Table of Content

05 April 2012, Volume 28 Issue 2

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生产实践

Process flow and its application practice at Shougang Jingtang new generation steelmaking plant

2012, 28(2):  1-6.  doi:

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The technology for clean steel production in a modern steelmaking plant is analyzed and the technological philosophy of the clean steel production with efficiency, manufacturing cost and product performance as its core is also put forward. By way of reviewing and integrating the manufacturing functions of the high efficiency, low cost and high quality steel produced by the steelmaking plant of new generation and by optimizatiing allocation of the operating procedures such as hot metal pretreatment, converter smelting, secondary refining and continuous casting with the help of the dynamic and precise design system in connection with the design and research of the steelmakingcontinuous casting process at Shougang Jingtang Iron & Steel Plant a clean steel production platform with dynamic and orderly production system as its base is built up.

Application of high efficient desulfurization process in KR complex desulfurater

2012, 28(2):  7-9.  doi:

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On the basis of the characteristics of the 200 KR desulfurization equipments and its operating processes in the No.4 Branch of General Steelmaking Plant of Wuhan Iron and Steel Corporation a high efficient desulphurization method is developed. Results of application show that by application of the newly developed process not only product quality and productivity as well as desulphurization effects can be ensured, but the ratio of the low sulphur steel products w(S)≤60×10^-6 is also raised by 31 % and in the meanwhile consumption of conventional CaObased desulphurizer is lowered by 24.0 % and consumption of passivation CaO based desulphurizer is reduced by 10.7 %. Thus both good technological and economical results have been achieved.

Development and application of prediction model of end pointphosphorus content in 260 t converter

2012, 28(2):  10-13,2.  doi:

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In light of process characteristics of the converter refining and the production data of the Steelmaking plant of hanbao Iron & Steel Co., Ltd. of Han Steel Group a PCA-GA-BP neural network based end point phosphor content prediction model for the converter is developed. Principal component analysic (PCA) is used to reduce dimension of the factors affecting the end point phosphor content and at the same time the genetic algorithm(GA) is applied for optimization of the initial weights of BP neural network. Then, a software of prediction model of end point phosphor content is developed by Java. And the software is applied in the converter mill. The results show that the hit rate to phosphor content predicted by model reaches 96.67%, 93.33 %and 86.67 %with control precision among ±0.007 %，±0.005 %and ±0.004 % for heats of the experiment respectively.

Technology of nitrogen regulation in steel during LF process and its practice

2012, 28(2):  14-16,2.  doi:

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The present paper introduces the nitrogen content in Al killed steel in the process of refining by route of “BOF→LF→CC” in the Vanadium Recovery and Steelmaking Plant of Pangang Group Panzhihua Steel & Vanadium Co., and analyzes the main factors affecting nitrogen pickup in steel in LF refining involving a few greater influential factors such as compositions of steel, effects of submerged arc in heating, argon blow and cladded wire rod feeding and puts forward certain counter measures. By adoption of such a few measures as manipulating the submerged arc more carefully, regulating the heating level more appropriately and stabilizing argon blow nitrogen pickup in LF refining is already well controlled and the quality fraction of nitrogen pickup in LF refining is steadily controlled within the limit of 2×10^-6.

Deoxidation and inclusion control of ER70S-6 welding wire steel during LF refining

2012, 28(2):  17-19.  doi:

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Deoxidation and inclusion control for ER70S6 welding wire steel are investigated through thermodynamic calculation and plantscale experiments. The morphology, chemical compositions and size of inclusions in liquid steel are analyzed by SEM/EDS. Thermodynamic calculation results show that the quality fraction of dissolved oxygen in liquid steel is more than
40×10^-6after deoxidation using SiMn alloy and the quality fraction of dissolved oxygen can be reduced to less than 10×10-6through control of slag chemical composition. Experimental results show that the number of inclusions with the diameters of more than 20 μm decreases from 22.3 % to 6.1 %; the inclusion type after LF refining is globular CaO-Al₂O₃-SiO₂-MnO-Ti₂O₃ inclusions and the melting points for 89.8 %of these inclusions are below 1 600 ℃. The quality fraction of total oxygen in final products is 24.5×10^-6averagely, which meets the requirement of downstream customers.

Effect of the position of soft reduction on the centralsegregation of 400 mm ultra-thick slabs

2012, 28(2):  20-23.  doi:

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The present paper introduces the production status of 400 mm ultra-thick slabs and analyzes the influence of the position of soft reduction on the central segregation of ultrathick slabs. Results show that expansion of the space between the dual phase zone and the solid phase is more beneficial to improve the central segregation of the ultra-thick slab. Results of C and S chemical analysis show that the central segregation of 400 mm ultra-thick slab is similar to that of 250 mm medium gauge slab and the distribution of chemical compositions of the liquid steel in the width direction is uneven and the liquid pool is in a W shape.

