EP2932102B1 - Can for magnetically coupled pumps and production process - Google Patents

Description

The invention relates to a containment shell for arrangement in a gap between a driver and a rotor of a magnetically coupled pump, and to a method for producing the containment shell.

In the promotion of fluids, especially in the chemical sector, usually high demands on the tightness of delivery lines and pumps must be made. At the same time a good efficiency of the pumps must be ensured. Pumps with only static seals, ie without shaft seals, can be made particularly fluid-tight. Magnetically coupled pumps can be statically sealed by placing a stationary containment shell between a drive side driver and a magnetically driven output side rotor and surrounding the rotor. The containment shell is arranged in the magnetic field between the driver and the rotor, and the magnetic forces are transmitted through the containment shell. To the rotor, a pump impeller can be coupled. Drivers and rotors are provided with permanent magnets and arranged as close to each other as possible in order to provide an efficient drive. The wall thickness of the side wall of the containment shell specifies how large the gap or gap between driver and runner must be at least.

Often, the distance and thus the width of the air gap formed between the driver and rotor, for example, only about 4 mm, and the containment shell then has a wall thickness of eg 2 mm. A narrow gap or a very brief interpretation of the wall thickness of the split pot with respect to a minimum width the gap provides advantages in efficiency, in particular with regard to minimizing drive losses, but at the same time reduces a safety factor and possibly also the service life of the can, depending on which fluids are to be conveyed. Nevertheless, in order to be able to realize the narrowest possible gap, it is of interest to produce the containment shell from a material of particularly high quality which, in addition to high strength, in particular high hardness, also has good corrosion resistance. The corrosion resistance is just in terms of the lowest possible wall thickness of the side wall of importance. At the same time, the containment shell is also to be reworked, in particular cold-formed, in order to be able to adjust the geometry of the side wall by forming processes. Nickel-based alloys have proven to be suitable material for containment pots.

From the EP 1 398 510 A1 is a wet-running centrifugal pump assembly with an asynchronous known, the rotor is constructed of a rotor core, which is interspersed with copper short-circuiting rods, wherein the rotor runs in a can and the can of ferritic stainless steel.

The DE 10 2009 049 904 A1 relates to a partition wall for an electric motor comprising a stator and a rotor unit rotatably mounted on a sliding body, wherein the partition wall sealingly between the stator and the rotor unit can be arranged and wherein a retaining element with a closed surface is formed integrally with the partition of a stainless thermoformable material ,

The object is to provide a containment shell in which, in addition to good structural material properties, a high corrosion resistance can be ensured. It is also an object to design the containment shell so that it can be easily brought into a desired geometry. Last but not least, it is the task to design a containment shell in such a way that it can easily be given a high material hardness.

At least one of these objects is achieved by a containment shell according to claim 1 and by a method according to claim 9. Advantageous developments of the invention are the subject of the dependent claims.

• ein Flanschteil, z.B. zum Verbinden des Spalttopfes mit der Pumpe oder dem Motor;
• einen Boden;
• eine in montiertem Zustand des Spalttopfes in dem Spalt anordenbare Seitenwandung, die zumindest teilweise aus einem Werkstoff mit einem Nickelbestandteil besteht.

An inventive containment shell, which can be used, for example, for arrangement in a gap between a driver and a rotor of a magnetically coupled pump or in a canned motor pump, comprises:

• a flange part, eg for connecting the containment shell to the pump or the motor;
• a floor;
• a arranged in the assembled state of the split pot in the gap side wall, which consists at least partially of a material with a nickel component.

According to the invention, it is proposed that the material is a nickel-chromium alloy which has at least 50 percent by weight nickel and 17 to 21 percent by weight chromium. In this way, a particularly resistant containment can be provided.

Preferably, not only a part of the side wall of the material, but the side wall is made uniformly from the material, in particular when the side wall is designed with a view to a minimum material thickness. Optionally, the entire containment shell made of the material, although in particular for the flange and deviating, especially less expensive materials can be selected.

Preferably, the material has cobalt (Co), and the cobalt content is at most 1 percent by weight. More preferably, the material boron (B), and the boron content is at most 0.006 weight percent.

