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A new type of optimized riser structure was proposed, in which a low-emissivity board was inserted into the hollow interlayer of the material to increase the yield of the steel ingot. The insulation effect of different riser heights on the solidification process of steel ingot is numerical simulated. The results show that when the riser height can be reduced from 350 mm to 300 mm, the ingot yield can be increased by 1,92%. As the number of low-emissivity boards is increases, the riser insulation performance is also increased. [ABSTRACT FROM AUTHOR]

In this paper, a novel prediction method for low carbon steel is proposed based on an improved twin support vector regression algorithm. 300 qualified samples are collected by the sublance measurements from the real plant. The simulation results show that the prediction models can achieve a hit rate of 96% for carbon content within the error bound of 0,005% and 94% for temperature within the error bound of 15 °C. The double hit rate reaches to 90%. It indicates that the proposed method can provide a significant reference for real BOF applications, and also it can be extended to the prediction of other metallurgical industries. [ABSTRACT FROM AUTHOR]

Steel strip feeding technology can reduce the degree of superheat of the molten steel, change the solidification order of the molten steel; raise the equiaxed crystal rate of the slab and improve the continuous casting quality. The paper establishes the mathematical model of heat transfer and temperature field of casting billet of steel strip feeding in continuous casting mold. Results show that if Plate Billet is 1 000 mm × 220 mm and the steel strip is 100 mm × 3 mm, feeding position of parallel is 250 mm from the narrow side. When the feeding speed is 3,6 m/min, the superheat degree can be reduced by 5 °C, and the solidification length can be reduced by 2,9 m. When the feeding speed is 6 m/min, the superheat degree can be reduced by about 9 °C, and the solidification length can be reduced by 3,7 m. The results of the test in a steel plant are in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

The effect of a hollow riser on the upper heat dissipation of 76 tons and 8 corners ingots is studied by numerical simulation in this paper. Through the simulation of the heat transfer of the traditional riser, the 1 gap riser and the 2 gaps riser ingot, this paper draws a conclusion that the solidification time of the riser part of the riser is the longest in the 2 gaps scheme, and the solidification time of the central molten steel is 31417s, which is far higher than the other two schemes. The heat flux in the riser of the 2 gaps scheme is obviously larger than the other two schemes, which slows down the advance of the solidification front. The 2 gaps scheme is stronger than the other two schemes for reducing the cooling speed of the riser line center and the shoulder joint. It is particularly significant to reduce the cooling rate of the shoulder joints, which is more conducive to expanding the angle of the solidification front and fully filling. [ABSTRACT FROM AUTHOR]

In this paper, the effect of exothermic riser on ingot solidification is studied by numerical simulation. Through the study, it is concluded that the combustion of exothermic risers delayed the solidification of steel in riser, and the solidification time increased significantly, extending about 8 143 / s. In the later stage of solidification, the temperature isotherm of the ingot is smoother than that of the ordinary ingot, making the angle of the solidification front larger, which is conducive to feed. The shrinkage of the ingot with heat riser is better than that of the common ingot. The shrinkage above 10% of the ingot is almost not found in the ingot with exothermic riser, and the shrinkage of the ingot is mainly concentrated above the riser line. And it obviously improves the internal quality of the ingot. [ABSTRACT FROM AUTHOR]

The thermal stress coupling calculation model of initial shell in groove mold is established for temperature field and stress field calculation. The calculated results show that groove mold can improve heat transfer of casting initial shell and form peaks and valleys of temperature and stress, and the whole curve corresponding to overall number of grooves. The surface temperature of initial shell increase with the width of grooves increase, the non-uniformity of initial shell surface temperature and stress also increases. The surface temperature of initial shell decrease with the space of grooves increase, the non-uniformity of surface temperature and surface stress of initial shell increases. Groove depth has a little influence on heat transfer of initial shell surface. [ABSTRACT FROM AUTHOR]

