ANOVA Analysis: Shielded Metal Arc Welding (SMAW)

Shielded Metal Arc Welding (SMAW) is the most widely used welding process in the small scale industries, because of its low cost, flexibility, portability and versatility. Shielded metal arc welding is one type of welding process which uses consumable electrode consist of filler core rod coated with chemicals that will help during welding by providing flux and shielding. This process give pure and clean weldment that has high material deposition rate compared to traditional welding process. The SMAW welding parameters are most important variables that will affect quality, productivity and cost of welding. It is related to strength of weld. The present work is to optimize the parameter of SMAW process by using Taguchi method and ANNOVA analysis.
On the selected parameters, trails have been conducted as per Taguchi method and fixed the levels for the parameters.

Keywords: Shielded metal are welding (SMAW),Optimization, Welding parameter, (MS) SA-516 Gr.70, Bending test, Tensile test, Impact test Taguchi technique, Orthogonal array, ANNOVA analysis.

I. INTRODUCTION
Low carbon steels containing <0.15% carbon and <0.6% manganese generally have good weldability, as the composition is too lean to give any significant hardening effect during welding. However, steels with <0.12% carbon and low levels of manganese can lead to porosity, although they are not affected to hydrogen cracking. Steels with carbon contents between 0.15 and 0.3% carbon and up to 0.9% manganese, have good weldability, basically those with carbon content below 0.22%. These are mild steels and rarely present problems, as long as impurity levels are kept low. They can be weldable without preheat, using any welding processes. Those at the top end of the composition range, above about 0.25% carbon, may be lead to crack under different situaion. They may be welded using any of the common welding processes, but are best welded with a low hydrogen process such as MIG or low hydrogen consumables.
The equipment is portable and can be easily move from one place to the other. Equipment is less costly. This process finds a number of applications because of the availability of a wide variety of electrodes which makes it possible to weld a number of metals and their alloys. The arc is generated by touching the tip of a coated electrode to the work piece and after to maintain arc by keeping some distance between electrode and work piece to stable an arc. When heating takes place through arc, melting of electrode tip and coating will occur during welding. After welding, Solidification will takes place in weld area. Impurities like oxides ,nitrides, and inclusion will float on upper side of welded area in form of slag. Welding can be done in all positions, both in shop and at site. Welded joints of sound quality and adequate mechanical properties can be obtained by using correctly designed electrodes and proper welding procedures. The process is intermittent, because welding has to be interrupted from time to time to discard the unused stub and to place afresh electrode into the holder and also to deslag the joint, i.e. to remove the layer of slag covering the weld. For higher productivity, semi-automatic or fully-automatic welding processes are