Experimental device for heat treatment of thin-wall magnesium alloy casting

Abstract

The utility model relates to an experimental device for heat treatment of a thin-wall magnesium alloy casting in the technical field of heat treatment of magnesium alloy castings, which comprises a furnace body and a furnace chamber, an electric heating device is wound on the outer side of the furnace chamber, a heat shielding device is arranged between the inner side wall of the furnace chamber and the magnesium alloy casting, and an upper area temperature sensor, a middle area temperature sensor and a lower area temperature sensor are arranged on the side wall of the furnace body; a top cover is hermetically arranged at the top of the furnace body, a rotating shaft penetrates through the center of the top cover, a fan is arranged below the top cover and penetrates through the top in the furnace cavity, and a protective gas inlet is formed in the bottom of the furnace cavity, is connected with a gas control cabinet through a gas inlet pipe and is used for filling protective gas into the furnace cavity. The device can be applied to heat treatment experiment verification of a thin-wall magnesium alloy casting with the wall thickness of less than 3mm, the furnace body is sealed, SF6 gas is introduced firstly, then argon is introduced for protecting the atmosphere, and the problems of environmental pollution and personnel harm caused by sulfur dioxide gas generated by a traditional process are solved; and meanwhile, the problems of overburning and local high temperature of the thin-wall magnesium alloy casting easily occurring in the heat treatment process are solved.

Description

Technical Field

[0001] The utility model belongs to the technical field of heat treatment of magnesium alloy castings, and particularly relates to an experimental device for heat treatment of thin-wall magnesium alloy castings. Background Technique

[0002] Magnesium alloy is an alloy material composed of magnesium as the base and other elements (such as aluminum, zinc, manganese, cerium, thorium, and a small amount of zirconium or cadmium). It has the characteristics of low density (about 1.8 g / cm 3 ), high strength, large elastic modulus, good heat dissipation, good shock absorption, greater ability to withstand impact loads than aluminum alloy, and good corrosion resistance. It is widely used in portable instruments and the automotive industry to achieve the purpose of lightweight. Among them, the most widely used is magnesium-aluminum alloy, mainly used in the fields of aviation, aerospace, transportation, chemical industry, rockets, etc. Although the specific gravity of magnesium alloy is heavier than that of plastic, the strength and elastic modulus per unit weight are higher than those of plastic. Therefore, in the case of parts with the same strength, the parts made of magnesium alloy (generally magnesium alloy castings) can be made thinner and lighter than those made of plastic. In addition, because the specific strength of magnesium alloy is also higher than that of aluminum alloy and iron, the weight of aluminum or iron parts can be reduced without reducing the strength of the parts. In order to enhance the mechanical properties of magnesium alloy, heat treatment of magnesium alloy castings is usually required, especially for thin-wall magnesium alloy castings.

[0003] Traditional heat treatment of magnesium alloy castings generally uses ferrous sulfide as a protective agent, which generates sulfur dioxide gas in the furnace body during heating to form gas protection for the castings. However, sulfur dioxide gas is toxic, which not only affects the environment but also causes certain health hazards to the operators when inhaled. Moreover, in the existing technology, the temperature control performance of the heat treatment furnace body for magnesium alloy castings is not good. And the wall thickness of thin-wall magnesium alloy castings is relatively thin. Therefore, during the heating process of thin-wall magnesium alloy castings, it is very easy to occur overheating and local high temperature, which may lead to problems such as softening and deformation of the castings, and is not conducive to ensuring the heat treatment performance of thin-wall magnesium alloy castings. Therefore, there is an urgent need for corresponding technical improvement and perfection of the heat treatment device for thin-wall magnesium alloy castings. Summary of the Utility Model

[0004] In view of the above situation, the utility model provides an experimental device for heat treatment of thin-wall magnesium alloy castings, which can be applied to the heat treatment experimental verification of thin-wall magnesium alloy castings with a wall thickness of less than 3 mm. By adopting a furnace body sealing design and a gas protection method of first introducing SF6 gas and then introducing argon gas, the problem of environmental pollution and personnel harm caused by sulfur dioxide gas generated by the traditional process is solved; at the same time, through good temperature control performance settings, the problems of overburning and local high temperature that are likely to occur during the heat treatment process are solved.

