Preparation method of TC4 titanium alloy disc round wire for low-cost fastener

Abstract

The invention discloses a preparation method of a TC4 titanium alloy disc round wire for a low-cost fastener, which comprises the following steps: on the basis of EB + VAR smelting, a hot-rolled coil is prepared by adopting rolling instead of forging and combining forging and rolling and cooperating with a continuous rolling technology of full-process temperature control and rolling and only by two-fire forging and three-fire rolling. According to the preparation method, the heating number of forging and rolling is reduced, the drawing pass is reduced, and even drawing is not needed, so that the production efficiency is greatly improved, and the consistency and the stability of the structure and the performance of the TC4 titanium alloy disc round wire can be improved at low cost.

Description

Technical Field

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

[0002] Titanium and its alloys have been successfully applied to industrial fields such as aviation, medical, chemical 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, it is mostly prepared by a process flow of three vacuum consumable arc furnace (VAR) melting ingots, forging, horizontal rolling, and multi-pass drawing. Among them, forging is an intermittent production method, and it requires 4 to 6 forgings. Between each forging, the billet needs to be ground, the head and tail cracking areas need to be sawed, etc., which has low production efficiency and low material utilization. Using multiple horizontal rolling mills and 2-fire 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 single weight of the billet. 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 transformed, and horizontal rolling has also been upgraded to vertical rolling. Although the preparation of hot-rolled coils with a single coil weight of >100kg can be achieved, the size of the hot-rolled coils is Φ12~15mm, and 10~18 drawing passes and 2~4 stress relief annealing are still required to prepare coils of wire of different sizes. The long processing cycle seriously restricts production efficiency. Summary of the invention

[0005] In view of the deficiencies of the above-mentioned prior art, the present invention aims to provide a method for preparing TC4 titanium alloy coil wire for aerospace fasteners at a low cost. Based on the melting in an electron beam cold bed (EB) furnace and a vacuum consumable arc (VAR) furnace, the method adopts "rolling instead of forging, combining forging and rolling", and cooperates with the continuous rolling technology of temperature control and rolling throughout the process to prepare hot-rolled coils with only 2-fire forging and 3-fire rolling. The preparation method reduces the number of forging and rolling passes, reduces the number of drawing passes, and even eliminates the need for drawing, thereby improving production efficiency and improving the consistency and stability of the structure and performance of coil wire at a low cost.

[0006] In order to achieve the above object, the present invention adopts the following technical solution.

[0007] On the one hand, the present invention provides a method for preparing TC4 titanium alloy coil wire for low-cost fasteners, comprising:

[0008] Step 1: Ingot smelting:

[0009] According to the predetermined element ratio, titanium sponge, aluminum vanadium, aluminum particles, iron particles, TiO 2 , titanium carbide, and pressing electrodes, and then performing electron beam cooling furnace smelting and vacuum consumable arc furnace smelting to obtain TC4 titanium alloy ingot blanks, and performing skinning, riser cutting and ingot bottom cutting on the TC4 titanium alloy ingot blanks to prepare TC4 titanium alloy ingots with a diameter of Φ700-820 mm;

[0010] Step 2: Ingot forging:

[0011] The TC4 titanium alloy ingot obtained in step 1 is heated to 1000-1200° C., and then forged into a □450-550×L square billet after heat preservation; after the square billet is polished, sawed and divided, it is heated to 920-980° C., and then upsetting and drawing into a □200-300×L square billet after heat preservation;

[0012] Step 3: Grinding:

[0013] Grinding the square 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, and 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 square billet is sawn and divided, the surface is polished, and then heated to 920~980℃. After the insulation is completed, a BD850 two-roller reversible rolling mill is used for multiple passes 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 one-hot rolling using a BD600 two-roll reversible rolling mill, an eight-roll tandem rolling mill, and a finishing / kocks tandem rolling 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 a TC4 titanium alloy round wire.

[0024] Furthermore, in step 1, the weight percentage of each element in the TC4 titanium alloy ingot is: 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 ingot is forged with a deformation of 30-45%; it is squared to □550-650×L, and a fire upsetting and chamfering is performed to □450-550×L, and then the surface of the ingot is polished and sawed for material division; then the □450-550×L forging ingot is heated to 920-980°C, kept warm for 90-150 minutes, and then the ingot is forged with a deformation of 30-45%, and then a fire upsetting and drawing is performed to a □200-300×L square ingot.

