Stainless steel is petroleum, chemical, fertilizer and other industrial sectors in the extensive use of metal materials. Ferritic stainless steel is a kind of stainless steel with ferrite structure, which is widely used in household appliances, building decoration, kitchen equipment, tableware and so on, which has a body-centered cubic crystal structure with chromium content between 11% and 30%. And people's lives are closely related to various fields.
1, the status quo
430 stainless steel as a representative of ferritic stainless steel, is a resource-saving stainless steel. Ferritic stainless steel due to high chromium content, corrosion resistance and oxidation resistance are better, but poor mechanical properties and process performance, so much less for the acid-resistant structure and the use of antioxidant steel. 430 stainless steel features just to meet the kitchen environment and stainless steel tableware material requirements, it is widely used in stainless steel tableware.
2, the problem
430 stainless steel
tableware as food in direct contact with the daily necessities, if used in the course of improper operation, stainless steel containing metal elements into the food through the cooking medium, which was the body's intake, slowly accumulate in the human body, when reached a certain level , It will endanger human health. So the health indicators is an important indicator of health, safety and health. Its heavy metals such as chromium, nickel, arsenic, lead precipitation, national and international have a strict health standards. Chromium on the human body is very serious poisoning for systemic injury. Chrome on the skin membrane has a strong stimulating effect, causing eczema, dermatitis, bronchitis and rhinitis, causing allergic and may cause cancer; on the body's organs affect, especially the kidney and liver, when these two organs problems, Maintain the body's metabolism will appear disorder, the emergence of liver ascites, cirrhosis, and even death. China and Germany standards require chromium precipitation ≤ 0.4mg • dm-2, but it is not the case.
3, causes and treatment
In 430 stainless steel tableware production process, due to improper heat treatment process leading to the segregation of impurities carbides and martensite residues, and then in the corrosive medium occurred in the galvanic corrosion reaction, leading to excessive precipitation of chromium ions (> 0.4mg • dm-2), harmful to health.
Ferritic stainless steel products after processing in the annealing process, can reduce the residual martensite. At the same time annealing process should be avoided in the intergranular corrosion sensitive temperature range (850 ~ 950 ℃) for a long time to stay, you can choose medium and low temperature and rapid cooling to avoid local corrosion.