异种高强钢焊接接头腐蚀及氢脆性能研究

发布时间：2018-04-29 13:16

本文选题：异种钢焊接接头 + 氢渗透　；参考：《青岛科技大学》2017年硕士论文

【摘要】：目前,在船舶等工程领域为了满足使用要求以及降低生产成本,常常采用异种钢材焊接件作为结构材料;为抑制其在海水等环境中被腐蚀,人们普遍采用阴极保护技术对钢材进行保护,但当保护电位不当时可能会诱发氢致失效。本文以屈服强度为800~1000 MPa的异种高强钢焊接接头为研究对象,采用氢渗透试验、电化学测试、慢应变速率试验和断口形貌分析,并结合金相观察、扫描开尔文探针测试和全浸腐蚀试验等,研究了异种高强钢焊接接头在海水中的氢渗透、氢脆敏感性和腐蚀行为规律。异种钢焊接接头的腐蚀性能分析结果表明:焊接接头中较高强度一侧母材区(1000 MPa级钢)的耐蚀性最好,焊缝区的耐蚀程度介于两种母材之间,两侧热影响区最容易发生腐蚀。这可能与热影响区的热输入使碳化物析出、晶格缺陷增多有关。通过异种钢焊接接头的电化学和氢渗透试验得出:异种钢焊接接头各区域的氢扩散系数相差不大,但热影响区的析氢电位最正,氢溶解度最大,说明热影响区更易于析氢,具有较强的吸氢倾向。此外,阴极极化电位对高强钢氢扩散系数的影响较小,但氢的溶解度随极化电位的负移近似以线性规律上升。对试样进行阴极充氢后,各微区的自腐蚀电位明显负移,析氢电位正移,表明充氢后焊接接头的耐腐蚀性减弱,析氢倾向加剧。氢脆敏感性研究结果显示:阴极极化电位会显著影响高强钢的断裂性能,随着极化电位的负移,1000 MPa级高强钢及异种钢焊接件的抗拉强度和屈服强度变化不明显,但延伸率和断面收缩率逐渐降低,断口形貌逐渐由塑性断裂向解理和沿晶断裂转变,材料的氢脆危险增大。由氢脆系数评价结果可知:1000 MPa级高强钢的最负阴极保护电位应不超过-910 mV,0.8强度比和0.9强度比异种钢焊接接头的最负阴极保护电位分别为-940 mV和-945 mV。同时可得出:采用异种钢焊接不会增加1000 MPa级高强钢的氢脆敏感性。
[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.
【学位授予单位】：青岛科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG407

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