Terms like:
Commercial Steel
Forming Steel
Drawing Steel
Deep Drawing
Extra Deep Drawing
Are commonly used in:
ASTM specifications
EN 10346
JIS standards
Global coated coil supply
Yet many buyers and even some manufacturers misunderstand what these classifications actually represent.
These are ductility classifications, not strength classifications.
They define:
How much the steel can stretch
How it behaves in bending and drawing
How resistant it is to cracking
Its suitability for complex shapes
They do NOT define:
Structural load capacity
Wind resistance
Span performance
Understanding this distinction is critical in roll forming.
Commercial steel is general-purpose cold-rolled steel designed for:
Basic forming
Light bending
Simple profiles
Non-load-bearing components
Examples:
ASTM A653 CS Type B
EN 10346 DX51D
JIS SGCC
Typical properties:
Yield strength: ~200–280 MPa
Moderate elongation
Good basic bendability
Not optimized for deep drawing
Commercial steel is the baseline grade.
Roofing panels (light-duty)
Wall cladding
Light trim
Appliance panels
Basic sheet metal fabrication
Forming steel is engineered for:
Improved ductility
Better bend performance
Reduced cracking
More complex forming
Compared to commercial steel, it allows greater plastic deformation.
Lower yield strength than structural grades
Higher elongation
Improved bend radius capability
Reduced springback
It tolerates tighter bends than commercial grade.
Complex roll formed shapes
Deep flange sections
Tight radii flashing
Automotive parts
Decorative cladding
Drawing steel is optimized for:
Deep drawing operations
Severe deformation
Multi-directional strain
This grade is used where material must stretch significantly without cracking.
Very high elongation
Lower yield strength
Excellent stretchability
Minimal cracking in deep draw
This grade supports extreme forming operations.
Automotive body panels
Pressed components
Appliance housings
Deep drawn industrial parts
Rarely used in structural roll forming.
Highest ductility classification.
Used for:
Very severe forming
Multi-stage deep draw
Complex stamped geometries
Not typically required in standard roll forming profiles.
| Grade Type | Yield Strength | Ductility | Bend Radius Capability | Structural Capacity |
|---|---|---|---|---|
| Commercial | Moderate | Moderate | Moderate | Low |
| Forming | Lower | Higher | Good | Low |
| Drawing | Lower | Very High | Excellent | Very Low |
| Structural (comparison) | High | Lower | Limited | High |
Ductility increases as structural strength decreases.
Roll forming is primarily bending — not deep drawing.
However:
Tight flange geometry
Narrow hems
Decorative shapes
Small bend radii
May require forming or drawing grades.
Using structural high tensile material in these shapes increases:
Edge cracking
Surface tearing
Springback
Tool wear
If you choose:
Structural Grade (e.g., S350GD, G550):
Higher load capacity
Higher dent resistance
Higher springback
Higher crack risk at tight radii
If you choose:
Forming/Drawing Grade:
Easier forming
Reduced cracking
Lower structural capacity
Increased denting
The grade must match the application.
Ductility grades exist under coated standards:
ASTM A653
EN 10346
JIS G3302
Coating type (Z, AZ, etc.) is independent of ductility classification.
Example:
DX51D + Z275
CS Type B + G90
SGCC + Z27
Strength and coating are separate decisions.
“Commercial steel is weak and useless.”
False. It is suitable for many non-structural applications.
“Drawing steel is stronger.”
False. Drawing steel is more ductile, not stronger.
“All galvanized roofing uses structural grade.”
Not always. Some markets use commercial or high tensile grades depending on design.
Ductility grades affect:
Forming force
Pass design
Springback compensation
Roll wear
Production speed
High ductility steel allows smoother forming and potentially higher speeds.
High tensile structural steel increases machine load.
Is the profile load-bearing?
What is minimum required yield strength?
What is the tightest bend radius?
Is cosmetic quality critical?
What is the environmental exposure?
What machine capability is available?
Tight bends required
Cosmetic finish critical
Non-load-bearing profiles
Deep drawn components
Wind load applies
Structural certification required
Span stiffness critical
Framing systems involved
Using commercial grade for structural purlins
Using structural grade for tight flashing
Confusing ductility with strength
Ignoring bend radius limitations
Blaming machine for crack caused by wrong grade
Not requesting elongation data
A general-purpose steel suitable for basic forming but not structural load-bearing.
A more ductile steel designed for improved bend performance.
Steel optimized for deep drawing and severe deformation.
No. It is more ductile, not stronger.
Not recommended unless yield strength meets structural requirements.
No. Ductility classification is separate from coating type.
Commercial, forming, and drawing steels are ductility classifications, not structural classifications.
They define how much strain the steel can tolerate before cracking.
Structural grades define load capacity.
Choosing the correct category depends on:
Profile geometry
Structural requirement
Bend radius
Cosmetic expectation
Machine capability
In roll forming, understanding this distinction prevents cracking, underperformance, and costly specification errors.
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