RU2301844C2 - Hardenable copper alloy - Google Patents

Abstract

FIELD: production of copper alloys.

SUBSTANCE: proposed copper alloy contains 1.2-2.7% of cobalt; 0.3-0.7% of beryllium; 0.01-0.5% of zirconium; 0.005-0.2% of magnesium and/or iron and maximum 0.15% of at least one element from the group including niobium, tantalum, vanadium, hafnium, manganese, titanium and cerium. The residue is copper with admixtures and technological additives. This alloy is used for manufacture of casting molds for side guards of belt-type tapping units.

EFFECT: high wear resistance to softening and loss of strength; high resistance to cracking in T-groove.

9 cl, 2 tbl

Description

The invention relates to a copper alloy, amenable to hardening and hardening, as a material for the manufacture of blocks for side barriers of tape filling devices.

The goal facing the whole world, especially in the steel and copper industries, which is to cast the workpiece as close as possible to the final size and thereby make the hot and / or cold forming stages economical, already by 1970 led to the development of the so-called Hazelett - tape filling devices in which molten metal solidifies in the gap of two parallel moving tapes. Side barriers in a tape filling device, known, for example, from US Pat. No. 3,865,176, consist of metal molds or blocks of side barriers with a T-slot (T-Nut), which are placed in a row on a flexible endless tape, for example, steel and which move synchronously with casting belts in the longitudinal direction. At the same time, blocks of side barriers (in English Damblocks) limit the cavity of the injection mold formed by means of tapes for casting.

Further, from the patent EP 0974413 A1 there are known rows of side barriers for tape filling devices formed from blocks with a groove and a key. The advantage of these further improved forms with a groove and a key is in a more accurate direction and orientation of the blocks during the casting process and leads to an improvement in the surface quality of the casting blank. In order to prevent premature wear of the side faces of the blocks through plastic deformation and cracking, a suitable material should be characterized by high hardness and strength, fine-grained structure and good resistance to long-term softening. In addition, in order to remove the solidification heat from liquid metal melts, high thermal conductivity of the material of the mold blocks is required.

Finally, the optimal fatigue behavior of the material is of particular importance, which ensures that after leaving the casting area, the thermal stresses encountered during re-cooling of the blocks do not lead to cracking of the blocks at the corners of the T-groove introduced to receive the steel strip. In this case, particularly high thermal stresses due to unfavorable geometry and mass distribution can be expected for blocks for side barriers when executed with a groove and a key.

If such cracks occur due to thermal shock, after a short time, the affected mold block falls out of the row of side barriers of the tape casting machine, and the molten metal flows uncontrollably out of the mold cavity and can damage parts of the device. To replace damaged mold blocks, the entire tape filling device must stop and the casting process is interrupted.

To test the tendency to crack, the test method proved to be suitable, in which the mold blocks are subjected to a two-hour heat treatment at 500 ° C and then quickly cooled (quenched) in water at 20-25 ° C. Also, with repeated repetition of this test by thermal shock, a suitable material could not cause cracking on the surface of the T-groove.

EP 0346645 B1 describes a hardenable and hardenable copper-based alloy consisting of from 1.6 to 2.4% nickel, from 0.5 to 0.8% silicon, from 0.01 to 0.2% zirconium, optionally up to 0.4% chromium and / or up to 0.2% iron, the rest is copper, including impurities. This well-known copper alloy is made fundamentally with the prerequisites for obtaining high durability, if it is used as a material for the manufacture of standard mold blocks for side barriers of tape filling devices. The following combination of properties is given for this copper alloy:

Strength (Rm) at 20 ° C: 635-660 MPa.

Strength (Rm) at 500 ° C: 286-372 MPa.

Brinell hardness: 185-191 HB (corresponding to approximately 195-210 HV).

Conductivity: 41.4-43.4% IACS (from the English International Annealed Copper Standert, i.e. the international standard for annealed copper for electrical purposes).

