JPS5850157A - Mold for continuous casting - Google Patents

Abstract

PURPOSE:To decrease the induction losses of magnetic fluxes penetrating through mold walls under electromagnetic agitation and to reduce equipment and running costs by constituting four faces of mold walls of composite plates wherein thin walled copper plates and non-magnetic stainless steel provided with cooling water passages are welded by pressure. CONSTITUTION:Four faces of mold walls 10 are constituted respectively of composite plates wherein copper or copper alloys 11 of <=10mm. thickness and non- magnetic stainless steel plates 12 of >=20mm. thickness are welded by pressure. Plural cooling water passages 15 are provided on the side of the plates 12 nearer than the press-welded surfaces 13. Here, the mold is constituted by using the composite plates satisfying t<=p<=2t and 0.5t<=s<=3t when the thickness of the copper or copper alloy plates 11 is 3-7mm. and the width in the press-welded parts between the passages 15 on the surfaces 13 is defined as (p) and the width of the passages 15 as (s).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of a mold having good penetration of electromagnetic force, which is used when improving the internal quality of a slab by electromagnetically stirring steel.

In general, continuously cast slabs tend to have defects such as shrinkage holes and segregation in the center. As a means of improving this, electromagnetic stirring of the molten steel within the slab shell during solidification is often adopted. The above defects are reduced as a result of microstructural refinement and homogenization by electromagnetic stirring.

Usually, for the stirring part, a secondary cooling zone is selected because it is structurally convenient to allow the electromagnetic force to penetrate into the slab shell. However, in the early stages of solidification, that is, closer to the casting surface,
Since the slab shell thickness is still small, the structure of a wider area of the slab cross section is improved by electromagnetic stirring.

Therefore, in such a case, it is effective to prevent not only the above-mentioned central defect but also internal cracks.

Stirring at the early stage of solidification is electromagnetic stirring of the self-melting steel in the mold.In terms of industrialization, it is relatively easy to carry out continuous casting of small-section slabs, but on the other hand, stirring of large-section slabs is carried out relatively easily. For continuous casting, considerable difficulties arise such as chipping.

Large cross-section continuous casting 7 is usually used for casting slab products.

In terms of mold cost, it is made by assembling four sides of thick copper plates, as shown in Figure 1 (a) and (b). (stomach)
The figure is a longitudinal sectional view, and the figure (b) is a view showing the AA' cross section shown in figure (a). In the figure, a thick copper plate 1 making up the entire mold wall is firmly attached to a water cooling jacket 2 with a large number of bolts 3. A plurality of cooling water grooves 5 are provided in the vertical direction on the back side of the copper plate 1, and the cooling water 6 enters the groove 5 from the water cooling jacket 2 through the entire lower header 7, and then passes through the entire lower header 7 and enters the upper header. It is discharged from 8. A mold 4 is constructed by assembling four such casting walls.

In such molds, continuous casting with a large cross section requires a large electromagnetic stirrer because the copper plate 1 has a thick wall for durability and cooling uniformity, and the resulting magnetic shielding becomes extremely large, resulting in insufficient stirring. equipment is required.

Incidentally, since the electromagnetic force of the electromagnetic stirring device attached around the mold is attenuated to several tenths of that (an effective electromagnetic stirring device becomes uneconomical).

To address this problem, the following methods have been proposed or implemented.

(1) Reduce the power supply frequency and reduce the magnetic shielding caused by the copper plate. Generally, 2 to IO cycles are appropriate for 1.

(2) Divide the copper plate appropriately to subdivide the induced current generated within the copper plate and reduce magnetic shielding.

(3) Make the copper plate as thin as possible. The copper plate is usually about 50M11, and we have taken measures to reduce the overall structure to about 20H.

The first method is always used as a necessary condition when electromagnetically stirring molten steel in a metal mold.

The second method is electrically advantageous but metallurgically extremely difficult. This is because joints are inevitably formed on the inner surface of the mold, which should be smooth, which not only tends to cause molten steel to adhere, but also tends to cause uneven cooling and increased thermal deformation of the mold.

In the third method, the magnetic shielding effect due to the copper plate can be suppressed to some extent, but it is not sufficient, and therefore, in practical use, a large-capacity power source and a coil with excessive output are used.

This is not only disadvantageous in terms of equipment costs, but also causes large power losses, and of course shortens the life of the mold.

The present invention was made to solve the above-mentioned problems, and uses a specially structured composite plate that forms the four walls of the mold, and by providing cooling channels on the joint surfaces, the molten steel inside the mold is reduced. When electromagnetic stirring is performed by a moving magnetic field from around the mold, the entire mold wall should have good penetration of electromagnetic force, so that the induction loss of magnetic flux penetrating the mold wall is less than that, and the size of the electromagnetic stirring device can be small. The present invention aims to provide a continuous casting mold that can reduce both equipment costs and operating costs.

The present invention is a four-sided assembled water-cooled mold for continuous steel casting, in which each of the four mold walls is made by vacuum-pressure welding a copper or copper alloy plate with a thickness of 15 fl or less and a non-magnetic stainless steel plate with a thickness of 20 HM or more. This continuous casting mold is made of a composite plate and has a plurality of cooling channels provided on the side of the stainless steel plate from the pressure contact surface, and has good penetration of electromagnetic force.

