Semi-finished casting products are intermediate castings produced in a steel mill that need further processing before being finished goods. There are four types: ingots, blooms, billets, and slabs.
Ingot
Ingots are large rough castings designed for storage and transportation. The shape usually resembles a rectangle or square with generous fillets. They are tapered, usually with the big-end-down.
Bloom
In the era of commercial
wrought iron, blooms were slag-riddled
iron castings poured in a
bloomery before being worked into wrought iron. In the era of commercial
steel, blooms are intermediate-stage pieces of steel produced by a first pass of rolling (in a blooming mill) that works the ingots down to a smaller cross-sectional area, but still greater than .
Blooms are usually further processed via
rotary piercing, structural shape rolling and profile rolling. Common final products include structural shapes,
rail tracks, rods, and
.
Billet
A
billet is a length of metal that has a round or square cross-section, with an area less than . Billets are created directly via continuous casting or
extrusion or indirectly via
hot rolling an ingot or bloom.
Billets are further processed via
profile rolling and drawing. Final products include
bar stock and
wire.
Centrifugal casting is also used to produce short circular tubes as billets, usually to achieve a precise metallurgical structure. They are commonly used as cylinder sleeves where the inner and outer diameters are ground and machined to length. Because their size is not modified significantly, they are not always classified as semi-finished casting products.
Slab
A slab is a length of metal that is rectangular in cross-section. The slab is created directly by continuous casting or indirectly by rolling an ingot on a slabbing mill.
Slabs are usually further processed via flat rolling,
, and pipe rolling. Common final products include
sheet metal, plates, strip
metal, pipes, and tubes.
Slab are mainly produced through
blast furnace route. One of the reasons to preferably produce slab through BF route is to achieve high quality.
[ Global Steel Slab Market Outlook. Commodity Inside. 16-08-2018.]
File:CC-OXY.jpg|An oxygen gas torch cutting a slab
File:Slabs stack.jpg|Steel slabs
