Liquid nitrogen cooling shielding gas system for regulating and controlling welding residual stress

Abstract

The invention discloses a liquid nitrogen cooling shielding gas system for regulating and controlling welding residual stress, and relates to the technical field of welding equipment. Protective gas of the liquid nitrogen cooling protective gas system flows out of a protective gas cylinder, is conveyed to a gas inlet valve of a temperature control liquid nitrogen cooling device through a gas inlet pipeline, enters a gas inlet heat exchange pipe located in a liquid nitrogen tank, flows through a gas outlet heat exchange pipe to be cooled, and then reaches a protective gas spray head of a welding platform from a gas outlet valve through a gas outlet pipeline. The temperature sensor is located at the front end of an arm of the welding robot, detects the center temperature of a welding shielding gas acting area and transmits the center temperature to the control cabinet in real time, an instruction is sent to the lifting table after program processing and analysis of the control cabinet, and shielding gas temperature change is achieved through vertical movement of the shielding gas cooler. Cooling protection gas with the set temperature can be locally applied to the welding seam of the workpiece, active cooling and thermal tension are generated, formation of incompatible compression plastic strain and thermal stress is controlled, and the purpose of controlling residual stress and welding deformation is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of welding equipment, and in particular to a liquid nitrogen cooling protective gas system for regulating welding residual stress. Background Art

[0002] Welding residual stress is inevitable in the welding process. Welding residual stress is mainly caused by the combined effects of thermal stress, phase change stress, plastic deformation and structural constraints caused by non-uniform heating and cooling. During the welding process, the rapid heating and cooling of the weld area leads to uneven expansion and contraction, accompanied by phase change and high-temperature plastic deformation, which causes irreversible residual stress to form in the weld area after cooling. Especially in multi-layer and multi-pass welding and complex structures, the geometric constraints of the structure further aggravate the accumulation of stress. Excessive welding residual stress will cause uneven shrinkage or warping of the welded parts, resulting in dimensional accuracy deviation, affecting the installation and use of the structure. At the same time, welding residual stress will also damage the fatigue resistance and corrosion resistance of the weld position. Moreover, due to the effect of residual stress, the welded structure already has internal stress under the condition of no external force, which may weaken the strength of the welded joint, reduce its bearing capacity, and affect the performance of the welded structure.

[0003] Common methods for reducing welding residual stress include post-weld heat treatment, vibration aging, preheating and post-heat treatment, local heat treatment and mechanical stress release (such as stretching, hammering), etc., but heat treatment is suitable for thick plates and large structures. However, its limitations are that it is time-consuming and energy-consuming, and is not suitable for thin plates or structures with limited size. The effect of vibration aging is difficult to quantify, and the effect on complex geometric structures is limited. Mechanical stress release is complicated to operate, has high requirements for the force application method and force uniformity, and will cause damage to the surface of the component. Preheating and post-heat treatment, local heat treatment will increase the complexity of the process, and there are limitations for materials that are not resistant to high temperatures. In addition, it is difficult to realize welding automation for the above methods. The local heat tensioning method uses a trailing radiator to generate active cooling and thermal tension on the hot metal between the radiator and the heat source, and controls the formation of incompatible compressive plastic strain and thermal stress. However, the trailing radiator requires additional equipment, and due to the influence of the coolant on the welding process, the scope of use is limited. For example, liquid nitrogen trailing cooling can be directly applied to stir friction welding, but it is not used for fusion welding. Summary of the invention

[0004] The purpose of the present invention is to provide a liquid nitrogen cooling shielding gas system for regulating welding residual stress, so as to reduce or eliminate welding residual stress and deformation, and solve the technical problems that the current trailing radiator has a limited scope of use due to the influence of the coolant on the welding process, cannot adapt to a variety of welding methods and is difficult to automate.

