There are many grades of stainless steel; the ability to attract a kitchen magnet varies with each grade, and exist on a gradient (some are more magnetic than others).
For example, my kitchen refrigerator is stainless, but does attract magnets, even very weak ones, so I’m relatively certain that it’s not sticking to a ferromagnetic “backing”. Additionally, I have stainless cookware that is magnetic. In fact, induction cooking requires that cookware be magnetic for it to work.
Application, cost and purpose.
Casting is easier, can be heavier and can be bigger - think of pillar.
Forged steel will handle impact better than casting, makes the steel stronger & tougher by itself, it’s also less porose, there is also less need for expensive alloys to be added to attain high strength components, can also be more flexible (knife).
I buy a lot of titanium equipment. Pipes, vessels, mixers, pumps and impellers. Good resistance to chlorine dioxide, although a regrettable tendency to work harden. Stainless alloys with 6% to 7% molybdenum is also pretty durable. Probably a lot of the scrap titanium ends up at my place.
Took me a couple of moments, but first I had to interpret “See the wheeze?” as meaning “Get it?”
(I presume that Rose of Castille is the name of an opera.)
Specifically, having a face-centered-cubic (FCC) crystal structure. Magnetizability, and brittle transition temperature, are associated with body-centered-cubic (BCC) crystal structures.
Depends on carbon content. Wrought iron is wrought.
No, a high carbon content makes material brittle and impossible to work, so it can *only *be cast. Casting steel gets trickier mainly because alloying elements tend to separate, and often a homogenization heat treatment is required.
The chips are recycled, either back at the materials supplier or by a third party that sells them back to the supplier.
Not necessarily lesser. If they’re clean (meaning a water-based coolant was used in machining) and uncontaminated by other scrap (a lot of shop discipline is required but it pays off), then it’s just as good a feed stock as what you dig out of the ground - even better, usually.
The aerospace market took a huge spike when the golf club industry went into a titanium craze, not too long ago. A number of suppliers decided not to bother with aerospace anymore, and not all came back.
No such thing.
Eh? There are all sorts of titanium or Ti-alloy auto parts, sunglasses, sports equipment (tennis racquets and golf clubs spring to mind), jewellery…
I think “wheeze” to mean a joke or gag is mainly a British usage, as in Weasleys’ Wizard Wheezes.
Certain steels have a better uses for certain tasks. Granted this is a huge area and there are many people more expert in it than I who post here, but the steel deemed to be the best steel for knife blades (according to the published experts) is Martensitic Stainless Steel.
It has the hardness and the durability without being too brittle to both 1) cut well and 2) still flex (some). Generally, those blades are magnetic.
Granted, you can make (mill /machine) a blade out of different steels, but cast iron will be hard-but-brittle. You could use Austenitic Stainless Steel (food grade quality SS) which is not magnetic, but I’m not sure that the result would be as high of a quality in terms or durability and utility in a folding knife as you might imagine.
PS- if you need high durability and corrosion resistance in a more exotic knife blade metal, have you considered an alloy like Naval Bronze…?
Dougie_monty, they make them from Austenitic SS because that is more corrosive and bacteria resistant. Granted, if all you want is the metal part of the outside door made of an SS that is magnetic ( Martensitic would do; Type 410 perhaps?),
all you would need is the exact dimensions of the surface door part of the refrigerator. (Blue print quality, not straight-edge measured)
A blue print of that one part could be taken to most metal fabrication shops by you and they could quote you a price for making that one part.
It probably won’t be cheap, but it actually can be done. After its made, as long as it is within the original part’s tolerances, its just a matter of removing the old metal exterior from the refrigerator door and replacing it (carefully) with the new (expensive) part.
“Careful and gentle, but firm” might be your motto for that project.
Generally, austenitic alloys are ductile/soft and easy to form, while martensitic alloys are stronger but
brittle and unformable. Depending on the alloy, one can be heat-treated into the other, conveniently. Food-handling equipment typically doesn’t need high strength but does need to take on some highly contoured shapes, pointing toward austenitic grades.
Yes, many people make entire careers out of this stuff. It’s a complex subject.
Yeah, I was wrong. If the molten metal has to be rolled out or otherwise mechanically treated in order to reach maximum strength/the desired properties for a specific alloy, this still limits the forms it can come from the foundry in. Plates, maybe cylinders, limited simple geometric shapes. So you have to machine out the component you want.
