DE2340291B2 - Process for the continuous casting of wide slabs - Google Patents

Description

observed in steels containing C and Mn, of which C 0.15 to 0.22%,

Sheets are made with high strength, such as Si 0.20-0.40%.

especially in mechanical engineering and steel construction, especially Mn 1.0 to 1.5%,

pipeline construction. 65 P max. 0.025%,

The aim is to avoid segregation S max. 0.030%,

or as far as possible, and Al was max. 0.1%,

for this purpose the observance of the lowest possible remainder essentially iron.

This steel is generally loaded with Si and Al. The invention is illustrated by an exemplary embodiment

calm, with the Si content around 0.3% and the Al-Ge explained in more detail,

stop is below 0.1%. The P and S content should be an example
be as low as possible; it is around 0.020% each.

For slabs produced according to the invention on a continuous slab caster, a

Process are produced, it is characteristic that steel with the following chemical composition is

their hardness determined in the segregated core zone (casting analysis):

a maximum of 30% above that in the unsegregated margin- 0 20V C 0 025V S

zone determined hardness is 0 * 30 y Si o'o3OVAl,

The method according to the invention results in 10 1 * 45 y Mn o'05y ° Nb

a pronounced equalizing flow, which in the case of narrow 0020y P 'rest iron'

len slabs or billets would not be possible. It ''

it was found that the mold size achieved according to the invention was 1600 χ 225 mm, which

Reduction of the segregation of no qualitative lowering speed of the strand 0.6 m / min. Dar-

This is accompanied by disadvantages, in particular there are no cracks 15, resulting in a casting capacity of 1.55 t / min. the

on the surface of the slab and strand diameter sump length L can be derived from the relationships

fractures occurred; regarding the content of non-,

metallic inclusions were no "difference - = c ·] / 7 ... (mm)

found in relation to cast strands, which after the 2

conventional processes have been produced. With the ao _{UQ (} j

preferably used steel type cherish the deoxy L = a-1

dation products essentially as manganese silicates j _{} ZW}

which are liquid when pouring, 'rapidly coagulate'. ,.,

and therefore already for the most part in the ladle L - a · f - \ ... (mm)

or excreted in the intermediate vessel; in the 25 \ 2c /
Continuous casting mold only gets a small part,

therefore, in this case, calculate the type and intensity of the currents. Where d is the strand thickness in mm, c is the

tion in the strand sump does not have a noticeable solidification factor, the one used at 27 mm / min

Have a look at the inclusion content of the strand. was, t is the first time in minutes and α is the lowering

The process according to the invention is carried out in a simple strand speed in mm / min.

Way carried out in such a way that the speed ν In the present example, the swamp length L

of the freely flowing out of the pouring pipe or into the calculated with 10.4 m. The steel temperature (casting tem-

liquid sump penetrating pouring stream - measured temperature) - measured in the intermediate vessel - was

at the level of the meniscus - it is set to 1530 ⁰ C. To avoid disruptive segregation

that the depth effect with increasing swamp length L 35 according to curve C of the diagram has a minimum outlet

increases. This creates a turbulence and speed of the steel from the pouring pipe 3 of in the sump

causes a current. While 68cm / sec is required in the middle of the strand. It therefore became a below

a strong downward movement of the steel occurs, open pouring pipe with a clear diameter of

the steel flows particularly in the edge area, i.e. used in the 60 mm. From the context »Gi; ß-

Area of the narrow sides of the slab, upwards. 40 output (in cm ⁸ / sec) is equal to the product of the casting

This equalizing flow enables a deep single-pipe cross-section (in cm ² ) and outlet speed

«Iringen of the pouring stream into the swamp. speed ν (in cm / sec) «is calculated for this example

In the diagram, the sump length L is on the abscissa an exit velocity ν of 127 cm / sec (point

in m and on the ordinate the exit velocity - 34 in the diagram). Half the length of the strand became one

ν of the G'eßstrahles sample taken from the immersion nozzle, deep-etched and the segregation

cm / sec. With 16 and 17 there are border lines; it only stands out slightly from the segregation

draws, within which the invention with advantage from free brake cross-section, which indicates a low

is applied. Within these border lines 16, 17 indicates segregation intensity.

to the present invention, the exit velocity ν The results of this melt were compared to the lower limit curve C, that is in the hatched 50 with another melt, which defines with otherwise completely range B whose upper limit is about by the spa same conditions using the previously venzug 18 is cherish. According to this, pouring was carried out using a conventional pouring technology, namely sump length L of 8 m, the exit velocity ν borrowed using a pouring pipe with two be at least 60 cm / sec and gradually up to the side at an angle of 45 ° obliquely down at least 110 cm / sec if the 55 inclined outlet openings, each 42 mm in diameter and sump length, are due to a higher lowering speed. As a result, the line's radiation exposure was increased up to 15 m. Directional speed of 130 cm / sec reached, but values for the upper limit of the depth to be selected. Penetration of the pouring stream into the liquid speed ν are shown in FIG. 2 sump avoided, which is important for the operation with these 120 and 180 cm / sec. The exit velocity would be 60 tubes is characteristic. A sample taken from the strand center speed ν below field B in area A showed a significantly stronger seepage, strong segregation in the core of the cast slab and a considerable increase in hardness in the process, which lead to a deterioration in quality. equal to the segregation-free material.

