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Topic-icon Problem with HSS and HS Steel "High Velocity"

  • Coliandro
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8 år 10 månader sedan #31970 av Coliandro
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Gentlemen,
I'm an Italian Man,Andrea (Coliandro). I speak English but not Swedish Language.
So,ask immediately to administrators for apologize if I write where I should not write and for any problem that i can made.
But I know that Swedish people know English better than me and I hope you are understanding.
I am a theoretical about steels.
I have a sort of problem to forge HS and HSS Steel (High Velocity Steel).
This kind of Steel are used also in Sheffield (England) from Knifemakers untill 1890.
This is my theory and i hope that you can help me to forge this kind of metal.

The peculiarity of high-speed steel and super-fast (M2, M35), as I taught, it is to maintain high hardness at high temperatures, the addition of high levels of Mo, W and Co and V ;Mo and W carbides are very hard resistant to coalescence. The molybdenum in this sense has a double effect than tungsten.

This is their chemical composition (generical)

Composition (%)
C - 0,91
Si - 0,45
Mn - 0,40
Cr - 4,15
Ni - 1,90
V - 6,30
Co - 4,75

Preheat to 870 degrees to achieve uniform temperature and then austenitising to 1180 degrees of 5-15min.
Quenching in oil or salt and three recoveries of 500 ° C.

he difference between HS and HSS is the content of Co.

For HSS then there is a hardness greater resistance to high temperatures.

The increase in hardness at tempering temperatures of about 450-550 ° C is typical not only of HS and HSS but in general for all high cable , especially good-contenent high levels of alloying elements that give rise to carbides.

The increase in hardness at high temperatures is due to the fact that you have the precipitation of hard carbides (Mo, W, V, Cr, etc.). It forms a structure very similar wing sorbitol (which he formed alloy steels at about the same temperatures), but there is no case of high-alloy the precipitation of cementite carbides but above.

These carbides are more resistant to coalescence (especially Mo and W, especially in the presence of high levels of Co) and greater toughness and higher hardness than cementite.

The effect of "secondary" but equally important discovery of these temperatures is to gradually deplete the C and other alloying elements the residual austenite, the horizon Mf increased accordingly and thus allowing its martensitic transformation. Findings in these two intervals of T should be sufficient to transform all the residual austenite into martensite and further favors the tempering of martensite transformation martensite found in TCC

For HS and HSS then strongly advised to take the tempering at high temperatures for this reason, in order to exploit the maximum hardness, wear resistance and strength and ability to maintain high hardness at elevated temperatures.

Note that, however, found in this interval there is a reduction of corrosion and oxidation resistance wing just because you also have the precipitation of chromium carbides.

For this reason, the high alloy is recommended that if you want to maintain maximum resistance to corrosion and oxidation, to soften at temperatures below the range of secondary hardening.

Even warming up there is the phenomenon of hysteresis (a much lesser extent than during cooling) and this, by heating too fast, resulting in a shift to higher temperatures limit Ac1 (what is considered for 'austenitising steels examined, being ipereutettoidi).

Stop at 850 ° C has the function to avoid thermal shock during heating and to enable better diffusion of alloying elements (in fact the rate of diffusion of atoms of Mo, W, Cr, etc is slower than that of C atoms).

Keep in mind that a higher hardening temperature solution allows you to enter a higher carbide content and then to exploit the secondary hardening.

The problem in HS and HSS is not only the high T (temperature) quenching but also necessary to maintain long time required to dissolve most of the carbides (though still a part of complex carbides always remains undissolved), having also the lowest rate of diffusion of various alloying.

For HS and HSS, however, the discovery is made in the range of secondary hardening in order to favor the complete precipitation of carbides and harness the potential of steel, while maintaining high hardness and toughness in an absolute sense and, in particular, high temperatures .
Moreover, finding the range of secondary hardening is eliminated effectively (by running a series of multiple discoveries-3) the residual austenite (martensite transforming first in TCC and then martensite tempered) and eliminate internal stress (as the cell returns to CCC), including improving the toughness (which are, in general, for steels and super fast speed is quite low).
The heating too fast, especially for steels HS and HSS not only can cause thermal stress, but raises the threshold for Ac1 the phenomenon of hysteresis (hysteresis although warming is much less marked than is the case when cooling ).
Hysteresis is the variation of transformation points. And 'thanks to fenomenti hysteresis that the steel can take, with appropriate cooling, structure martensitic, bainitic or troositic.

For processing of these steels think it is useful to keep an oven 500 ° C for one hour without huge fluctuations in domestic ovens for cooking, which also rarely exceed 250 ° C. You could make up to 500 ° C a mass of sand or salt, suitable to absorb evenly and to maintain the temperature for a period of time. We sell salt to find all types of steels, and for those special treatments such marquenching and austempering, working in different temperature ranges depending on the type.

