JPH069736U - Steel casting mold - Google Patents

Abstract

(57) [Summary] [Purpose] In a continuous casting mold for steel, which is made of copper or a copper alloy and has a surface protective coating of a dissimilar metal such as nickel or a nickel-based alloy layer on the inner surface This prevents abnormal wear on the inner surface of the mold due to chemical corrosion and electrolytic corrosion due to the presence of spray water. According to the present invention, in a steel continuous casting mold 1 of the above-mentioned type, the lower surface thereof is inclined or curved so that the lower end on the inner surface side of the mold extends downward from the lower end on the outer surface side.
It is characterized in that it is molded into a shape that suppresses the intrusion of spray water.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a continuous casting mold for steel, such as ordinary steel, high carbon steel, stainless steel, and special alloy steel.The internal surface of the mold caused by chemical corrosion and electrolytic corrosion generated at the bottom of the mold It prevents abnormal wear.

[0002]

[Prior art]

 In the continuous steel casting mold, the molten steel at high temperature is rapidly cooled to form solidified slabs, so the base material, that is, the substrate, is made of copper or copper alloy with good thermal conductivity, and the back surface is water-cooled. ing.

The inner surface of the mold is worn by the contact and sliding of the slab. As a result, when the copper component adheres to the surface of the slab, fine cracks called star cracks occur on it, resulting in defective products. Therefore, this is generally prevented by coating the inner surface of the mold with a dissimilar metal such as nickel or a nickel alloy. The absence of this coating and the exposure of copper means that the mold has reached the end of its life. Each time, it is necessary to suspend production for mold replacement, dismantle mold for recoating, repair assembly.

In order to avoid these as much as possible, various proposals have heretofore been made with respect to abrasion resistance of the coating itself and corrosion prevention of copper of a mold substrate which causes peeling of the coating. For example, JP-B-55-40341, JP-B-56-59564, JP-B-57-19130, and JP-B-62-92051 are examples thereof.

These prior art ones are based on the view that the coating mechanically wears or the substrate corrodes, causing the coating to peel off. However, it is clear that the early damage of the coating on the inner surface of the lower part of the mold is related to the intrusion of water from the spray nozzle for cooling the slab provided immediately below the mold.

That is, in the continuous mold of steel, the molten steel injected into the mold forms a thin solidified shell on the surface in contact with the mold and initially adheres to the mold, but as the solidified shell temperature decreases, It contracts and separates from the mold, creating a gap between the mold and the slab. Therefore, in the lower half of the mold, this gap hinders heat transfer from the molten steel to the mold cooling water. This is generally known in the literature for steel continuous casting.

The cast piece after the mold is sandwiched by rows of a large number of rolls facing each other, cooled by cooling water ejected from a large number of spray nozzles provided between the rolls, and solidified inside. The spray nozzle is also installed between the lower end of the mold and the first roll. The water jetted to the high temperature slab is vaporized or dispersed as fine particles and penetrates into the gap between the mold and the slab.

The following events indicate that the mold-slab gap and the ingress cooling water are associated with mold coating damage.

(1) The closer to the spray nozzle, the more severe the damage.

(2) In the size of the cast slab to be cast, the more the nozzles pass, the more serious the damage is.

(3) In the curved mold, a gap is easily formed on the upper surface, and the upper surface is more damaged than the lower surface.

A detailed examination of the worn part at the bottom of the mold revealed a corroded surface that was not mechanical wear, which clearly indicates that chemical or electrolytic corrosion occurred.

Cooling water contains many ions and is an electrolyte. It is known that there is a potential difference between the mold and the slab (JP-A-56-17165), and if there is a potential difference, the metal will be eluted from the mold on the ten side.

Further, there are the following factors that promote the dissolution.

(1) A foreign metal battery is formed between iron, nickel and copper.

(2) A local battery is formed between nickel and copper.

(3) O ₂ is taken by high-temperature Fe to form an O ₂ concentration cell.

If the surface is roughened by chemical erosion or electrolytic corrosion, mechanical wear due to sliding of the slab is promoted, and the coating damage of the mold proceeds at an abnormal speed.

Conventionally, no measures have been developed to prevent abnormal wear of the inner surface of the mold due to chemical corrosion or electrolytic corrosion that occurs at the bottom of the mold.

[0020]

[Problems to be solved by the device]

 An object of the present invention is to solve the above-mentioned problem of abnormal wear of the inner surface of the mold.

[0021]

[Means for Solving the Problems]

 The present invention focuses on and suppresses the infiltration of spray water into the gap between the mold and the slab.

