A method for controlling the frequency of a leaf during a closed-die forging process

Abstract

The application discloses a kind of control methods of frequency of precision forging process blade, within the design tolerance range of blade body, the thickness of blade body is adjusted using difference method, the thickness change in the direction from blade tip to root is uniform;According to the obtained blade, the cavity of corresponding blade final forging die is prepared, and the width of the edge bridge of the cavity is adjusted according to the thickness of the adjusted blade body;When the obtained blade final forging die is used to forge the blade to be forged, the thickness of the blade is controlled using lubricant according to the thickness fluctuation data during forging process;The hot correction of bending and distortion is carried out to the forged blade, and the indentation depth caused to the blade body during correction process is lower than the set value.The frequency control method of the blade body is researched from forging design, blade die design, thickness dispersion control during forging process and surface treatment deformation control, and the control relationship between a plurality of hot working control methods and frequency change is obtained, which can effectively solve the frequency out-of-tolerance problem of such precision forged blade after machining.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of forging technology, in particular to a control method for blade frequency in a precision forging process. BACKGROUND

[0002] The blade of an aero-engine is one of the important parts of an aero-engine, and often breaks due to resonance. The failure rate of the blade fatigue damage caused by resonance often accounts for 30% to 40% of the fatigue failure of the engine parts. The frequency of the aero-engine blade is mainly related to the design size and material density of the blade, also known as the natural frequency of the blade. In order to better meet the air flow control requirements of the engine blade, the design size of the blade is constantly optimized and improved, but at the same time, the vibration frequency of the blade changes, resulting in that the size of some blades meets the design requirements, but the frequency does not meet the design requirements.

[0003] At present, in the invention patent of "a correction method for the natural frequency of a fan blade of an aero-engine", for the case that the size of the blade is qualified but the frequency of the blade does not meet the requirements, a method of adjusting the arrangement and the frequency difference is used to select and arrange the blade, and the frequency is repeatedly corrected. This process needs to be repeated several times for the blade and needs to be detected until the frequency is qualified. However, this method cannot be applied to the hot processing forming process of the blade, and only the rework processing is carried out after the final size of the blade is qualified, the scrap rate is about 20%, and the surface integrity of the blade is often damaged, and even the service life of the blade is reduced.

[0004] In order to improve the qualified rate of the precision forged blade, it is necessary to improve the front end of the design and production process of the precision forged blade, so it is particularly important to study and control the design and forging stage of the precision forged blade. For example, the high-pressure 6-stage rotor blade is a TC11 titanium alloy precision forged blade, and the blade frequency is one of the technical problems in the assembly of the aero-engine blade. According to statistics, the first-order frequency value of the blade is between 875HZ and 1010HZ. In order to make the frequency of the blade meet the required frequency value, it is necessary to study the design of the titanium alloy precision forged blade, the design of the tooling die, the surface quality control, the deformation control and other technologies. By analyzing the relationship between the final size of the blade and the frequency, a new process is researched and improved to accurately control the size precision and surface quality of the blade, so as to solve the problem of blade frequency out of tolerance. Therefore, a frequency control method for the hot processing process of the precision forged blade is designed to solve the problem of blade frequency out of tolerance. SUMMARY

[0005] In view of the problems in the prior art, the present application provides a control method for blade frequency in a precision forging process, which realizes the control of the final blade frequency by means of precision forged blade forging design, forging size control and surface treatment process improvement.

[0006] The application is realized by the following technical scheme:

[0007] A control method of blade frequency in a precision forging process, comprising the following steps:

[0008] Step 1, within the design tolerance range of the blade body, the thickness of the blade body digital model is adjusted by using the difference method, so that the thickness changes uniformly from the blade tip to the blade root;

[0009] Step 2, a cavity corresponding to the blade finish forging die is prepared according to the blade body digital model obtained in step 1, and the width of the edge bridge of the cavity is adjusted according to the thickness of the adjusted blade body;

[0010] Step 3, the blade to be forged is forged by using the blade finish forging die obtained in step 2, and the thickness of the blade is controlled by using a lubricant during the forging process according to the thickness data of the blade;

[0011] Step 4, the forged blade is subjected to heat correction of bending and twisting, and the indentation depth caused by the blade body is less than a set value during the correction process.

