Method for optimizing parameters and expanding diameter for steel pipe diameter expanding process by using thermal simulation experiment technology
The optimal process parameter window was determined through thermal simulation experiments. By combining induction heating expansion equipment and expansion head, the stability and efficiency issues of steel pipe expansion process were solved, the microstructure and mechanical properties were optimized, and it is applicable to steel pipes of different materials and specifications.
Patent Information
- Application Number
- CN202512023704.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-05-01
AI Technical Summary
The existing steel pipe diameter expansion process suffers from poor process stability, low work efficiency, and uncontrollable microstructure and properties, especially making it difficult to guarantee the quality consistency and mechanical properties of different batches of pipes.
By determining the optimal process parameter window through thermal simulation experiments, and combining induction heating expansion equipment and expansion head, precise control of heating temperature, holding time, deformation rate and deformation amount can be achieved, and a process database can be established to guide actual production.
It achieves stability and consistency in the steel pipe diameter expansion process, improves production efficiency, optimizes microstructure and mechanical properties, reduces scrap rate, and is applicable to steel pipes of different materials and specifications.
Smart Images
Figure CN121955064A_ABST
Abstract
Description
A method for optimizing parameters and expanding diameter of steel pipes using thermal simulation experiments. Technical Field
[0001] This invention belongs to the field of metal pipe plastic processing technology, and particularly relates to a method for optimizing parameters of steel pipe diameter expansion process using thermal simulation experimental technology, and a diameter expansion method. Background Technology
[0002] In steel pipe production, it's common for some batches of finished products to have a diameter slightly smaller than customer requirements. To salvage these pipes and reduce costs, a localized heating and expansion process is often used for straightening and expansion. Currently, small-scale medium-frequency induction heating equipment is commonly used to heat the circumferential area of the steel pipe, followed by mechanical expansion using an expanding die. However, existing expansion processes have significant drawbacks:
[0003] (1) Poor process stability: Key parameters such as heating temperature, holding time, and deformation rate are mostly set by workers' experience. For different batches of pipes (even if the material is the same, the microstructure may be different), there is a lack of scientific and unified guidance, which leads to inconsistent roundness and straightness of the pipes after expansion, and even defects such as microcracks and orange peel texture.
[0004] (2) Low work efficiency: In order to avoid overheating or insufficient deformation, conservative process parameters are usually adopted, resulting in excessively long heating and deformation time and low production efficiency.
[0005] (3) Uncontrollable microstructure and properties: The expansion process is essentially a thermoplastic deformation process, the core of which is to refine the grains and optimize the microstructure through recrystallization. However, existing technologies cannot precisely control the recrystallization process, resulting in large fluctuations in the mechanical properties (such as strength and toughness) of the expanded pipe, which affects product quality. Summary of the Invention
[0006] The purpose of this invention is to provide a scientific, stable, and efficient method for optimizing the process parameters of steel pipe expansion and an expansion method that combines thermal simulation experiments with industrial production to achieve precise control of the expansion process.
[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0008] This invention discloses a method for optimizing parameters in a steel pipe diameter expansion process using thermal simulation experimental technology, comprising the following steps:
[0009] S1. Sample preparation: Multiple cylindrical thermal simulation samples were cut from the target steel pipe;
[0010] S2. Scheme Design: Set multiple combinations of process parameters including heating temperature T, holding time t, deformation rate ε1, and deformation amount ε2;
[0011] S3. Hot compression test: Multiple hot compression tests are performed on the sample according to the parameter combination on a thermal simulation test machine;
[0012] S4. Microstructure analysis: Analyze the metallographic structure of the samples after the experiment to determine the process parameters corresponding to the samples that have undergone complete recrystallization and grain refinement.
[0013] S5. Window Determination: Based on the analysis results of S4, determine the optimal process parameter window that enables complete recrystallization and grain refinement of the steel pipe;
[0014] The target steel pipe is made of Q345 steel; the heating temperature T is explored within the range of 50°C above the Ac3 phase transformation point to 50°C below the overheating temperature; the deformation amount ε2 is explored within the range of 5% to 30%.
[0015] 2. A method for expanding the diameter of a steel pipe, characterized by applying the optimal process parameter window determined as claimed in claim 1 or 2, comprising the following steps:
[0016] A. Parameter mapping: The heating temperature T, holding time t, deformation rate ε1 and deformation amount ε2 in the optimal process parameter window are mapped to the control commands of the induction heating expansion equipment.
[0017] B. Clamping and positioning: Place the steel pipe to be expanded between the induction coil and the expanding head of the equipment;
[0018] C. Perform diameter expansion: Start the equipment, the induction coil heats the steel pipe ring area according to the control command, and then the diameter expansion head radially expands the heated area according to the control command, causing it to undergo plastic deformation;
[0019] D. Continuous processing: Move the induction coil and the expanding head along the axial direction of the steel pipe, or move the steel pipe and repeat step C until the expansion of the entire pipe is completed.
[0020] Furthermore, in step A, the heat preservation time t is effectively controlled by controlling the scanning speed of the induction heating coil.
