FI88623C - Copper alloy and process for its preparation - Google Patents

Abstract

The copper alloy consists of 0.05 to 0.4 % of zinc, 0.02 to 0.3 % of magnesium and 0.02 to 0.2 % of phosphorus, the remainder being copper and impurities resulting from manufacture, and is intended to be used especially as a material for continuous casting moulds.

Description

1 88623

Copper alloy and method of making it

The invention relates to copper le jeerlnk and a process for its production.

5 Copper, mainly of the SF-Cu type, has long been used as a material for the production of bar castings for the continuous casting of high-melting metals such as steel, which, due to its high thermal conductivity, allows heat to be removed from melt-10 relatively quickly. The wall thickness of the molds is chosen to be large enough to withstand the expected mechanical stresses.

In order to improve the heat resistance, it has been proposed to make bar casting molds from an alloy containing at least 85% copper and at least one other alloying element which causes precipitation-hydrogenation. It is proposed to use up to 3% chromium, silicon, silver and beryllium as an alloying element. Bar casting molds made from this raw material have not been completely satisfactory either, because silicon and beryllium, used in particular as alloying elements, severely impair the thermal conductivity (AT patent publication 234,930).

None of these solutions has been entirely satisfactory as a raw material for bar casting molds.

It is therefore an object of the present invention to provide a copper alloy having good thermal conductivity, high mechanical strength, especially at temperatures above 300 ° C, and good thermoplasticity. The raw material must be particularly useful for the production of bar casting molds.

The process relates to a copper alloy characterized in that it contains 0.05 to 0.4% zinc, 0.02 to 0.3% magnesium, 0.02 to 0.2% phosphorus, up to 0.2%, preferably not more than 0,1%, silicon and not more than 0,15% of zirconium, the remainder being copper and impurities from manufacture.

2,88623

It is known that the addition of zinc or magnesium slightly reduces the conductivity of copper, while the addition of phosphorus leads to a sharp decrease in conductivity. Addition of zinc, magnesium or phosphorus pa-5 improves strength. Quite surprisingly, however, it has been found that the addition of all three of these elements together to the claimed concentrations does not or only slightly reduces the conductivity compared to commercially available SF copper. The strength is substantially higher than that of SF copper due to the curing phenomena caused by the mixed crystal curing as well as the additional formation of phosphodes which are capable of precipitation. In particular, the heat resistance is substantially better than that of SF copper. An alloy containing 0.1 to 0.25% zinc, 0.05 to 0.15% magnesium and 0.05 to 0.1% phosphorus has been found to be particularly advantageous, with the remainder being copper and manufacturing impurities.

The addition of silicon to a concentration of at most 0.2%, preferably at most 0.1%, has a positive effect on the hardness and thus the wear resistance.

Adding zirconium to a maximum concentration of 0.15% results in improved thermoformability.

In addition, these additives, when combined with controlled heat treatment, allow the softening behavior to be improved. Neither additive, at the concentrations given, leads to a significant deterioration in thermal conductivity.

The invention also relates to a method for producing the copper alloy described above. The process is characterized in that the alloy is thermoformed after casting, annealed for 1 to 6 hours at a temperature of about 300 to 550 ° C, and then cold-formed by at least 10%.

Cold molding of at least 10% between the hot molding and the precipitation annealing at 300 to 550 ° C has a positive effect on homogenization and the combination of properties.

3,88623

It is particularly preferred to thermoforming the alloy above the maximum solubility temperature of the alloying elements and then rapidly cooling it to at least 750 ° C. With this measure, an additional curing effect of 5 can be achieved. However, solution heating can also be done separately from thermoforming.

In order to improve the strength, it is advantageous to carry out another cold forming of at least 10% after the last precipitation annealing.

The invention will be further illustrated by means of an exemplary embodiment.

An alloy containing 0.19% zinc, 0.09% magnesium and 0.07% phosphorus with the remainder being copper and manufacturing impurities was thermoformed by extrusion after casting and then cold formed by drawing 20%. The alloy was then annealed for five hours at 500 ° C. Test pieces were then prepared, cold formed at 10, 20 and 40%. The properties of these samples are shown in Tables A, B20 and C compared to SF-copper and copper-chromium-zirconium alloy.

A comparison with bar casting molds with a frequently used raw material, SF copper, clearly shows that when the degree of molding is comparable, the strength values across the line are about 50% higher. Conductivity is also higher. What is essential, however, is that the softening behavior at high temperatures is clearly more advantageous. Thus, the raw material according to the invention softens when the conductivity is comparable only at temperatures above 30,500 ° C. An additional advantage is the substantially lower creep elongation at elevated temperatures, which results in better non-distortion. Overall, it can be expected that the copper alloy according to the invention is excellently suitable as a raw material for bar casting molds. Compared to the copper-chromium alloy, the alloy of 4,88623 according to the invention cuts quite well. Since the alloy according to the invention is substantially simpler to manufacture and the alloying elements are cheaper, bar casting molds of the same durability made from this new raw material should be cheaper.

The technical properties of the alloy are somewhat better if the thermoforming is performed at the solution heating temperature, then rapidly cooled, and then the operations described above are performed. By separating the 10 intermediate phases from the copper matrix, even better strength and conductivity values can be achieved.

5,88623

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Claims (5)

1. Copper alloy, characterized in that it contains 0.05 - 0.4% zinc, 0.02 - 0.3% magnesium, 0.02 - 0.2% phosphorus, not more than 0.2%, preferably at most 0.1%, silicon and at most 0.15% zirconium, the remaining part being copper and from the production of impurities. Copper alloy according to claim 1, characterized in that it contains 0.1 - 0.25% zinc, 0.05 - 0.15% magnesium and 0.05 - 0.1% phosphorus, wherein the remainder is copper and impurities from the production. 3. A process for making a copper alloy according to claim 1 or 2, characterized in that the alloy is hot-formed after casting, is annealed for 1-6 hours at a temperature of about 300-550 eC and then cold-formed at least 10%. 4. A process according to claim 3, characterized in that the alloy is cold-formed after hot forming at least 10%. 5. A process according to claim 3, characterized in that the hot forming is carried out above the maximum solubility temperature and the alloy is cooled rapidly from a temperature of 750 ° C.