There are many reasons for casting deformation defects. The following methods could prevent these defects.
(1) Improve casting structure
In the preparation of the casting process or in the production practice, it is found that the casting structure design is unreasonable and the wall thickness difference is too large, it is recommended that the relevant department propose a modification of the casting structure plan. Regarding the casting angle, adjust the position and number of gate risers to achieve sequential solidification, uniform cooling and simultaneous shrinkage.
(2) The casting itself is deformed due to casting stress
When making wooden molds or shapes, relative technical measures should be taken to make corresponding reflexes.
(3) When designing a sand box or selecting an old sand box, there should be a certain amount of sand between the box stop and the raised part of the casting.
Generally, the amount of sand eaten is not less than 60mm, and the medium and large pieces are not less than 120~180mm. If necessary, after pouring, when the casting has not yet shrunk, shovel or dig out the sand between the box stop and the protruding part of the casting to allow the casting to shrink freely and normally.
(4) Set the pouring (riser) position reasonably
There must be a certain distance between the pouring (riser) mouth and the box stop to keep a certain amount of sand. If necessary, after pouring, when the casting has not yet shrunk, knock out the molding sand at the pouring (riser) opening, and knock off the pouring (riser) opening when necessary to allow the casting to shrink freely and normally.
(5) When making core bones, you must leave a certain amount of sand to eat
(6) Boxing of castings after pouring should not be too early
After pouring, castings should not be boxed too early, especially for machine tool bed gearboxes and large and medium-sized castings. At the same time, water chilling is not allowed to avoid aggravated cooling of the castings and allow the castings to cool and shrink freely and obtain high-quality castings. However, there are some types of castings with simple structure, such as heavy dead iron, etc. In this case, watering and chilling in advance is allowed.
(7) To make a wooden mold, the wood must be dry and the structure must be reasonable. After the wooden mold is made, the core and movable parts must be marked. At the same time, the self-inspection and the special inspection are combined to avoid errors such as shrinkage of the wooden mold size and processing allowance. After modeling, the wooden mold should be laid flat and filled to avoid warping and deformation of the wooden mold.
(8) Wet pit modeling: Fill the top of the pit with paving sand, similar in shape to the wooden mold, and then put in the wooden mold, plug the molding sand and compact it with wooden strips. Place it on the wooden mold, use a hammer or wooden hammer to strike the strips in order to make the wooden mold sink and firm the surface to avoid warping of the wooden mold, and then put a pressure iron on the wooden mold to pick up sand balance and pound the sand in order to avoid the movement of the wooden mold.
Would like to cast high quality castings, except the deformation problems, the elements content, inoculant and spheroidizing agent also important need to pay more attention. |
