CN117778885A - Rare earth high-strength steel and preparation method and application thereof - Google Patents
Rare earth high-strength steel and preparation method and application thereof Download PDFInfo
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- 239000010959 steel Substances 0.000 title claims abstract description 137
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- 238000002360 preparation method Methods 0.000 title claims abstract description 13
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- 239000011572 manganese Substances 0.000 abstract description 16
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- 229910052758 niobium Inorganic materials 0.000 description 17
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- UNASZPQZIFZUSI-UHFFFAOYSA-N methylidyneniobium Chemical compound [Nb]#C UNASZPQZIFZUSI-UHFFFAOYSA-N 0.000 description 4
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- 229910000742 Microalloyed steel Inorganic materials 0.000 description 2
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Abstract
The invention discloses rare earth high-strength steel, a preparation method and application thereof, and relates to the technical field of steel smelting. By controlling the alloy composition of the high-strength steel, moderate carbon and manganese contents and low P, S content are adopted, cr, nb and Ti metals are added for composite alloying, and the functions of rare earth solid solution strengthening, fine grain strengthening, inclusion denaturation and the like are matched, so that the toughness of the steel is reasonably matched. In addition, in order to obtain higher strength and reduce the production cost of the steel grade, the steel grade adopts a component design with high B content, so that the addition amount of Mn, nb and Ti elements can be reduced, and the steel grade still has good strengthening effect, and further reduces the alloy cost.
Description
Technical Field
The invention relates to the technical field of steel smelting, in particular to rare earth high-strength steel, and a preparation method and application thereof.
Background
With the development of steel equipment towards the directions of light weight, large size, strengthening and toughening, the requirements on the toughness performance of the steel are higher and higher, and after the weight of the steel is reduced, the strength is improved and the toughness is excellent, the production cost of products can be reduced, the effective load of the equipment is improved, and the competitiveness of the products is improved.
The current common method for improving the strength of steel is mainly to increase the content of carbon and manganese elements, but the excessive addition of carbon and manganese also has an influence on the toughness and welding performance of the steel, and some schemes for improving the toughness and welding performance of the steel by adopting precious alloys exist at present, but the addition of precious metals is more, so that the production cost of the steel is increased. Therefore, how to improve toughness and weldability of steel while reducing production cost of steel is one of the problems to be solved in the art.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide rare earth high-strength steel, and a preparation method and application thereof.
The invention is realized in the following way:
in a first aspect, the invention provides a rare earth high-strength steel, comprising the following elements in percentage by weight: c: 0.06-0.15%, mn:1.45 to 1.6 percent, S is less than or equal to 0.015 percent, P is less than or equal to 0.022 percent, si:0.1 to 0.2 percent, cr:0.22 to 0.32 percent of Ti: 0.010-0.018%, nb:0.026 to 0.03 percent, B:0.003 to 0.004 percent, als: 0.010-0.030 percent of rare earth: 0.0042-0.0060%, mo less than or equal to 0.010%, ni less than or equal to 0.020%, as less than or equal to 0.014%, sn less than or equal to 0.0050%, cu less than or equal to 0.05%, V less than or equal to 0.004%, ca less than or equal to 0.0005%, and the balance Fe and unavoidable impurities.
In a second aspect, the present invention provides a method for preparing rare earth high-strength steel according to any one of the preceding embodiments, comprising smelting raw materials to prepare a casting, hot-rolling the casting, and tempering after the hot rolling is completed.
In a third aspect, the present invention provides a rare earth high strength steel according to any one of the preceding embodiments or a use of the preparation method according to any one of the preceding embodiments in the field of iron and steel smelting.
The invention has the following beneficial effects:
the invention provides a rare earth high-strength steel, a preparation method and application thereof, which are characterized in that the alloy composition of the high-strength steel is controlled, moderate carbon and manganese content and low P, S content are adopted, cr, nb and Ti metal are added for composite alloying, and the functions of rare earth solid solution strengthening, fine grain strengthening, inclusion denaturation and the like are matched, so that the toughness of the steel is reasonably matched. In addition, in order to obtain higher strength and reduce the production cost of the steel grade, the steel grade adopts a component design with high B content, so that the addition amount of Mn, nb and Ti elements can be reduced, and the steel grade still has good strengthening effect, and further reduces the alloy cost.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a 100-fold scanning electron microscope image of a rare earth high-strength steel provided in example 1 of the present invention;
FIG. 2 is a 200 Xscanning electron microscope image of the rare earth high strength steel provided in example 1 of the present invention;
fig. 3 is a 500-fold scanning electron microscope image of the rare earth high-strength steel provided in example 1 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The features and capabilities of the present invention are described in further detail below in connection with the examples.
