- 學位論文
以恆溫熱處理改善高碳工具鋼薄工件的機械性質
Improving the Mechanical Property of High Carbon Tool Steel with Isothermal Heat treatment
摘要
為了使高碳工具鋼薄工件能兼具平直度、強度與韌性的要求，本實驗嘗試以恆溫熱處理（沃斯回火與麻回火）取代傳統的淬火-回火處理，並配合適當高溫短時間的校直回火來改善高碳工具鋼薄工件的機械性質。探討各種熱處理參數對工件的硬度及彎斷角度的影響，並尋求最佳的處理參數，以供實際應用時參考，所得結果如下： 1.經810℃加熱15分鐘 → 120℃油淬火之試片，進行低溫（240℃~290℃）校直回火時，回火溫度越高彎斷角度越大，但當回火溫度高於280℃，彎斷角度反有略微下降之現象，此乃因一般淬火試片的麻田散鐵含量較高，故回火麻田散鐵脆化對試片影響較大。 2.不論是一般淬火、麻回火或沃斯回火試片，採用高溫短時間校直回火之試片的機械性質皆優於低溫長時間回火之試片。以405℃進行高溫回火之試片中，以麻回火之試片機械性質最佳，沃斯回火之試片次之，而一般淬火試片最差。 3.若將高溫短時間校直回火之溫度降至360℃時，所需的回火時間約為2 ~ 3分鐘，較以405℃回火，增長近兩倍的時間，對實際的回火作業較為方便。在相同硬度下，雖彎斷角度較高溫（405℃）回火之試片差，但仍優於低溫（240℃~290℃）回火之試片。 4.本實驗所得到最佳的高碳工具鋼薄工件之熱處理條件為： 810℃x15分鐘沃斯田鐵化 → 140℃×1小時麻回火 → 405℃×50秒校直回火
並列摘要
The purpose of the present experiment is to improve the mechanical property （hardness、toughness and flatness）of carbon tool steel by modifying the conventional heat treatment processeses. The proposed heat treating process is isothermal heat treatment followed by a high- temperature and short-time tempering, which is going to replace the traditional heat treatment of quenching and tempering. On condition that the flatness matches the requirement, the heat treatment parameter that affect the hardness and toughness are discussed. The best heat treatment process in the present experiment is reported for practical application. The results obtained are as follows: 1.For the traditional heat treatment （810℃ × 15 min Austenization → 120℃ × 1hr oil quenching → 1hr low-temperature tempering for 1 hr）, the critical bending angle of the specimen increases with the raising of temper temperature, but when the temperature is over 280℃, the critical angle will decrease. It’s because the martensite content of the specimen after traditional quenching was much more than that of the isothermal heat treatment specimen, so the Tempered Martensite Embrittlement effect was much more noticeable. 2.Either for the traditional quenching or isothermal heat treatment（Martempering、Austempering）, the mechanical property of specimen that tempered at 405℃ is better than that tempered at the temperature from 240℃ to 290℃. 3.If the temper temperature is lowered from 405℃ to 360℃, the tempering time will increase from 50sec to 2~3min, which is more feasible for practical heat treatment. By the comparisons of the critical bending angle at the same hardness level（Hv690）, the specimen which was tempered at 360℃ was inferior to that tempered at 405℃, but better than that tempered at 260℃. 4.The optimal heat treatment process of carbon tool steel in the present experimental condition is:810℃ × 15min Austenization → 140℃ × 1hr Martempering → 405℃ × 50sec Strengthening Tempering