S355J2钢板坯角部横裂纹成因及控制  

Cause Analysis and Control Measures of Corner Transverse Cracks in S355J2 Steel Slab

作　　者：赵文博[1,2] 王明林[2] 张慧[2] 袁守谦[1] 

机构地区：[1]西安建筑科技大学冶金工程学院,陕西西安710055 [2]钢铁研究总院连铸技术国家工程研究中心,北京100081

出　　处：《上海金属》2017年第3期62-67,共6页Shanghai Metals

摘　　要：针对S355J2钢连铸坯角部横裂纹,现场取样,利用扫描电镜、能谱仪等检测手段分别从裂纹形貌、夹杂物的组成及分布等方面进行分析;同时采用辐射温度计对连铸坯矫直段角部温度进行现场测量。结果表明,裂纹主要分为非封闭的主裂纹和许多细小的封闭裂纹,主裂纹内含有Al、Ca、Mg等氧化物夹杂,且裂纹已经被氧化;细小的封闭裂纹中有保护渣成分,说明钢液在凝固过程有保护渣卷入。夹杂物聚集导致连铸坯在矫直阶段因内弧受到拉应力作用而产生应力集中,成为横裂纹出现的内因。铸坯矫直段角部及其附近温度为850℃左右,处于第三脆性区,成为横裂纹产生的主要原因。优化保护渣制度和炼钢工艺可避免卷渣行为的发生;采用倒角结晶器可使角部温度避开第三脆性区。Aming at the transverse cracks fonned in S355J2 steel slab corner, through fiehl sampling, the crack morphology, eomposition and distribution of inclusions were analyzed using scanning electron microscopy and energy spectrum analyzer. The comer temperature at flattener part of continuously cast slab was measured using a radiation thermometer. The results showed that the cracks were divided into the unenclosed main cracks and many tiny closed cracks. The main cracks contained the oxide inclusions of AI, Ca and Mg, and cracks have been oxidized, and the tiny closed cracks contained protecting slag composition, which indicated that the protecting slag had involved in the liquid steel. The inclusions gathered leading to the stress concentration oeeured when the inner arc, was suhjected to tensile stress in the straightening stage, which become the internal reason of transverse craeks appearing. The corner temperature of the slab straightening section and the region near it was about 850℃, and was in the third brittle zone, which become the main reason of transverse craeks appearing. By optimizing the protecting slag and steelmaking process, the slag entrapment can be avoided, and using the chamfer mold can make the temperature of slab comer to avoid the third brittle zone.

关 键 词：S355J2钢 角部横裂纹 夹杂物 角部温度 

分 类 号：TF777.3[冶金工程—钢铁冶金]