激光焊接技术在电站锅炉制造中的应用前景探讨

激光焊接作为一种可靠高效的先进焊接方法,具有传统焊接方法无可比拟的优势,是电站锅炉制造技术发展的方向之一.采用激光自熔焊接和窄间隙激光填丝焊接技术,进行了电站锅炉用常规及新型耐热钢同质、异种接头的激光焊接工艺试验,获得了优化的焊接工艺参数,并测试了部分接头的力学性能和显微组织.结果表明:采用优化后的焊接工艺参数,可以获得正、背面成型良好的焊接接头.试样解剖后没有发现气孔、裂纹等缺陷,焊接接头经RT检验和PT检验合格.最后探讨了激光焊接技术在电站锅炉制造中的技术和经济可行性.     

10CrMo910钢小口径管电焊接头不作热处理的探讨

自发展高参数,大容量火力发电机组以来,锅炉用小口径低合金钢管的比例增加,从而促进了焊接技术和热处理工艺的发展。六十年代初期,生产中出现的最大变化要算焊后热处理方面。但是,由于对长期高温工作条件下,焊接接头的组织、性能变化的应用基础理论研究工作进行得很少,影响到焊后不作热处理工艺的正确运用。本文通过高温时效和持久强度试验,用     

改善汽轮机空心静叶焊接自动化应用的研究

以1000 MW汽轮机空心静叶的焊接制造应用为实例,通过研究焊前预处理工艺、机器人摆弧工艺、激光跟踪应用及半手动程序调制工艺来改善自动化焊接生产过程中的局限性,即解决焊接自动化对焊接件一致性要求极为苛刻的问题,从而提高空心静叶自动化焊接生产的工艺及质量稳定性。改善后的自动化焊接焊缝经目视(VT)、渗透(PT)、射线(RT)检测及低倍组织分析,质量符合EN 5817 C级。     

12Cr2MoWVTiB热强钢的焊接

我公司通过对12Cr2MoWVTiB进行焊接工艺试验,匹配合理的焊接材料,确定合适的焊接工艺参数,成功用于高压锅筒的焊接生产.     

BHW35高强钢的焊接

我公司通过对进口材料BHW35进行焊接工艺试验，匹配合理的焊接材料，确定合适的焊接工艺参数，成功地用于高压锅筒的焊接生产。     

小直径管内壁自动堆焊焊接工艺

对规格在Φ60mm～Φ500mm范围内,材质为15CrMo的加强管内壁采用不锈钢自动堆焊方法,并对其进行焊接工艺试验与分析,得到较理想的堆焊工艺参数,解决了手工堆焊该材料小管费时耗料成形差等难题,并将此焊接工艺运用在产品的制造中。     

激光焊接在油量控制套筒上的应用

针对喷油泵油量控制套筒顶端钢球焊接存在的问题,介绍了激光焊接工艺的机理与特点,对控制气氛钎焊与激光焊接进行了试验与分析,结果表明：激光焊接的抗拉强度普遍高于钎焊,因此认为激光焊接代替控制气氛钎焊是可行的。     

高频焊接与激光焊接翅片管传热性能对比试验

对高频焊接与激光焊接翅片管的传热性能进行对比试验,得到了两个试件在不同管外空气流速下的传热数据,运用直接分离法将管外空气侧对流换热系数从总的传热系数中分离,获取管外空气侧换热系数,再通过拟合方法获得管外空气侧换热关联式。研究表明:激光焊接翅片管的传热性能优于高频焊接翅片管,当空气流速为3m/s时,激光焊接翅片管的管外空气换热系数比同翅片尺寸的高频焊接翅片管的管外换热系数约高9%。     

AISI304钢埋弧焊工艺的研究

本文对AISI 3 0 4钢薄板的埋弧焊工艺进行了试验研究。并对焊材性能进行了工艺试验 ,在对试验结果分析的基础上确定了最佳焊接工艺参数。焊接接头的各项力学性能实验结果完全满足图纸要求。通过采取先进的焊接工艺装备 ,成功实现不锈钢薄壁筒体的焊接     

耐硫酸露点腐蚀09CrCuSb钢管焊接工艺研究

对耐硫酸露点腐蚀钢09CrCuSb的焊接性进行了研究,采用手工氩弧焊工艺对09CrCuSb钢管进行了焊接,并对焊接接头组织和性能进行了分析,最终获得了强度高、性能好、无缺陷的优良焊接接头,获得了一组合理的焊接工艺参数,为该材料在硫酸露点腐蚀环境中的应用提供了技术保障。     

