Double-wire welding method for low-alloy high-strength ship plate steel

Abstract

The invention provides a double-wire welding method for low-alloy high-strength ship plate steel, which comprises the following steps: S1, selecting two pieces of ship plate steel, processing the two pieces of ship plate steel to a preset size, and splicing the two pieces of ship plate steel according to a T shape in a spot welding manner; s2, determining a preheating program according to the thickness of the ship plate steel; and S3, double-wire welding is conducted on the fillet weld of the ship plate steel through a double-wire welding gun according to preset welding parameters, and the double-wire welding gun is obliquely arranged. The reasonable welding speed and the reasonable preheating temperature range are provided for welding of the low-alloy high-strength ship plate steel, the low-alloy high-strength ship plate steel can be attractive in weld joint forming, the macroscopic structure is compact and free of defects, detection items such as the microhardness of a fusion area meet the classification society and corresponding detection specifications and standards, and application and popularization are facilitated.

Description

Technical Field

[0001] This application relates to the technical field of shipbuilding, and more specifically, to a double-wire welding method for low-alloy high-strength ship plate steel. Background Art

[0002] The rapid development of the shipbuilding industry has put forward higher requirements for welding processes. Welding is an important connection method for ship plate steel, so welding technology is one of the main factors affecting the production efficiency of large ships. Research shows that the welding work cycle accounts for 30%-40% of the total working hours of ship manufacturing, and the welding cost accounts for about 30%-50% of the overall shipbuilding process. Therefore, improving welding efficiency, reducing costs and increasing efficiency have become the key breakthrough directions for the welding technology of large medium-thick ship plate steel. As the "tailor" in the shipbuilding industry, welding technology has developed towards intelligence and diversification.

[0003] Fillet welds account for a very large proportion in the process of shipbuilding, are the main form in shipbuilding technology, and have a significant impact on the overall construction cost and quality control of ships. In sectional construction, the consumable electrode consumption of fillet welds accounts for about 50% of the total consumable electrode consumption; calculated by the unit length of the weld, the total length of the fillet weld type of welds accounts for up to about 80% of the total welds in shipbuilding. Therefore, the welding efficiency of fillet welds has a significant impact on the construction period of the entire ship.

[0004] In the prior art, when using a single-wire welding method for fillet welds, the welding speed will be limited, and the welding speed generally does not exceed 45 cm / min. When increasing the welding speed, it is difficult to melt the base metal due to insufficient heat input, and the weld formation cannot be guaranteed.

[0005] In summary, there is an urgent need for a technical solution that can perform high-speed welding on ship plate steel, while the fillet weld formation and the highest microhardness in the fusion zone meet the requirements. Summary of the Invention

[0006] The purpose of the embodiments of this application is to provide a double-wire welding method for low-alloy high-strength ship plate steel, which can perform high-speed welding on ship plate steel, the fillet weld formation is beautiful and defect-free, and the highest microhardness requirements near the joint fusion zone meet the specifications and standards of the classification society.

[0007] This application specifically provides a double-wire welding method for low-alloy high-strength ship plate steel, including the following steps:

[0008] S1. Select two pieces of ship plate steel and process them to a predetermined size, and splice the two pieces of ship plate steel in a T shape by spot welding;

[0009] S2. Determine the preheating procedure according to the thickness of the ship plate steel;

[0010] S3. Perform double-wire welding on the fillet weld of the ship plate steel with a double-wire welding torch according to predetermined welding parameters, and the double-wire welding torch is inclined.

[0011] In an implementable manner, in step S3, the inclination angle of the double-wire welding torch is 25 - 45°.

[0012] In an implementable manner, in step S3, the double-wire dry elongation of the double-wire welding torch is 10 - 15 mm; the double-wire spacing is 8 - 12 mm.

[0013] In an implementable manner, in step S3, the welding wire is a metal cored wire with a diameter of 1.2 mm.

[0014] In an implementable manner, in step S3, the shielding gas used during welding is a mixed gas of argon and carbon dioxide, and the gas flow rate of the mixed gas is 18 - 23 L / min.

