Method for measuring concentration of cutting fluid in circulating water and application

Abstract

The invention relates to the technical field of cutting fluid concentration detection, in particular to a method for measuring the concentration of cutting fluid in circulating water and application. The invention provides a method for measuring the concentration of cutting fluid in circulating water. The method comprises the following steps: drawing a fitting curve 1 of cutting fluid with different concentrations and surface tension values; drawing a fitting curve 2 of the cutting fluid with different COD values and the surface tension values; and detecting the COD value of the circulating water, and obtaining the concentration of the cutting fluid in the circulating water according to the fitted curve 2 and the fitted curve 1. According to the method, preparation of a fitting curve of the cutting fluid concentration and the COD value which are prone to having large errors is avoided, the concentration of the cutting fluid in the circulating water can be obtained more accurately, accurate regulation and control of the concentration of the cutting fluid in a large circulating system are facilitated, it is guaranteed that the slicing process is stable, and undesirable abnormity of photovoltaic slicing is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of cutting fluid concentration detection, and specifically relates to a method for measuring the concentration of cutting fluid in circulating water and its application. Background Art

[0002] In the current photovoltaic slicing industry, the processing method of photovoltaic slicing is generally wire saw cutting, and a large amount of pure water and cutting fluid are required during the cutting process. The large circulation system has become the first major core power for waste liquid treatment and water recycling in the slicing process due to its advantages such as recycling and reusing, recovering cutting fluid to reduce liquid loss, reducing the pure water consumption of slicing, and reducing the cost of wastewater treatment. At the same time, it plays a crucial role in significantly reducing the production cost of the slicing process. For the entire industry, the use of the large circulation system has been in a popular state. While the large circulation system saves costs for the slicing process, the circulating water also affects various key cutting indicators in the slicing process. Among them, the content of the cutting fluid concentration in the circulating water directly affects important indicators such as wire breakage, additional cutting, wire marks, and contaminated wafers at the slicing site. Therefore, how to effectively control and adjust the concentration of the cutting fluid in the circulating water is of great significance.

[0003] Cutting fluid is composed of a mixture of high-molecular organic substances. Currently, only the data of COD test or surface tension test can be used to measure the concentration content of the cutting fluid in the circulating water, and then the concentration of the cutting fluid in the large circulating water is adjusted according to the test data. Among the above two test methods, due to the lack of an on-line detection device for surface tension test at present, it can only be measured manually, and it is difficult to achieve 24-hour on-line monitoring of personnel. Therefore, currently, the large circulation system generally uses an on-line COD test device to detect the COD of the circulating water for 24 hours to detect the concentration of the cutting fluid in the circulating water. However, this method has the following problems: The on-line COD test device can only real-time feedback the COD value of the circulating water and cannot directly obtain the concentration of the cutting fluid in the circulating water. In order to achieve the regulation of the cutting fluid concentration, it is necessary to draw a standard curve of different concentrations of cutting fluid and COD values for each different cutting fluid every time, and then calculate the concentration of the cutting fluid according to the detection result of the on-line COD test device. However, when drawing the standard curve of different concentrations of cutting fluid and COD values, the measured COD values are usually in the tens of millions level. Even a tiny sampling difference during sample dilution will cause an error of dozens or even hundreds in the measured value, resulting in the inaccuracy of the drawn standard curve. When calculating using the on-line COD detection data, the actual obtained is only the approximate concentration of the cutting fluid in the circulating water, which leads to the inability to accurately regulate the concentration of the cutting fluid. Summary of the Invention

[0004] Based on this, the present invention provides a method for measuring the concentration of cutting fluid in circulating water, which can accurately determine the concentration of the cutting fluid in the circulating water and is convenient for precise regulation of the cutting fluid concentration in the large circulation system.

[0005] The present invention also provides a method for adjusting the concentration of cutting fluid in circulating water, which can ensure higher accuracy in adjustment.

