Mushet steel was harder than standard water quenched steel.

Thus quenched steel is extremely hard but brittle, usually too brittle for practical purposes.

Quenched steel is approximately three to four (with more carbon) fold harder than normalized steel.

Tempering involves reheating quenched steel to a temperature below the eutectoid temperature then cooling.

Tempering will cause the dissolved alloying elements to precipitate, or in the case of quenched steels, improve impact strength and ductile properties.

Tempering is a method used to decrease the hardness, thereby increasing the ductility of the quenched steel, to impart some springiness and malleability to the metal.

Except in rare cases where maximum rigidity and hardness are needed, such as the untempered steel used for files, quenched steel is almost always tempered to some degree.

This localized area, called the heat-affected zone (HAZ), consists of steel that varies considerably in hardness, from normalized steel to steel nearly as hard as quenched steel near the edge of this heat-affected zone.