A method for low-cost rolling of wide titanium strip using an 18-roll single-stand mill

Abstract

This invention relates to a low-cost method for rolling wide titanium strip using an 18-roll single-stand rolling mill, belonging to the field of titanium rolling technology. The method includes the following steps: S1. Pre-rolling preparation: selecting an 18-roll mill, welding the ends of the hot-rolled titanium coil to guide the strip, and grinding it smooth; S2. Cold rolling: reciprocating multiple passes of rolling the hot-rolled titanium coil on the 18-roll mill; S3. Degreasing treatment; S4. Vacuum annealing; S5. Stretching and trimming to obtain the finished titanium coil. This method combines the deformation characteristics of the 18-roll mill and the titanium coil strip, achieving the transformation from hot coil to cold-rolled finished product in a single rolling pass on the 18-roll mill. This results in greater deformation than a 6-roll mill and lower rolling costs than a 20-roll mill. Simultaneously, three-stage vacuum annealing controls the mechanical properties of the titanium strip coil, reducing the strength difference between the inner and outer coils, and controlling the strength fluctuation within the same coil to ±15MPa. This solves the technical problems of small deformation and poor shape control in existing thin-gauge titanium strip rolling processes, resulting in high efficiency and low cost.

Description

Technical Field

[0001] This invention relates to a low-cost method for rolling wide titanium strip using an 18-roll single-stand mill, belonging to the field of titanium rolling technology. Background Technology

[0002] Titanium possesses advantages such as low density, high specific strength, good corrosion resistance, and excellent high-temperature performance, making it widely used in aerospace, petrochemical, and electronics industries. Cold-rolled titanium strip accounts for approximately 12% of the total titanium material production. It is characterized by high technological content and difficulty in manufacturing, making it a high-value-added product within the titanium material category.

[0003] In the field of titanium strip cold rolling, 6-roll and 20-roll mills are two mainstream technical routes. The 6-roll mill has advantages such as simple structure, low cost, flexible layout, and the ability to operate as a single machine, reversible, or continuous mill, making it widely used for rolling medium-thick titanium strips. For example, the method for cold rolling pure titanium strip disclosed in Chinese patent CN102002657A suffers from excessive rolling pressure, insufficient reduction capacity, poor shape control, and is prone to edge thinning and rib formation defects when rolling thin titanium strips. The 20-roll Sendzimir mill, with its tower-type roll system and small work rolls, is particularly suitable for rolling thin titanium strips. For example, the method for rolling pure titanium strip using a Sendzimir 20-roll mill disclosed in Chinese patent CN106734204A, however, suffers from difficulties in threading the strip, a roll changing time of 4-6 hours, and equipment costs more than three times that of a 6-roll mill. Furthermore, it is less economical for rolling medium-thick titanium strips, and its energy consumption is higher than that of a 6-roll mill.

[0004] The 18-roll mill, through its small roll diameter and side-supported roll system design, reduces the work roll diameter by 40% compared to the 6-roll mill. Combined with segmented back-bearing lateral support, this significantly reduces rolling force. Simultaneously, the open stand design improves strip threading efficiency by 50% compared to the 20-roll mill, and shortens roll changeover time to one hour. The 18-roll mill avoids the horizontal deflection defects of the 6-roll mill through structural reconstruction and overcomes the limitations of the closed structure of the 20-roll mill. The 18-roll mill is widely used in stainless steel continuous rolling and high-strength steel rolling. However, there is no precedent for 18-roll cold rolling of titanium strip. Therefore, developing a method for cold rolling titanium strip using an 18-roll mill is of great significance for expanding the cold rolling production mode of titanium strip. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing thin-gauge titanium strip has small deformation and poor shape control, resulting in high efficiency and low cost.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for low-cost rolling of wide titanium strip using an 18-roll single-stand rolling mill, comprising the following steps: S1. Pre-rolling preparation: Select an 18-roll mill according to the thickness specifications of the finished titanium strip, and weld the start and end of the hot-rolled titanium coil with the lead strip. After welding, grind the weld surface smooth. S2. Cold rolling: According to the finished product specifications, the hot-rolled titanium coil is rolled repeatedly in multiple passes on an 18-roll mill. The deformation of the first pass is 7% to 12%, and the rolling speed is 60 to 80 m / min. Then the deformation of the next pass is increased to 15% to 18%, and the rolling speed is increased to 120 to 150 m / min. Finally, the reduction of the next pass is gradually reduced, and the reduction of the last pass is controlled at 7% to 10%, and the rolling speed is reduced to 100 to 120 m / min. S3. Degreasing: The cold-rolled titanium coil obtained in step S2 is degreased on the degreasing line. S4. Vacuum annealing: Place the degreased titanium coil in a vacuum annealing furnace for annealing. S5. Straighten and trim the edges: Straighten and trim the annealed titanium coil on a leveling line to obtain the finished titanium coil.

