CN115216695B - Ultra-high strength alloy steel, 16.8-grade threaded fastener and preparation method thereof - Google Patents

Ultra-high strength alloy steel, 16.8-grade threaded fastener and preparation method thereof Download PDF

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CN115216695B
CN115216695B CN202210866288.5A CN202210866288A CN115216695B CN 115216695 B CN115216695 B CN 115216695B CN 202210866288 A CN202210866288 A CN 202210866288A CN 115216695 B CN115216695 B CN 115216695B
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alloy steel
threaded fastener
percent
quenching
ultra
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CN115216695A (en
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陆恒昌
董瀚
陈勤飞
胡杰
胡春东
赖建明
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Qifeng Precision Industry Sci-Tech Corp
Shanghai University Zhejiang High End Equipment Basic Materials Research Institute
University of Shanghai for Science and Technology
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Qifeng Precision Industry Sci-Tech Corp
Shanghai University Zhejiang High End Equipment Basic Materials Research Institute
University of Shanghai for Science and Technology
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Priority to PCT/CN2022/124015 priority patent/WO2024016484A1/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C21D1/28—Normalising
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B33/00—Features common to bolt and nut
    • F16B33/02—Shape of thread; Special thread-forms
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
    • F16B35/00—Screw-bolts; Stay-bolts; Screw-threaded studs; Screws; Set screws

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

The invention provides an ultrahigh-strength alloy steel, a 16.8-grade threaded fastener and a preparation method thereof, and belongs to the field of high-strength alloy fastener manufacturing. The invention provides ultra-high strength alloy steel, which comprises the following components in percentage by mass: c:0.35 to 0.60 percent, si:0.035 to 0.15 percent, mn:0.10 to 0.90 percent, P is less than 0.020 percent, S is less than 0.0010 percent, cr:1.50 to 2.50 percent, mo:2.00 to 3.00 percent, V:0.30 to 0.80 percent of Ni:0.25 to 1.00 percent, nb:0.001 to 0.200 percent and the balance of Fe. The invention can play a synergistic effect by controlling the dosage of each element, thereby ensuring that the threaded fastener prepared from the ultra-high strength alloy steel has excellent mechanical properties and simultaneously reducing the cost.

Description

Ultra-high strength alloy steel, 16.8-grade threaded fastener and preparation method thereof
Technical Field
The invention relates to the field of high-strength alloy fastener manufacturing, in particular to ultra-high-strength alloy steel, a 16.8-grade threaded fastener and a preparation method thereof.
Background
The high-end fastener is mainly applied to the high-end fields of aviation, aerospace, navigation, rail traffic equipment, national defense and the like, the highest strength level of the fastener developed in China is 16.9 level at present, the highest strength level of the international fastener is 17.8 level, the technical level and the competitive power of the fastener product are greatly different from those of developed countries, and many high-end fasteners are imported in a dependent manner, so that the promotion of the high-end upgrading of the domestic fastener product is accelerated in China, and the industrial structure is adjusted. Furthermore, in the present day "two carbon" context, low carbonization has become an important issue for the development of various industries. In the automobile manufacturing industry, the fuel efficiency can be improved and the oil consumption can be reduced through the weight reduction of the automobile, so that the exhaust emission of the automobile is reduced, and the aim of low carbonization is fulfilled. The data show that the fuel consumption can be reduced by 0.3 to 0.6 liter in hundred kilometers per 100kg of the whole vehicle weight, and the carbon dioxide emission can be reduced by 5g/km. The automobile industry is the industry with relatively large fastener demand, and the average number of fasteners for each automobile on a car is about 580, 50kg and 5000, accounting for 40% of the total number of automobile parts.
