US3746078A - Gating system for introducing additives to molten metal - Google Patents

Abstract

A gating system which includes a treating basin for treating molten metal such as cast iron with additives such as a nodularizing agent. Molten metal is introduced into the basin by way of a passage such as a downsprue and from the basin to a mold cavity by way of a passage such as runner bars and ingates. A restriction (dam gate) is provided in the last mentioned passage and controls the dwell time of molten metal in the treating basin. An additive reservoir is connected with the treating basin and a closure is provided which temporarily restrains flow from the basin.

Description

United States Patent 191 Moore et al.

[ GATING SYSTEM FOR INTRODUCING ADDITIVES TO MOLTEN METAL [75] Inventors: William H. Moore, Purchase, N.Y.;

Harry H. Kessler, Ladue, Mo.

[73] Assignee: Meehanite Metal Corporation, White Plains, NY.

[22] Filed: Feb. 4, 1971 [21] Appl. No.: 112,553

[52] US. Cl... 164/363, 164/362, 164/358, 164/55, 164/57, 164/80, 164/133, 164/134 [51] Int. Cl. B22c 9/08 [58] Field of Search....., 164/358, 362, 359, 164/363, 55, 80, 72, 133, 360, 134

[56] References Cited UNITED STATES PATENTS 1,664,452 4/1928 Daniels et al. 164/358 362,337 3/1887 Walker 164/362 1,239,586 9/1917 Gebhard 164/359 1,410,775 3/1922 Thomas 164/363 X 257,558 5/1882 Cross et al. 164/359 277,131 5/1883 Harrison 164/362 508,884 11/1893 James 164/362 2,247,777 7/1941 Hagemeycr 164/133 X [4 1 Jul 17, 1973 OTHER PUBLICATIONS Gating of Ductile Iron Castings," by R. W. White, Foundry Feb. 1960, pp. 101-407. Principles of Gating by Wallace, J. F. and Evans, E. B., Foundry, Oct. 1959, pp. 74-81.

Primary Examiner-J. Spencer Overholser Assistant Examiner-V. K. Rising Att0rneyWoodling, Krost, Granger & Rust [57] ABSTRACT A gating system which includes a treating basin for treating molten metal such as cast iron with additives such as a nodularizing agent. Molten metal is introduced into the basin by way of a passage such as a downsprue and from the basin to a mold cavity by way of a passage such as runner bars and ingates. A restriction (dam gate) is provided in the last mentioned passage and controls the dwell time of molten metal in the treating basin. An additive reservoir is connected with the treating basin and a closure is provided which temporarily restrains flow from the basin.

7 Claims, 5 Drawing Figures Patented July 17, 1973 3,746,078

2 Sheets-Sheet 1 INVENTORS 7 WILL/AM H. MOORE BY HARRY H. KESSLER Patented July 17, 1973 3,746,078

2 Sheets-Sheet 2 INVENTORS WILLIAM H. MOORE BY HARRY H. KESSLER GATING SYSTEM FOR INTRODUCING ADDITIVES T MOLTEN METAL Our invention relates to inoculation of cast iron in the mold during the pouring operation. It relates, also, to a method of alloy or other addition to the metal during the casting operation and, more particularly, to the addition of volatile alloys during the casting operation.

It has been realized for some time that the inoculation of cast iron for the purpose of graphitizing or nodularizing or both is not a permanent effect and tends to decrease in intensity of effect as the metal is held for some time in the ladle before casting. To overcome this fading effect, it has been proposed that inoculation be conducted in the mold or in the ladle during the actual pouring operation. Methods of accomplishing this late inoculation, well known to those skilled in the art, involve the addition of alloy in the gating system during pouring, the placement of alloy in the gating system prior to casting and other devices-such as rods or bars of inoculant material immersed in the stream of molten metal during the pouring operation. These methods are inclined to be non-uniform in practice and I do not act equally effectively during the complete pouring cycle of a given casting.