[0006] The present invention realizes the above technical purpose through the following technical solutions.

[0007] The present invention provides a method for measuring the concentration of cutting fluid in circulating water, including the following steps: drawing a fitting curve 1 of cutting fluid with different concentrations and surface tension values; drawing a fitting curve 2 of cutting fluid with different COD values and surface tension values; detecting the COD value of the circulating water, and obtaining the concentration of cutting fluid in the circulating water according to fitting curve 2 and fitting curve 1.

[0008] For the method for measuring the concentration of cutting fluid in circulating water described above, the range of surface tension values used for drawing the fitting curve 1 includes the range of surface tension values used for drawing the fitting curve 2.

[0009] For the method for measuring the concentration of cutting fluid in circulating water described above, the range of COD values used for drawing the fitting curve 2 includes the COD values of the circulating water when the concentration of cutting fluid in the circulating water is 0 and the maximum value.

[0010] For the method for measuring the concentration of cutting fluid in circulating water described above, the maximum value is the set concentration of cutting fluid during cutting in the slicing process.

[0011] For the method for measuring the concentration of cutting fluid in circulating water described above, the surface tension values for drawing the fitting curve 1 and the fitting curve 2 are detected by the capillary rise method or the maximum bubble pressure method or the pulling-off method.

[0012] For the method for measuring the concentration of cutting fluid in circulating water described above, the COD value of the cutting fluid when drawing the fitting curve 2 is detected by an online COD detector.

[0013] For the method for measuring the concentration of cutting fluid in circulating water described above, it includes the following steps: using the cutting fluid to prepare a series of standard solutions with gradient concentrations, detecting their surface tension values, and drawing the fitting curve 1 with the cutting fluid concentration as the abscissa and the surface tension value as the ordinate; using the cutting fluid to prepare a series of standard solutions with gradient COD values, detecting their surface tension values, and drawing the fitting curve 2 with the COD value as the abscissa and the surface tension value as the ordinate; detecting the COD value in the circulating water, obtaining the surface tension value of the circulating water according to the fitting curve 2, and then obtaining the concentration of cutting fluid in the circulating water from the surface tension value according to the fitting curve 1.

[0014] For the method for measuring the concentration of cutting fluid in circulating water described above, the volume concentration of the cutting fluid used when drawing the fitting curve 1 is 0.1 - 10%.

[0015] For the method for measuring the concentration of the cutting fluid in the circulating water as described above, the gradient range of the COD value when drawing the fitting curve 2 is 1000-10000 mg / L.

[0016] The present invention also provides a method for adjusting the concentration of the cutting fluid in the circulating water. The concentration of the cutting fluid in the circulating water is measured by using the above measurement method, and then the cutting fluid is added until its concentration reaches the set concentration of the cutting fluid during the slicing process.

[0017] The method for measuring the concentration of the cutting fluid in the circulating water provided by the present invention avoids the preparation of the fitting curve of the cutting fluid concentration and the COD value that is prone to large errors, can more accurately obtain the concentration of the cutting fluid in the circulating water, facilitates the precise regulation of the cutting fluid concentration in the large circulation system, ensures the stability of the slicing process, and reduces the defects of photovoltaic slicing (silicon wafers). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the fitting curve 1 of the cutting fluid with different concentrations and the surface tension value obtained by drawing in the specific embodiment of the present invention;

[0019] Figure 2 It is the fitting curve 2 of the cutting fluid with different COD values and the surface tension value obtained by drawing in the specific embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0021] During the photovoltaic slicing process, the cutting fluid forms a lubricating film, significantly reducing the friction coefficient between the cutting wire and the photovoltaic slice, increasing the cutting speed, extending the service life of the cutting wire, and reducing the mechanical impact on the surface of the photovoltaic slice to prevent microcracks and chipping defects. However, during actual cutting, when the cutting fluid is sprayed through the nozzle at a pressure of 5-10 Mpa, some droplets will atomize into the air and cannot be recovered. The high-speed movement of the diamond wire will also adhere to and carry away part of the cutting fluid. In addition, the silica gel generated by the slow hydrolysis of the silicon chips and water during the cutting process will wrap the cutting fluid molecules, resulting in a decrease in the concentration of the cutting fluid during the recycling process. Therefore, the concentration of the cutting fluid in the large circulation system of photovoltaic slicing is not stable. When it is recycled, it is necessary to re-adjust its concentration. The key to achieving precise adjustment lies in the precise detection of the concentration of the cutting fluid in the circulating water.

