US3364978A

US3364978A - Method of centrifugal casting of clean ingots

Info

Publication number: US3364978A
Application number: US414116A
Authority: US
Inventors: Tanoue Toyosuke; Sugitani Yasuo
Original assignee: Sumitomo Metal Industries Ltd
Current assignee: Nippon Steel Corp
Priority date: 1963-11-30
Filing date: 1964-11-27
Publication date: 1968-01-23
Anticipated expiration: 1985-01-23
Also published as: GB1092627A

Description

Jan. 23, 1968 TOYOSUKE TANOUE ET AL METHOD OF CENTRIFUGAL CASTING OF CLEAN INGOTS Filed NOV. 27, 1964 5 Sheets-Sheet l M J 12 5 I I5 INVENTORS:

ATTORNEYS Jan. 23, 1968 TOYOSUKE TANOUE ETAL 3,364,978

METHOD OF CENTRIFUGAL CASTING OF CLEAN INGOTS Filed Nov. 27, 1964 5 Sheets-Shegt 2 INVENTORS M 1 ATTORNEY;

Jan. 23, 1968 TOYOSUKE TANOUE ET AL 3,354,978

METHOD OF CENTRIFUGAL CASTING OF CLEAN INGOTS Filed Nov. 27, 1964 5 Sheets-Sheet 3 INVENT OR hwi United States Patent Office 3,364,978 Patented Jan. 23, 1968 3,364,978 METHOD F CENTRIFUGAL CASTING 0F CLEAN INGGTS Toyosulre Tanoue, Toyonaka, and Yasuo Sugitani, Nishinomiya, Japan, assignors to Sumitomo Metal Industries Limited, Osaka, Japan, a corporation of Japan Filed Nov. 27, 1964, Ser. No. 414,116 Ciaims priority, application Japan, Nov. 30, 1963, 38/64,6t)tl 6 Claims. ((11. 164-114) ABSTRACT OF THE DISCLOSURE Methods of producing clean ingots containing few nonmetallic inclusions by forcibly floating and separating nonmetallic inclusions present in molten steel including the steps of pouring the molten steel into a vertical ingoting mold while rotating said mold about its vertical axis so as to cause the nonmetallic inclusions to travel toward said vertical axis, and then while keeping the mold rotating even after the completion of pouring, bodily revolving the mold about a fixed vertical rotary axis spaced from the vertical axis of said mold and simultaneously inclining the same about a horizontal axis so that the head part of the mold approaches said vertical rotary axis. In some cases, for example, for alloy steels which are easily segregated into individual components, it is preferable to stop the mold from rotating about its own vertical axis during the step of inclining and revolving the mold around the spaced vertical rotary axis.

This invention relates to methods of producing clean ingots containing few nonmetallic inclusions by forcibly floating and separating nonmetallic inclusions present in molten steel produced during its solidification in making ingots by pouring the molten steel into an ingoting mold.

Generally it is well known that, in producing steel or specifically high grade steel, nonmetallic inclusions contained in steel will have a great influence on the quality of the product, production yield and the amount of conditioning. A great many efforts have been made to decrease and remove nonmetallic inclusions since long ago. As well known, as causes of the formation of nonmetallic inclusions in steel, there can be enumerated such facts that Mn, Si or Al added to remove 0 in the steel will form oxide which will remain in the product ingot and that, when the molten steel is tapped or poured, it will be oxidized in contact with air and various oxides will be formed in the steel. However, such inclusions are formed at various steps of the steel making process and there is no proper way to avoid these causes. Therefore, though there have been many studies and many investigations on preventing and decreasing nonmetallic inclusions, insofar as we are aware no entirely satisfactory method has been obtained prior to the present invention.

An object of the present invention is to produce clean ingots containing very few nonmetallic inclusions by pouring molten steel into a rotating mold in vertical portions and then revolving the rotating mold around a vertical rotary axis while gradually inclining the mold so that the head part of the mold approaches the vertical rotary axis. In some cases, after pouring the molten steel into the rotating mold, the rotation of the mold is stopped while revolving the mold around said rotary axis and gradually inclining the mold. In either case, centripetal force acts on nonmetallic inclusions in the molten steel to increase their buoyancy and thus the nonmetallic inclusions are forcibly floated up to the head part of the ingot and separated.

A second object of the present invention is to make unnecessary all the conventional efforts and measures of decreasing nonmetallic inclusions in melting, refining and ingoting.

A third object of the present invention is to produce high grade special steel by a converter or an open hearth furnace with lower production cost, instead of an electric furnace which has been regarded heretofore as the only furnace to be able to produce such steel.

