Match Chemical analysis to Material....

[entx]

Hello,

I sent out a sample of material to determine it's properties and chemical composition in the hope of narrowing down the material... Unfortunately the metallurgist cannot specify a material for this part as it's a non US spec material... Does anyone have any suggestions on how I can go about narrowing this down???

C = 0.40%
Mn = 0.87%
P = .013%
Si = 0.19%
Ni = 0.10%
Mo = 0.03%
Cr = 1.21%

0.2% YS = 112.4ksi
UTS = 127.9ksi

The sample was a ball joint stud for automotive suspensions...

 

[CoryPad]

37Cr4 according to EN 10083-1 or DIN 1654-4.

 

[entx]

I'm assuming the closest US spec is 4140....though the Cr is a bit lower and there is no Ni in 4140. But this is the closest I see....

Also going to 4340, assuming 4140 is the best US match, the nickel content should improve fatigue strength, is that right? Though 4340 normalized has a Rc of 40 and I do want to keep the hardness to about 30-35 for the core and case harden the part were the highest stresses will be concentrated to about 55, which should put the tensile stress in the 255ksi range...

Would it be possible to do this with either 4140 or 4340...and if so would 4340 be a better choice? Or would 4140 be sufficient?

 

[dbooker630]

The closest US (SAE) equivalent would be a 51XX series chromium steel such as 5135H or 5140H.

You can induction harden 4140 or 4340 after normalizing. 4340 would be a better (and costlier) choice, but I would get engineering test data before choosing 4140.

 

[entx]

Fantastic...that's exactly what I was looking at doing...using 4340 in a normalized state for easy machining and then induction harden the high stress area to increase the outer surface strength for the max compressive/tensile loads...

I had looked at even 300M, but that was getting to be cost prohibitive...

Thanks for the input....

 

[strider6]

try on matweb

http://www.matweb.com/

s

Corrosion Prevention & Corrosion Control

 

[entx]

I use matweb quite a bit...but their search based on composition doesn't work all that well...you have to hunt and peck abit.... but they do have a great resource if you do know what you want....

 

[Metalguy]

I wouldn't use 4340 for this. 4340 is a deep hardening steel, intended for thick sections over ~2+" thickness--as is 300M. 4140 is cheaper and would allow you to retain a softer core.

Have you considered a lower C steel and having it case hardened? Do you really mean having wear resistance instead of "high stress area"?

Gold is for the mistress - silver for the maid
Copper for the craftsman cunning in his trade.
"Good!" said the Baron, sitting in his hall
But iron - cold iron is the master of them all.
Rudyard Kipling

 

[TVP]

entx,

Did you perform any other testing on the sample besides chemical
composition? If you didn't, then you may not realize that the
ball stud is through hardened to have a 100% tempered martensite
microstructure, not a ferrite-pearlite structure that is produce by
normalizing. The threaded section requires high strength due to
the preload requirements of the joint. Induction hardening the
surface is commonly done on ball joints that havre a lot of side load,
but do you know how deep the case should be and what hardness
limits to use? Ball joints are extremely critical components on an
automobile and should not be treated lightly.

 

[entx]

TVP,

I did Tensile, composition as well as harness... Now I didn't have them polish and etch the part to see what structure the grains are...and now that you mention that, it probably wouldn't be a bad idea to have that done...

But for the harness I wanted to know where and how deep the hardening was... So I had one of the parts sectioned and tested for harness throughout the cross section to map out the hardness.... for the most part the entire stud is about 30-32 Rc, correlating to the strengths posted above, and it's only the casing that see the high stresses from side loads that was induction hardened to about 55 give or take...and the depth of the casing is quite easy to see in the right light by the naked eye...

But as metal guy mentioned...after looking at the material specs from Latrobe...it looks as though 4340 will not be my best choice as this material cannot be hardened past 52 with a yield of about 220-225ksi...and the core would be around 40Rc... Where as 4140 can have the center in the 30-35 Rc range, with a yield as measured and induction harden the out casing to 55 to an estimated 250ksi... Just to take the stresses on the outer surfaces...I only need a case hardened depth no greater than 0.1". I haven't yet talked to any HT'ers yet and the resources I have is quite limited...My only resource is Matweb and steel manufactures data sheet when I can find them...I really want to get some of the volumes from ASM... So I'm not 100% sure that 4140 will provide these properties after all said and done.... Hopefully it will...

But I do want to say thanks for all the feedback I really appreciate it...

 

[dbooker630]

4340 can be induction hardened higher than 52 HRC. As quenched hardness can go above 62 HRC, then temper back to 55-58 HRC for example.