C O N T I N U O U S C A S T I N G OF STEEL BARS

V. V. L o b a n o v , A. Ya. G l a z k o v , M. G. C h i g r i n o v , a n d N. M. F r o l o v s k i i

For continuous casting of square bars (82 X 82 ram) of carbon and a l loy steels "the Sibelektrostai ' p~ant ,ases

two-strand continuous casting machines (UNRS) of the ver t ica l type in which the bars are bent into the horizo~ta~ position below the withdrawal rolls. The overall height of the apparatus is 10. 5 m, the height of the casting p la t -

form being 9. 6 m (Fig. 1).

The in i t ia l period of operation revealed several defects in various units that had to be corrected. In casting

the first heat i t was found that the osci l lat ing movement was not strong enough ~o separate the strand from the wali of the mold. Therefore the slide valve was replaced by a thrott le valve with a booster. For convenience in servic-

ing the throttle valve and the e lec t romechanica l drive mechanism of the detainer, a mark was made at a height of 6.2 m. To prevent j amming of the para l le l hydraulic cylinders, they were mounted on the base plate with hinges. The improved oscil lat ion mechanism operated satisfactorily, but it was impossible to at tain the optimal freeuency and ampl i tude of oscillation, and therefore a new mec~hanism was developed with an e lec t romechanica l drive.

For even distribution of water on the surface of the strand in the zone of secondary cooling the guide shoes

were replaced with rollers; the three rows of slotted sprayers designed by Stal 'proekt were replaced with two rows of cy l indr ica l shoes employing a very fine spary. The entire secondary cooling unit was enclosed in a housing large enough to provide free access to all parts. For ever~ coot;rig

of the strand at the exit from the mold, the upper rows were

arranged with the jets at an angle to the strand~ This sub- s tant ial ly reduced the number of breakouts of meta l in cast ing high-carbon tool steels.

Bar 82. 82 T

Withdrawal rolls

Straighteni machine

Fig. 1. Diagram of continuous casting with automat ic

control of casting speed. 1) Tundish; 2) isotopic source; 3) isotopic detector; 4) discrete ievel indicator; 5) a m - plifier; 6) line regulator; q) regulator; 8) automat ic a c - celerat ion; 9) level indicator; 10)~MU; 11) drive me- chanism; 12) generator; 13) sensing e lement ; 14) au to-

mat ic loop regulator. Fig. 2,

Sibelektrostal ' Plant.

l t

1 !

[i i i

a b

Thick-wal led (a)and thin~walled (b) molds.

Central Scientif ic-Research Institute of Ferrous Metallurgy. ~ a l l u r g ,

No. 7, pp. 16-18, July, 1970.

�9 Consultants Bureau, a division of Plenum Publishing Corporation, 227 W:cst 17th S~reet, Ne~v t

York, N. Y. 10011. All rights reserved. This article cannot be reproduced ]'or an,/ purpose whatsoever t:

without permission o[ the publisher. A copy of this article is available from the publisher [or $15:00. t l

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Fig. 3. Diagram of four-rol l withdrawal machine.

The operation of severat was allowed to fa l l by gravity; instal led on the run-out table; ened to 150 ram, etc.

Gas-e lec t r ic cutt ing was planned, employing equipment manufactured by the Al l -Union Scient i f ic- Research Institute of Electric Welding Equipment. In the set-up and t ry-out period it was found that the head lasted for no more than 10 cuts; the hydraulic mechanism did not move the head at an even speed; the control panel for the e lec t r i ca l equipment was often put out of commission, etc. In addition, this cutt ing system uses a great deal of e lec t r ic i ty , hydrogen, argon, compressed air, and water. Therefore, this system was replaced with ordinary f lame

cutt ing for carbon steels.

Hydraulic shears were designed at the plant, but construction was set aside until final results were obtained

from tests of pulse cutt ing proposed by the Khar'kov Aviation Institute. The first stage of testing the apparatus with continuous casting showed good results. After a few modif icat ions of separate units, it was placed in commerc ia l use.

The original design did not ca l l for au tomat ic control of the withdrawal speed in relat ion to the level of meta l in the tundish. The absence of such equipment made it impossible to cast strands of small section at a speed higher than 2 m / r a i n . Thus, the need for an au tomat ic control system was developed at the plant. It consists of a rad io- isotopic s o u r c e (Cs137), radiat ion detector, and a relay receiving the signal from the detector and actuat ing the level indicator and regulator, which by means of the e lec t romechan ica l booster changes the potent ial at the outlet of the generator supplying the motive force to the withdrawal roils and straightening machine (Fig. 1). Later, an e lec t ron- ic regulator and level gauge manufactured by the Al l -Union Scient if ic-Research Institute of Automatic Ferrous Metallurgy Equipment were p laced in para l le l with the discrete regulator, which increased the operational re l iabi l a i ty of the system.

Automat ic acce le ra t ion and synchronization of the speeds were also added to the control system of the wi th- drawal roils and straightening machine.

The stopper mechanisms with an exposed rectangular shaft in the tundish were replaced with a covered system, which increased the operat ional re l iabi l i ty . Flat two-p iece covers were replaced by arched covers made of wedge- shaped firebricks, which substantially increased the durabil i ty and reduced the cost. The batch ladles were also i m - proved to provide constant heating of the ladle both before and during pouring.

The th ick-wal led copper mold (Fig. 2a) fastened to the frame with studs was replaced with a th in-wal led cop-

per mold (Fig. 2b) freely suspended from the frame, which tr ipled the service life of the mold faces. Also, the mold faces can be changed without removing the frame from the machine.

The two-high withdrawal roils caused compression of the strand, leading to the formation of internai cracks and some slipping due to slight gripping a t the point of transit ion from dummy bar to strand. A four-rol l withdrawal machine (Fig. 3) was designed and manufactured at the plant, and the use of bending rolls made it possible to re - duce the pressure on the strand to 1. 5 tons as wel l as e l imina te slipping.

The mold was lubricated with diesel fuel from a piston pump, ensuring even lubrication of the mold faces.

auxi l iary mechanisms was also improved. In the secondary cooling unit the water the head of the dummy bar was made with a short link (200 ram); a.c. motors were the angle of e levat ion of the dummy bar was increased; the run-out table was wid-

Al l these improvements have increased the re l i ab i l i ty of the apparatus in operation. The output of the con- tinuous casting machine amounted to about 2300 tons a month in a three-month period of operation. In 1969 more than 30,000 tons of continuously cast steel were produced (8-8. 5 heats per 24-h period) for an average annual out- put of 94. 5%

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