Uni- and bi-axial deformation behavior of laser welded advanced high strength steel sheets

Bead-on-plate butt joints of 2.5 mm hot rolled DP600/DP600 and 1.2 mm cold rolled TRIP700/TRIP700 steel sheets were performed using 6 kW CO₂ laser beam welding. The welding speed ranged from 1.5 to 3.0 and from 2.1 to 3.9 m/min in DP/DP and TRIP/TRIP steel weldments respectively. A top surface helium gas was used as a shielding gas at a flow rate of 20 l/min. Metallographic examinations and transverse tensile testing (DIN EN 895: 1995) were carried out to characterize the weldments. The formability of base metals and weldments were investigated by standard Erichsen test (DIN EN ISO 20482). It was found that the uniaxial plastic behavior of both DP600 and TRIP700 base metals was in agreement with Swift and modified Mecking–Kocks models respectively. In a perpendicular tensile test to the weld line, all specimens were fractured at the base metal however the strengths were somewhat higher than those of base metal. There was a significant reduction in formability caused by welding of both DP/DP and TRIP/TRIP steel weldments and the formability has been improved with the increase of the welding speed.     

On formability of tailor laser welded blanks of DP/TRIP steel sheets

Abstract

This paper aims to evaluate the formability of tailor welded blanks of dual phase (DP600)/transformation induced plasticity (TRIP700) steel sheets. In this work, bead on plate butt joints of 2·5 mm DP600 and 1·2 mm TRIP700 steel sheets were performed using CO₂ laser beam welding. Microhardness measurements and transverse tensile testing were carried out to characterise the welds. The formability of base metals and welds were investigated by standard Erichsen test. In a perpendicular tensile test to the weld line, all specimens were fractured at the TRIP base metal, and the strengths were somewhat higher than those of base metal. There was a significant reduction in formability caused by welding of the DP600/TRIP700 steel sheets, and the formability increased with increasing welding speed.     

GMAW-P工艺参数对TCS345不锈钢焊接接头缺口冲击韧度的影响

以TCS345铁素体不锈钢名义熔合线处的缺口冲击韧度为研究对象,采用一次回归正交试验,考察脉冲熔化极气体保护焊(pulse gas metal arc welding简称GMAW-P)脉冲工艺参数对名义熔合线处缺口冲击韧度的影响,分析脉冲电流、脉冲时间、脉冲频率、焊接速度及其交互作用对焊接接头名义熔合线缺口冲击韧度的影响规律.结果表明,TCS不锈钢焊接热影响区的组织为铁素体+马氏体.运用MATLAB优化函数对焊接工艺参数进行优化,优化结果为脉冲电流450A、脉冲时间2.3ms、脉冲频率250Hz、焊接速度500mm/min.     

PMMA与304不锈钢激光焊接

研究聚甲基丙烯酸甲酯(PMMA)塑料与304不锈钢激光焊接热传导技术,采用正交试验法分析聚甲基丙烯酸甲酯和304不锈钢之间的焊接质量. 对焊接后的试样进行拉伸测试和切片试验,用能量密度定量判定焊接结果,分析多种焊接因素对抗拉强度和焊缝宽度的影响. 利用正交试验极差分析法对试验数据进行处理,获得透明聚甲基丙烯酸甲酯和304不锈钢之间激光热传导焊接的最佳焊接工艺参数. 结果表明,焊接因素对焊接强度的影响从大到小的顺序为焊接速度、脉冲宽度、保护气体流量、峰值功率、光斑直径和脉冲频率.     

CO_2激光焊接600MPa DP钢接头组织与性能

采用CO2激光对抗拉强度为600MPa,厚度1.4mm的DP钢进行焊接.研究焊接速度对焊缝外观和截面成形的影响、接头的组织特点、硬度、强度和成形能力.结果表明,激光功率相同,焊接速度较低时焊缝易产生气孔,焊接速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝区组织主要由马氏体构成,从焊缝、焊接热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝出现马氏体组织,接头的塑性和韧性降低,板材的冲压成形能力下降.     

Nd:YAG激光焊接800 MPa TRIP钢的接头组织与性能

采用Nd:YAG激光对强度为800MPa,厚度为1.2mm的TRIP钢板进行焊接.研究焊接速度对焊缝外观和截面成形的影响及接头的组织特点、硬度、强度和成形能力.激光功率相同,焊接速度较低时焊缝易产生气孔,速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝组织主要由马氏体构成,从焊缝、热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝中出现马氏体,接头的塑性和韧性降低,板材的冲压成形能力下降.     

