Welding Distortion

ABSTRACT

Distortion is the main problem of welding industry. This problem can be solved by variety of techniques such as heat sinking and side heating. During the heating and cooling cycle thermal strains occurs in the weld and adjacent area. The strains produced during the heating stage of welding are always accompanied by plastic deformation of the metal. The stresses resulting from these strains combine and react to produce internal forces that cause a variety of welding distortions. Welding deformation needs to be minimized and also the designer should know beforehand the extent of deformation.

In this paper, side heating as a method of distortion mitigation has been studied. Side Heating has been affected by addition of heat.

The procedure

The heat source causes highly non uniform temperature distributions across the joint and in the parent metals. Therefore, the thermal expansion and contraction during heating and subsequent cooling as well as material plastic deformation at elevated temperatures result in inevitable distortions and residual.[3]

II. WELDING DISTORTION & CONTROL METHOD

Distortion in a welded structure results from the non-uniform expansion and contraction of the weld metal and adjacent base metal during the heating and cooling cycle of the welding process. During heating and cooling in the welding process, thermal strain occurs in the weld metal and base metal near the welded zone. The stresses resulting from the strain produces internal forces, which in turn causes shrinkage, bending, buckling and rotation.

The basic types of distortion that takes place during welding

However the metallurgical consequences that are associated with the change in thermal gradient and cooling rate must be accounted for in practical situation. But we are making use of the compressed air instead of water for heat sinking process to account for the changes in metallurgical properties.

III) SELECTION OF PROCESS PARAMETER:-

1. Transverse distance between welding torch & nozzle (a)

2. Longitudinal distance between arc & nozzle (b)

3. Vertical height between plate surface & nozzle (h)

TABLE 1 - Process parameters and levels

IV) EXPERIMENT DETAILS:-

The experimental setup for the experiment consists of a stand to locate two plates to be welded adjacent to each other and a special arrangement to provide side heating through the nozzles from top sides of the plate which can be easily mounted on the pug-welding machine to give automatic and uniform speed of heating. The distance between two nozzles can be adjusted as per the requirement as shown in the figure.[5]

Table 2: The compositions of the steel used in experiment C

(%)

Si (%) Mn

(%)

P (%) S (%) Ni

(%)

Cr (%) Fe (%)

.155

8

0.177