Indian Welding Journal

Nirmal Saha ¹, Tapan Kumar Pal ¹

Affiliations
1 Welding Technology Centre, Metallurgical and Material Engineering Department, Jadavpur University, Kolkata-700032, IN

Abstract

The effect of five different buffer layers followed by a hardfacing electrode deposited on gray cast iron plate (ASTM grade 2500) upon performance of interface between substrate cast iron and deposited layers as well as abrasive wear behaviour of hardfaced deposits were studied. The results show that high nickel buffer electrode attributed best performance of interface bond in terms of shear strength and relatively lower nickel buffer electrode attributed best abrasive wear properties. The shear strength at the interfaces and wear properties has been correlated with microstructure and micro-mechanism of fracture in shear strain and micro-mechanism of metal removal in abrasive wear.

Keywords

Buffer Layer, Hardfacing, Hardness, Carbides, Bond Strength, Abrasive Wear.

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Tapan Sarkar ¹, Ajit Kumar Pramanick ¹, Tapan Kumar Pal ¹

Affiliations
1 Welding Technology Centre, Metallurgical and Material Engg. Dept, Jadavpur University, Kolkata-700032, IN

Abstract

In this study, six different coated electrodes were manufactured to select compatible one for ADI and only two electrodes were further studied (Trial 3 and Trial 4) to check their compatibility. Welding conditions were established to obtain crack free weld deposit on DI plate by varying preheat (200°C, 300°C and 400°C for lhour) as well as PWHT (maintaining same preheat temperature) at constant heat input using two selected electrodes. Only preheating at 300°C was possible to obtain sound weld for Trial 3, whereasboth preheat (300°C) and PWHT (300°C) were required for Trial 4. Although the as-deposited microstructures of FZ and PMZ consisting of ledeburitic carbide and alloyed pearlite in both the electrodes were same, the amount of microstructural constituents varied significantly. More ledeburitic carbide and less alloyed pearlite were observed in Trial 3 compared to Trial 4. However, microstructures of HAZ for both the electrodes showed bainitic and pearlite. Austempering heat treatment comprising of austenitization at 900°C for 2 hr and austempering at two different temperatures (300°C and 350°C) for different holding time was carried out for both the weld deposits. Interestingly, for both the weld deposits austempered microstructures show bainitic ferrite and retained austenite with graphite nodules. Increasing austempering temperature from 300°C and 350°C the lower bainite transformed to upper bainite and vol. % of retained austenite was also increased.

Keywords

Electrode Development, Microstructure, Austempering, Microhardness.

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Ajit Kumar Pramanick ¹, Suman Modak ¹, Tapan Kumar Pal ²

Affiliations
1 Seacom Engineering College, Howrah - 711 302, IN
2 Welding Technology Centre, Metallurgical and Material Engineering Department, Jadavpur University, Kolkata-700 032, IN

Abstract

Three single oxide fluxes and two combined oxide fluxes were used to investigate the effect of different fluxes on depth/width ratio, microstructure and corrosion resistance in type 304 stainless steel. The result showed that the type of oxide flux has a significant effect on the 304 SS weld penetration, microstructure and corrosion resistance. The uses of oxide fluxes appear to promote the formation of deltaferrite and higher oxygen content resulted fine delta ferrite. Furthermore, the corrosion resistance of austenitic stainless steel welds improved with addition of oxide fluxes.

Keywords

Oxide Flux, Depth/Width Ratio, Microstructure, Corrosion Resistance, Gas Tungsten Arc Welding.

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Sushovan Basak ¹, Tapan Kumar Pal ¹, Mahadev Shome ²

Affiliations
1 Metallurgical and Material Engg. Dept., Jadavpur University, Kolkata - 700 032, IN
2 Material Characterization & Joining Group, R & D, Tata Steel, Jamshedpur - 831 007, IN

Abstract

MIG brazing is a potential process for joining coated automotive steel sheets over conventional fusion welding process such as gas metal arc welding (GMAW). However, understanding the process variables on the joint performance is not yet clear. This paper deals with details study on the effect of process parameters and two different modes of operation (push and pull) on bead geometry, microstructure, shear tensile strength and high cycle fatigue behavior of MIG brazed lap joint of 1.4 mm thick galvanized DP600 steel sheet using solid CuAl8 filler wire. It has been possible to obtain 98% joint efficiency due to dispersion hardening effect of fusion zone consisting of dispersed iron from base metal in copper matrix. Also, an interface region formed (~6 μm) inbetween fusion zone and steel substrate has been characterized. High cycle fatigue test of all MIG brazed joints showed fatigue endurance (2 million cycles) at 10% of tensile load and fatigue life increased with increasing heat input. Interestingly, three different fatigue failure paths were observed with different loading cycle, such as interfacial failure; fusion zone failure and fine grain heat affected zone failure where the bead geometry played an important role in brazed joint under dynamic loading condition.

Keywords

Galvanized Dual Phase Steel, MIG Brazing, Push and Pull Mode, Bead Geometry, Microstructure, High Cycle Fatigue.

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Tapan Kumar Pal ¹

Affiliations
1 Metallurgical Engg. Department Jadavpur University, Calcutta - 700032, IN

Abstract

Hydrogen Induced Cracking (HIC) is still a major problem encountered during the welding of high strength structural steels. Historically, the risk of HIC has been greatest in the HAZ of the parent metal as a result of the rapid cooling rate experienced during the welding thermal cycle. However, steelmakers have made considerable improvements in terms of solving HAZ hydrogen cracking problems and have implemented strategies involving carbon and alloy control, controlled rolling schedules, on-line accelerated cooling, and so on. However, as we move to steels which have higher yield strength hydrogen-induced cracking problems will shift from the HAZ to the weld metal. HIC formed in weld metal was reported by Flanigan et al [1] for the first time.

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Tapan Kumar Pal ¹

Affiliations
1 Metallurgical Engg. Department Jadavpur University, Kolkata, IN

Abstract

Ceramics are drawing more attention as materials for engineering devices having better heat resistance , abrasion resistance and corrosion resistance than metals. In many structural applications , specific characteristics of the ceramics have led to their selection for critical components forming parts of a total system that is largely metallic, and therefore depend for their success on the fabricator being able to form ceramic/steel joints of adequate quality [1]. Among the many techniques employed to join ceramics to steel, ranging from fusion welding to mechanical attachment, active metal brazing and diffusion bonding are g e n e rally preferred [2], Application s of diffusion bonding have been increased since materials difficult to be fusion -welded , including combination of different kinds of material, are possible to be joined and precise fabrications of complex shapes of components are possible. Diffusion bonding Involves the creation of a solid-state bond by interdiffusion across the interface between the two materials. However, the bonding parameters such as temperature, time and pressure have to be controlled for the formation of a reliable diffusion bonded joint [3].

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