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Patent Number: 2791815 Filing Date:
Application Number: Issue Date: May 14, 1957
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2 1 7 9 - 1 1 8 1 5 United States Patent Office Patented May, 14,.1957 2,791,815 RLSER CON20SITION AND A METHOD OF USING TBE SAME 5 Harry Baldwin Kinnear, Columbus, Ohio, assignor, by mesne assignments, to Chromium Nlining and Smeltin- Corpo ration, Linxited, Sault Ste. Marie,-On tario,.,Caii@ ads, a corporation of Ontario No Drawing. Application October 5,11953, 10 Serial No. 384,334 2 Claims. (Cl. 22.@-215) This invention relates to a riser composition and- to -a 15 metho d of using the same. More p4rtic ularly,,@he@@in- ventio n relates to a riser compositi6n for maintaining -the risers of copper-base castings fluid for a. period,@of time beyon d which such risers would normauy solidify whereby to substantially prevent pipe and to provide even shrinkage 20 of the riser. Heret ofore, riser compositioiis for copper-base 7castings such as brass or bronze castings have generally included coppe r oxide, a reducing agent for the copper oxide and a fluxing material. These known riser compositions are 25 exoth ermic and are ignited in contact with the molten riser of a copper-base casting to, react with formation. of metalli c copper and a supernatant slag and with the-evolut tion of considerable heat. The.known..exothermic@con:L-- positio ns provide a layer of inolten copper in. contact with 30 the top of the riser and do not contaminate the matekial of the. riser with undesired metallic constituents such @ as iron. While such riser compositions are gen erally,satis7 factor y, they are expensive. An object of I the present invention is to provid@- a riser 35 comp osition for copper-base alloy castings that wiu-main- tain the riser fluid for an extended pieriod of time without conta mination of the riser. The comppsitions of th@e prese nt ijivention d(i not necessarily include -.copper oxide as. an ingredient and are composed of relativily, inexpensive 40 iiff,- r,edients. Anoth er objert of @the invention is to provide a re,lativc@ly inexpe nsive riser composition-for coppjar-base castings that includes iron and.yet does not contaminate the,,xisers with. any -substantial 'quantity of iron.., 45 Anoth er object is to providd a ptocess fdi maintain'mg,, thd risers of coppqr-base castings-.ffiiid.tot an extended period of time by igniting -,in contact with the riser an iron- containiiig-, exothermic composition that burns to form a slag,containing,substantially no metallic ir6ii or 50 only very small amounts, of metallic iron as iin@clusions in the slag. Mlhdre metallic iron inclusions -are presenti in the slag,.they _are largply out of contact - with -th6,, copper aroy riser and hence dci not- add to the riser any iubstan- tial. quantity of iron. It is important that the, 55 not pick tip iron because-.they,are removect.from the cast- ings after solidification and are remelted witli - additional castin g metal for reuse. Any substantial iron pick-up in the risers, gates or hot tops would result in an - undesirably 2 normally.-isl-a solid material at ordinary room temperatures. The , sla:g-forming ingredient preferably is mill scale whi, substantially Fe3O4. Other fluxing or slag-forming @,ngi@edi6nis,such as other-oxides of iron or alumina may alsb be employed to advantage either sin-gly or - in combination@ The@ fluxing. agent may be, ferric oxide, Fi@20i- The. ingredients of the@ composition are so chosen and so.prolxQrtioned.- as to, liberate upon; combustion a. large amount, of.,heat that is. sufficient to, form:a fluid slag,.