Method for reducing residual stress of fusion welding joint of metal structure material in situ

Abstract

The invention relates to a method for reducing residual stress of a fusion welding joint of a metal structure material in situ. A high-speed particle flow with a certain temperature is utilized to impact a weld zone and the vicinity thereof, stress distribution is improved by generating pressure stress on the surface of a joint, the fatigue strength of the joint is improved, and the service life is prolonged. The combination of high-speed particle impact and hot air impact effects can effectively reduce or eliminate residual tensile stress of the component, improve the mechanical property of the joint and prolong the service life of the component. The method can be used for regulating and controlling the residual stress of the fusion welding joint of the metal structure material and also can be used for improving the residual stress distribution of various welding joints of other materials, so that the safety and reliability of the joint are improved, the process is simple, the problem that many parts are not allowed to be disassembled and subjected to post-heat treatment due to factors such as assembly is solved, and the production cost is reduced. The method is one of the most effective, most economical, most flexible and most designable methods, in-situ strengthening of complex parts of different sizes can be achieved, and automation is easy to achieve.

Description

Technical Field

[0001] The invention belongs to the technical field of metal structural material connection, and in particular relates to a method for reducing residual stress of a fusion welding joint. Background Art

[0002] During welding, the weld zone is heated and expanded locally, but is constrained by the parts far from the weld and cannot be extended freely, causing the weld zone to be compressed and plastically deformed; in the subsequent cooling process, the weld zone shrinks, but is constrained by the parts far from the weld zone and cannot be shortened freely, thus generating residual tensile stress after welding. The existence of residual tensile stress will not only reduce the bearing capacity of the component, but also have a significant impact on the accuracy and dimensional stability of the component. At the same time, residual tensile stress is also the main factor causing stress corrosion cracking. Therefore, necessary measures need to be taken to reduce or eliminate residual stress.

[0003] At present, the following methods are mainly used to reduce or eliminate residual stress after welding: First, the hammering method: using a steel hammer to hammer the part where the residual stress of the workpiece is concentrated, so that the surface of the workpiece is subjected to the compressive stress of the hammer and undergoes local plastic deformation, thereby reducing the residual stress peak and improving and balancing the residual stress distribution of the workpiece. However, it is difficult to control the impact force during operation of this method, and excessive force can easily cause work hardening and weld cracking. Second, the heat treatment method: reducing stress by heating the weldment as a whole or locally. The reduction effect mainly depends on the heating temperature, insulation time, weldment composition and organization, cooling rate, etc. This method is time-consuming and not suitable for larger parts. Third, the vibration method: resonance is generated by excitation of the vibration source, so that microscopic plastic deformation occurs inside the metal organization to reduce stress. The equipment used in this method is simple, the processing cost is low, and the time is short. However, it is not recommended to use it on structural parts to prevent fracture and stress corrosion failure. Fourth, the shot peening method: using pellets to bombard the surface of the workpiece and implant residual compressive stress to improve the fatigue strength of the workpiece. This method is low-cost and easy to operate, but the working environment is poor and the unit output is low.

[0004] Patent application number 200910024032.4 discloses a method for reducing residual stress of ferromagnetic metal materials. The method reduces residual stress by treating ferromagnetic metal materials with pulse current and pulse magnetic field. However, this method is only applicable to ferromagnetic materials and cannot reduce residual stress for non-ferromagnetic materials.

[0005] Patent application number 93101690.8 discloses a technology for dynamically controlling residual stress and deformation of thin plate components during welding. During the welding process of thin plate components, the cooling medium is atomized by high-pressure gas, and then the weld that is still in a high temperature state is locally forced to be quenched following the welding heat source. The internal stress and deformation of the welding area can be controlled by timely discharging the steam and residual cooling medium of the cooling medium through the exhaust pipe surrounding the cooling medium nozzle. However, when the weld is forced to be quenched, this method is prone to produce hardened structure in the weld area, and even cracks, which deteriorates the joint performance.

