What is JIS G 3313 SECC SECD and SECE?
JIS G 3313 is the Japanese Industrial Standard for Electrolytic Zinc-Coated Cold-Rolled Steel Sheets.
The grades SECC, SECD, and SECE represent a hierarchy of formability. While they all feature a smooth, corrosion-resistant electro-galvanized coating, their base metals differ to accommodate various levels of manufacturing complexity.
SECC, SECD, and SECE are the grades of electro-galvanised steel sheets specified in JIS G3313. SECC is general-purpose galvanised steel, SECD is deep-drawing grade galvanised steel, and SECE is ultra-deep-drawing grade galvanised steel. These three grades of electro-galvanised steel sheets differ in carbon content, formability, application scenarios, and surface quality.
| Model | Formability Grade | Applicable Scenarios |
| SECC | Regular Formability | Simple stamping (e.g., appliance housings, enclosures) |
| SECD | Deep Draw (Draw Quality) | Complex stamping (e.g., automotive parts) |
| SECE | Extra Deep Draw | High-complexity stamping (e.g., pipe fittings) |
Electrogalvanised Steel Performance Comparison
The core difference between different types of electrogalvanised steel lies in their formability. SECC, SECD, and SECE electrogalvanised steel have similar mechanical properties, zinc coating uniformity, and surface quality.
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Surface Quality
| Parameter | SECC | SECD | SECE |
| Surface Roughness Ra | 0.4–0.8 μm | 0.3–0.6 μm | 0.15–0.4 μm |
| Surface Treatment | Ordinary chromate | Fingerprint-resistant chromate treatment | Chromium-free environmentally-friendly passivation |
| Defect Control | Slight roller marks allowed | No roller marks/zinc particles | Zero defects (AA grade) |
| Coating Adhesion | 4B (Cross-hatch method) | 5B | 5B |
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Mechanical Performance
| Parameter | SECC | SECD | SECE |
| Tensile Strength (MPa) | 270–410 | 270–370 | 270–370 |
| Yield Strength (MPa) | ≥140 | ≥140 | ≥140 |
| Hardness (HRB) | 40–70 | 40–65 | 35–60 |
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Formability
| Parameter | SECC | SECD | SECE |
| Plastic Strain Ratio (r value) | 0.8–1.2 | 1.0–1.6 | 1.4–2.2 |
| Strain Hardening Index (n value) | 0.16–0.20 | 0.18–0.22 | 0.20–0.25 |
| Elongation (%) | ≥28 (t ≤ 0.4mm) | ≥34 (t ≤ 0.4mm) | ≥38 (t ≤ 0.4mm) |
| Limiting Drawing Ratio (LDR) | 1.8–2.0 | 2.0–2.2 | 2.2–2.5 |
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Uniformity of Zinc Layer
| Parameter | SECC | SECD | SECE |
| Coating Process | Electro-galvanizing (EG) | Electro-galvanizing (EG) | Electro-galvanizing + Grain Refinement |
| Coating Deviation | ±15% (JIS H 0401) | ±15% | ±10% |
| Coating Adhesion | Grade 3 (Cross-hatch method) | Grade 2 | Grade 1 (No peeling) |
| Salt Spray Test | 96h White rust | 120h White rust | 144h White rust |
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Application Comparison
JIS G 3313 SECC, SECD, and SECE galvanised steel are suitable for stamping processes ranging from simple bending to highly complex stamping. Applications cover multiple fields, including home appliances, automobiles, electronics, and construction.
- SECC Galvanised Steel (Standard Grade)
Home appliance field: Refrigerator, washing machine, and air conditioner shells, replacing plastic parts.
Electronics industry: server enclosures and housings.
Construction industry: construction scaffolding, interior ceilings, partitions.
- SECD galvanised steel (deep-drawing grade)
Automotive industry: door inner panels, fuel tank lids, seat frames, interior panels.
Lighting industry: streetlight housings, advertising light boxes.
Industrial industry: toolboxes, control cabinets, home appliance touch panels.
- SECE Galvanised Steel (Ultra-Deep Drawing Grade)
Automotive Industry: Engine hoods, fenders, chassis components.
Home Appliance Industry: Microwave oven interiors, oven housings.
Precision Industry: Electronic component housings, medical device components, battery casings, laptop computer housings.
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GNEE Steel also produces other galvanized steel grades:
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FAQ
1. What is the main difference between these three grades?
The difference is formability. SECC is for basic bending, SECD is for moderate drawing, and SECE is for complex deep drawing.
2. Why choose SEC (Electro-galvanized) over SGCC (Hot-dip)?
SEC grades provide a smoother, more uniform surface and better thickness precision, making them ideal for high-end electronics and precision painting.
3. Does the zinc coating thickness vary by grade?
No. Coating weight (e.g., 20/20 $g/m^2$) is independent of the steel grade and can be customized based on your rust-protection needs.
4. Can I use SECC for deep drawing?
Not recommended. SECC will likely crack or tear. You should use SECD or SECE for any part requiring significant material stretching.
5. Are these grades suitable for powder coating?
Yes. For the best adhesion, we recommend the Phosphated (P) surface treatment.
6. What is the advantage of SECE's "Non-Aging" property?
It prevents surface defects like stretcher strains (ripples) from forming, even if the steel is stored for months before use.
7. Is an "Anti-Fingerprint" (AF) coating available?
Yes. All three grades can be supplied with a clear AF organic film to prevent marks during assembly and handling.
8. What are the typical applications?
SECC: Computer chassis, server racks.
SECD: Appliance panels, shallow stamped parts.
SECE: Automotive oil pans, deep-drawn motor housings.
