Content of preshrunk process design for large iron castings
The design factors of preshrunk technology for large iron castings mainly include the composition of molten iron, molten iron temperature, sand mold conditions, pouring system, riser and cold iron. However, the emphases of different anti shrinkage processes of iron castings may be different. For example, some castings with uniform wall thickness and simple shape are mainly inclined to metallurgical factors such as molten iron composition and molten iron temperature, while some castings with large wall thickness change and complex shape are mainly inclined to the setting of pouring system, riser and chill.
However, for most large-scale iron castings, there are still the following main steps in the design of anti shrinkage process:
(1) According to the shape of the casting, the structural analysis of the casting is carried out to determine the shrinkage characteristics and the shrinkable position of the casting.
(2) According to the shape and technical requirements of the casting, theanalysis is carried out to obtain the control factors of the casting anti shrinkage process.
(3) According to the shrinkage characteristics of castings and the control factors of anti shrinkage factors, the part of anti shrinkage process of castings, such as the composition of molten iron, the temperature of molten iron and the pouring system, is formulated.
(4) , analyze and calculate the position and size of riser and cold iron determined by the casting.
(5) , carry out process verification for the casting anti shrinkage process, and put into production in batches after the verification is successful.
Problems faced by traditional shrinkproof process design
The design of traditional preshrunk process usually depends on the personal experience of the process designer, so there are several problems in the design process:
(1) . the judgment of the easily shrinkable parts of castings mainly depends on the personal ability of the designer, so there are randomness and errors in the judgment, especially for the castings with complex shapes.
(2) . in terms of setting riser and chill, the process personnel can only design through personal experience and can’t carry out auxiliary verification.
(3) . after the completion of the preshrunk process design, only the production test piece can be used for process verification, so the process verification cycle is long.