Measurements of paramagnetic susceptibility as a method of checking the heat treatment of alloy 40KKhNM

Conclusions

• 1. The paramagnetic susceptibility of alloy 40KKhNM is a structure-sensitive characteristic and, consequently, changes in relation to heat treatment.

• 2. The paramagnetic susceptibility is minimal (40–50·10⁻⁶ CGS units) after water quenching to a single-phase γ solid solution from temperatures above 1150°C.

• 3. The paramagnetic susceptibility increases with decreasing cooling rates after heating (water-oil-sand-furnace), which depends on the partial or complete decomposition of the γ solid solution and the precipitation of carbide phase.

• 4. Measurement of the paramagnetic susceptibility is recommended for checking the quality of quenching for alloy 40KKhNM. With tempering, the measurement of the paramagnetic susceptibility cannot be used to check the quality.

• 5. In the production of alloy 40KKhNM with a magnetic susceptibility not over 80·10⁻⁶ CGS units the quality must be checked at the ends of the wire.