Steelmaking

Numerical simulation and application on jetflow behavior of cluster oxygen lance

2011, 27(6): 1-4,15. doi:

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The jetflow behavior of two frequently used oxygen lances, namely the cluster oxygen lance and the common super sonic oxygen lance is numerically simulated by software Fluent and the position of the protection gas, the effects of jetflow angle and pressure intensity on the jetflow behavior of the cluster oxygen lance are analyzed and production practice is conducted at the 110 t EAF in Tianjin Iron & Steel Group. Results show that the EAF steelmaking in the corporation is improved and the average refining cycle reduced by 10 to 15 minutes and all indicators of consumption lowered since adoption of the cluster oxygen lance.

Application of poststirring process in 100 t converter

2011, 27(6): 5-7. doi:

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The present paper introduces the poststirring process in 100 t converter. Practice shows that when w(P) in the hot metal is less than 0.040 % in a single tapping the w(P) in the hot metal can be constantly controlled in the limit of less than 0.020 %, the quality fraction of average decarburization maintains at 0.01 % and L_Pimproved by 46.8 by adoption of poststirring exclusively or poststirring plus addition of small amount of ore for 120 to 150 s. Temperature drop of the hot metal is 10.2 and 31.4℃ by poststirring exclusively and poststirring plus addition of ore. Tests show that the dephosporization speed and temperature drop tend to maintain at a fixed value as soon as the poststirring time reaches 120 s and therefore the appropriate poststirring time shall be 120 to 150 s.

Analysis and control on resulfurization in the process of converter steelmaking

2011, 27(6): 8-11. doi:

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By combining theoretical calculation with site tests the resulfurization characteristics in the process of converter steelmaking for Q345R steel are analyzed. Results reveal that the raw materials, the basicity of slag, slag in melted iron and slag remainder in converter have a certain impact on the resulfurization. Under the same smelting technology conditions, the raw material with high content of sulfur is the main reason for resulfurization. Controlling the levels of sulphur in slag accessories and melted iron is an important tool to reduce the final sulfur content in converter. On that basis, the technological measures to reduce resulfurization for Q345R steel are put forward.

Application of skateboard type slag blocking system in 150 t converter in Angang Steel

2011, 27(6): 12-15. doi:

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The technological process of the converter slag blocking and the principle, structure and control process of the skateboard type slag blocking method are briefly described and the adaptable revamp measures and practical results introduces in connection with application of skate board type slag blocking system in the 150 t converter in Anyang Iron & Steel Group Corporation. By application of the skateboard type slag blocking process phosphor pickup is dramatically reduced and the amount of the outlet slag in tapping lowered as well and thus the steel quality is optimized and the purpose of improvement in the economic efficiencies achieved.

Research and application of mould powder for lowcarbon steel slab continuouscasting process

2011, 27(6): 16-19,2. doi:

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By analyzing causes of surface defect of lowcarbon coil in the 4^th Branch Work of the General Steelmaking plant of WISCO it is concluded that the entrapped slag in the mould is the primary cause. On the basis of study on the mechanism of the slag entrapment of the mould by properly readjusting the chemical compositions of the mould powder, raising the viscosity of the mould powder and conducting a comparison test a new mould powder with high viscosity which is most suitable for the continuous casting process of the plant is developed and the operating instructions are accordingly put forward. Results of application show that prominent effects of quality control of the finishing products and improvement in the production consistency can be achieved by adoption of the newly developed mould powder.

Compositions control of low carbon low silicon steel SPHC in thin slab continuous casting

2011, 27(6): 20-23. doi:

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The present paper mainly introduces the compositions control of steel SPHC in the thin slab continuous casting in Wuhan Iron & Steel Corporation, and particularly describes prevention secondary oxidation of the hot metal, reduction of amount of the endogenous and the foreign inclusions in the hot metal and cut down of the nozzle blockage and stopper rise by taking a series of technical measures such as controlling the contents of oxygen, silicon and Al_S in the hot metal, raising cleanliness of hot metal and optimizing the quality of the brick working lining of the tundish as well as implementation of protection casting in the overall process of continuous casting, thus the surface quality of the stock for cold rolling purpose is well improved.

