RU2308348C1 - Liner type mold for continuous casting of round billets - Google Patents

Abstract

FIELD: ferrous metallurgy.

SUBSTANCE: liner of mold of billet continuous casting machine includes upper funnel like portion and at least two arranged concentrically shaping portions. Funnel like portion has cross section in the form of rounded concave zones whose number is in range 4 - 10. Height of concave zones decreases from zero in boundary between funnel like portion and shaping portion. Length of funnel like portion consists of 30 - 45% of total length of liner. Conicity of funnel-like portion per maximum-concavity zone consists 3 - 10 %/m and between concave zones it is in range 1 - 2%/m.

EFFECT: stable process of drawing cast billet, rigid centering of billet, lowered out-of-roundness, decreased cracking of ingot, increased speed of casting.

2 cl, 3 dwg

Description

The invention relates to ferrous metallurgy, and in particular to continuous casting machines for round billets (CCM), and can be used in the design of molds CCM.

Known cited as a prototype of the mold sleeve with concavities in the upper part in the form of circles (US Pat. EP 0498296 B1).

The disadvantage of the prototype device is that during casting, due to the high conicity and length of the section with concavities, the formed crust of a continuously cast round billet turns out to be uneven in thickness, as a result, the ovality of the billets occurs, the shell of the ingot hangs in the mold, entailing breakthroughs .

An object of the present invention is to provide a mold sleeve that provides a stable casting process for continuously cast billets, rigid centering of the round billet, reduction of ovality, number of ingot cracks and reduction of the gas gap between the solidified workpiece and the mold shell wall.

The technical effect of the innovations is to increase the speed and seriality of continuous casting.

The task and the achieved technical effect is ensured by the fact that concavities are located in the upper part of the sleeve from the pouring side of the metal, while their number varies from 4 to 10, the length of the section with concavities is 30-45% of the total length of the sleeve, while the geometry of the concave sections in cross section obeys a sinusoidal or parabolic law, depending on the grade assortment and casting speed, along the concavity height are made curvilinearly decreasing from the maximum at the upper end of the sleeve to zero on to the boundary between the funnel-shaped and the forming part, the taper of the funnel-shaped section with concavities varies from 3 to 10% / m at the maximum concave part, and at the point between concavities - from 1 to 2% / m with a curved decrease in taper from top to bottom. Also, the sleeve contains at least two forming concentric sections with different tapers, which varies from 3 to 0.5% / m with decreasing taper downwards in each section. The location point of the base radius of the CCM lies at the junction between the bulges of the funnel-shaped part.

The drawings show an example of a structural embodiment of the proposed in the invention sleeve.

Figure 1 The cross section of the sleeve AA.

Figure 2 A longitudinal section of the sleeve bb.

Figure 3 Cross-section of the sleeve on CC.

Figure 1 shows the cross section of the sleeve on the pouring side of the metal. Concavities b are visible on it. The geometry of concavities in the cross section obeys a sinusoidal or parabolic law, depending on the grade mix and the casting speed. The height h ₁ (figure 2) concavity b made curvilinearly decreasing from the maximum at the upper end of the sleeve a ₁ to zero at the boundary between the funnel-shaped section h ₁ and the forming section h ₂ . In the funnel-shaped part of h ₁ in the concavity region, the taper from size a ₁ to size a ₃ varies from 3 to 10% / m, and from size a ₃ to size a ₂ from 1 to 2% / m with a curved decrease in taper from top to bottom. The taper along the length of the forming concentric sections h ₂ and h ₃ varies from 0.5 to 3% / m. For example, the taper of plot h ₂ is 2% / m and plot h ₃ is 0.9% / m.

Point F, indicated in figures 1 and 3, shows the location of the base radius of the CCM, and regardless of the number of concavities, point F is located at the junction between the bulges.

