The coiling temperature and cooling rate have a significant impact on the structure and pulverization performance of scale in the production of 700 MPa beam steel.However,adjusting the coiling temperature on a large scale can affect the micro-structure refinement and Ti element precipitation of 700 MPa beam steel,which can easily cause fluctuations in the mechanical and stamping properties of the product,and the control methods for the cooling rate after coiling are relatively limited.There-fore,from the perspective of adding alloying elements,this article studies the improvement effect of adding trace amounts Cr ele-ment on the thickness and pulverization performance of scale on the surface of 700 MPa beam steel(700L steel)while ensuring the mechanical properties of 700 MPa beam steel.The effects of adding 0.2％Cr element on the oxidation characteristics,scale growth pattern and pulverization performance of 700L steel were systematically studied using differential thermal analysis,scan-ning electron microscopy,and cold bending tests.The results showed that after adding 0.2％Cr element,the oxidation resist-ance of 700L steel increased below 1 050 ℃.At 1 000 ℃,the weight decreased percent of 700L steel during isothermal oxidation can reach 26％,and an element enrichment layer with a thickness of nearly 6 μm is formed at the interface of the scale.Industrial production tests have shown that under the same hot rolling process conditions,the surface scale thickness of 700L hot-rolled plate decreases from 10-15 μm to 6-8 μm after adding 0.2％Cr element.The proportion of scale pulverization and peeling has decreased from 40％to about 7％.
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