Product InformationOverview of Products
Tinmill products and related light-gauge, surface-critical steel and metal products are grouped together due to similar characteristics, manufacturing, processing and end users. These materials are manufactured by steel mills using either oxygen furnaces or electric arc furnaces and then sold into the market in coil form. Certain mills will provide further manufacturing of the coils, but usually cutting, slitting and coating is done by the end user or by service centers.
Tinmill products include electrolytic tinplate, electrolytic chromium coated steel (also referred to as tin-free steel or TFS), and black plate, the uncoated steel substrate. About 85% of tinmill products made in the world are used by the container industry in the manufacture of cans, ends, and closures, primarily for the food and beverage industry. The balance of production is used for automotive components, shelving, computer chassis, telecommunications cable, cookware, etc.
Related products include a wide range of light-gauge, surface critical “flat” products such as cold rolled steel, stainless steel, aluminum, laminated steel, coated steel and aluminized steel.
While coil fed processing lines are becoming more customary, for most end uses, these products are cut into sheets or slit into mults that can be easily formed or drawn into end products. The chemical compositions of the products make them easily workable and mills can produce a wide range of specifications that give end users further customization.
Modern steel making began in the 17th century with the development of the blast furnace to smelt of iron ore into pig iron. At this point, steel was already being used in a wide range of industries, but it was only 1812 that it was understood that tinplated steel could successfully preserve food.
The tinplate industry as we know it today is founded on Nicolas Appert’s invention of the process of preserving sterilized food for long periods of time. By 1812, Appert was successfully packaging a variety of products in glass containers for a growing market. The Appert process was adapted to the preservation of food in tinplate containers by John Hall in 1812 in London.
By the 1820’s, canned foods were widely sold in England and France, and by 1839, foods were being canned in the United States. The American can industry grew explosively as a result of the Civil War, the subsequent settling of the west, and the growth of the oil industry.
Starting in the 1880’s, a series of technical innovations transformed the tinplate industry. These included the replacement of wrought iron with steel for the black plate in about 1880; the development of continuous cold reduction in 1927, that eliminated hot-pack rolling; the introduction of continuous electro-tinning on a small scale in Germany in 1934 and on a commercial scale in the United States in 1937, which replaced the hot dip process; the invention of double cold reduction in 1960; and the invention of TFS in the early 1960’s in Japan and the United States.
Concurrently, many advances occurred in canmaking technology that exploited the improvements in the quality of tinmill products.
Tinmill products are also used by the automotive, building, appliance, and furniture industries, all of which take advantage of the unique properties of these light-gauge steel products.
Blackplate, tinplate and TFS are mainly used for food packaging, but are also used by a multitude of other end uses. Most prime tinmill sales are made directly with packaging manufacturing. As a result, Titan Steel deals heavily with the alternative uses for the material. These uses include automotive, consumer, electronics, filters, building products, and machined parts.
Tinmill products are available in three cast compositions. The cast compositions deal with the level of “impurities”. Lower levels of impurities allows the metal to be drawn further and used in specialty applications such as food products.
Black plate is usually a form of cold rolled steel with a thickness lighter than 0.015”. To improve critical characteristics, black plate will be further processed into tinplate or TFS. Tinplate will improve formability, corrosion, weldability and strength. TFS will improve corrosion, paint adhesion and strength.
Flat Rolled Products
Flat rolled products include cold rolled, galvanized and specialty coated/laminated products. These products are used for a multitude of applications such as appliances, exposed and unexposed parts, electric motors, and bathtubs. Today’s flat rolled products are much improved over those used in the past, offering better control of thickness, shape, width, surface finish, and other special quality features that compliment the emerging need for highly engineered end user applications. To meet the various end user requirements, flat rolled sheet products are metallurgically designed to provide specific attributes such as high formability, deep drawability, high strength, high dent resistance, good magnetic properties, enamelability, and paintability.
The cold reduction during formation induces very high strains (work hardening) into the sheet; thus, the steel not only becomes thinner, but also becomes much harder, less ductile, and very difficult to form. However, after the cold-reduced product is annealed (heated to high temperatures), it becomes very soft and formable. In fact, the combination of cold reduction and annealing lead to a refinement of the steel that provides very desirable and unique forming properties for subsequent use by the customer.
Without any further processing, the product is known as cold rolled coils. The product is typically available at thickness as low as 0.0142 inch although lighter gauges may be ordered. Typically, thicknesses lighter than 0.015” are ordered as Black Plate.
Cold rolled coils can go through further processing to create other flat roll products. The most common process is to coat the cold rolled coil in a combination of zinc an aluminum to create a galvanized product.
Stainless steel is the name given to a group of corrosion resistant and high temperature steels. Their remarkable resistance to corrosion is due to a chromium-rich oxide film which forms on the surface. When ordinary carbon steel is exposed to rain water, for example, it corrodes forming a brown iron oxide, commonly called rust, on the surface. This is not protective and eventually the entire piece of steel will corrode and be converted to rust. But when enough chromium (more than about 10%) is added to ordinary steel, the oxide on the surface is transformed – it is very thin, virtually invisible and protective in a wide range of corrosive media.
The manufacture of quality stainless steel, from heat to heat and year to year, demands precise control of raw material ingredients and melting practices. Exact quantities of presorted scrap and alloying elements are delivered to the mills’ melting furnaces so that the heats will be within specified composition ranges. Those composition ranges typically include a group of chemical elements for each grade of stainless steel:
- Chromium (Cr) forms a surface film of chromium oxide to make the stainless steel corrosion resistant. It also increases the scaling resistance at elevated temperatures.
- Nickel (Ni) stabilizes the austenitic structure and increases ductility, making stainless steel easier to form. It increases high temperature strength and corrosion resistance, particularly in industrial and marine atmospheres, chemical, food and textile processing industries.
- Molybdenum (Mo) increases corrosion resistance, strength at elevated temperatures, and creep resistance. It expands the range of passivity and counteracts tendency to pit especially in chloride environments.
- Aluminum (Al) is a very strong ferrite former and lowers the hardenability of stainless steel. It improves scaling resistance.
- Carbon (C) strengthens stainless steel but promotes the formation of precipitates harmful to corrosion resistance.
- Copper (Cu) is added to stainless steel to increase their resistance to certain corrosive environments. It also decreases susceptibility to stress corrosion cracking and provides age-hardening effects.
- Manganese (Mn) promotes the stability of austenite, at or near room temperature and improves hot working properties. Addition of up to 2% manganese has no effect on strength, ductility and toughness. Manganese is important as a partial replacement of nickel in 200 series stainless grades.
- Niobium (Nb) combines with carbon to reduce susceptibility to intergranular corrosion. It acts as a grain refiner and promotes the formation of ferrite.
- Silicon (Si) increases scaling resistance by forming a tight initial scale, which will withstand cyclic temperature changes. It resists carburizing at high temperatures and slightly increases tensile strength and hardness. Small amounts of silicon are added to all grades of stainless for deoxidizing.
- Titanium (Ti) combines with carbon to reduce susceptibility to intergranular corrosion. It acts as a grain refiner and promotes the formation of ferrite.