Equivalent Materials
Materials comparable to SS400 include ASTM A36 and EN S275JR. All three are mild steels with low carbon content, suitable for construction applications requiring flexibility and durability. They share similar characteristics in weldability, machinability, and corrosion resistance. The JIS G3101 specification also covers SS330, SS490, and SS540, but SS400 is the most prevalent by volume.
| Property | SS400 (JIS) | A36 (ASTM) | S235JR (EN) | St37-2 (DIN) | Q235B (GB) |
|---|---|---|---|---|---|
| Yield (MPa) | 245 | 250 | 235 | 235 | 235 |
| Tensile (MPa) | 400-510 | 400-550 | 360-510 | 360-510 | 370-500 |
| Elongation % | 21 | 23 | 26 | 26 | 26 |
| C max % | N/A | 0.26 | 0.19 | 0.21 | 0.20 |
| P max % | 0.050 | 0.040 | 0.045 | 0.065 | 0.045 |
| S max % | 0.050 | 0.050 | 0.045 | 0.065 | 0.045 |
Additional equivalents include ISO Fe360B, ASTM A283C for lighter plate, and A570 for strip. St37-2 and Q235B remain the closest German and Chinese matches. A steel plate produced to JIS G3101 may differ in documentation from one produced to ASTM even when mechanical properties overlap, so mill certificates should be verified against the governing specification before cutting begins.
Characteristics
SS400 demonstrates superior weldability and machinability due to its low carbon content. Its corrosion resistance makes it suitable for harsh environments, and a high strength-to-weight ratio makes it preferable for weight-sensitive structures. Hardness is relatively low but provides reasonable toughness and crack resistance.
- Density: 7.85 g/cm3
- Thermal conductivity: approximately 25.93 W/mK
- Hardness: relatively low, providing reasonable toughness and crack resistance
Uses
- Automotive: favored for excellent weldability in complex component manufacturing
- Construction: preferred for high tensile strength in structural applications
- Marine: superior corrosion resistance makes it suitable with appropriate coatings
Mechanical Properties
| Property | SS400 vs. Mild Steel |
|---|---|
| Tensile Strength | Lower in SS400 |
| Hardness | Lower in SS400 |
| Impact Resistance | Higher in SS400 |
| Ductility | Higher in SS400 |
| Fatigue Life | Mild steel slightly longer |
| Property | Yield Strength | Tensile Strength | Elongation |
|---|---|---|---|
| SS400 | >=245-205 N/mm2 (varies by thickness) | 400-510 N/mm2 | <=5% (plate <=5mm); >=17-23% (varies by product) |
Chemical Composition
| Grade | C | Mn | P | S |
|---|---|---|---|---|
| SS400 | - | - | <=0.050 | <=0.050 |
The JIS specification takes a minimal approach to composition. Unlike ASTM or European standards, it does not mandate maximum carbon or manganese limits and restricts only phosphorus and sulfur. In practice, mills hold carbon around 0.17% to 0.25% and manganese up to 1.40%, which contributes to ductility and ease of processing for bending, stamping, and welding.
How Does SS400 Compare to ASTM A36?
ASTM A36 is the most commonly cited American equivalent, and the two are often considered interchangeable. Both fall within similar tensile and yield ranges, but a few distinctions matter for engineering decisions. A36 specifies a maximum carbon of 0.26%, while JIS G3101 does not set a carbon limit. In yield, A36 requires 250 MPa versus 245 MPa for SS400 at plates 16 mm or less.
For most uses, A36 can replace SS400 without design changes. However, switching grades mid-build requires more than checking a properties table: tolerances, finish callouts, and any coating needs should be reviewed against the substitute before cutting starts.
Welding and Formability
SS400 accepts all arc welding methods, including MIG, TIG, shielded metal arc welding (SMAW), and flux-cored arc welding (FCAW), with no preheating required. The steel is a preferred choice for press brake bending, roll forming, stamping, and punching, and it cuts, drills, and mills easily on both CNC and manual equipment.
Surface finish options include mill finish (as-rolled), pickled and oiled, galvanized, and painted or primed. Plating and powder coat add build-up to surfaces, and if masking is not specified on the drawing, the default is to coat everything, including holes and threads that should remain bare. Specifying which features to mask prevents rework.
Frequently Asked Questions About SS400
What material is similar to SS400? ASTM A36 is the closest match under American standards. The European designation S235JR and GB Q235B also share similar mechanical properties and yield ranges. Each serves structural uses across building and metalwork, though documentation and testing needs differ by specification.
Is SS400 equivalent to A36? The two are often considered interchangeable for structural use. A36 has a slightly higher yield at 250 MPa versus 245 MPa, and specifies a maximum carbon of 0.26% while JIS does not define a carbon limit. Before substituting one for the other, confirm the governing specification and verify that coating, tolerance, and certification needs align.
What is SS400? SS400 is a Japanese structural steel defined by JIS G3101. The 'SS' stands for Steel Structural, and '400' represents the minimum tensile strength of 400 megapascals. Mills produce it as hot-rolled plates, coils, beams, and pipe for building and metalwork.
Is SS400 a carbon steel? SS400 is classified as a low-carbon structural steel. The JIS specification does not set an exact carbon limit, but typical values fall between 0.17% and 0.25%. This gives the steel high ductility and good weldability, making it widely used across many industries.
