珠光体耐热钢与奥氏体不锈钢的焊接

奥氏体不锈钢(1Cr18Ni9Ti)和珠光体耐热钢(12Cr12Mo)焊接时,用在珠光体耐热钢的坡口表面堆焊过渡层或附加中间过渡段的方法,可以得到奥氏体和少量铁素体的双相组织的焊缝,焊接接头在500℃以上的条件下工作,提高焊接接头的热持久强度,取得较好的使用效果。     

关于隔离开关各种常见故障的分析及措施

奥氏体不锈钢(1Cr18Ni9Ti)和珠光体耐热钢(12Cr12Mo)焊接时,用在珠光体耐热钢的坡口表面堆焊过渡层或附加中间过渡段的方法,可以得到奥氏体和少量铁素体的双相组织的焊缝,焊接接头在500℃以上的条件下工作,提高焊接接头的热持久强度,取得较好的使用效果。     

钛合金薄板激光和钨极氩弧焊残余应力测试研究

采用小孔释放法对钛合金薄板激光焊和钨极氩弧焊(TIG焊)的焊接残余应力进行了测试，并分析了焊接方法、焊接线能量和焊后热处理对残余应力分布规律的影响。研究结果表明：激光焊残余应力分布规律与普通熔焊方法相似，但其分布区域较窄；在热影响区内，激光焊残余拉应力值比TIG焊的约低100MPa；在焊缝及其熔合线附近，激光焊残余应力却比TIG焊的高。对于不同线能量激光焊接，线能量越大，焊缝越宽，热影响区的残余应力也越大。焊后真空热处理能降低残余应力90％。     

激光退火对1Cr5Mo钢焊接接头热拉伸性能的影响

利用CO_2激光对1Cr5Mo耐热钢焊接接头进行退火处理,通过拉伸实验分析温度对激光退火前后试样热拉伸性能的影响。采用扫描电镜观察激光退火前后晶粒变化情况、断裂形式和断口形貌,并通过X射线应力仪测定激光退火前后焊接接头表面残余应力状态。结果表明:在200℃时激光退火后试样的屈服强度、抗拉强度和伸长率比原始试样分别提高了32.5%,22.5%和4.6%,而在300℃时激光退火后试样的屈服强度、抗拉强度和伸长率比原始试样仅分别提高了6.6%,6.5%和7.5%;激光退火前后试样拉伸断口均为韧性断口,但激光退火后试样的韧窝尺寸大于原始试样,随着温度升高,韧窝尺寸进一步增大;激光退火后试样表面产生的晶粒细化和残余压应力是热拉伸性能提高的主要因素。     

船用TA5钛合金激光焊接接头组织和性能研究

采用IPG光纤激光器对8 mm厚的TA5钛合金进行激光自熔焊接,并对焊接接头的微观组织和力学性能进行分析。结果表明,激光焊接接头表面成形连续、均匀、无飞溅,内部无气孔和裂纹等缺陷。母材组织为细小均匀的等轴α相;焊缝区组织主要由粗大的β柱状晶粒、大量的针状马氏体α'以及少量的板条马氏体组成;热影响区组织主要由等轴α相、少量的针状马氏体α'和少量的残余β组成;在熔合线的边界,柱状晶粒与等轴晶粒联生结晶、外延生长,保证了焊接接头的稳定连接。焊接接头各区域的显微硬度差异较大,最高硬度出现在熔合线附近,焊缝区和热影响区的显微硬度明显高于母材的。对拉伸断裂部位进行观察,拉伸断裂发生在远离焊缝的母材处,这说明激光焊接接头的抗拉强度与母材等强或者略高于母材的,这与大量针状马氏体形成的网篮组织有直接的关系。      

高强度贝氏体钢板不同焊接方法接头的组织和性能

利用二氧化碳保护焊、埋弧焊、手工电弧焊研究了高强度贝氏体钢板焊接接头的组织和力学性能.结果表明:二氧化碳保护焊焊后不热处理接头焊缝组织为贝氏体、少量铁素体和珠光体,热影响区为新型贝氏体组织;手工焊焊后不热处理焊缝组织主要为块状铁素体和少量珠光体,热影响区组织为新型贝氏体组织;埋弧焊焊后不热处理焊缝部分组织为针状铁素体,熔合线结合良好,组织分布均匀,晶粒细小,热影响区组织为新型贝氏体.各种焊接方法焊接接头具有良好的强韧性.     