A further object of the present invention is to eliminate the fear of deteriorating the quality of the steel even if a cheap refractory is used in producing a high grade steel.

In the drawings,

FIGURE 1 is an explanatory view of the forces involved in the preferred embodiment of the present invention.

FIGURE 2 is a vertical sectional view of an apparatus that may be utilized to practice the present invention.

IGURE 2A is a vertical sectional view of another apparatus embodying the present invention.

FIGURE 3 is an explanatory view showing positions in a test ingot in which the degree of cleanness was tested.

FIGURE 4 is a vertical sectional view of a modification of the apparatus according to the present invention.

The principle of the method of the present invention shall be explained with reference to FIGURE 1.

When a mold 1 is revolved at a revolving velocity of n (r.p.m.) around a rotary axis 14, a nonmetallic inclusion of a radius r (cm.) in a molten steel in the mold 1 will be subjected to a buoyancy Fr (dyne) represented approximately by the formula I:

wherein p (gr./crn. is the density of the molten steel, p is the density of the nonmetallic inclusion, 1 (cm.) is the distance from the rotary axis 14 to the nonmetallic inclusion and g is the acceleration of the gravity, n (r.p.m.) is the revoluting velocity r (cm.) is the radiums of nonmetallic inclusion.

Further, the bouyancy Fg (dyne) by the gravity is represented by the Formula II:

Both of these buoyancies Pr and Fg will be combined to produce a resultant buoyancy Ft represented by the Formula III:

By this resultant buoyance Ft, the nonmetallic inclusion in the molten steel will be floated and separated. The floating direction of this nonmetallic inclusion will be given by the Formula IV:

lain 9-tan IV If the mold is revolved while the angle of the inclined mold is equal to the angle 0, representing the floating direction, the nonmetallic inclusion will be able to be floated up and separated at the upper surface of the ingot.

In the present invention, the molten steel is poured into the rotating mold and, then after the completion of the pouring, the mold is revolved while being inclined. As a result, the nonmetallic inclusion will be separated in the outer shell part of the solidifying ingot during the pouring.

The number of rotations per unit time of the mold required to effect the method of the present invention depends on the size of the ingot. In the case where the ingot is relatively large, the number of rotations is low. on the other hand, when the ingot is relatively small, the number of rotations may be higher. The preferable number of rotations is 30 to r.p.m. In case the number of rotations is less than 30 r.p.m., the nonmetallic Example 1 In making an Si Killed steel ingot of 100 kg, the amount of nonmetallic inclusions in an ingot made by the method of the present invention wherein the molten steel was poured into a mold rotating at a vertical position at a rotating velocity of 60 r.p.m., the rotation was stopped after the pouring and the mold was revolved around a rotary axis while being gradually inclined until the completion of solidification is shown in Table 1. The value of Ft/Fg is selected to be and also shown in this table for comparison are figuresfor an ingot made by a conventional method of top pouring. The positions in the ingot factor in this table represent those shown in FIGURE 3.

TABLE 2 Ingoting Methods 5 Conventional Method of the Present Method Invention Ft/Fg 0 2 4 7 10 Number of rotations 1O (r.p.m.) 0 s7 53 e9 82 Positions in the Ingot:

As evident from Table, 2, in the method of the present invention, the larger the value of F t/Fg or the larger the TABLE 1 Positions Sizes of Inclusions Producing Methods Composl- 1n the tlons ingot 5. 7 0 0 4. 4 0 0. 6 4. 4 0. 6 0 C, 0.02%--.. 10. l 0 0 Method 0! the present lnvention Si, 0.40%.-" 8.2 1. 8 0 0.09 13.9 1. 3 0 12. 7 2. 4 0 13. 3 0. 6 0 12. 0 5. 7 1. 8 6.3 0. 6 0

50. 0 12. 4 2. 5 30. 4 9. 3 1. 3 50.0 11.4 1. 3 Conventional top-pouring ingoting {g method- Mn, 0.07%... 46. a s. s 5.1

It is evident from Table 1 that, in the ingot made by the method of the present invention, as compared with the ingot made by the conventional method, the nonmetallic inclusions in the former are so much fewer as to decrease by 2% in 2.1 to 6.3;]. in size of inclusion, 80% in 6.3 to 12.6 1. in size of inclusion and 90% in 12.6 to 21.1 in size of inclusion and 94% in more than 21.1 in size of inclusion and that the ingoting method according to the present invention is very .efiective to separate and remove nonmetallic inclusions larger than 6n.

Example 2 angle of inclination of the mold revolving around the rotary axis, the less the nonmetallic inclusions in the ingot.

