Abstract
Abstract The article discusses the effect of large oxide impurities (a diameter larger than 10 μm in size) on the fatigue resistance of structural steel of high purity during rotary bending. The study was performed on 7 heats produced in an industrial plant. The heats were produced in 140 ton electric furnaces. All heats were desulfurized. The experimental material consisted of semi-finished products of high-grade, carbon structural steel with: manganese, chromium, nickel, molybdenum and boron. Steel sections with a diameter of 18 mm were hardened from austenitizing by 30 minutes in temperature 880°C and tempered at a temperature of 200, 300, 400, 500 and 600°C for 120 minutes and air-cooled. The experimental variants were compared in view of the heat treatment options. Fatigue tests were performed with the use of a rotary bending machine at a frequency of 6000 cpm. The results were statistical processed and presented in graphic form. This paper discusses the results of the relative volume of large impurities, the fatigue strength for various heat processing options.
Highlights
To ensure an appropriately high reliability of machine parts, research has been conducted on the effect of impurities on the performance characteristics of a construction material and its durability
Relative volume of non-metallic inclusions measuring over 35 μm were in limit of error
Bending fatigue strength of steel hardened and tempered at all ranges temperatures (200, 300, 400, 500 and 600°C) in depends of volume of inclusions larger than 10 μm are presented in Fig. 1, regression equation and correlation coefficients r at (4)
Summary
To ensure an appropriately high reliability of machine parts, research has been conducted on the effect of impurities on the performance characteristics of a construction material and its durability. The presence of oxygen and non-metallic inclusions in steel is a natural consequences of physical and chemical processes during production. Commercial iron alloys apart of typical chemical elements contain sulfur, oxygen, and those elements form solutions in liquid metal. The physical and chemical reactions that occur in the process of steel melting and solidification produce non-metallic compounds and phases, referred to as inclusions [14]. The quality, quantity and size of inclusions can be controlled, but such impurities cannot be eliminated in their entirety because they are natural components of the phases present in alloys. Steel has a relatively small number of non-metallic inclusions, those impurities have a considerable impact on the material's technological and strength parameters, in particular fatigue strength and life. The shape and distribution of microparticles change, and impurities undergo
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