A method for preparing TC4 titanium alloy coiled wire for low-cost fasteners

Abstract

This invention discloses a low-cost method for producing TC4 titanium alloy coiled wire for fasteners. This method utilizes a combination of rolling and forging, based on EB+VAR smelting, and utilizes continuous rolling technology with full temperature and rolling control to produce hot-rolled coils using only two forging passes and three rolling passes. This method reduces the number of forging and rolling passes and the number of drawing passes, sometimes eliminating the need for drawing. This significantly improves production efficiency and enables low-cost improvements in the consistency and stability of the microstructure and performance of TC4 titanium alloy coiled wire.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy processing, and in particular relates to a method for preparing TC4 titanium alloy coiled wire for low-cost fasteners. Background Art

[0002] Titanium and its alloys have been successfully applied to industrial fields such as aviation, medical care, chemical industry and shipbuilding due to their high specific strength, good corrosion resistance, biocompatibility and non-magnetic properties. Especially in aircraft, in addition to larger titanium alloy structural parts, titanium alloy fasteners are also used in tens of thousands or even hundreds of thousands of pieces.

[0003] The nominal diameters of the main specifications of TC4 titanium alloy coil wire for aviation are Φ4, 5, 6, and 8 mm. At present, the process of three-pass vacuum consumable arc furnace (VAR) melting ingots, forging, horizontal rolling, and multi-pass drawing is mostly used for preparation. Among them, forging is an intermittent production method and requires 4 to 6 forging passes. Between each pass, the billet needs to be ground, the head and tail cracking areas need to be sawed off, etc., resulting in low production efficiency and low material utilization. Multiple horizontal rolling mills are used for two-pass rolling. During the production process, due to the limitations of equipment capacity, tooling, personnel operation, and billet temperature drop, the closer to the finished product specifications, the smaller the billet weight. The final finished round wire weighs about 20 kg per coil, and there are certain differences in the organization and performance between batches.

[0004] In recent years, the production equipment of various titanium companies has been upgraded and renovated, and horizontal rolling has also been upgraded to vertical rolling. Although the preparation of hot-rolled coils with a single coil weight of more than 100kg can be achieved, the size of the hot-rolled coils is Φ12~15mm, and it still requires 10~18 drawing passes and 2~4 stress relief annealing to prepare coils of wire of different sizes. The long processing cycle seriously restricts production efficiency. Summary of the Invention

[0005] To address the shortcomings of the aforementioned prior art, the present invention aims to provide a low-cost method for producing TC4 titanium alloy coiled wire for aerospace fasteners. This method utilizes "rolling instead of forging, combining forging and rolling" based on melting processes in an electron beam cold hearth (EB) furnace and a vacuum consumable arc (VAR) furnace. This method utilizes continuous rolling technology with full temperature and rolling control to produce hot-rolled coils using only two forging passes and three rolling passes. This method reduces the number of forging and rolling passes, and reduces or even eliminates the need for drawing, thereby improving production efficiency and enhancing the consistency and stability of the coiled wire's microstructure and performance at a low cost.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions.

[0007] In one aspect, the present invention provides a method for preparing TC4 titanium alloy coiled wire for low-cost fasteners, comprising:

[0008] Step 1: Ingot melting:

[0009] Sponge titanium, aluminum vanadium, aluminum particles, iron particles, TiO2, and titanium carbide are mixed according to a predetermined element ratio and pressed into an electrode, and then subjected to electron beam cold hearth furnace melting and vacuum consumable arc furnace melting to obtain a TC4 titanium alloy ingot blank, and the TC4 titanium alloy ingot blank is peeled, and a riser and ingot bottom are cut to prepare a TC4 titanium alloy ingot with a diameter of 700 to 820 mm.

[0010] Step 2: Ingot forging:

[0011] The TC4 titanium alloy ingot obtained in step 1 is heated to 1000-1200° C., kept warm, and then forged into a 450-550×L billet; the billet is polished, sawn, and divided, and then heated to 920-980° C., kept warm, and then upsetting to a 200-300×L billet;

[0012] Step 3: Grinding:

[0013] Grind the billet obtained in step 2 to remove surface defects, including cracks and folds;

[0014] Step 4: First rolling:

[0015] The □200-300×L forging billet obtained in step 3 is heated to 920-980°C. After the heat preservation is completed, a BD850 two-roll reversible rolling mill is used for multiple passes to obtain a □140-180×L square billet;

[0016] Second rolling:

[0017] The □140~180×L billets are sawn and divided, the surface is polished, and then heated to 920~980℃. After the heat preservation is completed, they are rolled in multiple passes using a BD850 two-roll reversible rolling mill to obtain rolled bars;

