CN109811197B - Preparation method of blade root gasket material for 700-DEG C steam turbine regulating stage - Google Patents
Preparation method of blade root gasket material for 700-DEG C steam turbine regulating stage Download PDFInfo
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Abstract
A preparation method of a blade root gasket material for a 700 ℃ steam turbine regulating stage belongs to the field of metal materials. The components of the invention are Ni (25-35 wt%) Cr (5-7 wt%) Al. The hardness HB of the gasket prepared by the alloy with the components at room temperature is less than or equal to 140, and the gasket has excellent high-temperature oxidation resistance and high-temperature creep rupture strength; in addition, the alloy has excellent processing performance, the size precision of the gasket in the thickness range of 0.5mm to 2mm can reach +/-0.02 mm through hot rolling forming and cold rolling leveling, and the mechanical property and the size precision can completely meet the requirement of a high-pressure regulating-grade blade root gasket of a steam turbine at the 700 ℃ grade.
Description
Technical Field
The invention belongs to the field of metal materials, and relates to a preparation method of a blade root gasket material for a 700-DEG C steam turbine regulating stage.
Background
To further improve the thermal efficiency of combustion power plants, CO is reduced2The emission of SOX and NOx, ultra-supercritical (A-USC) power station technology of 700 ℃ grade has become an important direction for developing high-efficiency and low-consumption coal power units in some developed countries such as Europe, America, Japan and the like in the world at present. China formally establishes 'national 700 ℃ ultra-supercritical coal-fired power generation technology innovation alliance' in 2011 and organizes and develops corresponding research and development work. At present, the steam turbine factory in China generally uses 12% Cr heat-resistant steel as the steam turbineThe materials of the rotor and the moving blade of the machine cannot meet the strict requirement of 700 ℃ grade ultra-supercritical unit. The nickel-based high-temperature alloy has excellent corrosion resistance and high-temperature endurance strength, and is the preferred material for steam turbine materials of 700 ℃. A large number of research and application results show that Nimonic 80A and Waspaloy (called GH864 or GH738 domestically) in the nickel-based alloy have good structural stability at 700 ℃, high-temperature strength and good oxidation resistance, and are ideal materials for steam turbine fasteners and blades at 700 ℃. The assembling mode of the ultra-supercritical turbine blade with the 700 ℃ grade is different from the assembling mode of the blade with the grade below 650 ℃ at present. The blades with the temperature of below 650 ℃ are made of heat-resistant steel, and the assembly of the blades depends on the high dimensional precision and field processing of the blades to realize the gapless fit between the blade roots. The assembly method has a prominent problem that when the temperature of the blade is higher, the blade generates great thermal stress due to expansion, thereby affecting the high-temperature performance of the blade. In order to eliminate the potential influence on the service life of the blade caused by expansion thermal stress, the assembling mode of the 700 ℃ grade steam turbine blade is changed, a certain gap is reserved between the blade and the root of the blade, and the blade is matched by inserting a gasket into the gap. This assembly method has two advantages: (1) the processing precision of the blade is reduced, and the yield of the processed blade is improved; (2) through adding the gasket, reduced the assembly degree of difficulty of blade, can reduce the high temperature thermal stress between the blade root simultaneously, improved the security and the stability of blade work.
The gas pressure and the temperature of the turbine blade work are different, the selected gasket material also has certain difference, and the requirement on the gasket of the nickel-based alloy blade working at the high-pressure regulating stage has three aspects: (1) the gasket has low yield strength and high creep rupture strength to relieve thermal stress generated by expansion among the blades, and the room temperature hardness is lower than the hardness of the blades to reduce mechanical damage to the blades in the assembling process; (2) the gasket has good processing performance, can be processed into different thicknesses, and has the size precision of +/-0.02 mm. The existing mature-grade materials can not meet the requirements, and new high-temperature-resistant materials need to be developed.
