Stainless steel and copper alloy dissimilar metal electron beam welding process

Abstract

The invention provides a stainless steel and copper alloy dissimilar metal electron beam welding process. The process mainly comprises the following steps: (1) a pre-welding cleaning process; (2) adjusting the position of an impact point of the electron beam and the basic parent metal; and (3) welding process parameters are adjusted. By selecting the pre-welding cleaning process, the welding process parameters and the electron beam impact point position, a stainless steel and copper alloy dissimilar metal electron beam welding scheme is provided, reliable connection of the two kinds of metal is achieved, the post-welding strength reaches 90% or above of the strength of copper side base metal, and the method has the advantages of reducing the cost and improving the welding quality. The reduction of the weight of the whole structure is of great significance.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to an electron beam welding process for dissimilar metals of stainless steel and copper alloy. Background Art

[0002] Copper alloys are mainly used in the manufacture of thrust chambers and nozzle extensions of liquid and solid rocket engines due to their good high temperature performance. In some aerospace engines, the thrust chamber body is usually made of copper alloy, while the head is often made of stainless steel due to cost and weight factors. The whole can be welded by copper-hafnium alloy and stainless steel. The current welding technology has two problems: first, the welding strength is weak, and second, the cost of achieving the ideal welding strength is high. Summary of the invention

[0003] To solve the above problems, the present invention provides a stainless steel and copper alloy dissimilar metal electron beam welding process, which realizes the reliable connection of stainless steel and copper alloy dissimilar metals, and the connection strength reaches more than 90% of the strength of the copper alloy parent material.

[0004] The technical solution adopted by the present invention is: a stainless steel and copper alloy dissimilar metal electron beam welding process, comprising the following steps:

[0005] Step 1: Mechanically clean the alloy surface before welding. Clean the surface of stainless steel and copper alloy parts by mechanical processing or manual polishing, and then clean them with alcohol;

[0006] Step 2: Chemical cleaning of the alloy surface before welding: using an acid solution to clean the surface of stainless steel and copper alloy parts;

[0007] Step 3: Cleaning: First rinse the parts with running water, then rinse with distilled water;

[0008] Step 4: Drying: Use 30-75℃ hot air to dry the parts;

[0009] Step 5: Select the impact point of the electron beam and the base material. The electron beam is deflected to bias the impact point of the electron beam toward the copper alloy side.

[0010] Step 6: Welding: adjust the process parameters according to the thickness of the parts to be welded, the welding voltage is not less than 60KV, the welding beam current is 18-52mA, and the welding speed is 600-720mm / min;

[0011] Step 7: Use touch-up welding to treat the weld surface.

[0012] Further optimization, the acidic solution in step 2 is an aqueous solution of hydrofluoric acid, nitric acid or sulfuric acid.

[0013] Further optimization was performed, in step 5, the electron beam impact point was biased toward the copper alloy side by 0.3 to 0.6 mm.

[0014] With further optimization, the focusing current is focused below the surface.

[0015] The beneficial effects of the present invention are:

[0016] 1. Through pre-welding cleaning, the performance of the alloy is guaranteed and the weld performance is improved;

[0017] 2. Improve the uniformity of the weld structure by selecting the impact point position;

[0018] 3. Through the optimization of welding process parameters, the reliable connection of the two alloys is achieved, and the strength after welding reaches more than 90% of the strength of the copper side base material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the electron beam welding process for dissimilar metals of stainless steel and copper alloy;

[0020] Reference numerals: 1-Copper alloy 2-Stainless steel 3-Electron beam 511-Electron beam welding code DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings:

[0022] 1. Pre-welding cleaning process

[0023] Stainless steel and copper are both active metals, which easily react with elements such as nitrogen, hydrogen and oxygen at a certain temperature. Titanium absorbs a large amount of hydrogen at 300°C. When the hydrogen-containing β-copper alloy is eutectoidally decomposed and the hydrogen-containing α-titanium is cooled, TiH can be precipitated, making the alloy brittle. Stainless steel is relatively stable at room temperature, does not react with acid (including aqua regia) at room temperature, and can react with many non-metals (such as oxygen and chlorine) when heated. Stainless steel absorbs hydrogen at 250°C and nitrogen at 300°C, thereby reducing the performance of the weld.

