What are the factors that lead to the formation of stainless steel casting pores?
Intrusive pores are the key way to cause pores in lost foam steel castings. The reasons are as follows.
(1) During the whole pouring process, the pouring time is too short and the filling is too fast. The foam pattern cannot be quickly vaporized. The cracked liquid material enters the metal material liquid. After the casting is condensed, the vapor cannot be discharged. And pores are generated in the casting.
(2) The air supply volume of the foam plastic pattern increases greatly with the increase of the pouring temperature, as shown in the figure2In order to change the air pressure with the pouring time during pouring, it can be seen that the air pressure rises sharply at the moment of pouring, because the casting temperature of steel castings is relatively high, and the amount of air supplied at the moment of pouring is very large, and the steam is not It can be discharged immediately, especially when the desolubilization is in the flow field, the vapor will be drawn into it, resulting in pores.
(3) The wrong operation of the adhesive used to bond the foam pattern is the key reason for the intrusive pores. It is found in specific production that steel castings usually cause a lot of pores at the adhesion of the foam pattern. If you use connectors or nails to connect the foam pattern, this point is not easy to cause pores. It is because more adhesive is applied at the joint, no matter what851Super glue orABThe relative density of glue is several times or even dozens of times that of foam plastic. Its vaporization rate is much slower than foam plastic and its vaporization temperature is higher. When the glue has not vaporized, the metal material liquid rises and wraps the glue. The whole process of refrigeration continues to vaporize, which in turn creates pores in the casting.
(4) Moisture is also one of the factors that produce pores in steel castings. The key sources of moisture during pouring are the following aspects: First, the architectural coating is not completely air-dried, or because the water-based architectural coating containsCMC, Acrylic emulsion, white glue, tapioca starch and other organic chemical adhesives, if they are hung with architectural coatings and cannot be poured immediately after air-drying, they will digest and absorb moisture in the air. In addition, the sodium-based bentonite and other granules of architectural coatings mostly contain structural water and bound water, because the air-drying temperature of the appearance is generally only40At around ℃, the structural water and bound water generally still remain in the architectural coatings, and these water vaporizes under the effect of high temperature desolventization; second, because the foam shape is not dry enough, there is still more water remaining in the foam beads Steam; the third is from the moisture in the molding sand.