Technological Optinization For Pelagic Ship Rudder Horn And Research Of Riser Covering Flux

Rudder horn is the key unit of Large-scale pelagic ship rudder suspension. The nature and quality of rudder horn are very important to ship running. And the dimension of rudder horn casting is very large. The solidification of Large-Scale Pelagic Ship Rudder Horn is very difficult to control and because of many casting flaws, they cause large economic waste recurrently. In this paper, using HUAZHU CAE software to judge the rationality of casting technology and optimize the casting technology auxiliary can overcome the high cost and long production cycle shortcomings of the traditional craft design method. So that can improve designing quality and shorten production cycle as well as reduce the production cost. The temperature field numerical simulation of the casting for Large-Scale Pelagic Ship Rudder Horn has been made. Using three dimensional drawing software SolidWorks to make the three-dimensional entity's model of casting, pour system, rising head, rising head sleeve and cold iron, etc and lead out files whose forms are STL as the interface files. And then HUAZHU CAE software has been used to imitate the solidification process. The analogue result is used as the basic of improving the casting technology of the rudder horn. The cause of flaws witch appear in solidification process are analysed, and solution measures are enacted. In order to enhance the speed of solidifying, endo-cold irons are set up in the underpants hot spot of rudder horn and the combination section of cylinder and side extension. And to improve the feeding capacity of molten metal of the riser head, the insulating riser sleeve has been set up .In addition, the covering agent is covered on the open riser to make the casting solidify in order. Through the simulation analysis the original technology has been optimized and a satisfying simulation result has been attained.In this paper the influence of SiO₂, CaF₂, dilative graphite for risers covering flux are analysed. The results show that: with increasing content of SiO₂, multihole structure is formed in insulating layer and the thermal conductivity diminishes significantly; CaF₂ has strong fluxing action. With increasing content of CaF₂ the melting point of the flux reduces. Dilative graphite has apparent action to the expansibility and heat-insulating property of riser covering flux. The content of dilative graphite is larger and the expansibility and heat-insulating property is better. Then the optimal risers covering flux (Chemical constitution: SiO₂ 41.5%, Al₂O₃ 12, CaO8.5%, Fe₂O₃7.0%,C23.5%) which suit large steel casting is attained. The molten-slay layer of optimum risers covering flux is loosening, and the content of Al₂O₃, CaO, Fe₂O₃ are high, avail to form molten-slay. The transition layer assumes mesh structure, and it has good effecyiveness of heat insulation. X-ray diffraction shows that, at 1200℃, the major phase is SiO₂, subordinate phase is kyanite. The application effecyiveness is proofed in experiment.In the practice the Large-scale pelagic ship rudder horn is produced by CITIC heavy machinery COLTD with the technological optimization and practice experience, and using optimal risers covering flux. The yield strength, tensile strength, elongation percentage and shrinkage ration of specimen increases 35% 3% 11% 28% than technical requirement after 910℃normalize and 600℃temper heat processing. The microstructure of stretch fracture and impact fracture of specimen are analyzing by scanning electron microscope (SEM). There are many dimples in the fracture, and it shows that the plastic nature and ductility of the material are better. The result shows that rare earth can refine crystal grain and shift the pattern of inclusion in the steel, and the hazard of inclusion is reduced. And there is no casting defect in the rudder horn, the casting texture is dense. The rudder horn is acceptable through magnetic particle detecting and ultrasonic inspection, and it can meet the requirement of foreign merchant.