JPH03291133A - Mold for continuous casting - Google Patents

Abstract

PURPOSE:To continuously cast a high quality cast billet at high speed by specifying the hole diameter of a mold at the molten metal side, the hole diameter at the cast billet drawing side, the hole diameter at the intermediate part and step difference and inclining angle. CONSTITUTION:The diameter Da of a hole A at the molten metal supplying side in the mold, the diameter Db of a hole B at the cast billet drawing side and the diameter Dc of a hole C at the intermediate part, satisfy the inequality Da<Dc<Db, and boundary part between the hole A and the hole C is enlarged to this diameter by a step difference distance (d) satisfying the inequality I as step-like in the right angle direction to the mold axis from the hole A, and the hole C is made to the shape enlarging the diameter with the inclining angle theta satisfying the inequality II from the above step difference lower part to the position of the hole B in order. Under the condition, where the tip part 4 of a solidified layer reaches the step difference part 3 and does not yet reach the inner face of the hole A, the cast billet 2 is drawn by the prescribed distance and successively, stopped for the prescribed time to again solidify the molten metal. As the tip part 4 of a solidified layer can be formed to thick and the taper at the cast billet drawing side is applied in the mold, by drawing the cast billet at only a little, this is separated from the mold 1 and micro crack is not developed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a continuous casting mold capable of casting high quality ingots at high speed.

[Conventional technology and its issues]

In the conventional continuous casting method, for example, as shown in the main part of the horizontal continuous casting method in FIG. The molten metal 6 supplied from the casting furnace 8 is solidified in the mold 1 to form an ingot 2, and the ingot 2 is pulled out by a vinyl roll 9 and cast.

By the way, the above-mentioned drawing of the ingot 2 is carried out by intermittent drawing in which an intermittent electric signal is programmed to the vinyl roller 9 and the drawing and stopping operations are repeated alternately. The reason why the ingot 2 is drawn out intermittently is to form a thick solidified layer when the ingot is stopped and to prevent cracks from forming in the solidified layer even if the tension is increased during drawing. A method has also been proposed in which the tip of the thin coagulated layer is intentionally destroyed in place of pushing in part of the above-mentioned pulling out/stopping operation, and only the stronger coagulated layer is left behind to be pulled out.

However, even with these drawing methods, when trying to increase the casting speed, fine cracks occur on the surface of the ingot, and since these cranks are removed face-first, the manufacturing yield is significantly reduced. there were.

(Means and effects for solving !If) What is the present invention?
In view of the situation, pull out and stop, or pull out and push in,
As a result of intensive research into the mechanism by which micro-cracks occur when casting is performed by repeating alternating stopping operations,
As shown in Fig. 4, the solidification form inside the mold shows that when the ingot 2 is pulled out from the stopped state, static friction and kinetic friction occur between the solidified layer tip 4 before mold release and the inner surface of the mold 1. When the ingot 2 is pulled out, tension that overcomes these frictions acts, and as a result, microcracks occur in the thin solidified layer tip 4 that is sliding against the mold 1 and in the solidified layer 5 that has already been released. After discovering this, and conducting further research, the present invention was developed.

That is, the present invention provides a mold used in a continuous casting method in which molten metal is supplied from one end of a mold with both ends open, solidified to form an ingot, and the ingot is pulled out from the other end. A hole A with a diameter Da on the molten metal supply side, a hole B with a diameter Db on the ingot withdrawal side, and a hole B with a diameter Db on the ingot withdrawal side.
c gari, <D. <It is composed of a hole C that satisfies the formula of Da, and the boundary between the holes A and C is a step-like step in a direction perpendicular to the mold axis from the hole A that satisfies the following formula (1). A mold for continuous casting, characterized in that the diameter of the hole C is expanded by a distance d, and the diameter of the hole C is gradually expanded from the lower end of the step to the position of the hole B with an inclination angle θ that satisfies the following formula (2). It is.

