Heat-treatable steels, alloy steels and free-cutting steels - Part 4: Free-cutting steels (ISO 683-4:2016)

This technical specification establishes the classification and designation system for free-machining steels, covering both ferrous and alloyed varieties intended for automatic machining processes. The document serves as a specialized guide within the broader framework of heat treatment steel standards, specifically focusing on the fourth segment dedicated to materials optimized for high-volume automated production. It defines the chemical composition limits, mechanical property requirements, and metallurgical structures necessary to ensure consistent performance in machinery components manufactured via turning and milling operations. By aligning with international technical guidelines, this standard facilitates global trade and interoperability of steel products across different manufacturing sectors. It provides manufacturers with clear criteria for selecting appropriate grades based on machinability, strength, and dimensional stability. The content details specific designations used to identify various steel grades, ensuring that engineers and procurement specialists can accurately specify materials that meet industry demands. This resource supports quality control procedures by offering a unified reference point for testing and verification methods applicable to these specialized steel types.