As a bottom of the split pot is preferably a section to understand, which closes the gap pot pot-shaped at one end and thereby merges into the side wall.

A flange part of the containment shell is preferably a section which is designed to arrange and to fix the containment pot in a defined position and orientation in the pump.

According to one embodiment, the material is a nickel-chromium-iron alloy, in particular a nickel alloy called Alloy 718 (Nicofer 5219 Nb), wherein the nickel content is at most 55 weight percent and the iron content is between 10 and 25 weight percent. In other words, the invention relates to the use of a suitable nickel-chromium-iron alloy for a split pot, which is designed to be arranged in a gap between a driver and a rotor of a magnetically coupled pump. Such a material may be a nickel-chromium-iron alloy, which has high strength and is therefore particularly useful for splitters used in pumps operating at high pressures. At the same time it is well deformable in certain conditions, especially in one solution annealed condition, and therefore can be easily reworked, for example by spin forming. It is also advantageous that hydrogen embrittlement does not occur in this material, so that hydrogen-containing media can also be delivered by means of a pump with such a containment shell.

• ▪ in einem Ofen eine Temperatur im Bereich von 960 °C, insbesondere 960 °C ± 15 °C, bevorzugt genau 960 °C erzeugen;
• ▪ den Spalttopf in dem Ofen mindestens 60 Minuten lösungsglühen, wobei in Abhängigkeit von der Wandstärke der Spalttopf die Haltezeit mindestens 3 Minuten pro Millimeter Wandstärke beträgt;
• ▪ nach dem Lösungsglühen Abschrecken, insbesondere im Wasserbad.

Such a material also provides the advantage that it is curable without deformations occur. In this way, a high-strength containment can be provided in a simple manner, which has a high dimensional accuracy, so that an air gap in the pump can be made very narrow. The hardening can take place in that a heat treatment takes place over a predefined period of time and at a predefined temperature at at least one predefined temperature level. To avoid stress cracks, a preliminary solution annealing is useful. The solution annealing can preferably take place with the following parameters:

• ▪ produce in a furnace a temperature in the range of 960 ° C, especially 960 ° C ± 15 ° C, preferably exactly 960 ° C;
• ▪ solution-anneal the containment pot in the oven for at least 60 minutes, depending on the wall thickness of the containment shell, the holding time is at least 3 minutes per millimeter wall thickness;
• ▪ Quenching after solution heat treatment, especially in a water bath.

Although a number of other Lösungsglühvorgange possible with the material, in particular in a temperature range of 940 to 1080 ° C, and the quenching can also be done in air, however, it has been shown that especially for the side wall of the solution solution described above is preferable.

A hardness measurement is preferably carried out before and after the heat treatment.

It is recommended that the containment shell be kept free of grease, oils, lubricants or other contaminants before it is heat treated.

• ▪ in einem Ofen eine Temperatur im Bereich von 720 °C, insbesondere 720 °C ± 8 °C, bevorzugt genau 720 °C erzeugen, wobei der Schritt ein Kühlen des Ofens von der Temperatur fürs Lösungsglühen auf die Härtetemperatur umfassen kann;
• ▪ den Spalttopf in dem Ofen für eine erste Haltezeit von etwa 8 Stunden, bevorzugt genau 8 Stunden bei der Temperatur wärmebehandeln;
• ▪ die Temperatur in dem Ofen auf etwa 620 °C, insbesondere 620 °C ± 8 °C, bevorzugt genau 620 °C absenken, insbesondere innerhalb einer Zeit von 2 Stunden und in geschlossenem Zustand des Ofens, wobei der Spalttopf in dem Ofen verbleibt;
• ▪ den Spalttopf in dem Ofen für eine zweite Haltezeit von etwa 8 Stunden, bevorzugt genau 8 Stunden bei der niedrigeren Temperatur wärmebehandeln, wobei die zweite Haltezeit wahlweise ausgedehnt werden kann auf bis zu 12 Stunden, insbesondere aus prozesstechnischen Gründen; und
• ▪ Abkühlen an ruhender Luft.

