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2020 Vol. 39 No. 4
Published: 2020-08-20
Continuous Casting Technology
Strand Quality
Technology Exchange
Continuous Casting Technology
1
WANG Ai-dong, XU Hai-fang, FU Qiu-hua, LI Bo
Numerical simulation and optimization of flow field in FTSC tundish
Numerical simulation and optimization of flow field in FTSC tundish were studied based on finiteelement analysis software CFD. Turbulent flow controller is the important unit of tundish flow-control. Relationship between parameters such as inner diameter and height of spittoon type turbulence controller and turbulent kinetic energy in impact area was designed and analyzed. Tundish structure of spittoon type turbulence controller with different settings was studied and the best tundish structure was obtained.
2020 Vol. 39 (4): 1-6 [
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7
LI Hui-cheng, LIU Hai-ning, DENG Xiang-yang, XU Jia-lu, ZHU Fu-qiang, WANG Ying
Improvement of casting speed and composition homogeneity of continuous casting billet under PMO
In order to achieve the goal of increasing the electric furnace plant production efficiency, the application potential of pulsed magneto-oscillation (PMO) in improving casting speed was studied. The results show that the optimization of PMO processing parameters can meet the requirements of increasing the production speed, and can improve the central segregation and macroscopic segregation of the billet. When the casting speed is raised to 1.05 m/min, making the pulse frequency being 1.16
K
f
Hz and the peak voltage being 1.00
K
i
V (
K
f
and
K
i
are the discharge frequency and the voltage peak, respectively),the cross section carbon segregation index can be controlled in the range of 1±0.05;When the casting speed is raised to 1.15 m/min, making the pulse frequency being 1.28
K
f
Hz and the peak voltage being 1.00
K
i
V,the cross section carbon segregation index can be controlled in the range of 1±0.07.The experiment prove that the quality of continuous casting billet can be improved by ensuring the pulse energy applied to molten steel per unit time under the condition of high drawing speed.
2020 Vol. 39 (4): 7-11 [
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234
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12
WEI Qian-yong, LIU Cheng-bin, WAN Xiang
Production technology of high efficiency square billet continuous casting
Continuous casting and rolling is one of the developing technologies, and high temperature continuous casting slab control is the basis of continuous casting and rolling. Based on the improvement of high efficiency technology of square billet continuous casting machine in Shaogang Steel Plant and the technical characteristics of efficient square billet continuous casting machine in advanced enterprises at home and abroad, the factors affecting the drawing speed of square billet continuous casting machine are analyzed, and the measures to improve the drawing speed of square billet continuous casting are put forward.Through improvement, the maximum drawing speed of billet continuous casting in the Steelmaking Plant was increased from 2.8 to 3.4 m/min, and the production quality met the rolling requirements. By comparing the performance of high speed continuous casting machine at home and abroad, the key control technology to improve the drawing speed of billet continuous casting machine was found out, which laid a foundation for the production technology of high efficiency continuous casting machine.
2020 Vol. 39 (4): 12-16 [
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222
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17
YE De-xin, ZENG Ling-yu, QIU Wen-sheng, LIU Zhi-ming
Development and application of soft reduction technology in bloom continuous casting
Soft reduction technology of continuous casting is an important method to improve the internal quality of blooms and reduce the center porosity, center shrinkage and center segregation. Basic principle and main control parameters of continuous casting with soft reduction technology are described.Development method of soft reduction technology for bloom continuous casting at SGIS, the problems existing in the development process and the effect of application are introduced. Control method and key points of the soft reduction process, as well as the relationship between the parameters of the soft reduction process and the center porosity and center segregation of the bloom are mastered through the research on the soft reduction technology of bloom. The results show that the internal quality of bearing steels can be improved obviously by using the soft reduction technology in bloom continuous casting. The ratio of central porosity below 1.5 is increased by 18.8%, and the central segregation index is optimized from 0.877-1.247 to 0.944-1.038. The research results provide important technical support for SGIS to develop high quality, high performance and high added value products.
2020 Vol. 39 (4): 17-21 [
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Strand Quality
22
ZHANG Lei, ZHAI Bing-yu, WANG Wan-lin
A review of thin slab casting and formation of slab surface defects
Thin slab casting and rolling technology has become one of the main trends in the development of metallurgy technology. However, there is prone to occur surface defects of the as-cast slab during the process of thin slab continuous casting, such as surface inclusive slag and surface cracks, which is due to the high casting speed, and the fast solidification speed of slab, and its large ratio of width to thickness. Furthermore, the formation of the slab surface defects is directly related to the flow flied and the distribution of temperature, as well as the heat flux in mold. Therefore, the in-mold high temperature dynamic behavior during the process of thin slab continuous casting has been systemically summarized. Besides, the formation of slab defects has also been analyzed. The results indicated that there was the serious random turbulence and the faster vortex velocity of in-mold molten steel, which prevented the inclusion from floating up, and leaded to the occurrence of inclusive slag and cracks in slab surface. In addition, the temperature distribution in slab was easy to unevenness under the turbulence effect, and plus the high heat flux with the high casting speed, which resulted in the formation of slab cracks.
