A short process preparation method of titanium plate with weak anisotropy and high strength and plasticity

Abstract

The application provides a short-process preparation method of titanium plate with weak anisotropy and high strength and plasticity, which comprises the following steps: firstly, high-purity titanium sponge is smelted in an electron beam cold hearth furnace to obtain large-scale straight rolling flat ingot after face milling and grinding; then, the straight rolling flat ingot is cut into several block billets with appropriate specifications, the block billets are heated to above the beta phase transition point, and then two-time hot rolling is performed, the first-time hot rolling direction is perpendicular to the second-time hot rolling direction, after each pass rolling, straightening, correction, acid-alkali cleaning and grinding treatment are performed on the plate billet; then, annealing treatment is performed on the hot-rolled plate billet; finally, multi-pass alternating reversing cryogenic rolling is performed on the annealed plate billet, and the finished product titanium plate is obtained. The method adopts the electron beam cold hearth smelting technology to smelt the flat ingot for rolling in one time, reduces the process, greatly reduces the production cycle and cost; meanwhile, the reversing hot rolling, annealing treatment and alternating reversing cryogenic rolling process are combined, and the short-process preparation of the titanium plate with weak anisotropy and high strength and plasticity is realized.

Description

Technical Field

[0001] This invention relates to the field of high-strength titanium-plastic sheet preparation technology, specifically a short-process preparation method for high-strength titanium-plastic sheets with weak anisotropy. Background Technology

[0002] Titanium possesses lightweight, high specific strength, and excellent corrosion resistance, making it a promising candidate for applications in aerospace, shipbuilding, petrochemicals, metallurgy, and power generation. However, the continuously rising price of raw material sponge titanium makes it difficult to meet the demand for low-cost titanium plates. Reducing the smelting, billet preparation, and processing costs of titanium plates is a crucial research direction that urgently needs attention. Traditional titanium smelting methods primarily employ vacuum arc remelting (VAR), where raw materials are pressed and welded together with electrodes, undergoing 2-3 smelting processes to prepare titanium alloy ingots, followed by multi-fire forging, rolling, and grinding to obtain rolled slabs. This preparation method has the following drawbacks:

[0003] (1) The production process is long, the material loss is large, and the cost is high;

[0004] (2) Due to the hexagonal crystal structure and rolling texture of titanium, it exhibits strong anisotropy, and significant earing is prone to occur during the forging and rolling process, thus limiting the development and application of titanium. Currently, the commonly used rolling method for titanium plate manufacturing is unidirectional longitudinal rolling. During unidirectional longitudinal rolling of titanium plates, the pyramidal surface...<c+a> Slip coordination of c-axis motion easily produces a pyramidal texture, making the operable slip systems include easily activated cylindrical slip and more difficult-to-activate basal slip.<c+a> The slip ultimately causes the titanium plate to exhibit strong anisotropy in its microstructure.

[0005] (3) When preparing titanium plates by rolling, plasticity is always sacrificed while improving the strength of the titanium plates, so it is impossible to obtain titanium plates with both high strength and high plasticity. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a short-process preparation method for high-strength PVC-U sheets with weak anisotropy. This method employs electron beam cold hearth melting (EB) technology to melt flat ingots for rolling in a single process, reducing steps and significantly lowering the production cycle and cost. Simultaneously, it combines reversing hot rolling, annealing, and alternating reversing deep cold rolling processes, thereby achieving a short-process preparation of high-strength PVC-U sheets with weak anisotropy.

[0007] To achieve the above objectives, the specific solution adopted by the present invention is as follows:

[0008] A short-process preparation method for high-strength PVC-U plate with weak anisotropy mainly includes the following steps:

[0009] S1. The raw material, high-purity sponge titanium, is smelted once in an electron beam cold hearth furnace, and after milling and grinding, large-size TA1 straight-rolled flat ingots are obtained.

[0010] S2. Cut the straight-rolled flat ingot obtained in step S1 into several blocks of suitable specifications. Heat the blocks to above the β phase transformation point and then perform two hot rolling cycles. The direction of the first hot rolling cycle is perpendicular to the direction of the second hot rolling cycle. After each rolling cycle, straighten, correct, acid and alkali clean and grind the slab.