The adjustment of the hardness of the material can preferably take place with the following parameters:

• ▪ in a furnace, produce a temperature in the range of 720 ° C, in particular 720 ° C ± 8 ° C, preferably exactly 720 ° C, the step comprising cooling the furnace from the solutionizing temperature to the hardening temperature;
• ▪ heat the can in the oven for a first hold time of about 8 hours, preferably exactly 8 hours at the temperature;
• ▪ lower the temperature in the furnace to about 620 ° C, in particular 620 ° C ± 8 ° C, preferably exactly 620 ° C, in particular within a period of 2 hours and in the closed state of the furnace, wherein the containment shell remains in the furnace;
• ▪ annealing the can in the oven for a second hold time of about 8 hours, preferably exactly 8 hours at the lower temperature, the second hold time optionally being extended to up to 12 hours, especially for process engineering reasons; and
• ▪ Cooling in still air.

It may be important to bring the solution heat oven already to the target temperature before the workpiece is placed in the oven.

Compared to previously often used at high pressures titanium alloys that are subject to hydrogen embrittlement, thus resulting in a broader field of application. Apart from that, the material has a greater hardness compared to titanium. Furthermore, the material provides the advantage of high temperature resistance, in particular up to 600 ° C.

Such an alloy provides high strength with good residual strain, so also sufficient ductility to allow post-processing. In this case, a very good deformability can be ensured.

The split pot according to the invention preferably obtains its desired geometry by spin forming the side wall as a special type of cold deformation. By spin forming, the cup portion can be provided with a relatively thin sidewall, e.g. in the range of 1 mm, wherein the wall thickness of the side wall can also lie in a narrow tolerance range, in particular with deviations smaller 1/10. The thin wall thickness, but also the narrow tolerance range, offer the advantage of high drive efficiency in a magnetically coupled pump, because driver and rotor of the pump can be arranged very close together. At the same time, the manufacturing costs can be kept low because rework on the side wall of the split pot are not required. The sidewall can be made with such high accuracy and tolerance that a face turning or grinding or any other molding process is no longer required. In this context, flow-forming processes are preferably understood to mean a cold-forming process in which the side wall of the containment shell is brought to a defined thickness and receives a defined orientation, in particular a cylindrical geometry with a high dimensional stability, ie. a slight deviation from the cylindrical shape in the radial direction (accuracy better 1/10). In this case, the pressure-rolling can lead to an extension of the cylindrical side wall in the axial direction, without changing the diameter of the gap pot. In this case, a desired geometry is to be understood as a geometry which the containment shell is to assume at the end of the production process, in particular in the region of the side wall and the bottom. The desired geometry is preferably defined by the respective wall thickness of the side wall and the bottom, an outer diameter and tolerance ranges for the respective dimensions. A particular advantage of the described type of production is that the containment shell in the pressure-bearing areas completely eliminates welds or, in other words, has no pressure-bearing welds.

• ▪ Zugfestigkeit in N/mm²: 1240 bis 1275;
• ▪ Dehngrenze in N/mm²: etwa 1035, bevorzugt genau 1035;
• ▪ Bruchdehnung in Prozent: 6, 10, 12 oder ≥ 14;
• ▪ Brinellhärte in HB: ≥ 331, insbesondere ≥ 341;
• ▪ Korngröße in µm: bevorzugt ≤ 127.

The mechanical properties of the hot- or cold-formed material of the split can of the invention at room temperature in solution annealed condition and after curing can be determined by the tensile strength (Rm) in N / mm ² , the yield strength (Rp0.2) in N / mm ² , the elongation at break (A5) and constriction (Z) in percent, the Brinell hardness in HB and the grain size in μm define:

• ▪ tensile strength in N / mm ² : 1240 to 1275;
• ▪ yield strength in N / mm ² : about 1035, preferably exactly 1035;
• ▪ breaking elongation in percent: 6, 10, 12 or ≥ 14;
• ▪ Brinell hardness in HB: ≥ 331, in particular ≥ 341;
• ▪ Grain size in μm: preferably ≤ 127.

The modulus of elasticity may be, for example, in the range of 205 kN per mm ² for room temperature and, for example, in the range of 199 kN per mm ² for 100 ° C.

