Application of PAG in Heat Treatment of
50CrVA Steel Plate Spring
50CrVA steel belongs to Cr-V spring steel, which has good anti-decarburization ability and prevent austenite grain coarsening ability, and after heat treatment has high elastic limit, strength limit and good plasticity, is widely used in Automotive leaf spring manufacturing. With the domestic heavy-duty truck load from the past 4t increased to the current 40t or more, 50CrVA steel used in automotive leaf spring, the use of its cross-section thickness requirements increased from 8mm to 24mm and above, but 50CrVA steel conventional heat treatment The process, the use of quenching medium for ordinary quenching oil, the oil quenching critical quenching thickness of 24mm. By analyzing the failure of the traditional 50CrVA steel leaf spring and the quality of the production process, it is found that the quenching phenomenon can not be normal when the thickness of the steel plate is close to or greater than the critical quenching thickness of the oil quenching, which seriously affects the mechanical properties of the steel plate Fatigue life of springs. Water-soluble quenching medium --- PAG as a new type of quenching medium, because of its cooling performance, wide range of application, uniform hardening, environmental pollution, fire hazards and other advantages, more and more heat treatment researchers Favor. In this paper, using PAG water-soluble quenching medium and ordinary quenching oil, 24mm thick 50CrVA leaf spring material heat treatment, and heat treatment after the reed of the microstructure, hardness and fatigue life were studied.
The chemical composition of the test material is: 0.53C, 0.011S, 0.009P, 0.70Mn, 0.27Si, 0.99Cr, 0.12. The test material is made of 50CrVA material reed as heat treatment test material, its specification is 500mm × 90mm × 24mm. V, the balance being Fe. (900 ± 5 ℃ 20min) under the conditions of a step-quenching furnace for heating, insulation, respectively, the use of a certain concentration of water-soluble quenching medium and quenching oil quenching, and then (480 ± 5) ℃ Heat 120min water-cooled tempering, access to different quenching medium heat treatment samples.
The use of PAG water-soluble quenching medium instead of ordinary quenching oil, the success of 24mm thick 50CrVA steel leaf spring sample heat treatment, magnetic detection crack is not found. Using PAG water quenching medium heat treatment 24mm thick 50CrVA steel leaf spring sample, the quenching and tempering microstructure, hardness, are better than the use of ordinary quenching oil heat treatment sample. 24mm thick 50CrVA steel leaf spring samples, the use of PAG water quenching medium heat treatment after the average fatigue life of up to 15 million times, compared with the ordinary quenching oil heat treatment sample, fatigue life nearly doubled, a greater extent Quality of leaf spring.