Titanium alloy thick plate rolling method and system based on strain-temperature cooperative control

Abstract

The invention relates to the technical field of titanium alloy rolling machining, discloses a titanium alloy thick plate rolling method and system based on strain-temperature cooperative control, and aims to solve the problem of consistency control of titanium alloy thick plate performance. The scheme mainly comprises the steps that the size range and the phase change temperature of a titanium alloy plate blank are determined, and different rolling technologies are designed; thermal simulation software is adopted to simulate different rolling processes, and temperature distribution and stress distribution in the thickness direction of the plate of each pass under different deformation and pass distribution conditions are obtained; the conditions that the core temperature is smaller than the phase change temperature and the core strain is larger than or equal to 80% of the maximum strain serve as judgment conditions, and the optimal rolling technology meeting the judgment conditions is screened out; and the titanium alloy plate blank is rolled according to the optimal rolling technology. According to the method, the structure difference caused by overheating of the rolled core structure or insufficient deformation of the core structure is avoided, the consistency control problem of the performance of the titanium alloy thick plate is solved, and the method is particularly suitable for TC4 titanium alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy rolling processing, and in particular to a titanium alloy thick plate rolling method and system based on strain-temperature coordinated control. Background Art

[0002] Titanium alloys, due to their high specific strength and excellent corrosion resistance, have been widely used in aerospace, marine engineering and other fields. In recent years, as underwater equipment has had higher demands on diving depth, higher indexes of material strength and toughness have been put forward. Titanium alloys, with their performance advantages, have become the preferred material for the new generation of underwater equipment and have been applied to many new models. Among them, titanium alloy wide and thick plates are the most widely used. Due to the characteristics of the service environment, the performance consistency of this type of material is extremely high.

[0003] Due to their high deformation resistance and low thermal conductivity, titanium alloys are susceptible to the high deformation conditions of thick plate rolling, resulting in insufficient strain penetration and a low degree of core microstructure fragmentation. Alternatively, they can lead to a large temperature rise in the core and "overheating" of the microstructure. Both of these conditions can seriously affect the quality of titanium alloy plates. For the rolling of titanium alloy thick plates with a thickness of 30 mm or more, controlling microstructure uniformity across the entire cross-section has always been a key issue affecting product quality. Existing technologies rely primarily on engineers' experience to set process parameters, and conduct multiple, costly production trials to verify and adjust these parameters. This approach is incapable of addressing the invisible temperature and strain states within the thick plate. Improper deformation process design during rolling can easily lead to core overheating or coarsening of the core microstructure, resulting in significant performance variations across the thickness of the titanium alloy plate, which can deteriorate the overall performance of the product. Therefore, it is necessary to rationally design the rolling process to find a balance between deformation distribution and temperature control, achieve coordinated temperature-strain control at each thickness point of the plate, and achieve consistent microstructure and performance control across the entire cross-section. Summary of the Invention

[0004] The present invention aims to avoid the structural differences caused by overheating of the rolling core structure or insufficient deformation of the core structure, solve the problem of consistency control of the performance of titanium alloy thick plates, and propose a titanium alloy thick plate rolling method and system based on strain-temperature coordinated control.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: In a first aspect, the present invention provides a titanium alloy thick plate rolling method based on strain-temperature coordinated control, the method comprising: Determine the size range and phase transition temperature of titanium alloy slabs and design different rolling processes with different deformation amounts and pass distributions; Thermal simulation software is used to simulate different rolling processes to obtain the temperature and stress distribution in the thickness direction of the plate at each pass under different deformation amounts and pass distribution conditions. The core temperature is less than the phase transition temperature and the core strain is greater than or equal to 80% of the maximum strain as the judgment conditions, and the optimal rolling process that meets the judgment conditions is screened out based on the temperature distribution and stress distribution obtained by simulation; The titanium alloy slab is rolled according to the optimal rolling process.

[0006] Furthermore, the titanium alloy slab has a thickness of 280-320 mm, a width of 1500-1800 mm, and a length of 3200-3500 mm.