Our invention has, for its object, an improved controllable method of inoculating in the mold during casting.

Another object is to provide an improved gating system for adding materials to molten metal during pouring of the same into a mold.

Another object is the freedom from smoke and fume during the inoculating procedure.

Another object is the cleaning of the inoculated metal during casting, so as to provide a casting free of dross and inclusions.

Another object is the more efficient use of volatile inoculant by prevention of oxidation during the inoculating procedure.

Another object is to eliminate the fading of inoculating effect during the handling and casting of the metal.

Other objects of our invention will be apparent from the specification and drawings in which:

FIG. I is a schematic isometric view of the preferred gating system of this invention without the mold material such as sand being shown, in which:

1 is a downsprue for receiving molten metal,

2 is a runner connecting with 3 a basin or dam area,

4 is an alloy reservoir,

6 is the position a skimmer or strainer will occupy in the finished mold which in this instance will be shown as sand and the skimmer will also be of sand,

7 is a constricted opening or darn gate area having an area related to the flow rate of metal,

8 is a runner bar,

9 is an ingate to the casting,

10 is the casting or mold cavity, and

11 is the position of a consumable closure for the basin or dam area 3 in the mold prior to the pouring of molten metal;

FIG. 2 is an elevational view of the basin and alloy reservoir section of the mold in which:

4 is the reservoir containing alloy 12 to be added and closed at its upper end with sand,

6 is a skimmer placed just downstream of the basin,

7 is the dam gate area comprising a constricted passage having the smallest area in the system and related to the desired pouring rate,

8 is the runner bar leading to the casting 10 via ingate 9 and,

11 is a consumable closure for the basin or darn area FIG. 3 is a fragmentary view similar to FIG. 1 but showing a modification in which:

15 is an alloy reservoir similar to reservoir 4 but is located below the dam area or basin 3;

FIG. 4 is a fragmentary view similar to FIGS. 1 and 3 but showing a modification in which:

17 is an alloy reservoir similar to reservoirs 4 and 15 but is located ahead of the dam area or basin 3; and

FIG. 5 is an isometric view of the dam area or basin 3 prior to the pouring of molten metal, in which:

l9 and 21 are consumable polystyrene members placed longitudinally in the basin to provide increased metal flow channels, in this instance three in number 22, 23 and 24. In this embodiment it is preferred that the molten metal enter from the left end or the basin as viewed in this drawing but it is not absolutely necessary.

Our mold treatment system comprises essentially three parts, vix., a means of metal entry to a dam gate and from the dam gate to the casting, a polystyrene or other consumable support or closure for a darn area or basin, a dam gate and a dam area or basin where the alloy reaction takes place and where slag, dirt, dross or oxides from the alloy reaction is confined to this area by means of a strainer or other skimming device.

One function of the dam area is to provide a pool of metal to give time for the inoculation to take place. To make this possible we like to have a total volume in the dam area and to provide a dam gate size so as to provide between 1 second and 2 seconds treatment time for the metal in the basin or dam area. A lb. casting poured in 12 seconds, for example, would require a volume for the basin 3 of between about 35 and about 67 cubic inches.

The dam area, basin or inoculating area would have a volume on the average (1 A seconds dwell time) of about 143 cubic inches for a 500 lb. casting poured in 21 seconds. The exact dwell time required in the dam area is somewhat dependent upon the type of alloy being used, but in any case, we feel that at least one second is required for effective inoculation and that more than two seconds is wasteful of mold space and detracts from the casting yield obtained. Dwell time is particularly important where the inoculation is done with a nodularizing alloy, where it is necessary to time the inoculant reaction over the major part of the casting cycle. Too long. a dwell time will overinoculate the first metal and perhaps under-inoculate the last metal into the mold.

