Steel castings are subject in general to the same defects named for cast-iron castings, but particularly does the manufacturer of steel castings have to be continually on guard against three classes of defects named, as follows:

(1) Cavities on the surface or hollows in the body of the casting (piping) caused by runners, risers and feeding heads too small to feed the casting as it cools. The hollows are so small at times as to resemble blow holes.

(2) Shrinkage cracks or internal strains due to unequal rates of cooling of various parts or resistance of the mould to contraction of the metal.

(3) Blow holes or small globules of gas or air enclosed in the metal. They may be due to (a) poorly vented or poorly dried moulds in which air and steam do not escape from the mould cavity, or (b) to carbon monoxide and other gases dissolved in the metal while very hot in the converter and which are thrown out of solution as the metal cools, a defect greatly remedied by the chemical action of ferro-silicon or aluminum.

One test usually specified to determine the soundness of steel castings is to suspend and strike them with a hammer, or to hammer without suspending. This does not always show the defect a casting may have.

Sometimes a cracked casting which has been annealed may be made good by welding on a piece to repair the crack.