JPH02166248A - Mold material for precipitation hardening continuous casting - Google Patents

Abstract

PURPOSE:To manufacture the material having high strength and high heat conductivity, having excellent high temp. toughness, particularly having high fatigue resistance and by which long service life characteristics of a mold can be obtd. by forming it with the compsn. contg. each prescribed amt. of Ni, Be, Zr, Mg and the balance Cu with inevitable impurities. CONSTITUTION:The above material for a precipitation hardening continuous casting mold is formed with the compsn. constituted of, by weight, 0.2 to 2.0% Ni, 0.05 to 0.5% Be, 0.5 to 1.5% Zr, 0.01 to 0.1% Mg and the balance Cu with inevitable impurities. In the mold material, each element of Ni, Be, Zr and Mg is added, in the ratio, to Cu which is the main ingredient to drastically improve high temp. elongation and to exceedingly improve thermal fatigue resistance. Then, the mold material has higher thermal fatigue resistance than not only that of tough pitch copper, phosphorus deoxidized copper and Ag-contg. phosphorus deoxidized copper which are the non-precipitation hardening material but also that of the above invention which is the precipitation hardening alloy. Thus, the mold material is most preferable as the mold material in continuous casting of steel or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used for continuous casting of steel, etc., and not only has high strength and high thermal conductivity, but also has excellent high-temperature toughness, particularly high fatigue strength, and the inherent long life of the mold. This invention relates to a precipitation hardening type continuous casting mold material.

Since the introduction of the continuous steel casting method, non-precipitation hardening materials such as tough pitch copper, phosphorus-deoxidized steel, and phosphorus-deoxidized copper containing Ag have been used as mold materials. In place of these materials, precipitation hardening materials such as chromium copper and Cu-CrZr alloys have been adopted, extending the useful life of the mold by a large amount. This is because precipitation-hardened materials have slightly lower thermal conductivity than non-precipitation-hardened materials, but their strength at high temperatures is much greater, resulting in significantly less deformation, which is a factor that determines the lifespan of mold materials. It is from.

However, in the future, continuous casting of steel will tend to have a larger unit production volume than in the past, and the trend will be toward so-called high-speed continuous casting, so deformation during high-speed continuous casting will become a problem even for chromium copper etc. For mold materials, even if the thermal conductivity is reduced to some extent, further improvements in high temperature strength and fatigue strength are required.

In order to meet this demand, the present inventors have developed and already provided a Cu-Ni-Be-based precipitation hardening mold material for continuous casting that combines high strength, high thermal conductivity, and high-temperature toughness (
(Japanese Patent Publication No. 63-3940, hereinafter referred to as the "prior invention alloy").

It is true that the recently invented alloy has improved high-temperature strength compared to chromium copper, etc., and has also been found to be better able to prevent mold deformation, resulting in a significant improvement in terms of shortening mold life due to deformation. Furthermore, the life of the mold is affected by the problem of so-called fatigue strength, in which cracks occur on the mold surface near the menicus due to thermal fatigue during long-term use.

Such thermal fatigue cracking is closely related to the elongation of the mold material at high temperatures, and thermal fatigue cracking is suppressed in materials with high elongation at high temperatures. A material with high ductility (tensile elongation at high temperatures) is desired. However, the above-mentioned prior invention alloy has an elongation of 8% or less at a service temperature of 400°C, for example.
Further elongation is required for true longevity.

The mold material of the present invention was obtained by improving the alloy of the prior invention in view of the above circumstances, and has a weight ratio of Ni: 0.
2-2.0%, Be: 0.05-0.5%, Zr: 0.
6-1.5%, Mg: 0.01-0.1%, balance C
This material is made of U and inevitable impurities, and is heat treated by solution treatment and aging treatment to have high strength, high thermal conductivity, and high elongation at high temperatures, preventing thermal fatigue cracking, and forming molds. The present invention is characterized in that it is a precipitation hardening type continuous casting mold that can provide a long service life.

