S700MC Grade Definition and Supply Range
S700MC is a thermomechanically rolled, high yield strength structural steel plate defined in EN 10149-2, the European standard for hot-rolled flat products of high yield strength steels suitable for cold forming. The grade symbol follows the EN naming system: S for structural steel, 700 for the minimum yield strength in megapascals, M for thermomechanical rolling and C for cold-forming suitability. It belongs to the high-strength low-alloy (HSLA) family, in which controlled rolling, accelerated cooling and microalloy precipitation replace the quenching and tempering route used for grades such as EN 10025-6 S690QL.
Because the strength is obtained from a refined ferrite grain structure rather than from alloying for hardenability, S700MC offers a high strength-to-weight ratio together with good toughness, formability and weldability. Depending on the producing mill it is supplied in thicknesses from roughly 2 mm to 16 mm, widths of approximately 1000 mm to 2000 mm and lengths up to 12 m, with tolerances, surface condition and testing requirements agreed at the time of order.
Chemical Composition of S700MC
Carbon is deliberately kept low to protect toughness and weldability, while niobium, vanadium and titanium provide precipitation strengthening in the rolled microstructure. Typical product analysis limits for the grade are listed below.
| Element | Limit (% by mass) | Function in the steel |
|---|---|---|
| C | 0.12 max | Strength contributor, limited for toughness |
| Si | 0.50 max | Deoxidation and solid-solution strengthening |
| Mn | 2.10 max | Solid-solution strengthening, hardenability |
| P | 0.025 max | Restricted to protect ductility |
| S | 0.015 max | Restricted to control inclusions |
| Al | 0.015 min | Deoxidation and grain refinement |
| Nb + V + Ti | 0.22 max | Carbonitride precipitation strengthening |
The microalloying package is the heart of the grade. Niobium retards recrystallisation during rolling and refines the ferrite grain size, while vanadium and titanium add further precipitation strengthening during cooling. The low-carbon, microalloyed design also keeps the carbon equivalent within a range that can be welded using qualified procedures; the applicable equivalent formula and the plate thickness must be considered for each fabrication.
Mechanical Properties of S700MC Plate
| Property | Value | Test method |
|---|---|---|
| Yield strength ReH | 700 MPa minimum, typically 700 to 850 MPa | EN ISO 6892-1 |
| Tensile strength Rm | 750 to 950 MPa | EN ISO 6892-1 |
| Elongation A5 | 14 % minimum | EN ISO 6892-1 |
| Hardness | 200 to 250 HBW typical | EN ISO 6506-1 |
The values apply to test pieces taken transverse to the rolling direction from the delivered product, in the as-rolled thermomechanical condition. The superseded test method EN 10002-1 has been replaced by EN ISO 6892-1 for tensile testing, and hardness is measured according to EN ISO 6506-1. Impact testing is not mandatory in EN 10149-2; where low-temperature toughness is required, Charpy V-notch absorbed energy at the agreed test temperature is specified when the order is placed. The combination of high yield strength with at least 14 percent elongation is the reason the grade can carry heavy loads while still being formed into finished parts.
Physical Properties
| Property | Typical value |
|---|---|
| Density | 7.85 g/cm³ |
| Melting range | approximately 1,500 °C |
| Thermal conductivity | approximately 50 W/(m·K) |
| Specific heat capacity | approximately 0.49 kJ/(kg·K) |
| Modulus of elasticity | approximately 210 GPa |
These values are normal for low-alloy structural steel and are used for structural calculation, for thermal modelling of the welding cycle and for designing forming and machining operations.
Welding, Cutting and Forming Behaviour
Welding: gas metal arc, submerged arc and resistance welding are all used. A moderate heat input with matching consumables keeps the softened zone narrow and preserves joint efficiency. Thin sections generally need no preheating, while thick or highly restrained joints call for a qualified welding procedure.
Cutting: laser, plasma and abrasive waterjet cutting all produce clean edges. High strength plate carries greater residual stress, so the cutting sequence should be planned to limit distortion.
Cold forming: bending and roll forming are practical, the minimum bend radius being a function of thickness and of bend line orientation relative to the rolling direction. Springback is larger than for mild steel and has to be compensated in the tooling.
Machining: cutting forces are higher than for mild steel, so rigid setups and appropriate tool grades are needed to hold dimensional accuracy.
Typical Applications and End Uses
| Sector | Example part | Property used |
|---|---|---|
| Automotive and transport | chassis, subframes, longitudinal members | High yield strength with weight saving |
| Trailers and tippers | bodies, side walls, tipping structures | Strength combined with formability |
| Mobile machinery | crane booms, excavator arms, loader frames | Toughness under dynamic load |
| Agricultural equipment | implements, seeders, harvester components | Fatigue and impact resistance |
| Construction | cold-formed sections, storage racks, props | High strength-to-weight ratio |
| Rail and energy | wagon components, poles, tower parts | Durability in cyclic service |
Selecting S700MC Against Related Grades
| Grade | Standard | Selection note |
|---|---|---|
| S650MC | EN 10149-2 | Lower strength, easier forming, same thermomechanical family |
| S690MC | EN 10149-2 | Higher strength for the most demanding weight saving |
| S690QL | EN 10025-6 | Quenched and tempered; restricted forming, more demanding welding |
| ASTM A572 Grade 65 | ASTM A572/A572M | Widely available moderate strength HSLA plate |
| JIS G3106 SM490YA | JIS G3106 | Weldable structural steel with excellent formability |
Where weight saving drives the design and the part is formed before assembly, a thermomechanically rolled grade such as S700MC or S650MC is normally the economical choice, because it delivers strength without a heat treatment step. Where maximum strength at minimum thickness matters and forming is limited, quenched and tempered grades such as S690QL take over, at the cost of tighter welding control and reduced bendability.
Frequently Asked Questions
Q: What do the M and C in S700MC stand for?
M indicates thermomechanical rolling and C indicates suitability for cold forming, so the grade delivers 700 MPa class strength in a formable, as-rolled condition.
Q: What is the minimum yield strength of S700MC?
The specified minimum yield strength is 700 MPa, and plates are typically delivered in the range of 700 to 850 MPa with tensile strength of 750 to 950 MPa.
Q: Can S700MC be welded without preheating?
Thin, lightly restrained joints normally need no preheating because the low-carbon microalloyed design limits cold cracking sensitivity, but thick or restrained joints require a qualified procedure with controlled heat input.
Q: What thickness range is normally available?
Common supply covers approximately 2 mm to 16 mm, with some mills able to roll up to about 20 mm; width and length are matched to the mill rolling programme.
Q: Is S700MC a weathering steel?
No. It is a structural HSLA grade. Where atmospheric corrosion resistance is required, a weathering grade such as EN 10025-5 S355J2W or ASTM A588 should be selected instead.
Q: How does S700MC differ from S690QL?
S700MC is thermomechanically rolled and remains formable with a lower carbon equivalent, while S690QL is quenched and tempered, reaches higher strength but offers less bendability and demands stricter welding control.
