Extrusion-on-line heating-on-line quenching forming method for high-strength aluminum and magnesium alloy

Abstract

The invention discloses a high-strength aluminum and magnesium alloy extrusion-on-line heating-on-line quenching forming method, and relates to the technical field of metal material extrusion forming and heat treatment.The method comprises the steps that a unified constitutive model of the multi-pass forming process is established according to internal variables of a profile to be quenched; according to the unified constitutive model, machine learning is adopted to determine the change rule of the heat exchange coefficient of the corresponding profile in different preparation stages along with the technological parameters; establishing a joint simulation model; determining integrated forming process parameters according to the change rule of the heat exchange coefficients in different preparation stages along with the process parameters and the simulation model; and correspondingly controlling an extruder hydraulic system, a non-contact heating device and an on-line quenching system according to the parameters of the integrated forming process. Accurate control over the temperature in the extrusion, heating and quenching processes can be achieved, and unstable product structure performance caused by outlet temperature fluctuation can be effectively reduced.

Description

Technical Field

[0001] The present application relates to the technical field of metal material extrusion forming and heat treatment, and in particular to a high-strength aluminum, magnesium high-strength aluminum, and magnesium alloy extrusion-online heating-online quenching forming method. Background Art

[0002] Aluminum and magnesium alloys are ideal lightweight materials and are increasingly widely used in aerospace, rail transit, and automotive fields. With the development of processing technology for light metal materials such as aluminum and magnesium alloys, and the increasing requirements for energy conservation and consumption reduction, the development of short-process, high-efficiency, and energy-saving production processes is of great significance. At present, the extrusion and heat treatment forming processes of metal materials, especially aluminum alloys, are relatively mature. Conventional processes include extrusion-online quenching-aging treatment and extrusion-offline quenching-aging treatment. Online quenching is a highly integrated short-process process that quenches the high-temperature profiles that have just been extruded out of the die hole by air cooling, mist cooling, or water cooling. The process can greatly improve production efficiency and reduce energy consumption and manufacturing costs. In addition, due to the traction force applied by the traction machine during the extrusion process, the quenching warping can be suppressed, and the straightness of the profile can be effectively guaranteed. Offline quenching is the process in which the extruded profile re-enters a special heating furnace after cooling and is heated to a certain temperature before being quenched out of the furnace. Offline quenching has a relatively long process and high energy consumption, and the profile is prone to warping and deformation during the quenching process.

[0003] In order to achieve online quenching, two conditions must be met. First, the profile exit die temperature should be higher than the solid solution temperature of the material; second, the profile should enter the quenching zone in the shortest time after extrusion to prevent the temperature from dropping below the quenching temperature. In actual production, the extrusion speed is greater than 3m / min, and the time to reach the quenching cooling device does not exceed 20s to meet the process requirements of online quenching. However, highly alloyed aluminum and magnesium alloys, such as 7075 aluminum alloy and AZ80 magnesium alloy, have poor extrusion formability, low extrusion speed (generally less than 3m / min), and a large temperature drop after extrusion. The supersaturated solid solution will produce secondary phase precipitation before reaching the quenching device, affecting the quenching effect.

[0004] Therefore, a new online quenching method is urgently needed, which is to quench the profile after online heating at the extrusion outlet to ensure the online quenching effect of the profile under full solid solution state. At the same time, it can also reduce the instability of product microstructure and performance caused by outlet temperature fluctuations, and realize the short-process preparation process of online quenching of high-strength aluminum and magnesium alloy extrusion. Summary of the invention

[0005] The purpose of this application is to provide a high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method, which can achieve precise control of temperature during extrusion, heating and quenching, and can effectively reduce the instability of product structure and performance caused by outlet temperature fluctuations.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] The present application provides a high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method, the high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method comprising:

[0008] A unified constitutive model of a multi-pass forming process is established according to internal variables of the profile to be quenched; the internal variables include: dislocation density, secondary phase characteristics and grain size;

[0009] According to the unified constitutive model, machine learning is used to determine the variation of the heat exchange coefficient of the corresponding profiles at different preparation stages along with the process parameters;

[0010] Establishing a joint simulation model; the joint simulation model is used to simulate the profile extrusion process, the online heating and online quenching process, and the profile bending deformation during the online heating and quenching process;

[0011] Determine the integrated forming process parameters according to the variation law of the heat exchange coefficient with the process parameters in different preparation stages and the simulation model; the integrated forming process parameters include: the extrusion speed and temperature of the hydraulic system of the extruder, the current of the non-contact heating device, and the water inlet temperature and the water inlet and outlet flow of the online quenching system;

[0012] The extruder hydraulic system, non-contact heating device and online quenching system are controlled accordingly according to the integrated forming process parameters.

