1500MPa-grade ultrahigh-strength titanium alloy fastener

Abstract

The invention discloses a 1500MPa-grade ultrahigh-strength titanium alloy fastener which is obtained by sequentially performing heat treatment, head upsetting and thread rolling forming on ultrahigh-strength titanium alloy, and the ultrahigh-strength titanium alloy comprises the following elements in percentage by mass: 5-6% of Al, 3-4% of Mo, 3-4% of V, 5-6% of Cr, 1-2% of Nb, 2-3% of Zr, not more than 0.5% of Fe and the balance of Ti and inevitable impurities. According to the titanium alloy fastener, it can be guaranteed that the titanium alloy obtains high strength by adding the high Cr element, meanwhile, the machinability of the titanium alloy material is improved by adding the proper content of Mo and Nb elements, forming of the ultrahigh-strength titanium alloy fastener is facilitated, and the titanium alloy fastener is suitable for the technical field of titanium alloy fasteners.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy fasteners, and in particular relates to a 1500MPa-grade ultra-high strength titanium alloy fastener. Background Art

[0002] According to the application field, fasteners are divided into general-purpose fasteners and aerospace fasteners. In the aviation field, the connection method of aircraft is still mainly mechanical connection, and a large number of fasteners are used during assembly; in the aerospace field, the connection between aircraft sections also relies on fasteners. With the development of lightweight equipment, more and more aerospace fasteners favor titanium alloy materials. By replacing steel fasteners with titanium fasteners, the weight of the aircraft can be significantly reduced, its service life can be extended, and the flight technical characteristics and reliability of use can be improved without changing the structural form.

[0003] Weight reduction is an eternal theme for aviation and aerospace vehicles. The higher the material strength, the more obvious the weight reduction effect. With the development of the aerospace industry, the connection technology level used in new aircraft and aerospace vehicles has been continuously improved. In the future, high-performance aviation fasteners will put forward higher strength and higher fatigue performance requirements for the titanium alloy materials used to manufacture them. At present, high-strength titanium alloys used in aviation fasteners are usually TB3, TB8 (β21s), and TB9 (Ti38644). The highest strength level of fasteners does not exceed 1300MPa, and the shear strength does not exceed 800MPa. Therefore, the development of titanium alloy fasteners with higher strength levels is a research direction in the field of aviation fasteners. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and provide a 1500MPa-level ultra-high strength titanium alloy fastener. The titanium alloy fastener adds a relatively high Cr element to ensure that the titanium alloy obtains high strength, and adds a suitable content of Mo and Nb elements to improve the material processing performance, so that the titanium alloy can take into account both strength performance and processing performance, which is conducive to the formation of ultra-high strength titanium alloy fasteners above 1500MPa, and solves the problem that the highest strength level of fasteners used in the prior art does not exceed 1300MPa and the shear strength does not exceed 800MPa.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a 1500MPa grade ultra-high strength titanium alloy fastener, characterized in that the fastener is obtained by sequentially subjecting the ultra-high strength titanium alloy to heat treatment, head upsetting and thread rolling, and the ultra-high strength titanium alloy is composed of the following elements in mass percentage: Al 5% to 6%, Mo 3% to 4%, V3% to 4%, Cr 5% to 6%, Nb 1% to 2%, Zr 2% to 3%, Fe not more than 0.5%, and the balance is Ti and unavoidable impurities.

[0006] The above-mentioned 1500MPa grade ultra-high strength titanium alloy fastener is characterized in that the ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 5% to 5.5%, Mo 3% to 3.5%, V 3% to 3.5%, Cr 5% to 5.5%, Nb 1.6% to 2%, Zr 2% to 3%, Fe not more than 0.5%, and the balance is Ti and unavoidable impurities.

[0007] The above-mentioned 1500MPa grade ultra-high strength titanium alloy fastener is characterized in that the ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 5%, Mo 3%, V 3%, Cr 5.5%, Nb 2%, Zr 3%, Fe not more than 0.5%, and the balance is Ti and unavoidable impurities.

[0008] The above-mentioned 1500MPa-grade ultra-high strength titanium alloy fastener is characterized in that the tensile strength of the fastener is not less than 1500MPa, the double shear strength is not less than 830MPa, and the fatigue life is not less than 130,000 times.

