阅读说明：本技术 Cr12型冷作模具钢共晶碳化物的检测方法 (Method for detecting eutectic carbide of Cr12 type cold work die steel ) 是由 杨娥 周杨 杨智 李波 程坤 于 2019-07-26 设计创作，主要内容包括：本发明提供一种使用ASPEX扫描电镜对Cr12型冷作模具钢的共晶碳化物进行检测的方法,该方法检测结果准确、效率高,从检测结果能够直观清楚地看到共晶碳化物的颗粒形状。包括：将Cr12型冷作模具钢的金相试样置于ASPEX扫描电镜的样品室中；调节ASPEX扫描电镜直到通过屏幕能够看到清晰的图像；设置检测共晶碳化物所需的检测参数,直到屏幕上能够显示出金相试样的检测区域内的全部共晶碳化物颗粒,点击开始扫描；扫描结束,导出检测报告,给出检测结果,确认共晶碳化物级别。(The invention provides a method for detecting eutectic carbide of Cr12 type cold work die steel by using an ASPEX scanning electron microscope, which has accurate detection result and high efficiency, and the particle shape of the eutectic carbide can be visually and clearly seen from the detection result. The method comprises the following steps: placing a metallographic specimen of Cr12 type cold-work die steel in a sample chamber of an ASPEX scanning electron microscope; adjusting an ASPEX scanning electron microscope until a clear image can be seen through a screen; setting detection parameters required by detecting eutectic carbide until all eutectic carbide particles in a detection area of a metallographic sample can be displayed on a screen, and clicking to start scanning; and (5) after the scanning is finished, deriving a detection report, giving a detection result, and confirming the grade of the eutectic carbide.)

The method for detecting the eutectic carbide of the Cr12 type cold-work die steel is characterized by comprising the following steps:

placing a metallographic specimen of Cr12 type cold-work die steel in a sample chamber of an ASPEX scanning electron microscope;

adjusting an ASPEX scanning electron microscope until a clear image can be seen through a screen;

setting detection parameters required by detecting eutectic carbide until all eutectic carbide particles in a detection area of the metallographic specimen can be displayed on a screen, and clicking to start scanning;

and (5) after the scanning is finished, deriving a detection report, giving a detection result, and confirming the grade of the eutectic carbide.

2. The detection method according to claim 1,

the metallographic specimen is prepared according to a GB/T13298 metallographic microstructure inspection method and a JB/T7713 high-carbon high-alloy steel cold-work die microstructure inspection method, and the polished surface of the prepared metallographic specimen is used as a surface to be detected without corrosion.

3. The detection method according to claim 2,

sticking a single-sided copper conductive adhesive tape and a single-sided aluminum conductive adhesive tape on the surface to be detected of the metallographic specimen;

and placing the metallographic specimen in a sample chamber of the ASPEX scanning electron microscope, and keeping the surface to be detected in a horizontal state and perpendicular to the direction of the electron beam.

4. The detection method according to any one of claims 1 to 3,

the detection parameter settings include scanning resolution, gray level threshold, scanning particle size, and scanning area.

5. The detection method according to claim 4,

the scan resolution was set at 512 x 512psi and when local agglomerated particles were detected, the scan resolution was 1024 x 1024 psi.

6. The detection method according to claim 4,

and setting the gray threshold value to be 0-185 by utilizing the difference between the gray values of the aluminum conductive adhesive adhered to the detection surface of the metallographic specimen and the detection surface of the metallographic specimen.

7. The detection method according to claim 4,

according to the detection standard JB/T7713-2007 in the mechanical industry, the scanning size of the eutectic carbide is set to be more than or equal to 9 μm.

