DE3109438A1 - "METHOD FOR THE PRODUCTION OF TUBULAR, STRAIGHT OR CURVED CONTINUOUS CASTING CHILLS WITH PARALLELS OR CONICAL INTERIOR CONTOURS FROM CURABLE copper ALLOYS" - Google Patents

Description

Cable and metal works Gutehoffnungshütte Aktiengesellschaft

2-246 03/10/81

Process for the production of tubular, straight or curved continuous casting molds with parallel or conical inner contours from hardenable copper alloys

The invention relates to a method for producing tubular, straight or curved continuous casting molds made of copper alloys, in which the mold walls forming the mold cavity are hit by explosives on the geometric Dimensions of a die are brought.

From DE-AS 25 33 528 a method for deforming the walls of Stranggießkokxllen is known in which on the the mold walls forming the mold cavity, a force which deforms these walls is applied by means of explosives and through these the walls are deformed to the geometric dimensions of a die. The advantage of the known method is that the molds deformed by this process made of copper or copper alloys a particularly good surface quality and dimensional accuracy have in the mold cavity. In addition, the deformation forces cause the surface to harden. A starting material with a Rockwell B hardness of between 50 and 75 Rockwell B can be used hardened.

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the service life of highly stressed molds is severely limited. Higher strength values can be achieved with the known processes possibly through the use of higher alloyed Achieve copper grades. However, these have the disadvantage of insufficient thermal conductivity and the tendency for the formation of cracks in the bathroom mirror area.

The present invention is based on the object of specifying a method with which molds of any format, For example, very thick-walled tubular molds with large dimensions can also be produced for bloom systems, which in addition to a very high strength over the entire wall thickness, a high softening temperature and high temperature resistance have, whereby it is possible by selecting suitable alloy components, very high or for example in the case of molds for magnetic stirring, also defined lower heat or. set electrical conductivity values.

In a method, this task is the one mentioned at the beginning Art solved in that a tube made of a hardenable copper alloy is used as the starting material, that this tube is initially solution annealed in the temperature range typical for the alloy or the tube is formed the solution annealing temperature is made that the solution annealed Tube is cured at 400 - 600 C for a period of at least 15 minutes, and that finally

the explosion forming is carried out. In the case of curved tubular molds, there is an additional difference between solution heat treatment and Curing turned on a bending operation.

The molds produced by this process show already have strength values that are significantly higher than the molds produced by the known process. The reason is that hardenable copper alloys are used as the mold material. The increase in strength is achieved with these materials by annealing at 400 - 600 C through precipitation effects (hardening). The improved Properties of the mold lead to a longer service life, which is compared to a higher dimensional stability thermal stresses, especially at higher temperatures and from a higher wear resistance, which leads to less abrasion, results.

A further increase in strength is possible in the method according to the invention in that, after the solution heat treatment, the soft tube is mechanically cold-worked using conventional methods. This is expediently achieved by inserting a mandrel into the tubular mold - a correspondingly curved mandrel in the case of curved tubular molds - and pressing the mold together with the mandrel through a die. The degree of cold deformation can be set between 2 and 30 % depending on the desired final strength. Because of the in part very high strength values that result after the subsequent hardening, it is also expedient to aim for the final geometric dimensions of the tubular mold during the calibration after the solution heat treatment. This makes it possible to eliminate the distortion that occurs during curing in an explosion step and to produce an optimal end product.

The choice of age-hardenable copper alloys to be used depends on the specific requirements of the mold type. For the most common applications, special

Advantage of a copper alloy with 0.3 - 1.2% chromium and 0.05-0.2% zirconium used. With this material ensures the high thermal conductivity required for molds. Compared to the previous standard materials used such as SF copper, copper-silver-phosphorus alloys have molds made of the hardenable copper-chromium-zirconium material, which according to the Process according to the invention are produced, a significantly higher heat resistance and wear resistance. You are in Use practically distortion-free and have a very long service life.

The method according to the invention for producing a mold from copper-chromium-zirconium is based on an example explained in more detail.

A bolt was first cast from a copper alloy with 0.7 % chromium and 0.18 % zirconium, the remainder being copper and the usual impurities, and this was then extruded into a tube at 1,030 ° C. The extruded tube was quenched in water. Pipe sections were cut off from this pipe, pre-bent on a bending machine and a die with a circular cross-section was inserted into the cavity of the pipe section. An explosive charge was evenly distributed on the outside of the pipe section and detonated. The die was then removed from the pipe section and the pipe section was annealed at 475 ° C. for 4 1/2 hours. After it had cooled down, a die was inserted into the pipe section removed from the annealing furnace, which was slightly warped. Care was taken to ensure that the slightly curved die was inserted into the curved pipe section in such a way that the direction of curvature of the pipe section and the direction of curvature of the die point in the same direction. As described above, the explosion forming was carried out again and the tubular mold was thereby cold-formed to the desired extent.

