A three-roller skew rolling preparation method for optimizing the interface bonding strength of a bimetal composite pipe by reducing the wall rate

Abstract

This invention relates to the field of metal composite tube manufacturing technology. Addressing the problems of unstable interfacial bonding strength and difficulty in precisely controlling the wall reduction rate in existing methods, this invention provides a three-roll skew rolling method for preparing bimetallic composite tubes by optimizing the interfacial bonding strength through wall reduction rate regulation. The method involves raw material preparation, grinding, cleaning and drying, billet assembly and sealing, billet heating and insulation, roll die adjustment and skew rolling, and post-processing to obtain bimetallic composite tubes. This method achieves precise control of the wall reduction rate and interfacial bonding strength, promotes the interfacial metallurgical bonding of the bimetallic composite tubes, improves the interfacial bonding strength and stability, and provides a controllable process suitable for the efficient production of long-length bimetallic composite tubes.

Description

Technical Field

[0001] This invention relates to the field of metal composite tube manufacturing technology, specifically to a three-roll skew rolling method for manufacturing bimetallic composite tubes by optimizing the interfacial bonding strength through wall reduction ratio control. Background Technology

[0002] Carbon steel / titanium bimetallic composite pipes combine the high strength of carbon steel with the corrosion resistance of titanium, finding wide application in aerospace, chemical, and marine engineering fields. In practical use, these bimetallic composite pipes must withstand high mechanical loads while ensuring the long-term stable corrosion resistance of the interface formed during the composite process between the two different metals (carbon steel and titanium). Therefore, precise control of the manufacturing process is crucial. However, existing technologies face the challenge of precisely controlling the interfacial bonding strength during the manufacturing of such bimetallic composite pipes. Specifically, when the wall reduction ratio is too low, the plastic deformation of the bimetallic pipe is insufficient, making it difficult to form an effective interfacial diffusion layer between the metal layers, thus affecting the interfacial bonding strength. Conversely, when the wall reduction ratio is too high, defects such as Kirkendal voids or cracks easily appear at the interface, also leading to a decrease in interfacial bonding strength. At the same time, the relationship between process parameters and microstructure is not yet fully understood. Existing bimetallic composite pipe manufacturing methods fail to systematically regulate the evolution of the wall reduction ratio and interfacial structure, making it difficult to optimize the interfacial bonding strength. Moreover, the traditional two-roll rolling process has obvious drawbacks. This process easily causes uneven distribution of the circumferential wall reduction ratio of the pipe, which makes the bonding stability of the interface worse and further reduces the overall performance of the bimetallic composite pipe.

[0003] Therefore, there is an urgent need to develop a new method for preparing three-roll skew rolling mills: by precisely controlling the roll pass diameter of the three-roll skew rolling mill, the wall reduction rate can be closed-loop controlled, thereby optimizing the interfacial microstructure, simultaneously improving the interfacial bonding strength and long-term stability, and ensuring the continuous and controllable production process. Summary of the Invention

[0004] In view of this, the present invention provides a three-roll skew rolling preparation method for bimetallic composite tubes by optimizing the interfacial bonding strength through wall reduction ratio control, so as to solve the problems of unstable interfacial bonding strength and difficulty in controlling the wall reduction ratio in the prior art.

[0005] To achieve the above objectives, this invention provides a three-roll skew rolling method for preparing bimetallic composite tubes by optimizing the interfacial bonding strength through wall reduction ratio control, comprising the following steps:

[0006] Step S1: Raw material preparation: Based on the target service conditions of the bimetallic composite pipe, select the outer pipe material and inner pipe material suitable for the target service conditions, and carry out the cutting operation according to the predetermined design drawings. At the same time, determine the initial outer diameter, wall thickness and cutting length of the outer pipe material and inner pipe material of the bimetallic composite pipe to obtain the outer pipe and inner pipe.

[0007] Step S2, Grinding operation: Use a tube inner wall grinding machine and a tube outer wall polishing machine to grind the inner wall of the outer tube and the outer wall of the inner tube respectively until the oxide scale, passivation layer and defects of the inner wall of the outer tube and the outer wall of the inner tube are removed to obtain the metal substrate.

[0008] Step S3, Cleaning and Drying: Use industrial ethanol as a cleaning agent to clean the polished inner and outer tubes, and then dry the cleaned inner and outer tubes.

[0009] Step S4, Assembly and Sealing: The cleaned and dried inner tube is inserted into the outer tube and assembled using a hydraulic press to obtain an initial composite billet with a total wall thickness in the range of 5 to 10 mm. After the assembly is completed, the two ends of the initial composite billet are immediately sealed by welding to obtain a tube blank with a sealed cavity.

[0010] Step S5, billet heating and heat preservation: The billet is sent into the heating device for heating. The heating range is set according to the characteristics of the outer tube material. The heating device maintains the temperature in the heating range for 10 to 30 minutes.

[0011] Step S6: Adjusting the roll pass: The reduction of the rolls in the three-roll skew rolling mill is controlled by adjusting the roll pass diameter. The adjustment range of the roll pass diameter is 50~70mm, and the adjustment range of the mandrel diameter used to support the tube blank in the three-roll skew rolling mill is 35~45mm.

