Role of the analyzer in ductile iron production
Nodularization failure is usually not due to insufficient magnesium, but because the base iron was already off-spec before magnesium addition.
For ductile iron, composition affects not only strength but also graphite morphology after cooling. Even with sufficient magnesium added, deviations in carbon and silicon from the target range can lead to incomplete nodularization within the same grade.
Therefore, in the pig iron production line, the analysis equipment is used twice per batch: once on the raw pig iron before processing and again after processing to confirm quality prior to bulk pouring.
Key Control Points
Pre-processing
Read the C%, Si%, and equivalent carbon index of the base iron to confirm the iron matrix is correct before adding Mg.
Post-processing
Resample to check if the graphitization trend remains within the desired range or has declined.
Background Sulfur
Using excessive scrap material results in higher sulfur content in the base iron, leading to greater-than-expected magnesium consumption.
Pouring temperature
Correct composition, but pouring too cool still reduces spheroidization efficiency; temperature must be measured concurrently.
Real-world experience
- Use a coated cup suitable for ductile iron to ensure more stable cooling curves.
- Fix the time interval from processing to pouring and recording in the batch sheet.
- Keep the failed batch sample for root cause analysis when needed.
Compatible device
CYY-LK7 Cast Iron, Gray Iron, and Ductile Iron Analyzer
Gray Cast and Ductile Iron Analyzer CYY-LK7 — Analyzes C, Si, Mn, CEL, spheroidization ratio, tensile strength, and hardness. CE certified with 15-inch-inch TFT display.
Reference price: 1700-1900 USD
CYY-CE2 Tellurium Sampling Cup for Molten Iron Thermal Analysis — Sampling Cup for Foundries and Metallurgical Plants
CYY-CE2 Insulated Tellurium sampling cups for molten iron thermal analysis. Compatible with CYY-LK2/LK7, C%, Si%, CEL, and CE measurements. Designed for Vietnamese iron foundries.
Reference price: 0.5-1.5 USD
CYY-W660 Wireless Pre-Heating Liquid Iron Temperature Gauge — Wireless Large-Screen Iron Pyrometer
Wireless molten iron temperature control at the furnace with a large 5-inch display. CE certified, English interface.
Reference price: 500-600 USD
Frequently Asked Questions
Can a thermal analyzer measure Mg?
No. The device reads C%, Si%, and derived indices from the cooling curve; Mg requires spectroscopic or chemical methods.
Do I need to test every batch?
For ductile iron, test each batch; the cost of rework and the risk of scrapping a large lot far exceed that of sampling.
Related topics
Reference content from Changyouyi's technical article: original post on Sohu.
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