Modern trends in the production of corrosion-resistant and fire-resistant stress-free reinforcing bars

The aim of this work is to study modern methods of production of corrosion-resistant and fire-resistant stress-free reinforcing bars in the world. Non-stressed reinforcing bars are used as working, structural and assembly reinforcement in conventional building structures, as well as in various types of prestressed structures: from openwork prefabricated to huge monolithic hydraulic structures, therefore, its assortment produced by the domestic metallurgical industry in the range from 5,5 to 40 mm in the nominal diameter of a smooth profile and from 6,0 to 40 mm for a periodic profile. Recently, in the world, much attention is paid to the design and construction of buildings and structures with an improved complex of consumer properties, intended, in particular, for work in corrosive and fire hazardous environments. Such developments are not currently being conducted in Ukraine. In the world and in Europe, to increase corrosion resistance and fire resistance, as well as for the manufacture of seismically resistant reinforcing bars (δmax≥7,5 %), hot-rolled low-alloyed (additionally alloyed with V and Mo) and microalloyed steel grades without the use of heat treatment or cold-deformed (cоld stretched) from hot rolled strip of periodic profile. In GOST 34028-2016 for the countries of the Customs Union, it is clearly stated that for the reinforcement of prefabricated reinforced concrete structures and monolithic reinforced concrete, unstressed reinforcing bars in bars or coils with a nominal diameter of 4,0 to 40 mm are also used for the production of such rolled products, low-carbon and low-alloy steel grades are used, which microalloy V, Nb, Mo or add nitride-forming elements Al, Ti, V, Nb. In this case, either hot rolling or cold deformation or heat treatment in the flow of the rolling mill is used. An alternative way of producing corrosion-resistant and fire-resistant stress-free reinforcing bars in the world is the use of stainless steel as a material. Such profiled reinforcing bars are produced in the range of 3,0 to 50 mm by hot rolling or cold deformation. The use of modern technologies for the production of stainless steel reinforcing bars, starting with the addition of effective and high-quality alloying elements and additives in the production of liquid steel and effective methods of metal pressure treatment, which allows us to guarantee the material saving from corrosion and high temperatures in case of fire. A significant disadvantage of this rolled product is its rather high cost.