EN 10149-2 S355MC High-Strength Low-Alloy Steel
EN 10149-2 S355MC High-Strength Low-Alloy Steel for Automotive Cold Forming
S355MC is a thermomechanically rolled, high-strength low-alloy steel for cold forming, specified in EN 10149-2. It provides a minimum yield strength of 355 MPa with excellent formability and weldability, tailored for lightweight automotive structural applications.
Cold forming, bending, roll forming, stamping, punching, welding (all common methods), limited heat treatment (tempering or stress relieving is possible; the original mechanical properties are achieved by the thermomechanical rolling condition)
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EN 10149-2 S355MC High-Strength Low-Alloy Steel Introduction
S355MC is a high-strength low-alloy (HSLA) structural steel designed for cold forming. It is produced by thermomechanical rolling and belongs to the family of microalloyed steels with fine-grain practice. The alloying concept (Nb, V, Ti) ensures high strength and excellent weldability combined with good ductility. Typical applications include chassis components, reinforcements, and suspension parts in the automotive industry. The steel is supplied in the as-hot-rolled or pickled condition and is fully killed with a guaranteed minimum aluminium content. Its excellent bendability and consistent mechanical properties through the thickness make it suitable for safety-critical lightweight structures.
EN 10149-2 S355MC High-Strength Low-Alloy Steel Chemical Composition
Limits for chemical composition of grade S355MC according to EN 10149-2. The steel is fully killed with Al and microalloyed with Nb, V, Ti singly or in combination. The sum of Nb+V+Ti shall not exceed 0.22%. If sufficient other nitrogen-binding elements are present, the total aluminium content may be less.
| Chemical Element | Specified Limits (max or as noted, %) | Remarks |
|---|---|---|
| Carbon, C | ≤ 0.12 | Ladle analysis |
| Silicon, Si | ≤ 0.50 | |
| Manganese, Mn | ≤ 1.50 | |
| Phosphorus, P | ≤ 0.025 | |
| Sulfur, S | ≤ 0.015 | |
| Total Aluminium, Al total | ≥ 0.015 | Requirement for fine-grain practice |
| Niobium, Nb | ≤ 0.09 | Microalloy element; sum Nb+V+Ti ≤ 0.22% |
| Vanadium, V | ≤ 0.20 | Microalloy element |
| Titanium, Ti | ≤ 0.15 | Microalloy element |
| Nitrogen, N | No specific limit | Not normally specified; bound by Ti or Al |
EN 10149-2 S355MC High-Strength Low-Alloy Steel Thermal and Electrical Physical Properties
Physical constants for similar low-alloyed structural steels; exact values depend on exact composition and processing. These values serve as engineering guidelines.
| Property | Typical Value | Unit | Condition / Temperature |
|---|---|---|---|
| Density, ρ | ~7850 | kg/m³ | At 20 °C |
| Modulus of elasticity, E | ~210 | GPa | At 20 °C |
| Shear modulus, G | ~81 | GPa | Calculated from E and ν |
| Poisson's ratio, ν | ~0.3 | – | Elastic region |
| Thermal expansion coefficient, α | ~12.0 × 10⁻⁶ | K⁻¹ | Between 20 °C and 100 °C |
| Thermal conductivity, λ | ~50 | W/(m·K) | At 20 °C |
| Specific heat capacity, cp | ~460 | J/(kg·K) | At 20 °C |
| Electrical resistivity, ρe | ~0.15 – 0.25 | μΩ·m | At 20 °C |
EN 10149-2 S355MC High-Strength Low-Alloy Steel Mechanical Properties at Room Temperature
Mechanical properties as specified in EN 10149-2 for sheet/plate thickness t in mm. The values apply to the as-delivered condition (+M). For thicknesses ≤ 3 mm, ReH may be 20 MPa lower (still ≥ 335 MPa) but is guaranteed as per standard. Impact test is for longitudinal specimens, minimum average energy.
