High-strength bolt and method for manufacturing the same

Abstract

The application relates to the technical field of fasteners, and discloses a high-strength bolt and a preparation method thereof. The bolt body of the high-strength bolt is composed of the following components with the mass percentage of C 0.30%-0.38%, Si 0.20%-0.25%, Mn 0.55%-0.75%, P<=0.015%, S<=0.01%, Cr 1.05%-1.13%, Mo 0.34%-0.60%, Ni 0.25%-0.57%, Cu 0.09%-0.12%, V 0.15%-0.25%, Ti 0.01%-0.08%, Al 0.05%-0.15%, Nb 0.02%-0.05%, and the rest is Fe and inevitable impurities. Through the technical scheme, the problem of insufficient bolt strength in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of fastener technology, specifically to a high-strength bolt and its manufacturing method. Background Technology

[0002] Bolts are core components in mechanical connections, widely used in machinery manufacturing, construction, transportation, and many other industries. They fix components through threaded connections, directly determining the stability and load-bearing capacity of the connection structure. During their service life, bolts must withstand complex loads such as tension, shear, and vibration, and may also face harsh working conditions and corrosion. Therefore, their strength performance is crucial to ensuring the safe operation of equipment.

[0003] Currently, the problem of insufficient bolt strength is widespread, mainly due to two aspects: First, the unreasonable selection of materials during production leads to the bolt's tensile strength, yield strength, and other mechanical properties failing to meet design requirements; second, during long-term service, alternating loads and fatigue damage can cause bolt strength to decrease, resulting in problems such as thread wear and shank fracture.

[0004] This problem can easily lead to safety accidents and economic losses such as equipment downtime and structural collapse. Existing improvement methods mostly involve increasing bolt size and using high-strength materials, which can temporarily compensate for the defect, but increase costs and structural weight, and cannot fundamentally solve the problem. As industry develops towards higher precision and higher reliability, the limitations of traditional bolt strength become apparent, necessitating the research and development of methods to improve bolt strength. Summary of the Invention

[0005] This invention proposes a high-strength bolt and its manufacturing method, which solves the problem of insufficient bolt strength in related technologies.

[0006] The technical solution of the present invention is as follows: This invention proposes a high-strength bolt, the bolt body of which is composed of the following components by mass percentage: C 0.30%~0.38%, Si 0.20%~0.25%, Mn 0.55%~0.75%, P≤0.015%, S≤0.01%, Cr 1.05%~1.13%, Mo 0.34%~0.60%, Ni 0.25%~0.57%, Cu 0.09%~0.12%, V 0.15%~0.25%, Ti 0.01%~0.08%, Al 0.05%~0.15%, Nb 0.02%~0.05%, with the remainder being Fe and unavoidable impurities.

[0007] As a further technical solution, the bolt body is composed of the following components by mass percentage: The composition is as follows: C 0.30%~0.38%, Si 0.20%~0.25%, Mn 0.55%~0.75%, P≤0.015%, S≤0.01%, Cr 1.05%~1.13%, Mo 0.34%~0.60%, Ni 0.25%~0.57%, Cu 0.09%~0.12%, V 0.15%~0.25%, Ti 0.01%~0.08%, Al 0.05%~0.15%, Nb 0.02%~0.05%, with the remainder being Fe and unavoidable impurities, and 0.30%≤Ni+Ti-Al≤0.41%.

[0008] In this invention, the mass percentage relationship of Ni, Ti and Al elements in the bolt body is controlled at 0.30%≤Ni+Ti-Al≤0.41%, which further improves the strength of the bolt.

[0009] As a further technical solution, the bolt body is also provided with an auxiliary plating layer and a zinc plating layer in sequence; The flux used to prepare the plating layer consists of the following components in the indicated mass percentages: 26%~30% zinc chloride, 18%~20% ammonium chloride, 1%~2% cerium nitrate, 2%~3% nickel nitrate, 0.5%~1% stabilizer, 1.0%~2.0% functional additives, and the balance being water; the functional additives are cocamidopropyl betaine and amide-based polyoxyethylene ether magnesium sulfate in a mass ratio of 1:9~9:1.

