Showing papers in "Journal of Iron and Steel Research in 2015"

Fatigue properties of continuous-annealed and continuous hot-dip galvanized 590MPa grade dual phase steels

Abstract: S-N curves of continuous annealed and continuous hot-dip galvanized 590 MPa grade dual phase steels were drawn with tension-tension fatigue tests,and the fracture behaviors were also analyzed using scanning electron microscopy.The results show that the fatigue limits of continuous annealed and continuous hot-dip galvanized590 MPa grade dual phase steels are 217 MPa and 216 MPa with loading frequency of 15 Hz and R=0.1.The surface observation result shows that crack initiation zones are at the boundary of ferrite and martensite on the surface of the steels.

Multidimensional mixing features extraction and recognition for surface defect of steel strip

Abstract: In order to automatically obtain the most discriminative multidimensional mixing features,an improved ReliefF algorithm which can assess and select mixing features was put forward.Aiming at the shortcoming of algorithm,the maximum information compression criterion to remove the redundant features was introduced.On this basis,the steel strip defect recognition knowledge base was established by using genetic neural network.Genetic algorithms can identify the minimum searching space including optimum solution,and then BP network modifies the weights and thresholds in the negative gradient direction.The results show that the improved ReliefF provides the optimal feature vector for subsequent classification,reduces the data of computation and storage capacity;and the genetic neural network has acquired more efficiency of defect identification on the premise of ensuring accuracy.

Heat treatment process for Ni_3Al-based wrought superalloy

Abstract: Influence of solution treatment temperature on microstructure and high-temperature tensile properties of Ni3Al-based alloy sheet was investigated.The results show that volume fraction ofβphase reduces and volume fraction ofγ′+γregion increases with increasing heat treatment temperature up to 1280℃.When the temperature reaches to 1 310℃,volume fraction ofγ′+γregion keeps at the same level but that ofβphase increases.Due to precipitation ofβphase along grain boundary with the temperature raising,grains begin to grow up until the temperature reaches 1280℃.The grain sizes are different for different directions at the solution treatment temperature below 1280℃.Crack initiates at the interface ofβandγ′envelope during 1000℃tensile test.The increase of volume fraction ofγ′+γregion can increase the strength of the alloy.The alloy has excellent comprehensive mechanical properties after heating at 1 280℃for 16 min and AC.

Effect of dissolved oxygen on corrosion behavior of X80 pipeline steel and its mechanism

Abstract: Electrochemical impedance technology(EIS),potentiodynamic polarization and XRD were used to study the effect of dissolved oxygen concentration on electrochemical corrosion behavior of X80 pipeline steel in simulated Ku′erle soil solution.The results show that with the decrease of dissolved oxygen concentration,the corrosion current density of X80 steel reduces obviously,and the corrosion rate descends.Different dissolved oxygen concentration can lead to difference of corrosion products,so that the corrosion rate of the metal changes.When the dissolved oxygen concentration is 0.35mg/L,there is a corrosion product film of FeCO3 which restrains the corrosion of the metal.At this condition,corrosion phenomenon is not obvious.

Prediction model of blast furnace temperature based on ELM with grey correlation analysis

Abstract: Aiming at the inherent defects of the traditional blast furnace temperature model,a kind of grey relational analysis based ELM(extreme learning machine)temperature prediction model was put forwardDue to the characteristics of ironmaking process with multivariable nonlinear,strong coupling,the traditional modeling methods were unable to meet the requirements of high precision prediction of blast furnace temperatureFirstly,the correlation of input variables was analyzed with the gray correlation analysis,and then the performance of the model was improvedSecondly,combined with analytical variables,the neural network was trained by ELM learning algorithmFinally,the field data was used for training and testing of the network,and then compared with the traditional modelThe results show that the model can predict the blast furnace temperature quickly and accurately,and also can meet the guide workers to manipulate the needs of blast furnace

Austenization dynamics of 17-4PH steel during continuous heating process

Abstract: The austenization behaviors of 17-4PH steel under continuous heating condition were investigated.The results show that Ac1 and Ac3increase with increasing heating rate,and transformation zone also moves to high temperature field.The curve of transformation amount of anstenite-temperature shows"S"shape.The transformation rate(df/dt)is not a certain value and has a peak value.The austenization active energy is determined to be47.3kJ/mol by Kissinger method.

