904L Super Austenitic Stainless Steel Tube
904L stainless steel pipe (00Cr20Ni25Mo4.5Cu) austenitic stainless steel with better corrosion resistance. Because of the addition of 1.5% copper, 904L super austenitic stainless steel pipe is also excellent for reducing acids such as sulfuric acid and phosphoric acid Corrosion resistance · In addition, 904L super austenitic stainless steel pipe has low carbon characteristics in welding applications.
Specification of 904L stainless steel pipe
904L stainless steel seamless pipe: outer diameter 3-577MM, wall thickness 0.4-14MM.
904L stainless steel welded pipe: outer diameter 12-1820MM, wall thickness 0.3-40.0MM.
Chemical composition of 904L super austenitic stainless steel pipe
Mechanical properties of 904L super austenitic stainless steel pipe
904L stainless steel
904L super austenitic stainless steel is a low-carbon high-nickel, molybdenum austenitic stainless acid-resistant steel, which is a proprietary material introduced from French H · S company. It has a good activation-passivation conversion ability, excellent corrosion resistance, good corrosion resistance in non-oxidizing acids such as sulfuric acid, acetic acid, formic acid, and phosphoric acid, and good in neutral chloride ion-containing media The pitting corrosion resistance, at the same time has good resistance to crevice corrosion and stress corrosion resistance. It is suitable for sulfuric acid with various concentrations below 70 ℃. It is resistant to acetic acid and mixed acid of formic acid and acetic acid at any concentration and temperature at normal pressure.
904L austenitic stainless steel is designed for harsh environments. The alloy was originally developed to resist corrosion in dilute sulfuric acid. This feature has been proved to be very successful after years of practical application. Now 904L has been standardized in many countries, and has been approved for the manufacture of pressure vessels. 904L alloy, like other commonly used CrNi austenitic steels, has good resistance to pitting and crevice corrosion, high resistance to stress corrosion cracking, good resistance to intergranular corrosion, good workability and Weldability. The maximum heating temperature during hot forging can reach 1180 degrees Celsius, and the minimum stop forging temperature is not less than 900 degrees Celsius. The hot forming of this steel can be carried out at 1000-1150 degrees Celsius. The heat treatment process of the steel is 1100-1150 degrees Celsius, and it cools quickly after heating. Although this steel can be welded by a universal welding process, the most appropriate welding methods are manual arc welding and tungsten arc welding. When using manual arc welding to weld plates no larger than 6 mm, the diameter of the electrode is no more than 2.5 mm; when the thickness of the plate is more than 6 mm, the diameter of the electrode is less than 3.2 mm. When heat treatment is required after welding, it can be heated at 1075–1125 degrees Celsius and then cooled quickly. The filler metal when welding with tungsten argon arc welding can be the same material electrode. After welding, the weld must be pickled and passivated.
Corrosion resistance of 904L stainless steel
Because the carbon content of 904L stainless steel is very low (maximum 0.020%), in the case of general heat treatment and welding, there will be no carbide precipitation. This eliminates the risk of intergranular corrosion after general heat treatment and welding. Due to the high chromium-nickel-molybdenum content and the addition of copper, 904L stainless steel can be passivated even in a reducing environment, such as sulfuric acid and formic acid. The high nickel content makes it have a lower corrosion rate in the active state. In pure sulfuric acid in the concentration range of 0 ~ 98%, the service temperature of 904L stainless steel can be as high as 40 ℃. In pure phosphoric acid in the concentration range of 0 ~ 85%, its corrosion resistance is very good. In industrial phosphoric acid produced by the wet process, impurities have a strong influence on corrosion resistance. Among all kinds of phosphoric acid, the corrosion resistance of 904L stainless steel is superior to ordinary stainless steel. In highly oxidizing nitric acid, the corrosion resistance is lower than that of highly alloyed steels that do not contain molybdenum. In hydrochloric acid, the use of 904L stainless steel is limited to a lower concentration of 1-2%. In this concentration range. The corrosion resistance of 904L stainless steel is better than conventional stainless steel. 904L stainless steel has high resistance to pitting corrosion. Its resistance to crevice corrosion in chloride solutions is also very good. The high nickel content of 904L stainless steel reduces the corrosion rate at pits and crevices. Ordinary austenitic stainless steels may be sensitive to stress corrosion in a chloride-rich environment at temperatures above 60 ° C. This sensitization can be reduced by increasing the nickel content of the stainless steel. Due to the high nickel content, 904L stainless steel pipes have high resistance to stress corrosion cracking in chloride solution, concentrated hydroxide solution and hydrogen sulfide-rich environment.
AL-904L is a kind of austenitic stainless steel with very low carbon content and high alloying, which is designed for corrosive environments. It has better corrosion resistance than 316L and 317L, while taking into account price and performance, high Cost-effective. Due to the addition of 1.5% copper, it has excellent corrosion resistance to reducing acids such as sulfuric acid and phosphoric acid.
904L stainless steel metallographic structure
904L stainless steel is a complete austenitic structure. Compared with austenitic stainless steel with high molybdenum content, 904L is not sensitive to the precipitation of ferrite and α phase.
904L Stainless Steel Welding Performance
904L stainless steel is the same as general stainless steel. 904L904L stainless steel can be welded by various welding methods. The most commonly used welding method is manual arc welding or inert gas shielded welding. The electrode or wire metal is based on the composition of the base metal and has higher purity. The content of molybdenum is higher than that of the base metal. It is generally not necessary to preheat before welding, but in cold outdoor operations, in order to avoid the condensation of water vapor, the joint or the adjacent area can be uniformly heated. Note that the local temperature should not exceed 100 ° C to avoid carbon accumulation and intergranular corrosion. Welding should use small line energy, continuous and fast welding rate. Generally, no heat treatment is required after welding. If heat treatment is required, it must be heated to 1100-1150 ° C and then cooled rapidly.
Supporting welding materials: welding rod (E385-16 / 17), welding wire (ER385).
Machinability of 904L stainless steel
The machining characteristics of 90 4 L stainless steel are similar to other austenitic stainless steels, and there is a tendency to stick the knife and work harden during the processing. A positive rake carbide tool must be used, with vulcanized and chlorinated oil as the cutting coolant, and the equipment and process should be premised on reducing work hardening. Avoid slow cutting speeds and infeeds during the cutting process.
Application of 904L stainless steel
* Petroleum and petrochemical equipment, such as reactors in petrochemical equipment.
* Storage and transportation equipment for sulfuric acid, such as heat exchangers.
* The main use parts of flue gas desulfurization device of power plant are: tower body of absorption tower, flue, door plate, internals, spray system, etc.
* Scrubber and fan in organic acid treatment system.
* Seawater treatment equipment, seawater heat exchangers, paper industry equipment, sulfuric acid, nitric acid equipment, acid production, pharmaceutical industry and other chemical equipment, pressure vessels, food equipment.
* Pharmaceutical factory: centrifuge, reactor, etc.
* Plant food: soy sauce tank, cooking wine, salt shaker, equipment and dressing.
* For 904L of dilute sulfuric acid strong corrosive medium, it is the matching steel type.