Characterization method for surface layer of black wire

Abstract

Provided is a characterization method for a surface layer (100) of a black wire. The characterization method comprises a step of measuring the compound content of the surface layer (100), and further comprises the steps of measuring the thickness, phase and carbon content of the surface layer (100). The step of measuring the compound content of the surface layer (100) comprises: weighing a black wire sample, and recording the weight M1 of the black wire sample; subjecting the black wire sample to alkali boiling, soaking the black wire sample in an alkali liquor, heating same to a boiling state, and boiling same for 5-30 min; cleaning, drying and cooling the sample, which has been subjected to alkali boiling, and weighing same to obtain a weight M2; and calculating the compound content of the surface layer (100) of the black wire by means of a weight loss method. In addition, an ion beam is utilized to cut a cross section of the black wire sample so as to form a cross-section slice sample, and the cross-section slice sample is placed in an electron microscope to measure the thickness of the surface layer (100) and the phase of the surface layer (100). The characterization method can comprehensively characterize the characteristics of the surface layer (100) of a black wire, and measurement results are accurate, are good in terms of repeatability and can be used for guiding a drawing process.

Description

A method for characterizing the surface layer of black silk Technical Field

[0001] The present invention relates to the technical field of tungsten-molybdenum wire detection methods, and in particular to a method for characterizing a black wire surface layer. Background Art

[0002] Tungsten and molybdenum materials undergo multiple heating and drawing processes from billet to thick wire and finished filament. The specific process is as follows: 1) The wire passes through a high-temperature rapid annealing furnace; 2) The wire surface is oxidized at high temperature; 3) It passes through graphite emulsion, and the oxidized surface layer is coated with graphite emulsion, forming the tungsten wire surface layer; 4) It passes through a die for the next drawing step. As can be seen from the above, when passing through the drawing die, the wire surface needs to be coated with a lubricant (such as graphite emulsion) and annealed at a certain temperature to ensure smooth drawing. During the drawing process, the high-temperature annealing treatment oxidizes the surface of the tungsten and molybdenum wires and adheres to the graphite emulsion, forming a black surface layer. The wire is what the industry calls "black wire." This black wire surface layer contains W, C, O, and a series of compounds formed by these elements.

[0003] The characterization of the black surface layer formed on the surface of the black wire is very important for reducing die loss and allowing the wire to be drawn smoothly. Direct drawing of white wire without annealing and coating with a lubricating layer will cause great loss of wire and is difficult to process. Therefore, in the wire drawing process, the surface oxidation of tungsten and molybdenum wires and the performance evaluation and content determination of the surface layer formed are particularly meaningful for guiding the wire drawing process.

[0004] In the prior art, the surface layer of black silk is typically characterized by electron microscopy, resulting in surface morphology images such as those shown in Figures 1-2. However, there is no corresponding quantitative test method for determining the content of compounds on the black silk surface. Therefore, those skilled in the art urgently need to develop a method for determining the content of substances on the surface of black silk to obtain information about the surface layer.

[0005] Summary of the Invention

[0006] In order to solve the deficiencies of the prior art mentioned in the above background technology, the present invention provides a method for characterizing the surface layer of black silk, and its technical solution is as follows:

[0007] The method for characterizing the surface layer of black silk comprises the steps of alkali boiling to determine the content of compounds in the surface layer, wherein the process of the alkali boiling to determine the content of compounds in the surface layer is as follows:

[0008] Weigh the black silk sample and record its weight M1;

[0009] The black silk sample is subjected to alkali boiling treatment: the black silk sample is immersed in an alkali solution, heated to boiling and boiled for 5 to 30 minutes; wherein the alkali solution is one of a NaOH solution and a KOH solution or a mixture of the two, and the mass fraction thereof is 15% to 30%;

[0010] After washing, drying and cooling the sample after alkali boiling, weigh it to obtain the weight M2;

[0011] The compound content data of the black silk surface layer was obtained by weight loss method.

[0012] In one embodiment, the calculation formula for the compound content of the black silk surface layer is: compound content = (M1-M2)÷M1×100%.

