A low-cost preparation method for titanium alloy plates

Abstract

The present invention belongs to the technical field of titanium alloy sheet processing, and particularly relates to a low-cost preparation method for titanium alloy sheets, comprising the following steps: performing shot peening on an EB ingot produced by a titanium alloy vacuum consumable skull melting furnace; heating the titanium alloy EB ingot to 30-50 °C above the phase transformation point, with a holding time of t, and then performing thinning rolling. When the surface temperature drops to 50-100 °C below the phase transformation point, it is reheated to 30-50 °C above the phase transformation point and then rolled again; after cooling the thinned rolled titanium alloy slab, inspect the surface of the sheet, and perform local grinding on the cracked parts of the surface; remove the surface oxide layer of the titanium alloy slab and chamfer it, and spray a coating on the surface of the slab; heat the titanium alloy slab to 20-30 °C above the β phase transformation point temperature and perform multiple rolling. The present invention can effectively reduce the processing cost and cycle of the material, ensure the tissue performance of the sheet, and achieve the low-cost preparation of the sheet.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy plate processing, and in particular relates to a low-cost preparation method of a titanium alloy plate. Background Art

[0002] Titanium alloys have been widely used in aerospace, aviation, navigation, chemical industry, energy and other fields due to their excellent properties such as high specific strength, high impact toughness and good corrosion resistance. There are two main conventional processing and preparation methods for titanium alloy plates. The first is to obtain finished plates by rolling forged slabs. During the processing, continuous deformation is required to ensure the organization of broken and grain refinement. The traditional process has many forging and rolling fires and long processing flow. In addition, due to the poor thermal conductivity and plasticity of titanium alloys, grinding and other means are required to solve the problems of cracking during the processing. All of the above lead to a series of problems such as high cost and low yield of titanium alloy plates during the processing. The second is to directly roll the EB ingot (the full name of EB is Electron Beam Melting) produced by the solidification furnace. This process omits the forging process and reduces the production cost. However, due to the poor plasticity of the ingot, large cracks will occur during the rolling process, and the plate after rolling will have problems such as uneven organization and coarse grains. Therefore, it is necessary to use the characteristics of titanium alloys to design a low-cost preparation method for titanium alloy plates. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a low-cost preparation method for titanium alloy plates. The present invention is centered around a low-cost preparation method for titanium alloy plates. Based on the original process of rolling plates with EB cast in a solidification furnace, high-speed shot blasting on the surface of the plate and small deformation thinning rolling above the phase change point are used to improve the surface structure of the plate, and a basket structure plate is obtained by accurately controlling the temperature and rolling speed in one-fire rolling, which solves the problems of high processing cost and long manufacturing cycle of traditional titanium alloy plate forging and rolling, and also avoids the problems of cracking and uneven structure of EB cast in a solidification furnace. The structure and performance of the plate are controlled by controlling the rolling temperature and speed.

[0004] In order to achieve the above technical objectives, the technical solution adopted by the embodiment of the present invention is:

[0005] A low-cost preparation method for a titanium alloy plate comprises the following steps:

[0006] Step S1, subjecting the EB ingot produced by the titanium alloy vacuum consumable shell furnace to shot blasting at a speed of 3-5 m / min to remove surface oxide scale and minor defects and deform the surface grains;

[0007] Step S2: Heat the titanium alloy EB ingot blank after shot peening in Step S1 to 30 - 50°C above the phase transformation point, hold for a time t, then perform thinning rolling. The reduction per pass is 8 - 12 mm, and the rolling speed is 0.5 - 1 m / s. When the surface temperature drops to 50 - 100°C below the phase transformation point, heat it in the furnace to 30°C - 50°C above the phase transformation point and then perform rolling again;

[0008] Step S3: After cooling the titanium alloy slab blank after thinning rolling in Step S2, inspect the surface of the slab, and perform local grinding on the cracked areas on the surface;