The dam gate area must be held to definite size in order to regulate the speed of molten metal flow through the system. This is necessary to establish a base for the dwell time as well as for the rate at which inoculating alloy will flow into the dam area or basin from the alloy reservoir. In the process of our invention we vary the pouring speed by changing the darn gate exit area after the dam area. This area is the limiting or smallest area in the total system and varies according to casting weight. For castings up to 5,000 pounds in' weight, the dam gate exit area to casting weight is as follows:

TABLE I DAM GATE EXIT AREA 0.17 sq. in.

. in. in. in. in. in.

CASTING WEIGHT For castings above 5000 lbs. in weight we use e ormula Dam gate (in!) [weight (lbs.)]/[ 1.25 V weight (lbs.) X 15.8]

Volume of dam area (ini) [Weight (Lbs.) X 1.5 X 4]/[l.25 V weight (Lbs.)]

An essential feature of our invention is the alloy reservoir, which is used to supply alloy to the dam area during pouring of the casting.

This reservoir comprises a pocket above (FIG. 1) or below (FIG. 3) or prior to (FIG. 4) the dam area or basin. The dam area or basin 3 itself becomes a part of the alloy reservoir and excess alloy not contained in the darn area will be absorbed as the metal flows past the opening to the alloy reservoir. In some instances the basin itself may contain all of the alloy necessary to treat a given amount of metal.

The size of the dam area is such that its volume will provide at least 1 second and preferably 1% or 2 seconds of dwell time, according to the volume rate of flow of metal.

Another requirement is that maximum surface area of contact is provided between the alloy and the flowing metal. This may be done by using a dam area of maximum length and minimum thickness. We have fdund that the length of the dam gate area should be equal to about one-half inch for every second of pouring time. A casting being poured in 24 seconds, therefore, would have a dam gate area equal to 12 inches in length. The depth of the dam gate area is related normally to the skimming action to trap the products of re action. We like to keep this depth at about 3 to 3% inches for castings up to 100 lbs. in weight, at about 4 inches for castings between 100 and 200 lbs. in weight and at about 4% inches for castings above 200 lbs. in weight.

Having determined the volume of the dam area related to 1% seconds dwell time, the length at k inch for each second of pouring time and the depth according to the weight range we can easily calculate the width of the dam gate area. This works out at about 1% to 3 inches for most castings.

The reservoir 4 (FIG. 1) comprises a pocket above the dam area generally equal in size to the dam area or basin but being shorter in length (L). The length being defined as the distance from the inlet end of the dam area to the skimmer 6.

We find that a pocket or reservoir of this configuration will allow uninterrupted flow of the alloy into the metal. The size of the alloy is important but, in general, we prefer to use an alloy of about 8 mesh in size or smaller as it is essentially free flowing. The-size of the reservoir, above the point at which it contacts the dam area may be made larger if necessary in order to hold the total weight of alloy for the weight of the casting to be inoculated.

By providing free flow to the alloy, we find that it enters the metal at a rate equal to the rate of flow of metal from the dam gate.

In practicing our invention we place a piece of polystyrene or consumable material 11 in the dam area, so that on closing the mold it covers the opening under the strainer or skimmer 6. We then place the required weight of alloy in the reservoir and dam area and close it at the upper end by ramming molding sand in this opening or by closing it with a sand core. We prefer to close the opening above the alloy, particularly where volatile alloys are being used, so as to prevent an upward flow of gases against the flow of alloy in a downward direction.

The alloy reservoir may be placed above the dame gate (FIG. 1) area or below the dam gate area (FIG. 3). In the first case, alloy will flow into the metal as it is consumed and in the second case metal will flow through the alloy and consume it, as it flows through. In some cases the alloy reservoir may also be placed prior to the dam gate area (FIG. 4) as a pocket in the mold.

The consumable material 11 prevents the initial in mshing metal from carrying alloy out of the dam area or basin-underneath the strainer. As the basin fills the material 11 is destroyed, however, alloy and or slag are normally restrained by the strainer and absorbed alloy and metal pass on to the mold cavity underneath the strainer.

