Table of Content

05 August 2019, Volume 35 Issue 4

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Progress and prospects of steelmaking technology in Hesteel

2019, 35(4):  1-7. 

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The technological progress of steelmaking process in Hesteel was briefly introduced in this paper. And the key economic and technical indicators of Hesteel were comparative analyzed simultaneously. The following techniques were described in detail, and it include precise and clean steel control technology, dry dust removal in converter, automatic steelmaking technology based on flue gas analysis, continuous casting slab heavy pressure technology, steel slag quenching and waste heat recovery,and big data quality control system. All of above techniques have been applied in Hesteel production line which provided favorable support for low costing green steelmaking and high grade, high value-added product development. In addition, the direction of development would be point out in the paper. And the intelligent steelmaking, jet metallurgy for big scrap radio and process flow control technology being developed and applied in the further to show innovative ability of Hesteel were also introduced in the paper.

Experimental study on optimization of molten iron pre-desulfurization process by KR

2019, 35(4):  8-11. 

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Through the experiments of KR desulfurization operation and process parameters, the influencing factors of KR molten iron pre-desulfurization are analyzed and studied. The results show that, amount of blast furnace slag in ladle, insertion depth of stirring paddle, stirring time, stirring speed and quality of stirring paddle have a great influence on desulfurization rate of molten iron. Improvement measures such as the slag is removed before desulfurization, and controlling the insertion depth of the stirring paddle at about 1.0 m, the stirring time is 10–14 min, and the stirring speed is 80 r/min are formulated, and the application effect of improving desulfurization rate is achieved.

Influence of number and arrangement of bottom tuyeres on bath mixing in a combination blown converter

2019, 35(4):  12-18. 

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Influence of different arrangement of 4–12 bottom tuyeres of a 200 t top and bottom combination blown converter on its bath mixing was investigated in an 1:12 model with physical modeling experiment. Under the condition of combined blowing and the gas flowrates used in this work, the variation range of bath mixing time with different arrangements of 4 bottom tuyeres is large, being 20–49 s, the bath mixing time with different arrangements of 6 bottom tuyeres is 18–42 s, while that with different arrangements of 8–12 bottom tuyeres is 14–38 s. The ratios of bottom tuyere cases with mixing time smaller than 27 s to the corresponding total cases studied were 14 %, 13 %, 33 %, 39 % and 67 %, respectively. This means that 8–12 bottom tuyeres have more bottom tuyere arrangement cases with mixing time smaller than 27 s and these cases can be chosen for combined blowing during a converter campaign. The average values of bath mixing time of different cases at a certain number of bottom tuyeres decrease apparently when the bottom tuyeres increase from 4 to 8. As the bottom tuyeres increase from 8 to 12, the average values decrease a little for the bottom gas flowrtae of 0.57 m3/h, while the average values hardly vary for the bottom gas flowrtae of 2.29 m3/h.

Experimental study on semi-steel slag recycling after gasification dephosphorizationin Chengsteel

2019, 35(4):  19-22. 

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The coke powder can be used to remove the phosphoruselement ofmolten slag in the form of gaseous during the slag splashing process.Theindustrial test of semi-steel slag recycling after gasification dephosphorization was conducted in HBIS Group Chengsteel Company. The results showed that the initial product of gasification and dephosphorization at the steelmaking temperature existed as P2 gas.The recycling of semi-steel slag after gasification dephosphorization did not affect the dephosphorization effect of the subsequent heat. The average phosphorusmass fraction of the end molten steel of the test furnace was 0.019%，which satisfied the smelting demand.The recycling of gasification dephosphorization slag could reduce the consumption of lime by about 6.36kg/t，and the reduction ratio was 24.75%.The main phase of the gasification dephosphorization slag was silicate phase and RO phase，and phosphoruswas mainly concentrated in the C2S phase，and the slag contained partially unreacted coke powder.

Technical analysis of Conarc furnace smelting process and equipment

2019, 35(4):  23-27. 