Supposedly, though this sounds totally incredible and nuts, the cryogenic propellant tanks for a high end rocket start as a single gigantic block of metal that the interior volume is hollowed out from. That sounds ridiculous, for one thing because I don’t see how you could produce or move a piece of metal that large, and for another, it would sure chew through the cutting bits.
Well that doesnt answer why cast iron is used so much instead of cast steel.Is cast iron simply cheaper or does it have better properties(eg tensile strength) than cast steel. For eg why is a vice made out of cast iron.
You have to formalize your definitions. Iron can be cast, yes, but it has very little industrial use. It’s cast en route to being turned into steel.
Steel can be cast, forged, stack forged (from several lumps), or sintered to make powder steel. The trouble with cast steel is the resulting crystals are rarely uniform from the surface, going in. Also, it tends to have a lot planes of weakness. So depending on what you use it for, you may need to roll or forge, or heat treat your cast steel.
I’m a knife nut, by the way, and most knives have to have a gradational iron-carbide composition along the width of the blade. You can’t have that with just a cast steel. You have to heat treat it. Also, knives, springs and various cutting tools have to have a pretty uniform mega- and crystal pattern, as well as a good distribution of various alloying metals.
Hey, yeah, no worries. I’m no expert, which is why I toodled off to see about continuous casting. It looks like that process allows the steel mill to jump ahead in the forming sequence with an approximate shape to the final product.
That does sound a little nuts. Rocket fuel tanks can get pretty darn thin at times. See balloon tanks.
No, that’s a correlation specific to iron and not the cause of ferromagnetism. Nickel, for example, has an FCC crystal structure and is ferromagnetic.
It comes down to unpaired electrons. If a metal has unpaired electron(s) in its outermost (valence) shell, they can become aligned with other unpaired metal electrons, and you can get the familiar properties of an everyday magnet.
When are electrons paired up and when are they unpaired? Basically, it’s a question of energy balance, with the metal finding the best option given its environment. If there are atoms nearby that want to bond with the iron, sufficiently well that it’s ‘worth it’ energetically to pair those electrons and form bonds, then the iron will do that and be diamagnetic. If it’s just more iron atoms in its surroundings, or other unappealing things, the bonding energy gained by making more bonds would not be worth the energy cost of pairing up those electrons, so they stay unpaired and non-bonding and you get a ferromagnet.
Cause and effect are sort of mixed up here but the crystal structure of the iron isn’t really about the symmetry, but is about the local environment of the iron. Iron with all of its electrons paired ‘wants’ a different arrangement of atoms around it than does iron with unpaired electrons, so a ferromagnetic iron compound will form up with a different local environment for iron than what you’d find in a non-ferromagnetic iron compound. Metals other than iron will have different preferences for BCC and FCC that may not map well to what iron wants when diamagnetic and ferromagnetic.
I’ve worked on a couple of continuous caster projects over the years, so if you have any questions about them I’d be happy to answer them.
The basic idea is that all of the components (iron, nickel, etc) are thrown into a big ladle (as in about half a million pounds of metal big) and are heated in a blast oxygen furnace. When it’s all melted and mixed together, a crane carries the ladle over to the caster, and the molten steel is poured into the casting machine. There are two ladles, so there is always molten steel pouring into the machine, except for the very brief time when they switch ladles. As the steel drops into the machine, it is shaped by rollers, and the steel cools as it drops. When it has cooled enough that the outside of it is kinda solid (more gooey than solid, but solid enough to hold its shape) the rollers bend it around a curve so that it comes out horizontal out of the bottom of the machine. Once it cools a bit more (and it is sprayed with cooling water at this point to help it cool) a moving blowtorch follows the moving steel and cuts it into slabs. The torch has to move at the same speed as the steel so that it cuts a straight line across, and the steel speed is variable. Operators can speed it up or slow it down, to some degree. The more you slow it down, the closer to the machine it solidifies, and if you slow it too much it will turn into solid steel during the curve part, and at that point you’re stuck. The only way to get the solid steel out of the machine is to cut it up into pieces small enough to fit around the curve using hand-held blow torches and lift them out with a crane.
When you are standing on a catwalk about 3 floors up and about the same distance horizontally away from the steel, it still feels like someone is hitting you in the face with a hot hair dryer. It’s a wee bit warm near the steel. I stood on a catwalk that went over the steel when the first slab came off of a new line that was installed about 15 years ago in Baltimore. Nice and toasty. We expected to have the plant up and running by noon. It was 4 am when that first slab came off of it.
Steel mills are a little bit dirty (understatement) and the dust and dirt contains iron and steel particles which are conductive, which makes a lot of extra fun for the electronic controls.
