In the past, many shipyards not only carried out steel processing, hull assembly, welding and equipment system installation, but also had certain casting, forging and machining capabilities. At the same time, they also made the main engine, auxiliary machines, boilers and other equipment. Since 1950s, with the development of shipbuilding and its supporting industries, shipyards have been developing towards assembly, that is, building hulls is the main task. A large number of electromechanical equipment and outfitting parts are provided by professional or non-professional cooperative factories, and shipyards only install them to improve the quality and efficiency of shipbuilding.
Shipbuilding process The main technological process of shipbuilding can be represented by the following block diagram.
Pretreatment of steel The work of correcting, derusting and priming steel before marking. During the transportation and storage of marine steel, due to uneven rolling, uneven cooling shrinkage after rolling or other factors, various deformations often occur. For this reason, after the plates and profiles are taken out of the steel yard, they are respectively straightened by a multi-roll steel plate straightener and a steel plate straightener to ensure normal marking, trimming and forming processing. The corrected steel is generally polished and derusted first, then sprayed with primer and dried. In this way, the processed steel can be sent for marking. These processes often form an automatic pretreatment assembly line, and the conveying raceway is connected with the conveying lines of subsequent processes such as steel lifting, marking and edge processing in the steel yard, thus realizing the comprehensive mechanization and automation of hull parts preparation processing.
Setting out and marking the hull shape is usually a smooth spatial surface. The hull outline map provided by the design department with three-dimensional projection lines is called line drawing, which is usually drawn at the ratio of 1:50 or 1: 100. Because of the large proportion, there is a certain error in the three-dimensional fairing of the profile, so the hull construction can not be carried out directly according to the profile. Instead, the full-scale lofting with the ratio of 1: 1 or 1:5 and 1: 10 should be carried out on the lofting platform of the shipyard, so that the profile can be smoothed and obtained correctly. Hull lofting is the basic process of hull construction.
Marking is to draw the actual shape and size of the hull parts obtained after lofting on the plate or profile with templates, samples or sketches, and mark them for processing and assembly. The earliest lofting and marking methods were full-scale lofting and manual marking. In the early 1940s, there appeared proportional lofting and projection marking, that is, lofting was made into projection base map according to the ratio of 1:5 or 1: 10, and the projection base map was enlarged to the actual size with corresponding low-power projection equipment. Or reduce the projection base map to1/5 ~110 to make a projection negative, and then use high-power projection equipment to enlarge it by 50 ~ 100 times to form a three-dimensional part, and then put it on the steel label. Proportional lofting can also provide a copy map for photoelectric tracking cutting machine to directly cut steel plate, which saves the numbering process. Although projection marking has been greatly improved on the basis of manual marking, it still can't get rid of manual operation. In the early 1960s, electric marking materials were applied, that is, using the principle of electrostatic photography, photosensitive conductive powder was first sprayed on the surface of steel plate, and then orthographic exposure was carried out. After developing and fixing, the parts are displayed on the steel plate. The large-scale electrographic marking device suitable for large-size steel plates adopts a synchronous continuous exposure projection mode, that is, the base map and the steel plate move synchronously, and the exposure is continuously projected in the moving process. A small electric marking device suitable for small steel plate can project all graphics onto the steel plate at one time. This marking method has been widely used. With the application of computer in shipbuilding, mathematical lofting method appears again. That is to say, the mathematical equation is used to represent the hull line or hull surface, and the design value table and the necessary boundary condition values are used as the original data. Through repeated verification and calculation by computer, the hull line is modified and smoothed, so that the hull line is accurate, smooth and completely consistent with the corresponding projection points. Each hull line is represented by a characteristic mathematical spline curve equation, which can be drawn by a numerical control plotter (see drawing tool). Mathematical lofting can not only cancel the traditional full-scale lofting work, but also provide control information for subsequent processes such as cutting and forming, which plays a key role in the automation of hull construction process and is an important development of shipbuilding technology.
The processing of hull parts includes edge processing and forming processing. Edge processing is to cut the hull parts by shearing machine, oxyacetylene gas cutting and plasma cutting according to the actual shape drawn on the steel after marking. The edges of some parts need to be machined by gas cutting machine or plane edge. The photoelectric tracking gas cutting machine in gas cutting equipment can automatically track the lines on the scale chart and cut the steel plate through the synchronous servo system, which can be used in conjunction with manual marking and projection marking. Using numerical control gas cutting machine not only has high cutting precision, but also cuts directly according to mathematical lofting data, which can omit the numbering process and realize the automation of lofting and cutting process.
