Method for rolling a wide coil of tb, tc titanium alloy

Abstract

The application provides a wide strip rolling method of TB, TC titanium alloy, which comprises the following steps: S1, preparing electrode blocks, and smelting the electrode blocks after group welding to obtain titanium ingots; S2, forging the titanium ingots into slabs, and rolling the slabs after surface treatment to medium-rolled plates with a thickness of 50-60 mm, and further rolling the medium-rolled plates to 5-6 mm wide strips; S3, treating the wide strips, cold-rolling the wide strips through the first pass to the third last pass to obtain cold-rolled preformed wide strips, cold-rolling the preformed wide strips through the second last pass and the last pass to obtain 1 mm wide strips, and carrying out on-line annealing on the wide strips. According to the application, the titanium alloy is smelted to ingots according to the characteristics of the titanium alloy, the scales on the surface of the ingots are removed after coiling, and the ingots are directly cold-rolled after grinding, so that the titanium alloy wide strips of TB and TC series with a thickness of less than 1.0 mm can be rolled.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy strip rolling technology, specifically to a method for rolling wide strips of TB and TC titanium alloys. Background Technology

[0002] Titanium alloys are characterized by their light weight, high strength, low elasticity, high temperature resistance, and corrosion resistance, and are widely used in aerospace, marine, marine engineering, petroleum, and chemical industries. Titanium has a melting point of 1720℃ and exists in two allotropes: below 882℃, it exhibits a close-packed hexagonal crystal structure, called α-titanium; above 882℃, it exhibits a body-centered cubic lattice structure, called β-titanium. By appropriately adding alloying elements, the phase transformation temperature and phase content are gradually altered to obtain titanium alloys with different microstructures. α-titanium alloys are designated TA, β-titanium alloys are designated TB, and α+β titanium alloys are designated TC.

[0003] Currently, the production of TB and TC series titanium alloy strips in China mainly involves rolling single sheets to 2 mm and then welding them together before rolling. After the rolled strips are processed to below 1.0 mm, strip breakage frequently occurs at the welded areas, and the crystal structure at the welded areas is inconsistent with the bulk structure, which seriously affects product consistency. Furthermore, the existing sizes are mainly concentrated in strips with a width of less than 300 mm, and the strips without intermediate welds are imported from abroad, which is extremely expensive.

[0004] Therefore, solving the rolling problem of TB and TC series titanium alloy strips is particularly important. TB and TC series titanium alloys differ from TA series. TA series titanium alloys are annealed using a vacuum bell-type annealing furnace, but TB series cannot be annealed in the same way. This would cause the annealing of TB series alloys to become an aging treatment, which would increase the strength of the material but reduce its plasticity, making subsequent processing impossible. Therefore, this invention studies and designs a wide strip rolling method for TB and TC titanium alloys. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect that the rolling of titanium alloy strips in the prior art increases the strength of the material and reduces the plasticity of the material, so that subsequent processing cannot be carried out, thereby providing a method for rolling TB and TC titanium alloy wide strips.

[0006] To address the above problems, this invention provides a method for rolling wide strips of TB and TC titanium alloys, comprising the following steps:

[0007] S1: Prepare electrode blocks, and weld the electrode blocks together and then melt them to obtain titanium ingots;

[0008] S2: Titanium ingots are forged into slabs, surface treated, and then rolled into 50-60mm medium-sized plates, and further rolled into 5-6mm coils;

[0009] S3: After processing the coil, the coil is cold rolled in the first to third-to-last cold rolling passes to obtain a cold-rolled pre-cold rolled coil. The pre-cold rolled coil is then cold rolled in the penultimate and final cold rolling passes to obtain a 1mm cold rolled coil. The cold rolled coil is then annealed online.

[0010] Preferably, in step S1, sponge titanium is used as the main raw material, an alloy bag is added, the sponge titanium is divided into four equal layers, and an equal amount of alloy bag is filled between two adjacent layers of sponge titanium to form an electrode. The electrode is then placed in a rolling mill and rolled into an electrode block.

