Table of Content

05 December 2012, Volume 28 Issue 6

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生产实践

Optimization of melting process of 50 t ultra-high electric arc furnace

2012, 28(6):  1-6,10.  doi:

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The steelmaking process and the production data of 50 t ultrahigh power electric arc furnace are analyzed in this paper, and the values of electric power consumption and oxygen consumption are gained by the EAF mass and heat balance calculation of different hot metal charged ratio, including production practice in Laiwu Steel Pants. Then four steelmaking operation models for different working conditions helpful for the same kind of EAF plants are put forward.

Analysis on effect of 100 t converter bottom blowing components maintenance and combined-blowing

2012, 28(6):  7-10.  doi:

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The article introduces the top and bottom blowing technology of SHOUQIN 100 t converter. By controlling a reasonable thickness of the converter bottom, adjusting the final slag composition and optimizing the slag splashing process the campaign life of the converter reached 8 000 heats. The bottom gas supply gas of the elements are close to the designed strength. As the results the metallurgical effects are ensured and synchronization of the converter top and bottom combined blow with the furnace campaign is realized as well.

Application of RH-MFB oxygen blowing decarburization model

2012, 28(6):  11-14,2.  doi:

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In order to further explore the functions of RH-MFB in the Vanadium Recovery and Steelmaking Plant of Panzhihua Steel & Vanadium Co.，an oxygen blow decarburization model for the purpose to guide the deep decarburization process mode for the extralow carbon steel (IF steel) is built up and the process operation is persistently perfected and optimized as well. As the results the qualification rate of the end point of the w(C)≤30×10-6 reaches 90 %and marked results are achieved as well.

Optimization of F-EMS parameters in C70DA steel billet casting

2012, 28(6):  15-17,2.  doi:

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Liquid core and magnetic induction in high carbon steel C70DA billet with FEMS were investigated by using rivet shooting and Tesla meter CT3. The results indicated that wider liquid core and insufficient stirring force are the main causes for heavy center segregation and porosity. The casting and FEMS parameters were therefore optimized by increasing specific secondary cooling water from 1.51to 1.73 L/kgand adjusting F-EMS frequency and current to 11Hz and 500 A. Correspondingly, the thickness of liquid core at F-EMS has been decreased from 60 mmto 54 mm, and the maximum stirring force achieved. With the optimized parameters, center segregation and porosity are alleviated greatly in the C70DA steel billets.

Study on solidification rule for slab in Anyang Steel and its applicatio

2012, 28(6):  18-21.  doi:

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The present article introduces three methods for measurement of integration solidification factor of slab caster , i.e. measurement of the broken slab shell, the characteristics of defect slab and the nailshooting test aiming at checking the rationality of the integration solidification factors selected for various steel grades and fixing on the final solidification points for those steel grades in order to provide the necessary scientific data for optimization of the design on the roll gap shrinkage and improvement in the cooling system. By measurement, calculation and analysis the integration solidification factors 0.024 0,0.022 1and 0.022 4~0.025 5m·min-0.5 are obtained respectively and relationship between the shell thickness and the solidification time is depicted by way of the accidental shell measurement method and the practical solidification equation basically agrees with the theoretical equation. By optimizing the roll gap and by modifying the cooling system the rating of macrostructure of the slab namely 1.0grade for center segregation, 0.5 grade for center porosity and 0.5 grade for middle crack at class C are realized.

Process practice of low-carbon sulfur bismuth free-cutting steel

2012, 28(6):  22-24,3.  doi:

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The present paper sums up key factors in technology processes such as the metallurgical process, continuous casting process and rolling process to ensure the quality of the hot-rolled bar in production of low-carbon sulfur bismuth free-cutting steel 1214Bi.Test results show that distribution of inclusions in hotrolled bar of free-cutting steel 1214Bi is homogeneous and granule of Bi in the steel is exiguous and homogeneous and the cutting performance of free-cutting steel 1214Bi is excellent.

Trial production of 45Mn2 steel by round continuous casting process

2012, 28(6):  25-28.  doi:

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In consideration of the nozzle clogging in continuous casting process and quality requirements of 45Mn2 steel some effective countermeasures such as adding slag during tapping, adopting refining slag with high basicity and calcium treatment in LF refining. With these countermeasures, 45Mn2 steel with good quality can be produced successfully. Test results show that it is feasible to produce 45Mn2 steel by “BOF→LF→round continuous casting” process with semisteel, and there is no surface and internal quality defects for casting billets. The ratings of various macro defects are all below grade 1.0 and the rate of slab after rolling is 90.2 %, steel mechanical properties meet user requirements.

