The term quality steel is redefined since publication of DIN EN 10020, and it is distinguished by high quality steel alloyed and unalloyed. Until then quality steel was unalloyed regularly. As the Non-alloy steel grades, which are not provided for a uniform response to a heat treatment and to which no special requirements are placed on the purity apply. Compared to the basic steels, however, higher or additional requirements for ductility, grain size, brittle fracture insensitivity can be provided. In contrast: Alloy steel quality. The chemical composition of unalloyed steels must be such that certain limiting contents (for combinations of elements additional values apply) be exceeded in any case. The corresponding mass limit levels are: 0.0008 % for B; 0.05% for all the elements of the lanthanides, Ti, Zr and other; 0.10 % for Al, Bi, Co, Se, V, W; 0.30 % for Cr and Ni; 0.50 % of Si and 1.65% Mn. After their quality can be unalloyed steels in basic steels, unalloyed quality steels and unalloyed steels divide. They have a low strength (< 400 N / mm²), are good malleable and can be welded well. Without a prior carburizing or surface ( onset ) they can not be cured.