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2018 Vol. 37 No. 4
Published: 2018-08-20
Continuous Casting Technology
Strand Quality
Continuous Casting Equipment
continuous casting technology
1
TIAN Wei-guang，XU Jia-lin，LIU Guang-yong，YIN Bang-wu，LU Hai-fei，HE Jin-yuan，HUANG Ding-qin
Research on improving the free-opening rate of 75 t ladle
The effect of residence time of molten steel in ladle， tapping temperature， composition of stuffing sand， etc.， on free-opening rate of a 75 t ladle for the steelmaking process of 06Cr19Ni10 stainless steel is statistically analyzed. Also， the corresponding improvement measures are put forward. The result shows that the ladle annual free-opening rate can be stabilized at more than 99.2%.
2018 Vol. 37 (4): 1-4 [
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HE Qian，LIU Hua-song，LIU Ke，XU Guo-dong，ZHENG Hong-guang，ZHANG Jia-quan
Effect of hot charging process on austenite grain refinement in reheating process of as-cast Nb bearing steel
Microstructure refinement is an important method to control the surface cracks of continuous casting billets and to improve the properties of rolled products. In order to solve the defects of crack in surface of continuous casting billet， we acquired the austenite grain in low carbon steel SCX400 containing niobium， which can be used to simulate the state before transferring to the heating furnace. Then， the grain refining potential in the process of cooling-heating was investigated. Experimental result shows that after one γ→α→γ phase transformation， when the ferrite precipitation exceeds 85.9%， many fine grains appear at the edge of the coarse austenite grain， whose size is about 40 μm at the end， and the phenomenon of mixed grain is serious. It may result from the influence of Nb（C，N）， because they prevent austenite grain from growing and leave the big original austenite. It also shows that multiple γ→α→γ phase transitions can effectively refine the austenite grain， which has a positive impact on surface cracks control and the final product performance in the hot charging process.
2018 Vol. 37 (4): 5-10 [
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CAI Chang-qing，ZHENG Yuan-shou
Research on reasons and countermeasures of piling-up of steel in high speed wire rod
Reasons of the increase of rolling blank’s piling-up of steel in the first high-speed wire rod production line of Fujian Sangang Minguang Co.， Ltd were analyzed from August to October in 2017. By analyzing reasons for the occurrence of cracks in the head of steel， it aims to improve the secondary cooling water in the continuous casting of steel and the quality of macrostructure. The length of the 1# steel rolling’s flying shear head is extended from 110 mm to 160 mm. It can effectively reduce the cracking during the rolling process and improve the stability of the production process. By reducing the thickness of the cutting slag and lengthening the length of the cutting tail， the heap steel can be reduced effectively.
2018 Vol. 37 (4): 11-13 [
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CAO Xue-qian，WANG Ying，CHEN Jie
Finite element analysis of soft reduction for round bloom continuous casting
Based on the round bloom continuous caster， the finite element model of soft reduction was established， it found that the change for transformation of bloom on the various reduction amount. The results show that： 1） the reduction can be passed to the bloom core when solid fraction is above 0.35 and reduction amount of the single roll has to be greater than 10mm. 2）According to the design standard of the continuous caster， when the surface strain value of the slab exceeds 0.015， the surface of the slab is incline to appear cracks， so the maximum reduction of single roll should not exceed 8mm. Therefore， round bloom that be produced in a conventional manner is not suitable for the implementation of the soft reduction process. By adjusting the technological means or adding equipment to facilitate the soft reduction of round billets， it is necessary to study in subsequent work.
2018 Vol. 37 (4): 14-16 [
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XIE En-jing，LI Jing-yu，LIU Wei-dong，CHEN Yang，WEI Min
Optimization technology of continuous casting of stainless steel pipe billet
In order to improve the quality of stainless steel pipe， the continuous casting technology of stainless steel pipe billet was studied in this paper . Technological measures such as complex deoxidization， optimization of the tundish and mold flow field using the simulation software， improvement of the mold flux， installation of the S-EMS were investigated. These technology measures effectively enhanced the cleanliness of the molten steel and the quality of the billet， which supported the production development and the quality control of the high quality stainless steel pipe.
