Ship tail shaft and mounting method thereof

Abstract

The invention belongs to the technical field of ship engineering, and particularly relates to a ship tail shaft and an installation method thereof. The ship tail shaft comprises a ship body and a steel wire, the tail shaft comprises platform plates, the tail shaft is formed by splicing a plurality of platform plates, a shaft bracket structure is arranged on the tail shaft, the shaft bracket structure is connected with the ship body, and a supporting structure is arranged on the tail shaft; platform plates are manufactured in a segmented mode, and the platform plates, the front stern shaft bracket plate and the rear stern shaft bracket plate are spliced together to form a stern shaft. The invention further provides an installation method for the ship tail shaft, and the installation method is convenient for operators to understand and use.

Description

Technical Field

[0001] This invention belongs to the field of marine engineering technology. Specifically, this invention relates to a ship stern shaft and its installation method. Background Technology

[0002] As a core load-bearing component of the propulsion system, the stern shaft connects to the main engine at one end to transmit torque and drives the propeller to generate thrust at the other end. Its structural strength and operational stability directly determine the ship's navigation safety and propulsion efficiency. With the development of ships towards larger and heavier loads, the stern shaft needs to withstand the radial force, axial thrust, and periodic vibration loads generated by the propeller, while also adapting to the complex hull installation space.

[0003] The stern shafts of large ships are currently enormous, and the overall casting process presents challenges such as high mold costs and difficulties in transportation and hoisting. Therefore, segmented splicing has become the mainstream solution. However, existing segments mostly use simple steel plate welding, and the platform plates of the stern shaft segments are mostly formed by welding cast steel. During the welding of thick cast steel plates, residual stress and cold cracks are easily generated due to the differences in thermal expansion coefficients of dissimilar materials and uneven heat input. Existing processes lack precise standards for controlling preheating temperature and interpass temperature, often resulting in insufficient preheating range or excessive temperature fluctuations, leading to coarse weld grains and reduced toughness. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems, and aims to provide a ship stern shaft with higher welding strength and reduced post-weld cracking, as well as its installation method. To achieve the above objective, the technical solution adopted by this invention is as follows: a ship stern shaft, including a hull and steel wire, including a stern shaft, the stern shaft including a platform plate, the stern shaft being spliced ​​from multiple platform plates, a shaft frame structure being provided on the stern shaft, the shaft frame structure being connected to the hull, and a support structure being provided on the stern shaft.

[0005] The axle support structure includes a front stern axle support plate and a rear stern axle support plate. The stern axle is provided with a first mounting hole and a second mounting hole that cooperate with the front stern axle support plate and the rear stern axle support plate. The end of the front stern axle support plate is provided with a first connecting hole plate, and the end of the rear stern axle support plate is provided with a second connecting hole plate.

[0006] The support structure includes a water-dividing heel plate, which is disposed at one end of the stern shaft, and left and right rudder sticks are disposed on the stern shaft.

[0007] The stern shaft is provided with bulwark plates at both ends, and a structural reinforcing plate is provided between the bulwark plates and the stern shaft.

[0008] A method for installing a ship's stern shaft, specifically: The platform plates are manufactured and spliced ​​in sections. After splicing, the first and second mounting holes are made on the platform plates. Then, one end of the front stern shaft bracket plate is placed in the first mounting hole, and one end of the rear stern shaft bracket plate is placed in the second mounting hole. The front stern shaft bracket plate is spot welded to the first mounting hole, and the rear stern shaft bracket plate is spot welded to the second mounting hole. Then, each spliced ​​platform plate is polished. The main sections are assembled, and the spliced ​​platform plates are used to form the main sections. The gaps between the platform plates are welded together. The elongated shaft steel wire is used to position the front and rear shaft bracket plates. The front and rear shaft bracket plates are assembled onto the hull, and the first and second mounting holes are sealed with sealing plates.

[0009] Before spot welding and formal welding, the front and rear axle bracket plates should be preheated at a temperature of 100~150°C. Electric heating or oxy-acetylene flame should be used to uniformly preheat the width of the weld seam on both sides of the adjacent platform plates, which is 4 times the thickness of the platform plate but does not need to exceed 100mm.

