CN114309910B - Electron beam welding process and postweld heat treatment method for copper-chromium-zirconium alloy - Google Patents

Abstract

The invention discloses a copper-chromium-zirconium alloy electron beam welding process and a post-weld heat treatment method. Firstly, the surface treatment is performed on two CuCrZr alloy plates to be welded, and then the CuCrZr alloy to be welded is clamped by tooling to prevent deformation during the welding process. Influence; the alloy plate to be welded is first scanned and preheated with low power, and then welded at a constant speed and constant power. After standing to room temperature, the above welding operation is repeated once, and after aging heat treatment, a good double-sided welded joint can be obtained, and the obtained joint has a higher penetration depth/width ratio. The method of the present invention is suitable for the welding of high-precision accessories. The joint structure obtained by electron beam welding is better, and the tensile performance is better, which can reach 300 MPa. The welded joint after aging treatment can reach more than 350 MPa, which can even meet the requirements of actual engineering. Require.

Description

Electron beam welding process and post-weld heat treatment method of copper-chromium-zirconium alloy

Technical Field

The invention relates to an electron beam welding method, in particular to an electron beam welding process and a post-weld heat treatment method for a copper-chromium-zirconium alloy.

Background Art

Controlled thermonuclear fusion is an ideal new energy source that can meet the future energy needs of mankind. For this reason, my country has proposed a plan to build a Chinese fusion engineering test reactor. During the construction of the test reactor, copper-chromium-zirconium alloy, as an important high-performance material, became the key component material of the first wall and electron cyclotron (waveguide) in the test reactor reactor. In the past, the waveguide material used was 316 stainless steel, which is very easy to produce local overheating under the action of microwaves, affecting the stability and reliability of the Cu coating on its inner wall. In the microwave window waveguide design scheme, the CuCrZr alloy with high thermal conductivity, high electrical conductivity and low deformation replaces stainless steel and other materials as the main metal material of the microwave window component. It has the following advantages: ① The inner wall of the waveguide does not need to deposit a Cu coating, which simplifies the manufacturing process of the component; ② The entire component only contains CuCrZr alloy, copper ring and diamond, which reduces the mismatch between materials; ③ CuCrZr alloy has low welding deformation ~2-3%. The new copper alloy (CuCrZr) is used to replace stainless steel as the waveguide and is formed by electron beam precision welding to avoid energy loss caused by local overheating in the waveguide and achieve performance improvement of the microwave window. However, the scheme is still in the design stage and there are still many key issues, such as the welding stress and deformation control of CuCrZr alloy, the deformation behavior of copper alloy waveguide under service conditions, etc., and there is a lack of process and theoretical exploration.

At present, the research on electron beam welding technology is more inclined to titanium alloy, aluminum alloy materials, etc., and there is a lack of systematic research on the electron beam welding technology, molding, and post-welding performance of copper alloy materials. For copper-chromium-zirconium alloy with high thermal conductivity and high electrical conductivity, the research is mainly focused on the preparation processes such as smelting, casting, and forging of copper-chromium-zirconium alloy, and the welding technology and performance research of the alloy are less. Therefore, studying the electron beam welding technology of CuCrZr alloy and optimizing the post-welding performance has become a problem to be solved urgently. In order to solve these problems, the present invention adopts a low-power electron beam welder, adopts different electron beam welding processes to weld copper-chromium-zirconium alloy, obtains better welding process parameters, and invents a post-welding heat treatment process for electron beam welding copper-chromium-zirconium material.

Summary of the invention

In view of the above technical problems existing in the prior art, the object of the present invention is to provide an electron beam welding process and a post-weld heat treatment method for a copper-chromium-zirconium alloy.