[0007] In step S1 of the above method, the roll system of the 18-roll mill is selected according to the thickness specification of the finished titanium strip: when the thickness of the finished titanium strip is 0.8 to 2.5 mm, roll system I is selected, with a working roll diameter of 170 to 140 mm, a working roll roughness of 0.3 to 0.5 μm, and an intermediate roll diameter of 380 to 345 mm; when the thickness of the finished titanium strip is 0.3 to 0.8 mm, roll system II is selected, with a working roll diameter of 150 to 120 mm, a working roll roughness of 0.2 to 0.4 μm, and an intermediate roll diameter of 365 to 345 mm.

[0008] In step S1 of the above method, the concentration of the emulsion is 2.8% to 3.5%, and the temperature of the emulsion is 45 to 55°C.

[0009] In step S1 of the above method, the hot-rolled titanium coil is designated as TA1, with the following elemental mass fraction requirements: C < 0.02%, N < 0.005%, H < 0.002%, O < 0.05%, Fe < 0.02%, other impurity elements < 0.02%, and oxygen equivalent ≤ 0.08%. The oxygen equivalent calculation formula is: [O] = 2.5 × N + 1.0 × O + 0.7 × C + 0.5 × Fe. The hot-rolled titanium coil is in an annealed and pickled state, with a thickness of 2.8–6.0 mm and a thickness tolerance of ±0.22 mm, and a width of 1260–1530 mm. Mechanical properties include a yield strength R... p0.2 160~280MPa, tensile strength Rm: 280~400MPa, elongation after fracture A>50%, grain size 6.0~9.0; the lead strip material is TA1, the thickness difference between the lead strip and the hot-rolled titanium coil is ≤0.6mm, the lead strip width is 30~50mm wider than the hot-rolled titanium coil, and the lead strip length is 15~20m.

[0010] In step S2 of the above method, the tension before and after the rolling process is referenced to the yield strength R of the titanium coil. p0.2 The pretension is (0.3~0.5)×R p0.2 ×thickness × width, back tension is (0.2~0.4) × R p0.2 ×thickness × width.

[0011] Furthermore, in step S2 of the above method, the front and back tension coefficients for the first and last passes are 0.3 and 0.2, respectively; when the titanium coil thickness is less than 0.6 mm, the front and back tension coefficients are 0.4 and 0.3, respectively.

[0012] In step S3 of the above method, the degreasing speed is controlled at 20-30 m / min, and the speed is reduced by 30% at the beginning and end of the roll for 20 m; the unwinding tension is (1.2-3.5) × thickness × width, and the winding tension is (1.5-4.0) × thickness × width.

[0013] In step S4 of the above method, a three-stage heating process is adopted: in the first stage, the furnace temperature is raised to 200℃ at a rate of 100℃ / s and held for 6-8 hours; in the second stage, the furnace temperature is raised to 450-480℃ at a rate of 90-120℃ / s and held for 10-12 hours; and in the third stage, the furnace temperature is raised to 600-650℃ at a rate of 10-15℃ / s and held for 12-15 hours.

[0014] In step S4 of the above method, the initial vacuum degree of the vacuum annealing furnace is ≤1×10⁻⁶. -2 Pa, the vacuum degree inside the furnace during the heating process must be ≤5×10. -2 Pa.