[0013] In one embodiment, the surface color of the sample after alkali boiling and drying and cooling is observed to judge the removal of the surface layer of the sample; wherein, the surface of the sample is silvery white, indicating that the surface layer is fully removed and no compounds remain; the surface of the sample is yellowish brown and / or dark blue, indicating that the surface layer is not fully removed and compounds remain.

[0014] In one embodiment, before the step of alkali boiling to determine the content of surface layer compounds, carbon content is determined; wherein, a carbon-sulfur analyzer is used to measure the carbon content on the surface of the black silk sample.

[0015] In one embodiment, before the alkali boiling step of determining the content of the surface layer compounds, a phase structure determination step of the black silk surface layer is performed; in the phase structure determination step, the cross section of the black silk is cut to form a cross-sectional thin slice sample, and then the cross-sectional thin slice sample is placed in a scanning electron microscope and a transmission electron microscope to obtain characterization information; wherein, the characterization information includes one or more of the thickness information of the black silk surface layer, the trend information of the carbon content, oxygen content and matrix material content from the black silk surface to its matrix, the elemental distribution of carbon, oxygen and matrix material, and the phase structure information of the compounds on the black silk surface layer.

[0016] In one embodiment, an ion beam is used to cut the cross section of the black wire.

[0017] In one embodiment, after the alkali boiling step of determining the content of the surface layer compound, a sample surface layer observation step is performed; in the sample surface layer observation step, the sample is placed on a scanning electron microscope to obtain the sample surface profile roughness information and / or surface groove defect conditions.

[0018] In one embodiment, during the alkali boiling treatment, the amount of the alkali solution used is based on the amount that can immerse the black silk sample.

[0019] In one embodiment, during the cleaning process, the sample is first cleaned with water, then immersed in anhydrous ethanol for ultrasonic cleaning for 10 to 20 minutes, and then cleaned with water again; and / or, during the drying process, the sample is placed at 50 to 150° C. and dried for 30 to 90 minutes.

[0020] In one embodiment, the carbon content is measured with an accuracy of ppm.

[0021] Based on the above, compared with the prior art, the characterization method of the black silk surface layer provided by the present invention has the following beneficial effects:

[0022] The method of the present invention can quantitatively measure the compound content in the surface layer of black silk, the measurement result is accurate and has good repeatability, and the measurement result can be used to guide the wire drawing process.

[0023] Other features and beneficial effects of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The objectives and other beneficial effects of the present invention can be achieved and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work. The positional relationships described in the drawings in the following description are based on the directions of the components drawn in the diagrams, unless otherwise specified.

[0025] Figure 1 is a physical picture of the surface morphology of black silk;

[0026] FIG2 is a partial enlarged view of FIG1 ;

[0027] FIG3 is a surface morphology of the wire sample after the surface layer is fully removed;

[0028] FIG4 is a first diagram of the surface morphology of the wire sample after the surface layer of the wire sample is not fully removed;

[0029] FIG5 is a second diagram of the surface morphology of the wire sample after the surface layer is not fully removed;

[0030] FIG6 is a scanning electron microscope image of a cross section of a black silk sample obtained by cutting in Example 1;

[0031] FIG7 is a partial enlarged view of the surface layer of the cross section of the black silk sample in FIG6 ;

[0032] FIG8 is a scanning electron microscope image of the surface layer profile of the cross section of the black silk sample in FIG6 at different magnifications;

[0033] FIG9 is a schematic diagram of the surface layer thickness measurement site of the black silk sample cross section in Example 1;

[0034] FIG10 is a scanning electron microscope image of a cross section of a black silk sample in Example 1, obtained by line scanning from the surface of the black silk to the substrate;

[0035] FIG11 is a graph showing the change in carbon, oxygen, and matrix material content from the surface of the black wire to the matrix of the cross section of the black wire sample in FIG10 ;

[0036] FIG12 is a diagram showing the element distribution of carbon, oxygen, and matrix materials from the surface of the black wire to its matrix in a cross section of a black wire sample in Example 1;

[0037] FIG13 is a transmission electron microscopy morphology of the surface layer of the cross section of the black silk sample in Example 1;

[0038] FIG14 is a lattice diffraction spectrum obtained by Fourier transforming the substance at the box mark in FIG13 .

