Water immersion ultrasonic flaw detection method for mold

Abstract

The invention discloses a mold water immersion ultrasonic flaw detection method which comprises the following steps: step 1, pretreatment work: cleaning impurities adhered to the surface of a mold by using cleaning equipment, cleaning impurities adhered to the surface of a probe by using the cleaning equipment, and cleaning impurities on the inner wall of a container required by flaw detection of the mold by using the cleaning equipment; step 2, preparation work: water is put into a container required by the cleaned flaw detection mold, the water thickness is H, and a probe and the mold are put into the container respectively; 3, parameter determination: respectively setting the probes, 4, starting the test, and 5, analyzing the result, the flaw detection method does not need tight contact, so that the detection speed is very high; the whole mold is immersed in the water tank, surface waves can be eliminated, small discontinuous signals from the outer surface are irregularly increased due to the surface waves, and the flaw detection method is high in accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of ultrasonic flaw detection, in particular to a mold water immersion ultrasonic flaw detection method. Background Art

[0002] According to the basic principle, ultrasonic flaw detection can be basically divided into two categories: penetration method and reflection method. In the penetration method, a probe is placed on each side of the workpiece to be inspected, one of which transmits ultrasonic waves into the workpiece, and the other probe receives ultrasonic waves. When the workpiece is intact, a strong signal can be received; when there are small defects in the workpiece, part of the sound energy is reflected and only a weak signal can be received; when there are defects in the workpiece that are larger than the cross-section of the sound beam, the sound energy is completely reflected by the defect, and the other probe cannot receive the ultrasonic signal at all. The advantage of this method is that there is almost no blind spot and the sound path attenuation is reduced. However, the traditional flaw detection method has the following disadvantages: In daily ultrasonic flaw detection, some workpieces cannot be inspected by common direct contact method due to special reasons such as rough surface and irregular shape. For such workpieces, you may try to use liquid immersion ultrasonic flaw detection. For example, large cross-sectional products have variable shapes, contain many kinds of defects, relatively uneven organization, large differences in acoustic characteristics, and severe ultrasonic attenuation, which bring great difficulties to ultrasonic flaw detection. Taking large forged blades as an example, coarse grains are prone to appear in the core position, and when ultrasonic waves penetrate the grain boundaries, they are prone to scattering and diffraction, which greatly reduces the penetration and signal-to-noise ratio of ultrasonic waves, and produces grass-like clutter, which reduces the accuracy of flaw detection. Summary of the invention

[0003] The purpose of the present invention is to provide a method for ultrasonic flaw detection by water immersion in molds, so as to solve the problem mentioned in the above background technology that in daily ultrasonic flaw detection work, some workpieces cannot be ultrasonically detected by the common direct contact method due to special reasons such as rough surface and irregular shape. For such workpieces, it is advisable to try to use liquid immersion ultrasonic flaw detection. For example, for products with large cross-sectional dimensions, the product shapes are varied, contain many types of defects, the organization is relatively uneven, the acoustic characteristics vary greatly, and the ultrasonic wave attenuation is serious, which brings great difficulties to ultrasonic flaw detection. Taking large forged blades as an example, coarse grains are prone to appear at the core position, and when ultrasonic waves penetrate the grain boundaries, scattering and diffraction are easily generated, which greatly reduces the penetration and signal-to-noise ratio of ultrasonic waves, and grass-like clutter appears, which reduces the accuracy of flaw detection.

[0004] To achieve the above object, the present invention provides the following technical solution: a mold water immersion ultrasonic flaw detection method, comprising the following steps: Step 1: Pretreatment: Use cleaning equipment to clean impurities adhered to the mold surface, use cleaning equipment to clean impurities adhered to the probe surface, and use cleaning equipment to clean impurities on the inner wall of the container required for the flaw detection mold; Step 2: Preparation: Put water into the container required for the cleaned flaw detection mold, the water thickness is H, and put the probe and mold into the container respectively; Step 3, parameter determination: setting the probes respectively, the set parameters are specifically the repetition frequency f', the flaw detection speed v and the curvature radius r of the focusing probe acoustic lens; Step 4: Start the test: Start the probe device and start the test; Step 5. Result analysis: Analyze based on the test results and repair or replace any problematic areas.

[0005] As a preferred technical solution of the present invention, the probe in step one is a focused probe, which will produce more effective sensitivity in the far field area. In the near field area, the probe sound field is focused into a beam, and the sound beam diameter is reduced to the focus.