Example 3 In making an Al Killed steel ingot of 100 kg., the intimes the test of checking the number of nonmetallic inclusions on the intersection 400 as the field of vision in a microscope of a magnification of 400 was divided into sections 20 x 20; the result of this test for the positions in the ingot shown in FIGURE 3 being shown in Table 3. In this case the method of the present invention was utilized wherein the molten steel is poured into a mold rotating in vertical positionat a rotating velocity of 60 r.p.m., the rotation then being stopped and the 7 mold revolved around a rotary axis while being gradually inclined until the solidification occurs. The value of F t/F g shown in FIGURE 1 is selected to be 10 and results of an ingot made by a conventional top-pouring ingoting method are also shown in Table 3 for comparison.

As found from Table 3, it is evident that the Al Killed TABLE 3 Inclusion Cleanness Producing Positions Degrees Methods Compositions in the Ingot Type 13 Type C 0 0 0. 010 0. 224 Method of the 0 0.340 present inven- 0. 010 0. 224 tion. 0 0.120 Amount of addi- O. 002 0. 153 tion of A, 2.5 0 0. 056 kgJt. 0 0. 046 O 0. 021 O 0. 027

1. 600 0. 750 (C, 0.01% 0. 754 0. 380 Conventional Si, 0.01% 0.171 0. 4:26 top-pouring Mn, 0.02% d l. .117 0. 038 ingoting 0. 027 l. 140 method. Amount of add;'.- 0 l. 690 tion of A, 2.5 0. 250 0. 115 kgJt. 0. 022 0. 245 0. 071 0. I12 0 0. 183

steel ingot made by the method of the present invention is much higher in the inclusion cleanness degree than by the conventional top-pouring ingoting method. The type B inclusions (of the alumina series) present, as concentrated, decreased by more than 90%. The type C inclusions (of the other oxide series than silicate alumina) decreased by about 65%. That is to say, it is evident that, by the method of the present invention, not only the silicate inclusions in the Si Killed steel but also the alumina inclusions in the Al Killed steel can be separated and removed from the molten steels.

All the above described examples are of the case wherein a molten steel was poured into a rotating mold, then the rotation of the mold was stopped and the mold was bodily revolved around a rotary axis while being grad ually inclined until the solidification finished. However, in the result of the experiment of the present invention wherein a melt of an Al Killed steel was poured into a mold rotating at a vertical position at 60 rpm. and then while the rotation of the mold was being continued, the mold was revolved around a rotary axis while being gradnally inclined so that the value of Ft/Fg is selected to be 10, the inclusion cleanness degree was the same as before. That is, the degree of the decrease of inclusions was on the same level as in the case wherein the rotation of the mold was stopped after the pouring.

Further, comparison was made in the positions b, d, f, h and j in the ingot shown in FIGURE 3 of the result of an Al Killed steel made by conventional methods and the present method. In other words, in the former wherein the mold was not rotated but the molten steel was poured into the upright stationary mold and then, without being rotated, the mold was revolved while being inclined so that the value of Ft/Fg is the inclusions were about the same as with the method of the present invention wherein the mold was revolved and inclined while being rotated. But, in the outside positions a, c, e, g and i of the ingot, there was seen a result in the conventional method that the rate of separation of nonmetallic inclusions was lower than in the present inventive case wherein the mold was rotated. Thus, in the method of the present invention, wherein, after a melt is poured into a rotating mold, the mold is revolved and inclined while being rotated, nonmetallic inclusions in the outside part of an ingot are at a minimum.

An embodiment of the apparatus for working the method of the present invention shall be explained with reference to the drawings. In FIGURE 2, an ingoting mold 1 is fixed by fasteners 3 to a rotary plate 2 placed on a base plate 4 through a bearing.

Until the pouring is completed, a rotary shaft 5 engages with a rotation transmitting shaft 7 and the base plate 4 will engage with columns 6 so that the mold 1 may be rotated around its vertical center axis by power from an electric motor 8 working through a reduction gear 9. The rotation transmitting shaft 7 and the columns 6 are so made as to be raised and lowered through a change-over device by the power from the motor 8. When the rotation transmitting shaft 7 and the columns 6 rise, the rotation transmitting shaft 7 will engage with the rotary shaft 5, the columns 6 will engage with the base plate 4 and the mold will rotate. But, in case the rotation transmitting shaft 7 and the columns 6 fall, they will disengage respectively and the mold will not rotate. The ingoting mold 1 is hung on fulcra 12 of .a rotary arm 11 though two hooks 10 fixed to both sides of the base plate 4. Said rotary arm 11 is mounted on a center column 14 through a bearing 15 so as to be rotated around a rotary center axis by power received in the lower part of an auxiliary column 17 which is integral with the rotary arm 11. The column 17 is in contact with the center column 14 through rollers 18 and driven by means of an electric motor 19, reduction gear 20, bevel gears 21 and belts 22. When the rotary arm 11 begins to rotate around the rotary center axis 16, the mold 1 revolves and is inclined, as shown in FIGURE 2, by the centrifugal force. A pin 13 is required to so determine the angle of inclination of the mold as to substantially coincide with the determined floating direction of the nonmetallic inclusions.

