Alloy20 welding:
Alloy20 alloy (N08020) has better resistance to medium-strength sulfuric acid corrosion and chloride stress corrosion by adding molybdenum and copper, and has good resistance to pitting, crevice corrosion and stress corrosion compared with conventional 18-8 stainless steel. In engineering practice, if the corrosion resistance of 316L is not enough, a higher grade alloy20 alloy is selected.
Alloy20 alloy (N08020) is an austenitic structure, the welding performance is similar to that of austenitic stainless steel, the weldability is good, and no preheating and post-weld heat treatment are required. The problems when welding are similar to those of austenitic stainless steel welding, such as:
1) Welding thermal cracks: The main reason for welding thermal cracks is that the dirt on both sides of the weld is not cleaned, and harmful elements such as S and P are mixed into the molten pool to form low melting point eutectics, and the film strength formed by these low melting point eutectics is low, and they will tear under the action of residual stress, resulting in microcracksSecond, the large heat input in the welding process, especially the heat input with high heat affected zone, is easy to produce brittle phases, such as the embrittlement of phase and 475.
2) Porosity: Compared with low-alloy steel, the porosity tends to be large, and special attention should be paid to cleaning the unclean groove. (3) Corrosion resistance: chromium depletion may occur near the heat-affected zone of nickel alloy welding, resulting in the decline of intergranular corrosion and stress corrosion performance in some media.
4) Process characteristics: Alloy20 alloy weld metal is very viscous, poor fluidity, shallow penetration depth, only 50% of 304SS, welding needs to increase the groove angle and use a small weld root area to improve.
Alloy 20 is an austenitic stainless steel with a chemical composition that includes nickel (Ni), chromium (Cr), iron (Fe), copper (Cu), and molybdenum (Mo). The specific ingredients are as follows:
Nickel (Ni): 32-38%.
Chromium (CR): 19-21%.
Iron (Fe): Margin.
Copper (Cu): 3-4%.
Molybdenum (Mo): 2-3%.
Other elements include trace elements such as manganese, silicon, carbon, and phosphorus.
Hardness and density.
The hardness of Alloy 20 depends on the state of heat treatment and is typically in the range of 28-32 HRC. Its density is about 81 gram cubic centimeter, with moderate weight and strength characteristics.
Heat treatment.
Alloy 20 can be heat treated to improve its mechanical properties and corrosion resistance. Common heat treatment methods include annealing, solution treatment, and aging treatment to achieve the desired strength and corrosion resistance.
Mechanical and mechanical properties.
Alloy 20 has good tensile strength and yield strength, with a tensile strength of more than 60,000 psi and a yield strength of more than 30,000 psi. At the same time, Alloy 20 also has good ductility and impact toughness, which is suitable for use in a variety of complex working conditions.
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