淬火溫度及持溫時間對SKD61及其改良鋼種之機械性質的影響

Effects of Different Quenching Temperatures and Different Holding Time on the Mechanical Properties of SKD61 and Its Modified Steels

朱致成(Chi-Chen Chu)

指導教授 ： 陳永傳

國立臺灣大學/工學院/機械工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.02108

摘要

本實驗以不同淬火溫度、不同持溫時間、不同回火溫度、不同回火持溫時間，將SKD61 之規範鋼以及改良鋼以高速氣冷方式淬火，再回火至相同硬度後比較其衝擊值，並透過觀察顯微組織，以了解鋼料的淬火溫度、持溫時間和合金元素配置對機械性質的影響，並探討何種熱處理及合金配置對機械性質有最佳的結果。實驗結果顯示，SKD61 的改良鋼在不同淬火溫度及不同保溫時間下淬火，若鋼材合金含量越高，則硬化能越高，淬火後硬度值越高。
　　在回火條件的選擇上，有較高淬火硬度的鋼材，回火至相同硬度的溫度不一定較高，而與合金的配置有關。合金含量較低的規範鋼Z，回火溫度並不隨著淬火溫度和持溫時間的提升而有著明顯的增加；回火持溫時間也不隨著淬火溫度和持溫時間的不同而有顯著差別。但改良鋼B、C 相較於規範鋼Z，大量增加了Mo 含量，所以隨著淬火溫度的提升，Mo 溶入基地的量增加，因而增加了回火軟化抵抗，在回火溫度沒有增加時，無法以二次回火就達到目標硬度值48HRC，需經過第三次回火，硬度才能達到目標值。
　　從衝擊值的表現上來看，高合金含量的改良鋼B、C，以較低淬火溫度(1000℃)及較短持溫時間(30 分)熱處理後之衝擊值表現較佳，但不論淬火溫度的高低與持溫時間的長短，改良鋼B、C 大多可以具有一定的衝擊值，與硬度值的關聯性較低；而合金元素含量較低的改良鋼A，淬火持溫時間的長短對衝擊值影響很大，尤其當淬火溫度較低時。

關鍵字

熱作工具鋼 ； 淬火 ； 回火 ； 硬度 ； 衝擊值

並列摘要

This article of this study is to investigate the effect of different heat treatment parameters and different alloy elements on the microstructure and mechanical properties such as hardness and impact value of SKD61 and its modified steels. The results show that the modified steels containing higher alloy elements have higher hardenability and possess higher hardness after quenching at different temperatures and in different holding time. Steels with higher hardness after quenching will not always have higher hardness after tempering. It is more relevant to the elements of alloy. The tempering temperature of Z steel, which contains lower alloy elements, does not increase significantly with the quenching temperature and heating time. Its tempering time also changes little for all different quenching temperature and heating time. On the other hand, the modified steel B and C contain much more Mo in comparison to Z steel. The amount of Mo dissolved in the matrix will increase with the raise of quenching temperature, and increase the resistance of softening while tempering. It will take three or more times to temper to target hardness of 48HRC rather than twice if the temper temperature remains unchanged.
In the performance of impact value, high alloy containing steel B and C performed better at the lower quenching temperature of 1000℃ and shorter heating time of 30 minutes. The relevance between hardness and impact value of modified steel B and C is weak, because the materials always possess rather stable impact value. As for the modified steel A, the heating time of quenching affects the impact value markedly especially at the lower quenching temperature of 1000℃

並列關鍵字

quenchin ； tempering ； hot work tool steel ； hardness ； microstructure

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