The ultra-high strength fastener can reduce the weight and increase the installation space by reducing the size of the ultra-high strength fastener under the same clamping force, so that the function and the volume of the connected parts can be optimized, the purposes of overall weight reduction and performance optimization are achieved, and the ultra-high strength fastener has great use value. The patent CN01129512.0 discloses a high-strength bolt with the strength of 1400-1600 MPa, the chemical components of the bolt are that C is more than or equal to 0.35 and less than or equal to 0.50, si is more than or equal to 0.01 and less than or equal to 0.09, mn is more than or equal to 0.30, P is less than 0.010, S is less than or equal to 0.008, cr is more than or equal to 0.50 and less than or equal to 1.50,0.70 and Mo is more than or equal to 1.50,0.20 and less than or equal to 0.50, nb is more than or equal to 0.08,0.002 and less than or equal to 0.04,0.005 and Al is more than or equal to 0.05,0.006 and less than or equal to 0.015, the sum of any one or two of Ti and Zr is 0.01-0.15, and the balance is Fe, and the maximum tensile strength of the bolt is only 1580MPa in terms of weight percent and can only reach the performance requirement of 15.9-level bolt. Patent 200810049411 discloses a method for preparing a 16.9-grade bolt, which comprises the chemical components of 0.15-0.19% C, 0.10% Si, 0.10% Mn, 0.008% P, 2.00,0.10% S-0.005,1.80 Cr-0.90% Mo, 10.50% Ni-9.50% Co-13.50% 14.50% Ti-0.015% O-0.002% N-0.0015% Fe, and higher content of noble metals such as Ni and Co in the bolt, resulting in increased production cost. With the continuous development of industries such as automobiles, high-speed rails, aviation, aerospace, national defense and the like, the demands for various fasteners are continuously increased, and the performances of the existing fasteners can not meet the demands.
Therefore, the ultrahigh-strength alloy steel with low precious metal content is provided, so that a threaded fastener with high tensile strength can be prepared, and the technical problem to be solved in the field is urgent.
Disclosure of Invention
The invention aims to provide an ultra-high strength alloy steel, a 16.8-grade threaded fastener and a preparation method thereof. The ultra-high strength alloy steel provided by the invention only adds a small amount of noble metals such as Ni and Nb, has excellent mechanical properties, and can be used for preparing ultra-high strength (16.8 grade) MJ threaded fasteners.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides ultra-high strength alloy steel, which comprises the following components in percentage by mass: c:0.35 to 0.60 percent, si:0.035 to 0.15 percent, mn:0.10 to 0.90 percent, P is less than 0.020 percent, S is less than 0.0010 percent, cr:1.50 to 2.50 percent, mo:2.00 to 3.00 percent, V:0.30 to 0.80 percent of Ni:0.25 to 1.00 percent, nb:0.001 to 0.200 percent and the balance of Fe.
Preferably, the ultra-high strength alloy steel comprises the following components in mass percent: 0.35 to 0.55 percent, si:0.04 to 0.09 percent, mn:0.20 to 0.80 percent, P is less than 0.020 percent, S is less than 0.0010 percent, cr:1.75 to 2.25 percent of Mo:2.00 to 3.00 percent, V:0.30 to 0.80 percent of Ni:0.50 to 0.80 percent, nb:0.05 to 0.20 percent and the balance of Fe.
Preferably, the ultra-high strength alloy steel comprises the following components in mass percent: c:0.35 to 0.50 percent, si:0.05 to 0.08 percent, mn:0.30 to 0.70 percent, P is less than 0.020 percent, S is less than 0.0010 percent, cr:1.75 to 2.25 percent of Mo:2.00 to 3.00 percent, V:0.30 to 0.80 percent of Ni:0.50 to 0.80 percent, nb:0.10 to 0.20 percent and the balance of Fe.
Preferably, the ultra-high strength alloy steel comprises the following components in mass percent: c:0.40 to 0.45 percent, si: 0.06-0.07%, mn: 0.40-0.60%, P < 0.020%, S < 0.0010%, cr:1.75 to 2.25 percent of Mo:2.00 to 3.00 percent, V:0.40 to 0.70 percent of Ni:0.30 to 0.90 percent, nb:0.10 to 0.15 percent and the balance of Fe.
The invention provides a preparation method of a 16.8-level threaded fastener, which comprises the following steps:
(1) Sequentially carrying out first turning and hot upsetting on the ultrahigh-strength alloy steel to obtain a hot upsetting blank; the ultra-high strength alloy steel is the ultra-high strength alloy steel according to the technical scheme;
(2) Normalizing, quenching, tempering and shot blasting are sequentially carried out on the hot upsetting blank obtained in the step (1) to obtain a heat-treated blank;
(3) And (3) sequentially turning, grinding, thread rolling and R-angle rolling the heat-treated blank obtained in the step (2) for the second time to obtain the 16.8-level threaded fastener.
