What is the primary purpose of tempering in steel treatment?

Tempering is a heat treatment process applied to steel that significantly enhances its toughness, which is the ability to absorb energy and deform without fracturing. The process involves heating the hardened steel to a temperature below its critical point, followed by controlled cooling. This treatment reduces the brittleness that can result from processes like quenching, which typically increases hardness but may also create internal stresses and microstructural flaws.

By tempering, the microstructure of the steel is transformed, achieving a balance between hardness and toughness. The residual stresses are relieved, and some of the carbides may dissolve, leading to an improved microstructure that is more resistant to cracking under stress. This is essential in applications where the steel will be subjected to impact or varying loads, as it helps prevent failure.

The other options do not accurately reflect the primary aim of tempering. Producing a softer structure for easy machining is more characteristic of normalization or annealing processes rather than tempering. Increasing hardness and brittleness is contrary to the goal of tempering, which seeks to mitigate those traits for better performance. Lastly, while tempering does help relieve some internal stresses, it does not completely eliminate all internal stresses in steel, as that could require different treatments or processes. Thus, the focus