304 stainless steel and 316 stainless steel of thermos cup can be said to be the two most common metal materials that ordinary people can touch. What’s the difference between them? Or let’s broaden the question a little, what is stainless steel? What is 304 or 316 stainless steel? What is steel?
Iron and steel
We often hear the word “ironmaking”. The so-called “ironmaking” refers to the separation of impurities in iron ore. The highest content of impurities in iron ore is carbon – so we use the level of carbon as the standard to measure iron.
High carbon content (more than 2%), called iron (also known as pig iron); low carbon content (2% and below), called steel (also known as cooked iron). The higher the carbon content, the harder it is, but also the more brittle – so the steel has better toughness, but lower hardness.
Steel and stainless steel
The common name of steel is “cooked iron”. Maybe you can understand it better. The familiar iron in your impression has nothing to do with “no rusting”. There are many kinds of steel, and stainless steel is just one of them.
Stainless steel and austenitic stainless steel
What we usually call “stainless steel” or “stainless steel” in its full name is “stainless steel and acid resistant steel” – in fact, it is very simple to prevent steel from rusting by adding some metal impurities into alloy steel (such as adding chromium).
But not rusty, can only mean that it will not be corroded by the air, the ability is still too poor. So we also need it to be resistant to chemical corrosion, so there is “stainless acid resistant steel”.
If you want to make stainless and acid resistant steel, you need to add a lot of metals – in other words, there is a formula. There are only three common formulations: martensitic stainless steel, ferritic stainless steel and austenitic stainless steel.
Among them, austenitic stainless steel has the best comprehensive performance and no magnetism, so it is widely used in our daily life – 304316 belongs to austenitic stainless steel.
Post time: Jul-17-2020