Impact of Mn on Steel

[metboss]

Hi all,

As per Mill MTC (material: Low Alloy steel AISI 4140), it’s been noted that Mn, Cr & MO contents are slightly exceeding the maximum permissible limits as set in applicable standard ASME IIA (Table 2).

Test results in MTC - Mn: 1.10, Cr: 1.20 & Mo: 0.35

Max upper limit for AISI 4140 as per ASME II (Table 2): Mn: 1.00, Cr: 1.10 & Mo: 0.25

Can we accept this material? What is impact of Mn, Cr & Mo (if excess) on low alloy steel? Does it have any negative impact?

Regards

 

[cap1a79]

Please think about it by slightly different way.
When we are driving our cars at 71 miles per hour on the road whose limit is 70, is that really dangerous? Does car accident really happen? If no, then what about 72..If no, then 73?? 74??.......

Please note that limitations of each component are to achieve the expected level of quality for the materials. The limitations & guidelines are based on numerous testing & lesson learned behind them. Although the component is very slightly over the limit, we cannot say that we could achieve the expected level quality of the materials supported by numerous testing & lesson and learned.




Lee SiHyoung,
WorleyParsons Oman Engineering,

 

[kingnero]

Do you get the mechanical values you require?
Does the steel needs welding, heat treatment, ... afterwards?

There is more about it than to reject material based on slightly elevated alloy elements...

 

[cap1a79]

kingnero
Would you please tell me if there is any back-up reference to justify the off-spec material? Generally, I have never found it so far while 12.5% mil tolerance can be applied for wall thickness of ASME.
Although the value is slightly over the limit, it would be difficult to decide how many percepts would be allowed for each component and demonstrate it without laboratory testing.
I think, if there is client's discretion, it would be possible but the approach will not be from technically quantitative approach. I think....

Lee SiHyoung,
WorleyParsons Oman Engineering,

 

[MintJulep]

(35-25)/25 = 40% over.

Not exactly "slightly".

 

[mrfailure]

From a test lab perspective: If you only have Type 4140 (UNS G41400) as your only standard, then the answer is no: the standard is absolute and the material should be rejected. If the material is supposed to meet a specific standard that calls out 4140 grade, then you will need to see if an allowable tolerance for product composition for these elements is called out and whether your deviations are within the specified tolerance bands.

 

There are permissible tolerances in your ASTM or other standard, but off the top of my head I can say this is clearly out of spec for 4140. This material has not one, not two, but three strikes against it. The hardenability effects of alloy elements (including Mn, Cr, Mo) are compounding, so the response to heat treatment will be significantly different compared with 4140. And if carbon is in the upper end of the range, then that clinches it.
Somebody shipped you a different grade, possibly an offshore spec. Reject it.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[djhurayt]

not sure if this helps or is what you are looking for, but from this site:

http://www.diehlsteel.com/technical-information/effects-of-common-alloying-elements-in-steel

Manganese (MN)
A deoxidizer and degasifier and reacts with sulfur to improve forgeability. It increases tensile strength, hardness, hardenability and resistance to wear. It decreases tendency toward scaling and distortion. It increases the rate of carbon-penetration in carburizing.

Chromium (CR)
Increases tensile strength, hardness, hardenability, toughness, resistance to wear and abrasion, resistance to corrosion, and scaling at elevated temperatures.

Molybdenum (MO)
Increases strength, hardness, hardenability, and toughness, as well as creep resistance and strength at elevated temperatures. It improves machinability and resistance to corrosion and it intensifies the effects of other alloying elements. In hot-work steels and high speed steels, it increases red-hardness properties.

 

[weldstan]

The impact of increased Mn and Cr is increased hardenability upon quenching and tempering. It may well affect quenching media and tempering temp from your standards for the grade to meet your mechanical property requirements. Because it is not what you ordered, you can reject it and maybe should. What else might be wrong in its manufacture?

 

[EdStainless]

Is this a test of a product? If so then there is an analysis tolerance to apply.
OF course you also have to be using approved spectrometer techniques.
A product analysis can be outside of the stated ranges, but the heat analysis must meet the ranges.

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P.E. Metallurgy, Plymouth Tube

 

[metboss]

This is reported in raw material MTC (heat analysis). The received raw material (tubular forging) will be used to manufacture Down-hole completion equipment (drilling). The mechanical properties are within the acceptable limits and only concern on chemical compositions.
As per client specification, the maximum hardness limit for the finished product (Down-hole completion equipment) is 22 HRC.
But, hardness values (21 HRC avg.) as reported in MTC is close to maximum cut off value (22 HRC) and also, the said raw material will undergo cold working (machining & thread cutting operation) during manufacturing stages and there will be no heat treatment.
Is there any impact on final hardness value of finished product due to the combined effect (exceeding Mn, Cr & MO contents + cold working)?

 

[EdStainless]

If you ordered this to an ASME spec then it doesn't meet it, period.
There are no exceptions allowed.

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P.E. Metallurgy, Plymouth Tube

 

[Dhurjati Sen]

Dear metboss,

It is very simple to reject a material, but there could be many considerations like time & delays, availability & urgency etc.

In your case, you know best what are the constraints.

However, I suggest you to carry out PMI and corroborate it with the MTC. Also check hardness of the material.

The above results would help you arrive at a decision.

Regards.

DHURJATI SEN

https://www.nace.org/people/dhurjatisen

 

[mrfailure]

Pay attention to Ed's statements - you are done if the material does not meet specified requirements, period. It is never acceptable to still use it for the sake of expediency. That thinking will invite future lawsuits, especially if there is a failure. If you believe out of spec chemistry is incorrect, you can retest using lab quantitative techniques (i.e. OES, ICP, Carbon/Sulfur) but PMI is not suitable as it is a semi-quantitative technique that is good for material identification but not suitable for determining conformance.

 

[weldstan]

Your down hole tubular hardness max of 22 HRC is indicative of potential H2S exposure. Cold working may well increase hardness beyond tbe maximum. You seem determined to use the material but have not verified the hardness of the MTR. Do so! If the chemistry is out of spec for the specified material, why do you think the hardness and other mechanical properties on the MTR are valid?

Going fishing for fractured downhole tubing is one expensive chore.

 

[metboss]

Thank you all for your kind advice. I'll keep you updated if any further feedback from client.