Titanium alloy flat bar rolling system and preparation method

Abstract

The present application relates to a kind of titanium alloy flat strip rolling system, at least including heating furnace, continuous rolling line, annealing furnace composition in turn, the continuous rolling line is made of multiple two-roll flat-stand alternating high stiffness short stress line rolling mill, the roll of the rolling mill includes outer structure layer and inner structure layer, the outer structure layer is sleeved on the outer periphery of the inner structure layer, temperature isolation layer is arranged between the inner structure layer and outer structure layer, the temperature isolation layer includes porous metal framework and inert gas encapsulated in the porous metal framework, metal framework itself has certain mass and specific heat capacity, can absorb and temporarily store part of the instantaneous heat flow of rolling contact area, play buffering effect, dampen the rapid temperature fluctuation caused by rolling rhythm or contact condition change.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy manufacturing technology, and in particular to a titanium alloy flat bar rolling system and preparation method. Background Technology

[0002] Titanium alloys are widely used in aerospace, medical, 3C, automotive, and chemical equipment fields due to their high specific strength, excellent corrosion resistance, high temperature resistance, and good biocompatibility.

[0003] Titanium alloy flat strips are an important application of titanium alloy materials, and the demand for them is increasing. In the preparation process of titanium alloy flat strips, titanium alloy billets are heated in a furnace and then continuously rolled into flat strips through a rolling mill. However, due to the unstable temperature of the titanium alloy billets during rolling, the quality of the flat strips is unstable, making it impossible to consistently supply titanium alloy flat strip products. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects in the prior art and provide a titanium alloy flat bar rolling system and preparation method.

[0005] To achieve the above objectives, the technical solution of the present invention is to design a titanium alloy flat bar rolling system, which includes at least a heating furnace, a continuous rolling line, and an annealing furnace arranged in sequence. The continuous rolling line is composed of multiple two-roll alternating horizontal and vertical high-rigidity short-stress line rolling mills. The rolls of the rolling mill include an outer structural layer and an inner structural layer. The outer structural layer is sleeved on the outer periphery of the inner structural layer, and a temperature isolation layer is provided between the inner structural layer and the outer structural layer.

[0006] The porous metal skeleton is prepared by the following steps: First, alloy powder that meets the above component requirements is made into a slurry; then, polyurethane foam is used as a template for impregnation of the slurry; subsequently, the template and binder are removed after drying, and high-temperature sintering is carried out under a protective atmosphere to finally obtain a porous metal skeleton with a three-dimensional interconnected network structure.

[0007] In a further preferred embodiment, the temperature insulation layer comprises a porous metal skeleton and an inert gas encapsulated within the porous metal skeleton.

[0008] In a further preferred embodiment, the porous metal skeleton comprises, by mass percentage, 15.0%-22.0% chromium, 10.0%-18.0% tungsten, 5.0%-9.0% molybdenum, and 0.1%-0.35% carbon, with the balance being nickel and unavoidable impurities.

[0009] In a further preferred embodiment, the porous metal framework also contains no more than 5.0% cobalt and / or no more than 1.5% niobium.

[0010] In a further preferred technical solution, a heating and heat preservation device is also provided between two adjacent rolling mills. After the workpiece is rolled by the rolls, it enters the heating and heat preservation device for heating and heat preservation before entering the next roll. The heating and heat preservation device includes a box body with an inlet and an outlet on the side wall of the box body, and the inlet and outlet are located on the same straight line. An electromagnetic heating coil is installed inside the box body.

[0011] A method for preparing titanium alloy flat bars, comprising using the aforementioned titanium alloy flat bar rolling system to prepare titanium alloy flat bars, the method comprising at least: A titanium alloy billet is obtained, and the billet is surface treated to remove defects. The billet is heated and then rolled in multiple passes on a continuous rolling line to obtain a titanium alloy flat strip. The flat strip is then annealed and hot-straightened. The flat strip is then surface treated to remove surface oxide scale and defects to obtain a titanium alloy flat bar.

[0012] A further preferred technical solution involves heating the titanium alloy billet and then performing multiple rolling passes on a continuous rolling line, including: placing the titanium alloy billet in a heating furnace and heating it to a preset temperature range, holding it at that temperature for a preset time range; rolling the heated titanium alloy billet in twelve to eighteen passes on the continuous rolling line at a preset speed range, the rolling speed being configured to maintain stable tension between the front and rear stands; the tension is used to control the width and shape of the titanium alloy flat strip, with a preset thickness range and a preset width range; and the continuous rolling line is used to control the temperature of the titanium alloy flat strip, resulting in a titanium alloy flat strip with a uniform microstructure.

[0013] A further preferred technical solution establishes stable tension between the front and rear stands through precise speed matching, including: the continuous rolling line consists of multiple two-roll alternating horizontal and vertical high-rigidity short-stress line rolling mills; speed matching is performed according to the stand configuration of the continuous rolling line, and the speed matching is adjusted to maintain the tension; the tension ensures the uniformity of the thickness and surface quality of the titanium alloy flat strip.

[0014] In a further preferred embodiment, the titanium alloy billet is used as raw material. After surface treatment to remove oxide scale and defects, it is placed in a heating furnace for heating at a temperature of 850–950°C and a holding time of 80–120 min.

[0015] In a further preferred embodiment, the heated titanium alloy billet is rolled in 12 to 18 passes on a continuous rolling line at a rolling speed of 1.0 to 3.0 m / s to obtain a titanium alloy flat strip with a thickness of 3 to 8 mm and a width of 60 to 120 mm.

[0016] A further optimized technical solution involves rolling using 16 alternating horizontal and vertical short-stress rolling mills according to a roll pass system of: horizontal-vertical...horizontal-vertical; In the vertical rolling mill's pass system, the titanium alloy billet shrinks in the thickness direction; the flat rolling mill's pass system constrains the titanium alloy billet in the width direction; and / or in each rolling pass, the elongation coefficient of the titanium alloy billet in the length direction does not exceed 1.3.

[0017] In a further preferred embodiment, the titanium alloy flat strip is annealed in a continuous annealing furnace at a temperature of 700–800°C and a holding time of 60–90 minutes, followed by hot straightening.

