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Title: | 釩添加對硼系超高強度鋼之氫脆性質研究 Hydrogen Embrittlement of Vanadium-added Ulra High Strength Boron Steel |
Authors: | Hsiang-Yu Wang 王翔宇 |
Advisor: | 林新智 |
Keyword: | 氫脆,超高強度鋼,回火麻田散鐵, hydrogen embrittlement,ultra high strength steel,tempered martensite, |
Publication Year : | 2014 |
Degree: | 碩士 |
Abstract: | 15B30為硼系麻田散鐵超高強度鋼,雖然具有強度與硬化能高之優點,在結構鋼與汽車鋼板應用上有傑出的表現,但在實際應用上發現超高強度鋼容易受到氫脆破壞之影響。本實驗研究目標為建立氫脆破壞之評估方法以及抑制15B30超高強度鋼氫脆之方法,包括微合金元素之添加和熱處理程序。15B30在經過水淬後強度高達2000MPa,但延伸率只有4%,在回火處理後延性上升至6到7%。本實驗以化學強制充氫拉伸作為評估氫脆破壞之方法,在進行化學充氫30分鐘後,最大抗拉強度損失率高達70%,在經過回火熱處理後發現200℃回火具有較好的抗氫脆能力,其原因為ε碳化物的析出在板條內部,提供氫捕集位置,而300℃和400℃由於雪明碳鐵大量析出在原沃斯田鐵晶界以及板條介面上形成連續的雪明碳鐵,在氫含量高的狀態下,氫聚集於雪明碳鐵與基材的界面反而使材料更容易發生穿晶或沿晶破壞。600℃的回火使材料變態為肥粒鐵,充氫拉伸試驗發現破斷面上只有周圍存在小面積的穿晶破壞,並且其最大抗拉強度損失率只有2%,具有優良的氫脆抵抗能力。而從定應力拉伸發現添加釩元素的15B30V存活時間較15B30高,由此可知添加釩元素在淬火的狀態下會提高材料抵抗氫脆之能力。 15B30 steel, one kind of ultra-high strength boron steel, is prone to hydrogen embrittlement in practical usage. The aim of this research is to build up an evaluation method of hydrogen embrittlement and to improve hydrogen embrittlement by micro-alloy element addition and appropriate heat treatment. After water quenching, the tensile strength of 15B30 could reach 2000MPa with a low elongation about 4%. Tempering process decreases specimen strength but increases the elongation up to 6%. To evaluate the hydrogen embrittlement in this research, the specimens are subjected tensile test instantly after chemical hydrogen charging. The percentage loss of UTS after hydrogen charging for water quenched 15B30 is about 70%. Among various tempering processes at different temperatures, 200℃ tempering is found to promote effectively the resistance of hydrogen embrittlement. This feature is ascribed to that the ε precipitates in the martensite lath can provide hydrogen trapping sites. However, 300℃ and 400℃ tempering make specimens prone to hydrogen embrittlement due to the formation of cementite along the prior austenite grain boundary and the martensite lath interface. The ferrite recrystallization after 600℃ tempering exhibits an excellent hydrogen embrittlement resistance and hence has a lower percentage loss of UTS. Constant load test shows that vanadium addition improves effectively the hydrogen embrittlement of 15B30 steel because the 15B30V steel could sustain a longer fracture time during the testing. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/16953 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 材料科學與工程學系 |
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ntu-103-1.pdf Restricted Access | 16.27 MB | Adobe PDF |
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