US1726431A - Process for the surface treatment of metals - Google Patents

Description

Aug. 27, 1929. M. FOLJRMENT PROCESS FOR THE SURFACE TREATMENT OF METALS Filed Nov. 29, 1926 50 tions.

Aug. 27, 192.9.

I i 1,126,431 PATENT oFFicE.'

UNITED STATES nnen. somma', or uns, rauen rnocnss iron 'rmi suanon marxmor mais.

Application mei! November 89, 1986, Serial lv'e; 151,517,

Various processes are in use for roviding metal pieces or objects with a-su ace layer Y whose properties are different from those of -the metal constitutin such pieces orvobjects.-

16 feet of the temperature, throughout the sur-V e metal and thus forms a surpossessing the desired protecting feac region of t face layer properties.

For instance, in the cementation process, 20 the metal pieces are covered with a hard layer of carbide of iron, in the Cowper- Coles process, with a zinc-iron alloy, in the calorization process with an aluminium alloy, and' in the chrome treatment, with a chromium alloy.

' In accordance with the prior art, the pieces under treatment are disposed in suitable boxes which are externally heated by suitable means and in which the metal piece is raised to the proper temperature for the action of the treating substance. But this method of operation occasions an excessive wear of the boxes, thus increasing the cost of manufacture.

My invention relates to a method of heating the` pieces which consists essentially in the use of high frequency induction currents, to bring the said pieces to the proper temperature for the proposed diffusion.

I `may proceed for example in the following manner. The recipient containing the metal piece 'under treatment is surrounded by an inducing coil 'which is supplied by a source of'current. In this manner, Foucault currents will be produced in the surface portion of the metal piece by which such surface portion will be strongly heated, so that the treating agent or active substance will become diffused throughout'these surface por- Suitable means are Aemployed to regulate the current and hence the temperature of the pieces.

It is a well-known fact that if an iron bar or the like is placed within a conducting winding supplied with high frequency induction currents, Foucault currents will be set up and in France December 5, 1826.

in the bar, and chieiy in the surface portion, so that it can be heated to any desired temperature as shown by the fact that the metal can be melted and even volatilized.

It will be suilicient to thus heat the metal v`piece at the surface, since the treating substance will only act in the outer parts of the piece. The degree of the heat can be accurately regulate by suitably controlling the inducing current.

As will be further stated my said method can be readily employed in all cases in which the metal is to be treated under pressure, in vacuo, or in the presence of an active body with or without an inert bod Various embodiments of t e invention are shown by way of example in the appended drawings.

Fig. l is a sectional view of the apparatus.-

Fig. 2 is a modification, especially applicable to the casein which the treating substance is a liquid.

Fi 3 is a second modification which is especia y ap licable to the case in which the treating su stance is a gas.

Fig. 4 isa third modification, especially suitable for use in cases in which the treatment is to be carried out in an active 'or inert atmosphere under pressure above or below atmospheric.

Fig. 5 is a fourth modification which is parlticularl applicable to the continuous treatment o bars, wires, tubes, bands or the like.

In the example shown in Fig. l, the gear wheels 4 are to be treated by the cementation process. The inducing element consists of a copper tube 1 having an internal water circulation, said tube being connected with a so'urce of high frequency electric current. The vessel 2 (containing) the cementation agent 5 consists of a suitable dielectric such as fused silica. Heat losses are reduced by the protecting cover 3.

In the modification shown in Fig. 2 the active or treating substance 9 to be employed, which consists for example of zinc, aluminium or the like, is maintained in the melted and liquid state either by induced currents or by a suitable external source of heat. The inducing element 6 surrounds the Vessel 7. The piece 8 under treatment is immersed in the bath 9.

The second modification shown in Fig. 3 relates to the case in which the treating substance employed for coating purposes is employed in the gaseous state. The inducing has the owdered form and in which the operation o diffusion takes place in a gaseous atmosphere (optionally under pressure) or in a vacuum. This will be the case for instance for the chrome process, in which the desired result can be obtained either in an active or an inert gas, or in a yacuum. The piece under treatment is placed within the powdered f covering substance 18 which is contained in the Vessel 16. The vessel 12 analogous to the one shown in Fig. 3, is surrounded by the inducing element 15 and is pierced with the apertures 19 and 20 which are adapted to place the portion comprised between the two vessels in communication with a gas under pressure or with an apparatus producing a vacuum, or with an inert or active gas, according to requirements.

The fourth modification shown in Fig. 5

shows the arrangement employed for the continuous treatment of pieces having length, such as bars, bands, wire, tubes and the like. In this method, the bar 21 under treatment is causedto move at a slow rate and traverses the vessel 22 containing the treating mixture 23. The inducing element 24 surrounds the said vessel, which is provided with a stuingbox 25 for the continuous exit of the bar after it has been covered. Y 4

Obviously, such arrangements are only particular examples of my said process; the apparatus herein employed will allow the use of active :or treating substances of a Very refractory nature such as platinum, vanadium,

tungsten, zirconium and like metals which require the use of high temperature. I claim:

A process of causing a substance in a heated state to act upon the surface portion of a metallic article in which the said article is surrounded by and in contact with said substance and producing high frequency induction currents in said article, in such manner as to produce generation of high heat in the surface portion of the article.

In testimony whereof I have aiiixed my signature.

MARCEL FOURMENT.

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