DE102008015096A1 - Process for producing molded parts and molded parts produced by the process - Google Patents

Abstract

A method of producing castings from a silicon, nickel, chromium and zirconium and intermetallic primary phase containing copper alloy, wherein a cast billet is hot worked in only one direction in a ratio of at least 4: 1, wherein a molten metal contacting casting surface of a selected from the ironed cast block mold part is selected perpendicular to the ironing of the ingot. A molded part produced in this way is characterized by high wear resistance and increased service life, in particular Doppelbandgießanlage.

Description

The The invention relates to a process for the production of moldings from a silicon, nickel, chromium and zirconium as well as intermetallic Primary phases containing copper alloy according to the Features of claim 1.

The The invention further relates to mold parts produced according to this procedure.

The EP 0 346 645 B1 describes the use of a curable copper alloy of 1.6 to 2.4% nickel, 0.5 to 0.8% silicon, 0.01 to 0.20% zirconium, the remainder copper including manufacturing impurities and common processing additives, as the material of manufacture Molded parts that are subject to a permanently changing temperature stress during casting, especially in the form of blocks for side dams of Doppelbandgießanlagen. The performance of Doppelbandgießanlagen depends crucially on the proper functioning of the formed from block side dam chain. So it is necessary that the blocks have the highest possible thermal conductivity, so that the melting or solidification heat can be dissipated as quickly as possible. In order to avoid premature wear of the side edges of the blocks by mechanical stress, which leads to the formation of gaps between the blocks and then to the penetration of the melt in this gap, the material must not only have a high hardness and tensile strength and a small grain size. Ultimately of prime importance is an optimal fatigue behavior, which ensures that after leaving the casting line, the thermal stresses which occur during the cooling of the blocks do not lead to the tearing of the blocks in the corners of the T-slot incorporated for receiving the steel strip. Occur such caused by thermal shock cracks, after a short time the block in question falls out of the chain, the molten metal leak out of the mold cavity uncontrolled and can damage equipment. To replace the defective block, the system must be stopped and the casting process interrupted.

For checking The tendency to crack has proved itself a test method, at the blocks of a two-hour heat treatment at 500 ° C and then in water be quenched by 25 ° C. Even with multiple repetition This thermal shock test may at a suitable Material no cracks in the area of the T-slot occur.

The in the EP 0 346 645 B1 described zirconium-containing, curable CuNiSiCr alloy is ideal for blocks of side dams of Doppelbandgießanlagen. The addition of chromium increases the conductivity of the material. Fe addition limits grain growth during solution annealing without adversely affecting the other properties of the material.

It is known that in the structure of the chromium and zirconium-containing Material intermetallic primary phases occur, the during the solidification of the melt hypoeutectic, d. H. in inhomogeneous Crystallize distribution. These CrSi-containing and NiZr-containing Phases occur due to the process already in the cast round bolt on that as a starting material for the production of blocks for the side dams of Doppelbandgießanlagen be used. The cast material usually becomes for setting a fine-grained structure and to achieve the required hardness and electrical Conductivity with common forming processes, such as Extrusion, forging or rolling hot formed, then solution annealed and cured, wherein the eutectic, inhomogeneous distribution of the intermetallic primary phases the casting condition more or less well destroyed and the Primary phases aligned in the main Umformig direction become. In the usual production of the blocks made of extruded or hot-rolled bars with T-slot position vertical to Hauptumformrichtung, then lies a relatively uneven distributed, distinctly aligned primary phase array in the pouring area of the blocks in front. At the Forging plates from a cast blank usually becomes forging the reticular distribution of the intermetallic primary phases the casting condition is insufficiently eliminated, since the Gesamtumformgrad is limited and the plate in the longitudinal and transverse directions is formed approximately equally.

Of these, The invention is based on the object, a method for the production of molded parts, in particular for the production of blocks for side dams of double belt casters to optimize so that the wear of a molten metal used later in contact casting surfaces and progresses more slowly, so over a longer time Production period using the mold parts cast metal strip with impeccable surface quality can be produced. Furthermore, a mold part with the improved properties are shown.

