Yohei Yamada 1, Shohei Nakakubo 1 and Mikako Takeda 1
1 Materials Reserch Laboratory, KOBE STEEL, LTD
In the hot rolling process, the external appearance of steel can deteriorate due to spalling of oxide scales. We used a tensile test in order to evaluate and quantify the adhesion of the scales in the hot rolling process. When loaded with tensile stress, the behavior of the scales goes through the following three stages:
①The scales have only residual stress
②The scales and the steel are both elastically deformed
③The scales are elastically deformed but the steel is plastically deformed.
For these three stages, the strain energy accumulated in the scales before spalling was calculated and then the adhesion energy was derived. For about 4 μm thick scales on 99.9% Fe and Fe-1.0%C the adhesion energies were 1.70 J/m2 and 36.2 J/m2, respectively. The adhesion energies determined by a scratch test were 2.90 J/m2, and 31.6 J/m2 each. Thus, the results of the two tests are approximately in agreement.
iron oxide scale, adhesion energy, tensile test, scratch test
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