High-strength bolt

Abstract

The invention relates to the technical field of fasteners, and provides a high-strength bolt which is formed by processing a blank, the blank comprises a matrix and a reinforcing phase, and the matrix comprises the following components in percentage by weight: 0.13%-0.22% of C, 0.6%-2.4% of Mn, 0.6%-2.7% of V, 1.4%-2.4% of Zr, 0.1%-0.3% of Ni, 0.2%-0.5% of Cr, less than or equal to 0.01% of P, less than or equal to 0.01% of S and the balance of Fe and inevitable impurities; the reinforcing phase is molybdenum nitride, and the weight ratio of the matrix to the reinforcing phase is 100: (2-6). By means of the technical scheme, the problem that in the related technology, the bolt strength is low is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of fasteners, and in particular to a high-strength bolt. Background Art

[0002] As a key connection element, bolts play a vital role in many engineering applications, such as large bridges, high-rise buildings, and heavy machinery. The strength performance of bolts is directly related to the reliability and stability of the connection structure. With the continuous development of industry, engineering applications have increasingly stringent requirements on the strength of bolts.

[0003] Traditional ordinary bolts gradually expose their limitations in situations with high loads, high vibrations and extremely high safety requirements, and their strength is often difficult to meet the connection requirements under complex working conditions. In view of this situation, in order to further expand the service range of bolts, it is of great significance to develop a high-strength bolt. Summary of the invention

[0004] The present invention provides a high-strength bolt, which solves the problem of low bolt strength in the related art.

[0005] The technical solution of the present invention is as follows: The present invention provides a high-strength bolt, which is processed from a blank. The blank comprises a matrix and a reinforcement phase, wherein the matrix consists of the following components in weight percentage: C 0.13%-0.22%, Mn 0.6%-2.4%, V 0.6%-2.7%, Zr 1.4%-2.4%, Ni 0.1%-0.3%, Cr 0.2%-0.5%, P≤0.01%, S≤0.01%, and the rest are Fe and inevitable impurities; the reinforcement phase is molybdenum nitride, and the weight ratio of the matrix to the reinforcement phase is 100:2-6.

[0006] As a further technical solution, the ratio of the sum of the weights of the Mn and V to the weight of the Zr is 1≤(Mn+V) / Zr≤2.

[0007] In the present invention, when the weight ratio of the sum of Mn and V to the weight of Zr is 1≤(Mn+V) / Zr≤2, it helps to further improve the strength of the bolt.

[0008] As a further technical solution, the weight of the Mn is less than the weight of the V.

[0009] In the present invention, when the weight ratio of the sum of Mn and V to the weight of Zr is 1≤(Mn+V) / Zr≤2 and the weight of Mn is less than the weight of V, it helps to further improve the strength of the bolt.

[0010] As a further technical solution, the average particle size of the molybdenum nitride is 20-50 μm.

[0011] As a further technical solution, the molybdenum nitride is titanium-doped molybdenum nitride, and the raw materials of the titanium-doped molybdenum nitride include titanium powder and molybdenum nitride.

[0012] In the present invention, although molybdenum nitride is added to the matrix in the form of a reinforcing phase to improve the strength of the bolt to a certain extent, the inventors have found that the strength of the bolt can be further improved by doping titanium in molybdenum nitride. It is speculated that this is because titanium-doped molybdenum nitride has better wettability with molten steel than molybdenum nitride.

[0013] As a further technical solution, the average particle size of the titanium powder is 50-100 nm.

[0014] As a further technical solution, the weight ratio of the titanium powder to molybdenum nitride is 1:20~30.

[0015] In the present invention, when the weight ratio of titanium powder to molybdenum nitride is 1:20-30, it helps to further improve the strength of the bolt.

[0016] As a further technical solution, the preparation method of the titanium-doped molybdenum nitride comprises the following steps: uniformly mixing titanium powder and molybdenum nitride, hot pressing and sintering, and crushing to obtain the titanium-doped molybdenum nitride.

[0017] As a further technical solution, during the hot pressing sintering, the temperature is 1000-1200°C, the pressure is 20-30MPa, and the time is 2-4h.