[0006] Patent application number 201210248669.3 discloses a method for reducing the residual stress of thick plate welding by using the residual heat of welding between multiple layers and multiple passes to assist vibration. Through pre-vibration scanning, the excitation force is adjusted at the sub-resonance frequency to obtain the natural frequency of the workpiece to be welded. After welding one layer, vibration aging treatment is performed according to the determined natural frequency under the residual heat state of welding to reduce the residual stress of the thick plate weldment. However, this method is not particularly effective in reducing the residual stress after welding of thin plates, and for different materials, the natural frequency must be determined before welding, which reduces production efficiency.

[0007] Patent application number 201510295203.2 discloses an aging heat treatment method for maintaining the strength of aluminum alloy and reducing quenching residual stress. The aluminum alloy after solid solution and quenching is directly subjected to primary artificial aging, and then secondary artificial aging; the primary aging is to subject the aluminum alloy to at least three short-term artificial agings, and then air-cooling after being taken out of the furnace; the heating rate of each short-term artificial aging is increased to obtain a temperature field opposite to the quenching process, thereby generating a stress field opposite to the quenching state to offset the residual stress. This method is particularly suitable for forgings and plates with large thickness and regular shape. However, the aluminum alloy is subjected to heat multiple times during this process, which is prone to cause microstructure coarsening.

[0008] Patent application number 201610180639.1 discloses a system for controlling the residual stress of tungsten inert gas arc welding (TIG) joints by an external magnetic field device. Specifically, an external magnetic field generating device generates a longitudinal magnetic field to act on the TIG welding arc. The charged particles in the arc rotate toward the edge of the arc under the action of the external magnetic field, and the arc changes from a cone to a bell shape. The arc energy and current density become a double-peaked distribution, which leads to a decrease in the welding temperature field gradient and an improvement in the distribution of welding residual stress. However, this method is only applicable to TIG welded joints and cannot control the stress distribution of other solid phase welded joints.

[0009] In summary, there is currently no specific solution with a wider application range that can truly and effectively reduce the welding residual stress in the weld area between metal structural materials, which is a technical problem that needs to be urgently solved in this field. Summary of the invention

[0010] The purpose of the present invention is to overcome the defects of the prior art and provide a method for in-situ reducing the residual stress of a fusion welded joint of a metal structural material.

[0011] To achieve the above object, the technical solution adopted by the present invention is: a method for in-situ reducing residual stress of a fusion welded joint of a metal structural material, comprising the following steps:

[0012] Step 1: Use robot arm No. 1 to hold the welding gun and create a welding path for the welding gun;

[0013] Step 2: According to the welding area of ​​the workpiece to be welded, the motion trajectory of the second robot arm holding the processing gun is determined to ensure that the motion trajectories of the processing gun and the welding gun are coordinated and matched;

[0014] Step 3: Load the powder material into the powder feeder of the processing gun, control the gas pressure of the processing gun to generate a high-speed particle flow, and use a gas heater to preheat the gas;

[0015] Step 4: The No. 1 robot arm holds the welding gun to weld the welded parts, and the No. 2 robot arm holds the processing gun and uses the processing gun to perform high-speed particle flow spraying on the fusion welding joint formed by welding.

[0016] Furthermore, in step three, the powder material is ceramic powder or hard metal powder, and the powder particle size is 50 to 150 μm.

[0017] Furthermore, the ceramic powder is aluminum oxide or silicon oxide.

[0018] Furthermore, the metal powder is any one of copper, nickel and stainless steel.

[0019] Furthermore, in step three, the gas of the high-speed particle flow is high-pressure compressed air or nitrogen, and the gas pressure is 1.0 to 5.0 MPa.

[0020] Furthermore, in step three, the preheating temperature for preheating the gas is lower than the melting point of the powder material used.

[0021] Furthermore, the powder material is ceramic powder or hard metal powder, and the preheating temperature for preheating the gas is 25-900°C.

[0022] Furthermore, in step 4, the No. 2 robot arm holding the treatment gun to perform spraying treatment and the No. 1 robot arm holding the welding gun to perform welding are performed simultaneously or separately.

[0023] Furthermore, the No. 2 robot arm holding the processing gun for high-speed particle flow jetting processing is performed synchronously with the No. 1 robot arm holding the welding gun for welding processing, and the interval between the movement trajectories of the two is 10 to 100 cm to ensure that the working processes of the two do not affect each other.

