Grade confusion causes more quote mistakes than any other spec. DX51D, SGCC and G550 are not competing qualities — they come from different standards and serve different jobs.
Grade Equivalence Table
| Grade | Standard | Type | Typical Use |
|---|---|---|---|
| DX51D | EN 10346 | Soft, formable | Roll forming, bending, general roofing |
| SGCC | JIS G3302 | Soft, commercial | Same jobs — the JIS twin of DX51D |
| CS Type B | ASTM A653 | Soft, commercial | US-spec equivalent |
| G550 / DX51D+Z full hard | AS 1397 / EN | High tensile (550 MPa) | Thin corrugated roofing, purlins |
How to Choose
Bending or roll-forming complex profiles? Use soft grade (DX51D/SGCC). It bends without cracking the coating. Thin roofing sheet (0.30-0.45mm) that must span purlins? G550 full-hard gives stiffness at low thickness — the standard choice for corrugated roofing across Africa, the Middle East and Latin America.
Do not order full-hard for profiles with tight bends: it cracks. If your roll former handles both, stock G550 for corrugated and DX51D for ridge caps and flashings.
FAQ
Is SGCC lower quality than DX51D?
No. They are equivalent commercial grades under different standards. Quotes may differ slightly by mill certification, not by quality.
Which grade for PPGI roofing?
Related Products from ChinaCNU Steel
Both are common: G550 base for corrugated sheets, DX51D/SGCC where profiles need forming. See our DX51D coil page for full specs.