Showing papers in "Journal of Iron and Steel Research in 2011"

Effect of Rolling Parameters on Microstructure and Property of Vacuum Rolling Clad Steel Plate

Abstract: Under various total rolling reduction ratios,two same continuous casting slabs were subjected to vacuum rolling cladding to examine of possibility of achieving the heavy gauge clad steel plate with a high quality.The microstructure and mechanical properties of clad plate were mainly investigated.At a total rolling reduction ratio of 10%,some obvious like-strip defects,which existed in the interface of the clad plate,consisted of the interstice and Al-Si-Mn oxide indicating by in situ observation method and energy dispersive spectroscopy.At a total rolling reduction ratio(≥30%),the interstice at the interface vanishes.Enhancement of the total rolling reduction ratio results in decreasing of the oxide size.Furthermore,with enhancing total rolling reduction ratio,Z direction tensile strength and elongation increased significantly.While at a total reduction ratio of 10%,the brittle fracture appeared at the interface,at a total reduction ratio of 70%,the ductile fracture occurred in the parent material.

Melting Process of Steel Strip and Microstructure of Ingot With Steel-Strip Fed in Molten Steel

Abstract: Steel strip-feeding in mold process was a effective technical to improve quality of continuous casting product.Melting process of steel strip in mold was general researched.Ingot structure was tested simultaneously.Results show that feeding-strip melting in molten steel presents two stages: the solidified stage and melted stage.Remaining strip shows a thickness increase of 100 percent in solidifying stage.Terminal time of strip melted in molten steel is decided by strip thickness and degree of superheat.It is less than 100 s with maximal thickness of 14.6 mm.Equiaxed grain rate of cast ingot raises 49.3% from 51.2% to 75.3% with 3% strip fed.Size of refined grain decreases to 4.1 mm.A suitable area rate of steel strip-feeding recommended is 1%.

Research of Effect on Stress for Rolling Railway Axis by Multi-Wedge Synchrostep

Abstract: Multi-wegde synchrostep rolling by cross-wedge rolling is one of the most anvanced methods that can form rolling railway axis.The rolling quality main lies on inner transversal stress and shearing stress of rolling workpiece.Based on the rotated theory of multi-wegde rolling,through using Ansys/Ls-Dyna FEM software,multi-wegde synchrostep rolling railway axis by cross-wedge rolling was simulated.It was systemically researched that technics parameters effect on transversal stress and shearing stress.In the meantime,the calculating model was verified by experiment.It is obtained that the law of technics parameters has effect on rolling railway axis by multi-wegde synchrostep cross-wedge rolling.These conclusions can provide scientific basis for multi-wegde synchrostep rolling railway axis by cross-wedge rolling and rolling better quality.

Effect of Aluminium,Copper and Chromium on the Stacking Fault Energy and Mechanical Properties of Fe-21Mn-0.4C TWIP/TRIP Steel

Abstract: Based on bibliographic data,the thermochemical model of stacking fault energy(SFE) in Fe-Mn-C system was presented.Using the model SFE of Fe-21Mn-0.4C with few percent of Aluminium,Copper and Chromium in addition was calculated.The SFE increases with the content of Aluminium and copper,contrary to chromium.The SFE of Fe-21Mn-0.4C alloy was effected by its phase composition: when the SFE is below 10.7mJ/m2,its phases are γ+e,while the SFE is 10-19.02mJ/m2,its phases are γ+e+a,as long as the SFE is greater than 19.02mJ/m2,it is full of austenite.The change of SFE of Fe-21Mn-0.4C with few percent of Aluminium,Copper and Chromium in addition is not accordance with mechanical properties changes,more factors effect mechanical properties of Fe-21Mn-0.4C alloys,furthermore study is needed.

Research Progress on High Deformability Pipeline Steels

Abstract: Research progress on high deformability pipeline steels at home and abroad was reviewed and the corresponding microstructure characteristics of the steels were also introduced.The work on composition design,study of phase transformation behavior,determination of optimal thermo-mechanical controlled processing(TMCP) parameters and final production trial for an X65 grade high deformability pipeline steel with microstructure of(polygonal ferrite+bainitic ferrite) is described.