[0018] Step 5: Peeling, pickling and polishing

[0019] The rolled bar obtained in step 4 is peeled to remove the surface oxide scale, and then pickled and polished to remove surface cracks and folding defects;

[0020] Step 6: Third rolling:

[0021] The rolled bar obtained in step 5 is subjected to induction heating at a temperature of 850-950° C., and is sequentially subjected to single-hot rolling using a BD600 two-roll reversing mill, an eight-roll tandem mill, and a finishing / kocks tandem mill to prepare a hot-rolled coil;

[0022] Step 7: Finishing:

[0023] The hot-rolled coil obtained in step 6 is processed by a direct peeling process or a drawing process to obtain TC4 titanium alloy coiled wire.

[0024] Furthermore, in step 1, the weight percentages of the elements in the TC4 titanium alloy ingot are: Al content is 5.5-6.75%, V content is 3.5-4.5%; Fe content is ≤0.3%; C content is ≤0.08%; N content is ≤0.05%; O content is ≤0.2%; and the balance is Ti.

[0025] Furthermore, in step 2, the TC4 titanium alloy ingot is heated to 1000-1200°C and kept warm for 360-420 minutes, and then the blank is forged with a deformation of 30-45%; squared to □550-650×L, subjected to a first fire upsetting and chamfering to □450-550×L, and then the blank surface is polished and sawed for material division; then the □450-550×L forging blank is heated to 920-980°C, kept warm for 90-150 minutes, blanked with a deformation of 30-45%, and then subjected to a first fire upsetting to □200-300×L square blank.

[0026] Furthermore, in the first rolling of step 4, the multi-pass rolling is 7 to 11 passes.

[0027] Furthermore, in the second rolling in step 4, the multi-pass rolling is 9 to 13 passes.

[0028] Furthermore, in step 4, the diameter of the rolled bar obtained is 85 mm to 115 mm.

[0029] Furthermore, in step 6, the diameter of the obtained hot-rolled coil is 7 mm to 12 mm.

[0030] Furthermore, in step 7, the direct peeling process specifically includes the following steps in sequence: hot rolling coil, rounding, annealing, straightening, centerless turning peeling, fixed die peeling, polishing, eddy current testing, and quality inspection; the drawing process specifically includes the following steps in sequence: hot rolling coil, rounding, centerless turning peeling, drawing, annealing, straightening, fixed die peeling, polishing, eddy current testing, and quality inspection.

[0031] Furthermore, in step 1, the titanium sponge in the mixture is selected to be small particles with a particle size range of 0.83 mm to 12.7 mm.

[0032] On the other hand, the present invention also provides a low-cost TC4 titanium alloy coiled wire for fasteners, which is prepared by the above-mentioned preparation method.

[0033] Furthermore, the weight of a single coil of the TC4 titanium alloy round wire is greater than 100 kg.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1) The present invention adjusts the chemical composition and smelting method of the TC4 titanium alloy ingot and controls the forging, rolling, machining and heat treatment processes to ensure that the structure and performance of the TC4 titanium alloy coil wire meet the requirements for aerospace fasteners.

[0036] 2) The present invention adopts the technology of "rolling instead of forging, combining forging and rolling", which reduces the tedious forging and rolling steps in the traditional process, greatly reduces the number of drawing passes, and even eliminates the need for drawing, thereby effectively improving the overall production efficiency and material utilization rate.

[0037] 3) The present invention adopts continuous rolling technology with full-process temperature and rolling control, which avoids the disadvantages of multiple material separation in traditional horizontal rolling and shortens the process. The microstructure, mechanical property consistency and stability of the prepared TC4 titanium alloy round wire are higher than those of wire prepared by traditional methods. The weight of a single coil is greater than 100kg, which is equivalent to wire imported from the United States.

[0038] 4) The present invention adopts direct peeling and drawing production mode, which breaks through the traditional process of multiple drawing passes and intermediate annealing, improves production efficiency and reduces production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 (a)-(b) are transverse and longitudinal microstructure photographs of the Φ4.03 mm TC4 titanium alloy coil wire prepared in Example 1 of the present invention, respectively.

[0040] Figure 2 (a)-(b) are transverse and longitudinal microstructure photographs of the Φ5.03 mm TC4 titanium alloy disc wire prepared in Example 2 of the present invention, respectively.

[0041] Figure 3 (a)-(b) are transverse and longitudinal microstructure photographs of the Φ6.03 mm TC4 titanium alloy disc wire prepared in Example 3 of the present invention, respectively.

