碳钢热轧中厚板一次氧化铁皮形成机制-剥离性能和工艺改善

Formation Mechanism-Removability of Primary Scales of Carbon Steel Hot-Rolled Heavy-Medium Plate and Process Improvement

Q235B钢(/%:0.18C,0.20Si,0.34Mn,0.015P,0.005S,0.07Cr)230 mm铸坯轧成的30 mm板上出现(10~40)mm×(3~10)mm深1~3 mm氧化皮压入缺陷。分析了一次氧化铁皮缺陷形成机制与高压水除鳞作业中高温剥离性,并提出工艺优化措施:(1)通过优化加热工艺,使高压水除鳞时铸坯表面温度应保证在1170℃以上;(2)优化后高压水系统喷水压力由18 MPa提高至20 MPa,流速由161.2 m/s提高至170.0 m/s,使打击力由116.3 N提高至122.7 N。26炉次的试验及生产实践结果表明,工艺优化后氧化铁皮压入导致的封锁率控制在2%以下,显著改善了氧化铁皮压入缺陷。

The depressed defects of scales with dimension （ 10 ~ 40） mm× （ 3 ~ 10） mm and depth 1 - 3 mm occur at 30 mm plate hot-rolled from 230 mm casting slab of steel Q235B （/%： 0. 18C, 0.20Si, 0.34Mn, 0.015P, 0. 005S, 0. 07Cr）. The primary scale formation mechanism and removability at high temperature in high-pressure water descaling op- eration are analyzed and the measures to optimize the process are forward including （ 1 ） with optimizing heating process to insure the casting slab surface temperature being more than 1 170 ℃ for high-pressure water descaling; （2） with optimized high-pressure water parameters i.e. increasing spray-water pressure from 18 MPa to 20 MPa and flow velocity from 161.2 m/s to 170. 0 m/s, in order to increasing the impact force from 116. 3 N to 122. 7 N. The test and commercial production results by 26 heats show that after process optimization the closing off rate of slab caused by rolled-in scales reduces to less than 2%. it is obvious to imorove the rolled-in scales defects.