Table of Content

05 December 2009, Volume 25 Issue 06

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专题论述

Integrated technologies of the platform for clean steel production—an important direction of the technology progress in Steelmaking

2009, 25(06):  1-4.  doi:

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echnology of clean steel platform is an outcome of engineering science formed on the basis of assembly of new academic theories and integration of achievements of fundamental and technical sciences of steelmaking. It is also an important direction of steelmaking technology and has the universal characteristic in the new century. The concept and connotation of the platform for clean steel have been discussed. The concept of clean steel not only bears the meaning of quality, but also have the significance of economics. It will be the main symbol of competitive power of steelworks.

生产实践

Research and application of the long life technology of stirrer in KR desulphurization

2009, 25(06):  5-8.  doi:

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Based on the analysis of the damage of KR desulphurization stirrer, the influence of the metal core configuration, refractory of work liner, hot repair material and repair technology on the life of stirrer was particularly discussed in this paper. And thereupon a whole process control integrated technological plan for extension of the stirrer service life from the preparation of the stirrer to the effective usage is drawn up. By way of technological research in 3 aspects and various technological integration and repeated industrial experiments the reliable integrated technology for prolonging the service life of the stirrer has been achieved and put into practical application of actual production. Nowaday the service life of the stirrer remains on the level of 730 times successfully.

Study on the control of acid-soluble aluminum of high grade pipeline steel

2009, 25(06):  9-11.  doi:

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The relation of [%O],[%S], the refining slag and acid-soluble aluminum in high grade pipeline steel are calculated. When the contents of acid-soluble aluminum are 0.0045% to 0.0073% the contents of [%O] can be controlled within the range from 3 to 5ppm. And when the sulfide capacity(C'S) is higher than 0.02, 0.04 and 0.07 the content of [%S] should be kept below 20ppm, 8ppm and 5ppm respectively. Results of analysis on the high grade pipeline steel produced by LF-VD refining process show that when the content of acid-soluble aluminum is 0.035%, the content of [%O] is 1.76ppm, and the sulfide capacity(C'S) of top-slag is 0.01 during LF1, 0.022 during LF2, and 0.023 during the end of VD and the [%S] of steel is 80ppm during LF1, 20～30ppm during LF2, and below 20ppm during final phase of VD. They are in full agreement with the calculated result.

Application of control technique of low hot metal ratioin converter

2009, 25(06):  12-14.  doi:

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By taking a few technical measures such as solution of the problem of heat deficiency in the converter and optimization of the operating process in a bid to reduce the amount of the hot metal charge not only the hot metal ratio in the furnace is lowered but also the problem of matching of the productivity between the steel-making system and the iron-making system is solved simultaneously in Chongqing Steel.

Process of smelting low phosphorus steel in combined blowing converter

2009, 25(06):  15-19.  doi:

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The present paper discusses the process conditions of smelting low phosphorus steel by conventional process and hot metal dephosphorizing pretreatment and direct steel-making process in combined blowing converter. Steel Plants A and B adopted the conventional process. For those two Plants when the（%T.Fe）is 16～24% and the slag basicity is 3.5 the low phosphorus steel with [P] less than 0.01% can be consistently produced only if the end-point w(P) in steel is controlled in less than 0.01%. Nevertheless Plants C and D introduced the hot metal dephosphorizing pretreatment and direct steel-making process. For them the w(P) in steel can be controlled in less than 0.01% as soon as the condition of w(C)<0.10 % is achieved. For the latter one of those two processes the key points in the dephosphorizing and decarburizing phases are controlling the total slag volume and [P] after dephosphorizing pretreatment. In order to control the total slag volume/ton steel within 90kg in smelting the low phosphorus steel with [P] less than 0.01% the highest level of [P] after dephosphorizing pretreatment should be controlled in 0.026～0.037% when the deslagging rate in the period of dephosphorization arrives at 40 %～50 %.

Effect of oxygen used in steel-making on splash in converter

2009, 25(06):  20-21.  doi:

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The origin of splash in the converter including the oxygen supply schedule in the steel-making is analyzed in light of the actual production conditions in the three branch plants of the Central Steel-making Plant of WISCO and counter control measures put forward as well.

Optimization of the technology of furnace protection by slag splashingin combined blown converter

2009, 25(06):  22-25.  doi:

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The average final carbon of the liquid steel of the converter is 0.03-0.06% in the Medium Plate& Coil Plant in NISCO and therefore the erosion of furnace lining is very serious, as the results the effect of slag splashing on the furnace protection is of little use. In order to solve the problem physical simulation on the technology of furnace protection by slag splashing in the combined blown converter has been carried out and the processing parameters for the slag splashing technology optimized and as-hot test on the modification of the furnace slag conducted using the slag modifier and the modified furnace slag already applied to the actual production. In the end very satisfactory results are achieved.

