Control of Cast Grain Size of Steel Castings-Effect of Structure and Nonmetallics on Properties

摘要

The project was concerned with determining the influence of micro-structural refinement on the mechanical properties of cast high strength 4335 steel. The strength levels investigated were approximately 250,000 psi tensile strength and 205,000 psi yield strength obtained with a liquid quench and tempering treatment. The steel was cast in unidirectionally solidified cylinders and conventional sand mold keel blocks. It was determined that the addition of approximately 0.10% Ti to the steel subsequent to deoxidation provided considerable structural refinement. Studies of the micro-structure of the cast steel determined that nonmetallic inclusions were the primary factor (in the absence of microshrinkage) in determining the level of ductility. The loss in ductility that occurred because of the presence of these nonmetallic inclusions was reduced by low sulfur contents and by means of combined deoxidation treatments. (Author)