US3118195A

US3118195A - Continuous casting apparatus and method

Info

Publication number: US3118195A
Application number: US99791A
Authority: US
Inventors: Gouzou Jacques; Zaeytydt Jean
Original assignee: Centre de Recherches Metallurgiques CRM ASBL
Current assignee: Centre de Recherches Metallurgiques CRM ASBL
Priority date: 1960-04-05
Filing date: 1961-03-31
Publication date: 1964-01-21
Anticipated expiration: 1981-01-21

Description

Jan. 21, 1964 J. GOUZOU ETAL 3,118,195

CONTINUOUS CASTING APPARATUS AND METHOD Filed March 51. 1961 4 Sheets-Sheet 1 INVENTOR5 MM MM Jan. 21, 1964 J. eouzou ETAL 3,113,195

CONTINUOUS CASTING APPARATUS AND METHOD Filed March 51, 1961 4 Sheets-Sheet 2 f/ke , INVENTORS aka Z665 awzdw Ja Zaeyiydz ATTORNEYS Jan. 21, 1964 J. GOUZOU ETAL 3,118,195

CONTINUOUS CASTING APPARATUS AND METHOD Filed March 31, 1961 4 Sheets-Sheet 3 INVENTORS .faayzzes 'azazvzo rfaam 2a qyiydi,

i w Y W ATTORNEYfi United States Patent 3,113,195 CQNTEUGUS CASTING APPARATUS AND BETH-10D Jacques Gouzou, Angieur, and Jean Zaeytydt, Montignies=sur-Sambre, Belgium, assignors to (Ientre National de Recherches Metalinrgiqnes, Brussels, Belgium Filed Mar. 31, 1961, Ser. No. 99,791 Claims priority, application Belgium Apr. 5, 1964) 11 Claims. (Cl. 2257.2)

This invention relates to improvements in continuous casting apparatus in which a mold is reciprocated along the arms of the ingot according to a periodic time-displacement function. The improvements are particularly applicable to apparatus for casting steel.

in the continuous casting of steel, the molten metal is generally poured from above into a water-cooled mold from which it is drawn or guided out downwards by extractor rollers the speed of which can be varied to control the speed of casting. Lubricant is poured on the inside wall of the mold in order to facilitate extraction.

When the ingot emerges from the lower end of the mold it consists of a greater or lesser proportion of liquid core, depending on the time spent in the mold surrounded by a solid skin. The need to obtain a suliicient thickness of this skin limits the speed of casting processes in practice, since if the skin is not thick enough it will be torn by the pull of the extractor rollers and the friction against the walls of the mold. A number of procedures and methods have in fact already been proposed for preventing tears in the skin.

The highest rates of casting in continuous plant installations have been obtained with the mold reciprocating up and down parallel to the mold axis in such a manner that the upward strokes of the mold are faster than the downward strokes. The downward strokes are often slightly faster than the downward movement of the ingot.

Further objects will be apparent from the following de scription when considered in connection with the accompanying drawings in which:

FIGURE 1 is a vertical sectional view showing a mol ing installation,

FIGS. 2 to 4 are graphic diagrams showing operational curves,

FIG. 5 is a side view of one form of mold reciprocator,

FIG. 6 is a side view of a modified reciprocating mechanism for the mold,

FlG. 7 is a side view of a further modified reciprocating device with a pair of cranks,

FIGS. 8 and 9 are side views of two modified mold driving devices in which a crank cooperates with a slide,

FIG. 10 is a side diagrammatic view showing another modified driving structure in the form of electromagnets, and

FIGS. 11 to 13 are diagrammatic side views of three lever crank reciprocators for the mold.

FIG. 1 shows a casting device with a mold 1 reciprocated in a vertical direction by a lever 2 driven by a mechanism 3. The continuous ingot 4 is entrained and guided by extractor rollers 5. Although reci rocation of the mold enables the rate of casting to be increased, owing to there being less tears in practice, there is a demand for still higher speeds but they cannot be obtained with existing plants since tears form in the ingot during the upward travel of the mold and although the tears generally close when the mold again descends, they leave superficial scars, which make the steel unsuitable for many uses.

It has been discovered that the most likely time for a tear to be produced in the ingot skin is near or at the end of the upward stroke of the mold. The risk of tearing is not so great during the first part of t re ascent ddldddd Patented den. 21, 196

owing to the plasticity of the ingot skin, and there is, of course, no danger of tearing during the descent of the mold since the ingot is then under compression. The force necessary for causing tears is naturally transmitted from the mold to the ingot owing to the friction between the mold and the ingot. It has also been discovered that this friction increases as the relative velocity between mold and ingot increases. Therefore if the speed of the mold is reduced in the last part of its upward strokes, the speed of casting can be increased without increasing the number of tears.

