Study On The Preparation Technology Of Marine Tiller Steel Casting

Foundry Technology is one of the most important technologies to realize the nation's economic growth and sustainable development. It occupies a pivotal position in machinery manufacturing industry, especially in shipbuilding. Cast steel that has many excellent properties is used widely to promote the development of the shipbuilding industry energetically and enhance international competitiveness.Tiller steel castings are a kind of important parts of the rudder system, which have complex configuration, large differences in wall thickness, excessive hot spots and high quality requirements, therefore, it is prone to causing casting defects in the cast process, such as shrinkage porosity, crack, sand burning, distortion and so on. Cooperating with a metal manufactory company, the research used INTECAST software to carry out the solidification simulation and optimization of casting process, and then took the optimized process into practice, after that, the process would get further optimizing refer to the quality of the casting product. The results showed that the orbicular parts of the tiller have the biggest thickness, thus pouring positions were chosen at the circularity's axes which is perpendicular to the ground so as to feeding; Chillers should be set on the forked pedestal of the tiller to solve the shrinkage porosity. Transverse and lengthways ribs were also set on the forked pedestal to avoid distortion. At the hot spots, the high refractoriness sands painted by heat resisting coating were used to prevent the sand burning. All the designed technique ensured that the solidification of the steel casting meets the sequence solidification principles and acquiring high quality castings. On the other hand, under the premise of the requirements of technology and quality, the risers were also improved to heighten the yield rate and cut down the cost.The stability of the molding process is one of the most important points to ensure the production of the steel castings. The sodium silicate sand hardened by CO2 was used in the factory all the time, which caused higher residual strength of mold or sand core, bad collapsibility, hard sand reclamation and knockout & Cleaning. The enterprise is in the trial production period of the no-bake furan resin sand process currently. So, the molding process and cost of no-bake furan resin sand were also discussed in this paper.In the productive process of tiller steel casting, sand burning problem always happened, and sometimes there was also exterior skin crack. The microstructure of tiller casting samples was analyzed by modern testing technologies such as optical microscopy and electron probe. The results showed the matrix structure of the samples were consist of ferrite and pearlite as well as a little impurities like MnS and Al2O3.In the actual production process, sand burning problem can be solved by intensifying the sand mold compactability and painting twice. Hair crack can also be avoided effectively by using SiC deoxidizer together with pouring process in the ladle of the Yttrium-based heavy rare earth ferro silicon alloys. Otherwise, the tiller steel castings treated by appropriate normalizing process can meet the requirements of mechanical properties.