Titanium strip coil leveling method and leveled titanium strip coil

Abstract

The invention relates to the technical field of titanium strip coil preparation, in particular to a titanium strip coil leveling method and a leveled titanium strip coil. The titanium strip coil is prepared by the squaring method. The leveling method comprises the following steps: carrying out withdrawal and leveling treatment on an annealed prefabricated titanium strip coil; carrying out stress relief annealing treatment on the titanium strip coil subjected to withdrawal and straightening treatment to obtain a leveled titanium strip coil; wherein the annealing temperature adopted by the stress relief annealing treatment is 400 to 500 DEG C. According to the method, residual stress in the titanium strip coil can be effectively removed, the springback amount of the titanium strip coil after production is reduced, and the use qualification rate is increased.

Description

Technical Field

[0001] The invention relates to the technical field of titanium strip coil preparation, and in particular to a titanium strip coil leveling method and a leveled titanium strip coil. Background Art

[0002] After the production of titanium coils is completed, it is necessary to inspect the performance, surface morphology and flatness of the titanium coils. The production of titanium coils will go through two processes: cold rolling and annealing. During cold rolling, unreasonable roll matching or biased rolls may cause edge waves in the titanium coils. During annealing, the titanium coils are in a curled state, so that the temperature of the middle area of ​​the titanium coil in the width direction is higher than that of the edge area, causing the middle area to be more prone to deformation under the annealing stress than the edge area, i.e., a turtle back. In order to solve the problems of edge waves and turtle back, the industry performs a leveling treatment on the annealed titanium coils. However, there is residual stress inside the leveled titanium coils, which is prone to rebound deformation problems, resulting in unqualified use.

[0003] In summary, it is necessary to develop a titanium strip coil flattening method and a titanium strip coil flattening method to solve the problems existing in the prior art. Summary of the invention

[0004] The object of the present invention is to provide a titanium strip coil leveling method and a titanium strip coil leveling method. The specific technical scheme is as follows:

[0005] In a first aspect, the present invention provides a method for leveling a titanium strip coil, comprising:

[0006] Step S1, performing a straightening treatment on the annealed prefabricated titanium strip coil;

[0007] Step S2, subjecting the titanium strip coil after the tension and straightening treatment to stress relief annealing to obtain a straightened titanium strip coil; wherein the annealing temperature used for the stress relief annealing treatment is 400-500°C.

[0008] Optionally, the annealing time used in the stress relief annealing treatment is 6-10 hours.

[0009] Optionally, the stress relief annealing treatment is performed under a vacuum degree of 40-70Pa.

[0010] Optionally, the stress relief annealing treatment is performed under an inert atmosphere.

[0011] Optionally, the straightening tension used in the straightening treatment is 0.5-0.6 times the yield strength of the prefabricated titanium strip coil, and the straightening speed used is 5-10m / min.

[0012] Optionally, the yield strength of the prefabricated titanium strip coil is 120-500 MPa.

[0013] Optionally, the prefabricated titanium coil includes a pure titanium coil or a titanium alloy coil.

[0014] Optionally, before step S1, the process also includes welding the two adjacent prefabricated titanium strip coils before the straightening treatment end to end; and in step S1, the process also includes cutting the titanium strip coil after the straightening treatment and the adjacent prefabricated titanium strip coil before the straightening treatment end to end.

[0015] Optionally, the thickness of the prefabricated titanium strip coil before the tension-leveling treatment is 0.5-2.0 mm.

[0016] In a second aspect, the present invention provides a flattened titanium coil, which is produced by the titanium coil flattening method.

[0017] The application of the technical solution of the present invention has at least the following beneficial effects:

[0018] The present invention provides a titanium strip flattening method and a titanium strip flattening method. After the straightening treatment, a relatively low temperature stress relief annealing treatment is used to effectively remove the residual stress inside the titanium strip, reduce the amount of springback of the titanium strip after production, and improve the qualified rate of use. Specifically, at a relatively low temperature, that is, the annealing temperature is 400-500°C, when the stress relief annealing treatment is used, due to the recovery effect of the titanium strip, the dislocations in its cellular substructure are recombined through slip and climb, wherein the dislocations of opposite signs cancel each other out, the dislocation density is reduced, the elastic distortion of the lattice is reduced, and the internal stress is reduced. If a higher annealing temperature is selected, the metal in the titanium strip will recrystallize. Although the stress elimination will be more thorough, it will be accompanied by a deterioration of the material properties, mainly a significant decrease in strength. DETAILED DESCRIPTION

[0019] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0020] Embodiment 1:

[0021] A method for leveling a titanium strip coil, comprising:

[0022] Step S1, transport the prefabricated titanium strip coil (specifically pure titanium TA1 strip coil, thickness 2.0mm, width 1050mm, yield strength 220MPa) after annealing (conventional annealing process, specific annealing temperature is 620℃, annealing time is 10h.) to the front of the straightening unit, first weld the two adjacent prefabricated titanium strip coils before the straightening treatment, and then enter the straightening unit for straightening treatment; the titanium strip coil after the straightening treatment and the adjacent prefabricated titanium strip coil before the straightening treatment are cut head to tail. Welding and cutting processes are adopted to facilitate continuous straightening treatment and improve production efficiency. The straightening tension used in the straightening treatment is 0.5 times the yield strength of the prefabricated titanium strip coil, and the straightening speed used is 5m / min.

[0023] Step S2, transporting the titanium strip coil after the straightening treatment to a hood annealing furnace or a vacuum furnace, first evacuating the hood annealing furnace or the vacuum furnace to a vacuum degree of 50Pa, and backfilling with argon gas with a purity of 5ppm; then performing stress relief annealing treatment, the annealing temperature used in the stress relief annealing treatment is 400°C, and the annealing time is 6h to obtain a straightened titanium strip coil.

[0024] Embodiment 2:

[0025] Different from Example 1, in step S1, the prefabricated titanium strip coil is specifically a pure titanium TA2 strip coil with a thickness of 0.5 mm, a width of 1000 mm, and a yield strength of 330 MPa; the straightening tension used in the straightening treatment is 0.6 times the yield strength of the prefabricated titanium strip coil, and the straightening speed used is 10 m / min.

[0026] In step S2, the stress relief annealing treatment is performed at an annealing temperature of 500°C and an annealing time of 10 hours.

[0027] Comparative Example 1:

[0028] The difference from the first embodiment is that step S2 is cancelled.

[0029] Comparative Example 2:

[0030] Different from Example 2, in step S2, the annealing temperature used in the stress relief annealing treatment is 350°C.

[0031] Comparative Example 3:

[0032] Different from Example 2, in step S2, the annealing temperature used in the stress relief annealing treatment is 600°C.

[0033] Comparative Example 4:

[0034] Different from Example 1, in step S1, the straightening tension used in the straightening process is 0.4 times the yield strength of the prefabricated titanium strip coil; and step S2 is cancelled.

[0035] Comparative Example 5:

[0036] Different from Example 1, in step S1, the straightening tension used in the straightening process is 0.7 times the yield strength of the prefabricated titanium strip coil; and step S2 is cancelled.

[0037] The flattened titanium strip coils prepared in Examples 1-2 and Comparative Examples 1-5 were subjected to performance tests and edge wave height tests, respectively, and the results are shown in Table 1-2. In the performance test, tensile strength Rm represents tensile strength, and the test method used is the tensile test method in GBT228.1-2010; yield strength Rp0.2 represents yield strength, and the test method used is the tensile test method in GBT228.1-2010; A represents elongation; A50% represents that the tensile specimen is a non-proportional specimen with a gauge length of 50 mm, and the test method used is the tensile test method in GBT228.1-2010. The edge wave height test adopts a test method of measuring the height of the waves at the edge of the titanium strip coil using a height gauge; the test of the edge wave height after rebound is completed within 1-24 hours after the straightening treatment or the stress relief annealing treatment.

