Wire Melting Rate Research Articles

Characteristics of Pulse MIG Arc Welding with a Wire Melting Rate Change by Current Polarity Effect

Joining thin aluminum alloy is difficult using most welding techniques. Many of the problems are associated with bum-through by the high heat input. Common welding techniques are TIG (Tungsten Inert Gas), MIG (Metal Inert Gas), and PULSE-MIG welding. The method provides more control of the heat balance in the welding arc by taking advantage of the different arc characteristics obtained with each of the two polarities. In this paper, we proposed a new welding method by control DSP 320C32, and the characteristic and experiment result-voltage, current, welding bead, and penetrations by this method are presented.

Observations of abnormal arc voltage phenomena in AC/DC pulsed MIG welding

Arc stability in AC/DC pulsed MIG welding is mostly determined by the performance of the arc length control system. This system detects the arc voltage as arc length information for feedback purposes and varies the output of the welding power source so that the arc voltage is equal to the voltage set point. For example, at a high arc length, the arc voltage increases. The pulse frequency is reduced in response, the wire melting rate is reduced and the arc length is returned to normal.

Joule heating of solid wires in MAG welding

There are numerous studies1–12 concerning the melting rate of welding wire and various investigations have been carried out on welding current, welding current waveform, wire extension, polarity, chemical composition, wire diameter, arc length, shielding gas composition and melting rate. Joule heating of bulk wire has been a large contributory factor to the melting rate of solid wire for carbon steel (hereafter referred to as either wire or solid wire) and Joule heating is a crucial factor in aspects of melting stability. However, there are few case studies concerning the detailed measurement of Joule heating at the contacts between the contact tube and wire and the calculation of melting rate.

Wire melting phenomena in gas metal arc welding

The wire melting rate in gas metal arc welding using constant voltage power supplies is well described by a parabolic model that considers the effects of electrical resistance and arc heating. However, tests performed with constant current power supplies indicate that the melting rate can deviate from this model when welding current is close to the globular–spray transition value. Although the causes of this anomaly have not yet been well established, most authors consider them to be related to variations in liquid metal temperature close to the metal transfer mode transition current. The present work evaluates the effect of welding parameters on the wire melting rate when a constant current power supply is used. A numerical model that considers the contribution of both Joule and arc heating was developed to calculate the temperature distribution in the wire and its melting rate. The model was used to assess the changes in either arc heating or metal vaporisation that might explain the melting irregularities. High speed cinematography was used to analyse metal transfer in the current range associated with the melting irregularities.

A numerical model of wire melting rate in CO 2 gas-shielded welding

This paper first analyzes how the welding environment impacts on the welding process and quality, and how alteration of the wire extension can be adapted to the welding conditions. Subsequently, a method is put forward to ensure the arc length remains constant by shortening and lengthening the wire extension. The length of the wire extension is under control of the wire feed rate. The formula for the wire melting rate is proportional to the wire extension change. The formula is verified by experiments, and can be widely applied to theoretical research.

超狭開先ＧＭＡ溶接プロセスの開発 ４ 位相制御型ＧＭＡ溶接プロセスによる開先内でのアーク入熱分布制御

GMA welding process with synchronized control system consisting of a pulsed arc current waveform with cyclical variation of wire feed rate has been developed on the base of computer simulation. In the ultra-narrow gap (less than 5 mm gap) welding process, as the welding wire melting behavior is controlled by low frequency pulsated arc current waveform, the arc generating at the wire tip can be widely oscillated in the direction of thickness. The arc heat pole is dominated by wire melting tip position in consumable electrode welding process, and the arc heat distribution can be changed by this wire tip behavior. The wire melting tip position is represented by wire extension which is a function of wire feed rate and wire melting rate. In order to more-adequately control the arc heat distribution, this report describes synchronized control process between wire feed rate and pulse current waveform in the ultra-narrow gap GMA welding. The important control factor in the newly proposed process is phase shift θ between pulse current waveform and wire feed rate pattern. Firstly, the non-steady state simulation of the wire melting behavior is developed in the case that both arc current and wire feed rate change periodically with low frequency. From simulation results of wire tip behavior under various phase sifts and wire feed rates and pulse conditions, the adaptive welding conditions can be found effectively. Secondly, the synchronized control of welding was carried out under adaptive welding conditions. From the experimental results, it was verified that the arc heat distribution was effectively controlled with the phase shift method expected by numerical simulation thus adequate penetration shapes were obtained in the proposed welding process.

