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  • 1.  Silicon level of alloy steel

    Posted 03-18-2022 10:19
    What would be the purpose of specifying that an alloy steel has 0.10% max silicon, as opposed to 0.15%-0.35% silicon? Is an additional deoxidizer such as aluminum required to fully kill the steel with the lower silicon level?

    I'm specifically working with 86B30 for cold forming.

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    Ken Kirby
    Kenosha WI
    (262) 748-3836
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    Metkon USA - Technology behind Specimen


  • 2.  RE: Silicon level of alloy steel

    Posted 03-19-2022 04:30
    Typically silicon is restricted to 0.10% if it is intended to be galvanized.  Silicon levels above 0.10% tend to cause suppression of spangle, limit the formation of eta zinc, which provides the most sacrificial protection, and has a rougher appearance.

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    Christopher Hahin
    Engineer of Structural Materials & Bridge Investigations
    Illinois Department of Transportation
    Springfield IL
    (217) 522-4023
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    Metkon USA - Technology behind Specimen


  • 3.  RE: Silicon level of alloy steel

    Posted 03-20-2022 02:10
      |   view attached
    Not sure why that specific limit as for Si containing steels, the thickness is a bit more complicated as shown by the attached extract from an old Galvanizers Association of Australia.  Phosphorous gets in the act as well.

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    Graham Sussex
    Principal Consultant
    Sussex Materials Solutions Pty Ltd
    East Melbourne Vic VIC
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    Attachment(s)

    Metkon USA - Technology behind Specimen


  • 4.  RE: Silicon level of alloy steel

    Posted 03-20-2022 13:45

    Ken Kirby asked 2 questions.  Paraphrasing:

    1. …. the purpose of specifying that an alloy steel (86B30?) has 0.10% max silicon….
    2. ….is Al required to insure a fully-killed steel..?

     

    It seems to me, that if someone is specifying an element content outside of the normal range, you would ask that person, or organization, to explain the reason for the request, not try to assume a reasoning.

     

    Ken's second question has to do with steelmaking.  As all metallurgist know, the chemistry of a steel alloy is made in a batch of liquid.  Each batch of liquid steel must be converted into a solid.  In modern steelmaking, this conversion is done in a continuous casting machine (caster).  Continuous casting has replaced virtually 99% of ingot casting, the previous technology.  Gone are the days of ingot-cast un-deoxidized rimmed steel, which accounted for well over 50% of steel produced in North America prior to 1970.  All steel solidified in a continuous caster must be deoxidized, and Al is a de-oxidizing element used in most cases (steel for tire-cord wire is one exception).  Ken, if you run a check analysis on a sample of the 86B30 you are using, and ask for soluble-Al, I would be surprised if it is less than 0.015%.

     



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    Edward Szekeres
    Consultant
    Utica NY
    (585) 766-3536
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    Metkon USA - Technology behind Specimen


  • 5.  RE: Silicon level of alloy steel

    Posted 03-21-2022 09:16
    I would be curious to expand the question further to what is the justification for the common range about 15% to .35% in most "normal" alloy steels, not necessarily intended for galvanizing or arctic service or anything special like that but just the standard AISI grades. I realize that it's a deoxidizer but everything we buy pretty much is aluminum killed so would the steel suffer from having too little silicon provided that it's fully deoxidized with aluminum? Similarly, I know that you can get decreased ductility with excessive silicon but is that threshold really .35%, or is it higher? I've seen some specs for plate go higher, like in the .50's%, and some grades like 300M have much higher silicon than this (for totally different metallurgical objectives of course, but still) without suffering too much on ductility so it makes me wonder how consequential that maximum really is.

    To Ed's point, concast is of course very common now for commodity product forms but plenty of the billet we buy for reforge stock is still cast as bottom poured ingot prior to conversion.

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    Sean Piper
    Product / Process Metallurgist
    Ellwood Texas Forge Houston
    Houston TX
    (713) 434-5138
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    Metkon USA - Technology behind Specimen


  • 6.  RE: Silicon level of alloy steel

    Posted 03-22-2022 23:09
    Silicon and manganese are deoxidation elements in  most SAE/AISI barstock steels officially listed  ASTM A29 ​(NOTE AISI has note been involved in metallurgical grade for over 30 years and there is work in the ASTM committees to remove "AISI" - but old habits...)

