High-strength bolt and production process thereof

Abstract

The invention relates to the technical field of fasteners, and provides a high-strength bolt and a production process thereof.The production process of the high-strength bolt comprises the following steps that after a bolt blank is subjected to cold heading, thread machining, acid pickling and phosphating treatment, the high-strength bolt is obtained; the bolt blank body is composed of the following components in percentage by weight: 0.10% to 0.18% of C, 0.22% to 0.32% of Si, 0.65% to 0.85% of Mn, 0.50% to 0.65% of Cr, 0.012% to 0.03% of Ti, 0.010% to 0.025% of N, 0.01% to 0.015% of Al, 0.008% to 0.012% of Ce, 0.0015% to 0.0030% of B, and Slt; 0.015%, Plt; 0.020%, and the balance being Fe and inevitable impurities. Through the technical scheme, the problem of low bolt strength in related technologies is solved.

Description

Technical Field

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

[0002] The core function of a bolt is to transfer loads through the mechanical interlocking of its threads, fixing disparate components into a unified whole. It also possesses detachability, unlike welding, riveting, and other non-detachable or semi-detachable connection methods. It has become a key component for connecting major equipment such as machinery, new energy vehicles, high-speed trains, and wind power equipment.

[0003] The core function of bolts is to transmit loads, and their strength directly determines the stability and reliability of the connection structure. If the bolt strength is insufficient and cannot match the actual load requirements, it will cause the connection to loosen or separate, leading to equipment failure or even safety accidents. However, the strength of existing bolts cannot meet the high load requirements. Summary of the Invention

[0004] This invention proposes a high-strength bolt and its manufacturing process, which solves the problem of low bolt strength in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a manufacturing process for high-strength bolts, comprising the following steps: The bolt body undergoes cold heading, threading, pickling, and phosphating to obtain a high-strength bolt; the bolt body is composed of the following components by weight percentage: C: 0.10%~0.18%, Si: 0.22%~0.32%, Mn: 0.65%~0.85%, Cr: 0.50%~0.65%, Ti: 0.012%~0.03%, N: 0.010%~0.025%, Al: 0.01%~0.015%, Ce: 0.008%~0.012%, B: 0.0015%~0.0030%, S<0.015%, P<0.020%, with the remainder being Fe and unavoidable impurities; the mass ratio of Cr, Ce, and Ti satisfies the relationship: 15≤Cr / (Ce+Ti)≤31.

[0006] In this invention, C is the interstitial solid solution strengthening element in the bolt blank; Si is the substitutional solid solution strengthening element; and the remaining components further enhance the tensile strength of the bolt blank by improving the grain strength and further solid solution strengthening based on the basic strengthening of C and Si elements.

[0007] As a further technical solution, the mass ratio of Cr, Ce, and Ti satisfies the relationship: Cr / (Ce+Ti) = 20.

[0008] As a further technical solution, the mass ratio of Ce to Ti is Ce:Ti = 1.5~2.5, preferably 2.

[0009] As a further technical solution, the phosphating solution used in the phosphating treatment includes the following components in parts by weight: 60-80 parts zinc dihydrogen phosphate, 10-20 parts phosphoric acid, 10-20 parts zinc nitrate, 5-10 parts nitroguanidine, 6-8 parts additives, and 1000 parts water; the additives are composed of kaolin and silicon carbide.

[0010] In this invention, the addition of silicon carbide and kaolin can promote the density of the phosphating film and improve the corrosion resistance of the bolts.

[0011] As a further technical solution, the silicon carbide is aminated silicon carbide, which is obtained by treating silicon carbide with a modifier, the modifier being melamine.

[0012] In this invention, the silicon carbide is further amination treatment, which can increase the interaction force between silicon carbide and the surface of the bolt body, promote the formation of phosphating film, and further improve the corrosion resistance of the bolt.

[0013] As a further technical solution, the amount of modifier added is 3% to 5% of the mass of silicon carbide.

[0014] As a further technical solution, the mass ratio of aminated silicon carbide to kaolin is 4:1 to 3, preferably 2:1.

