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CN-122012989-A - Preparation method of low-cost TC4 titanium alloy fine-grain bar for fastener

CN122012989ACN 122012989 ACN122012989 ACN 122012989ACN-122012989-A

Abstract

The invention discloses a preparation method of a TC4 titanium alloy fine-grain bar for a fastener, which comprises the following steps of S1, preparing a TC4 titanium alloy cast ingot with the diameter of phi 700-800 mm, S2, forging the cast ingot, namely heating the cast ingot to 1100-1200 ℃, carrying out cogging forging after heat preservation, continuously drawing a round billet with the diameter of phi 170-190 mm back to a furnace, S3, carrying out first rolling, namely heating the round billet obtained in S2 to 900-930 ℃ for heat preservation, then rolling to a bar billet with the diameter of phi 95-105 mm, S4, carrying out second rolling, namely heating the round billet obtained in S3 to 880-920 ℃ for heat preservation, then rolling to a bar with the diameter of phi 10-25 mm, S5, carrying out heat treatment, namely carrying out heat treatment on the rolled bar with a heat treatment furnace, carrying out heat preservation for 60-90 min, S6, straightening, namely carrying out straightening after heating on the bar obtained after the heat treatment of S5, S7, polishing, and carrying out finishing, namely polishing to obtain a finished product of the TC4 titanium alloy bar with the diameter of phi 10-25 mm. The invention ensures excellent fatigue performance of the fastener and has good thread rolling formability.

Inventors

  • LIU XIANGHONG
  • MA HAN
  • SHI QI
  • ZHANG DING
  • WANG DONGBIN
  • WANG TAO
  • DU YUXUAN
  • FENG YONG

Assignees

  • 西部超导材料科技股份有限公司

Dates

Publication Date
20260512
Application Date
20260309

Claims (7)

  1. 1. The preparation method of the low-cost TC4 titanium alloy fine-grain bar for the fastener is characterized by comprising the following steps of: S1, ingot casting preparation: Taking a TC4 titanium alloy cast ingot with the diameter phi of 700 mm-800 mm, wherein the chemical components of the cast ingot comprise 6.20-6.65% of Al, 4.0-4.4% of V, 0.1-0.2% of Fe, 0.01-0.04% of C, less than or equal to 0.03% of N, 0.14-0.18% of O, less than or equal to 0.008% of H and the balance of Ti; S2, ingot casting forging: heating the TC4 titanium alloy cast ingot obtained in the step S1 to 1100-1200 ℃, carrying out cogging forging after heat preservation, and continuously returning to the furnace for drawing to obtain a round billet with the diameter of 170-190 mm; S3, rolling for the first time: Placing the round billet obtained in the step S2 into a heating furnace, heating to 900-930 ℃ for heat preservation, and then rolling to a bar billet with the diameter of 95-105 mm; s4, rolling for the second time: Placing the round billet obtained in the step S3 into a heating furnace, heating to 880-920 ℃ for heat preservation, and then rolling to a rolled bar with the diameter of phi 10-phi 25 mm; S5, heat treatment: carrying out heat treatment at 730-800 ℃ on the rolled bar by adopting a heat treatment furnace, and preserving heat for 60-90 min; S6, straightening: heating the bar subjected to the S5 heat treatment and straightening; s7, finishing: and (3) peeling and polishing the bar obtained in the step (S6) to prepare a TC4 titanium alloy fine crystal bar finished product with the diameter of phi 10mm to phi 25 mm.
  2. 2. The method for preparing the TC4 titanium alloy fine-grain bar for the fastener, which is disclosed in claim 1, is characterized in that in the step S1, the process of preparing the ingot is to mix and press titanium sponge, aluminum beans, aluminum-vanadium intermediate alloy, aluminum-iron intermediate alloy and titanium dioxide into electrodes, perform vacuum plasma welding, and then perform vacuum arc melting for 3 times to obtain the TC4 titanium alloy ingot with the diameter of phi 700 mm-phi 800 mm.
  3. 3. The method for preparing the low-cost TC4 titanium alloy fine-grain bar for the fastener, which is characterized in that in the step S2, ingot casting is subjected to hot material furnace return for 2 times, and the furnace return heating temperature is 1000-1100 ℃.
  4. 4. The method for producing a low-cost TC4 titanium alloy fine grain rod for fasteners according to claim 1, wherein in S3, two-roll reversing mill is used for rolling, and the rolling is performed in 10 passes, and the cumulative deformation is 65% -75%.
  5. 5. The method for preparing the low-cost TC4 titanium alloy fine-grain bar for the fastener according to claim 1, wherein in the step S4, 24 continuous rolling units are adopted for rolling, the continuous rolling passes through 18-22 passes, the accumulated deformation is 95% -99%, the continuous rolling finishing speed is controlled to be 1.0-4.0 m/S, and the finishing temperature is controlled to be 800-850 ℃.
  6. 6. The method for preparing the TC4 titanium alloy fine-grain bar for the fastener, which is disclosed in claim 1, is characterized in that in the step S6, the bar straightening heating temperature is 650-700 ℃, the heat preservation time is 30-60 min, a roller straightener is adopted for straightening, and the straightness of the straightened bar is less than or equal to 0.5mm/m.
  7. 7. The method for producing a low-cost TC4 titanium alloy fine-grain bar for fasteners according to claim 1, wherein in S7, the surface roughness Ra is 1.2 μm or less after polishing.