[0018] The present invention also provides a method for preparing a high-strength bolt, comprising the following steps: S1, mixing materials according to the weight percentage of the matrix, smelting, and obtaining molten steel; S2, adding a reinforcing phase into the molten steel, mixing, and casting to obtain a billet; S3. The blank is descaled, cold headed, threaded and heat treated to obtain a bolt.

[0019] As a further technical solution, in step S3, the heat treatment is performed at a temperature of 300-350°C and for a time of 1-2 hours.

[0020] In the present invention, the residual stress of the bolt after cold working can be eliminated by heat treatment, so that the internal structure of the bolt reaches the best.

[0021] The working principle and beneficial effects of the present invention are: In the present invention, on the one hand, the component composition of the matrix is ​​optimized, and on the other hand, a molybdenum nitride reinforcement phase is introduced, so that the bolt has a higher strength. Among them, the strength of the bolt is improved together by the complementary advantages of Mn, V and Zr. In addition, the addition of the molybdenum nitride reinforcement phase can play a pinning role of the second phase particles, improve the ability of the bolt to resist external forces, and thus improve the strength of the bolt. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In the following embodiments and comparative examples, unless otherwise specified, the manganese content in ferromanganese is 75.3wt%; the vanadium content in ferrovanadium is 62.5wt%; the zirconium content in ferrozirconium is 60wt%; the nickel content in ferronickel is 70.3wt%; the chromium content in ferrochrome is 55wt%; the iron content in scrap iron is 97.6wt%; the average particle size of molybdenum nitride is 45μm; and the average particle size of titanium powder is 50nm.

[0024] Example 1 A high-strength bolt is processed from a blank, the blank comprising a matrix and a reinforcement phase, the matrix consisting of the following components in weight percentage: C 0.13%, Mn 0.6%, V 0.6%, Zr 1.4%, Ni 0.1%, Cr 0.2%, P 0.01%, S 0.01%, the remainder being Fe and unavoidable impurities, the reinforcement phase being molybdenum nitride, and the weight ratio of the reinforcement phase to the matrix being 2:100; The preparation method thereof comprises the following steps: S1. Weigh ferromanganese, ferrovanadium, ferrozirconium, ferronickel, ferrochrome and scrap steel according to the target weight percentage of the components of the matrix, and smelt them to obtain molten steel; S2, adding a reinforcing phase into the molten steel, mixing, and casting to obtain a billet; S3. The blank is descaled, cold headed, threaded, and heat treated at 300°C for 2h to obtain a bolt.

[0025] Example 2 A high-strength bolt is processed from a blank, the blank comprising a matrix and a reinforcement phase, the matrix consisting of the following components in weight percentage: C 0.22%, Mn 2.4%, V 2.7%, Zr 2.4%, Ni 0.3%, Cr 0.5%, P 0.005%, S0.005%, the remainder being Fe and unavoidable impurities, the reinforcement phase being molybdenum nitride, and the weight ratio of the reinforcement phase to the matrix being 4:100; The preparation method thereof comprises the following steps: S1. Weigh ferromanganese, ferrovanadium, ferrozirconium, ferronickel, ferrochrome and scrap steel according to the target weight percentage of the components of the matrix, and smelt them to obtain molten steel; S2, adding a reinforcing phase into the molten steel, mixing, and casting to obtain a billet; S3. The blank is descaled, cold headed, threaded, and heat treated at 350°C for 1h to obtain a bolt.

[0026] Example 3 A high-strength bolt is processed from a blank, the blank comprising a matrix and a reinforcement phase, the matrix consisting of the following components in weight percentage: C 0.16%, Mn 0.9%, V 1.2%, Zr 2.4%, Ni 0.2%, Cr 0.4%, P 0.005%, S 0.005%, the remainder being Fe and unavoidable impurities, the reinforcement phase being molybdenum nitride, and the weight ratio of the reinforcement phase to the matrix being 6:100; The preparation method thereof comprises the following steps: S1. Weigh ferromanganese, ferrovanadium, ferrozirconium, ferronickel, ferrochrome and scrap steel according to the target weight percentage of the components of the matrix, and smelt them to obtain molten steel; S2, adding a reinforcing phase into the molten steel, mixing, and casting to obtain a billet; S3. The blank is descaled, cold headed, threaded, and heat treated at 350°C for 1h to obtain a bolt.

