Method for improving strip-shaped abnormal structure of TC1 titanium alloy sheet

Abstract

The invention discloses a method for improving a strip-shaped abnormal structure of a TC1 titanium alloy sheet. The method comprises the following steps: step 1, cogging, heating and rolling above a phase transformation point; 2, plate homogenization treatment is conducted above the phase transformation point; 3, reheating is conducted below the phase transformation point, and rolling operation with the deformation larger than or equal to 50% is executed; 4, recrystallization heat treatment is carried out; and 5, a finish rolling process (cold rolling) with the deformation being larger than or equal to 40% is conducted. By controlling the rolling temperature and the rolling deformation, the strip-shaped abnormal structure of the TC1 thin plate can be effectively improved, and the plate structure tends to be a uniform and fine two-phase region machining structure. The deformation resistance of the material can be effectively reduced by regulating and controlling the rolling temperature, internal stress caused by severe plastic deformation in the rolling process is reduced, and uniform deformation of the material is guaranteed. And by controlling the rolling deformation amount, crystal grains in the plate can be fully crushed, and abnormal structures are eliminated.

Description

Technical Field

[0001] The invention relates to the technical field of metal material processing, and more specifically to a method for improving the banded abnormal structure of a TC1 titanium alloy thin plate. Background Art

[0002] TC1 titanium alloy sheet is widely used in aerospace and navigation fields due to its excellent specific strength, corrosion resistance and formability, as well as good comprehensive mechanical properties. However, in recent years, TC1 thin sheet will inevitably have structural abnormalities caused by local non-uniform plastic deformation during rolling and preparation, resulting in cost waste of batch defective products and economic losses for manufacturers.

[0003] See also Figure 1 , where (a) 200X left part of the plate cross section; (b) 500X left part of the plate cross section; (c) 200X middle part of the plate cross section; (d) 500X middle part of the plate cross section; (e) 200X right part of the plate cross section; (f) 500X right part of the plate cross section. Observing the microstructure of multiple batches of TC1 titanium alloy sheets, it was found that there were banded abnormal microstructures in the microstructure, and the morphology was dark fine grain stripes.

[0004] By comparing and analyzing the chemical element content of normal tissue and "dark stripe" tissue, the formation of this type of tissue due to component segregation was ruled out. After multiple performance tests, it was finally concluded that the formation mechanism of the abnormal banded tissue in TC1 titanium alloy sheet was caused by uneven deformation.

[0005] Therefore, it is particularly important to provide a method for improving the banded abnormal structure of TC1 titanium alloy thin plate. Summary of the invention

[0006] In order to solve the above-mentioned tissue abnormality problem, the present invention provides a method for improving the banded abnormal tissue of TC1 titanium alloy thin plate.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for improving the banded abnormal structure of a TC1 titanium alloy sheet comprises the following steps:

[0009] Step 1: Heating and rolling above the phase change point

[0010] The TC1 slab is heated to 10-20°C above the phase transformation point, and after being kept at this temperature for a certain period of time, the slab is rolled;

[0011] Step 2: Homogenize the plate above the phase change point

[0012] After the slab is rolled, the plate rolled to the target thickness is heated to 20 to 60°C above the phase change point, and forcedly cooled after being kept at the temperature for a certain period of time;

[0013] Step 3: Reheat below the phase transformation point and perform rolling with a deformation of ≥ 50%

[0014] The plate after homogenization treatment is reheated at 50-100°C below the phase transition point, and after a certain period of heat preservation, a rolling operation with a deformation amount of ≥50% is performed;

[0015] Step 4: Perform recrystallization heat treatment

[0016] Semi-finished plates rolled to a specified thickness must undergo recrystallization heat treatment before finishing rolling. The recrystallization heat treatment system is 700-760℃ / 25-60min air cooling;

[0017] Step 5: Finish rolling with deformation ≥ 40%

[0018] Only plates that have undergone recrystallization heat treatment can be transferred to the finishing mill for rolling operations with a deformation of ≥40%.

[0019] Preferably, in step 1, the insulation time is specifically: slab thickness H×1.0~1.2min / mm.

[0020] Preferably, in step 2, the thickness of the homogenized heat treated plate is 10 to 25 mm.

[0021] Preferably, in step 2, the insulation time is specifically: plate thickness h×1.4~1.6min / mm.