[0026] Furthermore, in the first rolling of step 4, the multiple rolling passes are 7 to 11 rolling passes.

[0027] Furthermore, in the second rolling of step 4, the multiple rolling passes are 9 to 13 rolling 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] Further, in step 7, the direct peeling process specifically includes the following steps in sequence: hot rolled coil, rounding, annealing, straightening, centerless turning peeling, fixed die peeling, polishing, eddy current flaw detection, and quality inspection; the drawing process specifically includes the following steps in sequence: hot rolled coil, rounding, centerless turning peeling, drawing, annealing, straightening, fixed die peeling, polishing, eddy current flaw detection, 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 TC4 titanium alloy coil wire for low-cost fasteners, which is prepared by the above 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 so that the structure and performance of the TC4 titanium alloy coil wire meet the requirements for the use of aerospace fasteners.

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

[0037] 3) The present invention adopts the continuous rolling technology of full-process temperature control and rolling, which avoids the disadvantages of multiple material division 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 the wire prepared by the traditional method. The weight of a single coil is greater than 100kg, which is equivalent to the 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 disc 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 disc 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 for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0044] In the present invention, when it comes 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 value and the maximum value) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer within the numerical interval, it includes the two endpoint integers of the numerical range, and 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 integer 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 combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0045] The temperature parameters in the present invention, if not specifically limited, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

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

[0047] On the one hand, the present invention provides a method for preparing TC4 titanium alloy coil wire for low-cost fasteners, comprising:

[0048] Step 1: Ingot smelting:

[0049] According to the predetermined element ratio, titanium sponge, aluminum vanadium, aluminum particles, iron particles, TiO 2 , titanium carbide, and pressing electrodes, and then performing electron beam cooling furnace smelting and vacuum consumable arc furnace smelting to obtain TC4 titanium alloy ingot blanks, and performing skinning, riser cutting and ingot bottom cutting on the TC4 titanium alloy ingot blanks to prepare TC4 titanium alloy ingots with a diameter of Φ700-820 mm;

[0050] Step 2: Ingot forging:

[0051] The TC4 titanium alloy ingot obtained in step 1 is heated to 1000-1200° C., and then forged into a □450-550×L square billet after heat preservation; after the square billet is polished, sawed and divided, it is heated to 920-980° C., and then upsetting and drawing into a □200-300×L square billet after heat preservation;

[0052] Step 3: Grinding:

[0053] Grinding the square 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, and after the heat preservation is completed, a BD850 two-roller reversible rolling mill is used for multiple passes to obtain a □140-180×L square billet;

[0056] Second rolling:

[0057] The □140~180×L square billet is sawn and divided, the surface is polished, and then heated to 920~980℃. After the insulation is completed, a BD850 two-roller reversible rolling mill is used for multiple passes 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 one-hot rolling using a BD600 two-roll reversible rolling mill, an eight-roll tandem rolling mill, and a finishing / kocks tandem rolling 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 a TC4 titanium alloy round 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 smelting:

[0066] According to the predetermined element ratio, titanium sponge, aluminum vanadium, aluminum particles, iron particles, TiO 2, titanium carbide, and pressed electrodes, then smelted in an electron beam cooling hearth (EB) furnace and a vacuum consumable arc (VAR) furnace to obtain a TC4 titanium alloy ingot, and the TC4 titanium alloy ingot is peeled, the riser and the bottom are cut to prepare a TC4 titanium alloy ingot with a diameter of Φ700-820mm. Preferably, the weight percentage of each element in the TC4 titanium alloy ingot is: 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%; 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 360-420min. 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 fire upsetting and chamfering are performed to □450-550×L, and then the billet surface is polished and sawed for material division; 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 90-150min. A 2500T fast forging machine is used for billeting, with a deformation of 30-45%, □450-550×L, and then a fire upsetting and drawing is performed to □200-300×L.

[0069] Step 3: Grinding:

[0070] Grinding the square 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 for 7-11 times using a BD850 two-roll reversible rolling mill to obtain a □140-180×L square billet;

[0073] Second rolling:

[0074] The □140~180×L square billet is sawn and divided, and after surface grinding, it is placed in a box-type heating furnace and heated to 920~980℃, kept warm for 120~150min, and then rolled by a BD850 two-roller reversible rolling mill for multiple passes 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 of Φ85mm-115mm×L obtained in step 5 is subjected to induction heating at a temperature of 850-950°C, and is sequentially subjected to one-hot rolling using a BD600 two-roll reversible rolling mill, an eight-roll tandem rolling mill, and a finishing / kocks tandem rolling mill to obtain a hot-rolled coil of Φ7mm-12mm;

[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 a TC4 titanium alloy round wire.

