Chemical Composition Of Non-metallic Inclusions Research Articles

Ways to Improve the Quality of Die Steel 5KhNM

There was performed an analysis of influence of the deoxidation technology, hydrogen content and high concentration of titanium in steel 5KhNM (Rus. “5XHM”) on quality of die blanks, evaluated based on the results of the ultrasonic test.The fractographic examinations of fractures and the X-ray microprobe analysis of chemical composition of non-metallic inclusions were conducted, the evaluation of macro- and micro-structure of a die blank with high titanium content was performed.It is demonstrated that defects of dies from steel 5KhNM (Rus. “5XHM”) are cracks from merged flakes and micro-flakes; in most cases large concentrations of sulphides appeared to be hydrogen collectors for formation of flakes and micro-flakes.

Interpretation and Classification of Non-Metallic Inclusions

Abstract The non-metallic inclusions in steel are one of the most important parameters of metallurgical quality. Despite the extensive progress in thermodynamic description of non-metallic inclusions formation in the liquid and solidifying steel, a complete simulation of their evolution during secondary metallurgy, casting and solidification is impossible. The processes for non-metallic inclusion formation, growth and elimination, taking into account macro- and micro-segregation evolution, are too complicated. Therefore, a statistically reliable estimation of the amount, morphology, size distribution and chemical composition of non-metallic inclusions obtained by modern experimental approaches could be an important basis for understanding steelmaking technology. Automated feature SEM/EDS analysis of the chemical composition, size, and volume fraction of more than 600 non-metallic inclusions in rail steel was conducted. Analysis of these non-metallic inclusions' database by developed software found the following clusters of inclusions: (1) oxides, Al-Ca-Si-Mn-S-O; (2) predominantly sulfides, Mn-S-Al-Ti-O; (3) oxides and sulfides, Mn-S-O; and (4) complex non-metallic inclusions, Ti-Mn-O(N). All found compositions of non-metallic inclusions were placed on the ternary diagram Mn-Al-S and they lined up from the Al corner to the MnS point on the Mn-S axis. The chemical compositions of the non-metallic inclusions evolved from Al-Ca-Si-Mn-S-O to Mn-S-Al-Ti-O and, finally, to the Mn-S-O+Ti-Mn-O(N) system. Interpretation of the chemical composition of non-metallic inclusions by thermodynamic modeling revealed the nature of each cluster with correspondence to the secondary metallurgy stage where they were formed. This information could be useful for improvement of steelmaking technology. Accumulation of cluster analysis results for non-metallic inclusions in different steels could be a basis for the development of a universal classification of non-metallic inclusions produced by modern secondary metallurgy technologies.

Hydrogen effects on fracture of high-strength steels with different micro-alloying

Abstract Constant load tests of high-strength carbon steels with different micro-alloying using strengths in the range of 1000–1400 MPa were performed at ambient temperature under continuous electrochemical hydrogen charging. Hydrogen markedly affects delayed fracture of all the studied steels. Fractography of the studied steels shows that fracture mechanism depends on the chemical composition of the studied steels and hydrogen-induced cracking exhibits intergranular or transgranular character occurring often in the form of hydrogen flakes. The size and chemical composition of non-metallic inclusions are analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Hydrogen-induced cracking initiates at TiN/TiC particles in steels with Ti alloying. Crack paths are studied with electron backscatter diffraction mapping to analyze crack initiation and growth. The thermal desorption spectroscopy method is used to analyze the distribution of hydrogen in the trapping sites. The mechanisms of hydrogen effects on fracture of high-strength steels are discussed.

The Use of Barium and Calcium Alloys in the Ladle Furnace Treatment of Selected Grades of Continuously Cast Steels

AbstractThe subject of the paper are the results of laboratory and industrial investigations into the use of Si - Ca - Ba alloys for modifying non-metallic inclusions. Based on laboratory tests, the morphology and chemical composition of non-metallic inclusions in carbon steel were examined before and after refining with the use of the above-mentioned alloy as a refining addition. In particular tests, variable additions of the alloy were used at a constant refining time and temperature.Comparison of the process of casting of a sequence of seven heats of the same steel grade using the stopper system in the tundish was made under industrial conditions. In these heats, additions of Si - Ca (three heats) and Si - Ca - Ba (four heats) were introduced as a non-metallic inclusion modifier in the form of core wires during the process in the ladle furnace. For the investigated heats, the contents of total oxygen and calcium were assayed in the finished steel. A significant effect of the simultaneous addition of barium and calcium on steel castability, and thus on the process of continuous casting of the investigated heats, was found.

