Method of producing titanium alloy disc for eliminating overheated structure of core

Abstract

The application relates to the field of titanium alloy production and discloses a titanium alloy disc round preparation method for eliminating overheated core structure, which comprises the following steps: sequentially adopting a rough rolling mill set, a medium rolling mill set, a finishing rolling mill set, a reducing sizing mill set and a high-speed wire rolling mill set for rolling; the rough rolling mill set comprises a front rack, a middle rack and a rear rack which are sequentially arranged along a rolling direction; for the rough rolling mill set, the deformation amount of the middle rack is controlled to be greater than the deformation amounts of the front rack and the rear rack; the finishing rolling mill set comprises multiple racks and roller tables arranged between adjacent racks; for the finishing rolling mill set, the running speed of the roller table is dynamically adjusted based on a target temperature difference between a core and a surface layer of a rolled piece after finishing rolling, the length of the roller table, the diameter of the rolled piece on the roller table and the starting temperature of the rolled piece on the roller table. The titanium alloy disc round core overheated structure can be effectively eliminated.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy production technology, and specifically to a method for preparing titanium alloy discs that eliminates overheated structures in the core. Background Technology

[0002] In the high-speed continuous rolling process of titanium alloy wire rods, the formation of overheated microstructures in the core stems from a deep-seated contradiction between the material's thermophysical properties and the process. The extremely low thermal conductivity of titanium alloys (only 17% of that of steel) leads to severe heat accumulation in the core. When deformation heat and initial residual heat are superimposed, the core temperature often exceeds the β-phase transformation point, triggering abnormal coarsening of β grains (≥50μm) and aggregation of the α-phase along grain boundaries. These defects directly result in a sharp drop in product fatigue strength of 40-50%, a 35% loss in elongation, and become a major cause of wire breakage in aerospace fasteners.

[0003] Current solutions have fundamental limitations: induction heating technology can only heat the surface 20-30mm area, and the lag in core temperature rise results in a temperature difference >60℃; at the same time, its extremely high energy consumption increases costs by 25%. Forced cooling processes, on the other hand, suffer from a mismatch between the critical cooling rate of the titanium alloy's martensitic phase transformation (>20℃ / s) and the actual cooling rate of the core (<5℃ / s), causing the formation of a hard and brittle α' phase (hardness >500HV) on the surface, while coarse grains continue to grow in the core. Even more seriously, traditional processes are forced to reduce the cooling rate to <10m / s to suppress overheating, resulting in a 40% decrease in production capacity and an oxidation weight gain of 0.8-1.2kg / ton.

[0004] Therefore, existing technologies still need improvement. Summary of the Invention

[0005] The main objective of this invention is to provide a method for preparing titanium alloy discs that eliminates overheated structures in the core, thereby solving the technical problem of how to effectively eliminate overheated structures in the core of titanium alloy discs.

[0006] According to one aspect of the present invention, a method for preparing titanium alloy wire rods with the elimination of core overheating structure is proposed, comprising: sequentially rolling a roughing mill, an intermediate mill, a finishing mill, a sizing mill, and a high-speed wire rod mill; wherein, the roughing mill includes a front stand, an intermediate stand, and a rear stand arranged sequentially along the rolling direction; for the roughing mill, the deformation of the intermediate stand is controlled to be greater than the deformation of the front stand and the deformation of the rear stand; the finishing mill includes multiple stands and a roller table disposed between adjacent stands; for the finishing mill, the running speed of the roller table is dynamically adjusted based on the target temperature difference between the core and surface of the workpiece after finishing rolling, the length of the roller table, the diameter of the workpiece on the roller table, and the initial temperature of the workpiece on the roller table.

[0007] According to one embodiment of the present invention, for a roughing mill, the deformation amounts of the front stand, the intermediate stand, and the rear stand are controlled to be 8-12%, 25-30%, and 8-12%, respectively.

[0008] According to one embodiment of the present invention, for a roughing mill, the rolling speed of the intermediate stand is controlled to be greater than the rolling speed of the front stand and the rear stand, wherein the rolling speeds of the front stand, intermediate stand and rear stand are controlled to be 0.5-0.6 m / s, 1.6-1.8 m / s and 0.8-1.0 m / s, respectively.

[0009] According to one embodiment of the present invention, for a roughing mill, after rolling is completed on an intermediate stand, the rolled piece is allowed to remain for 3-5 seconds before entering the next stand; after rolling is completed on a rear stand, the rolled piece is allowed to cool for 8-10 seconds.

