Steelmaking

Production practice of high hot metal ratio refining pattern in 120 t converter

2013, 29(1): 1-3,14. doi:

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To realize the benefit maximization the offgas analysis and dynamic control technology as well as temperature control technology by addition of burnt dolomite in the ore are applied to solve the problem of severe temperature and composition fluctuation, high probability of splashing
and low end point hit ratio due to surplus heat and realize the targets of w(P)＜0.015 % in tapping, 91.2 % of dual hit ratio of end point C-T, reduction of the slag materials such as lime from 87.1 kg/t to 79.5 kg/t and decrease of the metal loss from 10.3 %to below 8.7 %in refining the low carbon and low phosphorous steel series with high hot metal ratio in the 120 t BOF converter in No.1 Steel Making and Rolling Mill in Maanshan Iron &Steel Co., Ltd and very satisfactory results have been achieved in reduction of production cost and material consumption.

Production practice of refining aluminum steel by argon blowing

2013, 29(1): 4-6. doi:

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The present paper introduces how to solve the influence of the deoxidizing products Al2O3 on quality of liquid steel and castability in the process of casting by optimization of deoxidization process and application of Ca treatment and realize consistent production of Al steel by "converterargon blowcontinuous casting" process route and thus tension of production of brand steeel by LF is relieved and the production cost is reduced as well without affecting the product quality in the over moded section of the steel making plants of Chongqing iron & Steel Co., ltd.

Production practice of optimization of low carbon and low silicon SPHC steel refining process

2013, 29(1): 7-10. doi:

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In combination with the basic situation of SPHC steel in a specific plant, the characteristics and the main problem of the process are analyzed. Based on the process optimization, the desulfurization rate has been raised to 45.5 %from original 35.7 % and the ratio of inclusions
in the slab less than 1.0grade comes up to 80 % . Thus quality of SPHC steel has been highly improved and the production cost

Technical development and application of 3D spray technology for 400 mm ultrathick slabs

2013, 29(1): 11-14. doi:

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Influences of slab thickness and 3D spray technology on the transverse corner cracks are analyzed. Results show that for the 400 mm ultrathick slab the mechanical properties in the low ductility region III are the internal cause and the over high cooling intensity at the corner of the slab in the leveling section is the external one for the transverse corner cracks. Thereupon a few effective measures for improvement in the transverse cracks of the 400 mm ultrathick slab are put forward. The transverse corner cracks of the slab are obviously reduced and the notching rate of the slabs is down to 0.35 % and the surface quality of slabs effectively improved.

Analysis on the cause and control of disqualification of Q345R steel plate by ultrasonic detection

2013, 29(1): 15-18,2. doi:

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In view of disqualification of Q345R steel plate (Thickness range from 14 to 22 mm) by ultrasonic detection, Zdirection tensile detection and SEM-EDS analysis are carried out to find out the origins and results indicate that centerline segregation, MnS inclusion and cracks and so on are main reasons of disqualification of Q345R steel plate by ultrasonic detection. Various factors related to qualified rate of Q345R steel plate by ultrasonic detection are analyzed. Qualified rate of Q345R steel plate by ultrasonic detection have been improved by taking a series of technological measures such as low superheat casting, reducing sulfur content, increasing of stacking slow cooling time of the slab and etc.

Inclusions control of pipeline steel in steelmaking process

2013, 29(1): 19-23. doi:

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The high grade pipeline steel produced in a specific steel work by the BOF→LF→RH process route is investigated. The inclusions in the steel
are examined and analyzed by application of certain analytical techniques such as metallographic examination、SEM and EDS and then the
mechanism of formation of the inclusions is studied according to the thermodynamics. Results show that when the w(AlS) is about 0.025 % the inclusion Al2O3 in steel can be easily modified to low melting point C12A7 if w(CaO)＞18×10-6，w(S)＜0.011 % in the steel. A series of technological measures have been put forward such as intensification of the topbottom combined blown process of the converter, improvemnt in the argon blow scheme in both the argon blow station and LF facility and adjustment of the refining slag series so as to control w(CaO)/w(SiO2) within the limit of 4.5 to 6.0 and w(CaO)/w(Al2O3) in 1.7 to 1.9and finally control w(S) in below 0.000 8 %and confine the grade of oxide and sulfide inclusions in grade 1.0in steel.

Study and practice of converter refining process of non-quenched crankshaft steel

2013, 29(1): 24-27. doi:

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In order to come up to the standard of nitrogen content in steel the process route of “converter→LF→RH→rectangular bloom CC”has been adopted in Benxi Iron & Steel (Group) Co., Ltd. and in the full RH process nitrogen is used as the lifting gas and at the same time manganese nitride alloy is added to meet the need of nitrogen in steel. Practice shows that the process is feasible and w(N) can be strictly controlled within the limit of (110~160)×10-6. Moreover w(H) in tundish liquid steel can be effectively controlled in less than 2.5×10-6 and the results of check and examination of the steel products conforms to standards.

