CN1206362A - Continuous-casting mould - Google Patents

Abstract

The invention relates to a process and a continuous-casting mold for casting thin slabs. The mold has an oblong inner cross-sectional area and cooled mold walls. The melt is poured in through at least one delivery nozzle which dips into the melt. To ensure that, during casting, markedly lower stresses and, as a consequence thereof, fewer cracks appear in the strand shell, at least at the casting level being established and at least over a part of the depth of immersion of the delivery nozzle, the ratio of the gap widths STI and SII/2 and the ratio of the cooling capacities LTI and LII of the mold wall are related by the equation: [STI/(SII/2)]/[LTI/LII]>1. STI is the width of the gap formed in the zone immediately surrounding the particular immersed delivery nozzle by the outer surface of the delivery nozzle and by the inner surface of the directly opposite mold wall, and SII/2 is half the width of the gap formed by the inner surfaces in the zones in which the inner surfaces of the mold walls are directly opposite each other. LTI and LII are the cooling capacities of the zones of the mold wall which form the respective gap or gap section.

Description

Continuous cast mold

The present invention relates to a kind of continuous cast mold that is used to pour into a mould thin slab, it has microscler interior cross section.The crystallizer wall of cooled is arranged and insert the melt input unit of the immersed outlet of melt by at least one.

Known, the internal cross section of continuous cast mold is designed to when the continuous casting of the strand with microscler cross section, makes to produce a kind of moulding strand near final size by continuous cast mold.In this case especially at profiled beam and have in the profiled beam of cross section (" dog bone (dog bone) " shape cross section) of its cross section end upsetting toward producing such problem with H tee section, that is, compare with web width that special-shaped beam increases and/or often there are crackle and stress and/or undesirable crystal structure in the end that thickens near the cast of final size the time.Then different in the non-profiled beam of pouring into a mould near final size, after casting, need the complicated and expensive operation of rolling technically, to reach desired final size.

By the known a kind of method and apparatus of making strip of DE 2034762A1, wherein, have along the thickening of its longitudinal extension, still have liquid fuse at thickening.This thickens below crystallizer and pushes back by pressure roller then.

US-PS 5082746 discloses the profiled beam of special size, and wherein, not allowing has the uniform crystal structure of predesignating above predetermined cross section parameter and they, so that and then obtain desired shape of cross section with minimum rolling workload.This type of profiled beam can be poured into a mould with one or more immersed outlets that are used for melt conveying by experience.Proved already in this case that only restricted cross sectional parameter and the desired crystal structure of regulation still were not enough to produce the profiled beam near final size that does not have crackle and uniform crystal structure is arranged along its entire cross section.Under the situation of strand section with the sidewall that is formed in the end, even as clearly advising among the US-PS 5082746, web width being chosen as to equate also still to be not enough with sidewall width, that is to say that the profiled beam of producing according to these particular provisions often has crackle and especially has than the more disadvantageous crystal structure of web in sidewall region, these situations show, when pouring into a mould with immersed outlet, casting condition is not just can reach by the limiting value of observing above-mentioned cross section parameter simply uniformly in any zone of cross section.

The purpose of this invention is to provide a kind of continuous cast mold, it is useful on the cooled crystallizer wall that cast has microscler interior cross section strand, for example pour into a mould shaping strand with H shape cross section and predetermined web width, and there is one to pass through the melt Conveying device that at least one inserts the immersed outlet in melt, in this continuous cast mold, stress obviously reduces in casting process, and consequently the crackle that occurs in the casting blank outer cover reduces.In addition, the strand of casting should have uniform crystal structure along entire cross section.

By the present invention is to reach this purpose by the illustrated feature of characteristic in Patent right requirement 1.Can further design this continuous cast mold by favourable mode by the described feature of dependent claims 2 to 8 characteristics.