[0010] The spot welding current should be 10% to 15% higher than that used for regular welding. The spot welding length should be 50 mm and the spacing should be 300 mm.

[0011] For platform plate welds, the interpass temperature between adjacent platform plates should not exceed 200℃, but should not be lower than 100℃; preheated welds must be welded continuously.

[0012] After welding, the welded area should be covered with insulation material for two minutes for every millimeter of weld, but the insulation time should be no less than two hours.

[0013] During welding, the joints of each weld layer should be staggered by 30-50mm. Welding should be stopped when the temperature is below -10℃ or the air humidity is above 85%.

[0014] The technical effects of this invention are as follows: First, the main body of the stern shaft is manufactured. A platform plate is prepared by welding cast steel, forming an open platform plate without an outer plate. Using the edge and center axis of the open platform plate as a reference, the installation positions of the internal ribs and longitudinal girder webs are marked according to the design coordinates using a total station. The cut internal ribs and longitudinal girder webs are then hoisted onto the platform plate according to the marked positions. Carbon dioxide gas shielded welding is used to weld the internal ribs and longitudinal girder webs to the platform plate, first welding the vertical welds, then the horizontal welds. After welding, the flux residue is removed, and the weld appearance is preliminarily inspected with the naked eye; if there are no porosity or slag inclusions, it is acceptable. Using the installation coordinates of the fore and aft stern shaft support plates as a reference, a total station is used to... The station marks the outlines of the first and second mounting holes on the platform plate at the corresponding positions, and then cuts them. After cutting, a crane lifts one end of the front stern shaft bracket plate and places it in the first mounting hole. The crane lifts one end of the rear stern shaft bracket plate and places it in the second mounting hole. The front and rear stern shaft bracket plates are initially positioned by pulling a steel wire as a reference line. After positioning, the front and rear stern shaft bracket plates are initially fixed by spot welding to the wall of the first mounting hole, and the rear stern shaft bracket plate is initially fixed by spot welding to the wall of the second mounting hole. Then, the platform plate, the front and rear stern shaft bracket plates are polished and can be sent to the assembly jig on the slipway to integrate multiple prefabricated segmented platform plates into a complete stern shaft section.

[0015] Multiple prefabricated platform panels were hoisted into the main assembly jig on the slipway using a gantry crane, according to their numbers. One panel was used as a reference section, and its horizontal and vertical alignment was calibrated using a total station. The platform panels were then spliced ​​and aligned. Other panels were then joined to the reference section, and the positions of adjacent panels were adjusted to align the edges, leaving a 2-3mm welding gap. Adjacent panels were temporarily fixed with spot welding, with a spacing of 300mm and a length of 50mm, to prevent displacement. Submerged arc welding was used to continuously weld the joints between panels, symmetrically welding from the middle of the main section towards both ends to minimize welding deformation. The inner welds were welded first, followed by the outer welds. Next, a steel line was used as a reference line to position the fore and stern shaft brackets. These brackets were then assembled onto the hull and connected. Finally, sealing plates were welded to close the first and second mounting holes, restoring the platform panels' airtightness and preventing seawater infiltration. After welding, the panels were inspected. Attached Figure Description

[0016] This manual includes the following figures, which illustrate the following: Figure 1 This is an overall structural diagram of a ship stern shaft and its installation method according to the present invention; Figure 2 This is a schematic diagram showing the connection between the stern shaft support plate and the platform plate of a ship stern shaft and its installation method according to the present invention. Figure 3 This is a schematic diagram of the connection between the fore-stern shaft bracket plate and the platform plate of a ship stern shaft and its installation method according to the present invention.

[0017] The markings in the diagram are as follows: 1. Stern shaft; 101. Platform plate; 2. Shaft support structure; 201. Forward stern shaft support plate; 202. Aft stern shaft support plate; 203. First mounting hole plate; 204. Second mounting hole plate; 3. Support structure; 301. Water divider plate; 302. Starboard and port rudder stock; 4. Bulwark plate; 5. Structural reinforcement plate. Detailed Implementation

[0018] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation.

