A high-quality titanium and titanium alloy roller drawing method
By improving the two-roll composite pass mill and the circular-elliptical-circular pass design, the problems of die friction and thermal effect during the drawing process of titanium alloy wire were solved, realizing efficient and low-cost one-time forming and obtaining high-quality titanium alloy wire.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GRIMAT ENG INST CO LTD
- Filing Date
- 2023-02-13
- Publication Date
- 2026-05-26
AI Technical Summary
In the existing titanium alloy wire drawing process, the existing technology involves die and deformation growth, which leads to heat effect caused by friction between the die and the contact surface between the die and the deformed metal. This friction and heat effect cause grain growth, making it easy to break. In addition, the processing steps are complicated, the production cost is high, and it is difficult to achieve one-time forming.
An improved two-roll composite pass mill is adopted. Through the design of circular-elliptical-circular pass and multi-angle composite rolls, residual stress in wire forming is controlled, one-time forming is achieved, the process is simplified, and intermediate annealing and pickling are avoided.
It enables one-time forming of titanium alloy wire, reduces production costs, improves production efficiency, obtains high-quality wire with smooth surface and high tensile strength, simplifies processing procedures, and reduces energy consumption and environmental pollution.
Smart Images
Figure BDA0004073520650000111
Abstract
Description
Technical Field
[0001] This invention relates to a high-quality titanium and titanium alloy roller drawing method, belonging to the field of titanium alloy material processing technology. Background Technology
[0002] Titanium and titanium alloy wires are widely used in high-tech fields such as aerospace due to their excellent corrosion resistance, high specific strength, non-magnetic properties, good biocompatibility, and shape memory function. They are also increasingly entering various civilian fields.
[0003] In the processing of titanium alloy wire, a common technique is fixed-die drawing after heating. A key problem with fixed-die drawing is the friction between the die and the deformed metal, along with the resulting heat effect. This leads to grain growth and fracture, significantly limiting the deformation amount per drawing cycle and increasing the number of drawing passes. Therefore, most processes strictly control the drawing amount per pass and perform annealing heat treatment after 1-2 draws to eliminate residual stress before continuing drawing. To avoid frictional heat generation during drawing, the wire undergoes surface treatments such as pickling before drawing, followed by a uniform application of a suitable lubricant. Since titanium alloys tend to adhere to the die during drawing, causing difficulties, in addition to using a good lubricant, other enhanced lubrication measures such as coating and oxidation are necessary. Titanium alloys are mostly oxidized or coated before drawing. Coatings used include graphite emulsion, lime-based coatings, and calcium-based coatings. However, the lubricant layer needs to be applied evenly and with appropriate thickness; too thin a layer will not provide lubrication, while too thick a layer will easily scab and peel off during drawing. This production method involves complicated processing steps, a long production cycle, and high production costs, and needs further improvement.
[0004] The titanium alloy wire preparation processes disclosed in patents CN114733738 A, CN103341520 A, and CN108421840 A all employ a combination of hot drawing and cold drawing to produce titanium alloy wire. From their disclosures, it can be seen that patent CN114733738 A refines the grains of the titanium alloy by coating the surface of the titanium alloy wire with a titanium diboride suspension, preventing coarse grains from affecting its mechanical properties during frequent heat treatment. Patent CN103341520 A obtains wire in β single-phase state through hot drawing, followed by cold drawing in β single-phase state to obtain high-strength, high-toughness cold-drawn wire. Patent CN108421840 A reduces the ellipticity of the rolled wire and improves the yield by adding a high-temperature rounding step. These solutions have improved the quality and forming rate of titanium alloy wire to some extent, but they still have the problem of complicated processes. The multiple pickling, heat treatment or oxide scale polishing processes during preparation increase production costs and are also detrimental to the environment.
