Effects of high temp. on welded structure. 1

[WardHollowayPE]

I have a pallet system that will carry a steel coil into a heated tunnel for conditioning. The temperature will be 750 Celsius. The exposure time can be up to 60 minutes. Is there a source of well documented effects of this temp. on a welded structure? Also what will happen to any bearings or hardened shafts that I have in my assembly? I am worried about warping and material degradation.
Thanks for any reply.

Ward Holloway, Jr, PE

 

[metengr]

WardHolloway;
Based on your post, the temperature effects on the material will depend on the material of construction (MOC). At 750 deg C (1382 deg F), all carbon and most low alloy steels will loose strength at this temperature. Materials that are hardened by thermal treatment will age and loose strength.

What are your MOC?

 

[WardHollowayPE]

Standard hot rolled plate and tubing.
UNS K02600 and UNS K03000

Ward Holloway, Jr, PE

 

[metengr]

The equivalent to K02600 is ASTM A36 structural steel, the equivalent to K0300 is ASTM A 500. Both of these materials and weldments are not recommended for use above 1000 deg F because of creep deformation concerns and oxidation.

I would suggest using 304 ss in lieu of carbon or low alloy. What you need is creep strength and oxidation resistance from exposure to repeated thermal cycling. The 304 tubing and plate would fit the bill, and is readily weldable. Any issues related to sensitization are mute because this is not exposed to aqueous service conditions.

 

[WardHollowayPE]

Stainless is not an option, each pallet is about 2500kg and there are 80 of them. The costs adds up quick. Is there a cast material that I can use? Do you have any link or hard data to back up that upper temp. limit? I will need hard data to convince my management to change materials.

Ward Holloway, Jr, PE

 

[metengr]

Spend some time here;

http://www.key-to-steel.com/default.aspx?ID=Articles

If you have access to ASM Handbooks, review Volume 1.

Last for effects on elevated temperature behavior, you can look for this free handbook over the Internet. it contains elevated temperature mechanical property data for low alloy steels;


MIL-HDBK-5H
Metallic Materials for Elements in Aerospace Vehicle Structures

 

[arunmrao]

I concur with metengr's recommendation. You have to get into ss materials for your application as time of exposure at 750C is quite long. Fortunately now prices of Ni is falling almost 12$/lb.

What sort of cast materials do you have on mind. Can you consider a Cr containing Cast iron having a chemistry


C 3-3.2%, Si 1.8-2%, Mn 1% max, Cr 0.6-0.7%, Ni 1%, Mo 0.2% (optional).

Ni Resist D1 type can also be considered .

However not all parts of the pallet can be made as cast for the shaft and bearings you may still need to consider 304,but this may be a small quantity and will not affect your cost.




" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke

 

[EdStainless]

Often heat treat tray systems are cast. The coarse grain structure lends itself to better creep resistance. I have used Ni-Resist, though I like D-2.
You will need an alloyed material to resist scaling, grain growth, and to have any strength at temp.
This cannot be done with plain carbon steels.

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