CN116770175A - High-strength steel with high delayed fracture resistance and energy-saving preparation method and application thereof - Google Patents
High-strength steel with high delayed fracture resistance and energy-saving preparation method and application thereof Download PDFInfo
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- 238000004381 surface treatment Methods 0.000 claims description 8
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Abstract
The invention discloses high-strength steel with high delayed fracture resistance, an energy-saving preparation method and application thereof, wherein the high-strength steel comprises the following chemical components in percentage by mass: 0.2 to 0.4% of C, 1.2 to 2.0% of Si, 0.1 to 0.3% of Mn, 0.6 to 1.2% of Cr, 0.8 to 1.5% of Ni, 0.5 to 1.0% of Al, 0.8 to 1.2% of Mo, 0.3 to 0.5% of V, 0.06 to 0.10% of Nb, 0.2 to 0.5% of Cu, 0.02 to 0.05% of B, 0.02 to 0.05% of N, 0 to 0.015% of P, 0 to 0.010% of S, 0 to 0.00015% of H, 0 to 0.0015% of O, and the balance of Fe and impurities. The invention can separate out carbide in different heat treatment process stages in multiple scales to form microstructure composed of bainite, residual austenite and carbide, which is favorable for forming hydrogen traps, enhancing toughness, improving delayed fracture resistance, shortening process flow, saving energy, reducing emission and reducing cost.
Description
Technical Field
The invention belongs to the technical field of steel manufacturing, and relates to high-strength steel with high delayed fracture resistance, and an energy-saving preparation method and application thereof.
Background
In recent years, the manufacturing industry in China achieves unprecedented achievement, the industrial system is more sound, the industrial chain is more complete, and some high-end equipment such as advanced rail transit equipment, new energy automobiles, ocean engineering equipment, high-technology ships, aerospace equipment and the like make great progress. Because the working environment of the high-end equipment is more severe and the performance requirement is more strict, a large number of ultrahigh-strength steel parts are used.
However, the challenges facing the use of ultra-high strength steel parts are delayed fracture problems, particularly when the strength of the steel is increased above 1200MPa, which severely limits the use of ultra-high strength steel parts. In addition, aiming at the problems of carbon emission of ultra-high strength steel parts, namely component design and subsequent processing and manufacturing, the steel products in China mainly adopt a long-flow converter steelmaking production mode, the carbon emission of ton steel is seriously out of standard, and heat treatment processes such as quenching and tempering, annealing and the like are repeatedly used in the downstream industrial chain manufacturing process, so that energy sources such as electric power and water environment pollution are seriously consumed. Taking the application of ultra-high strength steel in the fastener industry as an example, the ultra-high strength fastener with the grade of more than 12.9 contains V, mo, ni, cr and other elements, and the main effects are that the hardenability is improved, the tempering stability is enhanced and the mechanical property is improved. The fastener manufacturing process comprises the following steps: raw material, spheroidizing annealing, drawing, cold heading head, machining (thread rolling), quenching and tempering, and surface treatment. Obviously, the present ultra-high strength steel products have the following characteristics in the manufacturing process: alloy content in raw materials is high, and cost is high; the raw material strength is high, the process comprises more than one spheroidizing annealing treatment, and the processing cost is high; the traditional quenching and tempering process causes unstable precipitation of the second-phase carbide, so that grains are coarse, and the final delayed fracture resistance is difficult to meet the requirement of the use environment.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides high-strength steel with high resistance to delayed fracture, and an energy-saving preparation method and application thereof, and solves the technical problems of low delayed fracture resistance, emission reduction and carbon reduction of an ultrahigh-strength steel wire product.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the high-strength steel with high resistance to delayed fracture comprises the following chemical components in percentage by mass: 0.2 to 0.4 percent of C, 1.2 to 2.0 percent of Si, 0.1 to 0.3 percent of Mn, 0.6 to 1.2 percent of Cr, 0.8 to 1.5 percent of Ni, 0.5 to 1.0 percent of Al, 0.8 to 1.2 percent of Mo, 0.3 to 0.5 percent of V, 0.06 to 0.10 percent of Nb, 0.2 to 0.5 percent of Cu, 0.02 to 0.05 percent of B, 0.02 to 0.05 percent of N, 0 to 0.015 percent of P, 0 to 0.010 percent of S, 0 to 0.00015 percent of H, 0 to 0.0015 percent of O, and the balance of Fe and impurities.
