Processing method for aluminum grounding stud assembly

Abstract

The present invention relates to the technical field of stud processing, and provides a processing method for an aluminum grounding stud assembly. A bolt and a nut are separately formed by cold-heading a high-strength high-ductility aluminum alloy wire rod, and are subjected to work-hardening to improve product performance; then thread formation is achieved by means of thread rolling and form tapping, thereby avoiding cutting and machining and ensuring the smoothness of screw threads; subsequently, by means of a surface treatment and an overall lubricating treatment, the friction coefficient is controlled to be 0.18-0.23; and after the strength of the bolt and the nut is improved by means of a stabilizing treatment, an assembly torque of 7-9 Nm is used to assemble the bolt and the nut. By means of cold heading, the extrusion processing of screw threads, control over the friction coefficient and the stabilizing treatment, the product has both a high tightening torque and a high destructive torque in an assembled state; moreover, the phenomenon whereby screw threads are seized due to welding during the usage process is avoided.

Description

Processing method of aluminum grounding nut post assembly TECHNICAL FIELD

[0001] The present application belongs to the technical field of nut post processing, and more particularly relates to a processing method of an aluminum grounding nut post assembly. BACKGROUND

[0002] Fastener welding generally adopts resistance spot welding, and resistance spot welding is generally applied to steel fasteners. At present, with the application of aluminum vehicle bodies due to automobile lightweighting, the traditional resistance spot welding is greatly limited due to the high electrical conductivity and high thermal conductivity of aluminum alloys. Meanwhile, with the development of automobile electrification and intelligentization, the application of grounding and ironing parts is also more and more widely.

[0003] At present, there are some grounding nut post products for aluminum alloy grounding in the market. For example, a Chinese patent (publication number: CN105745793B) discloses a fixed device for electric contact conduction, which includes a bolt and a nut. The welding process includes: the nut post assembly is loaded into a welding gun; the bolt end face is pre-pressed against the sheet metal; the nut post is pulled to start the arc; the sheet metal forms a molten pool, and the screw head is melted; the power is turned off, and the bolt is quickly inserted into the molten pool; and cooling and crystallization are performed to form a welded joint. It is particularly emphasized that the surface treatment of the bolt must be coated with a lubricant coating in the threaded section, and the support surface of the bolt, the head of the bolt and the support surface of the nut are not allowed to be coated with a lubricant. In this way, it can be ensured that the bolt and nut threads are not welded and stuck after tightening. This technology only allows the threaded section of the bolt to be coated with a lubricant. If a small amount of lubricant contacts the support surface of the bolt, the tightening torque will fail. The harsh processing process causes great inconvenience in production, and it is difficult to manage the production quality and the production cost is high.

[0004] Therefore, in view of the defects of the prior art, a processing method of an aluminum grounding nut post assembly is provided to achieve a more practical purpose. SUMMARY

[0005] To solve the above technical problems, the present application provides a processing method of an aluminum grounding nut post assembly to solve the above problems.

[0006] A processing method of an aluminum grounding nut post assembly, comprising grounding bolt processing and grounding nut processing, wherein the grounding bolt processing comprises the following steps:

[0007] S1: 5019 cold upsetting wire, the wire meets the requirements of tensile strength >= 300 MPa and yield strength >= 250 MPa, and the cold upset meets the requirement of 75% cold extrusion without cracking;

[0008] S2: multi-station cold upsetting forming;

[0009] S3: cold extrusion and wire drawing processing;

[0010] S4: surface treatment, specifically comprising S41: pre-treatment; S42: alkali etching; S43: activation; S44: passivation; S45: lubrication;

[0011] S5: stabilization treatment;

[0012] S6: finished product screening;

[0013] The ground nut machining comprises the following steps:

[0014] S7: 5052 cold upsetting wire, the wire needs to meet tensile strength ≥ 230 MPa, yield strength ≥ 190 MPa, and cold upset meets 75% cold extrusion without cracking;

[0015] S8: multi-station cold upsetting forming;

[0016] S9: extrusion processing;

[0017] S10: surface treatment, specifically nitric acid pickling passivation;

[0018] S11: stabilization treatment;

[0019] S12: finished product screening.

[0020] Preferably, S44 passivation is completed by 1.5% to 4% Interlox 377A and 0.2% to 0.5% Interlox 377B, with a process of soaking for 150S to 300S, centrifugal drying, centrifugal speed of 500 to 1000r / min, and time of 100S to 200S.

[0021] Preferably, S45 lubrication is completed by 3% to 8% Rogard LUBE 200, with a process of soaking for 30 to 60S, centrifugal drying, centrifugal speed of 500 to 1000r / min, and time of 100S to 200S, and the overall lubrication is completed with a friction coefficient controlled between 0.18 to 0.23.

[0022] Preferably, the processes of S41 to S44 all need to be washed with pure water for 1 to 2 times, with a washing time of 20 to 60S.

[0023] Preferably, S10 surface treatment adopts nitric acid pickling, with a nitric acid concentration of 250 to 320ml / L, pickling time of 10 to 15min, and then water washing.

