밸브用 耐熱鋼의 高溫回轉굽힘 疲勞强度에 관한 硏究 = Study on High Temperature Rotary Bending Fatigue Strength of Heat Resistance Steel for Engine Valves

국문 초록 (Abstract)

Si-Cr系 耐熱鋼 SUH 3와 Cr-Ni系 stainless鋼 SUS 303을 1,060。C에서 溶體化處理하고 다시 700。C에서 10, 100時間 時效熱處理한 各 試驗片의 高溫 疲勞强度에 대한 時效 熱處理의 效果를 알기 위하여 700。C에서 高溫 回轉굽힘 疲勞試驗을 하여 다음과 같은 結果를 얻었다.
1) SUS 303의 高溫 疲勞强度는 時效 熱處理 時間의 增加와 함께 높아져서 無時效材에 대하여 10,100時間 時效材는 各各 9.1%, 10.7% 向上되나, SUH 3는 10時間 時效材의 疲勞强度가 가장 높아 無時效材에 대하여 20.6%, 100時間 時效材에 대하여 12.5% 높아졌다.
2) 700。C 高溫에서 長時間 이루어지는 高溫疲勞試驗에 있어, 溶體化處理材의 S-N 曲線 傾斜部의 기울기가 가장 급하게 나타났다.
3) SUH 3은 1,060。C에서 1時間 溶體化 處理하고 700。C에서 時效處理하는 경우 最適 時效時間은 10時間이었다.

다국어 초록 (Multilingual Abstract)

It is well-known that nowadays heat resistance materials have been widely used as the components materials of boilers, nuclear power plants and engines etc. in the fields of machine production industry.
And materials for engine components, like as the exhaust valve of combustion engine, have been asked to operate in the high temperature range of 700。C∼800。C for the high performance of engine.
Thus age hardening recently has been noticed to the heat resistance materials for further strengthening of high temperature strength, especially high temperature fatigue strength.
However, it is difficult to find out any report concerning the effects of age hardening for strengthening high temperature strength to SUH 3 and SUS 303, the heat resistance materials.
In this study the experiment was carried out as the high temperature rotary bending fatigue testing under the condition of 700。C high temperature using the materials which were 10hr., 100hr. aging heat treated SUH3, SUS303 at 700。C after solution treatment and solution treated materials 1hr. at 1,060。C for the purpose of observing the effects of the aging heat treatment on fatigue limits and obtaining the available design data.
The results obtained are summarized as follows:
1) The high temperature fatigue strength of SUS303 has been increased depend upon the extender of aging heat treatment time, thereby 10hr., 100hr. aging material obtaining the increasing rate of 9.1%, 10.7% to the solution treated material, respectively.
However, 10hr. aging treated SUH3 has most excellent in high temperature fatigue strength that has brought out the increase of 20.6% to the solution treated, and 12.5% to the 100hr. aging treatment material on SUH3.
2) The solution treatment material both SUH3, SUH303 have the highest inclination gradient on S-N curve due to the high temperature fatigue testing for long time at 700。C.
3) The optimum aging time of SUH3 has been recognized near the 10hr. at 700。C after the solution treatment of 1hr. at 1,060。C.