A cold rolling method for TC16 titanium alloy hexagonal rod

Abstract

The present invention discloses a cold rolling method for TC16 titanium alloy hexagonal bars, comprising selecting a TC16 bar blank that meets the requirements; then subjecting the bar blank to extended blanking rolling with a large deformation amount on a two-roll mill; then, during finish rolling, firstly, using a four-roll universal mill to pass through one rolling pass, then undergoing 120° vertical rolling and two precise rolling passes before hexagonal die forming; finally, during finished rolling, using a four-roll universal mill to pass through one rolling pass with a small deformation amount, thereby obtaining a hexagonal bar with a tolerance size within ±0.03mm; finally, undergoing pre-straightening treatment, cutting and breaking, cleaning and air drying, roller-type fine straightening, non-destructive testing, and excision and local grinding of the surface of the inspection blind area to obtain the target product. Compared with the existing technology, the present invention can significantly reduce the waste of raw materials, has high production efficiency, is suitable for large-scale production, and the obtained product has the advantages of good structural uniformity, reliable performance, high stability, etc., and is widely used in the aerospace field with higher requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal processing, and particularly relates to a cold rolling method for TC16 titanium alloy hexagonal bars. Background Art

[0002] TC16 alloy is a martensitic α+β two-phase high-strength titanium alloy with a nominal composition of Ti-3AI-5Mo-4.5V. It contains the α-stabilizing element Al and the isomorphous β-stabilizing elements Mo and V. This alloy has a slightly higher β stability coefficient, Kβ = 0.8, and exhibits excellent process plasticity, allowing it to be both heat-treated and cold-work hardened. Due to its excellent high plasticity, high strength, high shear strength, and hardenability, as well as its excellent fatigue resistance and weldability, and low sensitivity to stress concentration, the alloy can reach strengths exceeding 1030 MPa after solution aging treatment or cold work hardening. Therefore, it is one of the most ideal materials for manufacturing aerospace fasteners.

[0003] In recent years, with the high-quality development of aerospace technology, not only the uniformity and stability of the internal microstructure and performance of TC16 titanium alloy hexagonal bars are required, but also the following technical indicators are required for their external properties: only the three-sided dimensional deviation is allowed to be within ±0.03mm; the straightness deviation is ≯1mm / 1m; the torsion is ≯2° / 1m; and surface defects are not allowed. The existing technology usually adopts the following manufacturing methods: First, large-scale production adopts multi-stand three-roll continuous rolling mill for production, but the variety and specifications of large-scale production are limited, and the dimensional accuracy is poor; second, the use of mechanical processing methods to manufacture titanium alloy hexagonal bars (such as turning and milling the bars into hexagons), resulting in large waste of raw materials, low production efficiency and high production costs; third, the production method used in small batches: one is hot rolling + drawing, which requires the application of lubricant, pollutes the environment and cannot guarantee surface quality; the other is hot rolling + straightening + turning and peeling to remove processing defects and then cold rolling, but the production efficiency is low and the rolling cost is high.

[0004] In view of this, the inventors propose a cold rolling method for TC16 titanium alloy hexagonal bars to solve the problems existing in the existing processing methods. Summary of the Invention

[0005] The object of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a cold rolling method for TC16 titanium alloy hexagonal bars. The TC16 titanium alloy hexagonal bars produced by the cold rolling method have good structural uniformity, reliable performance, high stability, high finished product dimensional accuracy and no surface defects, especially the three-side dimensional deviation can be controlled within ±0.03mm, which solves the problems of limited specifications and low precision of existing TC16 hexagonal bars, or poor surface quality due to environmental pollution, or large waste of raw materials and high costs.

[0006] The purpose of the present invention is to solve the problem through the following technical solutions:

[0007] A cold rolling method for TC16 titanium alloy hexagonal bars, comprising the following steps:

[0008] Step 1: Select the rolling bar:

[0009] A TC6 titanium alloy bar blank having microstructure and properties in accordance with the national standard GB / T3620 is selected, and the bar blank is required to meet the cold forging requirements of a 1 / 4 large forging ratio. The diameter of the bar blank is D = (1.30-1.49) d, where d is the distance across flats of the target TC16 titanium alloy hexagonal bar.

[0010] Step 2: Pass rolling:

[0011] Step 2.1, slab rolling: This process consists of two-roll flat rolling and vertical rolling, and the bar is deformed and extended through three passes, with a single-pass deformation amount of ε = 8-18%, to obtain an intermediate bar with a cross-section approximately hexagonal.

[0012] Step 2.2, finishing rolling: A four-high universal rolling mill is first used to produce a concave hexagonal bar through one rolling pass to offset the flat convex defects of the finished bar caused by the rebound of the material in the subsequent rolling process and to make the edges and corners of the subsequent bar easier to fill. The bar is then subjected to two precise rolling passes before 120° vertical rolling and hexagonal pass forming. The deformation per pass is ε = 4-12%.

[0013] Step 2.3, finished product rolling: then rolling through a four-roll universal rolling mill in one pass, wherein the deformation amount per pass is ε=3-8%, to obtain a TC16 titanium alloy hexagonal bar with a tolerance within ±0.03 mm;

[0014] Step 3: performing roller pre-straightening treatment on the hexagonal bar obtained in step 2;

[0015] Step 4: The pre-straightened bar obtained in step 3 is subjected to water jet cutting and dividing;

[0016] Step 5: Clean and dry the surface of the formed rod after the treatment in step 4;

[0017] Step 6: Perform roller straightening on the bar processed in step 5;

[0018] Step 7: subjecting the bar material processed in step 6 to ultrasonic testing and taking physical and chemical samples for analysis;

[0019] Step 8: The rod processed in step 7 is subjected to surface treatments such as cutting off the blind area of ​​flaw detection, surface inspection, and grinding and polishing to obtain the target TC16 titanium alloy hexagonal rod.