[0024] Preferably, S5 and S11 are baking treatment, with a baking temperature controlled between 100 to 140℃, and a baking time of 1 to 2h.

[0025] Preferably, S2 and S9 both adopt cold extrusion thread forming.

[0026] Preferably, the ground bolt and the ground nut processed are screened respectively, and then combined and installed, and the combined torque is 7-9Nm.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] In the application, the selected material, thread processing, surface treatment and heat treatment are specially processed to cancel the local lubrication processing procedure of the bolt, control the appropriate friction coefficient and solve the technical problem of thread lubrication processing.

[0029] In the application, the thread processing of the nut adopts the extrusion processing mode to avoid cutting and tapping, firstly, the nut structure is a blind hole, and the aluminum chips generated by tapping are easy to remain in the nut cavity, secondly, the tapping is a cutting processing to form the nut, and the thread surface roughness is large, even with defects such as broken teeth, and these problems will cause the threads to be welded and stuck during use, and the extrusion processing ensures that the thread stress surface of the bolt and the nut is smooth and complete without defects. BRIEF DESCRIPTION OF DRAWINGS

[0030] Fig. 1 is a verification result of the ground nut column in the application;

[0031] Fig. 2 is a flowchart of the application;

[0032] Fig. 3 is a structural schematic diagram of the ground bolt in the application;

[0033] Fig. 4 is a structural schematic diagram of the ground nut in the application;

[0034] Fig. 5 is a structural schematic diagram of the ground nut column assembly in the application. DETAILED DESCRIPTION

[0035] The embodiments of the application will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate the application, but cannot be used to limit the scope of the application.

[0036] Please refer to Figs. 1-5, the application provides a processing method of an aluminum ground nut column assembly, which comprises ground bolt processing and ground nut processing, and the ground bolt processing comprises the following steps:

[0037] S1: 5019 cold upsetting wire;

[0038] S2: cold upsetting;

[0039] S3: wire twisting;

[0040] S4: surface treatment,

[0041] S5: stabilization treatment;

[0042] S6: finished product screening;

[0043] The ground bolt processing includes the following steps:

[0044] S7: 5052 cold upsetting wire;

[0045] S8: cold upsetting;

[0046] S9: extrusion;

[0047] S10: surface treatment;

[0048] S11: stabilization treatment;

[0049] S12: finished product screening.

[0050] The bolt material is selected as 5019 aluminum alloy wire, which is processed by cold upsetting. The cold upsetting wire needs to meet the requirements of tensile strength ≥ 300 MPa, yield strength ≥ 250 MPa, end face shrinkage rate ≥ 40%, hardness 100-120 HV, and cold upset performance meeting 75% cold extrusion without cracking. The 5019 wire can meet the above performance and ensure the cold upsetting forming of the aluminum bolt after special drawing and annealing treatment. Since the 5019 alloy is not sensitive to heat treatment strengthening, the product strength is mainly based on the original strength of the cold upsetting wire and the mechanical property improvement of cold upsetting work hardening. This process controls the performance of the cold upsetting wire, ensures the cold upsetting forming, and provides guarantee for the final strength of the product, ensures high breaking torque, and prevents breakage due to jamming;

[0051] S4 surface treatment adopts Anmeng medicine passivation treatment, and the friction coefficient is controlled between 0.18-0.23 to achieve moderate friction coefficient, so that the tightening torque can be tightened to obtain effective clamping force, and the threads are prevented from being welded and jammed, without the need to control the different lubrication states of the support surface and the threads. The specific surface treatment process includes the following five steps:

[0052] S41 pretreatment: pretreatment is carried out by using 1%-4% UniPrep SP 1150LL, the solution temperature is 30-50°C, and the soaking time is 200-400S;

[0053] S42 alkali etching: 3%-10% Qualietch and 0.2%-1% Uniprep CB 20 reagent are used for room temperature etching for 200-400S;

[0054] S43 activation: UniClean AS 30 with a concentration of 0.5%-2% is used for room temperature activation for 100-300S;

[0055] S44: Passivation: using reagent with concentration of 1.5%~4% Interlox 377A and 0.2%~0.5% Interlox 377B, passivation for 150S~300S, then centrifugal drying, centrifugal speed 500~1000r / min, time 100S~200S;

[0056] S45: Lubrication: using Rogard LUBE 200 with concentration of 3~8%, whole bolt sealing treatment, soaking for 30~60S, then centrifugal drying, centrifugal speed 500~1000r / min, time 100S~200S.

[0057] The above S41-S44 processes all need to be washed with pure water for 1~2 times, washing time 20~60S, the bolt after S41-S45 treatment needs to be baked, which also plays a role in stabilization treatment, baking temperature control at 100~140℃, baking time 1~2h, and the stabilization treatment further improves the product strength.

