Welding method for ship bulbous bow

Abstract

The invention provides a welding method for a ship bulbous bow. The welding method comprises the steps that a V-shaped groove is machined in the outer side face of the bulbous bow; the bulbous bow assembly is welded and fixed on the inner side surface of the bulbous bow by adopting a positioning piece; a ceramic gasket is installed on the inner side of the bulbous bow, the center of the ceramic gasket right faces the back face of the V-shaped groove, and a water-cooling sliding block is installed on the front face of the V-shaped groove; a flexible track special gas-electric welding trolley is adopted, welding parameters of a gas-electric all-position welding technology, power source polarity changes of gas-electric all-position welding, the welding wire distance, the gun angle, the swing width and the standing time are formulated, and single-face welding and double-face forming welding is carried out in a gas-electric all-position welding mode; welding seam inspection is conducted. According to the method, the assembling groove form is improved, and an inner Y-shaped groove is improved into an outer side V-shaped groove; a single-face welding and double-face one-time forming electro-gas all-position welding technology is used, the operation difficulty is lowered, the operation environment is improved, the operation quality is improved, and the operation efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of ship welding, and in particular relates to a welding method for a bulbous bow of a ship. Background Art

[0002] During the ship construction process, in order to reduce the wave resistance when the ship is sailing at high speed on the water surface, a huge protruding long spherical bulbous bow is designed at the bow of the ship. It not only increases the speed, but also plays a good balancing role on the hull. More importantly, it serves as a "sonar deflector". The bulbous bow section (F001 $ F002) is a closed joint connecting the bow tank. The material is low alloy steel and high strength steel. The outer plate welding method is as follows:

[0003] a) Assemble the inner Y-shaped groove with a blunt edge of 2-3mm and no gap, and fix it on the outer plate side with spot welding.

[0004] b) Using CO inside the bulbous bow 2 Semi-automatic welding is used for electric welding (4 passes).

[0005] c) Use carbon arc air planer to clean the root and open U-shaped groove on the outside of the bulbous bow.

[0006] d) Use CO on the U-shaped groove outside the bulbous bow 2 Semi-automatic welding is used for electric welding (2 passes).

[0007] After the bulbous bow is assembled, it is connected to the bow tank structure of the hull. The internal space is a closed space. The workers enter the bulbous bow through the bow tank to carry out construction. After the bulbous bow is installed, electric welding is required in the closed space inside and manual carbon arc air planing and root cleaning and beveling are required on the outside. The inner space of the bulbous bow is closed and has a hull structure. The workload of electric welding inside accounts for a large proportion and the operation difficulty is relatively high. A large amount of smoke and dust will be generated in a short period of time during the operation, and the environment is harsh. The existing technology has the following problems:

[0008] 1. The homework is difficult

[0009] The construction workers had to weld in the confined space inside the bulbous bow with obstacles from the hull structure. The welding work was difficult due to the high-tech workload of all-position welding, such as flat welding, slope welding, vertical welding, and inclined welding.

[0010] 2. Poor working environment

[0011] The inner side seam of the bulbous bow requires four multi-pass welding operations. A large amount of welding smoke swirls inside the bulbous bow space where air does not circulate, creating a harsh working environment for workers.

[0012] 3. Poor quality of work

[0013] The difficulty of all-position welding and the harsh working environment make the welding quality unable to meet the ideal expectations. After welding, the UT and MT flaw detection showed that the average first-time pass rate of the bulbous bow was only 86%, and a large amount of repairs were required in the later stage.

[0014] 4. Low operating efficiency

[0015] It takes 8 days to complete the welding of the bulbous bow, which is a long cycle and low efficiency. Summary of the invention

[0016] The object of the present invention is to provide a welding method for a bulbous bow of a ship with low difficulty and high efficiency.

[0017] The present invention provides a welding method for a bulbous bow of a ship, the method comprising:

[0018] Step S1: Processing a V-shaped groove on the outer side of the bulbous bow;

[0019] Step S2: The bulbous bow is assembled by welding and fixing the positioning piece on the inner side of the bulbous bow;

[0020] Step S3: installing a ceramic liner on the inner side of the bulbous bow, with the center of the ceramic liner facing the back side of the V-shaped groove, and installing a water-cooling slider on the front side of the V-shaped groove;

[0021] Step S4: using a gas-electric welding trolley dedicated to a flexible track, formulating welding parameters of gas-electric all-position welding technology, power polarity change of gas-electric all-position welding, welding wire distance, gun angle, swing width, and dwell time, and performing gas-electric all-position welding to perform single-sided welding and double-sided forming welding;

[0022] Step S5: Conduct weld inspection.

[0023] Optionally, in step S1, the groove angle of the V-shaped groove is between 25° and 30°, the assembly pair gap is 8mm-12mm, and the blunt edge is 0mm.

[0024] Optionally, in step S2, the positioning member includes a II-shaped card code plate;

[0025] The bulbous bow assembly adopts positioning parts to be welded and fixed on the inner side of the bulbous bow, including: V-shaped groove processed according to the design, Π-shaped clamping plate is installed on the back of the V-shaped groove joint and fixed by welding, and a Π-shaped clamping plate is installed for each gap of 250mm-300mm in length of the weld groove.