[0039] Figure symbols: 100 surface layer, 200 substrate. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the embodiments 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 drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meanings as those generally understood by ordinary technicians in the field to which the present invention belongs, and should not be understood as limiting the present invention; it should be further understood that the terms used in the present invention should be understood to have meanings consistent with the meanings of these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined as such in the present invention.

[0042] The present invention provides an operation example of a method for characterizing the surface layer of black silk as follows:

[0043] The detection method comprises the following steps:

[0044] Step 1: Carbon content determination steps:

[0045] A conventional carbon-sulfur analyzer was used to measure the carbon content on the surface of the black silk sample, and the measurement results were accurate to ppm.

[0046] Step 2: Determination of the physical structure of the black silk surface layer:

[0047] The cross section of the black silk is cut using an ion beam to form a cross-sectional thin sample, which is then placed in a scanning electron microscope and a transmission electron microscope to obtain characterization information; wherein the characterization information includes one or more of the following: the thickness of the black silk surface layer; the trend of changes in the carbon content, oxygen content, and matrix material content from the black silk surface to its matrix; the elemental distribution information of carbon, oxygen, and matrix material; and the phase structure information of the compound on the black silk surface layer. Specifically:

[0048] (1) Black silk surface thickness information

[0049] The cross-sectional thin slice sample was placed in a scanning electron microscope. The surface of the black wire had a surface layer that was obviously different from the tungsten matrix. The surface layer profile of the entire cross section was photographed using a combination of high and low magnifications. The surface layer thickness was measured using conventional measurement software, and the surface layer thickness distribution of the entire cross section could be statistically obtained.

[0050] (2) Information on the changing trend of carbon, oxygen and matrix material content from the surface of the black wire to its matrix:

[0051] This information can be obtained by placing the cross-sectional thin-section sample in a scanning electron microscope equipped with an energy spectrometer and performing a line scan of the C, O, and W elements from the black wire surface to the matrix along the radial direction of the cross section using the energy spectrometer.

[0052] (3) Phase structure information of compounds in the black silk surface layer:

[0053] The cross-section thin slice sample was placed in a transmission electron microscope, and the element distribution information of carbon, oxygen and matrix material in the surface layer was obtained by energy dispersive spectrometer. The phase structure analysis was performed on the gray-black part and the gray-white part of the surface layer. The phase structure analysis process was as follows: the surface layer morphology image and high-resolution image were taken by transmission electron microscope, and the high-resolution image was Fourier transformed to obtain the lattice diffraction spectrum. The above diffraction spectrum was combined with the obtained second phase element composition information, and the phase structure corresponding to each diffraction spectrum was obtained by calibrating and comparing the phase cards of the corresponding substances. 。

[0054] It should be noted that two types of cross-sectional thin-section samples are preferably used for separate testing. The sample used to determine the thickness of the black silk surface layer, the carbon content, oxygen content, and the trend of matrix material content from the black silk surface to its matrix is ​​obtained by argon ion beam cutting; the sample used to determine the elemental distribution and phase structure of the compounds in the black silk surface layer is obtained by focused ion beam cutting. That is, the sample slices used for scanning electron microscopy testing are cut with an argon ion beam, while the sample slices used for transmission electron microscopy testing are cut with a focused ion beam.

[0055] Step 3: Alkali boiling to determine the content of surface compounds. The process is as follows:

[0056] (1) Alkali boiling: weigh the black silk sample and record the original weight M1 of the sample. Immerse the black silk sample in alkali solution and start timing after heating to boiling. Boil for 5 to 30 minutes. The amount of alkali solution used is based on the amount of alkali solution that can immerse the black silk sample. The mass fraction of the alkali solution is 15% to 30%.

[0057] (2) After alkali boiling is completed, remove the alkali solution and clean the sample;

[0058] (3) After drying and cooling the sample, weigh it to obtain the weight M2;

[0059] (4) Calculate the compound content on the wire surface, and the calculation formula is:

[0060] Compound content (%) = (sample weight before treatment M1 - sample weight after drying M2) ÷ sample weight before treatment M1 × 100%.

