A vacuum hot pressing process for titanium foil

Abstract

This invention discloses a vacuum hot pressing process for titanium foil, comprising the following steps: S1, roll cutting; S2, sheet cleaning; S3, loading fixture; S4, vacuum hot pressing; ensuring the sheet surface is clean and dust-free during the cleaning process; the loading fixture ensures the sheet is flat and the fixture is locked; the vacuum heat treatment process ensures the vacuum degree of the heat treatment furnace, and the heat preservation temperature is adjusted according to the flatness standard; high-purity argon gas is introduced during the cooling process to ensure that no micro-oxide layer is generated on the sheet surface, thereby improving the surface quality of the titanium foil.

Description

Technical Field

[0001] This invention relates to the field of titanium foil material technology, specifically to a vacuum hot pressing process for titanium foil. Background Technology

[0002] Titanium foil has a wide range of applications, including aerospace, military, electronics and information technology, new energy power generation, and construction. It can be used to make shielding covers for electronic and communication equipment to effectively prevent electronic interference and protect electronic devices from external interference. When used in the manufacture of precision machining equipment, it can prevent magnetic interference and protect precision equipment in the electronics industry from external magnetic fields, improving the machining accuracy at the micrometer scale.

[0003] Furthermore, titanium foil possesses extremely high electronic conductivity, which can also improve the heat dissipation performance of equipment and protect equipment components from temperature damage. Currently, the main production process for titanium foil is mechanical rolling. Foil profile control, rolling tension stability control, and roll grinding processes have always been key technologies to ensure successful foil rolling. However, due to the numerous influencing factors, it is difficult to guarantee that the profile and quality of each roll of material remain uniform, thus affecting the yield of finished sheets and increasing costs, making it unsuitable for direct application in 3C electronic products.

[0004] Currently, the production process of titanium foil consists of major processes such as hot rolling, cold rolling of strip blanks, and precision rolling of thin strips, as well as auxiliary processes such as pickling, degreasing, heat treatment, grinding, and slitting. Among these, the control processes for precision rolling of thin strips, heat treatment, and grinding are complex, making it difficult to guarantee the quality of the final product. If substandard thin strips are slit, the material utilization rate will be greatly reduced, making it difficult to achieve stable mass production and hindering the mass delivery of titanium foil for 3C applications.

[0005] Therefore, this invention designs a vacuum hot pressing process for titanium foil to solve the above problems. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention provides a vacuum hot pressing process for titanium foil.

[0007] The technical solution of this invention is: a vacuum hot pressing process for titanium foil, comprising the following steps:

[0008] S1. Cutting with roll:

[0009] Titanium foil strip rolls are cut into sheets with a length of 155-180 mm, and the length tolerance is ±0.2 mm;

[0010] S2, Sheet Cleaning:

[0011] The sheets with unevenness > 0.3 mm from step S1 are stored separately in a Class 1000 cleanroom for dust removal;

[0012] S3. Loading fixture:

[0013] Place the cleaned sheets from step S2 into the fixture one by one and arrange them neatly in the area of ​​the limiting rods, ensuring that the sheets are flush around the edges. Each fixture can hold 2,500 sheets, and for every 500 sheets, add a 3-5mm stainless steel pad on top of the sheets. After all the sheets and stainless steel pads are loaded, ensure that there are no abnormal protrusions around the fixture, and then lock the limiting rods and fastening rods around the fixture to make the fixture flat and seamless after locking.

[0014] S4, Vacuum hot pressing calibration:

[0015] Place the fixture, after locking in step S3, into the iron frame, and then place the iron frame into the furnace chamber used for vacuum hot pressing. Place 4 sets of fixtures in each furnace chamber. When the vacuum degree in the furnace chamber is ≤1×10 -3 Start heating at Pa:

[0016] When the unevenness of the sheet is ≤5.0mm, the temperature is raised from 25℃ to 480℃ over 190 minutes and held for 200 minutes; when the unevenness of the sheet is >5.0mm, the temperature is raised from 25℃ to 490℃ over 190 minutes and held for 200 minutes.