[0015] In an implementable manner, the double-wire welding torch includes a front wire and a rear wire; the front wire and the rear wire are arranged front and back along the welding direction, and the extending ends of the front wire and the rear wire are inclined towards the axis direction of the double-wire welding torch.

[0016] In an implementable manner, in step S3, the predetermined welding parameters at least include:

[0017] The welding speed of the double-wire welding torch is 120 - 180 cm / min, the current of the front wire is 200 - 245 A, the current of the rear wire is 255 - 290 A, the voltage of the front wire is 22.5 - 28.5 V, the voltage of the rear wire is 23.5 - 28.5 V, the wire feeding speed of the front wire is 9.5 - 11.7 m / min, the wire feeding speed of the rear wire is 10.5 - 13.7 m / min, and the linear energy of the double-wire welding torch is 4.5 - 11.5 KJ / cm.

[0018] In an implementable manner, the thickness of the ship plate steel is 6 - 25 mm.

[0019] In an implementable manner, in step S2, when the thickness t of the ship plate steel is 12 - 25 mm, the calculation formula for the preheating temperature T is T = 100°C + (t - 12 mm) × 5°C.

[0020] In an implementable manner, after preheating, a contact thermometer is used to read the surface temperature of the ship plate steel, and the difference between the surface temperature and the preheating temperature is within 2 - 5°C.

[0021] In an implementable manner, when the thickness t of the ship plate steel is less than 12 mm, the preheating procedure can be omitted and welding can be directly performed.

[0022] Compared with the prior art, the beneficial effects of the present application are:

[0023] In the technical solution of the present application, through the double-wire common molten pool, on the premise of improving the welding speed, the welding quality of fillet welds is ensured, and the welding efficiency is 2-4 times that of single-wire welding. By setting specific welding parameters for double-wire high-speed welding, not only can a high welding speed be ensured, but also there is a large enough metal cladding amount and penetration depth to ensure the forming and arc stability; it can make the front wire and the rear wire melt in the same molten pool, and the heat generated by the front wire and the rear wire is borrowed from each other, that is, the heat dissipation of the front wire is used to melt the rear wire, and the heat generation of the rear wire speeds up the melting speed of the front wire, forming a cycle to further increase the cladding amount, while increasing the cladding amount, reducing the heat input to the base material, and improving the welding quality. It can determine whether preheating is required according to the plate thickness, provide different preheating temperatures for different plate thicknesses, achieve the use of the lowest preheating temperature, ensure the quality and performance of fillet welds, maximize the reduction of the preheating temperature, shorten the preheating time, and improve the welding efficiency.

[0024] The present application provides a reasonable welding speed and a reasonable preheating temperature range for the welding of low-alloy high-strength ship plate steel, and can achieve beautiful weld forming of low-alloy high-strength ship plate steel, with dense and defect-free macroscopic structure, and the inspection items such as the microhardness of the fusion zone meet the requirements of the classification society and the corresponding inspection specifications and standards, which is conducive to popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a flow chart of the double-wire welding method for low-alloy high-strength ship plate steel according to an embodiment of the present invention.

[0026] Figure 2 is a schematic diagram of the arrangement of the double-wire welding torch in the double-wire welding method for low-alloy high-strength ship plate steel according to an embodiment of the present invention.

[0027] Figure 3 is a macroscopic morphology diagram of the fillet weld of test plate five in the double-wire welding method for low-alloy high-strength ship plate steel according to an embodiment of the present invention.

[0028] Figure 4 is a microstructural diagram of the heat-affected zone of the fillet weld of test plate five in the double-wire welding method for low-alloy high-strength ship plate steel according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The following further describes in detail the specific embodiments of the present invention with reference to the accompanying drawings. These embodiments are only used to illustrate the present invention and are not intended to limit the present invention.

