This document specifies qualities for high-yield-strength quenched and tempered structural steels. It applies to steel plates and wide flats rolled on a reversing mill which are used in the quenched and tempered condition and normally intended for welded or bolted structures.This document covers 10 grades and 5 qualities. Grades S460Q, S500Q, S550Q, S620Q, S690Q, S890Q and S960Q are covered in Annex A. Grades SG460Q, SG500Q, and SG700Q are covered in Annex B. Not all grades are available in all qualities, and some qualities have Charpy V-notch requirements.The steels specified in this document are applicable to hot-rolled flat products with a minimum nominal thickness of 3 mm and a maximum nominal thickness of 200 mm for grades S460Q, S500Q, S550Q, S620Q and S690Q, a maximum nominal thickness of 125 mm for grades S890Q and S960Q, a maximum nominal thickness of 100 mm for grades SG460Q and SG500Q and a maximum nominal thickness of 150 mm for grade SG700Q.This document does not include the following structural steels, some of which are covered by other International Standards:— Sheet and strip — refer to ISO TC 17/SC 12, Continuous mill flat rolled products;— Tubular products — refer to ISO TC 5/SC 1, Steel tubes.NOTE 1 Lists of standards covered by ISO/TC 17/SC 12 and ISO/TC 5/SC 1 are available on the ISO website.NOTE 2 In all parts of ISO 630, the term of "thickness" is considered as "nominal thickness", unless otherwise stated.