20NiCrMo7

General Information

Ovako 157 is a high cleanliness case hardening steel used for bearing and transmission components. There are three different modifications of the grade.

157C - Bearing quality (BQ) variant with low sulphur content

157D - Bearing quality (BQ) variant with low sulphur content

157G - Regulated sulphur content for improved and consistent machinability

BQ-Steel^®
(Bearing Quality) is a bearing quality clean steel optimized for fatigue strength by a strict control of steel cleanliness. BQ-steel is also ideal for new design solutions in a wide array of demanding applications outside the bearing industry that require longer performance and higher loads. The BQ-steel offer is the result of the Ovako clean steel program. Purity of production means that the material has significantly smaller inclusions compared to conventional steel and, as a result, the fatigue strength of the steel is increased dramatically. Use of the material allows components to be manufactured in smaller sizes. The BQ-steel has for decades been the problem-solver.

BQ-Steel^®

BQ-steel® is a bearing quality clean steel optimized for fatigue strength and is also ideal for new design solutions outside the bearing industry.

Similar designations

ASTM 4320, ASTM 4320H, ASTM 4320RH

Variant	Cast	Weldability		C %	Si %	Mn %	P %	S %	Cr %	Ni %	Mo %	V %
157C	IC	CEV 0.65_max	Min	0.17	0.20	0.55	-	0.002	0.50	1.65	0.23	-
Pcm 0.36_max	Max	0.22	0.30	0.65	0.015	0.005	0.60	2.00	0.28	0.014
157D	IC	CEV 0.67_max	Min	0.17	0.20	0.55	-	0.002	0.50	1.65	0.23	-
Pcm 0.37_max	Max	0.22	0.30	0.65	0.015	0.005	0.60	2.00	0.28	0.100
157G	IC	CEV 0.7_max	Min	0.20	0.20	0.70	-	0.010	0.55	1.70	0.25	-
Pcm 0.38_max	Max	0.22	0.35	0.80	0.020	0.020	0.65	1.80	0.30	0.100

Variant

Cast

Weldability

C %

Si %

Mn %

P %

S %

Cr %

Ni %

Mo %

V %

157C

CEV 0.65_max

Min

0.17

0.20

0.55

0.002

0.50

1.65

0.23

Pcm 0.36_max

Max

0.22

0.30

0.65

0.015

0.005

0.60

2.00

0.28

0.014

157D

CEV 0.67_max

Min

0.17

0.20

0.55

0.002

0.50

1.65

0.23

Pcm 0.37_max

Max

0.22

0.30

0.65

0.015

0.005

0.60

2.00

0.28

0.100

157G

CEV 0.7_max

Min

0.20

0.70

0.010

0.55

1.70

0.25

Pcm 0.38_max

Max

0.22

0.35

0.80

0.020

0.65

1.80

0.30

0.100

Variant	Condition	Format	Dimension [mm]	Yield strength min [MPa]	Tensile strength [MPa]	Hardness
Rp_0.2 * R_eh, ** R_el
157C	+QT	Round bar	25 typical	1200	1300 typical	360 HB typical
157D	+QT	Round bar	25 typical	1200	1300 typical	360 HB typical

Variant

Condition

Format

Dimension [mm]

Yield strength min [MPa]

Tensile strength [MPa]

Hardness

Rp_0.2 * R_eh, ** R_el

157C

+QT

Round bar

25 typical

1200

1300 typical

360 HB typical

157D

+QT

Round bar

25 typical

1200

1300 typical

360 HB typical

	Temperature °C
MS	400
AC1	704
AC3	806

Temperature °C

400

AC1

704

AC3

806

Treatment	Condition	Temperature cycle	Cooling/quenching
Hot forging	+U	800-1200C	In air
Normalizing	+N	860-890C	In air
Soft annealing	+A	600-670/2h	In air
Quench & Tempering	+QT	840-890C	In oil
Quench & Tempering	+QT	780-830C Hardening of as-carburized components	In oil
Tempering	+T	160-250C	In air

Treatment

Condition

Temperature cycle

Cooling/quenching

Hot forging

800-1200C

In air

Normalizing

860-890C

In air

Soft annealing

600-670/2h

In air

Quench & Tempering

+QT

840-890C

In oil

Quench & Tempering

+QT

780-830C Hardening of as-carburized components

In oil

Tempering

160-250C

In air

Micro inclusions - BQ		Macro inclusions - BQ
Applied standard	ASTM E45	Applied standard	ISO 3763 (Blue fracture)
Sampling	ASTM A295	Sampling	Statistical testing on billets.
Maximum average limits	A	B	C	D	Limits	< 2,5 mm/dm²
Th	He	Th	He	Th	He	Th	He
2,0	1,5	0,8	0,1	0	0	0,5	0,4

Micro inclusions - BQ

Macro inclusions - BQ

Applied standard

ASTM E45

Applied standard

ISO 3763

(Blue fracture)

Sampling

ASTM A295

Sampling

Statistical testing on billets.

Maximum

average limits

Limits

< 2,5 mm/dm²

2,0

1,5

0,8

0,1

0,5

0,4

Youngs module (GPa)	Poisson´s ratio (-)	Shear module (GPa)	Density (kg/m3)
210	0.3	80	7800
Average CTE 20-300°C (µm/m°K)	Specific heat capacity 50/100°C (J/kg°K)	Thermal conductivity Ambient temperature (W/m°K)	Electrical resistivityAmbient temperature (µΩm)
12	460 - 480	40 - 45	0.20 - 0.25

Youngs module (GPa)

Poisson´s ratio (-)

Shear module (GPa)

Density (kg/m3)

210

0.3

7800

Average CTE 20-300°C (µm/m°K)

Specific heat capacity 50/100°C (J/kg°K)

Thermal conductivity Ambient temperature (W/m°K)

Electrical resistivityAmbient temperature (µΩm)

460 - 480

40 - 45

0.20 - 0.25

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Material data sheet

Steel grade

20NiCrMo7

General Information

Similar designations

Chemical composition

Mechanical Properties

Transformation temperatures

Heat treatment recommendations

Heat Treatment Guide generated Graphs

Hardenability

CCT - Ovako 157C

Carburizing response - Ovako 157C

Steel cleanliness - Ovako 157D

Other properties (typical values)

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