Using riser, chill and cast steel bar to obtain high quality castings is a common technological measure in foundry production.
The special process “cavity” that can store a certain amount of metal in the mold and can supplement the casting to prevent shrinkage cavity and porosity is called riser.
(1) Type of riser
According to the position of riser on casting, it can be divided into top riser and edge riser; according to whether the top of riser is covered by molding sand, it can be divided into open riser and dark riser.
(2) Shape of riser
The shape of riser directly affects its feeding effect. There are spherical, spherical top cylindrical, cylindrical, waist cylindrical and so on. The sphere with the smallest surface area and the slowest heat dissipation is the most ideal riser shape.
(3) Function of riser
The main function of riser is feeding casting, in addition, it also has the function of outgassing and slag collecting.
2, Chilled iron
Chill is the most common chill used to control the solidification of castings. The main functions of cold iron are as follows: (1) it can strengthen the sequence solidification of castings, enlarge the effective feeding distance of risers, improve the utilization rate of metal night, and prevent the casting from producing shrinkage cavity or porosity defects. (2) Accelerate the local cooling speed of the casting, realize the simultaneous solidification, and prevent the deformation and crack of the casting. (3) Speed up the cooling of special parts of castings, refine the matrix structure, and improve the surface hardness and wear resistance of castings.
3.Cast steel bar
For the molding method that can’t place cold iron, sometimes the steel bars are designed in the parts that need to be cooled to achieve the purpose of heat dissipation and cooling. Disa line is often used.