Cr12MoV钢热变形行为及组织性能研究
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摘要
Cr12MoV钢是广泛用于模具行业的冷作模具钢,具有高淬透性,淬火时的变形很小在300～400℃时仍可保持良好硬度和耐磨性,属于莱氏体型高碳高铬冷作模具钢。本文以宝钢股份特殊钢分公司项目“特种金属及合金板带生产工艺技术研究”为背景,研究了Cr12MoV钢的高温变形组织性能变化以及热处理工艺对组织性能的影响规律,并绘制了Cr12MoV钢的高温变形塑性加工图,分析该钢不同变形参数下微观变形机制,为该钢的生产提供技术支持,具体内容及结果如下：
(1)通过单道次压缩试验,研究了变形温度、变形程度和变形速率对Cr12MoV钢变形抗力的影响规律,建立了该钢的变形抗力数学模型。
(2)研究了Cr12MoV钢奥氏体区动态软化行为,回归得到动态再结晶激活能Q=538.712 kJ/mol,峰值应力σp与Z参数的关系如下：lnσp=-0.47989+0.11651lnZ(相关系数R=0.96982),峰值应变εp与Z参数的关系如下：lnεp=3.10906 lnZ-13.62152(相关系数R=0.96663)。
(3)通过双道次压缩实验,研究了实验钢奥氏体区热变形后等温保持时间里的静态再结晶行为,绘制了实验钢的静态软化率时间曲线。
(4)采用Prasad建立的失稳准则,利用三次样条函数拟和logσ与logε的关系曲线,绘制了Cr12MoV钢的塑性加工图,得出功率耗散因子峰值随着变形程度增加由中温区向高温区转移,功率耗散因子峰值最大为0.56,该钢塑性变形温度不宜低于950℃,真应变为0.6时,最佳变形温度范围为1050～1125℃,且变形速率不宜超过1s-1。
(5)通过X射线物相定性分析以及能谱分析等试验方法,研究不同淬火温度和不同回火温度以及冷却介质对Cr12MoV组织的影响,可知随着淬火温度升高,粒状碳化物减少,淬火温度为900℃时,随回火温度升高块状碳化物中Cr元素含量显著升高,淬火温度高于900℃时,回火温度对块状碳化物中Cr元素含量影响不明显；分析对比水淬和油淬两种冷却方式对组织的影响,可知油淬的二次碳化物比相同温度下的水淬二次碳化物析出更弥散细小,油淬的一次碳化物和水淬的一次碳化物相比,向球团化趋势发展,碳化物的尖角变得圆滑,减轻了一次碳化物对基体的割裂作用。
Cr12MoV is a cold working die steel which is widely used in die industry.It changes a little in size and is of good hardenability.It can abtain good hardness and abradability at 300℃-400℃.It is a ledeburite cold working die steel,rich in C and Cr.In the background of baosteel special steel corporation Project,that is about the technology research for plate and strip production of special metals and alloys,this article will research into the microstructure change in hot deformation process and the effect imposed by heat treatment parameters on the microstructure and mechanical properties.The processing maps of Cr12MoV steel are drawn from the experiment datas.The microscope deformation mechanisms at different deformation parameters are also researched in this article.All this can provide some help for the production of Cr12MoV steel.The main contents and results are as follows:
(1) When single press test is taken, the influence of the deformation temperature, deformation degree and deformation rate to the stress of the steel are researched, and the mathematical model of resistance of deformation is established.
(2) The softening behavior of Cr12MoV steel is researched in this article and the mathematical model between peak stressσp and Z parameters is obtained as follows: lnσp=-0.47989+0.116511nZ,the mathematical model between peak strain ep and Z parameters is obtained as follows:lnεp=3.10906 lnZ-13.62152.The activation energy of dynamic recrystallization is 538.712 kJ/mol.
(3)When double press test is taken, the behavior of static recrystallization during isothermal process after the hot deformation of the steel in austenitic area is researched.The softening rate curve of the steel to be tested is drawn.
(4) Based on the prasad instability criteria, the processing maps of Cr12MoV steel are drawn in this article with the cubic spline used in obtaining the relation beteen logσand logε.The power dissipation coefficience peak value transfer from medium temperature zone to high temperature zone with the increase of strain.The power dissipation coefficience peak value reaches 0.56.It is not advisable the Crl2MoV steel be defoemed below 950℃.The best deformation temperatures range from 1050℃to 1125℃at true strain 0.6 and the deformation rate should not excel ls-1.
