Gas Metal Arc Welding or GMAW (also known as Metal Inert Gas welding or MIG welding) is a welding process with over sixty years of history that uses consumable wire electrodes to produce an electric arc that melts and joins separate pieces of metals together. A shielding gas is fed through the welding gun to protect the welding process from being contaminated by gases like nitrogen and oxygen that can ruin the weld. The most common welds include the lap joint, butt joint, edge joint, and T-joint. But the process is commonly used with steel and sheet metals while argon, helium, and carbon dioxide are the most commonly used shielding gases. GMAW uses four main metal transfer methods which are short circuit, globular transfer, axial spray transfer, and pulsed spray transfer.
Gas metal arc welding is the most popular welding method because it is favored for its ease, versatility, speed, and for its ability to be used by robotics. Basically, MIG welders are considered some of the easiest to learn and operate in order to create strong, crisp welds. MIG welding is versatile, utilized for plenty of projects such as equipment maintenance, hobby welding, autobody work, and more. It’s a preferred technique among welders for a reason—It’s easy, cost-effective, and it produces top-quality welds!
It is thanks to MIG welding that the modern welding industry is where it’s at today, and without it, many of the products that we use in our day to day lives could not exist. That is why it is important to know and understand how (1) this incredible invention came about and (2) how it has been refined and evolved over the years into the welding process that we know and love today.
The Invention of MIG Welding
Welding has technically existed in an extremely rudimentary form since the Bronze Age where historians hypothesize that metals were hammered under high heat until they eventually joined together. True modern welding, however, first came about when Humphry Davy discovered the electric arc at the start of the 19th century and laid down a framework for innovators and scientists to improve upon. For the next century, more and more advancements were made in the field quite rapidly. Arc heat was used to join metal together for the first time and soon after welders were using carbon electrodes for welding. Metal electrodes were quickly introduced to the welding scene and were followed by an arc welding process that uses coated metal electrodes. Eventually, the welding process became automated thanks to the invention of consumable metal fillers at the end of the 19th century and humanity was one step closer to the conception of MIG welding.
Some precursors to modern MIG welding were invented in the early twentieth century, but they did not rely on inert gases to shield the weld and they weren’t suitable for usage due to some impracticalities. It wasn’t until 1948 that the Batelle Memorial Institute invented modern gas metal arc welding (GMAW). This early version of MIG welding used an electrode with smaller diameters than the ones commonly used today, used a constant power supply, came with a high deposition rate, and used an axial spray metal transfer method where metal droplets are dispersed axially across the arc. Early GMAW welders used argon for gas shielding, which greatly limited versatility thanks to its costliness and inability to produce adequately deep welds when using steel. Since the process was rather expensive and could only be used with nonferrous metals like aluminum, it was not a popular one until it was revolutionized later in the twentieth century.
The Advancement of MIG Welding Throughout the 20th Century
Mid 20th Century
Because the inert gasses that early MIG welding relied on were extremely expensive and unreliable with steels, the process was costly and welders were limited to inexpensive materials like aluminum and other metals. This all changed six years later in 1953 when Novoshilov and Lyubavshkii succeeded in using carbon dioxide as a gas shield following failed attempts made in 1924. Their work not only made this method of welding more cost efficient, but it gave welders the opportunity to work with steel since it can deeply penetrate the metals and allows for deep welds. The fact that MIG could now be used with steel bolstered the popularity of this welding method and carbon dioxide was commonly used as a shielding gas in favor of argon. The invention was not without its downsides, however, as using carbon dioxide as a welding atmosphere encourages oxidation, produces high amounts of splatter which leads to lower quality welds and an inability to use thin materials, and the heat input was discouraging for welders.
Following the introduction of carbon dioxide as a shielding gas, a variation using what is known as an inside-outside electrode was developed a year later. This process not only utilized external gas shielding like conventional GMAW methods do, but it also featured internal shielding via the gas that was produced in the core of the electrode wire. This method is known as Dualshield, its name referencing that the method uses both external and internal gas shielding.
