T E E M I N G OF 1 7 G S STEEL U N D E R S L A G BASED ON

A S H FROM HEAT AND E L E C T R I C POWER P L A N T

G. N. K a m y s h e v , D. N. N o s o v , M. I. E s i n , a n d F. T. M a z h a r t s e v

In recent years at a number of metallurgical plants liquid slags or exothermic mixtures in powder form have been used during bottom pouring to obtain a better ingot surface. However, the use of the former involves a num- ber of organizational difficulties and that of the latter is limited by their high cost.

At the Orsko-Khalilovsk Metallurgical Combine, pouring of 17GS tube steel into plate molds was tried under a slag based on ash from a heat and electric power plant. The ash had the following composition: 0. 12% S, 54.4% SiO 2, 21,6% A1203, 3. 5% CaO, 7. 09%o Fe203, 0. 20% P2Oa, 1. 35% FeO, 0. 45% MgO, 6.5% C, 0. 20% MnO, traces of Cr203, 1.9% calcination loss, and 2. 53% Na20 + K20.

The ash had a bulk density of 0. 8-0. 9 g / c m 3 and melting temperature of 1560~ The ash is formed when coal is burned in the combustion chambers of boilers Preparation of the mixture used during teeming consists of transporting the ash, drying it, mixing it with graphite, and packing the mixture in paper bags. There is no need to grind the ash (70%0 particles have a size of less than 0. 1-0. 2 ram). The cost of the mixture is 15-20 rubles/ton.

Four experimental heats were carried out using high hot-metal practice in 400-ton open-hearth furnaces. Each heat was tapped into two ladies. Slag-treated ingots obtained from one ladle were compared with untreated ingots obtained from the second ladle of the same heat. The slag-forming mixture was obtained by mixing the power-plant ash with 12% graphite. Paper bags containing the mixture were placed at the bottom of the mold before teeming. Consumption of the mixture was 2. 3-2.5 kg / ton steel. Ingots, weighing 13.1 tons, were bottom poured. Molds placed on mold stools holding four molds each were filled in 6 8 rain, which corresponded to a rate of rise of 230-310 ram/rain. No exothermic mixture was shoveled on top of the experimental ingots, whereas in the case of the ingots to be used for comparison, a 50 : 50 mixture of coke breeze and chamotte (1, 5-2. 0 kg / ton steel) was used.

The ingots, which were put into the soaking pits while still hot, were hot-rolled into 165 x 1025 x 1980-mm plates. During conditioning of the plates, their surface was inspected and the type and location of defects was noted.

The plate was roiled on a "2800" mill into 12. 5-ram-thick sheets. The quality of the surface was evaluated according to the amount of reject and subquality sheets not meeting specifications.

The mixture containing E power, plant ash is a good heat insulator but has a high melting point. During teem- ing, therefore, only those layers which are in contact with the metal get fused. Most of the mixture gets sintered only. Slag which melted during teeming had the following composition: traces of CaO, 33. 5% SiO 2, 5.2% FeO, 2.'/% FezO~, 19.2% MnO, 40.2% AI~O~, traces of MgO, and 0. 09% PzO~

During teeming of experimental ingots the rising stream of metal pushed the mixture towards the narrower edges of the mold, where the mixture got sintered and left the central part of the metal uncovered. A part of the mixture (about 0. 5 kg / ton) was, therefore, poured into the molds after they were filled up to half-height so that the surface of the metal was completely covered by the slag.

Orsko-Khallilovsk Metallurgical Combine. Translated from Metallurg, No. 12, pp. 19-20, December, 1970.

�9 1971 Consu l tan ts Bureau, a d iv is ion o f Plenum Pub l i sh ing Corporation, 227 West i7 th Street, New

York, N. Y. 10011. ~Ill rights reserved. This art icle cannot be reproduced for any purpose whatsoever

without permiss ion o f the publisher. A copy o f this art icle is avai lable from the pub l i sher for $15.00.

781

TABLE 1, Quality of the Surface of Slabs from Ingots Teemed under Slag and Ingots Treated with Grapkite

Quality of slab surface, %

Teeming

Under slag With graphite

Number of

melts

Number of faces

e x -

a m i n e d

564 586

wide face

ltrans- longi tu- clean vers dinat scabs

I craeks cracks

64.1 11.7 23.6 3.4 42. 1 21. 5 25. 8 15. 1

narrow face

}~rans- ilongi~u, I " clean vers dinal I scabs

t 1 ____@cracks cracks t

ss .5] 8.2 1 ,5----~ 4,8 86.5 I 6.4 1. V I 5.4

TABLE 2. Quality of the Surface of Sheets from Ingots Teemed under Slag and Ingots Treated with Graphite

Teeming

Under slag With graphite

Amount of rolled metal

tons

406. 6 299.2

Quality of sheets, %

rejects

0 . 1 0 1 - I 0.42

below specifications

Total

~.;i-- i 2 . 6 2.8~ - 1. oo 4. 34

Teeming under the slag considerably improved the surface of slabs (Table 1). Quality of s~heets obtained from experimental ingots was better than that of sheets obtained from the ingots teemed without slag (Table 2), Mechanical properties and the amount of nonmetallic inclusions were practically the same for botk

782