淬火温度对X80管线钢组织影响分析

Effect of quenching temperature on X80 pipeline steel

采用双相区加速冷却法(DPAC),X80管线钢经奥氏体化及缓冷后分别在760、740、720、700、680℃淬火。淬火组织分别经4%硝酸酒精与LePera试剂进行金相腐蚀,分别进行组织定性/定量分析及整体/组织硬度测试。结果表明,不同淬火温度下组织为多边形铁素体+针状铁素体+贝氏体/马氏体复相组织。与硝酸酒精腐蚀的微观结构相比,LePera试剂可清晰显示马氏体/奥氏体组织,但铁素体晶界模糊。随淬火温度下降,铁素体晶粒尺寸与含量增加;针状铁素体逐渐向贝氏体/马氏体复相组织转化;马氏体/奥氏体岛状组织分布上由铁素体/贝氏体两相晶界间向铁素体同相晶界间转变,组织形态上由薄膜状向颗粒状转变。

Dual Phase Accelerated Cooling(DPAC) was adopted to X80 pipeline steel which were quenched at 760,740, 720, 700 and 680 ℃ respectively after austenitization and slow cooling. Quantitative/qualitative analysis and overall/microstructure hardness test were used to characterize the quenching microstructures which were etched by 4% nital and LePera reagent respectively. The results show that microstructure of X80 steel is polygonal ferrite(PF)+acicular ferrite(AF)+ bainite/martensite complex phase(B/M) after being quenched. Compared with microstructure etched by nital, martensite/austenite island(M/A) can be shown clearly by LePera reagent, yet ferrite grain boundary is blurred. While the quenching temperature decreases, grain size and content of ferrite phase are increased;AF is gradually transformed into B/M complex phase;M/A which exist in ferrite/bainite phase grain boundary is transformed into ferrite in-phase grain boundaries, and morphology is changed from thin-film to granular.