Y309L不銹鋼軋延製程參數對δ肥粒鐵含量影響之研究

A Study for the Effect of Rolling Process Variables on the Content of δ-Ferrite in Y309L Stainless Steel for Welding

楊俊彬 ； 熊篤誠 ； 林東毅

《鍛造》 13卷2期 (2004/07) Pp. 47-53

摘要

Y309L(24Cr-14Ni-2Mn)乃用於銲條心線之高附加價值不銹鋼產品，在常溫組織既有沃斯田鐵又有肥粒鐵組織，具有良好的耐蝕性、銲接性、韌性、強度的優良特性。小鋼胚在高溫凝固的過程中，因屬非熱平衡冷卻而有δ－肥粒鐵殘留偏析，此相之存在可有效的防止銲接時熱裂的發生。
Y309L線材熱軋加工在生產初期該材料之軋延過程中常遇到裂縫、爆頭及剝片等狀況，易造成材料損失及設備損壞而增加製造成本，其主要原因為δ－肥粒鐵含量過高。而δ－肥粒鐵對軋延剝裂之影響在於(1)δ－肥粒鐵易固溶合金元素或不純元素，使得延性劣化。(2)δ－肥粒鐵在600－950℃分解生成σ相與γ相， 因而造成材料的機械性質與耐腐蝕性的劣化。(3)δ相的存在會與碳化物交互作用，則N2、H2等小分子有機會發生聚集，致使氫脆裂。(4)不銹鋼中δ－肥粒鐵的含量增加將改變鋼材之強度與韌性，影響熱加工性質。本研究即在探討Creq/Nieq當量比、軋延溫度、斷面減縮率對δ－肥粒鐵含量之影響。
結果顯示，(1)Creq/Nieq當量比愈高，δ－肥粒鐵含量愈高，線材耗損率有增加趨勢。(2)δ－肥粒鐵含量隨著軋延溫度升高而δ－肥粒鐵含量增加，當溫度在1100℃時，δ－肥粒鐵含量會有最大值，反之，當溫度在990℃時，δ－肥粒鐵含量會有較小值。(3)當溫度設在990℃～1100℃區間試驗，在同溫下δ－肥粒鐵含量似乎不會與斷面減縮率增加而增高趨勢。在本實驗之製程條件下，δ－肥粒鐵含量均控制在10％左右，軋延後之線材品質良好，其結果將可作為不銹鋼成形業者對於製造此類產品之參考。

並列摘要

Y309L stainless with high Cr and Ni contents is becoming an core material of high added value for welding wires. Its microstructures contain austenite and δ-ferrite and have some elements such as Mo, Si, Al, Ti, Nb solved in the matrix at the same time. The Y309L stainless has excellent characteristics in corrosion resistance, welding, tenacity, intensity and few cracking while welding. But this materials are difficult for hot rolling due to many kinds of defects happened during production, which are rolling crack, cobble and sliver. That can damage rolling facilities and take much time for repairing and much cost. The result comes from the high content of δ-ferrite. The content of δ-ferrite in hot workability influence (1) the character of δ-ferrite with tendency to melt in alloyed material or other element while in the milting decreasing. (2) δ-ferrite in 600-950℃ will resolve and compose of γ and σ phase, which will result in mechanical properties of material and corrosion resistance decreasing. (3) The existence of δ phase interact with carbide, so that N2, H2 molecule will have possibility of congregation. That will lead to hydrogen cracking. (4) Increasing content of δ-ferrite in stainless will influence intensity, tenacity of stainless material, and character of hot workability. Therefore, the content of δ-ferrite will influence quality significantly during the process of rolling and milling and this effects are worth to investigating. The research is to study the influence of the content of δ-ferrite in equivalent ratios of Creq, Nieq, the temperature of rolling and milling, and reduction ratio.
The result of research showed (1) The higher equivalent ratio of Creq/Nieq and high content of δ-ferrite, the more increasing diminished ratio of wirerod. (2) The δ-ferrite content is increased by increasing the temperature of rolling mill. As temperature in 1100℃, there exists a maximum value of δ-ferrite content. In contract, there is a minimum value of δ-ferrite content. (3) When temperature of experiment is between 990℃and 1100℃, there is no tendency of increasing δ-ferrite content with increasing cross reduction ratio with isothermal. Under the condition of experiment process δ-ferrite content keeping in 10% or so will have high quality of wire rod, the result will offer reference of improving product for manufacture.