[0027] Example 4 The only difference between this embodiment and embodiment 3 is that, in this embodiment, the matrix is ​​composed of the following components in weight percentage: C 0.16%, Mn 1.35%, V 1.75%, Zr 1.4%, Ni 0.2%, Cr 0.4%, P 0.005%, S 0.005%, and the rest is Fe and inevitable impurities.

[0028] Example 5 The only difference between this embodiment and embodiment 3 is that, in this embodiment, the matrix is ​​composed of the following components in weight percentage: C 0.16%, Mn 1%, V 1.25%, Zr 2.25%, Ni 0.2%, Cr 0.4%, P 0.005%, S 0.005%, and the rest is Fe and inevitable impurities.

[0029] Example 6 The only difference between this embodiment and embodiment 3 is that, in this embodiment, the matrix is ​​composed of the following components in weight percentage: C 0.16%, Mn 2%, V 1%, Zr 1.5%, Ni 0.2%, Cr 0.4%, P 0.005%, S 0.005%, and the rest is Fe and inevitable impurities.

[0030] Example 7 The only difference between this embodiment and embodiment 3 is that, in this embodiment, the matrix is ​​composed of the following components in weight percentage: C 0.16%, Mn 1.5%, V 1.5%, Zr 1.5%, Ni 0.2%, Cr 0.4%, P 0.005%, S 0.005%, and the rest is Fe and inevitable impurities.

[0031] Example 8 The only difference between this embodiment and embodiment 3 is that, in this embodiment, the matrix is ​​composed of the following components in weight percentage: C 0.16%, Mn 1%, V 2%, Zr 1.5%, Ni 0.2%, Cr 0.4%, P 0.005%, S 0.005%, and the rest is Fe and inevitable impurities.

[0032] Example 9 The difference between this embodiment and embodiment 8 is that in this embodiment, the reinforcing phase is titanium-doped molybdenum nitride, and the preparation method of titanium-doped molybdenum nitride comprises the following steps: uniformly mixing titanium powder and molybdenum nitride, hot-pressing and sintering at 1100° C. and 25 MPa for 3 h, and crushing to obtain titanium-doped molybdenum nitride with an average particle size of 45 μm; Among them, the weight ratio of titanium powder to molybdenum nitride is 1:15.

[0033] Example 10 The only difference between this embodiment and embodiment 9 is that, in this embodiment, the weight ratio of titanium powder to molybdenum nitride is 1:35.

[0034] Embodiment 11 The only difference between this embodiment and embodiment 9 is that, in this embodiment, the weight ratio of titanium powder to molybdenum nitride is 1:20.

[0035] Example 12 The only difference between this embodiment and embodiment 9 is that, in this embodiment, the weight ratio of titanium powder to molybdenum nitride is 1:30.

[0036] Comparative Example 1 The only difference between this comparative example and Example 1 is that, in this comparative example, the matrix consists of the following components in weight percentage: C 0.13%, Mn 1.2%, Zr 1.4%, Ni 0.1%, Cr 0.2%, P 0.01%, S 0.01%, and the rest is Fe and inevitable impurities.

[0037] Comparative Example 2 The only difference between this comparative example and Example 1 is that, in this comparative example, the matrix consists of the following components in weight percentage: C 0.13%, V 1.2%, Zr 1.4%, Ni 0.1%, Cr 0.2%, P 0.01%, S 0.01%, and the rest is Fe and inevitable impurities.

[0038] Comparative Example 3 The only difference between this comparative example and Example 1 is that, in this comparative example, the matrix consists of the following components in weight percentage: C 0.13%, Mn 1.3%, V 1.3%, Ni 0.1%, Cr 0.2%, P 0.01%, S 0.01%, and the rest is Fe and inevitable impurities.

