Treffer: Balancing weld performance and energy efficiency in resistance spot welding of 22MnB5 galvannealed steel.

Resistance spot welding (RSW) plays a critical role in automotive manufacturing, especially in the joining of advanced high-strength steels such as 22MnB5 galvannealed. However, the process remains energy-intensive, and balancing weld performance with energy efficiency continues to pose a challenge in engineering practice. While most previous studies have focused on optimizing energy efficiency, they often do not quantify CO₂ emissions directly, limiting their contribution to effective sustainable solutions. This study presents a statistically robust, multi-criteria process design and evaluation framework for RSW, using Response Surface Methodology to model the effects of four critical input parameters, effective welding time, current, upslope time, and quench time, on key process responses including weld geometry, mechanical strength, and energy consumption. To explore trade-offs among these potentially conflicting objectives, Factor Analysis was applied for dimensionality reduction, grouping correlated responses into latent factors, and the Normal Boundary Intersection method was used to generate a diverse set of Pareto-optimal solutions. A novel Sustainability Indicator (SI) is proposed to assist in selecting the most balanced solutions from the Pareto front. The SI combines (i) entropy-based diversification of objectives and (ii) direct CO₂ emissions calculated from energy usage and regional emission factors. Among the Pareto-optimal solutions obtained, the one with the highest SI value resulted in the following performance: energy consumption of 1.30 Wh, CO₂ emissions of 0.050 g CO₂ per weld, weld spot width of 4.136 mm, cross-section area of 4.134 mm², load-bearing capacity of 10,266.3 N, and energy absorption of 4,465.1 J. This configuration was validated through confirmation experiments, demonstrating strong agreement between predicted and measured values. In an industrial context, considering global registrations of 6.554 × 10⁷ passengers cars in 2024, with an average of 5,000 weld spots per vehicle, the adoption of this process design approach could reduce up to 2,289.45 tons of CO₂ emissions annually. This work advances the scientific understanding and engineering control of resistance spot welding, enabling informed process design for high-strength steels in modern manufacturing environments. [ABSTRACT FROM AUTHOR]

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