The Five Grades and What Separates Them
SPCC, SPCD, SPCE, SPCF and SPCG are cold-reduced carbon steel sheet and strip grades covered by JIS G3141. The designation sequence follows the drawing severity: SPCC is commercial quality for bending and simple forming, SPCD is drawing quality, SPCE is deep-drawing quality, SPCF is deep-drawing quality with superior uniformity, and SPCG is non-aging deep-drawing quality. The practical difference is chemical and metallurgical. Lower carbon means a softer, more ductile sheet that can be stretched further before it tears, while tighter limits on phosphorus and sulphur improve uniformity and reduce the risk of edge cracking. The non-aging grades additionally control interstitial nitrogen so that stretcher strains do not appear after the coil has been stored.
Chemical Composition Limits Under JIS G3141
| Grade | Carbon max, % | Manganese max, % | Phosphorus max, % | Sulphur max, % | Drawing severity |
|---|---|---|---|---|---|
| SPCC | 0.15 | 0.60 | 0.100 | 0.050 | Bending, simple forming |
| SPCD | 0.10 | 0.50 | 0.040 | 0.040 | Drawing |
| SPCE | 0.08 | 0.45 | 0.030 | 0.030 | Deep drawing |
| SPCF | Carbon, phosphorus and sulphur held below SPCE limits; uniform grain structure required | Deep drawing, high uniformity | |||
| SPCG | Lowest carbon level of the series, stabilized against aging | Non-aging deep drawing | |||
Values are the maximum permitted by the standard; mill certificates normally show the heat analysis actually achieved, which is often well inside these limits. Where a part is marginal in the press, a grade change from SPCC to SPCD or SPCE is usually more effective than increasing thickness, because the gain comes from ductility rather than from load-carrying capacity.
Mechanical Requirements and Temper
JIS G3141 grades are supplied in annealed and temper-rolled condition, with temper-rolled sheet designated by the suffix T, for example SPCC-T or SPCC-SD. Temper rolling removes the yield-point elongation that would otherwise produce visible Lüders bands on a formed surface. SPCC in the annealed and temper-rolled condition has a minimum tensile strength of 270 MPa. As the grade moves toward SPCE and SPCG, elongation and the plastic strain ratio rise, which is what allows a deeper punch before the blank fractures. Because mechanical properties vary with thickness, the standard states elongation as a function of thickness, so a specification written only as "SPCC, elongation 34%" is incomplete without the thickness and the test direction.
Typical Supply Range and Applications
JIS G3141 sheet and strip are normally produced in thickness from 0.18 mm to 3.0 mm and in widths from 600 mm to 1500 mm, which matches the range most appliance and general-engineering buyers order. Common uses are: SPCC for refrigerator and washing-machine housings, electrical cabinets, distribution boards and drums; SPCD for parts with moderate drawing such as motor housings and container components; SPCE and above for deep-drawn shells, automotive interior stampings and any part where the draw ratio is high. The same substrate is frequently the base for hot-dip galvanizing, and the grade must still satisfy the forming requirement after coating, since the zinc layer follows the surface strain of the steel beneath it.
Comparing JIS, EN and Other Designations
Buyers working across regions frequently need an equivalence for SPCC. The nearest European equivalents for continuously hot-dip coated cold-forming steel are the DX51D to DX54D series under EN 10346, and for uncoated cold-reduced sheet the DC01 to DC06 series under EN 10130, where DC01 is the standard commercial and drawing-quality grade and DC04 the deep-drawing grade. ISO 3574 covers cold-reduced carbon steel sheet of commercial and drawing qualities, and GB/T 11253 covers cold-rolled carbon steel sheet in the Chinese system. Equivalence tables are a purchasing aid, not a legal substitution: a drawing operation that fails on one standard's grade may not behave identically on the "equivalent" grade of another, so trial forming before a full release is recommended.
Frequently Asked Questions
Q: What is the main difference between SPCC and SPCD?
A: Carbon and impurity limits. SPCC allows up to 0.15% carbon and is intended for bending and simple forming, while SPCD caps carbon at 0.10% and is intended for drawing operations.
Q: Which grade should be used for a deep-drawn part?
A: SPCE or higher. If the draw is severe, or if the part must sit in storage before forming, SPCF or SPCG gives better uniformity and avoids stretcher strains.
Q: Does SPCC have a minimum strength guarantee?
A: JIS G3141 specifies a minimum tensile strength of 270 MPa for annealed and temper-rolled SPCC. Higher-strength structural applications should use a structural grade instead.
Q: Can SPCC be welded like mild steel?
A: Yes. It is a low-carbon steel and is readily welded; thin gauges are usually joined by resistance or gas-shielded processes with controlled heat input to avoid distortion.
Q: Is SPCC suitable for hot-dip galvanizing?
A: Yes, provided the surface is clean and the grade still meets the forming requirement after coating. Galvanized SPCC is common in appliance and construction panels.
Q: Are SPCC and DC01 interchangeable?
A: They overlap in use but are not identical. DC01 is defined by EN 10130 with its own carbon and property limits, so a substitution should be confirmed by forming trials rather than by an equivalence table alone.