Effect of ferrovanadium inoculation on microstructure and properties of high speed steel

The effect of ferrovanadium inoculation on the microstructure and properties of high speed steel (HSS) used for rolls was studied. The results showed that the as-cast eutectic carbide network tends to be broken after ferrovanadium inoculation, and the carbides are changed to rod-like or nodular shape. After heat treatment, the carbides in the inoculated HSS are spheroidized and distributed more uniformly in the matrix. The impact toughness of high speed steel with ferrovanadium inoculation is obviously improved. The action mechanism of ferrovanadium inoculation on the microstructure of the alloy is also discussed.

High-temperature performance prediction of iron ore fines and the ore-blending programming problem in sintering

The high-temperature performance of iron ore fmes is an important factor in optimizing ore blending in sintering. However, the application of linear regression analysis and the linear combination method in most other studies always leads to a large deviation from the desired results. In this study, the fuzzy membership functions of the assimilation ability temperature and the liquid fluidity were proposed based on the fuzzy mathematics theory to construct a model for predicting the high-temperature performance of mixed iron ore. Comparisons of the prediction model and experimental results were presented. The results illustrate that the prediction model is more accurate and effective than previously developed models. In addition, fuzzy constraints for the high-temperature performance of iron ore in this research make the results of ore blending more comparable. A solution for the quantitative calculation as well as the programming of fuzzy constraints is also introduced.

Strengthening pelletization of manganese ore fines containing high combined water by high pressure roll grinding and optimized temperature elevation system

Pelletization is one of useful processes for the agglomeration of iron ore or concentrates. However, manganese ore fines are mainly agglomerated by sintering due to its high combined water which adversely affects the roasting performance of pellets. In this work, high pressure roll grinding(HPRG) process and optimization of temperature elevation system were investigated to improve the strength of fired manganese ore pellets. It is shown that the manganese ore possesses good ballability after being pretreated by HPRG twice, and good green balls were produced under the conditions of blending 2.0% bentonite in the feed, balling for 7 min at 16.00% moisture. High quality roasted pellets with the compressive strength of 2711 N per pellet were manufactured through preheating at 1050 °C for 10 min and firing at 1335 °C for 15 min by controlling the cracks formation. The fired manganese pellets keep the strength by the solid interconnection of recrystallized pyrolusite grains and the binding of manganite liquid phase which filled the pores and clearance among minerals. The product pellets contain high Mn grade and low impurities, and can be used to smelt ferromanganese, which provides a possible way to use imported manganese ore fines containing high combined water to produce high value ferromanganese.

VCR and ASR technology for profile and flatness control in hot strip mills

The roll contour pattern and variety of work and backup rolls in service and its effect on profile and flatness control performance in 1 700 mm hot strip mill at Wuhan Iron and Steel(Group) Corporation were tested and analyzed by the developed finite element models of different typical roll contours configurations.A rather smooth local work roll contour near strip edges and an increase in rolled length can be obtained by application of long stroke work roll shifting system with conventional work roll contours that is incapable of the crown control.In comparison with the conventional backup and work roll contours configuration,the crown control range by the roll bending force enhances by 12.79% and the roll gap stiffness increases by 25.26% with the developed asymmetry self-compensating work rolls(ASR) and varying contact backup rolls(VCR).A better strip profile and flatness quality,an increase in coil numbers within the rolling campaign and a significant alleviated effect of severe work roll wear contours on performance of edge drop control are achieved by the application of ASR with crown control and wear control ability in downstream stand F5 and VCR in all stands of 1 700 mm hot strip mill.

Weldability and SAW welding wire of X80 pipeline steel

Weldability test was carried out on the newly developed fine grain, low sulphur, high strength and high toughness pipeline steel of X80 and its matching SAW wire. Test of maximum hardness in welding heat-affected zone and test of Y groove cracking show that X80 steel features low hardenability and good cracking resistance. The submerged arc welding joint made with the newly developed low carbon and multi-alloyed SAW wire of WGX2 exhibits a little higher strength than the base metal, qualified bending performance, under maximum limitation hardness and good impact toughness, which can completely meet the technical requirement of X80 steel. Despite somewhat coarsening the grain size in welding heat-affected zone is still much finer than that of traditional steels, and the microstructure in weld metal is almost full acicular ferrite. The results show that X80 steel and WGX2 wire are of great weldability.