8. The detection method according to claim 4,

setting the area of the scanning area according to the position and detection requirement of the metallographic specimen in a sample chamber of an ASPEX scanning electron microscope, wherein the area is 5mm²-10mm²Or 49mm²-51mm²。

9. The detection method according to claim 4,

according to the mechanical industry detection standard JB/T7713-2007, when a detection report is derived, the grading sizes of eutectic carbides are set to be six grades of 9-13 μm, 13-17 μm, 17-21 μm, 21-25 μm, 25-29 μm and more than 29 μm, the grading sizes respectively correspond to 1 grade, 2 grade, 3 grade, 4 grade, 5 grade and super-size carbides in the industry detection standard, and the grading condition of the detected eutectic carbides and the statistical quantity of the eutectic carbides in each grade are automatically displayed in the detection report.

Technical Field

The invention belongs to the technical field of detection of a microstructure of Cr12 type cold-work die steel, and particularly relates to a method for detecting eutectic carbide of Cr12 type cold-work die steel by using an ASPEX scanning electron microscope.

Background

Cr12 type steel is a main steel type in cold-work die steel series as high-carbon high-chromium steel, and is widely applied to the manufacturing industry for many years. The main chemical components of the alloy are 1.3-2.3% of carbon and 11-13% of chromium. In this composition range, eutectic carbides are inevitably present according to the iron-carbon phase diagram. Due to its compositional characteristics, the most eutectic carbides formed were M7C3 type eutectic carbides. The hardness of M7C3 type carbide is between 1800 and 2800HV, and the carbide can not only prevent the grain growth, but also improve the wear resistance of the steel. The Cr12 shaped steel has the features of high hardness, high wear resistance, less heat treatment distortion and great bearing capacity, and may be used in making cold punching die, trimming die, drawing die, cold heading die, cold extruding die, etc.

Generally, during the smelting and forging of such steel grades, if not properly controlled, severe segregation occurs, which affects the distortion of the die during the subsequent heat treatment. The accumulated massive eutectic carbide increases the brittleness of the material, and is a significant cause of corner breakage and brittle fracture of the cold work die. Therefore, the size and shape of eutectic carbides is particularly important in such steels.

The Cr12 type steel bulk carbide grade rating method is clearly specified in the mechanical industry standard JB/T7713-2007 high-carbon high-alloy steel cold-working die microstructure inspection. The eutectic carbide grade is determined in the standard mainly from two aspects of quantity and maximum size of single carbide. With the single carbides differing by 4 microns in their largest dimension rating and rated at 9 microns.

When the grades are graded by a metallographic microscope, at least 500X observation and measurement are needed to distinguish different grades. When the observation is carried out at 500X, the detection of the same area takes a long time because the size of a single visual field is small. In addition, when the method is observed manually, different carbides with close sizes, especially fine sizes on the classification boundary, cannot be identified manually, so that the classification quantity of the carbides cannot be counted accurately, and the accuracy of a detection result is poor.

Disclosure of Invention

Based on the problems, the invention provides the method for detecting the eutectic carbide of the Cr12 type cold work die steel by using the ASPEX scanning electron microscope, the method has accurate detection result and high efficiency, and the particle shape of the eutectic carbide can be visually and clearly seen from the detection result.

In order to achieve the purpose, the invention adopts the following technical scheme:

the detection method of the eutectic carbide of the Cr12 type cold work die steel comprises the following steps:

placing a metallographic specimen of Cr12 type cold-work die steel in a sample chamber of an ASPEX scanning electron microscope;

adjusting an ASPEX scanning electron microscope until a clear image can be seen through a screen;

setting detection parameters required by detecting eutectic carbide until all eutectic carbide particles in a detection area of a metallographic sample can be displayed on a screen, and clicking to start scanning;

and (5) after the scanning is finished, deriving a detection report, giving a detection result, and confirming the grade of the eutectic carbide.

Furthermore, the metallographic specimen is prepared according to a GB/T13298 metallographic microstructure inspection method and a JB/T7713 high-carbon high-alloy steel cold-work die microstructure inspection method, and the polished surface of the prepared metallographic specimen is used as a surface to be detected without corrosion.

