How to adjust the current and voltage of MIG welding? This is a question frequently encountered by many welding workers and enthusiasts. MIG welding, also known as Gas Metal Arc Welding (GMAW), is a welding method that uses carbon dioxide gas as a shielding gas to form a weld seam by melting the filler wire and base metal through an electric arc. MIG welding has the advantages of simple operation, high efficiency, low cost, and wide applicability, and is widely used in the welding of various metal materials. Click here to read GMAW vs. CO2 Welding: A Comparison of Two Metal Arc Welding Processes.
However, to perform MIG welding well, it is necessary to master the skills of adjusting the current and voltage. Current and voltage are two important factors that affect the quality of MIG welding. They directly determine the characteristics of the weld seam, such as penetration depth, bead width, spatter, and porosity. Improper adjustment of current and voltage can result in weak weld seams, deformation, cracks, and even burn-through or wire-sticking phenomena. So, how to correctly adjust the current and voltage of MIG welding? This article will introduce you to some practical methods and techniques.
I. Selecting appropriate welding parameters
Before MIG welding, it is necessary to select appropriate welding parameters based on welding conditions such as plate thickness, welding position, material, etc. These parameters, including welding current, voltage, wire feed speed, gas flow rate, etc., interact with each other and need to be comprehensively considered and balanced. Generally, the following principles can be followed:
Welding current: It mainly affects the penetration depth of the weld seam, that is, the welding penetration force. The greater the current, the greater the penetration depth; conversely, the smaller the penetration depth. If the current is too high, it is easy to cause burn-through or spatter; if the current is too low, it is easy to cause a lack of fusion or porosity. Therefore, a suitable current should be selected according to the plate thickness and wire feed speed.
Welding voltage: It mainly affects the arc length and bead width, that is, the shape of the weld seam. The higher the voltage, the longer the arc length and the wider the bead width; conversely, the shorter the arc length and the narrower the bead width. If the voltage is too high, it is easy to cause spatter or porosity; if the voltage is too low, it is easy to cause wire sticking or deformation. Therefore, a suitable voltage should be selected according to the wire feed speed and material.
Wire feed speed: It mainly affects the amount of filler wire fed into the weld pool, that is, the heat input of welding. The faster the wire feed speed, the more filler wire is fed into the weld pool, and the greater the heat input; conversely, the slower the wire feed speed, the less filler wire is fed, and the smaller the heat input. If the wire feed speed is too fast, it is easy to cause buildup or spatter; if the wire feed speed is too slow, it is easy to cause discontinuity or fracture. Therefore, a suitable wire feed speed should be selected according to the plate thickness and material.
Gas flow rate: It mainly affects the stability of the shielding gas around the arc, that is, the stability of the welding process. The greater the gas flow rate, the more stable the shielding gas, and the more stable the welding process; conversely, the less stable the shielding gas, and the less stable the welding process. If the gas flow rate is too high, it is easy to cause gas waste or nozzle blockage; if the gas flow rate is too low, it is easy to cause oxidation or porosity. Therefore, a suitable gas flow rate should be selected according to the arc length and ambient wind speed.
II. Methods for adjusting welding current and voltage
After selecting appropriate welding parameters, you can start adjusting the current and voltage. There are many methods for adjusting current and voltage, here are two commonly used methods:
1). Formula method: Calculate the theoretical values of current and voltage based on certain formulas, and then adjust according to these values. This method is relatively simple and suitable for beginners. The following two formulas are commonly used:
When welding current is less than 300A, the welding voltage can be calculated using the following formula:
U=（0.05I+14）±2V
Where U is the welding voltage, I is the welding current.
When welding current is greater than 300A, the welding voltage can be calculated using the following formula:
U=（0.05I+16）±2V
Where U is the welding voltage, I is the welding current.
For example: If the selected welding current is 200A, then according to the first formula, the welding voltage can be calculated as:
U=（0.05×200+14）±2V
U=（10+14）±2V
U=24±2V
In other words, the welding voltage should be between 22V and 26V.
2). Observation method: Judge whether the current and voltage are appropriate based on the phenomena such as sound, sparks, and droplets during the welding process, and then make fine adjustments. This method is more flexible and suitable for experienced individuals. The following are some commonly used observation standards:
If there are always droplet-shaped metal balls at the end of the wire and the frequency of excess is low, it indicates that the welding voltage is too high. In this case, the wire feed speed should be increased or the welding voltage should be decreased.
If the wire extension is slightly short and welding can be done normally, but wire sticking occurs when it is slightly longer, it indicates that the welding voltage is too low. In this case, the wire feed speed should be reduced or the welding voltage should be increased.
If the weld surface is smooth and free of spatter and porosity, and the sound is stable and crisp, it indicates that the welding current and voltage are appropriately matched.
III. Precautions
When adjusting the current and voltage of MIG welding, pay attention to the following points:
Ensure the normal operation and good connection of MIG welding machine, cables, nozzles, and other equipment to avoid affecting the accuracy of parameters due to equipment failures or looseness.
Adjust the parameters according to different welding positions (such as flat welding, vertical welding, horizontal welding, etc.) and directions (such as horizontal direction, vertical direction, uphill direction, etc.). Generally, positions and directions with greater difficulty require smaller parameters.
Related articles:
1. TIG Welding with DC vs. AC Current
2. Arc Length, Weld Speed and Welding Current
3. Why is AC current preferred in aluminum welding?
4. MIG Weld Push or Pull | When to Use Push vs Pull?
5. A Comprehensive Guide to Pulse MIG Welding