[0026] Optionally, the welding method in step S4 includes:

[0027] The welding gun is clamped by a gas-electric vertical welding auxiliary trolley, and gas-electric full-position welding with gas slag protection is performed from the lower end of the two hemispheres of the bulbous nose upward along the gear flexible track fixed next to the weld. During welding, a fiber ceramic pad is pasted on the back of the V-shaped groove joint, and a U-shaped groove water-cooled slider is used on the front of the groove to support the molten pool for forced formation.

[0028] Optionally, in step S3, installing the ceramic liner includes:

[0029] When installing the ceramic liner, it should be tightly attached to the groove steel plate inside the bulbous bow, and the ceramic liners should be pushed tightly without any gap. The groove surface end of the ceramic liner should be tightly attached to the back of the groove steel plate of the bulbous bow and aligned. The ceramic liner should be fixed by pressing the Π-shaped card plate hole with an iron wedge.

[0030] Optionally, the water-cooled slider is installed on the slider clamping mechanism of the welding trolley. The slider clamping mechanism is adjusted to make the water-cooled slider close to the edge of the V-groove steel plate on the outer side of the bulbous bow, and as the welding trolley moves left and right, the slider clamping force is adjusted, and the water-cooled slider moves close to the groove surface, so that the water-cooled slider supports the molten pool during the welding process to force the gas-electric all-position welding weld to form.

[0031] Optionally, in step S4, the welding sequence includes: dividing the bulbous bow into positions from 1 o'clock to 12 o'clock on the clock face according to the cross-sectional shape of the bulbous bow and separating the two hemispheres at positions of 6 o'clock and 12 o'clock, and performing gas-electric full-position welding with gas slag protection in the order of gas-electric full-position welding with the lower ends of the two hemispheres facing upward, welding one hemisphere and then welding the other hemisphere with the lower end facing upward, and adjusting relevant parameters according to different positions.

[0032] Optionally, in step S4:

[0033] The cross-sectional shape of the bulbous bow divides the bulbous bow into positions from 1 o'clock to 12 o'clock on the clock face. During welding, in order to ensure the formation of the back side of the weld in the upward and oblique upward positions of the gas-electric all-position welding, the power supply adopts the DC positive connection method, and the DC reverse connection method is used for welding in other positions.

[0034] Optionally, in step S4:

[0035] The extension length of the welding wire for gas-electric all-position welding is 30mm~35mm.

[0036] Optionally, after the bulbous bow gas-electric full-position welding is completed, welding inspection, examination and performance measurement are carried out, as follows:

[0037] Visual inspection shows that the weld is well formed on both sides, no welding defects are found, and the appearance inspection is qualified. 24 hours after welding, the weld is subjected to 100% UT+RT+MT nondestructive testing, and the result is qualified;

[0038] Mechanical properties of test plate welded joints: Tensile and bending tests, the average tensile strength of welded joints using gas-electric all-position welding method is 523MPa, and the strength of welded joints meets the minimum tensile strength requirement of 490MPa matching the strength of the parent material; impact tests are carried out on welded joints.

[0039] The beneficial effects brought by the present invention are as follows:

[0040] It can be seen from the above scheme that the embodiment of the present invention provides a method for welding a bulbous bow of a ship. Compared with the prior art, this new method has the following advantages:

[0041] 1. Reduce the difficulty of the task

[0042] Through method innovation, the welding workload of construction workers in the confined space inside the bulbous bow has been greatly reduced. At the same time, mechanized and automated welding operations have reduced the skill requirements for welders and the difficulty of welding operations.

[0043] 2. Improve the working environment

[0044] Through method optimization, manual CO removal in the confined space inside the bulbous bow was avoided. 2 Multi-layer and multi-pass welding reduces the generation of a large amount of smoke and dust in the confined space of the bulbous bow and improves the working environment of workers.

[0045] 3. Improve the quality of work

[0046] Through method optimization, a gas-electric full-position welding method with mechanized and automated single-sided welding and double-sided forming of the bulbous bow curved segmented outer plate is realized. The welding difficulty is reduced and the working environment is improved, which improves the welding quality. After welding, the UT, RT, and MT flaw detection results show that the bulbous bow has an average one-time qualified rate of 100%, which is 13.2% higher than the original method's one-time flaw detection qualified rate of 86.8%.

[0047] 4. Improve work efficiency

[0048] The original method of welding the bulbous bow required an 8-day operation cycle, but the current method only takes 1 day, reducing the operation cycle by 4 days, greatly improving efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a flow chart of a method for welding a bulbous bow of a ship according to an embodiment of the present invention;

[0050] Figure 2 Schematic diagram of a bulbous bow groove according to an embodiment of the present invention;

[0051] Figure 3 The front view and side view of the II-shaped card code plate according to the embodiment of the present invention;

[0052] Figure 4This is a schematic diagram of the installation of a II-type card code board according to an embodiment of the present invention;

[0053] Figure 5 A first welding state diagram of an embodiment of the present invention;

[0054] Figure 6 A schematic diagram of the welding sequence of an embodiment of the present invention;

[0055] Figure 7 Schematic diagram of the polarity of the welding power supply according to an embodiment of the present invention.

