A metallographic sample preparation method suitable for surface carburized samples

Abstract

The invention discloses a metallographic sample preparation method suitable for surface carburized samples, comprising: making a sample that needs metallographic inspection into a block or ring shape; selecting a titanium tube larger than the sample size according to the size of the prepared metallographic sample; placing the metallographic sample in the titanium tube and placing it on a plane; placing a lead-free tin solder wire or a tin solder rod in a container, heating it to the melting point to melt it, pouring the molten tin liquid into the titanium tube, so that the tin liquid fills the gap between the sample and the titanium tube; after the tin liquid condenses, the sample is removed together with the titanium tube, and then the sample is taken out of the titanium tube; grinding, polishing and etching the sample. The present invention can protect the surface of the surface carburized sample from being damaged during grinding, and can also directly determine the surface carbon element content without removing the embedded material. In practical applications, the present invention can not only be used for metallographic inspection, but also can be applied to other characterizations that require grinding and polishing, such as scanning electron microscopy, electron probe microscopy, EDS element determination, etc., and has broad application prospects.

Description

Technical Field

[0001] The invention relates to a metallographic sample preparation method, in particular to a metallographic sample preparation method suitable for surface carburized samples, and particularly to the inlaying of metallographic samples. Background Art

[0002] The development of contemporary materials science is inseparable from the study of the relationship between the composition, organization and performance of metals and alloys. The depth and breadth of these studies mainly rely on people's recognition of the structure of the internal organization of metals, that is, metallographic examination. Metallographic examination is one of the important means of experimental research on metal materials. In order to be able to truly and clearly observe the microstructure inside the material under a metallographic microscope, it is necessary to carefully prepare the metallographic specimen. The main steps of metallographic specimen preparation are: sampling, inlaying, grinding, polishing, and etching.

[0003] Surface carburizing is a kind of surface treatment for metals. It is to place the workpiece in an active carburizing medium, heat it to a certain temperature, and keep it warm for a sufficient time, so that the active carbon atoms decomposed in the carburizing medium penetrate into the metal surface, so that the surface of the material is high in carbon, while the core still retains the original composition. In order to study the effect of carburizing on material properties, it is necessary to conduct a variety of characterizations and tests such as metallography, element determination, and mechanical properties.

[0004] These samples need to be inlaid to protect the sample surface during metallographic examination. Common sample inlay methods are divided into cold inlay and hot inlay. The inlay materials used mainly include thermosetting plastics (such as bakelite powder), thermoplastics (such as polyvinyl chloride), condensable plastics (epoxy resin plus curing agent) and medical tooth tray powder plus tooth tray water. These materials can effectively protect the sample surface, but because the inlay materials used are mostly organic matter, the inlay materials must be removed when conducting surface element determination, otherwise it will affect the determination of the surface carbon content. However, it is difficult to remove the commonly used inlay materials without damaging the sample surface and to remove them completely, which brings certain difficulties to the research of carburizing materials and the improvement of carburizing processes. Summary of the invention

[0005] The object of the present invention is to provide a metallographic sample preparation method suitable for surface carburized samples, which can protect the surface of the surface carburized sample from being damaged during grinding, and can also directly determine the surface carbon content without removing the embedded material.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A metallographic sample preparation method suitable for surface carburized samples comprises the following steps:

[0008] S1. Make the sample to be examined by metallographic examination into block or ring shape;

[0009] S2. Select a titanium tube larger than the sample size according to the size of the metallographic sample;

[0010] S3, placing the metallographic sample in a titanium tube and placing it on a flat surface;

[0011] S4, place the lead-free tin solder wire or tin solder rod in a container, heat it to the melting point, and pour the molten tin liquid into the titanium tube in S3, so that the tin liquid fills the gap between the sample and the titanium tube;

[0012] S5. After the tin liquid condenses, remove the sample together with the titanium tube, and then remove the sample from the titanium tube;

[0013] S6. Grind, polish and etch the sample.

[0014] A further improvement of the present invention is that in step S3, the metallographic sample is located at the center of the titanium tube.

[0015] A further improvement of the present invention is that in step S4, the tin solder wire is a lead-free tin solder wire with a tin content of at least 99% to avoid affecting the subsequent determination of the surface carbon content.

[0016] A further improvement of the present invention is that, in step S4, the sample does not undergo phase change at the selected melting point of the tin solder wire.

[0017] A further improvement of the present invention is that in step S4, the tin liquid covers at least 5 mm of the bottom of the sample, and the cooling time of the tin liquid is at least 30 minutes.

[0018] A further improvement of the present invention is that in step S4, the container is an alumina corundum crucible.

[0019] A further improvement of the present invention is that, in step S6, when grinding the sample, the tin on the surface to be observed is completely removed, and a clear boundary can be observed in the polished state of the obtained sample.

