JP2926169B2 - Heating method of continuous cast slab - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for charging a continuous cast slab to a heating furnace for heating.

[0002]

2. Description of the Related Art Continuous cast pieces cast by a continuous casting machine are:
At the time when the solidification to the inside is completed, it is cut to a predetermined length by a cutting torch or the like. At that time, cutting burrs are formed in the continuous cast piece. For example, in the case of a curved continuous casting machine, since cutting is normally performed from the upper surface to the lower surface, cutting burrs are generated on the lower surface side of the continuous cast piece.

[0003] Conventionally, regardless of the orientation of the surface on which the cutting burrs are formed, the material is charged into a heating furnace in the same orientation as when the cutting was performed, heated to a certain temperature, and then rolled.

[0004]

The slabs produced by the continuous casting machine are classified into slabs, blooms and billets according to their shapes. Among them, blooms (hereinafter referred to as "continuously cast slabs") are Because it has a large cross section, it is usually rolled to a size of about 100 to 180 mm square by slab rolling (hereinafter, the material after rolling is referred to as “slab”), then heated again, and hot rolled to the final dimensions. You.

Normally, when a billet is manufactured from a continuous cast slab by a slab rolling machine, the material at the surface portion flows more in the rolling direction than at the center portion, so that the end portions are described later with reference to FIGS. b)
The shape is as follows. When a steel slab having such a shape is rolled as it is to the final shape and dimensions as it is, a rolling failure occurs. Therefore, the end is cut so that the subsequent rolling does not cause a failure. Further, in the continuous cast piece, burrs are generated at the time of cutting, and the burrs remain even after slab rolling. Therefore, if the cutting including the burrs is not performed at the time of cutting the end portion, the final product will be defective.

[0006] It is desirable to shorten the cutting length as much as possible from the viewpoint of yield in cutting the end portion. However, the conventional method has the following problems. That is, when manufactured by the conventional method, the continuous cast piece is charged into the heating furnace in the same direction regardless of the direction of the cutting burr.
In many cases, the continuously cast piece is continuously cut from the upper surface to the lower surface. For example, in a curved continuous caster, the continuous torch is cut by a cutting torch 4 as shown in FIG.
Is generated on the lower surface side of the continuous cast piece 1 and charged into the heating furnace in the same direction.

However, since the temperature inside the heating furnace is lower in the lower part than in the upper part, the surface on which cutting burrs are formed is:
Rolling is performed with the heating temperature lower than the other surfaces. As a result, the flow of the material in the rolling direction on the surface where the cutting burrs 2 are generated is reduced, as shown in FIG. When the shape of the end portion of the billet 3 is as shown in FIG. 2 (a), if the cutting including the cutting burr 2 is to be performed, the cutting weight increases and the yield decreases.

[0008] In the case of a curved continuous casting machine, the solidification structure is different between the upper surface and the lower surface, so that the problem is further exacerbated. Specifically, since the equiaxed crystal appearing in the center of the continuous cast piece is slightly shifted from the center to the lower surface side, the thickness of the columnar crystal appearing outside the equiaxed crystal is larger on the upper surface side,
This difference in structure appears as a difference in hot workability. That is, the thicker upper surface of the columnar crystals is easily stretched in the rolling direction by hot rolling, and furthermore, as described above, the upper portion of the heating furnace has a higher temperature. When heated and rolled, an end shape is obtained in which the elongation of the upper surface and the lower surface is largely biased. Therefore, on the lower surface side during continuous casting with cutting burrs, since the material flow in the rolling direction is small, the distance between the tip of the slab and the cutting burrs becomes longer, and the cutting amount increases.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems, and it is possible to reduce the amount of end cuts after slab rolling of continuous cast pieces and improve the yield. An object of the present invention is to provide a method for heating a slab.

[0010]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, the present invention performs various experiments while accurately grasping the relationship between the surface on which cutting burrs are formed and the orientation at the time of loading into a heating furnace. Do
It has been completed based on the obtained knowledge.

That is, according to the present invention, in a step of cutting a continuous cast piece cast by a continuous casting machine, transporting and loading the cast piece into a heating furnace, heating the same to a certain temperature, and rolling, a cutting burr of the continuous cast piece is provided. This is a method for heating a continuous cast slab, wherein the slab is charged into a heating furnace such that the surface on which is adhered becomes the upper surface, heated to a certain temperature, and then rolled.

For example, in a curved continuous casting machine, when a cast continuous cast piece is cut from the upper surface to the lower surface, transported and charged into a heating furnace, heated to a certain temperature, and then rolled, After the cutting, the upper surface and the lower surface are inverted, and they are charged into a heating furnace such that the upper surface during continuous casting becomes the lower surface, heated to a certain temperature, and then rolled.

[0013]

According to the present invention, when a continuous cast piece cut by a continuous casting machine is cut, conveyed and charged into a heating furnace, it is charged into the heating furnace such that the surface on which cutting burrs adhere is the upper surface. By doing so, the extension of the cutting burr side surface in the rolling direction increases, and the position of the cutting burr after rolling to the steel slab can be brought closer to the tip of the steel slab, so that the amount of end cutting is reduced, The yield can be improved.

