Effect of 48 Chemical Elements on Steel

Element 1: H(Hydrogen)

Hydrogen

H is the most harmful element in steel, and the solution of hydrogen in steel can cause hydrogen embrittlement and white spots of steel.

Like oxygen and nitrogen, the solubility of Hydrogen in solid steel is very low. When mixed into liquid steel in high temperature, it can not escape timely before cooling and accumulates in the organization, forming high-pressure fine pores, which makes steel plasticity, toughness and fatigue strength sharply reduce or even causes serious cracks and brittle fracture.

“Hydrogen embrittlement” mainly appears in martensitic steel, not very prominent in ferrite steel, and generally increases along with hardness and carbon content.

On the other hand, H can improve the magnetic conductivity of steel, but it also increases the coercivity and iron loss (the coercivity can be increased by 0.5 ~ 2 times after adding H).

 

Element 2:(Boron)

Boron

The main function of B in steel is to increase the hardenability of steel, thus saving other relatively rare metals like nickel, chromium, molybdenum, etc.

For this purpose, its content is generally stipulated in the range of 0.001% ~ 0.005%. It can replace 1.6% of nickel, 0.3% of chromium, or 0.2% of molybdenum.

When B is used to replace molybdenum, it should be paid attention to that as molybdenum can prevent or reduce the temper brittleness, but B is a slight tendency to promote the temper brittleness, molybdenum can not be completely replaced by B.

Adding B into carbon steel can improve the hardenability, which can largely improve the performance of steel with over 20 mm thickness, therefore, 40B and 40 MNB steel can replace 40 cr, 20Mn2TiB steel can replace 20 crmnti carburizing steel.

However, due to the effect of boron weakened, even disappeared, with the increase of the carbon content in steel, when choosing boron carburizing steel, it should be aware of that after parts being carburized, the hardenability of carburized layer will be lower than the hardenability of the core.

The spring steel is generally required to be fully quenched. Considering its small spring area, boron steel would be a good choice.

The effect of boron on high silicon spring steel is more volatile and thus it should not be used.

Boron, nitrogen and oxygen have a strong affinity. The addition of 0.007% of boron in rimming steel can eliminate the aging of steel.

 

Element 3: C(Carbon)

Carbon

C is the main element after iron, which directly affects the strength, plasticity, toughness and welding properties of steel.

When the carbon content in steel is below 0.8%, the strength and hardness of the steel increase with the adding of carbon content, while the plasticity and toughness decrease.

But when carbon content is above 1.0%, as the carbon content increases, the strength of the steel decreases.

With the increase of carbon content, the welding performance of the steel reduces( when the carbon content in steel is more than 0.3%, its weldability decreases significantly), the cold brittleness and the aging sensitivity increase, and the atmospheric corrosion resistance decreases.

 

Element 4: N(Nitrogen)

Nitrogen

The effect of N on steel performance is similar to that of carbon and phosphorus. With the increase of nitrogen content, it can significantly improve the strength of steel, reduce its plasticity, especially toughness and weldability, while enhancing its cold brittleness;

Meanwhile, the aging tendency, cold brittleness and hot brittleness are added, and the welding property and cold bending properties of steel are damaged.

Therefore, nitrogen content in steel should be minimized and restricted. The nitrogen content should be no higher than 0.018%.

Cooperated with aluminum, niobium, vanadium and other elements, Nitrogen can reduce its adverse effects on and improve the performance of steel.

Nitrogen can be used as alloy elements of low alloy steel.

Some stainless steel, with appropriate nitrogen content, can reduce the use of Cr, and thus effectively reduce the cost.

 

Element 5: O(Oxygen)

Oxygen

O is a harmful element to steel. It is naturally made into steel during the process of steel making, and it is impossible to remove it completely even though adding manganese, silicon, iron and aluminum at the end of the process.

During the solidification of molten steel, the oxygen and carbon reactions in the solution produce carbon monoxide, which can cause bubbles.

In steel, oxygen mainly exists in the form of FeO, MnO, SiO2, Al2O3, which reduces the strength and plasticity of steel, particularly, the fatigue strength and toughness will be affected seriously.

The oxygen will increase the iron loss in the silicon steel, weaken the magnetic conductivity and the intensity of the magnetic induction, and enhance the magnetic aging effect.

 

Element 6: Mg(Magnesium)

Magnesium

Mg can reduce the number of inclusions in steel, reduce the size, make distribution evenly and improve the shape.

Trace magnesium can improve the carbide size and distribution of bearing steel.

When the magnesium content is 0.002% ~ 0.003%, the tensile strength and yield strength increase by more than 5%, while the plasticity basically remains unchanged.

 

Element 7: Al(Aluminium)

Aluminium

Aluminum, added into steel as a deoxidizer or alloying element, is much stronger than silicon and manganese in terms of deoxidation.

The main role of aluminum in steel is to refine grains and stabilize nitrogen in steel, thus significantly improving the impact toughness of steel and reducing cold brittle tendency and aging tendency.

In the case of grade D carbon structural steel, the content of acid-soluble aluminum in steel is not less than 0.015%, and the content of acid-soluble aluminum in steel is 0.015%-0.065% for deep stamping with cold rolled sheet 08AL.

Aluminum can also improve the corrosion resistance of steel, especially when combined with molybdenum, copper, silicon, chromium and other elements.

Chromium molybdenum steel and chromium steel contain Al to increase its wear resistance.

The existence of Al in high carbon tool steel can make the quenching brittleness. The disadvantage of aluminum is that it can affect the thermal processing property, welding performance and cutting performance of steel.

 

Element 8: Si(Silicon)

Silicon

Si is an important reducing agent and deoxidizer in the process of steelmaking.

Many materials in carbon contain less than 0.5% of Si, and such Si is generally brought in the steelmaking process as reducing agent and deoxidizer.

Silicon can be dissolved into ferrite and austenite to increase the hardness and strength of steel, which is second only to phosphorus, and is stronger than manganese, nickel, chromium, tungsten, molybdenum and vanadium.

However, when the silicon content exceeds 3%, the plasticity and toughness of steel will be significantly reduced.

Silicon can improve the elastic limit, yield strength and yield ratio of steel (Os/ Ob), as well as fatigue strength and fatigue ratio (σ-1/σb), etc.

This is the reason why silicon or silicon manganese steel can be used as spring steel.

Silicon can reduce the density, thermal conductivity and conductivity of steel.

It can promote ferrite grain coarsening, reduce coercive force.

It has a tendency to reduce the anisotropy of the crystal, making it easy to magnetize and reducing the magnetic resistance, which can be used to produce electrical steel, so the magnetic block loss of the silicon steel sheet is low.

Silicon can improve the magnetic permeability of ferrite, so that the steel sheet has a higher magnetic intensity under the weaker magnetic field.

But in the strong magnetic field, silicon reduces the magnetic intensity of steel. Silicon has a strong deoxidizing force, which reduces the magnetic aging effect of iron.

When the silicon steel is heated in the oxidizing atmosphere, a layer of SiO2 film will be formed to improve the oxidation resistance of the steel at high temperature.

Silicon can promote the growth of columnar crystals in cast steel and reduce plasticity.

If the silicon steel cools rapidly when heated, due to the low thermal conductivity, the internal and external temperature difference of steel is large, which will easily cause steel to break.

Silicon can reduce the welding performance of steel.

Because silicon is easier to be oxygenized than iron, it is easy to generate the silicate with a low melting point during welding, which can increase the fluidity of slag and molten metal, cause splashing and affect the welding quality.

Silicon is a good deoxidizer.

When aluminum is deoxidized, a certain amount of silicon can be added, which can significantly improve the rate of deoxidization.

Silicon has a certain residual in the steel, which is brought into the steel as a raw material. In the rimming steel, the silicon is limited to < 0.07%, and when necessary, the silicon iron alloy is added to the steel making.

