Metallurgist question....

[deadin]

This may not be the place to ask the following question, but the depth of knowledge runs deep here....

The traditional way of manufacturing firearm receivers is by forging and then machining to final form followed by heat treating.
I have just read a claim from a small company that because they are milling the frame from a solid piece of "preheat-treated 4140 chrome-moly carbon steel", they are "picking up cross-grain strength" and therefore making a stronger part than one just forged, machined and heat-treated. (They also claim it is stronger than casting or MIM parts.)

Is there any truth in this or are they just trying to explain away their lack of expensive forging machinery?

 

[kf2qd]

Sounds like baloney to me... The reason for forging was to improve the grain structure of the forging and thus gain strength. Incedentally - another reason for some of the near finished shape forgings was because it made it easier to machine, as they didn't have some of our current machining options there was less metal to remove, and simpler setups to do multiple operations.

 

[mu38&Bg#]

Forging gives directional grain properties. Depending on how the part is designed, this may or may not be beneficial. If the forged part is made of weaker material they could be correct.

 

[Ken I]

Hmmmm - How long's a piece of string ?

Forging is going to be better - given the same material - so it sounds more like hype to me.

Steel quality and physical properties are influenced by how it was made - continuous cast - ingot poured - electroslag refined.

In each case there is an order of magnitude reduction in the number of inclusions and defects / size / distribution and an increace in mechanical properties of about 20%

So a forged piece of continuous cast crud will not be as good as a machined piece of refined steel.

I know this doesn't really answer your question.

Its complicated........

Ken

 

[rake60]

I was a machinist for more than half of my lifetime and I can't answer that.

I do know how to do a web search and found THIS
After reading through all of that several times my conclusion is..... scratch.gif

Still no answer from this camp...

Rick

 

[steamer]

Hi Ken,

I agree with you about the forgings.....provided! they are good forgings!

If their done too hot or cold....you can drive in all kinds of stress and imperfections

Then again, the same can be said of castings.

I'm thinking billet may be more consistent...part to part.

I know the Airforce doesn't use forged or rolled aluminum on air frame parts for cruise missiles....at least no in the late 80's, early 90's. The "sheetmetal" panels and frames were carved to shape from blocks of aluminum!...the company I worked for made the milling machines that they used

The reason was they wanted material they could examine before hand with Xrays for inclusions and voids, and apparently, forged aluminim parts with inclusions and voids from the forging process were very hard to detect.

Dave

 

[Ken I]

Dave,
The same is true of all metal making processes - some manufactures make crappy products for markets that don't require better.

Most metal end users don't bother with specifications such as ASTM cleanliness and surface conditions - even experienced industrial customers don't always get it.

A German engineer at Fichtel & Sacks once said to me "In Germany we have 5 steel suppliers - 4 of them are s..t"

They had sorted out their raw material quality problems by suppler selection rather than specification.

Back to the original gun question - if the supplier has a reputation for quality products then they probably do a good job.

The hype is questionable.

Ken

 

[Tin Falcon]

All sales and marketing departments have the job of convincing the consumer their products are somehow superior to the competition.

sometimes "Improvements "to a product are a real improvement.
sometimes they are a cheaper way of making things that are made to sound good. It can be both or not
Caravat emptor.
when plastic cases were first used for power tools the "double insulated" feature as touted.
Now green or contains recycled material are popular marketing words.
A quality part can be made in a number of ways. some quality is perceived real quality can only be tested with time or expensive testing equipment. that accelerates simulated use or years of service in a matter of days again time.

Tin

 

[Chazz]

I vaguely remember watching a movie of a huge steam of gas turbine construction (the stator?) where they took a massive block of alloy, heat it up and the squash it in these massive presses, over and over again until it was half the size of the original.
Still more heating and pressing to a round form.
The size of the furnaces and presses blew me away not to mention all the energy and all you have so far is a 'round blank'. IIRC it also had to 'age' for a long time too before machining could begin.
Unfortunately I can't remember if there was any 'post' treatment but they did say all that pressing ended in a perfect lattice throughout the entire piece of material.

Anyway, my 2 cent guess, the bean counters and R & D got together and yes, I would not be supprised today (think nano technology and such), they found an alloy that can be machined in their 20,000+RPM machining center, though costing more, provides an overall savings by eliminating an entire process and allows for more to be made during a given production cycle.

Cheers,
Chazz