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Special Steel, S99

S99 has the characteristics of a nickel-chromium-molybdenum steel and is used for general aerospace use.

Chemical Composition (Weight %)
  C Si  Mn P S Cr Mo Ni Al  Fe
Min 0.36 0.10 0.45

  0.45 2.30 0.015  
Max 0.44 0.35 0.70 0.025 0.015 0.80 0.65 2.80 0.050 Bal

Typical Mechanical Properties (Min unless stated)
Condition  Tensile Strength, Mpa Yield Strength 0.2%, Mpa  Elongation % Reduction of Area % Hardness HB Impact izod ft. ibf
S99A Forging

 
277 max
 S99B Softened



277 max
 S99C Soft Forgings 1230-1420
10
363-415 25
 S99D Bright Soft



277 max
 S99E HT 1230-1420 1080 10
363-415 25
 S99F HT Forgings 1230-1420 1080 10
363-415 25
 S99G HT Bright 1230-1420 1080 10
363-415 25
 

Related Specifications

40NiMoCr105, 1.6745, BS 999

Available Forms 

Round bar, flat bar, forgings 
 
Chemical Composition (Weight %)
  Min Max
C 0.36 0.44
Si 0.10 0.35
Mn 0.45 0.70
P   0.025
S   0.015
Cr   0.80
Mo 0.45 0.65
Ni 2.30 2.80
Al 0.015 0.050
Fe   Bal

Typical Mechanical Properties (Min unless stated)
S99A Forging
Tensile Strength, Mpa  
Yield Strength 0.2%, Mpa  
 Elongation %  
Reduction of Area %  
Hardness HB 277 max
Impact izod ft. ibf  
S99B Softened
Tensile Strength, Mpa  
Yield Strength 0.2%, Mpa  
 Elongation %  
Reduction of Area %  
Hardness HB 277 max
Impact izod ft. ibf  
S99C Soft Forgings
Tensile Strength, Mpa 1230-1420
Yield Strength 0.2%, Mpa  
 Elongation % 10
Reduction of Area %  
Hardness HB 363-415
Impact izod ft. ibf 25
S99D Bright Soft
Tensile Strength, Mpa  
Yield Strength 0.2%, Mpa  
 Elongation %  
Reduction of Area %  
Hardness HB 277 max
Impact izod ft. ibf  
S99E HT
Tensile Strength, Mpa 1230-1420
Yield Strength 0.2%, Mpa 1080
 Elongation % 10
Reduction of Area %  
Hardness HB 363-415
Impact izod ft. ibf 25
S99F HT Forgings
Tensile Strength, Mpa 1230-1420
Yield Strength 0.2%, Mpa 1080
 Elongation % 10
Reduction of Area %  
Hardness HB 363-415
Impact izod ft. ibf 25
S99G HT Bright
Tensile Strength, Mpa 1230-1420
Yield Strength 0.2%, Mpa 1080
 Elongation % 10
Reduction of Area %  
Hardness HB 363-415
Impact izod ft. ibf 25
 

Related Specifications

40NiMoCr105, 1.6745, BS 999

Available Forms 

Round bar, flat bar, forgings