[0009] The above-mentioned 1500MPa grade ultra-high strength titanium alloy fastener is characterized in that the fastener includes MJ6~MJ12 tensile bolts, shear bolts and long threaded bolts.

[0010] Compared with the prior art, the present invention has the following advantages:

[0011] 1. The present invention ensures that the titanium alloy obtains high strength by adding a relatively high Cr element, and at the same time adds a suitable content of Mo and Nb elements to improve the plasticity of the titanium alloy by refining the grains and increasing the deformation coordination ability, which is beneficial to the forming of ultra-high strength titanium alloy fasteners.

[0012] 2. The present invention utilizes the characteristic that the shear strength of titanium alloy is sensitive to the hardening rate, designs appropriate Al equivalent and Mo equivalent, so that the yield ratio of the titanium alloy is 0.90-0.95, and improves the hardening index of the alloy without significantly reducing the strength of the alloy, which can effectively improve the shear strength of the titanium alloy.

[0013] 3. The titanium alloy fasteners prepared by the present invention have a tensile strength of not less than 1500MPa and a double shear strength of not less than 830MPa, while also having excellent fatigue properties and a performance level significantly higher than existing TB3, TB8, TB9 and other alloys; they can replace traditional high-strength steel, achieve weight reduction of fastener structures, and thus significantly improve aircraft performance.

[0014] The technical solution of the present invention is further described in detail below through embodiments. DETAILED DESCRIPTION

[0015] Example 1

[0016] The fastener of this embodiment comprises the following steps:

[0017] Step 1, mixing the raw materials and performing vacuum consumable arc melting four times to obtain an ingot;

[0018] Step 2: Forging the ingot obtained in step 1 to obtain an ultra-high strength titanium alloy; the ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 5%, Mo 3%, V 3%, Cr 5%, Nb 1%, Zr 3%, Fe not more than 0.5%, and the balance being Ti and unavoidable impurities;

[0019] Step 3: The ultra-high-strength titanium alloy obtained in step 2 is subjected to heat treatment, head upsetting and thread rolling in sequence to obtain an MJ8 shear-resistant 100° small countersunk high-locking bolt.

[0020] After testing, the tensile ultimate strength of the bolt obtained in this embodiment is 1565 MPa, the double shear strength is 867 MPa, and the fatigue life exceeds 130,000 times.

[0021] Example 2

[0022] The fastener of this embodiment comprises the following steps:

[0023] Step 1, mixing the raw materials and performing vacuum consumable arc melting five times to obtain an ingot;

[0024] Step 2: Forging the ingot obtained in step 1 to obtain an ultra-high strength titanium alloy; the ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 6%, Mo 4%, V 4%, Cr 6%, Nb 2%, Zr 2%, Fe not more than 0.5%, and the balance being Ti and unavoidable impurities;

[0025] Step 3: The ultra-high-strength titanium alloy obtained in step 2 is subjected to heat treatment, head upsetting and thread rolling in sequence to obtain an MJ12 tensile-resistant 100° small countersunk high-locking bolt.

[0026] After testing, the bolt obtained in this embodiment has a tensile ultimate strength of 1515 MPa, a double shear strength of 835 MPa, and a fatigue life of more than 130,000 times.

[0027] Example 3

[0028] The fastener of this embodiment comprises the following steps:

[0029] Step 1, mixing the raw materials and performing vacuum consumable arc melting four times to obtain an ingot;

[0030] Step 2: Forging the ingot obtained in step 1 to obtain an ultra-high strength titanium alloy; the ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 5.5%, Mo 3.5%, V 3.5%, Cr 5%, Nb 1%, Zr 3%, Fe not more than 0.5%, and the balance is Ti and unavoidable impurities;

[0031] Step 3: The ultra-high strength titanium alloy obtained in step 2 is subjected to heat treatment, head upsetting and thread rolling in sequence to obtain an MJ10 long thread bolt.

[0032] After testing, the bolt obtained in this embodiment has a tensile ultimate strength of 1521 MPa, a double shear strength of 841 MPa, and a fatigue life of more than 130,000 times.