 

Element 9: (Phosphorus)

Phosphorus

P is brought into steel by ore, which is generally said to be a harmful element. Although phosphorus can increase the strength and hardness of steel, it causes a significant decrease in plasticity and impact toughness.

Especially at low temperature, it makes the steel significantly brittle, which is called ” cold brittleness “.

Cold brittleness weakens the steel’s cold processing and weldability. The higher the phosphorus content is, the cold brittleness is bigger, so the phosphor content in the steel is controlled strictly.

High quality steel: P < 0.025%; Quality steel: P < 0.04%; Common steel: P < 0.085%.

P is strong in solid solution strengthening and cooling hardening.

When combined with copper, it can improve the atmospheric corrosion resistance of high strength low alloy steel while reducing its cold stamping performance; when combined with sulfur, manganese, P can the improve steel’s machinability, temper brittleness and cold brittleness sensitivity.

Phosphorus can improve ratio resistance, and can reduce the coercive force and eddy current loss due to coarse grain.

For magnetic induction, the magnetic induction of steel with higher P content will be improved in the weak magnetic field.

The hot working of P- containing silicon steel is not difficult, but because P can make the silicon steel with cold brittleness, its content should ≯ 0.15% (such as in cold rolled electrical silicon steel, the P content is 0.07 ~ 0.10%).

Phosphorus is the most powerful element of ferrite. (the effect of P on the silicon steel recrystallization temperature and grain growth is 4 ~ 5 times that of silicon with the same content.)

 

Element 10: S(Sulfur)

Sulfur

Sulfur is derived from the ore and fuel coke made from steel. It is a harmful element to steel. Sulphur exists in steel in the form of FeS. FeS and Fe form compound at low melting point (985 ℃).

The hot working temperature of the steel is in commonly 1150 ~ 1150 ℃ above, so when hot working of steel is conducted, the workpiece will break due to the early melting of FeS compounds and this phenomenon is called “hot brittleness”.

It reduces the ductility and toughness of steel, causing cracks in forging and rolling.

Sulfur is also bad for welding performance, reducing corrosion resistance.

High quality steel: S < 0.02% ~ 0.03%; Quality steel: S < 0.03% ~ 0.045%; Common steel: S < 0.055% ~ 0.7%.

Because of its chip brittle and very shiny surface can be obtained, it can be used to produce steel parts which require low capacity and higher surface shineness (called fast cutting steel), such as Cr14 deliberately added a small amount of sulfur (= 0.2 ~ 0.4%).

Some high-speed steel and tool steel use S to process the surface.

 

Element 11 and 12: K/Na(Kalium / Natrium)

K/Na can be used as a modifier to spherify the carbides in the white iron, so that the toughness of white iron (and lestenite steel) can be improved twice when the hardness remains the same.

They can refine the structure of ductile iron and stabilize the treatment process of vermicular iron.

They are strong elements to promote austenitizing, for example, they can reduce the manganese/carbon ratio of austenitic manganese steel from 10:1~13:1 to 4:1-5:1.

 

Element 13: Ca(Calcium)

Adding calcium in steel can refine grain, partly desulfurization, and change the composition, quantity and form of non-metallic inclusions, similar to adding rare earth in steel.

It can improve corrosion resistance, wear resistance, high temperature and low-temperature performance of steel;

Also, it can improve the impact toughness, fatigue strength, plasticity and welding properties of steel.

It can enhance cold heading, shock resistance, hardness and contact strength of steel as well.

Adding calcium to cast steel increases the mobility of molten steel. The surface of the casting is improved, and the anisotropy of organizations in casting is eliminated.

Its casting performance, thermal cracking resistance, mechanical properties and machining performance have all increased.

Adding calcium in steel can improve the performance of anti-hydrogen crack and lamellar tear, and prolong the service life of equipment and tools.

Calcium is added to the mother alloy as deoxidizer and inoculation and microalloying.

 

Element 14: Ti(Titanium)

Titanium has a strong affinity with nitrogen, oxygen and carbon, also stronger affinity with S than iron, which is a good effective element for a deoxidizing deoxidizing agent and fixing nitrogen and carbon.

