Table of Content

05 October 2010, Volume 26 Issue 5

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生产实践

Application of high performance low magnesium desulfurization compound

2010, 26(5):  1-4.  doi:

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In order to lower S content in steel, hot metal pretreatment is widely used in steel production. In this paper both lowmagnesium highperformance desulfurizer and AD desulfurizer are used to carry out experiments of hot metal desulfurization. The results show that S content in hot
metal treated by lowmagnesium highperformance desulfurizer is lower than that treated by AD desulfurizer, and iron loss is reduced by
0.41% as well. On the basis of industrial production data of lowmagnesium highperformance desulfurizer practiced in Pangang,
the linear regression of desulfurization rate and injection process parameters are analyzed and mathematical model proposed. The
predictive values of this model exhibit a good agreement with experimental results.

Discussion about comprehensive economic lining life of 300 t BOF

2010, 26(5):  5-7.  doi:

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Through measurements on the refractory consumption of the 300 t converter and the carbon and oxygen concentration of the liquid steel
it’s demonstrated that with the increase of the campaign life of the converter the cost for furnace repair materials per ton steel rises and the
lining cost per ton steel drops and the the concentration of carbon and oxygen in the liquid steel increases. In consideration of the refractory
materials consumption, steel quality and production plan allsidedly the more appropriate comprehensive economic lining life for the
300 t converter is 5 516~7 200 heats.

Development and application of new synthetic slag for refining technique

2010, 26(5):  8-10,2.  doi:

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Research & development and application of the new synthetic slag refining technology is carried out and by way of flushing the synthetic slag, adding CaC₂ and modifying the top slag in the process of tapping the deoxidation and desulphurization of both the hot metal and the
slag are intensified. The quality fraction of (FeO+MnO) in the top slag of the ladle is reduced to 2.5% and desulphurization rate reaches
17% averagely. The agglomeration and floating of the inclusions are accelerated and thereby the quality of the liquid steel is improved, nozzle
clogging reduced and smooth operation of continuous casting proess ensured. Since the process burden for the LF refining equipments is
alleviated and the common low and micro carbon steels can be casted directly without LF refining treatment the availability of facilities and
the cost of production are improved.

Optimization of secondary refining process for ultralow carbon steel

2010, 26(5):  11-15.  doi:

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The LFRH process for refining ultralow carbon steel is designed. In the meanwhile control measures of basicity, oxidability and quantities of LF ladle slag, [Al_s] and argon flow rate as well as forced decarbonization of RH furnace, variation of the furnace slag property and time allocation of RH furnace are studied; and the temperature schedule of the design process is formulated and the production cost of the new design process is compared with that of the traditional one. Results show that The chemical compositions, temperature and time node control of the new design process can meet the production demand completely and the production cost of the new process is cut down by
32.6 yuan/ton steel in comparison with that of the traditional one.

Alloying design and composition control of 800 MPa grade cold rolled dual phase steel

2010, 26(5):  16-20.  doi:

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In light of the requirements of weldability, formability and platability of the autosheets the basic concept of development of the hot dip
galvanized cold rolled 800MPa grade high strength dualphase steel sheets for automobile use is put forward on the basis of the low carbon
and low silicon composition design. The designed mechanical properties are achieved by improvement of the hardenability and the refinement of the ferrite crystal through addition of the alloy elements such as Mo, Cr and Nb.The effects of Cr, Nb and Mo on the structures and properties of low carbon, low silicon dualphase steel are studied and the strength requirments of the test steel are obtained by implementation of the new technological concept namely combination of the alloying design with the process design. In the meanwhile on the basis of analysis of the composition characteristics of the low carbon low silicon cold rolled dual phase steel the requirements of the composition control and the refining process for the high strength hot dip galvanized cold rolled dual phase steel are put forward.

Q390 steel production practice and cleanliness analysis

2010, 26(5):  21-24.  doi:

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The present paper summarized essentials of the process adopted by Xinyu Iron & Steel Co., Ltd, in refining the microalloy high strength steel Q390 with a production flow route of BOFLFRHCC and analyzed the cleanliness and the evolvement of the inclusions change
in the steel grade by means of systematically sampling, SEM&EDS. Results show that by adoption of the process the production condition
is steadygoing and the cleanliness of the steel produced is higher. In 10kg sample of the slab the large sized inclusions amount to
1.2 mgand most of the inclusions are CaO-SiO₂、CaO-SiO₂-Al₂O₃.

