AISI 410 SS lateral expansion

[curious_eng]

Greeting,

I’m currently working on the 410 stainless steel shaft (8.5” OD x 100” long with a 3.5”ID via deep hole drilling prior to heat treatment) and having trouble with longitudinal lateral expansion.
Longitudinal lateral expansion is conducted at 21 degree C and requirement is 25 mils.
Longitudinal charpy impact is conducted at 21 degree C and requirement is 30 Joules.
I’m getting longitudinal lateral expansion of 14 to 23 mils.

Typical composition: 0.12% C, 0.55% Mn, 0.10% P, 0.001% S, 11.90% Cr, 0.19% Si, 0.32% Ni, 0.018% V, .024% N.

This product is forged and heat treated to following conditions. Heat treatment:
Austenitize at 1725°F (I have tried austenitizing for 12 hours and 20 hours and results are same).
Oil quench
Temper at 1125°F for 10 hours.

We always get hardness of 229 BHN. Minimum requirement is 223 BHN.
Tensile requirement: 105 KSI and actual result 107 -109 KSI
Yield requirement: 85 KSI and actual result 87 - 91 KSI
Longitudinal charpy impact requirement: 30J and actual result 35 – 57J

I looked at the broken charpy sample structure and it looks brittle (shinny condition). I verified the raw material and it conforms to required chemistry and no cleanliness issue.
Does anyone has experience with this grade? I'm not sure if it is a heat treatment or forging issue. Some reason all my mechanical result are at the bottom end of the spec. Thanks in advance.

 

[curious_eng]

Min 30J and 25 mils are specified.
I austenitize the next batch at 1800F as suggested and temper couple of shaft at 1125F and 1150F.
Charpy: 27 - 38J
Both temper (1125 and 1150F) failed for lateral expansion: 9 - 16 mils
As quench hardness is 415 BHN
Sample looks really brittle and I would say shear factor 10%
hardness of 1125F shaft: 241 BHN
hardness of 1150F shaft: 229 BHN
We buy material as ingot form and forge. We never normalize this grade.
Any other suggestions? Thanks everyone for input.

 

[MagBen]

Unless there is a good correlation between energy and lateral expansion, it makes less sense to specify both of them.
Are you lateral expansion the absolute values? I mean the specimen is often 10x10mm, if the expansion was measured at 9-16 mils, it would actually be 9-16 mils per 10 mm, which can be normalized to 23-41 mils per inch.

Have you look at the cooling rate after temper? Since you temper temperature is higher than "impact trough", your cooling should be quick enough to pass this temperature range.