[0033] Example 4

[0034] The fastener of this embodiment comprises the following steps:

[0035] Step 1, mixing the raw materials and performing vacuum consumable arc melting five times to obtain an ingot;

[0036] Step 2: Forging the ingot obtained in step 1 to obtain an ultra-high strength titanium alloy; the ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 5%, Mo 3%, V 4%, Cr 5%, Nb 1%, Zr 3%, Fe not more than 0.5%, and the balance being Ti and unavoidable impurities;

[0037] Step 3: The ultra-high strength titanium alloy obtained in step 2 is subjected to heat treatment, head upsetting and thread rolling in sequence to obtain an MJ12 long thread bolt.

[0038] After testing, the bolt obtained in this embodiment has a tensile ultimate strength of 1510 MPa, a double shear strength of 834 MPa, and a fatigue life of more than 130,000 times.

[0039] Example 5

[0040] The fastener of this embodiment comprises the following steps:

[0041] Step 1, mixing the raw materials and performing vacuum consumable arc melting five times to obtain an ingot;

[0042] Step 2: Forging the ingot obtained in step 1 to obtain an ultra-high strength titanium alloy; the ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 5.5%, Mo 3.5%, V 3.5%, Cr 5%, Nb 1.6%, Zr2%, Fe not more than 0.5%, and the balance is Ti and unavoidable impurities;

[0043] Step 3: The ultra-high strength titanium alloy obtained in step 2 is subjected to heat treatment, head upsetting and thread rolling in sequence to obtain an MJ12 long thread bolt.

[0044] After testing, the bolt obtained in this embodiment has a tensile ultimate strength of 1522 MPa, a double shear strength of 837 MPa, and a fatigue life of more than 130,000 times.

[0045] Example 6

[0046] The fastener of this embodiment comprises the following steps:

[0047] Step 1, mixing the raw materials and performing vacuum consumable arc melting five times to obtain an ingot;

[0048] Step 2: Forging the ingot obtained in step 1 to obtain an ultra-high strength titanium alloy; the ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 5%, Mo 3%, V 3%, Cr 5.5%, Nb 2%, Zr 3%, Fe not more than 0.5%, and the balance being Ti and unavoidable impurities;

[0049] Step 3: The ultra-high strength titanium alloy obtained in step 2 is subjected to heat treatment, head upsetting and thread rolling in sequence to obtain an MJ12 long thread bolt.

[0050] After testing, the bolt obtained in this embodiment has a tensile ultimate strength of 1530 MPa, a double shear strength of 841 MPa, and a fatigue life of more than 130,000 times.

[0051] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A 1500MPa ultra-high strength titanium alloy fastener, characterized in that: The fastener is obtained by sequentially subjecting an ultra-high strength titanium alloy to heat treatment, head upsetting and thread rolling. The ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 5% to 6%, Mo 3% to 4%, V 3% to 4%, Cr 5% to 6%, Nb 1% to 2%, Zr 2% to 3%, Fe not more than 0.5%, and the remainder being Ti and unavoidable impurities.

2. The 1500MPa ultra-high strength titanium alloy fastener according to claim 1, characterized in that: The ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 5% to 5.5%, Mo 3% to 3.5%, V 3% to 3.5%, Cr 5% to 5.5%, Nb 1.6% to 2%, Zr 2% to 3%, Fe not more than 0.5%, and the remainder being Ti and unavoidable impurities.

3. The 1500MPa ultra-high strength titanium alloy fastener according to claim 1, characterized in that: The ultra-high strength titanium alloy is composed of the following elements in percentage by mass: Al 5%, Mo 3%, V 3%, Cr 5.5%, Nb 2%, Zr 3%, Fe not more than 0.5%, and the balance being Ti and unavoidable impurities.

4. The 1500MPa ultra-high strength titanium alloy fastener according to claim 1, characterized in that: The tensile strength of the fastener is not less than 1500MPa, the double shear strength is not less than 830MPa, and the fatigue life is not less than 130,000 times.

5. The 1500MPa ultra-high strength titanium alloy fastener according to claim 1, characterized in that: The fasteners include MJ6-MJ12 tensile bolts, shear bolts and long thread bolts.