Step by step analysis of how to solve pitting spots in precision castings

For a long time, pitting has been a major problem in the surface quality of precision castings. After shot blasting and sandblasting, gray-black spots and pits will appear on the surface of the casting, causing waste of castings. A large amount of data shows that pitting is the inclusion of metal oxides in molten steel. The accumulation of objects on the surface of castings. Next, we will gradually analyze how to solve the pitting problem of precision castings.
1. Causes of pitting in precision casting.
1. Metal oxide inclusions caused by poor deoxidation of molten steel;
2. The conditions for complete deoxidation are: melt with dry and clean charge, add ferromanganese, add ferrosilicon, add calcium silicate, let it stand for 2 minutes without power, add aluminum, deoxidize, and then pour with heat preservation. After pouring, immediately add sawdust or waste wax , cover the box and seal to cool.
2. Preventive measures for precision casting pitting.
The important factor is the quality of the molten steel;
1. The operation should be carried out strictly in accordance with the smelting process. That is, pressing the bottom slag → covering plate during melting → pre-deoxidation after melting → slag removal during power outage → deoxidation before pouring.
2. The selection of deoxidizer must not only achieve the purpose of fully deoxidizing molten steel, but also make the oxidation formed after deoxidation have a low melting point and be easy to aggregate and float. The amount of aluminum used in the deoxidizer needs to be strictly controlled, as too much aluminum will promote the formation of pits.
3. The steel should be very clean, and it is not advisable to use too much reheating material to increase the original debris of the steel. During the melting process, the exposure time of the surface of the molten steel and the oxidation of Cr.Fe.Si elements should be prevented as much as possible.
3. Summary.

1. Pitting is a collection of iron, chromium, silicon, and aluminum complex oxide inclusions in the molten steel on the surface of the casting.
2. The main measures to prevent pitting are to completely deoxidize during the smelting process to make the deoxidized product float easily; to prevent secondary oxidation of the casting surface during the cooling process of the casting.

3. Strictly implement the shell baking process.