[0056] Figure 8 A schematic diagram of installing a ceramic liner according to an embodiment of the present invention;

[0057] In the figure, 1. bulbous bow; 2. Π-type clamping plate; 3. ceramic liner; 4. weld; 5. molten pool; 6. water-cooled slider; 7. welding gun; 8. iron wedge. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] The present invention designs a welding method for a bulbous bow of a ship, optimizes the operation process under the premise of meeting the quality requirements of the weld, improves the assembly groove form, and improves the inner Y-type groove to the outer V-type groove; according to the curve change of the bulbous bow outer plate, a single-sided welding and double-sided one-time forming gas-electric full-position welding technology is developed, and welding processes and operating methods such as changes in welding power polarity, welding wire position, welding gun angle, swing width, front and rear dwell time, welding sequence, welding parameters, etc. of the bulbous bow gas-electric full-position welding at different welding positions are formulated, so as to reduce the operation difficulty, improve the working environment, enhance the operation quality, and improve the operation efficiency.

[0060] See also Figure 1 The present invention provides a welding method for a bulbous bow 1 of a ship, the method comprising:

[0061] Step S1: Processing a V-shaped groove on the outer side of the bulbous bow 1; the groove angle of the V-shaped groove is between 25° and 30°, the assembly gap is 8mm-12mm, and the blunt edge is 0mm.

[0062] Specifically, combined Figure 2, Bulbous bow 1 groove design: the original inner Y-shaped groove of the bulbous bow 1 is improved and processed into an outer V-shaped groove of the bulbous bow 1. According to the 18mm plate thickness of the bulbous bow DH36 high-strength steel, in order to achieve single-sided welding and double-sided forming of gas and electric full-position welding, the groove angle is 25-30°, the assembly gap is 8-12mm, and the blunt edge is 0mm.

[0063] Step S2: The bulbous bow 1 is assembled by welding and fixing the positioning piece on the inner side of the bulbous bow 1; the positioning piece includes a Π-shaped clamping plate 2;

[0064] The bulbous bow 1 is assembled by welding and fixing the positioning piece on the inner side of the bulbous bow 1, including: according to the designed V-shaped groove, a Π-shaped clamping plate 2 is installed on the back of the V-shaped groove joint and fixed by welding, and a Π-shaped clamping plate 2 is installed every 250mm-300mm gap length of the weld groove 4.

[0065] Specifically, combined Figure 3 and Figure 4 The assembly method of the bulbous bow 1 includes: according to the designed V-shaped groove, the inner side of the bulbous bow 1 cabin (the back of the V-shaped groove joint) is installed with a Π-shaped card plate 2 and fixed by welding. The size of the Π-shaped positioning card plate required for assembly is: 200x120x15mm, and a Π-shaped card plate 2 is installed for each gap of 250-300mm in length of the weld 4 groove. The Π-shaped card plate 2 is welded firmly to ensure that the groove plane has no bad edges.

[0066] Step S3: installing a ceramic liner 3 on the inner side of the bulbous bow 1, with the center of the ceramic liner 3 facing the back side of the V-shaped groove, and installing a water-cooling slider 6 on the front side of the V-shaped groove; installing the ceramic liner 3 includes: when installing the ceramic liner 3, the ceramic liner 3 is tightly attached to the groove steel plate on the inner side of the bulbous bow 1, the ceramic liners 3 are pushed tightly without gaps, the groove surface end of the ceramic liner 3 is tightly attached to the back side of the groove steel plate of the bulbous bow 1 and is centered, and the ceramic liner 3 is pressed tightly to the hole of the Π-shaped card plate 2 by using an iron wedge 8 to fix it.

[0067] Step S4: adopting a gas-electric welding trolley specially used for flexible rails, formulating welding parameters of gas-electric full-position welding technology, power polarity change of gas-electric full-position welding, welding wire distance, gun angle, swing width, and dwell time, and performing gas-electric full-position welding to perform single-sided welding and double-sided forming welding; the welding method comprises: using a gas-electric vertical welding auxiliary trolley to clamp a welding gun 7, and performing gas-slag-protected gas-electric full-position welding upward from the lower end of the two hemispheres of the bulbous nose 1 along the gear flexible track fixed beside the weld 4; during welding, a fiber ceramic liner is pasted on the back of the V-shaped groove joint, and a U-shaped groove water-cooled slider 6 is used to support the molten pool 5 on the front of the groove to force forming. The water-cooled slider 6 is installed on the slider clamping mechanism of the welding carriage. The slider clamping mechanism is adjusted to make the water-cooled slider 6 close to the edge of the V-groove steel plate on the outside of the bulbous bow 1, and as the welding carriage moves left and right, the slider clamping force is adjusted, and the water-cooled slider 6 moves close to the groove surface, so that the water-cooled slider 6 holds the molten pool 5 during the welding process to force the gas-electric full-position welding weld 4 to form. The welding sequence includes: dividing the bulbous bow 1 into the positions of 1 to 12 o'clock on the clock face according to the cross-sectional shape of the bulbous bow 1 and separating the two hemispheres at the positions of 6 and 12 o'clock, and the gas-electric full-position welding is performed in the order of gas-slag protection gas-electric full-position welding with the lower ends of the two hemispheres upward, welding one hemisphere and then welding the lower end of the other hemisphere upward, and adjusting relevant parameters according to different positions. The cross-sectional shape of the bulbous bow 1 divides the bulbous bow 1 into the positions of 1 o'clock to 12 o'clock on the clock face. During welding, in order to ensure the back side formation of the weld 4 at the upper and oblique upper positions of the gas-electric all-position welding, the power supply adopts the direct current positive connection method, and the other positions adopt the direct current reverse connection method. The extension length of the gas-electric all-position welding wire is 30mm to 35mm.

