TC4 titanium alloy wide-thick plate and preparation method thereof

Abstract

The application discloses a TC4 titanium alloy wide-thick plate and a preparation method thereof, and adopts an EB furnace to melt and obtain a TC4 titanium alloy flat ingot, so that forging is omitted, direct rolling is carried out on a steel production line, and the temperature drop of the titanium alloy wide-thick plate is compensated by edge heating at the same time of asynchronous rolling, so that the generation of edge cracks is effectively prevented, and finally, the TC4 titanium alloy wide-thick plate with fine crystal structure and excellent performance is obtained, so that the "steel-titanium collinear" high-efficiency short process and low-cost rolling is realized, and the product quality is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium alloy, in particular to a TC4 titanium alloy wide-thick plate and a preparation method thereof, and especially to a method for preparing a TC4 titanium alloy wide-thick plate by adopting EB flat ingot of TC4 titanium alloy for direct rolling without forging. BACKGROUND

[0002] Titanium and titanium alloy are widely used in many fields such as aerospace, ocean engineering, petroleum chemical industry and biological medicine due to their advantages of strong corrosion resistance, high specific strength, good creep resistance and thermal stability; due to its excellent performance and development potential, titanium is gradually becoming the "fourth generation of metal materials" after copper, iron and aluminum. In the family of titanium alloys, TC4 (Ti-6Al-4V) titanium alloy is the most widely used alloy type, accounting for more than 50% of the total amount of various titanium alloys; in addition to excellent comprehensive performance and good processing performance, Al-V alloy raw materials have lower cost than other titanium alloy raw materials, so Ti-6Al-4V has obvious cost advantage, which is one of the key factors for the wide engineering application of TC4 titanium alloy.

[0003] At present, the mainstream way of producing TC4 titanium alloy plate at home and abroad is: through sponge titanium pressing into consumable electrode, and then through vacuum consumable arc furnace (VAR furnace) to prepare ingot through 2-3 times of melting, and then through multi-fire forging process to obtain a plate blank to be hot-rolled, and finally through multi-fire rolling to obtain TC4 titanium alloy wide-thick plate; but the above-mentioned way of producing TC4 titanium alloy wide-thick plate has the disadvantages of long production process, large material loss and high production cost.

[0004] Since there are problems such as high / low density inclusions in the VAR melting method of titanium alloy, the high / low density inclusions can be effectively eliminated by using electron beam cold hearth melting (EB) to realize the purification of titanium and titanium alloy materials, and in addition, EB furnace can also add a large amount of returned material to reduce cost; at present, there are technologies for preparing TC4 titanium alloy wide-thick plate by using EB furnace melting in related research, for example, Chinese patent CN111036703B proposes a preparation method for producing TC4 titanium alloy wide-thick plate by using direct rolling process, which uses EB furnace to melt TC4 titanium alloy flat ingot through two-fire hot rolling process to obtain TC4 titanium alloy plate with a width of 3600-4500mm, the organization and performance of the plate meet the national standard requirements, but the technology does not describe how to control the surface quality of the TC4 titanium alloy flat ingot during rolling to make the mechanical properties of the finished product meet the requirements, and the technology adopts two-fire rolling, which does not meet the requirements of high-efficiency rolling of titanium alloy.

[0005] In view of the above, it is urgent to develop a TC4 titanium alloy wide plate preparation method, which can not only realize the efficient short process and low cost preparation of TC4 titanium alloy wide plate, but also improve the product quality. SUMMARY

[0006] In view of the problems of long production process and how to control the plate shape and surface quality of the TC4 titanium alloy wide plate in the prior art, the purpose of the present application is to provide a TC4 titanium alloy wide plate and a preparation method thereof, which adopts EB furnace one-time smelting to obtain TC4 titanium alloy slab, eliminates the forging process, directly rolls on the steel production line, and compensates for the temperature drop of the edge of the titanium alloy wide plate through edge heating while asynchronous rolling, effectively prevents edge cracks, and finally obtains TC4 titanium alloy wide plate with good plate shape, qualified surface quality, fine grain structure and excellent performance, so as to realize "steel-titanium co-line" efficient short process, low cost rolling and improve product quality.

