Cracks. These are the most serious of weld defects because they can easily cause the failure of the welded structure. Depending on the orientation of the crack in the weld, it can be classified as longitudinal or transverse.
Among the commonly known welding defects, incomplete penetration and fusion, porosity and slag inclusions are the most common to affect welding strength.
Typical weld defects found in MIG welding are lack of fusion and penetration, craters and cracks, undercut, burn-through, and porosity in the weld metal.
MIG Welding
Materials: Thinner sheet metals and alloys such as mild steel, stainless steel as well as aluminum. Signs of a bad weld include: Lack of uniformity, cracks down the middle of the bead, too thin, and/or a lack of discoloration of the parent metal (which should be about 1/8 of an inch).
Porosity, one of the most common MIG welding defects, is the result of gas becoming trapped in the weld metal. Inadequate shielding gas coverage is among the biggest culprits, and this can be addressed in several ways. First, check the regulator or flow meter for adequate gas flow, increasing it as necessary.
Bubble Gum: A poor quality weld that looks like chewed bubble gum. Busted Out: Failed a weld test.
Where cracking occurs in or adjacent to welded joints, a satisfactory repair may be made by welding. It is important that the cracked material is gouged or machined away sufficiently to permit a full penetration repair weld to be made, with no traces of crack left behind and no new significant defects introduced.
The major cause of a crack is when internal stresses exceed the strength of the weld metal, the base metal, or both. And once a focal point for these stresses—that is, a stress riser—develops and accumulates, a crack can propagate.
Three of the most common are Arc, MIG (Metal, Inert Gas) or GMAW (Gas, Metal Arc Welding), and TIG (Tungsten Inert Gas) welding. In order to know which process is best for the particular job you're working on, here's what you should know about each of them. Arc welding is the oldest of these three welding processes.
The three most common welding types are – Arc, MIG and TIG welding.
Both acute and chronic health risks are associated with welding fume. Occupational lung disease, including lung cancer, is the most common health risk, but welding can also affect the eyes and skin. There is also a significant risk from asphyxiation when welding in confined spaces.
An edge joint is the weakest type of weld join, so isn't suitable for load-bearing jobs.
Porosity in welding happens when a contaminant or gas is absorbed into the weld puddle. These impure welds are commonly referred to as cavities.
Weld from the bottom up.
Like building a house, you cannot start the bricks at the top. Weld metal is a liquid. When it goes in it needs support, that is why we need to always start at the bottom.
It should be remembered that welding over weld metal is actually a very common occurrence. Multi-pass welds after all are manufactured by welding over weld metal! There are also many accepted procedures in which welds overlap.
Avoid Clutter
Sparks from the welding arc can fly up to 35 feet in distance, so it's important to keep your workspace clear, especially of any flammable materials. As a general rule, always stay organized and keep everything in its place.
Pushing usually produces lower penetration and a wider, flatter bead because the arc force is directed away from the weld puddle. In addition, pushing usually offers a better view and enables you to better direct wire into the joint.
Excessive heat input is usually to blame for the problem. To correct this, select a lower voltage range, reduce the wire feed speed and increase your travel speed. Conversely, insufficient heat input can cause lack of penetration, or the shallow fusion between the weld metal and the base metal.