Many massive steel products, as armor plate, large gun parts, and large shafting for marine engines or turbines, cannot be rolled because of their shape, or because their size makes rolling far more expensive than forging. These products are shaped from unusually large ingots which are forged either under impact of the steam hammer, or preferably pressed under the hydraulic forging press.

The blow of the steam hammer is delivered quickly, and its force is absorbed at first locally by the metal directly under the impact of the hammer, and as this becomes compacted, the force is transmitted deeper into the metal mass. The hydraulic forging press is preferable to the hammer for large forgings because its pressure makes itself felt entirely through the metal mass.

Some large forgings are made from rolled blooms, but these are commonly made in large manufacturing plants, as shipbuilding plants and locomotive works, by means of steam hammers.