Hastelloy itself is a nickel-based alloy, but different from ordinary pure nickel (Ni200) and Monel, it uses chromium-molybdenum as the main alloying element, and aims to improve the adaptability to various media and temperatures, and is targeted at different industries. Specially optimized. The chemical industry generally pursues high production capacity and continuously improves the process to increase the temperature and pressure to speed up the reaction speed, so that production is prone to unpredictable conditions and cause unscheduled maintenance. Hastelloy is designed to meet such a demand, adapt to various unforeseen harsh environments, and minimize unscheduled maintenance. At the same time, it also has good processing and welding performance, which is convenient for field maintenance.
Hastelloy classification. Corrosion resistant Hastelloy is mainly divided into C series, B series, G series and D series alloys.
C series alloy is nickel-chromium-molybdenum alloy. Because chromium can form a dense oxide film (passivation) on the surface of the alloy, it provides the ability to resist the oxidation environment, while molybdenum mainly provides the ability to resist the reducing environment. Therefore, C series alloys can be used in environments with both oxidizing and reducing media. The C series alloy is the most widely used alloy, especially the C-276 alloy. Since its invention in the 1960s, it has still shown strong vitality after more than 40 years of testing. After the C-4 was developed, it mainly met the needs of a small number of European users, which can only be seen in older equipment. The C-22 alloy has enhanced corrosion resistance without increasing cost, and is particularly cost-effective. As a new generation product, C-2000 provides a wider range of safe use, which is very suitable for users who want to improve equipment life and test new processes. C series alloys have been applied in many industries in China. Such as fine chemical industry (TDI, PTA, acetic acid / anhydride, acrylic acid, etc.); environmental engineering industry (FGD, sewage treatment); plate heat exchanger industry, etc. There are many other industries that have already used Hastelloy abroad, while domestic is still in the experimental stage, such as the pharmaceutical industry.
B series alloys are nickel-molybdenum alloys, which provide the most excellent corrosion resistance for completely reduced environments. Although B series alloys are excellent in reducing environments, they are very sensitive to oxidizing media (iron, copper ions). 50ppm of iron ions has sufficiently reduced the corrosion resistance of B series alloys. Because of its special properties, B series alloys are relatively concentrated in application. The most important one is the production of acetic acid (carbonyl synthesis method), and some series of sulfuric acid recovery systems are also used. The widely used grade is B-3, B-2 has gradually withdrawn from the market due to insufficient processing performance.
G series alloy is nickel-chromium-iron alloy (except G-35 alloy). The high chromium content makes this series of alloys outstanding in terms of oxidation resistance. At the same time, the new G series alloy (G-30 G-35) also has good resistance to pitting corrosion, plus a small amount of copper content, which enhances the ability to resist sulfuric acid and hydrofluoric acid. Therefore, G series alloys are mainly used in strong oxidizing environments and complex environments with mixed acids, such as wet-process phosphoric acid and steel plant pickling lines.
D series alloy is nickel-chromium-silicon alloy. Because this series of alloy contains a certain amount of silicon, it can produce a fairly stable oxide film on the surface, and it is extremely difficult to weld due to the extreme strong oxidizing environment. The D series alloy produced in series is D-205, which is a plate heat exchanger used in high temperature and concentrated sulfuric acid environment. The alloy is exclusively sold by Alfa Lafar and is only available in finished plates.
Hastelloy has been constantly developing, and new alloy materials have been derived to promote the development of the industry. It has a very good environmental adaptability, and its anti-corrosion ability is quite reliable. For the special environment of various industries, there are targeted solutions. As a mature commercial product, Hastelloy has a variety of product forms that can fully meet various needs.
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