CT781
Identification

 

Designation by Standards
Brand Name Ravne No. Mat. No. DIN EN AISI
CT781 781 1.6587 17CrNiMo6 17CrNiMo7 4820

 

Chemical Composition

 

Chemical Composition in Weight %
C Si Mn Cr Mo Ni V W Others
0.18 max.0.40 0.70 1.65 0.30 1.55 - - -

 

General Information

Description
Nickel-molybdenum alloy steel. Alloyed case hardening steel for heavy and high strained gear parts with high demands on toughness at core tensile strength of 1050-1350 N/mm2.

Applications
Severely stressed components for mechanical engineering and automobile industry.

 

Properties

Physical properties (avarage values) at ambient temperature:
Modulus of elasticity [103 x N/mm2]: 210
Density [g/cm3]: 7.87
Thermal conductivity [W/m.K]: 38.0
Electric resistivity [Ohm mm2/m]: 0.18
Specific heat capacity[J/g.K]: 0.46

Coefficient of Linear Thermal Expansion 10-6 oC-1
20-100 'C 20-200 'C 20-300 'C 20-400 'C 20-500 'C
11.2 12.1 12.9 13.4 13.9

Continuous Cooling Transformation (CCT) Diagram




Time-Temperature Transformation (TTT) Diagram



Heat Treatment

Soft Annealing
Heat to 650-700 'C, cool slowly in furnace. This will produce a maximum Brinell hardness of 229.

Intermediate Annealing: 630-650 'C.

Hardening
Carburising: 880-980 'C.
Core Hardening: 830-870 'C, water.
Case Hardening: 780-820 'C, water.

Normalizing
Normalizing: 850-880 'C, air.

Tempering
Tempering temperature: 150-200 'C.

Soft annealed treated: max. 229 HB.
Treated for cold shearability: max. 255 HB.
Treated for strength: max. 229 HB.
Treated for ferite and pearlite structure and hardness range: 159-207 HB.

Tensile Strength Rm in N/mm2 vs. Diameter in mm
After Hardening and Tempering at 200 'C
Diamter in mm d<=16 17<d<=40 41<d<=100
Tensile Strength Rm in N/mm2 min. 1200 min. 1100 min. 900

Diagram Hardness (HRC) vs. Distance from Quenched End (mm)
Workability


Forging
Hot forming temperature: 1050-850 'C.

Machinability
No data.