Steelmaking

Discussion on high efficient and low cost clean steel production platform:One of the key technologies for steel industry in 21st century

2011, 27(1): 1-10. doi:

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The high efficient and low cost clean steel production platform is a key technology for steel industry ,which basicly and largely affects on the efficiency,quality and cost of the steel production and it will final determine the marketing competitiveness enhancing of steel companies.The clean steel platform is the integration of pretreatment technology of hot metal, BOF technology,secondary metallurgy technology,100% continuous casting optimizedsimplified process network technology and dynamicorderly operating material flow technology.It emphasized that at present, the high efficient and low cost clean steels platform should foucs on following aspects: thoroughly understand that coordinationsteady is the core of the clean steel production platform；high efficient and constant continuous casting speed technology is the source for the clean steel production platform operating dynamically and orderly, and is also the key for highquality, engery saving and low cost.

Progress of production technology for clean steel at Baosteel

2011, 27(1): 11-14,1. doi:

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The main equipments of steelmaking plant of Baosteel are briefly introduced in this paper. The progress in control technology of phosphorus, sulphur, total oxygen, nitrogen, carbon in steel is discussed at Baosteel. The control level of residual elements in heavy plate is introduced too.

Practice of steelmaking production economically

2011, 27(1): 15-17. doi:

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In order to quicken steelmaking production rhythm and reduce energy consumption and material consumption of steelmaking process the producing feasibility of 5 converters in the Steelmaking Plant of Baosteel has been analyzed and different production schemes compared and the countermeasures for special steel production put forward as well. Since adoption of 5 converters production electric power consumption has been saved by over 100 000 kWh every day, average time of converter tap to tap reduced by 17 minutes, transferring and buffering time of converter decreased by 3 minutes and steelmaking production economically realized.

Process practice of steelmaking with 100% hot metal in 160 t EAF

2011, 27(1): 18-20,6. doi:

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The present article introduces technological process for manufacturing the dephosphorized hot metal at the 160 t EAF in the 1.5 million t stainless steel production line in Taigang using 100% hot metal as the raw material and by brief analysis on the quality, cost and production it's believed that the demand of refining in the stainless steel production line can be met by adoption of a 160 t EAF using 100% hot metal as the raw material. The process is an inseparated part of entire operating process of the 1.5 million t stainless steel production line in Taiyuan Stainless Steel Co., Ltd.

Practice of sulfur content control in smelting extralow sulfur pipe line steel

2011, 27(1): 21-23. doi:

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Based on the testing practice of extralow pipe line steel in tanggang, the present paper introduces the technology of sulfur control in the overall process, points out that the key control points for refining the extralow steel are hot metal pretreatment and LF refining，and key to HIC resistance is to control inclusions in steel. It's concluded that by controlling the sulphur content in the entire process the extralow sulphur pipe line steel can be produced.

Production practice of improving billet CC availability

2011, 27(1): 24-27. doi:

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By way of adoption of a series technical measures such as analyzing factors affecting the operating rate of the billet continuous caster, drawing up the stoppernozzle assembling principle, optimizing the physical and chemical indexes of various fluxes and the current intensity of the electromagnetic stirring, stabilizing the superheat degree, reducing break accidents caused by stopper malfunction and steel overflowleakage, the actual operating rate of CCM is increased.

Analysis and control on corner cracks of 45 steel in continuous casting of rectangular bloom

2011, 27(1): 28-30,7. doi:

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In this paper the formation mechanism and influence factors of corner cracks of 45 steel in continuous casting of rectangular bloom were analyzed. The results show that inhomogeneous heat transfer in mould is the primary cause to formation of the corner cracks and appropriate mould taper is the key factor to avoid corner cracks. Measures to reduce corner cracks such as improving quality of molten steel, strengthening technological control and optimizing mould taper are proposed. The production practice indicates that occurring rate of corner cracks is decreased from 89.73% to 18.05%, and cracks(≥1.0) are eliminated basically.