Optionally, the metallographic structure of the high-strength steel comprises pearlite, bainite and residual austenite, and carbonitrides are dispersed in a matrix of the high-strength steel.
Optionally, the grain size of the high-strength steel is greater than 8 grades, the volume fraction of the bainite is 90-95%, the volume fraction of the retained austenite is 3-5%, and the volume fraction of the carbonitride is 1-3%.
Alternatively, high strength steel tensile Strength R m Not less than 1510MPa, yield strength Rp 0.2 More than or equal to 1410MPa, the area shrinkage A more than or equal to 50%, the elongation epsilon more than or equal to 13% and the impact toughness K V More than or equal to 38J, and the transverse load delay fracture strength ratio is more than 0.73.
An energy-saving preparation method of high-strength steel with high resistance to delayed fracture comprises the steps of drawing, spheroidizing annealing, cold deformation, preliminary heat treatment, thermal refining and surface treatment on a workpiece to be processed in sequence.
Optionally, in the drawing process, when the first-pass drawing deformation is greater than 25% and the total drawing deformation is greater than 30%, sequentially performing intermediate spheroidizing annealing and secondary drawing on the workpiece to be machined after drawing and before spheroidizing annealing.
Optionally, the spheroidization rate of the workpiece to be machined after spheroidization annealing and before cold deformation is more than 90%.
Optionally, the surface coating passivation film obtained by the surface treatment contains Al.
The application of high-strength steel with high resistance to delayed fracture in long-axis parts.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides high-strength steel with high resistance to delayed fracture, and an energy-saving preparation method and application thereof, wherein the high-strength steel contains B, N, cu and high content of Si, al and other alloy chemical components, and a hot rolled wire rod obtained through reasonable smelting and rolling processes has excellent strong plasticity, so that a spheroidizing annealing treatment process before cold-drawing is avoided, the heating temperature and the heat preservation time of spheroidizing annealing treatment are reduced, and carbon reduction, efficiency improvement and cost reduction are realized while annealing procedures are saved;
by rational heat treatment techniques, a tissue is formed: the bainite, residual austenite and carbonitride have higher strength and high toughness, and the residual austenite film can reduce the diffusion rate of hydrogen atoms in steel, and the dispersed carbonitride serves as a hydrogen trap, so that the high strength and better delayed fracture resistance can be obtained;
the grain size of the ultra-high strength steel wire rod product is more than 8 grades, and the tensile strength R is at room temperature m Not less than 1510MPa, yield strength Rp 0.2 Not less than 1410MPa, area shrinkage A not less than 50%, elongation epsilon not less than 13% and impact toughness K V More than or equal to 38J, and the delayed fracture strength ratio is more than 0.73.
Drawings
FIG. 1 is a microstructure diagram of a high strength steel ball annealed with high resistance to delayed fracture according to an embodiment of the present invention;
FIG. 2 is a schematic view showing grain size of a high strength steel with high resistance to delayed fracture according to an embodiment of the present invention;
FIG. 3 is a microstructure of a high strength steel with high resistance to delayed fracture according to an embodiment of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical aspects of the present invention, and are not intended to limit the scope of the present invention.
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and such range or value should be understood to encompass values approaching those range or value. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, as used in the specification and the appended claims, are to be understood as being modified in all instances by the term "about". Furthermore, all ranges disclosed herein are inclusive of the endpoints and independently combinable.
The high-strength steel with high resistance to delayed fracture comprises the following chemical components in percentage by mass: 0.2 to 0.4 percent of C, 1.2 to 2.0 percent of Si, 0.1 to 0.3 percent of Mn, 0.6 to 1.2 percent of Cr, 0.8 to 1.5 percent of Ni, 0.5 to 1.0 percent of Al, 0.8 to 1.2 percent of Mo, 0.3 to 0.5 percent of V, 0.06 to 0.10 percent of Nb, 0.2 to 0.5 percent of Cu, 0.02 to 0.05 percent of B, 0.02 to 0.05 percent of N, 0 to 0.015 percent of P, 0 to 0.010 percent of S, 0 to 0.00015 percent of H, 0 to 0.0015 percent of O, and the balance of Fe and impurities.
