不同强度级别双相不锈钢激光焊接头的组织与力学性能

目的 为了合理制定不同强度等级DP钢同种和异种接头的激光焊接工艺,研究激光焊接工艺对接头组织性能的影响。方法 采用SEM、硬度试验、拉伸试验等手段,研究不同强度等级DP钢同种和异种激光焊接接头的微观组织和力学性能。结果 对于同种DP钢激光焊接,由于接头各个区域经历的热循环不同,因此其马氏体体积分数和形态、含碳量等存在明显差异。在焊缝熔合区,由于冷却速度较高,因此马氏体体积分数较高且为细条状,硬度高于母材硬度。在热影响区,由于马氏体发生了回火分解,因此其硬度值低于母材硬度,且软化的程度和范围大小与DP钢的强度级别相关。软化的热影响区成为接头的薄弱区域,降低了接头的拉伸性能。在异种DP钢激光焊接接头中,焊缝熔合区的硬度也明显高于母材硬度。靠近高强度级别母材侧的热影响区范围更大,软化程度更明显,接头硬度分布不再对称。接头的抗拉强度与低等级DP钢母材的抗拉强度基本一致。结论 激光焊接工艺对不同强度等级DP钢同种和异种接头组织性能的影响存在较大的差异,DP钢强度级别越高,接头或接头对应侧的热影响区软化程度越明显,这在制定焊接工艺以及焊后处理工艺过程中需要予以考虑。     

复合板基层厚度对激光焊接头腐蚀性能的影响

目的通过探索基层金属厚度对复合板激光穿透焊接的影响规律,分析其影响度与焊接速度、激光功率的差别,为双金属复合材料激光穿透焊接提供更多的技术支撑。方法以焊接速度、激光功率和基层金属厚度为变量,设计了三因素三水平的正交实验,对X65/DSS2205层状双金属复合材料进行激光穿透焊接实验,对不同焊接条件下接头的显微组织进行观察分析,采用EDS面扫方法对焊缝复层区进行成分扫描,测量接头复层侧动电位极化曲线,并比较了基层金属厚度的影响度较焊接速度与激光功率的大小。结果双金属复合板激光穿透焊接接头显微组织在厚度方向存在明显的分层;基层金属厚度为1.2 mm时,复层贵金属元素保留量最大;随着基层金属厚度的减小,接头综合耐腐蚀性能提高;基层金属厚度对接头耐腐蚀性能的影响小于焊接速度和激光功率2个变量;焊接速度为2.5 m/min,激光功率为3500 W,基层金属厚度为0.8 mm时,接头耐腐蚀性能最优。结论基层金属厚度对于复合板激光穿透焊接接头的焊缝复层元素含量、以及接头复层一侧耐腐蚀性能都有较为明显的影响,但相比于焊接速度与激光功率,其影响度相对较小,因此在进行复合板激光穿透焊接时,在选定基层金属厚度后,仍要对焊接速度和激光功率进行优化工艺设计。     

热成形淬火对QP1180/22MnB5激光拼焊板组织与性能的影响

目的 对QP1180和22MnB5激光拼焊板进行热成形试验,以解决超高强钢板材焊后的软化问题。方法 选择QP1180和22MnB5异种高强钢作为母材进行激光自熔焊,对焊后的激光拼焊板进行热成形试验,通过体式显微镜、扫描电子显微镜、液压拉伸试验机和维氏硬度计等手段,分析热成形前后激光拼焊板微观组织和力学性能的变化。结果 与焊态拉伸试样相比,热成形试样抗拉强度提高了135%,断后伸长率降低了55%,拉伸试样都在22MnB5母材处断裂,均为塑性断裂。在热成形后,对焊接接头进行组织分析,发现QP1180母材区马氏体含量增加,22MnB5母材区和临界热影响区组织由珠光体和铁素体转变为马氏体,焊接接头热影响区各亚区的组织均转变为大小不同的板条马氏体。硬度测试结果表明,焊态试样焊接接头的QP1180临界区存在软化现象,硬度值最低为335HV,22MnB5侧硬度值由母材处向焊缝升高,母材硬度最低为170HV;而在热成形后,QP1180临界区软化现象消失,硬度值趋于平缓,22MnB5母材处硬度比焊态试样硬度高了2倍。结论 与焊态试样相比,经热成形后激光拼焊板的焊后软化问题得到了解决。     

