Method for manufacturing water-erosion-resistant sheet for long blade of steam turbine and long blade of steam turbine

Abstract

The present invention provides a method for manufacturing an anti-water erosion sheet for long turbine blades and the long turbine blades, comprising the following steps: using an atomization pulverization process to form a Stellite alloy material into a powder; establishing a 3D model of the anti-water erosion sheet compatible with the long turbine blades; selecting a printing substrate; and using a laser selective melting process to form the powdered Stellite alloy material onto the printing substrate to obtain an alloy print of the anti-water erosion sheet; subjecting the alloy print to a vacuum solution heat treatment and then cooling it to room temperature to obtain the anti-water erosion sheet product for the long turbine blades; and subjecting the anti-water erosion sheet product to a Rockwell hardness test. If the Rockwell hardness at room temperature is ≥37 HRC, the anti-water erosion sheet product is considered qualified. The present invention enables mass production of anti-water erosion sheets for long turbine blades with a more compatible shape, stronger water erosion resistance, and higher hardness, further meeting the operating requirements of the turbine and simplifying the production process of the anti-water erosion sheet.

Description

Technical Field

[0001] The present invention relates to the technical field of steam turbines, in particular to a method for manufacturing a water erosion resistant sheet for a long blade of a steam turbine based on a laser selective melting technology and the long blade of the steam turbine. Background Art

[0002] It is well known that the use of long blades significantly improves turbine efficiency. However, the last-stage blades operate in a wet steam region, and the circumferential speed of the long blade ends is very high, making them more susceptible to water erosion. To reduce water erosion near the steam inlet edge of the blades, in addition to implementing appropriate dehumidification measures in the flow-through structure to mitigate impact on the blades, blade surface protection measures are also necessary. Due to its excellent structural stability and high hardness, Stellite 6 alloy only causes minor deformation when impacted by water droplets, and its high toughness makes it less susceptible to cracking. Therefore, many steam turbine manufacturers use Stellite 6 alloy as a water-resistant material for long blades, achieving good results. For self-locking long blades with shrouds, the structure of the shroud ends is relatively complex, and the corresponding Stellite 6 alloy sheets also present significant difficulties in the production process. The existing technology uses powder metallurgy to manufacture Stellite 6 alloy sheets with such complex structures, but this suffers from high mold costs and long production cycles.

[0003] An existing Chinese patent (publication number: CN109514058A) provides a method for treating steam turbine last-stage blades for water corrosion prevention. This method involves running an automated micro-arc plasma spray welding program to automatically spray Stellite alloy onto the groove to be overlaid. This method requires a robotic system and a rotary positioner, significantly increasing equipment costs.

[0004] An existing Chinese patent (publication number: CN108823564A) provides a method for preparing an anti-corrosion coating using laser cladding technology: S1. Pretreatment of the cladding substrate; S2. Drying of the cladding material; S3. Using a laser combined with a coaxial powder feeding method to simultaneously melt the cladding material and the surface layer of the cladding substrate to form an alloy coating, thereby obtaining the anti-corrosion coating; wherein, the cladding substrate in step S1 is Q960 steel; and the cladding material in step S2 is Stellite 6 alloy powder. This method is only applicable to solving the problem of poor water erosion resistance of Q960 steel. In addition, there is another disadvantage that needs to be emphasized: the structure of the long blade shroud end is relatively complex, making laser cladding relatively difficult, and the dimensional accuracy and cladding quality are difficult to meet the requirements of use. There is another disadvantage that needs to be emphasized: the above-mentioned method of preparing an anti-corrosion coating using laser cladding technology is not fully applicable to the special working environment of the last-stage blade. Summary of the Invention

[0005] In view of the shortcomings of the existing technology mentioned above, the technical problem to be solved by the present invention is to provide a method for manufacturing anti-water erosion sheets for long turbine blades based on laser selective melting technology and long turbine blades, which can mass-produce anti-water erosion sheets for long turbine blades with better matching shapes, stronger water erosion resistance and higher hardness, further meet the operating requirements of the turbine, and make the overall production process of anti-water erosion sheets simpler.