[0017] After the heat preservation is completed, the sheet is cooled to 280°C with the furnace, and then 4-5L of high-purity argon gas is introduced until the furnace temperature drops to 200°C. After that, the furnace door is opened and the fixture is taken out to obtain the titanium foil material after vacuum hot pressing.

[0018] Furthermore, in step S1, the height of the edge burrs of the sheet is less than 10% of the thickness of the titanium foil roll.

[0019] Note: Excessive burrs can cause scratches on the sheet material and affect the fit of parts during manufacturing. Therefore, it is necessary to control the height of the burrs to control the quality of the sheet material.

[0020] Furthermore, in step S4, the purity of the high-purity argon gas is 99.999%.

[0021] Note: High-purity argon gas is introduced during the vacuum hot pressing process to ensure that no micro-oxide layer is generated during the heat treatment of the sheet.

[0022] Further, in step S2, the dust removal step includes: placing each sheet into a dust removal machine for dust removal, wherein the rotation speed of the upper and lower rollers of the dust removal machine is 2.5 to 3 m / min, and the distance between the upper and lower rollers is 0.10 to 0.15 mm.

[0023] Explanation: The dust removal machine uses adhesive paper on the upper and lower rollers to remove metal debris and dust particles from the surface of the sheet material generated during the cutting process of titanium foil strip rolls.

[0024] Furthermore, after dust removal, the sheet is wiped with a lint-free cloth soaked in 70% anhydrous ethanol to remove dirt.

[0025] Note: Clean the surface of the sheet to prevent defects such as black spots or oxidation from forming on the surface of the finished sheet due to particulate carbonization or dirt during the vacuum hot pressing process.

[0026] Furthermore, after step S2 is completed and before proceeding to step S3, the sheet is pre-leveled, that is, the sheet is heated from 25°C to T at a heating rate of 8-10°C / min. f ℃, hold at that temperature for t min, and continuously apply pressure F during the holding period. After the holding period, cool to room temperature.

[0027] Among them, T f The formulas for calculating , t, and F are as follows:

[0028] T f =(200*10 -5 ) / {[λ*(18-L) / AL]+a},L∈[15.5, 18.0] (1)

[0029] t = T f / |18-L+d| (2)

[0030] F = P / (0.1a*T) f (3)

[0031] In formulas (1), (2), and (3), T f The insulation temperature is expressed in °C; A is the pre-leveled cross-sectional area of ​​the sheet, expressed in cm². 2 L is the length of the sheet in cm; a is the flatness of the sheet in mm; λ is the coefficient of thermal expansion of the sheet; t is the heat preservation time in min; d is the length tolerance in mm; P is the compressive strength of the sheet in MPa.

[0032] Note: A pre-leveling process is performed before vacuum hot pressing. Pre-leveling is achieved through a hot pressing process. However, compared to ordinary hot pressing, this invention correlates the insulation temperature with the relevant coefficients of the sheet (i.e., the coefficient of thermal expansion, the length of the sheet being cut, etc.), and then correlates the insulation time with the pre-leveling pressure. This allows for more effective control of the pre-leveling parameters, preventing over-leveling during the pre-leveling period and improving the sheet's ductility, thus laying the foundation for subsequent vacuum hot pressing.

[0033] Furthermore, the method for cooling to room temperature is to water-cool the sheet at a water cooling rate of 70-80 L / s.

[0034] Note: By using high-strength water cooling, the sheet can be cooled down rapidly without causing contamination to the sheet surface.

[0035] Furthermore, before pre-leveling, the sheet is first soaked in a sodium hydroxide solution with an alkalinity of 13-14% to degrease and remove oil for 3-5 minutes.

[0036] Note: Degreasing and removing oil from the sheet material in an alkaline solution beforehand can improve the effect of subsequent pre-leveling and vacuum hot pressing.

[0037] Furthermore, in step S4, after heating is started, the vacuum level inside the furnace is maintained at 1×10⁻⁶. -3 Below Pa.

[0038] Note: The vacuum degree is controlled during the vacuum hot pressing process to ensure that no micro-oxide layer is generated during the heat treatment of the sheet.

[0039] The beneficial effects of this invention are:

[0040] (1) The process of this invention precisely controls the size of the roll cutting to match the size of the finished sheet, ensuring production efficiency. After cutting, cleaning and vacuum hot pressing, the sheet surface is clean and dust-free. The loading fixture ensures the sheet is flat and the fixture is locked. The vacuum heat treatment process ensures the vacuum degree of the heat treatment furnace and adjusts the heat preservation temperature according to the flatness standard. High-purity argon gas is introduced during the cooling process to ensure that no micro-oxidation layer is generated on the sheet surface, thus improving the surface quality of the titanium foil.

[0041] (2) The process of the present invention performs a pre-leveling before vacuum hot pressing. By linking the insulation temperature with the correlation coefficient of the sheet, and then linking the insulation time and pre-leveling pressure with the insulation temperature, the parameters of pre-leveling can be controlled more effectively, thereby preventing over-leveling during the pre-leveling period and improving the extensibility of the sheet, laying the foundation for subsequent vacuum hot pressing. Attached Figure Description

[0042] Figure 1 This is a flowchart of process embodiment 1 of the present invention;

[0043] Figure 2 This is a flowchart of process embodiment 12 of the present invention. Detailed Implementation

[0044] The present invention will now be described in more detail with reference to specific embodiments, so as to better demonstrate the advantages of the present invention.

[0045] Example 1

[0046] A vacuum hot pressing process for titanium foil includes the following steps:

[0047] S1. Cutting with roll:

[0048] The TA4 strip roll is cut into sheets with a length of 162mm, the length tolerance is ±0.2mm, and the height of the edge burrs of the sheet is 8% of the thickness of the TA4 strip roll.

[0049] S2, Sheet Cleaning:

[0050] The sheets with unevenness > 0.3 mm from step S1 are stored separately in a Class 1000 cleanroom for dust removal;

[0051] The dust removal step includes: placing each sheet into a dust removal machine for dust removal, wherein the rotation speed of the upper and lower rollers of the dust removal machine is 2.8 m / min and the distance between the upper and lower rollers is 0.13 mm; after the dust removal is completed, the sheet is wiped with a lint-free cloth soaked in 70% anhydrous ethanol to remove dirt.

[0052] S3. Loading fixture:

[0053] Place the cleaned sheets from step S2 into the fixture one by one and arrange them neatly in the area of ​​the limiting rods, ensuring that the sheets are flush around the edges. Each fixture can hold 2,500 sheets, and for every 500 sheets, add a 4mm stainless steel pad on top of the sheets. After all the sheets and stainless steel pads are loaded, ensure that there are no abnormal protrusions around the fixture, and then lock the limiting rods and fastening rods around the fixture to make the fixture flat and seamless after locking.

[0054] S4, Vacuum hot pressing calibration:

[0055] Place the fixture, after locking in step S3, into the iron frame, and then place the iron frame into the furnace chamber used for vacuum hot pressing. Place 4 sets of fixtures in each furnace chamber. When the vacuum degree in the furnace chamber is ≤1×10 -3 Start heating at Pa:

[0056] When the unevenness of the sheet is ≤5.0mm, the temperature is raised from 25℃ to 480℃ over 190 minutes and held for 200 minutes; when the unevenness of the sheet is >5.0mm, the temperature is raised from 25℃ to 490℃ over 190 minutes and held for 200 minutes.

[0057] After heating is started, the vacuum level inside the furnace is maintained at 1×10⁻⁶. -3 Pa, after the heat preservation is completed, the sheet is cooled to 280°C with the furnace, and then 4.5L of high-purity argon gas with a purity of 99.999% is introduced until the furnace temperature drops to 200°C. Then the furnace door is opened and the fixture is taken out to obtain TA4 titanium foil material after vacuum hot pressing.

