控制棒驱动机构钩爪及连杆自动氩弧堆焊关键技术及装置研发

以控制棒驱动机构钩爪和连杆的自动氩弧堆焊技术为主要对象,在对钩爪及连杆的功能和性能要求以及成型工艺分析的基础上,通过研制专用的自动氩弧堆焊装置及配套堆焊制造工艺,采用自动氩弧堆焊技术制造钩爪,样件通过1000万次的耐磨性能试验,验证了堆焊钩爪及连杆满足性能要求,从而确保控制棒驱动机构安全可靠运行。该研究开发了小孔、齿面弧形多层自动化堆焊工艺技术和适用于钩爪及连杆堆焊的专用自动化焊接装置,实现自动化堆焊,焊接质量稳定、效率高、经济性好。     

反应堆CRDM钩爪堆焊工艺仿真研究

基于有限元软件建立了钩爪堆焊毛坯和终形模型,采用双椭球型热源模拟氧乙炔火焰,依照先堆焊两个内孔再堆焊齿面的顺序进行了瞬态热应力场仿真;根据探索得到的堆焊最优工艺进行零件试制,对钩爪堆焊半成品及成品件进行微观组织、渗透探伤和显微硬度检验.结果表明,由此堆焊优化方案制造的钩爪堆焊件质量优良.     

控制棒驱动机构钩爪齿复合冲击磨损可靠性分析

文中基于改进后的Lewis复合冲击磨损模型,利用蒙特卡洛仿真方法获得在不同步跃运动步数下的控制棒驱动机构钩爪齿磨损量分布,进而应用广义应力-强度干涉理论和有限差分法分别进行了钩爪复合冲击磨损的可靠性分析与灵敏度分析.采用某型号控制棒驱动机构的相关数据进行案例分析后,发现现有的钩爪能够满足600万步的步跃运动的设计寿命要求,但是运行至1800万步时可靠度有明显下降.此外依据灵敏度分析结果,发现钩爪齿面硬度和钩爪齿面相对滑移距离对复合冲击磨损可靠度的灵敏度较高.     

反应堆压力容器三交区堆焊技术研究

通过反应堆压力容器三交区带极堆焊、手工电弧堆焊、TIG堆焊3种焊接工艺方法的堆焊试验,并进行无损探伤检验,低倍、金相检验,对比分析不同镍基焊材及工艺方法焊接后三交区的焊接质量,确定出最佳堆焊工艺方案。     

一种月壤采样冲击机构的优化设计

凸轮是月壤采样冲击机构的关键零件。通过冲击机构寿命试验发现,凸轮防扭轴存在出现疲劳破坏的风险。基于冲击机构多体动力学仿真、静力学分析和瞬态力学分析,对凸轮进行优化设计,并通过对凸轮材料热处理工艺进行分析,采用更加合理的热处理手段。在论证充分和工艺成熟的基础上,冲击机构所有优化均以变动量最小、系统安全可靠、驱动功耗小和机构轻量化设计为原则。通过仿真分析和试验验证表明,优化后的冲击机构满足功能性能指标要求及寿命要求,优化措施有效。     

随焊旋转冲击对液压支架熔覆层性能影响研究

采用D112堆焊焊条在液压支架磨损处进行堆焊修复,研究了随焊冲击工艺对熔覆层性能的影响。采用小孔法对堆焊层进行了残余应力分析,并通过金相组织观察、硬度试验、耐磨性试验及耐蚀性试验对堆焊层的性能进行了比对分析。由试验结果知：随焊冲击可以有效地减小焊接残余应力,细化晶粒,提高堆焊层的硬度及耐磨耐蚀性能。     

