Study of welding technology on Baosteel high-strength heavy steel Bweldy620QL6

This study aims to conduct the weldability test for a high-strength structural steel, Bweldy620QL6, developed by Baosteel. This steel was subjected to welding,and the effects of two kinds of shielding gas,a binary gas of 80% Ar ＋ 20% CO, and ternary gas of 90% Ar ＋ 8% CO, ＋ 2% O2, on the performance of the welded joints of high-strength heavy steel were compared. The results show that Bweldy620QL6 has good weldability,and the joints obtained using binary gas and ternary gas meet common requirements.

DEVELOPMENT OF EFFECTIVE TECHNOLOGICAL PROCESSES OF HIGH-STRENGTH STEEL WELDING

Composition and service properties of high - strength low-alloyed steels with 590-980 MPa yield strength,which find an application in Russia, Belorus,Ukraine and other countries of the former USSR in manufacture of welded structures of a powerful mining and transport machinery, are given. Electrodes and wires for main processes of arc welding of these steels have been devel- oped on the basis of a rational use of different systems of alloying (08KhN2GM,08KhNG2M, and also economical systems of type 10G25, ect. ). Main approaches to the technological provess- es of manufacture of structures of high - strength steels are formulated.They are mainly directed to the weakening of de offect of the factors which contribute to a delayed fracture of joints (diffusive hydrogen,unfavourable rates of cooling,level of residual stresses). When there are no stress concentrators (and at a low level of residual stresses) the welded joints of these steels have a good resistance to fatigue and brittle fractures.As a rule, they are prevented with the help of the known approaches.It is shown that in addition to them and due to a proper selection of conditions of welding the life of welded joints of the high - strength steels can be 1. 2 - 1. 4 times in- creased.

Cutting and Welding of High-Strength Steels Using Non-Vacuum Electron Beam as a Universal Tool for Material Processing

Using a non-vacuum electron beam, a two-step process chain for plate materials is a feasible possibility. Cutting and welding can be performed in subsequent steps on the same machine for a highly productive process chain. The electron beam is a tool with high energy conversion efficiency, which is largely independent of the type of metal. Its high power density qualifies the non-vacuum electron beam as an outstanding energy source for the well-known NVEB welding as well as for high-speed cutting. Welding is possible with or without filler wire or shielding gas, depending on the application. The NVEB-cutting process employs a co-moving cutting head with a sliding seal for extremely high cutting speeds producing high quality edges. Due to direct removal of fumes and dust, NVEBC with local suction is an exceptionally clean and fast process. The NVEB welding process is possible directly after cutting, without further edge preparation. The potential directions of development of non-vacuum electron beam technologies are discussed. An exemplary two-step process chain using high-strength steel is presented to highlight possible application in industries such as general steel construction, automotive, shipbuilding, railway vehicle or crane construction. An analysis of the mechanical properties of the resulting weld seam is presented.

Laser Beam Welding of 600 MPa Quenched and Tempered High-Strength Steel

Conventional fusion arc welding of high-strength quenched and tempered steel can be improved through the use of non-conventional laser beam welding. This article presents the investigations of autogenous bead on plate and butt CO2 Laser Welding (LW) of 7 mm thick high-strength quenched and tempered low alloy SM570 (JIS) steel plates. The influence of laser welding parameters, mainly welding speed, defocusing distance and shielding gas flow rate on the weld profile, i.e., weld zone penetration depth and width, microstructure and mechanical properties of welded joints was determined. All welded joints showed smooth and uniform weld beads free from superficial porosity and undercuts. The selected best welding conditions were a laser power of 5.0 kW, welding speed of 500 mm/min, argon gas shielding flow rate of 30 L/min and a defocusing distance of -0.5 mm. It was observed that these conditions gave complete penetration and minimized the width of the weld bead. The microstructure of the welded joints was evaluated by light optical microscopy. The weld metal (WM) and heat-affected zone (HAZ) near weld metal achieved maximum hardness (355 HV). The tensile fractured samples showed the ductile mode of failure and ultimate tensile strength of 580 MPa.