In a first aspect, the invention provides a rare earth high-strength steel, comprising the following elements in percentage by weight: c: 0.06-0.15%, mn:1.45 to 1.6 percent, S is less than or equal to 0.015 percent, P is less than or equal to 0.022 percent, si:0.1 to 0.2 percent, cr:0.22 to 0.32 percent of Ti: 0.010-0.018%, nb:0.026 to 0.03 percent, B:0.003 to 0.004 percent, als: 0.010-0.030 percent of rare earth: 0.0042-0.0060%, mo less than or equal to 0.010%, ni less than or equal to 0.020%, as less than or equal to 0.014%, sn less than or equal to 0.0050%, cu less than or equal to 0.05%, V less than or equal to 0.004%, ca less than or equal to 0.0005%, and the balance Fe and unavoidable impurities.
By controlling the alloy composition of the high-strength steel, moderate carbon and manganese contents and low P, S content are adopted, cr, nb and Ti metals are added for composite alloying, and the functions of rare earth solid solution strengthening, fine grain strengthening, inclusion denaturation and the like are matched, so that the toughness of the steel is reasonably matched. In addition, in order to obtain higher strength and reduce the production cost of the steel grade, the steel grade adopts a component design with high B content, so that the addition amount of Mn, nb and Ti elements can be reduced, and the steel grade still has good strengthening effect, and further reduces the alloy cost.
The main elements have the following functions:
carbon: the carbon content is controlled between 0.06% and 0.15%, the carbon content in the steel is increased, the strength and the hardness are increased, but the plasticity, the impact toughness and the welding performance are reduced, and the strength is obtained by adopting the moderate carbon content, and meanwhile, the steel has good toughness and welding performance.
Silicon: the silicon content is controlled between 0.1% and 0.2%, which can strengthen ferrite, improve the strength and hardness of steel, reduce the critical cooling speed of steel, improve the hardenability of steel, and improve the hot cracking tendency when the silicon content is less than or equal to 0.40%, and the welding performance of steel is deteriorated when the silicon content is too high.
Manganese: the manganese content is controlled between 1.45 percent and 1.6 percent, and the manganese content with high proper amount can obtain higher strength, hardness and wear resistance, reduce the critical cooling speed of steel, improve the hardenability of steel, improve the hot processing performance of steel, reduce the size of precipitated carbide and promote the precipitation strengthening effect. However, the manganese content is too high, so that the welding performance is reduced, the corrosion resistance of the steel is weakened, the tempering brittleness phenomenon is obvious, and the growth of crystal grains is promoted, so that the inventor controls the manganese content within the range, and meanwhile, refined crystal grain elements such as niobium, titanium, aluminum and the like are added, so that the structure of the steel is effectively controlled.
Chromium: the chromium content is controlled between 0.22 percent and 0.32 percent, has great strengthening effect on low alloy steel, can improve the strength, the hardness and the wear resistance, reduce the critical cooling speed of the steel and improve the hardenability of the steel; too high a chromium content increases the brittle transition temperature of the steel and increases the temper embrittlement of the steel.
Niobium: the manganese content is controlled between 0.026% and 0.03%, niobium, carbon, nitrogen and oxygen have extremely strong binding force and form corresponding stable compounds with the niobium, so that the steel has the functions of refining grains and strengthening precipitation, reduces the overheat sensitivity and tempering brittleness of the steel, is beneficial to improving the low-temperature impact toughness, can improve the recrystallization temperature, can further refine the grains through controlled rolling and cooling, improves the toughness reduction caused by precipitation strengthening and improves the welding performance, and thereby the steel plate has the comprehensive performance of high strength and high toughness.
Titanium: the titanium content is controlled between 0.01% and 0.018%, titanium is a low-cost alloying element, the titanium can compact the internal structure of steel, refine grains, and can generate strong precipitation strengthening effect by separating titanium carbide particles out of ferrite after interphase or phase transformation, thereby greatly improving strength, effectively reducing ageing sensitivity and cold brittleness and improving welding performance.