The metallographic structure of the high-strength steel comprises pearlite, bainite and residual austenite, and carbonitride is dispersed in a matrix of the high-strength steel. The grain size of the high-strength steel is greater than 8 grades, the volume fraction of the bainite is 90-95%, the volume fraction of the retained austenite is 3-5%, and the volume fraction of the carbonitride is 1-3%. Tensile strength R of high-strength steel m Not less than 1510MPa, yield strength Rp 0.2 More than or equal to 1410MPa, the area shrinkage A more than or equal to 50%, the elongation epsilon more than or equal to 13% and the impact toughness K V More than or equal to 38J, and the transverse load delay fracture strength ratio is more than 0.73.
An energy-saving preparation method of high-strength steel with high resistance to delayed fracture comprises the following steps:
s1, directly performing cold-working drawing deformation on a hot rolled wire rod, performing intermediate spheroidizing annealing when the total cold-working drawing deformation is more than 30%, keeping the temperature for 0.5-8 h at 660-690 ℃, then cooling to 610-640 ℃ in a furnace, keeping the temperature for 3-6 h, cooling to 480-530 ℃ in the furnace at 10-15 ℃/h, cooling to room temperature, performing cold-working drawing after intermediate spheroidizing annealing, performing spheroidizing annealing after the cold-working drawing deformation is less than 30%, and finally performing spheroidizing annealing to obtain a wire rod; when the cold-working drawing deformation of the hot rolled wire rod is less than 30%, intermediate spheroidizing annealing and drawing treatment are not needed, and spheroidizing annealing is carried out after cold-working drawing deformation to obtain the wire rod; the spheroidizing annealing heating temperature is 600-640 ℃, the heat preservation is carried out for 0.5-3 h, then the furnace cooling is carried out to 560-590 ℃, the heat preservation is carried out for 0.5-3 h, and then the furnace cooling is carried out to 430-460 ℃ by 30-35 ℃/h for air cooling; the spheroidization rate of the wire rod is more than 90%; the cold drawing deformation of the first pass of drawing is more than 25%; the diameter of the hot rolled wire rod is 1 cm-4 cm, and the diameter of the wire rod is 0.5-3.4 cm;
s2, performing cold deformation treatment on the wire rod, wherein the cold deformation treatment comprises cold heading, cold bending, cold rolling, thread rolling and thread rolling processes;
s3, carrying out preliminary heat treatment on the wire rod subjected to cold deformation treatment, heating at 1050-1200 ℃, preserving heat for 30-50 min to ensure complete austenitization of a tissue and complete dissolution of carbides, simultaneously ensuring that the austenite grain size is greater than 8 grades, then cooling to 860-920 ℃ along with a furnace, preserving heat for 50-90 min to enable microalloy carbides such as Mo, V and Nb to be finely and uniformly dispersed and separated out in a nano scale (100 nm), cooling to 500-550 ℃ along with the furnace, preserving heat for 60-90 min, transforming the austenite tissue to a lower bainite tissue in the process, simultaneously alternately separating out nano-scale tiny dispersed Cr alloy carbides and nitrides such as Al and B, and finally cooling to room temperature along with the furnace; then quenching and tempering are carried out, the quenching and heating temperature is 920-960 ℃, the temperature is kept for 40-60 min, the oil is cooled to room temperature, submicron-scale (100-1000 nm) carbonitride is separated out in the quenching and tempering process, the temperature is kept for 60-90 min at 570-600 ℃, tempering is carried out again after the quenching and tempering process, the tempering temperature is kept for 90-120 min at 540-570 ℃, and Cr carbide with fine size and dispersed distribution, al, B and other nitrides are further separated out; and finally, carrying out surface treatment, wherein the surface treatment comprises phosphating treatment, blackening treatment, bluing treatment, galvanization, dacromet and nickel plating, and in the surface treatment process, the alloy steel contains Al element which promotes the surface passivation of the alloy steel, and meanwhile, the surface coating passivation films contain Al which is beneficial to reducing the diffusion rate of H and preventing the diffusion of the H element.
The use of high strength steel with high resistance to delayed fracture in long shaft type components, including fasteners and springs.
Example 1
As shown in fig. 1 to 3, a high strength steel with high resistance to delayed fracture comprises the following chemical components in percentage by mass: 0.2% C, 2.0% Si, 0.3% Mn, 1.2% Cr, 1.5% Ni, 0.5% Al, 1.2% Mo, 0.5% V, 0.06% Nb, 0.2% Cu, 0.05% B, 0.05% N, 0.005% P, 0.008% S, 0.00012% H, 0.0007% O, and the balance Fe and impurities.
