Rapid detection method for rolling oil acid value in emulsified liquid for cold rolling production

Abstract

The invention discloses a method for rapidly detecting the rolling oil acid value in emulsified liquid for cold rolling production, which comprises the following steps: S1, taking the cold rolling emulsified liquid to be detected, filtering, and then sequentially carrying out organic solvent mixing and extraction, high-speed centrifugal separation and negative pressure rotary evaporation operation on the cold rolling emulsified liquid to be detected, so as to obtain a rolling oil sample to be detected; s2, preparing rolling oil standard samples with different acid values; and S3, respectively detecting the rolling oil standard samples with different acid values and the rolling oil sample to be detected by utilizing an infrared spectroscopy method to obtain infrared spectrums of the corresponding samples so as to obtain a standard curve of the acid value of the rolling oil, and comparing to obtain the acid value of the rolling oil in the cold rolling emulsion to be detected. According to the method, the acid value of the rolling oil in the on-site emulsion can be quickly read and obtained, the result accuracy is high, the requirements for quick measurement and quick adjustment of on-site production of a modern cold rolling unit can be met, and high practicability is achieved.

Description

Technical Field

[0001] This invention relates to the field of steel cold rolling production technology, and more specifically, to a rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production. Background Technology

[0002] Modern steel production enterprises typically perform cold rolling on some steel materials. This cold rolling process utilizes emulsions, which are liquids (usually ≤5%) made by mixing industrial demineralized water and rolling oil and spraying them onto the strip and rolls. Emulsions provide excellent lubrication and cooling; therefore, the wear and tear on the rolls, mill energy consumption, and the surface quality of the strip all depend on the performance of the emulsion. Consequently, extensive testing of emulsions is necessary in daily cold rolling production. The performance of emulsions encompasses many aspects, with common testing items including the saponification value and acid value of the rolling oil within them.

[0003] Acid value is one of the most important routine tests for evaluating the performance of oils and greases. It indicates the number of milligrams of potassium hydroxide (KOH) required to completely neutralize the free carboxylic acid groups in 1 gram of rolling oil. Chemically speaking, it directly indicates the amount of free fatty acids in the oil sample. Unlike other traditional industrial oils, acid value is one of the most important performance indicators for cold rolling oils. This is because cold rolling oils themselves contain a large amount of free fatty acids as lubricating additives, as well as a large amount of animal, vegetable, and synthetic oils. Therefore, they are highly susceptible to generating free fatty acids under aqueous conditions. The test is mainly used to determine whether the rolling oil in cold rolling production has deteriorated or whether its lubrication performance meets production requirements. Overall production quality assurance is highly dependent on acid value.

[0004] As mentioned above, cold rolling production uses emulsions, and the testing focuses on the rolling oil within them. Therefore, when performing condition testing on cold rolling emulsions, it is first necessary to separate the oil and water in the emulsion on-site to obtain the rolling oil. This process involves heating the emulsion and using negative pressure rotary evaporation to remove some of the water. Sometimes, a large amount of sodium chloride is added to the emulsion before heating (≥80℃) to accelerate the oil-water separation rate. After prolonged operation, oil-water separation will occur. Next, the oil phase is sampled and the rolling oil is extracted using organic solvents such as methyl ethyl ketone (MEK). The extract is then sampled and heated to remove the solvent, finally yielding the rolling oil sample. Subsequently, titration with a standard potassium hydroxide solution is performed, and phenolphthalein indicator is used to indicate the reaction endpoint. The above process is time-consuming and labor-intensive, typically requiring 3-5 hours of operation. Moreover, the titration using these reagents needs to be measured in a laboratory. In actual production conditions, it often takes more than a day from sampling to obtaining the final titration result, which often makes it difficult to meet the rapid adjustment requirements of the unit.

[0005] Therefore, the ability to quickly measure the acid value of the rolling oil in the emulsion used in cold rolling production and simplify the measurement process is of great importance and practical significance to the cold rolling production process.

[0006] Based on the above, relevant technical information on methods for detecting acid value was retrieved within this field, mainly focusing on the following aspects:

[0007] Japanese Patent JP20190826 discloses an apparatus, procedure, and method for measuring the degree of deterioration of oils. The oil to be tested is placed in a specialized optical instrument, and then professional imaging equipment is used to record the color of the oil and perform computer colorimetric data analysis. By comparing the colors of standard oil samples with different acid values, the approximate acid value range of the oil can be quickly determined. This measurement method utilizes the principle that different colors appear after the oil sample undergoes a chemical decomposition reaction, resulting in an increase in free fatty acids. However, for cold-rolled emulsions on-site, it is still necessary to first demulsify to obtain pure rolling oil before measurement. This process is still time-consuming and labor-intensive. Furthermore, iron powder and water in the cold-rolled emulsion significantly affect the color of the final rolling oil sample, thus causing significant errors.