[0009] Step S4: Remove the surface oxide layer and chamfer the titanium alloy slab blank after grinding in Step S3, and spray a coating with a thickness of 0.5 - 1 mm on the surface of the slab;

[0010] Step S5: Heat the titanium alloy slab blank after spraying in Step S4 to 20°C - 30°C above the β phase transformation point temperature. Control the reduction deformation in the first pass to be 10 - 20 mm, and the rolling speed to be 1 - 2 m / s. After finishing the first pass, rotate 90° and then perform rolling. Control the reduction deformation in the second pass to be 10 - 20 mm, and the rolling speed to be 1 - 2 m / s. After finishing the second pass, rotate 90° and then perform rolling. Control the reduction deformation in the third pass to be 10 - 20 mm, and the rolling speed to be 1 - 2 m / s. After completing the third pass of rolling, monitor the surface temperature of the slab in real time for each pass. If the surface temperature of the slab is 100 - 120°C below the phase transformation point and the temperature of the slab relative to the previous pass has not started to rise, then control the reduction deformation in the next pass to be 12 - 15 mm for rolling, with a speed of 1 - 1.5 m / s. If the surface temperature of the slab is 100 - 120°C below the phase transformation point and the temperature of the slab relative to the previous pass has started to rise, then control the reduction deformation in each remaining pass to be 10 - 12 mm for rolling, with a speed of 0.2 - 0.5 m / s.

[0011] Further, when performing shot peening treatment in Step S1, determine the steel shot diameter and shot peening pressure according to the alloy grade and slab thickness. The steel shot diameter is 1 - 5 mm, and the shot peening pressure is selected between 0.2 - 1 MPa. Shot peen the entire surface of the slab 3 - 5 times to initially break the surface grains and achieve the purpose of reducing cracking during the rolling process.

[0012] Further, in Step S2, the holding time t = EB ingot blank thickness × 1 - 1.5, where the unit of EB ingot blank thickness is mm and the unit of holding time is min;

[0013] When performing thinning rolling in Step S2, the total deformation does not exceed 20% of the initial thickness of the slab blank. The purpose is to further break the surface grains, and at the same time apply a small amount of pre - deformation to the entire slab blank, initially coordinating the deformation between β grains and reducing the cracking tendency during subsequent rolling.

[0014] The beneficial effects brought by the technical solution provided in the embodiment of the present invention are as follows:

[0015] For the method for low-cost preparation of titanium alloy plates of the present invention, EB billets are directly rolled, and the surface structure of the billets is gradually improved by high-speed shot peening on the surface of the slab and small-deformation thinning rolling above the phase transformation point. The forging process is omitted from the preparation process, thereby reducing the processing cost and time brought by forging. In addition, the problem of large surface cracking caused by direct rolling of EB billets is solved, the processing costs such as grinding cracks during the rolling process can be reduced, and the yield rate is improved. In addition, through multiple reverse rolling above the phase transformation point and controlling the rolling temperature and speed below the phase transformation point to complete the cross-phase transformation point rolling of the plates, the tissue performance of the titanium alloy plates can be guaranteed. In summary, the preparation method of the present invention can effectively reduce the processing cost and processing cycle of the material, and can guarantee the tissue performance of the plates, realizing the low-cost preparation of the plates. Description of the Drawings

[0016] Figure 1 It is the surface structure of the plate in step S3 after thinning rolling in Example 1.

[0017] Figure 2 It is the rolling structure of the titanium alloy plate obtained by the preparation method of Example 1.