That is, Ni and Be are added to Cu to form a precipitation aging alloy to maintain high strength and high thermal conductivity at high temperatures, and 0.6% to 1.5% (weight ratio) of Zr and Mg are added to the alloy.
By further adding , this mold material has enhanced high temperature strength and further enhanced high temperature elongation, thereby significantly increasing the thermal fatigue strength of the above-mentioned prior invention alloy.

Next, in the mold material of the present invention, the reason why the component composition range is limited as described above will be explained.

Ni is added to lower the solubility of Be. If it is added less than 0.2%, the effect will be weak, and if it exceeds 2%, the effect will not increase in spite of the addition, and on the contrary, high thermal conductivity will be inhibited.

Be is an important element for increasing strength through precipitation aging, and if it is less than 0.05%, the strength will not increase, and if it is more than 0.5%, not only will the thermal conductivity become very poor, but it is also an expensive element. Therefore, it is uneconomical.

Since Zr performs coagulation binary precipitation aging with Cu, it is an element that is useful for increasing the strength of the material and at the same time is necessary for elongation at high temperatures. In particular, in order to prevent the occurrence of thermal fatigue cracking in molds as described above, if the amount is less than 0.6%, most effects can be expected, but if it is more than 1.5%, the effect is small, and the element oxidation is significant, resulting in poor castability.

Mg is added to improve elongation at high temperatures, but if it is less than 0.01%, the effect is small, and if it is more than 0.1%, the thermal conductivity deteriorates, making it unsuitable for mold materials.

As mentioned above, the mold material according to the present invention is mainly composed of C.
It is a precipitation-hardening copper alloy that has N1, Be, Zr, and Mg added in specific ratios to u, greatly improving high-temperature elongation and significantly improving thermal fatigue strength. Not only tough pitch copper, phosphorus-deoxidized copper, and phosphorus-deoxidized copper containing Ag, which are precipitation hardening materials, but also the above-mentioned previous invention, which is a precipitation hardening material.
It is a mold material for continuous casting that has higher thermal fatigue strength than the alloy (Comparative Example Alloy 1) and the conventional Cu-0r-Zr alloy (Comparative Example Alloy 2).

The table shows numerical values comparing the chemical composition and electrical conductivity of the example alloy group according to the present invention and the above-mentioned comparative example alloy, and Figures 1 to 3 show representative examples of each of the above-mentioned alloys. A performance test at high temperature for the following figures: (1) Comparison of high-temperature tensile strength (Figure 1), high-temperature yield strength (Figure 2), and high-temperature elongation (Figure 3) is shown in a curve graph. Moreover, FIG. 4 shows the rotating bending fatigue strength of representative examples of each alloy in a curve graph.

As is clear from FIGS. 1 to 4, the copper alloy of the present invention is compatible with Cu-Cr-Z, which is currently used as a mold material.
In addition to being stronger than the r-based alloy (comparative example alloy 2), it has greater elongation at the mold usage temperature of 300 to 400°C, and is a material with strength and toughness. Even when compared with the intermediate alloy (Comparative Example Alloy 1), it can be seen that it is excellent in high-temperature strength, high-temperature elongation, and especially fatigue strength, which are the objectives of the present invention.

As described above, the copper alloy of the present invention has further improved strength and elongation at high temperatures, particularly high fatigue strength, and has the optimum properties as a mold material for continuous casting of steel etc. .

Comparative example alloy 1: Preliminary alloy Comparative example alloy 2: Conventional example Cu-Cr-Zr alloy

[Brief explanation of the drawing]

Figures 1 to 3 show the high temperature tensile strength, high temperature yield strength, and
It is a curve graph comparing high temperature elongation. Moreover, FIG. 4 is a curve graph comparing the rotating bending fatigue strength of each of the above alloys. Chuetsu Alloy Hammer Co., Ltd. OJ Co., Ltd.

Claims (1)

[Claims] 1) Weight ratio: Ni: 0.2-2.0%, Be: 0.0
5-0.5%, Zr: 0.6-1.5%, Mg: 0.0
A precipitation hardening type continuous casting mold material having a composition of 1 to 0.1% Cu, the balance being Cu and unavoidable impurities.