Genetic-Algorithm-Based Computational Models for Optimizing the Process Parameters of A-TIG Welding to Achieve Target Bead Geometry in Type 304 L(N) and 316 L(N) Stainless Steels

The weld-bead geometry in 304LN and 316LN stainless steels produced by A-TIG welding plays an important role in determining the mechanical properties of the weld and its quality. Its shape parameters such as bead width, depth of penetration, and reinforcement height are decided according to the A-TIG welding process parameters such as current, voltage, torch speed, and arc gap. Identification of a suitable combination of A-TIG process parameters to produce the desired weld-bead geometry required many experiments, and the experimental optimization of the A-TIG process was indeed time consuming and costly. Therefore it becomes necessary to develop a methodology for optimizing the A-TIG process parameters to achieve the target weld-bead geometry. In the present work, genetic algorithm (GA)-based computational models have been developed to determine the optimum/near optimum process parameters to achieve the target weld-bead geometry in 304LN and 316LN stainless steel welds produced by A-TIG welding.     

OPTIMIZATION OF WELD BEAD DIMENSIONS IN GTAW OF ALUMINUM-MAGNESIUM ALLOY

The Gas Tungsten Arc Welding (GTAW) process is frequently used in welding of aluminum alloys, because of its possible heat input control. This control can be utilized through a good selection of the process variables, which in turn results in optimizing the bead dimensions. The object of this investigation was to study the effect of TIG process parameters on weld bead dimensions. Suitable combinations of tungsten electrode parameters and process variables can lead to optimum GTAW bead dimensions. With alternative current (AC) polarity, a weld bead may be formed between two 3-mm thick pieces of 5005 aluminum-magnesium alloy sheets. The effect of electrode diameter, vertex angle, and the welding current and speed on the bead dimensions were investigated. Results revealed that the rate of increase of bead width with current increase is greater than that produced by decreasing travel speed, and means that the bead width can be controlled more efficiently by welding current rather than by welding speed. For example, bead width can be reduced by half by increasing the welding travel speed three times, whereas it can be doubled when the current has is doubled. In contrast, bead depth is found to be more sensitive to welding speed rather than to the welding current. One of the important results of the present investigation was that the average heat-affected zone width decreased as the welding current and/or speed increased. On the other hand, it was found that the influences of electrode diameter and apex angle on the bead width were similar to their effects on the arc size. The bead width was found to decrease with an increase in the electrode diameter to a certain extent, and increase slightly with an increase of the apex angle.     

不同工艺参数对高硬度铁粉等离子弧增材熔覆的影响

目的优化马氏体不锈钢等离子弧增材熔覆工艺。方法利用等离子热源在300M表面对新型高硬度铁粉的增材熔覆工艺进行研究。基于三因素三水平熔覆工艺的正交试验,研究在大温度梯度熔覆环境下,等离子弧电流、焊枪移动速度及送粉速率对单道金属熔池的非平衡凝固组织的影响机制,综合考虑单道焊道宏观形貌、成形尺寸及稀释率,确定增材熔敷的电流、焊枪移动速度及送粉速率;在此基础上,基于多道单层及单道多层熔覆的宏观形貌及拉伸性能,确定多道多层增材熔覆的搭接率及熔覆工艺。结果在电流为140～180 A、移动速度为20～30 cm/min和送粉速率为20～30 r/min的工艺窗口内,电流对焊道的稀释率有较大影响,送粉速率次之;送粉速率对高宽比的影响最大,扫描速度次之。结论当电流大小为140 A,送粉速率为30 r/min,扫描速率为30 cm/min时,单道单层焊道的稀释率及宽高比最小,热影响区晶粒尺寸较小,叠加率为40%时,熔覆层表面平整度较高。     

Effect of heat-input and cooling-time on bead characteristics in SAW

Load-carrying capacity of weld joints could be identified by its shape and size where weld bead geometry and shape relationship parameters are of utmost importance. Heat input and preheating temperature together can control the cooling time of weld, which in turn determines the weld microstructure and its mechanical properties. To control the shape and geometry of weld bead, it is necessary to understand its relationship with cooling time. In present work, preheating temperature is used as process variable along with heat input varying parameters for understanding their effects on weld bead geometry and shape relationship parameters using submerged arc welding process on high-strength low alloy pipeline steel. The experimental investigation was then analyzed by using the mathematical modeling in context with response surface methodology. The mathematical model predicts the influential dependency of cooling time on the preheating temperature than the other weld process parameters. The associated effects in relation to the process parameters have been discussed and analyzed in the present study.     