[0042] Figure 4 (a)-(b) are transverse and longitudinal microstructure photographs of the Φ8.03 mm TC4 titanium alloy coil wire prepared in Example 4 of the present invention, respectively. DETAILED DESCRIPTION

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention are only used to describe the purpose of specific embodiments and are not intended to limit the present invention.

[0044] In the present invention, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical range, as well as each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval refers only to integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1-10, indicating that t is any integer selected from the group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges therein.

[0045] The temperature parameters in the present invention, unless otherwise specified, may be either constant temperature or fluctuating within a certain temperature range. It should be understood that the constant temperature treatment allows for temperature fluctuations within the precision range of the instrument control. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.

[0046] The present invention provides a method for preparing TC4 titanium alloy coiled wire for low-cost fasteners, which comprises:

[0047] In one aspect, the present invention provides a method for preparing TC4 titanium alloy coiled wire for low-cost fasteners, comprising:

[0048] Step 1: Ingot melting:

[0049] Sponge titanium, aluminum vanadium, aluminum particles, iron particles, TiO2, and titanium carbide are mixed according to a predetermined element ratio and pressed into an electrode, and then subjected to electron beam cold hearth furnace melting and vacuum consumable arc furnace melting to obtain a TC4 titanium alloy ingot blank, and the TC4 titanium alloy ingot blank is peeled, and a riser and ingot bottom are cut to prepare a TC4 titanium alloy ingot with a diameter of 700 to 820 mm.

[0050] Step 2: Ingot forging:

[0051] The TC4 titanium alloy ingot obtained in step 1 is heated to 1000-1200° C., kept warm, and then forged into a 450-550×L billet; the billet is polished, sawn, and divided, and then heated to 920-980° C., kept warm, and then upsetting to a 200-300×L billet;

[0052] Step 3: Grinding:

[0053] Grind the billet obtained in step 2 to remove surface defects, including cracks and folds;

[0054] Step 4: First rolling:

[0055] The □200-300×L forging billet obtained in step 3 is heated to 920-980°C. After the heat preservation is completed, a BD850 two-roll reversible rolling mill is used for multiple passes to obtain a □140-180×L square billet;

[0056] Second rolling:

[0057] The □140~180×L billets are sawn and divided, the surface is polished, and then heated to 920~980℃. After the heat preservation is completed, they are rolled in multiple passes using a BD850 two-roll reversible rolling mill to obtain rolled bars;

[0058] Step 5: Peeling, pickling and polishing

[0059] The rolled bar obtained in step 4 is peeled to remove the surface oxide scale, and then pickled and polished to remove surface cracks and folding defects;

[0060] Step 6: Third rolling:

[0061] The rolled bar obtained in step 5 is subjected to induction heating at a temperature of 850-950° C., and is sequentially subjected to single-hot rolling using a BD600 two-roll reversing mill, an eight-roll tandem mill, and a finishing / kocks tandem mill to prepare a hot-rolled coil;

[0062] Step 7: Finishing:

[0063] The hot-rolled coil obtained in step 6 is processed by a direct peeling process or a drawing process to obtain TC4 titanium alloy coiled wire.

[0064] In some embodiments, the present invention provides a method for preparing TC4 titanium alloy coil wire for low-cost fasteners, comprising:

[0065] Step 1: Ingot melting:

[0066] Sponge titanium, aluminum vanadium, aluminum particles, iron particles, TiO2, and titanium carbide are mixed according to a predetermined element ratio, and electrodes are pressed. The mixture is then smelted in an electron beam cooling hearth (EB) furnace and a vacuum consumable arc (VAR) furnace to obtain a TC4 titanium alloy ingot. The TC4 titanium alloy ingot is then peeled, and a riser and bottom are cut to prepare a TC4 titanium alloy ingot with a diameter of 700 to 820 mm. Preferably, the weight percentage of each element in the TC4 titanium alloy ingot is as follows: Al content is 5.5-6.75%, V content is 3.5-4.5%; Fe content is ≤0.3%; C content is ≤0.08%; N content is ≤0.05%; O content is ≤0.2%; and the balance is Ti.

[0067] Step 2: Ingot forging:

[0068] The TC4 titanium alloy ingot obtained in step 1 is placed in a box-type resistance heating furnace, heated to 1000-1200°C, and kept warm for 360-420 minutes. A 100MN fast forging machine is used for forging, with a deformation of 30-45%, and the billet is squared to □550-650×L. A first fire upsetting and chamfering are performed to □450-550×L, and then the billet surface is polished and sawed for material separation; then the □450-550×L forging billet is placed in a box-type resistance heating furnace, heated to 920-980°C, and kept warm for 90-150 minutes. A 2500T fast forging machine is used for forging, with a deformation of 30-45%, □450-550×L, and then a first fire upsetting and drawing is performed to □200-300×L.

