CN115216695A - Ultrahigh-strength alloy steel, 16.8-grade threaded fastener and preparation method thereof - Google Patents

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

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CN115216695A
CN115216695A CN202210866288.5A CN202210866288A CN115216695A CN 115216695 A CN115216695 A CN 115216695A CN 202210866288 A CN202210866288 A CN 202210866288A CN 115216695 A CN115216695 A CN 115216695A
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alloy steel
ultrahigh
strength alloy
strength
threaded fastener
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CN115216695B (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 CN202210866288.5A priority Critical patent/CN115216695B/en
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 ultrahigh-strength alloy steel, a 16.8-grade threaded fastener and a preparation method thereof, and belongs to the field of manufacturing of high-strength alloy fasteners. The ultrahigh-strength alloy steel provided by the invention comprises the following components in percentage by mass: c:0.35 to 0.60%, si:0.035 to 0.15%, mn: 0.10-0.90%, P < 0.020%, S < 0.0010%, cr:1.50 to 2.50%, mo: 2.00-3.00%, V:0.30 to 0.80%, ni:0.25 to 1.00%, nb: 0.001-0.200% and the balance Fe. The invention can play a synergistic effect by controlling the dosage of each element, thereby ensuring that the threaded fastener prepared from the ultrahigh-strength alloy steel has excellent mechanical property and simultaneously reducing the cost.

Description

Ultrahigh-strength alloy steel, 16.8-grade threaded fastener and preparation method thereof
Technical Field
The invention relates to the field of manufacturing of high-strength alloy fasteners, in particular to ultrahigh-strength alloy steel, a 16.8-grade threaded fastener and a preparation method thereof.
Background
The high-end fastener is mainly applied to high-end fields such as aviation, aerospace, navigation, rail transit equipment, national defense and the like, the highest strength level of the fastener developed in China is 16.9, the highest strength level of the fastener in the world is 17.8, the technical level and the competitiveness of the fastener product have great difference with the developed country, and a plurality of high-end fasteners depend on import, so that China needs to accelerate the promotion of high-end upgrading of the domestic fastener product and adjust the industrial structure. Furthermore, under the current 'dual carbon' background, low carbon has become an important issue for the development of various industries. In the automobile manufacturing industry, the fuel efficiency can be improved and the fuel consumption can be reduced through the light weight of the automobile, so that the emission of automobile exhaust is reduced, and the aim of low carbon is fulfilled. The data show that the oil consumption per hundred kilometers can be reduced by 0.3-0.6 liter and the carbon dioxide emission can be reduced by 5g/km when the weight of the whole vehicle is reduced by 100 kg. In addition, the automobile industry is an industry with a large demand of fasteners, and the average number of the fasteners used in each automobile on a car is about 580, 50kg and 5000 fasteners, which account for 40 percent of the total number of the automobile parts.
The ultrahigh-strength fastener can reduce weight and increase installation space by reducing self size under the same clamping force, and therefore can be optimized in function and volume of connected parts, so that the aims of overall weight reduction and performance optimization are fulfilled, and the ultrahigh-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 or equal to 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, mo is more than or equal to 1.50, V is more than or equal to 0.20 and less than or equal to 0.50, nb is more than or equal to 0.01 and less than or equal to 0.08, RE is more than or equal to 0.04,0.005 is more than or equal to Al is less than or equal to 0.05, N is more 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, the maximum tensile strength of the bolt is only 1580MPa in percentage by mass, and can only reach the performance requirement of a 15.9 grade bolt. Patent 200810049411 discloses a preparation method of a 16.9-grade bolt, the chemical components of the bolt are that C is more than or equal to 0.15 and less than or equal to 0.19, si is more than or equal to 0.10, mn is more than or equal to 0.10, P is more than or equal to 0.008, S is more than or equal to 0.005, cr is more than or equal to 2.00, mo is more than or equal to 0.10 and less than or equal to 0.90, ni is more than or equal to 9.50 and less than or equal to 10.50, co is more than or equal to 13.50 and less than or equal to 14.50, ti is more than or equal to 0.015, O is more than or equal to 0.002, N is less than or equal to 0.0015, and the balance is Fe, and the mass percentage is calculated, the precious metals such as Ni and Co are higher in content, so that the production cost is increased. With the continuous development of industries such as automobiles, high-speed rails, aviation, aerospace, national defense and the like, the requirements for various fasteners are continuously increased, and the performance of the conventional fasteners cannot meet the requirements.
