Joining metals together through welding gives you several options for the best method. Among your choices are MIG and TIG welding. Each has specific benefits in certain situations. If you ever wondered what the difference is between MIG and TIG welding, this guide will cover everything you need to know.
What Is MIG Welding?
MIG is an acronym for metal inert gas. This process also goes by the name gas metal arc welding (GMAW). Most welders learn this process first because it combines versatility with ease of use. Most metals and alloys adapt readily to the process.
The inert gas portion of the name comes from the fact the arc does not react to the oxygen in the atmosphere. A shielding gas surrounds the electric arc to prevent it from acting outside its designated area. This gas helps to increase the safety of MIG welding.
The welder uses a consumable electrode in the form of a metal filler. This metal will melt to connect the pieces of metal the welder wants to join. The type of electrode filler you use depends on the materials you need to join and their properties.
MIG offers a straightforward process compared to other forms of welding. Its simplicity also makes the process quick, so it’s ideal for last-minute projects, especially if you must conjoin thicker metals than TIG welding can handle.
Unlike other forms of welding that have a consumable filler, such as stick welding, MIG uses more of the filler material, producing less waste. For example, in stick welding, up to 25% of the filler electrode goes to waste as an unused stub. With MIG welding, for every 50 parts, 49 of those will deposit onto the metals as filler, leaving less than 2% as wasted filler.
MIG welding also offers the benefit of speed. The process takes much less time compared to stick or TIG welding. For applications that require the fastest weld possible, MIG welding may be the best choice. However, don’t forget about the metal thickness and appearance of the weld. When connecting thicker pieces, MIG offers an advantage over TIG. The filler used for MIG welding better adheres the metal parts together and thicker metal takes longer to heat for TIG to work.
While useful, fast and versatile, the biggest drawback for MIG welding is where you can do it. The gases used to shield the welding process do not perform well outside. Only conduct MIG welding indoors, with a better-controlled atmosphere.
MIG Welding Process
The process of MIG welding starts with thoroughly cleaning the metal surfaces you need to connect. Any dirt or contamination on the surface could prevent the filler from adequately adhering to the metal. Even dirt under the metal clamps holding down the parts could impede electrical current through the system, reducing the effectiveness of the weld.
Setting up the parameters for MIG welding depends on the metals you need to join.
- Amperage: The amount of current you use depends on the thickness of the metal. Generally, use one ampere per 0.001 inches of metal thickness.
- Filler electrode wire: The type of wire you use depends on the types of metal joined. The thickness of the electrode directly correlates to the metal’s depth.
- Gases: The gases selected also depend on the metals. For all-purpose welding of carbon steel, use a 75% argon, 25% carbon dioxide mixture. Using 100% carbon dioxide gas allows for deeper filler penetration for thicker metals though it creates more mess. For aluminum, use 100% argon, while equal parts argon, carbon dioxide and helium work well for stainless steel.
- Stickout: The length of wiring jutting from the end of the welding gun should measure 3/8 inch and produce a bacon-sizzling sound when used. If the sound production does not match expectations, you have too much wire out.
During welding, power flows through the welding gun to the wire. The weld sends an electric arc through the consumable electrode to the metal pieces. This process melts the consumable filler into a weld puddle that will cool and solidify to join the metal pieces.
During this process, you can choose to push the welding gun forward or pull it backward. The option you choose depends on your skill and the results you want to produce. Regardless of the method you choose, aim for a travel angle between 5 and 15 degrees between the surface and the welding gun. Angles measuring higher than this can increase splatter and reduce accuracy.
Pushing means you work ahead of the weld puddle, creating a shallower penetration and flatter weld. This method gives you better visibility of the process because you push away from the pool.
The pulling process requires you to drag the gun away from the puddle. Some call this the backhand method because your hand moves backward. Pulling the welding torch away makes a narrow bead that penetrates deeply.
What Is MIG Welding Used For?
MIG welding has several applications. Before identifying specific uses, though, be aware of the benefits of MIG welding to see how it suits itself better to some projects.
If you need speed over precision, choose MIG welding. It occurs faster, though the results do not appear as clean as with TIG welding.
For thicker metals, the filler used in MIG welding will help hold the parts together. TIG does not suffice for metals measuring 1/2-inch thick because the materials cannot heat enough during the process.
As long as you match the gas and wire to the types of metal you need to conjoin, MIG has a wide variety of applications you can use it for. Because it produces a visible weld line, choose it for projects that you can see from the outside or where the aesthetics matter.
Appropriate uses for MIG welding include the following:
- Metal component repairs
- Automotive repairs and manufacturing
- Trailer hitches
- Farm equipment
- Construction welding
- Pipe welding
- Underwater welding projects
- Railroad track repair
These options for MIG welding show how versatile the process is. As long as your project does not need to look perfect, requires speed for finishing or has thicker metals that TIG welding won’t work for, you can choose MIG for your welding.
What Is TIG Welding?
TIG is an acronym for tungsten inert gas. Its other name is gas tungsten arc welding or GTAW.