[0010] According to one embodiment of the present invention, the total deformation of the rolling mill is controlled to be 55-60%, and the rolling speed is 3.0-3.5 m / s.

[0011] According to one embodiment of the present invention, when rolling is performed using an intermediate rolling mill, the cooling equipment in the intermediate rolling mill is turned off, so that the temperature of the rolled piece is uniform during the process of transporting it through the roller conveyor between adjacent stands of the intermediate rolling mill.

[0012] According to one embodiment of the present invention, the running speed of the roller conveyor of the finishing mill is dynamically adjusted according to the following formula;

[0013] in, △T This indicates the target temperature difference between the core and surface of the workpiece after finishing rolling; L n Indicates the first n The length of the roller conveyor section; v n Indicates the first n The running speed of the roller conveyor; d n Indicates the first n The diameter of the workpiece rolled on the roller conveyor; T n Indicates the first n The initial temperature of the rolled piece on the section roller conveyor.

[0014] According to one embodiment of the present invention, the total deformation of the reducing and sizing mill is controlled to be 10-15%, the rolling speed is 16-18 m / s, and the final rolling temperature is 200-220°C below the phase transformation point.

[0015] According to one embodiment of the present invention, the high-speed wire rod mill includes a first mill and a second mill arranged sequentially along the rolling direction; wherein, for the first mill, the temperature of the rolled piece is controlled to rise by 10-20°C after passing through each stand; and for the second mill, the temperature of the rolled piece is reduced by 20-30°C after each stand.

[0016] According to one embodiment of the present invention, the temperature of the rolled piece is increased by reducing the lubrication between the rolled piece and the stand, and the temperature of the rolled piece is decreased by taking cooling measures; the final rolling temperature of the first unit is controlled at 160-180°C below the phase transformation point, and the final rolling temperature of the second unit is controlled at 250-260°C below the phase transformation point.

[0017] In the technical solution of this invention, for the roughing mill, the deformation of the intermediate stand is controlled to be greater than that of the front and rear stands, i.e., a "low-high-low" deformation distribution is adopted. This avoids excessively rapid core temperature rise through small deformation in the first pass, breaks up the original coarse grains through large deformation in the intermediate passes, and reduces heat accumulation through reduced deformation in the final pass, thus solving the problem of heat accumulation in the core of titanium alloy discs. For the finishing mill, the thermal balance of the core and surface of the titanium alloy discs can be maintained by dynamically adjusting the running speed of the roller table. Therefore, this invention can effectively eliminate overheated structures in the core of titanium alloy discs and improve their mechanical properties through the synergistic effect of different units in the continuous rolling production line. 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 drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The surface metallographic structure of the titanium alloy disk prepared in Example 1 of the present invention is shown. Figure 2 The microstructure of the core of the titanium alloy disk prepared in Example 1 of the present invention is shown. Figure 3 The surface metallographic structure of the titanium alloy disk prepared in Comparative Example 1 of the present invention is shown. Figure 4 The metallographic structure of the core of the titanium alloy disk prepared in Comparative Example 1 of the present invention is shown. 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] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0022] This invention proposes a method for preparing titanium alloy coils with the elimination of core overheating, comprising: sequentially rolling a roughing mill, an intermediate mill, a finishing mill, a sizing mill, and a high-speed wire rod mill; wherein, the roughing mill includes a front stand, an intermediate stand, and a rear stand arranged sequentially along the rolling direction; for the roughing mill, the deformation of the intermediate stand is controlled to be greater than the deformation of the front stand and the rear stand; the finishing mill includes multiple stands and roller tables located between adjacent stands; for the finishing mill, the running speed of the roller table is dynamically adjusted based on the target temperature difference between the core and surface of the workpiece after finishing, the length of the roller table, the diameter of the workpiece on the roller table, and the initial temperature of the workpiece on the roller table.

[0023] This invention addresses the core overheating problem in a continuous rolling mill production line, encompassing roughing, intermediate rolling, finishing, sizing, and high-speed wire rod mills, through process innovation. In the roughing mill, the deformation of the intermediate stands is controlled to be greater than that of the preceding and following stands, employing a "low-high-low" deformation distribution. This prevents excessive core temperature rise through small deformation in the first pass, breaks down the initial coarse grains through large deformation in the intermediate passes, and reduces heat accumulation through reduced deformation in the final pass, thus solving the problem of heat accumulation in the core of titanium alloy wire rods. For the finishing mill, dynamic adjustment of the roller speed maintains thermal balance between the core and surface of the titanium alloy wire rods. Therefore, this invention effectively eliminates overheated core structures in titanium alloy wire rods and improves their mechanical properties through the synergistic effect of different mills in a continuous rolling production line.

