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研究了高强度含铜钢HSLA80和HSLA100奥氏体连续冷却转变产物的强度和韧性随冷却速率的变化规律,探讨了连续冷却过程中形成的Cu沉淀的特征和熟化规律.在Gleeble3800热模拟试验机上进行0.1℃·s-1至20℃·s-1的连续冷却实验,利用扫描电镜和透射电镜分析了显微组织和Cu沉淀.结果表明,随冷却速率提高,HSLA80的连续冷却转变组织由多边形铁素体向块状铁素体和贝氏体转变,在冷速0.1~1℃·s-1范围内Cu发生沉淀,两者综合作用造成随冷却速率提高钢的硬度分阶段变化,而韧性逐渐提高;HSLA100的连续冷却转变组织以贝氏体为主,且不发生Cu的沉淀,随冷却速率提高钢的硬度基本保持不变,但韧性发生剧烈变化.连续冷却过程中形成的Cu沉淀在等温过程中的熟化符合Ostwald熟化规律,半径随时效时间t1/3变化.
The strength and toughness of the continuous cooling and reduction products of high strength copper-bearing HSLA80 and HSLA100 austenite were studied with the variation of cooling rate, and the characteristics of Cu precipitation and the ripening rule during continuous cooling were discussed. On the Gleeble3800 thermal simulation tester Continuous cooling experiments were carried out at 0.1 ℃ · s-1 to 20 ℃ · s-1, and the microstructure and Cu precipitation were analyzed by scanning electron microscopy and transmission electron microscopy.The results show that with the cooling rate increasing, the continuous cooling transformation structure of HSLA80 consists of polygons Ferrite changes to massive ferrite and bainite, and Cu precipitates in the range of 0.1-1 ℃ · s-1 at the cooling rate. The combined effect of the two results in the phase change of the hardness of the steel with the cooling rate. The toughness The hardness of HSLA100 is continuously increased and the microstructure of HSLA100 is dominated by bainite, and the precipitation of Cu does not occur. With the cooling rate increasing, the hardness of the steel remains almost unchanged, but the toughness changes drastically. The ripening in the isothermal process conforms to the Ostwald maturation rule, and the radius varies with the time-dependent t1 / 3.