Surface Roughness Of Steel Sheet Research Articles

漏洩磁束法による鋼板凹凸表面欠陥の検出法の開発

Concave and convex defects on steel sheets cause problems in the steel production line. These defects are usually invisible since their height or depth is as small as the normal surface roughness of steel sheets. Therefore, they can only be detected by human inspection after grinding the steel surface with a grindstone.We found that Magnetic Flux Leakage Testing (MFLT) is effective for detecting these kinds of defects. The MFLT method can detect not only magnetic flux caused by the shape of defects, but also that caused by the strain of defects. This paper describes the results of experiments to verify the principle of the detection method and in-line experiments. As a result of the in-line experiments, it was found that some defects cause MFLT signals which are too small to detect automatically. To solve this problem, we proposed a new periodical method to improve detectability. Based on these results, we developed an in-line concave and convex defect inspection technique.

鋼板表面凹凸欠陥の低角入射条件における光学的特性と欠陥検査への応用

Concave and convex defects on steel sheets sometimes become problem in steel production line. These defects are usually invisible because their height or depth is as small as surface roughness of steel sheets. Therefore they could be detected by human inspection only after grinding steel surface using grindstone. This paper describes optical characteristics of such kinds of defects on steel sheets with certain roughness, especially on low-angle light incident condition, and proposes optical inspection system utilized “Magic mirror” phenomenon with low angle laser incidence to detect these defects without grinding. The on-line inspection system has been built and proved to have the capability to detect such kinds of invisible defects.

대기압 Ar/O2플라즈마 표면처리된 자동차용 냉연강판의 표면특성 및 접착특성평가

Cold rolled steel sheet for automotive was treated by Ar/ atmospheric pressure plasma to improve the adhesive bonding strength. Through the contact angle test and calculation of surface free energy for cold rolled steel sheet, the changes of surface properties were investigated before and after plasma treatment. The contact angle was decreased and surface free energy was increased after plasma treatment. And the change of surface roughness and morphology were observed by AFM(Atomic Force Microscope). The surface roughness of steel sheet was slightly changed. Based on Taguchi method, single lap shear test was performed to investigate the effect of experimental parameter such as plasma power, treatment time and flow rate of gas. Results shows that the bonding strength of steel sheet treated in Ar/ atmospheric pressure plasma was improved about 20% compared with untreated sheet.

Discussion on Formation Mechanism of Surface Roughness of Cold Rolled Steel Sheets.

In order to clarify the formation mechanism of surface roughness of steel sheets in cold rolling, the cold rolling experiments are made using carbon steel (SPCC) and stainless steel (SUS430) sheets with various surface roughness at the entry of rolling, and in neat lubrication of two mineral oils with different viscosities. Also, the shifting coefficient of weighted average roughness, which is called m-value, in a surface roughness equation is calculated by applying the rolling experiment data to the surface roughness equation proposed in this paper. Then, the formation mechanism of surface roughness of cold rolled steel sheets is discussed. As a result, it has been found that the m-value is larger than 1 and increases with increase of the initial equivalent surface roughness.

Variation of phosphatability with chemical composition and surface roughness of steel sheet

The purpose of the present study is to investigate the effect of specific steel alloying elements, such as Cr, Ni, and Cu, and surface roughness of substrate on phosphatability of cold rolled sheet steel for drums. Phosphatability depends upon surface characteristics and can be estimated by using the electrochemical method and measuring the τ value, which is the time of exposure to the substrate Fe. In order to obtain good phosphatability, low contents of retained elements are desirable, although phosphatability can be improved indirectly by increasing the surface roughness of the steel sheet. Phosphatability of cold rolled steel sheet is also related to the treatment conditions in the phosphating bath. Increasing both the temperature and acceleration of the phosphating solution is desirable in order to obtain good quality.