[0018] In a further preferred embodiment, when the titanium alloy flat strip enters the aperture system, an auxiliary metal strip is attached to the side of the titanium alloy flat strip. The auxiliary metal strip has a Brinell hardness not exceeding 80% of the hardness of the titanium alloy flat strip, and the room temperature elongation of the auxiliary metal strip is above 20%. Preferably, the auxiliary metal strip includes a copper strip or an aluminum strip; Preferably, the hole system is configured with a width margin to accommodate the auxiliary metal strip; Preferably, the height of the auxiliary metal strip is adapted to the thickness of the titanium alloy flat strip, and the auxiliary metal strip is temporarily fixed to the titanium alloy flat strip using hot melt adhesive.

[0019] The advantages and beneficial effects of this invention are as follows: The metal skeleton itself has a certain mass and specific heat capacity, which can absorb and temporarily store some of the instantaneous heat flow in the rolling contact area, playing a buffering role and smoothing out rapid temperature fluctuations caused by changes in rolling rhythm or contact conditions.

[0020] A method for preparing titanium alloy flat strips addresses the unique challenges of titanium alloy processing, such as high temperature sensitivity, difficulty in controlling dimensional accuracy, high requirements for uniformity of mechanical properties, and the need to optimize surface quality. This method is achieved through fully automated control and multi-stage collaborative optimization.

[0021] This invention optimizes the surface treatment, heating, and continuous rolling processes of titanium alloy billets. It utilizes a continuous rolling line composed of multiple alternating horizontal and vertical short-stress rolling mills to achieve speed matching and stable tension control, effectively managing the impact of temperature changes on deformation resistance and microstructure properties. Simultaneously, it combines a continuous annealing furnace to precisely control annealing parameters and subsequent shot blasting and pickling surface treatments, ensuring that the final product has high dimensional accuracy, flatness, and excellent mechanical properties.

[0022] This invention is applicable to the preparation of various types of titanium alloy flat materials, significantly improving production efficiency and yield, reducing processing losses, and meeting the demand for high-performance titanium alloy materials in aerospace, medical, and chemical industries, demonstrating the comprehensive advantages of advanced processing technology. Attached Figure Description

[0023] Figure 1 This is a diagram of the roll pass system for a vertical rolling mill in a method for preparing titanium alloy flat bars according to the present invention. Figure 2 This is a schematic diagram of the roll used in a method for preparing titanium alloy flat bars according to the present invention. Figure 3 This is a schematic diagram of a heating and heat preservation device for a method of preparing titanium alloy flat strips according to the present invention. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0025] A titanium alloy flat bar rolling system comprises at least a heating furnace, a continuous rolling line, and an annealing furnace arranged in sequence. The continuous rolling line consists of multiple two-roll alternating horizontal and vertical high-rigidity short-stress line rolling mills. The rolling mill rolls include an outer structural layer and an inner structural layer. The outer structural layer is sleeved on the outer periphery of the inner structural layer, and a temperature isolation layer is provided between the inner structural layer and the outer structural layer.

[0026] like Figure 2 As shown, this invention provides a rolling mill roll employing a porous metal skeleton encapsulating an inert gas structure. Traditional solid rolling mill rolls or simple double-layer rolls have direct and efficient heat conduction paths, with heat from the rolled workpiece rapidly dissipating through the roll body. However, the porous metal skeleton in this structure physically breaks up the continuous, dense metal heat conduction path with its three-dimensional interconnected network, transforming it into a composite heat transfer path composed of numerous small, tortuous "metal-gas-metal" series and parallel connections. The metal skeleton itself acts as a rigid support, and its slender rod-like or sheet-like structure already has a higher thermal resistance than a solid body. More importantly, the inert gas sealed within the pores has an extremely low thermal conductivity (typically below 0.02 W / (m·K)), constituting an obstacle in the heat transfer path. Simultaneously, the metal skeleton itself has a certain mass and specific heat capacity, capable of absorbing and temporarily storing some of the instantaneous heat flow in the rolling contact area, acting as a buffer to smooth out rapid temperature fluctuations caused by changes in rolling rhythm or contact conditions.

[0027] The skeleton alloy composition is based on considerations of high-temperature strength, oxidation resistance, and process adaptability. Tungsten and molybdenum, as the main solid solution strengthening elements, cause severe lattice distortion in the nickel matrix due to their large atomic radii, greatly increasing the resistance to dislocation movement. This ensures that the skeleton possesses sufficient intrinsic strength and creep resistance from room temperature to rolling high temperatures, preventing collapse or plastic deformation under rolling pressure and thermal stress. Carbon, along with chromium and molybdenum, forms fine, dispersed carbide particles. These hard phases further pin dislocations and grain boundaries through a second-phase strengthening mechanism, improving the hardness and stiffness of the skeleton. Chromium's primary function is high-temperature oxidation resistance and corrosion resistance. It preferentially forms a dense, well-adhered protective film on the alloy surface, preventing embrittlement, pulverization, or changes in thermal conductivity caused by oxidation under long-term high-temperature service conditions, ensuring the long-term stability of thermal insulation performance. Nickel provides a stable and tough austenitic matrix, accommodating the aforementioned alloying elements and imparting good processability to the material.

[0028] This porous metal skeleton, formed through a three-dimensional mesh topology using biomimetic or controllable processes, achieves optimal mechanical-thermal performance matching in material distribution. From a mechanical perspective, it resembles a microscopic spatial truss structure, efficiently transferring the radial pressure and shear stress applied to the outer roll sleeve during rolling to the inner mandrel through the skeleton's members in the form of axial force and nodal bending moments. Thus, even with a porosity exceeding 85%, it still provides the macroscopic stiffness and compressive strength necessary to support rolling loads.

[0029] From a thermal perspective, this open structure with high porosity and large specific surface area maximizes the volume ratio of low thermal conductivity gas and the gas-solid interface area, greatly extending the effective path of heat transfer. It also utilizes the characteristic that convection of gas molecules almost disappears in tiny closed pores to limit the heat transfer mechanism mainly to inefficient gas molecule heat conduction and limited point contact heat conduction of the solid skeleton.