[0008] Chinese patent application number 202011007644.5 proposes a fully automated fatty acid value determination system and method for grains. Specifically, it still uses the principle of machine vision judgment to automate the process of manually observing the color change of phenolphthalein reagent in the traditional chemical titration process. Therefore, it can save the labor of measuring the acid value of rolling oil. However, this process still faces the time-consuming process of demulsification to prepare rolling oil. Therefore, its practicality in the measurement process of cold rolling emulsion is not high.

[0009] Chinese patent application number 201811292633.9 proposes a method for detecting the acid value of animal fats. Specifically, it involves directly titrating crude animal and vegetable oils with a standard sodium hydroxide solution, specifying that the titration endpoint is reached when the pH is 8.2. The acid value is then deduced based on the amount of sodium hydroxide solution used. However, this invention still faces the challenge of separating the rolling oil from the emulsion, which requires a significant amount of time and maneuvering. Therefore, it remains difficult to use for rapid measurement of the acid value of cold rolling emulsions.

[0010] Chinese patent application number 201010275565.2 proposes a method for determining the acid value of edible oils based on conductivity. The method involves mixing oil samples containing different fatty acids with an aqueous sodium hydroxide solution, measuring the conductivity, and then adding the oil sample to be tested to undergo a hydrolysis reaction with sodium hydroxide solution. The final conductivity is used to calculate the acid value of the oil being tested. However, this method, when performed in a conventional laboratory, requires the preparation of a large number of samples with different acid values. Furthermore, the time required to maintain a sufficient reaction between the sodium hydroxide solution and the oil being tested makes it inherently time-consuming and computationally expensive.

[0011] Chinese Patent Application No. 202011270488.1 proposes a non-destructive testing method for the acid value of turbine oil based on mid-infrared spectroscopy. The method uses infrared Fourier transform to measure the acid value, which involves scanning the oil in an infrared device at a range of 650–4000 cm⁻¹. -1 The signal value of the wavenumber is obtained, and then the least squares method-artificial neural network algorithm is used to compare it with the known acid value of the oil to be tested to obtain the acid value of the oil sample. The problem that still exists in the use of this method in cold rolling emulsion is how to quickly demulsify and avoid the influence of iron powder and trace water in the cold rolling emulsion.

[0012] Chinese patent application number 201510372342.0 proposes a method for detecting oxidative rancidity of Ganoderma lucidum spore oil based on Raman spectroscopy. For products like spore oil, a standard chart for evaluating the acid value and peroxide value of the sample oil is established by plotting the Raman peak intensity at 1655 cm⁻¹ in the Raman spectrum of a standard sample as the ordinate and the acid value or peroxide value as the abscissa. Then, the Raman spectrum of the test sample is detected, and the Raman peak intensity results at the same frequency are compared with the acid value and peroxide value evaluation charts to obtain the acid value and peroxide value of the test sample. Although this method avoids the operation of traditional titration methods in the detection stage, it still faces challenges in rapid demulsification and avoiding the influence of iron powder and trace amounts of water in the cold rolling emulsion when applied to cold rolling.

[0013] Therefore, from the above technical perspective, existing methods for measuring acid value primarily focus on optimizing the acid value titration process using various methods and employing automation to reduce operational steps. Furthermore, the inventions of existing acid value detection methods mainly target pure oils, making it difficult to reduce the process of preparing pure oil from emulsion demulsification. Additionally, trace amounts of iron powder and water introduced from cold-rolled emulsions can also affect measurement accuracy.

[0014] This invention proposes a rapid detection method specifically for measuring the acid value of rolling oil in cold rolling emulsion. The results obtained are highly accurate and are particularly suitable for use in on-site production to guide rapid production adjustments during unit operation. Summary of the Invention

[0015] To address the shortcomings of existing technologies, the purpose of this invention is to provide a rapid detection method for the acid value of rolling oil in emulsions used in cold rolling production. This method can quickly obtain the acid value of rolling oil in emulsions on-site, with high accuracy. It can meet the needs of rapid measurement and adjustment in modern cold rolling mills and has high practicality.

