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Metallic material is a human discovery and use of one of the oldest materials in our country and some developing countries are still dominated material industry. Metallic material is one of four commonly used packaging materials, with the development of technology and modern metal container forming metal plating technology, which plays an important role in the packaging industry. The following features and performance food packaging containers commonly used in the production and processing of steel sheet as an introduction.
At present, the main steel packaging sheet, press rolling can be divided into two types of hot-rolled steel sheets and cold-rolled steel. Packaging steel mostly ordinary carbon steel and low alloy steel ordinary hot-rolled steel sheet made for enhanced corrosion resistance, usually also need to surface coating treatment. According to different plating metal can be divided into tinplate, chrome-plated steel sheet, galvanized steel sheet three kinds.
Tinplate commonly known as tinplate, tin-plated surface is low-quality steel sheet to hot-dip process called hot-dip tin tin plate; electroplating process called electroplating tin tin plate. After the tinned steel sheet enhanced corrosion resistance, ductility, workability is further improved. This is because after the tin plate, between the inner and outer steel tin to form a dense layer of tin alloy, thin alloy which has good corrosion resistance. Japan to develop pre-nickel-plated steel sheet, in addition to improving the original plate weldability, but also improve the original board of paint adhesion and corrosion resistance. Another first in the original plate coated with chromium metal (100mg / m2), and then coated with a layer of tin (0.1 ~ 0.3g / m2) made of chrome-plated steel, tin floor. This steel weldability and corrosion resistance, reduced paint cost, high-temperature short-time baking. Special packaging tin tin plating process uses insoluble anodes way, the process is simple, high efficiency, uniform coating, strong, and can realize the pros and cons of different plating coating thickness, avoid hot dip caused by the need to contain phosphoric acid, emissions of toxic chromium waste water, thus saving the cost of wastewater treatment, reduce environmental pollution.
In the tinplate packaging applications often have the inside of the container that is made of materials that come into contact with one side coated with the coating, after drying and then packaged food and other contents. This coating dense, uniform, good adhesion to the surface of the tin plate, easy to fall off and damaged in the process. This coating is mostly raw materials, epoxy resins, phenolic resins, food is not contaminated, harmful to humans, but also has good corrosion performance, can prevent spoiled food in oil, media, so as to effectively protect the quality of the food . Tin cans of resistance welding technology using high-frequency welding, either reduce pollution, but also can improve the quality of welding.
Tinplate biggest feature is antiseptic and easy processing, can be made of red type, but also welding processing, and printing means easy, and non-toxic, harmless, it is suitable for a variety of foods, beverages, pharmaceuticals packaging ,, is mainly for canned food packaging materials.
In recent years, the French steel company first developed a new type of tinplate packaging, and put into the market, causing a revolution in the packaging industry. Depending on the requirements of the packaging industry, the thickness, the amount of tin, tinplate mechanical properties of materials and others have different needs. Currently, in Europe for the production of three-piece cans are the material thickness 0.13mm ~ 0.21mm, not only can save steel, reduce costs, and all aspects of product requirements are not reduced. Statistics of the situation by the European countries, due to the reduced thickness of the material, companies receive 20% of revenue, 3% to 4% of the gains to be much higher than the tank lower prices. Currently, tinplate production in France accounted for 40% of the European market, and is growing at 8 percent growth rate, the main reason is the development of special materials for different purposes. In Europe, some companies have begun production of tinplate cans two cans, but the device did not much change, still in use two aluminum cans production equipment. And to steel and aluminum cans, costs can be reduced by 15% to 18%, the mechanical strength of the tank increased by more than 60%.
At present, the overall development trend tinplate packaging is: reduce the thickness of the material to improve the mechanical properties of the material. Special packaging tinplate products has three main types of tin cans, spray cans and tin cans, cosmetics, closure cap and crown covered with tin, coatings and chemical products tinplate container, two tin cans, tin and other special purpose packaging.
1. tinplate beverage cans. This tinplate beverage cans is characterized by high purity, free of impurities, more corrosion resistant; drawing up width 1200mm; modeling is very Zhou Zheng, little error; continuous annealing, good toughness. It tinplate ensure good performance on the basis of greatly reduced thickness, so that tin has superior mechanical properties and plasticity.
2. Nippon Steel food cans horse. At present, European production of tinplate can be used in series production of a variety of different types and shapes of food cans. These are mainly tinplate continuous coating of tin (for coating the tank bottom DRD cans), easy open tinplate, tin cans stretch. Wherein the means for the production of ultra-thin tinplate cans and crown caps, that opens the bottle very safe and reliable.
3. spray cans and tin cans, cosmetics. For the manufacture of tinplate packaging high pressure spray can make such a container in accordance with international standards, environmentally friendly.
4. coatings and chemical products tinplate container. Due to special packaging tinplate with excellent impact resistance and flame resistance, these packaging containers packaging coatings and paints, not only in the transport of toxic substances, the relevant provisions of storage, and the manufacturer can save a lot of insurance.
5. special purpose tinplate packaging. Special purpose tinplate packaging has good printability, optimized for printing containers of various shapes.
Chrome plated mild steel sheet known as chrome steel, which is to reduce the amount of tin, lower production costs and develop new tinplate alternative materials, also known as chromium steel or tin-free steel sheet Wuxi. Chrome plate poor corrosion resistance must be to use after coating is applied. Chrome plate coating is applied after its large film adhesion, suitable for the manufacture of food cans and red bottom cupping. Tin-free steel tinplate following relative advantages and disadvantages:
1. The advantages of tin-free steel
(1) plating with less, so the cost is relatively low
(2) coating adhesion is good. Honeycomb surface oxide film and containing -OH and other genes, and thus the coating adsorption, wettability is very strong,
It is the same kind of paint adhesion on tinplate 2 times to 5 times, and will not appear prone to leaking tin coating called crater or fish eye.
(3) good heat resistance, low temperature does not appear tin "tin pest" phenomenon.
(4) having a high sulfur resistance, high alkali resistance. Because chromium and chromium oxides of sulfur and not with a base, it is a very good resistance to sulfur and alkali resistance, will not cure black, while its atmosphere, organic solvents, oils, etc. have good corrosion resistance .
2. The tin-free steel tinplate shortcomings exist with respect to
(1) chromium layer spot-adverse, which require special welding equipment or chromium layer is removed after welding, the general welding and bonding method carried cans seam. (2) when the oxide film is thick, the ductility is deteriorated. (3) acid corrosion resistance poor, generally should be applied to high acid coating, can be used for acidic environment.
Wuxi plate chrome two-step process using a low concentration of plating method not only reduces the consumption of chromium, but also reduce the amount of waste water treatment, help to reduce environmental load, its thin and uniform coating, low cost. Chrome-plated steel is currently the main applications beer bottle, beverage, food cans neutral paint cover, as food cans, little. The large number of foreign use within the outer coating Wuxi printed board for meat and fish cans, especially two-piece cans, give full play to the plate in Wuxi and excellent resistance to sulfur black paint adhesion becomes strong advantage.
Galvanized steel, commonly known as white metal, the surface is galvanized carbon steel sheet. A zinc coating is a protective coating to protect steel against atmospheric corrosion during use. Galvanized general must go through passivation layer, the passivation film passivation in chromate or chromate solution formed in the difficult role of moist air, anti-corrosion ability. But zinc soluble in acid or alkali, and reactive sulfide, so not suitable for packaging acidic, alkaline or sulfide product.