Changes to steel when heat treated

You are right, but it does depend on the nature of the treatment. Some only effect the surface, others the whole thickness.

You're right. Stiffness, ductility, tensile strength, etc. all change with heat threating. Often, the surface and interior will have different properties, and that is usually by design of the heat treating process. If he doesn't believe you, have him compare a piece of tempered steel with an annealed piece. In a thin sample, you can easily tell the difference by hand -- no equipment needed.

Stiffness (represented by elastic modulus) does not change significantly with heat treatment of metals. This is a common misconception even among engineers and has caused some embarrassing design failures. However the elastic limit will be different after heat treatment.

WT

Why confuse the issue with facts?

Yes, you are right. I too quickly listed a "bunch of stuff" that changes with heat treatment. Stiffness is hard to change much even when moving from one "steel" alloy type to another, or one "aluminum" alloy type to another.

Hello, the heat treatment changes on mechanical properties, therefore there are types of heat treatment e.g. normalizing, tempering, quenching (by water, oil, sand etc), annealing. These heat treatment are use for different application for different purposes. It changes toughtness, elaongation, ductility & brittleness , hardness.

Heat treatment always formed as part of the essential variables in terms of arc welding technology; metallurgical as it changes the above mechanical properties mentioned.

Hi there,

In brief; your supervisor is an imbecile fool!!! He probably was awarded the job by someone he hangs out with for drinking and other sessions.

This is only to show that these days workplaces are full of incompetent fools; where, say out of 100 probably less than 5 who know what to do while the rest is just to make up the numbers. Ah!!! Age factor does not even count any more. The older ones sometimes can be dummer then the younger ones especially if they are SMOKERS.

These are my personal observations both at my current job and my previous one where eventually my master tried to put a bullet to his head but, as fate had it, he could not even do that properly (coma finished him a few months later) yet this man used to claim he's fully aware of all the mechanical stresses in materials, obviously not in his head though.

Ofcourse, a pre/post heat treatment is applied to a metal to change its properties accordingly. Otherwise there's no point in wasting the energy. Just open up any text book and it will tell you, tell him that!

If your supervisor is like this on average then you better look for another job!!! Unless this is a one off debate.

Looks like you're going to have to keep the explanation simple for your supervisor, so here it goes:

chemistry + processing = microstructure => properties

For you, I add:

The earlier writers were all correct too, particularly in noting that elastic modulus is not a function of heat treatment (It is derived from interatomic bonding which is a function of the electronic structure of the material, i.e. each type of material, aluminum, copper, steel, alumina, all have a characteristic modulus of elasticity that changes little with heat treatment) while yield strength, tensile strength, elongation are governed by the generation and motion of dislocations (special kinds of defects) and their interaction with different phases, grain boundaries and precipitates, all of which are affected by heat treatment. A great book to read for basic materials science on mechanical properties and tables of materials properties is:

ENGINEERING MATERIALS 1

An Introduction to Properties, Applications and Design

By
Michael Ashby, Royal Society Research Professor at Cambridge University and Visiting Professor of Design at the Royal College of Art, London, UK
D R H Jones, Professor in the Engineering Department, Cambridge University, UK

http://en.wikipedia.org/wiki/Mechanics_of_materials (the books referenced herein are good too.)

...heat treatment is done to make a material either stronger or weaker...

Example: Sword makers, treat their steel to make it more flexible but not enough to the point of breaking, resistant to grind and shear, etc.

They heat the metal to increase it's molecular kinetics, thus becoming more pliable to temper-banging, which in turn, by means of self resonating in natural frequencies, better interweave molecules to the general direction of a lattice geometry, void of irregularities. The also keep injecting carbon to rid the metal of radicals, which disturb regular lattice orientation.

The more regular the lattice geometry is, the more kinetic energy (harsh banging) the steel may absorb, without increasing cracks into fissures, and from more incoming directions.

A spin-off: Japanese Katana makers, stretch and layer-fuse the chunk, to extend flexibility to extreme, in addition the the above.

The point of all this being: Heat and tonal vibration, to increase lattice regularity.

Excuse my poor English.

Dear boatwrench1,

You Said

<'the mechanical properties, ie. yield, elongation and tensile strength change when a given steel is heat treated.".

You are right-this is fundamental to Metallurgy

He argued that only hardness changes and the mechanical properties remain the same as the material in the raw state,( --un-heat-treated?)

He needs to go back to School for a course in Metalworking

I argued that heat treatment is done to make a material either stronger or weaker. So what is the answer: You are so right--Quench+temper to Harden, Anneal to Soften.(Weaker will not be the right word)

Such a complex subject. As a sword maker myself, I have several rules of thumb when I select metal. The most important one is...choose a steel which has a considerable amount of carbon in it so that it can be heat treated. All heat treating starts with making the metal hard, then tempering it so that is not so hard. Somewhere between "hard" and "soft" is "tough".

