| Currently,the high manganese steel,dual-phase wear-resistant steel and other low alloy steel are widely used in the mine crushing machine and the ball mill lining board.However,high manganese steel cannot be fully hardening,and their wear-resistant performance is always limited in a low stress abrasion condition.People want to use low alloy martensite/bainite dual-phase wear-resistant steel and 42CrMo steel to replace the high manganese steel.Strength,hardness and toughness are the main factors that affect the wear resistance,and these properties greatly affected by heat treatment.In addition to the quenching and tempering temperature,the quenching medium also has a certain effect.For this purpose,we choose 42CrMo steel and dual-phase steel,respectively,using water and quenching oil as their heat treatment quenching medium,to study the effect of different quenching medium on the microstructure and properties of wear-resistant cast steel.This thesis is mainly on the research of the following aspects:(1)The chemical composition of the steel was determined,according to the effect of elements of dual-phase steel on its properties,and the chemical composition of 42CrMo steel was fine tuned;(2)Water quenching and oil quenching of the dual-phase steel and 42CrMo steel were carried out,observe their microstructure of different quenching medium,and test the hardness,tensile properties and impact toughness;(3)Combining with the practical application conditions,tested the wear-resistance of two kinds of steels,to analysis the effect of different quenching media on the wear properties of the two test steels.Through comprehensive analysis of the experiment results,following conclusions can be reached:(1)The microstructure of the dual phase test steel by water quenching and oil quenching:lath martensite + needle-like bainite + carbide;The samples with oil quenching are more compact and finer than the samples with water quenching.In terms of 42CrMo test steel,The microstructure of test steel with water quenching treatment:tempered martensite +retained austenite;The microstructure of test steel with oil quenching treatment:tempered martensite + ferrite + bainite.The content of martensite of the samples with oil quenching is less than that of water quenching.(2)The optimum heat treatment process of dual-phase test steel was determined:950 ? oil quenching + 300 ? tempering.Its hardness is 425HBW,the impact toughness is 38.8J/cm2,the tensile strength and the yield strength can reach 1450MPa,1180MPa,and the elongation is 9.3%.(3)The optimum heat treatment process of 42CrMo test steel was determined:840 ?water quenching + 280?tempering..Its hardness is 445HBW,the impact toughness is 35J/cm2,the tensile strength and the yield strength can reach 1565MPa,1362MPa,and the elongation is 8%.(4)After 480 hours of the abrasive wear test,the total abrasion loss of 42CrMo test steel with water quenching was the least.Having the best wear resistance,the relative wear resistance is 1.558 times of high manganese steel.Observing the surface morphology,it shows that the abrasion mechanism is chiefly micro-cutting wear. |
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