metallurgy 101

[Dr Ada Not-a-fruit]

two stupid questions:

why is cast iron not cast steel? what is steel, anyhow, and why is it
good?

what's a good basic metallurgy book that assumes you have a working
(university first year) chemistry and physics, yet is practical? i'd
like to learn more about ferrous metallurgy as well as aluminium
metallurgy, and I want something that assumes that I have a brain and
I'm not afraid to use it; I'd like to have a working knowledge of
material choice by the end.

[Jason Lewis]

Hi Ada,

In terms of steel/iron it is all to do with the carbon content. pure
iron is relatively malleable and soft, as you add carbon to it, it gets
harder and more brittle. Tool steel or cutting steel is usually
relatively high, which makes the steel able to cut other softer steels.

Check out
http://en.wikipedia.org/wiki/Carbon_steel#Mild_and_low_carbon_steel for
the details of the % of carbon in the steel. usually steel has a carbon
content up to about 1%

Cast Iron is steel with very high carbon content, approximately 2% and
above (at least according to wikipedia). That makes it very brittle.


I did a tour of the Wollongong steel works once - in one part of the
process they inject liquid oxygen directly into 200 ton vats of molten
iron in order to burn off the carbon and achieve the carbon content
desired for that batch. It's quite a sight to behold!

I have no idea why cast iron is called cast iron when its a kind of
steel (I guess) just historical I suspect.

Hope that helps?

Jason

[David Lyon]

From what I understand, Steel is a very recent invention. Only readily
available from around the end of the 19th century with the invention
of the Bessemer process.

The process of casting Iron goes back a lot further than that. Thought
have started in Anatolia, now Turkey. If you are in Turkey, their metal
work is amazing. For example, to build a carpark, they don't use milled
RSJs, they actually make them onsite themselves and assemble. Ok,
it's harder but it saves some money.

Knowing how to cast-iron is a handy skill, not that I know.

From a process perspective, there's little difference between iron-casting
and steel casting. Only that buying iron rather than steel is getting a
little more difficult as time goes on.

[Gav]

As mentioned it's mostly about carbon content, impurities and also the speeds at which you transition from one point to another in the iron-carbon phase diagram. It's been a few years, but studying it seemed to make intuitive sense of work-hardening, different grades of steel, and crack propagation. 

I've just checked my work texts and they don't touch it more than discussions of how various irons make magnetic circuits. I'm pretty sure I've got a text which goes into detailed exploration of various points on the phase diagrams, and I'll grab it next time I'm at home. Not sure if it'll be detailed enough for your needs, but worth a shot. 

"I did a tour of the Wollongong steel works once - in one part of the

process they inject liquid oxygen directly into 200 ton vats of molten
iron in order to burn off the carbon and achieve the carbon content
desired for that batch. It's quite a sight to behold!"

Not at the same plant, but I wrote some code for (low level) control of that reaction a few years ago :-D

Cheers,

Gavin 

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[Terry Dawson]

On Thu, May 24, 2012 at 12:24 AM, Dr Ada Not-a-fruit <a...@panda2.net> wrote:
> two stupid questions:
>
> why is cast iron not cast steel?  what is steel, anyhow, and why is it
> good?

The Wikipedia page for "Cast Iron" provides a pretty good explanation.
Steel is a family of primarily Iron/Carbon alloys. Cast Iron isn't
necessarily, it can also be Iron/Silicon. Cast Iron isn't a name for
an alloy so much as it is a name for a class of materials based around
Iron and cast by pouring.

Interesting to see you asking a question rather than answering one.

Terry

[Dr Ada Not-a-fruit]

On May 24, 9:16 am, Gav <the.mechatronics....@gmail.com> wrote:
> As mentioned it's mostly about carbon content, impurities and also the
> speeds at which you transition from one point to another in the iron-carbon
> phase diagram. It's been a few years, but studying it seemed to make
> intuitive sense of work-hardening, different grades of steel, and
> crack propagation.
>
> I've just checked my work texts and they don't touch it more than
> discussions of how various irons make magnetic circuits. I'm pretty sure
> I've got a text which goes into detailed exploration of various points on
> the phase diagrams, and I'll grab it next time I'm at home. Not sure if
> it'll be detailed enough for your needs, but worth a shot.

What I want is a metallurgy equivalent of

http://en.wikipedia.org/wiki/The_Art_of_Electronics

(which is the introductory electronics textbook I would suggest for
anyone who understands calculus, btw).

