Where the SPCC Grade Comes From
SPCC is a grade of cold-rolled steel sheet and strip defined in JIS G 3141, the Japanese Industrial Standard for that product family. The current edition of the standard organises the family into five grades, each aimed at a different level of forming severity, and SPCC is the general-purpose member of that family. The full name of the grade is general purpose cold-rolled carbon steel sheet and strip, and it is often described simply as common steel because it is an extremely low carbon product that is easy to work.
That very low carbon content is the source of the defining strength of the grade. Low carbon means good ductility, predictable bending and squeezing behaviour, and a soft, uniform surface that can be finished or coated afterwards. It also means the sheet is not intended for structural load carrying; where strength is the governing requirement, other grades are available.
The Five JIS G 3141 Grades and What They Are For
The family moves from general forming through to severe deep drawing, and the grade name tells the buyer where a product sits on that scale.
| Grade | Category | Typical duty |
|---|---|---|
| SPCC | General purpose | Bending and general forming |
| SPCD | Drawing quality | Drawing work |
| SPCE | Deep drawing quality | Deeper drawing work |
| SPCF | Non-ageing deep drawing | Deep drawing with ageing control |
| SPCG | Non-ageing deep drawing | Severe deep drawing |
As the required drawing depth increases, the standard tightens the chemical and mechanical requirements so that the sheet can be stretched without localised thinning or tearing. A T may be added to any of these designations, as in SPCCT, when specific tensile or elongation properties are agreed between buyer and supplier; the suffix signals that those properties are guaranteed rather than left to the general requirements.
Temper Codes A and S, and Hardness Codes 1, 2, 4 and 8
Temper codes describe the heat treatment state of the delivered sheet. In JIS G 3141 the two codes are A and S: A indicates that the product has been annealed only, while S indicates that the standard temper has been achieved. The temper code does not describe strength on its own; it must be read together with the hardness code that accompanies it, because the two together tell the buyer how much cold work the sheet has received after annealing.
Hardness codes are written as the suffix numbers 1, 2, 4 and 8 and represent successive hardness levels obtained by adjusting the amount of rolling after annealing. Descriptions such as 1/8 hard and 1/4 hard refer to those levels. One point deserves emphasis: the hard implied by suffix 1 is not the same as a hard-rolled coil shipped without annealing. Even at the hardest of these levels the product still receives a low-temperature anneal, so it retains workability that a genuinely hard-rolled coil does not.
Surface Condition: Type D and Type B
The standard also controls surface condition, because it affects both appearance and processing. Two conditions are defined: Type D, a pitted surface, and Type B, a smooth surface.
Both conditions are produced by the temper rolls used in the final pass. The texture of the roll is pressed into the sheet, so a rough roll leaves a pitted surface and a smooth roll leaves a bright one. The choice is not a ranking of quality but a question of fit: the surface that suits a paint line is not necessarily the surface that suits a forming operation, so the specified condition should match the downstream process.
Specification Envelope for SPCC Coil
| Parameter | Typical specification |
|---|---|
| Thickness | 0.4 - 2.5 mm |
| Width | 600 - 1800 mm |
| Length | Coil, or cut to requirement |
| Coil inner diameter | 508 mm or 610 mm |
| Coil weight | 7 - 12 MT |
| Standards applied | EN, GB, JIS G, ASTM |
| Drawing grades traded alongside | ST12 to ST16, superseded by the DC01 to DC04 series under EN 10130 |
| Micro-alloyed high-strength grades | 170P1, 210P1, 250P1 |
| High-strength grade | 280VK |
| Coated base grades | DC01 to DC06 |
| Surface finish | FB to FD |
The table gathers the values normally quoted for SPCC coil so that they can be compared in one place. Where a value is shown as a range, the actual figure for a given order is fixed by the standard edition named on the mill certificate and by the agreement between buyer and supplier.
Frequently Asked Questions
Q: What does SPCC stand for?
The grade is general purpose cold-rolled carbon steel sheet and strip under JIS G 3141. It is the general-purpose member of a five-grade family and is widely described as common steel because of its very low carbon content.
Q: What is the difference between SPCC and SPCD?
Both come from the same JIS G 3141 family. SPCC is intended for general forming such as bending, while SPCD is a drawing-quality grade specified where the forming operation imposes a more demanding strain path.
Q: What does the T suffix mean, as in SPCCT?
The T suffix indicates that specific tensile or elongation properties have been agreed for the material. Without it, the product is supplied against the general requirements of the standard rather than against guaranteed mechanical values.
Q: What is the difference between Type D and Type B surface?
Type D is a pitted surface and Type B is a smooth surface. Both are set by the texture of the temper rolls, and the correct choice depends on whether the next process is painting or forming.
Q: Does hardness code 1 mean the coil is hard-rolled?
No. Hardness code 1 is the hardest of the suffix levels, but the product still receives a low-temperature anneal. A genuinely hard-rolled coil is not annealed at all, so the two conditions should not be confused.
Q: Can SPCC be used outdoors without a coating?
Bare SPCC is highly prone to rust and normally requires surface treatment before outdoor use. For exposed service the sheet is usually supplied with a zinc coating, and the coating requirement then comes from the relevant coating standard.