[0018] Figure 3 It is the rolling structure of the titanium alloy plate obtained by the preparation method of Comparative Example 1. Detailed Embodiments

[0019] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] Example 1

[0021] A low-cost preparation method for titanium alloy plates includes the following steps:

[0022] Step S1: Shot peen a certain new type of titanium alloy (by mass percentage, including the following components: Al: 5% - 7%, Mo: 1% - 2%, Cr: 1% - 2%, V: 1% - 2%, Zr: 2% - 3%) EB billet (the detected β phase transformation point is 900 - 910°C, and the plate thickness is 170 mm) at a speed of 3 m / min to remove surface oxide scales and fine defects and deform the surface grains. The diameter of the steel shot is 5 mm, the shot peening pressure is 0.7 MPa, and the surface is shot peened 5 times;

[0023] Step S2: Heat the titanium alloy EB ingot blank after shot peening in Step S1 to 950°C, with a holding time of 250 min. Then, perform thinning rolling, with a reduction per pass of 8 mm and a rolling speed of 1 m / s. When the surface temperature drops to 850°C, return it to the furnace and heat it up to 950°C before rolling again until the slab thickness reaches 140 mm, and the total deformation of the heat treatment is 17.6%;

[0024] Among them, the holding time t = the thickness of the EB ingot blank × 1 - 1.5, the unit of the thickness of the EB ingot blank is mm, and the unit of the holding time is min;

[0025] Step S3: After cooling the titanium alloy slab after thinning rolling in Step S2, inspect the surface of the sheet, and locally grind the cracked parts on the surface. The surface structure of the actual sheet after thinning is as Figure 1 shown;

[0026] Step S4: Milling the surface oxide layer of the titanium alloy slab after grinding in S3 and chamfering it, and spraying a coating with a thickness of 0.5 mm on the surface of the slab. The coating uses a glass protective lubricant;

[0027] Step S5: Heat the titanium alloy slab after spraying in Step S4 to 930°C, control the reduction of the first pass to be 15 mm, with a rolling speed of 2 m / s. After finishing the first pass, rotate 90° and then roll again, control the reduction of the second pass to be 15 mm, with a rolling speed of 2 m / s. After finishing the second pass, rotate 90° and then roll again, control the reduction of the third pass to be 15 mm, with a rolling speed of 2 m / s. After the third pass of rolling, monitor the surface temperature of the sheet in real time for each pass. If it is detected that the surface temperature of the sheet is 800°C (100 - 120°C below the phase transition point), and the sheet temperature has not started to rise compared to the previous pass, then control the reduction of each remaining pass to be 12 mm for rolling, with a speed of 1.5 m / s. If it is detected that the surface temperature of the sheet is 800°C (100 - 120°C below the phase transition point), and the sheet temperature has started to rise compared to the previous pass, then control the reduction of each remaining pass to be 10 mm for rolling, with a speed of 0.5 m / s, and finally obtain a sheet with a thickness of 62 mm. The structure of the sheet is as Figure 2 shown, and the properties of the sheet after double annealing at 880°C / 2 h / air cooling + 800°C / 2 h / air cooling are shown in Table 1.

[0028] Example 2

[0029] A low-cost preparation method for titanium alloy sheets, comprising the following steps:

[0030] Step S1: Shot peening treatment is carried out on the TC21 titanium alloy EB ingot blank (the detected β phase transformation point is 970 - 980 °C, and the plate thickness is 160 mm) at a speed of 3 m / min to remove the surface oxide scale and fine defects and deform the surface grains. The diameter of the steel shot is 5 mm, the shot peening pressure is 0.7 MPa, and the shot peening is carried out 5 times.

[0031] Step S2: Heat the titanium alloy EB ingot blank after shot peening in Step S1 to 1020 °C, keep it warm for 240 min, and then carry out thinning rolling. The reduction per pass is 8 mm, and the rolling speed is 0.5 m / s. When the surface temperature drops to 900 °C, heat it back to 1020 °C in the furnace and then carry out rolling until the thickness of the slab reaches 140 mm, and the total deformation of the heat is 17.6%.

[0032] The holding time t = the thickness of the EB ingot blank × 1 - 1.5, the unit of the thickness of the EB ingot blank is mm, and the unit of the holding time is min.

