一种高强无碳贝氏体非调质钢的过冷奥氏体动态连续冷却转变曲线

Dynamic continuous cooling transformation curves of under-cooled austenite of a kind of high strength carbide-free bainite non-quenched and tempered steel

利用Gleeble-3800热模拟试验机测定了自行研制的新型无碳贝氏体非调质钢在不同冷却速率下连续冷却转变的热膨胀曲线,结合显微组织和显微硬度,绘制了试验钢的过冷奥氏体动态连续冷却转变曲线。结果表明：试验钢冷却速率为0. 05℃/s时,组织为粒状贝氏体和少量的无碳贝氏体;冷却速率在0. 1～0. 3℃/s之间时,组织主要为无碳贝氏体;冷却速率到达0. 5℃/s时,组织为无碳贝氏体和少量马氏体;冷却速率在1℃/s以上时,组织为马氏体。力学性能测试表明无碳贝氏体钢实现了高强度与高韧性的结合,改善了珠光体-铁素体钢强度不足的问题。

Under-cooled austenite dynamic continuous cooling transformation curves of a new kind of high strength carbon-free bainitic nonquenched and tempered steel were measured by using Gleeble-3800 thermal mechanical simulator coupling with optical microstructure observation and Vickers hardness measurement. The results show that when the cooling rate is 0. 05 ℃/s,the microstructure is granular bainite and a small amount of carbide-free bainite. When the cooling rate is in the range of 0. 1 ℃/s to 0. 3 ℃/s,carbide-free bainite is observed. When the cooling rate reaches 0. 5 ℃/s,the microstructure is carbide-free bainite and a little martensite. When cooling rate is up to 1 ℃/s,the microstructure is completely martensite. The mechanical property test shows that the strength and toughness of the carbide-free steel are higher than those of the pearlite-ferrite steel,and the problem of insufficient strength of the pearlite-ferrite steel is resolved.