[0022] COD test, namely the test of Chemical Oxygen Demand, can be used to reflect the content of organic matter in water. Cutting fluid is a mixed liquid of organic matter, so COD can be used to reflect the concentration of cutting fluid. The higher the COD value, the higher the concentration of cutting fluid in the circulating water.

[0023] The COD test principle is as follows: under certain conditions, the amount of oxidant consumed to oxidize the reducing substances in 1L of water sample is used as an indicator, and converted into milligrams of oxygen required for each liter of water sample to be completely oxidized, expressed in mg / L.

[0024] At present, the COD testing method is relatively mature, and COD online automatic monitoring has become a mature technology.

[0025] The surface tension of a liquid is essentially a macroscopic manifestation of the intermolecular forces. Inside the liquid, the molecules are subject to symmetrical forces from the surrounding molecules, but on the surface, the molecules are only subject to unidirectional forces from the internal molecules, forming a combined force pointing to the inside of the liquid. This asymmetry of intermolecular forces causes the liquid surface to have a tendency to shrink spontaneously, forming a surface tension phenomenon. The surface tension of water at 20°C is 72.8mN / m.

[0026] When the liquid contains different solutes, the surface tension will change significantly. Inorganic salts (such as NaCl, KNO 3 ) will enhance the interaction between water molecules and increase the surface tension. For example, the surface tension of 0.1mol / L NaCl solution can reach 73.5mN / m. The introduction of organic matter will reduce the surface tension. For example, adding 1% ethanol can reduce the surface tension of water to below 50mN / m. This phenomenon is due to the directional arrangement of organic molecules in the surface layer. The arrangement of hydrophobic groups outward and hydrophilic groups inward destroys the hydrogen bond network between water molecules.

[0027] In the field of photovoltaic slicing processing, the cutting fluid is a mixture of organic compounds. These organic substances significantly improve the wetting ability of photovoltaic slices by reducing the surface tension of the solution. The lower the cutting fluid content, the smaller the surface tension, and the more effectively the solution can penetrate into the processing interface, taking away the cutting heat and reducing tool wear.

[0028] The testing methods for liquid surface tension mainly include static method and dynamic method.

[0029] The static methods include: the drop weight method, where the size of the liquid drop is related to the surface tension of the liquid. The greater the surface tension, the larger the dropped liquid drop; the capillary rise method, where a capillary is inserted into the liquid, and the liquid will rise along the capillary. After rising to a certain height, it reaches an equilibrium state. By measuring the height of the liquid level rise and combining the liquid density, gravitational acceleration, and contact angle, the surface tension is calculated; the maximum bubble pressure method, where a capillary is inserted into the liquid and gas is blown in to form bubbles. When the bubble radius is exactly equal to the capillary radius, the pressure inside the bubble is the largest, and the surface tension is calculated according to the Laplace formula; the ring method (Wilhelmy plate method): A ring is placed flat on the liquid surface, and the maximum force required to pull the ring away from the liquid surface is measured to calculate the surface tension.

[0030] The dynamic methods include: the pendant drop method, where the surface tension is calculated based on the shape of the liquid drop naturally formed on a horizontal plane. The shape of the liquid drop is directly related to the surface tension and density of the liquid, and the pressure difference inside and outside the curved surface is described by the Laplace formula; the spinning drop method, where the liquid drop is placed in a centrifugal force field by rotation, and the rotation speed is adjusted to change the equilibrium shape of the liquid drop for easy measurement; the oscillating jet method, etc.