This embodiment is of the case wherein the mold is revolved while being inclined around the rotary center axis by the rotation of the rotary arm. Another embodiment wherein the mold is revolved while being inclined around the rotary center axis by the rotation of the center column is illustrated in FIGURE 2A.

In FIGURE 2A, the center column 14 is mounted at the lower part thereof on a bearing 23 and has the rotary arm 11 integrally secured thereto in the upper part thereof. The mechanism which causes the mold 1 to rotate until the melt is poured is the same as in FIGURE 2. But, after the pouring, the molds 1 'hung through the two hooks 10 on the fulcra 12 of the rotary arm 11 made integral with the center column revolve around the rotary center axis. The molds 1 are thus caused to be inclined as shown in FIGURE 2 due to the centrifugal force by the rotation of the center column 14; power being transmitted from the motor 19 through the reduction gear 20, bevel gears 21 and belts 22, as before.

FIGURE 4 shows a modification of the apparatus of the present invention. In FIGURE 4, for rotating the mold 1 around its center axis, there is provided a pivotally mounted frame 24 for the mold 1, which frame 24 is rotatably mounted on a plate 27 through bearing means 25 provided between the bottom of the frame 24 and the plate 27 which is in turn fixed to a base frame 26. Provided Within the base frame 26 is a motor 28 having on an end of its shaft a bevel gear 29 to be engaged with a bevel gear 34} carried by the frame 24. The base frame 26 is pivotally supported by the rotary arm 11 in such manner as shown in FIGURE 2 so that the mold 1 may be revolved around the vertical rotary axis 16 While inclining of the mold as aforementioned takes place. Thus, the frame 24 along with the mold 1 is rotated around its center axis by the operation of the motor 28. The electric source of motor can be introduced through conventional rotary contact maker mechanism (not shown) fitted between the auxiliary column 17 or the center column 14.

In accordance with obvious variations of the above, the method of the present invention can be applied to various steels and to a mass-production system if desired. Furthermore, it is clear that operation of the apparatus of the present invention can be remote-controlled by employing conventional controls.

What is claimed is:

1. A method of producing clean ingots of steel comprising the steps of'pouring a molten steel into an ingoting mold while rotating said mold about its vertical axis and revolving and inclining said ingoting mold around a vertical rotary axis spaced from said first mentioned axis so as to cause the head part of the mold to approach said vertical rotary axis while maintaining the rotating action of said mold, whereby nonmetallic inclusions may be separated and removed at said head part by centripetal force caused by the rotating and revolving action.

2. A producing method claimed in claim 1, wherein said revolving operation is performed within the range of 30 r.p.m.150 r.p.-m.

3. A producing method claimed in claim 2, wherein said revolving and inclining operation is performed around the vertical rotary axis so that the ratio Ft/Fg is within the range of 2-10.

4. A method of producing clean ingots of steel comprising steps of pouring a molten steel into an ingoting mold while rotating said mold about its vertical axis, stopping the rotation of the mold, and revolving and inclining said ingoting mold around a vertical rotary axis spaced from said first mentioned axis so as to cause the head part of the mold to approach said vertical rotary axis while maintaining the rotating action of said mold, whereby nonmetallic inclusions may be separated and removed at said head part by centripetal force caused by the rothe vertical rotary axis so that the ratio Ft/Fg is within the range of 2-10.

References Cited UNITED STATES PATENTS 2,992,463 7/1961 Berger 164-289 444,162 1/1891 Sebenius -L. 164-114 1,951,881 3/1934 Northrup 164-118 X 2,023,040 12/1935 Adams 164-262 2,193,537 3/1940 Nelson 164-116 2,208,230 7/1940 Rubissow 164-114 2,659,107 11/1953 De Bell 164-116 2,961,703 11/1960 Pinotti 164-289 X 3,117,346 1/1964 Bertin et a1 164-290 X FOREEGN PATENTS 622,240 4/ 1949 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner.