A method for producing high-performance dispersion copper by a uniform external precursor particle method

Abstract

The application provides a method for preparing high-performance dispersed copper by a uniform external precursor particle method, and comprises the following steps: S1, gas atomization Cu powder preparation; S2, Al(OH)3 sol concentrate preparation; S3, Cu / γ-Al2O3 composite powder preparation: Al(OH)3 sol concentrate is added to main raw material Cu powder in a humidifying mixer in a spraying mode, and Cu / γ-Al2O3 composite powder is obtained after drying after discharging; S4, CIP processing: Cu / γ-Al2O3 granulation powder is pressed to form an ingot blank; S5, reduction and sealing welding; S6, preheating and extrusion: the sealed ingot blank is heated first, and then hot extrusion is performed to form an extruded rod blank; and S7, stretching and finishing. The method for preparing high-performance dispersed copper by the uniform external precursor particle method has low cost and low requirement on equipment; the finished product has fewer defects, and the comprehensive performance of the dispersed copper material is improved.

Description

Technical Field

[0001] This invention relates to the field of metal composite materials, and more specifically, to a method for preparing high-performance dispersed copper by uniformly adding precursor particles. Background Technology

[0002] Dispersion strengthening is a method of strengthening materials by adding uniform, fine oxide particles into a metal matrix to pin dislocations, grain boundaries, and subgrain boundaries, thus hindering dislocation movement. Dispersion-strengthened copper, due to the uniform, fine oxide particles dispersed throughout the copper matrix, exhibits high strength and a high softening temperature. Simultaneously, the finely dispersed oxide particles do not adversely affect the electrical and thermal conductivity of the copper alloy itself, allowing dispersion-strengthened copper to maintain its excellent electrical and thermal conductivity while improving strength.

[0003] Dispersion-strengthened copper alloys are considered to be new functional materials with great development potential and application prospects due to their excellent high-temperature resistance, high strength, and high conductivity. They have been widely used in many high-tech fields such as lead frames for ultra-large-scale integrated circuits, high-pulse magnetic field conductors, high-power microwave tubes, overhead conductors for high-speed rail transit, resistance welding electrodes, and crystallizers for continuous casting machines.

[0004] There are many methods for preparing Al2O3-dispersed copper composite materials, including mechanical alloying, powder metallurgy, composite electrodeposition, vacuum hybrid casting, co-precipitation, reactive jet deposition, sol-gel method, and internal oxidation. In current internal oxidation processes, further densification processes such as hot extrusion and hot isostatic pressing are necessary after cold pressing and internal oxidation-reduction. Therefore, traditional Al2O3-dispersed copper ingots do not pursue high ingot density before internal oxidation-reduction; cold isostatic pressing is generally in the range of 180–250 MPa, and the industry pays little attention to the density of the ingot before densification. However, because Al2O3-dispersed copper ingots with relatively low density may inherit porosity defects from the ingot to the densified finished product, the degree of influence of different densities on defects in the finished product varies, and these defects have a systematic or random impact on the performance of the finished product.

[0005] In summary, Al2O in existing technologies 3- Dispersed copper has high preparation costs, requires sophisticated equipment, produces more defects in the finished product, and has poor overall performance.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to propose a method for preparing high-performance dispersed copper by uniformly adding precursor particles, in order to solve the problem of Al2O in the prior art. 3-Dispersed copper has high preparation costs, high equipment requirements, many defects in the finished product, and poor overall performance.

[0008] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0009] A method for preparing high-performance dispersed copper by uniformly adding precursor particles, the method comprising the following steps:

[0010] S1, Preparation of Cu powder by gas atomization;

[0011] S2, Preparation of Al(OH)3 sol concentrate: Al(OH)3 powder was prepared into sol concentrate according to the amount of target Al2O3 particles introduced, and was always dispersed evenly using a high-speed disperser;

[0012] Preparation of S3 and Cu / γ-Al2O3 composite powder: Al(OH)3 sol concentrate was added to the main raw material Cu powder by spraying in a humidifying mixer, mixed evenly, and then placed in a clean oven to dry to obtain Cu / γ-Al2O3 composite powder.