Crack test does not show cracks. An advantage with respect to copper-based alloys containing beryllium is the ability to manually dry polish the mold blocks, since beryllium is not contained in grinding dust. Subsequent processing of the used blocks for side barriers with a groove and a key is associated with significant costs and requires, as a rule, mechanical (wet) cleaning of the T-groove and cast surfaces (for example, in closed chambers), which suppresses the release of grinding dust. Thus, the use of alloys containing beryllium in these conditions would be fundamentally possible.

However, the block for the side barriers of the CuNiSiZr alloy described in patent EP 0346645 B1 has a negative tendency at very high mechanical and thermal loads in the casting process in the tape casting device to premature wear of the side faces and casting surfaces. This wear is explained, according to research results, by softening the material of the side faces and surfaces to below 160 HV. Further, resistance to thermal shock of a known CuNiSiZr alloy is not always achieved when using a block for side barriers with a groove and a key in its quality in order to effectively suppress the formation of cracks in the T-groove during casting.

Based on the prior art, the object of the invention is to provide a hardening and hardening copper alloy as a material for the manufacture of blocks for side barriers of tape casting devices, especially when performed with a groove and a key, which are also insensitive to variables at high casting speeds temperature loads and are characterized by high wear resistance, for example resistance to softening and softening, as well as high resistance to formation cracks in the T-groove.

This problem is solved using the technical solution described by the features given in paragraph 1 of the claims.

Through the use of an alloy based on copper from 1.2-2.7 wt.% Cobalt, 0.3-0.7 wt.% Beryllium, 0.01-0.5 wt.% Zirconium, optionally 0.005-0.2 wt.% magnesium and / or iron and the rest of copper, including those caused by impurities and conventional processing aids, on the one hand, sufficient cure and hardenability of the material can be achieved to achieve high strength, hardness and conductivity. On the other hand, only a relatively small cold forming is required up to a maximum of 40% in order to give the (alloy) a fine-grained structure with sufficient ductility. Due to the fact that the zirconium content is deliberately divided into fractions or stages (from German abgestuften), both fatigue strength and heat-resistant properties are improved.

Further improvement of the mechanical properties of the blocks for side barriers, especially an increase in tensile strength, can be achieved according to paragraph 2, preferably in that the copper alloy contains 1.8-2.4 wt.% Cobalt, 0.45-0.65 wt.% beryllium, 0.15-0.3 wt.% zirconium up to 0.05 wt.% magnesium and / or up to 0.1 wt.% iron.

The following improvements in the mechanical properties of the block for side barriers can be achieved if the copper alloy contains up to a maximum of 0.15 wt.% At least one element from the group comprising niobium, tantalum, vanadium, hafnium, chromium, manganese, titanium and cerium. Conventional deoxidizing agents (deoxidizing agents) such as boron, lithium, calcium, aluminum and phosphorus can also be added up to a maximum of 0.03 wt.% Without adversely affecting the mechanical properties of the copper alloy according to the invention.

According to a further embodiment, a portion of the zirconium contained can be replaced by up to 0.15% by weight of at least one element from the group consisting of cerium, hafnium, niobium, tantalum, vanadium, chromium, manganese and titanium.

Preferably, the blocks for side barriers of a double belt filling device are made of a copper alloy according to the invention by a method comprising the steps of casting, hot forming (rolling), cold forming (rolling) up to 40%, annealing in the area of the solid solution (diffusion annealing) at a temperature lying in the temperature range from 850 to 970 ° C, as well as 0.5-16-hour curing and hardening treatment at 400-550 ° C.

With particular advantage, the copper alloy according to claim 6 can be cold formed from about 5 to 30%. Moreover, the degree of cold forming from 10 to 15%, lying inside this area, is particularly preferred.