[0016] To achieve the above objectives, the present invention adopts the following technical solution:

[0017] A rapid method for detecting the acid value of rolling oil in emulsion used in cold rolling production includes the following steps:

[0018] S1, the cold rolling emulsion to be tested is filtered, and then the organic solvent is mixed and extracted, high-speed centrifugation and negative pressure rotary evaporation are performed in sequence to obtain the rolling oil sample to be tested.

[0019] S2, prepare standard samples of rolling oil with different acid values;

[0020] S3. Infrared spectroscopy is used to detect standard samples of rolling oil with different acid values ​​and samples of rolling oil to be tested, respectively, to obtain the infrared spectra of the corresponding samples, thereby obtaining the standard curve of the acid value of rolling oil, and by comparison, the acid value of the rolling oil in the cold rolling emulsion to be tested is obtained.

[0021] Preferably, the process of step S1 is as follows:

[0022] S11, Take the cold-rolled emulsion to be tested and filter it using a filtration device with a microporous filter;

[0023] S12, pour organic solvent into the filtered cold rolling emulsion to be tested, and put it into a high-speed stirrer for stirring and mixing. The rolling oil in the emulsion to be tested enters the organic solvent through extraction.

[0024] S13, the mixture of the cold-rolled emulsion to be tested and the organic solvent is immediately centrifuged after stirring is stopped;

[0025] S14. Take the clear organic solvent phase from the top of the centrifuged liquid and place it in a hot water bath for negative pressure rotary evaporation to obtain the rolling oil sample to be tested.

[0026] Preferably, in step S11, the sampling amount of the cold-rolled emulsion to be tested is 400-800 ml, and the cold-rolled emulsion to be tested is an emulsion with a concentration of 1.5% or higher.

[0027] Preferably, in step S12:

[0028] The organic solvent is selected from a mixture of butanone, dichloroethane, isopropanol and petroleum ether, and the amount of the organic solvent added is 40-100 ml.

[0029] The stirring speed is ≥8000 rpm and the stirring time is 5-10 min.

[0030] Preferably, the centrifugal separation process in step S13 is as follows:

[0031] Place the mixture into multi-tube polypropylene centrifuge tubes, adding 15 mL of the mixture to each tube, and centrifuge on a high-speed centrifuge for 5–15 min.

[0032] Preferably, the process of step S14 is as follows:

[0033] Take 30-90 mL of the clear liquid from the upper organic solvent phase of the centrifuged liquid and place it in a rotary evaporator. Perform negative pressure rotary evaporation in a hot water bath at 60-85℃, with the negative pressure controlled at -640±20 mmHg. Evaporate to remove the organic solvent and trace amounts of water to obtain the rolling oil to be tested.

[0034] Preferably, in step S2, the preparation process of the rolling oil standard samples with different acid values ​​is as follows:

[0035] S21, take the crude oil from the rolling oil used in the preparation of emulsion for the on-site unit, titrate the acid value, and mark it as 1# standard sample;

[0036] S22, take the crude oil from the rolling mill, add different amounts of mineral oil, heat it to mix it thoroughly, and then titrate the acid value. The samples are labeled as standard sample #2, standard sample #3, standard sample #4, and standard sample #5 according to the amount of mineral oil added. The amount of mineral oil added in standard sample #2, standard sample #3, standard sample #4, and standard sample #5 is arranged from low to high.

[0037] Preferably, the mineral oil is Kunlun L-HM46 hydraulic oil.

[0038] Preferably, the specific process of step S3 is as follows:

[0039] S31. Instrument preparation: Turn on the infrared spectrometer and simultaneously open the high-purity nitrogen valve. Purge with nitrogen for at least 20 minutes until there are no interfering peaks in the infrared spectrometer.

[0040] S32, Instrument Settings: Open the infrared software and set the infrared spectrometer to scan the blank before each sample scan.

[0041] S33, after scanning the blank, scan the standard samples of rolling oil with different acid values ​​in sequence and save the infrared spectrum. After each sample scan, clean the sample cell used for measurement.

[0042] S34. To create a standard curve, open the infrared spectroscopy data processing software, set the path length of the infrared data processing method, and ensure the peak value of the tested rolling oil standard sample is at 1710 cm⁻¹. -1 The peak height is set at the wavenumber, and the infrared spectra of rolling oil standard samples with different acid values ​​are imported in sequence. The acid values ​​of the titrated standard samples are then input to obtain the standard curve of the rolling oil acid value.