Particularly advantageously, the material of the can of the invention can have (by suitable heat treatment) an elongation at break of ≥ 14% and a front impact test ≥ 20 Joule, preferably ≥ 27 Joule. Thus, the can according to the invention meets the requirements of the Pressure Equipment Directive (Directive 97/23 / EC on pressure equipment). This makes the containment shell suitable for use in pumps that operate with an internal overpressure of more than 0.5 bar.

• ▪ Nickel zwischen 50 und 55 Prozent;
• ▪ Chrom zwischen 17 und 21 Prozent;
• ▪ Molybdän zwischen 2,8 und 3,3 Prozent;
• ▪ Niob zwischen 4,75 und 5,5 Prozent (Niob und Tantal zusammen zwischen 4,87 und 5,2 Prozent);
• ▪ Aluminium zwischen 0,2 und 0,8 Prozent (0,4 und 0,6 Prozent);
• ▪ Titan zwischen 0,65 und 1,15 Prozent (0,8 und 1,15 Prozent);
• ▪ einen Rest Eisen.

Preferably, the alloy contains a substantial content of niobium and molybdenum and a low content of aluminum and titanium. The percentages by weight are preferably in the following ranges, with the values given in parentheses referring to a variant of the alloy that can be used in corrosive media, especially media having H ₂ S, CO _2, or Cl , The change in composition relates in particular to the alloying constituents carbon and niobium, but also to aluminum and titanium, with higher carbon and niobium fractions providing advantages in high-temperature applications and lower carbon and niobium levels for corrosive media applications are:

• ▪ Nickel between 50 and 55 percent;
• ▪ Chrome between 17 and 21 percent;
• ▪ Molybdenum between 2.8 and 3.3 percent;
• Niobium between 4.75 and 5.5 percent (niobium and tantalum together between 4.87 and 5.2 percent);
• ▪ Aluminum between 0.2 and 0.8 percent (0.4 and 0.6 percent);
• ▪ Titanium between 0.65 and 1.15 percent (0.8 and 1.15 percent);
• ▪ a remainder of iron.

The remainder of iron is preferably in a range of 11 to 24.6 weight percent (12 to 24.13 weight percent).

The alloy may have other trace elements, in particular up to 0.08 percent (0.045 percent) C, and / or up to 0.35 percent Mn, and / or up to 0.35 percent Si, and / or up to 0.3 Percent (0.23 percent) Cu, and / or up to 1.0 percent Co, and / or up to 0.05 percent Ta, and / or up to 0.006 percent B, and / or up to 0.015 percent (0, 01 percent) P, and / or up to 0.0015 percent (0.01 percent) S, and / or up to 5 ppm (10 ppm) Pb, and / or up to 3 ppm (5 ppm) S, and / or up to 0.3 ppm (0.5 ppm) Bi.

Preferably, the carbon content is exactly 0.08 weight percent (0.045 weight percent) or in the range of 75-100 percent of 0.08 weight percent (0.045 weight percent), that is between 0.06 and 0.08 weight percent (0.03375 and 0.045 weight percent). As a result, a good temperature resistance can be achieved. Alternatively, alternatively or additionally, the niobium content is exactly 5.5 weight percent (5.2 weight percent niobium and tantalum together) or in a range of 5.25 to 5.5 weight percent (5.1 to 5.2 weight percent niobium and tantalum together). According to one variant, the carbon content is 0.00 wt% (0.00 wt%) or in the range 0-25% of 0.08 wt% (0.045 wt%), ie between 0.00 and 0.02 wt% (0 , 00 and 0.011 weight percent). As a result, a good corrosion resistance can be achieved. Alternatively, alternatively or additionally, the niobium content is exactly 4.75 weight percent (4.87 weight percent) or in the range of 4.75 to 5.0 weight percent (4.87 to 4.98 weight percent niobium and tantalum together).

