Key Points for Production Preparedness of Duplex Stainless Steel Chemicals Ship
Pre-production preparation refers to combing and planning comprehensively from the aspects of technology, technology and materials before the formal start-up of construction, in order to find out the difficult and difficult work and solutions, and to pave the way for the smooth construction in the later period.
Compared with steel ships, duplex stainless steel chemical tankers have special construction environment, construction technology, special tooling tools and protection requirements for the construction process. Therefore, the preparation before production is the key to the smooth construction of duplex stainless steel chemical tankers. The preparation before production directly affects the progress and protection of the project. Completion quality. This paper summarizes the main points of preparation before construction of duplex stainless steel chemical tanker, which can be used for reference by peers.
2. Key Points for Production Preparation of Duplex Stainless Steel Chemical Ships
According to the experience of ship construction and relevant information, the following aspects should be considered and planned before the construction of duplex stainless steel chemicals:
2.1 Duplex Stainless Steel Protection Technology
The protection of duplex stainless steel is an important work in the construction of this type of ship. In the construction process of storage, transshipment, welding and grinding, a series of protection measures must be planned, and it is a very basic, important and key work. According to the experience of actual ship construction, protection should be considered in every link from the packing of steel mill or additional factory to the delivery of the ship. The following aspects should be taken into account in the preparation of protection technology:
- Mechanical damage, scratches and oil pollution should be avoided.
- Direct contact with carbon steel (including tooling tools) should be avoided.
- Saline media such as sweat should be avoided dropping on raw materials.
- It should avoid trampling directly on the surface of raw materials.
- After disassembly and assembly of raw materials, surface pollution should be avoided.
- When transporting and hoisting, oil pollution on slings and cranes should be avoided from falling on raw materials.
- The protection of the edge of the board when turning over in segments;
- Protection against iron powder and dust in the stages of sectional production, pre-outfitting and stacking;
- Protection against paint mist pollution during painting or outdoor stacking stage;
- Isolation and protection measures of steel scaffolding and duplex stainless steel, etc.
While doing a good job of protection, we should also strengthen the inspection and feedback of problems in the process, find problems and deal with them in time, such as finding damage, floating rust, oil pollution and so on. We should arrange personnel polishing, passivation and cleaning in time.
In addition, in addition to the protection of duplex stainless steel plates, stainless steel escalators, steps, pipe brackets and stainless steel heating coils in the cargo hold area also need to do a good job of corresponding protection measures.
2.2 Tools for Duplex Stainless Steel
In order to avoid carburizing, duplex stainless steel is usually not allowed to contact directly with carbon steel during storage and construction. Therefore, it is necessary to plan and manufacture a set of special tooling tools. For example, the tire frame tooling used in the stage of sectional manufacture, the pressing iron tooling to prevent welding distortion, the special welding arc plate, slag hammer, welding trolley track, stainless steel wire brush and other tools, and the scaffold tooling constructed in stainless steel cabin.
According to the experience of ship construction, in order to reduce the cost, carbon steel is used as the main material of some special tooling tools such as frame and iron pressing, and 316L stainless steel is used as the isolating material.
In addition, there are other special tooling tools that need to be prepared, as follows:
- (1) Plasma planer: It is forbidden to use carbon arc air gouging and flame cutting in cleaning the root or defect of stainless steel welding seam and cutting the process test plate. Usually, plasma air gouging or mechanical grinding are used.
- (2) Ferrite measuring instrument: metallographic method and magnetic method are usually used to inspect the ferrite after welding. In the welding process, in order to quickly check whether the ferrite content in the weld seam and heat affected zone is up to the standard, the magnetic method is usually used to check, and a special ferrite measuring instrument needs to be purchased.
- (3) Electric grinder and special grinding disc: In order to avoid oil pollution on the surface of duplex stainless steel in pneumatic grinder, electric grinder is usually used; in addition, in order to improve grinding efficiency and quality, special grinding disc is needed for duplex stainless steel.
- (4) Special sling: In order to avoid the pollution of dual-phase stainless steel by sling and oil pollution on it, it is usually necessary to prepare special sling for lifting; in addition, when lifting dual-phase stainless steel, electromagnetic lifting is not allowed, and special vacuum suckers need to be purchased or manufactured for lifting.
2.3 Production Planning
Production planning is the core of project management and the programmatic document that the project can be completed orderly and on time. Therefore, it is necessary to draw up a reasonable plan according to the requirements of the periodic nodes of the ship construction contract and the facts of the factory, such as personnel, equipment, engineering technology and so on. The promotion of the whole project is as follows: Crucial.