[0061] (5) Observe the color of the surface of the wire sample after alkali boiling to assist in evaluating the surface layer of the wire; wherein the evaluation method is:

[0062] 1) The surface of the sample is silvery white (silvery white is the color of tungsten and molybdenum metals themselves), indicating that the surface layer has been fully removed, that is, no compounds remain on the surface. As shown in FIG3 , when the alkali boiling process is able to fully remove the surface layer, the surface layer of the black wire is removed, and the wire sample exhibits its own silvery white color, forming a white wire, indicating that no compounds remain on the surface.

[0063] 2) The surface of the sample is blue-black, indicating that the surface layer has not been fully removed, that is, there are residual compounds on the surface; as shown in Figure 4, when the alkali boiling process cannot fully remove the surface layer, a lot of black substances (such as WO 2.9 The surface of the wire is blue-black.

[0064] 3) The surface of the sample is yellow-brown, indicating that the surface layer has not been fully removed, that is, compounds remain on the surface. As shown in FIG5 , when the alkali boiling process cannot fully remove the surface layer, substances such as WO2 that are difficult to remove remain on the surface of the sample. The color of WO2 is yellow-brown, and the surface of the wire is yellow-brown, indicating that compounds remain on the surface.

[0065] Step 4: Observation steps of sample surface layer:

[0066] In the sample surface layer observation step, the sample is placed on a scanning electron microscope to obtain the sample surface profile roughness information and / or surface groove defect conditions.

[0067] Among them, the following are emphasized:

[0068] During the process of surface oxidation annealing and subsequent lubricant (graphite emulsion) coating of the wire, compounds formed on the wire surface include tungsten oxide, graphite, and other substances. Aside from tungsten oxide, other impurities in the lubricant (e.g., graphite) are present at the ppm level, while the tungsten oxide formed is over 10 times greater than the other impurities. Therefore, since the other impurities in the surface layer differ from tungsten oxide by at least an order of magnitude, their content will not significantly affect the tungsten oxide content. The weight loss method can be used to calculate the percentage of surface layer compounds in the wire, which can be used to balance the percentage of oxides in the wire.

[0069] Preferably, in step 1, the weight M1 of the sample before processing is accurate to 0.0001 g; preferably, in step 1, the wire sample with a diameter of 0.1 mm to 0.5 mm is weighed 1 to 3 g (accurate to 0.0001 g), and the wire sample with a diameter of less than 0.1 mm is weighed 0.8 to 2 g.

[0070] Preferably, in step 2, after alkali boiling, the alkali solution is poured out, the sample is first cleaned with water, and then the sample is placed in anhydrous ethanol and ultrasonically cleaned for 10 to 20 minutes, the anhydrous ethanol is poured out, and the sample is then cleaned with water.

[0071] Preferably, in step three, the sample is placed in an oven at 50-150° C. for 30-90 minutes, then taken out of the oven, and the sample is weighed after cooling to obtain a weight M2; wherein the weight M2 of the sample after drying is accurate to 0.0001 g.

[0072] In summary, the present invention combines the following aspects to evaluate the surface layer of the wire:

[0073] 1. Carbon content of black silk surface layer:

[0074] The main element of graphite emulsion, a lubricant commonly used in the drawing process, is carbon. Measuring the carbon content in the surface layer of the black wire sample can be used to evaluate and quantify the amount of graphite emulsion remaining after applying the graphite emulsion to tungsten or molybdenum wire and then hot-drawing it through a die, thereby understanding the coating effect.

[0075] 2. Compound content of black silk surface layer:

[0076] Since most of the compounds in the surface layer are tungsten oxide (such as WO3, etc., and WO 2.02 ~WO 2.9 Tungsten trioxide accounts for a larger proportion). Tungsten oxide will react with sodium hydroxide (sodium hydroxide, potassium hydroxide strong base), while tungsten will not. By taking advantage of this property, the surface layer is peeled off by alkali boiling, and the content of the surface compound can be measured by the weight loss law.

[0077] 3. Black wire surface layer size and structure information: including the thickness of the black wire surface layer, the changes in carbon content, oxygen content and matrix material content from the black wire surface to its matrix, the elemental distribution of carbon, oxygen and matrix material, and the phase structure information of the compounds in the black wire surface layer.

