SS400 is a widely used carbon structural steel grade under the JIS G3101 standard, valued for its balanced mechanical properties, свариваемость, and cost-effectiveness in structural engineering projects. Engineers and manufacturers frequently search for ss400 material properties to validate designs, compare equivalents, and ensure compliance across international standards. This guide provides a comprehensive overview from a manufacturer’s perspective, helping you select and apply SS400 effectively in real-world applications.
What Is SS400 Material?
SS400 represents a foundational carbon structural steel in the JIS G3101 specification, primarily supplied as hot-rolled plates, sections, and bars for general construction and machinery. The “SS” prefix indicates “structural steel,” while “400” approximates its minimum tensile strength in MPa, distinguishing it from higher grades like SS490 or SS540. This grade’s design philosophy prioritizes versatility over specialized performance, making it a staple in Japanese and exported structural projects since the 1970s.
Its chemical makeup as a low-carbon steel features no rigid caps on carbon (typically ≤0.25%) or manganese (≤1.50%), but stringent limits on phosphorus (P ≤0.050%) и сера (S ≤0.050%) to curb brittleness and promote ductility. The resulting carbon equivalent (CE ≈0.35-0.40 per IIW formula) ensures low hardenability during welding, minimizing risks of cold cracking. Manufacturers appreciate this predictability, as it supports consistent fabrication without extensive pre- or post-weld treatments, even in multi-pass joints up to 40 mm thick.
Mechanical Properties of SS400 Material
Tensile, Yield Strength and Elongation
- Предел прочности: 400–510 MPa, providing robust load capacity for beams and columns.
- Предел текучести: Minimum 245 МПа (base value for thin sections), with actual values often 10-20% higher in modern mills.
- Удлинение: 17–21% (gauge length 5.65√A), indicating sufficient ductility for seismic or impact-prone designs.
Thickness Effect on Yield Strength
Thickness profoundly influences SS400’s performance due to grain size and cooling rate variations in rolling. JIS G3101 mandates conservative minima to reflect real-world variability.
| Thickness (t) | Мин. Предел текучести (МПа) | Design Implication |
|---|---|---|
| ≤ 16 мм | ≥ 245 | Optimal for light frames; max allowable stress ~165 MPa (FS=1.5) |
| 16–40 mm | ≥ 235 | Common for beams; adjust buckling calcs downward |
| 40–100 mm | ≥ 215 | Heavy girders; increase section sizes for same load |
| > 100 мм | ≥ 205 | Foundations; verify with UT for laminations |
Engineers must reference exact thickness from drawings and MTRs—overlooking this can inflate material costs or compromise safety margins.
Physical Properties and Workability
SS400’s physical attributes enable precise engineering simulations, while its workability streamlines fabrication workflows. Density at 7850 kg/m³ facilitates accurate mass estimates for cranes and foundations, with Young’s modulus of 200-210 GPa delivering predictable stiffness in deflection calculations. Thermal expansion coefficient (11.7 × 10⁻⁶/K) и проводимость (51-60 W/m · k) support thermal stress modeling in heated structures.
For workability:
- Свариваемость: CE <0.40 allows multi-pass welding without preheat (вплоть до 20 мм); use E4303 electrodes for fillets.
- Обрабатываемость: Feeds/speeds akin to mild steel (120 m/min carbide turning); low tool wear for prototypes.
- Formability: Bend radii ≥2t for 90° bends, cold workable up to 10 mm thick.
These traits reduce shop time by 20-30% versus higher-strength steels, per industry benchmarks.
Corrosion Protection and Surface Treatments
Unprotected SS400 corrodes at 50-100 µm/year in C3 atmospheres (urban/industrial), accelerating to 200+ µm/year near coasts due to chlorides. Pitting under coatings poses hidden risks, potentially halving design life without intervention. Standards like ISO 9223 classify exposures, guiding protection levels from rural (C2) to offshore (C5M).
Recommended strategies include:
- Galvanizing: 85 µm zinc (ИСО 1461) for 25+ years in C4; duplex with paint for C5.