The alloy elements such as niobium and titanium are beneficial to improving the solid solution quantity of the rare earth elements in steel, the solid solution rare earth is easy to gather at the grain boundary, the recrystallization process can be obviously delayed, the recrystallized grains can be refined, meanwhile, the rare earth can effectively increase the dissolution of the alloy elements such as niobium and titanium in steel, and the alloy precipitation phase dispersion precipitation of the niobium and titanium can be promoted by controlling cooling, so that the strengthening effect of the alloy elements is improved.
Boron: boron is easy to adsorb on austenite grain boundaries and gather at the grain boundaries, so that the transformation from austenite to ferrite can be effectively delayed, the solubility of alloy elements is improved, the aging effect is delayed, and the rolling can be further strengthened due to the aging effect; the segregation of boron in the grain boundary can reduce the diffusion coefficient of alloy elements such as niobium, titanium and the like in the grain boundary, increase the acting force of the niobium, the titanium and the like on the grain boundary, reduce the migration speed of the interface and the recrystallization driving force, refine grains and improve the strength.
Aluminum: the aluminum content should be controlled between 0.010% and 0.030%, proper amount of aluminum is added into the steel, so that grains can be refined, impact toughness is improved, the aluminum also has oxidation resistance and corrosion resistance, and the hot workability, welding performance and cutting workability of the steel are adversely affected by the excessive content.
Rare earth: the rare earth content should be controlled between 0.0042% and 0.0060%, the rare earth element and oxygen and sulfur are easy to generate oxide, sulfide, sulfur oxide and the like with high melting point and small plasticity at high temperature, and the proper amount of rare earth is added to fully exert the functions of rare earth desulfurization and deoxidation and inclusion denaturation, refine the crystal grain of steel, improve the cast structure, improve the normal and low temperature toughness and fracture property of steel, reduce the hot brittleness of steel and improve the hot workability and welding property.
The rare earth can purify molten steel, so that carbides such as niobium, titanium and the like are refined and separated out and dispersed, the strengthening effect of alloy elements is fully exerted, meanwhile, the deterioration effect of the rare earth on inclusions can be effectively reduced, and the plasticity and toughness are further improved. Rare earth dissolved in the steel is enriched in the grain boundary, so that segregation of impurity elements in the grain boundary is reduced, the grain boundary can be reinforced, the harm of segregation elements such as phosphorus, sulfur and the like is effectively improved, and the structure and performance of the steel are further improved.
In an alternative embodiment, the rare earth includes La and/or Ce.
Preferably, the addition amount of La is 30 to 40% and the addition amount of Ce is 60 to 70%. More preferably, the addition amount of La is 35% and the addition amount of Ce is 65%.
In an alternative embodiment, the content of C, N, cr, nb, ti and B in the elemental composition has the following relationship: ti/N is more than or equal to 2 and less than or equal to 5; (Ti+Nb)/N is more than or equal to 6 and less than or equal to 12; cr/C is more than or equal to 1.5 and less than or equal to 2.3. By controlling the content ratio of the elements in the above range, the solid solution temperature of titanium is lower, tiny and stable TiN is easy to form, austenite grains can be effectively prevented from growing, grains and structures can be refined, surplus titanium can inhibit the recrystallization process in the form of solid solution titanium or TiC, the functions of precipitation and precipitation strengthening are achieved, a proper amount of titanium can also promote the formation of niobium carbide, the niobium carbide is pinned to a grain boundary during rolling to prevent the growth of grains, the pinning of dislocation and the migration of subgrain boundary are prevented in the recrystallization process, the recrystallization time is greatly prolonged, recrystallization nucleation is effectively inhibited, more niobium in a solid solution state can be obtained, and the precipitation of solid solution niobium can further produce strengthening effect; chromium has great strengthening effect on microalloy steel, can reduce the critical cooling speed of the steel, expand the cooling speed range, refine the structure, improve the hardenability of the steel, and lead the steel to have better comprehensive mechanical properties after quenching and tempering.
In an alternative embodiment, the carbon equivalent Ceq is less than or equal to 0.45% and Pcm is less than or equal to 0.25%. The formula for calculating the carbon equivalent Ceq is as follows: ceq=c+mn/6+ (cr+v+mo)/5+ (cu+ni)/15. The calculation formula of Pcm is as follows: pcm=c+si/30+mn/20+cu/20+ni/60+cr/20+mo/15+v/10+5b. Controlling the carbon equivalent within the above range can avoid adversely affecting the toughness and welding performance of the steel.
