高強度高韌性壓鑄機活動曲臂鋼環研製

Abstract

壓鑄法是目前工業上可以大量生產鎂和鋁輕合金產品最符合經濟效益之方法。目前國內使用壓鑄機生產鎂鋁輕合金之廠商，主要乃應用熱室或冷室壓鑄機製作技術要求較低、尺寸較小、勞力密集及重視美觀之3C產品，因此，壓鑄機之壓鑄噸數僅100~800噸之間即可符合大量生產之需求。惠亞公司是擁有2000~3000高噸數壓鑄機之廠商，主要生產需較高壓鑄技術之大尺寸鋁、鎂輕合金產品，包括無塵室之鎂、鋁天花板與地板、32~65”大尺寸鎂合金電視框與汽車鎂鋁合金輪圈等等零組件。高噸數壓鑄機之活動曲臂鋼環需具備高強度、高韌性以及高耐磨耗之特性，其使用環境溫度約為60℃。目前高噸數壓鑄機之活動曲臂鋼環所使用的材料為SNCM815合金鋼。SNCM815合金鋼乃含有昂貴的4.5wt.%鎳之鎳鉬鉻合金鋼，為符合高強度、高韌性以及高耐磨耗之要求，SNCM815合金鋼鑄造成形後，需經過均質化、表面研磨拋光、滲碳、沃斯田鐵化、油淬、深冷處理以及回火處理等非常繁雜之製程。SNCM815合金鋼環產品的機械性質規格為：抗拉強度1080MPa、降伏強度970MPa、延伸率為17%，表面以及心部硬度分別為46和32HRc。所以，高噸數壓鑄機活動曲臂SNCM815合金鋼環十分昂貴，且鋼環的損耗率很高，更新損壞之鋼環時亦需停工，造成整體生產效率降低。近年來，本計畫主持人首次發現了高強度、高韌性以及高硬度之史賓諾多相分解型新Femac(FeMnAlC)合金，發現FeMnAlC合金中碳含量在1.8~2.0wt.%時，在固溶處理淬火狀態下會具有高密度且細微(Fe,Mn)3AlC碳化物(約22nm大小)均勻分佈在沃斯田鐵基地內，此類FeMnAlC合金在450℃時效處理6~12h時，可得到抗拉強度1262~1552MPa、降伏強度1119~1423MPa、延伸率40.3~25.8%，硬度45~51HRc。過去一般眾多學者專家研究的FeMnAlC合金(C≦1.3wt.%)，經固溶處理和時效處理後，延伸率大於30%時，所可得到之最佳機械性質為抗拉強度953~1259MPa、降伏強度665~1094MPa、硬度36~45HRc。本計畫主持人研發之高強度、高韌性以及高硬度之史賓諾多相分解型新Femac(Fe-(28-30)wt.%Mn-(8.5-9)wt.%Al -(1.8-2.0)wt.%C)合金相比較於過去一般eAlMnC (C≦1.3wt.%) 合金在相同延伸率時，其機械強度高約28%之多。同時亦比惠亞公司高噸數壓鑄機之SNCM815合金鋼環，無論強度、延性或硬度均優異甚多。開發之合金經技術轉移於高爾夫球頭製作廠，所製作高爾夫鑄件或鑄鍛件之高爾夫球桿於2006年12月獲得日本年度最佳鐵桿大獎殊榮。同時於2008年使用史賓諾多相分解型新Femac材料製作6mm厚抗彈薄鋼板通過中科院正常火藥量、彈速 930m/s、在5公尺距離處以彈重4.0g之鋼心實彈射擊而未被子彈貫穿之抗彈FJ (SS109)規範。另外，更進一步在2009年使用史賓諾多相分解型新Femac材料，在450℃低溫時效處理後製作更薄之4mm裝甲防彈鋼板，其抗彈速度亦可達770m/s。本計畫若能將高強度、高韌性以及高硬度之史賓諾多相分解型新Femac合金成功推動使用於高噸數壓鑄機活動曲臂鋼環，除了能提供惠亞工程公司在壓鑄生產製程的改善外，亦可降低大尺寸鎂、鋁輕金屬生產的成本，可提升國內鎂、鋁輕合金產業之技術與競爭力。

