KR20030069066A - Age-hardenable copper alloy - Google Patents

Abstract

Hardenable copper alloy comprises (in wt.%) 1.2-2.7 cobalt, 0.3-0.7 beryllium, 0.01-0.5 zirconium, 0.005-0.2 magnesium and/or iron, optionally up to maximum 0.15 niobium, tantalum, vanadium, hafnium, chromium, manganese, titanium and/or cerium, and a balance of copper. Preferred Features: The copper alloy contains (in wt.%) 1.8-2.4 cobalt, 0.45-0.65 beryllium, 0.15-0.3 zirconium, up to 0.05 magnesium, up to 0.1 iron and a balance of copper. Up to 80% of the cobalt content is replaced by nickel.

Description

Aging Hardenable Copper Alloy {AGE-HARDENABLE COPPER ALLOY}

The present invention relates to an age hardenable copper alloy as a material for producing blocks for side dams in strip casting equipment.

The global goal of reducing the hot forming step and / or cold forming step by casting semi-finished products as close to the final dimensions as possible, especially in the steel and copper industry, has already been established before the so-called Hazelett strip casting plant. Development has led to the formation of solidification in the gap of two belts which are guided in parallel. The side dam is a metal forming block with a T-shaped groove, for example in a strip casting plant known from US Pat. No. 3 865 176, which is arranged in a row on a forced flexible endless belt and moved longitudinally simultaneously with the casting belt or It consists of side dam blocks. In that case, the side dam block (dam block) defines the mold cavity formed by the casting belt.

Also known from EP 0 974 413 A1 are side dam chains for strip casting installations formed from blocks with grooves and springs. The advantage of such a developed block with grooves and springs is that it improves the surface quality of the cast billet by aligning and guiding the block accurately in the casting process. In order to prevent premature wear of the side edges of the block by plastic deformation and crack formation, suitable materials should be used that exhibit high hardness and strength, fine grain structure, and good long-term softening resistance. In addition, high thermal conductivity of the forming block material is required in order to remove solidification heat from the liquid solution.

Finally, after leaving the casting section, the optimal fatigue behavior of the material, which ensures that no cracking of the block occurs due to thermal stresses occurring during the recooling of the block at the corners of the T-shaped grooves provided for the acceptance of the steel strip, is crucial. very important. In that regard, it is anticipated that very high thermal stresses will occur in the side dam blocks of the configuration with grooves and springs due to inadequate geometry and mass distribution.

If such a crack occurs due to thermal shock, the forming block already falls short of the side dam chain of the strip casting apparatus even after a short time, in which case molten liquid metal can flow out of the mold cavity uncontrollably and damage the equipment parts. have. To replace the damaged molding block, the entire strip casting facility must be stopped to stop the casting process.

It has been found that a test method in which the forming block is heat treated at 500 ° C. for 2 hours and then quenched in water at 20 to 25 ° C. is useful for examining crack propensity. In suitable materials, the cracking shall not occur in the face of the T-shaped grooves even after repeated such thermal shock tests.

EP 0 346 645 B1 contains 1.6 to 2.4% nickel, 0.5 to 0.8% silicon, 0.01 to 0.2% zirconium, optional up to 0.4% chromium and / or iron up to 0.2%, and impurities in manufacturing conditions An aging hardenable copper-based alloy composed of balance copper is disclosed. Basically, such known alloys meet the prerequisite for long service life when used as a material for manufacturing standard forming blocks for side dams of strip casting equipment. Such copper alloys are given a combination of the following properties:

Rm at 20 ° C .: 635 to 660 MPa

Rm at 500 ° C .: 286 to 372 MPa

Brinell hardness: 185 to 191 HB (corresponding to about 195 to 210 HV)

Conductivity: 41.4 to 43.4% IACS.

There is no cracking in the thermal shock test. An advantage of such copper alloys over beryllium-containing copper-based alloys is that it is possible to dry regrind the forming blocks manually, since they do not contain beryllium in the abrasive dust. Such post-processing of side dam blocks with grooves and springs, which have been used, is quite costly and is usually carried out by mechanical cleaning (wet) of T-shaped grooves and casting surfaces (eg in a closed chamber). It is necessary to arrest the release. That is, using beryllium containing alloys is possible only under such conditions.