The following properties were found on this completed mold measured:

Thermal conductivity 87 %

Softening temperature 525 ° C

(10% drop in strength at R.T. after 1 hour of annealing)

Hardness HB 2.5 / 62.5 145

2 tensile strength 442 N / mm

Elongation at break 26 %

Hot strength at 200 ⁰ C 380 N / mm ² temperature strength at 350 ° C 318 N / mm

The continuous casting mold produced by the above-mentioned process was still sufficiently dimensionally stable and showed even after a casting trip of 450 batches in the bathroom mirror area only slight signs of wear at the base of the mold.

The production of a straight, conical square mold from the same material copper-chrome-zircon with even higher Strength properties are shown in a further example the teaching of the invention explained.

First, a round tube was extruded at 950 C and then formed into the desired square-edged format by drawing. The square tube was solution heat treated at 990 ° C. for 45 minutes. After cooling, pipe sections cut to length were calibrated to the final dimension using a mandrel and a die with a simultaneous reduction in wall thickness of 15 % and cured at 450 ° C. for six hours. Subsequently, the final calibration was carried out as described above by means of explosion forming.

The following properties were obtained on this completed mold measured:

Thermal conductivity 84 % Softening temperature 510 ° C Hardness HB 2.5 / 62.5 159 tensile strenght 521 N / mm Elongation at break 21st %

With such an intermediate deformed mold, the wear resistance becomes at the base of the mold further improved considerably.

For molds which require particularly high thermal conductivity, for example because of poor cooling water quality, molds made of a copper alloy with 0.05-0.3 % zirconium can advantageously be produced using the method according to the invention. By means of a suitable mechanical intermediate cold deformation, tensile

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strength values of around 350 N / mm can be achieved with a thermal conductivity of over 93%. The softening temperature of this material is above 550 C.

For special cases in which a magnetic stirring process is provided in the area of the mold insert, a mold material with the lowest possible electrical conductivity is desired in order to keep the field weakening low. Since the thermal conductivity of such a material is reduced to the same extent as the electrical conductivity, very high wall temperatures occur. In order to ensure freedom from distortion, the mold material must have a correspondingly higher heat resistance. These requirements are met, for example, by the hardenable materials copper-nickel-phosphorus with 0.6 - 1.5 % nickel, 0.1 0.3 % phosphorus and copper-cobalt-beryllium or copper-nickel-beryllium with 1 - 2, 5 % cobalt or 1 - 2.5 % nickel or 0.5 - 1.5 % nickel + 0.5 - 1.5 % cobalt and 0.3 - 0.6 % beryllium and also Rupfer-nickel-silicon 0.2-1.1 % silicon and 1.2-3.5 % nickel.

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According to the method according to the invention, for example, a curved rectangular tubular mold with the internal format 200 × 220 mm and a wall thickness of 14 mm from a copper-cobalt-beryllium alloy with 2.2% cobalt and 0.54 % beryllium was produced as follows.

First a square tube was produced by extrusion and then solution annealed at 935 ° C. for 45 minutes. The desired curvature was produced on a bending machine. A piece of pipe was then made by explosive forming calibrated using a mandrel as described above.

The mold was then cured at 480 ° C. for five hours. Finally, the warpage was caused by curing Explosion deformation eliminated with a mandrel and the mold recalibrated.

The following properties were measured on this tubular mold:

Thermal conductivity 54 % softening temperature
Hardness HB 2.5 / 62.5
tensile strenght
Elongation at break

High temperature strength at 200 ^° C. High temperature strength at 350 ° C.

When used in a so-called agitating mold, a considerably better agitating effect was achieved because of the lower field weakening than achieved with the previously known molds. The dimensional stability was still excellent even after more than 100 casting trips.

505 ° C. 235 805 N / mm ² 17th % 735 N / mm ² 622 N / mm

Claims (3)

Kabel- und Metallwerke Gutehoffnungshütte Aktiengesellschaft 2-246 03/10/81 Patent claims 1. A process for the production of tubular, curved continuous casting molds from a copper alloy, in which the mold walls forming the mold cavity are deformed to the geometrical dimensions of a die by means of explosives, characterized in that a tube made of a hardenable copper alloy is used as the starting material, that this tube initially solution annealed in the temperature range typical for the alloy or the tube is formed at solution annealing temperature, that the solution annealed tube is annealed at 400 to 600 ° C. for a period of at least 15 minutes and that finally the explosion forming is carried out. 2. The method according to claim 1, characterized in that the tube is cold formed between the operations of solution annealing and hardening. 3. The method according to claim 1 or 2, characterized in that a mandrel is inserted into the tubular mold and the mold is pressed together with the mandrel through a die. Process according to Claim 1 or one of the following, characterized in that a copper alloy with 0.3 to 1.2 % chromium and 0.05 to 0.2 % zirconium is used.