[0011] S3. Annealing is performed on the hot-rolled slab to eliminate the rolling bands and internal stresses, and to achieve the recovery and recrystallization of the slab.

[0012] S4. The annealed slab is subjected to multiple alternating deep cold rolling processes to obtain a high-strength titanium-plastic sheet with weak anisotropy.

[0013] Furthermore, the oxygen content in high-purity sponge titanium is less than 0.03%, and the total content of impurity elements does not exceed 0.2%;

[0014] Furthermore, the thickness of the flat ingot obtained in step S1 is 80–120 mm.

[0015] Furthermore, in step S2, the first hot rolling process involves 6 to 8 passes, with a total deformation of 60 to 90%, and the slab thickness after hot rolling is 5 to 15 mm; the second hot rolling process involves 4 to 6 passes, with a total deformation of 50 to 70%.

[0016] Furthermore, in step S2, the thickness of the slab obtained after two hot rolling processes is 3 to 8 mm.

[0017] Furthermore, in step S3, the annealing temperature is 600–700°C, and the annealing time is 2–4 hours.

[0018] Furthermore, in step S4, the transverse and longitudinal rolling processes are alternated 4 to 8 times each, with a total rolling deformation of 10 to 90%.

[0019] Furthermore, in step S4, the thickness of the obtained titanium plate is 2.5 to 4.5 mm.

[0020] Furthermore, in step S4, before rolling deformation, the annealed slab is immersed in liquid nitrogen for at least 20 minutes to ensure that the temperature of the slab is uniform from the core to the surface and maintained at the liquid nitrogen temperature. After immersion, the slab is immediately fed into the rolls for rolling.

[0021] Before each rolling pass, the slab must be immersed in liquid nitrogen for at least 20 minutes.

[0022] Beneficial effects:

[0023] 1) This invention uses electron beam cold hearth melting technology, which can melt flat billets that can be directly used for rolling, effectively avoiding the multi-fire forging process of billets, resulting in low cost, high production efficiency, and easy mass production.

[0024] 2) To address the anisotropy and stripe structure generated during the EB direct rolling process of titanium plates, which negatively impacts formability, this invention employs alternating orientation hot rolling technology. This promotes the formation of basal texture in the titanium plate, significantly reducing anisotropy and solving the problem of difficulty in processing titanium plates at room temperature in existing technologies. Simultaneously, annealing the titanium plate improves the uniformity of the deformed structure, further weakening the anisotropy.

[0025] 3) In order to achieve synergistic improvement of the strength and plasticity of titanium plates, the present invention performs alternating deep cold rolling deformation treatment on titanium plates, introduces more twin variants into titanium plates, realizes strain coordination of multiple twins in titanium plates, and improves the mechanical properties of titanium plates.

[0026] 4) This invention adopts the preparation method of "EB melting billet preparation - hot rolling billet opening - annealing treatment - alternating reversible deep cold rolling". This invention first performs hot rolling billet opening and annealing treatment. The recovery recrystallization during the annealing process can reduce or eliminate the banded structure generated by hot rolling deformation. Then, through alternating reversible deep cold rolling treatment, a large number of twin variants can be introduced during rolling, which significantly shortens the preparation process of titanium plate, can significantly reduce the anisotropy of titanium plate, and at the same time improve the strength and plasticity of titanium plate. Attached Figure Description

[0027] Figure 1 This is a process route diagram for the short-process preparation of titanium plates according to the present invention.

[0028] Figure 2 This is a schematic diagram of the process flow for preparing titanium plates using the short-process method of the present invention.

[0029] Figure 3 The following are EBSD pole diagrams of titanium plates with different cold rolling deformation amounts in this invention, where (a) the deep cold rolling amount is 0%, (b) the deep cold rolling amount is 10%, (c) the deep cold rolling amount is 30%, and (d) the deep cold rolling amount is 50%.

