Common type of welding defect:
Lack or incomplete of fusion
Usually referred as cold lapping or cold shuts. The weld material fails to fuse with the wall of the base material. It will significantly reduce the bearing area, low down the weld joint mechanical property, produce stress concentration area, which will cause cracks and failure.
Lack or excess of penetration
The weld bead fails to enter the root of the weld joint, or two opposing beads are failed to fuse to each other and the weld bead fails to touch the toe of a fillet weld.
Undercut
The weld material fails to fill up the weld joint and leaves a groove along with the weld. This defect will also reduce the bearing area of weld cross section and thus cause stress concentration.
Porosity
When weld beads are solidified, the gas remains in the liquefied weld material will form cavities and leaves porosity in the weld bead, or on the surface of the weld bead.
The porosity will reduce the bearing area of weld joint and cause potential cracks, failure
Slag inclusions
There are three kinds of inclusion: tungsten inclusion, oxide inclusion and slag
Tungsten inclusions.
Oxide inclusions
The slag flux used a byproduct of melting shielding material – flux- during welding process. As the weld bead cooling downing, the melt flux will be solidified on or in the weld beads. With the slag as impurity of weld beads, the strength and integration of weld is reduced.
Cracks
During and after welding, there are many factors affect the weld beads and left micro defects known as cracks.
There are two major types of cracks: hot cracks and cold cracks
Hot cracks: the hot cracks are generally over occurs at high temperature: usually higher than 538 ℃. There are two kinds of hot cracks: centerline and crater cracks. Centerline cracks are consisting of two types: segregation cracking, and bead shape cracking.
Another crack is crater crack. Crater cracking occurs when the welding operator stops welding prior to finishing a pass on a weld joint, leaving a wide, thin depression at the end. It can also appear in areas that have been tack welded when the corresponding weld passes does not meet fully against the tacks.
Cold cracks: cold crack occurs at lower temperature and it takes long time to show its effect. Cold cracking is often referred to as hydrogen-induced and/or heat-affected zone (HAZ) cracking
Distortions
After the welding, the base material will show certain extend of deformation, called distortions. The deformation results from the expansion and contraction in the heat effect area during heat and cool recycle in the welding process. The stress or even fracture could also result from the deformation. The distortion can be longitudinal, transverse, angular, twisting and bowing. The distortion will greatly affect the precision and load bearing capacity of weldment.
Burn-Through
When weld metal to penetrate the weld zone result from too much heat or excessive amount of root opening causes excessive, and leaves a hole on base metal, it is called burn-through.
Lack or incomplete of fusion
Usually referred as cold lapping or cold shuts. The weld material fails to fuse with the wall of the base material. It will significantly reduce the bearing area, low down the weld joint mechanical property, produce stress concentration area, which will cause cracks and failure.
Lack or excess of penetration
The weld bead fails to enter the root of the weld joint, or two opposing beads are failed to fuse to each other and the weld bead fails to touch the toe of a fillet weld.
Undercut
The weld material fails to fill up the weld joint and leaves a groove along with the weld. This defect will also reduce the bearing area of weld cross section and thus cause stress concentration.
Porosity
When weld beads are solidified, the gas remains in the liquefied weld material will form cavities and leaves porosity in the weld bead, or on the surface of the weld bead.
The porosity will reduce the bearing area of weld joint and cause potential cracks, failure
Slag inclusions
There are three kinds of inclusion: tungsten inclusion, oxide inclusion and slag
Tungsten inclusions.
Oxide inclusions
The slag flux used a byproduct of melting shielding material – flux- during welding process. As the weld bead cooling downing, the melt flux will be solidified on or in the weld beads. With the slag as impurity of weld beads, the strength and integration of weld is reduced.
Cracks
During and after welding, there are many factors affect the weld beads and left micro defects known as cracks.
There are two major types of cracks: hot cracks and cold cracks
Hot cracks: the hot cracks are generally over occurs at high temperature: usually higher than 538 ℃. There are two kinds of hot cracks: centerline and crater cracks. Centerline cracks are consisting of two types: segregation cracking, and bead shape cracking.
Another crack is crater crack. Crater cracking occurs when the welding operator stops welding prior to finishing a pass on a weld joint, leaving a wide, thin depression at the end. It can also appear in areas that have been tack welded when the corresponding weld passes does not meet fully against the tacks.
Cold cracks: cold crack occurs at lower temperature and it takes long time to show its effect. Cold cracking is often referred to as hydrogen-induced and/or heat-affected zone (HAZ) cracking
Distortions
After the welding, the base material will show certain extend of deformation, called distortions. The deformation results from the expansion and contraction in the heat effect area during heat and cool recycle in the welding process. The stress or even fracture could also result from the deformation. The distortion can be longitudinal, transverse, angular, twisting and bowing. The distortion will greatly affect the precision and load bearing capacity of weldment.
Burn-Through
When weld metal to penetrate the weld zone result from too much heat or excessive amount of root opening causes excessive, and leaves a hole on base metal, it is called burn-through.