Steelmaking

Control technology of surface quality of 360mm×450mm CC bloom

2009, 25(02): 1-3,28. doi:

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In view of defects of the surface pit and longitudinal crack on 360 mm×450 mm continuously cast blooms, the cooling scheme employed in the continuous bloom caster has been optimized. Production application shows that the surface quality of the bloom has been prominently improved ,for instance ,the defect rate of the bloom surface pit has been reduced to 0.14 %,from original 37.13% and the defect ratio of surface longitudinal crack of the bloom lowed down to 0.30 % from 53.52 % and therefore the technological requirements of the hot delivering and hot charging of the CC bloom can be satisfied.

Causes analysis and countermeasures on rhombic deformation of casting billet in Chongqing Steel

2009, 25(02): 4-7. doi:

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Reasons for rhombic deformation of continuous casting billet in Chongqing Iron and Steel Co.Ltd. are analyzed in this paper. The main factors causing the rhombic are found to be firstly the unmatching of the mould condition with the steel grade and the casting speed and at the same time the primary cooling and secondary cooling are not performed uniformly .Very good effects have been achieved since adoption of the optimized measures.

Productive Practice of X65 pipeline steel

2009, 25(02): 8-11. doi:

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The present paper discourse upon the productive features of X65 pipeline steel produced by the 150 ton converter - 3500mm Steckel mill in Anyang Iron and steel Co. Ltd., such as composition designing, technological process flow, metallurgical structure and performances and so on and results show that the properties of X65 pipeline steel produced by adoption of the low cost composition system bearing lower carbon-manganese-niobium and molybdenum free as well as by implementation of the inclusion control technology and the TMCP process are excellent and they are basically in conformity with the standard requirements of the X70 pipeline steel.

Analysis on breakout of bloom continuous caster and countermeasures

2009, 25(02): 12-15. doi:

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The statistics of breakout of the bloom continuous caster in No.1 steelmaking plant of WISCO in 2006 have been made and the main characteristics and mechanism of sticking breakout and longitudinal corner crack induced breakout analyzed. The main causes to the above mentioned breakouts are found to be such a few factors as the performance of mold powder, accuracy of mold, extent of hot metal overheat, casting speed, and alignment of the submerged entry nozzle with the mold and etc, and thereupon certain countermeasures have been taken up. As the results, the breakout rate of caster is decreased remarkably.

Low carbon steel production with BOF slag-remaining practice

2009, 25(02): 16-18. doi:

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A few problems occur such as slopping in the process of hot metal charging,difficulty of igniting the steel bath at the initial blow, frequent slopping and slag accumulation on the converter bottom during the whole process of oxygen blowing when the slag-remaining practice is adopted in making low carbon and ultra low carbon steels at the120t combined blown converter in Masteel. To solve those problems technological measures have been taken and effective results achieved accordingly.

Analysis and control on the cause of tundish’s nozzle clogging in casting ML35 steel

2009, 25(02): 19-21,3. doi:

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The cause of tundish nozzle clogging in casting KISC ML35 steel has been investigated and analyzed by X ray diffraction in connection with process analysis. The results show that the main cause of the clogging is inadequacy of Ca-treatment. Accroding to the investigation the process is optimized. As the result tundish nozzle clogging has been eliminated and the average heats of continuous casting increased from 8 heats/batch to 23 heats/batch and casting process stabilized thereupon.

Study and control practice of Als in GCr15 bearing steel strip

2009, 25(02): 22-25. doi:

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The characteristics of press forming type GCr15 bearing steel strip are described in this paper. The necessity and advantage of deoxidization with aluminum for producing this type bearing steel are put forward. The actual effects of feeding aluminum in different melting stages are practised and the influence of slag basicity on the aluminum feeding process and final Als content in steel is discussed in this paper.

Practice of dehydrogenation process of VD furnace for high quality forged steel

2009, 25(02): 26-28. doi:

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Hydrogen embrittlement and flake are common defects of high quality forged steel, which make mechanical performance of steel decrease seriously and even cause rejection of the steel. Minimization of hydrogen content in molten steel by adopting vacuum treatment in a VD furnace is an effective way to reduce the defect stated above. Dehydrogenation process of VD has been studied in this paper. Based on the analysis of effect of various factors on the dehydrogenation good results have been achieved by taking proper process parameters.