[0013] Optionally, the joint simulation model specifically includes: a master model built using a STAR-CCM+ model and an ABAQUS model, a slave model built using DEFORM, and a master model built using a STAR-CCM+ model and an ABAQUS model;

[0014] The STAR-CCM+ model is used to simulate and calculate the online heating and online quenching process, and the ABAQUS model is used to simulate and calculate the bending deformation of the profile during the online heating and quenching process; the STAR-CCM+ model inputs the calculated temperature field results into the ABAQUS model for thermal calculation;

[0015] The extrusion simulation model is used to simulate and calculate the profile extrusion process; the extrusion simulation model is a subordinate model of the joint simulation model; the subordinate model is used to input the temperature, stress and strain field distribution results of the profile after extrusion into the main model.

[0016] Optionally, the information exchange and transmission between the master model and the slave model is realized through the AMESIM platform.

[0017] Optionally, according to the unified constitutive model, machine learning is used to determine the variation law of the heat exchange coefficient of the corresponding profile in different preparation stages along with the process parameters, and then it also includes:

[0018] Establish a global temperature intelligent control model based on the change law;

[0019] Based on the global temperature intelligent control model, according to the temperature of the hydraulic system outlet of the extruder, the outlet of the non-contact heating device and the water inlet of the online quenching system, the extrusion speed, the current of the non-contact heating device and the water inlet and outlet flow of the online quenching system are adjusted in real time based on the change law and the synchronous control module;

[0020] Obtain the critical cooling rate of online quenching of different alloys based on the global temperature intelligent control model;

[0021] According to the CCT curve under dynamic conditions of critical cooling rate of online quenching of different alloys;

[0022] Determine the water inlet temperature of the online quenching system according to the CCT curve under dynamic conditions;

[0023] The distance between the non-contact heating device and the online quenching system is determined according to the water inlet temperature of the online quenching system.

[0024] Optionally, the non-contact heating device comprises distributed independently adjustable infrared heating elements; the distributed independently adjustable infrared heating elements are arranged in a two-petal structure that opens and closes up and down.

[0025] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0026] The present application provides a high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method. The present invention aims at the problem that high-strength aluminum and magnesium alloy profiles cannot be quenched online due to poor formability, low extrusion speed, and large cooling amplitude after extrusion. The scheme of online quenching is implemented on the profile through the extruder hydraulic system, non-contact heating device and online quenching system to ensure that the profile is quenched online in a fully solid solution state. By determining the integrated forming process parameters according to the variation law of the heat exchange coefficient with the process parameters in different preparation stages and the simulation model, and synchronously controlling the extruder hydraulic system, non-contact heating device and online quenching system according to the integrated forming process parameters, the precise control of the temperature during extrusion, heating and quenching can be achieved, which can effectively reduce the instability of product structure performance caused by outlet temperature fluctuations. Compared with traditional offline quenching after extrusion, extrusion-online heating-online quenching can not only shorten the profile preparation process, reduce energy consumption and manufacturing costs, but also reduce quenching warping under the action of traction. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 This is a schematic flow chart of a high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method in one embodiment of the present application;

[0029] Figure 2 A schematic diagram of the principle of a high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method provided in one embodiment of the present application;

[0030] Figure 3 A flow chart of the joint simulation implementation provided in one embodiment of the present application;

[0031] Figure 4 A schematic diagram of an extrusion speed control curve for achieving 420°C isothermal extrusion provided in an embodiment of the present application;

[0032] Figure 5 The extrusion outlet temperature variation curve provided in one embodiment of the present application

[0033] Figure 6 The temperature drop curve of the round bar under air cooling after extrusion provided in one embodiment of the present application

[0034] Figure 7 A comparison diagram of the metallographic structure of a magnesium alloy rod prepared by extrusion-online heating-online quenching forming and the metallographic structure of a magnesium alloy rod prepared by conventional extrusion-offline quenching provided in an embodiment of the present application; wherein, part (a) is the metallographic structure of the magnesium alloy rod prepared by the present application, and part (b) is the metallographic structure of the magnesium alloy rod prepared by conventional extrusion-offline quenching. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0036] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0037] In an exemplary embodiment, Figure 1 and Figure 2 As shown, a high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method is provided, and the method includes the following S101 to S105. Among them:

[0038] S101, establishing a unified constitutive model of a multi-pass forming process according to internal variables of the profile to be quenched; the internal variables include: dislocation density, secondary phase characteristics and grain size;

[0039] S102, based on the unified constitutive model, machine learning is used to determine the variation of the heat exchange coefficient of the corresponding profile at different preparation stages along with the process parameters;

[0040] S103, establishing a joint simulation model; the joint simulation model is used to simulate the profile extrusion process, the online heating and online quenching process, and the profile bending deformation during the online heating and quenching process;

[0041] S104, determining the integrated forming process parameters according to the variation law of the heat exchange coefficient in different preparation stages along with the process parameters and the simulation model; the integrated forming process parameters include: the extrusion speed and temperature of the hydraulic system of the extruder, the current of the non-contact heating device, and the water inlet temperature and the water inlet and outlet flow of the online quenching system;

[0042] S105, controlling the hydraulic system of the extruder, the non-contact heating device and the online quenching system accordingly according to the integrated forming process parameters.