大厚度奥氏体不锈钢筒体填丝激光焊接变形和应力分析

目的 研究大厚度奥氏体不锈钢筒体填丝激光焊接,优化结构设计和工艺设计。方法 建立大厚度奥氏体不锈钢筒体填丝激光焊接数值分析模型,通过数值模拟的方法,定量分析大厚度奥氏体不锈钢筒体焊接变形和应力。结果 零件下部38 mm厚焊缝位置处的最大径向收缩量为1.2 mm;零件下部60 mm厚焊缝位置处的最大径向收缩量为2.0 mm;零件中部60 mm厚焊缝位置处的最大径向收缩量为1.9 mm;零件上部60 mm厚焊缝位置处的最大径向收缩量为1.8 mm。填丝激光焊接轴向收缩量为0.55 mm。焊接残余应力最大值在450 MPa左右,应力主要分布在焊缝附近。热处理后,焊接残余应力都有明显降低,最大残余应力从450 MPa左右降低到200 MPa左右,焊接残余应力范围存在一定程度减小;焊接残余变形变化较小,热处理后某些位置的变形略微有所增大。结论 模拟结果表明,大厚度奥氏体不锈钢筒体填丝激光焊接变形和应力在可接受范围内,焊后热处理对释放残余应力有重要作用。     

小口径厚壁12Cr1MoVG钢管焊接残余应力的数值模拟

以小口径厚壁12Cr1MoVG珠光体耐热钢管多层多道焊接接头为对象,使用有限元模拟软件,采用生死单元法,计算焊接接头中的残余应力。计算结果表明:焊接接头外壁焊缝附近区域的残余应力为压应力,母材端的残余应力变化幅度要比焊缝区的小;焊接接头内壁焊缝及热影响区的残余应力为压应力,而母材承受拉应力。通过对比可知焊接接头内、外壁轴向残余应力分布的计算结果与实测结果高度吻合,说明数值模拟方法可以为管状接头的焊接工艺评定提供便利、可靠的技术支持。     

厚板钛合金磁控窄间隙TIG焊接技术发展现状

磁控窄间隙TIG焊接技术能有效解决厚板钛合金侧壁熔合不良的问题,其工艺稳定性好、设备成本较低,能为大型钛合金海工结构和装备制造提供有力支撑。围绕厚板钛合金磁控窄间隙TIG焊接技术及其研究现状展开论述。重点阐述了外加横向磁场对电弧摆动的作用机理,并讨论了主要焊接工艺参数(窄间隙坡口设计、焊接电流强度、外加磁场强度和频率及电极位置)对焊缝成形的影响。结合自研结果探讨了不同规格钛合金磁控窄间隙TIG焊接接头的显微组织和力学性能,并进一步概述了焊后残余应力分布特征。研究结果表明,利用外加磁场实现电弧周期摆动能有效调控热输入分布,进而改善侧壁熔合不良的问题;相比其他窄间隙焊接技术,磁控窄间隙TIG焊接能获得更加均匀的焊缝组织和优异的接头力学性能;磁控窄间隙TIG焊接后,接头表面存在较大拉应力,结合合适的热处理工艺能有效降低接头残余应力。最后,对磁控窄间隙TIG焊技术发展和前景进行了展望。     

热处理对GH4169激光焊接头组织性能的影响

针对2 mm厚的GH4169镍基合金板材进行激光对焊,研究热处理对GH4169激光焊接头组织和性能的影响。采用线切割方法制备激光焊接头试样,对热处理和非热处理激光焊接头进行拉伸实验、硬度测定、OM分析、SEM分析、EDS分析和XRD相分析。实验结果表明:热处理后接头抗拉强度为1372 MPa,延伸率为14%,焊缝平均硬度为473HV;较未热处理接头强度提高52%,延伸率降低71%,硬度提高69%。OM、SEM、EDS和XRD分析表明:对GH4169激光焊接头热处理能细化焊缝晶粒,改善枝晶形态,消除残余应力,析出δ相、γ′相和γ″相,使得焊接接头硬度和强度有所提高。     

