Marine low-magnetic steel laser welding method

Abstract

The invention provides a laser welding method for marine low-magnetic steel. The method comprises the steps that whether groove design is conducted or not is judged based on the plate thicknesses of two to-be-welded steel plates; if grooves need to be designed, grooves are formed in the two to-be-welded steel plates, and pretreatment is conducted; if the groove does not need to be designed, subsequent operation is carried out; arc striking and extinguishing plates are assembled at the ends of the two steel plates to be welded; and laser welding is conducted on the two to-be-welded steel plates based on the groove structure and the groove-free structure. The method has the advantages of concentrated welding heat, small welding deformation, one-side welding one-time forming, high welding speed and good welding seam forming.

Description

Technical Field

[0001] The invention relates to the field of ship welding, in particular to a laser welding method for ship low-magnetic steel. Background Art

[0002] With the improvement of steel smelting technology, low magnetic steel is widely used in the shipbuilding industry. Low magnetic steel can effectively avoid the interference of external magnetic fields and improve the performance and reliability of electronic equipment. In the design of some special ship construction, low magnetic steel is used as the main construction material of the hull structure.

[0003] In traditional low-magnetic steel welding methods, such as arc welding and gas shielded welding, the molten pool has poor fluidity during the welding process, which is prone to stress concentration and welding deformation. At the same time, the alloy elements in the deposited metal of the welding material are easily retained in the weld or not diluted, resulting in defects such as slag inclusions, pores, and cracks. In addition, double-sided welding of thick plates requires root cleaning and grinding on the reverse side by carbon planing, which results in low welding efficiency. Summary of the invention

[0004] In view of the shortcomings of the related art mentioned above, the purpose of the present invention is to provide a laser welding method for marine low-magnetic steel, which is used to solve the problems of deformation, defects and low welding efficiency in the low-magnetic steel welding process in the related art.

[0005] To achieve the above-mentioned purpose and other related purposes, the present invention provides a method for laser welding of marine low-magnetic steel, the method comprising: judging whether a groove design is required based on the thickness of two steel plates to be welded; if a groove design is required, opening a groove on the two steel plates to be welded and performing pretreatment; if a groove design is not required, performing subsequent operations; assembling arc-initiating and extinguishing plates at the ends of the two steel plates to be welded during welding; and laser welding the two steel plates to be welded based on structures with and without grooves.

[0006] Optionally, the condition that no groove design is required is: if the plate thickness is between 2 mm and 3 mm, no groove design is required.

[0007] Optionally, the condition for designing a groove is: if the plate thickness is between 4 mm and 10 mm, a groove is provided on the two steel plates to be welded.

[0008] Optionally, the groove form is a V-shaped groove, the root gap of the groove is 0 to 0.5 mm, and the groove root is 2 mm to 3 mm.

[0009] Optionally, the angle of the groove is designed to be 20° to 30°.

[0010] Optionally, the step of pre-treating the groove is: first grinding the inner surface of the groove and the left and right sides of the groove with a grinding wheel, and then heating both sides of the groove to remove moisture on the surface of the steel plate to be welded, or cleaning the groove with acetone.

[0011] Optionally, the step of assembling arc-strike-and-extinguishing plates at the ends of two steel plates to be welded during welding is: an arc-strike-and-extinguishing plate is respectively arranged at both ends of each steel plate to be welded, and the gap between two opposite steel plates to be welded at the same end is controlled within 0.5 mm.

[0012] Optionally, if there is no groove structure, laser is used to directly weld the two steel plates to be welded.

[0013] Optionally, if there is a groove structure, laser and welding wire are combined for welding, and arc guidance is used for welding, and shielding gas is used to protect the weld during the welding process.

[0014] Optionally, the method further comprises: after the welding of the two steel plates to be welded is completed, inspecting the weld.

[0015] As described above, the marine low-magnetic steel laser welding method of the present invention has the following beneficial effects: compared with traditional arc welding and gas shielded welding, the laser welding efficiency of the present invention is high. This method can be used for straight panel assembly during the production process of low-magnetic steel hull structures, and has the advantages of concentrated welding heat, small welding deformation, one-time forming of single-sided welding, fast welding speed, and good weld formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Shown is a flow chart of a laser welding method for marine low-magnetic steel according to an embodiment of the present invention.