[0068] Specifically, combined Figures 5 to 7 A special welding auxiliary trolley (EGW) is used to clamp the welding gun 7, and gas-slag-protected gas-electric full-position welding is performed from the lower end of the two hemispheres of the bulbous nose 1 upward along the gear flexible track fixed beside the weld 4; during welding, a fiber ceramic liner is pasted on the back of the V-shaped groove joint, and a U-shaped groove water-cooled slider 6 is used on the front of the groove to support the molten pool 5 for forced forming, so as to achieve a gas-electric full-position welding single-sided welding and double-sided forming welding method.

[0069] 1) Welding materials:

[0070] ① Fiber ceramic welding pad: It is formed by one-time welding on the back side of the inner groove of the bulbous bow 1 to ensure the height and width of the back weld 4. The requirements for the appearance size of the fiber ceramic pad groove are: width 43mm, height 10mm, groove width 14mm, and groove arc depth 1.5mm. Because the bulbous bow 1 has linear curved surface segments, in order to ensure the quality of gas and electric full-position welding, a layer of fiber protection is required on the front side of the ceramic welding pad groove. The ceramic has sulfur <0.05%, phosphorus <0.1%, moisture absorption rate ≤0.4%, volume density ≥1.75g / cm3, flexural strength ≥83g / cm2, 180° peeling force ≥20N / 2.5cm, and refractoriness 1300℃ technical performance.

[0071] ② Flux-cored welding wire: The outer plate of the bulbous bow is made of Grade D high-strength hull structural steel. Gas-electric all-position welding uses Grade 3Y flux-cored welding wire, and the composition of the flux-cored welding wire meets the following requirements: carbon ≤ 0.05%, sulfur < 0.004%, phosphorus < 0.007%, silicon ≤ 0.90%, manganese ≤ 2.0%, copper ≤ 0.35%, nickel ≤ 0.30%, molybdenum ≤ 0.35%, vanadium ≤ 0.08%.

[0072] ③ Gas: Bulbous bow outer plate D-grade high-strength hull structural steel, gas-electric all-position welding gas uses CO 2 Gas, the purity of which must be greater than 99.9%.

[0073] 2) Welding process parameters and welding operation design:

[0074] (I) The main welding process parameters for bulbous bow gas-electric all-position welding are: welding sequence, welding power polarity, welding gun 7 angle, welding wire extension length, welding current, arc voltage, welding speed, welding wire swing and dwell time, etc.

[0075] (1) Welding sequence

[0076] The bulbous bow 1 is divided into two hemispheres according to its cross-sectional shape. The welding sequence of gas-electric full-position welding is to perform gas-electric full-position welding with gas slag protection on the bulbous bow 1 with the lower end of the two hemispheres upward, and after welding one hemisphere, weld the lower end of the other hemisphere upward.

[0077] (2) Welding power polarity

[0078] The cross-sectional shape of the bulbous bow 1 divides the bulbous bow 1 into positions from 1 to 12 o'clock on the clock face. During welding, in order to ensure that the back side of the weld 4 is formed at the welding elevation position and the oblique elevation position (i.e., the 6 to 4 o'clock and 6 to 8 o'clock positions on the clock face of the bulbous bow 1) of the gas-electric all-position welding, the power supply adopts the DC positive connection method (i.e., the bulbous bow 1 base material is connected to the positive pole of the welding power supply, and the welding gun 7 is connected to the negative pole), and the other positions are welded by the DC reverse connection method (i.e., the bulbous bow 1 base material is connected to the negative pole of the welding power supply, and the welding gun 7 is connected to the positive pole).

[0079] (3) Welding gun angle

[0080] The angle of the gas-electric all-position welding torch 7 is adjusted according to different welding positions, and whether the angle is suitable or not directly affects the formation and defects of the front and back sides of the weld 4. The angle of the welding torch 7 at each position refers to the angle of the welding operation at the specific position of the bulbous bow 1.

[0081] (4) Wire extension length

[0082] The wire extension length of gas-electric all-position welding is 30-35mm. If the wire extension length is too long, the resistance heat will increase, the melting speed will be fast, and it will be easy to overheat and burn out, causing serious spatter and poor protection effect, affecting the stability of the welding process and making the weld 4 worse. If the wire extension length is too short, it will easily lead to blockage of the shielding gas outlet, resulting in poor protection and affecting the welding quality.