[0005] Simplifying the cold drawing process of titanium alloys while ensuring the quality of titanium alloy wire is an important way to achieve low-cost, high-quality industrial production of titanium alloy wire. For example, patent CN110976512 A discloses a cold rolling method for TC4 titanium alloy wire. This patent attempts to use a 4-station tandem continuous cold rolling mill with a round-polygonal-round rolling pass design, replacing the need for lubrication during wire drawing. However, the polygonal rolling method easily causes stress concentration near the edges, so this method requires frequent heat treatment to eliminate residual stress on the wire surface in actual use. It is not difficult to see that these inventions cannot solve the problem of excessive residual stress and the need for intermediate annealing heat treatment during the drawing process of titanium alloy wire, and cannot complete the one-time drawing and forming of titanium alloy wire.
[0006] This invention addresses the aforementioned problems in the drawing process of titanium alloy wires by improving the stress state during the drawing process and designing the deformation process during wire drawing. This results in an effective high-quality titanium and titanium alloy roller die drawing method that enables one-time stretching and forming of titanium alloy wires, significantly improving the quality and production efficiency of titanium alloy wires. This invention is of great significance in the titanium alloy wire processing industry. Summary of the Invention
[0007] The purpose of this invention is to solve the problems existing in the existing methods, simplify the preparation process of titanium alloy wire, and reduce its production cost. Based on the principle of small deformation accumulating into large deformation and residual stress mutually offsetting each other, the invention achieves effective control of residual stress in wire forming through a circular-elliptical-circular die design and a multi-angle composite roller design, and performs one-time processing of the wire, providing a simple, environmentally friendly, and low-cost high-quality titanium and titanium alloy roller drawing method.
[0008] This invention addresses the shortcomings of existing titanium alloy wire drawing processes, such as cumbersome procedures, the need for lubrication, and frequent intermediate annealing. It provides a cold drawing process suitable for one-time forming of titanium alloy wire. This process eliminates the need for pickling or multiple heat treatments of the wire in the early stages. It uses an improved two-roll composite pass mill to directly continue drawing the wire. By rationally allocating the elongation coefficient of each pass and the horizontal angle between the rolls, the one-time forming of the titanium alloy wire is completed. After annealing, no milling is required, and a bright titanium alloy wire that meets the standards is directly obtained.
[0009] To achieve the essential qualities of titanium alloy wire (surface smoothness, tensile strength, elongation, etc.), this invention abandons the cumbersome annealing process during each rolling stage of the traditional titanium alloy roll drawing process. Instead, it selects specific rolling pass shapes, elongation coefficients, and horizontal angle processes to achieve optimized control over the performance of the obtained titanium alloy wire.
[0010] This invention employs an improved two-roll composite pass mill for processing, providing a high-quality titanium and titanium alloy wire drawing method using roll dies. The specific operation is as follows:
[0011] (1) First cold rolling;
[0012] (2) Second cold rolling;
[0013] (3) Third cold rolling;
[0014] (4) Fourth cold rolling;
[0015] (5) Fifth cold rolling;
[0016] (6) Vacuum annealing.
[0017] The maximum total reduction in the wire drawing cross-section is 80%, and the single-pass elongation coefficient is 1.1 to 1.34.
[0018] Preferably, the elongation coefficient of the first cold rolling pass is 1.28 to 1.32, and the included angle between the center lines of the rolls is 90°.
[0019] Preferably, the elongation coefficient of the second cold rolling pass is 1.28 to 1.34, and the included angle between the center lines of the rolls is 40 to 50°.
[0020] Preferably, the elongation coefficient of the third cold rolling pass is 1.2 to 1.3, and the included angle between the roll centerlines is 90°.
[0021] Preferably, the elongation coefficient of the fourth cold rolling pass is 1.15 to 1.2, and the included angle between the roll centerlines is 130 to 140°.
[0022] Preferably, the elongation coefficient of the fifth cold rolling pass is 1.1 to 1.15, and the included angle between the roll centerlines is 90°.