2020 Vol. 39 (4): 22-28 [
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29
MA Jun-peng, LI Huan
Effect of mold flux on surface quality of 430 stainless steel billet
In order to solve the quality problems such as scab and depression on the surface of 430 stainless steel continuous casting slab produced by TISCO, hemispherical point melting point instrument, viscometer and SEM were used to study the influence of mold flux physical properties, continuous casting mold vibration parameters and cooling strength on surface defects. The results show that the main reasons for the surface defects are the low viscosity and weak crystallinity of the mold flux. Therefore, by optimizing the chemical composition of the mold flux, the viscosity of the protective slag is increased from 0.20 to 0.33 Pa·s, and the uniformity of slag film is improved; And the basicity is increased from 1.00 to 1.16, which improves the ability of the slag to control heat transfer. Therefore, the surface defects of the slab are eliminated, and the slab realizes no grinding. At the same time, due to the influence of fluorine content and viscosity in the slag, the life of immersion nozzle has been significantly improved, and the number of continuous casting furnaces has been increased from 10 to 12 furnaces.
2020 Vol. 39 (4): 29-33 [
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34
ZHAO Di, SHI Jiao-xing, LI Hong-yang, CHENG Ye, LI Bo
Measures to improve flaw detection quality of Q345B continuous casting on converter
According to the phenomenon that the qualified rate of Q345B steel plate produced by the process of converter straight up continuous casting on 250 mm×1 650 mm section of Nanyang Hanye Special Steel Co., Ltd. unqualified steel plate was sampled and analyzed by electron microscope. It is concluded that the main reasons for unqualified inspection are the central manganese segregation and the manganese sulfide inclusion. By optimizing the desulfurization process of converter to reduce sulfur content, strictly controlling the superheat of molten steel, optimizing the composition to reduce manganese content, optimizing the secondary cooling system of continuous casting and slow cooling of steel plate, central segregation of slab has been improved, and qualified rate of steel plate flaw detection has been improved after rolling.
2020 Vol. 39 (4): 34-39 [
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40
HUO Yu-kun, ZHAO Li-hua, BAO Yan-ping, WANG Min, ZHAO Jia-qi, MA Han
Numerical simulation of formation process of subcutaneous negative segregation zone in billet
In response to the internal quality problems of the bloom in a steel plant, coupled with electromagnetic-flow-heat-solute transport, three-dimensional mathematical model was established to study the formation process of negative segregation band under the surface of bloom. The results show that formation of negative segregation band is the result of combined action of the solidification front flow rate and solidification rate. For the four-hole nozzle, there will be undergo twice negative segregation under bloom surface, and the first negative segregation was caused by nozzle jet, the second is caused by the M-EMS. The change of magnetic stirring parameters will just affect the degree of negative segregation but neither can affect the position and width of the negative segregation band, nor can it improve the positive segregation degree of the bloom center.
2020 Vol. 39 (4): 40-44 [
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45
XIE Sen-lin, XIANG Wang, XIAO Lei, WANG Shi-hua, TANG Ling-feng, YANG Zhou
Analysis on crust problem of electric steel ladle slag
Compared with the normal non-crusted slag,phenomenon of ladle slag encrustation in the production process of electrical steel was analyzed from three aspects of composition, phase and viscosity of the material. The results shown that with the decrease of temperature, a large a mount of high-melting phase such as MgO, MgO·Al
2
O
3
and 2CaO·SiO
2
and so on were precipitated from the slag, which not only acts as a "pinning" reinforcement in the slag, but also can lead to an increase in the viscosity of the slag, so it was very easy adhesion to agglomerate into a shell. In addition, relevant measures have been proposed to prevent ladle slag encrustation.
2020 Vol. 39 (4): 45-48 [
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49
YANG Feng, LUO Hai-ming, WEI Xiao-dong
Inclusion control of oriented silicon steel
Different types, contents and sizes of the inclusions in oriented silicon steel have an important influence on magnetic properties. According to the alloying process of adding ferrosilicon during tapping, steel samples are taken after tapping and in the whole process of RH refining to analyze the inclusion. After deoxidizing and alloying, inclusions are mainly alumina and aluminosilicate, and the size is about 20 μm. Alkalinity of RH slag was maintained to be between 1.4 and 1.6, and the slag was placed in the low melting point area. After RH treatment, the average total oxygen mass fraction in steel was reduced to 0.001 2%.Inclusions in the hot rolled plate of oriented silicon steel are mainly the MnS precipitated out in the solidification process and the spherical or short rod-shaped composite inclusions of MnS and Al
2
O
3
. The size is 1-2 μm, which has little influence on the magnetic property.