[0005] In order to achieve the above purposes, the utility model adopts the following technical solutions:

[0006] An experimental device for heat treatment of thin-walled magnesium alloy castings comprises a heating furnace, and an electric control cabinet and a gas control cabinet arranged outside the heating furnace. The heating furnace comprises a cylindrical vertical shaft furnace body, and a furnace chamber coaxially sleeved in the middle of the furnace body for placing the thin-walled magnesium alloy castings, an electric heating device is coaxially wound between the outer wall of the furnace chamber and the furnace body, a heat shielding device is isolated between the inner wall of the furnace chamber and the thin-walled magnesium alloy castings, and three temperature sensors for correspondingly measuring the temperatures of the upper, middle and lower regions inside the furnace chamber are respectively arranged on the upper, middle and lower parts of the right side wall of the furnace body.

[0007] A circular opening is provided at the center of the top of the furnace body, an openable and closable top cover is provided above the opening, an asbestos rope sealing ring is provided between the top cover and the opening, a lifting and swinging arm mechanism for lifting and removing the top cover is provided above the right side wall of the furnace body, and a hydraulic cylinder can be preferably used, a through hole is vertically provided through the center of the top cover, a rotating shaft is movably provided in the through hole, a fan is provided under the top cover, a motor is provided above the top cover, the inside of the top cover is filled with heat insulation material, and the output end of the motor is connected to the fan through a rotating shaft.

[0008] An openable and closable cover is provided on the top of the furnace cavity, and a fan window for the fan to pass through is provided in the center of the cover. A protective gas inlet is provided at the bottom of the furnace cavity. The protective gas inlet is connected to the gas control cabinet through an inlet pipe and is used to fill the furnace cavity with protective gas. The fan, electric heating device and temperature sensors are all electrically connected to the electric control cabinet.

[0009] Preferably, the furnace body is made of 8mm thick Q235 steel shell, with a circular top plate welded on the upper end and a disc-shaped bottom plate sealed and welded on the lower end. The sealing of the furnace body needs to be ensured, and legs made of channel steel are provided under the bottom plate.

[0010] Preferably, the electric heating device is a spiral resistance wire heater, which generates heat when powered on, and then heats the magnesium alloy casting in the furnace cavity by heat radiation, and a heat-insulating material is filled between the resistance wire heater and the furnace body.

[0011] Preferably, the heat shielding device is a metal heat shielding cover made of stainless steel, which is used to prevent the heat source radiation of the resistance wire heater from causing local overheating of the thin-walled magnesium alloy casting.

[0012] Preferably, each of the temperature sensors is a thermocouple, the inner ends of the three thermocouples horizontally penetrate the right side wall of the furnace body and abut against the outer wall of the furnace cavity, and heat-resistant sealing rings are respectively provided at the perforated joints between the outer end of each thermocouple and the outer wall of the furnace body.

[0013] Preferably, the fan is a steplessly variable speed centrifugal fan for stirring the gas inside the furnace cavity to form circulating heat convection, thereby achieving uniform furnace temperature at various locations inside the furnace cavity.

[0014] Preferably, both the upper and lower ends of the inner wall of the furnace body are designed with 45° chamfers to enhance the air flow circulation speed inside the furnace body.

[0015] Preferably, an inflation pressure gauge is arranged vertically through the left side of the top cover to detect the pressure of the protective gas filled inside the furnace body.

[0016] Preferably, an argon gas cylinder and a sulfur hexafluoride gas cylinder, a pressure gauge one and a pressure gauge two for detecting the argon gas pressure and the sulfur hexafluoride pressure respectively, and a gas switch one and a gas switch two for controlling the argon gas inflation and the sulfur hexafluoride gas inflation respectively are arranged inside the gas control cabinet.

[0017] Preferably, a button panel, an instrument panel, a touch screen, a fan speed regulation panel and a temperature control alarm device for controlling each electrical component are arranged on the electric control cabinet.

[0018] The present utility model further includes other components that enable it to be used normally, which are all conventional means in the art. In addition, the devices or components not defined in the present utility model, such as: resistance wire heaters, thermocouples, fans, hydraulic cylinders, the gas control cabinet and the electric control cabinet and their internal settings, etc., all adopt the existing technologies in the art.