Preferably, the heat preservation temperature of the normalizing in the step (2) is 1000-1050 ℃, the heat preservation time of the normalizing is 30-60 min, and the cooling mode of the normalizing is air cooling.
Preferably, the heat preservation temperature of quenching in the step (2) is 1000-1050 ℃, the heat preservation time of quenching is 30-60 min, and the cooling mode of quenching is oil quenching.
Preferably, the oil temperature in the oil quenching is 40-60 ℃, and the oil quenching time is 10-20 min.
Preferably, the tempering heat preservation temperature in the step (2) is 550-600 ℃, the tempering heat preservation time is 100-150 min, and the tempering cooling mode is air cooling.
The invention provides the 16.8-grade threaded fastener prepared by the preparation method.
The invention provides ultra-high strength alloy steel, which comprises the following components in percentage by mass: c:0.35 to 0.60 percent, si:0.035 to 0.15 percent, mn:0.10 to 0.90 percent, P is less than 0.020 percent, S is less than 0.0010 percent, cr:1.50 to 2.50 percent, mo:2.00 to 3.00 percent, V:0.30 to 0.80 percent of Ni:0.25 to 1.00 percent, nb:0.001 to 0.200 percent and the balance of Fe. In the invention, the element C mainly plays a role in improving the strength of alloy steel; the Si element and the Mn element can improve the strength and the hardenability of the alloy steel through solid solution strengthening; the Cr element can be solid-solution strengthened to improve the material strength, and can have a synergistic effect with the alloy elements such as Si, mn and the like to further improve the tensile strength of the alloy steel, and can form carbide with the C element to be separated out in the tempering process, so that the material strength is further improved by secondary hardening; the Mo element can form carbide with the C element, and is separated out in the tempering process, so that the material strength is further improved by secondary hardening; the V element is a micro-precipitate element for separating out carbide, nitride or carbonitride in alloy steel, and by adding the V element, the V element can be used as a hydrogen trap to catch hydrogen for innocuity, improve the delayed fracture resistance of the material, and can also improve the strength of the material by means of the micro-precipitate, and meanwhile, the V element can refine grains, improve the hardenability and improve the tempering resistance; the Ni element can improve the strength of the material through solid solution strengthening, and meanwhile, the good plasticity and toughness are maintained, so that the hardenability can be improved; nb can improve the strength of the material by refining grains and forming fine precipitates with carbon and nitrogen, and can improve the hardenability and tempering resistance; the synergistic effect can be achieved by controlling the use amount of each element, so that the performance of the alloy steel is further improved. The results of the examples show that the 16.8-grade threaded fastener prepared from the ultra-high strength alloy steel provided by the invention has the tensile strength of 1600-1770 MPa, the yield strength of 1280-1416 MPa, the plasticity of more than or equal to 8%, the shearing force of more than or equal to 95KN, the fatigue life of 130000 times (load ratio=0.1), and the stress durability performance of 96 hours under the condition of 0.75 times of the tensile strength, and is an ultra-high strength (16.8-grade) MJ threaded fastener.
Drawings
FIG. 1 is a schematic drawing of the 16.8 stage threaded fastener tooling dimensions provided in example 2 of the present invention;
in the figure, 1 is a threaded fastener head, 2 is a threaded fastener transition zone, 3 is a threaded fastener shank, and 4 is a threaded fastener threaded zone;
FIG. 2 is a schematic representation of the finished dimensions of a 16.8 stage threaded fastener head provided in example 2 of the present invention;
FIG. 3 is a schematic illustration of the shank chamfer gauge of a 16.8 stage threaded fastener according to example 2 of the present invention;
FIG. 4 is a schematic view of the shank tooling dimensions of a 16.8 stage threaded fastener according to example 2 of the present invention;
FIG. 5 is a schematic illustration of the first and second turning process dimensions of a 16.8-stage threaded fastener according to example 2 of the present invention;
FIG. 6 is a schematic drawing of the process dimensions of the 16.8 stage threaded fastener grinding process provided in example 2 of the present invention;
FIG. 7 is a schematic illustration of the thread region tooling dimensions for a 16.8 stage threaded fastener provided in example 2 of the present invention;
FIG. 8 is a schematic view of the 16.8 stage threaded fastener transition zone tooling provided in example 2 of the present invention.