Study on Non-Metallic Inclusions in Laser-Welded TRIP-Aided Nb-Microalloyed Steel

Abstract The work concerns the studies on non-metallic inclusions occuring in laser-welded Si-Al TRIP steel containing Nb and Ti microadditions. Laser welding tests of 2 mm thick thermomechanically rolled sheets were carried out using keyhole welding and a solid-state laser. The results of laser welding in the air atmosphere for the heat input value of 0.048 kJ/mm are included. The distribution, type and chemical composition of non-metallic inclusions formed in the base metal, heat-affected zone, and fusion zone are analysed in detail. It was found that the base metal contains rare, fine oxysulphides. Their chemical composition was modified by rare earth elements. Numerous oxide inclusions of a various size and a chemical composition occur in the fusion zone. The dependence between a size of particles and their chemical composition was observed. A microstructure of steel was assessed using light microscopy and scanning electron microscopy techniques.

Modification of Non-Metallic Inclusions by Rare-Earth Elements in Microalloyed Steels

Modification of Non-Metallic Inclusions by Rare-Earth Elements in Microalloyed Steels The modification of the chemical composition of non-metallic inclusions by rare-earth elements in the new-developed microalloyed steels was discussed in the paper. The investigated steels are assigned to production of forged elements by thermo-mechanical treatment. The steels were melted in a vaccum induction furnace and modification of non-metallic inclusions was carried out by the michmetal in the amount of 2.0 g per 1 kg of steel. It was found that using material charge of high purity and a realization of metallurgical process in vacuous conditions result in a low concentration of sulfur (0.004%), phosphorus (from 0.006 to 0.008%) and oxygen (6 ppm). The high metallurgical purity is confirmed by a small fraction of non-metallic inclusions averaging 0.075%. A large majority of non-metallic inclusions are fine, globular oxide-sulfide or sulfide particles with a mean size 17 μm2. The chemical composition and morphology of non-metallic inclusions was modified by Ce, La and Nd, what results a small deformability of non-metallic inclusions during hot-working.

Secondary Steel Refining for Continuous Sequence Bloom Casting for High Oxide Cleanness Final Products

Secondary Steel Refining for Continuous Sequence Bloom Casting for High Oxide Cleanness Final ProductsSteelmaking and secondary refining process technology of resulphurized liquid steel with low content of total oxygen, assigned for continuous casting of strands for rolled and forged products for automotive industry was developed. The influence of secondary steel refining parameters on total oxygen content as well as amount and morphology of non-metallic inclusions was examined. It was found, that content of total oxygen and amount of non-metallic inclusions in steel decrease as steel refining time in the ladle becomes longer, and the chemical composition of non-metallic inclusions in steel changes from modified calcium aluminates to spinel inclusion of CaO·Al2O3·MgO type. The total oxygen content in steel from continuous casting in four cast sequence ranged from 6 to 25 ppm, with percentage share of non-metallic inclusions from 0.09 to 0.30 per cent and equivalent diameter 0.78 to 1.59 μm.

Effects of Mn and Ti on microstructure and inclusions in weld metal of high strength low alloy steel

The influences of alloying elements on chemical composition of non-metallic inclusions, impact toughness and microstructure in weld metals of high strength low alloy steels have been studied. Results indicated that microstructure had changed from a mixture of acicular ferrite, proeutectoid ferrite, ferrite side plates and microphases to a mixture of acicular ferrite, bainite and microphases due to the addition of Mn and Ti. The impact toughness of weld metal was improved correspondingly. The volume fraction and composition of inclusions both influenced the proportion of acicular ferrite. Mn and Si based oxide globular inclusions located at the boundary of acicular ferrite plates in the weld metal produced using C–Mn–Si–Cu wire. When Mn and Ti were added to welding wires, the inclusions within acicular ferrite plates permitted fewer primary acicular ferrite plates to grow into relatively larger dimensions. Secondary acicular ferrites nucleating on pre-existing ferrite plates refined microstructure effectively.