| Property | Specified Value | Unit | Test Condition / Remarks |
|---|---|---|---|
| Yield strength, ReH | ≥ 355 | MPa | Transverse specimen; for t ≤ 3 mm: ≥ 335 MPa |
| Tensile strength, Rm | 430 – 550 | MPa | Transverse specimen |
| Elongation after fracture, A | ≥ 19 | % | Gauge length 80 mm, t < 3 mm; A ≥ 23% for t ≤ 2 mm typically |
| Elongation after fracture, A5 | ≥ 23 | % | For t ≥ 3 mm, gauge length 5.65√S0 |
| Bend test, minimum bend radius | 0.5 t | – | 180° bend, t = sheet thickness; no cracking |
| Impact energy, KV (-20 °C) | ≥ 40 | J | Longitudinal, Charpy V-notch; applies for t ≥ 6 mm; for thinner gauges by agreement |
EN 10149-2 S355MC High-Strength Low-Alloy Steel Exactly Equivalent Standards and Substitutable Grades
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10149-2:2013 | S355MC | The original specification |
| International | ISO 6930-1:2017 | S355MC | Identical technical delivery conditions |
| Germany (historical) | DIN 1614-2 (withdrawn); SEW 092 | QStE 380 TM | Predecessor grade; closely matches S355MC |
| United Kingdom | BS 1449-1.4:1990 (obsolescent) | HSLA355 (FeE355) | Similar grade; the symbol FeE355 TM is often used |
| France | NF A36-231 (withdrawn) | E355MR | Equivalent thermomechanical steel |
| Japan (alternate) | JIS G3113:2006 | SAPH440 | Comparable, but careful check required; SAPH440 has higher tensile range |
EN 10149-2 S355MC High-Strength Low-Alloy Steel Application Introduction
S355MC is designed for cold-formed components requiring high yield strength and good weldability. It is suitable for light-weighting of structures without sacrificing safety. The microalloy composition delivers fine grain strengthening and precipitation hardening, enabling thinner gauges to replace conventional mild steels.
Product Applications: Passenger car chassis (longitudinal beams, cross members), Pickup and truck frame rails, Automobile suspension control arms and spring supports, Bumper reinforcement beams, Wheel rims and wheel discs, Cold-formed and welded hollow sections (RHS, CHS), Agricultural harvester frames
Processed into products: Side impact beams, Seat slide rails and seat frame structures, Subframe mounting brackets, Engine cradles, Tow-bar brackets, Forging-like parts produced by progressive cold stamping
Application industries: Automotive (passenger cars, light commercial vehicles), Heavy transport (trucks, trailers), Agricultural machinery, Construction equipment (crane booms, chassis components), General engineering (cold-formed profiles, tubes)
EN 10149-2 S355MC High-Strength Low-Alloy Steel Similar and Alternative Materials Recommendations
| Country/Region | Standard | Grade | Remarks |
|---|---|---|---|
| Europe | EN 10149-2 | S315MC | Lower yield strength (315 MPa) with similar formability; lighter applications |
| Europe | EN 10149-2 | S420MC | Higher yield strength (420 MPa); suitable where higher strength is needed with still good formability |
| Europe | EN 10025-3 | S355N / S355NL | Normalised fine-grain steel; lower carbon, good weldability but less optimised for cold forming |
| USA | ASTM A1011/A1011M | SS Grade 55 Class 2 (HSLAS-F) | Similar yield strength level; check thickness range |
| China | GB/T 20564.2 | HC355F | High strength steel for cold forming; suitable alternative |
Notes:
- For thicknesses > 6 mm, the impact energy of 40 J at -20 °C is mandatory; for thinner material, testing is by agreement.
- Surface quality: unless otherwise agreed, surface condition A (per EN 10163-2) is normally supplied, allowing slight imperfections inherent in the hot-rolled condition.
- Weldability: excellent for all common fusion welding methods; preheating is generally not required for thicknesses up to 10 mm.
- If hot-dip galvanizing is foreseen, the producer should be informed to adjust chemistry for best zinc adhesion.
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