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There are certain tips that can help you begin with proper MIG welding without making many mistakes by taking the correct steps before you begin. If you are one who does welding for a living, you might not have the idea of the measures that need to be taken to maintain optimal performance for your MIG welder.
Equipment
The equipment that you plan to use for welding is essential and hence needs to be analyzes before the purchase of one. If you are an occasional welder, then getting the Millermatic 211 or the Millermatic 215 is ideal. If you are a professional and you are earning a living out of it, then purchasing good-quality multi-welders is the way to go.
You can also purchase the welding machines that have the AutoSet function which allows automatic detection of parameters for the material thickness and wire diameter. This allows for proper usage of technique and better analysis of the work. It is better to look at guides and review articles before purchasing one.
Ideal Conditions
- Material Thickness: It is well known that 0.001 inches of metal thickness requires an amperage of 1 amp. Hence for a metal of thickness around 0.125 inches will need 125 amps of current to be supplied to the welding gun.
- Wire Size: Wire size also determines the amount of current that is supplied to the welding machine. It can be represented by:
| 30-130 amps | .023 inch |
| 40-145 amps | .030 inch |
| 50-180 amps | .035 inch |
| 75-250 amps | .045 inch |
- Voltage: Voltage helps us analyze the height and width of the bead. You can test for yourself by welding on scrap metal and slowly reducing the voltage until the arc stubs into the workpiece. Next, increase the voltage as you do so, and then do not stop until the arc electrode becomes sloppy in nature. The midway between these voltages can help you provide a good starting point.
- Wire-feed Speed: The wire speed of the MIG welder can help you maintain the amperage supplied and the amount of weld penetration.
| For wire size | Multiply by | Ex. using 1/8 inch (125 amps) |
|---|---|---|
| .023 inch | 3.5 inches per amp | 3.5 x 125 = 437.5 ipm |
| .030 inch | 2 inches per amp | 2 x 125 = 250 ipm |
| .035 inch | 1.6 inches per amp | 1.6 x 125 = 200 ipm |
| .045 inch | 1 inch per amp | 1 x 125 = 125 ipm |
Examination of Beads Obtained:
- Good Weld: Good base metal penetration, flat bead profile, accurate bead width, and good toes of weld.
- High Voltage: It causes poor arc control, improper weld penetration, and a wavering weld pool that altogether penetrates the base material.
- Low Voltage: This also causes poor arc control, improper penetration, and tampered weld pool. It would lead to a bad bead profile and a lot of spatter production.
- Fast Travel Speed: It causes a narrow bead profile with improper penetration and is not ideal for welding.
- Slow Travel Speed: This causes wider bead welds and poor penetration of the metal used. It causes a complete burn on thinner metals.
- No Shielding Gas: The absence of shielding gas in your welding causes porosity and pinholes in the weld and also on its interior causing poor welds.
| Stainless Steel Settings | ||||
|---|---|---|---|---|
| 18 Gauge | .035 | 120-150 ipm | 20 volts | 50-60 amps |
| 16 Gauge | .035 | 180-205 ipm | 20 volts | 70-80 amps |
| 14 Gauge | .035 | 230-275 ipm | 20-21 volts | 90-110 amps |
| 12 Gauge | .035 | 300-325 ipm | 20-21 volts | 120-130 amps |
| 3/16 Inch | .035 | 350-375 ipm | 21 volts | 140-150 amps |
| 1/4 Inch | .035 | 400-425 ipm | 21 volts | 160-170 amps |
| 5/16 Inch | .035 | 450-475 ipm | 22 volts | 180-190 amps |
| 3/8 Inch | 1.6mm | 140-170 ipm | 25 volts | 250-275 amps |
| 7/16 Inch | 1.6mm | 170-200 ipm | 27 volts | 275-300 amps |
| 1/2 Inch | 1.6mm | 200-230 ipm | 32 volts | 300-325 amps |
Metal Thickness for Aluminum
The wire type used commonly for aluminum welding for better rigidity and strength is ER5356 that can be used for all types of welding works.
