Effect of friction welding conditions on joint properties of austenitic stainless steel joints by friction stud welding

This study focuses on the opening mode of induction bends; this mode represents the deformation outside a bend. Bending experiments on induction bends are shown and the manner of failure of these bends was investigated. Ruptures occur at the intrados of the bends, which undergo tensile stress, and accompany the local reduction in wall thickness, i.e. necking that indicates strain localization. By implementing finite element analysis (FEA), it was shown that the rupture is dominated not by the fracture criterion of material but by the initiation of strain localization that is a deformation characteristic of the material. These ruptures are due to the rapid increase in local strain after the initiation of strain localization and suddenly reach the fracture criterion. For the evaluation of the deformability of the bends, a method based on FEA that can predict the displacement at the rupture is proposed. We show that the yield surface shape and the true stress–strain relationship after uniform elongation have to be defined on the basis of the actual properties of the bend material. The von Mises yield criterion, which is commonly used in cases of elastic–plastic FEA, could not predict the rupture and overestimated the deformability. In contrast, a yield surface obtained by performing tensile tests on a biaxial specimen could predict the rupture. The prediction of the rupture was accomplished by an inverse calibration method that determined the true stress–strain relationship after uniform elongation.     

奥氏体不锈钢小径管焊接接头的相控阵超声检测

针对奥氏体不锈钢小径管焊接接头的检测难点,开展了专用试块设计、检测参数优化、检测能力验证、缺陷分析评定等相关技术的研究,总结形成了一套相控阵超声检测工艺和评定方法.检测工艺适用于外径为32～100 mm,壁厚为4～20 mm的奥氏体不锈钢小径管焊接接头的质量评定,通过在火力发电机组安装和检修工程中的成功应用,验证了该工...     

奥氏体不锈钢焊接接头在含硫介质中的腐蚀性

利用恒电位极化曲线法及金相显微分析方法,研究了奥氏体不锈钢手弧焊焊接接头在含Na2S溶液中的腐蚀行为.结果表明,采用A102焊条的焊缝,其耐蚀性优于A307焊条焊缝;20℃条件下,Na2S质量分数的增加加速腐蚀反应的阴、阳极过程;在Na2S质量分数一定的条件下,温度升高到80℃时,在阳极极化区有钝化现象.     

奥氏体不锈钢焊缝金属的电化学腐蚀性能

采用PASTAT30型恒电位仪测试了SUS 316奥氏体不锈钢钨极氩弧焊TIG,熔化极氩弧焊MIG和钨极氩弧焊加填丝TIG M焊缝金属的电化学腐蚀性能.结果表明,在质量分数9.8%H2SO4溶液中,母材及焊缝的抗电化学腐蚀能力由大到小的顺序为母材＞TIG M焊缝＞MIG焊缝＞TIG焊缝,在质量分数5.0%HCl溶液中为母材＞MIG焊缝＞TIG M焊缝＞TIG焊缝,由此可知TIG焊缝金属的抗腐蚀能力最弱.由Tafel曲线可知,SUS316奥氏体不锈钢在H2SO4溶液中的钝化区间较长,在HCl溶液中的钝化区间很短暂,所以不锈钢在盐酸溶液比硫酸溶液中抗腐蚀性能差.晶间腐蚀试验结果与9.8%H2SO4溶液中电化学腐蚀试验结果相同.     

响应面方法在奥氏体不锈钢与铜合金异种材料摩擦焊接头的抗拉强度最大化和界面硬度最小化中的应用

在奥氏体不锈钢与铜合金异种材料摩擦焊接过程中,采用响应面方法优化摩擦焊接工艺参数,以获得抗拉强度最大和界面硬度最小的焊接接头。采用三因素、五水平中心复合正交矩阵来确定实验条件。得到20个焊接接头,测定了焊接接头的抗拉强度和界面硬度。采用方差分析(ANOVA)方法来确定起显著作用的、主要的及相互作用的参数,使用回归分析得到经验关系模型。用设计专家软件构造响应图和等高线图来优化摩擦焊接工艺参数。用得到的经验关系模型可以有效地预测焊接接头的抗拉强度和界面硬度,其置信水平达95%。从形成的等高线图可以得到所需的摩擦焊接的最佳条件。     