超狭開先ＧＭＡ溶接プロセスの開発 ２ ＧＭＡ溶接におけるワイヤ突出し部の非定常熱伝導解析

In order to obtain high quality welded joints, the ultra-narrow gap GMA welding (UNGW) process has been developed in which the arc moves up-to-downwards along the groove wall. In this process, the arc up-to-down oscillation pattern depends on the wire melting tip behavior that is controlled by low frequency pulse current waveform below 10 Hz. In the low frequency pulse arc welding condition, it can be suggested that the wire-melting behavior is in the non-steady state. Firstly, the one-dimensional heat coduction FDM analysis is proposed for the non-steady wire-melting behavior in GMA welding. For the numerical analysis, both values of the equivalent anode melting potential (Φ) and superheat temperature of droplet(ΔT) must be given, however there are significant experimental uncertainties in these values reported by many researchers. Therefore, in constant welding current, some pairs of these values are searched so that the wire extension calculated by the FDM analysis agrees with the measured one. As the results, the correlation between Φ and ΔT for each welding current can be found out in MIG and MAG arc welding. Secondly, unsteady wire melting behavior in low frequency pulse arc welding is simulated by the numerical analysis using the Φ-ΔT correlation. As the remarkable behavior in the simulation results, it can be found that the wire extension almost does not change for a few times under the transition period from the peak current to the base current. The wire melting rate by Joul’s heat energy stored in the wire extension during peak current period produced the delayed time. Finally, the high-speed camera and current data sampling system are used to measure the unsteady wire melting behavior, and the simulated results are compared with the measured results in UNGW. The measured locus of melting wire tip shows good agreement with the calculated one. From the results, the proposed one-dimensional heat conduction FDM analysis is effective for the prediction of the suitable arc up-to-down oscillation pattern in UNGW.

Physics of welding (III) ‐ Melting rate and temperature distribution of electrode wire

(1995). Physics of welding (III) ‐ Melting rate and temperature distribution of electrode wire. Welding International: Vol. 9, No. 5, pp. 348-351.

Spatter and blowhole formation phenomena in pulsed gas shielded metal arc welding

Abstract This paper investigates systematically the effect of pulse conditions, type of shielding gas, and wire composition on blowhole and spatter formation and on wire melting rate to obtain guidelines for selection of welding conditions. It was found that spatter formation can be reduced significantly by using a shielding gas of composition Ar + 2·4%O2 +20% CO2 for pulsed gas shielded metal arc (MAG) welding. It was also found that it is possible to reduce blowhole formation using pulsed MAG welding. However, blowhole formation is affected greatly by variations of pulse condition and by shielding gas composition.MST/1423

高圧ＡｒおよびＡｒ‐２０％ＣＯ２雰囲気における鋼のアーク溶接

Mild steel was welded in pressurized Ar, Ar-20%CO2 and CO2 atmospheres in the pressure range from 0.1-2.0 MPa abs. using a solid wire of 1.6 mm dia.. The effects of ambient pressure on the melting rate of electrode wire, the geometry of weld metal and the behaviour of alloying element during the arc welding process were studied.The results obtained are as follows:1) In Ar atmosphere, the melting rate of an electrode wire decreases with the increase of pressure. On the contrary, in CO2 atmosphere, it increases with the increase of pressure.2) In each atmosphere, the penetration width decreases, and penetration depth increases with the increase of ambient pressure.3) Except for manganese, the loss of alloying elements during the arc welding process is little in pressurized Ar atmosphere.4) In pressurized Ar-20%CO2 and CO2 atmospheres, Si, Mn, Ti loss are observed during the arc welding process.5) The decrease rate of alloying elements depend on the CO2 partial pressures at a same ambient pressure.6) In pressurized Ar-20%CO2 and CO2 atmospheres, the oxygen content of weld metal increases with increasing the pressure.7) The oxygen content of weld metal made in Ar-20%CO2 atmosphere is lowre than made in pure CO2 atmosphere at a same CO2 partial pressure.

ホットワイヤＴＩＧ溶接における溶着量制御方法に関する検討

The optimum relation between welding current and wire melting rate for the high-speed hot wire GTA welding is decided and a new power control system is developed.The new system has two merits, one is that the power source is simplified by using a part of the arc current as the wire heating current, and the other is that a stable melting of wire is realized by monitoring the voltage drop across the wire extension.The results in this study are as follows.(1) The welding speed can be increased by pre-heating the wire. The effect of speed-up is promoted especially in the case that the bead width is enlarged by adding the hot wire deposit.(2) The optimum relation between welding current and wire melting rate for high speed welding is almost independent of the plate thickness.(3) In the new control system, the welding speed can be raised up to two times of that obtained with the cold wire GTA welding without troublesome adjustments of the power source.