[0030] Integrating this composite structure into the roll addresses the issue that in continuous rolling of temperature-sensitive materials such as titanium alloys, fluctuations in "thermal crown" caused by uneven local heat dissipation in traditional rolls are a major cause of sheet shape defects. The optimized roll of this invention features an internal temperature isolation layer that forms a thermal barrier, not only reducing overall heat loss but, more importantly, rapidly homogenizing the transverse and longitudinal temperature gradients on the outer roll sleeve surface. When the temperature at a certain point in the workpiece is high, more heat is transferred to the roll surface, but this heat is absorbed by the local "thermal capacity buffering" effect of the isolation layer, delaying conduction to the roll core and preventing a sharp increase in roll surface temperature at that point (i.e., abrupt change in thermal crown). Ultimately, this results in improved sheet shape quality and an effective solution to performance consistency problems caused by excessive temperature differences between the beginning and end of the roll.

[0031] The following examples will provide a full explanation and illustration of the rolling mill rolls.

[0032] Example 1: A rolling mill roll includes a rolling mill mandrel as an inner structural layer and a working surface layer as an outer structural layer. The outer structural layer is tightly fitted onto the outer periphery of the inner structural layer by an interference fit. An integrally formed annular temperature insulation layer is provided between the two.

[0033] The core of this temperature insulation layer is a three-dimensional, porous metal framework. Its material, by mass percentage, consists of 18.0% chromium, 12.0% tungsten, 6.5% molybdenum, and 0.25% carbon, with the balance being nickel and trace amounts of silicon and manganese impurities. The porous metal framework is prepared through the following process: alloy micro-powder conforming to the above composition is mixed with an organic binder to form a uniform slurry with a solid content of 65%; open-cell polyurethane foam with a porosity of 95 PPI is selected as a template and vacuum-assisted impregnation is performed; subsequently, a stepped heating heat treatment is carried out under argon protection, sequentially removing the binder, pyrolyzing the polyurethane template, and finally sintering at 1280°C for 2 hours to form a rigid mesh structure with a porosity of approximately 85%. Argon gas is injected into the pores of the sintered framework within a vacuum chamber and sealed to complete the encapsulation of the temperature insulation layer.

[0034] When the rolls of this embodiment are used for continuous rolling of TA2 titanium alloy flat strip, their internal temperature insulation layer effectively blocks heat exchange between the cooling water in the roll core and the external rolling contact area. Compared with traditional integral chrome-plated rolls, the rolls of this embodiment reduce the temperature difference per unit length of titanium alloy flat strip during rolling by approximately 68%.

[0035] Example 2: A type of rolling mill roll has a structure comprising an inner alloy steel mandrel, an outer high wear-resistant alloy steel sleeve, and a composite temperature insulation layer between the two.

[0036] The temperature insulation layer in this embodiment also employs a porous metal framework encapsulating the inert gas. The alloy composition of the porous metal framework is optimized by mass percentage as follows: 16.5% chromium, 15.0% tungsten, 7.0% molybdenum, 0.18% carbon, 4.2% cobalt, with the balance being nickel. The addition of cobalt further enhances the solid solution strengthening effect of the matrix phase. The framework is manufactured using a slurry impregnation-sintering process similar to that of Example 1, but the sintering temperature is increased to 1320℃.

[0037] In this embodiment, when rolling Ti-6Al-4V alloy flat strip at high speed, compared with chrome-plated rolls under the same working conditions, this roll can significantly improve the temperature uniformity of the rolled part along the length direction, and reduce the temperature difference per unit length by about 85%.

[0038] Example 3: A type of rolling mill roll. The alloy composition of the skeleton, by mass percentage, is: 20.0% chromium, 10.5% tungsten, 8.0% molybdenum, 0.30% carbon, 1.2% niobium, with the balance being nickel. The addition of niobium forms highly stable NbC particles with carbon, effectively pinning grain boundaries and inhibiting grain growth during sintering and service, thereby obtaining a fine microstructure. The sintering temperature is 1250℃.

[0039] Using the rolls of this embodiment, the periodic temperature fluctuations of the titanium strip caused by heat dissipation from the rolls in the rolling direction are effectively suppressed, and the temperature difference per unit length is reduced by about 105% compared with the use of conventional chrome-plated rolls.

[0040] Example 4: A heavy-duty roll designed for rolling high-resistance titanium alloys, with a temperature insulation layer emphasizing extremely high structural rigidity and compressive strength.

[0041] The porous metal skeleton of this roll adopts a high-tungsten, high-carbon design, with a mass percentage composition of: 15.5% chromium, 17.5% tungsten, 5.5% molybdenum, 0.32% carbon, and the balance being nickel. During preparation, a high-viscosity slurry is used for multiple impregnations to increase the thickness of the skeleton members, and the porosity is finally controlled at around 80% after sintering.

[0042] This roll not only stabilizes the process temperature but also better maintains the roll gap shape, resulting in an exceptionally uniform temperature distribution along the length of the rolled part, with the measured temperature difference reduced by approximately 120%.

[0043] Example 5: A rolling mill roll has a porous metal skeleton composed of the following components by mass percentage: 19.0% chromium, 13.0% tungsten, 6.0% molybdenum, 0.22% carbon, with the balance being nickel. The sintering temperature is 1300℃.

[0044] The rolls described in this embodiment are suitable for conventional hot rolling processes of various titanium alloy grades (such as pure titanium, TC4, etc.). Using these rolls fundamentally improves the temperature uniformity of the titanium alloy flat strip at the beginning, end, and middle of the edges, reducing the average temperature difference per unit length during rolling by approximately 75%, thus improving strip shape quality and performance consistency.

[0045] like Figure 3 As shown, during the rolling process, heat is lost from the titanium alloy billet between the rolls, affecting the rolling effect. In some embodiments, a heating and heat preservation device is also provided between two adjacent rolling mills. After the workpiece is rolled by the rolls, it enters the heating and heat preservation device for heating and heat preservation before entering the next roll, so that the temperature of the workpiece is maintained at 850-950°C.

[0046] The heating and heat preservation device includes a box body with an inlet and an outlet on the side wall of the box body, and the inlet and outlet are located on the same straight line; an electromagnetic heating coil is installed inside the box body.

[0047] By effectively managing the impact of temperature changes on deformation resistance and microstructure properties through heating and heat preservation devices, and by combining continuous annealing furnaces to precisely control annealing parameters and subsequent shot blasting and pickling surface treatments, the final product is guaranteed to have high dimensional accuracy, flat shape, and excellent mechanical properties.

