Press Brake

For sheet metal bending, the press brake is a necessary machine. We have NC type and CNC type press brakes. At the same time, we can customize the punches and dies according to your practical use in sheet metal fabrication.

Shearing Machine

For the straight cutting of steel plate, hydraulic shearing machine is a good choice. It not only has high cutting efficiency, but also requires less investment. We have both swing beam shears and guillotine shears for your selection.

Laser Cutting Machine

In the current metal plate and pipe cutting, laser cutting machine is undoubtedly the best choice. It can not only cut various shapes, but also has small cutting gap, high precision and high cutting efficiency. Today, it is very cost-effective.

49 Elements Affecting The Properties Of Steel

49 Elements Affecting The Properties Of Steel

H (hydrogen)

H is the most harmful element in general steel. Hydrogen dissolved in steel will cause hydrogen embrittlement, white spots and other defects of steel.

Hydrogen, like oxygen and nitrogen, has very little solubility in solid steel.

It dissolves into liquid steel at high temperatures. It has no time to escape during cooling and accumulate in the structure to form high-pressure fine pores, which will sharply reduce the plasticity, toughness and fatigue strength of the steel, and cause cracks and brittle fracture in serious cases.

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

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

B (boron)

The main function of B in steel is to increase the hardenability of steel, so as to save other rare and precious metals, such as nickel, chromium, molybdenum, etc.

For this purpose, its content is generally specified in the range of 0.001% ~ 0.005%.

It can replace 1.6% nickel, 0.3% chromium or 0.2% molybdenum.

It should be noted that molybdenum can prevent or reduce tempering brittleness, while boron slightly promotes tempering brittleness, so boron can not completely replace molybdenum.

Adding boron to medium carbon steel can greatly improve the properties of steel with a thickness of more than 20mm after quenching and tempering due to the improvement of hardenability.

Therefore, 40B and 40MnB steel can be used to replace 40Cr, and 20mn2tib steel can be used to replace 20CrMnTi carburized steel.

However, since the effect of boron decreases or even disappears with the increase of carbon content in steel, when selecting boronized carbon steel, it must be considered that the hardenability of the carburized layer will be lower than that of the core after carburizing.

Spring steel is generally required to be fully quenched.

Generally, the spring area is small, so it is advantageous to use boron-containing steel. The effect of Boron on high silicon spring steel fluctuates greatly, which is inconvenient to use.

Boron has a strong affinity with nitrogen and oxygen.

Adding 0.007% boron to boiling steel can eliminate the aging phenomenon of steel.

C (carbon)

C is the main element second only to iron, which directly affects the strength, plasticity, toughness and weldability of steel.

When the carbon content in steel is below 0.8%, the strength and hardness of steel increase, while the plasticity and toughness decrease with the increase of carbon content; However, when the carbon content is more than 1.0%, the strength of steel decreases with the increase of carbon content.

With the increase of carbon content, the weldability of steel becomes worse (weldability of steel with carbon content greater than 0.3% decreases significantly), cold brittleness and aging sensitivity increase, and atmospheric corrosion resistance decreases.

N (nitrogen)

The effect of N on the properties of steel is similar to that of carbon and phosphorus.

With the increase of nitrogen content, the strength of steel can be significantly improved, the plasticity, especially the toughness, can be significantly reduced, the weldability becomes worse, and the cold brittleness increases;

At the same time, the aging tendency, cold brittleness and hot brittleness are increased, and the welding and cold bending properties of the steel are damaged.

Therefore, the nitrogen content in steel should be reduced and limited as much as possible. Generally, the nitrogen content shall not be higher than 0.018%.

Nitrogen, combined with aluminum, niobium, vanadium and other elements, can reduce its adverse effects and improve the properties of steel.

It can be used as an alloying element of low alloy steel.

For some grades of stainless steel, appropriately increasing the content of N can reduce the use of Cr and effectively reduce the cost.

O (oxygen)

O is a harmful element in steel. It naturally enters the steel in the steelmaking process. Although manganese, silicon, iron and aluminum should be added for deoxidation at the end of steelmaking, it can not be removed. During the solidification of molten steel, the reaction of oxygen and carbon in the solution will produce carbon monoxide, which can cause bubbles.

Oxygen mainly exists in the form of FeO, MnO, SiO2, Al2O3 and other inclusions in the steel, which reduces the strength and plasticity of the steel.

