The application status of the hottest chromium pla

The application status of chromium plated steel sheet in canned food packaging (Part 2)

Second, the main problems of the application of chromium plated steel sheet in food canning

from the above understanding, there are two main technical problems restricting the application of chromium plated steel sheet in food canning industry:

the first is the problem of corrosion resistance. This problem can be studied from the improvement of chromium plating technology and the improvement of coating after plating. It should be noted that any technical improvement should consider the cost in order to maintain the advantage of chromium plated plate. At present, although the corrosion resistance of chromium plated plate is not as good as that of tin plated plate, it also has a certain corrosion resistance. It is suitable for packaging weak acid food

this kind of food has a large market, such as meat, fish, poultry, dairy products, vegetables, carrots, wrist beans, beets, potatoes, as well as various beverages and soups. If the coating is strictly technically guaranteed, some acidic foods with pH between 3.7 and 4.5 can also be packaged with chromium plated plates, such as fruits, pickles, etc. It is worth mentioning that the study of the corrosion resistance of chromium plated plates should not be reduced to the general concept that chromium has a good corrosion protection effect on iron. Chromium plated plates are cathodic coatings that cannot play an electrochemical protection role. In the case of large porosity, the alloy effect between steel substrate and chromium layer is worth studying. Someone tested the corrosion resistance of chromium steel in seawater and found that chromium can improve the corrosion resistance of carbon steel after short-term (within 2 years) immersion; However, long-term immersion (after more than 2 years) is not only unhelpful, but also accelerates corrosion

the second is the canning process. Chromium plated plate has thin coating and poor toughness, and lacks punching hole slip agent like tin, so the punching process needs to be carefully studied. At present, it is feasible to adopt deep drawing process for two-piece tank. Since tin welding is not possible, fusion welding or bonding must be used when making three piece cans. If tinplate and chrome plate are used in combination, tinplate for tank body and chrome plate for tank bottom cover are also applications. In addition, the sealing between the tank body and the cover should not be double crimping process, otherwise it must be repaired

III. ideological understanding of the application of chromium plated plates

the above analysis shows that although the application of chromium plated plates in food packaging has its limitations, it also has its characteristics and advantages, and has a relatively broad market, so it can be promoted and developed. However, in terms of the current reality of our country, there are still two cognitive problems in the process of development

first, the manufacturing industry of chromium plated steel plate in China is almost blank

since the reform and opening up, China's iron and steel industry has developed rapidly. At the end of last century, China has become the world's four largest iron and steel producers, with steel output of 127 million tons and 130 million tons in 2000. But in terms of its variety and quality, it is quite different from developed countries in the world. Only about 40% of the products can meet the needs of variety and quality, 30% of the varieties are insufficient, 20% of the varieties are of poor quality, and 10% of the varieties cannot be produced. In fact, the steel products in our country are mainly wire rods and profiles, while plates and pipes are in short supply. While 25% of steel manufacturers are small enterprises, and 33% of steel production are small enterprises. Their equipment is old, the process is backward, and the composition of raw materials is unstable. Large enterprises are also facing a period of institutional reform and technological upgrading. Therefore, on the whole, the steel quality gap in China is still large, the chemical composition fluctuates greatly, the performance is unstable, the dimensional accuracy of the finished product is not high, and there are many surface defects, which obviously leads to a high scrap rate for users. Many enterprises have imported foreign advanced equipment to enable patients to heal their bones at the same time, but because domestic raw materials are not applicable, they also need to import materials. From the perspective of sheet steel materials, although the annual growth is very fast, the domestic production in 2000 was 19.0381 million tons, with a year-on-year increase of 10.20%, but the apparent consumption reached 39.23 million tons. Therefore, the gap of sheet steel in China is very large. It is conceivable that in this context, the packaging industry can only rely on imports if it wants to use chrome plated steel plates. It is worth mentioning that at present, the production capacity of tinplate in China is surplus. Unfortunately, most of them are low-grade production lines, and the products can only be used for dry food packaging. The high-grade tinplate for cans and beverage packaging still depends on imports to fully calculate the arithmetic mean value. It can be seen that raw materials themselves restrict the development and progress of food packaging, which involves many scientific management and coordinated development issues in our progress

second, how Chinese food canning enterprises understand their packaging containers. At present, canned food processing enterprises mainly use tinplate. Their food technology, canned goods sales, corresponding equipment and mechanism are all based on tinplate cans. Any technological transformation and innovation involves the benefit concern of the enterprise and the reputation of the market. Therefore, the application of chromium plated plates is a risk for them. Only with scientific economic analysis, reliable conditions and enterprisers with reform spirit can they have the courage to try. Whether foreign countries have ready-made experience and equipment to adapt to China's current situation must be carefully discussed. The author has learned about some factories. Due to the limitations of the enterprise mechanism, the factory director dare not take risks, because this is a major transformation. It can be seen that Chinese enterprises have both conditional and ideological problems in the connection of new things. Parker company hopes to help plastic packaging production enterprises achieve zero landfill through new technology. The key is to establish a mechanism for enterprises to constantly explore and improve, especially after China's entry into WTO, facing market internationalization, which must be strengthened and urgent