Of the procedural part of this task is through the features of claim 1 solved.

One Molded part with the advantageous properties is the subject of claim 6.

The each dependent claims relate to advantageous Further developments of the inventive concept.

The The object underlying the invention is achieved by that the intermetallic primary phases, which in the Copper alloy are included, by directional hot forming so be oriented, that one coming into contact with the molten metal Casting surface of a made of the ironed cast block Molded part is selected perpendicular to the ironing direction of the cast block.

Essential with this procedure is that during the hot forming of the ingot in addition to the fine-grained microstructure crystallization the originally coarse-grained cast structure a pronounced fiber orientation with comminution and Alignment of the intermetallic primary phases along of these fibers is produced. It is important that the fiber orientation as finely and evenly distributed Primary phases, which in the context of the invention thereby is achieved by a hot stamping in only a single direction takes place, with the ingot in a ratio of at least 4: 1, preferably more than 7: 1, is stretched. Hot forming can be achieved by processes such as forging and hot rolling respectively. A total summary of at least 4: 1 or preferably at least 7: 1 in different directions on the other hand not to the invention desired Graining.

One Another important feature of the procedure is that of the ironed out Cast block made moldings, one with a molten metal having in contact casting surface, the is selected perpendicular to the ironing direction. Only in this Fall is the wear of the casting surfaces significantly reduced so that it is possible over a longer production period a cast metal band produce with impeccable surface quality.

By the orientation of the fibers occurs the intermetallic primary phases in the casting surface essentially only as even distributed points in appearance. It is considered appropriate viewed when the quantity ratio of in a micrograph truncated intermetallic primary phases between the casting surface and perpendicular to the casting surface standing sides of the ironed cast block larger is set as 1.5: 1. That means that in the casting area or in a plane perpendicular to the ironing direction at least 50% more intermetallic primary phases are cut as in a side or plane perpendicular to the casting surface.

The in this way set quantity ratio of the trimmed intermetallic primary phases in combination with the orientation the casting surface, leads to moldings with optimized use behavior, as the crack initiation and crack propagation is inhibited in the casting area. This decreases the wear of the mold parts in use, since the crack propagation progresses more slowly, which leads to an increase of the Lifespan contributes. The resistance to Fatigue cracking is compared to mold parts, in which the intermetallic primary phases substantially are undirected, much larger.

The produced by the process according to the invention Molded part has a fiber profile, which requires that also the intermetallic primary phases in fibers or Lines are arranged. The average length of one in one Level primary phase is measurable. It will be beneficial viewed when the ratio between the mean length a line lying in the plane of the casting area to the average length of a line perpendicular to the casting surface runs, is less than 3:10. In other words are in the casting surface lines intermetallic Primary phases whose length is not more than 30% the length of a line of an intermetallic primary phase corresponds, which runs perpendicular to the casting surface.

The consists of the casting mold according to the invention made of a hardenable copper alloy used for this purpose Contains alloying constituents, which are called intermetallic Phase out. The hardenable copper alloy contains preferably nickel, which are at least partially replaced by cobalt can. In addition, the alloy contains at least one of the following alloying elements: chromium, zirconium, beryllium, Silicon.

The finished molded part is characterized by tailored to the specific application, excellent material properties, namely in particular a tensile strength of at least 600 MPa at a room temperature of 20 ° C and a tensile strength of at least 350 MPa at a temperature of 500 ° C.

The copper alloy has in the cured state at 20 ° C, a 0.2% proof strength of at least 470 MPA, an elongation at break A ₅ of at least 15%, a hardness of at least 190 HV10 and at 20 ° C, an electrical conductivity of at least 40% IACS (IACS = International Annealed Copper Standard, electrical conductivity compared to copper = 100%). Preferably, the electrical conductivity is at least 45%.

The hardened copper alloy should have a particle size of at most 130 .mu.m measured according to ASTM E 112 exhibit. The US standard ASTM E 112 (American Society for Testing and Materials) is a standard test method for determining the mean grain size.

