摘要
钢的连续冷却相变曲线(CCT)是组织调控的基本依据,为了优化紧固件用冷作硬化非调钢热轧态的组织和力学性能,采用DIL805A相变仪测定了试验钢在0.1~50℃/s不同冷却速率下的热膨胀曲线,结合金相-硬度法确定相变类型,并绘制了试验钢的CCT曲线。结果表明,试验钢马氏体转变点(M;)为280℃,在不同冷速范围内均有铁素体生成;随着冷速的增加,铁素体和珠光体转变开始温度降低,同时铁素体含量不断降低、晶粒尺寸减小;冷速小于3℃/s时,室温组织由先共析铁素体和珠光体组成,随冷速增加硬度变化不大,为156~166HV;当冷速达到3℃/s时,开始出现贝氏体和马氏体,硬度快速增加至181HV;当冷速大于3℃/s后,先共析铁素体和珠光体含量逐渐减少,贝氏体和马氏体含量增加,硬度不断提高;冷速为30~50℃/s时,组织以贝氏体和马氏体为主。Nb、V均对连续相变起到重要影响。利用Thermo-Calc软件计算试验钢Nb、V碳氮化物析出行为,计算得到V(C,N)、Nb(C,N)全固溶温度分别为780、1 144℃;在900℃奥氏体化条件下,V(C,N)全部固溶,Nb(C,N)固溶了8%,由于Nb、V的扩散速率比C慢得多,固溶的Nb、V在冷却转变过程中来不及扩散而聚集在两相界面上,降低铁素体的长大速率,抑制铁素体形成,促进贝氏体或马氏体相变。
The continuous cooling transformation(CCT) law of steel is the basic basis of microstructure regulation.In order to optimize the microstructure and mechanical properties of cold work hardening non-quenched steel for fasteners in hot rolling state,the thermal expansion curves of the test steel at cooling rates 0.1-50 ℃/s was measured by DIL805 A phase transformation instrument,combined with metallographic hardness method to determine the transformation type,and draw the static CCT curve of the test steel.The results show that the martensite transformation point(M;) of the test steel is 280 ℃,and ferrite is formed in different cooling rate ranges.With the increase of cooling rate,the transition temperature of ferrite and pearlite decreases,and the content and grain size of ferrite decrease.Cooling rate less than 3 ℃/s,the room temperature microstructure is composed of proeutectoid ferrite and pearlite,and the hardness changes little with the increase of cooling rate,which is 156-166 HV.When the cooling rate reaches 3 ℃/s,bainite and martensite begin to appear,and the hardness increases rapidly to 181 HV.When the cooling rate is greater than 3 ℃/s,the content of proeutectoid ferrite and pearlite decrease gradually,the content of bainite and martensite increase,and the hardness increase continuously.When cooling rate is 30-50 ℃/s,the microstructure is mainly bainite and martensite.Nb and V play important roles in the continuous phase transition.The precipitation behavior of Nb and V carbonitride in the test steel was calculated by Thermo-Calc software.The total solid solution temperatures of V(C,N) and Nb(C,N) were 780 ℃ and 1 144 ℃ respectively.Under the condition of austenitizing at 900 ℃,V(C,N) is completely solid solution,and Nb(C,N) is solid solution by 8%.Because the diffusion rate of Nb and V is much slower than that of C,the solid solution Nb and V have no time to diffuse in the cooling transformation process and gather at the two-phase interface,reducing the growth rate of ferrite,inhibitin
作者
江畅
王子波
王杨
陆恒昌
满廷慧
周蕾
JIANG Chang;WANG Zi-bo;WANG Yang;LU Heng-chang;MAN Ting-hui;ZHOU Lei(School of Materials and Science Engineering,Shanghai University,Shanghai 200444,China;Nanjing Iron and Steel Co.,Ltd.,Nanjing 210035,Jiangsu,China)
出处
《钢铁》
CAS
CSCD
北大核心
2022年第3期91-96,共6页
Iron and Steel
基金
国家自然科学基金资助项目(52031004)
上海市军民融合发展专项资金资助项目(2020-jmrh1-kj31)。
关键词
非调质钢
连续冷却转变
显微组织
冷作硬化
Nb、V碳氮化物
non-quenched and tempered steel
continuous cooling transformation
microstructure
cold work hardening
Nb、V carbonitride