Practice in reduction of corner crack in CC slab

2012, 28(2):  24-28.  doi:

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The corner crack of CC slab and the ratio of the down graded hot rolled plate and coil can be effectively reduced by implementation of a series of technological measures such as adopting the soft cooling schedule in both the mould and the secondary cooling zone, maintaining a constant casting speed, controlling the fluctuation of the mold level in 3 mm, using suitable narrow taper of mould, improving the basicity of powder, ensuring the precision of guiding roll in the segment section as well as controlling the deviation of roll gap within the limit of 0.5 mmand the deviation of mould oscillation within ±0.3 mm.

Control of oxide inclusion for low carbon and low silicon steel

2012, 28(2):  29-31.  doi:

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In order to improve the castability of molten steel and avoid casting break by nozzle clogging the processes of converter such as the poststirring, top slag deoxidization and carbon deoxidization by RH are optimized on the basis of the production practice in low carbon and low silicon steel in Chongqing steel. Since the process improvement, the quality fraction of BOF end point oxygen has been decreased by 127×10^-6, the quality fraction of FeO and MnO in the slag reduced to less than 5%, addition amount of ferroaluminum decreased by 0.38~0.43 kg/t, oxide inclusion decreased effectively and the quality fraction of T.O controlled in the range of （14~25）×10^-6. Production practice shows that by adoption of “BOF→RH→CC” processing route in production of low carbon and low silicon steel the cleanliness of the steel can be improved and the continuous casting heats of single tundish reaches 18 heats.

Development of high-quality 28MnCr5 gear steel

2012, 28(2):  32-35.  doi:

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28MnCr5 gear steel is successfully developed by adoption of “EAF→LF→VD→CC” processing in route in Laiwu Iron and Steel Group Co., Ltd. By precise control of C, Si, S and P in steel the liquid steel in conformity to the chemical composition specification can be obtained. Experimental results show that the high quality 28MnCr5 gear steel slab for automobile use (w(T.O)≤15×10^-6) can be refined and the type, morphology and size of the inclusions in steel can be effectively controlled and demand of hardenability for the steel can be met as well.

Quality control on thin slab of low-carbon steel by BOF→RH→CSP process

2012, 28(2):  36-40.  doi:

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The quality defects such as occurrence of non-metal inclusions, edge breaking and edge cracking exist in the low carbon steel sheets produced by processing route of “BOF→RH→CSP” in Lianyuan Iron & Steel Group and in CSP serious nozzle clogging also emerges as well. By analysis on factors affecting the quality of the CC slab a series of process measures such as optimization of converter refining, RH refining,Ca treatment on hot metal and Argon soft stirring have been put forward. Since implementation of those measures the average continuous casting number of low carbon steel reaches over 15 heats and quality of the sheet prominently improved.

Optimization of nitrogen control process in refining wheel steel

2012, 28(2):  41-43,4.  doi:

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The full course of wheel steel production in Hanbao Steelmaking Plant of Handan Iron & Steel Group Co., Ltd has been traced and variation of nitrogen content in each and every operating process in production of the wheel steel by “LD-LF-CC route studied and analyzed. By optimization of the control process and implementation of nitrogen control in the full course the w(N) in the finishing products of the wheel steel confines within the limit of 45.00×10^-6 and 31.61×10^-6 is average. Thus quality of the wheel steel is improved.

试验研究

Industrial test on hot metal desiliconizing process by slag washing

2012, 28(2):  44-47.  doi:

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An industrial test on hot metal desiliconization process is unfolded in Chongqing Iron and Steel Co.,Ltd. Results show that desiliconization
rate can reach 52.69 %by adoption of slag washing process for hot metal desiliconization and the primary factors affecting the desiliconization results are amount of desiliconizer addition, original silicon content and rate of siliconizer feeding. Hot metal temperature drop and foamization of desiliconization slag problems are discussed
as well.

Study on silicon control of low carbon and low silicon Al-killed steel in refining process

2012, 28(2):  48-51,6.  doi:

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n order to check silicon pick up in the low carbon and low silicon steel in smelting process，silicon content control in LF refining in CSP process at WISCO has been studied by industry experiments. The results show that silicon pick up happens primarily in LF refining process. Calcium treatment process is also an important factor affecting silicon pick up in molten steel besides the quantity of slag in tapping and soluble Al content in molten steel.Thermodynamic calculation shows that at the end of refining silicon pick up still carries on because reaction between Al_S in molten steel and SiO₂ in the slag is far from the equilibrium and the reducibility of Ca for SiO₂
in the slag is far more greater than that of AlS and silicon pick up can be alleviated by properly readjustment of the content of SiO₂in the top slag.

Effect of Ca-treatment on sulphide inclusions in 20CrMo gear steel

2012, 28(2):  52-55.  doi:

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On the basis of thermodynamic calculation the process conditions of Ca-treatment of the sulfur bearing 20CrMo gear steel is analyzed and the sample of rolled stock taken from the Ca treated sulfur bearing gear steel is studied in a specific Plant. Results show that in the liquid steel Ca treated in a RH device the sulfide inclusions and calcium aluminates bind together and form the spindle shaped low melting compound inclusions. In the meanwhile control of w(O) in steel below 10×10^-6 before Ca-treatment is more beneficial to the full modification of Al₂O₃and sulfide by the added calcium and to the formation of oxide and sulphide compound inclusion with MnS as its nucleus and after Al deoxidation S segregation can be reduced in the period of solidification only if w(Al_S) in steel is adjusted to 0.015 %～0.025 %and Si-Ca cladded wire is fed at higher temperature. The morphology of inclusions in the Ca treated sulfur bearing gear steel are acceptable and all
indicators of properties can meet the requirements of customers.