The electron beam welding process and post-weld heat treatment method of a copper-chromium-zirconium alloy are characterized by comprising the following steps:

1) Preparation stage: The surface to be welded of the CuCrZr alloy plate is processed by wire cutting to form a flat surface, and then the flat surface of the CuCrZr alloy plate after cutting is surface treated to form a welded part; the two treated welded parts are fixed on the fixture to prevent deformation during the welding process, so that the welded surfaces of the two welded parts are aligned and closely spliced to form a weld, and then the fixture is placed in the welding room, and the welding room is evacuated;

2) Welding stage: preheat the workpiece before welding, perform electron beam welding on the front of the weld, cool it in the welding room for 20 to 40 minutes after welding, then take it out and let it cool naturally to room temperature in the air; then turn the two workpieces over and fix them on the fixture again for the second time, and continue welding on the back of the weld according to the same steps as the first welding process, and finally obtain an electron beam double-sided welded joint;

3) Post-weld heat treatment: The welded joint after welding is placed in a muffle furnace for aging heat treatment to improve the strength of the joint, and the preparation is completed.

The electron beam welding process and post-weld heat treatment method of a copper-chromium-zirconium alloy are characterized in that the surface treatment method in step 1) is: the flat surface of the CuCrZr alloy plate after cutting is cleaned with a solvent to remove oil stains, rust spots and other impurities, and then the surface to be joined and the surfaces on both sides of the weld of the CuCrZr alloy plate are polished with sandpaper. Sandpapers with models of 180#, 320#, and 600# can be used to polish the surfaces to be joined step by step, so that the surfaces to be joined are free of oil stains, rust spots and other impurities, and the flatness of the surfaces to be joined should be ensured. Sandpapers with models of 320# and 600# can be used to polish the surfaces on both sides of the weld step by step until a better reflective surface appears and there are no impurities on the surfaces on both sides of the weld.

The electron beam welding process and post-weld heat treatment method of a copper-chromium-zirconium alloy are characterized in that in step 1), the butt gap of two pieces to be welded is ≤0.4 mm and they are fixed on a fixture, and the weld is not grooved.

The electron beam welding process and post-weld heat treatment method of the copper-chromium-zirconium alloy are characterized in that the process parameters of preheating before welding in step 2) are: welding voltage 60-70kV, welding current 4-6mA, seam beam 3-4mA, focusing beam 260-270mA; the preheating range is within 5mm of the weld center and both sides of the weld, and the preheating method is to use a small current beam to control the motor handle, first preheat the weld evenly, and then preheat both sides of the weld.

The electron beam welding process and post-weld heat treatment method of the copper-chromium-zirconium alloy are characterized in that the welding process parameters of the electron beam welding in step 2) are: welding voltage 60-70kV, welding current 45-50mA, welding speed 90-100mm/min, seam beam current 3-4mA, and focusing beam current 260-270mA.

The electron beam welding process and post-weld heat treatment method of the copper-chromium-zirconium alloy are characterized in that in step 3), the aging heat treatment step is: starting from room temperature, heating to 480-520°C at a heating rate of 8-12°C/min, keeping the temperature for 300-400min, and finally cooling to room temperature at a cooling rate of 8-12°C/min.

The electron beam welding process and post-weld heat treatment method of the copper-chromium-zirconium alloy are characterized in that in step 3), the aging heat treatment step is: starting from room temperature, heating to 500°C at a heating rate of 10°C/min, keeping the temperature for 360 minutes, and finally cooling to room temperature at a cooling rate of 10°C/min.

The beneficial effects achieved by the present invention are:

The method of the present invention is suitable for the welding of high-precision accessories. The joint obtained by electron beam welding has good structure and good tensile performance, which can reach 300MPa. The welded joint after aging treatment can reach more than 350MPa, which can meet the requirements of actual engineering.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a weldment fixed on a fixture in Embodiment 1 of the present invention;

FIG2 is a photograph of the appearance of the sample prepared by the welding process parameter conditions + post-weld heat treatment process of Experiment No. 3;

FIG3 is a metallographic structure diagram of the weld of the joint prepared by the welding process parameter conditions + post-weld heat treatment process of Experiment No. 3;

FIG4 is a cross-sectional morphology comparison diagram of the joints prepared by the welding process parameter conditions + post-weld heat treatment process of experimental numbers 1-9.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

The CuCrZr alloy plate base material used in the embodiment of the present invention has the contents of Cu, Cr and Zr components listed in Table 1, and the remainder is impurities. The base material is tested for tensile strength, yield strength and elongation, and the test method is as shown in "GB/T228.1-2010 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method"", and the test results are listed in Table 1.