[0015] As a further technical solution, the preparation method of the aminated silicon carbide includes the following steps: S1. Silicon carbide is treated with an ammonium carbonate aqueous solution to obtain pretreated silicon carbide; S2. After dispersing the pretreated silicon carbide in a solvent, a modifier is added and mixed to obtain aminated silicon carbide.

[0016] As a further technical solution, in step S2, the mixing temperature is 40~50℃ and the mixing time is 60~80min.

[0017] As a further technical solution, the phosphating temperature is 45~55℃ and the phosphating time is 15~20min. During the pickling process, a 20wt% hydrochloric acid solution is used, and the pickling time is 10~15min.

[0018] The present invention also proposes a high-strength bolt, which is produced from the aforementioned high-strength bolt.

[0019] The working principle and beneficial effects of this invention are as follows: In this invention, the tensile strength of the bolt body is improved by limiting the mass ratio of Cr, Ce, and Ti elements in the bolt body. The reason is that Cr mainly strengthens through solid solution and stabilizes the structure, Ti mainly strengthens through precipitation and refines the grain size, and Ce mainly purifies grain boundaries and improves the morphology of inclusions. By limiting 15 ≤ Cr / (Ce + Ti) ≤ 31, the tensile strength of the bolt body can be improved. Detailed Implementation

[0020] 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.

[0021] In the following embodiments and comparative examples: Silicon carbide, with an average particle size of 80 nm; Kaolin, with an average particle size of 3000 mesh.

[0022] Example 1 A manufacturing process for high-strength bolts includes the following steps: After cold heading, threading, pickling in 20wt% hydrochloric acid solution for 15 minutes, and phosphating at 55℃ for 15 minutes, high-strength bolts are obtained. The bolt body is composed of the following components by weight percentage: C: 0.10%, Si: 0.22%, Mn: 0.65%, Cr: 0.50%, Ti: 0.015%, N: 0.010%, Al: 0.01%, Ce: 0.008%, B: 0.0015%, S: 0.01%, P: 0.01%, with the remainder being Fe and unavoidable impurities; The phosphating solution used in the phosphating treatment comprises the following components by weight: 60 parts zinc dihydrogen phosphate, 10 parts phosphoric acid, 10 parts zinc nitrate, 5 parts nitroguanidine, 6 parts additives, and 1000 parts water; wherein the additive is silicon carbide.

[0023] Example 2 A manufacturing process for high-strength bolts includes the following steps: After cold heading, threading, pickling in 20wt% hydrochloric acid solution for 15 minutes, and phosphating at 55℃ for 15 minutes, high-strength bolts are obtained. The bolt body is composed of the following components by weight percentage: C: 0.15%, Si: 0.28%, Mn: 0.75%, Cr: 0.6%, Ti: 0.02%, N: 0.015%, Al: 0.012%, Ce: 0.01%, B: 0.002%, S: 0.008%, P: 0.010%, with the remainder being Fe and unavoidable impurities; The phosphating solution used in the phosphating treatment comprises the following components by weight: 70 parts zinc dihydrogen phosphate, 15 parts phosphoric acid, 15 parts zinc nitrate, 8 parts nitroguanidine, 7 parts additives, and 1000 parts water; wherein the additive is silicon carbide.

[0024] Example 3 A manufacturing process for high-strength bolts includes the following steps: After cold heading, threading, pickling in 20wt% hydrochloric acid solution for 15 minutes, and phosphating at 55℃ for 15 minutes, high-strength bolts are obtained. The bolt body is composed of the following components by weight percentage: C: 0.18%, Si: 0.32%, Mn: 0.85%, Cr: 0.65%, Ti: 0.03%, N: 0.025%, Al: 0.015%, Ce: 0.012%, B: 0.0030%, S: 0.008%, P: 0.012%, with the remainder being Fe and unavoidable impurities; The phosphating solution used in the phosphating treatment comprises the following components by weight: 80 parts zinc dihydrogen phosphate, 20 parts phosphoric acid, 20 parts zinc nitrate, 10 parts nitroguanidine, 8 parts additives, and 1000 parts water; wherein the additives are silicon carbide.

