Surface quenching and tempering heat treatment of straight seam welded pipes is usually carried out using induction heating or flame heating. The main technical parameters are surface hardness, local hardness, and effective hardened layer depth. Hardness testing of straight seam welded pipes can be done using a Vickers hardness tester, or a Rockwell or surface Rockwell hardness tester. When the surface heat-treated hardened layer of the straight seam welded pipe is thick, a Rockwell hardness tester can also be used. When the hardened layer thickness of the heat-treated straight seam welded pipe is 0.4–0.8 mm, the HRA scale can be used; when the hardened layer thickness exceeds 0.8 mm, the HRC scale can be used.

If the required local hardness of the straight seam welded pipe is high, local quenching heat treatment can be performed using induction heating or other methods. For such straight seam welded pipes, the location of the local quenching heat treatment and the local hardness value should usually be marked on the drawing. Hardness testing of straight seam welded pipes must be performed within the designated area. Hardness testing instruments can include a Rockwell hardness tester to measure HRC hardness values. If the heat-treated hardened layer is shallow, a surface Rockwell hardness tester can be used to measure HRN hardness values.

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