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Li C.,University of Science and Technology Beijing | Cheng G.,University of Science and Technology Beijing | Cui A.,Shougang Qianan Iron and Steel Co.
Advanced Materials Research

Through the mathematical model of RH vacuum decarburization, the decarburization mechanism of argon gas bubble surface was studied. By the RH equipment of Shougang Qian'an Iron and Steel Co. Ltd for background, the calculated results of this model showed that the decarburization quantity of argon gas bubble surface was about 8% that of overall decarburization. In the initial conditions was constant, the ascension of argon flowrate will promote the decarburization quantity of argon gas bubble surface, free surface and splash droplet surface as well as reducing the decarburization quantity of internal liquid steel decarburization. Based on the commercial production data, it was found the best opportunity of ascension blow argon flowrate to acquire lower carbon content in relatively shorter time. © (2011) Trans Tech Publications, Switzerland. Source

Yu Y.,Shougang Institute of Technology | Wang C.,Shougang Institute of Technology | Wang L.,Shougang Institute of Technology | Chen J.,Shougang Qianan Iron and Steel Co. | And 2 more authors.
Journal of Iron and Steel Research International

For high strength interstitial free (IF) steel containing P element, the salt and pepper (SP) defects exist on the strip surface and could not be eliminated effectively by optimizing the hot rolling process, such as temperature and cooling water. The combination effect of Si and P on the characteristic of tertiary scale has been studied comprehensively by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA), and the concept is proposed firstly that Si and P are of combination effect which can be utilized to eliminate the SP defect. The results show that the SP defects were induced by the rolled-in scale during finish rolling. P can be enriched at the interface between substrate and tertiary scale, which is easy to decrease the adhesion of tertiary scale. However, Si enrichment at the interface between substrate and tertiary scale can increase the adhesion. The SP defects can be eliminated completely, which is attributed to the accompanying enrichment of Si and P. © 2015 Central Iron and Steel Research Institute. Source

Jiang L.-Y.,Northeastern University China | Zhao C.-J.,Taiyuan University of Science and Technology | Shi J.-H.,Northeastern University China | Yuan G.,Northeastern University China | And 2 more authors.
Journal of Iron and Steel Research International

Temperature deviation between surface and the center of hot rolled strip is formed during ultra-fast cooling (UFC). Surface temperature would rise when temperature deviation goes up to an extent, and strip re-reddening phenomenon will appear. Strip re-reddening affects the stability of strip microstructure, property and temperature control precision. Thus, it is necessary to conduct research on re-reddening temperature changing law to improve strip property and temperature control precision. Strip temperature trends for various strip thicknesses and ultra-fast cooling rates were obtained by numerical calculation method. Re-reddening temperature, temperature deviation between surface and center, and boundary layer position changing law were obtained. By comparison, some conclusions were obtained: UFC re-reddening temperature and laminar cooling (LC) re-reddening temperature were linear to ultra-fast cooling rate respectively. Ultra-fast cooling rate affected UFC re-reddening temperature greatly, but it had little effect on LC re-reddening temperature. Equations which were used to calculate UFC re-reddening temperature, LC re-reddening temperature and maximum temperature deviation were obtained. The position of boundary layer stayed in 1/4 strip thickness. © 2015 Central Iron and Steel Research Institute. Source

Chen B.,Shougang Institute of Technology | Pang Z.,Shougang Institute of Technology | Liu B.,Shougang Institute of Technology | Qing J.,Shougang Qianan Iron and Steel Co.
Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015

High efficiency decarburization in RH refining process and carbon pick-up in continuous casting are two keys to produce extreme low carbon steel(C ≤ 0.0013%). Decarburization process can be divided into two stages, rapid decarburization period and slow decarburization period. The main parameters that affect the rapid decarburization rate are initial carbon and oxygen content before RH treatment and the pressure drop model in vacuum vessel. The ultimate vacuum treatment time is the main parameter that affects the slow decarburization and the end-point carbon content. In this paper the parameters that affect decarburization and carbon pick-up are studied and some conclusions can be made as follows. Control the initial [C] and initial [O] in molten steel and eliminating the pressure drop platform can accelerate the decarburization rate. The optimal initial [C] and initial [O] are (0.02-0.025)% and (0.05-0.07)% with the value of initial [C]/[O] is 0.3-0.4. By decreasing the carbon content of refractory materials of ladle, tundish powder and tundish working lining, the carbon pick-up in molten steel can be controlled less than 0.0002%. Through all the measures, the qualified rate of extreme low carbon steel has been improved from 30% to more than 95%. Source

Gao Y.-N.,Yanshan University | Peng Y.,Yanshan University | Sun J.-L.,Yanshan University | Su X.-T.,China National Heavy Machinery Research Institute Co. | And 2 more authors.
Kang T'ieh/Iron and Steel

For the abnormal vibration phenomena frequently occurring in the rolling of thin gauge products on Finisher 2 (F2) of 1580 hot strip mill of Qiangang, a comprehensive test about its torsional vibration, vertical vibration and horizontal vibration was done. The results show that the torsional vibration and vertical vibration are forced vibration, and the excitation is from horizontal vibration of work rolls. The too large gap between the work roll bearing liner and rack liner is the direct cause of the mill vibration. So, to suppress the vibration, a program which is to reduce the gap between the work roll bearing and rack has been suggested. On the site, two sizes liner gasket with thickness of 0.3 and 0.7 mm has been installed on the work roll bearing respectively. The tested signal shows that the abnormal vibration is significantly reduced or even disappeared. The results are satisfying. Source

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