[0024] In one specific embodiment, the continuous rolling production line includes 32 stands, wherein the roughing mill includes stands 1-6, the intermediate mill includes stands 7-12, the finishing mill includes stands 13-18, the reduction sizing mill includes stands 19-22, and the high-speed wire rod mill includes a first unit (BGV unit) and a second unit (TMB unit), wherein the BGV unit includes stands 23-26, and the TMB unit includes stands 27-32. It should be understood that other stand configurations may be used in other embodiments.

[0025] For a roughing mill, the front stand can be one or more stands located in the front region along the rolling direction from among multiple stands of the roughing mill; the intermediate stand can be one or more stands located in the middle region along the rolling direction from among multiple stands of the roughing mill; and the rear stand can be one or more stands located in the rear region along the rolling direction from among multiple stands of the roughing mill. In a specific embodiment, the roughing mill includes stands 1#-6#, with stand 1# as the front stand, stand 3# as the intermediate stand, and stand 6# as the rear stand.

[0026] In some embodiments, for roughing mills, the rolling speed of the intermediate stands is controlled to be greater than that of the front and rear stands, i.e., a "low-high-low" rolling speed distribution is adopted to work in conjunction with the deformation distribution. The initial low speed and small deformation can suppress the surface temperature rise caused by the intense deformation heat in the early stage of rolling and reduce the core-surface temperature difference; subsequently, the high speed and large deformation work together to achieve sufficient grain breakage in the core; in the later stage, the speed is reduced again and the deformation is reduced to reduce heat accumulation and allow the heat in the core to diffuse to the surface.

[0027] In some embodiments, the deformation amounts of the front stand, intermediate stand, and rear stand are controlled to be 8-12%, 25-30%, and 8-12%, respectively, and the rolling speeds of the front stand, intermediate stand, and rear stand are controlled to be 0.5-0.6 m / s, 1.6-1.8 m / s, and 0.8-1.0 m / s, respectively. After rolling is completed on the intermediate stand, the workpiece is held for 3-5 seconds before entering the next stand. After rolling is completed on the rear stand, the workpiece is cooled after 8-10 seconds to allow heat to diffuse from the core to the surface.

[0028] In some embodiments, the total deformation of the intermediate rolling mill is controlled at 55-60%, and the rolling speed is 3.0-3.5 m / s. By reasonably controlling the deformation and rolling speed, the uniformity of the core surface temperature is further ensured. In some embodiments, when rolling is performed using an intermediate rolling mill, the cooling equipment within the intermediate rolling mill (e.g., the cooling equipment between stands 7#-12#) is turned off, so that the temperature of the rolled piece is uniformized during the roller conveyor transport between adjacent stands of the intermediate rolling mill.

[0029] In some embodiments, the running speed of the roller conveyor between stands of the finishing mill is dynamically adjusted according to the following formula;

[0030] in, △T This indicates the target temperature difference between the core and surface of the workpiece after finishing rolling; L n Indicates the first n The length of the roller conveyor section; v n Indicates the first n The running speed of the roller conveyor; L n / v n Indicates the first n The transport time of the roller conveyor section; d n Indicates the first n The diameter of the workpiece rolled on the roller conveyor; d n 0.5 This reflects the impact of cross-sectional dimensions on core heat dissipation. T nIndicates the first n The initial temperature of the rolled piece on the section roller conveyor; T n -30) is used to correct the nonlinear temperature drop rate; the constant 0.25 is the thermal diffusivity coefficient of the titanium alloy.

[0031] By controlling the rolling speed of the finishing mill using the above-mentioned temperature drop control equation, the core-to-surface temperature difference can be ≤10℃, which can significantly improve the overheated structure of the core.

[0032] In some embodiments, the total deformation of the reducing and sizing mill is controlled at 10-15%, the rolling speed at 16-18 m / s, and the final rolling temperature at 200-220°C below the phase transformation point. These parameter settings effectively suppress grain coarsening.