Such an alloy provides the advantage of high temperature resistance up to 700 ° C with good strength even in the high temperature range. Furthermore, these alloys have a high fatigue strength, a good creep strength up to 700 ° C and a good oxidation resistance up to 1000 ° C. They also provide good low temperature mechanical properties, good corrosion resistance at high and low temperatures, and good resistance to stress corrosion cracking and pitting. The corrosion resistance, especially against stress cracks, can be ensured in particular by the chromium content. The alloy can therefore also be used in media that are used in petroleum production and oil processing, in H ₂ S-containing sour gas environments or in the field of marine technology.

The density of the alloy is for example in the range of 8 g / cm ³ , in particular it is 8.2 g / cm ³ .

The structure of the alloy is austenitic with several phases, in particular the phases carbides, laves ([Fe, Cr] 2Nb), δ (Ni3Nb) orthorhombic, γ "(Ni3Nb, Al, Ti) tetragonal body centered, and / or γ '(Ni3Al In any case, the phase γ "(Ni 3 Nb, Al, Ti) is preferably tetragonally centered in space, which can be adjusted by precipitation hardening. The phase γ "(Ni 3 Nb, Al, Ti) tetragonal body centered provides good resistance to aging deformation cracking.

The preparation of the alloy can be carried out by melting in the vacuum induction furnace and subsequent electroslag remelting. The remelting can also be done by a vacuum arc process.

According to one embodiment, the material has molybdenum, wherein the molybdenum content is between 2.8 and 3.3 percent by weight. In this way, a good corrosion resistance can be achieved, in particular independently of the temperature range in which the containment shell is used.

According to another embodiment, the material comprises niobium, wherein the niobium content is 4.75 to 5.5 percent by weight, or the material comprises niobium and tantalum, the proportion of niobium and tantalum together being 4.87 to 5.2 percent by weight. As a result, a good temperature resistance can be set. The niobium content thereby ensures the formation of at least one of the following phases of an austenitic microstructure, whereby the advantageous strength values of the material can be adjusted: phase δ (Ni 3 Nb) orthorhombic, phase γ "(Ni 3 Nb, Al, Ti) tetragonal body-centered, and / or phase γ '(Ni3Al, Nb) face centered cubic.

According to a further embodiment, the material comprises aluminum and titanium, wherein the aluminum content is between 0.2 and 0.8, preferably 0.4 and 0.6 percent by weight and / or the titanium content between 0.65 and 1.15, preferably 0 , 8 and 1.15 weight percent. As a result, particularly good mechanical properties can be achieved, in particular because aluminum and titanium can ensure the formation of at least one of the following phases of an austenitic structure: phase γ "(Ni 3 Nb, Al, Ti) tetragonal body-centered, and / or phase γ '(Ni 3 Al, Nb ) Cubic area-centered.

According to a further embodiment, the material is a nickel-chromium-molybdenum alloy, in particular the nickel alloy Hastelloy C-22HS or one of the variants of this alloy, wherein the chromium content is 21 percent by weight and the nickel content is at least 56 percent by weight, especially 56.6 percent by weight, and Molybdenum content is 17 percent by weight. In other words, the invention relates to the use of a suitable nickel-chromium-molybdenum alloy for a split pot, for example for arrangement in a gap between a driver and a Rotor of a magnetically coupled or for a canned motor pump. Such a material is a nickel-chromium-molybdenum alloy, which has a high corrosion resistance and a high ductility with high rigidity and thus also dimensional stability in relation to a generated desired geometry.

• Nickel als Hauptbestandteil in einem Prozentanteil abhängig von den Prozentanteilen der weiteren Bestandteile, mindestens jedoch 56,6 Prozent;
• Chrom (Cr): 21 Prozent;
• Molybdän (Mo): 17 Prozent;
• Eisen (Fe): maximal 2 Prozent;
• Kobalt (Co): maximal 1 Prozent;
• Wolfram (W): maximal 1 Prozent;
• Mangan (Mn): maximal 0,8 Prozent;
• Aluminium (Al): maximal 0,5 Prozent;
• Silizium (Si): maximal 0,08 Prozent;
• Kohlenstoff (C): maximal 0,01 Prozent;
• Bor (B): maximal 0,006 Prozent.