Development of gap corrosion resistant steel used for radiator

2010, 26(5):  25-29.  doi:

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Gap corrosion resistant steel plate used for radiator has been trialproduced for the first time based on QBOP→LF→FTSR production
process flow in order to improve steel grade development ability of thin slab continuous casting and rolling production line. Production
experience has been accumulated in the composition design, steelmaking and thin slab continuous casting and rolling technology.
Trialproduction results show that the yield strength, tensile strength and elongation of gap corrosion resistant steel plate after annealing
are 230～260 MPa, 350～360 MPa and 46.5％～49% respectively, which meet the need of this steel grade performance. The
comparative corrosion rate is below 50% of Q235 steel currently in use for radiator and
the gap corrosion resistant steel plate developed has better market prospect of application.

试验研究

Study on formation of IGF induced by Ti-Al complex deoxidization inclusion

2010, 26(5):  30-33.  doi:

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Formation of intragranular ferrite (IGF) induced by TiAl complex deoxidization inclusions in the hot metal has been investigated in a
tube resistance furnace in the laboratory. The effects of inclusions and cooling rate on the formation of IGF has been studied by changing
the compositions of the hot metal and the cooling rate. The Ti-Al complex inclusions which induce the formation of IGF are analyzed by
optical microscope and SEM. Experiment results show that large quantity of spherical Ti-Al complex inclusions in size of about
2 μm can be formed
by controlling the Ti and Al contents in the hot metal. In a specific cooling rate (10 ℃/s）those inclusions will be able to induce
formation of IGF. SEM observation results indicate that TiO_x,
Al₂O₃ and MnO are the main compositions of the Ti-Al complex inclusions.

Calculation of total reduction amount and ratio of dynamic soft reduction for slab continuous casting

2010, 26(5):  34-38,4.  doi:

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The dynamic soft reduction technology and the key technical parameters such as position, ratio, total amount and rate of soft reduction for continuous casting are described in this paper. In consideration of two aspects, namely technology and equipments the total amount of reduction and reduction rate for the dynamic soft reduction of the slab continuous casting are calculated and analyzed; and the method for calculation of the parameters of the soft reduction process is put forward, thus the theoretical basis for application of the software of the dynamic soft reduction is provided.

Study on increase of equiaxed crystal ratio of high carbon CC billet

2010, 26(5):  39-42.  doi:

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To eliminate or reduce the central segregation and increase the equiaxed crystal ratio a circular seam water cooling nozzle is designed and
an online control model and operating platform of the water cooling nozzle is developed. The industrial scale experiments on reduction of
hot metal overheat is carried out at the 150 mm×150 mm billet continuous caster in the Special Steel Co., Ltd of Huai Steel Corporation.
Results show that the circular seam water cooling nozzle is featured of high operability and closed loop control of the casting temperature of
the hot metal can be realized and the cooling medium online control system can meet the requirements of the
fluctuation of the casting parameters and stable drawing can last for 4 hours under the normal continuous casting process conditions and cast
about 400 t hot metal and reduce the overheat of the hot metal by14 ℃ and raise the equiaxed crystal ration by over 10%.

Study on mathematical model of vacuum degasification in VD refining process

2010, 26(5):  43-45.  doi:

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A mathematical model of vacuum degasification in VD refining process is developed according to the theory of gas solution thermodynamics
and degassing kinetics and a mathematical model for simulating the VD vacuum degasification process is established.
The model verified with the onsite production data is proved to be of high accuracy. In the meanwhile the effects of vacuum, process
time and hot metal stirring on the VD degasification process are analyzed.

Study on oxygen behavior during electroslag remelting

2010, 26(5):  46-50.  doi:

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Oxygen behavior has been analyzed during electroslag remelting.Results show that the oxygen has been increased during ESR when the
oxygen in the electrode is low and the increment of the oxygen hase close relations with the slag system. The findings through the experiment
and theoretical analysis show that the reaction between [Al] and [O] is the control reaction and the content of [O] in the ingots is
decided by [Al] in the electrode and Al₂O₃ in the slag pool. In order to obtain lower [O] in the ingots, the deoxidizers
should be added in the slag pool continuously during ESR and lowering the activities of Al₂O₃ in the slag pool.

