Views:1 Author:Site Editor Publish Time: 2020-11-05 Origin:Site
Stainless steel is no stranger to each of us, and even many imported tableware are using stainless steel. Speaking of tableware, we are most concerned about health issues-the most basic requirement of tableware is that it cannot be corroded by food, otherwise it will pose a hazard to human health.
Friends who have bought stainless steel tableware will find that there are four common stainless steel meals-304, 304L, 316 and 316L. What exactly do these four types of stainless steel mean? Which tableware is better?
When we talk about stainless steel every day, we don't just refer to "rust-free steel". Its full name is "stainless and acid-resistant steel", not only does not rust, but also resistant to acid corrosion. According to the ability of acid corrosion resistance, there are many more grades. The four types we are going to talk about today are some of the many grades.
The so-called 304 or 316 are all grades of the American ASTM standard. Of course they all have corresponding national standard brand names, but why don't we talk about the national standard brand names? Because the national standard brand is too complicated, take 304 stainless steel as an example, the national standard brand is called "06Cr19Ni10".
There is no direct stainless steel grade in the national standard, but various types of stainless steel are tested in accordance with the standard and it is found that 304 stainless steel is the lowest grade that meets the standard. There are many kinds of "grade" stainless steel, and 304 stainless steel is the lowest standard.
Basically, the common foods in life can not harm 304 stainless steel. Naturally, there is no need to worry about foods that corrode stainless steel and produce harmful substances to the human body, or eat them directly into the stomach.
But when faced with some special foods, such as carbonated drinks, milk, coffee, etc., 304 stainless steel appears to be relatively weak. At this time, we need stainless steel with stronger corrosion resistance-316 stainless steel is a product with a slightly higher corrosion resistance than 304 stainless steel. It has enough corrosion resistance without increasing the cost too much, so it is also widely used in tableware. .
There are many stainless steels with stronger corrosion resistance than 316 stainless steel, but the cost increases too much, and the super corrosion resistance cannot be reflected, so it is rarely seen on tableware.
Very few manufacturers may also produce 304L or 316L stainless steel tableware-first of all, the grades without "L" have no effect on the corrosion resistance. So we choose 304 or 316 tableware is enough, there is no need to choose 304L or 316L.
So what is the difference between stainless steel with "L" in the grade and stainless steel without "L"?
This is about the welding process of stainless steel: stainless steel will precipitate carbides during high-temperature welding. The presence of carbides on the solder joints will affect the stability of the welding-this process of precipitation of carbides is called "intergranular corrosion".
In order to prevent intergranular corrosion, it is necessary to artificially reduce the carbide content of stainless steel. The stainless steel with reduced carbide content will add an "L" to the original grade.
Stainless steel with reduced carbide content has no effect on the original corrosion resistance. In other words, if intergranular corrosion is not considered, 304 and 304L, 316 and 316L are the same.
Generally, in high-precision and high-risk industries, the existence of intergranular corrosion needs to be considered. For household tableware, there is no need to use stainless steel with "L".