JPH01148441A - Belt driving pulley for twin belt caster - Google Patents

Abstract

PURPOSE:To reduce tension force in the longitudinal direction of a belt by forming both ends of driving pulley at wider position than width of a cast slab in the axial direction of the driving pulley to smaller diameter than the diameter at center part of the pulley. CONSTITUTION:At the time of bringing the upper and lower belts 2, 3 into contact with molten metal, thermal expansion in the longitudinal direction of the belts is developed. Therefore, by developing this strain to cold frame part of the belt 3, the lower belt 3 can be equalized to expansion of the belt width and the whole width to the longitudinal direction. Further, by using a belt tension device, the tension force to the longitudinal direction corresponding to the tension stress is acted and also by stretching the thermal affected part, the floating-up of the lower belt 3 is restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for preventing belt thermal deformation using a belt drive pulley in a twin belt caster.

[Conventional technology and its problems]

Generally, twin belt casters are constructed as follows. That is, as shown in the conceptual diagram of the general twin belt caster as a whole in FIG. , and a pair of parallel dam blocks 6, a lower drive pulley 4 and an upper tension pulley 8 for the upper belt, a lower drive pulley 5 and a lower tension pulley 9 for the lower belt, and these belts 2.3. Belt tension device 10;1 that tensions the belt in the longitudinal direction
0 and a dam block guide 7 that supports and guides the dam block 6 inside.

Then, the hot water supply section W (see reference numeral 21 in FIG. 7)
Molten metal 11 is supplied to the hot water supply section A of the twin belt caster 1, and cooled by a primary cooling spray zone (not shown) of the twin belt caster 1 to cast a slab 12.

Here, when the molten metal 11 is supplied to the hot water supply section A, severe thermal distortion occurs in the upper and lower belts 2.3.

That is, the steel water-cooled upper and lower belts 2.3 are heated to high-temperature molten metal 11 (for example, about 1550°C for molten steel).
When these belts 2.3 come into contact with elongation (Y: elongation in the width direction) occurs. For example, the molten metal contact surface of the water-cooled lower belt 3 (hereinafter, only the lower belt will be described) is about 00°C to 200°C higher than the water-cooled surface on the back of the belt, so it has a convex shape with the high temperature side at the top. This occurs because the portion of the lower belt 3 that does not come into contact with the molten metal 11 within the plane of the lower belt 3 (referred to as the cold frame portion f) restricts thermal expansion due to the temperature rise of the contact portion. .

As a result, in the initial stage of solidification of the molten metal 11, the slab 12 is subjected to external force due to the deformation of the lower belt 3, and cracks and dents are generated on the surface of the slab.

In addition, contact between the surface of the slab and the lower belt 3 is lost, voids are created, a locally insulated state is created, and a non-uniform solidified structure grows, which has a very negative effect on the quality of the slab.

Therefore, in order to avoid such problems, in particular, as a means for avoiding thermal strain (X) in the longitudinal direction of the belt, a belt tension device 10 is generally used to strongly tension the entire belt and stretch the cold frame portion f. It is made equal to the elongation of the heat affected zone Ws.

However, in the belt tension device 10 as such a general avoidance device, the belt thickness is small (usually 1.5
-around the belt), the Pel+-a tension is too strong, causing a problem in the durability of the belt.

Additionally, as introduced in U.S. Pat. No. 3,123,874, the drive pulley has an inverted crown (the diameter at both ends is slightly larger than the diameter at the center) to counter thermal distortion. There has also been a proposal to reduce thermal distortion of the belt by applying tension to the entire belt.

However, even in such a proposal, since the belt edge portion (cold frame portion f) is attempted to be further stretched, there is a problem that the belt may crack.

[Means for solving problems]

Therefore, the present invention was created with a focus on solving the above-mentioned problems with twin belt casters all at once. , and a twin belt caster comprising a pair of parallel dam blocks, a drive pulley and a tensile pulley around which these belts are respectively wound, and a belt tension device for moving the tensile pulley, In the belt drive pulley for a twin belt caster, both ends of at least one of the drive pulleys at positions outside the slab width in the axial direction are formed to have a smaller diameter than the diameter of the center part of the pulley.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of the present invention will be explained in detail with reference to embodiments shown in the accompanying drawings.

Fig. 1 is a perspective view of the first embodiment of the present invention, Fig. 2 is a front view of the first embodiment, and Fig. 3 is a view of the belt in the width direction during casting to which the present embodiment is applied. Figure 4 is a diagram of internal tensile stress distribution in the belt width direction during casting using the conventional example, Figure 5 is a front view of another embodiment of the present invention, and Figure 6 is a diagram of internal tensile stress distribution in the belt width direction during casting using the conventional example. A front view of yet another embodiment,
FIG. 7 shows a conceptual diagram of a vertical twin belt caster.

Therefore, the first embodiment is a stepped pulley 14 suitable for the drive pulley of an inclined twin belt caster for slab casting.
The belt wound around the stepped drive boot 4 is also tensioned in the width direction by a belt width direction tensioning device (not shown).

Further, a belt preheating device may be attached to this.

Further, a stepped boob 914 is applied in place of the drive pulley 5 described in the prior art, and therefore, all the same parts as in the prior art are omitted.

Now, let's analyze the case where the upper and lower belts 2.3 contact the molten metal fill and thermally expand in the belt longitudinal direction. If the average temperature rise of the steel lower belt 3 is Δθ ("C), then the thermal expansion strain in the longitudinal direction of the belt is ε = α - Δ θ (mso/, 1.)
...■. Here, α is the linear expansion coefficient (-/”C-mm) of the lower belt 3.

