DEVELOPMENT OF LASER TECHNOLOGIES FOR OIL AND GAS INDUSTRY

Transcription

1 DEVELOPMENT OF LASER TECHNOLOGIES FOR OIL AND GAS INDUSTRY A. Grezev, V. Grezev, A. Sukhov, S. Shancurov, M. Malysh Laser Technological Center, Shatura, Russia Laser Technology Regional Center, Ekaterinburg, Russia Abstract Researches on development of laser welding, deposition and cutting for oil and gas industry were conducted. The technology of the combined laser welding by several laser beams was developed that allows to control the size of a weld pool. Laser welds for all studied steels showed uniform strength with the base metal. It is offered instead of arc welding of joints of the pipeline in field conditions to use the developed automated mobile complex for laser welding. Other directions of introduction of laser technologies in the gas and oil industry are deposition and cutting Keywords: laser welding, deposition and cutting, gas and oil industry, automated mobile complex Institute of Problems of Laser and Information Technologies of the Russian Academy of Sciences (IPLIT RAS) together with VNIIST, VNIIGAZ and pipe plants have conducted researches on development of technology of laser welding of pipes when have been made powerful technological lasers (1, 2). In particular, introduction of technology of laser welding of pipes from stainless steels on Novomoskovsk pipe plant is carried out. Laser welding has allowed to provide properties of pipes on all indicators at the level of the base metal and to increase in three times welding productivity. Researches of laser welding of austenitic class steels have shown a possibility of increase in productivity by times. The system of targeting of a laser beam to the welding joint with an accuracy of ±0,05 mm having metaloptical lenses with the high term of operation has been for the first time developed and installed on a pipe mill. Researches of laser welding of steels for the gas-and-oil pipeline tubes applied in production were at the same time conducted. Laser welds on all investigated steels have shown uniform strength with the base metal. However the hardness of a weld and a heat affected zone (HAZ) exceeded a standard indicator (HV 260). It is connected with the fact that at laser welding has too tough thermal cycle: high speeds of heating and cooling of weld metal therefore the weld acquires hardening structures and, as a result, weld metal has high hardness. Result of joint researches IPLIT RAS with Chelyabinsk Tube Rolling Plant (CTRP) and the Volzhsky Pipe Plant (VPP) was development of technology of the combined laser welding (CLW). The essence of technology consists in impact by several laser beams on a molten bath that allows to control the volume of a molten bath. As a result there is an opportunity to set the required speeds of heating and cooling of metal and to get necessary structure of metal of a weld. At the same time advantages of laser welding remain: high speed, small HAZ, a deep depth of penetration, welding for one pass of big thickness, lack of need of welding groove of edges. In IPLIT RAS researches of the CLW technology on the pipe steels (C0.14MnB, C0.08MnWBA, etc.) have been conducted. Part of researches are carried out in CTRP and VPP laboratories. Pipes by the size 530*2000*8mm has been welded. Then pipes have passed tests on a hydraulic fracturing (pressure of a fracturing has made 203kgs/mm2). 1-52

2 Researches have shown: 1. CLW doesn't limit the input power in a welded item as it occurs at traditional laser welding (because of emergence of the shielding plasma breakdown which shields laser radiation) that allows to use fiber lasers by power in several tens kilowatts and to considerably increase depth of a penetration (up to 50 mm and more for one pass) (fig. 1, a); 2. Increase in width of a weld happens both in the top part of a weld, and in the bottom part; 3. Microhardness of a weld is uniform on all depth and on the low-alloy pipe steels doesn't exceed 260HV10 (tab. 1); Table 1. Research of Vickers microhardness of a weld (HV 10 ) Number of a section Weld HAZ Base metal C0.08MnWBА average 249, 245, , 247, , 247, , , , , , , C0.09Mn2Si 1 2 average Impact strength of the welds made by CLW is in 10 times more than at submerged-arc welding, uniform strength of a weld to the base metal is also provided; 5. CLW with an filler wire considerably reduces requirements to assembly (the weld gap can make up to 3 mm at a 50 mm thickness of product); 6. CLW is possible in any welding positions, the weld form at the same time considerably doesn't change; 7. The CLW technology is demostrated as on lasers with the wavelength of 10.6 microns, and on fiber lasers with the wavelength of 1.06 microns (fig. 1, b). a b 1-53