基于回归方法和神经网络的电弧增材制造单道成形形貌预测

目的 针对电弧增材制造技术实际应用中工艺参数选取困难和成形结果难预测的问题,确定高效、准确的电弧增材制造单道成形形貌预测的数学方法,以快速、方便地选取丝材电弧增材制造工艺参数并指导成形质量控制。方法 在单道单层丝材电弧增材制造实验的基础上,采用多种回归方法和神经网络方法分别建立焊接电流、电压和焊枪移动速度等多个工艺参数与增材层宽度、增材层高度及熔池深度等成形形貌参数之间的数学关系模型。结果 电弧增材制造单道成形形貌与焊接电流、电压和焊枪移动速度显著相关,且各参数间存在非线性交互作用;采用多元线性回归法可较准确地预测单道增材层宽度,但对于增材层高度和熔深的预测效果较差;神经网络可良好地处理各工艺参数间复杂的非线性关系,其对增材层宽度、增材层高度和熔深的预测平均误差率分别为4.17%、6.60%和7.01%,显著优于多元线性回归法。结论 采用神经网络法可以准确预测电弧增材制造单道成形的形貌参数,进而指导增材制造工艺参数的选取和成形质量的控制。     

Manual metal arc weld modelling: Part 1 Effect of process parameters on dimensions of weld bead and heat-affected zone

Abstract

The properties of a weldment are determined largely by the size and distribution of microstructural regions within the weld metal and heat-affected zone (HAZ). It has been appreciated for some time that these properties may be controlled by adjusting the parameters of the welding process, although until recently this was done mainly qualitatively. Means of achieving more quantitative control are now beginning to be applied. In this paper measurements of the sizes of the weld bead and HAZ are presented for single manual metal arc weld beads. The process variables investigated were electrode type, gauge size, welding position, polarity, welding current, preheat, and welding velocity. Functional relationships between the process variables and the size of the weld bead and HAZ are determined. The generality of these relationships is examined by analysing measurements made previously on other materials. The results are discussed in terms of the theory of the welding process and, as shown in two accompanying papers, they can be used to develop models of multipass manual metal arc welding on which a practical welding procedure may be based.

MST/193a     

Effect of Welding Parameters on Dilution and Weld Bead Geometry in Cladding

The effect of pulsed gas metal arc welding （GMAW） variables on the dilution and weld bead geometry in cladding X65 pipeline steel with 316L stainless steel was studied. Using a full factorial method, a series of experiments were carried out to know the effect of wire feed rate, welding speed, distance between gas nozzle and plate, and the vertical angle of welding on dilution and weld bead geometry. The findings indicate that the dilution of weld metal and its dimension i.e. width, height and depth increase with the feed rate, but the contact angle of the bead decreases first and then increases. Meantime, welding speed has an opposite effect except for dilution. There is an interaction effect between welding parameters at the contact angle. The results also show forehand welding or decreasing electrode extension decrease the angle of contact. Finally, a mathematical model is contrived to highlight the relationship between welding variables with dilution and weld bead geometry.     

An Experimental Investigation and Analysis of PTAW Process

Experiments are conducted to deposit SS304 L powders on SS316 plates by plasma transfer arc welding process with varying four input process parameters, namely scanning speed, powder feed rate, stand-off distance, and current. The effects of these four input process parameters on deposition geometry, dilution, and bead continuity are investigated in this study. Attempts have been made to explain the experimental results with only two compound parameters, “energy deposition per length” and “powder deposition per length” instead of four independent input process parameters. It is observed that the variation of dilution is very little when the scanning speed increases from 100 to 600 mm/min and other process parameters remain constant. When the powder feed rate increases and other parameters remain constant, initially the dilution decreases rapidly and attains a minimum value which do not change further with increase in powder feed rate. It is also observed that the dilution remains almost constant around 6–9% as the stand-off distance changes from 7 to 11 mm and other process parameters remain constant. The formation of nonuniform bead is found to be due to insufficient energy deposition per length per mass of supplied powder.     

Experimental investigation on the effects of process parameters of GMAW and transient thermal analysis of AISI321 steel

Gas metal arc welding (GMAW) develops an arc by controlling the metal from the wire rod and the input process parameters. The deposited metal forms a weld bead and themechanical properties depend upon the quality of the weld bead. Proper control of the process parameters which affect the bead geometry, the microstructures of the weldments and the mechanical properties like hardness, is necessary. This experimental study aims at developing mathematical models for bead height (HB), bead width (WB) and bead penetration (PB) and investigating the effects of four process parameters
viz: welding voltage, welding speed, wire feed rate and gas flow rate on bead geometry, hardness and microstructure of AISI321 steel with 10 mm thickness. The transient thermal analysis shows temperature and residual stress distributions at different conduction and convection conditions.     

