Table of Contents
What does holes in a weld mean?
weld metal porosity
Figure 1: Round holes in the weld bead are a sign of a defect called weld metal porosity. Shielding gases or gases released as a result of the torch being applied to treated metal are absorbed into the molten metal and released as solidification takes place.
What is spatter in welding?
Weld spatter is formed from droplets of molten metal or non-metallic material that can be produced during a welding process. As they cool, they form small round balls of material where they landed. Most weld spatter problems occur as a result of gas metal arc welding (GMAW) – also known as MIG/MAG welding.
What is weld sputtering?
A very common occurrence in gas metal arc welding (GMAW) is the creation of what welders call “spatter,” which is essentially droplets of molten material that are generated at or near the welding arc.
What is Arc Strike in welding?
Arc strike This is a defect caused by instantaneously striking an arc on the base material. In other words, an arc strike is a spot of failed arc ignition which was not fused by subsequent welding and remained on the base material. Arc strike may be the cause of cracking in the base material.
What is the cause of pinholes and porosity?
Porosity is usually caused by the contamination of gases trapped inside the meld. This causes an uneven gas flow to the arc and creates pinholes. If there is a lot of moisture in the air, it can cause water molecules to get trapped in the weld that creates pinholes.
How can inclusions be prevented in welding?
The following techniques can be used to prevent slag inclusions:
- Use welding techniques to produce smooth weld beads and adequate inter-run fusion to avoid forming pockets to trap the slag.
- Use the correct current and travel speed to avoid undercutting the sidewall which will make the slag difficult to remove.
Why is CO2 used in welding?
Carbon Dioxide (CO2) Pure CO2 provides very deep weld penetration, which is useful for welding thick material. However, it also produces a less stable arc and more spatter than when it is mixed with other gases. It is also limited to only the short circuit process.
What is overlapping in welding?
Overlap. Overlap occurs when molten metal flows over the surface of the base material and then cools without fusing with the base material. A typical cause of overlap is the supply of too much weld metal due to low welding speed. Overlap in fillet welds is caused by the droop of excessive molten metal due to gravity.
How do you stop slag inclusions?
What is a pinhole Weld?
First of all, a pinhole is porosity, but not very much. Porosity is caused by atmospheric interference with the weld puddle, or trying to weld over dirt or rust or paints.
What causes pin holes in the weld bead during welding?
When the electrode is subjected to high temperature during welding the moisture in the flux turns into gaseous form and try to leave from the weld pool thus leaving pin holes on the weld bead.
What causes porous holes in welds?
The contaminated gas may also create pinholes in the weld. If the gas hose is contaminated with moisture or other impurities, it can also cause porous holes in the weld. Cuts, burns, or dents in the hosepipe also affect the gas flow and could cause pinholes in the welded joint. Improper welds are also a common cause of porous joints.
Why is the pinhole defect called a pin hole defect?
As the weld cools down the solubility of hydrogen decreases hence hydrogen molecules from interior try to escape in form of gas. So the treaced path of the hydrogen molecule from the interior to the surface resembles a pin. Hence it is termed as pinhole defect.