0.005Da≦d≦0.025 D, ・−・−(1
)0. OO3≦tanθ≦0.015 −・・・・・−
(2) The present invention will be specifically explained below with reference to the drawings.

FIG. 1 is an explanatory side sectional view of a cylindrical mold showing -JJpJ of the mold of the present invention.

The cylindrical mold l has a hole A with an inner diameter Db on the molten metal supply side,
It consists of a hole B in the inner diameter of the ingot drawer side, and a hole C in the middle between the holes A and B, and the hole C is perpendicular to the mold axis direction at the end of the ingot drawer side of hole A. A stepped portion 3 having a length d is provided in a step-like manner in the direction, and the stepped portion 3 is tapered and successively enlarged in diameter from the lower end E to the ingot drawing side, and is formed in a continuous manner with the hole B. .

The solidification form of the molten metal in the mold is such that the solidified layer tip 4 reaches the stepped portion 3, as illustrated in FIGS.
In a state where the ingot 2 does not reach the inner surface of hole A (Fig. A), the ingot 2 is pulled out a predetermined distance (the same quality), and then the drawing is stopped for a predetermined period of time to allow it to solidify again to the state shown in Fig. A (Fig. C).
, the ingot 2 is pulled out a predetermined distance to perform casting, and the tip 4 of the solidified layer is stopped from collapsing in the longitudinal direction at the step 3 and solidification progresses only in the thickness direction, so the tip 4 of the solidified layer The solidified layer 5 is formed thickly, and the static friction generated during drawing is reduced by the taper, and furthermore, the solidified layer 5 formed at the tapered part allows the taper of the mold 1 to be adjusted by just slightly drawing out the ingot 2. As a result, no kinetic friction occurs between the inner surface of the mold and the solidified layer 5, and therefore the tension applied to the solidified layer 5 during drawing is significantly reduced, causing microcracks in the solidified layer 5. There will be no need to enter.

In the mold of the present invention, the reason why the step distance d is limited to 0.005 Db or more and 0.025 Db or less is that 0°005
If it is less than Da, the solidified layer tip 4 will not be formed thickly and will break during extraction, causing microcracks.
．． When the temperature exceeds 025 Da, the tip 4 of the solidified layer is formed thickly in the stepped part 3, and the adhesion with the stepped part 3 increases, and the tension applied to the solidified layer 5 increases when the ingot 2 is pulled out, and microcracks 7 are formed in the solidified layer 5. This is because

In addition, in the present invention, the reason why the inclination angle θ of a part of the taper is limited to a range of 0.003 or more and 0.015 or less in terms of tan θ is that if it is less than 0.003, the effect of reducing static and kinetic friction due to the taper is insufficient. 0 again because I can't get enough
．． ．． This is because when the temperature exceeds O15, the slope of the outer circumference of the solidified layer 5 increases, and at the time of drawing out, the molten metal 6 enters between the solidified layer 5 and the mold 1 and solidifies, causing a fogging defect.

When casting using the mold of the present invention, the ingot 2 is cooled by a cooling jacket 7 that covers the outer periphery of the mold, as shown in FIG.
Alternatively, the ingot 2 may be cooled directly at the outlet of the mold, but it is preferable to control the position of the solidification tip within the mold by moving the cooling jacket 7 in the front-rear direction. In addition, the drawing pitch of the ingot 2 should be shortened to within the length of the tapered part of the hole C of the mold 1 shown in FIG.
This is preferable because the position of can be accurately controlled.

〔Example〕

The present invention will be explained in detail below using examples.

A rod-shaped ingot of 65/35 brass was cast using the mold of the present invention having the shape shown in FIG.

