Method and system for inhibiting C-shaped warping of titanium alloy plate based on asynchronous hot rolling process

Abstract

The invention discloses a method and a system for inhibiting C-shaped warping of a titanium alloy plate based on an asynchronous hot rolling process, and relates to the technical field of metal material hot processing, and the method comprises the following steps: pretreating a titanium alloy surface blank; feeding the pretreated blank into an asynchronous rolling mill, and carrying out asynchronous rolling parameter setting and tension control; dynamic process adjustment is conducted on the asynchronous rolling mill through temperature gradient compensation; and real-time quality monitoring is carried out on the asynchronous rolling mill, closed-loop regulation and control are carried out, and C-type warping suppression is completed. According to the method, the C-type warping restraining effect is remarkable, the flatness is greatly improved, the warping amount is reduced to be smaller than or equal to 0.5 mm / m from being larger than or equal to 1.5 mm / m in a traditional technology, the reduction amplitude exceeds 60%, the residual stress is optimized, the stress difference between the surface and the core is reduced to be + / -30 MPa from + / -150 MPa, and the cracking risk in follow-up machining is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of hot processing of metal materials, and in particular to a method and system for suppressing C-type warping of titanium alloy plates based on an asynchronous hot rolling process. Background Art

[0002] Titanium alloys are widely used in high-end fields such as aerospace, medical equipment, and marine engineering due to their excellent specific strength, corrosion resistance, and biocompatibility. Especially in aircraft engine blades, human implants, and deep-sea equipment, the dimensional accuracy and mechanical properties of titanium alloy plates directly determine the reliability and life of the products. Hot rolling is a key process for forming titanium alloy plates. Its core goal is to refine the grains and uniform the structure through plastic deformation at high temperatures, while ensuring the flatness of the plates. However, in the traditional synchronous hot rolling process, the residual stress differences caused by temperature gradients, uneven deformation, and anisotropy of the structure cause C-type warping (hereinafter referred to as "C-warping"), which seriously restricts product quality and production efficiency.

[0003] To address the C-warping problem, existing technologies mainly adopt the following methods: reducing the single-pass rolling reduction rate to reduce stress accumulation, but this leads to an increase in rolling passes and a decrease in production efficiency; increasing the rolling temperature to the β phase region to enhance the material's plastic deformation ability, but grain coarsening leads to a decrease in mechanical properties; there is also repeated bending through a multi-roll straightening machine to correct the warping, but the equipment investment is high; in addition, the rolling direction is alternately changed to balance the stress distribution, but multiple-pass reversing leads to a 30% increase in energy consumption and has limited effect on thick plates (>20mm).

[0004] Due to the residual stress differences caused by temperature gradient, uneven deformation and anisotropy of the structure during hot rolling of titanium alloys, the probability of C-warping in titanium alloys during hot rolling is very high, which poses great challenges to plate shape control and has become a major process bottleneck in the industrial production of high-precision titanium alloy sheets in the aerospace field. Summary of the Invention

[0005] In order to solve the problems in the above-mentioned background technology, the present invention provides a method and system for suppressing C-type warping of titanium alloy plates based on asynchronous hot rolling process, which systematically solves the C-type warping problem of titanium alloy plates caused by plate temperature gradient and residual stress difference during traditional hot rolling, improves the flatness of the plates, and optimizes the mechanical properties and microstructure.

[0006] To achieve the above object, the present invention provides a method for suppressing C-type warping of titanium alloy plates based on an asynchronous hot rolling process, the steps comprising:

[0007] Pre-treating the titanium alloy surface blank; the pre-treating steps include cleaning the oxide layer and preheating the titanium alloy surface blank;

[0008] The pre-treated billet is fed into the asynchronous rolling mill and asynchronous rolling parameters and tension control are performed; the asynchronous rolling parameters to be set include asynchronous ratio, rolling speed, single-pass reduction rate, and total deformation; tension control includes applying front tension and back tension during the rolling process;

[0009] Dynamic process adjustment of the asynchronous rolling mill is carried out through temperature gradient compensation. The steps include real-time monitoring of the rolling zone temperature through infrared thermometers and real-time control of the upper and lower roll speed ratio using a PLC controller.

[0010] The asynchronous rolling mill is subjected to real-time quality monitoring and closed-loop control to suppress C-type warping.

[0011] Preferably, the oxide layer on the surface of the titanium alloy blank is cleaned by sandblasting or pickling, and the surface roughness Ra is ≤ 3.2 μm; then, a high-temperature glass protective agent is sprayed on the surface of the titanium alloy blank; finally, the titanium alloy blank is preheated to the temperature of the α+β phase region or the β phase region, and the holding time is 1h~4h.

[0012] Preferably, the calculation formula of the asynchronous ratio includes:

[0013] ,

[0014] in, is the linear speed of the fast roller, is the linear speed of the slow roller.

