Steel chemical Composition is 4340 or not??

[wirotede]

C 0.4006 /Si 0.2819 / Mn 0.6389 / P 0.0231 / S 0.0045 / Cr 0.9655 / Mo 0.1468 / Ni 0.0309 / V 0.0126 / Al 0.0081 / Cu 0.0094 / Ti 0.0047 /Nb 0.0008 / Pb 0.0018 / As 0.0026 / Co 0.0120 / Fe Balance ( % Weight)

This is analysis result.What is the kind of metal that i can identify for this ?

 

[redpicker]

It would appear to be a 4140, not 4340.

Slightly outside the range for 4140H, but within the check analysis tolerance.

Do you know if this was made to AISI limits?

rp

 

[arunmrao]

Certainly not 4340 steel .Quite close to being 4140.

 

[wirotede]

Thank you for all answer.
This is from failure pump shaft in my plant. Now i try to find the root cause.

 

[Metalguy]

Can you post good pictures of the fracture surfaces? What diameter is the shaft? Required and actual hardness?

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[wirotede]

shaft OD 55 , and i don't know for hardness.

 

[wirotede]

2nd time

 

[Metalguy]

That looks like a somewhat unusual fatigue fracture. You need to find out how hard the shaft was supposed to be and how hard it is--from surface to core. You have a pretty "lean" heat of steel compared with real 4140, and it probably wouldn't harden if quenched in the usual oil/polymer.

It probably would harden in water. Find out what the design intended.

"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein

 

[wirotede]

I find the potential cause is higher load on shaft from process design (more radius load on pump. discharge valve less %opening.)

how to increasing strength on shaft if base on material improvement ??

 

[metengr]

wirotede;
Are you really sure about the statements below?

I find the potential cause is higher load on shaft from process design (more radius load on pump. discharge valve less %opening.)

how to increasing strength on shaft if base on material improvement ??

First off, viewing the fracture is only part of the solution. You have no specifics on the type of pump, the environment, etc. I would suggest you send this to a metallurgical lab that can perform a proper failure analysis.

Once you have confirmed the failure mechanism, the next step is to determine the root cause of the failure. Here is where you need to develop a checklist of operating conditions, materials of construction, etc. Once you have established the root cause, you can decide on corrective action plans - change in shaft material, change in heat treatment, possible re-design of shaft transitions, etc.

 

[mrfailure]

I would not even go so far as to say fatigue is the likely failure mode; the pictures are inconclusive in this regard. I concur with metengr's advice.

 

[Screwman1]

One thing about that photo is that there is certainly a big notch at the fracture site.
I agree with Met about the need for a proper analysis; a but of guys on the internet looking at fuzzy pics can't really make a definitive analysis.....

 

[Guest102023]

Determining conformance to a common alloy steel composition is done better and quicker by googling than by crowd-sourcing.

 

[apecush]

I would not even go so far as to say fatigue is the likely failure mode; the pictures are inconclusive in this regard. I concur with metengr's advice.

Those pictures are pretty conclusive evidence that failure occurred by fatigue. Flat initiation/propagation zone, large ratchet marks near the point of final failure all scream fatigue.

 

[mrfailure]

I'll stand by my original statement. It is highly likely given use that failure occurred under fatigue, but the photos are too low resolution, and the fracture features are too vague in them to make such definitive conclusions. The fracture may need to be cleaned and/or looked at under good lighting under a stereobinocular microscope to actually see what is going on. I cannot say there are definite ratchet marks in these photos, and flat initiation/propagation does not necessarily mean fatigue.