The Invention will be explained below with reference to some examples.

1 shows a micrograph of a cast round bolt, which is used as a starting material for the production of moldings of side dams of a Doppelbandgießanlage. This is the typical cast structure of a CuNiSiCrZr alloy with CrSi-containing or NiZr-containing intermetallic primary phases in eutectic arrangement. The material is then reshaped to form a fine-grained structure and to achieve the required hardness and electrical conductivity with forming processes, such as extrusion, forging or rolling, then solution annealed and cured, so that the eutectic, inhomogeneous distribution of the intermetallic primary phases will change.

Will the in 1 illustrated casting blank with a net-like distribution of the intermetallic primary phases in both the longitudinal and transverse directions equally shaped, the phase orientation does not change in the desired manner.

On the contrary shows 2 the distribution of the intermetallic primary phases of an already hot-formed cast block and thus the microsection in the region of the casting surface of a later casting component. It can be clearly seen that the intermetallic primary phases are very finely and evenly distributed. The fiber orientation of the intermetallic primary phases is perpendicular to the casting surface, whereby the truncated primary phases appear as dots in this figure.

The number of cut primary phases is about 1.7 times as high as in 3 which is a microsection perpendicular to the casting surface and thus perpendicular to the 2 shows. While in 2 the phase lines are only slightly recognizable and have a maximum length of approx. 100 μm, are in 3 Recognize significantly more primary phase lines, the phase line lengths are in the range of 100 to 400 microns and partially in areas above 400 microns. The following table illustrates the mechanical properties and the fatigue resistance of moldings made of CuNiSiCrZr alloys produced by the process according to the invention.

• Rest = Cu einschließlich unvermeidbarer Beimengungen.

Embodiment A is based on an alloy of the following composition in% by weight: 2.1% Ni 0.62% Si 0.30% Cr 0.17% Zr 0.15% Fe

• Remainder = Cu including unavoidable admixtures.

These Alloy was melted in an induction crucible furnace and in the Continuous casting process to a round block of dimensions diameter 425 mm × length 1,200 mm potted. The round block would be on a forging press in a temperature range between 950 ° C and 750 ° C to 800 mm height pre-compressed and then to a cuboid with the width of 500 mm × thickness 400 mm × length 850 mm formed. The cuboid was then in a second heat in the longitudinal direction a plate of dimensions width 500 mm × thickness 200 mm × length 1,700 mm forged. This forge Plate was then placed on a hot rolling mill in a heat between 950 ° C and 800 ° C to the dimensions width 500 mm × thickness 80 mm × length 4,250 mm rolled out. The total deformation ratio V in the longitudinal direction was from 800 mm burst length up to 4,250 mm rolled sheet length 5.3: 1. The plate was then solution annealed and cured. Cooling after curing was carried out in a furnace with low (<50 ° C / hour) cooling rate. Basically, the cooling rate should be lower than 80 ° C / hour, especially lower than 50 ° C / hour be. Subsequently, the plate was sawn into horizontal stripes and from these strips were molded parts, the so-called Dam blocks with the dimensions 70 mm × 50 mm × 40 mm manufactured.

alternative can in the same way the mold parts of the Dimensions 60 mm × 50 mm × 40 mm or 50 mm × 50 mm × 40 mm. The casting surfaces the mold parts come perpendicular to the longitudinal direction the plate and thus also perpendicular to the ironing direction of the formed Gussblocks or the fiber orientation to lie.

In The table shows the mechanical / technical characteristics as well the fatigue resistance of molded parts thus removed in comparison to moldings whose fibers are parallel to the Gießfläche lie or no preferred transformation with a ratio of at least 4: 1, played. The according to the invention Process produced moldings with an alignment the intermetallic primary phases perpendicular to the casting surface show in the laboratory test a 17% better fatigue resistance than Molded parts whose fiber layer is parallel to the casting surface runs.

• Rest = Cu einschließlich unvermeidbarer Beimengungen.

Embodiment B is based on an alloy having the composition: 2.2% Ni 0.60% Si 0.33% Cr 0.15% Zr 0.12% Fe

• Remainder = Cu including unavoidable admixtures.