For the hull plate with curvature, angle or hem, the steel plate needs to be formed after cutting, and cold bending is mainly carried out by using roll bending machine and plate bending machine; Or adopt the processing method of hydrothermal forming, that is, according to the predetermined heating line, use an oxygen-acetylene torch to locally heat the plate, and then use water to cool it, so that the plate is locally deformed and bent into the required curved surface shape. Profiles used as ribs, etc. Frame cold bending machine is often used to bend it into various shapes. With the development of numerical control technology, numerical control cold bending machine has been applied, and then numerical control plate bending machine has been developed. The processing of hull parts has developed from mechanization to automation.
Hull assembly and welding the process of assembling hull structural components into the whole hull. Generally, sectional construction is adopted, which is divided into three stages: component assembly welding, sectional assembly welding and slideway assembly welding.
① Assembly and welding of parts: also called small folding. The process of assembling processed steel plates or sections into plates, T-sections, rib frames or ship fore and aft columns is carried out on the assembly and welding platform in the workshop.
② Segmented assembly welding (generally segmented): also called middle sealing. Assemble parts into plane segments, curved segments or three-dimensional segments, such as bulkheads, bottoms, sides and superstructures; Or combined into an annular three-dimensional section passing through the main hull in the direction of the captain, which is called a general section, such as a bow general section and a stern general section. The assembly and welding of segments are carried out on the assembly and welding platform or fixture frame. The division of sections mainly depends on the characteristics of hull structure and the hoisting and transportation conditions of shipyard. With the enlargement of ships and the increase of crane capacity, there are more and more segmented sections and general sections, and their weight can reach more than 800 tons.
③ Assembly and welding of slipway (dock): namely hull assembly, also known as big closure. The hull parts, sections and sections are finally assembled and welded in the berth (or dock) to form the hull. For large ships with a displacement of more than 6,543,800 tons, most of them are assembled in shipyards to ensure the safety of launching. The common assembly methods are: taking the general section as the assembly unit, hoisting from the middle of the ship to the bow and stern, which is generally suitable for the construction of small and medium-sized ships; Firstly, a section of the bottom section at the eccentric position of the ship is hoisted, and the adjacent sections are hoisted to the bow, stern and upper floor as the construction benchmark, and the hoisting range is in the shape of a pagoda, which is called tower construction method; There are 2 ~ 3 construction benchmarks, which are built by tower construction method respectively, and finally connected to form a hull, which is called island construction method; When the first ship is built at the end of the berth (or dock), the tail of the second ship is also built at the front end of the berth. After the first ship is launched, move the tail of the second ship to the end of the slipway and continue hoisting other sections until the whole hull is assembled. At the same time, the tail of the third ship is built at the front end of the slipway, and so on. This method is called serial construction method. The hull is divided into two parts, the first section and the last section, which are launched on the slipway and then closed on the water. This is the so-called two-stage construction method. The choice of various assembly methods depends on the structural characteristics of the hull and the specific situation of the shipyard.
The workload of hull assembly and welding accounts for more than 75% of the total workload of hull construction, of which welding accounts for more than half. Therefore, welding is the key work of shipbuilding, which is not only directly related to the quality of shipbuilding, but also related to the efficiency of shipbuilding. Since 1950s, welding methods have developed from full manual welding to automatic submerged arc welding (SAW), semi-automatic welding, electroslag welding and gas shielded welding. Since the mid-1960s, new technologies such as one-sided welding and double-sided forming, gravity welding, automatic fillet welding, vertical welding and horizontal automatic welding have appeared. Welding equipment and welding materials have also developed accordingly. Due to the complexity of hull structure, manual welding is still needed in the position where automatic welding and semi-automatic welding are difficult to implement.
Combined with the development of welding technology, T-beam assembly and plane sectional assembly line have been used for hull parts and sectional assembly respectively since 1960s. T-shaped section is the basic component of plane segmented bone. Plane segments occupy a considerable proportion in the hull structure, for example, on large bulk carriers and oil tankers, plane segments can account for more than 50% of the total weight of the hull. Plane sectional assembly line includes all kinds of special assembly and welding equipment. It uses conveyor to continuously feed, tailor-welded assembly and weld the skeleton, which can significantly improve the mechanization degree of sectional assembly and become one of the main contents of technical transformation of modern shipyards. Some shipyards in the world also use assembly line to assemble and weld the three-dimensional sections of large oil tankers in mass production and dock assembly.
After the final assembly of the hull, the tightness test of the hull must be carried out, and then the shafting, propeller and rudder are installed at the tail of the shaft system and rudder system. Prepare to launch after completing various underwater projects.