It is preferable if the blocks for side barriers in the cured (i.e., with higher hardness) and hardened state are characterized by tensile strengths of at least 650 MPa, particularly preferably 700-900 MPa, Vickers hardness of at least 210 HV, particularly preferably 230-280 HV, electrical conductivity of at least 40% IACS, particularly preferably 45-60% IACS, heat resistance in tension (i.e., high temperature tensile strength) at 500 ° C of at least 400 MPa, particularly preferably at least at least 450 MPa, with a hardness of at least 160 HV after 500 hours at 500 ° C and a maximum grain size of ASTM E 112 of 0.5 mm.

Particularly preferred are the blocks for the side barriers made of copper alloy according to the invention, if they are in the cured and hardened state characterized by a grain size, determined according to ASTM E 112, between 30 and 90 microns. By means of the sequence of steps of the method, it is also possible in an unexpectedly simple way to eliminate the poor recrystallization properties observed in known CuCoBe alloys during hot plastic molding and processing in the form of annealing of the solid solution region. Poor recrystallization properties in the manufacture of mold blocks from CuCoBe alloys in the state after hot forming, annealing in the area of solid solution and hardening / hardening lead to a coarse-grained structure with grain sizes greater than 1 mm, which is unacceptable for the purpose of application. However, if the material between hot molding and annealing in the area of the solid solution is cold formed up to a maximum of 40%, preferably up to a maximum of 15%, then this additional processing step leads to a significantly finer grain structure. A number of relevant studies have confirmed that materials for mold blocks for side barriers of tape casting machines, cold formed below the crystallization temperature and then annealed in the area of the solid solution, are characterized by a distinctly finer structure with grain sizes below 0.5 mm, while more a high degree of cold forming is higher than about 40% with subsequent annealing in the region of the solid solution leads to coarsening of grains by means of secondary recrystallization to grain sizes above 1 mm.

Below the invention is illustrated by examples of implementation. The three alloys according to the invention (A, B and C) and the three comparative alloys (D, E and F) show the advantages of copper alloys according to the invention. The composition of copper alloys in mass percent is given in the following table 1:

Table 1 Alloy Co (%) Ni (%) Be (%) Zr (%) Si (%) Cr (%) Cu (%) BUT 2.1 - 0.54 0.18 - - The remainder AT 2.2 - 0.56 0.24 - - The remainder FROM 1.3 1,0 0.48 0.15 - - The remainder D - 2.0 - 0.16 0.62 0.34 The remainder E 2.1 - 0.55 - - - The remainder F 1,0 1,1 0.62 - - - The remainder

The alloy of composition D is the known alloy based on CuNiSi, while E and F are normalized CuCo2Be and CuCoNiBe materials.

All copper alloys were melted in an induction crucible furnace and cast into round billets with a diameter of 280 mm by continuous casting. The round alloy billets of Examples A, B, and C were pressed on a press at temperatures above 900 ° C to flat bars of 79 × 59 mm in size and then elongated by compression over a 12% cross section to a size of 75 × 55 mm. The blanks of the comparative alloys D, E, and F were directly pressed to the size of 75 × 55 mm at the same (identical) temperature and were not subjected to additional cold forming. CuCoBe and CuCoNiBe materials were then annealed in the region of solid solution at 900–950 ° C and slowly hardened and hardened for 0.5–16 hours at temperatures between 450 and 550 ° C.

The CuNiSi-based alloy was annealed in the region of the solid solution at 800–850 ° С and, under the same conditions, was hardened and hardened. In the cured and hardened state, tensile strength Rm, Vickers hardness HV10, electrical conductivity (as a substitute for thermal conductivity), grain size according to ASTM E 112, heat resistance Rm at 500 ° C and softening resistance were determined by measuring Vickers hardness (HV10 ) after exposure at 500 ° C for 500 hours.

Blocks (1) of molds with dimensions of 70 × 50 × 40 mm and blocks (2) of molds with a groove and a key of size 70 × 50 × 47 mm were finally tested in thermal shock mode. For this, the mold blocks were first annealed for two hours at 500 ° C and then quickly cooled with water at 20-25 ° C. The block T-groove was then examined with the naked eye and a microscope at 10x magnification for cracks.