The present invention regulation is at least on the height that forms mould inner metal liquid face and at least along immersed outlet part insertion depth, at the direct gap width S in immersed outlet regional _T1With the gap width S in the mutual direct neighbor of crystallizer wall inner surface zone opposite each other _L1/ 2 the ratio and the cooling power L of crystallizer wall respective regions _T1And L _L1Ratio be applicable to following formula:

〔S _T1／(S _l1／2)〕／〔L _T1／L _l1〕＞1。

S wherein _T1It is the gap width in the gap that constitutes of the inner surface by relevant immersed outlet outer surface and direct neighbor crystallizer wall opposite each other.S _L1The/2nd, 1/2nd gap widths in the gap that constitutes by inner surface, and be in more such zones, promptly opposite each other at the mutual direct neighbor of the inner surface of these regional intercrystalline walls, that is to say it is between those inner surfaces, not adorn in the zone of immersed outlet.L _T1And L _L1It is the cooling power of the crystallizer wall in these respective regions.Has so continuous cast mold of the internal cross section of design of size, even when high poring rate, also can make the evenly fusing and evenly discharges of the casting powder that is placed on the mould inner metal liquid face with slag, thus in whole cross section form a highly identical fusing slag-casting powder layer.The layer of a highly identical slag-casting powder advantageously impels the layer that forms a uniform slag-casting powder in the continuous casting process between crystallizer wall and casting billet surface.Can make casting blank outer cover that very good slip is arranged on whole crystallizer wall thus, and the heat of melt or strand can be discharged by crystallizer wall very equably in casting process, has very uniformly crystal structure and does not have stress and the casting blank outer cover of crackle thereby form.

Advantageously the whole insertion depth along immersed outlet makes (S _T1/ (S _L1/ 2))/(L _T1/ L _L1) between 1.05 and 1.30, therefore considered that especially the immersed outlet wall is to the influence of heat situation in the crystallizer during casting.

Under the situation that crystallizer wall evenly cools off, the size design of the desired internal cross section of continuous cast mold can be done following simplification, that is, and and (S _T1/ (S _L1/ 2))/＞1, best (S _T1/ (S _L1/ 2)) between 1.05 and 1.30, considered especially still that thus the immersed outlet wall is to the influence of heat situation in the crystallizer during casting.When an immersion mouthful geat especially was arranged in the web district, by the present invention's suggestion, this immersed outlet had microscler cross section, and therefore outwards need only there be smaller distortion in the zone relative with immersed outlet of wide side.

In addition, especially, in narrow side location, always arrange two immersed outlets by the present invention's suggestion in order to produce cross section (dog bone) with enlarged end.When immersed outlet for example has triangular cross section substantially, be favourable in this case for the product aspect that obtains near final size.

Cooling element for example cooling tube is used for the crystallisation by cooling wall, and they are provided with in such a way along the crystallizer wall of per unit area with distributing, that is, make crystallizer wall obtain the cooling power of regulation in corresponding zone.

Accompanying drawing has been represented embodiments of the invention and has been described in detail below.Wherein:

The cross section of continuous cast mold when Fig. 1 works by a central immersed outlet; And

Fig. 2 is arranged on the cross section that narrow side respectively has immersed outlet when work continuous cast mold of triangular-section by two.

Fig. 1 represent for the height place that casts the mould inner metal liquid face that continuous-cast blank forms in when work by have microscler in the cross section of continuous cast mold of cross section.Wide side crystallizer wall 1,1 and narrow side crystallizer wall 2,2 difference are (1-1 opposite one another; Arrange to constitute casting cavity, their the most handy coppers also are provided with the cooling tube 3 that is used to dispel the heat 2-2).Cooling tube 3 guarantees along crystallizer wall 1,2 Homogeneouslly-radiatings, and this is to reach by the cooling tube 3 that per unit area in crystallizer wall 1,2 is provided with respective numbers.When crystallizer shown in Figure 1 work, in order to import melt, be provided with an immersed outlet 4 in the insertion melt that preferably has a microscler cross section at the center.

