Selection of materials in contact with food and medicine in food and pharmaceutical machinery:
1. After the surface of the metal is corroded, it will be in contact with food and medicine, which will pollute food and medicine. Therefore, in such mechanical design, metal materials in contact with food and medicine are accustomed to using stainless steel. In addition, in high temperature environments, food is in contact with stainless steel, so the content of lead and nickel in stainless steel is also considered.
2. Use of non-metallic materials. Other materials may be used instead of stainless steel in terms of cost and hygiene. The currently suitable material is polypropylene, which is a polymer material (-[-CH3-CH]N-). It is a crystalline plastic with mechanical properties such as strong stiffness, hardness and modulus of elasticity superior to that of polyethylene, another non-toxic plastic. Polypropylene also has excellent heat resistance, which can be heated to a temperature of about 150 ° C without deformation, and is the only material that can withstand high temperatures in plastics. It is superior in corrosion resistance and cost compared to stainless steel, but not as good as stainless steel in terms of stress and surface hardness. This material can be used in many places in food machinery instead of stainless steel. In addition, materials such as ceramics may also be considered in the contact with food. When using stainless steel, pay attention to the characteristics of its various grades.
Which machines cannot use stainless steel
Generally, the shafts and bearings on the machine are made of 45 steel. Stainless steel material is expensive, difficult to process, and the heat treatment process is complicated. Therefore, the cost is very high. In comparison, 45# has better processing performance and lower price, and it can also adapt to the general situation after heat treatment. Therefore, if it is not special requirements, shafts and bearings will certainly not use stainless steel.