General treatment of steels

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ENLARGEMENT DEBATE FOR STEEL RAZORS AND CUTTING TOOLS: Leagues that affected the 'iron:
Index:
Nickel-iron alloy.

Influence of manganese on the properties' steels.

Influence of cobalt on the properties' steels.

Influence of copper on the properties' steels.

Influence of nitrogen on the properties' steels.

Influence of aluminum on the properties' steels.

Influence of molybdenum on the properties' of steel.

Influence of chromium on the properties' steels.

Influence of silicon on the properties' steels.

Influence of titanium on proprieta'degli steels.

Influence of vanadium on prprieta 'steels.

Influence of tungsten on the properties' steels.

Influence of boron on the properties' steels.

Pollutants steels
Nickel-iron
Nickel and 'element that bound the iron, among the most' of all other metals proprieta'base make changes to it.
Namely:
* Ni = 25-28% (loss proprieta'magnetiche)
* Ni = 36-38% (minimum or maximum net many curves representing the evolution of sizes represented), see fig.1
* Ni = 78% (peak of the curve in Figure 1, probably in connection with the phenomenon of the formation of a superstructure that slow cooling ordered alloys taking the next FeNi3 composition corresponding to Ni = 76%)
Figure 1: http://ntrs.nasa.gov/archive/nasa/casi. ... 020214.pdf, p.18-19-20, are the best I found.
Expansion coefficient:
The coefficient of thermal expansion liner undergoes with increasing nickel content very strong variations, namely:
the value
a (alpha) = 12x10alla (-6)
iron, salt, first slowly, then suddenly, through a transition zone, corresponding to intermediate structures, to the value
a (alpha) to 20x10 = (-6)
whose order of magnitude and 'what is common to all the usual austenitic structure, for a further increase of nickel content has a real and own up to touch a drop very low minimum of about
alpha = 2x10 (-6)
For a nickel content around 36%, with a large ring, followed by a stretch almost horizontally, then it reaches the value of about
alpha = 13x10 (-6) for pure nickel.
Proprieta'elettromagnetiche: Great importance are variations of this iron-nickel alloys proprieta'pe latter's duties.
Among the most 'interesting that we count with 25% of nickel makes the steel non-magnetic and one with 78.5% of nickel, which makes iron permeable or magnetic sense enables him to become magnetized.
Other proprieta'fisiche: The specific heat exhibits a maximum at about 38 very neto% of nickel, also conduttivita'termica and resistivity 'have similar electrical anomaly range = 30-40% nickel.
Properties' Chemical:


Since 20-25% of nickel resistance to many corrosive agents greatly improves.
Alloys Fe-Ni-C:

