Manufacturing Technology Today

S. K. Jain ¹, Rajesh Kumar ¹, S. S. K. Titus ¹

Affiliations
1 Force and Hardness Standards, National Physical Laboratory, New Delhi, IN

Abstract

Material hardness evaluation is one of the most important and commonly used methods of material or product testing. However, the hardness measurements being done in the industry are of limited accuracy due primarily to non-availability of standard hardness blocks having very precise and accurately assigned hardness values traceable to national primary standard. The National Physical Laboratory has recently added the primary standard of Brinell hardness scale to the other already available Vickers and Rockwell hardness primary standards. The uncertainty of the Brinell hardness standard is within ±1.5% for HB1/1 to HB1/30 and is within ±1.0% for other HB scales, which is reaffirmed through comparison with precision hardness standard blocks. Some of the salient features of the machine are described and the measurement results obtained on standard hardness blocks are reported.

Keywords

Brinell Hardness, CMC, Dead Weight Force, Standard Hardness Blocks.

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Rajesh Kumar ¹, Rupinder Singh ²

Affiliations
1 Mechanical Engineering Dept., R.I.E.I.T., Railmajra, Dist. Nawanshahr-144553, Punjab, IN
2 Mechanical & Production Engineering Dept., G.N.D.E.C, Ludhiana-141006, Punjab, IN

Abstract

In submerged arc welding (SAW), selection of appropriate values of process variables is essential in order to control heat-affected zone (HAZ) dimensions and to get the required bead size and quality. Also, conditions must be selected that will ensure a predictable and reproducible weld bead, which is critical for obtaining high quality. In this investigation, mathematical models were developed to study the effects of process variables and heat input on various metallurgical aspects, namely, the widths of the HAZ, weld interface, grain growth and grain refinement regions of the HAZ. The color metallographic technique and response surface methodology were used for analysis. Direct and interaction effects of the process variables and heat input on the characteristics of the HAZ were presented in graphical forms. The study revealed that heat input and wire feed rate have a positive effect, but welding speed has a negative effect on all HAZ characteristics; secondly width of grain growth and grain refinement zones increased and weld interface decreased with an increase in arc voltage; and width of HAZ is maximum (about 2.2 mm) when wire-feed rate and welding speed are at their minimum limits.

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Rajesh Kumar ¹, Rupinder Singh ²

Affiliations
1 Mechanical Engg. Dept., R.I.E.I.T., Railmajra, Distt. Nawanshahr-144553, Punjab, IN
2 Mechanical & Production Engg. Dept., G.N.D.E.C, Ludhiana-141006, Punjab, IN

Abstract

Micro-alloyed (MA) steels have matured during the past 40 years into an important class of high-strength structural materials. Their cost-effectiveness has been enhanced by the growth of steel making electric-arc-furnace (EAF) and the thin-slab-casting process. A recent project involving an ultra-light-steel auto body (ULSAB) concluded that high-strength-steels are the materials o f choice for the automotive industry. This study showed that replacing cheaper carbon steels with high-strength steels allowed automakers to reduce the weight of an auto body at the same or at potentially lower costs. The same economic principles can be applied to other applications. The strengthening effects of vanadium make microalloyed steels particularly suited for high-strength-steel applications. By effectively combining grain refinement and precipitation hardening, vanadium maximises the strengthening process and is compatible with current steel-processing technology. To dramatise the cost effectiveness o f these high-strength-steels in potentially new applications, a series of demonstration projects are needed involving the co-operation of steel producers, fabricators, and users. In many applications, the decision to replace plain-carbon steel with higher strength vanadium-bearing microalloyed steel can be shown to improve the profitability of both the steelmaker and the steel user.

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Sujeet Kumar ¹, A. Karpagaraj ¹, Rajesh Kumar ¹

Affiliations
1 Department of Mechanical Engineering, National Institute of Technology Patna, Bihar, IN

Abstract

Super Duplex Stainless Steels (SDSS) are playing an important role in mechanical, marine, gas industries and power plant. Welding is an important joining process involved in the construction of industrial structures. Selection of the welding method is a difficult task because the imbalance of austenite / ferrite ratio results in solidification cracking, reduce corrosion resistance and reduced ductility. Arc welding process like GTAW, GMAW and PAW are available to join the SDSS economically. The primary objective of this paper is to compare various arc welding processes and its welding parameters (welding speed, welding current, welding voltage etc.) for the joints of a thin sheet of SDSS 2507. Effects of SDSS alloying elements (Cr, Mo, Ni and N) on intermetallic phases is also discussed. This study can help to find out the best arc welding process and their welding parameter on phase balance to join the SDSS 2507.

Keywords

SDSS, Corrosion Resistance, Arc Welding, Thin Sheet.

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