Improvement of the microstructural features and mechanical properties of advanced high-strength steel DP590 welds

The effects of the welding current mode in resistance spot welding on the microstructure and mechanical properties of advanced high-strength steel dual-phase 590(DP590)sheets were investigated.Results showed that a rough martensitic structure was formed in the weld zone of the sample welded via the single-pulsed mode,whereas the microstructure in the heat-affected zone consisted of a very rough martensitic microstructure and rough ferrite.However,using the secondary pulse mode led to the formation of tempered martensite in the weld zone.The maximum load and the energy absorption to failure of the samples with the secondary pulsed cycle were higher than those of the samples with the single-pulsed mode.Tensile shear results indicated that the secondary pulsed mode could significantly change the mode of failure upon shear tension testing.Therefore,the obtained results suggest that the use of secondary pulsed mode can improve the microstructural feature and mechanical properties of advanced high-strength steel DP590 welds.

Microstructure development in high-strength low-alloy steel welds

The reliability of steel welds becomes more critical issue with increasing steel strength,because brittle phases are more likely to form in the weld metals and heat-affected zone(HAZ) and thereby the toughness and ductility of the welds are degraded.Therefore,refinement of microstructure and minimization of the brittle phases are necessary to improve the reliability of the high-strength steel welds.In this presentation,microstructure formation that controls the toughness of weld metals and HAZ in high-strength low-alloy(HSLA) steel welds is reviewed and possible routes to the improvement of the weld microstructure and weld toughness are discussed.

Microstructures and hardness of flat-overhead weld of the high strength steel thick plate using double-sided arc welding

High strength steel thick plate is widely used in shipbuilding, pressure vessels, etc. , the balance between weld quality and welding efficiency is becoming a research focus. In this paper, double-sided double arc fiat-overhead welding experiments for high strength steel thick plate were conducted. Microstructures of weld have been observed through optical microscope （OM） and scanning electron microscope （SEM）. Transformation of microstructures under thermal cycles of multi peaks was analyzed. Macro and micro hardness were also tested. The results show that the heat-affected zone （HAZ） near the fusion line experiences thermal cycles up to three times. The microstructures there are the most complex, including coarse lath martensite in original coarse-grained zone, and net-like structure along grain boundaries in critical reheat coarse-grained zone. After several times of tempering for bucking welding, the features of acicula and lath are weakened. Its microstructure approaches to the microstructure of base metal which is tempering sorbite. The hardness test shows that the maximum hardness occurs at critical reheat coarse-grained zone, the hardness of reticulation structure at grain boundary can be up to 450 HV.

Numerical simulation of temperature field in laser-arc hybrid welding of wear-resistant steel

Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear-resistant steel is proposed. The proposed model considers convection, radiation, molten pool flow, and heat conduction effect on temperature. A comparison of the simulation and actual welding test results confirms the reliability of the model. This welding heat-process model can provide the cooling rate at any position in the heat affected zone （HAZ） and can be used as a reference for the analysis of material properties and for process optimization.

Changes in microstructure and properties of weld heat-affected zone of high-strength low-alloy steel

The evolution of the microstructure and toughness of APL5L X80 pipeline steel after thermal welding simulation was investigated by X-ray diffraction,electron backscatter diffraction,and transmission electron microscopy.The results indicated that primary heat-affected zones can be divided into weld,coarse-grained,fine-grained,intercritical,and sub-critical zones.The microstructure of the weld zone is mainly composed of bainitic ferrite and a small amount of granular bainite;however,the original austenite grains are distributed in the columnar grains.The structure of the coarse-grained zone is similar to that of the weld zone,but the original austenite grains are equiaxed.In contrast,the microstructure in the fine-grained zone is dominated by fine granular bainite,and the effective grain size is only 8.15μm,thus providing the highest toughness in the entire heat-affected zone.The intercritical and subcritical zones were brittle valley regions,and the microstructure was dominated by granular bainite.However,the martensite-austenite(M/A)constituents are present in island chains along the grain boundaries,and the coarse size of the M/A constituents seriously reduces the toughness.The results of the crack propagation analyzes revealed that high-angle grain boundaries can significantly slow down crack growth and change the crack direction,thereby increasing the material toughness.The impact toughness of the low-temperature tempering zone was equivalent to that of the columnar grain zone,and the impact toughness was between those of the critical and fine-grained zones.