[0015] Preferably, the relationship between the asynchronous ratio and the reduction rate satisfies:

[0016] ,

[0017] Where ε is the reduction rate, which is expressed as:

[0018] ,

[0019] in, is the initial thickness of the blank, It is the thickness of the billet after rolling.

[0020] Preferably, the front tension and the back tension are applied in the following ways: the front tension is provided by the coiler, and the tension value = 0.1σ y ; The post-tension is provided by the uncoiler, tension value = 0.15σ y ; Among them, σ y It is the high temperature yield strength of the material; the tension control accuracy is ≤±5%.

[0021] Preferably, the rules for temperature gradient compensation include: when the temperature difference between the upper and lower surfaces of the rolling zone is greater than 30°C, the asynchronous ratio Δv is 1.3; when the temperature difference between the upper and lower surfaces of the rolling zone is between 10-30°C, the asynchronous ratio is selected as 1.2; when the temperature difference between the upper and lower surfaces of the rolling zone is lower than 10°C, the asynchronous ratio is selected as 1.1.

[0022] Preferably, the working principle of the PLC controller includes: using fuzzy PID to control the storage and tracing of data, and simultaneously controlling the dynamic adjustment of the asynchronous ratio and rolling speed; data storage and tracing are used to record the process parameters and quality data of each batch of plates and generate a unique ID code.

[0023] Preferably, the steps of real-time quality monitoring of the asynchronous rolling mill and closed-loop control include: using laser displacement sensors and X-ray stress meters to monitor the warping amount and residual stress distribution online, monitoring the surface flatness and residual stress of the plate online, and dynamically adjusting the asynchronous ratio and reduction rate to make the warping amount ≤0.5mm / m.

[0024] The present invention also provides a system for suppressing C-type warping of titanium alloy plates based on an asynchronous hot rolling process. The system is used to implement the above method and includes: a preprocessing module, a setting module, an adjustment module, and a monitoring module;

[0025] The pretreatment module is used to pretreat the titanium alloy surface blank;

[0026] The setting module is used to feed the pre-treated billet into the asynchronous rolling mill and perform asynchronous rolling parameter setting and tension control;

[0027] The adjustment module is used to dynamically adjust the process of the asynchronous rolling mill through temperature gradient compensation;

[0028] The monitoring module is used to perform real-time quality monitoring of the asynchronous rolling mill and perform closed-loop control to suppress C-type warping.

[0029] Preferably, the workflow of the pretreatment module includes: using sandblasting or pickling process to clean the oxide layer of the titanium alloy surface blank, and the surface roughness Ra≤3.2μm; then, spraying a high-temperature glass protective agent on the surface of the titanium alloy blank; finally, preheating the titanium alloy blank to the α+β phase region or β phase region temperature, and keeping it warm for 1h~4h.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The C-warpage suppression effect is significant, and the flatness is improved: the warpage is reduced from ≥1.5 mm / m in the traditional process to ≤0.5 mm / m, a reduction of more than 60%; the residual stress is optimized: the stress difference between the surface and the core is reduced from ±150 MPa to ±30 MPa, avoiding the risk of cracking during subsequent processing.

[0032] (2) Improved toughness: Tensile strength is increased by 10-15% (e.g., Ti-6Al-4V reaches 950-1050 MPa), and elongation is ≥12%, which is superior to conventional processes (800-900 MPa, elongation 8-10%). Dynamic recrystallization grain size is refined to 10-20 μm, and fatigue life is increased by 30%.

[0033] (3) Process simplification: Eliminating the offline straightening and pickling steps reduces production costs by 20-25%. Improved yield rate: The real-time feedback system increases the yield rate from 85% to ≥98%, reducing rework losses.

[0034] (4) Response speed: The online monitoring system enables millisecond-level parameter adjustments (traditional process delays ≥ 2 seconds), adapting to high-speed rolling (5 m / s). It accurately predicts the process window and reduces trial-and-error costs by 50%.

[0035] (5) Green manufacturing: Reduce pickling wastewater discharge, and the surface oxide layer thickness is less than 5 μm (traditional process ≥10 μm). BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 Schematic diagram of a method flow in an embodiment of the present invention;

[0038] Figure 2 Schematic diagram comparing stress distributions of conventional synchronous rolling and asynchronous rolling according to an embodiment of the present invention;

[0039] Figure 3 Schematic diagram of an asynchronous rolling mill structure and a temperature field control module according to an embodiment of the present invention;

[0040] Figure 4 This is a flow chart of an online monitoring and feedback system according to an embodiment of the present invention;

[0041] Figure 5 Comparison diagram of microstructures of asynchronous hot rolling at different temperatures according to an embodiment of the present invention; wherein (a) represents 950°C; (b) represents 900°C;

[0042] Figure 6 These are comparison photos of the warping amounts of different plates according to the embodiments of the present invention; (a) represents synchronous hot rolling; (b) represents asynchronous hot rolling. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Before proceeding with the description, the technical terms used in this embodiment will be first introduced.