[0020] Furthermore, the bar selected in step 1 is in the hot-rolled annealing state, and the annealing system is: 780℃±10℃ for 2h, furnace cooling to 550℃, and air cooling; at the same time, the mechanical properties of the bar at room temperature are required to be as follows: tensile strength σ b :800~950Mpa, elongation δ s : ≥14%, section shrinkage ψ: ≥65, shear strength τ: ≥620Mpa.

[0021] Furthermore, the surface roughness of the bar blank selected in step 1 is less than or equal to 1.2 μm, and the bar blank is required to be free of cracks, shrinkage tails, pores, delamination, segregation, metal and / or non-metallic inclusions and other metallurgical defects visible to the naked eye.

[0022] Preferably, the rod blank needs to be ultrasonically inspected. The longitudinal wave inspection should meet the requirements that a single defect is no larger than Φ0.8mm, and the shear wave inspection should not have any response signal greater than the reflection amplitude of the longitudinal groove. The groove depth is 0.2mm, the width is 0.1mm, and the length is 10mm.

[0023] It should be noted that pits are allowed on the surface of the rod blank, but the depth of the pits should not be greater than its dimensional tolerance, the width-to-depth ratio should not be less than 8, and a smooth transition is required.

[0024] Furthermore, the specific implementation process of the slab rolling in step 2 is as follows:

[0025] Step 2.1.1, rolling the TC16 titanium alloy billet selected in step 1 in a hexagonal pass A, wherein the parameters of the hexagonal pass A are: groove bottom width (0.8-0.95) d, pass height (1.1-1.2) d, and upper and lower pass sidewall angle a1 = 100° ± 6°;

[0026] Step 2.1.2, flipping the TC16 titanium alloy bar after rolling in step 2.1.1 by 90 degrees and rolling it in a rhombus pass A, wherein the parameters of the rhombus pass A are: vertex angle a2 = 100° ± 6°, pass width across flats (1.14-1.17) d, and vertex fillet r1 = 1-1.5 mm;

[0027] Step 2.1.3, flip the TC16 titanium alloy bar rolled in step 2.1.2 90° and roll it in a hexagonal hole B, where the parameters of the hexagonal hole B are: groove bottom width is (0.55~0.65)d, hole height is (1.03~1.08)d, and the angle between the upper and lower hole side walls is a3=100°±6°.

[0028] Furthermore, the specific implementation process of the finishing rolling in step 2 is as follows:

[0029] Step 2.2.1. Turn the TC16 titanium alloy bar after rolling in step 2.1.3 by 90 degrees and perform quarter-roll concave hexagonal pass rolling on a four-roll universal rolling mill. The pass configuration parameters are as follows: the pass profiles of the left and right rolls are single arcs, the arc radius R=(1.3-1.6) d, the minimum distance between the arcs on both sides is (1.0-1.02) d, the upper roll is a W-shaped double arc configuration, the lower roll is an M-shaped double arc configuration, the arc radius of the upper and lower rolls r=(1.0-1.2) d, the minimum spacing between the diagonal arcs of the upper and lower rolls is (1.05-1.085) d, and the diagonal spacing between the upper and lower rolls is (1.25-1.40) d;

[0030] Step 2.2.2, rolling the TC16 titanium alloy bar after step 2.2.1 in a rhombus pass B, wherein the parameters of the rhombus pass B are: vertex angle a4 = 120°, pass width d + (0.1-0.5 mm), and vertex fillet r2 = 0.5-1.5 mm;

[0031] Step 2.2.3, flip the TC16 titanium alloy bar rolled in step 2.2.2 by 90° and roll it in a regular hexagonal pass. The parameters of the regular hexagonal pass are: the distance across the flats is d+(0.0-0.2 mm), and each vertex angle a5 is 120°.

[0032] Furthermore, the specific implementation process of the finished product rolling in step 2 is as follows: the TC16 titanium alloy billet with a hexagonal cross-section obtained by the finishing rolling in step 2.2.3 is flipped 90° and subjected to high-precision finished product rolling with four rolls on a four-roll universal rolling mill. The hole parameters during finished product rolling are: the upper and lower roll top angles a6 = 120°, the upper roll is W-shaped, the lower roll is M-shaped, the minimum spacing between the upper and lower rolls is d-(0.05~0.20mm), and the spacing between the left and right side rolls is d-(0.05~0.20mm).

[0033] Furthermore, after the pass rolling in step 2 is completed, the total deformation of the bar blank ε is 35-50%.

