US2781260A - Process and apparatus for the treatment of molten ferrous alloys - Google Patents

Description

Feb. 12, 1957 M. c. M. GRANDPIERRE 2,781,250

PROCESS AND APPARATUS FOR THE TREATMENT OF MOLTEN FERROUS ALLOYS 6 Sheets-Sheet 1 Filed March 3, 1955 Feb. 12, 1957 M. c. M. GRANDPIERRE 2,781,260 PROCESS AND APPARATUS FOR THE TREATMENT OF MOLTEIN FERROUS ALLOYS Filed March 3, 1955 6 Sheets-Sheet 2 INVENTOR. MAURICE C M l'mmafi/sfies Feb. 12, 1957 M. c. M. GRANDPIERRE 2,781,260

PROCESS AND APPARATUS FOR THE. TREATMENT OF MOLTEN FERROUS ALLOYS 6 Sheets-Sheet 3 Filed March 3, 1955 UR/CE CM GRA IVDP/ERRE Feb. 12, 1957 M. c. M. GRANDPIERRE 2,781,260 PROCESS AND APPARATUS FOR THE TREATMENT OF MOLTEN FERROUS ALLOYS 6 Sheets-Sheet 4 Filed March 3, 1955 INVENTOR. MAUR/CA' C. M 'm wa /wfle ATTOR/V'y Feb 1957 M. c. M. GRANDPIERRE PROCESS AND APPARATUS FOR THE TREATMENGP OF MOLTEN FERROUS ALLOYS Filed March 3, 1955 6 Shee ts-She et 5:

Feb. 12, 1957 c. M. GRANDPIERRE 2,781,260

PROCESS AND APPARATUS FOR THE TREATMENT OF MOLTEN FERROUS ALLOYS 6 Sheets-Sheet 6 Filed March 3, 1955 INVENTOR.

United States Patent fifiee 2,781,260 Patented Feb. 12, 1957 PROCESS AND APPARATUS FOR THE TREAT- MENT OF MOLTEN FERROUS ALLOYS Maurice Charles Marie Grandpierre, P-ont-a-Mousson, Nancy, France, assignor to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware Application March 3, 1955, Serial No. 491,820

Claims priority, application France March 6, 1954 18 Claims. (Cl. 75130) The present invention is directed tothe treatment of i a liquid ferrous alloy such as cast iron and steel and, more particularly, to an improved method for introducing into such a liquid ferrous alloy an addition element having desulfun'zing properties.

It has been heretofore proposed to introduce addition elements having desulfurizing properties into liquid ferrous alloys to improve the quality of the resulting castings. it has also been discovered that many reactive elements having desulfurizing properties when used in the treatment of molten cast iron have the ability to control graphite occurring in the resulting castings to a spheroidal form with accompanying great improvement in the mechanical properties of the castings. It has been known that addition elements having desulfurizing properties, e. g., magnesium, cerium, calcium, etc., are quite Oxidizable and have low boiling points compared with the temperature of the liquid ferrous alloy. The result of this is that, in spite of the precautions that it has already been found possible to take by following various known procedures for introducing these elements, such as operating in an atmosphere which does not react with the addition element or by plunging the addition element into the interior of the ferrous alloy either with or without the presence of a neutral atmosphere, the losses by volatilization and/ or combustion of the addition element are considerable. The final result of this is that with a given total quantity of the element introduced, there remains in each case and by all known procedures a high degree of uncertainty regarding the final content of the addition element in the alloy.

To such an extent is this true that, in practice, there are observable in the alloys obtained considerable differencesas between one heat and another-in behavior and properties. This involves the necessity of a permanent check on every heat and a need to provide considerable margins of safety.

It has now been discovered that when is introduced into a molten ferrous alloy under highly specialized conditions, the addition reactions are placed under rigid control With resulting high recovery of the reactive addition agents in the molten ferrous alloy.

It is an object of the invention to provide an improved method for introducing reactive elements into molten ferrous alloys.

It is a further object of the invention to provide a method for introducing desulfurizing agents into molten cast iron in a particularly effective manner.

Another object of the invention is to provide a special apparatus adapted for the purpose of introducing reactive agents having desulfurizing properties into molten ferrous alloys.

