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GMAW is considered one of the easiest welding processes to perform. The entire process is very simple because it’s very easy to control and you always have only one element to operate at any time. However, even working with this simple tool can have its own complications. Knowing basic MIG welding troubleshooting techniques will help you to quickly find the right solution to the problem and continue with your welding. This article will look at some of the most common MIG welding problems and their solutions.
Table of Contents
- 1 Porosity In MIG Welding
- 2 MIG Wire Feed Problems
- 3 Lack Of Fusion
- 4 MIG Welding Spatter Causes
- 5 Excess/Lack of Penetration
- 6 Improper Weld Bead Profile
- 7 Wrap Up
Porosity In MIG Welding
Porosity is small pockets of gas that get caught in the weld metal. It can occur internally, as well as on the surface on the weld bead. In both cases, it weakens the strength of the weld. Here are a few instances of what causes porosity in MIG welding.
Problem 1: Surface Contaminants
- Cause: One of the most common causes is improper surface conditions. For example, if you haven’t cleaned the surface and there was oil, rust or dirt left on it, it will prevent proper weld penetration, leading to porosity. Other welding processes, such as SMAW and FCAW have better tolerance to surface contaminants. In GMAW, only the elements that are alloyed into the wire can provide any protection.
- Solution: Clean the metal surface before you start welding. Use a grinder or chemical solvents to remove rust, dirt, oil, grease, coatings or paint.
Problem 2: Base Metal Properties
- Cause: Simple chemistry of the base metal can also lead to weld porosity. For example, the base metal can have a high content of sulfur and phosphorous.
- Solution: The only solution for this MIG welding issue is to switch to a base metal that has a different composition or a slag-generating welding process.
Problem 3: Inadequate Gas Coverage
- Cause: Another very common cause of porosity in MIG welding is inadequate gas coverage. This welding process relies on the use of shielding gas for protecting the weld puddle from contaminants. Without proper shielding gas protection, the air can contaminate the weld puddle and result in porosity.
- Solution: Various welding conditions require a certain gas flow. You should use a flow meter to check if you have adequate gas flow. If you’re working in high wind conditions, erect wind screens to prevent the shielding gas being blown away from the weld puddle. Check the gun, cables, gas liners and gas fittings for any damages. Make sure that there are no leaks. Also, make sure that you’re using a proper MIG gun nozzle. It should be large enough for the application to provide proper shielding gas flow.
MIG Wire Feed Problems
Improper wire feeding can affect the welding arc and result in weakened weld bead. Most of the problems are usually attributed to faulty equipment setup.
Problem 1: Worn Out Drive Rolls
- Cause: Drive rolls tend to eventually wear out and so they need regular replacement.
- Solution: Check the grooves on the rolls for any visual indications of wear.
Problem 2: Birdnesting
- Cause: Birdnesting is an issue that involves tangled wire and which leads to halting the wire feed.
- Solution: Flip up the drive roll and pull the wire out of the gun. Trim the tangled wire and re-thread it back to the gun. Also, check the tension and make sure that it’s not too high. Other solutions can include using a larger diameter wire and using a shorter distance between the wired feeds.
Problem 3: Burnback
- Cause: Using very slow wire feed speed or placing the gun too close to the base metal can lead to wire melting and fusing with the contact tip.
- Solution: Start by replacing the damaged contact tips and then increase the wire feed speed and make sure that you maintain an appropriate distance between the gun and the workpiece.
Problem 4: Liner
- Cause: It can be liner blockages, the use of a wrong sized liner or improperly trimmed liners.
- Solution: The gun liner must be properly sized to the wire being fed through it. In case of a blockage, clean or replace the liner. Also, check the manufacturer’s directions on how to trim the liner.
Problem 5: Worn Out Gun
- Cause: The copper strands that are located inside the gun tend to break and wear out with time. This results in faulty wire delivery.
- Solution: If during use you notice that a particular area of the gun gets very hot, it’s an indication of internal damage. So prevent GMAW welding defects, immediately replace the gun.
Lack Of Fusion
- Cause: Cold lapping in the short arc transfer process is the most common cause for lack of fusion. This MIG welding defect occurs when the weld pool melts but since there’s not enough energy, it doesn’t fuse to the base plate. So the weld can look good, but the metal won’t actually be joined together.
- Solution: It’s important to use proper voltage and amperage settings. If this doesn’t solve the problem, you might also need to adjust your welding technique. You could switch to the arc-spray transfer method, make sure that you’re using a correct gun angle and check if the weld puddle is getting ahead of the electrode.
MIG Welding Spatter Causes
The weld puddle can expel molten metal and leave the spatter along the bead. This affects the weld appearance and the strength of the fusion.
- Cause: It can be caused by high wire feed speed and voltage settings. Other causes include the insufficient use of gas and dirty base material.
- Solution: Lower the wire feed and voltage settings and switch to a shorter electrode extension. Be sure to clean the base material and ensure proper gas coverage. Also, it’s important to use the correct contact tips and nozzles, as it can lead to an erratic arc and result in excessive spatter.
Excess/Lack of Penetration
Problem 1: Excess
- Cause: Excessive heat input can lead to the weld metal melting through the base metal.
- Solution: Decrease the voltage range and the wire feed speed. You can also increase the travel speed.
Problem 2: Lack Of
- Cause: Insufficient heat input, improper joint preparation or the thickness of the base material.
- Solution: Adjust the wire feed speed and voltage to higher settings. Reducing the travel speed is also a good remedy.
Improper Weld Bead Profile
Problem 1: Insufficient Heat Input
- Cause: A convex bead indicates that the heat input settings are too low, meaning there’s not enough heat for the weld to penetrate the base metal.
- Solution: Check that you’re using a proper amperage setting for the metal you’re welding. You can usually find a chart with guidelines on the MIG welding machine. If this doesn’t solve the problem, also check the voltage. A very low voltage will also create excess spatter. Very high voltage setting, on the other hand, will make it difficult for the welder to control the process and also result in undercutting.
Problem 2: Improper Technique
- Cause: Using a push or forehand technique often results in a flatter bead shape.
- Solution: The ideal technique is to use a push angle of 5-10 degrees.
Problem 3: Work Cable
- Cause: Using the wrong sized or damaged work cable, which results in inadequate voltage in the arc.
- Solution: Replace the cables with new ones that have the appropriate size and length.
Following these MIG welding troubleshooting guidelines will help both beginner and experienced operators diagnosing problems. Armed with some basic information, you’ll be able to quickly detect the problems and find efficient solutions.