For detailed information, check the Standard JIS G 0555 Microscopic testing methods for the non-metallic inclusions in steel. JIS G 0555: 2020 is based on ISO 4967:1998. JIS G 0555: 2023 is based on ISO 4967:2013.

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 and/or number, see the Standard in chapter 2 Principle, here table 1 and table 2. 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)
• Highly malleable, individual gray particles with a wide range of aspect ratios (length/width) and generally rounded ends.
• Inclusion type B (aluminate inclusion type)
• Numerous non-deformable, angular, low aspect ratio (generally < 3), black or bluish particles (at least three) aligned in the deformation direction.
• Inclusion type C (silicate inclusion type)
• Highly malleable, individual black or dark gray particles with a wide range of aspect ratios (generally ≥ 3) and generally sharp ends.
• Inclusion type D (globular oxide inclusion type)
• Non-deformable, angular or circular, low aspect ratio (generally < 3), black or bluish, randomly distributed particles.
• Inclusion type DS (single globular inclusion type)
• Circular, or nearly circular, single particle with a diameter ≥ 13 μm.

The NMI Analysis module provides the following test methods:

• Method A - worst fields
• Method B - field assessment

Method A - Worst fields

This method reports the worst fields with the largest severity values per inclusion type of the examined specimen. The worst field has the size of a standard measuring field and is located within the measurement area. According to the standard, the worst field can be located anywhere on the specimen and is usually not located on the grid of standard measuring fields. The NMI Analysis module calculates these true worst fields.

NMI Analysis reports the number and size of each inclusion type A, B, C, D and Ds (fine and thick) for each index number from 0 to 3 in half-severity level increments.

Note that fields with inclusions below the smallest severity level (0.5) are not rated and indicated in the field statistics of the field based inspection as non-ratable. Empty fields without a specific inclusion type are presented as n.a. for this inclusion type.

Method B - Field assessment

This method evaluates steel specimens with a low inclusion content. The total number of fields of each inclusion type A, B, C, D, Ds (fine and thick) per severity level are reported. The NMI Analysis module calculates for each standard measuring field the index number from 0 to 3 in whole or half-index number increments. For this method, the NMI Analysis module considers contiguous fields located on the grid of standard measuring fields.