パルスアーク溶接に関する研究 ＩＩＩ パルスＭＩＧ溶接におけるワイヤの溶融速度

Melting characteristics of mild steel, stainless steel and copper alloy wires, are investigated for pulsed or constant current MIG arc using transistor controlled power supply.Results obtained are summarized as follows;(1) Wire melting rate in MIG welding is affected by many factors; effective anode melting potential, length and resistance of the electrode wire extension, heat contents of metal droplets and electric current applied.(2) Wire melting rate in pulsed MIG welding is found to be independent of pulse frequency, and is expressed as a function of average value and effective value of pulsive current applied. Even if the average current is kept constant, melting rate of electrode wire is possible to increase as the effective value of pulsed current becomes higher.(3) Heat conteut of metal droplets depends on an anode heating of MIG arc and joule's heating in a segment of the electrode wire travelling from the contact tip to the arc.

対話形式による溶接熱伝導シミュレータの開発 Ｉ システムの基本設計思想とその機能

A welding heat conduction simulator to analyze melting, solidifying and cooling processes in arc welding has been developed using an interactive personal computer (CPU: Z80).The system is characterized in procedures as follows:1) Basic routine for the determination of welding conditions by interaction between an engineer and a computer: In the first step, desirable or expecting welding parameters are input by an engincer.Next, the computer checks whether these conditions are reasonable or not, and displays the results.Finally, if the results are not satisfied, the flow is returned to the first step and the conditions are corrected by the engineer.With repetition of the above trial, practicable and reasonable conditions can be found out.2) A method for presetting three dimensional weighted distribution as a simulation of arc heat source in each welding process: Geometrical heat elements, such as line, disk, half-elliptical plane or -ellipsoid composed of point heat sources are prepared. Then, each dimension and distribution of each element are set, and each direction and combination of the elements are input according to display on the CRT.3) A method for deciding position of heat source and its extent in a given groove: The first approximation of deposited and molten regions in the groove is carried out using the estimating value of melting efficiency, wire melting rate and mean bead width. The heat source can be set on the CRT on the basis of the result.4) A procedure for determining optimum welding conditions: Three routines, that is, approximation of deposited and molten regions, computation of a weld thermal cycle and shapes of penetration and HAZ boundary, and estimation of hardness and microstructural constituents with memorized SH-CCT diagrams, are utilized to determine optimum welding conditions.

ＭＡＧ溶接の気孔防止とスパッタ防止特性に及ぼすパルス溶接条件の影響

An investigation was carried out about the influence of pulse conditions of MAG welding (CO2, Ar+20CO2, Ar-O2, Ar+2.4%O2+20%CO2) upon spatter loss and porosity. And the test results are as follows.(1) Pulse welding with conditions of Iav=250A, Ip=500A N=300Hz, in Ar+2.4%O2+20%CO2, is found to decrease the spatter loss dramatically.(2) Pulse welding with condition of Iav=250A Ip=500A N=300Hz, in Ar+2.4%O2+20%CO2, is found to decrease the blowholes in weld metal to zero per 10cm bead.(3) Welding with pulse condition of Iav=250A, Ip=500A, N=250Hz is found to increase the wire melting rate to 1.5 times higher than the welding with no pulse.(4) Suitable wire composition for no blowhole and no spatter in MAG welding is DD50S; 0.05C-0.5Si-1.3Mn-0.05Ti.(5) Applying the pulse welding to the primer coated plates, it is found that the new inorganic zinc rich primer coated plates can be welding with condition of Iav=250, Ip=500A, N=300Hz, Ar+2.4%O2+20%CO2.

２電極スイッチング・アーク溶接法に関する研究 ＶＩＩ ホットワイヤスイッチングＴＩＧ溶接法におけるワイヤ溶融特性

A new hot wire TIG welding process has been developed to prevent magnetic interaction between TIG arc and hot wire current. In the new process, TIG arc current and hot wire current which are supplied from D.C power source are alternately switched by transistor switching circuit. Arc phenomena, wire heating and melting condition and upper limit of wire melting rate were investigated using this new process for stainless steel plate.The results obtained in this study are as follows.(1) Arc interaction at the time of TIG peak current was preventable and arc interaction at the time of TIG base current was slight when TIG base current was 50 A bellow.(2) Correlation of the hot wire feed rate and wire melting current was obtained in bead on plate deposition without TIG arc.(3) Relation between wire feed rate, deposition rate and wire current was obtained under bead on plate welding. Upper limit of wire melting rate was closely related to hot wire current.