(5) With the experiment methods such as X rays and energy spectrum,the effect on Cr12MoV steel imposed by quench temperatures and temper temperatures and cooling medium is researched.The quantity of granular carbide decrease with the increase of quench temperature.when Cr12MoV steel is quenched at 900℃. The content of Cr in block carbide increase rapidly with the increase of temper temperature.When Cr12MoV steel is quenched above 900℃, the content of Cr in block carbide almost keep steady with the increase of temper temperature. Comparing with the effect on microstructure by water cooling,we obtain that secondary carbide is smaller in size and more disperse by oil cooling.Spheroidization effect on primary carbide is obvious and the carbide sharp corners become circular,as a result,this can relieve the split effect on matrix imposed by primary carbide.
(1)通过单道次压缩试验,研究了变形温度、变形程度和变形速率对Cr12MoV钢变形抗力的影响规律,建立了该钢的变形抗力数学模型。
(2)研究了Cr12MoV钢奥氏体区动态软化行为,回归得到动态再结晶激活能Q=538.712 kJ/mol,峰值应力σp与Z参数的关系如下：lnσp=-0.47989+0.11651lnZ(相关系数R=0.96982),峰值应变εp与Z参数的关系如下：lnεp=3.10906 lnZ-13.62152(相关系数R=0.96663)。
(3)通过双道次压缩实验,研究了实验钢奥氏体区热变形后等温保持时间里的静态再结晶行为,绘制了实验钢的静态软化率时间曲线。
(4)采用Prasad建立的失稳准则,利用三次样条函数拟和logσ与logε的关系曲线,绘制了Cr12MoV钢的塑性加工图,得出功率耗散因子峰值随着变形程度增加由中温区向高温区转移,功率耗散因子峰值最大为0.56,该钢塑性变形温度不宜低于950℃,真应变为0.6时,最佳变形温度范围为1050～1125℃,且变形速率不宜超过1s-1。
(5)通过X射线物相定性分析以及能谱分析等试验方法,研究不同淬火温度和不同回火温度以及冷却介质对Cr12MoV组织的影响,可知随着淬火温度升高,粒状碳化物减少,淬火温度为900℃时,随回火温度升高块状碳化物中Cr元素含量显著升高,淬火温度高于900℃时,回火温度对块状碳化物中Cr元素含量影响不明显；分析对比水淬和油淬两种冷却方式对组织的影响,可知油淬的二次碳化物比相同温度下的水淬二次碳化物析出更弥散细小,油淬的一次碳化物和水淬的一次碳化物相比,向球团化趋势发展,碳化物的尖角变得圆滑,减轻了一次碳化物对基体的割裂作用。
Cr12MoV is a cold working die steel which is widely used in die industry.It changes a little in size and is of good hardenability.It can abtain good hardness and abradability at 300℃-400℃.It is a ledeburite cold working die steel,rich in C and Cr.In the background of baosteel special steel corporation Project,that is about the technology research for plate and strip production of special metals and alloys,this article will research into the microstructure change in hot deformation process and the effect imposed by heat treatment parameters on the microstructure and mechanical properties.The processing maps of Cr12MoV steel are drawn from the experiment datas.The microscope deformation mechanisms at different deformation parameters are also researched in this article.All this can provide some help for the production of Cr12MoV steel.The main contents and results are as follows:
(1) When single press test is taken, the influence of the deformation temperature, deformation degree and deformation rate to the stress of the steel are researched, and the mathematical model of resistance of deformation is established.
(2) The softening behavior of Cr12MoV steel is researched in this article and the mathematical model between peak stressσp and Z parameters is obtained as follows: lnσp=-0.47989+0.116511nZ,the mathematical model between peak strain ep and Z parameters is obtained as follows:lnεp=3.10906 lnZ-13.62152.The activation energy of dynamic recrystallization is 538.712 kJ/mol.
(3)When double press test is taken, the behavior of static recrystallization during isothermal process after the hot deformation of the steel in austenitic area is researched.The softening rate curve of the steel to be tested is drawn.