[0043] In order to ensure that the profile is accurately quenched online in a fully solid solution state, and at the same time effectively reduce the instability of product structure and performance caused by outlet temperature fluctuations, the extruder hydraulic system, non-contact heating device current and online quenching system are set in sequence.

[0044] In order to facilitate the extruded profile to pass through the heating zone and to facilitate the maintenance and replacement of the heating element, the non-contact heating device includes distributed and independently adjustable infrared heating elements; the distributed and independently adjustable infrared heating elements are arranged in a two-petal structure that opens and closes up and down.

[0045] like Figure 3 As shown, the multi-scale, multi-physics field coupled joint simulation model that can reflect the deformation-heat transfer-microstructure evolution specifically includes: a main model built using the STAR-CCM+ model and the ABAQUS model, a subordinate model built using DEFORM, and a main model built using the STAR-CCM+ model and the ABAQUS model; the STAR-CCM+ model is used to simulate and calculate the online heating and online quenching processes, and the ABAQUS model is used to simulate and calculate the bending deformation of the profile during the online heating and quenching process; the STAR-CCM+ model inputs the calculated temperature field results into the ABAQUS model for thermal calculation;

[0046] The extrusion simulation model is used to simulate and calculate the profile extrusion process; the extrusion simulation model is a subordinate model of the joint simulation model; the subordinate model is used to input the temperature, stress and strain field distribution results of the profile after extrusion into the main model.

[0047] The information exchange and transmission between the master model and the slave model is realized through the AMESIM platform. The changes in temperature, strain, dynamic and sub-dynamic recrystallization during the extrusion-online heating-online quenching of high-strength aluminum and magnesium alloys, as well as the artificial aging precipitation of secondary phases under different quenching conditions are tracked; by optimizing the integrated forming process parameters, the final microstructure and mechanical properties of the product can be precisely controlled.

[0048] In order to achieve the quantitative characterization of the microstructure evolution and mechanical response of materials during the integrated forming process of extrusion-online heating-online quenching and subsequent aging, a unified constitutive model was established.

[0049] S102 and later also include:

[0050] Establish a global temperature intelligent control model based on the change law;

[0051] Based on the global temperature intelligent control model, according to the temperature of the hydraulic system outlet of the extruder, the outlet of the non-contact heating device and the water inlet of the online quenching system, the extrusion speed, the current of the non-contact heating device and the water inlet and outlet of the online quenching system are adjusted in real time based on the change law and the synchronous control module; the global temperature intelligent control model arranges infrared thermal sensors based on the hydraulic system outlet of the extruder, the outlet of the non-contact heating device and the water inlet of the online quenching system to accurately capture the real-time temperature changes in the three areas;

[0052] Obtain the critical cooling rate of online quenching of different alloys based on the global temperature intelligent control model;

[0053] According to the CCT curve under dynamic conditions of critical cooling rate of online quenching of different alloys;

[0054] Determine the water inlet temperature of the online quenching system according to the CCT curve under dynamic conditions;

[0055] The distance between the non-contact heating device and the online quenching system is determined according to the water inlet temperature of the online quenching system.

[0056] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] Material preparation: Commercial AZ80 alloy is used as the raw material for this case. Its main components are: Al7.5%, Mn0.3%, Zn 0.5%, and the balance is Mg. Horizontal continuous casting rod, the diameter after the surface car skin is Before extrusion, the alloy was solution treated at 390°C for 24 hours.

[0058] Equipment preparation: First use an 800-ton extruder, the diameter of the extrusion barrel is (The ingot diameter is 3mm smaller than the extrusion barrel diameter for easy feeding), the mold is The round rod flat die has an extrusion ratio of 20.25.

