Surface quenching and tempering heat treatment of straight seam welded steel pipes is typically performed using induction heating or flame heating. The main technical parameters are surface hardness, local hardness, and effective hardened layer depth. Hardness testing can be conducted using a Vickers hardness tester, a Rockwell, or a surface Rockwell hardness tester. When the surface heat-treated hardened layer is thick, a Rockwell hardness tester can also be used. When the heat-treated hardened layer thickness 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 part requires high local hardness, local quenching heat treatment can be performed using induction heating or similar methods. For such straight seam welded steel pipes, the location of the local quenching heat treatment and the local hardness value must usually be marked on the drawings. Hardness testing of straight seam welded steel pipes must be performed within the designated area. Hardness testing instruments can use a Rockwell hardness tester to measure the HRC hardness value; if the heat-treated hardened layer is shallow, a surface Rockwell hardness tester can be used to measure the HRN hardness value.

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