[0013] S4, CIP processing: Cu / γ-Al2O3 granulated powder is placed in an isostatic pressing sleeve and pressed to form an ingot. The pressing process is as follows: the pressurization rate is 5-15 MPa / min, the maximum pressure is 300-400 MPa, and the holding time is 10-12 minutes.

[0014] S5. Reduction and Sealing: The CIP-treated billet is first placed in high-purity hydrogen for reduction at a temperature of 300-400℃ for 2-6 hours. Then the billet is placed in an oxygen-free copper sleeve, vacuumed, and sealed by argon arc welding.

[0015] S6. Preheating and extrusion: The sealed billet is first heated in an electric resistance furnace; then hot extrusion is performed to form an extruded bar billet.

[0016] S7. Stretching and finishing: The extruded billet is post-processed into a finished product.

[0017] The method for preparing high-performance dispersed copper by uniformly adding precursor particles as described in this invention has steps S1 to S7 that are interconnected and inseparable, playing multiple roles: 1. In-situ generation of dispersed Al2O3 particles, with fine particle size and uniform distribution; 2. High density of the finished product, few defects, and improved overall performance; 3. Low preparation cost and low equipment requirements.

[0018] Furthermore, in step S3, the spray rate is 50–70 ml / min.

[0019] Furthermore, in step S3, the drying temperature is 90–95°C, and the drying time is 20–30 h.

[0020] Furthermore, in step S3, after spraying, continue mixing for 20-30 minutes to ensure that the Al(OH)3 sol concentrate and Cu powder are mixed evenly.

[0021] Furthermore, step S1 specifically includes the following steps: atomizing powder with high-purity nitrogen, smelting in a 200kg medium-frequency melting furnace, adding high-purity oxygen-free electric copper in the medium-frequency furnace and smelting for 50-90 minutes; atomizing powder with high-purity nitrogen at a pressure of 0.3-1.9Mpa, drying, and sieving to obtain -100 mesh Cu powder for later use.

[0022] Furthermore, in step S2, Al(OH)3 powder is prepared into a sol concentrate according to the amount of target Al2O3 particles introduced, with a solid-liquid ratio of 1:4 to 1:3.

[0023] Furthermore, in step S2, the high-speed disperser rotates at 400 r / m and the dispersion time is 20 min.

[0024] Furthermore, in step S6, the heating temperature is 700–800°C, and the heating time is 2–3 hours.

[0025] Furthermore, in step S6, the extrusion ratio of the hot extrusion is 10 to 30.

[0026] Furthermore, in step S7, the extruded billet is processed by removing the head and tail, straightening, and stretching to the size required by the user, and then straightened and the head and tail are removed to become the finished product.

[0027] Compared with existing technologies, the method for preparing high-performance dispersed copper by uniformly adding precursor particles as described in this invention has the following advantages:

[0028] The method for preparing high-performance dispersed copper by uniformly adding precursor particles as described in this invention has steps S1 to S7 that are interconnected and inseparable, playing multiple roles:

[0029] (1) In-situ generation of dispersed Al2O3 particles with fine particle size and uniform distribution: Step S1 first prepares Cu powder by gas atomization, Step S2 then prepares Al(OH)3 sol concentrate, and Step S3 adds Al(OH)3 sol concentrate to the main raw material Cu powder by spraying in a humidifying mixer, mixes evenly, and then places it in a clean oven to dry to obtain Cu / γ-Al2O3 composite powder; Al2O3 particles are obtained by uniformly humidifying Al(OH)3 sol and drying at a temperature below 100℃, so they are γ-Al2O3 with high specific surface area and high activity, and after being processed in step S2... The heating process in the resistance furnace at 700-800℃ and the hot extrusion process in step S6 make it easy for γ-Al2O3 to migrate in the Cu matrix. The average distance between the dispersed Al2O3 particles is less than 40nm (taking Cu-0.6%Al2O3 product as an example), and the dispersion is uniform. In addition, since the billet is reduced in high-purity hydrogen at 300-400℃ in step S5 and heated in the resistance furnace at 700-800℃ before hot extrusion, the heat treatment temperature is relatively low. Therefore, the dispersed Al2O3 particles will not grow abnormally. The size of the Al2O3 particles is less than 10nm.

