淬回火工艺对N-Mo合金化Cr13型耐蚀塑料模具钢组织与力学性能的影响
Effect of Quenching and Tempering Process on Microstructure and Mechanical Properties of N-Mo Alloyed Cr13 Type Corrosion Resistant Plastic Die Steel
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摘要: 对N-Mo合金化Cr13型耐蚀塑料模具钢进行925~1 150 ℃保温0.5 h的油淬处理,再分别进行150~300 ℃保温2 h或者350~600 ℃保温1 h的回火处理,研究了淬回火工艺对该钢组织与力学性能的影响。结果表明：试验钢淬火后的组织主要为淬火马氏体,随着淬火温度的升高,晶粒长大,第二相逐渐固溶进基体,试验钢的硬度先增大后降低,当淬火温度为1 050 ℃时,硬度达到峰值,为57.7 HRC,此时第二相基本固溶进基体,残余奥氏体体积分数仅为8.49%。随着回火温度的升高,试验钢组织由回火马氏体向索氏体转变,第二相逐渐析出并长大；硬度呈先降低后升高再迅速降低的趋势,冲击吸收能量随回火温度的变化规律与回火硬度的变化规律相反,抗拉强度的变化规律与硬度的变化规律一致,屈服强度呈先增大后降低的趋势,并在回火温度为480 ℃时达到最大值,为1 445 MPa；在200 ℃以上温度回火后试验钢的塑性均保持在一个较好的水平。试验钢获得优异综合性能的热处理工艺为1 050 ℃×0.5 h淬火+200~300 ℃×2 h回火,此时组织为回火马氏体,硬度为48~53 HRC,抗拉强度为1 752~2 050 MPa,屈服强度为1 171~1 223 MPa,冲击吸收能量为41~51 J,断面收缩率为42%~51%,断后伸长率为17.1%~17.7%。Abstract: 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%.
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