SPCC vs SPCE – Composition, Heat Treatment, Properties, and Applications

Introduction

SPCC and SPCE are two JIS-designated cold-rolled carbon steel grades widely used in sheet and strip applications. Engineers and procurement teams commonly face the choice between these grades when balancing cost, formability, and end-use performance—decisions often driven by requirements for deep drawing, surface quality, and downstream processing such as welding, coating, and stamping.

The primary practical distinction between the two is their suitability for forming operations: SPCE is specified and processed for enhanced drawability and deep-drawing performance, while SPCC is a general commercial-quality cold-rolled steel with broader, less stringent formability control. Because they share the same low-carbon base chemistry, they are often compared in design and manufacturing contexts where forming limits, surface finish, and process yield matter more than strength differentiation.

1. Standards and Designations

• JIS: Both SPCC and SPCE are defined under JIS G3141 (Cold-reduced carbon steel sheet and strip).
• ASTM/ASME: There is no direct one-to-one ASTM grade; designers typically reference cold-rolled carbon steel specifications such as ASTM A1008 for comparable product forms.
• EN: European equivalents for cold-rolled mild steels (e.g., DC01–DC06 series) may align in product intent, but matching requires checking specific chemical and mechanical limits.
• GB (China): GB standards for cold-rolled steels provide similar product categories; exact equivalence requires cross-referencing.
• Classification: Both SPCC and SPCE are plain low-carbon cold-rolled carbon steels (not alloy, not tool steel, not stainless, and not HSLA).

2. Chemical Composition and Alloying Strategy

Table: relative elemental content and role (qualitative)

Element	SPCC (commercial cold-rolled)	SPCE (deep-drawing / improved formability)	Role / Notes
C (Carbon)	Low (controlled for general CAQ)	Low, often more tightly controlled	Carbon controls strength and hardenability; lower C improves ductility and stretch formability.
Mn (Manganese)	Low-to-moderate	Low-to-moderate	Deoxidizer and strength contributor; kept moderate to balance drawability and strength.
Si (Silicon)	Low (deoxidation)	Low	Deoxidizer; excessive Si can reduce ductility.
P (Phosphorus)	Present at controlled low levels	Lower control than SPCC (tighter in SPCE)	Phosphorus increases strength but embrittles and reduces formability; deep-drawing grades keep P lower.
S (Sulfur)	Controlled (may be present)	Tighter control / low	Sulfur promotes machinability but impairs ductility/formability; deep-drawing steels minimize S.
Cr, Ni, Mo, V, Nb, Ti, B	Not intentionally added (trace)	Not intentionally added (trace)	Microalloying generally absent; any presence is residual and kept minimal to prioritize formability.
N (Nitrogen)	Trace	Trace (controlled in some processes)	Nitrogen affects aging and formability; often controlled to prevent embrittlement.

Explanation - Both grades are essentially low-carbon cold-rolled steels with alloying limited to elements used for deoxidation and standard steelmaking practice. - SPCE’s processing and chemistry are tuned (by stricter P/S control, sometimes slightly lower C or modified processing) to increase strain-hardening capacity and achieve higher r-values (plastic strain ratio) or superior earing behavior in drawn parts. - Because neither grade is alloyed for hardenability (Cr/Mo/Ni are not intentionally added), post-rolling heat treatment to increase strength is not a common production route—mechanical properties are primarily controlled by cold work and process conditions.

3. Microstructure and Heat Treatment Response

Typical microstructures - SPCC: Predominantly ferritic microstructure with fine pearlite islands only where carbon and processing permit. Cold rolling produces elongated grains and a higher dislocation density, which increases yield and tensile strength relative to annealed condition. - SPCE: Also ferritic-dominant but processed and annealed to optimize isotropy and drawability; grain shape and texture control (e.g., through controlled annealing) produces better L/T balance and higher plastic strain ratio (r-value).

Heat treatment and processing response - Annealing: Both grades benefit from annealing to restore ductility after cold reduction. For SPCE, controlled annealing cycles (temperature and cooling rate) are often optimized to produce a favorable crystallographic texture for deep drawing. - Normalizing/Quench & Temper: These are not standard for SPCC/SPCE; such treatments are used for higher-strength steels but are unnecessary and counterproductive for deep-drawing steels which rely on low strength and high ductility. - Thermo-mechanical processing: In modern steelmaking, subtle thermo-mechanical treatments and precise cold-rolling schedules are used to tailor formability attributes—this is more relevant for SPCE where process control yields improved deep-drawing performance.

4. Mechanical Properties

Table: qualitative comparison of mechanical properties

Property	SPCC	SPCE	Typical implication
Tensile Strength	Moderate	Similar or slightly lower (to favor ductility)	Both are low-carbon cold-rolled grades; SPCE often targets a balance that favors elongation over peak strength.
Yield Strength	Moderate	Similar or slightly lower	Lower yield can facilitate deep drawing by reducing required forming loads.
Elongation (%)	Good	Better (higher elongation)	SPCE exhibits higher total elongation and local formability for complex draws.
Impact Toughness	Adequate at ambient	Comparable	Not a primary differentiator—both are not specifically toughness-hardened.
Hardness	Moderate	Slightly lower	Slightly lower hardness in SPCE reflects the emphasis on ductility and stretchability.

Explanation - SPCE is engineered to prioritize ductility and stretch/flange formability; therefore it often measures higher elongation and better drawability metrics than SPCC. - SPCC provides adequate strength and is satisfactory for parts that do not undergo severe plastic deformation.