However, the side dam block made of CuNiSiZr alloy disclosed in EP 0 346 645 B1 has the disadvantage that premature wear of side edges and casting surfaces tends to occur under very high mechanical and thermal stresses during casting operations of strip casting equipment. Such wear causes softening of the casting edge and casting surface material to less than 160 HV, as evidenced by the test. In addition, the thermal shock resistance of the known CuNiSiZr alloy is not always sufficient to effectively prevent the formation of cracks in the T-shaped grooves during the casting operation in applications as the side dam blocks with grooves and springs.

The object of the present invention, starting from such prior art, is a material for producing side dam blocks of strip casting equipment, in particular of side dam blocks with grooves and springs, and is insensitive to fluctuating temperature stresses even at high casting speeds. To provide an age hardenable copper alloy that exhibits high wear resistance or softening resistance as well as high resistance to crack formation in T-shaped grooves.

Such an object is achieved by the features described in claims 1 and 2.

1.2 to 2.7 weight percent cobalt, 0.3 to 0.7 weight percent beryllium, 0.01 to 0.5 weight percent zirconium, optional 0.005 to 0.2 weight percent magnesium and / or iron, and impurities on manufacturing conditions and conventional processing additives By using a copper-based alloy made of balance copper, on the one hand, sufficient aging hardenability of the material can be ensured, and high strength, hardness and conductivity can be obtained. On the other hand, only a relatively low cold processing of up to 40% is required to establish a fine enough plastic structure. By intentionally differentiating the zirconium content, the fatigue strength as well as the heat resistance properties are improved.

According to claim 3, Preferably the copper alloy is 1.8 to 2.4 wt% cobalt, 0.45 to 0.65 wt% beryllium, 0.15 to 0.3 wt% zirconium, up to 0.05 wt% magnesium and / or up to 0.1 wt% iron By further containing, further improvement of the mechanical properties of the side dam block, in particular improvement of tensile strength, can be realized.

In the present invention, up to 80% cobalt content in the copper alloy may be substituted with nickel according to the features of claim 4.

Further improvement in the mechanical properties of the side dam blocks can be realized when the copper alloy contains up to 0.15% by weight of one or more elements of the group consisting of niobium, tantalum, vanadium, hafnium, chromium, manganese, titanium, and cerium. have. Additional deoxidizers such as boron, lithium, calcium, aluminum, and phosphorus can also be added up to 0.03% by weight as needed without adversely affecting the mechanical properties of the copper alloy according to the invention.

According to another embodiment (claim 5), some of the zirconium content may be substituted up to 0.15% by weight with one or more elements of the group consisting of cerium, hafnium, niobium, tantalum, vanadium, chromium, manganese, and titanium.

The block for side dams of a double belt strip casting plant made of a copper alloy according to the invention is cast according to claim 6, hot formed, cold formed up to 40%, solution annealing to a temperature range of 850 to 970 ° C., and 400 to It is preferably produced by a method comprising an age hardening treatment at 550 ° C. for 0.5-16 hours.

According to claim 7, it is particularly preferred that the copper alloy can be cold formed by 5 to 30% after hot forming. In that case, the cold forming degree of 10 to 15% is especially preferable among the cold forming degrees which fall in such a range.

The side dam block in the age hardened state has a tensile strength of at least 650 MPa, in particular 700 to 900 MPa, at least 210 HV, in particular Vickers hardness of at least 230 to 280 HV, at least 40% IACS, in particular 45 to 60 according to claims 9 to 10. Electrical conductivity of% IACS, at least 400 MPa, in particular hot tensile strength at 500 ° C. of at least 450 MPa, minimum hardness after 500 hours aging at 500 ° C. of 160 HV, and maximum particle size according to ASTM E112 of 0.5 mm. desirable.