[0031] The method for measuring the concentration of the cutting fluid in the circulating water provided by the present invention includes the following steps: drawing the fitting curve 1 of the cutting fluid with different concentrations and the surface tension values; drawing the fitting curve 2 of the cutting fluid with different COD values and the surface tension values; detecting the COD value of the circulating water, and obtaining the concentration of the cutting fluid in the circulating water according to the fitting curve 2 and the fitting curve 1.

[0032] The method for measuring the concentration of the cutting fluid in the circulating water provided by the present invention avoids the preparation of the fitting curve of the cutting fluid concentration and the COD value that is prone to large errors, can more accurately obtain the concentration of the cutting fluid in the circulating water, and is convenient for the precise regulation of the cutting fluid concentration in the large circulation system.

[0033] In the present invention, the detection of COD is preferably carried out by using an on-line automatic COD monitor.

[0034] The method for detecting the surface tension in the present invention is not limited. Preferably, it is detected by the ring method, the capillary rise method, the maximum bubble pressure method, and the Wilhelmy plate method (i.e., the ring method).

[0035] In order to more accurately obtain the concentration of the cutting fluid in the circulating water, the range of the surface tension values used for drawing the fitting curve 1 includes the range of the surface tension values used for drawing the fitting curve 2, which is convenient for intuitively obtaining the cutting fluid concentration in the fitting curve 1 based on the surface tension value obtained from the fitting curve 2.

[0036] Furthermore, the range of COD values ​​used to draw fitting curve 2 includes the COD values ​​of circulating water when the cutting fluid concentration in the circulating water is 0 and the maximum value, so that the surface tension value can be intuitively obtained in fitting curve 2 according to the measured COD value of circulating water.

[0037] It can be understood that the maximum value mentioned above refers to the set concentration of the cutting fluid during the slicing process, and the set concentration will vary depending on the cutting fluid manufacturer and ingredients, and is specifically the amount given by the manufacturer or the amount determined after internal experimental research.

[0038] In the present invention, the fitting curve 1 and the fitting curve 2 can adopt the Origin function drawing software. As a professional function drawing software, Origin supports a variety of 2D / 3D graphics, and the data analysis functions include statistics, signal processing, curve fitting, peak analysis, etc. The drawing model of Origin can be divided into a basic graphics model, a data analysis model, an advanced fitting model, a custom model, and a template library model. The present invention does not limit the specific drawing model used when drawing the fitting curve 1 and the fitting curve 2, such as a line graph, a scatter plot, etc. in the basic graphics model, or an advanced fitting model.

[0039] The present invention preferably adopts an advanced fitting model, such as an exponential decay model (expdec3 third-order decay model). The exponential decay model is a mathematical fitting function used to describe a complex decay process, and its mathematical expression is: , where A 1 , A 2 , A 3 represents the initial amplitude of three independent decay processes; k 1 , k 2 , k 3 is the corresponding decay rate constant (unit: S -1 or min -1 );y 0 is the baseline offset.

[0040] In addition, to improve the accuracy of the fitting curve, multiple groups (such as 5 groups) of cutting fluids with different concentrations and different COD values ​​can be repeatedly prepared for testing when drawing the fitting curve to eliminate test errors and abnormal values. Then, multiple groups of test data are brought into the exponential decay model formula, including setting the function name, parameters and derivative parameters, and performing convergence processing to finally obtain the fitting curve and equation.

[0041] The fitting curve can be drawn by conventional processing methods in the art, and will not be described in detail here.

[0042] In the present invention, the COD value in the circulating water is detected by an on-line COD detector. Detection by the on-line detector can facilitate 24-hour monitoring, which is convenient for adjusting the addition amount of the cutting fluid in real time. Subsequently, it is also convenient to develop and introduce an automatic COD regulation function. After setting the required COD value, the system regulates according to the on-line detected COD data to ensure that the concentration of the cutting fluid in the circulating water remains stable all the time.

