US2513778A

US2513778A - Heat-treating apparatus

Info

Publication number: US2513778A
Application number: US708960A
Authority: US
Inventors: Edgar L Bailey
Original assignee: Chrysler Corp
Current assignee: Old Carco LLC
Priority date: 1946-11-09
Filing date: 1946-11-09
Publication date: 1950-07-04
Anticipated expiration: 1967-07-04

Description

July 4, 1950 E. BAILEY 2,513,778

FEAT-TREATING APPARATUS Filed NOV. 9, 1946 2 Sheets-Sheet l IN V EN TOR.

2 Sheets-Sheet 2 Filed Nov. 9, 1946 [J an L..Baile BY 3 3 FTTORNL'YS.

Patented July 4, 1950 HEAT-TREATING APPARATUS Edgar L. Bailey, Birmingham, Mich., assignor to Chrysler Corporation, Highland Park, Mich. a corporation of Delaware Application November 9, 1946, Serial No. l08,960

7 Claims. 1

This invention relates to heat treating apparatus and more particularly-to apparatus designed to combine inductive and conductive heating.

It is a well known phenomenon that when certain temperatures are attained in metals their magnetic properties diminish. The temperature at which this occurs is commonly referred to as the Curie point. It is an object of this invention to utilize this phenomenon and by the selection of a proper frequency of magnetic field to inductively heat objects to their Curie point and then transport them to a conductive heating means adapted to heat them to still higher temperatures. The fact that the magnetic properties of the objects diminish at their Curie point is utilized to release them from the induction heating system so that apparatus may carry them into a conductive heating zone for conductive heating to a temperature above their Curi point.

The initial heating by induction is desirable be cause inductive heating is generally faster than conductive heating and the size of the furnace required is less than that of a wholly conductive heating furnace.

A further object of the invention is to provide a conductive heating apparatus that has a controlled maximum temperature and to provide interchangeable liners by which this furnace temperature may be altered.

In the drawings:

Fig. l is a vertical elevation of a portion of a furnace embodying my invention;

Fig. 2 is a continuation in vertical elevation of Fig.1; and

Fig. 3 is an end View taken on the line 33 of Fig. 1 with the hopper omitted.

A base it has a hopper l I supported thereon by members l2. Spaced supports 13 and M are mounted on base I 0. Supports I3 and M are each provided with a plurality of laterally extending shafts l5 preferably three in number. Each shaft l5 has a roller l6 rotatably mounted thereon. A cylindrical furnace element ll is provided with collars l8 and I9 which are concentric thereto. The collar N3 is provided with a track 20 which is adaped to receive the rollers I6 of the support it. Collar I9 is provided with a circular periphery adapted to engage the rollers l6 ofthe support M. The support I3 is provided with a central opening 2!! which is adapted to receive the furnace element H. The cylindrical furnace element ii is thus rotatably mounted.

A sprocket or gear 22 is keyed to the collar l8 and adapted to be operatively connected to suit- 2 able driving means to rotate the cylindrical furnace element. Fig. 3 illustrates a motor 24 as driving a sprocket 25 and chain 26. The chain '26 is in driving engagement with the sprocket 22.

A cylindrical liner 2] is mounted inside the cylindrical furnace element I! in concentric relationship therewith and is secured thereto by a sleeve 23 and the set screws ll and 42. The liner 21 has an axial dimension which is less than the axial dimension of the furnace element H and is preferably positioned adjacent one end thereof. In Figs. 1 and 2 this is illustrated as the right end. A screw element 28 is positioned within the liner 2! in coaxial relationship therewith and has an extension 29 which is mounted in a hub 30 formed on the support [4. A suitable set screw 31 is positioned in engagement with the hub 30 and the extension 29 to prevent rotation of the screw element 28. The construction thus far described provides a rotatable furnace element H and a liner 2] and a stationary screw element 28. The furnace element 11 is provided with a lateral opening 32 adjacent the right end thereof in Fig. 2. The liner 21 is provided with a similar opening 33 which is aligned with the opening 32. A cylindrical insulating element 34 surrounds the furnace element ll. This insulating element is preferably stationary.