[0007] To achieve the above purpose, the present application adopts the following technical solutions:

[0008] The first aspect of the present application provides a preparation method of TC4 titanium alloy wide plate, comprising the following steps:

[0009] S1, using EB furnace one-time smelting to obtain TC4 titanium alloy slab, and applying glass lubricating paint on the surface of the TC4 titanium alloy slab at room temperature, and air drying for standby;

[0010] S2, using two-stage heating in an electric heating furnace to heat the TC4 titanium alloy slab after the step S1;

[0011] S3, asynchronous hot rolling+edge heating, rapidly transporting the heated TC4 titanium alloy slab to an asynchronous rolling mill for one-fire multi-pass asynchronous rolling to obtain TC4 titanium alloy wide plate, and using edge heating to compensate for the temperature of the edge of the TC4 titanium alloy wide plate during the asynchronous rolling;

[0012] S4, annealing, plate shape correction, pickling and local grinding of the TC4 titanium alloy wide plate obtained in the step S3 to obtain TC4 titanium alloy wide plate with qualified surface;

[0013] The unevenness of the TC4 titanium alloy wide plate with qualified surface is ≤8mm / m.

[0014] Preferably, in the step S1, the continuous ingot drawing process is adopted in the EB furnace one-time smelting process, the smelting speed in the smelting process is 600-1000kg / h, and the flow rate of the cooling water used when the TC4 titanium alloy slab is cooled is 1600-2200L / min.

[0015] Preferably, in the step S1, the blank obtained by one-time smelting of the EB furnace is subjected to face milling, grinding and chamfering treatment, and after underwater ultrasonic flaw detection treatment, the head is cut off to obtain the TC4 titanium alloy slab with a thickness of 15-30 mm and a width of 1500-2500 mm.

[0016] Preferably, in the step S2, in the two-stage heating process, the temperature in the electric heating furnace is first raised to 800-850℃, then the TC4 titanium alloy slab is loaded into the furnace, and after the temperature is stabilized, the temperature is maintained for 60-90 min, and then the temperature is continuously raised to 1000-1050℃, and after the temperature is stabilized, the temperature is continuously maintained for 180-240 min.

[0017] Preferably, in the step S3:

[0018] the TC4 titanium alloy slab is transported for 5-20 s; and / or

[0019] in the asynchronous rolling process, the initial rolling temperature is controlled at 970-1000℃, and the final rolling temperature is higher than 750℃; and / or

[0020] in the asynchronous rolling process, the speed ratio of the upper and lower rollers is 1-1.4.

[0021] Preferably, in the step S3:

[0022] in the one-fire multi-pass rolling process, the single-pass deformation amount is controlled at 10-30%, the back-and-forth rolling is 8-13 passes, and the total deformation amount is controlled at 80-90%; and / or

[0023] in the one-fire multi-pass rolling process, the single-pass rolling force is controlled at 900 tons-2000 tons.

[0024] Preferably, in the step S3, in the edge heating process, an infrared temperature measuring gun is used to measure the temperature of the TC4 titanium alloy wide and thick plate in real time, and the temperature compensation power of the edge heating is adjusted according to the temperature measurement result, so that the edge temperature of the target slab is close to the center temperature.

[0025] Preferably, in the step S3, the edge heating is performed by using an electromagnetic edge heater for temperature compensation.

[0026] Preferably, in the step S4:

[0027] the annealing temperature is 700-850℃, and the annealing time is 1-3 h; and / or

[0028] the pickling uses a mixed acid of hydrofluoric acid and nitric acid to remove the surface oxide scale; and / or

[0029] The local grinding adopts a chopper wheel to remove cracks, peeling, and indentation surface defects.

[0030] The surface qualified TC4 titanium alloy wide-thick plate has an average grain size of less than or equal to 10 mu m, a room temperature tensile strength of greater than or equal to 895 MPa, a yield strength of greater than or equal to 830 MPa, and an elongation of greater than or equal to 8%.