[0006] In order to solve the above technical problems, the present invention provides a method for manufacturing a water erosion resistant sheet for a long blade of a steam turbine based on the laser selective melting technology, comprising the following steps:

[0007] The Stellite alloy material is made into powder by adopting atomization powder making process;

[0008] A 3D model of a water-erosion-resistant sheet compatible with a long turbine blade is established. A printing substrate is selected, pre-processed, and placed in a molding chamber of a 3D printing device. A powdered Stellite alloy material is molded onto the printing substrate using a selective laser melting process to obtain an alloy print of the water-erosion-resistant sheet. The scanning strategy of the selective laser melting process is to first laser scan the solid portion of the alloy print and then laser scan the contour portion of the alloy print. The phase angle between the laser print widths of two adjacent layers is 45 to 135 degrees.

[0009] The alloy printed parts are subjected to vacuum solution heat treatment and then cooled to room temperature to obtain water erosion resistant sheets for long turbine blades;

[0010] The anti-water erosion sheet product is subjected to Rockwell hardness test. If the Rockwell hardness of the anti-water erosion sheet product at room temperature is ≥37HRC, it is qualified.

[0011] Preferably, the powder indicators of the atomization powder making process include:

[0012] The atomizing gas is argon, the pressure of the argon is 6-10 MPa, the heating temperature of the Stellite alloy material in a liquid state is 1450-1650° C., and the flow rate of the Stellite alloy material in a liquid state is 5-10 Kg / min.

[0013] Preferably, the process parameters of the atomization powder making process also include:

[0014] The powder flowability of the Stellite alloy material is ≤20s / 50g, the powder particle size distribution of the Stellite alloy material is 15-53μm, the powder sphericity of the Stellite alloy material is greater than 80%, and the powder hollowness of the Stellite alloy material is less than 2%.

[0015] Preferably, the mass percentages of the components of the Stellite alloy material are: C: 1.00-1.40%, Cr: 28.00-29.00%, Fe: ≤2.00%, Mn≤0.30%, Ni≤2.50%, Si: 0.80-1.50%; W: 4.00-5.00%, and the remainder is Co and impurities.

[0016] Preferably, the material of the printed substrate is stainless steel, and the preheating temperature of the printed substrate is 150-200°C.

[0017] Preferably, the process parameters of the selective laser melting process include:

[0018] For the solid part of the alloy print: solid scanning distance: 0.150~0.220mm, solid scanning speed: 1150~1250mm / s, solid laser power: 270~350W;

[0019] For the contour part of the alloy print: contour scanning speed: 1350~1450mm / s, contour laser power: 220~260W;

[0020] The diameter of the laser spot is 60 to 80 μm, and the layer thickness of the laser scanning is 55 to 70 μm.

[0021] Preferably, the process parameters of the selective laser melting process also include:

[0022] For the support parts of alloy prints: the support scanning speed is 1300-1400 mm / s, and the support scanning power is 240-280 W.

[0023] Preferably, the process parameters of the selective laser melting process also include:

[0024] The internal oxygen content of the molding chamber is ≤0.06%.

[0025] Preferably, the temperature of the vacuum solution heat treatment is 1100-1200° C., and the holding time of the vacuum solution heat treatment is 0.5-1.5 h.

[0026] The present invention also provides a long blade for a steam turbine, comprising:

[0027] long leaf base;

[0028] The anti-water erosion sheet is manufactured by the method for manufacturing the anti-water erosion sheet for long blades of a steam turbine based on the laser selective melting technology, and the anti-water erosion sheet is fixedly connected to the long blade substrate by a brazing process.