[0007] Furthermore, the thermal simulation software is Forge thermal simulation software.

[0008] Furthermore, the optimal rolling process is multi-pass rolling, the heating temperature of the titanium alloy slab is 950° C., and the holding time is 360-420 minutes.

[0009] Furthermore, the multi-pass rolling is 9-pass rolling.

[0010] Furthermore, the deformation amounts of each pass are 15%, 18%, 24%, 28%, 22%, 17%, 16%, 13%, and 10%.

[0011] Furthermore, during the rolling process, the maximum temperature of the core of the plate is controlled below 978°C.

[0012] Furthermore, the thickness of the plate after rolling is 30-80 mm.

[0013] Furthermore, the titanium alloy slab is a TC4 titanium alloy slab.

[0014] In a second aspect, the present invention provides a titanium alloy thick plate rolling system based on strain-temperature coordinated control, wherein the system adopts the titanium alloy thick plate rolling method based on strain-temperature coordinated control as described in the first aspect to roll the titanium alloy slab.

[0015] The beneficial effects of the present invention are: the titanium alloy thick plate rolling method and system based on strain-temperature coordinated control provided by the present invention adopts the idea of ​​strain-temperature coordinated control, and uses numerical simulation means to characterize the real-time temperature and strain conditions at different thickness positions of the entire section under different deformation amounts and pass distribution conditions, and screen out the optimal rolling scheme that meets the judgment conditions. The judgment conditions can not only ensure that brittle lamellar overheated structure will not be generated due to overheating, but also ensure that the deformation can fully penetrate into the core, and there is enough strain to break the original coarse grains, avoid the occurrence of coarse grains with insufficient deformation, thereby avoiding the organizational differences caused by overheating of the rolled core structure or insufficient deformation of the core structure, and solve the problem of consistency control of the performance of titanium alloy thick plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic flow chart of a titanium alloy thick plate rolling method based on strain-temperature coordinated control provided in an embodiment; Figure 2 A schematic diagram of the temperature distribution curve in the thickness direction of the plate during the first rolling pass provided in the embodiment; Figure 3 A schematic diagram of the temperature distribution curve in the thickness direction of the plate during the fifth rolling pass provided in the embodiment; Figure 4 A schematic diagram of the strain distribution curve in the thickness direction of the plate during the third rolling pass provided in the embodiment; Figure 5 A schematic diagram of the strain distribution curve in the thickness direction of the plate during the seventh rolling pass provided in the embodiment; Figure 6 This is a schematic diagram of tissue at different thickness positions before the implementation of the solution of the present invention; Figure 7 This is a schematic diagram of the tissue at different thickness positions after the implementation of the solution of the present invention. DETAILED DESCRIPTION

[0017] Currently, titanium alloy thick plate rolling relies primarily on engineers' experience to set process parameters, and multiple, costly production trials are conducted to verify and adjust these parameters. This approach is unable to address the invisible temperature and strain states within the thick plate, leading to recurring problems such as core overheating and insufficient deformation.

[0018] Based on this, the technical solution of the present invention is proposed. In the present invention, first, the initial size specification range and phase transition temperature critical value of the titanium alloy slab are determined, and based on this, multiple sets of candidate rolling process schemes with different deformation distribution and pass arrangements are designed; then, professional thermal simulation software is used to simulate the entire process of each candidate rolling process scheme, and quantitatively characterize the dynamic distribution characteristics of the temperature field and strain field of the plate along the thickness direction in each pass; then, a multi-objective collaborative judgment criterion with "the real-time peak temperature of the core is lower than the phase transition temperature, and the core strain value reaches 80% or more of the maximum strain value" as the core is set, and the optimal rolling process that meets both temperature control and deformation penetration requirements is screened out from the candidate schemes based on the simulation data; finally, according to the parameter setting of the selected optimal rolling process, the titanium alloy slab is rolled to achieve coordinated regulation of the microstructure and performance of the entire cross-section. The present invention introduces thermal simulation software as a core tool. Based on physical principles and mathematical models, this tool can quantitatively and visually simulate and predict the real-time temperature and strain field at any position inside the plate (especially the core) during the rolling process. At the same time, it proposes dual-objective collaborative judgment conditions, which can ensure that the thermodynamic conditions will not lead to overheated coarse structure in the core, and can also ensure that the mechanical conditions are sufficient to fully crush and refine the core grains, realizing the coordinated optimization of temperature and strain, and solving the problem of quality control of the core of titanium alloy thick plates.