The alloying ingredients are preferably in the following percentages by weight:

• Nickel as the main constituent in a percentage depending on the percentages of the other constituents, but at least 56.6 percent;
• Chrome (Cr): 21 percent;
• Molybdenum (Mo): 17 percent;
• Iron (Fe): maximum 2 percent;
• Cobalt (Co): maximum 1 percent;
• Tungsten (W): maximum 1 percent;
• Manganese (Mn): maximum 0.8 percent;
• Aluminum (Al): maximum 0.5 percent;
• Silicon (Si): 0.08 percent maximum;
• Carbon (C): maximum 0.01 percent;
• Boron (B): maximum 0.006 percent.

Such a material can be cured in a simple manner after a preliminary forming. It is highly hardening by age hardening after cold working, especially without intermediate solution heat treatment. The achievable hardness is a function of the degree of deformation. This provides the advantage that, for example, a spin forming of the side wall of the split pot can be done to set a defined wall thickness, and that after the spin forming hardening of the side wall takes place. Cold forming, in particular spin forming, preferably takes place after solution heat treatment. Thereby, the advantages of a high Dimensional accuracy can be easily combined with the advantages of high strength. The material is also of high acid resistance, which makes its use for pumps in the chemical industry (chemical pumps) particularly interesting.

Preferably, the material has tungsten, which distinguishes it from the nickel-chromium-iron alloy described above.

The strength of the material can be adjusted by a heat treatment in which Ni ₂ (Mo, Cr) particles are formed, and the heat treatment is preferably carried out in a temperature range of 605 to 705 ° C. However, the good corrosion resistance of the alloy can also already be achieved by annealing alone.

• Wärmebehandeln in einem Ofen bei 705 °C, insbesondere über eine Dauer von 16 Stunden;
• Abkühlen des Ofens auf 605 °C;
• Wärmebehandeln in dem Ofen bei 605 °C, insbesondere über eine Dauer von 32 Stunden; und
• Abkühlen an Luft.

Preferably, the heat treatment is performed to set a higher hardness under the following parameters:

• Heat treating in an oven at 705 ° C, especially over a period of 16 hours;
• Cooling the oven to 605 ° C;
• Heat treating in the oven at 605 ° C, especially over a period of 32 hours; and
• Cool in air.

The density is preferably in the range of 8.6 g / cm ³ in the solution-annealed condition or 8.64 g / cm ³ in the cured state.

• ▪ Zugfestigkeit in Mpa bzw. N/mm²: etwa 837 (806);
• ▪ Dehngrenze in Mpa bzw. N/mm²: etwa 439 (376);.

The modulus of elasticity is for example in the range of 223 GPa (or kN / mm ² ) for room temperature and for example in the range of 218 GPa (or kN / mm ² ) for 100 ° C. The mechanical properties of the formed material at room temperature in solution annealed condition can be determined by the tensile strength (Rm) in N / mm ² , the yield strength (Rp0.2) in N / mm ² , the elongation at break (A5) and constriction (Z) in percent , which define Brinell hardness in HB and grain size in μm, the first values being cold formed Refer to components and the second values in brackets to thermoformed components:

• ▪ tensile strength in Mpa or N / mm ² : about 837 (806);
• ▪ Yield strength in Mpa or N / mm ² : about 439 (376) ;.

• ▪ Zugfestigkeit in Mpa bzw. N/mm²: etwa 1230 (1202);
• ▪ Dehngrenze in Mpa bzw. N/mm²: etwa 759 (690);

By curing, the values can be set as follows:

• ▪ tensile strength in Mpa or N / mm ² : about 1230 (1202);
• ▪ Yield strength in Mpa or N / mm ² : about 759 (690);

The achievable hardnesses are in the following ranges, depending on the duration of a solution annealing before curing, the hardness values were determined according to Rockwell, either scale B (hardness values in the unit Rb) or C (hardness values in the unit Rc) , material form Hardness [Rb] or [Rc] annealed Hardened plate 92 Rb 30 Rc thin-walled sheet metal 90 Rb 30 Rc Bars / rod 88 Rb 30 Rc

For room temperature with a cold-formed side wall of the can, depending on the degree of deformation (in percent), the following hardness values of the side wall can be set by aging-hardening: Hardness [Rc] by degree of deformation [%] Duration of curing [h] 0% 10% 20% 30% 40% 50% 0 <20 29 35 37 40 45 1 <20 27 33 38 41 47 4 <20 26 33 39 41 48 10 <20 35 40 41 45 51 24 <20 40 43 44 48 52

As can be seen from the table above, the achievable hardness depends on the degree of deformation. The higher the degree of deformation, the higher the achievable hardness.