Carbide precipitates and mechanical properties of medium Mn steel joint with metal inert gas welding

Medium Mn steel was metal inert gas(MIG)welded with NiCrMo-3 and 307Si filler wires.The effect of filler wires on the microstructure and mechanical properties of joint was investigated,and the carbide precipitates were contrastively discussed.The results revealed that the microstructure of weld metal,heat-affected zone and base metal are austenite.Obvious grain coarsening occurred in the heat-affected zone(HAZ),and the maximum grain size grew up to 160 pm.In HAZ,C and Cr segregated at grain boundaries,the carbides was identified as Cr7C3.The dispersive(Nb,Mo)C phase was also found in weld metal with NiCrMo-3 filler wire.All the welded joints failed in HAZ during tensile tests.The tensile strength of welded joint with NiCrMo-3 filler wire was 675 MPa,which is much higher than that with 307Si filler wire.In comparison to base metal,higher microhardness and lower impact toughness were obtained in HAZ for these two welded joints,which was attributed to the precipitation of Cr7C3 phase and grain coarsening.The impact toughness around the fusion line is the worst for these two welded joints.     

汽车高强钢SG1000激光复合焊接力学性能研究

目的 针对汽车高强钢SG1000焊接接头恶化等问题,研究了SG1000激光复合焊接的力学性能。方法 选用等强匹配焊丝MG90-G对高强钢SG1000进行激光复合焊接,对焊接接头进行拉伸和低温冲击韧性试验,并结合扫描和硬度监测等手段对焊缝组织和断口形貌进行分析。结果 由于激光的预热作用,高强钢SG1000激光复合焊接成形件的焊缝美观,焊接过程稳定可靠,焊接熔池深度较大,有效改善了传统焊接的咬边、飞溅、气孔等缺陷。焊缝组织主要由板条马氏体和奥氏体晶粒组成,热影响区的过热区内部板条马氏体和奥氏体晶粒比较粗大,而焊接母材主要为细小的板条马氏体和奥氏体晶粒。焊接拉伸断口主要为细小且较浅的韧窝,且韧窝底部存在第二相粒子及夹杂物,焊接拉伸断口断裂于热影响区且微观形貌为韧性断裂;冲击微观形貌主要由准解理小平面及河流花样组成,且存在一定数量大小不一的韧窝交错分布,焊接冲击断口断裂于热影响区且微观形貌也为韧性断裂。结论 焊缝热影响区的晶粒比非热影响区的晶粒粗大,拉伸和冲击断裂均发生于热影响区;随着激光功率的增大,复合焊接接头的力学性能呈现逐渐增强的趋势;随着焊接速度的增大,复合焊接接头的力学性能呈现先增强后削弱的趋势。高强钢SG1000激光复合焊接最佳工艺参数如下:激光功率为9.5 kW,焊接速度为0.8 m/min,对应屈服强度为1 072 MPa,抗拉强度为1 175 MPa,断裂伸长率为13.5%,冲击断裂吸收的能量为30.8 J、焊缝中心显微硬度为342 HV。     

Microstructure in the Weld Metal of Austenitic-Pearlitic Dissimilar Steels and Diffusion of Element in the Fusion Zone

Microstructure and alloy element distribution in the welded joint between austenitic stainless steel (1Cr18Ni9Ti) and pearlitic heat-resistant steel (1Cr5Mo) were researched by means of light microscopy, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Microstructure, divisions of the fusion zone and elemental diffusion distributions in the welded joints were investigated. Furthermore, solidification microstructure and S-ferrite distribution in the weld metal of these steels are also discussed.     