Although titanium is a strong carbide forming element, it does not combine with other elements to form compounds.

Titanium carbide is strong in the binding force, stable, uneasy to decomposition and can only slowly dissolve into steel when the temperature is above 1000 ℃.

Before insolation, titanium carbide particles have the effect of preventing grain growth.

Due to the affinity between titanium and carbon is greater than the affinity between chromium and carbon, titanium is commonly used in stainless steel to fix the carbon, to remove chromium dilution in the grain boundary, so as to eliminate or reduce steel intergranular corrosion.

Titanium is also one of the elements of strong ferrite formation, which greatly enhances the temperature of A1 and A3 of steel.

Titanium can improve plasticity and toughness in ordinary low alloy steel. Because titanium fixes nitrogen and sulfur and forms titanium carbide, it increases the strength of steel.

Formed by normalizing the grain refinement, precipitation carbides can make the plasticity and impact toughness of the steel greatly improve.

Alloy structural steel containing titanium has good mechanical properties and process performance, but its main drawback is low hardenability.

In high chromium stainless steel, titanium content is usually 5 times that of carbon, which can not only improve the corrosion resistance of steel (mainly anti-intergranular corrosion) and toughness, but also promote the grain growth of steel at high temperature and improve the welding property of steel.

 

Element 15: V(Vanadium)

Vanadium has a strong affinity with carbon, ammonia and oxygen, and forms stable compounds with them.

Vanadium is mainly in the form of carbides in steel.

Its main function is to refine the structure and grain of steel and reduce the strength and toughness of steel.

When the solid solution is dissolved at high temperature, it can increase the hardenability. Conversely, if it exists in the form of carbides, the hardenability is reduced.

Vanadium increases the tempering stability of hardened steel and produces secondary hardening effect.

The amount of vanadium in steel is no more than 0.5% except for high-speed tool steel.

Vanadium can refine grain in ordinary low carbon alloy steel, improve the strength and yield ratio and low-temperature property of steel after the normal fire, and improve the welding property of steel.

In alloy structural steel, Vanadium can reduce the hardenability under normal heat treatment.

Therefore, it is used in combination with manganese, chromium, molybdenum and tungsten in structural steel.

Vanadium is mainly used to improve the strength and yield ratio of steel, refine grain and pick up overheating sensitivity.

In the case of carburizing steel, it can make the steel quench directly after carburizing, without secondary quenching.

Vanadium can increase the strength and yield ratio in spring steel and bearing steel, especially increase the ratio limit and elastic limit, reduce the carbon sensitivity during heat treatment, thus improving the surface quality.

The bearing steel with v – chromium containing vanadium has high dispersion degree and good performance.

Vanadium is used in tool steels to refine grain, reduce overheating sensitivity, increase tempering stability and wear resistance, thus extending the service life of tools.

 

Element 16:Cr(Chromium)

Chromium can increase the hardenability of steel and has the effect of the secondary hardening, and can improve the hardness and wear resistance of carbon steel without making it brittle.

When the Cr content is more than 12%, it makes the steel has good high-temperature oxidation resistance and oxidation resistance of corrosion, also increases its hot strength.

Chromium is the main alloy element in stainless steel, acid-resistant steel and heat-resistant steel.

Chromium can improve the strength and hardness of carbon steel under rolling, reduce the elongation and shrinkage of cross-section.

When the chromium content exceeds 15%, the strength and hardness will decrease, and the elongation and the shrinkage of cross section will be increased correspondingly. By grinding, parts of chromium steel are easy to obtain high surface quality.

The main function of Chromium in tempering structure is to improve the hardenability, make steel has good comprehensive mechanical performance after quenching tempering, produce chromium carbide in carburizing steel so as to improve the wear resistance of the material surface.

The chromium – bearing spring steel is not easy to decarbonize during heat treatment. Chromium can improve the wear resistance, hardness and red hardness of tool steel, and make it has good tempering stability.

In electrothermal alloys, chromium can improve the oxidation resistance, resistance and strength of the alloy.