[0029] As described above, the present invention's method for manufacturing a water-erosion-resistant sheet for a long turbine blade based on selective laser melting (SLM) technology and the long turbine blades thereof have the following beneficial effects: first, a stellite alloy material is formed into a powder using an atomization pulverization process; then, a 3D model of the water-erosion-resistant sheet adapted for the long turbine blade is established; a printing substrate is selected, used as the main body of the water-erosion-resistant sheet, pre-treated, and placed in a molding chamber of a 3D printing device; and the powdered stellite alloy material is formed onto the printing substrate using a SLM molding process to obtain an alloy print of the water-erosion-resistant sheet. It should be emphasized that the scanning strategy of the SLM molding process is to first laser scan the solid portion of the alloy print and then laser scan the contour portion of the alloy print, with the phase angle between the laser print widths of adjacent layers being 45 to 135 degrees. This ensures that the mechanical properties of the final water-erosion-resistant sheet are more adaptable to the operating environment of the turbine, thereby improving the water-erosion resistance and deformation resistance of the final water-erosion-resistant sheet, thereby extending the service life of the long turbine blades. Then, the alloy print is subjected to vacuum solution heat treatment and then cooled to room temperature, which can further improve the water erosion resistance and hardness of the final anti-water erosion sheet, and the anti-water erosion sheet product for long turbine blades is obtained. Finally, the anti-water erosion sheet product is subjected to a Rockwell hardness test. If the Rockwell hardness of the anti-water erosion sheet product at room temperature is ≥37HRC, it is qualified. The anti-water erosion sheet product that meets the preset Rockwell hardness is more suitable for application in the working environment of the steam turbine. Therefore, the manufacturing method of the anti-water erosion sheet for long turbine blades based on laser selective melting technology of the present invention can mass-produce anti-water erosion sheets for long turbine blades with more matching shapes, stronger water erosion resistance and higher hardness, further meet the working condition requirements of the steam turbine, and make the overall production process of the anti-water erosion sheet simpler. The manufacturing cost of the long turbine blades of the present invention is lower and the service life is longer. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A flow chart showing an embodiment of a method for manufacturing an anti-water erosion sheet for a long blade of a steam turbine according to the present invention;

[0031] Figure 2 Shown is a schematic diagram of a long blade for a steam turbine.

[0032] Component number description

[0033] 1 Long blade base

[0034] 2 Anti-water erosion film DETAILED DESCRIPTION

[0035] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0036] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions for implementation of the present invention. Therefore, they have no substantial technical significance. Any modification of the structure, change in the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose of the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0037] like Figure 1 As shown, the present invention provides a method for manufacturing a water erosion-resistant sheet for a long blade of a steam turbine based on the laser selective melting technology, comprising the following steps:

[0038] S1, using an atomization powder making process to prepare the Stellite alloy material into powder;

[0039] S2, establishing a 3D model of an anti-water erosion sheet compatible with a long blade of a steam turbine, selecting a printing substrate, pre-treating the printing substrate and placing it in a molding chamber of a 3D printing device, and using a laser selective melting molding process to mold a powdered Stellite alloy material onto the printing substrate to obtain an alloy print of the anti-water erosion sheet; the scanning strategy of the laser selective melting molding process is to first laser scan the solid portion of the alloy print and then laser scan the contour portion of the alloy print, and the phase angle between the laser printing formats of two adjacent layers is 45 to 135 degrees (i.e., the rotation angle between the laser printing format of the current layer and the laser printing format of the adjacent layer is 45 to 135 degrees);

[0040] S3, performing vacuum solution heat treatment on the alloy printed part and then cooling it to room temperature to obtain a water erosion resistant sheet product for a long blade of a steam turbine;

[0041] S4, conduct Rockwell hardness test on the anti-water erosion sheet product. If the Rockwell hardness of the anti-water erosion sheet product at room temperature is ≥37HRC, it is qualified.

