Electron beam welding method for 30CrMnSiA high-strength steel large-thickness and large-size rotary product

Abstract

The invention relates to the technical field of welding processes, and discloses an electron beam welding method for a 30CrMnSiA high-strength steel large-thickness and large-size rotary product, which comprises the steps of preparation before welding, welding preheating, welding, stress relief annealing after welding, turning of a lock bottom, heat treatment and inspection. According to the electron beam welding method, stress relief annealing is conducted within 2 h after welding, welding thermal stress can be effectively eliminated, welding thermal cracks and other welding defects are avoided, and the problems of air holes, cracks and the like of electron beam welding of the 30CrMnSiA high-strength steel large-thickness rotary products are solved; radiographic inspection is carried out according to NB / T 47013.2-2015, and the positions of welding seams all meet the I-level requirement; and after quenching and tempering, the mechanical properties of the weld joint can be as follows: the tensile strength is greater than or equal to 1550 MPa, the elongation A is greater than or equal to 9%, and the impact energy KU2 is greater than or equal to 45 J.

Description

Technical Field

[0001] The invention relates to the technical field of welding technology, and in particular to an electron beam welding method for 30CrMnSiA high-strength steel large-thickness and large-size rotary products. Background Art

[0002] Most of the 30CrMnSiA high-strength steel products with large thickness and large size (thickness greater than 30mm, outer diameter greater than 400mm) are formed by at least 3 parts after mechanical processing and then welded by at least 2 electron beam welds. 30CrMnSiA high-strength steel not only has very high strength, but also has certain toughness, wear resistance, fatigue resistance, impact resistance and easy processing and forming performance. Generally, it is mainly used for high-load parts such as shafts, gears, and housings. However, the welding performance of this material is poor, especially the welds with large penetration depth. During the welding process, it is easy to produce welding defects such as thermal cracks and pores, and it is also easy to produce delayed cracks after welding.

[0003] As a high-energy-density precision welding method performed in a vacuum environment, electron beam welding has many advantages, such as high welding power density, large aspect ratio, small deformation of the welding zone, low energy consumption, easy control and automation, etc. It has been widely used in the fields of aerospace, weapons and equipment manufacturing, and the electronics industry. Although compared with conventional fusion welding methods, electron beam welding technology can greatly improve the tensile strength of welded joints, reduce residual deformation, and improve the quality of welded joints, for the welding of 30CrMnSiA thick high-strength steel materials, due to the large welding penetration, pores and cracks are easily generated during electron beam welding, which is still the biggest obstacle to its application. Summary of the invention

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

[0005] In order to achieve the above object, the present invention provides an electron beam welding method for 30CrMnSiA high-strength steel large-thickness and large-size rotary products, wherein the rotary products include n welded parts, wherein: n≥3, n is a positive integer; the method comprises the following steps:

[0006] S1: cleaning and drying the surfaces of the n welded parts;

[0007] S2: n welded parts are butt-assembled to form n-1 welds and placed in a vacuum chamber to ensure that the assembly gap is less than 0.1 mm.

[0008] S3: preheating, spot welding, and vacuum cooling for 30-60 minutes are performed on the first to (n-1)th welds of the n welded parts in sequence to form a semi-finished welded product;

[0009] S4: Remove the vacuum and check the welding condition of the weld seam of the semi-finished product. If the inspection is qualified, execute step S5; if the inspection is unqualified, repeat step S3;

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

[0011] S6: within 2 hours after welding, the finished welded product is subjected to stress relief annealing heat treatment, and the weld seam on each weld pass is subjected to radiographic flaw detection;

[0012] S7: The machine is turned off the lock bottom position, and the finished welded product after the X-ray flaw detection is quenched and tempered in turn to obtain the rotary product, and the welded test pieces of the same batch as the furnace are subjected to mechanical property testing.

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

[0014] The welded part and the surrounding area within 50 mm are wiped with alcohol to remove surface oil and impurities.

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

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

[0017] Preferably, the vacuum degree in the vacuum chamber in step S2 is 9×10 -5 mbar.

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

[0019] The electron beam is focused within 1000 mm around the weld bead of the welded part for preheating before welding, and the preheating temperature before welding is 255°C.

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

[0021] Spot fix welding is performed symmetrically in sections.

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

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

[0024] Preferably, the step S7 wherein the vehicle falls out of the lock bottom position comprises:

[0025] Fixing the welded product that has been inspected by radiographic flaw detection on a lathe;

[0026] Carry off the welded joint and lock the bottom.

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

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

[0029] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

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

[0032] Figure 2 A schematic diagram of the micro-transparency and weld bump effects on the back of a weld according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

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

[0035] S1: Preparation before welding: Clean and dry the surfaces of the three welded parts. Specifically, wipe the welded part of each welded part and the area within 50 mm nearby with alcohol to remove surface oil and impurities.

[0036] S2: Assembly: n welded parts are butt-assembled to form n-1 welds and placed in a vacuum chamber to ensure that the assembly gap is less than 0.1 mm. Specifically, each welded part can be butt-assembled using a tooling and a three-jaw chuck, and the vacuum degree in the vacuum chamber is adjusted to 9×10 -5 mbar.

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

[0038] For electron beam welding of thick alloy steel, the preheating temperature can make the internal and external temperatures of the weld consistent, so that the molten pool temperature can be stable and consistent during the welding process, and it is beneficial to the escape of diffused hydrogen in the weld metal, avoiding the generation of hydrogen-induced cracks and pores, while also reducing the hardening degree of the weld and heat-affected zone, improving the crack resistance of the weld joint and ensuring the quality of the weld.