[0030] Figure 4 The following are EBSD inverse pole figures of titanium plates with different cold rolling deformation amounts in this invention, wherein (a) the deep cold rolling amount is 0%, (b) the deep cold rolling amount is 10%, (c) the deep cold rolling amount is 30%, and (d) the deep cold rolling amount is 50%. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0032] This invention provides a short-process method for preparing high-strength PVC-U plates with weak anisotropy, mainly including the following steps:

[0033] S1. High-purity sponge titanium is selected as raw material. The oxygen content in the high-purity sponge titanium is less than 0.03%, and the total content of impurity elements does not exceed 0.2%. The high-purity sponge titanium is smelted once in an electron beam cold hearth furnace. After milling and grinding, large-size TA1 direct-rolled flat ingots are obtained. The thickness of the flat ingots is 80-120mm.

[0034] S2. Cut the straight-rolled flat ingot obtained in step S1 into several blocks of suitable specifications. Heat the blocks to above the β phase transformation point, and then perform two-stage hot rolling. The direction of the first hot rolling is perpendicular to the direction of the second hot rolling. The first hot rolling has 6 to 8 passes, with a total deformation of 60 to 90%, and the thickness of the hot-rolled slab is 5 to 15 mm. The second hot rolling has 4 to 6 passes, with a total deformation of 50 to 70%. After each rolling pass, the slab is straightened, corrected, acid-alkali cleaned, and ground. The thickness of the slab obtained after two-stage hot rolling is 3 to 8 mm.

[0035] S3. Anneal the hot-rolled slab at a temperature of 600-700℃ for 2-4 hours to eliminate rolling strips and internal stress, and to achieve recovery and recrystallization of the slab.

[0036] S4. The annealed slab is subjected to multiple alternating deep cold rolling, with 4 to 8 alternating rolling passes in the transverse and longitudinal directions, and a total rolling deformation of 10 to 90%, thus obtaining a high-strength PVC-U plate with weak anisotropy and a thickness of 2.5 to 4.5 mm.

[0037] It should be noted that in step S4, before rolling deformation, the annealed slab is first immersed in liquid nitrogen for at least 20 minutes to ensure that the temperature of the slab is uniform from the core to the surface and maintained at the liquid nitrogen temperature. After immersion, the slab is immediately fed into the rolls for rolling. Before each rolling pass, the slab must be immersed in liquid nitrogen for more than 20 minutes.

[0038] The technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0039] Example 1

[0040] This embodiment provides a short-process preparation method for high-strength PVC-U plates with weak anisotropy. The process route diagram and flow chart are shown below. Figure 1 and Figure 2 As shown, the specific steps are as follows:

[0041] S1. Melting and billet preparation: The high-purity sponge titanium raw material is melted in a 3600KW electron beam cold hearth furnace (EB furnace) in one step. After milling and grinding, a large-size TA1 straight-rolled flat ingot with a thickness of about 120mm is obtained. The oxygen content in the sponge titanium raw material is less than 0.03%, and the total content of impurity elements does not exceed 0.2%.

[0042] S2. Hot Rolling: The flat ingots melted by EB are cut into suitable rolled specifications and heated to above the β phase transformation point. They are then subjected to two hot rolling passes on a 1500mm four-high reversible rolling mill. The first hot rolling pass consists of 8 passes with a total deformation of 87%, resulting in a slab thickness of 15mm. The second hot rolling pass consists of 6 passes with a total deformation of 66%, resulting in a slab thickness of 5mm. It is worth noting that the two hot rolling directions should be perpendicular. After hot rolling, the slab needs to be straightened, corrected, acid-alkali cleaned, and ground. An oxide layer forms on the slab surface after hot rolling, which can be removed by acid-alkali cleaning. Specific acid-alkali cleaning methods and solutions are existing technology and will not be elaborated upon in this invention.

[0043] S3. Annealing treatment: The hot-rolled titanium plate is annealed to eliminate the rolling strips and internal stress of the titanium plate, and to realize the recovery and recrystallization of the titanium plate. The annealing temperature is 650℃ and the annealing time is 3h.