[0031] The second aspect of the present application provides a TC4 titanium alloy wide-thick plate prepared by the preparation method of the TC4 titanium alloy wide-thick plate according to the first aspect of the present application, wherein the TC4 titanium alloy wide-thick plate has a roughness of less than or equal to 8 mm / m, an average grain size of less than or equal to 10 mu m, a room temperature tensile strength of greater than or equal to 895 MPa, a yield strength of greater than or equal to 830 MPa, and an elongation of greater than or equal to 8%.

[0032] Compared with the existing production technology, the present application has the following advantages:

[0033] 1. The present application directly obtains TC4 titanium alloy ingot by using EB furnace one-time smelting technology, compared with the conventional 2-3 times VAR smelting and forging process, the EB furnace billet is a kind of processing technology with obvious high efficiency short process and low cost advantage;

[0034] 2. The TC4 titanium alloy plate can be directly rolled by using the TC4 flat ingot smelted by the EB furnace, which eliminates the forging process and realizes the short process and low cost preparation of the TC4 titanium alloy plate blank;

[0035] 3. The present application can prevent the TC4 titanium alloy flat ingot from being seriously oxidized or absorbing hydrogen during the heating stage by coating glass lubricating paint on the TC4 titanium alloy flat ingot, which can meet the requirement of large reduction rate in one-time rolling, prevent the rolling piece from producing serious surface cracks, and fully break the as-cast structure of the rolling piece;

[0036] 4. The present application directly completes the rolling of the TC4 titanium alloy wide-thick plate by using the steel production line, and realizes the one-time rolling technology under the precise control of the heating system and rolling force of the asynchronous rolling mill, and realizes the efficient short process rolling of titanium materials;

[0037] 5. The present application adopts the edge heating device while rolling asynchronously, compensates for the too fast temperature drop of the edge of the TC4 wide-thick plate during the rolling process, avoids the generation of edge slits, and improves the surface quality of the product;

[0038] 6. The TC4 titanium alloy wide-thick plate prepared by the present application has an average grain size of less than or equal to 10 mu m, a room temperature tensile strength of greater than or equal to 895 MPa, a yield strength of greater than or equal to 830 MPa, and an elongation of greater than or equal to 8%. BRIEF DESCRIPTION OF DRAWINGS

[0039] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments thereof, when read in conjunction with the accompanying drawings:

[0040] Figure 1 A flowchart of the preparation method of the TC4 titanium alloy wide-thick plate of the present application is shown in the figure;

[0041] Figure 2 A schematic diagram of the EB furnace smelting TC4 titanium alloy flat ingot is shown in the figure;

[0042] Figure 3 A state diagram of the TC4 titanium alloy flat ingot surface coated with glass lubricating coating is shown in the figure, (a) and (b) are respectively the state diagrams of the TC4 titanium alloy flat ingot surface coated and coated;

[0043] Figure 4 A structural schematic diagram of the TC4 titanium alloy wide-thick plate obtained after the TC4 titanium alloy flat ingot is rolled by asynchronous rolling is shown in the figure, (a) is a picture of the TC4 titanium alloy wide-thick plate, and (b) is a metallographic structure schematic diagram of the TC4 titanium alloy wide-thick plate;

[0044] Figure 5 A stress-strain curve diagram of the TC4 titanium alloy wide-thick plate prepared by the present application is shown in the figure. DETAILED DESCRIPTION

[0045] In order to better understand the above technical solutions of the present application, the technical solutions of the present application are further described below in conjunction with examples.

[0046] High-efficiency rolling is an important trend for the future development of TC4 titanium alloy. As a "100,000-ton" metal, the processing of titanium materials, especially the companies relying on plates and coils as the main products to form production capacity, are facing the status of serious shortage of equipment utilization, large investment and low efficiency. The "steel-titanium co-line" method can utilize part of the steel rolling capacity to improve the rolling efficiency of TC4 titanium alloy. Therefore, using steel equipment to realize titanium material processing through the "steel-titanium co-line" method has become a development trend in the industry.

