Ferrous Metals Processing Industry
- Status:
- Published
- Code:
- FMP
This BREF addresses ferrous metals processing, specifically the activities under points 2.3 (a,c) and 2.6 of Annex I to the Industrial Emissions Directive 2010/75/EU:
- processing of ferrous metals - operation of hot rolling mills with a capacity exceeding 20 tonnes of crude steel per hour;
- processing of ferrous metals - application of protective fused metal coats with an input exceeding 2 tonnes of crude steel per hour; this includes hot dip coating and batch galvanising;
- surface treatment of ferrous metals using electrolytic or chemical processes where the volume of the treatment vats exceeds 30 m3, when it is carried out in cold rolling, wire drawing or batch galvanising.
The FMP BREF is related to the IS BREF but focuses on downstream processing of semi-finished iron and steel products. It covers rolling processes through which ingots, slabs, blooms and billets obtained from continuous or ingot casting are further transformed into a variety of steel products:
- hot rolled coils and heavy plates produced by hot rolling of flat products;
- beams, rails, bars, rods, tubes and rings produced by hot rolling of long products;
- cold rolled coils produced by cold rolling.
The FMP BREF also describes the processes involved in wire drawing, hot dip coating of sheets and wires and batch galvanising.
Overview of major processes
In hot rolling, the size, shape and metallurgical properties of the steel slabs, blooms, billets or ingots are changed by repeatedly compressing the hot metal as temperatures ranging from 1 050 °C to 1 300 °C between electrically powered rollers. Hot rolling mills usually comprise the following process steps:
- surface rectification (scarfing and grinding);
- reheating to rolling temperature;
- descaling;
- rolling ;
- cooling, coiling and finishing.
In cold rolling, the properties of hot rolled strip products, e.g. thickness and mechanical characteristics, are changed by compression between rollers, without previous heating of the input. The processing steps and the sequence of processing in a cold rolling mill depends on the quality of the steel treated. Low-alloy and alloy steel (carbon steels) processing usually follows the order: pickling, rolling, annealing, temper rolling/skin pass rolling and finishing. For high-alloy steel (stainless steel) requires an initial annealing step prior to pickling.
In wire drawing, wire rods (produced in tot rolling mills) are reduced in size by drawing them through cone-shaped openings of a smaller cross section, so-called dies. A typical wire drawing process line comprises the following steps:
- pretreatment of the wire rod (mechanical descaling, pickling);
- dry or wet drawing;
- heat treatment (continuous/discontinuous annealing, patenting, oil hardening);
- finishing.
Continuous coating lines for sheets comprise the following steps:
- surface cleaning by means of chemical and/or thermal treatment;
- heat treatment;
- immersion in a bath of molten metal;
- finishing treatment.
Continuous wire galvanising plants involve the following steps:
- pickling;
- fluxing;
- galvanising;
- finishing.
Batch galvanising is a corrosion protection process in which iron and steel fabrications are protected from corrosion by coating them with zinc. The items to be coated in batch galvanising plants are very different steel fabrications, such as nails, screws; construction parts; structural components, tubes and many more. A batch galvanising plant essentially consists of a series of treatment or process baths. The steel is moved between tanks and dipped into the baths using overhead cranes. The following process steps are usually carried out:
- degreasing;
- pickling;
- fluxing;
- galvanising (zinc bath);
- finishing.