Welding Defects

Welding Defects can be explained as the irregularities formed within the specified weld metal as a consequence of improper welding process or inaccurate welding patterns, and so forth. The defect may vary from the expected weld bead shape, size, and intended quality. Welding defects might arise either outside and / or inside the weld metal. A portion of the defects could possibly be allowed in the event the defects are within permissible limits, however, other defects including cracks will never be accepted.

Types of Welding Defects

Welding defects could be categorised into two types as external and internal defects:

• External Welding Defects:
1. Weld Cracks
2. Undercut
3. Spatter
4. Porosity
5. Overlap
6. Crater
• Internal Welding Defects:
1. Slag Inclusion
2. Incomplete Fusion
3. Necklace cracksing
4. Incompletely filled groove or Incomplete penetration

External Welding Defects

The various types of external defects with their causes and remedies are the following:

Weld Crack Defects

This may be the most undesired defect of all the other welding defects. Welding cracks are generally present at the work surface, inside of the weld material and / or at the heat affected zones.

Cracks could also show up at different temperatures:

• Hot Crack - It's much more prominent at the time of crystallisation of weld joints when the temperature might rise greater than 10,000-degree Celsius.
• Cold Crack - This variety of crack develops towards the end of the welding process where the temperature is rather low. Occasionally cold crack is visible several hours subsequent to welding or even following few days.

Causes Of Weld Crack Defects:

• Poor ductility of the specified base metal.
• The existence of residual stress can result in a crack on the weld metal.
• The rigidity of the joint that makes it difficult to expand or contract the metals.
• If there exists high content on sulphur and carbon in that case also the cracks can take place.
• Using hydrogen like a shielding gas while welding ferrous materials.

Remedies for Weld Crack Defects:

• Using suitable materials could possibly greatly reduce the chances of crack.
• Preheating the weld and additionally reducing the cooling speed of the joint facilitates in reducing crack.
• Reduce the gap between the weld joints through the use of reasonable weld joints.
• While welding releases the clamping force gradually which will increase the fill to capacity of welding material.

Undercut Welding Defects

When the base of metal melts away from the weld zone, then a groove is formed in the shape of a notch, in that case such type of defect is referred to as Undercut. This decreases the fatigue strength of the joint.

Causes of Undercut Welding Defect:

• If the arc voltage is very high in that case this particular defect can occur.
• If the incorrect electrode is used or in the event the angle of the electrode is incorrect, in that case also this defect might form.
• Using a large electrode is in addition never advisable.
• High electrode speed is furthermore among the many factors behind this defect.

Remedies for Undercut Welding Defect:

• Reduce the arc length and / or decrease the arc voltage.
• Maintain the electrode angle from 30 to 45 degree with the standing leg.
• The diameter of the electrode should really be small.
• Reduce the travel speed of the electrode.

Spatter Welding Defects

When some metal drops are expelled from the weld and continue to be stuck to the surface, in that case this particular defect is referred to as Spatter.

Causes Of Spatter Welding Defect:

• High Welding current could potentially cause this particular defect.
• The longer the arc the greater will be the probability of getting this particular defect.
• Incorrect polarity.
• Improper gas shielded may additionally induce this particular defect.

Remedies for Spatter Welding Defect:

• Reducing the arc length in addition to the welding current
• Using the correct polarity and in accordance with the conditions of the welding.
• Increasing the plate angle in addition to making use of suitable gas shielding.

Porosity Welding Defects

Porosity is the condition wherein the gas or small bubbles will become trapped within the welded zone.

Causes of Porosity Welding Defect:

• It develops in the event the electrode is not coated properly.
• Using a lengthier arc may additionally increase its chances.
• Increased welding currents.
• Rust or oil on the welding surface.

Remedies for Porosity Welding Defect:

• Proper selection of the welding electrode.
• Decreasing the welding current.
• Using smaller arc and additionally slowing the process to allow for the gases to escape.
• Remove rust or oil from the surface in addition to using a suitable technique.

