Steelmaking

Theoretical basis and practical application of dynamic control model for full automatic steel-making

2011, 27(4): 1-4,36. doi:

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According to the practical experience of applying the dynamic control model for many years,the definition,function and systematic derivation of the decarburization and heating formula,the main grouping principles and the management and technology measures for the dynamic control model are described in details.Since the No.4 Steel Plant of WISCO was put into commissioning in the end of 2007,the adaptability for the dynamic control model has been greatly improved and the function of OneKeySteelmaking has been realized by strengthening and refining the management of dynamic control model.In 2010 the average OneKeySteelmaking rate reached 87.21 % and the best one was 93.12 %,and in the second half year of 2010,the C-T hitting rate were over 90 % and the best one reached 94.04 %-.

Application of the automatic steelmaking technology of 300 t BOF

2011, 27(4): 5-8,40. doi:

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The present paper introduces the basic principle and function of steelmaking automation system which has been researched and developed by Danieli Corus and its application in the 300 t BOF of Ma'anshan Iron and Steel Co.,Ltd..In production practice the blowing procedure and the blowend targets are further enhanced by controlling the quality of raw material,ensuring the veracity of basic data,perfecting the function of data collection,optimizing parameters of static and dynamic model etc.

Optimization and practice of production process in 180 t top-bottom combined blown converter

2011, 27(4): 9-11,6. doi:

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In the early days there were many problems in the production such as high consumption and longer taptotap cycle in the No.2 Steelmaking Plant of the Stainless Steel Corporation of Taigang.By optimization of the oxygen blow process,slagmaking scheme and converter operating process and adoption of furnace shape control technology the \[%C\][DK]·\[%O\] of steel in smelting end is stabilized and oxygen consumption reduced to 2.3 m³/t and the service life of bottom blow device improved and the taptotap time shortened to 2 min and the resources comprehensive utilization increased as well.

Research and practice of increase in heavy rail steel endpoint carbon content

2011, 27(4): 12-16. doi:

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In view of the current conditions in the Steel making Plant of Panzhihua Steel & Vanadium Co., Ltd, it's affirmed that by improving the technologies of steel making it is possible to increase the endpoint carbon content of the steel to 0.1 % ~0.2 % in refining the heavy rail steel in the converter. Results show that the endpoint phosphor and oxygen content in steel are rduced in great breadth and the quality fraction of the endpoint carbon can be raised to 0.145 % and the quality fraction of the endpoint phosphor reduced to 0.006 % and thus the requirements of the steelmaking plant for production of high quality heavy rail steel can be met.

^{Development and application of ladle refining technology at argonblowing station}

2011, 27(4): 17-21,5. doi:

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In view of disadvantageous condition in Yuxi Iron & Steel Co., Ltd., which is lack of the ladle refining facility, the ladle refining technology has been developed and applied in the argonblowing station of the Corporation. Through optimization of slagmaking process and inclusions treatment technology as well as improvement of the equipments at argon station the quality of liquid steel and slab has arrived at the level of LF refining technology basically, the continuous casting of the tundish attained more than 18 heats, the qualified rate of smelting components 98.10 % and the qualified rate of slab 99.78 %, and thus the quality demand of various steel grades can be met. Steel grades 08Al, KNS, K510L are already developed successfully and the market competition of steel products in Yuxi Steel is improved.

Development of RH-LF duplex refining process for ULC steel

2011, 27(4): 22-24,2. doi:

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The present paper introduces the development of production process of ULC steel since the RH plant was put into production in Tangshan Guofeng Iron & Steel Co.，Ltd. By comparing different ways of refining the optimized LFRH duplex process is used to stabilize the control of C, N contents and etc. in liquid steel in order to realize continuous casting.

Reasons of formation and preventive measures for edge crack of CSP slab

2011, 27(4): 25-28. doi:

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According to the mechanism of formation of CSP slab edge crack the present paper analyses the reasons of defect proceeding from the aspects of composition of liquid steel in the mould, casting powder, second cooling condition and so on, and then puts forward the measures for effectively control on the edge crack.

