High-strength bolt and preparation method thereof

Abstract

The invention relates to the technical field of fasteners, and provides a high-strength bolt and a preparation method thereof.The blank comprises a base body and a reinforcing phase, and the base body is composed of, by weight, 0.25%-0.41% of C, 0.15%-0.37% of Si, 0.30%-0.90% of Mn, 0.4%-1.50% of Cr, 0.15%-0.55% of Mo, 0.5%-1.2% of Ni, 0.1%-0.15% of Cu, 0.01%-0.05% of Nb, smaller than or equal to 0.015% of P, smaller than or equal to 0.003% of S, smaller than or equal to 0.005% of N and the balance iron and inevitable impurities; the reinforcing phase is composed of zirconium oxide and aluminum oxide; the weight ratio of the matrix to the reinforcing phase is 100: (3-8). According to the technical scheme, the problem that in the prior art, the yield strength and tensile strength of a bolt are 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 and a preparation method thereof. Background Art

[0002] A bolt is a mechanical part, a cylindrical threaded fastener equipped with a nut. Bolts can firmly connect two or more parts together to form a complete system or machine, ensuring that the parts maintain a relatively fixed position relationship. Low-strength bolts have the following problems during use: 1. When the yield strength of the bolt is insufficient, when the stress on the bolt reaches the yield strength, the bolt will begin to produce permanent plastic deformation, affecting the machining precision of the machine tool; 2. When the tensile strength of the bolt is insufficient, when subjected to a large axial tensile force, the bolt can easily be elongated or even broken, posing a great safety hazard. Therefore, it is necessary to improve the tensile strength and yield strength of the bolt to expand the application range of the bolt, improve the safety of the structure and the reliability of the equipment. Summary of the invention

[0003] The present invention provides a high-strength bolt and a preparation method thereof, which solves the problem of low yield strength and tensile strength of the bolt in the related art.

[0004] The technical solution of the present invention is as follows: The 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 0.25%-0.41%, Si 0.15%-0.37%, Mn 0.30%-0.90%, Cr0.4%-1.50%, Mo 0.15%-0.55%, Ni 0.5%-1.2%, Cu 0.1%-0.15%, Nb 0.01%-0.05%, P≤0.015%, S≤0.003%, N≤0.005%, and the remainder is iron and unavoidable impurities; the reinforcement phase consists of zirconium oxide and aluminum oxide; and the weight ratio of the matrix to the reinforcement phase is 100:3-8.

[0005] As a further technical solution, the zirconium oxide is tetragonal zirconium oxide.

[0006] As a further technical solution, the alumina includes one or both of α-alumina and γ-alumina.

[0007] As a further technical solution, the alumina is γ-alumina.

[0008] As a further technical solution, the particle sizes of the zirconium oxide and aluminum oxide are both 30 nm.

[0009] In the present invention, when the alumina is limited to γ-alumina, it can be better compounded with zirconium oxide, and the tensile strength and yield strength of the bolt can be further improved.

[0010] As a further technical solution, the mass ratio of zirconium oxide to aluminum oxide is 1:3-5.

[0011] As a further technical solution, the mass ratio of zirconium oxide to aluminum oxide is 1:4.

[0012] As a further technical solution, the weight ratio of the sum of the masses of Ni and Cr to the weight of Mo is 3≤(Ni+Cr) / Mo≤14.

[0013] As a further technical solution, the weight ratio of the sum of the masses of Ni and Cr to the weight of Mo is 5≤(Ni+Cr) / Mo≤5.5.

[0014] In the present invention, by limiting the mass ratio of Ni, Cr and Mo, the advantages of each component can be better utilized and the tensile strength and yield strength of the bolt can be further improved.

[0015] As a further technical solution, the mass ratio of Ni to Cr is 0.5≤Ni / Cr≤2.

[0016] As a further technical solution, the mass ratio of Ni to Cr is Ni / Cr=1.

[0017] The present invention also proposes 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 subjected to heat treatment, drawing and thread processing to obtain a bolt.

[0018] As a further technical solution, the heat treatment is normalizing, quenching and tempering in sequence.

[0019] As a further technical solution, the thread processing is performed by rolling technology.

[0020] The working principle and beneficial effects of the present invention are: The present invention improves the tensile strength and yield strength of the bolt by designing the components such as Ni, Cr, Mo and the proportion of the components in the bolt matrix. The reinforcing phase composed of zirconium oxide and aluminum oxide can hinder the movement of dislocations in the alloy matrix and refine the grain structure, thereby further improving the tensile strength and yield strength of the bolt, expanding the application range of the bolt, and improving the safety of the structure and the reliability of the equipment. DETAILED DESCRIPTION

[0021] 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.

[0022] In the following examples and comparative examples: The particle size of tetragonal zirconia is 30 nm; the particle size of α-alumina is 30 nm, and the particle size of γ-alumina is 30 nm.

