The advantages of electron microscope analysis in the detection of defects in cast iron parts include high accuracy, rich information and strong guidance.

Recently, the China Foundry Association issued the "Electron Microscope Analysis Method for Defect Detection of Cast Iron Parts", which will be implemented on October 21, 2025, and the implementation standard number is T/CFA 0198-2025.Next, let's take a look at what the electron microscope analysis method is.

The electron microscope analysis method for defect detection of cast iron parts is a method of microscopic morphology observation, composition analysis and structural characterization of internal defects of cast iron parts by scanning electron microscope (SEM) or transmission electron microscope (TEM), which can effectively determine the defect type and guide the improvement of casting process. The following is a detailed introduction to this method:

1. Application background of electron microscope analysis method in defect detection of cast iron parts

Cast iron parts are prone to various defects during the casting process, such as slag inclusion, shrinkage, pores, sand holes, inclusions, cold shut, hot cracking, etc. These defects will reduce the metal continuity of the cast iron body, and even cause abnormal failure during use, affecting the working reliability and service life of the casting. At present, there is no relevant standard for the inspection method of defects in cast iron parts in China, so an accurate and reliable detection method is urgently needed. As an advanced material analysis technology, electron microscopy analysis has the advantages of high resolution, large depth of field and wide magnification range, and can clearly observe the microscopic morphology and structural characteristics inside cast iron parts. Through electron microscopy analysis, the type of defects in cast iron parts can be accurately determined, and the causes of their occurrence can be analyzed, providing strong support for the improvement of casting process.

2. Specific application of electron microscopy analysis method

Microscopic morphology observation Using scanning electron microscope (SEM) to observe the microscopic morphology of cast iron defects, the shape, size and distribution of defects can be clearly seen. For example, SEM observation can distinguish defects such as pores and shrinkage. Pores are usually smooth on the surface and pear-shaped, round or elliptical; while shrinkage is manifested as dispersed and small shrinkage cavities.

Transmission electron microscopy (TEM) can be used to observe the atomic scale structure inside cast iron parts, revealing information such as crystal defects and atomic arrangement, and providing an important basis for in-depth research on the phase change behavior and performance of cast iron parts. Composition analysis Combined with energy dispersive spectrometer (EDS) or X-ray spectrometer (WDS), electron microscopy analysis can quantitatively and qualitatively analyze the elemental composition of defective parts of cast iron parts. Through composition analysis, the types and contents of impurity elements in defects can be determined, and then their sources and causes can be analyzed.

For example, through EDS analysis, it is found that the defects contain a high level of oxygen, which may indicate that the defects are caused by oxide inclusions. Structural characterization Electron microscopy analysis can also characterize the phase composition and crystal structure in cast iron parts. Through high-resolution transmission electron microscopy (HRTEM) and electron diffraction (ED) technology, different phase structures and crystal orientations in cast iron parts can be observed, revealing the microscopic mechanism of their mechanical properties and thermal stability. This is of great significance for optimizing the composition and heat treatment process of cast iron parts.

3. Advantages of electron microscopy analysis in defect detection of cast iron parts

High accuracy: Electron microscopy analysis can provide high-resolution microscopic morphology images and detailed composition analysis results, which provides strong support for accurately determining the types of defects in cast iron parts.

Rich information: Through electron microscope analysis, not only can the morphological characteristics of defects be observed, but also their composition and structural characteristics can be analyzed, providing rich information for in-depth research on the causes and mechanisms of defects.

Strong guidance: The results of electron microscope analysis can directly guide the improvement of casting process. By optimizing the pouring system, adjusting the type and amount of inoculant, etc., the defects in cast iron parts can be effectively reduced and the quality and performance of castings can be improved.

4.Practical application cases of electron microscope analysis in defect detection of cast iron parts

Taking the slag inclusion defect of ductile iron motor housing as an example, scanning electron microscope analysis found that there were a large number of metal oxide inclusions in the defective part, the main component of which was FeO. Further analysis showed that the defect was caused by the unmelted FeSi inoculant used.

In response to this problem, measures such as changing the inoculation method from in-stream inoculation to out-of-furnace inoculation, adjusting the particle size and amount of inoculant, and increasing the pouring temperature were taken. After small-batch tests and mass production verification, the yield of motor housing castings increased from 85% to more than 98%, and slag inclusion defects were effectively controlled.

Conclusion:

Electron microscopy analysis has become the core tool for the foundry industry to transform from "experience-driven" to "data-driven". Its value is not only reflected in the "microscope-level" insight into defects, but also in providing scientific decision-making basis for casting process optimization, new material research and development, and quality control through correlation analysis between microstructure and macro performance.