[0033] Step S3: After cooling the titanium alloy slab after thinning rolling in Step S2, check the surface of the plate and perform local grinding on the cracked parts of the surface.

[0034] Step S4: Milling the surface oxide layer of the titanium alloy slab after grinding in Step S3 and chamfering it, and spraying a coating with a thickness of 0.8 mm on the surface of the slab. The coating uses a glass protective lubricant.

[0035] Step S5: Heat the titanium alloy slab after spraying in Step S4 to 1000 °C, control the reduction of the first pass to be 15 mm, and the rolling speed to be 2 m / s. After finishing the first pass, rotate 90° and then carry out rolling. Control the reduction of the second pass to be 15 mm, and the rolling speed to be 2 m / s. After finishing the second pass, rotate 90° and then carry out rolling. Control the reduction of the third pass to be 15 mm, and the rolling speed to be 2 m / s. After the third pass of rolling is completed, monitor the surface temperature of the plate in real time for each pass. If it is detected that the surface temperature of the plate is 860 °C (100 - 120 °C below the phase transformation point), and the plate temperature has not started to rise relative to the previous pass, then control the reduction of each remaining pass to be 12 mm for rolling, and the speed to be 1.2 m / s. If it is detected that the surface temperature of the plate is 860 °C (100 - 120 °C below the phase transformation point), and the plate temperature has started to rise relative to the previous pass, then control the reduction of each remaining pass to be 12 mm for rolling, and the speed to be 0.5 m / s. Finally, a plate with a thickness of 62 mm is obtained. The performance of the plate after double annealing at 940 °C / 1 h / air cooling + 600 °C / 4 h / air cooling is shown in Table 1.

[0036] Example 3

[0037] A low-cost preparation method for titanium alloy plates, comprising the following steps:

[0038] Step S1: Shot peening treatment is carried out on the TC4 titanium alloy EB ingot (the detected β phase transformation point is 980 - 990 °C and the plate thickness is 170 mm) at a speed of 4 m / min to remove the surface oxide scale and fine defects and deform the surface grains. The diameter of the steel shot is 5 mm, the shot peening pressure is 0.7 MPa, and the shot peening is carried out 5 times.

[0039] Step S2: Heat the titanium alloy EB ingot after shot peening in Step S1 to 1020 °C, keep it warm for 250 min, and then carry out thinning rolling. The reduction per pass is 8 mm, and the rolling speed is 0.5 m / s. When the surface temperature drops to 920 °C, heat it back to above the phase transformation point at 1020 °C and then carry out rolling until the slab thickness reaches 140 mm. The total deformation of the heat treatment is 17.6%.

[0040] The holding time t = EB ingot thickness × 1 - 1.5, where the unit of EB ingot thickness is mm and the unit of holding time is min.

[0041] Step S3: After cooling the titanium alloy slab after thinning rolling in Step S2, check the surface of the plate and perform local grinding on the cracked parts of the surface.

[0042] Step S4: Milling the surface oxide layer of the titanium alloy slab after grinding in Step S3 and chamfering it, and spraying a coating with a thickness of 0.8 mm on the surface of the slab. The coating uses a glass protective lubricant.

[0043] Step S5: Heat the titanium alloy slab after spraying in Step S4 to 1010 °C, control the reduction of the first pass to be 15 mm, and the rolling speed to be 2 m / s. After finishing the first pass, rotate 90° and then carry out rolling. Control the reduction of the second pass to be 15 mm, and the rolling speed to be 2 m / s. After finishing the second pass, rotate 90° and then carry out rolling. Control the reduction of the third pass to be 15 mm, and the rolling speed to be 2 m / s. After finishing the third pass, monitor the surface temperature of the plate in real time for each pass. If the detected surface temperature of the plate is 870 °C (100 - 120 °C below the phase transformation point) and the plate temperature has not started to rise compared to the previous pass, then control the reduction of the remaining passes to be 12 mm for rolling at a speed of 1 m / s. If the detected surface temperature of the plate is 870 °C (100 - 120 °C below the phase transformation point) and the plate temperature has started to rise compared to the previous pass, then control the reduction of the remaining passes to be 10 mm for rolling at a speed of 0.5 m / s, and finally obtain a plate with a thickness of 62 mm. The properties of the plate after double annealing at 950 °C / 2 h / air cooling + 750 °C / 2 h / air cooling are shown in Table 1.

