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Motors from Powder

17th July 1942, Page 28
17th July 1942
Page 28
Page 28, 17th July 1942 — Motors from Powder
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Our Contributor Forecasts that Forking, Stamping and Casting Will Be Replaced by Forming Parts from Metal Powder Subjected to Heat and Pressure

By "Azote "

IT sounds fantastic, but the manufacture of chassis parts from powder is an undoubted developinent of the future. Parts that are now made from castings, stampings or forgings, as well as bar material, will, in all probability, be formed from fine metal powders.

There are several points in favour of such a• system of produCtion of parts for motor vehicles. The highest grade of products can be -produced by the' powder metallurgy technique. There is nothing to prevent the manufacture of parts with the highest_tensile, impact and other properties. The sole difficulty is that of economics and is only a matter of volume . of production. Such difficulties are always encountered by new 'products or processes, but, in course of time, they are overcome by the growing volume of demand for the product. Powder Inetallurgyis no

exception to this rule.

In order to obtain the high-class . irons and steels to which we are acctistome& it is not necessary to use imported iron ores from Spain or _Sweden. The necessity of so-called high-class ores is Connected with the retmirements of the process. through which the ore is put to make our finished product. Actording to Ameril can reports, the system of preparation of the raw material by reducing it to powder eliminates most impurities, whilst the 'heat-treatment processes, being carried out at much lower temperatures, do not interfere so much with the physical properties of the Metal.' Therefore a lower-quality ore is.permissible as raw material, which is an important point in the case of this country, as there are large supplies of such ores available.

This consideration refers to iron, which forms the largest metallic demand on raw materials; conditions of other metals are somewhat different.

The general treatment, in making articles from powder, is the pressing of the powder into dies; and a subsequent 'heating of the formed piece when taken Out of the die to what amounts to a sufficiently high temperature to weld the particles of powder together to form „a solid whole.. This process is called sintering.

, However, the trmperature at which this sintering is carried out is obviously much lower than the melting heat necessary to make the metal flow into the sand mould.

In some cases , the treatment by modified temperatures referred to above has the result of imparting higher physical properties than in the case of the part produced by the highertemperature process of melting to pour into the mould.

Two Forming Methods There are two procestes to select from, :dependent upon the class of article and the particular metal or alloy in which the part is to be made. In one process a cold die is used; in the other a hot die.

In the sintering process following the forming of the piece to shape, two differing conditions result; in some 'cases' the article,,,swells, whereas in other cases it contracts as a result of heat treatment. This difference requires allowing for in the making of the dies, and is a matter crf experience. The later finishing processes • are also affected, if there be any.

It is possible to prepare the powdered material in such manner that any alloy can be made with the same or even greater accuracy as compared with that of the usual method of manufacture. I have in frost of me glass bottles containing powders of copper, aluminium, stainless steel, magnesium alloy, brass and several other metals.

The extent of pulverization at the present state of progress ia•not of high degree; it is of the order-of 400 mesh. It is possible that later on much finer powders will be demanded, as the requirements become more exacting. Pulverized coal for boiler firing is 85 per cent. through 200 mesh. Finer pulverization or micronization, as it is called, is available, down to as low as 5 microns. I dealt with the subjects of pulverization and micronization in "The Commercial Motor " dated August 29,1941.

Powder metallurgy is not a new process. So-called oilless bearings, known to every engineer, are an example of the art; they have been in production for many years. Their degree of porosity goes up to 35 per cent., providing high oil-containing capacity; they are supposed to outlast the machine of which they form a part, without the need for provision of other than their own store of .oil. The tungsten carbide tips of high-speed tools are another example of powder Metallurgy.

Filters for lubricants are being constructed of porous metal and are being 'increasingly used in engine lubricating circuits. Parts not requiring high qualities of strength are being made out of scrap tunings from the machine shop; washers are one example.

One of the most outstanding and successful recent products is a Steel pump gear for an engine lubricating system, which is turned out completely finished, without the necessity of boring, turtling or gear cutting; it forms a good example`of what is to come.

At the present time in this country the presses used for 'doing what little work is being, done in this field are those built for otheepurposes, and they form a limitation on the possibilities. The evidence that this limitation is by no means a basic one is afforded by the fact that specially built presses in American are performing quite successfully in the more advanced state of the development to which that country has attained in the science of powder metallurgy. ..

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