- 學位論文
淬火冷卻速率對JIS SKD61及其改良鋼種之 機械性質的影響
Effects of Different Quenching Cooling Rates on the Mechanical Properties of JIS SKD61 and Its Modified Steels
摘要
本研究以SKD61之規範鋼及其改良鋼種為實驗材料，施以固定的淬火溫度和保溫時間，並用四種不同的冷卻速率淬火後，進行硬度測試與金相組織觀察，接著回火至相同硬度並比較其衝擊值，最後探討淬火冷卻速率與合金元素配置對機械性質的影響。 本實驗主要探討下列兩種熱處理參數對熱作模具鋼機械性質之影響：(1)淬火冷卻速率；(2)合金成分配置。再依據各鋼種的硬度、衝擊值以及金相組織，瞭解其淬火冷速與合金成分對機械性質的影響。 研究結果顯示，淬火時碳化物的析出會影響鋼種的硬度與韌性表現，淬火冷速較快的試片碳化物析出較少，其淬火後硬度較高，且回火後韌性也較佳。此外，合金元素碳、鉻、錳含量較多的鋼種，淬火硬度也較佳；合金元素鉻、鉬、釩對抗回火軟化效果較為顯著，故回火至相同硬度所需的溫度較高。影響鋼料韌性的因素包含回火後硬度、合金元素配置、淬火冷速等。例如回火後硬度較低，添加適當錳合金含量，淬火冷速較快，這3種條件下皆可提升韌性。
並列摘要
In this study, the effect of four different quenching cooling rates was examined. The constant quenching temperature was set at 1020°C, holding was 30 min and different alloy elements on the mechanical properties, such as the hardness and microstructure of SKD61 and its modified steels, were investigated. After quenching, specimens were tempered to the target hardness of 46 HRC, and then, the impact toughness of these specimens was measured. This experiment focused on the effect of two heat treatments for hot work tool steel: (1) quenching cooling rates and (2) configuration of the alloy elements’ composition. As our results show, the precipitation of carbides will affect the hardness and impact toughness; the specimens which were cooled faster during quenching had fewer carbides and the higher hardness and impact toughness. Besides, the specimens which contained more carbon, chromium and manganese had the higher hardness. The specimens which contained more chromium, molybdenum and vanadium required higher temperatures to temper to the hardness of 46 HRC. The factors of impact toughness include the hardness after tempering, configuration of the alloy composition, quenching cooling rates, etc. So, impact toughness can improve by tempering to the lower hardness, adding the appropriate manganese composition and quenching at a faster cooling rate.