Steelmaking technology for a sustainable society

For the reduction of CO2 emission, two major developments are being conducted in COURSE50 (“ CO2 Ultimate Reduction in the Steelmaking Process by Innovative Technologies for Cool Earth 50”). The one is separation of CO2 gas from BFG (Blast Furnace Gas) and recharge of the rest of BFG including H2 and CO into blast furnace. Hydrogen iron ore reduction technology is also going to be developed. The other one is amplification of H2 gas from CH4, for example, in COG (Coke Oven Gas). The produced hydrogen gas will be supplied to the society or the reformed COG will be charged to blast furnace. In addition to these drastic challenging technology developments, a variety of measures for CO2 reduction is under taken. In the frame of Asia–Pacific Partnership on Clean Development and Climate, the best available technology for energy savings are discussed to be transferred within seven member nations, which has the effect of 1.27 million ton reduction of CO2 emission a year. By supplying energy saving steel products to society such as high strength steels for automobiles and ships, which realizes the fuel consumption reduction, high performance electrical steels for motors and transformers, which realize electricity loss reduction, and by recycling waste city plastics and tires in steel processes for hydrogen gas generation, chemical raw material conversion and iron ore reduction, etc., it is expected that equivalent 10% reduction of CO2 gas emission in steel production is counted. In steelmaking process the reduction of refining slags contributes materials use efficiency and less emission of unuseful byproducts. The control and utilization of nonmetallic inclusions, such as deoxidation products, are one of the key technology for obtaining product performance, which is required in the above-mentioned steel products. In order to optimize steelmaking process for these purposes, computational thermodynamics is applied. Optimization of demanganization, and control of chemical composition of nonmetallic inclusions by the use of computational thermodynamics are mentioned.

Study of the nature of non-metallic inclusions in samples of aluminum and silicon killed low carbon steels, collected in the refining treatment and continuous casting stages

The amount, distribution, size and chemical composition of non-metallic inclusions have a direct influence on steel properties. By controlling size and chemical composition of these inclusions, it is possible to get a product with good quality. The identification of the nature and the control of inclusion formation are very important for steel cleanness. The behavior of these inclusions is predictable, in some extent, by the determination of the chemical composition of non-metallic phases that form such inclusions. With the objective of studying the chemical composition, the size and the distribution of such inclusions, samples of aluminum and silicon killed low carbon steels were collected in a national steel industry in the secondary refining and continuous casting stages. These samples were analyzed in the scanning electron microscope (SEM) coupled to an energy dispersive analysis system (EDS). From the results, it was possible to evaluate the nature of inclusions and to analyze the effectiveness of the refining process in the reduction of the number and area fraction of the inclusions. It was also possible to verify that the inclusions that remained after treatment, are less damage both to the steel properties as to the continuous casting process (clogging of the submerged valve).

Influence of refining time on nonmetallic inclusions in a low-carbon, silicon-killed steel

Nonmetallic inclusions are harmful to the mechanical properties of every kind of steel produced worldwide. The greater the size of the inclusion present in the structure of a determined kind of steel, the greater its negative effect on the quality of the steel. Therefore, the objective of this work was to investigate the size, the quantity, the shape and the chemical composition of nonmetallic inclusions formed throughout the refining process of silicon-killed, low-carbon steel, as a function of the treatment time in a ladle furnace, trying to ensure the flotation of inclusions bigger than 25 μm. This investigation was carried out using a scanning electron microscope (SEM), with an analysis system using energy dispersive spectometry (EDS). Based on this work, it was possible to know more precisely the nature of the inclusions, the necessary time to ensure flotation of large inclusions, the efficiency of the slag to capture the inclusions, and the inclusion level of the steel throughout its refining process to try to obtain a higher quality steel product.

Investigation of the chemical composition of nonmetallic inclusions utilizing ternary phase diagrams

Nonmetallic inclusions are normally present in steel products, as they originate from reactions that occur during the steelmaking process. Inclusions, which consist of stable nonmetallic phases depending on their chemical composition, can strongly affect the final quality of the metallurgical product. In this sense, the influence of inclusions in the steel is determined by their chemical composition. The aim of this work is to present the evolution of the chemical composition of nonmetallic inclusions utilizing ternary phase diagrams by means of the analysis of steel samples collected during the steel (aluminum-killed steel, SAE 1015) manufacturing process. A computational program was developed to furnish the positions of the inclusions on appropriate ternary phase diagrams by using as input data the chemical composition of the inclusions, determined with a scanning electron microscope (SEM) connected to an energy-dispersive spectrometer (EDS).