[0011] The electrode block is placed in a vacuum chamber and vacuum plasma is used for electrode assembly welding. The assembled electrode block is then placed in a vacuum electrode consumable furnace for melting at least three times to reduce impurities and obtain titanium ingots.

[0012] Preferably, the surface treatment in S2 includes: detecting whether the composition meets the composition requirements, flaw detection and removal of risers, removal of oxide scale, defect detection, and grinding;

[0013] Whether the detected component meets the component requirements is as follows:

[0014] The composition of the titanium ingot is tested to determine the percentage of oxygen content by mass. If the percentage of oxygen content by mass is within the specified range, the next step is carried out; otherwise, the ingot is remelted.

[0015] The process of flaw detection and riser removal involves: performing ultrasonic flaw detection on the titanium ingot, removing the ingot riser, holding the titanium ingot at 1120-1200℃, and then forging it into a slab on a rolling mill.

[0016] The heat preservation time is increased by 2.5 min / mm based on the thickness of the titanium ingot;

[0017] The process of removing oxide scale involves sequentially subjecting the slab to alkali blasting and acid pickling to remove oxides.

[0018] The defect detection and grinding process involves: using a coloring agent to detect defects on the surface of the slab, and grinding the defective parts after detection to facilitate further rolling into medium-rolled plates.

[0019] Preferably, the rolling temperature of the intermediate plate is 980-950℃, the holding time is determined to be 150min / cm, the thickness of the intermediate plate is 50-60mm, and after the surface is polished, it is placed on a water jet cutting machine to cut into strips with a length of 2000mm and a width of 300-500mm, and rolled into 5-6mm coils on a rolling mill.

[0020] Preferably, the processing of the tape is as follows: heating, heat preservation, solution treatment, descaling treatment, and surface grinding of the tape;

[0021] The heating temperature of the tape is 800-880℃, and the heat preservation time is 30 minutes;

[0022] The solution treatment method is water-cooled.

[0023] The descaling process involves descaling the strip using a descaling machine. Before the descaling process, the strip is further cold-rolled and pressed down by 0.3-0.5 mm on the rolling mill.

[0024] The surface finishing process involves grinding the oxide scale and defects on the surface of the descaling strip using a grinding machine.

[0025] Preferably, during the pre-cooled coil cold rolling process, intermediate annealing is performed between the first pass and the third-to-last pass; online annealing is performed in the second-to-last pass and the last pass, and the annealing temperature is 750-820℃.

[0026] Argon gas is used for protection during the annealing process.

[0027] Preferably, the strip is cold-rolled to pre-cold-rolled strip after the first to third-to-last cold rolling passes, and the reduction rate of the rolling mill unit during the cold rolling process is controlled to be 10-20%.

[0028] The method for rolling wide strips of TB and TC titanium alloys provided by this invention has the following beneficial effects:

[0029] This invention utilizes the properties of TB alloys to roll titanium ingots into coils. The process involves pressing electrodes according to a specific ratio, melting and casting the ingot, forging a slab, rolling it to 5-6 mm, directly water-cooling, solution treatment, and coiling. After coiling, the surface is descaled, ground, and then directly cold-rolled. During cold rolling, argon-protected online annealing is employed. Argon protection is maintained throughout the annealing process to prevent surface oxidation. After annealing, cold rolling continues to approximately 1 mm. This process is repeated to roll TB and TC series titanium alloy coils with a thickness below 1.0 mm. This overcomes the defect that rolling titanium alloy coils increases material strength but reduces its plasticity, making subsequent processing impossible. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the TB and TC titanium alloy wide strip rolling method of the present invention. Detailed Implementation

[0031] like Figure 1 As shown, the present invention provides a method for rolling wide strips of TB and TC titanium alloys, which includes the following steps:

[0032] S1: Prepare electrode blocks, and weld the electrode blocks together and then melt them to obtain titanium ingots;

[0033] Specifically, sponge titanium is used as the main raw material, and an alloy bag is added. The ratio of the alloy bag to sponge titanium is in accordance with GB / T3620.1-2016 "Titanium and Titanium Alloy Grades and Chemical Composition". The sponge titanium is divided into four equal layers, and an equal amount of alloy bag is filled between two adjacent layers of sponge titanium to form an electrode. The electrode is rolled into an electrode block in a rolling mill. The electrode block is placed in a vacuum box and vacuum plasma is used for electrode assembly welding. The assembled electrode block is placed in a vacuum electrode consumable furnace for melting at least three times to reduce impurities and obtain titanium ingot.

