The Heat Treatment Characteristics of Ferritic Stainless Steel Investment Castings
The Chromium fraction of ferritic stainless steel investment castings is typically from 16% to 30%, no phase change when heated, and it can not use heat treatment to strengthen ferritic stainless steel investment castings. For improving the corrosion resistance and machining properties, we may use imposed annealing. In order to avoid brittle, the annealing temperature should not be less than 540℃ and can not be higher than 850℃. After the end of annealing heat it should be cooled or water cooled, not cooling with the furnace.
The heat treatment characteristics of Ferritic stainless steel investment castings are as follows:
(1) High chromium stainless steel investment castings heating can lead to grain coarsening, it will let the casting brittle and easy to produce intergranular corrosion, so please avoid overheating.
(2) It wil sensitization to intergranular corrosion when heat the ferritic stainless steel investment castings at 850℃ or more. So ferritic stainless steel investment castings's annealing temperature is preferably 850℃.
(3) Ferritic stainless steel investment castings, especially with 7.22 (Cr) for a z8%, when it heated to 700 ~ 800℃, it will produces d-phase and brittle. Therefore, slow cooling after annealing to easily become brittle. At the same time, stainless steel investment castings heating 370 ~ 540℃ will be brittle.