Production process of titanium alloy nut

Abstract

The invention relates to the technical field of nut machining, in particular to a titanium alloy nut production process which comprises the steps that 1, raw materials including a nylon gasket, a to-be-machined nut and the like are prepared; 2, the nylon gasket is heated, and then the nylon gasket is arranged in the nut in advance; step 3, locally heating the end part of the nut; step 4, pressing the nylon gasket; in the step 3, the heating mode of the nut is friction heating, and the end of the nut is locally heated through a friction piece rotating at a high speed relative to the nut. According to the method, the problem that titanium alloy is difficult to deform is solved through precise local softening, the problem that a gasket is easy to damage is solved through nylon preheating, and the titanium alloy nylon nut with excellent anti-loosening performance and high reliability is efficiently manufactured with high quality on the premise that the performance of a nut body is not damaged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nut processing, and in particular to a production process of a titanium alloy nut. BACKGROUND

[0002] In the high-tech fields of aerospace, high-performance automobiles, precision instruments and petrochemical industry, the reliability of fasteners is extremely demanding. Titanium alloy is the first choice for key connection parts in these fields due to its high specific strength and excellent corrosion resistance. However, titanium alloy threaded connection pairs are prone to loosening when subjected to severe vibration, impact load or temperature cycling. To solve this problem, an engineering plastic washer such as nylon is often embedded in the nut to generate a continuous friction torque using the elastic restoring force of nylon, thereby achieving anti-loosening.

[0003] Prior art and its problems: The traditional titanium alloy nut nylon washer assembly process mainly relies on strong external mechanical force for cold pressing. However, titanium alloy (such as TC4) has extremely high yield strength at room temperature and poor thermal conductivity, making the pressing process extremely difficult.

[0004] In the process of direct pressing, under the action of a large cold pressing force, the hard and brittle nylon washer is prone to edge micro-cracks or "whitening" phenomenon, resulting in premature failure of its sealing and locking performance, and the nut end is prone to cracking or damage. SUMMARY

[0005] In view of the deficiencies of the prior art, one of the purposes of the present application is to provide a production process of a titanium alloy nut with high reliability, high efficiency and lossless embedding and locking between high-strength titanium alloy and a nylon washer.

[0006] The above application purpose of the present application is achieved by the following technical scheme: A production process of a titanium alloy nut, comprising, Step 1, preparing raw materials including a nylon washer, a nut to be processed, etc.; Step 2, heating the nylon washer and then prepositioning the nylon washer inside the nut; Step 3, locally heating the end of the nut; Step 4, pressing the nylon washer; In step 3, the heating method of the nut is friction heating, which locally heats the end of the nut by a friction element rotating at high speed relative to the nut.

[0007] In a further embodiment of the production process of the titanium alloy nut, in step 3, the nut is clamped by a fixing element, and the nut rotates around its axis during heating.

[0008] A further embodiment of the production process of the titanium alloy nut, the friction member is a rotatable rotating wheel, the axis of the rotating wheel is at an inclined angle with the axis of the nut, and the friction member is in contact with the end of the nut at the inclined angle for friction heating.

[0009] A further embodiment of the production process of the titanium alloy nut, in step 3, the temperature of the local heating is controlled between 300℃ and 500℃.

[0010] A further embodiment of the production process of the titanium alloy nut, in step 2, the nylon gasket is preheated, and the preheating temperature is between 80℃ and 120℃.

[0011] A further embodiment of the production process of the titanium alloy nut, the friction member is made of a material with a higher thermal conductivity than titanium alloy.

[0012] A further embodiment of the production process of the titanium alloy nut, in step 3, the temperature of the end of the nut is monitored in real time by a non-contact infrared thermometer or a thermocouple, and the contact pressure and the rotating speed are adjusted by a closed-loop control system to stabilize the temperature within a preset range.

[0013] A further embodiment of the production process of the titanium alloy nut, in step 4, after the local friction heating of the end of the nut, a pressing die is used to apply pressure to the end of the nut to cause plastic deformation of the end of the nut and lock the nylon gasket inside.

[0014] A further embodiment of the production process of the titanium alloy nut, step 4 includes, a pre-pressing stage: the friction member contacts the end of the nut at a first pressure; a final pressing stage: after the pre-pressing stage, the pressure is increased to a second pressure higher than the first pressure to form a flange structure on the end of the nut to lock the nylon gasket.

[0015] A further embodiment of the production process of the titanium alloy nut, in the local friction heating step and the pressing step, the friction member and the pressing die are the same component, and after step 3 is completed, the friction member continues to apply pressure to the end face of the nut to perform the pressing step.