[0019] The beneficial effects of the present utility model are as follows:

[0020] The experimental device for heat treatment of thin-walled magnesium alloy castings provided by the present utility model can be used for experimental verification of heat treatment of thin-walled magnesium alloy castings with a wall thickness of less than 3 mm. The furnace body is designed with a sealed structure. During the heat treatment process, first, SF6 gas is introduced. After about 20 s, argon gas is introduced until the pressure reaches 0.02 MPa. After the pressure inside the furnace body is kept constant, power is supplied. The heating and heat preservation processes respectively follow the set heating-up and heat preservation programs and times, and the furnace temperature fluctuation does not exceed ±3°C. It solves the problems of environmental pollution and personnel hazards caused by the generation of sulfur dioxide gas in the traditional process; at the same time, the device has good temperature control performance, can solve the problems such as overburning and local high temperature that easily occur during the heat treatment process of thin-walled magnesium alloy parts, resulting in softening and deformation of the castings, and ensures the heat treatment performance of thin-walled magnesium alloy castings. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of the experimental device for heat treatment of thin-walled magnesium alloy castings in the embodiment. Detailed Embodiments

[0022] Next, the technical solutions of the present utility model will be clearly and completely described in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present utility model, rather than all embodiments.

[0023] It should be noted that the terms "upper", "lower", "front", "back", "left", "right", "inside", "outside" and the like indicating directions or positional relationships are based on the accompanying drawings and are only for the convenience of description.

[0024] Example

[0025] like Figure 1 As shown, an experimental device for heat treatment of thin-walled magnesium alloy castings includes a heating furnace, and an electric control cabinet 1 and a gas control cabinet 2 arranged on the outside of the heating furnace, the heating furnace includes a cylindrical vertical shaft furnace body 3, and a furnace chamber 4 coaxially sleeved in the middle of the furnace body for placing thin-walled magnesium alloy castings, the furnace body has an outer dimension of φ900mm×800mm, and the furnace chamber has an effective working space of φ300mm×300mm. An electric heating device 5 is coaxially wound between the outer wall of the furnace chamber and the furnace body, a heat shielding device 6 is isolated between the inner wall of the furnace chamber and the thin-walled magnesium alloy casting, and three temperature sensors 7 for correspondingly measuring the temperatures of the upper, middle and lower regions inside the furnace chamber are respectively arranged on the upper, middle and lower parts of the right side wall of the furnace body.

[0026] A circular opening is provided at the center of the top of the furnace body, an openable and closable top cover 8 is provided above the opening, an asbestos rope sealing ring 9 is provided between the top cover and the opening, a lifting and swinging arm mechanism 10 for lifting and removing the top cover is provided above the right side wall of the furnace body, the lifting and swinging arm mechanism is a hydraulic cylinder, a through hole is vertically provided through the center of the top cover, a rotating shaft 11 is movably provided in the through hole, a fan 12 is provided under the top cover, a motor 13 is provided above the top cover, the inside of the top cover is filled with heat insulating material 14, and the output end of the motor is connected to the fan through a rotating shaft.

[0027] An openable cover plate 15 is provided on the top of the furnace cavity, and a fan window for the fan to pass through is provided in the center of the cover plate. A protective gas inlet 16 is provided at the bottom of the furnace cavity. The protective gas inlet is connected to the gas control cabinet through an inlet pipe 17, and is used to fill the furnace cavity with protective gas. The fan, electric heating device and various temperature sensors are electrically connected to the electric control cabinet.

[0028] Specifically, the furnace body is made of 8mm thick Q235 steel shell, with a circular top plate 18 welded on the upper end, and a disc-shaped bottom plate 19 sealed and welded on the lower end. An overflow groove 20 is also provided in the center of the bottom plate. An air pressure gauge 21 is provided from top to bottom on the left side of the top cover to detect the pressure of the protective gas filled into the furnace body. After the top plate and the bottom plate of the furnace body are welded, a sealing test is required. If the leakage is not greater than 0.01MPa under a pressure of 0.05MPa for 10 minutes, it means that the sealing of the furnace body is good; a support leg made of channel steel is provided under the bottom plate to support the entire furnace body.

[0029] Specifically, the electric heating device is a spiral resistance wire heater, which generates heat when powered on, and then heats the magnesium alloy casting in the furnace cavity by heat radiation, and a heat-insulating material 22 is filled between the resistance wire heater and the furnace body, such as heat-insulating rock wool, etc. The resistance wire heater and the heat-insulating material are both based on existing technologies, and the specific configuration is not described in detail here.

[0030] Specifically, the heat shielding device is a metal heat shielding cover made of stainless steel, which is used to prevent the heat source radiation of the resistance wire heater from causing local overheating of the thin-walled magnesium alloy casting. A 3mm thick heat-resistant stainless steel heat radiation shielding device is used to prevent the heat source of the furnace wire from directly radiating on the magnesium alloy workpiece to cause local overheating and overburning that affect the performance of the casting or cause safety accidents. It plays a protective role against deformation or combustion caused by uneven heating during the heat treatment process of thin-walled and easily deformed magnesium alloy castings and ensures that the heat treatment performance meets the requirements. The process curve adopts a programming mode to achieve slow heating throughout the process and avoid the phenomenon of large fluctuations in the furnace temperature after reaching a high point. The stainless steel heat radiation shielding device adopts existing technology, and the specific settings will not be described in detail here.