Development and application of the real-time tracking & dynamiccontrol model for slab continuous casting

2009, 25(02): 29-32. doi:

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On the basis of the slab continuous casting solidification heat transfer model for calculation on the solidification of the coupling multi-element dual phase zone the real-time tracking & dynamic control model for slab continuous casting ( CCPS ONLINE) has been developed by use of the method of slice element in a mode of the discrete grids in constant interval. The model can be applied to adjust the key process parameters of slab continuous casting procedure (secondary cooling water amount, segment roll gap) dynamically according to the reasonable metallurgical rules and the online tracking information of as-cast slab, so as to obtain steady & reliant casting process conditions and good slab quality. The model has been put into industrial practice successfully. The results of the on-site production and the relevant tests show that the model has high reliance and strong practicability due to the reasonable control arithmetic and the good simulation precision. It can be widely used in the slab continuous casting industry.

Analysis on temperature field of submerged entry nozzle during preheating

2009, 25(02): 33-36. doi:

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The present paper analyzes the effects of factors such as the preheating device and preheating method on the preheating of the submerged entry nozzle and studies the transient heat transfer process in preheating the submerged entry nozzle using the finite element technique and acquires the distribution of the temperature field and the temperature of the key points of the nozzle after preheating of the nozzle. Results indicate that the preheating temperature of the nozzle neck can be increased by adopting the smaller size of preheating device, placing the fan system in a higher position, enlarging the evacuating flux and opening the plug after preheating the tundish for 30 minutes.

Optimization of flow field in slab mold of Liuzhou Steel

2009, 25(02): 37-40,4. doi:

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In accordance with the production condition of slab CCM in Liuzhou Steel’s steelmaking plant, applying the water model physical simulation, the effects of SEN outlet shape, outlet angle, immersion depth and pulling rate on the fluid flow in mold have been studied by measuring the wave amplitude and impact depth. The characteristics of the flow field in the mold and the flow rate of hot metal over the liquid level have also been studied by using numerical simulation. The results indicate that the reasonable flow field of mold could be obtained both at middle and high pulling rate when the outlet of SEN is made in ellipse shape with 18°of the outlet angle and 160 mm of the immersion depth. Breakout rate of the continuous caster has been cut down by 43.1%, and the conditioning rate of slab surface decreased by 44.9% since application of the new SEN in the production. The metallurgical effects are obvious.

Research on structural optimization of four-strand round billet tundish

2009, 25(02): 41-44. doi:

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In order to purify the liquid steel and raise the floating rate of the inclusions in the tundish the flow field and removal of non-metallic inclusions in a four-strand tundish under different weirs have been studied by water model experiments. The results show that a big difference in flow characteristics exists between two outlets at the same side of the tundish controlled by the present weir. Compared to the inside outlet, the outside outlet has longer minimum residence time and peak concentration time and larger dead volume fraction. So the present weir can not meet the technical requirements for inclusion floatation and temperature homogenization. The improved weir can satisfactorily settle the flow synchronism between outlets. The dead volume fraction is decreased by 6.65% and the removal effect for inclusions increases. The industrial test shows that the improved weir is better than the original one in reducing total oxygen and inclusions..

Analysis on degree of continuation of thin slab

2009, 25(02): 45-47,6. doi:

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In this paper, the concept of continuation degree is introduced into the thin slab casting and rolling process, and the continuation degree of the thin slab casting and rolling in Steel Company Z, T, and M is calculated respectively. The calculating express of the optimized continuous degree is proposed and the factor affecting the continuous degree analyzed.

Simulation study on optimization of flow control device for a single-strand tundish in slab continuous casting

2009, 25(02): 48-51,7. doi:

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The fluid flow in the tundish of stainless steel slab casting has been studied by water model experiment and numerical simulation. The results show that severe problem existed in the flow field of the original tundish; and short circuit phenomenon was obviously in existance and the ratio of the dead zone was relatively larger and thus the homogenization of the hot metal was not so acceptable; and by orthogonal optimization tests an optimal scheme of the dam and weir combination is drawn up and the flow field of the tundish is improved; and by application of the optimized plan in which the gas bubbling curtain is used in place of the original weir the flow field of the tundish is further improved. On the basis of the water model experiments and numerical simulation calculation and in combination of the actual conditions of the Steel Plant it’s strongly recommended the technology of the gas bubbling curtain should be be utilized in lieu of the original weir in the single strand continuous casting tundish and the optimal process parameters of the gas bubbling curtain of the tundish for the stainless steel continuous caster in Taigang be chosen as follows: the wall is positioned 1150mm away from the original weir and the bottom gas blow rate controlled within the limit of about 120 L/min.