[0034] Furthermore, in step 7, the bar needs to be subjected to solution aging treatment before taking physical and chemical samples for analysis. The specific treatment process is: solution treatment temperature is 780-830°C, holding temperature is 1.5-2.5 hours, water quenching, and quenching delay time is less than or equal to 10 seconds; aging treatment temperature is 500-580°C, holding temperature is 4-10 hours, and air cooling.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. A cold rolling method for TC16 titanium alloy hexagonal bars of the present invention, wherein step 2 of the cold rolling method uses a two-roll cold rolling process for blanking and a universal four-roll rolling mill for finishing and final product rolling. The advantages of this process are: first, the use of large-diameter two-roll rolling with large capacity and adjustable pressure improves the bite conditions of the bar billet, thereby allowing the input of larger-sized raw materials, thereby expanding the applicable range of product specifications, and extending the maximum specification of the product from S10 to S20; second, the finishing and final product passes use a dedicated four-roll universal rolling mill for small deformation rolling, ensuring higher dimensional accuracy, and the three opposite dimensions are adjustable, ensuring that the dimensional tolerance can reach ±0.03mm within; thirdly, the use of a four-roll universal rolling mill for concave hexagonal hole finishing rolling and finished product rolling not only ensures the filling of the corners, but also eliminates the convex defects on the surface of the finished product of high-elastic titanium alloy hexagonal rod due to the arc pre-rolling of the six faces, greatly improving the flatness of the product; fourthly, since the entire rolling process is axisymmetric rolling, the hole processing accuracy and rolling adjustment accuracy are easy to achieve, so the rolled products have no obvious bending and torsion phenomenon, and are easier to straighten than the products of Y-type rolling, roller drawing and dead die drawing; fifthly, due to the use of axisymmetric rolling, the raw material is very stable during the rolling process, eliminating the rolling guide, simplifying the operation and preventing the guide from damaging the surface of the rolled rod.

[0037] 2. The present invention provides a cold rolling method for TC16 titanium alloy hexagonal bars. This cold rolling method completely overcomes the numerous drawbacks of traditional TC16 titanium alloy hexagonal bar preparation processes, such as being time-consuming and material-intensive, uneconomical, limited in specifications, poor in dimensional accuracy, or numerous defects that are difficult to clean. By combining and matching rolling mills of varying capabilities, the cold rolling process expands product specifications and processing windows while also improving product precision. Furthermore, this cold rolling method enables the blank to be processed through fewer process steps than traditional methods to produce a finished product with excellent surface quality, thereby improving production efficiency and making it suitable for large-scale production. Furthermore, the TC16 titanium alloy hexagonal bars produced using the present invention possess the advantages of good structural uniformity and high stability, fully meeting all aerospace requirements for TC16 titanium alloy hexagonal bars. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the invention.

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0040] Figure 1 This is a schematic diagram of the cold rolling process and pass type of TC16 titanium alloy hexagonal bar in the present invention;

[0041] Figure 2 1 is a microstructure diagram of the TC16 titanium alloy hexagonal rod (specification S8) prepared in Example 1 of the present invention after heat treatment and strengthening;

[0042] Figure 3 1 is a microstructure diagram of the TC16 titanium alloy hexagonal rod (specification S10) prepared in Example 2 of the present invention after heat treatment and strengthening;

[0043] Figure 4 This is a microstructure diagram of the TC16 titanium alloy hexagonal rod (specification S14) prepared in Example 3 of the present invention after heat treatment and strengthening. DETAILED DESCRIPTION

[0044] Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present invention. Rather, they are merely examples of arrangements consistent with certain aspects of the present invention as detailed in the appended claims.

[0045] The present invention provides a cold rolling method for TC16 titanium alloy hexagonal bars, which specifically comprises the following steps:

[0046] Step 1: Select the rolling bar:

[0047] The TC6 titanium alloy billet with the microstructure and properties in accordance with the national standard GB / T3620 is selected, and the billet is required to meet the cold forging requirements of 1 / 4 large forging ratio. The diameter of the billet is D = (1.30 ~ 1.49) d, where d is the distance across the flats of the target TC16 titanium alloy hexagonal bar, as shown in the figure. Figure 1 (0) shown.

[0048] In addition, the bar selected in step 1 is required to be in the hot-rolled annealing state, and the annealing system is: 780℃±10℃ for 2h, furnace cooling to 550℃, and air cooling; at the same time, the mechanical properties of the bar at room temperature are required to be as follows: tensile strength σ b :800~950Mpa, elongation δ s : ≥14%, cross-sectional shrinkage ψ: ≥65, shear strength τ: ≥620Mpa; at the same time, the surface roughness of the selected bar blank is required to be less than or equal to 1.2μm, and the bar blank is required to be free of cracks, shrinkage tails, pores, delamination, segregation, metal and / or non-metallic inclusions and other metallurgical defects visible to the naked eye.

[0049] Step 2, groove rolling (this step uses only 7 passes and is divided into three stages: cogging, finishing and finished product rolling). The specific implementation process is as follows:

[0050] Step 2.1, billet rolling

[0051] The selected TC16 titanium alloy round bar is subjected to a large deformation (single-pass deformation ε=8-18%) in a two-roll mill, and the bar is extended through three large deformation passes to obtain an intermediate bar with an approximately hexagonal cross section;

[0052] Step 2.1.1: Roll the TC16 titanium alloy billet selected in step 1 into a hexagonal hole A. The parameters of the hexagonal hole A are as follows: Figure 1 (1) As shown: the groove bottom width is (0.8~0.95)d, the hole height is (1.1~1.2)d, and the angle between the upper and lower hole side walls is a1=100°±6°;

[0053] Step 2.1.2: Flip the TC16 titanium alloy bar after rolling in step 2.1.1 by 90° and roll it in a rhombus pass A. The parameters of the rhombus pass A are as follows: Figure 1 (2) As shown: the top angle a2 = 100° ± 6°, the hole width across the edges is (1.14-1.17) d, and the top corner fillet r1 = 1-1.5 mm;

[0054] Step 2.1.3: Flip the TC16 titanium alloy bar rolled in step 2.1.2 by 90° and roll it in hexagonal pass B. The parameters of the hexagonal pass B are as follows: Figure 1 (3) As shown: the groove bottom width is (0.55~0.65)d, the hole height is (1.03~1.08)d, and the angle between the upper and lower hole side walls is a3=100°±6°;

[0055] Step 2.2, finishing rolling

[0056] The TC16 titanium alloy billet with a nearly hexagonal cross-section obtained by slab rolling is then subjected to finish rolling with a small deformation (single pass ε = 4-12%) on a four-high universal rolling mill. First, a concave hexagonal bar is obtained through one rolling pass to offset the convex defects of the finished bar plane caused by the rebound of the subsequent rolling material and make the subsequent bar edges and corners easier to fill. Then, after 120° vertical rolling and two precise rolling passes before the hexagonal pass is formed, a hexagonal bar slightly larger than the finished product is obtained.

