搅拌摩擦点焊疲劳性能研究

使用回填式搅拌摩擦点焊设备,对6系列铝合金弧焊焊接接头进行了搅拌摩擦点焊补焊试验,点焊补焊后试样表面平整光滑。对搅拌摩擦点焊补焊、MIG焊焊接接头进行了疲劳性能试验,研究发现,搅拌摩擦点焊补焊接头的疲劳寿命高于MIG焊焊接接头,断口组织更为致密。     

基于复合搅拌摩擦焊的6063铝合金焊接接头残余应力控制研究

分别采用普通搅拌摩擦焊和带随焊旋转滚压装置及随焊水雾冷却装置的复合式搅拌摩擦焊对6063铝合金薄板进行焊接试验,并对两组试验的纵向残余应力数据进行对比分析。试验结果表明:普通搅拌摩擦焊接焊后试样的最大纵向残余应力是拉应力,其值为83.6 MPa,位于前进侧的搅拌头轴肩边缘处。前进侧与返回侧两侧的纵向残余应力基本对称,从焊缝中心到边缘,纵向残余应力由小变大后再变小,最后转变为压应力;复合搅拌摩擦焊接焊后试样的最大纵向残余应力比普通搅拌摩擦焊减小了38.9 MPa,其分布与普通搅拌摩擦焊时基本相同,但其变化范围窄。这说明随焊旋转滚压装置及随焊水雾冷却装置能有效减小纵向残余应力,从而能减小焊后变形,提高搅拌摩擦焊接接头质量。     

超声波测定摩擦焊接头残余应力

采用１５ＭＨｚ超声聚焦探头对４５号钢摩擦焊接头进行试验检测,根据有限弹性变形理论建立了超声波测定摩擦焊接头残余应力的计算模型,并计算出接头中轴向残余应力和径向残余应力的分布规律。结果表明,摩擦焊接头焊缝区和近缝区的轴向残余应力为压应力,而远离焊缝区域为拉应力;接头内径向残余应力在轴心处为压应力,随着远离轴心逐渐由拉应力变为压应力,在接头边缘区域为拉应力。试验结果还表明材料的各向异怀对超声波测定摩擦     

基于应力-强度干涉模型的摩擦焊接头寿命预测

应力-强度干涉模型是可靠性设计的基本理论模型,以此模型为基础,利用电站锅炉12Cr1MoV钢管摩擦焊接头的高温内压爆破持久加速试验数据外推得到的指定寿命持久强度极限和摩擦焊接头内部压力产生的折算工作应力,建立了带有可靠度指标的寿命预测模型。计算结果表明,摩擦焊接头在设计寿命期内是可靠的,摩擦焊这种工艺方法的质量是稳定的。     

K418涡轮盘与42CrMo轴异种材料惯性摩擦焊研究

采用惯性轴向摩擦焊技术对镍基K418高温合金与42CrMo调质钢两种异种材料进行了焊接工艺试验,并分析焊接接头的显微组织,测试其力学性能.结果表明,惯性摩擦焊过程中发生摩擦面转移现象,碳原子扩散导致K418侧含有少量非连续网状碳化物,焊接界面两侧硬度均匀过渡,焊接接头抗拉强度均在750 MPa以上,整体抗拉强度高,获得了优良的焊接接头,惯性摩擦焊工艺适合于焊接异种材料.     

铝合金T形接头搅拌摩擦焊研究进展

铝合金广泛应用于航空航天、汽车、船舶以及化学工业等领域中,T形接头作为铝合金薄板结构组装中的重要连接形式,对其焊接质量的要求也逐渐提高。采用传统熔焊的方式焊接铝合金T形接头时会导致应力集中、焊后残余变形大、多孔性等一系列问题。传统的搅拌摩擦焊具有产热少、焊前不用开坡口、焊后残余变形小等优势,很好的解决了这一技术难点。但是,传统的搅拌摩擦焊在焊后会产生大量的飞边以及弧纹缺陷。静止轴肩搅拌摩擦焊技术作为一种新型的搅拌摩擦焊技术,在铝合金T形接头焊接中具有很大的优势。文中综述了铝合金T形接头焊接特点、传统搅拌摩擦焊以及静止轴肩搅拌摩擦焊在T形接头中的研究进展,并对搅拌摩擦焊技术在T形接头的应用前景进行了展望。     

