US1634586A - Method of manufacturing malleable cast iron - Google Patents

Description

7' v 1,634,586 July 75, 1927. M. KUBO METHOD OF MANUFACTURING MALLEABLE CAST IRON Filed June 12, 1922 1@.5. 37 I4 v L- 3 n uen fox Patented July 5,1927".

a uAsAxrcnr :xnno, or TOKYO, JAPAN.

was or MANUIACTUBmQ HALLEABLE cAsr neon.

Application filed lune ia isaa. suial m. q67,869.-

My invention-relates to the process of manufacturing malleable cast iron (includ- .ing blackheart), and to the provision of a method of producing malleable cast iron with a considerable reduction of cost by decreasing the operating time.

' It is well known that malleable cast iron is cast in the form of hard white iron, and

.given a degree of malleability and toughness by subsequent annealing, during which,

, either the carbon is partially eliminated, and

the remainder left partly as combined carbon, and partly as amorphousor free carbon; or, in the case of blackheart, the amount of the carbon is scarcely altered, but the condition of the bulk ofit is changed to amorphous or free'carbon and the remainder is left as combined carbon. 1

In makin malleable cast iron, the castings are pac ed in retorts or annealing pots with oxide of iron (generally hematite ore), put in annealing furnace or oven for heating to a temperature somewhere between 700 degrees 0., and the melting point, and kept red hot for several days.

These processes are very expensive, as they need a great deal of fuel, materials, and labor. By meansof my invention, I have provided a method of making malleable cast iron from hard white cast iron, without heating the same fora long time as described above.

In carrying out my invention in one form, I have passed an electric current through white cast iron, which is the raw material of malleable cast iron, while buried in oxide of iron, and kept at a temperature of about 900 degrees 0., in a gas oven for a short period.

As results I have obtained in a short time a malleable cast iron which has a desirable characteristic malleability and tough ness; and unlike the original white cast iron, it can be drilled or bent. According to my experiments with alternating current of 200 amperes per square inch to the section of the material, at a suitable voltage, and a frequency of 50 cycles per second, it was found that almost a complete change in the material may be efl'ectedin from one half to one hour, when the thickness of the material is from one quarter to three-eighths of an inch, and the time required was found to A decrease as the current density increased.

According to aseries of my experiments I I declare the facts thatthe electricity can assist distinctly the elimination or separation of combinedcarbon in white cast iron if a.

age is,more efiective than a direct current or, voltage, and also an alternating current of higher frequency is more effective than that of a lower frequency. I

In order to explain and to illustrate some of the important applications .of my invention, reference will be made to the accompanylng drawings, in which Fig. 1 is intended to represent diagramnatically an electrical furnace, equipped with the electrodes, for annealing some conical dishes.

Fig. 2 is a gas or oil furnace for treating some white cast iron pieces, with a receptacle for containing hematite.

Fig. 3 is-a liquid bathfurnace, similar to Fig. 2, for making black-heart castings.

Fig. 4 is a special furnace in which castings are heated electrically.

InFig. 1, 11 represents walls of'the furnace, 13 the hematite ore, 14 the two electrodes, 15 an electric heating unit. As it will be seen the castings 12 are firmly packed in the inner compartment with the hematite 13. In placing the castings an effort should be made to pack them in such a way as to make electrical resistance as uniform throughout as possible. The electrodes 14:

are made of iron or othersuitable material which can resistchemical action of the hem- -perature; and an alternating current or voltatite 13. Now, the castings 12 and the hemafurnace, without keeping them in red hot condition for a long time as usually done.

In-Fig. 2, 21 represents the wall and cover of the furnace, built of fire brick, 28 the receptacle made of iron, 23 the hematite ore, 22 the castings, and 25 a gas or oil burner. By means of this-arrangement thecastings 22 andthe hematite 23 may be heated to a suitable temperature by means of the burner and a necessary electric current may be passed through the castings 22 and the hematite 23 at a suitable voltage for a necessary length of time, which is usually from one half to one hour, by a properadjustment of the regulator 27. Whenthis mallcablizin'g process is complete the casting may be removed from the furnace at once.

In Fig. 3, 31 represents the wall of the furnace built of fire brick, 38 a crucible, 33a suitable electrolyte, such asbarium chloride, which does not vaporize easily, 34 an electrode, 32 the casting, and 35 the gas or oil burner. By means of the burner the electrolyte 33 and the casting 32 can be heated to a suitable temperature in the critical range, and a necessary electric current may be passed through the electrolyte 33 and the casting 32 at a suitable voltage by a proper adjustment of the regulator 37, to obtain black-heart malleable cast iron castings in a short time. In Fig. 4%, 51 represents the wall of a furnace or receptacle made of fire bricks, 53 the I hematite ore, 52 the casting of a special form as it will be clear, and 54 the electrodes. As in the present case when a casting has a thick part it happens to be impossible to effect the desirable thermal or electrical treatment by one operation, as in the processes illustrated in Fig. 1, Fig.2 and Fig. 3, since experiences show that the thicker part of a casting rement. Therefore, after one operation,

as in the process illustrated in .Fig. 1,.

Fig. 2 and Fig. 3, has applied, it is advisable to give the second operation which is intended to be illustrated by 'thearrangement shown in Fig. 4. Thus, in the second operation, a suitable electric current is sent through the heavier part such as the hub of q a Wheel, for example,-by a proper adjustment of the regulator, 57 to heat principally that part of the casting to a temperature in the critical range, in order that that part of the casting may be annealed and electrically treated comparatively in a short time for the purpose of changing the composition of the white castiron into malleable cast iron which permits drilling or other machining.

