US1556642A - Process of casting malleable castings - Google Patents

Description

Oct- 13, 1925. 1,556,642

W. H. SMITH PROCESS OF CASTING MALI-JEABLE GASTINGS Filed April I0, 1924 A Wi w F III/11111111110101!!!\ Patented Oct. 13, 1525.

um'rl-zn STATES PATENT OFFICE.

WILLIAM H. SMITH, OF DEARBORN, MICHIGAN, ASSIGNOR TO FORD MOTOR COMPANY,

OF DETROIT, MICHIGAN, A CORPORATION OF DELAWARE.

PROCESS OF CASTING MALLEAIBLE CASTINGS.

Application filed April 10. 1924. Serial no. 705,409.

To all 'wkom z't may concern:

Be it known that I, WILLIAM H. SMITH, a citizen of the United States, residing at Dearborn, in the county of Wayne and State of Michigan, have invented certain new and useful Improvements in Processes of Casting Malleable Castings, of which the following is a specification, reference being had therein to the accompanying drawings.

Malleable gray iron castings when cast in metallic molds or dies, are first white iron, or chilled cast iron, and the combined carbon is then converted by special heat treatment into an uncombined, amorphous condition, which treatment renders the castings malleable.

The usual method of producing die cast iron castings is to produce white iron castings which are then annealed at a high temperature, causing a conversion ofthe carbon content to an amorphous, uncombined condition, the castings being permitted to slowly cool. Essential conditions are proper control of temperature and time, the cooling being sufliciently delayed to give proper annealing. The texture on malleability of castings cast in dies, is dependent upon the rate 0 temperature drop through the critical range of cooling, which is about 1200 F. The common practic involves several independent steps and separate annealing and handling, with difliculty arising from inaccurate control of time and temperature of cooling, oxidization, and required skill in producing a uniform product.

This invention relates to a process or method for producing malleable gray iron castings, and its object is to simplify methods, increase production, insure uniform product, and provide certain other new and useful features, all as hereinafter more fully described,.th e invention consisting in providing a method wherein the operation of cooling the metal to give the desired malleability is introduced into the casting opera tion and accurately controlled as to time and temperature by controlling the transfer of heat from casting. to cooling medium, and

further consists in certain other new and useful features, all as hereinafter more fully described, reference being had to the accompanying drawing illustrative of one means whereby the method embodying the invention may be performed.

In the drawing,

Figure l is a plan view of a mold construction shown for the purposeof illustrating the method embodying the invention;

Fig. 2 is a longitudinal vertical section through the same; 3

- Fig. 3 is a transverse section substantially upon the line 33 of Fig. 2, and

Fig. 4 is a sectional perspective detail of a casting cast in'the mold.

The present invention contemplates the casting of molteniron in a metallic mold or die, the temperature of whichv is raised to a proper degree of heat above 500 F. and

' maintained at such temperature by a suitable heat conducting fluid tomaintain a temperature equilibrium between the metal and .said heating medium, whereby the proper time in the fall of the temperature of the casting is secured to produce malleability of the casting. I

Formerly it has been deemed necessary to cast the metal and then reheat the casting to anneal the iron and produce malleability. The present invention contemplates the casting of the metal in dies and controlling the temperature of these dies to regulate the rate of coolingof the cast metal and produce malleability thereof. c-

As illustrative of a die construction which may be employed in the carrying out of the presentmethod or process, a two part die formed of a suitable material, preferably metal, is provided, the confronting faces of which parts are formed to give the desired configuration to the casting. These two parts 1 and 2 of the die or mold preferably together form a wall 4 which separates chambers 3, each die part forming a part of said wall andthe chambers forming receptacles or passages for a fluid body 5 which is thus in direct contact with the die or mold wall. The fluid is maintained, in any suitable manner, at the proper temperature to maintain a certain heat ratio between die walls have the desired structure without higher heating. This fluid which may be maintained at a uniform high temperature by the heat transferred thereto by the molten metal in casting or otherwise, may be Cl} culated in any suitable manner if found desirable, to graduallv carrv of? the heat imparted thereto by the metal through the cooled and at the same time maintained at the proper temperature to prevent too rapid cooling of the casting, by maintaining a body of molten tin at a temperature of 500 F.

, or over and in direct contact with the walls 4 of the metallic die which walls form the two parts of the die or mold proper, between V which the casting is formed. As tin is one 5 of the metals having a high heat conductivity and which can be maintained fluid at at the same time will have the proper egree a this comparatively low temperature (500 F.), the rate of drop in temperature of the feasting through its critical stage, is accurately controlled and proper malleability secured dur' the casting operation, and at the same time, the conductivity of the molten tin is such that the mold will be cooled, or its temperature prevented from rising to such a point that in ury to the mold 'willqresult therefrom. Metal molds may therefore be employed and will be protected against rapid disintegration so that they may be used through long periods of time. The conductivity; of the molten tin is not however so great as to cause a too rapid cooling of the casting but will absorb suflicient heat to provide the desired retardation of drop in temperature as the metal passes through its critical stage of approximately 1200 F. and give proper annealing, but sufficiently rapid to prevent the'forma'tion of graphite.

, Any fluid cooling-medium may be employed which will retain sufiicient heart to properly retard cooling of the castin and 6f heat conductivity to cool the casting and mold, but it has been found that molten tin is very efficient for the purpose and preferable.

In the drawing, a mold has been shown for the purpose of illustrating the method embodying the present invention, but it will be understood that an I suitable form or construction of mold w ich will rovide for maintaining contact of the cooling medium with the mold wall may be employed, suitable provision being made for separating the die mold parts land 2 to discharge the castings, as by making the parts relatively movable upon suitable guides 6 or the like and providing any suitable means, as a screw 7 for moving relatively theboxes or receptacles 8 forming the chambers 3, so that the formed castings 9 may be discharged from the die or mold.

By this method the cooling of the cast metal may be very accurately controlled and time regulated to produce a uniform product, and reheating of the castings is obviated, due to this acurate and delayed cooling of the metal within. the mold or die in which the casting is formed. Oxidization is also prevented as all air is excluded from the casting by its inclosure within the die.

The method embodying the present invention may be modified within the scope of the appended claim, and such modifications are contemplated.

What I claim is The method of casting malleable castings which consists in providin a mold, introducing molten metal into t e mold to form a castmg, and in maintaining a body of tin in fluid state in contact with the mold walls. In testimony whereof I alfix my signature.

WILLIAM SMITH.

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