[0015] In step S5 of the above method, the tension is (0.5~0.7)×R. p0.2 ×thickness×width, the straightening deformation is controlled at 0.2%~0.5%. For titanium coils with a thickness of 0.3~1.0mm, the straightening deformation is 0.2%~0.30%, and the straightening speed is 30~50m / min. For titanium coils with a thickness of 1.0~2.5mm, the straightening deformation is 0.35%~0.5%, and the straightening speed is 40~70m / min.

[0016] The beneficial effects of this invention are: (1) This method combines the deformation characteristics of the 18-roll mill and titanium coil strip, and realizes the rolling of hot coil into cold rolled finished product in one rolling stroke on the 18-roll mill. The deformation amount is larger than that of the six-roll mill and the rolling cost is lower than that of the 20-roll mill, thus expanding the cold rolling method of titanium coil.

[0017] (2) This method controls the composition, properties and structure of hot-rolled titanium coils and designs a cold rolling process in combination with the characteristics of an 18-roll mill, which can produce finished titanium coils with a width of 1250-1520 mm and a thickness of 0.3-2.5 mm.

[0018] (3) This method controls the mechanical properties of titanium plate rolls through three-stage vacuum annealing, reduces the strength difference between the inner and outer rolls of titanium rolls, and can control the strength fluctuation of the same roll by ±15MPa. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments.

[0020] The present invention provides a low-cost method for rolling wide titanium strip using an 18-roll single-stand rolling mill, comprising the following steps: S1. Pre-rolling preparation: Select an 18-roll mill according to the thickness specifications of the finished titanium strip, and weld the start and end of the hot-rolled titanium coil with the lead strip. After welding, grind the weld surface smooth. S2. Cold rolling: According to the finished product specifications, the hot-rolled titanium coil is rolled repeatedly in multiple passes on an 18-roll mill. The deformation of the first pass is 7% to 12%, and the rolling speed is 60 to 80 m / min. Then the deformation of the next pass is increased to 15% to 18%, and the rolling speed is increased to 120 to 150 m / min. Finally, the reduction of the next pass is gradually reduced, and the reduction of the last pass is controlled at 7% to 10%, and the rolling speed is reduced to 100 to 120 m / min. S3. Degreasing: The cold-rolled titanium coil obtained in step S2 is degreased on the degreasing line. S4. Vacuum annealing: Place the degreased titanium coil in a vacuum annealing furnace for annealing. S5. The annealed titanium coil is straightened and trimmed on a leveling line to obtain the finished titanium coil. Those skilled in the art will understand that the 18-roll mill, through its small roll diameter and side-supported roll system design, reduces the work roll diameter by 40% compared to a 6-roll mill. Combined with segmented backing bearings for lateral support, this significantly reduces rolling force. Simultaneously, the open stand design improves strip threading efficiency by 50% compared to a 20-roll mill, shortening roll change time to 1 hour. The 18-roll mill, through structural reconstruction, avoids the horizontal deflection defects of a 6-roll mill and overcomes the limitations of the closed structure of a 20-roll mill. It is widely used in stainless steel continuous rolling and high-strength steel rolling. Currently, there is no precedent for cold rolling of titanium strip using an 18-roll mill; therefore, this method preferably uses an 18-roll mill for cold rolling titanium strip. Step S1 is pre-rolling preparation. The 18-roll mill is selected based on the thickness specifications of the finished titanium strip, and the mill roll system and emulsion parameters are determined. Simultaneously, to ensure smooth rolling, the hot-rolled titanium coil needs to be welded to the lead strip in advance. Step S2 involves rolling, which is performed through multiple reciprocating rolling passes. The rolling deformation and speed are controlled to ensure cold-rolled quality. Specifically, the first pass has a rolling deformation of 7%–12% and a rolling speed of 60–80 m / min. This low rolling speed and small deformation improve the shape and thickness tolerance of the hot-rolled titanium coil, enhancing the stability of subsequent rolling passes. Then, the rolling deformation is increased to 15%–18%, and the rolling speed is increased to 120–150 m / min. This high rolling speed and large deformation allow for efficient thinning of the titanium coil. Finally, the reduction is gradually reduced to control the rolling stability and thickness uniformity of the titanium coil. In the final pass, the reduction is controlled at 7%–10%, and the rolling speed is reduced to 100–120 m / min to control the thickness tolerance of the finished titanium coil. Simultaneously, padding paper is applied to the entire coil to prevent interlayer damage caused by tension relief. Step S3 involves degreasing the cold-rolled titanium coil on a degreasing line to ensure the surface quality of the titanium strip. Step S4 places the degreased titanium coil in a vacuum annealing furnace, employing a three-stage heating process to ensure the uniformity of the titanium coil's microstructure and properties. Step S5 involves tensioning and trimming the edges to ensure the titanium strip meets the required specifications. The finished titanium coil in Step S5 has a thickness of 0.3–2.5 mm, with a thickness tolerance of ±0.015 mm for 0.3–0.8 mm, ±0.03 mm for 0.8–1.5 mm, and ±0.05 mm for 1.5–2.5 mm. The width is 1250–1520 mm, and the yield strength R... p0.2 160~300MPa, tensile strength R m 280~420MPa, elongation after fracture A>46%, strength fluctuation within the same roll ±15MPa.