[0024] Therefore, the two alloy parts are strictly cleaned before welding. Pre-weld cleaning includes mechanical cleaning and chemical cleaning. For mechanical cleaning, use mechanical processing or manual polishing, and then clean with alcohol; for chemical cleaning, it is mainly cleaned with acidic solution, which is generally composed of hydrofluoric acid, nitric acid, sulfuric acid and water. After pickling, rinse with running water, rinse with distilled water, and then blow dry with hot air at 30-75℃.

[0025] 2. Select the impact point of the electron beam 3 and the basic base material

[0026] The melting point of copper alloy 2 is about 800℃ higher than that of titanium alloy 1. During welding, copper alloy 1 will melt first, while stainless steel 2 will partially melt or melt later, which will reduce the uniformity of the weld structure and affect the performance of the weld. Therefore, when the heat transfer properties of the two metals are not much different, the electron beam impact point is biased toward the side of the high melting point metal, that is, toward the side of stainless steel 2. Figure 1 As shown, the electron beam 3 is positioned toward the stainless steel 2. Generally, the collision point between the electron beam 3 and the base material is 0.3 to 0.6 mm toward the stainless steel 2 according to the thickness of the alloy parts.

[0027] 3. Electron beam welding process optimization

[0028] Adjust the process parameters according to the thickness of the material to be welded. The adjusted process parameters include welding voltage, welding beam, and welding speed. The welding speed should not be too fast to ensure that the stainless steel 2 and the copper alloy 1 are fully fused. The focusing current is focused below the surface to ensure that the weld is well formed and penetrated. The electron beam 3 is deflected to ensure the uniformity of the weld structure. After welding, the weld surface is treated with touch-up welding, such as Figure 1 , electron beam welding code 511, indicating that the welding method is vacuum electron beam welding.

[0029] Embodiment 1

[0030] Several groups of alloy test pieces with a thickness of 2.0 mm were selected, the welding voltage was 60KV, the welding speed was 660mm / min, the distance of the impact point from the copper side was 0.5mm, and the welding beam currents were 12mA, 16mA, 18mA, 20mA, 23mA, 25mA, 28mA30mA, 33mA, and 35mA. After the post-weld tensile test, the welding strength was excellent in the range of 18-30mA, meeting the requirements.

[0031] Embodiment 2

[0032] Several groups of alloy test pieces with a thickness of 2.5mm were selected, the welding voltage was 60KV, the welding speed was 660mm / min, the distance of the impact point from the copper side was 0.5mm, and the welding beam currents were 22mA, 25mA, 28mA, 32mA, 35mA, 38mA, 40mA42mA, 45mA, and 48mA. After the post-weld tensile test, the welding strength was excellent in the range of 28-42mA, meeting the requirements.

[0033] Embodiment 3

[0034] Several groups of alloy test pieces with a thickness of 4.0mm were selected, the welding voltage was 60KV, the welding speed was 660mm / min, the distance of the impact point from the copper side was 0.5mm, and the welding beam currents were 32mA, 35mA, 38mA, 40mA, 42mA, 45mA, 48mA52mA, 55mA, and 58mA. After the post-weld tensile test, the welding strength was excellent in the range of 40-52mA, meeting the requirements.

[0035] Embodiment 4

[0036] Several groups of alloy test pieces with a thickness of 5.0mm were selected, the welding voltage was 60KV, the welding speed was 660mm / min, the distance of the impact point from the copper side was 0.5mm, and the welding beam currents were 32mA, 35mA, 38mA, 40mA, 42mA, 45mA, 48mA52mA, 55mA, and 58mA. After the post-weld tensile test, the welding strength was excellent in the range of 40-52mA, meeting the requirements.

[0037] Embodiment 5

[0038] Several groups of alloy test pieces with a thickness of 2.0mm were selected, the welding beam current was 25mA, the welding speed was 660mm / min, the distance of the impact point from the copper side was 0.5mm, and the welding voltages were 45KV, 50KV, 55KV, 60KV, 65KV, 70KV, 85KV, 100KV, 125KV, and 150KV. After the post-weld tensile test, the welding strength was excellent and met the requirements when the welding voltage reached or exceeded 60KV.

