JPS63194848A - Continuous casting method for solid composite and hollow composite round cast billet - Google Patents

Abstract

PURPOSE:To continuously and effectively produce a solid composite or a hollow composite round cast billet by making a drawing velocity in a mold at 0.45-2.0m/min, making over-heating degree of molten metal for cast-in at 20-100 deg.C and forming under satisfying the specific condition. CONSTITUTION:While inserting the stainless steel-made solid or hollow round material 3, into both end opening mold 2 directly connecting with a tundish 1 at one end thereof, the molten carbon steel 4 is poured around the core material 3 from the tundish 1. and, while continuously solidifying the molten steel 4 in the mold 2, it is intermittently or continuously drawn. This cast billet formed by satisfying the inequality after finding etad=d/D and etat=2t/D as dimensionless parameters, in which use D for the cast billet diameter, (d) for the core material outer diameter and (t) for thickness of the core material under condition of 0.45-2.0m/min drawing velocity and 20-100 deg.C the over-heating degree of the molten steel for the cast-in.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for continuously producing composite solid or composite hollow round slabs as materials for seamless clad steel pipes, for example.

(Conventional technology and its problems) In recent years, with the rapid progress and development of industrial technology and changes in social conditions, there has been an increasing demand for materials that have various characteristics that cannot be achieved with conventionally known single materials. In order to meet these demands, various composite materials including kraft steel have been proposed and put into practical use.

By the way, the methods for producing clad steel generally include the explosion bonding method,
The rolling method, overlay welding method, and casting method are well known, but the former three methods involve joining the laminated material to the surface of the base material using each method, and are low in terms of productivity and cost. However, there are problems with the method of manufacturing raw pipes for seamless clad steel pipes.

On the other hand, the casting method is a method of manufacturing by enclosing the core material with molten metal, and there is a possibility of continuous casting, and there are high expectations for productivity improvement and cost reduction.

Conventionally, as a promising means of practical application for continuously manufacturing composite materials by such a casting method, for example, Japanese Patent Application Laid-Open No. 53-29229 and Japanese Patent Application Laid-Open No. 54-71039 have been proposed.
A method such as that disclosed in Japanese Patent Application No.

The methods described in the above-mentioned publications attempt to continuously manufacture composite rolls and composite billets, and the method is to continuously manufacture composite rolls and composite billets by inserting a mold into a horizontal mold with both ends open and connected to the sides of a tundish that holds molten metal of different types. The idea is to manufacture a composite material with high efficiency by continuously inserting a core material from the side, solidifying and adhering molten metal around the core material, and continuously pulling it out with pinch rolls.

However, in such a horizontal continuous casting method, since the core material is supplied through the side of the tundish, an extremely complex and highly accurate mechanism is required to prevent molten metal from leaking from the core material supply section. Practical application on an industrial scale was extremely difficult.

On the other hand, as a method for manufacturing or recycling composite rolls,
Means as disclosed in Japanese Patent No. 4903 is also known.

The method for producing or reproducing a composite roll disclosed in Japanese Patent Publication No. 44-4903 is to use a graphite type with a thin copper plate placed under a fire-resistant heating type containing a hollow water-cooled copper coil through which high-frequency current is passed. Next, a stack of molds with both ends open is used, and a worn roll or a cylindrical body for new manufacturing is inserted vertically into these molds, and the surface is preheated with high-frequency current while being lowered. After this, molten metal of a desired material is continuously injected into the gap between the base body and the mold, and at the same time, the base body is continuously lowered to build up the molten metal on the surface of the base body.

However, in this method, the surface of the base material is coated with low-melting glass to prevent oxidation.
This coated glass will be caught at the interface between the matrix and the molten metal. Therefore, in this method,
The casting speed (drawing speed) must be reduced to about 50 to 100 m/min, which poses a problem in terms of productivity.

As mentioned above, many proposals have been made regarding continuous casting of composite materials, but none of them has been established as a practical technology, and so far, it has not been put into practical use.

Therefore, the present applicant has solved these problems, and has made it possible to cast composite hollow slabs as a material for seamless clad steel pipes at high speed and in long lengths, and to make it possible to completely connect them at the time of casting. Patent application for continuous casting method of composite hollow slabs in 1988-
It was proposed in the specification and drawings of No. 46829.

That is, as shown in Figure 1, there is a tanditsh l at one end.
While inserting the hollow core material 3 into a mold 2 with both ends open, the molten metal 4 is injected around the inserted core material 3 using the tundish 1, solidified continuously, and then pulled out intermittently or continuously. In a method of continuously casting composite slabs, only the outer surface of the hollow insertion core material 3 is melted, and a composite round slab with good bonding during casting is obtained.As an example, a billet size of 208 mm is used. (Mold diameter φ21
For 6m1) slabs, we melted only the outer surface of some hollow core materials and introduced joining in the cast state.

In FIG. 1, 5 indicates a support roll for the core material 3, 6 indicates a feed nozzle refractory, 7 indicates a connecting refractory, and 8 indicates a solidified shell.

