Steelmaking

Manual cleaning process on slag inclusion defects of continuous casting slab

2011, 27(3): 1-3. doi:

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The present paper introduces the law of slag defect distribution in the CC slab in Baosteel and improvement in the manual scarring process.Results of examination show that by adoption of the improved process the slag defects can be effectively reduced and the quality of the slab surface raised as well and moreover the new process is simple and easy to operate and popularize.

Introduction and controlling of hydrogenation in heavy rail steel

2011, 27(3): 4-6. doi:

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Effects of hydrogen in steel on the quality of steel and its harm to the heavy rail steel are described and detection method of hydrogen in steel and correlated equipments introduced as well.The origin and processing content of hydrogen in steel in production of the heavy rail steel by way of converter→LF→RH (VD) →continuous casting process route are expatiated and measures for effective control of hydrogen in the heavy rail put forward and actual results of application of the new method discussed.

Development of niobium microalloy long products at Ma Steel

2011, 27(3): 7-11,7. doi:

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Application of niobium microalloy technology in development of long products at Maanshan Iron & Steel Co.,Ltd.is introduced.In recent years niobium microalloy HRB400 bar,HRB500 bar,H beam used for offshore oil platform，H beam used for railway truck,H beam under American standard,fireresistant H beam,MFT8 non quenched non tempered wire rod are developed at Ma Steel.Great progress has been made in development of niobium microalloy long products in the corporation.

Effect of fluctuation of sulfur content on equiaxed grain rate of alloy steel slab

2011, 27(3): 12-14. doi:

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In light of heavy fluctuation of the equiaxed grain rate in the microalloy CC slab in a specific plant production experiments and theoretical analysis have been made in order to control the quality of the slab consistently.Results show that the primary factor affecting the equiaxed grain rate of the slab is the content of segregation susceptible elementsulphur,when the overheat degree in steel is stable and drawing speed and cooling intensity are equal.In order to prevent against great fluctuation of the equiaxed grain in the slab the content of sulphur and other segregation susceptible elements has to be controlled consistently besides reduction of fluctuation of overheat in the liquid steel and stabilization of the drawing speed and cooling intensity.

Process control of carbon content in IF steel

2011, 27(3): 15-18. doi:

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The change of the carbon content and the process of recarbonization in refining the IF steel in Panzhihua Iron & Steel (Group) Corporation are intradued.And the main factors for carbon pickup are aralyzed as well as quantity of recarbonization.By charging the globular oxide scale and adding Mn alloyinto the RH and implementing the enforced decarbonization by RH as well as controlling the carbon content in the mould flux and refractory materials the carbon content in steel are reduced.The above mentioned results can be used as a guide for future production practice of IF steelmaking.Since the improvement of the steelmaking process the average carbon mass fraction of the finish products of the IF steel have been reduced to about 18×10-6 and therefore prominent metallurgical effects achieved accordingly.

Equipment and application of LF refining furnace at Meishan Steel

2011, 27(3): 19-21. doi:

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The present paper introduces briefly the main equipments and technological parameters of No.2 LF refining furnace at Meishan Iron and Steel Company and describes its production effects in controlling temperature,desulfurization,deoxidation and nitrogen pickup.Through a period of production the equipments are running normally,the average rate of temperature rise reaches 3~4 ℃/min and the temperature control accuracy attains ±5 ℃and the lowest w(S) is about 4×10^-6and large quantity of ultralow sulfur steel with w(S)≤20×10^-6 could be produced steadily.The targets of w(O)≤35×10^-6 and the increased w(N)≤8×10^-6are realized and each technological index arrives at the designed specification.

Research on highefficiency oxygen blowing technology of 120 t converter at PZH Steel

2011, 27(3): 22-24. doi:

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In order to meet the requirements of semisteel making the original design of the nozzle of lance was optimized and all parameters concerning the new oxygen lance were reviewed in the industrial experiments in Vanadiumrecovering and Steelmaking Plant of PZH Steel in view of the practical conditions of steelmaking in the plant.Results shows that compared with the original oxygen lance the new designed one has a better metallurgical effect, the average slagforming time and blowing time was shortened by 1.37 min and 0.77 min respectively, oxygen consumption reduced by 1.05 m³/t and materials for slagforming decreased by 2.5 kg/t.

Process parameter optimization of mold electromagnetic stirring in billet continuous casting

2011, 27(3): 25-28. doi:

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By measurement on the magnetic induction intensity in axial and longitudinal direction of mold under the conditions of different electromagnetic stirring parameters it’s verified that the magnetic induction intensity value in the mold tends to be larger when the electrical current comes up to 510 A and frequency 3 Hz and the variation of magnetic induction intensity in the longitudinal direction of the mold becomes similar and the distribution of the magnetic field is uniform. Results of measurements on the macro photo of the equiaxed crystal in the section of the billet show that the ratio of the equiaxed crystal is highest when frequency comes to 3 Hz and the electrical current 510 A.