[0083] (5) Welding current

[0084] Due to the high current density, the droplet transfer of gas-electric all-position welding is a droplet transfer type. Its characteristics are small spatter, stable arc burning, and high deposition speed, so the appropriate current must be selected. Too large or too small welding current will affect the stability of the welding process and the good formation of the weld. The welding current of each position of the bulbous bow 1 can be seen in the welding parameters of the specific position welding operation of the bulbous bow 1.

[0085] (6) Arc voltage

[0086] The selected value of arc voltage for gas-electric all-position welding must match the welding current. If the arc voltage is too high, there will be large spatter and serious undercut of weld 4, but if the arc voltage is too low, the arc burning will be unstable. Therefore, under the condition of ensuring the stability of the welding process and the good formation of weld 4, the arc voltage should be reduced as much as possible to prevent pores and reduce the burning loss of alloy elements. The arc voltage for welding at each position of the bulbous bow 1 can be found in the welding parameters of the specific welding operation of the bulbous bow 1.

[0087] (7) Welding speed

[0088] The appropriate welding speed depends on the melting speed of the welding wire. The relationship between the metal liquid level of the molten pool 5 in the water-cooled slider 6 and the melting speed of the welding wire is that it is more appropriate to keep the metal liquid level of the molten pool 5 at least 2-3mm away from the bottom of the air inlet. If the welding speed is too fast, the metal liquid level of the molten pool 5 in the slider gradually drops and is not fully fused with the upper end of the flat fillet weld 4, or even the back of the flat fillet weld is not well fused, resulting in a lack of penetration defect. If the welding speed is too slow, the metal liquid level of the molten pool 5 in the water-cooled slider 6 rises, and the metal in the molten pool 5 rolls forward, which is prone to a lack of penetration defect. When the metal liquid level of the molten pool 5 rises to the bottom of the air inlet, the arc burning is unstable, and even forces the welding process to be interrupted. The welding speeds at various positions of the bulbous bow 1 refer to the welding parameters of the specific welding operation at the bulbous bow 1.

[0089] (8) Wire swing and dwell time

[0090] When the gas-electric all-position welding adopts the oscillator welding, the arc is stable, the spatter is small, the temperature on the cross section of the weld 4 is uniform, the metal crystallization state of the molten pool 5 is improved, and the grain size is fine, which is conducive to obtaining a dense weld 4 and beautiful forming. The swing amplitude and dwell time can be seen in the specific position welding operation of the bulbous bow 1.

[0091] (II) Welding operation of gas-electric all-position welding

[0092] (1) Fiber ceramic liner installation: Combine Figure 8 When installing the gasket, it must be ensured that the fiber gasket is in close contact with the groove steel plate inside the bulbous bow 1, the gaskets are pushed tightly without gaps, the groove surface end of the fiber gasket is in close contact with the back of the groove steel plate of the bulbous bow 1 and aligned, and the fiber gasket is pressed tightly against the hole of the Π-shaped card plate 2 by using an iron wedge 8 to fix it.

[0093] (2) Installation of the water-cooled slider 6: The water-cooled slider 6 is installed on the slider clamping mechanism on the welding trolley. The upper and lower knobs of the slider clamping mechanism are adjusted to ensure that the water-cooled slider 6 is in close contact with the edge of the V-groove steel plate on the outer front side of the bulbous bow 1. As the flexible guide rail welding trolley moves left and right, the slider clamping knob is finely adjusted to an appropriate pressure. The water-cooled slider 6 moves in close contact with the groove surface, so that the water-cooled slider 6 supports the molten pool 5 during the welding process, forcing the gas-electric all-position welding weld 4 to form.

[0094] (3) Welding:

[0095] The bulbous bow 1 is divided into the positions of 1 to 12 o'clock on the clock face and into two hemispheres at the positions of 6 and 12 o'clock according to the cross-sectional shape of the bulbous bow 1. The gas-electric full-position welding is performed in the order of gas-slag protection with the lower ends of the two hemispheres facing upward. After welding one hemisphere, the lower end of the other hemisphere is welded in the direction upward, and relevant parameters are adjusted according to different positions.

[0096] ① Welding of the cross-sectional shape of the bulbous bow 1 at the 6-5 o'clock position: This position is the arc starting position. Before starting the arc, the welding power supply is adjusted to adopt the DC positive connection method, the angle of the welding gun 7 is adjusted to be 5-8° tilted inward, the welding wire extension length is 30-35mm, the welding wire and the groove toe end are 4-6mm, the welding gun 7 swing amplitude is 6-8mm, the groove toe end face residence time is 1.0-1.2sec, the V groove front face residence time is 1.5-1.8sec, the swing speed is 31mm / sec, the welding current is 297-352A, and the arc voltage is 30-36V (see Table 1 for specific parameters). Press the start button to start the arc in the broken arc mode. After the molten pool 5 is established, press the welding wire swing button again to start normal welding. The welding speed is automatic tracking (about 11cm / min), and the welding pool 5 and the slider protective gas port are 2-7mm apart. At the same time, the spatter in the water-cooled slider 6 protective gas box should be removed at any time with an insulating rod.