[0057] Step 2.2.1. Turn the TC16 titanium alloy bar after rolling in step 2.1.3 by 90 degrees and roll it on a four-roll universal rolling mill with a concave hexagonal pass (the side lengths of the concave hexagonal pass are the same arc side). The pass composition parameters are as follows: Figure 1(4) As shown: the hole profile of the left and right rollers is a single arc, the arc radius R = (1.3 ~ 1.6) d, the minimum distance between the arcs on both sides is (1.0 ~ 1.02) d, the upper roller is a W-shaped double arc, the lower roller is an M-shaped double arc, the arc radius of the upper and lower rollers r = (1.0 ~ 1.2) d, the minimum spacing between the diagonal arcs of the upper and lower rollers is (1.05 ~ 1.085) d, and the diagonal spacing between the upper and lower rollers is (1.25 ~ 1.40) d;

[0058] Step 2.2.2: Roll the TC16 titanium alloy bar after step 2.2.1 in a rhombus pass B. The parameters of the rhombus pass B are as follows: Figure 1 (5) As shown: the top angle a4 = 120°, the distance between the sides is d + (0.1 to 0.5 mm), and the fillet r2 at the top corner is 0.5 to 1.5 mm;

[0059] Step 2.2.3: Flip the TC16 titanium alloy bar rolled in step 2.2.2 by 90° and roll it in a regular hexagonal die. The parameters of the regular hexagonal die are as follows: Figure 1 (6) As shown: the distance between the edges is d+(0.0~0.2mm), and each vertex angle a5=120°;

[0060] Step 2.3: Finished product rolling

[0061] The TC16 titanium alloy billet with a regular hexagonal cross section obtained by finishing rolling in step 2.2.3 is flipped 90° and subjected to high-precision finished product rolling with a small deformation amount (pass ε = 3-8%) on a four-roll universal rolling mill with a quarter-roller, to obtain a TC16 titanium alloy hexagonal bar with a tolerance size within ±0.03mm. The pass parameters during finished product rolling are as follows: Figure 1 (7) As shown: the top angle of the upper and lower rollers a6 = 120°, the upper roller is W-shaped, the lower roller is M-shaped, the minimum distance between the upper and lower rollers is d-(0.05~0.20mm), and the distance between the left and right rollers is d-(0.05~0.20mm).

[0062] Step 3: performing roller pre-straightening treatment on the hexagonal bar obtained in step 2;

[0063] Specifically, a 13-roller straightening machine with a large roller diameter of Φ100-120mm and a roller spacing of 160mm is used for straightening. Through 4-6 passes of large reduction straightening (60° flipping each pass, and full-directional straightening of three opposite sides), the torsion caused by rolling (torsion after straightening ≯2° / 1m) and small bends that are difficult to straighten are mainly eliminated.

[0064] Step 4: The pre-straightened bar obtained in step 3 is subjected to water jet cutting and dividing;

[0065] Specifically, water jet cutting or lathe is used to cut the pre-straightened bars according to the requirements of the user or relevant standards. Water jet cutting should prevent flying sand from damaging the surface of the bar; lathe cutting should prevent excessive speed from causing material bending and surface damage.

[0066] Step 5: Clean and dry the surface of the formed rod after the treatment in step 4;

[0067] Specifically, use metal cleaning agent and water to clean the surface of the bar, remove rolling lubricating oil and flying sand and other surface contaminants and air dry

[0068] Step 6: Perform roller straightening on the bar processed in step 5;

[0069] Specifically, a 5 / 11 roller straightening machine with a roller diameter of Φ80-85mm and a roller spacing of 90mm is used to perform fine straightening on the bars, mainly to eliminate the large bends caused by the previous process. Each straightening process should be based on the straightness of the bars and the pressure of the straightening rollers should be adjusted in time. After 3 to 7 straightening passes, it is ensured that the curvature of each bar is no more than 1.5mm / m, and the torsion after straightening is ≯2° / 1m.

[0070] Step 7: subjecting the bar material processed in step 6 to ultrasonic testing and taking physical and chemical samples for analysis;

[0071] Specifically, in step 7, the finely straightened bars are subjected to three-sided water immersion ultrasonic testing in accordance with relevant standards, and physical and chemical samples are taken for analysis. Performance parameters must meet the requirements of Table 1 below and relevant standards. Macrostructure is not allowed to contain cracks, shrinkage tails, pores, delamination, segregation, metallic and non-metallic inclusions, or other visible metallurgical defects. Cold work hardening is performed, but grain size testing is not performed. The microstructure is measured on heat-treated and hardened specimens and should meet standards or customer requirements. The heat treatment strengthening process includes a solution treatment temperature of 780-830°C for 1.5-2.5 hours, followed by water quenching with a quenching delay time of no more than 10 seconds; an aging treatment temperature of 500-580°C for 4-10 hours, and air cooling.

[0072] Step 8: The rod processed in step 7 is subjected to surface treatments such as cutting off the blind area of ​​flaw detection, surface inspection, and grinding and polishing to obtain the target TC16 titanium alloy hexagonal rod.