ST14钢激光拼焊板焊缝组织及成形性能分析

对1.5mm和0.8mm两种规格的ST14钢等厚激光拼焊板焊缝部位进行杯突试验,比较焊缝与母材杯突值;再对由这两种规格组合拼焊的不等厚激光拼焊板进行单向拉伸试验,检验拼焊板经拉伸后的断裂部位;分析焊缝区组织及其硬度变化,研究激光焊接参数变化对ST14钢拼焊板成形性能的影响.结果表明,焊缝深冲性能低于母材,焊缝杯突值受焊接速度影响,随焊接速度增加而增加;激光焊缝抗拉强度高于母材;对于1.5 mm拼焊板,提高焊接速度,加快焊缝冷却,有利于生成细小的针状铁素体,可提高激光拼焊板的成形性能;而0.8 mm板焊缝生成晶粒细小的粒状贝氏体组织,可使焊缝区材料成形性能接近母材;焊缝及其热影响区的硬度高于母材硬度.     

S355钢激光-MIG复合焊接头显微组织和残余应力

采用激光-MIG(metal inert gas welding, MIG)复合焊接方法对12 mm厚S355钢板进行焊接,分析了9 kW激光功率下复合焊接头显微组织和硬度分布规律. 建立了适合低合金高强钢激光-MIG复合焊接的双椭球 + 三维锥体复合热源模型来描述复合热源的能量分布,采用SYSWELD软件计算了1.0,1.5,2.0 m/min三种焊接速度下激光-MIG复合焊的温度场和接头的残余应力,分析了焊接速度对焊接过程的温度场和残余应力分布的影响. 结果表明,三种焊接速度下粗晶热影响区(coarse grained heat affected zone, CGHAZ)的组织为马氏体,接头的硬度水平较高,最高硬度均在350 HV以上. 焊接速度增加,熔池最高温度下降,焊后冷却速度增加. 等效残余应力水平较高,HAZ位置出现了应力集中;随着焊接速度增加,等效残余应力、纵向残余应力、横向残余应力和厚度方向的残余应力峰值均上升;但焊接速度从1.5 m/min增加到2.0 m/min时,各应力分量的拉应力峰值上升较少,而压应力峰值显著上升.     

铝合金光纤激光高速压力焊接

铝合金对近红外光纤激光反射率高,激光能量利用率低,目前通常采用"万瓦级"光纤激光实现铝合金的高速激光焊接.文中采用激光压力焊接的方法,实现了铝合金"千瓦级"光纤激光的高速焊接.研究了不同工艺参数下焊缝的成形性,计算了激光能量的汇聚规律,并利用电子背散射衍射技术(EBSD)对焊缝微观结构进行表征.结果表明,激光功率为1～...     

工艺参数对激光透射焊接聚碳酸酯影响

利用激光透射焊接技术对聚碳酸酯（PC）塑料进行焊接,通过正交试验法研究了激光功率、焊接速度、碳黑含量对焊接强度和焊接质量的影响.探讨了热输入对焊接强度的影响,通过对焊缝显微形貌分析,进一步研究了炭黑含量对焊接质量的影响.结果表明,对PC材料来说,激光功率是首要影响因素,其次是焊接速度,最后是碳黑含量.最佳的焊接工艺参数为激光功率40 W,焊接速度40 mm/s,含碳量0.1%.热输入对焊接质量有较大影响,热输入在0.5～1.3 J/mm可得到较好强度的焊件.     

快速冷却对DP1000双相钢激光焊接接头性能的影响

激光焊接DP1000双相先进高强钢的过程中,普遍存在焊接热影响区的软化现象,热影响区的软化严重影响了焊接结构的成形和使用性能. 为了能提高焊接接头的成形和使用性能,采用快速冷却的方式来改善其焊接热影响区的软化问题. 通过拉伸试验、显微硬度测试、扫描电镜和光学显微镜等手段对比研究了1.5 mm厚DP1000双相钢板有无快速冷却的焊接接头中组织和性能的变化. 结果表明,在快速冷却条件下,激光焊接DP1000双相钢的接头热影响区软化区较空冷焊接的窄,软化现象有所改善,强度和塑性均有所提高.     