[0043] In some specific embodiments of the present invention, the surface tension values of the fitting curve 1 and the fitting curve 2 are detected by the capillary rise method or the maximum bubble pressure method or the pulling-off method (i.e., the ring method).

[0044] The COD value of the cutting fluid when drawing the fitting curve 2 is obtained by an on-line COD detector or manual detection.

[0045] In the present invention, the abscissa in the fitting curve 1 can be either the concentration of the cutting fluid or the surface tension value, and the corresponding ordinate is the surface tension value or the concentration of the cutting fluid. That is, when the abscissa is the concentration of the cutting fluid, the ordinate is the surface tension value; when the abscissa is the surface tension value, the ordinate is the concentration of the cutting fluid.

[0046] Similarly, the abscissa in the fitting curve 2 can be either the COD value or the surface tension value, and the corresponding ordinate is the surface tension value or the COD value. That is, when the abscissa is the COD value, the ordinate is the surface tension value; when the abscissa is the surface tension value, the ordinate is the COD value.

[0047] In some specific embodiments of the present invention, the method for measuring the concentration of the cutting fluid in the circulating water includes the following steps: preparing a series of standard solutions with gradient concentrations of the cutting fluid, detecting their surface tension values, and drawing the fitting curve 1 with the concentration of the cutting fluid as the abscissa and the surface tension value as the ordinate; preparing a series of standard solutions with gradient COD values of the cutting fluid, detecting their surface tension values, and drawing the fitting curve 2 with the COD value as the abscissa and the surface tension value as the ordinate; detecting and obtaining the COD value in the circulating water, obtaining the surface tension value of the circulating water according to the fitting curve 2, and then obtaining the concentration of the cutting fluid in the circulating water according to the obtained surface tension value and the fitting curve 1.

[0048] It can be understood that the preparation method of the cutting fluid is to mix the purchased or self-made cutting fluid with water.

[0049] The method for measuring the concentration of the cutting fluid in the circulating water provided by the present invention is simple, convenient and fast. Even if the cutting fluid from different manufacturers is replaced, the latest data can be obtained by testing according to the above method without additional cost, and for the same cutting fluid, only the fitting curve 1 and the fitting curve 2 need to be made once.

[0050] In the present invention, the volume concentration of the prepared cutting fluid and the range of COD values when drawing the standard curve are determined according to the use concentration of the cutting fluid.

[0051] In some specific embodiments of the present invention, the volume concentration of the cutting fluid used when drawing the fitting curve 1 is 0.1 - 10%. That is, standard solutions with volume concentrations of 0.1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, and 10% are prepared using the cutting fluid and pure water, and then their surface tension values are tested one by one and recorded.

[0052] In order to improve the accuracy of the fitting curve, five groups of data are repeatedly prepared and tested, test errors and outliers are removed, and through the Origin function plotting software, the logistic model formulas of the five groups of test data, including setting function names, parameters, and derivative parameters, are subjected to convergence processing, and finally the fitting curve and equation are obtained, that is, the trend graph of the surface tension values corresponding to different concentrations of the cutting fluid (i.e., fitting curve 1) is obtained.

[0053] When drawing the fitting curve 2, the gradient range of the COD value is 1000 - 10000 mg / L. That is, standard solutions with COD values of 1000 mg / L, 1500 mg / L, 2000 mg / L, 2500 mg / L, 3000 mg / L, 3500 mg / L, 4000 mg / L, 4500 mg / L, 5000 mg / L, 5500 mg / L, 6000 mg / L, 6500 mg / L, 7000 mg / L, 7500 mg / L, 8000 mg / L, 8500 mg / L, 9000 mg / L, 9500 mg / L, and 10000 mg / L are prepared using the cutting fluid and pure water, and then their surface tension values are tested one by one and recorded.