Also this alloy was melted in an induction crucible furnace and in a continuous casting process to a round block of the diameter dimensions 820 mm × length 1,400 mm potted. The round block was then on a hot rolling mill in a heat between 950 ° C and 800 ° C to a plate of dimensions Width 900 mm × thickness 80 mm × length 10,300 mm rolled. The total deformation ratio V in the longitudinal direction is, based on the initial length of the ingot, 7.4: 1 and thus corresponds to the preferred inventive specification of at least 7: 1.

The further treatment of the hot rolled plate and the removal of the Molded parts takes place, as in the embodiment A.

In Table 1 again shows the strength properties of the moldings with perpendicular to the ironing direction extending primary phases compared to mold parts whose intermetallic primary phases parallel to the casting direction.

The moldings produced according to the invention according to embodiment B show in comparison In the laboratory test, mechanical properties are even 26% more resistant to fatigue than molded parts with a fiber orientation parallel to the casting surface.

The Embodiments show that the invention Molded parts give a 17 to 26% better fatigue behavior the casting surface have as comparable mold parts with fiber and phase alignment parallel to the casting surface or without preference.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 0346645 B1 [0003, 0005]

Cited non-patent literature

• ASTM E 112 [0020]
• - US standard ASTM E 112 [0020]

Claims (16)

Process for the production of molded parts from one at least one alloying element of each of the Groups a) and b), wherein the group a) nickel and cobalt and the Group b) includes chromium, zirconium, beryllium and silicon, as well as intermetallic primary phases containing copper alloy, wherein a cast ingot by hot forming in only one direction in a ratio of at least 4: 1 is strung, wherein a casting surface coming into contact with a molten metal a molded part produced from the ironed ingot is selected perpendicular to the ironing of the ingot. Method according to claim 1, characterized in that that the proportion of the cut in a micrograph intermetallic primary phases between the casting surface and perpendicular to the casting surface Sides of the ironed ingot larger than 1.5: 1 is set. Method according to claim 1 or 2, characterized that the ingot by hot forming in only one direction in one Ratio of at least 7: 1 is strung. Method according to one of claims 1 to 3, characterized in that the cast block by hot forging is stripped. Method according to one of claims 1 to 4, characterized in that the ingot is drawn by hot rolling becomes. Casting part produced by the method according to one of the claims 1 to 5th Casting part according to claim 6, characterized that the proportion of the cut in a micrograph intermetallic primary phases between the casting surface and perpendicular to the casting surface Sides of the ironed ingot larger than 1.5: 1. Casting part according to claim 6 or 7, characterized characterized in that, the intermetallic primary phases are arranged in rows, with the ratio between the average length of one in the plane of the casting surface lying line to the mean length of a line that is vertical to the pouring area, less than 3:10 is. Casting part according to one of the claims 6 to 8, characterized in that the copper alloy cured in the Condition at 20 ° C a tensile strength of at least 600 MPa and at 500 ° C a tensile strength of at least 350 MPa has. Casting part according to one of the claims 6 to 9, characterized in that the copper alloy in the cured Condition at 20 ° C a 0.2% proof strength of at least 470 MPa has. Casting part according to one of claims 6 to 10, characterized in that the copper alloy in the cured state at 20 ° C has an elongation at break A ₅ of at least 15%. Casting part according to one of the claims 6 to 11, characterized in that the copper alloy at 20 ° C. has a hardness of at least 190 HV10. Casting part according to one of the claims 6 to 12, characterized in that the copper alloy at 20 ° C. an electrical conductivity of at least 40% IACS having. Casting part according to one of the claims 6 to 12, characterized in that the copper alloy at 20 ° C. an electrical conductivity of at least 45% IACS having. Casting part according to one of the claims 6 to 14, characterized in that the cured Copper alloy has a grain size of at most 130 μm measured according to ASTM E 112. Casting part according to one of the claims 6 to 15, characterized in that it is a block for side dams of Doppelbandgießanlagen is.