Suitable electric conductors, preferably in the form of coils of wire 35, are arranged in'cylindrical form and positioned around the insulating element 34. This wire is supported by

members

36, 31, and 50 which are supported by base ID. A chute 38 is supported b the base below the aligned openings 32 and 33 and a similar opening 39 is provided in the base ID. The openings 32, 33, chute 38 and opening 39 form a discharge passage 40 from the furnace. Any desired quenching apparatus such as oil tanks may b placed below the base II] in alignment with the opening 39 so that objects which have been heated and discharged from the furnace will be directed by discharge passage 40 toward the quenching apparatus.

When an electric current of the proper frequency is sent through the coils 35 and the magnetic field created thereby is used to inductively heat the objects, heat will be imparted to them faster than the heat is lost by radiation. Extremely low frequencies are objectionable for they impart heat to the objects so slowly that the heat lost by radiation prevents a sufficient temperature rise. When the proper frequencies are used, the temperature will rise until the metal reaches its Curie point and the magnetic propenquency coupled with the diminished magnetic properties in the objects is then incapable of overcoming radiation sufficiently to heat the objects further. Too high a frequency willimpart energy to. the objects so rapidly that even the diminished magnetic ropertiesjand radiation are insufiicient to prevent a continued, if less rapid, temperature rise. It has been found that frequencies in the range of 180 to 500 cycles per second are satisfactory with a frequency in the neighborhood of 360 cycles per secondgiving the best results.

In operation, the coils 35 are energized and the motor 2 started. The motor 24 drives the sprocket 22 and rotates the collar l8, furnace element l1, and liner 21. The work pieces which it is desired to heat treat, arepreferably ferrous metal and may be dumped into hopper ll. These work pieca may be 01' various shapes such as ball bearings, nuts. bolts, etc. Ball bearings 5| have been illustrated. Objects 5| to be heat treated will fall by gravity and be drawn by the magnetic field through the spout 43 and through the opening 44 provided. in the end plate 45 ofthe furnace into the interior of the cylindrical furnace element IT. These objects will be magnetized by their presence in the magnetic field created by the electrical conductors 35., The magnetized objects when agitated by the rotation of the furnace element I! will tend to accumulate in a large mass in the furnace element II. This mass of objects is in the magnetic field of the conductors 35 ,andwili be inductively heated. The magnetic attraction of the objects will retain them in the mass during this heatin tion of the liner 21. The screw element 28 will define a path for the objects through the interior of the liner 21. This path may be of calculated length so that conductive heating may be timed. The conductors 35, which are concentric with the liner 21, cause an inductive heating of the liner 21.' The liner 21 is formed from a material such as a cobalt allot which has its Curie point at a considerably higher temperature than the Curie point of the objects being heat treated. The inductive heating of the liner 2'! may attain tem eratures impossible in.

the inductive heating of the ob ects. The high temperature of the liner 21 will by conduction heat the objects as they move around the screw element 28 to a temperature that is higher than the temperature which they possessed upon entering the screw element 28. At intervals when the opening 33 in the liner and the opening 32 in the furnace element are rotated into position below the screw element 28, objects which have completed their passage through the furnace will drop therethroughand out of the discharge path 40.

The liner 2! is formed from material which possesses a higher Curie point than iron. Cobalt iron alloys have been found to be very satisfactory materials. age of cobalt included in the alloy change the Variations in the percent 4- Curie point of the liner 21. A plurality of intel-changeable liners 2! having different percentages of cobalt therein may be selectively used to obtain the desired'temperature of theliner since the temperature is dependent upon the Curie point.

I claim:

1. In an apparatus for heat treating metal objects possessing magnetic properties, the combination of an elongated furnace element forming a passage, said furnace element having an inlet adjacent one end of said passage and an outlet adjacent the other end of said passage, means to deliver said objects to said inlet, a second means forming a first zone in said furnace element adjacent said inlet, said second means being adapted to simultaneously subject a plurality of said objects to a magnetic field, magnetize and inductively heat said objects until the objects have attained a temperature substantially corresponding to their Curie point at which time said objects separate from each other and are no longer efiected by said magnetic field, means forming a second zone in said furnace element positioned between said first zone and said outlet, means to transport said objects through said second zone from said' first zone to said outlet and means to conductively heat said objects during their travel through said second zone.

