A turbine blade narrow slot grinding method

Abstract

The application provides a turbine blade narrow slot grinding method, and the specific steps are as follows: selecting a CBN grinding wheel as a narrow slot grinding tool; according to the size of single grinding depth, the grinding process is divided into large depth of cut grinding and small depth of cut grinding; when the large depth of cut grinding is performed, the linear speed of the grinding wheel and the grinding depth are increased; when the small depth of cut grinding is performed, the linear speed of the grinding wheel and the workpiece feeding speed are increased, so that the rapid grinding of the narrow slot on the turbine blade is realized; and the tool wear form, machining efficiency, machining surface quality and the like in the cutting process are measured and analyzed, so that the problems of the original part failing to meet the design requirements and the machining efficiency being improved and the like are overcome.

Description

Technical Field

[0001] This invention belongs to the field of turbine blade processing technology, specifically to a method for grinding narrow grooves in turbine blades. Background Technology

[0002] Currently, the machining of locking grooves on turbine blades for gas turbines all employs turning processes. However, turbine blades are primarily designed using high-temperature alloys, which possess high strength, good toughness, and high-temperature resistance, making them typical difficult-to-machine materials. Despite continuous improvements in the selection and material of turning tools, the risk of tool breakage cannot be avoided during actual machining. Furthermore, existing turning processes are inefficient, making it difficult to guarantee the production of large quantities of blades.

[0003] High-efficiency precision grinding technologies, such as slow-infeed deep grinding, high-speed and ultra-high-speed grinding, and high-efficiency deep grinding, have high processing efficiency and are particularly suitable for the production and processing of difficult-to-machine materials such as high-temperature alloys. However, in narrow groove machining, especially in narrow grooves with a large depth-to-width ratio, the small machining surface of the grinding wheel and insufficient strength of the grinding wheel during the machining process can easily lead to grinding wheel breakage, affecting the machining quality of the blades. Furthermore, the large machining allowance in narrow groove grinding makes cooling difficult, and heat is hard to dissipate, which can easily cause machining burns or cracks. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for narrow-groove grinding of turbine blades. By measuring and analyzing the tool wear pattern, processing efficiency, and surface quality during the cutting process, it overcomes the problems of existing parts failing to meet design requirements and improving processing efficiency.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for grinding narrow grooves in turbine blades, the specific steps of which are as follows:

[0006] S1 selects CBN grinding wheels as the cutting tool for narrow groove grinding;

[0007] S2 classifies grinding processes into large depth of cut grinding and small depth of cut grinding based on the size of the single grinding depth. When performing large depth of cut grinding, the grinding wheel linear speed and grinding depth are increased; when performing small depth of cut grinding, the grinding wheel linear speed and workpiece feed speed are increased to achieve rapid grinding of narrow grooves on turbine blades.

[0008] Furthermore, in S1, the dimensions of the CBN grinding wheel are set according to the theoretical value of the narrow groove dimension.

[0009] Furthermore, in S2, the large depth of cut grinding is slow feed grinding, and the small depth of cut grinding is rapid feed grinding.

[0010] Furthermore, in S2, grinding processes with a single grinding depth of cut greater than 0.5 mm are considered large depth of cut.

[0011] Furthermore, in S2, when performing deep-cut grinding, the linear velocity of the CBN grinding wheel is not less than 40m / s, the feed rate is not greater than 200mm / min, and the depth of cut is not less than 0.5mm.

[0012] Furthermore, in S2, grinding processes with a single grinding depth of less than 0.2 mm are considered small depths of cut.

[0013] Furthermore, in S2, the linear velocity of the CBN grinding wheel is not less than 40m / s, the feed rate is not greater than 1000mm / min, and the depth of cut is not greater than 0.2mm.

[0014] Furthermore, when performing deep-cut grinding, we first use conventional machining parameters for trial processing, and then gradually increase the grinding wheel speed and grinding depth to obtain the optimal machining parameters under the constraints of grinding quality and equipment performance indicators.

[0015] Furthermore, when performing shallow depth-of-cut grinding, based on conventional machining parameters, the workpiece feed rate and grinding wheel linear speed are significantly increased to obtain the optimal machining parameters under the constraints of grinding quality and equipment performance indicators.