[0021] Furthermore, in step A, the deformation rate ε1 is precisely controlled by controlling the hydraulic or servo feed speed of the expanding head.
[0022] A steel pipe diameter expansion system, comprising:
[0023] A thermal simulation test chamber is used to perform optimal window optimization methods to determine the optimal process parameter window.
[0024] An induction heating device is used to locally heat the area of the steel pipe to be expanded.
[0025] An expanding actuator is used to apply radial force to a heated steel pipe to expand it.
[0026] The control system has a pre-stored window of optimal process parameters and is configured to convert the parameters in the window into control commands and send them to the induction heating device and the diameter expansion actuator, so that they work together according to the commands.
[0027] Furthermore, the control system controls the heating temperature T by adjusting the power and heating time of the induction heating device, and controls the equivalent heat preservation time t by adjusting the relative moving speed between the induction coil and the steel pipe.
[0028] Furthermore, the control system controls the deformation rate ε1 by adjusting the feed speed of the diameter expansion actuator, and controls the deformation amount ε2 by controlling its final stroke.
[0029] The core of this approach lies in using a thermal simulation testing machine to "reproduce" the thermo-mechanical processes involved in expanding the diameter of steel pipes in the laboratory, but on a smaller and more controllable scale. By designing multiple sets of experiments with different process parameters, it is possible to directly observe which parameter combinations induce the most ideal complete recrystallization and grain refinement. This process is equivalent to establishing a dedicated "process database" or "process map" for a specific steel pipe material (such as Q345, Φ460mm).
[0030] Then, the present invention maps the optimal process parameter window obtained above to the actual induction heating diameter expansion production. By controlling the power and scanning speed (equivalent to the holding time) of the induction heating equipment, as well as controlling the feed speed (controlling the deformation rate) and final displacement (controlling the deformation amount) of the diameter expansion die head, every step in the actual production is carried out within the scientifically optimized parameter range.
[0031] Compared with the prior art, the beneficial technical effects of the present invention are as follows:
[0032] 1. High scientific rigor and good stability: It abandons the traditional "trial and error" method that relies on experience, and guides production with scientific experimental data, ensuring the consistency and stability of the pipe diameter expansion process for different batches, and significantly reducing the scrap rate.
[0033] 2. Improved work efficiency: Through precise process windows, more efficient parameters (such as appropriately higher temperatures or faster deformation rates) closer to the material limits can be used while ensuring quality, thus shortening the production cycle.
[0034] 3. Controllable and optimized product quality: The expansion process is designed to promote complete recrystallization and grain refinement, thereby not only increasing the size but also optimizing the microstructure and overall mechanical properties of the pipe.
[0035] 4. High applicability: This method can be applied to steel pipes of different materials and specifications. Only by conducting thermal simulation experiments again for specific pipe materials can the optimal diameter expansion process be quickly determined, which has strong promotional value. Attached Figure Description
[0036] The present invention will be further described below with reference to the accompanying drawings.
[0037] Figure 1 is a process flow diagram of the present invention. Detailed Implementation
[0038] The present invention will be described in detail below using a specific Q345 material and 460mm diameter steel pipe as an example.
[0039] Part 1: Process Parameter Optimization
[0040] 1. Sample preparation: A standard cylindrical thermal simulation sample of Φ8mm×12mm is machined from the Q345 steel pipe to be expanded along the axial or circumferential direction.
[0041] 2. Design a thermal compression experiment scheme:
[0042] Heating temperature (T): Select four levels: 950℃, 1000℃, 1050℃, and 1100℃.
[0043] Insulation time (t): Select two levels: 60s and 120s.
[0044] Deformation rate (ε): 0.1 s -1 1s -1 Two levels.
[0045] Deformation amount (ε): Select three levels: 15%, 20%, and 25%.
[0046] Design approximately 20-30 sets of experiments using orthogonal or univariate methods.
[0047] 3. Perform experiments and analyze data: All experiments are conducted on a thermal simulation testing machine. After the experiments, the samples are cut, polished, and etched. The grain size and morphology are observed under a metallographic microscope to determine whether complete recrystallization has occurred. Microhardness testing can also be performed simultaneously.
[0048] 4. Determining the optimal window: It was found that when the temperature is between 1000℃ and 1100℃, the deformation is between 20% and 25%, and the deformation rate is 1 second. -1 At this stage, Q345 steel can undergo sufficient dynamic recrystallization, resulting in fine and uniform austenitic grains, and exhibits optimal microstructure and properties after cooling. This parameter range is determined as the optimal process window for expanding the diameter of this steel pipe.
[0049] Part Two: Practical Applications of Diameter Enlargement
[0050] 1. On the induction heating expansion device, set the power of the induction heater so that the target ring on the surface of the steel pipe is heated to 1050°C (within the above window) in about 30 seconds.
[0051] 2. Since it is a continuous scanning heating method, the holding time is determined by the coil width and the scanning speed. Through calculation, the scanning speed is controlled so that the dwell time of any cross-section near the peak temperature is approximately 60-90 seconds (equivalent to the holding time).
