The grades and application direction of common nickel and nickel-based alloys

Nickel and nickel-based alloys have a large family of members. Common nickel-based alloy products on the market is also a wide variety of different forms, the nickel and nickel alloy is how to classify it? In general, we are classified according to its main alloy components, the following is widely used in chemical equipment nickel and nickel alloy to do a brief introduction: Pure Nickel (201 UNS N02201) Good corrosion resistance, antigenic acid and salt, but encountered strong oxidation medium such as nitric acid pure nickel is not enemy. The most prominent advantage of pure nickel is the resistance to caustic alkali, and even the corrosion of molten caustic alkali is also excellent. Although the dry halogen medium can not be pure nickel, but its corrosion resistance is insufficient below the water dew point. For applications up to 600 °F, the alloy 201's brother grade, high carbon nickel 200(UNS N02200), is also available. 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 the corrosion resistance decreases sharply in the presence of aerated and oxidizing chemicals. Alloy 400 resistance to halogen acid and halide corrosion performance is very good, especially resistant to hydrofluoric acid and fluorine or hydrogen fluoride high temperature gas. It is understood that the alloy 400 was developed in 1905 and has been used for more than 100 years. Monel 400 can be described as the "originator" of all nickel alloys, which are widely used in the treatment of sulfuric acid solutions, sea water and salt water. For applications requiring high strength, such as valves 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 on the basis of nickel to add chromium, enhance its ability to adapt to the oxidizing environment. Although alloy 600 has general corrosion resistance to inorganic acids, it has excellent corrosion resistance to organic acids. Therefore, alloy 600 are widely used in the production and storage of processed fatty acids, hydroxides and alkaline chemicals. Alloy 600 has excellent heat resistance and corrosion resistance, and it can be used normally in high temperature halogen environment, so it is an ideal material for organic chlorination reaction process. The alloy 600 also has excellent resistance to high temperature degradation such as oxidation resistance, anti-carburizing and anti-nitrogen. Nickel-Chromium-Molybdenum Alloy 625 UNS N06625 Molybdenum is added to nickel-chromium alloy to make it resistant to 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 brand of alloy 625 and is mainly used for bellows. It has very good low cycle fatigue resistance and heat fatigue resistance. The alloy 625 can be used as both the corrosion-resistant material and the heat-resistant material like the alloy 600. Alloy 625 are widely used in chemical and petrochemical equipment in harsh high temperature environments with excellent performance of high temperature resistance, halogen corrosion resistance, oxidation resistance and carburizing resistance. It is understood that based on the difference of subsequent heat treatment, 625 alloy is also divided into Grade1 and Grade2, as well as low cycle fatigue LCF version. Nickel-Chromium Alloy 690 UNS N06690 Alloy 690 is known for its high chromium content, so it has strong oxygen resistance and better corrosion resistance. Can be effectively used as hot concentrated sulfuric acid, nitric acid and nitric acid/hydrofluoric acid mixed acid and oxidizing salt medium. High chromium content also improves the corrosion resistance of the material in high temperature vulcanization environment. Nickel-Chromium-Iron Alloy 825 UNS N08825 Since the alloy contains nearly 30% iron, the alloy 825 is sometimes included in the super austenitic stainless steel series. It performs well in sulfuric acid and phosphoric acid media, similar to Alloy 20, which was developed primarily for sulfuric acid and phosphoric acid media. Although the alloy 825 resistance to hydrochloric acid corrosion is acceptable, it is prone to chloride ion pitting and crevice corrosion, especially in non-flowing, non-aerated solutions. Alloy 825 high iron content, so its alkali and halogen corrosion resistance is lower than the higher nickel content of the alloy. 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 by sulfuric acid and impure phosphoric acid, and can withstand both reducing and oxidizing media conditions. The later developed alloy G-and G-35 alloys have better welding performance and improved corrosion resistance, especially the corrosion resistance of the weld heat affected zone. Nickel-chromium-molybdenum "C" alloy series alloys Alloy C- 276 is the chemical industry used to deal with highly corrosive media conditions (beyond the ability of stainless steel) excellent alloy materials, it has outstanding corrosion resistance in a variety of acids, acid salts and other types of corrosive chemicals. The alloy C- 276 performs well in harsh environments such as wet chlorine and hypochlorite. Due to the high molybdenum content C- 276 the alloy, it has good corrosion resistance to pitting and crevice corrosion caused by chloride ions. The search for materials with better metallurgical properties and corrosion resistance than alloys C- 276 promoted the development and commercialization of several patented "C" series alloys, which are alloys C- 22, 622, 59, 686 and C- 2000. The molybdenum content of these alloys is roughly equivalent, while the chromium content is much higher than the alloy C- 276. Some grades also contain tungsten or copper. Nickel-molybdenum "B" alloy series alloys The alloy B- 2 has outstanding corrosion resistance to reducing sulfuric acid, phosphoric acid and hydrochloric acid. It is particularly suitable for use in hydrochloric acid plants over the entire concentration range and at temperatures up to the boiling point. The corrosion resistance of such alloys is adversely affected by oxidizing chemicals, particularly strong oxidants such as iron and copper ions as impurities in the solution. Later developed alloy B- 3 and alloy B- 4 performed better than alloy B- 2. One benefit of these new grades is to minimize the formation of poor microstructure (which may cause embrittlement) during processing. After reading the above information, whether the common corrosion-resistant nickel-based alloys have a further understanding.





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