20HN3A

Gears, shafts, bushings, power pins, bolts, couplings, worms and other carburized parts, which are requirements of high strength, ductility and toughness core and high surface hardness, operating under the influence of shock loads and at low temperatures.

Classification

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

Chemical composition

Standard	Fe, %	Si, %	Mn, %	Cr, %	Cu, %	Ni, %	P, %	C, %	S, %
Standard	Fe, %	Si, %	Mn, %	Cr, %	Cu, %	Ni, %	P, %	C, %	S, %
GOST 4543-71	94.39–96.01	0.17–0.37	0.3–0.6	0.6–0.9	< 0.3	2.75–3.15	< 0.025	0.17–0.24	< 0.025

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Physical characteristics

Temperature, °C	$E\cdot 10^{9}$ , $MPa$	$\alpha\cdot 10^{6}$ , $K^{-1}$	$\varkappa$ , $\frac{W}{m\cdot K}$	$\rho$ , $\frac{kg}{m^3}$	$c\cdot 10^{-3}$ , $\frac{J}{kg\cdot K}$	$R\cdot 10^{-6}$ , $\Omega\cdot m$
Temperature, °C	$E\cdot 10^{9}$ , $MPa$	$\alpha\cdot 10^{6}$ , $K^{-1}$	$\varkappa$ , $\frac{W}{m\cdot K}$	$\rho$ , $\frac{kg}{m^3}$	$c\cdot 10^{-3}$ , $\frac{J}{kg\cdot K}$	$R\cdot 10^{-6}$ , $\Omega\cdot m$
20	212		36	7850		0.27
100	204	11.5	35	7830	0.494	0.3
200	194	11.7	34		0.507	0.35
300	188	12	33	7760	0.523	0.45
400	169	12.6	33		0.536	0.55
500	169	12.8	31		0.565	0.65
600	153	13.2	31	7660	0.586
700	138	13.6	30		0.624
800	132	11.2	28		0.703

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	15			930	735	12	55	1080	Hardening and tempering

Brinell hardness number

Rolling	Standard	Classifiers	Value, HBW
Rolling	Standard	Classifiers	Value, HBW
Alloy	GOST 4543-71	annealing	255

Technological Properties

Weldability	Flake Susceptibility	Propensity to temper brittleness
Weldability	Flake Susceptibility	Propensity to temper brittleness
Boundedly welded	sensitive	inclined

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
730	810	700	615	340

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
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)
$R\cdot 10^{-6}$	$\Omega\cdot m$	Electrical resistivity

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