The continuous casting mold to which the present invention is applied is a four-sided assembly type water-cooled mold in which an electromagnetic stirring device is provided around the mold for continuous casting of steel.

Hereinafter, the present invention will be explained by examples using the drawings. FIG. 2 is a diagram showing an embodiment of the mold of the present invention, in which (a) is a vertical cross-sectional view of the mold, (b) is a cross-sectional view taken along line B-B' shown in (a), and (c) is a longitudinal cross-sectional view of the mold. The figure shows a cross section of the mold wall.

In the figure, the mold 14 is assembled into a rectangular shape with four mold walls 1o1. As shown in Figure 09, the mold wall IO is made of thin copper or copper alloy plate C with a thickness of 5 mm or less (hereinafter referred to as copper plate) 11 and non-magnetic stainless steel C with a thickness of 2011 or more, simply referred to as stainless steel. ) Plate 12't
- Consists of composite plates joined by vacuum pressure welding.

A plurality of (two or more) grooves for cooling water channels 15 are provided on the surface of the stainless steel plate 12 facing the pressure contact surface 13.
It is joined at the surface excluding t.

As shown in Figures (A) and (0), the lower and upper ends of the cooling water channel 15 are provided with a cooling water inlet 16 and an outlet 17, respectively, and cooling water headers 18 and 19 mechanically cool the water. An electromagnetic stirring device 23 consisting of an iron core 21 and a coil 22 is attached around the 4° mold 14, which is connected to the water inlet 16 and the water outlet 17.
A coaxial rotating magnetic field is generated, and the molten steel in the mold is rotated and stirred around the center shaft, improving the internal quality of the slab.

In the above-described mold, the shape and dimensions of the mold wall IO are appropriately selected depending on the steel material, casting conditions, and electromagnetic stirring conditions, but the thickness of the copper plate II shown in FIG. It is desirable to have a related metal such as a missing part between the width P1 of the pressure contact portion between the cooling water channels 15 and the width S of the cooling water channel 15 between the pressure contact portion 10 and the pressure contact portion 10-.

First, the thickness of the copper plate 11 [balance 51M or less, Bokushikake 3
~7MM. If it exceeds 151 nl, the magnetic shielding becomes large and becomes inappropriate. Therefore, the thinner it is, the better, but if it is less than 3H, the strength will be insufficient and it will be difficult to press the stainless steel plate 12.

The thickness t' of the stainless steel plate 12 is 20 MN or more, preferably 30 to 4 QMM. Copper plate 11 for less than 20MM
There is insufficient strength to reinforce it, and a thickness exceeding 40ffi is unnecessary in terms of strength.

Next, it is desirable that the width P of the pressure contact portion satisfies t≦P≦2t. When P(t), the strength is insufficient to restrain the thermal distortion of the copper plate 11 by the stainless steel plate 12, and when P>2[, the cooling force of the pressure welding part becomes weak, resulting in uneven cooling within the mold surface.

In addition, the width S of the cooling channel 15 on the pressure contact surface lO is 0.5 [≦S≦
It is desirable to set it to 3t. When S<0.5t, it is difficult to improve the cooling capacity compared to conventional thick-walled molds, and when S>a
At <<t, the mold life is suddenly shortened because the thermal distortion of the copper plate 11 is restrained.

Next, vacuum pressure welding is essential for joining the copper plate 11 and the stainless steel plate 12, and is also advantageous in terms of cost. The reason is that the welding method introduces welding distortion to the thin copper plate 11, making it unsuitable for continuous casting molds that require precision. Furthermore, even in the mechanical joining method, members such as fasteners are attached to the thin steel plate 11, which causes uneven cooling. .

The 42 pressure welding method is advantageous in all practical conditions such as accuracy, strength, uniformity of joining force, uniformity of cooling performance, cost, and workability.

Note that the thin copper plate used in the present invention is not limited to pure copper.
It may be a copper alloy plate that has a thermal conductivity as high as that of light; it may also be plated with chromium or the like on the surface to ensure durability.

In addition, the non-magnetic stainless steel plate needs to be non-magnetic and have low conductivity in order to pass magnetic flux, and austenitic stainless steel is suitable.

The continuous casting mold of the present invention configured as described above has the following effects.

(a) Each of the four mold walls has a thickness of l 5 , MM
The following copper or i/i copper alloy plates and non-magnetic stainless steel sheets with a thickness of 20111 or more are vacuum pressure welded, and a plurality of cooling channels are provided on the stainless steel plate side from the pressure welding surface, so that the mold wall is a thin copper plate. Since it is composed of a non-magnetic stainless steel plate, the magnetic shielding is small, and the molten steel inside the mold is electromagnetically stirred through the entire mold wall.Is there an induction loss of magnetic flux penetrating the mold wall of the lid? Can the output of the electromagnetic stirring device and its power supply be reduced? Since it can be designed to be small, both equipment costs and operating costs can be reduced.

