Method For Heat Treating Metallic Articles

Abstract

The method and apparatus for heat-treating metallic articles, wherein the articles are embedded in a ceramic fiber work holder such that the embedded portion is prevented from reaching a temperature during the heat-treating operation that produces a hardening action thereon, the nonhardened portion of the articles being easily stamped or marked with identifying indicia thereon after the heat-treating operation.

Description

BACKGROUND OF THE INVENTION

The present invention has particular application in the heat treatment of metallic articles wherein a portion of the article is adapted to be marked with an identifying name, number or symbol, one example of this kind of a metallic article being an elongated tool such as a drill. Prior to the instant invention, special procedures were required in the heat treatment of tools such as drills if it was necessary to maintain the shank of the drill soft enough to have identifying indicia or lettering imprinted therein. In those prior known furnaces that employed a salt bath for hardening, the shanks of the drills were physically held in insulated grip tongs while the flutes were lowered into the hot salt. After the heat treatment, the flutes were quenched in air or in a lower temperature salt or in oil. However, after the quenching operation, a cleaning procedure was necessary before tempering and marking.

In another technique wherein the drill blanks were hardened in a salt bath, the blanks were allowed to be heat treated throughout the length thereof, and after the heat treatment operation and the cooling of the blanks, they were then subjected to a second treatment to soften the shanks. This treatment usually consisted of fixing the blanks in tongs and then lowering the shank into hot lead or salt. Thereafter, a cleaning operation was also necessary before further processing.

In another prior known procedure where an atmosphere-controlled furnace was utilized, the drills or drill blanks were loaded in trays or baskets and then placed in the furnace for the heat treatment thereof. After the heat treatment operation and the passage of the workload into a cooling chamber, the drills were file-hard all over. Although the drills were clean after this heat treatment procedure, they still had to be processed further to soften the shanks thereof. This further operation usually discolored the shanks and required a separate cleaning step.

Although these prior known procedures eventually accomplished the purpose of enabling the drill shank to be marked with appropriate identifying indicia, the additional steps involved, either in softening the shank or in cleaning the shank, necessarily increased the cost of manufacture of the articles and further caused considerable delays in obtaining the finished product.

SUMMARY OF THE INVENTION

The present invention provides for the heat treatment of metallic articles in an atmosphere furnace wherein the shank portion of the articles are sufficiently protected so that during the heat-treating operation they do not reach that temperature that results in a file-hard surface. This is accomplished by locating the shanks of the articles in a ceramic fiber block which acts as an insulator and prevents the shanks of the articles located therein from being heated to the same temperature as the exposed portions thereof. After the heat-treating operation, the ceramic fiber block with the metallic articles located therein is quickly moved to a cooling chamber where the articles are cooled by a fan that circulates a cooling atmosphere within the cooling chamber. Thus, the atmosphere that is forced over and around the articles removes the heat from the articles quickly enough so that the portions that are embedded in the ceramic fiber block never reach the hardening temperature.

Accordingly, it is an object of the invention to teach a method and provide apparatus for heat-treating metallic articles, wherein a portion of the articles is insulated during the heat-treating operation so as to be prevented from becoming file hardened.

Another object of the invention is to teach a method of preventing a portion of a metallic article from becoming file hardened during the heat-treating operation so that the nonhardened portion can be suitably marked or stamped with identifying indicia thereon.

Still another object is to provide apparatus for heat-treating metallic articles that includes a ceramic fiber block in which the articles are embedded, the embedded portion of each article being effectively insulated during the heat-treating operation and thereby being prevented from becoming file hardened so that the surface thereof may be suitably marked with identifying indicia.

Still another object is to provide apparatus for heat-treating metallic articles, wherein the articles are quickly quenched in a circulating medium, thereby preventing a portion of the articles that had been insulated during the heat-treating process from becoming file hardened.

Other objects, features and advantages of the invention will become obvious as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.

DESCRIPTION OF THE DRAWINGS

In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:

FIG. 1 is a sectional view of the furnace and cooling chamber associated therewith as employed in the present invention for carrying out the heat-treating operation of metallic articles; and

FIG. 2 is a perspective view with parts shown in section of the ceramic fiber block showing the location of the metallic articles therein during the heat-treating operation.

DESCRIPTION OF THE INVENTION

Referring now to the drawings and particularly to FIG. 1, a furnace assembly is illustrated and is generally indicated at 10. The furnace assembly 10 comprises a furnace unit 12 having a heat-treating chamber 13 located therein. The furnace unit 12 is comprised of conventional insulating blocks and heating elements which do not form any part of the present invention. Vertically movable doors 15 and 16 are adapted to seal openings 11 and 14 located at the ends of the heat-treating chamber 13 during the heat-treating operation and any conventional means may be employed for moving these doors to the open position thereof.