[0023] Preferably, the elongation coefficients of the above five cold rolling passes are set as follows: the elongation coefficient of the first cold rolling pass is 1.28–1.32, and the included angle of the roll centerlines is 90°; the elongation coefficient of the second cold rolling pass is 1.28–1.34, and the included angle of the roll centerlines is 40–50°; the elongation coefficient of the third cold rolling pass is 1.2–1.3, and the included angle of the roll centerlines is 90°; the elongation coefficient of the fourth cold rolling pass is 1.15–1.2, and the included angle of the roll centerlines is 130–140°; the elongation coefficient of the fifth cold rolling pass is 1.1–1.15, and the included angle of the roll centerlines is 90°; annealing is carried out in a vacuum furnace at a temperature of 600–800°C for 30–90 minutes, with a vacuum degree of 10. -3 Pa.
[0024] Preferably, the improved two-roll compound pass mill consists of six sets of rolls, of which the first five sets are compound rolls and the last set is a horizontal roll, and the rolling pass adopts a circular-elliptical-circular structure design.
[0025] Preferably, the sixth group of rolls has a circular die, an elongation coefficient of 1, and an included angle of 45° between the roll centerlines.
[0026] Compared with conventional titanium alloy wire preparation processes, this invention has the following advantages:
[0027] 1. No pickling, multiple heat treatments, lubricants, or other enhanced lubrication measures such as coatings and oxidation are required in the early stage of wire drawing, which greatly saves energy, simplifies the process, and is environmentally friendly.
[0028] 2. The circular-elliptical-circular deformation method is adopted instead of the traditional fixed die stretching. By adjusting the angle between the rollers, the stress state of the wire during stretching is changed, effectively controlling the generation and distribution of residual stress. This achieves one-time forming of titanium alloy wire, requiring only stress-relief annealing after drawing, without the need for intermediate stress-relief annealing.
[0029] 3. An improved two-roll composite pass mill is used to continuously roll the wire in a circular-elliptical-circular deformation pattern. While ensuring the quality of the wire, the stress state of the wire during the rolling process is changed, which effectively reduces the friction between the roll and the wire contact surface and the associated heat effect. No iron oxide scale is produced after rolling, and a bright wire can be obtained after heat treatment.
[0030] 4. The processing is stable. Due to the change in stress state, residual stress during processing has more ways to be released. This process is suitable for continuous processing of large single-coil wires. The produced wires have good consistency in mechanical properties and dimensional accuracy, high stability and no obvious defects. The yield is much higher than that of traditional titanium alloy wire drawing processes, and the product precision and performance meet national standards and customer requirements.
[0031] 5. The invention provides a simple, environmentally friendly, and low-cost method for high-quality titanium and titanium alloy roller drawing. The process requires no pretreatment, and the intermediate stress-relieving annealing and subsequent cutting and de-oxidation are suitable for industrial production. Detailed Implementation
[0032] The present invention will be further described below with reference to specific embodiments to provide a better understanding of the invention.
[0033] This invention addresses the problems of existing technologies that often employ non-perforated rolling and heat treatment after each rolling pass to control the rolling process and titanium alloy forming performance. However, these processes result in cumbersome titanium alloy wire preparation, requiring lubrication in the early stages of drawing, softening through heat treatment in the middle stages, and grinding off iron oxide scale in the later stages. The technical solution of this invention simplifies the preparation process of titanium alloy wire, reducing its production cost. Based on the principle of small deformation accumulating into large deformation and the mutual offsetting of residual stress, it effectively controls residual stress during wire forming through a circular-elliptical-circular die design and a multi-angle composite roller design. This allows for one-time forming of the wire, providing a simple, environmentally friendly, and low-cost method for high-quality titanium and titanium alloy roller drawing. This invention provides a cold drawing process suitable for one-time forming of titanium alloy wire. This process does not require pickling or multiple heat treatments of the wire in the early stage. It uses an improved two-roll composite pass mill to continue drawing the wire directly. By reasonably allocating the elongation coefficient of each pass and the horizontal angle between the rolls, the one-time forming of titanium alloy wire is completed. After annealing, there is no need for milling, and bright titanium alloy wire that meets the standards is obtained directly.