近等原子比钛镍合金氩弧焊接接头的组织和性能

借助金相显微镜、拉伸实验和弯曲回复法等手段研究了近等原子比钛镍形状记忆合金氩弧焊接接头的组织和性能。研究结果表明,近等原子比钛镍形状记忆合金氩弧焊接接头的显微组织可分为三个区,分别是粗大柱状晶区、细小柱状晶区和热影响区。由于焊接接头显微组织与母材之间的差别,在相同的应变下,近等原子比钛镍形状记忆合金氩弧焊接接头的回复温度明显高于母材,记忆性能变差。焊接后的近等原子比钛镍形状记忆合金的屈服强度与母材相近,但抗拉强度和延伸率远低于母材。氩弧焊接近等原子比钛镍合金的显微组织在热处理后不会发生明显变化,经过形变后,焊接接头的回复温度与母材仍有差别,显微组织的不同是造成这一现象的原因之一。     

Microstructure and tensile properties of laser beam welded Ti–22Al–27Nb alloys

Ti–22Al–27Nb alloys were welded using the laser beam welding process. The microstructure characterization and the tensile properties of the laser beam welded joints were investigated. The experimental results showed that a well-quality joint could be obtained using laser beam welding method. The fusion zone of the welded joint was composed of B2 phase. The tensile strength of the joints at room temperature was basically comparable to that of the base metal and the tensile ductility of the joints achieved 56% of the base metal. The average tensile strength of the welded joints at 650 °C was tested to be about 733 MPa, with the elongation of 2.93%.     

Superplastic Solid-Phase Welding of 40 Cr-T10A Steel

The microstructure of 40Cr and T10A steel sample and its surface to be welded is ultra-fined through salt-bath cyclic quenching and high frequency hardening, then the surface is cleaned. Under non-vacuum and no shielded gas, the welding parameter of isothermal superplastic solidphase welding and the effect of surface microstructure prior to pressure welding on the quality of joint are studied. At the temperature of 730~750℃ and at initial strain rate of (2~4) × 10-4 s-l, the strength of the joint is up to or close to that of 40Cr base metal in 3-5 min pressure welding     

焊接接头横向拉伸试验结果分析

通过一系列对比试验,研究分析了Q345焊接试板焊接接头横向拉伸性能与全焊缝和焊板母材之间的差异,探索接头横向拉伸所得屈服强度与断后伸长率的合理性。结果表明,接头横向拉伸所获得的屈服强度值介于母材与全焊缝的值之间,且试验结果受所用引伸计标距的影响较为显著;接头横向拉伸断裂位置虽在母材上,但抗拉强度值要高于母材强度近20 MPa,断后伸长率则比母材低了近10%,但仍高于全焊缝的值。     

Laser-beam welding of SiC fibre-reinforced Ti-6Al-4V composite

Three- and ten-ply SiC fibre-reinforced Ti-6Al-4V composites were joined using a laser beam. With a 300 m thick Ti-6Al-4V filler metal, fully penetrated welds without apparent fibre damage, could be obtained in welding directions both parallel and transverse to the fibre direction by controlling the welding heat input. Excess heat input resulted in the decomposition of SiC and subsequent TiC formation, and also caused degradation of joint strength. The welding of the three-ply composite in which full penetration was achieved at lower laser power, exhibited higher flexibility in heat input than that of the ten-ply composite. Heat treatment at 1173 K after welding improved the joint strength because of the homogenization of the weld metal and decomposition of TiC. The strengths of the transverse weld joints after the heat treatment were approximately 650 and 550 MPa for the three- and ten-ply composites, respectively. With the welding direction parallel to the fibre direction, the strengths both parallel and transverse to the weld joint were equivalent to those of the base plate.     

