摘要:
对成分为0.24%C-1.5%Si-2.0%Mn-0.16%V的冷轧试验钢,经780℃两相区退火后进行350~480℃不同温度下等温淬火和380℃等温60~1 200 s不同时间热处理对比试验,结合力学性能、显微组织、XRD分析,研究了热处理工艺对试验钢组织和性能的影响。结果表明,试验钢在780℃两相区退火180 s后,经380℃等温淬火处理360 s,可获得抗拉强度1 029 MPa、强塑积20.1 GPa·%、加工硬化指数0.22的良好综合性能。提高或降低等温温度均使其强度升高,延伸率降低;而延长等温时间至1 200 s,其强度及延伸率变化不大,但出现明显屈服平台。等温淬火温度及时间对残余奥氏体体积分数具有重要影响,在350~410℃范围内提高等温淬火温度,碳原子扩散能力提高,使残余奥氏体含量从2.58%增大到3.86%;而更高的等温淬火温度下,由于马氏体相变被抑制,发生贝氏体相变,残余奥氏体迅速下降;等温淬火时间超过180 s完成碳原子向奥氏体扩散富集,使其残余奥氏体稳定在3.5%左右。
关键词:
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含钒高强钢 /
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热处理 /
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组织 /
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性能
Abstract:
The 0.24%C-1.5%Si-2.0%Mn-0.16%V cold-rolled steel was heat treated at 780 ℃ intercritical annealing for 180 s,then quenching into 350～380 ℃ for 360 s,or quenching into 380 ℃ for holding 60～1 200 s.The microstructures and properties after heat treatments were tested by tension test,OM,SEM and XRD analysis.The results show that the good comprehensive property with tensile strength of 1 029 MPa,product of strength and elongation of 20.1 GPa·%,work hardening index of 0.22,is obtained by quenching into 380 ℃ for 360 s.The higher or lower quenching temperature,the higher tensile strength and the lower elongation are.As the holding time prolongs to 1 200 s,the strength and elongation are not varying much,but the yield platform appears.The volume fraction of retained austenite（RA） can be greatly affected by equal quenching temperature and time.The volume fraction of RA increases from 2.58% to 3.86% as isothermal the temperature increasing from 350 ℃ to 410 ℃,and then rapidly decreases in higher temperatures since martensite transformation is hindered and bainite transformation appears.And the RA maintains about 3.5% as the carbon has been enriched in austenite under isothermal quenching for 180 s.
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