A method for accelerating aging of oils and fats

Abstract

The present invention discloses a method for accelerated aging of grease, comprising the following steps: (1) applying oil to one side of a test plate, with the oiled edge 2-3 cm away from the edge of the test plate; sealing the unoiled side of the test plate with tape; (2) measuring the thickness of the oil film on the test plate after oiling; (3) placing the oiled test plate in a constant temperature and humidity test chamber for accelerated aging, wherein the temperature in the constant temperature and humidity test chamber is 45-55° C. and the relative humidity is 35%-45%; and (4) measuring the thickness of the oil film after accelerated aging for a period of time. The method provided by the present invention can effectively accelerate the aging speed of grease on the surface of the test plate. The oil film thickness measurement result after accelerated aging has good parallelism and accurate data, and is consistent with the phosphating micromorphology obtained after phosphating treatment of a test plate with the same oil film thickness obtained by normal placement. The test method is simple and efficient, and is of great significance to engineering and technical personnel in studying the influence of grease on phosphating quality.

Description

Technical Field

[0001] The invention relates to a method for accelerating aging of grease, and belongs to the technical field of test and detection. Background Art

[0002] Annealed automotive steel is oiled before leaving the factory for rust prevention and subsequent stamping. If the steel is unused for an extended period, it can be easily left uncleaned during pre-treatment in the automotive paint shop, resulting in insufficient crystallization of the phosphate film's micromorphology, seriously impacting the corrosion resistance of the automotive sheet. To compare the effect of aging grease from different manufacturers on the phosphated micromorphology of automotive sheet metal after grease aging, and to further understand the compatibility of different grease manufacturers with existing degreasing and phosphating agents, test panels were oiled and then left to stand for a period of time before their surface phosphating properties were compared. However, the evaporation rate of the grease is extremely slow, significantly impacting research efficiency.

[0003] Currently, there are no methods for accelerating grease aging in the literature. While some methods involve baking oiled test panels at high temperatures in a blast drying oven, the grease on the panels evaporates slowly, and the presence of wind on the surface during the test affects the accuracy of the test results, making it difficult to achieve the desired effect. Another method involves continuously blowing the oiled panels with a high-powered blower. While this method is highly efficient, some components in the grease are easily "carried away" by the high-speed airflow, seriously undermining the purpose of the test and the accuracy of the test results. Therefore, finding a method to accelerate grease aging is crucial. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for accelerating aging of grease, which uses a constant temperature and humidity chamber and a high temperature and low humidity test method to accelerate the aging of grease on the surface of a test plate. After accelerated aging, the oil film thickness measurement result has good parallelism and accurate data.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A method for accelerated aging of grease comprises the following steps: (1) applying oil to one side of a test plate, with the oiled edge being 2-3 cm away from the edge of the test plate; and sealing the unoiled side of the test plate with tape; (2) measuring the thickness of the oil film on the test plate after oiling; (3) placing the test plate in a constant temperature and humidity test chamber for accelerated aging, wherein the temperature in the constant temperature and humidity test chamber is 45-55°C and the relative humidity is 35%-45%; and (4) measuring the thickness of the oil film after accelerated aging for a period of time.

[0007] The present invention chooses to oil the test plate on one side because if both sides are oiled, the oil film thickness on the side in contact with the constant temperature and humidity test box bracket will decrease faster during the high temperature and low humidity accelerated aging process.

[0008] When applying oil in the present invention, the oiling edge is 2-3 cm away from the edge of the test plate and does not cover the entire surface of the test plate. The reason is as follows: after the single-sided oiled test plate undergoes accelerated aging at high temperature and low humidity, due to the "oil film traction effect", the oil film thickness on the test plate surface gradually decreases as the distance from the geometric center of the test plate increases, causing measurement errors in the accelerated aging results of the oil; while controlling the oiling edge to 2-3 cm away from the edge of the test plate, the oil will not flow to the edge of the sample and then reach the back of the sample, thereby ensuring the accuracy of the oil film thickness measurement.

[0009] The unoiled side of the test plate is sealed with tape to prevent rust from forming on the unoiled side during the test and spreading to the oiled side of the test plate, which would affect the subsequent measurement results of the oil film.

[0010] In the method for accelerated aging of oils and fats of the present invention, the test plate in step (1) is square in shape, with a side length of 200 mm to 220 mm.