Influence of Alkali and Alkali-Chloride on Coke in the Blast Furnace

Abstract: Aiming at the burden degradation and the problem of which alkali has a strong impact on blast furnace process in recent years,the influence of alkali on coke was studied.Predecessors mostly used the method of making the coke soak in the alkali carbonates solution("immersion") to research the influence of alkali on coke.According to the lower part of the blast furnace in which the most of alkali is in the form of gas,a equipment of adsorbing the alkali vapors was designed to research the influence of alkali vapors on coke.The calcium chloride,which was used to prevent reduction disintegration index of sinter,would react with alkali to produce other different chlorides in the blast furnace,and the impact of the different chlorides on high temperature strength of coke were tested.

Behavior of Oxide Precipitation in Solidification Process for Alumium-Titanium Deoxidized Steels

Abstract: To promote the precipitation of the dispersed oxide particles is an effective means for improving the heat afect zone toughness.By thermodynamic calculation of Al-Ti-O system,the behavior of the oxide precipitation during solidification in Al,Ti complex deoxidized steel was analyzed theoretically and the optimum processing condition for forming Ti2O3 nuclei was put forward at the beginning of solidification.The results show that small particles of Ti2O3 and complex precipitates can be precipitated by strict control the content of Al,Ti and the oxygen activity.The morphology,size and distribution of precipitates were statistically analyzed.

Properties on Titanium-Bearing Blast Furnace Slag

Abstract: Blast furnace slag is one of the decisive factors to ensure the smelting progress successfully.A large number of scholars at home and abroad have studied the physical and chemical characteristics of the slag.The similarities and differences of physical and chemical characteristics of three types,which have different contents of titanium,such as the contents of titanium in slag were more than 20%,in 5%-20% and less than 5% respectively,were summarized and compared,then the actual application of titanium-bearing blast furnace slag in the blast furnace production was introduced and the direction of the future research was pointed out.

Feature Dimensions Reduction and Its Optimization for Steel Strip Surface Defect Based on Genetic Algorithm

Abstract: The 32-dimensional feature vectors of intensity,texture and geometry characteristics for six kinds of steel strip surface typical defects images were extracted.The 32-dimensional feature vectors of steel strip surface defect images were reduced and optimized based on genetic algorithm,and 20-dimensional feature vectors were selected to classify types of the defects images.The recognition and classification experiments were carried out to contrast the 32-dimensional feature vectors with 20-dimensional feature ones with BP neural network for six kinds of steel strip surface typical defects images.Furthermore,the results using genetic algorithm was contrasted with principal component analysis.It is shows that the algorithms of features extraction and genetic algorithm are effective.

Study on the Mechanism of Trace Magnesium Improving Carbide in Bearing Steel

Abstract: The segregation of trace Mg in bearing steel is the key to improve the carbide.Considerable segregation of Mg in bearing steel when annealing was found out by the theoretic analysis.Additionally,it can be found the suitable addition of Mg content can affect the morphology and composition of carbide.It is the elastic distortion caused by Mg in carbide to spheroidize the carbide.

Microstructure and Mechanical Properties of Q and T Heavy Plate for Nuclear Power Station Purpose

Abstract: SA738Gr.B steel plate for nuclear power station purposes was quenched and tempered with the heat treatment technology obtained by lab-experiments.Industrial processing was implemented on 45 mm thick plates which displayed well tensile properties and Charpy V-notch impact energy.The plate also demonstrated well mechanical properties at 200 ℃.Well uniformity of fine lath-banite characterized the microstructure of the plate with nano-sized carbides dispersing inner the banite structure and its boundaries.

Analysis and Optimization of Spray Nozzles Arrangement in Slab Casting by Numerical Simulation

Abstract: The arrangement of spray nozzles has an important impact on the cooling of slab.A three-dimensional steady heat transfer and solidification model was used to analyze the cooling of slab with different spray nozzles arrangements.By modification of the spray nozzles arrangement,the two hot spots as like "glass shape" in the slab cross section was prevented,and the cooling condition of slab was improved.The simulation results match well with the real process,which indicates the reliability and practicability of the model.

Industrial Trial of 780 MPa Grade Heavy-Duty Truck Beams Steels

Abstract: With the component design ideas of low carbon composite added with microalloying elements Nb and Ti,and fine-grain strengthening,transformation strengthening and precipitation strengthening were used,the 780 MPa grade heavy-duty beams steels were carried out on a domestic factory 1 750 mm semi-continuous hot rolling mill.The results show that the finishing temperature to control in range of 780-860 ℃,and coiling temperature to control in range of 450-550 ℃.The microstructures of steel are bainite,small amounts of fine-grain ferrite,and a lot of dispersed(Nb,Ti)C precipitates with the scale of 10 nm and below.The yield and tensile strengths of the steel plate are about 700 MPa and 780 MPa,respectively.The elongation is 19%.The steel plate have good low-temperature impact toughness,cold bending forming and welding performance.

