GB1574431A - Metal powder production - Google Patents

Description

(54) METAL POWDER PRODUCTION (71) We, BRITISH STEEL CORPORA TION, a Corporation incorporated and existing under the Iron and Steel Act 1967 whose principal office is at 33 Grosvenor Place, London, S.W.1 do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of producing powder for use in powder metallurgy processes.

According to the present invention, there is provided a method of producing powder for use in powder metallurgy processes in which a freely falling liquid metal stream is atomised by impinging on to it at least one liquid jet comprising a long-chain polymer in solution in water.

By "long-chain polymer" is meant a longchain organic compound having a molecular weight of between 103 and 106 whose molecules are essentially linear with no substantial cross-linking to adjacent molecules.

The long-chain polymer may consist of polyethylene oxide or methyl cellulose or may comprise a mixture of polyethylene oxide and methyl cellulose or a mixture of polyethylene oxide and one or more other long-chain polymers.

The concentration of polyethylene oxide in solution in the water may range from 0.1 to 300 parts by weight of polyethylene oxide per million parts by weight of water; in one preferred example, the concentration comprises 10 parts by weight of polyethylene oxide per million parts by weight of water.

The invention will now be described by way of example with reference to the accompanying diagrammatic drawing in which the sole Figure is an elevational view in section of apparatus in accordance with the invention.

The apparatus illustrated in the drawing includes a vessel 1 containing a quantity of liquid metal 2 (e.g. liquid, iron, steel, copper or aluminium) which leaves the vessel through an outlet nozzle 3 to form a substantially coherent stream 4. The stream 4 falls freely through the central aperture of a ring-shaped atomiser assembly 5 which includes an annular downwardly and inwardly inclined nozzle 6 in communication with a manifold 7. The manifold 7 is connected through piping 8 to a source of water (not shown). Upstream of the assembly 5, a pipe 9 communicating with a source of polyethylene oxide or similar long-chain polymer connects with the piping 8.The respective rates at which polyethylene oxide and water are supplied through the pipe 9 and piping 8 are matched to provide the required concentration of polyethylene oxide in solution in the water and the required energy at impact of the water jet in the liquid metal stream.

In an alternative arrangement, the longchain polymer is mixed with the water in a reservoir and is pumped from the reservoir to the manifold through piping. The polyethylene oxide in solution in the water improves the coherency of the water jet issuing from the nozzle 6 thereby limiting the spread of this jet at its point of impact with the liquid metal stream 4 and maximising the efficiency of the interaction of the jet on the liquid metal stream. As a result, the energy of the water jet is concentrated into the liquid metal stream thus producing a fine metal powder for a given set of atomising conditions.

It will be appreciated that the amount of polyethylene oxide required depends upon the quantity of water supplied to the manifold, the pressure at which the water is discharged from the nozzle 6 and the distance travelled by the water prior to its point of impact on the liquid metal stream. However it is believed that concentrations of be tween 0.1 parts million and 300 parts per million of polyethylene oxide to water can usefully be employed.

In one trial carried out in connection with the invention, a liquid steel stream of diameter " was atomised by a water jet emerging from an annular nozzle. A concentration of 10 parts of polyethylene oxide per million parts water was employed.

Atomiser assemblies incorporating a number of alternative nozzle arrangements can be employed. For example, the nozzle 6 may be of annular configuration. Alternatively, a number of discrete nozzles 6 of circular or elongate cross-section may be employed or a single slot shaped nozzle may be used. In addition, the outlet nozzle 3 of the vessel 1 may be elongate in cross-section.

It is to be understood that the term 'liquid metal' as used herein includes metals at temperatures below liquidus where the metals are still flowable.

WHAT WE CLAIM IS: 1. A method of producing powder for use in powder metallurgy processes in which a freely falling liquid metal stream is atomised by impinging on to it at least one liquid jet comprising a long-chain polymer in solution in water.

2. A method as claimed in claim 1 in which the long-chain polymer is polyethylene oxide.

3. A method as claimed in claim 1 wherein the long-chain polymer is methyl cellulose or a mixture of polyethylene oxide and methyl cellulose or a mixture of polyethylene oxide and one or more other longchain polymers.

4. A method as claimed in claim 2 wherein the concentration of polyethylene oxide in solution in the water ranges from 0.1 to 300 parts by weight of polyethylene oxide per million parts by weight of water.

5. A method as claimed in claim 2 wherein the concentration of polyethylene oxide in solution in the water comprises 10 parts by weight of polyethylene oxide per million parts by weight of water.

6. A method of producing powder for use in powder metallurgy processes substantially as herein described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. tween 0.1 parts million and 300 parts per million of polyethylene oxide to water can usefully be employed. In one trial carried out in connection with the invention, a liquid steel stream of diameter " was atomised by a water jet emerging from an annular nozzle. A concentration of 10 parts of polyethylene oxide per million parts water was employed. Atomiser assemblies incorporating a number of alternative nozzle arrangements can be employed. For example, the nozzle 6 may be of annular configuration. Alternatively, a number of discrete nozzles 6 of circular or elongate cross-section may be employed or a single slot shaped nozzle may be used. In addition, the outlet nozzle 3 of the vessel 1 may be elongate in cross-section. It is to be understood that the term 'liquid metal' as used herein includes metals at temperatures below liquidus where the metals are still flowable. WHAT WE CLAIM IS:

1. A method of producing powder for use in powder metallurgy processes in which a freely falling liquid metal stream is atomised by impinging on to it at least one liquid jet comprising a long-chain polymer in solution in water.

2. A method as claimed in claim 1 in which the long-chain polymer is polyethylene oxide.

3. A method as claimed in claim 1 wherein the long-chain polymer is methyl cellulose or a mixture of polyethylene oxide and methyl cellulose or a mixture of polyethylene oxide and one or more other longchain polymers.

4. A method as claimed in claim 2 wherein the concentration of polyethylene oxide in solution in the water ranges from 0.1 to 300 parts by weight of polyethylene oxide per million parts by weight of water.

5. A method as claimed in claim 2 wherein the concentration of polyethylene oxide in solution in the water comprises 10 parts by weight of polyethylene oxide per million parts by weight of water.

6. A method of producing powder for use in powder metallurgy processes substantially as herein described with reference to the accompanying drawing.