[0030] (2) High finished product density, fewer defects, and improved overall performance: Since step S4 increases the maximum pressure of CIP to 300-400MPa, the relative density of the billet is increased by 5.98-7.88% compared to when it is 200MPa, and the porosity defects are significantly reduced, resulting in improved overall performance. Using this high-density billet for subsequent densification treatment, taking a Ф100×300 billet as an example (800t extruder, the extruded product is Ф25, extrusion ratio 16.3), after hot extrusion and stretching, it is stretched into a Ф16 finished product. After testing, the relative density of the finished product exceeds 99.1%.

[0031] (3) The preparation cost is low and the equipment requirements are low. Attached Figure Description

[0032] Figure 1 The microscopic SEM morphology of the product surface after processing with a maximum pressure of 200 MPa in the pressing process, according to an embodiment of the present invention, using a uniformly added precursor particle method to prepare high-performance dispersed copper, is magnified 5000 times.

[0033] Figure 2 The microscopic SEM morphology of the product surface after processing with a maximum pressure of 300 MPa in the pressing process, according to an embodiment of the present invention, using a uniformly added precursor particle method to prepare high-performance dispersed copper, is magnified 5000 times.

[0034] Figure 3The microscopic SEM morphology of the product surface after processing with a maximum pressure of 400 MPa in the pressing process, according to an embodiment of the present invention, using a uniformly added precursor particle method to prepare high-performance dispersed copper, is magnified 5000 times. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. The descriptions of "first," "second," etc., mentioned in the embodiments of the present invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0036] A method for preparing high-performance dispersed copper by uniformly adding precursor particles, the method comprising the following steps:

[0037] S1, Preparation of Cu powder by gas atomization;

[0038] S2, Preparation of Al(OH)3 sol concentrate: Al(OH)3 powder was prepared into sol concentrate according to the amount of target Al2O3 particles introduced, and was always dispersed evenly using a high-speed disperser;

[0039] Preparation of S3 and Cu / γ-Al2O3 composite powder: Al(OH)3 sol concentrate was added to the main raw material Cu powder by spraying in a humidifying mixer, mixed evenly, and then placed in a clean oven to dry to obtain Cu / γ-Al2O3 composite powder.

[0040] S4, CIP processing: Cu / γ-Al2O3 granulated powder is placed in an isostatic pressing sleeve and pressed to form an ingot. The pressing process is as follows: the pressurization rate is 5-15 MPa / min, the maximum pressure is 300-400 MPa, and the holding time is 10-12 minutes.

[0041] S5. Reduction and Sealing: The CIP-treated billet is first placed in high-purity hydrogen for reduction at a temperature of 300-400℃ for 2-6 hours. Then the billet is placed in an oxygen-free copper sleeve, vacuumed, and sealed by argon arc welding.

[0042] S6. Preheating and extrusion: The sealed billet is first heated in an electric resistance furnace; then hot extrusion is performed to form an extruded bar billet.

[0043] S7. Stretching and finishing: The extruded billet is post-processed into a finished product.

[0044] The method of dispersing copper has the following beneficial effects:

[0045] The method for preparing high-performance dispersed copper by uniformly adding precursor particles as described in this invention has steps S1 to S7 that are interconnected and inseparable, playing multiple roles:

[0046] (1) In-situ generation of dispersed Al2O3 particles with fine particle size and uniform distribution: Step S1 first prepares Cu powder by gas atomization, Step S2 then prepares Al(OH)3 sol concentrate, and Step S3 adds Al(OH)3 sol concentrate to the main raw material Cu powder by spraying in a humidifying mixer, mixes evenly, and then places it in a clean oven to dry to obtain Cu / γ-Al2O3 composite powder; Al2O3 particles are obtained by uniformly humidifying Al(OH)3 sol and drying at a temperature below 100℃, so they are γ-Al2O3 with high specific surface area and high activity, and after being processed in step S2... The heating process in the resistance furnace at 700-800℃ and the hot extrusion process in step S6 make it easy for γ-Al2O3 to migrate in the Cu matrix. The average distance between the dispersed Al2O3 particles is less than 40nm (taking Cu-0.6%Al2O3 product as an example), and the dispersion is uniform. In addition, since the billet is reduced in high-purity hydrogen at 300-400℃ in step S5 and heated in the resistance furnace at 700-800℃ before hot extrusion, the heat treatment temperature is relatively low. Therefore, the dispersed Al2O3 particles will not grow abnormally. The size of the Al2O3 particles is less than 10nm.