[0039] Embodiment 6

[0040] Several groups of alloy test pieces with a thickness of 2.5mm were selected, the welding beam current was 35mA, the welding speed was 660mm / min, the distance of the impact point from the copper side was 0.5mm, and the welding voltages were 45KV, 50KV, 55KV, 60KV, 65KV, 70KV, 85KV, 100KV, 125KV, and 150KV. After the post-weld tensile test, the welding strength was excellent and met the requirements when the welding voltage reached or exceeded 60KV.

[0041] Embodiment 7

[0042] Several groups of alloy test pieces with a thickness of 4.0mm were selected, the welding beam current was 45mA, the welding speed was 600mm / min, the distance of the impact point from the copper side was 0.5mm, and the welding voltages were 45KV, 50KV, 55KV, 60KV, 65KV, 70KV, 85KV, 100KV, 125KV, and 150KV. After the post-weld tensile test, the welding strength was excellent and met the requirements when the welding voltage reached or exceeded 60KV.

[0043] Embodiment 8

[0044] Several groups of alloy test pieces with a thickness of 5.0mm were selected, the welding beam current was 45mA, the welding speed was 600mm / min, the distance of the impact point from the copper side was 0.5mm, and the welding voltages were 45KV, 50KV, 55KV, 60KV, 65KV, 70KV, 85KV, 100KV, 125KV, and 150KV. After the post-weld tensile test, the welding strength was excellent and met the requirements when the welding voltage reached or exceeded 60KV.

[0045] Embodiment 9

[0046] Several groups of alloy test pieces with a thickness of 2.0mm were selected, the welding voltage was 60KV, the welding beam current was 25mA, the distance of the impact point from the copper side was 0.5mm, and the welding speeds were 560mm / min, 600mm / min, 630mm / min, 660mm / min, 690mm / min, 720mm / min, 760mm / min, and 790mm / min. After the post-weld tensile test, the welding strength was excellent when the welding speed was 660-720mm / min, meeting the requirements.

[0047] Embodiment 10

[0048] Several groups of alloy test pieces with a thickness of 2.5mm were selected, the welding voltage was 60KV, the welding beam current was 35mA, the distance of the impact point from the copper side was 0.5mm, and the welding speeds were 560mm / min, 600mm / min, 630mm / min, 660mm / min, 690mm / min, 720mm / min, 760mm / min, and 790mm / min. After the post-weld tensile test, the welding strength was excellent when the welding speed was 600-720mm / min, meeting the requirements.

[0049] Embodiment 11

[0050] Several groups of alloy test pieces with a thickness of 4.0mm were selected, the welding voltage was 60KV, the welding beam current was 45mA, the distance of the impact point from the copper side was 0.5mm, and the welding speeds were 560mm / min, 600mm / min, 630mm / min, 660mm / min, 690mm / min, 720mm / min, 760mm / min, and 790mm / min. After the post-weld tensile test, the welding strength was excellent when the welding speed was 600-720mm / min, meeting the requirements.

[0051] Embodiment 12

[0052] Several groups of alloy test pieces with a thickness of 5.0mm were selected, the welding voltage was 60KV, the welding beam current was 45mA, the distance of the impact point from the copper side was 0.5mm, and the welding speeds were 560mm / min, 600mm / min, 630mm / min, 660mm / min, 690mm / min, 720mm / min, 760mm / min, and 790mm / min. After the post-weld tensile test, the welding strength was excellent when the welding speed was 600-720mm / min, meeting the requirements.

[0053] Embodiment 13

[0054] Several groups of alloy test pieces with a thickness of 2.0 mm were selected, the welding voltage was 60 KV, the welding beam current was 25 mA, the welding speed was 660 mm / min, and the distances of the impact point from the copper side were 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, and 0.8 mm. After the post-weld tensile test, the welding strength was excellent when the distance of the impact point from the niobium side was 0.3-0.5 mm, meeting the requirements.

[0055] Embodiment 14

[0056] Several groups of alloy test pieces with a thickness of 2.5 mm were selected, the welding voltage was 60KV, the welding beam current was 35mA, the welding speed was 660mm / min, and the distances of the impact point from the copper side were 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, and 0.8mm. After the post-weld tensile test, the welding strength was excellent when the distance of the impact point from the niobium side was 0.4-0.6mm, meeting the requirements.