[0043] S35, Standard curve analysis: The correlation coefficient of the standard curve of the acid value of the rolled oil is calculated by infrared spectroscopy data processing software. If the correlation coefficient reaches 0.995 or above, the standard curve of the acid value of the rolled oil meets the requirements. Otherwise, the rolled oil standard sample is rescanned or reconfigured.

[0044] S36, Sample analysis: Take out the clean sample cell, put in the rolling oil sample to be tested, put it back into the cell seat, close the top cover, continue to purge with nitrogen, scan the rolling oil sample to be tested, and save the infrared spectrum.

[0045] S37, open the standard curve of rolling oil acid value, and calculate the acid value of the rolling oil in the cold rolling emulsion to be tested according to the linear interpolation fitting principle.

[0046] The rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production provided by this invention has the following beneficial effects:

[0047] 1. This invention can perform simple processing on the emulsion in the cold rolling production site, and then quickly measure the acid value of the rolling oil in the emulsion. The test results are highly accurate, making it particularly suitable for use in the field of on-site production to guide the rapid production adjustment of the unit.

[0048] 2. This invention takes into account the development of modern FTIR infrared detection technology. The main inventive point is to address the problem of long demulsification operation time in traditional emulsions by providing a method for quickly obtaining rolling oil from emulsions and efficiently removing iron powder and trace amounts of water. Then, by using FTIR infrared technology to detect pure rolling oil and comparing it with pre-titrated standard samples of different acid values, the acid value of the emulsion can be quickly obtained on-site. This process takes less than 1.5 hours, uses relatively simple equipment, and provides reliable and accurate results, meeting the needs of rapid measurement and adjustment in modern cold rolling mills and demonstrating high practicality.

[0049] 3. The implementation process of this invention is simple, requiring only a certain amount of manpower for manual operation, and the analytical instruments involved in the related work are also mature; it can accurately measure the acid value of rolling oil in cold rolling emulsion, especially reducing the influence of iron powder and moisture brought by on-site emulsion sampling, and the overall operation time can be basically controlled within 1.5 hours, which can quickly obtain the real-time status of the on-site emulsion, guide the on-site unit to quickly adjust the on-site emulsion, and has extremely high practical application value. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating the rapid detection method for the acid value of emulsion used in cold rolling production according to the present invention.

[0051] Figure 2 This is the infrared spectrum of standard sample #1 in this embodiment of the invention;

[0052] Figure 3 This is the infrared spectrum of standard sample #2 in this embodiment of the invention;

[0053] Figure 4 This is the infrared spectrum of standard sample #3 in this embodiment of the invention;

[0054] Figure 5 This is the infrared spectrum of standard sample #4 in this embodiment of the invention;

[0055] Figure 6 This is the infrared spectrum of standard sample #5 in this embodiment of the invention;

[0056] Figure 7 This is the acid value standard curve of an embodiment of the present invention;

[0057] Figure 8 This is the infrared spectrum of the rolling oil sample to be tested in an embodiment of the present invention. Detailed Implementation

[0058] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0059] This invention specifically proposes a rapid detection method for the acid value of rolling oil in cold rolling emulsions. The method yields highly accurate results and is particularly suitable for rapid production adjustments during on-site production guidance. This invention can quickly obtain the rolling oil from the emulsion and efficiently remove iron powder and trace amounts of water. Using FTIR infrared spectroscopy, the acid value of the rolling oil in the emulsion can be quickly determined by comparing it with pre-titrated standard samples of rolling oil with different acid values.

[0060] Combination Figure 1As shown, the present invention provides a rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production, comprising the following steps:

[0061] S1, the cold rolling emulsion to be tested is filtered, and then the organic solvent is mixed and extracted, high-speed centrifugation and negative pressure rotary evaporation are performed in sequence to obtain the rolling oil sample to be tested.

[0062] The process of step S1 is as follows:

[0063] S11, Take the cold-rolled emulsion to be tested and filter it using a filtration device with a microporous filter;

[0064] The cold-rolled emulsion to be tested is taken from various types of cold-rolled emulsions used in on-site production. It is then placed in a device equipped with a microporous filter for filtration to remove contaminants, primarily solid impurities such as iron powder. The sample volume of the cold-rolled emulsion to be tested is 400–800 ml, and the emulsion selected has a concentration of 1.5% or higher. During the filtration process, to ensure filtration efficiency and minimize the impact of residual iron powder on testing accuracy, it is preferable to place the emulsion in a filter device with a micropore diameter of 0.45 μm.