[0019] like Figures 1-3 As shown, a ship's stern shaft includes a hull and steel wires. The stern shaft 1 includes platform plates 101, which are assembled from multiple platform plates 101. A shaft frame structure 2 is installed on the stern shaft 1, connecting to the hull. A support structure 3 is also installed on the stern shaft 1. The main body of the stern shaft 1 is formed by assembling multiple platform plates 101. The platform plates 101 are formed by welding cast steel together. During segmented fabrication, the platform plates 101 are first welded from cast steel, resulting in an open platform plate. Structural lines are then drawn inside the platform plates 101. After welding all the internal structures of the platform plates 101, the outer plates of the platform plates 101 are welded to seal the opening. This seal is then used for subsequent assembly. The shaft support structure 2 is set on the platform plate 101 at the corresponding position for installation on the hull. The support structure 3 is used to support and reinforce the end of the stern shaft 1, and also to support the rudder stock.

[0020] The axle support structure 2 includes a front stern axle support plate 201 and a rear stern axle support plate 202. The stern axle 1 is provided with a first mounting hole and a second mounting hole that mate with the front stern axle support plate 201 and the rear stern axle support plate 202. The front stern axle support plate 201 is provided with a first connecting hole plate 203 at its end, and the rear stern axle support plate 202 is provided with a second connecting hole plate 204 at its end. The front stern axle support plate 201 and the first connecting hole plate 203 are integrally formed structures, and the rear stern axle support plate 202 and the second connecting hole plate 204 are integrally formed structures and are symmetrically arranged on the stern axle 1. On the platform plate 101 that needs to be connected to the front stern shaft bracket plate 201 or the rear stern shaft bracket plate 202, after the platform plate 101 is welded from cast steel and the outer plate of the platform plate 101 is welded on, a first mounting hole plate 203 is opened on the platform plate 101 on which the front stern shaft bracket plate 201 is to be installed, and a second mounting hole is opened on the platform plate 101 on which the rear stern shaft bracket plate 202 is to be installed. The front stern shaft bracket plate 201 is initially placed in the first mounting hole, and the rear stern shaft bracket plate 202 is initially placed in the second mounting hole. Then, the connection is made by pulling a steel wire. Using a wire as a guide, two preset reference points are connected to the two ends of the wire. The first mounting plate 203 and the second mounting plate 204 correspond to different reference lines. By pulling the wire through the first and second mounting plates 203 and 204 for initial positioning, the fore-stern shaft bracket plate 201 and the aft-stern shaft bracket plate 202 can be initially welded to the corresponding platform plate 101. Then, the platform plate 101, the fore-stern shaft bracket plate 201, and the aft-stern shaft bracket plate 202 are ground and sent to the slipway for assembly. The platform plates 101 are assembled into sections. After welding each platform plate 101 together, the first and second mounting plates 203 and 204 are precisely positioned by pulling the wire. The first and second mounting plates 203 and 204 are then assembled onto the hull. Finally, the outer plates of the platform plates 101 on which the fore-stern shaft bracket plate 201 and the aft-stern shaft bracket plate 202 are installed are welded to seal the first and second mounting holes.

[0021] The support structure 3 includes a water-dividing heel plate 301, which is located at one end of the stern shaft 1. The stern shaft 1 is equipped with port and starboard rudder sticks 302. The water-dividing heel plate 301 is welded to the platform plate 101 and is located in the middle of the entire structure. Situated at the end of the stern shaft 1 closest to the propeller, the water-dividing heel plate 301 directly bears the end load of the shaft system and acts on the water flow. During operation, the end of the stern shaft 1 will experience sinking, vibration, or bending due to the radial force generated by the propeller rotation, the axial thrust, and its own weight. The water-dividing heel plate 301, rigidly connected to the end of the stern shaft 1, effectively adds a bottom support to the stern shaft, effectively offsetting the end load, limiting its radial displacement, preventing shaft system wear and bearing overheating due to end instability, and ensuring the coaxiality and stability of the shaft system. The port and starboard rudder sticks 302 are used to support the rudder and ensure ship maneuverability.