Prediction of Equiaxed Crystal Ratio of Continuous Casting Round Billet of 37Mn5 Steel

Abstract: To control the quality of continuous casting round billets used for oil well pipes,a mathematical model based on slice moving method was developed for the solidification and heat transfer process of the round billet.Then,a mathematical simulation was done using the CA-FE module of Procast software for the solidification process of the 150 mm round billets of 37Mn5 steel.As a result,the simulated equiaxed crystal ratio was in accordance with testing results of industrial experiments,and then the criterion of columnar to equiaxed transition was found.The prediction results show that,with decreasing of superheat,increasing of continuous casting velocity and decreasing of second cooling water distribution in the first second cooling zone,the thermal gradient decreases and the undercooled liquid region ahead of the columnar dendrite tips becomes wider.Thus,the density of the grains nucleated in the solid-liquid region increases and their growth enough stops the columnar front,so the columnar to equiaxed transition occurs earlier and equiaxed crystal ratio increases.Considering controlling of equiaxed crystal ratio and surface and internal cracks,casting security and productivity synthetically,the suitable continuous casting parameters are as follows:superheat is(20±5) ℃,continuous casting velocity is 2.5 m·min-1,second cooling water distribution is 35∶28∶26∶11.

Experimental Research on Rotary Kiln One-Step Process DRI Productions

Abstract: Using Xinjiang magnetite concentrate,the process for preheated pellets with high strength and easy reduction,and coal-based direct reduction iron(DRI) were studied by novel one-step process for direct reduction.DRI production process of simulating tests of rotary in laboratory was studied.Influence of carbon capacity adding,reduction time,reduction temperature on the degree of metallization,sulphur content of rotary kiln DRI was analyzed.The best direct reduction process parameter of rotary kiln DRI production in this raw material conditions was proposed.The results show that for Xinjiang magnetite assaying with 64.39%Fe,preheated pellets are directly reduced at 1 025 ℃ for 70 min,directly reduced iron(DRI) assaying 93% metallic iron and 95.48% metallization degree are achieved.Compared with the traditional direct reduction of fired oxide pellets in coal-based rotary kilns,one-step process for direct reduction can avoid high temperature oxidation of pellets at 1 150-1 300 ℃,and possesses some advantages such as: greater economic profit,good quality of direct reduced iron.

Dissolution Kinetics of Lime in the Slag of Converter Dephosphorization

Abstract: The dissolution kinetics of solid lime was investigated by means of the rotating cylinder method in the FetO-SiO2-CaO-P2O5-5%MnO-5%MgO slagThe results indicate that the dissolution of CaO is controlled by the mass transport of CaO in liquid phase at 1 573-1 653 KThe activation energy for the dissolution rate is 16032 kJ/mol,and mass transport coefficient ranges are from 303×10-4 to 897×10-4 cm/s in the slag at 1 623 KThe dissolution rate significantly decreases with the increase in P2O5 contentAs the basicity increases,the dissolution rate increase firstly and then decrease

Effect of Znic on Strength of Coke

Abstract: In recent years,the catalysis effect of alkali metal on coke loss reaction has made a further and careful investigation,and the catalysis effect of other minerals on coke solution loss reaction is also a cause for concern.But,researches of zinc are mostly in its stay to the erosion of and warts of refractory material on the way.The damage for the catalysis effect of zinc on the coke loss reaction are ignored.The coke samples were prepared by air adsorption method with different zinc content,their strength was measured.The results show that the strength of coke will not be affected by zinc adsorption quantity.The coke reactivity with different zinc content will increase in some degree and coke strength after reaction will decrease with increase in zinc content of coke.Zinc is a catalyst for loss reaction of coke to promote the solution loss reaction,Zn will not directly impact on its strength.

Effect of Heat Treatment Process on Microstructure and Mechanical Properties of F550 Ship Plate Steel

Abstract: The effect of the different heat treatment processes on microstructure and the mechanical properties of a 60mm thick F550 ship plate steel which was produced by controlled rolling and cooling process was studied by utilizing optical microscope and the mechanical properties tests.The results show that after being treated by the two-phase region quenching and tempering,the steel has better mechanical properties,especially significantly higher low-temperature toughness compared to that by complete quenching and tempering.Complete quenching and tempering obtained single bainite,while intercritical heat treatment obtained the bainite and fine-grained ferrite two-phase structure.