[0022] Preferably, in step 2, the forced cooling method is water cooling, the medium is flowing water, the water temperature shall not exceed 80° C., the plate transfer time shall be ≤2s, and the water cooling time shall not be <1min.

[0023] Preferably, in step 3, the insulation time is specifically: plate thickness h×0.8~1.0min / mm.

[0024] Preferably, in step 4, the heat treatment holding time is as follows: when a continuous heat treatment method is adopted, the holding time for a plate thickness of h<3.19 mm is 20±5 min, and the holding time for a plate thickness of 3.19 mm<h<6.35 mm is 30±5 min; when an intermittent heat treatment method is adopted, the holding time is 60 min.

[0025] Technical effects and advantages of the present invention:

[0026] 1. By controlling the rolling temperature and rolling deformation, the abnormal banded structure of TC1 thin plate can be effectively improved, and the plate structure tends to be uniform and fine two-phase processing structure. By adjusting the rolling temperature, the deformation resistance of the material can be effectively reduced, the internal stress caused by large plastic deformation during the rolling process can be reduced, and the uniform deformation of the material can be ensured. By controlling the rolling deformation, the grains in the plate can be fully broken and the abnormal structure can be eliminated.

[0027] 2. This invention is applicable to TC1 titanium alloy plates produced in sheet form. This invention has a good control effect on the microstructure of TC1 titanium alloy plates with a thickness of 0.3 to 4.5 mm.

[0028] 3. It is suitable for small batch experiments and also suitable for batch and engineering preparation of TC1 titanium alloy thin plates. The invention content specifies the heating temperature, rolling deformation, homogenization temperature, recrystallization annealing temperature and deformation of the finishing process during the rough rolling process, which can ensure the stability of batch preparation and organizational control of plate products. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is an example of abnormal structure of 1.0mm thick TC1 titanium alloy plate in related technology;

[0030] Figure 2 This is the comparison organization diagram of 1.0mm thick TC1 plate under different parameters;

[0031] Figure 3 This is an example of the organization of the 1.0 mm thick TC1 titanium alloy plate of the present invention. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] The titanium alloy used in the embodiment provided by the present invention is TC1 alloy, and a 1.0 mm thick plate (width 1000 mm, length 2000 mm) is obtained by rolling. The plate is gradually subjected to blanking rolling, homogenization treatment, rough rolling, recrystallization heat treatment and finish rolling. Under the dual regulation of rolling temperature and rolling deformation, the plate structure gradually tends to be uniform, and finally a two-phase zone processed structure plate with uniform and fine structure and no internal banded abnormal structure is obtained.

[0034] The present invention sets 16 groups of comparative cases: please refer to Figure 2In each comparative case, the parameters such as the blank rolling temperature, rough rolling deformation and homogenization treatment are constant. The rough rolling reheating temperature ranges from 820 to 850°C, with a gradient of 10°C; the finishing rolling deformation is controlled at 25 to 40%, with a gradient of 5%.

[0035] Comparative Example 1: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by 820℃ reheating and 25% finishing rolling was tested according to the GB / T 5168 testing method. The test results show that the TC1 plate processed as above has multiple obvious band-shaped abnormal microstructures. Figure 2 -a as shown.

[0036] Comparative Example 2: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by 820℃ reheating and 30% finishing rolling deformation was tested according to the GB / T 5168 testing method. The test results show that the TC1 plate processed as above still has multiple obvious band-shaped abnormal microstructures. Figure 2 -b as shown.

[0037] Comparative Example 3: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by 820℃ reheating and 35% finishing rolling deformation was tested according to the GB / T 5168 testing method. The test results show that the TC1 plate processed as above still has multiple obvious band-shaped abnormal microstructures. Figure 2 -c.

[0038] Comparative Example 4: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by 820℃ reheating and 40% finishing rolling deformation was tested according to the GB / T 5168 testing method. The test results show that the TC1 plate processed as above still has multiple obvious band-shaped abnormal microstructures. Figure 2 -d. It is confirmed that after the plate is reheated at 820℃, the abnormal structure of the plate after finish rolling is difficult to eliminate.

[0039] Comparative Example 5: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by 830℃ reheating and 25% finishing rolling deformation was tested according to the GB / T 5168 testing method. The test results show that the TC1 plate processed as above still has multiple obvious band-shaped abnormal microstructures. Figure 2 -e as shown.