[0058] Example 2

[0059] The difference between this embodiment and Embodiment 1 is that, in step S1, the length of the sheet is 155mm.

[0060] Example 3

[0061] The difference between this embodiment and Embodiment 1 is that in step S1, the length of the sheet is 180mm.

[0062] Example 4

[0063] The difference between this embodiment and embodiment 1 is that, in step S2, the dust removal step includes: placing each sheet into a dust removal machine for dust removal, wherein the rotation speed of the upper and lower rollers of the dust removal machine is 2.5 m / min and the distance between the upper and lower rollers is 0.10 mm.

[0064] Example 5

[0065] The difference between this embodiment and embodiment 1 is that, in step S2, the dust removal step includes: placing each sheet into a dust removal machine for dust removal, wherein the rotation speed of the upper and lower rollers of the dust removal machine is 3m / min and the distance between the upper and lower rollers is 0.15mm.

[0066] Example 6

[0067] The difference between this embodiment and embodiment 1 is that in step S3, a 3mm stainless steel pad is added to the sheet for every 500 sheets loaded.

[0068] Example 7

[0069] The difference between this embodiment and embodiment 1 is that in step S3, a 5mm stainless steel pad is added to the sheet for every 500 sheets loaded.

[0070] Example 8

[0071] The difference between this embodiment and embodiment 1 is that in step S4, when the unevenness of the sheet is ≤5.0mm, the temperature is raised from 25℃ to 478℃ over 185 minutes and held for 195 minutes; when the unevenness of the sheet is >5.0mm, the temperature is raised from 25℃ to 488℃ over 185-195 minutes and held for 195 minutes.

[0072] Example 9

[0073] The difference between this embodiment and embodiment 1 is that in step S4, when the unevenness of the sheet is ≤5.0mm, the temperature is raised from 25℃ to 482℃ over 195 minutes and held for 205 minutes; when the unevenness of the sheet is >5.0mm, the temperature is raised from 25℃ to 492℃ over 195 minutes and held for 205 minutes.

[0074] Example 10

[0075] The difference between this embodiment and embodiment 1 is that in step S4, after the heat preservation is completed, the sheet is cooled to 275°C with the furnace, and then 4L of high-purity argon gas is introduced until the furnace temperature drops to 195°C before the furnace door is opened.

[0076] Example 11

[0077] The difference between this embodiment and embodiment 1 is that in step S4, after the heat preservation is completed, the sheet is cooled to 285°C with the furnace, and then 5L of high-purity argon gas is introduced until the furnace temperature drops to 205°C before the furnace door is opened.

[0078] Example 12

[0079] The difference between this embodiment and Embodiment 1 is that, after step S2 and before step S3, the sheet is pre-leveled, that is, the sheet is heated from 25°C to T at a heating rate of 9°C / min. f ℃, keep warm for t min, and continuously apply pressure F during the heat preservation period. After the heat preservation is completed, water cool the sheet at a rate of 75L / s until it is cooled to room temperature.

[0080] Among them, T f The formulas for calculating , t, and F are as follows:

[0081] T f =(200*10 -5 ) / {[λ*(18-L) / AL]+a},L∈[15.5, 18.0] (1)

[0082] t = T f / |18-L+d| (2)

[0083] F = P / (0.1a*T) f (3)

[0084] In formulas (1), (2), and (3), T f The insulation temperature is expressed in °C; A is the pre-leveled cross-sectional area of ​​the sheet, expressed in cm². 2 L is the length of the sheet, in cm; a is the flatness of the sheet, in mm; λ is the coefficient of thermal expansion of the sheet; t is the heat preservation time, in min; d is the length tolerance, in mm; P is the tensile strength of the sheet, in MPa.

[0085] Given L = 1.62 cm and λ = 1.3 × 10⁻⁶, we can determine the coordinates. -5 A = 1.62 * 13 cm 2Given a = 0.36 mm, d = +0.2 mm, and P = 735 MPa, substituting these values ​​into formulas (1), (2), and (3) yields T. f =555.56℃, t=250min, F=36.79MPa;

[0086] Before pre-leveling, the sheet is first soaked in a sodium hydroxide solution with an alkalinity of 13.5% to degrease and remove oil for 4 minutes.