Element 17:Mn(Manganese)

Mn can improve the strength of steel: since Mn is relatively cheap and can be fixed with Fe, it has little effect on plasticity while improving the strength of steel. Therefore, Mn is widely used to reinforce steel.

It can be said that almost all carbon steel contains Mn. Stamping soft steel, double phase steel (DP steel), transferable-phase induced plastic steel (TR steel)and martensitic steel (MS steel) contain manganese.

Generally, Mn content in soft steel will not exceed 0.5%. Mn content in high strength steel increases with the increase of intensity level, such as in martensitic steel, Mn content can reach up to 3%.

Mn improves the hardenability of steel and improves the thermal processing performance of steel: the typical example is 40Mn and No.40 steel.

Mn can eliminate the influence of S (sulfur): Mn can form MnS with a high melting point in steel smelting, thereby weakening and eliminating the adverse effects of S.

However, the content of Mn is also a double-edged sword. Mn content is not the higher the better.

The increase of mn content will reduce the plastic and welding properties of steel.

 

Element 18:Co(Cobalt)

Co is used in special steel and alloy. high-speed steel containing Co has strong high-temperature hardness.

Added to martensitic aging steel together with molybdenum, Co can make the steel have high hardness and good comprehensive mechanical properties.

In addition, Co is also an important alloy element in hot steel and magnetic materials.

Cobalt can reduce the hardenability of steel, so it can reduce the comprehensive mechanical properties of carbon steel.

Cobalt can strengthen ferrite. When added to carbon steel, under the condition of annealing or normalizing, Co can improve the hardness, the yield point and tensile strength of steel, but it has a negative effect on steel’s elongation and shrinkage of the cross-section.

When the Co content increases, steel’s impact toughness reduces.

Because Co has antioxidant properties, it is used in heat-resistant steel and heat-resistant alloys, especially in co-based alloy gas turbine shows.

 

Element 19:Ni(Nickel)

The beneficial effects of nickel are: high strength, high toughness, good hardenability, high resistance and high corrosion resistance.

On the one hand, it can strongly enhance the strength of steel, while on the other hand keep the iron’s toughness extremely high.

Its brittle temperature is extremely low. (when nickel < 0.3%, the brittle temperature is below ‐100℃; when Co content is increased to about 4 ~ 5%, the brittle temperature can drop to ‐180℃.

So it can improve the strength and plasticity of the hardened steel.

With Ni=3.5%, no Cr steel can be quenched, and Cr steel containing Ni=8% can be transformed into M type at very small cold speed.

The lattice constant of Ni is similar to that of γ‐Fe, so it can be a continuous solid solution.

This is conducive to enhancing the hardening of steel. Ni can reduce the critical point and increase the stability of austenite, so the quenching temperature can be reduced and the quenching is good.

In general, heavy parts of large sections are made of Ni steel.

When it is combined with Cr, W or Cr and Mo, the hardenability can be increased. Nickel-molybdenum steel also has a high fatigue limit. (Ni steel has good thermal fatigue resistance, capable of working in hot and cold.)

In stainless steel, Ni is used to make the steel have uniform A body to improve the corrosion resistance.

Ni steel is generally not easy to overheat, so it can prevent the growth of grain in high temperature, and can still maintain fine grain structure.

 

Element 20:Cu(cuprum)

The prominent role of Cu in steel is to improve the atmospheric corrosion resistance of ordinary low alloy steel, especially when mixed with phosphorus, Cu also can improve the strength and the yield ratio of steel, and no adverse effect on welding performance.

The steel rail steel (u-cu) containing 0.20% ~ 0.50% of Cu has a corrosion resistance period 2-5 times of that of normal carbon steel.

When the Cu content exceeds 0.75%, the aging effect can be produced after solid solution treatment and aging.

When the content is low, its effect is similar to nickel, but weaker. When the content is high, it is not good for thermal deformation processing, which leads to copper brittleness.

2 ~ 3% copper in austenitic stainless steel can enhance the corrosion resistance of sulfuric acid, phosphoric acid and hydrochloric acid and the stability of stress corrosion.