Therefore, it is an urgent technical problem in the art to provide an ultrahigh strength alloy steel with a low precious metal content, so that a threaded fastener with high tensile strength can be prepared.
Disclosure of Invention
The invention aims to provide ultrahigh-strength alloy steel, a 16.8-grade threaded fastener and a preparation method thereof. The ultrahigh-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 ultrahigh-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 ultrahigh-strength alloy steel which comprises the following components in percentage by mass: c:0.35 to 0.60%, si:0.035 to 0.15%, mn: 0.10-0.90%, P < 0.020%, S < 0.0010%, cr:1.50 to 2.50%, mo: 2.00-3.00%, V:0.30 to 0.80%, ni:0.25 to 1.00%, nb: 0.001-0.200% and the balance Fe.
Preferably, the ultra-high strength alloy steel comprises the following components in percentage by mass: 0.35 to 0.55%, si:0.04 to 0.09%, mn: 0.20-0.80%, P < 0.020%, S < 0.0010%, cr:1.75 to 2.25%, mo: 2.00-3.00%, V:0.30 to 0.80%, ni:0.50 to 0.80%, nb:0.05 to 0.20 percent and the balance of Fe.
Preferably, the ultra-high strength alloy steel comprises the following components in percentage by mass: c:0.35 to 0.50%, si:0.05 to 0.08%, mn: 0.30-0.70%, P < 0.020%, S < 0.0010%, cr:1.75 to 2.25%, mo: 2.00-3.00%, V:0.30 to 0.80%, ni:0.50 to 0.80%, nb: 0.10-0.20% and the balance of Fe.
Preferably, the ultra-high strength alloy steel comprises the following components in percentage by mass: c:0.40 to 0.45%, si:0.06 to 0.07%, mn: 0.40-0.60%, P < 0.020%, S < 0.0010%, cr:1.75 to 2.25%, mo: 2.00-3.00%, V:0.40 to 0.70%, ni:0.30 to 0.90%, nb: 0.10-0.15% and the balance Fe.
The invention provides a preparation method of a 16.8-grade 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 ultrahigh-strength alloy steel is the ultrahigh-strength alloy steel in the technical scheme;
(2) Sequentially normalizing, quenching, tempering and shot blasting the hot heading blank obtained in the step (1) to obtain a heat treatment blank;
(3) And (3) sequentially carrying out secondary turning, grinding, thread rolling and R angle rolling on the heat-treated blank obtained in the step (2) to obtain the 16.8-grade threaded fastener.
Preferably, the temperature of the normalizing in the step (2) is 1000-1050 ℃, the 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 during oil quenching is 40-60 ℃, and the time for oil quenching is 10-20 min.
Preferably, the temperature of the tempering in the step (2) is 550-600 ℃, the time of the tempering is 100-150 min, and the cooling mode of the tempering is air cooling.
The invention provides a 16.8-grade threaded fastener prepared by the preparation method in the technical scheme.
The invention provides ultrahigh-strength alloy steel which comprises the following components in percentage by mass: c:0.35 to 0.60%, si:0.035 to 0.15%, mn: 0.10-0.90%, P < 0.020%, S < 0.0010%, cr:1.50 to 2.50%, mo: 2.00-3.00%, V:0.30 to 0.80%, ni:0.25 to 1.00%, nb: 0.001-0.200% and the balance Fe. In the invention, the C element mainly plays a role in improving the strength of the alloy steel; si and Mn can improve the strength and hardenability of the alloy steel through solid solution strengthening; the Cr element can improve the material strength through solid solution strengthening, can simultaneously play a synergistic effect with alloy elements such as Si, mn and the like, further improve the tensile strength of the alloy steel, can form carbide with the C element, is precipitated in the tempering process, and further improves the material strength by utilizing secondary hardening; mo element can form carbide with C element, and is precipitated in the tempering process, and the strength of the material is further improved by secondary hardening; the V element is a fine precipitate element for precipitating carbide, nitride or carbonitride in the alloy steel, can be used as a hydrogen trap to capture hydrogen for harmlessness and improve the delayed fracture resistance of the material by adding the V element, and can improve the strength of the material by virtue of the fine precipitate; the Ni element can improve the strength of the material through solid solution strengthening, simultaneously keep better plasticity and toughness and improve hardenability; 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 the tempering resistance; by controlling the dosage of each element, a synergistic effect can be achieved, and the performance of the alloy steel is further improved. The results of the embodiments show that the 16.8-grade threaded fastener prepared from the ultrahigh-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 of = 0.1), the retention time of the stress endurance performance of 96h under 0.75 times of the tensile strength, and is an ultrahigh-strength (16.8-grade) MJ threaded fastener.