[0073] In order to further verify the efficacy of the cold rolling method of the present invention, the inventors conducted the following specific examples for verification.

[0074] Example 1 (Preparation of TC16 titanium alloy hexagonal rod with specification S8)

[0075] 1) Select rolled bar: Select the bar that meets the requirements of 1 / 4 large forging ratio cold top forging high cold deformation plasticity, the composition meets the requirements of GB / T3620 standard, is kept at 780℃±10℃ for 2h, furnace cooled to 550℃, air cooled annealed, ultrasonically tested, and the room temperature performance meets the tensile strength σ b :800~950Mpa, elongation δ s : ≥14%, cross-sectional shrinkage ψ: ≥65, shear strength τ: ≥620Mpa; TC16 bar billet with a surface roughness not greater than 1.2μm, free of cracks, shrinkage tails, pores, delamination, segregation, metallic and non-metallic inclusions, and other metallurgical defects visible to the naked eye. The bar billet specifications are set based on 45% of the total deformation, that is, the bar billet diameter D = 1.416d = 11.33mm (d = 8mm). The specific calculation process is as follows:

[0076] Cross-sectional area of ​​hexagonal rod

[0077] Cross-sectional area of ​​the billet

[0078] Total deformation

[0079] Therefore, the diameter of the billet

[0080] 2) Pass rolling:

[0081] First, the blank is rolled: the selected bar is rolled in the hexagonal groove of the two-roll mill with a large deformation (single pass ε = 12.0%). The groove composition parameters are shown in Figure 1 (1): The groove bottom width is 0.8d = 6.4 mm, the hole height is 1.125d = 9.0 mm, and the angle between the upper and lower hole side walls is a1 = 100°; after rolling, the bar is turned 90° and rolled in a rhombus hole (single pass ε = 11.0%). The hole configuration parameters are shown in Figure 1 (2): vertex angle a2 = 100°, pass width across flats 1.17d = 9.36 mm, vertex fillet r1 = 1 mm; the rolled bar is turned 90° and rolled in a hexagonal pass (single pass ε = 10.5%). The pass configuration parameters are shown in Figure 1 (3): The groove bottom width is 0.55d = 4.4 mm, the hole height is 1.05d = 8.4 mm, and the angle between the upper and lower hole side walls is a3 = 94°;

[0082] Then, finish rolling is performed: the bar is turned 90° and firstly rolled on a four-roll universal mill with a four-roll modified concave hexagonal groove (single pass ε = 8.0%). The groove composition parameters are shown in Figure 1(4): The hole profile of the left and right rollers is a single arc, with an arc radius of R = 1.4d = 11.2 mm, a minimum distance between the arcs on both sides of the rollers of 1.0d = 8.0 mm, an upper roller is a W-shaped double arc, and a lower roller is an M-shaped double arc, with arc radii of r = 1.1d = 8.8 mm, a minimum diagonal arc spacing of 1.06d = 8.48 mm between the upper and lower rollers, and a diagonal spacing of 1.27d = 10.16 mm between the upper and lower rollers; the rolled bar is not turned over and rolled in a rhombus hole (single pass ε = 7.0%), and the hole profile parameters are shown in FIG. Figure 1 (5): vertex angle a4 = 120°, pass width d + (0.15 mm) = 8.15 mm, vertex fillet r2 = 0.5 mm; the rolled bar is turned 90° and rolled in a regular hexagonal pass (single pass ε = 5.3%). The pass configuration parameters are shown in Figure 1 (6): The opposite side dimension is d = 8 mm, and each vertex angle a5 = 120°;

[0083] Finally, the finished product is rolled: the bar is turned 90° and then rolled on a four-roll universal mill with a small deformation (pass ε = 3.2%) to obtain a hexagonal bar with a finished product size tolerance within ±0.03mm. The pass configuration parameters are shown in Figure 1 (7): The top angle of the upper and lower rollers is a = 120°, the upper roller is W-shaped, the lower roller is M-shaped, the minimum distance between the upper and lower rollers is d-Δ(0.13mm) = 7.87mm, and the distance between the left and right rollers is d-(0.13mm) = 7.87mm;

[0084] Total deformation εtotal=1-(1-0.12)×(1-0.11)×(1-0.105)×(1-0.08)×(1-0.07)×(1-0.053)×(1-0.32)≈0.45;

[0085] 3) The finished rolled bars are pre-straightened by a 13-roller straightening machine with a large roller diameter of Φ100-120mm and a roller spacing of 160mm. They are straightened by 4-6 passes with large reduction (60° flipping each time, and all-directional straightening of three opposite sides), mainly to eliminate the torsion caused by rolling (torsion after straightening ≯2° / 1m) and small bends that are difficult to straighten.

[0086] 4) After pre-straightening, the bars are cut by water jet cutting or lathe as required. Water jet cutting should prevent flying sand from damaging the surface of the bars; when cutting on the lathe, the speed should be too fast to cause the material to bend and the surface to be damaged.

[0087] 5) After the rods are split, they should be cleaned with metal cleaning agent and water to remove surface contaminants such as rolling lubricating oil and flying sand, and then air-dried.

[0088] 6) Use a 5 / 11 roller straightening machine with a roller diameter of Φ80-85mm and a roller spacing of 90mm to perform fine straightening on the bars, mainly to eliminate the large bends caused by the previous process. Each straightening process should be based on the straightness of the bars and the amount of pressure of the straightening roller should be adjusted in time. After 3-7 straightening passes, ensure that the curvature of each bar is no more than 1.5mm / m, and the torsion after straightening is ≯2° / 1m.

