IMPREGNATION OF VACUUM CASTINGS
During the casting process, gases are released in the molten metals which cause a lack of continuity, inclusions, pores and lunkers in the frozen material. This causes scrap in castings where the liquid or gas tightness must be 100%. These disposable pieces can be largely economically saved by filling their pores with a vacuum-introduced polymerizable plastic.
There are three characteristic types of pore appearance
INCLUSIVE AND PORE TYPES
In a good case, this is not a problem. However, it is easy for the inclusion to open and become a bag or through-pore during removal of the material during further processing.
The bag has pores
In principle, this is not yet permeable, however, depending on the wall thickness, the internal corrosion easily breaks through the thinnest point. It is also disadvantageous due to the retention of dirt.
The cause of the problems, often invisible, is that the leak can only be detected under pressure.
WHY VACUUM SEAL?
The pores are often micron-sized, but the sealant is not absorbed into the mm channels or bag pores due to the resistance of the air inside and the viscosity of the sealant. In a vacuum seal, the pieces are surrounded by a vacuum and then the sealing fluid is filled in this vacuum. From this, as well as due to the overpressure applied to the surface of the sealing fluid, the pores absorb the material and also keep it under atmospheric pressure.
WHY A POLYMERIZABLE MATERIAL?
Although the pores hold the input material, there is no significant resistance to this under pressure. The company ULTRASEAL has developed a family of materials that are flexibly transformed into solids by heat treatment and are resistant to pressure, vibration and chemical effects. The materials have been tested and approved by all major quality control and users.
Microscopic image of cross section of castings.
Our company, as the Hungarian representative of ULTRASEAL, has the appropriate equipment, materials and licenses to perform this procedure. In addition to the typically small parts, we also specialize in the vacuum impregnation of large pieces that cannot be placed in a vacuum chamber (eg pump housings).
Simplified impregnation process.