Thanks for all the canned wikipedia answers, but I've already read
them all and I don't have a gut understanding of metallurgy.

If you heat wrought iron past its melting point in a neutral (neither
reducing nor oxidising) atmosphere and then cast it, does that make it
cast iron despite having a carbon content of (effectively) zero?
That's an unintuitive result.

If you carburise wrought iron past 2.1%, does that make it cast iron
without having been cast? That's an unintuitive result.

If you perform surface decarburisation of cast iron, does this produce
something with a cast iron core and a steel outer? or is the whole
thing steel? is the 2.1% number a local requirement or is it global;
at what scale do you average?

how does aging and work hardening occur, especially in relation to
aluminum alloys? (that's deliberate to annoy Gav)

aluminium nomenclature makes sense to me, but selecting grades of
steel (especially since the same steel can be called multiple
different names depending on what country you're in, and Australia
likes to use *all* the standards) is very confusing.

clank clank
-A

[Terry Dawson]

On Thu, May 24, 2012 at 12:02 PM, Dr Ada Not-a-fruit <a...@panda2.net> wrote:
> If you heat wrought iron past its melting point in a neutral (neither
> reducing nor oxidising) atmosphere and then cast it, does that make it
> cast iron despite having a carbon content of (effectively) zero?
> That's an unintuitive result.

I think you're being too literal and making the assumption that "Cast
Iron" is a technical term. It's not.

Within a liberal range of iron+impurities+casting it's a whole family
of materials.. it's more a marketing term .. or a general term ..

Terry

[David Lyon]

If it helps make things make more sense, 'Steel' was
a 19th century marketing term for a higher grade of Iron
having less impurities and a lower carbon content than
what was able to be delivered previous to that.

Therefore, what we know as "Steel" is closer to being
pure molecular Iron than 'traditional-Iron' (which had a
lower purity).

"Cast-Iron" is exactly that. Either Steel or Iron that has
been cast into some useful implement. "Cast-Iron" really
describes a moulding process rather than anything else.

[bowl Huynh]

This book covers materials pretty well. Text heavy and detailed. It was used as part of my degree a few years ago.

Materials Science and Engineering: An Introduction by William D. Callister, Jr.

---

Date: Thu, 24 May 2012 12:34:27 +1000
Subject: Re: metallurgy 101
From: david.lyon...@gmail.com
To: sydney-h...@googlegroups.com

[Mike]

I think I still have a copy of that.

[McGinnes Mark]

The key point about cast iron is that it contains so much carbon that it ceases to be malleable. This means that it cannot be forged, or extruded, or rolled etc. and must be cast, hence the name. The amount of carbon this requires depends on what else is in the alloy. You could conceivably have an alloy that was 4% carbon but was still malleable due to some other combination of ingredients, it would be steel and not cast iron.

Ada asked; "If you heat wrought iron past its melting point in a neutral (neither reducing nor oxidising) atmosphere and then cast it, does that make it cast iron despite having a carbon content of (effectively) zero?"
No - it would be iron-that-has-been-cast and not cast iron as it would still be malleable.

Ada asked; "If you carburise wrought iron past 2.1%, does that make it cast iron without having been cast?"
Yes - if you could magic so much carbon into iron that it became unmalleable without having to melt the iron then you would end up with cast iron even though it wasn't cast. But such a thing is unpossible. Probably.

David said; ""Cast-Iron" is exactly that. Either Steel or Iron that has been cast into some useful implement. "Cast-Iron" really describes a moulding process rather than anything else."
No - cast iron and cast steel are two very different materials. You can wail on a cast steel anvil for decades without putting a dent in it, but there is a reason cast iron anvils are called 'doorstops' or 'anvil shaped objects'.

Engineering books such as "Machinery's Handbook" generally have a good discussion on metallurgy, especially as it relates to properties and materials choice. They also explains the different naming schemes and standards, and give comparison charts between different naming conventions, and tables showing the compositions of different alloys. They also explain the process of heat treatment, basically everything you want to know, and lots of other stuff like bearing standards, gear standards, thread info, safety factors for flywheels, all kinds of great stuff. The electronic version is easy to find online.
There are lots of older, similar books such as "The Mechanical Engineers' Handbook" and "The Mining Engineers' Handbook" which you might be able to find in a second hand bookstore. The age of the book is almost irrelevant, as the chemistry has been known for ages.

