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、...     

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。     

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...     

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     

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.     

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.     

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.     

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.     

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.     

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.     

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…     

胶粘剂辅助下CFRP/低碳钢的电阻凸塞焊接头特性

为了实现CFRP与钢的可靠稳定连接,采用胶粘剂辅助下电阻凸塞焊方法对其进行焊接.观察、分析了接头中各区域的接合状态,探讨了焊接电流对接头几何特性与抗剪载荷的影响.结果表明:焊接电流小于5.5 kA时,接头主要是通过胶粘剂连接而成,焊接电流对接头的抗剪载荷影响较小;焊接电流超过5.5 kA时,接头的连接则是金属连接与胶接...     

Effect of joint design on the failure behaviour of three-stack-up austenitic stainless steel resistance spot welds

Tensile shear tests were carried out on three-stack-up austenitic stainless steel resistance spot welds having four types of joint design. Mechanics-based criteria were applied to reveal the difference in the stress state at the microstructural level. Optical microscopy and scanning electron microscopy showed evidence of the different stress states for different joint designs. Nugget rotation generated combined tensile/shear stress at the microstructural level. The peak load and the energy absorption of the joints reduced with the growth of the normal component of the global loads. Joints for which both interfaces bear the load were more prone to failure in pull-out mode.     

Mechanical property and microstructure of resistance spot welded twinning induced plasticity-dual phase steels joint

Abstract

The present paper deals with the joining of twinning induced plasticity and dual phase steels, carried out by spot welding process with two different pulse durations (200 and 380 ms), by keeping other parameters constant. The microstructural and elemental analysis of the joints was characterised by optical microscopy and electron probe microanalyser. The mechanical properties of the joint were understood from microhardness measurements across the fusion zone as well as through shear and cross-tensile tests. The pulse duration of 380 ms has resulted in good macrostructure with negligible shrinkage void. It also shows smooth transition in hardness across the twinning induced plasticity steel/nugget/dual phase steel interfaces and good mechanical properties as compared to the joint prepared by pulse duration of 200 ms. Larger pulse duration results in sufficient time for the diffusion of alloying elements and yields negligible void formation due to Kirkendall effect.     

热输入对低合金高强钢超窄间隙焊接热影响区组织和性能的影响

采用超窄间隙熔化极混合气体保护自动焊接技术,以低合金高强钢NK-HITEN610U2与国产焊丝为对象实施焊接.为了研究不同的焊接热输入对其热影响区的微观组织和力学性能的影响,分别设计了五组不同的热输入值(6 kJ/cm,10 kJ/cm,14 kJ/cm,18 kJ/cm,22 kJ/cm),对五组试件进行实验.分析了焊态(未经热处理)焊接热影响区各区显微组织、微区硬度和宏观形貌.结果表明,随着热输入的增大,热影响区宽度相应增加,微观组织也发生变化,晶粒随热输入增加而增大,晶内针状铁素体随热输入增加而减少,粒状贝氏体增多.     

铝合金与低碳钢的夹层电阻点焊接头特性

以钎料Al86Si6Mg8薄带为中间层对铝合金A6061与低碳钢Q235进行了点焊,观察分析了接合界面区反应层形貌及分布等微观组织结构特征,探讨了焊接电流、焊接时间与电极压力对熔核尺寸和接头抗剪力的影响。接头熔核直径与抗剪力随焊接电流、焊接时间的增加而增加,随电极压力的增大而降低,在19 k A的焊接电流条件下获得接头的抗剪力达到5.2 k N。试验结果表明,夹层的使用起到了抑制界面反应层生长和提高接头性能的效果。     

Joining phenomena and joint strength of friction welded joint between pure aluminium and low carbon steel

Abstract

This paper describes the joining phenomena and joint strength of friction welded joints between pure aluminium (P-Al) and low carbon steel friction welds. When the joint was made at a friction pressure of 30 MPa with a friction speed of 27·5 s^?1, the upsetting (deformation) occurred at the P-Al base metal. P-Al transferred to the half radius region of the weld interface on the low carbon steel side, and then it transferred toward the entire weld interface. When the joint was made at a friction time of 0·9 s, i.e. just after the initial peak of the friction torque, it had ～93% joint efficiency and fractured on the P-Al side. This joint had no intermetallic compound at the weld interface. Then, the joint efficiency slightly decreased with increasing friction time. The joint had a small amount of intermetallic compound at the peripheral region of the weld interface when it was made at a friction time of 2·0 s. When the joint was made at a friction time of 0·9 s, the joint efficiency decreased with increasing forge pressure, and all joints were fractured at the P-Al side. Although the joint by forge pressure of 90 MPa had hardly softened region, it had ～83% joint efficiency. To clarify the fact of decreasing joint efficiency, the tensile strength of the P-Al base metal at room temperature was investigated, and the tensile test was carried out after various compression stresses and temperatures. The tensile strength of the P-Al base metal has decreased with increasing compression stress at any temperature. Hence, the fact that the joint did not achieve 100% joint efficiency was due to the decrease in the tensile strength of the P-Al base metal by the Bauschinger effect. To obtain higher joint efficiency and fracture on the P-Al side, the joint should be made without higher forge pressure, and with the friction time at which the friction torque reaches the initial peak.     

辅助垫片对铝/钢电阻铆焊接头性能的影响

为提高接头强度,在铝合金与钢的电阻铆焊中施加辅助垫片以扩大铆钉肩部与上板铝合金的接触面.观察、分析了接头中各界面的接合状态,探讨了焊接电流对接头抗剪力与十字抗拉力的影响.结果 表明:在施加辅助垫片的电阻铆焊接头中,铆钉肩部与辅助垫片、铆钉腿端部与下板铝合金之间都实现了熔合,在铆钉腿端部与铝合金的接合界面观察到了金属间化合物形成.施加辅助垫片的铝合金与钢电阻铆焊接头的抗剪力与十字抗拉力均随焊接电流的增大而呈先增大后下降的变化趋势,其最大值分别达7.51 kN和4.23 kN.