[0042] In the present invention, first, a Stellite alloy material is made into a powder using an atomization pulverization process; then, a 3D model of an anti-water-erosion sheet compatible with a long turbine blade is established (for example, a technician can achieve this using 3D modeling software), a printing substrate is selected, the printing substrate is used as the body of the anti-water-erosion sheet, the printing substrate is pre-treated and placed in a molding chamber of a 3D printing device, and a laser selective melting molding process is used to mold the powdered Stellite alloy material onto the printing substrate to obtain an alloy print of the anti-water-erosion sheet. It should be emphasized that the scanning strategy of the aforementioned laser selective melting molding process is to first laser scan the solid portion of the alloy print and then laser scan the contour portion of the alloy print. The phase angle between the laser printing widths of two adjacent layers is 45 to 135 degrees, preferably 90 degrees. This can make the mechanical properties of the final anti-water-erosion sheet more adaptable to the working environment of the turbine, thereby improving the anti-water-erosion and anti-deformation capabilities of the final anti-water-erosion sheet, thereby increasing the service life of the long turbine blade. Then, the alloy print is subjected to vacuum solution heat treatment and then cooled to room temperature, which can further improve the water erosion resistance and hardness of the final anti-water erosion sheet, and the anti-water erosion sheet product for long turbine blades is obtained. Finally, the anti-water erosion sheet product is subjected to a Rockwell hardness test. If the Rockwell hardness of the anti-water erosion sheet product at room temperature is ≥37HRC, it is qualified. The anti-water erosion sheet product that meets the preset Rockwell hardness is more suitable for application in the working environment of the steam turbine. Therefore, the manufacturing method of the anti-water erosion sheet for long turbine blades based on laser selective melting technology of the present invention can mass-produce anti-water erosion sheets for long turbine blades with a more matching shape, stronger water erosion resistance, and higher hardness, further meeting the working condition requirements of the steam turbine, and making the overall production process of the anti-water erosion sheet simpler.

[0043] The above step S1 further includes: drying the powdered Stellite alloy material.

[0044] In order to make the powder parameters of the above-mentioned Stellite alloy material meet the operating requirements of the turbine, the process parameters of the above-mentioned atomization powder making process include: the atomizing gas is argon, the pressure of argon is 6~10MPa, the heating temperature of the Stellite alloy material in the liquid state is 1450~1650℃, and the flow rate of the Stellite alloy material in the liquid state is 5~10Kg / min. In addition, the raw material shape of the Stellite alloy material is a rod. Furthermore, the powder indicators of the above-mentioned atomization powder making process include: the powder flowability of the Stellite alloy material is ≤20s / 50g, the powder particle size distribution of the Stellite alloy material is 15~53μm, the powder sphericity of the Stellite alloy material is greater than 80%, and the powder hollowness of the Stellite alloy material is <2%. With this arrangement, the shape, mechanical properties and chemical properties of the alloy print formed by the Stellite alloy powder are more in line with the design requirements of the long blades of the turbine.

[0045] The aforementioned Stellite alloy material may be a Stellite 6 cobalt-based alloy. The weight percentages of the components of the Stellite alloy are as follows: C: 1.00-1.40%, Cr: 28.00-29.00%, Fe: ≤2.00%, Mn ≤0.30%, Ni ≤2.50%, Si: 0.80-1.50%, W: 4.00-5.00%, with the balance being Co and impurities. Testing has shown that this Stellite 6 cobalt-based alloy is more suitable for the operating environment of steam turbines.

[0046] In order to further improve the hardness of the above alloy printed parts, the material type of the printed substrate is stainless steel, and the preheating temperature of the printed substrate is 150-200°C.

[0047] To further improve the hardness of the alloy prints, the process parameters for the selective laser melting process include: for the solid portion of the alloy print: solid scanning spacing: 0.150-0.220 mm, solid scanning speed: 1150-1250 mm / s, solid laser power: 270-350 W; for the contour portion of the alloy print: contour scanning speed: 1350-1450 mm / s, contour laser power: 220-260 W; laser spot diameter: 60-80 μm, laser scanning layer thickness: 55-70 μm. Furthermore, the process parameters for the selective laser melting process also include: for the support of the alloy print: support scanning speed: 1300-1400 mm / s, support scanning power: 240-280 W. To ensure the molding quality of the alloy prints, the process parameters for the selective laser melting process also include: the internal oxygen content of the molding chamber is ≤ 0.06%.

[0048] In order to further improve the water erosion resistance and hardness of the final water erosion resistant sheet, the temperature of the vacuum solution heat treatment is 1100-1200° C., and the holding time of the vacuum solution heat treatment is 0.5-1.5 h.