[0019] The technical solution of this embodiment will be clearly and completely described below in conjunction with the drawings in this embodiment. Obviously, the described embodiment is only a part of the embodiments of the present invention, rather than all the embodiments.

[0020] Figure 1 A schematic diagram of a titanium alloy thick plate rolling method based on strain-temperature coordinated control is shown. Figure 1 , the method comprises the following steps: Step 1: Determine the size range and phase transition temperature of the titanium alloy slab, and design different rolling processes. Different rolling processes have different deformation amounts and pass distributions.

[0021] In this embodiment, the titanium alloy slab is a TC4 titanium alloy slab, the thickness of the TC4 titanium alloy slab is 280-320 mm, the width is 1500-1800 mm, the length is 3200-3500 mm, and the phase transition temperature is 985° C.-998° C.

[0022] After determining the size range and phase transition temperature of the titanium alloy slab, multiple groups of candidate rolling processes with different deformation distribution and pass arrangements are designed accordingly.

[0023] Step 2: Use thermal simulation software to simulate different rolling processes to obtain the temperature distribution and stress distribution in the thickness direction of the plate at each pass under different deformation amounts and pass distribution conditions.

[0024] In this example, the thermal simulation software used is Forge, a specialized numerical simulation tool specifically designed for metal forming and heat treatment. Its simulation accuracy far exceeds that of general-purpose software or empirical formulas. Using this specialized thermal simulation software, we simulated the entire process of each candidate rolling process, quantitatively characterizing the dynamic distribution characteristics of the temperature and strain fields through the thickness of the plate during each pass. This yielded the temperature and stress distributions through the thickness of the plate for each pass under varying deformation amounts and pass allocations.

[0025] Figure 2 and Figure 3 The temperature distribution curves along the thickness of the plate during different rolling passes are shown. Figure 2 and Figure 3 In the figure, the horizontal axis represents the plate thickness, 0 represents the center position, and the vertical axis represents the temperature. Figure 4 and Figure 5 The stress distribution curves in the thickness direction of the plate during different rolling passes are shown. Figure 4 and Figure 5 In the figure, the abscissa represents the plate thickness, 0 represents the center position, and the ordinate represents the strain. For the distribution of the core temperature and strain at each pass when rolling with different passes, please refer to Tables 1 to 3.

[0026] Table 1 Temperature and strain distribution of the core of each pass when 7 passes are used Table 2 Temperature and strain distribution of the core of each pass when 9 passes are used Table 3 Temperature and strain distribution of the core of each pass when 11 passes are used Step 3: Taking the core temperature less than the phase transition temperature and the core strain greater than or equal to 80% of the maximum strain as the judgment conditions, the optimal rolling process that meets the judgment conditions is screened out based on the temperature distribution and stress distribution obtained by simulation.

[0027] This embodiment sets a dual-objective collaborative judgment condition centered on "core temperature < phase transition temperature and core strain ≥ 80% of maximum strain." Based on simulation data, the optimal rolling process that simultaneously meets these criteria is selected from candidate solutions. The core temperature < phase transition temperature ensures that brittle lamellar structures will not form due to overheating, and the core strain ≥ 80% of maximum strain ensures that deformation can fully penetrate the core, providing sufficient strain to break up the original coarse grains and avoid the formation of under-deformed coarse grains. The judgment condition transforms simulation data into a clear, executable process selection criterion, ensuring the scientific nature of subsequent implementation.

[0028] Step 4: rolling the titanium alloy slab according to the optimal rolling process.