The presence of carbon, an element which also belongs to the group that promotes the enlargement of the field of existence of the iron greatly enhances the influence of nickel in lowering the critical points and makes it possible to obtain temperaura ordinary austenitic structure .
The diagram Guillet http://books.google.it/books?id=y1eTDQR ... Fr & f = false pag.304-leads to the realization of the structures obtained at ordinary temperatures and slow cooling for all steels with nickel up to 25% carbon and up to 2.06%. In this diagram are also listed the three areas corresponding to pearlitic, martensitic and austenitic.
The zones are not separated by clear lines of demarcation, but small areas of transition through which, depending on the particular conditions of steel or cooling, is obtained either one or the other structure or an intermediate structure.
Follows that to be sure a given structure, such as austenitic, and 'should the representative point of steel is well within its area, such as the point about 25%.
In short, according to Guillet structural diagram for each value of carbon and there 'a nickel content limit beyond which the annealing the austenite does not decompose more' in perlite, but the type of martensitic transformation becomes ; what 'occurs when the displacement curves and anisoterme' that door completely over the trajectory of annealing.
Main effects of nickel on steel: Please note that during the preparation of casting, nickel does not take part in any reaction, not the least oxidized and can 'then be added in any period of the flow.
* In reality, 'but' I think it is better to make the addition of nickel during the first part of the casting, when the bath and 'still effervescence, when nickel and' available as a raw material in the form of cathodes, in fact, this case, contains hydrogen must be avoided to pass him in the steel.
In normal practice, the steel is therefore suitably follow the following criteria: a part of nickel is usually located in the wreckage, one part is added just note the chemical composition of the molten bath so as to bring the nickel content within the limits set for steel making, and finally a possible small addition of cathodes, in the second period of the flow, can 'be made for a slight correction of chemical composition.
Since 'nickel with carbon, forms no stable carbide, it follows that all the nickel content in steels is always dissolved in solid solution alpha or lambda, unlike manganese and other elements, having back strong tendency to form carbides is sharing between the ferrite (or austenite) and carbides, thereby influencing a complex properties' steel.
And then 'to note that nickel and' one of the factors, such as silicon, carbon promotes grafitizazione and this has considerable importance to issues concerning the structures of cast iron .* In addition to the influence already 'tested on various physical constants , gives the steel a nickel complex proprieta'che important for easy heat treatments and improve the mechanical characteristics:
1) REDUCE THE TEMPERATURE OF ANNEALING AND TEMPERING: consequence of the lowering of the critical heating, with all the practical benefits arising therefrom;
2) speed reduction 'CRITIQUE: with the ability' to temper means less energy (oil), reducing the danger of cracking in pieces large and irregularly shaped.
3) increased penetration of hardening: as a consequence also of the lower speed 'critical influence of this great practical importance because it' allows you to undo or at least mitigate to a considerable extent the differences in features between the outskirts and the center of a piece medium or large.
4) INCREASE IN TENACITY 'A PARITA'DI Tensile strength: proprieta'di importance common to all structures of annealing and tempering of martensite, so in general for structural steels and nickel' to be considered a desirable element; becomes essential, and it 'characteristic, its presence in steels at low temperatures.
5) No worsening deformabilita'dell'acciaio it 'hot it' cold.
Influence of manganese on steel prorpieta'degli:
Although manganese and 'completely soluble in iron in all proportions.
The action of this critical points of iron and 'quite similar to that of nickel unless and' sufficient manganese to little more than '12% to bring the austenite stable at ordinary temperatures with a slow cooling.
Ultimately diagrams Guillet for manganese are similar to those for nickel.
In particular, the manganese steel gives the following properties':
Drop in temperature annealing and quenching:
Decreased velocita'critica: you can 'normally go to the quenching oil.
Increased penetration of hardening: Diminishing strain hardening: this property 'to deform very little with the character and' a significant and important feature of perlitic manganese steels, which allows a reduction in machining allowance legacies for finishing operations;
Increased tenacita'a parita'di tensile strength (pearlitic steels) compared to carbon steels, and this' especially in the quenched, although the improvement is less than that made from nickel;
Sharp increase in tensile strength, about 100 N/mm2 for every 1% manganese equivalent, from this point of view, 0.12% carbon;
Improved deformability 'hot, although this influence more specific' that manganese as an alloying element, both to relate to lower levels of oxygen and sulfur fluxes due to specific actions and desulphurising delmanganese during steelmaking .
Influence of cobalt on the properties' steels
The influence of cobalt on iron-cobalt alloys proprieta'delle 'steels and' in some respects similar to that of nickel, but it differs significantly for others.
Cobalt does not oxidize, can 'then be added, such as nickel, in every period of the flow.
A first significant difference compared to nickel, it has since the cobalt and 'the only factor that increases the value of speed' criticism, which decreases the penetration of the hardening.
Such as nickel, cobalt promotes graphitization, but aniera much more 'balanced.
An important property 'of cobalt and' to make more 'stable martensite, and therefore less sensitive to the alloys that contain the discovery.
The workability 'hot' reduced as a result of increased stabilita'delle structures warm the cold, as well as solderability 'are not practically changed.
On cobalt cementation finally an interesting effect: to reduce the maximum carbon and raising levels beyond a certain depth ', thus reducing the slope of the curve.
Influence of copper on steel proprieta'degli:
Even the copper or can also be added at any time of the manufacturing process is to be found in full in the steel at the end of casting.
It 's interesting to note that, following the increase of added copper and structural steel for various applications, since' all the copper present in charge goes to steel, and we 'have seen a progressive everywhere, although slow, increase average copper content of all charges from solid steel.
Sulga steels annealed copper causes an even improve the characteristics also hot nonnostante in certain temperature ranges may be a reduction in hot duttilita'a following the segregation of copper to grain boundaries.
An addition of 0.25% -0.30% copper extends the life of steel structures exposed to weathering.
More than 1, 7% copper in the steel causes the presence of a substantial reduction in ductility 'hot (deleterious effect).
This phenomenon 'due to the fact that copper when it is within range of the iron has a coefficient of activity' greater than 1, about 8.
Such a situation implies a low solubility thermodynamics' copper all'inetrno iron range and this' involves the segregation of copper sulbordo austenitic grains, all cio'puo 'lead to premature failure of steel, even after applying small deformations.