Ship launching is the process of moving the ship assembled in the berth (wharf) from land to water. The movement direction of a ship when launching is either parallel to the captain or perpendicular to the captain, which are called longitudinal launching and lateral launching respectively. The launching slideway mainly includes wooden fang slideway and mechanized slideway. The former depends on the self-weight of the ship to slide into the water and is widely used; The latter uses a small car to carry the hull and pull it into the water on the track, which is mostly used in small and medium-sized inland river shipyards.
Before launching vertically, transfer the hull docked on the pier to the skateboard and slideway, and the slideway is inclined to the direction of the ship entering the water. When the braking device between the skateboard and the slideway is released, the ship slides into the water together with the skateboard and the bracket due to its own weight, and then floats on the water by its own buoyancy. In order to reduce the friction resistance when sliding, a certain thickness of launching grease is often coated between the skateboard and the slideway; Steel balls can also be used to replace sewage grease, and sliding friction can be changed into rolling friction to further reduce friction. The ship assembled in the dock can float as long as it is poured into the dock, and its launching operation is much simpler and safer than launching under the dock.
Launching means that the ship construction has completed the key and main work. According to traditional customs, when a big ship is launched, a grand celebration ceremony is usually held.
Dock installation (installation of equipment and systems) After a ship is launched, it often relies on the outfitting dock in the factory to install hull equipment, electromechanical equipment, pipes and cables, and carry out carpentry, insulation and painting work in the cabin. There are many types of work involved in wharf installation, which have great influence on each other. With the increasing complexity of ship equipment and systems, the requirements for installation quality are constantly improving, so the installation work is directly related to whether the ship can be delivered quickly after launching. In order to shorten the installation period after launching, the above installation work should be carried out as early as possible to the stage of sectional assembly and hull assembly, which is called pre-outfitting. Changing the traditional single-piece installation into unit assembly can also greatly shorten the installation cycle, that is, determine the composition degree of installation units according to the layout and composition characteristics of engine room and other engine room equipment. For example, the main engine cooling device may include a heat exchanger, a pump, a thermostat, related pipes with accessories, and electrical equipment required by the device. Assembling the installation unit in the workshop, and then hoisting it to the section, general section or ship for installation, can advance the installation workload of 18 ~ 25% from the ship to the infield, and shorten the installation period of 15 ~ 20%.
Mooring test and navigation test After the completion of hull construction and installation, in order to ensure the perfection of construction and the reliability of various equipment, comprehensive and strict tests must be carried out, which are usually divided into two stages, namely mooring test and navigation test.
Mooring test, commonly known as dock trial operation, is a series of practical tests to check the installation quality and operation of the ship's main engine, auxiliary engine and other electromechanical equipment in mooring state. Mooring test takes the main engine test as the core, checks the working conditions of generator sets and distribution equipment, and creates conditions for the main engine and other equipment tests. The coordination, emergency, telemetry, remote control and automatic control of related systems also need to be tested for reliability and safety. During the mooring test, the ship is basically in a static state, and the main engine, shafting and related equipment systems cannot show the performance of full-load operation, so it is necessary to carry out navigation tests.
Navigation test is to comprehensively check the performance of the main engine, auxiliary engine and various electromechanical equipment and systems of the ship in the navigation state. Generally, there are light-load trials and heavy-load trials. In the navigation test, the speed, main engine power, maneuverability, gyration, course stability, inertia and seaworthiness of the designated navigation area are measured. After the test results are accepted by shipping agencies and users, the shipyard will officially deliver them to the ordering party for use.
The development of modern shipbuilding technology is a process from manual operation to mechanization and automation. Since 1950s, riveting has been replaced by welding in hull construction, which has improved the hull construction from sporadic bulk mode used for a long time in the past to sectional assembly mode, greatly improving the shipbuilding efficiency. Due to the complexity of hull structure and shape, manual operation has always occupied a large proportion in hull construction. The application of computer and numerical control technology is further changing the face of shipbuilding industry. Electronic computers were first used in mathematical lofting, and then numerical control plotters, numerical control cutting machines, numerical control rib cold bending machines, numerical control propeller processing machines and pipe processing machines with digital input and graphic output appeared. At the same time, electronic computing technology has been gradually applied to the production management, planning, material and equipment supply and cost accounting of shipyards. In order to reduce information preparation and eliminate the disconnection between design and production, a large-scale shipbuilding integrated numerical control system is developed, which includes general information of all functions of ship design, production and management, and can coordinate the whole working process from design to production. Therefore, expanding the application of computer in shipbuilding is the main direction to develop shipbuilding technology and further improve the degree of shipbuilding automation.
philology
Wang Yongyi et al., Hull Construction Technology, People's Communications Industry Press, Beijing, 1980.