CN115233101A - Ultrahigh-strength alloy steel, 18.8-grade threaded fastener and preparation method thereof - Google Patents

Ultrahigh-strength alloy steel, 18.8-grade threaded fastener and preparation method thereof Download PDF

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Publication number
CN115233101A
CN115233101A CN202210866454.1A CN202210866454A CN115233101A CN 115233101 A CN115233101 A CN 115233101A CN 202210866454 A CN202210866454 A CN 202210866454A CN 115233101 A CN115233101 A CN 115233101A
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alloy steel
strength
ultrahigh
strength alloy
threaded fastener
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董瀚
胡杰
胡春东
陆恒昌
韦习成
赵洪山
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Shanghai University Zhejiang High End Equipment Basic Materials Research Institute
University of Shanghai for Science and Technology
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Shanghai University Zhejiang High End Equipment Basic Materials Research Institute
University of Shanghai for Science and Technology
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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
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • 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)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • General Engineering & Computer Science (AREA)
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Abstract

The invention provides ultrahigh-strength alloy steel, an 18.8-grade threaded fastener and a preparation method thereof, and belongs to the field of high-strength alloy fastener manufacturing. The ultrahigh-strength alloy steel provided by the invention comprises the following components in percentage by mass: c:0.25 to 0.50%, si:0.10 to 0.35%, mn: 0.30-1.00%, P is less than 0.020%, S is less than 0.0010%, cr:2.50 to 3.50%, mo:3.01 to 4.00%, V: 0.20-0.70% and the balance Fe. The results of the examples show that the tensile strength of the threaded fastener is 1800-1970 MPa, the yield strength is 1440-1576 MPa, the plasticity is more than or equal to 8%, the shearing force is more than or equal to 100KN, the fatigue life is 130000 times (load ratio = 0.1), and the stress endurance performance is kept for 96h under 0.75 times of tensile strength.

