JPS63303658A - Squeezing type continuous casting method and its apparatus - Google Patents

Abstract

PURPOSE:To prevent sticking of solidified shell and to lengthen service life of side plates by making the tapered side plates arranged at both side edge parts in squeezing type continuous casting apparatus by water cooled metal plates, coating lubricator on the surface thereof and casting at more than the specific casting speed. CONSTITUTION:Molten metal is poured 6 in casting space formed by one pair of water cooled endless belts 1, 2 and the tapered side plates 4, 5 arranged at both side edges to continuously cast a cast slab 7. These tapered side plates 4, 5 are made to for example even copper-made or stainless steel-made water cooled side plates, and in the case of casting at >=4 m/min casting speed, the solidified shell is scarcely stuck on the side plates 4, 5 even without using refractory lining 4a, 5a, and the continuous casting operation is stabilized, and the service life of the side plates 4, 5 is lengthened. Further, by coating the lubricator of molibdenum disulfide, boron nitride, etc., on the inner faces of the side plates 4, 5, the sticking of the solidified shell can be further prevented.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a drawing type continuous casting method and its device, and in particular, by adding a device to the side plate of a thin slab continuous casting machine, breakouts and inability to pull out can be prevented. The aim is to enable stable casting for a long period of time without causing any trouble.

(Prior art) A continuous casting machine (which continuously manufactures thin slabs such as sheet bars directly from molten metal (explained below using the example of "molten steel"))
For example, various types of belt casters have recently been proposed. The illustrated synchronous belt caster, a typical example of which is shown in Figure 7, is of the narrowing type and maintains a gap to hold the cast metal (cast material such as molten steel or solidified shell) over a predetermined distance. At the same time, a metal belt 1.2 supporting a pair of long side surfaces disposed opposite to each other and moving circularly through a plurality of guide rolls 3a, 3b, and 3c, respectively, and a side edge of each metal belt located between the two metal belts. A casting space is created by confining the casting space on all sides by means of tapered side plates 4.5 for supporting the short side surfaces that are in close contact with each other. In particular, the side plate 4.5 is
In order to obtain a thin plate with a thickness of 30 mm or less, considering the diameter of the injection nozzle 6 (approximately 100 mm or less), the diameter of the injection nozzle 6 should be at least refractory, with an approximately inverted triangular shape that is wide at the top and gradually tapers toward the bottom, and has a constant width. Lining layer 4a, 5a of the object
A structure with the following is required.

In such a conventional belt caster, the above side plate 4.5
During casting, especially at the start of casting, due to heating, the solidified shell generated there is delayed from the solidified shell on the other (long side) side of the metal belt 1.2, and the growth rate increases. must be slowed down. The reason for this is that in order to obtain a thin slab 7 with a thickness of 801111 or less, for example, a considerable amount of reduction is required, and if a solidified shell forms on the 4.5 parts of the side plate at the same rate or faster than that on the long side,
Compression at the bottom where the casting space narrows can cause wrinkles,
This is because the pull-out resistance increases, and in extreme cases, the pull-out may not occur at all.

For this reason, as already proposed by the inventors in JP-A-58-32551 and JP-A-58-32552, the inner surface is made of refractory material and at the same time a heater is buried inside the side plate. In addition, prior to the start of casting, a partition plate was erected inside the side plate, and the flame of a gas burner was introduced into the gap to heat it, thereby slow solidifying the solidified shell of the side plates 4 and 5.

(Problems to be Solved by the Invention) As mentioned above, in the conventional belt caster that uses a narrowing method, the side plates are mainly made of refractory material in order to delay the formation and growth of solidified shells on the short sides. However, depending on the material, refractories can undergo thermal spalling and cause thermal cracking, and wear and tear can be significant especially when there is a lot of molten steel for continuous casting, so it is difficult to maintain the stability of continuous casting. There was a problem.

Another problem was that it took time and effort to set the refractory on the inner surface of the side plate.

This invention advantageously solves the above-mentioned problems, and not only eliminates the trouble of setting refractories on the inner surface of the side plate, but also achieves a drawing type continuous casting method that significantly improves the stability of continuous casting. The purpose is to propose a method along with a suitable continuous casting apparatus for its implementation.

(Means for solving problems) First, the background to the elucidation of this invention will be explained.

In the case of squeeze-type belt casters, if a solidified shell forms on the short side at the squeeze part, it becomes difficult to pull it out downwards, so as mentioned above, refractories were used to prevent this. .

