US1884748A - Heat treatment system - Google Patents

Description

Il E

H. E. KOCH ET AL HEAT TREATMENT SYSTEM Filed Deo.

Oct. 25, 1932.

Patented oa. 25,1932

.e conronarlon or WISCONSIN HAROLD E. KOCH, 0F WAUWATOSAQANID MELYILLE LOWE, 0F MILWAUKEE, WISCONSIN,

ASSIGNORS T0 HEVI DUTY ELECTRIC COMPANY, 0F MILWAUKEE, 'WISCQNSIIL A HEAT TREATMENT SYSTEM,

appunti-cn mea December a4, mso. semi no. scuse.

Our invention relates broadly to heat treatment rocesses and more, particularly to a method of heat treatment of articles within an atmosphere of forcibly directed circulatory fluids. i i

One of theobjects of our invention 1s to provide a method of heat treating articles within an atmosphere of centrifu ally circulated gases withln a sealed retort or securing an improved qualit of product.

Another object o our invention is to provide a method of cracking and circulating a process gas or fluid within a sealed retort and heating the same for subjecting varticles to a 'heat treatment process by contact With the heated circulatory gases, which are mechanically agitated and directed within the retort.

We have found that articlesV treated according to theprocess of our invention have better quality and may be treated ina time eriod relatively shorter than heretofore nown processes. Such heat treating processes may consist of a method of changing the lsurface characteristicsA of the material being processed, asin carbu'riz'ing and nitriding, or they may consist of a method for preventing changes in the surface, as in bright annealing, or they may consist in the use of reducing or inert gases for protection of the surface against oxidation lof the articles being heat treated.

In carrying out the process Vof our invention, We employ a furnace as set forth in Fred A. Hansens pending application, Serial No. 504,579 filed December 24, 1930, in Whichany heat process may be carried out in any selected gas so circulated in a sealedl retort as to cause a complete uniformityl of gas mixture and an unusually uniform distribution of heat and of the application of the processing gas or fluids uniformly to all parts of the charge. y i

The process is not restricted solely to heat treatment of metal but may also be used in.A

thermochemical processes.

Our invention will be more fully understood by detailed reference to the accompanying drawing which diagrammatically illusgally driven circulatory system connectedI vwith the retort are readily impinged on the heated face of the retort,v and are thereby cracked into two or more component parts, and we have found further that in the circulatory system described in the said c0- pending application that the dissociated parts lof such gases have a directed flow, in

such a manner as to make available and more uniformly, to every particle of the charge, the

process effect required for most perfect production. In a thermo-chemical reaction We may inject steam into the sealed retort Where the charge in the container may he charcoal. 'lhe dissociated components of steam combine With the carbon atmosphere created b the heating of the charcoal and thereby form a hydro-carbon gas. Furthermore, by the introduction of steam and then heated to a certain temperature, with the charge consisting of steel articles to be made oxide or rustproof, We produce a more uniform result because the steam is iirst dissociated by the cracking effect hereinbefore described and the circulation of the dissociated gases result in a more uniform deposit of iron oxide as the protective coating. One or more catalyzers may be inserted between the inner faces of the retort and the container holding the articles to be processed. We are therefore able to modify the gas mixture by means of the catalyzer in the circulatory system.

In the carburizing process, when using a hydro-carbon gas of correct quality, We have the carburizing method go through the same cracking process before contact with the charge as hereinbefore outlined. In a similar manner, we more uniformly, and in a shorter time, successfully performv the bright annealing of non-ferrous metal such as co er by means of a steam atmosphere; t e

6 right annealin of steel in the container` by the injection of ydrogen or inert ases into the circulatory system, or we per orm such operations as the tempering or drawing .of steel to a better uniformity mthout speclal 10 regard' to the control of atmosphere.

Our invention is applicable to Aman different processes, some of which we brie y describe as follows: v

N hiding-Subj ecting metallic substances, I6 such as-steel, malleable iron, Stellite, etc.,

to ammonia gases at approximately 950 F., Ato harden the surface and any required depth below the surface.

