Iro3d on Youtube recently uploaded a video showing a technique which 3D prints sand molds for metal casting. The process takes two different types of sand, first shell sand for creating the mold, and regular sand which acts as support material. You then bake it at around 180c for 2 hours to bond the shell sand together.
After that you can pour out the regular sand, and you’re left with a mold which you can pour molten metal directly into. In his experiment, Iro3d made some stainless steel parts using the technique.