DP780高强钢胶接点焊过程声发射信号特征及接头强度预测

针对1.2 mm厚的DP780高强钢板进行胶接点焊正交实验,采集胶焊过程的声发射信号,辨析其信号特征,建立接头强度与声发射信号特征参数之间的关系.结果表明:胶焊过程的电极加载、熔核形核和电极卸载三个物理阶段产生三段声发射信号;相比电阻点焊过程,由于胶焊过程存在胶层的烧灼与气化,其熔核形核阶段前段产生的声发射信号的振铃计数和幅值大于电阻点焊,并且飞溅出现时,声发射信号幅值增大;对于未发生飞溅的胶焊过程,焊接接头的失效载荷与熔核形核阶段声发射信号特征参数的振铃计数和正峰值具有较好的线性正相关性,据此可为胶接点焊过程焊接质量的在线检测与控制提供依据.     

DP780高强钢胶接点焊的多元非线性回归模型

基于Box-Behnken Design(BBD)设计方法,开展DP780高强钢胶接点焊的试验研究。以接头的失效载荷、熔核直径为目标量,将焊接电流、焊接时间、电极压力以及各参数之间的交互作用作为影响目标量的因素,建立DP780高强钢胶接点焊接头多元非线性回归模型。试验验证表明,建立的多元非线性回归数学模型具备高的显著性且拟合程度高,可实现对接头失效载荷、熔核直径的有效预测;胶焊接头的失效载荷、熔核直径随焊接电流增大及焊接时间的延长而增大,随电极压力的减小而递增;基于回归模型获得最优工艺参数:焊接电流8.3 kA,焊接时间150 ms,电极压力0.3 MPa,对应参数下接头的失效载荷达到16 369 N。借助超声C扫图像甄别出焊核外存在胶层烧灼气化区,当焊接时间较短时,焊接电流的增加会提供更多的热输入量,导致胶层烧灼气化面积增大,进而降低接头的静力学性能。     

激光焊接铜的组织性能研究

对铜板进行激光焊接研究,通过正交试验研究焊接电流、脉冲度宽、脉冲频率和焊接速度等工艺参数对接头的最大抗拉强度的影响,并对焊缝的金相组织和显微硬度进行分析.     

高铬铁基合金等离子熔覆层表面硬度工艺研究

为探究工艺参数对高铬铁基合金等离子熔覆涂层表面显微硬度的影响,以熔覆于Q235钢表面的单道高铬铁基合金硬质涂层为研究对象,开展二次回归正交旋转组合试验。利用Design-Expert 8.0.6分析软件对试验数据进行方差及响应面分析,建立了各因素与涂层表面显微硬度的数学模型,并探究了工作电流、送粉速度和扫描速度对涂层表面显微硬度的显著特性及影响规律,根据多元函数极值理论,确定最优参数组合并进行了试验验证。试验得到的最优参数组合为:工作电流105A,送粉速度14r/min,扫描速度80mm/min,此时涂层表面显微硬度可达到1075.03HV,约是基体材料的7.49倍。该结果可以为高铬铁基硬质涂层表面性能的改善研究提供理论依据。     

电化学改性提高飞机蒙皮胶接强度的工艺研究

前　言飞机在受到弹伤、烧伤或其他意外损伤 ,造成蒙皮严重变形、裂纹、破孔以及内部结构件断裂时 ,一般采用等强度铆接修理[1] 。在战伤抢修时 ,多采用胶接或胶铆结合修复工艺。对蒙皮采用托底平补法修理 ,对桁条采用接补法[2 ] 修理。实验发现 ,飞机蒙皮胶接效果不仅与胶粘剂有关 ,而且与胶接工艺有关[3] ,尤其与待修部位的表面状态有关。为提高胶接强度 ,采用原位电化学氧化技术 ,对待修表面进行电化学改性处理 ,得到锯齿形的活性表面 ,有效地增加胶接的表面积和孔锚数量 ,提高了胶接强度。2　基本原理将待修部位接电源阳极 ,用象形石…     

AA5052薄板磁脉冲胶焊复合接头动态力学性能研究

目的 研究AA5052铝合金薄板在高速冲击载荷下的磁脉冲胶焊复合接头的动态力学性能,探究不同载荷速率对该胶焊复合接头力学和失效行为的影响规律.方法 利用磁脉冲焊接系统成功制备了胶焊复合连接试件.采用万能拉伸试验机、高速拉伸试验系统,结合全场应变测量系统,获得胶焊复合接头的力学性能规律,以及渐进失效过程和搭接区应变变化....     

5052铝合金胶接-磁脉冲焊接复合接头盐雾腐蚀性能研究

目的 研究5052铝合金板胶接-磁脉冲焊接复合接头的抗腐蚀性能和腐蚀路径.方法 以AA5052铝合金板为研究对象,选用胶接-磁脉冲焊接复合工艺进行连接,并在35℃、质量分数为5％的氯化钠溶液中对样件进行中性盐雾腐蚀试验6～18 d,之后对接头的剪切性能进行测试,再结合SEM对接头的腐蚀路径进行分析.结果 在中性盐雾腐蚀...     