[0011] The method for accelerating aging of grease described in the present invention, wherein the thickness of the oil film formed by the oil coating in step (1) is 0.2μm-4.3μm. When grease is in a hot environment, its fluidity increases, and the effect of the oil film flow on the oil film thickness will mislead the measurement result of the oil film thickness due to grease aging, so the oil film thickness should be as small as possible. The oil film coating and oil film thickness control on the sample surface can be performed by, but is not limited to, a wire rod, the length of the wire rod is 16cm-18cm, and the pattern formed by the oil coating on the wire rod is the same or similar to the shape of the test plate. Generally, the sample with an oil film thickness of 0.2μm-1.4μm comes from the test plate newly produced on the production line, while the oil film thickness of 1.4μm-4.3μm can be controlled by a common wire rod on the market, and the common wire rod specifications are 1.5μm, 2μm, 3μm, and 4μm. The specific method is to drop grease on the sample surface and use a wire rod of a certain specification to scrape the grease on the sample surface to obtain the oil film thickness corresponding to the corresponding wire rod specification.

[0012] In the method for accelerated aging of grease of the present invention, the process of measuring the oil film thickness in step (2) is as follows: measuring the oil film thickness at two or more locations on the surface of the oiled test plate and taking the average value.

[0013] In the method for accelerated aging of oils and fats of the present invention, the distance between the oil film thickness measurement position in step (2) and the geometric center of the test plate is 5 cm to 10 cm.

[0014] In the method for accelerated aging of oils and fats of the present invention, the accelerated aging time in step (4) is 23h-25h.

[0015] In the method for accelerated aging of oils and fats described in the present invention, the oil film thickness measurement position in step (4) is the same as that in step (2).

[0016] The technical solution of this invention works as follows: Since the decomposition temperature of grease generally does not exceed 60°C, treating oil-coated test panels at a higher test temperature and a lower relative humidity than a constant temperature and humidity chamber can tolerate accelerates the volatilization of grease components from the panels' surfaces. Extensive testing has shown that when the oil film thickness obtained by treating the panels at 45-55°C and 35%-45% relative humidity for a certain period of time matches that obtained by naturally aging for a certain period of time, the microcrystalline morphology of the two panels remains consistent after phosphating.

[0017] The beneficial effects of adopting the above technical solution are: the method of the present invention can effectively accelerate the aging speed of grease on the surface of the test plate, the oil film thickness measurement results have good parallelism, the data are accurate, and are consistent with the phosphating micromorphology obtained after phosphating treatment of a test plate with the same oil film thickness placed normally. The test method is simple and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the microscopic appearance of the phosphate film of the grease-coated 1 test plate without aging phosphate treatment;

[0019] Figure 2 It is the microscopic appearance of the phosphate film of the grease-coated test plate after natural aging and phosphate treatment;

[0020] Figure 3 It is the microscopic morphology of the phosphate film of the grease-coated test plate 1 after accelerated aging and phosphating treatment;

[0021] Figure 4 This is the microscopic appearance of the phosphate film of the grease-coated 2 test plate without aging and phosphate treatment;

[0022] Figure 5 It is the microscopic appearance of the phosphate film of the grease-coated 2 test plate after natural aging and phosphating treatment;

[0023] Figure 6 This is the microscopic morphology of the phosphate film on the grease-coated test plate 2 after accelerated aging and phosphating treatment.

[0024] Figure 7 This is the microscopic appearance of the phosphate film of the grease-coated 3 test plate without aging and phosphate treatment;

[0025] Figure 8 It is the microscopic appearance of the phosphate film of the grease-coated 3 test plate after natural aging and phosphating treatment;

[0026] Figure 9 This is the microscopic morphology of the phosphate film on the grease-coated test panel 3 after accelerated aging and phosphating treatment. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions, and advantages of the invention examples more clear, the following will provide a clear and complete description of the technical solutions in the invention examples in conjunction with the accompanying drawings. Obviously, the described examples are only a small part of the invention examples, not all of the invention examples. Based on the examples in the invention examples, all other examples obtained by ordinary technicians in this field without creative work are within the scope of protection of the invention.

[0028] Select a certain brand of automotive annealed plate test plate and a certain manufacturer's grease to conduct grease accelerated aging test. The specific operation is as follows:

[0029] Example 1

[0030] (1) The test board is a newly produced test board on the production line, with a size of 200mm×200mm. A wire rod is used to apply oil film to the surface of the sample and control the oil film thickness. The length of the wire rod is 16cm, and the thickness of the oil film on the test board is controlled to about 0.2μm. The pattern formed by the oiling of the wire rod is the same as the shape of the test board, and the side length of the pattern formed by the oiling is 180mm; the oiling edge is 2cm away from the edge of the test board; the unoiled side of the test board is sealed with tape;

[0031] (2) Select three locations on the surface of the oiled test plate. The distance between the selected three locations and the geometric center of the test plate is 5 cm. Use an oil film thickness gauge to measure the oil film thickness. The average value of the oil film thickness is avg(H) = (H1 + H2 + H3) / 3. The measurement results are shown in Table 1.