[0048] A method for preparing titanium alloy flat strips, comprising using a titanium alloy flat strip rolling system, the method comprising: obtaining a titanium alloy billet as raw material; performing surface treatment on the titanium alloy billet to remove oxide scale and defects; heating the titanium alloy billet and then performing multi-pass rolling on a continuous rolling line to obtain titanium alloy flat strips; performing finished product annealing on the titanium alloy flat strips and then hot straightening; and performing surface treatment on the titanium alloy flat strips to remove surface oxide scale and defects to obtain titanium alloy flat strips.

[0049] Furthermore, the step of obtaining titanium alloy billets as raw materials and performing surface treatment on the titanium alloy billets includes: selecting titanium alloy square billets or bar billets as the titanium alloy billets; performing peeling or grinding treatment on the titanium alloy billets; removing the oxide scale and defects of the titanium alloy billets through the peeling or grinding treatment to obtain the treated titanium alloy billets.

[0050] Furthermore, the titanium alloy billet is heated and then rolled in multiple passes on a continuous rolling line, including: placing the titanium alloy billet in a heating furnace for heating at a preset temperature range and holding for a preset time range; rolling the heated titanium alloy billet in twelve to eighteen passes on the continuous rolling line at a preset speed range, establishing stable tension between the front and rear stands through precise speed matching; controlling the width and shape of the titanium alloy flat strip according to the stable tension to obtain a titanium alloy flat strip with a thickness and width within a preset range; and achieving precise temperature control of the titanium alloy flat strip through the continuous rolling line to obtain a titanium alloy flat strip with a uniform microstructure.

[0051] Furthermore, the speed matching based on the stand configuration of the continuous rolling line includes: obtaining the number and type of stands of the continuous rolling line; calculating speed matching parameters for the number and type of stands; establishing the stable tension between the front and rear stands using the speed matching parameters; determining whether the stable tension meets a preset stability standard; and outputting the shape control result of the titanium alloy flat strip if the preset stability standard is met.

[0052] Furthermore, establishing stable tension between the front and rear stands through precise speed matching includes: determining that the continuous rolling line consists of multiple two-roll alternating horizontal and vertical high-rigidity short-stress line rolling mills; performing speed matching according to the stand configuration of the continuous rolling line, and adjusting the speed matching to maintain the stable tension; and ensuring the uniformity of the thickness and surface quality of the titanium alloy flat strip through the stable tension.

[0053] Furthermore, the titanium alloy flat strip is subjected to finished product annealing and then hot straightening, including: placing the titanium alloy flat strip in a continuous annealing furnace for finished product annealing, with the annealing temperature within a preset annealing temperature range and the holding time within a preset holding time range; removing the titanium alloy flat strip from the continuous annealing furnace; and hot straightening the removed titanium alloy flat strip to obtain a flat titanium alloy flat strip.

[0054] Furthermore, the titanium alloy flat strip undergoes surface treatment to remove surface oxide scale and defects, including: shot blasting the titanium alloy flat strip; pickling the shot-blasted titanium alloy flat strip; removing surface oxide scale and defects from the titanium alloy flat strip through the shot blasting and pickling processes; obtaining the titanium alloy flat strip after defect removal as the titanium alloy flat bar, and determining the mechanical property indicators of the titanium alloy flat bar.

[0055] This embodiment of a method for preparing a titanium alloy flat bar may specifically include: The titanium alloy billet is used as the initial raw material. First, it undergoes surface treatment, removing oxide scale and defects through peeling or grinding to ensure the surface quality meets processing requirements, resulting in a treated titanium alloy billet. The treated billet is then placed in a box-type resistance heating furnace for heating. The heating temperature is controlled within a preset range, and the holding time is maintained within an appropriate range to ensure uniform heating of the billet's internal structure, resulting in a heated titanium alloy billet. For example, in one embodiment, the titanium alloy billet, after surface treatment to remove oxide scale and defects, is placed in a heating furnace for heating at 850–950°C for 80–120 minutes. The heated titanium alloy billet is then transferred to subsequent processing equipment to ensure that the next deformation process is performed at a high temperature to maintain the billet's processing performance and provide a suitable material state for subsequent rolling, resulting in a titanium alloy billet to be processed. Further process preparation is then performed on the titanium alloy billet to be processed, adjusting processing parameters based on the state of the heated billet to ensure uniform deformation based on the heating temperature and holding time, meeting the objectives of the titanium alloy billet heating process.

[0056] Specifically, the titanium alloy billet is used as the initial raw material for surface treatment. Peeling off the oxide scale can effectively prevent the oxide layer from interfering with heat conduction during subsequent heating, while grinding to remove defects can prevent the billet from cracking and expanding at high temperatures. This treatment method ensures that the billet surface is smooth, so that the heat is evenly distributed during heating, which is beneficial to improving the overall processing quality.

[0057] In one embodiment, for a round bar-shaped titanium alloy billet, the outer oxide scale is first peeled off using a mechanical peeling machine, and then the surface pits are ground off with a grinding wheel. This process reduces the surface roughness of the billet, which is beneficial to the temperature uniformity of subsequent heating and avoids uneven microstructure caused by local overheating. This surface treatment can also reduce contamination in the heating furnace, extend the service life of the equipment, and thus support the stable operation of the heating process.

[0058] In one embodiment, the treated titanium alloy billet is placed in a box-type resistance heating furnace for heating. Controlling the heating temperature within a preset range allows the billet to gradually reach the phase transformation temperature, while maintaining the holding time within an appropriate range allows the alloying elements to diffuse fully. This method is beneficial for refining the grains inside the billet and improving the material's plastic deformation capacity.

[0059] For example, for square bar billets, heating elements are evenly arranged in the furnace to ensure that the temperature gradient is minimized. This results in a uniform structure of the heated billet, which is beneficial for the smooth progress of subsequent deformation processing. Specifically, this heating process can also reduce the internal stress of the billet and prevent deformation caused by uneven heating, thereby providing a reliable material basis for rolling and enhancing the reliability of the overall process.