[0021] Preferably, in step S1 of the above method, the roll system of the 18-roll mill is selected according to the thickness specification of the finished titanium strip: when the thickness of the finished titanium strip is 0.8 to 2.5 mm, roll system I is selected, with a working roll diameter of 170 to 140 mm, a working roll roughness of 0.3 to 0.5 μm, and an intermediate roll diameter of 380 to 345 mm; when the thickness of the finished titanium strip is 0.3 to 0.8 mm, roll system II is selected, with a working roll diameter of 150 to 120 mm, a working roll roughness of 0.2 to 0.4 μm, and an intermediate roll diameter of 365 to 345 mm. Those skilled in the art will understand that, in order to ensure rolling quality, this method actually selects different roll systems for an 18-roll mill based on the thickness of the titanium strip. Specifically, when the finished titanium strip thickness is 0.8–2.5 mm, roll system I is selected, with a work roll diameter of 170–140 mm, a work roll roughness of 0.3–0.5 μm, and an intermediate roll diameter of 380–345 mm; when the finished titanium strip thickness is 0.3–0.8 mm, roll system II is selected, with a work roll diameter of 150–120 mm, a work roll roughness of 0.2–0.4 μm, and an intermediate roll diameter of 365–345 mm.

[0022] Preferably, in step S1 of the above method, the emulsion concentration is 2.8%–3.5%, and the emulsion temperature is 45–55°C. Those skilled in the art will understand that controlling the emulsion concentration and temperature is to better coordinate with the operation of the 18-roll mill and improve rolling quality. Specifically, the preferred emulsion concentration is 2.8%–3.5%, and the emulsion temperature is 45–55°C.

[0023] Preferably, in step S1 of the above method, the hot-rolled titanium coil is of grade TA1, with the following elemental mass fraction requirements: C < 0.02%, N < 0.005%, H < 0.002%, O < 0.05%, Fe < 0.02%, other impurity elements < 0.02%, and oxygen equivalent ≤ 0.08%. The oxygen equivalent calculation formula is: [O] = 2.5 × N + 1.0 × O + 0.7 × C + 0.5 × Fe. The hot-rolled titanium coil is in an annealed and pickled state, with a thickness of 2.8–6.0 mm, a thickness tolerance of ±0.22 mm, and a width of 1260–1530 mm. The mechanical property requirements include a yield strength R... p0.2 The tensile strength (Rm) is 280–400 MPa, the elongation after fracture (A) is greater than 50%, and the grain size is 6.0–9.0. The lead strip material is TA1, the thickness difference between the lead strip and the hot-rolled titanium coil is ≤0.6 mm, the lead strip width is 30–50 mm wider than the hot-rolled titanium coil, and the lead strip length is 15–20 m. Those skilled in the art will understand that this method further optimizes the grade, chemical composition, and related performance parameters of the hot-rolled titanium coil for later comparison.