[0034] The circular-elliptical-circular die rolling process used in this invention cleverly allows the rolled piece to smoothly transition from one cross-section to another, thereby avoiding the formation of localized high-stress concentration zones or high-temperature hot zones caused by severe deformation. In particular, the circular-elliptical-circular design, compared to the circular-prism or main-section composite design in existing technologies, is more effective in smoothing out sharp edges and burrs, removing iron oxide scale from the rolled piece surface, and improving the surface quality of the rolled piece. Compared to a single elliptical-circular or circular-elliptical system, the deformation is more stable and uniform because, in single-section deformation, the subsequent die has a significant impact on correcting the uneven deformation generated during the previous die rolling. The circular-elliptical-circular die design in this application utilizes the positive effect of circular die rolling on uniform deformation, while also considering the poor adaptability of circular die rolling to dimensional fluctuations caused by micro-deformation of the feed size of titanium alloy wire (elliptical die is subsequently used to correct and stabilize the dimensional fluctuations generated by the previous rolling). It also considers the further optimization of the surface quality of the rolled workpiece by using circular die at the end, such as eliminating rolling cracks and removing iron oxide scale from the rolled surface.
[0035] The present invention fully studies the generation and distribution of residual stress in wire during cold rolling. By designing the horizontal angle between each pass of the rolls, the distribution of residual stress during the rolling process is effectively controlled. After rolling by the improved two-roll composite pass mill, the residual stress generated in the wire during the rolling process is offset, minimizing the generation of residual stress during the rolling process, and homogenizing the distribution of residual stress. This ensures the stability of the wire during continuous rolling, thereby replacing the intermediate annealing step, simplifying the production process, shortening the production cycle, and reducing production costs.
[0036] While existing cold drawing processes for titanium alloy wires have solved the problems of multiple stretching and lubrication, the issue of multi-pass annealing during processing remains unresolved. This is the key problem addressed by the technical solution of this invention. Specifically, the invention employs two key features: a "round-ellipse-round" die design and a multi-angle composite roll. Based on this, the invention develops an improved two-roll composite die mill process for continuous rolling of titanium alloy wires. The resulting technical advantages are significant. The "round-ellipse-round" die design avoids localized stress concentration, and by precisely offsetting residual stress during each pass by changing the roll angle, the residual stress on the wire surface remains below the minimum acceptable residual stress level for continued processing during continuous rolling. This allows the wire to be formed in a single continuous rolling process without intermediate annealing.
[0037] In a specific implementation, the present invention can minimize the number of passes in the rolling process by controlling the elongation coefficient and the included angle of the roll centerline in the process parameters, thereby ensuring the quality of the wire and shortening the production cycle.
[0038] Below are specific examples and comparative examples used to prepare titanium alloy wires.
[0039] Example 1:
[0040] Prepare Φ6.0mm TC4 titanium alloy wire.
[0041] Billet grade: TB13, morphology: coiled wire, specification: Φ6.0mm. Cold rolling is performed using a modified two-roll compound pass mill, with a rolling method employing a circle-ellipse-circle structure design. The specific preparation includes the following steps:
[0042] 1. The first cold rolling pass has an elongation coefficient of 1.32 and an included angle of 90° between the roll centerlines;
[0043] 2. The second cold rolling pass has an elongation coefficient of 1.28 and an included angle of 40° between the roll centerlines;
[0044] 3. The third cold rolling pass has an elongation coefficient of 1.2 and an included angle of 90° between the roll centerlines;
[0045] 4. The fourth cold rolling pass has an elongation coefficient of 1.15 and an included angle of 140° between the roll centerlines;
[0046] 5. The fifth cold rolling pass has an elongation coefficient of 1.1 and an included angle of 90° between the roll centerlines;
[0047] After vacuum heat treatment at 700℃ for 60 min, a bright Φ2.5mm TC4 titanium alloy wire was obtained, and its mechanical properties are shown in Table 1.
[0048] Comparative Example 1:
[0049] Φ6.0mm TC4 titanium alloy wire was prepared by cold drawing;
[0050] Raw material grade: TC4, state: coiled wire, specification: Φ6.0mm.
[0051] Preliminary treatment: Grind off surface dirt such as rolled skin and oxide scale; wash, acid pickle, and repair damage until the surface is free of cracks and pits.