[0030] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In addition, in the description of the present invention, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0033] See Figures 1 to 2 , this application provides a double-wire welding method for low-alloy high-strength ship plate steel, including the following steps:

[0034] S1. Select two pieces of ship plate steel and process them to a predetermined size, and splice the two pieces of ship plate steel in a T shape by spot welding, as Figure 2 shown.

[0035] It should be noted that in this embodiment, the size of the ship plate steel is 1000mm×150mm.

[0036] It should also be noted that the thickness t of the ship plate steel is 6-25mm.

[0037] Specifically, the ship plate steel in this embodiment is low-alloy high-strength ship plate steel, and the contents of each element are as follows: the carbon C content does not exceed 0.13%, the silicon Si content does not exceed 0.40%, the manganese Mn content does not exceed 1.50%, the sulfur S content does not exceed 0.015%, the phosphorus P content does not exceed 0.015%, the aluminum Al content does not exceed 0.02%, the niobium Nb content does not exceed 0.05%, the titanium Ti content does not exceed 0.015%, the magnesium Mg content does not exceed 0.005%, and the iron Fe is the remaining content.

[0038] S2. Determine the preheating procedure according to the thickness of the ship plate steel.

[0039] Specifically, in step S2, a preheating plan is determined according to the thickness of the ship plate steel. When the thickness t of the ship plate steel is 12 - 25 mm, the calculation formula for the preheating temperature T is T = 100°C + (t - 12 mm) × 5°C. When the thickness of the ship plate steel is less than 12 mm, the preheating procedure can be omitted and welding can be carried out directly.

[0040] It should be noted that during preheating, a flame spray gun is used to fully preheat the steel plate.

[0041] It should also be noted that after preheating is completed, a contact thermometer is used to read the surface temperature of the ship plate steel, and the difference between the surface temperature and the preheating temperature is within 2 - 5°C.

[0042] S3. Double-wire welding is carried out on the fillet weld of the ship plate steel by a double-wire welding gun according to predetermined welding parameters, and the double-wire welding gun is inclined.

[0043] In an implementable manner, in step S3, the inclination angle of the double-wire welding gun is 25 - 45°.

[0044] In an implementable manner, in step S3, the double-wire dry elongation of the double-wire welding gun is 10 - 15 mm; the double-wire spacing is 8 - 12 mm.

[0045] In an implementable manner, in step S3, the welding wire is a metal cored wire with a diameter of 1.2 mm.

[0046] In an implementable manner, in step S3, the shielding gas used during welding is a mixed gas of argon and carbon dioxide, and the gas flow rate of the mixed gas is 18 - 23 L / min.

[0047] In an implementable manner, the double-wire welding gun includes a front wire and a rear wire. The front wire and the rear wire are arranged front and back along the welding direction, and the extended ends of the front wire and the rear wire are inclined towards the axis direction of the double-wire welding gun, as Figure 2 shown.

[0048] In an implementable manner, in step S3, the predetermined welding parameters at least include:

[0049] The welding speed of the double-wire welding gun is 120 - 180 cm / min, the current of the front wire is 200 - 245 A, the current of the rear wire is 255 - 290 A, the voltage of the front wire is 22.5 - 28.5 V, the voltage of the rear wire is 23.5 - 28.5 V, the wire feeding speed of the front wire is 9.5 - 11.7 m / min, the wire feeding speed of the rear wire is 10.5 - 13.7 m / min, and the linear energy of the double-wire welding gun is 4.5 - 11.5 KJ / cm. Through the design of the welding parameters in this application, it is possible to still have a weld with perfect forming and qualified performance during high-speed welding.

[0050] In an implementable manner, before step S1, the welding area of the ship plate steel is ground with a grinding wheel to remove the primer and rust, and then cleaned with acetone and dried.

[0051] In this embodiment, the following contents are further included:

[0052] AH36 ship plate steels with thicknesses t of 6 mm, 9 mm, 12 mm, and 16 mm are respectively selected and defined as test plate one, test plate two, test plate three, and test plate four. Test plate one, test plate two, test plate three, and test plate four are respectively processed according to steps S1 to S3.