[0047] (2) High finished product density, fewer defects, and improved overall performance: Since step S4 increases the maximum pressure of CIP to 300-400MPa, the relative density of the billet is increased by 5.98-7.88% compared to when it is 200MPa, and the porosity defects are significantly reduced, resulting in improved overall performance. Using this high-density billet for subsequent densification treatment, taking a Ф100×300 billet as an example (800t extruder, the extruded product is Ф25, extrusion ratio 16.3), after hot extrusion and stretching, it is stretched into a Ф16 finished product. After testing, the relative density of the finished product exceeds 99.1%.

[0048] (3) The preparation cost is low and the equipment requirements are low.

[0049] Specifically, in step S3, the spray rate is 50–70 ml / min.

[0050] Specifically, in step S3, the drying temperature is 90-95℃ and the drying time is 20-30h.

[0051] Specifically, in step S3, after spraying, continue mixing for 20-30 minutes to ensure that the Al(OH)3 sol concentrate and Cu powder are mixed evenly.

[0052] Specifically, step S1 includes the following steps: atomizing powder with high-purity nitrogen, smelting in a 200kg medium-frequency melting furnace, adding high-purity oxygen-free electric copper in the medium-frequency furnace and smelting for 50-90 minutes; atomizing powder with high-purity nitrogen at a pressure of 0.3-1.9 MPa, drying, and sieving to obtain -100 mesh Cu powder for later use.

[0053] Specifically, in step S2, Al(OH)3 powder is prepared into a sol concentrate according to the amount of target Al2O3 particles introduced, with a solid-liquid ratio of 1:4 to 1:3.

[0054] Specifically, in step S2, the high-speed disperser rotates at 400 r / m and the dispersion time is 20 min.

[0055] Specifically, in step S6, the heating temperature is 700-800℃ and the heating time is 2-3 hours.

[0056] Specifically, in step S6, the extrusion ratio of hot extrusion is 10 to 30.

[0057] Specifically, in step S7, the extruded billet is processed by removing the head and tail, straightening, and stretching to the size required by the user, and then straightened and the head and tail are removed to become the finished product.

[0058] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0059] Example 1

[0060] This embodiment takes Cu-0.6%Al2O3 and Ф100×300 ingot blanks as an example (800t extruder, extruded product Ф25, extrusion ratio 16) to propose a method for preparing high-performance dispersed copper by uniformly adding precursor particles. The method for preparing high-performance dispersed copper by uniformly adding precursor particles includes the following steps:

[0061] S1. Preparation of Cu powder by gas atomization:

[0062] High-purity nitrogen gas was used for atomization powdering, and a 200kg medium-frequency melting furnace was used for melting. High-purity oxygen-free electric copper was added to the medium-frequency furnace and melted for 70 minutes. High-purity nitrogen gas at a pressure of 1.2Mpa was used for atomization powdering, and the powder was dried and sieved to obtain -100 mesh Cu powder for later use.

[0063] Preparation of S2 and Al(OH)3 sol concentrate:

[0064] Based on the amount of Al2O3 particles introduced (Cu-0.6%Al2O3), Al(OH)3 powder was prepared into a sol concentrate at a solid-liquid ratio of 1:4. At the same time, it was always dispersed evenly using a high-speed disperser with a speed of 400 r / m and a dispersion time of 20 min.

[0065] Preparation of S3, Cu / γ-Al2O3 composite powder:

[0066] Al(OH)3 sol concentrate was sprayed into the main raw material Cu powder in a 20L V-type humidifying mixer at a spray speed of 50ml / min. After spraying, the mixture was continued for 30min to ensure that the Al(OH)3 sol concentrate and Cu powder were evenly mixed. After discharge, the mixture was placed in a clean oven to dry and obtain Cu / γ-Al2O3 composite powder. The drying temperature was 95℃ and the drying time was 30h.

