The characteristics and problems of the manufacturing process of stainless steel pipe bend

According to the manufacturing method, the stainless steel pipe bend can be divided into three kinds, namely, the simmer bend pipe, the stamping bend pipe and the welding bend pipe. Among them, the simmer bend can be divided into two kinds of cold bending and hot bending. When the stainless steel tube for bending the pipe along the longitudinal direction under pressure, leading to pipe wall thickness of the pipe is shortened, the lateral pipe subjected to tensile, elongation, wall thinning and tube; center without force, deformation will not occur. The cross section of the stainless steel tube is round and oval. When bending the pipe, it is necessary to pay attention to it. When the pipe is bent, the minimum bending radius of the pipe bend must be in line with a certain standard when there is no requirement for the design of the bending radius.

Cold bending of stainless steel bend. In the heating process, the elbow should be slowly and evenly during the heating process, so as to ensure the heat permeability of the pipe, and avoid overheating and carburization.

Elbow technology is widely used in the field of boilers and pressure vessels, the central air-conditioning manufacturing industry, the automotive industry. Among them, the quality of the elbow is directly related to the structural rationality, safety and reliability of the aerospace, shipbuilding and other industries. Therefore, bending out the quality of the pipe fittings is the most critical, and master the process of pipe fittings is the most important. It is necessary to select reasonable mandrel and grasp the correct method of use in cold bending pipe.

Because the inner side of the bending tube in bending when wrinkling, core tube is when they bend the tube relative bending radius is small, in order to obtain high quality pipe fittings, pipe is in the bending process, in which are inserted into a suitable mandrel, thereby avoiding method of flattening and wrinkling phenomenon stainless steel pipe bending appears when arc. Because the tube has a certain elasticity, so when bending force is removed, a rebound angle of elbow. In the bending angle, should consider increasing the angle.

 

Technological characteristics of stainless steel bend

 

If the processing technology of the stainless steel pipe bending is not handled properly, it is possible to relax and damage the pipe metal structure. This kind of damage is a fine grain boundary crack which affects the mechanical properties and service life of the pipe to some extent.

The heating range of the stainless steel bending tube is very small, and the temperature inside and outside the pipe wall is different. In the process of bending, the uniform degree of the cold and hot pipe is different. Chromium is the most basic element in the corrosion resistance of stainless steel stamping elbow. When the chromium content in stainless steel reaches a certain extent, it reacts with oxygen in the air to form a dense oxide film. Further corrosion of steel matrix can be prevented.

 

Protection and passivation treatment of stainless steel bend

 

Protection of stainless steel bend

 

How can we protect the stainless steel tube after production? First of all, after the completion of the stainless steel pipe bending, the nozzle should be sealed one hundred percent, and the bent should be handled with care. Followed by the passivation of the stainless steel elbow, in its surface are required to use three proofing canvas bundle, so as to increase the protection of the intensity. The third point is that because of the temporary support and the stainless steel pipe fittings body is made of stainless steel, if using pressure or bending tool, so it is necessary to protect the plate placed in contact with each other in the possible position of the stainless steel and protection, the protection board is mainly made of stainless steel plate or sheet made of.

Also note that when the transport of stainless steel materials, to put it in a closed box, an open box must use the canvas cover, and must have a plastic cover plug in two stainless steel pipe.

The last is to be placed in stainless steel pipe was not affected by impurities such as carbon steel, in the storage time to try to put in the drying room, and prevent moisture, salt water, dust and other contaminants in contact.

 

Passivation treatment of stainless steel bend

First of all, the operator must make clear the structure of all pickling equipment and the requirements of accompanying washing, and need to master the operation procedures of safe operation process well, and prepare the necessary pickling tools. Secondly, the on-site workers must wear good labor protection clothing, at least two operators, the surrounding environment should meet the requirements of pickling. Stainless steel pipe and pipe with pipe, can be used for on-site treatment in the passivation paste inside the shop, the main method is to use stainless steel pipe after welding after brush on weld clearance, and then use the brush of passivation paste evenly on the surface of stainless steel pipe to be treated, in about 20-30 minutes use a clean cloth to wipe off the passivation paste by washing with water, then, until the other position of weld and pipe as the light so far.

 

Emergency treatment of stainless steel elbow defect

Sometimes it is inevitable to have some defects in the stainless steel bend, but it will have a great negative effect on the quality of the pipe bend. The thickness of the pipe wall is thinned, which must reduce the ability to withstand internal pressure and affect its performance. For the distortion of the shape of the bending pipe section, it will not only reduce the cross-sectional area, increase the resistance of the fluid flow, but also have a certain effect on the function effect of the pipe fittings. The inner lining of the tube will affect the strength of the pipe and the normal use of the pipe bend will have some influence. Therefore, it is important to take certain measures to avoid the above defects before bending the bending system of stainless steel to produce high quality pipe fitting.

For stainless steel elbow with smaller radius, it is inevitable that the outside of the arc is determined by the characteristics of the bending process. In order to prevent thinning amount is too large, frequently used method is to use the side with a booster full-time or tail pipe bender with pushing device, after a boost or pusher to offset when bending the pipe resistance, improving the pipe section stress distribution state of the neutral layer to offshoring, further to decrease stainless steel elbow lateral closed thinning.

To the outer edge of the circular flat serious stainless steel pipe, in the coreless bend when compression mold can be designed as has anti deformation slot structure mode, when to have a core pipe bending, can choose a suitable mandrel, the correct installation, and at the time of installation mould to make sure each axis tube slot in the same horizontal plane.

Source: China Stainless Steel Bend Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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