Table 1 Content of each element in the material

Embodiment 1:

An electron beam welding process and a post-weld heat treatment method for a copper-chromium-zirconium alloy, comprising the following steps:

1. Use a wire cutting machine to cut the CuCrZr alloy plate into 100*65*5mm plates. The surface to be welded of the CuCrZr alloy plate is cut into a flat surface. The surface to be welded is wiped with acetone and dried. Then use sandpaper to grind the surface to be welded and the surfaces on both sides of the weld of the CuCrZr alloy plate step by step, and grind the surface to be welded to a state of being flat, free of impurities, moisture, rust spots, etc., and grind the surfaces on both sides of the weld to present a metallic luster and a state of being free of impurities. Referring to Figure 1, the two processed pieces to be welded 2 are fixed on the fixture 1, so that the surfaces to be welded of the two pieces to be welded are aligned and closely spliced to form a weld 3.

2. Turn on the main switch of the electron beam power supply.

3. Turn on the vacuum pump.

4. Open the console.

5. Open the welding chamber, place the workpiece fixed on the fixture into the welding chamber, and start the automatic vacuum program.

6. Then preheat the workpiece before welding, set the preheating parameters, turn on the focus, bias, filament, high voltage in sequence, and then preheat before welding. The preheating parameters before welding are: welding voltage 65kV, welding current 5mA, seam beam 3-4mA, focusing beam 265mA, preheating range is within 5mm of the center of the weld and both sides of the weld, the preheating method is small current beam, control the motor handle, first preheat the weld evenly, and then preheat both sides of the weld. Preheat for 5 minutes before welding.

7. Then, perform butt welding, set welding process parameters, perform the first welding operation, perform electron beam welding on the front side of the weld, cool in the welding room for 30 minutes after the front side welding, then take out the welded parts and place them in the air to cool naturally to room temperature; then, turn the two pieces to be welded over and fix them on the fixture again for the second time, and continue the welding operation on the back side of the weld according to the same steps as the first welding process, and finally obtain an electron beam double-sided welded joint.

The above welding process parameters are: welding voltage 65kV, welding current 45, 47 or 49mA, welding speed 90, 95 or 100mm/min, seam beam current 3.5mA, focusing beam current 265mA, surface focusing.

8. Turn on the cooling water of the muffle furnace, place the sample in the muffle furnace, and set the heat treatment process: the starting temperature is room temperature (20°C), heat up to 500°C at a heating rate of 10°C/min (heating time is 480min), keep warm for 360min, and finally cool to room temperature at a cooling rate of 10°C/min (cooling time is 480min). Finally, wait for the set temperature and the temperature in the furnace to cool to room temperature and take out the sample.

9. Take out the welded parts, clean the spatter on the weld surface, and grind the oxide scale.

10. Conduct joint performance evaluation tests such as mechanical behavior evaluation and metallographic analysis.

11. In order to explore the best welding process, 9 groups of control tests were designed. The specific scheme and tensile strength are shown in Table 2 (voltage is constant 65kV). The weld photo of the welded part is shown in Figure 1. The weld has no cracks, undercuts, or sagging.

Table 29 Welding process parameter conditions for group 29 control tests

For the joint prepared by the welding process parameter conditions + post-weld heat treatment process of Experiment No. 3 (the welded joint is divided into three parts: the base metal zone, the heat affected zone and the fusion zone), the weld metallographic structure diagram of the joint is shown in Figure 3. Figure 3 (a) is the metallographic structure result of the heat affected zone, and Figure 3 (b) is the metallographic structure result of the fusion zone. It can be seen that the internal structure is good, and no obvious welding defects such as cracks and holes are observed. The weld is divided into a fusion zone and a heat affected zone.

The appearance photo of the sample prepared by the welding process parameter conditions + post-weld heat treatment process of Experiment No. 3 is shown in Figure 2. As can be seen from Figure 2, the bonding degree of the two CuCrZr alloy plates is good.

The tensile strength, yield strength and elongation tests were carried out on the joints prepared by the welding process parameters and post-weld heat treatment process of experimental numbers 1-9. The test methods refer to "GB/T228.1-2010 "Tensile test of metallic materials Part 1: Room temperature test method"". The test results are shown in Table 3.

