45Mn2V锯片钢相变规律及热处理工艺研究

Research on phase transformation law and heat treatment processes of the 45Mn2V saw blade steel

针对当前锯片用钢油淬工艺污染空气、成本较高等缺点,开发了其水淬工艺。以实际工业生产的15.3 mm厚45Mn2V锯片用钢板为研究对象,结合热模拟试验,对试验钢相变过程进行了研究。同时,结合实验室模拟和工业水淬试验,并与工业油淬进行对比,研究了45Mn2V钢板水淬条件下组织和性能变化。结果表明:采用w(C)=0.43%~0.46%、w(Mn)=1.45%~1.60%、w(V)=0.040%~0.055%的化学成分设计,热模拟条件下45Mn2V钢Ac_(1)=728℃、Ac_(3)=774℃、Ar_(3)=685℃、Ar_(1)=633℃,Ms=272℃。当冷速不大于3℃/s时,试验钢板组织类型为先析铁素体+珠光体;随着冷速的增加,先析铁素体含量减少,珠光体片层间距逐渐变小,向索氏体及屈氏体组织转变;冷速不小于30℃/s时,基本得到全马氏体组织。随水淬温度由770℃提升至850℃,钢板硬度由55.4HRC增加至63.8HRC;回火后钢板硬度变化趋势与淬火态类似,硬度为25.4HRC~-29.3HRC;不同淬火温度下,钢板20℃冲击功均在30 J以下;随着淬火温度的升高,钢板冲击韧性逐渐降低;不同温度淬火并经580℃回火后,钢板冲击韧性大幅提高。工业生产表明:采用820℃水淬+580℃回火工艺与850℃油淬+550℃回火处理的钢板,组织均为回火索氏体,但前者残余奥氏体含量略微增加;力学性能方面,前者强度和硬度略微降低,但冲击韧性更加优异。

In view of the air pollution and high cost of the current oil quenching process for saw blade steel,the water quenching process was developed.The phase transformation process of the actual industrial production of 15.3 mm thicknecs 45Mn2V saw blade steel plate was studied combining with the thermal simulation test.At the same time,the microstructures and properties changing of 45Mn2V plate under water quenching were studied by combining laboratory simulation,industrial water quenching and comparing with industrial oil quenching.The results show that using chemical compositions design of w(C)=0.43%-0.46%,w(Mn)=1.45%-1.60%,w(V)=0.040%-0.055%,under thermal simulation conditions,the temperature of Ac_(1),Ac_(3),Ar_(3),Ar_(1),Ms of 4Mn2V steel is 728℃,774℃,685℃,633℃,272℃,respectively.When the cooling rate is less than 3℃/s,the microstructure of the test plate is proeutectoid ferrite+pearlite.With the increasing of cooling rate,the proportion of proeutectoid ferrite decreases,the lamellar spacing of pearlite becomes smaller,and the structures changes to sorbite and troisite.When the cooling rate is not less than 30℃/s,the whole martensite is basically obtained.With the increasing of water quenching temperatures from 770℃to 850℃,the hardness of plate increases from 55.4HRC to 63.8HRC.After tempering,the hardness variation trend of the plate is similar to that of the quenched state,which ranges from 25.4HRC to-29.3HRC.Under different quenching temperatures,the impact energy of the plate at 20℃is less than 30 J.With the increasing of quenching temperatures,the impact toughness of plate decreases gradually.After quenching at different temperatures and tempering at 580℃,the impact toughness of the plate is greatly improved.In the industrial production process,the microstructure of the plate treated by 820℃water quenching+580℃tempering process and 850℃oil quenching+550℃tempering process are all tempered sorbitite,but the content of residual austenite in the former is slightly increased.In terms of mechanical properties,the strength and hardness of the former are slightly reduced,but the impact toughness is better.