近红外光纤激光与蓝光半导体激光焊接紫铜工艺对比研究

目的 提高紫铜激光焊接接头的力学性能,并分析激光工艺参数对焊缝外观及焊缝微观组织的影响规律。方法 分别对蓝光半导体激光与近红外光纤激光焊接紫铜的工艺参数进行优化设计,采用光学显微镜观察焊缝的外观形貌,采用拉力机测试焊缝的抗拉强度,采用金相显微镜观察和分析焊缝的微观组织。结果 当采用近红外光纤激光进行焊接时,功率为2 000 W,焊接速度为20 mm/s,焊缝抗拉强度为156 MPa。当采用蓝光半导体激光进行焊接时,功率为500 W,焊接速度为20 mm/s,焊缝抗拉强度为246 MPa,达到母材抗拉强度的80%。结论 由于铜对蓝光波长的吸收率较高,当采用蓝光半导体激光进行焊接时,热量输入较低,焊缝的变形相对较小,并且焊缝中心各个方向上的温度梯度相同,容易形成等轴晶,有利于力学性能的提高。     

Ti75合金激光焊接接头的组织及力学性能

采用10 kW的连续光纤激光器对3 mm厚的Ti75合金板进行激光焊接,通过调整不同的激光功率来获得全熔透的焊接接头.同时,观察了不同热输入下焊接接头的宏观形貌、微观组织,测试了焊接接头的力学性能和显微硬度,对接头不同部位的组织特征及成形原因进行了分析.结果表明,随着焊接过程中激光功率的增加,焊缝的宽度逐渐变大,在不同...     

TWIP钢激光拼焊板的力学性能及微观组织分析

为评价TWIP钢的焊接性能,对1.2 mm厚的Fe-Mn-C系TWIP钢进行了激光拼焊实验,用线扫描分析了锰元素的分布,对拼焊板进行了拉伸试验,用扫描电镜观察了拉伸断口形貌,采用背散射电子分析技术分析了拉伸前后的组织变化及孪晶形成,测试了维氏硬度的分布曲线.实验结果表明:焊缝区未发生Mn元素的挥发,室温下为显著的柱状枝晶铸态组织;断裂发生在存在气孔等微小缺陷的焊缝区,拼焊板强度与母材接近,韧性显著降低;拉伸过程中有大量的形变孪晶形成,拉伸前后均为全奥氏体组织.     

SiCp/Mg复合材料激光焊规范参数对焊缝强度的影响及其数学模型的建立

对于焊接性较差的碳化硅颗粒增强镁基（SiCp／Mg）复合材料，采用高能激光束进行了焊接．通过选择合适的激光焊工艺参数，可焊成外观成形及性能均良好的焊接接头．激光焊的输出功率（P）、焊接违反（v）、脉冲频率（f）、脉冲宽度（w）对接头强度都有影响，其中尤以激光输出功率与焊接速度的比值，即焊接线能量P/v的影响最大．对于厚度为1mm的对接缝，试验所得最佳工艺参数为：P=170Wv=7.5mm/s,f=30Hz,w=5ms.焊接时使用氢气（Ar）进行保护．所得拉伸强度值为104．3MPa，达到了母材的52％．另外，本文还应用多项式回归法建立了焊接接头拉伸强度与工艺参数关系的数学模型．     

Ta/Ni/Mo异种薄板激光熔钎焊正交试验探究

目的探究Ta/Mo异种薄板激光熔钎焊的最佳焊接工艺参数。方法设计正交试验方案,得出理论最优工艺参数。采用SL-08型Nd:YAG脉冲激光焊机对薄板完成焊接得到焊接接头;通过微机控制电子万能试验机测试焊接接头的抗拉强度;通过显微硬度计测量焊接接头显微硬度;通过OM测试方法观察焊缝组织。并通过焊接接头的性能对得出的最优工艺参数进行验证。结果在最佳焊接工艺参数下,接头的最大平均抗拉强度为230 MPa,接近Ta母材的抗拉强度,拉伸试样断裂发生在近Ta热影响区;焊缝表面连续,可看到清晰的鱼鳞纹,焊缝背面宽度均匀,焊缝成形良好;焊缝中心区域出现了针状共晶组织,热影响区的晶粒都呈现不同程度的长大现象;形成接头的焊缝区硬度最高,钼母材次之,钽母材最小。结论通过正交试验得出的最优工艺参数是准确的,Ta/Mo异种薄板最佳焊接工艺参数为:激光功率P为20.8 W(激光功率百分比为26%),脉宽T为5.5 ms,脉冲频率f为4.0 Hz。     

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.     

