Deoxidization of CuCr25 alloys prepared by vacuum induction melting

The influence of crucible and vacuum on oxygen content of CuCr25 prepared by vacuum induction melting (VIM) has been investigated. The experimental results show that the selection of crucible is very important. Alkaline oxide MgO crucible can result in increment of oxygen content and segregation of Cr in the CuCr25 alloys prepared. Neutral oxide Al 2O 3 crucible has no contribution to oxygen in CuCr25. The results also indicate that some kinds of deoxidant, such as Al, are further beneficial to deoxidization of the alloys. [

Mathematical model of deoxidization with post stirring in a combined blowing converter

Dissolved oxygen in the steel at the terminal of the converter smelting process is the main cause for the formation of oxide inclusions, and the high terminal oxygen content worsens the steel cleanness. However, post stirring in a combined blowing converter can promote the carbon-oxygen reaction in the liquid steel and reduce the dissolved oxygen content at the terminal of the converter smelting process. Thus, the mathematical model of deoxidization in the post stirring process was obtained, and the rationality of which was further verified by industrial tests. Finally, it is concluded that the product of dissolved carbon and oxygen, i.e. w[C]·w[O], decreases obviously after adopting the new technique of post stirring in the combined blowing converter.

Development and prospects of molten steel deoxidation in steelmaking process

In the long traditional process of steelmaking,excess oxygen is blown into the converter,and alloying elements are used for deoxidation.This inevitably results in excessive deoxidation of products remaining within the steel liquid,affecting the cleanliness of the steel.With the increasing requirements for steel performance,reducing the oxygen content in the steel liquid and ensuring its high cleanliness is necessary.After more than a hundred years of development,the total oxygen content in steel has been reduced from approximately 100×10^(-6)to approximately 10×10^(-6),and it can be controlled below 5×10^(-6)in some steel grades.A relatively stable and mature deoxidation technology has been formed,but further reducing the oxygen content in steel is no longer significant for improving steel quality.Our research team developed a deoxidation technology for bearing steel by optimizing the entire conventional process.The technology combines silicon–manganese predeoxidation,ladle furnace diffusion deoxidation,and vacuum final deoxidation.We successfully conducted industrial experiments and produced interstitial-free steel with natural decarbonization predeoxidation.Non-aluminum deoxidation was found to control the oxygen content in bearing steel to between 4×10^(-6) and 8×10^(-6),altering the type of inclusions,eliminating large particle Ds-type inclusions,improving the flowability of the steel liquid,and deriving a higher fatigue life.The natural decarbonization predeoxidation of interstitial-free steel reduced aluminum consumption and production costs and significantly improved the quality of cast billets.

Effects of AlMnCa and AlMnFe Alloys on Deoxidization of Low Carbon and Low Silicon-Aluminum Killed Steels

To confirm the effects of AlMnCa and AlMnFe alloys on the deoxidization and modification of Al2O3 inclusions, experiments of 4-heat low carbon and low silicon aluminum killed steels deoxidized by AlMnCa and AlMnFe alloys were done in a MoSi2 furnace at 1 873 K. It is found that the 1^# AlMnCa alloy has the best ability of deoxidization and modification of Al2O3 inclusions than 2^# AlMnCa and AlMnFe alloys. Steel A deoxidized by 1^# AlMnCa alloy has the lowest total oxygen content in the terminal steel, which is 37× 10^-6. Most of the inclusions in the steel deoxidized by 1^# AlMnCa alloy are spherical CaO-eontaining compound inclusions, and 89.1% of them are smatter than 10 μm. The diameter of the inclusion bigger than 50 μm is not found in the final steels deoxidized by AlMnCa alloys. Whereas, for the steels deoxidized by AlMnFe alloys, most inclusions in the terminal steel are Al2O3 or Al2O3-MnO inclusions, and a few of them are spherical, and only 76.8% of them are smaller than 10 μm. Some in- clusions bigger than 50μm are found in the steel D deoxidized by AlMnFe alloy.

A NEW METHOD FOR DEOXIDIZATION AND CHLORINATION OF REFINED ILMENITE WITH HIGH MAGNESIA AND CALCIA CONTENTS

A new process is proposed to utilize refined ilmenite with high magnesia and calcia contents, which is the main secondary resource from vanadium-bearing titaniferous magnetite in Panzhihua, covering about 40% of the worlds titanium. The refined ilmenite was first deoxidized to separate the iron in the ore in order to enrich the titanium. The mechanism of chlorination of the titanium-rich slag was analyzed using the HSC chemistry software. Following deoxida-tion, a tandem fluidized bed was applied to chlorinating the titanium-rich slag. Modeling of the tandem fluidized bed ex-plains how this serial operation can effectively improve the convention ratio of TiO2 to TiCl4.