In particular, it has a serious impact on fatigue strength and impact toughness.

Oxygen will increase iron loss, weaken permeability and magnetic induction, and intensify the magnetic aging effect in silicon steel.

Mg (magnesium)

Magnesium can reduce the number, size, uniform distribution and morphology of inclusions in steel.

Trace magnesium can improve the carbide size and distribution of bearing steel, and the carbide particles of magnesium bearing steel are fine and uniform.

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

Al (aluminum)

When aluminum is added to steel as deoxidizer or alloying element, the deoxidation ability of aluminum is much stronger than that of silicon and manganese.

The main function of aluminum in steel is to refine grain and fix nitrogen in steel, so as to significantly improve the impact toughness of steel and reduce the tendency of cold embrittlement and aging.

For example, the content of acid soluble aluminum in grade D carbon structural steel is required to be no less than 0.015%, and the content of acid soluble aluminum in cold rolled steel sheet 08Al for deep drawing is required to be 0.015% – 0.065%.

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

Al in chromium-molybdenum steel and chromium steel can increase their wear resistance.

The existence of Al in high carbon tool steel can cause quenching brittleness.

The disadvantage of aluminum is that it affects the hot working performance, welding performance and cutting performance of steel.

Si (silicon)

Si is an important reducing agent and deoxidizer in the steelmaking process: many materials in carbon steel contain less than 0.5% Si, which is generally brought in as reducing agent and deoxidizer in the steelmaking process.

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

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

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

This is because silicon or silicon manganese steel can be used as spring steel.

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

It can coarsen ferrite grains and reduce coercivity.

It has the tendency to reduce the anisotropy of the crystal so that the magnetization is easy and the magnetoresistance is reduced.

It can be used to produce electrical steel, so the magnetoresistance hysteresis loss of silicon steel sheet is low.

Silicon can improve the permeability of ferrite and make the steel sheet have high magnetic induction under weak magnetic field.

However, under strong magnetic field, silicon reduces the magnetic induction strength of steel. Silicon has strong deoxidizing force, which reduces the magnetic aging effect of iron.

When the steel containing silicon is heated in an oxidizing atmosphere, a layer of SiO2 film will be formed on the surface, so as 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 silicon steel cools quickly when heated, it will break due to the low thermal conductivity and large temperature difference between the inside and outside of the steel.

Silicon can reduce the weldability of steel. Because silicon has a stronger binding capacity with oxygen than iron, it is easy to produce silicate with a low melting point during welding, which increases the fluidity of slag and molten metal, causes splashing and affects the welding quality.

Silicon is a good deoxidizer. When deoxidizing with aluminum, adding a certain amount of silicon can significantly improve the deoxidization of the rate.

Silicon has a certain residual in steel, which is brought in as raw material in iron and steel making.

In boiling steel, silicon is limited to < 0.07%. When it is intentionally added, ferrosilicon alloy is added during steelmaking.

P (phosphorus)

P is brought into steel by ore. generally speaking, phosphorus is also a harmful element.

Although phosphorus can increase the strength and hardness of steel, it can significantly reduce the plasticity and impact toughness. Especially at low temperatures, it makes the steel significantly brittle.

This phenomenon is called “cold embrittlement”. Cold brittleness deteriorates the cold working and weldability of steel.

The higher the phosphorus content, the greater the cold brittleness.

Therefore, the phosphorus content in steel is strictly controlled.

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

P has good solid solution strengthening and cold work hardening.

When used in combination with copper, it can improve the atmospheric corrosion resistance of low alloy high strength steel, but reduce its cold stamping performance.

When used in combination with sulfur and manganese, it can improve machinability and increase temper brittleness and cold brittleness sensitivity.

Phosphorus can increase the specific resistance and reduce the coercivity and eddy current loss due to easy coarse grain.

In terms of magnetic induction, the magnetic induction of steel with high phosphorus content under a weak medium magnetic field will increase, and the hot processing of silicon steel containing P is not difficult, but it will make silicon steel cold brittle, with a content of ≯ 0.15% (for example, silicon steel for cold rolling motor contains P = 0.07 ~ 0.10%).

Phosphorus is the strongest element to strengthen ferrite. (the effect of P on recrystallization temperature and grain growth of silicon steel will be 4 ~ 5 times higher than that of the same silicon content.)