[0032] (3) Place the oiled test panel in a constant temperature and humidity test chamber for accelerated aging. The temperature of the constant temperature and humidity test chamber is 45°C and the relative humidity is 35%;

[0033] (4) After 23 h of accelerated aging, the oil film thickness was measured. The measurement positions were the same as those in step (2), and were recorded as h1, h2, and h3, respectively. The average value of the oil film thickness was taken, i.e., avg(h) = (h1 + h2 + h3) / 3. The measurement results are shown in Table 1.

[0034] Comparative Example 1

[0035] The difference from Example 1 lies in the aging method. This comparative example subjected the oil-coated test panels to a natural aging test, allowing the grease film thickness to naturally decrease to the thickness corresponding to accelerated aging. This test verifies the effects of accelerated and natural aging on the surface quality of the test panels. The results are shown in Table 1.

[0036] Table 1 Oil film thickness of oil-coated test panels after aging in different aging methods

[0037]

[0038] The effect of grease aging on the surface quality of the test panel is mainly reflected in the phosphating ability of the automotive panel surface. Therefore, the micromorphology of the phosphating film is used to evaluate the effect of grease aging on the surface quality of the test panel.

[0039] The oil-coated test panels after aging in different aging methods were treated with the same degreasing and phosphating process of a certain manufacturer 1. The surface of the test panels after phosphating was observed using a field emission scanning electron microscope. The results are shown in Figures 1 to 3 .

[0040] Figure 1 The results show that the grease and the degreasing agent used in the test have a good match and can completely remove the grease on the test plate surface. The phosphating crystals are uniform, dense and granular, with a crystal size range of 2-8μm.

[0041] Figure 2 and Figure 3 The results show that: for the test plate coated with grease 1, the thickness of the residual grease film on the surface is similar after natural aging and accelerated aging. After degreasing and phosphating of the same batch, it is found that there are large uncrystallized areas in the microscopic phosphating crystals, and the crystal size ranges from 2 to 12 μm, with different lengths. The morphology of the phosphating crystals obtained by different grease aging methods is similar, indicating that the accelerated grease aging method provided by the present invention is equivalent to the effect of natural aging of the grease on the degreasing and phosphating quality of the test plate.

[0042] Example 2

[0043] (1) The test plate has a size of 210 mm × 210 mm. A wire rod is used to apply oil to one side of the test plate. The length of the wire rod is 17 cm. The thickness of the oil film on the test plate is controlled to about 2.3 μm. The pattern formed by the wire rod is similar to the shape of the test plate. The side length of the pattern formed by the oiling is 185 mm. The oiling edge is 2.5 cm away from the edge of the test plate. The unoiled side of the test plate is sealed with tape.

[0044] (2) Select three locations on the surface of the oiled test plate, each 7.5 cm away from the geometric center of the test plate. Use an oil film thickness gauge to measure the oil film thickness. The average value of the oil film thickness is avg(H) = (H1 + H2 + H3) / 3.

[0045] (3) Place the oiled test panel in a constant temperature and humidity test chamber for accelerated aging. The temperature of the constant temperature and humidity test chamber is 50°C and the relative humidity is 40%;

[0046] (4) After 24 h of accelerated aging, measure the oil film thickness at the same measurement locations as in step (2), recording them as h1, h2, and h3, respectively. The average value of the oil film thickness is avg(h) = (h1 + h2 + h3) / 3. The measurement results are shown in Table 2.

[0047] Comparative Example 2

[0048] This comparative example differs from Example 2 in the aging method. This comparison experiment used a natural grease aging method on the oiled panels, allowing the grease film thickness to naturally decrease to the thickness corresponding to accelerated aging. This approach verified the effects of accelerated and natural grease aging on the panel surface quality. The measurement results are shown in Table 2.

[0049] Table 2 Oil film thickness of oil-coated test panels after aging in different aging methods

[0050]

[0051] The effect of grease aging on the surface quality of the test panel is mainly reflected in the phosphating ability of the automotive panel surface. Therefore, the micromorphology of the phosphating film is used to evaluate the effect of grease aging on the surface quality of the test panel.

[0052] The oil-coated test panels after aging in different aging methods were treated with the same degreasing and phosphating process of a certain manufacturer 2. The surface of the test panels after phosphating was observed using a field emission scanning electron microscope. The results are shown in Figures 4 to 6 .

[0053] Figure 4 The results show that the grease and the degreasing agent used in the test have a good match and can completely remove the grease on the test plate surface. The phosphating crystals are uniform and dense, in the shape of short rods, and the crystal size ranges from 2 to 6 μm.