5. Weldability

Weldability drivers - Low carbon content in both grades generally gives good weldability for common processes (MIG/MAG, TIG, resistance welding). However, the presence and level of residual elements (P, S, Mn) and the sheet thickness and thermal input determine susceptibility to HAZ hardening or cold cracking. - Since neither grade contains significant alloying to increase hardenability, classical cold-cracking susceptibility is low compared with higher-carbon or alloy steels.

Useful weldability indices - The International Institute of Welding carbon equivalent: $$CE_{IIW} = C + \frac{Mn}{6} + \frac{Cr+Mo+V}{5} + \frac{Ni+Cu}{15}$$ - The more comprehensive Pcm for predicting cold cracking tendency: $$P_{cm} = C + \frac{Si}{30} + \frac{Mn+Cu}{20} + \frac{Cr+Mo+V}{10} + \frac{Ni}{40} + \frac{Nb}{50} + \frac{Ti}{30} + \frac{B}{1000}$$

Interpretation (qualitative) - For both SPCC and SPCE, $CE_{IIW}$ and $P_{cm}$ values are low because of low C and minimal alloying, indicating generally favorable weldability. - SPCE’s tighter chemistry control (lower P and S) can marginally improve weld quality and reduce porosity or inclusions that affect weld soundness. - Practical guidance: preheating is rarely necessary for thin-gauge cold-rolled SPCC/SPCE; thicker sections or complex welded assemblies should be evaluated for HAZ ductility and residual stress.

6. Corrosion and Surface Protection

• Both SPCC and SPCE are non-stainless carbon steels; atmospheric and aqueous corrosion protection is required unless used in benign environments.
• Typical surface protection methods: hot-dip galvanizing, electrogalvanizing, coil coating, painting, conversion coatings (phosphate), or organic film laminates.
• PREN (Pitting Resistance Equivalent Number) is not applicable to these grades because they lack corrosion-alloying elements (Cr, Mo, N) used in stainless steels: $$\text{PREN} = \text{Cr} + 3.3 \times \text{Mo} + 16 \times \text{N}$$
• Engineers should specify appropriate surface treatment based on service environment, intended life, and downstream processing (e.g., prepainted galvanneal for automotive trim).

7. Fabrication, Machinability, and Formability

• Cutting and machining: Both grades are readily sheared and punched in sheet form. Machinability is typical for low-carbon steels; select tooling and clearances to minimize burr and edge deformation when tight tolerances are required.
• Formability and stamping: SPCE is superior for deep drawing, stretching, and operations requiring high local strains without fracture. It yields better earing behavior and allows more complex stamped geometries with fewer rejects.
• Bending and hemming: SPCE gives cleaner radii and lower springback for deep-drawn shapes; SPCC performs well for general bending and light forming.
• Surface finishing: Both grades accept electroplating, painting, and coil coating well. SPCE may require more care in lubricant selection for severe drawing to avoid galling.
• Springback: Low carbon content reduces springback relative to higher-strength steels; however, cold work history and thickness determine the final behavior.

8. Typical Applications

Table: uses by grade

SPCC (commercial cold-rolled)	SPCE (deep-drawing / enhanced formability)
Appliance panels, furniture components, electrical enclosures, general-purpose stamped parts	Automotive inner panels, complex stamped components, deep-drawn kitchenware, fuel tanks requiring high drawability
Light structural panels, chassis components that do not require severe forming	Components with tight earing/anisotropy control and high local elongation demands
Prepainted, coated panels for general exterior or interior use	High-complexity parts where forming yield and surface continuity are critical

Selection rationale - Choose SPCE where severe stamping and deep drawing are primary production drivers—its improved formability reduces scrap and tooling load. - Choose SPCC for cost-sensitive applications with moderate forming requirements or where extreme drawability is not necessary.

9. Cost and Availability

• Availability: SPCC is more widely produced and stocked as a general commercial cold-rolled product; SPCE is commonly available but may be produced to tighter process and chemical controls, so lead times can be longer for some widths/thicknesses.
• Cost: SPCE typically commands a modest premium over SPCC because of additional processing controls (chemistry tighter control, specialized annealing/texturing). The premium is usually justified by reduced forming scrap, higher yields, and fewer secondary operations in deep-drawing applications.
• Product forms: Both are available in coils, cut-to-length sheets, and cut blanks; check with suppliers for specific surface finish options (BA/No.1/skin-pass) and coating choices.

10. Summary and Recommendation

Table: concise comparison

Attribute	SPCC	SPCE
Weldability	Good (general-purpose)	Good (slightly improved due to cleaner chemistry)
Strength – Toughness balance	Moderate strength, adequate toughness	Similar strength, higher ductility for forming
Cost	Lower (general commercial grade)	Higher (premium for deep-drawing capability)

Conclusions and practical recommendations - Choose SPCE if: - Your part requires deep drawing, significant stretch forming, complex stamped geometry, or tight earing control. - Reducing scrap and tooling load from forming operations is a priority. - Surface continuity and avoidance of wrinkle/tear in multi-draw sequences are essential.

• Choose SPCC if:
• Your parts are general-purpose cold-rolled components that do not undergo severe plastic deformation.
• Cost and wide availability are higher priorities than maximum formability.
• Welding, coating, and general fabrication are the primary considerations and deep-drawing is not required.

Final note - When specifying either grade, confirm exact chemical and mechanical limits with the supplier’s mill certificate (JIS G3141 or equivalent). For complex components, request formability metrics (e.g., r-value, n-value, cup drawing test results) and sample trials—these practical data points often decide between SPCC and SPCE more reliably than generic grade names.