S (sulfur)

Sulfur comes from ore and fuel coke for steelmaking.

It is a harmful element in steel. Sulfur exists in steel in the form of iron sulfide (FES).

FES and Fe form compounds with low melting points (985 ℃).

The hot working temperature of steel is generally above 1150 ~ 1200 ℃, so when steel is hot worked, the workpiece cracks due to the premature melting of FES compounds, which is called “hot brittleness”.

Reduce the ductility and toughness of steel and cause cracks during forging and rolling.

Sulfur is also unfavorable to welding performance and reduces corrosion resistance. High quality steel: S < 0.02% ~ 0.03%;

High quality steel: S < 0.03% ~ 0.045%; Ordinary steel: S < 0.055% ~ 0.7%.

Because its chips are brittle and can get a very shiny surface, it can be used to make steel parts with low load and high surface finish (called fast cutting steel).

For example, Cr14 deliberately adds a small amount of sulfur (= 0.2 ~ 0.4%). Some high speed steel tool steels are vulcanized.

K / Na (potassium / sodium)

Potassium/sodium can be used as modifier to spheroidize the carbide clusters in white iron, so that the toughness of white iron (and ledeburite steel) can be increased by more than twice under the condition of maintaining the original hardness;

The microstructure of nodular cast iron is refined and the treatment process of vermicular iron is stabilized;

It is an element that strongly promotes austenitization.

For example, it can reduce the manganese/carbon ratio of austenitic manganese steel from 10:1 ~ 13:1 to 4:1 ~ 5:1.

Ca (calcium)

Adding calcium to steel can refine grains, partially desulfurize, and change the composition, quantity and morphology of non-metallic inclusions.

The effect is basically similar to that of adding rare earth to steel.

Improve the corrosion resistance, wear resistance, high and low-temperature resistance of the steel;

The impact toughness, fatigue strength, plasticity and weldability of the steel are improved;

The cold heading, shock resistance, hardness and contact endurance strength of the steel are increased.

Adding calcium into cast steel greatly improves the fluidity of molten steel;

The surface finish of the casting is improved and the anisotropy of the structure in the casting is eliminated;

Its casting properties, hot crack resistance, mechanical properties and machining properties have increased in varying degrees.

Adding calcium into steel can improve the hydrogen-induced crack resistance and lamellar tear resistance, and prolong the use of equipment and tools life.

Calcium can be used as deoxidizer and inoculant in the master alloy and plays the role of microalloying.

Ti (titanium)

Titanium has strong affinity with nitrogen, oxygen and carbon, and has a stronger affinity with sulfur than iron.

It is a good deoxidizing and degassing agent and an effective element for fixing nitrogen and carbon.

Although titanium is a strong carbide-forming element, it does not combine with other elements to form composite compounds. Titanium carbide has strong adhesion, stability and is not easy to decompose.

It can slowly dissolve into solid solution only when heated to more than 1000 ℃ in steel.

Before dissolution, titanium carbide particles can prevent grain growth.

Because the affinity between titanium and carbon is much greater than that between chromium and carbon, titanium is often used to fix the carbon in stainless steel to eliminate the dilution of chromium at the grain boundary, so as to eliminate or reduce the intergranular corrosion of steel.

Titanium is also one of the strong ferrite forming elements, which strongly increases the A1 and A3 temperatures of steel.

Titanium can improve plasticity and toughness in ordinary low alloy steel.

Because titanium fixes nitrogen and sulfur and forms titanium carbide, the strength of steel is improved.

The plasticity and impact toughness of the steel can be significantly improved by refining the grain and precipitating carbides after normalizing.

The alloy structural steel containing titanium has good mechanical and process properties, and the main disadvantage is that the hardenability is slightly poor.

Titanium with about 5 times carbon content is usually added to high chromium stainless steel, which can not only improve the corrosion resistance (mainly intergranular corrosion resistance) and toughness of the steel;

It can also organize the grain growth tendency of steel at high temperatures and improve the weldability of steel.

V (vanadium)

Vanadium has strong affinity with carbon, ammonia and oxygen to form corresponding stable compounds.

Vanadium mainly exists in the form of carbide 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, the hardenability is increased;

On the contrary, if it exists in the form of carbide, the hardenability is reduced. Vanadium increases the tempering stability of quenched steel and produces secondary hardening effect.

