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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 ...


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 ...


16

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 ...


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

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, ...


10

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 ...


10

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)...


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 ...


9

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 ...


9

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 ...


7

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 ...


7

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

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 ...


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

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

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 ...


5

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 ...


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

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

Summary: If you are loading and unloading the same sample, the stress-strain curve will not change and the tensile strength will be the same, because stress and strain are calculated from the initial geometry. If you are comparing two otherwise-identical samples with different levels of cold work or strain hardening, their stress-strain curves will be ...


4

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 ...


4

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 ...


4

Annealing is a heat-treatment process for stress-relief of a material. Annealing facilitates reduction of internal stresses and total elastic energy stored in inter-atomic bonds within a treated material. The term is used for appropriate heat-treatments of metals, ceramic glasses, and high-performance polymers. An example would be a cold-rolled steel billet ...


4

CO2 lasers are not able to cut highly-reflective materials, for reasons which should be obvious to anyone who has shone a laser pointer into a mirror. It may be that the "laser plate" is just duller than regular plate, or has some other surface finish conducive to laser cutting. If the steel is certified as A36, I can't see how there will be chemical ...


4

I've found a couple things about these knives (and "stay-sharp" knives in general). First, the knives you have appear to be treated with tungsten carbide on the edges per this website and this one. Since TC is incredibly hard, it dulls very slowly, hence why it is used for heavy-duty metal cutting operations. Second, the edge of the blade probably has ...


4

Making a nozzle with that long and thin of a hole is not feasible, but you could make a larger hole behind it and just have the last 3mm be 0.6mm in diameter. This would be feasible in a ceramic, but due to cost, I might make the nozzle into an insert that goes into a larger piece made of cheaper material. Things to be concerned with: Stream breakup due to ...


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