Stainless steel pipe, as a very common metal material, is widely applied due to the rapid progress of material processing technology. These excellent machining processes help to enhance the performance of stainless steel pipes and meet the needs. But after a series of processing processes, especially after heat treatment, the stainless steel pipe must be cooled.
The cooling process is very important for the use of stainless steel pipes, because once any part of the process is wrong or wrong, it will lead to problems affecting the quality of stainless steel pipes, because we should pay special attention to several problems when cooling stainless steel pipes.
The first is the degree of stability of stainless steel pipe cold austenitic high hardenability is also great, even if the air cooling can be obtained martensite, but air cooling can cause the surface of stainless steel tool products formed oxidation, and may precipitate eutectoid carbide now, so try not to use air cooling process.
For large and complex structure of the stainless steel pipe, in order to reduce the deformation and cracking degree, can do a pre cooling treatment when quenching, but need to control the time, usually according to control the shape of the stainless steel pipe in a few seconds to tens of seconds, but the premise is not two carbon compounds can be precipitated and hard to reduce tool hardness and red, also can not form such as pitting corrosion.
The third is that the grading quenching temperature should not be higher than 650, to avoid the transition of pearlite and the precipitation of carbides.
The fourth is to take into account that the transformation temperature of the lower bainite is 320-250 degrees C, and the fastest transition temperature is 260 to 300 degrees. So the production is 260-280 to 300 hours. Because the retained austenite temperature after isothermal quenching is more and more stable, four tempering is required.
The fifth is the high temperature quenching to 580 to 620 DEG C neutral salt bath, can not use 500 to 550 DEG C nitrate graded cooling, it is the cause of nitrate will hot forming tool oxidation and corrosion, and even the sharp knife burning.
The last point is that the stainless steel pipe should be vertically placed in the cooling medium during the quenching operation so as to reduce the deformation of the stainless steel pipe.
Source: China Stainless Steel Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)