钛与低碳钢的夹铜电阻点焊接头的特性

为改善接头性能,以100 μm厚的铜箔为中间层对钛与低碳钢Q235进行电阻点焊.观察、分析了接头中各特征区域的微观结构,探讨了焊接电流、焊接时间和电极压力对接头熔核尺寸及抗剪载荷的影响.结果 表明:以铜为中间层的钛与低碳钢点焊接头熔核内部与端部分别由Ti-Fe系和Cu-Ti系金属间化合物构成.接头的抗剪载荷随焊接电流、...     

磁处理改善低碳钢焊接接头的耐腐蚀性能

研究了磁处理对低碳钢焊接接头耐腐蚀性能的影响.低碳钢平板焊接试样的全浸泡腐蚀试验结果表明,磁处理后,试样的腐蚀速率有一定量的下降,下降的相对平均值为2.58%.对低碳钢平板试样的TIG焊接过程进行了有限元数值模拟,分析了平板试样内的残余应力分布.并在此基础上,对试样在磁处理前后的腐蚀速率差异值进行了统计意义上的显著性检验.分析结果表明,磁处理引起试样的腐蚀速率下降值在显著性为5%的试验误差范围以外,由此可见,磁处理可在显著性水平为5%的意义上改善低碳钢焊接接头的耐腐蚀性能.     

基于铜镀层的低碳钢/铝合金电阻点焊接头性能

针对铝合金与钢二者难以直接焊接的问题,采用预先在低碳钢Q235钢板上镀铜,再与铝合金A6061进行电阻点焊的方法,并研究焊接参数对点焊接头的显微组织和力学性能的影响。结果表明:接头抗剪载荷和焊点直径随焊接电流和焊接时间的增加而增加,随电极压力的增大而减小;接头破坏形式出现了界面断裂和纽扣式破坏两种类型;熔核中铝合金的显微硬度相比原始态的铝合金有所升高。与未镀铜点焊接头相比,镀铜Q235与A6061接头界面生成的金属间化合物较薄,说明镀铜可以有效抑制铝合金/钢的界面反应。     

低碳钢点焊结构的力学参数分析

以低碳钢为母材的点焊结构为研究对象,分别使用调试引伸计、拉伸试验和ANSYS的数值仿真三种方法,研究点焊结构的变形和应力状态,得出角度变形与载荷之间的关系,仿真分析点焊结构分焊核、塑性环和母材三部分的力学模型的合理性. 采用点焊结构力学模型分析仿真结果. 结果表明,得出角度变形量随载荷之间的关系,过程中调整塑性环的屈服极限和塑形模量的数值,使得仿真的角度变形量和试验结果相一致. 有限元仿真的塑性环的屈服极限和塑形模量是可测的,可以为以后相关的研究提供参考.     

不锈钢A-TIG焊接头的抗腐蚀性能分析

用沸腾硝酸腐蚀法和室温硫酸加硫酸铜溶液浸蚀法对奥氏体不锈钢TIG焊和自制活性剂A-TIG焊接头进行了对比腐蚀试验.结果表明,自制活性剂A-TIG焊接头在室温下具有良好的耐硫酸腐蚀能力,比TIG焊接头有更强的抗沸腾硝酸腐蚀能力.焊缝金属的化学成分分析表明,自制活性剂在焊接过程中能抑制金属中Cr、Ni等合金元素的烧损,因此提高了A-TIG焊接头的抗腐蚀性能.     

Dependence of overload performance on weld attributes for resistance spot welded galvanized low carbon steel

Microstructure and failure behavior of galvanized low carbon steel resistance spot welds were investigated. Failure mode, peak load and energy absorption obtained in tensile-shear test were used to describe spot welds performance. It was found that weld fusion zone size, electrode indentation and expulsion can significantly affect the mechanical performance of spot welds. Failure mechanism of spot weld which fail via pullout mode during tensile-shear test was “through thickness” localized necking in the base metal. However, those spot welds which have experienced severe expulsion during welding, failed at the fusion zone/HAZ interface. This can contribute to the reduction in energy absorption capability of spot welds due to the harder microstructure of the fusion zone/HAZ compared to the soft ferritic base metal.     

超高强度钢与镀锌双相钢电阻点焊接头强度试验

试验研究了超高强度硼钢板/镀锌双相钢板的电阻点焊接头质量缺陷及其产生原因,通过正交试验设计,重点讨论了焊接电流、通电时间和电极压力对点焊接头强度的影响.结果表明:超高强度硼钢板/镀锌双相钢点焊中超高强度钢板侧更易出现飞溅和烧穿问题,通电时间和焊接电流强度时点焊接头拉剪强度影响显著,这类钢板组合的焊接应优先采用大电流、短...     

Interfacial characterization of resistance spot welded joint of steel and aluminum alloy

The dissimilar material resistance spot welding of galvanized high strength steel and aluminum alloy had been conducted. The welded joint exhibited a thin reaction layer composed of Fe2Al5 and Fe4Al13 phases at steel/aluminum interface. The welded joint presented a tensile shear load of 3.3 kN with an aluminum alloy nugget diameter of 5.7 ram. The interfucial failure mode was observed for the tensile shear specimen and fracture occurred at reaction layer and aluminum alloy fusion zone beside the interface. The reaction layer with compounds was the main reason for reduction of the welded joint mechanical property.     

低碳钢激光焊焊接接头金相组织

焊接方法激光焊母材材质Ｑ2 35钢低碳钢激光焊焊接接头金相组织$哈尔滨焊接研究所金相室@孙秀芳 $哈尔滨焊接研究所金相室@郭力力 $哈尔滨焊接研究所金相室@于捷     

Observation of twinned martensite in weld heat affected zone of Grade 100 low carbon microalloyed steel

Abstract

The microstructural changes caused by a low nominal heat input of 0.5 kJ mm^-1 in the coarse grained heat affected zone (CGHAZ) of Grade 100 microalloyed steel were investigated. Microhardness measurements suggested that the CGHAZ was martensite of maximum theoretical hardness for the carbon content of the steel. The bulk of the CGHAZ was lath martensite containing none of the small and few of the intermediate sized Nb precipitates responsible for strength and grain size control in the steel plate. Twinned martensite was unexpectedly observed in local areas of the CGHAZ. The formation of twins, which are normally seen in steels with a higher level of carbon, is explained by a combination of the rapid heating rates, high peak temperatures, precipitate dissolution and dispersion, and rapid cooling rates.     

Effect of post-weld heat treatment on joint properties of friction welded joint between brass and low carbon steel

Abstract

This paper describes the effect of post-weld heat treatment (PWHT) on joint properties of copper–zinc alloy (brass) and low carbon steel friction welded joints. The as-welded joint obtained 100% joint efficiency and the brass base metal fracture without cracking at the weld interface, and had no intermetallic compound layer. The joint efficiency with PWHT decreased with increasing heating temperature and its holding time, and its scatter increased with those increasing parameters. When the joint was heat treated at 823 K for 360 ks, it did not achieve 100% joint efficiency and fractured between the weld interface and the brass base metal although it had no intermetallic compound. The cracking at the peripheral portion of the weld interface was generated through PWHT. The cracking was due to the dezincification and the embrittlement of the brass side during PWHT.     

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.     

Effect of nickel with chromium on microstructure and toughness of heat affected zone in low carbon steel

Abstract

In the present work, the effects of nickel with chromium and of varying heat input on the microstructure and toughness of the grain coarsened heat affected zone (GCHAZ) of a low carbon steel were investigated. In the welding experiments, low carbon steel specimens having five different combinations of nickel and chromium content (0·9Ni–0·3Cr, 1·9Ni–0·8Cr, 2·8Ni–1·3Cr, 3·8 Ni–1·7Cr, and 4·9Ni–2·1Cr, all wt%) were welded using a submerged arc welding process with heat inputs of 0·5, 1, and 2 kJ mm^-1. Following welding, the microstructure, hardness, and toughness of the GCHAZs were investigated. From the results, attempts were made to establish a relationship between heat input, nickel and chromium contents, microstructure, hardness, and toughness of the GCHAZ. Charpy impact testing and microstructural observation showed that, for a heat input of 0·5 kJ mm^-1, nickel plus chromium contents in the range 1·9Ni–0·8Cr to 4·9Ni–2·1Cr promoted the formation of martensite, thereby producing lower toughness values. It was subsequently found that, taking into consideration the microstructure, hardness, and toughness of the GCHAZ, an intermediate heat input (1 kJ mm^-1) gave higher toughness values for all nickel and chromium contents. However, it was observed that satisfactory toughness values could not be obtained by varying the heat input for the 3·8Ni–1·7Cr and 4·9Ni–2·1Cr steels.     

Characterization of friction stir welded joint of low nickel austenitic stainless steel and modified ferritic stainless steel

Friction stir welding (FSW) of dissimilar stainless steels, low nickel austenitic stainless steel and 409M ferritic stainless steel, is experimentally investigated. Process responses during FSW and the microstructures of the resultant dissimilar joints are evaluated. Material flow in the stir zone is investigated in detail by elemental mapping. Elemental mapping of the dissimilar joints clearly indicates that the material flow pattern during FSW depends on the process parameter combination. Dynamic recrystallization and recovery are also observed in the dissimilar joints. Among the two different stainless steels selected in the present study, the ferritic stainless steels shows more severe dynamic recrystallization, resulting in a very fine microstructure, probably due to the higher stacking fault energy.     

Fracture resistance of simulated heat affected zone areas in HSLA structural steel

Abstract

The fracture toughness of some areas in the multi-pass heat affected zone (HAZ) of a high strength low alloy (HSLA) structural steel was analysed in a straightforward way using precracked, cylindrical specimens tested on a conventional tensile machine. The specimens were made from samples with a simulated HAZ microstructure; however, the size of the samples was restricted by the limitations of the Gleeble machine. The brittleness of the samples was an indication of the detrimental effect of welding on their toughness. The specimens were not large enough for a direct K_Ic measurement over a wide testing temperature range; it was necessary to modify the results. The low fracture toughness and the substantial shift of fracture transition temperatures suggest that welding of the investigated steel could be a delicate procedure.     

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.     

Evaluation of joint strength of friction welded carbon steel by heat input

In a search for increases in productivity and to comply with labour laws, companies have focused on questions related to health and safety at work. Among the many risks involved in the welding scenario (fumes, electric shock, mechanical crushing by movable parts in pressure processes, or jig systems, etc.), non-ionizing radiation stands out as a major concern in the arc welding process and some authors have called for attention to measuring ultraviolet (UV) radiation. This radiation measurement can be applied to the development of welding processes or to establish less hazardous conditions for human beings where robotic welding is not suitable. As a result, the aim of this work is to present a comparison of radiation levels in terms of different wavelength ranges (UV-total and visible, UV-A, UV-B, and UV-C) for different arc welding processes (GTAW, GMAW, SMAW, and FCAW). It is expected that the results will lead to a more in-depth discussion on this subject.     

Influence of microstructure and roughness level on corrosion resistance of the austenitic stainless steel welded joint

The influence of microstructure and surface roughness of the X5CrNi18-10 austenitic stainless steel-welded joint on resistance to uniform, pitting, and intergranular corrosion, as well as on the stability of the passive film, was evaluated. The microstructure was revealed by optical microscopy and scanning electron microscopy, whereas surface topography and roughness levels were determined by atomic force microscopy. Corrosion characteristics were obtained by the electrochemical potentiokinetic reactivation method with double loop, electrochemical impedance spectroscopy method, as well as by potentiodynamic measurements. The degree of sensitization of heat-affected zone (HAZ) was significantly lower than the threshold value required for the occurrence of intergranular corrosion. However, HAZ showed a significantly greater tendency to pitting and uniform corrosion compared to weld metal and base metal. No effect of roughness levels (RMS from 3.6 to 54 nm) on the pitting potential value of the welded joint was observed (unlike in HAZ). The polished surface shows significantly higher corrosion resistance than the grinded surface. Generally, polishing improved corrosion resistance, especially in HAZ, which is very important because HAZ is a critical place for the occurrence of pitting and other types of corrosion.     

Relationship between microstructures and mechanical properties of resistance spot welded joint of spring steel

0IntroductionSpring steel(65Mn,60Si2Mn) has a high carbon e-quivalent (Ceq≈0.9) and strong hardening capacity. Inresistance spot welding process, the cooling rate of nuggetand heat-affected zone is quite rapid (about 104 -105℃/ s),and martensite which has high hardness forms atthe spot welded joint. Martensite structure, which is hardand brittle, makes mechanical properties of the resistancespot welded joint of spring steels greatly decline. There-fore, the weldability of resistance spot w…