[0025] Example 4 Compared with Example 1, the only difference in this example is that, in this example, the bolt body is composed of the following components by weight percentage: C: 0.10%, Si: 0.22%, Mn: 0.65%, Cr: 0.59%, Ti: 0.028%, N: 0.010%, Al: 0.01%, Ce: 0.012%, B: 0.0015%, S: 0.01%, P: 0.01%, with the remainder being Fe and unavoidable impurities.

[0026] Example 5 Compared with Example 1, the only difference in this example is that, in this example, the bolt body is composed of the following components by weight percentage: C: 0.10%, Si: 0.22%, Mn: 0.65%, Cr: 0.61%, Ti: 0.012%, N: 0.010%, Al: 0.01%, Ce: 0.008%, B: 0.0015%, S: 0.01%, P: 0.01%, with the remainder being Fe and unavoidable impurities.

[0027] Example 6 Compared with Example 1, the only difference in this example is that, in this example, the bolt body is composed of the following components by weight percentage: C: 0.10%, Si: 0.22%, Mn: 0.65%, Cr: 0.6%, Ti: 0.018%, N: 0.010%, Al: 0.01%, Ce: 0.012%, B: 0.0015%, S: 0.01%, P: 0.01%, with the remainder being Fe and unavoidable impurities.

[0028] Example 7 Compared with Example 1, the only difference in this example is that, in this example, the bolt body is composed of the following components by weight percentage: C: 0.10%, Si: 0.22%, Mn: 0.65%, Cr: 0.6%, Ti: 0.022%, N: 0.010%, Al: 0.01%, Ce: 0.008%, B: 0.0015%, S: 0.01%, P: 0.01%, with the remainder being Fe and unavoidable impurities.

[0029] Example 8 Compared with Example 1, the only difference in this example is that the silicon carbide is aminated silicon carbide, and the preparation method of aminated silicon carbide includes the following steps: S1. Silicon carbide was placed in a 2wt% ammonium carbonate aqueous solution and stirred under closed conditions for 6 hours, then dried to obtain pretreated silicon carbide. S2. After dispersing the pretreated silicon carbide in dimethylformamide, a modifier is added and mixed at 40°C for 80 min, then dried to obtain aminated silicon carbide. The modifier is melamine, the mass ratio of silicon carbide to 2wt% ammonium carbonate aqueous solution is 1:5, the amount of modifier added is 4% of the mass of silicon carbide, and the mass ratio of silicon carbide to dimethylformamide is 1:5.

[0030] Example 9 Compared with Example 8, the only difference in this example is that the modifier is kaolin.

[0031] Example 10 Compared with Example 8, the only difference in this example is that the modifier is composed of aminated silicon carbide and kaolin in a 4:1 ratio; wherein, the preparation method of aminated silicon carbide is the same as that in Example 8.

[0032] Example 11 Compared with Example 8, the only difference in this example is that the modifier is composed of aminated silicon carbide and kaolin in a 2:1 ratio; wherein, the preparation method of aminated silicon carbide is the same as that in Example 8.

[0033] Example 12 Compared with Example 8, the only difference in this example is that the modifier is composed of aminated silicon carbide and kaolin in a 4:3 ratio; wherein, the preparation method of aminated silicon carbide is the same as that in Example 8.

[0034] Comparative Example 1 Compared with Example 1, the only difference in this comparative example is that the bolt body in this comparative example is composed of the following components by weight percentage: C: 0.10%, Si: 0.22%, Mn: 0.65%, Cr: 0.50%, N: 0.010%, Al: 0.01%, Ce: 0.008%, B: 0.0015%, S: 0.01%, P: 0.01%, with the remainder being Fe and unavoidable impurities.

[0035] Comparative Example 2 Compared with Example 1, the only difference in this comparative example is that the bolt body in this comparative example is composed of the following components by weight percentage: C: 0.10%, Si: 0.22%, Mn: 0.65%, Cr: 0.50%, Ti: 0.015%, N: 0.010%, Al: 0.01%, B: 0.0015%, S: 0.01%, P: 0.01%, with the remainder being Fe and unavoidable impurities.

