Steel Casting What Will Crack
Casting is a variety of casting methods to obtain the metal forming objects, that is, smelting good liquid metal, with casting, injection, suction or other casting method into the prepared mold, after cooling and other subsequent processing means , The resulting objects with a certain shape, size and performance. However, if the casting process is not rigorous, then the cast steel will be cracking phenomenon.
Why does casting steel crack?
1. After the molten steel is injected into the cavity, it begins to condense, and when the crystal skeleton has been formed and begins to shrink, the stress or plastic deformation occurs in the casting due to the fact that the internal molten steel does not complete solidification into a solid state, At this high temperature material strength limit, the casting will crack.
2. The theoretical and practical reasons for the formation of hot cracking are many, but the root cause is the solidification mode of the casting and the thermal stress and shrinkage stress of the casting during the solidification period.
How can we prevent this problem from cracking?
1. Test the structure of the model. Place the ribs and stiffeners; without affecting the geometrical dimensions and performance requirements of the foundry castings, the fillet size of the transition zone can be increased. For some of the larger proportion of foundry castings, such as machine bed, flat, platform, and so on, especially the rails of the machine parts, rails hot section larger, and other parts of the thin, prone to deformation, To take anti-deflection, to offset the castings casting solidification caused by deflection deformation. For larger, larger castings can be cast more than two of the sprue.
2. Casting system design. So that the metal liquid can quickly and smoothly into the mold. Which is particularly important for medium and large foundry castings
3. When the shape of sand to be uniform. Each layer of sand to be uniform, to prevent the sand is not uniform, vibration and real parts of the individual parts of the compact strength caused by foam deformation. Do not play box too early
4. Casting castings after casting. There should be enough incubation time in the box, which is especially important for medium and large foundry castings. May be appropriate to adjust the casting unit of chemical composition of castings