[0024] Preferably, the tension before and after the rolling process in step S2 of the above method is referenced to the yield strength R of the titanium coil. p0.2The pretension is (0.3~0.5)×R p0.2 ×thickness × width, back tension is (0.2~0.4) × R p0.2 ×thickness × width. Those skilled in the art will understand that the pre- and post-rolling tensions in this method are respectively: pre-tension is (0.3~0.5) × R. p0.2 ×thickness × width, back tension is (0.2~0.4) × R p0.2 ×thickness × width.

[0025] Preferably, in step S2 of the above method, the pre- and post-tension coefficients for the first and last passes are 0.3 and 0.2, respectively; when the titanium coil thickness is <0.6 mm, the pre- and post-tension coefficients are 0.4 and 0.3, respectively. Those skilled in the art will understand that this method preferably uses pre- and post-tension coefficients of 0.3 and 0.2 for the first and last passes to ensure rolling stability and the thickness tolerance of the finished product. When the titanium coil thickness is <0.6 mm, the pre- and post-tension coefficients are 0.4 and 0.3, respectively, to avoid rib formation in the titanium coil.

[0026] Preferably, in step S3 of the above method, the degreasing speed is controlled at 20-30 m / min, with a 30% reduction in speed at the beginning and end of the roll; the unwinding tension is (1.2-3.5) × thickness × width, and the winding tension is (1.5-4.0) × thickness × width. Those skilled in the art will understand that the degreasing speed is controlled at 20-30 m / min, with a 30% reduction in speed at the beginning and end of the roll; the unwinding tension is (1.2-3.5) × thickness × width, and the winding tension is (1.5-4.0) × thickness × width. The coefficients of unwinding tension and winding tension are related to the thickness of the titanium coil: 0.3–0.4 mm thickness, unwinding tension coefficient 3.5, winding tension coefficient 4.0; 0.4–0.8 mm thickness, unwinding tension coefficient 2.5, winding tension coefficient 3.0; 0.8–1.5 mm thickness, unwinding tension coefficient 2.0, winding tension coefficient 2.5; 1.5–2.5 mm thickness, unwinding tension coefficient 1.2, winding tension coefficient 1.5. By controlling the unwinding tension, winding tension, and degreasing speed, degreasing stability can be ensured while avoiding secondary scratches on the surface.

[0027] Preferably, step S4 of the above method employs a three-stage heating process: the first stage raises the furnace temperature to 200℃ at a rate of 100℃ / s and holds it for 6–8 hours; the second stage raises the furnace temperature to 450–480℃ at a rate of 90–120℃ / s and holds it for 10–12 hours; and the third stage raises the furnace temperature to 600–650℃ at a rate of 10–15℃ / s and holds it for 12–15 hours. Those skilled in the art will understand that the heating process requires a vacuum degree ≤5×10⁻⁶ inside the furnace. -2 Pa. The three-stage heating process involves prolonged holding at the recrystallization temperature to ensure uniform temperature between the inner and outer rings of the titanium coil. Then, the temperature is increased above the recrystallization temperature to soften the titanium coil through recrystallization, thus guaranteeing the uniformity of the titanium coil's microstructure and properties.

[0028] In step S4 of the above method, the initial vacuum degree of the vacuum annealing furnace is ≤1×10⁻⁶. -2 Pa, the vacuum degree inside the furnace during the heating process must be ≤5×10. -2 Pa. Those skilled in the art will understand that the initial vacuum level of the vacuum annealing furnace is further limited to ≤1×10⁻⁶. -2 Pa, the vacuum degree inside the furnace during the heating process must be ≤5×10. -2 Pa is used to ensure the quality of annealing.

[0029] Preferably, the tension in step S5 of the above method is (0.5~0.7)×R. p0.2 The tensioning deformation is controlled at 0.2%–0.5% for titanium coils with a thickness of 0.3–1.0 mm, with a tensioning deformation of 0.2%–0.30% and a tensioning speed of 30–50 m / min. For titanium coils with a thickness of 1.0–2.5 mm, the tensioning deformation is 0.35%–0.5% and the tensioning speed is 40–70 m / min. Those skilled in the art will understand that, to obtain titanium strips that meet the requirements, this method preferably uses a tensioning tension of (0.5–0.7) × R. p0.2 ×thickness×width, the straightening deformation is controlled at 0.2%~0.5%. For titanium coils with a thickness of 0.3~1.0mm, the straightening deformation is 0.2%~0.30%, and the straightening speed is 30~50m / min. For titanium coils with a thickness of 1.0~2.5mm, the straightening deformation is 0.35%~0.5%, and the straightening speed is 40~70m / min.

