1. HW refers to wide flange H-shaped steel, which means the flange width of H-shaped steel is consistent with the height of H-shaped steel.
2. HM refers to the middle flange of H-shaped steel, which means the flange width of the H-shaped steel is slightly smaller than the height of the H-shaped steel.
3. HN refers to narrow flange H-shaped steel, which means the flange width of H-shaped steel is much smaller than the height of H-shaped steel. HN means that the ratio of H-shaped steel height to flange width is greater than or equal to 2.

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