[0060] In one possible approach, further process preparation is performed on the titanium alloy billet to be processed. Adjusting the processing parameters according to the state after heating can ensure uniform deformation. Achieving this goal based on the heating temperature and holding time optimizes the microstructure of the alloy. This preparation method is beneficial to improving the mechanical properties of the final product.

[0061] For example, in flat strip processing, adjusting the rolling speed to match the billet temperature satisfies the objectives of the titanium alloy billet heating process and is beneficial for obtaining high-quality flat strip.

[0062] Specifically, this adjustment can also prevent stress concentration caused by excessively rapid deformation, thus forming a complete chain with the aforementioned heating and transfer steps, supporting the full realization of the heating process.

[0063] The heated titanium alloy billet is rolled in 12 to 18 passes on a continuous rolling line at a rolling speed of 1.0 to 3.0 m / s to obtain a titanium alloy flat strip with a thickness of 3 to 8 mm and a width of 60 to 120 mm. The continuous rolling line consists of multiple alternating flat and vertical short-stress rolling mills, and stable tension is established through speed matching to control the width and shape of the strip.

[0064] The heated titanium alloy billet is placed in a continuous rolling line for rolling. This line consists of multiple alternating horizontal and vertical short-stress rolling mills. The number of rolling passes is controlled within a certain range, and the rolling speed is maintained within a preset range to form a preliminary titanium alloy flat strip shape. The thickness and width of the preliminary flat strip must meet the requirements of subsequent processing. For the initially formed titanium alloy flat strip, a precise speed matching mechanism is used during continuous rolling to establish stable tension control between the front and rear stands. This tension is used to adjust the width uniformity and flatness of the flat strip, ensuring that the flat strip does not twist or deviate during rolling. During the rolling of the titanium alloy flat strip after tension control is completed, the speed and tension parameters are continuously monitored. For possible width or thickness fluctuations, the speed matching relationship between the stands is adjusted in real time to further optimize the dimensional accuracy of the flat strip. The titanium alloy flat strip, after the above adjustments, undergoes final rolling and shaping to ensure that its thickness and width reach the target range. This flat strip serves as the basis for subsequent processing, maintaining the stability of its shape and dimensions, and providing a guarantee for achieving high-quality titanium alloy flat strips.

[0065] The heated titanium alloy billet is placed in a continuous rolling line for rolling. The continuous rolling line consists of multiple alternating horizontal and vertical short-stress rolling mills. This mill design provides high rigidity support and reduces vibration during the rolling process, which helps to form the initial titanium alloy flat strip shape. The thickness and width of the initial flat strip need to meet the requirements of subsequent processing. This results in uniform material deformation and avoids cracks caused by local stress concentration.

[0066] In one embodiment, for the initially formed titanium alloy flat strip, a stable tension control is established between the front and rear stands through a precise speed matching mechanism during continuous rolling. This tension control is achieved by adjusting the speed difference between each stand. For example, when the upstream stand speed is slightly faster than the downstream stand, tensile tension is generated to adjust the width uniformity and flatness of the flat strip, ensuring that the flat strip does not twist or deviate during rolling. This results in higher dimensional accuracy and effectively prevents an increase in product scrap rate.

[0067] In the rolling of titanium alloy flat strip after tension control is completed, the speed and tension parameters during the rolling process are continuously monitored. This monitoring can be achieved by collecting data in real time through sensors installed on the stand. In response to possible fluctuations in width or thickness, the speed matching relationship between the stands is adjusted in real time to further optimize the dimensional accuracy of the flat strip. This results in a stable production process, reduces the need for human intervention, and increases overall output.

[0068] In one possible implementation, the titanium alloy flat strip, after the above adjustments, undergoes final rolling and shaping to ensure that its thickness and width meet the target range. This shaping process involves final reduction control. The flat strip serves as the basis for subsequent processing, maintaining the stability of its shape and dimensions to ensure the production of high-quality titanium alloy flat strips. This results in excellent surface quality and mechanical properties, meeting the stringent requirements of aerospace and other fields.

[0069] From another perspective, the alternating flat and vertical short-stress rolling mill configuration in continuous rolling lines can provide multi-directional deformation forces when the number of rolling passes is controlled within a certain range. For example, the flat mill emphasizes thickness reduction, while the vertical mill focuses on width expansion. This mutually supportive mechanism brings about a comprehensive shape control effect, which helps the initial flat strip meet subsequent requirements.

[0070] In one possible implementation, a precise speed matching mechanism not only establishes tension but also integrates with monitoring parameters. For example, when thickness fluctuations are detected, the speed can be fine-tuned to restore balance. This provides mutual support in terms of width uniformity and flatness, resulting in rolling results without twisting deviations and improving product reliability and consistency.

[0071] The combination of continuous monitoring and real-time adjustment, focusing on the dynamic management of speed and tension parameters, enables a rapid response when fluctuations occur. For example, when the thickness increases slightly, the downstream speed can be slowed down to increase tension. This multi-directional support ensures optimized dimensional accuracy, resulting in an efficient rolling process and a lower defect rate.

[0072] In one possible implementation, the final rolling and shaping process, from the perspective of ensuring the target range of thickness and width, can be connected with the previous tension control. For example, by inheriting a stable plate shape as a foundation, further shaping can bring about high-quality flat strips. In this way, the support from multiple aspects forms a consistent argument that the entire process improves the overall performance and processing adaptability of titanium alloy flat strips.

[0073] like Figure 1 As shown, in one specific embodiment, rolling is performed by 16 alternating horizontal and vertical short-stress rolling mills according to a roll pass system of: horizontal-vertical…horizontal-vertical; during the horizontal-vertical-horizontal-vertical roll pass system, as follows: Figure 1 As shown, in the vertical rolling mill pass system, the relative shrinkage direction is indicated by the dashed arrow, causing the titanium alloy billet to shrink significantly in the thickness direction. In the flat rolling mill pass system, a pair of symmetrically arranged rolls roll and shape the titanium alloy billet after the previous rolling step in the width direction. After multiple passes of flat-vertical-flat-vertical pass system rolling, a titanium alloy flat strip is formed, and the elongation coefficient of each pass does not exceed 1.3.

[0074] The titanium alloy flat strip is annealed in a continuous annealing furnace at a temperature of 700-800℃ and a holding time of 60-90 minutes. After annealing, it is hot straightened to ensure the flatness of the strip.

