Differences between valve materials 304, 304L, 316 and 316L

Corrosion resistance
The corrosion resistance of 316 stainless steel is better than 304 stainless steel, and it has good corrosion resistance in the process of pulp and paper production. Moreover, 316 stainless steel is also resistant to marine and corrosive industrial atmosphere.
Generally speaking, the chemical corrosion resistance of 304 stainless steel and 316 stainless steel is not different, but it is different in some specific media.
The stainless steel originally developed was 304, which is sensitive to pitting corrosion in certain cases. An additional 2-3% increase in molybdenum reduces this sensitivity, resulting in 316. In addition, these extra molybdenum can reduce the corrosion of some hot organic acids.
316 stainless steel has become almost the standard material of food and beverage industry. Because of the shortage of molybdenum in the world and the nickel content in 316 stainless steel, the price of 316 stainless steel is more expensive than 304 stainless steel.
Spot corrosion is a phenomenon mainly caused by deposition corrosion on stainless steel surface, which is because of lack of oxygen, it can not form chromium oxide protective layer.
Especially in small valves, the possibility of deposition on the valve plate is very small, so spot corrosion is rarely occurred.
In various types of water media (distilled water, drinking water, river water, boiler water, seawater, etc.), 304 stainless steel and 316 stainless steel have almost the same corrosion resistance, unless the content of chloride in the medium is very high, 316 stainless steel is more suitable.
In most cases, the corrosion resistance of 304 stainless steel and 316 stainless steel is not much different, but in some cases, it may also be different, and specific analysis is required. Generally speaking, valve users should know well, because they will choose the materials of containers and pipelines according to the media conditions, and do not recommend materials to users.
Heat resistance
In the intermittent use of below 1600 degree and continuous use under 1700 ℃, 316 stainless steel has good oxidation resistance. In the range of 800-1575 degrees, it is better not to use 316 stainless steel continuously, but when 316 stainless steel is used continuously outside the temperature range, it has good heat resistance. 316L stainless steel has better carbide resistance than 316 stainless steel, and the above temperature range can be used.
heat treatment
Annealing is performed in the temperature range of 1850-2050 degrees, then annealed rapidly, and then cooled rapidly. 316 stainless steel shall not be hardened by overheating treatment.
316 stainless steel has good welding performance. All standard welding methods can be used for welding. When welding, 316cb, 316L or 309cb stainless steel filler rod or electrode can be used for welding according to the application. In order to obtain the best corrosion resistance, the welded section of 316 stainless steel needs post weld annealing treatment. If 316L stainless steel is used, post weld annealing is not required.

Post time: Apr-13-2021