[0078] Among them, the thickness of the black wire surface layer is related to the subsequent wire drawing effect. If the surface layer is too thick, the friction with the die during wire drawing increases, resulting in high die loss. If the surface layer is too thin, it cannot protect the tungsten wire matrix and is likely to scratch the internal tungsten wire. Therefore, obtaining information on the thickness of the black wire surface layer is beneficial for guiding the design and adjustment of the subsequent wire drawing process. Since the tungsten wire is first oxidized at high temperature and then coated with graphite emulsion, the changes in carbon content, oxygen content, and matrix material content from the black wire surface to its matrix, as well as the phase structure information of the surface layer compound, can also reflect the effect of the oxidation coating, which is also beneficial for guiding the design and adjustment of the subsequent wire drawing process.

[0079] 4. Observation of the surface morphology of the wire after alkali boiling:

[0080] Combined with the surface morphology and surface layer content test of the wire after alkali boiling, it is possible to determine whether the surface layer has been fully removed during the alkali boiling process, thereby judging whether the determination of the compound content is accurate, and to judge which compounds remain on the surface layer of the wire. For example, if the wire is yellowish-brown after alkali boiling, it proves that there is WO2 on the surface layer of the wire. This substance is difficult to remove and is not conducive to the wire drawing process.

[0081] It should be noted that:

[0082] The "black wire" described herein is a base wire or alloy base wire containing tungsten and / or molybdenum, which is formed after the surface is coated with lubricant and annealed and drawn. Since the drawing process is a hot working process in an air environment, at this temperature and atmosphere, the surface of the base wire is oxidized and adheres to the lubricant, and the surface is blackened, so it is called black wire. Among them, "base wire or alloy base wire containing tungsten and / or molybdenum" refers to tungsten wire, molybdenum wire, tungsten alloy wire, molybdenum alloy wire, tungsten-molybdenum alloy wire, that is, the "base material" described herein corresponds to tungsten, molybdenum, tungsten alloy, molybdenum alloy, tungsten-molybdenum alloy; among them, tungsten alloy wire refers to alloy wire of tungsten and other metal elements; molybdenum alloy wire refers to alloy wire of molybdenum and other metal elements; tungsten-molybdenum alloy wire refers to alloy wire of molybdenum, tungsten, or alloy wire of molybdenum, tungsten and other metal elements.

[0083] When there is no surface layer left on the wire surface, the base material itself appears silvery white, and is therefore known as "white wire" in the industry;

[0084] The carbon-sulfur analyzer used is an existing detection device, and its working principle for detecting carbon content will not be repeated here.

[0085] The carbon content determination in step 1 and the phase structure determination in step 2 can be performed before alkali boiling. The two steps of carbon content determination and phase structure determination can be swapped, regardless of the order.

[0086] The present invention also provides the following embodiments and comparative examples:

[0087] 1. Alkali cooking process parameters of the embodiment and comparative example are shown in Table 1 below:

[0088] Table 1

[0089] Wherein, the specific measurement process of Example 1 is:

[0090] Selected sample specifications: black wire sample with a diameter of 0.4mm (the base material is tungsten wire):

[0091] Step 1: Carbon content determination step: Use a conventional carbon-sulfur analyzer to measure the carbon content on the surface of the black silk sample, and the measurement result is accurate to ppm.

[0092] Step 2: Determination of the physical structure of the black silk surface layer 100:

[0093] The cross section of the black wire is cut by an ion beam to form a cross-sectional thin slice sample, as shown in FIG6 . The cross-sectional thin slice sample is placed in a scanning electron microscope and a transmission electron microscope to obtain the thickness information of the black wire surface layer 100, the trend information of the change of the carbon, oxygen, and matrix material (tungsten) content from the black wire surface to its matrix 200, and the phase structure information of the compound in the black wire surface layer 100.

[0094] The specific information acquisition process is as follows:

[0095] (1) Thickness information of black silk surface layer 100

[0096] The cross-sectional thin slice sample was placed in a scanning electron microscope. As shown in FIG7 , the surface of the black wire had a surface layer 100 that was obviously different from the tungsten substrate 200. As shown in FIG8 , the contour of the surface layer 100 of the entire cross section was photographed using a combination of high and low magnifications. The thickness of the surface layer 100 was measured using conventional measurement software, and the thickness distribution of the surface layer 100 of the entire cross section could be statistically obtained. FIG8 shows that the thickness of the surface layer 100 of the black wire is between 1 and 4 μm.

