阅读说明：本技术 一种防盗型螺母及其加工工艺 (Anti-theft nut and processing technology thereof ) 是由 张书翰 于 2020-06-01 设计创作，主要内容包括：本发明涉及一种防盗型螺母及其加工工艺,属于机械零件加工技术领域。该防盗型螺母的成分及其质量百分比为：C0.36-0.42％,Si0.88-1.2％,Mn1.6-2.5％,P≤0.025％,S≤0.025％,Cr0.55-0.78％,Mo0.25-0.35％,V0.12-0.22％,Ti0.12-0.25％,Nb0.05-0.15％,余量为Fe和不可避免的夹杂。本发明防盗型螺母提高影响小成本低的硅和锰作为主要合金元素,并通过后期加工中的轧制和二次退火细化组织,提高螺母合金钢的强度和韧性,同时提高螺母的塑形性。(The invention relates to an anti-theft nut and a processing technology thereof, belonging to the technical field of mechanical part processing. The anti-theft nut comprises the following components in percentage by mass: 0.36 to 0.42 percent of C, 0.88 to 1.2 percent of Si, 1.6 to 2.5 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, 0.55 to 0.78 percent of Cr0.25 to 0.35 percent of Mo0.12 to 0.22 percent of V, 0.12 to 0.25 percent of Ti0.05 to 0.15 percent of Nb0.05 to 0.15 percent of Ti, and the balance of Fe and inevitable impurities. According to the anti-theft nut, silicon and manganese which are small in influence and low in cost are used as main alloy elements, the structure is refined through rolling and secondary annealing in later processing, the strength and toughness of nut alloy steel are improved, and meanwhile the formability of the nut is improved.)

1. The anti-theft nut is characterized by comprising the following components in percentage by mass: 0.36 to 0.42 percent of C, 0.88 to 1.2 percent of Si, 1.6 to 2.5 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, 0.55 to 0.78 percent of Cr0.25 to 0.35 percent of Mo0.12 to 0.22 percent of V, 0.12 to 0.25 percent of Ti, 0.05 to 0.15 percent of Nb0.05 to 0.15 percent of Ti, and the balance of Fe and inevitable impurities.

2. The anti-theft nut according to claim 1, characterized in that the components and mass percentages of the anti-theft nut are as follows: 0.38 percent of C, 0.95 percent of Si, 2.2 percent of Mn2, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, 0.66 percent of Cr0.66 percent, 0.28 percent of Mo0.12 percent to 0.22 percent of V, 0.16 percent of Ti, 0.08 percent of Nb0, and the balance of Fe and inevitable impurities.

3. The process for machining the anti-theft nut according to claim 1, wherein the machining method comprises the following steps:

melting and casting the alloy of claim 1 into a billet;

the steel billet is subjected to intermediate frequency heating, and then hot rolling and cold rolling are sequentially carried out to prepare a steel plate;

and (3) carrying out secondary annealing treatment on the steel plate, and then carrying out cold forging and thread machining to obtain the anti-theft nut finished product.

4. The processing technology of the anti-theft nut as claimed in claim 3, wherein the temperature of the intermediate frequency heating is 960-1020 ℃ and the frequency is 15-25 s.

5. The processing technology of the anti-theft nut as claimed in claim 3, wherein the hot rolling is specifically hot rolling at 920-.

6. The processing technology of the anti-theft nut according to claim 3, wherein the cold rolling adopts multiple cold rolling passes, and each cold rolling pass adopts rolling with small deformation.

7. The machining process of the anti-theft nut according to claim 3, wherein the secondary annealing treatment specifically comprises the following steps: heating the steel plate to 750 plus 760 ℃ and preserving heat for 2-5min, then cooling to 580 plus 620 ℃ within 2-3min, preserving heat for 2-5min at 580 plus 620 ℃, and then cooling to room temperature; then heating to 750 ℃ at 720 and keeping the temperature for 2-5min, cooling to 280 ℃ at 250 and 280 ℃ within 3-5min, keeping the temperature for 2-5min at 250 and 280 ℃, and then cooling to room temperature.

8. The process for manufacturing an anti-theft nut according to claim 3, wherein the average heating rate is 20-50 ℃/sec.

Technical Field

The invention relates to an anti-theft nut and a processing technology thereof, belonging to the technical field of mechanical part processing.