[0044] Comparative Example 1

[0045] A new type of titanium alloy ingot with the same chemical composition as in Example 1 (by mass percentage, including the following components: Al: 5% - 7%, Mo: 1% - 2%, Cr: 1% - 2%, V: 1% - 2%, Zr: 2% - 3%) is subjected to a conventional forging and rolling process. It is heated to 1150°C, in two heating passes, with two upsetting and two drawing operations, and the deformation amount is 50%. After each heating pass, it is ground; then it is heated to 880°C, in 4 heating passes, with one upsetting and one drawing operation in each pass, and the deformation amount is 30%. Then, it undergoes 2 finishing heating passes to forge and draw it into a slab. The forged titanium alloy slab has its surface oxide layer milled off and chamfered, and a coating with a thickness of 0.5 mm is sprayed on the slab surface. The coating uses a glass protective lubricant. It is rolled in one pass at 940°C: the rolling process is 20 mm per pass. After rolling to 90 mm, it is cooled to room temperature, ground, and then reheated to 870°C for two-pass rolling, 10 mm per pass, and rolled to a thickness of 62 mm. The rolling structure is as Figure 3 , and the properties of the sheet after double annealing at 880°C / 2 h / air cooling + 800°C / 2 h / air cooling are shown in Table 1.

[0046] Comparative Example 2

[0047] A TC21 titanium alloy ingot with the same chemical composition as in Example 2 is subjected to a conventional forging and rolling process. It is heated to 1200°C, in two heating passes, with two upsetting and two drawing operations, and the deformation amount is 45%. After each heating pass, it is ground; then it is heated to 930°C, in 5 heating passes, with one upsetting and one drawing operation in each pass, and the deformation amount is 30%. Then, it undergoes 2 finishing heating passes to forge and draw it into a slab; the forged titanium alloy slab has its surface oxide layer milled off and chamfered, and a coating with a thickness of 0.5 mm is sprayed on the slab surface. The coating uses a glass protective lubricant; it is rolled in one pass at 1020°C: the rolling process is 20 mm per pass. After rolling to 90 mm, it is cooled to room temperature, ground, and then reheated to 870°C for two-pass rolling, 12 mm per pass, and rolled to a thickness of 62 mm. The properties of the sheet after double annealing at 940°C / 1 h / air cooling + 600°C / 4 h / air cooling are shown in Table 1.

[0048] Comparative Example 3

[0049] The TC4 titanium alloy ingot with the same chemical composition as that in Example 3 is subjected to a conventional forging and rolling process. It is heated to 1200 °C, in two heating passes, with two upsetting and two drawing operations, and the deformation amount is 45%. After each heating pass, it is ground; then heated to 940 °C, in 6 heating passes, with one upsetting and one drawing operation in each heating pass, and the deformation amount is 35%. Then, it is subjected to 2 finishing heating passes to forge and draw it into a slab; the forged titanium alloy slab is milled to remove the surface oxide layer and chamfered, and a coating with a thickness of 0.5 mm is sprayed on the surface of the slab. The coating uses a glass protective lubricant; it is rolled in one heating pass at 940 °C: the rolling process is 20 mm per pass. After rolling to 90 mm, it is cooled to room temperature and ground, and then heated to 870 °C for the second rolling pass, 12 mm per pass, and rolled to a thickness of 62 mm. The properties of the sheet after double annealing at 950 °C / 2 h / air cooling + 750 °C / 2 h / air cooling are shown in Table 1.

