| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface treated steel sheet on which an anodic oxidation film having excellent insulation properties and uniformity in film thickness is formed by using a molten Al-based plated steel sheet containing Si and having good workability.SOLUTION: A surface treated steel sheet having good insulation properties is obtained by performing anodic oxidation treatment on a surface layer part of a plating layer of a molten Al-based plated steel sheet having an Si content in the plating layer of 3.0-15.0 mass%, and sequentially includes an Al-Fe-Si-based alloy layer, an Al-based plating layer, and the anodic oxidation film on the surface of a substrate steel sheet, wherein particles of an Si phase are dispersed in the Al-based plating layer and the anodic oxidation film, and the amount of the existing particles of the Si phase, whose length in the through-thickness direction in the Al-based plating layer and the anodic oxidation film in a cross-sectional surface parallel to the through-thickness direction is at least 10 μm, is controlled to be 100 pieces/mm or less per unit length in the direction parallel to the surface of the substrate steel sheet. |