[0044] S4. Reversing Deep Cryogenic Rolling: The slab treated in step S2 is subjected to multiple alternating reversing deep cryogenic rolling passes, with four passes each in the transverse and longitudinal directions. The total rolling deformation is 30%, and the thickness of the titanium plate after deep cryogenic rolling is 3.5 mm. Before rolling deformation, the titanium plate needs to be immersed in liquid nitrogen for at least 20 minutes to ensure uniform temperature from the core to the surface and to maintain it at the liquid nitrogen temperature (77 K). After immersion, the titanium plate must be immediately fed into the rolls for rolling. Before each rolling pass, the titanium plate needs to be immersed in liquid nitrogen for at least 20 minutes.

[0045] Example 2

[0046] This embodiment is the same as the embodiment of steps S1 to S2 in Example 1, except that: in step S3 of this embodiment, the annealing temperature is 600℃ and the annealing time is 3h; in step S4, multi-pass alternating deep cold rolling is used, with 6 alternating rollings in the transverse and longitudinal directions, and a total rolling deformation of 10%, resulting in a final rolled titanium plate thickness of 4.5mm.

[0047] Example 3

[0048] This embodiment is the same as the embodiment of steps S1 to S2 in Example 1. The difference is that the annealing temperature used in step S3 of this embodiment is 600℃ and the annealing time is 3h. Step S4 of this embodiment also adopts multi-pass alternating deep cold rolling, with 6 alternating rollings in the transverse and longitudinal directions, a total rolling deformation of 30%, and a final rolled titanium plate thickness of 3.5mm.

[0049] Example 4

[0050] This embodiment is the same as the embodiment of steps S1 to S2 in Example 1. The difference is that: in step S3 of this embodiment, the annealing temperature is 600℃ and the annealing time is 3h. In step S4, multi-pass alternating deep cold rolling is used, with 6 alternating rollings in the transverse and longitudinal directions, and the total rolling deformation is 50%. The final rolled titanium plate thickness is 2.5mm.

[0051] Example 5

[0052] This embodiment is the same as the embodiment of steps S1 to S3 in Example 1. The difference is that step S4 in this embodiment also adopts multi-pass alternating directional deep cold rolling, with 8 alternating rollings in the transverse and longitudinal directions, a total rolling deformation of 30%, and a final rolled titanium plate thickness of 3.5 mm.

[0053] Example 6

[0054] This embodiment is the same as the embodiment of steps S1 to S2 in Example 1, except that: in step S3 of this embodiment, the annealing temperature is 700℃ and the annealing time is 3h; in step S4, multi-pass alternating deep cold rolling is used, with 6 alternating rollings in the transverse and longitudinal directions, and a total rolling deformation of 10%, resulting in a final rolled titanium plate thickness of 4.5mm.

[0055] Example 7

[0056] This embodiment is the same as the embodiment of steps S1 to S2 in Example 1, except that: in step S3 of this embodiment, the annealing temperature is 700℃ and the annealing time is 3h; in step S4, multi-pass alternating deep cold rolling is used, with 6 alternating rollings in the transverse and longitudinal directions, and the total rolling deformation is 50%, and the final rolled titanium plate thickness is 2.5mm.

[0057] Comparative Example 1

[0058] The implementation methods of steps S1 to S3 in Comparative Example 1 and Example 2 are the same, except that step S4 is not included.

[0059] Organizational performance analysis

[0060] (1) EBSD tests were performed on the plates obtained in Examples 2-4 and Comparative Example 1 to obtain pole figures and inverse pole figures along the rolling direction. The results are as follows: Figure 3 and Figure 4 As shown, where, Figure 3 (a) and Figure 4 (a) shows the EBSD pole figure and inverse pole figure of Comparative Example 1 when cold rolling is not performed (i.e., the initial state). Figure 3 (b) and Figure 4 (b) shows the EBSD pole figure and inverse pole figure for 10% rolling deformation in Example 2. Figure 3 (c) and Figure 4 (c) EBSD pole figure and inverse pole figure for 30% cold rolling deformation. Figure 3 (d) and Figure 4 (d) EBSD pole figure and inverse pole figure for 50% cold rolling deformation. Figure 3 and Figure 4 It can be seen that, with the increase of deformation, the TA1 pure titanium sheet gradually changes from the initial bimodal texture to... <0001> / / The basal texture changes. When the rolling deformation is 30%, the basal texture begins to appear; when the rolling deformation is 50%, there is a strong basal texture component. The generation of the basal texture component is more conducive to the isotropic tensile properties of pure titanium sheets.