According to a further embodiment, the material comprises iron, wherein the iron content is at most 2 percent by weight.

According to a further embodiment, the side wall is a side wall brought into a desired geometry by a forming step, which has a degree of deformation of more than 10 percent, preferably between 20 and 50 percent, more preferably between 30 and 40 percent, in particular 35 percent. By forming a particularly high hardness can be achieved by a subsequent hardening.

• Ausbilden eines Flanschteils der Spalttopf zum Verbinden des Spalttopfes mit der Pumpe;
• Ausbilden eines Bodens des Spalttopfes;
• Ausbilden einer in montiertem Zustand des Spalttopfes in dem Spalt anordenbaren Seitenwandung zumindest teilweise aus einem Werkstoff mit einem Nickelbestandteil, wobei die Seitenwandung durch einen Umformschritt, insbesondere durch Drückwalzen, in eine Sollgeometrie gebracht wird.

The invention also relates to a method for producing a split pot for arrangement in a gap between a driver and a rotor of a magnetically coupled pump, comprising the steps of:

• Forming a flange portion of the split pot for connecting the split pot with the pump;
• Forming a bottom of the split pot;
• Forming a side wall which can be arranged in the gap in the assembled state of the can, at least partially made of a material having a nickel component, wherein the side wall is brought into a desired geometry by a forming step, in particular by spin forming.

According to the invention, the material selected is a nickel-chromium alloy in a solution-annealed state, which has at least 50 percent nickel by weight and 17 to 21 percent chromium by weight, hardening being effected by heat treatment after forming.

The curing can be done either directly or after an intermediate solution annealing. The curing is preferably carried out by a heat treatment in the temperature range of 605 to 728 ° C, in particular over a period of 18 to 48 hours, wherein the heat treatment is in any case two-stage with respect to the selected temperature and a respective stage is maintained for at least 8 hours.

According to one embodiment, the forming is a cold forming, wherein after the cold forming a paging hardening takes place, in particular in a temperature range of 605 to 728 ° C and without intermediate solution annealing after the cold forming. The cold forming is preferably a spin forming. Paging hardening can be done either directly after cold forming or after an intermediate step for solution annealing. For the nickel-chromium-molybdenum alloy described, aging is preferably carried out without solution annealing intermediate step. In this case, increasing hardness can be achieved with increasing hardening times, wherein the hardening times are e.g. be selected in the range of 1, 4, 10, 24 or 32 hours, preferably 32 hours at 605 ° C, since the longer duration, the hardness Rc to Rockwell scale C can be increased by over 10 percent.

Figur 1:

ein Diagramm zu typischen Kurzzeiteigenschaften einer Legierung gemäß einem ersten Ausführungsbeispiel der Erfindung;

Figur 2:

ein Diagramm zu typischen Zeitstandfestigkeiten der Legierung gemäß dem ersten Ausführungsbeispiel der Erfindung; und

Figur 3:

in einer schematischen Darstellung einen Spalttopf mit einem Werkstoff gemäß dem ersten oder zweiten Ausführungsbeispiel der Erfindung.

Embodiments of the invention will be described below with reference to the drawings. Show it:

FIG. 1:

a diagram of typical short-term properties of an alloy according to a first embodiment of the invention;

FIG. 2:

a diagram of typical creep strength of the alloy according to the first embodiment of the invention; and

FIG. 3:

in a schematic representation of a containment shell with a material according to the first or second embodiment of the invention.

In the Fig. 1 are typical short-term properties of a nickel-chromium-iron alloy in a solution annealed and cured state as a function of temperature in ° C shown. It can be seen from the diagram that quite constant mechanical properties are present in a temperature range from room temperature to 600 ° C., which applies in particular to the breaking elongation (A5) and the constriction (Z), which provides advantages with regard to good dimensional accuracy of the containment shell.

