HY-industry tell you what is Incoloy825
Overview of incoloy825 features and application areas:
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The alloy is a general-purpose engineering alloy with high resistance to acid and alkali metal corrosion in both oxidizing and reducing environments. The nickel component provides effective corrosion cracking resistance to the alloy. Corrosion resistance is good in various media such as sulfuric acid, phosphoric acid, nitric acid and organic acids, alkali metal such as sodium hydroxide, potassium hydroxide and hydrochloric acid.
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Overall performance of the alloy is manifested in a variety of nuclear combustion dissolvers, such as sulfuric acid, nitric acid and sodium hydroxide, which are processed in the same equipment. It is used in various industrial fields where the temperature is not more than 550 °C, such as: heating pipes, containers, baskets and chains for sulfuric acid pickling plants, seawater cooling heat exchangers, marine product piping systems, acid gas environmental pipelines, phosphoric acid production. Heat exchangers, evaporators, washing, dip tubes, etc., air heat exchangers in petroleum refining, food engineering, chemical processes, flame retardant alloys for high pressure oxygen applications, etc.
UNS N08825 is a stabilized austenitic nickel-iron-chromium alloy.
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Approximate grades are: NS142 (China), NC21FeDu (France), W.N r.2.4858 NiCr21Mo (Germany) NA16 (UK) Incoloy825, UNS NO8825 (USA) NiFe30Cr21Mo3 (ISO)
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Manufacturers are: China HY-industry Germany VDM, US SMC, US ATI and Japan MetallurgyExecutive Standard: ASTM B424, ASME SB424
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Due to the 42% nickel content, the lower density nickel alloy is slightly higher, about 8.25 g/cm3.
N08825 (Incoloy825, 2.4858) nickel-based alloy has the following characteristics:
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N08825 has good resistance to pitting corrosion and crevice corrosion. -
N08825 has good oxidation resistance and non-oxidative thermal acid properties.
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N08825 has acid and alkali corrosion resistance in both oxidizing and reducing environments.
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N08825 is used in various applications such as sulfur and phosphorus. It has strong resistance to hydrochloric acid corrosion, especially in non-flowing and non-ventilating solutions, and is susceptible to chloride pitting and crevice corrosion.
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N08825 high nickel composition makes the alloy effective against stress corrosion cracking, but the corrosion resistance to strong alkali and halogen is lower than that of nickel containing higher alloy.
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N08825 has good mechanical properties at room temperature and high temperatures up to 550 °C.
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N08825 is certified for pressure vessels up to 450 °C.
When welding N08825 nickel-based alloy, HY-industry internal requirements:
Tool preparation：
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The work site should be separated from the processing area of carbon steel by a sufficient distance or separated separately to keep the site as clean as possible.
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Wire brush should be made of stainless steel.
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Remove oxide scale, oil stains and various markings.
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Clean the base metal and filler alloy (such as welding rod) within 3 cm around the weld area with acetone. Note that halides such as trichloroethylene TRI, perchloroethylene PER and tetrachloride TETRA cannot be used.
edge preparation:
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It is best to use machining, such as turning, milling and planing. When the conditions are not allowed, plasma cutting can also be carried out. When the latter is used, the cutting edge (welding surface) must be ground and smooth, allowing for fine grinding.
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The area of the base material on both sides of the weld is about 25mm wide and is polished to a metallic bright color.
Groove angle:
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Compared with carbon steel, the physical properties of nickel-based alloys and special stainless steels are mainly low thermal conductivity and high expansion coefficient. These characteristics should be considered in the preparation of welding groove, including widening the bottom gap (1~) 3mm), and due to the viscosity of the molten metal, a larger groove angle (60 ~ 70 °) should be used in the butt welding to offset the shrinkage of the material.
Welding arcing :
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Can not arc on the surface of the workpiece, should be arcing on the welding surface to prevent corrosion caused by the arcing point.
Welding process:
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N08825 is suitable for welding with the same material or other metals by any traditional welding process, such as tungsten electrode inert gas shielded welding, plasma arc welding, manual sub-arc welding, metal inert gas shielded welding, molten inert gas shielded welding . When using manual arc welding, it is recommended to use (Ar+He+H2+CO2) a mixture of various protective gases.
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In the welding of the N08825 weld root, in order to obtain a stable root weld quality, it is best to use high purity argon 99.99% protection, so that the weld will not produce oxide after the root is welded.The color produced by the weld heat affected zone should be brushed with stainless steel when the weld zone is not cooled.
Welding materials:
For gas shielded welding processes, the following methods are recommended:
Metal filler wire:
- Nicrofer S6020-FM625
2.4831
SG- NiCr21Mo9Nb
AWS A5.14: ERNiCrMo-3 - Medicine electrode:
2.4621
EL- NiCr20Mo9Nb
AWS A5.11: ENiCrMo-3
There are also users who choose the electrode as required: ENiCrMo-4, welding wire: ERNiCrMo-4, which is no problem. Among the users who come into contact with HY-industry, there are such materials. Among the users of bellows expansion joints, there are many examples of such welding consumables.