1 sheet of drawings

Claims (2)

rieen just above the liquidus line Hegenden Gieß- ", t ^ rnnLrature of the steel, an increased cooling of the patent claims: S5Sta £ cast strand and as low as possible 1. Process for the continuous casting of rige ^^ ff ^^ SSkSS ^ t wide, especially over 1000 mm wide slabs. At VoBO & wAal ^ eSaUen it is often un men Jos to segregate steels under possible these ** «* ** " _re ^ £ SJ" use of a vertical, essentially avoidable, steel with ^^ straight, water-cooled mold into which the steel is poured. It's ^ J ^ Ä ^ S; by means of a submersible spout let flow in system with extxem ¹ J ^ f Stogtoggwn ^ and from the one liquid swamp and one er i. ness to operate as _ς ^^^ esch wind ^ ness of the staring surface layer having excluded cast strand cast strand on the ^S ^ ^e ™ _ß 3 ^de 4 _h ™ _c ^; is pulled, characterized in that the system must be coordinated. It is important to ensure that the exit velocity (v) of the casting stream exiting the immersion nozzle in vertical direction during cooling, in the first total direction, so that cracks during solidification are avoided as a function of the length (L) .5 which is why it is not possible to increase the cooling above the liquid sump at a certain level: this is higher than a range of 60 to a reduction in segregation would be desirable, 110 cm / sec, through curve C of the slide task of the discovery it is em Sbanggußver- lower limit value represented in grams. drive to create the production of 2. Application of the method according to claim 1 »poor continuous casting slabs made of steel which usually tend to seigern for the casting of steels with the following combination. A _seat . The special aim of the invention is then to produce steels ⁶ 'of a high-performance continuous casting machine ^To C 015 to ^make 0227 ^"without ^ ^{13 the} casting temperature ⁱⁿ Si 0.20 to 0.40%! »5 ^s 8 ^s borders kept and strong Sckundärküh- Mn 10 to 15 ° / ° ' development must be applied. P max 0 O25V The invention consists in a method of S max'o'o3O ° 7 gangs designated species in the fact that the Ausnttsge- Al max! o | l%, speed ν des in the vertical direction from the The remainder is essentially iron. 3 ° immersion outflow of the exiting pouring stream depending on the speed of the length L of the liquid sump is kept at a value which is higher than one in the range from 60 to 110 cm / sec, through curve C des Lower limit value represented in the diagram. Purpose-35 moderately, for the implementation of the inven- The invention relates to a method for the continuous method known per se, among the Detailed casting of wide areas, especially those that are immersed in the continuous casting mold via the meniscus 1000 mm wide slabs made of prone to segregation- refractory pouring pipes are used, which are often below The steels using a vertical, im are, so that the pouring stream freely flowing out as possible Essentially straight, water-cooled mold, in which 40 penetrate deep into the liquid sump of the strand the steel can flow in by means of an immersion nozzle. So far it has been considered that a let and from the one liquid sump and a deep penetration of the pouring stream m the liquid A cast strand having a solidified edge layer is detrimental to the core and should be avoided because is pulled. as a result of the formation in the liquid sump Segregations in the core of cast strands arise 45 flow an irregular thickness of the solidified known because of various elements, such as the edge layer and thus the risk of rili formation C, Mn and S, could result in a higher solubility in liquid steel (see e.g. »RADEX-Rundschau«, have speed than in solid steel; these elements enrich 1971, No. 5, pp. 595 to 599). It was believed therefore when solidifying in the residual melt. that deep penetration is therefore undesirable In zones where the steel solidifies last, for example 50, because the non-metallic contained in the steel in the core of inclusions generated by continuous pouring are conveyed deep into the sump and Cast strands, therefore, can hardly reach the sump surface from there much higher Ge consider these elements to be demonstrated as in the could. As a result, pouring pipes became general Randzor.e. used, in which the liquid metal through sideways Segregations cause a reduction in quality, horizontally or diagonally downwards or diagonally did the rolled products made from cast strands; upwardly directed openings flows out, segregated sheets show lower elongation and The method according to the invention can with special Impact values. Their deformability is also their advantage for the production of cast slabs worsened by the segregation. In the case of welded constructions made from a killed steel, the following assemblies Internal cracks in the weld 60 can be used: seams occur. These disadvantages become particular