[0069] Step 3: Grinding:

[0070] Grind the billet obtained in step 2 to remove surface defects, including cracks and folds;

[0071] Step 4: First rolling:

[0072] The □200-300×L forging billet obtained in step 3 is placed in a box-type heating furnace, heated to 920-980°C, kept warm for 120-200 minutes, and then rolled using a BD850 two-roll reversible rolling mill for 7-11 passes to obtain a □140-180×L square billet;

[0073] Second rolling:

[0074] The 140-180×L square billets were sawn and divided, and after surface grinding, they were placed in a box-type heating furnace and heated to 920-980°C. After keeping the temperature for 120-150 minutes, they were rolled in multiple passes using a BD850 two-roll reversible rolling mill to obtain Φ85mm-115mm×L rolled bars.

[0075] Step 5: Peeling, pickling and polishing

[0076] The rolled bar of Φ85 mm to 115 mm × L obtained in step 4 is peeled to remove the surface oxide scale, and then pickled and polished to remove surface defects such as cracks and folds;

[0077] Step 6: Third rolling:

[0078] The rolled bar with a diameter of 85 mm to 115 mm × L obtained in step 5 is subjected to induction heating at a temperature of 850 to 950° C., and is sequentially rolled using a BD600 two-roll reversing mill, an eight-roll tandem mill, and a finishing / kocks tandem mill to obtain a hot-rolled coil with a diameter of 7 mm to 12 mm;

[0079] Step 7: Finishing:

[0080] The hot-rolled coil obtained in step 6 is processed by a direct peeling process or a drawing process to obtain TC4 titanium alloy coiled wire.

[0081] The direct peeling process specifically includes the following steps in sequence: hot rolling, rounding, annealing, straightening, centerless turning peeling, fixed die peeling, polishing, eddy current testing, and quality inspection.

[0082] The drawing process specifically includes the following steps in sequence: hot rolling, rounding, centerless turning and peeling, drawing, annealing, straightening, fixed die peeling, polishing, eddy current testing, and quality inspection.

[0083] To clarify the objectives, technical solutions and advantages of the present invention, the present invention will be described in detail below with reference to specific embodiments and the accompanying drawings. The specific embodiments described herein are only used to explain the present invention and the present invention is not limited thereto.

[0084] Example 1 Preparation of Φ4.03 mm TC4 titanium alloy coil wire

[0085] This embodiment provides a method for preparing a low-cost titanium alloy bar for fasteners, the method comprising:

[0086] Step 1: Ingot Melting:

[0087] According to a predetermined element ratio, titanium sponge, aluminum vanadium, aluminum particles, iron particles, TiO2, and titanium carbide are mixed and pressed into electrode blocks, placed in the hoppers on both sides of the EB furnace, and melted into liquid titanium alloy in the furnace at a certain speed to produce EB ingots (φ735mm). The EB ingots are smelted in a VAR furnace once, and then peeled, cut into risers and ingot bottoms to prepare TC4 titanium alloy ingots with a diameter of φ820mm. The titanium sponge in the mixture is selected from small particles with a particle size range of 0.83mm to 12.7mm. The interstitial C element is added in the form of a compound, and the raw materials are fully mixed. The percentage of each element content in the TC4 titanium alloy ingot in this embodiment is shown in Table 1 below.

[0088] Step 2: Ingot forging:

[0089] The TC4 titanium alloy ingot obtained in step 1 is placed in a box-type resistance heating furnace, heated to 1150°C, and kept warm for 360-420 minutes. Then, a 100MN fast forging machine is used for forging, with a deformation of 30-45%, and the billet is squared to □620×L. After a first fire upsetting and chamfering to □480-550×L, the billet surface is polished and sawed for dividing the material; then, the □480×L forging billet is placed in a box-type resistance heating furnace, heated to 970°C, and kept warm for 90-150 minutes. Then, a 2500T fast forging machine is used for forging, with a deformation of 30-45%, □480×L, and then a first fire upsetting and drawing to □240×L.