[0034] S2: Titanium ingots are forged into slabs, surface treated, and then rolled into 50-60mm medium-sized plates, and further rolled into 5-6mm coils;

[0035] Specifically, the composition of the titanium ingot is tested to determine whether the oxygen content mass fraction in the titanium ingot is between 0.07% and 0.12%. If it meets the requirement, the next step is carried out; otherwise, it is remelted and subjected to ultrasonic flaw detection. The ingot riser is removed, and the titanium ingot is heated at 1120-1200℃ with the holding time increased by 2.5 min / mm according to the thickness of the titanium ingot to remove the riser. The slab is then subjected to alkali blasting and pickling to remove oxidation. After that, the surface of the slab is inspected for defects with a coloring agent. After the defects are detected, the defective parts are ground. The holding time is determined at 980-950℃ and 150 min / cm. The slab is rolled into a medium-rolled plate with a thickness of 50-60 mm. After the surface is ground, it is placed on a water jet cutting machine to cut into strips with a length of 2000 mm and a width of 300-500 mm. The strips are then rolled into coils of 5-6 mm on the rolling mill.

[0036] S3: After processing the coil, the coil is cold rolled in the first to third-to-last cold rolling passes to obtain a cold-rolled pre-cold rolled coil. The pre-cold rolled coil is then cold rolled in the penultimate and final cold rolling passes to obtain a 1mm cold rolled coil. The cold rolled coil is then annealed online.

[0037] Specifically, the strip is heated to 800-880℃ and held for 30 minutes, then solution-treated using water cooling. The strip is then descaled using a descaling machine. Before descaling, the strip is further cold-rolled on a rolling mill to reduce the surface thickness by 0.3-0.5mm. Afterwards, the oxide scale and defects are removed using a grinding machine. The strip is then cold-rolled through the first to third-to-last passes to obtain a cold-rolled pre-cooled strip. This pre-cooled strip is then annealed at 750-820℃, and finally subjected to the penultimate and final cold-rolled passes. The final cold rolling pass yields a 1mm cold-rolled strip. Online annealing is performed at 750-820℃, with argon protection throughout the process. The reduction rate of the rolling mill is controlled at 10-20% during the cold rolling process to obtain a 1mm strip. The reduction rate is the percentage (%) of the reduction amount Δh to the height H of the workpiece before rolling or the height h after rolling, i.e., Δh / H×100 or Δh / h×100. It is a deformation parameter that represents the degree of relative compression deformation in the height direction during rolling.

[0038] Example 1

[0039] In this embodiment, TB9 is used as an example. Four layers of sponge titanium are coated with an alloy package and then subjected to electrode pressing to obtain an electrode block. Sponge titanium is the main raw material, with the alloy package added. Equal amounts of alloy package are filled between adjacent layers of sponge titanium to form electrodes. The electrodes are then rolled into electrode blocks on a rolling mill. The electrode blocks are then welded in a vacuum chamber and melted three times in a vacuum electrode consumable furnace to obtain titanium ingots. After testing the composition of the titanium ingots, flaw detection is performed to remove the risers, and the ingots are held at 135 minutes before forging into slabs. The composition of the titanium ingots is tested to determine that the oxygen content by mass fraction is 0.09%, and then further processing is performed. The titanium ingots are then subjected to ultrasonic flaw detection, the risers are removed, and the ingots are held at 1150°C before being forged into slabs on a rolling mill. The slabs are then subjected to alkali blasting and pickling to remove oxidation. A coloring agent is used to detect defects on the slab surface. Defective parts are then ground to facilitate further rolling into 50mm thick medium-thickness plates. The rolling temperature of the medium-thickness plates is... The strips were heated to 980℃ for 75 minutes, then polished before being cut into strips 500mm long and 2000mm wide using a waterjet cutting machine. These strips were then rolled into 5mm thick coils on a reciprocating strip mill. The coils underwent heating, heat preservation, solution treatment, and descaling, followed by surface polishing. The heating temperature was 850℃ for 30 minutes; the solution treatment was water-cooled; and the descaling process involved using a descaling machine. Before descaling, the coils were... The strip is further cold-rolled on the rolling mill to a reduction of 0.3mm; the oxide scale and defects on the surface of the strip after descaling are removed by grinding on a grinding machine; the treated strip is then cold-rolled in three passes to obtain a pre-cold-rolled cold-rolled strip, which is then annealed at 820℃ in the middle, and then cold-rolled in two passes to obtain a 1mm cold-rolled strip, which is then annealed online at 820℃. Argon gas protection is used throughout the process, and the reduction rate of the rolling mill is controlled at 9% during the cold rolling process to obtain a 1mm strip.

