Diànjìng fēnxī fǎ zài zhùtiě jiàn quēxiàn jiǎncè zhōng de yìngyòng, wèi zhùzào hángyè dài láile cóng wéiguān céngmiànjīngzhǔn bǎ kòngzhìliàng, yōuhuà gōngyì de gémìng xìng túpò. , Qí jiàzhí guànchuān yú quēxiàn fēnxī, gōngyì gǎijìn, zhìliàng kòngzhì, yánf

The application of electron microscopy in defect detection of iron castings has brought revolutionary breakthroughs to the foundry industry, enabling precise quality control and process optimization at the microscopic level. Its value permeates multiple dimensions, including defect analysis, process improvement, quality control, R&D innovation, and industry standardization. Specifically, it is reflected in the following aspects:

1. Accurate defect diagnosis and reduced quality risks

1) Accurate determination of defect type

Traditional inspection methods (such as visual inspection and X-rays) can only identify macroscopic defects. However, electron microscopy, through high-resolution imaging (SEM resolution of 1-10 nm, TEM resolution down to the atomic level), can clearly distinguish the morphological characteristics of microscopic defects such as pores, shrinkage, slag inclusions, and cold shuts. 

Case study: A crack appeared on the surface of a ductile iron casting. SEM observation revealed that the crack propagated along a grain boundary. Combined with EDS analysis, it was confirmed that brittle fracture was caused by phosphorus segregation at the grain boundary, rather than casting stress or improper heat treatment. This provided a basis for targeted improvements. 

2) In-depth Analysis of Defect Causes 

Electron microscopy analysis, combined with compositional analysis (EDS/WDS) and structural characterization (TEM diffraction, HRTEM), can reveal the chemical composition and crystal structure anomalies of defects. 

Case Study: A company's iron castings frequently experienced slag inclusion defects. SEM-EDS analysis revealed excessive FeO content in the slag inclusions. Further TEM observation confirmed that the FeO was present in the form of flakes at the grain boundaries. The root cause was ultimately identified as incomplete melting of the inoculant. Guidance was provided to the company to adjust the inoculation process, resulting in a 90% reduction in the slag inclusion rate. 

2. Process Optimization Guidance to Improve Production Efficiency

1) Precise Control of Casting Process Parameters 

Electron microscopy analysis results provide direct feedback to key process steps, such as gating system design, inoculant selection, and cooling rate control. 

Case Study: In the production of a motor housing, SEM revealed that slag inclusion defects were associated with in-stream inoculation. Switching to post-furnace inoculation and adjusting the grain size resulted in a 98% increase in yield and a 20% reduction in production cycle time.

2) Correlation Research between Material Properties and Defects

Combined with TEM analysis of phase composition and crystal structure, a quantitative defect-performance-process relationship model can be established.

Case Study: During the development of a high-strength iron casting, TEM revealed the matching relationship between graphite nodule size and matrix pearlite content. After optimizing the heat treatment process, the tensile strength increased by 15%, while the elongation remained stable.

3. Upgrading the Quality Control System and Promoting Industry Standardization

1) Quantifying Defect Determination Standards

Electron microscopy analysis provides the industry with a unified description and determination of defect microscopic characteristics, such as:

Slag inclusion area ratio threshold (e.g., ≤0.5%);

Pore diameter distribution range (e.g., ≤50μm);

Shrinkage porosity classification standards.

Significance of the Standard: The "Electron Microscopic Analysis Method for Defect Detection of Iron Castings" (T/CFA 0198-2025), issued by the China Foundry Association, fills a domestic gap, making test results comparable and traceable, and providing a scientific basis for arbitration of quality disputes. 2) Full-Process Quality Monitoring

Electron microscopy analysis can be applied to raw material inspection (such as charge impurity analysis), process control (such as smelting oxide film detection), and finished product acceptance (such as fatigue fracture analysis), establishing a closed-loop quality management system.

Case Study: A company used SEM to analyze the morphology of inclusions in incoming pig iron, screening for low-oxygen raw materials and reducing the hydrogen-induced cracking rate of castings from 3% to 0.1%.

4. Driven by R&D and Innovation to Break Through Technical Bottlenecks

1) Support for New Material Development

Electron microscopy provides a microstructural design basis for the development of new materials such as lightweight cast iron (such as ADI ductile iron) and high-thermal conductivity cast iron.

Case Study: During the development of high-thermal conductivity cast iron, TEM was used to observe the effect of the interfacial bonding between graphite nodules and the matrix on thermal conductivity. This guided the company to optimize graphite morphology by adjusting the carbon equivalent, resulting in a 20% improvement in thermal conductivity.

2) Upgrading Failure Analysis Technology

Combined with in-situ electron microscopy techniques (such as heating/stretching stages), dynamic observation of defect evolution under service conditions can be achieved, providing data support for product life prediction and reliability design. Case Study: During fracture analysis of a wind turbine casting, in-situ SEM observations revealed cracks extending along the edges of graphite spheres under alternating loads. This led to guidance from the company on strengthening the matrix-graphite interface through heat treatment, resulting in a threefold increase in fatigue life.

5. Enhanced Economic and Social Benefits

1) Direct Economic Benefits

Defect Rate Reduction: After process improvements guided by electron microscopy analysis, a company reduced annual scrap losses by over 5 million yuan.

Improved Production Efficiency: After process optimization, unit production time was reduced by 15%, and annual production capacity increased by 10%.

Improved Customer Satisfaction: Improved product reliability resulted in a 40% decrease in customer complaints and a 25% increase in order volume.

2) Social Benefits

Promoting Technological Advancement in the Industry: The widespread adoption of electron microscopy analysis has enabled small and medium-sized enterprises to master high-end testing technologies, narrowing the gap with internationally advanced standards.

Promoting Green Manufacturing: By precisely controlling defects, material waste and energy consumption are reduced, helping the foundry industry achieve its carbon emission reduction goals.

Conclusion:

Electron microscopy analysis has become a core tool in the foundry industry's transition from an "experience-driven" to a "data-driven" approach. Its value lies not only in its "microscopic" insight into defects but also in providing a scientific basis for decision-making in casting process optimization, new material development, and quality control through correlation analysis between microstructure and macroscopic properties. With the integration of AI-assisted analysis and in-situ electron microscopy, electron microscopy analysis will play a greater role in the intelligent and green development of the foundry industry, propelling China from a major foundry nation to a powerful one.