[0097] As shown in FIG9 , in this embodiment, during the thickness test of the surface layer 100, 24 measurement points are uniformly located along the periphery of the cross section for thickness measurement. Those skilled in the art may adapt the location and number of measurement points based on actual conditions, with 20 or more measurement points being a preferred method.

[0098] (2) Trend information of carbon, oxygen, and matrix material (tungsten) content from the black wire surface to its matrix 200:

[0099] The cross-sectioned thin slice sample was placed in a scanning electron microscope equipped with an energy dispersive spectrometer. As shown in Figure 10, a line scan of the C, O, and W elements was performed along the radial direction of the cross section, from the black wire surface to the substrate 200. As shown in the test results in Figure 11, it can be seen that the region within the outermost layer (0.8 μm) primarily contains C, with low O and W content within this region. The C content in the subsequent regions gradually decreases, while the O and W content increases.

[0100] (3) Element distribution information and phase structure information of the 100 compounds in the black silk surface layer:

[0101] The cross-sectioned thin slice sample was placed in a transmission electron microscope, and the elemental distribution of carbon, oxygen, and the matrix material in the surface layer was scanned. Figure 12 shows the distribution of C, O, W, and La in the surface layer. The upper left, upper right, lower left, and lower right of Figure 12 show the distribution of C, W, La, and O, respectively.

[0102] The gray-black part and the gray-white part of the surface layer 100 are taken for phase structure analysis. The phase structure analysis process is as follows:

[0103] The topography and high-resolution images of the surface layer are captured by transmission electron microscopy, and the high-resolution images are Fourier transformed to obtain lattice diffraction spectra. The above diffraction spectra are combined with the obtained information on the elemental composition of the second phase and the corresponding material phase cards are calibrated and compared to obtain the phase structure corresponding to each diffraction spectrum;

[0104] As shown in Figures 13-14, the gray-black portion of the black wire surface layer 100 in Figure 13 represents a graphite structure, while the gray-white particles represent a WO2 structure. A high content of WO2 in the surface layer 100 is detrimental to wire drawing. This phase structure information can be used to evaluate coating performance. The lattice diffraction spectrum shown in Figure 14 is that of WO2.

[0105] It should be noted that two types of cross-sectional slice samples were used for separate testing in this embodiment. The sample used to determine the thickness of the black silk surface layer, as well as the carbon content, oxygen content, and matrix material content variation trends from the black silk surface to its matrix, was obtained by argon ion beam cutting. The sample used to determine the elemental distribution and phase structure of the compounds in the black silk surface layer was obtained by focused ion beam cutting. Specifically, the sample slices used for scanning electron microscopy were cut using an argon ion beam, while the sample slices used for transmission electron microscopy were cut using a focused ion beam.

[0106] Step 3: Alkali boiling to determine the compound content of the surface layer 100. The process is as follows:

[0107] (1) Weigh 1 g of a 0.4 mm diameter tungsten wire sample, with its mass M1 accurate to 0.0001 g (perform three parallel tests), place it in an 800 ml beaker, add 400 ml of NaOH solution, heat and boil for a certain period of time, and start timing after boiling.

[0108] (2) After alkali boiling, pour out the alkali solution, clean the sample with water first, then put the sample into an 800ml beaker, add 400ml of anhydrous ethanol, and ultrasonically clean it for 20 minutes. Finally, pour out the anhydrous ethanol and clean the sample with water.

[0109] (3) Place the sample in an oven and bake at 100°C for 60 minutes. Then take the sample out of the oven, cool it for 10 minutes, and weigh it to obtain the weight M2 (accurate to 0.0001g).

[0110] (4) Calculate the compound content on the surface of the wire material. The calculation formula is: Compound content (%) = (sample weight before treatment M1 - sample weight after drying M2) ÷ sample weight before treatment M1 × 100%.

