Welding what is undercut

Specifically for MAG metal active gas welding processes, the right selection of the gas is pertinent. A wrong choice is the primary cause of undercuts, so watch out for that. To avoid this from happening, first, assess the material type and thickness. Then you will identify the correct gas composition accordingly.

Trying to weld too quickly by using high temperatures is calling for trouble. By increasing the temperature, you get the main metal to melt faster. Pay attention to the welding temperature. Watch out for thinner metals and reduce the current and arc speed accordingly. By investing a little bit of time and attention, you can avoid an undercut. If you want to master the craft of welding, then knowing your electrode angle and size is essential.

Here are a few tips:. Even though undercutting is common, it is best to try and avoid it altogether. It is costly to fix and results in a reduction in speed and productivity. So, preventive measures are the way to go. Undercuts 0. In low-carbon steel plates, you can even let go of a 10 mm thick cut. They are easily fixable, though. For an external undercut, you can place a stringer bead along the entire length of the cut.

In some cases, you may even need to use a grinder to blend the pieces together. Internal undercuts typically occur at the butt joint weld near the base metal.

They can also be found right next to the roof of the weld. Another type of internal undercut is one found within a weld. It is a groove left near the sidewall of the roof of the weld. Preventive measures for both internal and external uppercuts are the same.

You can fix an internal undercut by weld beads. Place a weld bead within the weld area. These beads will form inclusions in the weld fixing the flaw. In the case of a T-joint, you actually need to spend more time on the upper side of the joint to form normally shaped bead. One more form of the internal undercutting can be seen within the weld itself.

It can be seen as a groove left on the sidewall. When the ensuing weld bead is put in the weld area, it may form inclusions on the metal. Also known as the crown undercut —it is a kind of undercut in welding that is apparent on the outside of the weld. It can be seen as a groove or erosion alongside the edge of the weld. This often results in weak weld and workpiece. Some of its causes include the following:.

Sometimes, making a fillet weld in a horizontal-vertical spot also results in undercuts. In this case, there will be a formation of droplets because of the inadequate metal filling on the edges of the joint. To prevent this, you can weld in a flat position to make sure that there is enough electrode consumption. The issue of undercut may also arise when a welder tries making a weld run using an excessive style of weaving. Standards and codes require the suggested width of weaving, according to the size of the electrode.

Weaving size must be exceeded to its acceptable limit. When the weld bead undercuts your base material, you have actually taken away some of that original metal. It causes the weld to be more likely to crack or break.

Once you dial in your settings and your travel speed, it will be much easier to avoid undercut. This defect is often caused by common beginner errors, and many experienced welders will never have this problem. If your amperage is too high with Stick and TIG welding, the welding arc is too hot and it burns away your base material. This excess heat takes away the material at the edges of the weld. It is best to turn your heat down and then see how the next weld turns out. With MIG , too high of a voltage setting will dig into your base material — despite filler wire being added, high heat can still cause undercut.

We recommend incrementally lowering your voltage until your undercut disappears. Start with a small reduction, and then go from there. Another reason for undercut is that your filler wire is being fed too slow.

Not adding enough material to your weld results in undercut quite often. With TIG welding, this is often an issue of having a filler rod diameter that is too small. This means that each dab will add more material to your TIG weld when using the wider filler rod.

Conversely, electrodes that are too small generate an insufficient amount of molten metal, leading to welding defects. A welding rod of the correct size should also carry high amounts of current without interfering with the molten metal supply or deform the metal.

The arc is the gap from the tip of the welding rod and the metal to be welded. If the arc's size is larger than the electrode's diameter, the molten metal covers a broader area than initially intended, leading to increased undercuts. As with any welding defect like porosity or welding cracks, the first and most important way to prevent undercuts is by studying what causes them.

Just having this knowledge can significantly reduce any welding defect. Alongside being knowledgeable, there are numerous preventive methods you can apply to further reduce undercuts in your welds.

The following methods are the most useful ones you should be practicing. With multi-pass welding, after the first weld is placed and cooled another weld is placed on top of the first. This process helps in stabilizing the fusion properties of the metal, thus reducing undercut occurrence. If you need help mastering the multi-pass welding process, you can find an amazing guide here. Welding with a rod that is too far from the molten metal leads to spattering and can cause the formation of undercuts.

Generally, the arc length should not be more than the diameter of the rod's metallic part. For example, when welding an eight-inch diameter, the electrode should be about an eighth of an inch from the base.

Mastering the weaving technique is another way of preventing undercutting. Timely pauses on each side of the weld allow for beads' build-up, thus minimizing undercuts from forming. More undercuts form when the electrode weaves at high speeds due to the splashing of the molten metal. Generally, the rod should move within the intended path without deviating too far around. Using the proper shielding gas protects the molten metal from being exposed to oxygen and other atmospheric gases.

If the molten metal gets into contact with air, the resulting reaction could lead to the formation of undercuts. The mixture of gases in the shield should be appropriate for the metal type and thickness. As mentioned previously, holding the gun, rod, or wire at incorrect angles while you are welding can significantly increase the chance of undercutting.

Here are a few tips that might help:. Wire Welding - As you are pushing in the direction of the weld, the gun should be at a degree angle.

Stick Welding - You need to keep an angle of degrees as you are dragging. While welding, having a too slow or fast travel speed can be a reason for undercuts to form.