Although the invention described in Japanese Patent Application No. 61-46829 previously proposed by the present applicant is an excellent method, it is necessary to adjust the joining conditions at the time of casting for various billet sizes in order to respond to the diversification of product thalassod sizes. This had the inherent problem of being extremely inefficient because it had to be discovered through experimentation.

The present invention aims to provide a continuous manufacturing method for composite solid and composite hollow round slabs that can solve these problems.

(Means for Solving the Problems) The present invention involves inserting a solid or hollow round core material of stainless steel into a mold with both ends open to which a tundish is directly connected, and then inserting carbon steel from the tundish around the core material. A method of producing a composite solid or composite hollow round slab by injecting molten metal and drawing it intermittently or continuously while solidifying the molten metal continuously in the mold, the drawing rate being 0.45 to 2. Continuous production of composite solid and composite hollow round slabs at a speed of .0 m/min, with a superheating degree of the cast molten metal of 20 to 100°C, and satisfying the conditions of the following formula. It's a method.

That is, the present invention sets the conditions for melting only the outer surface of the core material inserted for any round billet size and joining it during casting, using dimensionless parameters η4 and η,
The reason is that the shaded area shown in FIG. 2 was presented. Here, the dimensionless parameters η4, η are the billet diameter D,
When the outer diameter of the core material is d and the thickness of the core material is t, η, = d/D
, η, = 2t/D.

FIG. 2 is a diagram obtained in the following process by carrying out radiation heat transfer analysis in the composite continuous casting method shown in FIG.

First, the core material wall thickness is changed for various core material outer diameters using the slab diameter as a parameter, and the correlation graph between the maximum temperature reached on the inner and outer surfaces of the core material and the core material thickness in the casting calculation at that time (Fig. Figure 3)
Find the point A that cuts these lines and the solidus temperature of the core material.
, B, the state of the core material is classified as follows.

■ Thickness below point A: Hollow core material completely melted ■ Thickness between point A and below point B: Semi-molten (only the outer surface melted) ■ Thickness above point B: Non-melted, and varies depending on the above classification Regarding round slab sizes A and B
The points were determined and rearranged using dimensionless parameters η1 and η5 to create the final Figure 2.

In FIG. 2, the horizontal axis η is the core outer diameter/slab outer diameter ratio. Then, the possible values of η4 are O≦η4≦1
However, when η4=0, there is no core material, or when the core diameter is a certain finite value and the outside diameter of the slab is infinitely large, and when ηd-1, the outside diameter of the core material is the same as that of the slab. Since this is a case in which the diameter is equal to the outer diameter and both values are not realistically possible, the condition range for the hollow cladding to actually exist is 0<η6<1.

On the other hand, the vertical axis η is the ratio of twice the core material thickness/core material outer diameter,
Theoretically, this can also take 0≦η, ≦1, but for the same reason as above, the value that can actually be taken is O<η, <1.

Furthermore, since the outer diameter of the core material cannot be larger than twice the wall thickness, the condition for the core material to exist as a hollow material is 2t<d, that is, η, <η4.

2t=d, that is, η,=η, means that the core material is solid. Therefore, 2t>d or η, 〉η,
The area conditionally does not exist.

Using the dimensionless parameters η4 and ηt in this way,
The conditions for inserting the solid core material are all covered on the straight line of η and -η4 in FIG. On the other hand, the conditions for inserting the hollow core material are all covered by the triangular area at the lower right of the straight line η, = η4.

Note that FIG. 2 was created under the conditions shown in Table 1 below, with η6 and η being arbitrarily changed.

In the first expression, the half-molten region of the core material obtained by calculation, that is, the bonding region during casting, is -0,25ηd +0.25<ηL <-0,45ηd
+0.45 However, it is within the range of η, ≦ηd, which is the shaded area 0 in FIG.

Among the other regions, ■, that is, η, ≦−0.25ηd +0.25 However, in η, ≦η ml, the core material is completely melted and the shape of the hollow round core material cannot be maintained.

Further, in region 0, that is, −0,45ηd +0.45≦η, where η,≦ηd”1, the outer surface of the core material does not melt. Therefore, welding during casting cannot be expected, resulting in a non-bonded region.

Note that *1 in the proviso in each of the above formulas is core material thickness x
This indicates the condition that 2≦the outer diameter of the core material.

(Example) The results of implementing the method of the present invention will be explained below.

FIG. 4 shows an enlarged view of the section where η in FIG. 2 is from 0 to 0.6.

In FIG. 4, the examples shown in Table 2 and the subsequent additional test data shown in Table 3, which were partially shown in the specification of Japanese Patent Application No. 61-46829 by the present applicant, are plotted.

In Tables 3 and 4 above, = X100 (%)1-(
η4-η) 2 - ηd''X100 (%) Table 4 below shows the chemical compositions and solidification temperatures of the core material and the molten metal in which it is cast.

In this example, the scum repellent side was coated with a 1:1 mixture of NH4BF and +binder (resin) on the surface of the core material.

