SS400 material is well known in building and structural construction. SS400 material is a kind of mild steel.
What is the difference between mild steel and SS400 material?
First, we need to understand what is mild steel.
Mild steel is the mildest type of carbon steel. Its carbon content is low, which is 0.16–0.29% approximately by weight. Mild steel can contain other elements as well. For example, manganese, silicon, and trace amounts of phosphorous. Those elements protect the integrity of the structure of metal iron by preventing dislocations within the iron crystals.
SS400 material belongs to mild steel.
The biggest difference between mild steel and SS400 material is that mild steel is a general concept, and it covers a lot of steel grades, and SS400 is only one of them.
- General Classification
| Property | Mild Steel | SS400 |
|---|---|---|
| Definition | A broad category of low-carbon steel. | A specific structural steel grade under JIS G 3101 (Japanese Industrial Standard). |
| Standards | Varies (e.g., ASTM A36, EN S235, etc.) | Standardized under JIS G 3101. |
- Chemical Composition
| Element | Mild Steel | SS400 |
|---|---|---|
| Carbon (C) | ≤ 0.25% (low for weldability) | ≤ 0.30% (varies by spec.) |
| Manganese (Mn) | Typically ≤ 1.00% | ≤ 1.60% (higher for strength) |
| Sulfur (S) | ≤ 0.05% (general) | ≤ 0.05% |
| Phosphorus (P) | ≤ 0.04% | ≤ 0.04% |
Note: SS400 allows slightly higher carbon and manganese than most mild steels, enhancing strength.
- Mechanical Properties
| Property | Mild Steel | SS400 |
|---|---|---|
| Tensile Strength | ~370–500 MPa (e.g., ASTM A36) | 400–510 MPa (as per JIS) |
| Yield Strength | ~250 MPa (e.g., ASTM A36) | ≥ 245 MPa (minimum) |
| Elongation | ~20–23% (higher ductility) | 17–21% (lower ductility) |
Key Insight: SS400 prioritizes tensile strength over elongation compared to mild steel.
- Applications
| Material | Typical Uses |
|---|---|
| Mild Steel | General-purpose (e.g., automotive panels, pipes, construction frames, machinery parts). |
| SS400 | Structural applications in Japan (e.g., bridges, buildings, ships) and industrial equipment. |
- Key Distinctions
Strength vs. Ductility: SS400 has a higher tensile strength (400+ MPa) but slightly lower ductility than mild steel.
Regional Use: SS400 aligns with Japanese standards, while ASTM A36 (USA) or S235 (EU) are regional equivalents.
Composition: SS400 allows higher manganese, improving strength without significant cost.
- Equivalents
| Property | Mild Steel | SS400 |
|---|---|---|
| Equivalents | ASTM A36 (USA), EN S235 (Europe) | JIS G 3101 |
Summary
Mild steel is a generic term for low-carbon steels with good weldability and ductility.
SS400 is a standardized Japanese structural steel optimized for strength and used in heavy-load applications. While chemically similar to mild steel, its higher Mn content and stricter compliance with JIS make it distinct regionally and mechanically.
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FAQ
Q: What is the difference between SS400 and SS490?
A: SS490 has superior tensile strength compared to SS400 steel. It is employed in thicknesses ranging from 6 mm to 120 mm. Its chemical makeup includes a maximum of 0.050 percent of both Phosphorous and Sulphur, with iron and minor impurities.
Q: What is SS400 steel material?
A: SS400 is a structural steel with high tensile strength, equal to 400N/mm² or more. SS400 is known for being more affordable and accessible compared to other metal materials. It is also easy to process through methods like welding and cutting.
Q: Is SS400 equivalent to mild steel?
A: SS400 material belongs to mild steel. The biggest difference between mild steel and SS400 material is that mild steel is a general concept, and it covers a lot of steel grades, and SS400 is only one of them. Note: SS400 allows slightly higher carbon and manganese than most mild steels, enhancing strength.
Q: What is the hardness of SS400 steel?
A: SS400 Hardness (HBW): 180-220 Brinell; Impact Resistance: 27 Joules at 20°C; Modulus of Elasticity (GPa): 190-210; Density (kg/m3): 7,800-8,700
| Other steel plate | ||||
| Name | Material | Specification (mm) | Tons | Remark |
| Low Alloy | Q345A, Q345B, Q345C, Q345D, Q345E, Q390, Q420, Q460C, ST52-3, S355J2+N, SS400, SA302GrC, S275NL, 35CrMo | 6 - 350 | 5788.56 | Normalizing, tempered ,controlled rolling, hot rolling , Hot rolling,1st inspection, 2nd inspection, 3rd inspection |
| Pressure Vessel Plate | Q245R, Q345R, Q370R, 16MnDR, 09MnNiDR, 15CrMoR, 14Cr1MoR, 12Cr2Mo1R, SA516Gr60, SA516Gr70, SA516Gr485, SA285, SA387Gr11, SA387Gr12, SA387Gr22, P265,P295,P355GH,Q245R(R-HIC),Q345R(R-HIC) | 3 - 300 | 8650 | Normalizing, tempered ,controlled rolling, hot rolling , Hot rolling,1st inspection, 2nd inspection, 3rd inspection |
| High-Strength Plate | WH785D/E,Q960D/E, Q890D/E,WH60D/E,WH70B,Q550D,Q590D,Q690D/E | 8 - 120 | 3086.352 | Quenched and tempered |
| Wear-Resistant Plate | NM360, NM400, NM450, NM500 | 6 - 150 | 3866.297 | Quenched and tempered |
| Bridge Plate | Q235qC, Q345qC, Q370qC, Q420qC, Q345qDNH, Q370qDNH, A709 - 50F - 2, A709 - 50T - 2 | 8 - 200 | 2853.621 | Hot rolling, normalized ,hot rolling controlled rolling, quenched and tempered + toughness and brittleness |