However, according to the inventors' research on this point,
Even if a thin solidified shell forms on the short side of the drawing part due to low molten steel temperature or insufficient preheating of the refractory,
It has been found that when the amount of cooling water is abundant and a sufficient water film is maintained between the belt and the cooling vat, and the belt driving force is sufficient, it is possible to pull out the slab. From this fact, the inventors newly came to the conclusion that the side plates on the short sides of the throttle part do not necessarily need to be made of refractory material.

Therefore, the inventors investigated various materials that could replace conventional refractories as side plates that support the short sides, and found that stainless steel, which has high heat resistance and is said to have slow heat conduction among metals, It has been found that a substrate made of a metal such as the following is advantageously suitable.

In other words, when we conducted a casting experiment using a stainless steel plate as the side plate, we found that only a slight solidified shell on the short side was visible in the area corresponding to the meniscus in contact with the metal side plate, and it was fully possible to pull it out.

Furthermore, if casting was continued for a long time using such a metal side plate, breakout from the short side or failure to pull out may occur due to increased pullout resistance. This problem was solved by adding a lubrication function to the In particular, a lubricant with high lubricity may be applied to the metal surface corresponding to the latter half of the drawing.

This invention is based on the above knowledge.

That is, the present invention is formed by a pair of circulating bodies arranged opposite each other and a pair of side plates disposed on both side edges of the circulation body, and the cough side plates taper into a casting space as they move downward. , A drawing method that consists of continuously supplying molten metal to continuously produce thin slabs while drawing the metal, and casting at a casting speed of 4 m/win or more while cooling the short side of the cast metal. This is a continuous casting method.

Further, in this invention, a casting space is formed by a pair of circulating bodies arranged opposite each other and a pair of side plates arranged on both side edges of the circulating body, and the space is formed in a narrowing type with a wide top and a narrow bottom. This continuous casting apparatus is a drawing type continuous casting apparatus in which the side plate is a water-cooled metal plate.

In this invention, a water-cooled metal plate such as a copper plate or a stainless steel plate is used as the side plate used on the short side, and by improving the durability of the side plate, it is possible to perform high-speed drawing over a long period of time. When a water-cooled metal plate is used as the side plate, a frictional force is generated between the solidified shell of the cast metal and the stationary side plate, and if this frictional force is large, high-speed drawing may be difficult.

Therefore, in this invention, in such a case, the inner surface of the side plate is coated with a lubricant such as molybdenum disulfide or boron nitride in order to reduce the frictional force and enhance the lubrication function. The coating method may be any method such as applying and drying a lubricant slurry or plating using a plating solution in which a lubricant is suspended, and the coated area may be entirely coated or partially coated.

Figure 1 shows the following conditions on the surface of the water-cooled copper plate: i) when no lubricant is applied, ii) when molybdenum disulfide is applied, and iii) when boron nitride is applied, respectively.
The results of an investigation of the drawing torque ratio during steady speed casting are shown.

As is clear from the figure, the drawing torque ratio is reduced by applying a lubricant such as molybdenum disulfide or boron nitride to the surface of the water-cooled copper plate, and therefore more stable casting can be expected.

In addition, when conventional powder used in continuous casting machines is used as a lubricant, the powder also enters the moving belt surface, impairing the cooling effect and surface quality of the slab, which is undesirable. A side plate in which the meniscus portion of the side plate and the lower straight portion of the short side plate are made of metal, and a refractory material is placed between them is disadvantageous for casting because lubricant adheres to the refractory material.

The upper half of the short side plate (corresponding to the area near the meniscus) can be made into a short piece shell that easily deforms by applying lubricant to the metal plate surface or roughening the metal plate surface to reduce heat conduction without using refractories. It becomes easier to pull out the slab.

The casting speed here needs to be 4 m/+min or more. This is because when it is less than 4 m/lll1n, a thick solidified shell grows from the short side of the cast metal, and the shell cannot be squeezed at the bottom where the casting space narrows, and the pull-out resistance becomes large, making it impossible to pull out or restricting the metal. This is because breakouts may occur.

Figures 2a and b show the relationship between casting speed and the incidence of non-pullout and restrictive breakout when water-cooled copper plates and water-cooled stainless steel plates are used as side plates, and when the inner surface of the side plates is coated with lubricant. The results of the investigation are shown below.

As is clear from the figure, regardless of the presence or absence of lubricant,
Stable casting is achieved by setting the casting speed to 4 m/min or more.

Also, the distance d (
m) That is, as the distance for performing narrowing increases, the pull-out resistance also increases, and there is a greater possibility that pull-out will become impossible or that a restrictive breakout will occur.

