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The difference and application fields of ordinary stainless steel and special stainless steel

Views:98     Author:Ronsco     Publish Time: 2021-05-11      Origin:Ronsco

Nickel-based alloys are generally referred to as alloys with Ni content exceeding 30wt%. Common products have Ni content exceeding 50wt%. Due to their superior high-temperature mechanical strength and corrosion resistance, they are collectively called superalloys with iron-based and cobalt-based alloys ( Superalloy) is generally used in high temperature environments above 540°C, and according to its use occasions, different alloy designs are selected, and they are mostly used in special corrosion-resistant environments, high-temperature corrosion environments, and equipment that requires high-temperature mechanical strength. It is often used in aerospace, energy, petrochemical industry or special electronics/optoelectronics fields.


The nickel content is generally less than 30, and the iron-based stainless steel belongs to the stainless steel.


Super stainless steel and nickel-based alloy are a kind of special stainless steel. Firstly, they are different from ordinary stainless steel in chemical composition. They refer to a kind of high-alloy stainless steel with high nickel, high chromium and high molybdenum.


One of the more famous steels is 6% Mo steel (254SMo). This type of steel has very good local corrosion resistance. It has good pitting corrosion resistance (PI≥ 40) and good stress corrosion resistance, it is a substitute material for Ni-based alloy and titanium alloy.


Secondly, in terms of high temperature resistance or corrosion resistance, it has more excellent high temperature or corrosion resistance, which is irreplaceable for 304 stainless steel. In addition, from the classification of stainless steel, the metallographic structure of special stainless steel is a stable austenitic metallographic structure.


Because this special stainless steel is a high-alloy material, the manufacturing process is quite complicated. Generally, people can only rely on traditional processes to manufacture this special stainless steel, such as infusion, forging, rolling, and so on.


In many fields, such as:


1. Ocean: Marine structures in the marine environment, seawater desalination, mariculture, seawater heat exchange, etc.

2. Environmental protection field: flue gas desulfurization device for thermal power generation, waste water treatment, etc.

3. Energy field: nuclear power generation, comprehensive utilization of coal, sea tide power generation, etc.

4. Petrochemical industry: oil refining, chemical and chemical equipment, etc.

5. Food field: salt making, soy sauce brewing, etc.


In the above-mentioned many fields, ordinary stainless steel 304 is not competent. In these special fields, special stainless steel is indispensable and cannot be replaced. In recent years, with the rapid economic development and the continuous improvement of the industrial level, more and more projects require higher-grade stainless steel-special stainless steel (super stainless steel, nickel-based alloy).


Some representative special stainless steels are:


1. Super stainless steel, that is to say, it is a special stainless steel containing about 6% molybdenum. There are more than ten kinds of steel in the world. Everyone too

Called 6 molybdenum stainless steel. For example, the main component is: 25Ni-23Cr-5.5Mo-0.2N

2. Incoloy series alloys, such as Incoloy 800, the main components are: 32Ni-21Cr-Ti, Al

3. Inconel series alloys, such as Incone l600, the main components are: 73Ni-15Cr-Ti, Al

4. Hastelloy, such as C-276, the main component is: 59Ni-15Cr-16Mo-4W

5. Monel alloy, such as Monel 400, the main component is: 65Ni-32Cu


Based on the above examples, if ordinary stainless steel (such as 304) is used instead of special stainless steel, ordinary stainless steel (304) is not suitable for such a high temperature or high corrosion environment, and the material will corrode immediately, or high temperature will occur. Oxidation. Therefore, special stainless steel is the best choice in many environments that require high temperature resistance and corrosion resistance.


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