Welding defects

In the welding time there are some weld defects are found, which is may cause of damaging the job or reducing the job life. If we take some awareness of welding then it may be prevented. The welding defects are

 

Lack of penetration:

The lack of penetration is one kind of welding faults. If the molten base metal does not filled the correct design depth of base metal it is called lack of penetration. Whether that penetration can be obtained depends upon the accessibility of the heat source and filler rod to the face area. The lack of joint penetration may result from improper technique, insufficient welding heat, improper fit-up,  or improper joint design.

If all other factors are correct, proper fusion depends on the skill and technique of the welder, the technique of welder mostly depends on the type and position of the joint. The lack of penetration may also depends of too long arc, always keep the arc as short as possible.

Porosity or blow holes:

If air trap inside the molten metal or trapping air comes out through the molten metal it makes the small holes it caused  porosity or blow holes. The entrapped gas comes from either the gas used in the welding process or the gas released from chemical reaction occurring during the welding process. Proper welding technique avoids gas formation and entrapment. One o the main factors contributing to this fault is the condition of the electrode, particularly the moisture content of the coating. The essential factor depends upon electrodes design which should be base metal related.

The current is the essential part for the porosity, too low a welding current is generally more frequent cause of porosity than too high current. Rust, scale, galvanizing, oil or dampness on the work surface promote porosity.

Slag inclusion:

Slag or other non-metallic foreign matter entrapped in the weld joint its called slag inclusion. The usual source is the slag formed by the electrode coating and dirty surface is also other cause. The correct weld joint design is can play very important part. The another most cause of slag inclusions is inadequate removal of the slag between the deposition of successive runs in which is associated with undercutting or unevenness of surface.

Cracks:

Cracks are occur in the weld and /or base metal when localized stress is exceed. The crack generally associated with notches, discontinuity welding and base metal, with high residual stresses and sometimes with hydrogen embrittlement. Where the metal were harden there are generally observed cracks. Cracks are generally divided into two major parts, which is hot cracks and cold cracks. The hot cracks are formed in high temperature and cold cracks are formed after solidification is completed. To avoiding the cracks the welder should avoid rapid cooling the weld.

 

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Various weld defects

 

 

Classification of welding

Effect of welding speed

Welding defects

Types of welding joints

Welding position

Welding electrodes

Types of welding flame

Welding flux

Welding techniques

Welding symbol

Welding edge preparation

Advantages of welding joints

Thermal properties of metal

Welding safety

Types of welds

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