Preparation method of high-straightness titanium alloy extra-thick plate

Abstract

The invention relates to the technical field of titanium alloy thick plate preparation, and discloses a high-straightness titanium alloy extra-thick plate preparation method, which comprises: providing a titanium alloy plate blank, heating the titanium alloy plate blank to a two-phase region temperature, and carrying out heat preservation, with the thickness of the titanium alloy plate blank being 200-400 mm; the heated plate blank is subjected to multi-heating-number rolling, the warping state of the plate blank is monitored in the rolling process, and based on the warping state, the upper surface and / or the lower surface of the plate blank are / is dynamically cooled through an intermediate cooling device between rolling passes; the rolled plate is subjected to hot straightening and air cooling; and the straightened plate is subjected to gradient heat treatment, then hot straightening is conducted again, air cooling is conducted, and the finished titanium alloy plate is obtained. By dynamically regulating and controlling the temperature of the upper surface and the lower surface of the titanium alloy plate blank, upper and lower coordinated deformation in the rolling process is achieved, the plate is straightened through a hot straightening machine after rolling, and the high-toughness titanium alloy extra-thick plate with the good plate shape is obtained.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy thick plate preparation technology, and in particular to a method for preparing a high-flatness titanium alloy extra-thick plate. Background Technology

[0002] Titanium alloys possess excellent comprehensive properties such as low density, high specific strength, corrosion resistance, and crack propagation resistance. With the rapid development of the marine engineering field, new requirements have been placed on the specifications, strength, and toughness of titanium alloys. However, high-strength and high-toughness titanium alloys are prone to uneven heating during hot working. Their hot deformation behavior is highly sensitive to processing temperature, leading to inconsistent deformation of thick titanium alloy plates, resulting in severe warping and buckling. Subsequent straightening cannot improve the straightness of the ends, increasing material loss by 5% to 10%, causing resource waste and economic losses. In addition, severe warping and buckling can cause collisions between the plates and equipment, causing production line shutdowns and affecting subsequent plate processing while causing significant losses to the production line.

[0003] CN 119819710 A discloses a high-impact toughness Ti80 titanium alloy plate with a thickness ≥50mm and its preparation method. Although this method can alleviate the warping at the head and tail by adjusting the roller speed difference, it will lead to the deterioration of the plate shape in the middle position. If a hot straightener is used for straightening, it will overload the plate and easily damage the equipment. CN 118847718 A discloses a slab warping control method based on rolling speed. It solves the warping problem of the plate by setting a reasonable roller speed difference. However, for extra-thick plates with high deformation resistance, even adjusting the roller speed difference to the limit cannot save the head warping. The torque deviation between the upper and lower rollers is too large, and the large temperature difference between the upper and lower surfaces of the plate results in different microstructures and performance differences.

[0004] Therefore, there is a need to improve the preparation method of ultra-thick titanium alloy plates with high flatness in the existing technology. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a method for preparing a high-flatness titanium alloy extra-thick plate. By dynamically controlling the temperature of the upper and lower surfaces of the titanium alloy slab, coordinated deformation of the upper and lower surfaces is achieved during the rolling process. After rolling, the plate is straightened by a hot straightening machine, resulting in a high-strength and high-toughness titanium alloy extra-thick plate with good plate shape.

[0006] To achieve the above objectives, this invention provides a method for preparing a high-flatness, extra-thick titanium alloy plate, wherein the thickness of the titanium alloy plate is 200–400 mm. The method includes the following steps: S1 provides titanium alloy slabs with a thickness of 200-400 mm, heats the titanium alloy slabs to the two-phase region temperature and holds them at that temperature; S2 performs multi-pass rolling on the heated slab, monitors the warping state of the slab during the rolling process, and uses an intermediate cooling device to dynamically cool the upper and / or lower surfaces of the slab between rolling passes based on the warping state. S3 performs hot straightening and air cooling on the rolled sheet material; S4 performs gradient heat treatment on the straightened sheet material, followed by hot straightening and air cooling to obtain the finished titanium alloy sheet material.

