FEATURES OF MECHANICAL CHARACTERISTICS OF HIGH-VOLUME APPLIED STEEL GRADES USED IN INDUSTRIAL PIPELINE IN THE OPERATING TEMPERATURE INTERVAL

Abstract

Industrial pipelines operate in a variety of conditions, are under the influence of significant pressures and high temperatures, are subject to corrosion and experience periodic cooling and heating. They are operated at different ambient temperatures. According to the generally accepted classification, techno-logical pipelines are divided according to the temperature of the transported medium into cold (temperature below 0 °C), normal (temperature from 0 to 50 °C) and hot (temperature over 50 °C). In most regulatory documents for pipe products from massively used steel grades, the maximum operating temperature is de-termined of up to 80 °C. In the company standard Gazprom 2-4.1-713-2013 “Technical requirements for pipes and fitting parts”, the upper limit of operating temperatures is set at 120 °C. At the same time, the ac-tual temperature of the transported medium may significantly exceed these values. The Institute has con-ducted a study of the mechanical characteristics of steel grades used in process pipelines – Steel 20, 09Г2С, 13ХФА, 17Г1С-У. The analysis of strength properties (yield strength, tensile strength, percentage elongation, percentage reduction) at elevated (up to plus 250 °C) and lowered (down to minus 80 °C) temperatures was carried out. The analysis of viscoplastic properties during the impact bending test of Sharpie samples was carried out, the dependences of the impact strength on temperature in the range from minus 100 to 0 °C were constructed. The results presented in the article allow us to better understand the influence of opera-ting temperature on the mechanical properties of pipelines made of various grades of steel.