[0016] In summary, the present application includes at least one of the following beneficial technical effects: 1.The titanium alloy nut production process provided by the present application realizes efficient and reliable combination of high-strength titanium alloy nuts and nylon washers through local friction heating and staged pressing technology. A shallow softening zone is generated at the end of the nut through precise local friction heating, which greatly reduces the flow stress at this position and makes it easy to deform plastically to form a mechanical locking structure, and the original high strength of the nut body and threaded portion is completely retained. Secondly, the preheated nylon washer is pressed in a high-elastic state, and its flowability and filling capacity are enhanced, effectively avoiding micro-cracks and whitening, and ensuring the structural integrity and long-term service performance of the washer.

[0017] 2.The titanium alloy nut production process provided by the present application integrates heating and pressing functions in the same set of devices, simplifies the equipment structure, optimizes the production rhythm, and is suitable for assembly line production. 3.The titanium alloy nut production process provided by the present application gives the material sufficient flow and redistribution time through staged pressing, and the "clamp" type locking structure formed is more dense and firm, with low residual stress, thereby greatly improving the locking ability and sealing performance of the nut. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 is a flowchart of the titanium alloy nut production process disclosed by the present application; Fig. 2 is a schematic diagram of the heating and pressing process in the titanium alloy nut production process disclosed by the present application. DETAILED DESCRIPTION

[0019] The present application will be further described in detail below with reference to the accompanying drawings.

[0020] Referring to Figs. 1-2 The overall process of the titanium alloy nut production process disclosed by the present application includes in turn: raw material preparation, nylon washer preheating, nylon washer prepositioning, nut end local friction heating, nylon washer pressing, and nut forced cooling.

[0021] Specifically, Step 1: Prepare raw materials.

[0022] This step is the basis of the process, the quality of raw materials directly determines the performance of the final product. Raw materials include titanium alloy nut and nylon washer, etc. The selected titanium alloy nut is a semi-finished product that has completed all machining such as turning and tapping. Its material is usually Ti-6Al-4V (TC4), which has a room temperature yield strength of about 830 MPa and a tensile strength of about 900 MPa. It should be understood that it is precisely because of the high strength of titanium alloy that traditional pressing process is difficult to achieve the pressing of nylon washer. The nut should be cleaned before being put into the process to remove surface dirt, cutting fluid and metal debris to ensure the purity of subsequent heating and bonding.

[0023] The nylon washer can be made of Teflon material, which has the characteristics of high temperature resistance and corrosion resistance, and has been adapted to the titanium alloy nut. Its size needs to match the groove or pressing area inside the nut. The inner and outer diameter and thickness tolerance of the washer should be strictly controlled, usually within 0.05-0.1 mm, to ensure the smoothness of the preset and the tightness of the combined pressing.

[0024] Optionally, the raw materials need to be sampled and tested before being put into the warehouse, including size measurement, material composition analysis and mechanical property test, to ensure batch consistency. For titanium alloy nuts, a spectrometer can be used to verify the material composition, and a thread go-no-go gauge can be used to check the thread accuracy; for nylon washers, a hardness tester can be used to measure their Shore hardness, and the surface can be observed for defects.

[0025] Step two: Preposition the nylon washer inside the nut.

[0026] First, the nylon washer is preheated. Nylon material has a certain hardness and brittleness at room temperature. When embedded under great pressure, its molecular chain segments are not easy to move, which may cause micro-cracks or "whitening" on the edge of the washer, affecting the sealing performance and long-term durability. Preheating can activate the movement ability of nylon molecules, making them change from glassy state to high elastic state, greatly improving their toughness and plastic deformation ability, and reducing internal stress during pressing.

[0027] The specific preheating operation is as follows: place the nylon gasket in a temperature controllable oven or infrared heating device. The oven should be designed with forced convection to ensure temperature uniformity, and the infrared heating can achieve rapid response by adjusting the wavelength and power. The preheating temperature should be strictly controlled between 80°C and 120°C. Below 80°C, the nylon softening effect is not obvious, and the gasket is still prone to cracking during compression; above 120°C, the nylon may begin to soften and deform, even melt on the surface, resulting in a decrease in dimensional accuracy or adhesion. The preferred preheating temperature is 100°C ± 5°C, at which the nylon gasket can achieve the best plasticity without significant thermal degradation. The preheating time is adjusted according to the thickness and batch size of the gasket: for gaskets with a thickness of 1-2mm, the holding time is usually 5-15 minutes; for thicker or larger batch gaskets, it can be appropriately extended to 20 minutes to ensure that the heat penetrates uniformly to the core of the gasket. During the preheating process, the gasket can be turned over or shaken to prevent local overheating.

[0028] The preheated nylon gasket becomes soft and flexible, allowing better flow and filling of the space in the nut during compression, while reducing the risk of cracking of the gasket itself. The preheated gasket should be placed within 30 seconds to prevent performance degradation due to temperature drop.