输变电铁塔用耐候钢闪光焊接

文中对闪光焊接在铁塔用耐候钢上的应用展开研究,闪光焊接是通过焊接面的短路进行加热,加载顶锻变形过程界面上动态再结晶形成焊缝。焊接件经退火后,焊缝与热影响区均得到与基体相近的珠光体+铁素体组织,焊接试样与基体力学性能趋于一致。耐候钢闪光焊接无需引入其他焊料从而保证了焊缝与基体化学成分相同,并可通过热处理消除焊缝与基体之间组织差异,获得焊缝与基体力学性能的一致性。这对于无涂装输变电铁塔应用,闪光焊接一方面保证了焊接构件机械性能稳定性,另一方面避免了焊缝与基体之间因组织成分差异所带来的较大电位差,在自然环境下导致电化学腐蚀,从而满足耐候钢焊接构件免涂装服役性能要求。

耐候钢Q370qENH埋弧焊焊接接头锈蚀行为与机理研究

为了研究耐候钢Q370qENH埋弧焊材的锈蚀机理,对Q370qENH埋弧焊焊缝试样和基材试样进行浸泡腐蚀实验和电化学腐蚀实验,并对Q370qENH浸泡腐蚀后形成的锈层形貌和成分进行表征。结果表明,Q370qENH埋弧焊焊材焊缝处的耐蚀能力低于基材,其电化学阻抗为基材的38%。分析了Q370qENH埋弧焊材焊缝耐蚀能力低于基材的原因和表面锈层的形成机理,研究结果可为耐候钢在高速铁路钢桥等工程项目中的服役安全评估和维修养护提供科学依据和理论基础。

强度匹配对WELDOX960钢焊接接头组织与性能的影响

WELDOX960作为新一代低合金高强钢,广泛应用于工程机械等重载领域。本文采用混合气体保护焊对WELDOX960钢进行多层多道焊接。打底焊是多层多道焊接中最重要的工艺过程,对接头性能有着重要影响。分别用ER50-6焊丝及Tunion GM120焊丝打底制备了二组焊接试样,对焊接接头的拉伸及冲击性能进行了测试,对接头的显微组织及冲击断口形貌进行了观察分析。结果表明,两种打底焊接头抗拉强度均能满足使用要求,ER50-6焊丝打底的焊接接头韧性明显高于Tunion GM120焊丝打底的接头,断口形貌呈现韧窝特征。

压力管道工程中有关焊接诸多认知误区和盲区浅析(一)——焊接接头

焊接接头形式和焊缝形式是两个不同概念,而压力管道单面焊焊接接头要达到相当于双面焊同样质量要求是一个综合性的问题,主要涉及焊接方法、母材类别、焊接材料、焊接位置、预热、背面充气保护、热处理、电特性及技术措施等9个因素的影响,同时也与焊工技能有关。熟练焊工按照合格的焊接工艺评定进行施焊、加强焊缝目视检测(VT),尤其是焊接接头坡口加工和焊道VT检测是保障质量的重要要素。

碳钢焊缝典型缺陷的非线性特征

为了揭示碳钢焊缝典型缺陷的非线性特征,应用相控阵超声检测仪对6个碳钢试块焊缝进行检测,基于递归图、盒维数、最大Lyapunov指数和近似熵方法对采集的5种典型缺陷信号进行了分析。试验结果表明,缺陷信号递归图具有周期性和随机性共存的复杂结构,表明超声波在含缺陷试块内的传播具有非线性特征,验证了基于非线性动力学理论研究缺陷信号的可行性;缺陷信号均有较为稳定的盒维数,表明缺陷信号具有分形特征;缺陷信号的最大Lyapunov指数均大于零,表明缺陷信号具有混沌特征;缺陷信号的近似熵不一样,表明各种缺陷信号的复杂程度不同;缺陷信号的盒维数值相近,单纯采用盒维数无法对缺陷信号进行准确分类,采用最大Lyapunov指数和近似熵可以有效识别出纵向裂纹,但对其他4种缺陷信号分类效果不佳。为了更准确地对缺陷信号进行有效识别,需要融合多种非线性特征指标进行综合判定。

钢箱梁顶板-U肋疲劳裂纹钢板加固参数与效果分析

为研究钢板加固钢箱梁顶板-U肋疲劳裂纹的具体加固参数与加固效果,以加固件长度与厚度、是否设置加劲肋为变化参数,建立局部有限元分析模型,通过分析顶板-U肋焊趾处应力,评估受损构件的钢板加固效果,并提取裂纹尖端应力强度因子,研究不同参数对于加固效果的影响规律。结果表明:采用钢板加固顶板-U肋焊缝细节,可使模型中焊趾应力峰值降低约40%;胶层破坏时通常从顶板处开始破坏,现场加固时应确保顶板处胶层粘贴紧固;当钢板长度大于裂纹长度时,钢板长度对裂纹尖端应力水平影响较小,加固时保证钢板能够完全覆盖裂纹即可;当钢板板厚达母材板厚的1/2时加固效果趋于稳定,实桥加固时可取板厚为母材板厚的一半;与未加固裂纹相比,采用带加劲肋钢板可将裂纹尖端应力强度因子降低约50%,建议在加固时采用带加劲肋钢板,进一步提升加固效果。

