28CrMnMoV钢过冷奥氏体连续冷却转变  

Continuous cooling transformation of undercooling austenite about 28CrMnMoV steel

作　　者：李红英[1,2] 李阳华[1,3] 王晓峰[1] 赵延阔[1] 谢凯意[3] 苏阳[3] 

机构地区：[1]中南大学材料科学与工程学院,湖南长沙410083 [2]中南大学有色金属材料科学与工程教育部重点实验室,湖南长沙410083 [3]衡阳华菱钢管有限公司技术中心,湖南衡阳421001

出　　处：《中南大学学报（自然科学版）》2013年第7期2702-2711,共10页Journal of Central South University:Science and Technology

基　　金：湖南省重大科技专项(2008FJ1003)

摘　　要：利用Gleeble-3500热模拟机测量28CrMnMoV钢以不同速度连续冷却时的膨胀曲线,结合差热分析法和金相硬度法,确定临界点及相变温度点,绘制并分析和应用过冷奥氏体的连续冷却曲线（CCT图）,研究实验钢连续冷却时的奥氏体转变。研究结果表明：实验钢过冷奥氏体在高温区可能发生铁素体转变和珠光体转变,中温区可能发生贝氏体转变,低温区可能发生马氏体转变;当冷却速度为0.05~0.5℃/s时,转变产物为多边形铁素体、珠光体和少量贝氏体的混合组织;在1~5℃/s的冷却速度范围内,转变产物为贝氏体;当冷却速度大于5℃/s时,转变产物为马氏体;合金元素Cr,Mo,V有抑制奥氏体扩散分解的作用,以低于1℃/s的速度冷却才会有先共析铁素体和珠光体;锰质量分数较高对贝氏体转变有明显的促进作用,在0.05~10℃/s的较宽速度范围内连续冷却会发生贝氏体转变。根据测得的CCT图指导28CrMnMoV钢的分级控冷工艺,可在减小钢管淬火应力的同时,为V150油套管的高强韧性提供组织保障。The dilatometric curves of 28CrMnMoV steel during continuous cooling process at different cooling rates were measured on Gleeble 3500 thermal mechanical simulator.According to DSC analysis and microstructure observation combined with hardness test,the critical temperatures and phase transformation temperatures were determined from the dilatometric curves,which were used to determine the continuous cooling transformation（CCT） diagram of 28CrMnMoV steel.The results show that ferrite（or pearlite） can be formed in supercooled austenite of tested steel during higher temperature interval,and bainite transformation and martensite transformation can occur during intermedium temperature and low temperature zones respectively.The transformation product consists of polygonal ferrite,pearlite and a small amount of bainite at the cooling rates of 0.05 0.5 ℃/s.When the cooling rate is ranging from 1 to 5 ℃/s,the product is mainly composed of bainite.When the cooling rate is higher than 5 ℃/s,martensite is the main transformation product.Because the alloy elements of Cr,Mo and V can inhibit the decomposition of austenite,pro-eutectoid ferrite and pearlite can be formed only at the condition of cooling rate below 1 ℃/s.Higher manganese content can greatly accelerate the bainite transformation,and therefore bainite can be easily formed during the continuous cooling process for a large range of cooling rate.It is an effective way of decreasing the quenching stress of steel tubes to use the obtained CCT diagram to guide the multiple controlled cooling process,which indicates that the CCT diagram can provide guarantee for excellent touthness of V150 tubing and casing.

关 键 词：28CrMnMoV钢 连续冷却 CCT图 相变 奥氏体 

分 类 号：TG151.2[金属学及工艺—热处理] TG151.3[金属学及工艺—金属学]