US3881937A - Shaped inoculation means for iron casting melts - Google Patents

Abstract

An inoculation body is cast or sintered with grains of a silicide in a matrix of a metal having a lower melting point than iron, such as aluminum, tin or zinc, in the shape of a main body having a flat bottom surface with a perpendicularly projecting peg or stem in the mid-portion of the bottom surface. The stem may be tapered slightly. Such an inoculation body is used by seating it on its flat bottom surface on a strainer grate core of a casting mold, with the stem or peg projection extending into a perforation of the strainer grate core. The flat bottom and the projection cooperate to maintain the inoculation body in its central position on the grate core during transportation of the mold to the pouring position, as well as during the pouring operation.

Description

United States Patent 1 [111 3,881,937

Teufel [4 1 May 6, 1975 SHAPED INOCULATION MEANS FOR IRON CASTING MELTS [21] Appl. No.: 438,651

[30] Foreign Application Priority Data Feb. 27, 1973 Germany 2309654 U.S. Cl 75/130 R; 75/58; 75/93 G Int. Cl C22c 37/02; C216 7/00, C22b 9/12 Field of Search 75/130 R, 58, 93 G, 130 B References Cited UNITED STATES PATENTS S/l95l Tour 75/93 IT 7/1968 Robertson........ 75/]30 R Primary Examiner-P. D. Rosenberg Attorney, Agent, or FirmFlynn & Frishauf {57] ABSTRACT An inoculation body is cast or sintered with grains of a silicide in a matrix of a metal having a lower melting point than iron, such as aluminum, tin or zinc, in the shape of a main body having a flat bottom surface with a perpendicularly projecting peg or stem in the mid-portion of the bottom surface. The stem may be tapered slightly. Such an inoculation body is used by seating it on its flat bottom surface on a strainer grate core of a casting mold, with the stem or peg projection extending into a perforation of the strainer grate core. The flat bottom and the projection cooperate to maintain the inoculation body in its central position on the grate core during transportation of the mold to the pouring position, as well as during the pouring operation.

4 Claims, 2 Drawing Figures SHAPED INOCULATION MEANS FOR IRON CASTING MELTS This invention relates to means for inoculating iron casting melts with ferrosilicon and similar seeding inoculants to improve the casting properties of the melts. In particular the invention relates to the provision of solid bodies containing the silicide additive in a form to be taken up readily by the melt and dispersed therein shortly prior to solidification.

It is known that the addition of an inoeulant such ferrosilicon during the casting process improves the quality of iron castings. The inoculant is dissolved in the melt and has a favorable influence on the progress of solidification of the melt.

The casting so treated freezes in the gray iron condition throughout, whereas in the case of casting without inoculation, especially when the wall thickness ratios are unfavorable, the formation of cementite takes place. The latter situation is accompanied by a considerable reduction of the mechanical qualities of the casting. The amount of inoculant to be added is related to the weight of the casting. Thus for a casting of 30 kg, for instance, the addition of 30 g of inoculant is sufficient and advantageous. lnoculation by adding to the melt at the time of casting is more favorable than when the inoculant is provided beforehand in the casting ladle, since in the latter case the favorable influence on the cast iron structure falls off exponentially with time.

Ferrosilicon can be cast at a temperature of about 3,()O()C. The practice heretofore has been to shatter plates of ferrosilicon so cast. sort the fragments according to weight or size and provide the material in this form to foundries. Thus if a foundryman should need 30 g of inoculant for a particular casting, he would take a fragment of that weight and place it on the strainer grate core in the gate system of the casting mold shortly before the melt is poured.

This method of foundry production is very expensive, because obtaining the necessary weight for the lumps of inoculant is more or less a matter of chance. Attempts to control the apportionment of the quantity of ferrosilicon by providing powdered material typically agglomerated with an organic binder, have led to no satisfactory results, because of irregularity in the rate of solution. The production of cast blocks of ferrosilicon in the desired sizes is difficult and troublesome, because of the high melting point of ferrosilicon and the high surface tension of the molten material. At the same time a surface oxidation of this inoculant takes place which reduces the solution tension.

It is known from German published patent application DAS No. 1,508, l 74 to provide an inoculant in tablet form made of granular ferrosilicon and a fusible organic binder as a matrix, and to introduce such a tablet in the casting mold. It is also known, from Swiss Pat. Nos. 457.738 and 465.78l to provide shaped inocula tion bodies of ferrosilicon or ferrosilicon alloys that contain. either as impurities or as purposeful additions, metals that melt at temperatures lower than the melting point of iron, such as aluminum or magnesium, with the use of an inorganic matrix-forming material such as molding sand or hardened water glass and to place these inoculation bodies as plates in core marks of the pouring or gate system used for casting. In the prior pa tent application ofJ. Zcllerer and E. W. Rath, Ser. No. 312,796, filed Dec. 7, W72, an improved inoculation body was disclosed utilizing metal melting at a lower temperature than iron as the matrix material itself and disclosed the utilization of such a body either by placing it before the casting process on a strainer grate core of appropriate size or by sintering the inoculation body material together with this strained grate core to form a single firmly bound body.

It is an object of the present invention, in the interest on the one hand of maintaining the proper position of the body and on the other hand assuring that the inoculation process proceeds properly, to provide a certain freedom of design and interchangeability in the uniting of strainer grate core and inoculation body (which is not present in the previously mentioned combined body produced by sintering the strainer grate core and inoculation body materials together) and nevertheless, to assure that when the structure consisting of strainer grate core and inoculation body is brought to the place of casting, that the inoculation body will maintain its proper position on the strainer grate core so that the inoculation process will effectively take place.

