Table of Content

05 October 2009, Volume 25 Issue 05

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生产实践

Application of crystallized carbon-determinatin instrument in tapping technology of high carbon steel

2009, 25(05):  1-4.  doi:

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The present paper introduces the application of crystallized carbon-determination instrument in high carbon steel tapping technology and analyzes the factors affecting the carbon-determination accuracy in accordance to the crystallized carbon determination principle. By means of optimizing the operating parameters to stabilize the usage environment of crystallized carbon-identification instrument and to clear up the factors affecting the carbon-determination accuracy the hit rate of carbon determination has been raised. The usage of the instrument is of great significance in raising the carbon content and lowering the oxygen content in steel in the process of converter tapping.

Production practice of IF steel in RH furnace at Meigang

2009, 25(05):  5-7，38.  doi:

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In producing the IF steel products by RH refining furnace in Meishan Iron & Steel Co. the metallurgical technologies and practices such as vacuum decarburization, temperature control and micro- alloying have already come into a mature and consistent stage. In accordance to the basic theory of vacuum decarburization and aluminum temperature rising the present paper introduces the production practice of conventional decarburization and decarburization by intensified oxygen blow in the hot metal RH vacuum treatment in the Plant and in meanwhile summarizes the technological requirements in the production practice on the basis of the actual data of the hot metal temperature control and micro-alloying.

Optimization of bottom argon blowing in 150 t ladle

2009, 25(05):  8-11.  doi:

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By establishing a water model for the 150t ladle of Meishan Steel the influence of the nozzle arrangement (layout of single nozzle, double nozzle in 90° inclination and double-nozzle in 180° inclination ) and location (0.40R, 0.55R and 0.70R from ladle bottom center) of nozzle and flow rate of Argon blowing (35~60 m3/h) on mixing time and slag entrapment in the gas-stirring ladle has been investigated. The optimum process determined for the bottom Argon blowing of 150t ladle is single nozzle at 0.55R and 45 m3/h flow rate of Argon blowing. Since application of the process in the production average difference in two adjacent temperature measurements of the hot metal in the tundish is only 2.66℃, the inclusion content decreases by 30.1% after gas-stirring and the yield of Al increases by 50%.

Optimization of secondary cooling scheme of combined caster

2009, 25(05):  12-15.  doi:

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In this paper, the defects existing in the secondary cooling scheme of the billet/slab combi-caster in Valin Xiangtan Iron & Steel Co., Ltd, are described, the reasons for internal corner cracks of rectangular bloom analyzed, and the secondary cooling parameters optimized. The production practice indicates that the secondary cooling scheme has already been optimized and excellent results achieved as well. The internal corner cracks of the rectangular bloom are eliminated basically, the proportion of qualified macroscopic sample increased from24.7% to 97.7%, the ratio of the central segregation (≤1.0) increases from 52.1% to 98.9%; and the unqualified rate of round-rod rolling steels caused by the defects in rectangular bloom reduced from38.7% to 1.53%.

Effect of continuous casting process parameters on solidifying structure of low carbon steel billets

2009, 25(05):  16-18，3.  doi:

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To study the effect of continuous casting parameters on the structure pattern of the low-carbon round billets，metallographic analysis method was used. Conclusions can be drawn as following: the lower the degree of superheat of molten steel is, the smaller the secondary dendrite arm spacing is; and the medium flux of the secondary cooling water and the lower pulling rate contribute to the formation of center equiaxed grain as well as smaller secondary dendrite arm spacing; Thus, to ensure the homogeneity of the round billet solidifying structure, it is necessary to reduce the secondary cooling intensity and the temperature fluctuation of the secondary cooling zone when increasing the pulling rate.

Application of home made dynamic soft reduction equipments

2009, 25(05):  19-21，3.  doi:

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The home made dynamic soft reduction equipment was installed in the 5# continuous casting machine being put into production in later of 2006 in Baotou Iron & Steel Corp.,and then dynamic soft reduction test was made on the heavy rail steel using the equipment. Results of trial for about one year show that by application of this dynamic soft reduction equipment quality of heavy rail steel can be improved obviously under the reasonable technology conditions including improvement in the average deviation index of carbon element of the heqvy rail slab and reduction of the internal defects of the rail steel and as the results the composition deviation of the conventional rail steel reduced to the level of the high speed rail steel.

Production practice of 700 MPa grade low carbon bainitic steel

2009, 25(05):  22-24，5.  doi:

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The present paper introduced productive features of high strength low alloy bainitic AH70DB steel plate independently developed by Anyang Iron and Steel Co. Ltd. including the composition design, productive process and quality control of the products. Results of examination show that the AH70DB plate, which was produced by independently designing the compositions and by TMCP processing and without any heat treatment has reached the technological requirments of 700 MPa grade low carbon bainitic steel entirely and the composite properties of the steel is excellent.