Figure 2 shows a longitudinal section of the mold sleeve for casting round billets with the upper funnel-shaped part of the sleeve of length h ₁ and the lower forming parts of the sleeve of length h ₂ and h ₃ . In the upper part of the sleeve, from the pouring side of the metal, concavities of height b are located, while their number ranges from 4 to 10, due to the fact that concavities are located symmetrically with respect to the caster axis, and with an increase in the diameter of the continuously cast billet, the number of concavities increases. The length of the section with concavities h ₁ is 30-45% of the total length of the sleeve h, since in this section the forming crust of the continuously cast billet is the most plastic. The larger the diameter of the workpiece, the lower the casting speed and the greater the thickness of the crust in the transition zone to the forming section h ₂ , respectively, the lower the ductility of the crust of a continuously cast billet. The sleeve contains at least two forming concentric sections (in this example, sections h ₂ and h ₃ ) with different tapers. The axis k goes along the technological axis of the continuous casting machine, and the inner (working) surface of the liner is concentric with respect to the axis k.

Figure 3 shows the upper section of the forming section h ₂ .

Size a ₂ shows the largest diameter of the cross section of the plot h ₂ , or the smallest diameter of the plot h ₁ . Dimensions a ₄ and a ₅ show the larger and smaller diameters of the cross section of section h ₃ .

The claimed device operates as follows.

Liquid steel from the tundish enters the mold sleeve, where solidification and solid crust formation of the continuously cast ingot takes place. The shell on the plot h _{1 is} straightened over the concave sections, due to this has a tight contact, which helps to center the shell of the ingot in the mold. The taper in the area h ₁ at the joints of the concave sections should provide a minimum gas gap. On the plot h _{2 the} shape of the shell of the workpiece becomes round, i.e. this section is the beginning of the shaping of the round billet. The shrinkage of the shell in this section depends on the casting speed, the diameter of the workpiece, and the taper of the walls in this section should correspond to the shrinkage of the shell. The larger the diameter of the workpiece and, accordingly, the lower the casting speed, the taper of this section increases.

In the case of casting round billets under a slag layer, the overall conicity of the liner, as well as the conicity of the sections h ₂ and h ₃ decreases due to a decrease in heat removal from the liquid metal to water through the slag layer and the wall of the liner. In section h _3, heat transfer through the ingot crust decreases and the surface temperature of the shell decreases, therefore, the taper of section h _{3 is} less than the taper of section h ₂ .

At a distance of 150-200 mm from the lower end, which corresponds to section h ₃ , the greatest wear of the walls is observed, therefore, it is recommended to cover the lower part of the mold sleeve with a thicker layer of wear-resistant coating.

The outer walls of the liner are cooled by water flowing between the liner and the shell. With the help of pull-correct devices (TPU), a continuously cast billet is pulled out of the mold with a certain speed. After the mold, the ingot enters the secondary cooling zone, where complete solidification occurs. TPU are located immediately after the secondary cooling zone.

After the caster pulling device, the ingot enters the cutting section to measured lengths, then the workpiece is sent to the refrigerator for further processing.

The proposed design provides centering of the ingot in the mold, increasing the stability of the continuous casting process by reducing the likelihood of a gas gap between the wall of the mold barrel and the hardened billet, and ensuring the hard centering of the ingot using concavities in the upper part of the shell.

Claims (2)

1. The mold for continuous casting, comprising a round sleeve with an internal cavity open on both sides, an upper funnel-shaped part, which is made from the metal pouring side in cross section in the form of rounded concave sections, and a concentrically arranged lower forming part, the height of the concave sections decreases from a maximum at the upper end of the sleeve to zero at the boundary between the upper funnel-shaped and lower forming parts of the sleeve, characterized in that the length of the funnel-shaped part with The contoured sections make up 30-45% of the total length of the liner, and their number is from 4 to 10, the concave sections in the cross section are made sinusoidal or parabolic, the funnel-shaped part has a maximum conicity of 3 to 10% / m, and between concavities from 1 to 2% / m, while the sleeve is made with at least two concentrically located forming sections with different tapering downward, ranging from 3 to 0.5% / m. 2. The shell mold according to claim 1, characterized in that for a curvilinear continuous casting machine, the point of the base radius lies at the junction between the bulges of the funnel-shaped part of the mold.

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