904L fittings (UNS N08904)

Metallurgical structure
**4L is a fully austenitic organizations, **4L of ferrite and the precipitation of α phase insensitive compared to the general molybdenum high austenitic stainless steel.

Corrosion resistance
In general welding and heat treatment, there will not be carbide precipitation because of the carbon content is very low (0.**0% 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 **4L 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 ~ *8% concentration pure sulfuric acid , **4L of the use of temperature can be as high as *0°C. In the range of 0 ~ *5% 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.**4L corrosion resistance is better than ordinary stainless steel in all kinds of phosphoric acid.In strong oxidation of nitric acid, **4L lower corrosion resistance compared to non-molybdenum high alloy steel; In the hydrochloric acid, **4L limited to the use of lower concentrations of **2%. In this concentration range. **4L corrosion resistance better than generic stainless steel. **4L with a high resistance to pitting, its crevice corrosion resistance are also very good Chloride solution. **4L high nickel content, reducing the corrosion rate in gap and insurface blemish. Ordinary austenitic stainless steel in the temperature higher than *0 °C, 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, **4L with high stress corrosion cracking capacity in chloride solution, the concentration hydroxid solution and rich sulfureted hydrogen environment.

Applied field:

Alloy **4L 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.

There are a lot of style can be choosed: