SPCC is the default cold-rolled coil grade in Asian manufacturing, but its performance in the press depends on the temper, the tooling and the handling. Most SPCC processing complaints trace back to five recurring issues, and each has a known, controllable answer. This guide collects them in one place for production engineers and purchasing teams.
Why SPCC Stamping Cracks and How to Fix It
Cracks during stamping are usually caused by one of four conditions: material too hard (for example 1/4-hard or harder temper), excessive alloy content in the cast, insufficient die radius, or inadequate lubrication. The fixes follow the cause:
Change to annealed (fully soft) material when the part demands deep deformation.
Optimise the die geometry: increase the punch and die radii and check the clearance.
Improve lubrication, and confirm the lubricant suits the press speed and material surface.
If cracking persists on annealed SPCC, the drawing ratio may exceed the grade, so step up to SPCD or SPCE.
Coating Peel After Bending
When painted, plated or otherwise coated SPCC peels at the bend, the cause is usually the strain exceeding the coating's elongation at the outer fibre. Practical remedies: increase the bending radius, switch to a more flexible coating system, or coat after bending instead of before. For galvanized SPCC (that is, hot-dip coated), apply a zinc-rich paint or touch-up zinc at the bend after forming to restore protection where the zinc has cracked.
Rust on Cut Edges
Shearing and laser cutting expose bare steel at the edge, and on bare SPCC that edge rusts first. The standard countermeasures are: passivate or oil the edge after cutting, apply rust-preventive oil or paint, and after laser cutting remove the slag and clean the edge before oiling. For coated products, a zinc-rich touch-up paint on cut edges closes the exposed zone.
Yield Plateau and Stretcher Strains
Annealed SPCC shows a yield plateau (Luders band) that produces surface wrinkles and slip lines during stamping, known as stretcher strains. The solution is to specify skin-passed or levelled material: the -S designation (annealed and skin-passed) or a secondary levelling pass removes the plateau and gives a clean surface after forming. This is the single most common specification change between a rejected batch and an accepted one in visible parts.
Grade Selection: SPCC, SPCD or SPCE
| Grade | Forming level | Typical use |
|---|---|---|
| SPCC | General bending, simple stamping | Brackets, enclosures, flat parts |
| SPCD | Medium stamping, drawing | Drawn housings, covers |
| SPCE | Deep drawing, complex forming | Deep-drawn parts, automotive pressings |
The ladder exists because elongation and deep-drawing behaviour improve with each step; upgrading is cheaper than scrapping cracked parts. For very high forming demands, SPCF and SPCG extend the series further.
Frequently Asked Questions
1. What does SPCC stand for?
SPCC is the JIS G3141 designation for commercial-quality cold-reduced carbon steel: Steel, Plate, Cold rolled, Commercial. Its carbon limit is 0.12% with manganese up to 0.50%.
2. Why does my stamped part show surface lines even though it is annealed?
That is the yield plateau phenomenon: annealed steel deforms in bands. Skin-passed (temper-rolled) SPCC eliminates the plateau and is the correct material for visible stamped surfaces.
3. Can SPCC be welded?
Yes, its low carbon content makes it readily weldable by resistance and arc processes; standard low-carbon filler practice applies.
4. What is the thickness range of SPCC coil?
SPCC coil is commonly supplied from 0.3 mm to 3.0 mm, with sheet up to about 4.5 mm at most mills and widths depending on the mill's rolling schedule.
5. Is SPCC corrosion resistant?
No. SPCC is bare steel; it must be oiled, painted or coated for protection. The coated form of the same family is SGCC (hot-dip) or SECC (electro), which carry a zinc layer.
6. What certificate should SPCC orders carry?
Ask for a mill test certificate per EN 10204 type 3.1 (or the equivalent JIS documentation) showing chemistry, mechanical results and the temper designation, so the delivered condition is verifiable.