What would be a JIS steel that is very close to our 4820?

[PhilSBT]

Right now we are using JIS 420 and are not real happy with the durability of the gears and are looking for an alterative.

 

[TVP]

How did you arrive at SCM 420 as an alternative to SAE 4820? It is certainly understandable that the durability may not be equivalent, given that 4820 is a 3% Ni alloy steel, and SCM 420 is only a moderately hardening Cr-Mo grade. The following is the chemical composition for each grade:

SCM 420 (JIS G4105) SAE 4820 (SAE J404)
C = 0.18-0.23 0.18-0.23
Si = 0.15-0.35 0.15-0.35
Mn = 0.60-0.85 0.50-0.70
P & S = 0.030 0.030 & 0.040
Cr = 0.90-1.20 0.20 max
Mo = 0.15-0.30 0.20-0.30
Ni = 0.25 max 3.25-3.75

SAE 4820 is a very deep hardening grade. I recommend you investigate the following JIS grades for improved hardenability: SNC 815H (JIS G4052) or SNCM 420 (JIS G4103).

 

[PhilSBT]

Thanks for the reply.We are already using the SNCM 420 (sorry about the confusion on my part).Do you think that the SNC 815H is a more durable steel then the SNCM 420?We are getting varying results when hardness testing.Some gears we are getting 56-58 HRC and others we are getting 60-62 HRC.We are not doing the heat treating here in the states so I am not sure of their process.