Study on gas metal arc welding of two types of TMCP steels

Gas metal arc welding experiments were conducted on two types of steels with 0.41% carbon equivalent(Ceq) and 0.31% Cequsing WER70T wire and 20% CO_(2)and 80% Ar as shielding gas.The two types of steels show satisfactory weldability.The transition temperatures of 50% upper shelf energy(Tk0.5) for Charpy-V impact test of both the welded joints are below-40 ℃.However, the toughness of the fusion line zone and heat-affected zone(HAZ) of the two steel joints exhibits differences, with the toughness of 0.41% Ceqsteel being better than that of 0.31% Ceqsteel.The Tk0.5of the fusion line zone and the HAZ of 0.41% Ceqsteel is below-60℃,whereas that of 0.31% Ceqsteel is above-40℃.The welded joint of 0.41% Ceqsteel has low hardness fluctuation, while that of 0.31% Ceqsteel exhibits a narrow, softened zone, which has no obvious influence on the tested tensile strength.The coarse grain heat-affected zone(CGHAZ)microstructure of 0.41% Ceqsteel is bainite, while that of 0.31% Ceqsteel is bainite with ferrite and minor pearlite.

Digital control of pulsed gas metal arc welding inverter using TMS320LF2407A

A digital control of pulsed gas metal arc welding inverter was proposed. A control system consisting of analogue parts was replaced with a new digital control implemented in a TMS320LF2407A DSP chip. The design and constructional features of the whole digital control were presented. The resources of the DSP chip were efficiently utilized and the circuits are very concise, which can enhance the stability and reliability of welding inverter. Experimental results demonstrate that the developed digital control has the ability to accomplish the excellent pulsed gas metal arc welding process and the merits of the developed digital control are stable welding process, little spatter and perfect weld appearance.

焊装车身CO_(2)焊接工艺对涂胶烧蚀的影响分析

利用钣金试板施加CO_(2)焊接及车身用胶涂敷工艺,研究胶到CO_(2)焊道距离远近对胶烧蚀的影响。结果表明:涂胶到CO_(2)焊距离对胶烧蚀影响显著,随着涂胶到CO_(2)焊距离的增大,车身用胶烧蚀情况逐渐减弱,当涂胶压覆后的胶边缘到CO_(2)焊距离大于30mm时,车身用胶未出现烧蚀情况。

Feature Extraction and Dimensionality Reduction of Arc Sound under Typical Penetration Status in Metal Inert Gas Welding

Arc sound is well known as the potential and available resource for monitoring and controlling of the weld penetration status,which is very important to the welding process quality control,so any attentions have been paid to the relationships between the arc sound and welding parameters.Some non-linear mapping models correlating the arc sound to welding parameters have been established with the help of neural networks.However,the research of utilizing arc sound to monitor and diagnose welding process is still in its infancy.A self-made real-time sensing system is applied to make a study of arc sound under typical penetration status,including partial penetration,unstable penetration,full penetration and excessive penetration,in metal inert-gas（MIG） flat tailored welding with spray transfer.Arc sound is pretreated by using wavelet de-noising and short-time windowing technologies,and its characteristics,characterizing weld penetration status,of time-domain,frequency-domain,cepstrum-domain and geometric-domain are extracted.Subsequently,high-dimensional eigenvector is constructed and feature-level parameters are successfully fused utilizing the concept of primary principal component analysis（PCA）.Ultimately,60-demensional eigenvector is replaced by the synthesis of 8-demensional vector,which achieves compression for feature space and provides technical supports for pattern classification of typical penetration status with the help of arc sound in MIG welding in the future.

Study on chaos in short circuit gas metal arc welding process

Based on the chaos theory, an idea is put forward to analyze the short circuit Gas Metal Arc Welding （ GMAW-S） process. The theory of phase space reconstruction and related algorithms such as mutual information and so on, are applied to analyze the chaos of the GMAW-S process. The largest Lyapunov exponents of some current time series are calculated, and the results indicate that chaos exists in the GMAW-S process. The research of the chaos in the GMAW-S process can be help to get new knowledge of the process.