Other objects and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings in which:

Figure 1 depicts the design of an apparatus constructed in accordance with the present invention and adapted for the purpose of introducing reactive desulfurizing agents into molten ferrous metals;

a reactive element F Fig. 2 is a horizontal view of a portion of the apparatus depicted in Figure l with the apparatus being shown in the open position;

Figure 3 is a view on an enlarged scale of an immersion container utilized for introducing the reactive addition alloy;

Figure 4 is a partial view in elevation of a first variant with a device for stirring by induction;

Figure 5 is a similar view of a second variant;

Figure 6 is a view in perspective of an immersion container of this second variant;

Figure 7 is a partial view in elevation of a third variant;

Figures 8 and 9 are horizontal sections along lines VIII-Vlll and IXIX of Figure 7 but on a larger scale;

Figure 10 is an elevation, partly in section, of a further apparatus;

Figure 11 is a section on the line Xl-Xi in Figure 10;

Figure 12 is a section on the line Xil-XII in Figure 10; and

Figure 13 is an elevation of apparatus, essentially as shown in Figure 10, mounted on a carriage.

Broadly stated, the present invention is directed to a method for introducing reactive addition metals having desulfurizing properties into molten ferrous metal while the molten ferrous metal is subjected to substantial pressure and while the molten ferrous metal is being stirred. The pressure utilized in accordance with the invention preferably is generated by introducing into the space above the molten ferrous metal a gas under high pressure.

In the invention, the introduction of the addition element is effected in a closed vessel maintained under a gas pressure at least equal to the vapor pressure of the addition element at the temperature within the vessel so that the addition element is liquefied, and the molten metal is vigorously stirred to mix the liquid addition element with the molten metal. The liquefied addition agent will normally fioat on the molten iron or steel, and the stirring ensures that intimate mixing takes place despite the tendency to float. If more than one addition element is to be introduced, the pressure in the vessel is maintained above that of the addition element with the highest vapor pressure. It is found possible in this Way to retain in the solidified metal a greater proportion of a highly volatile addition agent than has been possible hitherto, and also to control more effectively than hitherto the actual amount of the addition agent retained in the solidified metal.

The result of this is that it is possible, for a given desired content, to know in advance with an adequate degree of accuracy the total amount of the addition ele ment to be introduced, account being taken of unavoidable small losses, such as those due to partial evaporation of some of the addition element during the course of the treatment and those due to slight condensations on the walls of the receptacle in which the treatment is efiected.

The pressure in the vessel should be very high if the best results are to be obtained. For instance, molten iron to be cast is commonly at a temperature of the order of 1500 C. and at this temperature the vapor pressure of magnesium is about lbs./in. in adding magnesium to molten iron at this temperature, therefore, it is necessary for the pressure to be higher than 185 lbs./ in. and preferably it is greater than 225 lbs/i11 To determine the pressure to be used for a particular addition element at the desired operating temperature,

' the Clapeyron equation, as given, for example, in Basic log P +5.158

Pressures of this magnitude can easily be set up by introducing a compressed gas into the vessel. The gas used depends on the nature of the addition agent. If oxidation of the addition element must be prevented in order to prevent loss, the compressed gas should be inert, being preferably argon or nitrogen, and is recovered from the vessel after the mixing is complete for the sake of economy. On adding magnesium to molten iron according to the invention, however, it has surprisingly been found that if compressed air is used the loss of magnesium by oxidation is comparatively small and is more than balanced by the cheapness of compressed air and the simplification of the necessary apparatus.

A vessel equipped with a stirring device and constructed to withstand the high pressure involved cannot readily be used as a ladle into which the metal is poured. The process is therefore preferably carried out in an apparatus comprising a pressure vessel made in upper and lower parts, the upper part being movable to allow a ladle containing molten metal to be put in the lower part and thereafter to make a gas-tight closure with the lower part.

Generally speaking, the apparatus contemplated in accordance with the present invention comprises such a pressure vessel or jacket adapted to hold a ladle of the molten ferrous alloy to be treated, said vessel being provided with gas-tight opening through which the molten metal to be treated and the addition material can be introduced, means for applying gaseous pressure upon the molten metal in said vessel and means for stirring the molten metal while said pressure is being applied thereto.