@that maintaiiis the riser fluid for a substantial, period of - time, The composition of the,slag formed is, more or@ less a neu@ tral sodiiim-iroii, silicate. Sdffieieilt oxidizing: agent -is incorporated in the compositlfcin . to oxidize- all,.of the. silicon, of @ the ferrosihcon @ to SiO2., If:. iiisufficient oxidizing, agent is used, the. sili6on of the.,feirosili@on miy reduce some -of..the fluxing,material to.,yield ;metallic iron - which must be kept at a niinimum.; in,,-the slag.@ Where. sodium,nitrate is used as@.the oxidizing agent, the reaction is b6lieved to proceed substantially. in.accordance with fthe.- following equation: Eq.uationNo. I.- 5Si+4NaNO3->5SiO2+2Na2O+-2N2 The stoichiometric ratio of sodiiim, nitrate to sili@on,, in accordanca withthis reaction is ab6ut 2'45 parts of.sodium nitrqte. b@, weight. to each part by,. weight of - silicon. Hbwever, the..ratio of sodium nittate, to silicon may,,.be varied Within,reasonable Iiihit@ and amounts rangijig,,from abbut 2 --@Arts o,f @odium. nitrate to 31/2' parts -.of sodium. niT trate fo@ each part of silicon can be used., Pri@ferably, from 2;--3 p4rts of sodium nitrate, for each.part of silkon.are employ@@d. Where -mill 8cale is used @as. th6 fluxing., material. suffi@ient mill scale is incorporated to: form a -neutral irort @ilicate slag,.with that part of: the- silica prodliced by the exothermi-c reaction that is not. associated. with -the mletal,oxide residue of the@.oxidizing..@agent- in a.neutral alkali-metal, silidate. As mentioned h6reinbefore th&. compoaents@,of the. exor thermic aiixture are p@eferably so chosen -that the reSulting-@lagwillbe asub@tantiaUyneutraLone. Themetal oxid& fraction of thd oxidizing - 4gexit enters. th6. slag as a, neutral @ilicate. Fbr example, where sodium @ nitrate is the oxidizer, two, niole'cules of Ntt2O combine- wi-th.@.,One molecule of SiO2 to provid& neutral sodium. sili64te of th6 fDrmul4 Na4SiO4. R6ferring to Equation No.. 1,.hereinb6foie it will be seen that for- each two moldcules,.of NA20 p@o-duced, tive molecules of SiO2 are- concurrently. yieldod. Since the two molecules of Na2O combine with one.molecule Of SiO2, it, will, be seen. that four. molecules ofSiO2, are in excess of the amount required-for, a neutral slag., A fluxing, material. is added to the ingredi@,nts of the exothermic reaction mixture to satisfy the requirements of th6.,excess.silica to form, a neutral slag.. Thus,.,where mill@ @scale'i@ used as a ffuxiiig agent, four molebul6s of Fe3O4 in the form of mill scale are included for each five molecules of silicon and four molecules of sodium nitrate in the reaction mixture. The four molecules of high iron analysis of casting metal in which such risers 60 Fe3O4 combine with the four molecules excess of SiO2 and the like are reused. resulting from the exothermic reaction to provide a neuThe- ,exothermiz- riser- compositions- of-the-present-- inveii4- tral-.- irom-silicate slag of the composition Fe3SiO6. The tion include an intimate mixture of finely-,divided-.- reducing reaction thus may be summarized in the following equaagent,,an- oxidizingageTiti and-aflu- xing@,or-slag- forming-in--- I tion:.. gredient.- Preferably ferrosilicon ha-ving,. a high @silicon 65;, content is used as the reducing agent@ althoug@-.-othdr,re,-, ducing-agent s..sti-cli.,as-calcium sili@ide, may. bd used. A siliconi content of 90 9o or more is preferred. Preferably, sodium nitrate; is used as-the -oxidizing.,Agent an alkhli metal chlorate, an alkali metal - p6rchlorate or manganese dioxide may be used. The oxidiz-l--ng'ag-ent althougli- other oxidizing agqnts- such as potassium @;nitrate 70 slag may,@be either acid or basic within reasonable Iiinits. -E-q,4ation No. 2 5Si+4NaNO3+4Fe3O4-> 2N2+Na4SiO4+ 4Fe3SiOG The amount of fluxing agent may vary somewhat from t-hat-teqi ',red to yield a neutral silicate slag. The resulting For,. e'xample, for each five molecule@ of Si and four mole- c' ule--s" "o-f -@odiuzn nitrate in the teaction niixture, from twQ