[0039] For the first weld, use electron beam focusing within 1000mm range near the weld bead of the welded part to preheat to 255℃ before welding, perform spot fixed welding symmetrically in sections, and then vacuum cool for 30-60min. 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, amplitude 50-100mA.

[0040] For the second weld, use electron beam focusing within 1000mm around the weld bead of the welded part to preheat to 255℃ before welding, perform spot fixed welding symmetrically in sections, and then vacuum cool for 30-60min. 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, amplitude 50-100mA.

[0041] The above-mentioned segmented symmetrical spot fixing welding can be performed in two sections, one section at 180°.

[0042] S4: Surface inspection: Remove the vacuum and inspect the weld fixing condition. If the inspection is qualified, proceed to step S5. If the inspection is unqualified, repeat step S3. The specific inspection can visually inspect the surface quality of the fixed weld. Visible cracks, pores and other welding defects are not allowed on the surface, and whether the test ring is firmly connected. If there are visible surface defects in the weld, the test ring needs to be cut open, and step S3 is repeated to reprocess the welding interface.

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

[0044] The official 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. A lot of heat will be generated during electron beam welding, which will cause welding residual stress and deformation. Setting the interval time can cool the heat of the first weld, so that the residual stress and thermal deformation of the first weld will not affect the welding quality of the second weld, thus ensuring the welding quality of the two welds.

[0045] S6: The finished welded product shall be subjected to stress relief annealing heat treatment within 2 hours after welding, and the welds on each weld pass shall be subjected to radiographic flaw detection. Stress relief annealing heat can effectively eliminate welding thermal stress and avoid welding thermal cracks and other welding defects.

[0046] S7: Turn off the lock bottom position, and perform quenching and tempering heat treatment on the finished welding products after X-ray flaw detection in turn to obtain rotating products. The same batch of welding test pieces in the furnace are subjected to mechanical property testing. The test results are: tensile strength ≥1550MPa, elongation A ≥9%, and impact energy KU2 ≥45J.

[0047] The method for turning off the locking bottom position is specifically as follows: fix the finished welding product that has been inspected by radiographic flaw detection on a lathe, and turn off the locking bottom of the welding joint.

[0048] The method of this embodiment achieves the internal quality of the weld to Grade I in the NB / T47013-2015 standard through preheating before welding and appropriate welding process parameters, and the back of the weld is formed into a micro-transparent shape, such as Figure 2 After the product is welded, the back of the weld needs to be machined. If the weld bump on the back of the weld is large, the turning process is intermittent, which causes serious wear on the tool and poor surface quality. The method of this embodiment is used to turn off the lock bottom position, and the back is slightly transparent, which can ensure the penetration of the weld and facilitate subsequent mechanical processing.

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

[0050] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0051] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. An electron beam welding method for 30CrMnSiA high-strength steel large-thickness and large-size rotary products, characterized in that: The rotary product includes n welded parts, wherein: n≥3, n is a positive integer; the method includes the following steps: S1: cleaning and drying the surfaces of the n welded parts; S2: Butt-assemble n of the welded parts to form n-1 welds and place them in a vacuum chamber to ensure that the assembly gap is less than 0.1 mm. S3: Preheating, spot welding, and vacuum cooling are performed on the first to (n-1)th welds of the n welded parts in sequence for 30-60 minutes to form a semi-finished welded product; S4: Remove the vacuum and check the welding condition of the weld seam of the semi-finished product. If the inspection is qualified, execute step S5; if the inspection is unqualified, repeat step S3; S5: performing formal welding on the first to (n-1)th welds of the semi-finished welding product in sequence, with each weld being welded for 30-60 minutes at an interval, to obtain a finished welding product; S6: Perform stress relief annealing heat treatment on the finished welded product within 2 hours after welding, and perform radiographic flaw detection on each weld; S7: The machine is turned off the lock bottom position, and the finished welded product after the X-ray flaw detection is quenched and tempered in turn to obtain the rotary product, and the welded test pieces of the same batch as the furnace are subjected to mechanical property testing.

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

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

4. The electron beam welding method for 30CrMnSiA high-strength steel large-thickness and large-size rotary products according to claim 1 is characterized in that: The vacuum degree in the vacuum chamber in step S2 is 9×10 -5 mbar.

5. The electron beam welding method for 30CrMnSiA high-strength steel large-thickness and large-size rotary products according to claim 1 is characterized in that: The preheating before welding in step S3 includes: The electron beam is focused within 1000 mm around the weld bead of the welded part for preheating before welding, and the preheating temperature before welding is 255°C.

6. The electron beam welding method for 30CrMnSiA high-strength steel large-thickness and large-size rotary products according to claim 5 is characterized in that: The spot fixing welding in step S3 includes: Spot fix welding is performed symmetrically in sections.

7. The electron beam welding method for 30CrMnSiA high-strength steel large-thickness and large-size rotary products according to claim 6 is characterized in that: The spot fixed welding parameters in step S3 are: voltage 140-150 kV, welding current 70-120 mA, focusing current 390-450 mA, welding speed 600-800 mm / min, circular scanning, frequency 400-700 Hz, amplitude 50-100 mA.

8. The electron beam welding method for 30CrMnSiA high-strength steel large-thickness and large-size rotary products according to claim 1 is characterized in that: The formal welding parameters in step S5 are: voltage 140-150 kV, welding current 120-160 mA, focusing current 390-450 mA, welding speed 700-1000 mm / min, circular scanning, frequency 400-700 Hz, amplitude 50-100 mA.

9. The electron beam welding method for 30CrMnSiA high-strength steel large-thickness and large-size rotary products according to claim 1 is characterized in that: The step S7 in which the vehicle falls out of the lock bottom position includes: Fixing the finished welded product after the radiographic flaw detection on a lathe; Carry off the welded joint and lock the bottom.

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

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