[0005] In order to achieve the above-mentioned object, one embodiment of the present invention provides a liquid nitrogen cooling shielding gas system for regulating welding residual stress, including a temperature-controlled liquid nitrogen cooling device, a shielding gas delivery pipeline, a welding shielding gas cylinder, a welding platform, and a control cabinet;

[0006] The temperature-controlled liquid nitrogen cooling device consists of a liquid nitrogen tank, a lifting platform, and a protective gas cooler. The liquid nitrogen tank body is an insulated outer shell, which is isolated from contact with the air environment to prevent liquid nitrogen from volatilizing. The upper part is a handrail ring, which is convenient for carrying and protecting the lifting platform and the protective gas cooler in the ring. The insulating sealing ring is in close contact with the outer surface of the protective gas cooler to prevent liquid nitrogen leakage and a large amount of external heat from being transferred to the liquid nitrogen cooling tank. The inner ring of the insulating sealing ring is composed of 15 inner teeth in a circular array.

[0007] Preferably, it is characterized in that the lifting platform located on the upper part of the temperature-controlled liquid nitrogen cooling device is composed of three multi-section hydraulic cylinders and a bearing platform which are equidistantly arranged in a circle on the liquid nitrogen tank body, the upper end of the multi-section hydraulic cylinder is connected to the bearing platform, the bearing platform is fixed to the upper end of the protective gas cooler, and the three multi-section hydraulic cylinders are lifted and lowered simultaneously to drive the bearing platform to move, thereby realizing the up and down movement of the protective gas cooler in the liquid nitrogen tank.

[0008] Preferably, it is characterized in that the upper end of the protective gas cooler is respectively connected to the air inlet valve and the air outlet valve (132), which are respectively connected to the air inlet pipeline and the air outlet pipeline. The surface of the protective gas cooler is provided with 15 cooling fins in an equidistant array around the circumference to increase the contact area with the liquid nitrogen and achieve a better heat exchange effect. The surface of the cooling fins is in close contact with the inner ring of the thermal sealing ring. The air inlet heat exchange pipe and the air outlet heat exchange pipe are distributed in a spiral rotation inside the protective gas cooler and are in close contact with the inner walls of the 15 cooling fins. The upper part passes through the sealing cover and is respectively connected to the air inlet valve and the air outlet valve.

[0009] Preferably, it is characterized in that one end of the air inlet pipeline is connected to the air inlet valve and the other end is connected to the welding shielding gas cylinder to provide welding shielding gas, and one end of the air outlet pipeline is connected to the air outlet valve and the other end is connected to the shielding gas nozzle of the welding platform (4) to provide a protective environment for the welding process.

[0010] Preferably, it is characterized in that the welding platform is composed of a temperature sensor, the protective gas nozzle, a welding robot (43), and a clamp platform, and the temperature sensor is located at the front end of the welding robot arm and is used to detect the central temperature of the welding protective gas action area.

[0011] Preferably, it is characterized in that the temperature sensor transmits the detected temperature signal to the control cabinet, and after its program processing and analysis, the command is sent to the lifting platform to control the lifting of the multi-stage hydraulic cylinder to achieve the up and down movement of the protective gas cooler in the liquid nitrogen tank. The control cabinet can set the temperature range of the cooling area. If the temperature is too high, the lifting platform will be controlled to lower the protective gas cooler to immerse more part of it in liquid nitrogen to lower the temperature of the protective gas. When the temperature of the cooling area drops to the set temperature range, it will no longer drop. When the temperature is lower than the set temperature range, the protective gas cooler rises until the temperature sensor detects that the cooling area reaches the set temperature range.

[0012] The beneficial effect of the present invention is that a liquid nitrogen cooling shielding gas system for regulating welding residual stress is provided. The welding shielding gas is transported to the inlet valve of the temperature-controlled liquid nitrogen cooling device through the inlet pipe, and the temperature drops after passing through the shielding gas cooler. Then, the shielding gas is transported to the shielding gas nozzle through the outlet valve and the outlet pipe to act on the weld position, generating active cooling and thermal tension on the hot metal, and controlling the formation of incompatible compressive plastic strain and thermal stress, reducing residual stress and welding deformation, and at the same time, since the liquid nitrogen does not directly contact the weld area, but cools the shielding gas to achieve the cooling purpose, it is suitable for a variety of welding methods, and the temperature sensor can detect the temperature of the cooling area, and the shielding gas cooler is controlled to rise or fall through the control cabinet to achieve shielding gas output at different temperatures, which is suitable for a variety of process intervals, achieves different cooling effects, and achieves the best residual stress and welding deformation control. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A cross-sectional view of a temperature-controlled liquid nitrogen cooling device of a liquid nitrogen cooling protective gas system for regulating welding residual stress provided in an embodiment of the present application.