[0036] Comparative Example 3 Compared with Example 1, the only difference in this comparative example is that the bolt body in this comparative example is composed of the following components by weight percentage: C: 0.10%, Si: 0.22%, Mn: 0.65%, Cr: 0.50%, N: 0.010%, Al: 0.01%, B: 0.0015%, S: 0.01%, P: 0.01%, with the remainder being Fe and unavoidable impurities.

[0037] The properties of the bolt bodies and bolts in Examples 1-12 and Comparative Examples 1-3 were measured using the following methods: (1) Tensile strength: The tensile strength of the bolt body was determined according to the method in GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test method at room temperature"; (2) Corrosion resistance: The bolts were immersed in a 5wt% sodium chloride solution at room temperature. The time it took for rust spots to appear was observed and recorded. The statistical results are shown in Table 2.

[0038] Table 1. Tensile strength test results of bolts in Examples 1-7 and Comparative Examples 1-3

[0039] As shown in Table 1, the tensile strength of the bolt body in Examples 1 to 7 is higher than that in Comparative Examples 1 to 3, indicating that the tensile strength of the bolt body is improved by limiting the composition of the bolt body in this invention.

[0040] Table 2 Corrosion resistance of bolts in Examples 1 and 8-12

[0041] As shown in Table 2, the corrosion resistance of the bolts in Examples 10-12 is higher than that in Examples 1 and 2-9, indicating that the use of melamine and polyacrylamide to treat silicon carbide in the phosphating solution in this invention can further improve the corrosion resistance of the bolts.

[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 manufacturing process for high-strength bolts, characterized in that, Includes the following steps: The bolt blank is subjected to cold heading, threading, pickling, and phosphating to obtain a high-strength bolt; the bolt blank consists of the following components by weight percentage. Composition: C: 0.10%~0.18%, Si: 0.22%~0.32%, Mn: 0.65%~0.85%, Cr: 0.50%~0.65%, Ti: 0.012%~0.03%, N: 0.010%~0.025%, Al: 0.01%~0.015%, Ce: 0.008%~0.012%, B: 0.0015%~0.0030%, S<0.015%, P<0.020%, with the remainder being Fe and unavoidable impurities; the mass ratio of Cr, Ce, and Ti satisfies the relationship: 15≤Cr / (Ce+Ti)≤31.

2. The manufacturing process for a high-strength bolt according to claim 1, characterized in that, The mass ratio of Ce to Ti is: Ce:Ti = 1.5~2.

5.

3. The manufacturing process for a high-strength bolt according to claim 1, characterized in that, The phosphating solution used in the phosphating treatment comprises the following components in parts by weight: 60-80 parts zinc dihydrogen phosphate, 10-20 parts phosphoric acid, 10-20 parts zinc nitrate, 5-10 parts nitroguanidine, 6-8 parts additives, and 1000 parts water; the additives are composed of kaolin and silicon carbide.

4. The manufacturing process for a high-strength bolt according to claim 1, characterized in that, The silicon carbide is aminated silicon carbide, which is obtained by treating silicon carbide with a modifier, namely melamine.

5. The manufacturing process for a high-strength bolt according to claim 4, characterized in that, The amount of modifier added is 3% to 5% of the mass of silicon carbide.

6. The manufacturing process for a high-strength bolt according to claim 5, characterized in that, The mass ratio of aminated silicon carbide to kaolin is 4:1~3.

7. The manufacturing process for a high-strength bolt according to claim 4, characterized in that, The preparation method of the aminated silicon carbide includes the following steps: S1. Silicon carbide is treated with an ammonium carbonate aqueous solution to obtain pretreated silicon carbide; S2. After dispersing the pretreated silicon carbide in a solvent, a modifier is added and mixed to obtain aminated silicon carbide.

8. The manufacturing process for a high-strength bolt according to claim 7, characterized in that, In step S2, the mixing temperature is 40~50℃ and the mixing time is 60~80min.

9. The manufacturing process of the high-strength bolt according to claim 1, characterized in that, The phosphating treatment temperature is 45~55℃, and the phosphating treatment time is 15~20min; During the pickling process, a 20wt% hydrochloric acid solution is used, and the pickling time is 10~15min.

10. A high-strength bolt, characterized in that, It is produced from a high-strength bolt as described in any one of claims 1 to 9.

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