Method for preventing generation of hot cracks in magnesium alloy casting repair welding process under assistance of water cooling

Abstract

The invention relates to a method for preventing generation of hot cracks in a magnesium alloy casting and repair welding process, in particular to a method for preventing generation of hot cracks in a magnesium alloy casting and repair welding process under the assistance of water cooling. The technical problem that hot cracks are generated in the current magnesium alloy casting electric-arc welding repair welding process is solved. According to the method, the magnesium alloy casting repair welding position is forcibly cooled through active cooling, so that the purposes of controlling the temperature of a molten pool and a heat affected zone, improving the high-temperature residence time in a thermal cycle curve and reducing heat accumulation are achieved, and specifically, the repair welding position is locally cooled in a circulating water water-cooling copper plate heat transfer mode; the method can effectively reduce heat accumulation of the magnesium alloy component and improve the performance of the component. By the adoption of the technical scheme, the magnesium alloy repair welding structure can be refined, the forming precision is improved, and the heat affected zone range is reduced. The water-cooling copper plate is attached to the surface of the repair welding component, so that the temperature gradient of the component is increased, heat dissipation is accelerated, and the effect of reducing heat accumulation is achieved.

Description

Technical Field

[0001] The invention relates to a method for preventing thermal cracks from being generated during magnesium alloy casting repair welding. Background Art

[0002] Lightweight and refined manufacturing of aero engines and related parts is a development requirement for new high-tech aircraft. As the lightest metal structural material at present, magnesium alloys have been widely used in the aviation field due to their low density, high specific strength and specific stiffness, good vibration damping performance and good cutting performance. At present, 95% of magnesium alloy parts in the aviation field are produced by casting, of which die casting accounts for the largest proportion. Die casting equipment is expensive, the production cycle is long, the cost is high, and there are forming defects such as pores, shrinkage holes, and inclusions, which seriously affect the performance of castings. In order to reduce production costs, magnesium alloy castings that can be repaired are often reworked by arc welding. However, due to the material properties of magnesium alloys with high thermal conductivity, arc welding repairs often use high-power welding, which on the one hand leads to increased heat input, and on the other hand leads to multiple thermal cycles at the welding position, and increased heat accumulation. According to the welding characteristics of magnesium alloys, large heat input will cause large welding stress during magnesium alloy welding, while the cooling rate is reduced, the grains are coarsened, and the formation of low-melting eutectics at the grain boundary is promoted, which increases the tendency of hot cracks in the weld and heat-affected zone. Therefore, during the arc welding repair process of magnesium alloy casting, some specific methods must be adopted to reduce the heat accumulation degree of the repair welding or improve the local heating effect of the arc, so as to reduce the tendency of thermal cracking. Summary of the invention

[0003] The present invention aims to solve the technical problem that hot cracks may occur during the current magnesium alloy casting arc welding repair process, and to provide a method for preventing hot cracks from occurring during the magnesium alloy casting repair welding process with the aid of water cooling.

[0004] The method of the present invention for preventing thermal cracks from occurring during magnesium alloy casting repair welding with water cooling assistance is carried out in the following steps:

[0005] A plurality of water-cooled copper plates are arranged around the part to be repaired by welding of the magnesium alloy casting and attached to the surface of the magnesium alloy casting, the water-cooled copper plates are connected to a water cooling device, the water cooling device is started to cool the part to be repaired by welding of the magnesium alloy casting, and then the arc welding repair is started. After the repair welding is completed, the water cooling device can be turned off.

[0006] The present invention provides an active cooling method for forced cooling of the repair weld of magnesium alloy casting to achieve the purpose of controlling the temperature of the molten pool and the heat-affected zone, improving the high-temperature residence time in the thermal cycle curve, and reducing heat accumulation. Specifically, the repair weld is locally cooled by circulating water-cooled copper plate heat transfer. This method can effectively reduce the heat accumulation of magnesium alloy components and improve component performance. By adopting the above technical scheme, the present invention can refine the repair weld structure of magnesium alloy, improve the forming accuracy, and reduce the range of the heat-affected zone. The water-cooled copper plate is bonded to the surface of the repair weld component, thereby increasing the temperature gradient of the component, accelerating heat dissipation, and achieving the effect of reducing heat accumulation.