[0007] In some embodiments, in S1, the upper and lower surfaces of the titanium alloy slab are pre-laminated with pure titanium plates, and the laminated surfaces are coated with an anti-oxidation coating.

[0008] In some embodiments, in S1, heating to the two-phase region temperature includes: heating to T β -60~70)℃ and hold at that temperature for 0.5~1.5h, then increase the temperature to T at a rate of 60℃ / h. β -(30~40)℃ and maintain the temperature, with a heat preservation coefficient of 1.2~2.0 min / mm; where T β β is the β-phase transformation temperature of the titanium alloy slab.

[0009] In some implementations, in S2, the multi-pass rolling includes a first pass reversing rolling and a second pass full longitudinal rolling, with a total deformation of ≥55%.

[0010] In some implementations, during the first reversing rolling process, at least one intermediate reheating is performed, with a reheating temperature of T. β -(30~40)℃, the temperature replenishment time is 1~2h.

[0011] In some implementations, in S2, the single-pass reduction Δh of the rolling process satisfies: Δh≤k / B Where k is a parameter related to the slab deformation resistance and mill load, and B is the width of the slab in the current pass, in mm.

[0012] In some implementations, in S2, dynamic cooling based on the warp state includes: dynamically adjusting the speed v of the slab passing through the intermediate cooling device according to the real-time monitored warp length l and the current slab thickness h, wherein the speed control function is v=f(h, l, n), and n is the cooling intensity parameter of the cooling device.

[0013] In some embodiments, the intermediate cooling device employs at least one of atomized water cooling, air mist cooling, or laminar flow cooling.

[0014] In some implementations, in the hot straightening steps of S3 and S4, the roller gap setting of the straightener is 0.5 to 3.0 mm less than the current plate thickness h, and the straightening is repeated 3 times.

[0015] In some implementations, in S4, the gradient heat treatment includes: first at T β Hold at -(55~75)℃ for 1~2h, then increase the temperature to T at a rate of 30℃ / h. β -(25~45)℃ and kept at that temperature, with a heat preservation coefficient of 2.0~3.0 min / mm; during the heat treatment process, the roller conveyor inside the furnace continuously oscillates.

[0016] The present invention has at least the following beneficial technical effects: 1. This invention reduces the surface temperature difference of titanium alloy slabs by using intermediate cooling. Titanium alloy plates prepared by this method have higher flatness, more uniform microstructure on the upper and lower surfaces, smaller deviations in mechanical properties, and reduced head and tail cutting losses.

[0017] 2. This invention eliminates warping of the rolled workpiece during the rolling process and prevents damage to equipment such as rolling mills, conveyor rollers, dust hoods, and hot straighteners. Compared with the method of controlling the speed of the upper and lower rolls, it has obvious advantages in the preparation of high-strength and tough titanium alloy extra-thick plates. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of an embodiment of the method for preparing a high-flatness titanium alloy extra-thick plate provided by the present invention; Figure 2 This is a microstructure test image of the upper surface in Embodiment 1 provided by the present invention; Figure 3 This is a test image of the lower surface microstructure in Example 1 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0021] The terms "comprising" and "having," and any variations thereof, used in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion; the terms "first," "second," etc., used in the specification, claims, and accompanying drawings are used to distinguish different objects, not to describe a particular order. "A plurality of" means two or more, unless otherwise explicitly specified.

[0022] Furthermore, the reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] like Figure 1 The diagram shown is a schematic representation of an embodiment of a method for preparing a high-flatness, extra-thick titanium alloy plate provided by the present invention, comprising: S1 provides titanium alloy slabs with a thickness of 200-400 mm, heats the titanium alloy slabs to the two-phase region temperature and holds them at that temperature; S2 performs multi-pass rolling on the heated slab, monitors the warping state of the slab during the rolling process, and uses an intermediate cooling device to dynamically cool the upper and / or lower surfaces of the slab between rolling passes based on the warping state. S3 performs hot straightening and air cooling on the rolled sheet material; S4 performs gradient heat treatment on the straightened sheet material, followed by hot straightening and air cooling to obtain the finished titanium alloy sheet material.