Development of hot rolling product as the substitution of cold rolling product by boron micro-alloy technology

2013, 29(1): 28-31,3. doi:

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By taking technologies of boron micro-alloy low-carbon softening steel, strictly control the chemical compositins and nitrogen content in
the liquid steel and optimization of the continuous casting and rolling processes in the thin slab casting and rolling production line(FTSR) in
Tonghua Iron and Steel Co.,Ltd., the steel grade of TG270 has been successfully developed as the substitution of SPHC used for raw material
of cold rolling. Both quality and mechanical properties of the products reach the requirements of customers.

Study on sulfur control technology for non-orientation electrical steel

2013, 29(1): 32-35,5. doi:

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In cognizance of the problems of low desulphurization rate for hot metal, large sulfurrecovery in converter as well as high sulfur content in
products in producing non-orientation electrical steel with vanadiumcontent hot metal countermeasures have been carried out. Sulfur
content in non-orientation electrical steel is decreased obviously by way of study on technologies of desulphurization for hot metal with
vanadium & titanium, sulfurrecovery control in converter and desulphurization in RH refining process as well. The results of industrial tests
show that w（S）=0.001 9 %~0.006 9 %, and 0.004 2 %is average,
the rate w（S）≤0.008 % is as high as 100 %, and the rate w（S）≤0.005 % reaches 91.43 %.

Analysis on sulfur control in ultra low sulfur steel by LF-RH process

2013, 29(1): 36-39. doi:

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The present paper mainly studies how the LF slag deoxidizer, LF dynamics condition and the Ca-treatment affect the desulphurization after
RH. The results show that the w(FeO+MnO) can be controlled in below 0.5 % after adding more than 300 kg aluminum particles in the refining slag and w(S) in the steel is reduced from original 30×10-6to 630×10-6; and when the bottom gas flow rate is 500 L/min w(S) in the steel can be reduced to 6×10-6 after 10 min and too high or too low blow argon flow rate will affect the desulfurization efficiency. In this research later Ca-treatment in RH has no desulfurization ability, but addition of the calcium
cladded wire can inhibit the sulfur pickup and keep the sulfur content in a low level.

Influence of AOD processing on nitrogen content of 0Cr18Ni9 stainless steel

2013, 29(1): 40-43,4. doi:

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In light of the problem of heavier fluctuation of nitrogen content and argon consumption in steel in refining the stainless steel 0Cr18Ni9 the effects of such a few AOD pocessing factors as carbon content in the initial liquid steel, alloy element content and temperature as well as blow rate of oxygen, nitrogen and argon and blow time on the end point nitrogen content are investigated and in the meanwhile the AOD operating process parameters are studied and optimized as well.

Transformation of non-metal inclusions in ultra-low oxygen steel for petroleum steel pipe in LF-VD refining process

2013, 29(1): 43-47. doi:

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The total oxygen content,nitrogen content,the formation and transformation of non-metallic inclusions and the influence of refining slag on inclusion removal in the experiment steel at each phase of EAF→LF→VD→CC process have been analyzed and studied.The results show that w(T.O) in the experimental steel drops by 42.83 % on average in the process of LF refining and after VD vacuum treatment w(T.O) and w(N) fall by 48.77 % and 10.72 % respectively. In the LF refining process the nonmetal inclusions in the liquid steel are transformed in such a proper order as “Al2O3series inclusion MgO-Al2O3series inclusion→CaO→MgO→Al2O3 series inclusion” from external part gradually to internal part, in which the transformation of MgO-Al2O3 series into CaO-MgO-Al2O3series is carried out gradually from outside to inside and CaO and MgO in the inclusion are incompatible. Control of basicity of the initial refining slag in about 2.5 will be more advantageous for absorption of inclusions in the slag.

Experimental study of ladle furnace desulfurization with CaO-Al2O3-SiO2 based refining slag

2013, 29(1): 48-51. doi:

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The experiment on desulfurization of molten steel using CaO-Al2O3-SiO2 based refining slag is carried in a small furnace in the laboratory. The effects of refining slag basicity, Al2O3, CaF2on desulfurization of molten steel are
studied. The results show that the dusulfurization rate is over 80 % when the refining slag basicity is changed from 2.85to 3.45. However, when the mass fraction of Al2O3 in refining slag is 24 %, the desulfurization rate is 83.7 %. With the increase of CaF2 in refining slag the desulfurization rate rises initially and then falls down. The optimum composition of the refining slag is w(CaO)/w(SiO2) =3.0, w(CaF2)=7 %、w(MgO)=6 %、w(Al2O3)=24 %.

