SUS 420麻田散鐵系不銹鋼之氣體滲氮·滲碳研究

Abstract

SUS420不銹鋼為麻田散鐵系，因鋼料中含有鉻元素，可在表面形成氧化膜保護鋼料內部，阻隔外界環境，因此具有良好的耐蝕性。麻田散鐵系不 麻田散鐵系不 銹鋼 的碳含量 較高， 可以透過熱處理程序來提升其機械性質， 可以透過熱處理程序來提升其機械性質， 可以透過熱處理程序來提升其機械性質， 具有高硬度、耐 有高硬度、耐 有高硬度、耐 有高硬度、耐 磨的特點。 本研究 實驗 分三部進行 ：(1)鋼料先經氣體滲氮碳再淬火、回處理 鋼料先經氣體滲氮碳再淬火、回處理 鋼料先經氣體滲氮碳再淬火、回處理 鋼料先經氣體滲氮碳再淬火、回處理 ：先 以 經過預分解的氨氣混合木精進行滲氮碳處理 ，在試片表面固溶氮、碳原子 ，在試片表面固溶氮、碳原子 ，在試片表面固溶氮、碳原子 ，在試片表面固溶氮、碳原子 ， 接著實施淬火 、回接著實施淬火 、回接著實施淬火 、回以增強硬度 ，期望透過改善熱處理程序來避免 表面硬化 鋼料 中心硬度偏低的情況發生 ；(2)傳統氣體軟氮化 ：鋼料先經淬火再進行後續滲氮碳 處理 ；(3)傳統氣體滲碳氮化 傳統氣體滲碳氮化 ：高溫下進行滲碳氮化 並淬火，再進行回處理。 並淬火，再進行回處理。 並淬火，再進行回處理。 並淬火，再進行回處理。 探 討不同 溫度、 溫度、 時間 對麻田散鐵系不銹鋼之硬度分布、顯微組織耐蝕性的影響。 對麻田散鐵系不銹鋼之硬度分布、顯微組織耐蝕性的影響。 對麻田散鐵系不銹鋼之硬度分布、顯微組織耐蝕性的影響。 對麻田散鐵系不銹鋼之硬度分布、顯微組織耐蝕性的影響。 對麻田散鐵系不銹鋼之硬度分布、顯微組織耐蝕性的影響。 對麻田散鐵系不銹鋼之硬度分布、顯微組織耐蝕性的影響。 對麻田散鐵系不銹鋼之硬度分布、顯微組織耐蝕性的影響。 對麻田散鐵系不銹鋼之硬度分布、顯微組織耐蝕性的影響。 本研究主要實驗結果如下 : (1) 在氣體滲氮碳時，持溫 在氣體滲氮碳時，持溫 在氣體滲氮碳時，持溫 時間增長，析出物層也跟著變厚 時間增長，析出物層也跟著變厚 時間增長，析出物層也跟著變厚 時間增長，析出物層也跟著變厚 。在低溫滲氮碳 低溫滲氮碳 低溫滲氮碳 時， 析出物層與基材的分界不明顯 出物層與基材的分界不明顯 出物層與基材的分界不明顯 出物層與基材的分界不明顯 ；而高溫滲氮碳 高溫滲氮碳 時，析出物層與基材有明顯的 時，析出物層與基材有明顯的 時，析出物層與基材有明顯的 時，析出物層與基材有明顯的 分界 。 (2) 氣體 滲氮碳時 在不超過 Fe-C、Fe-N的共析溫度且持時間短的情況下 共析溫度且持時間短的情況下 硬度較 高，例如在 570℃×6hr滲氮碳可得到本實驗最大硬度 ，但 次表層 會有軟層區 的產生。 (3) SUS420不銹鋼先經 570℃×3hr滲氮碳再淬火 、回火後 ，對鹽酸 、硫酸 、硝酸 的耐蝕性都有提升。 (4) SUS420不銹鋼施以 傳統氣體軟氮化 時，鋼料心部硬度會因滲氮碳處理 ，鋼料心部硬度會因滲氮碳處理 溫度過 高使中心硬度偏低。 (5) SUS420不銹鋼施以 傳統氣體滲碳氮化 時，短時間即可達到 ，短時間即可達到 顯著的表面硬化 效 果， 但鋼料表層 會有粒界氧化的情形 產生 。

SUS420 stainless steel is martensitic series stainless steel and its steel material contains chromium and it can form oxidation film on its surface to protect the steel from oxidation, so it has excellent corrosion resistance. As the martensitic series stainless steel contains higher carbon content, it can improve mechanical properties through thermal treatment and it is characterized by high hardness and high wear resistance. The experiment in this research was implemented in three parts: (1) First of all, the steel materials went through gas nitriding/carburizing and then quenching and tempering were done. Pre-dissociated ammonia gas and methanol dissociation gas were mixtured for the treatment of nitriding/carburizing; nitrogen and carbon atom solution treatment was performed on the surface of specimen and then quenching and tempering were implemented to increase hardness. It is expected to avoid the occurrence of surface hardening and low hardness in the center of steel through the improvement of thermal processing ; (2) The traditional gas nitrocarburizing: the steel material was firstly quenched and then the subsequent gas nitriding/carburizing treatment was done. (3) The traditional gas carbonitriding: the carbonitriding and quenching were done under high temperature and then tempering was performed, so as to discuss the effect of different temperature and time on the hardness distribution, microstructure and corrosion resistance of martensitic series stainless steel. The main experimental results in this research are shown as below: (1)With the holding time increases, the precipitate layer grows thicker during gas nitriding/carburizing. During low-temperature gas nitriding/carburizing, the boundary between precipitate layer and base material is not obvious; during high-temperature gas nitriding/carburizin, there exists obvious boundary between precipitate layer and base material. (2)During gas nitriding/carburizin, the hardness is higher when the eutectoid temperature is less than Fe-C and Fe-N and holding time is short. For example, 570℃×6hr nitriding/carburizin can gain the maximum hardness in this experiment, but the soft layer area is generated on the subsurface layer. (3)SUS420 stainless steel should firstly go through 570℃×3hr nitrocarburizing and then it is quenched ,and finally it is tempered, the corrosion resistance to hydrochloric acid, sulfuric acid and nitric acid will be improved. (4)After traditional gas nitrocarburizing, the hardness in the center of SUS420 stainless steel will become lower because the treatment temperature of nitrocarburizing is too high. (5)After traditional gas carbonitriding, the significant surface hardening effect can be achieved in a short time, but the intergranular oxidation appears on the steel surface.