ETA: Rule #1 in a steel mill: Slab haulers always have the right of way. They are carrying a few hundred thousand pounds of solid steel and can’t stop quickly even if they want to. They will crush your little pickup truck like a bug if you get in their way.
First of all, as others noted, steel is cast very often. Cast iron and cast steel both have many industrial applications currently. Also, ferrous metallurgy is extremely complicated.
The primary difference between cast steel and cast iron is the carbon content: typically carbon weight % is < 2% in steels, typically > 2% in cast irons.
The carbon in alloy steels or carbon steels is typically in the form of certain phases such as cementite at grain boundaries, dissolved in ferrite, stacked as lamellar pearlite (alternating layers of ferrite & pearlite), as spheroidal cementite for spheroidized steels, locked up in diffusionless transformation as martensite and/or bainite allotrope in quench hardened steels, or in a combination of martensite and various carbides in tool steels. In cast steels, the silicon content is typically relatively high, i.e. > 1%, compared to wrought counterparts in order to promote fluidity during the cast pour. Die casting, centrifugal casting, continuous casting (often in rolling mills), or other pressure-added cast techniques are common among steels compared to cast irons.
In cast irons, the some or all of the carbon typically exists in either graphite phase or iron carbide phase depending on alloy composition, cooling rate, and inoculation procecure. There are lots of different cast irons: gray cast iron (carbon in graphite flakes and pearlite), pearlitic ductile cast iron (carbon in graphite spheroids and pearlite), austenitic ductile iron (carbon in sort of spheroids in matrix of non-magnetic austenite), white iron (carbon in iron carbides), and malleable cast iron (rough spheriods of graphite) are among the most common.
Stainless steel may or may not be magnetic depending on the alloy. Austenitic stainless steels alloys (nickel % is ≥ 8%) have little or no magnetism. Martensitic and ferritic stainless alloys are always magnetic to varying extents depending on composition. Austenite is a face-centered cubic (FCC) crystallographic structure, while other forms of iron are magnetic body centered cubic (BCC) or, in the case of some heat treated components, magnetic body centered tetragonal (BCT). The only characteristic that all stainless steels share is the relatively high chromium content which boosts corrosion resistance in some environments.
There are iron-neodymium-boron alloys that are the gold standard of magnetism to density ratio, so that’s why consumer electronics and some higher end audio speakers use iron-neodymium-boron magnetic material components.
Crankshafts can be either forged alloy steel, ductile cast iron, or cast steel in my experience. I do not know which is more common among current manufacturers.
By the way, the different alloys of steel are made in the same continuous caster without stopping the caster. The machine keeps track of when the different ladle was added, tracks the steel through the machine, and cuts the slabs so that it knows which slabs have which mix of metals in them.
The length, width, and height of the slabs can also be changed on the fly.
Just a nit pick: the pig iron that comes out of a blast furnace (the initial conversion from ore to iron) is not really iron or something even close. It’s actually ultra-high carbon steel with carbon content above 2%. You convert it to usable steel by burning off excess carbon, among others.
It’s not even a matter of hours. The slabs that engineer_comp_geek mentioned are conveyed almost immediately to the hot rolling mill. The transit time can be as little as 15 minutes. I’ve followed the process from ladle to coil; it’s fast.
The result is hot rolled steel. You can do other things to the steel by cold rolling it, but that’s not a continuous process from ladle to coil like hot rolling is. Cold rolling may occur days later, for example. Cold roll mills are really, really awesome to have a look at, too, and their size is unbelievable.
I’ve been given “insider” tours to several steel mills as a function of my job, and if you think making automobiles is cool, it has nothing on making sheet steel! It’s an amazing, fabulous process and I feel like a kid full of wonder every, single time I visit a supplier. Really, it’s a sense of “I want to do that!”
Hot stamping is incredibly expensive, but it allows the use of very thin, 1000MPa+ materials in auto body applications that also require highly-contoured shapes.
That leaves out many steps.
They cast a bloom. Blooms are too big for transport, so they squash a bloom and cut it into billets.
Billets are then able to be transported, and fed into rollers.
Rollers can make plates and bar and long rods, I beams and girders and the like… Then to make a forged item you take a billet or bar or rod, and drop forge the piece into the new piece.
Or to make a machined item, you take a billet or bar and cut it to size and machine it down from there…
The heat treatment at each step is far beyond the scope of this, but don’t forget heat treatment ! The temperature for rolling, any qunching done before or after forging ? rolling ? machining ?