铝合金搅拌摩擦与MIG焊接接头疲劳性能对比试验

根据疲劳S-N曲线试验结果,对5A06铝合金搅拌摩擦焊(FSW)和MIG焊接接头的疲劳性能进行了初步比较,分析讨论了搅拌摩擦焊过程中所产生的焊接缺陷对其疲劳性能的影响.结果表明,在焊态下由于焊接接头几何形状等的影响,FSW的疲劳强度明显高于MIG焊接接头;对FSW焊缝根部的"吻接"缺陷(kissing-bonds)是降低FSW焊接接头疲劳寿命的主要因素,旋转搅拌工具在焊缝表面形成的多余飞边将对疲劳行为产生明显影响.     

SMA490BW耐侯钢超射流过渡焊接头残余应力与疲劳性能

分别采用超射流过渡MAG焊和传统的脉冲MAG焊,对转向架焊接构架用SMA490BW耐侯钢进行了对接焊试验,测试分析了接头的残余应力和疲劳强度。结果表明:与传统的脉冲MAG焊相比,采用超射流过渡MAG焊接工艺时,SMA490BW耐侯钢接头的残余应力峰值仍位于焊缝及近焊缝区域,但残余应力明显减小;超射流过渡MAG接头在指定寿命107周次的疲劳强度提高4%。     

铝合金焊接接头冲击强化的性能

为了提高铝合金焊接接头的力学性能,试验分别采用超声波和调Q脉冲YAG激光对A6061-T6铝合金焊接接头焊趾附近处进行冲击强化,研究了超声波和激光冲击强化下铝合金焊接接头的性能.两种冲击强化模式下,铝合金焊接接头焊趾处近表面均发生了冲击强化效果,并产生了较大的残余压应力,超声波和激光冲击强化后产生的最大残余压应力分别为 -158 MPa和 -145 MPa左右.超声波与激光冲击强化铝合金焊接接头的疲劳寿命差别不大,均比焊态下试样的疲劳寿命提高1倍以上.两种冲击强化方法的疲劳试验样件断裂位置均发生在基体金属上,而焊趾处没有疲劳裂纹产生.     

惯性摩擦焊接头组织与性能分析

采用惯性摩擦焊方法进行了CH4169高温合金的焊接,用金相显微镜、扫描电镜下EDS分析和硬度试验等方法分析了接头组织和性能,结果表明：惯性摩擦焊焊缝与母材无明显界线,结合良好,焊缝成份均匀与母材基本相同,接头硬度分布均匀,为其在工程实际中的应用提供了有效而可靠的技术保证。     

变幅载荷下摩擦焊接头疲劳寿命的分布及模拟

试验研究并分析了45钢摩擦焊接头切口件恒幅载荷下的疲劳性能,表明其疲劳寿命结果可很好地表示当量应力幅的函数,即Ni=C[△σ∧2/（1 n）eqv-(△σeqv)∧2/(1 n)th]∧-2,表达式中疲劳抗力系数C和疲劳门槛值（△σeqv)th服从对数正态分布。根据C和（△σeqv）th的物理意义及概率分布,可知疲劳试件个体间的差异可以由C、（△σeqv)th来区别,而疲劳试验结果的随机分散性产生于试件个体间的差异,据此提出了一种新的模拟45钢摩擦焊接头切口件变幅载荷下疲劳寿命试验及其分布的方法,给出了相应的模拟计算步骤,模拟结果与试验结果进行了比较,结果表明,45钢摩擦焊接头切口件在变幅载荷下的疲劳寿命分布的模拟结果服从对数正态分析,并与试验结果符合得很好。因此该模式方法可用于摩擦焊接结构的疲劳可靠性分析,从而节省大量的人力、物力。     