大直径“堆焊＋喷涂”工艺辊技术研究

通过对该类辊制造难点的分析,确定采用“堆焊＋喷涂”工艺来开展该产品的国产化研发。首先通过小样落球试验,测得最合适堆焊层硬度;然后通过制作等效模拟辊,对所开发的不同堆焊材料的硬度、显微组织、抗裂性能等进行了分析,并优选出最佳的焊接材料。最后对优选的堆焊材料的喷涂试样进行了孔隙率、显微硬度和结合性能的分析。基于试验分析的结果,本项目采用最佳工艺成功制造了一根实物辊。     

汽车半轴45钢的表层堆焊修复及焊后热处理

采用等离子弧堆焊工艺对45钢表层堆焊高铬高镍粉末合金,并对堆焊试样整体分别进行空冷及500℃焊后热处理。利用金相显微镜、显微硬度计、冲击试验机对焊后空冷及焊后热处理条件下的焊接热影响区及堆焊层的组织、硬度、断口形貌进行分析。试验结果表明,焊后不同处理条件下热影响区及堆焊层的组织形貌、硬度及焊接熔合区的断口形貌具有较大差异。焊后空冷条件下,热影响区主要为方向各异的针片状魏氏体,堆焊层主要为粗大的针状马氏体。热影响区与堆焊层之间的硬度梯度较高,且堆焊层硬度均匀性较差,同时焊接熔合区的冲击韧性较低。焊后500℃热处理条件下,热影响区的魏氏组织转变为大小均匀的粒状铁素体和珠光体,堆焊层转变为细小的板条状回火马氏体,焊接热影响区与堆焊层之间硬度梯度明显降低,同时堆焊层的硬度分布均匀且焊接熔合区冲击韧性较高。     

双相钢焊条电弧焊堆焊工艺研究

在不同焊接电流、焊接电压和冷却速度下进行了系统的双相钢焊条电弧堆焊工艺研究,分析了焊接规范对双相钢堆焊金属铁素体含量的影响。试验表明：在双相钢焊接过程中,电弧电压对堆焊金属铁素体含量的影响最大,堆焊金属铁素体含量随着电弧电压的提高而急剧下降。堆焊金属铁素体含量会随着焊接电流的降低及冷却速度的加快而有所提高。经过优化的堆焊工艺下,堆焊金属各项性能均能满足相关标准及技术文件要求。     

换热器管板堆焊数值模拟及残余应力分析

针对换热器管板堆焊实际情况,确定了堆焊试验模型及工艺参数,并进行了堆焊试验。同时,在相同模型及工艺条件下,利用Ansys软件进行了堆焊数值模拟,使用APDL语言进行参数化编程,得到了模拟结果温度场和应力场的分布规律。通过试验结果与数值模拟结果的对比分析,证明了分析方法的合理性,对于今后产品局部结构优化设计、焊接残余应力分析及焊接工艺优化等均有直接帮助。     

Modeling of multiple characteristics of an arc weld joint

Process parameters modeling have always been one of the key aspects in development of an adaptive control of arc welding process. The welding process parameters are inherently nonlinear, time-delayed, and interdependent, and their on-time adjustment highly influences a sound weld bead formation and process monitoring. During the welding process, parameters control is the primary goal to leads a quality welding. Moreover, the final weld joint behavior, i.e., residual stress, welding strength, and micro-crack formation are generally observed after cooling of the weld product. Thus, it has always been a difficult task to control mechanical properties of a final weld joint. To obtain the best mechanical properties, the final weld joint characteristics needed to be controlled and predicted during the process itself by precise adjustment of the process parameters. The paper presents a neuro-fuzzy modeling approach to provide adaptive control for the automatic process parameter adjustment. Three input parameters wire feed speed, welding gap, and torch speed are modeled with welding current output, providing control over weld bead formation during the welding. The same input process parameters are also modeled to predict final weld joint characteristics, i.e., dilution ratio, hardness of weld bead, hardness of fused zone, and bead width. In order to ascertain the effectiveness of the neuro-fuzzy modeling approach, multiple regression models were also developed to compare the performances.     

