A method for electron beam welding of a 30CrMnSiA high-strength steel large-thickness large-size rotary product

Abstract

The present application relates to the technical field of welding process, and discloses a kind of 30CrMnSiA high-strength steel large-thickness large-size rotary product electron beam welding method, comprising welding preparation step, welding preheating, welding step, stress relief annealing after welding, car drop lock bottom, heat treatment and inspection step.The present application carries out stress relief annealing within 2h after welding, can effectively eliminate welding thermal stress, avoid producing welding hot crack and other welding defects, solve the problem such as porosity, crack of 30CrMnSiA high-strength steel large-thickness rotary product electron beam welding;According to NB / T 47013.2-2015, the weld position all meets the requirement of I level;After quenching and tempering, the mechanical property at weld can reach: tensile strength ≥1550MPa, elongation A ≥9%, impact energy KU2 ≥45J.

Description

Technical Field

[0001] This invention relates to the field of welding technology, specifically to an electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel. Background Technology

[0002] Large-thickness, large-size (thickness greater than 30mm, outer diameter greater than 400mm) rotating products made of 30CrMnSiA high-strength steel are mostly formed by machining at least three parts and then welding them together through at least two electron beam welds. 30CrMnSiA high-strength steel not only possesses very high strength but also certain toughness, wear resistance, fatigue resistance, impact resistance, and easy machinability. It is generally used for high-load parts such as shafts, gears, and housings. However, this material has poor weldability, especially for deep welds. During welding, it is prone to hot cracking, porosity, and other welding defects, and delayed cracking is also likely to occur after welding.

[0003] Electron beam welding, a high-energy-density precision welding method performed in a vacuum environment, boasts numerous advantages such as high welding power density, large aspect ratio, small deformation in the weld zone, low energy consumption, and ease of automation. It is currently widely used in aerospace, weapon manufacturing, and the electronics industry. Although electron beam welding technology can significantly improve the tensile strength of welded joints, reduce residual deformation, and enhance joint quality compared to conventional fusion welding methods, the large penetration depth of thick, high-strength 30CrMnSiA steel makes it prone to porosity and cracking defects during the electron beam welding process, which remains the biggest obstacle limiting its application. Summary of the Invention

[0004] The purpose of this invention is to provide an electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel, in order to solve the technical problems in the prior art.

[0005] To achieve the above objectives, this invention provides an electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel. The rotary products comprise n welded parts, where n ≥ 3 and n is a positive integer. The method includes the following steps:

[0006] S1: Clean and dry the surfaces of the n welded parts;

[0007] S2: Assemble n of the aforementioned weldable parts by butt joint to form n-1 weld seams and place them in a vacuum chamber, ensuring that the assembly gap is less than 0.1mm.

[0008] S3: Sequentially preheat, spot weld, and vacuum cool for 30-60 minutes for the first to (n-1)th welds of the n welded parts to form a semi-finished welded product;

[0009] S4: Remove the vacuum and check the weld fixation of the welded semi-finished product. If the inspection is qualified, proceed to step S5. If the inspection is unqualified, repeat step S3.

[0010] S5: Perform formal welding on the first to (n-1)th welds of the semi-finished welded product in sequence, with a formal welding interval of 30-60 minutes between each weld, to obtain the finished welded product;

[0011] S6: Within 2 hours after welding, the welded product shall be subjected to stress-relieving annealing heat treatment, and the weld on each weld pass shall be subjected to radiographic testing.

[0012] S7: The bottom of the machine is removed, and the welded finished products after radiographic testing are quenched and tempered in sequence to obtain the rotary products. The test pieces are welded together with the furnace and their mechanical properties are tested.

[0013] Preferably, the surface treatment in step S1 includes:

[0014] Wipe the area to be welded and the surrounding 50mm area with alcohol to remove surface oil and impurities.

[0015] Preferably, the docking assembly in step S2 includes:

[0016] The welded parts are assembled by using tooling and a three-jaw chuck.

[0017] Preferably, the vacuum level in the vacuum chamber during step S2 is 9 × 10⁻⁶. -5 mbar.

[0018] Preferably, the preheating before welding in step S3 includes:

[0019] Preheating is performed by focusing an electron beam within a 1000mm radius of the weld bead on the weldment, with a preheating temperature of 255°C.

[0020] Preferably, the spot welding in step S3 includes:

[0021] Segmented symmetrical spot welding is performed.

[0022] Preferably, the spot welding parameters in step S3 are: voltage 140-150kV, welding current 70-120mA, focusing current 390-450mA, welding speed 600-800mm / min, circular scanning, frequency 400-700HZ, amplitude 50-100mA.

[0023] Preferably, the formal welding parameters in step S5 are: voltage 140-150kV, welding current 120-160mA, focusing current 390-450mA, welding speed 700-1000mm / min, circular scanning, frequency 400-700HZ, amplitude 50-100mA.