[0052] 3. Set the hydraulic feed speed of the expanding head so that the circumferential deformation rate of the steel pipe is equivalent to 1 second. -1 about.
[0053] 4. Control the final expansion displacement of the machine head to ensure that the diameter deformation in this area reaches 22% (falling within the 20% to 25% window).
[0054] 5. Start the equipment and perform continuous or step-by-step diameter expansion. After each pipe is completed, perform dimensional and ultrasonic flaw detection inspections.
[0055] Through the above process, the results of laboratory thermal simulation research can be directly and accurately applied to industrial sites, ensuring the stability and efficiency of the diameter expansion process and the high quality of the products.
[0056] The workflow is as follows:
[0057] 1. The operator loads the steel pipe into the system.
[0058] 2. Select the corresponding steel pipe material and specifications (such as Q345, Φ460mm) from the touch screen of the control system, and the system will automatically call the pre-stored optimal process parameters.
[0059] 3. Initiate the automatic operation program. The control system first commands the induction heating device to heat the initial ring of the steel pipe at a specific power, and to bring its surface temperature to 1050°C within approximately 30 seconds. By controlling the scanning speed of the coil in this area, the equivalent holding time of this area at the peak temperature is approximately 80 seconds.
[0060] 4. After the heat preservation is completed, the control system immediately commands the diameter expansion actuator to feed at a preset speed (corresponding to a deformation rate ε1 = 1s). -1 The ring is moved forward to expand its diameter after being heated and softened until the preset stroke is reached (corresponding to a deformation of ε2 = 22%).
[0061] 5. Subsequently, the system moves the induction coil and the expanding head to the next adjacent ring, repeating steps 3 and 4 until the entire steel pipe is expanded.
[0062] The above methods and systems enable the direct, accurate, and automatic application of laboratory thermal simulation research results to industrial sites, ensuring the stability and efficiency of the diameter expansion process and the high quality of the products.
[0063] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for optimizing parameters in steel pipe diameter expansion process using thermal simulation experimental technology, characterized in that, Includes the following steps: S1. Sample Preparation: Multiple cylindrical thermal simulation samples are cut from the target steel pipe; S2. Scheme Design: Multiple combinations of process parameters are set, including heating temperature T, holding time t, deformation rate ε1, and deformation amount ε2; S3. Hot Compression Experiment: Multiple hot compression experiments are conducted on the samples according to the parameter combinations on a thermal simulation testing machine; S4. Microstructure Analysis: The metallographic structure of the samples after the experiment is analyzed to determine the process parameters corresponding to the sample that undergoes complete recrystallization and grain refinement; S5. Window Determination: Based on the analysis results of S4, the optimal process parameter window for achieving complete recrystallization and grain refinement in the steel pipe is determined; the target steel pipe is made of Q345; the exploration range of the heating temperature T is 50°C above the Ac3 phase transformation point to 50°C below the overheating temperature; the exploration range of the deformation amount ε2 is 5% to 30%.
2. A method for expanding the diameter of a steel pipe, characterized in that, The application of the optimal process parameter window as determined in claim 1 or 2 includes the following steps: A. Parameter mapping: Mapping the heating temperature T, holding time t, deformation rate ε1, and deformation amount ε2 in the optimal process parameter window to control commands for the induction heating expansion device; B. Clamping and positioning: Placing the steel pipe to be expanded between the induction coil and the expansion head of the device; C. Executing expansion: Starting the device, the induction coil heats the ring area of the steel pipe according to the control commands, and then the expansion head radially expands the heated area according to the control commands, causing it to undergo plastic deformation; D. Continuous processing: Moving the induction coil and the expansion head along the axial direction of the steel pipe, or moving the steel pipe, repeating step C until the entire pipe is expanded.
3. The method according to claim 2, characterized in that, In step A, the heat preservation time t is effectively controlled by controlling the scanning speed of the induction heating coil.
4. The method according to claim 1, characterized in that, In step A, the deformation rate ε1 is precisely controlled by controlling the hydraulic or servo feed speed of the expanding head.
5. The method according to claim 2, characterized in that, The system, based on a steel pipe diameter expansion mechanism, includes: a thermal simulation testing machine for performing an optimal window optimization method to determine the optimal process parameter window; an induction heating device for locally heating the area of the steel pipe to be expanded; an expansion actuator for applying radial force to the heated steel pipe to expand it; and a control system, which has the optimal process parameter window pre-stored and is configured to convert the parameters in the window into control commands and send them to the induction heating device and the expansion actuator, so that they work together according to the commands.
6. The method according to claim 5, characterized in that, The control system controls the heating temperature T by adjusting the power and heating time of the induction heating device, and controls the equivalent heat preservation time t by adjusting the relative moving speed between the induction coil and the steel pipe.
7. The method according to claim 5, characterized in that, The control system controls the deformation rate ε1 by adjusting the feed speed of the diameter expansion actuator, and controls the deformation amount ε2 by controlling its final stroke.