400mm厚连铸坯轧制时缺陷的压合模拟

对某宽厚板厂最新投产的400mm连铸坯,以刚-粘塑性有限元模拟分析了其轧制Q345特厚钢板时的缺陷压合过程和临界压合条件。结果表明：在足够的压下率下,特厚板中心矩形裂纹能够被压合;缺陷尺寸、轧辊半径和坯料厚度对缺陷压合影响很大。缺陷尺寸和轧辊半径越大、坯料厚度越小,压合所需的临界压下率越小;在1120mm×4300m...     

首钢Q420qENH高性能耐候桥梁钢板的开发

针对传统桥梁钢板强度低,冲击韧性、焊接性能、耐蚀性能差的问题,首钢公司采用低碳成分设计、添加Ni、Cr、Cu耐候元素以及Mo、Nb元素,并优化了轧制和水冷工艺,开发出具有强韧性匹配和良好耐候性的Q420qENH耐候桥梁钢板。对Q420q ENH钢板的显微组织、力学性能进行了检测,同时采用周期浸润加速腐蚀试验对Q420qENH耐候桥梁钢板和Q420qE普通桥梁钢板的腐蚀失重和腐蚀速率进行了对比分析,研究了Q420qENH钢板的锈层形貌及成分。结果表明:Q420qENH耐候桥梁钢板组织为细小的M-A岛粒状贝氏体、准多边形铁素体和针状铁素体的混合组织,具有高强度、低屈强比和良好的低温韧性;其表面生成结构致密的α-FeOOH锈层,能够阻止钢板被进一步腐蚀,因此相同条件下其耐大气腐蚀性能是Q420qE普通桥梁钢板的2倍以上。     

Application of geometric midline yield criterion to analysis of three-dimensional forging

A kinematically admissible continuous velocity field was proposed for the analysis of three-dimensional forging. The linear yield criterion expressed by geometric midline of error triangle between Tresca and Twin shear stress yield loci on the π-plane, called GM yield criterion for short, was firstly applied to analysis of the velocity field for the forging. The analytical solution of the forging force with the effects of external zone and bulging parameter is obtained by strain rate inner product. Compression tests of pure lead are performed to compare the calculated results with the measured ones. The results show that the calculated total pressures are higher than the measured ones whilst the relative error is no more than 9.5%. It is implied that the velocity field is reasonable and the geometric midline yield criterion is available. The solution is still an upper-bound one.     

Application of Geometric Midline Yield Criterion for Strip Drawing

 In this paper, a new linear yield criterion expressed by the geometric midline of error triangle between Tresca and Twin shear stress yield loci on the π-plane in Haigh-Westergaard space is introduced. The criterion is written in terms of the principal values of stress deviator and called GM yield criterion for short. Together with a Cartesian coordinate velocity field different from Avitzur’s, the GM criterion is used to get a analytical solution for strip drawing .With working example of the strip drawing through wedge-shaped die, the calculated results of relative drawing stress by the GM criterion are compared with those by Mises criterion from Avitzur formula. It turns out that the calculated results according to analytical solution of present paper are in good agreement with the numerical solution by Avitzur formula     

Q345E厚板低温冲击韧性不合格的原因分析与改进措施

用金相显微镜、扫描电镜等对60—85mm规格的Q345E低温冲击韧性不合格厚板进行检验分析,结果表明,其主要原因是钢板终轧温度高、粗轧道次压下量小,且轧后多采用空冷造成钢板带状组织严重,晶粒尺寸较大。在生产中通过提高粗轧道次压下率、降低精轧温度及采用水冷等措施,改善了Q345E厚板的低温冲击韧性,显著提高了产品的合格率。     

Q345E厚板低温冲击性能不合原因分析与对策

针对首秦公司4300mm轧机生产60-85mm规格Q345E钢板低温冲击韧性不合问题，分析了其主要影响因素，指出钢板终轧温度高、粗轧道次压下量小，且轧后多采用空冷造成钢板带状组织严重，晶粒尺寸粗大是该问题的主要原因。在生产中通过增大粗轧道次压下率、降低精轧温度、采用水冷等措施，改善了Q345E厚板的低温冲击韧性，大大提高了产品的合格率。     

应变速率矢量内积解三维锻压

将三维锻压的等效应变速率表示成二维的应变速率矢量,然后利用积分中值定理确定应变速率比值函数及该矢量的方向余弦,再对其内积进行逐项积分。将逐项积分结果求和,并得出三维锻压力的计算公式与鼓形测量公式的解析解,经纯铅锻压试验将锻压力的计算结果与实测结果比较表明,由该解析解计算的结果高于实测结果,优化后的误差缩小到不大于11.2%,说明此解仍属于上界解。     

低温环境用厚壁大管径X80直缝埋弧焊管宽厚板的开发

根据中亚天然气管道工程C线压气站用直缝管线钢管的技术条件,采用合理的成分设计、严格的炼钢质量控制及控轧控冷工艺,成功开发出具有良好低温韧性的X80宽厚板。产品微观组织以细小均匀的贝氏体为主,复合第二相弥散均匀分布的M/A组元。钢板具有高强度、低屈强比、优良的低温韧性和止裂韧性,在制管焊接过程中表现出良好的焊接性能,经过合理的JCOE工艺制成的直缝埋弧焊管成功应用于中亚C线压气站管线工程。     

Q390低合金高强钢厚板热处理工艺

采用显微组织观察和力学性能测定,研究了不同热处理工艺对Q390低合金高强钢厚板组织和力学性能的影响.结果表明,经920℃×36 min正火,可使Q390低合金高强钢厚板热轧态中的混晶组织经完全奥氏体化后实现晶粒细化,在随后的冷却过程中转变为多边形铁素体和珠光体;获得良好的综合力学性能,伸长率和冲击韧性都比热轧态提高很多;并完全消除拉伸断口分层现象.     

特厚钢板轧制缺陷压合和双鼓形有限元分析

针对某厂采用400mm厚 Q345连铸坯生产120mm特厚钢板时铸坯中心缺陷压合及轧后钢板出现双鼓形缺陷的问题，以刚-粘塑性有限元软件模拟了缺陷压合条件和双鼓形形成过程。结果表明，400mm厚铸坯不能在开轧后1~3道次内压合缺陷，但随压合参数l/的增大和应变累积作用，中心裂纹被压合；第1道次压合400mm厚铸坯中心矩形裂纹的临界压下率为158%，转化为几何参数l/=0511；400mm厚铸坯在轧制的各个阶段均存在双鼓形缺陷，双鼓形最大峰值的临界变形条件为l/=0542，增大轧辊尺寸、减少横轧道次可减轻双鼓形缺陷。