CONTINUOUS CASTING MACHINES

Abstract: A continuous casting machine comprises a plurality of mould blocks (1) connected to form two endless tracks (2) which cooperate to define a mould cavity and a tundish (13) which supplies melt through a tundish nozzle (20) into one end of the mould cavity into which the tundish nozzle extends. A hydraulic cylinder (27) is arranged to adjust the angle of inclination of the tundish nozzle (21). Position sensors (29, 29′) positioned adjacent the said one end of the mould cavity are arranged to produce signals representative of the distance (L, L′) of the mould blocks (1) of each endless track. Control means (32) are responsive to the signals and arranged to supply a command signal to the cylinder (27) to cause it to adjust the angle of inclination of the tundish nozzle (21) to maintain the gaps between the tundish nozzle and the endless track substantially at predetermined values.

Description: The present invention relates to continuous casting machines and is concerned with the melt pouring apparatus of such machines. More specifically, the invention is concerned with a continuous casting machine of the type comprising a plurality of mould blocks connected to form upper and lower endless mould block assemblies having respective opposed runs which, in use, are moved in the same direction to define together a mould cavity and a tundish which, in use, supplies melt through a tundish nozzle into one end of the mould cavity into which the tundish nozzle extends, the angle of inclination of the tundish nozzle being adjustable. A known continuous casting machine of moving mould type is shown in Figure 1 which is a diagrammatic side elevation. This machine comprises a plurality of mould blocks 1 connected to form a pair of endless mould assemblies 2 and 2′. These mould assemblies 2 and 2′ are disposed one above the other to define a continuous mould cavity between them. In use, the mould assemblies 2 and 2′ are driven by drive wheels 3 and 3′ in the direction indicated by the arrows 4 and 4′ and melt is poured into the mould cavity at one end through a tundish nozzle 6 extending from a tundish 5 and a cast strand 7 is withdrawn from the other end of the mould cavity, as indicated by the arrow. In order to prevent leakage of melt in the machine described above, the gap between the tundish nozzle 6 within the mould cavity and the mould blocks 1 defining the mould cavity must be maintained at a predetermined small value with a high degree of dimensional accuracy. To this end, a tundish nozzle aligning system is generally used of the type shown in Figures 2 to 5 in which Figure 2 is a diagrammatic side elevation of the aligning system and Figures 3 to 5 are views in the direction of the arrows III, IV and V in Figure 2, respectively. In this system the vertical position as well as nose-up and nose-down of the nozzle can be adjusted by operating hand wheels 45 operatively connected to jacks 44 mounted on the tundish supporting stand 48. The horizontal position of the nozzle 6 can be adjusted by moving the jack stand 49 located below the tundish supporting stand 48 by operating push bolts 46 and draw bolts 47, as shown schematically in Figure 4. As best shown in Figure 5, rotational alignment (inclination in the plane perpendicular to the nozzle axis) of the nozzle can be adjusted by adjusting nuts 53 of specially designed bolts 52 pivotably connected by pivot pins 51 to a car frame 50. However, this system is not always effective in keeping the gap between the nozzle and the mould blocks at the predetermined small value. This is because any vertical deviation in the position of the individual mould blocks 1 must be compensated for by adjusting the nozzle 6 by manual operation of the hand wheels 45. This is in practice impossible, which results in failure to maintain the gap at the predetermined size. As a result, the tundish nozzle 6 tends to contact the blocks 1 with considerable force and thus to become non-uniformly worn or damaged. The present invention aims to substantially overcome the above and other problems encountered in conventional pouring apparatus for moving mould type continuous casting machines and has as its object the maintainance of a small gap of predetermined size between the tundish nozzle and the mould blocks at all times, thereby ensuring the safety of the tundish nozzle and the moving mould blocks. Continuous casting apparatus including tundishes whose angle of inclination is controlled automatically by means of sensors are disclosed in JP-A-56-151143 and JP-A-62-57747. JP-A-56-151143 discloses sensors which sense the distance between them and the mould blocks of a casting machine: the preamble of claim 1 is based on this document. According to the present invention a continuous casting machine comprises a plurality of mould blocks connected to form upper and lower endless mould block assemblies having respective opposed runs which, in use, are moved in the same direction to define together a mould cavity and a tundish which, in use, supplies melt through a tundish nozzle into one end of the mould cavity into which the tundish nozzle extends, the angle of inclination of the tundish nozzle being adjustable, actuating means arranged to adjust the angle of inclination of the tundish nozzle, one or more position sensors positioned adjacent the said one end of the mould cavity and arranged to produce signals representative of the distances between the sensors and the mould blocks of each endless track and control means responsive to the signals and arranged to supply a command signal