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通过I&Q&P(两相区退火+淬火+配分)热处理工艺,采用SEM和XRD等手段,研究了奥氏体化保温温度对低碳钢组织与性能的影响。结果表明:当奥氏体化温度AT升高到950℃时,双相区中产生的铁素体完全转变为奥氏体,得到的室温组织为马氏体;随着奥氏体化温度的升高,马氏体板条变粗大,板间距离变大,晶粒变大。当AT=930℃时,室温组织含有铁素体,Mn元素未能完全聚集到奥氏体晶粒中,此时伸长率最大(25.45%),抗拉强度最小(1084MPa),残余奥氏体量最小(7.02%)。当AT=950℃时,实现了完全奥氏体化,Mn元素富集程度最高,伸长率降低,抗拉强度和残余奥氏体量最大值分别是1267 MPa、9.83%。当AT=970℃,奥氏体中的Mn元素扩散均匀化,马氏体晶粒变大,板条间距变宽,伸长率达到最小值(23.2%),抗拉强度降低,残余奥氏体量降低8.87%。
The effects of austenitizing heat preservation temperature on microstructure and properties of mild steel were studied by means of I & Q & P (two-phase annealing + quenching + blending) heat treatment with SEM and XRD. The results show that when the austenitizing temperature (AT) increases to 950 ℃, the ferrite produced in the two-phase zone completely changes to austenite and the obtained martensite at room temperature. With the increase of austenitizing temperature Rise, martensite slab becomes coarse, the distance between the plates becomes larger, the grain becomes larger. When AT = 930 ℃, the microstructure at room temperature contains ferrite. The Mn element fails to fully aggregate into the austenite grains. At this time, the elongation is the highest (25.45%), the lowest is the tensile strength (1084 MPa) The smallest body (7.02%). When AT = 950 ℃, the complete austenitization was achieved, and the maximum enrichment of Mn was observed. The elongation decreased, and the maximum tensile strength and retained austenite were 1267 MPa and 9.83% respectively. When AT = 970 ℃, the elemental Mn in austenite dispersed homogeneously, the martensite grains became larger, the spacing of slats widened, the elongation reached the minimum (23.2%), the tensile strength decreased, and the residual austenite Body mass decreased by 8.87%.