Macca

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[David Lyon]

Hi Macca,

> No - cast iron and cast steel are two very different materials.

Nope. The tolerence between cast Iron and cast steel less than 3%. That
makes it only subtly different. It's no different than saying stainless steel
is not steel. The difference between elemental Iron and Steel is a mere few
percent.

It's taken a few thousand years for mankind to get Iron into a really pure
state. Before 150 years ago, the definition of 'pure' iron was a lot different.

Pure Iron is not such a useful material. It's much more useable when
alloyed with other compounds according to the desired application.

The people that injected oxygen into the molten 'iron' may/may-not have
had the measuring tools to know that what they came up with was
just a purer form of Iron than could be made before, but that doesn't
change that was exactly (only) what they achieved.

Called it 'steel' to make it sound sexy, but all it was was a purer form
of Iron.

That's my story anyway :-) I'm sticking to it.

[Nick Johnson]

On Fri, May 25, 2012 at 12:49 PM, David Lyon <david.lyon...@gmail.com> wrote:

Hi Macca,

> No - cast iron and cast steel are two very different materials.

Nope. The tolerence between cast Iron and cast steel less than 3%. That
makes it only subtly different. It's no different than saying stainless steel
is not steel. The difference between elemental Iron and Steel is a mere few
percent.

By the same standard, CO2 makes up less than 0.4% of the atmosphere, so our atmosphere is only subtly different from one with no CO2, or with twice as much.

Only, no, that's not right.

-Nick

 

It's taken a few thousand years for mankind to get Iron into a really pure
state. Before 150 years ago, the definition of 'pure' iron was a lot different.

Pure Iron is not such a useful material. It's much more useable when
alloyed with other compounds according to the desired application.

The people that injected oxygen into the molten 'iron' may/may-not have
had the measuring tools to know that what they came up with was
just a purer form of Iron than could be made before, but that doesn't
change that was exactly (only) what they achieved.

Called it 'steel' to make it sound sexy, but all it was was a purer form
of Iron.

That's my story anyway :-) I'm sticking to it.

[McGinnes Mark]

Chemically they may be very similar, but the physical properties vary wildly between the different alloys. The Demarcation between cast iron and steel is based on physical properties, namely malleability, not (strictly) on chemical makeup.

 

Macca

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[David Lyon]

But the reference standard for 'Iron' surely must be 'elemental' Iron (Fe).

"The iron itself is usually found in the form of magnetite (Fe₃O₄), hematite (Fe₂O₃), goethite (FeO(OH)), limonite (FeO(OH).n(H₂O)) or siderite (FeCO₃)" (http://en.wikipedia.org/wiki/Iron_ore)

The Bessemer process was just a cool way to improve the purity of the processing of the Iron Ore.

[McGinnes Mark]

I’m not quite sure what your point is David. We are specifically talking about alloys of Iron. An alloy that contains both Iron (Fe) and Carbon (C) will be called either steel or cast iron. What it gets called depends on whether it is malleable or not. Not what else it contains, not how it was made, not where it was smelted, not what colour it is. Cast iron is a name for a material that has specific physical properties, it is just a name, it could just as easily be called i-can’t-believe-it’s-not-steel or unsteel, or banana (except that last one is already taken).

 

Macca

 

From: sydney-h...@googlegroups.com [mailto:sydney-h...@googlegroups.com] On Behalf Of David Lyon
Sent: Friday, 25 May 2012 1:03 PM
To: sydney-h...@googlegroups.com
Subject: Re: metallurgy 101

 

But the reference standard for 'Iron' surely must be 'elemental' Iron (Fe).

"The iron itself is usually found in the form of magnetite (Fe₃O₄), hematite (Fe₂O₃), goethite (FeO(OH)), limonite (FeO(OH).n(H₂O)) or siderite (FeCO₃)" (http://en.wikipedia.org/wiki/Iron_ore)

The Bessemer process was just a cool way to improve the purity of the processing of the Iron Ore.

[Ada Lim]

Mark/mike/huynh/gav, thanks for the information.  I'll ask you more questions privately, mark, if I may.

[David Lyon]

Yeah, but it's very possible to make a cast-iron banana.

Take a banana, make a mould of it, pour iron into the mould, let
it cool - voila!

[McGinnes Mark]

Certainly.

