Photobiological hazards in shielded metal arc welding

PURPOSE

Photobiological hazards caused by artificial optical radiation are assessed for the most commonly used arc welding technique, the SMAW (Shielded Metal Arc Welding), which operates with a hand-held system and is widely used both at occupational and domestic environments, expanding our previous investigation of a robotic arc welding process.

METHODS

The complex exposure limits of the emitted blue and visible light, ultraviolet and infrared, are assessed through the European Directive 2006/25/EC, using three dedicated sensors set to measure irradiance from various typical welding procedures in the controlled environment (currents, electrodes, etc.) of a welding laboratory. In this sense, field measurements are employed, applying existing policies. Occupational limits are also applicable to the domestic welding.

RESULTS

Apart from sub-minute overexposures, which were detected in every spectral band, overexposures in the order of one second were also observed at very close distances, which are common at complex working environments. Investigation of the initial welding procedure, which is often performed without the use of Personal Protective Equipment, revealed exposure of the order of the corresponding limit.

CONCLUSIONS

Simulation of a 'bad' welding procedure revealed increased exposure, indicating the importance of training in the occupational environment. Concern for the exposure of near-by workers (working a few meters away from the welding point) is also crucial. Future work needs to incorporate more welding techniques and measurements from original workplaces, in order to set the basis for an integrated risk assessment and provide valuable information concerning occupational diseases.

Effect of SMAW process parameters on similar and dissimilar metal welds: An overview

Shielded metal arc welding (SMAW) is the most economical and portable and robust welding processes which utilizes the power source, electrode holder and electrode to weld metals. It is utilized successfully in welding ferrous metals. Nowadays due to increased application of non ferrous metals, the joining of the same with this welding has been on rise. The further advancement in the field of material science, the welding of ferrous and non ferrous metals has found many takers. So SMAW has been tried in welding of ferrous and non ferrous metals i.e of oxygen rich copper with chromium and nickel rich stainless steel 304. The stainless steel due to its properties like corrosion resistance, high resilience, higher toughness has been utilized in automobile, household aerospace applications. Copper has wide spread application in engineering structure, electrical components, power plant industry due to its unique mechanical, physical and chemical properties. The purpose of review is to find work done by different researchers in the area of arc welding of similar and dissimilar metals, study the findings related to research, check the feasibility to weld oxygen rich copper to chromium and nickel rich Stainless steel 304 using SMAW process and to study the, economics, sustainability of SMAW in terms of green technology and eco-social aspects and to find the suitable electrode to weld.

The Effect of Polarity and Hydrostatic Pressure on Operational Characteristics of Rutile Electrode in Underwater Welding

In order to provide a better understanding of the phenomena that define the weld bead penetration and melting rate of consumables in underwater welding, welds were developed with a rutile electrode in air welding conditions and at the simulated depths of 5 and 10 m with the use of a hyperbaric chamber and a gravity feeding system. In this way, voltage and current signals were acquired. Data processing involved the welding voltage, determination of the sum of the anodic and cathodic drops, calculation of the short-circuit factor, and determination of the melting rate. Cross-sectional samples were also taken from the weld bead to assess bead geometry. As a result, the collected data show that the generation of energy in the arc–electrode connection in direct polarity (direct current electrode negative-DCEN) is affected by the hydrostatic pressure, causing a loss of fusion efficiency, a drop of operating voltage, decreased arc length, and increased number of short-circuit events. The combination of these characteristics kept the weld bead geometry unchanged, compared to dry weld conditions. With the positive electrode (direct current electrode positive-DCEP), radial losses were derived from greater arc lengths resulting from increasing hydrostatic pressure, which led to a decrease in weld penetration.

The Applicability of the Standard DIN EN ISO 3690 for the Analysis of Diffusible Hydrogen Content in Underwater Wet Welding

The European standard ISO 3690 regulates the measurement of diffusible hydrogen in arc-welded metal. It was designed for different welding methods performed in dry atmosphere (20% humidity). Some details of the standard are not applicable for wet underwater welding. The objective of this study was to extend the applicability of DIN EN ISO 3690:2018-12 to underwater wet-shielded metal arc welding (SMAW). Four different aspects regulated within the standard were accounted for: (1) sample dimensions and number of samples taken simultaneously; (2) time limitations defined by the standard regarding the welding and the cleaning process; (3) time, temperature, and method defined for analysis of the diffusible hydrogen content; (4) normalization of the hydrogen concentration measured. Underwater wet welding was performed using an automated, arc voltage-controlled welding machine. The results are discussed in light of standard DIN EN ISO 3690, and recommendations are provided for the analysis of diffusible hydrogen content upon underwater wet welding.

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

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.