Papers by Keyword: Inclusion

Abstract: In order to improve the purity of bearing steel, the VIM+ESR+VAR triple smelting process was used to smelt 9Cr18Mo stainless bearing steel. The content of harmful elements, non-metallic inclusions and microstructure of the steel were studied. The results show that, the content of harmful elements of the steel is very low. A fairly small number of non-metallic inclusions are uniformly distributed and fine. The purity of the steel reaches a higher level. After thermal processing and heat treatment, the microstructure of the steel is the same as 9Cr18Mo bearing steel smelted by normal process, but the primary carbides in the steel is more uniform distribution and finer.

Abstract: Magnesium alloys have low density, light weight, strength, stiffness, high heat resistance, good shock absorption, convenient recycling use and other characteristics, which make it have the potential of widely using in aerospace, transportation, weapons, 3C products and other fields. AZ61 magnesium alloy melt was purified by using composite refining technology. The AZ61 micro-structure and mechanical properties were studied after casting, rolling and annealing. Using SF₆ and Ar mixed gas to protect melting AZ61 magnesium alloy, the effect was good, and size of inclusion was all blow 50μm. The effect of blowing Ar on inclusion removal was obviously. The inclusion contents were decreased from an initial 1.37% to a final 0.58%. Alloy elongation was increased obviously, which was from an initial 4.02% to a final 7.09%.

Abstract: Fatigue crack initiation usually starts from defects or inclusion (s) in the material in the zone of stress concentration. The stress concentration zone can be at the surface of the specimen or inside the material. The fatigue crack starts to propagate, depending on stress amplitude, if the range of the stress intensity factor is higher than the fatigue threshold. The aim of this paper is to present the procedure for determining the fatigue crack initial stage by using the Wöhler S-N curve and the fatigue crack propagation parameters obtained by experiment for the loading range R=-1. Determination of the fatigue initial stage has been determined by the analysis of tensile smooth specimens and notched bending specimens. Results show that linear elastic fracture mechanics is applicable in order to establish a model for fatigue crack propagation.

Abstract: In this study, two cases of crack growth initiation from a foreign particle in a representative elementary volume are analyzed. The task is completed with a cohesive model implemented in ABAQUS. The results are compared with those obtained for an inclusion-free cell.

Abstract: The present study evaluates the von Mises stress distribution around the crack tip and stress Intensity Factor (SIF) under biaxial mixed modes during the propagation of a crack interacting with two nearby circular inclusions. The finite element method is used for determination of stress intensity factors by ABAQUS software. The stress field and the SIF are determined for different crack’s length .A brittle material such as a glass having an equivalent elasticity modulus and a Poisson rain this research work. Besides, the proposed model is a rectangular specimen with an edge crack subjected to tensile stresses according to the modes (I & II) of rupture .Obtained results are compared and agreed with those determined by other researchers.

Abstract: Thermodynamic analysis of the phase equilibria in the Fe–Mn–Cr–Si–Al–Ti– Ni–V–Mo–B–S–P–C–N–O system at fixed concentrations of boron, manganese, chromium, silicon, aluminum, titanium, nickel, vanadium, molybdenum, sulfur, phosphorus, carbon and nitrogen was performed. Formation of nonmetallic phases upon cooling and crystallization of liquid metal solutions of various compositions was studied. It was established how aluminum and nitrogen content in the liquid metal solution affects the composition and amount of separated excess phases. Calculations demonstrated that boron nitride was not formed in the liquid metal and during crystallization.

Abstract: In recent years, very high cycle fatigue has become a major concern in design and durability of engineering components and structures such as railway wheels, rails, offshore structures, bridges, load bearings, etc. There are some factors which have been assumed to influence the fatigue behavior for metallic materials in VHCF regime. But most factors influencing the VHCF behavior have not been studied thoroughly. In order to deeply understand the essence of material fatigue, the experimental and theoretical aspects of the factors influencing on very high cycle fatigue for metallic materials should be studied further more. This paper deals with an overview on the effect of factors on the property in very high cycle fatigue regime. Research trends and some conclusions in this field are briefly discussed and obtained.

Abstract: The influence of inclusion on pitting corrosion of X80 pipeline steel was investigated by using electrochemical test and atomic force microscope. The results indicated that corrosion potential of X80 pipeline steel sample with higher grade inclusion was lower, and decreased significantly with chloride ion concentration increasing. Inclusion was not conducive to corrosion resistance of X80 pipeline steel. The way of X80 pipeline steel pitting corrosion was that pit formed at the inclusion dissolution, and grew to pitting. There were less corrosion products near the pit hole, forming a cathode ring.

Abstract: At present, China's IF steel production has get a certain scale. But IF steel production is still in the primary stage of development. Therefore, the process control of inclusions in IF steel have become a pressing matter of the moment. This has important theoretical value and practical significance for further development of IF steel production in China. According to the size, the inclusions can be divided into super micro inclusions, micro inclusions and micro inclusions in the steel. According to the deformation capacity, inclusions can be divided into plastic inclusions, semi plastic inclusion and brittle inclusion.

Abstract: The fracture of a carbon steel pneumatic control valve rod used for Nuclear Power Plants was analyzed in terms of the microstructure, inclusions and fractogragh by means of tensile test, charpy V-Notch impact test, optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. The results indicated that the fracture of the rod is induced by the unqualified chemical composition: a large number of inclusions which distribute in grain boundaries reduce the material plasticity and toughness, and eventually cause fracture.