为了适应LNG燃料罐、储罐使用需要,对9Ni钢进行冶炼、轧制关键工艺控制,研究两相区热处理工艺及Nb微合金化对组织性能的影响.结果表明,随着亚温淬火温度的升高,屈服强度、抗拉强度、屈强比先降低后升高.随着回火温度的升高,屈服强度与抗拉强度逐渐降低,伸长率升高;当回火温度为600℃时,屈服强度与抗拉强度达到最低值,伸长率达到最高值.亚温淬火态组织呈现大、小晶粒并存状态,有助于降低钢板屈强比.Nb微合金化9Ni钢板成品组织主要为回火索氏体组织及3%～8%残余奥氏体.0.015%Nb的加入使9Ni钢平均屈服强度提高约50 MPa,抗拉强度提高约40 MPa,-196℃横向夏比V型冲击吸收能提高约40 J.
Effect of Heat-treatment Process and Nb Microalloying on Microstructure and Properties of 9Ni Steel
To meet the use needs of LNG fuel tanks and storage tanks,the key process control of steel-making and rolling of 9Ni steel were carried,and the influence of two-phase area heat-treatment processes and Nb microalloying on micro-structure and properties of 9Ni steel was studied.The results show that with the increase of intercritical quenching(IQ)temperature,the Yield stress(YS),tensile strength(TS)and the ratio between YS and TS(Y/T)decreases firstly,then increases.Subsequently as the tempering temperature increases,the YS and TS gradually decrease,while the elongation increases;When the tempering temperature is 600℃,the YS and TS reach their lowest values,and the elongation(EL)reaches its peak.The microstructure after intercritical quenching presents distribution of large and small grains,which contributes to the reduction of Y/T ratio of steel plate.The microstructure of Nb micro-alloyed 9Ni steel plate is mainly composed of tempered sorbite structure and 3%-8%reverse austenite.The addition of 0.015%Nb increases the average YS and TS of 9Ni steel by about 50 MPa and 40 MPa,respectively.The impact absorption energy increases by about 40 J tested at-196℃.
万方数据
维普