[0046] Pure titanium undergoes a crystal structure transformation at 882°C. This example involves the following two allotropes:

[0047] α-Ti (low-temperature phase): Hexagonal close-packed structure (HCP), exists below 882°C. It is characterized by few slip systems and weak plastic deformation ability.

[0048] β-Ti (high temperature phase): Body-centered cubic structure (BCC), exists above 882°C. It is characterized by multiple slip systems, good plasticity, and easy deformation.

[0049] When the titanium alloy is below the α phase transition point, the α phase and the β phase coexist, forming an "α+β dual-phase region." This is because the β-stabilizing element (such as 4% V in Ti-6Al-4V) inhibits the complete transformation from β to α, allowing the β phase to be partially retained at low temperatures.

[0050] For example, the β transformation point of Ti-6Al-4V is T~β~≈ 980℃ (pure titanium is 882℃). Its temperature range is:

[0051] T~β~< 980℃: α + β two-phase region (e.g., 750–980℃);

[0052] T~β~≥ 980℃: single-phase β zone.

[0053] Example 1

[0054] like Figure 1 FIG. 1 is a flow chart of the method of this embodiment, and the steps include:

[0055] S1. Pre-treat the titanium alloy surface blank.

[0056] The surface of the titanium alloy blank is cleaned of oxide layer by sandblasting or pickling process, and the surface roughness is Ra≤3.2μm; then, the surface of the titanium alloy blank is sprayed with high-temperature glass protective agent (protective agent of silicon-based glass system, the main components are SiO2+Al2O3+CaO, etc.); before spraying, acetone is used to thoroughly remove oil, dust and any pollutants on the surface of the titanium alloy, and then the surface is roughened by sandblasting, and then the residual sand and dust are cleaned again with a detergent to ensure that the workpiece is completely dry before spraying; the glass protective agent is diluted to prepare a spray suspension of tens of microns, and a low-pressure spray gun is used to spray the layer thickness of the titanium alloy surface to one hundred microns in multiple times. Each layer needs to be dried in intervals to prevent sagging; the workpiece after spraying is fully dried at room temperature or in a low-temperature oven (60-80℃); finally, the titanium alloy blank is preheated to the temperature of the α+β phase region or the β phase region, and the holding time is 1h~4h.

[0057] S2. The pre-treated billet is fed into the asynchronous rolling mill and asynchronous rolling parameters and tension control are performed.

[0058] The speed ratio of the upper and lower rolls is set to 1.05-1.5 (asynchronous ratio ∆v), the rolling speed is 0.5-5m / s; the single-pass reduction is 7-15%, and the total deformation is 60-95%. During the rolling process, front tension and back tension are applied, and the tension value is 10-30% of the material yield strength. The asynchronous ratio ∆v is calculated as follows:

[0059] ,

[0060] in, is the linear speed of the fast roller, is the linear speed of the slow roller; when the plate thickness is ≤10mm, the asynchronous ratio is 1.2-1.5; when the thickness is >10mm, the asynchronous ratio is 1.05-1.2.

[0061] According to the volume invariance condition of plastic processing, the volume of metal flowing into the deformation zone per unit time is equal to the volume flowing out:

[0062] ,

[0063] in, is the velocity at the plate entrance, is the velocity at the plate outlet, is the initial thickness of the blank, is the thickness of the billet after rolling, is the width of the plate. You can make an appointment and get:

[0064] .

[0065] Because the plate is often close to the roller with faster speed when it is rolled out, the plate outlet speed is Approximately equal to , and the speed of the plate at the rolling entrance Approximately equal to :

[0066] .

[0067] The reduction rate ε is equal to:

[0068] .

[0069] Therefore, the relationship between the asynchronous ratio and the reduction rate satisfies:

[0070] ,

[0071] The conversion yields:

[0072] ,

[0073] This relationship is achieved by adjusting the speed of the uncoiler and the coiler to ensure equal flow rate and stable tension during the rolling process.

[0074] The front tension and back tension are applied as follows: the front tension is provided by the coiler, and the tension value = 0.1σ y (σ y =High temperature yield strength of the material); the post-tension is provided by the uncoiler, and the tension value = 0.15σ y ;Tension control accuracy ≤±5%. Figure 2 Schematic diagram comparing stress distribution of traditional synchronous rolling and asynchronous rolling.

[0075] S3. Dynamic process adjustment of asynchronous rolling mill through temperature gradient compensation.

[0076] like Figure 3 As shown, an infrared thermometer monitors the rolling zone temperature in real time, and a PLC controller controls the speed ratio of the upper and lower rolls in real time. Specifically, the asynchronous ratio Δv is dynamically adjusted to 1.1-1.3 based on the infrared temperature data. When the temperature difference between the upper and lower surfaces of the rolling zone is greater than 30°C, the asynchronous ratio Δv is set to 1.3; when the temperature difference is between 10-30°C, the asynchronous ratio is set to 1.2; and when the temperature difference is less than 10°C, the asynchronous ratio is set to 1.1.