[0020] A further improvement of the present invention is that, in step S6, when grinding the sample, at least 2000-mesh sandpaper is used for grinding.

[0021] The present invention has at least the following beneficial technical effects:

[0022] The present invention provides a metallographic sample preparation method suitable for surface carburized samples. For surface carburized samples, conventional cold mounting or hot mounting methods are used to prepare samples. When determining the content of doped non-metallic elements, the mounting material needs to be removed, which easily damages the surface, and the residue of the mounting material has a certain influence on the determination of the element content. The present invention does not affect the determination of the non-metallic element content, and the mounting material does not need to be removed during the test, so the surface of the metallographic sample can be better protected. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of a metallographic sample preparation method suitable for surface carburized samples. DETAILED DESCRIPTION

[0024] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] The present invention introduces a metallographic sample preparation method suitable for surface carburized samples. In practical applications, it can not only be used for metallographic inspection, but also for other characterizations that require grinding and polishing, such as scanning electron microscopy, electron probe microscopy, EDS (energy dispersive spectrometer) element determination, etc. The sample preparation process mainly includes sampling, mounting, grinding, polishing, and etching. The following is a detailed description of each step in conjunction with this embodiment.

[0026] Step 1, sampling:

[0027] The sample is cut into samples with a suitable detection surface size by wire cutting. The specific size of the sample is selected according to actual test needs and is not a limitation of the present invention.

[0028] Step 2, inlay:

[0029] 1) According to the sample size obtained in step 1, select a titanium tube of appropriate size. The inner diameter of the titanium tube should be at least 5 mm larger than the sample size, so that a sufficient amount of tin liquid can be filled between the titanium tube and the sample, so that the titanium tube and the sample are tightly connected and not easy to fall off. The reason for using titanium tubes is that titanium is cheap, low cost, easy to process, has a high melting point, and stable chemical properties.

[0030] 2) Place the sample and titanium tube obtained in step 1 on a plane so that the sample is located at the center of the titanium tube.

[0031] 3) Take a suitable lead-free tin solder wire and place it in a clean alumina corundum crucible, heat it to 250°C to completely melt the tin solder wire, and pour the tin liquid into the above titanium tube. The purity of the tin solder wire used should be at least 99% to avoid other elements affecting the determination of the carbon content of the carburized layer on the sample surface.

[0032] 4) After the tin liquid is completely cooled, the sample is removed as a whole, and then the obtained sample is taken out of the titanium tube.

[0033] Step 3, grinding:

[0034] The present invention does not limit the grinding process, and the obtained samples are ground by manual or automatic methods. It should be noted that in order to make the heat-treated samples easier to observe, at least 2000-mesh sandpaper should be used for grinding.

[0035] Step 4, Polishing:

[0036] The present invention does not limit the polishing process, and various polishing methods and various types of polishing agents can be used.

[0037] Step 5, erosion:

[0038] A suitable etchant is selected according to the sample material for etching. The present invention does not limit the type of etchant and etching time.

[0039] Finally, it should be noted that for those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation methods here. However, the obvious changes or modifications derived from this are still within the scope of protection of the present invention.

Claims

1. A metallographic sample preparation method suitable for surface carburized samples, characterized in that: The following steps are involved: S1. Make the sample to be examined by metallographic examination into block or ring shape; S2. Select a titanium tube larger than the sample size according to the size of the metallographic sample; S3, placing the metallographic sample in the titanium tube so that the metallographic sample is located at the center of the titanium tube and placed on a plane; S4, place the lead-free tin solder wire or tin solder rod in a container, heat it to the melting point, and pour the molten tin liquid into the titanium tube in S3, so that the tin liquid fills the gap between the sample and the titanium tube; the tin solder wire is lead-free tin solder wire, and the tin content is at least 99% to avoid affecting the subsequent determination of the surface carbon content; the sample does not undergo phase change at the selected tin solder wire melting point; the tin liquid covers at least 5mm of the bottom of the sample, and the cooling time of the tin liquid is at least 30min; S5. After the tin liquid condenses, remove the sample together with the titanium tube, and then remove the sample from the titanium tube; S6. Grind, polish and etch the sample.

2. A metallographic sample preparation method suitable for surface carburized samples according to claim 1, characterized in that: In step S4, the container is an alumina corundum crucible.

3. A metallographic sample preparation method suitable for surface carburized samples according to claim 1, characterized in that: In step S6, when the sample is ground, the tin on the surface to be observed is completely removed, and a clear boundary can be observed in the polished state of the obtained sample.

4. A metallographic sample preparation method suitable for surface carburized samples according to claim 1, characterized in that: In step S6, when grinding the sample, at least 2000-mesh sandpaper is used for grinding.

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