Effect of aluminum content on the formation of acicular ferrite and Ti composite oxide

2009, 25(05):  25-27，4.  doi:

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The effect of aluminum content on inclusions and metal solidification was investigated by experiment and thermodynamic calculation in Ti bearing steel. The results show that the inclusions in the steel are mainly aluminum oxides as the aluminum content is higher than 0.003wt%. Aluminum oxides could not promote the formation of acicular ferrite. The microstructures consist of side lath ferrites arranged in parellel. The inclusions in the steel are composed of Ti, Al, Ca, Si, Mn composite oxides with size<3μm as the aluminum content is lower than 0.003wt%. Ti composite oxide could promote the formation of acicular ferrite and the microstructures consist of large amount of acicular ferrites.

试验研究

Water modeling experiment research on auxiliary deslaggling process by side blowing in hot metal ladle

2009, 25(05):  28-31.  doi:

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In light of the problem of high rate of resulphurization existing in the desulphurization process by granular Mg due to the fact that slag occuring in this process is quite rare and watery, water modeling experiments are carried out on the auxiliary deslagging process by side blowing in the hot metal ladle and then the appropriate locations for installation of the porous brick as well as proper flow rate of the side blowing gas are determined so as to raise and improve the efficiency of deslagging after desulphurization by the granular Mg.

Experimental research on dust reduction in steelmaking by CO2

2009, 25(05):  32-34.  doi:

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The dust occuring in steel-making is about 10～20 kg/t steel. Increase in the dust amount not only reduces the yield of metal, but also adds the load of dust removal. The traditional method of controlling the dust is to recycle and utilize the dust produced. However the dust removal techniques in the smelting process are rarely seen and reported. By means of the thermodynamic calculation and the theoretical analysis an exploratory experiment on reduction of the dust using CO2 has been made and results show that the dust generation declines step by step and the iron loss tends to decrease obviously with the increase of the proportion of CO2 in the mixed injection.

Experimental research on desulphurizing process by BaO slag washing

2009, 25(05):  35-38.  doi:

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The present paper introduced the industrial test on out-of-furnace slag-washing desulphurizing process in the 50t converter of Jinan Steel by adopting BaO slag series. Result indicates that under the condition of adding 8 kg/t, the average desulphurizing rateηS≥35%, which, compared with that of CaO-based desulphurizing agent without BaO, was relatively improved by 40%.It also discusses the theoretical and technical problems about desulphurization by BaO containing slag series.The research shows that the process is simple, rapid, economic and effective and can be put into large scale industrial production.

Numerical simulation of surface temperature of Q345 bloom in continuous casting

2009, 25(05):  39-42.  doi:

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In order to clarify the surface temperature variation of the CC slab a finite element mathematical model for heat transfer during solidification in continuous casting is established and a 1/4 profile of Q345 bloom is confined as the object of investigation by the model and then the temperature distribution of any profile on the casting blank, the solidified shell thickness and the solidified state of any node and so on are calculated by application of the finite element software ANSYS. Finally by linking up every characteristic points the variation curve of surface temperature of casting blank can be clearly drawn up. Thereby the processing parameters of the continuous casting can be optimized and the slab quality be improved as well.

Study on Numerical Simulation for Heat Transfer of Slab during Hot Transferring and Charging in CC-HR Region

2009, 25(05):  43-47.  doi:

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According to temperature changing of typical slab in hot transferring and charging process, the mathematical model has been established and its result has been analyzed. The results show that the hot conveying temperature has little influence on the cooling rate of slab during conveying. The difference of cooling rate is obvious between slab surface and center. At 850℃ conveying, the cooling rate of slab-broad center is 6.4 K•min－1 ,the cooling rate of slab center is 7.8 K•min－1;The temperature distribution of slab in heat－preserved process is almost uniform. Its cooling rate is a little slow in the range of 8.3～9.0 K•h－1;The cooling rate of stack cooling is within the range of 11.3～18.6 K•h－1.Different thermal history of slab is formed because of different hot-charging temperature in the heating process. Temperature changing regularity of slab in different hot transferring and charging process is simulated. The reference for the improvement of interface-technique has been provided in different conditions for different steel.

Nucleation kinetics of niobium carbonitride in microalloyed austenite

2009, 25(05):  48-51.  doi:

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The kinetics model is optimized and the constant in the model is revised and the interfacial energy modifier in the presence of boron is 0.38. The derived value of constant B is 1.365×1010 in the kinetic calculation. The different strain and different strain rate of the Nb bearing steel at 980℃ and 950 ℃ are calculated. Results show that with the increase of the strain and strain rate the precipitation time is reduced and the quickest precipitation juncture is at 930 ℃.