[0014] Figure 2 A schematic structural diagram of a thermal insulation sealing ring of a liquid nitrogen cooling protective gas system for regulating welding residual stress provided in an embodiment of the present application.

[0015] Figure 3 A structural schematic diagram of a lifting platform of a liquid nitrogen cooling protective gas system for regulating welding residual stress provided in an embodiment of the present application.

[0016] Figure 4 A schematic structural diagram of a shielding gas cooler of a liquid nitrogen cooling shielding gas system for regulating welding residual stress provided in an embodiment of the present application.

[0017] Figure 5 A schematic diagram of the internal heat exchange tube structure of a shielding gas cooler of a liquid nitrogen cooling shielding gas system for regulating welding residual stress provided in an embodiment of the present application.

[0018] Figure 6 A schematic diagram of the structure of a liquid nitrogen cooling shielding gas system for regulating welding residual stress provided in an embodiment of the present application.

[0019] 1. Temperature-controlled liquid nitrogen cooling device; 11. Liquid nitrogen tank; 12. Lifting platform; 111. Insulating shell; 112. Handrail ring; 113. Insulating sealing ring; 121. Multi-stage hydraulic cylinder; 122. Carrying platform; 13. Protective gas cooler; 131. Inlet valve; 132. Outlet valve; 133. Heat dissipation fins; 134. Inlet heat exchange pipe; 135. Outlet heat exchange pipe; 136. Sealing cover;

[0020] 2. Protective air pipeline; 21. Inlet pipeline; 22. Outlet pipeline;

[0021] 3. Welding protection gas cylinder;

[0022] 4. Welding platform; 41. Temperature sensor; 42. Shielding gas nozzle; 43. Welding robot; 44. Fixture platform;

[0023] 5. Control cabinet; DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0025] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connection", "matching" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] In the description of this embodiment, the terms "upper", "lower", "right", "upper end", "lower end", "front end" and other directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0027] The present invention provides a liquid nitrogen cooling protective gas system for regulating welding residual stress, such as Figure 6As shown, it includes a temperature-controlled liquid nitrogen cooling device 1, a protective gas delivery pipeline 2, a welding protective gas cylinder 3, a welding platform 4, and a control cabinet 5;

[0028] Specifically, Figure 1 , 2 As shown, the temperature-controlled liquid nitrogen cooling device 1 consists of a liquid nitrogen tank 11, a lifting platform 12, and a protective gas cooler 13. The tank body of the liquid nitrogen tank 11 is an insulated outer shell 111, which is isolated from contact with the air environment to prevent liquid nitrogen from volatilizing. The upper part is an armrest ring 112, which is conducive to carrying and protecting the lifting platform 12 and the protective gas cooler 13 in the ring. The insulating sealing ring 113 is in close contact with the outer surface of the protective gas cooler 13 to prevent liquid nitrogen leakage and a large amount of external heat from being transferred to the liquid nitrogen cooling tank. The inner ring of the insulating sealing ring 113 is composed of 15 inner teeth in a circular array, which is tightly fitted with the heat dissipation fins 133 of the protective gas cooler 13 and can slide up and down.

[0029] Specifically, Figure 1 , 3 As shown, the lifting platform 12 located at the upper part of the temperature-controlled liquid nitrogen cooling device 1 is composed of three multi-section hydraulic cylinders 121 and a bearing platform 122 arranged equidistantly in a circle on the tank body of the liquid nitrogen tank 11. The upper end of the multi-section hydraulic cylinder 121 is connected to the bearing platform 122, and the circular bearing platform 122 is fixed to the upper end of the shielding gas cooler 13. The three multi-section hydraulic cylinders 121 are lifted and lowered at the same time, driving the bearing platform 122 to move, so as to realize the up and down movement of the shielding gas cooler 13 in the liquid nitrogen tank 11. When moving upward, the more part of the shielding gas cooler 13 is in the air, the less obvious the cooling effect of the liquid nitrogen tank 11 on the welding shielding gas is. When descending downward, the more part is immersed in the liquid nitrogen tank 11, and the better the cooling effect is.