The vanadium content in steel, except for high-speed tool steel, is generally not greater than 0.5%.

Vanadium in ordinary low carbon alloy steel can refine grain, improve the strength, yield ratio and low-temperature characteristics after normalizing, and improve the weldability of steel.

Vanadium is often used in combination with manganese, chromium, molybdenum and tungsten in structural steels because it will reduce hardenability under general heat treatment conditions.

Vanadium in quenched and tempered steel is mainly to improve the strength and yield ratio of steel, refine grains and improve the overheating sensitivity of steel.

In carburized steel, because the grain can be refined, the steel can be quenched directly after carburization without secondary quenching.

Vanadium in spring steel and bearing steel can improve the strength and yield ratio, especially the proportional limit and elastic limit, reduce the decarburization sensitivity during heat treatment, and improve the surface quality. Five chromium bearing steel containing vanadium has high carbonization dispersion and good service performance.

Vanadium refines grains in tool steel, reduces overheating sensitivity, increases tempering stability and wear resistance, and prolongs the service life of tools.

Cr (chromium)

Chromium can increase the hardenability of steel and has the effect of secondary hardening.

It can improve the hardness and wear resistance of carbon steel without making the steel brittle.

When the content exceeds 12%, the steel has good high-temperature oxidation resistance and oxidation corrosion resistance, and also increases the thermal strength of the steel. Chromium is the main alloying element of stainless steel, acid-resistant steel and heat resistant steel.

Chromium can improve the strength and hardness of carbon steel in rolling state, and reduce elongation and reduction of area.

When the chromium content exceeds 15%, the strength and hardness will decrease, and the elongation and reduction of area will increase accordingly.

Parts containing chromium steel are easy to obtain high surface processing quality after grinding.

The main function of chromium in the quenched and tempered structure is to improve the hardenability, so that the steel has better comprehensive mechanical properties after quenching and tempering.

Chromium-containing carbides can also be formed in carburized steel, so as to improve the wear resistance of the material surface.

Spring steel containing chromium is not easy to decarburize during heat treatment.

Chromium can improve the wear resistance, hardness and red hardness of tool steel, and has good tempering stability.

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

Mn (manganese)

Mn can improve the strength of steel: because Mn is relatively cheap and can be infinitely solid dissolved with Fe, it has relatively little effect on plasticity while improving the strength of steel.

Therefore, manganese is widely used as strengthening element in steel.

It can be said that basically, all carbon steels contain Mn.

Our common stamping mild steel, dual phase steel (DP steel), transformation induced plasticity steel (TR steel) and martensitic steel (MS steel) all contain manganese.

Generally, the Mn content in mild steel will not exceed 0.5%;

The Mn content in high-strength steel will increase with the increase of strength level.

For example, the Mn content in martensitic steel can be as high as 3%.

Mn improves the hardenability of steel and improves the hot workability of steel: typical examples are 40Mn and No. 40 steel.

Mn can eliminate the influence of S (sulfur): Mn can form MNS with high melting point with S in iron and steel smelting, so as to weaken and eliminate the adverse effect of S.

However, the content of Mn is also a double-edged sword. The higher the Mn content, the better.

The increase of manganese content will reduce the plasticity and weldability of steel.

Co (cobalt)

Cobalt is mostly used in special steels and alloys.

High-speed steel containing cobalt has high high high-temperature hardness.

Adding molybdenum to maraging steel at the same time can obtain ultra-high hardness and good comprehensive mechanical properties.

In addition, cobalt is also an important alloying element in thermal strength steel and magnetic materials.

Cobalt reduces the hardenability of steel. Therefore, adding carbon steel alone will reduce the comprehensive mechanical properties after quenching and tempering. Cobalt can strengthen ferrite. When added to carbon steel, it can improve the hardness, yield point and tensile strength of steel under annealing or normalizing state, which has an adverse effect on elongation and reduction of area.

The impact toughness also decreases with the increase of cobalt content.

Due to its oxidation resistance, cobalt has been used in heat-resistant steel and heat-resistant alloy.

Cobalt base alloy shows its unique role in gas turbine.

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 not only strongly improves the strength of steel, but also keeps the toughness of iron at a very high level.

