超快冷工艺对厚规格X80管线钢组织性能的影响

Effect of ultra fast cooling process on microstructure and mechanical properties of X80 pipeline steel

采用低Mo成分体系,研究超快冷工艺对厚规格X80微观组织和力学性能的影响规律。试验结果表明:随冷速的提高,屈服强度、抗拉强度均呈上升趋势,但屈服强度上升更明显,导致超快冷工艺下屈强比大幅提高;但由于冷速的提高导致晶粒细化析出物长大受到抑制,试验钢韧性不降反升,冲击和DWTT性能均有所提高。随冷速的增加,钢板沿厚度方向的冷速差异增大更明显,贝氏体板条的过度细化导致试验钢表层与心部硬度差异增大,表层硬度超标,冷成型开裂风险增大。

The effect of ultra fast cooling process on microstructure and mechanical properties of thick X80 was studied by using low level of Mo component system. Experimental results showed that with the increase of cooling rate,yield strength and tensile strength showed an upward trend,but the yield strength increased more significantly,resulting yield ratio improved greatly under ultra fast cooling process. Because of the increase of cooling rate,the grain size was refined,the precipitate size was restrained,The toughness of trail steel did not decrease,impact and DWTT properties were improved. With the increase of cooling rate,difference between cooling rate along the direction of the plate thickness increased more significantly,the bainite transition refinement leaded to hardness difference increase between the steel surface and core,resulting in excessive surface hardness,the risk of cracking increase during cold forming.