An energy-saving preparation method of high-strength steel with high resistance to delayed fracture comprises the following steps:
s1, performing cold-working drawing deformation on a hot rolled wire rod with the diameter of 22mm, performing intermediate spheroidizing annealing on the hot rolled wire rod with the first-pass drawing deformation of 28%, the second-pass drawing deformation of 20% and the total cold-working drawing deformation of 42.4%, performing furnace cooling to the temperature of 610 ℃ for 6 hours at the heating temperature of 660 ℃, performing furnace cooling to the temperature of 480 ℃ at the speed of 15 ℃/h, performing air cooling to the room temperature, performing cold-working drawing again after the intermediate spheroidizing annealing, performing spheroidizing annealing on the cold-working drawing deformation of 21%, and finally, performing spheroidizing annealing to obtain a wire rod; the spheroidizing annealing heating temperature is kept at 600 ℃ for 3 hours, then furnace cooling is carried out to 560 ℃ for 3 hours, and then furnace cooling is carried out to 430 ℃ for air cooling at 35 ℃/h; the spheroidization rate of the wire rod is 93%;
s2, performing cold heading on the bolt head into a hexagon and performing cold rolling on the bolt rod part to obtain an M10 hexagon head bolt;
s3, carrying out preliminary heat treatment on the bolts, keeping the temperature at 1050 ℃ for 50min, then cooling to 860 ℃ along with the furnace for 90min, then cooling to 550 ℃ along with the furnace for 60min, and finally cooling to room temperature along with the furnace; carrying out tempering treatment on the bolt, wherein the quenching heating temperature is 920 ℃ and the temperature is kept for 60min, the oil is cooled to room temperature, then the temperature is kept for 60min and tempering treatment is carried out at 600 ℃, and after the tempering treatment, tempering is carried out again and the tempering temperature is kept for 90min at 570 ℃; and (3) carrying out phosphating treatment on the surface of the bolt, wherein the surface phosphating layer films contain Al element.
The M10 bolt prepared by the technology has the grain size of 8.5 grade, the volume fraction of bainite of 92%, the volume fraction of retained austenite of 5% and the volume fraction of carbonitride of 3%. Tensile Strength R at room temperature m =1595 MPa, yield strength Rp 0.2 1468MPa, surface shrinkage a=57%, elongation epsilon=18%, impact toughness K V =46J, and the transverse load delay fracture strength ratio was 0.77.
Example two
As shown in fig. 1 to 3, a high strength steel with high resistance to delayed fracture comprises the following chemical components in percentage by mass: 0.4% C, 1.2% Si, 0.1% Mn, 0.6% Cr, 0.8% Ni, 1.0% Al, 0.8% Mo, 0.3% V, 0.10% Nb, 0.5% Cu, 0.02% B, 0.02% N, 0.005% P, 0.009% S, 0.0001% H, 0.0008% O, the balance being Fe and impurities.
An energy-saving preparation method of high-strength steel with high resistance to delayed fracture comprises the following steps:
s1, performing cold-drawing deformation on a hot rolled wire rod with the diameter of 12mm, performing intermediate spheroidizing annealing on the hot rolled wire rod with the first-pass drawing deformation of 35%, the second-pass drawing deformation of 22% and the total cold-drawing deformation of 49.3%, performing furnace cooling to 640 ℃ for 3 hours at the heating temperature of 690 ℃, performing furnace cooling to 530 ℃ at the speed of 10 ℃/h, performing air cooling to room temperature, performing cold drawing again after the intermediate spheroidizing annealing, performing spheroidizing annealing on the cold-drawn wire rod with the cold-drawing deformation of 17.8%, and performing spheroidizing annealing to obtain a wire rod; the spheroidizing annealing heating temperature is kept at 640 ℃ for 0.5h, then the furnace is cooled to 590 ℃ for 0.5h, and then the furnace is cooled to 460 ℃ for air cooling at 30 ℃/h; the spheroidization rate of the wire rod is 94%;
s2, cold rolling the wire to prepare a spiral spring with the diameter of 5 mm;
s3, carrying out preliminary heat treatment on the spring, keeping the temperature at 1200 ℃ for 30min, then cooling to 920 ℃ along with the furnace, keeping the temperature for 50min, then cooling to 500 ℃ along with the furnace, keeping the temperature for 90min, and finally cooling to room temperature along with the furnace; carrying out tempering treatment on the bolt, wherein the quenching heating temperature is 960 ℃ and the temperature is kept for 40min, oil is cooled to room temperature, then the temperature is kept for 90min at 570 ℃, tempering is carried out again after the tempering treatment, and the tempering temperature is kept for 120min at 540 ℃; and phosphating the surfaces of the springs, wherein the surface phosphating films contain Al element.
