back roll是什么意思

用法例句

Introduced heat treatment method of the replace material 3Cr2W8V steel using in compress roller of tube welding machine,and brief analyzed the test result.

介绍了焊管机压缩轧辊所用替换材料3Cr2W8V钢的热处理,并对试验结果做了简要工艺分析。