IMPROVEMENT OF HEAT TREATMENT MODES FOR FORGINGS FROM 40KhN2MA STEEL

Abstract

Equipping the oil industry with pumps for main line pumping issues a challenge for equipment manufacturers to ensure a set of mechanical properties allowing for stable operation under various conditions. Due to the wide range of the applied pumps, simplicity and the speed of manufacture become another factor during manufacture. The forging facility MFT LLC identified issues during the production of the pump shafts made from steel 40KhN2MA, related to the manufacturing conditions limitations. The regulatory and reference documents mention the use of oil as a quenching medium, but no analogues are given. The availability of oil tanks has a set of unfavorable factors: flammability, combustibility and toxic vapors. Using oil for quenching requires additional safety measures and equipment. A safely equipped oil tank, in comparison to a water or water-polymer tank, is the expensive equipment that requires daily monitoring. The paper studies the effect of various cooling environments during quenching on the mechanical properties and deformation resistance of 40KhN2MA steel. The results of mechanical property measurements are presented. Three shafts were produced using open-die forging from forged ingots of the same heat. The open-die forging and heat treatment process procedures for obtaining the required properties were identical. Sampling was carried out in accordance with GOST 8479–70. A comparison of the mechanical property results indicates the achievement of the complex during quenching in experimental environments. The average values of impact strength at sub-zero temperatures increased by 51 J/mm² when quenched in water and by 26 J/mm² when quenched in a water-polymer medium. The tensile strength value increased by 36 MPa when quenched in water and by 45 MPa when quenched in a water-polymer medium, the yield strength increased by 59 MPa when quenched in water and by 57 MPa when quenched in a water-polymer medium.