 

From: sydney-h...@googlegroups.com [mailto:sydney-h...@googlegroups.com] On Behalf Of Ada Lim
Sent: Friday, 25 May 2012 1:20 PM
To: sydney-h...@googlegroups.com
Subject: RE: metallurgy 101

 

Mark/mike/huynh/gav, thanks for the information.  I'll ask you more questions privately, mark, if I may.

 

[Tom Davies]

On Friday, 25 May 2012 12:30:45 UTC+10, Macca wrote:

...

Ada asked; "If you carburise wrought iron past 2.1%, does that make it cast iron without having been cast?"
Yes - if you could magic so much carbon into iron that it became unmalleable without having to melt the iron then you would end up with cast iron even though it wasn't cast. But such a thing is unpossible. Probably.

Apologies for performing necromancy on this thread. I thought the 1896 process of making Krupp armour plate was interesting:

"[starting from low carbon steel]... The plate was then arranged face up on a truck and covered with a mixture of animal and vehgetable charcoal to a depth of 6in and another plate laid on top. The whole was then covered with sand and then run into a furnace where it was kept at a high temperature for up to three weeks. Immediately after being withdrawn, the plate was bent to the final shape and toughened by re-heating and cooling in an oil bath. The edges were cut to final shape and all holes were drilled and plugged with clay. The face was then heated to a higher temperature than the back by protecting the latter in the furnace and the plate was suddenly chilled on both sides by water jets. The face was now very hard whilst the back, which was not carburised, and was heated to a lower temperature, remained tough. ... Any final adjustments were made by grinding as the face was now too hard to cut..."

[Ada Lim]

ok, I decided to think about this some more, and after pondering the concept of "malleable cast iron", I found this web page:

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[Ada Lim]

www.tf.uni-kiel.de/matwis/amat/mw1_ge/kap_8/backbone/r8_4_1.html

[Ada Lim]

stupid transformer keyboard.  anyhow, with a bit of staring at the phase diagram, I finally understand cast iron and steel.  as that web page says:  the iron-carbon phase diagram:  one of the most important pieces of information to mankind, yet not taught in school.

[Mike]

It might not be taught in school but it's a first year university
subject (not that I remember a lot of it).
I still have the materials textbook if you want some further reading.


Mike

[Terry Dawson]

On Thu, May 31, 2012 at 1:02 AM, Ada Lim <a...@panda2.net> wrote:
> www.tf.uni-kiel.de/matwis/amat/mw1_ge/kap_8/backbone/r8_4_1.html

I ended up being more interested in this question than I thought I'd be.
The more places I look for definitions of Cast Iron, the more
definitions I find. It's clearly not well standardised.
There is a hand-wavy line between Steel and Cast Iron at the bottom
end. I think the hand-waviness is because addition of other metals
into the alloy move things around quite a bit.
The commonality does seem to be what (was it Macca?) offered with
respect to where the Fe-C alloy become brittle. At around the 4.4%
mark it's easy to melt (easy to pour?), but is brittle. At around the
2% mark it starts becoming tough but requires high temperatures to
cast.

On an orthogonal note, I want to see a drop forge in operation. Just
remind me to keep my fingers out of the way.

Terry

[Terry Dawson]

On Thu, May 31, 2012 at 10:49 AM, Terry Dawson <vk2...@gmail.com> wrote:
> The more places I look for definitions of Cast Iron, the more
> definitions I find. It's clearly not well standardised.

No sooner had I said that than I discovered that Standards Australia
do have standards for these things.

Malleable Cast Iron - AS1832 for example.

regards
Terry

[Ada Lim]

On Thu, May 31, 2012 at 10:49 AM, Terry Dawson <vk2...@gmail.com> wrote:

> On Thu, May 31, 2012 at 1:02 AM, Ada Lim <a...@panda2.net> wrote:
>> www.tf.uni-kiel.de/matwis/amat/mw1_ge/kap_8/backbone/r8_4_1.html
>
> I ended up being more interested in this question than I thought I'd be.
> The more places I look for definitions of Cast Iron, the more
> definitions I find. It's clearly not well standardised.
> There is a hand-wavy line between Steel and Cast Iron at the bottom
> end. I think the hand-waviness is because addition of other metals
> into the alloy move things around quite a bit.

If you stare at the phase diagram long enough, you will see that cast
iron is that group of Fe-C alloys which do not form austenite, whereas
steel is the group of Fe-C alloys which form austenite.

