R O L L I N G BAR S T E E L ON A 250 M I L L

B. M. I l y u k o v i c h a n d S. E. M e r k u r ' e v UDC 621.771.251M.019

The 250 mi l l of our plant rolls 12 • 16 m m bar steel for the bands of automobi le starters to specif icat ions in which the requirements for some parameters are somewhat higher than the requirements of the state standards for hot- rol led bar steel. The requirements for bar thickness are 12 +~ ram, for width 16 +*.o mm, edge camber of not more than 5 m m per running foot, twist around the axis is not al lowed, and the devia t ion from a right angle between

adjoining faces may not be more than 3 ~ .

The rol l ing method used in the plant with one edging pass provides the required shape without surface defects

and within the l imits of the a l lowable deviat ions from the cross-section dimensions. However, the right angle be -

tween adjoining faces is not always sufficiently accura te .

In roll ing without repeaters the bar maintains its r igh t -angle shape over its whole length, but the productivi ty of the mi l i drops by almost one and a half t imes and there is an increase in the cost of manual labor. Therefore in developing a rol l design and roll ing method providing proper shape p iece and an increase in mi l l product ivi ty a nec-

essary condition was the use of repeaters.

The basic reasons for not producing a right angle (not taking into account improper p lacement of the guides,

which must be uncondit ional ly e l imina ted) are:

1) a nonsymmetr ica l cross sect ion in the bars leaving stand I as a result of d i sp lacement of the roll grooves or their overfi l l ing, which causes a rhombic shape in the bar leaving stand III;

2) p lac ing Of the bar in stand IV with underfil l ing of the groove over its width or excessive reduction in height

and also as the result of osci l la t ion of the loop as the bar enters the groove;

3) lack of consistency in the posit ion of the barrel-shaped bar in the roils of the finishing stand;

4) d i sp lacement of the grooves or misa l ignment of r_he axes of the rolls in a horizontal plane in stand IV, caus-

ing twisting of the bar.

To provide r ig idi ty of the bar in stand IV and e l imina te overfi l l ing of the groove the slope of the walls of the grooves in this stand was cut in half, increasing it in the area of the rol l part ing l ine. In stand III grooved rolls were used instead of a f lat body. The concaveness of 20.5 mm wide bar leaving this stand is 0.2 ram, which provides f lat

but not convex side edges for the bar in stand IV.

To transfer the bar to stand IV a repeater was instal led with low overshooting of the loop, which provides

smoother feeding of the bar without sharp osci l lat ions in bending of the loop, while the use of narrow troughs make i t possible to use step-by-step regulat ion of the rolls in the horizontal d i rect ion and therefore to e l imina te misa l ign- ment of their axes. In stands IV and V double-row roller input guides have been instal led.

As a result, there has been an increase in the product ivi ty of the mi l l in roi l ing bar steel and an improvement in quali ty, with scrap dropping almost in half.

Chusov Meta l lurg ica l Plant. Translated from Metal lurg, No. 12, p. 32, December , 1973.

�9 1974 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, me- chanica!, photocopying, microfilming, recording or otherwise, without written permission of the publisher. A copy of this article is available from the publisher for $15.00.

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