Influence of nitrogen on the properties' for steel:
On this issue are controversial hypothesis, the few things we consider common ground about the benefits that this might have sgli steels are:
1.The 'action to stabilize sull'austenite nitrogen (extends the range of existence of the phase range) and therefore would be useful to add the item to alloys such as stainless steel, chromium, chromium-nickel-chromium-nickel-manganese.
2.Aumenta the surface resistance of the steel (nitriding), improves the tensile strength and elongation.
Influence of aluminum on steel proprieta'degli:
The aluminum gives the steel a remarkable resistance to oxidation.
In the manufacture of steel to aluminum should be given great care to avoid oxidation of this element as the alumina is very harmful because 'polluter steel as non-metallic inclusion, is considerably perche'peggiora properties' as the resilience .
Aluminum promotes the separation of graphite hinders the diffusion of carbon, it forms very hard nitrides with nitrogen.
Influence of molybdenum on the properties' of steels
The molybdenum complexes such as chromium carbides form very hard and stable, in particular:
1.Il molybdenum can 'be added, such as nickel, the metallurgical process at any time, except if present in scrap quantity, add it in the form of ferro-alloy;
2.With about 3% molybdenum, close the field of existence of the phase range, the solubility 'of iron and alpha' limited ordianria temperature, about 10%, above this percentage appears composed Fe3Mo2;
3.Il molybdenum increases temprabilita'ancor most 'of chromium;
4.Ha a greater hardening effect of chromium
5.Aumenta so strong stability 'of martensite at high temperatures, a feature possessed by molybdenum and tungsten, which are two basic elemnti tool steel quickly.
6.Migliora mechanical properties, especially the fatigue limit and to creep.
7.Conferisce proprieta'magnetiche suitable for permanent magnets.
8.Diminuisce the effect of overheating.
9.Aggiunto chromium steels, chromium-nickel-chromium-manganese, etc.., Fragilita'di eliminates the danger of discovery.
10.Conserva steel good workability 'when cold or hot, and good solderability'.
Influence of chromium on steel proprieta'degli
Because of its tendency to oxidize chromium reducing agent is added during the manufacturing process, and after 'complete the deoxidation.
Chromium and 'one element piu'spiccata has the tendency to form stable carbides in steels.
http://www.calphad.com/pdf/Fe_Cr_Phase_Diagram.pdf
http://www.calphad.com/thermo_calc.html
http://www.calphad.com/iron-chromium.html
About these diagrams struturali of chromium steels are first some observations regarding the areas in which it is' in:
1.Il field of steel structure of the annealed and pearlitic type 'divided into two parts for steel structures and hypo-ipereutettoidi.
2.Il field structures ferritic steels which belong to non-critical and can be heated to any temperature up to those of fusion without any phase transformation occurs.
3.Il field of cast iron, ledeburitica structure.
About the mechanical properties you can 'say that in general, until the structure is pearlitic steel (annealed, cooled very slowly), chromium increases the tensile strength without elongation, necking and resilience are too low; vice versa, to structures with double carbides are very low impact strength.
Hardenability on 'Steel and' significant influence of chromium, in fact, especially for smaller pieces, will soon be quenching air; cosi'considerando a series of steels with 1% carbon and increasing levels of chromium and gradually raising the temperature, it first obtains the temper using as a means of cooling water, then oil and finally the air.
Among other proprieta'interessanti for implementation laid the chromium can 'give and will be discussed in detail in the study of various categories of steel there' high resistance to wear by friction, the rust 'with respect to many corrosives.