Detailed Description
The invention provides ultra-high strength alloy steel, which comprises the following components in percentage by mass: c:0.35 to 0.60 percent, si:0.035 to 0.15 percent, mn:0.10 to 0.90 percent, P is less than 0.020 percent, S is less than 0.0010 percent, cr:1.50 to 2.50 percent, mo:2.00 to 3.00 percent, V:0.30 to 0.80 percent of Ni:0.25 to 1.00 percent, nb:0.001 to 0.200 percent and the balance of Fe.
The ultrahigh-strength alloy steel provided by the invention comprises the following components in percentage by mass: 0.35 to 0.60%, preferably 0.35 to 0.55%, more preferably 0.35 to 0.50%, and still more preferably 0.40 to 0.45%. In the invention, the element C mainly plays a role in improving the strength of alloy steel; by controlling the dosage, the influence of excessive C element on the ductility and toughness of the alloy steel can be avoided.
The ultrahigh-strength alloy steel provided by the invention comprises the following components in percentage by mass: 0.035 to 0.15%, preferably 0.04 to 0.09%, more preferably 0.05 to 0.08%, still more preferably 0.06 to 0.07%. In the invention, the Si element can improve the strength and the hardenability of the alloy steel through solid solution strengthening, and the content of the Si element is controlled within the range, so that the alloy steel has better strength and hardenability, and meanwhile, the toughness of the alloy steel is prevented from being reduced, thereby further improving the mechanical property of the alloy steel.
The ultrahigh-strength alloy steel provided by the invention comprises the following components in percentage by mass: 0.10 to 0.90%, preferably 0.20 to 0.80%, more preferably 0.30 to 0.70%, and even more preferably 0.40 to 0.60%. In the invention, mn element can improve the strength and hardenability of alloy steel through solid solution strengthening, and by controlling the content of Mn element in the above range, not only can the alloy steel have better strength and hardenability, but also the ductility and toughness of the alloy steel can be avoided from being reduced, and the phenomenon of cracking during heat treatment caused by the fact that Mn element is easy to segregate at grain boundaries to cause embrittlement of the grain boundaries can be prevented, thereby further improving the mechanical properties of the alloy steel.
The ultra-high strength alloy steel provided by the invention comprises less than 0.020% of P by mass percent. In the invention, the P element is an impurity element, and the influence of the P element on the plasticity and impact toughness of the steel can be reduced by controlling the content of the P element in a lower range.
The ultra-high strength alloy steel provided by the invention comprises less than 0.0010 percent of S in percentage by mass. In the invention, the S element is an impurity element, and the influence of the S element on the ductility, toughness and corrosion resistance of the steel can be reduced by controlling the content of the S element in a lower range.
The ultra-high strength alloy steel provided by the invention comprises the following components in percentage by mass: 1.50 to 2.50%, preferably 1.75 to 2.25%. In the invention, cr element can improve the material strength through solid solution strengthening, and can have a synergistic effect with alloy elements such as Si, mn and the like, so that the tensile strength of alloy steel is further improved, and meanwhile, cr element can form carbide with C element, and is separated out in the tempering process, so that the material strength is further improved through secondary hardening; by controlling the dosage, the mechanical property of the alloy steel can be further improved.
The ultra-high strength alloy steel provided by the invention comprises the following components in percentage by mass: 2.00 to 3.00%, preferably 2.20 to 2.80%, and more preferably 2.40 to 2.50%. In the invention, mo element can form carbide with C element, and is separated out in the tempering process, and the material strength is further improved by secondary hardening; by controlling the dosage, the mechanical property of the alloy steel can be further improved.