[0006] As a preferred technical solution of the present invention, in the step 1, the volume of the container is greater than the volume of the mold.

[0007] As a preferred technical solution of the present invention, in step 2, placing the probe and the mold in the container respectively is specifically to completely place the cleaned mold and the probe into water and ensure that they are completely covered.

[0008] As a preferred technical solution of the present invention, the position where the probe is placed in the container in step 2 is specifically to place the probe above the area to be detected and make it contact vertically with the mold surface.

[0009] As a preferred technical solution of the present invention, the test in step 4 is specifically to judge whether there are defects or foreign matter by observing the signal waveform and data reflected on the display of the device connected to the probe, and further determine its position and size information.

[0010] As a preferred technical solution of the present invention, the repetition frequency f' in step 3 is specifically the number of pulses emitted by the flaw detection instrument per unit time or the number of ultrasonic waves emitted by the probe per unit time, which is determined by the following formula: , where: f' is the repetition frequency; L is the effective width of the focused sound velocity; 60 is the coefficient.

[0011] As a preferred technical solution of the present invention, the calculation formula of the flaw detection speed v in step 3 is: , where v is the detection speed; n is the relative rotation speed between the probe and the mold; t is the pitch.

[0012] As a preferred technical solution of the present invention, in step 3, the curvature radius r and the curvature radius r' of the focusing probe acoustic lens are calculated by the following formula: , where C1 is the speed of longitudinal waves in the acoustic lens, 2700 m / s, and C2 is the speed of sound in water, 1500 m / s.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This flaw detection method does not require close contact, so the detection speed is very fast; The entire mold is immersed in the water tank, which helps to eliminate surface waves. Because surface waves irregularly increase the smaller discontinuity signals from the outer surface, this flaw detection method has a high accuracy rate; This flaw detection method does not require special probes or wedges to match the workpiece when changing the size or shape of the inspected mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a flow chart of the present invention; Figure 2 It is a focusing schematic diagram of the present invention; Figure 3 This is a schematic diagram of the probe position of the present invention; Figure 4 This is the TGG curve diagram of the test block of the present invention. DETAILED DESCRIPTION

[0015] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0016] See also Figure 1-4 The present invention provides a mold water immersion ultrasonic flaw detection method, comprising the following steps: Step 1: Pretreatment: Use cleaning equipment to clean impurities adhered to the mold surface, use cleaning equipment to clean impurities adhered to the probe surface, and use cleaning equipment to clean impurities on the inner wall of the container required for the flaw detection mold; Step 2: Preparation: Put water into the container required for the cleaned flaw detection mold, the water thickness is H, and put the probe and mold into the container respectively; Step 3, parameter determination: setting the probes respectively, the set parameters are specifically the repetition frequency f', the flaw detection speed v and the curvature radius r of the focusing probe acoustic lens; Step 4: Start the test: Start the probe device and start the test; Step 5. Result analysis: Analyze based on the test results and repair or replace any problematic areas.

[0017] In step 1, the probe is a focused probe, which will produce more effective sensitivity in the far field. In the near field, the probe sound field is focused into a beam, in the process of reducing the sound beam diameter to the focus.

[0018] In step 1, the volume of the container is greater than the volume of the mold.

[0019] In step 2, the probe and the mold are placed in the container respectively, specifically, the cleaned mold and the probe are completely placed in water and ensured to be completely covered.

[0020] The position where the probe is placed in the container in step 2 is specifically to place the probe above the area to be detected and make it contact vertically with the mold surface.

[0021] The test in step 4 is specifically to judge whether there are defects or foreign objects by observing the signal waveform and data reflected on the display of the device connected to the probe, and further determine their location and size information.

[0022] The repetition frequency f' in step 3 is specifically the number of pulses emitted by the flaw detection instrument per unit time, or the number of ultrasonic waves emitted by the probe per unit time, which is the repetition frequency and is determined by the following formula: , where: f' is the repetition frequency; L is the effective width of the focused sound velocity; 60 is the coefficient.

[0023] The calculation formula for the flaw detection speed v in step 3 is: , where v is the detection speed; n is the relative rotation speed between the probe and the mold; t is the pitch.