[0077] Specifically, asynchronous rolling introduces a gradient shear strain within the sheet by creating a speed difference between the upper and lower rollers (asynchronous ratio of 1.05-1.5). This strain distribution can offset the uneven thermal stress distribution caused by temperature gradients. Specifically, asynchronous rolling causes the deformation rates of the upper and lower surfaces of the sheet to differ, forming a gradient stress field within the sheet. During the rolling process, the temperature difference between the upper and lower surfaces of the sheet causes uneven thermal expansion and contraction, which in turn generates residual stress. By monitoring the temperature gradient in real time (e.g., with an infrared thermometer) and dynamically adjusting the asynchronous ratio, the distribution of the gradient shear strain can be optimized to better compensate for the thermal stress caused by the temperature gradient.

[0078] The synergistic effect of the asynchronous ratio and temperature is reflected in dynamic regulation. When the temperature gradient is large (e.g., the temperature difference between the upper and lower surfaces is greater than 30°C), the asynchronous ratio is set to a larger value (e.g., 1.3) to introduce a stronger gradient shear strain to offset thermal stress. When the temperature gradient is small (e.g., the temperature difference is less than 10°C), the asynchronous ratio is set to a smaller value (e.g., 1.1) to avoid excessive shear strain.

[0079] The algorithm of the above-mentioned PLC controller includes: using fuzzy PID control data storage and tracing, and controlling the dynamic adjustment of asynchronous ratio and rolling speed; data storage and tracing are used to record the process parameters and quality data of each batch of plates and generate a unique ID code.

[0080] S4. Conduct real-time quality monitoring of the asynchronous rolling mill and perform closed-loop control to suppress C-type warping.

[0081] Laser displacement sensors and X-ray stress meters are used to monitor the warpage and residual stress distribution online, as well as the surface flatness and residual stress of the sheet metal. The asynchronous ratio and reduction rate are dynamically adjusted to ensure that the warpage is ≤0.5mm / m. The current detection and feedback process is as follows: Figure 4 shown.

[0082] In terms of optimizing and controlling residual stress, asynchronous rolling alters the stress distribution within the plate through gradient shear strain, reducing residual stress caused by uneven deformation. Since temperature gradients can cause thermal stress within the plate, controlling the rolling temperature (such as preheating to the α+β phase or β phase temperature) and real-time monitoring of the temperature distribution can reduce the generation of thermal stress.

[0083] The synergistic effect of the asynchrony ratio and temperature is achieved through online monitoring and feedback control (such as laser displacement sensors and X-ray stress meters). Based on the real-time monitoring of residual stress distribution and temperature data, the asynchrony ratio and reduction rate are dynamically adjusted to ensure that the sheet's surface compressive stress is ≤-50 MPa and the core tensile stress is ≤+30 MPa, thereby optimizing the sheet's stress state.

[0084] In terms of optimizing sheet microstructure and properties, asynchronous rolling introduces gradient shear strain, promoting dynamic recrystallization and grain refinement within the sheet, thereby improving its strength and toughness. Controlling the rolling temperature (e.g., 750-1000°C) ensures the sheet is in the α+β or β phase region, which promotes uniform grain deformation and recrystallization. The synergistic effect of the asynchronous ratio and temperature is achieved by optimizing deformation dynamics. At the appropriate temperature, the gradient shear strain of asynchronous rolling promotes uniform grain deformation and refinement, thereby improving the sheet's tensile strength (≥950 MPa) and elongation (≥13%).

[0085] To improve plate flatness, asynchronous rolling introduces gradient shear strain to offset plate warping caused by uneven deformation and temperature gradients. Temperature control ensures uniform plate deformation during rolling, reducing warping caused by thermal stress. The synergistic effect of the asynchronous ratio and temperature is achieved through real-time monitoring and dynamic adjustment. Based on online warpage (laser displacement sensor) and temperature data, the asynchronous ratio and reduction rate are dynamically adjusted to ensure plate flatness (warpage ≤ 0.5 mm / m).

[0086] In summary, the synergistic effect of the asynchronous ratio and temperature achieves a comprehensive improvement in the performance of titanium alloy plates through the introduction of gradient shear strain, optimization of residual stress, improvement of microstructure and properties, and control of plate flatness. The synergistic effect of the two is mainly reflected in:

[0087] Dynamic regulation: real-time adjustment of the asynchronous ratio according to the temperature gradient to optimize the stress distribution.

[0088] Online monitoring and feedback: warpage and residual stress are monitored in real time through laser displacement sensors and X-ray stress meters, and process parameters are adjusted dynamically.

[0089] Optimization of structure and performance: at appropriate temperature, asynchronous rolling promotes grain refinement and uniform deformation, and improves strength and toughness.

[0090] This synergistic effect ultimately enables the titanium alloy plate to obtain excellent comprehensive properties: tensile strength of 970±5 MPa, elongation of 14.2±0.3%, warpage of 0.2±0.04 mm / m, and residual stress gradient of 23±0.7 MPa / mm.

