共查询到18条相似文献,搜索用时 156 毫秒
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采用钛钙型药皮堆焊焊条D172,以手工电弧焊工艺在基体材料上堆焊一定厚度的耐磨金属.为了消除焊态过程中残留的残余应力,提高堆焊层熔敷金属的耐磨性能,本试验对基体材料进行了焊前预热,控制层间温度,焊后回火等工艺,分析了焊态、回火工艺下获得的耐磨熔敷金属的显微组织和显微硬度.结果表明,回火温度在400℃时,堆焊层熔敷金属显微组织和硬度与焊态基本一致,其显微组织主要为马氏体和网状残奥氏体;550℃时,残余奥氏体转变为马氏体,且碳化物析出量增多,硬度升高;700℃时,马氏体分解,产生大量碳化物和α-Fe铁素体,硬度显著降低;保温时间延长,堆焊层熔敷金属显微组织和硬度变化不大. 相似文献
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分别采用D227和D237两种堆焊焊条,在45号钢基体上进行了焊条电弧焊堆焊试验.分析了在相同焊接条件下获得的堆焊层金属的显微组织和显微硬度,讨论了合金元素对堆焊层金属显微组织及显微硬度的影响.研究表明,堆焊金属与基体金属具有良好的冶金结合,第一层堆焊金属受基体金属的稀释程度影响明显,界面处金属过渡层的宽度因焊条种类的不同而异;各层堆焊金属中合金元素Cr、Mo、V含量随堆焊层数的增加而提高,堆焊金属的显微组织及显微硬度与堆焊焊条合金元素的含量有关,与其硬质相的类型、性能及分布等有关. 相似文献
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选用D057(EDPCrMoV-Al-15)堆焊焊条,采用焊条电弧焊在Q345B钢基体上以不同的焊接电流进行了堆焊试验.多层堆焊后,对熔覆金属进行回火热处理,并分析回火后堆焊熔覆金属的显微组织.两种焊接电流所得堆焊层的显微组织无明显差别,所得堆焊熔覆金属的组织:第一道为回火索氏体;第二道为回火索氏体+白色残余奥氏体枝晶组织;第三道为回火索氏体+马氏体+白色残余奥氏体枝晶组织,其中马氏体由残余奥氏体分解所得.堆焊熔覆金属回火后的显微硬度约为600 HV. 相似文献
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采用D132焊条在45钢母材金属上进行焊条电弧堆焊,熔敷金属为两层。为了减小熔敷金属内的焊接残余应力,改善其组织结构和硬度,对试样进行焊后热处理,回火温度分别为400℃、550℃和700℃,保温时间均为2 h。分析焊态及焊后热处理的熔敷金属显微组织和硬度,试验结果表明:焊态时的熔敷金属存在魏氏组织,但随着热处理温度的升高,魏氏组织消失,残余奥氏体的含量却在增多;对比发现,熔敷金属硬度值在回火温度为400℃时最大,在回火温度为700℃时最小,回火温度为550℃时熔敷金属的硬度值处在二者之间,由此可见,随着温度升高熔敷金属硬度值却在下降。 相似文献
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罗怡 《稀有金属材料与工程》2017,46(2):496-502
研究了真空电子束焊接热效应对AZ91D和AZ31B镁合金焊缝显微硬度的影响机制,实验结果表明,真空电子束焊接热效应对AZ91D、AZ31B镁合金焊缝均有不同程度的强化作用。当焊接热输入较大时,影响AZ91D镁合金焊缝硬度的主要因素为因Mg元素烧损而产生的强化相变化,焊接热输入越大,焊缝中的Mg元素烧损增加,使Al元素含量(质量分数,下同)逐渐增加,从而在焊缝中生成了更多的强化β相,使焊缝硬度得到提高,产生的强化相越多,焊缝硬度相对越大;当焊接热输入较小时,影响AZ31B镁合金焊缝硬度的主要因素为焊后冷却速度,焊接热输入越小,焊后冷却速度越快,焊缝晶粒越细小,焊缝硬度相对越大。 相似文献
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为避免热冲压高强钢电阻点焊在热输入较大时产生飞溅和满足激光点焊装配要求,提出一种将电阻点焊和激光点焊组合的新焊接工艺方法.通过电阻+激光组合点焊工艺获得了热冲压高强钢焊接接头,分析了接头各区域的显微组织、显微硬度分布、力学性能,并分析了断裂模式及其断裂机理.结果表明,电阻+激光组合点焊接头明显分为电阻焊接区和激光焊接区.母材和激光焊核区硬度值较大,与回火区对应的软化区硬度值下降约60%,激光环外侧软化区为拉剪断裂薄弱环节.此种组合工艺获得的焊接接头相对于单独电阻点焊或激光点焊强度和韧性都有明显提高. 相似文献
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Laser welding is an important process for fabricating complex components involving NiTi shape memory alloy. As welding is a thermal process, the amount of heat input and the rate of cooling have significant impact on the microstructure and hence the resultant characteristics of NiTi. In this study, the effect of laser welding and post-weld-annealing from 573 K to 1173 K on the thermal phase transformation behaviors, tensile deformation and micro-hardness characteristics of the laser-welded NiTi thin foils were investigated. It was found that the as-welded sample exhibited inferior super-elasticity compared to the base material, and the super-elasticity could be partially restored by annealing at 573 K. On the other hand, annealing of the weldment above the recrystallization temperature would lower the super-elasticity. 相似文献