3 to eight molceules of Fe3O4 may be incorporated in the reaction mixture. The employment of-other fluxing agents such as alumina is governed by similar principles. In accordance with Equation No. 2, each part by weight of 5 siiicon requires 2.45 parts by weight of sodium nitrate and 6.6 parts by weight of Fe3O4. For each part by weight of silicon the sodium nittrate may fafl within the range of 2 to 31/2 parts by weight and the Fe3O4 may fall within the range 3 to 12 parts by weight. Riser compositions in accordance with the invention are 10 in the form of an intimate mixture of finely divided ma- terials. The compositions may be employed as mixtures of powered ingredients or the powdered ingredients pref- erably are formed into agglomerates or briquettes. @ If agglomerates are desired, it is beneficial to employ ..a 15 binder. The oxidizing agent itself may form the binder or an auxiliary binding material may be added to the powdered mixture and the mixture thereafter formed into . agglomerates. Binders such as molasses water, waste sul- fite liquor or inorganic binders such as sodium silicate,may 20 be used. Conventional methods are employed to, form agglomerates such as pressing or rolling the powd@r @into balls. Agglomerates approximating spheres having di- ameters from 1/4 " to V2 " are especiary suitable but the size and shape of the agglomerates may vary. - - 25 In use, the riser compositio'ns of the invention are placed upon the top of a molten riser of a copper-base afloy casting immediately after pouring and while the riser is stir fluid. The heat of the molten metal in the riser ignites the composition of the invention which burns with the 30 evolution of large amounts of heat. The slag formed by the self-contained combustion of the material is fluid and remains hot for a sufficiently long time to insure proper feeding of the casting from the riser during solidifi- 6ation of the casting. Any metalhc iron that remains 35 from: the ferrosilicon of the composition tends to ag- glomerate into minute shot-like particles that remaiii susp@-nded in the slag and do not come in contact with the metal of the riser. It is highly desirable and very im- portant that the ferrosilicon be of a high silicon graide in 40 order that residual iron be k-ept at a minimum. F6rros@ili- con having at least 90% silicon and preferably having 95% silicon is preferred. Ferrosilicon metal of 98% or greater purity may be used in whole or in part. After the copper-base casting has solidified, the frozeli 45 slag resulting from treatment of the riser in accordance with the present invention is readuy and cleanly broken away from the riser and discarded. The tiser is separated from the casting in the usual manner. The ri . sers treated by the compositions of the present invention show prac- 50 ticahy no iron pick-up and are essentially of,the sam6 composition as the original copper-base alloy. Tb6se risers are clean and can be re-melted for further casting operations., The following table iflustrates the iron pick-up in risers 55 per application of a typical riser composition (Mill scale 65 parts, sodium nitrate 24 parts, and ferrosilicoh-95% Si-1 1 parts by weight), the maximum iron build up where each melt subsequent to the first contains 40% of risers 60 mix mm Scale I- 514 ------ 6co 3 ------ 6&0 2,791,815 4 from a previous cast to which the riser composition of the-invention is applied and a comparison of these values with ASTM specifications for maximum iron content. TABLEI Iron Pie], Maximum Maximum UP per Iron Build Iron Con- Applica- Up with 40% tent; A. S. Type of Copper-Base Alloy tion of of Riser in T. M. Spee- Riser Com- Each Melt, ifications, position, percent percent percent (1) Leaded Red Brass: 85 Cu, 5 Sn, 5 Pb, 5 Zn ----------- 0.01--0.03 0.017-0.05 0.30 (2) Yellow Brass: 60 Ca. 40 Zn- 0.06-0.15 0.10 - 0.25 0.60-0.75 (3) Leaded Tiu Bronze: 87 Cu, 8 Sn, I Pb, 4 Zn ----------- 0.01-0.05 0.017--0.084 0. 