25 votes
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How can I tell if I got counterfeit aluminum?

I figured out a simple test. Since the density of 6061 is 2.5 g/cm3 and the density of zinc is over 7 g/cm3, all I had to do was measure the density of the material. This showed that indeed it was ...
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  • 1,595
21 votes
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What material is used to hold molten iron in a furnace?

Summary Crucibles are lined with refractory materials. Steel processing makes use of graphite or a combination of chromite and magnesite for direct contact with the melt. Cast iron processing often ...
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  • 3,971
21 votes

Can titanium be used as I-beams?

Not to repeat, but in addition to being very expensive it is very expensive to work with. So, pretty much only governments can afford it. It absorbs oxygen and nitrogen from air at the hot ...
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  • 5,720
19 votes

Can titanium be used as I-beams?

Yes, but titanium is very difficult to roll into structural shapes like I-beams in a rolling mill and extremely sensitive to chemical attack by washing solutions that contain chlorine, for example. So ...
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18 votes
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What made bronze the first widely used (non-ornamental) metal in human civilization?

The first thing to remember is that the naming of eras such as the Stone Age or the Bronze Age is never done by those living during the period. It was always done by others much later. To a certain ...
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  • 9,382
16 votes
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Can we change steel properties by application of magnetic field while quenching?

This will at least depend on the: Rate of Cooling Magnetic field strength Exact composition The magnetic field will alter the microstructure as you can read in, for example, Yudong Zhang, Nathalie ...
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  • 1,618
16 votes
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Could a gold/{second metal} crown be created that would pass the Archimedes test cost effectively?

Yes. Especially considering gold and platinum prices as of today, Pt costs less than Au. - but let's earn much more with more modern solution and simultaneously slowly murder the king in a very ...
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  • 6,113
16 votes

Copper is more conductive, so why use lead battery terminals?

Yes, copper is more conductive than lead, but that is not necessarily the primary criterion for selecting the connector material. For car batteries, making sure there's a good connection between the ...
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  • 6,719
15 votes
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Unknown metal-piece connected to the case of an iPod Nano 2

It's a naked piezoelectric buzzer. Some piezoelectric crystal grown on a metal circle are the active part and the bottom contact glued on the back cover. The top is then metallised to get the second ...
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  • 265
13 votes
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At what temperature do I risk altering the structure of steel?

In general, you want to stay below the recrystallization temperature. Steel is composed of grains, and different types of steel have different grain sizes. The size of these grains affects the steels ...
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12 votes
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How can the alloying materials of recycled steels be separated?

That is correct, there are a number of unwanted, or tramp, metals (Cu, Sn, Sb, As) that enter the recycling stream from, for example, car bodies that are ground into scrap without removing all the ...
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  • 3,971
12 votes

What is the purpose of grid-like details on engine blocks?

This pattern is to provide sufficient strength while minimising the mass of the block. These "webs" are designed to prevent any vibration, if the block wall was made thin and the full length and ...
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12 votes

Can titanium be used as I-beams?

Yes. Besides aerospace, titanium structural elements are fairly common in offshore oil and gas and chemical industries. You can order titanium I-beams online, with prices available at some websites. I'...
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  • 221
11 votes

What material is used to hold molten iron in a furnace?

Molten ferrous metals are often handled in steel ladles with a refractory lining. It's only since about the 1860s that any ferrous metals other than cast iron (which has a significantly lower ...
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11 votes
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Galvanized Steel (Zinc Plated Steel) vs Stainless Steel

Stainless steel can be used up to temperatures of about 1000C. The corrosion resistance of zinc plating decreases rapidly above 100C, and embrittlement can occur above 500C. Zinc plating has lower ...
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  • 12.5k
11 votes

Why does corrosion take place at certain stressed regions?

One of the mechanism that affect corrosion is known in the literature as Stress Corrosion Cracking (SCC). The idea is that tensile stressed regions are prone to crack development. Crack development ...
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  • 22.6k
10 votes

How can I tell if I got counterfeit aluminum?

You can confirm the alloy and heat treating condition by measuring conductivity. It's like a fingerprint for any given combination of alloy composition and heat treatment. Reference values can be ...
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9 votes

Why use a 'dogbone' shape for tensile testing specimens?

You half-answered your own question. Preventing failure in the grips is important. Additionally, grips of tensile testing machines have teeth to achieve a sufficiently strong grip that can withstand ...
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  • 3,971
9 votes

Can titanium be used as I-beams?

Yes, Titanium can be used as a structural material (not necessarily I beam), though rare. Here are two structures made of titanium, Monument to Yuri Gagarin and Monument to the Conquerors of Space, ...
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  • 7,253
8 votes
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What bolts should I specify with Weathering Steel?

For structural applications (in the US), the most common bolt for weathering steel is ASTM A 325 Type 3. Type 1 is a plain steel bolt that can be galvanized, but in this situation the zinc in the ...
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  • 10.6k
8 votes

Could a gold/{second metal} crown be created that would pass the Archimedes test cost effectively?

Using the values of metals in 287 BCE – 212 BCE, could it be cost effective for the crown maker? Of the metals known and used in antiquity (copper, gold, silver, lead, iron, tin, mercury, zinc), gold ...
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  • 335
8 votes

Copper is more conductive, so why use lead battery terminals?

A lead-acid battery has only lead and acid. If copper was used for the terminal posts galvanic corrosion would eat them. It is better to keep the same metal for the cell plates and the terminals. Also ...
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7 votes
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Can you get quality welds from a multiple metal wire feed welder, or do you need separate units for steel and aluminum?

The short answer: it's not optimal, but may work. Hopefully if these welds are critical, they're being performed to some code (In the US, for most structural work they'd be AWS D1.1 and D1.2 ...
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  • 4,501
7 votes

How can I tell if I got counterfeit aluminum?

Unlikely you have anything except aluminum alloy. What is the heat treatment supposed to be ; what grades are offered in the spec? On the net, I see reference to T-5, that is- as extruded, then aged; ...
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  • 5,720
6 votes

Can you get quality welds from a multiple metal wire feed welder, or do you need separate units for steel and aluminum?

This assumes US codes are used. The question of whether or not a quality weld can be produced needs to be proven through testing. Per AWS (American Welding Society) codes (D1.1, D1.5, etc) the welder ...
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  • 10.6k
6 votes

How can the alloying materials of recycled steels be separated?

To the best of my knowledge, such separation of components is not attempted. I have a friend who at one time worked for Lukens Steel in Coatesville, PA. His job was to write computer software that ...
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  • 6,719
6 votes
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Schaeffler, De Long, and WRC welding diagrams - which steels can be used?

You are not exactly right. The purpose of Cr and Ni in stainless steel, besides the stainless part, is to tailor the microstructure. Cr promotes ferrite, Ni promotes austenite. Other elements have ...
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  • 3,971
6 votes

Why use a 'dogbone' shape for tensile testing specimens?

Starrise gave a good explanation of the reasons why a dog-bone shape is important to the tension portion of a tension test, but there is another property that is typically measured at the same time: ...
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  • 10.6k
6 votes
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Determining the microstructure of steel after welding in modern computer software

Summary: 1) The answer to this question is difficult. You would need to know how austenite and ferrite behave in relation to what you are doing to them. You would also need to know their compositions,...
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  • 3,971
6 votes
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Word for the tendency of one metal to rub off on another?

"Galling" is probably the word you want here. It's the tendency of a (usually) soft metal to break down under pressure and adhere to the harder material. It's common with soft metals like aluminium, ...
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