Other steels are treated like the M35:

All content with sufficient levels of high alloy steels alloying formation of carbides and carbonitrides (Mo, V, W, Cr mainly but also Nb, Ta, Ti, N and Al) are subject to secondary hardening.

So even martensitic stainless steels, including the VG10.

For this category of steel but it would be good to do some more consideration.

In fact favoring the precipitation of hard carbides, including those of Cr decreases the amount of chromium free, what form the protective oxide (transparent) typical of stainless steels.

It is also free of chromium that increases microchipping wire, and carbides of Cr.

Then, finding the range of temperatures at which one has the phenomenon of secondary hardening, there is a decrease in resistance to oxidation and corrosion, but improves the grip of the wire.

Keep in mind that the vanadium carbides precipitate preferentially compared to chromium.

Link: http://www.metalravne.com/selector/steels/brcmo.html *

* Notes:
M35 for the first cooling path (left, the faster) is because they encode a wild softer than the temperature from austenitising a bit 'too low.

Remains true that for some steels (such as the K340 Bohler Uddeholm) for cooling too fast you have a decrease in hardness, because it increases the amount of residual austenite after power off.

Finally, note that in this photo of a Wostenholm (Sheffield) is present on the blade says "Dubly Carbonized.

http://holli4pirating.wordpress.com/200 ... meback-70/

Maybe it 's been heat treated with the processes mentioned above?

Thank you for your consideration and answers....

I wrote this kind of article also here http://www.ilrasoio.com/viewtopic.php?f=17&t=533
But any answers....
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8 år 10 månader sedan #31971 av mr_president
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To much text. can't find the question.....

Har du slagit din lärling idag ??
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8 år 10 månader sedan #31973 av Coliandro
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A pot full of sand flow already at 500-550 ° C homogeneously covered with refractory bricks in a pre-heated (such as a mold) maintains temperature for hours ... The temperature would reach even the heart of steel? Contact with the sand will absorb heat faster than in contact with the air of an oven, right?

I know that maintaining 500 ° C for an hour is not possible, but heating at that temperature a large amount of sand and putting it in a perfectly isolated, perhaps even pre-heated, I can keep the heat long enough?
I forge a brick outside, and when isolate the hot coke with refractory bricks, that maintains temperature for hours, and returns to light up perfectly just turned on the fan. Who knows who used coke coal, as hot air without forced injection of air go out into no more than a quarter of an hour.
Clearly, before putting any blade in the sand will measure the actual heat loss of the latter over an hour.

Thank you for your replies,and your support to me,
Sincerely
Andrea
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8 år 10 månader sedan #31974 av mr_president
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Är det en spamrobot ?? Bara en massa galamatias.

Får se om det kommer ett autosvar på detta.

Har du slagit din lärling idag ??
  • Coliandro
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8 år 10 månader sedan #31975 av Coliandro
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Sorry, i'm not a sort of spam robot.
I supposed that a Nation like Sweden that forged iron and steel (cast steel)for Royal Navy (England) was more expert to explain me about the kind of bakery that can i use to forge HS and Hss Steel.
Finally, i'm an informatic engineer and i can say that spam robot are not so complex to explain their thinking.
So, bye bye and sorry ...because 'I have caused much trouble.
P.S.:You can write me with PM if you have a problem about spam robot, quiet, it's free for you because you are "a sort of knifemakers"and i respect you (although I felt offended by your words).
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8 år 10 månader sedan #31976 av Johan Sangberg
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Hello

Welcome Coliandro!!

Ok please do not get angry on each other, we try to help out and Coliandro need some help here. It's a lot of text and if this could be split up in different questions it would be easier to help u. Please be more specific about your questions and we will try to answer. This forum is for blacksmiths and knife makers too! We mostly speak Swedish but English is understood!

:)

//johan

Johan Sangberg
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8 år 10 månader sedan #31977 av Coliandro
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Hi Mr. Johan Sangberg,
thank you for your interest.
My question is:

1.-"A pot full of sand flow already at 500-550 ° C homogeneously covered with refractory bricks in a pre-heated (such as a mold that has just stopped working) maintains temperature for hours ... the temperature reaches the heart of steel? I think that contact with the sand will absorb heat faster than in contact with the air of a bakery.Right?"

2.-"How do I keep the temperature of 500 ° C for one hour?"

Finally I think that i must to use, for this kind of steel, Verhoeven techniques (multiple-3 hardening,quenching,discoveries).But in which way?Infact this problem is cable to second question (above).
Thank,best reguards,
Andrea
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