The grain size of the spring prepared by the technology is 8.5, the volume fraction of bainite is 94%, the volume fraction of retained austenite is 5%, and the volume fraction of carbonitride is 1%. Tensile Strength R at room temperature m =1653 MPa, yield strength Rp 0.2 1512MPa, a surface shrinkage a=51%, an elongation epsilon=15%, and an impact toughness K V =39j, the transverse load delay break strength ratio was 0.76.
Example III
As shown in fig. 1 to 3, a high strength steel with high resistance to delayed fracture comprises the following chemical components in percentage by mass: 0.25% C, 1.6% Si, 0.16% Mn, 0.77% Cr, 0.91% Ni, 0.69% Al, 0.92% Mo, 0.41% V, 0.063% Nb, 0.45% Cu, 0.03% B, 0.03% N, 0.007% P, 0.009% S, 0.00011% H, 0.0009% O, and the balance Fe and impurities.
An energy-saving preparation method of high-strength steel with high resistance to delayed fracture comprises the following steps:
s1, carrying out cold-work drawing deformation on a hot rolled wire rod with the diameter of 24mm, wherein the cold-work drawing deformation amount is 25%, and finally carrying out spheroidizing annealing to obtain a wire rod, wherein the spheroidizing annealing heating temperature is 630 ℃ and is kept for 2.5 hours, then the furnace cooling is carried out to 580 ℃ and is kept for 1 hour, and then the furnace cooling is carried out to 450 ℃ by a 32 ℃/h furnace for air cooling; the spheroidization rate of the wire rod is 93%;
s2, performing cold working thread rolling treatment on the rod part of the wire rod to prepare a stud with the diameter of 18 mm;
s3, carrying out preliminary heat treatment on the stud, keeping the temperature at 1080 ℃ for 47min, then cooling to 880 ℃ along with the furnace for 58min, then cooling to 520 ℃ along with the furnace for 72min, and finally cooling to room temperature along with the furnace; carrying out quenching and tempering on the stud, keeping the quenching and heating temperature at 930 ℃ for 43min, cooling the oil to room temperature, keeping the temperature at 585 ℃ for 75min, carrying out tempering again after quenching and tempering, and keeping the tempering temperature at 550 ℃ for 105min; and (3) carrying out phosphating treatment on the surface of the stud, wherein the surface phosphating layer contains Al element.
The fastener stud prepared by the technology has the grain size of 8.5 grade, the volume fraction of bainite of 95%, the volume fraction of retained austenite of 3% and the volume fraction of carbonitride of 2%. Tensile Strength R at room temperature m =1545 MPa, yield strength Rp 0.2 1420MPa, surface shrinkage a=51%, elongation epsilon=14%, impact toughness K V =39j, the transverse load delay fracture strength ratio was 0.74.
Comparative example
The steel for the high-strength bolt comprises the following chemical components in percentage by weight: c0.35-0.45; si 0.15-0.24; mn 0.20-0.40%; cr0.75-1.35; mo is 0.55-1.00; v is 0.08 to 0.30; 0.005 to 0.10 percent of Al; s0-0.005, and the balance of Fe and impurities.
The preparation process comprises the following steps: smelting and casting, soaking treatment, rough rolling and cogging, rolling wire rods, quenching and tempering treatment and finally obtaining the finished product. The specific parameters are as follows: quenching and tempering the wire rod, wherein the selected quenching temperature is log { [ V ] [ C ] } > 6.72-9500/T (wherein [ V ] is the mass percent of V in the high-strength bolt steel, [ C ] is the mass percent of C in the high-strength bolt steel, T is the quenching temperature, and the unit of the quenching temperature T is K), the wire rod is subjected to oil quenching after being insulated for 60-80 min at the quenching temperature, is cooled to below 80 ℃ by mineral oil at 40-60 ℃, is tempered by heating for more than 90min at the temperature of not lower than 500 ℃, is subjected to oil quenching after being insulated for 60-80 min at the quenching temperature T, is tempered by adopting the temperature of not less than 500 ℃ for not less than 90min, and is air cooled to obtain the high-strength bolt steel.
