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2018 Vol. 37 No. 03
Published: 2018-06-20
Continuous Casting Technology
Strand Quality
Continuous Casting Equipment
continuous casting technology
1
QIN Wen-bin
Development and application of clearance-free roll gap adjustable segments
In consideration of the shortcomings of segments of three-hinged design， clearance-free roll gap adjustable segments have been researched， developed， and applied to continuous casters in real operation. Through finite element analyses&simulations and testing of the prototypes during the R&D process， knowledge has been obtained about the effects of strength， stiffness and tilting of the segments on the roll gap accuracy. Then compensation measures were put forward in order to achieve accurate roll gap control of the segments. The segments of clearance-free roll gap adjustable design， compared to those of hinged design， have significantly improved accuracy. Online roll gap accuracy was controlled within ±0.5 mm， leaving no zigzagged roll gaps of the secondary cooling guide segments， which make the roll gap shrink more evenly. With implementation of dynamic soft reduction， the accumulative errors of roll gaps generated during the lifting up and down of the rolls were eliminated. And the elastic deformation of the segments can be compensated， allowing more accurate reduction control. The segments permit more stable roll gap control during operation and easier maintenance.
2018 Vol. 37 (03): 1-6 [
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7
YU Xue-cheng，JIA Jian-sheng，BI Ze-yang，MA Wei，LI Ning
Application of automatic operation technology in continuous casting of slab
Application of automatic operation technology in continuous casting of slab can reduce the labor intensity of workers. This technology palys a positive role and is applied widely and effective in the areas of unsteady state operations， such as improving the accuracy and quality of slab casting operation， SEN changing， fast-change of tundish， on-line width control of mold， partition pluging and cease pouring.
2018 Vol. 37 (03): 7-10 [
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11
LIU Jian，LI Hao
Effect of Al and Ca treatment on rust layer of low alloy steel on upper deck conditions
A simulated-corrosion test apparatus was used to investigate the effect of inclusions on the corrosion behavior of a low alloy steels under simulated upper deck conditions in a cargo oil tank （COT） of tankers. The results indicate that Al promotes the formation of Al2O3 in the inner rust layer. The test steel mainly contains spheroidized CaS-Al2O3-MnS complex inclusions after Ca treatment. Al and CaS-Al2O3-MnS complex inclusions help to form a dense inner rust layer in the inner region of the rust that corresponding to the interface of inner rust layer and substrate with an enrichment layer of Al and Ca. In the inner rust layer， Al is present as Al2O3， and Ca is present as CaO， CaS and CaCO3.
2018 Vol. 37 (03): 11-17 [
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18
FENG Yong-shan，HOU Yu-yang，CHENG Guo-guang
Research on continuous casting solidification heat transfer model and structure of No.70 steel
The cooling system of the continuous casting process directly affects the billet quality and the solidified structure. Therefore， the two-dimensional solidification heat transfer mathematical model was established and the continuous casting process was simulated. The change of the temperature field and the thickness of the billet were obtained. Firstly， the slab looseness problem was studied through combining the simulation results with the solidification structure of the continuous casting billets. The results showed that the most serious area of loosening was generated in the residual liquid phase after the slab entered the straightener. After that， in the process of simulation， the influence of the superheat， the amount of water in the mold， the casting speed and the specific water amount on the temperature and thickness of the billet was studied by controlling variable of the continuous casting process. A series of laws of continuous casting have been obtained， which provide an important basis for secondary cooling water distribution of actual production.
2018 Vol. 37 (03): 18-24 [
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25
ZHU Xian-fei，WEN Guang-hua，PU Da-zhi，TANG Ping，FU Da-chao
Study on effective thermal conductivity of solid slag film for mold flux under steady state heat conduction
It has been reported that two methods could be used to measure the thermal conductivity of mold flux， including the instantaneous hot-wire method and the laser pulse method. However， during continuous casting process， the heat transfer between the shell and the mold involves conduction and radiation. Therefore， the thermal conductivity could not be used to evaluate the total heat flux in the mold. Thus， it is necessary to use the effective thermal conductivity to calculate the total heat flux through the slag film. In this paper， the effective thermal conductivity of the solid slag film was investigated through heat flux simulator and laser confocal microscope. The results show that， with the increase of the basicity from 1.1 to1.4， the crystallization capability of mold flux increases， which leads to the increase of the surface roughness of the solid slag film. Meanwhile， the effective thermal conductivity of the flux increases from 1.20W/（m·K） to 2.46W/（m·K）.
