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对γ+α两相区淬火后的试验钢板进行300～600℃的回火处理,研究了回火温度对F500级海洋平台用钢组织及性能的影响。结果表明,400℃×1 h回火试样拉伸过程中出现屈服平台,并且回火温度越高不连续屈服现象越明显;回火中,马氏体板条束合并长大,部分位错发生静态回复,密度降低,多边形铁素体含量增加,基体上有大量20～40 nm富Nb的(Nb,Ti)C析出;500～550℃回火可以获得优良的强韧性能,达到F500级别海洋平台钢的要求。
The quenched test steel plate of γ + α two-phase zone was tempered at 300-600 ℃. The effect of tempering temperature on microstructure and properties of F500 grade offshore platform steel was studied. The results show that the yielding platform appears during the tempering process of 400 ℃ × 1 h tempering specimen, and the more the tempering temperature is, the more obvious the discontinuous yielding phenomenon. In the tempering, the martensite laths coalesce and grow up, The static recovery occurs, the density decreases and the content of polygonal ferrite increases, and a large amount of (Nb, Ti) C rich in Nb is precipitated on the substrate. The tempering at 500-550 ℃ can obtain the excellent toughness, reaching F500 level Marine platform steel requirements.