[0054] Figure 5 and Figure 6 The results show that after natural aging and accelerated aging, the thickness of the residual grease film on the surfaces of the two test plates coated with grease is similar. After degreasing and phosphating of the same batch, it is found that there are large uncrystallized areas in the microscopic phosphating crystals, and the crystal sizes range from 1 to 30 μm, with different lengths. The morphologies of the phosphating crystals obtained by different grease aging methods are similar, indicating that the accelerated grease aging method provided by the present invention is equivalent to the effect of natural aging of the grease on the degreasing and phosphating quality of the test plates.

[0055] Example 3

[0056] (1) The test plate has a size of 220 mm × 220 mm. A wire rod is used to apply oil to one side of the test plate. The length of the wire rod is 18 cm. The thickness of the oil film on the test plate is controlled to about 4.3 μm. The pattern formed by the wire rod is similar to the shape of the test plate. The side length of the pattern formed by the oiling is 190 mm. The oiling edge is 3.0 cm away from the edge of the test plate. The unoiled side of the test plate is sealed with tape.

[0057] (2) Select three locations on the surface of the oiled test plate, with the distance from the geometric center of the test plate to each location being 10.0 cm. Use an oil film thickness gauge to measure the oil film thickness, and take the average value of the oil film thickness, i.e., avg(H)=(H1+H2+H3) / 3;

[0058] (3) Place the oiled test panel in a constant temperature and humidity test chamber for accelerated aging. The temperature of the constant temperature and humidity test chamber is 55°C and the relative humidity is 45%;

[0059] (4) After 25 h of accelerated aging, measure the oil film thickness at the same measurement locations as in step (2), recording them as h1, h2, and h3, respectively. The average value of the oil film thickness is avg(h) = (h1 + h2 + h3) / 3. The measurement results are shown in Table 3.

[0060] Comparative Example 3

[0061] This comparative example differs from Example 3 in the aging method. This comparison experiment used a natural aging method on the oiled panels, allowing the grease film thickness to naturally decrease to the thickness corresponding to accelerated aging. This allowed the effects of accelerated and natural aging on the surface quality of the panels to be verified. The measurement results are shown in Table 3.

[0062] Table 3 Oil film thickness of oil-coated test panels after aging in different aging methods

[0063]

[0064] The effect of grease aging on the surface quality of the test panel is mainly reflected in the phosphating ability of the automotive panel surface. Therefore, the micromorphology of the phosphating film is used to evaluate the effect of grease aging on the surface quality of the test panel.

[0065] The oil-coated test panels after aging in different aging methods were treated with the same degreasing and phosphating process of a certain manufacturer 3. The surface of the test panels after phosphating was observed using a field emission scanning electron microscope. The results are shown in Figures 7 to 9 .

[0066] Figure 7 The results show that the grease and the degreasing agent used in the test have a good match and can completely remove the grease on the test plate surface. The phosphating crystals are uniform and dense, in the shape of short rods, and the crystal size ranges from 2 to 6 μm.

[0067] Figure 8 and Figure 9The results show that: for the test panels coated with grease 3, the thickness of the residual grease film on the surface is similar after natural aging and accelerated aging. After degreasing and phosphating the same batch, it is found that microscopic phosphating crystals have uncrystallized areas, and the crystal size ranges from 1 to 10 μm, with different lengths. The morphology of the phosphating crystals obtained by different grease aging methods is similar, indicating that the accelerated grease aging method provided by the present invention is equivalent to the effect of natural aging of the grease on the degreasing and phosphating quality of the test panels.

[0068] In summary, the grease accelerated aging method provided by the present invention can be used to evaluate the effect of grease aging on the quality of the phosphate film after degreasing and phosphating of the test panels, and the measurement results are equivalent to natural aging.

[0069] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for accelerating aging of oils and fats, characterized in that: The method comprises the following steps: (1) applying oil to one side of the test plate, with the oiling edge being 2-3 cm away from the edge of the test plate; and sealing the unoiled side of the test plate with tape; (2) measuring the thickness of the oil film on the test plate after oiling; (3) placing the oiled test plate in a constant temperature and humidity test chamber for accelerated aging, wherein the temperature in the constant temperature and humidity test chamber is 45-55°C and the relative humidity is 35%-45%; and (4) measuring the thickness of the oil film after accelerated aging for a period of time; The test plate in step (1) is square, with a side length of 200 mm to 220 mm, and the pattern formed by the oiling is the same as or similar to the shape of the test plate; the thickness of the oil film formed by the oiling is 0.2 μm to 4.3 μm; The process of measuring the oil film thickness of the test plate in step (2) is as follows: on the surface of the test plate after oiling, select two or more positions to measure the oil film thickness and take the average value; the oil film thickness measurement position is 5 cm to 10 cm away from the geometric center of the test plate; The accelerated aging time in step (4) is 23h-25h; The oil film thickness measurement position in step (4) is the same as that in step (2).

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