[0087] Example 13

[0088] The difference between this embodiment and embodiment 12 is that the heating rate of the sheet is 8°C / min, and the sheet is water-cooled at a water cooling rate of 70L / s.

[0089] Example 14

[0090] The difference between this embodiment and embodiment 12 is that the heating rate of the sheet is 10℃ / min, and the sheet is water-cooled at a water cooling rate of 80L / s.

[0091] Example 15

[0092] The difference between this embodiment and Embodiment 12 is that, before pre-leveling, the sheet is first soaked in a sodium hydroxide solution with an alkalinity of 13% to remove oil and grease for 3 minutes.

[0093] Example 16

[0094] The difference between this embodiment and Embodiment 12 is that, before pre-leveling, the sheet is first soaked in a sodium hydroxide solution with an alkalinity of 14% to remove oil and grease for 5 minutes.

[0095] Experimental Example

[0096] For each embodiment of the TA4 titanium foil, five samples were taken from each embodiment to test the mechanical properties of the TA4 titanium foil. The average value of the test results of the five samples in each embodiment was taken as the test result of that embodiment. The specific investigation is as follows:

[0097] 1. The mechanical properties of TA4 tape rolls without vacuum hot pressing and the present invention were compared, and the results are shown in Table 1.

[0098] Table 1 Mechanical properties of TA4 titanium foil in Example 1 and Comparative Example 1

[0099]

[0100] The difference between Comparative Example 1 and Example 1 is that the TA4 titanium foil in Comparative Example 1 was not subjected to vacuum hot pressing.

[0101] As shown in Table 1, although the elongation after fracture of the TA4 titanium foil after vacuum hot pressing was lower than that of the control example 1, it was still quite good. Moreover, the tensile strength and other properties were stronger than those of the control example 1. This indicates that the mechanical properties of the material after vacuum hot pressing did not decrease significantly. Therefore, the sheet after vacuum hot pressing significantly improved its flatness while ensuring that the mechanical properties met the standards.

[0102] 2. The effects of various parameters on the mechanical properties of TA4 titanium foil during vacuum hot pressing of TA4 tape rolls were investigated. The results are shown in Table 2.

[0103] Table 2. Tensile strength and unevenness of TA4 titanium foil in Examples 2-11

[0104]

[0105]

[0106] As shown in Table 2, the tensile strength of A4 titanium foil material will be reduced and the unevenness will be increased if the length of the sheet is too short or too long, the dust removal parameters are too small or too large, the thickness of the stainless steel pad is too thin or too thick, the vacuum hot pressing parameters are too small or too large, and the cooling parameters are too small or too large. Therefore, the parameters of Example 1 are better.

[0107] 3. The mechanical properties of TA4 tape rolls were investigated after pre-leveling before vacuum hot pressing. The results are shown in Table 1.

[0108] Table 3 Tensile strength and unevenness of TA4 titanium foil in Examples 12-16

[0109]

[0110] As shown in Table 3, the unevenness after pre-leveling is lower than that of Examples 1 to 11, indicating that pre-leveling can further correct the TA4 strip roll. In addition, the overall tensile strength of Examples 12 to 16 remains above 750, and the mechanical properties remain excellent. Therefore, pre-leveling improves the overall performance of TA4 titanium foil.

[0111] Comparing Examples 12-16, it can be seen that excessively small or large heating and cooling parameters, as well as excessively small or large degreasing and oil removal parameters, will reduce the maintenance of tensile strength and the adjustment of unevenness. Therefore, in summary, the parameters of Example 12 are more effective.

