Hot Rolling
I. The
rolling process in a modern steel plant comprises two stages: 1) rolling ingots
into semifinished products and 2) rolling the semifinished products into the
finished ones. Ingots are usually of a square cross-section with rounded
corners, and are first rolled
into blooms or billets. These blooms or billets are simply square or
rectangular bars of steel which are to be reheated and rolled
into the final shapes. (Present Indefinite
Passive voice )
A bloom differs from a billet only in size. It is
larger and is sometimes reheated and rolled into billets. (Present Indefinite Passive voice )
Slabs are
merely thick plates to be reheated and rolled into thinner
plates. (Present Indefinite Passive voice )
Blooms, slabs and billets are called
the semifinished products as they are subjected to some additional
finishing operations. (Present Indefinite
Passive voice )
The term
“finished” product is usually applied to rails, plates, rounds
and different shapes. (Present Indefinite
Passive voice )
1)
special shapes or sections;
2) plate
and sheet steel;
3) tubes;
4)
special types of rolled products.
Steel sections are widely used in
many branches of the industry for the manufacture of machines, steel structures
and so on. (Present Indefinite Passive voice )
Plate and sheet steela are classified
according to their thickness. (Present Indefinite
Passive voice )
All
products over 4 mm thick are called plate steel, comparatively wide
products less than 4 mm in thickness are called sheet steel. (Present Indefinite Passive voice )
Special
types of rolled products include shapes for automobile and tractor industries,
railway industry, for building construction.
III. The
main requirements in rolling the finished products are: 1) to obtain a finished
product of high quality not only in physical and mechanical properties, but to
obtain a good surface as well; 2) to obtain a finished product of the desired
size and shape at the highest rate of production and the lowest cost.