to the actuating means to cause it to adjust the angle of inclination of the tundish nozzle to maintain the gaps between the tundish nozzle and the endless tracks substantially at predetermined values and is characterised in that the tundish nozzle is pivotally connected to the tundish whereby the angle of inclination of the tundish nozzle is adjustable with respect to the tundish and in that the upstream end of the tundish nozzle is part-spherical and is urged into sealing contact with a correspondingly shaped portion of the tundish by biasing means. Further features and details of the invention will be apparent from the following description of one specific embodiment which is given by way of example with reference to Figures 6 to 9 of the accompanying drawings, in which:- Figure 6 is a side view of a preferred embodiment of the present invention; Figure 7 is a view taken along the line VII-VII in Figure 6; Figure 8 is a block diagram illustrating the hydraulic cylinder actuating system; and Figure 9 is a graph illustrating the relationship between the position sensor output and time. A tundish 13 having a short melt outlet 12 is mounted on a tundish car frame 11 comprising a tundish support 8 and a water-cooled jacket 10 with cooling water passages 9. An intermediate member 14 is securely attached to the car frame 11 by joint means 15, such as bolts, in coaxial relationship with the axis of the melt outlet 12. The intermediate member 14 is made of a refractory material and has an axially extending melt pouring passage 17 which is in alignment with a melt pouring passage 16 of the melt outlet 12. The end of the member 14 remote from the outlet 12 is formed with a semispherical recess 19. A tundish nozzle 21, made of a refractory material and surrounded by a steel shell 20, has an axially extending melt passage 18 in coaxial relationship with the melt passage 17. A spherical projection 22 which fits snugly into the semispherical recess 19 in the manner of a ball and socket joint is formed at the upstream end of the tundish nozzle 21. Supporting brackets 24, each having a through hole 23, are securely attached to the upper and lower surfaces of the tundish nozzle 21. Respective guide rods 25, which are pivotally connected at one end by a horizontally extending pin 40 to the tundish car frame 11, are slidably received in the through holes 23 of the brackets 24. The other end of each guide rod 25 carries spring means 26, such as a compression spring, so as to normally bias the supporting bracket 24 toward the tundish car frame 11, whereby the tundish nozzle 21 is pressed against the intermediate member 14. A hydraulic cylinder 27 is pivotally connected at its base end to the tundish car frame 11 by a pin 41 which is parallel to the pins 40. The piston rod 28 of the cylinder 27 is pivotally connected at its leading end to the lower surface of the tundish nozzle 21 by a pin 42 which is parallel to the pin 41 so that when the rod 28 is extended or retracted, the inclination of the tundish nozzle 21 is altered. The cylinder 27 is controlled by a servo valve 37 and is connected to a hydraulic tank 38 via a pump 39. At the inlet to the mould cavity defined by the two endless loops of connected mould blocks 1, i.e. at the position where the mould blocks have passed around the drive wheels 3 and 3′ and have moved into opposing relationship with each other, position sensors 29 and 29′, such as eddy-current position sensors, are securely fixed at the midpoints of brackets 31 and 31′, which extend in the widthwise direction of the mould cavity between supporting columns 30 (see Figure 7). The sensors 29, 29′ are arranged to measure the distances L and L′ from the surfaces of the passing mould blocks 1. As shown in Figure 8, the outputs of the position sensors 29 and 29′ are delivered to a control device, generally indicated by numeral 32, and the results of the arithmetic operations performed by the control device 32 are delivered to the servo valve 37. The control device 32 comprises A/D converters 33 and 33′, arithmetic units 34 and 34′, a comparator 35 and a D/A converter 36. As the leading end X of a mould block 1 passes over the associated position sensor 29 the distance ℓ₁ therebetween is measured and after a time interval t₁, determined on the basis of the velocity of the mould blocks 1, the distance ℓ₂ to the midpoint Y of the mould block is measured (see Figure 9); the size of the gap Δ c between the leading end of the tundish nozzle 21 and the mould blocks corresponding to the distance ℓ₂ is calculated on the basis of data obtained in an initial trial. In like manner, after the leading end X of a mould block 1 passes over the position sensor 29′ and distance ℓ₁′ therebetween is measured and after a time t₁ determined on the basis of the velocity of the mould blocks 1, the distance ℓ₂′ measured to the midpoint Y of the block mould 1. Thereafter, gap Δ c′ between the leading end of the tundish nozzle 21 and the mould blocks corresponding to the distance ₂′ calculated on the basis of the data obtained in trial operation. The signals representative of the gaps Δ c and Δ c′ thus obtained are delivered to the comparator 35 a certain time after the mould blocks 1 come into opposing relationship with each other and the difference signal is fed from the comparator 35 to the servo valve 37 which actuates the hydraulic cylinder 27 to eliminate the difference. The mode of operation of the preferred embodiment is as follows: First, in an initial trial without using melt, the value of the gaps Δ c and Δ c′ between the leading end of the tundish