Stainless steel castings produce the main reason for stomata

Stomatal problems often occur in the process of stainless steel casting, causing many troubles to the casting process. The pores are the bubble defects formed by the deposited gas in the ingot during cooling and solidification of the metal liquid. The following analysis of the main reasons for the generation of stomatal:

01
Poor air permeability or negative pressure paint, sand filled air permeability is poor, can not be timely discharge of gas and residue within the cavity, filling pressure in the formation of pores.

02
Casting speed is too slow, failed to fill the sprue cup, sprue exposed, into the air, inhalation of the slag quality, the formation of entrained stoma and slag hole.

03
Foam model gasification and decomposition generated a large number of gas and residue can not be promptly discharged from the mold, foam, paint layer filled dry sand poor drying, surrounded by the liquid alloy under high temperature, cracking a large amount of hydrogen and oxygen into the casting is the formation of pores main reason.
 
04
Due to the unreasonable design of the pouring system, the filling speed of the molten metal is greater than that of the bubble gasification and gas evacuation speed, which causes the gasification residue to be entrapped in the metal liquid and vaporized again to form the black stomatal decomposition of the inner wall tobacco.

05
Sprue cup and sprue and pouring system at the connection between the seal is not good, especially sprue and gate cup connection seal is not good, under the action of negative pressure is very easy to form sand and pores, this Phenomena can be calculated and explained using the Bernoulli equation.

06
Sand particle size is too small, high dust content, poor air permeability, negative pressure pipeline blockage caused by negative pressure distortion, so that the pressure around the cavity is far below the indicated negative pressure, gasification can not be timely discharge of the coating to form pores Or wrinkled skin.

07
Pouring temperature is low, filling the front of the liquid metal can not be fully vaporized foam, undecomposed residue floating too late to riser and solidified in the casting to form pores.

08
Poor deoxidation of molten steel, stove, furnace, the bag does not remove the net, the calm time is too short, poor slag in the pouring process, casting process unreasonable slag hole.

09
The gate is located at an unreasonable position, forming a dead zone during filling. Due to the gas pressure in the cavity, gasification residue accumulates in the dead space to form pores, and the runner cross-sectional area is too large, so that the filling speed is greater than that of the foam gas The rate of retreat, swallow the foam, gasification within the alloy decomposition, and the gas can not be discharged to form pores.

10
Gate cup capacity is too small, the formation of liquid metal vortex, invaded the air to generate porosity.