[0081] 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 flaw detection, and quality inspection.

[0082] 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 flaw detection, and quality inspection.

[0083] To clarify the purpose, technical solutions and advantages of the present invention, the present invention will be described in detail below in conjunction with specific embodiments and 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 smelting:

[0087] According to the predetermined element ratio, titanium sponge, aluminum vanadium, aluminum particles, iron particles, TiO 2 , titanium carbide are mixed and pressed into electrode blocks, put into the silos on both sides of the EB furnace, and enter the furnace at a certain speed to melt into liquid titanium alloy, and smelt EB ingots (φ735mm), and the EB ingots are smelted in a VAR furnace, and then peeled, cut the riser and the ingot bottom to prepare TC4 titanium alloy ingots with a diameter of φ820mm. Sponge titanium in the mixed material is selected from small particles with a particle size range of 0.83mm to 12.7mm, and 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 the following Table 1.

[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. A 100MN fast forging machine is used for forging, with a deformation of 30-45%, and the billet is squared to □620×L. A fire upsetting and chamfering are performed to □480-550×L, and then the billet surface is polished and sawed for material division; 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. A 2500T fast forging machine is used for billeting, with a deformation of 30-45%, □480×L, and then a fire upsetting and drawing is performed to □240×L.

[0090] Step 3: Grinding:

[0091] Grinding the square 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, and then rolled by BD850 two-roller reversible rolling mill for 7-9 passes to obtain a □160×L square billet, wherein 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 mode, improves production efficiency, and improves the consistency of 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°C. After keeping the temperature for 120-150 minutes, BD850 two-roller reversible rolling mill was used for 9-11 passes 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 the 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 is subjected to induction heating at a temperature of 950°C, and is sequentially subjected to one-hot rolling using a BD600 two-roll reversible rolling mill, an eight-roll tandem rolling mill, and a finishing / kocks tandem rolling mill to prepare φ8.0 and 9.4 hot-rolled coils;

[0100] Step 7: Finishing:

[0101] The φ8.0 hot-rolled coil obtained in step 6 is used to prepare φ4.03 round wire by drawing process: hot-rolled coil→inspection→720℃ rounding→centerless turning peeling→drawing→760℃ annealing→720℃ straightening→fixed die peeling→polishing→eddy current flaw detection→quality inspection.

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

[0103] Step 1: Ingot Melting:

[0104] According to the predetermined element ratio, titanium sponge, aluminum vanadium, aluminum particles, iron particles, TiO 2 , titanium carbide are mixed and pressed into electrode blocks, put into the silos on both sides of the EB furnace, and enter the furnace at a certain speed to melt into liquid titanium alloy, and EB ingots (φ735mm) are smelted. The EB ingots are smelted in a VAR furnace, and then peeled, cut the riser and the ingot bottom to prepare TC4 titanium alloy ingots with a diameter of φ820mm. The percentage of each element content in the TC4 titanium alloy ingot in this embodiment is shown in the following Table 1.

[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. A 100MN fast forging machine is used for forging, with a deformation of 30-45%, and the billet is squared to □620×L. A fire upsetting and chamfering are performed to □480-550×L, and then the billet surface is polished and sawed for material division; 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. A 2500T fast forging machine is used for billeting, with a deformation of 30-45%, □480×L, and then a fire upsetting and drawing is performed to □240×L.

