18HGT

Improve or carburized parts critical applications, by requiring the increased strength and toughness core and high surface hardness, operating under the influence of shock loads.

Classification

Country	Section	Category
Country	Section	Category
CIS, Russia, Ukraine	Structural steel	Alloyed structural steel

Chemical composition

Standard	Fe, %	Si, %	Mn, %	Cr, %	Ti, %	Cu, %	Ni, %	P, %	C, %	S, %
Standard	Fe, %	Si, %	Mn, %	Cr, %	Ti, %	Cu, %	Ni, %	P, %	C, %	S, %
GOST 4543-71	96.24–97.83	0.17–0.37	0.8–1.1	1–1.3	0.03–0.09	< 0.3	< 0.3	< 0.035	0.17–0.23	< 0.035

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Physical characteristics

Temperature, °C	$E\cdot 10^{9}$ , $MPa$	$\alpha\cdot 10^{6}$ , $K^{-1}$	$\varkappa$ , $\frac{W}{m\cdot K}$	$\rho$ , $\frac{kg}{m^3}$	$c\cdot 10^{-3}$ , $\frac{J}{kg\cdot K}$
Temperature, °C	$E\cdot 10^{9}$ , $MPa$	$\alpha\cdot 10^{6}$ , $K^{-1}$	$\varkappa$ , $\frac{W}{m\cdot K}$	$\rho$ , $\frac{kg}{m^3}$	$c\cdot 10^{-3}$ , $\frac{J}{kg\cdot K}$
20	211		37	7800
100	205	10	38		0.495
200	197	11.5	38		0.508
300	191	12.3	37		0.525
400	176	12.8	35		0.537
500	168	13.3	34		0.567
600	155	13.6	31		0.588
700	136		30		0.626
800	129		29		0.705

Mechanical properties at 20 °C

Rolling	Standard	Size, mm	Tension	Classifiers	$\sigma _{U}$ , $MPa$	$\sigma_{P}$ , $MPa$	$\epsilon_L$ , %	$\psi$ , %	$KCU\cdot 10^{3}$ , $\frac{J}{m^2}$	Treatment
Rolling	Standard	Size, mm	Tension	Classifiers	$\sigma _{U}$ , $MPa$	$\sigma_{P}$ , $MPa$	$\epsilon_L$ , %	$\psi$ , %	$KCU\cdot 10^{3}$ , $\frac{J}{m^2}$	Treatment
Rod	GOST 4543-71				980	885	9	50	780	Hardening and tempering
Steel		5			1520	1320	12	50	720	Tempering 850 ° C, oil, leave 200 ° C, air
Steel		20			980	730	15	55	1130	Tempering 850 ° C, oil, leave 200 ° C, air

Brinell hardness number

Rolling	Standard	Classifiers	Value, HBW
Rolling	Standard	Classifiers	Value, HBW
Alloy	GOST 4543-71	annealing	217
Alloy	GOST 4543-71	cold-work	229

Technological Properties

Weldability	Flake Susceptibility	Propensity to temper brittleness
Weldability	Flake Susceptibility	Propensity to temper brittleness
no limits	not sensitive	loathsome

Critical point temperatures

Ac₁, K	Ac₃(Ac_m), K	Ar₃(Arc_m), K	Ar₁, K	Mn, K
Ac₁, K	Ac₃(Ac_m), K	Ar₃(Arc_m), K	Ar₁, K	Mn, K
740	825	730	650	360

Analogues

Germany
Germany
20MnCr5G

Standards

Standard	Description
Standard	Description
GOST 4543-71

Description of chemical elements

Element	Units of measurement	Description
Element	Units of measurement	Description
Fe	%	Iron
Si	%	Silicon
Mn	%	Manganese
Cr	%	Chrome
Ti	%	Titan
Cu	%	Copper
Ni	%	Nickel
P	%	Phosphorus
C	%	Carbon
S	%	Sulfur

Description of physical characteristics

Parameter	Units of measurement	Description
Parameter	Units of measurement	Description
$E\cdot 10^{9}$	$MPa$	Elastic modulus
$\alpha\cdot 10^{6}$	$K^{-1}$	Coefficient of thermal (linear) expansion (range 20°C–T)
$\varkappa$	$\frac{W}{m\cdot K}$	Coefficient of thermal conductivity (the heat capacity of the material)
$\rho$	$\frac{kg}{m^3}$	The density of the material
$c\cdot 10^{-3}$	$\frac{J}{kg\cdot K}$	The specific heat of the material (range 20°C–T)

Description of mechanical properties

Parameter	Units of measurement	Description
Parameter	Units of measurement	Description
$\sigma _{U}$	$MPa$	Ultimate tensile strength
$\sigma_{P}$	$MPa$	Proportionality limit
$\epsilon_L$	%	Elongation at break (longitudinal)
$\psi$	%	Reduction in cross section on fracture
$KCU\cdot 10^{3}$	$\frac{J}{m^2}$	Impact toughness

Designation of types of weldability

Parameter	Units of measurement	Description
Parameter	Units of measurement	Description
no limits		Welding is performed without heating and without subsequent heat treatment
Boundedly welded		Welding is possible with heating up to 100–120 °C and subsequent heat treatment
Difficult to weld		For obtaining quality welded joints, additional operations are required: heating up to 200–300 °C for welding, heat treatment after welding — annealing
Not applicable for welded structures

Description of temperatures of critical points

Parameter	Units of measurement	Description
Parameter	Units of measurement	Description
Ac₁	K
Ac₃(Ac_m)	K
Ar₃(Arc_m)	K
Ar₁	K
Mn	K