[0022] The stern shaft 1 is equipped with bulwark plates 4 at both ends, and a structural reinforcing plate 5 is installed between the bulwark plates 4 and the stern shaft 1. The bulwark plates 4 can block seawater, rainwater, and wash water from rising, while the structural reinforcing plate 5 can increase the connection strength between the bulwark plates 4 and the stern shaft 1. The platform plates 101 are fabricated and assembled in sections. After assembly, the first and second mounting holes are made on the platform plates 101. Then, one end of the front stern shaft bracket plate 201 is placed in the first mounting hole, and one end of the rear stern shaft bracket plate 202 is placed in the second mounting hole. The front stern shaft bracket plate 201 is spot welded to the first mounting hole, and the rear stern shaft bracket plate 202 is spot welded to the second mounting hole. Then, each assembled platform plate 101 is ground. First, the main body of the stern shaft 1 is made, and the platform plates 101 are prepared by welding cast steel. Before welding, the appearance of the cast steel should be carefully inspected. If defects such as sand holes or cracks are found, they should be dealt with in time. After welding, an open platform plate 101 is formed, but the outer plate is not installed. Using the edge and center axis of the open platform plate 101 as a reference, the installation position lines of the internal ribs and longitudinal girder web structure are marked according to the design coordinates using a total station. The cut internal ribs and longitudinal girder webs are then hoisted onto the platform plate 101 according to the marked positions. Carbon dioxide gas shielded welding is used to weld the internal ribs and longitudinal girder webs to the platform plate 101. The vertical welds are welded first, followed by the horizontal welds. After welding, the flux residue is removed, and the weld appearance is preliminarily inspected with the naked eye. If there are no porosity or slag inclusions, it is acceptable. The installation coordinates of the fore-stern shaft support plate 201 and the aft-stern shaft support plate 202 are as follows. Using a total station as a reference, the outlines of the first and second mounting holes are drawn on the platform plate 101 at the corresponding positions. Then, cutting is performed. After cutting, a crane lifts one end of the front stern shaft support plate 201 and places it into the first mounting hole. The crane then lifts one end of the rear stern shaft support plate 202 and places it into the second mounting hole. Using a steel wire as a reference line, the front and rear stern shaft support plates 201 and 202 are initially positioned. After positioning, the front and rear stern shaft support plates 201 and 202 are initially fixed by spot welding to the wall of the first mounting hole, and the rear stern shaft support plate 202 is initially fixed by spot welding to the wall of the second mounting hole. After spot welding, the flux residue is cleaned off. Next, the platform plate 101, the front and rear stern shaft support plates 201, and the rear stern shaft support plates 202 are ground and then sent to the assembly jig on the slipway to integrate multiple prefabricated segmented platform plates 101 into a complete stern shaft 1 section. The main section is assembled and the spliced ​​platform plate 101 is assembled into a main section and the gap between the platform plates 101 is welded. The elongated shaft steel wire is used to position the front and rear shaft bracket plates 201 and the rear shaft bracket plates 202. The front and rear shaft bracket plates 201 and the rear shaft bracket plates 202 are assembled onto the hull and the sealing plates of the first and second mounting holes are sealed. Multiple prefabricated platform panels 101, numbered according to their number, are hoisted and placed onto the main assembly jig on the slipway. One of the panels is used as a reference section, and the horizontal and verticality of the reference section are calibrated using a total station. The platform panel 101 panels are then spliced ​​and aligned. The other panels are then joined with the reference section, and the positions of adjacent panels are adjusted to align the edges of the platform panels 101, leaving a 2-3mm welding gap. Adjacent panels are temporarily fixed with spot welding, with a spacing of 300mm and a length of 50mm between the weld points to prevent splicing displacement. Submerged arc welding is used to continuously weld the splicing gaps between the panels, with the welding sequence proceeding symmetrically from the middle of the main section to both ends to reduce welding deformation. The inner welds are welded first, followed by the outer welds. At the same time, the water-dividing heel plate 301, the port and starboard rudders 302, the bulwark plate 4, and the structural reinforcing plate 5 are welded together. Next, steel wires are used as reference lines to position the front and rear shaft support plates 201 and 202. The front and rear shaft support plates 201 and 202 are then assembled onto the hull and connected to it. Finally, sealing plates are welded to close the first and second mounting holes, restoring the platform plate's airtightness and preventing seawater infiltration. 48 hours after welding, non-destructive testing (NDT) of the welded area must be performed, requiring 100% UT, to ensure the weld quality meets requirements. If any problems are found, repairs will be carried out, followed by inspection.