[0090] Step 3: Grinding:

[0091] Grind the billet obtained in step 2 to remove surface defects, including cracks and folds;

[0092] Step 4: First rolling:

[0093] The □240×L forging billet obtained in step 3 is placed in a box-type heating furnace, heated to 970°C, and kept warm for 120-200 minutes. Then, a BD850 two-roll reversible rolling mill is used to perform 7-9 passes of rolling to obtain a □160×L square billet. The 7-9 passes of rolling are completed in one pass, and the rolling temperature, deformation amount, and deformation rate are consistent, which breaks through the traditional multi-pass forging production method, improves production efficiency, and improves the consistency of the billet microstructure.

[0094] Second rolling:

[0095] The □160×L square billet was sawn and divided, and after surface grinding, it was placed in a box-type heating furnace and heated to 970℃. After keeping the temperature for 120-150 minutes, it was rolled in 9-11 passes using a BD850 two-roll reversing rolling mill to obtain Φ100×L rolled bars.

[0096] Step 5: Peeling, pickling and polishing

[0097] The Φ100 rolled bar obtained in step 4 is peeled to remove surface oxide scale, and then pickled and polished to remove surface defects such as cracks and folds;

[0098] Step 6: Third rolling:

[0099] The Φ100 rolled bar obtained in step 5 was induction heated to 950°C, and then rolled using a BD600 two-roll reversing mill, an eight-roll tandem mill, and a finishing / kocks tandem mill to produce Φ8.0 and Φ9.4 hot-rolled coils.

[0100] Step 7: Finishing:

[0101] The φ8.0 hot-rolled coil obtained in step 6 was used to prepare φ4.03 round wire using the drawing process: hot-rolled coil → overhaul → rounding at 720°C → centerless turning and peeling → drawing → annealing at 760°C → straightening at 720°C → fixed die peeling → polishing → eddy current testing → quality inspection.

[0102] Example 2 Preparation of Φ5.03mm TC4 titanium alloy coil wire

[0103] Step 1: Ingot Melting:

[0104] Sponge titanium, aluminum vanadium, aluminum particles, iron particles, TiO2, and titanium carbide are mixed according to a predetermined element ratio and pressed into electrode blocks. The blocks are placed in the hoppers on both sides of the EB furnace and fed into the furnace at a certain speed to melt into liquid titanium alloy. EB ingots (φ735 mm) are smelted. The EB ingots are then smelted in a VAR furnace, and then peeled, cut into risers and ingot bottoms to prepare TC4 titanium alloy ingots with a diameter of φ820 mm. The percentages of the elements in the TC4 titanium alloy ingots in this embodiment are shown in Table 1 below.

[0105] Step 2: Ingot forging:

[0106] The TC4 titanium alloy ingot obtained in step 1 is placed in a box-type resistance heating furnace, heated to 1150°C, and kept warm for 360-420 minutes. Then, a 100MN fast forging machine is used for forging, with a deformation of 30-45%, and the billet is squared to □620×L. After a first fire upsetting and chamfering to □480-550×L, the billet surface is polished and sawed for dividing the material; then, the □480×L forging billet is placed in a box-type resistance heating furnace, heated to 970°C, and kept warm for 90-150 minutes. Then, a 2500T fast forging machine is used for forging, with a deformation of 30-45%, □480×L, and then a first fire upsetting and drawing to □240×L.

[0107] Step 3: Grinding:

[0108] Grind the billet obtained in step 2 to remove surface defects, including cracks and folds;

[0109] Step 4: First rolling:

[0110] The □240×L forging billet obtained in step 3 is placed in a box-type heating furnace, heated to 970°C, kept warm for 120-200 minutes, and then rolled using a BD850 two-roll reversible rolling mill for 7-9 passes to obtain a □160×L square billet;

[0111] Second rolling:

[0112] The □160×L square billet was sawn and divided, and after surface grinding, it was placed in a box-type heating furnace and heated to 970℃. After keeping the temperature for 120-150 minutes, it was rolled in 9-11 passes using a BD850 two-roll reversing rolling mill to obtain Φ100×L rolled bars.

[0113] Step 5: Peeling, pickling and polishing

[0114] The Φ100 rolled bar obtained in step 4 is peeled to remove surface oxide scale, and then pickled and polished to remove surface defects such as cracks and folds;

[0115] Step 6: Third rolling:

[0116] The Φ100 rolled bar obtained in step 5 was induction heated to 950°C, and then rolled using a BD600 two-roll reversing mill, an eight-roll tandem mill, and a finishing / kocks tandem mill to produce Φ8.0 and Φ9.4 hot-rolled coils.

[0117] Step 7: Finishing:

[0118] The φ9.4 hot-rolled coil obtained in step 6 was used to prepare φ5.03 round wire by drawing process: hot-rolled coil → overhaul → rounding at 720℃ → centerless turning and peeling → drawing → annealing at 760℃ → straightening at 720℃ → fixed die peeling → polishing → eddy current testing → quality inspection.

