416 Stainless Steel Heat Treatment Question
416 Stainless Steel Heat Treatment Question
(OP)
I have three studs made from 416 stainless steel, consistent with ASTM A582. Two of them have a hardness of ~RB 90 while the third has a hardness of RB 99. Similarly, tensile specimens machined from these three studs have a tensile strength of 87 ksi vs 105 ksi. The two lower strength bolts are just over the minimum limit for A582 Condition A, but the higher hardness/strength stud is not high enough in tensile strength to meet the "T" condition. These studs are from a main boiler feed pump, so the service temperatures should be between 250°F and 350°F, so I believe 400-500°C embrittlement mechanism can be ruled out. Are there any thoughts that might explain the elevated hardness (other than a(n) [expletive]'d up heat treatment)?





RE: 416 Stainless Steel Heat Treatment Question
RB99 is still within range for annealed material isn't it? I thought that this was RB100max.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: 416 Stainless Steel Heat Treatment Question
RE: 416 Stainless Steel Heat Treatment Question
RE: 416 Stainless Steel Heat Treatment Question
I'm leaning towards improper heat treatment, with the harder stud coming from a different heat/manufacturer. As for why this material was used, this is a failure analysis project - three studs, all broken, with two fatigue failures at one end and one overload (microvoid coalescence) on the third stud at the other end relative to the fatigue failures - the higher hardness stud is the overload fracture.
RE: 416 Stainless Steel Heat Treatment Question
Interesting. As part of your RCA, I would avoid this material specification for studs in this type of service.
RE: 416 Stainless Steel Heat Treatment Question
2. 416 is a free machining grade and is deliberately loaded with sulfide inclusions, it is not an appropriate fastener grade. The B16 would be amuch better choice.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: 416 Stainless Steel Heat Treatment Question
RE: 416 Stainless Steel Heat Treatment Question
When hardened at 1800F + >1200F tempered, this alloy will yield a similar hardness as solely annealed condition, but will have a totally different structure.
RE: 416 Stainless Steel Heat Treatment Question
RE: 416 Stainless Steel Heat Treatment Question
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
RE: 416 Stainless Steel Heat Treatment Question
https://cartech.ides.com/ImageDisplay.aspx?E=79&am...
Annealing yes. With values near 100 Rb scale.