温度对Super304H焊缝金属再热裂纹敏感性的影响

Super304H奥氏体不锈钢是超超临界火电机组中过热器与再热器管的重要材料,在高温长期服役条件下,管道焊接接头的装配处易产生再热裂纹。本文使用预压缩CT试样的方法系统的研究了温度对Super304H奥氏体不锈钢焊缝金属再热裂纹敏感性的影响。结果表明,650 ℃试验温度下的焊缝金属产生裂纹所需的时间比600 ℃试验温度下的焊缝金属所需要的时间更短,具有更高的再热裂纹敏感性。导致该现象的主要原因在于650 ℃试验温度下晶界强度随时间衰减更快,应力松弛速率更高,而不同温度下晶内强化差异带来的影响较小。     

低镍含氮奥氏体不锈钢激光-电弧焊电弧特性及组织性能

采用100％Ar2,98％Ar+2％N2,92％Ar+8％N2,85％Ar+15％N2四种混合比例的保护气体对08Cr19MnNi3Cu2N低镍含氮奥氏体不锈钢进行激光-脉冲MAG电弧复合焊接,研究保护气体中氮气比例对焊缝中气孔数量、焊缝熔深和熔宽、电弧形态、微观组织及铁素体含量等影响机制.结果表明,随着保护气体中氮气...     

马氏体和奥氏体不锈钢TIG焊端接接头失效分析

针对船舶设备采用的马氏体和奥氏体不锈钢钨极氩弧焊焊接接头的泄漏问题,采用光学显微镜和扫描电镜观察、显微硬度测定等方法,分析了1Cr17Ni2马氏体不锈钢和1Cr18Ni9Ti奥氏体不锈钢焊接接头各个区域的组织变化和硬度分布.结果表明,在1Cr17Ni2一侧的热影响区紧邻焊缝部位,铁素体受热作用明显长大,显微硬度较低,在热影响区的较高温度区,快冷得到高硬度马氏体,该区断口呈典型的解理与准解理脆性断口,成为焊接接头的薄弱地带,容易产生裂纹导致泄漏.还分析了接头失效的其它原因并提出了改进措施.     

残余应力对Super304H焊缝金属再热裂纹敏感性的影响

采用预压缩CT试样的方法研究了残余应力对Super304H奥氏体不锈钢焊缝金属再热裂纹敏感性的影响。通过ABAQUS模拟结合EBSD表征分析了不同残余应力下的焊缝金属的塑性应变分布和位错密度分布,并从残余应力诱导焊缝金属晶内析出相的方面解释了残余应力对焊缝金属再热裂纹敏感性的影响。结果表明：高预压缩载荷的CT试样具有更高的残余应力,更容易产生再热裂纹。随着残余应力的增加,焊缝金属拉伸试样的抗拉强度逐渐降低。焊缝金属CT试样靠近U型口的高残余应力区域具有更高的位错密度和更高比例的亚晶,促进了晶内小颗粒相的析出,使得晶内硬化更为严重,再热裂纹更容易产生。     

薄板TC4钛合金TIG电弧和激光焊接接头晶粒尺寸与微观组织

为探究焊接方法对316L不锈钢焊缝抗辐照损伤性能的影响,采用原子力显微镜(atomicforce microscopy, AFM )、扫描电子显微镜(scanning electron microscopy,SEM )、掠入射X射线衍射(grazing incidence X-ray diffraction,GIXRD )、拉伸和纳米压痕技术等方法,对不同焊接方法制备的经能量为70 keV、剂量为1 × 10¹⁷ ions/cm²的He ⁺ 辐照后的316L奥氏体不锈钢焊缝损伤情况及力学性能进行了研究. 结果表明,离子辐照后不同焊缝表面均产生了空洞等微观缺陷,力学性能呈现不同程度的降低. 辐照后TIG焊缝表现出更优异的抗辐照损伤性能. TIG焊缝中更多的缺陷阱有效阻碍了辐照点缺陷的相互聚集,使辐照后焊缝内形成的缺陷数量更少、尺寸更小. 表明改变焊接方法、细化焊缝晶粒来提高焊缝抗辐照损伤性能及抗辐照硬化性能,是一种可行的思路与方法.     