[0024] Furthermore, in step 4, the second robot arm holding the processing gun performs spray processing on the fusion welding joint of the welded part, specifically: single-side processing of the weld and part of the base material area or double-side processing of the weld and part of the base material area.

[0025] The beneficial effects of the present invention are:

[0026] 1. The present invention utilizes a high-speed particle flow with a certain temperature to impact the weld area and its vicinity, thereby generating compressive stress on the joint surface, improving stress distribution, and increasing joint fatigue strength and service life.

[0027] 2. By preheating the gas used in the treatment gun, the high-speed particle impact is combined with the hot gas shock effect, which can effectively reduce or eliminate the residual tensile stress of the component, improve the mechanical properties of the joint, and extend the service life of the component.

[0028] 3. In addition to being used to regulate the residual stress of fusion welded joints of metal structural materials, the present invention can also be used to improve the residual stress distribution of various welded joints of other materials, thereby improving the safety and reliability of the joints.

[0029] 4. The present invention has a simple use process and overcomes the problem that many parts are not allowed to be disassembled and post-heat treated due to assembly and other factors. It is one of the most effective, economical, flexible and designable methods. It can realize in-situ strengthening of complex parts of different sizes and is easy to automate. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the system principle diagram and embodiment drawings of the present invention are briefly introduced below.

[0031] Figure 1 This is a working principle diagram of the treatment gun of the present invention;

[0032] Figure 2 This is a working schematic diagram of Embodiment 1 of the present invention;

[0033] In the figure: 1-processing gun, 2-powder feeder, 3-gas heater, 4-high-pressure gas source, 5-high-speed particle flow, 6-welding part, 7-welding gun, 8-area to be processed. DETAILED DESCRIPTION

[0034] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0035] In general, the present invention adopts the following working principle to solve the problem of reducing welding residual stress in the weld zone between metal structural materials:

[0036] See Figure 1-2, use the No. 1 robot arm to hold the welding gun 7 to complete the welding of the welded part 6, load the powder particles into the powder feeder 2, connect the high-pressure gas source 4, turn on the gas heater 3, preheat the high-pressure gas, and form a high-speed particle flow 5 through the processing gun 1. Use the No. 2 robot arm to hold the processing gun 1, and the high-speed particle flow 5 carried in the gun hits the area to be processed 8 and its vicinity along the same welding path. By generating compressive stress on the joint surface, the stress distribution is improved, and the fatigue strength and service life of the joint are improved.

[0037] Specifically, the present invention provides the following specific embodiments:

[0038] Embodiment 1:

[0039] A method for in-situ reducing residual stress of a fusion welded joint of a metal structural material comprises the following steps:

[0040] Step 1: Use robot arm No. 1 to hold the super-frequency pulse VPTIG welding gun and create a welding path for robot arm No. 1;

[0041] Step 2: Select the welding area of ​​2219 aluminum alloy plate (specification 300mm×150mm×8mm), determine the motion trajectory of the second robot arm for clamping the processing gun 1, and keep the distance between the first robot arm and the second robot arm at 50cm to ensure the coordinated matching of the motion trajectory of the processing gun and the welding gun;

[0042] Step 3: Load the copper powder material with a particle size distribution of 53-106 μm into the powder feeder, connect the high-pressure gas source, the high-pressure gas source uses nitrogen, the pressure is controlled to be 2.6 MPa, turn on the gas heater to preheat the nitrogen, the preheating temperature is 400 ° C, and pass through the treatment gun 1 to form a high-speed particle flow;

[0043] Step 4: Robot arm No. 1 holds the welding gun to weld the 2219 aluminum alloy plate to form a fusion weld joint, and robot arm No. 2 holds treatment gun 1 and uses the high-speed particle flow it generates to spray the weld and part of the base material area of ​​the fusion weld joint of the 2219 aluminum alloy plate.

[0044] Referring to GB / T31310-2014, the blind hole method was used to detect the residual stress of the fusion welded joint. The results showed that the stress peak value of the weld area of ​​the fusion welded joint in the welded state was 152MPa. Under the action of high-speed particle impact and hot gas shock, the stress distribution of the fusion welded joint was improved, the maximum stress was 25MPa, and the area around the weld was mostly in a compressive stress state.

