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標題: | 金屬射出成形17-4 PH不鏽鋼之機械性質及加工性之改進 Improvements in Mechanical Properties and Machinability of MIM 17-4 PH Stainless Steel |
作者: | Po-Han Chen 陳柏翰 |
指導教授: | 黃坤祥(Kuen-Shyang Hwang) |
關鍵字: | 金屬射出成形,17-4 PH不銹鋼金,屬射出成形,17-4 PH 不,銹鋼,時效處理,深冷,處理, Metal injection molding,17-4 PH stainless steel,aging treatment,cryogenic treatment, |
出版年 : | 2010 |
學位: | 碩士 |
摘要: | 摘要
17-4 PH射出成形不銹鋼因結合了良好的機械性質與抗腐蝕能力,已被廣泛的運用於航太工業與醫療市場。一般17-4 PH不銹鋼粉末均使用真空與氫氣燒結,這是因為在這些氣氛中可利用δ + γ 雙相燒結得到高密度與良好的抗腐蝕性。而本實驗欲提升17-4 PH射出成形件強度並降低製程成本,故以裂解氨為燒結氣氛;期望利用滲氮增加不銹鋼之強度,且裂解氨氣氛也常使用於一般的高溫連續爐中。此外,由於一般17-4 PH燒結後硬度超過25 HRC,不易整形或加工,故本實驗也調整17-4 PH成分期望在裂解氨中燒結後之材料,於固溶淬火後不致過硬不利整形、加工,但在時效之後仍可得到兼具高強度、高韌性和優良抗腐蝕性的不銹鋼。 實驗中先比較了17-4 PH在真空、氫氣與裂解氨氣氛下燒結緻密化行為、機械性質和抗腐蝕性,結果顯示,在1320℃真空與氫氣下燒結已可達97.0%理論密度,但裂解氨下燒結只有94.3%,此是因為在1320℃裂解氨燒結時δ-肥粒鐵比例只有38%,遠低於氫氣中之61%,而此問題可藉由提高燒結溫度至1350℃或添加1 wt% Mo而解決,兩者在高溫時之δ-肥粒鐵已可達56%或57%,燒結後有97%理論密度。 在比較1350℃各燒結工件機械性質方面,真空與氫氣試片經熱處理後,硬度、強度分別為37.6 HRC、1180 MPa與38.6 HRC、1040 MPa,遠低於裂解氨試片之45.7 HRC、1350MPa,但是氫氣或裂解氨試片在熱處理後延性與衝擊能分別只有4.3%、5.8J和2.5%、6.3J遠低於真空之7.8%、67J。在抗腐蝕性方面,真空與氫氣試片經熱處理後,重量損失為0.0032與0.0040 g/dm2/day,而裂解氨試片高達0.0160 g/dm2/day,此已超過MPIF規範(0.005 g/dm2/ day)。 實驗後半部嘗試藉由元素之添加與熱處理以改善材料性質。當17-4 PH添加1 wt% Ni並於裂解氨燒結後經固溶、時效後之硬度與強度分別為39.7 HRC與1365 MPa,且延性與衝擊能可達6.4%與43.6 J,而17-4 PH添加 15 wt% 316L於裂解氨燒結者,經固溶、深冷後時效之硬度與強度為36.6 HRC與1264 MP且延性與衝擊能可達12.2%與64.7 J,兩者強度皆高於17-4 PH於真空和氫氣下燒結數據,且延性皆達MPIF規範。在改善整形和加工性方面,17-4 PH添加1 wt% Ni或15 wt% 316L於裂解氨燒結後在固溶階段硬度、強度已可由17-4 PH之32.3 HRC、1052MPa分別降至25.4 HRC、1020MPa及21.5 HRC、934MPa,此已有利於在固溶階段對材料進一步整形和加工。而在抗腐蝕方面,17-4 PH添加1 wt% Ni於裂解氨燒結並經固溶、時效後之重量損失已降至0.0089 g/dm2/day;而添加15 wt% 316L之試片於裂解氨中燒結並經固溶、深冷後時效後之重量損失更降至 0.0044 g/dm2/day,已符合MPIF 0.005 g/dm2/ day之規範。 Abstract Metal injection molded (MIM) 17-4 PH stainless steels are wildly used in the aircraft and medical industries due to the good mechanical properties and corrosion resistance. The 17-4 PH stainless steel is typically sintered in the dual phase region of δ+ γ under vacuum or hydrogen. Since nitrogen provides solution strengthening and dissociated ammonia (DA) is widely used in continuous furnaces in the industry, the 17-4PH was sintered in DA in this study and its effect on mechanical properties and corrosion resistance was investigated. Results showed that when the 17-4 PH was sintered in vacuum or hydrogen at 1320℃, 97.0% density was achieved, higher than the 94.3% of that sintered in DA. This was because the amount of delta ferrite is about 61% in hydrogen but only 38% in DA. By increasing the sintering temperature to 1350℃ or adding 1 wt% Mo into 17-4 PH, the amount of delta ferrite increased to 56% and 57%, respectively. Thus, high sintered density was attained. Specimen sintered in DA at 1350℃ reached 45.7 HRC hardness and 1350 MPa tensile strength, which are much higher than those of sintered in vacuum and hydrogen at 1350℃. However, the elongation and impact energy of the specimen sintered in hydrogen or DA were very low, around 4% and 6J. The corrosion resistance of 17-4 PH sintered in DA was poor at a rate of 0.0160 g/dm2/day, which exceeded the MPIF limit. To improve the properties of the 17-4PH sintered in DA, 1 wt% Ni was added into 17-4 PH. A hardness of 39.7 HRC, a tensile strength of 1365 MPa, an elongation of 6.4%, and an impact energy of 43.6 J was attained after solutioning and aging treatment. On other hand, when 15 wt% 316L was added into 17-4PH, the hardness, tensile strength, elongation, and impact energy were 36.6 HRC, 1264 MPa, 12.2%, and 64.7J was attained after solutioning, cryogenic, and aging treatment. Both these two methods decreased the hardness after solution treatment to 25.4 and 21.5 HRC for the specimen added with 1 wt% Ni and 15 wt% 316L, respectively. This hardness range is good for machining. The corrosion resistance was also improved by adding Ni and 316L addition. The weight loss rates of the specimens with the addition of 1 wt% Ni and 15wt% 316L were decreased to 0.0089 and 0.0044 g/dm2/day, respectively, after heat treatment. Keywords: Metal injection molding, 17-4 PH stainless steel, aging treatment, cryogenic treatment |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/22451 |
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顯示於系所單位: | 材料科學與工程學系 |
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