The embrittlement temperature is very low. (when nickel is less than 0.3%, its embrittlement temperature is below – 100 ℃. When the amount of Ni increases, it is about 4 ~ 5%, and its embrittlement temperature can be reduced to – 180 ℃.

Therefore, it can improve the strength and plasticity of quenched structural steel at the same time.

Ni = 3.5%, Cr free steel can be air quenched, and Cr steel with Ni = 8% can also be transformed into m-body at a very small cooling rate.

Lattice constants of Ni and γ‐ Iron is similar, so it can form a continuous solid solution.

This is beneficial to improve the hardenability of steel.

Ni can reduce the critical point and increase the stability of austenite, so its quenching temperature can be reduced and its hardenability is good.

Generally, heavy parts with large section 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 heat fatigue resistance and works repeatedly in cold and hot. σ、aK high)

The purpose of using Ni in stainless steel is to make the steel have uniform A-body structure and improve corrosion resistance.

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

Cu (copper)

The prominent role of copper in steel is to improve the atmospheric corrosion resistance of ordinary low alloy steel.

Especially when used in combination with phosphorus, the addition of copper can also improve the strength and yield ratio of steel, but has no adverse effect on the welding performance.

In addition to wear resistance, the corrosion resistance life of rail steel (U-Cu) containing 0.20% ~ 0.50% copper is 2-5 times that of general carbon rail.

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

When the content is low, its effect is similar to that of nickel, but weak.

When the content is high, it is unfavorable to thermal deformation processing, which leads to copper embrittlement.

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

Ga (gallium)

Gallium is an element in the closed γ zone in steel.

Trace gallium is easily dissolved in ferrite to form a substitutional solid solution.

It is not a carbide forming element, nor does it form oxides, nitrides and sulfides.

In the γ+a-phase region, trace gallium is easy to diffuse from austenite to ferrite, and its concentration in ferrite is high.

The effect of Trace Gallium on the mechanical properties of steel is mainly solid solution strengthening.

Gallium has little effect on improving the corrosion resistance of steel.

As (arsenic)

Only a part of arsenic in ore can be removed during sintering, or it can be removed by chlorination roasting.

All arsenic is reduced into pig iron during blast-furnace smelting.

When the arsenic content in steel is more than 0.1%, the brittleness of steel is increased and the welding performance is deteriorated.

The arsenic content in the ore shall be controlled and the arsenic content in the ore shall not exceed 0.07%.

Arsenic has the tendency to increase the yield point σs, tensile strengthσb and reduce the elongation δ5 of low-carbon round steel, and the effect of reducing the normal temperature impact toughness Akv of ordinary carbon round steel is obvious.

Se (selenium)

Selenium can improve the machinability of carbon steel, stainless steel and copper, and the surface of parts is smooth.

MnSe2 is often used as an inhibitor in high magnetic induction oriented silicon steel. MnSe2 beneficial inclusions have stronger inhibition on the growth of primary recrystallized grains than MnS beneficial inclusions, and are more conducive to promoting the preferred growth of secondary recrystallized grains, so as to obtain high orientation (110) [001] texture.

Zr (zirconium)

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

Adding a small amount of zirconium can degass, purify and refine grains, which is conducive to the low temperature performance of steel and improve the stamping performance.

It is commonly used in ultra-high strength steel and nickel base superalloy used in the manufacture of gas engine and ballistic missile structure.

Nb (niobium)

Niobium often coexists with tantalum, and their role in steel is similar.

Niobium and tantalum are partially dissolved into the solid solution to strengthen the solid solution.

The hardenability of steel is significantly improved when austenite is dissolved. However, in the form of carbide and oxide particles, the grains are refined and the hardenability of the steel is reduced.

It can increase the tempering stability of steel and has secondary hardening effect.

Trace niobium can improve the strength of steel without affecting the plasticity or toughness of steel.

Because of the effect of grain refinement, the impact toughness of steel can be improved and its brittle transition temperature can be reduced.

When the content is more than 8 times of carbon, almost all carbon in the steel can be fixed, so that the steel has good hydrogen resistance.

In austenitic steel, the intergranular corrosion of steel by oxidation medium can be prevented.

Due to the role of fixed carbon and precipitation hardening, it can improve the high-temperature properties of thermal strength steel, such as creep strength.