[0065] S12, pour organic solvent into the filtered cold rolling emulsion to be tested, and put it into a high-speed stirrer for stirring and mixing. The rolling oil in the emulsion to be tested enters the organic solvent through extraction.

[0066] This step is the extraction process. An organic solvent is poured into the filtered cold-rolled emulsion and placed in a high-speed stirrer for mixing. At this time, the rolling oil in the emulsion to be tested will enter the organic solvent through the extraction process.

[0067] The organic solvent is selected from a mixture of butanone, dichloroethane, isopropanol and petroleum ether, preferably a mixture of isopropanol and petroleum ether (isopropanol: petroleum ether = 1:2, volume ratio), and the amount of organic solvent added is 40-100 ml. After the organic solvent is poured into the cold rolling emulsion, it is stirred in the laboratory using a high-speed stirrer with a stirring speed ≥8000 rpm for 5-10 min, and then the stirring operation is stopped.

[0068] S13, After the mixture of cold-rolled emulsion and organic solvent to be tested is stopped from stirring, it is immediately centrifuged.

[0069] In this step, after the mixture of cold-rolled emulsion and organic solvent to be tested is stopped from stirring, the mixture is immediately taken with a pipette and placed into multi-tube (e.g., 2-8 tubes) polypropylene centrifuge tubes. The liquid enriched with organic solvent is centrifuged at high speed to accelerate separation. 15 mL of the mixture is added to each tube, and the tubes are centrifuged at high speed for 5-15 minutes.

[0070] S14. Take the clear organic solvent phase from the top of the centrifuged liquid and place it in a hot water bath for negative pressure rotary evaporation to obtain the rolling oil sample to be tested.

[0071] This step is a negative pressure rotary evaporation process, used to evaporate all organic solvents and trace amounts of water. The specific process is as follows: Take 30–90 mL of the supernatant organic solvent phase from the centrifuged liquid and place it in a rotary evaporator. Perform negative pressure rotary evaporation in a hot water bath at 60–85°C, controlling the negative pressure at -640 mm ± 20 mmHg. Evaporation removes the organic solvents and trace amounts of water, yielding the rolling oil sample to be tested.

[0072] S2, prepare standard samples of rolling oil with different acid values;

[0073] This step is the preparation process of standard samples. The preparation process of rolling oil standard samples with different acid values ​​is as follows:

[0074] S21, take the crude oil from the rolling oil used in the preparation of emulsion for the on-site unit, titrate the acid value, and mark it as 1# standard sample;

[0075] S22, take the crude oil from the rolling mill, add different amounts of mineral oil, heat it to mix it thoroughly, and then titrate the acid value. The samples are labeled as standard sample #2, standard sample #3, standard sample #4, and standard sample #5 according to the amount of mineral oil added. The amount of mineral oil added in standard sample #2, standard sample #3, standard sample #4, and standard sample #5 is arranged from low to high.

[0076] A certain amount of mineral oil was added to the above-mentioned rolling oil crude oil sample, heated to 50°C and mixed thoroughly, and then its acid value was titrated and labeled as No. 2 standard sample.

[0077] Add a certain amount of mineral oil to the above-mentioned rolling oil crude oil sample, heat it to 50°C and mix it thoroughly, then titrate its acid value and label it as standard sample #3.

[0078] A certain amount of mineral oil was added to the above-mentioned rolling oil crude oil sample, heated to 50°C and mixed thoroughly. The acid value was then titrated and labeled as standard sample #4.

[0079] Add a certain amount of mineral oil to the above-mentioned rolling oil crude oil sample, heat to 50°C and mix thoroughly, then titrate its acid value and label it as 5# standard sample;

[0080] The mineral oil addition amounts in the above-mentioned standard samples 1#, 2#, 3#, 4#, and 5# are arranged from low to high. Preferably, Kunlun L-HM46 hydraulic oil can be used as the mineral oil in the preparation of these standard samples.

[0081] S3. Infrared spectroscopy is used to detect standard samples of rolling oil with different acid values ​​and samples of rolling oil to be tested, respectively, to obtain the infrared spectra of the corresponding samples, thereby obtaining the standard curve of the acid value of rolling oil, and by comparison, the acid value of the rolling oil in the cold rolling emulsion to be tested is obtained.

[0082] This step involves infrared spectroscopy detection and acid value acquisition, and the specific process is as follows:

[0083] S31. Instrument preparation: Turn on the infrared spectrometer and simultaneously open the high-purity nitrogen valve. Perform the first nitrogen purging for at least 20 minutes until there are no interfering peaks in the infrared spectrometer. The nitrogen flow rate can be controlled at around 30 mL / min.