Research and control on the steelmaking process for Q420B high strength angle steel

2011, 27(4): 29-32,4. doi:

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The steelmaking process and quality control method of Q420B high strength angle steel is introduced.The results show that the quality and performance of Q420B can meet the standard requirements through the rational process of smelting, refining, continuous casting and microalloying with V and N.

Inclusion control on X70 pipeline steel

2011, 27(4): 33-36. doi:

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The present paper investigated the effect of ladle top slag composition,argon flowrate of soft stirring and casting temperature on the cleanliness of slabs through plantscale experiments during X70 pipeline steel production; ultrasonic CScan method was used to detect the macro inclusions (≥100 μm) in the slabs; inclusion compositions and morphology were analyzed using SEM/EDS.The experimental results show that the micro inclusions could be removed efficiently by soft stirring when the argon flow rate is controlled at around 15 m³/h,and when the oxygen potential of ladle top slag decreases and w(CaO)/w(Al₂O₃) is controlled within the limit of about 1.8 and the argon flow rate of the soft stirring is lowered to 15 m³/h from 30 m³/h as well as the casting temperature of the slab properly rises,[JP2]the index of the large inclusions in the slab goes down obviously.Results of the SEM/EDS show that the inclusions in the slab mainly consist of CaO·xAl₂O₃+CaS,in which the core portion is calcium aluminates (most w(CaO)/w(Al₂O₃) are in the range of 0.75～1.10) wrapped with a layer of calcium sulfide.

Study on the reactivity of lime fast calcined at high temperature

2011, 27(4): 37-40. doi:

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The effect of temperature and time of calcination as well as different type of the test pieces on the reactivity of the fast calcined lime has been researched in the laboratory. Research results show that provided that the limestone with size 12～15 mm is calcined at the temperature from1 300 ℃ to 1 400 ℃ for 7 minutes, the reactivity of lime is higher than 335 mL and it will increase with the calcining temperature. When the calcining time is more than 12 minutes the overburning of lime calcined at temperature from 1 300 ℃ to 1 400 ℃ appears and the reactivity of lime obviously decreases. Increasing the size of limestone will decrease the reactivity of lime. If the limestone sample calcines at 1 400 ℃, the cylindrical sample pressed with limestone fines is more easily overburning contrasting to grain limestone sample.

Numerical simulation of three dimensional fluid flow of basic oxygen furnace

2011, 27(4): 41-46. doi:

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Numerical simulation of the 3dimensional flow field of the 100 t basic oxygen furnace(BOF) has been carried out by commercial software FLUENT. The gas flow distribution, bath surface morphology and velocity distribution in different periods, and velocity distribution in different bath depth have been analyzed and discussed according to the simulation results. The results show that the maximum velocity appeared at the dent, whereas the velocity decreases obviously at the exterior area of the dent. The bath velocity decreases sharply with the increase of the bath depth. The weak stirring zone lies in the middlebottom and the edge region of the bath.

Simulation study on optimization of bottomblown scheme for 120 t top-bottom combined blown converter

2011, 27(4): 47-50. doi:

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In this paper, bottomblown scheme of Tian Steel 120 t converter has been investigated by cold physical simulation for seeking the optimum
bottomblown scheme, and the production practice carried out as well. The results show that bottom blowing has a great effect on the
minimum mixing time of molten steel and the mixing time trends to decrease with the increase of number of tuyeres. Comparing with traditional bottom blowing scheme the differential bottom blowing schemes (linear and V type) decrease the mixing time of molten steel, especially
linear scheme. An obvious improvement of BOF performance has been observed since the optimization of the bottom blowing gas supply and
the steelmaking process improved as well.

Study on the composition change of low-carbon low-silicon high-aluminum steel in smelting process

2011, 27(4): 51-53,5. doi:

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According to the actual converter production in No.3 Steelmaking Plant of MaSteel, 38 heats of lowcarbon lowsilicon highaluminum
(Low-C Low-Si High-Al) steel are smelted using doubleslag process and singleslag process respectively. By analyzing the element
changes in the process of steel smelting such as carbon pick up, silicon pick up, Al loss and Ca loss the key technology steps are obtained to
control the change of different elements in the smelting process of LowC LowSi and HighAl steel.