Overlap Welding Defects

In the event the weld face extends further than the weld toe, in that case this particular defect develops. In this particular condition, the weld metal rolls and forms an angle less than 90 degrees.

Causes of Overlap Welding Defect:

• Improper welding technique.
• Through the use of large electrodes this particular defect could possibly occur.
• High welding current

Remedies for Overlap Welding Defect:

• Employing a suitable technique for welding.
• Use small electrode.
• Work with a reduced amount of welding current.

Crater Welding Defects

This occurs in the event the crater is not filled prior to when the arc is broken, which then causes the outer edges to cool faster ın comparison to the crater. The following results in a stress and after that crack is usually formed.

Causes of the Crater Welding Defect:

• Inaccurate torch angle.
• Use of large electrode
• Inappropriate welding technique

Remedies for Crater Welding Defect:

• Using a accurate torch angle might reduce the stress on the metal
• Utilizing a small electrode may additionally diminish the crater.
• Make use of a suitable technique.

Internal Welding Defects

The various types of internal welding defects with their causes and remedies are the following:

Slag Inclusion Welding Defects

Should there be any slag in the weld, in that case this has an affect on the toughness and metal weldability of the specified material. The following decreases the structural performance of the weld material. Slag is produced on the surface of the weld or between the welding turns.

Causes Of Slag Welding Defect:

• Slag is usually produced in the event the welding current density is very small, because it fails to supply the necessary amount of heat for melting the metal surface.
• In case the welding speed is much too fast in that case also slag could possibly manifest.
• In case the edge of the weld surface is not cleaned properly in that case additionally slag could possibly form.
• Incorrect welding angle in addition to travel rate of the welding rod.

Remedies for Slag Inclusion:

• Increase the current density
• Adjust the welding speed in order that the slag and weld pool don't mix with each other.
• Clean the weld edges and eliminate the slags associated with previous weld layers
• Employ a suitable electrode angle and travel rate.

Incomplete Fusion Welding Defects

Incomplete fusion develops in the event the welder does not accurately weld the material and the metal pre solidifies that leads to a gap that's not filled with the molten metal.

Causes of Incomplete fusion:

• This develops as a consequence of low heat input.
• In the event the weld pool is very large and runs ahead of the arc.
• In the event the angle of the joint is definitely very low.
• Improper electrode and torch angle may additionally be responsible for incomplete fusion.

Remedies for Incomplete Fusion:

• Increasing the welding current and decreasing the travel speed facilitates in removing the probability of incomplete fusion.
• Reducing the deposition rate.
• Increasing the joint angle.
• Endeavor to position the electrode and torch angle appropriately in order that the edges of the plate melt away.
• Positioning the bead properly in order that the sharp edges along with other beads could be prevented.

Necklace Cracking Welding Defects

This transpires in the usage of electron beam welding where the weld does not penetrate properly. Consequently, the molten metal does not flow into the cavity and this results in a cracking referred to as “Necklace Cracking”.

Causes of Necklace Cracking:

• Incorrect welding technique.
• This develops in materials which include nickel base alloys, stainless steel, carbon steels and Tin alloys.
• Making use of high speed of electron beam welding

Remedies for Necklace Cracking:

• Employing an appropriate welding technique minimizes the possibilities of necklace cracking.
• Working with suitable materials meant for welding.
• Employing a constant speed during the welding process.
• The wrong type of welding technique

Incomplete Penetration Welding Defect

These kind of defects manifest only in the butt welds where the groove of the metal is not filled completely. It is additionally referred to as incomplete penetration defect.

Causes of an Incomplete filled groove are generally:

• Reduced deposition of the weld metal
• Usage of inappropriate size of the electrode
• Incorrect welding technique

Remedies for Incomplete filled groove are generally:

• Additional deposition of the weld metal.
• Make use of a suitable size of the electrode.
• Employing a appropriate welding technique.

These are typically the different types of welding defects found in the course of any sort of manufacturing process. While welding, it cannot be overemphasized to eliminate all of the defects of welding present in the workpiece. In case there might possibly be defects in the welding material, in that case in severe conditions the components of the material would certainly fail.