[0010] In this invention, a flux coating and a zinc plating layer are formed on the outside of the bolt body, and the composition of the flux coating is improved by adding cocamidopropyl betaine and amide polyoxyethylene ether magnesium sulfate as functional additives, thereby improving the wear resistance of the bolt.

[0011] As a further technical solution, the stabilizer includes at least one of sodium fluoride and potassium fluoride.

[0012] As a further technical solution, the mass ratio of cocamidopropyl betaine to amide-based polyoxyethylene ether magnesium sulfate is <1.

[0013] As a further technical solution, the mass ratio of cocamidopropyl betaine to amide-based polyoxyethylene ether magnesium sulfate is 3:7 to 4:6.

[0014] In this invention, when the mass ratio of cocamidopropyl betaine to amide polyoxyethylene ether magnesium sulfate is <1, the wear resistance of the bolt can be further improved: especially when the mass ratio of cocamidopropyl betaine to amide polyoxyethylene ether magnesium sulfate is 3:7~4:6, the wear resistance of the bolt reaches the optimal level.

[0015] As a further technical solution, the zinc plating solution used to prepare the zinc plating layer is composed of the following components by mass percentage: Al 0.1%~0.3%, Ti 0.01%~0.04%, La 0.02%~0.03%, Fe 0.02%~0.03%, Ce 0.01%~0.02%, with the balance being Zn and unavoidable impurities.

[0016] This invention also proposes a method for preparing a high-strength bolt, comprising the following steps: The components are melted, cast, rolled, hot-forged, and thread-rolled according to the percentage of the bolt body mass to obtain the billet; The blank is heat-treated to obtain the bolt body; After the bolt body is washed with water and pickled, it is placed in a fluxing agent for fluxing to obtain a pretreated bolt. The pretreated bolts are placed in a zinc plating solution for hot-dip galvanizing, cooled, and passivated to obtain high-strength bolts.

[0017] As a further technical solution, the temperature of the fluxing process is 50~60℃ and the time is 60~70s; the temperature of the hot-dip galvanizing process is 400~500℃ and the time is 15~25s; the passivation time is 2~3min.

[0018] As a further technical solution, the passivation solution comprises the following components in parts by weight: 5-8 parts titanate, 5-6 parts silica, 2-3 parts acrylic resin, 1-2 parts ultraviolet absorber, 0.5-1 part organic acid, and 12-15 parts water.

[0019] As a further technical solution, the titanate includes ammonium fluorotitanate.

[0020] As a further technical solution, the ultraviolet absorber includes at least one of UV-531, UV-327 and UV-328.

[0021] As a further technical solution, the organic acid includes at least one of malic acid, citric acid and tartaric acid.

[0022] The working principle and beneficial effects of this invention are as follows: In this invention, the alloy composition of the bolt body is precisely proportioned, and the synergistic effect of each element enhances the bolt strength. C is the core strengthening element, ensuring the bolt's basic hardness and tensile strength; Cr, Mo, V, Ti, and other elements refine the grain, suppress impurity precipitation, and improve hardenability and wear resistance; Si and Mn assist in strengthening the matrix and improve machinability; the content of harmful impurities P and S is strictly controlled to avoid cracking defects; Ni, Cu, Al, and Nb further optimize mechanical properties, synergistically improving the overall strength and service stability of the bolt. This component synergy achieves a precise increase in bolt strength, effectively solving the problem of insufficient bolt strength and adapting to complex load conditions; the content of harmful impurities is extremely low, reducing the risk of cracking and extending service life; there is no need to increase bolt size, balancing lightweight and economy; the composition is compatible with conventional processing techniques, facilitating mass production, and has a wide range of applications, meeting the needs of various fields for high-strength bolts and improving the reliability of connection structures. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 High-strength bolts, the bolt body is composed of the following components by mass percentage: The composition is as follows: C 0.30%, Si 0.20%, Mn 0.55%, P 0.015%, S 0.008%, Cr 1.05%, Mo 0.34%, Ni 0.25%, Cu 0.09%, V 0.15%, Ti 0.01%, Al 0.05%, Nb 0.02%, with the remainder being Fe and unavoidable impurities. The method for preparing high-strength bolts includes the following steps: The components are melted, cast, rolled, hot-forged, and thread-rolled according to the percentage of the bolt body mass to obtain the billet; The blank is heat-treated to obtain high-strength bolts.