All research results are summarized in the following table 2.

table 2 Alloy Rm, MPa Hv10 Wire.% IACS Grain size, microns Rm (500 ° C), MPa Hardness HV10 after exposure at 500 ° C for more than 500 hours Properties after the thermal shock test Block 1 Block 2 BUT 801 254 fifty 30-90 523 173 no cracks no cracks AT 804 245 51.5 45-90 464 175 no cracks no cracks FROM 812 255 49.5 45-90 485 167 no cracks no cracks D 652 205 43 45-90 387 118 no cracks cracks E 786 260 50,5 Up to 5000 423 150 cracks cracks F 807 248 48.5 Up to 3000 434 152 cracks cracks

The propagation of cracks in the T-groove at the sides of the forms, classified as “cracks”, ranges from 2 to 5 mm, in some cases up to 10 mm. From the above comparison, we can conclude that, in comparison with materials E and F, only copper alloys A, B and C obtained according to the invention with an additional small (insignificant) cold forming, with optimal properties, unexpectedly are characterized by a uniform and fine-grained structure and the necessary stability with respect to cracking when used as a block (injection) mold with a groove and a key. Also, when used as conventional mold blocks, copper alloys according to the invention are characterized by clearly better softening resistance to the known CuNiSi alloy D and somewhat better softening resistance to alloys E and F.

So, the copper alloy according to the invention is extremely suitable as a material for the manufacture of all mold blocks for side barriers of tape filling devices subjected to a typical variable temperature load during the casting process. We are talking about the still used mold blocks, and mold blocks when executed with a groove and a key according to the application EP 0974413 A1.

Claims (9)

1. Curable and hardened copper alloy containing 1.2-2.7% cobalt, 0.3-0.7% beryllium, 0.01-0.5% zirconium, optionally 0.005-0.2% magnesium and / or 0.005-0.2% iron and, accordingly, up to a maximum of 0.15% of at least one element from the group consisting of niobium, tantalum, vanadium, hafnium, chromium, manganese, titanium and cerium, the rest is copper and due to the receipt of impurities, used as a material for the manufacture of blocks for side barriers of tape filling devices. 2. The copper alloy according to claim 1, which contains 1.8-2.4% cobalt, 0.45-0.65% beryllium, 0.15-0.3% zirconium, up to 0.05% magnesium, up to up to 0.1% iron, the rest is copper. 3. The copper alloy according to any one of claims 1 and 2, in which part of the zirconium contained is replaced up to 0.15% by at least one element from the group consisting of cerium, hafnium, niobium, tantalum, chromium, manganese, titanium, and vanadium. 4. The copper alloy according to any one of claims 1 to 3, which is subjected to cold forming up to about 40% after hot molding of the cast billet, then annealing in the solid solution region at a temperature lying in the temperature range from 850 to 970 ° C, and then 0.5-16 hour curing and hardening treatment at 400-550 ° C. 5. The copper alloy according to claim 4, which is subjected after the stage of hot forming to cold forming from about 5 to 30%. 6. The copper alloy according to claim 4 or 5, which is subjected after cold forming to cold forming from about 10 to 15%. 7. The copper alloy according to any one of claims 1 to 6, which is characterized in a cured and hardened state by tensile strength of at least 650 MPa, Vickers hardness of at least 210 HV, electrical conductivity of at least 40% IACS, high temperature tensile strength tensile at 500 ° C of at least 400 MPa, hardness of at least 160 HV after 500 hours exposure at 500 ° C and a maximum grain size according to ASTM B 112 of 0.5 mm. 8. The copper alloy according to any one of claims 1 to 7, which is characterized in a cured and hardened state by tensile strength of 700-900 MPa, Vickers hardness of 230-280 HV, electrical conductivity of 45-60% IACS, high temperature tensile strength at 500 ° C of at least 450 MPa and a hardness of at least 160 HV after 500 hours at 500 ° C. 9. The copper alloy according to any one of claims 1 to 8, which is characterized by ASTM E 112 average grain size between 30 and 90 microns.