The steel billets produced by steel making plants are not ready for various industrial productions, they need one further step of the process - the hot rolling mill.
What a hot rolling mill does is rolling the heated steel billets over and over again, just like a baker preparing his dough. The billets come out as thin strips after the continuous and efficient process. You can then pack them as plates or coils, and now they are ready for all kinds of productions.
Sometimes the client requires for thinner plates, that’s what cold-rolling mills do. The coils delivered form hot-rolling plants need to be processed with hydrochloric acid first to remove the oxidation film before the cold-rolling process. After uncoiling the clean steel coils, the steel strips will be fed into the cold-rolling mill and rolled again.
Hot-rolled products are divided into steel coil and spindle board, the hot rolled steel rail is generally in a few mm thick. If customer requirements steel plate thinner, it needs to cold rolling one more time.