R E F R A C T O R I E S IN SERVICE SERVICE V.

OF ZIRCON

NOZZLES

FOR CONTINUOUS

M.

and

Pitak

Strelets

N. V.

STEEL

CASTING*

Ukraine Scientific Research Institute for Refractories A. I .

Kulik

and

M.

S. L o g a c h e v

Chasov-yar Refractories Combine Translated from Ogneupory, No. 4, pp. 163-165, April, 1963

A technology for making zircon nozzles has been developed by the Ukraine Institute (UNIIO) and introduced at the Chasov-yar Combine [1]. A trial batch of nozzles was tested on continuous steel casting equipment (UNRS) at the Donet M e t a l l u r g i c a l Factory. The batch for making the nozzles was 50~/o zircon fraction 1.5-0.5 m m and 5~0 finely ground mixture c o n t a i n ing 90% zircon fraction finer than 0.088 m m and 10% Ch-1 clay. The batch also contained 1% (on the dry weight) of sulfite lye. The refractoriness of the zircon products m a d e from different mixtures is shown in Fig. 1 . Nozzles were pressed on the "Tagilets" friction press. The body was filled into the m o l d by weight, depending on the d i a m e t e r of the nozzle aperture in the range 13.5-14.2 kg.

\ %

/gO0

After pressing, the nozzles were dried in the department, then in a drier to a residual moisture content of 1-1.5~ The bulk density of the dried nozzles was 3.06-3.09 g / c m s.

O

o

Nozzles were fired in a tunnel kiln at 1540~ is shown in Fig. 2.

The firing curve

Apparent porosity of the fired nozzles varied from 21 to 2770; bulk density from 3.10 to 2.86 g / c m s. The ZrO z content was about 53~

O

t700

tO

4O

8O

80

1178

Amount of clay, % Fig. 1. Refractoriness of zircon products with different contents of Ch-1 clay.

The zircon nozzles were tested in i n t e r m e d i a t e ladles (Fig. 3) casting killed steel.* * The intermediate ladle was heated with gas burners to 1000-1100~ Nozzle% in addition, were heated from the bottom of the ladle when the stoppers were closed. The m e t a l t e m perature in the ladles varied from 1510 to 1560~ The casting t i m e was on average 50-60 min, the amount of m e t a l cast 30-50 tons.

Previously [2, 3] it was noted that zircon inserts and dosers have a high erosion resistance and do!not tighten up as a result of products of reduction during the casting of steel in the continuous process. Other work is also known on the use of zircon for m a k i n g steel casting nozzles [4, 5]. Recent tests showed that zircon nozzles in some cases,when casting killed steel, also tighten up, but much less than others. Skins formed on the working surface of fireclay and h i g h - a l u m i n a nozzles and other refractories during steel casting chiefly consist of corundum, spinel and m u l l t t e [2, 6]. On the working surface of zircon nozzles in most * T. M. Vysotskaya-Kvitko took part in the work. * * K. P. Murzov, F. N. Grtgor'ev, A. M. Kondratyuk, I. I. Druzhinin, M. S. Gordienko, V. G. Osipov, V. B. Evtushenko, V. T. Sladkoshteev, and IL V. Potanin took part in the tests.

177

cases the skin does not develop. In some cases the products are covered with a thin glass-Itke layer, which does not contain the above reduction products (corundum, spinel, mullite)r On the basts of observations and an analysis of the meitings, Lt was shown that when 28 kg of a l u m i n u m ts added to 140 tons of steel, regardless of the ratio of ether reducing agents, the nozzles are not tightened up. With the addition of 37-55 kg of a l u m i n u m per 140 tons of steel, some of the tested nozzles tightened up and were burned out with oxygen; and with the addition of 80-84 kg of a l u m i n u m for the same a m o u n t of steel, almost all the nozzles tightened up. It was shown that the m a i n cause of tightening of nozzles [s the amount of added reducing agent - a l u m i n u m , In 1961 extra studies were made on the service of zircon nozzles with hote diameters of 23-24 m m .

~600

--

- -

u f2N d I~---~ 8oo L~ N0 - - - i

200

--

-

t

-

5

r

r

20

25

30

35

/~

46

Position Fig. 2. Firing curve for zircon nozzles,

Fig. 3. Intermediate ladle for continuous steel casting equipment. The amount of a l u m i n u m remained constant (48 kg per 140 tons of steel). When pouring steel contaLnLng 0.08-0,1'27o carbon, the nozzles did not tighten up. When pouring steel containing O. 13-0.20% carbon the nozzles tightened up especially with O, 18-0.20% carbon. Erosion of the zircon nozzles reached 2 m m on the hot working side. When using nozzles with 28 m m apertures and higher, tightening did not occur even with an increased content of carbon and reducing agent ( a l u m i n u m ) in the steel.

CONCLUSIONS The Chasov-yar Refractories Combine has [ntroduded a technology developed by UNIIO for making zircon nozzles for continuous steel casting equipment. Zircon nozzles possess a high erosion resistance and give a more stable casting for killed and unk[lled steels compared with other types of nozzle.

178

Tightening of the nozzles when pouring killed steel depends on a number of factors (amount of reducing agent, casting temperature, chemical composition of the Steel, refractory, etc.) and requires further study. LITERATURE CITED 1. 2. 3. 4. 5. 6.

V. M, Strelets et al., Ogneupory, No. 6 (1962). V.M. Strelets and N. V. Pitak, All Union Conference of Refractory Workers, Metallurgizdat, Moscow (1961). V . T . Sladkoshteev et al., Metallurgicheskaya t gornorundnaya promyshlennost', No, 1 (1961). V. M, Tsynkina, Collection of Papers Commemorating the 60th Birthday of P. P. Budnikov, Moscow (1946). J. Just, Hutnik, 27, No. 4 (1960). B.V. Ivanov, DAN, USSR, Vol. 58, No. 6 (1947).

A l l a b b r e v i a t i o n s of p e r i o d i c a l s in the a b o v e b i b l i o g r a p h y are l e t t e r - b y - l e t t e r t r a n s l i t e r a t i o n s of t h e a b b r e v i a t i o n s a s g i v e n in the original R u s s i a n j o u r n a l S o m e or all o f t h i s p e r i o d i c a l l i t e r a t u r e m a y w e l l b e a v a i l a b l e in E n g l i s h t r a n s l a t i o n . A c o m p l e t e l i s t of the c o v e r - t o . c o v e r E n g l i s h t r a n s l a t i o n s a p p e a r s at the b a c k of this i s s u e .

1'19