The ultra-high strength alloy steel provided by the invention comprises the following components in percentage by mass: 0.30 to 0.80%, preferably 0.40 to 0.70%, more preferably 0.50 to 0.80%. In the invention, the V element is a micro-precipitate element for separating out carbide, nitride or carbonitride in alloy steel, and the V element is added to not only be used as a hydrogen trap to catch hydrogen for innocuity and improve the delayed fracture resistance of the material, but also improve the strength of the material by means of the micro-precipitate, and meanwhile, the V element can refine grains, improve the hardenability and improve the tempering resistance; by controlling the amount of the alloy steel, the effect can be further improved, and the performance of the alloy steel is improved.
The ultrahigh-strength alloy steel provided by the invention comprises the following components in percentage by mass: 0.25 to 1.00%, preferably 0.40 to 0.85%. In the invention, ni element can improve the material strength through solid solution strengthening, and meanwhile, the invention keeps better plasticity and toughness, and can improve the hardenability; by controlling the dosage, the increase of the residual austenite content caused by the temperature of the martensite transformation temperature can be avoided, thereby improving the mechanical property of the material and reducing the cost.
The ultra-high strength alloy steel provided by the invention comprises the following components in percentage by mass: 0.001 to 0.200%, preferably 0.10 to 0.15%. In the invention, nb element can improve the material strength by refining grains and forming fine precipitates with carbon element and nitrogen element, and can improve the hardenability and tempering resistance; by controlling the dosage, the effect can be optimized, and the supersaturation of Nb element can be avoided, so that the mechanical property of the material is further improved, and the cost is reduced.
The ultrahigh-strength alloy steel provided by the invention comprises the balance of Fe in percentage by mass. In the present invention, the Fe element serves as a matrix element of the alloy steel.
The ultra-high strength alloy steel provided by the invention only needs to be added with a small amount of Ni, nb and other metals, and has good mechanical properties by adjusting the components of elements.
The invention provides a 16.8-grade threaded fastener which is prepared from the ultrahigh-strength alloy steel prepared by the technical scheme or the ultrahigh-strength alloy steel prepared by the preparation method.
The invention provides a preparation method of the 16.8-level threaded fastener, which comprises the following steps:
(1) Sequentially carrying out first turning and hot upsetting on the ultrahigh-strength alloy steel to obtain a hot upsetting blank;
(2) Normalizing, quenching, tempering and shot blasting are sequentially carried out on the hot upsetting blank obtained in the step (1) to obtain a heat-treated blank;
(3) And (3) sequentially turning, grinding, thread rolling and R-angle rolling the heat-treated blank obtained in the step (2) for the second time to obtain the 16.8-level threaded fastener.
The invention sequentially carries out first turning and hot upsetting on the ultra-high strength alloy steel to obtain a hot upsetting blank.
In the invention, the first numerical control machine preferably carries out plane chamfering and cutting according to the sequence shown in fig. 3, then turns around and clamps, and the plane and acute angle are dulled. According to the invention, the first turning is performed according to the process, so that the size of the 16.8-grade threaded fastener can meet the requirement.
In the present invention, the hot header is preferably header-shaped according to fig. 4. The hot upsetting temperature is not particularly limited, and the hot upsetting temperature is determined according to the technical common sense of a person skilled in the art, so that the defects of overheating, overburning, material shortage and the like are overcome. In the present invention, the cooling means of the hot header is preferably air cooling. According to the hot upsetting method, the hot upsetting is carried out through the process, so that the machining size of the head of the threaded fastener can meet the requirement.
After the hot upsetting blank is obtained, the hot upsetting blank is subjected to normalizing, quenching, tempering and shot blasting in sequence to obtain a heat treatment blank.
In the invention, the heat preservation temperature of the normalizing is preferably 1000-1050 ℃, more preferably 1020-1040 ℃; the heat preservation time of the normalizing is preferably 30-60 min, more preferably 40-50 min; the normalizing cooling mode is preferably air cooling. In the present invention, the normalizing is preferably performed in a vacuum furnace. The vacuum degree of the vacuum furnace is not particularly limited, and the vacuum furnace is determined according to the technical common sense of the person skilled in the art, and can avoid oxidation in the normalizing process. The temperature increase rate to be increased to the normalizing temperature is not particularly limited, and may be determined according to the technical knowledge of a person skilled in the art. According to the invention, by controlling the normalizing parameters within the above range, the grains in the alloy steel can be further refined, and the carbide distribution is homogenized, so that the mechanical property of the threaded fastener is further improved.