- Organic Coatings: Epoxy primer (80 мкм) + PU topcoat (60 мкм); inspect every 5 годы.
- Metallizing: Arc-sprayed aluminum (150 мкм) for high-heat or abraded areas.
Prep via Sa 2.5 blasting ensures adhesion >5 MPa. Lifecycle analysis often favors galvanizing for 50-year bridges, balancing upfront costs with minimal maintenance.
Equivalent Grades and Global Standards
| Region/Standard | Grade | Key Similarities | Differences from SS400 |
|---|---|---|---|
| США | АСТМ А36 | Tensile 400-550 МПа; Yield ≥250 MPa (t≤200 mm) | More chemistry specs; optional NDT |
| Китай | ГБ/Т 700 Q235B | Similar strength; good weldability | Impact tested; yield sub-grades (A/B/C/D) |
| Европа | В 10025 S235JR | Yield ≥235 MPa; Tensile ~360-510 MPa | 27J Charpy at +20°C mandatory |
| Korea | KS D3503 SS400 | Direct match | Identical JIS alignment |
Ss400 material equivalent swaps work for 80% of cases but verify toughness, thickness effects, and welding consumables. A36 suits U.S. codes seamlessly; Q235D for cold regions.
Available Forms and Supply Specifications
SS400 ships in standardized forms optimized for structural efficiency:
- Plates/Sheets: 1.6-200 mm thick, widths 1.0-3.5 m, lengths 2-12 m.
- Sections: H-beams (100-900 mm height), каналы (50-400 мм), угловой (25×25 to 200×200 mm).
- Бары: Rounds (10-250 mm dia.), flats (up to 300×40 mm).
Tolerances per JIS G3193: thickness ±0.5 mm (6-20 mm plates), width ±10-15 mm, flatness ≤1.5% of width. MTRs include chemistry, UT (per JIS G0303 Level 2), and marking (grade/heat/batch). Stock mills offer normalized or as-rolled; custom cut-to-length saves logistics. Specify EN 10204 3.1 certs for exports.
Typical Applications of SS400 Material
SS400’s balanced profile shines in structural roles demanding weldability and moderate strength. Key sectors include:
- Строительство: Welded beams and columns for warehouses, platforms, and multi-story frames; angle iron for bracing in seismic retrofits.
- Infrastructure: Bridge girders, approach slabs, and rail supports where fatigue resistance (~150 MPa at 10^7 cycles) handles traffic vibrations.
- Marine & Heavy Industry: Ship hull stiffeners and bulkhead frames enduring flexure; crane runway beams resisting cyclic hoist loads.
- Machinery & Fabrication: Bases for presses, conveyor frames, and storage racks—its machinability cuts setup time by 25%.
In die casting specifically, SS400 forms mold bases and non-core support fixtures. These low-stress components prioritize stability and cost over high polish, allowing premium tool steels (например, H13) for cavities. Paired with aluminum castings like A380 or ADC12, SS400 jigs enable precise production of EV motor housings and lighting shells without distortion.
Die Casting Manufacturer’s Perspective
Select SS400 when yield needs (205-245 MPa per thickness) align with budget and fabrication ease—ideal for mold bases, рамки, and prototypes. Escalate to higher grades for high-cycle fatigue or harsh environments; always calculate equivalents with site-specific factors like corrosion class.
В BIAN Die Cast, we leverage SS400 mold bases as reliable foundations for crafting A380, АЦП12, and AlSi9Cu3 cavities—perfect for LED road lamp housings, automotive inverter shells, и industrial control корпуса. Our integrated mold shop (10+ cold chamber die casters from 160-1250T, 100+ CNCs, in-house spray lines) produces full assemblies from steel frameworks to surface-finished castings.
Dual China-Мексика facilities cut U.S. tariffs and delivery times. МАТФ 16949 certification ensures every component traces back with compliant MTRs and RoHS reports.
Seamless integration awaits