Disclosure of Invention
The invention designs a material for manufacturing a high-pressure regulating grade blade root gasket of a steam turbine at the 700 ℃ grade based on the excellent high-temperature characteristic of a nickel-based alloy, the room-temperature hardness HB of the gasket prepared from the alloy is less than or equal to 140, and the gasket has excellent high-temperature oxidation resistance and high-temperature creep rupture strength; in addition, the alloy has excellent processing performance, can be processed into a gasket with the thickness range of 0.5mm to 2mm through hot rolling, and then is flattened through cold rolling, so that the thickness precision of the gasket can reach +/-0.02 mm, and the mechanical property and the size precision can completely meet the requirement of a high-pressure regulating-grade blade root gasket of a steam turbine at the 700 ℃ grade.
A preparation method of a blade root gasket material for a 700 ℃ steam turbine regulating stage comprises the following components: ni to (25-35 wt%) Cr to (5-7 wt%) Al, wherein the content ratio of the added Cr to the Al is 5: 1, the grain size of the gasket is 100-150 microns. The main manufacturing process of the blade root gasket comprises alloy smelting, forging and cogging, precise hot rolling, solution heat treatment, cold rolling and flattening of a plate and laser cutting.
The specific manufacturing process and requirements are as follows:
(1) alloy smelting: according to the weight percentage of Ni to (25-35 wt%) Cr to (5-7 wt%) Al, wherein the content ratio of the added Cr to the Al is 5: 1, selecting raw materials according to the alloy composition requirement, and then carrying out vacuum melting to obtain the master alloy. Carrying out vacuum electroslag remelting on the master alloy, wherein the electroslag formula comprises the following components in percentage by weight: al (Al)2O335-55%; CaO is 40-55%; CaF is 5-10%, and the vacuum degree of electroslag is 0.1 Pa.
(2) Alloy forging: and forging the electroslag ingot into a plate blank with a certain thickness, wherein the furnace entry heat preservation temperature of a workpiece is 1250 ℃ during forging, and the heat preservation time is determined according to the standard of 20 minutes/cm and by combining the actual diameter of the blank. The deformation amount of the alloy during the first heat forging is controlled within a range of 15 to 20%, and the forging deformation amount at each time when the second heat is started is controlled within a range of 40 to 60%. The final forging temperature of each fire forging is 1000 ℃, and the holding temperature of the blank returning in the furnace between each fire is 1200 ℃. And (3) returning the plate blank to the furnace for heat preservation heat treatment after forging, wherein the heat treatment temperature is 1170 ℃, and the heat preservation time is determined according to the standard of 30 minutes/cm and by combining the actual thickness of the forged plate blank.
(3) Precision hot rolling: and hot rolling the forged plate blank into a plate with the required thickness, wherein the hot rolling temperature is 1100-1180 ℃, the rolling stop temperature is more than 900 ℃, the thickness range of the hot-rolled plate is 0.5-2.0 mm, and the tolerance precision is +/-0.05 mm.
(4) Solution heat treatment: and carrying out solution heat treatment on the plate after hot rolling at 1150-1170 ℃, setting the heat preservation time according to the thickness of 3-5 minutes/mm, and carrying out air cooling after the solution heat treatment.
(5) Cold rolling and flattening: and (3) carrying out cold rolling flattening treatment on the hot rolled plate subjected to the solution treatment, and improving the tolerance precision of the hot rolled plate from +/-0.05 mm in a hot rolling state to +/-0.02 mm.
(6) Laser cutting and forming: and cutting the cold-rolled sheet which is cold-rolled to the required thickness into the required size and shape by adopting laser to obtain the finished product blade root gasket.
The gasket prepared by the process has high thickness and size precision which can reach 0.02mm because the raw materials have good hot working and cold working properties; by adding Cr and Al and strictly controlling the proportion of the Cr and the Al and the grain size of the material, excellent room temperature and high temperature performance can be obtained, the room temperature tensile strength exceeds 750MPa, the yield strength is only 200MPa, the elongation is more than 60 percent, the hardness HB is less than 140, the creep rupture time under the conditions of 700 ℃ and 140MPa exceeds 1.5 ten thousand hours, and the high temperature oxidation resistance is excellent. The size and performance of the gasket prepared by adopting the alloy components and the preparation process can completely meet the requirements of the high-pressure regulation grade blade root gasket of a steam turbine at the 700 ℃ grade.