低功率激光-双电弧焊接钛合金中厚板工艺及机理

采用单钨极惰性气体保护焊(single tungsten inert gas welding,STIG焊)、双钨极惰性气体保护焊(double tungsten inert gas welding,DTIG焊)、激光-STIG电弧(L-STIG)复合焊和激光-DTIG电弧(L-DTIG)复合焊4种方式对6 mm 厚TA2钛合金进行对接焊试验,实现单面焊双面成形. 结果表明,L-DTIG复合焊的电弧能量更为集中,焊接速度可达680 mm/min. L-DTIG复合焊的热输入为605.5 J/mm,仅是DTIG焊的35.5%和L-STIG复合焊的59.0%. L-DTIG复合焊接头的焊缝区晶粒细小,显微硬度可达229.5 HV. 拉伸试样在母材处断裂,接头抗拉强度优于母材. 加入激光后,L-DTIG复合焊的电弧等离子体中心导电区在xOz和yOz平面电弧分别收缩51.0%,45.5%,电弧根部收缩75.0%. 测得L-DTIG复合焊热源在工件上的电弧压力为3 465 Pa,分别是DTIG焊和L-STIG复合焊的4.17和2.25倍. 较高的电弧收缩比和电弧压力可显著提高焊接效率,降低焊接热输入.     

Tailored blank welding between low carbon steel sheet and STS 304 stainless steel sheet by CO2 laser beam

A basic reseach of tailored blank welding between a low carbon steel sheet and a STS 304 stainless steel sheet was carried out with CO₂ laser beam. The materials used in this work were a low carbon steel sheet with a thickness of 0.9 mm and a STS 304 stainless steel sheet with the same thickness. Experiments were carried out by applying the Taguchi method to obtain optimized conditions in order to apply this tailored blank laser welding method in the practical manufacturing process. In order to compare the laser welding results with the conventional welding process, GTA welding was carried out for the same materials. Optical microscopy, SEM and XRD analyses were performed to observe the microstructures and to analyze the various phases. A tensile test, hardness test and Erichsen test were performed to evaluate the formability of welded specimens. In addition, immersion test was carried to estimate corrosion resistance. A WDS analysis showed that laser welding resulted in almost the same dilution of both low carbon steel and stainless steel in welded metal, meanwhile, GTA welding resulted in more dilution of stainless steel due to its slower heat conductivity. The formability of the laser welded specimen reached 83% of that in base metal. On the other hand, it was 63% in the case of GTA welding. During the tension test, base metal was fractured in the case of a laser welded specimen, meanwhile the welded zone was fractured in the case of the GTA welded specimen. The corrosion test showed that weight loss per unit area was less in the laser welded specimen than that of the GTA welded specimen.     

TA2中厚板低功率激光诱导双电弧高效焊接及机理

采用低功率脉冲激光诱导双TIG复合焊接热源(LITTW)实现了6 mm厚TA2纯钛中厚板的高效焊接,基于Ti粒子的动力学行为,研究了激光脉冲对电弧等离子体的影响.结果表明,LITTW比激光诱导单TIG焊接(LISTW)的电弧能量更加集中,焊接能耗仅为LISTW的50.9%,速度却达到LISTW的2.3倍.激光脉冲作用后,电弧等离子体由能量集中状态恢复到原始电弧形态存在一个恢复时间,在本试验条件下,LITTW的恢复时间为6.5 ms,比LISTW延长了3 ms. LITTW中稳定的匙孔形态为Ti粒子持续向电弧等离子体转移提供了条件,延长了电弧等离子体的恢复时间.     

Optimization of Ti6Al4V titanium alloy laser–arc hybrid weld parameters

This article reports the results of a study aimed at using statistical methods to optimize the parameters for laser–arc hybrid butt welding of Ti6Al4V titanium alloy sheets with a thickness of 3.0 mm. The study has examined the effects of the hybrid welding process parameters, such as laser beam power, arc pulse frequency, arc length, arc current, wire speed, laser and arc relative positions, and weld speed. Microstructure has been studied using light microscopy and morphological analysis of weld bead cross sections. This article reports the results of energy and morphological tests.     

Nd:YAG laser micro-welding of ultra-thin FeCo–V magnetic alloy: optimization of weld strength

The main aim of this research is to optimize the tensile strength of laser welded FeCo–V alloy. A mathematical relationship was developed to predict tensile strength of the laser beam welded FeCo–V foils by incorporating process parameters such as lamping current, welding speed, pulse duration and focused position. The procedure was established to improve the weld strength and increase the productivity. The results indicate that the pulse duration and welding speed have the greatest influence on tensile strength. The obtained results showed that the tensile strength of the weld joints increase as a function of increasing pulse duration reaching to a maximum at a pulse duration value of 2.25 ms. Moreover, the tensile strength of joints increases with decrease in welding speed reaching to a maximum at a welding speed of 125 mm/min. It has been shown that increase in pulse duration and decrease in welding speed result in increased effective peak power density and hence formation of more resistant welds. At higher pulse durations and lower welding speeds, the tensile strength of weld joints decreases because of formation of solidification microcracks in the fusion zone.     

