Fluid sprinkling – spraying – and diffusing – Processes – Including mixing or combining with air – gas or steam
Patent
1990-05-23
1991-12-10
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Processes
Including mixing or combining with air, gas or steam
239 82, 239296, 425 7, B05B 1700, B22F 908
Patent
active
050710672
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of atomizing liquids, preferably metal melts, by disintegration of a preferably vertical tapping stream of the liquid with the aid of preferably horizontal media jets consisting of gas or liquid. The invention also relates to a means for performing said method.
When liquids are atomized by disintegration of the liquid with the aid of a gas or fluid, extremely particles are obtained within certain size intervals, the intervals sometimes being considerable.
These known methods can be used for most types of liquids. However, they apply primarily to the production of powder from metal melts where a gas, e.g. nitrogen or argon, is used as atomization medium. Powder manufactured in this manner is often said to be manufactured inertly and is characterised by its low oxygen content and spherical form.
Powder-metallurgy processes using inertly manufactured powder encounter various problems relating to the size of the powder particles and/or their distribution.
Finer and/or narrower fractions of inertly manufactured powder is desirable for many applications nowadays. Such powder is conventionally obtained by screening off a coarser fraction, resulting in low yield, or via atomization processes using extreme gas flows and pressures. This powder is only used to a limited extent due to its high cost.
Typical fractions for unscreened powder manufactured by a number of conventional methods are: 0-300 my, 0-500 my, 0-1000 my. The average particle size in these fractions is 80, 110 and 120 my, respectively.
Problems have been encountered in reducing the particle size and the wide spread of particle sizes in the finished powder, at a reasonable cost.
A number of powder-metallurgy (PM) processes are described below, showing the required or preferred powder sizes and fractions which can be achieved by means of the present invention.
PM methods in which products are obtained in almost finished form by means if hot isostatic pressing without subsequent heat treatment: Established process are today limited when it comes to achieving high fatigue-resistance values since fatigue resistance is usually determined by the largest non-metallic inclusions in the material. The impurities come from the powder manufacture and can only be eliminated with certainty by using a screened fraction in which the max. powder size (=max. impurity size) is no greater than the acceptable defect magnitude. Powders desirable here may be <80 my, <60 my, <40 my, etc.
Powder for surface coating by means of welding or spraying:
Certain powders for these purposes are currently produced with yields of less than 50% due to the wide fraction distribution in the manufacturing processes. Typical fractions for these purposes are: 50-150 my, 20-550 my, 20-70 my, 34-104 my, etc.
Injection moulding (IM) is a relatively new technique in the PM field:
An extremely fine fraction of metal powder is mixed with plasticizer, and components are then injection-moulded within extremely narrow tolerances. The binder is then burnt off in a furnace, after which the component is sintered to high density. Typical powder sizes desired may be: <15 my, <22 my, <44 my, respectively, depending on the process used.
Production of alloys which acquire their properties through extremely rapid cooling:
A method of manufacturing powder of fine fraction can in principle automatically be used to produce these alloys since the completely dominating factor for the cooling rat is inversely proportional to the size of the drops.
The method of, by means of sintering, producing large products in almost finished form and blanks for further heat-treatment such as rolling, as an alternative to the more expensive HIP method.
The size desired is substantially the same as for IM.
The method of creating fiber-reinforced composites with matrices of metal
Hitherto the technique has not been developed to any great extent but where successful experiments have been carried out via PM, the technique has been based on extremely fine powder fractions.
The
REFERENCES:
patent: 2341704 (1944-02-01), Ervin
patent: 2614619 (1952-10-01), Fuller
patent: 3593976 (1971-07-01), Hager
patent: 4221554 (1980-09-01), Oguchi et al.
H. G. Tech AB
Kashnikow Andres
Weldon Kesin P.
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