2020 Vol. 39 (4): 49-53 [
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54
MA Chao, SUN Li-gang, ZHANG Wei, GUAN Sheng, JIA Gui-jun
Analysis and control of longitudinal crack on hot rolled coil in CSP plant of Baotou Steel
In order to study the cause of longitudinal crack defect of hot rolled coil in CSP production line of thin plate factory, continuous casting process and operating parameters of equipment were investigated and analyzed. The results show that the poor vibration accuracy of vibrating table of continuous casting machine and scaling of the copper plate in the mould are the main reasons for the longitudinal crack of hot rolling.After adjusting the vibration parameters, improving the alignment accuracy of the shaking table and controlling the scale formation of the copper plate, the longitudinal crack defect on the surface of the hot rolled coil plate was reduced, and the longitudinal crack rate decreased from the highest 1.15% to less than 0.10%.In view of CSP casting machine, on the premise of ensuring good thermal conductivity of the mould copper plate, the joint bearing clearance of the four-link mechanism of the mould vibrator should be strictly controlled within 0.02 mm.Elevation deviation of shaking table should be strictly controlled within 0.05 mm.Horizontal displacement of mould vibration is suggested to be controlled within 0.1 mm.
2020 Vol. 39 (4): 54-59 [
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60
HU Jiao, MEI Feng, FENG Chang-bao
Causes and improvement of side crack formation in low carbon boron steel
In order to solve the problem of side crack of low carbon boron steel, industrial experiments were carried out. The results show that the poor performance of the mold power can easily lead to the uneven shell and the stress concentration, resulting in the formation of slab side cracks; The condition of casting machine, such as mold oscillate, the arc state of mold and bending, has a great influence on the crack sensitive side crack of low carbon boron steel; Components N and B further aggravate the side crack of low carbon boron steel.After adopting measures such as mold power optimization, equipment state adjustment, composition control, the steel block rate of edge warping in the hot rolling plant decreased by 2.35%.
2020 Vol. 39 (4): 60-65 [
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66
SHI Ke-wei, ZHANG Hong-cai, ZHENG Li-ning, LEI Ming, ZUO Hui
Cast macrostructure and rolling genetics of gear steel round bloom
Based on the production process of 22CrMoH automobile gear steel by continuous casting and continuous rolling of 500 mm large round billet, through the analysis of low-magnification structure, high-magnification metallurgical structure and strip structure of rolled billet, the as-cast microstructure and rolling of gear steel large round billet were carried out. It was found that the dendritic size of the 22CrMoH gear steel continuous casting large round billet were significantly different in the near surface fine grain region, the columnar crystal region and the central equiaxed crystal region. The secondary dendrite spacing from the surface to the core gradually increases, and ferrite dominated the main dendritic trunk and pearlite dominated the dendrite. After rolling, the banded structure is mainly affected by the secondary dendrite spacing and rolling deformation of the as-cast microstructure, and the bandwidth of annealed ferrite increased from surface to core after rolling
2020 Vol. 39 (4): 66-69 [
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70
SUN Li-gang, JIA Sheng, LI Xin
Causes and control of surface crack on continuous casting billets of wide and thick plates
In view of the surface cracks in batch in the thin slab continuous casting and rolling mill of CSP Plant of Baotou Steel. main causes of surface cracks on the slab were analyzed by investigating the types of surface defects, crack morphologies and characteristics, combined with the continuous casting process conditions, molten steel quality and equipment conditions.The measures of optimizing the vibration parameters, controlling the nitrogen content of molten steel, improving the vibration accuracy, adjusting the performance of protective slag and improving the quality of secondary cooling water were put forward to improve the surface defects of the casting billet, and the obvious results were obtained, and the surface cracks of the casting billet were effectively controlled.
2020 Vol. 39 (4): 70-73 [
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74
XU Hai-fang, SUN Ya-ping, WANG Ai-dong, WU Yuan-gang
Improvement and practice on ladle free-opening rate of Tanggang
In order to solve the problem of low free-opening rate of ladle nozzle, the influence factors on free-opening rate of 150 t ladle in the First Rolling Plant of Tangang were studied. By selecting reasonable ladle nozzle packing sand, improving sand adding device, improving the cleanliness of upper nozzle, shortening the residence time of liquid in ladle and other measures, the ladle free-opening rate is increased from original 98.5% to 99.8% at present.
2020 Vol. 39 (4): 74-77 [
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Technology Exchange
78
HE Yu-ming
Discussion on improving capacity of large slab caster to pass steel and service life of spare parts
With the deepening of the work of production capacity and the strike of steel bars, the steel output in mainland China in 2018 has created a new record. The first year after the successful reorganization of Limited by Share Ltd, the Chongqing Iron and Steel Company began to implement the full production strategy and achieved good results. How to improve the capacity of slab caster in steelmaking plant (a series of) on the basis of improving the service life of equipment spare parts is an important work of steelmaking plant. The six aspects of human, machine, material, method, environment and measurement were analyzed, and the work that needs to be carried out in three aspects of production, technology and equipment was proposed, so as to promote the realization of the design goal of continuous casting process and steel-making capacity to further meet the standard.
2020 Vol. 39 (4): 78-82 [
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