Research on desulphurization using recycled LF as hot slag with added lime

2011, 27(4): 54-57. doi:

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According to the data of slag recycling at the Second Steelmaking Plant in XinYu Iron and Steel Group the present article analyzes the effect of desulfurization using the as hot slag with proper addition of lime. The results show that the refining slag with the alkalinity from 2 to 3 still has some sulfur capacity and the as hot slag can increase the desulfurization capacity by supplying a certain amount of lime. Industrial experiments show that by supplying 3～4 kg/t lime to the as hot slag and adding a certain amount of fluorite the desulfurization rate can come up to 80 % or more. Phases of the recycled LF hot slag have been analyzed by XRD and EDS and the morphology change of the recycled slag examined by the ore phase microscope as well. Analytical results demonstrate that the slag phase of the as hot slag which has been reused twice basically remains intact and it consists primarily of C₂S、C₃S、C₂A、CA，and the calcium aluminate compounds increases with the increase of the number of recycle and slag mixing condition improves to some extent. The significance of reuse of the as hot slag lies not only at cost reduction, but also lower the hazard of environmental contamination.

Influence of RH process and nozzle blocking on mixing time

2011, 27(4): 58-60. doi:

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A water model of 1/4 linear scale for 210 t RH has been established. The mixing time of different number of blocked nozzles and different
processing parameters such as the lift gas flow rate, dipping depth and liquid level of vacuum chamber was measured. The results show that
when the lift gas flow rate is larger than 800 L/min, the dipping depth is over 560 mm, the liquid level of the vacuum chamber exceeds
315 mm and the number of blocked nozzles are not more than 3 the hot metal in the RH chamber is better mixed. On the basis of the experiments the onsite operating processes are further improved and thus the RH refining efficiency is raised accordingly.

Study on the production process of 610 MPa grade NbTi microalloy hot rolled plate for auto beam by FTSR line

2011, 27(4): 61-64. doi:

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The 610 MPa grade hot rolled steel for auto beam use has been studied and produced by proper design of chemical compositions of the steel
and adoption of the processing route of hot metal pretreatment→120 t top and bottom combined blown converter→LF refining→FTSR
(Flexible Thin Slab Rolling) continuous casting machine→2R+5F mill coiling with TMCP process. The examination results show that the
structure of plate consists of ferrite+ bainite + minor MA with grain size
2.08 μm. And the mechanical properties of the steel grade are in
conformity to the standard requirements. By way of SEM observation it is found that the impact fracture belongs to the toughness fracture
and at the bottom of the toughness dimples exist many spherical micro CaS particles.

Effect of alloying elements on mechanical properties of maraging stainless steel

2011, 27(4): 65-69. doi:

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The effects of alloying elements on the mechanical properties of the maraging stainless steel are studied. Results show that the principal
alloying element affecting the strength and hardness of the steel is element Ti， and Cu is the element that can most effectively improve the
fracture toughness of the maraging stainless steel， and as far as the effects on the strength and toughness of the steel is concerned alloying
elements Ni and Mo are of little significance. On the basis of the studies the alloying compositions of the maraging stainless steel are further
optimized and thus the alloy steel containing such compositions possesses super high strength (R_m=1 610 MPa) and high toughness (K_IC=94 MPa·m^1/2) simultaneously and conforms with the standards of the super high strength and high toughness alloying steel.

Technical development status of steelmaking by electrical arc furnace in TISCO

2011, 27(4): 70-73. doi:

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The conditions of the steelmaking equipments of five EAFs in Taiyuan Stainless Co., Ltd.are introduced. In light of the characteristics of different steel grade refining as well as the raw materials in use, different refining processes of EAF are developed. Application and development of the technologies for refining the carbon steel and stainless steel are described in particular.

Research status of surface crack in medium and heavy plateof microalloyed steel during hot charging

2011, 27(4): 74-78. doi:

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The research status of surface crack in microalloy steel medium and heavy plate domestic and overseas is introduced. A variety of reasons are summarized and analyzed, the influence of original slab cracks, residual harmful elements, hot charging temperature, carbonitride precipitation behavior resulting from microalloy elements, rolling reduction summed up. The problems existing in microalloy steel medium and heavy plate was analyzed and put forward the orientation of the research in the future.

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