[0091] The laser displacement sensor in the above-mentioned online monitoring and feedback module is a linear array CCD with a resolution of 0.01 mm; the X-ray stress analyzer is equipped with a two-dimensional detector with a scanning speed of ≥10 points / second; the PLC controller processes data in real time, and the adjustment instruction response time is ≤1 second.

[0092] Example 2

[0093] The following examples illustrate the advanced nature of this invention, using specific examples in conjunction with this embodiment. This embodiment regulates the speed ratio of the upper and lower rolls (asynchronous ratio of 1.05-1.5) to introduce gradient shear strain during the rolling process, offsetting residual stress differences in the titanium alloy caused by temperature gradients and uneven deformation. Laser displacement sensors and X-ray stress gauges are used to monitor warpage and residual stress distribution online, providing real-time feedback to adjust the asynchronous ratio, reduction rate (20-50%), and rolling speed (0.5-5 m / s) to ensure plate flatness (warpage ≤ 0.5 mm / m).

[0094] Specifically, a Ti-6Al-4V titanium alloy with a thickness of 35 mm, a length of 100 mm, and a width of 50 mm is used, and the oxide layer on the surface of the blank is cleaned by sandblasting or pickling, and the surface roughness Ra is ≤ 3.2 μm.

[0095] The surface of the Ti-6Al-4V titanium alloy billet was sprayed with a silicate-graphite-based protective agent; the β transformation point of the Ti-6Al-4V titanium alloy was 980°C, and the Ti-6Al-4V titanium alloy billet was preheated to 950°C in the α+β phase region for 1 hour. An infrared thermal imager was used to monitor the temperature difference in the thickness direction to ensure that it was less than 5°C.

[0096] The Ti-6Al-4V titanium alloy billet was fed into the asynchronous rolling mill, and the upper roll speed was set to 10 rpm, the lower roll speed was set to 8 rpm, the asynchronous ratio was set to 1.25, the single-pass reduction rate was 10%, and the rolling was thinned to 18 mm; then the upper roll speed was set to 13 rpm, the lower roll speed was set to 10 rpm, the asynchronous ratio was set to 1.3, and the 18 mm Ti-6Al-4V titanium alloy plate was hot rolled again with a single-pass reduction rate of 12%, and the rolling was thinned to 10 mm; finally, the upper roll speed was set to 15 rpm, the lower roll speed was set to 11 rpm, the asynchronous ratio was set to 1.36, and the 10 mm thick Ti-6Al-4V titanium alloy plate was hot rolled again with a single-pass reduction rate of 10%, and the rolling was thinned to 3 mm.

[0097] During the rolling process, front tension and back tension are applied, with the front tension value being 7MPa and the back tension value being 10MPa. During the rolling process, the asynchronous ratio Δv is dynamically adjusted to 1.1-1.5 according to the infrared temperature measurement data. When the temperature difference between the upper and lower surfaces is greater than 30°C, the asynchronous ratio Δv is 1.4; when the temperature difference between the upper and lower surfaces is between 10-30°C, the asynchronous ratio is selected to be 1.2; when the temperature difference between the upper and lower surfaces is less than 10°C, the asynchronous ratio is selected to be 1.1.

[0098] The surface flatness and residual stress of the plate are monitored online, and the asynchronous ratio and reduction rate are dynamically adjusted to make the warpage ≤ 0.5 mm / m. The metallographic diagram of the Ti-6Al-4V titanium alloy plate prepared in this embodiment is shown in Figure 5It can be seen that a large number of dynamically recrystallized grains appear in the microstructure of the Ti-6Al-4V titanium alloy plate after asynchronous hot rolling at 950℃, and the material strength reaches 900MPa, the tensile strength reaches 980MPa, and the elongation reaches 12%. The plate shape after asynchronous hot rolling is as follows Figure 6 shown.

[0099] Example 3

[0100] In this embodiment, the preheating temperature is reduced from 950° C. to 900° C. (the lower limit of the α+β phase region), and other parameters are the same as those in the second embodiment.

[0101] Performance results: tensile strength: 940 MPa (down 4.1% compared to Example 2), elongation: 10.5% (down 12.5% ​​compared to Example 2), warpage: 0.6 mm / m, residual stress gradient: 35 MPa / mm (surface compressive stress -60 MPa, core tensile stress +45 MPa), microstructure as shown Figure 5 As shown in (b), the proportion of dynamically recrystallized grains is reduced to 60% (85% in Example 2), the grain size distribution is uneven (5-15 μm), and there are elongated grains that have not been recrystallized.

[0102] Cause Analysis:

[0103] Effect of temperature on phase transformation: 900℃ is close to the lower limit of the α+β phase region, and the volume fraction of the β phase decreases (about 30% vs. 45% at 950℃), resulting in weakened plastic deformation ability and insufficient driving force for dynamic recrystallization.

[0104] Limited microstructure refinement: The insufficiently recrystallized area becomes a stress concentration point, reducing the elongation.

[0105] Insufficient residual stress compensation: The yield strength of the material increases at low temperatures, the shear strain of asynchronous rolling is difficult to completely offset the thermal stress, and the residual stress gradient increases.