In order to give those skilled in the art a better understanding of the operation of the invention as adapted to the apparatus depicted in Figures 1 to 3, the following description is given:

The apparatus includes a pressure vessel 3 consisting of a lower part or body 6 and an upper part or a lid 11, the body being carried on a support 5 in a pit 2 which also contains a steel framework 1. The body 6 can be raised and lowered by an hydraulic ram 4. The lid 11 is carried by a frame 12 which can swing in a horizontal plane about a pin 13 in the top of the framework 1, which is made with a slot 14 engaging with a T-shaped projection 15 on the framework. In the position shown in Figure 1 the projection 15 lies in the slot 14, and the frame 12 therefore holds the lid 11 fixed. The ram forces the body 6 hard against the lid 11 to make a pressure-tight joint. In the position shown in Figure 2 the ram 4 has been lowered and the frame 12 swung horizontally to give free access to the interior of the body 6 of the vessel.

Operating fluid is supplied to and released from the ram 4 through a pipe 7 controlled by a three-way cock 8.

When the vessel 3 is open, a ladle 48 containing molten metal 49 can be put into or removed from the body 6. The bottom of the body 6 is recessed at 50 to receive and locate the ladle 48.

The lid 11 carries an openwork container 20 for the addition agent, and this also serves as a stirring device. The container 20 is a bell of graphite or of iron with a refractory coating and has openings 21 in its wall. Before the ladle is introduced into the vessel 3, addition agent 53, e. g. magnesium in small pieces, is put on an asbestos plate 52, and this plate is inserted through the open underside of the container and supported by a grid 22 which is held in position by rods 9. When the ladle is in the vessel 3, the container 20 is immersed in the molten metal, which then enters the container through the openings 21 and causes the addition agent to melt and flow out through the openings. 7

To allow the container 26 to be immersed in the molten metal, it is carried by a rod 19 mounted to slide through the upper part of the vessel and connected externally to a reciprocating piston 10. The rod 19 is secured by a collar 42 to a rod 18 which passes through the lid 11 and carries the piston in a cylinder 17. This cylinder is fixed in a bridge 16 rigid with the frame 12 and so swings with the frame. It is connected by flexible pipes 23 to a valve 24 which controls the supply of compressed air from a pipe 25 to the cylinder 17, each end of the cylinder being put under pressure in turn while the other end is exhausted to the atmosphere through a pipe 26. The valve 24 is operated by a solenoid 27 under to control of a switch 28, opening and closing of the switch causing the valve, and therefore the piston 10 and the container 20, to reciprocate vertically.

The apparatus shown in Figure l is designed for operation with a non-oxidizing gas, 6. g. argon. This is supplied from a high-pressure container 32 through a pipe 39 controlled by a valve 31 to an opening 29 in the body 6. In order to fill the vessel 3 with argon under high pressure, it is necessary first to expel the air, and this is done through an opening 39 in the lid 11, the opening being connected by a flexible pipe 40 to a three-way cock 41 which puts the pipe 40 into communication with the atmosphere during the air expulsion and subsequently is closed.

It will now be appreciated that the sequence of opera tions is to charge the container 20; insert the ladle 48 containing the molten metal 49 in the vessel 3; close the vessel by swinging the frame 12 and then operate the ram 4; expel the air by opening the valve 31 and turn the cock 41 to exhaust the air to atmosphere; close the cock 41 to allow the pressure in the vessel 3 to build up to the desired high value; close the switch 28 to lower the container 20 into the molten metal; and then repeatedly open and close the switch 28 to cause the container 20 to reciprocate and stir the molten metal so as to mix the addition agent with it.

When the liquid metal makes contact with the addition element or elements, the latter melts with a tendency to evaporation. As, however, the pressure in the container is greater than the vapor pressure of this element at the temperature under consideration, it remains liquid. Owing to its low density, compared with that of the alloy being treated, the liquid element tends to float and it is the successive dippings of the container 20 into the metal which ensure the intimate mixing of the said element with the whole of the alloy contained in the ladle.

When the mixing is complete, the valve 31 is closed. Before opening the vessel 3 to remove the ladle and cast the metal it is necessary to release the pressure and recover as much as possible of the argon. This is done by turning the cock 41 to put the vessel 3 into communication with a low-pressure gas reservoir 44 of large capacity through a pipe 43 and then turning the cock 41 to the closed position again. Thereafter the vessel 3 is opened, the ladle is removed and the metal is cast.

To enable the argon to be used again, a valve 46 in a pipe 47 leading from the reservoir 44 to a compressor 38 is opened and the compressor is started. The compressor forces the argon through a pipe 37 controlled by a threeway cock 33 into the cylinder 32. Additional argon to make up for losses can be supplied through a pipe 35 and the cock 33.

