What are the main grades and application fields of nickel and nickel based alloy families

 　　The nickel and nickel based alloy family is vast and has a wide range of members. The common nickel based alloy products in the market are also diverse and diverse, so how are nickel and nickel alloys classified? Generally, we classify them according to their main alloy composition. Below is a brief introduction to nickel and nickel alloys widely used in chemical equipment:

　　Pure nickel (201 UNS N02201)

　　It has good corrosion resistance and can resist original acid and salt, but it will be defeated when encountering strong oxidizing media such as pure nickel nitrate.

　　The most prominent advantage of pure nickel is its resistance to caustic soda, and even its excellent performance in corrosion of molten caustic soda.

　　Although dry halogen media cannot achieve pure nickel, its corrosion resistance is insufficient below the water dew point.

　　For applications with temperatures not exceeding 600 ℉, alloy 201's sibling brand - high carbon nickel 200 (UNS N02200) can also be used.

　　Nickel copper alloy 400 UNS N04400

　　The corrosion resistance of nickel copper alloy 400 is the same as that of pure nickel, which performs well under reducing medium conditions, but its corrosion resistance sharply decreases in the presence of gas and oxidizing chemicals. Alloy 400 has excellent corrosion resistance to hydrogen halide acid and halides, especially to hydrofluoric acid and high-temperature gases containing fluorine or hydrogen fluoride. It is understood that alloy 400 was developed in 1905 and has been in use for over a hundred years. The Monel 400 can be regarded as the "ancestor" of all nickel alloys, which are widely used to treat sulfuric acid solutions, seawater, and salt water. For applications that require high strength, such as valve and pump components, alloy K-500 (NO5500) is often used, which is a precipitation hardening derivative of alloy 400.

　　Nickel chromium iron alloy 600 UNS N06600

　　Alloy 600 has chromium added to the nickel base, enhancing its adaptability in oxidizing environments. Although Alloy 600 exhibits average corrosion resistance to inorganic acids, it exhibits excellent corrosion resistance to organic acids. Therefore, Alloy 600 is widely used in the production and storage of processed fatty acids, hydroxides, and alkaline chemicals. Alloy 600 has excellent heat and corrosion resistance, and can be used normally in high-temperature halogen environments, making it an ideal material for organic chlorination reaction processes. Alloy 600 also has excellent high-temperature degradation resistance such as oxidation resistance, carburization resistance, and nitrogen resistance.

　　Nickel chromium molybdenum alloy 625 UNS N06625

　　Adding molybdenum to nickel chromium alloy gives it the ability to resist oxidizing and reducing inorganic acids and salts. Molybdenum can make the alloy resistant to chloride ion pitting and crevice corrosion. Alloy 625 is such a high-strength material with excellent fatigue resistance. Alloy 625CF is a derivative of alloy 625 and is mainly used for corrugated pipes, with excellent low cycle fatigue resistance and heat fatigue resistance. Alloy 625, like alloy 600, can be used as both a corrosion-resistant and heat-resistant material. Alloy 625 is widely used in chemical and petrochemical equipment in harsh high-temperature environments due to its excellent performance in high-temperature resistance, halogen corrosion resistance, oxidation resistance, and carburization resistance.

　　It is understood that based on different subsequent heat treatments, 625 alloy is also divided into Grade1 and Grade2, as well as LCF versions that are resistant to low cycle fatigue.

　　Nickel chromium alloy 690 UNS N06690

　　Alloy 690 is known for its high chromium content, so it has extremely strong oxygen resistance and better corrosion resistance. It can be effectively used as a medium for hot concentrated sulfuric acid, nitric acid, nitric acid/hydrofluoric acid mixtures, and oxidizing salts. The high chromium content also improves the corrosion resistance of the material in high-temperature vulcanization environments.

　　Nickel chromium iron alloy 825 UNS N08825

　　Due to the alloy containing nearly 30% iron, alloy 825 is sometimes included in the super austenitic stainless steel series. It performs well in sulfuric acid and phosphoric acid media conditions, similar to Alloy 20, and their main purpose of development is for use in sulfuric acid and phosphoric acid media. Although alloy 825 has acceptable resistance to hydrochloric acid corrosion, it is prone to chloride ion pitting and crevice corrosion, especially in non flowing and non ventilated solutions. Alloy 825 has a high iron content, so its corrosion resistance to alkali and halogen is lower than that of alloys with higher nickel content.

　　Nickel chromium iron molybdenum "G" series alloys

　　The corrosion resistance of alloy G-3 exceeds that of alloy 400, alloy 600, and alloy 825 in many applications. This alloy is particularly resistant to corrosion from sulfuric acid and impure phosphoric acid, and can withstand both reducing and oxidizing medium conditions. Later developed alloys G - and G-35 have better welding performance and corrosion resistance, especially the corrosion resistance of the weld Heat-affected zone.

　　Nickel chromium molybdenum "C" alloy series alloys

　　Alloy C-276 is an excellent alloy material used in the chemical industry to cope with highly corrosive medium conditions (beyond the capabilities of stainless steel). It has outstanding corrosion resistance in various acids, acidic salts, and other corrosive chemicals. Alloy C-276 exhibits excellent performance in harsh environments such as wet chlorine and hypochlorite. Due to the high molybdenum content of alloy C-276, it has good corrosion resistance to pitting and crevice corrosion caused by chloride ions. The process of seeking materials with better metallurgical and corrosion resistance than alloy C-276 has promoted the development and commercialization of several patented "C" series alloys, including alloys C-22, 622, 59, 686, and C-2000. The molybdenum content of these alloys is roughly the same, while the chromium content is significantly higher than that of alloy C-276. Some brands also contain tungsten or copper.

　　Nickel molybdenum "B" alloy series alloys

　　Alloy B-2 has outstanding corrosion resistance to reducing sulfuric acid, phosphoric acid, and hydrochloric acid. It is particularly suitable for hydrochloric acid equipment with a full concentration range and temperatures up to boiling points. Oxidizing chemicals have an adverse effect on the corrosion resistance of this alloy, especially strong oxidants such as iron ions and copper ions that act as impurities in the solution. The later developed alloys B-3 and B-4 have better performance than alloy B-2, and one advantage of these new grades is that they minimize the formation of poor microstructures (which may cause embrittlement) during processing.