Comparison of formability of friction stir welded and laser welded dual phase 590 steel sheets

Abstract

The formability of welded dual phase 590 (DP 590) steel sheets was investigated, using both friction stir welding and laser welding. Similar and dissimilar gauge sheets were joined using both processes. The laser welded sheets were produced under process conditions typical of industrial production of tailor welded blanks. The friction stir welded specimens were produced in a lab, where different tool rotational speeds and translation speeds were investigated in order to obtain good weld properties. The formability of the welded sheets was evaluated using a series of mechanical tests, including transverse tension and plane strain formability testing. Friction stir welded specimens performed about the same as laser welded specimens in transverse tension testing; however, hardness profiles showed that the laser welds had greater peak hardness than the friction stir welds. Therefore plane strain formability tests were performed with the welds oriented along the major strain direction. When this type of weld stretching was performed the friction stir welded sheets were shown to be ～20% more formable than the laser welded sheets.     

Microstructure and Mechanical Properties of Friction Stir Welded 1.5 GPa Martensitic High-Strength Steel Plates

In this study, 2.4 mm thick high-strength martensitic steel plates with a tensile strength of 1500 MPa were friction stir welded at various welding speeds of 40, 60, 80, 100, 120 mm/min and a constant rotation speed of 300 rpm. Sound joints could be obtained when the welding speed was 40, 60 and 80 mm/min, while a kissing bond was found in the joint welded at 100 and 120 mm/min. It was revealed that the peak temperature exceeded A_C3 (the end temperature at which all ferrite transformed to austenite when the steel was heated) for all the welding conditions and martensitic structures were finally formed in the stir zone of the joints. A significant decrease in hardness was located in the heat-affected zone, which had a transitional microstructure from tempered martensite near base metal to a mixed structure containing hard martensite, soft ferrite and bainite near stir zone. For the sound joints, the specimen was fractured in the heat-affected zone during tensile tests and the highest tensile strength could reach about 1058 MPa.     

基于试验设计与统计分析的双相钢激光焊工艺优化

为了优化激光焊接接头力学性能,利用试验设计方法对厚度为1.7 mm的DP600双相钢进行对接焊接试验,采用回归分析得到了激光焊接功率、焊接速度、离焦量、侧吹保护气体流量与接头抗拉强度之间的数学模型. 分析了焊接速度与侧吹气流量对焊缝抗拉强度的交互影响作用. 通过遗传算法优化该模型并得到了最优的焊接工艺参数组合,当焊接功率为1.7 kW,焊接速度为25 mm/s,侧吹气流量为2.4 m3/h,离焦量为-1 mm时焊缝的抗拉强度最大. 验证试验所测的焊缝抗拉强度值与模型预测值的相对误差在5%以内. 结果表明,文中研究可以有效的预测与优化厚度为1.7 mm的双相钢激光焊接质量.     

Effects of welding velocity on the impact behavior of droplets in gas metal arc welding

The influence of welding velocity on the impact behavior of the globular metal transfer was studied by high speed video photography with a laser source during gas metal arc welding of E36 steel. The welding current and voltage were 180 A and 30 V during the welding process. The results indicated that the impact location of a droplet depended strongly on the welding velocity. There was a critical welding velocity (0.4 m/min) that when the welding velocity was lower than this value the droplet impacted inside the weld pool, while the welding velocity was higher than this value the droplet impacted outside the weld pool. The results showed that when a droplet impacted outside the weld pool it would rebound or adhere on the workpiece, which was depended on the kinetic energy of the droplet. The rebound percentage of droplets increased with increasing kinetic energy. With increasing welding velocity, the mass of droplets was not changed obviously, but the flight velocity of the droplet increased, i.e. the kinetic energy of droplets increased with increasing welding velocity. The results also showed that when a droplet impacted outside the weld pool, the droplet which rebounded away from the workpiece surface formed weld spatters, resulting in discontinuous weld appearance, while the droplet which adhered on the workpiece surface streamed to the weld pool and good weld joint would still be obtained. Molten metal decreases with increasing welding velocity. When the welding velocity increases from 0.4 m/min to 2.0 m/min, the weld width decreases from 12.9 mm to 6.3 mm and the weld penetration decreases from 5.4 mm to 2.1 mm.