[0023] Example 1 A high-strength bolt is processed from a blank, wherein the blank comprises a matrix and a reinforcement phase, wherein the matrix consists of the following components in weight percentage: C 0.25%, Si 0.15%, Mn 0.30%, Cr 0.4%, Mo 0.3%, Ni 0.5%, Cu 0.1%, Nb 0.01%, P 0.015%, S 0.003%, N 0.005%, and the remainder is iron and unavoidable impurities; the reinforcement phase consists of tetragonal zirconia and α-alumina in a mass ratio of 1:3, and the weight ratio of the matrix to the reinforcement phase is 100:3.

[0024] A method for preparing a high-strength bolt comprises the following steps: S1, after batching according to the weight percentage of the above-mentioned group components, smelting to obtain molten steel; S2, adding a reinforcing phase into the molten steel, mixing, and casting to obtain a billet; S3. The blank is normalized, quenched, tempered, drawn, and threaded by rolling to obtain a bolt.

[0025] Example 2 A high-strength bolt is processed from a blank, wherein the blank comprises a matrix and a reinforcement phase, wherein the matrix consists of the following components in weight percentage: C 0.35%, Si 0.25%, Mn 0.40%, Cr 0.90%, Mo 0.35%, Ni 0.9%, Cu 0.12%, Nb 0.03%, P 0.014%, S 0.002%, N 0.003%, and the remainder is iron and unavoidable impurities; the reinforcement phase consists of tetragonal zirconia and α-alumina in a mass ratio of 1:4, and the weight ratio of the matrix to the reinforcement phase is 100:5.

[0026] A method for preparing a high-strength bolt comprises the following steps: S1, after batching according to the weight percentage of the above-mentioned group components, smelting to obtain molten steel; S2, adding a reinforcing phase into the molten steel, mixing, and casting to obtain a billet; S3. The blank is normalized, quenched, tempered, drawn, and threaded by rolling to obtain a bolt.

[0027] Example 3 A high-strength bolt is processed from a blank, wherein the blank comprises a matrix and a reinforcement phase, wherein the matrix consists of the following components in weight percentage: C 0.41%, Si 0.37%, Mn 0.90%, Cr 1.50%, Mo 0.42%, Ni 1.2%, Cu 0.15%, Nb 0.05%, P 0.012%, S 0.002%, N 0.003%, and the remainder is iron and unavoidable impurities; the reinforcement phase consists of tetragonal zirconia and α-alumina in a mass ratio of 1:5, and the weight ratio of the matrix to the reinforcement phase is 100:8.

[0028] A method for preparing a high-strength bolt comprises the following steps: S1, after batching according to the weight percentage of the above-mentioned group components, smelting to obtain molten steel; S2, adding a reinforcing phase into the molten steel, mixing, and casting to obtain a billet; S3. The blank is normalized, quenched, tempered, drawn, and threaded by rolling to obtain a bolt.

[0029] Example 4 Compared with Example 2, the only difference of this embodiment is that the matrix in this embodiment is composed of the following components in weight percentage: C 0.35%, Si 0.25%, Mn 0.40%, Cr 1.0%, Mo 0.15%, Ni 1.0%, Cu 0.12%, Nb 0.03%, P0.014%, S 0.002%, N 0.003%, and the rest is iron and unavoidable impurities.

[0030] Example 5 Compared with Example 2, the only difference of this embodiment is that the matrix in this embodiment is composed of the following components in weight percentage: C 0.35%, Si 0.25%, Mn 0.40%, Cr 0.8%, Mo 0.55%, Ni 0.8%, Cu 0.12%, Nb 0.03%, P0.014%, S 0.002%, N 0.003%, and the rest is iron and unavoidable impurities.

[0031] Example 6 Compared with Example 2, the only difference of this embodiment is that the matrix in this embodiment is composed of the following components in weight percentage: C 0.35%, Si 0.25%, Mn 0.40%, Cr 1.1%, Mo 0.35%, Ni 0.7%, Cu 0.12%, Nb 0.03%, P0.014%, S 0.002%, N 0.003%, and the rest is iron and unavoidable impurities.

[0032] Example 7 Compared with Example 2, the only difference of this embodiment is that the matrix in this embodiment is composed of the following components in weight percentage: C 0.35%, Si 0.25%, Mn 0.40%, Cr 0.6%, Mo 0.35%, Ni 1.2%, Cu 0.12%, Nb 0.03%, P0.014%, S 0.002%, N 0.003%, and the rest is iron and unavoidable impurities.

[0033] Example 8 Compared with Example 2, the only difference of this example is that the reinforcement phase in this example is composed of tetragonal zirconia and α-alumina in a mass ratio of 1:3.

[0034] Example 9 Compared with Example 2, the only difference of this example is that the reinforcement phase in this example is composed of tetragonal zirconia and α-alumina in a mass ratio of 1:5.

[0035] Example 10 Compared with Example 2, the only difference of this example is that the reinforcing phase in this example is composed of tetragonal zirconia and γ-alumina in a mass ratio of 1:4.