Further, in the case of a continuous cast piece cast by a curved continuous casting machine and cut from the upper surface to the lower surface, a difference in hot workability occurs due to a difference in thickness of columnar crystals depending on the surface. In the case, the upper surface side during continuous casting, which has better hot workability than the lower surface side during continuous casting, is charged so as to be a lower surface in the heating furnace, which has a lower temperature. The change in hot workability is well-balanced and the difference in material flow between the upper surface and the lower surface in the rolling direction is small, so that the cutting length can be kept short.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be described below with reference to embodiments. A continuous cast slab obtained by casting molten steel of SUP9 Cr-Mn spring steel melted in an electric furnace with a curved continuous caster (slab slab cross-sectional size: 370 mm × 480 mm) with a gas from the upper surface to the lower surface with a length of approx. 34
It was cut to 00 mm. At that time, cutting burrs having a length of about 10 to 30 mm were formed on the lower surface of the continuous cast slab.

The continuous slab thus manufactured was charged into a heating furnace and heated to 1150 ° C., and thereafter, a steel slab having a cross section of 130 mm square was manufactured by a slab mill. When the continuous cast piece in the middle of this manufacturing is loaded into the heating furnace, it is manufactured separately when it is loaded so that the surface on which the cutting burrs are formed is turned upside down, and when it is loaded without being inverted as before. did. The experiment was performed under the same manufacturing conditions except for the direction of the cutting burrs when the heating furnace was charged.

After the end of the slab rolling, the end was cut into a suitable length, and the shape of the end was examined. Fig. 2
As shown in the figure, the measurement was performed by measuring the difference a in the length in the longitudinal direction between the upper surface and the lower surface, the distance from the tip to the cutting burr 2 (hereinafter referred to as the cutting burr remaining position) b, and the depth c of the turning-up. Table 1 shows the measurement results. In addition, a shown in Table 1,
The values of b and c are the differences a in the longitudinal length according to the conventional method.
The average value of the measured values is shown as 100, and the average value is shown as an integer ratio.

[0018]

[Table 1]

As is apparent from Table 1, by applying the method of the present invention, the difference between the upper surface and the lower surface of the material flow in the longitudinal direction is significantly reduced, and the longitudinal direction of the surface on which the cutting burr is present is obtained. As a result, the position of the cutting burr was shifted to the tip side as compared with the conventional method, and the value of the cutting burr remaining position b could be suppressed by 40 to 60%.

The required cutting length is determined on the basis of the larger one of the remaining cutting burr position b and the curving depth c. That is, in consideration of the variation in the end shape, the required cutting length is 150 + α in the conventional method, which can be reduced to 110 + α in the present invention.

Therefore, the method according to the present invention was repeatedly carried out in order to grasp how much the cutting length can be actually reduced. As a result, it was confirmed that the final rolling quality was not affected even if the cutting length was shortened by 25% as compared with the conventional case.
In order to grasp the effect more accurately, the steel slab manufactured by the conventional method was cut at the same time with the same cutting amount, and the end after cutting was observed. Some remained, and it was confirmed that the cutting amount could not be reduced unless the method of the present invention was applied.

The method of the present invention was first tested with spring steel, but the effect was confirmed as described above.
Similar trial production tests were also conducted on other steel types such as carbon steel, Cr steel, and Cr-Mo steel, which have a large production volume. As a result, similar results were obtained for all steel types, and the effect of the method of the present invention was confirmed.

[0023]

According to the method for heating continuous cast slabs of the present invention, when charging a continuous cast slab cast by a continuous casting machine into a heating furnace, the direction in which cutting burrs are attached is changed to the upper surface. Therefore, the position of the cutting burrs after the slab rolling can be moved closer to the tip of the billet, and the cutting length can be reduced. Since this method can be applied to many types of steel in the same manner, it can greatly contribute to improvement of the yield when manufacturing steel slabs from continuous cast slabs.

[Brief description of the drawings]

FIG. 1 is a view showing a state of generation of cutting burrs of a continuous cast piece in a curved continuous casting machine.

FIGS. 2A and 2B are diagrams showing an end shape of a continuous cast piece after slab rolling, wherein FIG. 2A is a diagram showing an end shape according to a conventional method, and FIG. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous cast piece 2 Cutting burr 3 Steel piece 4 Cutting torch 5 Mold 6 Tundish

Claims (1)

(57) [Claims] In a process of cutting a bloom cast by a continuous casting machine (hereinafter, referred to as a “continuous cast piece”), transporting the charged bloom into a heating furnace, heating it to a certain temperature, and then rolling, A method for heating a continuous cast piece, wherein the cast piece is placed in a heating furnace such that the surface of the cast piece to which the cutting burrs adhere is the top face, heated to a certain temperature, and then rolled.