Figures 3a and b show the drawing distance d (m) and casting speed v (m/win) when water-cooled copper plates and water-cooled stainless steel plates are used as the side plates, and when the inner surface of the side plates is coated with lubricant. The relationship between the ratio d/v and the incidence of non-retractable and restrictive breakout is shown.

As is clear from the figure, in order to perform stable casting, it is preferable that d/v be 0.5 or less regardless of the presence or absence of a lubricant.

Next, Fig. 4a and b show the effect of casting speed v (m) on stable casting.
), the results of investigating the effects of the slab thickness t (m) and the length l (m) of the side plate straight section at the time of completion of drawing are j! /(v-t) and the short-side breakout incidence rate.

If the casting speed is increased, solidification of the short side shell tends to be insufficient, so it is preferable that the length l of the side plate straight part be long and the slab thickness t be thin, as shown in the figure. It is desirable to perform casting under conditions where /(v-t) is 0.005 or more.

(Example) Example 1 Using the apparatus shown in Fig. 7 as a drawing type continuous casting machine and the side plate having the shape shown in Fig. 5, drawing was carried out as shown in Fig. 6. road fid=0.5
m, length of the side plate straight part! Thin slabs were continuously cast under conditions of = 0.3 m, casting speed Vx2 m/a+in, and 6 m/win.

The casting speed is 2m/1lIin below the lower limit of this invention.
When casting at a speed of 5 m/min, which is the appropriate range for this invention, it was stable without the above problems. It was possible to carry out casting for a long time.

Example 2 The device shown in Fig. 7 was used as a drawing continuous casting machine, and the side plate was a water-cooled copper plate having the shape shown in Fig. 5. As shown in Fig. 6, the narrowing distance d = 0.5 m, the length of the side plate straight part l = 0.03 m, and the casting The speeds are a) V=6m/win, b) V=10m/a+i, respectively.
n, c) A thin slab with a width of 1000 mm and a thickness (t) of 30 mm was manufactured under the conditions of V = 12.5 m/lll1n.

As a result, stable casting could be performed under any casting speed without any failure to pull out or restrictive breakout.

In addition, compared to the conventional case in which a fused silica refractory was used as the side plate, the continuous use time of the side plate was 8 to 10 times longer under each of conditions a), b), and c).

(Effects of the Invention) Thus, according to the present invention, in continuous casting of the drawing type in which the casting space is wide at the top and narrow at the bottom, the side plate is a water-cooled metal plate, particularly preferably a water-cooled metal plate whose surface in contact with the cast metal has a lubricating function. By doing so, compared to the case of using conventional refractories, it is possible to extend the continuous use time of the side plate with high-speed stable casting, and further reduce the time and cost of setting the refractories. be able to.

[Brief explanation of drawings]

Figure 1 is a graph comparing the pull-out torque ratio depending on the presence or absence of lubricant on the side plate surface, Figure 2 a, b
are graphs showing the relationship between casting speed and the incidence of non-pullout and restrictive breakout, respectively. Graphs showing the relationship between the occurrence rate of failure and restrictive breakout, Figures 4a and b, respectively, show the effect of casting speed V on stable casting.
, a graph showing the influence of the slab thickness t and the length 2 of the side plate straight part, FIG. 5 is a diagram showing a preferred example of the water-cooled metal plate according to the present invention, FIG. 6 is a drawing distance d, The length of the side plate straight part! FIG. 7 is a schematic diagram illustrating the slab thickness t, and FIG. 7 is a schematic diagram of a drawing type continuous casting machine. 1.2... Metal belt 3... Guide roll 4.
5... Side plates 4a, 5a... Refractory lining 6... Injection nozzle 7... Thin slab 8... Cooling vat

Claims (1)

[Scope of Claims] 1. It is formed of a pair of opposing circulating bodies that move circularly, and a pair of side plates arranged on both side edges of the circulating body, and the side plates taper downward. By continuously supplying molten metal to the casting space, thin slabs are continuously produced while being squeezed, and the casting is performed at a casting speed of 4 m/min or more while cooling the short side of the cast metal. This is a continuous narrow casting method. 2. Continuous casting in which a casting space is constituted by a pair of circulating bodies arranged opposite each other and a pair of side plates arranged on both side edges of the circulating body, and the space is narrowed with a wide top and a narrow bottom. A drawing type continuous casting device, characterized in that the side plate is a water-cooled metal plate. 3. The apparatus according to claim 2, wherein the water-cooled metal plate is provided with a lubricant on its surface.