ERW Straight Seam Welded Pipe Surface Quenching Heat Treatment

The surface quenching and tempering heat treatment of ERW straight welded pipe is usually carried out by induction heating or flame heating. The main technical parameters are surface hardness, local hardness and effective hardening layer depth. The hardness can be tested by Vickers or Rockwell or surface Rockwell.  The selection of test force (scale) is related to the effective depth of hardening layer and the surface hardness of straight welded pipe. There are three hardness machines involved.


Vickers hardness tester is an important means to test the surface hardness of heat-treated straight welded pipe. It can be used to test the case with a test force of 0.5-100kg to a thickness of 0.05mm. It has the highest accuracy and can distinguish the surface of heat-treated workpiece. The hardness difference is very small. In addition, the effective case depth is also determined by Vickers hardness tester. Therefore, it is necessary to equip surface heat treatment unit for Vickers hardness tester or a large number of straight welded pipes for surface heat treatment.


Surface Rockwell hardness tester is also very suitable for testing the hardness of surface hardening workpiece. There are three scales for surface Rockwell hardness tester. It can be used to test various surface hardened straight welded pipes with effective hardening depth more than 0.1 mm. Although the accuracy of the surface Rockwell hardness tester is not as high as that of the Vickers hardness tester, it has been able to meet the requirements as a means of quality management and inspection in the heat treatment plant. In addition, it also has the advantages of using surface Rockwell hardness tester for rapid nondestructive testing of parts, simple operation, convenient use, low price, rapid measurement, direct reading of hardness value, etc. A batch of Hunan straight seam welded pipes with surface heat treatment. This is very important for the straight welded pipe processing and machinery manufacturers.


The Rockwell hardness tester can also be used when the hardened layer of surface heat treatment is thick. HRA oxide can be used when the thickness of the hardened layer is 0.4 to 0.8mm, and HRC oxide can be used when the thickness of the hardened layer is more than 0.8mm.


Vickers, Rockwell and surface Rockwell hardness values can be easily converted to each other, or to hardness values required by standards, drawings or users. The corresponding conversion table is given in international standard ISO, American Standard ASTM and Chinese standard GB / T.


If the local hardness of parts is high, local quenching heat treatment can be carried out by induction heating. This kind of straight welded pipe is usually marked with local quenching heat treatment position and local hardness value on the drawing. The hardness test of straight welded pipe shall be carried out in the designated area. The hardness tester can use the Rockwell hardness tester to test the HRC hardness value. If the heat treatment hardening layer is shallow, the hrn hardness value can be tested with the surface hardness tester.