A graphite mold is used for the mold, and its shape is 25011 mm in length.
II+, a cylindrical shape with an outer diameter of 50 a + m, the inner diameter of the hole A on the molten metal supply side was 13 mm, the length was 5 (1 + m), and the inner diameter of the hole B on the ingot outlet side was 151111. The length of the hole B,
The step distance d and the taper angle θ of the hole C were varied. The melting temperature of the above brass is 1150°C, the amount of water in the cooling jacket is 2012/sin, the amount of direct cooling water at the mold outlet is 5J2/in, and the drawing pattern of the ingot is 30-1 drawing pitch and 0.5 drawing time. sec
, the stopping time was 0.5 sec, and the average casting speed was 18
00 mm/win. In addition, the mold temperature at the lower end E of the step was controlled to 890°C, which is about 10°C lower than the solidus temperature of the brass, by moving the cooling jacket back and forth, so that this step became the solidification tip position. .

For comparison, a 65/35 brass rod-shaped ingot was cast under the same casting conditions as above using a conventional cylindrical graphite mold with an inner diameter of 151I11, an outer diameter of 50 mm, and a length of 250 mm.

Each of the 65/35 brass rod-shaped ingots thus obtained was examined for the presence or absence of micro cranks and fogging. The results are shown in Table 1.

As is clear from Table 1, the ingots of the examples of the present invention had no microcracks or fogging defects and were of excellent quality.

On the other hand, the ingots of Comparative Examples were all inferior in quality. That is, in No. 5, since the taper angle exceeded the limit value of the present invention, molten metal entered the outer periphery of the solidified layer, causing a fogging defect.

In addition, microcracks occurred in Nos. 6 to 8, but this was because the step part in No. 6 was too long and high tension was required to separate the tip of the coagulated layer from the step part, and in No. 7, the length of the step part was too long. Because the length was too short, it was not possible to form a thick tip of the solidified layer, and because No. 8 used a conventional mold with a flat inner surface, the thickness of the tip of the solidified layer was thin, and static and kinetic friction were applied during drawing. It is.

When the ingots Nos. 1 to 8 above were processed into wire rods with a diameter of 3 openings by drawing and the surface properties were observed, it was found that the ingots Nos. 1 to 8 of the present invention
Wire rods Nos. 1 to 4 had a smooth surface, and no influence of the stepped portion on the inner surface of the mold was observed.

On the other hand, Comparative Examples Nos. 5 to 8 had many splinter-like defects caused by rock cracks or fogging defects, and all required peeling.

Among the comparative examples above, in No. 8 using a conventional mold, the casting speed was changed to 1 in order to prevent micro cranks from occurring.
It was necessary to reduce the rate to about 30 ss/sin and form a thick solidified layer.

Although 65/35 brass has been described above, the mold of the present invention can be applied to any other metal such as copper, copper alloy, Af or A1 alloy, and the same effects as in the case of brass can be obtained.

〔effect〕

As described above, according to the mold of the present invention, high-quality ingots can be continuously cast at high speed, and this has an industrially significant effect.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing the -IQ aspect of the mold of the present invention, Fig. 2 A to C are side sectional views showing the -IQ aspect of the solidification form of the inventive mold, and Fig. 3 is an explanation of the horizontal continuous casting method. 4 are side sectional views showing the solidification form of a conventional mold. 1--Mold, 2--Ingot, 3--Step part, 4--
・Tip of solidified layer, 5... Solidified layer, 6... Molten metal,
7... Cooling jacket, 8... Casting furnace, 9... Vinci roll.

Claims (1)

[Scope of Claims] A mold used in a continuous casting method in which molten metal is supplied from one end of a mold with both ends open, solidified to form an ingot, and the ingot is pulled out from the other end, the mold The hole A has a diameter D_a on the molten metal supply side, and a diameter D on the ingot withdrawal side.
A hole B called __b and a hole B in the middle part with a diameter D_c of D_a
<D_c<D_b, and the boundary between hole A and hole C satisfies the following formula (1) in a stepped manner from hole A in a direction perpendicular to the mold axis. step distance d
The continuous casting mold is characterized in that the diameter of the hole C is gradually expanded from the lower end of the step to the position of the hole B with an inclination angle θ that satisfies the following formula (2). 0.005D_b≦d≦0.025D_b……(1)
0.003≦tanθ≦0.015……(2)