[0053] The sizes of test plate one, test plate two, test plate three, and test plate four are all 1000 mm × 150 mm. The chemical composition of the AH36 ship plate steel is as follows: the carbon C content is 0.12%, the silicon Si content is 0.20%, the manganese Mn content is 1.34%, the sulfur S content is 0.004%, the phosphorus P content is 0.010%, the aluminum Al content is 0.016%, the niobium Nb content is 0.04%, the titanium Ti content is 0.013%, and the magnesium Mg content is 0.005%. The gas flow rate during welding is 20 L / min. The angle between the twin-wire welding torch and the vertical direction is 30°, the twin-wire dry elongation is 12 mm, and the twin-wire spacing is 10 mm. The welding speed is 120 cm / min, the current of the front wire is 225 A, the current of the rear wire is 260 A, the voltage of the front wire is 25.5 V, the voltage of the rear wire is 27.5 V, the wire feeding speed of the front wire is 10.7 m / min, the wire feeding speed of the rear wire is 12.7 m / min, and the heat input is 8.8 KJ / cm.

[0054] Among them, the thicknesses t of test plate one and test plate two are 6 mm and 9 mm respectively, both of which are less than 12 mm. Therefore, test plate one and test plate two are welded directly without preheating. The thickness t of test plate three is 12 mm, and test plate three is preheated to 100 °C. The thickness t of test plate four is 16 mm, and test plate four is preheated to 120 °C.

[0055] After welding is completed, the macroscopic morphology diagrams of the fillet welds and the microstructural diagrams of the heat affected zones of test plate one, test plate two, test plate three, and test plate four are respectively obtained, and the microhardness of the fusion zone of the fillet welds is measured ten times with a load of 10 Kg. The test results are shown in Table 1.

[0056] The fillet welds of Test Plate 1, Test Plate 2, Test Plate 3, and Test Plate 4 have beautiful forming, dense macro and microstructures, and no defects. The maximum value of the microhardness in the fusion zone of the fillet weld of Test Plate 1 is 224 HV, the minimum value is 202 HV, and the average value is 208 HV, all of which are less than 350 HV, meeting the specifications and standards of the classification society. The maximum value of the microhardness in the fusion zone of the fillet weld of Test Plate 2 is 309 HV, the minimum value is 249 HV, and the average value is 286 HV, all of which are less than 350 HV, meeting the specifications and standards of the classification society. The maximum value of the microhardness in the fusion zone of the fillet weld of Test Plate 3 is 237 HV, the minimum value is 184 HV, and the average value is 213 HV, all of which are less than 350 HV, meeting the specifications and standards of the classification society. The maximum value of the microhardness in the fusion zone of the fillet weld of Test Plate 4 is 240 HV, the minimum value is 195 HV, and the average value is 224 HV, all of which are less than 350 HV, meeting the specifications and standards of the classification society.

[0057] Three groups of DH36 ship plate steels are selected and defined as Test Plate 5, Test Plate 6, and Test Plate 7 respectively. The thickness t of Test Plate 5, Test Plate 6, and Test Plate 7 is all 12 mm, and Test Plate 5, Test Plate 6, and Test Plate 7 are all processed according to Step S1 to Step S3.

[0058] The sizes of Test Plate 5, Test Plate 6, and Test Plate 7 are all 1000 mm × 150 mm. The chemical composition of the DH36 ship plate steel is as follows: carbon content is 0.078%, silicon content is 0.20%, manganese content is 1.42%, sulfur content is 0.015%, phosphorus content is 0.015%, aluminum content is 0.012%, niobium content is 0.04%, titanium content is 0.015%, and magnesium content is 0.005%. The welding areas to be welded of each test plate are polished and cleaned with a grinding wheel and then dried. Subsequently, they are spot welded and fixed to form a T shape. The test plates are preheated to 100 °C with a flame spray gun.

[0059] The gas flow rate during welding is 20 L / min. The angle between the twin-wire welding gun and the vertical direction is 30°, the twin-wire dry elongation is 12 mm, and the twin-wire spacing is 10 mm.