[0024] In step 3, the radius of curvature r of the focusing probe acoustic lens and the radius of curvature r' are calculated by the following formula: , where C1 is the speed of longitudinal waves in the acoustic lens, 2700 m / s, and C2 is the speed of sound in water, 1500 m / s.

[0025] In the present invention, a cleaning device is used to clean impurities adhered to the surface of the mold, a cleaning device is used to clean impurities adhered to the surface of the probe, and a cleaning device is used to clean impurities on the inner wall of a container required for the flaw detection mold. Water is put into the container required for the flaw detection mold after cleaning, and the water thickness is H. The probe and the mold are respectively put into the container, and the probe is set respectively. The set parameters are specifically the repetition frequency f', the flaw detection speed v and the curvature radius r of the focusing probe acoustic lens. The probe equipment is started and the test is started; analysis is performed based on the test results, and the problematic areas are repaired or replaced.

[0026] In the present invention, in conjunction with the specification Figure 2 The longer the focal area, the better the signal-to-noise ratio and sensitivity of the detection; the smaller the focal area diameter, the better the lateral resolution. According to the above principles, different probes can be effectively selected; after statistical analysis, at this stage, the chip diameter and focal length of the common focusing probes in the industry are linearly related, and the relative change of the focal area diameter is relatively stable, which also brings convenience to the selection of actual probes and the setting of process parameters. The focus diameter will not be too different due to the use of different types of probes in each layer. The depth range of the layer should be in the position of the probe sound field. If each layer is within the theoretical focusing area of ​​the corresponding probe, it is guaranteed that the difference in the detection results of each layer is relatively small, and the detection data is relatively real and reliable, and will not interfere with the acceptance and judgment. Through process tests, under the premise of meeting the good detection signal-to-noise ratio, resolution, and sound pressure linearity, the length range of each layer should be as large as possible. Of course, this layering method subdivides the length range of each layer according to the theoretically calculated range, which is suitable for detection under very high sensitivity acceptance standards, such as water immersion ultrasonic detection of powder alloys, combined with the attached manual Figure 3 The position of the probe relative to the workpiece is mainly determined by the water distance and the amount of sinking of the focus in the material. The theoretical water distance length must exceed 1 / 4 of the layer thickness t, otherwise the secondary reflection signal of the interface will appear before the primary bottom surface reflection signal. By calculating the water distance and the amount of sinking of the focus in the material, the focus of the probe is placed at the center of the corresponding layered area, and the secondary reflection signal of the interface will not appear before the primary bottom surface reflection signal.

[0027] In the present invention, in conjunction with the specification Figure 4, in the case of high sensitivity and high acceptance level, the acoustic field characteristics in the inspected material should be very good, so as to ensure the observability of the inspected defects. At this time, the subdivided layering method should be considered to make the probe focus within the layered range, greatly improving the acoustic field characteristics of the probe in the inspected material. First, for small defects, high-frequency probes should be considered; secondly, in order to obtain a larger focal area depth range, large chip diameter and long focal length probes should be considered. In order to achieve good detection results for each layer, the different types of probes used in each layer are calculated by the above theory to calculate the focus sinking amount and the focal area length, and then the layers are overlapped and combined to achieve subdivision; the first layer is the near-surface layer. In order to ensure the near-surface resolution, the water distance should use the nominal focal length, then a high-frequency, small-diameter probe is selected to meet the requirements of high resolution, high sensitivity, and high signal-to-noise ratio in the shallow detection depth range, such as HGE-5827-A, IS1010GA. In the subsequent layers, due to the increase in detection depth, high-frequency, large chip diameter, and long focal length probes should be considered, such as V322 Series probes, chip diameter 25.4mm, focal length 8 inches, 10 inches, 12 inches, 16 inches, HGE-5827-A probe, through the measurement to obtain the Φ0.4FBH test block TCG curve, observe the TCG curve, in the depth range of 3.2-20mm, the curve linearity is good, and the signal-to-noise ratio of the test block hole wave and the surrounding clutter is good. The first layer uses the HGE-5827-A probe, using the nominal water distance 89.6mm, the layer depth range 3.2-20mm, the near-surface burial depth 3.2mm test block for dynamic response, meet the regulations ±1dB requirements, through actual testing to verify that the actual test results of the first layer of the inspected material meet the acceptance requirements, clutter is lower than Φ0.4mm-12dB, that is, the first layer plan is feasible, then the subsequent layer should use the V322 series probes, chip diameter 25.4mm, focal length 8 inches, 10 inches, 12 inches, 16 inches Inch, according to theoretical derivation, the tentative stratification is as follows: the second stratification, the probe with a nominal focal length of 8 inches is selected, the actual detection water distance is 140mm, and the stratification range is 15-30mm; the third stratification is the probe with a nominal focal length of 10 inches, the actual detection water distance is 150mm, and the stratification range is 25-50mm; the fourth stratification is the probe with a nominal focal length of 12 inches, the actual detection water distance is 100mm, and the stratification range is 45-70mm; the fifth stratification is the probe with a nominal focal length of 16 inches, the actual detection water distance is 100mm, and the stratification range is 65-110mm. The TCG used for the fifth stratification test shows that the focus sinks to a depth of about 75mm in the material, and the length of the -6dB focal area in the material is about 40mm, which is consistent with the theoretical calculation. It can be seen that the 16-inch probe, the focal length of 100mm, and the stratification range of 65-110mm are feasible. The actual test results of the fifth stratum of the inspected material meet the acceptance requirements, and the clutter is lower than Φ0.4mm-12dB, that is, the fifth layer scheme is feasible, and the verification of other layers is the same. From the TCG curve of the Φ0.4FBH powder alloy test block measured by each layer probe, the range of each layer is in the sound field area with good curve linearity, high sensitivity and signal-to-noise ratio, which is conducive to detection. The dynamic response of each layer system is good. It can be seen that this layer scheme is feasible.