The important feature of the invention is that where the calculated dam area has insufficient volume to hold all of the alloy required, a reservoir is supplied of size sufficient to hold the remaining alloy and is so disposed as to supply alloy by solution to the flowing stream of molten metal. The primary source of control of alloy flow into the molten metal system is the size of the dam area to give I to 2 seconds of dwell time and the length of this area being about one-half inch of length per second of pouring time.

While this system works particularly well for the incorporation of nodularizing alloys into the casting during pouring, we have found that it works equally well for other types of alloys, such as graphitizing inoculants and even ferro alloys, where it is desired to alter the composition of the metal being cast by adding chromium, copper, nickel, manganese and the like, without adding it to all the metal contained in the pouring alloy.

For certain alloys, such as chromium, which dissolve slowly, it may be necessary to adjust the speed of flow of the metal or increase the dwell time in the dam gate area by size adjustment, so as to give time for adequate solution.

In an adaptation of our process it is possible to add certain alloys to part of the metal flowing into a mold. This is done by the simple expedient of incorporating an additional gating system in the mold, so that the darn gate of this invention may be bypassed for certain length of time during casting. At any desired time the metal may be caused to flow through this dam gate system by a device like a removable plug in the pouring basin or even by pouring from another ladle. Metal flowing through the dam gate system of this invention will then be alloyed while that which by-passes this dam gate system will remain unalloyed.

In many castings of complex configuration, particularly those where the molten metal may have to travel a considerable distanceand where it is customary to use more than one downsprue and gating system, we prefer to incorporate a plurality of dam gates and alloy reservoirs in the system. Thus, in some cases, the metal from the downsprue may be divided into more than one channel and each channel would incorporate a dam gate system with an alloy reservoir. 'The choice between the use of a single or a multiple inoculation system is a matter of choice, but in any case, each inoculation system will be designed according to the essential features already described. In some cases where it is not physically possible to use a length of dam area or basin corresponding to one-half inch for each second of pouring time, we find a shorter length may be used, but we place strips 19 and 21 of consummable polystyrene material (FIG. 5) in the dam area to provide chan' nels 22, 23, 24 for metal flow. The total length of the channels in such a case would be at least equal to onehalf inch for each second of metal flow.

The working of this invention may be described by a typical example in this example a nodular cast iron casting of generally uniform section and weighing 500 pounds was to be cast using a molten metal that would require at 2 percent addition of nodularizing alloy to make it nodular. For this purpose a quantity of alloy weighing lbs. and consisting of 50 percent, 8 mesh magnesium ferrosilicon, 5 percent rare earth fluoride, percent calcium fluoride and 30 percent calcium silicide, was prepared.

The mold was made entirely in the drag half and a dam gate system having an exit area of 1.48 inch to pour in 21 seconds, was rammed into position between the downsprue and the runner bar to the casting. The exit area of the dam gate was 10 percent less than the cross-sectional area of any other part of the gating system. An alloy reservoir was rammed in'position in the cope, so that it was immediately above the center of the dam area. The dam area itself had a capacity of 144 cubic inches and measured 4 inches wide by 4 inches deep by 9 inches long. A piece of polystyrene was placed in the dam area ahead of the strainer (as in FIG. 2) and the mold was closed. The 10 lbs. of alloy was placed in the reservoir, which alloy also extended into the basin and sand and was rammed into the reservoir above the alloy level. The metal was then poured into the downsprue, which connected to the darn area and pouring was substantially complete in 21 seconds.

Substantially no smoke or fume was observed during the pouring and the casting was found to be completely clean, having a completely nodular structure when a portion of it was examined under the microscope.

The magnesium content of this portion was found to be 0.037 percent. To check the uniformity of magnesium content an analysis was conducted in the gating area attached to the casting. This was found to contain 0.038 percent magnesium. v 8

While we have described our invention with a certain degree of particularity, it is understood that various changes in detail may be resorted to without departing in spirit and scope from the invention as herein claimed.