Microstructural,compositional and mechanical investigation of Shielded Metal Arc Welding (SMAW) welded superaustenitic UNS N08028 (Alloy 28) stainless steel

Shielded Metal Arc Welding (SMAW) was performed on UNS N08028 (Alloy 28) superaustenitic stainless steel sheets. In the present work, the microstructure and the mechanical properties of base metal (BM), weld metal (WM), and welded joint (WJ) are investigated. Optical micrographs show that the base metal presents austenitic grains, and the weld metal exhibits a fully austenitic dendritic structure, confirming the Schaeffler diagram estimations. Microhardness measurements indicate that the hardness increases in the weld bead due to the rapid cooling and thermal cycle during welding procedure. The measured mechanical properties and the analysis of the fracture profiles show that the two materials are ductile but the ductility is less pronounced in the weld metal. Consistently the yield stress, the plastic strength and the impact toughness are lower than in the base metal. In addition, the BM presents a higher cyclic hardening and plastic strain compared to those of WM. Cyclic stress–strain hysteresis loops show that WM and WJ have almost the same cyclic behavior and especially at high imposed strain levels.     

Laser shock welding of aluminum/aluminum and aluminum/copper plates

This work describes an advanced technique for metal welding and composite production, namely laser shock welding. A series of laser shock welding experiments were conducted to verify the welding ability of aluminum/aluminum and aluminum/copper plates. Two kinds of interface morphologies were observed by metallographic investigation on cross-sections of the joint areas, including the linear and wavy interfaces. Besides, micro-hardness testing results show the welded interface has a much greater hardness than the base metals. The lap shearing test was used to characterize the joint. According to the experimental results, it can be imply that this kind of technique shares the same bonding mechanism with explosive welding and magnetic welding.     

Microstructure and mechanical properties of laser welded joints between 2198/2060 Al–Li alloys

Dissimilar Al–Li alloys (2198 and 2060) were laser welded without the addition of filler material. The effects of welding parameters on the formation of the welded joints, microstructure evolution, solute segregation, porosity and their relationships with the mechanical properties of the joint were investigated. It was found that reducing the weld heat input can effectively prevent grain coarsening, while decreasing porosity and reducing the tendency for hot cracking, thereby enhancing the properties of the joint. The dissolution of precipitates such as the T1 phase and θ′ phase in the base metal, and the variations in Cu and Mg content between grain interiors and boundaries, resulted from solute segregation during welding, leading to reductions in the strength of the weld.     

Elucidation of fatigue characteristics and fracture mechanism of friction stir spot‐welded tension–shear joint steels

The fatigue life and fracture mechanism of friction stir spot welded tension–shear joints using 590‐MPa class steel as a base material under constant‐amplitude conditions were investigated with focus on welding dimension variations caused by tool wear. The fatigue limit of the friction stir spot welding (FSSW) joint used for this study is significantly low compared with the static tensile strength of the joint itself. It was clarified that the FSSW joint in this study exhibited two different failure morphologies regardless of the applied load level: base metal fracture and weld area fracture. Although the welding state changes due to the tool wear phenomenon that produce two types of fracture modes in relation to the welding rip diameter, they have no effect on the fatigue strength, regardless of the applied load.     

Cr12MoV钢焊接区表面高频淬火后的超塑性焊接

对Cr12MoV钢进行表面高频淬火后超塑性焊接,选用的工艺参数为:加热温度为800℃,焊接时间t=5min,预压应力σ0=56.6MPa,初始应变速率ε0=2.5×10-4s-1。对接头组织进行了观察和分析。试验结果表明,焊接区局部高频淬火后的Cr12MoV钢在其超塑变形温度及应变速率范围内,经短时间超塑焊接,其接头抗拉伸强度可以达到母材值。     

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。