OH253
  
Identification

 

Designation by Standards
Brand Name Ravne No. Mat. No. DIN EN AISI
OH253 253 1.2357 50CrMoV13-1 - S7

 

Chemical Composition

 

Chemical Composition in Weight %
C Si Mn Cr Mo Ni V W Others
0.50 0.50 0.70 3.25 1.50 - 0.25 - -

 

General Information

Description
S7 is a general purpose air hardening tool steel having high impact and shock resistance. It has good resistance to softening at moderately high temperatures. This combination of properties makes it suitable for many hot-work and cold-work applications.

Applications
Chisels, rivet sets, punches, driver bolts. Hot punching and shearing.

 

Properties

Physical properties (avarage values) at ambient temperature:
Density [g/cm3]: 7.86

Coefficient of Linear Thermal Expansion 10-6 oC-1
20-100 'C 20-200 'C 20-300 'C 20-400 'C 20-500 'C 20-600 'C 20-700 'C
11.7 12.9 13.3 13.8 14.1 14.3 14.6

Continuous Cooling Transformation (CCT) Diagram



Time-Temperature Transformation (TTT) Diagram


 

Heat Treatment

Soft Annealing
Heat to 810-850 'C, cool slowly in furnace. This will produce a maximum Brinell hardness of 229.

Stress Relieving
To relieve machining stresses for greater accuracy in hardening - first rough machine, then anneal below the critical at 649/677 'C a minimum of one hour at temperature and cool slowly, then finish machine.

Hardening
Harden from a temperature of 930-960 'C followed by air or oil quenching. Hardness after quenching is 59-61 HRC.

Tempering
Tempering temperature: 150-400 'C.

Tempering Temperature ( 'C) vs. Hardness (HRC)
100 'C 200 'C 250 'C 300 'C 400 'C 500 'C 550 'C 600 'C 650 'C
59 57 55 54 53 52 52 48 41

Effect of Tempering Temperature on Hardness

 

Workability


Forging
Hot forming temperature: 1066-1121 'C.

Machinability
The machinability of S7 alloy may be rated at about 75/80 % of a 1 % carbon tool steel.

Corrosion Resistance: Corrosion resistance of this alloy is better than that of plain carbon steels. However it will rust unless given protective treatment.