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在相同热输入下分别采用熔化极活性气体保护焊(MAG)和钨极氩弧焊(TIG)进行1 000 MPa级熔敷金属试验,通过光学显微镜、透射电镜及断口分析等手段研究焊接方法对其组织和性能的影响. 结果表明,MAG焊熔敷效率明显高于TIG焊,MAG焊中出现了明显的"指状熔深". MAG焊熔敷金属及道间热影响区组织明显较TIG焊粗化. TIG焊熔敷金属组织细化、分布取向多样化且均匀分布的较多残余奥氏体是TIG焊低温冲击韧性优异的原因之一;MAG焊中生成大量非金属夹杂物易成为解理断裂起裂源,是导致熔敷金属冲击韧性恶化的因素之一. TIG焊力学性能明显优于MAG焊,这与焊接方法所导致的组织构成及夹杂物有直接关系. 相似文献
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《Science & Technology of Welding & Joining》2013,18(4):233-239
AbstractThe fatigue crack growth behaviours of two weld metals deposited by shielded metal arc welding (SMAW) and flux cored arc welding (FCAW) processes have been compared. Load carrying cruciform joints, with a lack of penetration (LOP) defect, were fabricated from high strength, quenched and tempered steel of ASTM 517 ‘F’ grade. Fatigue crack growth experiments were carried out in a vertical pulsator (Schenck 200 kN capacity) with a frequency of 30 Hz under constant amplitude loading (stress ratio R = 0). It was found that the fatigue crack growth resistance of the weld metal deposited by the SMAW process is superior, compared to the weld metal deposited by the FCAW process. The high heat input involved in the FCAW process probably contributes to the changes in weld metal properties, which result in a change in fatigue crack growth behaviour. 相似文献
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Effect of heat input on microstructure and properties of welded joint in magnesium alloy AZ31B 总被引:3,自引:0,他引:3
Using the optical microscope, tensile test machine and micro-hardness meter, the effect of heat input on the microstructure and mechanical properties in fusion welding joints of AZ31B wrought alloys was investigated systematically, the mechanism on joint properties losing was analyzed, and a valid method to improve joint properties of the magnesium alloy fusion welding was explored. The results show that the heat input has an obvious effect on the microstructure and properties. Under the condition of penetration, with the heat input decreasing, the crystal grain in the weld and heat-affected zone (HAZ) becomes fine, the width of HAZ becomes obviously narrow, and the molding of the weld is improved, so the tensile strength and elongation are increased and the hardness of joints is improved. When the heat input reaches 60 J/mm, the high quality joints can he gained. 相似文献
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