Then in 1958, only a short 5 years after the groundbreaking introduction of carbon dioxide gas as a welding atmosphere, a variation of GMAW was released that utilized a shorter arc. The usage of electrodes with a smaller diameter enabled short-circuiting transfer which used lower levels of heat. The weld pool produced by this method is small and relatively easy to control which meant that welders could work in a variety of positions and also work with thinner materials, with the only downside being the excess splatter produced. Short-circuiting transfer quickly became the most popular GMAW variation due to its versatility and ease to work with in spite of the low quality welds it often produced.
The sixties saw the advent of the spray-arc transfer variation of GMAW. By injecting small amounts of oxygen into the inert gasses used for shielding, very little splatter would be produced and tiny droplets would spray across the arc similarly to how water droplets are sprayed out of a gardening hose. This arc has even seen more recent advancements with the invention of the pulsed spray-arc variation. By using a pulsed current that switches from high currents to low currents at breakneck speeds, welders could reduce the amount of splatter produced while welding while also working with lower heat outputs and ultimately producing higher quality welds. This new variation of using a pulsed current in welding has been given the name GMAW-P and was a huge step towards the future of MIG welding.
Further GMAW welding developments in this decade relied on the advancement of power source technology. New inventions in this field allowed for the GMAW and GMAW-P processes to be refined and improved. Thyristors, which were invented in the year 1950, were starting to be used in commercial power sources at this time. These new thyristor power sources were able to stabilize high voltages and were convenient thanks to their small sizes and large number of uses, although they were most commonly used for light dimmers.
A study done by the Welding Institute of the United Kingdom proved that there was a linear relationship between how fast wires are fed and the pulsed frequency output. This study allowed for the development of one knob control transistor controlled power sources that gave welders more power over the process by allowing them to control the wire feed speed and therefore the amount of pulsed energy with a single twist of a knob.
The early eighties saw a new method of MIG welding come about, the rotary spray arc that featured high deposition rates when controlled properly. This sprung forth more inventions that sought to achieve high deposition rates without the rotary spray arc like the T.I.M.E process as well as a patent developed in 1984 that used a unique gas mixture that would allow for both the normal spray arc as well as a rotary spray arc. Another advancement sought to minimize the splatter produced during short arc by developing a power source that used shorter and lower peak currents. These advancements continued to inspire others to further improve upon the MIG welding process until huge gains were eventually made in the next decade.
In 1994, the company Lincoln Electric produced and sold the first commercial unit for a new MIG welding process that is now used by almost every major welding contractor in the world. This process utilizes surface tension transfer which offers greater control to welders and minimizes splatter, allowing for the highest quality welds. Surface tension transfer technology is powered by a waveform generator that controls the current and heat independent of wire feed speed, meaning that the current can be controlled without adding more wire and heat is never removed from the bead. This allows for consistent, high quality welds that take significantly less time to produce than they do when using other welding methods favored for precision. Surface tension transfer improves on the widely favored short arc method by vastly improving welding quality without sacrificing any of the versatility that many appreciated. This invention has changed MIG welding for the better, and brings us to the MIG welding of today.
The State of MIG Welding in the 21st Century
The twenty-first century is truly the golden age of MIG welding. And while GMAW isn’t suited for welding outdoors, underwater, or in space, its use is still widespread. MIG welding has been put into the hands of robots who use the process to mass produce countless goods and products, especially in the sheet metal and automobile industry where this method of welding is a highly favored one. This is all thanks to the decades of improvements and the hard work of many inventors and scientists that continued to revolutionize and innovate until GMAW became what it is today.
Nowadays, advancements are being made by several companies who have been relying on modern technology to study the characteristics of the arcs produced by MIG welding so that starts, weld over gaps, and the amount of spatter produced can also be improved. These innovations can allow MIG to be used more frequently in other countries, like Japan, where inert gases like argon are costlier. Other developments continue to simplify the welding process, like the QSET welder which automatically sets the right parameters depending on what type of wire and gas you are using, eliminating the need to rigorously teach and train welders on how to configure their equipment depending on the materials they are working with. And even further advancements are being made in the way of optimizing the way shielding gas is delivered to ensure that gas is always delivered properly without any of it being wasted, especially during the startup process.
With modern day inventors and scientists creating even newer methods of welding, like friction welding which uses heat by friction to generate heat that can strengthen parts or laser welding which is being used where tight precision welds are needed, there are high hopes that the future is bright for MIG welding. We will continue to see more and more innovations that will further revolutionize the industry and build upon GMAW’s rich history.