Experimental study on rational technology of desiliconization pretreatment for high phosphorus content hot metal

2011, 27(3): 29-32,3. doi:

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The effects of solid oxygen and gaseous one on desiliconization pretreatment efficiency and temperature drop of high phosphorus content hot metal were experimentally studied.The results showed that in desiliconization by using solid oxygen the reaction completed in just two minutes because the slag volumes were high,temperature drops were great and oxidation rates of silicon and manganese were fast whereas in desiliconization by using gaseous oxygen in partial replacement of solid oxygen the final desiliconization effects were not deteriorated and the desiliconization rate arrived at greater than 92 % even if the slag volumes were low,temperature drops less and desiliconization velocities slow Therefore the rational technology of desiliconization pretreatment for high phosphorus content hot metal is to control the amount of the solid desiliconizing agents,use appropriate amount of gaseous oxygen in replacement of solid oxygen (higher than 33 % in weight percent) and restrict to shorter treatment time (about eight minutes).

Researches of desulfurization and dephosphorization efficiency of 150 t convert

2011, 27(3): 33-35. doi:

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The influence of converter conditions,bottom blowing effect and Si and Mn content in the molten steel on the dephosphorization and desulphurization is analyzed by using a large number of the industrial experimental data.Results show that the primary factors affecting the dephosphorization efficiency involve bottom blowing effect,end point temperature,endpoint carbon,basicity of the converter slag,hot metal compositions (silicon,manganese and phoshorus) and process operation control whereas the principal factors impacting desulphurization are mainly bottom blowing effect,end carbon,basicity of converter slag,initial sulphur content and process operation control.

Effect of different deoxidizer on nonmetallic inclusions of highpressure boiler steel

2011, 27(3): 36-39. doi:

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The high pressure boiler tube steel P12 produced by EAF→LF→VD→MC process route is deoxidized by two different deoxidizers Si-Ca and Si-Al-Ba and sample is taken out of the tube steel in each and every process step and then law of variation of the total oxygen content,quantity and sizes of inclusions in steel in each process step,compositions of the inclusions in the forged products and content and average size of various Al inclusions are studied.Results show that w（T.O） can be controlled in less than 20×10^-6 using two different deoxidizers after VD treatment and the inclusions in steel in each process step by deoxidizer Si-Al-Ba is less than by Si-Ca.However the molten steel deoxidized by Si-Al-Ba is more severely reoxidized although in the process of casting reoxidization apparently occurs in the molten steel deoxidized by both deoxidizers.

Experimental study on effect of magnesium-aluminum alloy on deoxidation of molten steel

2011, 27(3): 40-43. doi:

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Deoxidation behavior of ZG25 molten steel is investigated using magnesium alloy as deoxidizers. Al, Al-Mg and Mg-Al are chosen as deoxidizers for
deoxidization of the molten steel and then changes of the inclusions in steel after deoxidization are compared with one another. Results show that Mg bearing alloy can not only deoxidize the molten steel but also has much stronger desulfurizing capacity and majority of inclusions of the Mg bearing alloy after deoxidization have transformed into compound inclusions, in which the Al₂O₃inclusions mainly change into MgO·Al₂O₃ and the sulphide inclusions FeS and MnS turn into compound sulphide inclusions MnS·MgS.

Thermodynamics analysis of TiN inclusion formation in tyre cord steel

2011, 27(3): 44-46. doi:

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Thermodynamics of TiN inclusion formation in tyre cord steel has been calculated. By the theoretical calculation it’s found that in the later stage of solidification of the tyre cord steel TiN inclusions are extremely easy to occur due to the lower equilibrium concentration of TiN at the solidliquid interface. In contrast to the tyre cord steel with lower carbon content the high carbon one is more sensitive to formation of TiN inclusions because in the later stage of solidification lower temperature at the solidliquid interface inevitably leads to lower equilibrium concentration of TiN and thus the TiN inclusions are very easy to occur. On the basis of the theoretical analysis appropriate technological measures have been taken and as the results the ratio of the qualified tyre cord steel closely related to the TiN inclusions has been apparently raised.