[0039] Comparative Example 4 The only difference between this comparative example and Example 1 is that, in this comparative example, the matrix consists of the following components in weight percentage: C 0.13%, Zr 2.6%, Ni 0.1%, Cr 0.2%, P 0.01%, S 0.01%, and the rest is Fe and inevitable impurities.

[0040] Comparative Example 5 The only difference between this comparative example and Example 1 is that in this comparative example, no molybdenum nitride reinforcement phase is added.

[0041] The tensile strength and yield strength of the bolts prepared in Examples 1 to 12 and Comparative Examples 1 to 5 were tested using a GL2000 microcomputer-controlled electro-hydraulic servo universal testing machine, wherein the test rate was 0.006 s -1 The final result was the average of the three samples in each group.

[0042] The test results are shown in Table 1 below.

[0043] Table 1 Tensile strength and yield strength test results

[0044] Comparison between Example 1 and Comparative Examples 1 to 4 shows that the strength of the bolt can be improved by the complementary advantages of Mn, V and Zr. Comparison between Example 1 and Comparative Example 5 shows that the addition of molybdenum nitride reinforcement phase can significantly improve the strength of the bolt.

[0045] Comparison between Examples 3-4 and Examples 5-8 shows that when the weight ratio of Mn and V to the weight of Zr is 1≤(Mn+V) / Zr≤2, it helps to further improve the strength of the bolt. Comparison between Example 8 and Examples 6-7 shows that when the weight ratio of Mn and V to the weight of Zr is 1≤(Mn+V) / Zr≤2 and the weight of Mn is less than the weight of V, it helps to further improve the strength of the bolt.

[0046] Comparison between Example 8 and Examples 9 to 12 shows that the strength of the bolt can be further improved by doping titanium in molybdenum nitride. Comparison between Examples 9 to 10 and Examples 11 to 12 shows that when the weight ratio of titanium powder to molybdenum nitride is 1:20 to 30, it helps to further improve the strength of the bolt.

[0047] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-strength bolt, processed from a blank, characterized in that: The blank comprises a matrix and a reinforcement phase, wherein the matrix is ​​composed of the following components in weight percentage: C 0.13%-0.22%, Mn 0.6%-2.4%, V 0.6%-2.7%, Zr 1.4%-2.4%, Ni 0.1%-0.3%, Cr 0.2%-0.5%, P≤0.01%, S≤0.01%, and the rest are Fe and unavoidable impurities; the reinforcement phase is molybdenum nitride, and the weight ratio of the matrix to the reinforcement phase is 100:2-6.

2. A high-strength bolt according to claim 1, characterized in that: The ratio of the sum of the weights of the Mn and V to the weight of the Zr is 1≤(Mn+V) / Zr≤2.

3. A high-strength bolt according to claim 2, characterized in that: The weight of the Mn is smaller than the weight of the V.

4. A high-strength bolt according to claim 1, characterized in that: The average particle size of the molybdenum nitride is 20-50 μm.

5. The high-strength bolt according to claim 1, characterized in that: The molybdenum nitride is titanium-doped molybdenum nitride, and the raw materials of the titanium-doped molybdenum nitride include titanium powder and molybdenum nitride.

6. A high strength bolt according to claim 5, characterized in that: The weight ratio of the titanium powder to molybdenum nitride is 1:20-30.

7. A high strength bolt according to claim 5, characterized in that: The preparation method of titanium-doped molybdenum nitride comprises the following steps: uniformly mixing titanium powder and molybdenum nitride, hot-pressing and sintering, and crushing to obtain the titanium-doped molybdenum nitride.

8. A high strength bolt according to claim 7, characterized in that: During the hot pressing sintering, the temperature is 1000-1200° C., the pressure is 20-30 MPa, and the time is 2-4 hours.

9. A method for preparing a high-strength bolt according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, mixing materials according to the weight percentage of the matrix, smelting, and obtaining molten steel; S2, adding a reinforcing phase into the molten steel, mixing, and casting to obtain a billet; S3. The blank is descaled, cold headed, threaded and heat treated to obtain a bolt.

10. A method for preparing a high-strength bolt according to claim 9, characterized in that: In step S3, during the heat treatment, the temperature is 300-350° C. and the time is 1-2 hours.

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