Effect of Quenching and Tempering Process on Microstructure and Mechanical Properties of N-Mo Alloyed Cr13 Type Corrosion Resistant Plastic Die Steel
The N-Mo alloyed Cr13 type corrosion resistant plastic die steel was oil quenched at 925-1 150 ℃ for 0.5 h,and then tempered at 150-300 ℃ for 2 h or 350-600 ℃ for 1 h.The effect of quenching and tempering on the microstructure and mechanical properties of the steel was studied.The results show that the microstructure of the test steel after quenching was mainly quenched martensite.With the increase of quenching temperature,the grain grew up,and the second phase was gradually solidly dissolved into the matrix.With the increase of quenching temperature,the hardness of the test steel first increased and then decreased.When the quenching temperature was 1 050 ℃,the hardness reached the peak value of 57.7 HRC.At this time,the second phase was basically solidly dissolved into the matrix,and the residual austenite volume fraction was only 8.49％.With the increase of tempering temperature,the microstructure of the test steel changed from tempered martensite to sortensite,the second phase gradually precipited and grew up,and the hardness decreased first,then increased and then decreased rapidly.The change law of impact absorption energy with tempering temperature was opposite to that of tempering hardness,and the change law of tensile strength was consistent with that of hardness.The yield strength increased first and then decreased with increasing tempering temperature,and reached the maximum value of 1 445 MPa when the tempering temperature was 480 ℃.After tempering at above 200 ℃,the plasticity of the test steel was relatively good.The heat treatment process to obtain excellent comprehensive properties of the test steel was quenching at 1 050 ℃ for 0.5 h and tempering at 200-300 ℃ for 2 h.At this time,the test steel had the microstructure of tempered martensite with hardness of 48-53 HRC,tensile strength of 1 752-2 050 MPa,yield strength of 1 171-1 223 MPa,impact absorption energy of 41-51 J,percentage reduction in area of 42％-51％,and percentage elongation after fracture of 17.1％-17.7％.
corrosion resistant plastic die steelquenching and temperingmechanical propertyN-Mo alloying
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