Stainless steel is a type of steel. The types of stainless steel often used are 304, 304L (L is low carbon), 316 and 316L, which are austenitic stainless steels of the 300 series. So what's the difference between them? Today Ace lobe pump's will tell you.
316 stainless steel has better corrosion resistance than 304 stainless steel and has good resistance to corrosion in the production of pulp and paper. Furthermore 316 stainless steel is also resistant to marine and aggressive industrial atmospheres.
In general, there is little difference between 304 and 316 stainless steel in terms of chemical resistance, although there are differences in some specific media.
The original stainless steel developed was 304, a material that is sensitive to pitting corrosion in certain circumstances. The addition of an extra 2-3% molybdenum reduces this sensitivity, resulting in 316. in addition, this extra molybdenum reduces the corrosion of certain hot organic acids.
316 stainless steel has almost become the industry standard material for food and beverage. Due to the worldwide shortage of molybdenum and the greater nickel content of 316 stainless steel, 316 stainless steel is more expensive than 304 stainless steel.
Pitting corrosion is a phenomenon caused mainly by corrosion deposited on the surface of stainless steel, which is due to the lack of oxygen and the inability to form a protective layer of chromium oxide.
In small valves in particular, the likelihood of deposits on the valve plate is minimal and therefore pitting corrosion rarely occurs.
In all types of aqueous media (distilled water, drinking water, river water, boiler water, seawater, etc.), 304 stainless steel has almost the same corrosion resistance as 316 stainless steel, unless the media has a very high chloride ion content, at which point 316 stainless steel is more suitable.
In most cases there is little difference between the corrosion resistance of 304 stainless steel and 316 stainless steel, but in some cases there can be a significant difference, which needs to be analysed on a case-by-case basis. Generally speaking valve users should have a good idea of what they are looking for, as they will choose the material of the vessel and piping according to the medium and it is not recommended to recommend the material to the user.
In intermittent use up to 1600 degrees and in continuous use up to 1700 degrees, 316 stainless steel has good resistance to oxidation. In the range of 800-1575 degrees, it is preferable not to use 316 stainless steel continuously, but when used continuously outside this temperature range, 316 stainless steel has good heat resistance. 316L stainless steel has better resistance to carbide precipitation than 316 stainless steel and is available in the above temperature range.
Annealed in the temperature range of 1850-2050 degrees, then rapidly annealed and then rapidly cooled. 316 stainless steel cannot be overheated for hardening.
316 stainless steel has good welding properties. It can be welded using all standard welding methods. Welding can be carried out using 316Cb, 316L or 309Cb stainless steel filler bars or welding rods respectively, depending on the application. To obtain the best corrosion resistance, welded sections of 316 stainless steel require a post-weld annealing treatment. If 316L stainless steel is used, post-weld annealing is not required.