Once you form austenite, you can undergo martensitic transformation,
and that's what makes steel amazing.

So I have answered my original question, at long last.

[Terry Dawson]

On Thu, May 31, 2012 at 10:55 AM, Ada Lim <a...@panda2.net> wrote:
> If you stare at the phase diagram long enough, you will see that cast
> iron is that group of Fe-C alloys which do not form austenite, whereas
> steel is the group of Fe-C alloys which form austenite.

AS1833 - Austenitic Cast Iron.

Keep looking.

Terry

[David Lyon]

For Steel lovers and all things Steel, start in Australia where the
Iron Ore is dug.

Next suggested stop is Turkey where age old methods are still used to
make things like gates and buildings. Of course they have modern
equipment too but many Iron Age ways/tools still are to be found
there.

Go onto England to see what they did in the 17th/18th/19th/20th centuries.

Sit on a 1000km steel rail and go to Germany and get a grasp on modern
steel chemistry.

Spend a morning watching steel processing on Japanese TV you can see
things done with steel that just aren't allowed here.

The Sydney Opera House and Harbour Bridge are themselves wonders of
steelmaking but interest has been somewhat lost over the last two or
three decades, maybe due to economic rationalism, but that's how it
is.

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[Ada Lim]

So, what's Austenitic Cast Iron, eh? Is it a Fe-C alloy, eh?

[David Lyon]

In Japan, there's about six hours of program on Steel every day on
their free-to-air tv.

Then you can go outside, and actually ride/touch/see use it..

Here Steel processing is a bit different. and we have lots of the stuff.

[David Lyon]

Authentic cast Iron is what you get when you melt Iron Ore.

The chemical impurities depend on what's in the Iron Ore and that
changes depending on the area that the Iron Ore is dug.

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[Ada Lim]

but I do appreciate the mention; googling for it led me to the
Springer Handbook which, although the wrong colour, does look very
interesting.

[Terry Dawson]

On Thu, May 31, 2012 at 11:07 AM, Ada Lim <a...@panda2.net> wrote:
>> AS1833 - Austenitic Cast Iron.
>
> So, what's Austenitic Cast Iron, eh?  Is it a Fe-C alloy, eh?

No, they're Fe-C-Magic alloys.

AS1833 says: "Austenitic cast irons are high alloy materials in which
the metallic matrix has been rendered austenitic at ambient
temperature by the use of alloying elements and in which the carbon is
present predominantly as either flake or spheroidal graphite. Carbides
are often also present, particularly in the high chromium grades."

regards
Terry

[Terry Dawson]

On Thu, May 31, 2012 at 11:15 AM, Ada Lim <a...@panda2.net> wrote:
>> So, what's Austenitic Cast Iron, eh?  Is it a Fe-C alloy, eh?
>
> but I do appreciate the mention;  googling for it led me to the
> Springer Handbook which, although the wrong colour, does look very
> interesting.

It's an example of where "Cast Iron" refuses to fit inside the Fe-C
box. "Cast Iron" resists your desire to define it simply.

Terry

[Madox]

I PM'ed Ada, it was taught in 2U Engineering Science in Year 11/12 HSC some years ago.

Example/Proof (Exam Paper)

http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2000exams/hsc00_enginsci/99enginstudies_eer.pdf

Page 20

//Defending NSW Public Education...

[Ada Lim]

Not in my state!  we didn't have engineering science, and I took a "classic" education instead.

anyhow, even if engineering science was taught in my school I wouldn't have taken it at that age;  it looks a bit stamp-collector for teenage-me.

On Jun 1, 2012 1:32 AM, "Madox" <mado...@gmail.com> wrote:

[Ada Lim]

do you actually have an understanding of the topic, or is this the
metallurgical equivalent of Dr Google?   you've contributed no useful
correct information to this thread;  misquoted and misunderstood
pieces of wikipedia do not count as either correct nor useful.  this
topic started off as me not having a fundamental understanding of the
difference between cast iron and steel.  if you want to snipe and be
snarky, be my guest! but be correct when you do so;  don't be an
idiot.

so I read the relevant bits of callister, and they're pretty good for
giving a basic understanding.  then I found exactly what I was looking
for by *gasp* going to the library:  the ASM Handbook Volume 1:
Properties and Selection: Irons, Steels, and High-Performance Alloys
http://www.amazon.com/ASM-Handbook-Volume-Properties-High-Performance/dp/0871703777

for those still interested in this topic, it's *amazing*. succinct
yet in depth. also, the springer handbook of mechanical engineering
has an excellent section (not very long) on ferrous alloys.

now that I've read the theory: is there a place to practice practical
metallurgy at R&D?