[0067] S4, CIP processing:

[0068] Cu / γ-Al2O3 granulated powder was placed in an isostatic pressing chamber and pressed to form an ingot. The pressing process was as follows: the pressurization rate was 10 MPa / min, the maximum pressure was 400 MPa, and the holding time was 12 minutes.

[0069] S5, reduction and sealing:

[0070] The CIP-treated ingot was first placed in high-purity hydrogen for reduction at a temperature of 400°C for 6 hours. Then the ingot was placed in an oxygen-free copper sleeve, evacuated, and sealed by argon arc welding.

[0071] S6. Preheating and extrusion:

[0072] The sealed ingot is first heated in an electric resistance furnace at a temperature of 800℃ for 3 hours; then it is hot extruded to form an extruded bar billet with an extrusion ratio of 16.

[0073] S7. Stretching and Finishing:

[0074] The extruded billet is processed by removing the head and tail, straightening, and stretching to the size required by the user, and then straightening and removing the head and tail to obtain the finished product.

[0075] Example 2

[0076] In this embodiment, unlike in Embodiment 1, the maximum pressure of the pressing process in step S4 is 300 MPa.

[0077] Comparative Example 1

[0078] In this comparative example, unlike Example 1, the maximum pressure of the pressing process in step S4 is 200 MPa.

[0079] Comparative Example 2

[0080] Dispersed copper material prepared using the method in Example 1 of CN202310730926.5.

[0081] Performance testing

[0082] The dispersed copper materials prepared in Examples 1-2 and Comparative Example 1 were subjected to SEM morphology analysis, and the results are as follows: Figure 1 , Figure 2 and Figure 3 As shown.

[0083] The dispersed copper materials prepared in Examples 1-2 and Comparative Example 1 were subjected to flaring tests, and the results are shown in Table 1.

[0084] The performance of the dispersed copper materials prepared in Examples 1-2 and Comparative Examples 1-2 was tested, and the results are shown in Table 1.

[0085] Table 1

[0086]

[0087] from Figure 1 , Figure 2 and Figure 3 It can be seen that when the maximum pressure of the pressing process is 200MPa, the product has a higher probability of more defects. When the maximum pressure of the pressing process is 300MPa and 400MPa, the porosity defects are significantly reduced and the probability of defects is lower.

[0088] As can be seen from Table 1, the Ф16mm rods prepared in Examples 1 and 2 have a relative density of 98.8% to 99.0%, significantly reduced porosity and defects, a flaring depth of 3.68 to 3.74mm, a tensile strength of 681MPa, a yield strength of 687MPa, a hardness (HRB) of 83.6% to 84.4%, and a conductivity of 80.4% to 80.6% IACS, indicating improved overall performance.

[0089] The method of dispersing copper has the following beneficial effects:

[0090] The method for preparing high-performance dispersed copper by uniformly adding precursor particles as described in this invention has steps S1 to S7 that are interconnected and inseparable, playing multiple roles:

[0091] (1) In-situ generation of dispersed Al2O3 particles with fine particle size and uniform distribution: Step S1 first prepares Cu powder by gas atomization, Step S2 then prepares Al(OH)3 sol concentrate, and Step S3 adds Al(OH)3 sol concentrate to the main raw material Cu powder by spraying in a humidifying mixer, mixes evenly, and then places it in a clean oven to dry to obtain Cu / γ-Al2O3 composite powder; Al2O3 particles are obtained by uniformly humidifying Al(OH)3 sol and drying at a temperature below 100℃, so they are γ-Al2O3 with high specific surface area and high activity, and after being processed in step S2... The heating process in the resistance furnace at 700-800℃ and the hot extrusion process in step S6 make it easy for γ-Al2O3 to migrate in the Cu matrix. The average distance between the dispersed Al2O3 particles is less than 40nm (taking Cu-0.6%Al2O3 product as an example), and the dispersion is uniform. In addition, since the billet is reduced in high-purity hydrogen at 300-400℃ in step S5 and heated in the resistance furnace at 700-800℃ before hot extrusion, the heat treatment temperature is relatively low. Therefore, the dispersed Al2O3 particles will not grow abnormally. The size of the Al2O3 particles is less than 10nm.

