Welding Metallurgy of

Welding distortion is a critical issue as it leads to severe deterioration of structural integrity of welded work piece and dimensional precision. This study aims at studying the effects of shielded metal arc welding (SMAW) parameters on the evolution of mechanical properties, including tensile strength, impact toughness, and hardness, along with angular distortion on a welded joint from SA 516 grade 70. Such parameters are analyzed and optimized by employing the Taguchi method and Grey relational analysis. SA 516 grade 70 is commercially used for fabrication of storage tanks, boilers and pressure vessels. SMAW is investigated with three levels of root gap, groove angle, electrode diameter, and pre-heat temperature, which were varied on a butt joint in flat (1 G) position to determine their effects on response variables at room temperature. Nine experiments were designed using a Taguchi L9 orthogonal array, welded according to American Society of Mechanical Engineers (ASME) section IX, and samples were prepared and tested as per ASTM A 370. The Taguchi method and Grey relational analysis were employed to observe the most significant parameters and optimal levels that synergically yield improved responses. Results are validated by conducting confirmatory experiments that show good agreement with optimum results.

An Integrated Approach of GRA Coupled with Principal Component Analysis for Multi-Optimization of Shielded Metal Arc Welding (SMAW) Process.

Influence of groove angle on hardness and reinforcement height of shielded metal arc welded joints for low carbon AISI 1016 steel plates

This study investigates mechanical and microstructural properties of P460N steel after Shielded Metal Arc Welding (SMAW). Three specimens with groove angles of 45 °, 60 ° and 75° were prepared and welded for this purpose. Tensile strength test, impact test, grain size test, macro and micro hardness test and metallographic test were performed on weld metal (WM), Heat Affected Zone (HAZ) and Base Metal (BM) and the results were compared. In the specimen with groove angle of 60°, yield strength was more than the base metal. Impact energy results in HAZ were different, so that HAZ areas in the specimens with 45° and 60° groove angles have less impact energy compared to the base metal but in the specimen with 75° groove angle, impact energy was more than the base metal. This increase can be due to formation of intermetallic compounds. After checking mechanical and microstructural properties of all the specimens, the groove angle of 60° was confirmed to be used at designing and construction of a reservoir with thickness of 14mm and working pressure of 40 bars.

Groove Angles Influence on Mechanical and Microstructural Properties of P460N Steel in SMAW

Objective: To investigate the effects of groove angle on tensile and impact strength of the joints. Methods: To achieve above objective various groove designs having included angle of 50°, 60° and 70° were prepared using a shaper. The weld grooves were completely filled using shielded metal arc welding process. All the weld joints were subjected to visual inspection, dye penetration test and radiographic test. Then tensile and impact specimens were removed from these joints. The tensile and impact specimens were machined in accordance with ASTM E8M-09 and ASTM E23-12C specifications. The tensile and impact strength was evaluated using universal testing machine. Findings: The tensile strength of the specimen having groove angle as 50° is 513.68 MPa which is more than that of the specimen having 60° and 70° groove angle. The tensile strength of base material used is 540 MPa. It is clear that the tensile of the joint is less than base material used. The joint efficiency obtained is 95.12% which is the highest compared with other joint i.e. 60° and 70°. It is further observed maximum impact strength achieved is 53.45 Joule at 50° groove angle. The tensile and impact strength provided by the joint having groove angle as 70° is 471.29 MPa and 39.15 J respectively which is minimum amongst all the joints produced.It can be concluded that 50° groove angle is the best groove design. Moreover less number of welding electrodes is required to fill this joint compared with 60° or 70° groove angle. Hence it is more economical also. Application: This research is useful for industries which are engaged in fabrication work for designing of correct and economical welding grooves.
Keywords: Groove Design, Impact Strength, Radiography, Shielded Metal Arc Welding, Tensile Strength

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Effect of Groove Design on the Mechanical Properties of Shielded Metal Arc Welded Joints

For a major telecom infrastructure company operating pan India including the state of Haryana, over 400 of their telecom infrastructure operation sites in Haryana had connected running power load more than the load sanctioned by the Haryana State Electricity Board (HSEB). As per the Standard Operating Procedure of this telecom infrastructure company (SOP), these 400 plus sites did not qualify under load upgrade category since the load had been increased without attracting any new tenancy i.e. Base Transceiver Station (BTS) of other telecom operators (service providers). Power load at these 400 sites had increased because of additional load due to sector expansion, cabinet expansion and 3G additions.Since running power load for a BTS cannot be more than the sanctioned load, these 400 sites were non compliant as per HSEB norms. If these sites were to be inspected by State Electricity Board inspectors and identified for non-conformity, it would have lead to heavy commercial penalties and even permanent disconnection of electricity to these sites. This inturn would entail using 24x7 diesel generators to keep sites active, increasing the operation cost manifold and also threatening environment pollution.A business case was prepared for this problem using the Define, Measure, Analyze, Improve and Control (DMAIC) methodology, a Six-Sigma approach. Cause of power overload and its effect was detailed out using root cause analysis and possible optimal remedial solution was arrived at for this project. The total penalties calculated as per the HSEB guidelines came out to be Rs.35 million whereas the total expenditure being involved in complying and coming out of this issue came out to be Rs.12 million approximately, thus making it a net saving of Rs.23 million for the telecom company. It was also observed that for the sites where the sanctioned load was 35%-50% of the required load, net saving potential was more compared to the sites where the sanctioned load was 55%-80% of the required load. A similar business case was carried out by the same company in the state of Himachal Pradesh and found that net saving potential was more compared to the state of Haryana.This was practically achieved by calling different partners (vendors) to discuss this project in an open forum. Non compliant site allocation was carried out on the basis of partner's confidence, band width and operational capabilities to deliver these sites. A reward per site was declared to motivate the partners for quick achievement of the desired results (compliance) with a gate criterion of ≥80% of the total site allocation done. The partners provided power usage receipts from HSEB as a proof of job done and payments were released accordingly. The change in power load was reflected in the subsequent electricity bills. The target set for the change over to the HSEB compliance was three months during which rigorous monitoring and review mechanism was put in place including circulation of Daily Progress Report to all internal and external stakeholders. To ensure that this issue does not repeat in future, the technical guidelines (SOP) was amended in terms of the power load to be upgraded for every new asset being deployed at site.

Sumit Saini

Papers

Effect of Groove Design on the Mechanical Properties of Shielded Metal Arc Welded Joints

Compliance driven Cost Control for Telecom Infrastructure Operation Management