It is particularly preferred that the side dam block made of a copper alloy according to the invention exhibits a particle size of 30 to 90 μm calculated according to ASTM E112 in an age hardened state according to claim 11.

In addition, according to the procedure of the method of claim 6, the poor recrystallization behavior during hot forming and solution annealing observed from the known CuCoBe alloy can be surprisingly easily removed. In the production of molded blocks made of CuCoBe alloys, unacceptable microstructures of use for which the particle size exceeds 1 mm in hot formed, solution annealed and age hardened due to poor recrystallization behavior This occurs. However, if the material is cold formed up to 40%, preferably up to 15% between the hot forming and the solution annealing treatment, such additional processing steps result in significant particulate microstructure. According to a series of inspections, the material of the forming block for the side dam of the strip casting apparatus, which was cold formed below the recrystallization temperature and then solution-treated, showed a remarkable fine microstructure having a particle size of less than 0.5 mm, Subsequent solution-annealing at high levels above about 40% has been shown to result in particle granulation with a particle size above 1 mm due to secondary recrystallization.

Hereinafter, the present invention will be described in more detail with reference to Examples. The copper alloys according to the invention appear to be better in the three alloys (A, B, and C) and the three comparative alloys (D, E, and F) according to the invention. The composition of the copper alloy in weight percent is shown in Table 1 below:

alloy Co (%) Ni (%) Be (%) Zr (%) Si (%) Cr (%) Cu (%) A 2.1 - 0.54 0.18 - - Balance B 2.2 - 0.56 0.24 - - Balance C 1.3 1.0 0.48 0.15 - - Balance D - 2.0 - 0.16 0.62 0.34 Balance E 2.1 - 0.55 - - - Balance F 1.0 1.1 0.62 - - - Balance

Alloy D is a composition of known CuNiSi based alloys, while alloys E and F are compositions of standardized CuCo ₂ Be or CuCoNiBe materials.

All copper alloys were melted in a crucible furnace and cast into circular blocks 280 mm in diameter in a continuous casting process. Circular blocks of alloys A, B, and C according to an embodiment of the present invention were extruded at a temperature above 900 ° C. in an extrusion press to obtain a bar having a dimension of 79 × 59 mm, followed by 75 × 55 by a cross section reduction of 12%. It was drawn to the dimension of mm. The blocks of Comparative Alloys D, E, and F were directly extruded at the same temperature to dimensions of 75 × 55 mm, and no further cold forming was performed. The CuCoBe or CuCoNiBe material was then solution annealed at 900-950 ° C. and then age hardened at a temperature of 450-550 ° C. for 0.5-16 hours.

The CuNiSi-based alloy was solution annealed at 800 to 850 ° C. and then age hardened under the same conditions. Tensile strength Rm, Vickers hardness HV10, electrical conductivity (as an alternative to thermal conductivity), particle size according to ASTM E112, hot strength Rm at 500 ° C, and Vickers hardness after 500 hours of aging in the age-hardened state The softening resistance associated with the measurement (HV10) was investigated.

Finally, thermal shock behavior was examined in the forming block 1 having a dimension of 70 × 50 × 40 mm and the forming block 2 having a groove and a spring and having a dimension of 70 × 50 × 47 mm. For that purpose, the forming block was first annealed at 500 ° C. for 2 hours and then quenched in water at 20-25 ° C. Subsequently, the T-shaped groove of the block was cracked with a naked eye and a microscope of 10 magnification.

The overall test results are summarized in Table 2 below.

alloy RmMPa HV10 Conductivity% IACS Particle size㎛ Rm (500 ℃) MPa Hardness HV10 after aging for 500 hours at 500 ° C Behavior under thermal shock test Block (1) Block (2) A 801 254 50 30-90 523 173 Crackless Crackless B 804 245 51.5 45-90 464 175 Crackless Crackless C 812 255 49.5 45-90 485 167 Crackless Crackless D 652 205 43 45-90 387 118 Crackless Crack metaphor E 786 260 50.5 Up to 5000 423 150 Crack metaphor Crack metaphor F 807 248 48.5 Up to 3000 434 152 Crack metaphor Crack metaphor

The extension of the cracks identified in the T-shaped grooves was 2 to 5 mm in the case of molded blocks classified as "crack oil" and the crack lengths individually reached up to 10 mm. Compared to materials E and F, only copper alloys A, B, and C produced by a low degree of additional cold forming according to the invention have surprisingly uniform particulate structure, grooves and springs with optimum properties. It turns out that the crack resistance required when used as a forming block is shown. The copper alloy according to the present invention exhibits significantly better softening resistance than the known CuNiSi alloy D, even when used as a conventional forming block, and slightly better than the alloys E and F.