Niobium in common low alloy steel for construction can improve yield strength and impact toughness, reduce brittle transition temperature and improve welding performance.

In carburized and quenched and tempered alloy structural steel, while increasing hardenability.

Improve the toughness and low temperature properties of steel. It can reduce the air hardenability of low-carbon martensitic heat-resistant stainless steel, avoid hardening tempering brittleness and improve creep strength.

Mo (molybdenum)

Molybdenum in steel can improve hardenability and thermal strength, prevent tempering brittleness, increase remanence, coercivity and corrosion resistance in some media.

In quenched and tempered steel, molybdenum can make the parts with large cross-section quenched deeply and thoroughly, improve the reinjection resistance or tempering stability of the steel, and make the parts tempered at higher temperature, so as to more effectively eliminate (or reduce) residual stress and improve plasticity.

In addition to the above functions, molybdenum can also reduce the tendency of carbides to form a continuous network on the grain boundary in the carburized layer, reduce the residual austenite in the carburized layer, and relatively increase the wear resistance of the surface layer.

In forging die steel, molybdenum can also keep the steel with relatively stable hardness and increase the deformation.

Resistance to cracking, abrasion, etc.

In stainless acid resistant steel, molybdenum can further improve the corrosion resistance to organic acids (such as formic acid, acetic acid, oxalic acid, etc.) and hydrogen peroxide, sulfuric acid, sulfite, sulfate, acid dyes, bleaching powder, etc.

Especially due to the addition of molybdenum, the pitting corrosion tendency caused by the presence of chloride ion is prevented. W12Cr4V4Mo high speed steel containing about 1% molybdenum has wear resistance, tempering hardness and red hardness.

Sn (TIN)

Tin has always been a harmful impurity element in steel.

It affects the quality of steel, especially the quality of continuous casting billet, causes thermal brittleness and temper brittleness, cracks and fractures, and affects the welding performance of steel.

It is one of the “five hazards” 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 tin segregation, which hinders grain growth. The higher the tin content, the greater the amount of grain precipitation, which effectively hinders grain growth.

The higher the tin content, the greater the amount of grain precipitation, the stronger the ability to hinder grain growth, the smaller the grain and the less iron loss.

Tin can change the magnetism of silicon steel, improve the favorable texture {100} strength in the finished products of oriented silicon steel, and the magnetic induction intensity increases sigWhen a small amount of tin is contained in cast iron.

It can not only improve its wear resistance, but also affect the fluidity of molten iron.

Pearlite ball milled cast iron has high strength and high wear resistance.

In order to obtain as cast pearlite, tin is added into the alloy liquid during smelting.

Since tin is an element that hinders the spheroidization of graphite, the addition amount should be controlled.

Generally controlled at ≤ 0.1%.nificantly.

Free cutting steel can be divided into the sulfur system, calcium system, lead system and composite free cutting steel.

Tin tends to segregate near inclusions and defects.

Tin can not change the shape of sulfide inclusion in steel, but improve the brittleness and free cutting performance of steel through the segregation of grain boundary and phase boundary.

When the content of tin is > 0.05%, the steel has good machinability.

Sb (antimony)

After adding Sb to high magnetic induction oriented silicon steel, the grain size of primary recrystallization and secondary recrystallization is refined, the secondary recrystallization structure is more perfect and the magnetism is improved.

After cold rolling and decarburization annealing, the texture components {110} < 115} or {110} < 001} which are conducive to the development of secondary recrystallization are strengthened, and the number of secondary crystal corrections is increased.

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

W (tungsten)

In addition to forming carbides in steel, tungsten partially dissolves into iron to form a solid solution.

Its effect is similar to that of molybdenum. According to the mass fraction, the general effect is not as significant as that of molybdenum.

The main sample of tungsten in steel is to increase tempering stability, red hardness, thermal strength and wear resistance due to the formation of carbides.

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

Tungsten forms refractory carbide in high-quality spring steel.

When tempered at higher temperature, it can alleviate the aggregation process of carbide and maintain high temperature strength. Tungsten can also reduce the overheating sensitivity of steel, increase hardenability and improve hardness.

65SiMnWa spring steel has high hardness after hot rolling and air cooling.