[0089] 7) After fine straightening, the bars shall be subjected to three-sided water immersion ultrasonic testing in accordance with relevant standards, and physical and chemical samples shall be taken for analysis. The performance parameters must meet the requirements of Table 1 below and relevant standards. Cracks, shrinkage tails, pores, delamination, segregation, metallic and non-metallic inclusions, and other metallurgical defects visible to the naked eye are not allowed in the macrostructure. Grain size testing is not performed on cold-worked hardened bars. The microstructure is measured on heat-treated and strengthened specimens and should meet the standards or customer requirements (heat treatment strengthening process: solution treatment temperature of 780-830℃, holding temperature of 1.5-2.5h, water quenching, quenching delay time of no more than 10s; aging treatment temperature of 500-580℃, 4-10h, air cooling).

[0090] Table 1 Room temperature mechanical properties of TC16 titanium alloy hexagonal bars

[0091]

[0092] 8) After flaw detection, the bar needs to remove the flaw detection blind area and defective parts, inspect and measure the surface and size, and grind and polish as required to eliminate local defects, and finally produce TC16 titanium alloy hexagonal bar. The performance test of the final product is shown in Table 2 below, and the microstructure metallographic diagram is shown in Figure 2 , from the performance data and microstructure in Table 2 Figure 2 It can be seen that the TC16 titanium alloy hexagonal rod produced by this cold rolling method has reliable performance, high stability and uniform microstructure under room temperature tension.

[0093] Example 2 (Preparation of TC16 titanium alloy hexagonal rod with specification S10)

[0094] 1) Select rolled bar: Select the bar that meets the requirements of 1 / 4 large forging ratio cold top forging high cold deformation plasticity, the composition meets the requirements of GB / T3620 standard, is kept at 780℃±10℃ for 2h, furnace cooled to 550℃, air cooled annealed, ultrasonically tested, and the room temperature performance meets the tensile strength σ b :800~950Mpa, elongation δ s: ≥14%, cross-sectional reduction rate ψ: ≥65, shear strength τ: ≥620Mpa; TC16 bar billet with a surface roughness not greater than 1.2μm, free of cracks, shrinkage tails, pores, delamination, segregation, metallic and non-metallic inclusions and other metallurgical defects visible to the naked eye. The bar billet specifications are set according to the total deformation of 48.3%, that is, the bar billet diameter D = 1.46d = 14.6mm (d = 10mm);

[0095] 2) Pass rolling:

[0096] First, the blank is rolled: the selected bar is rolled in a two-roll mill with a large deformation (single pass ε = 14.0%). The parameters of the pass are shown in Figure 1 (1): The groove bottom width is 0.843d = 8.43mm, the hole height is 1.1d = 11mm, and the angle between the upper and lower hole side walls is a1 = 101°; after rolling, the bar is turned 90° and rolled in a rhombus hole (single pass ε = 12%). The hole configuration parameters are shown in Figure 1 (2): vertex angle a2 = 101°, pass width across flats 1.14d = 11.4 mm, vertex fillet r1 = 1.5 mm; the rolled bar is turned 90° and rolled in a hexagonal pass (single pass ε = 11%). The pass configuration parameters are shown in Figure 1 (3): The groove bottom width is 0.55d = 5.5 mm, the hole height is 1.08d = 10.8 mm, and the angle between the upper and lower hole side walls is a3 = 95°;

[0097] Then, finish rolling is performed: the bar is turned 90° and firstly rolled on a four-roll universal mill with a concave hexagonal groove of four rolls (single pass ε = 8.5%). The groove composition parameters are shown in Figure 1 (4): The hole profile of the left and right rollers is a single arc, with an arc radius of R = 1.5d = 15 mm, a minimum distance between the arcs on both sides of the rollers of 1.03d = 10.3 mm, the upper roller is a W-shaped double arc, and the lower roller is an M-shaped double arc, with arc radii r = 1.2d = 12 mm, a minimum diagonal arc spacing of the upper and lower rollers of 1.06d = 10.6 mm, and a diagonal spacing of the upper and lower rollers of 1.33d = 13.3 mm; the rolled bar is not turned over and rolled in a rhombus hole (single pass ε = 5.7%), and the hole profile parameters are shown in Figure 1 (5): vertex angle a4 = 120°, pass width d + (0.20 mm) = 10.2 mm, vertex fillet r2 = 0.5 mm; the rolled bar is turned 90° and rolled in a regular hexagonal pass (single pass ε = 6.5%). The pass configuration parameters are shown in Figure 1 (6): The opposite side dimension is d+0.1=10.1mm, and each vertex angle a5=120°;

[0098] Finally, the finished product is rolled: the bar is turned 90° and then rolled on a four-roll universal mill with a small deformation (pass ε = 4.9%) to obtain a hexagonal bar with a finished product size tolerance within ±0.03mm. The pass configuration parameters are shown in Figure 1 (7): The top angle of the upper and lower rollers is a = 120°, the upper roller is W-shaped, the lower roller is M-shaped, the minimum distance between the upper and lower rollers is d-(0.15mm) = 9.85mm, and the distance between the left and right rollers is d-(0.15mm) = 9.85mm. The subsequent processing process is the same as that of Example 1 and will not be repeated here. The performance test of the final product is shown in Table 2 below, and the microstructure metallographic diagram is shown in Figure 3 , from the performance data and microstructure in Table 2 Figure 3 It can be seen that the TC16 titanium alloy hexagonal rod produced by this cold rolling method has reliable performance, high stability and uniform microstructure under room temperature tension.