[0075] The titanium alloy flat strip is placed in a continuous annealing furnace for finished product annealing. The annealing temperature is controlled within a preset range, and the holding time is maintained within a specified duration to ensure the homogeneity of the internal structure of the material, resulting in a pre-annealed flat strip. The pre-annealed flat strip is then immediately subjected to hot straightening after exiting the furnace. To address the issue of unevenness, appropriate pressure is applied to the flat strip using straightening equipment to adjust its shape, resulting in a straightened flat strip with high flatness. The surface condition of the straightened flat strip is then checked for residual stress or minor deformation. If any are found, a secondary fine-tuning is performed on the localized areas using an auxiliary straightening device to ensure that the overall flatness of the straightened flat strip meets the target requirements, forming a final titanium alloy flat strip that conforms to the sheet shape standard.

[0076] In the finished annealing process of titanium alloy flat strips, the material is placed in a continuous annealing furnace and internal stress is eliminated by uniform heating. This process can rearrange the crystal structure, thereby improving the ductility and toughness of the material and helping to avoid cracking during subsequent processing.

[0077] In one possible implementation, temperature control within a preset range ensures that heat penetrates evenly into the core area of ​​the flat strip. After the heat preservation time is maintained at a specified value, the internal structure of the material changes from a non-uniform state to a uniform state, which can bring about the technical effect of stable material performance.

[0078] For example, when processing flat strips of medium thickness, the hardness of the strips decreases after annealing, making them easier to deform and less prone to breakage. From multiple perspectives, this homogenization can also support the improvement of the material's corrosion resistance because grain boundary defects are reduced. The mutually supporting directions include microstructure analysis and macroscopic performance testing.

[0079] Specifically, if the temperature of the flat strip is too high during heating, it may lead to coarse grains, but this problem is avoided through precise control, thus ensuring the reliability of the overall quality.

[0080] It should be noted that the cause of this annealing process is the stress accumulation generated after rolling, and the result is a preliminarily annealed flat strip with improved flatness. The beneficial effects are reflected in increased production efficiency and product qualification rate.

[0081] In one embodiment, the flat strip after preliminary annealing is obtained from the continuous annealing furnace and then immediately subjected to hot straightening. This step addresses the problem of unevenness in the strip shape by applying pressure through a straightening device to adjust the shape, which can effectively correct the bending deformation caused by thermal expansion and contraction during annealing and is beneficial for obtaining a straightened flat strip with high flatness.

[0082] When processing wide flat strips, the pressure applied by the equipment can be evenly distributed on the surface to prevent local warping. This is considered from multiple perspectives, including the selection of equipment type and optimization of pressure parameters. These aspects support each other to form a complete straightening solution.

[0083] Specifically, the function of hot straightening is to respond in real time to the thermal state when the product comes out of the furnace, and to prevent deformation and fixation after cooling. This results in a stable plate shape.

[0084] It should be noted that the cause is that the flat strip is easily deformed in the hot state after annealing. The consequence is that the flat strip with optimized shape can be obtained by adjustment, and its surface condition is more suitable for subsequent inspection. The beneficial effects include reducing the scrap rate and improving the appearance quality of the finished product. In another embodiment, if the flat strip is long, the straightening equipment can apply pressure in sections to ensure end-to-end flatness and consistency, thereby supporting the continuity of the overall process.

[0085] The surface condition of the straightened flat strip is inspected. If residual stress or slight deformation is found, a secondary fine-tuning is performed on the local area using an auxiliary straightening device. This further ensures that the overall flatness meets the target requirements, resulting in a titanium alloy flat strip that ultimately conforms to the plate shape standard.

[0086] The annealed titanium alloy flat strip undergoes surface treatment, including shot blasting and pickling, to remove surface oxide scale and defects, resulting in a final titanium alloy flat strip with a tensile strength ≥930MPa, yield strength ≥800MPa, and elongation ≥15%.

[0087] The annealed titanium alloy flat strip undergoes preliminary surface cleaning using shot blasting to remove larger oxide scale and some defects, ensuring the surface roughness meets the requirements for subsequent processing, resulting in a pre-cleaned flat strip surface. The pre-cleaned flat strip surface is then acid-washed to further dissolve residual oxide scale and minor defects through a chemical reaction, obtaining a smoother titanium alloy flat strip surface and ensuring surface quality meets processing standards. The acid-washed titanium alloy flat strip is inspected to determine the presence of residual defects. If the test results meet the preset surface quality threshold, it is determined to be the final titanium alloy flat strip, possessing the required tensile strength, yield strength, and elongation. The final titanium alloy flat strip undergoes dimensional calibration, fine-tuning for deviations in thickness and width to ensure it conforms to predetermined specifications while maintaining the performance parameters after surface treatment, achieving the business targets for tensile strength, yield strength, and elongation.

[0088] Specifically, when performing preliminary surface cleaning on annealed titanium alloy flat strips, shot blasting can be used to impact the surface of the flat strip with high-speed steel shot. This can effectively remove large oxide scale and some defects because shot blasting removes these adhering substances through mechanical force, thereby forming a pre-cleaned flat strip surface, which is beneficial to improving the adhesion and uniformity of subsequent processing.

[0089] In one embodiment, if the flat strip surface has a stubborn oxide layer, increasing the shot blasting time can further optimize the surface roughness, which helps prevent uneven corrosion during pickling, thereby supporting the improvement of overall surface quality.

[0090] In the specific implementation of pickling treatment on the surface of the flat strip after initial cleaning, a chemical reaction is initiated by immersing it in a diluted hydrofluoric acid solution to further dissolve residual oxide scale and minor defects. This results in a flat strip with a smoother surface, as pickling can precisely target and remove micro-defects through corrosion, which is beneficial for enhancing the corrosion resistance and mechanical properties of the material.

