Riser is a cavity used to store liquid metal in the mold. It supplies metal when the casting is formed, which can prevent shrinkage, porosity, exhaust and slag collection.
General principles for determining riser location
① The riser shall be placed at the upper part of the last feeding part of the casting or near the hot joint.
② The riser shall be placed at the highest and thickest place of the casting as far as possible, so as to make use of the self weight of the liquid metal for feeding. For the hot spot at the lower position, add subsidies or use cold iron to realize sequential solidification.
③ The riser shall not be set at the important and stressed parts of the casting to prevent rough structure and reduce the strength of the casting.
④ Feeding the hot spot at different height of casting
The risers can be placed separately. But cold iron shall be used
Separate the feeding range of each riser to prevent
To cast by feeding the lower riser with the upper riser
Shrinkage cavity or porosity occurs at the height of the part.
⑤ The riser shall not hinder the shrinkage of the casting as much as possible,
Not placed in the stress concentration of the casting to avoid
⑥ The riser shall be set to facilitate removal and subsequent
Riser design: adopt modulus method to design riser
Where V is the volume of the casting and a is the heat transfer surface area of the casting
After calculation, v = 0.9479dm3 a = 0.643dm2
According to the foundry engineer’s manual, M: Mn: Mr = 1:1.1:1.2 is generally taken, that is, the proportion of the part of the casting to be fed: riser neck: riser’s modulus is 1:1.1:1.2, so Mr = 1.474 * 1.2 = 1.769
According to table 6-134 of foundry engineer’s manual, the standard open riser type I d = H = 100mm is taken