SAE1038線材機械除銹表面品質評估

The Evaluation on Surface Properties of Mechanically Descaled SAE1038 Wires

本研究為建立一機械除銹製程之除銹效率評估技術，並探討機械除銹後線材表面品質變化對後續加工之影響，其次為建立中鋼供應下游線材之銹皮基本結構與特性，作為生產上之重要參考數據。研究結果顯示目標鋼種SAE1038樣品銹皮厚度在5 ~ 27μm的範圍，經多次除銹試驗評估發現，以粗糙度平均值與標準差數值分析方式，可作為線材經機械除銹與電解除渣後，除銹試驗後表面粗細和均勻程度的指標。整體而言，機械除銹後Ra值範圍約在1.1 ~ 1.8μm之間，標準差為0.4 ~ 0.9μm，而原始底材粗糙度較大者，機械除銹後的粗糙度值也有較大的趨勢。本研究也採用酸溶法得到機械除銹率約為80%，電解除渣的除銹效果則可達98%以上。進一步以SEM進行機械除銹後橫截面觀察，發現除銹層下方底材有晶粒組織變形現象，顯示有殘留銹皮被外在機械力軋入底材，而電解除渣後軋入殘留銹層現象卻不易被發現，顯示出經機械除銹軋入的殘留銹皮組織，可在電解除渣製程中被去除，最後殘留的少部分殘銹，則是最內層未被機械除銹鬆動的銹皮組織。

In this study, we measured the surface properties of mechanically descaled SAE1038 wires and evaluated the effect of surface property changes on the successive forming. The scale structure and its characteristics were also studied. The results demonstrated that the scale thickness of the SAE1038 wire ranged from 5 to 27μm. After a number of tests, it was confirmed that roughness and its standard deviation data were proper indexes for the evaluation of evenness and uniformity of a descaled metal surface. After a mechanical descaling, the roughness of the wire was between 1.1 and 1.8 μm, and the standard deviation was between 0.4 and 0.9 μm. It was found that the larger the roughness of the material is, the larger the roughness of it would be after the mechanical descaling. The efficiency of the mechanical descaling was around 80% based on the acidic dissolution method, while the descaling efficiency by electrochemical desmutting was as high as 98%. According to the cross-sections of the descaled samples, it was observed that grains underneath the residual scale were deformed. It was believed that some residual scales were rolled into the substrate and were then removed by electrochemical desmutting. The remaining scales on the substrate were the innermost layer not removable by mechanical descaling.