(b) In addition, a cooling channel is provided on the pressure welding surface, and since the copper plate between it and the slab is thin, the cooling capacity is large, which is not only advantageous. Because it is pressure welded, it is stronger and has a longer lifespan than conventional molds. Vacuum pressure welding provides good accuracy, strength, uniformity of joining force, and uniformity of cooling performance. It is also an electromagnetic mold that is comfortable to work with and allows continuous casting at low cost. A stirring mold is provided.

[Brief explanation of the drawing]

Figure 1 (a) and (b) are diagrams showing examples of conventional continuous casting molds, in which (a) is a vertical cross-sectional view, and (b) is a cross-sectional view taken along line AA' shown in (a). FIG. Figures 2 (a), (b), and (c) are views showing examples of the mold of the present invention, (a) is a vertical cross-sectional view of the mold, and (b) is (b) a longitudinal cross-sectional view of the mold.
B) A diagram showing a cross section along line B-B' shown in the figure, (Figure -9 is a diagram showing a cross section of the mold wall. 1... Copper plate, 2... Water cooling jacket, 3... Porto, 4... Mold, 5... Cooling water groove, 6... Cooling water, 7... Lower header, 8... Upper header, 10
...Mold wall, 11...Copper or ll'i copper alloy plate, 12
...Nonmagnetic stainless steel plate, I3... Pressure contact surface, 14
...Mold, 15...Cooling channel, 16...Inlet, 1
7...Exit, 18.19...7 goo to cooling water, 21
... Iron core, 22 ... Coil, 23 ... Electromagnetic stirring device, 1.1 / ... Thickness, P ... Width of pressure welding part, S ...
・Width of cooling channel. Yoshi 1 Figure (a) Procedural amendment dated 1982/1980 Commissioner of the Japan Patent Office Shima 1) Haruki Tono1, Patent indicated in the case 1981 Yoshitori I Hitomi Takahan No. 1503272, Invention bird mockery Name of Continuous Casting Mold 3, Relationship with the case of the person making the amendment Patent Applicant Address 5-15 Kitahama, Higashi-ku, Osaka Name (21
B) Sumitomo Electric Industries Co., Ltd. Representative: President Masao Kamei 4, Agent Address: 1-9-20Ji Nishinakajima, Yodoyo-ku, Osaka + In the specification, the claims column and the detailed description of the invention column. 7. Contents of amendment (1) The scope of claims on page 1, lines 4 to 718 of the specification will be corrected as shown in the attached sheet. (2) In the specification, page 5, line 166, "15" is corrected to "10". (3) Delete "vacuum" on page 5, line 188 of the specification. (4) Specification, page 5, line 200: “A road was established.”
[The path is provided, and the thickness t of the steel or copper alloy plate is 3 to 7
11 m1, and when the width of the pressure contact between the cooling channels on the pressure contact surface is P1 and the width of the cooling waterway on the pressure contact surface is S, the relationship is as follows: t≦P≦2t O15t≦S≦8t Correct. (5) Specification, No. 6, line 122, “15” is replaced with “l”
Correct to "O". (6) Delete "vacuum" on page 6, line 155 of the specification. (7) Correct "15" to "10" from page 7, line 15 of the specification. (8) In the specification, page 7, line 166, "15" is corrected to "10". (9) Specification, page 8, line 14 to page 9, line 3, “
Next, divide "copper plate...it's convenient" by 11. 00) Specification, page 9, line 133, "15" is corrected to "10". 61) Specification, page 9, line 155, "vacuum" is deleted. 6, Akira #al, page 1O, line 4, “Because it is thin,
``Because it is thin and has a relationship like the above formula,''
Correct. (l → Specification, page 10, line 6, "vacuum" is deleted. 64) Specification, page 10, lines 7 to 9, "Vacuum pressure welding... Good workability," Therefore, it should be corrected to "Accordingly." Claims ``(1) In a four-sided assembled water-cooled mold for continuous casting of steel, the four mold walls each have a copper or copper alloy plate with a thickness of 0 mm or less and a copper or copper alloy plate with a thickness of 20 mm or more. A mold for continuous hook making with good penetration of electromagnetic force, characterized in that it is made of a composite plate in which non-magnetic stainless steel plates are pressed together, and that a plurality of cooling channels are provided on the side of the stainless steel plate from the pressure-welded surface. ” Japanese Patent Publication No. 58-50157 (6)

Claims (1)

[Claims] (1) In a four-sided assembled water-cooled mold for continuous casting of dt4, each of the four mold walls is made of a copper or copper alloy plate with a thickness of 150 or less and a non-magnetic stainless steel with a thickness of 2011I1 or more. A mold for continuous casting with good penetration of electromagnetic force, characterized in that it is made of a composite plate in which steel plates are vacuum-pressed and is provided with a plurality of cooling channels on the side of the stainless steel plate from the pressure-welded surface. (2) The thickness t of the copper or copper alloy plate is 3 to 71'II,
When the width of the press-contact portion between the cooling channels on the press-contact surface is P, and the width of the cooling channel 1 m above the press-contact surface is S, the following claims have the following relationships: t≦P≦21 0.5t≦S≦3t The continuous casting mold as described in item 1, which has good penetration of electromagnetic force.