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Common machining defects of flame quenched stainless steel pipe and its prevention

Release time: November 4, 2020 Views: 34 come from: Chengdu Zhengshang Stainless Steel Co., Ltd

Sichuan stainless steel pipe Compared with the high frequency quenching stainless steel pipe, the flame quenching device is simple and the price is low. Parts such as the end face of small shaft can be heated and quenched by welding machine. However, for the larger quenching area, the progressive quenching method and rotary progressive method as shown in the figure are needed for surface quenching. Because the flame quenching is heated by the high-temperature flame emitted from the nozzle, and then quenched by sudden cooling, the factors such as the size and number of flame nozzles (some are slit type nozzles), the amount of gas supplied, the distance between the nozzle and the surface of stainless steel pipe and the moving speed are different. The heating speed and temperature gradient from the surface to the inside of the steel pipe will change, which will affect the quenching Properties of post hardening layer.

 Sichuan stainless steel pipe

In progressive quenching, the position from the beginning of heating gradually moves forward. Due to the result of heat conduction, the preheating degree of stainless steel pipe surface is gradually increased before the nozzle reaches. Therefore, although set The heat of the flame to set The higher the heating speed, the greater the tendency of overheating. In order to prevent this phenomenon, sometimes spray water is used in front of the heating nozzle to keep the heating condition set Because of the local quenching, the deformation is smaller than the whole quenching, just like the high frequency quenching. However, some special stainless steel pipes also need to consider the deformation problem. According to the author's experiments on pearlitic cast iron, bending deformation can be seen when the depth of hardened layer reaches more than 1 / 10 of the cross-section thickness when the plate sample is quenched by one side flame. In order to prevent deformation, the non quenched part of the workpiece can also be immersed in water during heating.

 Sichuan stainless steel pipe

If it is found that the hardening depth of the nitrided stainless steel tube is insufficient, supplementary nitriding can be used to increase the hardening depth. However, the surface hardness of the workpiece with a part of nitrided layer grinded off after nitriding is higher than that before nitriding. As an example, the figure shows the hardness value of steel pipe sample with nitrided surface hardness of HRC70, ground to the surface of hardness hrc58, and then added nitriding (indicated by dotted line)

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