3D heat transfer model of hybrid laser Nd:Yag-MAG welding of S355 steel and experimental validation

A three-dimensional heat transfer model was developed to predict the temperature fields, the weld geometry and the shape of the solidified weld reinforcement surface during hybrid laser-MAG arc welding of fillet joints. Melt pool deformation due to arc pressure was calculated by minimizing the total surface energy. A series of hybrid welding experiments was conducted on S355 steel for different welding speeds and wire feeding rates. A high speed video camera was used to measure weld pool depression and surface weld pool geometry. Visualization of the weld pool during welding has also allowed for a better understanding of the interaction between the keyhole and droplets. The various weld bead shapes were explained through these observations. The arc pressure, the surface energy distribution, and arc efficiency were evaluated by comparing experimental data and numerical results for a wide range of welding operating parameters. Good correlation was found between the calculated and experimental weld bead shapes obtained for the hybrid laser-MAG arc welding process as well as for laser or MAG alone.     

An investigation of heat transfer and fluid flow on laser micro-welding upon the thin stainless steel sheet (SUS304) using computational fluid dynamics (CFD)

A transient three-dimensional model is numerically developed using the method of computational fluid dynamics (CFD) to characterize some thermal phenomena and characterization of heat transfer and fluid flow in laser micro-welding by considering the heat source and the material interaction leads to rapid heating, melting and thermal cycles in the heating zone. The application of developed thermal models has demonstrated that the laser parameters, such as laser power, scanning velocity and spot diameter, have considerable effects on the peak temperature and resulted weld pool. The heat source model is consisted of surface heat source and adaptive volumetric heat source that could be well represented the real laser welding as the heat penetrates into the material. In the computation of melt dynamics, mass conservation, momentum and energy equations have been considered to compute the effects of melt flow and the thermo-fluid energy heat transfer. The simulation results have been compared with two sets of experimental research to predict the weld bead geometry and solidification pattern, which laser welds are made on thin stainless steel sheet (SUS304). The shape comparison describes those parameters relevant to any changes in the temperatures and melt dynamics are of great importance on the heat distribution and formation of weld pool during laser micro-welding process. The fair agreement between simulated and experimental results, demonstrates the reliability of the computed model.     

Effect of welding process parameters on embrittlement of Grade P92 steel using Granjon implant testing of welded joints

Precipitation of Cr-rich carbides, diffusible hydrogen content and heterogeneous microstructure formation across the weldments makes heat-affected zone (HAZ) susceptible to intergranular cracking and makes weldability of creep strength enhanced ferritic (CSEF) Grade P92 steel a critical issue. In the present research work, the Granjon implant test and mercury method (for diffusible hydrogen measurement) have been performed on Grade P92 steel welded specimens to study the effect of welding parameters on diffusible hydrogen levels and their subsequent effect on hydrogen-assisted cracking (HAC). The weld metal was deposited by a shielded metal arc welding process on Grade P92 steel samples using P92 matching filler. The three different welding conditions are used to measure the diffusible hydrogen level in the deposited metal. Granjon implant test was performed to evaluate HAZ HAC susceptibility with similar welding conditions which were used in the mercury method. Lower critical stress (LCS) was also evaluated using the Granjon implant test. The higher susceptibility of CSEF Grade P92 steel welded plate towards HAZ HAC was noticed in case of lower heat input or higher diffusible hydrogen content. However, by considering LCS, fracture mode and diffusible hydrogen content, the weld deposited using the highest heat input (condition III) offers great resistance to HAZ HAC.     

海水主冷凝器焊接材料及焊接工艺试验研究

对841焊条、Ni102焊条和Cu307焊条进行研制,通过材料焊接性试验,焊缝金属化学成分的调整和力学性能试验,焊接工艺试验及焊接工艺评定等工作,最后确定焊接工艺规范和编制工艺规程指导生产。     

SA213 T22换热管与12Cr2Mo1管板焊接工艺

对于SA213 T22换热管与12Cr2Mo1管板从焊接工艺,焊接材料、焊接工艺参数及焊缝金组组织等方面进行了焊接工艺检验,分析总结出了合适的焊接工艺并成功应用于国产化设备10万t/a苯乙烯装置高压蒸汽发生器设备的制造.     