[0097] Table 1 Welding parameters

[0098]

[0099] ② Welding of the cross-sectional shape of the bulbous bow 1 at the 5-4 o'clock position: when welding from the 6-5 o'clock position to the 5 o'clock position, the same welding power source adopts the DC positive connection method, the welding wire extension length is 30-35mm, and the welding gun 7 is slowly adjusted to be inclined 4-6° inward, the welding wire and the groove toe end are 5-8mm, the welding gun 7 swings 4-6mm, the groove toe end face stay time is 1.0-1.2sec, the V groove front face stay time is 1.3-1.4sec, the swing speed is 31mm / sec, the welding current is 320-355A, the arc voltage is 34-38V (see Table 2 for specific parameters), the welding speed is automatically tracked (about 12cm / min), and the welding pool 5 and the slider protective gas port are 2-6mm, and the spatter in the water-cooled slider 6 protective gas box should be removed at any time with an insulating rod.

[0100] Table 2 Welding parameters

[0101]

[0102] ③ Welding of the cross-sectional shape of the bulbous bow 1 at the 4-2 o'clock position: When welding from the 5-4 o'clock position to the 4 o'clock position, adjust the welding power supply to adopt the DC reverse connection method, the welding wire extension length is 30-35mm, slowly adjust the angle of the welding gun 7 to be 3-4° tilted inward, the welding wire and the groove toe end are 8-10mm, the welding gun 7 swing amplitude is 3-5mm, the groove toe end face residence time is 1.0~1.2sec, the V groove front face residence time is 1.1~1.3sec, the swing speed is 30mm / sec, the welding current is 340-370A, the arc voltage is 36-40V (see Table 3 for specific parameters), the welding speed is automatic tracking (about 10cm / min), and the welding pool 5 is 2-5mm away from the slider protective gas port. At the same time, the spatter in the water-cooled slider 6 protective gas box should be removed at any time with an insulating rod.

[0103] Table 3 Welding parameters

[0104]

[0105] ④ Welding of the cross-sectional shape of the bulbous bow 1 at the 2-1 o'clock position: when welding from the 4-2 o'clock position to the 2 o'clock position, the same welding power supply adopts the DC reverse connection method, the welding wire extension length is 30-35mm, and the welding gun 7 is slowly adjusted to tilt inward 8-10°, the welding wire and the groove toe end are 12-14mm, the welding gun 7 swings 2-3mm, the groove toe end face stay time 0.4~0.6sec, the V groove front face stay time 0.8~1.0sec, the swing speed is 30mm / sec, the welding current is 340-380A, the arc voltage is 36-39V (see Table 4 for specific parameters), the welding speed is automatically tracked (about 8cm / min), and the welding pool 5 and the slider protective gas port 3-7mm position, and the insulating rod should be used to remove the spatter in the water-cooled slider 6 protective gas box at any time.

[0106] Table 4 Welding parameters

[0107]

[0108] ⑤ Welding of the cross-sectional shape of the bulbous bow 1 at the 1-12 o'clock position: when welding from the 2-1 o'clock position to the 1 o'clock position, the same welding power supply adopts the DC reverse connection method, the welding wire extension length is 30-35mm, and the welding gun 7 is slowly adjusted to balance the angle with the steel plate groove, the welding wire and the groove toe end are 13-15mm, the welding gun 7 swing amplitude is 3-4mm, the groove toe end face residence time is 0.2-0.5sec, the V groove front face residence time is 0.6-1.0sec, the swing speed is 30mm / sec, the welding current is 340-400A, the arc voltage is 36-40V (see Table 5 for specific parameters), the welding speed is automatic tracking (about 7cm / min), and the welding pool 5 and the slider protective gas port are 3-8mm, and the spatter in the water-cooled slider 6 protective gas box should be removed at any time with an insulating rod.

[0109] Table 5 Welding parameters

[0110]

[0111] ⑥ The other side of the bulbous bow 1 is welded in the same way as this side. After the welding of both sides is completed, the upper and lower closed joints are planed into U grooves with a length of 50-100mm by air planing, and CO 2 Semi-automatic welding is used, and the reverse side of the joint is processed in the same way.

[0112] Step S5: perform weld 4 inspection. After the gas-electric full-position welding of the bulbous bow 1 is completed, welding inspection, examination and performance measurement are performed, as follows: visually inspect the front and back sides of the weld 4 to be well formed, no welding defects are found, and the appearance inspection is qualified. After 24 hours after welding, the weld 4 100% UT+RT+MT non-destructive testing is performed, and the result is qualified; Mechanical properties of the test plate welded joint: tensile and bending tests, the average tensile strength of the welded joint using the gas-electric full-position welding method is 523MPa, and the strength of the welded joint meets the minimum tensile strength requirement of 490MPa for matching the parent material strength; Impact test is performed on the welded joint.

[0113] Post-weld inspection:

[0114] After the completion of the gas-electric all-position welding of the bulbous bow 1, welding inspection, examination and performance measurement were carried out in accordance with the classification society's "Welding and Materials", and all were qualified, as follows:

[0115] ① Visual inspection shows that the front and back sides of weld 4 are well formed, no welding defects are found, and the appearance inspection is qualified. 24 hours after welding, weld 4100% UT+RT+MT non-destructive testing is carried out, and the result is qualified.