In the Fig. 2 For example, typical creep ruptures of the nickel-chromium-iron alloy in a solution-annealed and cured state are shown as a function of time in hours, with time plotted logarithmically, and with creep ruptures on the y-axis in N / mm ² . It can be seen from the diagram that even over a period of 10 ⁵ hours corresponding to a good 11 years at temperatures below 500 ° C., a loss of mechanical strength is hardly noticeable.

In the Fig. 3 a split pot 1 is shown, which is formed symmetrically with respect to a symmetry axis S and a bottom 2, a side wall 3 and a flange 4 has. The containment shell 1 has a nickel-chromium alloy, so it is partially or completely made of a material which can be formed from nickel and chromium and other alloying constituents. A partial embodiment of the split pot in the material may, for example, relate only to the side wall 3. Preferably, at least the side wall 3 is formed entirely of the material.

LIST OF REFERENCE NUMBERS

1

containment shell

2

ground

3

sidewall

4

flange

S

axis of symmetry

Claims (11)

1. A can (1) comprising:

   - a flange part (4);

   - a bottom (2);

   - a side wall (3) that can be arranged in a gap in the mounted status of the can, said side wall consisting at least partially of a material containing a nickel constituent,

   characterized in that the material is a nickel-chromium alloy which contains at least 50 percent by weight of nickel and 17 to 21 percent by weight of chromium.
2. The can according to claim 1, characterized in that the material is a nickel-chromium-iron alloy, with the nickel portion being maximally 55 percent by weight, and the iron portion ranging between 10 and 25 percent by weight.
3. The can according to claim 2, characterized in that the material contains molybdenum ranging between 2.8 and 3.3 percent by weight.
4. The can according to any of the preceding claims 1 to 3, characterized in that the material contains niobium, with the portion of niobium amounting to 0.5 to 10, preferably 3 to 7, particularly perferably 4.75 to 5.5 percent by weight, or that the material contains niobium and tantalium, with the portion of niobium and tantalium together accounting for 0.5 to 10, preferably 3 to 7, particularly preferable 4.87 t 5.2 percent by weight.
5. The can according to any of the preceding claims 1 to 4, characterized in that the material features aluminum and titanium, with the portion of aluminum ranging between 0.2 and 0.8, preferably between 0.4 and 0.6 percent by weight and/or the titanium portion ranging between 0.65 and 1.15, preferably between 0.8 and 1.15 percent by weight.
6. The can according to any of claims 1, characterized in that the material is a nickel-chromium-molybdenum alloy, with the portion of chromium amounting to 21 percent by weight and the portion of nickel amounting to at least 56 percent by weight, in particular to 56.6 percent by weight, and the molybdenum portion amounting to 17 percent by weight.
7. The can according to claim 6, characterized in that the material contains iron, with the iron portion amounting to maximally 2 percent by weight.
8. The can according to claim 6 or 7, characterized in that the side wall (3) is a side wall (3) brought by way of a reshaping step into a desired target geometry, said side wall having a reshaping degree of over 10 percent, preferably between 20 and 50 percent, further preferably between 30 and 40 percent, in particular 35 percent.
9. The can according to any of the preceding claims 1 to 8, characterized in that it does not have any pressure-bearing welding seams.
10. A method for manufacturing a can (1), said method comprising the steps of:

    - forming a flange part (4) of the can (1);

    - forming a bottom (2) of the can;

    - forming a side wall (3) arrangeable in the gap in mounted condition of the can at least partially from a material containing a nickel constituent, with the side wall (3) being brought by a reshaping step into a target geometry

    characterized in that for use as material a nickel-chromium alloy in solution annealed condition is chosen which contains at least 50 percent by weight of nickel and 17 to 21 percent by weigth of chromium, and that a hardening by way of heat treatment is performed after reshaping.
11. The method according to claim 10, characterized in that reshaping is a cold forming procedure and that precipitation hardening is performed after cold forming, in particular in a temperatrure range from 605 to 728 °C, i.e. without an intermediate solution annealing after cold forming.

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