3 Fig. 1. Structure of the weld (a) made by CLW and the scheme of CLW process (b) At the present time welding of a joint is made generally by manual arc welding at construction of gas pipelines. Duration of the welding which is carried out by two, and sometimes three welders makes about stream day. The developed automated mobile complex (fig. 2, a) and the module (fig. 2, b) for laser welding of the pipeline joints in field conditions it is offered to use instead of arc welding. Pipe alignment at assembly is carried out by means of the special device. а Fig. 2. The automated mobile complex (a) and the module (b) for laser welding of pipeline joints of in field conditions б 1-54

4 The main technical characteristics of the automated mobile complex: Laser type ytterbium fiber laser; Power of radiation, kw 45-50; Diameter of the welded pipes, mm 1420; Thickness of a pipe wall, mm 15 30; Speed of welding, m/min 3 6; Automobile transport type on track; Loading capacity, kg 10000; Diesel generator: power, kw 500. The module can be installed on a specialized mobile complex, on the deck of the ship, etc. The main advantages of technology of laser welding of pipelines joints are: uniform strength of the weldment with the base metal; small (to 1 mm) HAZ of weldment; lack of residual tension; duration of welding of the pipeline joint will make no more than 4 minutes, speed of construction of the gas pipeline by the one complex will make to 1 km in 22 days. Other direction of introduction of laser technologies in the oil and gas industry is the laser deposition. IPLIT RAS has put a robotic laser complex on the basis of the fiber LS-3 laser for recovery of rotors of the gas-distributing equipment (fig. 3, a). The laser deposition allows to make a complete recovery of a shaft, to eliminate chips and craters. The built-up layer has required strength characteristics as a result of the high speed of heating and cooling, and also presence of the alloying elements at filler material. At the same time the product doesn't change the geometrical parameters. The error makes 0,2 mm. This method of a deposition can be used not only for recovery of shafts, but also for more complex massive products, for example, of turbine blades (fig. 3, b). A number of the western companies offer the similar equipment. It should be noted that this method allows to make recovery of the damaged gas-turbine blades directly on a shaft that economically profitable. a b Fig. 3. Recovery process by a laser deposition of a rotor of the gas-distributing equipment (a) and gas-turbine blades (b) 1-55

5 One of the main directions of effective application of laser technologies is laser cutting of details (3). Laser cutting possesses a number of advantages in comparison with other ways of cutting, are basic of which: - possibility of cutting of volume products; - high speed and accuracy of processing, etc. Examples of application of laser cutting are presented in fig. 4, 5. Fig. 4. Examples of laser perforation of pipes with thickness of a wall of 2 mm Fig. 5. 3D-laser cutting of openings in the bottom of the oil refining device with a diameter of 1900 mm and about 500 mm high It is established that at laser cutting of hollow carrier perforating systems and the bottoms of the oil refining device the high quality of edges which isn't demanding the subsequent additional processing is provided. At the same time changes of structure of metal in a heataffective zone don't have influence on mechanical properties and corrosion resistance of edges, their high quality which isn't demanding the subsequent additional processing is provided. It is also established that there is no formation of the structures prone to formation of cracks. Production of products, including rectangular welded pipes, from titanium alloys with application of laser volume cutting and welding (fig. 6) is organized. 1-56

6 Fig. 6. Laser welding of beams from titanium alloys Influence of laser welding on mechanical properties and structure of welds of a PT3-V titanium alloy was investigated. Research has shown a good weldability of the welds. It is established that mechanical properties of welds are close to the base metal, destruction of samples at tensile tests happened on the base metal. The microstructure of the laser weld represents transition, uniform on microhardness, from the globulyarny fine-grained metal consisting of a α-phase to more coarse-grained structure of a weld metal consisting of colonies of a lamellar α-phase with a narrow transitional zone for lack of a noticeable pores or microcracks. The technologies of 3D-laser processing of titanium alloys which have allowed to reduce deformations of large-size products by 7 8 times and to provide high quality of welds with thickness to the 3-5mm are developed. References 1. Grezev A. Development of physicotechnological fundamentals of constructional steels laser welding by powerful CO2 lasers.: Dr. sciences thesis M.: IPLIT the Russian Academy of Sciences, Grezev A., Romantsov N., Goritsky V. Full-sized tests of the oil and gas pipes with a diameter of 530 mm welded by a laser beam.//ferrous metallurgy (9) Grezev A., Suhov A., Shanchurov S. Developmen and industrial application of laser technologies. The Eights International Conference on Material Technologies and Modeling MMT-2014, University of Ariel,