[0119] Example 3 Preparation of 6.03 mm Φ TC4 titanium alloy coil wire

[0120] Step 1: Ingot Melting:

[0121] Sponge titanium, aluminum vanadium, aluminum particles, iron particles, TiO2, and titanium carbide are mixed according to a predetermined element ratio and pressed into electrode blocks. The blocks are placed in the hoppers on both sides of the EB furnace and fed into the furnace at a certain speed to melt into liquid titanium alloy. EB ingots (φ735 mm) are smelted. The EB ingots are then smelted in a VAR furnace, and then peeled, cut into risers and ingot bottoms to prepare TC4 titanium alloy ingots with a diameter of φ820 mm. The percentages of the elements in the TC4 titanium alloy ingots in this embodiment are shown in Table 1 below.

[0122] Step 2: Ingot forging:

[0123] The TC4 titanium alloy ingot obtained in step 1 is placed in a box-type resistance heating furnace, heated to 1150°C, and kept warm for 360-420 minutes. Then, a 100MN fast forging machine is used for forging, with a deformation of 30-45%, and the billet is squared to □620×L. After a first fire upsetting and chamfering to □480-550×L, the billet surface is polished and sawed for dividing the material; then, the □480×L forging billet is placed in a box-type resistance heating furnace, heated to 970°C, and kept warm for 90-150 minutes. Then, a 2500T fast forging machine is used for forging, with a deformation of 30-45%, □480×L, and then a first fire upsetting and drawing to □240×L.

[0124] Step 3: Grinding:

[0125] Grind the billet obtained in step 2 to remove surface defects, including cracks and folds;

[0126] Step 4: First rolling:

[0127] The □240×L forging billet obtained in step 3 is placed in a box-type heating furnace, heated to 970°C, kept warm for 120-200 minutes, and then rolled using a BD850 two-roll reversible rolling mill for 9-11 passes to obtain a □160×L square billet;

[0128] Second rolling:

[0129] The □160×L square billet was sawn and divided, and after surface grinding, it was placed in a box-type heating furnace and heated to 970℃. After keeping the temperature for 120-150 minutes, it was rolled in 11-13 passes using a BD850 two-roll reversing rolling mill to obtain Φ100×L rolled bars.

[0130] Step 5: Peeling, pickling and polishing

[0131] The Φ100 rolled bar obtained in step 4 is peeled to remove surface oxide scale, and then pickled and polished to remove surface defects such as cracks and folds;

[0132] Step 6: Third rolling:

[0133] The Φ100 rolled bar obtained in step 5 was induction heated to 950°C, and then rolled using a BD600 two-roll reversing mill, an eight-roll tandem mill, and a finishing / kocks tandem mill to produce Φ8.0 and Φ9.4 hot-rolled coils.

[0134] Step 7: Finishing:

[0135] The φ8.0 hot-rolled coil obtained in step 6 was used to prepare φ6.03 round wire using a direct peeling process: hot-rolled coil → overhaul → rounding at 720°C → annealing at 760°C → straightening at 720°C → centerless turning peeling → fixed die peeling → polishing → eddy current testing → quality inspection.

[0136] Example 4 Preparation of Φ8.03mm TC4 Titanium Alloy Coil Wire

[0137] Step 1: Ingot Melting:

[0138] Sponge titanium, aluminum vanadium, aluminum particles, iron particles, TiO2, and titanium carbide are mixed according to a predetermined element ratio to obtain a mixture and pressed into an electrode block. The mixture is placed in the hoppers on both sides of the EB furnace and fed into the furnace at a certain speed to melt into a liquid titanium alloy. The EB ingot (φ735mm) is melted and the EB ingot is subjected to a VAR furnace smelting process. The EB ingot is then peeled, the riser and the ingot bottom are cut, and a TC4 titanium alloy ingot with a diameter of φ820mm is prepared. The percentage of each element content in the TC4 titanium alloy ingot in this embodiment is shown in Table 1 below.

[0139] Step 2: Ingot forging:

[0140] The TC4 titanium alloy ingot obtained in step 1 is placed in a box-type resistance heating furnace, heated to 1150°C, and kept warm for 360-420 minutes. Then, a 100MN fast forging machine is used for forging, with a deformation of 30-45%, and the billet is squared to □620×L. After a first fire upsetting and chamfering to □480-550×L, the billet surface is polished and sawed for dividing the material; then, the □480×L forging billet is placed in a box-type resistance heating furnace, heated to 970°C, and kept warm for 90-150 minutes. Then, a 2500T fast forging machine is used for forging, with a deformation of 30-45%, □480×L, and then a first fire upsetting and drawing to □240×L.