[0029] Then the nylon gasket is placed inside the nut. For small batches or experimental production, it can be placed directly by hand using anti-static tweezers or special tools, ensuring that the gasket is in flat contact with the nut groove bottom. In the production line, through the feeding mechanism such as vibration disc, guide rail or six-axis mechanical arm, the preheated nylon gasket is accurately placed into the specified annular groove or end position of the titanium alloy nut. The mechanical arm can be equipped with a vision system for positioning correction to ensure that the gasket is placed without skewing or lifting. After placement, the gasket can be confirmed in place by slight air blowing or light pressure.

[0030] Step three, local friction heating of the end of the nut.

[0031] First, use a high-precision pneumatic or hydraulic clamp, such as a spring chuck or three-jaw chuck, Fig. 2 In the embodiment shown, a three-jaw chuck is used to clamp the titanium alloy nut. The design of the clamp should meet the following requirements: the clamping force should be large enough, usually 0.5-2kN, to prevent the nut from loosening or slipping during subsequent rotation and compression; the clamping position should be reasonable, usually selecting the non-threaded part of the nut, such as the outer hexagonal or light pole section, to avoid scratching or deforming the threaded working area, while ensuring that the end of the nut to be heated is fully exposed. The inside of the clamp can be inlaid with hard alloy or coated to improve wear resistance, and a cooling channel can be provided to prevent heat conduction to the clamp body.

[0032] Then, the clamped nut is rotated at a uniform speed around its own axis by a servo motor or a step motor connected to the fixture. The rotation speed can be adjusted according to the size and material properties of the nut, and is usually set in the range of 500-2000 rpm. Smaller diameter nuts are preferably rotated at a higher speed, such as 1500-2000 rpm, and larger diameter nuts are preferably rotated at a lower speed, such as 500-1000 rpm, to balance the heat generation efficiency and temperature uniformity.

[0033] Next, the friction element is moved to contact the end of the nut. In this embodiment, the friction element is a rotatable wheel. The material of the wheel can be a material with a higher thermal conductivity than titanium alloy, such as beryllium bronze or high-conductivity copper-tungsten alloy. This is because the friction generates a large amount of heat, and if the friction element itself has poor heat conduction, the heat will accumulate on its surface, causing its own temperature to be too high and annealing softening, losing hardness, and even sticking to the titanium alloy. A high thermal conductivity friction element can quickly conduct the surface heat to the interior and dissipate it through its large volume or external cooling system, thereby maintaining the hardness and cleanliness of the working surface. The surface hardness of the wheel should not be less than HRC50, and can be polished or coated to reduce the friction coefficient.

[0034] The axis of the wheel is at an angle to the axis of the nut, which is usually between 10° and 45°. The preferred angle is 20°-30° to achieve a balance between line contact and pressure optimization. The wheel is driven by a feed mechanism, which can be a servo motor or a ball screw, so that its circumferential side is obliquely attached and pressed against the end of the rotating nut. This "oblique attachment" method achieves line contact, which has higher pressure than surface contact under the same pressure, has very high heat generation efficiency, and can effectively prevent structural interference. The feed speed can be adjusted, usually between 0.1-1 mm / s, and low speed is used at the initial contact to avoid impact.

[0035] As a specific embodiment of the present application, a non-contact infrared thermometer or an implanted K-type thermocouple can be used to monitor the temperature of the heated area at the end of the nut in real time. By controlling the contact and separation of the friction element and the nut, as well as the rotation speed of the nut, the temperature of the end of the nut can be controlled precisely between 300°C and 500°C. This is a key temperature window for dynamic recrystallization and significant softening of titanium alloy TC4. Within this range, its flow stress can be reduced to 1 / 5 or even lower at room temperature, becoming extremely easy to deform plastically. At the same time, this temperature is much lower than the phase transition point of titanium alloy, and will not cause harmful phase transition.

[0036] Further, in the specific use scenario, when the temperature reaches the constant temperature value, for example, 350℃, the current contact pressure and relative rotation speed are maintained for a period of time, for example, 1-3 seconds, so that the heat is evenly spread in the end circumference to form a softened layer with a depth of about 0.5-1.0 mm. When the temperature continues to rise and exceeds the high temperature value, for example, 450℃, the contact pressure and rotation speed are reduced. If the temperature continues to rise and exceeds the dangerous value, for example, 500℃, the friction member and the nut are directly separated. When the temperature is reduced to below the constant temperature value, the temperature rising operation is performed again.

[0037] Step four: compression of the nylon gasket.

[0038] After the heating is completed, compression is immediately performed by the compression mold. During the compression, the mold acts on the end of the nut with constant or staged pressure, so that the end surface of the nut is plastically deformed and the nylon gasket is locked at the same time. After the compression, the nut is cooled and shaped to form a stable annular sealing structure, thereby effectively improving the locking force and sealing performance of the connection part.

[0039] As a specific embodiment of the present application, the compression mold can be integrated with the aforementioned friction member or designed independently. Preferably, the compression mold of the present application is the aforementioned friction member, which continues to apply pressure to the end surface of the nut after the heating is completed, so as to seamlessly connect the heating and compression. The pressure application stage includes a pre-compression stage and a final compression stage.

[0040] In the pre-compression stage, the friction member contacts the softened end of the nut with a relatively low first pressure. The main purpose of this stage is to preliminarily position the nylon gasket and make the titanium alloy end begin to produce plastic deformation in the hot state, so as to avoid displacement or damage of the nylon gasket due to sudden stress. The duration of this stage is relatively short, usually about 1 second, and during this stage, the slight curling of the end of the nut can be observed.

[0041] The final compression stage is a continuous process with the pre-compression stage, that is, after the pre-compression stage ends, the compression force is rapidly increased to a higher second pressure within 0.5 seconds. This stage is the key to forming, and the softened titanium alloy is extruded inward and downward to produce a curling or riveting effect, like a "clamp" tightly locking the nylon gasket below. The final compression time is usually 2-5 seconds to ensure that the deformation is sufficient and the nylon gasket is completely filled in the sealing space. After the compression, the end of the nut forms a continuous flange to mechanically lock the nylon gasket in the groove.

[0042] The staged pressure application avoids damage to the material and equipment caused by a single large impact force, gives the nylon gasket material time to flow and redistribute, and forms a more dense and firm mechanical locking structure with smaller residual stress.

[0043] After the pressing is completed, the forced cooling process is entered: the nut end is rapidly cooled through air cooling or water cooling nozzles, and the cooling index is specified according to the specific titanium alloy material and nylon material, such as being reduced to below 100 DEG C within 10 seconds, so as to fix the deformation shape and prevent the nylon from overheating and aging. After the cooling, the pressing quality can be checked through visual inspection or automatic detection equipment, such as checking the edge folding integrity, whether the nylon gasket is exposed uniformly, etc.

[0044] The entire process can be coordinated by a programmable logic controller to realize parameter setting, data recording and fault diagnosis, and ensure production efficiency and consistency.

[0045] The embodiments of the specific implementation are the preferred embodiments of the present application, and do not limit the protection scope of the present application, so that: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A process for producing a titanium alloy nut, characterized by: The method comprises the following steps: Step 1, preparing raw materials, including nylon gasket, nut to be processed, etc. Step 2, heating the nylon gasket, and then prepositioning the nylon gasket inside the nut; Step 3, locally heating the end of the nut; Step 4, pressing the nylon gasket; In step 3, the heating mode of the nut is friction heating, and the end of the nut is locally heated by a friction element rotating at a high speed relative to the nut.

2. A process for producing a titanium alloy nut according to claim 1, characterized in that: In step 3, the nut is clamped by a fixing element, and the nut rotates around its axis during the heating process.

3. A process for producing a titanium alloy nut according to claim 1, characterized in that: The friction element is a rotatable rotating wheel, the axis of which forms an inclined angle with the axis of the nut, and the rotating wheel is in frictional contact with the end of the nut at the inclined angle for friction heating.

4. The process for producing a titanium alloy nut according to claim 1, characterized by: In step 3, the local heating temperature is controlled between 300-500℃.

5. The process for producing a titanium alloy nut according to claim 1, characterized by: In step 2, the nylon gasket is preheated, and the preheating temperature is 80-120℃.

6. The process for producing a titanium alloy nut according to claim 1, characterized by: The friction element is made of a material with a higher thermal conductivity than titanium alloy.

7. The process for producing a titanium alloy nut according to claim 1, characterized in that: In step 3, the temperature of the end of the nut is monitored in real time by a non-contact infrared thermometer or a thermocouple, and the contact pressure and rotating speed are adjusted by a closed-loop control system to stabilize the temperature within the preset range.

8. The process for producing a titanium alloy nut according to any one of claims 1 to 7, characterized in that: In step 4, after the local friction heating of the end of the nut, a pressing die is used to apply pressure to the end of the nut, so that the end of the nut is plastically deformed and the nylon gasket is locked inside.

9. A process for producing a titanium alloy nut according to claim 8, characterized in that: Step 4 comprises: Pre-pressing stage: the friction element contacts the end of the nut at a first pressure; Final pressing stage: after the pre-pressing stage, the pressure is increased to a second pressure higher than the first pressure, so that the end of the nut forms a flange structure to lock the nylon gasket.

10. A process for producing a titanium alloy nut according to claim 9, characterized in that: In the local friction heating step and the pressing step, the friction element and the pressing die are the same component, and after step 3 is completed, the friction element continues to apply pressure to the end face of the nut to perform the pressing step.

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