[0059] Process preparation: using Figure 3 The simulation process shown in the figure shows that the forming process is as follows: the initial temperature of the billet is 380°C, the initial temperature of the extrusion barrel and the die is 360°C, and in order to ensure the stability of the extrusion outlet temperature, the isothermal extrusion speed curve obtained by simulation is as follows Figure 4 The corresponding extrusion outlet temperature is shown in Figure 5 As shown, the temperature is maintained at about 420℃, with fluctuations within ±5℃. After extrusion, it passes through the heating and insulation zone, is water quenched, and then aged at 170℃ for 5h. In order to compare with the round bars prepared by the traditional off-line quenching process after extrusion, the extruded round bars are air-cooled, solid-solution treated at 420℃ for 3h, and then water quenched, and then aged at 170℃ for 5h, and the microstructures and properties of the two are compared. Figure 6 It can be seen that the temperature of the round bar drops significantly under air cooling conditions after it leaves the die.

[0060] Organization and performance testing:

[0061] According to GB / T13298-2015 "Methods for the inspection of metal microstructures", the grain structure of the metallographic specimen was observed under an optical microscope. Due to the long-term high-temperature heating of the solid solution, the grain structure of the magnesium alloy bar prepared by extrusion-online heating-online quenching is ( Figure 7 (a) of the conventional extrusion-offline quenching magnesium alloy rod grain structure ( Figure 7 (b) The average grain size increases from about 10 μm to about 20 μm.

[0062] According to GB / T228-2010 "Room Temperature Tensile Test Method for Metallic Materials", the prepared magnesium alloy material was subjected to a quasi-static tensile test to test its tensile strength and elongation. As shown in Table 1, compared with the various performance indicators of the magnesium alloy bar prepared by extrusion-online heating-online quenching, the yield strength and tensile strength of the magnesium alloy bar prepared by conventional extrusion-offline quenching are basically the same, while the elongation is reduced by about 2%.

[0063] Table 1 Quasi-static tensile test results

[0064]

[0065]

[0066] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0067] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method, characterized in that: The high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method comprises: A unified constitutive model of a multi-pass forming process is established according to internal variables of the profile to be quenched; the internal variables include: dislocation density, secondary phase characteristics and grain size; According to the unified constitutive model, machine learning is used to determine the variation of the heat exchange coefficient of the corresponding profiles at different preparation stages along with the process parameters; Establishing a joint simulation model; the joint simulation model is used to simulate the profile extrusion process, the online heating and online quenching process, and the profile bending deformation during the online heating and quenching process; Determine the integrated forming process parameters according to the variation law of the heat exchange coefficient with the process parameters in different preparation stages and the simulation model; the integrated forming process parameters include: the extrusion speed and temperature of the hydraulic system of the extruder, the current of the non-contact heating device, and the water inlet temperature and the water inlet and outlet flow of the online quenching system; The extruder hydraulic system, non-contact heating device and online quenching system are controlled accordingly according to the integrated forming process parameters.

2. The high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method according to claim 1 is characterized in that: The joint simulation model specifically includes: a main model built using the STAR-CCM+ model and the ABAQUS model, a subordinate model built using DEFORM, and a main model built using the STAR-CCM+ model and the ABAQUS model; The STAR-CCM+ model is used to simulate and calculate the online heating and online quenching process; the ABAQUS model is used to simulate and calculate the bending deformation of the profile during the online heating and quenching process; the STAR-CCM+ model inputs the calculated temperature field results into the ABAQUS model for thermal calculation; The extrusion simulation model is used to simulate and calculate the profile extrusion process; the extrusion simulation model is a subordinate model of the joint simulation model; the subordinate model is used to input the temperature, stress and strain field distribution results of the profile after extrusion into the main model.

3. The high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method according to claim 2 is characterized in that: The information exchange and transmission between the master model and the slave model is realized through the AMESIM platform.

4. The high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method according to claim 1 is characterized in that: According to the unified constitutive model, machine learning is used to determine the variation of the heat exchange coefficient of the corresponding profiles at different preparation stages with the process parameters, and then it also includes: Establish a global temperature intelligent control model based on the change law; Based on the global temperature intelligent control model, according to the temperature of the hydraulic system outlet of the extruder, the outlet of the non-contact heating device and the water inlet of the online quenching system, the extrusion speed, the current of the non-contact heating device and the water inlet and outlet flow of the online quenching system are adjusted in real time based on the change law and the synchronous control module; Obtain the critical cooling rate of online quenching of different alloys based on the global temperature intelligent control model; According to the CCT curve under dynamic conditions of critical cooling rate of online quenching of different alloys; Determine the water inlet temperature of the online quenching system according to the CCT curve under dynamic conditions; The distance between the non-contact heating device and the online quenching system is determined according to the water inlet temperature of the online quenching system.

5. The high-strength aluminum and magnesium alloy extrusion-online heating-online quenching forming method according to claim 1, characterized in that: The non-contact heating device comprises distributed independently adjustable infrared heating elements; the distributed independently adjustable infrared heating elements are arranged in a two-petal structure that opens and closes up and down.

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