Experimental on production of aluminium steel by BOF→Ar→CC process route

2011, 27(6): 24-27. doi:

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The present paper introduces experiments on production of Al steel by 80 t BOF→argonblowing station→CC process route at the Steelmaking Plant of Chongqing Iron & Steel Co., Ltd., analyzes the control measures for Al and S content in steel and castability in the process of Al steel production and the better results achieved. The chemical compositions of the steel meets the requirements and inclusions and gas contents in the steel are low and its castability good and the quality of the physical products excellent.

Numerical simulation study on jetflow of 100 t converter oxygen lance

2011, 27(6): 28-30,4. doi:28

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Taking 100 t BOF oxygen lance as research object the jet flow of oxygen lance is simulated with Fluent software in order to study the effect of throat diameter, outlet diameter and oxygen flow rate of the lance on the jet flow. By mean of study on the oxygen jetflow the intensity of oxygen supply can be raised, oxygen supply time shortened and production cost cut. Study shows that the best production parameters are throat diameter 36.8 mm, outlet diameter 47.6mm and oxygen flow rate 20 000m³/h.

Study on switch mode about bottom blowing and nitrogen pickup for 260 t topbottom combined blowing converter

2011, 27(6): 31-33. doi:29

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Effects of different flow rate of the bottom blow and switch over time of nitrogen and argon on the nitrogen content in steel are analyzed. It’s concluded that w(N) in the hot metal can be controlled in the limit of less than 30×10^-6 by adopting the switch over mode of nitrogen and argon with 70 % oxygen supply or by taking the bottom blow mode of 85 % oxygen supply switch over with a small quantity of nitrogen bottom blow (not larger than 0.077 m³/(mint)). In the meanwhile by analysis on the processes of smelting and tapping of steel it is affirmed that the best tapping mode for converter is rimming pattern. If addition of deoxidation alloy elements is required in tapping such a few measures as feeding in batch pattern and controlling the oxygen blow time and tapping time have to be taken to prevent against nitrogen pickup in the hot metal.

Study on the influence of Coriolis Force on converter’s flow field using water model

2011, 27(6): 34-39. doi:

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Based on the principle of Coriolis Force and the converter structure, the relationship between Coriolis Force and the converter was analyzed theoretically. It is concluded that Coriolis Force influents converter's flow field via affecting the flow rate of top and bottom gas. And the water model was designed to test and verify the influence of Coriolis Force on converter's flow field primarily. It is shown from the investigation that the counterclockwise trend of bottom gas caused by Coriolis Force take the dominant position in the flow field; when bottom tuyeres was in concentrated configuration. The array of bottom tuyeres must be symmetrical and the distance between tuyeres must be suitable, or the shortest mixing time would increase; the counterclockwise trend caused by bottom tuyeres configuration could be superimposed with the counterclockwise trend of bottom gas caused by Coriolis Force, which can decrease the shortest mixing time of converter's flow field.

Research on factors affecting residual manganese content and its yield in the endpoint hot metal of converter

2011, 27(6): 40-43. doi:

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The factors affecting the endpoint residual content of manganese and its yield rate in the converter process has been researched on the basis of the statistic analysis of the steelmaking production data. Results show that the end point carbon content of converter process and initial silicon content of hotmetal are the key factors affecting the endpoint residual content of manganese and its yield rate. Under the condition of catching carbon operation, the carbon content of molten steel plays a leading role for reduction of the manganese oxide. At this juncture the effect of end point FeO content of slag and end point molten steel temperature of converter on the yield of manganese are not so apparent.