Combustion Characteristics and Kinetic Analysis of Blended Coal in BF

Abstract: Experimental research on non-isothermal combustion characteristics and dynamic parameters of coal blends were conducted by thermo-gravimetric balance.The combustion characteristics parameters such as ignition temperature,peak temperature at maximum weight loss rate,burnout temperature,and maximum rate of combustion were investigated by thermo-gravimetric analysis and the kinetics parameters of samples in different ratio such as activation energy and the frequency factor were also investigated.The experimental results show that the temperature of releasing rate of volatile,ignition temperature and burnout temperature decrease with the increase of ratio of bituminous coal.The apparent activation energy(Ea) and the frequency factor(A) decrease with increasing of the ratio of bituminous coal in the blend and the "kinetic compensation effect" exists in the two parameters.There also exists an optimum mixture ratio between lean coal and bituminous coal,which is 1∶1.

Temperature Forecast Model of VD Vacuum Refining

Abstract: The perfect VD end-point temperature on-line forecast system was established.The main factors that influenced the VD process temperature drop were found out by MINITAB software,such as pumping time,vacuum keeping time,argon-blowing time,normal time,VD original superheat degrees,LF treatment time and ladle transferring time from converter to the first temperature measurement of VD.The forecasting system was applied to forecast the VD end-point temperature on-line based on the neural network method.For continuous 95 heats,the forecast accuracy for the difference less than 5℃ between the forecasting temperature and measured temperature is up to 93.7%.

Technology Research and Development Trend of Direct Reduction

Abstract: Direct reduction is an iron smelting process for producing metallic iron using gas,liquid fuels and non-coke coal as energy to reduce pellets,lump ore and fine ore under solid state.The research situation of global direct reduction technology was introduced and reviewed,which showed that development of direct reduction technology would have greater market demand.Rotary hearth furnace methods were introduced emphatically.Large-scale production of this technology has not yet reached the mature stage,but has good prospects for development.

Effects of High Temperature Large Deformation and Ultra Fast Cooling Process on Microstructure and Mechanical Properties of X70 Pipeline Steel

Abstract: The microstructural evolution,phase transformation kinetics and strengthening and toughening mechanism of X70 pipeline steel rolled by process of high temperature large deformation and ultra fast cooling were investigated in comparison with traditional TMCP process.It is showed that comprehensive mechanical properties of the tested steel are improved by means of refining grain,increasing dislocation density and refining precipitation in the process of high temperature large deformation and ultra fast cooling.In addition,ductile-brittle transition temperature firstly decreases and then increases with decreasing of finish cooling temperature.Degenerated pearlite resulting from higher finish cooling temperature and carbide from lower finish cooling temperature weaken toughness of the tested steel and optimal specification parameters are as follows: finish rolling temperature being 930 ℃,finish cooling temperature 600 ℃ and cooling rate 80 ℃/s.

Slag-Steel Sulfur Distribution in the Converter Steelmaking Process

Abstract: In the steelmaking process of low sulfur steel,converter was the key to control sulfur content.Through thermodynamic analysis,the desulfurization reaction on the slag-steel interface in converter was investigated.The result show that desulfurization reaction in steelmaking process is cotrolled by oxygen mass transfer from slag to steel.The sulfur distribution calculated from production data has good linear relationship with that from(FeO)-O-S thermodynamic model.The desulfurization reaction in converter steelmaing is close to equilibrium.The key influencing factors on LS are binary basicity(R),mass fraction of FeO in slag,mass fraction of MgO in slag,and temperature of steel in sequence by weight.Based on thermodynamic analysis and production data regression,the semiempirical equation has been gained,which could direct effectively the industrial production.

Continuous Cooling Phase Transformation of ERW-N80-1 Steel for Oil Casting

Abstract: The CCT carve of ERW-N80-1 steel was determined with Gleeble-3800 thermal simulation testing machine.Microstructures and secondary phase after different cooling rates were characterized by optical microscope and electronic microscope(SEM and TEM).The results show that along with increase of cooling speed the microstructures are changed in turn from polygonal ferrite,granular bainite,lath bainite,needle-like bainite,lath martensite and needle-type martensite,slender form,triangle,quadratic form or circle for M/A microstructures.With increase in high hardness phase,sample′s macrohardness is high.At the same time,the size of the secondary phase is homogeneous and fine gradually.