To illustrate the importance of the high pressure, the results of some processes carried out in an apparatus as shown in Figure 1 will now be given as Tests I to III and Examples IV and V, Tests I to III illustrating the effects when the pressure, even though high, is not as high as is required by the invention, and Examples IV and V being examples of the invention. In each case magnesium was added to molten iron, and the final contents of magnesium and sulfur retained in the iron as cast were determined. Assuming that all the sulfur removed from the iron reacted with the magnesium, the recovery of magnesium, i. e. the percentage of the added magnesium accounted for, can be expressed as follows: Percent recovery:

Percent retained Mg+ (initial percent S-final percent S) Percent added Mg Test I The molten iron contained:

C Si Mn P S Percent Percent Percent Percent Percent 3. 75 1. 70 0.08 0. 04 0. 032

The temperature of the iron when introduced into the ladle 48 was 1440" C. as read from an optical pyrometer without compensation for emissivity (i. e. a true temperature of about 1500 C.). The mixing operation lasted 2 minutes, the argon pressure being maintained between 42 and 75 lbs./in. During this time the container 20 plunged up and down fifteen times. The temperature of the iron at the end of the operation was 1315 C. (as read). Analysis of the iron showed that the amount of magnesium retained was 0.01%, and the sulfur content was 0.017%. Microscopic examination revealed a flake graphite structure and mechanical properties equivalent to those of an ordinary gray cast iron. The magnesium recovery was 21%.

Test II The molten iron contained:

(3 Si Mn P f S I Percent Percent Percent Percent Percent The temperature (as read) of the iron at the start of the operation was 1420 C. Mixing lasted 1 /2 minutes, the argon pressure being held between 130 and 145 lbs./in. i. e., still well below the vapor pressure of magnesium at the temperature of the iron. The retained magnesium content was 0.01% and the final sulfur content 0.008%. The magnesium recovery was thus 23%, and the graphite was in flake form.

Test III The molten iron contained:

o St I Mn I P s i Percent Percent Percent Percent Percent Example IV The molten iron contained:

l C 1 Si Mn 1 i S 1 Percent Percent] Percent Percent Percent 3. 74 1. 70 0. 08 0. 04 0. 036

The temperature (as read) of the iron at the start of the operation was 1465" C. The operation lasted 2 minutes with an argon pressure between 225 and 268 lbs./in.

i. e., a pressure greater than the vapor pressure of magnesium. The final temperature (as read) was 1300 C. This iron was inoculated with 1% of ferro-silicon (75% Si) which gave a final silicon content of 2.43%. The retained magnesium content of the cast iron was 0.04% .and the final sulfur content 0.007%. The magnesium recovery was thus 62% and the graphite was spheroidal.

A test piece 25 mm. thick, cast in dry sand from the inoculated iron, had a tensile strength, as cast, of 76 leg/mm. (48 tons/m an elongation at fracture of 4% and a Brinell hardness of 229.

Example V The molten iron contained:

The temperature (as read) of the iron at the start of the operation was 1470 C. The operation lasted 2 minutes in a nitrogen atmosphere, the pressure of which was be tween 225 and 254 lbs./in. 1 ie retained magnesium content was 0.05% and the sulfur content 0.007%. The recovery was thus 68%, and microscopic examination showed spheroidal graphite. The mechanical properties of the iron, as cast, were approximately equivalent to those of the iron obtained in Example IV.

The above-cited Examples I V and V show that application of this procedure in accordance with the invention enables contents of magnesium to be obtained which ensure the presence of graphite in spheroidal form in cast iron as a result of quite small additions (0.10%) of magnesium to molten cast iron. Furthermore, the use of magnesium in the pure state ensures economical manufacture. The tests and examples also show clearly that the results desired are only obtained with a treating pressure which is at least equal to the vapor pressure of the addition element at the temperature of the treatment. Those skilled in the art will appreciate that the maximum pressure employed is a practical consideration influenced by the strength of the materials used in the apparatus an the requirements of the particular application.

Stirring of the cast iron or other ferrous alloy during treatment can, or" course, be effected by other means than that described in the course of Test I. There is shown in Figure 4 a first variant in which stirring is obtained by electrical induction, a device already known as such. For this to be done, the vessel 3 is provided inside with a winding 54 suitably insulated from the wall of the container and connected with a high frequency generator 55. The rest of the apparatus is identical with that in Figure 1. It may be noted that, in view of the stirring obtained by means of the winding 54, it is not necessary duringthe treatment to move the bell containing the addition element or elements.

