Dual-phase steel flat welded flanges are mainly used in pipeline installations. High-pressure flange connection is an important connection method for pipeline construction. The connection between the receiver and the pipe is the first to achieve important effects and value. The high-pressure flange connection is to fix two pipes, pipe fittings or devices on a flange first, add flange pads between the two flanges, and fasten them together with bolts to complete the connection. Some pipe fittings and devices now have their own flanges, which are also attributed to flange connection.

Product features of high-pressure flanges: Wear resistance: The Al2O3 content in the lining ceramic layer of the ceramic composite steel pipe is greater than 95%, and the microhardness is HV1000-1500, so it has extremely high wear resistance, and its wear resistance is higher than that after quenching. The medium carbon steel is more than ten times higher than that of tungsten carbide. Corrosion-resistant ceramics are neutral materials with stable chemical functions, excellent corrosion resistance and acid resistance, resistance to various inorganic and organic acids, and their corrosion resistance is more than ten times that of stainless steel.

1. The phase ratio needs to be controlled. The ratio is about half of the ferrite phase and the austenite phase, and the number of one phase cannot exceed 65%, so as to ensure some comprehensive performance. If the two phase ratios are out of balance, for example, the number of ferrite phases is too large, it is easy to form single-phase ferrite in the welded HAZ, which is sensitive to stress corrosion in some media.

2. It is necessary to master the microstructure transformation law of duplex stainless steel, and be familiar with the TTT and CCT transformation curves of each steel grade. This is the key to correctly guide the formulation of heat treatment, hot forming and other processes of duplex stainless steel. Austenitic stainless steel is much more sensitive.

3. The continuous use temperature range of duplex stainless steel is -50~250℃, the lower limit depends on the brittle transition temperature of the steel, the upper limit is limited by the brittleness of 475℃, and the upper limit temperature cannot exceed 300℃.

4. After solid solution treatment of duplex stainless steel, rapid cooling is required. Slow cooling will cause the precipitation of brittle phases, which will lead to a decrease in the toughness of the steel, especially the resistance to local corrosion.

5. The lower limit temperature of hot working and hot forming of duplex steel flat welding flange cannot be lower than 950℃, super duplex stainless steel cannot be lower than 980℃, low chromium molybdenum duplex stainless steel cannot be lower than 900℃, to avoid brittle phase Precipitation causes surface cracks during processing

6. The commonly used 650-800°C stress relief treatment for austenitic stainless steel cannot be used, and solution annealing treatment is generally used. After surfacing duplex stainless steel on the surface of low-alloy steel, when the overall anti-corrosion treatment at 600-650°C is required, the toughness and corrosion resistance caused by the precipitation of brittle phases must be considered, especially the local corrosion resistance. The problem of declining, shorten the heating time in this temperature range as much as possible. The heat treatment of low-alloy steel and duplex stainless steel clad plates should also be considered in the same way.