【作者】 郭诚；

【导师】 任海鹏；

【作者基本信息】 东北大学 ， 材料学， 2009， 硕士

【摘要】 盘条也叫线材,主要供作拉丝的坯料,也可直接用作建筑材料和加工成机械零件。盘条的内在质量是保证盘条全长组织性能一致性的关键,盘条对表面质量、氧化铁皮的成分及厚度、脱碳层深度等,均有严格的要求。近年来紧固件工业的发展对高性能热轧盘条的需求日益迫切,而国产盘条存在诸如各种缺陷如耳子、折叠、裂纹、分层、混晶等一些问题,因此分析混晶产生原因对提高热轧盘条的综合性能有重要意义。本文以国内某钢铁企业生产的20钢和1OB21钢热轧盘条为研究对象,通过检验不同热处理后的奥氏体晶粒度,采用Gleeble一2000热模拟试验机研究两种钢不同条件下的热变形行为,确定其混晶程度及发生较严重混晶时的变形条件。所得主要结果如下：1.1OB21钢单道次变形时的混晶程度随着冷却速度的变大而增大,多道次变形时混晶程度随着冷却速度的变大而趋缓；20钢的混晶程度随着冷却速度的增大而减小。两种钢的晶粒尺寸都随着变形温度的升高而增大,在相同条件下(变形温度、变形量、冷却速度),1OB21钢平均晶粒大小明显小于20钢。2.多道次累积变形时,道次变形量只有在15%以上时才可得到细小均匀的等轴晶,而小于此变形量时都将会得到混晶组织。10821钢道次变形量为10%和12%变形后冷速较慢会加剧混晶现象发生。20钢除道次变形量8%外,其余变形量的多道次变形后加快冷速(4℃/s)有利于减轻混晶现象的发生3.单道次变形时,变形量对于20钢变形后的奥氏体晶粒形貌有显著的影响,而变形温度的影响较小。在70%的大变形量变形时,变形后的奥氏体晶粒除1050℃出现混晶外,其余各温度变形后都为较均匀的等轴晶,其平均晶粒度约为5级。变形温度为950℃和1000℃时,变形量为30%时混晶现象最严重。4.10B21钢单道次变形时,变形量为10%和70%时,在各变形温度变形后都可获得较均匀的细小晶粒,其它变形量变形后会出现混晶,变形量增加出现混晶的温度向高温推进。在850℃和1050℃温度下变形时,无论变形量大小,均能获得均匀细小的晶粒度。降低形变后的冷速有利于1OB21钢混晶的减轻或消除。更多还原

【Abstract】 Also known as wire rod,drawing mainly for the billets, but also can be directly used as building materials and processed into machine parts.The intrinsic quality of rod is to ensure consistency in the performance of the key organizations.On the surface quality of wire rod,iron oxide composition and thickness of skin,the depth of decarburization layer and so on,have strict requirements.In recent years the development increasingly demand of industrial fasteners for high-performance hot-rolled rod. And the domestic wire rod exist a variety of defects such as the handle, folding, cracking, delamination, mixed grain and so on. Therefore the cause of mixed grain is signifigant to improve the performance of hot-rolled coil.In this paper, the specimen is from domestic iron and steel enterprise where produced 20 and 10B21 hot-rolled wire rod. By the examination of the austenite grain size with different heat treatment, use Gleeble-2000 thermal simulation machine to test two steel under different hot conditions. Make sure the extent of mixed grain and conditions when mixed grain occurred more serious. The main results obtained are as follows:1 10B21 steel,the degree of mixed grain size increases with the cooling rate raises when single-pass deform and increase slowly when multi-pass deform.20 steel,the degree of mixed grain size decreases with the cooling rate raises. The grain size of two types steel enhance when deformation temperature increase. Under the same conditions (deformation temperature,deformation,cooling rate), the average grain size of 10B21 steel is smaller than 20 steel.2 Multi-pass accumulation of deformation, small homogeneous grains only can be got when pass deformation at more than 15%,and mixed structure will be got when the deformation is less than the amount.10B21 steel pass deformation of 10% and 12% will increase mixed grain size when slower cooling rate after deformation. In addition to deformation 8% of 20 steel, The remaining deformation when speed up the cooling rate (4℃/s) will help reduce the occurrence of the phenomenon of mixed grain size after the multi-pass deformation.3 Single-pass deformation, the amount of deformation have significant effects on the 20 steel and little with deformation temperature. When 70% of the amount deformation, Deformed austenite grain of the remaining deformation are uniform in addition to 1050℃, and the average grain size is about 5. The deformation amount of 30% for the mixed grain size is the most serious with the temperature of 950℃and 1000℃.4 10B21 steel, single-pass deformation, the deformation of 10% and 70%, the small grain is got at every deformation temperature,other deformation will be mixed. Deformation appears to increase the temperature of mixed grain to high temperature to promote. At 850℃and 1050℃temperature deformation, no matter the size of deformation, have access to a small uniform grain size. Reduce the cooling rate after deformation in favor of mixed grain size of 10B21 steel to eliminate.更多还原