Why do steel parts need to be QT? What is the effect?

Quenching and tempering treatment: The heat treatment method of high-temperature tempering after quenching is called quenching and tempering treatment. High temperature tempering refers to tempering between 500-650 ℃. Quenching and tempering can greatly adjust the properties and materials of steel, with good strength, plasticity, and toughness, and excellent comprehensive mechanical properties.

There are two main types of quenched and tempered steel: carbon quenched and tempered steel and alloy quenched and tempered steel. Whether it is carbon steel or alloy steel, its carbon content is strictly controlled. If the carbon content is too high, although the strength of the quenched and tempered workpiece is high, the toughness is not enough. If the carbon content is too low, the toughness increases but the strength is insufficient. In order to achieve good comprehensive performance of the quenched and tempered parts, the carbon content is generally controlled between 0.30% and 0.50%.