Therefore, the copper alloy according to the present invention is very suitable as a material for producing the forming blocks for side dams of strip casting equipment, which are subject to thermal stresses that vary throughout the casting process. Such a forming block may be a forming block having a groove and a spring according to EP 0 974 413 A1 as well as a forming block conventionally used.

The age hardenable copper alloy according to the present invention is insensitive to fluctuating temperature stress even at high casting speed, and exhibits high wear resistance or softening resistance as well as high resistance to crack formation, thus forming blocks for side dams of strip casting equipment, In particular, it is very suitable as a material for manufacturing the forming block for side dams provided with the groove and the spring.

Claims (11)

As an age hardening copper alloy as a material for manufacturing the block for side dams of a strip casting installation, In the group consisting of 1.2 to 2.7 weight percent cobalt, 0.3 to 0.7 weight percent beryllium, 0.01 to 0.5 weight percent zirconium, up to 0.15 weight percent niobium, tantalum, vanadium, hafnium, chromium, manganese, titanium and cerium An age hardenable copper alloy comprising at least one element and balance copper containing impurities on manufacturing conditions and conventional processing additives. The aging hardenable copper alloy according to claim 1, further comprising 0.005 to 0.2% by weight of at least one element of magnesium and iron. The process according to claim 2, wherein at least one of 1.8 to 2.4 wt% cobalt, 0.45 to 0.65 wt% beryllium, 0.15 to 0.3 wt% zirconium, up to 0.05 wt% magnesium and up to 0.1 wt% iron, and manufacturing conditions An age hardenable copper alloy comprising residual copper containing impurities in a phase and a conventional treatment additive. The age hardening copper alloy according to any one of claims 1 to 3, wherein up to 80% of the cobalt content is substituted with nickel. The method of claim 1, wherein a portion of the zirconium content is substituted with up to 0.15% by weight of one or more elements in the group consisting of cerium, hafnium, niobium, tantalum, vanadium, chromium, manganese, and titanium. The age hardenable copper alloy characterized by the above-mentioned. The method according to claim 1, wherein the cast blank is hot formed and then cold formed up to 40%, followed by solution annealing to a temperature in the temperature range of 850 to 970 ° C. An age hardening copper alloy, which is subjected to an age hardening treatment at 400 to 550 ° C. for 0.5 to 16 hours. 7. The age hardenable copper alloy according to claim 6, which is cold formed by 5 to 30% after hot forming. The age hardenable copper alloy according to claim 6, wherein the hot forming is cold formed by 10 to 15% after hot forming. The tensile strength of at least 650 MPa, Vickers hardness of at least 210 HV, electrical conductivity of at least 40% IACS, hot tensile strength at 500 ° C. of at least 400 MPa, 160 in the age-cured state, 160. The age-hardenable copper alloy which shows the minimum hardness after 500-hour aging at 500 degreeC which is HV, and the maximum particle size according to ASTM E112 which is 0.5 mm. The method according to any one of claims 1 to 3, wherein the tensile strength is 700 to 900 MPa, Vickers hardness is 230 to 280 HV, electrical conductivity is 45 to 60% IACS, and 500 ° C. or more at 500 ° C. The age-hardenable copper alloy which shows the lowest hardness after aging treatment for 500 hours at 500 degreeC of hot tensile strength of 160 HV. The age hardening copper alloy according to any one of claims 1 to 3, wherein the particle size calculated according to ASTM E112 is 30 to 90 µm.