Study on desulphurization slag system in RH refining process for electric steel

2013, 29(1): 52-56. doi:

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In light of the difficulty of production of high level electrical steel w(S)≤0.006 %steadily in Panzhihua steel & vanadium Co., Ltd. the process technology of RH desulfurization system has been formed by developing the RH desulfurizer, modifying the ladle slag and controlling the process parameters. Industrial experiments show that the desulfurization rate of hot metal rises to 42 % and the w(S) of the finished products is controlled in below 0.005% and total oxygen and nitrogen contents are also well controlled and no carbon pick up occurs in the hot metal due to addition of desulfurizer since this technology is implemented. Therefore requirments for production of high level electrical silicon steel grade are satisfied.

Study on deformation inclusions of calcium treatment on high quality pipe line steels

2013, 29(1): 57-60. doi:

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A investigation was carried on the variations of inclusion types in B(PSL1) steel before and after calcium treatment. The modification mechanism of Al2O3 and high level of CaS was analyzed by thermodynamics. The results show that Al2O3 can be modified into 12CaO·7Al2O3 inclusions which are liquid at steelmaking temperature, while majority of CaS were generated,and MnS can be completely modified partially into CaS under the present amount of CaSi wire fed.

Analysis of inner cracks of AH32 steel continuous casting slab

2013, 29(1): 61-64,7. doi:

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Taking ship steel plate AH32 as the object of study the precipitation behaviour of MnS in the steel is analog computed with thermodynamics software TheroCalc and in the meanwhile the effects of change of element content on the law of MnS precipitation as well as characteristics of solidification process of ship steel plate AH32 are studied and micro observation and energy spectrum analysis on the inner cracks of the steel plate are conducted using SEM Quanta-400. It’s concluded that the primary cause to the inner crack is schistose MnS precipitant arising from eutectic reaction. A series of counter measures such as reduction of sulfur content, low drawing speed and weak cooling in the secondary cooling zone, optimization of electromagnetic stirring process and calcium treatment have been implemented and very sound results have been achieved.

Analysis on reason of small surface longitudinal cracks of Q345B steel plate

2013, 29(1): 65-68. doi:

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In order to find the causes of small surface longitudinal cracks in Q345B steel plate rolled from continuous casting slab, spectrum analyzer, optical microscope, scanning electron microscopy and energy spectrum analysis are employed to examine the chemical compositions and microstructures of surface crack and type of inclusions in the cracks. The results show that cracks are caused by skin blowhole in continuous casting slab. The skin blowhole exposed and burned in the heating process prior to rolling can not be pressed due to oxidation. The defect area cannot participate in synchronous deformation in the process of rolling extension and eventually forms the small surface longitudinal cracks.

Design of guide baffles in tundish and metallurgical effects analysis

2013, 29(1): 69-73. doi:

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In order to improve metallurgy effect of sixstrand billet tundish, the hydraulic simulation experiments are conducted to investigate the effects of the guide holes parameters on flow field characteristics in sixstrand billet tundish in the Metallurgy Engineering Technology Center of University of Science and Technology Liaoning. And the range analysis is conducted on them. Finally it is determined that the affecting factors are diameter, height and leanangle of the guide holes. The affecting level for flow field characteristics in tundish is: diameter>lean-angles>height. Using it as the guiding ideology the guide baffles are designed by CFD numerical simulation and the diameters of three guide holes are determined to be 93 mm,72 mm and 36 mm, positions, (220 mm,140 mm),(350 mm,280 mm) and (700 mm,300 mm) and leanangle, (21°,15°),(8°,23°) and (10°,28°) respectively. Industrial experiments indicate that installation of the guide baffles in the tundish will effectively improve the characteristics of molten steel flow and increase the effect of tundish metallurgy.

Analysis on main quality defect of beam blank production and prevention

2013, 29(1): 74-78. doi:

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In order to improve the beam blank quality and the qualification rate of the products all factors causing formation of the defects of the beam blank have been analyzed comprehensively. The surface defects of the beam blank occur essentially in the process of shell solidification in the mould and the defects mainly involve surface longitudinal cracks, longitudinal corner cracks, transversal surface cracks, star cracks, inclusions on the surface, blow holes and concave pit. The inner defects mainly including central cracks, straightening cracks, segregations, center porosity and triangular zone cracks are closely related to over high S & P content in the hot metal, unreasonable distribution of the secondary cooling water, misalignment of the support system and surface temperature rise of the beam blank. The shape defects of which the main representation is deviation of flange parallelism, arise principally from inhomogeneous cooling on the inner and outer bow. In light of the above mentioned defects of the beam blank preventive measures are accordingly put forward.

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