Firmodur 1249 QT Steel – High-Performance Quenched & Tempered Grade for Automotive & Industrial Applications

1.1249 (Cf70) a quenched and tempered steel suitable for the Flame and Induction hardening. It is mainly used for components in automotive engineering, such as connecting rods, but also for components used in the rolling and bearing industry.

Properties

General

Property	Value
Density	7.7 g/cm³

Dimension

Property	Value	Comment
Diameter	40 mm	max.

Mechanical

Property	Value	Comment
Elastic modulus	210 GPa
Elongation	11 - 13 %	A5
Hardness, Brinell	223 [-]	annealed
Reduction of area	25 - 30 %
Tensile strength	740 - 930 MPa
Yield strength	480 - 560 MPa

Thermal

Property	Temperature	Value	Comment
Coefficient of thermal expansion	100 °C	1.15e-05 1/K	for 20°C to the mentioned temperature
	200 °C	1.25e-05 1/K	for 20°C to the mentioned temperature
	300 °C	1.33e-05 1/K	for 20°C to the mentioned temperature
	400 °C	1.39e-05 1/K	for 20°C to the mentioned temperature
Specific heat capacity		470 J/(kg·K)
Thermal conductivity		42.6 W/(m·K)

Electrical

Property	Value
Electrical resistivity	1.9e-07 Ω·m

Chemical properties

Property	Value
Carbon	0.68 - 0.75 %
Iron	Balance
Manganese	0.2 - 0.35 %
Phosphorus	0.025 %
Silicon	0.15 - 0.35 %
Sulfur	0.035 %

Technological properties

Property
Application areas	It is mainly used for components in automotive engineering, such as connecting rods, but also for components used in the rolling and bearing industry.
Heat Treatment	Normalizing 820-850°C (Air), Soft annealing: 650-700°C (slow cooling), Quenching: 790-820°C (Water), Tempering: 550-660°C (Oil, Polymer,Water)
Hot forming	It is formable at 800-1000°C and should be then slowly cooled.
Processing history	Quenched and Tempered
Welding	It is usually not weldable and should will not be used in welded constructions.

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Metal