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Introduction to super stainless steel and high nickel corrosion resistant alloys

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Release time:2014-09-10

Super stainless steel refers to super ferrite stainless steel (high chromium, high molybdenum, and pitting resistance value ≥35), super austenitic stainless steel (high chromium, high molybdenum, high nitrogen, and pitting resistance value ≥40) and super dual-phase stainless steel (pitting resistance value ≥40). The three kinds of stainless steel in the 60 s ~ 90 s of the 20th century appeared successively, their corrosion resistance, especially the resistance to pitting corrosion, crevice corrosion and other local corrosion resistance is far better than the original stainless steel, and fill the long stainless steel (iron base corrosion resistant alloy) and high nickel corrosion resistant alloy (iron nickel and nickel based) between not high corrosion resistance of stainless steel blank.

High nickel corrosion resistant alloy in the Fe-Ni base corrosion resistant alloy refers to Ni≥30%, Ni+Fe≥60% of those grades. Fe-Ni based corrosion resistant alloys are industrial grades of chromium-nickel austenitic stainless steel with increased nickel content, which began to be produced in 1940. Up to now has experienced more than half a century of development process, the brand is increasing, increasingly widely used, has formed a complete series of Fe-Ni base corrosion resistant alloy.

Nickel based corrosion resistant alloys refer to those grades with Ni≥50%. Since 1905, the first brand NI68CU28 (namely Monel 400) has been more than one hundred years. In 1930 of Ni - Cr, Ni, Mo binary system and Ni - Cr - Mo (W) three elements as well as the emergence of Ni - Cr - 1940 Mo - Cu four component system corrosion resistant alloy has experienced since 70 ~ 80 years of development, according to the demand in developing continuously improve and perfect, some brand has experienced the first generation, second and third generation and generation and is still in improvement.
To understand the basic knowledge of super stainless steel and Fe-Ni base, Ni base corrosion resistant alloy, as well as the grade, chemical composition, structure and performance characteristics of the material and its application, based on the following considerations.

First, around the iron base corrosion resistant alloy or stainless steel (including super stainless steel, high nickel corrosion resistant alloy (including iron nickel and nickel base corrosion resistant alloy) nearly hundred years development course, it can be seen that: since the super stainless steel, the further extension of stainless steel, iron and iron nickel and nickel base corrosion resistant alloy between nature, closely linked together, form the brand, variety complete, yield is the largest, most properties of strong adaptability, most widely application scope, the most complete system of corrosion resistant metal materials.

Second, it is well known that the super austenitic and super duplex stainless steel was belong to Fe - Ni - Cr alloy, and super ferritic stainless steel in addition to the individual brand, at present are nickel containing 2% ~ 4%, therefore, this kind of stainless steel were also voted into the Fe - Ni - Cr alloy system, iron and nickel and nickel based corrosion resistant alloy, in addition to the Ni - Cu, Ni, Mo, two kinds of ternary alloys, other alloy have been in Fe - Cr - Ni (or Ni - Cr - Fe) system. From Fig. 5, we can find the position of super stainless steel and Fe-Ni base and Ni-Ni base corrosion resistant alloys in the ternary phase diagram of Fe-Cr-Ni (or Ni-Cr-Fe) and the approximate range of their Cr, Ni and Fe contents.

Third, nickel-based super stainless steel and iron and nickel base corrosion resistant alloy in the process of development and improvement, in order to obtain the best performance, the study of the content is mainly material chemical composition, organizational structure and various performance (ingredients - organization - performance) and the relationship between purity and uniformity, the influence of surface condition and so on (see figure 6). At the same time, one of the urgent problems to be solved is how to solve the decrease of thermal stability of material components and the deterioration of molding, toughness and corrosion resistance caused by the increasing amount of chromium, molybdenum and nitrogen in materials.

Finally, and most importantly, China is now the world's largest producer and consumer of stainless steel. But to build a stainless steel industry power, it is a long way to go. At present, in order to realize energy saving and emission reduction, the production and application of materials with high performance, high quality, long life cycle and low cost have become an important direction of the development of stainless steel and high nickel corrosion resistant alloy. In the face of modern industry in the process of industrialization in our country, such as petroleum, chemical, petrochemical, machinery, energy (coal, fuel power plant and nuclear power, as well as land, sea deep Wells and ultra deep Wells, etc.) of oil and gas field development industry and environmental protection (such as flue gas desulfurization), ocean development, such as desalination, Marine engineering), and other fields, large equipment and key equipment, components of high corrosion resistance and high quality super stainless steel and high nickel corrosion resistant alloy material to achieve localization and development with independent intellectual property rights in our country's new super stainless steel and high nickel corrosion resistant alloy material demand, An understanding of the fundamentals of super stainless steel and high nickel corrosion resistant alloys with an emphasis on practicality is necessary.

For super stainless steel and high nickel corrosion resistant alloy production, use, and practitioners in the field of research, design and so on, at home and abroad to understand the development process of stainless steel and high nickel corrosion resistant alloy, the present situation and the latest progress, grasp the basic knowledge of stainless steel and high nickel corrosion resistant alloy, familiar with all kinds of specific brand of material chemical composition, organizational structure and various performance characteristics and its influencing factors, is necessary.