[0016] Furthermore, the narrow groove grinding is performed using a three-axis grinding machine or a five-axis grinding center.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] This invention provides a method for narrow groove grinding of turbine blades. CBN grinding wheels are selected as the cutting tools for narrow groove grinding. The grinding process is divided into two categories based on the depth of cut in a single pass. The processing parameters for these two types of grinding methods are adjusted accordingly to improve processing efficiency. Furthermore, this method can quickly resolve the issues of grinding burns and cracks in narrow groove grinding, ensuring that the dimensions of the parts are within acceptable limits, especially the dimensional accuracy of the narrow groove transition radius. Simultaneously, optimizing the processing parameters increases the processing efficiency of the parts by more than 200%. Attached Figure Description

[0019] Figure 1 Schematic diagram of the dimensions of the grinding and machining of the lock plate groove;

[0020] Figure 2 This is a schematic diagram showing the dimensions of the inner and outer edge plate grooves during grinding. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] This invention provides a method for grinding narrow grooves in turbine blades. The method is designed by considering the turbine blade material, design dimensions, structural characteristics of the machining area, equipment capabilities, and economic benefits, as detailed below:

[0023] 1) Selection of cutting tools

[0024] In the selection of grinding tools, due to the limitation of narrow groove width, ordinary grinding wheels have insufficient bonding strength, making them prone to chipping or cracking during machining, posing safety hazards. CBN grinding wheels, using cubic boron nitride as the abrasive and metal powder, resin powder, ceramic, and electroplated metal as binders, can be manufactured into corresponding tool shapes according to the machining shape and size. Compared to ordinary grinding wheels, they have high hardness and high toughness, with a hardness second only to diamond, and can maintain the sharpness of the abrasive micro-edges for a long time, resulting in high cutting performance. Furthermore, compared to ordinary grinding wheels, there is no need for roller dressing. The overall structure of the CBN grinding wheel is stable, with good shape retention and high machining accuracy, giving it a natural advantage in narrow groove machining. Therefore, CBN grinding wheels are chosen as the tool for narrow groove machining, and they are designed and manufactured according to the theoretical values ​​of narrow groove dimensions.

[0025] 2) Selection of processing parameters

[0026] When machining using a three-axis grinding machine or a five-axis grinding center, the grinding wheel linear speed must be no less than 40 m / s, according to the linear speed formula. The CBN grinding wheel has a diameter of φ300mm, the wheel spindle speed should be no less than 2546.47 r / min, and the spindle feed speed should be no less than 1000 mm / min. Based on the equipment's processing capabilities, appropriate processing parameters are selected. Two grinding parameter schemes are formulated according to the grinding principle, as follows:

[0027] ① Large depth of cut slow feed grinding technology

[0028] In the grinding of high-temperature alloy turbine blades, grinding processes with a single grinding depth greater than 0.5 mm are defined as large depth of cut. Large depth of cut grinding is a form of creep grinding that uses a high grinding wheel speed and a large material removal rate. It is a combination of creep grinding and high-speed grinding, thus achieving a large material removal rate and good surface roughness.

[0029] Specific parameters for deep-cut, slow-feed grinding: generally, the grinding wheel linear speed is not less than 40m / s, the feed rate is not greater than 200mm / min, and the depth of cut is not less than 0.5mm;

[0030] The specific operation process of large depth of cut slow feed grinding is as follows:

[0031] First, we adopted relatively conservative machining parameters to observe their feasibility. Based on this, we increased the grinding wheel linear speed v. s And correspondingly increase the grinding depth a p Based on the grinding quality and equipment performance indicators, while ensuring the quality of the grinding process, the processing parameters are continuously improved to increase the processing efficiency, and finally the optimal processing parameters are determined.

[0032] ② Small depth of cut and rapid feed grinding technology

[0033] In the grinding of high-temperature alloy turbine blades, grinding with a single grinding depth of less than 0.2 mm is defined as small depth of cut. Small depth of cut grinding refers to a rapid feed grinding method that uses a higher workpiece feed rate and a smaller material removal rate.

[0034] Specific parameters for shallow depth-of-cut, rapid-feed grinding: generally, the grinding wheel linear speed should not be less than 40 m / s, the feed rate should not exceed 1000 mm / min, and the depth of cut should not exceed 0.2 mm.

[0035] Compared with ordinary on-site machining parameters, the workpiece feed rate v is significantly increased. w Increase the linear speed v of the grinding wheel s Based on the grinding quality and equipment performance indicators, while ensuring the quality of the grinding process, the processing parameters are continuously improved to increase the processing efficiency, and finally the optimal processing parameters are determined.

[0036] 3) Inspection of machined surface quality

[0037] High-temperature alloy turbine blades have improved machining efficiency through grinding wheel selection and machining parameter optimization. However, the machining quality of turbine blades is an important indicator of grinding effect. The grinding effect needs to be verified by means of surface roughness, fluorescence, metallographic analysis, etc. The influence of workpiece feed rate, grinding wheel linear speed, and cutting depth on the surface roughness and microstructure of turbine blades should be analyzed to determine the optimal machining parameters.