The specific implementation mode is as follows:
(1) since the thickness of the root shim is usually in the range of 0.5mm to 2.0mm, three typical thicknesses of 0.5mm, 1.0mm and 2.0mm are selected for the description of the embodiment, and 100 pieces of shim with the specification of 3cm (length) × 2cm (width) × 2.0 ± 0.02mm (thickness) are manufactured, 100 pieces of shim with the specification of 3.5cm (length) × 2.5cm (width) × 1.0 ± 0.02mm (thickness) are manufactured, and 100 pieces of shim with the specification of 2.5cm (length) × 1.5cm (width) × 0.5mm ± 0.02mm are manufactured by the following steps:
firstly, mother alloy smelting: a vacuum induction melting furnace with 200kg of equipment is adopted, the total weight of the melted alloy is 150kg, the weight of each element is proportioned according to Ni-30 wt% Cr-6 wt% Al, 9kg of Al, 45kg of Cr and 96kg of Ni are respectively required. The casting temperature of the smelted master alloy is 1550 ℃, and the diameter specification of a cast master alloy ingot is 15 cm.
Secondly, vacuum electroslag remelting of the master alloy: the vacuum electroslag remelting furnace with 100kg of equipment is adopted, the vacuum degree of the electroslag is 0.1Pa, and the component of the electroslag is Al2O3Is 50 percent; CaO accounts for 40 percent; CaF is 10%, calculated by electroslag total 3kg, Al is required2O31.5 kg; CaO is 1.2 kg; CaF is 0.3kg, and the specification of the electroslag ingot is 20 cm.
And thirdly, forging and cogging the electroslag ingot, wherein the temperature of the electroslag ingot in the furnace is 1250 ℃, and the heat preservation time is 400 minutes, so that the steel billet is fully heated, the further diffusion of internal alloy elements is realized, and the internal components are more uniform. After the heat preservation is finished, performing first fire forging, wherein the first fire deformation is controlled to be 15%, so that coarse grains and precipitates are primarily crushed; and (3) increasing the deformation of the forging stock by the second fire, controlling the deformation of each fire to reach 40%, controlling the finish forging temperature of each fire to be 1000 ℃, and controlling the heat preservation temperature of the returning of the stock to be 1200 ℃. And forging the electroslag ingot into a plate blank, wherein the thickness of the plate blank is 10 mm. And (3) after the final hot forging, carrying out remelting heat preservation heat treatment on the plate blank, wherein the heat treatment temperature is 1170 ℃, the heat preservation time is 30 minutes, and then carrying out air cooling.
And the fourth part is subjected to precision hot rolling: hot rolling the forged slab with the thickness of 10 mm, wherein the initial hot rolling temperature is 1150 ℃, the rolling stopping temperature is more than 900 ℃, the slab with the thickness of 10 mm is firstly hot rolled into the thickness of 2mm +/-0.05 mm, and then certain size is cut out for processing a gasket with the thickness of 2 mm; then, the rest plate blanks are heated to 1150 ℃ again, the heat preservation temperature is kept for 10 minutes, the plate blanks with the thickness of 1mm +/-0.05 mm are continuously hot-rolled, and then certain size is cut out to be used for machining gaskets with the thickness of 1.0 mm; finally, the rest plate with the thickness of 1.0mm is reheated to 1150 ℃, the heat preservation temperature is 4 minutes, and the plate with the thickness of 0.5mm +/-0.05 mm is hot rolled to be used for processing a gasket with the thickness of 0.5 mm.
And fifthly, carrying out solution heat treatment on the hot rolled plates with the three specifications, wherein the solution heat treatment temperature is 1170 ℃, the heat preservation time of the plate with the specification of 0.5mm is 2 minutes, the heat preservation time of the plate with the specification of 1.0mm is 4 minutes, the heat preservation time of the plate with the specification of 2.0mm is 8 minutes, and air cooling is carried out after the solution heat treatment of all the plates.
