下料帶寬設計對焊管品質之影響分析

Abstract

金屬有縫焊管應用廣泛，包含石油、化工與輕工業等工業輸送管道，以及機械與建築結構用焊管。隨著業界追求更高之結構輕量化與低碳排放量，有縫焊管之生產技術日益精進，製管廠也逐漸生產先進高強度鋼(Advanced High Strength Steel, AHSS)之高頻感應焊管(High-Frequency Induction Welding Process, HFIW)。在實際製程中，傳統製管廠會先依據經驗公式設計下料帶寬，並委外繪製輥輪模具以及開模，最終進行鋼捲剪裁與輥軋成形。然而，若想生產同管徑不同材料或同管徑不同厚度，可能會因為鋼板材料差異與幾何結構不利於此輥輪模具之原設計，現場亦會進行多次下料帶寬修正，甚至需對輥輪進行打磨，以達到順利穿帶之效果。本論文建立一套可針對不同材料之幾何尺寸進行下料帶寬的調整，分別在輥軋成形之預焊接前進行下料帶寬修整與HFIW製程以擠壓量進行下料帶寬修整，最終藉以探討材料成形性與焊接性，進而提出下料帶寬優化設計。 本論文利用有限元素軟體進行全線製管製程分析，以實際之輥軋成形機台為基礎，並以先進高強度鋼DP780、DP980與機械結構用鋼AISI 4130於不同厚度進行輥軋成形與擠壓量之設計，其中分為成形模擬與焊接模擬。於成形模擬中，使用相經驗公式建立下料帶寬，並針對不同材料與幾何尺寸進行管件成形。此外，製管廠無法逐站量測帶寬總長變化，加上經驗公式下之料寬過長，所以透過有限元素法模擬材料成形狀態進一步歸納出材料伸長比例因子，並利用比例因子修正下料帶寬，進而改善鋼板邊緣撞模等問題，觀察出較薄之厚度改善此問題顯著。 然而，修正後之下料帶寬因寬度縮短，會面臨到鋼板邊緣成形量不足之問題。於精成形站中，亦發現管件邊緣之開口回彈效應增加，此帶寬之寬度無法有效將焊接時的氧化物順利擠出，進而藉由焊接製程之擠壓量進行下料帶寬二次調校。於焊接製程中，為確保焊接製程之完整，先進行加熱線圈功率、線圈與線圈間距以及線圈圈數等製程參數探討溫度場分布，建立完整高頻感應焊接模型，並挑選製程參數中加熱效率較佳者，進行不同材料於不同厚度下之焊接模擬，觀察出厚度較厚的加熱效率較差。 最後，利用焊接擠壓量進行需求下料帶寬調整，進一步配合焊接品質控管，包含金屬焊流線、焊道硬度與壓扁試驗等作為判斷焊道品質之指標，並依此定義擠壓量修正因子，成功使預焊接前料寬量減少，並且穿帶順利，亦不會發生鋼板與輥輪間之捲料問題，進而用壓扁試驗間接檢測焊道品質，確保焊後管件強度之一致性，本論文之擠壓量設計方式可提供製程上參考用。 本論文對全線輥軋成形高頻感應焊接製程技術的貢獻在提供業界，以模擬結果輔助輥軋成形製程與高頻感應焊接對下料帶寬設計之調校，並且可應用於開設新產線之評估，有效控管焊接品質，進一步減少試誤法下修正下料帶寬與打磨輥輪模具之成本與時間，提升製程生產效率與穩定生產品質。

Seam-welded tubes are widely used in different fields including petroleum, chemical engineering, light industry, mechanical engineering, and building construction. Due to the lightweight requirement and low-carbon structures, advanced high strength steels (AHSS) are widely adopted for manufacturing seamed tubes with high frequency induction welding (HFIW). In traditional tube manufacturing processes, manufacturers typically design the strip width based on empirical formulas, then outsource the design and creation of the rollers. Finally, they conduct the full-line roll forming process for seamed tube production. However, it can be challenging to manufacture tubes of the same diameter using different materials or thicknesses. These challenges might arise due to differences in the steel sheet's material and geometric structure, which may not be conducive to the original roll design. Consequently, multiple on-site adjustments to the strip width might be required, and it might even be necessary to grind the rollers to ensure smooth strip threading. This study proposes a method for adjusting the strip width based on the geometric dimensions of different materials. The study establishes a method to adjust the strip width based on the geometric dimensions of different materials. Adjustments are made prior to pre-welding in the roll forming process and during the HFIW process according to the amount of welding extrusion. The ultimate aim is to investigate the formability and weldability of the materials, leading to an optimized design for strip width. The Study uses finite element analysis to conduct a comprehensive analysis of the tube manufacturing process, based on the actual roll forming machine. DP780, DP980, and mechanical structural steel AISI 4130 are used at different thicknesses for roll forming and amount of welding extrusion design. In the roll forming process, the strip width is established using empirical formulas, and tube forming is performed for different materials and geometric dimensions. Moreover, since tube manufacturers are unable to measure the total change in strip width at each station, and given that the strip width calculated using empirical formulas is often excessive, the study uses simulations to identify a factor of material elongation during the roll forming process. This factor is then used to adjust the strip width, which subsequently reduces problems such as the collision of the steel sheet's edge with the roller. Using this method can result in noticeable improvements in thinner materials. However, the adjusted strip width may face the problem of insufficient forming at the edge of the steel sheet due to its shortened width. In the Fin-Pass forming, it is also found that the opening springback effect at the edge of the tube is increased. This strip width cannot effectively squeeze out the surplus during welding. Therefore, a second adjustment to the strip width is made based on the amount of welding extrusion during the welding process. In the welding process, to ensure the completeness of the process, the HFIW parameters such as heating coil power, coil-to-coil spacing, and the number of coil turns are investigated to study temperature field distribution and establish a comprehensive HFIW model. The process parameters with better heating efficiency are selected for welding simulations of different materials with different thicknesses. It is observed that thicker materials have poorer heating efficiency. Finally, the strip width is adjusted based on the amount of welding extrusion, further coordinating with welding quality control. Indicators such as welding flow lines, weld hardness, and flattening test are used to judge weld quality. The extrusion adjustment factor is defined based on the quality of the welding flow lines, successfully reducing the strip width at the pre-welding station and ensuring smooth strip threading. This also prevents the problem of material coiling between the steel sheet and the roller. A flattening test is used indirectly to assess the weld quality, ensuring consistency in the strength of the tubes after welding. The extrusion design method presented in this study can serve as a reference for tube manufacturing. The contribution of full line roll forming seamed tube manufacturing process with High-Frequency Induction Welding is to provide the industry with a method for adjusting the strip width design based on simulation results. It can also be applied in the evaluation of setting up new production lines, effectively controlling the welding quality, further reducing the cost and time of adjusting strip width and grinding rollers by trial and error, thereby enhancing the efficiency of the manufacturing process and ensuring consistent product quality.