Study on cleanliness of stainless steel of turbine by VOD refining

2011, 27(3): 47-50. doi:

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With the help of metallographic microscope, big sample electrolysis and SEM, cleanliness of ultralow carbon stainless steel during VOD process has been studied. It is found that w(O) reaches 250×10^-6 because of the endpoint control delay of blowing oxygen in VOD. Higher oxygen content in steel and
low basicity of the refining slag are primary causes for higher inclusion contents in steel. The number of inclusions larger than 10 μm are 0.56~0.58 pieces per square millimeter, in which the large and medium size inclusions in each 10 kg sample come up to 1.71~2.41 mg. In view of lower cleanliness of the steel certain technological measures have been put forward such as prolonging the vacuum holding time to 10~12 min, selecting high quality refining slag, ensuring the basicity of slag R≥3 and prolonging the soft blowing process time by 15~20 min. Since the improvement of the steel-malaig process w(T.O) have been reduced to （60~77）×10^-6.

Study on precipitation model of TiN during solidification of microalloyed steel SAPH440

2011, 27(3): 51-54. doi:

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The precipitation model of TiN during solidification of the titanium containing microalloyed steel has been studied by mathematical model. By using the model TiN will not precipitate in steel SAPH440 of liquid phase. During solidification, TiN begins to precipitate when f_s equals to 0.65. The precipitation of TiN may curb the segregation of titanium and nitrogen. The results show that occasion and condition of TiN precipitation in the microalloyed steels can be controlled by adjusting the content of titanium and nitrogen and continuous casting process and its detriment to the steel properties can be reduced.

Study on segregation of sulphur in freecutting steel 38MnVS

2011, 27(3): 55-59. doi:

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The microsegregation of sulphur resulting in the uneven distribution of MnS in freecutting steel 38MnVS is studied by using a mathematical model in which the transition of solidification and the precipitation of MnS are considered. The segregation of carbon, silicon, manganese, phoshorus, sulphur during the solidification process and the effects of carbon, manganese, sulphur and cooling rate on the interdendritic segregation of sulphur are discussed. The results show that carbon content in steel influences the interdendritic segregation significantly. The segregation of sulphur decreases with the increase of ferrite, but increases with the
increase of austenite when the mass fiaction of carbon is 0.1 %~0.5 %. The concentration of sulphur in the dendrite is exacerbated by the increase of sulphur content at the end of solidification. Increasing manganese content and cooling rate are conducive to inhibit the segregation of sulphur.

Study on center porosities and shrinkage cavities of rectangular blooms in continuous casting of 45 steel

2011, 27(3): 60-63. doi:

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In light of the defects of center porosities and shrinkage cavities of 240 mm×280 mm 45 steel the formation mechanism and influence factors of those defects are analyzed and thereupon such a few technical measures as strengthening technological control, optimizing the flow rate of secondary cooling water, applying dynamic secondary cooling and optimizing MEMS parameters are proposed. The results show that center porosities (≥1.0) are obviously decreased and basically eliminated. The occurring rate of shrinkage cavities is decreased from 46.15 % to 22.31 %, and shrinkage cavities (≥1.0) basically
eliminated.

Comparison on the arrangements of ladle furnace

2011, 27(3): 64-67. doi:

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The present paper discusses a few different patterns of the ladle furnace arrangements and compares the building complex conditions, function disposition and annual processing capacity of the plant comprehensively and points out that the arrangement patterns should be adopted according to the technological conditions of the engineering project and the production requirements. In the end it's determined that in the new project of an additional LF installed in Pugang of Baosteel a stationary type two transfer cars arrangement pattern should be acceptable.

Design and application of CAS-OB

2011, 27(3): 68-70. doi:

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CAS-OB liquid steel composition and temperature homogenizing speed, temperature rising speed and alloy yielding rate are affected by correct selection of design parameters such as intensification of oxygen supply and position control of the CAS-OB oxygen lance and outline dimension of the submerge tube, depth of the submerging tube and position of the submerge tube as well as the argon pressure, flow rate and position of the ladle argon hole. The present paper introduces the design and application of CAS-OB in combination of the practical project.

Development and application of MgO-C sprayingrepair material for converter

2011, 27(3): 71-73. doi:

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In order to improve the converter lining life and reduce steelmaking cost, a new type of MgO-C sprayingrepair material was developed. The main factors affecting the sprayingrepair material such as particle distribution and carbon source are discussed according to the wearing mechanism of the basic sprayingrepair material. Through series of tests the sprayingrepair material with good flowability, high adhesion ratio, good corrosionresistant properties and erosionresistant performance was developed. The life expectance is increased by 30 % and this can make good economic benefits.

Technical progress in smelting process of MnCr gear steel

2011, 27(3): 74-78. doi:

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The properties and application of MnCr gear steel series are introduced and the problems currently existing in production of the steel series in China analyzed and the results and difficulties in production of the steel in Laigang Group particularly discussed. In the end in order to improve the quality of the steel products certain technological measures for improvement of the steel grade such as intensifying the electromagnetic stirring, refining molten steel and controlling the cleanliness and chemical compositions of the steel are put forward.

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