In the invention, the heat preservation temperature of quenching is preferably 1000-1050 ℃, more preferably 1020-1040 ℃; the heat preservation time of quenching is preferably 30-60 min, more preferably 40-50 min; the quenching cooling mode is preferably oil quenching; the oil temperature during oil quenching is preferably 40-60 ℃, more preferably 50 ℃; the oil quenching time is preferably 10 to 20 minutes, more preferably 15 minutes. In the present invention, the quenching is preferably performed in a vacuum furnace. The vacuum degree of the vacuum furnace is not particularly limited, and the vacuum degree is determined according to the technical common sense of the person skilled in the art, and can be used for avoiding oxidation in the quenching process. The rate of heating up to the quenching temperature is not particularly limited, and may be determined according to the technical knowledge of those skilled in the art. The invention can further improve the rigidity, hardness, wear resistance and other performances of the threaded fastener by quenching through the process.
In the invention, the tempering heat preservation temperature is preferably 550-600 ℃, more preferably 560-580 ℃; the tempering heat preservation time is preferably 100-150 min, more preferably 120-130 min; the tempering cooling mode is preferably air cooling. In the present invention, the tempering is preferably performed in a vacuum furnace. The vacuum degree of the vacuum furnace is not particularly limited, and the vacuum furnace is determined according to the technical common sense of the person skilled in the art, and can avoid oxidation in the tempering process. The invention eliminates internal stress through high temperature tempering, thereby further improving the toughness and plasticity.
The specific operation of the shot blasting is not particularly limited, and the oxide scale on the surface of the heat-treated blank can be completely removed.
After the heat-treated blank is obtained, the heat-treated blank is sequentially subjected to second times of turning, grinding, thread rolling and R angle rolling, and the 16.8-level threaded fastener is obtained.
In the invention, the second number of turns is preferably sequentially performed with a turning hexagon head, a plane chamfer, a turning clamping, a plane end face chamfer, a wire blank diameter, a turning rod diameter and an under-head R angle according to FIG. 5. The invention can make the machining size of the number of fastening pieces meet the requirement through the process.
In the present invention, the grinding is preferably performed by grinding the wire stock diameter to the lower head chamfer by grinding the shank according to fig. 6. According to the grinding process, the grinding is carried out through the process, so that the machining size of the threaded fastener in the grinding process can meet the requirements.
In the present invention, the thread rolling machine is preferably used to roll threads according to fig. 7. The thread rolling is carried out by the process, so that the processing size of the threaded area of the threaded fastener can meet the requirements.
In the present invention, the roll R angle is preferably rolled out as shown in fig. 8 to form the transition between the fastener head and the fastener shank. In the invention, the specific process of the roller R angle is preferably to install the roller of the roller R on a rolling fixture, apply a certain pressure to the fastening piece through the roller R equipment and drive the fastening piece and the roller to rotate for rolling. In the present invention, the rolling time is preferably 3±1s; the rolling pressure is preferably 10-13 Kg, more preferably 12Kg; the radius of the roller is preferably 0.8+/-0.1 mm; amax of the thread is preferably 0.030mm; the Bmax of the thread is preferably 0.025mm; the Cmax of the threads is preferably 2.5mm. According to the invention, the R angle is rolled and the parameters are controlled through the process, so that the processing size of the transition region of the threaded fastener can meet the requirements.
The preparation method for preparing the threaded fastener is simple, can be used for large-scale preparation only by using conventional equipment, and is suitable for large-scale production by a process.
The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The ultra-high strength alloy steel comprises the following components in percentage by mass: c:0.35%, si:0.047%, mn:0.26%, P:0.005%, S:0.0005%, cr:2.25%, mo:2.04%, V:0.50%, ni:0.85%, nb:0.075% and the balance Fe.