Description

Ultrahigh-strength alloy steel, 18.8-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, an 18.8-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 and national defense, but the fastener industry in China is generally at a middle and low end level, 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, many high-end fasteners depend on import, the imported countries are mainly developed countries such as Japan, europe and America and the like, the high-end fasteners are imported for a long time, high cost pressure can be caused to enterprises, and the high-end fasteners can easily become neck products of key parts of the heavy equipment in China. Therefore, our country needs to accelerate the promotion of high-end upgrading of the domestic fastener products and adjust the industrial structure. Furthermore, 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. The automobile industry is an industry with larger fastener demand, and the average number of the fasteners used for each automobile on a car is about 580, 50kg and 5000 pieces, 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, and 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 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 0.002 and less than or equal to 0.04, al is more than or equal to 0.05, N is more than or equal to 0.006 and less than or equal to 0.015, any one or the sum of Ti and Zr is 0.01-0.15, and the balance of Fe, and the maximum tensile strength of the bolt can only reach the performance requirement of a 15.9-grade bolt in percentage by weight. Patent 200810049411 discloses a preparation method of a 16.9-grade bolt, which comprises the following chemical components of 0.15-0.19% of C, 0.10% of Si, 0.10% of Mn, 0.008% of P, 0.005,1.80-2.00,0.10-0.90% of Mo, 9.50-10.50 of Ni, 13.50-14.50 of Co, 0.015% of Ti, 0.002% of O, 0.0015 of N and the balance of Fe, wherein the mass percent of the precious metals such as Ni and Co are higher in content, and 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 low precious metal content, so that a threaded fastener with high tensile strength can be prepared from the ultrahigh strength alloy steel.
Disclosure of Invention
The invention aims to provide ultrahigh-strength alloy steel, an 18.8-grade threaded fastener and a preparation method thereof. The ultrahigh-strength alloy steel provided by the invention does not contain precious metals such as Ni and Co, has excellent mechanical properties, and can be used for preparing ultrahigh-strength (18.8-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:0.25 to 0.50%, si:0.10 to 0.35%, mn: 0.30-1.00%, P is less than 0.020%, S is less than 0.0010%, cr:2.50 to 3.50%, mo:3.01 to 4.00%, V:0.20 to 0.70 percent and the balance of Fe.
Preferably, the composition comprises the following components in percentage by mass: c:0.30 to 0.50%, si:0.15 to 0.35%, mn: 0.40-0.90%, P is less than 0.020%, S is less than 0.0010%, cr:2.50 to 3.50%, mo:3.01 to 4.00%, V: 0.30-0.70% and the balance Fe.
Preferably, the composition comprises the following components in percentage by mass: c:0.35 to 0.50%, si:0.20 to 0.35%, mn: 0.50-0.80%, P < 0.020%, S < 0.0010%, cr:2.50 to 3.00%, mo:3.01 to 3.50%, V: 0.40-0.70% and the balance Fe.
Preferably, the composition comprises the following components in percentage by mass: c:0.40 to 0.45%, si:0.25 to 0.30%, mn: 0.60-0.70%, P is less than 0.020%, S is less than 0.0010%, cr: 2.80-3.00%, mo:3.20 to 3.50%, V: 0.50-0.60% and the balance Fe.
The invention provides a preparation method of an 18.8-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 carrying out normalizing, quenching, tempering and shot blasting on 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 18.8-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 of the oil quenching is 40-60 ℃, and the time of the 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 an 18.8-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:0.25 to 0.50%, si:0.10 to 0.35%, mn: 0.30-1.00%, P less than 0.020%, S less than 0.0010%, cr:2.50 to 3.50%, mo:3.01 to 4.00%, V: 0.20-0.70% 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 and C element can form carbide, and the carbide 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; 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 examples show that the ultrahigh-strength (18.8-grade) MJ threaded fastener prepared from the ultrahigh-strength alloy steel provided by the invention has the tensile strength of 1800-1970 MPa, the yield strength of 1440-1576 MPa, the plasticity of more than or equal to 8%, the shearing force of more than or equal to 100KN, the fatigue life of 130000 times (load ratio = 0.1), the retention time of the stress endurance performance of 96h at 0.75 times of the tensile strength, and the ultrahigh-strength (18.8-grade) MJ threaded fastener.
Drawings
FIG. 1 is a schematic drawing showing machining dimensions of an 18.8-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 18.8-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 an 18.8-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 grade 18.8 threaded fastener provided in accordance with example 2 of the present invention;
FIG. 5 is a schematic diagram of the first and second lathing process machining dimensions of a 18.8-grade threaded fastener provided by embodiment 2 of the invention;
FIG. 6 is a schematic drawing showing the machining dimension of the 18.8-grade threaded fastener grinding process provided in example 2 of the present invention;
FIG. 7 is a schematic view of the machining dimensions of the threaded zone of the 18.8-grade threaded fastener provided in example 2 of the present invention;
fig. 8 is a schematic view of the transition zone processing of a 18.8-grade threaded fastener provided in embodiment 2 of the present invention.
Detailed Description
The invention provides ultrahigh-strength alloy steel which comprises the following components in percentage by mass: c:0.25 to 0.50%, si:0.10 to 0.35%, mn: 0.30-1.00%, P less than 0.020%, S less than 0.0010%, cr:2.50 to 3.50%, mo:3.01 to 4.00%, V:0.20 to 0.70 percent and the balance of Fe.