Thus it is clear that my invention may beconveniently applied for practical purposes, as exemplified above by means of these'simple apparatus.

The underlying principle involved in this invention seems to be extremely profound and to require a careful study if it is attempted to theorize and to explain the phenomena. In fact it has not been explained or published as far as I know that the separation of carbon from iron carbide comp0unds,in state of solid at any temperature, can be accelerated by an electric current, altliough it is a well known fact that the sepapounds in state of fusion, or in state of a chemical solution in a liquid solvent, can'be effected or accelerated by an electric current.

As stated in the foregoing paragraph, it is extremely diflicult to theorize such a delicate intermolecular phenomenon as this. In spite of'that, I shallpoint out and attempt to explain briefly the underlying principle of the fact, as follows 7 It is a well known fact that white cast iron is mostly composed of iron and carbide of iron (chemically pure iron and cementite), but when it is heated to a temperature of the critical range, the carbide of .iron becomes chemically unstable. Under thiscondition the molecule seems to be in the state of 1 ionization, having a molecular bipolar condition such that one of the atoms in the molecule has the positive ion and another part has the negative ion, and the amplitudes of both electronic and molecular vibrations within and among the molecules may reach such an extent as to separate carbon atoms from the molecules by molecular vibratiou and electronic collision, in addition to the action of the separation caused by said bipolar condition. But the rate of the chemical change is exceedingly slow; especially, as it approaches to a point of'an equilibrium as a limit, because the efiects of the bipolar condition between each molecule manifested by said intramolecular ionization, and of the ration of carbon from iron carbide commolecular vibration or electronic collision this condition, the electric current will induce efiectively an electromotive-force in the molecules, in addition to the thermal action by said electric current, and the free electrons within the molecules will migrate un-- 1 der' this electromotive force and may speed up to a limit which is a function of the ap plied electromotive force, and may produce an effective electronic collision, in addition to the -molecular vibration, and cause a a speedy separation of carbon atoms from the lI'Ol'l carbide molecules and white cast iron may be made 1nto malleable cast iron or blackheart under a suitable condition. And

the rate of the chemical change is found to be greater, especiallywhen the applied electromotive force is an alternating one, than when only the electromotive force is applied as described in' above, due to the fact that the maximum velocity of the free electrons attained may be much greater, as the crest value of the voltage or current is greater than that of the continuous voltage or current'of the same effective value, and electronic movement is then much ater and more effective than otherwise, position of the electric potentials change'in every half cycle.

In the foregoing ,anfemphasis has been laid on the fact that an alternating electromotive force or electric current is more effective than a continuous electromotive force or electric current. This fact also seems to be, in my opinion, due to the fact that the direction of. the applied electromotive force or currcntchanges every half cycle, and when the electric currentdecreases'to zero, the separated carbon which is in the ionicstate can change to a neutralized state, and settles to amorphous or free carbon, and

when the carbon has settled to the amorhous or free carb'on state, it cannot recomine with the iron because the carbon is changed to graphitrc carbon, and the temperature, the current, or voltage, which are p used in this process, cannot change the grfiphitic carbon to the unstable state chemica y. A series of my experimental investigations reveal the facts in addition to the above, that a pulsating voltage or current is more effective than a continuous'uniform voltage or current because of the above reasons, and a high frequenc alternating voltage or current is more e ective than a low frequency alternating yoltage or current, because it constitutes the greater number of alternations per second and can greater and more effective electromc and 40 magnetic or molecular momentum to accelerate the chemical change within white cast iron.

While I have described the v rinciple of operation of my invention toget er with apparatus which 'I now consider to represent the best embodiment thereof, I desire to have it understood that the exact process described and the apparatus shown are merely illustrative and; that the invention may be carried out also by other means.

What is claimed is c. 1.- The process of converting the combined carbon of white cast iron into uncombined condition without fusion, consisting in encause the we avelo ing the same in a suitable medium, in t5 heatln the same to a temperature .in the critic range, and passin an electrical current therethrou h while t us heated, for the purpose of acce erating the desirable chemical change.

2. The process of manufacturing malle--' able castings by converting the combined carbon of white cast ironinto uncombined condition without fusion, consisting in enveloping the same in a refractory material, in heating the same, by fuel or electric heat to a temperature in the critical ran e, an I passing an electrical current there rough while thus heated, for the purpose of accelerating the desirable chemical change.

3. The process of manufacturing malleable castings by converting thecombined carbon of white cast iron into uncombined condition without fusion, consisting in em veloping the same in a suitable medium, such as. iron oxide (Fe,O or hematite ore, in heating the same by fuel or. electric heat, to a temperature in the critical ran e, and' assing an electric current" theret ough, while thus heated, for the purpose ofaccelerating the desirable chemical change.

4. The process of manufacturing malleable'castings by converting the combined carbon of white'cast-iron into uncombinedcondition without fusion, consisting in enveloping the same in a suitable medium, such as iron oxide (Fe,O,) or hematite ore, in heating the same with said medium by fuel or electric heat, to a temperature in the critical range, and pass'in an electrical current therethrough while t us heated, forthe purposeof acce crating the desirable chemical change. 5. The process of manufacturing malleable castings by converting the combined 05 carbon of white cast iron into uncombined condition without fusion, consisting in enveloping the same in a suitable medium, such as iron oxide (Fe,O,)for hematite ore in heating the same with said medium, by 100 fuel or electric heat, to a temperature in the critical range, and passing an electrical current through the sameand said medium, while hus heated, for the purpose of accelerati the desirable chemical change. .10

In testimony whereof I aflix my signature.

MASAKIGHI KUBO.

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