技術學刊 第二十五卷 第二期 民國九十九年 121 Journal of Technology, Vol. 25, No. 2, pp. 121-130 (2010) 構造用鎳鉻鉬合金鋼 JIS-SNCM 439 熱處理之研究 曾春風 郭央諶 國立虎尾科技大學材料科學與工程系 摘 要 本研究旨在了解熱處理對構造用合金鋼 JIS-SNCM 439 之影響。Charpy V 型槽衝擊試片實施淬火處理經由衝擊試驗、硬度量測以尋找 SNCM 439 之最佳 淬火條件。淬火試片並於 200°C~600°C 實施 2 小時二次之回火處理,以了解淬 火及回火對機械性質、顯微組織以及破斷面型態的影響。 實驗結果發現 JIS-SNCM 439 最佳淬火溫度為 875°C 、加熱時間 30 分鐘, 而最佳強韌性組合的回火溫度約 250°C。隨回火溫度的增加,硬度及抗拉強度 皆呈現下降趨勢,衝擊值在 300°C 附近呈現下降且達到最小值。於 200°C~300°C 回火之衝擊斷口皆為劈裂 (或準劈裂) 型態,但在 300°C 回火之衝擊斷口的台 階大、韌帶少;於 500°C 以上回火之衝擊斷口皆由韌窩及韌帶組成之韌性破 斷。回火溫度在 300°C 以下,拉伸之巨觀破斷面呈現銑刀狀破斷型態,回火溫 度在 400°C 以上,則呈現杯錐狀破斷型態。 關鍵詞:顯微組織,破斷面型態,劈裂,韌窩,銑刀狀破斷,杯錐狀破斷。 A STUDY ON HEAT TREATMENT OF Ni-Cr-Mo STRUCTURAL ALLOY STEEL JIS-SNCM 439 Chun-Feng Tseng Iang-Chern Kuo Department of Materials Science and Engineering National Formosa University Yunlin, Taiwan 632, R.O.C. Key Words: microstructures, fracture surface morphology, cleavage, dimple, milling cutter fracture, cup-and-cone fracture. ABSTRACT The purpose of this article is to investigate the effect of heat treatment on Ni-Cr-Mo structural alloy steel JIS-SNCM 439. Charpy V-notch impact specimens quenching treatment had carried out to find optimum quenching conditions by conducting impact tests and hardness measurements. The impact specimens and tensile specimens were quenched using above the optimum quenching conditions, then tempered for 2 hours double temper- ing at 200°C~600°C, and impact tests, tensile tests, hardness measurements, microstructures and SEM fracture surface morphology observations were conducted to reveal the effect of quenching and tempering conditions on mechanical properties, microstructures and fracture surface morphology. The results show that the optimum quenching temperature is 875°C and austenitizing time is 30 minutes for JIS-SNCM 439, and the tempering temperature for the optimum combination of strength and toughness is
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技術學刊 第二十五卷 第二期 民國九十九年 121
Journal of Technology, Vol. 25, No. 2, pp. 121-130 (2010)
構造用鎳鉻鉬合金鋼 JIS-SNCM 439 熱處理之研究
曾春風 郭央諶
國立虎尾科技大學材料科學與工程系
摘 要
本研究旨在了解熱處理對構造用合金鋼 JIS-SNCM 439之影響。Charpy V
型槽衝擊試片實施淬火處理經由衝擊試驗、硬度量測以尋找 SNCM 439之最佳
淬火條件。淬火試片並於 200°C~600°C實施 2小時二次之回火處理,以了解淬
火及回火對機械性質、顯微組織以及破斷面型態的影響。
實驗結果發現 JIS-SNCM 439最佳淬火溫度為 875°C、加熱時間 30分鐘,
而最佳強韌性組合的回火溫度約 250°C。隨回火溫度的增加,硬度及抗拉強度
皆呈現下降趨勢,衝擊值在 300°C附近呈現下降且達到最小值。於 200°C~300°C
回火之衝擊斷口皆為劈裂 (或準劈裂) 型態,但在 300°C回火之衝擊斷口的台
階大、韌帶少;於 500°C 以上回火之衝擊斷口皆由韌窩及韌帶組成之韌性破
斷。回火溫度在 300°C以下,拉伸之巨觀破斷面呈現銑刀狀破斷型態,回火溫
度在 400°C以上,則呈現杯錐狀破斷型態。
關鍵詞:顯微組織,破斷面型態,劈裂,韌窩,銑刀狀破斷,杯錐狀破斷。
A STUDY ON HEAT TREATMENT OF Ni-Cr-Mo STRUCTURAL ALLOY STEEL JIS-SNCM 439
Chun-Feng Tseng Iang-Chern Kuo
Department of Materials Science and Engineering National Formosa University Yunlin, Taiwan 632, R.O.C.
The purpose of this article is to investigate the effect of heat treatment on Ni-Cr-Mo structural alloy steel JIS-SNCM 439. Charpy V-notch impact specimens quenching treatment had carried out to find optimum quenching conditions by conducting impact tests and hardness measurements. The impact specimens and tensile specimens were quenched using above the optimum quenching conditions, then tempered for 2 hours double temper- ing at 200°C~600°C, and impact tests, tensile tests, hardness measurements, microstructures and SEM fracture surface morphology observations were conducted to reveal the effect of quenching and tempering conditions on mechanical properties, microstructures and fracture surface morphology.
The results show that the optimum quenching temperature is 875°C and austenitizing time is 30 minutes for JIS-SNCM 439, and the tempering temperature for the optimum combination of strength and toughness is
122 技術學刊 第二十五卷 第二期 民國九十九年
about 250°C. The hardness and tensile strength will decrease with increasing tempering temperature, the toughness increases initially with tempering temperature but declines sharply reaching a minimum in toughness at 300°C. The fracture of impact specimens has a cleavage (or quasi-cleavage) morphology while tempering temperature is at 200°C~ 300°C, the fracture has a ductile morphology which shows many dimples while tempering temperature is above 500°C. The fracture surface of tensile specimens shows a milling cutter fracture when tempering temperature is under 300°C, and a cup-and-cone fracture when tempering temperature is above 400°C.