Main Elements of A955
The governing manufacturing guide for SSR is the international industry standard ASTM A955/A955M – Standard Specification for Deformed and Plain Stainless Steel Bars for Concrete Reinforcement.
The A955 Standard includes information on the dimensional bar profiles, the grade structure (strengths), ribbed and smooth bar diameters, and the fabrication bend diameters all of which follow those of the conventional carbon steel standards. The exception is the stainless standard includes an option of a three sided ribbed bar in addition to the more commonly available two sided bar
Where A955 diverges from the carbon steel standards is the inclusion of a table listing the various commonly available types of stainless steel rebar that meet the standard and their chemistry composition, guidance on surface finish and pickling, information relating to mandatory corrosion tests and a specification of magnetic permeability.
Product Manufacturing
The main raw material used in the production of stainless steel is recycled steel scrap – about 60 to 90% depending on the mill and market conditions – with the balance made up of various virgin alloys.
The rebar production process consists of :
melting the scrap material and the various alloys in an electric arc furnace,
removing impurities and reducing carbon in an argon oxygen decarborization vessel,
casting of ingots,
hot rolling to different ribbed or smooth bar diameters, and
finishing the bars which includes
the removal of mill scale usually by mechanical means, and
pickling which is the removal of a thin layer of metal with nitric and hydrofluoric acids to provide a clean metallic and passivated surface.
This last step of “finishing” is a requirement of A955 and ensures the highest level of corrosion resistance of the bar material. These bars are shipped and received by customers in a fully passivated state.
Buy America
In the United States in order for public authorities to obtain federal funding for infrastructure projects, both the production of the ingots used to manufacture the stainless steel reinforcement material and the process of rolling of the bars must have been performed in the U.S.A.