Aisi4130 & Aisi4140 strength @ 150deg C 1

[Spiralis]

I am looking for strength at temperature for the Chromium-Molybdenium steels AISI4130 & AISI4140.

I can find alot of info about strength for stainless steels at temperature, but when I am going to verify the strength of equipment at temperatures up to 150deg C for carbon steel alloys it is not easy to find.

Somebody who knows where to look or actually have a paper showing typical og minimum values of these 2 alloys at 100deg C or 150deg C.

 

[ijzer]

AISI 4130 and 4140 only specify a chemical composition range. The strength will depend on the heattreatment performed on the material.

 

[Spiralis]

I forgot to specify the heat treatment for the alloys we use:

Material certificates for AISI4130 show hardening at 860deg C for 5 hours then water quench, + tempering at 670deg C for 6 hours. Yield strength 570MPa and tensile strength 735MPa

Normal ?:
AISI4130 (DIN 1.7218) annealed @ 865deg C (Yield at RT. min. spec. 360MPa )
AISI4140 (DIN 1.7225) annealed @ 815deg C (Yield at RT min. spec. 420MPA)

Since we need to test the equipment at high pressure and temperatures up to 150deg C, I need to make a calculation and find out what is the recommended highest pressure we can use, dependent of what material safetyfactor we put in the formula.

 

[TVP]

Spiralis,

Fig. 2.3.1.1.1 of MIL-HDBK-5J shows that alloy steels like 4130 and 4140 retain about 90% of their yield strength and about 95% of their tensile strength at a temperature of 150 C (300 F). You can obtain MIL-HDBK-5J from the ASSIST website (huge download) or you can access a web-friendly version of the older revision MIL-HDBK-5H by going to the Granta site. Use the following links for more info:

http://assist.daps.dla.mil/quicksearch/

http://www.grantadesign.com/cgi-bin/stat-tree.cgi?src=MIL5-H.xml&br=0

 

[unclesyd]

At 150°C you can use the RT properties with an appropriate safety factor as the drop off in these properties will not be measurable.

May I ask why you have a 5 hour soak in the hardening process?
Your time @ temperature is getting in the range of troublesome grain growth.

 

[EdStainless]

I also don't like your 5 hour soak.
But to your original question, looking at the tables in my High Temp ASM reference. It looks like with your high temper temperature there will be no drop in yield strength and ~5% drop in tensile.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[metengr]

One additional comment to the above posts, make sure you have sufficient design margin with your pressure test to avoid local plastic deformation of the vessel.

I would recommend a value of either ULT/3.5 or 2/3 of the yield strength, whichever is lower, at the pressure test temperature.

 

[Spiralis]

Unclesyd and EdStainless,

The unit I am to calculate is not designed by me. The material certificate for the AISI4130 alloy just list 5 hours as soaking time. If I had designed the unit, I would have selected 17-4PH Stainless Steel, to have some corrosion resistance and be able to follow the ASME rules when calculating the pressure vessel.

I am not a metallurgist. I do not now the effect of such long hardening time, but I can relate to the fact that the grains will grow slightly. From my knowledge as mechanical engineer, larger grains will give a lower strength. Will larger grains have a positive effect on corrosion resistance? I know that there is a risk of H2S in the system, so a softer material might help in the case of cracking?

Anyway thank you all for the information about the strength decrease at increasing temperature. TVP's enclosed links gives alot of info for my work. Also nice to have a reference.