Fracture toughness for S154 (S96). 1

[RPstress]

Can anyone tell me a (room temp) fracture toughness (KIc, Kq) for the UK corrodible aerospace steel spec S154 (or S96)?? There's nothing in the Metallic Materials Data Handbook.

In hope,
Richard Perry.

 

[Carburize]

Can you give any more information on the chemical analysis of the material, its heat treatment and strength? There may be closely related materials for which fracture toughness data are published.

 

[RPstress]

It's a 2-1/2% Ni Cr Mo steel, 150 mm (6&quot ruling section, in a low(ish) strength high(ish) toughness condition. It's one of a series developed in the UK with very few international equivalents, though on re-checking I find AECMA spec FE-PL 2105 is apparently equivalent, though I can't find that in IHS.

Here's a bunch of stuff about it:

[tt]Element Min % Max %
C 0.27 0.35
Si 0.15 0.35
Mn 0.45 0.70
P - 0.025
S - 0.015
Cr 0.50 0.80
Mo 0.45 0.65
Ni 2.3 2.8
Al 0.015 0.05[/tt]

B-basis Ftu = 906 MPa (131 ksi) & t2 = 711 MPa (103 ksi) (t2 = 0.2% proof stress).
Izod is 54 J at 6" thick.

B.S. S154 spec. requirements are:
Ftu 880 to 1080 MPa (128 to 157 ksi), t2 690 MPa (100 ksi) min, e = 12% min, Izod 40 J min.

Hardness: 255 to 321 HB and 270 to 340 HV as hardened and tempered.
In the softened condition (reached by heating at 650 C (1200 F)) hardness must be <= 248 HB (Ftu =~ 120 ksi?).

Heat treat (durations unspecified).
Harden: 850+-10 C (1560+-20 F), cool in oil.
Temper: 600 C (1110 F), cool in air.

 

[TVP]

There are some approximations developed by Barsom-Rolfe and others for converting charpy impact values to fracture toughness. Check out the following thread for more information:

thread330-24020

References for this equation include ASM HANDBOOK Volume 19 Fatigue and Fracture and Barsom & Rolfe's book, Fracture and Fatigue Control in Structures: Applications of Fracture Mechanics, Third Edition, published by ASTM. You can even download portions of this for free using the following link:

http://www.astm.org/BOOKSTORE/MNL41PDF/

 

[Carburize]

Take a look at the tables in ASM Handbook Vol 19 in the Section on Fracture Mechanics Properties of Carbon and Alloy Steels. Depending on how precise a value is needed for your calculation I would use 100 ksi/in as a first estimate.

 

[RPstress]

100 ksi.rt&quot; sounds like a good safe starting point. A sister alloy S99 (180 ksi Ftu, identical but for .36-.44C and 835 C harden, 550 C temper) has KIc ~ 120 ksi.rt&quot; and Izod 40 J (spec min 25 ft-lb = 34 J).

I looks like there's at least some correlation between Izod and Charpy...any feel for what risk there may be in using Izod energies in place of CVN ones for estimating KIc/d, etc.?

 

[Carburize]

The correlations between impact test results and Kic, Kid values are purely empirical so no, I don't think you can use the Izod values. See if you can find a copy of any of the papers published by Marandet and Sanz on their correlation methodology, there may be something in their approach that you can use.

 

[RPstress]

Many thanks to Carburize and TVP. We've decided 100 ksi.rt&quot; is safe for now, and suspect that the actual value may be between 120 and 140. Unfortunately, we will probably never know...

 

[chrisbullough]

Some aspects of this request were also addressed in thread330-60518, which you might like to see.

ESDU in the UK is usually the best source of data on these steels, but you need a subscription to use it.

http://www.esdu.com

Probably the best approach would be to do a limited amount of testing, backed by ESDU's data/correlations for steels of this type.

 

[RPstress]

I have access to ESDU, and had checked out the Metallic Materials Data Handbook. I didn't know about 83023. Alas, S96/154 doesn't ssem to be in it. However, there's a lot of other good data in there. Thanks.