Stainless Steel 316

Stainless Steel 316
Performance of stainless steel 316
Stainless steel 316 has excellent corrosion resistance, atmospheric corrosion resistance and high-temperature strength due to the addition of molybdenum, and can be used under harsh conditions. It also has excellent work hardening.
 
Applications of stainless steel 316
Stainless steel 316 is applied to seawater equipment, chemical, dye, paper, oxalic acid, fertilizer and other production equipment; photography, food industry, coastal facilities, bolts and nuts.
 
Stainless steel 316L
Performance of stainless steel 316L
As a low carbon series of 316 steel, in addition to having the same characteristics as 316 steel, its resistance to grain boundary corrosion is excellent.
 
Applications of stainless steel 316L
Stainless steel 316L is used for products with special requirements for resistance to grain boundary corrosion.
 
Chemical composition

 
Stainless steel 316 and 316L are stainless steels containing molybdenum. The molybdenum content in stainless steel 316L is slightly higher than that of stainless steel 316. The overall performance of the steel is better than that of stainless steel 310 and 304 due to the molybdenum in the steel. Under high temperatures, when the concentration of sulfuric acid is lower than 15% and higher than 85%, stainless steel 316 is widely used. Stainless steel 316 also has good resistance to chloride corrosion, so it is often used in marine environments. Stainless steel 316L has a maximum carbon content of 0.03 and can be used in applications where annealing cannot be performed after welding and maximum corrosion resistance is required.
 
Corrosion resistance
The corrosion resistance of stainless steel 316 is better than that of stainless steel 304, and it has good corrosion resistance in the production process of pulp and paper. Also, stainless steel 316 is resistant to erosion by marine and aggressive industrial atmospheres. Generally speaking, stainless steel 304 and 316 have little difference in chemical corrosion resistance, but there are differences in some specific media. The stainless steel originally developed is 304, which is sensitive to pitting corrosion under certain circumstances. Adding an additional 2 to 3% molybdenum reduces this sensitivity, thus giving birth to 316. In addition, this additional molybdenum can also reduce the corrosion of some hot organic acids.
 
Stainless steel 316 has almost become the standard material in the food and beverage industry. The price of stainless steel 316 is more expensive than that of 304 stainless steel due to the worldwide shortage of molybdenum and the higher nickel content of stainless steel 316.
 
Pitting corrosion is a phenomenon mainly caused by the deposition corrosion of stainless steel surfaces, which is caused by the lack of oxygen and the inability to form a protective layer of chromium oxide. The possibility of deposits on the valve plate is very small, especially for valves with small diameters, so pitting corrosion is also rare. In various types of water such as distilled water, drinking water, river water, boiler water and seawater, the corrosion resistance of stainless steel 304 and 316 is almost the same, unless the content of chloride ions in the medium is very high. At this time, stainless steel 316 is more suitable.
 
In most cases, the corrosion resistance of stainless steel 304 and 316 is not much different, but it may be very different and needs to be analyzed on a case-by-case basis in some cases. Generally speaking, valve users should be aware of it, because they will choose the material of the container and pipeline according to the medium. It is not recommended to recommend materials to users.
 
Heat resistance
In intermittent use below 1600 degrees and continuous use below 1700 degrees, stainless steel 316 has good oxidation resistance. At temperatures of 800 to 1575 degrees, it is best not to use stainless steel 316 continuously. However, when stainless steel 316 is used continuously beyond this temperature range, stainless steel 316 has good heat resistance. The carbide precipitation resistance of stainless steel 316L is better than that of stainless steel 316, and stainless steel 316L can be used at the above temperature range.
 
Heat treatment
Anneal in the temperature range of 1850 to 2050 degrees. Then, rapidly anneal and cool. Stainless steel 316 cannot be hardened by overheating.
 
Welding
Stainless steel 316 has good weldability. All standard welding methods can be used for welding. When welding, stainless steel 316Cb, 316L or 309Cb filler rods or electrodes can be used for welding according to the application. In order to obtain the best corrosion resistance, the welded fracture surface of stainless steel 316 needs to be post-weld annealed. Post weld annealing is not required if stainless steel 316L is used.
 
Mechanical properties

 
Austenitic stainless steel has the lowest yield point in all steels. Therefore, from the perspective of mechanical properties, austenitic stainless steel is not the best material for the valve stem. To ensure a certain strength, the diameter of the valve stem will increase. The yield point cannot be increased by heat treatment, but can be increased by cold forming.
 
Magnetism
People have the false impression that all stainless steel are not magnetic due to the widespread use of austenitic stainless steel. Austenitic stainless steel can be regarded as being non-magnetic, and this is true of quenched forged steel. However, the 304 processed by cold forming will be somewhat magnetic. For cast steel, it is not magnetic if it is 100% austenitic stainless steel.