机械振动对激光焊接接头组织的影响

振动焊接工艺能有效细化接头组织晶粒,降低残余应力,提高焊接质量。为了研究振动焊接工艺在激光焊接方面的应用,选用316不锈钢作为试验材料,利用机械振动辅助激光焊接的工艺方法,通过改变机械振动参数和焊接速度,利用光学显微镜和扫描电镜观察焊后接头组织,对比分析不同振动频率和焊接速度下接头的微观组织形貌。结果表明,机械振动可以细化焊后组织中形成的柱状晶,使柱状枝晶破碎且向不同方向生长,晶轴间与焊缝中心处的等轴晶增加。提高焊接速度后,振动的加入能够细化焊缝区出现的粗大柱状晶。同时,振动可以减少焊后在奥氏体基体晶界处形成的网状高温铁素体和点状碳化物,使其趋于弥散。试验还对焊接接头进行显微硬度测试,发现振动焊接下得到的焊缝区接头组织硬度较高,且较高共振频率下硬度增加明显。     

用Nd:YAG激光焊接殷钢薄板材料

用Nd:YAG脉冲激光作为焊接热源,对殷钢材料Invar36分别进行了平板单道焊接试验和对焊试验,分析了工艺参数(激光功率、焊接速度、脉冲宽度和离焦量)变化对焊缝的表面形貌、熔宽以及熔透性的影响.检测了0.85 mm厚的殷钢薄板对焊接头的硬度、成分以及拉伸强度.结果表明:激光功率和脉宽是影响焊缝熔深、熔宽和热影响区面积的主要因素;扫描速度对焊缝表面的鱼鳞状条纹间距影响尤为明显;离焦量主要影响焊缝的宽度和熔透性;合理匹配工艺参数能够实现0.85 mm厚度薄板的对焊,并且获得形貌良好的焊缝.焊缝的组织成分没有发生明显变化,拉伸强度和基体强度相当,显微硬度略低于基体硬度.     

Optimisation of the weld bead geometry in gas tungsten arc welding by the Taguchi method

In this paper, determination of the welding process parameters for obtaining an optimal weld bead geometry in gas tungsten arc welding is presented. The Taguchi method is used to formulate the experimental layout, to analyse the effect of each welding process parameter on the weld bead geometry, and to predict the optimal setting for each welding process parameter. Experimental results are presented to explain the proposed approach.     

Slag recycling in submerged arc welding and its influence on weld quality leading to parametric optimization

Slag generated during conventional submerged arc welding (SAW) has been recycled by mixing varying percentages of crushed slag with fresh flux to use in subsequent runs. The influence of using flux-slag mixture on various aspects of SAW weld parameters of bead geometry have been investigated in a quantitative basis. Slag has been reprocessed and reused in submerged arc welding to produce bead-on-plate weld on mild steel plates. Apart from conventional process parameters: voltage (OCV), wire feed rate, nozzle to plate distance (stick-out) and traverse speed, welding has been carried out using various percentages of flux-slag mixture; the % of fused flux in the mixture has been treated as a process parameter. Various bead geometry parameters viz. bead width; reinforcement, depth of penetration and depth of HAZ have been measured for each of weld prepared in the study. Using experimental data, a grey-based Taguchi approach has been applied for parametric optimization of this non-conventional SAW process. The aim was to reveal the optimal amount of slag-mix%, which could be applied in SAW process without imposing any adverse effect on features of bead geometry and HAZ. Optimal result has been checked through confirmatory test.     