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This article mainly introduces and analyses the production process characteristics and the structure characteristics of the main equipment of the 80 t Conarc furnace of one iron and steel group Co. in China. Comparing the main equipment of Conarc furnace with traditional electric arc furnace, the equipment type of Conarc furnace can better meet the production process requirements of large proportion hot metal charging. The Conarc furnace is highly flexible and adaptable to the type and proportion of raw materials. When hot metal direct charging is used to smelt steel in Conarc, the smelting process consists of electric arc furnace process and converter process. Electrode heating, carbon and oxygen injector of furnace shell, foam slag submerged arc smelting, charging hot metal from slag door, top blown oxygen decarburization, and the technical of dominant slag and steel to reduce production costs, increase production efficiency, shorten the production cost and tapping cycle.

Study on Reducing Oxygen Transfer from IF Ladle Slag to Molten Steel

2019, 35(4):  28-31. 

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In this paper, the effect of oxygen transfer from RH ladle slag to molten steel on the purity of molten steel is analyzed. The reasonable dissolved oxygen level of RH ladle slag is determined by calculation to ensure that the balanced top slag FeO activity is in a lower range. In addition, the effect of top slag composition on activity coefficient of top slag FeO was analyzed, and reasonable slag composition was determined: from the end of tapping to decarburization of RH, the top slag w(SiO2)=4 %–5 %, w(MgO)=8 %–9 %, w(CaO)/w(Al2O3) of IF steel was controlled between 1.8–2.2, and after the end of RH deoxidation, the slag w(CaO)/w(Al2O3)=1.3–1.5 was ensured, which not only reduced oxygen transfer between slags, but also ensured the top slag adsorption. The ability of inclusion.

Design of whole process ladle capping device under limited clearance

2019, 35(4):  32-37. 

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By improving the thermal insulation of ladle, the whole process of ladle capping technology has changed the original ladle operation process, which provides an effective way for iron and steel enterprises to reduce cost, save energy and reduce emissions. This paper demonstrates the possibility of adding ladle capping device in a steel plant, and puts forward a windlass ladle capping device, which can adapt to the situation where the clearance of some old steel plants is limited, and makes it possible for these steel plants to carry out energy-saving transformation.

Research on periodic fluctuation of liquid steel level in the slab mold based on feedforward compensation method

2019, 35(4):  38-42. 

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Slab continuous casting in the process of producing stainless steel and peritectic steel, the problem of periodic fluctuations of the liquid steel level in the mold often occurs. As the casting speed increases, the periodic fluctuation problem becomes more serious. When the liquid steel level fluctuation of the molten steel is excessive, the slag entrainment phenomenon occurs. When the liquid level fluctuation of the molten steel is too calm, the inclusions in the molten steel cannot rise. This ubiquitous problem not only reduces the efficiency of continuous casting production, but also causes the decline of the quality of the slab. Therefore, the research on the periodic liquid level fluctuation during the casting process of stainless steel and peritectic steel is particularly important. In this paper, the actual production situation of a steel plant was analyzed in detail, and the causes of the liquid level fluctuation of the mold were analyzed. For the periodic liquid level fluctuation (bulging phenomenon) of the liquid steel level control system, the feedforward compensation method is used to finely adjust the stopper to reduce the periodic fluctuations of liquid level. The effectiveness of this technology has been verified in the production process of a steel plant, which has improved its production efficiency.

Study on heat transfer and solidification of Q235B steel rectangular billet in mold during continuous casting

2019, 35(4):  43-52. 

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The model of the heat transfer and solidification in the 165 mm×225 mm Q235B steel rectangular billet continuous casting process was carried out by coupling solidification shrinkage, bulging deformation, air gap, slag and mold flux heat transfer. And this model was used to calculate heat transfer and solidification of molten steel in the mold with 1.5 m/min casting speed. The results show that the wide surface temperature distribution of continuous casting billet is uneven under the influence of air gap distribution, and the formation of vibration marks can be divided into four stages compared with the shell. The first stage occurs within 0-0.17 m from the meniscus. The normal direction of the high temperature distribution is perpendicular to the direction of casting, and the vibration marks which normal direction is perpendicular to the direction of casting are formed. The second stage occurs within 0.17-0.26 m from the meniscus, the temperature distribution presents W-shape, and the vibration marks which are parallel to the casting direction are formed. The third stage occurs within 0.26-0.36 m from the meniscus, the temperature in the width direction is further homogenized, and the vibration marks parallel to the casting direction are also further homogenized. The fourth stage occurs within 0.36～0.80 m from the meniscus. The temperature distribution along the width direction of slab tends to be stable and the vibration mark also tends to be stable. The vibration marks morphology of the breakout billet is similar to the calculated temperature distribution. The calculation model can be used to explain the heat transfer and solidification behavior of continuous casting billet under this condition. After increasing the taper of the mold and adjusting the rigidity of the mold, the breakout ratio, the bulging ratio and the ratio of out-of-square exceeding the standard decrease significantly.