[0106] Example 4

[0107] Other parameters are the same as those in Example 2, except that the roll speed is reduced (first rolling: upper roll 7.2 rpm / lower roll 6 rpm, asynchronous ratio 1.2 → final asynchronous ratio 1.33), and the total number of rolling passes is reduced (3 passes → 3 passes, but the reduction rate distribution is different).

[0108] Performance results: tensile strength: 960 MPa, elongation: 11%, warpage: 0.7 mm / m, residual stress gradient: 40 MPa / mm, microstructure: grain size 8-12 μm (coarsened compared to Example 2), reduced shear band density, and localized deformation texture.

[0109] Cause Analysis:

[0110] Matching rolling speed and strain rate: Low-speed rolling (roller speed reduced by 30%) leads to reduced deformation heat accumulation and incomplete dynamic recrystallization.

[0111] Insufficient asynchronous ratio gradient: The asynchronous ratio is improved slightly (1.2→1.33 vs. 1.25→1.36 in Example 2), resulting in insufficient gradient shear strain distribution and reduced residual stress neutralization effect.

[0112] Process window limitation: When rolling thick plates (25→15→10 mm), the core dissipates heat slowly, requiring a higher asynchronous ratio to compensate (which is not actually adjusted), resulting in higher tensile stress in the core.

[0113] Example 5

[0114] Other parameters were the same as those in Example 2, except that the front tension was reduced from 7 MPa to 5 MPa and the rear tension was maintained at 10 MPa.

[0115] Performance results: tensile strength: 970 MPa, elongation: 11.8%, warpage: 0.9 mm / m (close to the upper threshold limit), residual stress gradient: 45 MPa / mm, edge flatness: local wavy deformation (amplitude ≤ 0.3 mm).

[0116] Cause Analysis:

[0117] Unbalanced tension distribution: The reduction in front tension (5 MPa vs 7 MPa) leads to increased material flow resistance at the entrance of the rolling zone and uneven lateral deformation.

[0118] Stress field interference: The imbalance of the front / back tension ratio (0.5:1 vs. 0.7:1 in Example 2) induces additional shear stress, which, when superimposed on the asynchronous rolling stress field, produces micro-area stress concentration.

[0119] Failure of plate shape control: Insufficient tension adjustment leads to insufficient local stress release and the warping amount is close to the allowable upper limit.

[0120] Example 6

[0121] The upper and lower rolls were rolled synchronously (asynchronous ratio 1.0), and other parameters were the same as those in Example 2.

[0122] Performance results: tensile strength: 880 MPa; elongation: 9%; warpage: 2.0 mm / m (significant C-type warpage); residual stress gradient: >80 MPa / mm (surface compressive stress -120 MPa, core tensile stress +100 MPa).

[0123] Microstructure: Coarse α phase grains (20-30 μm) and β phase are distributed in a network pattern; deformation bands run through the grains, and there is no sign of dynamic recrystallization.

[0124] Cause Analysis:

[0125] No compensation for thermal stress: Synchronous rolling cannot introduce gradient shear strain, and the temperature difference between the upper and lower surfaces (about 40°C) causes thermal stress accumulation.

[0126] Microstructure degradation: lack of shear strain-driven dynamic recrystallization, grain coarsening and the presence of brittle β phase, resulting in significant deterioration of mechanical properties.

[0127] Stress concentration: High residual stress gradient causes spontaneous warping of the plate, forming obvious C-type defects.

[0128] Example 7

[0129] Other parameters are the same as those in Example 2, except that the first rolling adopts an asynchronous ratio of 1.25, and subsequent passes are synchronous rolling.

[0130] Performance results: tensile strength: 910 MPa; elongation: 9.5%; warpage: 1.5 mm / m; residual stress distribution: first rolling area: surface compressive stress -70 MPa; subsequent synchronous rolling area: core tensile stress +80 MPa.

[0131] Microstructure: The grains in the first rolling zone are refined to 10 μm; the grains in the subsequent rolling zone are coarsened to 25 μm.

[0132] Cause Analysis:

[0133] Process discontinuity: The subsequent synchronous rolling offsets the shear strain advantage of the initial asynchronous rolling, resulting in a stress distribution fault.

[0134] Inhomogeneous structure: The deformation mechanisms at different rolling stages conflict, causing grain size jumps and reducing material homogeneity.

[0135] Residual stress superposition: The stress directions in the asynchronous and synchronous areas are contradictory, exacerbating the overall warping.

[0136] Example 8

[0137] Cancel the front and rear tensions, and other parameters are the same as those in Example 2.

[0138] Performance results: tensile strength: 950 MPa; elongation: 10%; warpage: 1.8 mm / m; residual stress gradient: 60 MPa / mm; edge defect: "fishtail" edge wrinkles (depth 0.5 mm).

[0139] Cause Analysis:

[0140] Uncontrolled material rheology: The lack of tension guidance leads to intensified lateral flow, and the material accumulates at the edges to form wrinkles.