[0023] Before both spot welding and formal welding, the front and rear axle bracket plates 201 and 202 should be preheated to 100-150°C. Preheating should be done using electric heating or an oxy-acetylene flame to uniformly preheat a width four times the thickness of the platform plate 101 on both sides of the weld initiation point of adjacent platform plates 101, but not exceeding 100mm. Since the front and rear axle bracket plates 201 and 202 are made of different materials than the platform plate 101, direct welding at room temperature would cause a significant temperature difference, leading to rapid expansion and contraction of the weld area upon cooling, resulting in intense thermal stress. A preheating temperature of 100-150°C can raise the temperature of the weld area and surrounding platform plates 101 in advance, reducing the temperature difference, lowering thermal stress, and preventing welding cracks.

[0024] When welding adjacent platform plates 101, the preheating range on both sides of the weld start point is limited to 4 times the thickness of platform plate 101 but not exceeding 100mm. This ensures that the stress concentration area is fully preheated and avoids uneven overall temperature caused by excessive expansion of the preheating range.

[0025] After preheating, the temperature of the welding area increases, which reduces the loss of arc heat to the low-temperature area, ensuring that the weld metal melts fully and improving the density and connection strength of the weld.

[0026] Using electric heating or an oxy-acetylene flame can avoid grain coarsening caused by local overheating, ensure the stability of the material properties in the heat-affected zone of the weld, and allow the weld to withstand the load of the shaft operation while having sufficient fatigue resistance.

[0027] The spot welding current should be 10%~15% higher than that of the formal welding, with a spot welding length of 50mm and a spacing of 300mm. The 10%~15% increase in spot welding current ensures thorough penetration and sufficient strength, compensates for heat loss, and guarantees penetration. This improves the problem of insufficient penetration and weak fixation in spot welding at room temperature or preheating. A 50mm spot welding length creates a sufficient effective weld, preventing fixation failure due to an excessively short weld. The core of spot welding is temporary fixation; the subsequent assembly of platform plate 101 still requires adjustment of the shaft bracket plate position based on the steel wire positioning. If the spot welding length is too long and the weld strength is too high, the weld needs to be ground away during adjustment, which is time-consuming and laborious. A 50mm length provides both fixation and quick removal during adjustment without affecting the positional calibration of the front and rear shaft bracket plates 201 and 202. A 300mm spacing ensures even distribution of the fixing force, preventing local displacement. Appropriate spacing can optimize construction efficiency and reduce costs.

[0028] For the 101 weld seam on platform plate, the interpass temperature between adjacent 101 weld seams should not exceed 200℃, but should not be lower than 100℃. Preheated weld seams must be welded continuously. The surface of each weld metal pass must be thoroughly cleaned before the next pass. An interpass temperature not exceeding 200℃ prevents coarse weld grains, ensuring weld toughness and strength. An interpass temperature not lower than 100℃ reduces thermal stress and inhibits cold cracking and hydrogen-induced cracking. Preheated weld seams must be welded continuously: maintaining a stable welding area ensures consistent weld quality. Continuous welding coordinates with the interpass temperature, preventing temperature runaway due to interruptions. Continuous welding ensures the welding area remains within a stable temperature range of 100~200℃, eliminating the need for repeated adjustments to process parameters and ensuring consistent welding conditions for each layer and pass, ultimately achieving uniform weld quality. Continuous welding avoids overlapping weld joints or arc start-up / extinguishing defects caused by interruptions, reduces stress concentration points, ensures consistent overall mechanical properties of the weld, and uniformly transfers loads.

[0029] After welding, the welded area must be covered with insulation material for two minutes, with a minimum insulation time of two hours for every millimeter of weld. After welding, the weld and its surrounding area are at a high temperature, while areas further away from the weld are at a lower temperature. If allowed to cool naturally, the high-temperature area will rapidly contract, creating a significant temperature difference with the low-temperature area, resulting in strong residual welding stress. This stress can easily exceed the material's crack resistance, leading to cold cracks in the weld or heat-affected zone. Using insulation material after welding slows down the cooling rate, significantly reducing residual welding stress and preventing cold cracks. By slowing down the cooling rate, the problems of excessive residual stress and cold cracks are solved, the weld microstructure is optimized, residual hydrogen is expelled, and ultimately, a smooth weld quality is ensured.