Dual-phase stainless steel chemical tanker has not only the production of carbon steel section, but also the production of stainless steel section, as well as the assembly of carbon steel section and stainless steel section. Therefore, it is necessary to rationally arrange the production plan of carbon steel section and stainless steel section according to the specific placement, material arrival plan and construction period of section. The construction plan of stainless steel chemical tanker should be considered.
In addition, due to the carbon steel and stainless steel in the cargo compartment of duplex stainless steel chemicals, there are different technical requirements for the selection of abrasives in sand washing. Therefore, the shipyard needs to arrange the painting plan of the duplex stainless steel chemicals vessel according to the resources of the painting site.
2.4 Welding Procedure for Duplex Stainless Steel
Welding technology of duplex stainless steel is one of the most important and difficult problems in the construction of this type of ship. There are strict requirements for energy of welding line and temperature between layers when welding duplex stainless steel. The content of ferrite in welding seam has important value for mechanical properties and corrosion resistance of welded joints. According to the requirements of specifications, it is usually controlled at 30%-70%.
Welding procedure is an important process document before the start of construction. Without the approval of classification society, the project can not start. In the design of welding procedure for duplex stainless steel, the main welding methods are carbon dioxide gas shielded welding, submerged arc automatic welding, tungsten argon arc welding and manual electrode welding. Common forms of base metal combination are: duplex stainless steel + duplex stainless steel; duplex stainless steel + carbon steel; duplex stainless steel + 316L stainless steel. In addition, steel grade, thickness and welding position should be fully covered according to the planning of welding process.
According to the experience of ship construction, due to the high strength of duplex stainless steel, poor metal fluidity, shallow penetration, slow heat dissipation and large welding deformation, the design of joint groove usually adopts double-sided symmetrical groove, and the groove angle should be increased appropriately, usually about 110-120 degrees.
2.5 Precision Control Scheme for Duplex Stainless Steel
The welding groove of duplex stainless steel is usually machined. Shipyard usually entrusts professional companies outside to process. In the stage of construction and assembly, secondary cutting should be avoided as far as possible. Therefore, duplex stainless steel sectional cutting blanking is usually used.
Dual-phase stainless steel is easily deformed after welding. It is usually forbidden to adopt initiation correction, but only mechanical correction. Therefore, the precision control of duplex stainless steel has very high requirements.
According to the experience of actual ship construction, a lot of precision data collection, analysis and test work are needed before shipyard starts construction, so as to set reasonable welding shrinkage and compensation amount, which is an important work of precision control. In addition, the control of welding sequence, the control of welding foot size, the control of CM nodes, the manufacturing and installation accuracy of grooved bulkhead, and the installation accuracy of reinforcement under grooved bulkhead are also the key planning items of precision control.
2.6 Personnel Training and Examination
Since most shipyards are transformed from steel ships to dual-phase stainless steel chemical ships, the key is to change people’s habits and consciousness. Especially, whether the special construction requirements of dual-phase stainless steel can be effectively implemented and implemented determines the success or failure of the project.
How to let each of these specific requirements participate in understanding and mastering, and how to let each constructor carry out according to the requirements, practice has proved that this is an extremely important work in production preparation, the main preparatory work is as follows:
- (1) It is necessary to compile special training textbooks and examination papers, and organize training and examination repeatedly according to the construction progress on site and the key and difficult work in the process.
- (2) All welders must be trained, tested and evidenced. They should be listed on the construction site, and the welders should choose the welders who have been engaged in stainless steel welding for a long time.
- (3) All polishers, painters and plumbers must undergo special training and technical presentation before taking up their posts, and it is better to select experienced and professional teams for their work.
- (4) All business managers and lifting operators must clearly understand and master the characteristics, technical requirements and construction requirements of duplex stainless steel, and also carry out training and examination from time to time.
3. Concluding remarks
Based on the training of classification societies, the training of welding material manufacturers, consulting relevant information and visiting other shipyards for learning and exchanging, as well as the experience of the company’s actual ship construction, the above-mentioned contents are summarized and summarized as some key points to be paid attention to and considered in the production preparation work before the start of the duplex stainless steel chemical ship. The main points of the work can be used for reference by peers in practical work.
Source: China Duplex Stainless Steel Pipe Fittings Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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