A method for preparing a lithium-boron alloy thin strip

Abstract

The present invention relates to the technical field of metal processing, and particularly relates to a method for preparing a lithium boride alloy thin strip, comprising the following steps: (1) extruding into a strip blank; (2) homogenizing heat treatment; (3) cold rolling; (4) annealing treatment; (5) repeating steps (3) and (4) until the thickness of the lithium boride alloy strip is ≤ 0.3 mm; (6) cryogenic treatment and cryogenic rolling; (7) annealing treatment; (8) cutting and storing. During the extrusion and rolling processes of the present invention, homogenizing heat treatment and annealing treatment can effectively eliminate the residual stress caused by extrusion and rolling, effectively preventing edge cracking; cryogenic treatment can improve the strength of the lithium boride alloy thin strip, enabling normal rolling even when the thickness is small, and can also effectively prevent sticking of the rollers, avoiding surface wrinkles and tearing problems caused by too low strength and sticking of the rollers, greatly improving the yield of the final product.

Description

Technical Field

[0001] The present invention relates to the technical field of metal processing, and particularly relates to a method for preparing a lithium boron alloy thin strip. Background Art

[0002] With the development of the miniaturization application of thermal batteries, the lithium boron alloy strip, as a key anode material, needs to be processed to less than 0.3 mm. Currently, there are mainly two methods for preparing the lithium boron alloy thin strip: the first is to directly forge and press the lithium boron alloy ingot, then rough roll it into a billet, and then finish roll it into a thin strip; the second is to extrude the alloy ingot into a strip billet, and then finish roll it into a thin strip. The first method cannot achieve continuous production, while the second method can achieve continuous production, meeting the requirements of future development.

[0003] Patent CN109317933B discloses a processing technology of lithium boron alloy. This technology first puts the lithium boron alloy ingot into an extrusion die barrel to extrude it into an alloy strip billet of a certain specification, and then puts the obtained alloy strip billet into a vacuum treatment furnace for heat treatment processing; after cooling, it is then put on a rolling mill for rolling. The alloy strip billet undergoes two processes of rough rolling and finish rolling to obtain an alloy strip product with cracked edges, and the product thickness is 0.1 - 1 mm. A trimming machine is equipped after the rolling mill to trim the cracked edges of the alloy strip to obtain a regular alloy. In the actual production and processing process, there are phenomena of cracked edges and local non-uniformity. Especially when the lithium boron alloy strip is rolled to less than 0.3 mm, due to multiple passes of rolling, stress concentration occurs, and the strip billet will show different degrees of waviness and camber, and is prone to sticking to the roll, discoloration, and fracture, resulting in a very low product yield. Summary of the Invention

[0004] Aiming at the technical problems of local non-uniformity of the product, easy sticking to the roll, discoloration, fracture, and low product yield in the processing of the existing lithium boron alloy thin strip, the present invention provides a method for preparing a lithium boron alloy thin strip, which can stably and efficiently prepare a lithium boron alloy thin strip with a flat surface and no discoloration, and has a high product yield.

[0005] A method for preparing a lithium boron alloy thin strip provided by the present invention includes the following steps:

[0006] (1) Extruding a lithium boron alloy round ingot into a lithium boron alloy strip billet; (2) Homogenization heat treatment; (3) Normal temperature rolling; (4) Annealing treatment; (5) Repeating steps (3) and (4) until the thickness of the lithium boron alloy strip ≤ 0.3 mm; (6) Low temperature treatment and low temperature rolling; (7) Annealing treatment; (8) Trimming and storing.

[0007] Furthermore, in the step (1), the thickness of the lithium boron alloy strip billet is 1 - 5 mm.

[0008] Further, the homogenization heat treatment is to place a lithium-boron alloy strip blank with a thickness of 1-5 mm into a vacuum heat treatment furnace, heat it up to 190-300 °C, and hold for 24-48 h.

[0009] Further, in the cold rolling at normal temperature, the reduction per pass is 4%-10%, and when the total reduction reaches 30%-60%, the rolling is stopped.

[0010] Further, the annealing treatment is to transfer the lithium-boron alloy strip into a vacuum heat treatment furnace, heat it up to 190-300 °C, hold for 1-5 hours, and then slowly cool it down to room temperature.

[0011] Further, in step (6), the low-temperature treatment is to place the lithium-boron alloy strip into a low-temperature experimental box protected by argon, and perform low-temperature cooling treatment at a temperature of -10 to -40 °C.

[0012] Further, in the low-temperature treatment in step (6), the roll is cooled with liquid argon to make the roll temperature the same as that of the lithium-boron alloy strip, and then low-temperature rolling is carried out.

[0013] Further, in the low-temperature rolling in step (6), the reduction per pass is kept at 4%-10%.