Example 2
A preparation method of a 16.8-grade threaded fastener comprises the following steps:
(1) Sequentially carrying out first turning and hot upsetting on the ultrahigh-strength alloy steel to obtain a hot upsetting blank; in the invention, the first turning is sequentially subjected to plane chamfering and cutting according to the figure 3, then turning and clamping, and the plane and the acute angle are inverted; the hot upsetting is preferably performed according to the upsetting head of FIG. 4, and the cooling mode of the hot upsetting is air cooling; the ultra-high strength alloy steel is the ultra-high strength alloy steel provided in the embodiment 1;
(2) Normalizing, quenching, tempering and shot blasting are sequentially carried out on the hot upsetting blank obtained in the step (1) to obtain a heat-treated blank; the heat preservation temperature of the normalizing is 1030 ℃, the heat preservation time of the normalizing is 60min, and the cooling mode of the normalizing is air cooling; the heat preservation temperature of quenching is 1030 ℃, the heat preservation time of quenching is 60min, and the cooling mode of quenching is oil quenching; the oil temperature during oil quenching is 50 ℃, and the oil quenching time is 15min; the heat preservation temperature of tempering is 560 ℃, the heat preservation time of tempering is 120min, and the cooling mode of tempering is air cooling;
(3) Sequentially turning, grinding, thread rolling and R-angle rolling the heat treatment blank obtained in the step (2) for the second time to obtain a 16.8-level threaded fastener; turning for the second time sequentially comprises turning a hexagon head, carrying out plane chamfering, turning and clamping, carrying out plane end face chamfering, turning a wire blank diameter, turning a rod diameter and carrying out an R angle under the head according to FIG. 5; the grinding is carried out according to the figure 6, the wire blank diameter is finely ground, and the rod part is ground to the chamfer position below the head; the thread rolling machine is used for rolling threads according to fig. 7; the roll R angle rolls out the transition between the fastener head and the fastener shank according to fig. 8; the specific process of the roller R angle is that the roller of the roller R is arranged on a rolling clamp, and certain pressure is applied to the fastening piece through roller R equipment and the fastening piece and the roller are driven to rotate for rolling; the rolling time is 3s.
The 16.8-grade threaded fastener prepared in example 2 was subjected to mechanical property testing, and the test standard is: room temperature uniaxial tension test, double shear test and fatigue test reference standard GJB 3376-1998, "MJ threaded alloy Steel and stainless Steel bolt and screw general Specification", stress durability test reference standard GJ/B715.12-1990 "fastener Experimental method stress durability".
Through testing, the 16.8-grade threaded fastener prepared in example 2 has a tensile strength of 1623MPa, a yield strength of 1380MPa, a plasticity of 10.0%, a shearing force of 95KN, a fatigue life of 130000 times (load ratio=0.1), and a retention time of 96 hours at 0.75 times of the tensile strength, and is an ultra-high strength (16.8-grade) MJ threaded fastener.
Example 3
The tempering temperature in the step (2) was 570℃and the other conditions were the same as in example 2.
The 16.8-grade threaded fastener prepared in example 3 was subjected to mechanical property test, and the test standard was the same as that of example 2.
Through testing, the 16.8-grade threaded fastener prepared in example 3 has a tensile strength of 1655MPa, a yield strength of 1403MPa, a plasticity of 10.5%, a shearing force of 95KN, a fatigue life of 130000 times (load ratio=0.1), and a retention time of 96 hours at 0.75 times the tensile strength, and is an ultra-high strength (16.8-grade) MJ threaded fastener.
Example 4
The tempering temperature in the step (2) was 580 ℃, and other conditions were the same as in example 2.
The 16.8-grade threaded fastener prepared in example 4 was subjected to mechanical property testing, and the test standard was the same as that of example 2.
Through testing, the 16.8-grade threaded fastener prepared in example 4 has the tensile strength of 1667MPa, the yield strength of 1395MPa, the plasticity of 11.0%, the shearing force of 95KN, the fatigue life of 130000 times (load ratio=0.1), and the retention time of the stress durability performance at 0.75 times of the tensile strength of 96 hours, and is an ultra-high strength (16.8-grade) MJ threaded fastener.