[0012] Step S7, Inclined Rolling Composite and Post-processing: The heated and heat-preserved tube blank is fed into a three-roll skewed rolling mill with an adjusted pass for rolling. Under the pressure applied by the rolls of the three-roll skewed rolling mill and the support of the mandrel, the tube blank undergoes diameter reduction and wall reduction elongation. The interface between the inner and outer tubes of the tube blank achieves atomic-level composite under the pressure applied by the rolls, resulting in an initial composite tube. The initial composite tube is then subjected to controlled cooling at a rate of 10~50℃ / min. After cooling, a bimetallic composite tube is obtained.

[0013] In an optional implementation, step S4 further includes:

[0014] During the assembly process using a hydraulic press, a laser diameter gauge and an online coaxiality monitoring device are introduced to detect the relative eccentricity of the inner and outer tubes, the change in outer diameter, and the pressing stroke of the hydraulic press in real time. Based on the real-time detection results, the pressing speed and pressing force of the hydraulic press are controlled, and the posture of the outer and inner tubes is adjusted in real time.

[0015] In an optional implementation, step S7 further includes:

[0016] According to the performance requirements of the target service conditions, the bimetallic composite tube is subjected to heat treatment again.

[0017] In one alternative implementation, it further includes:

[0018] Step S8, Performance Testing: The bimetallic composite tube is cut and processed to obtain a bimetallic composite tube sample, and the bimetallic composite tube sample is tested using a universal testing machine to obtain the predicted value of the interface bonding strength.

[0019] In one alternative implementation, the formula for predicting the interface bonding strength is as follows:

[0020]

[0021] In the formula, This represents the predicted value of the interface bonding strength; Indicates the wall reduction rate. , Indicates the diameter of the aperture. Indicates the diameter of the mandrel. Indicates the total wall thickness; This indicates the insulation temperature, which is the heating range set according to the characteristics of the outer tube material; This indicates the heating temperature during the rolling process in a three-roll skew mill. This indicates the total temperature.

[0022] In one optional implementation, the wall reduction rate is controlled within a range of 0% to 75%, and within this range, the interface changes from mechanical bonding to metallurgical bonding.

[0023] In one optional implementation, step S1 involves selecting outer and inner tube materials suitable for the target service conditions, including:

[0024] The outer tube material is a medium-high carbon steel base tube, and the model is one of 45# steel, 50# steel, carbon tool steel, 65Mn, GCr15, and SK5 steel;

[0025] The inner tube material is a pure titanium sleeve, with a model number of TA0, TA1, TA2, TA3 or TA4.

[0026] In an optional implementation, step S7 further includes:

[0027] Microscopic observation of the initial composite tube confirmed the existence of the interface. The existence of the interface was based on the following: dynamic recrystallization occurred on the outer tube side, resulting in grain refinement; dislocations accumulated on the inner tube side, forming diffusion channels; and TiC was diffusely distributed at the generated interface.

[0028] Compared with the prior art, the beneficial effects of this invention patent are:

[0029] This invention employs a three-roll skew rolling mill process, precisely controlling the wall reduction rate of the bimetallic composite tube by adjusting the die diameter, thereby achieving controllable and stable interfacial bonding strength. At the microscopic level, observations revealed that the bimetallic composite tube prepared using this process exhibits a continuous and dense diffusion layer at the interface. Simultaneously, the grains on the outer tube side are refined, dislocation accumulation occurs on the inner tube side, and TiC particles effectively inhibit crack propagation; these factors work together to strengthen the interface.

[0030] Furthermore, the three-roll skew rolling process improves the uniformity of the circumferential wall reduction ratio of the bimetallic composite tube, further enhancing the stability of the interfacial bonding strength. The preparation method of this invention is simple and particularly suitable for the production of large-size, long-length medium-high carbon steel / pure titanium bimetallic composite tubes, showing broad application prospects. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is a schematic flowchart of a three-roll skew rolling method for preparing bimetallic composite tubes with controlled wall reduction ratio according to an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the skew rolling of a bimetallic composite tube according to an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the microstructure of a bimetallic composite tube with a wall reduction rate of 8% according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the microstructure of a bimetallic composite tube with a wall reduction rate of 15.8% according to an embodiment of the present invention.

[0036] Figure 5This is a schematic diagram of the microstructure of a bimetallic composite tube with a wall reduction rate of 26.3% according to an embodiment of the present invention.

[0037] Figure 6 This is a schematic diagram of the microstructure of a bimetallic composite tube with a wall reduction rate of 36.8% according to an embodiment of the present invention.

[0038] Figure 7 This is a schematic diagram of the wall reduction ratio and interfacial shear strength variation curve according to an embodiment of the present invention.

[0039] In the diagram, 201 is the rolling mill roll, 202 is the initial composite tube, and 203 is the mandrel. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] This embodiment provides a three-roll skew rolling method for preparing bimetallic composite tubes by optimizing the interfacial bonding strength through wall reduction ratio control, such as... Figure 1 As shown, the process includes the following steps:

[0042] Step S1: Raw material preparation: Based on the target service conditions of the bimetallic composite pipe, select the outer tube material and inner tube material suitable for the target service conditions, and perform the cutting operation according to the predetermined design drawings. At the same time, determine the initial outer diameter, wall thickness and cutting length of the outer tube material and inner tube material of the bimetallic composite pipe to obtain the outer tube and inner tube.