[0049] like Figure 2 As shown, the present invention also provides a long blade for a steam turbine, comprising:

[0050] Long blade base 1;

[0051] The anti-water erosion sheet 2 is manufactured using the aforementioned method for manufacturing an anti-water erosion sheet for a long turbine blade based on laser selective melting technology. The anti-water erosion sheet 2 is fixed to the long blade substrate 1 using a brazing process. The steam turbine long blade of the present invention has lower manufacturing costs and longer service life.

[0052] Specifically, the anti-water erosion sheet 2 is fixedly connected to the portion of the long blade base 1 having the shroud and the vicinity of the shroud by a brazing process.

[0053] As a first specific embodiment of the above-mentioned method for manufacturing the anti-water erosion sheet for long turbine blades, the method comprises the following steps:

[0054] S1, using Stellite 6 high-temperature alloy rods for gas atomization powder production, to obtain metal powder with a particle size range of 15 to 53 μm, the powder composition is C: 1.00%, Cr: 28.15%, Fe: 1.80%, Mn: 0.25%, Ni: 2.10%, Si: 0.85%; W: 4.25%, the balance is Co and impurities;

[0055] S2, performing laser selective melting molding using the powder obtained in step S1 to obtain a Stellite 6 cobalt-based alloy component having a shape that meets preset requirements, i.e., an alloy print;

[0056] S3, performing vacuum solution heat treatment on the alloy printout obtained in step S2 whose shape and size meet the preset requirements, to obtain a water-erosion-resistant sheet product whose shape and hardness meet the preset requirements.

[0057] In the above step S1, Stellite 6 high-temperature alloy rods are used as raw materials, and a gas atomization powder making process is adopted. The atomizing gas is argon, the argon pressure is 6 MPa, the heating temperature of the Stellite 6 alloy liquid is 1450°C, and the flow rate of the Stellite 6 alloy liquid is 10 kg per minute, to obtain alloy powder with a particle size range of 15 to 53 μm.

[0058] In the above step S2, the process parameters of the above laser selective melting forming process are: entity scanning spacing: 0.15mm, entity scanning speed: 1150mm / s, entity laser power: 290W, contour scanning speed: 1350mm / s, contour laser power: 220W, spot diameter is 70μm, scanning strategy is entity first and then contour, phase angle is 90°, scanning layer thickness is 60μm; support scanning speed is 1300mm / s, support scanning power is 250W.

[0059] In the above step S3, the above vacuum solution heat treatment step includes: placing the printed alloy print in a vacuum heat treatment furnace at 1150°C and keeping it warm for 40 minutes, and cooling it to room temperature along with the furnace.

[0060] The mechanical properties of the obtained anti-water erosion sheet products were tested using samples from the same batch, and the Rockwell hardness of the anti-water erosion sheet products was measured to be 37.8HRC, which met the design requirements.

[0061] As a second specific embodiment of the above-mentioned method for manufacturing the anti-water erosion sheet for long turbine blades, the method comprises the following steps:

[0062] Stellite 6 high-temperature alloy rods were used for gas atomization powder production. The argon pressure was 10 MPa, the heating temperature of the Stellite 6 alloy liquid was 1550°C, and the flow rate of the Stellite 6 alloy liquid was 8 kg per minute. Metal powder with a particle size range of 15 to 53 μm was obtained. The powder composition was C: 1.35%, Cr: 28.85%, Fe: 0.05%, Mn: 0.10%, Ni: 0.10%, Si: 1.50%, W: 4.85%, and the balance was Co and impurities. The obtained metal powder was used as raw material and the following methods were used: Laser scanning technology: solid scanning pitch: 0.22mm, solid scanning speed: 1250mm / s, solid laser power: 340W, contour scanning speed: 1450mm / s, contour laser power: 260W, spot diameter: 80μm, scanning strategy: solid first, then contour, phase angle: 90°, scanning layer thickness: 70μm; support scanning speed: 1400mm / s, support scanning power: 280W. Stellite6 cobalt-based alloy components (i.e., alloy prints) were prepared, then placed in a 1200℃ vacuum furnace for 1.5 hours and cooled to room temperature. The resulting anti-water erosion sheet was tested for Rockwell hardness of 38.5HRC, meeting the design requirements of the steam turbine.