Ni-P-PTFE化学复合镀工艺的正交优化

采用正交试验方法研究了Ni-P-PTFE化学复合镀工艺,探讨了氨基乙酸、丁二酸、乳酸、表面活性剂对镀层沉积速度和显微硬度的影响.获得了Ni-P-PTFE化学复合镀优化工艺:15 g/L氨基乙酸,15g/L丁二酸,8 mL/L乳酸,复合表面活性剂(全氟辛基磺酰胺碘化物型阳离子表面活性剂+全氟辛基磺酰胺型非离子表面活性荆).     

加辅助阴极钛板的离子渗氮工艺参数对TC4合金渗层厚度的影响

在辉光离子气体技术的基础上加上辅助阴极钛板,对TC4合金基材进行渗氮处理。通过选择典型的基体温度、保温时间和气体介质,设计了一组正交试验,并以渗层厚度为依据分析了渗氮工艺中基体温度、保温时间和气体介质对渗层厚度的影响。同时采用Axiovert 25CA（Zeiss）光学图像分析仪和GDA750辉光光谱分析仪观察了优化工艺条件下改性层的显微组织及元素分布。结果表明,在辉光离子渗氮工艺中基体温度对TC4合金渗层厚度影响最大,在最优工艺条件下渗氮改性层的形成能显著提高基材表面硬度。     

基于正交试验的Cu-Ni-Si合金加工工艺研究

利用L9(34)表对Cu-3.2Ni-0.75Si-0.3Zn合金的时效工艺进行了正交试验,结果发现,各因素对合金导电率和显微硬度影响程度的主次顺序分别为:时效温度＞合金状态＞时效后冷变形量＞时效时间和时效温度＞冷变形量＞合金状态＞时效时间.在保证合金性能不降低的情况下,该合金热轧板材经60%冷变形后,可直接进行时效而省去固溶处理.本试验所得合金的性能为:抗拉强度830MPa,显微硬度220Hv,导电率51%IACS,延伸率6%;同时材料厚度＜0.120 mm.     

Effect of multi pulse current treatment on microstructure and microhardness of resistance spot welded dual phase steel DP590

In this paper, microhardness and microstructural characteristics of dual phase DP590 steel resistance spot weld joint under two different welding conditions (i. e. single pulse and multi pulse) were studied. It was observed that applying multi pulse currents resulted in quasi-equiaxed grains of tempered martensite in fusion zone (FZ) of the weldment. The refinement of microstructure in fusion zone using multi pulse current treatment resulted in reduced hardness of the weld joint.     

NiCrBSi粉末火焰喷焊钢管的抗拉强度研究

采用氧乙炔火焰喷焊工艺在耐热钢管表面制备了镍基合金喷焊层,分别利用OM、SEM、EDS、TEM等方法分析了喷焊管表面与横截面的显微组织、形貌、元素分布及物相结构.通过拉伸实验测定了喷焊管的抗拉强度,观察了喷焊管的拉伸变形规律.结果表明,在实验工艺参数下,喷焊层内部形成了以γ-Ni固溶体为基体,呈弥散分布的富Cr针状第二相,以及硼硅酸盐玻璃相,在第二相粒子周围,γ-Ni固溶体内有大量位错缠绕.喷焊层与基体形成了冶金结合,整体抗拉强度高达522 MPa.拉伸后,钢管基体产生了延性裂纹,喷焊层发生了半脆性断裂.喷焊管同时具备了外层耐蚀耐磨性能与基材的良好韧性,综合性能有较大改善.     

Pulse current treatment effect on the strength of reinforcing steel and its weld joint under impact loading

We present results of static and impact tension tests of as-received reinforcing steel specimens, specimens with weld joints in their test portion, as well as specimens pretreated by high-density pulse current. As test results demonstrate, an increased strain rate enhances strength, and the pulse current treatment greatly influences the strength and plasticity of a defect-containing weld metal under static and impact tension. Translated from Problemy Prochnosti, No. 3, pp. 89–96, May–June, 2009.     

DP590双相钢点焊接头的正交试验及超声检测分析

对DP590双相钢点焊接头进行正交试验,研究不同工艺因素对点焊接头失效载荷和焊核直径的影响,确定最优点焊工艺参数,并探讨点焊接头压痕深度的超声测量方法.采用超声波水浸聚焦入射法对1.5 mm厚的DP590双相钢点焊接头进行超声C扫描,获得接头焊核直径,利用超声A扫信号,计算点焊接头压痕深度,并与实际测量结果对比.研究表明:焊接参数对DP590点焊接头的失效载荷与焊核直径的显著性影响一致,从大到小依次为焊接电流、焊接时间、电极压力;DP590点焊接头最优的焊接工艺参数为:焊接时间70 ms,焊接电流15.0 k A,电极压力6.5 k N,在此参数下接头的抗拉强度为9 521.4 N;超声A扫信号计算得到的点焊接头表面压痕率与实际压痕率的误差在2.5%~9.7%,超声计算所得压痕深度与实际测量压痕率较为接近.     

热输入对Q890高强钢焊缝组织及性能的影响

针对国内某钢厂最新研制的Q890高强钢,采用三种不同的热输入对其进行气体保护焊接,研究了不同热输入对焊缝金属组织、硬度及冲击韧性的影响.结果表明,3种热输入下,焊缝组织主要以板条贝氏体为主,并含有粒状贝氏体、少量的板条马氏体和残余奥氏体.随着热输入的增大,焊缝组织中贝氏体铁素体板条粗化,板条马氏体逐渐减少,而粒状贝氏体逐渐增多,部分残余奥氏体由薄膜状向块状转变;焊缝金属硬度随着热输入的增大而下降;焊缝金属的冲击韧性亦呈逐渐下降的趋势.     

Friction stir weld assisted diffusion bonding of 5754 aluminum alloy to coated high strength steels

In the present paper friction stir-induced diffusion bonding is used for joining sheets of 5754 aluminum alloy to coated high strength steels (DP600 and 22MnB5) by promoting diffusion bonding in an overlap configuration. Mechanical performance and microstructures of joints were analyzed by overlap shear testing, metallography, and X-ray diffraction. Our results show that the strength of joint is dependent upon tool travel speed and the depth of the tool pin relative to the steel surface. The thickness and types of intermetallic compounds formed at the interface play a significant role in achieving a joint with optimum performance. That is, the formation of high aluminum composition intermetallic compounds (i.e. Al₅Fe₂) at the interface of the friction stir lap joint appeared to have a more negative effect on joint strength compared to the presence of high iron composition intermetallic phases (i.e. FeAl). This is in agreement with previously reported findings that FeAl intermetallic can improve the fracture toughness and interface strength in Al/St joints.     

Microstructure and strength of high nitrogen steel joints brazed with Ni-Cr-B-Si filler

Brazing of high nitrogen austenitic stainless steels was carried out by using Ni-Cr-B-Si filler metal. The effects of brazing temperature (1020–1100°C) on the microstructure and shear strength of the joints were investigated. The results show that BN compounds with hexagonal structure are formed at the interface by the reaction of N from substrate and B from filler. The brittle Cr₅B₃ compounds with high microhardness are observed in the centre of brazing seam. The BN content increases and the Cr₅B₃ content decreases with the increase in brazing temperature. However, the content of BN compounds played a determinable role on the joint strength. The optimal shear strength of joints was 176.7?MPa when the joining temperature was 1020°C.     

不同基底上Ni微结构镀层结合强度的研究

在玻璃基底上溅射Ti或Cr/Cu种子层,并对Ti基板表面进行预处理,研究基底表面粗糙度、热处理温度对于Ni微结构镀层结合强度的影响。结果表明,基底表面粗糙度、热处理温度对Ni微结构镀层与基底的结合强度有较大影响,经过200℃的热处理,溅射Ti及Cr/Cu种子层与Ni微结构的结合强度提高近1倍。通过EC-SPM、SEM等分析手段,初步探讨了结合强度的影响机制。     

正交切削高强度钢绝热剪切带组织和硬度研究

为了研究切削速度和工件硬度对高强度钢锯齿形切屑内绝热剪切带显微组织和硬度的影响,利用光学显微分析、SEM和TEM以及硬度测量等方法观察和测量了不同切削速度下正交切削两种回火硬度的30CrNi3MoV钢形成的锯齿形切屑中绝热剪切带的微观组织和显微硬度的变化过程.结果表明:低速下形成以组织剧烈拉长为特征的形变带,高速下形成以组织严重细化为特征的转变带;工件硬度的提高有利于形成转变带;增加切削速度和工件硬度对转变带硬度影响很小,但会显著提高形变带硬度.     

Influence of precipitation on dislocation substructure and creep properties of P91 steel weld joints

Abstract

Two trial weld joints were prepared using the GTAW and SMAW methods and they underwent creep testing at temperatures between 525 and 625°C. The longest time to rupture was 45,811 h. Two main processes occurred during creep exposures: recovery and precipitation of secondary phases. Slight coarsenings of the M₂₃C₆ carbide, precipitation of Laves phase and Z-phase were observed after long tests at high temperatures. Some differences in microstructure and creep failure were found in the individual zones of weldments. After long exposure at temperatures up to 600°C, fractures occurred in the fine-grain heat-affected zone as a result of a low density of fine vanadium nitride and a high density of coarse particles at grain and subgrain boundaries. At 625°C, growth of Laves phase caused a softening of the ferritic matrix and crack propagation in the weld metal.