The higher the carbon, the more likely it will crack at any given hardness.

The longer the sword blade, the more likely it will crack in use. Therefore, the longer the blade, the lower the carbon content should be present in the steel.

The colder it is, the more likely it will crack at any given hardness.

I can't put carbon in the steel, but I have to beware that my forging operations won't burn any out. I don't know what the chemistry of Katana steel is...but I believe (from watching them being made) that they layer high carbon steel in with low carbon steel. Some believe that this results in a physical combination of properties, but I suspect that so much carbon migration occurs within the thin layers that the net result is a medium carbon steel which is then heat treated in a tricky way to leave hard metal on the edge, and softer, more tempered metal on the back.

Note that I have not even touched on metals added to the steel to change its Brinnel (cracking) points, surface beauty, tensile strength, resistance to cold, and so forth. (But I do know that a relatively small fire will turn a 5 line bolt into a 3 line bolt.) And I also know that a tiny amount of chromium will result in cracks in use...so don't even think of using stainless steel springs on your car!

All the rest of it is codification and chemistry, and I will be the first person to admit that my eyes glaze over when I see the pearlite, austenite and other materials tables, and am in awe of people that actually understand what is going on inside the metal when two swords clash!

further study....google Rockwell C Scales, Brinnel hardness scale, Austenitic Steel, Reducing and Oxidizing atmospheres

At last, a hands-on post!

...I don't know what the chemistry of Katana steel is...but I believe (from watching them being made) that they layer high carbon steel in with low carbon steel...

The explanation given in the documentary, was that the carbon injection was done when banging the hot metal on a layer of straw, probably carbonised on the spot.

Does it make sense?

Swords in the 21st Century--do you sell enough of these?

Who buys-pray

And do you sell in the Net?

Your Site--please

Been an ex-fencer,Dramatist,DAMASCUS swords collector?

Remarkable, Passionate Loyalist

Horse rider too?

Chenghis Khan memorabilia collector?

Wonderful!

http://www.southtower.on.ca

Who buys? Anybody who believes that honour, courtesy, chivalry and loyalty, faith and rectitude are still valid virtues. Swords represent these virtues. As weapons, they are pretty bad. As symbols they are pretty good.

I do collect swords...I have several that are made in Syria 250 to 300 years ago. I guess those are Damascus swords. Nice swords. Very pretty. I do not make folded steel swords, sorry. I know people that do, and they do nice work.

I don't collect Ghengis Khan memorabilia. Armour from the Chin era is very fascinating and to my eye, very beautiful. Hard to make.

But this thread was about carbon content in steel, not about swords. My experience is only through what I know. And that is swords and armours. Terms like "elastic modulus" may as well be Greek for what they mean to me. (tough I suspect it has something to do with why you cannot straighten a bent sword by bending back against the bend.)

Regards.

...I guess those are Damascus swords...

If I remember correctly Yusef, the "Damascus" reference for swords was first made in the middle ages, to the origin of invention of carbonated-steel, forged to resist abrasive abuse.

I always thought Damascus Steel swords were made in Damascus, Syria and other places from Wootz steel which originated in smelters along the west coast of India and into what is now Pakistan. The wootz steel was made from layers of iron and steel, melted together in a primitive sort of hill side blast furnace. I have heard that it isn't made any more because the mines no longer produce an ore suitable for this primitive method to work. But that is all I know. I have not done the research to verify any of that historical stuff, I mean, aside from the usual Google searches. Its kind of interesting in a sort of forensic sense, but I really have not studied the subject with the depth it deserves. A trip to Bangalore seems in order..grin!

Lots of other things are tied into this...trade routes, trade winds, boat and barge technology, literacy, irrigation supported cities capable of supporting trade surpluses and politics at several levels seem to have played their part. We forget in this modern day and age how lucky we are to be able to purchase pretty good steel alloys for dirt cheap prices. (Well, dirt cheap compared to ancient times!) And note that none of these things seem to have anything to do with the development of any specific technology, like steel making. Yet they have everything to do with it.

...Steel swords were made in Damascus, Syria and other places...

The term I mentioned above as to the origin of the name in the middle-ages, is to be found in Wiki as "Damascus Steel", and it would make sense that original and authentic Syrian, Turkish, Afghan and Indian antique swords may be very valuable these days, because these sources are considered technology-centers in their time of fame.

...pretty good steel alloys for dirt cheap prices...