Description

Preparation method of low-cost TC4 titanium alloy fine-grain bar for fastener Technical Field The invention belongs to the technical field of titanium alloy processing, and particularly relates to a preparation method of a low-cost TC4 titanium alloy fine-grain bar for a fastener. Background The titanium alloy fastener has the characteristics of low density, high specific strength, good corrosion resistance, no magnetism, small thermal expansion coefficient, small elastic modulus and the like, is widely applied to the fields of aviation, aerospace, high-end automobiles and the like pursuing light weight, and can directly improve the carrying efficiency and reduce the energy consumption. The TC4 (Ti-6 Al-4V) bolts are firstly applied to the B-52 bombers in the United states, a remarkable weight reduction effect is achieved, TC4 (Ti-6 Al-4V) fasteners are largely adopted in various civil and military aircraft (such as C-5A and Boeing 747) in European and American developed countries, the traditional 30CrMnSiA steel is replaced, the weight reduction of parts can be achieved by about 30%, and TC4 (Ti-6 Al-4V) becomes a main stream material of the aerospace fasteners and accounts for more than 95% of the titanium alloy fasteners. The TC4 fasteners M4, M5, M6, M8 and other specifications in the aerospace field at home and abroad are large in consumption, the corresponding titanium alloy raw materials are wire rods with the diameter of less than 10mm, a large number of heavy point project researches are conducted on the fasteners in the specification range by each national institute at present, and localization is achieved gradually. The related researches on TC4 raw materials for large-size bolts such as M16, M18 and M20 are less, the raw materials TC4 titanium alloy bar still has a certain gap between the structure and the performance and an inlet, and mainly shows that grains are thicker, the performance after heat treatment strengthening is lower, and the problems of upsetting, thread rolling cracking, lower part fatigue strength and the like can occur in the preparation process of the fastener. The domestic TC4 titanium alloy bars are rolled by a horizontal rolling mill, are limited by equipment, have small rolling deformation, are required to be matched with multi-firing forging to prepare rolling blanks with fine and uniform tissues, have long overall processing period and higher production cost, and have a certain gap between the prepared finished products and imported products in tissue performance. Therefore, the research on the preparation process of the TC4 titanium alloy fine-grain straight bar for the fastener has important engineering significance. Disclosure of Invention The invention aims to provide a preparation method of a TC4 titanium alloy fine-grain bar for a fastener, which is used for preparing a fine-grain straight bar with horizontal and longitudinal structures reaching A1 and AA1 level of ETTC < titanium alloy bar microstructure standard > through a shorter production flow, ensuring excellent fatigue performance of the fastener product and good thread rolling formability. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: The preparation method of the low-cost TC4 titanium alloy fine-grain bar for the fastener comprises the following steps: S1, ingot casting preparation: Taking a TC4 titanium alloy cast ingot with the diameter phi of 700 mm-800 mm, wherein the chemical components of the cast ingot comprise 6.20-6.65% of Al, 4.0-4.4% of V, 0.1-0.2% of Fe, 0.01-0.04% of C, less than or equal to 0.03% of N, 0.14-0.18% of O, less than or equal to 0.008% of H and the balance of Ti; S2, ingot casting forging: heating the TC4 titanium alloy cast ingot obtained in the step S1 to 1100-1200 ℃, carrying out cogging forging after heat preservation, and continuously returning to the furnace for drawing to obtain a round billet with the diameter of 170-190 mm; S3, rolling for the first time: Placing the round billet obtained in the step S2 into a heating furnace, heating to 900-930 ℃ for heat preservation, and then rolling to a bar billet with the diameter of 95-105 mm; s4, rolling for the second time: Placing the round billet obtained in the step S3 into a heating furnace, heating to 880-920 ℃ for heat preservation, and then rolling to a rolled bar with the diameter of phi 10-phi 25 mm; S5, heat treatment: carrying out heat treatment at 730-800 ℃ on the rolled bar by adopting a heat treatment furnace, and preserving heat for 60-90 min; S6, straightening: heating the bar subjected to the S5 heat treatment and straightening; s7, finishing: and (3) peeling and polishing the bar obtained in the step (S6) to prepare a TC4 titanium alloy fine crystal bar finished product with the diameter of phi 10mm to phi 25 mm. Preferably, in the step S1, the ingot casting preparation process comprises the steps of mixing and pressing titanium sponge, aluminum beans, alum