[0111] (5) The color of the surface of the wire sample after alkali boiling is observed to assist in evaluating the surface layer 100 of the tungsten wire; wherein, the evaluation method is as follows: the surface is silvery white, which is the color of the white wire, indicating that there are no residual compounds on the surface of the wire; the surface is blue-black or yellow-brown, which is the blue-black color of the black wire surface layer that has not been boiled off by alkali, and yellow-brown is the color of tungsten dioxide, indicating that there are residual compounds on its surface.

[0112] Step 4: Observation of the sample surface layer 100:

[0113] In the sample surface layer 100 observation step, the sample is placed on a scanning electron microscope to obtain the sample surface profile roughness information and / or surface groove defect conditions.

[0114] The test samples and testing processes for Examples 2-3 and Comparative Examples 1-4 were consistent with those of the Examples, differing only in the alkali boiling process parameters shown in Table 1. The processes for obtaining other characterization information for the other Examples and Comparative Examples were the same as those for Example 1, with differences in the analysis results. For example, the processes for obtaining information on the thickness of the black silk surface layer, information on the trend of changes in carbon content, oxygen content, and matrix material content from the black silk surface to its matrix, and information on the phase structure of compounds in the black silk surface layer were consistent with the steps in the Examples.

[0115] The measurement results of the above examples and comparative examples are shown in Table 2 below:

[0116] Table 2

[0117] Based on the above examples and comparative examples, it is analyzed that:

[0118] Comparison data between the comparative example and the embodiment of the present application shows that:

[0119] The alkali concentration used was below the specified range of this application, resulting in insufficient removal of the compounds on the surface of the wire, a yellowish-brown color on the wire surface, inaccurate compound content test results, and poor test repeatability. The alkali boiling time was below the specified range of this application, insufficient removal of the compounds on the surface of the wire, a yellowish-brown or bluish-black color on the wire surface, inaccurate compound content test results, and poor test repeatability (as can be seen from the data in Table 2: the alkali concentration and other parameters in Comparative Examples 1-4 exceeded the specified range of this application. Under the conditions of testing the same sample, the compound content data of Comparative Examples 1-4 had large deviations and fluctuations, resulting in poor test accuracy and poor repeatability).

[0120] It can be seen from the data in the examples that the present application uses a specific type of alkali solution, a specific alkali solution concentration, and a specific alkali boiling time to accurately measure, so that the measurement results of the present application are accurate and reproducible (it can be seen from the data in Table 2 that the parameters such as the alkali solution concentration in Examples 1-4 are within the specified range of the present application. Under the conditions of testing the same sample, the compound content data of Examples 1-4 have very small deviations and fluctuations, and the detection accuracy is good and the repeatability is excellent).

[0121] From the above, it can be seen that if a different solution from the present application is adopted: if the alkali solution concentration and alkali boiling time are lower than the specified range of the present application, the surface compound of the wire material is not fully removed, the surface color of the wire material is yellow-brown or blue-black, the test results are inaccurate, and the test repeatability is poor; while the alkali solution concentration is higher than the specified range of the present application, it is easy to increase the risk of operation; and if the alkali boiling time is higher than the specified range of the present application, the efficiency is too low, because the compound content on the surface of the wire material is fixed, and after a certain period of alkali boiling, the weight value of the wire material will be constant (as can be seen from the measurement results of Examples 1 and 3, and Examples 2 and 4 in Table 2). Therefore, increasing the alkali boiling time will reduce the efficiency to a certain extent. In summary, the present application adopts a specific type of alkali solution, a specific alkali solution concentration, and a specific alkali boiling time, which not only makes the measurement results of the present application accurate and repeatable, but also reduces the risk of operation, effectively controls time costs, and has high measurement efficiency.

[0122] In summary, the method of the present invention can comprehensively characterize the surface layer characteristics of the black wire, including the carbon content, compound content, surface layer thickness and phase information of the black wire surface layer. The measurement results are accurate and reproducible, and the measurement results can be used to guide the wire drawing process.

[0123] It should be noted that:

[0124] Although the base material of the black wire of the test sample in the embodiment of the present invention is tungsten wire, it can be seen from the design concept of the present invention that the scheme of the present invention is not limited to the surface layer characterization of black wire with tungsten as the base material, and it can be applied to the surface layer characterization of the "black wire" mentioned above (whose base is a base wire or alloy base wire containing tungsten and / or molybdenum).