[0030] Specifically, Figure 4 , 5 As shown, the upper end of the protective gas cooler 13 is respectively connected to the air inlet valve 131 and the air outlet valve 132, the protective gas is input from the air inlet valve 131, and output from the air outlet valve 132, and 15 heat dissipation fins 133 are distributed in an equidistant array on the surface of the protective gas cooler 13 to increase the contact area with the liquid nitrogen and achieve a better heat exchange effect. The surface of the heat dissipation fin 133 is in close contact with the inner ring of the thermal insulation sealing ring 113 to prevent the liquid nitrogen from leaking out, causing the liquid nitrogen to volatilize, and the cooling effect is weakened. The air inlet heat exchange pipe 134 and the air outlet heat exchange pipe 135 are distributed in the protective gas cooler 13 in a spiral rotation, which also achieves the purpose of increasing the contact area, and is in close contact with the inner walls of the 15 heat dissipation fins 133 to enhance the heat exchange effect. The upper part passes through the sealing cover 36 and is respectively connected to the air inlet valve 131 and the air outlet valve 132.

[0031] Specifically, Figure 1 , 6As shown, one end of the air inlet pipeline 21 is connected to the air inlet valve 131, and the other end is connected to the welding shielding gas cylinder 3, which is used to provide welding shielding gas. The shielding gas flows out from the shielding gas cylinder 3, is transported to the air inlet valve of the temperature-controlled liquid nitrogen cooling device 1 through the air inlet pipeline 21, enters the air inlet heat exchange pipe 134 located in the liquid nitrogen tank 11, flows through the air outlet heat exchange pipe 135, and reaches the shielding gas nozzle 42 of the welding platform 4 from the air outlet valve through the air outlet pipeline 22, thereby providing a protective environment for the welding process.

[0032] Specifically, Figure 6 As shown, the welding platform 4 is composed of a temperature sensor 41, the protective gas nozzle 42, a welding robot 43, and a fixture platform 44. The temperature sensor 41 is located at the front end of the welding robot arm and is used to detect the central temperature of the welding protective gas action area and transmit the temperature signal to the control cabinet 5 in real time.

[0033] Specifically, Figure 1 , 6 As shown, the temperature sensor 41 transmits the detected temperature signal to the control cabinet 5. After being processed and analyzed by its program, the instruction is sent to the lifting platform 12 to control the lifting and lowering of the multi-stage hydraulic cylinder 121, so as to realize the up and down movement of the protective gas cooler 13 in the liquid nitrogen tank 11. The control cabinet 5 can set the temperature range of the cooling area. If the temperature is too high, the lifting platform 12 will be controlled to lower the protective gas cooler 13, immerse more parts in liquid nitrogen, reduce the temperature of the protective gas, and the temperature of the area where the protective gas acts on the workpiece will be reduced. When the temperature of the cooling area is reduced to the set temperature range, it will no longer decrease. When the temperature is lower than the set temperature range, the temperature signal is also transmitted to the control cabinet 5 to control the multi-stage hydraulic cylinder 121 to rise, drive the protective gas cooler 13 to move up, reduce the cooling effect, and the protective gas temperature rises accordingly. The temperature of the area where the protective gas acts on the workpiece will also rise. Until the temperature sensor 41 detects that the cooling area reaches the set temperature range, the multi-stage hydraulic cylinder 121 will no longer work, and the protective gas cooler 13 will not move, so as to realize that the temperature of the protective gas action area of ​​the workpiece is within the set temperature range.