Development and application of RH pre-melted desulphurizer

2009, 25(06):  26-28.  doi:

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In light of the disadvantages of desulphurizer of CaO-CaF2 system such as severe erosion to the RH immersion tube and heavy contamination of the environment，a new CaO-Al2O3-SiO2 system based pre-melted desulphurizer was developed by adding some components with high basicity and good sulfur capacity. The results obtained from the experiments shows that the new pre-melted desulphurizer is characterized with rapid desulphurization rate, less erosion to the RH refractory and good desu1furization efficiency．The average desu1furization efficiency is over 50%.

Production practice of hot rolled ribbed bars by alloying with MnSi and SiC

2009, 25(06):  29-32.  doi:

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The present paper introduces the production practice of hot rolled ribbed bars by Alloying with MnSi and SiC in KISC. The results show that alloying with MnSi and SiC in converter can not only ensure the quality and mechanical property of hot rolled ribbed bars, but also the alloy consumption cost is largely reduced and better economic benefits achieved.

Study on the effect of roll gap shrinkage optimization on slab quality

2009, 25(06):  33-36.  doi:

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The present paper briefly describes the principles and functions of roll gap static shrinkage. By study on the reduction zone choosing and reduction control proportioning of each segment a few of new plans of roll gap shrinkage are determined and their utilizing effects are compared. In the practical production it’s proved that the level of central segregation of the slab is prominently lowered and the central porosity removed and thus the internal quality of the slab improved and the quality rate of the post rolled slab raised and the problem of central lamellation of the sample occurring after drawing solved and the satisfactory results achieved.

Application of new technologies of liquid steel cleanliness improvementin continuous casting process

2009, 25(06):  37-39.  doi:

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The present paper introduces the latest improvement of continuous casting technologies and equipments in the 2nd Branch Works of the Central Steel-making Plant, WISCO including automatic control system for crystallizer level, vibration detection technology for outflow slag process at ladle, application of ceramic filter at tundish, development & application of IFD pre-melt tundish slag, application of continuous temperature-testing technology, etc. Furthermore, it outlines the actual effect on improving the cleanliness of the liquid steel in our branch Works through the application of the above-mentioned new technologies and equipments.

试验研究

Influential factors of end-point sulfur content in the process of hot metal desulphurization by magnesium injection

2009, 25(06):  40-42.  doi:

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In refining the tire cord steel, the end-point sulfur content in hot metal should be controlled in a relatively low level in the process of desulphurization by magnesium injection. However, the controlling model does not work very accurately at present. To increase the utilization rate of granular magnesium and analyze the factor affecting the end-point content of sulphur a statistics model is built according to the equilibrium relation between magnesium and sulphur in the hot metal in a purpose to establish a theoretical relationship between the end-point sulphur and magnesium utilization, magnesium consumption / ton steel, initial sulphur content and sulphur equilibrium constant and then a relationship between magnesium utilization and the process parameters is set up by regression analysis. The model can depict the effects of various factors on the sulphur. Model analysis show that the utilization of magnesium can be raised and the end-point sulphur content reduced by properly lowering the injection rate of magnesium, raising the nitrogen flow and designing a reasonable configuration of the nozzle.

Experimental research on the effect of slagging schedule on deep dephosphorization in converter

2009, 25(06):  43-45.  doi:

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The effect of the slagging schedule on the deep dephosphorization in the late period of dephosphorization by double slag technology has been studied in an intermediate frequency induction furnace by simulating the hot metal refining conditions in a converter. Results show that basicity and amount of slag are the two main factors affecting the deep dephosphorization .When phosphorus content in steel comes up to 0.022% and FeO content increases from 25.0% to 30.0% in the slag more than 82% dephosphorization rate and less than 0.0030% phosphorus content can be obtained, in certain case 0.0005% (the lowest level) can even be realized by using the slag with basicity of 3.2 to 4.0 and slag amount from 6.2 to 8.4 kg / t.

Study on the total oxygen content control of steel in the process of RH treatment

2009, 25(06):  46-49.  doi:

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According to the production data about ultra-low-carbon (ULC) Al-killed steel produced by RH(300 t ladle) Process the present paper analyzes changes of the total oxygen content and the amount of inclusions in steel during the RH process and discusses the effects of the processing factors such as the argon blowing intensity, the chemical compositions of the top slag, the treatment time, the initial dissolved oxygen content and oxygen pickup in the processing on the inclusions and total oxygen amount in steel, thus providing the technological support for further optimizing the RH treatment process and raising the cleanliness of liquid steel.

