For detailed information, check the Standard SEP 1571 Evaluation of inclusions in special steels based on their surface areas – Part 1: Basics. The scope of testing for methods K and M is described in SEP 1571 Part 2.

This standard specifies the examination of non-metallic inclusions in special steels.

The NMI Analysis module generates a report document showing the method results and corresponding characteristic values.

Inclusion assessment

For information on the inclusion classification by size, see the Standard in Annex E. To obtain a reasonable evaluation of the inclusion distribution within a lot, at least six locations, chosen to be as representative of the lot as possible, should be examined.

Inclusion categories

According to the shape and arrangement of the inclusions, this standard defines the following inclusion types.

• Inclusion type A (sulfide inclusion type)
• Light gray elongated inclusion or stringer, usually MnS.
• Inclusion type B (aluminium or magnesium oxide inclusion type)
• Dark gray to black stringer that consists of at least three non-contiguous, predominantly globular particles, usually aluminum oxides or magnesium oxides.
• Dark gray to black compact, elongated inclusion consisting of at least three contiguous non-deformable particles.
• Inclusion type C (oxide inclusion type)
• Black elongated inclusion or inclusion line that consists of one or more deformable elongated particles, generally a silicate.
• Inclusion type D (aluminium or magnesium oxide inclusion type)
• Dark gray to black globular inclusion, randomly distributed, generally an aluminum oxide or magnesium oxide.
• Inclusion type D_sulf (sulfide inclusion type)
• Gray globular inclusion, randomly distributed, e.g. CaS.

The NMI Analysis module provides the following test methods:

• Method M - Maximum inclusion value
• Method K - Mean inclusion value

Method M - Maximum inclusion value

The NMI Analysis module evaluates the largest inclusion of each type for each specimen as described in SEP 1571 - Part 2. The result is the sum of these maximum rating values divided by the number of the examined specimen. Compared to DIN 50602, individual inclusions are inspected instead of a field based evaluation.

Method K - Mean inclusion value

The NMI Analysis module evaluates the non-metallic inclusions separately for the individual inclusion types. The frequency of each size class is recorded as described in SEP 1571 - Part 2. To determine the inclusion content, the individual frequencies are multiplied by a factor so that larger inclusions are weighted more heavily than smaller inclusions.

Depending on the agreement the summation or the reporting respectively begins with a certain size class, e.g. only inclusions of sizes 4 and greater are considered (method K4).