What is the surface roughness of castings
The melting point of cast steel is high, so is its pouring temperature. Under high temperature, the interaction between molten steel and mold material is very easy to produce sand sticking defects. Therefore, the artificial quartz sand with high fire resistance should be used as the mold, and the coating made of quartz powder or zirconium sand powder should be brushed on the surface of the mold. In order to reduce the gas source, improve the fluidity of molten steel and mold strength, most steel castings are cast with dry mold or quick dry mold, such as CO2 hardened sodium silicate sand mold.
The corrosion or discoloration of metals or alloys in the atmosphere caused by oxygen, moisture, acid, salt and humid air is called rust or rust. It can turn the metal surface with high strength into a compound with low strength. For this reason, investment castings often need medium-term anti rust treatment. The method of rust prevention is usually water or oil. No matter which method is used for rust prevention, the castings shall be cleaned in advance to remove the dirt on the surface and promote the formation of passive film. Composition, temperature and use of the lotion. After washing, the castings shall be dried with hot and dry compressed air and then treated for rust prevention.
Castings shall be free from cracks, under casting, porosity, bubbles and any penetrating defects. Castings are not allowed to have defects such as scratches, dents, lack of flesh, mesh burrs and isosceles triangle. The gate, flash, overflow port and separator of the casting shall be cleaned, but traces are allowed to be left. No defect is allowed within four thread pitches of initial screwing in the threaded hole.
Under the condition of not affecting the use of castings, the supplier can carry out infiltration and repair (such as welding repair, deformation correction, etc.) on castings with the consent of the demander. The die castings after repair shall be subject to corresponding quality inspection. Surface roughness of inner surface of casting: 25um
The important processing surface or main processing surface of the precision casting faces down or is located on the side: during pouring, the gas, slag in the molten metal and sand particles in the mold will float up, which may cause defects such as air holes, slag inclusions and sand holes in the upper part of the casting, while the structure is dense in the lower part of the casting.
