The MSS SP-55 standard provides a critical visual evaluation method for assessing surface irregularities in steel castings, employing 60 reference photographs to categorize 12 types of defects. Adopted to ensure quality in high-pressure components, the latest revisions continue to set industry benchmarks for acceptable surface conditions, often referencing SCRATA standards. To view the official standard, visit Manufacturers Standardization Society (MSS) . MSS 55-2025 | PDF - Scribd

Type II: Shrinkage

– Voids left due to solidification freezing. Type III: Sand Inclusions – Sand trapped in molten metal. Type IV: Gas Porosity – Voids caused by entrapped gas. Type V: Veining – Ridge-like features from mold cracking. Type VI: Scabs – Depressions from mold surface buckling.

Key Technical Clauses You Must Know (Based on MSS SP-55)

4.4 – Inclusions (Sand/Slag)

The standard categorizes irregularities into 12 types, each representing a different metallurgical or process-related defect: