СУЧАСНІ ТЕНДЕНЦІЇ ВИРОБНИЦТВА КОРОЗІЙНОСТІЙКОГО І ВОГНЕСТІЙКОГО НАПРУЖЕНОГО АРМАТУРНОГО ПРОКАТУ

Abstract

The aim of the work is to study modern methods of production in the world of corrosion-resistant and fire-resistant high-strength reinforced rolled steel, designed for pre-stressed reinforced concrete structures. The specific cost of reinforcement is determined by the ratio of its value to the design resistance and decreases with increasing strength class. In Ukraine, economically alloyed steel grades are used for the production of prestressed high-strength reinforcing steel with a diameter of 6-40 mm of periodic profile according to DSTU 3760: 2019. It is also possible to use thermal strengthening of rolled products from rolling heating in the rolling mill stream, or from special (separate) heating. Hardening, tempering and also cold deformation of smooth profiles with the subsequent drawing of a periodic profile are also applied. According to the Interstate GOST 34028-2016 for the countries of the Customs Union, high-strength reinforcing steel of periodic profile of class A600p is made in bars and skeins with a diameter of 10-40 mm, and classes A800 and A1000 only in bars with a diameter of 10-40 mm from low-alloy steel grades. Depending on the diameter of the reinforcing steel, different production methods are used. GOST 34028-2016 contains clear requirements for corrosion resistance and methods of its testing. Many foreign requirements for the production of high-strength prestressed reinforcement, depending on the diameter of the profile (6-50 mm) and the method of production use carbon steels with different maximum carbon content from 0.37 to 0.8%, maximum silicon content from 0.55 up to 2.0% and a maximum manganese content of 1.8 to 2.0%. Thermomechanical reinforcement of reinforcing steel from rolling heating in the flow of rolling mills, hardening from separate (special) heating followed by tempering and strengthening by mechanical extraction followed by low-temperature tempering are used. Corrosion is the main cause of damage and destruction of reinforced concrete structures and buildings of prestressed reinforced steel from carbon steels. This problem in the world today is solved with the use of stainless steels, which have high corrosion resistance and fire resistance. Prestressed stainless steel reinforcement has higher strength and, especially, ductility than carbon steel. Stainless steel grades are used for the production of prestressed reinforcing steel with a diameter of 5 to 75 mm. In the production of periodic profiles of stainless steel reinforcement, there are two main technological routes: hot rolling and cold rolling. A promising way is the use of controlled hot rolling and thermomechanical treatment. As the rolling temperature decreases, the hardness of the austenite phase increases. For two-phase stainless steels, this allows to achieve high strength and ductility. Examples of the use of prestressed high-strength rebar in the world are: the construction of sealed shells that prevent the release of radioactive substances into the environment in severe accidents at nuclear power plants; construction of tanks for nuclear waste; construction of offshore platforms for oil production; construction of sea and river bridges, long-span ceilings, high-rise buildings, roads and other similar facilities.