EFFECT OF GMA WELDING PARAMETERS ON MECHANICAL PROPERTIES AND MICROSTRUCTURE OF IS 2062 AND AISI 304 STEELS

Abstract

Welding is recognized all over the globe, today as remarkable versatile means of metal fabrication. There are several kinds of welding processes. The wide range and variety of welding processes enable the modern engineering to weld almost all commercial metals and alloys. Because of the wide applications and casy availability of IS 2062 structural steel and AISI 304 steel were selected as workpiece materials. The final report "Effect of GMA Welding Paranmeters on Mechanical Properties and Microstructure of IS 2062 and AISI 304 steels" consists of five chapters. A brief explanation of every chapter is presented below Chapter 1: A brief introduction to the background of the work and objective of the present work is undertaken in this chapter. This chapter includes welding of different steel e.g. low carbon steel, medium carbon steel, and high carbon steel and the effect of different welding process parameters on mechanical and metallurgical properties of the materials. Various arc welding processes are used in the fabrication and manufacturing industries such as GMAW, GTAW, SAW. and FCAW etc. The Gas Metal Are Welding (GMAW) process is increasingly employed in various manufacturing industries. The GMAW process is suitable for ferrous and non-ferrous materials. Challenges and objective of the present report and the scope of the thesis are also discussed in this chapter. Chapter 2: Literature Survey' describes related information pertaining to weldability issues of steels ie. IS 2062 steel and AISI 304 steel and its different alloys characteristics, Welding metallurgy, welding process parameters, and eflect of wire feed speed and gas flow rate, arc voltage, mixture of different shielding gases on mechanical properties and microstructure of weldment. The microstructure of weldment plays a vital role in providing the properties desired for each application. In some studies, the different shielding gases mixtures improve the metallurgical structure of the weldments. Little work has been done by the researcher to determine the effect of GMAW welding parameters on mechanical properties and microstructure of IS 2062 structural steel and AISI 304 steel weldment. ER70S-6M grade filler wire for IS 2062 and ER308 grade filler wire of 1.2 mm diameters is used for AISI 304 steel to weld. Nucleation grain growth takes place during the solidification of weldment.Fine grain size is produced during the slow cooling of weldment and coarse grains are formed i during the fast cooling. Chapter 3: This chapter clearly explain the designs and fabrication of the experimenta materials, methodology, and testing used in the current research work. For welding under diferent welding conditions, a set-up was designed and fabricated. The set-up consists of a base plate, fixture. Welding table, and a non-ferrous material back plate to avoid the workpiece welding with fixture plate. The basic objective of the present research is to understand the effect of different welding parameters on mechanical properties and metallurgical characteristics of IS 2062 steel and AISI 304 steels weldment.The detailed experimental procedures involved in each stage of this experimental work are briefed in the following sections. To determine the basic objective of the present experimental research. the experimental research work was planned in the following manner. Work plan: Work plan for the present research work is as under Selection of the different work-picce materials and electrodes for their welding. Preparation of welded joints under different welding conditions Preparation and testing of test specimens for tensile test, impact test and hardness tests, microstructure examination of welded test specimen of IS 2062 and AISI 304 steel Chapter 4: Results and Discussion' present the results of various experiments and in-depth discussions on the results obtained. This chapter deals with the experimental results obtained during the investigation. The wire feed speed varied from 6.35 to 11.43m/min and gas flow rate from 5 to 20 m. Welding was performed under different welding conditions, having a different value of Yield strength. Ultimate tensile strength. Toughness. microhardness (VHN), and % elongation for weldment of 1S 2062 structural steel and AISI 304 stecl. The microstructure of weldment of IS 2062 structural steel and AISI 304 steel has also been observed to vary with the variation in wire feed speed and gas flow rate. The experimental results of IS 2062 structural steel compared with AISI 304 steel and the conclusions were derived from results. Chapter 5 Conclusion and scope of future work presents the concluding remarks of :he present resecarch work with recommendations for future work Mechanical nopertie end microstructures of IS 2062 structural steel and AISI 304 steel under different welding conditions were examined. In microstructural properties, the average grain size, and morphological properties of widsmantatten ferrite, pearlite and bainite of IS 2062 structural steel and austenite, and 8 ferrite of AISI 304 steel weldment have been discussed, whereas in mechanical properties such as Yield strength, Ultimate tensile strength, Toughness, microhardness (VHN) and the % elongation have been taken up. The salient conclusions from the present investigation are summarized as follows: For IS 2062 steel Mechanical properties were correlated with microstructure characterization. SEM images of the Toughness test specimen of IS2062 shows that on low heat input, mode of fracture was ductile, whereas, on high heat input, the image shows a brittle fracture. The microstructural constituents like AF, WF, and PF in IS 2062 structural steel weld metals are affected by the carbon dioxide and oxygen content which are present in the shielding gas. The SEM image of a tensile fractured surface of IS 2062 steel welded joint reveals that the fracture mode is brittle. It shows dimples with bright cleavage. >Shielding gas mixture of 75%Art+25%C02 produced acceptable weld metal properties due to the balance of cooling rate and the formation of a high amount of AF which leads to the enhancement of strength and impact toughness. For AISI 304 steel Highest tensile strength and impact strength of weldment was found at 21V The microstructure of welded samples showed no any cracking, tearing or any other related defects and full penetration was achieved. Grain sizes of Stainless Steel 304H welded joints were different at different gas flow rates and wire feed speeds. Grain size of welded joint increased with increasing heat input. There is a sudden decrement in microhardness (VHN) values from low heat input to higher heat input. It is observed from microhardness (VHN) measurements that hardness near the upper surface of the weldment is highest and lowest near the center of the weld The list of references is given at the end of the thesis.