nozzle 21 and the opposing block moulds 1 corresponding to distances ℓ₂ and ℓ₂′, respectively, at the intermediate points Y of the block moulds 1 are actually measured and the data thus obtained is fed into the arithmetic units 34 and 34′ in the control device 32. In actual operation, the distances L and L′ measured by the position sensors 29 and 29′ located at the inlet of the mould cavity are converted by the A/D converters 33 and 33′ into digital signals which in turn are delivered to the arithmetic units 34 and 34′ where distances ℓ₂ and ℓ₂′ to the midpoints Y of the mould blocks 1 are used to produce values of the gaps Δ c and Δ c′ by arithmetic operation on the basis of the data obtained in the trial operation. The signals representative of the gaps Δ c and Δ c′ thus obtained are delivered to the comparator 35 after a sufficient period of time for the mould blocks 1 to have reached the leading end of the tundish nozzle 21 so that difference between gaps Δ c and Δ c′, i.e. the deflection of the leading end of the tundish nozzle 21 toward the upper or lower mould blocks 1 is obtained. The difference signal thus obtained is converted by the D/A converter 36 into an analog signal which in turn is delivered to the servo valve as an actuating signal for the hydraulic cylinder 37. The servo valve 37 is thus actuated to extend or retract the rod of the cylinder 27 by such a distance that the tundish nozzle 21 is tilted or inclined about the portions 19 and 22 and the gaps between the leading end of the tundish nozzle 21 and the opposing mould blocks 1 are maintained substantially constant to prevent contact of the leading end of the tundish nozzle 21 with the upper or lower mould blocks 1 which would otherwise result in local wear or breakdown of the leading end of the tundish nozzle 21. Tilting movement of the tundish nozzle 21 due to extension or retraction of the rod of the cylinder 27 does not result in leakage of melt from the connection of the nozzle 21 since the nozzle 21 is urged against the intermediate member 14 by the springs 26. Even if some deformation results in the inclination of the axis of the melt outlet 12 of the tundish 13 with respect to the axis of the tundish nozzle 21, leakage of melt from the connection of the nozzle is prevented since no gap is produced due to the cooperation of the semispherical surfaces 19 and 22. It will be understood that the present invention is not limited to the preferred embodiment described above and that various modifications may be effected. For instance, a plurality of position sensors 29 and 29′ may be arranged spaced apart across the width of the mould blocks and the tilt of the leading end of the tundish nozzle 21 controlled in response to the mean value of the outputs of the position sensors, whereby any inclination in the widthwise direction of the mould blocks 1 and any surface roughness do not adversely affect the positioning of the leading end of the tundish nozzle 21. It will also be understood that in the embodiment described above although the distance ℓ, is measured the actual value of this distance is not used and the measurement is made only to establish the position of the leading end of the mould blocks.

Claims: A continuous casting machine comprising a plurality of mould blocks (1) connected to form upper and lower endless mould block assemblies (2) having respective opposed runs which, in use, are moved in the same direction to define together a mould cavity and a tundish (13) which, in use, supplies melt through a tundish nozzle (20) into one end of the mould cavity into which the tundish nozzle extends, the angle of inclination of the tundish nozzle being adjustable, actuating means (27,28) arranged to adjust the angle of inclination of the tundish nozzle (21), one or more position sensors (29,29′) positioned adjacent the said one end of the mould cavity and arranged to produce signals representative of the distances (L,L′) between the sensors (29,29′) and the mould blocks (1) of each endless track and control means (32) responsive to the signals and arranged to supply a command signal to the actuating means (28) to cause it to adjust the angle of inclination of the tundish nozzle (21) to maintain the gaps between the tundish nozzle and the endless tracks substantially at predetermined values, characterised in that the tundish nozzle (21) is pivotally connected to the tundish (13) whereby the angle of inclination of the tundish nozzle (21) is adjustable with respect to the tundish (13) and in that the upstream end of the tundish nozzle (21) is part-spherical and is urged into sealing contact with a correspondingly shaped portion (14) of the tundish by biasing means (26). A machine as claimed in claim 1 characterised in that the control means (32) includes two arithmetic units (34,34′) which are arranged to produce signals representative of the magnitude of the gaps (Δc, Δc′) between the tundish nozzle (21) and the mould blocks (1) of the two mould assemblies and which are connected to a comparator (35) arranged to produce a difference signal. A machine as claimed in any one of the preceding claims characterised in that the actuating means comprises a hydraulic cylinder (27) and piston rod (28) which are pivotally connected to the tundish nozzle (21) and a tundish car frame (11) carrying the tundish (13).

Inventors: HASEBE, NOBUHISA, NAKADA, MASAYUKI, OSADA, SHIRO, TAKAHASHI, SHUZO, TSUCHIDA, YUTAKA
Applicants: ISHIKAWAJIMA-HARIMA  JUKOGYO KABUSHIKI KAISHA, NIPPON KOKAN KABUSHIKI KAISHA
Application year: 1989
Main classification: B22D11
IPC codes: B22D11