Deformation heat treatment
High temperature deformation heat treatment can increase the yield ratio and elastic limit of spiral steel tubes
. Improve the comprehensive mechanical properties, fatigue properties and stress relaxation properties of spiral steel tubes. It reduces the ductile-brittle transition temperature of steel, reduces the temper brittleness of steel, and has the advantages of simple process and energy saving.
The spiral steel pipe is highly effective when it is subjected to high temperature deformation heat treatment. The specific process is as follows: heating temperature is 920-950 °C, shape variable is 10%-30% during hot rolling, air cooling time is 10-30s, oil quenching; then ordinary tempering or high temperature rapid tempering above 400 °C.
Ferrite state chemical heat treatment
The ferritic chemical treatment such as nitriding and nitrocarburizing can significantly improve the surface hardness, wear resistance, corrosion resistance, residual compressive stress and fatigue life of the spiral steel pipe. The chemical heat treatment temperature is generally in the range of 450-600 ° C. For the quenched and tempered spiral steel pipe, chemical heat treatment and tempering can be combined; for the precipitation hardened spiral steel pipe, the chemical heat treatment temperature and the precipitation hardening temperature are consistent.
With the increasing use of spiral steel pipes, the technical requirements and product diversity requirements of spiral steel pipes are also increasing.