[0036] Comparative Example 1 Compared with Example 5, the only difference of this comparative example is that the reinforcing phase in this comparative example is tetragonal zirconia.

[0037] Comparative Example 2 Compared with Example 5, the only difference of this comparative example is that the reinforcing phase in this comparative example is α-alumina.

[0038] Comparative Example 3 Compared with Example 5, the only difference of this comparative example is that the reinforcing phase in this comparative example is γ-alumina.

[0039] Comparative Example 4 Compared with Example 5, the only difference of this comparative example is that the matrix in this comparative example is composed of the following components in weight percentage: C 0.35%, Si 0.25%, Mn 0.40%, Cr 0.40%, Mo 0.27%, Ni 0.4%, Cu 0.12%, Nb 0.03%, P 0.014%, S 0.002%, N 0.003%, and the rest is iron and unavoidable impurities.

[0040] Comparative Example 5 Compared with Example 5, the only difference of this comparative example is that the matrix in this comparative example does not contain Ni.

[0041] Test example The tensile strength and yield strength of the bolts prepared in Examples 1 to 10 and Comparative Examples 1 to 5 were tested using a WAW-300B0 microcomputer-controlled electro-hydraulic servo universal testing machine, wherein the test rate was 0.008 s -1 The final result was the average of the results of three samples in each group.

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

[0043] Table 1 Test results of tensile strength and yield strength in Examples and Comparative Examples

[0044] Compared with Comparative Examples 4-5, the tensile strength and yield strength of the bolts in Examples 1-10 are higher than those in Comparative Examples 4-5, indicating that the present invention can improve the tensile strength and yield strength of the bolts by limiting the components of the substrate and the mass ratio of each component.

[0045] Compared with comparative examples 1 to 3, the tensile strength and yield strength of the bolts in embodiments 1 to 10 are higher than those in comparative examples 1 to 3, indicating that the present invention can improve the tensile strength and yield strength of the bolts by limiting the reinforcing phase to consist of zirconium oxide and aluminum oxide.

[0046] Compared with Example 2, Examples 4~5 change the mass ratio of Ni, Cr, and Mo. As a result, the tensile strength and yield strength of the bolt in Example 2 are higher than those in Examples 4~5, indicating that when the mass relationship of Ni, Cr, and Mo in the substrate is (Ni+Cr) / Mo=5.14, the tensile strength and yield strength of the bolt can be improved.

[0047] Compared with Example 2, Examples 6-7 change the ratio of Ni to Cr. As a result, the tensile strength and yield strength of the bolt in Example 2 are higher than those in Examples 6-7, indicating that when the mass relationship between Ni and Cr in the substrate is Ni / Cr=1, the tensile strength and yield strength of the bolt can be improved.

[0048] Compared with Example 2, Examples 8 to 10 changed the ratio of zirconium oxide to aluminum oxide and the crystal form of aluminum oxide. As a result, the tensile strength and yield strength of the bolt in Example 10 were higher than those in Example 2, Example 8, and Example 9, indicating that when the reinforcing phase is composed of zirconium oxide and γ-alumina in a mass ratio of 1:4, the tensile strength and bending strength of the bolt can be further improved.

[0049] 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 0.25%-0.41%, Si 0.15%-0.37%, Mn 0.30%-0.90%, Cr0.4%-1.50%, Mo 0.15%-0.55%, Ni 0.5%-1.2%, Cu 0.1%-0.15%, Nb 0.01%-0.05%, P≤0.015%, S≤0.003%, N≤0.005%, and the remainder is iron and unavoidable impurities; the reinforcement phase is composed of zirconium oxide and aluminum oxide; and the weight ratio of the matrix to the reinforcement phase is 100:3-8.

2. A high-strength bolt according to claim 1, characterized in that: The zirconium oxide is tetragonal zirconium oxide.

3. A high-strength bolt according to claim 1, characterized in that: The aluminum oxide includes one or both of α-aluminum oxide and γ-aluminum oxide.

4. The method for preparing a high-strength bolt according to claim 3, characterized in that: The alumina is γ-alumina.

5. The high-strength bolt according to claim 1, characterized in that: The mass ratio of the zirconium oxide to the aluminum oxide is 1:3-5.

6. A high strength bolt according to claim 1, characterized in that: The weight ratio of the sum of the masses of Ni and Cr to the weight of Mo is 3≤(Ni+Cr) / Mo≤14.

7. A high strength bolt according to claim 6, characterized in that: The mass ratio of Ni to Cr is 0.5≤Ni / Cr≤2.

8. A method for preparing a high-strength bolt according to any one of claims 1 to 7, 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 subjected to heat treatment, drawing and thread processing to obtain a bolt.

9. A method for preparing a high-strength bolt according to claim 8, characterized in that: The heat treatment is normalizing, quenching and tempering in sequence.

10. The method for preparing a high-strength bolt according to claim 8, characterized in that: The thread is processed by rolling process.

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