Cold Temperature Metal Properties

[NDA277]

I understand that if metal undergoes a cold temperature excursion, its mechanical properties (e.g. ductility, yield strength, tensile strength) should return to "normal" once the material warms back to ambient temperature. Would carbon steel (say, A106) material return to "normal" properties if it underwent an extreme cold temperature excursion? If the temperature dropped to -300 Deg. F, and the temperature eventually returned to ambient (70 Deg. F), would the mechanical properties of the steel have been compromised permanently?

Thanks.

 

[katrinali]

Hi NDA277-
I am very interested in this question, hope someone might know ,,
Just by guessing, according to me, should be back to normal since at such temperature -300F, no microstructure change will happen, so the properties should be the same...

however, in normal sense if you freeze an apple and then put it back it wont be the same tho..that's due to the chemical reaction/ water expending while freeze, so if metal shrink at low temperature.. will the microstructure the same? i doubt..

 

[stanweld]

Yes, the properties would revert to that established during room temp testing. Having said that, you may have subjected the material to loads during the "excursion" that have damaged the material and any welds thereto.

 

[arunmrao]

The material may come back to its R.T properties, but during its journey to subzero range and subsequent return to R.T, the integrity of the fabrication will have been compromised. The weld joints will have cracked and a few members of the assembly might have distorted.

 

[consultmet]

Couple of years ago, we had a project to investigate a weld repair of a carbon alloy steel for high temperature service which goes under a sub-zero freezing at temperatures from, -100F to -300F and held at that temperature for extended periods from 24 hrs. to 2 weeks. and then allowed to warm to Room temperature for impact testing.

Result: No change in impact properties

Considering grade A106, I would expect no change, if no applied loading was done.

 

[Guest102023]

The question is about mechanical properties, not structural integrity. For many alloys the return journey leaves it unchanged (at least not measurably so). Certainly carbon steels like A106 fall into this category.

However I can think of a few exceptions, such as alloy steels that require cryogenic temperature treatment to undergo complete transformation to martensite, the desired structure. Cryogenic temperature could also effect the activity of interstitial elements in some alloys.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[Frederick]

A lot depends on how fast the temperature changed. With a slow drop in temperature several things will happen:

1. A slow drop in temperature will cause point defects out of the crystal structure. In the end there will be fewer vacancies in the matrix.

2. The solubility of the alloying elements in the matrix will change. This is part of the driving force that causes the formation of tiny carbide particles in the steel. Carbon is precipitated out and joins with any carbide forming elements.

3. The metallic bonds that have extra energy due to atoms not being at the precise most efficient distance from each other may lose that energy and the crystal lattice structure will become more regular.

If the temperature drop is sudden, for instance created by dropping the part into liquid nitrogen, there will be the creation of large temperature gradients at the surface, which can cause residual stress or cracks. The changes listed above will not have enough time to happen.

 

[MagBen]

just offer an example of phase transsformation at low temperature: Kovar alloy (FiNiCo) could have a martensic transofrmation at low temeprature, say -200F, and this transofrmtaion is not reversible when tem is back to RT. We have tried to lower the tran. temperature or even eliminate the transformation by lots of means, since the transformation will affect (increase
)the thermal expansion coefficient which is undesirable. While Invar (Fe-36Ni) never has this problem.

 

[CJHirst]

Would API 5L behave differently than A106?

Why wouldn't martensite form that would need tempering?

 

[weldstan]

The high strength grades of API 5LX-65,-70,-80 will behave somewhat differently based on the actual chemistry of the materials. The other gerades of API 5L will behave similarly with A-106 B. The percentage of martensite in the API 5L or A-106 B will be a function of cooling rate and carbon equivalent. Cooling rate will be based on thickness, preheat and interpass temperature.