In a second aspect, the present invention provides a method for preparing rare earth high-strength steel according to any one of the preceding embodiments, comprising smelting raw materials to prepare a casting, hot-rolling the casting, and tempering after the hot rolling is completed.
In an alternative embodiment, hot rolling includes heating the casting in a furnace and then rolling the casting, and cooling the rolled product after each rolling operation. The alloy structure of the steel grade reaches the phase transition temperature by controlling the hot rolling temperature, and then the appearance of the alloy structure is fixed by controlling the cooling step, so that the steel strength is improved, and the production cost of the steel is reduced.
Preferably, when it is desired to obtain a steel product having a relatively thin thickness, the number of hot rolling is twice, and the cast product is first hot rolled to a product thickness of 40 to 45mm and then hot rolled to a product thickness of 10 to 12mm.
Preferably, the heating rate of the heating furnace for the first hot rolling is 5-10 ℃/min, the heating temperature of the heating furnace is 1200-1250 ℃, the heat preservation time is 90-120 min, the initial rolling temperature is 1100-1150 ℃, and the final rolling temperature is 850-900 ℃. The rolling pass is 5-7, the rolling reduction rate of the first two passes is 20-30%, and the rolling reduction rate of the remaining passes is 15-25%. By controlling the hot rolling parameters within the above-described ranges, a high-strength steel having higher strength can be obtained.
Preferably, the heating rate of the heating furnace for the second hot rolling is 8-12 ℃/min, the heating temperature of the heating furnace is 1200-1250 ℃, the heat preservation time is 60-90 min, the initial rolling temperature is 1100-1130 ℃, and the final rolling temperature is 870-900 ℃. The rolling pass is 6-8, the rolling reduction rate of the first two passes is 20-25%, and the rolling reduction rate of the remaining passes is 15-20%.
In an alternative embodiment, the cooling medium in the first hot rolling process is air, the temperature of the rolled piece entering the cooling section after the hot rolling is 1050-1060 ℃, the temperature of the rolled piece exiting the cooling section is 1000-1050 ℃, and the speed of a roller way of the cooling section is 0.1-0.3 m/s. The first hot rolling mainly aims at reducing the thickness of the steel, and simultaneously makes alloy materials in the steel fully solid-solved so as to achieve the effects of improving the strength of the steel and refining grains in the steel.
In an alternative embodiment, the cooling medium in the second hot rolling process is water, the cooling mode is laminar cooling, the temperature of the rolled piece entering the cooling section after the hot rolling is 780-990 ℃, the speed of a roller way of the cooling section is 0.2-0.4 m/s, the cooling speed is 35-45 ℃/s, the final cooling temperature is 120-150 ℃, the water temperature of the cooling section is 22-26 ℃, and the water pressure is 50-60 KPa. The rolled piece obtained by the second hot rolling can be directly used for subsequent treatment, so that the temperature is controlled by adopting a water cooling mode after the second hot rolling, the grain refinement of the steel structure after the hot rolling is finished can be ensured, the phase transformation is complete, and the strength of the steel is high.
In an alternative embodiment, tempering is to obtain comprehensive mechanical properties of good strength, plasticity and toughness, so that the tempering temperature is 600-650 ℃ and the heat preservation time is 40-60 min.
In an alternative embodiment, the method of smelting the feedstock includes smelting using a vacuum induction furnace. In other embodiments, the smelting may be performed by a converter, an LF furnace, an RH furnace, or other equipment.
Preferably, the parameters of vacuum induction furnace smelting include: the pressure of compressed air is 0.4-0.5 MPa, the pressure of argon is 1.1-1.2 MPa, and the pressure of cooling water is 0.2-0.3 MPa; the opening vacuum degree of the secondary vacuum pump is less than or equal to 450Pa, and the ultimate vacuum degree of the secondary vacuum pump is less than or equal to 4Pa; the medium frequency power supply has 15-16 KW of power transmission, 50-60 KW of melting power and 100-110 KW of melting power; the temperature of the added alloy molten steel is 1590-1600 ℃ and the temperature of the cast steel is 1560-1570 ℃.
Preferably, the addition sequence of the raw materials is as follows: chromium, niobium and scrap steel are added into a crucible together, aluminum particles, ferrosilicon, manganese metal, ferrotitanium, ferroboron and rare earth are added from a storage bin, aluminum particles are added after the scrap steel begins to melt, protective gas is filled into a furnace after the scrap steel is melted, the pressure is 10000-11000 Pa, ferrosilicon, ferrotitanium, manganese metal, ferroboron and rare earth are sequentially added, and each alloy is added at intervals of 1-2 min.
