Stainless Steel Pipe Fittings

Comparison of performance between duplex stainless steel pipes and other stainless steel pipes

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Duplex stainless steel pipe is in the solution structure of ferrite in the microstructure and the austenite microstructure about each accounted for 50%, the less content usually have reached 30%, so the duplex stainless steel pipe with ferrite stainless steel and austenitic stainless steel pipe properties.

Among them, compared with austenitic stainless steel pipe, duplex stainless steel pipe has more advantages, first of all, its yield strength is stronger than ordinary austenitic stainless steel pipe, but also has enough plastic and toughness needed for molding. The wall thickness of tanks or pressure vessels made of duplex stainless steel is reduced by 30%~50%, which greatly reduces the cost.

The second is the pipe resistance to stress corrosion cracking excellent duplex stainless steel, especially in chloride environment, even the lowest levels containing alloy stainless steel pipe, resistance to stress corrosion cracking ability than the austenitic stainless steel pipe, and the stress corrosion resistance and is difficult to solve the problems often common austenitic stainless steel pipe.

The third point is that in many media most commonly applied in 2205 duplex stainless steel pipe corrosion resistance must be better than ordinary 316L austenitic stainless steel, this is because the super duplex stainless steel pipe corrosion resistance is extremely high, in some medium, such as acetic acid and formic acid can replace the high alloy austenitic stainless steel pipe, and corrosion resistance alloy.

The fourth point is the duplex stainless steel pipe has good resistance to local corrosion resistance, compared with the alloy content equivalent of austenitic stainless steel pipe, pipe corrosion and wear and corrosion fatigue properties of duplex stainless steel are better than austenitic stainless steel pipe.

The fifth point is the duplex stainless steel pipe line expansion coefficient than the austenitic stainless steel pipe for low carbon steel and carbon steel, close to, to connect engineering significance, for example can be used in the production of stainless steel pipe composite plate or lining etc..

The final point is that the energy absorption capacity of the duplex stainless steel pipe is better than that of the austenitic stainless steel pipe under dynamic or static load conditions. In dealing with sudden accidents such as collision and explosion, the practical application value of duplex stainless steel pipe is very obvious.

However, compared with austenitic stainless steel pipes, duplex stainless steel pipes are also defective. First of all, the universality and versatility of duplex stainless steel pipes are not comparable to those of austenitic stainless steel pipes, such as long term applications, which must be controlled below 250 degrees celsius.

Secondly, its plastic toughness is lower than that of austenitic stainless steel pipe, and its cold, hot working process and formability are also inferior to austenitic stainless steel pipe.

Duplex stainless steel pipe also has medium temperature brittleness zone, so it is necessary to strictly control the heat treatment and welding process system, so as to avoid the occurrence of harmful phase and damage the performance.

The most obvious disadvantage of duplex stainless steel pipe compared with austenitic stainless steel pipe is that the former contains a large amount of ferrite structure.

What are the advantages and disadvantages of duplex stainless steel pipe and ferritic stainless steel pipe?. The first advantage is that the comprehensive mechanical properties are higher than those of ferritic stainless steel pipes, especially plastic toughness. Brittleness is not as sensitive as ferritic stainless steel pipes. Secondly, in addition to the stress corrosion resistance, other local corrosion resistance is better than the ferritic stainless steel pipe. The cold working properties and cold forming properties of duplex stainless steel pipes are much better than those of ferritic stainless steel pipes. In addition, the welding performance of duplex stainless steel pipe is much better than that of ferritic stainless steel pipe, and it is not necessary to preheat before welding and no heat treatment after welding. Another point is that the duplex stainless steel pipe is wider than the ferritic stainless steel pipe.

However, compared with ferritic stainless steel pipes, the disadvantage of duplex stainless steel pipes is the high content of alloying elements and the relatively high price, because the common ferritic stainless steel pipes do not contain nickel.

The use of duplex stainless steel pipe performance and process performance are excellent, with excellent comprehensive performance of mechanics and corrosion resistance of the popular, is an engineering material corrosion resistance to save weight and save investment outstanding.

Source: China Duplex Stainless Steel Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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Steel Pipe

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