Genetic algorithm for optimisation of A-TIG welding process for modified 9Cr–1Mo steel

Abstract

It is essential to set up the activated tungsten inert gas (A-TIG) welding process parameters to produce the desired weld bead geometry and heat affected zone (HAZ) width in modified 9Cr–1Mo steel weld joints. Therefore, it becomes necessary to develop a tool for optimisation of A-TIG welding process. Genetic algorithm (GA) based model has been developed to determine the optimum process parameters. In this methodology, first independent ANN models correlating depth of penetration, weld bead width and HAZ width with current, voltage and torch speed respectively were developed. Then, GA code was developed in which the objective function was evaluated using the ANN models. There was good agreement between the target and actual values of bead geometry and HAZ width obtained using the GA optimised process parameters. Thus, a methodology using GA has been developed for optimising the A-TIG process parameters for modified 9Cr–1Mo steel.     

Temperature distribution and residual stresses due to multipass welding in type 304 stainless steel and low carbon steel weld pads

Welding is a reliable and efficient metal-joining process widely used in industry. Due to the intense concentration of heat in the heat source of welding, the regions near the weld line undergo severe thermal cycles, thereby generating inhomogeneous plastic deformation and residual stresses in the weldment. Plates of different thickness are used in industry and these plates are normally joined by multipass welding. In a multipass welding operation, the residual stress pattern developed in the material changes with each weld pass. In the present experimental work, thermal cycles and transverse residual stresses due to each pass of welding have been measured in the weld pads of AISI type 304 stainless steel and low carbon steel with 6, 8 and 12 mm thickness. X-ray diffraction method was used for residual stress measurements. The welding process used was the Manual Metal Arc Welding (MMAW) process. In this paper, the peak temperatures attained at different points during deposition of weld beads in stainless steel and low carbon steel weld pads are compared. The residual stress patterns developed, the change in the peak tensile stress with the deposition of weld beads, and the relation between the peak temperatures and the residual stresses in the weld pads are discussed.     

Thermomechanical modelling of weld microstructure and residual stresses in P91 steel pipe

Abstract

A multipass circumferentially butt welded P91 steel pipe, typically used for high temperature applications in power plants, has been numerically analysed to determine residual stresses, induced by the process of welding, as well as microstructural regions in the weld, caused by thermal cycles. The finite element (FE) method has been applied to simulate residual stresses generated in the weld region and heat affected zone (HAZ), which are then validated by published experimental data. The axisymmetric FE simulation incorporates solid state phase transformation by allowing for volumetric changes and associated changes in yield stress and hardening behaviour due to austenitic and martensitic transformations. The thermal cycles during welding cause different microstructural regions to emerge within the weld metal and HAZ. Columnar and equiaxed microstructural zones have been numerically modelled in the weld region of the pipe. The predicted FE microstructural regions have been corroborated by columnar and equiaxed zones that have been mapped out on a cross-sectional macroimage of the weld.     

Comparative analysis of TIG welding distortions between austenitic and duplex stainless steels by FEM

In this study, thermal stress analyses were performed in the tungsten inert gas (TIG) welding process of two different stainless steel specimens in order to compare their distortion mode and magnitude. The growing presence of non-conventional stainless steel species like duplex family generates uncertainty about how their material properties could be affected under the welding process. To develop suitable welding numerical models, authors must consider the welding process parameters, geometrical constraints, material non-linearities and all physical phenomena involved in welding, both thermal and structural. In this sense, four different premises are taken into account. Firstly, all finite elements corresponding to the deposition welding are deactivated and, next, they are reactivated according to the torch’s movement to simulate mass addition from the filler metal into the weld pool. Secondly, the movement of the TIG torch was modelled in a discontinuous way assuming a constant welding speed. Thirdly, the arc heat input was applied to the weld zone using volumetric heat flux distribution functions. Fourthly, the evolution of the structural response has been tackled through a stepwise non-linear coupled analysis. The numerical simulations are validated by means of full-scale experimental welding tests on stainless steel plates. Finally, the results and conclusions of this research work are exposed.     

不锈钢中厚板激光全熔透焊的有限元模拟

运用有限元计算软件ABAQUS对16mm厚不锈钢板的激光全熔透焊的温度场和应力场进行了模拟.采用一体两面的复合焊接热源模型来刻画激光全熔透焊过程中的热输入特征,以柱状体热源代表焊接小孔传热模式,以2个超高斯面热源代表等离子体/金属蒸气云对熔池的辐射传热模式.结果表明:温度场模拟结果得到了与实验结果相一致的"沙漏状"焊缝;钢板内纵向残余应力最大,横向应力次之,板厚方向横向应力最小;纵向拉应力主要分布在焊缝两侧约25mm的区域内,最大值已超过材料的屈服强度;经测算,钢板焊后的角变形量仅为0.35°,这是由于激光焊接能量输入高且集中、可不用开坡口而一次性将钢板焊透.