Die casting is the most beneficial way for mass production of light alloys in the industry so far. In Taiwan, the companies which produce the Al & Mg light alloys by the die casting machines mostly apply hot-room or cool-room die casting machines for the production of low-class, small-sized, labor-intensive and good-looking 3C products. Therefore, the 100~800 tonnage die casting machines can meet the needs of mass production. The Vero company which has 1000~2000 tonnage die casting machine mainly produces high-technology and big-sized Mg and Al light alloys, including the ceiling and floor boards in cleaning room, 32~65＂big-size Mg alloy TV frames, and auto wheels etc. The steel ring fixed in high-tonnage die casting machine must be high strength, high toughness, and high wear resistance. So far, the steel ring fixed in high-tonnage die casting machine is SNCM815 alloy steel. The SNCM815 alloy steel contains expensive 4.5wt.% Ni. In addition¸ the SNCM815 steel ring needs to go through homogenization, surface polishing, carburization, austenitizing, oil quenching, sub-zero treatment, and tempering treatment etc which is a complicated process flow. The SNCM815 steel ring has a good mechanical property, such as 1080MPa tensile strength, 970MPa yield stress, 17% elongation, 46HRc surface hardness, and 32HRc heart-division hardness. The SNCM815 steel ring is very expensive and the loss rate of steel ring is very high. In order to change the steel ring, the production line must suspend work, and it would cause overall production rate descend. In recent years, we discovered the spinodal-decomposition FeMnAlC alloys with high strength, high toughness, and high hardness. We found that in the FeMnAlC alloys with 1.8~2.0 wt.% carbon content, a high density of extremely fine (Fe,Mn)3AlC carbides (about 22nm) could be observed within the austenite matrix. The extremely fine κ' carbides were formed by spinodal decomposition during quenching. When the as-quenched alloys was aged at 450℃ for 6~12 hours, the mechanical properties were in the range of 1262~1552MPa tensile strength, 1119~1423MPa yield stress, 40.3~25.8% elongation, and 45~51HRc hardness. In the previous studies of fully austenitic FeMnAlC (C≦1.3wt.%) alloys, it was found that with an elongation better than 30%, the best mechanical properties 953~1259MPa tensile strength, 665~1094MPa yield stress, and 42~45HRc hardness were obtained. Compared to the previous studies, it is clear that with almost equivalent elongation the strength of the spinodal-decomposition Femac (Fe-(28-30)wt.%Mn-(8.5-9) wt.%Al-(1.8-2.0)wt.%C) alloys is about 28% higher than that of the austenitic FeMnAlC alloys with C≦1.3wt.%. In addition, the mechanical properties of the spinodal-decomposition Femac alloys are much better than those of the SNCM815 steel used for the steel ring of the high-tonnage die-casting machine in Vero. Through the technology transfer of the developed Femac alloys, the golf club manufacturer won the best irons of the year award in December 2006 with their casting and forging golf clubs. In 2008, the 6mm bulletproof steel plate made by the spinodal-decomposition Femac alloys passed the FJ(SS109) standard of Chung-Shan institute of Science and Technology. It means that the steel plate is bulletproof to a solid shot with regular gunpowder, bullet speed 930 m/s and 5m away from the target. Furthermore, after being aged at 450℃, the 4mm light armored vehicle bulletproof steel plate made by spinodal-decomposition Femac alloys was also bulletproof with the bullet speed up to 770 m/s in 2009. If this project could achieve the purpose to successfully make the steel ring of the high-tonnage die-casting machine by the spinodal-decomposition Femac alloys, it will improve the die-casting manufacturing process for Vero company. Moreover, it will cut down the production costs for the big-size Mg and Al light alloys, and advance the technology and competitiveness of the Mg and Al light alloys industry in Taiwan.