[0045] Embodiment 2:

[0046] A method for in-situ reducing residual stress of a fusion welded joint of a metal structural material comprises the following steps:

[0047] Step 1: Use the No. 1 robot arm to clamp the super-frequency pulse VPTIG welding gun and create a welding path for the No. 1 robot arm to weld the 2219 aluminum alloy plate (specification 300 mm×150 mm×8 mm) to form a fusion welding joint;

[0048] Step 2: The processing area of ​​the selected processing gun is the entire fusion welding joint weld area on both sides and the two sides of the weld extending 20mm from the parent material; determine the motion trajectory of the second robot arm used to clamp the processing gun;

[0049] Step 3: Load the copper powder material with a particle size distribution of 53 to 106 μm into the powder feeder, connect the high-pressure gas source, the high-pressure gas source uses nitrogen, the pressure is controlled to be 2.0 MPa, turn on the gas heater to preheat the nitrogen, the preheating temperature is 200° C., and pass through the treatment gun 1 to form a high-speed particle flow;

[0050] Step 4: The No. 2 robotic arm holds the treatment gun and uses the high-speed particle flow it generates to spray the entire fusion weld area on both sides of the 2219 aluminum alloy plate, as well as both sides of the weld extending 20 mm to the parent material.

[0051] Referring to GB / T31310-2014, the blind hole method was used to detect the residual stress of the fusion welded joint. The results showed that the stress peak value in the weld area of ​​the fusion welded joint was 160MPa in the welded state. Under the action of high-speed particle impact and hot gas shock, the stress distribution of the fusion welded joint was improved. The maximum stress on the front side was 18MPa, and the maximum stress on the back side was 6MPa. In addition, the area around the weld was mostly in a compressive stress state.

[0052] Embodiment 3:

[0053] A method for in-situ reducing residual stress of a fusion welded joint of a metal structural material comprises the following steps:

[0054] Step 1: Use the No. 1 robot arm to clamp the TIG welding gun and create a welding path for the No. 1 robot arm to weld the 2024 aluminum alloy plate (specification 300 mm × 150 mm × 4 mm) to form a fusion welding joint;

[0055] Step 2: The processing area of ​​the selected processing gun is the entire fusion welding joint weld area and the two sides extending 20 mm from the parent material; determine the motion trajectory of the second robot arm used to clamp the processing gun 1;

[0056] Step 3: Load the alumina powder material with a particle size distribution of 100-150 μm into the powder feeder, connect the high-pressure gas source, the high-pressure gas source uses nitrogen, the pressure is controlled to 2.0 MPa, turn on the gas heater to preheat the nitrogen, the preheating temperature is 200 ° C, and pass through the treatment gun to form a high-speed particle flow;

[0057] Step 4: The No. 2 robot arm holds the treatment gun and uses the high-speed particle flow it generates to spray the entire fusion welding joint of the 2024 aluminum alloy plate and both sides of the joint extending 20 mm toward the parent material.

[0058] Referring to GB / T31310-2014, the blind hole method was used to detect the residual stress of the fusion welded joint. The results showed that the stress peak value of the weld area of ​​the fusion welded joint in the welded state was 103MPa. Under the action of high-speed particle impact and hot gas shock, the stress distribution of the fusion welded joint was improved, the maximum stress was 8MPa, and the area around the weld was mostly in a compressive stress state.

[0059] Embodiment 4:

[0060] A method for in-situ reducing residual stress of a fusion welded joint of a metal structural material comprises the following steps:

[0061] Step 1: Use the No. 1 robot arm to clamp the MIG welding gun and create a welding path for the No. 1 robot arm to weld the Q235 plate (specification 300 mm × 150 mm × 4 mm) to form a fusion welding joint;

[0062] Step 2: The processing area of ​​the selected processing gun is the entire fusion welding joint weld area and the two sides extending 20 mm from the parent material; determine the motion trajectory of the second robot arm used to clamp the processing gun 1;

[0063] Step 3: Load the stainless steel powder material with a particle size distribution of 53 to 106 μm into the powder feeder, connect the high-pressure gas source, the high-pressure gas source uses nitrogen, the pressure is controlled to be 3.0 MPa, turn on the gas heater to preheat the nitrogen, the preheating temperature is 200°C, and pass through the treatment gun 1 to form a high-speed particle flow;

[0064] Step 4: Robot arm No. 2 holds the treatment gun and uses the high-speed particle flow it generates to spray the entire weld area of ​​the fusion welding joint of the Q235 plate and both sides extending 20 mm toward the base material.

