What Is Tinplate Sheet?
Tinplate Sheet is a metal product made of sheets of steel (or wrought iron before cheap milled steel became available) coated with tin to prevent rusting. It is used to make tin cans and household utensils.
It has a beautiful metallic luster and can be printed on and lacquered. It is also recyclable. The coating weight is selected to obtain appropriate corrosion resistance against container contents.
Hot Rolling
Tinplate is a corrosion-resistant and strong metal sheet that is often used in the packaging industry. It is made of cold-rolled steel coated with a thin layer of Tinplate Sheet pure tin. It is commonly used for preserving foods, but it can be also applied to metal containers, deep-drawn oil filter shells and metal hoses.
The process of hot rolling is a compressive metal forming method which takes place under high temperatures (above the material recrystallisation temperature). Initially, the starting material is in the form of billets or slabs which are fed into continuous hot rolling machinery to obtain a strip (3 mm and above) with the desired shape.
Microstructure control during hot rolling has traditionally been rather limited but with the advancement of microstructure modeling techniques and advanced sensors it is becoming possible to directly monitor and influence the evolution of the micro structure and texture. The average stress field in Figure 5.3 agrees with the experimental data presented by Pietrzyk and Lenard describing the effect of reduction ratio on the work-roll contact zone.
Cold Reduction
The tin plate industry depends on several technological innovations that have made it possible to produce low carbon steel electrolytic tinplate at economical costs. These include replacing wrought iron with steel for blackplate in the 1880s; the invention of continuous cold reduction (CCR) which eliminated hot-pack rolling; and the invention of double cold-reduction, which improved forming characteristics.
After cold rolling, the strip is side trimmed and electrolytically cleaned and pickled. The material is then continuously annealed in a bell-type furnace in a range of heating, soaking and cooling zones under a slightly reducing atmosphere to obtain a smooth surface suitable for coating.
The characterization of the texture by means of the plastic strain ratio (rm), Dr or earing test and the grain misorientation distribution were studied in DR tinplate with different secondary cold reduction rates. The results show that the microstructure characteristics, solid solution carbon content and texture characteristics improve as the cold-rolling rate increases.
Temper Rolling
The steel that has been made hot rolled and cold reduced is tempered to make it soft enough for rolling and forming into tinplate. This is accomplished through temper rolling, which involves lightly rolling the sheet.
During temper rolling, the center-line averaged roughness Ra of the work rolls is preferably set to more than 0.5 um. If the high roughness roll is used, a load decrease effect due to the transcription elongation effect can be obtained.
Since the correction load of the work rolls has a serious influence on a steel strip shape, an apparatus Stainless Hardened SteelStrip and a system for ensuring accurate shape control must be developed. Furthermore, a temper mill that can impart such a heavy correction load has to be built with a large installation space and facility cost. Therefore, a method for temper rolling that can reduce this burden is greatly desired.
Plating
Plating is the process of applying a thin layer of tin to the surface of a metal. This process is done electrolytically using sodium stannate as the electrolyte. The current density, production speed, and cathode efficiency of this process are very high.
This tin plating produces a high-quality, durable product with good solderability and formability. It also offers excellent corrosion resistance. In addition, it is non-toxic and tasteless. These properties make tinplate an ideal material for food packaging.
Tinplate is also used for other applications, such as craft projects and building decorations. It is known for its beautiful metallic luster and can be printed with various inks and lacquers. It is also highly durable and can withstand a variety of conditions, including temperature changes. It is also easy to open and recyclable, making it a greener option than other types of metal lids. Tinplate is also highly versatile and customizable for specific purposes, allowing it to meet a wide range of demands.
Pickling
Pickling is a chemical process that cleans the surface of metal, leaving it with lots of microscopic valleys and pores to provide strong adhesion for coatings. It also restores the electrical conductivity of metals like copper by stripping away corroded layers and scale. The left-over pickling sludge is a hazardous waste and must be disposed of properly.
After picking, the steel sheet is rinsed to remove any acid residue and neutralised with an alkaline solution such as baking soda. This helps to maintain a neutral pH and prevents the buildup of rust on the steel surface.
The tin on tinplate protects against corrosion, making it ideal for the production of food can lids. The tin coating also enables the lids to resist high temperatures and vacuum pressures, which protects the contents of the can from oxidation. These benefits make tinplate the preferred material for food can lids.
Double Reduction
Double reduction is a key part of the tinplate manufacturing process. It produces a stronger product with better earing properties, and it also allows manufacturers to use lighter gauge steel. The process begins with batch annealing to soften the steel. The resulting tinplate is then cold reduced twice, before being annealed and rolled into the final product.
The experimental materials used in this study were a simply rolled sheet and a double reduced sheet that was rolled to reduce by 40% (e2). Both materials were characterized by optical microscopy, scanning electron microscopy and X-ray diffraction. The earing propensity of the material was determined by using both uniaxial and biaxial tensile testing.
The results showed that DR packaging sheets have a deformed structure and a more pronounced anisotropy compared with the simply rolled sheet. These directional properties make it important to specify the direction of rolling when purchasing tinplate for built-up can bodies.
