Duplex steel flange, as the name implies is a duplex steel bar, ingot or plate or the like as the raw material and the flange produced, referred to as duplex steel flange, flange is also called flange or flange edge. It is a part of the interconnection between the tube and the pipe. Connected at the end of the pipe. Flange with eyelets, can wear bolts, so that the two flanges tightly connected. The flange is sealed with a gasket. The flange connection consists of a pair of flanges, a gasket and a number of bolts and nuts. The gasket is placed between the sealing surfaces of the two flanges, and after tightening the nut, the air pressure on the surface of the gasket reaches a certain value and deforms, and fills the unevenness on the sealing surface, so that the connection is tight and does not leak. Some pipe fittings and equipment already come with their own flange, which also belongs to the flange connection. Flange connection is an important connection method for pipeline construction.
1. Duplex steel flange using duplex steel as raw materials for production
The so-called duplex stainless steel is in its solid solution organization in the ferrite phase and austenite phase about half of each, the general amount of less phase content also needs to reach 30%. In the case of low C content, Cr content in 18% to 28%, Ni content in 3% to 10%. Some steels also contain Mo, Cu, Nb, Ti, N and other alloying elements. The steel has both austenitic and ferritic stainless steel characteristics, compared with ferritic, plasticity, toughness, no room temperature brittleness, intergranular corrosion resistance and welding performance are significantly improved, while also maintaining a ferritic stainless steel 475 ℃ brittleness and high thermal conductivity, with super plasticity and other characteristics. Compared with austenitic stainless steel, high strength and resistance to intergranular corrosion and chloride stress corrosion has been significantly improved. Duplex stainless steel has excellent resistance to pore corrosion, but also a section of nickel stainless steel.
2. Duplex steel flange performance and characteristics
①The yield strength of duplex stainless steel flange is double more than that of ordinary austenitic stainless steel and has the molding needs of sufficient plasticity and toughness.
② Duplex steel flanges have excellent stress corrosion rupture resistance, especially in the chloride ion environment.
③ Super duplex steel has a very high corrosion resistance, in some media, such as acetic acid, formic acid, etc., can even replace high-alloy austenitic stainless steel, and even corrosion-resistant alloys.
④ Super duplex flanges have good local corrosion resistance, compared with austenitic stainless steel with comparable alloy content, its wear corrosion resistance and fatigue corrosion performance are better than austenitic stainless steel.
3. Duplex steel flange applications
Due to these advantages of duplex steel flanges are widely used in a variety of sewage treatment pipelines, deep-sea operations, seawater desalination, paper industry equipment, food industry processing equipment, offshore oil platforms (heat exchanger tubes, water treatment and water supply systems) desalination (desalination) equipment, oilfield pipelines and equipment, all kinds of acid and alkali environment. Due to good wear and corrosion resistance, service life than the general stainless steel four to five years more time, such as in the seawater pipeline, the use of duplex steel flange, due to the long life, can greatly reduce the cost of product replacement, labor costs, relatively speaking, the cost performance is still quite high.