[0058] The material of the nut is 5052 aluminum alloy wire, which is processed by cold heading. The wire needs to meet the requirements of tensile strength ≥230MPa, yield strength ≥190MPa, end face shrinkage rate ≥40%, hardness 60~80HV, and cold upset performance meets 75% cold extrusion without cracking. The 5052 wire after special drawing and annealing treatment can meet the above performance and ensure the cold heading forming of the aluminum nut. The 5052 alloy is also not sensitive to heat treatment strengthening, and the product strength is mainly based on the original strength of the cold heading wire and the cold heading work hardening to improve the mechanical properties. This process controls the performance of the cold heading wire to ensure cold heading forming and provides guarantee for the thread strength of the product to prevent breakage due to jamming;

[0059] The thread processing of the nut must use extrusion machining method to avoid cutting tapping. Firstly, the nut structure is blind hole, and aluminum chips generated by tapping are easy to remain in the nut cavity. Secondly, tapping is a cutting process to form the nut, and the thread surface roughness is large, even with defects such as broken teeth, which can cause thread welding and jamming during use. Extrusion machining must be used to ensure that the thread stress surface of the bolt and nut is smooth and complete without defects;

[0060] The surface treatment of the nut can use nitric acid pickling, nitric acid concentration 250~320ml / L, pickling time 10~15min, then water washing and drying. The drying process also serves as a stabilization treatment, baking temperature control at 100~140℃, baking time 1~2h, and the stabilization treatment further improves the thread strength;

[0061] The bolt and the nut are screened respectively, and then the bolt and the nut are installed and combined, the combination torque is 7-9 Nm, the combination is carried out on an automatic combination machine, and the delivery state of the two needs to be combined according to a certain torque, and the two are welded by using an arc welding machine at a client end, the welded aluminum alloy plate can be deformed aluminum or cast aluminum plate with a thickness of more than 1.5 mm, and the verification result of the grounding nut column is shown in Fig. 1, and the specific structures of the prepared bolt and nut are shown in Figs. 3 and 4 respectively, and the structure of the prepared grounding nut column assembly is shown in Fig. 5.

[0062] Embodiments of the application are presented by way of example and description, and are not intended to be exhaustive or to limit the application to the form disclosed. Many modifications and variations will be apparent to those skilled in the art. Embodiments are chosen and described in order to best explain the principles of the application and its practical application, and to enable others skilled in the art to best utilize the application with various modifications as are suited to the particular use contemplated.

Claims

1. A method of machining an aluminum ground nut post assembly, the method comprising: The grounding bolt processing and the grounding nut processing are included; ​ The grounding bolt processing includes the following steps: S1: 5019 cold upsetting wire rod, the wire rod meets the tensile strength ≥ 300 MPa, the yield strength ≥ 250 MPa, and the cold upset meets 75% cold extrusion without cracking; S2: multi-station cold upsetting forming; S3: cold extrusion wire drawing processing; S4: surface treatment, specifically including S41 pretreatment; S42 alkali etching; S43 activation; S44 passivation; S45 lubrication; S5: stabilization treatment; S6: finished product screening; The grounding nut processing includes the following steps: S7: 5052 cold upsetting wire rod, the wire rod needs to meet the tensile strength ≥ 230 MPa, the yield strength ≥ 190 MPa, and the cold upset meets 75% cold extrusion without cracking; S8: multi-station cold upsetting forming; S9: extrusion processing; S10: surface treatment, specifically nitric acid pickling passivation; S11: stabilization treatment; S12: finished product screening.

2. The method of claim 1, wherein the aluminum ground nut post assembly is formed by a process comprising: S44 passivation is completed by 1.5% to 4% Interlox 377A and 0.2% to 0.5% Interlox 377B, the process is soaking for 150S to 300S, centrifugal drying, centrifugal speed 500 to 1000 r / min, time 100S to 200S. ​ 3. The method of claim 1, wherein the aluminum ground nut post assembly is formed by a process comprising: S45 lubrication is completed by 3% to 8% Rogard LUBE 200, the process is soaking for 30 to 60S, centrifugal drying, centrifugal speed 500 to 1000 r / min, time 100S to 200S, the overall lubrication is completed, and the friction coefficient is controlled between 0.18 to 0.

23. ​ 4. The method of claim 1, wherein the aluminum ground nut post assembly is formed by a process comprising: The S41-S44 process needs to be washed with pure water 1 to 2 times, and the washing time is 20 to 60S. ​ 5. The method of claim 1, wherein the aluminum ground nut post assembly is formed by a process comprising: S10 surface treatment adopts nitric acid pickling, the nitric acid concentration is 250 to 320 ml / L, the pickling time is 10 to 15 min, and then water washing. ​ 6. The method of claim 1, wherein the aluminum ground nut post assembly is formed by a process comprising: S5 and S11 are baking treatment, the baking temperature is controlled at 100 to 140℃, and the baking time is 1 to 2h. ​ 7. The method of claim 1, wherein the aluminum ground nut post assembly is formed by a process comprising: S2 and S9 adopt cold extrusion thread forming. ​ 8. The method of claim 1, wherein the aluminum ground nut post assembly is formed by a process comprising: The bolts and nuts processed by the grounding bolt processing and the grounding nut processing are screened respectively, and then the bolts and nuts are assembled, and the assembly torque is 7 to 9 Nm on the automatic assembly machine. ​

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