[0012] Preferably, the thickness adjustment method of the blade body in step 1 is as follows:

[0013] The thickness of the blade tip is adjusted to the upper tolerance band, the thickness of the blade body in the blade root direction is adjusted to the lower tolerance band, and the thickness of the blade body changes uniformly from the blade root to the blade tip.

[0014] Preferably, the adjustment method of the bridge of the blade finish forging die in step 2 is as follows:

[0015] The bridge width corresponding to the region where the thickness of the blade body increases is narrowed, and the bridge width corresponding to the region where the thickness of the blade body decreases is widened.

[0016] Preferably, the lubricant in step 3 is a graphite lubricant.

[0017] Preferably, the indentation depth in step 4 is less than 0.025mm.

[0018] Preferably, the blade root adapter R of the blade obtained in step 3 is measured, and the blade finish forging die is trimmed according to the measurement result, so that the blade root adapter R of the forged blade meets the requirements.

[0019] Preferably, the method further comprises the following steps: when the thickness of the blade body does not meet the requirements, a chemical milling method is used to adjust the thickness, so that the thickness of the blade body meets the requirements.

[0020] Preferably, the chemical milling method is to immerse the blade body in an acid solution for corrosion.

[0021] Preferably, when the thickness of the blade body near the blade root region is greater than a set value, the blade tip is fixed downward in the solution.

[0022] Preferably, when the thickness of the tip region of the blade is greater than a set value, the blade root is fixed downward in the solution.

[0023] Compared with the prior art, the present application has the following beneficial technical effects:

[0024] The blade frequency control method provided by the present application first adjusts the three-dimensional model of the precision forged blade, adjusts the thickness of the blade body within the design tolerance range, makes the thickness change distribution uniform, then designs the corresponding precision forging die by using the adjusted blade model, controls the bridge width of the precision forging die according to the thickness adjustment parameter, makes the burr distribution uniform in the forging process, and further ensures that the blade body thickness size changes uniformly, secondly controls the thickness of the blade body by using the lubricant in the forging process, so that the frequency of the blade body meets the design requirements, and finally controls the indentation thickness in the heat correction process, so that the frequency of the blade body meets the requirements. The blade frequency control method is researched from the aspects of forging part design, blade die design, thickness dispersion control in the forging process, and surface treatment deformation control, and a plurality of control relationships between the control method of hot working and the frequency change are obtained, so that the frequency out-of-tolerance problem of the precision forged blade after machining can be effectively solved. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Fig. 1 is a structural schematic diagram of the blade of the present application;

[0026] Fig. a is a front view of the blade, and Fig. b is a side view of the blade;

[0027] Figure 2 Fig. 3 is a sectional view of the blade of the present application;

[0028] Figure 3 Fig. 4 is a thickness adjustment schematic diagram of the blade of the present application;

[0029] Figure 4 Fig. 5 is a structural schematic diagram of the blade final forging die of the present application;

[0030] Figure 5 Fig. 6 is a bridge adjustment schematic diagram of the blade final forging die of the present application;

[0031] In the figure: 1, bridge; 2, cavity; 3, blade root positioning boss; 4, blade root adapter R; 5, blade body; 6, blade tip positioning boss; 11, upper tolerance band; 12, nominal value of blade; 13, adjusted blade shape; 14, lower tolerance band; 21, first section; 22, second section; 23, third section; 24, fourth section. DETAILED DESCRIPTION

[0032] The present application will be further described in detail below in combination with the drawings, which is an explanation of the present application rather than a limitation.

[0033] Referring to Figure 1 and 2 , the blade of the aero-engine includes a blade body 5 and a blade root, the tip end of the blade body 5 is provided with a tip positioning boss 6, the end of the blade root is provided with a blade root positioning boss 3, and the connection between the blade body 5 and the blade root is a blade root adapter R.