Water modeling on the configuration of turbulence inhibitor in tundish

2011, 27(1): 31-35. doi:

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The influence of the configuration of turbulence inhibitor on the characteristics of fluid flow in a tundish is studied through water modeling experiments. The results show that the fluid flow behavior in the tundish is greatly affected by the configuration of turbulence inhibitor. Turbulence inhibitor with grooved shape inside, 30 mm in length of its extending lip at the top of the sidewall and flat bottom inside has the best flow field in the tundish. It is propitious to prolong minimum breakthrough time and average residence time, decrease its dead volume fraction and increase the ratio of the plug volume fraction to dead volume fraction. Also, it is the most favorable to remove inclusions in the tundish. Besides, the length of its extending lip at the top of the sidewall influences on the flow field much higher than its inside shape and bottom shape.

Effect of different combinations of weirs and dams on flow field in two strand tundish

2011, 27(1): 36-40. doi:

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Based on the similarity theory the flow field in twostrand slab continuous casting tundish with three different combinations of weirs and dams has been studied by water modelling experiments. The results show that in case 1 the distance between weir and dam ( “weirdamend dam” plan) is undesirable because the end dam can not effectively control the flow field in tundish, and consequently the mean residence time and the minimum residence time of the flow in the tundish is short and the volume fraction of dead zone is larger (27.9%); in case 2 (“damweirend dam” plan) the flow field conditions are prominently improved since the volume fraction of the full mixing flow zone and plug flow zone is increased and the dead zone decreased to 21%; in case 3 (“two weirtwo dam” plan) the residence time of the flow in the tundish is obviously reduced and the dead zone rate is minimum (16.7%) because the route of the flow fluid is extended due to installation of a group of dams and in the meanwhile the fluctuation value of the micro conductance is minimum (0.025 ms/cm). The optimal plan is therefore case 3.

Study on key technology of X80 pipeline steel

2011, 27(1): 41-45. doi:

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The present paper expatiates the key technology taches of control on the oxygen, sulphur, nitrogen and inclusions in refining the X80 pipeline steel. The quality fraction of the dissolved oxygen of the pipeline steel X80 can be certainly controlled within the limit of (3~5)×10^-6, and the oxygen in steel exists basically in the form of inclusions and it can be removed by means of Ca treatment, soft blowing, vacuum treatment and floating-up of inclusions in the tundish. In the meanwhile the hot metal protection has to be well made in the overall process and low sulphur slag shall be well prepared. The key tache for control of sulphur in steel is to keep the oxygen content in steel at an extremely low level and the initial Al addition fully in place in LF refining helps promote desulphurization. N pickup in the pipeline steel involves key taches:1), exposure of surface of liquid steel to the open air and insufficiency of continuous casting protection, 2), N pickup in the process of converter tapping as well as LF refining, and 3), vacuum treatment greatly help remove N. In Catreatment and modification of the inclusions in the pipeline steel the contents of Al, O, S and Ca shall be controlled appropriately and the quality fraction of the dissolved oxygen in the pipeline X80 is(3～5)×10^-6 and at the temperature of 1,600 ℃ and lower the permissible quality fraction of sulphur in steel is(25.8～43.0)×10^-6 and 21.6～36.0)×10-⁶ respectively.

Study on high temperature mechanical properties of NbTi orNbTiV microalloyed steels

2011, 27(1): 46-49. doi:

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High temperature mechanical properties of cast slab of Nb Ti or Nb Ti V microalloyed steels have been tested by using a Gleeble2000 thermal simulation test machine. The test results indicate that the third brittle temperature range of tested steel are 600~850 ℃ and 750~900 ℃ respectively．The cracking sensibility and the mechanism of brittleness at the third brittle zone are investigated. The fracture morphology of billet at plastic temperature range and brittle temperature range are analyzed by SEM. The results will provide theoretical evidence for solving the defect of corner cracking of Nb Ti or Nb Ti V microalloyed slabs.

Study of billet continuous casting technology for martensitic stainless steel

2011, 27(1): 50-53. doi:

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A series of severe problems such as upgrowth of columnar crystals, central porosity and shrinkage cavity as well as hollow surface exist in the martensitic stainless steel due to the special properties of this steel grade. In light of the above mentioned conditions the solidification characteristics and high temperature physical feature of this steel grade are investigated and the processing problems in the process of casting the martensitic stainless steel solved and thus the quality of the products guaranteed.

