FILLET WELD

WHAT IS FILLET WELD AND ITS PROCESS

    Weld is the process of joining two pieces of metal by creating a strong metallurgical bond between them by heating or pressure or both. It is distinguished from other forms of mechanical connections. Such as riveting or bolting, which are formed by friction or mechanical interlocking. It is one f the oldest and reliable methods of joining.

     Welding offers many advantages over bolting and riveting. Welding enables direct transfer of stress between members eliminating gusset and splice plates necessary for bolted structures. Hence,   the weight of the joint in minimum.  In the case of tension members, the absence of holes improves the efficient of the section. It involves less fabrication cost compared to other methods due to handling of fewer parts and elimination of operations like drilling, punching etc. and consequently less labor leading to economy. Welding offers air tight and water tight joining and hence is ideal  for oil storage tanks, ships etc. welded structures are more rigid compared to structures with riveted and bolted connections. A truly continuous structure Is formed by the process of fusing the members together. Generally welded joints are as strong or stronger than the base metal, thereby placing no restriction on the joists, 

Stress concentration effect is also considerably less in a welded connection.

Some of the disadvantages of welding are that it requires skilled manpower for welding as well as inspection. Also, non-destructive evaluation may have to  be  carried out to detect defects in welds. Welding in the field may be difficult due to the location or environment. Welded   joists are highly prone to cracking under fatigue loading. Large residual stresses and distortion are developed in welded connections.

    Fundamentals  of welding

     A welded joint is obtained when two clean surfaces are brought into contact with each other and either pressure or heat, or both are applied to obtain a bond. The tendency of atoms to bond is the fundamental basis of welding.. The inter-diffusion between the materials that ate joined is the underlying principle in all welding processes

Welding process

     In general ,  gas and welding are employed, but almost all structural welding is arc welding.

The most common welding processes, especially for structural steel , use electric energy as the heat source produced by the electric arc IS 816 in this process, the base metal and the welding rod are heated to the fusion temperature by an electric arc. The arc is a continuous spark formed when a large current at allow voltage is discharged between the electrode and base metal through  a thermally ionized gaseous column, called plasma. The resistance of the air or gas between the electrode and the objects being welded changes the electric energy into heat. A temperature of 3300⁰ C to 5500⁰ C is produced in the arc.

The welding rod is connected to one terminal of the current source and the object to be welded to the other. In arc welding fusion takes place by the flow of material from the welding rod across the arc without pressure being applied.