Characterization of Mechanical Properties and Residual Stress in API 5L X80 Steel Welded Joints

The use of high-strength and low-alloy steels, high design factors and increasingly stringent safety requirements have increased the operating pressure levels and, consequently, the need for further studies to avoid and prevent premature pipe failure. To evaluate the possibility of improving productivity in manual arc welding of this type of steel, this work characterizes the mechanical properties and residual stresses in API 5L X80 steel welded joints using the SMAW and FCAW processes. The residual stresses were analyzed using x-ray diffraction with the sin² ψ method at the top and root of the welded joints in the longitudinal and transverse directions of the weld bead. The mechanical properties of the welded joints by both processes were characterized in terms of tensile strength, impact toughness and Vickers microhardness in the welded and shot peening conditions. A predominantly compressive residual stress was found, and shot peening increased the tensile strength and impact toughness in both welded joints.     

基于SINTAP标准的海底外输管线安全评定

采用欧共体提出的结构完整性评定方法SINTAP（Structural Integrity Assessment Pmcedure）对海底外输管线API5L X56焊接接头埋藏裂纹进行了安全评定。根据母材和全焊缝拉伸试验结果建立评定曲线；根据BS7448：Part4标准采用多试样方法进行了低温断裂韧性试验，建立了焊缝和HAZ的CTOD-R阻力曲线，从而确定了启裂CTOD值δ0.2。在评定计算中取不同水深的应力最大值，考虑残余应力的影响，针对由DNV OS-F101中规定的最大错位情况，给出了在铺设条件下的容许埋藏裂纹尺寸。为管线铺设工程中的焊接缺陷验收和拒收提供了依据。     

Fatigue strength improvement of stainless steel using weld toes dressing with low transformation temperature welding wire

In the present study, low transformation temperature welding wire (LTTW), which can induce residual compressive stress around 304L welded joints, has been developed to improve the fatigue performance of welded joints. Procedure of design and chemical composition of weld metal and deposited metal of LTTW are introduced. The microstructure of weld metal of LTTW is composed of low carbon martensite and residual austenite. The residual stress distribution of a single welding bead of LTTW was measured and the result shows that compressive residual stress is generated. In addition, fatigue test was also carried out on no-load cruciform welded joints of 304L stainless steel under three conditions: as welded, 308L dressing and LTTW dressing. The result shows that the fatigue life of LTTW dressing joints (2×10⁶ cycles) is improved by 14–23 times and 3–6 times compared with that of as welded joints and 308L dressing joints.     

Using friction welding for producing heat exchanger equipment from martensitic 15Kh5M steel

The results of mechanical and other types of tests of metal of welded joints in pipe blanks of 15Kh5M martensitic steel, produced by friction welding with rotation, are presented. On the basis of the analysis of the test results it is concluded that 15Kh5M can be efficiently welded by friction welding and that the method can also be used for producing the tube–tube plate sections of heat exchangers made of 15Kh5M steel with appropriate modernization of welding equipment.     

Fatigue properties of welded joints using steel with high resistance to fatigue crack growth

It has been generally recognized that the fatigue life of welded joints is little influenced by the strength of steels owing to the high-stress concentration and the tensile residual stress near the weld toe. In this paper, improvement of the fatigue life of welded joints using steel with high resistance to fatigue crack growth (ferrite/martensite (F/M) steel) is investigated. F/M steel has a microstructure with an elongated and banded martensite phase distributed in a ferrite matrix and a fatigue crack growth rate of about one-half to one-tenth in the thickness direction, compared with conventional steel. As a result, the fatigue life of an out-of-surface gusset-welded joint increases with the decrease of the fatigue crack growth rate. The fatigue life of welded joints using F/M steel with the highest resistance to fatigue crack growth increases to about twice that of joints using conventional steel. Whereas the fatigue crack growth rate decreases significantly, the fatigue life of welded joints increases only slightly. This can be attributed to the stress ratio independent of the fatigue crack growth rate. In other words, the fatigue crack growth rate of F/M steel increases with the increase of the stress ratio, approaching that of conventional steel. In the case of welded joints, even if a fatigue test is carried out at a low-stress ratio, the region near the weld toe is under a high-stress ratio due to tensile residual stress. Therefore, improvement of the fatigue life of welded joints becomes comparatively small so that the effect of fatigue crack retardation of F/M steel decreases.     

