What are the quenching technologies for straight seam welded pipes

Surface quenching and tempering heat treatment for straight seam welded pipes is typically performed using induction heating or flame heating. The main technical parameters are surface hardness, localized hardness, and effective hardened layer depth. Hardness testing can be done 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, an HRA scale can be used; when the hardened layer thickness exceeds 0.8 mm, an HRC scale can be used.

If the part requires high localized hardness, localized quenching heat treatment can be performed using induction heating or similar methods. For such straight seam welded pipes, the location of the localized quenching heat treatment and the localized hardness value must usually be marked on the drawing. Hardness testing of straight seam welded 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 the 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.