[0052] Hot drawing: Φ6.0→Φ5.5→Φ5.0mm;
[0053] Atmospheric furnace heat treatment: hold at 700℃ for 30 minutes.
[0054] Cold drawing (using graphite emulsion lubricant):
[0055] The first mold was drawn at low temperature with a deformation rate of 20%, annealed in an atmospheric furnace, and held at 700℃ for 60 minutes.
[0056] The second drawing was performed at low temperature with a deformation rate of 18%, followed by atmospheric furnace annealing and holding at 700℃ for 60 minutes.
[0057] The third mold was drawn at low temperature with a deformation rate of 15%, annealed in an atmospheric furnace, and held at 700℃ for 60 minutes.
[0058] Alkali washing and acid washing; vacuum annealing, holding at 700℃ for 60 min, and grinding to obtain Φ2.5mm TC4 titanium alloy wire. Its mechanical properties are shown in Table 1.
[0059] Example 2:
[0060] Prepare Φ7.0mm TB2 titanium alloy wire.
[0061] Billet grade: TB2, state: coiled wire, specification: Φ7.0mm. Cold rolling is performed using a modified two-roll compound pass mill, with a rolling method employing a circle-ellipse-circle structure design. The specific preparation includes the following steps:
[0062] 1. The first cold rolling pass has an elongation coefficient of 1.3 and an included angle of 90° between the roll centerlines;
[0063] 2. The second cold rolling pass has an elongation coefficient of 1.3 and an included angle of 45° between the roll centerlines;
[0064] 3. The third cold rolling pass has an elongation coefficient of 1.25 and an included angle of 90° between the roll centerlines;
[0065] 4. The fourth cold rolling pass has an elongation coefficient of 1.18 and an included angle of 145° between the roll centerlines;
[0066] 5. The fifth cold rolling pass has an elongation coefficient of 1.13 and an included angle of 90° between the roll centerlines;
[0067] After vacuum heat treatment at 600℃ for 90 min, a bright Φ4.0mm TB2 titanium alloy wire was obtained, and its mechanical properties are shown in Table 1.
[0068] Comparative Example 2:
[0069] Cold drawing to produce Φ7.0mm TB2 titanium alloy wire
[0070] Raw material grade: TB2, state: coiled wire, specification: Φ7.0mm.
[0071] Preliminary treatment: Grind off surface dirt such as rolled skin and oxide scale; wash, pickle, and repair until the surface is free of cracks and pits.
[0072] Hot drawing: Φ7.0→Φ6.5→Φ6.0mm;
[0073] Atmospheric furnace heat treatment: hold at 700℃ for 30 minutes.
[0074] Cold drawing (using graphite emulsion lubricant):
[0075] The first mold was drawn at low temperature with a deformation rate of 19%, annealed in an atmospheric furnace, and held at 700℃ for 60 minutes.
[0076] The second drawing was performed at low temperature with a deformation rate of 17%, followed by atmospheric furnace annealing and holding at 700℃ for 60 minutes.
[0077] The third low-temperature drawing process was carried out with a deformation rate of 16%, followed by atmospheric furnace annealing and holding at 7°C for 60 minutes.
[0078] Alkali washing and acid washing; vacuum annealing, holding at 700℃ for 60 min, and grinding to obtain Φ4.0mm TB2 titanium alloy wire. Its mechanical properties are shown in Table 1.
[0079] Example 3:
[0080] Prepare Φ5.0mm TA1 pure titanium wire.
[0081] Billet grade: TA1, state: coiled wire, specification: Φ5.0mm. Cold rolling is performed using a modified two-roll compound pass mill, with a rolling method employing a circle-ellipse-circle structure design. The specific preparation includes the following steps:
[0082] 1. The first cold rolling pass has an elongation coefficient of 1.3 and an included angle of 90° between the roll centerlines;
[0083] 2. The second cold rolling pass has an elongation coefficient of 1.28 and an included angle of 45° between the roll centerlines;
[0084] 3. The third cold rolling pass has an elongation coefficient of 1.2 and an included angle of 90° between the roll centerlines;
[0085] 4. The fourth cold rolling pass has an elongation coefficient of 1.16 and an included angle of 145° between the roll centerlines;
[0086] 5. The fifth cold rolling pass has an elongation coefficient of 1.1 and an included angle of 90° between the roll centerlines;
[0087] After vacuum heat treatment at 600℃ for 90 min, a bright Φ2mm TA1 pure titanium wire was obtained, and its mechanical properties are shown in Table 1.