[0014] Further, in step (6), when the temperature rises above -10 °C during the low-temperature rolling process, the lithium-boron alloy strip is cooled again to -10 to -40 °C, and then low-temperature rolling is carried out.

[0015] Further, the processing process of the lithium-boron alloy is carried out in a dry environment with a dew point temperature ≤ -50 °C.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. During the extrusion and rolling processes, the homogenization heat treatment and annealing treatment can effectively eliminate the residual stress caused by extrusion and rolling, effectively prevent edge cracking, and improve the yield of the final product.

[0018] 2. During the heat treatment process, lithium is in a molten state while the lithium-boron skeleton remains solid, and lithium can be redistributed in the skeleton to make the alloy more uniform. The lower heat treatment temperature is beneficial to keeping the surface of the lithium-boron alloy bright.

[0019] 3. Low-temperature treatment can improve the strength of the lithium-boron alloy strip, enabling normal rolling even when the thickness is small. At the same time, it can effectively prevent sticking of the rollers, avoiding surface wrinkles and tearing problems caused by low strength and roller sticking. Low-temperature rolling is also beneficial for heat dissipation, effectively eliminating the heat generated during the rolling process of the strip, avoiding problems such as waviness and camber caused by uneven heat dissipation of the lithium-boron alloy strip, and preventing local blackening and discoloration problems caused by heat accumulation, making the product of high quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 is a flowchart of the preparation method of the lithium-boron alloy strip.

[0022] Figure 2 is the measurement result of the finished product thickness of the product in Embodiment 1 of the present invention.

[0023] Figure 3 is the measurement result of the finished product thickness of the product in Embodiment 3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] Embodiment 1

[0026] A preparation method of a lithium-boron alloy strip mainly includes the following steps: The processing process of the lithium-boron alloy is carried out in a dry environment with a dew point temperature ≤ -50°C.

[0027] (1) Extrusion: Put the lithium-boron alloy ingot into an extruder and extrude it into a lithium-boron alloy strip blank with a thickness of 2 mm.

[0028] (2) Homogenization heat treatment: Put the lithium-boron alloy strip blank into a vacuum heat treatment furnace, quickly heat it up to 300°C, and keep it warm for 24 hours.

[0029] (3) Normal temperature rolling: After cooling the heat-treated lithium-boron alloy strip blank to room temperature, it is rolled using a rolling mill. The reduction per pass is 0.1 mm, and it is rolled until the thickness reaches 1 mm.

[0030] (4) Annealing treatment: The 1-mm-thick lithium-boron alloy strip is transferred to a vacuum heat treatment furnace, heated to 300 °C, held for 1 hour, and then slowly cooled to room temperature.

[0031] (5) Normal temperature rolling: Continue rolling. The reduction per pass is 0.05 mm, and it is rolled until the thickness of the lithium-boron alloy strip reaches 0.5 mm.

[0032] (6) Annealing treatment: The 0.5-mm-thick lithium-boron alloy strip is transferred to a vacuum heat treatment furnace, quickly heated to 300 °C, held for 1 hour, and slowly cooled to room temperature.

[0033] (7) Normal temperature rolling: Continue rolling. The reduction per pass is 0.02 mm, and it is rolled until the thickness of the lithium-boron alloy strip reaches 0.2 mm.

[0034] (8) Low-temperature treatment: The 0.2-mm-thick lithium-boron alloy strip is placed in a dry cold box at -20 °C and stored for 0.5 hour. At the same time, the rolling mill rolls with internal coiled pipes is cooled with liquid argon.

[0035] (9) Low-temperature rolling: After the temperature of the roll surface drops to -20 °C, continue rolling the lithium-boron alloy strip. The reduction per pass is 0.01 mm until the thickness of the lithium-boron alloy strip reaches 0.1 mm.

[0036] During low-temperature rolling, if the temperature rises above -10 °C, the lithium-boron alloy strip needs to be cooled to -20 °C again before continuing low-temperature rolling.

[0037] (10) Annealing treatment: The 0.1-mm-thick lithium-boron alloy thin strip is transferred to a vacuum heat treatment furnace, quickly heated to 300 °C, held for 1 hour, and slowly cooled to room temperature.

[0038] (11) Cutting and storage: The lithium-boron alloy thin strip is cut into lithium-boron alloy thin strip products with a thickness of 0.1 mm using a cutting machine, wound into a roll, and stored in a vacuum in an aluminum-plastic bag.

[0039] Example 2

[0040] A method for preparing a lithium-boron alloy thin strip mainly includes the following steps: The processing process of the lithium-boron alloy is carried out in a dry environment with a dew point temperature ≤ -50 °C.

[0041] (1) Extrusion: The lithium-boron alloy ingot is placed in an extruder and extruded into a lithium-boron alloy strip blank with a thickness of 3 mm.