Background

In China, the property and personal safety loss of public facilities can reach more than one hundred million yuan each year due to the connection looseness or the artificial theft and damage of components in the mechanical department, and great influence is brought to the healthy operation of national economy. The existing anti-theft nut is formed in one step by a cold pier without two processes, and the surface is hot-galvanized. The internal thread is provided with a pair of blind grooves, the cross section of each blind groove is arc-shaped, the radial depth of each blind groove is gradually increased along the direction opposite to the direction of the thread turning, and two balls are arranged in the two blind grooves and are provided with special plastic inner linings and plastic gaskets so as to ensure that the balls move freely. When the nut is screwed clockwise, the ball rolls along the arc-shaped blind groove, and the plastic inner bushing of the nut automatically falls off. When the nut is unscrewed anticlockwise, the ball is clamped in the thread because the radial size of the blind groove is gradually reduced, and the nut cannot be unscrewed, so that the anti-theft effect is achieved. The anti-theft nut is widely used for national electric power iron towers and signal iron towers, and has convenient operation and strong anti-theft effect.

However, the anti-theft nut has strict requirements on permanent elongation in the using process and is not allowed to generate excessive deformation, the high-strength bolt made of cold-work strengthened non-quenched and tempered steel is directly manufactured under cold-work strengthening operations such as cold drawing, cold heading, thread rolling and the like, the permanent elongation performance of the fastened nut is determined by the deformation structure state of the cold-work strengthened non-quenched and tempered steel, the non-quenched and tempered steel is easy to generate plastic deformation because of not being subjected to stabilizing treatment in the tempering process, the permanent elongation is large, and the permanent elongation performance of the nut made of the non-quenched and tempered steel cannot meet the requirements.

Non-quenched and tempered steel used as automobile fastener bolts at home mainly comprises LF20Mn2, LF18Mn2, LF10MnSiTi and the like, and NHF55, NHF60 and NHF85 produced by Nippon Nissan iron company at abroad; MC7 and MC8 from Daido Special Steel Co, Japan. The method is characterized in that a part of V, Nb, Ti, B and other microalloy elements are properly added on the basis of low-carbon steel, the steel is produced into a bar or a wire through a steel-making and rolling process, the performance of a hot rolled material of the bar or the wire is generally not more than 900MPa, cold-drawing deformation is needed to improve the strength, the required strength is achieved, but partial plasticity is sacrificed, and the toughness of the bolt is influenced.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the anti-theft nut with high strength, good plasticity, strong toughness and high comprehensive performance.

The above object of the present invention can be achieved by the following technical solutions:

the anti-theft nut comprises the following components in percentage by mass: 0.36 to 0.42 percent of C, 0.88 to 1.2 percent of Si, 1.6 to 2.5 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, 0.55 to 0.78 percent of Cr0.25 to 0.35 percent of Mo0.12 to 0.22 percent of V, 0.12 to 0.25 percent of Ti, 0.05 to 0.15 percent of Nb0.05 to 0.15 percent of Ti, and the balance of Fe and inevitable impurities.

Preferably, the anti-theft nut comprises the following components in percentage by mass: 0.38 percent of C, 0.95 percent of Si, 2.2 percent of Mn2, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, 0.66 percent of Cr0.66 percent, 0.28 percent of Mo0.12 percent to 0.22 percent of V, 0.16 percent of Ti, 0.08 percent of Nb0, and the balance of Fe and inevitable impurities.

The processing method of the anti-theft nut comprises the following steps:

smelting and casting the alloy with the chemical composition as described above into a billet;

the steel billet is subjected to intermediate frequency heating, and then hot rolling and cold rolling are sequentially carried out to prepare a steel plate;

and (3) carrying out secondary annealing treatment on the steel plate, and then carrying out cold forging and thread machining to obtain the anti-theft nut finished product.

Preferably, the temperature of the intermediate-frequency heating is 960-1020 ℃, and the frequency is 15-25 s.

Preferably, the hot rolling is specifically hot rolling at 920-940 ℃, and then cooling to room temperature at a cooling rate of 60-80 ℃/sec.

Preferably, the cold rolling is performed in multiple cold rolling passes, and each cold rolling pass is performed in a small deformation rolling process.

Preferably, the secondary annealing treatment specifically comprises: heating the steel plate to 750 plus 760 ℃ and preserving heat for 2-5min, then cooling to 580 plus 620 ℃ within 2-3min, preserving heat for 2-5min at 580 plus 620 ℃, and then cooling to room temperature; then heating to 750 ℃ at 720 and keeping the temperature for 2-5min, cooling to 280 ℃ at 250 and 280 ℃ within 3-5min, keeping the temperature for 2-5min at 250 and 280 ℃, and then cooling to room temperature.

Preferably, the average rate of heating is 20 to 50 ℃/sec.

Compared with the prior art, the anti-theft nut has the advantages that silicon and manganese which are small in influence and low in cost are used as main alloy elements, the structure is refined through rolling and secondary annealing in later-stage processing, the strength and toughness of nut alloy steel are improved, and the plasticity of the nut is improved.

Detailed Description

The following are specific examples of the present invention and further describe the technical solutions of the present invention, but the present invention is not limited to these examples.