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Join Date: Apr 2009
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JK Inclusion Rating in Steel Metallography

08/10/2009 2:45 AM

Hi all,

could you please explain me what JK inclusion rating in steel, what type of INCLUSIONS comes under JK?

THANKS

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Guru

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#1

Re: what is JK inclusion rating in Steel metallography

08/10/2009 4:04 AM

JK rating (Jernkontoret) is now modified into the ASTM E45 inclusion rating scheme.

This was originally developed from 1920s to 1930s in the SKF for checking steel cleanliness.

This currently covers four types of inclusions

A: Sulfides

B: Aliminates

C: Silicates

D: Globular Oxides.

Each are further subdividied into Thin and heavy.

The referred standards for these are ASTM E45, ASTM E1122 and ASTM E1245

There are supposed to be some mathematical formulae for this, but at our labs it is done by the equipment itself (with analyser) or the reference charts available with the standard (Hence don't have the theory )

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#2
In reply to #1

Re: what is JK inclusion rating in Steel metallography

08/10/2009 4:46 AM

Thank you so much Mr. sb.

Nice answer.

How can avoid these type of inclusions in steel and what is the impact of those?

Caould you please explain?

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#3
In reply to #2

Re: what is JK inclusion rating in Steel metallography

08/10/2009 9:42 AM

I can tell you the impact, but not how to avoid, these are out of my expertise and comes under high class clean steel environments. We only buy these, not make.

The inclusions in any steel are critical for the fatigue properties of the steel. These works as a nuclii for the fatigue crack to start and are one of the major reasons of failure of heavily stressed components especially gears and bearings. Quite a few of the shafts we procure also are controlled by the inclusion rating, though not as severe as that of bearing/gear steels.

Look at the following link

http://steel.keytometals.com/default.aspx?ID=CheckArticle&NM=198 - sorry, link no longer available

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#4
In reply to #3

Re: what is JK inclusion rating in Steel metallography

08/10/2009 10:10 AM

Wow.....

very useful link.....a quantum of valuble information i got it.....

I am regularly viewing this CR4, all your answers provide useful information on the particular subject.

Many thanks for sharing your knowledge and technical informations to ignite the brains of younger generartions...

Keep it up..

Many thanks again

Regards

R Vairamuthu.

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#5
In reply to #4

Re: what is JK inclusion rating in Steel metallography

08/10/2009 12:52 PM

You are Welcome .

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#7
In reply to #2

Re: what is JK inclusion rating in Steel metallography

08/10/2009 2:43 PM

How can avoid these type of inclusions in steel

Chemical composition control, desulfurization, ladle met, clean steel practices such as argon stir, porous plug, Vac. degas. vac. arc Remelt if money is no object.

As you can see 3 of the 4 classes are Oxides- aluminates, silicates, and globular oxides. So reducing them implies oxygen control, OTHER THAN SHOVELING IN ALUMINUM TO OXIDIZE, or SIlicon, etc.etc. (these elements turn into the inclusion oxides by reactingto the oxygen in the melt)

If you don't want Sulfides, reduce Sulfur in melt and carryover in slags, desulfurize, etc.

what is the impact of those?

They are all 'nonmetallic discontinuities' in the metallic matrix. If a bearing is supposed to be steel, and a nonmetallic inclusion on a machined portion of a surface is 'nonmetal', don't you agree that the nonmetallic material will behave differently than the base metal? And that this can happen two ways. Softer (sulfides- tearouts and brinelling) and harder ( Aluminates and scratching scoring.) either way leads to loss of precision, possibly loss of lubricating film strength, and accelerates failure of other components through contamination of lubricant and abrasion, build up and welding.

Again, hats off to sb for his authoritative post earlier.

milo

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#9
In reply to #7

Re: what is JK inclusion rating in Steel metallography

08/10/2009 11:35 PM

same to you (GA).

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#6
In reply to #1

Re: what is JK inclusion rating in Steel metallography

08/10/2009 2:26 PM

Great answer sb.

milo

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#8
In reply to #6

Re: what is JK inclusion rating in Steel metallography

08/10/2009 11:32 PM

I waited for you to chip in a lot earlier. Since my experience is more from a user point of view and the expert was silent here (Breaking bathtubs?)

The inclusions again was a favourite topic of my research 5-6 years ago- due to a few breakages that finally I could trace to sulfide stringers.

Then attending the seminars of a few bearing-men especially Timken and FAG where they went into details about bearing steels (UBQ) which seems to be made strictly in-house by a few of them, since they don't get that quality steel outside (at least in those times- now it seems some times they outsource from China - not officially confirmed but these come out in the negative sales talks the back-biting business). However when we confront them, they all say "not for you. And rest be assured we maintain our quality even when we insource from anywhere and blah blah blah"

Here you know the problem is quite critical, as a steel maker you must be aware as we are as machine (OEM).

We land up in choice of

Cut price (drastically ) to regain market and throw quality out of window.

Maintain price and Quality and lose market.

The scenario is bleak. We are still continuing in route#2, and being high end OEMs, some how surviving on customer goodwills, but don't know for how long. Currently we are approximately 50% costlier than you know who.

The same problem is with others too. The concept we are getting (from bearing manufacturers) that the cost of the steel is approx 60-70% of the bearing final cost. So this is only area where they can attack and they are doing it.

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