2018 Vol. 37 (4): 17-22 [
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ZENG Zhi，JI Chen-xi，ZHANG Hong-yan，LI Xiang-kui，LI Feng，YANG Xiao-shan
Optimization experiment of soft reduction for continuous casting slab
With the development of the new?steel grades， the requirements of internal quality control for continuous casting slab have been becoming more and more strict. The steel plant of Shougang Jingtang owns four high-efficiency slab casters， equipped with a series of advanced process technologies， including dynamic secondary cooling and dynamic soft reduction. The core of dynamic secondary soft reduction system is the mathematical model of slab temperature distribution field， which is used to calculate the end point of slab solidification online， so as to determine the appropriate reduction area in real time. Taking pipeline steel production for example， the pin shooting test has been carried out for the measurement of solidifying shell thickness to verify the accuracy of the solidification thermal model， proved to be within a relative error of 1.0%. Meanwhile， process comparison test was carried out to study the effect of the soft reduction on central segregation. Results showed that the degree of central segregation decreased with the soft reduction amount increased from 4.2 mm to 7.2 mm， and the type C segregation of pipeline slab could be controlled within Class 0.5 without any cracks.
2018 Vol. 37 (4): 23-26 [
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strand quality
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LI Yu-jun，LI Liang，LAN Peng，ZHANG Jia-quan，CHEN Lie，KOU Yu-shan
Reduction amount model for dynamic soft reduction in bloom continuous casting of special steels
Based on overall mass balance in the casting direction， a theoretical model of reduction amount， suitable for any rectangular continuous casting products， was presented. The impact of arbitrary rectangular section， solidification contraction， thermal shrinking， deformation and temperature on reduction amount can well be described by the formula as [Ri＝2373(fSC,i－fSC,i－1)Thηi，] or [Ri＝－2373ΔTC,iTl－TSThηi]. Where[Ri]is the reduction amount，[(fSC,i－fSC,i－1)]is the center solid fraction increment， Th is the thickness of casting product，[ηi]is the reduction efficiency，[ΔTC,i] is the center temperature increment，[TS]and[Tl]are the solidus and liquidus temperature， respectively. A finite difference numerical method of solving heat transfer and solidification was developed to calculate the reduction amount with consideration of different steel grades，section sizes，casting speeds，superheat and specific water flow. It was found that the soft reduction amount under each reduction roll should increase upon approaching the crater end due to the increased final solidification and decreased reduction efficiency. The effect of carbon and alloy contents， bloom width， casting speed， superheat and specific water flow on the effective total reduction amount is rather limited， while the bloom thickness influences the soft reduction amount remarkably. The soft reduction amount increases by 1 mm as the bloom thickness increases by 30 mm.
2018 Vol. 37 (4): 27-32 [
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TIAN Wei-guang，XU Jia-lin，LU Hai-fei，HE Jin-yuan，HUANG Ding-qin
Study on the width control of continuous casting slabs of 410S stainless steel
Aiming at solving the problem about unstable width of continuous casting slab of ferritic stainless steel， effects of composition of molten steel， tundish temperature， casting speed and secondary cooling water on the width of continuous casting slab of 410S stainless steel were systematically investigated. It was found that the composition of molten steel has a great influence on the width of steel billet， and the width of 410S stainless steel slabs decreases with the increase of γmax value. According to statistical analysis of actual production data， an optimization scheme of production process was obtained as： γmax was 68-72， tundish temperature was 1 543-1 553 ℃， casting speed was 0.95-1.00 m/min， and the adjusted secondary cooling water was adopted. After the optimization of the process， the billet steel width achieving rate was as high as 94.27%， which provided a guarantee for the stability of billet quality.