[0141] Disordered stress distribution: asynchronous rolling shear strain competes with free deformation, and the residual stress gradient increases.

[0142] Dynamic recrystallization inhibition: Grain refinement in local high strain rate areas (edges) is hindered and elongation decreases.

[0143] Embodiment 9

[0144] Fixed asynchronous ratio rolling (not dynamically adjusted) situation.

[0145] Process parameters: Same as those in Example 2, but the asynchronous ratio is fixed at 1.25 (not adjusted with temperature gradient).

[0146] Performance results: warpage: 1.2 mm / m (significantly higher than ≤0.5 mm / m of Example 2); tensile strength: 920 MPa, elongation: 10%; residual stress gradient: 50 MPa / mm (surface compressive stress -80 MPa, core tensile stress +60 MPa).

[0147] Cause Analysis:

[0148] A fixed asymmetry ratio cannot dynamically compensate for thermal stresses based on temperature gradients. When the temperature difference between the upper and lower surfaces exceeds 30°C, failing to increase the asymmetry ratio (to 1.4) results in thermal stresses not being offset by shear strains, increasing the residual stress gradient and causing excessive warpage. Furthermore, a fixed asymmetry ratio results in insufficient microstructure refinement and dynamic recrystallization, leading to decreased strength and elongation.

[0149] Example 10

[0150] There is no temperature gradient control (not uniform preheating).

[0151] Process parameters: The same as those in Example 2, but the infrared thermal imager was not used to monitor the temperature, and the temperature difference in the thickness direction of the blank was 20°C.

[0152] Performance results: warpage: 0.8 mm / m; tensile strength: 940 MPa, elongation: 11%; microstructure: uneven grain size (5-20 μm), with local non-recrystallized areas.

[0153] Cause Analysis:

[0154] Uneven temperature distribution leads to poor matching between thermal stress and shear strain during asynchronous rolling, resulting in poor residual stress neutralization. Furthermore, insufficient plasticity in localized low-temperature regions leads to incomplete dynamic recrystallization and uneven grain refinement, resulting in fluctuations in mechanical properties.

[0155] Example 11

[0156] Other parameters were the same as those in Example 2, but only a single rolling pass was performed (reduction rate 30%, total deformation 35 mm→3 mm).

[0157] Performance results: Warping: 2.5 mm / m (severe C-type warping); tensile strength: 850 MPa, elongation: 8%; edge cracking: multiple microcracks appeared.

[0158] Cause Analysis:

[0159] High reduction rates in a single pass lead to concentrated deformation heat, exacerbating temperature gradients (temperature differences >50°C), and preventing the asynchronous ratio from compensating for thermal stresses. Furthermore, high strain rates inhibit dynamic recrystallization, leading to grain coarsening (average grain size 15 μm) and stress concentration that triggers edge cracking.

[0160] The results of the indicators of each embodiment are shown in Table 1:

[0161] Table 1

[0162] .

[0163] Example 12

[0164] This embodiment also provides a system for suppressing C-type warping of titanium alloy plates based on an asynchronous hot rolling process, including: a pretreatment module, a setting module, an adjustment module and a monitoring module.

[0165] The pretreatment module is used to pretreat the titanium alloy surface billet; the pretreatment steps include cleaning the oxide layer and preheating the titanium alloy surface billet. The setting module is used to feed the pretreated billet into the asynchronous rolling mill and set the asynchronous rolling parameters and control the tension; the set asynchronous rolling parameters include: asynchronous ratio, rolling speed, single-pass reduction rate and total deformation; tension control includes: applying front tension and back tension during the rolling process. The adjustment module is used to dynamically adjust the process of the asynchronous rolling mill through temperature gradient compensation. The steps include real-time monitoring of the rolling zone temperature through an infrared thermometer and real-time control of the upper and lower roller speed ratio using a PLC controller. The monitoring module is used to perform real-time quality monitoring of the asynchronous rolling mill and perform closed-loop regulation to suppress C-type warping.

[0166] The workflow of the pretreatment module includes: using sandblasting or pickling process to clean the oxide layer of the titanium alloy surface blank, and the surface roughness Ra≤3.2μm; then, spraying the surface of the titanium alloy blank with a high-temperature glass protective agent (a protective agent of a silicon-based glass system, the main components of which are SiO2+Al2O3+CaO, etc.); before spraying, using acetone to thoroughly remove oil, dust and any contaminants on the surface of the titanium alloy, and then roughening the surface by sandblasting, and then using a detergent to clean off the remaining sand and dust again to ensure that the workpiece is completely dry before spraying; diluting the glass protective agent to prepare a spray suspension of tens of microns, and using a low-pressure spray gun to spray the layer thickness on the titanium alloy surface in multiple times to tens of microns to more than one hundred microns, and each layer needs to be dried in intervals to prevent sagging; the workpiece after spraying is fully dried at room temperature or in a low-temperature oven (60-80℃); finally, preheating the titanium alloy blank to the temperature of the α+β phase region or the β phase region, and the holding time is 1h~4h.