摩擦焊接头温度场二维轴对称瞬态数值模拟

采用交替方向隐式差分法对３５号钢管摩擦焊接头二维轴对称瞬态温度场进行数值模拟,利用热电偶测温技术对摩擦焊接头易测准部位的焊拉热循环进行了计算机实时自动检测。结果表明,所建立的数学模型及计算结果是合理的并有助于制订合理的焊接工艺规范。     

Influence of Multi-Thermal Cycle and Constraint Condition on Residual Stress in P92 Steel WeldmentEI北大核心CSCD

P92 steel is a typical 9%similar to 12% Cr ferrite heat-resistant steel with good high temperature creep resistance, relatively low linear expansion coefficient and excellent corrosion resistance, so it is one of important structural materials used in supercritical thermal power plants. Fusion welding technology has been widely used to assemble the parts in thermal power plant. When the supercritical unit is in service, its parts are constantly subjected to combination of tensile, bending, twisting and impact loads under high temperature and high pressure, and many problems such as creep, fatigue and brittle fracture often occur. It has been recognized that welding residual stress has a significant impact on creep, fatigue and brittle fracture, so it is necessary to study the residual stress of P92 steel welded joints. The evolution and formation mechanism of welding residual stress in P92 steel joints under multiple thermal cycles were investigated in this work. Based on SYSWELD software, a computational approach considering the couplings among thermal, microstructure and mechanics was developed to simulate welding residual stress in P92 steel joints. Using the developed computational tool, the evolution of residual stress in Satoh test specimens was studied, and welding residual stress distribution in double-pass welded joints was calculated. In the numerical models, the influences of volume change, yield strength variation and plasticity induced by phase transformation on welding residual stress were taken into account in details. Meanwhile, the hole-drilling method and XRD method were employed to measure the residual stress distribution in the double-pass welded joints. The simulated results match the experimental measurements well, and the comparison between measurements and predictions suggests that the computational approach developed by the current study can more accurately predict welding residual stress in multi-pass P92 steel joints. The simulated results show that the longitudinal residual stress distribution around the fusion zone has a clear tension-compression pattern. Compressive longitudinal residual stresses generated in the fusion zone and heat affected-zone (HAZ) in each pass, while tensile stresses produced near the HAZs. In addition, the numerical simulation also suggests that the transverse constraint has a large influence on the transverse residual stress, while it has an insignificant effect on the longitudinal residual stress.     

地质钻杆摩擦焊接头组织与性能

首次采用摩擦焊接工艺对地质勘探用钻杆的管体与接头进行了焊接试验。探讨了不同的热处理工艺条件对DZ60钢钻杆管体与40Cr钢接头摩擦焊接头组织与性能的影响,并与采用热墩粗工艺生产的钻杆管体组织与性能进行了对比。试验结果表明,采用摩擦焊接及焊后调质热处理工艺制造的DZ60地质钻杆焊接接头的常规力学性能指标均高于地矿部DZ60地质钻杆管材的技术标准规定的数值,并优于采用现行热墩粗工艺制造的钻杆管材的力学性能数值。同时发现,采用合适的焊后回火热处理温度,可以有效提高焊接接头的抗拉强度与屈服强度,使其各项力学性能达到DZ60钻杆管材的技术标准,从而有效减少地质钻杆摩擦焊接头焊后热处理工艺,降低制造成本。