316 Stainless Steel Round Pipe

How is How is 316 stainless steel round pipe produced?

316 stainless steel pipe corrosion resistance, high temperature resistance performance is good, often used in chemical, food, light industry, mechanical instrumentation and other industrial transmission pipes and mechanical structural components. Do you know how 316 stainless steel pipe is produced? Here's how to find out.

1. Material selection

The cold-rolled stainless steel strip is used as raw material, and the surface state is BA grade. Before the steel is brought into the factory for use, the steel strip must be inspected in detail. Inspection items include: thickness, width, edge quality status, appearance and physical property inspection. If necessary, the grain size of the raw material should be checked, and it can be used for production after passing the inspection.

2. Open the book

Before the steel strip enters the welding pipe unit, it is necessary to use the steel strip uncoiler to unfold the steel strip. After comparing the steel strip, it is necessary to add a leveling mechanism to the steel strip for leveling treatment to ensure that the steel strip enters the forming part of the welding pipe unit in a flat state and successfully completes the bending and forming of the steel strip

3, tube forming

Using continuous roll bending molding equipment, the steel strip is deformed by continuous roll bending to make open tube blank. The steel belt needs to pass the joint action of several functional modules of the welding pipe unit, including the introduction module, rough rolling module and closing module. Each module uses different types of rolls to achieve bending and forming of different parts of the steel belt, and finally the steel belt is gradually bent from the plane to form an open tube blank, ready for welding into 304 stainless steel pipe.

4. Continuous welding

After the steel strip passes through the continuous roll bending forming machine, the open tube blank is made. Using TIG welding equipment, continuous welding is performed to make round tubes. Argon is used as a protective gas in the welding process to prevent oxidation of the weld in contact with oxygen before solidification and cooling. Argon gas is passed into the tube to protect the internal weld, and the argon gas passed into the welding gun is used to protect the tungsten electrode. A protective layer of argon gas is formed around the molten pool to protect the molten pool and weld from oxidation.

5, weld smoothing

Due to the impact force of welding current and the influence of gravity, the internal welds of stainless steel products pipe will be prominent, and the external welds will also be depressed. If these problems are used in ordinary low-pressure fluid environment, they will not be affected. If used in high temperature, high pressure, high-speed fluid environment, it will cause problems. This defect must be eliminated using dedicated weld smoothing equipment.

6, online heat treatment

In the process of roll bending, the steel strip will produce work hardening, which is not conducive to the later processing of the pipe, especially the bending process. During the welding process, there will be welding stress at the weld, which will cause potential cracking in the later use process, which requires heat treatment.

At present, the commonly used heat treatment process is bright solid solution treatment under the hydrogen protection atmosphere, heating 304 stainless steel pipe to more than 1050°, after a period of time of insulation, the internal organizational form is transformed, forming a uniform austenitic organization, under the protection of hydrogen atmosphere, no oxidation.

7. Sizing and finishing

The outer diameter of the welded pipe will be deformed in the process of welding and heat treatment, resulting in the outer diameter size can not meet the requirements of use, and it is necessary to carry out sizing and finishing. The sizing finishing unit usually used is composed of 4 groups of flat rolls and 4 groups of side rolls. The flat roll is designed into a flat oval (or round), and the side roll is designed into an oval (or round). Sizing depends on the outside diameter of the pipe and the wall thickness, generally in the range of 0.20 ~ 0.50mm. After sizing and finishing, the outer diameter tolerance of the pipe can be controlled within ±0.05mm, which can fully meet the accuracy requirements of use.

8. Online flaw detection

Due to certain pressure and reliability, it is difficult to detect internal defects of welds only by pressure detection. Online eddy current testing or ultrasonic testing can be used for 100% real-time online detection. According to the alarm information, the welding state can be corrected at any time to reduce the production of unqualified products.

9, cutting

Using on-line sizing cutting equipment, according to the length required by customers, sizing cutting can be performed using rotary cutting (chip free) technology, compared with chip cutting, chip free cutting has the characteristics of no cutting burrs, and the port can not be deburred in the later period.

10. Straighten it

The straightness of the welded pipe produced by the roll bending molding unit can not meet the requirements of use, and the straightness of such welded pipes generally needs to be controlled at 0.10/100mm. It is necessary to use a straightener to straighten the welded pipe to meet the required product requirements.

11. Stress test

The use of automatic static hydraulic testing machine, 304 stainless steel pipe pressure test, loading, flushing, pressure test, blanking all automatically completed, after a certain period of pressure through the differential pressure method to sort out unqualified welded pipe

12. Clean and dry

After the mechanical processing of the welded pipe, it is necessary to carry out the final cleaning and drying to remove the remaining coolant, oil and other pollutants on the inner wall or outer wall of the pipe, and then use the hot air drying to prevent rust during transportation and storage. Finally, the finished product inspection and packaging of the stainless steel welded pipe can be delivered.

The above is the production process of 316 stainless steel pipe, the production process includes material selection, uncoiling, tube billet forming, continuous welding, and a series of processes.

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