Modification of converter slag with acidic oxides

Abstract: The acidic oxides of analytical reagents such as SiO2,B2O3,P2O5 were used as modifier to fix f-CaO in the converter slag in this paper,respectively.The experimental results show that,the mass fraction of f-CaO in coverter slag decreases from 4.27%to less than 0.5% when the mass ratio of acidic oxide to f-CaO is fixed at 1:3.It means that acidic oxides such as SiO2,B2O3,P2O5 can reduce the content of f-CaO significantly,leading to the stability of modified converter slag improved.According to the analysis results of mineral phases and microstructural aspects of the modified slag,it is indicated that the modifier can not only fix f-CaO in the converter slag,but also capture the CaO of C2 F,resulting in the content of C2 S in the prepared modified converter slag increased.Low f-CaO,low C2 F and high C2 S slag was generated by adding modifier into converter slag,which was benefit for the modified converter slag used in the field of cement.

Effect of plastic addition on direct reduction of carbon-containing pellets

Abstract: Energy conservation and emissions reduction is an important challenge to iron and steel industry.Renewable biomass-derived reducing agents had gained attention as possible substitutes for fossil-based reducing agents in the iron making blast furnace.Waste plastic was mixed together with limonite powder and bentonite for producing carbon-containing pellets.The heat released by waste plastic combustion was used as the heat source of pellet preheating and reduction.Compared with carbon-containing pellets without plastic addition,the porosity of carboncontaining pellets with plastic addition is higher,which makes the process of reducing gas transfer in the pellets easier,so that reduction rate of carbon-containing pellets increases gradually.The effects of reduction time,species and percentage content of waste plastic on the direct reduction of carbon-containing pellets were experimentally studied.The results show that under the optimum parameters of reduction time of 6min,temperature of 1 350℃,pellet diameter of 10 mm and percentage content of polycarbonate of 4%,the porosity of reduced pellets can be improved by 74%,the reduction rate can be up to 98.89%.Speaking on the reduction system of carbon-containing pellets during the reaction,inside with a certain proportion of waste plastics,reduction time can be shortened,reduction temperature can be reduced and the reduction rate can be improved.

Induced rupture of AISI 347 stainless steel for automotive in acidic solution

Abstract: Induced rupture of AISI 347 stainless steel for automotive in acidic NaCl water solution was studied.The results show that after heat treatment at 650 ℃,AISI 347 stainless steel has an ability to resist sensitization.The passive range of corrosion potential reduces with increase of heat treatment time at 650 ℃.At 25 ℃ in 3.5%(mass fraction)NaCl aqueous solution(pH=2)or at 90 ℃in 1%(mass fraction)NaCl aqueous solution(pH=2),the fracture modes for tensile test mainly are ductile dimple,stress corrosion cracking is limited in the edge of cross section of specimen,and the resistance to environment induced cracking of the steel is good.The steel has an excellent resistance to stress corrosion rupture.

Effect of TiO_2 content on microstructure of sinter

Abstract: The effect of titanium on microstructure of sinter was investigated by metallographic microscope and sintering test.The results show that,with the increase of TiO2 content,the content of perovskite in binder phase has a notable increase,the content of calcium ferrite has a trend to decrease,the content of glass phase rises,the content of dicalcium silicate remains stable,the pores in sinter reduce significantly.In the structure of ore phase,most perovskite shows amorphous and allotriomorphic,which fills in the mineral powder.A little perovskite shows dendritic,which distributes intensively.Calcium ferrite shows acicular,columnar and platy structure,which distributes unequally.Dicalcium silicate distributes with willow structure.The shapes of gas hole are irregular and crack exists throughout them.Binder phase strength of sinter reduces with increase of the content of TiO2.Through the sintering cup test verifying,with the increase of TiO2 content,the tumbler decreases,which meets the influencing law of titanium on microstructure of sinter.