[0047] The present application provides a TC4 titanium alloy wide-thick plate and a preparation method thereof. The TC4 titanium alloy flat ingot obtained by one-time smelting of an EB furnace is rolled on a steel production line. The surface of the TC4 titanium alloy flat ingot is uniformly coated with high-temperature glass lubricating coating before being loaded into the furnace to prevent temperature drop, oxidation and reduce friction and wear. Subsequently, the TC4 titanium alloy flat ingot is subjected to one-fire multi-pass large deformation hot rolling process on a four-roll asynchronous rolling mill. The edge heating device is used to compensate for the temperature drop of the edge of the titanium alloy wide-thick plate. Finally, the TC4 titanium alloy wide-thick plate with good plate shape, qualified surface quality, fine grain structure and excellent performance is obtained, and the "steel-titanium co-line" high-efficiency short-process rolling can be realized.

[0048] In combination with Figure 1As shown, the preparation method of the TC4 titanium alloy wide plate of the present application comprises the following steps:

[0049] S1, using EB furnace one-time smelting to obtain TC4 titanium alloy slab, and coating glass lubricating paint on the surface of the TC4 titanium alloy slab at room temperature, and air drying for standby;

[0050] Specifically, a 3150kW electron beam cold bed furnace (EB furnace) is selected for one-time smelting to produce TC4 titanium alloy slab meeting the standard requirements; compared with the conventional 2-3 times VAR smelting and forging plate blank, the TC4 titanium alloy slab obtained by one-time smelting of the EB furnace can be directly rolled into a finished product, eliminating the traditional cogging forging process, greatly improving the titanium alloy yield, shortening the production cycle and reducing the production cost;

[0051] Among them, when the EB furnace is one-time smelting, the smelting speed is 600-1000kg / h, the cooling water flow used during the cooling of the TC4 titanium alloy slab is 1600-2200L / min, and the continuous ingot drawing process is adopted. After the blank obtained by one-time smelting of the EB furnace is milled, ground and chamfered, and determined to be correct by underwater ultrasonic flaw detection, the head is cut off, and finally the TC4 titanium alloy slab with a specification of: thickness 150-350mm, width 1000-2000mm and length 3000-5000mm is obtained. In order to facilitate subsequent hot rolling, it is sawn into the above-mentioned specification of plate blank along the length direction (see Figure 2 As shown).

[0052] The above-mentioned TC4 titanium alloy slab is coated with glass lubricating paint at room temperature, the main components of the paint are SiO2, Al2O3, B2O3, CaO, MgO, Na2O, TiO2, etc., machine spraying is adopted to improve the use effect of the paint, and after the glass lubricating paint is air dried, the TC4 titanium alloy slab coated with the glass lubricating paint can be heated in the furnace. The glass lubricating paint can play the role of oxidation prevention and hydrogen absorption prevention, and during subsequent rolling, the glass lubricating paint can stretch and peel off with the deformation of the metal, playing the roles of heat insulation and heat preservation, reducing the deformation resistance, prolonging the service life of the die, improving the surface precision and surface quality, Figure 3 (a) and (b) in the figure are respectively the state of the TC4 titanium alloy slab after coating and coating the glass lubricating paint.

[0053] S2, heating the TC4 titanium alloy slab treated in step S1 in the electric heating furnace by two-stage heating;

[0054] Specifically, the TC4 titanium alloy slab after step S1 is transferred to an electric heating furnace, and two-stage heating is adopted for slab heating. First, the temperature in the electric heating furnace is raised to 800-850℃, and then the TC4 titanium alloy slab is loaded into the furnace. After the temperature is stabilized, the slab is kept for 60-90min, and then the temperature is continuously raised to 1000-1050℃. After the temperature is stabilized, the slab is kept for another 180-240min, and then the slab is unloaded for rolling.

[0055] Through the above two-stage heating, firstly, the slab is heated to ensure uniform temperature; secondly, the slab is prevented from being severely oxidized due to excessively high temperature and long single heating time.