 

Element 21:Ga(Gallium)

Ga is an element in the enclosed γ section. The microgallium is soluble in ferrite and forms a substitutive solid solution.

It is not a carbide forming element, but also does not form oxides, nitrides and sulphides.

In the γ+a two-phase regions, the microgallium is easily diffused from austenite to ferrite, which is high in ferrite.

The effect of microgallium on mechanical properties of steel is mainly solid solution strengthening. Ga has a small improvement in the corrosion resistance of steel.

 

Element 22:As(arsenic)

As in ore can only be removed partially in the process of sintering. It can be removed with Chloridizing roasting.

As will be mixed into pig iron in the blast furnace smelting process.

When As content is more than 0.1% in steel, it can increase steel brittleness while weakening welding performance.

The As content in ore should be controlled and the amount of As in ore should not exceed 0.07%.

Arsenic has a tendency to increase the yield point σs and the tensile strength σb of low carbon round steel while reducing its elongation.

Also, its effect on reducing the impact toughness Akv of carbon round steel under normal temperature is obvious.

 

Element 23:Se(selenium)

Se can improve the machining properties of carbon steel, stainless steel and copper, and make the surface of parts bright and clean.

High magnetic induction oriented silicon steel often uses MnSe2 as inhibitor whose good inclusion, compared with that of MnS, is stronger in curbing the growth of initial recrystallization grain and is more conducive to promoting the selected secondary recrystallization grain growth, which can obtain high orientation (110) [001] texture.

 

Element 24:Zr(zirconium)

Zr is a strong carbide forming element, and its role in steel is similar to that of niobium, tantalum and vanadium.

Adding a small amount of Zr has the effects of degassing, purifying and refining the grain, which is advantageous to the low-temperature performance of steel, improve the stamping performance.

It is often used in the manufacture of gas engine and in the ultra high strength steel and Ni-based high-temperature alloy that is necessary to missile structure.

 

Element 25:Nb(niobium)

Nb is often associated with tantalum, and their roles in steel are similar. Nb and tantalum are partially dissolved in solid solution, and can strengthen the solid solution.

The quenching of steel is significantly improved when the austenitic body is dissolved.

However, in the form of carbides and oxide particles, it can refine the grain and reduce the hardenability of steel.

It can increase the tempering stability of steel and has the secondary hardening effect. Microniobium can improve the strength of steel without affecting the plasticity or toughness of steel.

As it can refine the grain, it can improve the impact toughness of steel and reduce its brittle transition temperature.

When the Zb content is more than 8 times that of carbon, almost all of the carbon in the steel can be fixed, making the steel has good anti-hydrogen performance.

In austenitic steels, it can prevent the oxidizing medium from doing intergranular corrosion of steel.

Due to its fixed carbon and precipitation hardening effect, it can improve the high-temperature performance of hot steel, for example creep strength.

The Nb can improve yield strength and impact toughness of ordinary low alloy steel, and reduce its brittle transition temperature, which is good for welding.

In the carburizing and tempering alloy structural steel, it can increase hardenability while improving toughness and low-temperature performance of steel. It can reduce the air hardening of low carbon martensitic stainless steel, avoid the hardening temper brittleness, and increase the creep strength.

 

Element 26:Mo(molybdenum)

Mo can improve the hardenability and heat intensity of steel, prevent temper brittleness, increase residual magnetism, coercivity and resist corrosion in some medium.

In the quenched and tempered steel, Mo can strengthen the quenching depth, hardening of large cross-section parts, improve the drawability resistance or tempering stability of steel, make the parts tempering under high temperature and thus more effectively eliminate (or reducing) residual stresses and improve the plasticity.

In carburizing steel, in addition to the above-mentioned effects, Mo can reduce the tendency of carbide forming continuous mesh at the grain boundary during the carburized layer, reduce the residual austenite in carburized layer, relatively increase the surface wear resistance.

In forging die steel, Mo can also maintain a stable hardness of steel and increase its resistance to deformation, cracking and abrasion.