[0007] The water-cooled copper plate in the present invention can be attached to different positions of the repair welding component as needed to meet the repair needs of different parts. According to actual working conditions, multiple water-cooled copper plates can be set to cool multiple positions of the repair welding component, including the front and back sides of the repair welding component.

[0008] The present invention is based on a consumable electrode gas shielded welding arc power source. Before the magnesium alloy component is repaired by welding, a water-cooled copper plate is attached to the component surface, the water cooling flow is controlled by a water cooling device, the wire feeding speed, the welding speed and the shielding gas flow are set, the magnesium alloy arc repair welding program is started, the shielding gas is turned on, and the water cooling device starts to operate, so as to achieve auxiliary water cooling in the magnesium alloy repair welding process and reduce the effect of heat accumulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the device for the method of using water cooling to assist in preventing thermal cracks during magnesium alloy casting repair welding in Experiment 1;

[0010] Figure 2 This is the macroscopic morphology of the weld point after arc repair welding of the magnesium alloy casting casing assisted by water cooling in Experiment 1;

[0011] Figure 3 This is the microstructure of the weld point after arc repair welding of the water-cooling assisted magnesium alloy casting casing in experiment 1. DETAILED DESCRIPTION

[0012] Specific implementation method 1: This implementation method is a method for preventing thermal cracks during magnesium alloy casting repair welding with water cooling assistance, which is specifically carried out in the following steps:

[0013] A plurality of water-cooled copper plates are arranged around the part to be repaired by welding of the magnesium alloy casting and attached to the surface of the magnesium alloy casting, the water-cooled copper plates are connected to a water cooling device, the water cooling device is started to cool the part to be repaired by welding of the magnesium alloy casting, and then the arc welding repair is started. After the repair welding is completed, the water cooling device can be turned off.

[0014] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that a flow channel is provided inside the water-cooled copper plate. The rest is the same as the specific implementation method 1.

[0015] Specific implementation method 3: This implementation method is different from the specific implementation method 2 in that the water cooling device is a water cooling machine. The rest is the same as the specific implementation method 2.

[0016] Specific implementation method 4: This implementation method is different from specific implementation method 3 in that the flow channel of the water-cooled copper plate is connected to the water return port and the water outlet of the water cooler. The rest is the same as specific implementation method 3.

[0017] Specific implementation method 5: This implementation method is different from specific implementation method 4 in that the water flow rate of the water chiller is 17 L / min. The rest is the same as specific implementation method 4.

[0018] Specific implementation example 6: This implementation example is different from specific implementation example 5 in that a plurality of water-cooled copper plates are arranged around the part to be repaired by welding of the magnesium alloy casting, including the back side of the part to be repaired by welding.

[0019] Specific implementation example 7: This implementation example is different from specific implementation example 6 in that: a plurality of water-cooled copper plates are connected via water pipes. The rest is the same as specific implementation example 6.

[0020] Specific implementation example eight: This implementation example is different from specific implementation example seven in that the magnesium alloy casting is a magnesium alloy casting casing. The rest is the same as specific implementation example seven.

[0021] Specific implementation method 9: This implementation method is different from specific implementation method 8 in that the water flow rate of the water chiller is 18 L / min. Other aspects are the same as specific implementation method 8.

[0022] Specific embodiment 10: This embodiment is different from specific embodiment 9 in that the water flow rate of the water chiller is 20 L / min. Other aspects are the same as specific embodiment 9.

