US-20260124673-A1 - ROTARY DEVICE FOR TREATING MOLTEN METAL

Abstract

A rotor for use in the treatment of molten metal. The rotor comprises a roof having a central axis and comprising a plurality of peripheral cut-outs. An intermediate plate extends axially from the roof and comprises a plurality of sides having arcuate portions. A plurality of blades extend axially from the intermediate plate. The rotor is intended for use in casting operations, particularly in the treatment of non-ferrous metals.

Inventors

• Dirk Schmeisser
• Ronny Simon

Assignees

• FOSECO INTERNATIONAL LIMITED

Dates

Publication Date

20260507

Application Date

20230914

Priority Date

20220923

Claims (16)

1. 1 . A rotor for use in the treatment of molten metal, the rotor comprising: a roof having a central axis and comprising a plurality of peripheral cut-outs; an intermediate plate extending axially from the roof, comprising a plurality of sides having arcuate portions; and a plurality of blades extending axially from the intermediate plate, characterised in that the intermediate plate is directly adjacent to, and contiguous with, the roof, wherein the arcuate portions of the plurality of sides are concave such that the centre of each arcuate portion is closer to a central axis of the rotor than the ends of the arcuate portions.
2. 2 . The rotor according to claim 1 , wherein the plurality of peripheral cut-outs comprises at least six cut-outs.
3. 3 . The rotor of claim 1 , wherein the intermediate plate is located between the roof and the blades.
4. 4 . The rotor of claim 1 , wherein the intermediate plate and/or the blades extend up to the edge of the roof.
5. 5 . The rotor of claim 1 , wherein the roof and intermediate plate comprise a central aperture therethrough for fluid communication with a fluid supply.
6. 6 . The rotor according to claim 5 , wherein the rotor comprises a chamber defined axially by the intermediate plate and radially by an internal surface of the blades, and wherein central aperture opens into the chamber.
7. 7 . The rotor according to claim 6 , wherein the chamber has a width or nominal radius greater than the width or radius of the central aperture.
8. 8 . The rotor of claim 1 , wherein the intermediate plate comprises three sides connected by three ends or corners, and wherein each end or corner comprises at least one of said plurality of blades.
9. 9 . The rotor of claim 1 , wherein the plurality of sides of the intermediate plate each comprise a pair of straight portions separated by one of said arcuate portions.
10. 10 . The rotor of claim 1 , wherein the blades have a cross sectional shape the same as the adjacent portions of the intermediate plate.
11. 11 . The rotor according to claim 1 , wherein the peripheral ends of the blades are tapered and form a pointed, flat or rounded edge.
12. 12 . The rotor of claim 1 , wherein the rotor has C3 rotational symmetry.
13. 13 . The rotor of claim 1 , wherein the roof, intermediate plate and plurality of blades are integrally formed such that the rotor is contiguous.
14. 14 . A rotary device comprising the rotor according to claim 1 , and a shaft, and wherein the rotor is provided at one end of the shaft.
15. 15 . The rotor according to claim 1 , wherein rotor and/or the rotary device is formed from an isostatic pressed refractory material.
16. 16 . A method of treating molten metal comprising the steps of: immersing the rotor, and optionally part of the shaft, of the rotary device according to claim 14 into the molten metal, rotating the rotor, and passing one or more molten metal treatments through the rotary device.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application is a National Stage Application of PCT International Application No.: PCT/GB2023/052387 filed on Sep. 14, 2023, which claims priority to European Patent Application 22197556.8, filed with the European Patent Office on Sep. 23, 2022, and European Patent Application 23177819.2, filed Jun. 6, 2023 the disclosures of which are incorporated herein by reference in its entirety. TECHNICAL FIELD The present invention relates to a rotary device for treating molten metal. In particular, the present invention relates to a rotary device for removing unwanted impurities from molten metal, such as dissolved gas and solid inclusions. BACKGROUND For casting applications (in particular casting of non-ferrous metals such as aluminium or aluminium alloy), the molten metal must be treated before casting-typically by one or more of the following processes: i) Degassing and inclusion removal—The presence of dissolved gas in molten metal can introduce defects in the solidified product and may detrimentally affect its mechanical properties. Hydrogen has a high solubility in liquid aluminium which increases with melt temperature, but its solubility in solid aluminium is very low which can lead to gas pores in the solidified casting. Gas may also diffuse into voids and discontinuities (e.g. oxide inclusions) resulting in pores or blister formation during the production of castings or other products made from aluminium or aluminium alloys.ii) Grain refinement—The mechanical properties of the casting can be improved by controlling the grain size of the solidifying metal.iii) Modification—The microstructure and properties of metal alloys can be improved by the addition of small quantities of certain ‘modifying’ elements such as sodium or strontium. Modification increases hot tear resistance and improves alloy feeding characteristics, decreasing shrinkage porosity.iv) Cleaning and alkali removal—Significant concentration of alkali elements can have an adverse effect on alloy properties, and so these alkali elements need to be removed or reduced. The above treatment processes may be carried out individually or simultaneously by a variety of methods and equipment. Degassing of molten metal is typically conducted using a rotary degassing unit, which flushes the molten metal with fine bubbles of a dry gas. The gas can be inert, such as argon or nitrogen, or reactive, such as chlorine or hydrogen or may be mixtures thereof. The rotary degassing unit typically comprises a hollow shaft to which a rotor is attached. In use, the shaft and rotor are rotated and gas is passed down the shaft and dispersed into the molten metal via the rotor. As the gas bubbles rise through the melt, hydrogen diffuses into them and is ejected into the atmosphere when the bubbles reach the surface. The rising bubbles also collect solid inclusions and carry them to the top of the melt, where they can be skimmed off. In addition to introducing gas to remove hydrogen (and oxide inclusions), the rotary degassing unit may also be used to inject metal treatment agents into the melt through the shaft together with the inert gas, or through a tube adjacent to the shaft. Examples of rotary devices for use in rotary degassing units are the “XSR rotor” described in WO2004/057045, the “FDR rotor” described in WO2009/004283, and as described in DE202013102823. The geometry of the rotors is important, since it has a direct effect on the time needed for the metal treatment to be completed. Existing products have complex configurations and intricate shapes in order to provide desirable metal treatment rates. Rotors for treating molten metals, such as aluminium, magnesium, copper and relevant alloys have traditionally been manufactured by machining a solid block of graphite into the desired shape. However, machining can be a difficult and costly process and is not well suited to producing intricate shapes—particularly on interior surfaces of the rotor, since line-of-sight access is required for the drilling tool. Machining also limits the selection of materials that the rotor can be made from, since the drilling tool may be unable to bore through more durable or more abrasive ceramic materials. Such machining processes are often relatively expensive and/or slow, with a subsequent effect on unit price. Rotors for use in molten metal treatments are typically consumable products. The harsh conditions of the molten metal limits the number of times a rotor can be re-used before it needs to be replaced. Extending rotor lifetimes would have cost savings for end users who consume fewer rotors. Longer service periods also minimises downtime due to maintenance and rotor replacement, which has further positive effects on cost and productivity. The present invention intends to resolve or mitigate one or more of the above problems with respect to rotors for use in molten metal treatments. SUMMARY OF THE INVENTION According to a first