Inspection of the Strength Characteristics and Heat-Treatment Quality of Ferromagnetic Articles According to Parameters of the Residual-Magnetization Hysteresis Loop during Their Local Magnetization and Magnetization Reversal in a Pulsed Magnetic Field with a Variable Amplitude: III. Steel 50ΧΓΦΑ

Abstract

Effects of the tempering temperature on specimens' hardness and on parameters of both the anomalous-hysteresis loop and the recovery curves for the gradient of the residual magnetization field's strength are studied experimentally. Test specimens made of steel 50 ïÉîÄ intended for laminated springs are quenched in water from 850 ° C and subjected to local magnetization and magnetization reversal by a pulsed magnetic field created by an attachable solenoid whose axis is perpendicular to the surface. The amplitude of pulses changes with increment ∆ H p . Parameters enabling nondestructive testing of the hardness of multiple-leaf springs made from steel 50 ïÉîÄ within three ranges of temperingtemperature variation (0-300, 300-600, and 0-600 ° C) are determined.High-quality chrome-manganese steel 50 ïÉîÄ intended for laminated springs is used in manufacturing of critical multiple-leaf springs for vehicles. It differs from silicon steel 60C2 investigated earlier [1] by improved technological properties attained at the same cost.An increase in the content of manganese in a medium-carbon chrome-alloy steel results in improved strength properties, minor variations of plasticity, and increased hardening characteristics. Owing to the presence of vanadium, this steel has a fine-grained structure that additionally improves its hardening characteristics. If this steel is tempered in the range 400-500 ° C, vanadium carbides that dissolved when the steel was heated for quenching become deposited at the nodes of the dislocation lattice. This process slows softening of steel in the tempering process until noticeable coagulation of these carbides begins, a process which takes place at tempering temperatures above 500 ° C.Vanadium positively affects the process of nitrogen binding as well. Low sensitivity to the growth of austenite grains and a uniform distribution of carbides in the structure of steel 50 ïÉîÄ after tempering ensure increased impact viscosity [2].Manufacturing instructions stipulate that a bundle of plates made of this steel, which is intended for making a single multiple-leaf spring, should be heated for quenching in a belt furnace with a temperature of 800-810 ° C at the entry, 890-910 ° C in the central zone, and 890-910 ° C at the exit. The heated leaves are bent and tempered in oil for 15 to 20 min. The oil temperature should not exceed 90 ° C. The hardness after quenching, which is measured once every hour, should be in the range 477-712 HB (55-63.5 HRC ).The quenched leaves are tempered also in a belt furnace whose temperature at the entry and the exit is 500-520 ° C. Heating for tempering lasts 100 min. The hardness after cooling is measured at three points: at the two ends of a leaf and on the convex surface at its center. The value of hardness should be 363-444 HB (39-47 HRC ). The hardness of individual leaves within the same multiple-leaf spring must not exceed 40 HB (4 HRC ).Owing to the dimensions and weight of a multiple-leaf spring (the length is >2 m and the weight is 30 kg) and to the necessity to...

Multiparameter methods in magnetic structuroscopy and instruments for their realization (Review): II. The pulsed magnetic multiparameter method and IMA-M instrument for its performance

“…For #50ХГФА steel [28], the four parameter equation (3) allows the calculation of the hardness HRC p in the temperature range of tempering from 100 to 600°C at the correlation coefficient R = 0.991 and root mean square deviation S n = 0.997HRC. [29] of the parameters of hysteresis loops via ∇H rn and recoil curves was per formed on wheel nuts that are manufactured from structural quality carbon steel #35.…”