[0091] In one possible implementation, to optimize stress distribution and deformation uniformity during the rolling process, and improve the shape and dimensional accuracy of the titanium alloy flat strip, especially its head and tail sections, the rolling sequence of the adjacent die systems for a unit length of titanium alloy flat strip is configured as follows: the middle section, the rear section, and the front section of the titanium alloy flat strip are rolled sequentially. This is mainly applied to the stable rolling stage of the continuous rolling process (excluding the threading or tail-throwing stage). When a titanium alloy flat strip with a specific cross-section passes through two adjacent stands consecutively, the rolling deformation of the subsequent stand (the N+1th stand) does not immediately act on the portion of the cross-section that was just rolled out from the previous stand (the Nth stand). Instead, through precise speed matching and tension setting, the cross-section undergoes a brief asynchronous deformation process between the preceding and following stands. The section is first rolled on the N stand; when its middle section leaves the N stand roll gap and enters the tension zone between the N and N+1 stands, the rolls on the N+1 stand bite in first and begin rolling the middle section of the section; as the strip travels, the rear section of the section then enters the N+1 stand for rolling; finally, the front section of the section is rolled. This asynchronous rolling sequence breaks through the traditional continuous rolling model where all points of the section undergo almost simultaneous continuous deformation. It allows for a very short, segmented stress relaxation and redistribution time window between adjacent passes for titanium alloy flat strips. For titanium alloys, which have high deformation resistance and are sensitive to deformation rate, this effectively alleviates local stress concentration caused by excessively rapid deformation accumulation, reduces the tendency of strip to produce wavy, warped, and other shape defects during rolling, and is particularly beneficial for improving the shape stability of the strip's head and tail sections, reducing head and tail trimming losses.

[0092] In one possible implementation, controlling the pickling temperature within the room temperature range can prevent excessive corrosion of the flat strip substrate. This, combined with the rough surface formed by shot blasting, can mutually support each other to achieve more thorough defect removal, thereby ensuring that the surface quality meets processing standards.

[0093] When inspecting the pickled titanium alloy flat strip, an ultrasonic flaw detector can be used to determine whether there are residual defects on the surface. If the test result meets the preset surface quality threshold, it is determined to be the final titanium alloy flat strip. This can verify the treatment effect and meet the performance requirements of tensile strength, yield strength and elongation. Because the test can detect potential problems early, it is beneficial to improve the reliability and consistency of the product.

[0094] In one possible implementation, when the heated titanium alloy billet is placed on a continuous rolling line for multi-pass rolling, an auxiliary metal strip process is introduced to control the edge shape of the titanium alloy flat strip and prevent edge cracking. Specifically, before the titanium alloy flat strip enters the alternating flat and vertical pass rolling system, auxiliary metal strips are symmetrically attached to both sides of its edges. The selection of the auxiliary metal strips must meet the following requirements: their Brinell hardness (HB) value is not higher than 80% of the hardness of the rolled titanium alloy flat strip, to ensure that during the rolling deformation process, the auxiliary metal strips can undergo plastic flow before the titanium alloy edges, thereby forming an effective lateral wrapping and soft support for the titanium alloy edges; their room temperature ductility must be superior to that of the titanium alloy flat strip. If the plastic reserve of the auxiliary metal strips is insufficient, they will crack prematurely under the large deformation conditions of rolling, not only losing their supporting function, but their fragments may also be pressed into the titanium alloy surface, causing defects and deteriorating the edge quality.

[0095] For example, when the room temperature elongation of the target titanium alloy flat bar is about 15%, the elongation of the selected auxiliary metal bar should be no less than 20%; if the elongation of the titanium alloy is 10%, then the elongation of the auxiliary metal bar should be no less than 15%.

[0096] Furthermore, the auxiliary metal strip is preferably made of pure copper or pure aluminum. These materials not only have low hardness (typically HB in the range of 40-80), but also excellent room temperature ductility, which is much higher than the elongation of most titanium alloys in the rolled state.

[0097] The initial thickness of the auxiliary metal strip needs to match the thickness of the titanium alloy flat strip before entering the pass, typically 10%-25% of its thickness. The width is determined based on the area to be covered on the side. During attachment, a thermolytic or water-soluble adhesive is used to temporarily fix the auxiliary metal strip to the side of the titanium alloy flat strip. This adhesive must provide sufficient adhesion before and during the initial rolling process to prevent the strip from falling off. Simultaneously, it must be completely decomposed or dissolved during the temperature rise generated during rolling or subsequent heat treatment and pickling processes, facilitating final separation. Preferably, hot melt adhesive can also be used for temporary fixation. However, it is important to note that the continuous rolling line can pull the auxiliary metal strip at the same speed as the titanium alloy flat strip. During continuous rolling, the hot melt adhesive can naturally detach with the deformation of the titanium alloy caused by the continuous rolling line, especially in subsequent passes with larger deformation, where this is usually easier to achieve.

[0098] To achieve the auxiliary metal strip process, the roll pass system of the continuous rolling line needs to be specifically designed. The opening width of the roll pass must be configured with a width margin suitable for the auxiliary metal strip. Specifically, the design width of the roll pass (i.e., the width of the roll groove bottom) should be equal to the sum of the target width of the titanium alloy flat strip in that pass, the expected total thickness of the auxiliary metal strips on both sides after rolling, and the necessary process allowance, to ensure that the main body of the titanium alloy flat strip and the auxiliary metal strips on both sides can smoothly enter the roll pass as a whole and be evenly stressed, avoiding excessive compression of the auxiliary metal strip or limitation of the width of the titanium alloy main body due to insufficient space.

[0099] In the actual rolling process, when the titanium alloy flat strip with auxiliary metal strips attached enters the die, due to the lower hardness and better ductility of the auxiliary metal strips, they preferentially widen laterally and extend longitudinally under the pressure of the rolls, quickly filling the area near the roll gap sidewall in the die. This filling behavior applies a uniform and gentle lateral pressure to the edge of the titanium alloy flat strip. This pressure effectively constrains the disordered longitudinal and transverse flow of the titanium alloy edge metal, suppresses the generation of uneven deformation, and makes the deformation more concentrated on thickness reduction, thereby obtaining a rectangular cross-section with relatively straight edges and clear right angles. The good plasticity of the auxiliary metal strips themselves allows them to adhere tightly to the die sidewall and the edge of the titanium alloy, forming a temporary, flexible deformation pad that absorbs the shear stress that may be generated due to deformation incoordination, thereby reducing the risk of microcracks in the edge of the titanium alloy under high deformation resistance.

