Cold Metal Transfer Plug Welding of Aluminum AA6061-T6-to-Bare Mild Steel

It was known that it is challenging to join lapped aluminum and bare steel with cold metal transfer (CMT) process because of the formation of significant brittle intermetallics. In this study, another attempt was made to join aluminum AA6061-T6 and bare mild steel with CMT plug welding. Welding tests were performed and the bonding mechanisms, fracture modes, and strengths of CMT plug welded joints were systematically characterized. It was found that it is feasible to join 1 mm thick bare mild steel-to-1 mm thick aluminum AA6061-T6. The material stacking sequence and the presence of a predrilled hole significantly affected the weldability of CMT plug welding bare mild steel-to-aluminum AA6061-T6. By positioning bare steel with a predrilled hole in the top aluminum AA6061-T6 and aligning a torch in the center of an 8 mm hole improved significantly the weld appearance and joint strength.

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Cold Metal Transfer Spot Joining of AA6061-T6 to Galvanized DP590 Under Different Modes

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4029093 ◽

2015 ◽

Vol 137 (5) ◽

Cited By ~ 19

Author(s):

HaiYang Lei ◽

YongBing Li ◽

Blair E. Carlson ◽

ZhongQin Lin

Keyword(s):

Heat Input ◽

Mechanical Performance ◽

Welding Process ◽

High Strength ◽

Metal Transfer ◽

Cold Metal Transfer ◽

Spot Joining ◽

Predrilled Hole ◽

Joint Quality ◽

Cold Metal

In order to meet the upcoming regulations on greenhouse gas emissions, aluminum use in the automotive industry is increasing. However, this increase is now seen as part of a multimaterial strategy. Consequently, dissimilar material joints are a reality, which poses significant challenges to conventional fusion joining processes. To address this issue, cold metal transfer (CMT) spot welding process was developed in the current study to join aluminum alloy AA6061-T6 as the top sheet to hot dip galvanized (HDG) advanced high strength steel (AHSS) DP590 as the bottom sheet. Three different welding modes, i.e., direct welding (DW) mode, plug welding (PW) mode, and edge plug welding (EPW) mode were proposed and investigated. The DW mode, having no predrilled hole in the aluminum top sheet, required concentrated heat input to melt through the Al top sheet and resulted in a severe tearing fracture, shrinkage voids, and uneven intermetallic compounds (IMC) layer along the faying surface, leading to poor joint properties. Welding with the predrilled hole, PW mode, required significantly less heat input and led to greatly reduced, albeit uneven, IMC layer thickness. However, it was found that the EPW mode could homogenize the welding heat input into the hole and thus produce the most stable welding process and best joint quality. This led to joints having an excellent joint morphology characterized by the thinnest IMC layer and consequently, best mechanical performance among the three modes.

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Microstructure and mechanical properties of cold metal transfer welded galvanized steel/magnesium alloy dissimilar joints

International Journal of Modern Physics B ◽

10.1142/s0217979220400603 ◽

2019 ◽

Vol 34 (01n03) ◽

pp. 2040060

Author(s):

Chao Zhang ◽

Mingfang Wu ◽

Yuxin Wang ◽

Juan Pu

Keyword(s):

Magnesium Alloy ◽

Heat Input ◽

Interface Layer ◽

Metal Transfer ◽

Galvanized Steel ◽

Cold Metal Transfer ◽

Welding Joint ◽

Welding Heat Input ◽

Weld Appearance ◽

Cold Metal

The joining of magnesium alloy to galvanized steel was realized by cold metal transfer method with AZ31 magnesium alloy welding wire. Weld appearance, microstructure and tensile properties of Mg–steel joints under various welding parameters were investigated with different welding heat inputs. The results showed that magnesium alloy-steel brazed joints had good weld appearance. When the welding heat input was 141 J/mm, Zn elements were enriched in the Zn-rich zone (ZRZ), and the interface layer was composed of a large portion of Mg–Zn phases and minor Mg–Al phases. With the increase of welding heat input, Zn elements in the ZRZ gradually decreased, Fe/Al phase appeared in the interface layer, and the strength of welding joint increased. When the welding heat input was 159 J/mm, the tensile strength of welding joint reached the maximum value of 198 MPa. However, when the welding input was increased to 181 J/mm, Zn element in the ZRZ was burnt and volatilized seriously, resulting in poor wetting and spreading properties of liquid phase at the interface zone of the steel.

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Weldability and Distortion of Mg AZ31-to-Galvanized Steel SPOT Plug Welding Joint by Cold Metal Transfer Method

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4034009 ◽

2016 ◽

Vol 139 (2) ◽

Cited By ~ 4

Author(s):

R. Cao ◽

Q. W. Xu ◽

H. X. Zhu ◽

G. J. Mao ◽

Q. Lin ◽

...

Keyword(s):

Mild Steel ◽

Weld Metal ◽

Base Metal ◽

Metal Transfer ◽

Galvanized Steel ◽

Feed Speed ◽

Process Variables ◽

Cold Metal Transfer ◽

Wire Feed Speed ◽

Cold Metal

In this study, cold metal transfer (CMT) plug welding of 1 mm thick Mg AZ31 to 1 mm thick hot-dipped galvanized mild steel (i.e., Q235) was studied. Welding tests were performed and the process variables optimized with Mg AZ61 wire and 100% argon shielding gas for a plug weld located in the center of the 25 mm overlap region. It was found that it is feasible to join 1 mm thick Mg AZ31 workpiece to 1 mm thick galvanized mild steel using CMT plug welding. The optimized process variables for CMT plug welding Mg AZ31-to-galvanized mild steel were a wire feed speed of 10.5 m/min, a predrilled hole with a diameter of 8 mm in Mg AZ31 workpiece and a welding time of 0.8 s. CMT plug welded Mg AZ31-to-galvanized mild steel joints were composed of the fusion zone between Mg AZ31 base metal and Mg weld metal, Mg weld metal (i.e., combined base metal, filler wire and Zn coating), and the brazing interface between magnesium weld metal and galvanized mild steel. The brazing interface mainly consisted of Al, Zn, Mg, Si intermetallic compounds and oxides (i.e., Fe3Al, Mg2Si, MgZn, and MgZn2), and magnesium solid solution. The static strength of CMT welded-brazed Mg AZ31-galvanized steel was determined primarily by the strength and area of the brazed interface and thickness of the intermetallic reaction layer.