[0116] ② Mechanical properties of test plate welded joints: Tensile and bending tests, the average tensile strength of welded joints using gas-electric all-position welding method is 523MPa, and the strength of welded joints meets the minimum tensile strength requirement of 490MPa matching the strength of the parent material; impact tests were carried out on welded joints, and the results were qualified.

[0117] The original bulbous bow 1 welding method is as follows:

[0118] a) The bulbous bow outer plate is assembled with an inner Y-shaped groove with a groove angle of 35°, a blunt edge of 2-3mm, and no gap.

[0119] b) Manual CO is used inside the bulbous bow 2 Semi-automatic welding is used for electric welding (4 passes).

[0120] c) Use carbon arc air planer to clean the root and open a U-shaped 45° groove on the outside of the bulbous bow.

[0121] d) Manual CO on the outside of the bulbous bow 2 Semi-automatic welding is used for electric welding (2 passes).

[0122] The invention provides a bulbous bow welding method as follows:

[0123] a) The original Y-shaped inner groove is improved to a V-shaped outer groove, realizing single-sided welding and double-sided forming gas-electric full-position welding of the outside. The groove angle is 25-30°, reducing the amount of welding metal filling at the 4 grooves of the weld; the groove gap is 8-12mm, reducing the impact of precision assembly; the blunt edge of the groove is 0-1mm.

[0124] b) A fiber ceramic liner 3 is used to realize a single-sided and double-sided forming welding method for gas-electric all-position welding.

[0125] c) A special welding auxiliary trolley is used, and the arc of the bulbous bow 1 plate can be connected to the high-temperature resistant, flexible and bendable rail with magnetic attraction, so as to realize automatic welding of the curved surface segmented upward, vertical and flat welding in all positions.

[0126] d) Mechanized gas-electric full-position welding is used to perform an automated welding operation on the outside of the bulbous bow 1, and welding processes and operating methods such as changes in welding power polarity, welding wire position, welding gun 7 angle, swing width, front and rear dwell time, welding sequence, welding parameters, etc. for gas-electric full-position welding of the bulbous bow 1 at different welding positions are formulated.

[0127] Compared with the prior art, this new method has the following advantages:

[0128] 1. Reduce the difficulty of the task

[0129] Through method innovation, the welding workload of construction workers in the confined space inside the bulbous bow 1 is greatly reduced. At the same time, mechanized and automated welding operations reduce the skill requirements for welders and the difficulty of welding operations.

[0130] 2. Improve the working environment

[0131] Through method optimization, manual CO removal in the confined space inside the bulbous bow 1 was avoided. 2 The multi-layer and multi-pass welding reduces the generation of a large amount of smoke and dust in the confined space of the bulbous bow 1, and improves the working environment of the workers.

[0132] 3. Improve the quality of work

[0133] Through method optimization, a gas-electric full-position welding method with mechanized and automated single-sided welding and double-sided forming of the bulbous bow 1 curved segmented outer plate is realized. The welding difficulty is reduced and the working environment is improved, which improves the welding quality. After welding, the UT, RT, and MT flaw detection results show that the first-time qualified rate of the bulbous bow 1 is 100% on average, which is 13.2% higher than the first-time flaw detection qualified rate of 86.8% of the original method.

[0134] 4. Improve work efficiency

[0135] The original method required an 8-day welding cycle for the bulbous bow assembly, but the current method only requires 1 day, reducing the operation cycle by 4 days, greatly improving efficiency.

[0136] In summary, the present invention has the following beneficial effects:

[0137] a) The Y-shaped groove inside the enclosed space of the bulbous bow 1 was improved to a V-shaped groove outside, and the back-knob root cleaning process was improved to the fiber ceramic liner 3 single-sided welding and double-sided forming gas-electric full-position welding technology method, which optimized the operation process and reduced the carbon arc gas gouging root cleaning process and other work.

[0138] b) Innovative application of gas-electric full-position welding of the bulbous bow, realizing technological innovation of full-position automatic welding of ship curved surface sections.

[0139] c) Develop a single-sided double-sided one-time forming gas-electric full-position welding technology, formulate welding processes and operation methods such as welding power polarity change, welding wire position change, welding gun 7 angle, swing width, front and back dwell time, welding sequence, welding parameters, etc. for bulb nose 1 gas-electric full-position welding at different welding positions, and avoid manual CO 2 The number of arc-stopping joints in the base welding is large, thereby reducing the occurrence of welding defects such as joint speed holes and speed hole microcracks.

[0140] According to the statistics of ro-ro passenger ships, the installation and welding of the bulbous bow 1 requires (4 assemblers + 4 welders + 2 carbon planers + 2 grinders). Calculated based on the reduction of 4 days in the operation cycle of the bulbous bow 1, the total man-hours that can be saved for the bulbous bow 1 are: 6 people * 4 days * 8 hours / day * 45 yuan / man-hour = 8,640 yuan.

[0141] Assuming 27 product ships are built per year, the annual cost savings can be 8,640 yuan*27 = 233,280 yuan.

