Ruukki Norge is a part of Ruukki Metals which has facilities in 26 countries. In Norway Ruukki supplies different types of steel and steel components to the industries such as construction, offshore, shipping. It has many departments in Norway: from Kristiansand in the south till Tromsø in the north. Elkem AS is represented in Norway which is a supplier of special alloys for the foundry industry, carbon, etc.
The rest steel and iron companies in Norway produce mainly steel finished products based on the imported crude steel. The type of steel finished products is usually depended on the requirements of the end consumers.
Norsk Stålforbund is a Norwegian Steel Association responsible for steel branch in Norway.
It certifies the steel products according to Scandinavian and European standards.
We want to emphasize that there is a little data available about Norwegian steel industry. As we mentioned above the reason is that iron and steel industry is a really small part of the metal industry in Norway.
8.5 Steel and Types
Steel is an alloy of iron and carbon. It contains mostly iron and up to 2 percent carbon. In practice, it usually contains some additional chemical elements such as phosphorus, silicon and sulfur which may cause impurities. Depending on the steel type, it may contain many different alloying chemical elements.
Crude (raw) steel is the first solid state after melting the raw materials and is suitable for further processing or sale. By finishing processes in rolling mills, raw steel is turned to semi-finished and final products such as ingots and blooms, sheets and strip, rails and accessories, wire and wire rods, bars and tool steels. Steel has more than 3,500 different products that have many different physical and chemical properties. (Fenton, 2005)
According to Key to Metals database, Steels can be classified by a various methods depending on:
• The composition, such as carbon, low-alloy or stainless steel.
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• The manufacturing methods, such as open hearth, basic oxygen process, or electric furnace methods.
• The finishing method, such as hot rolling or cold rolling
• The product form, such as bar plate, sheet, strip, tubing or structural shape
• The deoxidation practice, such as killed, semi-killed, capped or rimmed steel
• The microstructure, such as ferritic, pearlitic and martensitic
• The heat treatment, such as annealing, quenching and tempering, and thermomechanical processing
• Quality descriptors, such as forging quality and commercial quality.
We will deal with the first classification method which is composition based and the most common one. Thus we can sort the steel types in 3 main categories: Carbon steel; Low-alloy steel; High-alloy steel. Following information is obtained through research in Key to Metals steel database.
8.5.1 Carbon Steels
The American Iron and Steel Institute (AISI) defines carbon steel as follows: “Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium or zirconium, or any other element to be added to obtain a desired alloying effect; when the specified minimum for copper does not exceed 0.40 per cent; or when the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65, silicon 0.60, copper 0.60.”
Carbon (C) steels are most frequently used steels in the world. There are three sub-categories of carbon steels:
• Low carbon steels contain up to 0.3 % C. The largest category of final products that uses this class of steel is sheet and strip products.
• Medium carbon steels contain C within ranges from 0.30 to 0.60% and the manganese from 0.60 to 1.65%. The uses of medium carbon steels include shafts, axles, gears, crankshafts, couplings, forgings, rails, railway wheels and rail axles.
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• Ultrahigh carbon steels contain C from 1.25 to 2.0 %.
8.5.2 Low-alloy Steels
Low-alloy steels constitute alloying elements such as nickel, chromium, and molybdenum that exhibit properties superior to plain carbon steels. Total alloy content can range from 2.07% up to levels just below that of stainless steels, which contain a minimum of 10% Cr. For many low-alloy steels, the primary function of the alloying elements is to increase hardenability in order to optimize mechanical properties and toughness after heat treatment. In some cases, however, alloy additions are used to reduce environmental degradation under certain specified service conditions.
Low-alloy steels can be categorized into 4 major groups: (1) low-carbon quenched and tempered (QT) steels; (2) medium-carbon ultrahigh-strength steels; (3) bearing steels and (4) heat-resistant chromium-molybdenum steels.
8.5.3 High-alloy Steels
These are strong corrosion resistant; heat resisting and wear resistant steels. The group includes Stainless steels which are iron-based alloys containing at least 10.5% Chromium (Cr). Few stainless steels contain more than 30% Cr or less than 50% Iron (Fe). They achieve their stainless characteristics through the formation of an invisible and adherent chromium-rich oxide surface film. There are some other chemical elements also added to improve characteristics including nickel, molybdenum, copper, titanium, aluminum, silicon, niobium, nitrogen, sulfur, and selenium. Carbon is normally present in amounts ranging from less than 0.03% to over 1.0% in certain grades.
Over the years, stainless steels have become widely used for cooking utensils, fasteners, cutlery, flatware, decorative architectural hardware, and equipment for use in chemical plants, dairy and food-processing plants, health and sanitation applications, petroleum and petrochemical plants, textile plants, and the pharmaceutical and transportation industries.
Stainless steels are commonly divided into five groups: Martensitic stainless steels; Ferritic stainless steels; Austenitic stainless steels; Duplex stainless steels; and Precipitation-hardening stainless steels.
Following figure demonstrates the steel types and finished steel products.
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Figure 8-1 Steel types and final products