US2363741A - Heat treating - Google Patents

Description

Nov. 28, 1944.

D. H; MONTGOMERY HEAT TREATING Filed Feb. 18, 1942 INVENTOR 00mm h. uoyraauzev ATTORNEYS Patented Nov. 28, 1944 UNITED STATE s PATENT oi-Pica y I nga'r'ranamd Donald H. Montgomery, West Hartford, Conn; as:

sis-nor to The New Britain Machine Com New Britain, Conn., a corporation or Connecticut Application February 18, 1942, Serial No. 431,311 1 Claim. 7 ('Cl. 148-10) form a protective coating thereon so as to prevent or minimize oxidation of the article both during heating and during any subsequent operations to be performed thereon.

venting or minimizing oxidation thereof during and subsequent to heat treatment.

Another object is to provide an improved method of progressively heating an article such as a wire or shaft and protecting the same against oxidation.

Another object is to provide an improved method of heating a metal article to the critical temperature and quenching the same, all while immersed in a, quenching liquid.

Other objects and various features, of novelty and improvement will be hereinafter pointed out or will become apparent to those skilled in the art.

In the drawing which shows; for illustrative P rposes on1y, and more or less diagrammatically. preferred forms of apparatus Fig. l is a view in vertical section of apparatus for heat treating an article;

Fig. 2 is a similar view of a modifled'form of apparatus;

Fig. 3 is a vertical sectional view of apparatus 1 for progressively heating an .article, such as a shaft or rod; and for coating the article to prevent oxidation thereof.

In the form shown in Fig. l, I employ a crucible or other container 5 to hold a coating material 6, preferably in the form of a reducing ornon-oxidizing salt or other medium, which may be melted and which will serve to coat the metal article immersed therein. I provide means for inductively heating an article, such as a shaft I, which dips into or is immersed or partially immersed in the coating'material 6. As shown in Fig. 1, there may, be an induction heating coil 8 within the contively heated article immersed therein. The induction coil 8 may be a greater or less extent act as a resistance heater-to'maintain the coating material 8 in a liquid condition. The coating material 8 is preferably of Such a nature that it willadhere to the'surface of the article 8 and In the preferred form shown in Fig. 1, I provide further induction means, which may be in the form of a separate induction coil lpositioned above the coil 8 and through which the article I may pass. when the. immersedportion of the article is heated by the induction coil I and the coating material maintained in a fluid condition, oxidation of the article will be prevented by the immersion of the article in a non-oxidizing'coating material. If ahigher degree of heating is coating bath, say, to the dot-dash line position as shown in Fig. 1, where the article with the protective coating adhering thereto may be heat. ed to the desired temperature by the second induction coil 8. When the article has been heated to a point, say, above the critical temperature by the coil 9, the article may be quickly dropped back into the bath 8 and be thereby quenched. In that connection it will, of course, be understood that the bath 6 will be at a temperature sufficiently low to act as a quench when the article has been heated outside of the bath. It will of course be understood that the induction heating means 8-! will ordinarily be separately controlled so that the heating is done when andforth. On the other hand, the bath ll may consist or various other media, in some cases even water.

"coll I2 in the form shown in Fig. 2, is not immersed in the bath l I but surrounds the container and serves to heat the article II when the latter ispasseddownintothecoilandimmersedinthe bath H. It wilibe imderstood that the bath II is of a character to be liquid at a relatively low temperature. It may be. used to quench the article II.

The article I: when immersed in the bath u' may, with the proper inductioncoil, be very rapidly heated to or above the critical temperature even thoughitbeinunersedinthebath. When thearticle is soheated abdve the critical temperahire,thecurrentmaybeturnedoflsoastoprevent further heating and the article maybe then qucnchedin situ bythe bath in which it is im Instead oi immersing the article in a coating Induction heating means, such as the 'of coating material bath, I'may employ other means for coating the article so as to prevent oxidation thereof, and

in Fig. 3 I have disclosed means for progressively heating and coating an article which may be a shaft, rod, wire, or the like.

In the form shown in Fig. 3, I provide means for progressively moving the article H through or past induction heating means, such .as an induction coil 15. The article will thereby be heated either to the critical temperature or to such temperature as may be required for any subsequent operations which it is desired to perform on the article. At some point, the article is coated with a coating material so as to prevent oxidation thereof.

I may provide a hopper IE to carry a supply ll, which, for example, might be a salt of the che character above referred to. The hopper has an outlet tube or spout l8 opening just above the article l4,'and in the form shown positioned so as to drip or flow molten coating material over the article l4 and between the coils of the induction coil l5. As illustrated; I employ a small induction coil I9 for heating the tube H8 or' the material therein, or both, so as to liquefy the coating material so it will flow down and thoroughly coat the article l4. When the coil 19 is used to heat.

relatively small quantities of the coating material in a more or less continuous manner, a relatively steadyfiow will be maintained even though the bulk of the material I"! may remain in the solid state and fall down into the heating zone and be liquefied only as needed.

The heated article, whether heated in the apparatus of the form shown in Figs. 1, 2 or 3, may be subsequently forged or otherwise acted on or may be quenched. When a non-oxidizin coating is applied to the article, the article will not be oxidized during any subsequent operations and the material will stay bright and there will be substantially no loss in scale formation if the article be subsequently forged or otherwise treated. The bath material, as stated, may be of a non-oxidizing and even of a reducing character. In most cases, a neutral coating serving simply to exclude air from the surface of the article will sufllce and will serve to adequately protect the article against oxidation after the coating is applied. The coating should be such as to adhere quite firmly so as to protect the metal, but should also be readily removable as by dissolving in water or'other solvent.

While the invention has been described in considerable detail and preferred method setforth and preferred apparatus more or less diaframmatically shown, it is to be understood that various changes may be made within the scope of the invention as defined --in the appended claim.

- the material of the bath forming an oxidation preventing coating thereon, then inductively heating the coated article, and thereafter reimmersing the article in the bath to quench the same.

DONALD H. MONTGOMERY.

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