On the other hand, the tensile stress σe required to generate an elongation strain ε equal to the thermal expansion strain in the longitudinal direction of the belt according to equation (2) in the cold frame part f (see Figure 9) is ey e = e −E (kg/s++* ” )
, -■Here, Snake is the Young's modulus of the lower belt 3 (k
By generating this σe in the cold frame part f of the belt 3, the lower belt 3 can be made to have the same elongation over the entire belt width W in the X direction in FIG. The stress of σ e acts only on the cold frame part f, and does not act on the heat-affected zone Ws corresponding to the slab width wb as the tensile stress in the X direction. Therefore, as shown in Fig. 4, the belt tension device (
(see reference numeral 10 in Fig. 8), X corresponding to σS
It is necessary to further apply a tension force in the direction to tension the heat affected zone Ws to suppress floating of the lower belt 3 (see FIG. 9).

Therefore, as the tension force F of the lower belt 3, if the thickness of the lower belt 3 is t (ss), then F -ty 5-Wb
−t+ ty e(Wb−W+) ・t−■ is required.

Here, since Wl represents the stepped width of the pulley, Ws<W
+ <Wb.

Therefore, the service pulley 14 is used in place of the drive pulley 5 in FIG. 8, and the lower belt 3 is
When tension is applied to the lower belt 3, which corresponds to the portion with a diameter D1 at the center of the pulley, a tensile strain occurs in the lower belt 3 corresponding to the portion with a diameter D1 at the center of the pulley, since the winding distance is longer than in the portions with a diameter D: at both ends. To explain this in detail, this strain ε8
Although the winding of the stepped pulley 14 occurs at a certain point, in the actual device, the elasticity of the lower belt 3 causes it to remain in a certain range even after it is separated from the stepped pulley 14.

That is, by winding the lower belt 3 around the stepped pulley 14, the tensile strain ε1 obtained by equation This means that it has been assigned to A in advance.

Therefore, of the X-direction thermal expansion strain ε generated by the contact of the lower belt 3 with the molten metal 11, the above-mentioned ε1 is subtracted.

Therefore, the cold frame portion r (Wb-W
The amount of supplementary strain to be added to s) is Δε=ε−ε1(m−
/ms) = °■.

Converting this to belt stress (σa), σ a −Δ
ε・E (kg/■-2) ・・・■
becomes.

Therefore, as is clear from a comparison between FIG. 5 and FIG. 6, the tension force to be applied to the lower belt 3 is σ−ε , · E σ eN σ I+ σ a The tension force in the X direction can be reduced.

To explain this by substituting specific numerical values, φ DI 1
1 = 61O-1I φ D, proverb 609.5vw
W b =1650mmS W l fog 145
0 ■-Ws = 1320mm, W
c = 65 amey s -5,
0kg/am", a-1, L2 x LO-'am7mm
"cΔ・θ -100℃, E=2.I XIO'
kg/++s't -1,4am, (1650-1450) xl, 4-18134-18
130 ((+u+/as) From formula 0 σa = 3.OXl0-'X2.I XIO
'-6.3 (kg/ms") X100-44.4 (%) In other words, the required belt tension in the X direction is
F, l -18130xo, 444 tan 8046kg compared to 18130kg.

In formula (2), including the second example described below, the diameter D8 at both ends is D, with respect to the diameter at the center.
E Here, σy: The dimension may be slightly smaller than the yield stress of the belt.

Next, to explain the second embodiment of the present invention, as shown in FIG. 5, by making the drive pulley 15 have a barrel-shaped outer shape, it is possible to suppress the elongation of the lower belt 3 in the width direction (Y direction). ,
Thermal strain 13 can be reduced. This barrel-shaped drive pulley 16 does not necessarily have to be stepped, as shown in FIG.

Note that the present invention is not necessarily limited to an inclined twin belt caster, but can also be applied to the input pulley 18 and the pulleys 18 and 19 of a vertical twin belt caster as shown in FIG. In addition, in FIG. 7, 20 indicates a tension pulley.

〔Effect of the invention〕

In the present invention, in the axial direction of the drive pulley, both ends of the drive pulley at positions wider than the width of the slab are formed to have a smaller diameter than the diameter of the central part of the pulley. The tension force in the longitudinal direction of the belt can be halved. As a result, the belt tension device and the like can be downsized. Furthermore, with regard to the tensile stress generated in the belt, the stress at both ends of the belt is reduced, so the elongation of the ears on both sides of the belt is eliminated, and the life of the belt can be further extended.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the first embodiment of the present invention, Fig. 2 is a front view of the first embodiment, and Fig. 3 is a view of the belt in the width direction during casting to which the present embodiment is applied. Figure 4 is a diagram of internal tensile stress distribution in the belt width direction during casting using the conventional example, Figure 5 is a front view of another embodiment of the present invention, and Figure 6 is a diagram of internal tensile stress distribution in the belt width direction during casting using the conventional example. A front view of yet another embodiment,
FIG. 7 is a conceptual diagram of a vertical twin belt caster, FIG. 8 is a conceptual diagram of a general twin belt caster as a whole, and FIG. 9 is a conceptual perspective view of belt thermal distortion. 1... Twin belt caster, 2.3... Belt, 6... Dam block, 4, 5... Drive pulley, I
O... Belt tension device, 12... Slab, 14
...Stepped Boo Li. Figure 4 Figure 5 Figure 6 Figure 7 F1

Claims (1)

[Scope of Claims] A pair of belts, a pair of dam blocks sandwiched between the ears of these belts and constructed in parallel, a drive pulley and a tension pulley around which these belts are wound, respectively; and a belt tension device for moving a tension pulley, in which both ends of at least one driving pulley at a position outside the slab width in the axial direction have a diameter smaller than the diameter of the center portion of the pulley. Belt drive pulley for twin-belt casters.