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2021 Vol. 40 No. 3
Published: 2021-06-18
Continuous Casting Technology
Strand Quality
Continuous Casting Equipment
Technology Exchange
Continuous Casting Technology
1
CHEN Sai, YANG Shu-feng, YE Mao-lin, ZHAO Meng-jing, WANG Yi-hang, LI Jing-she
Effect of plasma heating on performance of tundish covering flux
Plasma heating in the tundish can make up for the molten steel temperature loss during the casting process and improve the quality of the continuous casting slab, but the high temperature in the heating zone will have a series of effects on the covering flux. By means of X-ray diffraction (XRD), light microscopy and scanning electron microscopy, the covering flux samples before and after plasma heating in industrial field tundish were compared and analyzed, and the liquidus projection of the covering flux before and after heating was drawn by FactSage thermodynamics software.The results showed that the morphology of the tundish covering flux changed significantly after plasma heating, the specific performance is that the samples are loose and porous before heating, and the samples have low crystallization rate, a dense glass, and a more homogeneous surface after heating. Phase identification of the tundish flux before and after plasma heating by XRD. The heated flux changes from crystal to amorphous, showing a certain regularity. Observing the sample under the light microscope showed that the surface of the covering agent sample after plasma heating was more uniform than before heating. The observation under scanning electron microscope and phase analysis revealed that the covering agent sample before plasma heating mainly consisted of a single homogenized composition. The sample had a gray-black insoluble oxide on the substrate.There is little change in the area of the low melting point area of the covering flux before and after heating.
2021 Vol. 40 (3): 1-6 [
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7
HOU Yu-yang, CHENG Guo-guang
Solidification characteristics and control measures of equiaxed zone ratio of ferritic stainless steel slab
A ferritic stainless steel slab having a high equiaxed zone ratio can significantly avoid ridging defects during cold forming. The solidification characteristics and equiaxed crystal ratio control mechanism of Ti and Nb bistabilized ultra-pure ferrite stainless steels were studied by means of microstructure observation, second phase characteristic analysis and solidification model calculation.The results show that the equiaxed crystal ratio of continuous casting is significantly improved when Ti and Nb were alloyed to ferritic stainless steels. According to the solidification calculation, the solidification parameters evolution characteristic varied little,but the composition and morphology of the second phase particles in the steel changed significantly. The heterogeneous nucleation ability of the second phase particles is significantly enhanced. The solidification model established in this study can better predict the equiaxed crystal ratio of continuous casting slab. It was also pointed out that the stable increase of the equiaxed crystal ratio requires the reasonable design of the trace element composition, nucleation effect and smelting process of the steel.
2021 Vol. 40 (3): 7-12 [
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13
PENG Xia-lin, YI Bing, LI Wei-hong, XIAO Hong, LIU Shun, MA Zhi-min
Effect of electromagnetic stirring on metallurgical effect of slab under optimization of continuous casting process
In order to study the influence of roller electromagnetic stirring on the metallurgical effect of slabs, the effect of electromagnetic stirring on the metallurgical effect of slabs under the optimized process conditions was revealed by the field test method changing the parameters of EMS and continuous casting.The results show that the metallurgical effect of the slab improved with the electromagnetic stirring force increasing gradually under the frequency at 7 Hz and the current at 0, 100 and 400 A. With the increase of the number of roller electromagnetic stirring, the low quality of slab can be improved. When a set of electromagnetic stirring parameters are used for the same steel, good metallurgical effect can be obtained under the condition of comprehensive optimization of continuous casting process parameters. The best metallurgical effect of the slab can be achieved with the frequency of electromagnetic stirring at 7 Hz, the casting speed at 0.9 m/min and the current at 400 A.
2021 Vol. 40 (3): 13-17 [
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18
WANG Chong, ZHONG Kai
Research and application of long life technology in RH chromium free vacuum tank
In order to improve the service life of RH chromium free vacuum tank and ensure the stability of the service process, through the mechanism analysis of the factors affecting the service life of RH vacuum tank, Technical breakthroughts have been carried out in a targeted manner. Some measures were taken, such as improving the bricklaying process of impregnated pipe and circulating pipe, increasing the retaining wall process, optimizing the lower channel steel structure, detecting the welding leakage of RH vacuum tank and melting cool steel technology. The service life of Jingtang RH vacuum tank was increased from 100 heats to 135 heats,one set of lower groove and two sets of impregnation tube and circulating pipe are used together. All these measures have improved the stability of production and achieved good economic and social benefits.
2021 Vol. 40 (3): 18-23 [
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Strand Quality
24
FAN Cong-cong, MO Zhi-ying, LI Hai-xu, ZHAO Zheng-zhi, CUI Heng
Detection and characterization of inclusions in tinplate base steel slabs
Due to the thin rolling thickness of tinplate products, the quality of tinplate used for packaging must be strictly controlled and must not have defects. Therefore, it is particularly necessary to explore the composition, morphology, size, and quantity distribution of the inclusions in the tinplate cast slab. The size and quantity distribution of inclusions in the tin-plated substrate steel casting slab were inspected and analyzed by using high-frequency water-immersion ultrasonic testing technology, and the composition, types and morphology of inclusions in the tin-plated substrate steel casting slab were analyzed by combining scanning electron microscope and slime method.The results show that there are obvious inclusions at 1/4 of the inner arc and the outer arc of the cast slab. The number density of inclusions in the whole range is 6.25×10
2
m
-3
, and the number density of local inclusions is 3.33×10
9
m
-3
; the main composition of large inclusions is Al
2
O
3
, and there are a small amount of inclusions such as SiO
2
and CaO in the cast slab. In addition, large inclusions containing K
2
O are also found.
2021 Vol. 40 (3): 24-27 [
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28
CHEN Bo-tao, ZHANG Ze-feng, XING Li-dong, WANG Min, ZENG Fan-zheng, BAO Yan-ping
Analysis of TiN precipitation during solidification of Ti-containing micro-alloy steel
Effects of separation crystallization on the precipitation of TiN inclusions during the solidification process of low carbon Titanium micro-alloy steel were studied from the aspects of thermodynamics and kinetics respectively. Thermodynamic analysis showed that TiN could not precipitate out above liquidus temperature. Due to the enrichment of TiN in the solidification front during the solidification process, when the solidification fraction reaches 0.377, TiN begins to precipitate out from the solid phase in the solidification front. At the end of solidification, the enrichment degree of Ti and N further increases, and TiN is precipitated in both solid and liquid phases. The dynamic analysis showed that the size of TiN inclusion during solidification increased significantly with the decrease of cooling rate, When the cooling rate was higher than 50 K/s, the theoretical radius of TiN was 5.5 μm. when the cooling rate was lower than 5 K/s, the theoretical radius of TiN was above 17.5 μm. TiN precipitation in solid phase is nano-level. TiN precipitates mainly ranged from 1 to 5 μm in the billet, and large size inclusions mainly precipitated at 1/4 and center of the billet, indicating that large size inclusions were precipitated during solidification.
2021 Vol. 40 (3): 28-34 [
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35
LI Yong-chao, LU Cai-ling, ZUO Jian-cheng, BAI Rui-juan, WANG Wei, HAN Huai-bin
Analysis and control of macro-inclusion of bearing steel in tundish first heat
In order to realize the rapid analysis of the cleanliness of bearing steel, the macro-inclusion in different heats of tundish was detected by high-frequency immersion ultrasonic testing. The results show that the macro-inclusion in tundish first heat severely exceed the limit. The major components of the macro-inclusion was calcium aluminate type inclusions by scanning election microscopy after locate sawing. According to the production practice of bearing steel in a certain factory, the main source of macro-inclusion is reoxidation of molten steel and its product adhesion to the nozzle inner wall, which promotes the deposition of the original calcium aluminate type inclusions in the molten steel, finally the clogging drop into the molten steel. By optimizing baking temperature of tundish, decreasing reoxidation of molten steel, applying four-port swirling nozzle, the cleanliness value of tundish first heat was significantly decrease. The water immersion ultrasonic inspection results showed that the cleanliness value (total defect length/test volume) of tundish first heat was reduced from 170.4 to 12.0 mm/dm
3
.
2021 Vol. 40 (3): 35-39 [
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Continuous Casting Equipment
40
MEI Ning, WANG Bao-dong, LIU Yan-qiang, XIAO Hua-sheng, ZHAO Lu-ming, YANG Chun-bao
Analysis on cause of peritectic steel breakout at slab joint in process of quick change of tundish
In order to study the problem of breakout at the slab joint of peritectic steel in the process of quick change tundish, the occurrence law was continuously investigated on site, and the breakout mechanism was analyzed by scanning electron microscope. The results show that the breakout is related to the shrinkage of slab shell and the accumulation of non-metallic inclusions at the joint mark, in which the non-metallic inclusion is mold flux. By optimizing the shell cooling and feeding program, optimizing the superheat of molten steel, adding connectors, optimizing the cleaning operation of mold flux and slag strip, and improving the casting start operation, the breakout of slab joint mark in the process of quick change of tundish of peritectic steel was effectively restrained, and the breakout rate was reduced from 1.08% to 0.