[0034] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A liquid nitrogen cooling shielding gas system for regulating welding residual stress, characterized in that: include: Temperature-controlled liquid nitrogen cooling device (1), protective gas delivery pipeline (2), welding protective gas cylinder (3), welding platform (4), control cabinet (5); The temperature-controlled liquid nitrogen cooling device (1) is composed of a liquid nitrogen tank (11), a lifting platform (12), and a protective gas cooler (13). The tank body of the liquid nitrogen tank (11) is an insulating outer shell (111) which is isolated from contact with the air environment to prevent liquid nitrogen from volatilizing. The upper part is a handrail ring (112) which is convenient for carrying and protecting the lifting platform (12) and the protective gas cooler (13) in the ring. The insulating sealing ring (113) is in close contact with the outer surface of the protective gas cooler (13) to prevent liquid nitrogen leakage and a large amount of external heat from being transferred into the liquid nitrogen cooling tank. The inner ring of the insulating sealing ring (113) is composed of 15 inner teeth in a circular array.

2. A liquid nitrogen cooling shielding gas system for regulating welding residual stress according to claim 1, characterized in that: The lifting platform (12) located on the upper part of the temperature-controlled liquid nitrogen cooling device (1) is composed of three multi-section hydraulic cylinders (121) and a bearing platform (122) which are equidistantly arranged in a circle on the tank body of the liquid nitrogen tank (11); the upper end of the multi-section hydraulic cylinder (121) is connected to the bearing platform (122); the bearing platform (122) is fixed to the upper end of the protective gas cooler (13); the three multi-section hydraulic cylinders (121) are lifted and lowered simultaneously, driving the bearing platform (122) to move, thereby realizing the up and down movement of the protective gas cooler (13) on the liquid nitrogen tank (11).

3. The liquid nitrogen cooling protective gas system for regulating welding residual stress according to claim 1, characterized in that: The upper end of the protective gas cooler (13) is respectively connected to an air inlet valve (131) and an air outlet valve (132), and is respectively connected to an air inlet pipeline (21) and an air outlet pipeline (22). Fifteen heat dissipation fins (133) are distributed in an equidistant array on the surface of the protective gas cooler (13) to increase the contact area with liquid nitrogen and achieve a better heat exchange effect. The surface of the heat dissipation fins (133) is in close contact with the inner ring of the thermal insulation sealing ring (113). The air inlet heat exchange pipe (134) and the air outlet heat exchange pipe (135) are distributed in a spiral rotation inside the protective gas cooler (13) and are in close contact with the inner walls of the 15 heat dissipation fins (133). The upper part passes through a sealing cover (136) and is respectively connected to the air inlet valve (131) and the air outlet valve (132).

4. The liquid nitrogen cooling shielding gas system for regulating welding residual stress according to claim 1, characterized in that: One end of the air inlet pipeline (21) is connected to the air inlet valve (131) and the other end is connected to the welding shielding gas cylinder (3) for providing welding shielding gas; one end of the air outlet pipeline (22) is connected to the air outlet valve (132) and the other end is connected to the shielding gas nozzle (42) of the welding platform (4) for providing a protective environment for the welding process.

5. The liquid nitrogen cooling shielding gas system for regulating welding residual stress according to claim 1, characterized in that: The welding platform (4) is composed of a temperature sensor (41), the protective gas nozzle (42), a welding robot (43), and a fixture platform (44); the temperature sensor (41) is located at the front end of the welding robot arm and is used to detect the temperature of the central area of ​​the welding protective gas.

6. A liquid nitrogen cooling shielding gas system for regulating welding residual stress according to claim 5, characterized in that: The temperature sensor (41) transmits the detected temperature signal to the control cabinet (5), and after being processed and analyzed by the program, the command is sent to the lifting platform (12) to control the lifting and lowering of the multi-stage hydraulic cylinder (121) to achieve the up and down movement of the protective gas cooler (13) in the liquid nitrogen tank (11). The control cabinet (5) can set the temperature range of the cooling area. If the temperature is too high, the lifting platform (12) will be controlled to make the protective gas cooler (13) descend, immerse more parts in liquid nitrogen, and reduce the temperature of the protective gas. When the temperature of the cooling area is reduced to the set temperature range, it will no longer decrease. When the temperature is lower than the set temperature range, the protective gas cooler (13) will rise until the temperature sensor (41) detects that the cooling area reaches the set temperature range.

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