Figures 5 and 6 illustrates another variant in which the container 20 is carried by a shaft 34 mounted to slide through the upper part of the vessel and externally connected to a motor 56, so that the container can be rotated within the metal 49. To ensure adequate stirring the container 20 is provided with vanes 57. The motor 56 and shaft 34 can be moved up and down as a unit by a piston 10 on a shaft 18 secured to a frame 36 in which the motor is mounted. In this variant the rest of the apparatus is identical with that in Figure 1.

Figures 7 to 9 illustrate another variant in which the vessel 3 has dimensions enabling it to receive two ladles, one on top of the other. The molten metal is allowed to run out of the upper ladle 62 onto pieces of magnesium 53 in the lower ladle 53. These pieces are held down by a perforated plate 60 with peripheral notches 61 shaped,

' to pass axially past lugs 59, the plate, after partial rotation, being held by the lugs against axial movement.

The molten metal in the upper ladle 62 can pass through a hole in the bottom of the ladle when a plug 63 is removed. This plug is in position when the ladle is put in the vessel 3 and its upper end is pivoted to a lever 64. This lever is pivoted on the ladle 62, and after the ladle has been put in the vessel 3 the free end of the lever 64 is in contact with a disc 65 on a rod 19 similar to the rod 19 in Figure 1. Then downward movement of the disc 65 rocks the lever and lifts the plug 63. The metal flows into the ladle 58 and the magnesium retained by the plate 60 melts progressively, flowing through the metal, which is stirred by the further metal entering from the ladle 62.

When compressed air can be used to set up the pressure, it is possible to use the much simpler apparatus shown in Figures 10 to 13. This also includes yet another form of stirring device.

in this apparatus a pressure vessel T consists of a relatively shallow lower part and a relatively large upper part 109. The lower part 101 has a refractory lining T02 and lugs 103 which locate and support a ladle 48 containing molten metal 49. The upper edge of the part 101 is frusto-conical as shown at 107 to mate with a complementary surface on the upper part 109, which carries a heat-resistant packing 113 to ensure a tight joint between the two mating surfaces. The part 19? has a flange 110 and the lower part 101 has lugs 103. A ring 114, U-shaped in cross-section, surrounds the flange 110 and the lower arm of the U is recessed to clear the lugs 10% on axial movement. On turning the ring 114 the lower arm of the U engages beneath the lugs 108 to hold the parts 101 and 109 together. The engaging surfaces of the ring 114 and lugs 103 are slightly inclined to produce a wedging action when the ring 114 is turned.

The ring 114 is turned mechanically by a pneumatic ram 115 having a casing connected by a lever 116 to the part 109 and a plunger 117 connected to the ring at 118. The stroke of the ram plunger is such as to bring the ring either into the position in which the lug 108 can pass through the recesses in the ring or into the position in which the parts 101 and 109 of the vessel are urged towards one another to the maximum extent.

The upper part 109 of the vessel in this apparatus has a throat 120 leading to a compartment 119 closed by a cover plate 121 and housing a rod 122 carrying a stirring device 126. This device is a disc and differs essentially from the device of Figure 1 in that it does not contain the addition agent. The addition agent 150, in stick form, is introduced into the part 109 through an opening 141 above the disc 126 while the disc is in its uppermost position shown in dotted lines. The disc supports the addition agent 150 and keeps it from falling into the molten metal 49 until the disc is moved downwards. The opening 141 is closed by a cover plate 142.

The stirring device 126, the rod 122 of which has a refractory covering 127 and carries a centering collar 125, is articulated to a double-armed lever 123 which is rigid with a pivot mounting 124 which passes in fluid-tight fashion through the upper part 109 of the vessel. The lever 123 carries a counterweight 129 and is rocked by an hydraulic ram 131 pivotally mounted on the outside of the upper part 109 of the vessel with its plunger pivotally connected to the lever 123. It will be seen that by causing the ram to reciprocate, the stirring device 126 is first moved downward to allow the addition agent 150 to fall into the ladle 48 and then is moved up and down with some rocking movement in the molten metal, to stir it. To ensure that a magnesium addition agent will readily dissolve in molten iron, the speed of movement of the disc 126 should be about 6 inches per second.