In stainless acid-resistant steel, Mo can further improve steel’s corrosion resistance to organic acids such as formic acid, acetic acid, oxalic acid, etc. and hydrogen peroxide, sulfuric acid, sulfurous acid, sulfate, acid dyes and bleaching powder or fluid.

In particular,because of the addition of Mo, the corrosion tendency of chlorine ion is prevented.

The W12Cr4V4Mo high speed steel with about 1% Mo has wearability, tempering hardness and red hardness etc.

 

Element 27:Sn(Stannum)

Sn has been considered as harmful impurity elements in steel.

It affects the quality of steel, especially the continuous casting billet quality.

It makes steel produce hot brittleness, temper brittleness, crack and fracture, affecting the welding performance of the steel and is one of the “five evils” to steel.

However, Sn plays an important role in electrical steel, cast iron and easy cutting steel.

The size of silicon steel grains is related to the segregation of Sn and the segregation of Sn prevents the growth of grain.

The higher the content of Sn is, the larger the grain precipitation is, the more effective it is to hinder the growth of grain.

The smaller the grain size, the less the iron loss. Sn can change the magnetic properties of silicon steel and improve the strength of favorable texture {100} in the finished product of oriented silicon steel, and the magnetic induction intensity is obviously increased.

When a small amount of Sn is contained in cast iron, it can improve the wear resistance of steel and can affect the fluidity of molten iron.

The pearlite ball mill cast iron has high strength and high wear resistance.

In order to get the cast pearlite, Sn is added to the alloy solution during melting.

Since Sn is an element that blocks the spherification of graphite, it is necessary to control the amount of Sn addition, which generally is less than 0.1%.

Easy cutting steel can be divided into sulfur, calcium, lead and composite easy cutting steel.

Sn has an obvious tendency to gather around inclusions and defects. Sn does not change the shape of sulfide inclusions in steel, but it can improve the brittleness and cutting performance of steel by the segregation of grain boundary and phase boundary.

When the Sn content is >0.05%, steel has a good cutting ability.

 

Element 28:Sb(Stibium)

After adding Sb in the high magnetic orientation silicon steel, the grain size of the first recrystallization and the secondary recrystallization can be refined, and the second recrystallization will be more perfect and the magnetism will be improved.

After cold rolling and decarbonization of Sb steel, in its texture composition, the components {110} < 115 > or {110} < 001 > favorable to the development of secondary recrystallization will be enhanced, and the number of secondary crystal schools will be increased.

In building welding steel that contains Sb, under austenitic temperature, Sb precipitates around Mn S inclusions and along the original austenite grain boundary.

Precipitation enriched around Mn S inclusion can make the organization of the steel refined and its toughness improved.

 

Element 29:W(tungsten)

In steel, W is partially dissolved in iron forming a solid solution, in addition to producing carbide.

Its effect is similar to that of Mo, and the general effect is not as significant as Mo if calculated as per quality.

The main role of W in steel is to increase tempering stability, red hardness, heat intensity and wear resistance due to the formation of carbide.

Therefore, it is mainly used for tool steel, such as high-speed steel, hot forging steel.

W is a refractory carbide in high-quality spring steel, which can reduce the concentration process of carbides and maintain high-temperature strength at higher temperature.

W can also reduce the overheating sensitivity of steel, increase its hardenability and hardness.

Air cooling makes 65SiMnWA spring steel has high hardness after hot rolling.

50mm2 cross section the spring steel can be hardening in oil and can bear a heavy load, heat-resistant (not greater than 350 ℃).

30W4Cr2VA high strength heat resistant high-quality spring steel has large hardenability and its tensile strength can be 1470 ~ 1666 pa after 1050 ~ 1100 ℃ quenching and 550 ~ 650 ℃ tempering.

It is mainly used for manufacturing springs that are used under high temperature (500 ℃).

Because of the addition of W, it can significantly improve the abrasion and cut properties of steel, so W is the main element of alloy tool steel.