And sixthly, cold rolling and flattening the hot rolled plates with the three specifications after the solution heat treatment, and improving the tolerance precision of the hot rolled plates from +/-0.05 mm to +/-0.02 mm in a hot rolling state.
And seventhly, carrying out laser cutting forming on the plates with the three specifications according to the size requirement to obtain a finished product blade root gasket.
Claims (1)
1. A preparation method of a blade root gasket material for a 700 ℃ steam turbine regulating stage is characterized by comprising the following steps of: the gasket material comprises the following components: ni to (25-35 wt%) Cr to (5-7 wt%) Al, wherein the content ratio of the added Cr to the Al is 5: 1, the grain size of the gasket is 100-150 microns;
the manufacturing process of the blade root gasket comprises alloy smelting, forging and cogging, precise hot rolling, solution heat treatment, cold rolling and flattening of a plate and laser cutting;
the specific manufacturing steps are as follows:
(1) alloy smelting: according to the weight percentage of Ni to (25-35 wt%) Cr to (5-7 wt%) Al, wherein the content ratio of the added Cr to the Al is 5: 1, selecting raw materials according to the alloy component requirement, and then carrying out vacuum melting to obtain a master alloy; carrying out vacuum electroslag remelting on the master alloy, wherein the weight percentage of the electroslag formula is as follows: al (Al)2O335-55%; CaO is 40-55%; CaF25-10% and the vacuum degree of electroslag is 0.1 Pa;
(2) alloy forging: forging the electroslag ingot into a plate blank with a certain thickness, wherein during forging, the furnace entry heat preservation temperature of a workpiece is 1250 ℃, and the heat preservation time is determined according to the standard of 20 minutes/cm and by combining the actual diameter of the blank; controlling the deformation of the alloy in the first fire forging within the range of 15-20%, and controlling the forging deformation of each time when the second fire begins to be 40-60%; the final forging temperature of each fire forging is 1000 ℃, and the heat preservation temperature of the blank returning between each fire is 1200 ℃; returning the plate blank to the furnace for heat preservation heat treatment after forging, wherein the heat treatment temperature is 1170 ℃, and the heat preservation time is determined according to the standard of 30 minutes/cm and by combining the actual thickness of the forged plate blank;
(3) precision hot rolling: hot rolling the forged plate blank into a plate with the required thickness, wherein the hot rolling temperature is 1100-1180 ℃, the rolling stop temperature is more than 900 ℃, the thickness range of the hot-rolled plate is 0.5-2.0 mm, and the tolerance precision is +/-0.05 mm;
(4) solution heat treatment: after hot rolling, carrying out solution heat treatment on the plate at 1150-1170 ℃, setting the heat preservation time according to the thickness of 3-5 minutes/mm, and carrying out air cooling after the solution heat treatment;
(5) cold rolling and flattening: carrying out cold rolling leveling treatment on the hot rolled plate subjected to the solution treatment, and improving the tolerance precision of the hot rolled plate from +/-0.05 mm of a hot rolling state to +/-0.02 mm;
(6) laser cutting and forming: and cutting the cold-rolled sheet which is cold-rolled to the required thickness into the required size and shape by adopting laser to obtain the finished product blade root gasket.
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| CA1212020A (en) * | 1981-09-14 | 1986-09-30 | David N. Duhl | Minor element additions to single crystals for improved oxidation resistance |
| EP1780294A1 (en) * | 2005-10-25 | 2007-05-02 | Siemens Aktiengesellschaft | Alloy, protective coating for protecting a structural member against corrosion and oxidation at high temperatures and structural member |
| CH699716A1 (en) * | 2008-10-13 | 2010-04-15 | Alstom Technology Ltd | Component for high temperature steam turbine and high temperature steam turbine. |
| US8177516B2 (en) * | 2010-02-02 | 2012-05-15 | General Electric Company | Shaped rotor wheel capable of carrying multiple blade stages |
| CN103898371B (en) * | 2014-02-18 | 2016-04-06 | 上海发电设备成套设计研究院 | 700 DEG C of grade ultra supercritical coal power station nickel base superalloys and preparation thereof |
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