[0100] After this rolling pass, the titanium alloy flat bar, along with the auxiliary metal strip, enters subsequent passes or is produced as a finished product. Finally, during the surface treatment stage after annealing, the auxiliary metal strip, which has weak adhesion to the matrix or has become brittle, can be easily removed through the mechanical impact of shot blasting or the chemical dissolution effect of pickling. Because of the differences in acid corrosion resistance and bonding state between the auxiliary metal strip and the titanium alloy, this removal process typically does not damage the titanium alloy flat bar itself. The titanium alloy flat bar obtained through this process exhibits improved edge neatness, perpendicularity, and microstructural integrity in the edge region.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A titanium alloy flat bar rolling system, comprising at least a heating furnace, a continuous rolling line, and an annealing furnace arranged sequentially, wherein the continuous rolling line consists of multiple two-roll alternating horizontal and vertical high-rigidity short-stress line rolling mills, characterized in that, The rolling mill rolls include an outer structural layer and an inner structural layer. The outer structural layer is sleeved on the outer periphery of the inner structural layer, and a temperature insulation layer is provided between the inner structural layer and the outer structural layer.

2. The titanium alloy flat bar rolling system according to claim 1, characterized in that, The temperature insulation layer includes a porous metal skeleton and an inert gas encapsulated within the porous metal skeleton.

3. The titanium alloy flat bar rolling system according to claim 2, characterized in that, The porous metal framework comprises, by mass percentage, 15.0%-22.0% chromium, 10.0%-18.0% tungsten, 5.0%-9.0% molybdenum, and 0.1%-0.35% carbon, with the balance being nickel and unavoidable impurities.

4. The titanium alloy flat bar rolling system according to claim 3, characterized in that, The porous metal framework also contains no more than 5.0% cobalt and / or no more than 1.5% niobium.

5. A titanium alloy flat bar rolling system according to any one of claims 1-4, characterized in that, A heating and heat preservation device is also provided between two adjacent rolling mills. After the workpiece is rolled by the rolls, it enters the heating and heat preservation device for heating and heat preservation before entering the next roll. The heating and heat preservation device includes a box body with an inlet and an outlet on the side wall of the box body. The inlet and outlet are located on the same straight line. An electromagnetic heating coil is installed inside the box body.

6. A method for preparing a titanium alloy flat bar, characterized in that, Titanium alloy flat bars are prepared using a titanium alloy flat bar rolling system according to any one of claims 1-5, wherein the method comprises at least: A titanium alloy billet is obtained, and the surface of the titanium alloy billet is treated to remove defects; the titanium alloy billet is heated and then rolled in multiple passes on a continuous rolling line to obtain a titanium alloy flat strip; the titanium alloy flat strip is subjected to finished product annealing and then hot straightening. The titanium alloy flat strip is surface treated to remove surface oxide scale and defects, resulting in a titanium alloy flat bar.

7. The method for preparing titanium alloy flat bars according to claim 6, characterized in that, The process involves heating the titanium alloy billet and then rolling it in multiple passes on a continuous rolling line, including: placing the titanium alloy billet in a heating furnace and heating it to a preset temperature range, holding it at that temperature for a preset time range; rolling the heated titanium alloy billet in twelve to eighteen passes on the continuous rolling line at a preset speed range, the rolling speed being configured to maintain stable tension between the front and rear stands; the tension is used to control the width and shape of the titanium alloy flat strip, with a preset thickness range and a preset width range; and the continuous rolling line is used to control the temperature of the titanium alloy flat strip, resulting in a titanium alloy flat strip with a uniform microstructure.

8. The method for preparing titanium alloy flat bars according to claim 7, characterized in that, Establishing stable tension between the front and rear stands through precise speed matching includes: the continuous rolling line consists of multiple two-roll alternating horizontal and vertical high-rigidity short-stress line mills; speed matching is performed according to the stand configuration of the continuous rolling line, and the speed matching is adjusted to maintain the tension; the tension ensures the uniformity of the thickness and surface quality of the titanium alloy flat strip.

9. The method for preparing titanium alloy flat bars according to claim 7, characterized in that, The titanium alloy billet is used as raw material. After surface treatment to remove oxide scale and defects, it is placed in a heating furnace for heating at a temperature of 850-950℃ and a holding time of 80-120 minutes.

10. The method for preparing a titanium alloy flat bar according to claim 7, characterized in that, The heated titanium alloy billet is rolled in 12 to 18 passes on a continuous rolling line at a rolling speed of 1.0 to 3.0 m / s to obtain a titanium alloy flat strip with a thickness of 3 to 8 mm and a width of 60 to 120 mm.

11. The method for preparing titanium alloy flat bars according to claim 7, characterized in that, The rolling process is carried out by 16 alternating horizontal and vertical short-stress rolling mills according to a roll pass system of: horizontal-vertical...horizontal-vertical; In the vertical rolling mill's pass system, the titanium alloy billet shrinks in the thickness direction; the flat rolling mill's pass system constrains the titanium alloy billet in the width direction; and / or in each rolling pass, the elongation coefficient of the titanium alloy billet in the length direction does not exceed 1.

3.

12. The method for preparing titanium alloy flat bars according to claim 7, characterized in that, The titanium alloy flat strip is annealed in a continuous annealing furnace at a temperature of 700–800°C for 60–90 minutes, and then hot straightened.

13. The method for preparing titanium alloy flat bars according to claim 11, characterized in that, When the titanium alloy flat strip enters the aperture system, an auxiliary metal strip is attached to the side of the titanium alloy flat strip. The auxiliary metal strip has a Brinell hardness not exceeding 80% of the hardness of the titanium alloy flat strip, and the room temperature elongation of the auxiliary metal strip is above 20%.

14. The method for preparing titanium alloy flat bars according to claim 12, characterized in that, The auxiliary metal strip includes copper or aluminum strips.

15. The method for preparing titanium alloy flat bars according to claim 12, characterized in that, The hole system is configured with a width margin to accommodate the auxiliary metal strip.

16. The method for preparing titanium alloy flat bars according to claim 12, characterized in that, The height of the auxiliary metal strip is adapted to the thickness of the titanium alloy flat strip, and the auxiliary metal strip is temporarily fixed to the titanium alloy flat strip with hot melt adhesive.

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