[0040] Comparative Example 6: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by 830℃ reheating and 30% finishing rolling deformation was tested according to the GB / T 5168 testing method. The test results show that the TC1 plate processed as above still has multiple obvious band-shaped abnormal microstructures. Figure 2 -f as shown.

[0041] Comparative Example 7: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by 830℃ reheating and 35% finishing rolling deformation was tested according to the GB / T 5168 testing method. The test results show that the TC1 plate processed as above still has multiple obvious band-shaped abnormal microstructures. Figure 2 -g as shown.

[0042] Comparative Example 8: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by reheating at 830°C and finishing with a deformation of 40% was tested according to the GB / T 5168 test method. The test results showed that the TC1 plate processed as above still had a number of obvious banded abnormal microstructures. Figure 2 -h. It is confirmed that after the plate is reheated at 830℃, the abnormal structure of the plate after finish rolling is difficult to eliminate.

[0043] Comparative Example 9: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by 840℃ reheating and 25% finishing rolling deformation was tested according to the GB / T 5168 testing method. The test results show that the TC1 plate processed as above still has multiple obvious band-shaped abnormal microstructures. Figure 2 -i as shown.

[0044] Comparative Example 10: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by 840℃ reheating and 30% finishing rolling deformation was tested according to the GB / T 5168 testing method. The test results show that the TC1 plate processed as above still has multiple obvious band-shaped abnormal microstructures. Figure 2 -j as shown.

[0045] Comparative Example 11: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate obtained by reheating at 840°C and finishing with a deformation of 35% was tested according to the GB / T 5168 test method. The test results showed that the TC1 plate processed as above still had a number of obvious band-like abnormal microstructures. Figure 2 -k as shown.

[0046] Comparative Example 12: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate obtained by reheating at 840°C and finishing with a deformation of 40% was tested according to the GB / T 5168 test method. The test results showed that the TC1 plate processed as above still had a number of obvious banded abnormal microstructures inside, but the number of abnormal microstructures was improved compared with other comparative examples at the same reheating temperature. Figure 2 -l as shown.

[0047] Comparative Example 13: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate processed by reheating at 850°C and finishing with a deformation of 25% was tested according to the GB / T 5168 test method. The test results showed that the TC1 plate processed as above still had a number of obvious banded abnormal microstructures. Figure 2 -m as shown.

[0048] Comparative Example 14: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 plate obtained by reheating at 850°C and finishing with a deformation of 30% was tested according to the GB / T 5168 test method. The test results showed that the TC1 plate processed as above still had a number of obvious band-like abnormal microstructures. Figure 2 -n as shown.

[0049] Comparative Example 15: Using an optical microscope, the TC1 sheet with a size of 1.0×1000×2000 mm, which was processed by reheating at 850°C and finishing with a deformation of 35%, was tested according to the GB / T 5168 test method. The test results showed that there was still a small amount of inconspicuous banded abnormal tissue inside the TC1 sheet processed as above, but compared with the other comparative examples above, the morphology and quantity of the abnormal tissue were improved. Figure 2 -o as shown.

[0050] Comparative Example 16: Using an optical microscope, the microstructure of the 1.0×1000×2000mm TC1 sheet processed by 850°C reheating and 40% finishing rolling deformation was tested according to the GB / T 5168 testing method. The test results show that the microstructure of the TC1 sheet processed as above is uniform and fine, and there is no abnormal banded microstructure inside. Figure 2 It is confirmed that the plate after reheating at 850℃ has a uniform structure after finishing rolling with a deformation of 40%, and the band-like abnormal structure is effectively eliminated.

[0051] Implementation Cases

[0052] The specific process of this implementation case is:

[0053] Step 1: Heating and rolling above the phase change point

[0054] The 150mm thick (705mm wide × 1040mm long) TC1 slab was heated at 940℃ in a heating furnace and kept at this temperature for 180min. After the heat preservation, the slab was rolled to a thickness of 15.0mm with a width of 1040mm.