[0050] Table 1 Mechanical properties of 60 mm rolled sheets of different titanium alloys

[0051]

[0052] It can be seen from Figure 1 and Figure 2 that the surface microstructure after thinning in Example 1 is significantly refined and is Widmanstätten structure. Figure 2 The rolling structure in Example 1 is basically similar to that in Comparative Example 1. By performing different reverse rolling during the rolling process, the grains can be further broken, and by controlling the rolling temperature and rolling speed, the structure can be made more uniform. The microstructures of the rolling structures obtained in Example 1 and Comparative Example 1 of the present invention are basically the same.

[0053] It can be seen from Table 1 that compared with Comparative Example 1, the tensile strength of the sheet prepared by low-cost processing in Example 1 is slightly lower than that of the sheet prepared by the conventional process, but the plasticity and toughness are better than those of the conventional process. Combining Example 2 and 3 and Comparative Examples 2 and 3, generally speaking, the mechanical properties of the titanium alloy sheets prepared by low-cost processing have no significant difference compared with those of the sheets prepared by the conventional process.

[0054] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A low-cost preparation method for a titanium alloy plate, characterized in that: The following steps are involved: Step S1, subjecting the EB ingot produced by the titanium alloy vacuum consumable shell furnace to a shot blasting process at a speed of 3-5 m / min to remove surface oxide scale and minor defects and deform the surface grains; Step S2, heating the titanium alloy EB ingot after shot blasting in step S1 to 30-50°C above the phase transition point, holding time t, then performing thinning rolling, each pass reduction amount is 8-12mm, rolling speed is 0.5-1m / s, when the surface temperature drops to 50-100°C below the phase transition point, returning to the furnace and heating to 30-50°C above the phase transition point before rolling; Step S3, after cooling the titanium alloy slab after thinning and rolling in step S2, checking the surface of the slab and performing local grinding on the cracked parts of the surface; Step S4, removing the surface oxide layer of the titanium alloy slab after grinding in step S3, chamfering the edges, and spraying a coating with a thickness of 0.5 to 1 mm on the surface of the slab; Step S5, heating the titanium alloy slab after spraying in step S4 to a temperature 20-30°C above the β phase transformation point, controlling the first pass reduction deformation to be 10-20mm, the rolling speed to be 1-2m / s, rotating 90° after the first pass and then rolling, controlling the second pass reduction deformation to be 10-20mm, the rolling speed to be 1-2m / s, rotating 90° after the second pass and then rolling, controlling the third pass reduction deformation to be 10-20mm, the rolling speed to be 1-2m / s, After the third rolling pass is completed, the surface temperature of the plate is monitored in real time at each pass. If the surface temperature of the plate is 100~120℃ below the phase change point and has not started to rise relative to the temperature of the previous pass, the remaining deformation of each pass is controlled to be 12~15mm for rolling at a speed of 1~1.5m / s. If the surface temperature of the plate is 100~120℃ below the phase change point and has started to rise relative to the temperature of the previous pass, the remaining deformation of each pass is controlled to be 10~12mm for rolling at a speed of 0.2~0.5m / s.

2. The low-cost preparation method of the titanium alloy sheet according to claim 1, characterized in that: When performing shot blasting in step S1, the diameter of the steel shot and the shot blasting pressure are determined according to the alloy grade and the thickness of the plate. The diameter of the steel shot is 1-5 mm, the shot blasting pressure is selected between 0.2-1 MPa, and the entire plate surface is shot blasted 3-5 times.

3. The low-cost preparation method of titanium alloy sheet according to claim 1, characterized in that: In step S2, the holding time t=EB billet thickness×1-1.5, the unit of EB billet thickness is mm, and the unit of holding time is min; During the thinning rolling in step S2, the total deformation does not exceed 20% of the initial thickness of the slab.

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