ASTM A247 Standard Test Method for Evaluating the Microstructure of Graphite in Iron Castings

Scope:

ASTM A247 is used as a reference to define concisely the graphite microstructure required. To permit accurate reporting of the microstructure and to give the comparison reports of cast iron microstructure, these standards are offered primarily by the investigators or labs.

Test Procedure:

In ASTM A247, there are two procedures, one generates the nodularity percentage and the second generates the nodularity count. The nodularity percentage is expressed by counting the nodular particles and reporting the results as a percentage of the total amount of graphite present in the microstructure. Nodule count is expressed as the number of graphite nodules/mm² and is performed at a magnification of 100x. A high nodal count indicates good metallurgical quality. 

Video 01: ASTM A247 Standard Test Method for Evaluating the Microstructure of Graphite in Iron Castings

Test Specimen:

The preferred sample for ASTM A247 is a section cut from an actual casting that is being evaluated at a location agreed upon between the manufacturer and purchaser

Data:

Types found in iron casting 

• Type I: Nodular in shape and normal graphite.
• Type II: Irregular nodules and have no effect on properties
• Type II: Most often seen in malleable iron casting 
• Type IV: Predominant Graphite form in compacted graphite form.
• Type V: Spiky Graphite form 
• Type VI: Exploded nodule graphite form 
• Type VII: Flake Graphite Form 

Conclusion:  

ASTM A247 is used to evaluate the microstructure of graphite in iron coatings. This test method is allowed to be only used for all iron-carbon alloys containing graphite particles and may be applied to gray irons and ductile irons.