[0060] Among them, the welding speed of Test Plate 5 is 120 cm / min, the current of the front wire is 230 A, the current of the rear wire is 270 A, the voltage of the front wire is 25.5 V, the voltage of the rear wire is 27.5 V, the wire feeding speed of the front wire is 9.5 m / min, the wire feeding speed of the rear wire is 12 m / min, and the heat input is 8.0 KJ / cm.

[0061] Among them, the welding speed of Test Plate 6 is 150 cm / min, the current of the front wire is 240 A, the current of the rear wire is 280 A, the voltage of the front wire is 26 V, the voltage of the rear wire is 28 V, the wire feeding speed of the front wire is 9.5 m / min, the wire feeding speed of the rear wire is 12 m / min, and the heat input is 8.8 KJ / cm.

[0062] Among them, the welding speed of test plate seven is 180 cm / min, the current of the front wire is 245 A, the current of the rear wire is 290 A, the voltage of the front wire is 27.5 V, the voltage of the rear wire is 28.5 V, the wire feeding speed of the front wire is 9.5 m / min, the wire feeding speed of the rear wire is 12 m / min, and the heat input is 11 KJ / cm.

[0063] After welding is completed, the macroscopic morphology diagrams of the fillet welds and the microstructural diagrams of the heat affected zones of test plates five, six, and seven are obtained respectively, and the microhardness of the fusion zone of the fillet welds is measured ten times with a load of 10 Kg. The test results are shown in Table 1.

[0064] As Figure 3 and Figure 4 shown, the fillet welds of test plates five, six, and seven have beautiful forming, dense macro and microstructures, and no defects. The maximum value of the microhardness of the fusion zone of the fillet weld of test plate five is 322 HV, the minimum value is 291 HV, and the average value is 305 HV, all of which are less than 350 HV, meeting the specifications and standards of the classification society. The maximum value of the microhardness of the fusion zone of the fillet weld of test plate six is 336 HV, the minimum value is 308 HV, and the average value is 321 HV, all of which are less than 350 HV, meeting the specifications and standards of the classification society. The maximum value of the microhardness of the fusion zone of the fillet weld of test plate seven is 344 HV, the minimum value is 319 HV, and the average value is 335 HV, all of which are less than 350 HV, meeting the specifications and standards of the classification society.

[0065] Table 1 Statistical table of test results of multiple test plates

[0066] Example PT test Macroscopic metallography Fracture test Microhardness (HV) of the fusion zone Conclusion Test plate 1 Qualified No defects Qualified 202-224 Qualified Test plate 2 Qualified No defects Qualified 249-309 Qualified Test plate 3 Qualified No defects Qualified 184-237 Qualified Test plate 4 Qualified No defects Qualified 195-240 Qualified Test plate 5 Qualified No defects Qualified 291-322 Qualified Test plate 6 Qualified No defects Qualified 308-336 Qualified Test plate 7 Qualified No defects Qualified 319-344 Qualified

[0067] In summary, the present application uses double-wire welding, which can achieve beautiful fillet weld formation and defect-free structure at a high welding speed of 120 - 180 cm / min. The maximum microhardness of the weld fusion zone of low-alloy high-strength ship steel plate is lower than 350 HV, meeting the specifications and standards of the classification society. The present application realizes a double-wire common molten pool, with more concentrated welding energy and less post-weld deformation. On the premise of increasing the welding speed, it effectively improves the weld formation and welding quality, and the welding efficiency is 2 - 4 times that of single-wire welding. When performing single-wire welding, it is impossible to simultaneously take into account the penetration and formation of the weld. Therefore, the welding speed of single-wire welding will be limited. When increasing the welding speed, it is difficult to melt the base metal due to insufficient heat input, and the weld formation cannot be guaranteed. Therefore, the present application adopts double-wire high-speed welding and provides specific welding parameters for double-wire high-speed welding, which can not only ensure a high welding speed but also have a large enough metal cladding amount and penetration to ensure formation and arc stability; it can make the front wire and the rear wire melt in the same molten pool, and the heat generated by the front wire and the rear wire is borrowed from each other, that is, the heat dissipation of the front wire is used to melt the rear wire, and the heat generated by the rear wire speeds up the melting speed of the front wire, forming a cycle to further increase the cladding amount, while reducing the heat input to the base metal when increasing the cladding amount and improving the welding quality.

