Steels for thermal improvement, i.e. hardening and tempering - characteristics of the material group
The grades of this carbon structural steel feature greater tensile strength, plasticity, crack resistance at dynamic loads, better hardening capacity, and uniform properties across the entire cross section. The group of structural steel alloys with a carbon range of about 0.25-0.50%, which require good mechanical properties with good ductility, and the ability to perform machining after heat treatment.The heat treatment (+ QT, -T) of the materials consists of a combination of tempering operations at about 800-1000 and high tempering at about 500-700 , resulting in the formation of a sorbite (ferrite and cementite), thanks to which the material acquires the appropriate qualities. The described structural steels only in improved state achieve their properties in relation to, for example, softened state.By hardening and tempering, you can obtain parameters which are determined by the chemical composition of the material and the specification. The rule confirms that quality alloy constructional steels should only be used in an improved condition. Products in the described grades are delivered in a softened state (steels for improvement), heat-treated (steels improved thermally), normalized, or raw.