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Hastelloy alloy is a kind of nickel based alloy
- Apr 17, 2018 -

It is mainly divided into three series of B, C and G. It is mainly used in strong corrosive media such as iron based Cr-Ni or Cr-Ni-Mo stainless steel, non-metallic material and so on. It has been widely used in many fields such as oil, chemical industry and environmental protection in foreign countries.

Corrosion resistance:

B-2 alloy is a Ni-Mo alloy with very low carbon content and silicon content. It reduces the precipitation of carbides and other phases in the weld and heat affected areas, thus ensuring good corrosion resistance even in the welding state.

As we all know, Hastelloy B-2 alloy has excellent corrosion resistance in various reducing media, and it can withstand any temperature, any concentration of hydrochloric acid corrosion under atmospheric pressure. It has excellent corrosion resistance in non inflatable medium concentration of non oxidizing sulfuric acid, various concentration phosphoric acid, high temperature acetic acid, formic acid and other organic acids, bromine acid and hydrogen chloride gas, and it also corrode the halogen catalyst. Therefore, Harris B-2 alloy is usually used in a variety of harsh petroleum and chemical processes, such as distillation, concentration of hydrochloric acid, alkylation of ethylbenzene and low pressure carbonyl acetic acid.

But in the industrial application for years of Hart's B-2 alloy, it was found that: (1) two sensitized regions have a considerable influence on the intergranular corrosion resistance of hasteld's alloy: the high temperature zone at 1200~1300℃ and the middle temperature zone at 550~900℃; (2) the weld metal and the heat affected zone of the Hart's B-2 alloy are due to the dendrite segregation, the intermetallic phase and the carbide edge. Grain boundary precipitation makes it more sensitive to intergranular corrosion. (3) the meso temperature stability of Hastelloy B-2 alloy is poor. When the content of iron in Hastelloy B-2 alloy is below 2%, the alloy is sensitive to the transformation of beta phase (i.e. Ni4Mo phase, an ordered intermetallic compound). When the alloy residence time is longer in the temperature range of 650~750, the beta phase is generated instantaneously. The existence of the beta phase reduces the toughness of the B-2 alloy and makes it sensitive to the force corrosion. It may even cause the B-2 alloy in the raw material production (such as hot rolling), the equipment manufacturing process (such as the holistic heat treatment after the welding of hastelis B-2 alloy equipment) and the preparation of Harris's B-2 alloy in the service environment. Nowadays, the standard test methods for the intergranular corrosion resistance of B-2 alloy in China and all the countries of the world are normal pressure boiling hydrochloric acid method, and the method of evaluation is weightlessness. Because Hastelloy B-2 alloy is an alloy which is resistant to hydrochloric acid corrosion, so it is quite insensitive to test the intergranular corrosion tendency of Hastelloy B-2 alloy by atmospheric boiling hydrochloric acid. The study of hhhh B-2 alloy by high temperature hydrochloric acid found that the corrosion resistance of B-2 alloy depends not only on its chemical composition, but also on the control process of heat processing.ZHENGFENG VALVES is a professional butterfly valve manufacturer.