Influence of silicon on the properties' of steels
The elements silicon and manganese are always present in steels.
Mccaniche the characteristics of steels, silicon has a significant impact, raising the strength, the limit of sneravameto and hardness, while reducing elongation, necking and resilience and 'first, for a limited content of silicon, in agreement with that increase, the further increase of silicon content toughness' Steel falls, so that approximately 5% of silicon, elongation, necking and resilience are reduced to practically zero.
Although silicon and 'one of the elements that increase the hardenability,' because 'reduce speed' critical cooling.
The silicon steel then gives special properties' chemical properties: resistance to acids and other corrosive agents and resistance to heat.
The hardening of silicon has a detrimental effect, because 'reduces the speed' of diffusion of carbon and thus reduces both its depth ', is the carbon content.
The silicon has a detrimental impact on deformability 'hot deformability on' cold on solderability 'and gives all'accaio a tendency to overheat (grain growth).

Influence of titanium (niobium and tantalum) on the properties' of steels
Titanium also belongs to the group of chromium: with about 1% titanium closes the field esitenza phase range.
Titanium lends itself, firstly, the manufacture of steel suitable for a singular precipitation hardening by particles of the compound intermentallico Fe3Ti or more 'frequently is precipitated with ceramic cell cfc type TiN and TiC.
Titanium and 'characterized by a remarkable affinita'per oxygen and nitrogen, and is therefore frequently used in the manufacture of special ACIA as energetic flux and denitrurante.
The tendency of titanium to form carbides, and 'used in austenitic stainless steels.
Influence of vanadium on the properties' steels
Vanadium, chromium belong to the same group in terms of state diagram with iron, and having the same strong tendency to form carbide, iron and steel gives the properties' perfectly similar to those of chromium.
Influence of tungsten on the properties' steels.
The tungsten combined with iron produces effects similar to Fe-Mo alloys.
Influence of boron on the properties' steels
The addition of boron can greatly increase the hardenability 'of carbon steel and low alloy steels with a modest increase of manufacturing cost, since boron can' be found at relatively low prices.
Boron and 'likely to promote a substantial increase in the quantity' delel bainitiche.Questo structures and effect 'due to precipitation of carbides of iron and boron that will be developed to fine grain boundaries during the tempering treatment unit on cooling.
Other advantages are identified in relation to this material, in the field of hardware and construction, then let go and I will not dwell on such arguments.
Pollutants steels
They sulfur, nitrogen, oxygen, hydrogen and phosphorus.
All these, some in far more valuable, some lesser extent, act to the detriment of mechanical properties, solutions of continuity 'in steels, increased sensitivity' warming, deterioration of workability 'hot.

IRONS AND THEIR CLASSIFICATION
Pig iron, including ferrous products, have the most 'high percentage of carbon.
This circumstance, in addition to providing their properties' completely different from those of steel, provide a liquid state at very low temperatures and thus makes them suitable for obtaining paricolarmente jets, ie those products gain a final shape and size directly after solidification and suitable for production of parts of different shapes and sizes, so as to have ineressato virtually all areas of engineering, civil construction and industrial.
CLASSIFICATION OF IRONS
Pig iron, foundry castings, said second fusion irons can be classified according to different criteria in regard to the fracture, microstructural constituents or special property '; a practical point of view and there' but why 'of change classification universally adopted, providing for subdivision in the following 5 groups.
That underlined part and 'a phrase which I faithfully reported that the prof.Nicodemi during one of his seminars.
Allow me to contradict at least in part because I simply say that:
For a critical examination of such distribution is not homogeneous, since each group and 'characterized by others based on factors such loroeterogenei between the appearance of the fracture, the proprieta'meccaniche, the structural form of graphite, alloying elements.

Grey cast iron: the characteristic appearance of fractures due to the presence of flake graphite
White cast iron: with appearance of the fracture, which differs markedly from the previous type because 'carbon and' combined;
Malleable Cast Iron: the name derived from the particular proprieta'di able to deform permanently;
DUCTILE IRONS: in which the graphite, the headings through a process of production, appears frma nodules;
IRONS WITH: deliberately manufactured to meet specific requirements such as resistance to corrosion or heat.

THE END