600 MPa级热轧双相钢组织与性能优化分析

 通过热轧厂实际生产试制，研究了钛、铌微合金元素对600 MPa级低成本低温卷取型铁素体/马氏体双相钢组织和性能的影响，并与同强度级别中温卷取双相钢进行对比。研究结果表明，沿晶界分布的纳米级（Nb，Ti）C第二相显著细化了铁素体/马氏体两相组织，由此解决了不含钛、铌元素的低温卷取双相钢马氏体岛粗大的问题，提高其强度和塑性。此外，试制生产对比发现，中温卷取双相钢存在晶粒尺寸较粗，马氏体体积分数较少，强度相对略低等特征，并提出了相应的热轧工艺改进思路。

Microstructure and properties optimization of hot rolled 600 MPa dual phase steel

The effects of Ti and Nb micro-alloying elements on the microstructure and properties of low-cost 600 MPa grade ferrite-martensite dual phase steel coiled at low temperature were studied by hot rolling trial-production and compared with the dual phase steel coiled at medium temperature.The results showed that the inter-phase precipitation of nanometer (No,Ti)C phase mainly distributed along the grain boundaries,synchronously refined the grain size of ferrite and martensite phases,as well as improved the comprehensive strength and plastic properties of the dual phase steel.Thus,it solved the problem of coarse martensite phase formation that existed in the dual phase steel without the addition of Ti and Nb elements.In addition,the modification of the hot rolling process for dual phase steel coiled at medium temperature was proposed under the consideration of its unfavorable characteristics,such as coarse grain size,less martensite content and slightly low strength property.