Desulphurization behavior of an 80 t multifunctional single snorkel vacuum refining furnace

2011, 27(6): 44-48. doi:

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To develop the reasonable desulfurization operation parameters of the multifunctional single snorkel vacuum refining furnace, 37 heats desulfurization tests have been carried out to refine ultralow carbon and sulfur steel in an 80 ton multifunctional single snorkel vacuum refining furnace at No. 2 Steelmaking Plant, Shanxi Taigang Stainless Steel Company Limited. The desulfurization results show that the maximum desulfurization ratio of 81.2 % can be achieved, while the lowest sulfur content of molten steel maintains at the level of 10×10^-6. The influences of some basic operation parameters, such as mass of added lime and fluorite as desulfurizer, mass of added metal aluminum as deoxidizer and thickness of topslag in the ladle, on desulphurization rate have been analyzed and discussed. The recommended operation parameters of the 80 ton multifunctional single snorkel vacuum refining furnace with ideal desulfurization ability are summarized as follows, the ideal mass of the added lime and fluorite as desulfurizer is 5.0～6.0and 3.0～3.5 kg/t, while the reasonable metal aluminum as deoxidizer is 5.0 kg/t. Although the thickness of top slag in the ladle has no obvious effect on the final sulfur content and desulfurization rate, the thickness of top slag in the ladle should be strictly controlled as thin as possible because thicker top slag in the ladle has negative effect on other functions, such as decarburization and degassing of the developed multifunctional single snorkel vacuum refining furnace.

Effect of secondary cooling schedule on internal quality of steel round billet for wheel of high speed train

2011, 27(6): 49-52. doi:

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In order to optimize the internal quality of round steel billet for the highspeed train wheel the differences among surface temperature, solidification structure and macrosegregation of casting billets under the two different secondary cooling schedules have been compared in this study. The results show that under both two cooling schedules the surface temperatures of the billets at the straightening segment are all higher than 900 ℃ and thus the straightening cracks will avoid occur since the wheel steel is in such a high temperature zone at the time. The differential rate of equiaxed crystal ratio of the billets is of insignificance and under the condition of overheat less than 55 ℃ both better symmetrical solidification structures and better internal quality of the billets are achieved. Difference lies in that under the condition of No.1 cooling schedule the central segregation of the casting billets is lighter and central shrinkage smaller, however the area of central porosity is relatively larger and the fluctuation of segregation along the direction of upper radius tends to be more severe. It's disadvantageous for the rolling operation at the down stream as well as the quality of the finishing products. Therefore the No.1 cooling schedule is not suitable for production of high quality wheel steel.

Study on the effect of different cooling technology on equiaxed grainratio of coldheading steel billet

2011, 27(6): 53-56. doi:

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By studying cooling technique of continuous casting it is found that primary cooling and secondary cooling intensity have an important effect on ratio of equiaxed grain of billet. When water rate in mould is decreased both the difference of temperature of inlet and exit cooling water in the mould and the heat carried by cooling water are increased and the contact condition between mould and billet and temperature distribution at the solidifying front are improved, thus growth of columnar grain is restrained and ratio of equiaxed grain in the center of billet is enlarged. Change of the secondary cooling water intensity is more advantageous to the growth of equiaxed grain. Comparison experiments show that ratio of equiaxed grain of SWRCH8A and SWRCH35K steel billet is increased through adopting reasonable primary cooling and secondary cooling technique.

Research on cleanliness of 82B steel produced by LD→LF→CC process

2011, 27(6): 57-61. doi:

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The total oxygen and nitrogen content, the number and particle size distribution as well as the chemical composition of micro inclusions and macro inclusions of steel samples taken from different procedures of the whole route have been analyzed systematically by means of using tracer to show the source of nonmetallic inclusions, sampling steel systematically in the whole process and comprehensive analysis in laboratory. The results show that the quality fraction of total oxygen and number of micro inclusions of the steel samples decreased by 62.06 % and 43.57 % respectively after LF refining. The quality fraction of total oxygen and the number of micro inclusions in billet were 28.42×10^-6 and 17.78pieces/mm² respectively on average, and the micro inclusions not exceeding 4 μm accounted for 87.21 %. The refractory of the ladle lining was eroded seriously during LF refining process, especially before LF soft blowing. There was slag entrainment to a certain extent in tundish and mould procedure. The reoxidation caused by air suction during the LF refining before soft blowing and ladle pouring process was relatively serious.

