JPS5973164A - Continuous casting method of steel - Google Patents

Abstract

PURPOSE:To change the width of a slab without discarding the width change part thereof by determining a sizing schedule that permits the rolling intact the width change part and setting the moving speed of a short side. CONSTITUTION:The sizing schedule having the relation shown by the equation wherein the length in the broad part 6A of a slab 6 is designated as l1, the length in a width change part 100C as l2, and the length in a width narrowing part 6B as l3 and taking the parameter such as the size of a casting mold, the drawing speed of a slab, the movement of the short side of the casting mold, etc. into consideration is determined in the stage of changing the width of the slab during continuous casting. The moving speed of the short side of the casting mold is set in accordance with the schedule. The width change part is rolled as it is widthout being cut away by the above-mentioned method, whereby the change of the width is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous casting method for copper, and its purpose is to provide an economical continuous casting method that has low yield loss of slabs and low energy loss.

As is well known, in continuous casting of steel, in order to improve productivity, the short piece of the mold is moved at any time during continuous casting to change the mold width, that is, to expand or reduce the width of the slab. A method to do this has been proposed and partially implemented. In FIG. 1, approximately 100B of the slab (in this case, strand P) 1 which has undergone such a width change is the width change part, and 2a to 2f indicate the planned cutting lines based on the measuring schedule.

Now, the unit slab including the width changing portion is, for example, shown in Fig. 2 (
The slabs 38 to 3D have shapes as shown in a) to (d),
Conventionally, such slabs 38 to 3D are obtained by cutting and removing diagonally shaded portions 4A to 4D (hereinafter referred to as truncated portions) in FIGS. (called slab)
However, in this case, cutting and removal must be carried out after the slab has been cooled to around room temperature to form cold slabs, which causes a decrease in yield due to the occurrence of cut-off parts. A significant amount of thermal energy is required for pre-heating the good slab before rolling, which is disadvantageous in terms of productivity and economy.

From the point of view of high productivity and thermal economy, it is desirable to send continuously cast slabs to the rolling process while keeping them as hot as possible, but due to technical difficulties regarding quality and heat retention. Until now, implementation has been postponed. but,
Recently, with the development of various technologies such as secondary cooling in continuous casting, heat retention of slabs, and induction heating of the ends of slabs, continuously cast slabs can be rolled without being reheated midway. The so-called direct rolling method, in which light heating such as edge induction heating is performed to perform rolling processing, has come to be practiced industrially.

The direct rolling method is a process that directly connects continuous casting and rolling, and is extremely advantageous in terms of thermal energy.Therefore, in continuous casting, slabs are continuously supplied to the rolling process as much as possible, so it is called continuous casting. t] means will be adopted.

By the way, the slab (including the width-changing section) (hereinafter simply referred to as the width-changing slab) needs to be cut and removed at the cut-off section as described above, so it must be sent to the cooling and cutting process, and it is continuously cast. This has become one of the factors hindering the improvement of productivity and thermal economy.

In order to fundamentally solve the problems of yield reduction and energy loss caused by the truncated portion, the present inventors have researched a method that allows rolling without cutting off the width changing portion, and conducted numerous experiments.
We have developed the method of the present invention.

That is, the present invention sets a measuring schedule in advance so that the mold strip can be rolled without moving it during continuous casting, and changes the strip width by setting the moving speed of the mold strip. This is a continuous casting method for steel.

Now, the conventional slab including the width changing part is shown in Figs. 2(a) to (d).
), the shape of the slab 3A as shown in FIG. Although the aim has been to create a shape in which L is the boundary between a narrow width slab and a medium width slab, the present inventors have made it possible to perform rolling without cutting and removing the cutout portion. Casting and rolling experiments were conducted with various dimensions of the unit slab 6 having a width changing portion 1000 as shown in FIG. 3.

That is, in Fig. 3, if the length of the wide part 6A of the slab is tl, the length of the width changing part 100C is 12 s, and the length of the narrow part 6B is t3, then Q41 in Fig. m2 (,l) In the case of only < t2+t* for slab 3A, and for slab 3 in the same figure (d)
In the case of D < t2 only, the width accuracy and end structure of the product coil after rolling are poor, and Figs. 2(b) and (c)
) as shown in < 11 +4 +1g or p:z t
, +t, slabs 313, 30
The width accuracy and edge texture were both good.

Since it was found that the cast slabs having a boat-shaped appearance like the slabs 3B and 30 were good, next we added boat-shaped slabs 78 to 7DK as shown in Fig. 4, and the dimension t of the width changing part was determined.
An experiment was carried out by holding constant , and varying 11 and t3, and it was found that the larger the dimension of s t , the better the formation.

Next, as shown in Fig. 5, slab 8A~ with constant dimensions < 1+
In the case of 81), the longer the length t2 of the width changing part is, the more
It was found that the coil width accuracy and coil end structure were good.

In addition to the above, as a result of numerous experiments, it was found that if the slab has the relationship shown in (1) 2 below, it can be welded in iM without cutting off the width changing part. .

1 1, 0 ) , □, 4〉0.30・・・・・・・・・(
1) Therefore, the present inventors carried out all the layouts and carried out the measuring schedule so that the relationship of the above-mentioned equation (1) was satisfied for the slab having the width changing part, and achieved a significant improvement in productivity and 5 to 10 % improvement in yield and energy saving effect.

In the present invention, the meaning that the unit slab including the width changing part can be rolled into a shape that can be rolled as it is without cutting and removing the width changing part is used in the sense of satisfying the relationship of formula (1) above. It is something.

The measurement schedule is determined in accordance with the orders received, taking into consideration parameters such as @mold dimensions, slab withdrawal speed, and mold short piece movement speed.

The present inventors have developed a method for easily casting a slab that satisfies the above formula (1) by changing the width of the strip at a high speed of moving the strip at 30 wxA or more and at a high speed of pulling out the slab at 1.4 m7 minutes or more. As explained above, the present invention provides an extremely economical casting method.

[Brief explanation of the drawing]

Figure 1 is a schematic top view of the slab whose width has been changed, Figure 2 (
a) to (■1) are schematic diagrams of various slabs having width changing parts;
Figure 3 is an explanation of the dimensions of each part of the unit slab, Figure 4 (a) -
(d) Schematic diagrams of various slabs when the length of the li width changing part is constant; FIGS. 5(a) to (d) are schematic diagrams of various slabs when the wide part is constant. 1 person... Maximum width slab, IB-... Middle ring slab % IC.
...Narrow width slab, 100A, 100B...Width change part, 2
a to 2f... Cutting plan line, 3A to 3D... Slab, 4
A to 4D...Truncation part, 5A to 5D...Good slab, 6.
... Slabs, 7A to 7D... Ship-shaped slabs agent, patent attorney Masamitsu Akizawa, and 2 others/Diagram

Claims (1)

[Claims] (1) In a continuous casting method for steel in which the width of the slab is changed by moving a mold short piece during continuous casting, the unit slab including the width changing part has a shape that can be rolled as is without cutting and removing the width changing part. A continuous casting method for steel, characterized in that a measuring schedule is determined in advance so that the width of the slab is changed by setting the moving speed of the short mold piece.