Optimization of cost and performance of the material used in the mechanism unit of Air Circuit Breaker (ACB) based on various analysis approach

Abstract

Air Circuit Breakers are used for circuit protection from the faulty current that might damage the subsystems of the circuits like motors, transformers, transmission systems, etc. The cost optimization of the component used in the mechanism unit of Air Circuit Breaker (ACB). This can be achieved by replacing the existing material AISI 9260 to equivalent proposed material AISI 4140. This material exhibits the better mechanical properties in all aspects, along with low process cost involved during manufacturing of the components. This paper presents comparative dealing with the properties like hardening & tempering, hardenability, weldability, stamping-ability, endurance limit, and modification factors of the existing material AISI 9260 to proposed material AISI 4140. The proposed steel AISI 4140 is suitable for ACB mechanism parts which exhibits the same reliability and better mechanical properties than presently used AISI 9260 steel. The proposed AISI 4140 steel reduces the cost of the component by elimination and replacing the partial or fully heat treatment cost and wire electric discharge machining (WEDM) cost respectively. Because the component manufactured with AISI 4140 steel shows the desired mechanical properties only in hot rolled conditions with additional localized hardening, wherever the rolling surface is present. The elimination and replacement of heat treatment and WEDM process cost involved in present AISI 9260 steel components, can be achieved by partial induction hardening and stamping process employed on proposed AISI4140 steel respectively. There are three conditions that is, when fully elimination of heat treatment saves 27% of the total process cost, when partial elimination of heat treatment cost saves 25.5% of the total process cost, and when replacing the WEDM to stamping saves 22% of the total component cost. The proposed material and process also maintain the same reliability for the rated 20,000 operations.