Increasing the durability of highly loaded threaded connections by induction heat treatment

The authors present results of testing Induction Heat Treatment (IHT) to enhance the mechanical properties of 40Kh steel, used for sucker rods in thin-walled rod deep well pumps (SRPs). They describe IHT benefits including rapid heating, surface decarburization minimization, and energy efficiency. Calculations for necessary hardening depth and justifications for equipment selection in conducting IHT and temperature measurement are provided, along with main technical specifications of the inductor and pyrometer. The impact of IHT on steel’s microstructure, strength, and fatigue resistance is analyzed, showing microhardness changes in the hardened layer and fatigue test results of full-sized sucker rod samples under transverse bending during rotation. IHT with quenching at 850 ˚C in water and tempering at 400 оC is shown to significantly improve fatigue resistance compared to thread rolling and bulk hardening using thermally hardened UNS G41400 steel of class D strength. An economic analysis demonstrates the potential for cost reduction and increased profitability in SRP production through the implementation of IHT in the manufacturing process of 40Kh steel pump rods.The work was carried out with the support of JSC ELKAM-Neftemash.