[0068] The present application can determine the preheating procedure according to the plate thickness, provide different preheating temperatures for different plate thicknesses, realize the use of the lowest preheating temperature to ensure the quality and performance of fillet welds, maximize the reduction of the preheating temperature, shorten the preheating time, and improve the welding efficiency. The present application provides a reasonable welding speed and a reasonable preheating temperature range for the welding of low-alloy high-strength ship plate steel, which can achieve beautiful weld formation of low-alloy high-strength ship plate steel, dense and defect-free macrostructure, and the detection items such as the microhardness of the fusion zone meet the classification society and corresponding detection specifications and standards, facilitating popularization and use.

[0069] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A double-wire welding method for low-alloy high-strength ship plate steel, characterized in that, It includes the following steps: S1. Select two pieces of ship plate steel and process them to a predetermined size, and splice the two pieces of ship plate steel in a T shape by spot welding; S2. Determine the preheating procedure according to the thickness of the ship plate steel; S3. Perform twin-wire welding on the fillet weld of the ship plate steel by a twin-wire welding torch according to predetermined welding parameters, and the twin-wire welding torch is inclined.

2. The double-wire welding method for the low-alloy high-strength ship plate steel according to claim 1, characterized in that, In step S3, the inclination angle of the twin-wire welding torch is 25-45°.

3. The double-wire welding method for the high-strength low-alloy ship plate steel according to claim 2, wherein, In step S3, the twin-wire dry elongation of the twin-wire welding torch is 10-15 mm; the twin-wire spacing is 8-12 mm.

4. The double-wire welding method for the low-alloy high-strength ship plate steel according to claim 1, characterized in that, In step S3, the welding wire is a metal cored wire with a diameter of 1.2 mm.

5. The double-wire welding method for the low-alloy high-strength ship plate steel according to claim 1, wherein, In step S3, the shielding gas used during welding is a mixed gas of argon and carbon dioxide, and the gas flow rate of the mixed gas is 18-23 L / min.

6. The double-wire welding method for the high-strength low-alloy ship plate steel according to claim 1, wherein, The twin-wire welding torch includes a front wire and a rear wire. The front wire and the rear wire are arranged front and rear along the welding direction, and the extending ends of the front wire and the rear wire are inclined towards the axis direction of the twin-wire welding torch.

7. The double-wire welding method for the low-alloy high-strength ship plate steel according to claim 6, characterized in that, In step S3, the predetermined welding parameters at least include: The welding speed of the twin-wire welding torch is 120-180 cm / min, the current of the front wire is 200-245 A, the current of the rear wire is 255-290 A, the voltage of the front wire is 22.5-28.5 V, the voltage of the rear wire is 23.5-28.5 V, the wire feeding speed of the front wire is 9.5-11.7 m / min, the wire feeding speed of the rear wire is 10.5-13.7 m / min, and the linear energy of the twin-wire welding torch is 4.5-11.5 KJ / cm.

8. The double-wire welding method for the low-alloy high-strength ship plate steel according to claim 1, characterized in that, The thickness t of the ship plate steel is 6-25 mm.

9. The double-wire welding method for the low-alloy high-strength ship plate steel according to claim 8, characterized in that, In step S2, when the thickness t of the ship plate steel is 12-25 mm, the calculation formula for the preheating temperature T is T = 100°C + (t - 12 mm) × 5°C.

10. The double-wire welding method for the low-alloy high-strength ship plate steel according to claim 8, characterized in that, When the thickness t of the ship plate steel is less than 12 mm, the preheating procedure is omitted and welding is directly performed.

Images