The name for the process comes from the tungsten electrode inside the welding gun. In MIG, this electrode is a consumable metal that creates the filler. Tungsten, however, does not melt as readily as other materials. It conducts the arc of electricity directly to the components you need to join.
Unless you touch the tungsten electrode to the weld pool or materials, you will not consume it during the process. Should the tungsten touch the metal, an incident known as dipping, you will need to grind off the tip. How often you accidentally dip the tungsten into the metal determines the life of the tip.
While MIG uses a filler, TIG does not require one. Its ability to conjoin two metals without a filler means the parts have a cleaner joint without defects from misused filler material.
The TIG process requires more skill than MIG, which means only experienced welders will use this method. Since TIG requires two hands to weld, in instances that use a filler, the welder controls the current using a foot pedal. Unless the welder regulates the current properly, the metals could get too hot. If the metals overheat during welding, they could crack from the stress.
The precision required of TIG welding considerably slows the process. TIG welding takes at least twice as long compared to a similar project using MIG welding. That time investment, though, ensures the product from TIG welding has a smooth, precise weld between a pair of metal sheets.
Since TIG welding requires you to heat the metal pieces you need to join, the parts need to have a thin enough design to allow for the current to pass through them to reach the proper temperature. Very thick pieces require the filler used in MIG welding for a more secure bond.
TIG Welding Process
Unlike the MIG process that only requires one hand to hold the welding torch, though two hands for steadiness is preferable, TIG welding requires two hands if using a filler material. While the filler is inside the welding torch in MIG welding, you hold it with one hand during TIG welding.
For the TIG welding process, tungsten fits into the welding torch where the consumable filler would be in MIG welding. This tungsten retains its form during the process, allowing for repeated use.
The welding torch sends an electric current to the metals joined. This current heats the metals, enabling them to slightly melt to create a weld puddle between them. Since the electric current heats the metals, TIG welding works best for extremely thin pieces, as narrow as 0.005 inches. MIG welding would overwhelm such thin sheets of material.
If you need a filler for the process, you hold a rod of the material in one hand while you have the torch in your dominant hand. You use a foot pedal to regulate the current through the welding gun.
The tungsten rod will have a point or a rounded ball end, depending on what you will weld and the power source. For aluminum and magnesium welding, use AC power and a ball end on the tungsten. Stainless steel and steel use direct current electrode negative (DCEN) and a pointed tip on the tungsten.
With TIG welding, use argon gas whether joining stainless steel, aluminum or steel. While push and pull both work well for MIG welding, with TIG, always use the push method.
TIG welding requires extreme care and precision. Don’t be afraid to take time. For best results, ensure the cleanliness of the surfaces welded. Dirt causes serious complications with the weld, especially when using TIG without filler. Taking the time to clean the surface and to complete the weld will create a better weld than if you rushed through with dirty surfaces. While a slower process, TIG welding produces much more aesthetically pleasing results.
What Is TIG Welding Used For?
Since TIG requires extreme precision and produces cleaner welds, it’s best suited for applications where appearance and strength matter. When working without filler, TIG creates finished products that do not have any visible weld filler above the surface. TIG also does not generate splatter during the process, since it does not need filler to create a bond.
Also, consider the thickness of the metal. For thicker pieces, TIG will not produce adequate heat in the parts to join them. TIG works very well with extremely thin metal sheets and does not need filler for such welds. Parts that do not conduct electricity well but heat up instead work especially well with TIG welding, which relies on heat generation in the metal for creating a weld pool.
Whereas MIG should only conjoin like metals, TIG can bond dissimilar materials. For instance, you can weld together carbon steel with copper alloys or stainless steel.
When choosing TIG welding, the parts must fit tightly together before welding them. If not, the weld will not correct any errors in fit since TIG generally does not use filler. Should the parts not have the desired fit, you can still use TIG if you do the welding with a pulsed current. While this may not fix problems with fit, it accommodates the parts better.
TIG welding has some applications required by construction codes. For many projects, a minimum of the first weld between parts must use TIG welding. These applications include piping, visible consumer goods and nuclear work.
Since TIG welds do not have visible filler when finished, it works well for piecing together auto body parts, aerospace components, ship parts, bicycle parts and pipes. These applications also value the corrosion-resistance and strength of welds TIG produces.
One use of TIG welding that showcases its strength and reliability is its use for spent nuclear fuel. After nuclear rods have completed their use, welders choose TIG welding to seal these still radioactive substances to prevent leaks of the material inside.
If you have experience with welding and need a strong, corrosion-resistant, visually appealing connection and have the time to devote to the process, choose TIG welding.
Contact PBZ for Full-Service Manufacturing
Welding is a vital part of any metalworking project. At PBZ, we understand this concept, which is why we hire only certified welders who can successfully do both TIG and MIG welding to fulfill the most extensive variety of jobs. These welders make up a part of our team who offer our customers resourceful manufacturing from design through shipping. If your business needs a comprehensive service, contact us at PBZ Manufacturing.