Calculating Strength 1

[OffRoad10]

What equation or theory would I use to calculate the yield strength and/or tensile strength of a material at an elevated temperature? Given: Yield strength at room temp; grade/chemistry; and desired elevated temperature.

 

[metengr]

OffRoad10;
You don't calculate, you either look up this mechanical property information from known sources or you perform standard tests on your won to determine the values.

 

[OffRoad10]

I can not test due to the volume of grades, gauges, and production practices I need information for. You see; I'm on the hot side of metals.

 

[MatieMan]

OffRoad10,
Tensile or yield strenght values are material properties, they are detemined by test (not by calculations). In general they are available in the material standard (European materials), for American materials most of these values can be found in ASTM standards or ASME II tables.
Which material are you talking about... maybe we can say where to find these values for that material. What do you want to calculate?

 

[OffRoad10]

Ultimatley, I would like to calculated torsion forces viewed by the mandrel on a down coiler. My boss is convinced that material properties effect the forces seen at the madrel. More robust material equates to more torque.

The grades envolved are everything from plain carbon steels, Mn steels, HSLA's, Boron treated, medium carbon, and high carbon. I'm putting together a capabilities chart for our entire product range. But mechanical properties for these steels at the coiling temperature is most relevant since we coil at the coiling temperature and not at room temperature.

I'm starting to think the torque at the mandrel has nothing to do with the material properties at all. It is a statics problem with the torque resulting from the tension in the material placed there by the different rotational speeds from F7 and the coiler mandrel.

 

[metengr]

For a project like this, I would suggest you review ASM International Handbooks; Volumes 1 and 14. You can try a local engineering library or convince your boss to pay for an on-line subscriber service.

http://www.asminternational.org/

 

[TVP]

OffRoad10,

The mechanical properties at coiling temperatures (550-750C, 1020-1380F) are going to be quite low: the stress-to-rupture (essentially tensile strength) will be less than 50 MPa for most ferritic steels, so the yield stress will be even lower than that. Fig. 2.3.1.1.1 in MIL-HDBK-5J shows a graph of strength vs. temperature for low alloy steels up to 1200F, where the value is 23% of the room temperature value. You can obtain MIL-HDBK-5J from the following website:

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

 

[mewhg]

TVP

What if the material was M2 hardened to 60 HRC and was running at 1300F? Would the tensile strength still be so low?

 

[EdStainless]

How about the ASM 'High Temperature Property Data: Ferrous Alloys' ed Rothman.

M2 at 1000F 248ksi yld, 55 Rc
on another table it shows hot hardness, Rc.
1000F 51
1200F 34

The data mostly comes from 'Steel Product Manual, "High Temperature High Strength Alloys", AISI, 1963'.

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[TVP]

mewhg,

As EdStainless illustrated the answer to your question is no. Highly alloyed grades such as tool steels, precipitation hardening steels, etc. would be stronger/harder than typical ferritic grades. High carbon concentrations and stable carbides will promote higher strength at elevated temperatures.

 

[EdStainless]

but, just like with any ferritic material the hardness will drop quickly when the carbides begin to dissolve. Even after this drop though the metal will be stronger than a plain steel because the carbon and heavy elements (W and Mo) will provide some solution strengthening.
I would think that hot rolling would follow similar rules to forging and that you wouldn't want to finish at temps below about 1700F.

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