[0054] In order to improve the accuracy of the fitting curve, five groups of data are repeatedly prepared and tested, test errors and outliers are removed, and through the Origin function plotting software, the five groups of test data are brought into the exponential decay model formula, including setting function names, parameters, and derivative parameters, and convergence processing is carried out, and finally the fitting curve and equation are obtained, that is, the trend graph of the surface tension values corresponding to the cutting fluid with different COD values (i.e., fitting curve 2) is obtained.

[0055] The present invention also provides a method for adjusting the concentration of the cutting fluid in the circulating water. The concentration of the cutting fluid in the circulating water is measured by using the above measurement method, and then the cutting fluid is added until its concentration reaches the set concentration of the cutting fluid during the slicing process. For example, if the required concentration (i.e., the set concentration) of the cutting fluid during the slicing process is 4 L of cutting fluid added to every 480 L of pure water, that is, the volume concentration of the cutting fluid is 0.83%. When the measured volume concentration of the cutting fluid in the circulating water is 0.25%, at this time, manual or automated equipment can be used to add cutting fluid to the circulating water until its volume concentration reaches 0.83%.

[0056] To make the measurement method of the concentration of the cutting fluid in the circulating water described in the present invention clearer, the following will be introduced in detail with specific embodiments.

[0057] Taking a certain cutting fluid as an example, the set value of the usage concentration of this cutting fluid during the slicing process is 0.83%.

[0058] (1) Use the above cutting fluid and pure water to prepare standard solutions with volume concentrations of 0.1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, and 10% respectively, and then use the pull-off method (ring method) to measure the surface tension one by one and record it. The pull-off method measurement method is as follows.

[0059] a. Fix the force-sensitive sensor on the bracket, hang the weight tray, and adjust the instrument to be horizontal through the base adjustment screws; use a plumb line or a level to verify the verticality of the equipment to ensure that the hanging ring is parallel to the liquid surface;

[0060] b. Gradually add standard weights (such as 0.5 g, 1.0 g, etc.), record the corresponding voltage output value U i, fit the F−U curve by the least squares method, and calculate the sensor sensitivity B = ΔU / ΔF (unit: mV / N);

[0061] c. Use a vernier caliper with a least count of 0.02 mm to measure the outer diameter D 1 and the inner diameter D 2 , and calculate the average circumference L = π(D 1 +D 2 );

[0062] d. Immerse the metal ring in a 5 wt% sodium hydroxide solution for 20 - 30 s to remove grease, rinse with distilled water and dry with hot air, avoiding finger contact with the surface; hang the cleaned metal ring on the sensor hook, adjust the lifting platform so that the liquid surface is close to the lower edge of the ring, ensuring that the ring is parallel to the liquid surface; adjust the zero adjustment knob of the digital voltmeter so that the initial reading U 0 = 0 mV (no-load state);

[0063] e. Rotate the lifting platform counterclockwise to raise the liquid level. After completely submerging the lifting ring, change to clockwise and slowly lower the liquid level (or raise the lifting ring) to form a liquid film. Observe the liquid film stretching process and record the peak voltage U at the moment of liquid film rupture 1 and the stable value U after rupture 2 . Calculate the voltage difference ΔU = U 1 - U 2 .

[0064] f. Re-zero after each measurement. Conduct at least 5 sets of parallel tests to reduce random errors, and calculate the surface tension according to the surface formula .