As can be seen from the descriptions of examples 2 to 4, the 16.8-grade threaded fastener prepared from the ultra-high strength alloy steel provided by the invention has excellent mechanical properties and is an ultra-high strength (16.8-grade) MJ threaded fastener; by adjusting the parameters of the heat treatment, the mechanical property of the threaded fastener can be further improved.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (5)

1. A 16.8 grade threaded fastener, the 16.8 grade threaded fastener being made from ultra-high strength alloy steel;
the ultra-high strength alloy steel comprises the following components in percentage by mass: c: 0.35-0.60%, si:0.035 to 0.15%, mn: 0.10-0.90%, P < 0.020%, S < 0.0010%, cr: 1.50-2.50%, mo: 2.00-3.00%, V: 0.30-0.80%, ni: 0.25-1.00%, nb: 0.001-0.200% and the balance of Fe;
the preparation method of the 16.8-grade threaded fastener comprises the following steps:
(1) Sequentially carrying out first turning and hot upsetting on the ultrahigh-strength alloy steel to obtain a hot upsetting blank;
(2) Normalizing, quenching, tempering and shot blasting are sequentially carried out on the hot upsetting blank obtained in the step (1) to obtain a heat-treated blank;
(3) Sequentially turning, grinding, thread rolling and R-angle rolling the heat treatment blank obtained in the step (2) for the second time to obtain a 16.8-level threaded fastener;
the heat preservation temperature of the normalizing in the step (2) is 1000-1050 ℃, the heat preservation time of the normalizing is 30-60 min, and the cooling mode of the normalizing is air cooling;
the heat preservation temperature of quenching in the step (2) is 1000-1050 ℃, the heat preservation time of quenching is 30-60 min, the cooling mode of quenching is oil quenching, the oil temperature during oil quenching is 40-60 ℃, and the time of oil quenching is 10-20 min;
and (3) tempering in the step (2) at a temperature of 550-600 ℃, wherein the tempering temperature is 100-150 min, and the tempering cooling mode is air cooling.
2. The 16.8 grade threaded fastener of claim 1, wherein the ultra-high strength alloy steel comprises, in mass percent: c: 0.35-0.55%, si:0.04 to 0.09%, mn: 0.20-0.80%, P < 0.020%, S < 0.0010%, cr: 1.75-2.25%, mo: 2.00-3.00%, V: 0.30-0.80%, ni: 0.50-0.80%, nb: 0.05-0.20% and the balance of Fe.
3. The 16.8 grade threaded fastener of claim 2, wherein the ultra-high strength alloy steel comprises, in mass percent: c: 0.35-0.50%, si: 0.05-0.08%, mn: 0.30-0.70%, P < 0.020%, S < 0.0010%, cr: 1.75-2.25%, mo: 2.00-3.00%, V: 0.30-0.80%, ni: 0.50-0.80%, nb: 0.10-0.20% and the balance of Fe.
4. A 16.8 grade threaded fastener as claimed in claim 3, wherein the ultra-high strength alloy steel comprises the following components in mass percent: c: 0.40-0.45%, si: 0.06-0.07%, mn: 0.40-0.60%, P < 0.020%, S < 0.0010%, cr: 1.75-2.25%, mo: 2.00-3.00%, V: 0.40-0.70%, ni: 0.30-0.90%, nb: 0.10-0.15% and the balance of Fe.
5. The method for preparing the 16.8-stage threaded fastener according to any one of claims 1 to 4, comprising the following steps:
(1) Sequentially carrying out first turning and hot upsetting on the ultrahigh-strength alloy steel to obtain a hot upsetting blank; the ultra-high strength alloy steel is the ultra-high strength alloy steel according to any one of claims 1 to 4;
(2) Normalizing, quenching, tempering and shot blasting are sequentially carried out on the hot upsetting blank obtained in the step (1) to obtain a heat-treated blank;
(3) Sequentially turning, grinding, thread rolling and R-angle rolling the heat treatment blank obtained in the step (2) for the second time to obtain a 16.8-level threaded fastener;
the heat preservation temperature of the normalizing in the step (2) is 1000-1050 ℃, the heat preservation time of the normalizing is 30-60 min, and the cooling mode of the normalizing is air cooling;
the heat preservation temperature of quenching in the step (2) is 1000-1050 ℃, the heat preservation time of quenching is 30-60 min, the cooling mode of quenching is oil quenching, the oil temperature during oil quenching is 40-60 ℃, and the time of oil quenching is 10-20 min;
and (3) tempering in the step (2) at a temperature of 550-600 ℃, wherein the tempering temperature is 100-150 min, and the tempering cooling mode is air cooling.
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