Research on cleanliness of ULC Alkilled steel produced by LD→RH→CC route

2010, 26(5):  51-55.  doi:

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In this paper variation of T[O], [N] and inclusions in the ULC Al-killed steel during production with LD-RH-CC route is introduced, and the RH refining slag analyzed as well. Results show that total oxygen is (40.8~42.9)×10^-6 after RH refining. Total
oxygen content at the end of RH refining is completely independent of the total oxygen content in steel at the time of 3 min RH alloying.
w(T.O) and w(N) are23.55×10^-6 and 19.70×10^-6 in slab. The macro inclusions in the steel produced by
different processes are primarily composed of complex inclusions of aluminates resulting from reaction between Al deoxidizing products and
the entrapped slag. Whereas the micro inclusions mainly consist of Al deoxidizing products. Slag with high Al2O3 is propitious
to absorption of inclusions of Al₂O₃. If higher content of (FeO+MnO) exists in the slag it's of great necessity to lower the
(FeO+MnO) content as much as possible so as to raise the cleanliness of the hot metal.

Research on behavior of the nonmetallic inclusions in steel grade 45 in the metallurgy process

2010, 26(5):  56-59,7.  doi:

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By means of metallographic observation, sampleelectrolysing, SEM and EPMA, the quantity, dimension, morphologies and compositions
of nonmetallic inclusions in 20CrMnTi steel were investigated. Results show that the nonmetal inclusions can be removed in the RF
refining, but the T\[O\] and \[N\] contents in slab come to be 98.32×10^－6 and 43.46×10^－6, respectively because
air inhale exists in the process of casting; the diameter of microinclusions in slab are smaller and their volume fraction is 0.027%;
the microinclusions in the liquid steel are primarily composed of oxide, sulfide, calcium aluminates and silicate aluminates complex
inclusions. They are typical deoxidization and desulfurization products and microinclusions in the slab mainly consist of calcium
aluminates and silicate aluminates complex inclusions; the macroinclusions in the tundish and in a 10 kg slab reach 18.92mg and
12.53mg respectively and they are primarily silicates, silicate aluminates and calcium aluminates complex inclusions, in which silicate
aluminates takes up a larger portion.

Effect of TiN nanoparticles addition on microstructure and mechanical properties of 55SiMnMo steel

2010, 26(5):  60-64.  doi:

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Industry production experiments have been carried out on 55SiMnMo steel by adding TiN nano particles and the structure and the condition of TiN particle existance analyzed by SEM & EDS. Results show that the yield strength of 55SiMnMo steel with TiN nanoaddition has been increased by 10.0% and the size of the bainite refined to some extent than that without TiN addition. The TiN nanoparticles added in the 55SiMnMo steel exist in the steel in the form of pure substance and play the role of heterogeneity nucleation, nail and precipitation strengthening
in steel.

Effect of carbon segregation of billet on mechanical properties of 60Si2MnA spring steel

2010, 26(5):  65-68.  doi:

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60Si2MnA is one of typital spring steel grades. As far as the steel grade is concerned it require not only high strength but also good
ductibility. Besides, the interior and exterior mechanical property index of the steel grade needs to be uniform. In order to improve the
mechanical properties of 60Si2MnA steel in the core portion the effects of carbon segregation of billet on the mechanical properties are
analyzed using billets of various solidification structures produced with different continuous casting processes. Results show that the carbon
segregation in the core portion can be reduced and thus the uniformity of the interior mechanical properties of the steel prominently raised
by improvement in the equiaxed crystal ratio and refinement of the solidification structure.

Production practice of cylindersteel 34Mn2V produced by BOF→rectangular bloom CC route

2010, 26(5):  69-72.  doi:

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The high pressure cylinder steel 34Mn2V is produced by process route of BOF→LF+RH→rectangular bloom
CC→800mm mill using 90% hot metal and 10% home produced high quality scrap as the raw materials. The chemical compositions of the steel are more consistent and less fluctuated and their harmful residual elements extremely low and the grain size of the structure of the post normalized steel product smaller,their strength increased,higher impact ductility maintained and the security of the stamping formed cylinder improved.

辅助技术、材料及设备

Numerical study on flow characteristics of the cojet oxygen lance used in electric arc furnance

2010, 26(5):  73-75.  doi:

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The jet flow field of the cojet oxygen lance used in the production is calculated and analyzed by numerical simulation method and the characteristics of the cojet are compared with that of the conventional supersonic jet and effects of changes of the structural parameters on the characteristics of the oxygen lance jet discussed and the influence of the structure damage out of wear abrasion on the oxygen lance jet pointed
out from the viewpoint of practical operation.

Application of exhaust flow rate change and composition change to the maintenance of RH Vacuum System

2010, 26(5):  76-78.  doi:

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Changes of the exhaust flow and compositions in the leakage of the vacuum system at the typical location is analyzed. Based upon those characteristics of changes the running conditions of the vacuum system can be determined and the location of the leakage identified and the scope
of check on the leakage reduced as well. Therefore it's one of the most effective means to shorten the maintenance time of the RH vacuum
system.