本文選題：異種鋼焊接接頭 + 氫滲透　； 參考：《青島科技大學(xué)》2017年碩士論文

【摘要】：目前,在船舶等工程領(lǐng)域?yàn)榱藵M足使用要求以及降低生產(chǎn)成本,常常采用異種鋼材焊接件作為結(jié)構(gòu)材料;為抑制其在海水等環(huán)境中被腐蝕,人們普遍采用陰極保護(hù)技術(shù)對鋼材進(jìn)行保護(hù),但當(dāng)保護(hù)電位不當(dāng)時可能會誘發(fā)氫致失效。本文以屈服強(qiáng)度為800~1000 MPa的異種高強(qiáng)鋼焊接接頭為研究對象,采用氫滲透試驗(yàn)、電化學(xué)測試、慢應(yīng)變速率試驗(yàn)和斷口形貌分析,并結(jié)合金相觀察、掃描開爾文探針測試和全浸腐蝕試驗(yàn)等,研究了異種高強(qiáng)鋼焊接接頭在海水中的氫滲透、氫脆敏感性和腐蝕行為規(guī)律。異種鋼焊接接頭的腐蝕性能分析結(jié)果表明:焊接接頭中較高強(qiáng)度一側(cè)母材區(qū)(1000 MPa級鋼)的耐蝕性最好,焊縫區(qū)的耐蝕程度介于兩種母材之間,兩側(cè)熱影響區(qū)最容易發(fā)生腐蝕。這可能與熱影響區(qū)的熱輸入使碳化物析出、晶格缺陷增多有關(guān)。通過異種鋼焊接接頭的電化學(xué)和氫滲透試驗(yàn)得出:異種鋼焊接接頭各區(qū)域的氫擴(kuò)散系數(shù)相差不大,但熱影響區(qū)的析氫電位最正,氫溶解度最大,說明熱影響區(qū)更易于析氫,具有較強(qiáng)的吸氫傾向。此外,陰極極化電位對高強(qiáng)鋼氫擴(kuò)散系數(shù)的影響較小,但氫的溶解度隨極化電位的負(fù)移近似以線性規(guī)律上升。對試樣進(jìn)行陰極充氫后,各微區(qū)的自腐蝕電位明顯負(fù)移,析氫電位正移,表明充氫后焊接接頭的耐腐蝕性減弱,析氫傾向加劇。氫脆敏感性研究結(jié)果顯示:陰極極化電位會顯著影響高強(qiáng)鋼的斷裂性能,隨著極化電位的負(fù)移,1000 MPa級高強(qiáng)鋼及異種鋼焊接件的抗拉強(qiáng)度和屈服強(qiáng)度變化不明顯,但延伸率和斷面收縮率逐漸降低,斷口形貌逐漸由塑性斷裂向解理和沿晶斷裂轉(zhuǎn)變,材料的氫脆危險增大。由氫脆系數(shù)評價結(jié)果可知:1000 MPa級高強(qiáng)鋼的最負(fù)陰極保護(hù)電位應(yīng)不超過-910 mV,0.8強(qiáng)度比和0.9強(qiáng)度比異種鋼焊接接頭的最負(fù)陰極保護(hù)電位分別為-940 mV和-945 mV。同時可得出:采用異種鋼焊接不會增加1000 MPa級高強(qiáng)鋼的氫脆敏感性。
[Abstract]:At present, in order to meet the requirements of use and reduce the production cost of ships and other engineering fields, dissimilar steel welds are often used as structural materials, and in order to restrain their corrosion in seawater and other environments, Cathodic protection technology is widely used to protect steel, but hydrogen-induced failure may be induced when the protection potential is not present. In this paper, the welded joints of dissimilar high strength steel with yield strength of 800 ~ 1 000 MPa were studied. Hydrogen permeation test, electrochemical test, slow strain rate test, fracture morphology analysis and metallographic observation were used. The hydrogen permeation, hydrogen embrittlement sensitivity and corrosion behavior of dissimilar high strength steel welded joints in seawater were studied by scanning Kelvin probe test and full immersion corrosion test. The results of corrosion resistance analysis of dissimilar steel welded joints show that the corrosion resistance of the welded joints is the best in the higher strength side of the base metal zone (1 000 MPa grade steel), the corrosion resistance of the weld zone is between the two kinds of base metal, and the heat affected zone on both sides is the most prone to corrosion. This may be related to the precipitation of carbides and the increase of lattice defects due to the heat input in the HAZ. Through electrochemical and hydrogen permeation tests of dissimilar steel welded joints, it is concluded that the hydrogen diffusion coefficient of dissimilar steel welded joints is not different, but the hydrogen evolution potential is the most positive and the hydrogen solubility is the largest in the heat affected zone, which indicates that the heat affected zone is easier for hydrogen evolution. It has a strong tendency to absorb hydrogen. In addition, the cathodic polarization potential has little effect on the hydrogen diffusion coefficient of high strength steel, but the hydrogen solubility increases linearly with the negative shift of the polarization potential. After cathodic hydrogen charging, the self-corrosion potential and hydrogen evolution potential of each microzone are obviously negative, which indicates that the corrosion resistance of welded joints is weakened and the tendency of hydrogen evolution is increased after hydrogen charging. The results of hydrogen embrittlement sensitivity study show that cathodic polarization potential can significantly affect the fracture properties of high strength steel. With the negative shift of polarization potential, the tensile strength and yield strength of welded parts of 1 000 MPa high strength steel and dissimilar steel have no obvious change. However, the elongation and section shrinkage decreased gradually, the fracture morphology gradually changed from plastic fracture to cleavage and intergranular fracture, and the hydrogen embrittlement danger of the material increased. The results of hydrogen embrittlement coefficient show that the negative cathodic protection potential of high strength steel of 1 000 MPa grade should not exceed -910 MV / 0. 8 and 0. 9% respectively. The negative cathodic protection potentials of welded joints of dissimilar steels are -940 MV and -945 MV, respectively. At the same time, the hydrogen embrittlement sensitivity of 1000 MPa high strength steel can not be increased by using dissimilar steel welding.
【學(xué)位授予單位】：青島科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG407

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