Stainless steel production process
The world’s first stainless steel futures were listed on the Shanghai Futures Exchange on September 25. Stainless steel production mainly includes crude steel smelting, hot rolling, cold rolling and other links. Today, let us popularize the production process of stainless steel:
One, Stainless steel crude steel smelting process
At present, the smelting process for producing stainless steel in the world is mainly divided into one-step method, two-step method and three-step method, as well as new integrated production methods. The one-step smelting method is: molten iron + AOD (argon oxygen refining furnace); the two-step method is: EAF (electric arc furnace) + AOD (argon oxygen refining furnace). The three-step method is: EAF (electric arc furnace) + AOD (argon oxygen refining furnace) + VOD (vacuum refining furnace). In addition to several traditional production processes, the current integrated production process, that is, the production process from molten iron directly to stainless steel, has also been adopted by many companies. The production process is: RKEF (Rotary Kiln Electric Furnace) + AOD (Argon Oxygen Refining Furnace).
Second, stainless steel hot rolling process
The stainless steel hot rolling process uses slabs (mainly continuous casting billets) as raw materials, which are heated to produce strip steel from the rough rolling mill and the finishing mill. The hot steel strip from the last rolling mill of finishing rolling is cooled to a set temperature by laminar flow, and then coiled into a steel coil by the coiler. The cooled steel coil has oxide scale on the surface and appears black, commonly known as “stainless steel black coil” . After annealing and pickling to remove the oxidized surface, it is called “stainless steel white skin coil”. Most of the hot-rolled products circulating in the stainless steel market are stainless steel white skin coils. The specific stainless steel hot rolling production process is as follows:
Three, stainless steel cold rolling process
After the stainless steel is hot-rolled, some hot-rolled stainless steel products are directly used downstream, and some hot-rolled products need to be processed into cold-rolled before use.
For stainless steel cold rolling, hot-rolled stainless steel products with a thickness of 3.0-5.5mm are mostly used. After rolling by cold-rolling equipment, they are produced into stainless steel cold-rolled products. At present, the main production processes of stainless steel cold rolling are two types: stainless steel single-stand cold rolling and stainless steel multi-stand cold rolling. The specific production process is as follows:
After the stainless steel is cold rolled, it needs to go through an annealing and pickling line. Annealing of stainless steel after cold rolling is to eliminate work hardening through the process of recrystallization to achieve the purpose of softening; the purpose of pickling is to remove the oxide layer formed on the surface of the steel strip during the annealing process, and the second is to passivate the surface of the stainless steel. , Improve the corrosion resistance of steel plate.
Why is 316 stainless steel more expensive than 304?
In our daily life, the most common ones are 304 and 316 stainless steel. We use stainless steel every day. Many people may not know what type of stainless steel pot and water cup they use at home. Which one is better?
Today I will introduce you to the difference between 304 and 316 stainless steel. What is the difference?
1. 304 stainless steel
First of all, the pots and pans commonly used in our family, as well as the daily drinking cups, tableware, etc., are all made of 304 stainless steel, that is, food equipment, which is widely used.
Daily food design is also exposed to more acid and alkali. The biggest advantage of 304 stainless steel is acid and alkali resistance, and it has high density and no bubbles in polishing.
2. 316 stainless steel
316 stainless steel uses food equipment a bit extravagant, but its function is better than 304, generally mainly used in medical, food, machinery, petroleum, etc.
And 316 stainless steel is commonly used in some parts of machinery and equipment, or it is more commonly used in the production of some gun barrels and weapons.
3. How to distinguish
Nowadays, regardless of the fierce competition in the industry, some people sell 304 stainless steel at the price of 316. The price of 316 stainless steel is more expensive than 304. It is invisible to the naked eye and needs to be tested by us.
316 stainless steel contains molybdenum (Mo), which is more corrosive than 304 stainless steel. Generally, mechanical engineers use 316 material for parts in high temperature environments.
Nowadays, the different grades corresponding to 304 and 316 are: 304 corresponds to 0Cr18Ni9, and 316 corresponds to 0Cr17Ni12Mo2. If you want to know more about it, you can directly search (304 and 316 corresponding grades, and chemical composition).
316 stainless steel mainly reduces the content of chromium (Cr) to increase nickel (Ni), and increases Mo2%~3%. Therefore, if you are not an engineer or a manufacturer of parts and equipment, 304 is enough for the commonly used choice in our lives.
Summary: 316 adds two more elements, Ni and Cr, than 304, and 316 has better oxidation resistance than 304, and 316 has a higher hardness than 304. For families with high life requirements, choose 316 stainless steel, and choose 304, which is less demanding. There is no harm.