[0099] Example 3 (Preparation of TC16 titanium alloy hexagonal rod with specification S14)

[0100] 1) Select rolled bar: Select the bar that meets the requirements of 1 / 4 large forging ratio cold top forging high cold deformation plasticity, the composition meets the requirements of GB / T3620 standard, is kept at 780℃±10℃ for 2h, furnace cooled to 550℃, air cooled annealed, ultrasonically tested, and the room temperature performance meets the tensile strength σ b :800~950Mpa, elongation δ s : ≥14%, cross-sectional reduction rate ψ: ≥65, shear strength τ: ≥620Mpa; TC16 bar billet with a surface roughness not greater than 1.2μm, free of cracks, shrinkage tails, pores, delamination, segregation, metallic and non-metallic inclusions and other metallurgical defects visible to the naked eye. The bar billet specifications are set according to the total deformation of 46%, that is, the bar billet diameter D = 1.4285d = 20mm (d = 14mm);

[0101] 2) Pass rolling:

[0102] First, the blank is rolled: the selected bar is rolled in the hexagonal groove of the two-roll mill with a large deformation (single pass ε = 12.3%). The groove composition parameters are shown in Figure 1 (1): The groove bottom width is 0.843d = 11.8 mm, the hole height is 1.1d = 15.4 mm, and the angle between the upper and lower hole side walls is a1 = 101°; after rolling, the bar is turned 90° and rolled in a rhombus hole (single pass ε = 12.2%). The hole configuration parameters are shown in Figure 1 (2): vertex angle a2 = 101°, pass width across flats 1.14d = 16 mm, vertex fillet r1 = 1.5 mm; the rolled bar is turned 90° and rolled in a hexagonal pass (single pass ε = 10.2%). The pass configuration parameters are shown in Figure 1(3): The groove bottom width is 0.55d = 7.7 mm, the hole height is 1.08d = 15.12 mm, and the angle between the upper and lower hole side walls is a3 = 95°;

[0103] Then, finish rolling is performed: the bar is turned 90° and firstly rolled on a four-roll universal mill with a concave hexagonal groove of four rolls (single pass ε = 8.5%). The groove composition parameters are shown in Figure 1 (4): The hole profile of the left and right rollers is a single arc, with an arc radius of R = 1.5d = 21 mm, a minimum distance between the arcs on both sides of the rollers of 1.03d = 14.42 mm, a W-shaped double arc composition for the upper roller, and an M-shaped double arc composition for the lower roller, with arc radii of r = 1.2d = 16.8 mm, a minimum diagonal arc spacing of 1.06d = 14.84 mm for the upper and lower rollers, and a diagonal spacing of 1.33d = 18.6 mm for the upper and lower rollers; the rolled bar is not turned over and rolled in a rhombus hole profile (single pass ε = 7.0%), and the hole profile parameters are shown in FIG. Figure 1 (5): vertex angle a4 = 120°, pass width d + (0.28 mm) = 14.28 mm, vertex fillet r2 = 1 mm; the rolled bar is turned 90° and rolled in a regular hexagonal pass (single pass ε = 5.0%). The pass configuration parameters are shown in Figure 1 (6): The opposite side dimension is d+0.2=14.2 mm, and each vertex angle a5=120°;

[0104] Finally, the finished product is rolled: the bar is turned 90° and then rolled on a four-roll universal mill with a small deformation (pass ε = 3.5%) to obtain a hexagonal bar with a finished product size tolerance within ±0.03mm. The pass configuration parameters are shown in Figure 1 (7): The top angle of the upper and lower rollers is a = 120°, the upper roller is W-shaped, the lower roller is M-shaped, the minimum distance between the upper and lower rollers is d-(0.15mm) = 13.85mm, and the distance between the left and right rollers is d-(0.15mm) = 13.85mm. The subsequent processing process is the same as that of Example 1 and will not be repeated here. The performance test of the final product is shown in Table 2 below, and the microstructure metallographic diagram is shown in Figure 4 , from the performance data and microstructure in Table 2 Figure 4 It can be seen that the TC16 titanium alloy hexagonal rod produced by this cold rolling method has reliable performance, high stability and uniform microstructure under room temperature tension.

[0105] Table 2 TC16 hexagonal rod performance results

[0106]

[0107]

[0108] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0109] It should be understood that the present invention is not limited to the above description and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A cold rolling method for TC16 titanium alloy hexagonal bars, the cold rolling method comprising the following steps: Step 1: Select the rolling bar: A TC16 titanium alloy bar blank having microstructure and properties in accordance with the national standard GB / T3620 is selected, and the bar blank is required to meet the cold forging requirements of a 1 / 4 large forging ratio. The diameter of the bar blank is D = (1.30-1.49) d, where d is the distance across flats of the target TC16 titanium alloy hexagonal bar. Step 2: Pass rolling: Step 2.1, billet rolling: It consists of two-roll flat rolling and vertical rolling pass, and the billet is deformed and extended through three deformation passes, with the deformation amount of each pass ε=8~18%, to obtain an intermediate bar with a cross section approximately hexagonal; The specific implementation process of the slab rolling is as follows: Step 2.1.