A compressed air reservoir 1.34 is mounted on a bracket 133 on the part 109 and is fed through a pipe 135 controlled by a valve 136. This reservoir is connected to the interior of the vessel 100 by a passage 137 of substantial cross-section, controlled by a valve 138. The size of this passage allows the vessel to be put under pressure quickly.

At the end of the mixing the pressure can be released by opening a valve 140 in an outlet 139 also of substantial cross-section.

The upper part 109 of the vessel can be lifted by a hook on the end of a cable 143 which carries a counterweight 144 and runs over a pulley 146 and a dmm 147 on a rotary beam 148. The drum 147 can be turned by an electric motor 128. The beam 148 which supports the cable can turn on a pillar 149. The upper part 109 can therefore be lowered in succession onto different lower parts 101 arranged around the pillar 149, each lower part containing a ladle of molten metal to be treated. Figure 13 shows two lower vessel parts 101A and 101B mounted on a carriage 151 which can run between end positions determined by chocks 152 and 153 to bring each lower part in turn beneath an upper part 109 arranged to be lifted and lowered by a lifted mechanism fixed in position.

The apparatus shown in Figures 10 to 13 presents the advantage that the time taken by the operations preliminary to the treatment proper with the addition agent is very considerably reduced and thus the metal is at a higher temperature for casting when the mixing is complete. Moreover, with energetic stirring by the device 126 the time of mixing is also reduced, say to 1 minute or 1 /4 minutes, thus reducing the loss of addition agent by oxidation and by condensation on the walls of the pressure vessel.

The results of two processes carried out according to the invention with the apparatus shown in Figtue 10 will now be given. As in the earlier tests and examples, 200 grams of magnesium were added to 200 kgs. of molten iron in each case.

Example VI The molten iron contained:

0 Si Mn P S m-- Per- Per- Percent cent cent cent Percent 3. 85 1. 72 0. 05 0.05 0. 010

Example VII The molten iron contained:

0 Si Mn P S Per- Per- Par- Percent cent cent mu Percent 3. 6 1. 7 0. 07 0. 04 0. 019

The temperature (as read) when the vessel was closed was 1430 C. The total duration of the operation was 2 /2 minutes, the mixing occupying one minute, and the air pressure was between 239 and 268 lbs./in. The final temperature (as read) was 1370 C., the fall in temperature being thus only 60 C. The retained magnesium content was 0.049% and the final sulfur content 0.008%, so the magnesium recovery was 57%. All the graphite was spheroidal.

The apparatus may be modified further in that the lower part may be no more than a plate-like support for a ladle, and the upper part may be a bell wholly surrounding the ladle.

Naturally if the apparatus shown in Figures to 13 is to be used with a non-oxidising gas, a gas-recovery system similar to that shown in Figure 1 may be added.

The method and apparatus contemplated in accordance with the invention may be used for the purpose of de sulfurizing ferrous alloys or may be used for the purpose of producing alloys of ferrous metals, such as cast iron and steel containing one or more metals, having desulfunizing properties in ferrous metal. As has previously been mentioned herein, magnesium, calcium and cerium are elements having such desulfurizing properties. Those skilled in the art will appreciate that other members of the alkali and alkaline earth metal groups, etc, also are recognized to have such desulfurizing properties, These metals all have melting points lower than that of iron. It will be appreciated that when desulfurization is the primary object then quite small amounts of the reactive elements may be employed. Thus, in the case of magnesium, an amount of magnesium approximately equal on a weight basis to the amount of sulfur in the metal, e. g., cast iron being treated, is usually sufiicient to effect desulfurization. When it is desired to produce alloys containing the reactive metal then somewhat larger additions of reactive metal are employed. For example, in the case of magnesium, amounts of magnesium on the order of up to about 0.5% may be added to the molten cast iron in accordance with the present invention.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

I claim:

1. The method for introducing a reactive metal into a molten ferrous alloy which comprises applying to a bath of said molten alloy a gas pressure at least equal to the vapor pressure of the reactive metal at the temperature of said molten alloy, inserting a reactive metal beneath the surface of said molten alloy and energetically stirring said molten alloy in contact with said reactive metal until substantially all of said reactive metal has become incorporated in said molten alloy.

2. The method for alloying molten metal from the group consisting of cast iron and steel with a reactive metal from the group consisting of magnesium, calcium and cerium which comprises establishing a bath of metal from the group consisting of cast iron and steel, applying to said bath a gas pressure at least equal to the vapor pressure at the temperature of said bath of the reactive metal added, inserting a reactive metal from the group consisting of magnesium, calcium and cerium into said bath and energetically stirring said bath while maintaining said pressure for suflicient time to incorporate said reactive metal substantially in said bath.

3. The process for introducing magnesium into molten cast iron which comprises establishing a bath of molten cast iron, applying thereto a gas pressure at least equal to about the vapor pressure of magnesium at the temperature of said molten cast iron, inserting magnesium into said molten bath and agitating said bath while applying gas pressure thereto until the alloying of magnesium with the molten cast iron is effected.

4. The process for introducing magnesium into molten cast iron which comprise establishing a bath of molten cast iron, applying thereto an air pressure at least equal to about the vapor pressure of magnesium at the temperature of said molten cast iron, inserting magnesium into said molten bath and agitating said bath While applying 10 said air pressure thereto until the alloying of magnesium with the molten cast iron i effected.

5. The process for introducing magnesium into molten cast iron which comprises establishing a bath of molten cast iron, applying thereto a substantially non-oxidizing gas at a pressure at least equal to about the vapor pressure of magnesium at the temperature of said molten cast iron, inserting magnesium into said molten bath and agitating said bath while applying said gas pressure thereto until the alloying of magnesium with the molten cast iron is effected.

6. The process for introducing magnesium into molten cast iron which comprises establishing a bath of molten cast iron, applying thereto argon gas at a pressure at least equal to about the vapor pressure of magnesium at the temperature of said molten cast iron, inserting magnesium into said molten bath and agitating said bath while applying pressure thereto until the alloying of magnesium with the molten cast iron is elfected.

7. The process for introducing magnesium into molten cast iron which comprises establishing a bath of molten cast iron, applying thereto air at a pressure of at least about 225 lbs. per square inch, inserting magnesium into said molten cast iron and agitating said molten cast iron while maintaining said pressure until said magnesium is alloyed with said molten cast iron.

8. An apparatus adapted for the treatment of molten metal under pressure of a gas whereby said gas may be recovered which comprises, in combination, a pressure vessel adapted to hold molten metal, a source of highpressure gas connected to said pressure vessel by a control valve, a low-pressure reservoir connected to said pressure vessel by a control valve and a compressor connected between said low-pressure reservoir and said highpressure source, said compressor being adapted to pump gas from said low-pressure reservoir to said high-pressure source and thereby to recover gas received in said low-pressure reservoir.

9. An apparatus particularly adapted for the introduction of reactive metals into molten ferrous melts and comprising, in combination, a pressure vessel having an opening provided with a gas-tight closure, a container for holding molten metal disposed within said vessel, means for introducing gas under high pressure into said vessel, means for controllably introducing addition material below the surface of molten metal held in said vessel, and a high-frequency induction coil disposed about the molten metal container whereby stirring is effected by electromagnetic induction.

lO. An apparatus adapted for the treatment of molten metal comprising, in combination, a vessel having a lid and being adapted to hold molten metal under pressure, means for supplying gas pressure within said vessel, and a receptacle disposed within said vessel and adapted to hold addition material, said receptacle being provided with outer vanes and being connected through said lid with means for imparting rotational motion to said receptacle.

11. An apparatus adapted for the treatment of molten metal under pressure which comprises, in combination, a pressure vessel adapted to hold molten metal, a source of high-pressure gas connected to said vessel, and mixing means disposed within the pressure vessel and having two ladles placed one atop the other, with the lower ladle adapted initially to contain addition material, and with the upper ladle being provided with a stopper openable from without the vessel.

12. An apparatus adapted for the introduction of reactive metals into molten ferrous alloys and comprising a pressure vessel made in upper and lower parts, the upper part being removable to allow a ladle containing molten metal to be placed in a lower part and thereafter to make a gas-tight closure with said lower part, means for placing the interior of the closed vessel under gas pressure, means for introducing an addition element into the metal '11 in the ladle after the closing of the vessel, and means for bringing aboutvigorous stirring of the metal in theladle while the vessel is closed, the stirring means beinga disc mounted in its uppermost position to support an addition agent introduced through an opening above it, whereby on downward movement of the disc the addition agent is allowed to enter the metal and the metal is stirred by the disc.