[0065] Referring to GB / T31310-2014, the blind hole method was used to detect the residual stress of the fusion welded joint. The results showed that the stress peak value of the weld area of ​​the fusion welded joint in the welded state was 186MPa. Under the action of high-speed particle impact and hot gas shock, the stress distribution of the fusion welded joint was improved, the maximum stress was 23MPa, and the area around the weld was mostly in a compressive stress state.

[0066] In summary, the present invention can effectively reduce the residual stress of the fusion welding joint of metal structural materials. After the weld and part of the base material area are impacted by high-speed particles and hot gas shock, plastic deformation occurs, and the stress is released to a certain extent. The load-bearing capacity of the component is improved, the fatigue strength is greatly improved, and stress corrosion cracking is alleviated.

[0067] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not depart from the spirit and scope of the present invention, and should be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for in-situ reduction of residual stress in a fusion welded joint of a metal structural material, characterized in that: The steps include: Step 1: Use robot arm No. 1 to hold the welding gun and create a welding path for the welding gun; Step 2: According to the welding area of ​​the workpiece to be welded, the motion trajectory of the second robot arm holding the processing gun is determined to ensure that the motion trajectories of the processing gun and the welding gun are coordinated and matched; Step 3: Load the powder material into the powder feeder of the processing gun, control the gas pressure of the processing gun to generate a high-speed particle flow, and use a gas heater to preheat the gas; Step 4: The No. 1 robot arm holds the welding gun to weld the welded parts, and the No. 2 robot arm holds the processing gun and uses the processing gun to perform high-speed particle flow spraying on the fusion welding joint formed by welding.

2. The method for in-situ reducing residual stress of a fusion welded joint of a metal structural material according to claim 1, characterized in that: In step three, the powder material is ceramic powder or hard metal powder, and the powder particle size is 50 to 150 μm.

3. The method for in-situ reducing residual stress of a fusion welded joint of a metal structural material according to claim 2, characterized in that: The ceramic powder is aluminum oxide or silicon oxide.

4. The method for in-situ reducing residual stress of a fusion welded joint of a metal structural material according to claim 2, characterized in that: The metal powder is any one of copper, nickel and stainless steel.

5. The method for in-situ reducing residual stress of a fusion welded joint of a metal structural material according to claim 1, characterized in that: In step three, the gas of the high-speed particle flow is high-pressure compressed air or nitrogen, and the gas pressure is 1.0 to 5.0 MPa.

6. The method for in-situ reduction of residual stress in a fusion welded joint of a metal structural material according to claim 1, characterized in that: In step three, the preheating temperature for preheating the gas is lower than the melting point of the powder material used.

7. The method for in-situ reducing residual stress of a fusion welded joint of a metal structural material according to claim 6, characterized in that: The powder material is ceramic powder or hard metal powder, and the preheating temperature for preheating the gas is 25-900°C.

8. The method for in-situ reducing residual stress of a fusion welded joint of a metal structural material according to claim 1, characterized in that: In step 4, the No. 2 robot arm holding the treatment gun for spraying treatment and the No. 1 robot arm holding the welding gun for welding are performed simultaneously or separately.

9. The method for in-situ reducing residual stress of a fusion welded joint of a metal structural material according to claim 1, characterized in that: The No. 2 robot arm holding the processing gun for high-speed particle flow jetting processing is synchronously performed with the No. 1 robot arm holding the welding gun for welding processing, and the interval between the movement trajectories of the two is 10 to 100 cm to ensure that the working processes of the two do not affect each other.

10. The method for in-situ reducing residual stress of a fusion welded joint of a metal structural material according to any one of claims 1 to 9, characterized in that: In step 4, the second robot arm holding the processing gun performs spray processing on the fusion welding joint of the welded part, specifically: processing one side of the weld and part of the parent material area or processing both sides of the weld and part of the parent material area.

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