[0030] During welding, the joints of each weld pass should be staggered by 30-50mm. Welding should be stopped when the temperature drops below -10℃ or the air humidity exceeds 85%. Staggering the joints of each weld pass by 30-50mm disperses weak points, improving the overall strength and fatigue resistance of the weld. Distributing weak points in different locations prevents stress concentration, significantly reducing the risk of overall weld cracking. Stopping welding when the temperature drops below -10℃ prevents weld embrittlement and cold cracking. At low temperatures, the platform plate 101, the front and stern shaft support plates 201, and the rear stern shaft support plate 202 are extremely cold. During welding, the heat from the electric arc is rapidly conducted away, causing a sharp increase in the cooling rate of the weld pool. Rapid cooling causes the weld metal to form a martensitic structure, making the weld prone to cold brittleness and cracking under slight external force.

[0031] At low temperatures, materials have poor deformation capacity and cannot shrink with the weld, resulting in huge residual stress inside the weld, which directly causes cold cracks.

[0032] Welding should be stopped when the air humidity exceeds 85% to inhibit hydrogen-induced cracking and porosity. In high-humidity environments, moisture in the air can enter the weld through the following pathways: During welding, moisture decomposes to produce hydrogen gas, and water vapor decomposes into hydrogen gas, which then dissolves into the molten pool. When the weld cools, the solubility of hydrogen gas drops sharply. If it cannot escape in time, it will remain inside the weld as tiny bubbles, forming porosity; or it may accumulate at weld defects, forming hydrogen traps, which can trigger hydrogen-induced cracking under stress.

[0033] First, the main body of the stern shaft 1 is fabricated. Platform plate 101 is prepared by welding cast steel, forming an open platform plate 101 without an outer plate. Using the edge and center axis of the open platform plate 101 as a reference, the installation positions of the internal ribs and longitudinal girder webs are marked according to the design coordinates using a total station. The cut internal ribs and longitudinal girder webs are then hoisted onto the platform plate 101 according to the marked positions. Carbon dioxide gas shielded welding is used to weld the internal ribs and longitudinal girder webs to the platform plate 101, first welding the vertical welds, then the horizontal welds. After welding, the flux residue is removed, and the weld appearance is preliminarily inspected with the naked eye; it is acceptable if there are no porosity or slag inclusions. Using the installation coordinates of the fore stern shaft support plate 201 and the aft stern shaft support plate 202 as a reference, the platform plates at the corresponding positions are marked using a total station. The outlines of the first and second mounting holes are drawn on platform 101, and then cutting is performed. After cutting, one end of the front stern shaft bracket plate 201 is lifted by a crane and placed in the first mounting hole. After the crane lifts one end of the rear stern shaft bracket plate 202 and places it in the second mounting hole, the front stern shaft bracket plate 201 and the rear stern shaft bracket plate 202 are initially positioned by pulling a steel wire as a reference line. After positioning, the front stern shaft bracket plate 201 is initially fixed by spot welding to the wall of the first mounting hole, and the rear stern shaft bracket plate 202 is initially fixed by spot welding to the wall of the second mounting hole. Then, after grinding the platform plate 101, the front stern shaft bracket plate 201 and the rear stern shaft bracket plate 202, they can be sent to the assembly jig on the slipway to integrate multiple prefabricated segmented platform plates 101 into a complete stern shaft 1 section.