The spring steel with 50Mn2 section can be quenched in oil and can be used as an important spring bearing large load, heat resistance (no more than 350 ℃) and impact. 30W4Cr2VA high-strength heat-resistant high-quality spring steel has great hardenability.

After quenching at 1050 ~ 1100 ℃ and tempering at 550 ~ 650 ℃, the tensile strength reaches 1470 ~ 1666pa.

It is mainly used to manufacture springs used at high temperature (no more than 500 ℃).

Because the addition of tungsten can significantly improve the wear resistance and machinability of steel, tungsten is the main element of alloy tool steel.

Pb (lead)

Lead can improve machinability. Lead free cutting steel has good mechanical properties and heat treatment.

Due to environmental pollution and harmful effects in scrap recovery and smelting process, lead has a tendency to be gradually replaced.

It is difficult for lead and iron to form solid solution or compound, and it is easy to segregate at the grain boundary in a spherical shape, which is one of the root causes of brittleness of steel and crack of weld at 200 ~ 480 ℃.

Bi (bismuth)

The cutting performance of free cutting steel can be improved by adding 0.1 ~ 0.4 bismuth.

When bismuth is evenly dispersed in the steel, the fine bismuth melts after contact with the cutting tool, acts as a lubricant, breaks the cutting and avoids overheating, so as to improve the cutting speed.

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

Bi exists in free-cutting steel in three forms: alone in steel matrix, wrapped by sulfide and between steel matrix and sulfide.

In s-bi free cutting steel ingot, the deformation rate of MnS inclusions decreases with the increase of Bi content.

Bi metal in steel can inhibit sulfide deformation during ingot forging.

Adding 0.002-0.005% bismuth into cast iron can improve the casting properties of malleable cast iron, increase the white tendency and shorten the annealing time, and improve the elongation of parts.

Adding 0.005% bismuth to nodular cast iron can improve its seismic resistance and tensile elongation.

It is difficult to add bismuth to steel because bismuth has volatilized at 1500 ℃, so it is difficult to infiltrate bismuth into steel evenly.

At present, Bi Mn composite with melting point of 1050 ℃ is used as additive instead of bismuth, but the utilization rate of bismuth is still only about 20%.

Nippon Steel, POSCO and Kawasaki iron have successively proposed that adding Bi can significantly improve the B8 value of oriented silicon steel.

According to statistics, the total number of inventions of Nippon Steel, JFE and Bi to produce high magnetic induction oriented silicon steel has exceeded 100.

After adding Bi, the magnetic induction reaches more than 1.90t, and the highest reaches 1.99t.

Rare earth

Generally speaking, the rare earth elements refer to the lanthanide elements with atomic numbers from 57 to 71 in the periodic table of elements (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium), plus 21 scandium and 39 yttrium, a total of 17 elements.

They are similar in nature and are not easy to separate. What is not separated is called mixed rare earth, which is relatively cheap.

Rare earth can deoxidize, desulfurize and microalloy in steel, and can also change the deformation ability of rare earth inclusions.

In particular, it can denature brittle Al2O3 to a certain extent, which can improve the fatigue properties of most steel grades.

Rare earth elements, like Ca, Ti, Zr, Mg and Be, are the most effective deforming agents for sulfides.

Adding an appropriate amount of Re into steel can turn oxide and sulfide inclusions into fine dispersed spherical inclusions, so as to eliminate the harm of MNS and other inclusions.

In production practice, sulfur exists in the form of FES and MnS in steel.

When Mn in steel is high, the formation tendency of MnS is high.

Although its melting point is relatively high to avoid thermal embrittlement, MnS can extend into a strip along the processing direction during processing deformation, and the plasticity, toughness and fatigue strength of the steel are significantly reduced. Therefore, it is necessary to add Re to the steel for deformation treatment.

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

The effect of oxidation resistance exceeds that of silicon, aluminum, titanium and other elements.

It can improve the fluidity of steel, reduce non-metallic inclusions and make the steel structure dense and pure.

The main functions of rare earth in steel are purification, modification and alloying.

With the gradual control of oxygen and sulfur content, the traditional purification and modification of molten steel are weakening day by day, which is replaced by more perfect cleaning and purification technology and alloying.

Rare earth elements increase the oxygen resistance of Fe Cr Al alloy, maintain the fine grain of steel at high temperature and improve the high-temperature strength, so the service life of electrothermal alloy is significantly improved.

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