厚规格Q690D高强钢板的连续冷却转变行为

Continuous cooling transformation behavior of high-strength Q690D heavy steel plate

通过Gleeble-1500热模拟试验机,结合微观组织观察和硬度测试,绘制了Q690D厚规格钢板以不同速度连续冷却至室温的CCT曲线。结果表明,当冷速较低时,组织中存在先共析铁素体和珠光体区域,但其范围较小;冷却速度为3℃/s时,组织中出现板条贝氏体。试验钢在较宽的冷速范围内能够获得粒状贝氏体、粒状贝氏体+板条贝氏体组织。冷速达到15℃/s时,组织中即出现马氏体,试验钢淬透性较好,硬度值变化不明显。从试验钢板的调质组织观察发现,厚度截面不同位置的硬度值差异很小,组织特征相同,说明热模拟试验的结果同实际生产的厚规格钢板的组织及硬度具有高度的一致性。

By using Gleeble-1500 thermo-simulator along with microstructure and hardness analysis,the continuous cooling transformation(CCT)curves of Q690D heavy steel plate were measured at different cooling rates.The results demonstrate that the proeutectoid ferrite and pearlite zones are observed at slow cooled rates.When the cooling rates reaches 3℃/s,the lath bainite appears.At larger range cooling rates,the microstructure of granular bainite and granular+lath bainite can be obtained for the tested steel.Moreover,when the cooling rate reaches 15℃/s,the martensite can be observed which indicates that the hardenability of the tested steel is better and the hardness values have little change.The hardness values of different thickness sections keep almost unchanged of the quenched and tempered Q690D heavy steel plate,the microstructure are uniformity.The microstructure and harness values for simulated specimens show the highly consistent with the Q690D heavy steel plate actually produced.