Research progress on physicochemical properties of continuous casting protective slag under electromagnetic field

2019, 35(4):  53-58. 

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The thermal history of the mold flux in the crystallizer was analyzed to understand the specific role of the mold flux in the crystallizer. At the same time, the melting characteristic, crystallization characteristic and rheological behavior characteristic of the protective slag under electromagnetic field were analyzed, and the influence of Joule heat generated by electromagnetic field was analyzed. It provides a reference for the systematic study of the metallurgical properties of the protective slag under electromagnetic field and further theoretical research.

Online judgment of longitudinal facial cracking on slab based on LMBP-MIV

2019, 35(4):  59-65. 

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The longitudinal facial crack is a kind of slab defect with high incidence. Online judgment of the influence factors of longitudinal facial cracks is of great importance to realize the intelligence and green of continuous casting production.According to the formation mechanism and influential factors of longitudinal facial cracks, an nonlinear relationship model of influence factors and longitudinal facial crack was established by BP neural network. Then, the model was optimized by the slab data and the LM algorithm. Furthermore, the weight of each influential factor was calculated using the MIV algorithm. Based on the above processes, the online judgment in the intelligence of the weight of influential factors of longitudinal facial cracks could be realized. When the longitudinal facial crack was occurred, the occurrence probability of longitudinal facial cracks was decreased by adjusting the process parameters online based on the judgment results. And the formation cause of longitudinal facial cracks could be promptly found based on the judgment resultsAfter the cast.

Prcatice of controlling the inclusion of SA516Gr70 acid resistant steel

2019, 35(4):  66-70. 

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In this paper, the main reason of cracking of an acid resistant sample of a large steel company in China is the inclusion of type B and Ds in the steel, which is modified by the operation of the LF furnace, calcification treatment, inhibiting the formation of the CaS, MnS inclusion ,the vacuum treatment of the RH, the vacuum treatment of the steel, and the protection measures to control the secondary oxidation of the steel, controlling the size of inclusions in molten steel less than10 μm, ensuring that the acidity of steel plate can meet the requirements.

Study on formation mechanism and control of layered defects in ingot rolling materials

2019, 35(4):  71-75. 

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In this paper, the causes and control measures of laminar defects in rolled steel during ingot rolling in Wuyang Iron and Steel Works are studied. The results show that cluster Al2O3 inclusions with a size of more than 80 μm in the middle zone along the thickness direction of the plate and inclusions formed by the inclusions involved in the mold flux are the main reasons for the unqualified ultrasonic flaw detection. Based on this, a scheme to solve the laminar defect of ingot tail part is proposed: adopting sequential deoxidization method, implementing soft argon blowing system, and implementing protective casting；optimizing the physical and chemical properties of mold powder to prevent its involvement. Through the above measures, the laminar defects of ingot tail decreased from 3.5 % to 1.5 %.

Causes analysis on outer fold of 60Si2Mn spring steel during piercing process

2019, 35(4):  76-80. 

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The outer folding problem of 60Si2Mn spring steel was studied by means of metallographic observation and scanning electron microscope analysis.The results of the metallographic study showed that the outer folding of 60Si2Mn spring steel originated from the surface crack defects of the round steel. Due to the processing rotation characteristics, the macroscopic rotation distribution and the microscopic dislocation shape were formed. The results of the electron microscope analysis showed that SiO2,SiO2-MnS-FeO,SiO2-MnO-FeO inclusions were distributed in the root, near surface and inside the defect . By tracing the process of smelting, it is inferred that the late addition of ferrosilicon in the process of smelting is the reason for the surface crack defects of round steel.