What is an Underbead Crack in Welding?

An underbead crack is a type of welding defect that occurs in the heat-affected zone (HAZ) of a weld. It is characterized by a crack that does not extend to the surface of the base metal. Underbead cracks are often caused by improper welding techniques or by using too much heat during the welding process.

Underbead cracks can be difficult to detect, as they are often hidden beneath the weld bead. However, they can be detected through radiographic inspection or by using a probe to check for cracks underneath the weld bead.

What causes Underbead cracking in welding?

There are a number of factors that can contribute to under bead cracking in welding, including:

Improper welding techniques.
Excessive heat input.
Incompatible filler metals.
Improper joint design.

What are the 3 basic types of cracks in the weld metal?

Cracks are a common form of weld defects. Cracks can occur in the weld metal or in the heat-affected zone (HAZ) of the base metal. The three most common types of cracks are:

Underbead cracks – These cracks occur in the HAZ of the base metal. They are caused by improper welding techniques or by using too much heat during the welding process.
Lamellar tears – These cracks occur in the weld metal and are caused by stresses that exceed the yield strength of the material.
Hot cracks – These cracks occur in the weld metal and are caused by the rapid cooling of the weld pool.

What are the consequences of an underbead crack?

Underbead cracks can have serious consequences, as they can weaken the structural integrity of a welded joint. If left unrepaired, underbead cracks can lead to complete failure of the joint.

How can underbead cracks be repaired?

Underbead cracks can be repaired by welding over the crack with a filler metal that is compatible with the base metal. The heat from the welding process will cause the cracked area to expand, which will close the crack and prevent it from propagating further.

Crater cracks in welding

A crater crack is a type of welding defect that occurs at the end of a welding bead. Crater cracks are caused by the rapid cooling of the weld pool, which causes the metal to contract and form a crack.

How to fix cracks in welding?

It is important to note that underbead cracks can re-occur if the root cause of the defect is not addressed. For this reason, it is crucial to determine the cause of the underbead crack before attempting to repair it.