As seen from Figure 1, wide side crystallizer wall 1,1 is outwardly-bent respectively in the zone that directly centers on immersed outlet 4, and exactly, there is constant basically gap width S in the gap 7 by wide side crystallizer wall 1,1 and immersed outlet 4 constitute along whole insertion depth _T1Represented embodiment reaches above-mentioned requirements like this in Fig. 1, that is, the outer surface 6 of immersed outlet 4 has one and crystallizer broad side walls 1 mutually direct interior surface opposing 5 similar contour shapes.Adopt the shape of this length of immersed outlet 4, need only outwards there be smaller distortion in wide side 1 and immersed outlet 4 relative zones.

In all the other zones on immersed outlet 4 left sides and the right side, wide side crystallizer wall 1 direct interior surface opposing 8 (that is immersed outlet is not set between them) constitutes gap 9, its 1/2nd gap width S _L1/ 2 equal S at most _T1, in other words, the gap width of direct opposed inner surface 8 mostly is the gap width S in gap 7 most _T1Twice so big.

Fig. 2 has represented to have the another kind of scheme of continuous cast mold by the interior cross section of design size of the present invention.In the narrow sidewall of crystallizer 2 zones, have the increase of crystallizer internal cavity at the continuous cast mold shown in Fig. 2, wherein respectively be provided with an immersed outlet 4 (cross section with enlarged end is also referred to as dog bone cross section).The outer cross section of immersed outlet 4 can be an arbitrary shape almost; Immersed outlet 4 has leg-of-mutton basically outer cross section in by the embodiment of Fig. 2.In this case, in immersed outlet 4 zones, the gap 7 that is made of immersed outlet 4 outer surfaces 6 and the direct opposed inner surface 5 of crystallizer wall still is designed to make gap width S along the size of whole insertion depth _T1Basically constant.

At the middle part of continuous crystalizer, the inner surface that wherein constitutes the crystallizer broad side walls in gap 9 directly stands facing each other, 1/2nd width S in gap 9 _L1/ 2 are slightly less than S _T1That is to say that gap 9 itself still mostly is most gap 7 width S in the profile end region _T1Twice so big.

Adopt basically that the gap width of constant refers in these embodiments, in less zone, for example, can occur departing from desired gap width is constant at place, immersed outlet 4 triangular cross section angles; Therefore the constancy at these regional internal clearance width is approximate satisfied, but should not surpass the value of twice.In like manner, sidewall (shown in Fig. 1 left side) also can omit outwards distortion.

Obviously, when the cooling power of 7 regional interior crystallizer broad side walls 1 respective regions in the gap reduced or increases, the gap width in these two embodiment can reduce or increase.A crucial factor is, at any position gap width of continuous cast mold (S _T1Or S _L1/ 2) with the cooling power (L of crystallizer wall 1 respective regions _T1Or L _L1) ratio be constant, and be preferably in the scope between 1.05 and 1.30.This value is 1.05 in these embodiments.

When the continuous cast mold work of pressing Fig. 1 or Fig. 2, molten steel injects crystallizer continuously via one or more immersed outlets 4, and the moulding strand of casting is discharged with constant speed.In having the casting process of the constant velocity of discharge, the molten steel of the as much of just importing continuously as discharging in the crystallizer exit, therefore the height of the mould inner metal liquid face that forms under the situation of the molten steel in continual renovation is trapped in this zone is constant, and is that these molten steel also impel fusing and infeeded and be placed on casting powder on the mould inner metal liquid face.Meanwhile, in embodiment, be essentially the gap width of constant by Fig. 1 and Fig. 2, guarantee the hot-fluid that in the whole transverse cross-sectional area of continuous cast mold, has a kind of uniform direction to make progress, consequently in the metal bath surface zone, melted the casting powder equably, that is to say that the per unit surface area of metal bath surface and time per unit melt the casting powder of same amount continuously.In addition, when the moulding strand velocity of discharge of casting is constant, because by internal cross section shape of the present invention, so the floor of the slag that constitutes in the metal bath surface district-casting powder forms identical height in all positions of interior cross section.Associated ground, between crystallizer wall 1,2 and melt or casting blank outer cover, in all positions of casting billet surface, equally automatically forming thickness is the film of the slag-casting powder of constant.