New steelmaking process based on clean deoxidation technology

After the converter steelmaking process,a considerable number of ferroalloys are needed to remove dissolved oxygen from the molten steel,but it also forms a lot of oxide inclusions that cannot be completely removed.At the same time,it increases the carbon emis-sions in the steel production process.After years of research,our team have developed a series of clean deoxidation technologies,includ-ing carbon deoxidation,hydrogen deoxidation,and waste plastic deoxidation of molten steel to address the aforementioned issues.In this study,thermodynamic calculations and laboratory experiments were employed to verify that carbon and hydrogen can reduce the total oxygen content in the molten steel melt to below 5×10^(-6) and 10×10^(-6),respectively.An analysis of the deoxidation mechanisms and ef-fects of polyethylene and polypropylene was also conducted.In addition,the applications of carbon deoxidation technology in different steels with the hot-state experiment and industrial production were discussed carefully.The carbon deoxidation experimental results of different steels were as follows:(1)the oxygen content of bearing steel was effectively controlled at 6.3×10^(-6) and the inclusion number density was lowered by 74.73%compared to aluminum deoxidized bearing steel;(2)the oxygen content in gear steel was reduced to 7.7×10^(-6) and a 54.49%reduction of inclusion number density was achieved with almost no inclusions larger than 5μm from the average level of industry gear steels;(3)a total oxygen content of M2 high-speed steel was as low as 3.7×10^(-6).In industrial production practice,car-bon deoxidation technique was applied in the final deoxidation stage for non-aluminum deoxidized bearing steel,and it yielded excellent results that the oxygen content was reduced to below 8×10^(-6) and the oxide inclusions in the steel mainly consist of silicates,along with small amounts of spinel and calcium aluminate.

Thermodynamic model for deoxidation of liquid steel considering strong metal-oxygen interaction in the quasichemical model framework

Herein,a thermodynamic model aimed at describing deoxidation equilibria in liquid steel was developed.The model provides explicit forms of the activity coefficient of solutes in liquid steel,eliminating the need for the minimization of internal Gibbs energy preliminarily when solving deoxidation equilibria.The elimination of internal Gibbs energy minimization is particularly advantageous during the coupling of deoxidation equilibrium calculations with computationally intensive approaches,such as computational fluid dynamics.The model enables efficient calculations through direct embedment of the explicit forms of activity coefficient in the computing code.The proposed thermodynamic model was developed using a quasichemical approach with two key approximations:random mixing of metallic elements(Fe and oxidizing metal) and strong nonrandom pairing of metal and oxygen as nearest neighbors.Through these approximations,the quasichemical approach yielded the activity coefficients of solutes as explicit functions of composition and temperature without requiring the minimization of internal Gibbs energy or the coupling of separate programs.The model was successfully applied in the calculation of deoxidation equilibria of various elements(Al,B,C,Ca,Ce,Cr,La,Mg,Mn,Nb,Si,Ti,V,and Zr).The limitations of the model arising from these assumptions were also discussed.

Deoxidization effect of boron on the pure copper melting

The metal oxide dissolved in pure copper is usually cuprous oxide （Cu2O）, so thedeoxidization of pure copper means the reduction of cuprous oxide to copper by addingdeoxidizers such as an element. It is required that the oxide of this element must be morestable than Cu2O, i.e. its decomposition pressure is less than that of Cu2O. The more

Controlling oxygen content in electro-slag remelting steel by optimizing slag-steel reaction process

The thermodynamic equilibrium of deoxidation reactions between molten slag and steel was calculated using a slag-steel coupling thermodynamic model and the mass conservation model based on the ion-molecular coexistence theory.The study focused on the effects of slag composition and deoxidizer type on the oxygen content of low alloy steel during the electroslag remelting(ESR)process.The measured and predicted values of the oxygen content in remelted ingots,and the contents of FeO and MnO in slags were compared and analyzed.Results show that the measured content of total oxygen has a certain correlation with the trend of dissolved oxygen predicted by the model when using Ca-Si alloys as deoxidizer,but it is not correlated with the trend of dissolved oxygen predicted by the model when using Al as deoxidizer.The deoxidation mechanisms of Ca-Si and Al are different.Ca-Si alloy directly reacts with FeO and MnO in slag to reduce the oxygen potential of slag,hence it can inhibit the transfer of oxygen from the slag to molten steel.While,when Al deoxidizer is used,the oxygen content in steel is mainly reduced through floating up the alumina inclusions.Compared to Al,utilizing Ca-Si alloy as a deoxidizer is more effective in reducing the oxygen content and the amount of inclusions in ESR ingot.