[0030] Example 1 The incoming material is grade TA1, with a chemical composition of C: 0.011%, N: 0.003%, H: 0.0010%, O: 0.040%, Fe: 0.011%, and oxygen equivalent of 0.06%. The incoming material thickness is 2.8 mm, with a thickness tolerance of ±0.15 mm, a width of 1260 mm, a yield strength of 220 MPa, a tensile strength of 360 MPa, an elongation after fracture of 55%, and a grain size of 6.5. An 18-roll system (roll II) is used, with a work roll diameter of 150 mm, a work roll surface roughness of 0.22 μm, and an intermediate roll diameter of 365 mm. The emulsion concentration is 3.2%, and the emulsion temperature is 48℃. Lead strips are welded to the beginning and end of the hot-rolled titanium coil, and the weld surface is polished smooth after welding. The lead strip material is TA1, with a lead strip thickness of 2.5 mm, a lead strip diameter of 1300 mm, and a lead strip length of 20 m. The cold rolling process parameters are shown in the table below.

[0031]

[0032] Cold-rolled titanium coils undergo degreasing on a degreasing line. The degreasing speed is 20 m / min, and the speed at the coil head and tail is 14 m / min for every 20 m of degreasing. The unwinding tension is 1320 DaN, and the winding tension is 1512 DaN. The degreased titanium coils are then placed in a vacuum annealing furnace and heated in three stages. In the first stage, the furnace temperature is raised to 200℃ at a rate of 100℃ / s and held for 6 hours. In the second stage, the furnace temperature is raised to 450℃ at a rate of 90℃ / s and held for 10 hours. In the third stage, the furnace temperature is raised to 600℃ at a rate of 10℃ / s and held for 12 hours. The vacuum level inside the furnace during the heating process is 2.5 × 10⁻⁶. -2 Pa. The annealed titanium coil is straightened and trimmed on a leveling line to obtain the finished titanium coil. The straightening tension is 65 kN, the straightening deformation is 0.23%, and the straightening speed is 30 m / min. The finished titanium coil has a thickness of 0.3 mm, a thickness tolerance of ±0.013 mm, a width of 1520 mm, a yield strength of 275 MPa, a tensile strength of 384 MPa, an elongation after fracture of 52%, and a strength fluctuation of ±12 MPa within the same coil.

[0033] Example 2 The incoming material is grade TA1, with the following chemical composition: C: 0.010%, N: 0.003%, H: 0.0009%, O: 0.036%, Fe: 0.010%, and oxygen equivalent: 0.06%. The incoming material thickness is 3.75 mm, with a thickness tolerance of ±0.20 mm, a width of 1350 mm, a yield strength of 200 MPa, a tensile strength of 352 MPa, an elongation after fracture of 56%, and a grain size of 6.0. An 18-roll system (roll II) is used, with a work roll diameter of 142 mm, a work roll surface roughness of 0.23 μm, and an intermediate roll diameter of 358 mm. The emulsion concentration is 3.2%, and the emulsion temperature is 46℃. Lead strips are welded to the beginning and end of the hot-rolled titanium coil. After welding, the weld surface is ground smooth. The lead strip material is TA1, with a lead strip thickness of 3.5 mm, a lead strip diameter of 1380 mm, and a lead strip length of 18 m. The cold rolling process parameters are shown in the table below.