[0034] Multiple precast platform slabs 101, numbered according to their number, were hoisted and placed onto the main assembly jig on the slipway. Using one segment as a reference segment, the horizontal and vertical alignment of the reference segment was calibrated with a total station. The platform slab 101 segments were then spliced ​​and aligned. The other segments were then aligned with the reference segment, and the positions of adjacent segments were adjusted to align the edges of the platform slab 101, leaving a 2-3mm welding gap. Adjacent segments were temporarily fixed with spot welding, with a weld spacing of 300mm and a length of 50mm, to prevent splicing displacement. Submerged arc welding was employed. Continuous welding is performed on the joints between the sections, with the welding sequence proceeding symmetrically from the middle of the main section towards both ends to reduce welding deformation; the inner welds are welded first, followed by the outer welds; then, steel lines are used as reference lines to position the front and rear shaft support plates 201 and 202, and the front and rear shaft support plates 201 and 202 are assembled onto the hull and connected to it; finally, sealing plates are welded to close the first and second mounting holes, restoring the platform plate's airtightness and preventing seawater infiltration; after welding is completed, an inspection is conducted.

[0035] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A ship stern shaft, comprising a hull and steel wire, characterized in that, Includes a stern shaft (1), the stern shaft (1) includes a platform plate (101), the stern shaft (1) is spliced ​​from multiple platform plates (101), the stern shaft (1) is provided with a shaft frame structure (2), the shaft frame structure (2) is connected to the hull, and the stern shaft (1) is provided with a support structure (3).

2. The ship stern shaft according to claim 1, characterized in that: The axle support structure (2) includes a front stern axle support plate (201) and a rear stern axle support plate (202). The stern axle (1) is provided with a first mounting hole and a second mounting hole that cooperate with the front stern axle support plate (201) and the rear stern axle support plate (202). The front stern axle support plate (201) is provided with a first connecting hole plate (203) at its end, and the rear stern axle support plate (202) is provided with a second connecting hole (204) at its end.

3. The ship stern shaft according to claim 1, characterized in that: The support structure (3) includes a water-dividing heel plate (301), which is located at one end of the stern shaft (1), and the stern shaft (1) is provided with left and right rudder rods (302).

4. The ship stern shaft according to claim 1, characterized in that: The stern shaft (1) is provided with bulwark plates (4) at both ends, and a structural reinforcing plate (5) is provided between the bulwark plates (4) and the stern shaft (1).

5. A method for installing a ship's stern shaft according to any one of claims 1 to 5, characterized in that: Specifically: The platform plates (101) are manufactured and spliced ​​in sections. After splicing, the first mounting hole and the second mounting hole are opened on the platform plate (101). Then, one end of the front stern shaft bracket plate (201) is placed in the first mounting hole, and one end of the rear stern shaft bracket plate (202) is placed in the second mounting hole. The front stern shaft bracket plate (201) is spot welded to the first mounting hole, and the rear stern shaft bracket plate (202) is spot welded to the second mounting hole. Then, each spliced ​​platform plate (101) is polished. The main section is assembled and the spliced ​​platform plate (101) is assembled into a main section and the gap between the platform plates (101) is welded. The long shaft steel wire is used to position the front and rear shaft bracket plates (201) and the rear shaft bracket plates (202). The front and rear shaft bracket plates (201) and the rear shaft bracket plates (202) are assembled onto the hull and the first and second mounting holes are sealed with sealing plates.

6. The method for installing a ship's stern shaft according to claim 5, characterized in that: Before spot welding and formal welding, the front stern shaft support plate (201) and the rear stern shaft support plate (202) should be preheated at a temperature of 100~150°C. Electric heating or oxy-acetylene flame should be used to uniformly preheat the width of the weld start point of the adjacent platform plate (101) on both sides of a width that is 4 times the thickness of the platform plate (101) but does not need to exceed 100mm.

7. The method for installing a ship's stern shaft according to claim 5, characterized in that: The spot welding current should be 10% to 15% higher than that used for regular welding. The spot welding length should be 50 mm and the spacing should be 300 mm.

8. The method for installing a ship's stern shaft according to claim 5, characterized in that: For the weld seam of platform plate (101), the interpass temperature of adjacent platform plates (101) should not exceed 200℃, but should not be lower than 100℃; the preheated weld seam must be welded continuously.

9. The method for installing a ship's stern shaft according to claim 5, characterized in that: After welding, the welded area should be covered with insulation material for two minutes for every millimeter of weld, but the insulation time should be no less than two hours.

10. The method for installing a ship's stern shaft according to claim 5, characterized in that: During welding, the joints of each weld layer should be staggered by 30-50mm. Welding should be stopped when the temperature is below -10℃ or the air humidity is above 85%.

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