[0042] (2) Homogenization heat treatment: Put the lithium-boron alloy strip blank into a vacuum heat treatment furnace, quickly raise the temperature to 250 °C, and keep it warm for 36 hours.

[0043] (3) Cold rolling at room temperature: After cooling the heat-treated lithium-boron alloy strip blank to room temperature, roll it with a rolling mill. The reduction per pass is 0.15 mm, and roll it until the thickness reaches 1.5 mm.

[0044] (4) Annealing treatment: Transfer the lithium-boron alloy strip with a thickness of 1.5 mm into a vacuum heat treatment furnace, quickly raise the temperature to 250 °C, keep it warm for 2 hours, and then cool it to room temperature with the furnace.

[0045] (5) Cold rolling at room temperature: Continue rolling. The reduction per pass is 0.1 mm. After rolling to 1 mm, change the reduction per pass to 0.05 mm and roll until the thickness reaches 0.5 mm.

[0046] (6) Annealing treatment: Transfer the lithium-boron alloy strip with a thickness of 0.5 mm into a vacuum heat treatment furnace, quickly raise the temperature to 250 °C, keep it warm for 2 hours, and then cool it to room temperature with the furnace.

[0047] (7) Cold rolling at room temperature: Continue rolling. The reduction per pass is 0.02 mm and roll until the thickness of the lithium-boron alloy strip reaches 0.2 mm.

[0048] (8) Low-temperature treatment: Put the lithium-boron alloy strip with a thickness of 0.2 mm into a cold box with argon protection at -30 °C and store it for 0.5 hours. At the same time, cool the rolling mill rolls with internal coiled pipes with liquid nitrogen.

[0049] (9) Low-temperature rolling: After the roll surface temperature of the rolling mill drops to -30 °C, continue to roll the lithium-boron alloy strip. The reduction per pass is 0.01 mm until the thickness reaches 0.1 mm.

[0050] During low-temperature rolling, if the temperature rises above -10 °C, the lithium-boron alloy strip needs to be cooled to -30 °C again before continuing low-temperature rolling.

[0051] (10) Annealing treatment: Transfer the lithium-boron alloy thin strip with a thickness of 0.1 mm into a vacuum heat treatment furnace, quickly raise the temperature to 250 °C, keep it warm for 2 hours, and then cool it to room temperature with the furnace.

[0052] (11) Cutting: Cut the lithium-boron alloy thin strip into lithium-boron alloy thin strip products with a thickness of 0.1 mm with a cutting machine, gather them into rolls, and store them in an aluminum-plastic bag under vacuum.

[0053] Example 3

[0054] A preparation method of a lithium-boron alloy thin strip mainly includes the following steps: The processing process of the lithium-boron alloy is carried out in a dry environment with a dew point temperature ≤ -50°C.

[0055] (1) Extrusion: Put the lithium-boron alloy ingot into an extruder and extrude it into a lithium-boron alloy strip blank with a thickness of 2 mm.

[0056] (2) Homogenization heat treatment: Put the lithium-boron alloy strip blank into a vacuum heat treatment furnace, quickly heat it up to 190°C, and keep it warm for 48 hours.

[0057] (3) Normal temperature rolling: After cooling the heat-treated lithium-boron alloy strip blank to room temperature, roll it with a rolling mill, and the reduction per pass is 0.1 mm until the thickness reaches 1 mm.

[0058] (4) Annealing treatment: Transfer the lithium-boron alloy strip with a thickness of 1 mm into a vacuum heat treatment furnace, quickly heat it up to 190°C, keep it warm for 5 hours, and then cool it to room temperature with the furnace.

[0059] (5) Normal temperature rolling: Continue rolling, with the reduction per pass being 0.05 mm until the thickness of the lithium-boron alloy strip reaches 0.5 mm.

[0060] (6) Annealing treatment: Transfer the lithium-boron alloy strip with a thickness of 0.5 mm into a vacuum heat treatment furnace, quickly heat it up to 190°C, keep it warm for 5 hours, and then cool it to room temperature with the furnace.

[0061] (7) Normal temperature rolling: Continue rolling, with the reduction per pass being 0.02 mm until the thickness of the lithium-boron alloy strip reaches 0.2 mm.

[0062] (8) Low-temperature treatment: Put the lithium-boron alloy strip with a thickness of 0.2 mm into a cold box with argon protection at -30°C and store it for 0.5 hours. At the same time, cool the rolling mill rolls with internal coiled pipes with liquid nitrogen.

[0063] (9) Low-temperature rolling: After the temperature of the roll surface drops to -40°C, continue rolling the lithium-boron alloy strip, with the reduction per pass being 0.01 mm until the thickness of the lithium-boron alloy strip reaches 0.1 mm; then change the reduction per pass to 0.005 mm and roll until the thickness reaches 0.05 mm.