[0107] Step 3: Grinding:

[0108] Grinding the square 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 to 200 minutes, and then rolled for 7 to 9 times using a BD850 two-roll reversible rolling mill 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°C. After keeping the temperature for 120-150 minutes, BD850 two-roller reversible rolling mill was used for 9-11 passes 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 the 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 is subjected to induction heating at a temperature of 950°C, and is sequentially subjected to one-hot rolling using a BD600 two-roll reversible rolling mill, an eight-roll tandem rolling mill, and a finishing / kocks tandem rolling mill to prepare φ8.0 and 9.4 hot-rolled coils;

[0117] Step 7: Finishing:

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

[0119] Example 3 Preparation of Φ6.03mm TC4 titanium alloy coil wire

[0120] Step 1: Ingot Melting:

[0121] According to the predetermined element ratio, titanium sponge, aluminum vanadium, aluminum particles, iron particles, TiO 2 , titanium carbide are mixed and pressed into electrode blocks, put into the silos on both sides of the EB furnace, and enter the furnace at a certain speed to melt into liquid titanium alloy, and EB ingots (φ735mm) are smelted. The EB ingots are smelted in a VAR furnace, and then peeled, cut the riser and the ingot bottom to prepare TC4 titanium alloy ingots with a diameter of φ820mm. The percentage of each element content in the TC4 titanium alloy ingot in this embodiment is shown in the following Table 1.

[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. A 100MN fast forging machine is used for forging, with a deformation of 30-45%, and the billet is squared to □620×L. A fire upsetting and chamfering are performed to □480-550×L, and then the billet surface is polished and sawed for material division; 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. A 2500T fast forging machine is used for billeting, with a deformation of 30-45%, □480×L, and then a fire upsetting and drawing is performed to □240×L.

[0124] Step 3: Grinding:

[0125] Grinding the square 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 by 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°C. After keeping the temperature for 120-150 minutes, it was rolled for 11-13 times using a BD850 two-roller reversible 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 the 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 is subjected to induction heating at a temperature of 950°C, and is sequentially subjected to one-hot rolling using a BD600 two-roll reversible rolling mill, an eight-roll tandem rolling mill, and a finishing / kocks tandem rolling mill to prepare φ8.0 and 9.4 hot-rolled coils;

[0134] Step 7: Finishing:

[0135] The φ8.0 hot-rolled coil obtained in step 6 is used to prepare φ6.03 round wire by direct peeling process: hot-rolled coil → overhaul → 720℃ rounding → 760℃ annealing → 720℃ straightening → centerless turning peeling → fixed die peeling → polishing → eddy current flaw detection → quality inspection.

[0136] Example 4 Preparation of Φ8.03mm TC4 titanium alloy coil wire

[0137] Step 1: Ingot Melting:

[0138] According to the predetermined element ratio, titanium sponge, aluminum vanadium, aluminum particles, iron particles, TiO 2 , titanium carbide to obtain a mixed material and press it into an electrode block, put it into the silos on both sides of the EB furnace, and enter the furnace at a certain speed to melt into a liquid titanium alloy, and melt out an EB ingot (φ735mm) to obtain an EB ingot, which is smelted in a VAR furnace once, and then peeled, cut the riser and the ingot bottom to prepare a TC4 titanium alloy ingot with a diameter of φ820mm. The percentage of each element content in the TC4 titanium alloy ingot in this embodiment is shown in the following Table 1.

[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. A 100MN fast forging machine is used for forging, with a deformation of 30-45%, and the billet is squared to □620×L. A fire upsetting and chamfering are performed to □480-550×L, and then the billet surface is polished and sawed for material division; 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. A 2500T fast forging machine is used for billeting, with a deformation of 30-45%, □480×L, and then a fire upsetting and drawing is performed to □240×L.

[0141] Step 3: Grinding:

[0142] Grinding the square 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 by 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°C. After keeping the temperature for 120-150 minutes, it was rolled for 11-13 times using a BD850 two-roller reversible 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 the 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 is subjected to induction heating at a temperature of 950°C, and is sequentially subjected to one-hot rolling using a BD600 two-roll reversible rolling mill, an eight-roll tandem rolling mill, and a finishing / kocks tandem rolling mill to prepare φ8.0 and 9.4 hot-rolled coils;

[0151] Step 7: Finishing:

[0152] The φ9.4 hot-rolled coil obtained in step 6 is used to prepare φ8.03 round wire by direct peeling process: hot-rolled coil → overhaul → 720℃ rounding → 760℃ annealing → 720℃ straightening → centerless turning peeling → fixed die peeling → polishing → eddy current flaw detection → 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 The transverse and longitudinal microstructure schematic diagrams of Φ4.03mm, Φ5.03mm, Φ6.03mm and Φ8.03mm TC4 titanium alloy round wires prepared in Examples 1 to 4 of the present invention are shown respectively. It can be seen from the figure that the microstructure of the prepared TC4 titanium alloy finished round wire consists of equiaxed α and intergranular β, the α size is between 5-10μm, the intergranular β size is relatively small, uniform, and the head, middle and tail are consistent and stable.