[0033] In some embodiments, the high-speed wire rod mill includes a first mill (e.g., a BGV mill) and a second mill (e.g., a TMB mill) arranged sequentially along the rolling direction. For the first mill, the temperature of the rolled piece is controlled to rise (e.g., by 10-20°C) after passing through each stand (e.g., each of stands 23-26), activating dynamic recrystallization through high-temperature rolling, and the final rolling temperature of the first mill is controlled to be 160-180°C below the phase transformation point. This temperature rise can be achieved by reducing lubrication between the rolled piece and the stands, increasing friction. For the second mill, the temperature of the rolled piece is reduced (e.g., by 20-30°C) after rolling through each stand (e.g., each of stands 27-32), suppressing grain enlargement, and the final rolling temperature of the second mill is controlled to be 250-260°C below the phase transformation point. This temperature reduction can be achieved by implementing cooling measures (e.g., increasing the cooling water volume). In this invention, the high-speed wire rod mill adopts reverse double-pass thermomechanical treatment. The first mill (e.g., BGV mill) adopts heating rolling, and the second mill (e.g., TMB mill) adopts rapid cooling rolling, forming a dynamic recrystallization activation + grain freezing synergistic effect to eliminate the overheated structure in the core.

[0034] The following description is based on specific embodiments and comparative examples.

[0035] Example 1 1. The roughing mill uses a "low-high-low" deformation distribution across its six stands. The deformation on stand #1 is controlled at 10%, with a rolling speed of 0.5 m / s; the deformation on stand #3 is controlled at 25%, with a rolling speed of 1.6 m / s and a 5-second post-rolling hold; the deformation on stand #6 is controlled at 10%, with a rolling speed of 1.0 m / s and a 10-second cooling delay.

[0036] 2. The total deformation of the intermediate rolling mill is set at 55%, the rolling speed is controlled at 3.0 m / s, and the cooling equipment between stands 7#-12# in the intermediate rolling mill is shut down.

[0037] 3. The rolling speed of the finishing mill is dynamically adjusted according to the formula mentioned above to maintain the core-surface thermal balance of the titanium alloy disc.

[0038] 4. The total deformation of the sizing mill is set at 10%, the rolling speed is controlled at 16.0 m / s, and the final rolling temperature is locked at 210℃ below the phase transformation point.

[0039] 5. In the BGV of the high-speed wire rod mill, the lubrication effect is reduced, and the friction is increased, raising the temperature of each stand by 15°C and controlling the final rolling temperature 160°C below the phase transformation point. Meanwhile, in the TMB, the cooling water volume is increased in stands 27-32, lowering the temperature of each stand by 25°C and controlling the final rolling temperature 250°C below the phase transformation point.

[0040] Comparative Example 1 1. The roughing mill has 6 stands with an equal deformation of 20% per stand, and the rolling speed is controlled at 1.0 m / s. The intermediate mill has a total deformation of 55%, and the rolling speed is controlled at 3.0 m / s. The finishing mill has a constant rolling speed of 5.0 m / s. The reducing and sizing mill has a total deformation of 10%, and the rolling speed is controlled at 16.0 m / s.

[0041] 2. The high-speed wire rod mills use a uniform final rolling temperature, and both the BGV and TMB mills employ full-process water cooling.

[0042] Metallographic analysis and mechanical property testing were performed on the titanium alloy discs prepared in Example 1 and Comparative Example 1. Figure 1 and Figure 2 The metallographic structures of the surface layer and core of the titanium alloy disk prepared in Example 1 are shown separately. Table 1 shows the microstructural characteristics of the titanium alloy disk prepared in Example 1. Figure 1-2 As shown in Table 1, the titanium alloy disk prepared in Example 1 has a uniform core and surface structure with fine grains. Figure 3 and Figure 4 The metallographic structures of the surface layer and core of the titanium alloy disk prepared in Comparative Example 1 are shown separately. Table 2 shows the microstructural characteristics of the titanium alloy disk prepared in Comparative Example 1. Figure 3-4 As shown in Table 2, the core and surface microstructure of the titanium alloy discs prepared in Comparative Example 1 are uneven, with fine surface grains and coarse core grains. In Comparative Example 1, the uniform deformation during the roughing stage resulted in a rapid temperature rise in the core of stand #3. The uniform final rolling temperature and continuous water cooling in the high-speed wire rod mill led to a large temperature difference between the core and surface, resulting in large β-grains remaining in the core of the TMB section. Table 3 shows a comparison of the core properties of the titanium alloy discs prepared in Example 1 and Comparative Example 1. As shown in Table 3, Example 1 can reduce the core-surface temperature difference, effectively eliminating the overheated microstructure in the core of the titanium alloy discs during continuous rolling, thereby improving the mechanical properties of the titanium alloy discs.

[0043] Table 1. Microstructure characteristics of titanium alloy disks prepared in Example 1

[0044] Table 2. Microstructure characteristics of titanium alloy disks prepared in Comparative Example 1

[0045] Table 3 Comparison of core performance between Example 1 and Comparative Example 1

[0046] In summary, this invention provides a method for eliminating overheated microstructure in the core of titanium alloy discs through multi-unit coordinated rolling. This method achieves the elimination of overheated microstructure in the core of titanium alloy discs by coordinating and controlling the process parameters of the roughing mill, intermediate mill, finishing mill, sizing mill, and high-speed wire rod mill. This invention relates to a temperature-controlled crystallization suppression technology that does not rely on induction heating, is compatible with high-speed continuous rolling lines, and requires no equipment modification. Through stand function reconstruction and thermodynamic synergy, comprehensive optimization of the microstructure in the core of titanium alloy discs is achieved on a 32-stand high-speed continuous rolling line. This invention can refine the β-grain of the titanium alloy disc core to ≤15μm (compared to ≥50μm in traditional processes), achieve a cross-sectional microstructure uniformity deviation of ≤5%, and increase the yield of aerospace-grade products from 62.7% to 98.5%.

[0047] 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 the different aspects of the invention as described above 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 titanium alloy discs with eliminated core overheating structure, characterized in that, include: The rolling process is carried out sequentially using a roughing mill, an intermediate mill, a finishing mill, a sizing mill, and a wire rod mill. The roughing mill includes a front stand, an intermediate stand, and a rear stand arranged sequentially along the rolling direction; for the roughing mill, the deformation of the intermediate stand is controlled to be greater than the deformation of the front stand and the deformation of the rear stand. The finishing mill includes multiple stands and roller conveyors located between adjacent stands; for the finishing mill, the running speed of the roller conveyors is dynamically adjusted based on the target temperature difference between the core and surface of the workpiece after finishing, the length of the roller conveyors, the diameter of the workpiece on the roller conveyors, and the initial temperature of the workpiece on the roller conveyors.

2. The method according to claim 1, characterized in that, For the roughing mill, the deformation amounts of the front stand, the intermediate stand, and the rear stand are controlled to be 8-12%, 25-30%, and 8-12%, respectively.

3. The method according to claim 1, characterized in that, For the roughing mill, the rolling speed of the intermediate stand is controlled to be greater than the rolling speed of the front stand and the rear stand, wherein the rolling speeds of the front stand, the intermediate stand and the rear stand are controlled to be 0.5-0.6 m / s, 1.6-1.8 m / s and 0.8-1.0 m / s, respectively.

4. The method according to claim 1, characterized in that, For the roughing mill, after the intermediate stand rolling is completed, the rolled piece is allowed to remain for 3-5 seconds before entering the next stand; after the rear stand rolling is completed, the rolled piece is allowed to cool for 8-10 seconds.

5. The method according to claim 1, characterized in that, The total deformation of the intermediate rolling mill is controlled to be 55-60%, and the rolling speed is controlled to be 3.0-3.5 m / s.

6. The method according to claim 1, characterized in that, When rolling with the intermediate rolling mill, the cooling equipment in the intermediate rolling mill is turned off to ensure that the temperature of the rolled piece is uniform during the process of transporting it through the roller conveyor between adjacent stands of the intermediate rolling mill.

7. The method according to claim 1, characterized in that, The running speed of the roller conveyor of the finishing mill shall be dynamically adjusted according to the following formula; in, △T This indicates the target temperature difference between the core and surface of the workpiece after finishing rolling; L n Indicates the first n The length of the roller conveyor section; v n Indicates the first n The running speed of the roller conveyor; d n Indicates the first n The diameter of the workpiece rolled on the roller conveyor; T n Indicates the first n The initial temperature of the rolled piece on the section roller conveyor.

8. The method according to claim 1, characterized in that, The total deformation of the sizing mill is controlled to be 10-15%, the rolling speed to be 16-18 m / s, and the final rolling temperature to be 200-220℃ below the phase transformation point.

9. The method according to claim 1, characterized in that, The high-speed wire rod mill includes a first mill and a second mill arranged sequentially along the rolling direction; wherein, for the first mill, the temperature of the rolled piece is controlled to rise by 10-20°C after passing through each stand; and for the second mill, the temperature of the rolled piece is reduced by 20-30°C after each stand.

10. The method according to claim 9, characterized in that, The temperature of the rolled piece is increased by reducing the lubrication between the rolled piece and the stand, and the temperature of the rolled piece is decreased by taking cooling measures; the final rolling temperature of the first unit is controlled at 160-180℃ below the phase transformation point, and the final rolling temperature of the second unit is controlled at 250-260℃ below the phase transformation point.

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