[0064] During the low-temperature rolling process, when the temperature rises above -10°C, cool the lithium-boron alloy strip to -40°C again and then carry out low-temperature rolling.

[0065] (10) Annealing treatment: Transfer the lithium-boron alloy thin strip with a thickness of 0.05 mm into a vacuum heat treatment furnace, quickly heat it up to 190°C, keep it warm for 5 hours, and then cool it to room temperature with the furnace.

[0066] (11) Cutting: The lithium-boron alloy thin strip is cut into a lithium-boron alloy thin strip product with a thickness of 0.05 mm by a cutting machine, gathered into a roll, and stored in an aluminum-plastic bag under vacuum.

[0067] In the above embodiments, as Figures 2 to 3 shown, the obtained lithium-boron alloy thin strip product has a flat and bright surface, without phenomena such as sticking to the roller, wrinkling, and unevenness, and the product yield can reach over 96%.

[0068] Comparative Example

[0069] A method for preparing a lithium-boron alloy thin strip mainly includes the following steps: The processing process of the lithium-boron alloy is carried out in a dry environment with a dew point temperature ≤ -50°C.

[0070] (1) Extrusion: The lithium-boron alloy ingot is put into an extruder and extruded into a lithium-boron alloy strip blank with a thickness of 2 mm.

[0071] (2) Heat treatment: The lithium-boron alloy strip blank is put into a vacuum heat treatment furnace, heated to 500°C, and kept warm for 6 hours.

[0072] (3) Cold rolling: After the heat-treated lithium-boron alloy strip blank is cooled to room temperature, it is rolled by a rolling mill. The reduction per pass is 0.1 mm, and it is rolled to a thickness of 1 mm;

[0073] Continue to roll, with the reduction per pass being 0.05 mm, and roll until the thickness of the lithium-boron alloy strip is 0.5 mm;

[0074] Continue to roll, with the reduction per pass being 0.02 mm, and roll until the thickness of the lithium-boron alloy strip is 0.2 mm.

[0075] When the thickness of the lithium-boron alloy strip is 0.2 mm, phenomena such as sticking to the roller, tearing, and wrinkling have occurred, and the lithium-boron alloy is locally blackened, so rolling is no longer continued.

[0076] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope of the present invention / Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention.

Claims

1. A method for preparing a lithium-boron alloy thin strip, characterized in that, It includes the following steps: (1) Extruding a lithium-boron alloy ingot into a lithium-boron alloy strip blank; (2) Homogenizing heat treatment; (3) Normal temperature rolling; (4) Annealing treatment; (5) Repeating steps (3) and (4) until the thickness of the lithium-boron alloy strip is ≤ 0.3 mm; (6) Low-temperature treatment and low-temperature rolling; (7) Annealing treatment; (8) Cutting and storing; The homogenizing heat treatment is to put the lithium-boron alloy strip blank with a thickness of 1 - 5 mm into a vacuum heat treatment furnace, heat it up to 190 - 300 °C, and keep it warm for 24 - 48 h; The annealing treatment is to transfer the lithium-boron alloy strip into a vacuum heat treatment furnace, heat it up to 190 - 300 °C, keep it warm for 1 - 5 hours, and then cool it down to room temperature.

2. The preparation method of a lithium-boron alloy thin strip according to claim 1, characterized in that, In step (1), the thickness of the lithium-boron alloy strip blank is 1 - 5 mm.

3. The preparation method of a lithium-boron alloy thin strip according to claim 1, characterized in that, In the normal temperature rolling, the reduction per pass is 4% - 10%, and when the total reduction reaches 30% - 60%, stop rolling.

4. The preparation method of a lithium boron alloy thin strip as described in claim 1, characterized in that, In step (6), the low-temperature treatment is to put the lithium-boron alloy strip into a low-temperature experimental box protected by argon and conduct low-temperature cooling treatment at a temperature of -10 to -40 °C.

5. The preparation method of a lithium-boron alloy thin strip as described in claim 1, characterized in that, In step (6), cool the rolling rolls with liquid argon to make the temperature of the rolling rolls the same as that of the lithium-boron alloy strip, and then conduct low-temperature rolling.

6. The preparation method of a lithium-boron alloy thin strip as described in claim 1, characterized in that, In step (6), the reduction per pass of the low-temperature rolling remains 4% - 10%.

7. The preparation method of a lithium-boron alloy thin strip as described in claim 1, wherein, In step (6), when the temperature rises above -10 °C during the low-temperature rolling process, cool the lithium-boron alloy strip to -10 to -40 °C again, and then conduct low-temperature rolling.

8. The preparation method of a lithium boron alloy thin strip as described in claim 1, characterized in that, The processing process of the lithium-boron alloy is carried out in a dry environment with a dew point temperature ≤ -50 °C.

Images