[0034]

[0035] Cold-rolled titanium coils undergo degreasing on a degreasing line. The degreasing speed is 30 m / min, with a speed of 21 m / min for both the coil head and tail. The unwinding tension is 1680 DaN, and the winding tension is 2025 DaN. The degreased titanium coils are then placed in a vacuum annealing furnace for three-stage heating. In the first stage, the furnace temperature is raised to 200℃ at a rate of 100℃ / s and held for 8 hours. In the second stage, the furnace temperature is raised to 480℃ at a rate of 120℃ / s and held for 12 hours. In the third stage, the furnace temperature is raised to 620℃ at a rate of 15℃ / s and held for 12 hours. The vacuum level inside the furnace during the heating process is 3.2 × 10⁻⁶. -2 Pa. The annealed titanium coil is straightened and trimmed on a leveling line to obtain the finished titanium coil. The straightening tension is 92 kN, and the straightening deformation is 0.26%. The finished titanium coil has a thickness of 0.5 mm, a thickness tolerance of ±0.015 mm, a width of 1340 mm, a yield strength of 236 MPa, a tensile strength of 350 MPa, an elongation after fracture of 53%, and a strength fluctuation of ±13 MPa within the same coil.

[0036] Example 3 The incoming material is grade TA1, with a chemical composition of C: 0.011%, N: 0.003%, H: 0.0013%, O: 0.048%, Fe: 0.020%, and oxygen equivalent of 0.08%. The incoming material thickness is 6.0 mm, with a thickness tolerance of ±0.22 mm, a width of 1530 mm, a yield strength of 280 MPa, a tensile strength of 400 MPa, an elongation after fracture of 52%, and a grain size of 9.0. An 18-roll system (roll I) is used, with a work roll diameter of 170 mm, a work roll surface roughness of 0.42 μm, and an intermediate roll diameter of 380 mm. The emulsion concentration is 2.8%, and the emulsion temperature is 53℃. Lead strips are welded to the beginning and end of the hot-rolled titanium coil, and the weld surface is polished smooth after welding. The lead strip material is TA1, with a lead strip thickness of 6.0 mm, a lead strip diameter of 1560 mm, and a lead strip length of 10 m. The cold rolling process parameters are shown in the table below.

[0037]

[0038] Cold-rolled titanium coils undergo degreasing on a degreasing line. The degreasing speed is 20 m / min, and the speed at the coil head and tail is 14 m / min for every 20 m of degreasing. The unwinding tension is 4590 DaN, and the winding tension is 5740 DaN. The degreased titanium coils are then placed in a vacuum annealing furnace for three-stage heating. In the first stage, the furnace temperature is raised to 200℃ at a rate of 100℃ / s and held for 7 hours. In the second stage, the furnace temperature is raised to 460℃ at a rate of 100℃ / s and held for 12 hours. In the third stage, the furnace temperature is raised to 650℃ at a rate of 12℃ / s and held for 15 hours. The vacuum degree inside the furnace during the heating process is 4.5 × 10⁻⁶. - 2 Pa. The annealed titanium coil was straightened and trimmed on a leveling line to obtain the finished titanium coil. The straightening tension was 560 kN, the straightening deformation was 0.42%, and the straightening speed was 46 m / min. The finished titanium coil had a thickness of 2.5 mm, a thickness tolerance of ±0.05 mm, a width of 1520 mm, a yield strength of 289 MPa, a tensile strength of 402 MPa, an elongation after fracture of 49%, and a strength fluctuation of ±15 MPa within the same coil.