[0024] Preferably, the location where the vehicle bottom lock falls off in step S7 includes:

[0025] The welded product, which has undergone radiographic testing, is fixed on a lathe;

[0026] The car lost its welded joint and lock bottom.

[0027] Preferably, the mechanical properties of the welded product after tempering heat treatment in step S7 are: tensile strength ≥1550MPa, elongation A ≥9%, and impact energy KU2 ≥45J.

[0028] The beneficial effects of this invention are as follows: through preheating before welding and appropriate welding process parameters, the internal quality of the weld reaches Grade I in the NB / T 47013-2015 standard, and the back of the weld is formed as a micro-penetration with a penetration depth greater than 30mm. After heat treatment, the mechanical properties of the weld are far higher than the standard requirements, reaching tensile strength ≥1550MPa, elongation A ≥9%, and impact energy KU2 ≥45J.

[0029] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0030] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0031] Figure 1 A schematic diagram of an electron beam welding joint structure according to an embodiment of the present invention is shown;

[0032] Figure 2 A schematic diagram of the back-side penetration and weld bead effect of a weld according to an embodiment of the present invention is shown. Detailed Implementation

[0033] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0034] Please refer to Figure 1This embodiment discloses an electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel. The rotary products include n welded parts, where n ≥ 3 and n is a positive integer. In this embodiment, three welded parts are used as an example. The specific welding method includes seven steps: pre-welding preparation, assembly, spot welding, surface inspection, formal welding, stress-relieving annealing, and testing.

[0035] S1: Pre-welding preparation: Clean and dry the surfaces of the three components to be welded. Specifically, wipe the area to be welded on each component and the surrounding 50mm area with alcohol to remove surface oil and impurities.

[0036] S2: Assembly: Assemble n welded parts by butt joints to form n-1 weld seams and place them in a vacuum chamber, ensuring the assembly gap is less than 0.1mm. Specifically, tooling and a three-jaw chuck can be used to butt-assemble the welded parts. The vacuum level in the vacuum chamber is adjusted to 9×10⁻⁶. -5 mbar.

[0037] S3: Spot welding: The first and second welds of the three welded parts are preheated, spot welded, and vacuum cooled for 30-60 minutes in sequence to form a semi-finished welded product.

[0038] For electron beam welding of thick alloy steel, the preheating temperature can make the internal and external temperatures of the weld uniform. This ensures a stable and consistent temperature in the molten pool during the welding process, facilitates the escape of diffusible hydrogen from the weld metal, avoids hydrogen-induced cracks and porosity, reduces the hardening degree of the weld and heat-affected zone, improves the crack resistance of the welded joint, and ensures weld quality.

[0039] For the first weld, use an electron beam to preheat to 255°C within a 1000mm radius of the weld bead. Perform symmetrical spot welding in segments, followed by vacuum cooling for 30-60 minutes. The welding parameters are: voltage 140-150kV, welding current 70-120mA, focusing current 390-450mA, welding speed 600-800mm / min, circular scanning, frequency 400-700HZ, and amplitude 50-100mA.

[0040] For the second weld, the electron beam is focused within a 1000mm radius of the weld bead on the weldment and preheated to 255℃. The weld is then symmetrically spot-fixed in segments, followed by vacuum cooling for 30-60 minutes. The welding parameters are: voltage 140-150kV, welding current 70-120mA, focusing current 390-450mA, welding speed 600-800mm / min, circular scanning with a frequency of 400-700HZ and an amplitude of 50-100mA.

[0041] The above-mentioned segmented symmetrical spot welding can be performed in two segments, each segment measuring 180°.

[0042] S4: Surface Inspection: De-vacuum and inspect the weld seam fixing. If the inspection is qualified, proceed to step S5; if the inspection is unqualified, repeat step S3. Specifically, the surface quality of the fixing weld seam can be visually inspected. No visible cracks, porosity, or other welding defects are allowed on the surface, and the test ring must be securely connected. If visible surface defects are present in the weld seam, the test ring needs to be cut open, step S3 repeated, and the weld joint re-machined.

[0043] S5: Perform formal welding on the first and second welds of the semi-finished product in sequence, with a formal welding interval of 30-60 minutes between each weld, to obtain the finished weld.

[0044] The formal welding parameters are: voltage 140-150kV, welding current 120-160mA, focusing current 390-450mA, welding speed 700-1000mm / min, circular scanning, frequency 400-700HZ, amplitude 50-100mA. Electron beam welding generates a large amount of heat, resulting in residual stress and deformation. Setting an interval allows the first weld to cool down, preventing residual stress and thermal deformation from the first weld from affecting the welding quality of the second weld, thus ensuring the quality of both welds.

