共查询到18条相似文献,搜索用时 65 毫秒
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针对奥氏体不锈钢和铁素体类热钢两类母材金属的特点以及相应的焊接工艺。为了研究时效因素对异种钢焊接接头碳先锋的影响规律,利用电子探针测定了铁素体母材一侧界面的碳分布状态,并为此设计了三个系列的试验,讨论了利用最小二乘法对试验数据进行拟合和对异种钢接头界面两侧碳迁移进行状态辨识的可能性,并从现象学上对碳迁移试验结果及拟合结果进行了分析,通过对试验结果的分析,发现随着服役温度的提高和时间的延长,碳迁移加剧,异种钢接头的槽,胶碳层也逐渐变宽;对于这种接头的碳迁移,用最小二乘法拟合得到满意的结果。 相似文献
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对躯工体焊缝与珠光体耐热钢母材的异种钢焊接接头,采用热处理加速碳迁移法,分析了加热温度T和保温时间t对接头增碳层厚度h的影响规律和由此而引起的该区力学性能(即缺口拉伸强度σb、冲击韧性αKU和冷弯角α)的变化。通过非线性回归分析,建立了h、σb、αKU和α对加热温度T和保温时间t的数学模型。理论分析与试验结果拟合良好。随着加热温度的提高和加时间的延长,h增大而σb、αKU和α减小。据此规律可分析接 相似文献
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由于异种钢理化特性的差异,在焊接过程中导致焊接接头的界面分布和裂纹失效机理与同种钢有所不同。文中从异种钢焊接接头的失效机制入手,介绍碳迁移导致熔合区出现软化和脆化现象,分析在焊接过程中导致其力学性能降低的本质原因,详细解释Type-II晶界和“白亮层”的形成机理,分析在高应力水平下异种钢焊接裂纹的形成机理和抑制措施。通过对异种钢焊接接头失效的本质原因进行系统性论述,为异种钢焊接失效机制的深入研究和工程应用提供理论指导,并提出针对异种钢焊接接头常见失效问题的解决方案。创新点: (1)从焊缝过渡区域的特性着手,分析异种钢焊接接头失效机制的研究进展,提出抑制过渡区域中Type-II晶界的形成、缩小“白亮层”的宽度是提高焊接接头性能的关键措施。通过整理前人对异种钢焊接过程中的碳迁移过程的定量研究,明确了由于碳迁移造成的异种钢焊接接头软化和脆化机理。(2)提出基于精确施加冷源从而定量控制焊接热应力和残余应力的分布情况,是可能改善异种钢焊接裂纹失效问题的有效措施。 相似文献
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碳钢渗氮过程中碳原子的迁移 总被引:1,自引:1,他引:0
对45,T8,T13钢试样进行气体渗氮。应用X-ray,SEM,TEM研究了渗氮过程中碳原子的迁移,结果表明:由渗氮试样的碳浓度分布曲线可精确确定渗氮层深。并对碳迁移机制进行了初探。 相似文献
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将正火40Cr钢样在不同温度下进行不同时间的气体渗氮,对其横断面进行波谱分析,发现渗氮前沿附近自始至终存在着典型的贫碳区,其两侧为富碳区,透射电镜分析结果表明,碳原子的重新分布包括碳化物的回溶、碳的扩散及碳化物长大三个过程。 相似文献
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ZHANG Zhen-xia WANG Cong-zeng ZHANG Wen-quan SU Xue-kuan Institution of Electronics Chinese Academy of Sciences Beijing China College of Materials Science Engineering Beijing University of Technology Beijing China 《材料热处理学报》2004,25(5)
CARBON migration problem has attracted a lot ofresearchers'attentions[1-3].In paper[4]the previousexperimental results about carbon migration in double-glow discharge plasma alloying process was reported.The experimental results indicate that different alloyingmetal has significant influences on carbon migrationprocess,and there is certain relationship between actualdecarburized depth and process parameters,microscopic morphology of decarburized layer.In thispaper,the differential diffusion … 相似文献
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采用双辉等离子渗铬技术,对T8钢进行了900℃温度表面渗铬合金化;使用GDA750.测量了试样渗铬合金层中Fe、Cr和C等元素的浓度分布。通过热力学分析计算,研究了渗铬合金化层形成过程中碳迁移机理和规律。指出驱动碳迁移的动力是碳的括度梯度,并推导出富碳区碳质量分数随铬质量分数变化的数学关系式:w(C)=0.8 0.3536w(Cr)。计算结果与试验结果相当吻合。 相似文献
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S.P. Kumaresh Babu S. Natarajan 《Journal of Materials Engineering and Performance》2007,16(5):620-625
Welding plays an essential role in fabrication of components such as boiler drum, pipe work, heat exchangers, etc., used in
power plants. Gas tungsten arc welding (GTAW) is mainly used for welding of boiler components. Pulsed GTAW is another process
widely used where high quality and precision welds are required. In all arc-welding processes, the intense heat produced by
the arc and the associated local heating and cooling lead to varied corrosion behavior and several metallurgical phase changes.
Since the occurrence of corrosion is due to electrochemical potential gradient developed in the adjacent site of a weld metal,
it is proposed to study the effects of welding on the corrosion behavior of these steels. This paper describes the experimental
work carried out to evaluate and compare corrosion and its inhibition in SA 516 Gr.70 carbon steel by pulsed GTAW process
in HCl medium at 0.1, 0.5, and 1.0 M concentrations. The parent metal, weld metal and heat affected zone are chosen as regions
of exposure for the study made at room temperature (R.T.) and at 100 °C. Electrochemical polarization techniques such as Tafel
line extrapolation (Tafel), linear polarization resistance (LPR), and ac impedance method have been used to measure the corrosion
current. The role of hexamine and mixed inhibitor (thiourea + hexamine in 0.5 M HCl), each at 100 ppm concentration is studied
in these experiments. Microstructural observation, surface characterization, and morphology using SEM and XRD studies have
been made on samples exposed at 100 °C in order to highlight the nature and extent of film formation. 相似文献