The ultrahigh-strength alloy steel provided by the invention comprises the following components in percentage by mass: 0.25 to 0.50%, preferably 0.30 to 0.50%, more preferably 0.35 to 0.45%, 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: 0.10 to 0.35%, preferably 0.15 to 0.35%, more preferably 0.20 to 0.30%, and still more preferably 0.25%. In the invention, si element can improve the strength and the hardenability of the alloy steel through solid solution strengthening, and the content of 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 provided by the invention comprises the following components in percentage by mass: 0.30 to 1.00%, preferably 0.40 to 0.90%, more preferably 0.50 to 0.80%, and still more preferably 0.60 to 0.70%. In the invention, the Mn element can improve the strength and the hardenability of the alloy steel through solid solution strengthening, and the content of the Mn element is controlled within the range, so that the alloy steel has better strength and hardenability, simultaneously the reduction of the ductility and the toughness of the alloy steel can be avoided, and the phenomenon of cracking during heat treatment caused by grain boundary embrittlement due to easy segregation of the Mn element in the grain boundary can be prevented, thereby further improving the mechanical property of the alloy steel.
The ultrahigh-strength alloy steel comprises P which is 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 comprises, by mass, S which is less than 0.0010%. 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.
The ultrahigh-strength alloy steel comprises the following components in percentage by mass: 2.50 to 3.50%, preferably 2.75 to 3.25%, and more preferably 3.00%. 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: 3.01 to 4.00%, preferably 3.25 to 3.75%, and more preferably 3.50%. 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: 0.20 to 0.70%, preferably 0.40 to 0.70%, and more preferably 0.50 to 0.60%. 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 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, and meanwhile, the V element can refine crystal grains, improve the hardenability and improve the tempering resistance; by controlling the dosage, the effect can be further improved, thereby improving the performance of the alloy steel.
According to the mass percentage, the ultrahigh-strength alloy steel provided by the invention comprises the balance of Fe. 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 does not need to be added with precious metals such as Ni and Co, and has good mechanical properties by adjusting the components of the elements.
The preparation method of the ultrahigh-strength alloy steel is not particularly limited, and the cast alloy steel can be obtained by adopting the operation of preparing the alloy steel, which is well known to those skilled in the art.
The invention provides a preparation method of an 18.8-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 18.8-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-time counting is preferably performed with planar chamfering and cutting in sequence according to the figure 3, then the head is turned and the clamp is clamped, and the planar chamfering and acute-angle blunting are performed. According to the invention, the first time of turning is carried out according to the process, so that the size of the 18.8-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 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-treated 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 heating rate of the heating to the normalizing temperature is not particularly limited, and may be determined according to 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; by adopting the vacuum furnace for normalizing treatment, the problems of oxidation and the like in the normalizing process can be avoided.
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 the 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 technical personnel in the field, and the oxidation can be avoided in the quenching process. 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 carries out quenching through the process, and can further improve the performances of rigidity, hardness, wear resistance and the like of the threaded fastener; by adopting the vacuum furnace for quenching treatment, the problems of oxidation and the like in the quenching process can be avoided.
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 the internal stress through high-temperature tempering, thereby further improving the toughness and plasticity of the alloy; by adopting the vacuum furnace for tempering treatment, the problems of oxidation and the like in the tempering process can be avoided.
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 18.8-grade threaded fastener.
In the invention, the second-time turning preferably sequentially carries out turning of a hexagonal head, planar chamfering, turning and clamping, flat end face chamfering, turning of a blank diameter, turning of a rod diameter and turning of an underhead R angle according to the drawing 5. The invention can make the machining size of the fastener in the turning process 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 in accordance with fig. 8 in the transition between the fastener head and the fastener shank. 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 by the roller R equipment and the fastener and the roller are driven 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 is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Example 1
The ultrahigh-strength alloy steel consists of the following components in percentage by mass: c:0.33%, si:0.26%, mn:0.55%, P:0.01%, S:0.0005%, cr:3.06%, mo:3.54%, V:0.55% and the balance Fe.
Example 2
A preparation method of an 18.8-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 counting trolley sequentially performs plane chamfering and cutting according to the figure 3, then turns around and clamps, and performs plane and acute-angle blunting; the hot heading is preferably in a heading head shape according to a 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 carrying out normalizing, quenching, tempering and shot blasting on 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 1040 ℃, 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 quenching time is 15min; the heat preservation temperature of the tempering is 570 ℃, 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 an 18.8-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 was done using a thread roller to roll the threads as per 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 is 3s.