[Gav]

Take a walk and cool off, please Ada. 

Terry is not an idiot and saying so is not helpful. No one is apparently up to your standards of metallurgical knowledge or correctness here, so I suggest we finish this thread here. 

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[Ada Lim]

On Fri, Jun 1, 2012 at 9:50 PM, Gav <the.mechat...@gmail.com> wrote:
> Take a walk and cool off, please Ada.

I'm not sure what I'm cooling off from....

> to your standards of metallurgical knowledge or correctness here, so I

I didn't realise that I had standards for knowledge or correctness,
other than, you know, not spouting obviously incorrect material.
there are enough people on this mailing list who do that without
adding to that set.

I think it's reasonable to presume that you don't want to be made more
stupid ignorant by reading this mailing list, so replies or like:

"I think you're being too literal and making the assumption that "Cast
Iron" is a technical term. It's not."

"The Wikipedia page for "Cast Iron" provides a pretty good
explanation. Steel is a family of primarily Iron/Carbon alloys. Cast
Iron isn't necessarily, it can also be Iron/Silicon. Cast Iron isn't a
name for an alloy so much as it is a name for a class of materials
based around Iron and cast by pouring."

" You could conceivably have an alloy that was 4% carbon but was still
malleable due to some other combination of ingredients, it would be
steel and not cast iron."

"The Demarcation between cast iron and steel is based on physical
properties, namely malleability, not (strictly) on chemical makeup."

"No, they're Fe-C-Magic alloys."

"It's an example of where "Cast Iron" refuses to fit inside the Fe-C
box. "Cast Iron" resists your desire to define it simply."

"From what I understand, Steel is a very recent invention. "

"Nope. The tolerence between cast Iron and cast steel less than 3%.
That makes it only subtly different. It's no different than saying
stainless steel is not steel. The difference between elemental Iron
and Steel is a mere few percent. "

"If it helps make things make more sense, 'Steel' was
a 19th century marketing term for a higher grade of Iron
having less impurities and a lower carbon content than
what was able to be delivered previous to that."


If you read those posts and take them as truth, you would actually
finish the thread more misguided than you start. I don't know if you
get off on becoming more stupid, but I certainly don't. I started
asking stupid questions, and finished reading stupid answers. The
whole experience was enlightening in a peculiar sort of way.

[Terry Dawson]

On Fri, Jun 1, 2012 at 9:01 PM, Ada Lim <a...@panda2.net> wrote:
> do you actually have an understanding of the topic, or is this the
> metallurgical equivalent of Dr Google?   you've contributed no useful
> correct information to this thread;  misquoted and misunderstood
> pieces of wikipedia do not count as either correct nor useful.  this
> topic started off as me not having a fundamental understanding of the
> difference between cast iron and steel.  if you want to snipe and be
> snarky, be my guest! but be correct when you do so;  don't be an
> idiot.

Wow, was this directed at me? If so my opinion of you dropped considerably.

My assertion from the start was that "Cast Iron" is as much a
marketing term as any sort of formal definition of a material.

The AS documents I've been quoting are Australian Standards documents.
I'm not sure what you use as your reference for standard terms and
definitions but I find it hard to go past formal standards bodies.

I wasn't sniping or being snarky, I was intending to be playful. I've
been on personal quests a number of times in my life seeking neat and
formal definitions of things only to find that in reality sometimes
there are no such thing, sometimes definitions are arbitrary.

You've also conflated some of David's responses and some of mine.

Terry

[Ada Lim]

On Fri, Jun 1, 2012 at 10:36 PM, Terry Dawson

> Wow, was this directed at me? If so my opinion of you dropped considerably.

I'm not really interested in your opinion of me.

> My assertion from the start was that "Cast Iron" is as much a
> marketing term as any sort of formal definition of a material.

and that assertion is false. it's reasonably clearly defined, with a
definition that separates it from steel. as I said, it requires
looking at the phase diagram more clearly.

> The AS documents I've been quoting are Australian Standards documents.
> I'm not sure what you use as your reference for standard terms and
> definitions but I find it hard to go past formal standards bodies.

did you actually read the standards, or just the blurbs?

