904L is a very low carbon containing high alloy austenitic stainless steel. The steel designed for the harsh corrosion condition
Characteristic904L is a very low carbon containing high alloy austenitic stainless steel. The steel designed for the harsh corrosion conditions. 904L has been standardized in many countries now, and have already been approved in the manufacture of pressure vessels. 904L alloy with the same used as CrNi austenitic steel, has a good resistance to pitting and crevice corrosion capabilities, very high stress corrosion cracking capacity, good intergranular corrosion resistance property, good processability and Solderability. The highest temperature heating up to 1180 when hot forging, the lowest temperature stop forging not less than 900. This steel may hot forming during1000 - 1150. The steel heat treatment process is 1100 - 1150 , cold fast afrer heated. Although this may use common steel welding technology for welding, but the best way are manual arc welding and TIG welding. When using manual arc welding, the welding rod diameter should no more than 2.5 mm when welding 6 mm plate; the welding rod diameter is less than 3.2 mm when the thickness is greater than 6 mm. When need to heat treatment after welding, can fast-cooling after heat in 1075 - 1125. When useTIG welding, the filling metal can use with the same material, seam is subject to pickling,passivatingtreatment after the welding.
Metallurgical structure904L is a fully austenitic organizations, 904L of ferrite and the precipitation of α phase insensitive compared to the general molybdenum high austenitic stainless steel.
Corrosion resistanceIn general welding and heat treatment, there will not be carbide precipitation because of the carbon content is very low (0.020% maximum). This eliminates the intergranular corrosion after the welding and heat treatment. Due to high nickel chromium molybdenum content, and copper element, so even if the 904L in reducing environments, such as in sulfuric acid and formic acid can be deactivationcan be deactivation. High nickel content also has a lower corrosion rate in the activity state. In the range of 0 ~ 98% concentration pure sulfuric acid , 904L of the use of temperature can be as high as 40. In the range of 0 ~ 85% concentration pure sulfuric acid, its corrosion resistance is very good. In the industrial phosphoric acid production of Wet method,the impurities are strongly influence of corrosion.904L corrosion resistance is better than ordinary stainless steel in all kinds of phosphoric acid.In strong oxidation of nitric acid, 904L lower corrosion resistance compared to non-molybdenum high alloy steel; In the hydrochloric acid, 904L limited to the use of lower concentrations of 1-2%. In this concentration range. 904L corrosion resistance better than generic stainless steel. 904L with a high resistance to pitting, its crevice corrosion resistance are also very good Chloride solution. 904L high nickel content, reducing the corrosion rate in gap and insurface blemish. Ordinary austenitic stainless steel in the temperature higher than 60 , maybe sensitive of the stress corrosion resistance in a rich chloride environment, by increasing the nickel content in stainless steel, can reduce this sensitivity. Due to the high content of nickel, 904L with high stress corrosion cracking capacity in chloride solution, the concentration hydroxid solution and rich sulfureted hydrogen environment.
Applied fieldAlloy 904L is a multi-purpose material can be applied in many industrial : 1. Petroleum, petrochemical equipment, such as the reactor in petrochemical equipment.2. Sulfuric acid storage and transportation equipment, such as heat exchanger.3. Power plant flue gas desulphurization equipment, the main parts: the absorption tower, flue , stopping plate, internal part, spray system. 4. The scrubber and the fans in the organic acid treatment system.
904L UNS N08904 tube