[0043] Optionally, in step S1, the outer tube material and inner tube material suitable for the target service conditions are selected, including: the outer tube material is a medium-high carbon steel base tube, and the model is one of 45# steel, 50# steel, carbon tool steel, 65Mn, GCr15, SK5 steel; the inner tube material is a pure titanium sleeve, and the model is one of TA0, TA1, TA2, TA3 or TA4.

[0044] In this embodiment, firstly, based on the target service conditions of the bimetallic composite pipe (such as corrosion resistance and strength requirements), a medium-high carbon steel base pipe is selected as the outer pipe material to improve structural strength and rigidity; the inner pipe material is a pure titanium sleeve to ensure excellent corrosion resistance. Strictly following the predetermined design drawings, the initial outer diameter, wall thickness, and cutting length of the outer and inner pipe materials of the bimetallic composite pipe are precisely cut and determined to obtain the outer and inner pipes, ensuring that the chemical composition and mechanical properties of the outer and inner pipes meet the relevant national or industry standards.

[0045] Step S2, Grinding Operation: First, use an inner wall grinding machine to grind the inner wall surface of the outer tube; then, use an outer wall polishing machine to polish the outer wall surface of the inner tube; through the above two grinding operations, the oxide scale, passivation layer and local surface defects on the inner wall surface and the outer wall surface are removed respectively, and a metal matrix suitable for subsequent skew rolling composite is obtained.

[0046] In this embodiment, an inner wall polisher and an outer wall polisher are used to perform comprehensive and uniform polishing operations on the inner wall surface of the outer tube and the outer wall surface of the inner tube, respectively, to thoroughly remove the oxide scale, passivation layer, and local surface defects on both the inner and outer wall surfaces until a fresh, uncontaminated metal substrate is exposed. After polishing, the interface formed between the outer and inner tubes should exhibit a uniform metallic luster, without any visible rust or oxidation.

[0047] Step S3, Cleaning and Drying: Use industrial ethanol as a cleaning agent to clean the polished inner and outer tubes, and then dry the cleaned inner and outer tubes.

[0048] In this embodiment, after grinding, a cleaning process is immediately initiated to remove grinding debris and contaminants. High-purity industrial ethanol is used as the cleaning agent, and the inner wall of the outer tube and the outer wall of the inner tube are thoroughly cleaned by immersion wiping or spraying. After cleaning, the outer and inner tubes must be air-dried in a clean, dry environment or blown dry with oil-free air to prevent secondary contamination.

[0049] Step S4, Assembly and Sealing: The cleaned and dried inner tube is inserted into the outer tube and assembled using a hydraulic press to obtain an initial composite billet with a total wall thickness in the range of 5 to 10 mm. After the assembly is completed, the two ends of the initial composite billet are immediately sealed by welding to obtain a tube blank with a sealed cavity.

[0050] In this embodiment, the cleaned and dried inner tube is precisely fitted into the outer tube, and the fitted double-layer tube is placed in a hydraulic press. Under the constraint of the radial limiting device and axial centering device of the hydraulic press, a stable axial pressing force is applied by the hydraulic press, causing the outer wall of the inner tube to gradually press against the inner wall of the outer tube during the pressing process, reducing the tiny gap between the outer and inner walls of the inner and outer tubes, and obtaining an initial composite billet with a total wall thickness controlled within the range of 5-10 mm. During this process, to ensure the accuracy of the billet assembly process, a laser diameter gauge and an online coaxiality monitoring device are set up around the hydraulic press to detect the relative eccentricity of the inner and outer tubes, the change in outer diameter, and the pressing stroke of the hydraulic press in real time. Based on the real-time detection results, the pressing speed and pressing force of the hydraulic press are controlled, and the posture of the outer and inner tubes is adjusted in real time. After the billet assembly is completed, the two ends of the initial composite billet are immediately sealed using argon arc welding or laser welding technology to obtain a tube billet with a sealed cavity.

[0051] Step S5, billet heating and heat preservation: The billet is sent into the heating device for heating. The heating range is set according to the characteristics of the outer tube material. The heating device maintains the temperature in the heating range for 10 to 30 minutes.

[0052] In this embodiment, the sealed tube blank is fed into a walking beam furnace or a box-type resistance furnace for homogenization heating. Depending on the characteristics of the outer tube material, the tube blank is heated to a specific heating range of 600~900℃ and held at this temperature for 10~30 minutes.

[0053] Step S6: Adjusting the pass shape: The reduction of the roll 201 in the three-roll skew rolling mill is controlled by adjusting the pass shape diameter. The adjustment range of the pass shape diameter is 50~70mm, and the adjustment range of the diameter of the mandrel 203 used to support the tube blank in the three-roll skew rolling mill is 35~45mm.

