DX51D+Z100 appears on more quotations than any other galvanized coil specification, yet the designation is often misunderstood. The name carries three pieces of information: the steel grade (DX51D), the coating metal (Z, pure zinc) and the coating mass (100 g/m2). Once these are clear, comparing offers and choosing substitutes becomes straightforward.
What Does DX51D Mean?
In EN 10346, DX marks a steel for cold forming where the substrate may be hot-rolled or cold-rolled, the number 51 identifies the forming class, and D stands for the product form (strip and sheet). DX51D is a low-carbon steel with good tensile strength and formability, a maximum carbon content of 0.18%, a minimum elongation of 22% and a tensile range of 270-500 MPa; yield strength is not specified for this grade. It is the general-purpose bending and forming grade of the galvanized coil family.
The Z100 Coating and Regular Spangle
Z100 means a nominal zinc coating of 100 g/m2 measured as the total mass on both surfaces. The typical zinc layer is about 7 micrometres per side, which suits indoor and light industrial service. Regular spangle is the visible crystallised zinc pattern left by normal solidification; it is the default surface for building components. Where a smooth painted or unlacquered surface is needed, zero-spangle (minimised spangle) or skin-passed options are available at a premium.
| Surface option | Appearance | Typical use |
|---|---|---|
| Regular spangle | Visible crystallised pattern | Roofing substrate, ducts, keels |
| Minimised spangle | Fine or invisible pattern | Painted parts, appliances, visible panels |
| Zero spangle | Uniform matte | Precision painting, auto parts |
DX51D versus DX52D and DX53D
| Grade | Yield strength | Tensile strength | Elongation A80 | Forming level |
|---|---|---|---|---|
| DX51D | Not specified | 270-500 MPa | Min 22% | Bending, general forming |
| DX52D | 140-300 MPa | 270-420 MPa | Min 26% | Stamping, deeper bending |
| DX53D | 140-260 MPa | 270-380 MPa | Min 30% | Drawing, complex stamping |
The series number reflects formability: as it rises, the guaranteed elongation increases and the strength range narrows. DX52D has higher ductility than DX51D; DX53D goes further still. For simple bends and profiles, DX51D is the economical choice.
DX51D versus DC51D
The old EN 10142/10147 practice used DC for grades where the substrate is cold-rolled, while DX covered both hot-rolled and cold-rolled substrates. In current EN 10346 supply, DX51D is the traded grade and DC51D is rarely specified; it should not be treated as a different product for substitution purposes. Similarly, DX51D is often quoted as the European counterpart of SGCC (JIS G3302), and the two are broadly interchangeable for commercial building applications.
Frequently Asked Questions
1. What is DX51D equivalent to?
In JIS terms, SGCC per JIS G3302; in Chinese practice, grades supplied to GB/T 2518 with similar chemistry. Equivalents are practical guides, so verify the certificate for critical orders.
2. Is Z100 enough for outdoor roofing?
For painted or profiled roofing in moderate climates, Z100-Z140 is common; for aggressive coastal or industrial environments, Z200-Z275 or an AZ coating is safer.
3. What does +Z mean versus +ZF or +AZ?
+Z is pure zinc, +ZF a zinc-iron alloy coating, +ZA a zinc-aluminium (about 5% aluminium) coating, and +AZ an aluminium-zinc (about 55% aluminium) coating. The letter changes corrosion behaviour and weldability.
4. Can DX51D+Z be deep drawn?
For deep drawing, select DX53D or DX54D instead. DX51D is a bending and forming grade, and its elongation guarantee of 22% is not designed for high deformation.
5. How is coating mass measured?
By weighing a sample before and after stripping the coating, normally by the triple-spot method defined in the standard, and expressed in g/m2 total for both surfaces.
6. What thickness range is standard?
DX51D coil is commonly supplied from 0.30 mm to 3.00 mm, with widths up to about 1520 mm; the EN 10346 standard itself covers a wider range.