In a third aspect, the present invention provides a rare earth high strength steel according to any one of the preceding embodiments or a use of the preparation method according to any one of the preceding embodiments in the field of iron and steel smelting.
Example 1
The embodiment provides rare earth high-strength steel, which comprises the following elements in percentage by weight: c:0.13%, mn:1.47%, S:0.013%, P:0.021%, si:0.3%, cr:0.34%, ti:0.018%, nb:0.026%, B:0.0031%, als:0.024%, rare earth: 0.0042%, mo:0.010%, ni:0.020%, as:0.012%, sn:0.0028%, cu:0.03%, V:0.003 percent of Ca is less than or equal to 0.0005 percent, and the balance is Fe and unavoidable impurities.
Wherein, the addition amount of rare earth La is 35 percent and the addition amount of Ce is 65 percent.
In this example, the carbon equivalent ceq=0.448% and pcm=0.248% of the rare earth high-strength steel.
The embodiment also provides a preparation method of the rare earth high-strength steel, which comprises the following steps:
s01, vacuum induction furnace steelmaking
Adding chromium, niobium and scrap steel into a crucible together, adding aluminum particles, ferrosilicon, manganese metal, ferrotitanium, ferroboron and rare earth from a storage bin, adding aluminum particles after the scrap steel begins to melt, charging protective gas into a furnace after the scrap steel is melted, sequentially adding ferrosilicon, ferrotitanium, manganese metal, ferroboron and rare earth at the pressure of 10080pa, and pouring steel 1.5min after each alloy is added.
The pressure of compressed air is controlled to be 0.43MPa, the pressure of argon is controlled to be 1.2MPa, the pressure of cooling water is controlled to be 0.22MPa, and the oil pressure of a hydraulic station is controlled to be 6MPa in the steelmaking process; the vacuum degree of the secondary vacuum pump is 445Pa, and the ultimate vacuum degree of the secondary vacuum pump is 3Pa; the medium-frequency power supply has 15.6KW of power transmission, 50.4KW of melting power and 100KW of melting power; adding alloy molten steel at 1590 ℃ and casting steel at 1560 ℃ and then casting steel to obtain the casting.
S02, first hot rolling
And (3) placing the casting prepared in the step S01 into a heating furnace for primary hot rolling, and rolling the rolled piece to a thickness of 40mm. The casting was heated to 1230 c in a furnace at a heating rate of 6 c/min, held for 100min, and then hot rolled was started. The initial rolling temperature is 1100 ℃, and the final rolling temperature is 870 ℃; the rolling pass is 5, the rolling reduction rate of the first two passes is 24%, and the rolling reduction rate of the remaining passes is 20%.
And after the first hot rolling is finished, feeding the hot rolled product into a cooling section for air cooling, wherein the temperature of the rolled product entering the cooling section after the hot rolling is finished is 1054 ℃, the temperature of the rolled product exiting the cooling section is 1016 ℃, and the speed of a roller way of the cooling section is 0.2m/s.
S03, second hot rolling
And (3) feeding the rolled piece obtained in the step S02 into a heating furnace again for carrying out secondary hot rolling, and rolling the rolled piece to a thickness of 12mm. The casting was heated to 1230 c in a furnace at a heating rate of 8 c/min, held for 60min, and then hot rolled was started. The initial rolling temperature is 1078 ℃ and the final rolling temperature is 876 ℃; the rolling pass is 6, the rolling reduction rate of the first two passes is 24.5%, and the rolling reduction rate of the remaining passes is 18%.
And after the second hot rolling is finished, feeding the hot rolled steel into a cooling section for laminar cooling, wherein the cooling speed is 45 ℃/s, and the final cooling temperature is 125 ℃. The temperature of the rolled piece entering the cooling section after the hot rolling is 816 ℃, the speed of a roller way of the cooling section is 0.3m/s, the water temperature of the cooling section is 23.9 ℃, and the water pressure is 57.6KPa.
S04, tempering
Tempering the rolled piece with the thickness of 10mm obtained by cooling in the step S03, wherein the tempering temperature is 620 ℃, and the temperature is kept for 60 minutes.
The rare earth high-strength steel provided in example 1 was subjected to scanning electron microscopy to obtain the results shown in fig. 1 to 3. The structure of the rare earth high-strength steel is amplified in sequence according to fig. 1 to 3, and the structure in the rare earth high-strength steel is tempered sorbite.
Example 2
The embodiment provides rare earth high-strength steel, which comprises the following elements in percentage by weight: c:0.12%, mn:1.5%, S:0.013%, P:0.021%, si:0.3%, cr:0.30%, ti:0.020%, nb:0.025%, B:0.0030%, als:0.025%, rare earth: 0.0045%, mo:0.010%, ni:0.020%, as:0.012%, sn:0.0028%, cu:0.03%, V:0.003 percent of Ca is less than or equal to 0.0005 percent, and the balance is Fe and unavoidable impurities.
Wherein, the addition amount of rare earth La is 35 percent and the addition amount of Ce is 65 percent.
In the embodiment, the carbon equivalent Ceq=0.436% and Pcm is less than or equal to 0.238% of the rare earth high-strength steel.
The rare earth high-strength steel provided in this example was prepared in the same manner as in example 1.
Example 3
The present example provides a rare earth high strength steel having the same elemental composition as example 1, the preparation method being similar to example 1, except that: the cooling rate was 35 ℃/s.
Comparative example 1
The comparative example provides a high-strength steel, which is prepared by the same method as in example 1, and comprises the following elements in parts by weight: c:0.11%, mn:1.53%, S:0.004%, P:0.022%, si:0.29%, cr:0.07%, ti:0.012%, nb:0.031%, B:0.0002%, als:0.024%, mo:0.011%, ni:0.02%, as:0.0125%, sn:0.0055%, cu:0.03%, V:0.036%, ca:0.0011%, and the balance of Fe and unavoidable impurities.
Comparative example 2
This comparative example provides a rare earth high-strength steel having the same elemental composition as in example 1, the preparation method differing from example 1 in that: the cooling speed of laminar cooling of the rolled piece is 20-30 ℃/s.
Test example 1
The rare earth high-strength steels prepared in examples 1 to 3 and comparative examples 1 to 2 were subjected to tensile test and impact test, the tensile test method was GB/T228.1, the impact test method was GB/T229, and the results shown in Table 1 were obtained.
TABLE 1 tensile Property results of rare-earth high-strength steels
As shown in Table 1, the overall performance of the rare earth high-strength steel is superior to that of the conventional high-strength steel, and the main characteristic is that Cr, nb, ti, B and rare earth composite strengthening effect is fully exerted, and meanwhile, rare earth has the effects of modifying inclusions and purifying molten steel, so that the strength of the steel is improved, and meanwhile, the comprehensive performances such as plasticity, toughness and the like can be improved.
The rare earth high-strength steel provided by the invention, and the preparation method and application thereof have at least the following advantages:
by controlling the alloy composition of the high-strength steel, moderate carbon and manganese contents and low P, S content are adopted, cr, nb and Ti metals are added for composite alloying, and the functions of rare earth solid solution strengthening, fine grain strengthening, inclusion denaturation and the like are matched, so that the toughness of the steel is reasonably matched. In addition, in order to obtain higher strength and reduce the production cost of the steel grade, the steel grade adopts a component design with high B content, so that the addition amount of Mn, nb and Ti elements can be reduced, and the steel grade still has good strengthening effect, and further reduces the alloy cost.
The solid solution temperature of titanium is lower, small and stable TiN is easy to form, austenite grains can be effectively prevented from growing, grains and structures can be thinned, the surplus titanium can inhibit the recrystallization process in the form of solid solution titanium or TiC, the functions of precipitation and precipitation strengthening are achieved, a proper amount of titanium can also promote the formation of niobium carbide, the niobium carbide is pinned to grain boundaries during rolling to prevent the growth of the grains, the pinning of dislocation and the migration of subgrain boundaries are prevented during the recrystallization process, the recrystallization time is greatly prolonged, the recrystallization nucleation is effectively inhibited, more niobium in a solid solution state can be obtained, and the precipitation of the solid solution niobium can further produce the strengthening function; chromium has great strengthening effect on microalloy steel, can reduce the critical cooling speed of the steel, expand the cooling speed range, refine the structure, improve the hardenability of the steel, and lead the steel to have better comprehensive mechanical properties after quenching and tempering.