[0025] Example 2 High-strength bolts, the bolt body is composed of the following components by mass percentage: The composition is as follows: C 0.38%, Si 0.25%, Mn 0.75%, P 0.012%, S 0.005%, Cr 1.13%, Mo 0.60%, Ni 0.57%, Cu 0.12%, V 0.25%, Ti 0.08%, Al 0.15%, Nb 0.05%, with the remainder being Fe and unavoidable impurities. The method for preparing high-strength bolts includes the following steps: The components are melted, cast, rolled, hot-forged, and thread-rolled according to the percentage of the bolt body mass to obtain the billet; The blank is heat-treated to obtain high-strength bolts.

[0026] Example 3 High-strength bolts, the bolt body is composed of the following components by mass percentage: The composition is as follows: C 0.35%, Si 0.23%, Mn 0.65%, P 0.010%, S 0.005%, Cr 1.09%, Mo 0.45%, Ni 0.25%, Cu 0.1%, V 0.20%, Ti 0.01%, Al 0.05%, Nb 0.03%, with the remainder being Fe and unavoidable impurities. The method for preparing high-strength bolts includes the following steps: The components are melted, cast, rolled, hot-forged, and thread-rolled according to the percentage of the bolt body mass to obtain the billet; The blank is heat-treated to obtain high-strength bolts.

[0027] Example 4 The only difference between this embodiment and Embodiment 3 is that the bolt body is composed of the following components by mass percentage: The composition is as follows: C 0.35%, Si 0.23%, Mn 0.65%, P 0.010%, S 0.005%, Cr 1.09%, Mo 0.45%, Ni 0.57%, Cu 0.1%, V 0.20%, Ti 0.08%, Al 0.15%, Nb 0.03%, with the remainder being Fe and unavoidable impurities.

[0028] Example 5 The only difference between this embodiment and Embodiment 3 is that the bolt body is composed of the following components by mass percentage: The composition is as follows: C 0.35%, Si 0.23%, Mn 0.65%, P 0.010%, S 0.005%, Cr 1.09%, Mo 0.45%, Ni 0.48%, Cu 0.1%, V 0.20%, Ti 0.05%, Al 0.12%, Nb 0.03%, with the remainder being Fe and unavoidable impurities.

[0029] Example 6 The only difference between this embodiment and Embodiment 3 is that the bolt body is composed of the following components by mass percentage: The composition is as follows: C 0.35%, Si 0.23%, Mn 0.65%, P 0.010%, S 0.005%, Cr 1.09%, Mo 0.45%, Ni 0.34%, Cu 0.1%, V 0.20%, Ti 0.05%, Al 0.09%, Nb 0.03%, with the remainder being Fe and unavoidable impurities.

[0030] Example 7 High-strength bolts, comprising a bolt body and a galvanized layer and a plating layer sequentially disposed outside the bolt body; The bolt body is composed of the following components by mass percentage: The composition is as follows: C 0.35%, Si 0.23%, Mn 0.65%, P 0.010%, S 0.005%, Cr 1.09%, Mo 0.45%, Ni 0.48%, Cu 0.1%, V 0.20%, Ti 0.05%, Al 0.12%, Nb 0.03%, with the remainder being Fe and unavoidable impurities. The method for preparing high-strength bolts includes the following steps: The components are melted, cast, rolled, hot-forged, and thread-rolled according to the percentage of the bolt body mass to obtain the billet; The blank is heat-treated to obtain the bolt body; After washing and pickling the bolt body, it is placed in a flux at 50°C for 70 seconds to obtain a pretreated bolt. The flux consists of the following components by mass percentage: 26% zinc chloride, 18% ammonium chloride, 1% cerium nitrate, 2% nickel nitrate, 0.5% stabilizer, 1.0% functional additive, and the balance being water. The functional additive is cocamidopropyl betaine and amide-based polyoxyethylene ether magnesium sulfate in a mass ratio of 9:1. The pretreated bolts were placed in a zinc plating solution and hot-dip galvanized at 400℃ for 25 seconds, then cooled and passivated at 30℃ for 2 minutes to obtain high-strength bolts. The zinc plating solution consisted of the following components by weight percentage: Al 0.1%, Ti 0.01%, La 0.02%, Fe 0.02%, Ce 0.01%, with the balance being Zn and unavoidable impurities. During passivation, the passivation solution consisted of the following components by weight: ammonium fluorotitanate 5 parts, silicon dioxide 5 parts, acrylic resin 2 parts, UV absorber UV-531 1 part, citric acid 0.5 parts, and water 12 parts.