Computer-based sensing and visualizing of metal transfer mode in gas metal arc welding

Using Xenon lamp lights to overcome the strong interference from the welding arc, a computer-based system is developed to sense and visualize the metal transfer in GMAW. This system combines through-the-arc sensing of the welding current and arc voltage with high speed imaging of the metal transfer. It can simultaneously display the metal transfer processes and waveforms of electrical welding parameters in real-time The metal transfer videos and waveforms of electrical welding parameters can be recorded. Metal transfers under various welding conditions have been investigated with the system developed.

Numerical Simulation of Molten Metal Droplet Behavior in Gas Metal Arc Welding by Three-Dimensional Incompressible Smoothed Particle Hydrodynamics Method

The numerical model was developed using a SPH (Smoothed Particle Hydrodynamics) method and the projected transfer phenomena during a GMA (Gas Metal Arc) welding were simulated by the model to clarify mechanisms of the phenomena. As a result, the droplet transfer mode obtained from this calculation was regarded as a projected transfer mode in which the liquid column grew about 1 mm and a droplet grew up until its diameter became large the same as a wire diameter,?after that it was detached from the tip of the column. In addition, 10 droplets were formed for 0.1 s through these growth and detachment processes at the tip of a wire. To compare with the numerical results, actual GMA welding was carried out and molten metal droplet transfers were taken by high speed camera. The diameter of a wire, the length of a liquid column, the velocity of a droplet right before it reached a weld pool obtained by simulation showed good agreement with experiment.

Determining chaotic invariant properties of short-circuiting gas metal arc welding from an observed time series

The experimental time series of welding current produced by carbon dioxide gas metal arc welding with shortcircuiting transfer were recorded and subsequently evaluated. Based on phase space reconstruction, the correlation dimeusions and Kolmogorov entropies of the corresponding system have been numerically calculated using the Grassberger-Procaccia algorithm at different time delays. It was found out that the time delay has little effect on the estimation of correlation dimension; conversely, it plays a key role in producing precise results on the estimation of Kolmogorov entropy.

A novel single wire indirect arc metal inert gas welding process operated in streaming mode

Dilution of a pad weld must be limited to a certain critical level to improve its wear and/or corrosion properties.To do that,a novel single wire indirect arc metal inert gas welding process operated in streaming mode was realized.A metal inert gas welding torch,arranged perpendicular to a substrate in vertical position,is fixed with an auxiliary tungsten electrode horizontally.The arc is ignited between a wire through the torch and the auxiliary electrode.The substrate is not electrically connected.The welding current is set in the range of streaming mode.304 stainless steel was pad welded on Q235 substrates in vertical position by this process.Microstructures were analyzed with optical microscope.Dilution ratios were measured with stereo light microscope and calculated.The results show that,after eliminating interference of the massive torch setup,the dilution ratio of the pad weld with optimized parameters is 5.07%,much less than that with a metal inert gas welding process,which is 26.46%.The pad weld is bonded to the substrate without defects.Microstructures of the pad weld consist of columnar austenite and ferrite between the columns.The dilution ratio increases with increasing welding current or welding velocity,and decreases with increasing distance to the substrate.

Effect of arc physics on developing CO_2 arc welding

The mechanisms of weld formation, spatter and projected transfer in CO2 arc welding are revealed based on the experiment and study of the arc physics. The views are beneficial to develop CO2 arc welding technology.

Comparison of mechanical properties in welded joint for CO_2 arc welding by using the micro－shear test and impact test

A micro shear testing method which can suit to measure the mechanical properties of heterogeneous materials is introduced, and the properties in each zone of welded joint for CO2 arc welding can be evaluated by using this method in this paper. Moreover, these results are compared with those results of Charpy V-notch impact test and their correlation is discussed.