Avaliação do tamanho, da morfologia e da composição química de inclusões não metálicas em aço baixo carbono desoxidado ao alumínio

A presença de inclusões não metálicas endógenas e exógenas prejudica a lingotabilidade e as propriedades mecânicas dos aços. A busca contínua pelo controle da quantidade, do tamanho, da morfologia e da composição química de inclusões não metálicas tem sido tema de estudos nas últimas décadas, em especial durante o processo de refino secundário dos aços. Através do controle, principalmente, do tamanho e da composição química das inclusões, é possível obter um produto final de boa qualidade. A identificação da natureza e o controle da formação de inclusões são de suma importância para a obtenção de aços limpos. Este trabalho tem como objetivo fazer uma investigação de inclusões não metálicas em aço de baixo teor de carbono(SAE 1015), desoxidado ao alumínio, através de um método de dissolução parcial e total da matriz metálica e posterior análise ao Microscópio Eletrônico de Varredura (MEV), acoplado a um sistema de análise por energia dispersiva (EDS), permitindo uma visualização do tamanho, da forma e da composição química das inclusões com maior precisão, sem interferência da matriz ferrítica.

Simulación de la precipitación de inclusiones en diferentes etapas del procesamiento del acero líquido

Steelmaking processes are continuously improved in order to attend the increasing requirements of the cleanness of the liquid metal. At the refining stages, as deoxidation and desulphuration, the formation of inclusions of oxides and sulphides is promoted, which on the other hand, are the most frequent inclusions. In this work a mathematical simulator of the precipitation and chemical composition of non-metallic inclusions at different steps of the steelmaking process is presented. To this purpose, it is assumed that inclusions formed by reoxidation can be simulated by increasing arbitrarily the oxygen levels consumed by the residual elements (aluminium, calcium, etc.) and starting the chemical reaction with less powerful deoxidants (silicium and manganese). Accordingly, different operative conditions can be simulated. Numerical predictions are compared with experimental results of industrial trials, as well as results included in the bibliography.

Effects of chemical composition of nonmetallic inclusions on fatigue strength of high steels: Murkami, Y., Toriyama, T., Koyasu, Y. and Hishida, S. Tetsu-to-Hagane (J. Iron and Steel Inst. Jpn) (June 1993) 79 (6), 678–684 (in Japanese)

Effects of chemical composition of nonmetallic inclusions on fatigue strength of high steels: Murkami, Y., Toriyama, T., Koyasu, Y. and Hishida, S. Tetsu-to-Hagane (J. Iron and Steel Inst. Jpn) (June 1993) 79 (6), 678–684 (in Japanese)

高強度鋼の疲労強度に及ぼす非金属介在物の化学組成の影響

高強度鋼の疲労強度に及ぼす非金属介在物の化学組成の影響

SEM based automatic image analysis of non-metallic inclusions in steel weld metals

The application of SEM based automatic image analysis to the determination of the volume fraction, size distribution, shape, and chemical composition of non-metallic inclusions in steel weld metals is described. Both carbon extraction replicas and mechanically polished specimens are used to obtain reliable data which, in turn, can serve as a basis for future theoretical treatments of weld metal microstructure development.MST/750

Effect of Non-metallic Inclusion of Flange Cracking of Drawn and Ironed Can from Tinplate

Flange cracking of Drawn and Ironed can from tinplate is caused mainly by non-metallic inclusions in the end of the can. In this study, the chemical composition and the minimum size of non-metallic inclusions causing flange cracking in tinplate of Al-killed steel were examined. The chemical composition of non-metallic inclusions is composed of CaO-Al2O3 and the minimum size is 5μm in thickness and 50μm in width. Countermeasures for reducing inclusions were taken in the continuous casting process, and the tinplate quality was inspected by a magnetic inclusion detector, thus leading to a reduction in the flange cracking rate of Drawn and Ironed cans.