Views: 0 Author: Site Editor Publish Time: 2021-05-10 Origin: Site
The control of stainless steel flanges should start with material reduction or hydrogen damage from the selection of materials, control technology and optimal environment, and the first choice of alloys with strong resistance to interference. The pure and high-quality steel without impurities and uneven phases has better resistance to hydrogen bubbling. Comparing boiling steel with more impurities to hydrogen damage. In an acidic environment containing sulfur and hydrogen, such as oil fields, stone refining, gas well platforms, and geothermal mining sites, the development and application of high-quality pure steel is the goal to avoid hydrogen damage. The use of austenitic stainless steel face-centered cubic instead of ferritic stainless steel body-centered cubic is a common method to prevent hydrogen-induced cracking, and nickel alloy is also a means to replace ferritic stainless steel. However, it should be noted that most materials, even face-centered cubic structures, can crack hydrogen to a certain extent. The inert coating on the metal surface can also prevent hydrogen damage. The tensile strength is inversely proportional to the hydrogen-induced cracking resistance, so alloy substitution or annealing treatment can appropriately reduce the strength of the material to reduce or avoid hydrogen damage.
Steels with lower tensile strength can resist hydrogen-induced cracking in a sulfur-free environment. Therefore, low-alloy steels can be used to reduce the strength through alloying or heat treatment, but when the content of metal materials exceeds the content, use in a sulfur-containing environment Will reduce the ability to resist hydrogen-induced cracking. Hydrogen-induced cracking is sometimes reversible, that is, hydrogen dissolved in metal materials can be released by baking. Baking the electroplated and pickled metal materials can remove hydrogen and restore the toughness of carbon steel and alloy steel. In addition, it is possible to remove hydrogen and residual stress through annealing treatment. Using sandblasting to reduce tensile stress can reduce hydrogen-induced cracking. The galvanized coating can reduce the absorption and ingress of hydrogen on the metal surface.
For the alloy, the surface contaminants can be removed and the surface oxygen layer can be thickened in the ammonium sulfate solution to improve the ability to prevent hydrogen from entering; heat treatment in an inert atmosphere to prevent hydrogen wrist: the hydrogen in the alloy can be recovered by vacuum baking Tough use of the environment Adjusting the environment is an important means to reduce hydrogen damage. Reducing the sulfur content in the medium to below will increase the resistance of carbon steel and low-alloy steel to hydrogen damage. Moisture and temperature will exacerbate hydrogen damage. Therefore, keeping the temperature below or below can avoid decarburization of hypoeutectoid steel, while increasing the content of stainless steel flanges can also help resist hydrogen damage and decarburization. In the sulfur and hydrogen environment, moisture can greatly reduce the hydrogen embrittlement of the material. The use of steel at a temperature higher than room temperature will reduce hydrogen-induced cracking; the above hydrogen damage will be very serious, but the use of corrosion inhibitors and increasing the value of the aqueous solution to the above will not only significantly reduce the corrosion rate but also Reducing the adsorption of hydrogen on the surface can reduce hydrogen damage.
High-velocity corrosive fluid, that is, the combination of corrosive fluid and high-velocity damage to the material is called erosion corrosion, static or slow-flowing corrosive medium has a small corrosion rate on the material; the surface high-speed corrosive fluid does not only directly contact the corroded substrate The material, at the same time, damages the surface corrosion product protective film, forms mortar, and exposes the fresh metal surface, resulting in rapid scrubbing and corrosion. Erosion corrosion is a common corrosion problem in steel structure piping systems that transmit steam containing condensed water droplets; in the inflection of pipelines, turbines, water pumps, etc., which can change the flow direction or speed and enhance the vortex, erosion and corrosion are common. Cause Erosion corrosion is the result of high-speed impact of corrosive media. Materials that are not resistant to corrosion, the design structure of stainless steel flanges, the increase in media corrosion, and the degree of severe corrosion due to the solid suspended solids in the media. Shown is a sketch of the turbulence mechanism that causes erosion and corrosion. Materials with low strength and poor corrosion resistance, such as carbon steel, copper alloys, aluminum alloys, cast austenitic stainless steels, have been reported to have erosion corrosion in vapor-liquid media, acid media, sea water, salt water, and river water containing solid particles. , Form groove marks, corrugations, grooves, teardrops, horseshoe-shaped grooves on the metal surface.