[0040] Example 2

[0041] Compared with Example 1, this implementation, taking TB9 as an example, differs in that the processed coil is cold-rolled twice to obtain a cold-rolled pre-cold-rolled coil, which is then annealed at 820°C in the middle, and then cold-rolled twice to obtain a 1mm cold-rolled coil, which is then annealed online at 820°C. Argon gas protection is used throughout the process, and the reduction rate of the rolling mill is controlled at 16% during the cold rolling process to obtain a 1mm coil.

[0042] Example 3

[0043] Compared with Example 1, this implementation, taking TB9 as an example, differs in that the processed coil is cold-rolled once to obtain a cold-rolled pre-cold-rolled coil, which is then annealed at 820°C in the middle, and then cold-rolled twice to obtain a 1mm cold-rolled coil, which is annealed online at 820°C. Argon gas protection is used throughout the process, and the reduction rate of the rolling mill is controlled at 21% during the cold rolling process to obtain a 1mm coil.

[0044] Example 4

[0045] Compared with Example 1, this implementation, taking TC11 as an example, differs in that the processed coil is cold-rolled twice to obtain a cold-rolled pre-cold-rolled coil, which is then annealed at 810°C in the middle, and then cold-rolled three times to obtain a 1mm cold-rolled coil, which is annealed online at 810°C. Argon gas protection is used throughout the process, and the reduction rate of the rolling mill is controlled at 10% during the cold rolling process to obtain a 1mm coil.

[0046] Example 5

[0047] Compared with Example 1, this implementation, taking TC11 as an example, differs in that the processed coil is cold-rolled twice to obtain a cold-rolled pre-cold-rolled coil, which is then annealed at 810°C in the middle, and then cold-rolled twice to obtain a 1mm cold-rolled coil, which is then annealed online at 810°C. Argon gas protection is used throughout the process, and the reduction rate of the rolling mill is controlled at 15% during the cold rolling process to obtain a 1mm coil.

[0048] Example 6

[0049] Compared with Example 1, this implementation, taking TC11 as an example, differs in that the processed coil is cold-rolled once to obtain a cold-rolled pre-cold-rolled coil, which is then annealed at 810°C in the middle, and then cold-rolled twice to obtain a 1mm cold-rolled coil, which is annealed online at 810°C. Argon gas protection is used throughout the process, and the reduction rate of the rolling mill is controlled at 21% during the cold rolling process to obtain a 1mm coil.

[0050] The surface temperature drop and mid-section temperature rise of the coil under different reduction rates were investigated to observe the effect of the reduction rate on the temperature field of the rolling deformation zone during the rolling process. The results are shown in Table 1.

[0051] Table 1: Surface temperature drop and center temperature rise at different reduction rates

[0052] Compression ratio (%) Surface temperature drop / °C Central temperature rise / °C Example 1 9 26.1 2.88 Example 2 16 17.5 5.76 Example 3 21 21.3 3.43 Example 4 10 25.3 3.12 Example 5 15 18.6 6.11 Example 6 21 20.6 3.4