If the jet direction of the spray water is shaken to the side opposite to the mold, the direction in which the water splashes can be made to be the same, but the water is sprayed from the spray nozzle through the slight gap between the lower end of the mold and the first roll. In reality, it is ejected to the slab, and it is impossible to shake the water ejection direction because the roll interferes with the spray nozzle itself (see Fig. 2). In FIG. 2, 14 is a spray nozzle, 15 is an inner surface of the mold, 16 is a foot roll, 17 is a copper plate of the mold, and 18 is a cooling box (frame).

Therefore, the inventors of the present invention changed the flow of the spray water in the direction opposite to the mold without changing the jetting direction of the spray water, and in order to suppress the intrusion into the mold, the lower end of the inner surface in contact with the slab was The lower surface of the mold was inclined or curved so as to extend downward from the lower end on the outer surface side cooled by the cooling box.

As a result, the direct cooling of the spray water on the slab is not hindered, and the indirect cooling at the lower end of the mold is positively energized in addition to the cooling by the cooling water in the cooling box. Therefore, the slab and mold cooling are extremely effective.

[0025]

【Example】

 Next, embodiments will be described with reference to the drawings.

In the figure, reference numeral 1 denotes a steel continuous casting mold, the base body or substrate 10 of which is made of copper or a copper alloy, and the inner surface of which is made of a different metal such as nickel or a nickel-base alloy layer. A surface protective coating 11 is applied. On the outer surface of the mold 1, a cooling box 12 for cooling the mold 1 with water is provided.

The lower surface of the mold 1 is formed in a slant or curved shape that is slanted downward from the outer surface side to the inner surface side, and the lower end on the inner surface side in contact with the slab is lower than the lower end on the outer surface side cooled by the cooling box 12. It is designed to extend downward. The reference numeral 13 is attached to the inclined or curved portion. The example shown is for an inclined type.

The degree to which the lower end on the inner surface side of the mold 1 extends downward from the lower end on the outer surface side due to the formation of the sloped or curved portion 13 can be changed in a wide range, but generally a copper plate (substrate 10) The thickness may be 1/2 or less.

The inclined or curved shape may be formed on the entire lower surface of the mold 1, or may be formed as shown in the figure, that is, in the region from the outer surface to the inner surface to the intermediate portion. In addition, the inclined or curved shape may be formed on a new mold or on an existing mold. In the existing mold, the required shape may be obtained by overlay welding.

A test example of the mold according to the present invention is shown below.

Cast steel type; ordinary steel Mold dimensions; thickness 253 mm, maximum width 2100 mm, height 904 mm Mold coating specifications: 1st layer nickel plating, 2nd layer nickel alloy plating (Hc or hypercoat) Mold bottom surface specifications; diagram 1 Average casting speed: 1.2 m / min When the operation was performed under the above conditions, the following results were obtained.

Operation example 1; 906 charge does not cause abnormal wear on the upper surface side, 1525 charge does not cause abnormal wear on the lower surface side Operation example 2; 909 charge does not cause abnormal wear on the upper surface side, 1051 charge does not cause abnormal wear on the lower surface side Operation example 3; 557 No abnormal wear on the upper surface side when charged, no abnormal wear on the lower surface side at 1036 charges. On the other hand, conventional wear caused abnormal wear at 600 charges.

[0033]

[Effect of device]

 As is clear from the above description, according to the present invention, it is possible to perform casting in an amount of about 1.5 to 2 times as long as the life of the casting mold, as compared with the casting using the conventional casting mold. In addition, a great effect can be obtained in terms of cost, the above-mentioned effects can be achieved, and the desired problem solution can be achieved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a mold according to the present invention.

FIG. 2 is an explanatory view in which the spray nozzle cannot be directed downward in relation to a roll, and FIG. 2 (A) is a plan view thereof.
(B) shows a partially longitudinal side surface.

[Explanation of symbols]

 1 Mold 10 Mold Substrate 11 Surface Protective Coating 12 Cooling Box 13 Inclined or Curved Part 14 Spray Nozzle 15 Mold Inner Surface 16 Foot Roll 17 Mold Copper Plate 18 Cooling Box (Frame)

Claims (1)

[Scope of utility model registration request] 1. A steel continuous casting mold, which is made of copper or a copper alloy and has a surface protective coating of a dissimilar metal such as nickel or a nickel-based alloy layer provided on the inner surface, the lower end on the inner surface side in contact with the slab. However, the lower surface of the mold is formed to be inclined or curved so as to extend downward from the lower end on the outer surface side cooled by the cooling box, for continuous casting of steel.