Drawings
FIG. 1 is a schematic drawing showing the machining dimensions of a 16.8-grade threaded fastener provided in example 2 of the present invention;
in the drawing, 1 is a head of a threaded fastener, 2 is a transition zone of the threaded fastener, 3 is a rod of the threaded fastener, and 4 is a threaded zone of the threaded fastener;
FIG. 2 is a schematic drawing of the machining dimensions of the head of a 16.8-grade threaded fastener provided in example 2 of the present invention;
FIG. 3 is a schematic view of the chamfer machining dimension of the shank of a 16.8-grade threaded fastener provided in embodiment 2 of the present invention;
FIG. 4 is a schematic drawing of the machined dimensions of the shank of a 16.8-step threaded fastener provided in accordance with example 2 of the present invention;
FIG. 5 is a schematic diagram of the first turn and second turn process dimensions of a 16.8-grade threaded fastener provided in embodiment 2 of the present invention;
FIG. 6 is a schematic drawing showing the machining dimension of a 16.8-grade threaded fastener grinding process provided in example 2 of the present invention;
FIG. 7 is a schematic drawing showing the machining dimensions of the threaded zone of a 16.8-grade threaded fastener provided in example 2 of the present invention;
fig. 8 is a schematic view of a 16.8-stage threaded fastener transition zone provided in example 2 of the present invention.
Detailed Description
The invention provides ultrahigh-strength alloy steel which comprises the following components in percentage by mass: c:0.35 to 0.60%, si:0.035 to 0.15%, mn: 0.10-0.90%, P is less than 0.020%, S is less than 0.0010%, cr:1.50 to 2.50%, mo: 2.00-3.00%, V:0.30 to 0.80%, ni:0.25 to 1.00%, nb: 0.001-0.200% and the balance 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 C element mainly plays a role in improving the strength of the 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%, and still more preferably 0.06 to 0.07%. In the invention, the Si element can improve the strength and 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 can be prevented from being reduced, thereby further improving the mechanical property of the alloy steel.
The ultrahigh-strength alloy steel 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 still more preferably 0.40 to 0.60%. In the invention, the strength and hardenability of the alloy steel can be improved by solid solution strengthening of the Mn element, and the content of the Mn element is controlled within the range, so that the alloy steel has better strength and hardenability, simultaneously the ductility and toughness of the alloy steel can be prevented from being reduced, and the phenomenon of cracking during heat treatment caused by grain boundary embrittlement due to easy segregation of the Mn element in grain boundaries can be prevented, thereby further improving the mechanical properties of the alloy steel.
The ultrahigh-strength alloy steel provided by the invention comprises P less than 0.020% in percentage by mass. In the invention, the P element is an impurity element, and the influence of the P element on the plasticity and the impact toughness of the steel can be reduced by controlling the content of the P element in a lower range.
The ultrahigh-strength alloy steel provided by the invention comprises, by mass, less than 0.0010% of S. In the invention, the S element is an impurity element, and the influence of the S element on the ductility, the toughness and the corrosion resistance of the steel can be reduced by controlling the content of the S element in a lower range.
According to the mass percentage, the ultrahigh-strength alloy steel provided by the invention comprises the following components: 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 simultaneously can play a synergistic effect with alloy elements such as Si, mn and the like to further improve the tensile strength of alloy steel, and meanwhile, cr element can form carbide with C element to be precipitated 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 ultrahigh-strength alloy steel 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 and C element can form carbide, which is precipitated in the tempering process, and the strength of the material is further improved by secondary hardening; by controlling the dosage, the mechanical property of the alloy steel can be further improved.