[0053] As the reduction rate increases, the temperature rise in the middle also increases. The maximum and minimum reduction rates of the coil, and the greater the reduction, the greater the temperature drop at the surface nodes. After the coil leaves the rolling zone, the surface temperature drops more slowly due to the heat conduction of the rolled piece itself. The difference between the surface temperature drop and the temperature rise in the middle is smallest when the reduction rate is between 10-20%, which meets the requirements of online annealing. This fully utilizes the heat introduced during the plastic deformation of the last cold rolling pass, and then heats up to the required recovery temperature through online annealing. After that, the recovery process is completed through a slow cooling process of natural cooling, stabilizing the microstructure and properties required for the annealed state. This eliminates the need for the natural cooling process of the cold-rolled coil and shortens the process flow. The method provided by this invention directly performs online annealing on a single layer of coil after the last cold rolling pass, making the annealing temperature of the prepared coil uniform, thereby ensuring the stability of the coil structure and properties.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for rolling wide strips of TB and TC titanium alloys, characterized in that, Includes the following steps: S1: Prepare electrode blocks, and weld the electrode blocks together and then melt them to obtain titanium ingots; S2: Titanium ingots are forged into slabs, surface treated, and then rolled into 50-60mm medium-sized plates, and further rolled into 5-6mm coils; S3: After the strip is processed, the strip is cold rolled from the first pass to the third-to-last pass to obtain a pre-cold rolled strip. The pre-cold rolled strip is then cold rolled in the second-to-last pass and the last pass to obtain a 1mm cold rolled strip. The surface treatment in S2 includes: detecting whether the composition meets the composition requirements, flaw detection and removal of risers, removal of oxide scale, defect detection, and grinding. Whether the detected component meets the component requirements is as follows: The composition of the titanium ingot is tested to determine the percentage of oxygen content by mass. If the percentage of oxygen content by mass is within the specified range, the next step is carried out; otherwise, the ingot is remelted. The process of flaw detection and riser removal involves: performing ultrasonic flaw detection on the titanium ingot, removing the ingot riser, holding the titanium ingot at 1120-1200℃, and then forging it into a slab on a rolling mill. The heat preservation time is increased by 2.5 min / mm based on the thickness of the titanium ingot; The process of removing oxide scale involves sequentially subjecting the slab to alkali blasting and acid pickling to remove oxide scale. The defect detection and grinding process involves: using a coloring agent to detect defects on the surface of the slab, and grinding the defective parts after detecting the defects to facilitate further rolling into medium-rolled plates; The rolling temperature of the medium-rolled plate is 950-980℃, and the holding time is determined according to 150min / cm. After the surface of the medium-rolled plate is polished, it is placed on a water jet cutting machine to cut into strips with a length of 2000mm and a width of 300-500mm, and then rolled into 5-6mm coils on the rolling mill. The processing of the tape is as follows: the tape is heated, kept warm, dissolved, descaled, and its surface is polished. The heating temperature of the tape is 800-880℃, and the heat preservation time is 30 minutes; The solution treatment method is water-cooled. The descaling process involves descaling the strip using a descaling machine. Before the descaling process, the strip is further cold-rolled and pressed down by 0.3-0.5 mm on the rolling mill. The surface grinding process involves grinding the oxide scale and defects on the surface of the descaling strip on a grinding machine. During the pre-cooled strip cold rolling process, intermediate annealing is performed between the first pass and the third-to-last pass; online annealing is performed in the second-to-last pass and the last pass, and the annealing temperature is 750-820℃. The reduction rate of the rolling mill unit during the cold rolling process of cold-rolled strip is controlled at 10-20%.

2. The method for rolling wide strips of TB and TC titanium alloys according to claim 1, characterized in that: In S1, sponge titanium is used as the main raw material, an alloy bag is added, the sponge titanium is divided into four equal layers, and an equal amount of alloy bag is filled between two adjacent layers of sponge titanium to form an electrode. The electrode is placed in a rolling mill and rolled into an electrode block. The electrode block is placed in a vacuum chamber and vacuum plasma is used for electrode assembly welding. The assembled electrode block is then placed in a vacuum electrode consumable furnace for melting at least three times to reduce impurities and obtain titanium ingots.

3. The method for rolling wide strips of TB and TC titanium alloys according to claim 1, characterized in that: Argon gas is used for protection during the annealing process.

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