熱處理對Custom 475 鑄造不銹鋼機械性質的影響;Effects of Heat Treatment on the Mechanical Properties of Custom 475 Stainless

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题名:	熱處理對Custom 475 鑄造不銹鋼機械性質的影響;Effects of Heat Treatment on the Mechanical Properties of Custom 475 Stainless
作者:	金家興;Chin, Chia-Hsing
贡献者:	機械工程學系在職專班
关键词:	Custom 475不銹鋼材;鑄造;熱處理;機械性質;Custom 475 stainless steel;Casting;Heat treatment;Mechanical properties
日期:	2019-06-25
上传时间:	2019-09-03 16:36:52 (UTC+8)
出版者:	國立中央大學
摘要:	本研究主旨是探討美國卡本特公司所生產之Custom 475不銹鋼材，藉由鑄造製程取得試片後，利用DSC熱差分析尋找出適合之熱處理參數包括固溶條件以及時效條件進行熱處理。熱處理後對試片進行進一步分析包括硬度、拉伸、X光繞射結構分析與微觀金相分析，另外針對拉伸後試片之破斷面也以SEM進行微觀分析。實驗結果得知當時效溫度越高材料所得之析出相就越多相對的硬度就越高。經XRD分析觀察發現時效溫度500 ℃熱處理後有一明顯析出物繞射峰產生、而時效溫度400 ℃與450 ℃則未產生析出相繞射峰，研判該時效溫度過低。從金相顯微結構觀察得知熱處理後其組織為板條狀麻田散鐵。從拉伸性質比較分析得之，未熱處理試棒強度並不高，只有降伏強度589 MPa、抗拉強度955 MPa及伸長率約13 %，熱處理後降伏強度及抗拉強度分別提升至1300 MPa及1460 MPa以上，本實驗做兩組時效條件一為硬度值較高之時效條件500 ℃、二為硬度值相對較低的時效條件400 ℃，其結果為硬度較高試棒之斷面呈現脆性破裂，而硬度較低的試棒斷面呈現延性破裂，此結果與拉伸機械性質成正比關係。 ;The purpose of this study is to explore the process condition of heat treatment for Custom 475 stainless steel produced by Carpenter in the United States. DSC thermal analysis was used to find the phase transformation temperature for setting the suitable heat treatment parameter, including the solid solution and aging treatment. After heat treatment, the microstructure and mechanical properties of all samples were characterized by XRD analysis, metallographic observation, hardness test, and tensile test, respectively. In addition, the fracture surface of tensile tested samples was microscopically examined by SEM. The results of hardness test show that higher aging temperature would form more precipitates in the material and results in a higher hardness. XRD analysis presents that one diffraction peak corresponding to the precipitate occurred after aging at 500 ℃. However, the aging temperature at 400 ℃ and 450 ℃ seems too low to obtain enough precipitates and cannot be resolved in XRD pattern. Meanwhile, the results of metallographic observation confirm that the matrix microstructure of heat treated sample is lath martensite. Results of tensile test reveal that the effect of heat treatment can significantly improve the mechanical properties from the yield strength of 589 MPa, tensile strength of 955 MPa, and the elongation is about 13 % up to the yield strength of 1300 MPa and tensile strength of 1460 MPa. Two aging conditions, 500 ℃/6 h and 400 ℃/6 h, were used in this study for comparing their tensile ductility. The results show that, the sample after aging at higher temperature can reach higher hardness but presents brittle fracture. On contrary, the sample after aging at lower temperature exhibits relative lower hardness and ductile fracture. These results are in good agreement with the results of tensile test.
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