热输入对Inconel 617镍基高温合金激光焊接接头显微组织与力学性能的影响EI北大核心

采用两种热输入不同的焊接工艺参数对3 mm壁厚的Inconel 617镍基高温合金进行激光焊接。通过光学显微镜和扫描电子显微镜对焊接接头显微组织进行观察分析,并测试了焊接接头在室温(25℃)及高温(900℃)下的拉伸性能。结果表明:激光焊接热输入对Inconel 617焊接接头显微组织及力学性能影响明显。在高热输入(200 J/mm)条件下,焊缝正面宽度3.88 mm,熔化区中部晶粒尺寸粗大,取向杂乱,树枝晶二次枝晶间距较大(6.71μm),枝晶间碳化物颗粒尺寸较为粗大,枝晶间Mo,Cr等合金元素的凝固偏析较为严重。焊接接头热影响区宽度约0.29 mm,在晶界和晶内形成了γ+碳化物共晶组织,这是由于焊接升温过程中,热影响区内球状碳化物颗粒与周边奥氏体发生组分液化,并在焊后凝固过程中形成共晶。低热输入(90 J/mm)工艺参数获得的焊缝正面宽度为2.28 mm,焊缝呈沿熔合线母材外延生长并沿热流方向定向凝固形成的柱状晶形态。焊缝中部树枝晶二次枝晶间距较小(2.26μm),枝晶间碳化物颗粒尺寸细小,热影响区宽度约0.15 mm。室温(25℃)拉伸测试表明:高热输入下获得的焊接接头由于焊缝中固溶元素偏析造成的局部组织弱化,从焊缝中部破坏,强度与伸长率有所降低,低热输入条件下获得的焊接接头从母材破坏。而高温实验条件下(900℃),母材晶界发生弱化导致所有试样均从母材破坏。     

Comparison of creep behaviour of 2.25Cr–1Mo/9Cr–1Mo dissimilar weld joint with its base and weld metals

Abstract

Evaluation of the creep behaviour of 2.25Cr–1Mo and 9Cr–1Mo ferritic steel base metals, 9Cr–1Mo steel weld metal, and 2.25Cr–1Mo/9Cr–1Mo ferritic–ferritic dissimilar weld joints has been carried out at 823 K in the stress range 100–260 MPa. The weld joint was fabricated by shielded metal arc welding using basic coated 9Cr–1Mo electrodes. Investigations of the microstructure and hardness variations across the joint in the as welded, post-weld heat treated (973 K/1 h), and creep tested conditions were performed. The heat affected zone (HAZ) in both the steels consisted of a coarse prior austenitic grain region, a fine prior austenitic grain region, and an intercritical structure. In the post-weld heat treated condition, a white etched soft decarburised zone in 2.25Cr–1Mo steel base metal and a black etched hard carburised zone in 9Cr–1Mo steel weld metal around the weld fusion line developed. Hardness troughs also developed in the intercritical HAZ regions of both the steels. The width of the carburised and decarburised zones and hardness differences of these zones were found to increase with creep exposure. The 9Cr–1Mo steel weld metal showed higher creep strength compared to both the base metals. The 9Cr–1Mo steel base metal exhibited better creep resistance than the 2.25Cr–1Mo steel base metal at lower applied stresses. The dissimilar joint revealed lower creep rupture strength than both the base metals and weld metal. The creep strain was found to concentrate in the decarburised zone of 2.25Cr–1Mo steel and in the intercritical HAZ regions of both the steels. Creep failure in the stress range examined occurred in the intercritical HAZ of 2.25Cr–1Mo steel even though this region showed higher hardness than the decarburised zone. Extensive creep cavitation and cracks were observed in the decarburised zone.     

