The main substrates are tin-plated sheets, chrome-plate […]
The main substrates are tin-plated sheets, chrome-plated sheets and aluminum sheets.
Tin-plated sheets are made of low-carbon steel by cold rolling, annealing, leveling, tinning, reflow, passivation, and oiling. By adjusting the content of certain elements in the ingot, or by appropriately changing some of the above process parameters, it is possible to produce tin-plated sheets with different corrosion resistance characteristics or adapted to different can making methods. Its typical cross-sectional structure is shown in Figure 1. The surface of the steel substrate is clean, and the reflow temperature is appropriate, so that a high corrosion-resistant thin plate (commonly called K plate) with a dense tin-iron interface alloy layer can be obtained. By adjusting the annealing temperature time, products with different tempering degrees (hardness) can be obtained. The low-profile quality (T-52) is suitable for deep-drawing cans, and the thinner plate with higher tempering (T-61) can be thinner (~0.2mm). After two cold-rolled sheets, the thickness is usually 0.18 to 0.14 mm, and the strength (tempering degree) is higher.
In order to save tin resources, the canning industry in the 1960s gradually adopted a large number of chrome-plated sheets, and since the 1980s, various low-tin sheets have been developed. These sheets are made on the original steel base and changed by plating. The former is plated with 35-100 mg/m2 of metallic chromium; the latter is either changed by tin plating or pre-plated with very thin nickel or chromium, which in turn makes the surface coating thin and dense. These new sheets have good canning characteristics and can meet the requirements of high speed welding.
After the 1960s, a large number of aluminum sheets for cans were mainly made of aluminum manganese and aluminum-magnesium alloy aluminum. It is also produced by processes such as cold rolling, annealing, leveling and passivation. It is characterized by better calendering and stretchability.