21

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 uses engineered clays, also known as alumina-magnesia-silica mixtures. Graphite is harder to form than clay-type refractories. To be suitable as a refractory, a ...


18

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 degree, the reason why bronze was the first important alloy was luck. For whatever reason, design or mistake, someone at some stage during antiquity mixed copper ...


16

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 nefarious plot: Gold is 40 $\$/g$ at 19.3 $g/cm^3$ Platinum is 39 $\$/g$ at 21.45 $g/cm^3$ Depleted Uranium is about 6 $\$/g$ at 19.1 $g/cm^3$ (1) [sorry for the ...


15

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 contact. Wires could be soldered to the contacts and/or the device could be cased in some plastic box but, since space is a premium here, it's used as is without ...


14

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 Gey, Changshu He, Xiang Zhao, Liang Zuo, Claude Esling, High temperature tempering behaviors in a structural steel under high magnetic field, Acta Materialia, ...


13

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 behavior once it gets past the yield point. At the recrystallization temperature, new grains will nucleate and grow, which undoes any sort of hardening that the ...


13

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 two pieces of metal (the stud on the battery and the connector on the wire) is more important, and lead wins out here because it is so much more malleable (soft)...


11

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 copper wiring, or tin-coated steel cans. Antimony and arsenic tend to creep in from low-quality and low-cost primary iron sources. The answer to the question is no....


11

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 melting point than steel) were handled in a molten state in any sort of quantity. Before that, steel production generally involved carburisation of iron or ...


10

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 width it would buckle or fail under the loads / stresses applied. This design allows the wall to be thin in-between the webs so reducing the mass and helping to ...


10

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 resistance to chemical corrosion from acids and alkalis than stainless steel. Aside from mechanical damage caused by scratching, the rate of corrosion may not be ...


10

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 essentially maximizes the area that corrosion can develop. Since corrosion, degrades the properties of the material, this accelerates further the crack ...


9

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 the forces required to deform the sample longitudinally. The teeth typically cause plastic deformation of the gripped portion of the sample. The plastic ...


8

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 galvanizing will quickly be used trying to protect the rest of the structure. Update for British bolts Interestingly, the only option for UK seems to be to get ...


8

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 is by far the densest, at $19.30 \text{ g/cm}^3$; mercury is in second place at $13.53 \text{ g/cm}^3$. Platinum may have been known, but it certainly wasn't ...


7

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 respectively.) Aluminum is considered among the hardest metals to weld well, so quality control is especially important there. Overall, the wire feeder itself doesn't ...


6

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 kept track of the composition of all of the scrap steel they had in their yards and to come up with the correct proportions of which kinds of scrap to use for any ...


6

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 (person) must be certified for the weld type (FCAW, SMAW, etc), the materials to be joined, and the position to be welded (flat, vertical, overhead, etc). In ...


6

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 similar effects and must be taken into consideration. Beware of carbide formation changing properties and reducing weldability. The three different graphs plot ...


6

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: Elongation. Elongation is measured by placing a gauge on the reduced section. It is important that the elongation occurs in this area so that the measurements ...


6

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, temperature field, etc. The results here could vary significantly depending on the specific parameters and how they change with time and with each other. 2) ...


6

"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, so that's why I think this is what you've noticed on lead too. However harder materials like stainless steel can gall too in certain circumstances, so it's not ...


6

Strictly speaking, very few metals are "stable" in terms of the laws of thermodynamics. True chemical stability is when the atoms are in their lowest energy state. For most metallic elements, various oxides, sulfides, and chlorides are lower energy states than the pure or alloyed metal. This is why corrosion occurs in the first place--the atoms ...


5

Convection, Conduction, Radiation Of the three modes of heat transfer, only one is affected by the vacuum. As you noted in your question, gaseous convection should be eliminated. That being said, the thermal shock is present as soon as the hot material hits the mold. As soon as the two materials come into contact, the heat transfer will be by conduction. ...


5

The answer to your question depends a lot based on what kind of steel and what kind of heat treatment you're thinking of. For one point of reference, if you were working on a steel structure in the United States, AWS D1.1 would limit the maximum heat in quenched and tempered steels to 1100 deg F. This temperature is compatible with preheating for welds or ...


5

I'd like to add to what @Fred said. Bronze wasn't the first. Before the Bronze Age, there was a comparatively brief Copper Age [also this]. Copper is comparatively abundant, and it sometimes naturally occurs in pure state (nuggets), as well as ores. In some places, polymetallic ores were used for producing copper. Early metalworkers noticed that the ...


5

To concur with the David Tweed & starrise, it is uneconomic to separate the individual metals in steel alloys. To do so would first require the alloys to be crushed and ground to the size of the crystal grains within the alloys. Then some form of mineral/crystal selection process would need to be devised to segregate and separate the wanted from the ...


5

There is a lot more going on in this question than appears at first glance. Density of austenite is fairly straightforward: it is approximately the atom-weighted sum of the face-centered cubic densities of the substitutional constituents as the microstructure consists of a single phase. In other words, Fe, Mo, V, etc. The interstitial constituents, i.e. C, N,...


5

As Brian Drummond noted, the "basin" is called a crucible: A crucible is a container that can withstand very high temperatures and is used for metal, glass, and pigment production as well as a number of modern laboratory processes. While crucibles historically were usually made from clay, they can be made from any material that withstands temperatures ...


5

Assume for the rest of my answer that, unless otherwise stated, the material in question is a macroscopic single crystal of some metallic element, free of volumetric defects (e.g. carbides, graphite, etc). Summary: single crystals with no dislocations are soft and yield readily because there are no dislocations to prevent the movement of newly introduced ...


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