[0029] In this embodiment, the optimal rolling process is multi-pass rolling, which consists of 9 passes. The deformation of each pass is 15%, 18%, 24%, 28%, 22%, 17%, 16%, 13%, and 10% respectively. The heating temperature of the titanium alloy slab is 950°C, and the holding time is 360~420min. During the rolling process, the maximum temperature of the core of the plate is controlled below 978°C, and the thickness of the plate after rolling is 30~80mm.

[0030] Through multiple rolling passes, the initial deformation is greater, aiming to efficiently break up the grains and generate deformation heat. The deformation gradually decreases in the middle and later passes, likely to control the rapid temperature rise, allowing more time for heat to dissipate and prevent overheating in the core. The heating temperature of 950°C and the peak core temperature of 978°C strictly meet the criteria for being below the phase transition temperature.

[0031] Finally, after rolling is completed, the steel can be straightened online and air-cooled to ensure the flatness of the steel plate and obtain a uniform equiaxed structure, avoiding the introduction of new internal stress or uneven structure due to excessive cooling.

[0032] Figure 6 A schematic diagram of the tissue at different thickness positions before the implementation of the present invention is shown. Figure 6 In the middle, from left to right are the surface, 1 / 4 thickness, and core. Figure 7 A schematic diagram of the tissue at different thickness positions before the implementation of the present invention is shown. Figure 7 The figure shows the surface, quarter thickness, and core from left to right. It can be seen that the implementation of the present invention significantly avoids structural variations caused by overheating or insufficient deformation of the core during rolling, thereby solving the problem of consistent performance control in titanium alloy thick plates.

[0033] Example 1: ① The dimensions of the TC4 titanium alloy slab used are: thickness 320mm × width 1550mm × length 3300mm; the measured phase transition temperature of the material is 995℃; ② The TC4 titanium alloy thick plate was rolled using a single-fire rolling process: the slab heating temperature was controlled at 950°C and the holding time was 390 min; 9 rolling passes were used, with the deformation distribution of each pass being 15%, 18%, 24%, 28%, 22%, 17%, 16%, 13%, and 10% respectively. The plate dimensions after rolling were: 55 mm thick × 2450 mm wide × 11700 mm long; ③ The rolled slab is straightened online and then air-cooled to room temperature; ④ Samples were taken from the head of the rolled plate, and after annealing heat treatment at 850℃×2h, the structure of the entire cross-section was evaluated using a metallographic microscope: from the surface to the core, the structure type was equiaxed structure, the grain size was 22~36μm, and the structure uniformity was good.

[0034] Example 2: ① The dimensions of the TC4 titanium alloy slab used are: thickness 300mm × width 1550mm × length 3200mm; the measured phase transition temperature of the material is 995℃; ② The TC4 titanium alloy thick plate was rolled using a single-fire rolling process: the slab heating temperature was controlled at 950°C and the holding time was 360 min; 9 rolling passes were used, with the deformation distribution of each pass being 15%, 18%, 24%, 28%, 22%, 17%, 16%, 13%, and 10% respectively. The plate dimensions after rolling were: thickness 48 mm × width 2250 mm × length 12500 mm; ③ The rolled slab is straightened online and then air-cooled to room temperature; ④ Samples were taken from the head of the rolled plate, and after annealing heat treatment at 850℃×2h, the structure of the entire cross-section was evaluated using a metallographic microscope: from the surface to the core, the structure type was equiaxed structure, the grain size was 19~25μm, and the structure uniformity was good.

[0035] Example 3: ① The dimensions of the TC4 titanium alloy slab used are: thickness 280mm × width 1550mm × length 3200mm; the measured phase transition temperature of the material is 995℃; ② The TC4 titanium alloy thick plate was rolled using a single-pass rolling process: the slab heating temperature was controlled at 950°C and the holding time was 300 min; 9 passes were used, and the deformation distribution of each pass was 15%, 18%, 24%, 28%, 22%, 17%, 16%, 13%, and 10%, respectively. The plate dimensions after rolling were: 40 mm thick × 2300 mm wide × 13600 mm long; ③ The rolled slab is straightened online and then air-cooled to room temperature; ④ Samples were taken from the head of the rolled plate, and after annealing heat treatment at 850℃×2h, the structure of the entire cross-section was evaluated using a metallographic microscope: from the surface to the core, the structure type was equiaxed structure, the grain size was 23~29μm, and the structure uniformity was good.