Table 3. Joint strength under various welding processes

The cross-sectional morphology comparison diagram of the joints prepared by the welding process parameters and post-weld heat treatment process of Experiment No. 1-9 is shown in Figure 4. As can be seen from Figure 4, the welding current is too small (45mA) and the welding speed is too fast (100mm/min), and the upper and lower welds are not fused together.

The tensile strength, yield strength and elongation tests were carried out on the joints prepared by the welding process parameters of experiment number 3 + the post-weld heat treatment process, and the joints prepared by the welding process parameters of experiment number 3 + the post-weld heat treatment process. The test results are shown in Table 4.

Table 4. Comparison of strength of heat treated and unheat treated welded joints

It can be seen that the average strength of the welded joint is about 300MPa, and the joint strength obtained by post-weld heat treatment is 350MPa, reaching 70% of the parent material, meeting the engineering requirements. The final conclusion is: qualified.

The contents described in this specification are merely an enumeration of implementation forms of the inventive concept, and the protection scope of the present invention should not be regarded as being limited to the specific forms described in the embodiments.

Claims (4)

1. An electron beam welding process and a postweld heat treatment method for copper-chromium-zirconium alloy are characterized by comprising the following steps:

1) A preparation stage: performing linear cutting processing on the surface to be welded of the CuCrZr alloy plate to form a flat surface, and then performing surface treatment on the flat surface after the CuCrZr alloy plate is cut to form a piece to be welded; fixing the two processed parts to be welded on a fixture, aligning and splicing the welding surfaces of the two parts to be welded to form a welding line, then placing the fixture in a welding chamber, and vacuumizing the welding chamber;

2) And (3) a welding stage: preheating a workpiece to be welded before welding, carrying out electron beam welding on the front surface of a welding seam, cooling in a welding chamber for 40-60min after welding is finished, and then taking out the workpiece and placing in the air for naturally cooling to room temperature; then, turning over the two pieces to be welded for the second time and repeatedly fixing the two pieces to be welded on the fixture, and continuously carrying out primary welding operation on the reverse side of the welding seam according to the same steps as the primary welding process to finally obtain an electron beam double-side welding joint;

3) Postweld heat treatment: placing the welded joint into a muffle furnace for aging heat treatment to improve the strength of the joint, thus completing the preparation;

the process parameters of preheating before welding in the step 2) are as follows: the welding voltage is 60-70kV, the welding current is 4-6mA, the butt-joint beam current is 3-4mA, and the focusing beam current is 260-270mA; preheating the welding line uniformly and then preheating the two sides of the welding line within 5mm of the center of the welding line and the two sides of the welding line;

the welding process parameters of the electron beam welding in the step 2) are as follows: welding voltage is 60-70kV, welding current is 45mA, welding speed is 95-100mm/min, butt-joint beam current is 3-4mA, and focusing beam current is 260-270mA;

in the step 3), the aging heat treatment comprises the following steps: taking the room temperature as an initial temperature, heating to 480-520 ℃ at a heating rate of 8-12 ℃/min, then preserving the heat for 300-400min, and finally cooling to the room temperature at a cooling rate of 8-12 ℃/min.

2. The electron beam welding process and the postweld heat treatment method of the copper-chromium-zirconium alloy according to claim 1, wherein the surface treatment in the step 1) is performed by: and cleaning the cut flat surface of the CuCrZr alloy plate by using a solvent so as to remove oil stains, rust spots and other impurities, and then polishing the surface to be combined of the CuCrZr alloy plate and the surfaces of two sides of the welding line by using abrasive paper.

3. The electron beam welding process and the postweld heat treatment method of the copper-chromium-zirconium alloy according to claim 1, wherein in step 1), the butt joint gap between two pieces to be welded is less than or equal to 0.4mm and is fixed on a clamp, and a weld joint is not beveled.

4. The electron beam welding process and the postweld heat treatment method for copper-chromium-zirconium alloy according to claim 1, wherein in the step 3), the aging heat treatment step is: taking room temperature as the initial temperature, heating to 500 ℃ at a heating rate of 10 ℃/min, then preserving heat for 360min, and finally cooling to room temperature at a cooling rate of 10 ℃/min.

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