ASTM A403 WPS31254-W (254SMO) Duplex Stainless Steel Reducer Butt Weld Fitting B16.9

ASTM A403 WPS31254-W / 254SMO Duplex Stainless Steel Reducer Butt Weld Fitting B16.9

Corrosion resistance and main usage environment: 254SMO stainless steel is a highly corrosion-resistant super austenitic stainless steel developed for halide and acid environments, widely used in harsh working conditions such as high concentration chloride ion media and seawater. In various industrial applications in acidic media, especially in acids containing halides, 254SMO is far superior to other stainless steels, and in some cases can be comparable to Hastelloy and titanium. The low carbon content and high molybdenum content make it have good resistance to spot corrosion and Crevice corrosion, and excellent resistance to intergranular corrosion. It is a kind of stainless steel with high cost performance and is widely used in chemical industry, desulfurization and environmental protection at home and abroad.

In pure sulfuric acid, 254SMO has much greater corrosion resistance than 316 ordinary stainless steel. However, compared with 904L (NO8904) stainless steel at high concentrations, 254SMO has slightly weaker corrosion resistance. In sulfuric acid containing chloride ions, 254SMO has the greatest corrosion resistance. Due to the possibility of localized and uniform corrosion, 316 ordinary stainless steel cannot be used in hydrochloric acid, but 254SMO can be used in diluted hydrochloric acid at normal temperatures. There is no need to worry about point corrosion in the area below the boundary line. But we must try to avoid the existence of gaps. In Hexafluorosilicic acid (H2SiF4) and hydrofluoric acid (HF), the corrosion resistance range of ordinary stainless steel is very limited, while 254SMO can be used in a wide range of concentrations and temperatures. 

254SMO is an austenitic stainless steel. Due to its high molybdenum content, it has very high resistance to spot corrosion and crevice corrosion. This grade of stainless steel was developed for use in halogenated environments such as seawater. 254SMO also has good resistance to uniform corrosion. Especially in acids containing halides, the steel is superior to ordinary stainless steel. Its C content is <0.03%, so it is called pure austenitic stainless steel (<0.01% is also called super austenitic stainless steel). Super stainless steel is a kind of special stainless steel, first of all, different from ordinary stainless steel in chemical composition, it refers to a high-alloy stainless steel containing high nickel, high chromium, high molybdenum. Among them is 254SMo containing 6%Mo, this kind of steel has very good local corrosion resistance, in seawater, inflation, there are gaps, low speed erosion conditions, has good pitting resistance (PI≥40) and better stress corrosion resistance, is a substitute material for Ni-based alloys and titanium alloys. Secondly, in the performance of high temperature or corrosion resistance, it has more excellent high temperature or corrosion resistance, and is irreplaceable in 304 stainless steel. In addition, from the classification of stainless steel, the metallographic structure of special stainless steel is a stable austenitic metallographic structure.

High temperature resistance

1. A large number of field experiments and extensive use experience show that even at slightly higher temperatures, 254SMO also has a high resistance to crevices corrosion in seawater, and only a few types of stainless steel have this performance.

2.The corrosion resistance of 254SMO in acidic and oxidizing halide solutions such as those required for paper bleaching production is comparable to that of nickel-based alloys and titanium alloys with strong corrosion resistance.

3. Due to the high nitrogen content of 254SMO, its mechanical strength is higher than that of other types of austenitic stainless steel. In addition, 254SMO has high ductility and impact strength, as well as good weldability.

4. The high molybdenum content of 254SMO allows it to have a higher oxidation rate in annealing, so that it has a rougher surface than ordinary stainless steel after pickling. However, this has no adverse effect on the corrosion resistance of the steel.

Chemical Composition

Mechanical Properties

Equivalent Grades

Application field:
Chemical processing equipment
Seawater desalination equipment
Flue gas desulfurization scrubber
Food processing equipment
Heat exchanger
Hydrometallurgy
Oil and gas production equipment
Pulp Mill Bleaching System
Seawater treatment equipment
Tall oil distillation tower and equipment