[0036] In summary, this embodiment adopts the idea of ​​strain-temperature coordinated control, and uses numerical simulation to characterize the real-time temperature and strain conditions at different thickness positions of the entire section under different deformation amounts and pass distribution conditions, and screen out the optimal rolling scheme that meets the judgment conditions. The judgment conditions can not only ensure that brittle lamellar overheated structure will not be generated due to overheating, but also ensure that the deformation can fully penetrate into the core, and there is enough strain to break the original coarse grains, avoid the occurrence of coarse grains with insufficient deformation, thereby avoiding the organizational differences caused by overheating of the rolled core structure or insufficient deformation of the core structure, and solve the problem of consistency control of the performance of titanium alloy thick plates.

[0037] Based on the above technical solution, this embodiment also proposes a titanium alloy thick plate rolling system based on strain-temperature coordinated control, and the system adopts the titanium alloy thick plate rolling method based on strain-temperature coordinated control described in the embodiment to roll titanium alloy slabs.

[0038] It can be understood that since the titanium alloy thick plate rolling system based on strain-temperature coordinated control described in this embodiment is a system for implementing the titanium alloy thick plate rolling method based on strain-temperature coordinated control described in the embodiment, for the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple. For relevant matters, please refer to the partial description of the method, and no further details will be given here.

Claims

1. A titanium alloy thick plate rolling method based on strain-temperature coordinated control, characterized in that: The method comprises: Determine the size range and phase transition temperature of titanium alloy slabs and design different rolling processes with different deformation amounts and pass distributions; Thermal simulation software is used to simulate different rolling processes to obtain the temperature and stress distribution in the thickness direction of the plate at each pass under different deformation amounts and pass distribution conditions. The core temperature is less than the phase transition temperature and the core strain is greater than or equal to 80% of the maximum strain as the judgment conditions, and the optimal rolling process that meets the judgment conditions is screened out based on the temperature distribution and stress distribution obtained by simulation; The titanium alloy slab is rolled according to the optimal rolling process.

2. The titanium alloy thick plate rolling method based on strain-temperature coordinated control according to claim 1, characterized in that: The titanium alloy slab has a thickness of 280-320 mm, a width of 1500-1800 mm, and a length of 3200-3500 mm.

3. The titanium alloy thick plate rolling method based on strain-temperature coordinated control according to claim 1, characterized in that: The thermal simulation software is Forge thermal simulation software.

4. The titanium alloy thick plate rolling method based on strain-temperature coordinated control according to claim 1, characterized in that: The optimal rolling process is multi-pass rolling, the heating temperature of the titanium alloy slab is 950° C., and the holding time is 360-420 minutes.

5. The titanium alloy thick plate rolling method based on strain-temperature coordinated control according to claim 4, characterized in that: The multi-pass rolling is 9-pass rolling.

6. The titanium alloy thick plate rolling method based on strain-temperature coordinated control according to claim 5, characterized in that: The deformation amounts of each pass are: 15%, 18%, 24%, 28%, 22%, 17%, 16%, 13%, and 10%.

7. The titanium alloy thick plate rolling method based on strain-temperature coordinated control according to claim 5, characterized in that: During the rolling process, the maximum temperature of the core of the plate is controlled below 978℃.

8. The titanium alloy thick plate rolling method based on strain-temperature coordinated control according to claim 5, characterized in that: The thickness of the plate after rolling is 30~80mm.

9. The titanium alloy thick plate rolling method based on strain-temperature coordinated control according to any one of claims 1 to 8, characterized in that: The titanium alloy slab is a TC4 titanium alloy slab.

10. Titanium alloy thick plate rolling system based on strain-temperature coordinated control, characterized in that: The system rolls the titanium alloy slab using the titanium alloy thick plate rolling method based on strain-temperature coordinated control as described in any one of claims 1 to 9.

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