[0024] Furthermore, in S1, the upper and lower surfaces of the titanium alloy slab are pre-laminated with pure titanium plates, and the laminated surfaces are coated with an anti-oxidation coating.

[0025] Specifically, heating to the two-phase region temperature is: heating to T β -60~70)℃ and hold at that temperature for 0.5~1.5h, then increase the temperature to T at a rate of 60℃ / h. β -(30~40)℃ and maintain the temperature, with a heat preservation coefficient of 1.2~2.0 min / mm; where T β β is the β-phase transformation temperature of the titanium alloy slab.

[0026] Furthermore, in S2, the multi-pass rolling includes a first-pass reversing rolling and a second-pass full-longitudinal rolling, with a total deformation of ≥55%. In some embodiments, during the first-pass reversing rolling, at least one intermediate reheating is performed, with a reheating temperature of T. β -(30~40)℃, the temperature replenishment time is 1~2h.

[0027] The single-pass reduction Δh in the rolling process satisfies: Δh≤k / B Where k is a parameter related to the slab deformation resistance and mill load, and B is the width of the slab in the current pass, in mm.

[0028] Furthermore, dynamic cooling based on warpage includes: dynamically adjusting the speed v of the slab passing through the intermediate cooling device according to the real-time monitored warpage length l and the current slab thickness h, with the speed control function being v=f(h, l, n), where n is the cooling intensity parameter of the cooling device.

[0029] In some embodiments, the intermediate cooling device employs at least one of atomized water cooling, air mist cooling, or laminar flow cooling.

[0030] Furthermore, in the hot straightening steps of S3 and S4, the roller gap setting of the straightener is the current plate thickness h minus 0.5~3.0 mm, and the straightening is repeated 3 times.

[0031] Furthermore, in S4, the gradient heat treatment includes: first at T β Hold at -(55~75)℃ for 1~2h, then increase the temperature to T at a rate of 30℃ / h. β -(25~45)℃ and kept at that temperature, with a heat preservation coefficient of 2.0~3.0 min / mm; during the heat treatment process, the roller conveyor inside the furnace continuously oscillates.

[0032] The present invention will be further explained below with reference to specific embodiments.

[0033] Example 1 The preparation method of the extra-thick titanium alloy plate in this embodiment includes the following steps: A 1.5mm thick pure titanium sheet is laminated to the upper and lower surfaces of the Ti80 titanium alloy slab, and an anti-oxidation coating is applied to the laminated surface to obtain a titanium alloy slab with dimensions of 344mm×1950mm×3200mm.

[0034] The slab is first in T β Hold at -65℃ for 1 hour, then increase the temperature at a rate of 60℃ / h to T. β The slab is held at -35℃ for 8.5 hours. After heating, the slab is rolled in two passes. The first pass involves horizontal rolling to a width of 2100mm followed by longitudinal rolling, with the slab returning to the furnace for reheating at temperature T. β -35℃, 1 hour, followed by reheating and subsequent rolling, with a deformation of 39.0%. The second rolling process uses full longitudinal rolling, and the single-pass reduction during the rolling process is controlled as follows:

[0035] The deformation was 38.1%.

[0036] The cooling water on the upper surface of the intermediate cooling device is turned on separately. The warping length of the slab head is 1000mm. The speed of passing through the intermediate cooling device is set to 1.2m / s. The size of the rolled titanium alloy plate is 130mm×2100mm×7800mm.

[0037] The roller gap of the hot straightener is set to 129.3mm, and the straightening is performed in three reciprocating cycles, followed by air cooling.

[0038] Titanium alloy sheet at temperature T β Hold at -65℃ for 1 hour, then increase the temperature to T at a rate of 30℃ / h. β The plate is kept at -35℃ for 5 hours, and the roller conveyor inside the furnace continuously oscillates to ensure the flatness of the plate. The roller gap of the hot straightener is set to 129.3mm, and the plate is straightened in three cycles. After straightening, the plate is air-cooled to obtain the finished titanium alloy plate.