Hollow side wall insulation mathematical model of unidirectional solidification temperature field was carried out. With the aid of finite element analysis software ProCAST, directionally solidified ingot temperature field with hollow lateral wall insulation during the process of unidirectional solidification was simulated. The results show that the numerical simulation results are in good agreement with experimental results. The hollow side wall significantly improves the thermal insulation effect, inhibits heat transfer directionally solidified casting side wall, and reduces the lateral heat of the ingot. As the hollow side wall was used in nuclear power, large-scale steel and other special steel ingot improve the yield and quality, provide the basis of theory and application. [ABSTRACT FROM AUTHOR]

The ladle bottom argon blowing process has an important influence on the refining liquid steel. The effects of diameters, insertion depth of immersed cylinder and bottom gas flow rate on the flow state of liquid steel and the amplitude of liquid steel surface are numerically simulated for 150t ladle. The results show that the slag entrapment of liquid steel surface can be confined by changing the diameters and insertion depths of immersed cylinder. The effects of gas flow rate, diameter and insertion depth with immersed cylinder on the flow of molten steel in the ladle were analyzed. [ABSTRACT FROM AUTHOR]

According to the air insulation, the use of riser hollow way to reduce the riser heat transfer, improve the riser insulation effect. In the experimental simulation, the corundum brick inner and outer wall and the air gap temperature were measured. The optimal air gap is 25 mm from the heat transfer theory and the outer wall temperature, but the insulation effect is not obvious. To further explore, proposed in the inner and outer walls to 25 mm as a unit into the insulation board improvement measures. The results show that the insertion of the insulation board can greatly reduce the temperature of the outer wall and improve the insulation effect. When inserting a heat shield, the heat flow can be reduced by about 50 %. With the increase in the number of inserts inserted, the insulation effect is gradually increased [ABSTRACT FROM AUTHOR]

In this paper, the solidification process of eleven tons flat steel ingot is simulated by the finite element analysis software PROCAST, and the solidification state of the ingot with and without chassis is analyzed and compared. The results show that the forced cooling chassis makes low temperature area of the bottom ingot enlarged. And it has little influence on the temperature field and the solidification speed of the upper ingot. For the small flat steel ingot, the forced cooling chassis will deteriorate the shrinkage. [ABSTRACT FROM AUTHOR]

In this paper, cooling plan is optimized to solve the central porosity problem of 450 mm diameter steel electrode ingot. The central porosity of ingot in corresponding cooling plans is calculated by the finite element analysis software ProCAST. The results show that in the plan of independent riser and strengthened cooling in lower ingot part, the central porosity has been significantly reduced. [ABSTRACT FROM AUTHOR]

Objective: Data from the HIV/AIDS surveillance sentinel sites was used to identify the recent HIV-1 infections and to estimate the HIV-1 incidence and epidemic trends among intravenous drug users (IDU), MSM, female sex workers and men attending the sexually transmitted disease clinics in Sichuan province. Methods: Specimens collected from IDUs, MSM, female sex workers and men attending the sexually transmitted disease clinics sentinel sites were confirmed as HIV-1 positive and tested with BED-CEIA. Annual HIV-1 prevalence and incidence rates were calculated and the incidence was adjusted by McNermar method. Results: A total number of 194 223 serum specimens were collected and HIV antibody tested, with 5 297 HIV-1 positive. 4 640 of the positives underwent BED-CEIA, with 749 identified as recent infections. During 2011-2015, HIV-1 incidence rates of the four types of population appeared as 5.16% (95% CI : 4.65-5.66), 0.22% (95% CI :0.16-0.28), 0.57%(95% CI : 0.45-0.69), 7.53% (95% CI : 6.06-9.01) and 0.44% (95% CI : 0.36-0.53) respectively. Significant differences were seen in the HIV-1 incidence rates. Conclusions: The HIV-1 incidence rates of IDUs from other sentinel sites in Sichuan province, female sex workers and men attending the sexually transmitted disease clinics appeared low, showing that the AIDS prevention and control activities worked effectively. However, the HIV-1 incidence of MSM was still at high level and even rising, suggesting that HIV-1 transmission between MSM and IDUs was possible.