2018 Vol. 37 (03): 25-30 [
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31
LIU Shu-guang，ZHAO Jian-ping，WANG Shuai，XU Wei，LIU Xin，YAO Hong-yong
Reasons and preventing measures of sticking in medium slab caster
In the paper， the causes of the sticking in medium slab caster of tangsteel are analysed. Concluded that is concerned with the composition of steel， lifting tundish car operation， exchanging submerged nozzle operation， control capacity of submerged nozzle， overheating extent of molten steel as well as concision of equipment. Through the improved measures including optimization of lifting tundish car operation and exchanging submerged nozzle operation， decrease of submerged nozzle thickness from 30 mm to 27.5 mm， optimize the properties of mould powder， decrease of unsteady state operation etc. By means of corresponding measures being taken， the average monthly sticking times was decreased from 10 to 4.
2018 Vol. 37 (03): 31-34 [
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35
HUANG Xin-wu
Numerical simulation study on plug flow operation of ten- strand tundish
A ten-strand tundish was studied by mathematical simulation in No. 1 steelmaking plant of Baowu group Xinjiang Bayi Iron and Steel Co. Ltd. The flow field and temperature distribution of molten steel were investigated by numerical simulation software Fluent. The flow field and temperature field were studied by numerical simulation. When the ten strands of tundish are fully working， the problems of equipment failure and shortage in molten steel often appear. The plugging operation is often applied to solve the problems. According to the temperature distribution of the tundish， the fluctuation of the liquid steel level， the distribution and inclusion removal ratio， the plugging scheme was evaluated to determine the plugging operation scheme.
2018 Vol. 37 (03): 35-40 [
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41
LU Lun，ZHAO Yan，SUN Li-jun
Research on the heat treatment process and microstructure of a quenched and tempered X12Cr13 stainless steel
A series of heat treatment experiments of this paper have been made on X12Cr13 stainless steels in QT condition， research on the effect of quenching temperature， tempering temperature and cooling method on the 0 ℃ impact energy. The result shows that carbide distribution and morphology are critical for mechanical properties of Q-T X12Cr13， and the optimized heat treatment parameters are： 930-940 ℃ for quenching temperature and 650-660 ℃ for tempering temperature， and rapid cooling is recommend after temper treatment.
2018 Vol. 37 (03): 41-46 [
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47
ZHANG Xue-mei，WANG Hong-feng，CHENG Nai-liang
Study on peritectic reaction and cracking susceptibility of slab
The peritectic reaction of iron-carbon alloy with the carbon content of 0.09%-0.53% is a very important phenomenon in the continuous casting process. It leads to cracking susceptibility of slab， longitudinal surface cracks and the longitudinal breakout. The relationship between the characteristics of the peritectic reaction of different steels and the sensitivity of the continuous casting slab to the crack was discussed.
2018 Vol. 37 (03): 47-50 [
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51
YANG Qi-min，NONG Zhi-jiang，FENG Bao，AO Yong-ming，XIE Jie-zhi，XIE Gui-long
Analysis and Improvement of cracking causes of swrch22a round head cross bolt
When the cold heading steel rod SWRCH22A is deformed during use， the head of the bolt undergoes cold heading and cracking during the processing of the round head cross bolt. In order to improve the performance of SWRCH22A wire rod and reduce the cracking probability of cold heading， the metal cracking specimens were detected and analyzed by means of metallographic examination， scanning electron microscopy and energy spectrum analysis. The results show that there is no obvious surface defect in the position corresponding to the stem at the cracked head of the bolt， and there is a long slag inclusion on the near surface. The composition of the slag is similar to that of the continuous casting mold. The main reason for the cracking of the SWRCH22A round head cross bolt is that the slag in the continuous casting process causes the slag on the near surface of the material to crack during cold forming.
2018 Vol. 37 (03): 51-54 [
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strand quality
55
HOU Yu-yang，CHENG Guo-guang
The pinning effect of Nb on the ferrite stainless steel grains
Ridging defect can be significantly relieved by increasing the equiaxed ratio and grain density of ferritic stainless steel （FSS）. In this work， the pinning effect of Nb on the ferrite stainless steel grains was studied. When Nb was added to FSS， the as-cast grain size became smaller， and nanoscale particles were found at the grain boundary， of which the composition was dominated by[(Ti，][Nb)x(C，][N)y.]With the increase of Nb content， the number of fine precipitates is increased， and the Nb content in precipitates is gradually increased. Further analysis showed that， the solidification region will be extended by Nb， and Nb-rich[(Ti，][Nb)x(C，][N)y]will form at the end of solidification. The pinning effect of[(Ti，][Nb)x(C，][N)y]will also prevent the occurrence of grain boundary sliding and grain merging， refine the as-cast structure and increase the compactness degree of FSS.
