RESEARCH TO CHEMICAL INFLUENCE FOR SLEBS QUALITY CONTINOUS CASTING Beatrice TUDOR, Stela CONSTATINESCU, Stefan DRAGOMIR Dunărea de Jos University of Galaţi, Romania This paper show a method for determination the flaw who is produce in the slab at the continuous casting. We used fore evidence the macrostructure flaw the method named Baumann stamp. Key words: shape, cooling zone, casting, slab, Baumann stamp 1.INTRODUCTION The casting is produce by a free fall of molten steel from ladle (by nozzle) in a metallically shape (free cooling) without bottom cooling by water named mold. This form for obtain slabs is named casting in mold. In the next figure is show the main functionary scheme for continuous casting fig.1. Fig.1.Continuos casting installation The casting speed mean, the speed of slab who is insurance by mold for continuous casting is the mold who insurance the solidification and the create of the slab shape. The molds are diverse and is made by welding or casting from cuppru, steel, aluminium or graphit. The mold is characterize by a great liquid alloy, by using a circuit with water, under pressure. 1
2.PHENOMENAS, SCHEME AT THE CONTINUOUS CASTING The continuous casting is characterize by a great productivity and quality This method give us the possibility for important mechanized (fig.2) and introduced a large number of authomatisation during the casting proceeding. Fig.2.Schematic of flow phenomena in mold region of continuous casting process 3.EXPERIMENTAL METHOD FOR QUALITY MONITORING OF SLAB To obtained a good quality for continuous casting slab it mast to correlate the casting speed with cooling speed and the solidification speed (table 1) and rigorously monitoring of thermical regime like (table 2). 2
Table 1 Casting speed and cooling flow SHAPE 200x1000 steel types I, II Mold water flow 2x1700 ( 102 m 3 ) 500 ( 30 m 3 ) Casting speed (m/min) Secondary cooling Min. : 0,9 Med.: 1,0 Max.: 1,1 L/min m3/h L/min m3/h L/min m3/h Zone - I.a 485 29,1 485 29,1 560 33,6 Zone - I.b 345 20,7 345 20,7 390 23,4 Lateral` 80 4,8 80 4,8 90 5,4 Zone II 350 21,0 350 21,0 420 25,2 Fixed 130 7,8 130 7,8 130 7,8 Zone III Mobile 110 6,6 110 6,6 110 6,6 Fixed - - 110 6,6 130 7,8 Zone IV Mobile - - 90 5,4 110 6,6 Table 2 Parameter Sample Sample Gr. I Gr. II Gr. III Gr. IV Gr. I Gr. II Gr. III Gr.IV Ladle 1615 1610 1605 1600 1610 1605 1600 1595 0 C 1635 1630 1625 1620 1630 1625 1620 1615 Ladle before the bubblings 1605 1600 1595 1590 1600 1595 1591 1585 1625 1620 1615 1610 1620 1615 1610 1605 Ladle 1585 1580 1575 1570 1580 1575 1570 1565 after bubbling 1595 1590 1585 1580 1590 1585 1580 1575 3
Tundinsh 1545 1540 1535 1525 1555 1550 1545 1535 For the continuous increase of casting slab is important to know and find the default of obtained product. By using the Baumann stamp like in figure 3, with aid photographical paper with AgBr and this paper is introduced for 2 min. in a solution with 5% H 2 SO 4 in distillated water. While the practically experiments is produce the next reactions: H 2 SO 4 = FeSO 4 + H 2 S H 2 S + 2AgBr=Ag 2 S+2HBr 4
Fig.3. Baumann stamp of slab The deposing of sulph is show by Ag 2 S like spot and light brown points, who identify the chemical unomogenity, who is produce after solidification. 4.CONCLUSION The experiment show there is many types of segregations, who determinate the produce of flaw after slab solidification. The causes of segregation are: - the alloy solidification in a most interval of, - a little capacity diffusion of company elements, - is necessary to create a correlation between casting speed - cooling speed, solidification speed and themical regime. 5
- Is very important to have a geometrically direction of orientation of macrostructures dendrites with casting direction and for that is recommended to do a electromagnet cal agitation of metallurgical bath. BIBLIOGRAPHY 1)Chira I., Sofroni L., Brabie V., Procedee speciale de turnare, Editura didactica si pedagogica Bucuresti, 1990 2)Drouzy M. L adaptation automatique de la cadence de coulee a la du moule metallique. In: Fonderie, Franta nr. 346, iunie, 1995 3)Gutu M., Takacs O. Turnarea continua si semicontinua a materialelor metalice, Bucuresti, Editura tehnica, 1977 6