[0038] This invention provides a method for narrow-groove grinding of turbine blades. By selecting tools, setting machining parameters, and inspecting surface machining quality, a complete set of high-speed grinding process schemes for single-crystal turbine blades is determined, avoiding surface ablation of parts and improving machining quality and efficiency.

[0039] Example 1

[0040] like Figure 1 As shown in the part drawing, the machining method for the narrow locking groove of a turbine working blade is as follows: This blade material has a high Cr and Co content, belonging to a cast high-temperature alloy with good high-temperature performance, but its thermal conductivity and thermal diffusivity are very low, resulting in poor machinability. Furthermore, this machining area is a narrow and deep groove, making it prone to localized overheating during processing. The narrow groove grinding width is generally no more than 3mm. The material is titanium alloy or high-temperature alloy. The required locking groove width for the turbine working blade, which is made of K444 high-temperature nickel-based alloy, is as follows: Its depth dimension is bottom like Figure 1 As shown.

[0041] The grinding wheel is made of electroplated CBN, with dimensions of 350*22*127*1.15 and a grit size of 120 / 140.

[0042] The following are the optimal grinding parameters:

[0043]

[0044] Verification of processing:

[0045] Grinding was verified at the machining site. The optimal grinding time per piece was 51 seconds, while the current grinding time was 23 minutes (the original machining method was turning). Visual inspection and fluorescent examination revealed no burns or cracks at the bottom of the groove. The dimensions are machined to the correct size in one go, requiring no adjustments.

[0046] Example 2:

[0047] like Figure 1 As shown in the part drawing, the machining method for the rim groove of a turbine guide vane is as follows: The blade material is a cobalt-based high-temperature alloy K40M, which is prone to localized overheating during machining. The rim groove width is 2.4±0.1mm, and the groove depth is... trough bottom like Figure 2 As shown.

[0048] Electroplated CBN grinding wheels are used: wheel dimensions are Φ300×2.4×76.2 mm, and the machining parameters are as follows:

[0049]

[0050]

[0051] Verification of processing:

[0052] Grinding was verified at the processing site. The optimal grinding time per piece was 7 minutes and 10 seconds, while the current grinding time was 13 minutes. Visual inspection and fluorescent testing revealed no burns or cracks at the bottom of the groove. The dimensions are machined to the correct size in one go, requiring no adjustments.

Claims

1. A method for grinding narrow grooves in turbine blades, characterized in that, The specific steps are as follows: S1 selects CBN grinding wheels as the cutting tool for narrow groove grinding; S2 classifies grinding processes into large depth of cut grinding and small depth of cut grinding based on the size of the single grinding depth. When performing large depth of cut grinding, the grinding wheel linear speed and grinding depth are increased; when performing small depth of cut grinding, the grinding wheel linear speed and workpiece feed speed are increased to achieve rapid grinding of narrow grooves on turbine blades. In S2, grinding processes with a single grinding depth of cut greater than 0.5 mm are considered large depth of cut. In S2, grinding processes with a single grinding depth of less than 0.2 mm are considered small depth of cut. In S1, the dimensions of the CBN grinding wheel are set according to the theoretical value of the narrow groove dimension; In S2, the large depth of cut grinding is slow feed grinding, and the small depth of cut grinding is rapid feed grinding; In S2, when performing deep cutting grinding, the linear speed of the CBN grinding wheel shall not be less than 40m / s, the feed rate shall not be greater than 200mm / min, and the depth of cut shall not be less than 0.5mm. In S2, when performing small depth-of-cut grinding, the linear speed of the CBN grinding wheel should not be less than 40m / s, the feed rate should not be greater than 1000mm / min, and the cutting depth should not be greater than 0.2mm.

2. The method for grinding narrow grooves of turbine blades according to claim 1, characterized in that, When performing deep cutting grinding, first use conventional machining parameters for trial processing, and gradually increase the grinding wheel speed and grinding depth to obtain the optimal machining parameters under the constraints of grinding quality and equipment performance indicators.

3. The method for grinding narrow grooves of turbine blades according to claim 1, characterized in that, When performing shallow depth-of-cut grinding, based on conventional machining parameters, the workpiece feed rate and grinding wheel linear speed are significantly increased to obtain the optimal machining parameters under the constraints of grinding quality and equipment performance indicators.

4. The method for grinding narrow grooves of turbine blades according to claim 1, characterized in that, The narrow groove grinding is performed using a three-axis grinding machine or a five-axis grinding center.

Images