[0084] S32, Instrument Settings: Open the infrared software and set the infrared spectrometer to scan the blank before each sample scan; the preferred number of scans is "32".

[0085] S33, after scanning the blank, scan the standard samples of rolling oil with different acid values ​​in sequence and save the infrared spectrum. After each sample scan, clean the sample cell used for measurement.

[0086] This step mainly involves obtaining the infrared spectra of standard samples of rolling oil with different acid values:

[0087] First, after scanning the blank, remove the clean sample cell, fill it with standard sample #1, and place it back in the cell holder. Close the top cover and continue purging with nitrogen for 10 minutes. Scan the sample and save the standard spectrum;

[0088] Then, the sample cell used for measurement was cleaned by alternating cleaning with petroleum ether and isopropanol until it was clean; then the No. 2 standard sample was loaded, and the scanning process of the No. 1 standard sample was repeated until standard spectra were obtained for all 5 standard samples.

[0089] S34. Create a standard curve. Open the infrared spectroscopy data processing software, set the path length of the infrared data processing method, and set the peak value of the standard sample to 1710 cm⁻¹. -1The peak height is set at the wavenumber, and the infrared spectra of rolling oil standard samples with different acid values ​​(infrared spectra of standard sample 1 to standard sample 5) are imported in sequence. The acid value of the titrated standard sample is then entered for each standard sample to obtain the standard curve of the rolling oil acid value.

[0090] S35, Standard Curve Analysis: The correlation coefficient of the standard curve for the acid value of rolled oil is calculated using infrared spectroscopy data processing software. If the correlation coefficient reaches 0.995 or higher, the standard curve for the acid value of rolled oil meets the requirements and can be saved for use; otherwise, the rolled oil standard sample should be rescanned or reconfigured.

[0091] S36, Sample analysis: Take out the clean sample cell, put in the rolling oil sample to be tested, put it back into the cell seat, close the top cover, continue to purge with nitrogen, scan the rolling oil sample to be tested, and save the infrared spectrum.

[0092] S37, open the standard curve of rolling oil acid value, and calculate the acid value of the rolling oil in the cold rolling emulsion to be tested according to the linear interpolation fitting principle.

[0093] Example

[0094] The rapid detection method for the acid value of rolling oil in the emulsion used in cold rolling production in this embodiment is as follows:

[0095] (1) Before testing, prepare standard samples of rolling oil with different acid values ​​and obtain a standard curve of rolling oil acid value.

[0096] a. Take an unused crude oil sample from the on-site unit, measure its acid value using the traditional titration method, and find it to be 144.5 mgKOH / g. Then label it as standard sample #1.

[0097] b. Take Kunlun L-HM46 hydraulic oil, and add a certain amount of L-HM46 oil to the above cold-rolled oil sample according to the mass percentage of the rolling oil crude oil 9:1. Heat to 50℃ and mix thoroughly. Then, measure the acid value of the mixture using the traditional titration method. The result is 130.9 mgKOH / g. Then, label it as standard sample #2.

[0098] c. Take Kunlun L-HM46 hydraulic oil, and add a certain amount of L-HM46 oil to the above cold-rolled oil sample according to the mass percentage of the rolling oil crude oil and the oil: 8:2. Heat to 50℃ and mix thoroughly. Then, measure the acid value of the mixture using the traditional titration method. The result is 115.8 mgKOH / g. Then, label it as 3# standard sample.

[0099] d. Take Kunlun L-HM46 hydraulic oil, and add a certain amount of L-HM46 oil to the above cold-rolled oil sample according to the mass percentage of the rolling oil crude oil and the oil: 7:3. Heat to 50℃ and mix thoroughly. Then, measure the acid value of the mixture using the traditional titration method. The result is 101.3 mgKOH / g. Then, label it as 4# standard sample.

[0100] e. Take Kunlun L-HM46 hydraulic oil, and add a certain amount of L-HM46 oil to the above cold-rolled oil sample according to the mass percentage of the rolling oil crude oil 6:4. Heat to 50℃ and mix thoroughly. Then, measure the acid value by conventional titration method. It is 85.3mgKOH / g, and then label it as 5# standard sample.

[0101] Infrared spectroscopy was used to detect standard samples #1, #2, #3, #4, and #5, and the corresponding infrared spectra were obtained. (See [reference needed]). Figures 2-6 As shown.

