中碳鋼熱軋鋼捲酸洗製程效率提升之研究

Efficiency Improvement on the Pickling Process for Hot-rolled Strips of Medium Carbon Steels

本研究的目的為開發熱軋酸洗產線之高效率酸洗製程，並於年產70萬噸的酸洗線進行實際試製，以驗證實際產線生產之可行性，研究方法為先以光學顯微鏡與X光繞射分析現場取得中碳鋼S50C鋼材樣品之銹皮結構，再建立酸洗動態模擬技術，並以此模擬系統找出可提升銹皮酸洗之配方，最後進行現場試驗計畫，將實驗室數據實際於現場生產試製，以驗證之。研究結果獲得以下結論：經銹皮結構解析發現，中碳鋼S50C難酸洗的主因為銹皮過厚及組成含有難酸洗的Fe2O3較多所致。更新的動態模擬酸洗設備可更快速及準確的評估鋼材動態酸洗性質，而實驗室酸洗模擬試驗結果與現場試製結果接近，二者皆顯示添加Fe+3可提升酸洗效率。現場試製結果證實，添加Fe+3溶液可提升3 mm厚度S50C鋼捲酸洗線速達20%以上。試製過程藥液分析結果也顯示Fe+3添加量可準確控制。

A high efficiency pickling process was developed and the practicability of a hot-rolled strip pickling line in which carbon steel strips are produced at a quantity of about 700,000 tons per year was investigated. The thickness and composition of oxide scales on specimens of hot-rolled medium carbon steels (S50C) were examined by optical microscopy and XRD, respectively. A modified dynamic pickling pilot line was then established in the lab for pickling rate measurements in various pickling solutions. Tests were also carried out in the pickling production line, and the results were compared with the lab ones. It was found that the oxide scale of the S50C steel strip was difficult to remove by the pickling process because of its thick scale and a high Fe2O3 content. By adding Fe+3 ions to the pickling solution, the efficiency of the pickling process was improved by 20% and the scale on the S50C steel strip was removed completely. It was also shown that the concentration of Fe+3 in the solution could be precisely controlled.