[0167] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for suppressing C-type warping of titanium alloy plates based on asynchronous hot rolling process, characterized in that the steps include: Pre-treating the titanium alloy surface blank; The pretreatment steps include cleaning the oxide layer and preheating the titanium alloy surface blank; The pre-treated billet is fed into the asynchronous rolling mill and asynchronous rolling parameters are set and tension is controlled; The set asynchronous rolling parameters include: asynchronous ratio, rolling speed, single-pass reduction rate and total deformation; tension control includes: applying front tension and back tension during the rolling process; Dynamic process adjustment of the asynchronous rolling mill is carried out through temperature gradient compensation. The steps include real-time monitoring of the rolling zone temperature through infrared thermometers and real-time control of the upper and lower roll speed ratio using a PLC controller. The asynchronous rolling mill is subjected to real-time quality monitoring and closed-loop control to suppress C-type warping.

2. The method for suppressing C-type warping of titanium alloy plates based on asynchronous hot rolling process according to claim 1 is characterized in that: The oxide layer on the surface of the titanium alloy blank is cleaned by sandblasting or pickling process, and the surface roughness Ra is ≤ 3.2μm; then, the surface of the titanium alloy blank is sprayed with a high-temperature glass protective agent; finally, the titanium alloy blank is preheated to the temperature of the α+β phase region or the β phase region, and the holding time is 1h~4h.

3. The method for suppressing C-type warping of titanium alloy plates based on asynchronous hot rolling process according to claim 1, characterized in that: The calculation formula of the asynchronous ratio includes: ， in, is the linear speed of the fast roller, is the linear speed of the slow roller.

4. The method for suppressing C-type warping of titanium alloy plates based on asynchronous hot rolling process according to claim 3, characterized in that: The relationship between the asynchronous ratio and the reduction rate satisfies: ， Where ε is the reduction rate, which is expressed as: ， in, is the initial thickness of the blank, It is the thickness of the billet after rolling.

5. The method for suppressing C-type warping of titanium alloy plates based on asynchronous hot rolling process according to claim 1, characterized in that: The application methods of front tension and back tension include: front tension is provided by the coiler, tension value = 0.1σ y ; The post-tension is provided by the uncoiler, tension value = 0.15σ y ; Among them, σ y It is the high temperature yield strength of the material; the tension control accuracy is ≤±5%.

6. The method for suppressing C-type warping of titanium alloy plates based on asynchronous hot rolling process according to claim 1, characterized in that: The rules for temperature gradient compensation include: when the temperature difference between the upper and lower surfaces of the rolling zone is greater than 30°C, the asynchronous ratio Δv is 1.3; when the temperature difference between the upper and lower surfaces of the rolling zone is between 10-30°C, the asynchronous ratio is selected as 1.2; when the temperature difference between the upper and lower surfaces of the rolling zone is less than 10°C, the asynchronous ratio is selected as 1.

1.

7. The method for suppressing C-type warping of titanium alloy plates based on asynchronous hot rolling process according to claim 1, characterized in that: The working principle of the PLC controller includes: using fuzzy PID control data storage and tracing, while controlling the dynamic adjustment of the asynchronous ratio and rolling speed; data storage and tracing are used to record the process parameters and quality data of each batch of plates and generate a unique ID code.

8. The method for suppressing C-type warping of titanium alloy plates based on asynchronous hot rolling process according to claim 1, characterized in that: The steps of real-time quality monitoring and closed-loop control of the asynchronous rolling mill include: using laser displacement sensors and X-ray stress meters to monitor the warpage and residual stress distribution online, monitoring the surface flatness and residual stress of the plate online, and dynamically adjusting the asynchronous ratio and reduction rate to make the warpage ≤0.5mm / m.

9. A system for suppressing C-type warping of titanium alloy plates based on an asynchronous hot rolling process, the system being used to implement the method according to any one of claims 1 to 8, characterized in that: include: Pre-processing module, setting module, adjustment module and monitoring module; The pretreatment module is used to pretreat the titanium alloy surface blank; The setting module is used to feed the pre-treated billet into the asynchronous rolling mill and perform asynchronous rolling parameter setting and tension control; The adjustment module is used to dynamically adjust the process of the asynchronous rolling mill through temperature gradient compensation; The monitoring module is used to perform real-time quality monitoring of the asynchronous rolling mill and perform closed-loop control to suppress C-type warping.

10. The system for suppressing C-type warping of titanium alloy plates based on asynchronous hot rolling process according to claim 9, characterized in that: The workflow of the pretreatment module includes: using sandblasting or pickling process to clean the oxide layer of the titanium alloy surface blank, with the surface roughness Ra≤3.2μm; then, spraying a high-temperature glass protective agent on the surface of the titanium alloy blank; and finally preheating the titanium alloy blank to the α+β phase region or β phase region temperature, and keeping the temperature for 1h~4h.

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