JPH03285742A - Graphite mold for continuous casting - Google Patents

Abstract

PURPOSE:To stably cast an alloy containing element of high vapor pressure with high quality for a long time by specifying penetrated porosity and penetrated pore radius in a graphite mold. CONSTITUTION:Volume ratio of the penetrated pores penetrating from inner face of the graphite mold 4 facing to a molten metal to the face except the inner face is made to 15-18%, and the average value of radius in the penetrated pores is made to >=1.7mum. By this method, the vapor or the oxide, etc., of metal having high vapor pressure is passed through the penetrated pores with heat flux and discharged to outside of the mold and sticking of oxide, etc., to the inner face, etc., in the mold is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a graphite mold suitable for continuous Elf manufacturing of copper alloys and the like having high vapor pressure.

[Conventional technology and its issues]

As shown in FIG. 1, which shows the main parts of the continuous casting method by taking the horizontal continuous casting method as an example, the continuous casting method includes a casting mold 2 in which molten metal 1 is stored and a graphite mold 4 whose outer periphery is covered with a cooling jacket 3.
The molten metal 1 supplied from the casting furnace 2 is solidified in the graphite mold 4 to form an ingot 5,
This is a method of pulling out this material with pinch rolls 6 and casting it.

By the way, the solidification form of the molten metal in the continuous casting method as described above is as shown in FIG. 4 A thin coagulated layer 7 is formed on the inner surface, and this coagulated layer 7
As the thickness increases, it solidifies and shrinks and separates from the inner surface of the graphite mold 4, and a gap 8 is created between the inner surface of the graphite mold 4 and the solidified layer 7.

Therefore, in order to satisfy the characteristics of thermal conductivity, heat resistance, and high-temperature strength required for a mold, the graphite mold described in - has traditionally been made of a material with a high density, that is, a low porosity, and a small pore radius. A small graphite mold was used.

However, when casting copper alloys etc. containing elements with high vapor pressure by the continuous ↓17 casting method using such graphite molds, it is necessary to Evaporates from layer 7, forms fine oxide particles either as is or by reacting with oxygen in the atmosphere, adheres to the inner surface of the graphite mold, grows, and finally solidifies into coarse protrusions. The artifacts came into contact with the surface of the layer 7 and roughened the surface of the solidified layer 7, that is, the casting surface, and were also entangled in the ingot 5, causing blow balls.

Therefore, it is necessary to remove such roughened areas and blowholes by rubbing the surface of the ingot, etc., resulting in a problem of significantly lowering productivity.

[Means and effects for solving the problem] The present invention has been made by conducting intensive research in such a situation, and by limiting the through porosity and through pore radius of the graphite mold to predetermined values, the thermal conductivity, etc. It was discovered that the adhesion of the oxide etc. to the inner surface of the 11i mold could be prevented without functioning as a mold, and after further research, the present invention was completed.

I! According to the present invention, the volume ratio of through pores penetrating from the inner surface to the surface other than the surface of the tJi metal forming graphite type 11i is 15 to 18%, and the average radius of the through pores is 1. This is a graphite mold for continuous casting which has a '4I+' sign that it is 7 μm or more.

In the present invention, through porosity and titanium oxide of lead mold
This is the volume ratio of the pores uniformly distributed in a graphite mold having one opening on the surface facing the metal and the other opening on the other surface to the total volume of the black ship mold.

However, in the mold of the present invention, since such 5-membered pores are present in the mold, it is difficult to absorb heat from the high pressure steam of 7 atmospheres or the oxides of the metals listed in I-1. , it passes through the f3i three-membered hole and is released to the outside of the mold, thereby preventing the oxides and the like from sticking to the inner surface of the mold.

In the present invention, the through porosity of the graphite mold is 15 to 18%.
Also, the radius of the ten through holes is
The reason for limiting the size to 7 μm or more is that the porosity through each bundle is 15%.
less than or ij1 vent ゛1'-average diameter ([6 or 1.7
This is because in the case of 71'Ii less than 11m, the oxides etc. adhere to the rock vents over time and block the through pores, making it impossible to cast high quality ingots stably over time. Also, the through porosity is 18
%, the proportion occupied by the entire pores increases and the thermal conductivity of the 517 type decreases, making it impossible to obtain the desired casting speed.

〔Example〕

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

Example 1 Using the horizontal continuous casting apparatus shown in Fig.
A 5/35 brass rod was continuously cast for 150 hours with intermittent withdrawal at an average speed of 250 mm/min. A graphite mold with an outer diameter of 50 mm, an inner diameter of 15 mm, and a length of 25 (] mm) was used as the mold, and the graphite material of the graphite mold was made of various materials with different through-hole porosity and through-pore radius. .

The quality of various ingots produced using graphite molds of different +A quality was investigated. In addition, the gas permeability was measured for the graphite≦lf type before and after JLJ construction.

The results are shown in Table 1.

In addition, a sample was taken from the vicinity of a cut out Elf type of graphite material with a through porosity of 1.1, and this sample was immersed in mercury, and then degassed to inhale mercury into the through pores in the sample. Calculated based on weight change before and after inhalation.

The radius of the through pores was measured by observing the cross section of the sample after inhaling mercury using an electron microscope. Further, the gas permeability was measured by an air suction method (DIN5] 058).

As is clear from Table 1, when graphite type 2.1 of the present invention is used (No. 1, 2), the speed is 250 mm/min.
Continuous casting was possible for 150 hours at a predetermined speed.

In addition, the ingot was of excellent quality with a good casting surface and no defects such as cave holes.

On the other hand, in Comparative Example No. 3.5.6, the 11f surface became rough and blow balls occurred during casting. This is because the CJ/B1 vent radius on the inner surface of the through hole is outside the limit value of the present invention, so Znn adheres to the inner surface of the through hole as Znn vapor oxide, etc., blocking the through hole, and as a result, oxidation occurs on the inner surface of the mold. This is due to something sticking to it and growing into a coarse protrusion.

When the inner surface of the mold was observed after the completion of ILI production, it was observed that many protrusions such as oxides were adhered to the inner surface of the mold of No. 3.5.6 of the above comparative example.

On the other hand, Comparative Example No. 4 had a large through-porosity, so the overall porosity increased, the thermal conductivity of the mold decreased, and a predetermined casting speed could not be obtained.

The difference in gas permeability of the mold before and after casting was small in the graphite mold of the present invention, whereas in the comparative examples, the permeability significantly decreased after casting, except for No. 4. This is the [] of the through pores.
This confirms that the blockage has progressed.

Although the 65/35 brass round bar has been described above, the graphite mold of the present invention can be applied to other alloys containing elements with high vapor pressure such as Cu-Mg alloys, and the shape can be square or plate-like. However, the same effect as described above can be obtained.

〔effect〕

As described above, according to the mold of the present invention, an alloy containing an element with a high vapor pressure can be stably cast with high quality over a long period of time, and this has an industrially significant effect.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams of essential parts, respectively, showing an example of a continuous casting method and a solidification mode of the above method. 2. Casting furnace, 3. Cooling jacket, 4. Graphite type 11i, 5. 7P lump, 6 pinch roll, 7 coagulation layer, 8 gap.

Claims (1)

[Claims] The volume ratio of through pores penetrating from the inner surface of the graphite mold to a surface other than the above surface relative to the cast metal is 15 to 18%.
. A graphite mold for continuous casting, characterized in that the average radius of the through pores is 1.7 μm or more.