[0031] Specifically, each of the temperature sensors is a thermocouple, and the inner ends of the three thermocouples horizontally penetrate the right side wall of the furnace body and touch the outer wall of the furnace cavity, and the perforated joints between the outer end of each thermocouple and the outer wall of the furnace body are respectively provided with a heat-resistant sealing ring 30. The temperature control in the furnace adopts the middle zone temperature control and the upper and lower zone monitoring method. The thermocouple specification adopts a diameter of 3mm nickel-chromium-constantan I grade accuracy to achieve accurate collection of temperature data. The upper and lower three-zone furnace temperature control and monitoring are adopted, and the temperature control accuracy is ±3°C, which is higher than the temperature control accuracy of traditional heat treatment solid solution furnaces and can achieve continuous and real-time effective control of the overall furnace temperature without exceeding the maximum temperature specified by the process. The thermocouple adopts existing technology, and the specific settings will not be described in detail here.

[0032] Specifically, the fan adopts an impeller-type stepless speed-variable centrifugal fan, which is used to stir the gas inside the furnace cavity to form circulating heat convection, thereby achieving furnace temperature uniformity at various locations inside the furnace cavity.

[0033] Specifically, the upper and lower ends of the inner wall of the furnace body are designed with 45° chamfers, the furnace body adopts a well-type furnace body design, and a 45° backflow design is adopted to enhance the airflow circulation speed; a stepless variable speed fan with a maximum speed of 2500r / min (adjustable speed) is installed on the top cover of the furnace body, and circulating heat convection is used to achieve temperature uniformity in all parts of the furnace cavity.

[0034] Specifically, an argon gas cylinder 23 and a sulfur hexafluoride gas cylinder 24 are arranged inside the pneumatic control cabinet, a first pressure gauge and a second pressure gauge for correspondingly detecting the argon gas pressure and the sulfur hexafluoride gas pressure, and a first gas switch and a second gas switch for correspondingly controlling the argon gas inflation and the sulfur hexafluoride gas inflation. The atmosphere inside the furnace adopts an inert gas protection method, which is green and environment-friendly. The furnace cavity has good sealing performance. During operation, SF6 + argon protective gas is introduced into the furnace. The atmosphere inside the furnace is safe and environment-friendly, and can effectively prevent the oxidation of magnesium alloy castings and play a protective role.

[0035] Specifically, a button panel 25, an instrument panel 26, a touch screen 27, a fan speed regulation panel 28 and a temperature control alarm device 29 (with high-temperature alarm and over-temperature power-off functions) for controlling each electrical component are arranged on the electric control cabinet. An over-temperature control system is arranged inside the electric control cabinet to prevent high-temperature safety accidents. An audible and visual over-temperature alarm and a system automatic power-off device are adopted. A PLC programmable control circuit is arranged inside the electric control cabinet. Both the electric control cabinet and the pneumatic control cabinet adopt existing technologies, and the specific settings are not described in detail here.

[0036] The specific operation steps of the present utility model are as follows:

[0037] 1. Before using the device, check whether the fan, sealing ring, etc. of the equipment device are in good condition, and whether the air pressures of the argon gas cylinder and the sulfur hexafluoride (SF6) gas cylinder are normal, etc.

[0038] 2. Turn on the power supply, start the program control panel, and set the heating and heat preservation process programs in the process curve module. Generally, it is set to heat up to 300 °C in 120 minutes, start heating after heat preservation for 60 min, heat up to the solution temperature of 410 °C in 120 minutes, and cut off the power supply and cool in the furnace after heat preservation for 12 - 18 hours.

[0039] 3. Load the thin-walled magnesium alloy casting, open the SF6 valve, send gas at a pressure of 0.02 MPa for 20 s, and close the furnace cover; close the SF6 valve, open the argon valve, and keep the air pressure inside the furnace body at 0.01 - 0.02 MPa. Keep the argon valve open throughout the operation process.

[0040] 4. Start the fan, press the power-on button, and the program starts.

[0041] 5. After the program runs to completion, cut off the power supply of the heating system, automatically close the other systems, and cool the casting in the furnace.

[0042] The technical solution of the present utility model is not limited to the above specific embodiments. Without departing from the scope and spirit of the described embodiments, many modifications and changes are obvious to those of ordinary skill in the art. Any technical deformation made within the spirit and principle of the present utility model falls within the protection scope of the present utility model.