[0028] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Mould water immersion ultrasonic flaw detection method, characterized in that: The following steps are involved: Step 1: Pretreatment: Use cleaning equipment to clean impurities adhered to the mold surface, use cleaning equipment to clean impurities adhered to the probe surface, and use cleaning equipment to clean impurities on the inner wall of the container required for the flaw detection mold; Step 2: Preparation: Put water into the container required for the cleaned flaw detection mold, the water thickness is H, and put the probe and mold into the container respectively; Step 3, parameter determination: setting the probes respectively, the set parameters are specifically the repetition frequency f', the flaw detection speed v and the curvature radius r of the focusing probe acoustic lens; Step 4: Start the test: Start the probe device and start the test; Step 5. Result analysis: Analyze based on the test results and repair or replace any problematic areas.

2. The mold water immersion ultrasonic flaw detection method according to claim 1, characterized in that: In the step 1, the probe is a focused probe, which will produce more effective sensitivity in the far field. In the near field, the probe sound field is focused into a beam, and the diameter of the sound beam is reduced to the focus.

3. The mold water immersion ultrasonic flaw detection method according to claim 1, characterized in that: In the step 1, the volume of the container is greater than the volume of the mold.

4. The mold water immersion ultrasonic flaw detection method according to claim 1, characterized in that: In the step 2, placing the probe and the mold into the container respectively is specifically to completely place the cleaned mold and the probe into water and ensure that they are completely covered.

5. The mold water immersion ultrasonic flaw detection method according to claim 1, characterized in that: The position where the probe is placed in the container in step 2 is specifically to place the probe above the area to be detected and make it contact vertically with the mold surface.

6. The mold water immersion ultrasonic flaw detection method according to claim 1, characterized in that: The test in step 4 is specifically to judge whether there are defects or foreign objects by observing the signal waveform and data reflected on the display of the device connected to the probe, and further determine their location and size information.

7. The mold water immersion ultrasonic flaw detection method according to claim 1, characterized in that: The repetition frequency f' in step 3 is specifically the number of pulses emitted by the flaw detection instrument per unit time, or the number of ultrasonic waves emitted by the probe per unit time, which is the repetition frequency and is determined by the following formula: , where: f' is the repetition frequency; L is the effective width of the focused sound velocity; 60 is the coefficient.

8. The mold water immersion ultrasonic flaw detection method according to claim 1, characterized in that: The calculation formula of the flaw detection speed v in step 3 is: , where v is the detection speed; n is the relative rotation speed between the probe and the mold; t is the pitch.

9. The mold water immersion ultrasonic flaw detection method according to claim 1, characterized in that: In step 3, the curvature radius r and curvature radius r' of the focusing probe acoustic lens are calculated by the following formula: , where C1 is the speed of longitudinal waves in the acoustic lens, 2700 m / s, and C2 is the speed of sound in water, 1500 m / s.

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