by George D. Haley

Number One:

    Controlling the pickup of oxygen during melting and casting can result in substantial savings.  The two primary sources of oxygen introduced during melting and pouring are:  a) Rust in the scrap b) Oxidation of solid and liquid iron.
     There is some reoxidations of the iron as it enters the mold.   Minimizing the oxygen pickup can lead to less casting defects, less furnace slag, increased refractory life, increased and consistent magnesium recovery and consistent recovery of carbon and silicon additions.
     Loose rust in the charge should be screened out prior to charging.  The vibratory connectors with screens should be inspected daily to avoid plugging of the screen with rust.
     Heavy coatings on steel scrap (another potential source of oxygen) should be removed prior to use or the scrap should be rejected.  Badly oxidized pig iron should be avoided.
     Shot blasting badly oxidized charge should be looked into, if it is cost effective.
     The oxides (rust) that accumulate in the bottom of the scrap bins should be disposed of as a waste.  It should never be charged into the melting furnace.
     Clean scrap can be oxidized in preheaters, if the burners are not properly adjusted.
     It is not advisable to put steel scrap at the bottom of the induction furnace.  It will cause oxidation of the scrap prior to melting.
     Keep the furnace covered as much as possible.  Always cover ladles when transporting iron.
     Silicon carbide addition to the melt can deoxidize the iron.
     The rate of oxidation depends upon temperature, time and area exposed.  Overheating (super heating) increases oxide (oxygen) content.
     Exposure of metal through aspiration of air causes oxidation.
     Fans positioned to cool operators can inadvertantly blow on metal surfaces and cause oxidation.
     Cold metal left in the ladle should be pigged.
     Gating systems that create turbulance increase oxidation of the iron.
     Do not use cover steel that is oxidized.

Number Two:

     Use of fluorospar in the treatment ladle (about four to eight ounces of acid grade fluorospar (97% CaF2, 100 mesh and down) per 1000# base metal) with MgFeSi can provide consistent, improved magnesium recovery.  The life of the treatment ladle is increased.  Slag does not build up on the lining, dams, etc.

Conclusions:

1.  Reduce oxygen (oxidation) of the iron and reduce casting defects.
2.  Controlled addition of fluorospar to the treatment improves magnesium recovery and increases treatment ladle life.

Reviewer's Comments:  (P.H. Mani)

1.  Foundries can greatly benefit from following the number one suggestion of the author.

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