We claim:

l. A gating system for a mold to provide for alloy additions to molten cast iron'which is poured into the mold including in combination a mold cavity, a downsprue for introducing molten cast iron into the mold, a basin interposed between said mold cavity and said downsprue and being fluidly connected to said downsprue, said basin adapted to receive alloy which is to be added to molten cast iron, a consumable plastic member located in said basin and closing the exit end thereof until consumed by the .action of the molten cast iron thereon, a skimmer located in said basin, passageway means fluidly connecting said basin to said mold cavity, a. restriction in said passageway means comprising the smallest cross sectional flow area in the gating system and determining the dwell time of molten cast iron in said basin during a pouring cycle, the cross sectional area of said restriction being related to the casting weight as set forth as follows:

and being of such a size that the dwell time of the molten cast iron in said basin is between about 1 and 2 seconds, the volume of said basin being determined by the following formula:

V (in?) [Wgt. (lbs.) D.T. (Dwell Time in seconds) X 4]/[l.25 V weight (lbs.

2. A gating systemas claimed in claim I, wherein an alloy reservoir is located above said basin and comm unicates directly therewith.

'3. A gating system as claimed in claim 1, wherein an each second of pouring time infilling the mold cavity.

6. A gating system'as claimed in claim 1 wherein at least one lengthwise partition of consumable plastic material is placed in said basin to produce a plurality of'flow channels through aid basin.

7. A gating system for a mold to provide for additions to molten cast iron which is poured into the mold including in combination a mold cavity, a downsprue for introducing molten cast iron into'the mold, a basin interposed between said mold cavity and said downsprue andbeing fluidly connected to downsprue, at least one partition of consumable material positioned in said basin to produce a plurality of flow channels through said basin, a consumable member located in said basin and closing the exit end thereof, passageway means fluidly connecting said basin' to said mold cavity, a restriction insaid passageway means-comprising the smallest cross sectional flow area in the gating system and deter mining the dwell time of molten castiron in said basin during a pouring cycle, the cross'sectional area of said restriction being related to forth as follows: V

the casting weight as set (Dwell Time in seconds) 1 1 s q 1 v a: r

CASTING WEIGHT DAM GATE EXIT AREA 10 1 0.17 sq. in. 20 1 0.28 s in. 30 0.32 s 40 0.46 sq. in. 0.55 sq. in. I 0.65 .sq. in. 0.72 s 111.. 0.8l sq. in. 0.90 sq. in. 115 0.98 sq. in. 200v 1.06 sq. in. 250 l.l5.sq. in. 300 L24 sq. in. 350 1.32 sq. in. 400. 1.40 sq. in. 500 1.48 sq. in. 600 L56 sq. in.

700 1.72 sq. in. v 800 L87 sq. in. 900 2.03 sqJin. 1000 2.18 sq. in. 1250 2.4] sq. in. I500 2.64 sq. in. 1750 2.85 sq. in. 2000 3.06 sq. in. 2500' 3.35 sq. in. 3000 3.70 sq. in. 4000 4.20 sq. in.

. 5000 4.00 sq. in.

and being of such a size that the dwell time of molten cast iron in said basin is between about 1 and 2 seconds, the volume of said basin being determined by the following formula: cl V (in.) =.[Wgt.'(lbs.) X D.T.

in. s

Claims (7)