铝合金/不锈钢惯性摩擦焊接头的组织特性和力学性能研究

惯性摩擦焊是一种连接异种金属理想的焊接方法,对铝合金/不锈钢采用惯性摩擦焊进行焊接,并详细研究了焊接接头的形貌、组织、界面成分和力学性能.结果表明,在惯性摩擦焊接头的界面处形成了很薄的金属间化合物(IMC)反应层,该反应层主要由Al、Fe 元素组成,是富集Si 元素的FeAl3相.惯性摩擦焊接头组织由焊核区、完全动态再...     

Formation of interfacial microstructure in a friction stir welded lap joint between aluminium alloy and stainless steel

The interfacial microstructure produced through tool transit of a friction stir welded lap joint between an aluminium alloy and stainless steel was studied by transmission electron microscopy in order to clarify its early stages of formation. Transmission electron microscopy studies of the bottom surface of the exit hole revealed the presence of several mixed layers of an ultrafine intermetallic compound (IMC) and stainless steel. The joining between dissimilar materials was achieved through a continuous flow of the stirred aluminium alloy into the mixed layers and the resultant growth of the ultrafine IMCs due to the heat induced by the friction between the tool and the specimen. The continuous thin reaction layer finally produced at the interface was found to be stronger than the base aluminium alloy.     

多层焊对A/P异种钢复合管SMAW接头组织及性能的影响

不锈层焊缝及熔合区组织对奥氏体(A)/珠光体(P)异种钢复合管焊接接头性能有重要影响.采用E309L型超低碳奥氏体不锈钢焊条的焊条电弧焊(SMAW,shielded metal arc welding)方法制备了0Cr18Ni9/20复合管单层焊和多层焊接头,并应用光学金相、能谱(EDS,energy dispersive spectrum)成分及线扫描、扫描电镜(SEM,scanning electron microscope)、X射线衍射以及显微硬度等方法对焊接接头进行了对比分析研究.结果表明,基层焊缝的再热作用可以使不锈层焊缝的δ-Fe相细化,熔合区合金元素分布更加均匀,且无Cr23C6相析出,对接头性能产生有利影响.     

低合金高强钢激光电弧复合焊热模拟热影响区组织与冲击韧性

研制了一种Mn-Si-Ni-Cr系实心焊丝,用于新型船用440 MPa级低合金高强度(HSLA)钢焊接,采用热输入11.5,16.5和21.5 kJ/cm对该钢材进行了熔化极活性气体保护电弧焊,并使用光学显微镜、扫描电镜和透射电镜等设备重点研究了热输入对焊缝组织及性能的影响. 结果表明,随着热输入的增大,焊缝组织先以粒状贝氏体和板条贝氏体为主转变为以针状铁素体为主,再转变为以针状铁素体、侧板条铁素体和先共析铁素体为主,而且焊缝中M-A组元含量、直径大于 1 μm的夹杂物占比和夹杂物的平均直径均逐渐增大;随着热输入的增大,焊缝硬度不断减小,焊缝、熔合线和熔合线 + 2 mm处的冲击韧性均先增大后减小,同时焊缝的耐腐蚀性能也先增大后减小;3种焊接接头的板拉伸弯曲试样均在母材处断裂,弯曲试样均完好.     

