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通过成分设计、相变规律研究、工业规模试制,分别获得了(PF+B)双相组织及AF组织的管线钢钢板。二者的试验研究结果表明,当弛豫终止温度低于相变开始温度后,组织中将出现多边形铁素体(PF)。弛豫终止后以20℃/s左右的冷速加速冷却时,未转变的奥氏体转变为由粒状铁素体(GF)及贝氏体铁素体(BF)组成的贝氏体B组织。相比于AF组织管线钢,(PF+B)组织管线钢具有较低的屈强比及较高的伸长率。试验获得的(PF+B)组织管线钢的轧板厚度达30.8mm,强度级别达到X70级,拥有较低的屈强比和较高的伸长率,满足海底管线对抗变形性能的要求。
Through the study of composition design, phase change law and industrial scale trial production, (PF + B) dual-phase and AF-organized pipeline steel sheets were respectively obtained. The experimental results show that polygonal ferrite (PF) will appear in the microstructure when the relaxation relaxation temperature is lower than the onset temperature of transformation. When relaxation is accelerated at a cooling rate of about 20 ° C / s after relaxation, the untransformed austenite is transformed into bainite B microstructure composed of granular ferrite (GF) and bainitic ferrite (BF) . Compared with AF tissue pipeline steel, (PF + B) tissue pipeline steel has a lower yield ratio and higher elongation. The thickness of rolled (PF + B) structured pipeline steel reached 30.8mm and its strength level reached X70. It has lower yield ratio and higher elongation to meet the requirements of submarine pipeline against deformation.