Steel has become quite expensive here in Israel lately, because China imports it world-over, at higher and higher cost.

Well, its all relative isn't it! Good knife making steel would be pretty expensive back then, and for that matter, its pretty pricey even now! Have you bought "drill rod" lately? Plain re-bar and other non-heat treatable steels are still comparatively cheap. A friend of mine is actually smelting iron and steel (as a re-enactor,) and he will tell you that it is labour and materials intensive to produce. http://warehamforgeblog.blogspot.com/

But the whole concept of steel as a "pure" alloy is simply a laboratory curiosity. In reality, ancient steel was full of slag, and modern steel is made up of lots of recycled material, and contains quite a bit of other metals; copper, aluminum, carbon, and whatever is in the paint of the melted auto come to mind. Most heat treating facilities must know the composition of the alloy you bring them before they can heat treat your sample with any assurance that it will perform to your standards. An assay would be required somewhere along the line!

Anyway, this "comment" has turned into an essay. As you can see, the subject interests me as a collector and craftsman, and as I stated at the beginning, it is a very complex field. I must thank some of the actual metalurgists who have commented here....it is an amazing field of study, and though sometimes I wish that I could go back to school and learn a whole new trade, I know that there are not enough years left to do everything I want to do!

And Yuval, nowadys, the term "damascus" steel is normally applied to any layered or folded steel made anywhere. I think this is mis-labeling, but who am I to go against the marketing divisions of huge corporations producing thousands of units of "damascus steel swords" and "damascus steel shotgun barrels" every day. A true collector of ancient weapons is a little more careful of using the term. I am not sure of the intrinsic value of Syrian, ancient Indian, or Turkish swords, because collectors don't really care about using them for their original purpose. They drive the price up (or drag it down!) because of other factors...they are symbolic, they are accessible to the common collector, they are comparatively rare, and most of all, they are pretty. None of these factors have anything to do with the quality of the metal! They might have had excellent wear characteristics, who knew? Guess that helps when you are beating a sword into a plowshare!

Be that as it may, modern layered steels perform remarkably well. Nothing is better than a folded steel shotgun barrel, for instance. It is a mistake however to assume that a modern layered steel filleting knife from Finland would perform as well as an ancient backup dagger from Istanbul...there are too many differences to allow for valid comparison. However much I might "suspect" that the filleting knife will do a better job at filleting a Viking, I am not about to destroy an antique to prove it!

Regards,

Yusef1

When I was young (15-17), I was quite an avid knife maker.

I used to completely fashion the blade and handle as one piece usually cut and ground on a milling-stone to completion, from car flat suspension spring, of industrial, thick, high-speed mechanical saw, and cast the handle from polyester, atop the handle's grooves.

I made hunting and throwing knives, and gave them all as presents to friends.

It was a hobby, since I had free access to a metal-shop nearby.

.

Tell him to check this website: http://www.matweb.com

It got annealed and heat treated material properties.

4140 Annealed Rc 29 Tensile Strength 95000PSI

4140 Prehard Rc 40-45 Tensile Strength 148000PSI

4140 Harden Rc 55 Tensile Strength 270000PSI

Pineapple

Heat treatment in accordance with a specified Code will improve the mechanical properties : Strength, Hardness & Ductility. So the area underneath the Stress-Strain curve increased (this area represents what we called Toughness of the material). Also the slope of elastic portion of that curve may be increased (this slope represents the Modulus of Elasticity, E).

So all mechanical properties are changed due to heat treatment.

yes man as you think is absolutely right .we give heat treatment to metals to make it stronger to improve its qualities such as tensile strength compresive strength brittleness to relisve stresses developed during working and machining

Heat treatment is necessary to remove residual stresses, which affect in mechanical properties of material.

A. In steel mill, the mechanical properties of thick plate are differ from the mechanical properties of the thin plate of the same material due to rate of cooling (e.g. in air) :

1. In case of thick plate, the cooling rate is slow due to excess bulk of mass, therefore the strength decreased, hardness decreased while ductility increased.

2. In case of thin plate, the cooling rate is rapid due to small bulk of mass, therefore the strength increased, hardness increased while ductility decreased.

B. In weldments, the vice versa happened to the mechanical properties due to :

1.Rapid cooling of the weld bead in thick welded joints: strength increased, hardness increased while ductility decreased.

2.Slow cooling of the weld bead in thin welded joints : strength decreased, hardness decreased while ductility increased.

So, we have to control rate of heating and rate of cooling before, during and after welding (preheat, interpass & PWHT) to improve the mechanical properties of the welded joints and avoid weld imperfections.

This has been a great thread! Lot's of really interesting contributions.