Bower-Bar# procesa-subjecting steel to tEl) a steam atmosphere under pressure at approximately 1450 F. to impart a rust-proof nish.

arburz'zz'ng.-The process of subjecting comparatively low carbon steel to temperatures of 1650 to 1725 F. in a carbon gas atmosphere to impart a high carboncase thereon. In this process any carburizing compounds, such as hydrocarbon oils or hydrocarbon gases, bone ash, charcoal, coal, etc., may be used as a carburizing agent or carburizer. Bone ash, charcoal, coal, etc., are usuall used in a powdered or granular form.

rocessz'ng.-In these processes, steam, gases or liquids (such as compounds of hydrocarbon oil) may be referred to as processing iiuids.

Annealng non-ferrous meterla- Copper in a steam atmosphere will anneal at temperatures from 600 to 1200 F. according to the time cycle at such tem eratures.

Annealz'ng or nomalzzz'ng steel.-This can be done by a. bright finishing process by introducing an inert gas inthe retort.

`Drawing and tempering sterf -Temperatures-vary from 400 to 1200 F. approximately. At above 950 F. the atmosphere may be hydrogen to prevent scaling.

Referring to the drawing in detail, reference character 1 desi ates the furnace casing which is lined with heat insulation material 2 providing a furnace chamber which is lined interiorly with electric heating elements indicated at 3. While the chamber is shown heated electrically it may be understood that the furnace can be heated b fuel and be effective in the processes describe The electric heating elements employed along the interior walls of the furnace chamber are of the construction shown more clearly in Letters Patent No. 1,768,865 to Edwin L. Smalley, dated July 1, 1930. The upper portion of the casing is closed by a top plate 4 in combination with a retort 9, the top plate 4 having a trough 5 therein into which the downwardly extending flange 6 of the rim plate 7 extends for establishing a seal for chamber 10 by means of sand indicated at 8. The rim plate 7 is sealed, as by welding to the upper extremity of the retort 9 indicated at 9a, the retort 9 depending downwardly into the furnace chamber' 10. A container 11 is mounted within the retort 9 and `is spaced from the interior walls thereof by means of lugs 13 to allow the free circulation of s therearound. The container 11 is e evated from the bottom of the retort 9 by suitable brackets shown at 12. The container 11 isapertured around the side walls thereof and in the bottom thereof as indicated at 14. The container 11 encloses the charge indicated at 15. A top deflector 16 is mounted upon the container 11, the closure being frusto-conical in shape and being centrally apertured as designated at 17.

The retorty is closed by a heat insulated cover member indicated at 18. The cover member projects downwardly into the retort and has a laterally projecting flange 19 which is secured to rim plate 7 by means 'of bolt members 19a. A gasket 20 provides a gas tight seal between the cover member 18 and the rim plate 7 so that the retort is thereby sealed. The cover member 18 is lilled with heat insulation material indicated at 18a. A tripod support consisting of .frame members 21 is mounted on the cover member 18 and carries the driving motor 22. The rotatableg shaft .23 extends from motor 22 and projects through cover member 18 into the retort 9. A fan 24 is carried b the end of the shaft within the retort an serves to centrifugally circulate gases within the retort. A fan 25 carried by shaft 23 is located'outside of the retort 9 and above the cover member 18 and serves to establish a forced draft for cooling the motor and shaft 23. That the shaft 23 is maintained in a lubricated condition during a carburizing process, may be understood by observing the arrangement of the journal 26 in the cover member 18 having stufiing box 27 in the upper portion thereof. The packing 28 is continuously saturated by the deposit of carbon particles liberated in the carburizing process which particles are forced upwardly along a shaft 23 into the packing 28. The shaft is not only thereby lubricated but leakage which might otherwise result is prevented by the cumulative collection of carbon deposits in the acking.