[0056] S3, asynchronous hot rolling + edge heating, the TC4 titanium alloy slab after heating is rapidly transferred to an asynchronous rolling mill for one-fire multi-pass asynchronous rolling to obtain a TC4 titanium alloy wide and thick plate. In the asynchronous rolling process, edge heating is adopted to compensate for the temperature of the edge of the TC4 titanium alloy wide and thick plate.

[0057] Specifically, the TC4 titanium alloy slab after unloading is rapidly transferred to the side of a four-high asynchronous rolling mill, and the transfer time is controlled within 5-20s. Then, the TC4 titanium alloy slab is subjected to one-fire multi-pass asynchronous rolling, with an upper and lower roll speed ratio of 1-1.4, an initial rolling temperature of 970-1000℃, a single-pass deformation amount of 10-30%, 8-13 passes of back-and-forth rolling, a total deformation amount of 80-90%, and a final rolling temperature higher than 750℃. The TC4 titanium alloy wide and thick plate finally obtained has a thickness of 15-30mm and a width of 1500-2500mm. In the above one-fire multi-pass asynchronous rolling process, the rolling force is controlled within a range of 900-2000 tons, and the rolling force of each pass is dynamically adjusted within the above range according to actual conditions (such as reduction rate, etc.).

[0058] In the above entire asynchronous rolling process, edge heating is adopted to compensate for the temperature of the edge of the TC4 titanium alloy wide and thick plate, and an infrared temperature gun is used to measure the temperature of the TC4 titanium alloy wide and thick plate in real time. According to the measurement result, the temperature compensation power of the edge heating is adjusted so that the edge temperature of the target slab is close to the center temperature. An electromagnetic edge heater is used for edge heating. It is detected that after the TC4 titanium alloy slab is subjected to one-fire multi-pass large deformation hot rolling, the microstructure is uniformly distributed, and the original as-cast structure is basically completely disappeared, as shown in FIG. 2. Figure 4

[0059] S4, the TC4 titanium alloy wide and thick plate obtained in step S3 is subjected to annealing, plate shape correction, pickling and local grinding to obtain a TC4 titanium alloy wide and thick plate with a qualified surface.

[0060] ​Specifically, the TC4 titanium alloy wide-thick plate obtained in step S3 is directly transported to a cover type slow cooling furnace to complete online annealing, the annealing treatment temperature is 800-880 DEG C, the annealing time is 1-3h, after annealing, a hot straightening machine is used for plate shape correction, finally, a mixed acid of hydrofluoric acid + nitric acid is used for pickling to remove the surface oxide skin, cracks, peeling and indentation surface defects are removed by local grinding of the thousand blade wheel, and the surface qualified TC4 titanium alloy wide-thick plate is obtained.

[0061] The surface qualified TC4 titanium alloy wide-thick plate is specifically considered from two aspects, one is the plate shape, and the other is the surface quality. The plate shape is mainly affected by the rolling process, and if the hot-rolled titanium alloy rolling piece produces a certain degree of undesirable deformation in the hot rolling process, the plate shape quality of the rolling piece will be affected. The plate shape of the hot-rolled rolling piece refers to the flatness of the plate and strip, that is, the presence or absence of the degree of wave shape, buckling or side bending. The specific forms of plate shape defects are edge wave, middle wave, edge thinning, thickness unevenness in the width direction of the strip, etc. No obvious wave shape or buckling is allowed for all plates and strips, and the plate shape is required to be good, which can be represented by unevenness. The surface quality requires that the surface of the TC4 titanium alloy wide-thick plate is smooth, and there is no conventional folding and pit uneven defects.

[0062] The plate shape index of the surface qualified TC4 titanium alloy wide-thick plate in the application is unevenness ≤8mm / m; the surface quality index is excellent surface quality, high smoothness, and no conventional folding and pit uneven defects. The average grain size is ≤10μm, the room temperature tensile strength is ≥895MPa, the yield strength is ≥830MPa, and the elongation is ≥8%; the stress-strain curve of the TC4 titanium alloy wide-thick plate is as shown in Figure 5 In a further preferred embodiment, the average grain size of the TC4 titanium alloy wide-thick plate is ≤5.0μm, the room temperature tensile strength is ≥915MPa, the yield strength is ≥855MPa, and the elongation is ≥11%.