This novel method of moving the mold is preferably carried out in such a manner that during an upward stroke its instantaneous speed during the last quarter of the distance of the stroke is less than the instantaneous speed when it was at a similar distance from the bottom of the stroke. The frequency of reciprocation can conveniently be in the range 2 to c.p.s. inclusive. Preferably the downward speed of the mold should exceed that of the ingot by not more than 50% of the speed of the ingot.

These novel methods of reciprocating the mold are of course applicable to continuous casting where the direction of movement of the mold is horizontal. When it is desired to imply that a particular movement of the mold may be applied to vertical or horizontal continuous casting, the terms upstream and downstream are used instead of upwards and downwards.

Several novel devices have been constructed to carry out these methods of reciprocation of the mold, but in order to make the description thereof as clear as possible, it is first proposed to discuss the derivation of particular periodic reciprocating motions at a more general level with the aid of FIGS. 2 to 4 of the drawings. In FIG. 2 the compound time-displacement curve 6 is derived by adding together the two sinusoidal time-displacement curves '7 and 8. Curves 9 and ill represent the first and second time differentials of the curve 6, speed and acceleration. It can be seen by drawing a vertical line UVW so that W is on the displacement curve 6, V is on the horizontal axis and U is the intercept on the speed curve 9, that UV is equal to YZ in the vertical line XYZ in which XZ is equal to VW. Since the curve 6 extends for an equal distance above and below the horizontal line, it therefore follows that at the point W, a given distance from the bottom of the stroke of the curve 6, the velocity is equal to the velocity at the point X at an equal distance from the top of the preceding stroke.

However, if instead of the

curves

3 and 7 being in phase as shown in FIG. 2, they are out of phase by onesixth of the fundamental interval of the curve 7, as shown in FIG. 3, or by one thirty-sixth as shown in FIG. 4, no such relationship with regard to speeds at equal distances from the top and bottom of a stroke of the motion represented by curve 6 will be obtained. It has been fact determined that the speed at a given point on the curve 6 during the last quarter of an upward stroke is less than at a point of a similar distance from the bottom of the upward stroke. In the practical application to the reciprocation of a mold in continuous casting, this relationship is best achieved by using two fundamentals of a frequency ratio of 1:2 and an amplitude ratio in the inclusive range 1:10 to 3 10. The phase shift should not be greater than one-sixth of the fundamental interval of the fundamental motion 7 with the lower frequency.

The devices, all of which are adapted for reciprocating the mold of a continuous casting plant so that its speed at a given instant during the last quarter of the distance of an upward stroke is less than its speed at a similar distance from the beginning of the upward stroke, will now be particularly described.

All the devices shown in FIGS. 5 to 10 are preferably operated so that during the last two-thirds of the downward strokes, the speed of the mold exceeds that of the ingot by not more than 56% of that of the latter. in Belgian Patents Nos. 579,648 and 579,659, methods are described to determine the difference in speed between the ingot and the mold.

in the devices of to abutments are provided on the mold 2-3 so as to cooperate with compression springs 26 at the ends of the travel of the mold. The moduli of compression of the springs are so chosen as to minimize the power needed to drive the mold at the selected frequency. The first device shown in FlG. 5 illustrates a double-acting cam 21 engaging a follower pin 22 on the mold 23 in such a manner that when the cam 21 is rotated by any suitable means, not shown, the mold is reciprocated. Four rollers 24 serve to guide the mold so that it moves in a direction parallel to th axis of the ingot, in this ease, up and down.

In the device for reciprocating the mold as shown in FIGS. 6, a lever 31 is journaled on the pin 22. The ends of this lever 31 slidab-ly engage bushes 3.2 mounted on eccentrics 2'7 and 28, the latter being caused to rotate at a 2:1 speed ratio by the gear drive 29 and 3G. Counter-weights, not shown, can be provided for ensuring the equilibrium in rotation of the eccentrics 27 and 28, and such weights can be alternatively, driven from the

gear drive

29 and 3 3 through shafts with universal joints therein. The phase shift between the up and down movements of the ends of the lever 31 can be adjusted by disengaging the

drive

29 and 3 and turning one gear wheel in relation to the other before engaging it again.

In the device of FIG. 7, the ends of the lever 41 are driven by

cranks

37 and 3? acting through pitmans 38 and iii. The speed ratio of the cranks is fixed at 2:1 by a gearing, not shown.

In the devices of FIGS. 8 and 9, the mold is driven through a mechanism resembling that commonly used in shaping machines. in both devices the crank 51 rotating counter-clockwise at a constant speed bears against a bush 52 which slides in a straight slot as in FIG. 3 or a curved slot as in FIG. 9, as a slotted end 49 of a lever 47 so that this latter is swung up and down about a fixed pivot 48. The other end 5d of the lever is also slotted and engages a bush mounted on the pin 22. In these devices the speed of the ingot mold towards the top stroke is less than that towards the bottom of the stroke because the crank 51 rotates in a counter-clockwise direction. In the device of FIG. 9 the speed relationship is somewhat modified due to the curvature of the end 49.