SUBJECT MATTER OF THE PRESENT lNVENTlON Briefly, the inoculation body is provided with a peg or stem that is insertable in a hole in the strainer grate core on which it is used. It is desirable and effective for this projection provided on the inoculation body to be cast onto the inoculation body in such a way that it projects out of a flat supporting surface of the inoculation body.

This configuration has the advantage that the body provided with a stem or peg can be used within certain limits for strainer grate cores of differing dimensions. The users of the improved casting process are not, in accordance with the present invention, either relegated to the use of combination bodies in which the core and inoculation material are sintered together or to sticking a rod or pin of inoculation material of a particular shape where it will lodge in position. Such rods or pins are no longer necessary. Manufacture, positioning and securing are simplified and improved. The user is assured that the configuration provided by the mounting of the inoculation body on the strainer grate core will maintain its correct position when set into the casting mold and transported to the place of pouring on a roller conveyer, i.e. that the inoculation body cannot fall off or out of its central placement on the strainer grate core. This provides a saving in labor and an increased assurance of the correct operation of the inoculation.

The invention is further described by way of example with reference to the accompanying drawings, in which:

FIG. I is a cross-section of a casting mold and gate system with an inoculation body with a positioning stem in accordance with the invention, and

FIG. 2 is a side elevation view on a larger scale of the inoculation body itself with its positioning stem.

The casting mold shown in FIG. 1 consists of an upper mold and a lower mold, both shown partly broken away, each with one channel. The upper mold body has the pouring basin 1 and the reaction chamber 2. The lower mold body contains the collecting chamber 3, in the inlet to which is seated a perforated strainer grate core 4.

In the central perforation of the strainer grate core 4 is inserted the stem or peg 6 of the inoculation body 5.

The main part of this body itself has a flat lower sup porting surface 7 that surrounds the stem or peg 6. When the inoculation body is cylindrical as shown in FIGS. 1 and 2, the supporting surface 7 is of flat annular shape. The provision of this supporting surface enables the inoculation body to be seated firmly on the surface of the strainer grate core 4. The insertion peg 6 cast onto the inoculation body projecting into the perforation of the strainer grate core 4 may be very slightly tapered towards its extremity, as shown in FIG. 2. Likewise the upper part of the body 5, above the plane of the line 8 of FIG. 2 may be slightly tapered towards the top.

The stem or peg 6 is preferably cast at the same time and of the same material as the inoculation body when it is made by flooding the ferrosilicon grains with aluminum, in a mold, or by sintering the ferrosilicon grains with aluminum powder in a chill mold. Alternatively, it could be cast on later with the same or a compatible material in a separate operation.

In practice the casting melt is poured into the mold through the strainer grate core and around the inoculation body. The aluminum or other light metal (e.g. tin, zinc) component is quickly released by melting and floats on the surface of the melt. The ferrosilicon grains thus freed with their surfaces in reactive condition are quickly and fully dissolved by the iron. so that the intended inoculation effect is obtained to the highest possible degree.

Although the invention has been described with reference to a particular embodiment, it will be under stood that variations and modifications may be made within the inventive concept.

I claim:

1. Shaped body inoculation means for introducing a silicide additive into an iron casting melt consisting of grains of said silicide embedded in a metal having a melting point lower than that of iron and shaped in a main body and peg-like projection means extending outward therefrom for positioning said body on a perforated strainer grate core with said projection in a perforation of said core.

2. Shaped body inoculation means as defined in claim 1, in which said main body has a flat seating surface surrounding said projection and said projection extends outward in a direction perpendicular thereto, whereby said body may be seated by said flat surface resting on said grate core when said body is positioned by said projection thereon as aforesaid.

3. Shaped body inoculation means as defined in claim 2, in which said main body and said projection are of the same material having the grains of said silicide homogeneously dispersed in the bulk of said main body and projection in the said metal in which they are em' bedded.

4. Shaped body inoculation means as defined in claim 2, in which said projection is tapered down to a slightly smaller cross-section at its extremity from a larger cross-section at its base where it adjoins said main body.

Claims (4)

1. SHAPED BODY INOCULATION MEANS FOR INTRODUCING A SILICIDE ADDITIVE INTO AN IRON CASTING MELT CONSITING OF GRAINS OF SAID SILICIDE EMBEDDED IN A METAL HAVING A MELTING POINT LOWER THAN THAT OF IRON AND SHAPED IN A MAIN BODY AND PEG-LIKE PROJECTION MEANS EXTENDING OUTWARD THEREFROM FOR POSITIONING SAID BODY ON A PERFORATED STRAINER GRATE CORE WITH SAID PROJECTION IN A PERFORATION OF SAID CORE.

2. Shaped body inoculation means as defined in claim 1, in which said main body has a flat seating surface surrounding said projection and said projection extends outward in a direction perpendicular thereto, whereby said body may be seated by said flat surface resting on said grate core when said body is positioned by said projection thereon as aforesaid.

3. Shaped body inoculation means as defined in claim 2, in which said main body and said projection are of the same material having the grains of said silicide homogeneously dispersed in the bulk of said main body and projection in the said metal in which they are embedded.

4. Shaped body inoculation means as defined in claim 2, in which said projection is tapered down to a slightly smaller cross-section at its extremity from a larger cross-section at its base where it adjoins said main body.

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