Further, adhering a single-sided copper conductive adhesive tape and a single-sided aluminum conductive adhesive tape to the surface to be detected of the metallographic specimen;

and (3) placing the metallographic specimen in a sample chamber of an ASPEX scanning electron microscope, and keeping the surface to be detected in a horizontal state and perpendicular to the direction of the electron beam.

Further, the detection parameter settings include scan resolution, gray scale threshold, scan particle size, and scan region area.

Further, the scan resolution was set at 512 × 512psi, and when local agglomerated particles were detected, the scan resolution was 1024 × 1024 psi.

Further, the gray threshold value is set to be 0-185 by utilizing the difference of the gray values of the aluminum conductive adhesive adhered to the detection surface of the metallographic sample and the detection surface of the metallographic sample.

Further, according to the detection standard JB/T7713-2007 in the mechanical industry, the scanning size of the eutectic carbide is set to be more than or equal to 9 μm.

Further, according to the position and detection requirement of the metallographic specimen in a sample chamber of the ASPEX scanning electron microscope, the area of a scanning area is set to be 5mm²-10mm²Or 49mm²-51mm²。

Further, according to a mechanical industry detection standard JB/T7713-2007, when a detection report is derived, six grades of eutectic carbide with the grading sizes of 9-13 μm, 13-17 μm, 17-21 μm, 21-25 μm, 25-29 μm and more than 29 μm are set, the grading sizes respectively correspond to 1 grade, 2 grade, 3 grade, 4 grade, 5 grade and over-size carbide in the industry detection standard, and the grading condition of the detected eutectic carbide and the statistical quantity of the eutectic carbide in each grade are automatically displayed in the detection report.

The technical scheme provided by the invention has the beneficial effects that:

1) the detection result is accurate, and the particle shape of the eutectic carbide can be visually and clearly seen from the detection result.

2) For eutectic carbides with different size grades, the grade range of the detected eutectic carbide particles can be accurately distinguished according to the set standard size range.

3) The device can automatically and accurately identify the grain size of the eutectic carbide, and carries out grading statistics according to the set standard size, so that the detection efficiency is higher.

4) Provides more accurate technical support for the processing of Cr12 type cold-work die steel, and improves the service performance of Cr12 type cold-work die steel.

Drawings

FIG. 1 shows the distribution of carbide particles on a substrate when a gray threshold is set reasonably;

FIG. 2 is a graph showing the distribution of carbide particles on a substrate detected when a threshold value of gray scale is set too small;

FIG. 3 is a graph showing the distribution of carbide particles on a substrate detected when a threshold value of gray scale is set to be too large;

FIG. 4 is a statistic of the test results of sample # 1 in example 1 of the present invention;

FIG. 5 is a statistic of the test results of sample No. 2 in example 1 of the present invention;

FIG. 6 is a graph showing distribution of eutectic carbides in the test report of sample No. 1;

fig. 7 is a distribution diagram of eutectic carbides in the test report of sample # 2.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The ASPEX scanning electron microscope has been used for detecting nonmetallic inclusions in steel, and the detection of carbides has not been attempted. The inventor discovers through a large number of detection tests that the characteristics and the detection purpose of the eutectic carbide are pertinently set through scanning detection parameters of an ASPEX scanning electron microscope, the eutectic carbide in Cr12 type cold-work die steel can be accurately detected, and compared with a metallographic microscope, the detection result is more accurate, visual and clear, and the detection efficiency is high.

The invention provides a method for detecting eutectic carbide of Cr12 type cold-work die steel by using an ASPEX scanning electron microscope. And preparing a metallographic sample according to a GB/T13298 metallographic microstructure inspection method and a JB/T7713 high-carbon high-alloy steel cold-work die microstructure inspection method. And adhering a single-sided copper conductive adhesive tape and a single-sided aluminum conductive adhesive tape on the surface to be detected of the metallographic specimen. And (3) placing the sample adhered with the copper foil and the aluminum foil into a sample chamber of an ASPEX scanning electron microscope, and keeping the surface to be detected in a horizontal state and perpendicular to the direction of the electron beam.

