For tin bronze liner castings, when their length and thickness are greater than 25mm and sand casting is used, it is difficult to fill due to insufficient filling channels. In centrifugal casting of copper alloys, the difficulty of centrifugal casting of large tin bronze liners is relatively high, especially under the condition of red sleeve assembly, the difficulty of centrifugal casting of large tin bronze stern shaft liners is even higher.
Stern shaft bushings usually have the following two characteristics: first, poor repair ability of defects - ship stern shaft bushings are usually three in a group, and the outer circle is initially machined and the inner circle is finely machined. After heating (red sleeve), the bushings are installed into the stern shaft in one direction. The structure of tin bronze material is loose, and micro looseness called "mosquito feet" is prone to occur during precision machining of the outer circle. Due to the directionality of the liner during installation on the stern shaft and the difficulty in disassembling the liner assembled with the red sleeve, if there is micro looseness defect in the inner end liner during precision turning, only the three liners on the stern shaft can be removed together, so the manufacturing risk of this type of liner is relatively high; Secondly, it is easy to produce penetrating pores - due to the relatively thin stern shaft of the ship, the stern shaft liner is relatively long, that is, the length/outer diameter is relatively large. Based on experience, for tin bronze liners, the larger the length/outer diameter value, the more likely it is to produce penetrating pores.
For large tin bronze bushings, it is also easy to produce heavy skin, which needs to be carefully addressed in the process. Due to the high scrap rate of the tin bronze liner matched with the red set, many casting manufacturers are quite troubled, indicating that centrifugal casting of the tin bronze stern shaft liner is a challenging problem. The development trend of centrifugal casting for this type of product is that the consideration of various factors is no longer singular and isolated, but systematic and comprehensive. To achieve the goal of preventing casting defects and producing high-quality castings, it is necessary to consider the matching between equipment, casting molds, process parameters, casting shape and gate form, and the selection of coatings, and to harmoniously integrate these elements through the coordinated application of multiple process methods.
Dongguan Sanhe Machinery Co., Ltd
Main productsCopper sleeve, copper bearing, copper worm gear, copper guide plate, copper ball seat.
Scope of supporting services: punching and forging machine tools, powder forming machinery, die-casting and peripheral spray machinery, rubber and plastic machinery, mining, metallurgical machinery, engineering machinery, air, port and marine equipment, recreation facilities, die cutting, printing machinery, etc.
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