MICROSTRUCTURE AND MECHANICAL PROPERTY DEVELOPMENT IN THE SIMULATED HEAT AFFECTED ZONE OF V TREATED HSLA STEELS

The simulated heat affected zone （HAZ） of the high strength low alloy （HSLA） steels containing 0%, 0.047%, 0.097% and 0.151% vanadium, respectively, were studied with Gleeble-2000 thermomechanical simulator to determine the influence of vanadium addition on the mechanical properties of the HAZ. The HAZ simulation involved reheating the samples to 1350℃, and then cooling to ambient temperature at a cooling rate of 5℃/s ranging from 800 to 500℃ （△8/5=60s）. The mechanical properties including tensile strength and -20℃ impact toughness were conducted. The microstructures of the base steel and the simulated HAZs were investigated using optical microscope, scanning electron microscope （ SEM ） and transmission electron microscope （TEM）. Based on the systemutic examination, the present work confirmed that about 0.05% vanadium addition to low carbon low alloy steels resulted in expected balance of strength and toughness of the HAZ. And more than 0.10% levels addition led to detrimental toughness of the HAZ SEM study showed that the simulated 0.097% and 0.151%V HAZs consisted of more coarse ferrite plates with greater and more M-A constituents along austenite grain and ferrite plate bound- aries. The impact fracture surfaces of the simulated 0.097% and 0.151%V HAZs showed typically brittle mode with predominant cleavages. The size of the facet in the fracture surface increased with increasing vanadium level from 0.097% to 0.151%.As a result, the simulated 0.151% V HAZ has the lowest impact toughness of the four specimens.

Effects of Rare Earth on Behavior of Precipitation and Properties in Microalloyed Steels

The influence of rare earths on the behavior of precipitation of 14MnNb,X60 and 10MnV steels was studied by STEM, XRD, ICP and thermal simulation method. The main carbonitride precipitates are Nb(C, N),(Nb, Ti)(C, N)and V(C, N). In austenite RE delays the beginning of precipitation, and decreases the rate of precipitation. In ferrite RE promotes precipitation and increases the amount of equilibrium carbonitride precipitation. RE can make precipitates fine, globular and dispersed in the microalloyed steels. With the increase of the amount of RE in steel, the amount of precipitation increases. The promotion effect is weakened with excessive RE. RE has only little influence on the strength of microalloyed steel, but it can improve impact toughness effectively.

Correlation of morphological anisotropy and Lankford value of deep drawing sheets hot-rolled by compact strip production

Cold-rolled steel sheets in automotive applications require an excellent deep draw ability, which is characterized by the Lankford value （r-value）. In this study, a correlation was identified between r-value and pancake-shaped grain flatness which is indicated as the ratio of grain diameter in the rolling direction （RD） and normal direction （ND） of sheets （dr/dn）. A mathematical model （ r = e^0.345（dn^1/2-dr^1/2） ） was developed to calculate r-value by the microstructure of steel sheets hot-rolled by compact strip production （CSP）. It is shown that the r-value is higher, if the microstructure of steel sheet is of pancake-shaped grains elongated in the rolling direction. The calculated r-value is confirmed to fit exactly to the measured one from the large-scale production.

Preparation of ZrB_2-SiC Powders via Carbothermal Reduction of Zircon and Prediction of Product Composition by Back-Propagation Artificial Neural Network

Phase pure ZrB2-SiC composite powders were prepared after 1 450℃/3 h via carbothermal reduction route,by using ZrSiO4,B2O3 and carbon as the raw materials.The influences of firing temperature as well as the type and amount of additive on the phase composition of final products were detailedly investigated.The results indicated that the onset formation temperature of ZrB2-SiC was reduced to 1 400℃by the present conditions,and oxide additive（including CoSO4·7H2O,Y2O3 and TiO2）was effective in enhancing the decomposition of raw ZrSiO4,therefore accelerating the synthesis of ZrB2-SiC.Moreover,microstructural observation showed that the as-prepared ZrB2 and SiC respectively had well-defined hexagonal columnar and fibrous morphology.Furthermore,the methodology of back-propagation artificial neural networks（BP-ANNs）was adopted to establish a model for predicting the reaction extent（e g,the content of ZrB2-SiC in final product）in terms of various processing conditions.The results predicted by the as-established BP-ANNs model matched well with that of testing experiment（with a mean square error in 10^（-3） degree）,verifying good effectiveness of the proposed strategy.