1. Roll the TC16 titanium alloy billet selected in step 1 in a hexagonal pass A, wherein the parameters of the hexagonal pass A are: groove bottom width (0.8-0.95) d, pass height (1.1-1.2) d, and upper and lower pass sidewall angle a1 = 100° ± 6°; Step 2.1.2, flipping the TC16 titanium alloy bar rolled in step 2.1.1 by 90 degrees and rolling it in a rhombus pass A, wherein the parameters of the rhombus pass A are: vertex angle a2 = 100° ± 6°, pass width across flats (1.14-1.17) d, and vertex fillet r1 = 1-1.5 mm; Step 2.1.3, flipping the TC16 titanium alloy bar rolled in step 2.1.2 by 90 degrees and rolling it in a hexagonal pass B, wherein the parameters of the hexagonal pass B are: groove bottom width (0.55-0.65) d, pass height (1.03-1.08) d, and upper and lower pass sidewall angle a3 = 100° ± 6°; Step 2.2, finishing rolling: A four-high universal mill is used to first roll a concave hexagonal bar through one pass to offset the convex defects of the finished bar caused by the rebound of the material in the subsequent rolling process and to make it easier to fill the corners of the subsequent bar. The bar then undergoes 120° vertical rolling and two precise rolling passes before the hexagonal groove is formed. The deformation of each pass is ε = 4-12%; Step 2.3, finished product rolling: then passing through a four-roll universal rolling mill in one pass, wherein the deformation amount per pass is ε = 3-8%, to obtain a TC16 titanium alloy hexagonal bar with a tolerance within ±0.03 mm; Step 3: performing roller pre-straightening treatment on the hexagonal bar obtained in step 2; Step 4: The pre-straightened bar obtained in step 3 is subjected to water jet cutting and dividing; Step 5: Clean and dry the surface of the formed rod after the treatment in step 4; Step 6: Perform roller straightening on the bar processed in step 5; Step 7: subjecting the bar material processed in step 6 to ultrasonic testing and taking physical and chemical samples for analysis; Step 8: The rod processed in step 7 is subjected to surface treatments such as cutting off the blind area of ​​flaw detection, surface inspection, and grinding and polishing to obtain the target TC16 titanium alloy hexagonal rod.

2. The cold rolling method of TC16 titanium alloy hexagonal bar according to claim 1, characterized in that: The bar blank selected in step 1 is in a hot-rolled annealing state, and the annealing system is as follows: 780°C ± 10°C for 2 hours, furnace cooling to 550°C, and air cooling; at the same time, the mechanical properties of the bar blank at room temperature are required to be as follows: tensile strength σb: 800-950 MPa, elongation δs: ≥14%, cross-sectional shrinkage ψ: ≥65, and shear strength τ: ≥620 MPa.

3. The cold rolling method of TC16 titanium alloy hexagonal bar according to claim 1, characterized in that: The surface roughness of the rod blank selected in step 1 is less than or equal to 1.2 μm.

4. The cold rolling method of TC16 titanium alloy hexagonal bar according to claim 1, characterized in that: The specific implementation process of the finishing rolling in step 2 is as follows: Step 2.2.

1. The TC16 titanium alloy bar rolled in step 2.1.3 is turned 90 degrees and rolled on a four-roll universal mill using a concave hexagonal groove with four rolls. The groove configuration parameters are as follows: the groove profiles of the left and right rolls are single arcs with an arc radius R = (1.3-1.6) d, the minimum distance between the arcs on both sides is (1.0-1.02) d, the upper roll is a W-shaped double arc configuration, the lower roll is an M-shaped double arc configuration, the arc radius of the upper and lower rolls is r = (1.0-1.2) d, the minimum spacing between the diagonal arcs of the upper and lower rolls is (1.05-1.085) d, and the diagonal spacing between the upper and lower rolls is (1.25-1.40) d. Step 2.2.2, rolling the TC16 titanium alloy bar after step 2.2.1 in a rhombus pass B, wherein the parameters of the rhombus pass B are: vertex angle a4 = 120°, pass width across flats d + (0.1-0.5 mm), and vertex fillet r2 = 0.5-1.5 mm; Step 2.2.3, flip the TC16 titanium alloy bar rolled in step 2.2.2 by 90 degrees and roll it in a regular hexagonal pass. The parameters of the regular hexagonal pass are: the distance across the flats is d+ (0.0 to 0.2 mm), and each vertex angle a5 = 120 degrees.

5. The cold rolling method of TC16 titanium alloy hexagonal bar according to claim 4, characterized in that: The specific implementation process of the finished product rolling in step 2 is as follows: the TC16 titanium alloy billet with a regular hexagonal cross-section obtained by the finishing rolling in step 2.2.3 is flipped 90° and subjected to high-precision finished product rolling with four-roller four-roll universal rolling mill. The hole parameters during the finished product rolling are: the top angle of the upper and lower rollers a6 = 120°, the upper roller is W-shaped, the lower roller is M-shaped, the minimum spacing between the upper and lower rollers is d- (0.05~0.20mm), and the spacing between the left and right side rollers is d- (0.05~0.20mm).

6. The cold rolling method of TC16 titanium alloy hexagonal bar according to claim 1, characterized in that: After the die rolling in step 2 is completed, the total deformation of the bar billet ε is 35-50%.

7. The cold rolling method of TC16 titanium alloy hexagonal bar according to claim 1, characterized in that: After the pre-straightening treatment in step 3 and the fine straightening treatment in step 6, the straightening curvature of the TC16 titanium alloy hexagonal bar is less than or equal to 1.5 mm / m, and the torsion is less than or equal to 2° / 1 m.

8. The cold rolling method of TC16 titanium alloy hexagonal bar according to claim 1, characterized in that: In step 7, the bar needs to be subjected to solution aging treatment before taking physical and chemical samples for analysis. The specific treatment process is: solution treatment temperature is 780-830°C, holding temperature is 1.5-2.5 hours, water quenching, and quenching delay time is less than or equal to 10 seconds; aging treatment temperature is 500-580°C, holding temperature is 4-10 hours, and air cooling is performed.

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