S235 vs S355

S355 and S235 are about equally stiff. Their densities are about the same. Per unit mass they are about equally stiff (26.75 and 26.75 MJ/kg). Strength: f_y = 235 MPa for S235, f_y = 355 MPa for S355.

S235 EN 10025-2 · t ≤ 16 mm S355 EN 10025-2 · t ≤ 16 mm

Side by side

ratio = S355 / S235 · log scale

Property	S235	S355	Unit	Ratio
E Young's modulus	210	210	GPa	1×
G Shear modulus	81	81	GPa	1×
ν Poisson's ratio	0.3	0.3	–	1×
ρ Density	7850	7850	kg/m³	1×
α Coefficient of thermal expansion	12	12	10⁻⁶/K	1×
λ Thermal conductivity	53.33	53.33	W/(m·K)	1×
c_p Specific heat capacity	439.8	439.8	J/(kg·K)	1×
f_y Yield strength (R_eH / R_p0.2)	235	355	MPa	1.51×
f_u Tensile strength (R_m)	360	470	MPa	1.31×
f_u,max Tensile strength, upper limit	510	630	MPa	1.24×
f_y (T3.1) Yield strength, EN 1993-1-1 Table 3.1	235	355	MPa	1.51×
f_u (T3.1) Tensile strength, EN 1993-1-1 Table 3.1	360	490	MPa	1.36×
E/ρ Specific stiffness E/ρ · derived	26.75	26.75	MJ/kg	1×
c₀ Bar wave speed √(E/ρ) · derived	5172	5172	m/s	1×
f/ρ Specific strength f/ρ · derived	29.94	45.22	kJ/kg	1.51×

Values at the first thickness band or product form of each material (EN 10025-2 · t ≤ 16 mm; EN 10025-2 · t ≤ 16 mm). A minimum and a characteristic value are not the same kind of number — read the ratio as a guide. Each material's page lists every band and every source.