Practice of economically producing GCr15 steel by new short process route in EAF

2012, 28(6):  29-32.  doi:

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In order to lower the production cost and meet the market demand a new money saving process technology for EAF, namely “flexible ultrashort process” for refining special steel is developed. By application of the process continuous casting billets in different sections can be casted simultaneously in the similar tundish and similar casting and then the bearing ring can be forged directly with rolling. Therefore batch production of the round billets of Φ150 mm and Φ180 mm for the bearing steel such as GCr15 in low cost through CCM can be realized in EAF. The quality of the round billets is excellent and the production cost can be
cut down by 255 yuan/t.

试验研究

Key technologies of smelting 40Cr steel with converter

2012, 28(6):  33-36.  doi:

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To solve the problems of low cleanliness level and surface transverse cracks and longitudinal cracks of slab, the steelmaking process for 40Cr was optimized such as raising the content of carbon in molten steel, optimizing the deoxidation process and the composition of LF refining slag, selecting proper alloy and accessories and controlling reasonable calcium content. The industrial practice shows that by increasing the amount of Al alloy deoxidizer and using the low nitrogen alloy materials the composition of LF refining slag can be controlled in the range of w(CaO)=50 %～55 %，w(Al2O3)=22%～26%，w(SiO2)=10%～12%，w(MgO)=5 %～8 % and w(Ca)/w(Al) controlled in the range of 0.06~0.18and w(Ca)/w(S) controlled in the range of 0.14~0.36after calcium treatment for 10 min in ladle and the mass fraction of T.O of slab controlled below 20×10-6,and the mass
fraction of nitrogen below 60×10-6. Furthermore, The pourability can be improved obviously.


Analysis on refining effects of ladle furnace for pipeline steel

2012, 28(6):  37-39,5.  doi:

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The refining effects of LF used in pipeline steel production in a specific Iron and Steel Works are analyzed and the influence of basicity of the refining slag on the T.O in steel, variation of (MnO+FeO) and mannesmann index（R/w(Al2O3)）in the slag as well as the desulfurization effect of the
slag are investigated. Results indicate that the basicity of refining slag can be controlled with the range of 5.47~7.53, which conforms to the specification of basicity for high quality steel grade. However the mass fraction of (MnO+FeO）is higher (2.0%on average) and the mannesmann index in the LF refining slag is lower relatively and thus the flow ability and inclusion absorb ability of the slag are jeopardized to some extent. The desulfurization rate arrives at 62.5%averagely in the process of LF refining and thus the desulfurization results are quite acceptable.

Study on numerical simulation of liquid steel flow field in RH refining process

2012, 28(6):  40-43,4.  doi:

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Mathematical simulation and analysis of the flow field in the 170 t RH refining bath are carried out by application of Oulerian model as well as the boundary calculation conditions and initial conditions more close to the actual production. The results show that the flow filed and circulation flow rate gained with the revised model are similar with the laboratory results. The steel velocity in the up leg presents M shape distribution and the rising Ar bubbles present cyclical fluctuations while the steel velocity in the downleg is distributed uniformly. The inner wall in the up-leg is more easily eroded than that in the down-leg because of the gasliquid two phase flow in it.

Analysis on factors affecting slab surface transversal corner crack for boron bearing medium-carbon steel in continuous casting

2012, 28(6):  44-48.  doi:

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Based on the production practice of boron microalloyed mediumcarbon steel A36LB, the influence of molten steel compositions, boron content in steel,
oscillating curve, cooling water flow in mould, secondary cooling scheme and and rolling gap precision on the transversal corner cracks in slab are analyzed, and the corresponding control measures are put forward such as making w(S) less than 0.015%, making the w(Mn)/w(S) not less than 37.6,
strictly controlling the w(Ca)/w(Als) more than 0.09 in molten steel, decreasing stroke by 1mm and improving frequency to reduce negative
sliding time by 32%, maintaining the cooling water volume on the level of 4000 and 380L/min at the wide and narrow face of the mould, adopting
the soft cooling curve to reduce the total volume of the secondary cooling water and at the same time cutting down the water volume at the edge portion of the slab
by 50% to raise the temperature of the slab edge, measuring the roll gap with the roll gap meter regularly so as to check, repair and exchange the worn out
roll group timely and maintain the precision of the roll gap with in an appropriate range. As the results the corner cracks of the slabs are effectively improved and thus
both the degradation rate and quality dispute rate are lower than that of the steel grade Q235 refined in the Plant.

Experiment study on improving solidification structure of concast slab with electromagnetic stirring

2012, 28(6):  49-51.  doi:

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By application of the orthogonal design method the effect of the process parameters of the electromagnetic stirring on the quality of the slab is studied and at the same time a series industrial scale experiments are carried out using the optimized parameters of the electromagnetic stirring to find out the effects of electromagnetic stirring on the equiaxed crystal rate and dendrite arm spacing of the solidification structure of the slab. The results show that the equiaxed crystal rate of the slab raised by
9.48 %, the primary and secondary dendritic spacing decreased by 6 %, 11.7 %respectively and refined the slab structure. EMS has improved the slab quality effectively.

