CLANAE 24.1—Basic iron and steel industries

Where 24.1 sits

1. C Manufacturing industry
2. 24 Manufacturing of common metals
3. 24.1 Basic iron and steel industries

Contains 1 narrower code

• 24.10 Basic iron and steel industries

What 24.1 includes

• The activities included in this group, along with several of the processes incorporated in group 25.9, constitute iron and steelmaking or ferrous metallurgy. The reduction process transforms ore, scrap, or other ferrous waste into pig iron in blast furnaces or electric arc furnaces, in the form of spongy iron or lumps, billets, ingots, etc. In direct reduction plants (reduction furnaces), in the case of high-purity iron for special uses, iron is obtained by electrolysis or other essentially chemical processes.
• Blast furnace: the reducing agents used are basically metallurgical coke combined with coal and hydrocarbons. The resulting product is pig iron or raw iron in a liquid state, and the byproducts are slag, gas, and blast furnace dust. Reduction furnaces: these are generally gaseous but can be liquid or consist of coal, which eliminates the need for metallurgical coke.
• Most molten pig iron is directly transformed into steel in steel mills. A portion is used in its liquid state in foundries, primarily for the production of ingots and cast iron tubes.
• Pig iron is also cast in ingot form, either in casting machines or on sand casting beds; it may occasionally be found in irregular masses. It can also be granulated by pouring it into water. In its solid state, it is remelted in steel mills with scrap metal and transformed into steel, or it is remelted in foundries in cupola furnaces or electric furnaces with old pig iron and other scrap metal, and then cast into molded parts.
• The basic materials used for steel production are molten or solid pig iron, ferrous products obtained by direct reduction, and scrap metal. To these raw materials are added certain substances, such as quicklime, fluorspar, deoxidizers—for example, ferromanganese, ferrosilicon, and aluminum—as well as various alloying elements. Two fundamental groups of steel production systems are distinguished:
• Converter blowing, or pneumatic blowing, requires no external heat input. It is used when most of the charge consists of liquid pig iron. The oxidation of certain elements present with iron (carbon, phosphorus, silicon, manganese, etc.) releases enough heat to keep the steel liquid and even to remelt some of the added scrap metal.
• Heat refining, on the other hand, requires an external heat input. It is used when a solid charge is required, for example, scrap, sponge iron, and solid pig iron. The two main processes in this group are the Martin-Siemens furnace, in which the heat input comes from fuel oil or gas, and the electric arc or induction furnace, in which the heat input comes from electricity.
• The liquid steel obtained by the above processes, possibly followed by further refining, is generally collected in ladles. At this stage, alloying elements or deoxidizers can be added to the steel in solid or liquid form. To achieve a greater degree of degassing, the steel can be subjected to vacuum treatment during this stage. The steel thus obtained is classified according to its alloying element content as unalloyed steel and alloy steel, stainless steel, or other types.
• Based on its specific characteristics, it is further classified, for example, as free-machining steel, silicon steel (also called magnetic steel), high-speed steel, or silicon-manganese steel. Although liquid steel can also be poured into molds (foundries) to achieve its final shape—cast steel parts—most of it is poured into ingot molds to obtain ingots. Another portion is poured directly as semi-finished products in continuous casting facilities.
• Die casting consists of injecting a liquid or paste-like alloy into a mold at a relatively high pressure. Sintering consists of heating powders in a suitable furnace, which are then compacted by molding, generally combined with pressing.
• The semi-finished products and ingots are then transformed into finished products. Semi-finished products are those that result from rolling ingots, such as billets, bar stock, rounds, etc.; or they are transformed into forged semi-finished products using a drop hammer or forging press. Subsequently, some of the ingots and semi-finished products are transformed into flat, non-flat, or long finished products.
• These transformations occur primarily through hot plastic deformation of ingots or semi-finished products (hot rolling, forging, hot extrusion) or through cold deformation of hot-formed products (cold rolling, extrusion, wire drawing, drawing), sometimes followed by finishing operations such as grinding, turning, or calibrating cold-formed bars.
• Hot rolling refers to rolling carried out within a temperature range between the rapid crystallization temperature and the beginning of melting.
• Forging refers to the hot deformation of metal in bulk using a drop hammer and/or forging press to obtain parts of any shape.
• Hot extrusion refers to the hot passing of metal through a die to obtain bars, tubes, or profiles of various shapes. Hot stamping refers to the production of metal parts, generally in series, by the hot transformation of a portion of material, which is shaped between dies—either closed or with gaps for flash—using specially adapted tools. The stamping or pressing process is usually carried out in two successive stages after rolling, forging, or drawing operations. Cold rolling refers to rolling carried out at ambient temperature without causing heating that reaches the recrystallization temperature.
• Cold stamping refers to the production of metal parts using techniques analogous to those of hot stamping. Extrusion refers to the deformation, generally at room temperature, of metal in bulk, under high pressure between a die and a press tool, in a space enclosed on all sides except the side through which the material moves, acquiring the desired shape. Wire drawing refers to the cold drawing of wire rod in coils or rolls through one or more dies at high speed to obtain wire of a smaller diameter.
• Drawing refers to the cold drawing of long products in the form of bars or wire rod through one or more dies at relatively low speed to obtain products of a smaller cross-section or a different shape.

24.1 in other systems