Please use this identifier to cite or link to this item:
http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/76752
Title: | 深冷處理與熱處理程序對硼系超高強度鋼之
氫脆性質研究 The influence of sub-zero and tempering treatments on the hydrogen embrittlement of ultra-high strength boron steel |
Authors: | Wen-Hao Chien 簡文昊 |
Advisor: | 林新智 |
Keyword: | 超高強度鋼,深冷處理,回火麻田散鐵,氫脆, ultra-high strength steel,sub-zero treatment,tempered martensite,hydrogen embrittlement, |
Publication Year : | 2016 |
Degree: | 碩士 |
Abstract: | 15B30為硼系超高強度鋼,在結構鋼及汽車鋼板應用上有出色的表現。淬火後呈現麻田散鐵組織,其抗拉強度高達1768Mpa,再經由200℃~400℃回火後顯現回火麻田散鐵組織,其抗拉強度仍可維持1200MPa以上。然而超高強度鋼之缺點為易受到氫脆效應的影響,在應用上此因素可能會造成無法預測之破壞。本實驗研究之目的為利用化學充氫及拉伸試驗檢測15B30鋼材之氫脆以及延遲破壞行為,並實施深冷處理與不同回火熱處理程序,藉以改善15B30鋼材之氫脆現象。
未實施深冷處理時,15b30水淬後仍有約3.6%的殘留沃斯田鐵組織,殘留沃斯田鐵組織存在於原沃斯田鐵晶界以及麻田散鐵板條間。15b30其淬火態之抗氫脆能力差,回火過後抗氫脆能力有明顯的提升,其中200℃回火時,其抗氫脆能力最佳,主要之原因為在低溫回火時,麻田散鐵板條內部析出細小的碳化物,提供了氫捕集位置,但在300℃以及400℃回火時,殘留沃斯田鐵會分解並析出碳化物。而此類碳化物屬於非整合性(incoherent)析出物,為不可逆之氫捕集位置,其周圍會有較多量之氫原子聚集,因而容易誘發氫脆現象。 15B30合金鋼淬火組織經過深冷處理後,其抗氫脆能力可明顯提升。此現象係因為深冷處理可以降低存在於麻田散鐵板條介面之殘留沃斯田鐵量,因而可減少300℃及400℃回火時於板條介面產生粗大碳化物,進而有效提升其抗氫脆能力。 15B30 steel is an ultra-high strength boron steel and exhibits excellent performance in the structural and automotive applications. It exhibits a high tensile strength of 1768MPa in the as-quenched state. After tempering at 200℃~400℃, its tensile strength still remains above 1200Mpa. However, the ultra-high strength steels are prone to suffer the problem of hydrogen embrittlement, which will induce the unpredicted fracture during the practical applications. The present study aims at examining the behavior of hydrogen embrittlement of the 15B30 steel, by using the methods of hydrogen charging and mechanical tensile test. Meanwhile, the sub-zero treatment and a series of tempering processes are also carried out to improve the hydrogen embrittlement of 15B30 steel. The as-quenched 15B30 specimen without sub-zero treatment has about 3.6% retained austenite which exists along the prior austenite grain boundaries and the interfaces between martensite laths. The as-quenched 15B30 exhibits a worse resistance of hydrogen embrittlement. After tempering, the resistance of hydrogen embrittlement is improved significantly. The specimen with 200℃ tempering has the best resistance of hydrogen embrittlement. This feature is ascribed to the formation of fine carbides within the interior of martensite laths. These fine carbides can provide the hydrogen-trapping sites. However, during the tempering at 300℃ and 400℃, the retained austenite will decompose and the cementite forms. The cementite precipitated at higher temperatures is incoherent and belongs to the irreversible hydrogen trapping site. More hydrogen atoms will concentrate around these sites and result in a weak resistance of hydrogen embrittlement. The as-quenched 15B30 specimen can increase obviously the resistance of hydrogen embrittlement through the sub-zero treatment. This feature is ascribed to that the sub-zero treatment reduces the amount of retained austenite and leads to the reduction of coarse cementite precipitated at the interfaces between martensite laths during the tempering process. Therefore, the resistance of hydrogen embrittlement of 15B30 steels can be effectively improved even after tempering at 300℃ and 400℃. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/76752 |
DOI: | 10.6342/NTU201601193 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 材料科學與工程學系 |
Files in This Item:
File | Size | Format | |
---|---|---|---|
ntu-105-R03527051-1.pdf Restricted Access | 9.44 MB | Adobe PDF |
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.