HISTORY OF MIG (GMAW) WELDING

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TANDEM MIG

I was somewhat surprised when searching the patent record to find two patents from friends on a process I did not realize was even contemplated at that time period, Two Wire MIG!

The first, Patent Number 2,906,861 was filed in September 1957 by Lesnewich, assigned to Airco (figure upper left).  This was truly a Multipower-Multiwire system using two torches and two DC power sources. Variations are covered including the use of AC power.  The company Lesnewich worked for, Airco, produced an emissive coated MIG wire which ran on AC.  It was difficult to keep the coating consistent and it was not commercially successful.

Some innovative MIG techniques were developed in the early days of the process development.  Some were very creative.  One was the narrow gap MIG weld (photo left) was made at 25 lbs per hour deposition rate in a 1/2 inch straight side wall gap.  This weld sample was sufficiently innovative that I have kept it along with only a few others over the approximately 40 years since it was made!  The economics and tracking systems at the time made some of these processes not as attractive as they would be today.  Click to see a proposal regarding a Report on this development.

PULSE ARC WELDING

One of the next major MIG innovations was Pulse Arc welding.  Short Arc was fine for sheet metal and thinner materials.  However on thicker sections it was more difficult to assure adequate penetration.  Some folks knew how to control the process and train welders.  J. Ray McDermott in Louisiana was a case in point for doing it right.  They built heavy section off shore drill rigs almost exclusively with Short Arc with excellent results. 

However Pulse Arc welding gave added assurance the welds would be free from "cold laps" (lack of penetration.)  Needham from The British Research Association filed a patent, Number 3,249,735, assigned to them on July 1963 which defined the process. As he states; " The basic principle is the arc shall work cyclically on at least two cyclically reoccurring levels..." 

In October 1968, Anderson filed patent 3,588,465 assigned to Airco that defined a line voltage compensated Pulsed Arc power supply.  In January 1969, Daggett filed a patent number 3,588,466 also assigned to Airco for a Pulsed Arc power supply with a background level to help stabilize the process.  These first Pulsed Arc systems were not easy to set-up but did provide excellent all position results on heavy plate as well as on materials such as aluminum and bronze.  In fact the first model, called the PA-1, was so difficult to set, when I saw one in the fabrication shop at Sun Ship in Philadelphia, I asked the welding engineer if they had evaluated it for welding heavy steel plates.  He said, "No way, it is set for repairing bronze propellers and if anyone changes those settings I'll break their arm."  One could only select from a few pulse frequencies and setting the background and peak current was much more hit or miss than science.

A variant of the Pulsed Arc system was a much similar process, albeit not as flexible, called Ripple Arc.  Manz was awarded a patent, number 3,524,041 assigned to Linde, for that system having filed in September 1966.

HI DEPOSITION MIG WELDING

Lesnewich in a paper published in the Welding Journal in 1958 (reference 1) described a unique mode of metal transfer-Rotary Spray.  The phenomena occurs at high currents on small diameter wires.  If controlled, it produces very high deposition rates.  See photo of a Rotary Spray Arc on the left.  The wire is tapering due to the electrical pinch forces.  As it tapers the magnetic fields cause the end of the wire to rotate rapidly.

Lyttle in an AWS paper published in the Welding Journal in 1983 (reference 2) described a practical use of the Rotary Spray Arc process on welding "Fifth Wheels."  The fabricator was welding at 20 lbs/hr with 0.035 inch diameter solid wire!  The process was developed by a Linde Division of UCC Field Representative who was very creative and willing to spend the time to train welders on its use.  It was referred to as the Hi-Dep process.

The photo on the right is  the "5th Wheel" application which consisted of making 3/8 inch and larger fillet welds.  The basic problem with this mode of Spray transfer is that it becomes stable at only high metal deposition rates.  The transition from the normal Spray transfer mode to Rotational Spray is a rather wide unstable range.

Church in a patent filed in August 1982 (Patent Number 4,463,243) introduced what he called the T.I.M.E. process.  It had a number of elements but produced high deposition rates with solid MIG wires without the need to have Rotational Spray.  His success however was much like that of the Linde Field Sales Representative.  When there was extensive ongoing welder training they process could be used successfully.

Similar to the deposition rate range of the T.I.M.E. process, a patent by DeVito, et al (I was one of the et al's!) assigned to Linde Division of UCC described a similar process.  Patent number 4,645,903 filed in July 1984, describes how the process works.  It used a conventional water cooled  MIG Gun with a recessed tip and long cup to achieve increased wire extension.  It also used a special gas mixture which allowed it to operate below Rotational Spray mode while maintaining a stable arc.  The process operated between normal Spray Arc and the Rotary-Spray defined by Lesnewich, above.  The minimum current and wire feed speed for  Rotary Spray was much higher than many welders could handle successfully.

The graph on the right is from the patent and shows deposition rates with 0.045 inch diameter wire. This intermediate deposition process could be controlled over a much wider wire feed speed and welding current range.  The process variant can operate with wire deposit rates into the "very high deposition rate mode" as well.  The figure in the upper left shows the deposition rate curves for 0.035 wire.  The wire feed speeds are more practical for 0.045 inch diameter wire although feeding at 700 ipm is not easy.  A special high speed wire feed motor was needed for 0.035 inch diameter wire which required  1200 ipm wire feed speed to achieve 20 pounds per hour.  The advantage is only 340 amps was needed to achieve 20 pounds per hour where 0.045 requires 400 amps. Spray arc welding at 400 amps is very hot!  You need special MIG guns and a product called "Cool Hand Luke" to make this a usable process.  However achieving 20 lbs/hr deposition rate (or more) with solid wire is a very productive, economical method for some applications.

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Demand Pulse

Many innovations came from individuals or smaller companies.  A patent by Hoyt, et al filed June 16, 1983 (Patent Number 4,523,077)  took advantage of then state of the art fast switching power components, MOSFET's, and designed and marketed a successful power source that performed like "Short Arc" but without or with very few shorts.  This eliminated the spatter that accompanies the short circuiting MIG.  The process has lower peak currents than Pulse MIG (100 to 400 amps depending on setting) and they last for a little as 3 milliseconds.  Oscilloscope photo of the process in operation, right. The patent was assigned to Big Four Manufacturing Company.

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