Heat Treatment

Heat treatment is the process of optimizing the internal structure (microstructure) and mechanical properties of steel through controlled heating-cooling cycles. Different heat treatment recipes are applied according to each steel grade and application area. This process determines the balance of hardness, strength, toughness, and machinability of steel.

Annealing: The process of softening steel by heating to 680–900°C and slowly cooling. It is applied to relieve internal stresses, create a homogeneous grain structure, and prepare for subsequent processing (machining, cold forming). Machinability of steel is maximized through spheroidizing annealing.

Quenching & Tempering: The process of heating steel to 830–880°C, rapidly cooling in oil or polymer medium (hardening), and then tempering at 150–700°C. Martensite structure is formed by hardening; the desired hardness-toughness balance is achieved by tempering. Quenched and tempered steels like 42CrMo4 and 34CrNiMo6 gain their service properties through this process.

Case Hardening: The process of forming a hard shell on the surface of low-carbon steels (C10, 16MnCr5, 20MnCr5) through carbon diffusion at 880–950°C. Surface hardness reaches 58–62 HRC while the core remains tough. Applied in parts requiring wear resistance such as gears, camshafts, and bearing rings.