WS provide inlet and outlet pipes represented at and 31 respectively, the pipes projecting through the cover member 18 constituting the top of the retort, horizontally beyond the perimeter of the fan 24 and provide means for introducing hydro-carbon oils, hydrocarbon gases, or any processing fluid, into the retort and into the circulatory system during the heat treatment process for establishing the required gas mixture and also for introducing oil or other fiuids during the cooling cycle subsequent to the heat treatment cyc e. Pipe 31 serves as a dlscharge pipe for exhausting the retort. It is to. e noted that the introduction of any processing fluid at room temperature intoa highly heated temperature results in expansion of the resulting gases, and that therefore b changing Athe amount of opening throug the valve controllingthe exhaust, all gases and pressure may be retained in the retort. In order to determine the temperature within the retort, we provide a pipe 3 2 with closed bottom into which a thermo-couple may be positioned. y

Between the inner wall of retort 9 and the container, 11 we may provide one or more catal zers indicated at 35 in the ath of the circu atory gases. We are there ore able to modify the gas mixture by means of the catalyzer in the circulatory system. The processing fluids are preferably injected into the discharge of the centrifugal fan, causing atomization and subsequently a forced impact against the side of retort 9, which being heated readily cracks the processing fiuid into two or more component parts into gaseous" form. Such gases being in the directed flow from the centrifugal force are immediately available for intimate contact with every part of the charge, thus insuring a uniform treatment by the combination of heat and the processing fluid.

Processing fluids may be injected on to the fan, on retort, or contalner, and subsequently cracked and circulated, but not with the most satisfactory results obtained by the above described procedure.` A centrifugal circulation of gases thus created is thereby directed in contact with the catalyyzers and through the perforated side walls and Vperforated bottom of the container for the gas treatment of the heated charge within the retort.

After the charge has been heat treated for the required time period the retort is removed from the furnace chamber while maintaining the seal between the cover member 18 and the retort 9, and maintaining forced circulation in the retort, if desired. In a carburizing process using hydro-carbon oil, we find it of value to continue the dripping of oil in very small quantities during the cooling process. The oil thus induced and expanded into gases obviates the necessity of letting in air to prevent the collapse of the retort by vacuum resulting from sudden chilling. And if air were allowed during the cooling process it would result in an oxidation of the charge. Furthermore, the oil induced in the cooling cycle continues to be a carburizing means down to about 1400 F. We have discovered, too, that the case produced in such a process, instead of having a marked line of demarkation between the case and the core, gradually changes to the core condition without having reduced the depth or eectiveness of the case, thereby improvin the quality by reducing the otherwise ten ency to brittleness.

Fig. 2 shows the retort with cover and driving motor thereon detached from the fur-l nace, as when utilized for rapid cooling. Reardless of the fact that the retort has been etached from the heat treatment chamber, the circulatory s stem may continue to operate thereby enab in the charge to be cooled under uniform con itions producing a uniform product of high quality, as a uniform cooling produces a gram structure common to the entire charge.

We have found the heat processing in circulatory gases of our invention to be highly practical and while we have described the pocess of our invention in its preferred emdiment, we desire that it be understood that modifications ma be made and that no limitations upon our lnvention are intended other than are imposed-bythe scope of the appended claims. Y

What we claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a heat treatment system includin a furnace having a sealed retort insertale therein with means extending through and rotatively sealed in a cover for the retort and into the retort. for centrifugally distributing the atmosphere in said retort, the method of sealing the passage between the centrifugal drive means and the retort cover which consists in liberating carbon during a heat treatment process and forcing the carbon thus liberated into the seal between the centrifugal drive means and the retort cover.

2. In a heat treatment system including a furnace having a sealed retort insertable therein and a shaft extending thiough the cover for the retort and having a centrifugal fan thereon for establishing a centrifugal circulation of fluids within the retort, the methodof lubricating the shaft which consists in liberating carbon lwithin the retort and forcibly ejecting the carbon along the shaft and into the sealing means between the shaft and the cover.

3. In a heat treatment system including a furnace having a sealed retort insertable therein with means extending through and rotatively sealed ina cover for the retort and into the retort for forcefully distributing the atmosphere in said retort, the method of sealing the passage between the centrifugal drive means and the retort cover which consists in liberating carbon during a heat treatment process and forcing the carbon thus liberated into the seal between the drive means and the retort cover.

4. In a heat treatment system includin a furnace having a sealed retort insertale therein and a shaft 4extending through the cover for the retort and having a fan thereon for establishing a, forced ircultion of uids the retort, the method of lubrieating the shaft which consists in liberating l' carbon within the retort and forcibly eject- -5 ing the carbon along the shaft and into the sealing means between the shaft and the COVel.

tures.

HAROLD E. KOCH. MEINILLE LQWE.

In testimony whereof we aix our signai'

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