[0054] In this embodiment, the reduction of the rolls 201 in the three-roll skew rolling mill is controlled by adjusting the roll diameter. The heated and heat-preserved tube blank is placed in the rolling zone of the three-roll skew rolling mill. The roll diameter is gradually adjusted by the rolls 201 in the three-roll skew rolling mill, with an adjustment range of 50~70mm. The diameter of the mandrel 203 is adjusted by the trolley device of the three-roll skew rolling mill, with an adjustment range of 35~45mm. In practical applications, the trolley device of the three-roll skew rolling mill is also equipped with a detachable spiral interface, allowing for the replacement of mandrels 203 of different diameters according to different process requirements. This achieves support and sizing of the inner cavity of the tube blank, resulting in a bimetallic composite tube with excellent interfacial bonding performance.

[0055] Step S7, Inclined Rolling Composite and Post-processing: The heated and heat-preserved tube blank is fed into a three-roll skewed rolling mill with an adjusted pass for rolling. Under the pressure applied by the rolls 201 of the three-roll skewed rolling mill and the support of the mandrel 203, the tube blank undergoes diameter reduction and wall reduction elongation. The interface between the inner and outer tubes of the tube blank achieves atomic-level composite under the pressure applied by the rolls 201, resulting in an initial composite tube 202. The initial composite tube 202 is then subjected to controlled cooling at a rate of 10~50℃ / min. After cooling, a bimetallic composite tube is obtained.

[0056] Optionally, it also includes: subjecting the bimetallic composite tube to further heat treatment according to the performance requirements of the target service conditions.

[0057] In this embodiment, as Figure 2 As shown, the uniformly heated and heat-preserved tube blank is rapidly fed into a three-roll skew mill with an adjusted pass for rolling. Under the strong pressure of the rolls 201 and the support of the mandrel 203 in the three-roll skew mill, the tube blank undergoes diameter and wall reduction elongation. Through the application of enormous triaxial compressive stress by the rolls 201, atomic-level composite formation is achieved at the interface between the inner and outer tubes of the tube blank, resulting in an initial composite tube 202. The rolled initial composite tube 202 immediately enters a controlled cooling stage, employing forced air cooling or cooling with a specific medium, and controlling the cooling rate at 10~50℃ / min until the temperature of the initial composite tube 202 reaches room temperature, thus obtaining a bimetallic composite tube with an ideal microstructure.

[0058] Subsequently, based on the performance requirements of the target service conditions, heat treatments such as normalizing and annealing may be performed if necessary. Heat treatment can be performed by heating the initial composite tube 202 as a whole using a tube furnace, or by using electromagnetic induction heating to perform rapid and uniform localized treatment on the initial composite tube 202.

[0059] In this embodiment, by observing the microstructure of the initial composite tube 202 after rolling, it is determined that the interface of the initial composite tube 202 after rolling satisfies the interface bonding mechanism. The interface bonding mechanism mainly includes: dynamic recrystallization and grain refinement on the outer tube side (carbon steel side in this embodiment); dislocation accumulation on the inner tube side (pure titanium side in this embodiment) to promote the formation of diffusion channels; and the generated interface is diffusely distributed with titanium carbide (TiC), which plays a role in hindering crack propagation and improving the interface bonding strength.

[0060] Optionally, it also includes: step S8, performance testing: cutting the bimetallic composite tube to obtain a bimetallic composite tube sample, and testing the bimetallic composite tube sample using a universal testing machine to obtain a predicted value of the interface bonding strength.

[0061] In this embodiment, standard-sized bimetallic composite tube samples are precisely cut and processed from the final-processed bimetallic composite tube along the axial or circumferential direction. The predicted interfacial bond strength is then measured using a universal testing machine according to standard testing methods (such as the technical specification ASTM A265 for nickel and nickel alloy composite steel plates or corresponding national standards).

[0062] The formula for predicting the interface bonding strength is as follows:

[0063]

[0064] In the formula, This represents the predicted value of the interface bonding strength; Indicates the wall reduction rate. , Indicates the diameter of the aperture. This indicates the diameter of mandrel 203. Indicates the total wall thickness; This indicates the insulation temperature, which is the heating range set according to the characteristics of the outer tube material; This indicates the heating temperature during the rolling process in a three-roll skew mill. This indicates the total temperature.

[0065] The value range and units of some parameters are shown in Table 1.

[0066] Table 1

[0067]

[0068] In this embodiment, the coefficients in the prediction formula for interfacial bonding strength are obtained by performing nonlinear regression and other fitting operations on experimental data under different wall reduction ratios and temperature combinations. The coefficients -0.1258 and 174 are determined by fitting, so that the part of the prediction formula for interfacial bonding strength regarding wall reduction ratio can better reflect the influence of wall reduction ratio on interfacial bonding strength in the experimental data. For the temperature-related part, the correlation coefficient and expression form are also determined by a similar fitting method.

[0069] In this embodiment, the wall reduction rate is controlled within the range of 0% to 75%, and within this range, the interface is transformed from mechanical bonding to metallurgical bonding.

[0070] The present invention will now be described in detail with reference to specific embodiments, but the protection of the present invention is not limited to the specific embodiments listed. It should also include various modifications to the disclosed methods that are obvious to those skilled in the art without departing from the scope of the present invention.