Physical simulation of sink-vortex slag entrainment in 120 t ladle

2012, 28(2):  56-59,7.  doi:

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By way of water modelling the slag entrainment process in ladle casting of a 120 t ladle is observed. The effects of slag quantity in the ladle and nozzle diameter of the ladle
on the height of slag entrainment are studied as well. Results show that when the slag amount in the ladle rises from 0 % to 1.0 % the onset height of slag entrainment is reduced by 57 % and height of stable vortexing funnel slag entrainment reduced by 56 %; as soon as the slag amount reaches 7.0 % from 1.0 %the onset height of slag entrainment is raised by 63 %and the height of the stable sinkvortex raised by 62 %; and as the flowrate of ladle nozzle accelerates to 22.465 m³/h from 2.884 m³/h the onset height of slag entrainment increases by 60 % and as the flowrate of ladle nozzle rises to 19.211m³/h from 2.361 m³/h the stable height of sinkvortex increases by 75 %.

Research on simulation of liquid steel flow in a ASF billet 8-strand continuous casting tundish

2012, 28(2):  60-64.  doi:

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Three-dimensional flow field of molten steel in a 8-strand continuous casting tundish is investigated by numerical simulation method and then the results are verified by
water model experiment and industrial production. The simulation result shows that the baffle and inhibitor in ASF tundish can improve the flow coditions and temperature
distribution of liquid steel remarkablely. The flow conditions will be much better if double dams are installed in the tundish. Since there are four circulation zones for flowing of the liquid steel not only mixability of the liquid steell is improved, but also the temperature distribution of the liquid steel in the tundish is more homogeneous and low temperature zone is much less as well. Water model experiments show that the similarity of the flow characteristics of each strand can be prominently improved by installation of
inhibitor and baffle in an empty tundish and the flowability of the liquid steel can become much better if double dams are further added in the tundish upon the above mentioned base. The results of numerical simulation are completely in agreement with that of the water modelling. Beside the expected purposes have also been achieved in the industrial production.

李峰¹ ，白月琴¹，唐建平²，兰月光²

2012, 28(2):  65-66.  doi:

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In the present paper measures for control over aluminium content in rail steel used for high speed train are studied by calculating. Results show that in the process of LF refining the Al₂O₃in the slag can be reduced to the liquid steel by silicon in the heavy rail steel, thus resulting in an increase of aluminum content in steel. And therefore by controlling the basicity and AlAl₂O₃content of the slag at the low level and keeping the silicon content in the steel on the bottom line the aluminum content in steel can be held at a lower level.

Fundamental research on CO₂ and O₂ mixed injection stainless steelmaking process

2012, 28(2):  67-70.  doi:

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Through a great number of theoretical calculations and laboratory tests the COMI process (CO₂and O₂ mixure blow refining) has been successfully applied into the stainless steel refining by the research personnel of University of Science & Technology Beijing. Experimental results show that COMI process not only has little influence on the normal refining of the stainless steel, but it can also promote decarbonization and preservation of chromium and reduce nickel loss. All those are beneficial to improvement in the quality of stainless steel. Besides, in this process a part of CO₂ can be used to replace argon gas and O₂, and thus the production cost per ton steel can be saved by about 20 to 45 yuan and further more reclamation of CO₂ is in favor of development of green carbon economy.

Analysis on control of oxide inclusions in the valve spring steel 54SiCr6 at home and abroad

2012, 28(2):  71-74.  doi:

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Through comparison and analysis on the size and composition of the oxide inclusions in the valve spring steel 54SiCr6 at home and abroad it's found that the size of oxide inclusions is well controlled in A Steel Work at home. However there is still a certain difference in the field of plasticity of the steel in comparison with the foreign steel works. The primary cause is determined to be occurrence of over greater amount of Al₂O₃ in the oxide inclusions. The plasticity of oxide inclusions can be improved by adopting a few measures to reduce the Al_Sin the liquid steel.

Optimization and practical application of measurement method for dendrite arm spacing of continuous casting slab

2012, 28(2):  75-78.  doi:

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The present paper introduces tests on the optimization of the measurement method for dendrite arm spacing in the continuous casting slab and its application. By analysis on the solidification cooling process and data acquisition of the CC slab the typical region of dendrite arm spacing is determined and a scientific method for measurement on the dendrite arm spacing is established. By application of this method in the CC slab production the law of change of dendrite arm spacing of CC slab with the variation of secondary cooling intensity can be quickly and accurately determined. By adjustment of the intensity of the secondary cooling of continuous casting the size of the primary and secondary dendrite arm spacings can be controlled and thus the purpose of alleviation and removal of the slab cracking defect and improvement in the quality of the slab is achieved.