> I wasn't sniping or being snarky, I was intending to be playful. I've
> been on personal quests a number of times in my life seeking neat and
> formal definitions of things only to find that in reality sometimes
> there are no such thing, sometimes definitions are arbitrary.

Yes, but in this case they're not.

> You've also conflated some of David's responses and some of mine.

I was collating the list of not-very-useful responses on this thread,
not all (far from all) of which have come from you.

-A

[Terry Dawson]

On Fri, Jun 1, 2012 at 10:57 PM, Ada Lim <a...@panda2.net> wrote:
> On Fri, Jun 1, 2012 at 10:36 PM, Terry Dawson
>> Wow, was this directed at me? If so my opinion of you dropped considerably.
>
> I'm not really interested in your opinion of me.

I'll end this here.

Terry

[Dr Ada Not-a-fruit]

and in the interests of truth, beauty and knowledge:

On Jun 1, 10:28 pm, Ada Lim <a...@panda2.net> wrote:
]> "I think you're being too literal and making the assumption that

"Cast
> Iron" is a technical term. It's not."

in a handwavy sort of way, cast irons are (in the Fe-C system) iron
alloys which are not steels. i know this ignores the existence of
things like Invar which I guess is a high alloy steel by this
definition. more formally, cast irons are irons which melt/solidify
in a eutectic fashion. this means that they start to melt at 1150
degrees (but might not finish melting until a much higher
temperature). steels are those alloys which start to melt at a higher
temperature. this is due to the formation of "pure" austenite - or
rather, of all the carbon going into the austenite and none being left
over to lower the melting point.

> "The Wikipedia page for "Cast Iron" provides a pretty good
> explanation. Steel is a family of primarily Iron/Carbon alloys. Cast
> Iron isn't necessarily, it can also be Iron/Silicon. Cast Iron isn't a
> name for an alloy so much as it is a name for a class of materials
> based around Iron and cast by pouring."

silicon isn't theoretically vital for cast iron, but is crucial for
commercial cast irons because it alters the microstructure (pushes it
toward "grey" or graphitic cast iron rather than white or cementitic
cast iron, which is less useful commercially.)

> " You could conceivably have an alloy that was 4% carbon but was still
> malleable due to some other combination of ingredients, it would be
> steel and not cast iron."

it would be cast iron because it would be a near eutectic mixture.

> "The Demarcation between cast iron and steel is based on physical
> properties, namely malleability, not (strictly) on chemical makeup."

it's based on physical properties (the melting behaviour) which is
heavily influenced by chemical makeup. malleability is a funny thing
when it comes to ferrous alloys; martensite isn't very malleable, for
example. you can water-quench a high carbon steel rod and it is no
longer malleable; it hasn't changed from being steel to cast iron.

> "No, they're Fe-C-Magic alloys."

No such thing as magic.

> "It's an example of where "Cast Iron" refuses to fit inside the Fe-C
> box. "Cast Iron" resists your desire to define it simply."

Did it above: cast irons are ferrous alloys with eutectic melting/
solidification. pretty simple, and that was the definition I was
after which I couldn't find easily on wikipedia or with googling.

> "From what I understand, Steel is a very recent invention. "

Invented more than two thousand years ago.

> "Nope. The tolerence between cast Iron and cast steel less than 3%.
> That makes it only subtly different. It's no different than saying
> stainless steel is not steel. The difference between elemental Iron
> and Steel is a mere few percent. "

The difiference between cast iron and (very) high carbon steel is
infinitesimal, and the difference between elemental iron and (very)
low carbon steel is infinitesimal. The devil is in the details.

> "If it helps make things make more sense, 'Steel' was
> a 19th century marketing term for a higher grade of Iron
> having less impurities and a lower carbon content than
> what was able to be delivered previous to that."

BS.

Wrought irons have a lower carbon content than steel, and were
developed before widespread commercial steel production. most early
steels were produced through carburising wrought iron, but the
production of wrought iron is pretty slow and painful. the novelty of
the bessemer converter was that it could decarburise cheap easily
available cast iron into steel instead of having to produce expensive
labor-intensive wrought iron first.

but I get the feeling truth and beauty's strange charms are
unappreciated here.

[David Lyon]

If there are problems with Iron/Steel there are other
metals that can be used and are slightly easier to
work with.

Like Aluminium for example.