Claims

1. A method for low-cost rolling of wide titanium strip using an 18-roll single-stand rolling mill, characterized in that... Includes the following steps: S1. Pre-rolling preparation: Select an 18-roll mill according to the thickness specifications of the finished titanium strip, and weld the start and end of the hot-rolled titanium coil with the lead strip. After welding, grind the weld surface smooth. S2. Cold rolling: According to the finished product specifications, the hot-rolled titanium coil is rolled repeatedly in multiple passes on an 18-roll mill. The deformation of the first pass is 7% to 12%, and the rolling speed is 60 to 80 m / min. Then the deformation of the next pass is increased to 15% to 18%, and the rolling speed is increased to 120 to 150 m / min. Finally, the reduction of the next pass is gradually reduced, and the reduction of the last pass is controlled at 7% to 10%, and the rolling speed is reduced to 100 to 120 m / min. S3. Degreasing: The cold-rolled titanium coil obtained in step S2 is degreased on the degreasing line. S4. Vacuum annealing: Place the degreased titanium coil in a vacuum annealing furnace for annealing. S5. Straighten and trim the edges: Straighten and trim the annealed titanium coil on the leveling line to obtain the finished titanium coil. In step S1, the roll system of the 18-roll mill is selected according to the thickness specifications of the finished titanium strip: when the thickness of the finished titanium strip is 0.8–2.5 mm, roll system I is selected, with a work roll diameter of 170–140 mm, a work roll roughness of 0.3–0.5 μm, and an intermediate roll diameter of 380–345 mm; when the thickness of the finished titanium strip is 0.3–0.8 mm, roll system II is selected, with a work roll diameter of 150–120 mm, a work roll roughness of 0.2–0.4 μm, and an intermediate roll diameter of 365–345 mm; the hot-rolled titanium coil grade is TA1. The elemental mass fraction requirements are: C < 0.02%, N < 0.005%, H < 0.002%, O < 0.05%, Fe < 0.02%, other impurity elements < 0.02%, oxygen equivalent requirement ≤ 0.08%, oxygen equivalent calculation formula: [O] = 2.5 × N + 1.0 × O + 0.7 × C + 0.5 × Fe; and the hot-rolled titanium coil is in the annealed and pickled state, with a thickness of 2.8–6.0 mm, a thickness tolerance of ±0.22 mm, and a width of 1260–1530 mm; mechanical property requirements, yield strength R p0.2 : 160~280MPa, tensile strength Rm: 280~400MPa, elongation after fracture A>50%, grain size 6.0~9.0; the lead strip material is TA1, the thickness difference between the lead strip and the hot-rolled titanium coil is ≤0.6mm, the lead strip width is 30~50mm wider than the hot-rolled titanium coil, and the lead strip length is 15~20m; The tension before and after rolling in step S2 is referenced to the yield strength R of the titanium coil. p0.2 The pretension is (0.3~0.5)×R p0.2 ×thickness × width, back tension is (0.2~0.4) × R p0.2 ×thickness × width; In step S4, three-stage heating is used. In the first stage, the furnace temperature is raised to 200℃ at a rate of 100℃ / s and held for 6-8 hours. In the second stage, the furnace temperature is raised to 450-480℃ at a rate of 90-120℃ / s and held for 10-12 hours. In the third stage, the furnace temperature is raised to 600-650℃ at a rate of 10-15℃ / s and held for 12-15 hours. In step S5, the tension is (0.5~0.7)×R. p0.2 ×thickness×width, the straightening deformation is controlled at 0.2%~0.5%. For titanium coils with a thickness of 0.3~1.0mm, the straightening deformation is 0.2%~0.30%, and the straightening speed is 30~50m / min. For titanium coils with a thickness of 1.0~2.5mm, the straightening deformation is 0.35%~0.5%, and the straightening speed is 40~70m / min.

2. The method for low-cost rolling of wide titanium strip using an 18-roll single-stand rolling mill according to claim 1, characterized in that: In step S1, the emulsion concentration is 2.8%–3.5%, and the emulsion temperature is 45–55°C.

3. The method for low-cost rolling of wide titanium strip using an 18-roll single-stand rolling mill according to claim 1, characterized in that: In step S2, the front and back tension coefficients for the first and last passes are 0.3 and 0.2, respectively; when the titanium coil thickness is less than 0.6 mm, the front and back tension coefficients are 0.4 and 0.3, respectively.

4. The method for low-cost rolling of wide titanium strip using an 18-roll single-stand rolling mill according to claim 1, characterized in that: In step S3, the degreasing speed is controlled at 20-30 m / min, and the speed is reduced by 30% at the beginning and end of the roll for 20 m; the unwinding tension is (1.2-3.5) × thickness × width, and the winding tension is (1.5-4.0) × thickness × width.

5. The method for low-cost rolling of wide titanium strip using an 18-roll single-stand rolling mill according to claim 1, characterized in that: The initial vacuum degree of the vacuum annealing furnace in step S4 is ≤1×10 -2 Pa, the vacuum degree inside the furnace during the heating process must be ≤5×10. - 2 Pa.

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