Effects of deoxidizing degree on the pitting corrosion behavior of carbon and manganese steels

Nine steels with different deoxidizing degrees and two comparative steels were selected. Their pitting initiation susceptibility was compared by means of potentiodynamic polarization tests in 3wt% NaCl solution. The pit propagation rate was evaluated in artificial sea water and 3wt% sea salt solution by simulating occluded corrosion cell （SOCC） test and hanging plate test, respectively. The composition of inclusions and corrosive feature were studied by scanning electron microscopy （SEM）, electron probe micro-analysis （EPMA）, and optical microscopy （OM）. The results indicate that sulfide inclusions in steel are the sites for pit nucleation. The sulphide inclusions vary in shape from short spindle-like to long strip-like with increasing deoxidizing degree. Under the same conditions, the lower the deoxidizing degree gets, the lower the pitting initiation susceptibility becomes, and the stronger the resistance to pit propagation exhibits. For steels with different deoxidizing degrees, their pitting initiation susceptibility is mainly influenced by thermodynamic stability, while the pit propagation rate is primarily subject to the characteristics of inclusions in steel.

The Study of the Preparation of Catalysts for Carbonyl Sulfide Hydrolysis under Moderate Temperature

Multifunctional composite catalyst for carbonyl sulfide hydrolysis under moderate temperature was prepared by impregnation method. The hydrolysis and deoxidization ability of the prepared catalyst was investigated in a fixed bed reactor. It was found that deoxidization ability of the prepared catalyst was raised by the increase of the content of potassium loading catalyst and reaction temperature. And the concentration of H2S had no effect on deoxidization while COS improved the deoxidization ratio. And deoxidization rates were nearly scaled up with concentration of H2. The hydrolysis ability was decreased by the decrease of the surface basicity.

Design, Selection and Application of High Efficient Complex Alloys

The design, selection and application principles of complex alloys according to the requirements of making low-alloy steels are discussed. The designed complex alloys containing calcium, barium, magnesium, strontium, rare earth elements, etc. should not only be able to deoxidize, desulphurize and refine liquid steel, but also alloy it. The application principles of alloys are as follows: using Si-Mn or Si-Mn-Al alloys for pre-deoxidizing, Si-Al-Ba or Si-Al-Ca-Ba alloys for final deoxidizing and Si-Ca-Ba-Mg(Sr) alloys for refining.

EQUILIBRIA OF Sr,Ba AND O,S IN LIQUID Fe

The equilibrium constants between Sr-O,Ba-O and Sr-S,Ba-S in liquid iron at 1570℃ and the interaction coefficients concerning these elements have been determined as follows: K_(Sro)=1.897×10^(-7),e_O^(Sr)=-43.8 K_(BaO)=8.204×10^(-8),e_O^(Ba)=-98.0 K_(SrS)=8.356×10^(-7),e_S^(Sr)=-3.9 K_(BaS)=4.083×10^(-7),e_S^(Ba)=-3.5

OXIDE METALLURGY-ITS PURPOSES AND PRACTICAL APPROACHES

Under certain conditions, nonmetallic inclusions such as oxides, sulfides, nitrides and carbides are no longer harmful to steel service properties. With the new concept of oxide metallurgy, these properties can be improved by generating fine oxide inclusions which serve as heterogeneous nuclei for sulfide and fine ferrite. A novel continuous casting (CC) process is expected to be created with the utilization of oxide metallurgy. This is also useful for the forthcoming technologies of direct rolling and near-net-shape casting. The main idea of oxide metallurgy consists of an alternative oxidation technology. It is based on steels treated by complex metals such as Ti, Zr, Ti-Zr alloys and rare earth metals. The selected deoxidants should follow the required conditions which are concluded in this paper. (Author abstract) 45 Refs.

Optimal Batching Plan of Deoxidation Alloying based on Principal Component Analysis and Linear Programming

As the market competition of steel mills is severe,deoxidization alloying is an important link in the metallurgical process.To solve this problem,principal component regression analysis is adopted to reduce the dimension of influencing factors,and a reasonable and reliable prediction model of element yield is established.Based on the constraint conditions such as target cost function constraint,yield constraint and non-negative constraint,linear programming is adopted to design the lowest cost batting scheme that meets the national standards and production requirements.The research results provide a reliable optimization model for the deoxidization and alloying process of steel mills,which is of positive significance for improving the market competitiveness of steel mills,reducing waste discharge and protecting the environment.

Calculation of phase diagram of Ti-Ni-O system and application to deoxidation of TiNi alloy

The Ti-Ni-O ternary system was assessed by means of Calphad method using ternary experimental data in previous study.Isothermal sections at 1 173 and 1 273 K were calculated.The result shows that the present calculated results are in good agreement with most of the experimental results.The consistent model parameter set determined in this work may provide theoretical guidance for the deoxidation of TiNi alloy.