(4) Based on the prasad instability criteria, the processing maps of Cr12MoV steel are drawn in this article with the cubic spline used in obtaining the relation beteen logσand logε.The power dissipation coefficience peak value transfer from medium temperature zone to high temperature zone with the increase of strain.The power dissipation coefficience peak value reaches 0.56.It is not advisable the Crl2MoV steel be defoemed below 950℃.The best deformation temperatures range from 1050℃to 1125℃at true strain 0.6 and the deformation rate should not excel ls-1.
(5) With the experiment methods such as X rays and energy spectrum,the effect on Cr12MoV steel imposed by quench temperatures and temper temperatures and cooling medium is researched.The quantity of granular carbide decrease with the increase of quench temperature.when Cr12MoV steel is quenched at 900℃. The content of Cr in block carbide increase rapidly with the increase of temper temperature.When Cr12MoV steel is quenched above 900℃, the content of Cr in block carbide almost keep steady with the increase of temper temperature. Comparing with the effect on microstructure by water cooling,we obtain that secondary carbide is smaller in size and more disperse by oil cooling.Spheroidization effect on primary carbide is obvious and the carbide sharp corners become circular,as a result,this can relieve the split effect on matrix imposed by primary carbide.
引文
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[3]吴承建,陈国良,强文江.金属材料学[M].冶金工业出版社,2002,66-69
[4]王占学.塑性加工金属学[M].北京：冶金工业出版社,1989,94-103
[5]周纪华,管克智.金属塑性变形阻力[M].北京：机械工业出版社,1989,211-229
[6]雍岐龙,马鸣图,吴宝榕编.微合金钢——物理和力学冶金[M].机械工业出版社,1989,284-400
[7]沈开照.低成本Mn-Cu耐候钢热轧过程组织性能控制[D].沈阳东北大学,2007
[8]高珊.应用Processing Map研究D2钢的高温变形行为[D].沈阳东北大学,1997
[9]杨节.轧制过程数学模型[M].北京：冶金工业出版社,1992：137-146
[10]Siamak Serajzadeh. A mathematical model for evolution of flow stress during hot deformation[J]. Materials Letters 2005(59):3319-3324
[11]Siamak Serajzadeh, et al. Prediction of flow stress at hot working condition[J]. Mechanics Research Communications,2003(30):87-93
[12]Xiaoming He, Zhongqi Yu, Xinmin Lai. A method to predict flow stress considering dynamic recrystallization during hot deformation[J]. Computational Materials Science,2008
[13]Y.C. Lin, Ming-Song Chen, Jue Zhong. Prediction of 42CrMo steel flow stress at high temperature and strain rate[J]. Mechanics Research Communications,2008(35):142-150
[14]兰英斌,窦连福,刘建华.钢的原奥氏体晶界的显示[J].物理测试,1994(6)：40-41
[15]屠世润,高越等.金相原理与实践[M].机械工业出版社,1990,320-322
[16]张卫东,卢文增.高温形变条件下的奥氏体晶界腐蚀[J].物理测试,1986(4)：34-38
[17]周纪华,管克智.合金结构钢的变形阻力[J],北京钢铁学院学报,1986(4)：46-52
[18]孙一康,孙民生,周纪华.高温高速下金属塑性变形阻力的实验研究[J],钢铁,1979,14(2)：95-107
[19]戴铁军,刘战英,刘相华等.30MnSi钢金属塑性变形抗力的数学模型[J].塑性工程学报,2001,18(3)：16-20
[20]第一机械工业部上海材料研究所等.工具钢金相图谱[M].机械工业出版 社,1979,82-85
[21]余永宁编.金属学原理[M].冶金工业出版社,2003,441-470
[22]徐光,张丕军编.金属低温变形理论与技术[M].冶金工业出版社,2007,116--126
[23]John J. Jonas,Xavier Quelennec, Lan Jiang. The Avrami kinetics of dynamic recrystallization[J].Acta materialia,2009,33(2):1-9
[24]S.F.MEDINA,C.A.HERNANDEZ. Modelling of the dynamic recrystallization of austenite in low alloy and microalloyed steels [J], Acta materialia,1996,44(1):165-171
[25]Medina S F,et al.Modelling of the Dynamic Recrystallization of Austenite in Low Alloy and Microalloyed Steels.[J] Acta Mater,1996,44 (1):165-171
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