[0063] In the preparation method: using EB furnace smelting method, only through once smelting obtains TC4 large specification flat ingot, without forging can directly carry out hot rolling, saves once smelting, multi-fire forging and grinding process, greatly shortens production flow, reduces material loss, realizes the high efficiency rolling of titanium and titanium alloy slab. According to statistics, the cost of TC4 titanium alloy slab accounts for more than 60% of the total cost of plate production, and the deformation processing cost accounts for 26% of the total cost, therefore, reducing the slab cost and processing cost is an effective way to save the cost of TC4 plate. Asynchronous rolling increases the shear strain compared with synchronous rolling in the deformation process of the rolled piece due to the different speeds of the upper and lower work rolls, which has a certain influence on the microstructure and texture of the material, and then reflects to the macro mechanics of the material; Asynchronous rolling is not only beneficial to the formation of shear texture, but also can refine the grains along the thickness direction. Because the deformation resistance of TC4 titanium alloy is large during hot working, cracks easily appear on the surface, so that the yield is not high, under the same heating system, the slab edge cools down fast, the plasticity is poor, so the rolling deformation rate is large and the edge of the plate appears more cracks when the final rolling temperature is lower than 800 DEG C; The edge heating equipment is used for the edge temperature drop compensation of TC4 titanium alloy during hot rolling, which can effectively prevent cracks.

[0064] The TC4 titanium alloy wide and thick plate and the preparation method thereof will be further described below with specific examples.

[0065] Example 1

[0066] The preparation of the TC4 titanium alloy plate wide and thick plate with a thickness of 15 mm in this embodiment is as follows:

[0067] (1) TC4 titanium alloy flat ingot meeting the standard requirements is produced by using 3150 kW electron beam cold bed furnace once smelting, wherein the smelting speed is 800 kg / h, the cooling water flow is 1800 L / min, the continuous ingot drawing process is adopted, the blank is milled, ground and chamfered, etc., and then underwater ultrasonic detection is carried out. After determining that there is no error, the head of the flat ingot is cut off, and finally the flat ingot specification is: TC4 titanium alloy flat ingot with a thickness of 200 mm, a width of 1250 mm and a length of 4100 mm; The TC4 titanium alloy flat ingot is coated with glass lubricating paint at room temperature, the main components of the paint are SiO2, Al2O3, B2O3, CaO, MgO, Na2O, TiO2, etc., artificial brushing is adopted, and heating and insulation are carried out after air drying;

[0068] (2) the TC4 flat ingot obtained in step (1) is heated in two stages in an electric heating furnace, the electric heating furnace is preheated to 800 DEG C before loading, after the temperature is stable, it is kept for 60 min at this temperature, then it is continuously heated to 1000 DEG C, after the temperature is stable, it is continuously kept for 240 min, and finally it is discharged for rolling;

[0069] (3) The TC4 titanium alloy slab obtained in step (2) is quickly transported to the side of the four-roll asynchronous rolling mill, the transportation time is controlled within 20s, and then it is subjected to one-pass multi-pass asynchronous rolling, the roll speed ratio of the upper and lower rolls is 1.2, the initial rolling temperature is controlled at 970℃, the single-pass deformation amount is controlled at 10%, the single-pass rolling force dynamically changes in the range of 900-2000, the back-and-forth rolling is about 10 passes, the total deformation amount is 80%, the final rolling temperature is higher than 750℃, and the final TC4 titanium alloy wide-thick plate has a thickness of about 15mm and a width of 1500mm.

[0070] (4) The TC4 titanium alloy wide-thick plate obtained in step (3) is directly transported to a cover-type slow cooling furnace to complete online annealing, the annealing treatment temperature is 700℃, the annealing time is 3h, after the annealing is completed, a plate shape correction is performed by using a hot straightening machine, finally, the TC4 titanium alloy wide-thick plate with a qualified surface is obtained by using a mixed acid of hydrofluoric acid and nitric acid for pickling to remove the surface oxide skin, and by using a leaf wheel to locally grind and remove cracks, peeling and indentation surface defects.