Research of influence of electromagnetic brake on ultra-low carbonsteel surface quality

2012, 28(6):  52-54,7.  doi:

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n this article the influence of mold electromagnetic brake on the slab surface inclusion defect and quality of cold rolled sheet are studied. The results show that by using electromagnetic brake the larger inclusions in the surface layer of the slab can be reduced and the surface quality improved significantly and the occurrence rate of the surface defect of the cold rolled sheet is reduced from 0.68 % to 0.14 %.

生产实践

Effects of secondary cooling intensity and two different crosssection on central carbon segregation of billet and bloom of 82B steel

2012, 28(6):  55-59.  doi:

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The secondary dendrite arm spacing (SDAS) and central carbon segregation of 240 mm×180 mm bloom and 150 mm×150 mm billet of 82B are studied. Results show that under the similar condition of the secondary cooling water ratio the cooling intensity by mist cooling can be doubled than that by the spray cooling. For billets the central carbon segregation can be reduced by an increase of the secondary cooling water since the SDAS decreases with increase of the secondary cooling water. In the meanwhile the central carbon segregation of the billets can be more effectively reduced by application of F-EMS to increase the equiaxed grain ratio than by reduction of SDAS. The central carbon segregation of bloom is usually worse than that of the billets. The central carbon segregation of the bloom can hardly be reduced by increase of the intensity of the secondary cooling and the central carbon segregation of the bloom can be reduced to certain extent by application of F-EMS but the segregation index of the bloom is still higher than that of the billet.

试验研究

Optimization of installation location of permeable bricks for 250 t ladle

2012, 28(6):  60-64.  doi:

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The optimal installation location of the permeable bricks of ladle and the best immersion depth of the CAS hood are experimentally simulated by application of a 1/4 scale water model. The optimal gas blow rate is determined for the ladle argon blow process and the appropriate argon blow rate for the different thick slag layer is discussed as well. Results of the study are not only beneficial for improving uniformity of composition and temperature, but also for increasing purity of the molten steel and improving the metallurgical effect of argon blowing.

设计改造

Optimization and design of cooling water channels for copper plate wall of beam blank mold during continuous casting

2012, 28(6):  65-69.  doi:

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Two-dimensional heat conduction models of beam blank molds were developed by using finite element software. Thermal behavior of mold copper plate was evaluated in detail with different cooling channels. Attention was focus on the peak temperature and temperature uniformity along hot face. The results show that the peak temperature of existing mold, about 339.6 ℃, is located in the fillet, and two valleys of hot face temperature are found in flange corner and junction of wide face and narrow face, respectively. Increasing diameter of restrictor rods and changing the surface shape of restrictor rods can all reduce peak temperature and improve temperature uniformity along the hot face. Also, the effect of conventional water channels design can be improved by adding a small hole in fillet and changing the small holes in fillet into large hole. However, the best way to decrease peak temperature and improve temperature uniformity along hot face is to redesign the water channels. The water channels design of unevenly distributed equal diameter small holes and unevenly distributed annular channels plus small holes can greatly decrease peak temperature and thermal gradient of mold，which have good application effect in plant test.

辅助技术、材料及设备

Numerical simulation and optimization research of combustion characteristics of the ladle baking equipment

2012, 28(6):  70-74.  doi:

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Using commercial soft Fluent, and finite difference and Simplec methods, numerical simulation and optimization research of gas flow, combustion and heat transfer in ladle during the baking process has been carried out. The influences of airfuel ratio, preheated air temperature and gas flux on the temperature distribution of ladle are quantitatively analyzed. Results show that when the air-fuel ratio is four, raising the flux of gas appropriately and preheated air temperature are effective measures to obtain the better baking temperature of the ladle. It is of great importance to guide the practical production. The simulation results are basically consistent with the measured ones.

Extraction of metal iron from steel slag by using a two-stage wet grinding magnetic separation method and initiative study on re-utilization of mud tailings

2012, 28(6):  75-78.  doi:

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In order to extract the residual metal iron from the steel slag tailings, the side products left by several stage of dry crushing and magnetic separation in a specific Steelmaking Plant by wet milling and separating the steel slag tailing which contains 22.05 % T.Fe and 2.99 % metal iron in two stages respectively T.Fe with iron grade of 89.88 % has been obtained. T.Fe yield is 11.25 % of iron fine. By XRD spectrum analysis only a monophase of metal iron can be recognized in the iron fine. The mixture of mud tailings out of the magnetic separation with a small quantity of desulfurized gypsum from flue gas waste can be prepared into pure mud blocks. The compressive strength of those prepared blocks can reach 1.13 MPa after curing for 3 days and the compressive strength will arrive at 4.85 MPa after 60 day curing and the strength is expected to further increase afterward. Those pure mud blocks could be used as a cementing materials in the underground mining backfilling in substitution of the ordinary portland cement.