The microstructure of the fastener bolt prepared by the technology is tempered sorbite, and the original austenite grain size of the tempered sorbite is less than or equal to 20 mu m. The tensile strength is more than 1400MPa, the yield strength reaches 1260MPa, and the area reduction rate is more than 50%.
C: carbon is the main element for obtaining the strength of alloy steel, the strength of the common ultra-high strength steel is more than 1280MPa, the carbon content is more than 0.2%, but when the C content is increased to be more than 0.4%, the toughness is reduced although the strength is increased, and particularly the delayed fracture resistance of the alloy steel is obviously reduced. Therefore, the C content in the present invention is controlled to be 0.2 to 0.4%.
Si: the silicon element has solid solution strengthening effect in steel, is free from carbide forming elements, is beneficial to increase of austenite quantity, so that hydrogen diffusion rate is reduced, and has good tempering resistance, so that alloy steel can be tempered at a high temperature. In addition, the addition of Si element can also promote the residual austenite films distributed between bainite to reduce the diffusion rate of hydrogen atoms. It is apparent that the Si element contributes to improvement of the delayed fracture resistance, but when the Si element content is more than 2.0%, the toughness of the steel is drastically reduced. Comprehensively considering, the Si content is controlled to be 1.0-2.0 percent in the invention.
Mn: manganese can facilitate the removal of oxygen, sulfur, etc., while manganese is an austenite forming element, facilitating austenite formation, and hindering austenite transformation to form retained austenite. However, when the manganese content is increased, the P element segregation is promoted. Comprehensively considering that the content of Mn element is controlled to be 0.1-0.3 percent.
Cr: the chromium element is a carbide forming element, and can improve strength and delayed fracture resistance when being precipitated as carbide, and also improves hardenability of steel, but if the Cr content is excessive, cold workability is deteriorated, the upper limit content of the Cr element needs to be controlled, and comprehensively considered, the Cr element content is controlled to be 0.6-1.2%.
Ni: the nickel element is an austenite forming element, can improve the strength, is beneficial to promoting the formation of residual austenite, improves the toughness of a residual austenite film, particularly obviously improves the delayed fracture resistance, but has higher Ni cost, can be replaced by N, B, and comprehensively considers that the Ni content is controlled to be 0.8-1.5 percent.
Al: the aluminum element can effectively remove oxygen, and the aluminum element can form AlN, so that the strength and the delayed fracture resistance are improved; in addition, aluminum promotes passivation of the steel surface, and the Al element contained in the passivation film of the steel surface is beneficial to blocking diffusion of H element and reducing the H diffusion rate. The above effect is exhibited when the aluminum content is more than 0.5%, however, when the aluminum content is more than 1.0%, toughness is lowered, workability is lowered, and the Al content is controlled to be 0.5 to 1.0% in the present invention, comprehensively.
Mo: the molybdenum element is a strong carbide forming element, does not dissolve when heated at a proper temperature, can be separated out to form secondary strengthening in the tempering process, improves the strength and the delayed fracture resistance, is an indispensable element in the ultra-high strength steel, and comprehensively considers that the Mo content is controlled to be 0.8-1.2%.
V: the vanadium element can form stable carbide, refine grains, play a secondary strengthening role in tempering, improve strength and delayed fracture resistance, and is a common additive element in ultra-high strength steel, but the vanadium element can deteriorate the processing performance and increase the cost when the content is more than 0.5%, and the V content is controlled to be 0.3-0.5% in comprehensive consideration.
Nb: the niobium element has the same function as the V element, mainly forms stable carbide, but has lower solubility in steel not more than 0.10 percent and higher cost, and the content of Nb is controlled to be 0.06-0.10 percent comprehensively.
Cu: copper is an austenite forming element and can be used for replacing part of Ni element, meanwhile, the formation of residual austenite is promoted, the toughness is improved, and the delayed fracture resistance is particularly obviously improved. However, cu has limited solubility in iron, and also deteriorates hot workability when the content is high. Comprehensively considering, the Cu content is controlled to be 0.2-0.5 percent in the invention.
