What properties determine a light-colored mild steel

Manufacture of steel sheets

Tinplate is one of the most environmentally friendly packaging materials available. Tinplate is a sheet of steel that is coated with tin on both sides. This combines the strength of steel with the corrosion resistance and solderability of tin.

Steel used to make tinplate is low carbon thin sheet. There are many important steps involved in manufacturing that can affect the properties of tinplate.

Hot rolling: Continuous cast steel slabs are used because they produce cleaner steel. These plates are peeled or cleaned to remove surface imperfections, then heated to 1200 to 1300 ° C and rolled into thin sheets.

Pickling: These panels are cooled and cleaned of any oxide that occurs during pickling. Earlier acids were used, but innovations have made this step acid-free, oil-free, and more environmentally friendly.

Cold reduction: The hot steel sheets are cooled with water and lubricating oil and rolled further.

Cleaning: The cooling liquids are removed with alkaline phosphates, silicates and caustic soda and finally with hot air.

Annealing: This step softens the steel and achieves the desired grain structure. Batch annealing produces deep-drawable as well as hard and rigid steel that can withstand vacuum and pressure, so best for making cans and bottles. Continuous annealing is a shorter process that results in smaller grained steel.

Tempering: The mild steel is lightly rolled after annealing in order to produce sheets with the desired final thickness.

Double reduction: Sometimes a second reduction round is used instead of tempering to roll the steel. This creates sheets that are thinner and stronger. The sheets produced can be as thin as 0.14-0.24 mm, which makes them more attractive as packaging material, as they save transport costs and reduce CO2 emissions.

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Tin has been electrolytically applied to steel sheets since the 1940s. Previously, tin was applied using a hot dip process. Tinplate production is the main purpose of tin and consumes 30% of all tin produced. By 2018, 30% of all tin production came from recycled sources.

Electrolysis has the advantage that thin layers of tin are achieved and the layer thickness is controlled. This is important because the coating thickness can vary on the two sides of the steel sheet to create "differentially coated tinplate". Modern tinplate has layers of tin that are only 0.1 to 1.5 microns thick.

Coating: The steel sheets are passed through electroplating tanks filled with electrolytes in which 99.9% pure tin anodes are immersed and covered with a layer of tin by electrolysis. In the end, excess tin on the sheet is removed and recycled.

Flux Melting: In some cases, the tin layer is heated so that it melts into an iron-tin alloy layer that improves the anti-corrosive properties of tin.

Passivation: The tin layer can be oxidized to a thin film. To prevent this layer from growing, a layer of chrome is added followed by a layer of food grade oil during passivation to stabilize the coating.

The tinplate has a thickness of 0.13 mm to 0.50 mm. The steel sheets make up most of the thickness as the tin layer is measured in microns (1 micron = 0.001 mm). Thousands of combinations of steel and tin are possible, so customers should educate manufacturers on how to use the tinplate so they can get the right quality.

There are other factors, such as the condition, surface and quality of the tinplate, which also determine its suitability for various applications.

Tempered tinplate: tinplate can have different states, which depend on the quality of the steel and the various production steps such as hot rolling, annealing and quenching and tempering. The quality of steel and tin is in turn regulated by various national and international standards such as ASTM or ISO.

Surfaces: Tinplate is available in various designs such as light, light gray, stone, matt and silver.

Qualities: There are two types of tinplate. Standard quality tinplate has optimal properties and can be painted and printed. While second grade tinplate of the standard grade tinplate is sorted out% MCEPASTEBIN%.

Tinplate is one of the most commonly recycled materials in Europe. In the past, the production method was heavily dependent on chemicals.
Taking into account consumer preferences and health and environmental concerns, innovations aim to make tinplate more convenient and sustainable.

  • Chemical consumption during processing has been reduced by eliminating the use of acids and oils for pickling.
  • The passivation process has been improved, resulting in better preservation of canned food.
  • The paints used today are sustainable.
  • Cans are lighter, which means less steel and tin are used. In many cases there has been a 46% weight reduction over the past 30 years.
  • Using recycled tinplate reduces energy consumption by 60% and air pollution by 30%.

Because steel and tin are made independently, different types of steel and different tin coatings can be applied, creating thousands of tinplate. The range of this material, which is more than any other metal, combined with a high recycling rate of over 90%, makes it a versatile and sustainable material for packaging.