[0125] In this article, “~” is used to indicate a numerical range, and the range of this expression includes both endpoint values;

[0126] The specific parameters or some commonly used reagents in the above embodiments are specific embodiments or preferred embodiments of the present invention, but are not intended to limit the present invention. Those skilled in the art may make adaptive adjustments within the scope of the present invention.

[0127] In addition, unless otherwise specified, the raw materials used may also be conventional commercial products in the art, or may be prepared by conventional methods in the art.

[0128] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present invention may be improved in only one or several aspects, without having to simultaneously solve all the technical problems listed in the prior art or background art. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as limiting the claim.

[0129] Although terms such as black silk and carbon-sulfur analyzer are often used herein, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitations is contrary to the spirit of the present invention.

[0130] 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 above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, 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 characterizing the surface layer of black silk, characterized in that: The method comprises the step of alkali boiling to determine the content of the surface layer compounds, wherein the process of the step of alkali boiling to determine the content of the surface layer compounds is as follows: Weigh the black silk sample and record its weight M1; The black silk sample is subjected to alkali boiling treatment: the black silk sample is immersed in an alkali solution, heated to boiling and boiled for 5 to 30 minutes; wherein the alkali solution is one of a NaOH solution and a KOH solution or a mixture of the two, and the mass fraction thereof is 15% to 30%; After washing, drying and cooling the sample after alkali boiling, weigh it to obtain the weight M2; The compound content data of the black silk surface layer was obtained by weight loss method.

2. The method for characterizing the surface layer of black silk according to claim 1, characterized in that: The calculation formula for the compound content of the surface layer of the black silk is: Compound content = (M1-M2) ÷ M1 x 100%.

3. The method for characterizing the surface layer of black silk according to claim 1, characterized in that: Observe the surface color of the samples after alkali boiling, drying and cooling to judge the removal of the surface layer of the samples; The sample surface is silvery white, indicating that the surface layer is fully removed and no compound remains; the sample surface is yellowish brown and / or dark blue, indicating that the surface layer is not fully removed and some compound remains.

4. The method for characterizing the surface layer of black silk according to claim 1, characterized in that: Before the step of alkali boiling to determine the content of the surface layer compounds, the carbon content is determined; Wherein, a carbon-sulfur analyzer is used to measure the carbon content on the surface of the black silk sample.

5. The method for characterizing the surface layer of black silk according to claim 4, characterized in that: Before the step of alkali boiling to determine the content of the surface layer compounds, a step of determining the phase structure of the surface layer of the black silk is performed; In the phase structure determination step, the cross section of the black silk is cut to form a cross-sectional thin slice sample, and then the cross-sectional thin slice sample is placed in a scanning electron microscope and a transmission electron microscope to obtain characterization information; The characterization information includes the thickness information of the black silk surface layer, from the black silk surface to its matrix. One or more of the following: information on the changing trends of carbon content, oxygen content and matrix material content, element distribution of carbon, oxygen and matrix material, and phase structure information of compounds in the surface layer of black silk.

6. The method for characterizing the surface layer of black silk according to claim 5, characterized in that: The cross section of the black wire was cut using an ion beam.

7. The method for characterizing the surface layer of black silk according to claim 5, characterized in that: After the step of determining the content of the surface layer compound by alkali boiling, a step of observing the surface layer of the sample is performed; In the sample surface layer observation step, the sample is placed on a scanning electron microscope to obtain the sample surface profile roughness information and / or surface groove defect conditions.

8. The method for characterizing the surface layer of black silk according to claim 1, characterized in that: During the alkali boiling treatment, the amount of the alkali solution used is based on the amount that can immerse the black silk sample.

9. The method for characterizing the surface layer of black silk according to claim 1, characterized in that: During the cleaning process, the sample is first cleaned with water, then the sample is immersed in anhydrous ethanol for ultrasonic cleaning for 10 to 20 minutes, and then the sample is cleaned with water again; And / or, during the drying process, the sample is dried at 50-150° C. for 30-90 minutes.

10. The method for characterizing the surface layer of black silk according to claim 4, characterized in that: The carbon content is measured to the nearest ppm.

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