In all the devices, FTGS. 5 to 9, so far described, the drive is such that the speed of reciprocation is proportional to the speed of the extractor rollers, and this can be conveniently achieved by linking the device with the extractor rollers through a fixedor variable-ratio mechanical-electrical or hydraulic gearing.

In the device shown in FIG. 10, armatures 58 and 59 are moved up and down by electromagnets fed with alternating or pulsating current. The armatures 59 and 58 are connected with the ends of the lever 31 by links 31a whose axial movements can be modified as regards amplitude and wave-form by adjustable leaf-springs 655 and 61. By the use of a variableor fixed-ratio mechanical or hydraulic gearing, the frequency of the pulsating or alternating current can be made proportional to the speed of the extractor rollers. On the other hand, satisfactory results can be obtained with a constant frequency current supply by merely adjusting the stroke of the mold to suit the speed or" the ingot.

Various modifications can be made in the devices described. Thus, instead of transmitting the reciprocating motion directly to the pin 22 on the mold, the motion can be transmitted first at point 59 on an intermediate lever 7-8, FIGS. 11 to 13, pivoted at 63, so that the lever moves the pin 22 up and down.

As another modification, the mass or" the mold could be balanced by springs during the whole or most of its reciprocatory movements.

We claim:

1. A continuous casting method comprising the step of reciprocating the mold in a direction parallel to the ingot axis so that during the last quarter of each upstrean stroke of the mold the instantaneous speed of the mold at a given distance from the end of the upstream stroke is less than the instantaneous speed of the mold during the first part of the upstream stroke at a distance equal to the given distance but measured from the beginning of said stroke.

2. A method according to claim 1, in which during the last two-thirds of the downward strokes of the mold the speed of the mold exceeds that of the ingot by not more than of the speed of the latter.

3. A method according to claim 1, in which the reciprocation of the ingot is in a vertical direction.

4. An apparatus for the continuous casting of steel comprising a mold, and means connected to the mold to periodically reciprocate the mold according to a time displacement law obtained by adding together two fundamental motions in accordance with periodic time displacement laws whose frequencies are different; at least one of the fundamental motions being sinusoidal and the frequency ratio of the periodic fundamental motion being 2:1.

5. An apparatus according to claim 4, in which there are provided means to change the phase shift between the two periodic fundamental motions, said phase shift being not greater than one-sixth of the period of the fundamental motion with the lower frequency.

6. An apparatus according to claim 4, in which a lever and two cranks are connected to the mold, and in which a pitman is provided for each crank.

7. An apparatus according to claim 4, in which two armatures are provided connected to the mold to electromagnetically reciprocate the mold.

8. An apparatus according to claim 4, in which springs are provided for adjusting the amplitude of movement of the mold.

9. An apparatus according to claim 4, in which extractor rollers are provided to guide the mold during the reciprocation.

10. An apparatus according to claim 4, in which a spring is connected to each end of the mold at both ends of its reciprocating travel.

11. An apparatus according to claim 4, in which a crank is provided connected to the mold and in which a lever is provided with the mold to be reciprocated by the crank making a sliding connection with a straight part of the lever.

References Cited in the file of this patent UNITED STATES PATENTS 2,815,551 Hessenberg et al. Dec. 10, 1957 FOREIGN PATENTS 849,418 Great Britain Sept. 28, 1960

Claims

1. A CONTINUOUS CASTING METHOD COMPRISING THE STEP OF RECIPROCATING THE MOLD IN A DIRECTION PARALLEL TO THE INGOT AXIS SO THAT DURING THE LAST QUARTER OF EACH UPSTREAM STROKE OF THE MOLD THE INSTANTANEOUS SPEED OF THE MOLD AT A GIVEN DISTANCE FROM THE END OF THE UPSTREAM STROKE IS LESS THAN THE INSTANTANEOUS SPEED OF THE MOLD DURING THE FIRST PART OF THE UPSTREAM STROKE AT A DISTANCE EQUAL TO THE GIVEN DISTANCE BUT MEASURED FROM THE BEGINNING OF SAID STROKE.

4. AN APPARATUS FOR THE CONTINUOUS CASTING OF STEEL COMPRISING A MOLD, AND MEANS CONNECTED TO THE MOLD TO PERIODICALLY RECIPROCATE THE MOLD ACCORDING TO A TIME DISPLACEMENT LAW OBTAINED BY ADDING TOGETHER TWO FUNDAMENTAL MOTIONS IN ACCORDANCE WITH PERIODIC TIME DISPLACEMENT LAWS WHOSE FREQUENCIES ARE DIFFERENT; AT LEAST ONE OF THE FUNDAMENTAL MOTIONS BEING SINUSOIDAL AND THE FREQUENCY RATIO OF THE PERIODIC FUNDAMENTAL MOTIONS BEING 2:1.