressure

applications.

Socket Weld Flange

The socket weld flange is

counter-bored to accept the pipe before being fillet welded. This type of flange

is similar to a slip-on flange. The bore of the pipe and flange are the same,

which provides good flow characteristics.

Threaded Flanges

Threaded flanges, which are threaded in

the bore to match an external thread on the pipe, are attachable to a pipe

without welding.

Weld Neck Flanges

Weld neck flanges have a long tapered

hub and are often used for high-pressure applications. The pipe and flange bores

match, which reduces turbulence and erosion inside the pipeline.

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Duplex & Super Duplex Pipe Fittings

 Collection of industrial duplex stainless steel and super duplex steel offered

by us is manufactured in sound infrastructure facilitated with modern and

advanced machines. Developed in compliance with industrial norms, our stainless

steel pipes and duplex steel pipes are well suitable for being used in varied

industrial applications. They are corrosion proof and are sure to offer their

service for longer time.

RANGE :

1/2”NB TO24”NB IN SCH 5 TO SCH XXS

FORM :

ELBOW IN LONG & SHORT RADIUS IN 45DEG, 90 DEG, 180DEG.

EQUAL, UNEQUAL TEE & BERRED TEE

CAPS & CROSSES

LONG & SHORT STUB END

SWAGE NIPPLE & BARREL NIPPLE

QUALITY : 

DUPLEX & SUPER DUPLEX STEEL

UNS S31803, S32205 (2205),S32750 (2507), S32760 (Z-100)

S32900 (329), S32304, F-51, F-53, F-54, F-55 & F-60 & HIGH NICKEL

ALLOYS

TYPE :

WELDED (ERW, FEBRICATED & SEAMLESS

DIMENTIONAL STANDARDS :

ANSI B16.9

SCHEDULES :

Sch 5 to Sch XXS (special wall thicknesses on request)

SIZE RANGE:

½” to80”NB

VALUE ADDED SERVICES :

• Annealed

• Casting

• Electroplating

• Forging

• Heat Treatment (Hardening & Tempering)

• Machining (CNC)

• Pickled

• Polish (Electro & Commercial)

• Rolling

• Threading (As per Guage)

TEST CERTIFICATION :

Our Materials Are Tested To Relevant Standard And Wherever Possible We Give

Original / Copy Of Test Certificate With Heat Number As Well As Govt. Approved Laboratories

Test Certificate Can Also Be Provided.  We Supply the Material under

Inspection of Any Third Party Inspection Agency as per the Client’s

Requirements Such As :

1) Bv- Bureau VERITAS Industrial Services (India)

Pvt. Ltd

2) Lloyds Inspection Agency

3) Rina

4) Irs – International Register Of Shipping (Irs)

5) Dnv – Det Norske Veritas

6) Tcs – Tata Consultancy Services

7) TuvIndia

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Quality management measures of pressure vessel manufacturing materials

 Reasonable selection, proper storage and correct use of manufacturing materials are the prerequisite and basis for ensuring the quality of pressure vessels. This article makes some meaningful discussions on the material quality management issues in pressure vessel manufacturing, hoping to serve as a reference and reference for colleagues in the industry.

As a special pressure-bearing equipment, pressure vessel has been widely used in petrochemical, energy, scientific research and military industries. Its quality is directly related to the production safety of these industrial fields, so it must be given full attention.

In order to ensure the manufacturing quality of pressure vessels, the first requirement is to manage and control the quality of vessel materials. If the pressure vessel manufacturing materials used have quality defects, no matter how the subsequent optimization and improvement of the process process, the final product quality is difficult to guarantee.

Therefore, reasonable selection, proper storage and correct use of manufacturing materials are the prerequisite and basis for ensuring the quality of pressure vessel products. Based on this standpoint, this article makes some meaningful discussions on the material quality management issues in pressure vessel manufacturing, hoping to serve as a reference for colleagues in the industry.

The pressure vessel parts are as follows:
1. Tube sheets
2. Baffles
3. Flanges
4. Heat Exchanger Bundle Tubes, etc
Overview of pressure vessel manufacturing
Contents [hide]

1 Overview of pressure vessel manufacturing
2 Matters needing attention in material substitution
3 Material quality management measures in pressure vessel manufacturing
3.1 Material procurement measures
3.2 Measures in the acceptance link
3.3 Material storage measures
3.4 Material recycling measures
As a special pressure-bearing equipment, the pressure vessel’s manufacturing quality is very important for the safety application in the industrial field. At present, in order to ensure the production quality of pressure vessels, my country has issued corresponding standards and specifications, which must be designed and manufactured in strict accordance with the requirements of the national standard.

In practical applications, the types of pressure vessels are different, and their functioning principles and application fields are also different. This requires that in the process of manufacturing them, the manufacturing quality must be ensured to meet the actual application requirements.

In addition, as a special type of equipment, pressure vessels are more difficult to manufacture than general vessel products. The entire manufacturing process has very high quality and safety requirements, requiring close coordination and cooperation from multiple disciplines.

In reality, there are many factors that affect the quality of pressure vessel manufacturing, and any error in any of them will affect the quality of the final product. Material selection is the first step of manufacturing, and strict quality control is also necessary.

Considering that there are many types of materials available in practice, and the final material quality still depends on the control of storage and other links, it is of great significance to strengthen the control of factors related to material quality in the manufacturing process and must be given sufficient attention.

Matters needing attention in material substitution
In the manufacturing process, if a thick plate is used instead of a thin plate, the structure of the joint may be changed. For example, when the thickness increases more, the welding structure may change.

When the overall thickness is replaced by thinness, even if the local stress at the joint between the head and the cylinder is not increased, it will affect the quality of the container product to a certain extent, and it will also cause the welding, flaw detection and heat treatment processes used in the original design to be changed. Land no longer applies.

In addition, the substitution of materials for pressure vessels may also lead to changes in the weight of the container products, which in turn will affect the supporting support and foundation of the products.

In short, in the manufacture of pressure vessels, in principle, it is not allowed to substitute materials randomly, because different materials will have different performances. Even if one performance has reached a higher level, it may be replaced by another. In terms of low-to-high, and these will make the process measures and schemes used in the entire production process must be modified accordingly, but this change often results in poor solderability and doubled manufacturing process difficulty. So we must be cautious about material substitution.

Material quality management measures in pressure vessel manufacturing
Material procurement measures
For machinery manufacturing, the procurement of raw materials is a key basic link to control the quality of the final product, and the manufacturing of pressure vessels is naturally no exception.

Taking into account the chaotic order of the current material supply market, even for materials of the same specification, quality differences caused by different manufacturers abound. Therefore, pressure vessel manufacturers must strengthen management of the procurement of raw materials.

First of all, we must conduct credit checks on the production and suppliers of materials, and select those with good credit and long-term cooperative relations.

Secondly, after each material purchase is completed, the company should evaluate the supplier’s supply speed, service quality and product quality, and record the evaluation results in the material supplier’s files for future material supplier selection Provide evidence.

Finally, pressure vessel manufacturers should establish a sound and complete material procurement quality control system, strengthen supervision of whether the purchased materials comply with relevant national and industry standards, and strengthen inspections of the material quality certificates and other certification materials provided by suppliers. The responsibility for inspection is assigned to the individual, and strive to ensure that the selected materials meet the design performance index requirements.

Measures in the acceptance link
The quality management department shall strengthen the quality acceptance of the delivered materials, and the inspectors and engineers may conduct quality inspections on whether the materials meet the relevant standard requirements. Before the materials are put into storage, they must go through scientific acceptance and supervise whether the acceptance process meets the relevant process specifications.

Make sure that the procedures are complete when materials are put into storage. Acceptance records of materials must be filled in accurately. All the above processes must form a clear process specification. Once there is an acceptance problem, the responsibility traceability mechanism can be activated immediately to find out the problems in the acceptance process and improve it.

Material storage measures
The purchased materials shall be classified and stored when they are put into the warehouse. They shall be kept scientifically according to the specifications, composition and physical and chemical properties of the materials, and shall be marked accordingly.

The material storage warehouse should meet relevant requirements such as ventilation and drying, and different sensors should be set up in the storage area according to different materials to monitor whether the storage environment meets the storage requirements of the materials in real time to ensure that the materials will not appear in storage Degeneration and other issues.

Finally, in the process of distributing materials, we must strictly abide by the “application-review” system, standardize the application and distribution process of materials, and ensure the scientific and reasonable use of materials.

Material recycling measures
Before using the material, the size and specification of the material should be checked according to relevant regulations and drawings. Only after the inspection is qualified can it be used for pressure vessel manufacturing. Mark the materials that have been received and still have surplus after manufacturing. After the materials pass the inspection and confirmation, the return procedures can be processed.

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What is stainless steel strip?

 Contents [hide]

1 What is stainless steel strip?

2 Classification of stainless steel strip

2.1 Cold rolled stainless steel strip

2.2 Stainless steel hot rolled strip

2.3 Difference between cold and hot rolled stainless steel strip

3 Properties of stainless steel strip

3.1 Correlation between physical properties and temperature

3.2 Physical properties at low temperature

Stainless steel strip can be regarded as the extension product of ultra-thin stainless steel plate. It is a kind of long and narrow stainless steel plate which is usually manufactured to meet the needs of various industrial mechanical products. Stainless steel strip is also called stainless steel strip. The maximum width of stainless steel strip can not exceed 1220 mm, but the length is not limited. According to the processing method, the stainless steel strip can be divided into cold-rolled stainless steel strip and hot-rolled stainless steel strip.

Stainless steel strip has excellent strength, precision, surface finish and other properties, which is widely used in aerospace, petrochemical, automobile, textile, electronics, household appliances, computer and precision machining and other pillar industries.

Stainless steel strip

Classification of stainless steel strip

Stainless steel sheet supplied in coils can also be called strip steel. Divided into hot rolling, cold rolling, ordinary stainless steel strip, high quality stainless steel strip and precision stainless steel strip.

There are many kinds of stainless steel belts, including 201 stainless steel belt, 202 stainless steel belt, 304 stainless steel belt, 301 stainless steel belt, 302 stainless steel belt, 303 stainless steel belt, 316 stainless steel belt, J4 stainless steel belt, 309S stainless steel belt, 316L stainless steel belt, 317L stainless steel belt, 310S stainless steel belt, 430 stainless steel iron belt, etc.

The thickness is 0.02mm-4mm, and the width is 3.5mm-1550mm.

Stainless steel with domestic (imported) stainless steel strip: stainless steel coil strip, stainless steel spring band, stainless steel stamping band, stainless steel precision belt, stainless steel mirror belt, stainless steel cold rolling strip, stainless steel hot rolling strip, stainless steel etching strip, stainless steel stretching belt, stainless steel polishing belt, stainless steel soft belt, stainless steel hard belt, stainless steel medium hard belt, stainless steel high temperature resistant belt, etc.

stainless steel strip

Cold rolled stainless steel strip

Cold rolled stainless steel strip

Stainless steel strip or coil is used as raw material and rolled by cold rolling mill at room temperature. The conventional thickness is 0.1 mm ~ 3 mm, while the width is 100 mm ~ 2 000 mm.

Cold rolled stainless steel strip has the advantages of smooth surface, smooth surface, high dimensional accuracy and good mechanical properties. Most products are rolled and can be processed into coated steel plate.

The production process sequence of cold-rolled stainless steel strip or coil is acid pickling, normal temperature rolling, process lubrication, annealing, leveling, fine cutting and packaging.

Stainless steel hot rolled strip

Stainless steel hot rolled strip

Hot rolled stainless steel strip is made by hot rolling mill with thickness of 1.80mm-6.00mm and width of 50mm-1200mm. Hot rolled stainless steel has the advantages of low hardness, easy processing and good ductility. Its production processes are acid pickling, high temperature rolling, process lubrication, annealing, leveling, fine cutting and packaging.

Difference between cold and hot rolled stainless steel strip

There are three main differences between cold-rolled stainless steel strip and hot-rolled stainless steel strip

Firstly, the strength and yield strength of cold-rolled stainless steel strip are better, and the ductility and toughness of hot-rolled stainless steel strip are good.

Secondly, the thickness of cold-rolled stainless steel strip is ultra-thin, while the thickness of hot-rolled stainless steel strip is larger.

In addition, the surface quality, appearance and dimensional accuracy of cold-rolled stainless steel strip are better than those of hot-rolled stainless steel strip.

Properties of stainless steel strip

Like other materials, the physical properties of stainless steel strip mainly include the following three aspects: melting point, specific heat capacity, thermal conductivity and linear expansion coefficient, electromagnetic properties such as resistivity, conductivity and permeability, and mechanical properties such as young’s modulus of elasticity and rigidity coefficient. These properties are generally considered to be inherent characteristics of stainless steel materials, but they are also affected by such factors as temperature, processing degree and magnetic field strength. In general, the thermal conductivity and electrical resistance of stainless steel are lower than that of pure iron.

Correlation between physical properties and temperature

(1) Specific heat capacity

With the change of temperature, the specific heat capacity will change, but in the process of temperature change, once the phase transformation or precipitation occurs in the metal structure, the specific heat capacity will change significantly.

(2) Thermal conductivity

Below 600 ℃, the thermal conductivity of all kinds of stainless steel is in the range of 10 ~ 30W / (m · ℃), and the thermal conductivity increases with the increase of temperature. At 100 ℃, the order of thermal conductivity of stainless steel is 1Cr17, 00Cr12, 2Cr25N, 0cr18ni11ti, 0Cr18Ni9, 0cr17ni12m ο 2 and 2cr25ni20. At 500 ℃, the order of thermal conductivity is 1 CR 13, 1 CR 17, 2 CR 25 n, 0 CR 17 Ni 12 m o 9 2, 0 CR 18 Ni 9 Ti and 2 CR 25 Ni 20. Compared with ordinary carbon steel, the thermal conductivity of austenitic stainless steel is about 1 / 4 of that at 100 ℃.

(3) Coefficient of linear expansion

In the range of 100-900 ℃, the linear expansion coefficients of the main stainless steel grades are basically in the range of 10 ˉ 6 ˉ 6 ˉ 1 ˉ 130 * 10 ˉ 6 ˉ 1, and it increases with the increase of temperature. For precipitation hardening stainless steel, the linear expansion coefficient is determined by aging treatment temperature.

(4) Resistivity

At 0 ~ 900 ℃, the specific resistance of the main grades of stainless steel is 70 * 10 ˉ 6 ~ 130 * 10 ˉ 6 Ω· m, and it increases with the increase of temperature. When it is used as heating material, the material with low resistivity should be selected.

(5) Permeability

Austenitic stainless steel is also known as non-magnetic material because of its low permeability. Steel with stable austenite structure, such as 0 CR 20 Ni 10, 0 CR 25 Ni 20, etc., will not be magnetic even if it is processed with large deformation more than 80%. In addition, austenite stainless steels with high carbon, high nitrogen and high manganese, such as 1cr17mn6nisn, 1Cr18Mn8Ni5N and high manganese austenitic stainless steels, will undergo phase transformation under large reduction, so it remains non-magnetic. At high temperatures above the Curie point, even strong magnetic materials lose their magnetism. However, some austenitic stainless steels, such as 1cr17ni7 and 0Cr18Ni9, have metastable austenite structure, so martensitic transformation will occur during large reduction or low temperature processing, which will have magnetic properties and increase permeability.

(6) Elastic modulus

At room temperature, the longitudinal elastic modulus of ferritic stainless steel is 200kn / mm2, and that of austenitic stainless steel is 193kn / mm2, which is slightly lower than that of carbon structural steel. With the increase of temperature, the longitudinal elastic modulus decreases, the Poisson’s ratio increases, and the transverse elastic modulus (rigidity) decreases significantly. The longitudinal elastic modulus will affect the work hardening and microstructure aggregation.

(7) Density

The density of ferritic stainless steel with high chromium content is small, while that of austenitic stainless steel with high nickel and manganese content is high, and the density becomes smaller due to the increase of spacing between the elements at high temperature.

Physical properties at low temperature

(1) Thermal conductivity

The thermal conductivity of all kinds of stainless steel is slightly different at very low temperature, but generally speaking, it is about 1 / 50 of that at room temperature. At low temperature, the thermal conductivity increases with the increase of magnetic flux (flux density).

(2) Specific heat capacity

At very low temperatures, the specific heat capacities of various stainless steels are different. The specific heat capacity is greatly affected by temperature. The specific heat capacity at 4K can be reduced to less than 1 / 100 of the specific heat capacity at room temperature.

(3) Thermal expansion

For austenitic stainless steel, there is a little difference in shrinkage rate (relative to 273k) below 80K. The content of nickel has a certain effect on the shrinkage.

(4) Resistivity

At very low temperature, the difference of resistivity between different grades increases. The alloy elements have great influence on the resistivity.

(5) Magnetism

At low temperature, the effect of mass susceptibility on load magnetic field of austenitic stainless steel is different with different materials. The contents of different alloying elements are also different.

There is no difference in permeability between different grades.

(6) Elastic modulus

At low temperature, the Poisson’s ratio of austenitic stainless steel with magnetic transformation has an extreme value.

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How to choose valve material under high temperature condition?

 The high temperature valve has good quenching property and can be deeply quenched instead of the surface quenching of anti saw lock on the market. In general information, the valve with working temperature T > 450 ℃ is called high temperature valve. However, there is no unified standard for the classification of high temperature grade of high temperature valves.

How to choose valve material under high temperature condition?

High temperature working conditions mainly include sub high temperature, high temperature grade I, high temperature grade II, high temperature grade III, high temperature grade IV and high temperature grade V, which are respectively introduced below.

Sub high temperature

Sub high temperature refers to the valve working temperature in the 325 ~ 425 ℃ region. If the medium is water and steam, WCB, WCC, A105, wc6 and wc9 are mainly used. If the medium is sulfur-containing oil, C5, CF8, CF3, CF8M and cf3m are mainly used. At this time, the valves made of CF8, CF8M, CF3 and cf3m are not used to resist the corrosion of acid solution, but are used in sour oil products and oil and gas pipelines. In this condition, the upper limit of the maximum operating temperature of CF8, CF8M, CF3 and cf3m is 450 ℃.

High temperature grade I

When the working temperature of the valve is 425 ~ 550 ℃, it is high temperature class I (referred to as PI). The main material of PI valve is CF8 in astma351 standard, which is “high temperature grade I medium carbon chromium nickel rare earth titanium high quality heat resistant steel”. Because PI grade is a specific name, the concept of high temperature stainless steel (P) is included here. Therefore, if the working medium is water or steam, high temperature steel wc6 (t ≤ 540 ℃) or wc9 (t ≤ 570 ℃) can also be used, while high temperature steel C5 (zg1cr5mo) can also be used for sour oil, but they can not be called PI grade here.

High temperature grade II

The working temperature of the valve is 550 ~ 650 ℃, which is designated as high temperature class II (referred to as P Ⅱ). Grade II high temperature valve is mainly used in heavy oil catalytic cracking unit of refinery. It includes high temperature lining wear-resistant gate valve used in three swirl nozzle and other parts. The main material of P Ⅱ valve is CF8 in astma351 standard, which is “high temperature grade II medium carbon chromium nickel rare earth titanium tantalum strengthened heat resistant steel”.

High temperature grade III

The working temperature of the valve is 650 ～ 730 ℃, which is designated as high temperature class III (referred to as P Ⅲ). The P Ⅲ high temperature valve is mainly used in heavy oil catalytic cracking unit of refinery. The main material of P Ⅲ high temperature valve is CF8M in astma351 standard, which is “high temperature grade III medium carbon chromium nickel molybdenum rare earth titanium tantalum strengthened heat resistant steel”.

High temperature grade IV

The operating temperature of the valve is 730 ~ 816 ℃, which is designated as high temperature grade IV (referred to as P Ⅳ). The upper limit of operating temperature for class P IV valves is set at 816 ℃ because the maximum temperature provided in the standard asmeb16134 pressure temperature class selected for valve design is 816 ℃ (1500 V). In addition, when the working temperature exceeds 816 ℃, the steel is close to entering the forging temperature region. At this time, the metal is in the plastic deformation range, and the metal has good plasticity, and it is difficult to bear high working pressure and impact force without deformation. The main material of P IV valve is CF8M in astma351 standard, which is “high temperature grade IV medium carbon chromium nickel molybdenum rare earth titanium tantalum strengthened heat resistant steel”. F310 (C content ≥ 01050%) and f310h in CK-20 and astma182 standards.

High temperature grade V

If the working temperature of the valve is higher than 816 ℃, it is referred to as p-v. the P-V high-temperature valve (used as cut-off valve instead of regulating butterfly valve) must adopt special design means, such as lining insulation lining or water or air cooling, etc., to ensure the normal operation of the valve. Therefore, there is no stipulation on the upper limit of the operating temperature of the p V class high temperature valve. This is because the control of the working temperature of the valve is not only based on the material, but also solved by special design means, and the basic principle of the design means is the same. According to the working medium, working pressure and special design method, the reasonable material which can meet the valve can be selected. In P V class high temperature valve, the insert plate or butterfly plate of flue gate valve or butterfly valve is usually made of hk-30 and HK-40 superalloys in astma297 standard. They can resist corrosion in oxidation resistance and reducing gas below 1150 ℃, but can not bear impact and high pressure load.

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What is silver bright steel?

 Silver bright steel It is also called silver steel branch, commonly known as bright round bar or smooth circle. It refers to the round steel with bright surface without rolling defects and decarburization layer. All kinds of steel, carbon steel, easy cutting steel, bearing steel, tool steel, stainless steel, valve steel, etc., can be processed into silver bright steel.

What is silver bright steel?

Classification method
Contents [hide]

1 Classification method
1.1 Flake steel
1.2 Polish steel
1.3 Buff steel
1.3.1 What is drawing?
2 Application of silver bright steel
3 Instructions for ordering (GB/T 3207-2008)
3.1 Straightness and roughness regulations
3.2 Tolerance table
According to different processing methods, silver bright steel can be divided into peeling material, polishing material and polishing material.
Flake steel
Round steel straightened after removing rolling defects and decarburized layer by turning and peeling.
Polish steel
Round steel that is polished after drawing or peeling.
Buff steel
Round steel which is polished after drawing, turning, peeling or polishing.
What is drawing?
Drawing is a method of plastic deformation of steel at room temperature. It can be divided into cold-drawing and pinching-out according to different processes.
Cold-drawing: the method of applying tension at both ends of a metal material to produce tensile deformation.
Pinching-out: a method of deforming the material through a die hole by applying a pulling force at one end of the material. The diameter of the die should be smaller than the diameter of the material. Pinching-out can also produce profiles other than round bar, and the final product is usually obtained after several passes of pinching-out.
Application of silver bright steel
Hot rolled steel annealed into silver bright steel has the advantages of high dimensional accuracy and good surface quality, especially the peeled and polished materials are effectively removed from the surface decarburized layer, surface cracks and various external defects, which can be directly used, save working hours and reduce tool loss. Therefore, it is widely used in machinery and equipment manufacturing, electronics, petroleum, chemical, automobile, railway and manufacturing Shipbuilding, aerospace, nuclear power and other industries.
Instructions for ordering (GB/T 3207-2008)
In addition to the conventional materials and specifications, yinliang steel orders usually have diameter tolerance (tolerance), straightness (straightness) and surface roughness requirements.
Straightness and roughness regulations
Delivery status

Code name

Straightness

Roughness Ra

Peeling

SF

≤1mm/m

≤3.0μm

polish

SP

≤2mm/m

≤5.0μm

polishing

SB

≤1mm/m

≤0.6μm

Tolerance table
Nominal diameter

h7

h8

h9

h10

h11

1.0~3.0

0

-0.010

0

-0.014

0

-0.025

0

-0.040

0

-0.060

＞3.0~6.0

0

-0.012

0

-0.018

0

-0.030

0

-0.048

0

-0.075

＞6.0~10.0

0

-0.015

0

-0.022

0

-0.036

0

-0.058

0

-0.090

＞10.0~18.0

0

-0.018

0

-0.027

0

-0.043

0

-0.070

0

-0.11

＞18.0~30.0

0

-0.021

0

-0.033

0

-0.052

0

-0.084

0

-0.13

＞30.0~50.0

0

-0.025

0

-0.039

0

-0.062

0

-0.100

0

-0.16

＞50.0~80.0

0

-0.030

0

-0.046

0

-0.074

0

-0.12

0

-0.19

＞80.0~120

0

-0.035

0

-0.054

0

-0.087

0

-0.14

0

-0.22

＞120~180

0

-0.040

0

-0.063

0

-0.100

0

-0.16

0

-0.25

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Austenitic stainless steel should also pay attention to: cold work hardening, high temperature aging embrittlement

 The intergranular corrosion tendency test of stainless steel is a common content in design documents, and the relevant content in standards such as HG/T 20581 is relatively clear. The water pressure test or the chloride ion content in the operating medium is also the basic content of the austenitic stainless steel equipment design. In addition to chloride ions, wet hydrogen sulfide, polythionine and other environments that may generate sulfides can also cause stress corrosion cracking of austenitic stainless steel.

It is worth mentioning that although austenitic stainless steel is not mentioned in the chapter of HG/T 20581 wet hydrogen sulfide corrosion, the reference points out that although austenitic stainless steel has a much greater ability to dissolve atomic hydrogen than ferritic stainless steel, But hydrogen-induced wet hydrogen sulfide stress corrosion cracking will still occur, especially after cold work hardening appears deformed martensite structure transformation.

Cold work hardening increases stress corrosion cracking sensitivity

Austenitic stainless steel has excellent cold working properties, but its work hardening is very obvious. The greater the degree of cold working deformation, the higher the hardness rise. The increase in hardness caused by work hardening is also an important reason for the stress corrosion cracking of stainless steel, especially those where the base material is not welded.

There are some cases:

The first type of case is the cold spinning of austenitic stainless steel oval or dish-shaped head, the cold deformation of the transition zone is the largest, and the hardness also reaches the highest. After commissioning, chloride ion stress corrosion cracking occurred in the transition zone, resulting in equipment leakage.

The second type of case is a U-shaped corrugated expansion joint made by hydroforming after the stainless steel sheet is rolled. The cold deformation is the largest at the wave crest, and the hardness is the highest. The stress corrosion cracking occurs along the wave crest the most, and even cracking along the wave crest occurs. Explosion accident with low stress and brittle fracture.

The third case is the stress corrosion cracking of the corrugated heat exchange tube. The corrugated heat exchange tube is cold-extruded from a stainless steel seamless tube. The wave crests and troughs are subjected to different degrees of cold deformation and thinning. The crests and troughs may cause several stress corrosion cracks.

The essence of cold work hardening of austenitic stainless steel is to produce deformed martensite. The greater the cold work deformation, the more deformed martensite and the higher its hardness. At the same time, the greater the internal stress within the material. In fact, if solution heat treatment is carried out after its processing and forming, the effect of reducing the hardness and greatly reducing the residual stress can be achieved, and the martensite structure can also be eliminated, thereby avoiding stress corrosion cracking.

The embrittlement problem of long-term service under high temperature

At present, the container and pipe materials at 400～500℃ are mainly Cr-Mo steel with higher high temperature strength, and at 500～600℃ or even 700℃, various austenitic stainless steels are mainly used. In the design, people often pay more attention to the high temperature strength of austenitic stainless steel, and require its carbon content not to be too low. The allowable stress at high temperature is basically obtained by the extrapolated high temperature endurance strength test, which can ensure that no creep rupture occurs under the design stress of 100,000 hours of service.

However, the ageing embrittlement problem of austenitic stainless steel at high temperature cannot be ignored. After long-term service at high temperature, austenitic stainless steel will have a series of changes in the structure, which will seriously affect a series of mechanical properties of steel, especially the brittleness Significantly rise, resilience drops significantly.

The embrittlement problem after long-term service at high temperature is generally caused by two factors, one is the formation of carbides, and the other is the formation of σ phase. The carbide phase and σ phase continue to precipitate along the crystal after long-term service of the material, and even form a continuous brittle phase on the grain boundary, which is very easy to form intergranular fracture.

The formation temperature range of σ phase (Cr-Fe intermetallic compound) is about 600-980 ℃, but the specific temperature range is related to the alloy composition. As a result of the precipitation of σ phase, the strength of austenitic steel is greatly increased (the strength may be doubled), and it becomes hard and brittle. High chromium is the main reason for the formation of high-temperature σ phase, and Mo, V, Ti, Nb, etc. are alloy elements that strongly promote the formation of σ phase.

The formation temperature of carbide (Cr23C6) is in the sensitization temperature range of austenitic stainless steel, which is 400～850 ℃. Cr23C6 will dissolve above the upper limit of the sensitization temperature, but the dissolved Cr will promote the further formation of σ phase.

Therefore, when austenitic steel is used as a heat-resistant steel, the understanding and prevention of high-temperature aging embrittlement should be strengthened. Like the metal monitoring of thermal power plants, the metallographic structure and hardness changes can be checked regularly. If necessary, samples can be taken out for metallographic and hardness inspections, and even comprehensive mechanical properties and endurance strength tests can be performed.

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the Comparison of sand blasting, shot blasting and shot peening

 Contents [hide]

1 What is shot peening?
2 What is sand blasting?
3 Comparison of sandblasting, shot blasting and shot peening
3.1 Difference between shot blasting and shot peening
3.2 Difference between shot blasting and sand blasting
3.3 Difference between sand blasting and shot blasting
3.4 Difference between sand blasting and shot peening

Shot peening uses the high-speed rotating impeller to throw out small steel shot or small iron shot and impact the part surface at high speed, so the oxide layer on the part surface can be removed. At the same time, steel shot or iron shot impacts the part surface at high speed, resulting in lattice distortion and deformation on the part surface and increasing the surface hardness. Shot peening is a method to clean the part surface. Shot peening is often used to clean the casting surface or strengthen the part surface.

Generally, shot peening is used for regular shapes. Several throwing heads are up, down, left and right together, with high efficiency and little pollution.
In the shipbuilding industry, shot peening and sand blasting are widely used. Shot peening uses the high-speed rotating impeller to throw out the abrasive; Sand blasting is the use of compressed air to blow out the abrasive at high speed. Of course, shot peening does not have to use a high-speed rotating impeller. In the repair and shipbuilding industry, generally speaking, shot peening (small steel shot) is mostly used in steel plate pretreatment (rust removal before coating); Sand blasting (mineral sand is used in repair and shipbuilding) is mostly used in formed ships or sections to remove the old paint and rust on the steel plate and repaint it. In the repair and shipbuilding industry, the main function of shot peening and sand blasting is to increase the adhesion of steel plate coating paint.
The research shows that in terms of damage, when there is tensile stress on the surface of metal materials, it is much easier than compressive stress. When there is compressive stress on the surface, the fatigue life of materials is greatly improved. Therefore, shot blasting is usually used to form surface compressive stress for parts prone to fatigue fracture such as shafts, so as to improve the product life. In addition, metal materials are very sensitive to tension, This is the reason why the tensile strength of materials is much lower than the compressive strength. This is also the reason why metal materials generally use tensile strength (yield, tensile) to represent material properties.
The steel plate working face of our daily car is strengthened with shot blasting, which can significantly improve the fatigue strength of the material. Shot peening uses the motor to drive the impeller body to rotate, and by the action of centrifugal force, throws the balls (including cast shot, cut shot, stainless steel shot, etc.) with a diameter of 0.2 – 3.0 to the surface of the workpiece, so as to make the workpiece beautiful, or change the welding tensile stress of the workpiece to compressive stress, so as to improve the service life of the workpiece. Almost used in most fields of machinery, such as repair, shipbuilding, auto parts, aircraft parts, gun and tank surfaces, bridges, steel structures, glass, steel plates, pipelines, etc. Sand blasting (shot) uses compressed air as power to spray sand with a diameter of 40 – 120 mesh or shot with a diameter of about 0.1 – 2.0 to the surface of the workpiece, so that the workpiece can achieve the same effect. The treatment effect will be different if the size of the shot is different.
It is emphasized that shot blasting can also play a role in strengthening. Now the domestic equipment has entered a misunderstanding that only shot peening can achieve the purpose of strengthening. Enterprises in the United States and Japan use shot blasting for strengthening, and each has its own advantages. For example, for a workpiece such as a gear, the shot angle of shot peening cannot be changed, and the initial speed can only be changed by frequency conversion. However, it has large processing capacity and fast speed, while shot blasting is just the opposite. The effect of shot peening is not as good as that of shot blasting.
What is sand blasting?
Sand blasting is a method that uses compressed air to blow out quartz sand at high speed to clean the surface of parts. It is also called sand blowing in the factory. It can not only remove rust, but also remove oil. It is very useful for coating. Commonly used for rust removal on the surface of parts; Surface modification of parts (this is the purpose of small wet sand blasting machine sold in the market. The sand is usually corundum and the medium is water); In the steel structure, the application of high-strength bolts for connection is a more advanced method. Because the high-strength connection uses the friction between the joint surfaces to transfer the force, the quality requirements of the joint surface are very high. At this time, the joint surface must be treated by sand blasting.
Sand blasting is used for complex shape, easy to remove rust by hand, low efficiency, poor site environment and uneven rust removal. General sandblasting machines have sandblasting guns of various specifications. As long as they are not a particularly small box, they can put the gun in and clean it. The supporting product of pressure vessel – head adopts sand blasting to remove the oxide scale on the workpiece surface. One kind of processing is to use water as a carrier to drive emery to process parts, which is a kind of sand blasting.
Both shot peening and sand blasting can clean and decontaminate the workpiece. The purpose is to prepare for the next process, that is, to ensure the roughness requirements of the next process. In addition, in order to ensure the consistency of the surface, shot blasting can strengthen the workpiece, so sand blasting is not obvious. Generally, shot blasting is a small steel ball and sand blasting is quartz sand. According to different requirements, the mesh number. Sand blasting and shot peening are used in precision casting almost every day.
Supplement:
1. Both shot peening and sand blasting are surface treatment, but it does not mean that only castings are shot peening.
2. The main function of sand blasting is to remove rust and oxide scale on the surface, such as parts after heat treatment, while shot peening has many functions and functions. It not only removes rust and surface oxide scale, but also improves surface roughness, removes machining burrs of parts, eliminates internal stress of parts, reduces deformation of parts after heat treatment, and improves wear resistance and pressure resistance of parts.
3. There are many processes for shot blasting, such as castings, forgings, parts surface after machining, parts surface after heat treatment, etc.
4. Sand blasting is mainly manual operation, while shot peening is more automatic and semi-automatic.
Add again (some repetition, some conflict):
1. Shot and sand
Shot is generally spherical particles without edges and corners, such as cast steel shot, steel wire grinding shot, etc; Sand refers to angular sand particles, such as cast steel sand, brown corundum, white corundum, river sand, etc.
2. Spraying and throwing
Spraying is to use compressed air as power to spray sand or shot onto the material surface to achieve removal and certain roughness. Polishing is a method of impacting the material surface with centrifugal force generated when the shot rotates at high speed to achieve removal and certain roughness.
Comparison of sandblasting, shot blasting and shot peening
Difference between shot blasting and shot peening
The sandblasting process shot blasting uses high-pressure air or compressed air as power, while shot peening generally uses a high-speed rotating flywheel to eject the steel sand at high speed. Shot peening has high efficiency, but there will be dead corners, while shot blasting is more flexible, but the power consumption is large.
Although the two processes have different injection power and methods, they both aim at high-speed impact on workpieces, and their effects are basically the same. In comparison, shot blasting is relatively fine and easy to control accuracy, but its efficiency is not as high as shot peening. Shot peening is suitable for small workpieces with complex shapes. Shot peening is more economical and practical, easy to control efficiency and cost, and can control the particle size of pellets to control the injection effect, However, there will be dead corners, which is suitable for batch processing of workpieces with single shape and surface.
The selection of the two processes mainly depends on the shape of the workpiece and the machining efficiency.
Difference between shot blasting and sand blasting
Both shot blasting and sand blasting use high-pressure air or compressed air as power to blow it out at high speed and impact the workpiece surface to achieve cleaning effect, but the effect is also different due to different media.
Difference between sand blasting and shot blasting
After sand blasting, the dirt on the workpiece surface is removed, the workpiece surface is slightly damaged, and the surface area is greatly increased, thus increasing the bonding strength between the workpiece and the coating/coating.
The surface of the workpiece after sand blasting is of the natural color of metal, but because the surface is rough and the light is refracted, it has no metal luster and is a darkened surface.
After shot blasting treatment, the dirt on the workpiece surface is removed, the workpiece surface is slightly damaged without damage, and the surface area is increased. Because the workpiece surface is not damaged in the machining process, the excess energy generated during machining will lead to the surface strengthening of the workpiece matrix.
After sandblasting, the surface of the workpiece is also the natural color of metal. However, because the surface is a spherical surface, part of the light is refracted, so the workpiece is processed into matte effect.
Difference between sand blasting and shot peening
1. The two are different in meaning: shot peening uses the high-speed rotating impeller to throw out small steel shot or small iron shot and impact the part surface at high speed, so the oxide layer on the part surface can be removed. Sand blasting is the process of cleaning and roughening the substrate surface by using the impact of high-speed sand flow.
2. Different in nature: shot peening uses the high-speed rotating impeller to throw out the abrasive; Sand blasting is the use of compressed air to blow out the abrasive at high speed.
3. The two are suitable: shot peening is often used to clean the casting surface or strengthen the part surface; After sand blasting, the dirt on the workpiece surface is removed, the workpiece surface is slightly damaged, and the surface area is greatly increased, thus increasing the bonding strength between the workpiece and the coating/coating.
The steel plate working face of our daily car is strengthened with shot blasting, which can significantly improve the fatigue strength of the material. Shot peening uses a motor to drive the impeller body to rotate, relying on the action of centrifugal force; Shot peening is usually a high-speed rotating flywheel that ejects steel sand at high speed.

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the Quality inspection of welding elbow

The weld of the welded elbow must be inspected, which is also an important measure to ensure the quality of the weld. After the completion of the elbow welding, the weld joint shall be inspected according to the technical requirements of the product. Any defects that do not meet the technical requirements shall be repaired in time (such as direct disposal that cannot be repaired if it is seriously unqualified). Common inspections of welding quality include visual inspection, non-destructive testing and mechanical performance testing. These three are complementary to each other, and they are mainly based on non-destructive testing.

1. Visual inspection: generally based on the naked eye observation, sometimes with a 5-20 times magnifying glass for observation. Through visual inspection, surface defects of weld elbow welds, such as undercuts, welds, surface cracks, pores, slag inclusions, and weld penetration, can be found. The dimensions of the weld can also be measured using a weld detector or template.

2. Non-destructive testing: Inspection of defects such as slag inclusions, pores and cracks hidden inside the weld. At present, the most common use is X-ray inspection, as well as ultrasonic flaw detection and magnetic flaw detection. The X-ray inspection uses X-rays to photograph the weld seam, and judges whether there are defects, the number and type of defects in the interior based on the image of the film. Then, according to the technical requirements of the product, the weld is qualified. The basic principle of ultrasonic flaw detection is shown in the figure below. The ultrasonic beam is emitted by the probe and transmitted to the metal. When the ultrasonic beam is transmitted to the metal-air interface, it is refracted and passed through the weld. If there is a defect in the weld, the ultrasonic beam is reflected to the probe and accepted, and a reflected wave appears on the screen. Based on the comparison and discrimination of these reflected waves with normal waves, the size and position of the defects can be determined. Ultrasonic flaw detection is much simpler than X-ray photography and is therefore widely used. However, ultrasonic flaw detection often can only be judged based on operational experience, and can not leave a test basis. For internal defects that are not deep from the surface of the weld and extremely small cracks on the surface, magnetic flaw detection can also be used.

3. Hydraulic test and air pressure test: For pressurized containers requiring sealing, hydraulic pressure test and/or air pressure test shall be carried out to check the sealing and pressure bearing capacity of the weld. The method is to inject 1.25-1.5 times working water or a working pressure gas (mostly air) into the container for a certain period of time, then observe the pressure drop in the container and observe whether there is leakage outside. According to these, it can be assessed whether the weld is qualified.

4. the mechanical performance test of the elbow: non-destructive testing can find the inherent defects of the weld, but can not explain the mechanical properties of the metal in the heat affected zone of the weld, so sometimes the welded joint should be subjected to tensile, impact, bending and other tests. These tests were performed by the test panels. The test panels used are preferably welded together with the longitudinal joints of the cylinder to ensure consistent construction conditions. The test panels were then tested for mechanical properties. In actual production, only welded joints of new steel grades are generally tested in this respect.

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the Four surface treatments usefulmethods for fastener anti-corrosion

 Fasteners are the most common parts in mechanical equipment, and they are also very important to function. Machines that operate like air compressors are particularly large, and the role of fasteners can be imagined. However, corrosion is the most common problem during the use of fasteners. In order to prevent the corrosion of fasteners during use, the manufacturer will surface the fasteners after the fasteners are produced. So, which surface treatments can improve the corrosion resistance of fasteners?

In industrial manufacturing, there are mainly four surface treatment methods to prevent corrosion of fasteners. When purchasing air compressors, we can combine the actual working conditions and pay attention to the anti-rust treatment method of fasteners.

Fasteners

1 Plating

Electroplating the standard parts by placing the standard parts in a metal solution and then applying a current to the surface of the standard part with a layer of metal. There are many effects on this layer of metal. For example, we can use some different functions. Choose some different plating metals, if we want to prevent the standard parts from rusting, then we can plate zinc on the surface of the standard parts.

2 Mechanical plating

The mechanical plating of standard parts is to let the metal particles cold-weld the standard parts to ensure some functions of the surface of the standard parts. Mechanical plating and electroplating are basically similar, except that the method we use is different, and the result can be said to be the same.

3 Heat treatment

The surface of the standard part is heat treated. There are some standard parts, such as the hard-drilled surface of the self-drilling screw, so you can heat-treat the self-drilling screws to ensure that the self-drilling screws have sufficient hardness. This is the reason for the heat treatment.

4 Surface passivation

For standard surface passivation, passivation has two main functions, one is to enhance the hardness of the standard part, and the other is to greatly reduce the oxidation of the standard part. When performing fastener surface treatment processes, we can choose the most appropriate method based on the specific needs. This way the fasteners can play a better role during use.

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good of the forming way process for large stamping elbows

 The forming process of the stamping elbow is complicated, and it needs to be welded according to different materials and uses, and gradually formed under a certain pressure. The forming of the stamping elbow needs to be carried out according to a certain process, and the corresponding process is strictly followed, otherwise the quality of the stamping elbow produced will be produced. If required, a circular ring shell can be cut into 4 90 ° elbows or 6 60 ° elbows or other specifications of elbows. This process is suitable for making any elbow and elbow inner diameter ratio greater than 1.5D. Specifications Large stamping elbows are an ideal way to make large stamping elbows.

This process molding method is used in the production of different elbows and exhibits good use value in different fields, so that the process has a good value in different elbow production.

The advantages of the forming process of large punching elbows are mainly reflected in the following aspects:

(1) It is not necessary to use the tube blank as a raw material, which can save the cost of the pipe making equipment and the mold, and can obtain a stamping elbow of any large diameter and relatively thin wall thickness. The material of the stamping elbow is special, and it is not necessary to add the raw material of the tube blank, and it is easy to control during processing.

(2) The blank for processing the punching elbow is a flat plate or a developable curved surface, so the material is simple to cut, the precision is easy to ensure, the assembly and welding are convenient, the raw materials are easily controlled during processing, the operation is relatively simple, there is no complicated process, and the welding and assembly are convenient.

(3) Due to the above two reasons, the manufacturing cycle can be shortened and the production cost is greatly reduced. Because it does not require any special equipment, it is especially suitable for processing large punching elbows on site.

The material of the stamping elbow is made of carbon steel, stainless steel or alloy steel. The carbon steel stamping elbow is cheap and large in use. The elbow of alloy steel is used in a special position.

The surface quality and mechanical properties are basically the same as the tube. For the convenience of welding, the steel grade of the pipe to be connected is the same.

Requirements for packaging: For small pipe fittings, such as export, you need to make a wooden box, about 1 cubic meter. The number of elbows in this box is about no more than one ton. The standard allows suits, that is, large sets, but total The weight generally cannot exceed 1 ton. For large pieces, a single package, like a 24″, must be a single package. The other is the packaging mark, the mark is to indicate the size, steel number, batch number, manufacturer’s trademark. On the stamping elbow to be stamped with Packing list and other documents.

Any large-scale stamping elbow that produces a bend with a median diameter of elbow and an inner diameter of the elbow greater than 1.5D is an ideal way to make large stamping elbows. This process molding method is used in the production of different elbows and exhibits good use value in different fields, so that the process has a good value in different elbow production.

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process making stainless steel elbows

 There are many processing methods for stainless steel elbows, many of which are mechanical processing. The most used ones are stamping method, forging method, roller processing method, rolling method, bulging method, stretching method, bending method, and combined processing method. . Stainless steel elbow processing and metal force processing are combined organically.

Here are some ways to share the processing of stainless steel elbows as follows:

Forging method of stainless steel elbow: The end of the pipe or a section is punched by a swaging machine to reduce the outer diameter. The common type forging machine has a rotary type, a link type and a roller type.

Rolling method: Generally, the mandrel is not used, and it is suitable for the inner edge of the thick-walled tube. The core is placed in the tube, and the outer circumference is pressed by a roller for round edge processing.

Stamping method: The pipe end is expanded to the required size and shape with a tapered core on the punching machine.

Bending forming method: There are three methods that are more commonly used. One method is called stretching method, the other method is called pressing method, the third method is roller method, there are 3-4 rollers, two fixed rollers, one adjusting roller, and adjustment. With the fixed roll distance, the finished pipe is curved.

Inflating method: one is to place rubber in the tube, and the upper part is compressed by a punch to make the tube protrude and formed; the other method is to form a hydraulic bulge, fill the middle of the tube with liquid, and the liquid pressure drums the tube into the required The shape, the bulk of the production of bellows is used in this way.

The processing method of the stainless steel elbow is mainly the above five methods, and everyone can choose the processing method suitable for their own processing.

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the Processing way of stainless steel elbow

 A stainless steel elbow is a pipe fitting that changes the direction of the pipe. According to the angle, there are three common types, such as 45°, 90°, and 180°. The processing methods of stainless steel elbows are generally mechanical processing such as: stamping method, forging method, roller processing method, rolling method, bulging method, stretching method, bending method, and combined processing method;

However, in the current production and processing, there are not many common methods for processing stainless steel elbows.

There are three commonly used forming methods for stainless steel elbows: stretching, stamping, and roller.

Forging method: The end portion or a part of the stainless steel pipe is punched by a swaging machine to reduce the outer diameter. The common type forging machine has a rotary type, a link type, and a roller type.

Stamping method: The end of the tube is expanded to the required size and shape with a tapered core in the stainless steel elbow.

The stamping forming of stainless steel elbows is the earliest forming process for mass production of elbows. At present, it has been replaced by hot push or other forming processes in the production of seamless elbows of common specifications, but in some specifications of elbows It is still used because of the small amount of production, excessive wall thickness or special requirements of the product. The stamping elbow is formed by using a tube blank equal to the outer diameter of the elbow, and is directly press-formed in the mold using a press.

Before the stamping, the tube blank is placed on the lower mold, the inner core and the end mold are loaded into the tube blank, the upper mold is moved downward to start pressing, and the punching elbow is formed by the constraint of the outer mold and the support of the inner mold.

Compared with the hot push process, the appearance quality of stamping is not as good as the former; when the punch elbow is in the stretched state when forming, there is no excess metal in other parts to compensate, so the wall thickness at the outer arc is about 10% thinner. . However, due to the characteristics of single-piece production and low cost, the stamping elbow process is mostly used for the manufacture of small batches and thick-walled elbows.

Stamping elbows are divided into cold stamping and hot stamping. Cold stamping or hot stamping is usually selected according to material properties and equipment capabilities.

The forming process of the cold extrusion elbow is to use a special elbow forming machine to put the tube blank into the outer mold. After the upper and lower molds are closed, the blank is reserved along the inner and outer molds under the push of the push rod. The gap moves to complete the forming process.

The elbow manufactured by the inner and outer mold cold extrusion process has beautiful appearance, uniform wall thickness and small dimensional deviation, so the stainless steel elbow, especially the thin-walled stainless steel elbow forming, is mostly manufactured by this process. The precision of the inner and outer molds used in the stamping elbow process is high; the wall thickness deviation of the billet is also demanding.

Roller method: The core is placed in the tube of the stainless steel elbow, and the outer circumference is pressed by the roller for the round edge processing.

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Welding technical of stainless steel the bellows

Stainless steel bellows are widely used and have applications in oil, water and gas pipelines, and most of them still have some pressure. Such thin corrugated tubes are often welded, and because of the thinness (about 0.2 mm), welding is difficult. Welding methods include welding, brazing, and the like. Here, the tungsten argon arc welding of stainless steel bellows and stainless steel flanged tubes is introduced. The key to welding is to prevent burn through.

