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316 Stainless Steel Has Good Oxidation Resistance

Feb 01, 2021

316 and 316L stainless steel (see below for the properties of 316L stainless steel) are molybdenum-containing stainless steels. The molybdenum content in 316L stainless steel is slightly higher than that in 316 stainless steel. Due to the molybdenum in the steel, the overall performance of this steel is better than 310 and 304 stainless steel. Under high temperature conditions, when the sulfuric acid concentration is lower than 15% and higher than 85%, 316 stainless steel has a wide range of uses. 316 stainless steel also has good chloride corrosion properties, so it is usually used in marine environments.


316L stainless steel has a maximum carbon content of 0.03, which can be used in applications that cannot be annealed after welding and require maximum corrosion resistance.


Corrosion resistance: The corrosion resistance is better than 304 stainless steel, and it has good corrosion resistance during the pulp and paper production process. And 316 stainless steel is also resistant to the erosion of the ocean and corrosive industrial atmosphere.


Heat resistance: 316 stainless steel has good oxidation resistance in intermittent use below 1600 degrees and continuous use below 1700 degrees. In the range of 800-1575 degrees, it is best not to continuously act on 316 stainless steel, but when 316 stainless steel is continuously used outside this temperature range, the stainless steel has good heat resistance. 316L stainless steel has better resistance to carbide precipitation than 316 stainless steel, and the above temperature range can be used.


Heat treatment: annealing in the temperature range of 1850-2050 degrees, then rapid annealing, and then rapid cooling. 316 stainless steel cannot be hardened by heat treatment.


Welding: 316 stainless steel has good welding performance. All standard welding methods can be used for welding. During welding, 316Cb, 316L or 309Cb stainless steel filler rods or welding rods can be used according to the application. In order to obtain the best corrosion resistance, the welded section of 316 stainless steel needs to be annealed after welding. If 316L stainless steel is used, post-weld annealing treatment is not required.


Typical use:


Pulp and paper equipment heat exchangers, dyeing equipment, film washing equipment, pipelines, exterior materials for buildings in coastal areas


Carbon content of 316L<0.03%


The carbon content of 316 is <0.08%


The chemical composition of 0Cr18Ni9 material is as follows:


1. Physical properties of nickel and nickel alloys


It is silvery white, can maintain a beautiful luster for a long time after polishing, the specific gravity is 8.9, and the crystal lattice is face-centered cubic.


2. Chemical properties


The two elements of chromium and nickel cooperate to form chromium-nickel stainless steel, which is a better stainless steel. A large amount of nickel is added to this stainless steel to obtain a single austenite structure, thereby improving its corrosion resistance and processability. It has strong plasticity and toughness at normal temperature and low temperature, is not magnetic, and has good resistance to intergranular corrosion.


(1) Chromium plays a major role in the corrosion resistance of stainless steel


Chromium is the main element that determines the corrosion resistance of stainless steel, because the chromium contained in steel can make stainless steel passivation in the oxidizing medium, that is, a very thin film is formed on the surface, and chromium is enriched in this film. The higher the chromium content in steel, the stronger the corrosion resistance. In addition, chromium can play a very good role in strengthening the mechanical and technological properties of steel.


(2) The influence of nickel on stainless steel


Only when it cooperates with chromium can it be fully expressed. Nickel is an alloying element that forms austenite. When nickel is used in combination with chromium, the metallographic structure can be changed from single-phase ferrite to austenite and ferrite dual-phase structure. After heat treatment, the strength can be improved. , So that it has stronger corrosion resistance and good deformation performance.


2. The impact of impurities on performance


When the carbon content is between 0.1% and 0.3%, after annealing, carbon will precipitate on the crystal lattice boundary in a graphite state, destroying the bonding force between the crystal grains, and strongly reducing the strength and plasticity of nickel. Make processing deformation difficult.


In addition, 316 stainless steel carbon has a strong affinity with chromium and can form a series of carbides. The higher the carbon content in steel, the more chromium carbide is formed, and the chromium content in the solid solution will be relatively reduced, and the corrosion resistance of steel will be reduced. Sulfur is a harmful impurity. Sulfur and nickel form Ni3S2 compound. Ni3S2 and nickel form a low-melting eutectic at 625℃, which is distributed on the grain boundary. When the thermal deformation temperature exceeds the eutectic melting point, it cracks along the grain boundary. , Resulting in the so-called "hot brittleness" phenomenon.