[0142] In addition, the innovative application of gas-electric all-position welding of the bulbous bow can effectively improve the quality, reduce the welding rework workload, kinetic energy, welding materials, etc. The cost savings are huge and immeasurable.

[0143] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A welding method for a bulbous bow of a ship, characterized in that: The method comprises: Step S1: Processing a V-shaped groove on the outer side of the bulbous bow; Step S2: The bulbous bow is assembled by welding and fixing the positioning piece on the inner side of the bulbous bow; Step S3: installing a ceramic liner on the inner side of the bulbous bow, with the center of the ceramic liner facing the back side of the V-shaped groove, and installing a water-cooling slider on the front side of the V-shaped groove; Step S4: using a gas-electric welding trolley dedicated to a flexible track, formulating welding parameters of gas-electric all-position welding technology, power polarity change of gas-electric all-position welding, welding wire distance, gun angle, swing width, and dwell time, and performing gas-electric all-position welding to perform single-sided welding and double-sided forming welding; Step S5: Conduct weld inspection.

2. The welding method for a bulbous bow of a ship according to claim 1, characterized in that: In step S1, the groove angle of the V-shaped groove is between 25° and 30°, the assembly gap is 8mm-12mm, and the blunt edge is 0mm.

3. The welding method for a bulbous bow of a ship according to claim 1, characterized in that: In the step S2, the positioning member includes a II-shaped card code plate; The bulbous bow assembly adopts a positioning piece to be welded and fixed on the inner side of the bulbous bow, including: according to the designed and processed V-shaped groove, a Π-shaped clamping plate is installed on the back of the V-shaped groove joint and fixed by welding, and one Π-shaped clamping plate is installed for each gap of the weld groove with a length of 250mm-300mm.

4. The welding method for a bulbous bow of a ship according to claim 3, characterized in that: The welding method in step S4 includes: The welding gun is clamped by a gas-electric vertical welding auxiliary trolley, and gas-electric full-position welding with gas slag protection is performed from the lower end of the two hemispheres of the bulbous nose upward along the gear flexible track fixed next to the weld. During welding, a fiber ceramic pad is pasted on the back of the V-shaped groove joint, and a U-shaped groove water-cooled slider is used on the front of the groove to support the molten pool for forced formation.

5. The welding method for a bulbous bow of a ship according to any one of claims 1 to 4, characterized in that: In the step S3, the step of installing the ceramic liner includes: When installing the ceramic liner, it should be tightly attached to the groove steel plate inside the bulbous bow, and the ceramic liners should be pushed tightly without any gap. The groove surface of the ceramic liner should be tightly attached to the back of the groove steel plate of the bulbous bow and aligned. The ceramic liner should be fixed by pressing the Π-shaped card plate hole with an iron wedge.

6. The welding method for a bulbous bow of a ship according to claim 5, characterized in that: The water-cooled slider is installed on the slider clamping mechanism of the welding trolley. The slider clamping mechanism is adjusted to make the water-cooled slider close to the edge of the V-groove steel plate on the front side of the bulbous bow, and as the welding trolley moves left and right, the slider clamping force is adjusted, and the water-cooled slider moves close to the groove surface, so that during the welding process, the water-cooled slider supports the molten pool to force the gas-electric all-position welding weld to form.

7. The welding method for a bulbous bow of a ship according to claim 6, characterized in that: In step S4, the welding sequence includes: dividing the bulbous bow into positions from 1 o'clock to 12 o'clock on the clock face according to the cross-sectional shape of the bulbous bow and separating the two hemispheres at the 6 o'clock and 12 o'clock positions, and performing gas-electric full-position welding with gas slag protection in the order of gas-electric full-position welding with the lower ends of the two hemispheres facing upward, welding one hemisphere and then welding the other hemisphere in the direction with the lower end facing upward, and adjusting relevant parameters according to different positions.

8. The welding method for a bulbous bow of a ship according to claim 7, characterized in that: In step S4: The cross-sectional shape of the bulbous bow divides the bulbous bow into positions from 1 o'clock to 12 o'clock on the clock face. During welding, in order to ensure the formation of the back side of the weld in the upward and oblique upward positions of the gas-electric all-position welding, the power supply adopts the DC positive connection method, and the DC reverse connection method is used for welding in other positions.

9. The welding method for a bulbous bow of a ship according to claim 8, characterized in that: In step S4: The extended length of the gas-electric all-position welding wire is 30 mm to 35 mm.

10. The welding method for a bulbous bow of a ship according to any one of claims 1 to 4, characterized in that: After the bulbous bow gas-electric full-position welding is completed, welding inspection, examination and performance measurement are carried out, as follows: Visual inspection shows that the weld is well formed on both sides, no welding defects are found, and the appearance inspection is qualified. 24 hours after welding, the weld is subjected to 100% UT+RT+MT nondestructive testing, and the result is qualified; Mechanical properties of test plate welded joints: Tensile and bending tests, the average tensile strength of welded joints using gas-electric all-position welding method is 523MPa, and the strength of welded joints meets the minimum tensile strength requirement of 490MPa matching the strength of the parent material; impact tests are carried out on welded joints.

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