Research on tiny MgO•Al2O3 spinel inclusion in Mg treated steel

2009, 25(05):  52-54，7.  doi:

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The modification of inclusions in magnesium treated steel was calculated by thermodynamic method. Results show that under the condition of dissolved aluminum content within 0.01% to 0.04%, trace of Magnesium in molten steel will lead to the formation of MgO•Al2O3 spinel inclusions. Based on the thermodynamic calculation, deoxidation experiments of bearing steel were done using magnesium aluminum alloy. The experimental results show that the inclusions in the steel treated by magnesium aluminum alloy are mainly composed of MgO•Al2O3 randomly distributed in the steel. The spinel inclusions with such tiny grain size is of very little harm on the mechanical properties of steel, such as the fatigue capability. Magnesium dissolved in steel will help spheroidize the carbide and this effect increases with the augment of the magnesium content in the magnesium aluminum alloy.

辅助技术、材料及设备

Laboratory research on molding of steel-making slag prepared melting agent

2009, 25(05):  55-58.  doi:

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The laboratory research on molding of the smelting agent prepared with the steelmaking slag is carried out by application of the cold compression molding process under the conditions of addition of the organic binder and the effect of the dosage of binder, the water volume allocation and the molding pressure on the mechanical properties of the compressed lump is reviewed. When the dosage of binder reaches 0.25%~0.30%, water volume allocation 12% and the compression strength for molding 50KN the dropping strength of the prepared dry and wet compression lump probably exceeds 19 times/ball and the compression resistant strength surpasses 1KN/ball. Thus they can basically meet the requirements of the industrial production for strength of the smelting agent. The prepared smelting agent is featured of low melting point, quick dissolution of slag and high capability of removing the injurants in steel and its metallurgical performance can meet the need of steelmaking plant for smelting agent.

Research on slab surface temperature data real time acquisition system

2009, 25(05):  59-61，6.  doi:

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In order to measure the temperature of the slab surface temperature, the Delphi7.0-based infrared temperature measurement system is developed. By utilization of the communication function of Dolphi micro-computer serial port the communication connection of the computer with three infrared radiation thermometers is established. By means of the data acquisition software below Windows the functions of slab surface temperature display and saving are realized. Experimental results show that the surface temperature of the slab can be accurately measured out by this system.

On-line detection method of carbon content in molten bath using light intensity

2009, 25(05):  62-65.  doi:

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Currently the methods for measurement of carbon content in metallurgical (iron & steel) industry are thermal analysis, chemical analysis and spectrometry. Although these three methods have high accuracy in the measurement of carbon content and other elements , yet its inadequacy lies that they are all off-line measurements, which can not meet the on-line and real-time measurement requirements in a highly automated production process. In Modern AOD furnace steelmaking by application of the method of light intensity measuring the on-line determination of the carbon content has already been realized and thus the on-line measurement problem is solved.

综述

Objective analysis on thin slab continuous casting and rolling technology

2009, 25(05):  66-69.  doi:

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In comparison with the traditional continuous casting extremely changes have taken place in the thin slab continuous casting in the aspects of slab gauge, casting speed, microstructures of strand and on-line rolling. Although the new technology enjoys the advantages of high cooling intensity, short production line and low energy consumption, yet it shows certain disadvantages such as undesirable surface quality and short scope of product adaptability and etc. Analysis and comparison have been made on the structures of the continuous casting products, the precipitation of compounds and the adaptability of products in order to evaluate objectively the thin slab continuous casting and rolling technology.

Study on the speed of on-line mould width adjustment

2009, 25(05):  70-72.  doi:

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On-line as hot mold width adjustment has been studied and the principle that has to be followed in the process of on-line as hot mold width adjustment, namely the strain rate of the shell be equal to the shrinkage rate is proposed. The quantitative relationship of the taper change speed and parellel shift with the drawing speed, slab width and the size of the upper and lower outlets of the mold is derived. It’s of great significance in guiding the study on the on-line as hot mold width adjustment.

论文

) Comparison of application of KR method with that of injection method in hot metal desulphurization

2009, 25(05):  73-77.  doi:

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The two different hot metal desulphurization methods, namely the injection method and KR mechanical stirring method have been compared comprehensively with each other in the aspects of technical equipments, desulphurization effect, temperature drop, iron loss, desulphurization agent, running cost and effect on the operating flow. Results show that for large and medium iron and steel enterprises the KR hot metal desulphurization method is generally superior over the other method.