 

Element 30:Pb(Plumbum)

Pb can improve machinability of steel. Pb cutting steel has good mechanical properties and heat treatment. Due to its environmental pollution and harmful effects in the recycling process of waste steel, Pb has been gradually replaced.

Pb is difficult to form solid solution or compounds with Fe, instead, it is easy to gather in the grain boundary in the form of globular, therefore, it is the reason why brittleness happens in steel under 200 ~ 480 ℃ and cracks form when welding.

 

Element 31:Bi(Bismuth)

The cutting performance of steel can be improved by adding 0.1-0.4 Bi in free cutting steel.

When Bi is evenly distributed in steel, particles of Bi will be melted after contacting with the cutting tool, acting as a lubricant, making the cutting to break so as to avoid overheating and increase cutting speed.

Recently, Bi has been added to much stainless steel to improve the cutting performance of stainless steel.

Bi exists as three types of free-cutting steels: independently in steel matrix, wrapped by sulfide and between steel matrix and sulfide.

The deformation rate of MnS inclusions decreases with the increase of Bi content in s-bi free cutting steel ingots.

The Bi-metal in steel can restrain the deformation of sulfide in the forging process of steel ingot.

Adding 0.002-0.005% of Bi to cast iron can improve casting performance of malleable cast iron, increase the whitening tendency, shorten annealing time and optimize the extension performance of the parts.

Adding 0.005% of Bi to nodular cast iron can improve its Anti- Seismicity and tensile strength.

It is kind of difficult to add Bi to steel because Bi will largely volatile at 1500 ℃ and thus difficult to be evenly infiltrated into steel.

Currently, in abroad, Bi is replaced by Bi – Mn alloy plate with melting point 1050 ℃ as the additive, but the utilization rate of Bi is still about 20%.

Nippon Steel& Sumitomo Metal, Posco, TYO and other enterprises have proposed that adding Bi can obviously improve the B8 value of oriented silicon steel.

According to statistics, Nippon Steel& Sumitomo Metal and JFE have over one hundred high magnetic oriented silicon steel inventions having added Bi.

After adding Bi, the magnetic induction reaches 1.90T, and the maximum is 1.99T.

 

Other Element 32-48:Re (Rare Earths)

Rare earth elements, commonly refers to the periodic table of atomic number from 57 to 71 lanthanides (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium) plus No.21 scandium and No. 39 yttrium, a total of 17 elements.

Their nature is close, not easy to separate.

Those unsplit is called mixed rare earth, which is cheaper.

The rare earth can deoxidize, desulfurize,  microalloying and can also change the deformation ability of rare earth inclusions.

In particular, to a certain extent, they can affect the brittleness of Al2O3 and improve the fatigue performance of most steel types.

The rare earth elements, like Ca, Ti, Zr, Mg and Be, are the most effective deforming agents for sulfide.

Adding the proper amount of RE to the steel can transform the oxide and sulfide inclusions into small, dispersed globular inclusions and thus eliminate the harmful effects of MnS and other inclusions.

In production practice, sulfur is in the form of FeS and MnS in steel.

When Mn content is high in steel, MnS is more likely to be formed.

Although its melting point is high and can avoid the generation of heat brittle, MnS, when machining deformation, can extend in the direction of the processing and form into strips, then, steel’s plasticity, toughness, and fatigue strength will be significantly reduced, so it is necessary to make deformation processing of RE to be added to steal.

Rare earth elements can also improve the oxidation resistance and corrosion resistance of steel.

Their effect of oxidation resistance is greater than that of silicon, aluminum and titanium.

They can improve the flow of steel, reduce non-metallic inclusion, and make the steel structure dense and pure.

The role of rare earth in steel is mainly purification, metamorphism and alloying.

With the gradual control of oxygen sulfur content, traditional purification of the molten steel and the metamorphism gradually weakens, while the new purification technology and alloying effect are being improved.

The rare earth elements increase the antioxidant capacity of alloy in ferrochrome aluminum alloy, keep the fine grain of steel at high temperature, and increase their high-temperature strength, which increases the service length of electrothermal alloy significantly.

2018-02-05T14:04:59+00:00 Steel|

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