KR20020091154A - Use of a hardenable copper alloy for molds - Google Patents

Abstract

The present invention produces a wide slab of thin slab continuous casting molds with an aging hardenable copper alloy having a beryllium content of 0.1% to 0.5% and a nickel content of 0.5% to 2.0% with a casting speed of at least 2 to 6 m / min. It is about the use to use.

Description

USE OF A HARDENABLE COPPER ALLOY FOR MOLDS}

In the prior art, the wide plates of the molds of thin slab plants and in particular CSP (Compact Strip Production) plants are made of copper alloys such as CuCrZr (copper chromium zirconium) or CuAg (copper silver). In that case, the CuAg alloy for CSP casting plate turned out to be preferable since the elongation is relatively high at the time of temperature rise.

However, wide plates of molds made of CuAg or CuCrZr are not able to accommodate the high thermal stresses spread in the area of the bath water level of the cast metal and tend to crack the plates in those areas, especially CuCrZr which cracks very prematurely. Tends to cause. If so, such crack formation is a criterion of shutdown for the wide plate of the mold, which incurs a large repair and replacement cost for the operator of the continuous casting plant.

CuAg, despite its lower tensile strength, can only reduce stress in the mold plate due to its higher elongation at higher temperatures, resulting in reduced crack formation due to the relatively low thermal conductivity at its average operating temperature. It was observed to be visible.

Prior art typically uses CuCrZr with a hardness of about 125 HB on the narrow plate of the thin slab mold, the lateral contact surface of which is plated with nickel to increase the hardness.

The criterion for stopping work on such narrow plates is not the formation of cracks, as opposed to the wide plates, but the wear or wear of the face in contact with the steel. On the other hand, the criterion for stopping work on the wide plate is often crack formation in the casting liquid level zone.

Document DE 31 20 978 C2 in particular is a number of precipitation hardenable copper alloys with various CuNiBe alloys containing niobium (Nb), zirconium (Zr), magnesium (Mg), and / or titanium (Ti) as additional alloying components. And the use of the copper alloy in a fixed continuous casting mold.

Document US-PS 2 137 281 discloses a CuZrNiBe copper alloy for strip molds (twin-belt casting) characterized by a combination of relatively high thermal conductivity and relatively high hardness.

From document GB-PS 95 47 96 a CuBeZrTi copper alloy is known which has a relatively good thermal conductivity and a relatively high strength value.

In particular, in the casting of thin slabs without interruption at high casting speeds of, for example, 6 m / min or more, the mechanical properties of existing mold materials are not sufficient to suppress the high temperatures generated during casting in particular in the casting liquid zone. Not enough

The present invention relates to the use of aging hardenable copper alloys in molds, in particular in the manufacture of broad side plates of thin slab continuous casting molds.

An object of the present invention, starting from the prior art described above, is a copper alloy that is well suited for producing wide plates of thin slab continuous casting molds with high casting speeds, which are used in casting operations, especially in the region of the casting liquid surface, prematurely cracking. To prevent this from forming, to reduce the wear of the contact surface with the liquid steel, and to provide a copper alloy that is used for a long time and exhibits a very high thermal stress and mechanical stress generated during the casting operation.

Such an object is achieved by using an age hardenable copper alloy (CuNiBe) having a beryllium content of 0.1% to 0.5% and a nickel content of 0.5% to 2.0% to produce a wide plate of thin slab continuous casting molds.

Such copper alloys, after age hardening, can preferably prevent crack formation while accepting high temperature stresses in the casting liquid level zone and can be used continuously over long working hours.

Hereinafter, the present invention will be described in more detail with reference to Examples.

The CuNiBe copper alloys used in accordance with the invention have significantly higher tensile strengths, such as from about 770 to about 650 N / mm 2 and about 500 N / mm 2, at 20 ° C. as well as the copper alloys such as CuCrZr or CuAg described above at 300 ° C. The advantageous material properties, showing a yield strength of 0.2% of, give a successful working result as already mentioned. Exemplary selected material properties of CuCrZr, CuAg, and CuNiBe copper alloys may be identified from the following tables.

Chemical composition Approximate unit Aging Cured CuCrZr Cold Formed CuAg Specially age hardened CuNiBe Chemical composition % 0.70 Cr 0.09 Ag 1.80 Ni % 0.10 Zr 0.006 P 0.30 Be

Physical properties Approximate unit Aging Cured CuCrZr Cold Formed CuAg Specially age hardened CuNiBe Thermal conductivity W / mK 340 370 300

Mechanical properties Approximate unit Aging Cured CuCrZr Cold Formed CuAg Specially age hardened CuNiBe RT at 20 ℃ 0.2% Yield Strength Rp N / mm2 300 265 500 Tensile strength Rm N / mm2 415 280 770 Elongation A5 % 25 18 15 RT at 300 ° C 0.2% Yield Strength Rp N / mm2 240 195 420 Tensile strength Rm N / mm2 330 200 650 Elongation A5 % 18 10 8 RT at 20 ℃ Hardness HB 125 100 220

Further desirable properties are provided from the high hardness of about 220 HB of the material used according to the invention, such as wear resistance against mechanical wear, which shows that CuNiBe exhibits approximately the same hardness as about 220 to 230 HB of the electroplated nickel layer. Because. That is, the wide plate of the mold no longer needs to be plated with nickel.

The thermal conductivity of about 300 W / mK of CuNiBe copper alloys compared to CuAg with thermal conductivity of about 370 W / mK can be compensated by reducing the copper wall thickness facing water by about 25%. As a result, the cost of the material to be manufactured can be reduced.

According to the invention CuNiBe copper alloys used to produce wide plates of thin slab continuous casting molds, for example with high casting speeds of 2 to 6 m / min, range from 0.1% to 0.5% of beryllium relative to the total weight, from 0.5% to 2.0% nickel and up to 99.5% copper as alloy components. The content of impurities should be 0.5% or less, where impurities refer to small amounts of other metals such as Fe, Zr, Ag, Cr, Mg, and the like.

The present invention makes it possible to cast thin slabs at high casting speeds of at least 2 to 6 m / mim and beyond by using a special CuNiBe copper alloy in the wide plate of the continuous casting mold, which is not apparent from the prior art. As a result of the special selection of the alloying components according to the invention, the copper alloy can be used longer, in particular the formation of cracks in the bath bath liquid level zone is minimized and the material and manufacturing costs are lower.

Claims (4)

Use of an age hardenable copper alloy having a beryllium content of 0.1% to 0.5% and a nickel content of 0.5% to 2.0% in a mold, in particular for use in making wide plates of thin slab continuous casting molds. Use of an age hardenable copper alloy according to claim 1, which is used to produce a wide plate of thin slab continuous casting molds with a casting speed of at least 2 to 6 m / min. 3. Use of an age hardenable copper alloy according to claim 1 or 2, characterized in that the alloying component is 0.1% to 0.5% beryllium and 0.5% to 2.0% nickel with up to 99.5% copper component. The use of an age-curable copper alloy according to any one of claims 1 to 3, which contains up to 0.5% of impurities in addition to the alloying components of beryllium, nickel and copper.