Quenching treatment of erw steel pipe

Posted by chase Liu on March 9th, 2023

"ERW pipe" is straight seam electric resistance welded pipe. The welded steel tubes are used to transport vapor and liquid objects such as oil and natural gas, which can meet various requirements of high and low pressure, and occupy a pivotal position in the field of transportation pipes in the world.

The surface quenching and tempering heat treatment of erw steel pipe is usually carried out by induction heating or flame heating. The main technical parameters are surface hardness, local hardness and effective hardened layer depth. Vickers hardness tester can be used for hardness testing, and Rockwell or superficial Rockwell hardness tester can also be used. The selection of the test force (scale) is related to the depth of the effective hardened layer and the surface hardness of the erw steel pipe.

The Vickers hardness tester is an important means to test the surface hardness of heat-treated erw steel pipes. It can use a test force of 0.5-100kg to test the surface hardening layer as thin as 0.05mm thick. Its precision is the highest, and it can distinguish the slight difference in the surface hardness of heat-treated workpieces. In addition, the depth of the effective hardened layer is also detected by a Vickers hardness tester. Therefore, it is necessary to equip a Vickers hardness tester for units that perform surface heat treatment or use a large number of surface heat treated erw steel pipes.

The surface Rockwell hardness tester is also very suitable for testing the hardness of the surface quenched workpiece. The surface Rockwell hardness tester has three scales to choose from. Various case-hardened erw steel pipes with an effective hardening depth exceeding 0.1mm can be tested. Although the accuracy of the surface Rockwell hardness tester is not as high as that of the Vickers hardness tester, it can already meet the requirements as a detection method for quality management and qualification inspection of heat treatment plants. Moreover, it also has the characteristics of simple operation, convenient use, low price, rapid measurement, and direct reading of hardness values. Using the surface Rockwell hardness tester can quickly and non-destructively detect batches of surface heat-treated erw steel pipes one by one.

When the surface heat treatment hardened layer is thick, the Rockwell hardness tester can also be used. When the thickness of the heat-treated hardened layer is 0.4-0.8mm, the HRA scale can be used, and when the thickness of the hardened layer exceeds 0.8mm, the HRC scale can be used.

The three hardness values of Vickers, Rockwell and Superficial Rockwell can be easily converted to each other and converted into hardness values required by standards, drawings or users. The corresponding conversion tables are given in the international standard ISO, the American standard ASTM and the Chinese standard GB/T.

If the parts require high local hardness, local quenching heat treatment can be carried out by induction heating and other methods. Such erw steel pipes usually need to mark the position of local quenching heat treatment and local hardness value on the drawing. The hardness test of erw steel pipe should be carried out in the designated area. The hardness testing instrument can use a Rockwell hardness tester to test the HRC hardness value. If the heat-treated hardened layer is shallow, a surface Rockwell hardness tester can be used to test the HRN hardness value.