    The silicon 0.15/0.30 was expanded to 0.15/0.35 sometime in the 1970's simply because of different killing practices among steelmakers involved with ASTM required it  - silicon is more or less of a residual element in most common carbon and alloy steel barstock,  rather than an addition, due to all steel melting is done with a BASIC slag.  The  0.10 max silicon is common in free-cutting grades (coarse grain practice) - like gun barrel SAE 1137, StressProof and FatiegueProof (TM Nag-LaSalle -1144)  to limit Silicon Oxide non-metallic inclusions (NMI)  detrimental to machinability (tool life).

    Aluminum deoxidation was considered as "doping" the steel and looked down upon by early steel makers as poor steel making -but  with the fast pace of continuous casting it is a necessity to the extend that calcium additions are required to stop the aluminum oxide "galaxies" clogging the nozzles on tundish  by forming Ca/Al eutectics and forming globular NMI.  The best steel makers (Koreans) have moved to titanium under strict control and secrecy.

    It is true Silicon is used as alloy elements in high strength steel low carbon as  Hy-Tuf and in most forging steel to 0.50/ 0.75 ("4330") - but I doubt used in steel of high carbon due to it graphitization effects.

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    Edward Vojcak
    Senior Metallurgical Engineer
    SGS North America
    Blue Island IL
    (708) 595-8734
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    Metkon USA - Technology behind Specimen


  • 7.  RE: Silicon level of alloy steel

    Posted 03-21-2022 11:44
    The specification comes from within my company, but it was written a long time ago and there is disagreement about the need or benefit, if any, of the silicon restriction.

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    Ken Kirby
    Snap-on, Inc.
    Kenosha WI
    (262) 748-3836
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    Metkon USA - Technology behind Specimen


  • 8.  RE: Silicon level of alloy steel

    Posted 06-16-2022 12:09
    Ken - Now the real problem is identified!  Very common these days. 
    First, Mn-Si killed steels without Al are prevalent for long product billet cast products where open stream metering nozzle casting is used.  Al is problematic in those cases.  In slab cast products with SEN's, Al additions are common, almost universal. 
    If the spec was written many years ago, the product was probably ingot cast.  A 0.10% max Si would suggest a semi-killed ingot casting process.  The purpose of semi-killed was to maximize steel yield, minimizing the normal center line "pipe" that occurred on fully killed ingot cast steels and must be discarded.  But semi-killed steels were never "B" steels. 
    Now you are asking for a 86B30 steel.  Boron steels normally have Al added to deoxidize the steel sufficiently to protect the Ti from oxidation, allowing the Ti to tie up the N, so that the B will work for hardenability and not form BN.  Al is required because the Si, even at normal levels up to 0.35%, is not a strong enough deoxidizer to protect the Ti.  But there is no obvious reason for restricting the Si level unless it is for scaling or plating/coating  reasons.  Even if ingot cast, the steel will have to be fully killed to allow the B to work.  If you don't have Al and Ti contents stated in the mill cert, i would question whether you have a B grade. 

    Bob Glodowski
    RJG Metallurgical LLC
    bobglodowski@rjgmet.com

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    Robert Glodowski
    RJG Metallurgical LLC,Stratcor Incorporated
    Gibsonia PA
    (412) 680-3308
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    Metkon USA - Technology behind Specimen


  • 9.  RE: Silicon level of alloy steel

    Posted 06-16-2022 12:52
    Thanks for your reply.

    The material has always been vacuum degassed, cold-heading quality steel, never semi-killed. We do have Al, Ti, and B on the certs and also have verified with our LECO glow discharge spectrometer in-house.

    The low silicon, aluminum-killed material was said to provide greater fatigue life and impact strength than Si-killed 86B30 according to some publication from Republic Steel and in-house investigations in the early 1980s, but I don't have copies of any of those sources.

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    Ken Kirby
    Snap-on, Inc.
    Kenosha WI
    (262) 748-3836
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    Metkon USA - Technology behind Specimen