[0157] Table 2 below shows the properties of the TC4 titanium alloy disc 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 the traditional process, the number of times of dividing materials, sawing the head and tail of materials in the preparation method of Examples 1 to 4 of the present invention is reduced, thereby improving the material utilization rate. It adopts the method of direct peeling of hot-rolled coils, and 5 to 6 drawing passes without stress relief annealing in the middle to prepare finished round wires of different specifications with a unit weight of >100kg, which significantly shortens the processing cycle and improves production efficiency. The direct peeling method is used to prepare round wires of Φ6 and 8 specifications; the drawing method is used to prepare round wires of Φ4 and 5 specifications. 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 controls the forging, rolling, machining and heat treatment processes by adjusting the chemical composition and smelting method of the TC4 titanium alloy ingot, and adopts the "rolling instead of forging, forging and rolling combined" technology to effectively improve production efficiency and material utilization. The continuous rolling technology with temperature control and rolling throughout the entire process enables the preparation of hot-rolled coils of more than 100kg, and the uniformity and consistency of its organization and performance are significantly improved, avoiding the drawbacks of multiple material divisions in traditional horizontal rolling, shortening the process, and enabling the preparation of TC4 titanium alloy coils and round wires that meet the requirements of aerospace applications at low cost.

[0162] It should be noted that the above-described embodiments are only preferred embodiments of the present invention. For those skilled in the art, without departing from the principles of the present invention, the present invention may be modified, improved and replaced with equivalents, and these modifications, improvements and equivalent replacements are also considered 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 smelting: Sponge titanium, aluminum vanadium, aluminum particles, iron particles, TiO2, and titanium carbide are mixed according to a predetermined element ratio and an electrode is pressed, and then electron beam cold hearth furnace smelting and vacuum consumable arc furnace smelting are performed to obtain a TC4 titanium alloy ingot blank, and the TC4 titanium alloy ingot blank is peeled, and a riser and an ingot bottom are cut to prepare a TC4 titanium alloy ingot with a diameter of Φ700-820 mm; Step 2: Ingot forging: The TC4 titanium alloy ingot obtained in step 1 is heated to 1000-1200° C., and then forged into a □450-550×L square billet after heat preservation; after the square billet is polished, sawed and divided, it is heated to 920-980° C., and then upsetting and drawing into a □200-300×L square billet after heat preservation; Step 3: Grinding: Grinding the square 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, and after the heat preservation is completed, a BD850 two-roller reversible rolling mill is used for multiple passes to obtain a □140-180×L square billet; Second rolling: The □140~180×L square billet is sawn and divided, the surface is polished, and then heated to 920~980℃. After the insulation is completed, a BD850 two-roller reversible rolling mill is used for multiple passes 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 subjected to one-hot rolling using a BD600 two-roll reversible rolling mill, an eight-roll tandem rolling mill, and a finishing / kocks tandem rolling mill to prepare a hot-rolled coil; 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 round wire.

2. The method for preparing TC4 titanium alloy round wire for low-cost fasteners according to claim 1, characterized in that: 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.

3. The method for preparing TC4 titanium alloy round wire for low-cost fasteners according to claim 1, characterized in that: In step 2, the TC4 titanium alloy ingot is heated to 1000-1200°C and kept warm for 360-420 minutes, and then the ingot is forged with a deformation of 30-45%; it is squared to □550-650×L, and a fire upsetting and chamfering is performed to □450-550×L, and then the surface of the ingot is polished and sawed for material division; then the □450-550×L forging ingot is heated to 920-980°C, kept warm for 90-150 minutes, and then the ingot is forged with a deformation of 30-45%, and then a fire upsetting and drawing is performed to a □200-300×L square ingot.

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

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

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

7. The method for preparing TC4 titanium alloy round wire for low-cost fasteners according to claim 1, characterized in that: In step 6, the diameter of the obtained hot rolled coil is 7 mm to 12 mm.

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

9. A TC4 titanium alloy coil wire for low-cost fasteners, characterized in that: The method is prepared according to any one of claims 1 to 8.

10. The TC4 titanium alloy round wire for low-cost fasteners according to claim 9, characterized in that: The weight of a single coil of the TC4 titanium alloy round wire is greater than 100 kg.

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