[0092] (2) High finished product density, fewer defects, and improved overall performance: Since step S4 increases the maximum pressure of CIP to 300-400MPa, the relative density of the billet is increased by 5.98-7.88% compared to when it is 200MPa, and the porosity defects are significantly reduced, resulting in improved overall performance. Using this high-density billet for subsequent densification treatment, taking a Ф100×300 billet as an example (800t extruder, the extruded product is Ф25, extrusion ratio 16.3), after hot extrusion and stretching, it is stretched into a Ф16 finished product. After testing, the relative density of the finished product exceeds 99.1%.

[0093] (3) The preparation cost is low and the equipment requirements are low.

[0094] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method of making high performance dispersion copper by a uniform applied precursor granule process, characterized by, The method for preparing high-performance dispersed copper by uniformly adding precursor particles includes the following steps: S1, Preparation of Cu powder by gas atomization; S2, Preparation of Al(OH)3 sol concentrate: Al(OH)3 powder was prepared into sol concentrate according to the amount of target Al2O3 particles introduced, and was always dispersed evenly using a high-speed disperser; Preparation of S3 and Cu / γ-Al2O3 composite powder: Al(OH)3 sol concentrate was added to the main raw material Cu powder by spraying in a humidifying mixer, mixed evenly, and then placed in a clean oven to dry to obtain Cu / γ-Al2O3 composite powder. S4, CIP processing: Cu / γ-Al2O3 granulated powder is placed in an isostatic pressing sleeve and pressed to form an ingot. The pressing process is as follows: the pressurization rate is 5-15 MPa / min, the maximum pressure is 300-400 MPa, and the holding time is 10-12 minutes. S5. Reduction and Sealing: The CIP-treated billet is first placed in high-purity hydrogen for reduction at a temperature of 300-400℃ for 2-6 hours; then the billet is placed in an oxygen-free copper sleeve, vacuumed, and sealed by argon arc welding. S6. Preheating and extrusion: The sealed billet is first heated in an electric resistance furnace; then hot extrusion is performed to form an extruded bar billet. S7. Stretching and finishing: Post-processing the extruded billet into finished products; In step S3, the spray rate is 50~70 ml / min; In step S3, the drying temperature is 90~95℃ and the drying time is 20~30h; In step S3, after spraying, continue mixing for 20-30 minutes to ensure that the Al(OH)3 sol concentrate and Cu powder are mixed evenly. In step S2, Al(OH)3 powder is prepared into a sol concentrate according to the amount of target Al2O3 particles introduced, with a solid-liquid ratio of 1:4 to 1:

3.

2. A method of making high performance dispersion copper by a uniform feedstock granule method according to claim 1, characterized in that, Step S1 specifically includes the following steps: atomizing powder with high-purity nitrogen, smelting in a 200kg medium-frequency melting furnace, adding high-purity oxygen-free electric copper in the medium-frequency furnace and smelting for 50-90 minutes; atomizing powder with high-purity nitrogen at a pressure of 0.3-1.9Mpa, drying, and sieving to obtain -100 mesh Cu powder for later use.

3. A method of making high performance dispersion copper by a uniform feedstock granule approach as claimed in claim 1, wherein, In step S2, the high-speed disperser rotates at 400 r / m and the dispersion time is 20 min.

4. A method of making high performance dispersion copper by a uniform feedstock granule approach as claimed in claim 1, wherein, In step S6, the heating temperature is 700~800℃ and the heating time is 2~3h.

5. A method of making high performance dispersion copper by a uniform feedstock granule approach as claimed in claim 1, wherein, In step S6, the extrusion ratio of hot extrusion is 10~30.

6. The method for preparing high-performance dispersed copper by uniformly adding precursor particles according to claim 1, characterized in that, In step S7, the extruded billet is processed by removing the head and tail, straightening, and stretching to the size required by the user, and then straightened and the head and tail are removed to become the finished product.

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