[0034] Referring to Figures 3-5 , a control method of blade frequency in a precision forging process, comprising the following steps:

[0035] Step 1: within the design tolerance range of the blade body, the thickness of the blade body is adjusted by using the difference method, so that the thickness changes uniformly from the tip to the root.

[0036] Specifically, according to the design data of the blade body, the thickness of multiple sections of the blade body is obtained along the length direction of the blade body, and the thickness of each section is adjusted within the design tolerance range by using the difference method, so that the thickness of the tip approaches the upper tolerance band of the design, the thickness of the root direction approaches the lower tolerance of the design, and the thickness of the blade body from the root to the tip changes uniformly and meets the thickness design tolerance requirements of the blade body. The method adjusts the tolerance of each section of the blade body, although the tolerance of each section is compressed, the purpose of adjusting the frequency during the rotation of the blade is achieved.

[0037] For example, referring to Figure 3 , the thickness of the blade is adjusted based on the nominal value 12 of the blade, the thickness of the tip is adjusted to the upper tolerance band 11, and the root part of the blade body is adjusted to the lower tolerance band 14, forming the adjusted blade shape 13.

[0038] Step 2: according to the blade obtained in step 1, the cavity of the corresponding blade finish forging die is prepared, and the width of the edge bridge of the cavity is adjusted according to the thickness of the adjusted blade body, so that the thickness of the forged blade changes uniformly.

[0039] Specifically, due to the different thicknesses of each section of the blade body, the burr distribution of the blade during forging will be uneven. In order to control the uniformity of the burr during hot forming, and at the same time to make the forged blade have good streamline, it is necessary to adjust the width of the bridge of the blade finish forging die multiple times. When adjusting, the bridge width corresponding to the area where the thickness of the blade body increases is narrowed, and the bridge width corresponding to the area where the thickness of the blade body decreases is widened, so that the thickness of the forged blade changes uniformly.

[0040] The burr is the material that is extruded out of the die cavity 2 and located on the surface of the bridge 1 after the blade body is forged by the upper die and the lower die.

[0041] Referring to Figure 5According to the thickness of the adjusted blade, the mold cavity is divided into five sections from the blade root to the blade tip, which are the first section 21, the second section 22, the third section 23 and the fourth section 24 in sequence.

[0042] The first section corresponds to the blade thickness that needs to be thinned by 0.038, and the corresponding bridge region width is narrowed by 1.5mm;

[0043] The second section corresponds to the blade thickness that needs to be thinned by 0.019, and the corresponding bridge region width is narrowed by 0.75mm;

[0044] The third section corresponds to the blade thickness that needs to be increased by 0.019, and the corresponding bridge region width is widened by 0.75mm;

[0045] The fourth section corresponds to the blade thickness that needs to be increased by 0.038, and the corresponding bridge region width is widened by 1.5mm.

[0046] Step 3, when the blade is forged by the blade final forging die obtained in step 2, the thickness of the blade is controlled by using lubricant during the forging process, so that the thickness of the blade changes uniformly.

[0047] Specifically, during the forging process, when the thickness of the blade is greater than the adjusted design value, a certain amount of graphite lubricant is sprayed, specifically, when the thickness of the blade is greater than the design value, more graphite lubricant is sprayed on the blade, and when the thickness of the blade is less than the design value, less graphite lubricant is sprayed on the blade.

[0048] During the forging process of the precision forged blade, the thickness of the blade increases from the blade root to the blade tip, and the thickness of each cross section of the blade must be within the designed tolerance range, which can reduce the first order frequency of the blade, and vice versa.

[0049] Step 4, measure the blade root adapter R of the blade obtained in step 3, and according to the measurement result, the blade final forging die is trimmed, so that the frequency of the forged blade meets the design requirements.

[0050] Specifically, the blade root adapter R is the transition fillet at the junction of the blade body and the blade root. During the forging process, the surface often needs to be polished with abrasive belt to eliminate the defects caused by drawing, which causes the blade root R to gradually decrease and the blade frequency to increase. Therefore, within the design range, the blade root R needs to be repaired to increase R to reduce the frequency of the blade, or to reduce R to increase the frequency of the blade.