FIG. 4 also shows curves of equal cladding ratios in 5% increments from 5% to 30%. As a result, once the required product cladding ratio and billet size D are determined, the outer diameter d and wall thickness t of the core material to be welded during casting can be determined from FIG. 3, which is very practical. Particularly in the joint area 0 during casting, the closer to area (2) the weld area from the outer surface of the core material becomes wider relative to the thickness of the core material, while the closer to area (2) the weld area becomes narrower.

From the correspondence between the example shown in FIG. 4 and the calculation area, it is found that -〇, 3ηd +0.
If the conditions are set in the region of 3 <ηt<0.4ηd +0.4 (η, ≦ηd) (the leakage area in Fig. 5), a better bonding state between the core material and the cast material during casting will be achieved. I confirmed what I could get.

Furthermore, as a result of calculating calculations for the cases where the drawing speed, degree of superheating of the molten metal, and stainless steel core material were changed, we found that: ■ The joining area during casting as shown in Figure 2 depends on the upper bounds of the degree of superheating of the molten metal and the drawing speed. Although it slides slightly upward, it is close to the molten metal supermaturity level T = 20℃ to 100℃, which is normally carried out in continuous casting.
, and a drawing speed of 0.45 m/min to 2. Since the deviation is small at Om/min, prediction based on the area ζ shown in FIG. 2 is sufficient as the setting area.

■ Regarding the core material material, as the solidus temperature of the core material becomes lower for the same molten metal y heat of the casting material, the joining area during casting shown in Figure 2 shifts upwards, but the solidus temperature When casting molten metal or carbon steel is in the range of around 1300°C to 150°C, it is possible to sufficiently estimate the joint failure during casting in the range shown in Fig. 2.

It has been found.

To confirm this, Table 5 shows an example in which an additional test was conducted using a billet size of 216φ.

When the drawing speed is increased, the effect of the scum anti-iB agent applied to the surface of the core material is weakened, and when it exceeds 2 m/min, it becomes virtually ineffective, and impurities are entrapped at the cladding interface, causing the interface to fail even when bonded. It becomes defective.

Slight entrainment was also observed in the case 401.5 m/min in Table 5.

In addition, the solidus temperature of the core material is 5US304
Good bonding was also observed in the test of 5US316, which was about 30°C lower than (1400°C) (Case 5).

Strictly speaking, it is best to create Figure 2 based on individual conditions such as the type of core material and casting material, drawing speed, and degree of superheating of the molten metal. In the continuous casting shown in Figure 1, which is made of carbon steel,
Condition range with high casting frequency: ■ Drawing speed: 0.45 m/min ~ 2. Om/min■ Core material solidus temperature: 1300~1500℃■ Cast walnut carbon steel superheating degree: △T - Cladding slab design by presenting the joining condition range during core material casting at 20℃~100℃ This made it easier.

(Effects of the Invention) As explained above, according to the present invention, the following effects can be obtained.

1) In continuous casting of composite solid or composite hollow round slabs of arbitrary size (core material: stainless steel, casting material: carbon steel), the joint area during casting is organized by dimensionless parameters η4, η. Quantified.

2) From the joint area during casting shown in Figure 2, η4, η,
By reading this, it is easier to obtain bonded clad material during casting, making billet design easier.

3) The lack of generality caused by the conventional arrangement simply based on the cladding ratio has been overcome, and by omitting the joint confirmation test during casting, it has become possible to reduce the number of man-hours and streamline the process.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the method of the present invention, Figure 2 is a diagram of the relationship between η and η6 used in the present invention, and Figure 3 is the relationship between core material thickness and maximum temperature to obtain Figure 2. 4 is an enlarged view of the main part of FIG. 2, and FIG. 5 is a drawing used for explaining the embodiment and is the same drawing as FIG. 2. 1 is a tandish, 2 is a mold, 3 is a core material, 4 is a molten metal,
8 is a solidified shell. Fig. 1 Fold height to far wet Tomoji # Thickness 〆 2/4 Shou Kata Sogai light a l-1 = 2 jira Fig. 4 Tail net t tato 4 mo/Saki hatato person smell 4 shi 5” Gin et al. 5th figure

Claims (1)

[Claims] (1) A solid or hollow round stainless steel core material is inserted into a mold with both ends open to which a tundish is directly connected, and molten carbon steel is injected from the tundish around the core material. In a method of producing composite solid or composite hollow round slabs by drawing the molten metal intermittently or continuously while solidifying it continuously, the drawing speed is set to 0.
．． Continuous composite solid and composite hollow round slabs characterized by being manufactured at a speed of 45 to 2.0 m/min, with a superheating degree of the cast molten metal of 20 to 100°C, and satisfying the conditions of the following formula. Production method. -0.25η_d+0.25<η_t<-0.45η_
d+0.45 (η_t≦η_d) η_d=d/D η_t=2t/D Where, D: Slab diameter d: Core outer diameter t: Core wall thickness