1. A gating system for a mold to provide for alloy additions to molten cast iron which is poured into the mold including in combination a mold cavity, a downsprue for introducing molten cast iron into the mold, a basin interposed between said mold cavity and said downsprue and being fluidly connected to said downsprue, said basin adapted to receive alloy which is to be added to molten cast iron, a consumable plastic member located in said basin and closing the exit end thereof until consumed by the action of the molten cast iron thereon, a skimmer located in said basin, passageway means fluidly connecting said basin to said mold cavity, a restriction in said passageway means comprising the smallest cross sectional flow area in the gating system and determining the dwell time of molten cast iron in said basin during a pouring cycle, the cross sectional area of said restriction being related to the casting weight as set forth as follows: CASTING WEIGHT DAM GATE EXIT AREA 10 0.17 sq. in. 20 0.28 sq. in. 30 0.32 sq. in. 40 0.46 sq. In. 50 0.55 sq. in. 75 0.65 sq. in. 100 0.72 sq. in. 125 0.81 sq. in. 150 0.90 sq. in. 175 0.98 sq. in. 200 1.06 sq. in. 250 1.15 sq. in. 300 1.24 sq. in. 350 1.32 sq. in. 400 1.40 sq. in. 500 1.48 sq. in. 600 1.56 sq. in. 700 1.72 sq in. 800 1.87 sq. in. 900 2.03 sq. in. 1000 2.18 sq. in. 1250 2.41 sq. in. 1500 2.64 sq. in. 1750 2.85 sq. in. 2000 3.06 sq. in. 2500 3.35 sq. in. 3000 3.70 sq. in. 4000 4.20 sq. in. 5000 4.60 sq. in. and being of such a size that the dwell time of the molten cast iron in said basin is between about 1 and 2 seconds, the volume of said basin being determined by the following formula: V (in.3) (Wgt. (lbs.) X D.T. (Dwell Time in seconds) X 4)/(1.25 square root weight (lbs.))

2. A gating system as claimed in claim 1, wherein an alloy reservoir is located above said basin and communicates directly therewith.

3. A gating system as claimed in claim 1, wherein an alloy reservoir is located below said basin and communicates directly therewith.

4. A gating system as claimed in claim 1, wherein an alloy reservoir is located upstream of said basin.

5. A gating system as claimed in claim 1, wherein the length of said basin is on the order of one-half inch for each second of pouring time in filling the mold cavity.

6. A gating system as claimed in claim 1, wherein at least one lengthwise partition of consumable plastic material is placed in said basin to produce a plurality of flow channels through aid basin.

7. A gating system for a mold to provide for additions to molten cast iron which is poured into the mold including in combination a mold cavity, a downsprue for introducing molten cast iron into the mold, a basin interposed between said mold cavity and said downsprue and being fluidly connected to said downsprue, at least one partition of consumable material positioned in said basin to produce a plurality of flow channels through said basin, a consumable member located in said basin and closing the exit end thereof, passageway means fluidly connecting said basin to said mold cavity, a restriction in said passageway means comprising the smallest cross sectional flow area in the gating system and determining the dwell time of molten cast iron in said basin during a pouring cycle, the cross sectional area of said restriction being related to the casting weight as set forth as follows: CASTING WEIGHT DAM GATE EXIT AREA 10 0.17 sq. in. 20 0.28 sq. in. 30 0.32 sq. in. 40 0.46 sq. in. 50 0.55 sq. in. 75 0.65 sq. in. 100 0.72 sq. in. 125 0.81 sq. in. 150 0.90 sq. in. 175 0.98 sq. in. 200 1.06 sq. in. 250 1.15 sq. in. 300 1.24 sq. in. 350 1.32 sq. in. 400 1.40 sq. in. 500 1.48 sq. in. 600 1.56 sq. in. 700 1.72 sq. in. 800 1.87 sq. in. 900 2.03 sq. in. 1000 2.18 sq. in. 1250 2.41 sq. in. 1500 2.64 sq. in. 1750 2.85 sq. in. 2000 3.06 sq. in. 2500 3.35 sq. in. 3000 3.70 sq. in. 4000 4.20 sq. in. 5000 4.60 sq. in. and being of such a size that the dwell time of molten cast iron in said basin is between about 1 and 2 seconds, the volume of said basin Being determined by the following formula: cl V (in.3) (Wgt. (lbs.) X D.T. (Dwell Time in seconds) X 4)/(1.25 Square Root weight (lbs.))

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