免退火小规格SCM435盘条控轧控冷工艺优化  

Optimization of controlled rolling and controlled cooling process of non-annealed small gauge SCM435 wire rod

作　　者：甄先锋 朱帅 王广顺 陈猛 曹长法 李向春 ZHEN Xianfeng;ZHU Shuai;WANG Guangshun;CHEN Meng;CAO Changfa;LI Xiangchun(Qinggang Branch Research Institute,Qingdao Special Iron and Steel Co.,Ltd.,Qingdao 266043,China)

机构地区：[1]青岛特殊钢铁有限公司青钢分院,山东青岛266043

出　　处：《轧钢》2023年第5期76-79,113,共5页Steel Rolling

摘　　要：采用免退火控轧控冷工艺生产φ5~φ7 mm小规格SCM435盘条产品时,因盘条同圈组织性能差异较大导致其在首道次拉拔、自然存放和热处理阶段发生波浪弯曲,且盘条表层易出现先共析铁素体组织造成其截面硬度不均。为此,通过对比分析常规轧制、控轧控冷以及优化的控轧控冷工艺生产的SCM435盘条的组织性能,研究了盘条同圈组织性能差异的原因和产生机理。结果表明:低温轧制表面畸变能会促进先共析铁素体形成,小规格盘条因在风冷辊道排布致密,搭接区和辊道中部盘条冷速差异大于大规格盘条,导致性能波动较大,同时在搭接位置冷速较慢,先共析铁素体长大形成了深度10~45μm类似全脱碳的组织。通过工艺优化,将吐丝温度从780℃提高至810℃,同时调整辊道速度(0.15 m/s提高至0.20 m/s)和保温罩开启数量,采用空冷后入保温罩缓冷的分段控制冷却工艺,基本消除了盘条表层连续的先共析铁素体组织,其同圈抗拉强度和断面收缩率波动分别比原工艺降低16%和27%,组织和力学性能均匀性得到明显改善。Waviness occurring during the first drawing,natural storage and heat treatment due to the difference in microstructure and properties of the same circle,and uneven cross-section hardness resulting by surface proeutectoid ferrite microstructure were observed in non-annealedφ5-φ7 mm small gauge SCM435 wire rod produced by controlled rolling and controlled cooling process.Therefore,by comparing the microstructure and properties of SCM435 wire rods produced by conventional rolling controlled rolling and controlled cooling and optimized controlled rolling and controlled cooling process,the reason and mechanism of the difference in microstructure and properties of the same circle of the wire rod were studied.The results show that surface deformation energy can promote the formation of proeutectoid ferrite.Due to its dense arrangement on the air-cooled roller table,the difference in cooling speed between the lap zone and the middle of the roller table is greater for small guage wire rods than for large gauge wire rods,resulting in significant property fluctuations.And proeutectoid ferrite with depth of 10-45μm similar to fully decarburized microstructure was formed at the lap zone because of slow cooling speed.By increasing laying temperature from 780℃to 810℃,adjusting the roller table speed(0.15 m/s to 0.20 m/s)and the amount of opening cover,thereby to achieve segmented controlled cooling process of air cooling and slow cooling under the cover,the continuous proeutectoid ferrite on the SCM435 wire rod surface was eliminated.The fluctuation of tensile strength and area reduction of the same circle of the wire rod were reduced by 16%and 27%respectively compared with the original process,and the uniformity of the microstructure and mechanical properties of the wire rod was significantly improved.

关 键 词：免退火 SCM435盘条 控轧控冷 形变诱导铁素体相变 先共析铁素体 同圈组织性能 

分 类 号：TG335[金属学及工艺—金属压力加工]