中国稀土资源开采现状及发展趋势

世界稀土资源丰富,含量偏低,分布不均。中国是世界上稀土资源最丰富的国家,已探明的稀土资源量约6588万t,内蒙古白云鄂博、四川凉山冕宁牦牛坪、山东微山、南方七省区等地是中国稀土资源集中分布区。中国稀土精矿生产能力较大,稀土精矿生产能力可达10万t以上。介绍了稀土资源储量,概述了中国稀土矿床的稀土资源开采情况,分析了中国境内典型的稀土资源存在的问题,探讨了稀土资源发展方向。     

Study on non-metallic inclusions in Al killed high strength alloy steel refined by high basicity and high Al_2O_3 content slag

Laboratory and industrial studies were carried out to investigate non-metallic inclusions in high strength alloy steel refined by high basicity and high Al₂O₃ slag.It was found that the steel/slag reaction time largely affected non-metallic inclusions.With the reaction time increased from 30 min to 90 min in laboratory study,MgO-Al₂O₃ spinels were gradually changed into CaO-MgO-Al₂O₃ system inclusions surrounded by softer CaO-Al₂O₃ surface layers.By using high basicity slag which contained as much as 41%Al₂O₃ in the laboratory study,ratio of low melting temperature CaO-MgO-Al₂O₃ system inclusions was remarkably increased to above 80%.In the industrial experiment,during the secondary refining,the inclusions changed in order of "Al₂O₃→MgO-Al₂O₃→CaO-MgO-Al₂O₃".Through the LF and RH refining,most inclusions could be transferred to lower melting temperature CaO-Al₂O₃ and CaO-MgO-Al₂O₃ system inclusions.     

Research on the grain refinement under pulsed magnetic field

In this paper,the principle of Pulsed Magnetic Field(PMF) force was analyzed through mathematical analyses.By theoretical analysis and calculation,the results show that the great electromagnetic force is made in the melt under pulsed magnetic field,as well as changing its direction in different places of melt at the same time.It enforces the crystallizing nucleus and brittle crystallite to fragment in the solidification processing.From the point of view,one of the main factors of grain refinement is that the fragmentations occur under a pulsed magnetic field by preliminary judgement. The feasibility of application in the metallurgical industry under PMF was discussed through comparing the results of grain refinement under EMS.According to the theoretic calculation,the power consumption under EMS is 5 -8 times the amount under PMF,when both of magnetic flux density B are 0.07T.That is to say,the better effect on grain refining can be obtained under PMF,compared with EMS,even in the lower power consumption.The solidification experiments of Sn-20%Pb alloy are conducted under the same experimental conditions that the magnetic intensity is 0.07T in the center of the crucible,it also shows that PMF has a better effect on grain refining than EMS. Combined with the continuous casting process,the influence of pulsed parameters and the metallurgical effects with applying PMF at different solidification stages was investigated.There are different grain refining effects under PMF in different solidification stages,and there are different grain refining effects under PMF in different PMF parameters.For the Sn-20%Pb alloy or silicon steel,it is more effective during the initial stage,in which the pulse frequency is 5Hz.For the Sn-20%Pb alloy,the average grain size ofβphase is the smallest,when applying the PMF during the temperature of melt decreasing from 201℃to 184℃.Further investigation of the specified technique parameters for industrial applications are required.     

The grain refining mechanism of C-Mn steel by CSP

The grain refining mechanism of C-Mn steel sheet on compact strip production(CSP) line was investigated in this study.The grain was about 100μm after F1 pass and decreased all the way of the rolling process(F2-F6) to 15μm.Repeated phase transformation experiment was conducted to the steel for grain refinement.The phase transformation at 860℃and 920℃can refine the grain size to 7.5μm.     

Development of simulation system of strip flatness for hot tandem mill

Using three-dimensional rigid-plastic finite element method base on Lagrange multiplier to analyze the deformation of strip,influence function method to calculate the elastic deflection of rolls and three-dimensionalelastic FEM to analyze the flattening deformation between work roll and strip,a coupled model was established with a iteration way.The effect of various kinds flatness control method such as bending force,rolls shift and cross angle and also various kind of influence factors such as friction ...     

Application of rolling technique lubrication system of 2150 mm hot rolling line

In order to reduce the friction force between the roll and rolling material,decrease the rolling force and consumed power,enhance the product quality and rolling efficiency,rolling technique lubrication has been applied widely in mordern hot rolling mill at present.The constitution and control principle of rolling technique lubrication System of 2 150 Hot Rolling Line are analyzed.In light of the problems that took place while testing and applicating,the reformation measures are pointed out.Since taking ...     

Application of cluster analysis on optimization of rolling force learning

The rolling force learning function is an important part of the hot strip parameter calculation process, and the steel classification is the basis of the model parameter calculation,which has a direct impact on the model calculation precision,and the classification of steel quality will directly affect the accuracy of the model calculation.This paper is for the classification of a certain type of steel,in order to find the optimal classification of steel model to achieve greater precision of the rolling ...     

Study on strip buckling in continuous annealing lines/hot galvanizing

In continuous annealing lines/hot galvanizing,strips are guided by upper and lower rolls in an alternate up and down vertical motion.This kind of process consisting of heating,soaking,and cooling furnaces(or zones) has several advantages in terms of productivity and product quality.Main problems encountered in continuous annealing lines are misguiding and formation of buckling.The strip buckling causes the strip to be rejected and,in the worst case,the strip breaks and the continuous annealing lines are ...     

Theory research on use efficiency of emulsion in cold rolling

Lubrication in cold rolling process is used not only to control friction,but also to control surface quality and thermal chamber.Successful cold rolling of strip at high speeds requires an optimum presence of lubricant film thickness at the contact.In order to have a better control on rolling process the awareness for the prediction and maintenance of desired minimum film thickness.On the basis of learning and summarizing the theories early founded by experts around the world,this paper constructed the m...     

Development of Cr-free anti-fingerprint hot-dip galvanized sheet for household appliances

China has become the maximum household appliances manufacturing base worldwide.It is a new challenge facing the steel industry to develop the low-cost and environment-friendly sheet for household appliance industry,so Cr-free anti-fingerprint hot-dip galvanized sheet for household appliances is the upgraded product which satisfies the requirement of China household appliance industry' s nuisanceless treatment.The paper discusses the technical key points of development on Cr-free anti-fingerprint galvaniz...