Final answer:
Steel is a sculptural material that can be formed as separate pieces and then welded together in the final work.
Step-by-step explanation:
The sculptural material that is sometimes formed as separate pieces and then welded together in the final work is steel. While marble, bronze, and wood are commonly used in sculpture, steel is frequently chosen for its strength and versatility. Artists can fabricate different parts of a sculpture using steel and then weld them together to create the final piece. For example, the famous sculpture 'The Tilted Arc' by Richard Serra is made of steel plates that were cut and welded together.