According to the mass percentage, the ultrahigh-strength alloy steel provided by the invention comprises the following components: 0.30 to 0.80%, preferably 0.40 to 0.70%, and more preferably 0.50 to 0.80%. In the invention, the V element is a fine precipitate element for precipitating carbide, nitride or carbonitride in the alloy steel, and the V element can be added to serve as a hydrogen trap to capture hydrogen for harmlessness and improve the delayed fracture resistance of the material, and can improve the strength of the material by virtue of the fine precipitate, and meanwhile, the V element can refine crystal 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 can be 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, the Ni element can improve the strength of the material through solid solution strengthening, simultaneously keep better plasticity and toughness and improve the hardenability; by controlling the dosage, the increase of the content of the retained austenite 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 ultrahigh-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 strength of the material by refining crystal grains and forming fine precipitates with carbon element and nitrogen element, and can improve hardenability and tempering resistance; by controlling the dosage, the effect can be optimized, and the supersaturation of Nb element can be avoided, thereby further improving the mechanical property of the material and reducing the cost.
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 ultrahigh-strength alloy steel provided by the invention only needs to be added with a small amount of metals such as Ni and Nb, and has good mechanical properties by adjusting the components of the elements.
The invention provides a 16.8-grade threaded fastener which is prepared from the ultrahigh-strength alloy steel or the ultrahigh-strength alloy steel prepared by the preparation method in the technical scheme.
The invention provides a preparation method of a 16.8-grade threaded fastener in the technical scheme, 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) Sequentially normalizing, quenching, tempering and shot blasting the hot heading blank obtained in the step (1) to obtain a heat treatment blank;
(3) And (3) sequentially carrying out secondary turning, grinding, thread rolling and R angle rolling on the heat-treated blank obtained in the step (2) to obtain the 16.8-grade threaded fastener.
According to the invention, the ultrahigh strength alloy steel is sequentially subjected to first-time counting and hot upsetting to obtain a hot upsetting blank.
In the invention, the first counting trolley preferably performs plane chamfering and cutting in sequence according to the figure 3, then turns around and clamps, and performs plane and acute-angle blunting. According to the invention, the first time of turning is carried out 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 heading is preferably heading a heading according to fig. 4. The temperature of the hot heading is not particularly limited, and the defects such as overheating, overburning, material shortage and the like can be prevented according to the determination of the technical common knowledge of the technical personnel in the field. In the present invention, the cooling means of the hot heading is preferably air cooling. The invention carries out hot heading by the process, and can ensure that the head machining size of the threaded fastener meets the requirement.
After the hot heading blank is obtained, normalizing, quenching, tempering and shot blasting are sequentially carried out on the hot heading blank to obtain a heat treatment blank.
In the invention, the heat preservation temperature of the normalizing is preferably 1000-1050 ℃, and more preferably 1020-1040 ℃; the heat preservation time of the normalizing is preferably 30-60 min, and more preferably 40-50 min; the cooling method of the normalizing 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 specially limited, and the vacuum degree is determined according to the technical common knowledge of the technical personnel in the field, and the oxidation can be avoided in the normalizing process. In the present invention, the rate of temperature increase to the normalizing temperature is not particularly limited, and may be determined based on the technical common knowledge of those skilled in the art. By controlling the normalizing parameter within the range, the invention can further refine the crystal grains in the alloy steel and homogenize the carbide distribution, thereby further improving the mechanical property of the threaded fastener.
In the invention, the heat preservation temperature of quenching is preferably 1000-1050 ℃, and more preferably 1020-1040 ℃; the heat preservation time of quenching is preferably 30-60 min, and more preferably 40-50 min; the cooling mode of quenching is preferably oil quenching; the oil temperature during oil quenching is preferably 40-60 ℃, and more preferably 50 ℃; the time for oil quenching is preferably 10 to 20min, and more preferably 15min. In the present invention, the quenching is preferably performed in a vacuum furnace. The vacuum degree of the vacuum furnace is not specially limited, and the vacuum degree is determined according to the technical common knowledge of the technicians in the field, and the oxidation in the quenching process can be avoided. In the present invention, the rate of temperature increase to the quenching temperature is not particularly limited, and may be determined based on the technical common knowledge of those skilled in the art. The invention can further improve the performances of rigidity, hardness, wear resistance and the like of the threaded fastener by quenching through the process.
In the invention, the tempering heat preservation temperature is preferably 550-600 ℃, and more preferably 560-580 ℃; the tempering heat preservation time is preferably 100-150 min, and more preferably 120-130 min; the cooling mode of tempering 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 specially limited, and the vacuum degree is determined according to the technical common knowledge of the technical personnel in the field, and the oxidation can be avoided in the tempering process. The invention eliminates internal stress through high-temperature tempering, thereby further improving the toughness and the plasticity.