[0039] Example 2 A 2mm thick pure titanium sheet is laminated to the upper and lower surfaces of the Ti80 titanium alloy slab, and an anti-oxidation coating is applied to the laminated surface to obtain a titanium alloy slab with dimensions of 370mm×2000mm×3300mm.

[0040] The slab is first in T β Hold at -60℃ for 1.5 hours, then increase the temperature in the furnace at a rate of 60℃ / h to T. β The slab is held at -30℃ for 9 hours. After heating, the slab is removed from the furnace and rolled in two passes. The first pass involves horizontal rolling to a width of 2700mm followed by longitudinal rolling, with the slab returning to the furnace for reheating at a temperature of T. β -30℃, 1.5h, followed by reheating and subsequent rolling, with a deformation of 35.1%. The second rolling process uses full longitudinal rolling, and the single-pass reduction during the rolling process is controlled as follows:

[0041] The deformation amount is 35.4%.

[0042] The cooling water on the upper surface of the intermediate cooling device is turned on separately. The warping length of the slab head is 500mm. The speed of passing through the intermediate cooling device is set to 1.5m / s. The size of the rolled titanium alloy plate is 155mm×2700mm×5800mm.

[0043] The roller gap of the hot straightener is set to 154.5mm, and the straightening is performed in three reciprocating cycles, followed by air cooling.

[0044] Titanium alloy sheet at temperature T β Hold at -60℃ for 1 hour, then increase the temperature to T at a rate of 30℃ / h.β The plate is kept at -30℃ for 6 hours, and the roller conveyor inside the furnace continuously oscillates to ensure the flatness of the plate. The roller gap of the hot straightener is set to 154.5mm, and the plate is straightened in three cycles. After straightening, the plate is air-cooled to obtain the finished titanium alloy plate.

[0045] Example 3 A 1.5mm thick pure titanium sheet is laminated to the upper and lower surfaces of the Ti80 titanium alloy slab, and an anti-oxidation coating is applied to the laminated surface to obtain a titanium alloy slab with dimensions of 260mm×1900mm×3200mm.

[0046] The slab is first in T β Hold at -70℃ for 0.5 hours, then increase the temperature in the furnace at a rate of 60℃ / h to T. β The slab is heated to -40℃ and held at this temperature for 6.5 hours. After heating, the slab is removed from the furnace and rolled in two passes. The first pass involves horizontal rolling to a width of 2100mm followed by longitudinal rolling, with the slab returning to the furnace for reheating at a temperature of T. β -40℃, 1 hour, followed by reheating and subsequent rolling, with a deformation of 46.2%. The second rolling process uses full longitudinal rolling, and the single-pass reduction during the rolling process is controlled as follows:

[0047] The deformation was 35.7%.

[0048] The cooling water on the upper surface of the intermediate cooling device is turned on separately. The warping length of the slab head is 600mm. The speed of passing through the intermediate cooling device is set to 1.8m / s. The size of the rolled titanium alloy plate is 95mm×2100mm×7900mm.

[0049] The roller gap of the hot straightener is set to 93mm, and the straightening is repeated 3 times. After straightening, the machine is air-cooled.

[0050] Titanium alloy sheet at temperature T β Hold at -55℃ for 1 hour, then increase the temperature to T at a rate of 30℃ / h. β The plate is kept at -25℃ for 3.5 hours, and the roller conveyor inside the furnace continuously oscillates to ensure the flatness of the plate. The roller gap of the hot straightener is set to 93mm, and the plate is straightened in three cycles. After straightening, the plate is air-cooled to obtain the finished titanium alloy plate.

[0051] like Figure 2 The image shown is a microstructure test diagram of the upper surface in Embodiment 1 provided by the present invention; Figure 3 The image shown is a microstructure test diagram of the lower surface in Embodiment 1 provided by the present invention.

[0052] The microstructure diagrams of the upper and lower surfaces both show a uniform bimodal structure, with the volume fraction of the equiaxed α phase being 27.2% and 28.6%, respectively. Combined with the mechanical properties, it can be seen that the upper and lower surfaces of the plate exhibit good microstructure uniformity and performance stability after dynamic cooling control.

