Flexural Strength Improvement of Welded Joints Prepared by Vibratory Welding Process

Introduction

In manual metal arc welding (MMA) process, an electric arc is produced between a consumable electrode and the specimens to be welded. The electrode is melted by the arc and is passed in to the weld pool as drops of molten metal. The electrode coating has also been melted to act as a gas shield around the arc and the weld pool. Slag has been formed on the surface of the weld pool and the slag must be removed after each layer. Because the low price of the equipment and maintenance costs of the process and easy to transfer the equipment, this process is suitable for repair work .Advantages of MMA Welding are: Flexible, Low initial and operating Cost, and easy for Repairs. There are different types of welding processes are available for joining materials. In the present work butt-welding is investigated under vibratory conditions. And also, it is most economical and consistent way of welding process without using supplementary components. This process is more suitable for fabrication and manufacturing special fittings.

Shigeru Aoki et al.(2007)developed a new process for reducing residual stress of butt welded joints by using harmonic vibrations during welding. The developed method has been compared the welded joints made with and without vibration. Two plates are fixed on the shaker and butt-welded joints are made using an automatic CO₂ gas shielded arc welding machine. Residual stress along the direction of the weld bead has been measured with X-ray diffractometer with scintillation counter after removing quenched scale chemically. At first, rolled steel plates are welded for some excitation frequencies during welding. Specimens have been welded along the groove on both sides. For all frequencies, residual stress near the weld bead is greatly reduced. When excitation frequency nearly equals to natural frequency of specimens to be welded, residual stresses highly reduced. Finally, these results have been compared experimentally and analytically. Shigeru Aoki et al.(2005) have been compared residual stresses of welded joints made with and without vibration. Finally, residual stresses reduced for joints prepared with random vibration.

Lu Qinghua et al.(2008) developed the method for improving the quality of full welded valve by using vibratory weld conditioning (VWC). The VWC on the welded joint properties has been studied. Cylinders with differed thicknesses were welded by submerged arc welding (SAW). The experiments have been concluded that the vibration given during welding reduces the residual deformation and stress. The yield strength and the tensile strength, does not change significantly in vibratory SAW (V-SAW) when compared with that in normal SAW (N-SAW).But the bend properties have been improved in V-SAW.

Alaa Raad Hussein et al. (2011) discussed the increase of the welding mechanical properties and the quality of the fusion metal is taken by using vibrations during welding. In this paper, the different harmonic frequencies were given to specimens which are nearer to the natural frequency of plate to improve the mechanical Properties of welded joints and got the good shape of welding surface.

Lakshminarayanan A.K. and Balasubramanian. V (2010) discussed the improvement of tensile strength properties of 409M ferritic stainless steel welded joints when compared with base metal. Ductility and impact strength of welded joints also were tested.

Lu Qinghua et al.(2006) discussed about the applications of vibration during submerged arc multi-pass welding to improve welded valve quality. The reduction in residual deformation and stress due to vibratory weld conditioning is discussed. The improvement of the impact strength of weld joint prepared by vibratory weld conditioning has been discussed.

Munsi A S M Y et al. (2001) discussed about the effect of vibratory stress on the welding microstructure and residual stress distribution of steel welded joints. Hardness improvement of weld joint is 25%.

Sewari S P and Shanker A(1993) discussed about improvements on yield strength, ultimate Tensile strength and breaking strength on shielded metal arc welded joints due to vibratory conditions like longitudinal vibration and frequency. The drop in percentage of elongation due to the vibratory conditions is discussed.