2018 Vol. 37 (4): 33-36 [
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YU Jie，WANG Wan-lin，XIAO Dan，ZHU Chen-yang
Effects of MgO and BaO on the melting and crystallization behaviors of the mold flux in CaO-Al2O3 series
Mold flux determines whether continuous casting process can proceed smoothly or not. In this study， SHTT（single hot thermocouple technology） was used to investigate the influence of different content of BaO and MgO on the property of mold flux. The experimental results of melting show that MgO can improve the melting temperature of mold flux. With the decreasing of BaO， the melting temperature of the mold flux improved a lot. It found that the existence of MgO inhibit crystallization. When BaO partially replace CaO， the increasing of the ratio of BaO/CaO has suppressive effect on crystallization. Different magnesium content and different barium oxide content does not affect the crystal morphology and composition of the mold flux.
2018 Vol. 37 (4): 37-41 [
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LIN Peng，ZHANG Hong-cai，MA Jian-chao，ZHAI Wan-li，YIN Chuan-lei
Study on the typical quality defect control process of 65Mn billet
There is off-square，angle concaves and corner cracks in 200 mm square billet of 65Mn in a certain steel plant，which are caused by the uneven cooling of mold and secondary cooling zone by analyzing. The process optimization schemes of enlarging the[R]Angle and the taper and increasing the secondary cooling water flow have been carried out. The method of enlarging the[R]Angle and the taper of the mold improve the heat transfer of the mold cooling. The increase of the secondary cooling water and the water pressure of the foot roller improve the cooling effect of the secondary cooling section. The cooling uniformity of casting billet has been increased. The test shows the quality problems of off-square，angle concaves and corner cracks have been controlled effectively and the quality of casting billet has been greatly improved.
2018 Vol. 37 (4): 42-45 [
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LIU Ya-li，ZHANG Jun-ping
Analysis of the characteristics of internal crack in[?350 mm]round billet of ASTM4130 continuous casting
For analysis of internal crack problem of ASTM4130[?350 mm]continuous casting round billet in the Special Steel Plant of Shandong Iron and Steel Company， high temperature mechanics test， microstructure observation and analytical means such as scanning electron microscope were adopted. Systematic analysis of ASTM4130 as-cast organization in different high temperature mechanical properties， fracture morphology and organization transformation were conducted. Test results show that the main cause of internal cracks of ASTM4130 steel round billet is that the slab solidification organization is straightening at in 900-750 ℃ in the first Ⅲ brittleness temperature zone. At that time steel plastic is not high， and the steel billet straightening process force is large， this results in internal crack. According to the experiment data， through the optimization of continuous casting cooling parameters， slab surface temperature drop 150 ℃/m or less to ensure the slab transfered into the machine before the surface temperature ＞900 ℃. The 5 frames continuously straighteners replace the four 3-point straighteners used in the system. The working pressure of each tension machine was adjusted to 4MPa， which can avoid the casting billet crack by great stress or deformation in this temperature range.
2018 Vol. 37 (4): 46-50 [
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WU Chun-lei，，WANG Yi-nuo，YANG Xie-guang，ZHAO Zhi-ming，XU Qing-tai5
Causes and countermeasures of pen-tip shaped fractures in 82B steel wires
During the steel wire drawing production or the tensile test from 82B wire rods， those processes cannot be carried out continuously due to brittle fracture of steel wires. The shape of fractures is pen-tip or cone shaped. In this study， some selected samples with fractures from a steel plant were cut， polished and analyzed by means of macrostructure and metallographic examinations to investigate the reason of fracture. The results show that the direct cause of brittle fracture is the existence of cementite network， cavity and micropore in the center of 82B steel wires， which originate from central segregation， shrinkage cavity and porosity in continuous casting billets. Therefore， those defects in wire rods and final products are derived from continuous casting billets in the early stage. Some countermeasures， such as proper molten steel composition and pouring temperature， heat treatment， conventional electromagnetic stirring and electromagnetic swirling flow in nozzle and so forth， are proposed to improve solidification structure and eliminate the pen-tip shaped fracture defect in the end.