Effect of welding heat input on fatigue life of quenched boron steel and FB steel lap joint

The effect of welding heat input on the fatigue life of a quenched boron steel and ferrite-bainite (FB) steel lap joint was investigated. Boron steel was quenched and welded with FB steel in heat input ranging from 0.29 to 0.67 kJ/mm. Boron, which can increase hardenability, affected the microstructure and hardness of the weld metal and heat affected zone (HAZ). The hardness of the weld metal and HAZ increased with decreasing welding heat input, and the high hardness of the weld metal and boron steel HAZ prevented the initiation of cracks in the stress concentration area around the bead. The bead width increased with increasing heat input, and the results of finite element method (FEM) showed that the maximum stress in the notch of the weld joint decreased when the bead width was increased. That is to say, the fatigue life increased when the weld joint had wider bead width. Finally, while the fatigue life was affected by the residual stress, the variation of the welding heat input used in this study had hardly any affect on the residual stress distribution.     

Mathematical models for control of weld bead penetration in the GMAW process

This paper presents the effects of welding process parameters on weld bead penetration for the gas metal arc welding (GMAW) process. Welding process parameters included wire diameter, gas flow rate, welding speed, arc current and welding voltage. The experimental results have shown that weld bead penetration increased as wire diameter, arc current and welding voltage increased, whereas an increase in welding speed was found to decrease the weld bead penetration. However, the weld bead penetration is not affected significantly by gas flow rate changes. Mathematical equations for study of the relationship between welding process parameters and weld bead penetration have also been computed by employing a standard statistical package program, SAS.     

A study on the prediction of bead geometry in the robotic welding system

The gas metal are (GMA) welding is one of the most widely-used processes in metal joining process that involves the melting and solidification of the joined materials. To solve this problem, we have carried out the sequential experiment based on a Taguchi method and identified the various problems that result from the robotic GMA welding process to characterize the GMA welding process and establish guidelines for the most effective joint design. Also using multiple regression analysis with the help of a standard statistical package program, SPSS, on an IBM-compatible PC, three empirical models (linear, interaction, quadratic model) have been developed for off-line control which studies the influence of welding parameters on bead width and compares their influences on the bead width to check which process parameter is most affecting. These models developed have been employed for the prediction of optimal welding parameters and assisted in the generation of process control algorithms.     

Modeling and optimization of features of bead geometry including percentage dilution in submerged arc welding using mixture of fresh flux and fused slag

Quality has now become an important issue in today’s manufacturing world. Whenever a product is capable of conforming to desirable characteristics that suit its area of application, it is termed as high quality. Therefore, every manufacturing process has to be designed in such a way that the outcome would result in a high quality product. The selection of the manufacturing conditions to yield the highest desirability can be determined through process optimization. Therefore, there exists an increasing need to search for the optimal conditions that would fetch the desired yield. In the present work, we aim to evaluate an optimal parameter combination to obtain acceptable quality characteristics of bead geometry in submerged arc bead-on-plate weldment on mild steel plates. The SAW process has been designed to consume fused flux/slag, in the mixture of fresh flux. Thus, the work tries to utilize the concept of ‘waste to wealth’. Apart from process optimization, the work has been initiated to develop mathematical models to show different bead geometry parameters, as a function of process variables. Hence, optimization has been performed to determine the maximum amount of slag--flux mixture that can be used without sacrificing any negative effect on bead geometry, compared to the conventional SAW process, which consumes fresh flux only. Experiments have been conducted using welding current, slag-mix percentage and flux basicity index as process parameters, varied at four different levels. Using four³ full factorial designs, without replication, we have carried out welding on mild steel plates to obtain bead-on-plate welds. After measuring bead width, depth of penetration and reinforcement; based on simple assumptions on the shape of bead geometry, we calculated other relevant bead geometry parameters: percentage dilution, weld penetration shape factor, weld reinforcement form factor, area of penetration, area of reinforcement and total bead cross sectional area. All these data have been utilized to develop mathematical models between predictors and responses. Response surface methodology (RSM), followed by the multiple linear regression method, has been applied to develop these models. The effects of selected process parameters on different responses have been represented graphically. Finally grey relational analysis coupled with the Taguchi method (with Taguchi’s orthogonal array) has been applied for parametric optimization of this welding technique. Confirmatory experiments have been conducted to verify optimal results.