13. An apparatus adapted for the introduction of reactive metals into molten ferrous alloys and comprising a pressure vesselmade in upper and lower parts, the upper part being removable to allow aladle containing molten metal to be placed in a lower part and thereafter to make a gas-tight closure with said lower part, means for placing the. interior of the .closed vessel under gas pressure, means for introducing an addition element into the metal llIl the ladle afterthe closing of the vessel, and means for bringing. about vigorous stirring of the metal in the ladle while the vessel is closed, the stirring means being articulated to a double-armed lever having a pivot mounting which passes through theupper part of the vessel, the lever being rockedby adevice itself mounted on the outside of the upper part of the vessel.

14. An apparatus adapted for the introduction of reactive metals into molten ferrous alloys and comprising a pressure vessel made in upper and lower parts, the upper part being removable to allow a. ladle containing molten metal to be placed in a lower part and thereafter to make a gas-tight closure with said lower part, means for placing the interior of the closed vessel under gas pressure, means for introducing an addition element into the metal in the ladle after the closing of the vessel, and means for bringing about vigorous stirring of the metal in the ladle 'while the vessel is closed, the upper part of the vessel being engageable by a hook on a lifting cable carried by a rotary support, whereby the upper partcan be lowered onto different lower parts in succession.

15. An apparatus adapted for the introduction of reactive metals into molten ferrous alloys and comprising a pressure vessel made in upper and lower parts, the upper part being removable to allow a ladle containing molten metal to be placed in a lower part and thereafter to make a gas-tight closure with said lower part, means for placing the interior of the closed vessel under gas pressure,

means for introducing an addition element into the metal inthe ladle after the closing of the vessel, and means for bringing about vigorous stirring of the metal in the ladle while the vessel is closed, two or more lower vessel parts being mounted on a carriage which carries them in turn beneath a single upper part.

16. An apparatus adapted for the introduction of reactive metals into molten ferrous alloys and comprising a pressure vessel made in upper and lower parts, the upper part being removable to allow a ladle containing molten metal to be placed in a lower part and thereafter to make a gas-tight closure with said lower part, means for placing the interior of the closed vessel under gas pressure, means for introducing an addition element into the metal in the ladle after the closing of the vessel, and means for bringing about vigorous stirring of the metal in the ladle while the vessel is closed, the upper and lower parts of the vessel presenting conical mating surfaces, one of which is recessed to receive a packing.

17. An apparatus adapted for the introduction of reactive metals into molten ferrous alloys and comprising a pressure vessel made in upper and lower parts, the upper part being removable to allow a ladle containing molten metal to be placed in a lower part and thereafter to make a gas-tight closure with said lower part, means for placing the interior of the closed vessel under gas pressure, means for introducing an addition element into the metal in the ladle after the closing of the vessel, and means for bringing about vigorous stirring of the metal in the ladle while the vessel is closed, the two parts of the vessel interengaging by relative axial movement followed by rotary movement of a locking ring on one part into engagement with fixed lugs on the other part, and a poweractuated device being provided on the first part to turn the locking ring.

18. The process for introducing magnesium into molten cast iron which comprises establishing a bath of molten cast iron, applying thereto air at a pressure of at least about 185 pounds per square inch, inserting magnesium into said molten cast iron and agitating said molten cast iron while maintaining said pressure until said magnesium is alloyed with said molten cast iron.

References Cited in the file of this patent UNITED STATES PATENTS Re. 13,849 Simpson Dec. 15, 19l4 1,707,161 Hoy Mar. 26, 1929 1,808,145 Machlet June 2, 1931 2,485,760 Millis et al. Oct. 25, 1949

Claims (1)

1. THE METHOD FOR INTRODUCING A REACTIVE METAL INTO A MOLTEN FERROUS ALLOY WHICH COMPRISES APPLYING TO A BATH OF SAID MOLTEN ALLOY A GAS PRESSURE AT LEAST EQUAL TO THE VAPOR PRESSURE OF THE REACTIVE METAL AT THE TEMPERATURE OF SAID MOLTEN ALLOY, INSERTING A REACTIVE METAL BENEATH THE SURFACE OF SAID MOLTEN ALLOY AND ENERGETICALLY STIRRING SAID MOLTEN ALLOY IN CONTACT WITH SAID REACTIVE METAL UNTIL SUBSTANTIALLY ALL OF SAID REACTIVE METAL HAS BECOME INCORPORATED IN SAID MOLTEN ALLOY.

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