Composition Optimization of Nb-Ti Microalloyed High Strength Steel

Four Nb-Ti microalloyed steels were refined and rolled to study the composition optimization of Nb-Ti microalloyed steels. The effects of Nb and Ti on the microstructures, precipitates and properties of Nb-Ti microalloyed steel were investigated. The results showed that an increase in Ti content resulted in the appearance of many fine precipitates leading to a strong precipitation strengthening effect. Hence, the yield strength increased. Besides, the increased strength by the combined increase of Nb and Ti was similar to that observed for the increase in Ti content alone. This increase in strength was attributed widely to the increase in the Ti content alone rather than Nb. Moreover, the increase in Nb content beyond 0.036 wt% exerted no significant effect on the strength of Ti-Nb microalloyed steels, in which more Ti could be added to further improve the strength of steels.

The Effects of Cooling Mode on the Properties of Ti–Nb Microalloyed High-strength Hot-rolled Steels

The industrial trials of two cooling modes, i e, water cooling in forepart + air cooling in later part (WAC) and air cooling in forepart + water cooling in later part (AWC), were carried out for a Ti- Nb microalloyed steel. The average cooling rates and coiling temperature were the same for two modes. The continuous cooling transformation (CCT) curve of the tested steel was drawn. The effects of the cooling mode on the microstructure, precipitates, and properties of the steels were investigated. Results show that the strength of the steel in the WAC mode is significantly larger than that in the AWC mode, mainly because the smaller the grain size, the more and finer the grain precipitates. Therefore, when the average cooling rate is constant, the fast cooling in the forepart is an effective method to increase the strength of steels. However, the increase in the strength is accompanied by the decrease in toughness, so that the toughness of the steel should be considered when changing the cooling mode.

Wearing Property and Friction Mechanism of Ceramic Side Dams Used in Thin Strip Continuous Casting

In this paper,based on three different kinds of ceramic side dams for thin strip antinuous casting,the friction and wearing property were studied.The effects of friction pressure,temperature and friction time on the friction and wearing property of the ceramic side dam were researched.What’s more,the friction mechanism and wearing mechanism of the ceramic side dam were researched as well.Results show that the ceramic side dam of BN-SiA lO N has the best wearing resistance property.while at room temperature,16 min of friction time and0.35 MPa of friction pressure,the test friction coefficient is 0.60 and wearing capacity is 272.358 mm-3.In addition,when at 400℃,16 min of friction time and 0.18MPa of friction pressure,the test friction coefficient is0.70.The friction mechanism of ceramic side dam with the opposite wearing material is mainly the composite wear of adhesion,abrasive and fatigue.

Research and Application of Wear Resistant Refractories for Cooling Zone of Large Scale Coke Dry Quenching Ovens

In order to prolong the service life of the cooling zone of large scale coke dry quenching ovens,six kinds possible refractories for the cooling zone of large scale coke dry quenching ovens： SiC containing brick A,SiC containing brick B,mullite-andalusite brick,spinel containing brick,zirconia containing brick,corundum-mullite brick and grade B mullite brick,were analyzed in properties. It is found that the cooling zone lining adopting SiC containing bricks or mullite-andalusite bricks has much longer service life. Based on this,a new type of wear resistant brick was developed. The brick has a compressive strength of 135 MPa,a wear loss of 2. 10cm^3（only a quarter of that of the grade B mullite brick）,and a higher bulk density than the grade B mullite brick. The application of the brick in a 140t·h^（-1）coke dry quenching oven showed that it performed better than the grade B mullite brick. The cooling zone adopting the new bricks has a lower coke discharging temperature,which is beneficial to the enhancement of heat recovery efficiency and steam power generation.

Point-of-Interest Recommendation in LocationBased Social Networks with Personalized Geo-Social Influence

Point-of-interest(POI) recommendation is a popular topic on location-based social networks(LBSNs).Geographical proximity,known as a unique feature of LBSNs,significantly affects user check-in behavior.However,most of prior studies characterize the geographical influence based on a universal or personalized distribution of geographic distance,leading to unsatisfactory recommendation results.In this paper,the personalized geographical influence in a two-dimensional geographical space is modeled using the data field method,and we propose a semi-supervised probabilistic model based on a factor graph model to integrate different factors such as the geographical influence.Moreover,a distributed learning algorithm is used to scale up our method to large-scale data sets.Experimental results based on the data sets from Foursquare and Gowalla show that our method outperforms other competing POI recommendation techniques.