[0057] Embodiment 15

[0058] Several groups of alloy test pieces with a thickness of 4.0mm were selected, the welding voltage was 60KV, the welding beam current was 45mA, the welding speed was 600mm / min, and the distances of the impact point from the copper side were 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, and 0.8mm. After the post-weld tensile test, the welding strength was excellent when the distance of the impact point from the niobium side was 0.4-0.6mm, meeting the requirements.

[0059] Embodiment 16

[0060] Several groups of alloy test pieces with a thickness of 5.0 mm were selected, the welding voltage was 60KV, the welding beam current was 45 mA, the welding speed was 600 mm / min, and the distances of the impact point from the copper side were 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, and 0.8 mm. After the post-weld tensile test, the welding strength was excellent when the distance of the impact point from the niobium side was 0.4-0.6 mm, meeting the requirements.

[0061] After the test, the welding process parameters were optimized. The welding strength can be significantly improved by selecting the appropriate range of welding parameters. The conclusion is shown in the following table. Table 1 lists the welding process parameters of the electron beam welding structure of copper alloy 1 and stainless steel 2 with different thicknesses.

[0062] Table 1 Electron beam welding process parameters of copper alloy 1 and stainless steel 2 with different thicknesses

[0063] Structure thickness (mm) Welding voltage (KV) Welding beam current (mA) Welding speed (mm / min) Distance from impact point to copper side (mm) 1.0-2.0 ≥60 18-30 600-720 0.3-0.5 2.0-3.5 ≥60 28-42 600-720 0.4-0.6 3.5-5.0 ≥60 40-52 600-720 0.4-0.6

[0064] Table 2 Mechanical properties of 2.5 mm thick copper alloy 1 and stainless steel 2 after welding

[0065] Test temperature / ℃ Tensile strength / MPa Yield strength / MPa Elongation / % Fracture location Room temperature 427 358 20 Copper side base metal 400 306 256 30 Copper side base metal 800 108 83 -- Fusion zone near the steel side

[0066] It can be seen from Table 2 that the present invention proposes a solution to the electron beam welding of dissimilar metals of copper alloy 1 and stainless steel 2 by selecting the pre-welding cleaning process, welding process parameters and the position of the electron beam impact point, and realizes a reliable connection of the two metals. The strength after welding reaches more than 90% of the strength of the copper side parent material. When the temperature does not exceed 400°C, the fracture position is in the copper side parent material, indicating that the strength performance of the weld is excellent, and when the temperature reaches 800°C, the fracture position occurs in the fusion zone, indicating that the weld has a certain high temperature strength.

Claims

1. A stainless steel and copper alloy dissimilar metal electron beam welding process, characterized in that: The following steps are involved: Step 1: Mechanically clean the alloy surface before welding. Clean the surface of stainless steel and copper alloy parts by mechanical processing or manual polishing, and then clean them with alcohol; Step 2: Chemical cleaning of the alloy surface before welding: using an acid solution to clean the surface of stainless steel and copper alloy parts; Step 3: Cleaning: First rinse the parts with running water, then rinse with distilled water; Step 4: Drying: Use 30-75℃ hot air to dry the parts; Step 5, selecting the impact point position of the electron beam and the basic base material, and using the deflection method of the electron beam to deflect the electron beam impact point to the copper alloy side; Step 6: Welding: adjust the process parameters according to the thickness of the parts to be welded, the welding voltage is not less than 60KV, the welding beam current is 18-52mA, and the welding speed is 600-720mm / min; Step 7: Use touch-up welding to treat the weld surface.

2. The electron beam welding process for stainless steel and copper alloy dissimilar metals according to claim 1, characterized in that: The acidic solution in step 2 is an aqueous solution of hydrofluoric acid, nitric acid or sulfuric acid.

3. The electron beam welding process for stainless steel and copper alloy dissimilar metals according to claim 1, characterized in that: In step 5, the electron beam impact point is biased toward the copper alloy side by 0.3 to 0.6 mm.

4. The electron beam welding process for stainless steel and copper alloy dissimilar metals according to claim 1, characterized in that: The focusing current is focused below the surface.

Images