[0053] The mechanical properties and shape data of the upper and lower parts of the titanium alloy plates in Examples 1-3 of this invention are shown in Table 1.

[0054] Table 1

[0055] By implementing this invention, the shape and surface uniformity of high-strength and high-toughness titanium alloy extra-thick plates can be greatly improved, and the flatness of the extra-thick plates can reach ≤5mm / m, thereby increasing the yield. On the other hand, it can reduce the damage to rolling mills, front roller conveyors and hot straighteners during the rolling process, with an estimated economic benefit of 500,000 yuan.

[0056] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0057] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0058] The embodiment numbers disclosed in the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0059] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for preparing a high-flatness, extra-thick titanium alloy plate, characterized in that, include: S1 provides a titanium alloy slab with a thickness of 200-400 mm, heats the titanium alloy slab to the two-phase region temperature and holds it at that temperature; S2 performs multi-pass rolling on the heated slab, monitors the warping state of the slab during the rolling process, and uses an intermediate cooling device to dynamically cool the upper and / or lower surfaces of the slab between rolling passes based on the warping state. S3 performs hot straightening and air cooling on the rolled sheet material; S4 performs gradient heat treatment on the straightened sheet material, followed by hot straightening and air cooling to obtain the finished titanium alloy sheet material.

2. The method for preparing a high-flatness, extra-thick titanium alloy plate according to claim 1, characterized in that, In S1, the upper and lower surfaces of the titanium alloy slab are pre-laminated with pure titanium plates, and the laminated surfaces are coated with an anti-oxidation coating.

3. The method for preparing a high-flatness, extra-thick titanium alloy plate according to claim 1, characterized in that, In S1, heating to the two-phase region temperature includes: heating to T β -60~70)℃ and hold at that temperature for 0.5~1.5h, then increase the temperature to T at a rate of 60℃ / h. β -(30~40)℃ and maintain the temperature, with a heat preservation coefficient of 1.2~2.0 min / mm; where T β The β-phase transformation temperature is the temperature of the titanium alloy slab.

4. The method for preparing a high-flatness, extra-thick titanium alloy plate according to claim 1, characterized in that, In S2, the multi-stage rolling process includes a first-stage reversing rolling process and a second-stage full longitudinal rolling process, with a total deformation of ≥55%.

5. The method for preparing a high-flatness, extra-thick titanium alloy plate according to claim 4, characterized in that, During the first reversing rolling process, at least one intermediate reheating is performed, with a reheating temperature of T. β -(30~40)℃, the temperature replenishment time is 1~2h.

6. The method for preparing a high-flatness, extra-thick titanium alloy plate according to claim 1, characterized in that, In S2, the single-pass reduction Δh in the rolling process satisfies: Δh≤k / B Where k is a parameter related to the slab deformation resistance and mill load, and B is the width of the slab in the current pass, in mm.

7. The method for preparing a high-flatness, extra-thick titanium alloy plate according to claim 1, characterized in that, In S2, the dynamic cooling based on the warp state includes: dynamically adjusting the speed v of the slab passing through the intermediate cooling device according to the real-time monitored warp length l and the current slab thickness h, with the speed control function being v=f(h, l, n), where n is the cooling intensity parameter of the cooling device.

8. The method for preparing a high-flatness, extra-thick titanium alloy plate according to claim 1 or 7, characterized in that, The intermediate cooling device employs at least one of atomized water cooling, air mist cooling, or laminar flow cooling.

9. The method for preparing a high-flatness, extra-thick titanium alloy plate according to claim 1, characterized in that, In the hot straightening steps of S3 and S4, the roller gap setting of the straightener is the current plate thickness h minus 0.5~3.0 mm, and the straightening is repeated 3 times.

10. The method for preparing a high-flatness, extra-thick titanium alloy plate according to claim 1, characterized in that, In S4, the gradient heat treatment includes: first at T β Hold at -(55~75)℃ for 1~2h, then increase the temperature to T at a rate of 30℃ / h. β -(25~45)℃ and kept at that temperature, with a heat preservation coefficient of 2.0~3.0 min / mm; during the heat treatment process, the roller conveyor inside the furnace continuously oscillates.

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