[0017] Figure 2 Shown is a schematic diagram of the groove design in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0019] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general scale, and the schematic view is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional space dimensions of length, width and depth should be included.

[0020] For ease of description, spatial relational terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatial relational terms are intended to include other directions of the device in use or operation in addition to the directions depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or there can be one or more intervening layers. As used herein, "between..." means including the end point values.

[0021] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0022] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0023] like Figure 1 and Figure 2 As shown, this embodiment provides a laser welding method for marine low-magnetic steel, the method comprising:

[0024] The groove design of the steel plate to be welded is carried out based on the plate thickness.

[0025] In this embodiment, the two steel plates to be welded are welded in a butt-jointed manner. If the plate thickness is 2mm to 3mm, there is no need to open a groove in the steel plates to be welded. If the plate thickness t of the two steel plates to be welded is 4mm to 10mm, a V-shaped groove is selected. The specific groove design dimensions are: the root gap C of the groove = 0 to 0.5mm, the groove root P = 2mm to 3mm, and in order to ensure the welding quality, the groove angle is designed to be α = 20° to 30°. If the groove angle is greater than 30°, the weld size will also be larger, which will affect the welding efficiency and the welding efficiency will be lower; if the groove angle is less than 20°, the shape of the weld on the back of the steel plate to be welded will become irregular and the quality will be poor.

[0026] The specific steps for creating a groove on the steel plate to be welded are: first use a plasma cutting machine to cut the steel plate to be welded, then use automatic milling equipment to process the straight edge of the groove, and after the straight edge processing is completed, process the bevel edge on the steel plate to be welded. By adopting this processing sequence, the straightness of the groove and the smoothness of the processed surface can be guaranteed.

[0027] Clean the groove before welding.

[0028] The specific cleaning steps are as follows: first, use a grinding wheel to grind the inner surface of the groove and 30mm on both sides of the groove to remove oil, rust, scale and other substances harmful to welding; then use oxyacetylene to heat both sides of the groove to remove water vapor on the surface of the steel plate to be welded, so as to prevent defects during welding; or use acetone to clean the groove to remove water vapor.

[0029] At the same time, before welding, arc striking and extinguishing plates are installed at the front and rear ends of the two steel plates to be welded.

[0030] During the welding process, when the arc is started, due to the low welding temperature and shallow molten pool, defects such as slag inclusion and lack of fusion are easy to occur; and when the arc is closed, the molten pool temperature is high, and defects such as arc pits and cracks are easy to appear. By setting arc-initiating and extinguishing plates at both ends of the weld, the defects can be led to the non-stressed parts to ensure the quality of the weld. In this embodiment, two opposite arc-initiating and extinguishing plates are set at both ends of the weld, and the two arc-initiating and extinguishing plates at each end are respectively connected to the two steel plates to be welded, and the arc-initiating and extinguishing plates are flush with the steel plates. The thickness and material of the arc-initiating and extinguishing plates are consistent with those of the steel plates to be welded, and the two arc-initiating and extinguishing plates are provided with the same grooves as the steel plates to be welded, and the gap between the two opposite arc-initiating and extinguishing plates is controlled within 0.5mm. In this embodiment, the length of the arc-initiating and extinguishing plates is not less than 50mm, and the width is not less than 50mm. When the welding is completed, the arc-initiating and extinguishing plates are removed.

[0031] Laser welding is performed on two steel plates to be welded.

[0032] If the thickness of the plate to be welded is between 2mm and 3mm, due to the thinness of the plate, laser welding can be directly used after the two steel plates to be welded are placed in position.