2018 Vol. 37 (03): 55-61 [
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CAO Zhi-gang， DU Zhong-ze， FANG Yi-yuan， ZHANG Xiao-yuan， WANG Xiao-guo
Cause and analysis of crack and scratches on the surface of sucker rod steel
As an important component of drilling equipment， sucker rod steel must possess strict physical and chemical properties and surface quality. In this paper， surface crack and scratch defects of sucker rod steel were taken as research object， through macrostructure and metallographic analysis of surface defects on the hot upsetting test specimen ， the surface crack of casting billet and the scratches caused by furnace roller and rolling line guide is considered as the main reason.Thus the control is carried out， and the crack and scratch of the surface of the rod steel is reduced.
2018 Vol. 37 (03): 62-66 [
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LIANG Feng-rui，CHAI Feng，SU Hang，SHI Zhong-ran
Influence of quenching way on microstructure and mechanical properties of high strength flat bulb steel at tempering process
Using OM， EBSD and other test techniques，the difference of microstructure and properties of high strength bulb flat steel after induction-heat quenching and furnace-heat quenching was studied， and the tempering microstructure and properties of the quenched samples were also analyzed after tempering 3 h at different temperatures （600， 630， 650， 670， 680， 690 ℃）. The results show that microstructure of the two kinds of quenching methods are martensite and a small amount of bainite， and the microstructure of induction heating quenched sample is slightly thinner than that of furnace-heating， and the strength is slightly higher. The results of EBSD show that the martensite blocks in the two quenching modes are both large angle grain boundaries and the laths are small angle grain boundaries. The average effective grain size （MED2°） of bulb head and flat for the induction heating quenching is 2.815 μm， and for the furnace-heating is 3.015 μm. For tempering microstructures with different quenching methods， the higher tempering temperature is beneficial to the disappearance of lath interface， which is conducive to the growth and spheroidization of precipitates at the interface between lath and original austenite grain boundaries； The higher the tempering temperature， the decrease of the strength and the increase of the ductility and toughness. For batch production， the induction heat treatment is preferred to obtain the flat ball steel products with good strength and toughness and uniform properties； For small batch production， in practice， the proper quenching and tempering standard can be selected according to the performance requirements， and the furnace-heating could be used to heat treatment of the ball flat steel.
2018 Vol. 37 (03): 67-71 [
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continuous casting equipment
72
PENG Yu
Application of electrical non-sinusoidal oscillation system on no.1 slab continuous casting machine of panzhihua iron and steel company
The mechanical vibration device of the four link eccentric wheel for No.1 slab casting machine is not only high failure rate， but also can not adjust the amplitude online， it can not achieve the requirements of high vibration frequency and small amplitude casting， and the vibration marks of the billet is deeper， the surface quality is poor. In view of the problems of the four link eccentric wheel mold vibration， a digital electric actuator repalced the original four link eccentric wheel mechanism， realizing the non-sinusoidal imitation arc vibration of four digital electric actuator by EtherCAT technology. Through more than 2 years of production， it has proved that the depth of vibration marks produced by the electric non sinusoidal vibration system and the surface quality of the slabimproved obviously. The system is stable， non maintenance and low failure rate. It also effectively improves the casting speed and production capacity of CCM.
2018 Vol. 37 (03): 72-76 [
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77
HUANG Xiao-dong
Influence of content of carbon and B2O3 in tundish slag on nitrogen content in liquid steel
In order to research the influence of B2O3 and carbon content in the tundish slag of nitrogen， the basic slag system of CaO-SiO2-Al2O3 was chosen as a basic ingredient in the experiment， By researching experiment results， though B2O3 and carbon contents have some effects on removal of nitrogen from molten steel， their result is different.
2018 Vol. 37 (03): 77-79 [
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WANG Wen-xue，YANG Chao-wu，HUANG Jin-chun，SHI Xue-liang，ZENG Jing，ZHANG Hua
Analysis and measures to wear problem on copper lower side of slab CCM mould
The wear situation on copper plate lower side was heavy serious in one domestic CCM mould. After the amount of casting steel was only 30，000 ton through wide and narrow copper plates， the copper material had emerged because of the coating on copper plate completely wearing out. After analysis on wear situation and mould structure， some measures can be adopted to improve the wearing problem obviously， for example， to increase the strength of coating material， such as using Ni - Co high-resistant coating material and optimize the alignment between copper plate and rollers and aligning in rollers assembly， optimize the structure of narrow copper plates， which will promote the CCM productivity and enterprise economic benefit.
2018 Vol. 37 (03): 80-85 [
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