Question Mark
Industry experts answer some of the most common questions welders encounter in the shop, including cutting quality, welding safety, aluminum TIG welding, shielding gas selection, and techniques for successfully welding thin sheet metal. Practical guidance for welders of all skill levels.
Why do I get so much slag on the backside of my torch cuts?
The slag on the backside of a torch or plasma cut is also referred to as dross, and whether you are using an oxy-fuel cutting torch or a plasma torch, it’s caused primarily by incorrect travel speed. Beginners often move slowly with the plasma or oxy-fuel cutting torch. The phenomenon is very similar to what we see with travel speeds relative to welding. The only difference is that you aren’t watching the puddle and carrying it across the joint. You’re watching the metal be removed. However, the principle is the same. With an oxy-fuel torch, the flame setting is important but the travel speed is critical for a clean cut. Material thickness plays an important role in adjusting either the plasma cutter or the oxy-fuel torch, but when the big variables are correct, clean cuts come down to travel speed. Most of the time, you can move the torch with either process a bit faster than you think you can if you have the skill. This will help produce a cleaner cut on the back side of your material.
Are shaded goggles a necessity when cutting with an oxy-fuel torch?
Bottom line, proper personal protective equipment – eye-related or otherwise – should always be used when welding or cutting. These are processes that generate light at intensities that are potentially dangerous to the human eye. The light from an oxy-fuel welding or cutting torch is referred to as visible light – similar to looking at the sun for a few seconds or having a flashlight beam pointed directly at your eyes at night. This type of light causes temporary blindness, but the effect usually dissipates after a few seconds. But while it’s not permanent, it can damage your eyesight over time – in the same way that not wearing proper hearing protection can cause permanent hearing impairment over time. Bottom line, you need to wear shaded lenses as a basic safety precaution when using a cutting torch. In addition to protecting against light exposure, they can also protect your eyes against exposure to particulates resulting from dirty tips, malfunctioning torches and other factors. Don’t take unnecessary risks. Eye injuries can be very serious. Always wear proper protection.
Why is TIG welding aluminum more difficult than TIG welding steel?
People who learn to TIG weld steel often find welding aluminum a bit more difficult. Most of the difficulty stems from the need for cleanliness and oxide removal. This is why we use AC current on aluminum when TIG welding. The AC current removes the oxide and melts the material at the same time. The other important difference between welding steel and aluminum is the melting point. The melting temperature of aluminum is approximately half that of steel. This means the welder must develop faster reaction times when moving and dipping the filler, because the melting time is much quicker. It takes practice, time and patience to develop the proper reaction time to the puddle, but when you finally get it, welding aluminum can be a satisfying experience.
What is difference between Argon mix and CO2 gas use for MIG welding?
The two most typical gases used for welding short circuit MIG are CO2 and 75/25 Argon/CO2 mix. For reasons too complex to explain here, MIG welding steel with 100% is not an option. CO2 produces a slightly hotter arc and is cheaper than 75/25, so it’s a good choice for industrial applications. CO2 creates a more erratic arc and has a less attractive appearance. The best choice for all of your MIG welding needs – and by far the most common gas – is 75% Argon and 25% CO2. This creates a stable arc, good penetration characteristics and better weld bead appearance, assuming you know what you are doing. The difference in gas can make a huge difference in the quality of your welds.
Why do I keep burning through my sheet metal even when my MIG machine is turned way down?
Welding thin sheet metal can be tricky, even for experienced welders who weld thicker materials all the time. The MIG process is good for welding sheet metal, especially if you don’t have access to the backside of the metal. Depending on how you’re planning to finish the metal, the MIG process can be a good option. If you turn down your machine to the point of spitting and sputtering, you probably need to move to a smaller electrode size. If you’re using a .035 wire on 20-gauge sheet metal, the material is .037. This means you need as much electricity to melt the wire as you do to melt the material. This scenario makes it almost impossible to make the welds without burning through. Of course, we’re assuming all variables are appropriate to the equipment you’re using and to your skill level. Reducing the filler (wire) size will allow it to melt at lower temperatures than the material. This is the same principle that governs TIG welding. You wouldn’t want to use 3/32-inch filler when welding 16-gauge material. The filler must always be equal to or less than the material thickness, which is why filler is available in so many different diameters. Personally, I use .025 or .030 wire size for all sheet metal. Anyone with aspirations to become a skilled welder still needs need to put in the hood time.