Effects of Chemical Elements on Stainless Steel Pipes (Part Two)

Sulfur(S): Sulfur is also a harmful element under the normal circumstance. It will create the hot brittleness of stainless steel pipes, decrease the impact ductility of stainless steel pipes and bring cracks to stainless steel pipes in the forging and rolling processes. Besides, sulfur will also have negative impacts on the welding performance of stainless steel pipes and make stainless steel pipes have poor corrosion resistance. Therefore, in general, the content of sulfur is supposed to be less than 0.055%, and even less than 0.040% in some high-quality stainless steel pipes. However, if we add 0.08% to 0.20% sulfur to the steel of which the stainless steel pipes are made, the machinability of the steel can be much improved.

Chromium(Cr): Chromium can significantly improve the oxidation resistance and corrosion resistance of steel, increase the strength, hardness and wear resistance of stainless steel pipes, and decrease the plasticity and toughness of stainless steel pipes at the same time, which makes it an important element in the heat-resistant steel.

Nickel(Ni): Nickel can improve the strength and maintain good plasticity and toughness of steel. Nickel has very high corrosion resistance to acid and alkali, and has good rust and heat resistance at high temperatures. However, nickel is a scarce resource, so it would be better for us to use other elements instead of nickel.

Molybdenum(Mo): Molybdenum can make the grain of steel refined, improve the hardenability and thermal strength of stainless steel pipes and maintain the sufficient strength and creep resistance of the steel at high temperatures. The creep means that the steel will deform under the impact of stress if it is put at high temperatures for a long time. Adding molybdenum to the structural steel can help increase the mechanical properties of the structural steel and curb the brittleness of the alloy caused by fire.

Titanium(Ti): Titanium is a strong deoxidizer in steel. It can make the internal organization of steel dense, refine the grain, decrease the aging sensitivity and cold brittleness and improve welding performance of steel.

Vanadium(V): Vanadium is an excellent deoxidizer for steel. Adding 0.5% of vanadium to the steel can refine the grain as well as improve the strength and toughness of steel. Vanadium and carbon can form the carbide which can improve the hydrogen corrosion resistance of stainless steel pipes under high temperature and high pressure conditions.

Tungsten(W): Tungsten is a precious alloy element and has the high melting point. Tungsten carbide formed by the tungsten and carbon has high hardness and good wear resistance. Adding tungsten to the tool steel can significantly improve the red hardness and thermal strength of the tool steel.

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