[0033] If the thickness of the welded plate is between 4mm and 10mm, due to the relatively thick plate, grooves need to be opened on the two steel plates to be welded first, and then after the two steel plates to be welded are placed in position, laser and welding wire composite welding is used. Here, the welding speed is 1300mm / min~1400mm / min, and the welding wire is elongated by 10mm~15mm. The welding wire material is the same as the parent material. For example, the welding wire diameter is 1mm, and the welding wire has the characteristics of good crack sensitivity resistance and low magnetic permeability. During the welding process, a shielding gas needs to be used at the same time, for example, argon is used as the shielding gas; the gas flow range is selected from 20L / Min to 25L / Min. If the gas flow is too small, it is easy to produce pores, and if the gas flow is too large, it is easy to cause turbulence and poor forming.

[0034] After the two steel plates to be welded are welded, the weld is inspected.

[0035] 48 hours after welding, the weld is subjected to nondestructive testing. The testing items include color testing and radiographic testing. Color testing is used to detect microscopic defects on the weld surface, such as cracks, pores, slag inclusions, looseness, delamination, etc. Radiographic testing is used to detect internal defects in the weld, such as pores, inclusions, cracks, etc. After completing the above tests, the weld can be subjected to tensile and bending tests.

[0036] The present invention ensures the performance of the welding joint and the formation of the surface weld seam through reasonable groove design, welding process parameters, welding materials, operation methods, etc. Compared with traditional arc welding and gas shielded welding, laser welding is more efficient. This method can be used for straight paneling in the process of manufacturing low-magnetic steel hull structures. It has the advantages of concentrated welding heat, small welding deformation, one-time formation of single-sided welding, fast welding speed, and good weld formation. In addition, this method can reduce the width of the heat-affected zone to a minimum as much as possible to ensure the performance of the welding joint under the premise of ensuring that the arc has sufficient penetration through welding parameter adjustment.

[0037] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A marine low magnetic steel laser welding method, used for welding two butt-jointed steel plates, characterized in that: The method comprises: Determine whether to design a groove based on the thickness of the two steel plates to be welded; If groove design is required, grooves shall be opened on the two steel plates to be welded and pre-processed; If no groove design is required, proceed with the subsequent operations; During welding, arc striking and extinguishing plates are assembled at the ends of the two steel plates to be welded; Laser welding is performed on two steel plates to be welded based on structures with and without grooves.

2. The laser welding method for marine low magnetic steel according to claim 1, characterized in that: The condition that no groove design is required is: if the plate thickness is between 2 mm and 3 mm, no groove design is required.

3. The laser welding method for marine low magnetic steel according to claim 1, characterized in that: The condition for designing the groove is: if the plate thickness is between 4 mm and 10 mm, a groove is opened on the two steel plates to be welded.

4. The laser welding method for marine low magnetic steel according to claim 3, characterized in that: The groove form is a V-shaped groove, the root gap of the groove is 0-0.5mm, and the groove root is 2mm-3mm.

5. The laser welding method for marine low magnetic steel according to claim 4, characterized in that: The angle of the groove is designed to be 20° to 30°.

6. The laser welding method for marine low magnetic steel according to claim 1, characterized in that: The steps of pre-treating the groove are: firstly grinding the inner surface of the groove and the left and right sides of the groove with a grinding wheel, then heating both sides of the groove to remove moisture on the surface of the steel plate to be welded, or cleaning the groove with acetone.

7. The laser welding method for marine low magnetic steel according to claim 1, characterized in that: The step of assembling arc-strike-and-extinguishing plates at the ends of two steel plates to be welded is as follows: an arc-strike-and-extinguishing plate is respectively arranged at both ends of each steel plate to be welded, and the gap between two opposite steel plates to be welded at the same end is controlled within 0.5 mm.

8. The laser welding method for marine low magnetic steel according to claim 1, characterized in that: If there is no groove structure, laser is used to directly weld the two steel plates to be welded.

9. The laser welding method for marine low magnetic steel according to claim 1, characterized in that: If there is a groove structure, laser and welding wire are used for welding, and arc guidance is used for welding. During the welding process, shielding gas is used to protect the weld.

10. The laser welding method for marine low magnetic steel according to claim 1, characterized in that: The method further comprises: after the welding of the two steel plates to be welded is completed, testing the weld.

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