Thread machining method for 1500MPa-grade titanium alloy bolt

Abstract

The invention discloses a thread machining method for a 1500 MPa titanium alloy bolt. The thread machining method comprises the following steps of blank machining, primary thread pre-forming, heat treatment and secondary thread final forming. The high-fatigue-resistance thread rolling forming die has high fatigue performance, meanwhile, has small forming resistance compared with a traditional one-time rolling thread, and can avoid thread breakage and cracks in the thread rolling process.

Description

Technical Field

[0001] The present invention relates to the technical field of bolts, and in particular to a thread processing method for a 1500MPa grade titanium alloy bolt. Background Art

[0002] At present, there are generally two methods for processing titanium alloy bolt threads: turning and non-cutting (i.e. rolling). The threads of 1100MPa and 1300MPa titanium alloy bolts for aerospace use one-time rolling. The advantage is that the bolt threads retain complete material deformation streamlines and certain compressive stresses, and have good fatigue performance relative to bolts with turned threads.

[0003] However, 1500MPa grade titanium alloy has extremely high strength, but its elongation is only about 8%, and its plasticity is poor. When the bolt threads are formed by one-time rolling, problems such as thread rot, thread rolling cracks, or folding defects exceeding the standard are prone to occur, which cannot meet the technical index requirements of the bolts. Summary of the invention

[0004] The object of the present invention is to overcome the above-mentioned disadvantages and provide a thread processing method for 1500MPa grade titanium alloy bolts which has higher fatigue performance and smaller forming resistance than the traditional one-time rolled thread and can avoid tooth decay and cracks during thread rolling.

[0005] The purpose of the present invention and the solution of its main technical problems are achieved by adopting the following technical solutions: A thread processing method for a 1500MPa grade titanium alloy bolt of the present invention comprises the following steps: 1) Billet processing: First, the bolt head is determined and formed according to the bolt head shape and structure, then the solid solution heat treatment is carried out according to the material heat treatment parameters, and finally the thread forming blank is turned according to the thread size specifications; 2) One-step thread preforming: The thread is preformed by turning 1 / 3 to 1 / 5 of the thread or rolling the thread with a rolling wheel 1 / 3 to 1 / 5, and the thread is preformed into a blank. The shape of the blank can be adjusted according to the final thread shape, alloy plasticity and bolt fatigue index; 3) Heat treatment: Perform aging heat treatment according to the alloy heat treatment process parameters; 4) Secondary thread final forming: According to the final size requirements of the bolt thread, select the thread rolling wheel of the corresponding specification, adjust the relative position of the thread rolling wheel and the pre-formed thread, and finally roll the thread to form it.

[0006] The material heat treatment parameters described in step 1) are 800-870°C for 1 hour and water quenching.

[0007] The heat treatment process parameters in step 3) are kept at 500-600°C for 3-8 hours.

[0008] Compared with the prior art, the present invention has obvious beneficial effects. It can be seen from the above technical scheme that the present invention adopts one-time thread preforming: turning 1 / 3 to 1 / 5 of the thread, rolling the thread 1 / 3 to 1 / 5 of the thread, preforming the thread blank, and the blank shape can be adjusted according to the final thread shape, alloy plasticity and bolt fatigue index; aging heat treatment is performed according to the alloy heat treatment process parameters; secondary thread final forming: according to the final size requirements of the bolt thread, a thread rolling wheel of corresponding specifications is selected, the relative position of the thread rolling wheel and the preformed thread is adjusted to align, and finally the thread is rolled to form. The two-step forming method is adopted to reduce the deformation amount of single thread forming. First, the thread is preformed by turning or rolling in the solid solution state of the semi-finished bolt, and the thread is rolled again after aging heat treatment to achieve the final thread size and performance requirements. There will be no problems of thread rot, thread rolling cracks or folding defects exceeding the standard, and high fatigue performance is achieved. At the same time, it has a smaller forming resistance than the traditional one-time rolling thread, and can avoid thread rot and cracks during thread rolling. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the one-step thread preforming of the present invention; Figure 2 It is a schematic diagram of the secondary thread final forming of the present invention. DETAILED DESCRIPTION

[0011] The specific implementation methods, structures, features and functions of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0012] Example 1 A thread processing method for a 1500MPa grade titanium alloy bolt of the present invention comprises the following steps: 1) Billet processing: First, the bolt head is determined and formed according to the bolt head shape and structure, then the solid solution heat treatment is carried out according to the material heat treatment parameters, and finally the thread forming blank is turned according to the thread size specifications; 2) One-step thread preforming: The thread is preformed by turning 1 / 3 of the thread, and the thread is preformed into a blank. The shape of the blank can be adjusted according to the final thread shape, alloy plasticity and bolt fatigue index; 3) Heat treatment: Perform aging heat treatment according to the alloy heat treatment process parameters; 4) Secondary thread final forming: According to the final size requirements of the bolt thread, select the thread rolling wheel of the corresponding specification, adjust the relative position of the thread rolling wheel and the pre-formed thread, and finally roll the thread to form it.

[0013] The material heat treatment parameters described in step 1) are 830°C, kept for 1 hour, and water quenched.

[0014] The heat treatment process parameters described in step 3) are kept at 540°C for 4-8 hours.

[0015] Example 2 A thread processing method for a 1500MPa grade titanium alloy bolt of the present invention comprises the following steps: 1) Billet processing: First, the bolt head is determined and formed according to the bolt head shape and structure, then the solid solution heat treatment is carried out according to the material heat treatment parameters, and finally the thread forming blank is turned according to the thread size specifications; 2) One-step thread preforming: Use rolling wheel to roll 1 / 5 pre-formed threads, pre-formed thread blanks, and the blank shape can be adjusted according to the final thread shape, alloy plasticity and bolt fatigue index; 3) Heat treatment: Perform aging heat treatment according to the alloy heat treatment process parameters; 4) Secondary thread final forming: According to the final size requirements of the bolt thread, select the thread rolling wheel of the corresponding specification, adjust the relative position of the thread rolling wheel and the pre-formed thread, and finally roll the thread to form it.

[0016] The material heat treatment parameters described in step 1) are 830°C, kept for 1 hour, and water quenched.

[0017] The heat treatment process parameters described in step 3) are kept at 540°C for 4-8 hours.

[0018] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A thread processing method for a 1500MPa grade titanium alloy bolt of the present invention comprises the following steps: 1) Billet processing: First, the bolt head is determined and formed according to the bolt head shape and structure, then the solid solution heat treatment is carried out according to the material heat treatment parameters, and finally the thread forming blank is turned according to the thread size specifications; 2) One-step thread preforming: The thread is preformed by using one of 1 / 3 to 1 / 5 of the turning thread and 1 / 3 to 1 / 5 of the rolling wheel thread, and the thread is preformed into a blank, and the blank shape can be adjusted according to the final thread shape, alloy plasticity and bolt fatigue index; 3) Heat treatment: Perform aging heat treatment according to the alloy heat treatment process parameters; 4) Secondary thread final forming: According to the final size requirements of the bolt thread, select the thread rolling wheel of the corresponding specification, adjust the relative position of the thread rolling wheel and the pre-formed thread, and finally roll the thread to form it.

2. A thread processing method for a 1500MPa grade titanium alloy bolt as claimed in claim 1, wherein: The material heat treatment parameters described in step 1) are 800-870°C for 1 hour and water quenching.

3. A method for manufacturing a carbon steel barrel nut for aviation use as claimed in claim 1, wherein: The heat treatment process parameters described in step 3) are kept at 500-600°C for 4-8 hours.

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