A comparative study of multiple regression analysis and back propagation neural network approaches on plain carbon steel in submerged-arc welding

Weld bead plays an important role in determining the quality of welding particularly in high heat input processes. This research paper presents the development of multiple regression analysis (MRA) and artificial neural network (ANN) models to predict weld bead geometry and HAZ width in submerged arc welding process. Design of experiments is based on Taguchi’s L16 orthogonal array by varying wire feed rate, transverse speed and stick out to develop a multiple regression model, which has been checked for adequacy and significance. Also, ANN model was accomplished with the back propagation approach in MATLAB program to predict bead geometry and HAZ width. Finally, the results of two prediction models were compared and analyzed. It is found that the error related to the prediction of bead geometry and HAZ width is smaller in ANN than MRA.     

电弧增材制造成形工艺影响因素研究

采用Ti6321A焊丝进行电弧增材制造,研究了焊枪姿态和摆动参数等工艺因素对成形的影响。结果表明,不同的焊枪角度对增材制造焊缝堆焊成形形貌具有显著的影响,当焊枪姿态由推焊变化到拉焊时,焊缝熔宽减小,余高变高,即焊缝表面铺展能力减弱;焊缝熔深在焊枪垂直时达到最大值。焊枪摆动会使增材制造表面呈现纹路特征,纹路之间的宽度直接由摆长参数决定,摆宽对焊缝熔宽有显著影响,呈近似线性关系。     

Effect of Welding Parameters on the Size of Heat Affected Zone of Submerged Arc Welding

This paper discusses the effect of welding parameters on the size of the heat affected zone (HAZ) and its relative size as compared to the weld bead of submerged arc welding. It is discovered that the welding parameters influences the size of weld bead and HAZ differently which can be relate to the effect of welding parameters on the various melting efficiencies. This difference in behavior of HAZ and weld bead can be explored to minimize the harmful effect of HAZ in future welds.     

Mathematical Modeling of Metal Active Gas (MAG) Arc Welding

In the present paper. a numerical model for MAG (metal active gas) arc welding of thin plate has been developed. In MAG arc welding, the electrode wire is melted and supplied into the molten pool intermittently. Accordingly, it is assumed on the modeling that the thermal energy enters the base-plates through two following mechanisms, i.e., direct heating from arc plasma and "indirect" heating from the deposited metal. In the second part of the paper, MAG arc welding process is numerically-analyzed by using the model. and the calculated weld bead dimension and surface profile have been compared with the experimental MAG welds on steel plate. As the result. it is made clear that the model is capable of predicting the bead profile of thin-plate MAG arc welding, including weld bead with undercutting.     

Robust sensing of arc length

During arc welding, the arc heats and melts the workpiece as heat flux. When the welding current is given, the distribution and the intensity of the heat flux are determined by the length of the are. The measurement and control of the are length are fundamental in robotic and automated welding operations. Length of welding arc determines the distribution of the arc energy and thus the heat input and width of the weld. This work aims at improving the measurement accuracy of arc length using the spectrum of are light at a particular wavelength during gas tungsten arc welding (GTAW) with argon shield. To this end, effects of welding parameters on spectral distributions were studied. To verify the effects of base metal and arc length, the arc column was also sampled horizontally as Layers for spectral analysis. Results show that spectral lines of argon atoms are determined by are length, independent of welding parameters other than the current. Based on these findings, a compact arc light sensor has been designed to measure the arc length with adequate accuracy. A closed-loop arc length control system has been developed with the proposed sensor     

Optimization of A-TIG process parameters using response surface methodology

In the present work, the influence of process parameters such as welding current (I), welding speed (S), and flux coating density (F) on different aspects of weld bead geometry for example depth of penetration (DOP), bead width (BW), depth to width ratio (D/W), and weld fusion zone area (WA) were investigated by using the central composite design (CCD). 9–12% Cr ferritic stainless steel (FSS) plates were welded using A-TIG welding. It was observed that all input variables have a direct influence on the DOP, BW, and D/W. However, flux coating density has no significant effect on WA. Mathematical models were generated from the obtained responses to predict the weld bead geometry. An optimized DOP, BW, D/W, and WA of 6.95?mm, 8.76?mm, 0.80, and 41.99?mm², respectively, were predicted at the welding current of 213.78 A, the welding speed of 96.22?mm/min, and the flux coating density of 1.99?mg/cm². Conformity test was done to check the practicability of the developed models. The conformity test results were in good agreement with the predicted values. Arc constriction and reversal in Marangoni convection were considered as major mechanisms for the deep and narrow weld bead during A-TIG welding.     