Technology of waste heat recovery from EAF high temperature exhaust gas

2011, 27(6): 62-65,7. doi:

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Large quantity of nonsteadystate high temperature waste fume may generate in the process of EAF steelmaking. In view of this fact residual heat recovery is carried out by means of a watercarbon steel hot pipe type steam generating device and system. The problems such as ash blockage, wear, corrosion and thermal stress have been effectively solved by research and development of the appropriate multielement module structure as well as the ash removal method using powerful shock wave and thus the temperature of the waste fume is effectively lowered to less than 180 ℃ from the original 1 000 ℃ and then it will be delivered to the down stream dust removal device and finally let off. In this way both the purposes of reclamation of residual heat and energy saving can be realized.

Study and practice of reutilization of dust retracted from stainless steel refining

2011, 27(6): 66-69. doi:

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In order to recover and reutilize chromium oxide, nickel oxide and ferric oxide in the reclaimed dust in the process of stainless steel refining a new technology for treatment and application of the reclaimed dust in the stainless steel refining has been developed independently in the Taiyuan Stainless Steel Co., Ltd. The reclaimed dust mixed with reducing agent and bonder is pressed into pellet and then sintered in the high temperature rotary kiln. The sintered material out of the pressed pellet is more convenient for use as the raw material in an EAF. By using the pressed pellet out of the reclaimed dust in combination with oxygen blow by an oxygen lance at the furnace gate in refining the stainless steel stable foaming slag can be formed and the condition of slag sticking on the furnace lining is acceptable and therefore it's more favorable for raising the service campaign of EAF.

Quality estimation system for continuous casting slab

2011, 27(6): 70-73. doi:

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Based on the Quality Estimation System（QES）independently developed by CCTEC, the present paper introduces the principles, functions and application of QES, which is composed of four key modules: data acquisition, quality event triggering, quality tracking and quality estimation. It also involves several major functions such as: tracking continuous casting production in the whole process, monitoring abnormal information, rating slab quality, replying heats and accumulating the experience of metallurgical experts, etc.. This QES used for slab caster in Laiwu Steel is of great in rating slab quality. Its accuracy rate reaches as high as 90.6 %.

Quality estimation system for continuous casting slab

2011, 27(6): 70-73. doi:

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Based on the Quality Estimation System（QES）independently developed by CCTEC, the present paper introduces the principles, functions and application of QES, which is composed of four key modules: data acquisition, quality event triggering, quality tracking and quality estimation. It also involves several major functions such as: tracking continuous casting production in the whole process, monitoring abnormal information, rating slab quality, replying heats and accumulating the experience of metallurgical experts, etc.. This QES used for slab caster in Laiwu Steel is of great in rating slab quality. Its accuracy rate reaches as high as 90.6 %.

Contrast of inclusions in wire rod for steel cord from domestic and overseas

2011, 27(6): 74-78. doi:

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Inclusions in wire rods for steel cord produced at home and abroad are investigated by means of optical microscope, SEM and EDX. The results show that the inclusions of wire rod from Kobe Steel, Nippon Steel Corp, the domestic steel companies A and C are in a low amount and small size. The inclusions in wire rods from POSCO and the domestic steel companies B, D are not only in a relatively large amount but also in bigger size. The inclusions in wire rods from Kobe, Nippon Steel, Saarstahl and the domestic steel companies A, D are distributed in the lowmelting point district (≤1 400 ℃) of the phase diagram while the ones from POSCO and the domestic steel companies B, C are not in the lowmelting point district of the phase diagram. In the inclusions of wire rod from Kobe no MgO can be found, but MgO exists in large quantity in Saarstahl and the domestic steel companies B, D.

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