1. Determine the five characteristics of non-metallic inclusions in
square and rectangular tubes
Although the content of non-metallic inclusions in square and rectangular pipes is small, it has a great impact on the performance of the pipe, so the detection of non-metallic inclusions has become one of the important items in the production process. A correct understanding of the source, composition, form, hazard principle, distribution and microscopic characteristics of inclusions is of great significance for controlling or reducing the content of inclusions in square and rectangular pipes and improving quality.
To determine the type of non-metallic inclusions in square and rectangular tubes, you can refer to the following characteristics:
(1) Alumina: Most of them are undeformed, angular, small black or bluish particles, arranged in a line along the rolling direction, with at least three particles.
(2) Spherical oxides: non-deformable, angular or rounded, small black or bluish in shape, irregularly distributed particles.
(3) Single-particle spherical type: single-particle inclusions that are round or nearly round, with a diameter of ≥13 μm.
(4) Sulfides: Single gray inclusions with high ductility and a wide range of aspect ratios. In square and rectangular tube materials, the ends are generally rounded.
(5) Silicates: They have high ductility and a wide range of aspect ratios. They appear individually as black or dark gray inclusions, and generally have sharp angles at their ends.
Traditional types of inclusions can also be evaluated by comparing their shape with the five inclusion categories mentioned above and noting their chemical characteristics. The evaluation of deposit phase types such as boride, carbide, carbonitride or nitride in square and rectangular tubes can also be based on their morphology and comparison with the above five types of inclusions, and their chemical characteristics can be expressed according to the above method.
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