2021 Vol. 40 (3): 40-44 [
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45
WU Hong-jie, XU Yu, CHU Cheng-yang, ZHANG Chuang, ZHOU Li
Physical simulation of nozzle crystallizer nozzle structure under blowing
In order to improve the flow field of the beam blank continuous casting mold in a steel plant, the physical simulation research was carried out based on this mold, and the nozzle structure was optimized. The flow field display, wave height measurement and conductivity measurement were used to study the influence of different nozzle structure on the mold flow field and the change rule of mold flow field under different nozzle structure. The results show that the liquid level fluctuation of the mold is better under the experimental conditions with the bottom hole diameter of 17 mm and the air blowing capacity of 3 L/min, and there are better particle and ink flow fields in the mold. In the actual production, it is beneficial to the uniformity of temperature and composition in the mold, which is conducive to the formation of good solidified shell, and it is not easy to produce slag in the casting process.
2021 Vol. 40 (3): 45-53 [
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54
YUE Zhi-kun
Fault analysis and modification of flame-cutting engine for continuous casting slab
The failure of the mechanical system of K7043 flame-cutting engine in continuous casting workshop of a steel mill is characterized by the fracture of the transmission mechanism of the lifting mechanism. Common faults in the media system are caused by blockage of pipeline components and blockage of the cutting gun. Common faults in electrical systems are manifested by encoder failure, cable damage, proximity switch failure. Analysis of common faults of the cutting machine, indicating that the fracture of the transmission mechanism is caused by the stress concentration in the transmission mechanism of the lifting mechanism. The blockage of pipeline components is caused by the precipitation of tar in the gas, and the clogging of the cutting nozzle is blocked by the hot metal slag. Common faults in electrical systems are caused by the complicated working conditions of the cutting machine. Then the flame cutting machine was adapted, the stress concentration of the lifting mechanism transmission box was eliminated, the blockage of the media system pipeline components was improved, the cutting nozzle replacement time was shortened, and the failure rate of electrical components was reduced. Observing its actual operation, the failure rate of the cutting machine has been significantly reduced.
2021 Vol. 40 (3): 54-58 [
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Technology Exchange
59
ZHANG Qi-dong, ZHONG Kai, JIA Pei-ri, WANG Chong, NIE Zuo-lu
Application and practice of intelligent ladle management technology in Jingtang Company
In order to realize real-time control of key information such as the ladle position and molten steel temperature of Jingtang Steel Plant, the position information of trolleys and cranes is tracked through laser positioning technology,and all data collection equipment and data servers are realized through wireless transmission technology. Through the optimization model, the optimization management of package distribution and temperature has been realized, thereby establishing a complete set of intelligent management system for steel ladle. After the system went online for one year, the total ladle turnover time was shortened from 213.0 to 191.4 min, which was 21.6 min, with a decrease rate of 10%. The proportion of normal turnover ladle increased from 81% to 86%. The converter tapping temperature is reduced by 2 ℃, and the hit rate of molten steel temperature after the converter smelting end furnace is improved.
2021 Vol. 40 (3): 59-64 [
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65
FAN Xing-chen, MENG Zhi-duo, CHEN Wei-gang
Failure analysis and countermeasures of swing shear reducer
In order to reduce the failure of the weak link of the pendulum shear reducer, ensure the long-term efficient work of the swing shear, a factory optimized and improved the operation side bearing, drive side bearing failure, one-shaft speed and two-shaft clutch and lubrication system optimization, etc. The service life of the oscillating shear is greatly increased. The results show that the bearing failure of the pendulum shear reducer is closely related to the bearing form, lubrication, bearing speed and clutch engagement time. As long as the above problems are dealt with, the bearing life of the pendulum shear reducer can be greatly improved, so as to ensure the normal use of the swing shear.
2021 Vol. 40 (3): 65-68 [
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SUN Yun-peng, WANG Fu-hai, CHEN Lin-quan
Calculation and practice of steam emission in secondary cooling chamber of continuous caster
Based on the reconstruction of three machines and three streams stainless steel continuous caster in a special steel plant in China, in order to study the steam exhaust in the secondary cooling zone of the continuous caster, the steam quantity in the secondary cooling zone of 1Cr13 steel was calculated by heat method and water method, and the direction of steam pipe was improved and the type selection of fan was verified. The results show that the power of the existing steam induced draft fan is relatively small, and the steam pipe is replaced.The runner and fan completely solve the long-term problems of steam retention and overflow in the casting process of continuous casting machine, which has certain reference significance for the treatment of steam emission in the secondary cooling chamber of continuous casting machine.
2021 Vol. 40 (3): 69-72 [
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