Claims

1. A vacuum hot pressing process for titanium foil, characterized in that, Includes the following steps: S1. Cutting with roll: Titanium foil strip rolls are cut into sheets with a length of 155-180 mm, and the length tolerance is ±0.2 mm; S2, Sheet Cleaning: The sheets with unevenness > 0.3 mm from step S1 are stored separately in a Class 1000 cleanroom for dust removal; S3. Loading fixture: Place the cleaned sheets from step S2 into the fixture one by one and arrange them neatly in the area of ​​the limiting rods, ensuring that the sheets are flush around the edges. Each fixture can hold 2,500 sheets, and for every 500 sheets, add a 3-5mm stainless steel pad on top of the sheets. After all the sheets and stainless steel pads are loaded, ensure that there are no abnormal protrusions around the fixture, and then lock the limiting rods and fastening rods around the fixture to make the fixture flat and seamless after locking. S4, Vacuum hot pressing calibration: Put the fixture after step S3 into the iron frame, and then put the iron frame into the furnace for vacuum heat pressing. Put 4 sets of fixtures into each furnace, and start heating when the vacuum degree in the furnace is ≤1×10 -3 Pa. When the unevenness of the sheet is ≤5.0mm, the temperature is raised from 25℃ to 478~482℃ over 185~195min and held for 195~205min; when the unevenness of the sheet is >5.0mm, the temperature is raised from 25℃ to 488~492℃ over 185~195min and held for 195~205min. After the heat preservation is completed, the sheet is cooled to 275-285°C with the furnace, and then 4-5L of high-purity argon gas is introduced until the furnace temperature drops to 195-205°C. After that, the furnace door is opened and the fixture is taken out to obtain the titanium foil material after vacuum hot pressing.

2. The vacuum hot pressing process for titanium foil according to claim 1, characterized in that, In step S1, the height of the edge burrs of the sheet is less than 10% of the thickness of the titanium foil roll.

3. The vacuum hot pressing process for titanium foil according to claim 1, characterized in that, In step S4, the purity of the high-purity argon gas is 99.999%.

4. The vacuum hot pressing process for titanium foil according to claim 1, characterized in that, In step S2, the dust removal step includes: placing each sheet into a dust removal machine for dust removal, wherein the rotation speed of the upper and lower rollers of the dust removal machine is 2.5 to 3 m / min, and the distance between the upper and lower rollers is 0.10 to 0.15 mm.

5. The vacuum hot pressing process for titanium foil according to claim 4, characterized in that, After dust removal, wipe the sheet with a lint-free cloth soaked in 70% anhydrous ethanol to remove dirt.

6. The vacuum hot pressing process for titanium foil according to claim 1, characterized in that, After step S2 is completed and before proceeding to step S3, the sheet is pre-leveled, that is, the sheet is heated from 25°C to T at a heating rate of 8-10°C / min. f ℃, hold at that temperature for t min, and continuously apply pressure F during the holding period. After the holding period, cool to room temperature. Among them, T f The formulas for calculating , t, and F are as follows: T f =(200*10 -5 ) / {[λ*(18-L) / AL]+a},L∈[15.5, 18.0] (1) t=T f / |18-L+d| (2) F=P / (0.1a*T f ) (3) In formulas (1), (2), and (3), T f The insulation temperature is expressed in °C; A is the pre-leveled cross-sectional area of ​​the sheet, expressed in cm². 2 L is the length of the sheet in cm; a is the flatness of the sheet in mm; λ is the coefficient of thermal expansion of the sheet; t is the heat preservation time in min; d is the length tolerance in mm; P is the compressive strength of the sheet in MPa.

7. The vacuum hot pressing process for titanium foil according to claim 6, characterized in that, The method for cooling to room temperature is as follows: the sheet is water-cooled at a water cooling rate of 70-80 L / s.

8. The vacuum hot pressing process for titanium foil according to claim 6, characterized in that, Before pre-leveling, the sheet is soaked in a sodium hydroxide solution with an alkalinity of 13-14% for 3-5 minutes to degrease and remove oil.

9. The vacuum hot pressing process for titanium foil according to claim 1, characterized in that, In step S4, after heating is started, the vacuum level inside the furnace is maintained at 1×10⁻⁶. -3 Below Pa.

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