板厚对不锈钢车体激光叠焊接头抗剪强度和疲劳强度的影响

为了研究板厚对不锈钢激光叠焊接头抗剪强度和疲劳强度的影响,该文针对0.8 mm +2 mm和2 mm +2 mm2种不同板厚搭配的不锈钢激光叠焊接头分别进行了拉伸试验和疲劳试验。结果表明,2 mm +2 mm接头的抗剪强度和疲劳强度均高于0.8 mm +2 mm接头。失效分析发现,2种接头的拉伸破坏由焊肉部位剪断引起的;2种接头的疲劳裂纹均萌生于2 mm未焊透板,裂纹起始位置在2个焊板之间靠近焊核附近未焊透板的热影响区,裂纹沿着焊核边缘向未焊透板外表面方向扩展,直至穿透未焊透板。对焊接接头部位的有限元受力分析可知,2种接头的应力集中程度的不同是造成它们抗剪强度和疲劳强度差异的主要原因。     

固溶处理对2205双相不锈钢焊接接头组织与性能的影响

针对2205双相不锈钢多层多道手工电弧焊焊接接头,分别进行了不同温度的固溶处理;采用金相观察和力学性能测试相结合的方法对比分析了固溶处理及其温度对焊接接头显微组织及力学性能的影响规律.结果表明,随着固溶温度的升高,焊缝中σ相减少,而奥氏体含量增加;尽管固溶处理对2205双相不锈钢焊接接头的强度没有明显的影响,但能显著改善接头的塑性和冲击韧性;且随着固溶温度的升高,接头的断后伸长率、断面收缩率及冲击吸收能量也随之升高.     

Effects of chemical compositions and microstructure on hydrogen embrittlement of austenitic stainless steel weld metal in high-pressure gaseous hydrogen environment

The effect of chemical compositions and microstructures on hydrogen embrittlement of austenitic stainless steel weld metals in high-pressure hydrogen gas was surveyed by using the slow strain rate test (SSRT). As a result, hydrogen embrittlement of the weld metal was hardly influenced by δ ferrite in the weld metal, but by stability of austenite phase, which was estimated by Md30 value or Ni equivalent. In the weld metal with poor stability of austenite, α′-martensite was formed near a crack induced by SSRT. In addition, although the crystal structure of α′-martensite is as same as δ ferrite, susceptibility of hydrogen embrittlement became higher with the increase in α′-martensite. The mechanism to explain the difference between δ ferrite and α′-martensite was considered as following. The hardness, which increases the hydrogen embrittlement susceptibility in bcc structure, is higher in α′-martensite than in δ ferrite. In addition, α′-martensite might be formed continuously with propagation of a crack. Therefore, the effect of α′-martensite on hydrogen embrittlement could be larger compared with δ ferrite.     

Influence of deep cryogenic treatment on the microstructure and properties of AISI304 austenitic stainless steel A-TIG weld

Appropriate deep cryogenic treatment can improve comprehensive mechanical properties of the AISI304 austenitic stainless steel activating flux tungsten inert gas (A-TIG) welds. The microstructure of the welds before and after deep cryogenic treatment was all austenite with a small amount of δ-ferrite. The vermiform ferrite + austenite distributed in the whole weld, but the lath-shaped ferrite + austenite mixed components only distributed in the centre of the weld. The phases in the two welds were all Cr–Ni–Fe–C and Fe–Ni solid solutions, ferric carbide (i.e. Fe₃C) and chromic carbides (i.e. Cr₂₃C₆ and Cr₇C₃). After deep cryogenic treatment, the grain size of the weld was decreased a certain of degree, and the carbide phase content was increased. The strength and micro-hardness of the weld joints were increased due to the grain refinement. The intergranular corrosion resistance of the weld was reduced because the precipitation of chromium carbides at the austenite grain boundary.     

30mm厚不锈钢电子束焊接接头组织与性能

对30 mm厚0Cr18Ni10Ti不锈钢进行电子束焊接试验,在合适的工艺参数下得到焊接变形小、无内部缺陷、成形良好的接头。在室温下测试该接头的显微组织、显微硬度和力学性能,结果显示焊缝区组织为奥氏体和呈骨架铁素体,接头的硬度分布均匀,无明显弱化区域。接头处抗拉强度为578 MPa,焊接系数0.91,焊缝处冲击韧值A_(KV)达到300 J/cm^2,焊缝韧性与母材相比显著提高。