Because this special size design of crystallizer and the film that during casting, forms the constant slag-casting powder of thickness thus, so in the zone of crystallizer wall, discharge continuously the proportional heat of area with wall from molten steel, and molten steel by even cooling with the formation casting blank outer cover.The influence of film aspect amount of slag-casting powder is directly by its unit thermal conductivity and the thickness decision of formed film; When the temperature difference is given regularly, cause constant thermal resistance being arranged when melt is discharged by crystallizer wall 1,2 at heat in crystallizer wall 1,2 other constant thickness.Total thermal resistance is drawn by the summation of each several part thermal resistance, in the each several part thermal resistance each other in succession the layer (crystallizer wall-slag/casting powder-casting blank outer cover-melt-immersed outlet wall) the unit thermal conductivity represent with their inverse respectively.The unit thermal conductivity of slag-casting powder film is about 1w/km, and thereby has determined the cooling of heat radiation and strand as experiment research institute proof.Adopt the present invention, the film by formed slag-casting powder has constant thickness, makes that the heat along whole length of mould horizontal direction is conducted homogenising in crystallizer.Temperature difference in casting blank outer cover/crystallizer wall frontier district thereby obviously reduction so only also have very little stress in the casting blank outer cover of the strand of casting, have consequently reduced the danger that cracks greatly.In addition, lubricated by the very good homogeneous that obtains therefrom, the wall wearing and tearing of continuous cast mold reduce, so additionally gone back significant prolongation its service life.

Claims (8)

1. the continuous cast mold of thin slab is used to cast, it has microscler interior cross section, the crystallizer wall of cooled is arranged and a melt input unit by the immersed outlet of at least one insertion melt is arranged, it is characterized by: at least on the height that forms mould inner metal liquid face and at least along immersed outlet part insertion depth, gap width S _T1And S _L1/ 2 ratio and crystallizer wall (1,2) cooling power L _T1And L _L1Ratio be applicable to following formula:

(S _T1/ (S _L1/ 2))/(L _T1/ L _L1)＞1, wherein S _T1Be directly in the zone of the immersed outlet (4) that inserts by the gap width in the gap (7) of inner surface (5) formation of the outer surface (6) of immersed outlet (4) and the opposed crystallizer wall of direct neighbor (1), and S _L1The/2nd, 1/2nd gap widths in the gap (9) that in the mutual opposed zone of direct neighbor of the inner surface (8) of crystallizer wall (1), constitutes by inner surface (8), and, L _T1And L _L1It is the cooling power that constitutes crystallizer wall (1, the 2) zone of corresponding gap or gap portion.

2. according to the described continuous cast mold of claim 1, it is characterized by: for the whole insertion depth of immersed outlet, gap width S _T1And S _L1The cooling power L in/2 ratio and corresponding crystallizer wall (1,2) zone _T1And L _L1Ratio be applicable to following formula:

〔S _T1／(S _l1／2)〕／〔L _T1／L _l1〕＝1．05-1．30。

3. according to the described continuous cast mold of claim 1, it is characterized by: gap width S under the uniform situation of whole crystallizer wall (1,2) cooling power _T1And S _L1/ 2 ratio is

〔S _T1／(S _l1／2)〕＞1。

4. according to the described continuous cast mold of claim 1, it is characterized by: gap width S under the uniform situation of whole crystallizer wall (1,2) cooling power _T1And S _L1/ 2 ratio is

〔S _T1／(S _l1／2)〕=1．05-1．30。

5. according to the described continuous cast mold of one of claim 1 to 4, it is characterized by: immersed outlet (4) has microscler cross section at outlet area at least.

6. according to the described continuous cast mold of one of claim 1 to 4, it is characterized by: immersed outlet (4) has leg-of-mutton basically cross section.

7. according to the described continuous cast mold of claim 6, it is characterized by: respectively establish an immersed outlet (4) in the location of narrow side (2).

8. according to the described continuous cast mold of one of above-mentioned all claims, it is characterized by: crystallizer wall (1,2) is provided with cooling element (3), and they distribute matchingly with the cooling power of regulation.

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