基于BSCWEformer的退火炉内分组式辊速序列预测

退火炉内带钢的长度受到温度、张力等因素的影响而变化,导致辊的转速改变以及焊缝位置的不确定,从而威胁生产安全.为了准确预测辊的转速以计算焊缝的实时位置,本文提出基于带状稀疏柯西自注意力的BSCWEformer (banded sparse Cauchy weight enhanced Transformer)模型.模型采用带状稀疏的、使用基于相对位置计算的柯西分布权重值增强的自注意力结构,在提高相邻输入序列的重要性的同时,将自注意力的复杂度由二次方降低为线性.通过实际生产数据进行实验,并与LogSparse Transformer、Transformer、RNMT+等模型进行对比,得出本文所提出的BSCWEformer模型在退火炉内分组式辊速序列预测任务上具有较高的预测精度.

核电厂一回路主管道铸造奥氏体不锈钢热老化管理现状与展望

在核电厂老化管理中,一回路主管道铸造奥氏体不锈钢母材与焊缝的结构完整性对于核电厂的安全运行至关重要。主管道在运行工况下面临热老化问题,需要采取有效的管理手段。本文综合介绍了目前主管道热老化问题的国际及国内工程管理现状,总结了主管道在实际管理过程中的难点与不足,结合无损检测手段和研究现状,提出了未来的关注方向。通过对母材和焊缝的热老化评估与检查实现有效管理,为核电厂主管道的安全服役提供有力支撑。

局部自主智能化焊接机器人系统设计

传统焊接机器人由于设置时间长、焊接过程无法自我校正等缺陷,无法满足现代工业自动化生产发展需求。通过分析钢结构焊接工艺与实际应用环境特征,结合视觉传感、建模和智能控制方面的研究成果,设计了包括自由度视觉伺服、焊缝引导、焊缝跟踪、焊接熔深控制、知识数据、系统模拟及中央控制计算等单元的智能机器人焊接系统。提出用于机器人焊接的关键智能技术。这些技术主要包括基于视觉伺服的焊缝识别和启动、焊缝局部自主引导和跟踪、焊缝焊透实时智能控制、焊缝精细成形及熔池动态控制等。基于局部自主智能化焊接技术,构建了一种局部自主智能化焊接机器人系统。工程试验结果表明,系统的应用可以使钢结构焊接质量和效率得到有效提高。该结果验证了系统的有效性。

奥氏体不锈钢管环焊缝超声相控阵检测分析讨论

本文通过分析奥氏体不锈钢晶粒粗大对超声检测的影响,结合超声衰减的特性,在NB/T 47013—2015《承压设备无损检测》和NB/T 47013.15—2021《承压设备无损检测第15部分:相控阵超声检测》标准下设计了两个对比实验。通过两次超声检测对比实验和超声检测-射线检测对比实验,验证了相控阵超声检测相较于常规超声检测在不锈钢管环焊缝检测中更可靠、更准确。

基于视觉特征的机车钢结构焊接机器人焊缝跟踪方法研究

机车钢结构在智能焊接过程中,受到热输入、材料变形等因素的影响,焊缝的实际位置和形状会发生变化,在焊缝跟踪时,当前视觉帧间差方法容易忽略位置信息和焊缝轨迹位置偏差,导致跟踪误差大。对此,提出基于视觉特征的机车钢结构焊接机器人焊缝跟踪方法。选取以“棋盘格&条纹”混合图像作为基础,标定机车钢结构焊接机器人立体视觉位置,对焊接机器人激光条纹的中心线特征进行捕获;通过Roberts算子提取焊缝边缘信息,引入Hough变换确定焊缝中心线,实现焊缝识别,并将焊缝坐标展开转换,将其映射至机车钢结构焊接机器人的基础坐标系,在三维空间中构建焊缝轨迹;基于焊枪当前的位置信息和焊缝轨迹计算位置偏差,通过三次分均匀有理B样条对焊缝轨迹数据进行实时修正,实现机车钢结构焊接机器人焊缝实时跟踪。试验结果表明,所提方法可以有效提升机车钢结构焊接机器人焊缝跟踪精度。