[0023] The present invention is verified by the following tests:

[0024] Test 1: This test is a method of water cooling to assist in preventing thermal cracks during magnesium alloy casting repair welding. Figure 1 As shown, the specific steps are as follows:

[0025] A plurality of water-cooled copper plates 2 are arranged around and on the back of the area to be repaired 7 of the magnesium alloy casting 1 and attached to the surface of the magnesium alloy casting, the water-cooled copper plates 2 are connected to a water cooler 4, and the water cooler 4 is started to cool the area to be repaired 7 of the magnesium alloy casting, with a water flow rate of 18 L / min; then the arc welding machine 5 is turned on, the arc repair welding supporting program is edited, and the process parameters are set: the wire feeding speed is 3.5 m / min, and the welding speed is 0.6 m / min; the welding head 6 is aimed at the area to be repaired 7, and arc welding is performed, and the water cooler 4 can be turned off after the repair welding is completed; the magnesium alloy casting is a magnesium alloy casting casing;

[0026] The water-cooled copper plate 2 is provided with a flow channel inside, and multiple water-cooled copper plates 2 are connected through water pipes 3. The flow channel of the water-cooled copper plate 2 is connected to the return water port and the water outlet of the water chiller 4 to form a loop.

[0027] Figure 2 This is the macroscopic morphology of the weld point after arc repair welding of the water-cooled assisted magnesium alloy casting casing in Experiment 1. It can be seen that the repair weld point is well formed and no cracks are generated.

[0028] Figure 3 This is the microstructure of the weld point after arc repair welding of the water-cooled assisted magnesium alloy casting casing in Experiment 1. It can be seen that the grains in the weld area and the heat-affected zone are fine, and no microcracks are generated.

Claims

1. A method for preventing thermal cracks during magnesium alloy casting repair welding with water cooling, characterized in that The method of water cooling to assist in preventing thermal cracks during magnesium alloy casting repair welding is carried out in the following steps: A plurality of water-cooled copper plates are arranged around the part to be repaired by welding of the magnesium alloy casting and attached to the surface of the magnesium alloy casting, the water-cooled copper plates are connected to a water cooling device, the water cooling device is started to cool the part to be repaired by welding of the magnesium alloy casting, and then the arc welding repair is started. After the repair welding is completed, the water cooling device can be turned off.

2. The method of claim 1 for preventing thermal cracks during magnesium alloy casting repair welding with water cooling assistance, characterized in that A flow channel is arranged inside the water-cooled copper plate.

3. The method of preventing thermal cracks during magnesium alloy casting repair welding with water cooling as an aid according to claim 2, characterized in that The water cooling equipment is a water cooling machine.

4. The method of preventing thermal cracks during magnesium alloy casting repair welding with water cooling as an aid according to claim 3 is characterized in that The flow channel of the water-cooled copper plate is communicated with the water return port and the water outlet of the water cooler.

5. The method of preventing thermal cracks during magnesium alloy casting repair welding with water cooling as an aid according to claim 2, characterized in that The water flow rate of the water cooler is 17L / min.

6. The method of claim 1 for preventing thermal cracks during magnesium alloy casting repair welding by using water cooling as an aid, characterized in that A plurality of water-cooled copper plates are arranged around the part of the magnesium alloy casting to be repaired by welding, including the back side of the part to be repaired by welding.

7. The method of claim 2 for preventing thermal cracks during magnesium alloy casting repair welding by using water cooling as an aid, characterized in that Multiple water-cooled copper plates are connected through water pipes.

8. The method of claim 1 for preventing thermal cracks during magnesium alloy casting repair welding by using water cooling as an aid, characterized in that The magnesium alloy casting is a magnesium alloy casting casing.

9. The method of claim 2 for preventing thermal cracks during magnesium alloy casting repair welding by using water cooling as an aid, characterized in that The water flow rate of the water chiller is 18L / min.

10. The method of preventing thermal cracks during magnesium alloy casting repair welding with water cooling as an aid according to claim 2, characterized in that The water flow rate of the water cooler is 20L / min.

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