[0051] Step 5, the forged blade is subjected to bending and twisting heat correction, and the indentation depth caused by the blade body during the correction process is lower than the set value.

[0052] Specifically, the control method of the indentation of the hot correction process of the precision forged blade: due to the large internal stress and deformation rebound of the titanium alloy blade after forging, the blade will produce bending and torsional deformation, and needs to be corrected to eliminate. Therefore, in order to eliminate the bending and torsional deformation of the blade, hot correction is one of the most effective control methods. Hot correction eliminates bending and torsion, but leaves indentation on the surface of the blade. Finally, the indentation of the blade needs to be eliminated by some means, and the indentation depth is controlled within 0.025mm, and the corrected indentation is controlled at both ends of the blade. The indentation at the blade tip frequency will increase, and the indentation at the blade root final frequency will decrease.

[0053] Step 6, measuring the blade obtained in step 5, when the thickness of the blade does not meet the thickness requirement, adjusting the thickness of the blade by chemical milling to meet the requirement.

[0054] Specifically, the method of chemical milling is to immerse the blade in a solution tank filled with an acidic solution, and the tank solution will flow upward to flush the blade. When chemical milling, the area with thickness not meeting the requirement is placed above.

[0055] For example, when the thickness of the blade tip area does not meet the requirement, the blade root is downward and the blade tip is upward, and the blade is immersed in the solution. A small amount of water ripples or flow marks will appear on the blade tip during the chemical milling process. The thickness of the blade is controlled by chemical milling to realize the control of the blade frequency; fixing the blade tip downward to reduce the blade frequency, fixing the blade root downward to increase the blade frequency, and chemical milling in the horizontal state of the blade, the frequency of the blade does not change.

[0056] The above content is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A method of controlling the frequency of a leaf in a closed-die forging process, characterized by, The method comprises the following steps: Step 1, within the design tolerance range of the blade body, the thickness of the blade body digital model is adjusted by using the difference method, so that the thickness changes uniformly from the blade tip to the blade root; The blade body thickness adjustment method is as follows: The thickness of the blade tip is adjusted to the upper tolerance band, the thickness of the blade body in the blade root direction is adjusted to the lower tolerance band, and the thickness of the blade body changes uniformly from the blade root to the blade tip; Step 2, according to the blade body digital model obtained in step 1, the cavity of the corresponding blade final forging die is prepared, and the width of the cavity edge bridge is adjusted according to the thickness of the adjusted blade body; The adjustment method of the bridge of the blade final forging die is as follows: The width of the bridge corresponding to the area where the thickness of the blade body increases is reduced, and the width of the bridge corresponding to the area where the thickness of the blade body decreases is widened; Step 3, the blade to be forged is forged by using the blade final forging die obtained in step 2, and the thickness of the blade is controlled by using a lubricant during the forging process according to the thickness data of the blade; Step 4, the forged blade is subjected to heat correction of bending and twisting, and the indentation depth caused by the blade body during the correction process is less than the set value; Step 5, when the thickness of the blade body does not meet the requirements, the thickness adjustment is performed by using a chemical milling method, so that the thickness of the blade body meets the requirements; When the thickness of the blade body near the blade root area is greater than the set value, the blade tip is fixed downward in the solution; When the thickness of the blade tip area of the blade body is greater than the set value, the blade root is fixed downward in the solution.

2. A method of controlling the frequency of a closed-die forged blade as claimed in claim 1, wherein, The lubricant in step 3 is a graphite lubricant.

3. A method of controlling the frequency of a closed-die forged blade as claimed in claim 1, wherein, The indentation depth in step 4 is less than 0.025 mm.

4. A method of controlling the frequency of a closed-die forged blade as claimed in claim 1, wherein, The blade root adapter R of the blade obtained in step 3 is measured, and the blade final forging die is trimmed according to the measurement result, so that the blade root adapter R of the forged blade meets the requirements.

5. A method of controlling the frequency of a closed-die forged blade as claimed in claim 1, wherein, The chemical milling method is to immerse the blade body in an acid solution for corrosion.

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