[0071] The TC4 titanium alloy wide-thick plate with a qualified surface has a roughness of ≤8mm / m, excellent surface quality and high smoothness, and does not have conventional folding and concave pit uneven defects; the average grain size of the TC4 titanium alloy wide-thick plate is 5μm, the room temperature tensile strength is 925MPa, the yield strength is 960MPa, and the elongation is 11%.

[0072] Example 2

[0073] In this embodiment, the TC4 titanium alloy plate wide-thick plate with a thickness of 30mm is prepared as follows:

[0074] (1) A 3150kW electron beam cold bed furnace is selected to produce a TC4 titanium alloy slab in accordance with the standard requirements, wherein the melting casting speed is 800kg / h, the cooling water flow is 1800L / min, a continuous ingot drawing process is adopted, the blank is subjected to face milling, grinding and chamfering, etc., and then underwater ultrasonic detection is adopted. After it is determined to be correct, the slab head is cut off, and finally a TC4 titanium alloy slab with a thickness of 340mm, a width of 1510mm and a length of 4200mm is obtained. The TC4 titanium alloy slab is coated with glass lubricating paint at room temperature, the main components of the paint are SiO2, Al2O3, B2O3, CaO, MgO, Na2O, TiO2, etc., manual brushing is adopted, and after waiting for air drying, heating and insulation are performed;

[0075] (2) The TC4 slab obtained in step (1) is subjected to two-stage heating in an electric heating furnace, the electric heating furnace is preheated to 850℃ before loading, after the temperature is stabilized, it is kept at this temperature for 75min, then it is continuously heated to 1050℃, after the temperature is stabilized, it is continuously kept for 240min, and finally it is discharged for rolling;

[0076] (3) The TC4 titanium alloy slab obtained in step (2) is quickly transported to the four-roll asynchronous rolling mill within 20 seconds, and then is subjected to one-pass multi-pass asynchronous rolling, the roll speed ratio of the upper and lower rolls is 1.4, the initial rolling temperature is controlled at 990℃, the single-pass deformation amount is controlled at 15%, the single-pass rolling force dynamically changes in the range of 900 tons-2000 tons, the forward and return rolling is about 12 passes, the total deformation amount is 90%, the final rolling temperature is higher than 750℃, and the final TC4 titanium alloy wide and thick plate has a thickness of about 30mm and a width of 2500mm.

[0077] (4) The TC4 titanium alloy wide and thick plate obtained in step (3) is directly transported to a cover type slow cooling furnace to complete online annealing, the annealing treatment temperature is 820℃, the annealing time is 2h, after the annealing is completed, a plate shape correction is performed by using a hot straightening machine, finally a mixed acid of hydrofluoric acid and nitric acid is used for pickling to remove the surface oxide skin, the cracks, peeling and indentation surface defects are removed by using a thousand-blade wheel local grinding, and the TC4 titanium alloy wide and thick plate with a qualified surface is obtained.

[0078] The TC4 titanium alloy wide and thick plate with a qualified surface has a unevenness of ≤8mm / m, excellent surface quality and high smoothness, and does not have the conventional folding and concave uneven defects; the average grain size of the TC4 titanium alloy wide and thick plate is 4.5μm, the room temperature tensile strength is 915MPa, the yield strength is 855MPa, and the elongation is 12.5%.

[0079] The person skilled in the art of the present technical field should realize that the above embodiments are only used to illustrate the present application, and are not used as a limitation on the present application, as long as the changes and modifications of the above described embodiments are within the scope of the spirit of the present application, the changes and modifications of the above described embodiments will fall within the scope of the claims of the present application.