The 18.8-grade threaded fastener prepared in example 2 was subjected to mechanical property tests with the following test standards: the room temperature uniaxial tension test, the double shear test and the fatigue test are referenced by GJB 3376-1998 general Specification for MJ threaded alloy steel and stainless steel bolts and screws, and the stress durability test is referenced by GJ/B715.12-1990 stress durability of fastener test method.
Through tests, the 18.8-grade threaded fastener prepared in the example 2 has the tensile strength of 1860MPa, the yield strength of 1504MPa, the plasticity of 8.5%, the shearing force of 104KN, the fatigue life of 130000 times (load ratio = 0.1), the retention time of the stress endurance performance of 96h under 0.75 times of tensile strength, and the ultrahigh-strength (18.8-grade) MJ threaded fastener.
Example 3
The tempering temperature in the step (2) was 580 ℃, and other conditions were the same as in example 2.
The 18.8-grade threaded fastener prepared in example 3 was subjected to mechanical property testing, which was the same as in example 2.
Through tests, the 18.8-grade threaded fastener prepared in example 3 has the tensile strength of 1885MPa, the yield strength of 1530MPa, the plasticity of 9.0%, the shearing force of 104KN, the fatigue life of 130000 times (load ratio = 0.1), the retention time of the stress endurance property of 96h under 0.75 times of tensile strength, and is an ultrahigh-strength (18.8-grade) MJ threaded fastener.
Example 4
The tempering temperature in the step (2) was 590 ℃, and other conditions were the same as in example 2.
The 18.8-grade threaded fastener prepared in example 4 was subjected to mechanical property testing, which was the same as in example 2.
Through tests, the 18.8-grade threaded fastener prepared in example 4 has the tensile strength of 1905MPa, the yield strength of 1535MPa, the plasticity of 9.5%, the shearing force of 104KN, the fatigue life of 130000 times (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 (18.8-grade) MJ threaded fastener.
The records of the embodiments 2 to 4 show that the 18.8-grade threaded fastener prepared from the ultrahigh-strength alloy steel provided by the invention has excellent mechanical properties, and is an ultrahigh-strength (18.8-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 decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded 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:0.25 to 0.50%, si:0.10 to 0.35%, mn: 0.30-1.00%, P is less than 0.020%, S is less than 0.0010%, cr:2.50 to 3.50%, mo:3.01 to 4.00%, V: 0.20-0.70% and the balance Fe.
2. The ultra-high strength alloy steel of claim 1, comprising, in mass percent: c:0.30 to 0.50%, si:0.15 to 0.35%, mn: 0.40-0.90%, P < 0.020%, S < 0.0010%, cr:2.50 to 3.50%, mo:3.01 to 4.00%, V: 0.30-0.70% 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:0.20 to 0.35%, mn: 0.50-0.80%, P < 0.020%, S < 0.0010%, cr:2.50 to 3.00%, mo:3.01 to 3.50%, V: 0.40-0.70% and the balance of Fe.
4. The ultra-high strength alloy steel according to claim 3, comprising, in mass percent: c:0.40 to 0.45%, si:0.25 to 0.30%, mn: 0.60-0.70%, P < 0.020%, S < 0.0010%, cr:2.80 to 3.00%, mo: 3.20-3.50%, V: 0.50-0.60% and the balance of Fe.
5. A method of making an 18.8-grade 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-upset blank; the ultra-high strength alloy steel is the ultra-high 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 18.8-grade threaded fastener.
6. The preparation method according to claim 5, characterized in that 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.
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 of claim 7, wherein the oil quenching temperature is 40-60 ℃, and the oil quenching time is 10-20 min.
9. The preparation method according to claim 5, characterized in that the temperature of the tempering in the step (2) is 550-600 ℃, the temperature of the tempering is 100-150 min, and the cooling mode of the tempering is air cooling.
10. The 18.8-grade screw fastener prepared by the preparation method of any one of claims 5 to 9.
CN202210866454.1A 2022-07-22 2022-07-22 Ultrahigh-strength alloy steel, 18.8-grade threaded fastener and preparation method thereof Pending CN115233101A (en)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0525585A (en) * 1991-07-15 1993-02-02 Hitachi Ltd Roll for rolling excellent in wear resistance and grindability
EP0672761A2 (en) * 1994-02-17 1995-09-20 Uddeholm Strip Steel Aktiebolag Use of a steel alloy
JP2001049344A (en) * 1999-08-02 2001-02-20 Nippon Steel Corp Production of combined roll for cold-rolling and roll
CN105803314A (en) * 2016-05-09 2016-07-27 天津钢研海德科技有限公司 High-grade hot work die steel with high performance and manufacturing method of high-grade hot work die steel
WO2019233962A1 (en) * 2018-06-07 2019-12-12 Voestalpine Böhler Edelstahl Gmbh & Co Kg Method for producing an object from a hot work steel
JP2020026567A (en) * 2018-08-17 2020-02-20 日立金属株式会社 Hot stamp die steel, hot stamp die and method for producing the same
CN111842774A (en) * 2020-07-29 2020-10-30 苏州畅利永紧固件有限公司 Outer hexagonal cross bolt machining process

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0525585A (en) * 1991-07-15 1993-02-02 Hitachi Ltd Roll for rolling excellent in wear resistance and grindability
EP0672761A2 (en) * 1994-02-17 1995-09-20 Uddeholm Strip Steel Aktiebolag Use of a steel alloy
JP2001049344A (en) * 1999-08-02 2001-02-20 Nippon Steel Corp Production of combined roll for cold-rolling and roll
CN105803314A (en) * 2016-05-09 2016-07-27 天津钢研海德科技有限公司 High-grade hot work die steel with high performance and manufacturing method of high-grade hot work die steel
WO2019233962A1 (en) * 2018-06-07 2019-12-12 Voestalpine Böhler Edelstahl Gmbh & Co Kg Method for producing an object from a hot work steel
JP2020026567A (en) * 2018-08-17 2020-02-20 日立金属株式会社 Hot stamp die steel, hot stamp die and method for producing the same
CN111842774A (en) * 2020-07-29 2020-10-30 苏州畅利永紧固件有限公司 Outer hexagonal cross bolt machining process

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