Oxide Inclusions at Different Steps of Steel Production

The formation of oxide inclusions in one of the carbon steel productions of Mobarakeh Steel Complex of Isfahan has been evaluated. Several samples from different steps of steel production were taken, from arc furnace, ladle furnace, tundish, and continuous casting mold. Moreover, samples of slab and hot rolling products were prepared. The samples were investigated by optical and scanning electron microscopes equipped with the EDS system. According to the results, the number, composition, and kind of inclusions were directly influenced by the production variables. It was found that when the amount of dissolved oxygen was high （say more than 0. 002 5%）, the dissolved aluminum was able to reduce silicon oxide and react with the dissolved oxygen simultaneously, whilst, the dissolved aluminum could reduce the magnesium oxide only when the oxygen content was below 0. 000 5%. Based on this research, a mechanism for forming the complex inclusions was suggested. It was also found that if the aluminum is added to the melt as late as possible, a cleaner melt with fewer inclusions is prepared; this method will be more effective, especially in the case of complex inclusions.

Allelopathic effect of Acorus tatarinowii upon algae

Besides competing with algae for light and mineral nutrients (i. e. N, P, etc.), the root system of Acorus tatarinowii excretes some chemical substances, which injure and eliminate alga cells, to inhibit the growth of the algae. When the algae cells were treated in 'A. tatarinowii water', some of the chlorophyll a were destroyed and the photosynthetic rate of algae decreased markedly and the ability of alga cells to deoxidize triphenyltetrazolium chloride (TTC) reduced greatly. Then alga cells turned from bright red to bluish green under fluorescence microscope. These showed that the allelopathic effects of A. tatarinowii on algae were obvious and planting A. tatarinowii can control some green algae. The experiment on the extractions of the secretions of the root system showed that the inhibitory effect had a concentration effect. If the concentration of the root secretion was below 30 μl/disc, the inhibitory rate was negative; if it was over 45 μl/disc, the inhibitory rate was positive. This proved that the influence of the root secretion on the same acceptor was a kind of concentration effect. When the concentration of the root secretion was low, it promoted the growth of algae; when the concentration reached a definite threshold value, it restrained the growth of algae. In present case, the threshold value was between 30 μl/disc and 45 μl/disc.

Ultrahigh cycle fatigue fracture mechanism of high-quality bearing steel obtained through different deoxidation methods

The mechanism of oxide inclusions in fatigue crack initiation in the very-high cycle fatigue(VHCF)regime was clarified by subjecting bearing steels deoxidized by Al(Al-deoxidized steel)and Si(Si-deoxidized steel)to ultrasonic tension-compression fatigue tests(stress ratio,R=−1)and analyzing the characteristics of the detected inclusions.Results show that the main types of inclusions in Si-and Al-deoxidized steels are silicate and calcium aluminate,respectively.The content of calcium aluminate inclusions larger than 15μm in Si-deoxidized steel is lower than that in Al-deoxidized steel,and the difference observed may be attributed to different inclusion generation processes during melting.Despite differences in their cleanliness and total oxygen contents,the Si-and Al-deoxidized steels show similar VHCF lives.The factors causing fatigue failure in these steels reveal distinct differences.Calcium aluminate inclusions are responsible for the cracks in Al-deoxidized steel.By comparison,most fatigue cracks in Si-deoxidized steel are triggered by the inhomogeneity of a steel matrix,which indicates that the damage mechanisms of the steel matrix can be a critical issue for this type of steel.A minor portion of the cracks in Si-deoxidized steel could be attributed to different types of inclusions.The mechanisms of fatigue fracture caused by calcium aluminate and silicate inclusions were further analyzed.Calcium aluminate inclusions first separate from the steel matrix and then trigger crack generation.Silicate inclusions and the steel matrix are closely combined in a fatigue process;thus,these inclusions have mild effects on the fatigue life of bearing steels.Si/Mn deoxidation is an effective method to produce high-quality bearing steel with a long fatigue life and good liquid steel fluidity.

Mathematical Simulation of Flow Phenomena in CAS-OB Refining Ladle

The deoxidation behaviors of alloys bearing barium in pipe steel were researched with MgO crucible under argon atmosphere in MoSi 2 furnace at 1 873 K. The total oxygen contents of molten steel, the distribution, size and morphology of deoxidation products in the steel were surveyed. The metamorphic mechanism for deoxidation products of alloy bearing barium was also discussed. The results show that applying alloy bearing barium to the pipe steel, very low total oxygen contents can be obtained, and deoxidation products, which easily float up from molten steel, can be changed into globular shape and uniformly distributed in steel. The equilibrium time of total oxygen is about 25 min, and the terminal total oxygen contents range from 0 002 0 % to 0 002 2 % after treating with SiCa wire. The best deoxidizers are SiAlBaCa and SiAlBaCaSr.