[0071] In the specific embodiments described below, the interfacial shear strength is characterized by the interfacial shear strength obtained by tensile shearing tests on bimetallic composite tube samples. The specific embodiments described below show that the average interfacial shear strength can reach 130-180 MPa in the range of 5% to 35% wall reduction.

[0072] Example 1:

[0073] like Figure 3 As shown, Example 1 illustrates the process of preparing bimetallic composite tubes by skew rolling with a wall reduction rate of 8%.

[0074] S1. Raw material preparation: Carbon steel of grade 45# is selected as the outer tube material and pure titanium of grade TA2 is selected as the inner tube material. Their chemical composition meets the standards of GB / T 711-2017 and GB / T 3620.1-2016 respectively.

[0075] S2. Grinding operation: First, use an inner wall grinding machine to grind the inner wall surface of the outer tube; then, use an outer wall polishing machine to polish the outer wall surface of the inner tube; through the above two grinding operations, the oxide scale, passivation layer and local surface defects on the inner wall surface and the outer wall surface are removed respectively, and a metal matrix suitable for subsequent skew rolling composite is obtained.

[0076] S3. Cleaning and drying: Use industrial ethanol to clean the outer and inner tubes after polishing to ensure that there is no dust or oil residue.

[0077] S4. Assembly and Sealing: The outer tube material of 45# steel has an outer diameter of 70 mm and a wall thickness of 6.5 mm; the inner tube material of TA2 pure titanium has an outer diameter of 57 mm and a wall thickness of 3 mm. The inner tube material of TA2 pure titanium and the outer tube material of 45# steel are assembled together to obtain the initial composite billet. To ensure the accuracy of the assembly process, a laser diameter gauge and an online coaxiality monitoring device are introduced during the pressing process to detect the relative eccentricity of the inner and outer tubes, the change in outer diameter, and the pressing stroke of the hydraulic press in real time. Based on the detection results, the pressing speed, pressing force, or the posture of the outer and inner tubes of the hydraulic press are adjusted in real time. Then, argon arc welding is used to seal the two ends of the initial composite billet to obtain a tube blank with a sealed cavity.

[0078] S5. Billet heating and heat preservation: The sealed billet is sent into the box-type resistance furnace, heated to 750 ℃ ​​and kept at that temperature for 20 minutes to ensure that the inner and outer tubes of the billet are at a uniform temperature.

[0079] S6. Adjusting the die shape: The reduction is controlled by adjusting the die shape diameter of the three-roll skew mill. The die shape diameter is adjusted to 57.5mm and the diameter of mandrel 203 is adjusted to 40mm to achieve the interface formation of bimetallic composite tube with a wall reduction rate of 8%, thereby obtaining a bimetallic composite tube with excellent bonding performance.

[0080] S7. Inclined Rolling Composite and Post-processing: The uniformly heated tube blank is rapidly fed into a pre-adjusted three-roll skew mill for rolling. Under the strong pressure of the rolls 201 and the support of the mandrel 203, the tube blank undergoes diameter and wall reduction elongation. The interface between the inner and outer tubes of the tube blank achieves atomic-level composite under enormous triaxial compressive stress, resulting in the initial composite tube 202. The rolled initial composite tube 202 is immediately placed into a controlled cooling stage, using air cooling, with the cooling rate controlled at 10-50℃ / min.

[0081] S8. Performance Testing: Standard-sized bimetallic composite tube samples are precisely cut and processed from the final-processed bimetallic composite tube along the axial or circumferential direction. The predicted interfacial bond strength is measured using a universal testing machine according to standard testing methods.

[0082] In Example 1, the tube blank was heated to 750 ℃ ​​and held for 20 min before being fed into a three-roll skew mill. By adjusting the die diameter, an initial composite tube 202 with a wall reduction ratio of 8% was obtained. After being cooled by air cooling, the initial composite tube 202 was placed in a universal testing machine to test the interfacial properties. The results showed that no effective diffusion layer was formed at the interface under an 8% wall reduction ratio, and the interfacial shear strength was 134 MPa.

[0083] Example 2:

[0084] like Figure 4 As shown, Example 2 is the process of preparing bimetallic composite tubes by skew rolling with a wall reduction rate of 15.8%.

[0085] S1. Raw material preparation: Carbon steel of grade 45# is selected as the outer tube material and pure titanium of grade TA2 is selected as the inner tube material. Their chemical composition meets the standards of GB / T 711-2017 and GB / T 3620.1-2016 respectively.

[0086] S2. Grinding operation: First, use an inner wall grinding machine to grind the inner wall surface of the outer tube; then, use an outer wall polishing machine to polish the outer wall surface of the inner tube; through the above two grinding operations, the oxide scale, passivation layer and local surface defects on the inner wall surface and the outer wall surface are removed respectively, and a metal matrix suitable for subsequent skew rolling composite is obtained.

[0087] S3. Cleaning and drying: Use industrial ethanol to clean the outer and inner tubes after polishing to ensure that there is no dust or oil residue.

