JIS SKD61熱作模具鋼真空熱處理性能研究

A Study in Vacuum Heat Treatment of JIS SKD61 Hot-Work Steels

張凱嵐(Kai-Lan Chang)

指導教授 ： 邱六合

大同大學/工程學院/材料工程學系所/碩士(2011年)

摘要

本研究探討熱作模具鋼經不同淬火回火及鹽浴軟氮化處理之微結構及耐蝕性變化，選用傳統型A材、H材及改良型M材熱作模具鋼為研究材料。實驗試片使用1000~1025℃持溫25分鐘，進行2kg/cm2 氮氣氣淬，並於200~650℃區間進行不同溫度回火處理，並選用600℃回火試片進行580℃鹽浴軟氮化。結構分析包括金相組織及X-ray繞射，並進行熱疲勞及熱熔損等量測。試片經1025℃沃斯田體化持溫25min後以氮氣氣淬，硬度可達53.4±0.3HRC(A材)、54.5±0.5HRC(H材)及55.0±0.2HRC(M材)，並在525℃回火(55.8±0.2HRC、55.7±0.2HRC和55.4±0.1HRC)觀察出有二次硬化現象。由掃描速率1.2°/min之X-ray分析，可知A材、H材及M材經氣淬及回火後試片主要結構均為麻田散鐵相（Martensite），氮化處理試片表面皆有Fe3N與Fe4N相生成。由熱熔損分析顯示改良型鋼種鋁熔損量(9%)比傳統型(13及9.5%)更能抗鋁熔損，且三種鋼種經580℃鹽浴軟氮化80分鐘能均降低熔損率至1%。經由熱疲勞分析顯示改良型鋼種耐疲勞性比傳統型SKD61鋼種優良，經鹽浴軟氮化並不能有效的提升耐熱疲勞性，傳統型A材氮化後試片熱疲勞裂紋由215μm成長到520μm。

關鍵字

熱作模具鋼

並列摘要

Three hot-work steels, standard A、H and modified M, have been vacuum heat treated by using different quenching and tempering processes to observe the change of microstructure and corrosion resistance. Some specimens, austenitized at 1025℃ for 25 min, were gas quenched to room temperature and tempered at 200 ~ 650℃. Selected specimens were salt bath nitrocarburized at 580 ℃. The microstructures, X-ray diffration, heat crack and aluminum erosion tests were conducted. The results show that hardness of as-quenched specimens, austenitized at 1025℃ for 25 min, were 53.4±0.3HRC(standard A), 54.5±0.5HRC (standard H) and 55.0±0.2HRC (modified M) and the phenomenon of secondary hardening was observed at 525℃ (55.8±0.2HRC, 55.7 ± 0.2HRC and 55.4 ± 0.1HRC). By using the scan rate of 1.2°/min for X-ray diffractometer, the martensite phase was existed at the standard A and modified B by gas quenching and tempering, the phases of nitrocarburized specimen were Fe3N and Fe4N. Aluminum erosion resistance tests showed the loss rate of the modified specimen B is lower than standard one, and the salt-bath nitrocarburizing can effectively reduce the loss rate by 10.5%(A), 7.9% (H) and 8.4% (M). From the heat crack tests the heat crack resistance of modified M was better than standard A; however, the salt-bath nitrocarburizing can not effectively enhance the thermal fatigue resistance, the depth of fatigue crack of the nitrocarburized specimen was grown from 215μm to 520μm.

並列關鍵字

Hot-Work Steels

參考文獻

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