The invention has no special limitation on the specific operation of the shot blasting, and can completely remove the oxide skin on the surface of the heat treatment blank.
After the heat treatment blank is obtained, the heat treatment blank is sequentially subjected to secondary turning, grinding, thread rolling and R angle rolling to obtain the 16.8-grade threaded fastener.
In the invention, the second-time turning is preferably carried out according to the figure 5, such as turning a hexagon head, chamfering a plane, turning and clamping, chamfering a flat end face, turning a blank diameter, turning a rod diameter and turning an R angle under the head in sequence. The invention can make the machining size of the number turning process of the fastening pieces meet the requirement through the process.
In the present invention, the grinding preferably grinds the rod portion to the underhead chamfer as per FIG. 6. The invention can lead the processing size of the threaded fastener in the grinding process to meet the requirements by grinding through the process.
In the present invention, the thread rolling is preferably performed using a thread rolling machine according to fig. 7. The invention can make the processing size of the thread area of the thread fastener meet the requirement by rolling the thread through the process.
In the present invention, the roll R angle is preferably rolled out of the transition between the fastener head and the fastener shank according to fig. 8. In the invention, the specific process of rolling the R angle is preferably that a roller of the roller R is arranged on a rolling clamp, and certain pressure is applied to the fastener through the roller R equipment and drives the fastener and the roller to rotate for rolling. In the invention, the rolling time is preferably 3 +/-1 s; the rolling pressure is preferably 10-13 Kg, more preferably 12Kg; the radius of the roller is preferably 0.8 +/-0.1 mm; the Amax of the thread is preferably 0.030mm; the thread Bmax is preferably 0.025mm; the thread preferably has a Cmax of 2.5mm. The invention rolls the R angle and controls the parameters thereof by the process, so that the machining size of the transition area 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 of the process.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be apparent that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The ultrahigh-strength alloy steel consists of 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 in 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-upset blank; in the invention, the first-time counting lathe is sequentially subjected to plane chamfering and cutting according to the figure 3, then is turned around and clamped, and is subjected to plane chamfering and acute-angle blunting; the hot heading is preferably in a heading head shape according to the figure 4, and the cooling mode of the hot heading is air cooling; the ultra-high strength alloy steel is the ultra-high strength alloy steel provided in example 1;
(2) Sequentially normalizing, quenching, tempering and shot blasting the hot heading blank obtained in the step (1) to obtain a heat treatment 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 the quenching is 1030 ℃, the heat preservation time of the quenching is 60min, and the cooling mode of the quenching is oil quenching; the oil temperature during oil quenching is 50 ℃, and the oil quenching time is 15min; the heat preservation temperature of the tempering is 560 ℃, the heat preservation time of the tempering is 120min, and the cooling mode of the tempering is air cooling;
(3) Sequentially carrying out secondary turning, grinding, thread rolling and R angle rolling on the heat-treated blank obtained in the step (2) to obtain a 16.8-grade threaded fastener; the second-time secondary turning is carried out according to the figure 5, and then a hexagonal head, a plane chamfer, a turning clamping, a flat end face chamfer, a turning blank diameter, a turning rod diameter and a lower-head R angle are turned in sequence; the grinding is carried out according to the diameter of the fine grinding wire blank of figure 6, and the rod part is ground to the lower chamfer; the thread rolling uses a thread rolling machine to roll threads according to fig. 7; the roll R angle rolls out the transition between the fastener head and the fastener shank as per fig. 8; the concrete process of the rolling R angle is that a roller of the rolling R is arranged on a rolling clamp, and certain pressure is applied to the fastening piece through the rolling R equipment to drive the fastening piece and the roller to rotate for rolling; the rolling time was 3s.
The 16.8-grade threaded fastener prepared in example 2 was subjected to mechanical property tests with the following test standards: room temperature uniaxial tension test, double shear test and fatigue test reference standard GJB 3376-1998 general Specification for MJ threaded alloy steel and stainless steel bolts and screws, and stress durability test reference standard GJ/B715.12-1990 stress durability for fastener test methods.
Through tests, the 16.8-grade threaded fastener prepared in example 2 has the tensile strength of 1623MPa, the yield strength of 1380MPa, the plasticity of 10.0%, the shearing force of 95KN, the fatigue life of 130000 times (the load ratio = 0.1), the retention time of the stress endurance property of 96h under 0.75 times of the tensile strength, and is an ultrahigh-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 testing, which was the same as in example 2.
