Actually, lots of people supply MP35N. As described Salmon is looking for cold reduced/cold drawn material. I know that Latrobe and Allvac have supplied in the past.
Salmon, from experience, you may be specing something that no one in the world can produce ....at the very least it could have a very, very long lead time (+1 year). This forum may help prvide guidance, but you really need to talk to a mill and have them on-board when trying to acheive these...
I think Ed may be onto something. Were these parts heat treated in a salt bath? An incorrect wash and then a temper would give you something similar to that.
Also, is this a as-cast part, forged, or cast and HIP? That surface looks either forged or at least peened.
Other options are the high-strength PH grades - such as ATI S240 or C465. Each of these grades have good corrosion resistance with YS about 210ksi for the H1000 .....230ksi in the H950.
I don't have a datasheet for C465 but here is one for S240...
Talk to Ti Industries - they stock a grade that is very similar to 465. 465 is under patent but there are a couple of other alloys that are virtually identical.
Take a look at 13-8 SuperTough - it does not have the strength of C250 or Aermet 100, but it does offer fantastic tougness with Room Temp K1C of greater than 120
http://www.alleghenytechnologies.com/allvac/pages/PDF/tech/SS-238%2013-8SuperTough.pdf
Hello Mark,
Distortion will be tough to create a specific formula, since there are many factors that contribute... processing history, heat-up rate, quench rate...
As far as you call-out - you need to add a minimum temper say 300- 350F just to make sure you don't have a surface of virgin...
I would say skip measuring parts and start using callibration standards. Use the same 15N or HRC block at your shop and at the heat treaters.
If you really want to get an idea you could use a microhardness standard and check it on both pieces of equipment. Then you verify the measurement by...
Anytime you purposely mispresent information on a contract you are committing fraud. Mill Certs are, in essence a contract, they state that certain conditions were reached and the specifications were adhered to.
Who within the mill would go to jail? Start with the cert auditors and the quality...
Hartmandb stated, "We are trying to verify the honesty/integrity of the mill, so asking them for more samples wouldn't be a good solution."
Where is this mill located? In the United States fraudulent mill certs is a ticket to a 8' x 8' jail cell. I would be shocked to find out a mill knowingly...
One thing to watch about 4140 is tempering in the "blue brittleness" range. I am working from memory, but I think toughness is severely impacted (no pun intended) if you temper 500-800F.
Arunmrao covered it - but I have some *ahm* experience in pricing HT services.
1 - When do you need it? Many HT's will expedite... for a fee.
2 - Time in the furnace and to a lesser extent... temperature.
3- Is it a common practice or is it an oddball. A 350F +/- 25F for 2hours is cycle is easy...
I used to use 6150 and 4140M (.43%C) interchangably. 4340 is a step-up in price and is likely overkill. You may want to look into 4145 - which should be readily available.
How was the tube produced? Cartech does not extrude, so I am assuming that this is a bored bar. Was the ID cleaned up?
Was it solution treated and aged prior to boring? I know some companies prefer receiving PH steels in the fully aged condition and then they bore.
246ksi yield is on the...
Here is the quick checklist-
Alloy
Time at temperature
temperature
heat extraction rate
I worked at a company that made thin walled tubes (.018") out of 4140. Out process was to drop them into a furnace at 1600F and quench them 5 minutes later - fully martensitic.
Another possibility is segregation during the solidification process. This can lead to "hot spots" during testing.
Cold work or strain hardening in general is a prime suspect. As it was pointed out that the introduction of strain could cause the formation of martensite... which is magnetic.
I doubt it is due to thermal expansion. The delta in size would be rather small within a normal temperature range for the outdoors. I bet the parts have seen less than a 20C shift in temperature over the course of a summer.
There are lots of application below 750F where superalloys come into play. 718 has a nice combination of strength, toughness, corrosion resistance, and low magnetic permeability.
If I had to pick one my guess is that it is the magnetic permeability which made it required for a satelite...