2. In an apparatus, for heat treating metal objects possessing magnetic properties, the combination of an elongated furnace element forming a passage, said furnace. element having an inlet adjacent one end of said passage and an outlet adjacent the other end of said passage, means to deliver said objects to said inlet, an electrical conductor, means to furnish electrical energy to said conductor, said electrical'conductor being disposed around said furnace element and comprising means to induce a magnetic field in a portion of said passage adjacent said inlet whereby objects in said portion are retained therein by the magnetic held and are inductively heated until they have attained a temperature substantially corresponding to their Curie point when their magnetic properties diminish and they are released from the magnetic field, means to transport said released objects from said first portion of said furnace and to deliver said objects to said outlet and sup plemental heating means adapted to heat said objects during their travel from said first portion to said outlet and to materially raise the temperature of the objects above their Curie point.

3. In an apparatus for heat treating ferrous metal objects having magnetic properties the combination of an elongated furnace element forming a passage, said furnace element havin an inlet adjacent one end of said passage and an outlet adjacent the other end of said passage, means to deliver said objects to said inlet, means disposed around said furnace element to create an alternating magnetic field in a portion of said heat said objects by conduction during their travel from said first portion to said outlet.

4. In an apparatus for heat treating metal objects possessing magnetic properties, the combination of an elongated furnace element forming a passage, said furnace element having an inlet adjacent one end of said passage and an outlet adjacent the other end of said passage, means to deliver said objects to said inlet, second means forming a first zone in said furnace element adjacent said inlet, said second means being adapted to subject said objects to a magnetic field, magnetize and inductively heat said objects until the objects have attained a temperature substantially corresponding to their Curie point, third means forming a second zone in said furnace element positioned between said first zone and said outlet, said third means including an element formed from a metal having a higher Curie point than the objects, means to inductively heat said element to a temperature higher than the maximum temperature obtainable in the first zone, means to transport said objects through said second zone in close proximity to said element and to deliver said objects to said outlet whereby said objects are heated by conduction from said element during their travel from said first zone to said outlet.

5. In an apparatus for heat treating various metal objects having magnetic properties, the

combination of a cylindrical furnace element forming a passage, said furnace element having an inlet and an outlet displaced axially from said inlet, a cobalt alloy liner positioned within said cylindrical furnace element adjacent said outlet whereby a first axial portion adjacent said inlet of said cylindrical furnace element extends beyond said cobalt alloy liner and a second axial portion of said cylindrical furnace element is concentric with said cobalt alloy liner, means to deliver said objects to said inlet, electrical conductors concentrically disposed around saidcylindrical furnace element, means to transmit an alterto its Curie point and the objects being transnating current through said conductors whereby ported through said liner are further heated by conduction from said liner.

6. A method of heat treating a plurality of metal objects which have magnetic properties comprising feeding individual objects into a magnetic zone, magnetizing said objects in said zone and simultaneously agitating said objects to accumulate a mass of said individual objects therein, inductively heating said mass of objects in said magnetic zone 'with a current frequency between 180 to 500 cycles per second, continuing said heating until the individual objects become magnetically nonadherent and separate from said mass, and then positively moving the objects out of said zone.

7. A method of heat treating a plurality of metal objects which have magnetic properties comprising feeding individual objects into a magnetic zone, magnetizing said objects in said zone and simultaneously agitating said objects to accumulate a mass of said individual objects therein, inductively heating said mass of objects in said magnetic zone with a currrent frequency between 180 to 500 cycles per second, continuing said heating until the individual objects become magnetically nonadherent and separate from said mass, then positively moving the objects out of said zone into and through a second zone, inductively heating the second zone, and conductively heatin the individual objects to a predetermined temperature above their Curie points while moving said objects through said second zone.

EDGAR L. BAILEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 686,836 Ruthenburg Nov. 19, 1901 995,636 Ruthenburg June 20, 1911 1,296,896 Wright Mar. 11, 1919 1,412,484 Mordley Apr. 11, 1922 1,538,365 Wilison May 19, 1925 1,687,656 Brown Oct. 16, 1928 1,732,917 Summey Oct. 22, 1929 1,734,536 Sorrel et al. Nov. 5, 1929 1,747,934 Heidenhain Feb. 18, 1930 1,782,359 Linnhofl Nov. 18, 1930 1,799,102 Kelley Mar. 31, 1931 2,286,024 Tama et al. June 9, .1942