[0088] S4. Assembly and Sealing: The outer tube material of 45# steel has an outer diameter of 70 mm and a wall thickness of 6.5 mm; the inner tube material of TA2 pure titanium has an outer diameter of 57 mm and a wall thickness of 3 mm. The inner tube material of TA2 pure titanium and the outer tube material of 45# steel are assembled together to obtain the initial composite billet. To ensure the accuracy of the assembly process, a laser diameter gauge and an online coaxiality monitoring device are introduced during the pressing process to detect the relative eccentricity of the inner and outer tubes, the change in outer diameter, and the pressing stroke of the hydraulic press in real time. Based on the detection results, the pressing speed, pressing force, or the posture of the outer and inner tubes of the hydraulic press are adjusted in real time. Then, argon arc welding is used to seal the two ends of the initial composite billet to obtain a tube blank with a sealed cavity.

[0089] S5. Billet heating and heat preservation: The sealed billet is sent into the box-type resistance furnace, heated to 750 ℃ ​​and kept at that temperature for 20 minutes to ensure that the inner and outer tubes of the billet are at a uniform temperature.

[0090] S6. Adjusting the die shape: The reduction is controlled by adjusting the die shape diameter of the three-roll skew mill. The die shape diameter is adjusted to 56.0 mm and the mandrel 203 diameter is adjusted to 40 mm to achieve the interface formation of the bimetallic composite tube with a wall reduction rate of 15.8%, thereby obtaining a bimetallic composite tube with excellent bonding performance.

[0091] S7. Inclined Rolling Composite and Post-processing: The uniformly heated tube blank is rapidly fed into a pre-adjusted three-roll skew mill for rolling. Under the strong pressure of the rolls 201 and the support of the mandrel 203, the tube blank undergoes diameter and wall reduction elongation. The interface between the inner and outer tubes of the tube blank achieves atomic-level composite under enormous triaxial compressive stress, resulting in the initial composite tube 202. The rolled initial composite tube 202 is immediately placed into a controlled cooling stage, using air cooling, with the cooling rate controlled at 10-50℃ / min.

[0092] S8. Performance Testing: Standard-sized bimetallic composite tube samples are precisely cut and processed from the final-processed bimetallic composite tube along the axial or circumferential direction. The predicted interfacial bond strength is measured using a universal testing machine according to standard testing methods.

[0093] In Example 2, when the wall reduction rate was 15.8%, a continuous metallurgical bonding layer was formed at the interface, and the interfacial shear strength increased to 158 MPa, indicating that appropriately increasing the wall reduction rate is beneficial to element diffusion and interfacial bonding strengthening.

[0094] Example 3:

[0095] like Figure 5 As shown, Example 3 is the process of preparing bimetallic composite tubes by skew rolling with a wall reduction rate of 26.3%.

[0096] S1. Raw material preparation: Carbon steel of grade 45# is selected as the outer tube material and pure titanium of grade TA2 is selected as the inner tube material. Their chemical composition meets the standards of GB / T 711-2017 and GB / T 3620.1-2016 respectively.

[0097] S2. Grinding operation: First, use an inner wall grinding machine to grind the inner wall surface of the outer tube; then, use an outer wall polishing machine to polish the outer wall surface of the inner tube; through the above two grinding operations, the oxide scale, passivation layer and local surface defects on the inner wall surface and the outer wall surface are removed respectively, and a metal matrix suitable for subsequent skew rolling composite is obtained.

[0098] S3. Cleaning and drying: Use industrial ethanol to clean the outer and inner tubes after polishing to ensure that there is no dust or oil residue.

[0099] S4. Assembly and Sealing: The outer tube material of 45# steel has an outer diameter of 70 mm and a wall thickness of 6.5 mm; the inner tube material of TA2 pure titanium has an outer diameter of 57 mm and a wall thickness of 3 mm. The inner tube material of TA2 pure titanium and the outer tube material of 45# steel are assembled together to obtain the initial composite billet. To ensure the accuracy of the assembly process, a laser diameter gauge and an online coaxiality monitoring device are introduced during the pressing process to detect the relative eccentricity of the inner and outer tubes, the change in outer diameter, and the pressing stroke of the hydraulic press in real time. Based on the detection results, the pressing speed, pressing force, or the posture of the outer and inner tubes of the hydraulic press are adjusted in real time. Then, argon arc welding is used to seal the two ends of the initial composite billet to obtain a tube blank with a sealed cavity.

[0100] S5. Billet heating and heat preservation: The sealed billet is sent into the box-type resistance furnace, heated to 750 ℃ ​​and kept at that temperature for 20 minutes to ensure that the inner and outer tubes of the billet are at a uniform temperature.

[0101] S6. Adjusting the die shape: The reduction is controlled by adjusting the die shape diameter of the three-roll skew mill. The die shape diameter is adjusted to 54mm and the mandrel 203 diameter is adjusted to 40mm to achieve the interface formation of the bimetallic composite tube with a wall reduction rate of 26.3%, thereby obtaining a bimetallic composite tube with excellent bonding performance.