[0063] In summary, the present invention's method for manufacturing long turbine blade anti-erosion sheets based on selective laser melting technology and the long turbine blades thereof enable mass production of anti-erosion sheets for long turbine blades with more precisely matched shapes, enhanced erosion resistance, and higher hardness, further meeting turbine operating requirements and simplifying the overall production process. The long turbine blades of the present invention have lower manufacturing costs and longer service lives. Therefore, the present invention effectively overcomes the shortcomings of the prior art and possesses high industrial value.

[0064] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for manufacturing a water-erosion-resistant sheet for a long blade of a steam turbine based on laser selective melting technology, characterized in that: The following steps are involved: A stellite alloy material is made into powder by an atomization powder making process. The process parameters of the atomization powder making process include: the atomizing gas is argon, the pressure of the argon is 6 to 10 MPa, the heating temperature of the stellite alloy material in a liquid state is 1450 to 1650° C., the flow rate of the stellite alloy material in a liquid state is 5 to 10 kg / min, and the mass percentages of the components of the stellite alloy material are: C: 1.35%, Cr: 28.85%, Fe: ≤2.00%, Mn ≤0.30%, Ni ≤2.50%, Si: 1.50%; W: 4.85%, and the balance is Co and impurities; A 3D model of an anti-water erosion sheet compatible with a long turbine blade is established. A printing substrate is selected, pre-treated, and placed in a molding chamber of a 3D printing device. A powdered Stellite alloy material is molded onto the printing substrate using a selective laser melting process to obtain an alloy print of the anti-water erosion sheet. The scanning strategy of the selective laser melting process is to first laser scan the solid portion of the alloy print and then laser scan the contour portion of the alloy print. The phase angle between the laser print widths of two adjacent layers is 45 to 135 degrees. The printing substrate is made of stainless steel and preheated to a temperature of 150 to 200°C. The alloy printed parts are subjected to vacuum solution heat treatment and then cooled to room temperature to obtain water erosion resistant sheets for long turbine blades; The anti-water erosion sheet product is subjected to a Rockwell hardness test. If the Rockwell hardness of the anti-water erosion sheet product at room temperature is ≥37HRC, it is qualified. The process parameters of the laser selective melting forming process include: For the solid part of the alloy print: solid scanning distance: 0.150~0.220mm, solid scanning speed: 1150~1250mm / s, solid laser power: 270~350W; For the contour part of the alloy print: contour scanning speed: 1350~1450mm / s, contour laser power: 220~260W; The diameter of the laser spot is 60-80 μm, the layer thickness of the laser scanning is 55-70 μm, the internal oxygen content of the molding chamber is ≤0.06%, the temperature of the vacuum solution heat treatment is 1100-1200° C., and the holding time of the vacuum solution heat treatment is 0.5-1.5 h.

2. The method for manufacturing a water-erosion-resistant sheet for a long blade of a steam turbine based on the selective laser melting technology according to claim 1, characterized in that: The powder indicators of the atomization powder making process include: The powder flowability of the Stellite alloy material is ≤20s / 50g, the powder particle size distribution of the Stellite alloy material is 15-53μm, the powder sphericity of the Stellite alloy material is greater than 80%, and the powder hollowness of the Stellite alloy material is less than 2%.

3. The method for manufacturing a water-erosion-resistant sheet for a long blade of a steam turbine based on the selective laser melting technology according to claim 1, characterized in that: The process parameters of the laser selective melting process also include: For the support parts of alloy prints: the support scanning speed is 1300-1400 mm / s, and the support scanning power is 240-280 W.

4. A long blade for a steam turbine, characterized in that: include: long leaf base; The anti-water erosion sheet is made by the method for manufacturing anti-water erosion sheets for long blades of a steam turbine based on laser selective melting technology as described in any one of claims 1 to 3, and the anti-water erosion sheet is fixed to the long blade substrate by a brazing process.

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