Effect of Nitrogen on the mechanical properties of 21Cr-11Ni-N heat resistant steel

2009, 25(06):  50-52.  doi:

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n this study, test samples of 21Cr-11Ni-N heat resistant steels with different amount of nitrogen were smelted by vacuum induction furnace, and their room and elevated temperature mechanical properties were investigated. The results show that at room temperature the yield strength and the tensile strength of the test steel are improved with an increase of the nitrogen content and at the elevated temperature the creep rupture strength can be raised by increasing the nitrogen content.

Effect of slab strain on Nb(C,N) precipitation in continuous casting process

2009, 25(06):  53-55.  doi:

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The effect of slab strain on Nb(C,N) precipitation in the continuous casting is analyzed by a strain-induced precipitation model. The results show that change of the drawing speed may affect the minimal Nb(C,N) precipitation time to some extent and under the conditions of the similar strain and strain temperature the quicker the drawing speed is, the shorter the duration of the quickest precipitation time of Nb(C,N) will become. In the bending zone and leveling zone the effect of change of slab strain on the Nb(C,N) precipitation behavior can be ignored in the process of Nb(C,N) precipitation in continuous casting due to less strain and strain rate of the slab.

Research on influence of unstable casting on slab quality

2009, 25(06):  56-58.  doi:

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By way of investigation of the slab quality in the process of unstable continuous casting of the slab as well as analysis of the sample the effects of various unstable castings on the surface quality and inner quality of the slab are analyzed, and thereupon a reliable basis for determination of the slab quality and special treatment of the undesirable cast slab is provided in production of the high quality and high added value products by unstable casting.

Study on periodic fluctuation of mould level in slab caster

2009, 25(06):  59-62.  doi:

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The present paper introduces the general situation of the No.2 Slab Caster in Meishan Iron & Steel Works as well as the feature of the mould level fluctuation of the caster and it’s proved that casting blank bulging and disarrangement of the equal space rollers in the 2nd cooling zone are primary causes to the periodical fluctuation, and the process conditions may have effect on it to some extent. Results show that the mould level fluctuation is in direct proportion to the roller space and in inverse proportion to the drawing speed. This conclusion is verified by measuring displacement of the frames in the segment section and load on the pull rod. It is of guiding significance for the continuous caster design and production in the future.

Industrial experiment on production of heavy rail steel with continuous casting process

2009, 25(06):  63-66.  doi:

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The quality control test of rail steel production by EAF steelmaking→LF refining→VD degassing→round bloom concasting process is briefly discussed. The internal quality and non-metallic inclusions of round bloom were improved by application of the Al free deoxidization process and vacuum degassing device and proper control of the the overheat of the hot metal and the drawing speed in the process of casting. In the heavy rail steels produced in this way the T[O]≤20×10﹣6 and inclusions Class A≤1.5, Class B≤1.5, Class C≤1.0, Class D≤1.0, general porosity≤1.0, central porosity≤1.5, the scattered segregation ≤1.0 and the ratio of equiaxed crystal zone ≥40%. By optimization of the mould electromagnetic stirring process parameters and proper design of the ingredient of the mould flux for the heavy rail steel the surface quality of the bloom can be ensured and the surface defects of the round blooms such as surface crack , blowhole, scar, laminar, pit and slag entrapment be removed and the surface defect free round blooms exceed over 90%.

辅助技术、材料及设备

Operating practice of tapping hole maintenance and repair in 300 t converter in Baosteel

2009, 25(06):  67-69.  doi:

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The present paper discusses the general pattern of the maintenance and repair on the tapping hole of the electric arc furnace ( EAF) and by improving the maintenance pattern of the 150t EAF in Baosteel changes of the complete tapping hole are reduced and the service life of the inner lining of the tapping hole prolonged and the production rhythm stabilized and the construction method simplified. It’s more convenient to operate and popularize.

Application of dry dedusting process in 250 t converter

2009, 25(06):  69-73.  doi:

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The Dry dedusting process (LT Process) has been applied in the flue gas purification and recovery in the 2x250t converters of Steel-making Plant of Hanbao Co., and the LT process is composed of flue gas cooling, purifying, and control system and the equipments of the system mainly consist of evaporation cooler(EC), Electrostatic Precipitator(EP),Axial Flow ID Fan, Switchover Station, Exhaust Stack and Gas Cooler. Production practice demonstrates that the system is running smoothly and the dust removal rate is high, its running cost low and the dust content in the flue gas after purification only 6.8mg/Nm3.

综述

Stability processing technology and application prospect of steel slag

2009, 25(06):  73-78.  doi:

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Steel slag has an excellent physical and mechanical properties and some hard-water activity, fully meet the specification of engineering materials, but the size of its potential instability has seriously hampered the application of steel slag works. This paper summarizes the utilization of domestic and foreign steel slag research, analyzed the factors that caused the reasons for expansion of steel slag, to improve the stability of the process approach, and look forward to prospect the engineering application of steel slag.