316L/S32101异种金属焊接接头的显微组织与力学性能研究

目的 研究乏燃料水池用钢板316L与覆板S32101双相不锈钢的焊接性、接头不同区域显微组织特征及接头与母材之间的性能差异.方法 利用氩弧焊接技术对5 mm厚的316L底板与3 mm厚的S32101覆板以搭接的形式进行焊接,利用金相显微镜、扫描电镜、维氏显微硬度仪和电子万能材料试验机对焊接接头的宏观形貌、显微组织以及力学性能进行研究.结果 316L/S32101焊缝组织主要由铁素体基体、晶界树枝状奥氏体以及晶内细小片状奥氏体所组成;316L侧靠近焊缝处存在一个较窄的熔合区,其组织由奥氏体基体和少许细小分散的铁素体组成,而S32101侧靠近焊缝处组织则由粗大铁素体晶粒和沿晶粒边界分布的若干小块状奥氏体组成.从316L母材区到焊缝区,硬度显著增大,而从焊缝区到S32101母材区,硬度变化很小;焊接接头的抗拉强度高达510 MPa,为两侧316L和S32101母材强度的87.9％和88.6％.结论 在焊接电流为240 A和焊接速度为300 mm/min的条件下,可以通过氩弧焊获得成形良好的搭接接头,且接头的力学性能优异.     

Micrometre scale residual stress measurement in fusion boundary of dissimilar steel welded joints using nanoindenter system

Abstract

In the present paper, an approach for measuring the micrometre scale residual stress around the fusion boundary in dissimilar steel welded joints was introduced. An as welded joint and a post-weld heat treated joint were examined using a nanoindenter system. The results revealed that a compressive residual stress existed around the fusion boundary in a range 200 μm extending to the overheated heat affected zone (HAZ) and 300 μm to the weld metal, and the compressive stresses were reduced after post-weld heat treatment. The maximum compressive stress occurred in the fusion boundary and then dramatically decreased in the adjacent HAZ base metal and weld metal. In comparison with the regular approaches for macrometre scale measurement, the nanoindentation has the advantages of high resolution and precision for effectively evaluating the residual stresses in a narrow region. The measuring error was analysed.     

Microstructure and mechanical properties of friction stir welded 18Cr–2Mo ferritic stainless steel thick plate

In this study, microstructure and mechanical properties of a friction stir welded 18Cr–2Mo ferritic stainless steel thick plate were investigated. The 5.4 mm thick plates with excellent properties were welded at a constant rotational speed and a changeable welding speed using a composite tool featuring a chosen volume fraction of cubic boron nitride (cBN) in a W–Re matrix. The high-quality welds were successfully produced with optimised welding parameters, and studied by means of optical microscopy (OM), scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD) and standard hardness and impact toughness testing. The results show that microstructure and mechanical properties of the joints are affected greatly, which is mainly related to the remarkably fine-grained microstructure of equiaxed ferrite that is observed in the friction stir welded joint. Meanwhile, the ratios of low-angle grain boundary in the stir zone regions significantly increase, and the texture turns strong. Compared with the base material, mechanical properties of the joint are maintained in a comparatively high level.     

S275低合金钢焊接接头的组织与力学性能

通过拉伸、冲击、硬度测试和金相检验等方法对S275低合金钢熔化极活性气体保护焊(MAG)焊接接头的力学性能与显微组织进行了研究。结果表明:采用JM一56焊丝对S275低合金钢进行焊接时,接头具有较好的抗剪强度;开45。坡口,拉伸后均断在离焊缝位置较远的母材上,焊接接头抗拉强度满足技术要求。焊缝组织晶内为细小密集的针状铁素体,有极少量珠光体,焊缝局部有魏氏组织;熔合区、过热区为沿晶界析出的块状先共析铁素体和向晶内生长的条状铁素体以及少量的珠光体;正火区组织为细小的铁素体和珠光体;母材组织为铁素体和珠光体,晶粒也比较细小。最后得出S275低合金钢用于转向架焊接构架是可行的。     

高温临氢Cr5Mo管线异质焊接接头延寿分析

通过对一服役１０＾５ｈ的Ｃｒ５Ｍｏ工艺管线异质焊接接头的力学性能，焊缝界面组织变化，碳扩散和热应力的测试分析，发现异质焊接接头的焊接过程中存在一些焊接缺陷，如未熔合，夹渣等，其中未熔合深度达壁厚的２／３，但这些缺隐在服役过程中并未扩展，主要原因是管线中应力水平较低，母材与焊缝组织是正常的，焊缝熔点线处应力最高；焊接熔合区存碳迁移，因此焊接熔合区是薄弱环节，应加强监控，综合上述分析结果，在高温低应力