Investment Cast vs Forged
Investment Cast vs Forged
(OP)
We have an application where a rod end needs to be designed. A grade 8 3/8 bolt will thread into this rod end. I have calculated the loads (axial through the bolt) and determined that I will need to use a 4130 type of material.
The question I have is that I am unable to find any comparisons of forged material and investment cast material for fatigue life. Of course everyone knows that the forging will be stronger, but a number of machining process will have to be performed on it (higher cost). Versus the investment cast piece would be as cast.
How does one choose on the process, I have requested information on the material from the investment cast company, all they have is YS, TS and Elongation%.
I have request similar information from the forging companies and they have pointed me to MATWEB.
I am looking for the proof in numbers that castings are more brittle than forgings.
The question I have is that I am unable to find any comparisons of forged material and investment cast material for fatigue life. Of course everyone knows that the forging will be stronger, but a number of machining process will have to be performed on it (higher cost). Versus the investment cast piece would be as cast.
How does one choose on the process, I have requested information on the material from the investment cast company, all they have is YS, TS and Elongation%.
I have request similar information from the forging companies and they have pointed me to MATWEB.
I am looking for the proof in numbers that castings are more brittle than forgings.





RE: Investment Cast vs Forged
What they are, is much less likely to have internal flaws that will fail in service, since the forge hammer will probably open any pre-existing flaws and make them apparent before the part undergoes any further processing.
Mike Halloran
Pembroke Pines, FL, USA
RE: Investment Cast vs Forged
From your post it appears that you would like to go with forging but need some ammunition for persuasion. But maybe I am reading too much between the lines.
If Matweb will give you YS,TS,EL%, you can plot stress/strain curves and compare the area under the curves. Or maybe the curves are given. More area more toughness -- less area more brittle. However this does not tell the complete story if impact is involved you need CVN or comparable values.
What is the environment? Temperature? Atmosphere? vibration?
RE: Investment Cast vs Forged
http:
http://www.forging.org/fierf/pdf/Fatigue.pdf
h
http://www.sfsa.org/sfsa/pubs/cvf/ecs.php
RE: Investment Cast vs Forged
Obviously I am not the OP but thanks because just for personal interest and edification I am reading the last two links.
The first two links do not work for me therfore I need computer help so I will go to tech-forums.net. and/or tek-tips.com.
RE: Investment Cast vs Forged
Although the cast piece is strong enough its really comes down to the elongation before break of the cast piece 15% or the forging 25%. Although this should really only come into play if the piece is not strong enough or the load exceeds what it was designed for.
Thanks for the links, Metengr my numerous google and bing searches only come up with 1 of the 4 being common.
RE: Investment Cast vs Forged
What sort of heat treat procedure are you planning?
RE: Investment Cast vs Forged
RE: Investment Cast vs Forged
Somewhat off the topic - we are investigating the use of a cast plus HIP process to replace a forging. Initial results look promising, but too early to be conclusive.