[0038] Table 1 Performance test results and side wave height test results

[0039]

[0040]

[0041] Table 2 Test results of side wave height after rebound

[0042] Grouping Height of side wave after rebound / mm Example 1 5 Example 2 4 Comparative Example 1 11 Comparative Example 2 10 Comparative Example 3 8 Comparative Example 4 11 Comparative Example 5 9

[0043] It can be seen from Table 1-2 that compared with Comparative Example 1, the height of the edge waves after the rebound of the leveled titanium strip coil prepared by Example 1-2 of the present invention is significantly reduced, which indicates that the stress relief annealing treatment adopted by the present invention after the straightening treatment can effectively remove the residual stress inside the titanium strip coil, reduce the rebound amount of the titanium strip coil after production, and improve the qualified rate of use.

[0044] Compared with Example 2, the height of the edge waves of the flattened titanium strip coil prepared by Comparative Example 2 after rebound is significantly increased, which indicates that the temperature used in the stress relief annealing treatment is too low to remove the residual stress inside the titanium strip coil.

[0045] Compared with Example 2, the A50% of the leveled titanium strip coil prepared by Comparative Example 3 has no significant increase, but the edge wave height after rebound is significantly increased. This shows that although the temperature used in the stress relief annealing treatment is too high, the grain growth will increase the elongation, but the titanium strip coil is in a bent state during the annealing process, and the heating process will cause the inner and outer coils to be heated unevenly. The edge of the titanium strip coil is heated first and the middle part is heated later, resulting in a large internal stress. After annealing, the macroscopic arch (i.e., turtle back) is present, and increasing the annealing temperature will aggravate the uneven internal stress, further deteriorating the poor plate shape, and then the edge wave height will increase significantly after rebound.

[0046] Compared with Example 1, the tension used in Comparative Example 4 is too low and cannot flatten the titanium strip coil; in addition, since the stress relief annealing treatment in step S2 is not adopted, residual stress exists inside the titanium strip coil, showing a very high rebound rear edge wave height.

[0047] Compared with Example 1, the tension of the straightening in Comparative Example 5 is too high. Although the titanium strip can be straightened, A50% is significantly reduced, resulting in a decrease in the elongation of the titanium strip, which is prone to defects in subsequent use, such as breakage in the stamping process; in addition, because the stress relief annealing treatment in step S2 is not adopted, residual stress exists inside the titanium strip, showing a higher height of the rear edge wave after rebound.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for leveling a titanium strip coil, characterized in that: include: Step S1, performing a straightening treatment on the annealed prefabricated titanium strip coil; Step S2, subjecting the titanium strip coil after the tension and straightening treatment to stress relief annealing to obtain a straightened titanium strip coil; wherein the annealing temperature used for the stress relief annealing treatment is 400-500°C.

2. The method for leveling a titanium strip coil according to claim 1, characterized in that: The annealing time used in the stress relief annealing treatment is 6-10 hours.

3. The method for leveling a titanium strip coil according to claim 1, characterized in that: The stress relief annealing treatment is performed under a vacuum degree of 40-70Pa.

4. The method for leveling a titanium strip coil according to claim 1, characterized in that: The stress relief annealing treatment is performed under an inert atmosphere.

5. The method for leveling a titanium strip coil according to claim 1, characterized in that: The tension used in the straightening treatment is 0.5-0.6 times the yield strength of the prefabricated titanium strip coil, and the straightening speed used is 5-10m / min.

6. The method for leveling a titanium strip coil according to claim 5, characterized in that: The yield strength of the prefabricated titanium strip coil is 120-500 MPa.

7. The method for leveling a titanium strip coil according to claim 1, characterized in that: The prefabricated titanium strip coil comprises a pure titanium strip coil or a titanium alloy strip coil.

8. The method for leveling a titanium strip coil according to claim 1, characterized in that: Before step S1, the process also includes welding the two adjacent prefabricated titanium strip coils before the straightening treatment end to end; and in step S1, the process also includes cutting the titanium strip coil after the straightening treatment and the adjacent prefabricated titanium strip coil before the straightening treatment end to end.

9. The method for leveling a titanium strip coil according to claim 1, characterized in that: The thickness of the prefabricated titanium strip coil before the tension straightening treatment is 0.5-2.0 mm.

10. A flattened titanium strip coil, characterized in that: The titanium strip is prepared by the titanium strip flattening method as described in any one of claims 1 to 9.

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