M I Rafiqul

Bio: M I Rafiqul is an academic researcher from Universiti Malaysia Pahang. The author has contributed to research in topics: Vickers hardness test & Heat-affected zone. The author has an hindex of 1, co-authored 1 publications receiving 8 citations.

Effects of heat input on mechanical properties of metal inert gas welded 1.6 mm thick galvanized steel sheet

Abstract: It is usually a lot easier and less expensive to galvanize steel before it is welded into useful products. Galvanizing afterwards is almost impossible. In this research work, Galvanized Steel was welded by using the ER 308L stainless steel filler material. This work was done to find out an alternative way of welding and investigate the effects of heat input on the mechanical properties of butt welded joints of Galvanized Steel. A 13.7 kW maximum capacity MIG welding machine was used to join 1.6 mm thick sheet of galvanized steel with V groove and no gap between mm. Heat inputs was gradually increased from 21.06 to 25.07 joules/mm in this study. The result shows almost macro defects free welding and with increasing heat input the ultimate tensile strength and welding efficiency decrease. The Vickers hardness also decreases at HAZ with increasing heat input and for each individual specimen; hardness was lowest in heat affected zone (HAZ), intermediate in base metal and maximum in welded zone. The fracture for all specimens was in the heat affected zone while testing in the universal testing machine.

Study of Resistance Spot Welding Between AISI 301 Stainless Steel and AISI 1020 Carbon Steel Dissimilar Alloys

Abstract: Joining dissimilar metals has recently become very popular in industries because of the advantages associated with the weld joint. This paper focuses on an investigation of mechanical and material properties, and the optimization of mechanical properties in resistance spot welding methods in lap configurations between AISI 301 stainless steel and AISI 1020 carbon steel.The Taguchi method was used to design experiments. Welding was conducted using a spot welder. Tensile and Charpy impact test specimens were prepared from the welded sheets in appropriate dimensions and tensile and Charpy impact test s were performed for each specimen. The depth and width of weld nuggets were investig ated. It can be concluded from the investigation that the welding joint in this method can offer moderate strength and moderate Charpy impact energy. From the results of the Taguchi analysis, the combination of optimum parameters for dissimilar stainless s teel - carbon steel resistance spot welding is : welding current , 5.0kA ; welding squeeze time , 3.0 cycle ; and welding pressure , 40 psi. In order to improve significant mechanical and metallurgical properties of the joint, o ther variable parameters like voltag e, electrode tip diameter etc . can also be introduced and investigated so that the most influential parameters and their suitable ranges can be identified .

The effects of welding parameters on butt joints using robotic gas metal arc welding

Abstract: Robotic gas metal arc welding (GMAW) is one of the most popular welding methods in the manufacturing industries. The main focus of this paper is how welding parameters affect the joining process. The butt joint will be used in this study to identify suitable welding parameters for welding voltage, welding current and welding speed. The experiment involves using a specimen of low carbon steel A1008 as base metal and AWS ER 70S-6 as the filler metal in the butt joint process. The joint was tested to determine the tensile strength, which is identified as the main characteristic of the weld, and the hardness of the weld is also recorded. The results show that a welding voltage of 24 volts, current of 200-220 ampere, and speed of 45-50 cm/min gave the highest tensile hardness of 239.05 MPa (180HV).

Micromechanical characterisation of weld metal susceptibility to hydrogen-assisted cold cracking using instrumented indentation

Abstract: Hydrogen-assisted cold cracking is generally accepted to be the consequence of a critical concentration of hydrogen trapped within a susceptible microstructure and subjected to a threshold level of stress. Traditionally, hardness has been used as a proxy for establishing the critical limits above which the risk of a hydrogen crack propagating is considered significant. However, developments in the steel-making process, in particular thermomechanically controlled processing, has brought into question the suitability of empirical hardness limits developed using older generation steels. In this paper, a safe welding boundary was established for single-pass root runs for API 5 L X70 steel welded with E6010 electrodes. Across this boundary, it was shown that hydrogen cracks were present in welds with hardness’s well below the traditionally accepted threshold of 350 HV. This paper explores the use of nanoindentation as means of quantifying the susceptibility of welds deposited on high-strength low-alloy steels, using shielded metal arc welding, to hydrogen-assisted cold cracking. It is suggested that the use of the hardness/elastic modulus (H/E) ratio, which is directly related to the yield strength of a material, is a more suitable parameter to predict weld metal hydrogen-assisted cold cracking (HACC) susceptibility than is the hardness alone.

Characterization of heat-treated gas metal arc-welded boron steel sheets

Abstract: The effect of heat treatment on the microstructure and mechanical properties of 1.6-mm-thick boron steel welded by using gas metal arc welding was investigated. The microstructure and mechanical properties of welded boron steel were determined before and after heat treatment. The heat treatment process was conducted according to manufacturer recommendation for optimum outcome. In results, the microstructure of heat treated specimen was completely transformed to martensite. The soften region that was detected and caused fracture of tensile test is located. EDX analysis found that boron element was concentrated at heat-affected zone. Fractography on heat-treated samples shows an intergranular fracture at heat-affected zone because of microvoid existence at grain boundaries. Consequently, this fracture decreased sample strength and promoted fracture propagation.