Experimental study on gas metal arc welding and laser hybrid welding of WYS700 steel

Gas metal arc welding, laser welding, and laser-metal active gas welding(MAG) hybrid welding methods were applied to WYS700 steel.Different welding procedures were performed and different welding technologies were compared.Macro metallographs of the welded joints were obtained, and the mechanical properties(such as tensile strength, bending property, and hardness) of the joints formed using the different welding technologies were determined.The results revealed that the joint of the WYS700 steel could be formed well through gas metal arc welding, laser welding, and laser-MAG hybrid welding.Furthermore, the softening of the welding heat affected zone can be effectively reduced to obtain good strength and plasticity by using a suitable welding procedure.Laser-MAG hybrid welding allows the realization of high efficiency and deep penetration for the welding of thick plates with specifications above 3 mm.

The alternate wire-feed control in the automatic CO_2 arc welding

In the automatic CO_2 arc welding, the alteration of the vertical distance between the welding torch and the workpiece has a strong effect on the welding parameters such as welding current and voltage, with the result that the appearance and quality of weld are not steady. To weaken the influence of the distance alteration, a method is put forward in the paper. The method is that the alternate wire-feed control is used for compensating the welding current. On the basis of theoretical analysis, a static numerical model for alternate wire-feed control is established. The experiments show that the model-based regulation of the wire feed rate can compensate the welding current and ensure the appearance of weld. When the alteration of vertical distance between the torch and the workpiece is greater, not only is the wire feed rate regulated, but the output voltage of the power source is adjusted to ensure the appearance and quality of weld.

Gas metal arc welding of duplex stainless clad steel plates

The 2205 duplex stainless ＋ DH36 clad steel plate was welded by gas metal arc welding（GMAW）, and the welding performance of the clad steel plate was investigated. The results show that the adaptability of the welding procedure for the base metal of carbon steel, the transition layer, and the cladding material is excellent. The test results indicate that the phase proportion and component dilution of the GMAW-welded joints of clad steel plate can be effectively controlled to yield joints with good mechanical properties and corrosion resistance.

Wear resistance of surface metal matrix composite produced by gas tungsten arc melt injection of Cr3C2 -NiCr particles into low carbon steel

Cr3 C2-NiCr particles were injected into the melted surface of Q235 low carbon steel to make a surface metal matrix composite （MMC） layer by gas tungsten are melt injection （GTAMI） process. Hardness of the surface MMC layer was tested. Wear resistance of the surface MMC was investigated with a ball-on-disk dry sliding setup. Microstrnetures of the surface MMC layer and morphology of the worn surfaces were investigated with scanning electron microscopy （SEM）. The results showed that the hardness of the MMC was as high as 1 960. 7 HV. Wear loss of the upper part of the MMC layer is onlyO. 8% of that of the substrate under the dry sliding condition given. Wear loss of the bottom part is 2. 5 % of that of the substrate.

Investigate Weld Quality of Gas Metal Arc Welding Process Through Online Monitoring of Input Parameters

Gas metal arc welding(GMAW)is also referred as the metal inert gas(MIG)welding which is a process of welding done by the formation of an electric arc between the consumable wire electrode and the workpiece.Through the welding process,a continuous flow of inert gas is supplied,and it avoids the weld being subjected to react with atmospheric air.The process can be automatic or semi-automatic where the main input parameters like current and the voltage can be direct and constant,respectively.Not only the current and voltage the welding quality depends on some more input parameters such as arc gap,velocity,and temperature.In this paper,we explain about a setup which is capable of real-time monitoring of input parameters mentioned above and selecting the best MIG welding parameters for the mild steel.The setup is composed of several sensors and microcontrollers for the collection and the measurement of the input parameters.The samples were categorized according to the federate and the voltage adjustment of the selected welding machine.Then the final objective was to identify the samples of the weld with different parameter changes which are monitored through the system.For the analysis,the samples were subjected to tensile and hardness tests,and microstructure tests to find the dependence of the input parameters which effect for the weld quality.Finally,the experimental results verified the effectiveness of the system for the selection of the quality weld.