[0045] S6: Within 2 hours after welding, stress-relief annealing heat treatment is performed on the welded product, and radiographic testing is performed on the weld seam on each weld bead. Stress-relief annealing heat treatment can effectively eliminate welding thermal stress and avoid welding hot cracks and other welding defects.

[0046] S7: The bottom of the machine is locked off. The welded products after radiographic testing are quenched and tempered in sequence to obtain rotary products. The test pieces are welded together with the furnace and their mechanical properties are tested. The test results are: tensile strength ≥1550MPa, elongation A ≥9%, impact energy KU2 ≥45J.

[0047] The specific method for machining the bottom lock position is as follows: Fix the welded finished product that has undergone radiographic testing on a lathe, and machine the bottom lock of the welded joint.

[0048] The method in this embodiment, through preheating before welding and appropriate welding process parameters, achieves the internal quality of the weld to Grade I in the NB / T47013-2015 standard, and the back of the weld is formed as a micro-penetration weld. Figure 2 As shown. After welding, the back of the weld needs to be machined. If the weld bead on the back is large, the machining process is intermittent, resulting in severe tool wear and poor surface finish. The method in this embodiment removes the bottom lock position, allowing the back to be slightly exposed, which ensures weld penetration and facilitates subsequent machining.

[0049] In summary, the electron beam welding method in this embodiment effectively solves the defects of porosity and cracks in the welding of thick, high-strength 30CrMnSiA steel rotating parts, obtaining a uniform and aesthetically pleasing electron beam weld. Simultaneously, the internal quality of the weld meets the Class I requirements of the NB / T 47013-2015 standard. After quenching and tempering heat treatment, its mechanical properties are greatly improved, with tensile strength ≥1550MPa, elongation A ≥9%, and impact energy KU2 ≥45J.

[0050] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. Furthermore, it should be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0051] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for electron beam welding of thick, large-size rotary products made of 30CrMnSiA high-strength steel, characterized in that, The rotary product comprises n welded parts, where n ≥ 3 and n is a positive integer; the method includes the following steps: S1: Clean and dry the surfaces of the n welded parts; S2: Assemble n of the aforementioned weldable parts by butt joint to form n-1 weld seams and place them in a vacuum chamber, ensuring that the assembly gap is less than 0.1mm. S3: Sequentially preheat, spot weld, and vacuum cool for 30-60 minutes for the first to (n-1)th welds of the n welded parts to form a semi-finished welded product; S4: Remove the vacuum and check the weld fixation of the welded semi-finished product. If the inspection is qualified, proceed to step S5. If the inspection is unqualified, repeat step S3. S5: Perform formal welding on the first to (n-1)th welds of the semi-finished welded product in sequence, with a formal welding interval of 30-60 minutes between each weld, to obtain the finished welded product; the formal welding parameters are: voltage 140-150kV, welding current 120-160mA, focusing current 390-450mA, welding speed 700-1000mm / min, circular scanning, frequency 400-700HZ; S6: Within 2 hours after welding, the welded product shall be subjected to stress-relieving annealing heat treatment, and each weld shall be subjected to radiographic testing. S7: The bottom of the machine is removed, and the welded finished products after radiographic testing are quenched and tempered in sequence to obtain the rotary products. The test pieces are welded together with the furnace and their mechanical properties are tested.

2. The electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel according to claim 1, characterized in that, The surface treatment in step S1 includes: Wipe the area to be welded and the surrounding 50mm area with alcohol to remove surface oil and impurities.

3. The electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel according to claim 1, characterized in that, The docking assembly in step S2 includes: The welded parts are assembled by using tooling and a three-jaw chuck.

4. The electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel according to claim 1, characterized in that, In step S2, the vacuum level in the vacuum chamber is 9 × 10⁻⁶. -5 mbar.

5. The electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel according to claim 1, characterized in that, The preheating before welding in step S3 includes: Preheating is performed by focusing an electron beam within a 1000mm radius of the weld bead on the weldment, with a preheating temperature of 255°C.

6. The electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel according to claim 5, characterized in that, The spot welding in step S3 includes: Segmented symmetrical spot welding is performed.

7. The electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel according to claim 6, characterized in that, The spot welding parameters in step S3 are: voltage 140-150kV, welding current 70-120mA, focusing current 390-450mA, welding speed 600-800mm / min, circular scanning, and frequency 400-700HZ.

8. The electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel according to claim 1, characterized in that, The locations where the vehicle bottom lock falls off in step S7 include: The welded product, which has undergone radiographic testing, is fixed on a lathe; The car lost its welded joint and lock bottom.

9. The electron beam welding method for large-thickness, large-size rotary products made of 30CrMnSiA high-strength steel according to claim 1, characterized in that, The mechanical properties of the welded product after tempering heat treatment in step S7 are: tensile strength ≥1550MPa, elongation A ≥9%, and impact energy KU2 ≥45J.

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