[0031] Example 8 High-strength bolts, comprising a bolt body and a galvanized layer and a plating layer sequentially disposed outside the bolt body; The bolt body is composed of the following components by mass percentage: The composition is as follows: C 0.35%, Si 0.23%, Mn 0.65%, P 0.010%, S 0.005%, Cr 1.09%, Mo 0.45%, Ni 0.48%, Cu 0.1%, V 0.20%, Ti 0.05%, Al 0.12%, Nb 0.03%, with the remainder being Fe and unavoidable impurities. The method for preparing high-strength bolts includes the following steps: The components are melted, cast, rolled, hot-forged, and thread-rolled according to the percentage of the bolt body mass to obtain the billet; The blank is heat-treated to obtain the bolt body; After washing and pickling the bolt body, it is placed in a flux at 60°C for 60 seconds to obtain a pretreated bolt. The flux consists of the following components by mass percentage: 30% zinc chloride, 20% ammonium chloride, 2% cerium nitrate, 3% nickel nitrate, 1% stabilizer, 2.0% functional additive, and the balance is water. The functional additive is cocamidopropyl betaine and amide-based polyoxyethylene ether magnesium sulfate in a mass ratio of 1:9. The pretreated bolts were placed in a zinc plating solution and hot-dip galvanized at 500℃ for 15 seconds, then cooled and passivated at 30℃ for 3 minutes to obtain high-strength bolts. The zinc plating solution consisted of the following components by weight percentage: Al 0.3%, Ti 0.04%, La 0.03%, Fe 0.03%, Ce 0.02%, with the balance being Zn and unavoidable impurities. During passivation, the passivation solution consisted of the following components by weight: ammonium fluorotitanate 8 parts, silicon dioxide 6 parts, acrylic resin 3 parts, UV absorber UV-531 2 parts, citric acid 1 part, and water 15 parts.

[0032] Example 9 The only difference between this embodiment and Example 8 is that the functional additives are cocamidopropyl betaine and amide polyoxyethylene ether magnesium sulfate in a mass ratio of 9:1.

[0033] Example 10 The only difference between this embodiment and Example 8 is that the functional additives are cocamidopropyl betaine and amide polyoxyethylene ether magnesium sulfate in a mass ratio of 5:5.

[0034] Example 11 The only difference between this embodiment and Example 8 is that the functional additives are cocamidopropyl betaine and amide polyoxyethylene ether magnesium sulfate in a mass ratio of 3:7.

[0035] Example 12 The only difference between this embodiment and Example 8 is that the functional additives are cocamidopropyl betaine and amide polyoxyethylene ether magnesium sulfate in a mass ratio of 4:6.

[0036] Example 13 The only difference between this embodiment and Embodiment 8 is that the functional additive is cocamidopropyl betaine.

[0037] Example 14 The only difference between this embodiment and Embodiment 8 is that the functional additive is amide-based polyoxyethylene ether magnesium sulfate.

[0038] Experimental Example The bolts obtained in Examples 1-14 were subjected to the following performance tests: high-temperature (700℃) yield strength test was conducted according to standard GB / T 228.2-2015 "Metallic Materials - High-Temperature Tensile Testing Method"; and high-temperature (700℃) friction and wear test was conducted using a UMT-Tribolab multifunctional friction and wear testing machine. The results are shown in Tables 1-2 below.

[0039] Table 1 Test Results

[0040] Table 2 Test Results

[0041] Examples 5-6 controlled the mass percentage relationship of Ni, Ti, and Al elements in the bolt body to 0.30%≤Ni+Ti-Al≤0.41%, which improved the strength of the bolt. Examples 7-12 set a flux coating and a zinc plating layer on the outside of the bolt body, and improved the composition of the flux by adding cocamidopropyl betaine and amide-based polyoxyethylene ether magnesium sulfate as functional additives, which improved the wear resistance of the bolt. In particular, when the mass ratio of cocamidopropyl betaine to amide-based polyoxyethylene ether magnesium sulfate is 3:7~4:6, the wear resistance of the bolt reaches the optimal level.