Claims

1. An experimental device for heat treatment of thin-walled magnesium alloy castings, characterized in that: The invention comprises a heating furnace, and an electric control cabinet and a gas control cabinet arranged outside the heating furnace. The heating furnace comprises a cylindrical shaft-type furnace body, and a furnace cavity coaxially sleeved in the middle of the furnace body for placing thin-walled magnesium alloy castings. An electric heating device is coaxially wound between the outer wall of the furnace cavity and the furnace body, and a heat shielding device is arranged to isolate the inner wall of the furnace cavity from the thin-walled magnesium alloy castings. Three temperature sensors for correspondingly measuring the temperatures of the upper, middle and lower layers of the furnace cavity are arranged on the upper, middle and lower parts of the right side wall of the furnace body respectively; a circular opening is opened in the center of the top of the furnace body, an openable top cover is arranged above the opening, and an asbestos rope sealing ring is arranged between the top cover and the opening. A lifting swing arm mechanism for lifting and removing the top cover is arranged above the right side wall of the furnace body, a through hole is vertically opened through the center of the top cover, a rotating shaft is movably inserted in the through hole, a fan is arranged below the top cover, a motor is arranged above the top cover, the inside of the top cover is filled with heat insulation material, the output end of the motor is connected to the fan through the rotating shaft, an openable cover is arranged on the top of the furnace cavity, a fan window for the fan to pass through is arranged in the center of the cover, a protective gas inlet is arranged at the bottom of the furnace cavity, the protective gas inlet is connected to the gas control cabinet through an inlet pipe, and is used to fill the furnace cavity with protective gas, and the fan, electric heating device and each temperature sensor are electrically connected to the electric control cabinet.

2. The experimental device for heat treatment of thin-walled magnesium alloy castings according to claim 1, characterized in that: The furnace body is made of 8mm thick Q235 steel shell, with a circular top plate welded on the upper end and a disc-shaped bottom plate sealed and welded on the lower end, and legs made of channel steel are arranged under the bottom plate.

3. An experimental device for heat treatment of thin-walled magnesium alloy castings according to claim 1, characterized in that: The electric heating device is a spiral resistance wire heater, and a heat-insulating material is filled between the resistance wire heater and the furnace body.

4. An experimental device for heat treatment of thin-walled magnesium alloy castings according to claim 2, characterized in that: The heat shielding device is a metal heat shielding cover made of stainless steel, which is used to prevent the heat source radiation of the resistance wire heater from causing local overheating of the thin-walled magnesium alloy casting.

5. An experimental device for heat treatment of thin-walled magnesium alloy castings according to claim 3, characterized in that: Each of the temperature sensors is a thermocouple, the inner ends of the three thermocouples horizontally penetrate the right side wall of the furnace body and abut against the outer wall of the furnace cavity, and the perforated joints between the outer ends of the thermocouples and the outer wall of the furnace body are respectively provided with heat-resistant sealing rings.

6. An experimental device for heat treatment of thin-walled magnesium alloy castings according to claim 1, characterized in that: The fan adopts a stepless speed-variable centrifugal fan, which is used to stir the gas inside the furnace cavity to form circulating heat convection, so as to achieve uniform furnace temperature in various parts inside the furnace cavity.

7. An experimental device for heat treatment of thin-walled magnesium alloy castings according to claim 6, characterized in that: The upper and lower ends of the inner wall of the furnace body are both chamfered at 45° to increase the air circulation speed inside the furnace body.

8. An experimental device for heat treatment of thin-walled magnesium alloy castings according to claim 1, characterized in that: A gas pressure gauge is provided on the left side of the top cover from top to bottom to detect the pressure of the protective gas filled into the furnace body.

9. An experimental device for heat treatment of thin-walled magnesium alloy castings according to claim 8, characterized in that: The gas control cabinet is provided with an argon gas cylinder and a sulfur hexafluoride gas cylinder, a pressure gauge 1 and a pressure gauge 2 for correspondingly detecting the argon pressure and the sulfur hexafluoride pressure, and a gas switch 1 and a gas switch 2 for correspondingly controlling the argon gas filling and the sulfur hexafluoride gas filling.

10. An experimental device for heat treatment of thin-walled magnesium alloy castings according to claim 1, characterized in that: The electric control cabinet is provided with a button panel, an instrument panel, a touch screen, a fan speed control panel and a temperature control alarm device for controlling various electrical components.

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