The New Technology Of Welding With Ilmenite Preparation

There are rich ilmenite resources in Yunnan province.Presently,the utilizatioh of ilmenite focuses on selling raw materials and producing high titanium slags,but the main problem is the low utilization rate of resources.Hence,how to exploit ilmenite resource independently,raise the utilization rate of resources and increase the accessional value is very important and has attracted a great deal of attention. According to the current production equipments,the production processes of reduction ilmenite can be divide into "steamed" kiln,tunnel kiln and rotator kiln. However,there are a few disadvantages as like complicated technique process,high energy consumption and low quality of reduction ilmenite in these processes.In order to overcome these disadvantages,the main objective of this study is to develop a new production technique of reduction ilmenite.On the basis of analyzing the present status of production of reduction ilmenite, we developed a novel technique for the reduction ilmenite preparation.The compound additive was employed to reduce the reduction temperature and shorten the reduction time.After reduction,the problem of high w(C)content which exists in compound orb could be solved and,the high quality of reduction ilmenite were ensured.The microstructures of ilmenite,pre-oxidized ilmenite and reduced ilmenite were characterized by using DTA,XRD,SEM and so on.A preliminary study of the compound additive mechanism,pre-oxidation mechanism and ilmenite carbon reduction mechanism was carried out.The main conclusions are as follows:(1)when the proportion of adhesive C is 3%,the wetting grinding time is 10min and the water proportion of compound orb is 8-9%,the dry orbs have the optimal falling intensity and compressive strength,according with the requirement of the preparation and reduction of compound orbs.Moreover,the alkali oxides thermally decomposed from adhesive C could also catalyze the carbothermic reduction of ilmenite.(2)The optimal conditions of ilmenite pre-oxidation are:The pre-oxidation temperature is 850-900℃;the pre-oxidation time is 10min.The XRD and SEM spectrum indicated that mostly TiO₂ are transformed into rutile,few of TiO₂ are transformed into anatase,and the FeO and Fe₃O₄ are transformed into Fe₂O₃.The pre-oxidation can change the crystal structure of ilmenite,Under this condition,the pre-oxidation process is advantageous to carbothermic reduction.During the pre-oxidation,the Sulfur exists in compound orbs can be removed completely.(3)The compound additive is the main innovation in this thesis.The catalysis of compound additive includes two aspects:1)They can reduce the activation energy of ilmenite,facilitate the Boudoir Reduction and reduce the reduction temperature;2)The alkali metal steam in compound orbs is propitious to the looseness of orbs and the diffusion of CO.Furthermore,because alkali metals are more active than Fe,they can replace the location of Fe in hematite to cause iron oxide crystal distortion,increase vacancy for a new crystal phase formation,and then make iron crystal continued to gather and grow up..(4)The optimal technical condition of carbothermic reduction are as follow:the reduction temperature is 1100-1150℃,the reduction time is 240min,the proportion of C/Fe is 2.4 and the proportion of compound additive is 5%.Under these conditions, the reduction ilmenite in which w(TiO₂)is 52.78%,w(FeO)is 4.6%and w(C)is 0.034%are prepared.The XRD and SEM analyses indicated that there are mainlyα-Fe powder and rutile in reduction ilmenite,and the grownα-Fe crystal and rutile are enwrapped by each other.Generally,in production of reduction ilmenite,the compound additive was used to reduce reduction temperature and decrease reduction time.Under this condition,the high quality of product could be obtained and the problem of high w(C)could be solved.The new process overcome some drawbacks of the existing reduction of ilmenite and is quite practical.