Tempering for investment castings

Tempering is a way for heat treatment in the investment casting process.So why we do need to do tempering for investment castings?Below are the answer for this question:

1.Reduce the brittleness and eliminate or reduce internal stress--As investment castings have big internal stress and brittleness after quenching.So if they are not tempered timely,it will result in deformation and cracking of investment castings.

2.To obtain required mechanical prperties of castings.

3.Stable sizes of castings.

4.To some alloy steel castings,which are different to soften after annealing,will be high-temperature tempered after quenching to gather carbide in steel.Thus to reduce the hardness so that it will be good for machining.