Porosity casting defects of bucket teeth

Porosity is one of the most common casting defects in castings. According to the different formation mechanism, it is mainly divided into the following three categories.

① Invasive porosity casting defect: it is a porosity casting defect formed by gas invading into the liquid metal from the outside and cannot be eliminated. The gas comes from molding sand, mold cavity and cold iron, and may also be involved in gas during pouring. It often appears in parts of bucket teeth castings, on the surface of bucket teeth castings or inside castings. Most of the porosity casting defects are round or oval, trumpet shaped, and the root often refers to the place where gas invades. Most gases are steam, Co, CO2 or carbon compounds;

② Precipitation porosity casting defect: the gas dissolved into the metal during melting. When the metal cools and solidifies, it precipitates from the metal due to the decrease of solubility. Most of the gas is hydrogen and nitrogen, with scattered pitted small round holes, bright surface and often covered with the whole casting section;

③ Reactive porosity casting defect: porosity formed by chemical reaction between mold and metal, between metal and slag, or between some components in metal. The gases of cast iron and steel castings are mostly CO and hydrogen. Reaction pores can be divided into subcutaneous pores, surface pores and internal pores.