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Influence of chemical elements on properties of steel and iron (iv)

Views:1     Author:Site Editor     Publish Time: 2019-06-03      Origin:Site

Effects of arsenic on properties of steel

Element 22: As (arsenic)

 

Arsenic in ore can only be removed in the sintering process, and can also be removed by the method of chlorination roasting. In the smelting process of blast furnace, all arsenic is reduced into pig iron. When the arsenic content in steel is more than 0.1%, it will increase the brittleness of the steel and make the welding performance worse. The arsenic content in the ore shall be controlled and shall not exceed 0.07%.

 

Arsenic has a tendency to improve yield point sigma s, tensile strength sigma b and delta-5 elongation of low carbon round steel, and to reduce Akv impact toughness at room temperature.

 

Effects of selenium on steel properties

Element 23: Se (selenium)

 

Selenium can improve the cutting performance of carbon steel, stainless steel and copper.

 

MnSe2 is often used as an inhibitor in high magnetically sensitive oriented silicon steel. MnSe2 beneficial inclusion has stronger inhibition on the growth of primary recrystallized grain than MnS beneficial inclusion, and is more conducive to promoting the selective growth of secondary recrystallized grain, so as to obtain the texture of high orientation (110) [001].

 

Effect of zirconium on steel properties

Element 24: Zr (zirconium)

 

Zirconium is a strong carbide forming element, and its effect in steel is similar to that of niobium, tantalum and vanadium. The addition of a small amount of zirconium helps degassing, purifying and refining grains, improving the low temperature properties of steel and improving its stamping properties.

 

Effect of niobium on steel properties

Element 25: Nb (niobium)

 

Niobium often coexists with tantalum, and their functions in steel are similar. Niobium and tantalum are partially dissolved into the solid solution to strengthen the solution. When dissolved into austenite, the hardenability of steel is significantly increased. But in the form of carbides and oxide particles, the grains are refined and the hardenability of steel is reduced. It can increase the tempering stability of steel and has secondary hardening effect. Trace niobium can increase the strength of steel without affecting its plasticity or toughness. The effect of grain refinement can improve the impact toughness and reduce the brittle transition temperature of steel. When the content of carbon is more than 8 times, almost all the carbon in the steel can be fixed, so that the steel has good hydrogen resistance. Intercrystalline corrosion of austenitic steel by oxidizing medium can be prevented. High temperature properties, such as creep strength, can be improved by carbon fixation and precipitation hardening.

 

Niobium can improve yield strength and impact toughness, and decrease brittle transition temperature. While increasing hardenability in carburizing and tempering alloy structural steel. Improve toughness and low temperature properties of steel. It can reduce the air hardening of low carbon martensitic heat resistant stainless steel, avoid hardening and tempering brittleness, and improve the creep strength.

 

Effect of molybdenum on steel properties

Element 26: Mo (molybdenum)

 

Molybdenum can improve hardenability and thermal strength in steel, prevent temper brittleness, increase residual magnetism and coercivity, and resist corrosion in some media.

 

In tempered and tempered steel, molybdenum can make the parts with large sections quench deeply and thoroughly, improve the anti-tempering property or tempering stability of steel, and make the parts temper at a higher temperature, so as to eliminate (or reduce) residual stress more effectively and improve plasticity.

 

In the carburized carbon steel in addition to the above role, but also in the carburized layer to reduce the carbide on the grain boundary to form a continuous network tendency, reduce the residual austenite carburized layer, relatively increased the wear resistance of the surface layer.

 

In forging die steel, molybdenum can also keep the steel with stable hardness and increase the deformation. Resistance to cracking, abrasion, etc.

 

In stainless steel, molybdenum can further improve the corrosion resistance of organic acids (such as formic acid, acetic acid, oxalic acid, etc.), hydrogen peroxide, sulfuric acid, sulfite, sulfate, acid dyes, bleaching powder solution, etc. Especially, the addition of molybdenum prevents the pitting corrosion tendency caused by chloride ion. W12Cr4V4Mo high speed steel containing about 1% molybdenum has abrasion resistance, temper hardness and red hardness.

 

Effect of tin element on steel properties

Element 27: Sn (tin)

 

Tin has always been a harmful impurity element in steel, which affects the quality of steel, especially the quality of continuous casting billet, makes steel produce hot brittleness, temper brittleness, crack and fracture, and affects the welding properties of steel. However, tin plays an important role in electrical steel, cast iron and free cutting steel.

 

The grain size of silicon steel is related to the segregation of tin which hinders the grain growth. The higher the content of tin, the larger the precipitation of grain, which effectively hindered the growth of grain. The higher the content of tin, the larger the grain precipitation, the stronger the ability to hinder the grain growth, the smaller the grain, the less iron loss. Tin can change the magnetic properties of silicon steel, improve the texture strength of {100} and increase the magnetic induction intensity.

 

When the cast iron contains a small amount of tin, it can improve the wear resistance and affect the fluidity of molten iron. Pearlitic ball mill cast iron has high strength and wear resistance. In order to obtain as cast pearlitic, tin is added into the alloy liquid. Since tin is an element that prevents graphite spheroidization, the amount added should be controlled. Generally controlled at less than 0.1%.

 

Free cutting steel can be divided into sulfur series, calcium series, lead series and composite free cutting steel. Tin has a distinct tendency to concentrate near inclusions and defects. Tin does not change the shape of sulfide inclusion in steel, but improves brittleness through segregation of grain boundary and phase boundary, and improves the free cutting property of steel. When tin content is >0.05%, steel has good cutting property.

 

Effect of antimony on properties of steel

Element 28: Sb (antimony)

 

After adding Sb, the grain size of primary recrystallization and secondary recrystallization were refined, the secondary recrystallization structure was more perfect, and the magnetism was improved. After cold rolling and decarbification annealing, Sb steel, in its texture components, is conducive to the development of secondary recrystallization components {110} < 115 > or {110} < 001 > enhanced, the number of secondary crystal calibration increased.

 

In building welding steel containing Sb, Sb in the steel precipitates at Mn S inclusion and along the grain boundary of original austenite at austenite temperature, and increases the enrichment precipitation on Mn S inclusion, which can refine the structure of the steel and improve its toughness.


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