[0141] Step 3: Grinding:

[0142] Grind the billet obtained in step 2 to remove surface defects, including cracks and folds;

[0143] Step 4: First rolling:

[0144] The □240×L forging billet obtained in step 3 is placed in a box-type heating furnace, heated to 970°C, kept warm for 120-200 minutes, and then rolled using a BD850 two-roll reversible rolling mill for 9-11 passes to obtain a □160×L square billet;

[0145] Second rolling:

[0146] The □160×L square billet was sawn and divided, and after surface grinding, it was placed in a box-type heating furnace and heated to 970℃. After keeping the temperature for 120-150 minutes, it was rolled in 11-13 passes using a BD850 two-roll reversing rolling mill to obtain Φ100×L rolled bars.

[0147] Step 5: Peeling, pickling and polishing

[0148] The Φ100 rolled bar obtained in step 4 is peeled to remove surface oxide scale, and then pickled and polished to remove surface defects such as cracks and folds;

[0149] Step 6: Third rolling:

[0150] The Φ100 rolled bar obtained in step 5 was induction heated to 950°C, and then rolled using a BD600 two-roll reversing mill, an eight-roll tandem mill, and a finishing / kocks tandem mill to produce Φ8.0 and Φ9.4 hot-rolled coils.

[0151] Step 7: Finishing:

[0152] The φ9.4 hot-rolled coil obtained in step 6 was used to prepare φ8.03 round wire using a direct peeling process: hot-rolled coil → overhaul → rounding at 720°C → annealing at 760°C → straightening at 720°C → centerless turning peeling → fixed die peeling → polishing → eddy current testing → quality inspection.

[0153] Table 1 below shows the chemical composition of the TC4 titanium alloy ingots used in Examples 1 to 4 of the present invention.

[0154] Table 1 Chemical composition of TC4 titanium alloy ingot (wt%)

[0155] Sampling location Al V Fe C N O superior 6.27 4.08 0.16 0.019 0.004 0.164 middle 6.26 4.19 0.16 0.02 0.004 0.165 Down 6.28 4.21 0.17 0.02 0.004 0.161

[0156] Figures 1 to 4 Schematic diagrams of the transverse and longitudinal microstructures of 4.03 mm, 5.03 mm, 6.03 mm, and 8.03 mm TC4 titanium alloy coiled wires prepared in Examples 1 to 4 of the present invention are shown, respectively. As can be seen from the figures, the microstructure of the resulting TC4 titanium alloy coiled wires consists of equiaxed α and intergranular β structures, with α sizes ranging from 5 to 10 μm. The intergranular β structures are relatively small and uniform, with high consistency and stability at the head, middle, and tail.

[0157] Table 2 below shows the properties of the TC4 titanium alloy coiled wires prepared in Examples 1 to 4 of the present invention.

[0158] Table 2 Mechanical properties of TC4 coiled wire in M ​​state

[0159]

[0160] Compared with traditional processes, the number of times of dividing materials, sawing the head and tail of materials in the preparation methods of Examples 1 to 4 of the present invention is reduced, thereby improving the material utilization rate. It adopts a direct peeling method of hot-rolled coils, and 5-6 drawing passes without stress relief annealing in between to prepare finished round wires of different specifications with a unit weight of >100kg, which significantly shortens the processing cycle and improves production efficiency. Direct peeling is used to prepare Φ6 and 8 specification round wires; drawing is used to prepare Φ4 and 5 specification round wires. The size correspondence between hot-rolled coils and round wires is: hot-rolled coil Φ8.0 → round wire Φ4, 6, hot-rolled coil Φ9.4 → round wire Φ5, 8.

[0161] In summary, the present invention effectively improves production efficiency and material utilization by adjusting the chemical composition and smelting method of the TC4 titanium alloy ingots, controlling the forging, rolling, machining, and heat treatment processes, and adopting a "rolling instead of forging, forging and rolling combined" technique. This continuous rolling technology, with temperature and rolling control throughout the entire process, enables the production of hot-rolled coils weighing >100kg, significantly improving the uniformity and consistency of their structure and performance. This avoids the drawbacks of traditional horizontal rolling with multiple material splitting, shortens the process, and enables the low-cost production of TC4 titanium alloy coil wire that meets the requirements of aerospace applications.