[0102] Open the infrared spectroscopy data processing software, set the path length of the infrared data processing method, and set the peak value of the analyte to 1710 cm⁻¹. -1 Set the peak height value at the wavenumber. Import the infrared spectra of standard samples 1 to 5 in sequence, and input the acid value of the titrated standard sample for each standard sample to obtain the following result: Figure 7 The standard curve of the rolled oleic acid value is shown, and the correlation coefficient of the standard curve is calculated to be 0.998, which meets the requirements of the correlation coefficient and can be saved for use.

[0103] (2) Secondly, in order to speed up the measurement time of the FTIR infrared spectrometer analysis, the following preparatory work was carried out on the relevant instruments:

[0104] a. Before the experiment, turn on the infrared spectrometer and open the high-purity nitrogen valve at the same time. Control the flow rate to about 30 mL / min. First, purge with nitrogen for 20 minutes until no interfering peaks appear.

[0105] b. Open the auxiliary software of the infrared spectrometer, set the instrument scanning to "scan blank before each sample scan" and set the number of scans to "32"; after scanning the blank, take out the clean sample cell and prepare to load the sample to be tested.

[0106] (3) Preparation of rolling oil samples to be tested

[0107] The following operations were performed inside a cold rolling mill on site:

[0108] The cold-rolled emulsion to be tested was taken from the cold-rolled emulsion currently in use on site, with a total volume of 500 ml. The concentration of the emulsion was measured to be 1.95%.

[0109] The cold-rolled emulsion to be tested was placed in a filter device with a micropore diameter of 0.45 μm to remove iron powder and oil. Then, 60 ml of a mixed organic solvent of isopropanol and petroleum ether (isopropanol: petroleum ether = 1:2, volume ratio) was added to the remaining cold-rolled emulsion to be tested. After simple mixing, the mixture was stirred for 5 min at 10000 rpm with a high-speed stirrer and then stopped.

[0110] Immediately afterwards, use a pipette to take 4 tubes of the mixture of the cold-rolled emulsion and organic solvent to be tested and place them in polypropylene centrifuge tubes. Add 15 ml of liquid to each tube and centrifuge for 10 min on a high-speed centrifuge.

[0111] At this point, the organic solvent in the polypropylene centrifuge tube will extract the rolling oil and accumulate in the upper part of the liquid in the test tube. Take a total of 40 ml of the clear liquid of the upper organic solvent phase in the centrifuge tube and place it in a rotary evaporator in a hot water bath that has been heated to 80°C in the early stage for negative pressure rotary evaporation. The negative pressure is controlled at -640 mmHg. Evaporation removes the organic solvent and trace amount of water. What remains is the rolling oil sample to be tested.

[0112] (4) Take a certain amount of the rolling oil sample obtained in (3) and place it in the sample cell of the FTIR infrared detector. Then, put it back in the cell holder and close the top cover. Scan the sample and save the spectrum. The infrared detection equipment yielded... Figure 8 The infrared spectrum of the rolling oil sample to be tested is shown.

[0113] At the same time, the standard curve is opened, and the software automatically calculates the acid value of the sample to be tested as 108.5 mg KOH / g according to the linear interpolation fitting principle;

[0114] The acid value obtained by the traditional titration acid value measurement method for the rolling oil sample to be tested was 110.8 mgKOH / g. Based on this result, the method developed in this invention has high accuracy. The entire operation process, excluding the preparation of standard samples and instruments, can be controlled within 1 hour and 30 minutes.

[0115] In summary, the implementation process of this invention is simple, requiring only a certain amount of manual operation, and the analytical instruments involved in the related work are mature. This invention can accurately measure the acid value of rolling oil in cold rolling emulsion, and in particular, it can reduce the influence of iron powder and moisture from on-site emulsion sampling. Moreover, the overall operation time can be controlled within 1 hour and 30 minutes, and it can quickly obtain the real-time status of the on-site emulsion, guiding the on-site unit to quickly adjust the on-site emulsion. It has extremely high practical application value.

[0116] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production, characterized in that, Includes the following steps: S1, the cold rolling emulsion to be tested is filtered, and then it is subjected to mixing and extraction with organic solvents, high-speed centrifugation and negative pressure rotary evaporation to obtain the rolling oil sample to be tested. S2, prepare standard samples of rolling oil with different acid values; S3. Infrared spectroscopy is used to detect standard samples of rolling oil with different acid values ​​and samples of rolling oil to be tested, respectively, to obtain the infrared spectra of the corresponding samples, thereby obtaining the standard curve of the acid value of rolling oil, and by comparison, the acid value of the rolling oil in the cold rolling emulsion to be tested is obtained.