B: the boron element increases the hardenability of the steel, part of the boron element can replace nickel, chromium and other elements, the manufacturing cost is reduced, the tendency of forming cracks when the boron is used for quenching the alloy steel is small, in addition, B and N have stronger affinity to form BN, thereby being beneficial to refining grains and improving the toughness and the delayed fracture resistance. However, B tends to slightly promote temper brittleness, and coarse crystals are easily caused. In the invention, the content of B is controlled to be 0.02-0.05% by comprehensive consideration.
N: is an austenite forming element capable of substituting for Ni and C, and the N content is required to be more than 0.02% in order to improve strength and delayed fracture resistance, however, when the content is more than 0.05%, the steel is liable to be porous. In the invention, the N content is controlled to be 0.02-0.05% by comprehensive consideration.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and variations could be made by those skilled in the art without departing from the technical principles of the present invention, and such modifications and variations should also be regarded as being within the scope of the invention.
Claims (10)
1. The high-strength steel with high resistance to delayed fracture is characterized by comprising the following chemical components in percentage by mass: 0.2 to 0.4 percent of C, 1.2 to 2.0 percent of Si, 0.1 to 0.3 percent of Mn, 0.6 to 1.2 percent of Cr, 0.8 to 1.5 percent of Ni, 0.5 to 1.0 percent of Al, 0.8 to 1.2 percent of Mo, 0.3 to 0.5 percent of V, 0.06 to 0.10 percent of Nb, 0.2 to 0.5 percent of Cu, 0.02 to 0.05 percent of B, 0.02 to 0.05 percent of N, 0 to 0.015 percent of P, 0 to 0.010 percent of S, 0 to 0.00015 percent of H, 0 to 0.0015 percent of O, and the balance of Fe and impurities.
2. The high strength steel with high resistance to delayed fracture according to claim 1, wherein: the metallographic structure of the high-strength steel comprises pearlite, bainite and residual austenite, and carbonitride is dispersed in a matrix of the high-strength steel.
3. The high strength steel with high resistance to delayed fracture according to claim 2, characterized in that: the grain size of the high-strength steel is greater than 8 grades, the volume fraction of the bainite is 90-95%, the volume fraction of the retained austenite is 3-5%, and the volume fraction of the carbonitride is 1-3%.
4. The high strength steel with high resistance to delayed fracture according to claim 1, wherein: tensile strength R of high-strength steel m Not less than 1510MPa, yield strength Rp 0.2 More than or equal to 1410MPa, the area shrinkage A more than or equal to 50%, the elongation epsilon more than or equal to 13% and the impact toughness K V More than or equal to 38J and strong delayed fracture under transverse loadThe ratio of degrees is greater than 0.73.
5. An energy-saving method for producing high strength steel having high resistance to delayed fracture according to any one of claims 1 to 4, characterized in that: and drawing, spheroidizing annealing, cold deformation, preliminary heat treatment, quenching and tempering and surface treatment are sequentially carried out on the workpiece to be processed.
6. The energy-saving preparation method of high-strength steel with high resistance to delayed fracture according to claim 5, characterized by comprising the following steps: in the drawing process, when the first-pass drawing deformation is more than 25% and the total drawing deformation is more than 30%, sequentially performing intermediate spheroidizing annealing and secondary drawing on the workpiece to be machined after drawing and before spheroidizing annealing.
7. The energy-saving preparation method of high-strength steel with high resistance to delayed fracture according to claim 5, characterized by comprising the following steps: the spheroidization rate of the workpiece to be machined after spheroidizing annealing and before cold deformation is more than 90 percent.
8. The energy-saving preparation method of high-strength steel with high resistance to delayed fracture according to claim 5, characterized by comprising the following steps: and nano-scale carbonitride is precipitated in the preliminary heat treatment process, and submicron-scale carbonitride is precipitated in the quenching and tempering process.
9. The energy-saving preparation method of high-strength steel with high resistance to delayed fracture according to claim 5, characterized by comprising the following steps: the surface coating passivation film obtained by the surface treatment contains Al.
10. Use of a high strength steel with high resistance to delayed fracture as claimed in any of claims 1 to 4 in long shaft type components.
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