Gas Metal Arc Welding
GMAW (Gas Metal Arc Welding) is a type of arc welding that uses electrical energy to produce an arc at the tip of the electrode. The arc generated causes heat to the electrodes and the base metal. When the welding wire is brought close to the workpiece, a welding arc (generating heat) occurs which is able to melt the two metals (welding wire + workpiece), so they will melt together and form a permanent connection. The current used in the GMAW welding process is direct current (DC) and the position of the positive pole electrode or called reverse polarity so that metal transfer can be perfect.
In GMAW welding, we use a shielding gas to protect the molten metal from the oxidation process. The influence of outside air can have an effect on the quality of the weld. There are 2 types of gas used, namely inert gas and active gas. The inert gases are the noble gases, namely Argon and Helium. While the active gas example CO2. Welding that uses inert gas is hereinafter referred to as MIG (Metal Inert Gas) and those that use active gas are called MAG (Metal Active Gas).
1. MAG (Metal Active Gas) Welding Process
In this welding process CO2 gas is used as a protective gas which is an oxidizing agent. This welding is good for welding on construction. In addition, the operating cost of this welding is cheaper than welding using other protective gases such as Argon (Ar).
In the use of CO2 gas as a protective gas, it affects the transfer of molten metal from the electrode to the parent material in the form of relatively large balls. This is because the molten metal remains attached to the tip of the electrode due to a poor arc. In the GMAW process, a lot of spatter or sparks often occur, but this spatter can be reduced by shortening the arc welding distance so that the tip of the electrode looks like molten metal. MAG is often used in welding mild steel and carbon steel in general.
2. MIG (Metal Inert Gas) Welding Process
In the MIG welding process the shield used is an inert gas or noble gas such as Argon (Ar), Helium or Helium mixed with Argon. in practice, the welders make several gas mixture compositions, for example argon + helium, argon + CO2 or argon + oxygen. MIG welding process is usually used to weld materials made of aluminum, stainless steel, copper alloys or nickel alloys.
The advantages of GMAW welding are very efficient processes, do not cause scale, fast processing, can be used in all welding positions. The GMAW (Gas Metal Arc Welding) welding process can be done semi-automatically or automatically. There is less smoke and welding spark that occurs in the GMAW process compared to SMAW, and there is no slag or slag that must be cleaned after welding is complete. Welding speed and filling rate are equal to or greater than SMAW. But the penetration of GMAW is shallower than that of SMAW welding.
GMAW welding is that burn back can occur at any time, unstable arc, difficult set-up at the beginning, porosity welding defects often occur.
Welding Parameters Affecting GMAW
- Wire feed speed
- Welding speed
- Type of shielding gas
example setting for GMAW
– AMPERE and VOLTAGE settings :
100-135 A VOLTAGE 21 V, on plates with a minimum thickness of 8 mm
– For vertical down welding, the amperage is lower compared to vertical up. For horizontal position welding, the amperage setting is around 100-150, but it all also depends on the speed of your hand to swing or weld.
GMAW welding machine
GMAW welding machines are also often used to perform FCAW welding. The following is an example of a GMAW welding machine.
- STAHLWERK MIG 270 ST IGBT– full equipment set – MIG MAG inert gas inverter welder 270 Ampere, suitable for Flux Cored Wire, with MMA ARC, 4 wire drive 7 years warranty
- MIG/MAG – Metal arc gas welding with direct current (DC). You can weld with inactive / inert (MIG, e.g., argon) or active (MAG, e.g., CO2) gases. Gas and welding wire come from a torch head and allow the work to be carried out with just one hand.
- 2 in 1 combined device – MIG/MAG & MMA welding with up to 270 A.
- IGBT Technology – latest transistor technology enables highest power and a duty cycle of 60% at full power. No transformer, no MOSFET, modern IGBT.
- Lightweight & compact design – only 16.6 kg and dimensions of 590 x 220 x 590 mm. Innovative IGBT transistors save space and weight compared to the old MOSFET technology. No heavy carrying!
- High frequency ignition– allows non-contact ignition and ensures a much better welding result.
source : https://www.stahlwerk-schweissgeraete.de/MIG-270-ST-IGBT-full-equipment-set