Claims

1. A method for preparing a TC4 titanium alloy thick plate, characterized in that, Includes the following steps: S1. TC4 titanium alloy flat ingots are obtained by one-time melting in an EB furnace, and glass lubricating coating is applied to the surface of the TC4 titanium alloy flat ingots at room temperature and then air-dried for later use. The TC4 titanium alloy flat ingot has a thickness of 200mm, a width of 1250mm, and a length of 4100mm, or a thickness of 340mm, a width of 1510mm, and a length of 4200mm. The glass lubricating coating includes SiO2, Al2O3, B2O3, CaO, MgO, Na2O, and TiO2; S2, The TC4 titanium alloy flat ingot processed in step S1 is heated in an electric heating furnace using a two-stage heating process. In the two-stage heating process, the temperature inside the electric heating furnace is first raised to 800-850℃, and then the TC4 titanium alloy flat ingot is loaded into the furnace. After the temperature stabilizes, it is held for 60-90 minutes, and then the temperature is raised to 1000-1050℃. After the temperature stabilizes, it is held for 180-240 minutes. S3, Asynchronous hot rolling + edge heating: The heated TC4 titanium alloy flat ingot is quickly transferred to the asynchronous rolling mill and subjected to one-fire multi-pass asynchronous rolling to obtain TC4 titanium alloy thick plate. During the asynchronous rolling process, edge heating is used to compensate for the temperature of the edge of the TC4 titanium alloy thick plate. In step S3: The transfer time of the TC4 titanium alloy flat ingot is controlled within 5 to 20 seconds. During the asynchronous rolling process, the initial rolling temperature is controlled at 970-1000℃, and the final rolling temperature is higher than 750℃. During the asynchronous rolling process, the speed ratio of the upper and lower rolls is 1 to 1.4; In the single-pass multi-pass rolling process, the deformation amount of a single pass is controlled at 10-30%, and the reciprocating rolling is 8-13 passes, with the total deformation amount controlled at 80-90%. In the single-pass multi-pass rolling process, the rolling force of a single pass is controlled between 900 tons and 2000 tons, and the rolling force of each pass is dynamically adjusted within the range according to the reduction rate. During the edge heating process, an infrared thermometer is used to measure the temperature of the TC4 titanium alloy thick plate in real time. The temperature compensation power of the edge heating is adjusted according to the temperature measurement results so that the edge temperature of the target plate is close to the center temperature. The edge heating method is to use an electromagnetic edge heater for temperature compensation; S4, the TC4 titanium alloy thick plate obtained in step S3 is annealed, the plate shape is straightened, pickled and locally ground to obtain a TC4 titanium alloy thick plate with qualified surface. The thickness of the qualified TC4 titanium alloy thick plate is 15mm or 30mm, the flatness is ≤8mm / m, the average grain size is ≤10μm, the room temperature tensile strength is ≥895MPa, the yield strength is ≥830MPa, and the elongation is ≥8%.

2. The method for preparing TC4 titanium alloy thick plates according to claim 1, characterized in that, In step S1, the continuous ingot pulling process is adopted in the EB furnace one-time melting process, the melting and casting speed in the melting process is 600-1000 kg / h, and the flow rate of cooling water used for cooling the TC4 titanium alloy flat ingot is 1600-2200 L / min.

3. The method for preparing TC4 titanium alloy thick plates according to claim 1, characterized in that, In step S1, the blank obtained from the EB furnace in one melting process is milled, ground and chamfered, and after underwater ultrasonic testing to confirm that there are no errors, the head is removed, and finally the TC4 titanium alloy flat ingot with a thickness of 15-30 mm and a width of 1500-2500 mm is obtained.

4. The method for preparing TC4 titanium alloy thick plate according to claim 1, characterized in that, In step S4: The annealing temperature is 800–880℃, and the annealing time is 1–3 hours; and / or The pickling process uses a mixture of hydrofluoric acid and nitric acid to remove surface oxide scale; and / or The localized grinding process uses a flap wheel to remove cracks, peeling, and indented surface defects.

5. A TC4 titanium alloy thick plate prepared according to the preparation method of any one of claims 1 to 4, characterized in that, The TC4 titanium alloy thick plate has a flatness of ≤8mm / m, an average grain size of ≤10μm, a room temperature tensile strength of ≥895MPa, a yield strength of ≥830MPa, and an elongation of ≥8%.

Images