2. The rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production according to claim 1, characterized in that, The process of step S1 is as follows: S11, Take the cold-rolled emulsion to be tested and filter it using a filtration device with a microporous filter; S12, pour organic solvent into the filtered cold rolling emulsion to be tested, and put it into a high-speed stirrer for stirring and mixing. The rolling oil in the emulsion to be tested enters the organic solvent through extraction. S13, the mixture of the cold-rolled emulsion to be tested and the organic solvent is immediately centrifuged after stirring is stopped; S14. Take the clear organic solvent phase from the top of the centrifuged liquid and place it in a hot water bath for negative pressure rotary evaporation to obtain the rolling oil sample to be tested.

3. The rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production according to claim 2, characterized in that, In step S11, the sample size of the cold-rolled emulsion to be tested is 400-800 ml, and the cold-rolled emulsion to be tested is selected as an emulsion with a concentration of 1.5% or higher.

4. The rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production according to claim 2, characterized in that, In step S12: The organic solvent is selected from a mixture of butanone, dichloroethane, isopropanol and petroleum ether, and the amount of the organic solvent added is 40-100 ml. The stirring speed is ≥8000 rpm and the stirring time is 5-10 min.

5. The rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production according to claim 2, characterized in that: The centrifugal separation process in step S13 is as follows: Place the mixture into multi-tube polypropylene centrifuge tubes, adding 15 mL of the mixture to each tube, and centrifuge on a high-speed centrifuge for 5–15 min.

6. The rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production according to claim 2, characterized in that, The process of step S14 is as follows: Take 30-90 mL of the clear liquid from the upper organic solvent phase of the centrifuged liquid and place it in a rotary evaporator. Perform negative pressure rotary evaporation in a hot water bath at 60-85℃, with the negative pressure controlled at -640±20 mmHg. Evaporate to remove the organic solvent and trace amounts of water to obtain the rolling oil to be tested.

7. The rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production according to claim 1, characterized in that, In step S2, the preparation process of the rolling oil standard samples with different acid values ​​is as follows: S21, take the crude oil from the rolling oil used in the preparation of emulsion for the on-site unit, titrate the acid value, and mark it as 1# standard sample; S22, take the crude oil from the rolling mill, add different amounts of mineral oil, heat it to mix it thoroughly, and then titrate the acid value. The samples are labeled as standard sample #2, standard sample #3, standard sample #4, and standard sample #5 according to the amount of mineral oil added. The amount of mineral oil added in standard sample #2, standard sample #3, standard sample #4, and standard sample #5 is arranged from low to high.

8. The rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production according to claim 7, characterized in that, The mineral oil used is Kunlun L-HM46 hydraulic oil.

9. The rapid detection method for the acid value of rolling oil in emulsion used in cold rolling production according to claim 1, characterized in that, The specific process of step S3 is as follows: S31. Instrument preparation: Turn on the infrared spectrometer and simultaneously open the high-purity nitrogen valve. Purge with nitrogen for at least 20 minutes until there are no interfering peaks in the infrared spectrometer. S32, Instrument Settings: Open the infrared software and set the infrared spectrometer to scan the blank before each sample scan. S33, after scanning the blank, scan the standard samples of rolling oil with different acid values ​​in sequence and save the infrared spectrum. After each sample scan, clean the sample cell used for measurement. S34. Create a standard curve. Open the infrared spectroscopy data processing software, set the path length of the infrared data processing method, and set the peak value of the standard sample to 1710 cm⁻¹. -1 The peak height is set at the wavenumber, and the infrared spectra of rolling oil standard samples with different acid values ​​are imported in sequence. The acid values ​​of the titrated standard samples are then input to obtain the standard curve of the rolling oil acid value. S35, Standard curve analysis: The correlation coefficient of the standard curve of the rolled oleic acid value is calculated by infrared spectroscopy data processing software. If the correlation coefficient reaches 0.995 or above, the standard curve of the rolled oleic acid value meets the requirements. Otherwise, the emulsion standard sample is rescanned or reconfigured. S36, Sample analysis: Take out the clean sample cell, put in the rolling oil sample to be tested, put it back into the cell seat, close the top cover, continue to purge with nitrogen, scan the rolling oil sample to be tested, and save the infrared spectrum. S37, open the standard curve of rolling oil acid value, and calculate the acid value of the rolling oil in the cold rolling emulsion to be tested according to the linear interpolation fitting principle.

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