[0162] It should be noted that the above-described embodiments are merely preferred embodiments of the present invention. Persons skilled in the art will appreciate that various modifications, improvements, and equivalent substitutions may be made to the present invention without departing from the principles of the present invention, and such modifications, improvements, and equivalent substitutions are deemed to fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing TC4 titanium alloy coil wire for low-cost fasteners, characterized in that: include: Step 1: Ingot melting: Sponge titanium, aluminum vanadium, aluminum particles, iron particles, TiO2, and titanium carbide are mixed according to a predetermined element ratio and pressed into an electrode, and then subjected to electron beam cold hearth furnace melting and vacuum consumable arc furnace melting to obtain a TC4 titanium alloy ingot blank, and the TC4 titanium alloy ingot blank is peeled, and a riser and ingot bottom are cut to prepare a TC4 titanium alloy ingot with a diameter of 700 to 820 mm. Step 2: Ingot forging: The TC4 titanium alloy ingot obtained in step 1 is heated to 1000-1200° C., kept warm, and then forged into a 450-550×L billet; the billet is polished, sawn, and divided, and then heated to 920-980° C., kept warm, and then upsetting to a 200-300×L billet; In step 2, the TC4 titanium alloy ingot is heated to 1000-1200°C and kept warm for 360-420 minutes, and then subjected to blanking forging with a deformation of 30-45%; squared to □550-650×L, subjected to a first-time upsetting and chamfering to □450-550×L, and then the blank surface is polished and sawn; the □450-550×L forging blank is then heated to 920-980°C, kept warm for 90-150 minutes, and then blanked with a deformation of 30-45%, and then subjected to a first-time upsetting and drawing to □200-300×L square blank; Step 3: Grinding: Grind the billet obtained in step 2 to remove surface defects, including cracks and folds; Step 4: First rolling: The □200-300×L forging billet obtained in step 3 is heated to 920-980°C. After the heat preservation is completed, a BD850 two-roll reversible rolling mill is used for multiple passes to obtain a □140-180×L square billet; Second rolling: The □140~180×L billets are sawn and divided, the surface is polished, and then heated to 920~980℃. After the heat preservation is completed, they are rolled in multiple passes using a BD850 two-roll reversible rolling mill to obtain rolled bars; Step 5: Peeling, pickling and polishing The rolled bar obtained in step 4 is peeled to remove the surface oxide scale, and then pickled and polished to remove surface cracks and folding defects; Step 6: Third rolling: The rolled bar obtained in step 5 is subjected to induction heating at a temperature of 850-950° C., and is sequentially hot-rolled using a BD600 two-roll reversing mill, an eight-roll tandem mill, and a finishing / kocks tandem mill to produce a hot-rolled coil; in step 6, the hot-rolled coil obtained has a diameter of 7 mm to 12 mm; Step 7: Finishing: The hot-rolled coil obtained in step 6 is processed by a direct peeling process or a drawing process to obtain a TC4 titanium alloy coil wire; the weight of a single coil of the TC4 titanium alloy coil wire is greater than 100 kg.

2. The method for preparing low-cost TC4 titanium alloy coil wire for fasteners according to claim 1, characterized in that: In step 1, the weight percentages of the elements in the TC4 titanium alloy ingot are as follows: Al content is 5.5-6.75%, V content is 3.5-4.5%; Fe content is ≤0.3%; C content is ≤0.08%; N content is ≤0.05%; O content is ≤0.2%; and the balance is Ti.

3. The method for preparing low-cost TC4 titanium alloy coil wire for fasteners according to claim 1, characterized in that: In the first rolling of step 4, the multi-pass rolling is 7 to 11 passes.

4. The method for preparing low-cost TC4 titanium alloy coil wire for fasteners according to claim 1, characterized in that: In the second rolling of step 4, the multi-pass rolling is 9 to 13 passes.

5. The method for preparing low-cost TC4 titanium alloy coil wire for fasteners according to claim 1, characterized in that: In step 4, the diameter of the rolled bar obtained is 85 mm to 115 mm.

6. The method for preparing low-cost TC4 titanium alloy coil wire for fasteners according to claim 1, characterized in that: In step 7, the direct peeling process specifically includes the following steps in sequence: hot rolling coil, rounding, annealing, straightening, centerless turning peeling, fixed die peeling, polishing, eddy current testing, and quality inspection; the drawing process specifically includes the following steps in sequence: hot rolling coil, rounding, centerless turning peeling, drawing, annealing, straightening, fixed die peeling, polishing, eddy current testing, and quality inspection.

7. A low-cost TC4 titanium alloy coiled wire for fasteners, characterized in that: The method is prepared according to any one of claims 1 to 6.

Images