Pipe fittings, flanges, tubes (seamless and welded), plates, bars, etc.
| Material | % | Ni | Cr | Mo | Cu | Fe | C | Mn | Si | P | S |
| 904L | 最小 | 23 | 19 | 4 | 1 | Bal | |||||
| Max | 28 | 23 | 5 | 2 | 0.02 | 2 | 1 | 0.045 | 0.035 |
| Density | 8.9g/cm3 |
| melting | 1300-1390 ℃ |
| Material | Tensile strength Rm N/mm2 |
Yield strength RP0.2N/mm2 |
Elongation A5 % |
| 904L | 490 | 216 | 35 |
904L is a highly alloyed austenitic stainless steel with a very low carbon content. The steel is designed for environments with harsh corrosive conditions. Originally this material was developed for corrosion resistance in dilute sulfuric acid. This property has been proven successful over many years of practical application. Now standardized in many countries and approved for use in the manufacture of pressure vessels, 904L material, like other commonly used CrNi austenitic steels, has good resistance to pitting and crevice corrosion, high resistance to stress corrosion rupture, good resistance to intergranular corrosion, and good machinability 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. This steel hot forming can be carried out at 1000 - 1150 degrees Celsius. The heat treatment process of this steel is 1100 - 1150 degrees Celsius, heated and then cooled quickly. Although this steel can be welded using a common welding process, but the most appropriate welding method is manual arc welding and tungsten arc welding. When using manual arc welding not more than 6 mm plate when the diameter of the welding rod is not more than 2.5 mm; when the plate thickness is greater than 6 mm when the diameter of the welding rod is less than 3.2 mm. When heat treatment is required after welding, can be heated at 1075 - 1125 degrees Celsius after fast cooling for processing. Welding with tungsten argon arc welding filler metal available with the same material welding rod, after welding the weld shall be acid cleaning, passivation treatment.
904L is completely austenitic, compared with austenitic stainless steel with high molybdenum content, 904L is not sensitive to the precipitation of ferrite and alpha phase.
Since the carbon content of 904L is very low (max. 0.020%), there is no carbide precipitation under normal heat treatment and welding. This eliminates the risk of intergranular corrosion that occurs after general heat treatment and welding. Due to the high chromium-nickel-molybdenum content and the addition of copper elements, 904L can be passivated even in reducing environments such as sulfuric acid and formic acid. The high nickel content gives it a low corrosion rate even in the active state. In the concentration range of 0 to 98% pure sulfuric acid, 904L can be used at temperatures up to 40 degrees Celsius. Its corrosion resistance is very good in pure phosphoric acid in the concentration range of 0~85%. In industrial phosphoric acid produced by the wet process, impurities have a strong influence on the corrosion resistance. In all kinds of phosphoric acid, 904L corrosion resistance is better than ordinary stainless steel. In strongly oxidizing nitric acid, 904L has lower corrosion resistance compared to highly alloyed steel grades without molybdenum. In hydrochloric acid, the use of 904L is limited to a lower concentration of 1-2%. In this concentration range. 904L has better corrosion resistance than conventional stainless steels. 904L steel has a high resistance to pitting corrosion. Its resistance to crevice corrosion is also good in chloride solutions. 904L's high nickel content reduces the rate of corrosion at pits and crevices. Ordinary austenitic stainless steels may be sensitive to stress corrosion in a chloride-rich environment at temperatures above 60 degrees C. This sensitization can be reduced by increasing the nickel content of the stainless steel. Due to the high nickel content, 904L has a high resistance to stress corrosion rupture in chloride solutions, concentrated hydroxide solutions and hydrogen sulfide-rich environments. Welding rod (E385-16), welding wire (ER385)
904L is a versatile material that can be used in many industrial applications in:
1. P;etroleum and petrochemical equipment, such as reactors in petrochemical equipment.
2. Sulfuric acid storage and transportation equipment, such as heat exchangers, etc.
3. Power plant flue gas desulfurization equipment, the main parts used are: tower of absorption tower, flue, stall door plate, inner parts, spraying system, etc.
4. Scrubber and fan in organic acid treatment system.
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