[0061] (2) The strength and plasticity of the titanium plates prepared in Examples 1-7 were tested, and the results are shown in Table 1 below.

[0062] Table 1. Strength and plasticity test results of titanium plates prepared in Examples 1-7

[0063] Tensile strength / MPa (transverse / longitudinal) Elongation / % (Lateral / Longitudinal) Example 1 765MPa / 769MPa 10％ / 9％ Example 2 469MPa / 404MPa 14％ / 18％ Example 3 571MPa / 542MPa 13％ / 14％ Example 4 783MPa / 789MPa 9％ / 8％ Example 5 771MPa / 775MPa 10％ / 10％ Example 6 413MPa / 379MPa 16％ / 20％ Example 7 756MPa / 759MPa 11％ / 10％ Comparative Example 1 386MPa / 359MPa 23％ / 29％

[0064] As shown in Table 1, the strength of the titanium plate gradually increases and the elongation gradually decreases as the rolling deformation increases. According to Example 4, when the deep cold rolling deformation is 50%, the strength and elongation of its transverse and longitudinal tensile strengths are the closest and are at a relatively high level of strength and plasticity.

[0065] In summary, the use of multi-pass alternating deep cold rolling and appropriate heat treatment processes can effectively reduce the anisotropy of the transverse and longitudinal tensile properties of titanium plates. When the alternating rolling passes are 6, the deformation is 50%, and the annealing process is 600℃ / 3h, the prepared titanium plate has weak anisotropy and exhibits high tensile strength and elongation.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention in any way. All equivalent transformations or modifications made in accordance with the essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A short-process preparation method for a high-strength, weakly anisotropic titanium-plastic sheet, characterized in that, The main steps include the following: S1. The raw material, high-purity sponge titanium, is smelted once in an electron beam cold hearth furnace, and after milling and grinding, a large-size TA1 direct-rolled flat ingot is obtained; the thickness of the obtained large-size TA1 direct-rolled flat ingot is 80~120mm. S2. Cut the straight-rolled flat ingot obtained in step S1 into several blocks of suitable specifications. Heat the blocks to above the β phase transformation point, and then perform two-pass hot rolling. The direction of the first hot rolling is perpendicular to the direction of the second hot rolling. After each rolling pass, the slab is straightened, corrected, acid-alkali cleaned, and ground. The first hot rolling pass has 6 to 8 passes, the total deformation is 60 to 90%, and the thickness of the hot-rolled slab is 5 to 15 mm. The second hot rolling pass has 4 to 6 passes, the total deformation is 50 to 70%, and the thickness of the slab obtained after two hot rolling passes is 3 to 8 mm. S3. Anneal the hot-rolled slab at a temperature of 600-700℃ for 2-4 hours to eliminate rolling strips and internal stress, and to achieve recovery and recrystallization of the slab. S4. The annealed slab is subjected to multiple alternating deep cold rolling, with 4 to 8 alternating rollings in the transverse and longitudinal directions, and a total rolling deformation of 10 to 90%, thus obtaining a high-strength PVC-U plate with weak anisotropy.

2. The short-process preparation method for a high-strength, weakly anisotropic titanium-plastic sheet according to claim 1, characterized in that, The oxygen content in high-purity sponge titanium is less than 0.03%, and the total content of impurity elements does not exceed 0.2%.

3. The short-process preparation method for a high-strength, weakly anisotropic titanium-plastic sheet according to claim 1, characterized in that, In step S4, the thickness of the obtained titanium plate is 2.5~4.5mm.

4. The short-process preparation method of a high-strength, weakly anisotropic titanium-plastic sheet according to claim 1, characterized in that, In step S4, before rolling deformation, the annealed slab is immersed in liquid nitrogen for at least 20 minutes to ensure that the temperature of the slab is uniform from the core to the surface and is maintained at the liquid nitrogen temperature. After immersion, the slab is immediately fed into the rolls for rolling. Before each rolling pass, the slab must be immersed in liquid nitrogen for at least 20 minutes.

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