Optimization of weld bead geometry of laser welded ANSI 304 austenitic stainless steel using grey-based Taguchi method

This paper investigates the quality characteristics of the welding geometry of the laser welding process for the ANSI 304 austenitic stainless steel, with the use of a pulsed Nd:YAG laser welding system. Laser welding of 2 mm thick ANSI 304 stainless steel is performed at three different levels of three factors, i. e., peak power, welding speed and pulse duration. In this study, a multi-response optimization problem is developed to achieve weld bead geometry with full penetration as well as a narrow bead width and minimum crater. Grey relational analysis based on Taguchi orthogonal array is used to present an effective approach for the optimization of laser welding process parameters. Regression equations between the welding parameters and the bead dimensions for laser welded austenitic stainless steels are developed, which are used in predicting the penetration, width and crater. Finally, the equations are tested for values different from the levels of the parameters in the orthogonal array. It will be beneficial to engineers for continuous improvement in laser welded product quality.     

Optimization of Plasma Arc Welding Parameters by Using the Taguchi Method with the Grey Relational Analysis

The optimal parameters process of plasma arc welding (PAW) by the Taguchi method with Grey relational analysis is studied. The Grey relational grade is used to find optimal PAW parameters with multiple response performance characteristics. The welding parameters (welding current, welding speed, plasma gas flow rate, and torch stand-off) are optimized with consideration of the multiple response performance characteristics (the penetration of root, the weld groove width, and the weld pool undercut). As a result, the improvement percentage of the Grey relational grade with the multiple performance characteristics is 31.8%. It is shown that the multiple response performance characteristics are greatly improved through this study.     

Control of submerged arc weld penetration by radiographic means

The application of real-time radiography for in-process weld quality evaluation is discussed. The advantages of this technique are on-line testing of weld penetration and the possibility of using this information for welding current control. The experimental system developed includes the arc welding unit, the welding manipulator, the real-time X-ray machine and the videorecording and computerized image processing units. In this system welding current can be remotely controlled during weld observation. The experimental results are demonstrated for the submerged arc welding process. In this process the welding pool is covered by a thick layer of welding flux and is therefore optically invisible. By using computer data on the grey levels of the weld images and their histogram distributions, the three-dimensional shape of the submerged arc pool can be recognized, image-digitized and analysed in real time at the rate of 30 frames per second. The depth of the welding pool which characterizes the weld penetration is a very important characteristic of the weld quality. This characteristic can be measured in real time and used for weld tracking and welding current control.     

基于 CMT 电弧增材的焊缝成形尺寸规律研究

目的研究焊接参数对焊缝成形尺寸的影响规律。方法基于冷金属过渡技术,采用正交试验方法得到在不同参数组合下焊缝熔宽、余高和第2层增高,通过多元线性回归拟合,建立了焊缝熔宽、余高和第2层增高与焊接参数之间的回归模型。结果影响焊缝熔宽和余高的主要焊接参数是焊接速度,影响焊缝第2层增高的主要焊接参数是送丝速度,而层间温度的变化对熔宽会有显著影响,但是对余高和第2层增高的影响不大,而且焊缝第2层的增高与余高在数值上存在较大的差异,对比预测值和试验值验证了回归模型的准确性。结论通过改变焊接速度可以引起熔宽和余高的显著变化,层间温度对余高和第2层增高不会造成很大影响。     

Experimental Investigation of Wire Arrangements for Narrow-Gap Triple-Wire Gas Indirect Arc Welding

A new narrow-gap welding process is proposed by applying triple-wire gas indirect arc (TW-GIA). There are double power supplies and triple wires in this system. Power supplies are only connected between electrode wires and base materials are not linked to power supplies. Since there are different wire arrangements with TW-GIA, this article studies these wire arrangements and their effects on sidewall fusion for narrow-gap welding. Results show that different wire arrangements lead to variant arc behaviors and metal transfer, and consequently they lead to different situation of sidewall fusion. The heat to melt sidewalls is mainly from the indirect arc column and metal transfer with narrow-gap TW-GIA. When side wires deviate from the main wire to opposite directions, heat from arc columns and metal transfer can concentrate toward groove sidewalls. When the whole weld torch is lowered, heat from the indirect arc column and metal transfer increases at the weld bead root.