JPS5938865B2 - Mold material for continuous casting equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to a mold material for continuous casting equipment.

The properties required of mold materials for continuous casting equipment are becoming increasingly diverse and severe as the speed of continuous casting machines increases, and wear resistance is one of the important properties.

Copper is usually used as a mold material, and various surface treatments have been used to improve the wear resistance of the mold, but the method of the present invention does not require surface treatment. You have to deal with it yourself.

By the way, the wear of the mold not only affects the dimensional accuracy of the strand, but also picks up Cu and impairs the surface quality of the strand.

Therefore, in order to solve the above problem, the inventors 11,
By adding other elements to copper to precipitate a second phase different from the copper α phase, we investigated the relationship between the metal structure of the mold material and the surface texture rating based on Cu pickup.

As a result, even with copper alloy mold materials, the second phase (different phase)
It was discovered that it is possible to significantly reduce surface cracks by rubbing the area occupied by a certain value or more.
The present invention has been completed.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a graph showing the relationship between the area ratio and crack score when a second phase is precipitated in the copper α phase.

As can be seen from this graph, as the area ratio of the copper α phase decreases, the crack score decreases and the surface quality improves.

For example, up to 70% the improvement is small, but 65%
When it becomes less than %, the surface quality rapidly improves by 1,
If 50% is 1/8, the score will be 4.

If the material is further improved, it approaches a nickel surface-treated material.

In FIG. 1, A corresponds to pure copper, and B corresponds to a nickel surface-treated material.

In this way, the reason why a decrease in the area ratio of the copper α phase leads to an improvement in the crack score is not only because the area ratio of the copper α phase in contact with the strand decreases, but also because the decrease in the area ratio of the copper α phase leads to an improvement in the crack score. This corresponds to an increase of 2 in the second phase other than the α phase,
Therefore, the improvement in wear resistance due to the increase in the second phase has a synergistic effect with the decrease in the area ratio of the copper α phase.

By the way, considering that the metal element added to copper is a mold material, it is necessary to satisfy the following requirements.

■ High hardness.

For example, intermetallic compounds are promising.

■ Mutual solid solubility with copper is small.

■ Adding as little amount as possible increases the formation of the second phase.

■ Avoid reducing thermal conductivity as much as possible.

For example, when a β phase, which is not as hard as the α phase in a copper-zinc system, is precipitated as a second phase, the copper α phase decreases as shown by the dotted line in Figure 1. becomes less effective.

Therefore, excluding special manufacturing methods such as sintering, melting and casting method 1
As a result of considering the above-mentioned alloy system, limiting it to one that can be manufactured, it was found that it is sufficient to satisfy the following conditions.

That is, the formation rate of the second phase shown in Figure 1 is 3.
The minimum addition amount is 5% or more, and the maximum addition amount is determined by the amount where the thermal conductivity of the alloy is 12% or more of pure copper.

Cu-5 to 18% satisfies these conditions.
Zr alloys are mentioned.

The reason for ensuring that the thermal conductivity of the alloy was not lower than 12% of that of pure copper was that if it were lower than this, the mold temperature would rise, resulting in an increase in thermal stress within the mold, which would cause problems.

However, as normal molds are used over and over again, they become deformed and worn out, reaching the end of their service life. Deformation is the biggest cause of longevity.

It has been pointed out that the main cause of this fan-shaped deformation is creep deformation due to thermal stress generated on the copper plate during operation.
Therefore, in order to increase the life of the mold, it is desirable that the mold material has a small amount of creep deformation, that is, a cleave strength of 1-1 and a small creep strain.

Therefore, a further improved creep strain of the above-mentioned Cu-5 to 18% Zr alloy will be described below.

This is the above-mentioned Cu-5~18% Zr alloy 1 cochromium,
At least one element selected from titanium and iron is added.

That is, chromium is an element that undergoes precipitation hardening in steel, causing precipitation so fine that it must be observed with an electron microscope, and contributing to improving the creep strength of the CuZr alloy.

As a result of examining the appropriate amount of ROM to be added to improve this cleave strength, we found that the amount of ROM added was 0.6 to 1.5 as shown in Figure 2.
It was found that %.

Note that if it is less than 0.6%, the effect is not sufficient, and if it is more than 1.5%, the effect is saturated.

Next, titanium is an element that has the same effect as chromium, and the appropriate amount of titanium to be added is 0.02 to 0.0, as shown in Figure 3.
It is 20%.

Iron has the effect of refining crystal grains, and the amount of iron added is 0.
0.3% or more is required, and the effect does not change even if it is added in an amount greater than 1.0%.

In this way, chromium, titanium, and iron are each individually 1
Although it is effective even if these are added, the effect becomes more pronounced when they are added in combination.

For example, Cr-Ti. Cr-Fe, Ti-Fe, Cr-
When a compound such as Ti-Fe is added, the creep properties are improved as shown in Table I.

E, Table 1, test conditions for 8, temperature 3
The temperature was 30° C., the stress was 22 kg f /mrA, and the time was 8 hours.

Among the alloys in the table above, Cu6%Zr alloy and Cu
A mold was made from -6%Zr-0,13%Ti-0,5%Fe alloy, and the surface quality of the strand and the conventional copper mold and nickel-plated copper mold (compared in terms of durability of this mold) As shown in Table 2, the result is 1.

The S1 casting speed is 1 or 1.1 m/min, and the casting steel type is low carbon steel.

0 crack rating: 10 (significant crack) 1 (
No cracks) 0 Durability: Ratio of the number of charges that can be cast
As can be seen from Table 2, the mold according to the present invention has improved strand surface properties compared to one pure copper mold.
The mold life is significantly improved.

Note that throughout this specification, % representing the amount of added bIXl in the alloy indicates weight %.

As described above, the Cu 5-18% Zr alloy and the Cu-5-18% Zr alloy of the present invention have Cr: 0.6-1.
5%, Ti: 0.02-0.20%, and Fe: 0.0
By using a mold using an alloy containing at least one element among 3 to 1.0%, the strand surface quality and mold life can be significantly improved compared to conventional pure copper molds.

[Brief explanation of the drawings] Figure 1 is a graph showing the relationship between the area ratio of copper per copper alloy and the crack score on the strand surface.
-A graph showing the relationship between the amount of chromium added to 6% Zr and creep strain, and FIG. 3 is a graph showing the relationship between the amount of titanium added to Cu 6% Zr and creep strain.

Claims (1)

[Claims] 1. In one Cu-Zr alloy, the amount of Zr added is 5 to 1.
Mold material for continuous casting equipment characterized by 8% 1%. 2Cu-5-18% Zr alloy, Cr: 0.6-1.
5%, Ti: 0.02-0.20%, and Fe:
A mold material for continuous casting equipment, characterized in that at least one element selected from 0.03% to 1.0% is added in the above-mentioned proportions.