Research on decarburization process of ultrapure ferrite stainless steel in VOD

2011, 27(1): 54-56,6. doi:

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Based on the feature of stainless steel melting the effect of VOD process parameters on the decarbonization rate and end carbon is investigated by dynamics and thermodynamics analysis of decarbonization and a lot of industrial tests are carried out. The results indicate that higher decarbonization rate and lower end carbon content can be achieved by raising the melting temperature, increasing O2 flow rate and Ar blowing rate, reducing oxygen pressure and oxygen lance position.

Effect of Ce on the impact toughness of 202 stainless steel

2011, 27(1): 57-60. doi:

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The changes in the impact toughness of 202 stainless steel by adding different contents of RE Ce element are investigated through mechanical performance testing, SEM and EDS. The results show that the inclusion morphology is changed and the impact toughness of 202 stainless steel is improved obviously within an appropriate limit since proper content of RE Ce element is added. 202 stainless steel with RE Ce element of 0.016% in mass fraction has the best impact toughness.

Analysis on coupled thermal stress of the submerged nozzle in pouring the steel

2011, 27(1): 61-65. doi:

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Using finite element method the temperature and thermal stress distribution of the submerged nozzle during preheating and pouring liquid steel is simulated. The results show that in the process of pouring liquid steel the submerged nozzle is subject to serious thermal shock, and the temperature undergoes a tremendous change in a short time, particularly the temperature at the region from the neck part to the top surface of the nozzle varies obviously with a stepshape distribution; Thermal stress at the interior wall in contact with liquid steel is very small and that at the exterior wall is much larger and with the advance of time the thermal stress field region gradually decreases along the radial direction of the nozzle. The higher the preheating temperature, the lower the thermal stress of the nozzle during pouring steel.

Endpoint control techniques for converter steelmaking

2011, 27(1): 66-70. doi:

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The present paper summarized development of the end point control technique for converter steelmaking，introduced methods for end point control of converter steelmaking such as artificial experience control, static state control, dynamic state control and automatic control and etc，pointed out end point that application of the intelligence control technique including the neural network，fuzzy inference，and expert system etc, is proved to be the direction of development of the endpoint control technique for the large and medium sized converter steelmaking and affirmed that by introduction of the artificial intelligence endpoint control technique in steelmaking the compositions and temperature of the liquid steel can be accurately predicted, measured and controlled on the line at the end point of converter steelmaking and thus the duration of steelmaking can be effectively shortened, consumption reduced cost cut and product quality improved.

Discussion on effective utilization coefficient of onlinetwooperating position LF

2011, 27(1): 71-74. doi:

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In order to raise the effective utilization coefficient of the twooperating position LF in the steelmaking process flow of BOFLFCC the concept of effective utilization coefficient η for the online twooperating position LF is put forward under the specific hypothetical conditions by analyzing the process time of the twooperating position LF refining and the relation of η with the upstream process and downstream process discussed. Thereupon the effective utilization of the LF equipments can be evaluated and the number of related converters and maximum productivity of the continuous caster can be calculated as well. In the meanwhile the information can be used for guiding the design of the steelmaking plant and organization of production of the steelmaking shop.

Calculation on the tilting moment of AOD and analysis on the strengthof its attached structure

2011, 27(1): 75-78. doi:

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In order to determine the tilting moment and strength of the important structures under different angles for 36 t AOD software “Solidworks” is applied to find out the position of gravity center of converter shell, steel liquid and attached structure at different angle. And thereupon by calculating the tilting moment the variation curve of the tilting moment is achieved and at the same time it's determined that at the rotation angle of 45~75 the AOD has larger tilting force. In the end the strength of the trunnion ring, an important component of AOD is analyzed with finite element software ANSYS and the stress value of trunnion ring Von-miseses with the variation of the rotation angle is obtained. As the results a calculation method and means is provided for the safety running and assessment of the structure of the similar kind.

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