2018 Vol. 37 (4): 51-55 [
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YANG Jie，YAO Hai-ming，LI Meng-ying，HAO Chang-xin，FU Jian-jun
Key quality control technologies of FTSC thin slab in tangsteel
Key quality control technologies of FTSC thin slab in Tangsteel was introduced. According to the matching principle between mould cavity shape and solidification shrinkage characteristics of steel grade， by using the integrated control technology of mould wide face funnel shape + narrow face shape + mould powder performance， the longitudinal crack can be controlled on thin slab surface effectively. And the longitudinal crack control technology of peritectic steel on this basis has been developed. Through using dynamic soft reduction， liquid pool control model， dynamic secondary cooling， and the roll gap measuring instrument for detection of segment alignment accuracy， thin slab internal quality is controlled well. By adopting the above key technologies， the slab surface longitudinal crack rate reduced from 7% to 0.4%， and according to the internal quality evaluation of Mannesmann standard， internal crack of medium carbon steel achieve level 1.5， segregation achieve level 1， internal cracks and segregation of low carbon steel achieve level 1.
2018 Vol. 37 (4): 56-63 [
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JIANG Zhong-kuai， ， ，SU Zhi-jian， ，HE Ji-cheng
Acquisition and positioning of parameters during slab continuous casting for slab quality judgement
Real-time collection and precise location for parameters of continuous casting slab is the basis of real-time analysis and judgment of continuous casting slab quality. On the basis of the actual production experience， this paper summarizes a new location method for parameters of continuous casting slab. The method， by means of modified casting length， can locate the real-time parameters of continuous casting slab to section of continuous casting slab. It overcomes shortages of the traditional location method for parameters of continuous casting slab. In addition， it saves accurate localization production process parameters of continuous casting slab to information group center around section of continuous casting slab by database technology. Based on this method， the system makes useage of judgement rule in database to diagnose anomalous production process parameters of continuous casting slab. The system also makes useage of many information groups of section of continuous casting slab to establish judgment model of continuous casting slab quality or to judge quality defects of section of continuous casting slab. The accuracy rate of this model has reached 95.4%.
2018 Vol. 37 (4): 64-68 [
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continuous casting equipment
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JIN An-lin，YANG Guan-long，CAOYun，CHEN Ai-lin，SUN Hua-lin，WANG Xiang FENG Zai-wu，NUO Wen-kun，LI Dong
Application of side slagging method of continuous casting tundish
Continuous casting billet?casting tundish??problems in?Honghe steel Co.， LTD. was introduced. The service life of?the casting tundish?is directly related to the use of straightening?machine， it?also has a great impact on?the quality of casting billet and?production cost. Causes that affect service life of the casting tundish were analyzed and countermeasures were put forward. Practical results were obtained through these measures. By side discharging method， metal yield was increased by 0.5%， the mean life of tundish was greatly improved， the annual cost reduction was more than one million two hundred and seventy thousand yuan. In the increasingly severe situation of steel industry， it is of great practical significance.
2018 Vol. 37 (4): 69-72 [
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CHEN Xiang，PENG Yu
Application of mould level control system of the electric cylinder in the No.1 slab continuous casting machine of panzhihua iron and steel company
The slab surface quality is mainly determined by the stability of mould level control system. Excessive fluctuation of liquid level will lead to unnecessary grinding procedure or even degrade. This paper proposes a method based on the mould level control system of electric cylinder control. On September 7， 2017 in Panzhihua steel vanadium Co. Ltd. vanadium steel mill， No.1 slab continuous casting machine cast successfully. The practice proves that the system can accurately work on the slab mould level control， and help to obtain good quality of slab.
2018 Vol. 37 (4): 73-76 [
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WANG Pu，HAN Geng-wei，SUN Fu-long，LI Liang，JIANG Xian-xun，BAO Wei-Feng，LAN Peng， ZHANG Jia-quan
Effect of roll gap and casting practices on the mid-way cracks of slab castings
Aiming at the frequently occurred mid-way crack defects in slab castings of steel Q235B， the influence factors have been investigated through production experiments and quality analysis. It is shown that the mid-way crack index is closely related to factors such as casting speed， secondary cooling intensity， steel composition and roll gap alignment. Among them， the roll gap factor is of special importance. Under the present conditions， the mid-way crack can be effectively controlled by proper casting speed， Mn/S ratio and improved secondary cooling strategy.
2018 Vol. 37 (4): 77-80 [
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