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Integrity of 5052 Al-mild steel dissimilar welds fabricated using MIG-brazing and cold metal transfer in nitric acid medium

Journal of Materials Processing Technology ◽

10.1016/j.jmatprotec.2019.01.010 ◽

2019 ◽

Vol 268 ◽

pp. 97-106 ◽

Cited By ~ 7

Author(s):

Sravanthi S.S. ◽

Swati Ghosh Acharyya ◽

Phani Prabhakar K.V. ◽

Padmanabham G.

Keyword(s):

Nitric Acid ◽

Mild Steel ◽

Acid Medium ◽

Metal Transfer ◽

Nitric Acid Medium ◽

Cold Metal Transfer ◽

Dissimilar Welds ◽

Cold Metal

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Cold metal transfer joining aluminum alloys-to-galvanized mild steel

Journal of Materials Processing Technology ◽

10.1016/j.jmatprotec.2013.04.004 ◽

2013 ◽

Vol 213 (10) ◽

pp. 1753-1763 ◽

Cited By ~ 113

Author(s):

R. Cao ◽

Gang Yu ◽

J.H. Chen ◽

Pei-Chung Wang

Keyword(s):

Aluminum Alloys ◽

Mild Steel ◽

Metal Transfer ◽

Cold Metal Transfer ◽

Cold Metal

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Effect of welding speed on microstructure and mechanical properties of titanium alloy/stainless steel lap joints during cold metal transfer method

Metallurgical Research & Technology ◽

10.1051/metal/2020052 ◽

2020 ◽

Vol 117 (5) ◽

pp. 506

Author(s):

Gang Li ◽

Shengyu Xu ◽

Xiaofeng Lu ◽

Xiaolei Zhu ◽

Yupeng Guo ◽

...

Keyword(s):

Mechanical Properties ◽

Stainless Steel ◽

Fusion Zone ◽

Welding Speed ◽

Joint Strength ◽

Metal Transfer ◽

Lap Joints ◽

Cold Metal Transfer ◽

Microstructure And Mechanical Properties ◽

Cold Metal

Cold metal transfer (CMT) technique is developed for lap joining of titanium (Ti) alloy to stainless steel (SS) with CuSi3 filler wire. The effect of welding speed on the microstructure and mechanical properties of Ti/SS lap joints is investigated. The results indicate that the wetting angle of the lap joints gradually increases and the weld width decreases with increasing the welding speed. It is found that many coarse phases in the fusion zone are rich in Ti, Fe and Si etc, inferring as Fe–Si–Ti ternary phase and/or Fe2Ti phase at low welding speed. Many fine spherical particles in the fusion zone are considered as iron-rich particles at high welding speed. The transition layer are exhibited at the Ti–Cu interface. With increasing the heat input, the intermetallic layer becomes thicker. A variety of brittle intermetallic compounds (IMCs) are identified in the lap joints. The shear strength of the joints increases with increasing the welding speed. Two fracture modes occur in the lap joints at low welding speed. Thicker reaction layer causes brittle fracture and poor joint strength. The Fe–Ti–Si and Fe2Ti phase within the fusion zone are detrimental to the joint strength. The fracture surface of the joints is dominated by smooth surface and tear pattern at high welding speed. The fracture mode of the joints is merely along the Ti–Cu interface.

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Modeling of Cold Metal Transfer Spot Welding of AA6061-T6 Aluminum Alloy and Galvanized Mild Steel

Journal of Manufacturing Science and Engineering ◽

10.1115/1.4027673 ◽

2014 ◽

Vol 136 (5) ◽

Cited By ~ 9

Author(s):

Zhenghua Rao ◽

Jiangwei Liu ◽

Pei-Chung Wang ◽

Yunxiao Li ◽

Shengming Liao

Keyword(s):

Mild Steel ◽

Weld Pool ◽

Spot Welding ◽

Steel Surface ◽

Metal Transfer ◽

Upward Flow ◽

Zinc Vapor ◽

Cold Metal Transfer ◽

Arc Pressure ◽

Cold Metal

In this article, a three-dimensional (3D) transient unified model is developed to simulate the transport phenomena during the cold metal transfer (CMT) spot welding process of 1 mm thick aluminum AA6061-T6 and 1 mm thick galvanized mild steel (i.e., AISI 1009). The events of the CMT process are simulated, including arc generation and evolution; up-and-down movement of electrode, droplet formation and dipping into the weld pool; weld pool dynamics; zinc evaporation, and zinc vapor diffusion in the arc. The effects of the gap between the two workpieces and effects of zinc vapor evaporated from the steel surface on CMT process are studied. The results show that the arc temperature, velocity, and pressure keep changing during the CMT process, which is related to the variations of welding current, arc length, and zinc evaporation. It is found that the zinc evaporation leads to the extremely high arc pressure and the upward flow of zinc vapor near the steel surface, which would induce the arc instability and provide the drag force for the droplet impingement. The presence of the gap between the two workpieces can improve the expansion of the arc plasma, resulting in the smaller arc pressure and the more intensive upward flow of zinc vapor from the steel surface. The phenomena observed in the experiment are in agreement with the modeling results.

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