The rare earth can purify molten steel, so that carbides such as niobium, titanium and the like are refined and separated out and dispersed, the strengthening effect of alloy elements is fully exerted, meanwhile, the deterioration effect of the rare earth on inclusions can be effectively reduced, and the plasticity and toughness are further improved. Rare earth dissolved in the steel is enriched in the grain boundary, so that segregation of impurity elements in the grain boundary is reduced, the grain boundary can be reinforced, the harm of segregation elements such as phosphorus, sulfur and the like is effectively improved, and the structure and performance of the steel are further improved.
The rare earth high-strength steel provided by the invention has good comprehensive mechanical property, cold and hot workability and welding property after being rolled, and can be used for ships, bridges, vehicles, engineering, other welding structural members and the like.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The rare earth high-strength steel is characterized by comprising the following elements in percentage by weight: c: 0.06-0.15%, mn:1.45 to 1.6 percent, S is less than or equal to 0.015 percent, P is less than or equal to 0.022 percent, si:0.1 to 0.2 percent, cr:0.22 to 0.32 percent of Ti: 0.010-0.018%, nb:0.026 to 0.03 percent, B:0.003 to 0.004 percent, als: 0.010-0.030 percent of rare earth: 0.0042-0.0060%, mo less than or equal to 0.010%, ni less than or equal to 0.020%, as less than or equal to 0.014%, sn less than or equal to 0.0050%, cu less than or equal to 0.05%, V less than or equal to 0.004%, ca less than or equal to 0.0005%, and the balance Fe and unavoidable impurities.
2. The rare earth high strength steel according to claim 1, wherein the rare earth comprises La and/or Ce;
preferably, the addition amount of La is 30-40% and the addition amount of Ce is 60-70%.
3. The rare earth high-strength steel according to claim 1 or 2, wherein the contents of C, N, cr, nb, ti and B in the elemental composition have the following relationship: ti/N is more than or equal to 2 and less than or equal to 5; (Ti+Nb)/N is more than or equal to 6 and less than or equal to 12; cr/C is more than or equal to 1.5 and less than or equal to 2.3.
4. A rare earth high-strength steel according to claim 1 or 2, characterized in that the carbon equivalent Ceq is equal to or less than 0.45% and Pcm is equal to or less than 0.25%.
5. A method for producing a rare earth high-strength steel according to any one of claims 1 to 4, comprising producing a casting after smelting a raw material, hot-rolling the casting, and tempering after the completion of the hot rolling.
6. The method according to claim 5, wherein the hot rolling comprises heating the cast product in a heating furnace and then rolling the cast product, and cooling the rolled product after each rolling;
preferably, the number of hot rolling is two, the casting is firstly hot rolled to the thickness of 35-40 mm of rolled piece, and then hot rolled to the thickness of 10-12 mm of rolled piece;
preferably, the heating rate of the heating furnace for the first hot rolling is 5-10 ℃/min, the heating temperature of the heating furnace is 1200-1250 ℃, the heat preservation time is 90-120 min, the initial rolling temperature is 1100-1150 ℃, and the final rolling temperature is 850-900 ℃;
preferably, the heating rate of the heating furnace for the second hot rolling is 8-12 ℃/min, the heating temperature of the heating furnace is 1200-1250 ℃, the heat preservation time is 60-90 min, the initial rolling temperature is 1100-1130 ℃, and the final rolling temperature is 870-900 ℃.
7. The method according to claim 6, wherein the cooling medium in the first hot rolling process is air, the temperature of the rolled piece entering the cooling section after the hot rolling is 1050-1060 ℃, the temperature of the rolled piece exiting the cooling section is 1000-1050 ℃, and the speed of the roller way of the cooling section is 0.1-0.3 m/s.
8. The method according to claim 6, wherein the cooling medium in the second hot rolling process is water, the cooling mode is laminar cooling, the temperature of the rolled product entering the cooling section after the hot rolling is 780-990 ℃, the speed of the roller way of the cooling section is 0.2-0.4 m/s, the cooling speed is 35-45 ℃/s, the final cooling temperature is 120-150 ℃, the water temperature of the cooling section is 22-26 ℃ and the water pressure is 50-60 KPa.
9. The method according to claim 5, wherein the tempering temperature is 600-650 ℃ and the holding time is 40-60 min.
10. Use of the rare earth high-strength steel according to any one of claims 1 to 4 or the preparation method according to any one of claims 5 to 9 in the field of iron and steel smelting.
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