Microstructure and mechanical properties of AZ31B magnesium alloy gas metal arc weld

Wrought magnesium alloy sheets were butt welded with gas metal arc welding process. Pores in the weld were investigated under different welding parameters, the causes of pore formation were systematically disposed, and the effects of porosity on the microstructure and mechanical properties of the joint were analyzed. The microstructure examination shows that the pores mainly appear close to the top or bottom part of the weld, and could connect to each other and lead to the formation of cracks in the welds. However, the pores can be controlled with proper welding parameters. The tensile testing results reveal that the average joint strength is close to or higher than that of the base metal. The microhardness in the weld can be even higher than that in the base metal due to the second ohase strengthening of β-Mg17（A1, Zn）12 formed in the weld.

The comparison of multi-layer narrow-gap laser and arc welding of S32101 duplex stainless steel

Multi-layer narrow-gap welding of thick S32101 duplex stainless steel was conducted using laser welding with beam wobble process.The phase transition,grain size,phase proportion and crystal texture of welded joint were also studied and compared with gas metal arc welding process.The microhardness and tensile strength were measured and fracture surface was analyzed to evaluate the mechanical properties of welded joints.The results showed that beam wobble technology improved the misalignment of laser beam and filler wire in narrow groove and helped to avoid incomplete fusion defects.Compared to arc welding process,the groove size and heat input were reduced,while welding efficiency was increased.The faster cooling rate and lower temperature gradient of laser wobble welding favored grain refinement,while the austenite content in weld zone decreased.Both the beam wobble and swing arc were conducive to stir weld pool,optimizing the weld microstructure and joint formation.The microstructural variance in various weld passes was caused by the heat input and heat dissipation ability.The microhardness of laser welded joint was lower,while the tensile strength and elongation percentage were higher.The fracture surface of arc welded joint was featured with shallower dimples and cleavage steps.

Fatigue life prediction of gas metal arc welded crucifrom joints of AA7075 aluminium alloy failing from root region

Empirical relationship was developed to predict the fatigue life of gas metal arc welded （GMAW） cruciform joints failing from root region. High strength, age hardenable aluminium alloy of AA7075-T6 grade was used as the base material. The design of experiments concept was used to optimize the required number of fatigue testing experiments. Fatigue experiment was conducted in a servo hydraulic controlled fatigue testing machine under constant amplitude loading. The empirical relationship was developed. By using the developed empirical relationship, the fatigue life of GMAW cruciform joints failing from root region was predicted at 95% confidence level. The effect of cruciform joint dimensions on fatigue life was discussed in detail.

Influence of shielding gas on the mechanical and metallurgical properties of DP-GMA-welded 5083-H321 aluminum alloy

In the present research, 6-mm-thick 5083-H321 aluminum alloy was joined by the double-pulsed gas metal arc welding （DP-GMAW） process. The objective was to investigate the influence of the shielding gas composition on the microstructure and properties of GMA welds. A macrostructural study indicated that the addition of nitrogen and oxygen to the argon shielding gas resulted in better weld penetration. Furthermore, the tensile strength and bending strength of the welds were improved when oxygen and nitrogen （at concentrations as high as approximately 0. 1vol%） were added to the shielding gas; however, these properties were adversely affected when the oxygen and nitrogen contents were increased further. This behavior was attributed to the formation of excessive brown and black oxide films on the bead surface, the formation of intermetallic compounds in the weld metal, and the formation of thicker oxide layers on the bead surface with increasing nitrogen and oxygen contents in the argon-based shielding gas. Analysis by energy-dispersive X-ray spectroscopy revealed that most of these compounds are nitrides or oxides.