[0102] S7. Inclined Rolling Composite and Post-processing: The uniformly heated tube blank is rapidly fed into a pre-adjusted three-roll skew mill for rolling. Under the strong pressure of the rolls 201 and the support of the mandrel 203, the tube blank undergoes diameter and wall reduction elongation. The interface between the inner and outer tubes of the tube blank achieves atomic-level composite under enormous triaxial compressive stress, resulting in the initial composite tube 202. The rolled initial composite tube 202 is immediately placed into a controlled cooling stage, using air cooling, with the cooling rate controlled at 10-50℃ / min.

[0103] S8. Performance Testing: Standard-sized bimetallic composite tube samples are precisely cut and processed from the final-processed bimetallic composite tube along the axial or circumferential direction. The predicted interfacial bond strength is measured using a universal testing machine according to standard testing methods.

[0104] In Example 3, when the wall reduction rate was 26.3%, the metallurgical bonding of the interface was more complete, the element diffusion at the interface was significantly enhanced, and the interfacial shear strength was further increased to 174 MPa. This indicates that the higher deformation amount helps the interfacial atomic interdiffusion and plastic flow, thereby significantly improving the interfacial bonding quality.

[0105] Example 4:

[0106] like Figure 6 As shown, Example 4 illustrates the process of preparing bimetallic composite tubes by skew rolling with a wall reduction rate of 36.8%.

[0107] S1. Raw material preparation: Carbon steel of grade 45# is selected as the outer tube material and pure titanium of grade TA2 is selected as the inner tube material. Their chemical composition meets the standards of GB / T 711-2017 and GB / T 3620.1-2016 respectively.

[0108] S2. Grinding operation: First, use an inner wall grinding machine to grind the inner wall surface of the outer tube; then, use an outer wall polishing machine to polish the outer wall surface of the inner tube; through the above two grinding operations, the oxide scale, passivation layer and local surface defects on the inner wall surface and the outer wall surface are removed respectively, and a metal matrix suitable for subsequent skew rolling composite is obtained.

[0109] S3. Cleaning and drying: Use industrial ethanol to clean the outer and inner tubes after polishing to ensure that there is no dust or oil residue.

[0110] S4. Assembly and Sealing: The outer tube material of 45# steel has an outer diameter of 70 mm and a wall thickness of 6.5 mm; the inner tube material of TA2 pure titanium has an outer diameter of 57 mm and a wall thickness of 3 mm. The inner tube material of TA2 pure titanium and the outer tube material of 45# steel are assembled together to obtain the initial composite billet. To ensure the accuracy of the assembly process, a laser diameter gauge and an online coaxiality monitoring device are introduced during the pressing process to detect the relative eccentricity of the inner and outer tubes, the change in outer diameter, and the pressing stroke of the hydraulic press in real time. Based on the detection results, the pressing speed, pressing force, or the posture of the outer and inner tubes of the hydraulic press are adjusted in real time. Then, argon arc welding is used to seal the two ends of the initial composite billet to obtain a tube blank with a sealed cavity.

[0111] S5. Billet heating and heat preservation: The sealed billet is sent into the box-type resistance furnace, heated to 750 ℃ ​​and kept at that temperature for 20 minutes to ensure that the inner and outer tubes of the billet are at a uniform temperature.

[0112] S6. Adjusting the die shape: The reduction is controlled by adjusting the die shape diameter of the three-roll skew mill. The die shape diameter is adjusted to 52.0 mm, and the mandrel 203 diameter is adjusted to 40 mm, so as to achieve the interface formation of the bimetallic composite tube with a wall reduction rate of 36.8%, thereby obtaining a bimetallic composite tube with excellent bonding performance.

[0113] S7. Inclined Rolling Composite and Post-processing: The uniformly heated tube blank is rapidly fed into a pre-adjusted three-roll skew mill for rolling. Under the strong pressure of the rolls 201 and the support of the mandrel 203, the tube blank undergoes diameter and wall reduction elongation. The interface between the inner and outer tubes of the tube blank achieves atomic-level composite under enormous triaxial compressive stress, resulting in the initial composite tube 202. The rolled initial composite tube 202 is immediately placed into a controlled cooling stage, using air cooling, with the cooling rate controlled at 10-50℃ / min.

[0114] S8. Performance Testing: Standard-sized bimetallic composite tube samples are precisely cut and processed from the final-processed bimetallic composite tube along the axial or circumferential direction. The predicted interfacial bond strength is measured using a universal testing machine according to standard testing methods.

[0115] In Example 4, when the wall reduction ratio was further increased to 36.8%, the diffusion layer at the interface was continuously distributed, but Kirkendal pores and a brittle TiC continuous layer appeared, leading to local stress concentration and interface embrittlement, and the interface shear strength decreased to 164 MPa. The results show that an excessively high wall reduction ratio can cause excessive interfacial reaction and pore formation, reducing the strength of the composite interface.

[0116] Depend on Figure 7 As shown, the correlation between wall reduction ratio and interfacial shear strength can be intuitively obtained, verifying that the wall reduction ratio preparation process with controlled aperture diameter proposed in this invention can significantly improve the bonding performance of the composite interface and has operability and promotion value. At the same time, it also demonstrates that compared with the traditional two-roll rolling method, the method of this invention can obtain a more uniform circumferential wall reduction ratio distribution, thereby improving the interfacial bonding stability.