Through tests, the 16.8-grade threaded fastener prepared in example 3 has the tensile strength of 1655MPa, the yield strength of 1403MPa, the plasticity of 10.5%, the shearing force of 95KN, the fatigue life of 130000 times (the load ratio = 0.1), the retention time of the stress endurance property of 96h under 0.75 times of the tensile strength, and is an ultrahigh-strength (16.8-grade) MJ threaded fastener.
Example 4
The tempering temperature in step (2) was 580 deg.C, and the 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, which was the same as in example 2.
Through tests, 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 (the load ratio = 0.1), the retention time of the stress endurance property of 96h under 0.75 times of the tensile strength, and is an ultrahigh-strength (16.8-grade) MJ threaded fastener.
The records of the embodiments 2 to 4 show that the 16.8-grade threaded fastener prepared from the ultrahigh-strength alloy steel provided by the invention has excellent mechanical properties, and is an ultrahigh-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 only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and amendments can be made without departing from the principle of the present invention, and these modifications and amendments should also be considered as the protection scope of the present invention.

Claims (10)

1. The ultrahigh-strength alloy steel comprises the following components in percentage by mass: c:0.35 to 0.60%, si:0.035 to 0.15%, mn: 0.10-0.90%, P is less than 0.020%, S is less than 0.0010%, cr:1.50 to 2.50%, mo: 2.00-3.00%, V:0.30 to 0.80%, ni:0.25 to 1.00%, nb: 0.001-0.200% and the balance Fe.
2. The ultra-high strength alloy steel of claim 1, comprising, in mass percent: c:0.35 to 0.55%, si:0.04 to 0.09%, mn: 0.20-0.80%, P < 0.020%, S < 0.0010%, cr:1.75 to 2.25%, mo: 2.00-3.00%, V:0.30 to 0.80%, ni:0.50 to 0.80%, nb:0.05 to 0.20 percent and the balance of Fe.
3. The ultra-high strength alloy steel of claim 2, comprising, in mass percent: c:0.35 to 0.50%, si:0.05 to 0.08%, mn: 0.30-0.70%, P is less than 0.020%, S is less than 0.0010%, cr:1.75 to 2.25%, mo: 2.00-3.00%, V:0.30 to 0.80%, ni:0.50 to 0.80%, nb: 0.10-0.20% and the balance of Fe.
4. The ultra-high strength alloy steel of claim 3, comprising, in mass percent: c:0.40 to 0.45%, si:0.06 to 0.07%, mn: 0.40-0.60%, P < 0.020%, S < 0.0010%, cr:1.75 to 2.25%, mo: 2.00-3.00%, V:0.40 to 0.70%, ni:0.30 to 0.90%, nb: 0.10-0.15% and the balance of Fe.
5. A method of making a grade 16.8 threaded fastener comprising the steps of:
(1) Sequentially carrying out first turning and hot upsetting on the ultrahigh-strength alloy steel to obtain a hot upsetting blank; the ultrahigh-strength alloy steel is the ultrahigh-strength alloy steel of any one of claims 1 to 4;
(2) Sequentially normalizing, quenching, tempering and shot blasting the hot heading blank obtained in the step (1) to obtain a heat treatment blank;
(3) And (3) sequentially carrying out secondary turning, grinding, thread rolling and R angle rolling on the heat-treated blank obtained in the step (2) to obtain the 16.8-grade threaded fastener.
6. The preparation method according to claim 5, characterized in that the temperature of the normalizing in the step (2) is 1000-1050 ℃, the time of the normalizing is 30-60 min, and the cooling mode of the normalizing is air cooling.
7. The preparation method according to claim 5, wherein the quenching in the step (2) is carried out at a holding temperature of 1000-1050 ℃, for 30-60 min, and in a cooling mode of oil quenching.
8. The preparation method according to claim 5, wherein the oil temperature during oil quenching is 40-60 ℃, and the time for oil quenching is 10-20 min.
9. The preparation method according to claim 5, characterized in that the tempering in the step (2) is carried out at a holding temperature of 550-600 ℃, the tempering is carried out for 100-150 min, and the tempering is carried out by air cooling.
10. 16.8-grade screw fastener prepared by the preparation method of any one of claims 5 to 9.
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