Investment casting heat treatment
The heating and cooling conditions of investment castings are different, so it has a lot of heat treatment ways.Below are main method of investment casting heat treatment ways:annealing,normalizing,homogenization processing,quenching and tempering,solution treatment,precipitation hardening, eliminating stress treatment,eliminating hydrogen treatment.
1.Annealing:annealing is to heat steel investment castings above 20℃~30 ℃, apply to all grades of steel investment castings.
2.Normalizing:normalizing is a hreatment way heating cast steel parts above Ac Celsius above, 30 ~ 50 degrees Celsius heat preservation,austenitizing completely,and then cooled in the still air.Generally engineered carbon steel investment castings and thick,big and complex alloy steel investment castings use normalizing treatment.
3.Quenching:quenching is a way heating cast steel parts to austenitizing, keep a certain time and cooling in the proper manner.Common quenching ways are water quenching, quenching oil cooling quenching and air cooling, etc.Cast steel should timely do the tempering after quenching treatment, in order to eliminate the quenching stress and to obtain comprehensive mechanical properties required.
4.Tempering,tempering is heating cast steel parts to Ac after quenching or normalizing, under a certain temperature,cooling at an appropriate rate making instability into stable after quenching or normalizing,eliminate the quenching (or normalizing) stress to improve plasticity and toughness of investment castings.
5.Solid solution treatment:solid solution treatment is heating castings to proper temperature and heat preservation,dissolved surplus parts in full, and then quickly cooling in order to obtain the heat treatment process of supersaturated solid solution.The main purpose of the solid solution treatment is to make carbides precipitate or other phase solubility in the solid solution, get the supersaturated single-phase organization.
6.Eliminating stress:the purpose is to eliminate casting stress and quenching stress and machining formated stress to stabilize sizes.
7.Eliminating hydrogan treatment:The purpose is to remove hydrogen,improve the plasticity of steel castings.
9.Carburizing treatment: This can increase the strength, impact property and wear resistance of the investment castings.