[0065] Using the Origin function plotting software, substitute the data of the five sets of designed tests into the exponential decay model formula, including setting the function name, parameters, and derived parameters, and perform convergence processing. Finally, obtain the fitting curve 1 and the equation, as Figure 1 shown

[0066] (2) Use the above cutting fluid and pure water to prepare standard solutions with COD values of 1000mg / L, 1500mg / L, 2000mg / L, 2500mg / L, 3000mg / L, 3500mg / L, 4000mg / L, 4500mg / L, 5000mg / L, 5500mg / L, 6000mg / L, 6500mg / L, 7000mg / L, 7500mg / L, 8000mg / L, 8500mg / L, 9000mg / L, 9500mg / L, 10000mg / L respectively. Then use the above-mentioned pull-off method (ring method) to test the surface tension one by one and record it. Conduct at least 5 sets of parallel tests to reduce random errors

[0067] Using the Origin function plotting software, substitute the data of the five sets of designed tests into the exponential decay model formula, including setting the function name, parameters, and derived parameters, and perform convergence processing. Finally, obtain the fitting curve 2 and the equation, as Figure 2 shown

[0068] (3) Obtain the COD value in the circulating water through an online COD detector (RUN-ST-COD700). Calculate the surface tension value using this COD value combined with the equation of the fitting curve 2, and calculate the specific concentration of the cutting fluid in the circulating water according to the calculated surface tension value combined with the equation of the fitting curve 1

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring the concentration of cutting fluid in circulating water, characterized in that: The following steps are involved: Draw a fitting curve 1 of different concentrations of cutting fluid and surface tension value; Draw the fitting curve 2 of cutting fluid with different COD values ​​and surface tension values; The COD value of the circulating water is detected, and the concentration of the cutting fluid in the circulating water is obtained according to the fitting curve 2 and the fitting curve 1.

2. The method for measuring the concentration of cutting fluid in circulating water according to claim 1, characterized in that: The range of surface tension values ​​used to draw the fitting curve 1 includes the range of surface tension values ​​used to draw the fitting curve 2.

3. The method for measuring the concentration of cutting fluid in circulating water according to claim 1 or 2, characterized in that: The range of COD values ​​used to draw the fitting curve 2 includes the COD values ​​of the circulating water when the cutting fluid concentration in the circulating water is 0 and the maximum value.

4. The method for measuring the concentration of cutting fluid in circulating water according to claim 3, characterized in that: The maximum value is the set concentration of the cutting fluid during the slicing process.

5. The method for measuring the concentration of cutting fluid in circulating water according to any one of claims 1 to 4, characterized in that: The surface tension values ​​of the fitting curve 1 and the fitting curve 2 are obtained by capillary rise method, maximum bubble pressure method or pull-off method.

6. The method for measuring the concentration of cutting fluid in circulating water according to any one of claims 1 to 5, characterized in that: When drawing the fitting curve 2, the COD value of the cutting fluid is obtained by detecting it through an online COD detector.

7. The method for measuring the concentration of cutting fluid in circulating water according to any one of claims 1 to 6, characterized in that: The following steps are involved: A series of standard solutions with gradient concentrations are prepared using the cutting fluid, and their surface tension values ​​are detected. A fitting curve 1 is drawn with the cutting fluid concentration as the abscissa and the surface tension value as the ordinate; A series of standard solutions with COD value gradients are prepared using cutting fluid, and their surface tension values ​​are detected. Fitting curve 2 is drawn with COD value as the horizontal coordinate and surface tension value as the vertical coordinate; The COD value in the circulating water is detected, and the surface tension value of the circulating water is obtained according to the fitting curve 2. Then, the concentration of the cutting fluid in the circulating water is obtained according to the fitting curve 1 from the surface tension value.

8. The method for measuring the concentration of cutting fluid in circulating water according to claim 7, characterized in that: The volume concentration of the cutting fluid used in drawing the fitting curve 1 is 0.1-10%.

9. The method for measuring the concentration of cutting fluid in circulating water according to claim 7 or 8, characterized in that: When drawing fitting curve 2, the gradient range of COD value is 1000-10000 mg / L.

10. A method for adjusting the concentration of cutting fluid in circulating water, characterized in that: The concentration of the cutting fluid in the circulating water is measured by the measuring method described in any one of claims 1 to 9, and then the cutting fluid is added until its concentration is the set concentration of the cutting fluid during the slicing process.

Images