The transverse rib geometry of imported rebar is mainly ordinary square thread or ordinary oblique square thread. The transverse rib geometry of domestic rebar mainly includes spiral shape, herringbone shape and crescent shape. The order principle of rebar is generally based on the mechanical process performance or mechanical strength index on the basis of meeting the gripping performance requirements required by engineering design.

Hot rolled steel bar is the main reinforcement material of reinforced concrete building structure. With the emergence of multi-functional building structures such as high-rise, large span, earthquake resistance, low temperature resistance and fire resistance, the steel bar is required to have higher strength, toughness and better weldability.

SD400 is one of the hot rolled ribbed rebar grades with characteristic yield strength of 400MPa in Korea KSD3504:2011 standard. In the KSD3504:2011 standard, the composition, performance and dimensions of SD400 steel bars are clearly specified.