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kayak karl
12-17-2007, 13:57
Have 6 pots some are aluminum, some steel, others are shiny. they look like steel but a magnet won't stick. what are they? they are 15 years old (I. Goldberg's)

Grumpy Ol' Pops
12-17-2007, 14:21
Could be stainless steel -- that's not magnetic.

kayak karl
12-17-2007, 14:24
Could be stainless steel -- that's not magnetic.
Thanks, is titaium lighter or is aluminum

StarLyte
12-17-2007, 14:28
Thanks, is titaium lighter or is aluminum

Come to the PA Ruck and we'll let you play with some :D

Appalachian Tater
12-17-2007, 14:29
Could be stainless steel -- that's not magnetic.

Yes, stainless steel is magnetic. Go into your kitchen and take one of the magnets off the fridge and stick it on a knife blade and see.


Thanks, is titaium lighter or is aluminum
Titanium is lighter than aluminum. Aluminum can be very shiny and it is not magnetic. If you look on the bottom of a pot, it often states the material. Titanium pots are generally only made for camping and they are relatively recent in manufacture.
The pot in your picture obviously has a copper or copper-plated bottom. It looks like the body is stainless steel. Copper is not magnetic.

JAK
12-17-2007, 14:29
Aluminum is 1/3 weight of steel for same thickness.
Titanium is 2/3 weight of steel for same thickness.

In practice titanium stuff will b lighter than the others for the same durability,
but aluminum can be just as light if you don't mind dings and dents.

That pot looked like stainless steel with a copper clad bottom.

JAK
12-17-2007, 14:36
Many stainless steels are not magnetic.

There are basically 4 differents types of stainless steel:
1. Ferritic - pretty sure these are magnetic.
2. Austenitic - pretty sure these are not magnetic.
3. Martensitic - pretty sure these are magnetic.
4. Precipitation Hardenable - not sure.

russb
12-17-2007, 14:41
Thanks, is titaium lighter or is aluminum

To compare one would need equal volume of the material, thus comparing density:

Al density: 2.7 g/cm^3 (approx since there are different aluminums)
Ti density: 4.9 g/cm^3

source: http://edboyden.org/constants.html

Thus comapring densities Aluminum will be be lighter when compared to an equal volume of Titanium. The other variable to consider is whether one requires more or less volume to create the requisite structural integrity of the pot. This would be noticeable in the thickness of the pot material.

When we compare the modulus or strength of the materials:

Al is 7 x 10^10 Pa (N/m^2)
Ti is 1.16 x 10^11 Pa

So the strength of Ti is much greater than Al so one could get away with using less.

In the end since the only real metric one cares about is the end weight, just look at the weight of the pots and not the material it is made of.

1oz of Ti is the same weight as 1oz of Al.

Appalachian Tater
12-17-2007, 14:45
Hmmm. All of my knife blades are magnetic. Do they use non-magnetic stainless steel in the manufacture of cooking pots?

take-a-knee
12-17-2007, 15:01
Hmmm. All of my knife blades are magnetic. Do they use non-magnetic stainless steel in the manufacture of cooking pots?

Most SS knife blades are magnetic 'cause they have carbon (or some other alloy) in them so as to take and hold an edge. Something intended for salt water use will usually not be magnetic.

taildragger
12-17-2007, 15:07
Most SS knife blades are magnetic 'cause they have carbon (or some other alloy) in them so as to take and hold an edge. Something intended for salt water use will usually not be magnetic.


How would carbon effect whether or not its magnetic? I figured that the stainless steels that had other metals in them might not be "magnetic" in the sense that we are used to.

russb
12-17-2007, 15:13
How would carbon effect whether or not its magnetic? I figured that the stainless steels that had other metals in them might not be "magnetic" in the sense that we are used to.


Stainless steel is a generic term, there are many different types. Basically stainless is a steel alloy with a certain percentage of chromium (to make is rustfree). Other metals are often added as well. For example carbon is added to increase the hardness, these alloys are magnetic. In some, nickel is added which modifies the structure of the alloy making it non-magnetic. Thus it is not the carbon which makes the SS alloy magnetic, it is the nickel which makes it non-magnetic.

kayak karl
12-17-2007, 15:32
Come to the PA Ruck and we'll let you play with some :D
Wouldn't miss it:)

JAK
12-17-2007, 15:46
Close. Its not the carbon that makes steel magnetic.
Its the Base-Centered Cubic structure of the Ferrite.
Martensite is a Base-Centered-Tetragonal, but is still magnetic.

Austenite is Face-Centered-Cubic, which seems to make it non-magnetic. On the downside they are no heat treatable, but can be cold worked for hardening and strengthening. Some precipation hardenable stainless steels might be non-magnetic. Not sure. Stainless steel that is primarily for corrosion resistance are most likely to be austenitic and therefore non-magnetic. Good stainless steel cutlery might be magnetic. I know my fridge isn't. Haven't checked by cutlery. Normal tableware cutlery might by austenitic. Stainless steel knives are not likely to be austenitic, so they are most likely to be magnetic.

Here are some examples of stainless steels of different types:

Ferritic:
409 - 0.08%C, 11.0%Cr, 1.0%Mn, 0,5%Ni, 0.75% Ti - Automotive Exhaust
446 - 0.20%C, 25.0%Cr, 1.5%Mn - Valves, Glass Molds, Combustion Chambers

Austenitic:
304 - 0.08%C, 19.0%Cr, 9.0%Ni, 2.0%Mn - Chemical and food processing
316L- 0.03%C, 17.0%Cr, 12%Ni, 2.5%Mo, 2.0%Mn - Welding Construction

Martensitic:
410 - 0.15%C, 12.5%Cr, 1.0%Mn - Rifle Barrels, Jet Engine Parts
440A - 0.70%C, 17.0%Cr, 0.75%Mo, 1.0%Mn - Cutlery, Bearings, Surgical Tools

Precipitation Hardenable:
17-7PH 0.09%C, 17%Cr, 7.0%Ni, 1.0%Al, 1.0%Mn - Springs, Knives, Pressure Vessels

From Callister, but adapted from ASM Handbook.

take-a-knee
12-17-2007, 16:02
How would carbon effect whether or not its magnetic? I figured that the stainless steels that had other metals in them might not be "magnetic" in the sense that we are used to.

I'm guessing it would be carbon's hexagonal shape and the way it bonds to most everything it comes near. I'll admit I'm out of my league here, maybe a chemist/engineer can enlighten us.

Appalachian Tater
12-17-2007, 16:17
I must say I have learned quite a bit today, prompted by this thread. Thanks, JAK.

NICKTHEGREEK
12-18-2007, 17:11
I must say I have learned quite a bit today, prompted by this thread. Thanks, JAK.
Thanks to both Tater and Jak.