Investigation in morphology and composition of inclusions in wire rod for Steel cord

2009, 25(02): 52-55. doi:

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By way of comparative analysis on the morphology and composition of inclusions in wire rod produced by five different steel factories at home and abroad，a difference was found out on the control level of morphology and composition of inclusions between domestic and foreign steel factories，especially on the two aspects of plasticity and size of inclusions. At the meantime, the comparison about the contents of T[O], [N] and [Al]s in wire rod was performed, and the results show that the foreign steel factories have a better control effect than domestic ones.

Study on self-adapting control system for large electrode arc furnace of Steelworks

2009, 25(02): 56-58. doi:

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In light of the characteristics of non-linearity,heavy lag behind,strong coupling, time change, heavy working environmental interference as well as stochastic disturbance and according to the self-adapting control theory the control device with PLC as its core element is used to realize the automatic and accurate control on the lift-up and fall-down of the electrode of electric arc furnace. As the results the arc breaking、short circult and oscillation are reduced effectively; the labor intensity reduced and the quality of products improved. The control system has been used reliably by several steelworks for years.

Sublance measuration and Composition Prediction in BOF Steelmaking

ZUO Kang-lin;ZOU Jun-su;SUN Xiao-hui;WU Jian_zhong; Marrten Spanjers

2009, 25(02): 59-61. doi:

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In Meishan Steel-making Plant the newly developed Heraeus sublance technology is used in connection with the self developed compositions prediction model to control the overall process of the converter refining. Results show that the prediction accuracy of the processing carbon content and end-point carbon content has been improved and their prediction deviation rates lowered down to 0.023% and0.006% respectively.

Research on variable parameters of SIMULINK based Mould hydraulic vibration system

2009, 25(02): 62-65. doi:

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Based on the mould hydraulic vibration mathematics model in connection with actual operation of the hydraulic vibration equipment, the present paper analyzed the dynamic characteristics of the mould hydraulic vibration system with the MATLAB/Simulink module. Simulation has been made on the displacement of the hydraulic cylinder output under the conditions of different control parameters and different hydraulic component characteristic parameters. Results show that the dynamic characteristics of the system can be improved by reducing the load stiffness and load viscosity , increasing oil source pressure and oil volume modulus of elasticity in an appropriate limit.

New progress and trend of development of oxide metallurgy process

2009, 25(02): 66-69,7. doi:

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The main content of the oxide metallurgy technology and the effect of the application of this technology on the microstructure and properties of the steel are described. The progress of the oxide metallurgy in the Japanese and Chinese steel plants and the most advanced technologies and application in the high heat input welding developed by some of the steel corporations are introduced. The new application of the oxide metallurgy technology in the solidification, press work, non-modified steel and heavy plate production is recommended and the trend of development of this technology foreseen as well.

Study on evaluation method of steel cleanliness

2009, 25(02): 70-73. doi:

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Based on the experimental results characteristics of various evaluation methods are analyzed and application scope of every method is determined. It is recommended that several different methods have to be appropriately selected to evaluate the cleanliness of steel in light of the different process and different steel grade. For evaluation on the cleanliness of the super low carbon steel the appropriate method is to analyze the cluster shaped inclusions over the surface of the slab. With the development of refining technologies inclusions of steel come to be less than before, thus better evaluation methods should be developed for evaluating cleanliness of steel.

Control and elimination of contamination of large sized EAF

2009, 25(02): 74-77. doi:

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Proceeding from such a few aspects as the fume purification system, furnace slag disposal and treatment of the ferric dust of the EAF the present paper discourses upon the development of the control and elimination of the comination of EAF at home and abroad and the problems existing and in the meanwhile points out the direction to the development of the control and elimination of the EAF contamination in China.

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