[0042] The above are merely 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 within the protection scope of the present invention.

Claims

1. A high-strength bolt, characterized in that, The bolt body is composed of the following components by mass percentage: C 0.30%~0.38%, Si 0.20%~0.25%, Mn 0.55%~0.75%, P≤0.015%, S≤0.01%, Cr 1.05%~1.13%, Mo 0.34%~0.60%, Ni 0.25%~0.57%, Cu 0.09%~0.12%, V 0.15%~0.25%, Ti 0.01%~0.08%, Al 0.05%~0.15%, Nb 0.02%~0.05%, with the remainder being Fe and unavoidable impurities.

2. The high-strength bolt according to claim 1, characterized in that, The bolt body is composed of the following components by mass percentage: The composition is as follows: C 0.30%~0.38%, Si 0.20%~0.25%, Mn 0.55%~0.75%, P≤0.015%, S≤0.01%, Cr 1.05%~1.13%, Mo 0.34%~0.60%, Ni 0.25%~0.57%, Cu 0.09%~0.12%, V 0.15%~0.25%, Ti 0.01%~0.08%, Al 0.05%~0.15%, Nb 0.02%~0.05%, with the remainder being Fe and unavoidable impurities, and 0.30%≤Ni+Ti-Al≤0.41%.

3. A high-strength bolt according to claim 2, characterized in that, The bolt body is also provided with a plating flux layer and a zinc plating layer in sequence. The flux used to prepare the plating layer consists of the following components in the indicated mass percentages: 26%~30% zinc chloride, 18%~20% ammonium chloride, 1%~2% cerium nitrate, 2%~3% nickel nitrate, 0.5%~1% stabilizer, 1.0%~2.0% functional additives, and the balance being water; the functional additives are cocamidopropyl betaine and amide-based polyoxyethylene ether magnesium sulfate in a mass ratio of 1:9~9:

1.

4. A high-strength bolt according to claim 3, characterized in that, The stabilizer includes at least one of sodium fluoride and potassium fluoride.

5. A high-strength bolt according to claim 3, characterized in that, The mass ratio of cocamidopropyl betaine to amide-polyoxyethylene ether magnesium sulfate is <1.

6. A high-strength bolt according to claim 5, characterized in that, The mass ratio of cocamidopropyl betaine to amide-based polyoxyethylene ether magnesium sulfate is 3:7 to 4:

6.

7. A high-strength bolt according to claim 3, characterized in that, The zinc plating solution used to prepare the zinc plating layer is composed of the following components in mass percentage: Al 0.1%~0.3%, Ti 0.01%~0.04%, La 0.02%~0.03%, Fe 0.02%~0.03%, Ce 0.01%~0.02%, with the balance being Zn and unavoidable impurities.

8. A method for preparing a high-strength bolt, used to prepare the high-strength bolt according to any one of claims 3 to 7, characterized in that, Includes the following steps: The components are melted, cast, rolled, hot-forged, and thread-rolled according to the percentage of the bolt body mass to obtain the billet; The blank is heat-treated to obtain the bolt body; After the bolt body is washed with water and pickled, it is placed in a fluxing agent for fluxing to obtain a pretreated bolt. The pretreated bolts are placed in a zinc plating solution for hot-dip galvanizing, cooled, and passivated to obtain high-strength bolts.

9. A method for preparing a high-strength bolt according to claim 8, characterized in that, The temperature for fluxing is 50-60℃ and the time is 60-70s; the temperature for hot-dip galvanizing is 400-500℃ and the time is 15-25s; the passivation time is 2-3min.

10. A method for preparing a high-strength bolt according to claim 8, characterized in that, During passivation, the passivation solution comprises the following components in parts by weight: 5-8 parts titanate, 5-6 parts silica, 2-3 parts acrylic resin, 1-2 parts ultraviolet absorber, 0.5-1 part organic acid, and 12-15 parts water.

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