15-0.25 (4) Manganese Bronze (High Strength Yellow Bram) --- 0.11 0.18 2.0 -3.0 (5) AliiTniniim -Bronze ---------- 1 0.03 0 .05 2.5 -5.0 From the foregoing table it is seen that where riser conipositions of the present invention are employed the iron- pick-up in risers per application of the riser composition Df the invention is negligible and the maximum iron build up where 40% of risers are reused in subsequent melts is far below maximum ASTM specifications. The invention will be illustrated and described with greater particularity in the following detailed examples. Example I Mill scale and ferrosilicon (95% Si) are separately gyound in a ball mill to finenesses of about 55- 65% throitgh a 200 mesh screen and all of the material t a - 100 mesh screen. The sodium nitrate is employe in a fine, -ranular condition substantially all throtigh a 100 mesh screen. To 506 lbs. of ground miil scale are added 85 lbs. of ground ferrosilicon and 185 lbs. of granular sodium nitrate. These powders are thoroughly mixed and to the mixture is added 31 lbs. of molasses water containing 8 lbs. of black strap molasses and 23 lbs. of water as a binder. The mixture is tumbled in a rotary mixer to form nodules ranging in size from V4" tO 'A" in diameter. As the nodules are formed they are removed from the tumbling mixture. The green nodules are dried in an oven at II 0'C. until the moisture content is less than about, 1%. The nodules as dried are ready for use in treating risers of ropper-base castings. Sufficient of the riser compound is employed to provide from 112, to 3/411 of slag on the riser. The rnixture is igmted on the top of a risdr of a freshly poured yenow brass casting. The mixture ignites readily from the heat of the risdr and burns rapidly. The slag produced by the riser composition is broken and examined after freezing and only a few tiny beads of metal are found dispersed in the slag. The brass casting is sound and the riser . is flat on top and has no pipe. , Table 11 hereinafter shows the composition of additional riser mixtures in accordance with the invention. The procedures for making and using the mixtures are similar to those described in Example I. TABLE It Composition, percent Ratio, Ratio. Mfil Approx. NaNO3 S(-ale: Temp. reqi, silicon FeSt NaNO,+FeSi ot Slag, NaNos gm5% metal otber OF Grade 33.3 -------- 13.3 -------- i 2 5 1.14 zom i47 1.98 2,875 U6 10.4 -------- MnOs I 2.0 2LO '11.0 --------- -------- 2.18 1.86 21800

5 Each of the mixtures of Table 11 ignites readily and burns rapidly. Only a few tiny beads of metal are found in the slags resulting from combustion of the mixes. I claim: 1. An exothermic riser composition for providing a hot top on the risers of copper-containing castings to prevent pipe consisting essentially of ferrosilicon containing more than 90% silicon, sodium nitrate and miH scale in the substantial molecular ratio of 5 molecules of silicon to 4 molecules of sodium nitrate to 4 molecules of Fe3O4. 2. A process for maintaining the ris,-rs of copper-containing castings fluid to prevent pipe which con-lprises igniting in contact with the top of a molten riser of a copper-containing casting an exothermic riser composition 6 sodium nitrate and mill scale in the substantial molecular ratio o@' 5 molecules of silicon to 4 molecules of sodium nitrate to 4 molecules of Fe3O4. 5 References Cited in the file of this patent UNITED STATES PATENTS 2,280,87Z Udy ------------------ Apr. 28, 1942 2,513,602 Udy ------------------- July 41 1950 10 FOREIGN PATENTS 673,605 Great Britain ----------- June 11, 1952 OTHER REFERENCES Metallurgy of Copper, by Newton-Wilson (1942 edi- consisting essentially of an intimate mixture of finely di- 15 tion), pages 120 and 121 relied on. vided ferrosilicon containing more than about 90% silicon,

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