[0088] Comparative Example 3:
[0089] Φ5.0mm TA1 pure titanium wire was prepared by cold drawing.
[0090] Raw material grade: TA1, state: coiled wire, specification: Φ6mm.
[0091] Preliminary treatment: Grind off surface dirt such as rolled skin and oxide scale; wash, pickle, and repair until the surface is free of cracks and pits.
[0092] Hot drawing: Φ5→Φ4.5→Φ4mm;
[0093] Atmospheric furnace heat treatment: hold at 700℃ for 30 minutes.
[0094] Cold drawing (using graphite emulsion lubricant):
[0095] The first mold was drawn at low temperature with a deformation rate of 20%, annealed in an atmospheric furnace, and held at 700℃ for 60 minutes.
[0096] The second drawing was performed at low temperature with a deformation rate of 15%, followed by atmospheric furnace annealing and holding at 700℃ for 60 minutes.
[0097] The third mold was drawn at low temperature with a deformation rate of 10%, annealed in an atmospheric furnace, and held at 7°C for 60 minutes.
[0098] Alkali washing and acid washing; vacuum annealing, holding at 700℃ for 60 min, and grinding to obtain Φ2.0mm TA1 pure titanium wire. Its mechanical properties are shown in Table 1.
[0099] Table 1 Comparison of Titanium Alloy Wire Properties
[0100]
[0101] Compared with the comparative technical solution, the present invention significantly omits the annealing process during each rolling. The TC4 wire sample obtained by the present invention shows that, compared with the sample of the prior art, the tensile strength and elongation are increased by more than 20%, while ensuring wire quality and shortening the production cycle. As can be seen from the test table in the embodiments, compared with the traditional wire drawing process, the titanium alloy wire prepared by the high-quality titanium and titanium alloy roller drawing method provided by the present invention maintains the original high strength while exhibiting better plasticity, and its tensile strength and plasticity are better matched.
[0102] The preferred embodiments of the present invention have been described above, but are not intended to limit the invention. Those skilled in the art can make modifications and variations to the embodiments disclosed herein without departing from the scope and spirit of the invention.
Claims
1. A high-quality titanium and titanium alloy rod drawing method, which is processed using a modified two-roller compound groove rolling mill, characterized in that, The following operations are performed on titanium and titanium alloy wire blanks: (1) First cold rolling; (2) Second cold rolling; (3) Third cold rolling; (4) Fourth cold rolling; (5) Fifth cold rolling; (6) Vacuum annealing; Among them, the total reduction in the wire drawing cross section is up to 80%, and the single-pass elongation coefficient is 1.1 to 1.34; The elongation coefficient of the first cold rolling pass is 1.28–1.32, and the included angle of the roll centerlines is 90°; the elongation coefficient of the second cold rolling pass is 1.28–1.34, and the included angle of the roll centerlines is 40–50°; the elongation coefficient of the third cold rolling pass is 1.2–1.3, and the included angle of the roll centerlines is 90°; the elongation coefficient of the fourth cold rolling pass is 1.15–1.2, and the included angle of the roll centerlines is 130–140°; the elongation coefficient of the fifth cold rolling pass is 1.1–1.15, and the included angle of the roll centerlines is 90°. The improved two-roll compound pass mill consists of six sets of rolls, the first five of which are compound rolls and the last set is a horizontal roll. The rolling pass adopts a circular-elliptical-circular structure design. The sixth set of rolls all have circular passes with an elongation coefficient of 1 and a roll centerline angle of 45°.
2. The method of claim 1, wherein the high quality titanium and titanium alloy roll die wire drawing method is characterized by, The annealing is performed in a vacuum furnace at a temperature of 600-800 °C for a time of 30-90 min and a vacuum of 10 -3 Pa.