| 1/8 Inch | .035 | 350-400 ipm | 1.2mm | 240-270 ipm |
| 3/6 Inch | .035 | 425-450 ipm | 1.2mm | 300-325 ipm |
| 1/4 Inch | 1.2mm | 350-375 ipm | 1.6mm | 170-185 ipm |
| 5/16 Inch | 1.2mm | 400-425 ipm | 1.6mm | 200-210 ipm |
| 3/8 Inch | 1.2mm | 450-480 ipm | 1.6mm | 220-230 ipm |
| 7/16 Inch | 1.6mm | 240-270 ipm | 280 amps | |
| 1/2+ Inch | 1.6mm | 290-399 ipm | 300 amps | |
Tips for Sheet Metal welding
- Since sheet metal is much thinner than normal metals, it is recommended to use precautionary measures and techniques to weld them. This can prevent warping, accidental burn-through, and overheating metal parts. It must also have enough mechanical strength. Short-circuit MIG welding, TIG, and pulsed-TIG welding are the preferred processes to overcome these challenges.
- It is recommended to use a very small diameter for the wire feed used. This takes more amperage to heat the wire with more time and it will also heat the metal much less than normal wire conditions. You also get more control over the welding process and wire bead too.
- Never apply filler metal more than the amount of base metal available. It is recommended to use 0.023- 0.024-inches wire for such sheet metals. If you are willing to weld mild steel, use a wire that has a certification from the American Welding Society like the ER870S-6.
- Make sure the shielding gas that you use is having high argon content like about 75% argon and 25% carbon dioxide. This is because less argon produces less heat for the metal and hence you will get less spatter produced.
- If you are welding a 304 stainless steel type, using ER308, ER308L, and ER308LSI wires are preferred. Whereas, for welding 316L stainless steel, you need to use the 316L wire. The shielding gas used for stainless steel must be a tri-mix gas comprising 90% helium, 8% argon, and 2% carbon dioxide.
- In order to weld sheet metal using solid wire, it is recommended to use positive polarity for the wires. Using flux-core wires can damage your metal if you use it to weld sheet metal surfaces.
Techniques Used
Always make sure the arc that you are using currently must not be placed in any zone for a very long time. The more it stays in proximity to the metal, the more it heats the metal up. This must be monitored to prevent any sort of burn-through and warping.
Another important measure is to have a very high speed for the wire and must travel along with the metal in a straight line. The push technique for the MIG welding technique is also recommended to be used frequently.
Let us now see some refined techniques:
- Skip Welding: When the heat applied to the weld of the metal is not uniform, it causes distortion, cracks, and warping in the weld. Skip welding is a method where intermittent or stitch types of multiple welds are done.
- Backing Bars: To allow the escape of heat from the metal much quicker than traditional atmospheric cooling, it is recommended to place the heated metal close to a chilled bar or backing bar. This chilled bar can even be of the material using copper or aluminum.
- Fit-up and Joint Technique: When you need to weld up thin sheets of metals, then a tight fit is essential to do it effectively. To avoid any sort of failure or refurbishment, follow the “measure twice, cut once” rule. Redesign the metal parts in such a way that they can withstand a lot of heat. Using a plug weld can be helpful where you won’t require a solid weld bead profile.
Pulsed MIG Welding
Pulsed MIG welding is the technique of welding where you use current pulses from the power source to slowly transfer droplets of filler metal that is molten to produce no spatter in the weld even using low welding data conditions. It was first developed by JC Needham at ‘The Welding Institute’ in the 1960s.
It is mainly used for welding aluminum and stainless steel commonly and carbon steel also. This method of controlling and moderating the flow of the droplets of the filler metal using pulsed current (30Hz-300Hz).
These pulses of current have two major functions which are: melting the filler metal and removing one droplet of molten filler for every pulse. The pulse frequency is directly proportional to the wire-feed speed. The current magnitude in each pulse will be high but the average current and heat input are kept low.
- Good control over the weld and no production of distortion, sparks, and cracks.
- Within the normal spray arc range, you can do better penetration into the metal.
- Even if you use a thick filler wire, a stable arc can be produced.
- If you are able to do efficient droplet pinch-off of filler metal, you can reduce the overall heat of the metal.
- The production rate is less compared to short arc welding technique.
- You will have a restriction in the use of customized shielding gases.
Sean Coby is a welder par excellence and well respected among the welding community in Woodbridge, VA. He prides himself to be the fabricator and mechanic in the automotive/ diesel industry for the past more than eight years now. As the chief editor of his https://weldinginfocenter.com, he shares his experience to be safe during welding and to take proactive steps for becoming a successful welder like him.