[0117] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A three-roll skew rolling method for preparing bimetallic composite tubes by optimizing the interfacial bonding strength through wall reduction ratio, characterized in that, Includes the following steps: Step S1: Raw material preparation: Based on the target service conditions of the bimetallic composite pipe, select the outer pipe material and inner pipe material suitable for the target service conditions, and carry out the cutting operation according to the predetermined design drawings. At the same time, determine the initial outer diameter, wall thickness and cutting length of the outer pipe material and inner pipe material of the bimetallic composite pipe to obtain the outer pipe and inner pipe. Step S2, Grinding Operation: First, use an inner wall grinding machine to grind the inner wall surface of the outer tube; then, use an outer wall polishing machine to polish the outer wall surface of the inner tube; through the above two grinding operations, the oxide scale, passivation layer and local surface defects on the inner wall surface and the outer wall surface are removed respectively, and a metal matrix suitable for subsequent skew rolling composite is obtained. Step S3, Cleaning and Drying: Use industrial ethanol as a cleaning agent to clean the polished inner and outer tubes, and then dry the cleaned inner and outer tubes. Step S4, Assembly and Sealing: The cleaned and dried inner tube is inserted into the outer tube and assembled using a hydraulic press to obtain an initial composite billet with a total wall thickness in the range of 5 to 10 mm. After the assembly is completed, the two ends of the initial composite billet are immediately sealed by welding to obtain a tube blank with a sealed cavity. Step S5, billet heating and heat preservation: The billet is sent into the heating device for heating. The heating range is set according to the characteristics of the outer tube material. The heating device maintains the temperature in the heating range for 10 to 30 minutes. Step S6: Adjust the pass shape: Control the reduction of the roll (201) in the three-roll skew rolling mill by adjusting the pass shape diameter. The adjustment range of the pass shape diameter is 50~70mm, and the adjustment range of the diameter of the mandrel (203) used to support the tube blank in the three-roll skew rolling mill is 35~45mm. Step S7, skew rolling composite and post-processing: The heated and heat-preserved tube blank is fed into a three-roll skew rolling mill with an adjusted pass for rolling. Under the pressure applied by the rolls (201) of the three-roll skew rolling mill and the support of the mandrel (203), the tube blank undergoes diameter reduction and wall reduction elongation. The interface between the inner tube and the outer tube of the tube blank achieves atomic-level composite under the pressure applied by the rolls (201), resulting in an initial composite tube (202). The initial composite tube (202) is subjected to controlled cooling at a rate of 10~50℃ / min. After cooling, a bimetallic composite tube is obtained. Also includes: Step S8, Performance Testing: The bimetallic composite tube is cut and processed to obtain a bimetallic composite tube sample, and the bimetallic composite tube sample is tested using a universal testing machine to obtain the predicted value of the interface bonding strength. The formula for predicting the interface bonding strength is as follows: In the formula, This represents the predicted value of the interface bonding strength; Indicates the wall reduction rate. , Indicates the diameter of the aperture. This indicates the diameter of the mandrel (203). Indicates the total wall thickness; This indicates the insulation temperature, which is the heating range set according to the characteristics of the outer tube material; This indicates the heating temperature during the rolling process of a three-roll skew mill; Indicates the total temperature; The wall reduction rate is adjustable within the range of 0% to 75%, and within this range, the interface changes from mechanical bonding to metallurgical bonding.

2. The three-roll skew rolling method for preparing bimetallic composite tubes by optimizing the interfacial bonding strength through wall reduction ratio control according to claim 1, characterized in that, Step S4 also includes: During the assembly process using a hydraulic press, a laser diameter gauge and an online coaxiality monitoring device are introduced to detect the relative eccentricity of the inner and outer tubes, the change in outer diameter, and the pressing stroke of the hydraulic press in real time. Based on the real-time detection results, the pressing speed and pressing force of the hydraulic press are controlled, and the posture of the outer and inner tubes is adjusted in real time.

3. The three-roll skew rolling method for preparing bimetallic composite tubes by optimizing the interfacial bonding strength through wall reduction ratio according to claim 1, characterized in that, Step S7 also includes: According to the performance requirements of the target service conditions, the bimetallic composite tube is subjected to further heat treatment.

4. The three-roll skew rolling method for preparing bimetallic composite tubes by optimizing the interfacial bonding strength through wall reduction ratio control according to claim 1, characterized in that, Step S1 involves selecting outer and inner tube materials suitable for the target service conditions, including: The outer tube material is a medium-high carbon steel base tube, and the model is one of 45# steel, 50# steel, carbon tool steel, 65Mn, GCr15, and SK5 steel; The inner tube material is a pure titanium sleeve, with a model number of TA0, TA1, TA2, TA3 or TA4.

5. The three-roll skew rolling method for preparing bimetallic composite tubes by optimizing the interfacial bonding strength through wall reduction ratio control according to claim 1, characterized in that, Step S7 also includes: Microscopic observation of the initial composite tube (202) confirmed the existence of the interface. The basis for the existence of the interface is: dynamic recrystallization occurs on the outer tube side, resulting in grain refinement; dislocations accumulate on the inner tube side, forming diffusion channels; and TiC is diffusely distributed on the generated interface.

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