Effect of Acid Rain on Corrosion Behavior of Mild Steel

Abstract: Corrosion behavior of mild steel in the simulated acid rain environment was investigated by optical microscopy(OM),scanning electron microscopy(SEM) and X-ray diffraction(XRD),and electrochemical methodsIt is found that corrosion of carbon steel in acid rain environment is a coexistent process of localized corrosion and uniform corrosionSO2-4 and Cl-ions can accelerate the formation and growth of pits on the surface of mild steel,which preferentially appeared on the ferrite phaseThe corrosion products were mainly composed of γ-FeOOH,Fe3O4,a little α-FeOOHFrom the microscopic point of view,needle-like and cotton-ball type corrosion products existedThe mass loss curve is divided into two stages which both followed the linear growth lawDuring the first 72h,the mass loss rapidly increased,and from 72h to 1104h,the corrosion rate was relatively slowElectrochemical measurement showed that there were the more negative corrosion potential Ecorr and the larger corrosion current density Icorr with the extension of time,indicating the increasing corrosion tendency

Effects of Finish Rolling Temperature on Microstructure and Mechanical Properties of Low Silicon Containing Phosphorus TRIP Steel

Abstract: The microstructure and mechanical properties of different finishing temperatures for hot rolled low silicon containing phosphorus TRIP steel were investigated using a laboratory hot rolling mill.The results show that when finishing temperature is decreased from 900 to 790 ℃,the volume fraction of ferrite is increased;the volume fraction of bainite is decreased;and the volume fraction of retained austenite has no evident changes.When finishing temperature are 900 and 820 ℃,bainite is used as matrix microstructure.Lower temperature deformation enhances the transformation rate of austenite to ferrite,also the fine,uniform and equiaxed ferrite grains can be obtained as matrix microstructure,the average ferrite grain size is about 4.5 μm,and the dislocations is observed in matrix,when finishing temperature is decreased to 790 ℃.Compared with other kind of processes,the steels have excellent mechanical properties when finishing temperature is 790 ℃:ultimate tensile strength,elongation and yield/strength ratio are 825 MPa,21.5% and 0.64 respectively.

Phase Transformation Characteristics of Vanadium Microalloying Low Carbon Bainitic Steel in Continuous Cooling Process

Abstract: The continuous cooling transformation(CCT) curves of experimental steels were tested with heat dilatometer.The results show that the low carbon steel containing V and B can obtain fully bainitic microstructures more than 0.3℃/s of cooling rate.Compared to V-B steel,low carbon steels microalloying with V-N have higher critical cooling rate to achieve fully bainite,also bainite start temperature is about 20℃ higher than V-B steel.The element of Mo and Cr additions to V-N microalloyed low carbon steels can promote bainite transformation and Mo is more effective than Cr.Adding Mo and Cr into V-N microalloyed low carbon bainitic steels can lower bainite transformation temperature at least 30℃ and refine bainitic microstructures,thus increase the Vickers hardenss HV10-30.

Microstructure and Properties of High Performance Carburizing Bearing Steel

Abstract: The effect of heat treatment process on microstructure and mechanical properties of bearing steel was studied,and the mechanism of strengthening-toughening of the steel was also discussed.The results show that,with the increasing of quenching and tempering temperature and the number of tempering,as well as the use of acryogenic technology,the strength and hardness of carburizing bearing steel increases and the impact ductility decreases.Quenching at 910℃ and tempering twice at 180℃,the mechanical properties of bearing steels can reach HRC is 45.2,Rm is 1450MPa,ReL is 1240MPa and AKU is 105J;Residual austenite quantity can be controlled less than 1%.The better match of strength and toughness is attributed to grain refinement,ultra-fine martensitic variants,and large number of fine dispersed carbides.The dimensional stability of the steel is due to the control of the content of residual austenite.

Online Cooling Technology of Oil Tanker Steel 12MnNiVR

Abstract: In order to meet the strategic demands of National Oil Reserve,Ansteel developed 12MnNiVR for large oil storage tank,which has high strength,high impact energy,low harmful element such as S and P,as well as high performance of welding and low crack sensitivity.The plate can bear 100J/cm high energy input;keep good strength and toughness after welding.The study on online cooling process of 12MnNiVR was introduced.