Research And Improvement Of Outside-heat Crucible Td Salt-bath Furnace

Presently, seeping metal element with TD salt-bath is on incipient phase, and compared with Japan, there are many huge gaps not only in applied range, scale and society economic benefits, but also in many relevant technical tasks which are waiting for research and development. Then we all know equipments of TD salt-bath are seemingly blank. Some companies which seep metal element with TD salt-bath mainly use outside-heat crucible salt bath furnace. Because there are no company which could produce this kind of appliance, some problems are exist for example: (1) thermal efficiency is low; (2) life of crucible is short; (3) salt bath defending oxidation; (4) operation mechanization and autoimmunization are not advanced; (5) salt bath segregation is serious.According the problems above, this thesis investigates items such as:(1) material of crucible defending oxidation and corrosion analysis; (2) how to improve thermal efficiency of outside-heat crucible salt bath furnace effectively; (3) how to avoid salt bath segregation effectively.Investigating metal materials of salt bath, to avoid emerging carbide layer on the surface of sample during the experiment, and the main elements of salt bath could seem to the elements in disposal, and mass fraction is NaCl 12.5%; dehydrate borax 87.5%. The main elements contributing to defending high temperature corrosion and oxidation are Ni and Cr, and Cr 15%～25%, Ni 9%～80%, so these including all heat-resisting and corrosion resistant stainless steels.By improving the lining structure, lining material and the application of infrared radiant material, to improve the thermal efficiency of outside-heat crucible TD salt bath furnace.The proportion of salt bath element is different, so there will be segregation seriously; this affects the formation of TD salt bath carbide layer. To avoid the problems above, we make use of churn-dasher.We have some results for above contents as follow:1) in selected Cr-Ni stainless steel, Cr20Ni35 stainless steel have the best corrosion resistance in borax salt-bath; the main area of corrosion is interface behavior between borax bath surface and air, and in borax salt-bath, Na2O and B2O3 enhance corrosion; 2) because it is large-size structure of assembly, many convex platforms which is used to fix resistance wire evenly distributed in the furnace, smearing the infrared radiation ceramic coating which mainly made of Cr2O3 and Fe2O3, which improve the radiation intensity further, the thermal efficiency improve largely; 3) using salt-bath churn-dasher improved the problem of segregation; fix the simple device for avoiding high-temperature oxidation is valid to prevent the bath salt from aging.Making use of above research conclusions and some technology of patents, to improve and design the outside-heat crucible TD salt bath furnace, resulting in its function, performance, operation convenience, thermal efficiency all improve largely.