Improved Roberts operator for detecting surface defects of heavy rails with superior precision and efficiency

An experimental platform accompanying with the improved Roberts algorithm has been developed to achieve accurate and real-time edge detection of surface defects on heavy rails.Detection results of scratching defects show that the improved Roberts operator can attain accurate positioning to defect contour and get complete edge information.Meanwhile,a decreasing amount of interference noises as well as more precise characteristic parameters of the extracted defects can also be confirmed for the improved algorithm.Furthermore,the BP neural network adopted for defects classification with the improved Roberts operator can obtain the target training precision with 98 iterative steps and time of 2s while that of traditional Roberts operator is 118 steps and 4s.Finally,an enhanced defects identification rate of 13.33%has also been confirmed after the Roberts operator is improved.The proposed detecting platform will be positive in producing high-quality heavy rails and guaranteeing the national transportation safety.

New Application of Stainless Steel

Several rigid substrates such as stainless steel, titanium alloy, aluminum alloy, nickel foil, silicon, and sodium lime glass have been employed for manufacturing high quality TiO2 films by metal organic chemical vapor deposition （MOCVD）. The as-deposited TiO2 films have been characterized with SEM/EDX and XRD. The photocatalytic properties were investigated by decomposition of aqueous orange Ⅱ. UV VIS photospectrometer was employed to check the absorption characteristics and photocatalytic degradation activity. The results show that films synthesized on metal substrates display higher photoactivities than that on absolute substrates such as silicon and glass. It is found that solar light is an alternative to UV-light used for illumination during photodegradation of orange Ⅱ. TiO2 film on stainless steel substrate was regarded as the best one for photocatalysis.

Application of Sol Self-Clean Bonded Al_2O_3-SiC-C Castable for Iron Runner

The properties and microstructure of sol self-clean bonded Al2O3-SiC-C castable in iron runner were studied, and the relation between the amount of sol self- clean binder and the properties of castable were discussed. It is believed that the addition of sol self-clean binder can improve the compressive strength, but has little effect on the bulk density and the apparent porosity, which enable the castable to be applicable in different conditions.

MICROSTRUCTURE TRANSFORMATION IN THE WELDING HEAT AFFECTED ZONE OF 800MPa GRADE ULTRA FINE STRUCTURED STEEL

The transformation behavior and microstructure development in the heat affected zone(HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found thatthe HAZ has intermediate temperature transformation characteristics in a wide rangeof cooling rates, with the bainite sheaves consisting of bainite ferrite plates withoutcarbide precipitation and retained austenite in the fast cooling regime. At relativelyhigh cooling rates, which corresponded to low heat inputs, the hardness of the simulatedHAZ was above that of the base metal. When the cooling rate was below 9℃/s, thewelding HAZ would have an obvious softening. The analysis of transformation ratesin continuous cooling processes was completed by numerical differential method. Theresult indicated that the microstructure transformation rate of the HAZ in 800MPagrade ultra fine structured steel changed sharply to slow speeds when the cooling timet_(8/5) is longer than 7s.

Optimization of Culture Components for Laccase Activity from Pleurotus Ostreatus P40 Using Response Surface Methodology

High enzymatic activity is required for laccase applications.Central composite design(CCD)-based response surface methodology(RSM)can effectively increase the enzymatic activity of Pleurotus ostreatus P40 in liquid substrate fermentation.Initial screening of the nutritional components was performed using a Plackett-Burman design.The variables,namely,bran,bagasse,Tween 80,and yeast extract,were found to have statistically significant effects on laccase activity.These variables were further optimized using CCD-based RSM.Optimal concentrations for the maximum laccase activity were 8.144 2 g/L bran,50 g/L bagasse,0.424 1 mL/L Tween 80,and 2.832 5 g/L yeast extract.Under optimized conditions,the maximum measured laccase activity reached 96 480 U/L,which was close to the predicted value(104 830 U/L)by RSM.Therefore,RSM can be used to optimize culture components for laccase activity from Pleurotus ostreatus P40.

Mathematical modeling of electromagnetic dimensionless number for electromagnetic casting of metals and its application

In order to estimate the feasibility of electromagnetic casting (EMC) for different metals, a mathematical model named the electromagnetic dimensionless number (EMDN) was presented, and its validity was proved by the experiments of aluminum and Sn-3%Pb alloy. From the experiment and the analysis of EMDN it can be concluded that the EMC of steel can be attained only when the magnetic flux density is larger than 0.09T, while that required for aluminum is only 0.04T. The mathematical expression of the electromagnetic dimensionless number was given out.