[0055] Step 2: Homogenize the plate above the phase change point

[0056] After the blanking and rolling, the plate is cut to size according to the plan, and the shaped plate is heated to 970℃ in the heat treatment furnace and kept warm for 23 minutes. After the insulation is completed, the plate is immediately placed in running water for forced cooling, and then taken out and safely stacked after standing for 1 to 2 minutes;

[0057] Step 3: Reheat below the phase transformation point and perform rolling with a deformation of ≥ 50%

[0058] The homogenized plate is reheated at 850℃ for 15 minutes. After the insulation, the plate is rolled to 6.0mm thick and cut to size as planned. The plate is reheated at 850℃ for 6 minutes according to the above operation. After the insulation, the plate is rolled to 3.0mm thick;

[0059] Step 4: Perform recrystallization heat treatment

[0060] The semi-finished plate rolled to 3.0mm thickness is recrystallized in a heat treatment furnace at a temperature of 740℃±10℃ for 20min. The heat-treated plate must be surface treated and then transferred to the cold rolling unit for finishing rolling;

[0061] Step 5: Finish rolling process (cold rolling) with deformation ≥ 40%

[0062] At room temperature, the 3.0 mm thick plate is rolled to 1.8 mm thick by a cold rolling unit, and the above step 4 is repeated for the 1.8 mm thick plate. Then, at room temperature, the 1.8 mm thick plate is rolled to 1.0 mm thick by a cold rolling unit. After finished product heat treatment and surface treatment, a finished plate with uniform structure and no abnormal banded structure is finally obtained.

[0063] Treatment result evaluation: The final organization of each area of ​​the 1.0×1000×2000mm TC1 plate was tested using an optical microscope according to the GB / T 5168 testing method. Figure 3 As shown, (a) the left part 200X of the cross section of the plate; (b) the left part 500X of the cross section of the plate; (c) the middle part 200X of the cross section of the plate; (d) the middle part 500X of the cross section of the plate; (e) the right part 200X of the cross section of the plate; (f) the right part 500X of the cross section of the plate.

[0064] After the whole process of the invention, the board structure is uniform and fine, and there is no dark band-like abnormal structure in each board area, and a good treatment effect is achieved.

[0065] The above description is only a preferred implementation case of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving the banded abnormal structure of TC1 titanium alloy thin plate, characterized in that: The following steps are involved: Step 1: Heating and rolling above the phase change point The TC1 slab is heated to 10-20°C above the phase transformation point, and after being kept at this temperature for a certain period of time, the slab is rolled; Step 2: Homogenize the plate above the phase change point After the slab is rolled, the plate rolled to the target thickness is heated to 20 to 60°C above the phase change point, and forcedly cooled after being kept at the temperature for a certain period of time; Step 3: Reheat below the phase transformation point and perform rolling with a deformation of ≥ 50% The plate after homogenization treatment is reheated at 50-100°C below the phase transition point, and after a certain period of heat preservation, a rolling operation with a deformation amount of ≥50% is performed; Step 4: Perform recrystallization heat treatment Semi-finished plates rolled to a specified thickness must undergo recrystallization heat treatment before finishing rolling. The recrystallization heat treatment system is 700-760℃ / 25-60min air cooling; Step 5: Finish rolling with deformation ≥ 40% Only plates that have undergone recrystallization heat treatment can be transferred to the finishing mill for rolling operations with a deformation of ≥40%.

2. The method for improving the banded abnormal structure of TC1 titanium alloy sheet according to claim 1, characterized in that: In the step 1, the insulation time is specifically: slab thickness H×1.0~1.2min / mm.

3. The method for improving the banded abnormal structure of TC1 titanium alloy sheet according to claim 1, characterized in that: In step 2, the thickness of the homogenized heat-treated plate is 10 to 25 mm.

4. The method for improving the banded abnormal structure of TC1 titanium alloy sheet according to claim 1, characterized in that: In step 2, the insulation time is specifically: plate thickness h×1.4~1.6min / mm.

5. The method for improving the banded abnormal structure of TC1 titanium alloy sheet according to claim 1, characterized in that: In step 2, the forced cooling method is water cooling, the medium is flowing water, the water temperature shall not exceed 80° C., the plate transfer time shall be ≤ 2s, and the water cooling time shall not be < 1min.

6. The method for improving the abnormal banded structure of TC1 titanium alloy sheet according to claim 1, characterized in that: In step 3, the insulation time is specifically: plate thickness h×0.8~1.0min / mm.

7. The method for improving the banded abnormal structure of TC1 titanium alloy sheet according to claim 1, characterized in that: In step 4, the specific heat treatment holding time is: when a continuous heat treatment method is adopted, the holding time for a plate thickness of h<3.19mm is 20±5min, and the holding time for a plate thickness of 3.19mm<h<6.35mm is 30±5min; when an intermittent heat treatment method is adopted, the holding time is 60min.

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