And (4) starting the lamp filament, and after the lamp filament is preheated and stabilized, adjusting the parameters of the focal length, brightness and contrast of the equipment to ensure that clear images can be seen through the screen. The gray threshold is adjusted through the contrast difference between the single-sided aluminum conductive adhesive (aluminum foil) adhered to the surface of the metallographic specimen and the detection surface of the specimen. When the gray threshold is adjusted, all carbides on the matrix can be detected, and other substances (such as a metal substrate) cannot be judged as the carbides by mistake. Generally, the upper limit of the detection gray threshold is set to 180-190, and specifically, the upper limit of the detection gray threshold can be 180, 185, 190. Fig. 1, fig. 2, and fig. 3 show carbide images detected on a substrate under three different gray threshold settings, as shown in fig. 1, the parameters are set reasonably, the upper limit of the gray threshold is set to 185, and the dark carbide particles are clearly distinguished from the substrate, so as to meet the detection requirements. As shown in fig. 2, the upper limit of the gray level threshold in fig. 2 is set too small, the upper limit of the gray level threshold is 175, and part of the dark carbide particles are not included in the detection result, which results in inaccurate detection result. As shown in fig. 3, the upper limit of the grayscale threshold in fig. 3 is set too large, the upper limit of the grayscale threshold is 188, and part of the matrix is also recorded as the detected particles, so that the detection result is inaccurate.

In the invention, experiments show that when detecting the eutectic carbide in Cr12 type cold-work die steel, the scanning resolution is optimal at 512 x 512psi according to the characteristics of the carbide, when detecting local agglomerated particles, the ASPEX scanning electron microscope can be automatically adjusted to a local amplification mode, and meanwhile, the scanning resolution can be adjusted to 1024 x 1024 psi. The upper limit 185 of the gradation threshold thereof is set to be optimum, and at the time of detection parameter setting, the gradation threshold thereof is set to be 0 to 185. The gray threshold value is within the range, so that eutectic carbide can be completely detected without mixing the matrix. According to the detection standard JB/T7713-2007 in the mechanical industry, the scanning size of the eutectic carbide is set to be more than or equal to 9 μm. And setting the area of the scanning area according to the position of the metallographic specimen in a sample chamber of the ASPEX scanning electron microscope and detection requirements. If sampling detection is carried out in order to obtain the detection result more quickly, a smaller area of the scanning area can be set to be 5mm²-10mm²And (4) finishing. If the condition of the target object in the metallographic specimen needs to be comprehensively known, a larger scanning area needs to be arranged, and the scanning area is generally set to be 49mm²-51mm²Specifically, it may be 49mm²，50mm²，51mm². In the present application, a large scanning area is required to obtain the number of eutectic carbides and images in the metallographic specimen. And clicking to start scanning after all the parameter settings are confirmed to be correct. And automatically generating a detection report after scanning is finished, setting the grading sizes of eutectic carbides to be 9-13 microns, 13-17 microns, 17-21 microns, 21-25 microns, 25-29 microns and six grades greater than 29 microns when the detection report is derived according to a mechanical industry detection standard JB/T7713-2007, wherein the grading sizes respectively correspond to 1 grade, 2 grade, 3 grade, 4 grade, 5 grade and super-size carbides in the industry detection standard, and automatically displaying the grading condition of the detected eutectic carbides and the statistical quantity of the eutectic carbides in each grade in the detection report. The automatically derived report is the number of different size ranges, and the size ranges are set to different level requirements specified by the industry standard, so that the level of the eutectic carbide can be visually seen, and the size and number distribution condition of the carbide can be obtained.

In order to further explain the scheme provided by the invention in detail, the following embodiments are combined with the attached drawings for detailed description.