【摘要】 以E550级超高强度船板钢为研究对象,采用SEM,TEM分析和力学性能测试等手段,研究了亚温淬火时宽回火温度范围内微观组织和力学性能的演变规律.研究结果表明,试验钢在820℃淬火后由板条马氏体和18.8%体积分数的准多边形铁素体组成.随回火温度升高,马氏体板条逐渐分解转变为回火屈氏体和回火索氏体,其中Fe₃C由薄片状转变为球状,并不断粗化;铁素体板条的位错密度下降,最终再结晶成为等轴晶粒.上述变化导致材料强度下降,伸长率和低温韧性提高.试验钢经820℃淬火和440⁶00℃的宽温度范围回火后具有优异的强韧性,力学性能与调质处理（930℃淬火和600⁶70℃回火）的试验钢相当,可显著节省热处理工艺成本.更多还原

【Abstract】 A 550 MPa strength grade ship plate steel was studied. The effects of intercritical quenching and tempering process on the microstructure and properties of the steel were studied by scanning electron microscope（ SEM） and transmission electron microscope（ TEM） analysis and mechanical tests. Experimental results show that the steel consists of lath martensite and 18. 8% volume fraction of quasi-polygonal ferrite after intercritical quenching at 820 ℃. With the increase of tempering temperature,the lath martensite is decomposed to troostite and sorbite gradually,within which the precipitated Fe₃ C changes from flake to spherical form and coarsens constantly,and the dislocation density in lath ferrite decreases continuously and equiaxed ferrite finally appears due to recrystallization.The above evolutions of the microstructure lead to the decrease in strength and increase in ductility and toughness. The steel quenched at 820 ℃ and then tempered at 440-600 ℃possesses excellent properties equivalent to those of the steel quenched at 930 ℃ and tempered at 600-670 ℃. The process in the present study thus gives a feasible way to remarkably reduce the cost of heat treatment.更多还原