Welding technique of stainless steel bellows

Second, pre-weld preparation

Clean the stainless steel corrugated pipe to be welded and the oil on the flange pipe. If it is cracked and leaked at the weld, the original weld bead should be cleaned off, and the metal luster should be ground at the straight pipe of the flange pipe. The straight pipe of the bellows is too thin to be ground and polished, and the sand is brightened by hand sand. Just fine.

Welding assembly: the best assembly clearance is 0, due to processing error, sometimes the gap is too large, the welding is easy to burn through, the solution can be overlapped on the straight pipe of the flange pipe (usually 3 ~ 5mm) heap One layer of welding, machined to 0 ~ 0.05mm gap or hand grinding. If the sleeve does not go up, the small outer diameter of the straight tube of the flange tube should be small or small until it is suitable.

Welding machine selection: WS315 type, using DC positive connection.

Welding consumables selection: ER308, Ø0.8mm

Third, the welding operation

Welding parameters: welding current 25 ~ 30A, protective gas flow 4 ~ 7L / min.

The arc must be carried out on the flange tube, the arc should be on the thick tube, the arc outer flame is used to heat the bellows, and the wire is used to block the edge of the bellows, and the bellows is melted with the molten stainless steel wire.

Welding time strip must be carried out on thick tubes, using short weld welding or spot welding for welding.

When welding, it is necessary to observe the melting condition of the bellows at all times. Generally, one to three molten pools are melted at a time, which is not suitable for continuous welding, especially when the gap is large.

In summary, the arc welding of stainless steel bellows and stainless steel flanged tubes (or other tubes) is based on the fact that the arc cannot directly point to the bellows, and the bellows is used to weld the bellows.

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What's the Steel of Q235 Q235B

 Q235 steel is a kind of carbon structural steel. It is equivalent to A3 and C3 steel in the old standard gb700-79, and the Russian toct brand is used. Q in the steel grade represents the yield strength. In general, the steel is directly used without heat treatment.

Q235 ordinary carbon structural steel is also called A53 steel.

Ordinary carbon structural steel plate is a kind of steel material.

Q represents the yield limit of this material, and the following 235 refers to the yield value of this material, which is about 235mpa. The yield value decreases with the increase of the thickness of the material. Due to the moderate carbon content, good comprehensive properties, good combination of strength, plasticity and welding properties, it is widely used.

The yield strength decreases with the increase of the thickness of the material (the yield strength is 235mpa when the plate thickness / diameter is ≤ 16mm; 225MPa is the yield strength when the thickness is 16mm < plate thickness / diameter ≤ 40mm; 215mpa is the yield strength when 40mm < plate thickness / diameter ≤ 60mm; 205mpa is the yield strength when 60mm < plate thickness / diameter ≤ 100mm; 195mpa when the plate thickness / diameter is ≤ 150mm; 195mpa when the thickness / diameter is less than 150mm; and ≤ 200mm when the thickness / diameter is less than 150mm The yield strength is 185mpa).

Due to its low carbon content, good comprehensive properties, good combination of strength, plasticity and welding properties, it is widely used.

It is composed of Q + number + quality grade symbol + deoxidation method symbol. Its steel grade is prefixed with “Q” to represent the yield point of the steel, and the subsequent number represents the yield point value in MPa. For example, Q235 represents the carbon structural steel with yield stress (σ s) of 235 MPa.

If necessary, the symbol indicating the quality grade and deoxidation method can be marked after the steel grade.

The quality grade symbols are a, B, C and D.

Symbol of deoxidation method:

• F stands for rimmed steel;
• B represents semi killed steel;
• Z is killed steel;
• TZ stands for special killed steel.

Killed steel can not be marked, that is, Z and TZ can not be marked. For example, q235-af stands for class a rimmed steel.

Carbon steel for special purposes, such as bridge steel, marine steel, etc., basically adopts the expression of carbon structural steel, but the letter indicating the purpose is added at the end of steel grade.

According to GB / T 700-2006 standard, carbon structural steel Q235 is divided into four grades according to metallurgical quality: A, B, C and D.

Q235: Grade A, B, C and D (GB / T 700-2006)

• Q235A contains C ≤ 0.22% Mn ≤ 1.4% Si ≤ 0.35% s ≤ 0.050, P ≤ 0.045
• Q235B grade contains C ≤ 0.20% Mn ≤ 1.4% Si ≤ 0.35% s ≤ 0.045 P ≤ 0.045 (with the consent of the demander, the carbon content may not be greater than 0.22%)
• Q235C contains C ≤ 0.17% Mn ≤ 1.4% Si ≤ 0.35% s ≤ 0.040, P ≤ 0.040
• Q235D contains C ≤ 0.17% Mn ≤ 1.4% Si ≤ 0.35% s ≤ 0.035, P ≤ 0.035

There are many examples of cold working dies made by low carbon martensite hardening process in China.

The thickness of Mo CR bowing layer is more than 100 μ m, the surface Mo Cr content can reach 20%, Cr content can reach 10%, the carbon content of supersaturated carburizing surface is more than 2.0%, the surface composition is close to molybdenum high speed steel, and the surface hardness is up to 1300hv after quenching and tempering, More than general metallurgical high speed steel. The wear test shows that the friction coefficient increases with the increase of contact stress, and the average relative wear resistance is 2.2 times of GCr15 carburized and quenched steel.

The main uses of Q235 are as follows:

• ① It is widely used in construction and engineering structure, or mechanical parts with low performance requirements. C. Grade D steel can also be used as some professional steel.
• ② It can be used for all kinds of mold handle and other unimportant mold parts.
• ③ Q235 steel is used as punch material. After quenching, it can be directly used without tempering. The hardness is 36 ~ 40HRC, which solves the problem of punch cracking in use.

Standard of Q235

Brand			Q235 （ GB/T 700-2006 Carbon structural steel)
Grade			A	B	C	D
Deoxidation method			F 、 Z	F 、 Z	Z	TZ
Chemistry component	C		≤ 0.22	≤ 0.20	≤ 0.07	≤ 0.07
	Si		≤ 0.35	≤0.35	≤0.35	≤ 0.35
	Mn		≤ 1.40	≤ 1.40	≤ 1.40	≤ 1.40
	P		≤ 0.045	≤ 0.045	≤ 0.045	≤ 0.045
	S		≤ 0.050	≤ 0.050	≤ 0.050	≤ 0.050
Yield strength	thick degree or straight path	≤ 16	≥ 235MPa
		＞ 16~40	≥ 225MPa
		＞ 40~60	≥ 215MPa
		＞ 60~100	≥ 215MPa
		＞ 100~150	≥ 195MPa
		＞ 150~200	≥ 185MPa
Tensile strength			370~500MPa
Posthumous elongation rate	thick degree or straight path	≤ 40	≥ 26%
		＞ 40~60	≥ 25%
		＞ 60~100	≥ 24%
		＞ 100~150	≥ 22%
		＞ 150~200	≥ 21%
to attack test	Temperature (℃)		—	+20	0	-20
	Impact energy J		—	≥ 27

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