Located adjacent to the furnace unit 12 and communicating therewith through a duct 17 is a cooling station generally indicated at 18. The cooling station 18 includes an outer jacket 25 that envelops a cylinder 27 in which a cooling chamber 19 is defined. A cooling medium may be circulated within the jacket 25 and mounted in the cooling chamber 19 is a fan 20 that is driven by a motor 21 for circulating a conditioning gas within the cooling chamber. The conditioning gas such as hydrogen, enters the cooling chamber through an inlet pipe 22, and it is understood that a similar conditioning gas is also circulated in the heat-treating chamber 13 during the heat-treating operation.

Mounted for movement on a track 24 that extends through the furnace unit 12 and into the cooling chamber 19 is a tray generally indicated at 26 on which a workbasket 28 is located. The workbasket 28, as will be described, contains a work holder therein in the form of a ceramic fiber block generally indicated at 30, the ceramic fiber block 30 being especially designed for retaining the articles therein that are to be heat treated. The tray 26 with the workbasket 28 located thereon is adapted to moved from the heat-treating chamber 13 into the cooling chamber 18 after the heat-treating operation in which area the articles are quickly quenched by introducing the conditioning gas through the inlet pipe 22 and rapidly circulating the conditioning gas within the cooling chamber by means of the fan 20. Although not shown, the basket 28 and the tray 26 are movable by any convenient means such as a push rod to and from the heat-treating chamber 13 and the cooling chamber 18. If required, a conveyor belt may also be employed for carrying the tray 26 through the heat-treating chamber 13 and cooling chamber 19 in which case the heat-treating operation could be continuous. As further shown in FIG. 7, a duct 23 also communicates with the cooling chamber 19 and may be employed as a discharge area for removing the block 30 and the articles embedded therein from the cooling chamber following the cooling cycle. Any suitable door or gate will be located in the duct 23 to seal the cooling chamber from the outside atmosphere.

Referring now to FIG. 2, the tray 26 and basket 28 as mounted thereon are shown in detail, and, as illustrated, the tray 26 includes spaced-parallel members 32 on which similar crossmembers 32 are fixed to form a framework. End crossmembers 34 are joined to the ends of one set of the members 32 and are fixed to vertical brackets 36. Upstanding pins 38 are joined to the ends of the members 32 and define the end limiting means for retaining the basket 28 therebetween. Longitudinally extending members 39 support the crossmembers 32 and are received on the track 24 for movement thereon.

One of the features of the invention is providing for the heat treatment of metallic articles wherein a portion of each article is effectively embedded or insulated during the heat-treating operation so as to be prevented from reaching the austenitizing or hardening temperature. By preventing the embedded portion of the articles from reaching the hardening temperature, this portion may later be suitably marked with identifying indicia without the requirement of additional procedures for softening a portion of the metal and cleaning the metal thereafter.

In the present invention, it is contemplated that metallic articles such as drills will be heat treated, and, as shown in FIG. 2, a plurality of drill blanks of various lengths are illustrated and are indicated at 40, 42 and 43. The drill blank 40 which is representative of one size of a drill includes a first portion indicated at 44 and a second portion indicated at 46, the first portion 44 defining the portion of the drill blank that will be formed with the flutes thereon and the second portion 46 defining the shank of the drill. It is conventional to mark the shank 46 of the drill with identifying indicia, and it is for this purpose that the present invention provides for insulating the shank portion 46 of the drill during the heat-treating operation so as to prevent the portion from reaching the hardening temperature.

In order to prevent the shank portion 46 of the drill blanks from reaching the hardening temperature during the heat-treating operation, the mounting block 30 is provided and receives the drill blanks therein. As illustrated in FIG. 2, the mounting block 30 is formed of a ceramic fiber material of special construction and is comprised essentially of 51.2 percent aluminum oxide and 47.4 percent silicon oxide. The ceramic fiber material of the block 30 is defined by short staple fibers that are compressed together to form the mass as indicated. In order to mount the drill blanks in vertical position in the block 30 during the heat-treating operation, a plurality of holes 48 are bored therein, each of the holes 48 receiving a metallic insert 50 therein. The metallic inserts are formed of a mild steel material and have a central opening 52 extending therethrough, the diameter of which is adapted to accommodate a drill shank therein. It is seen that when the drill blanks are mounted in the block 30 for the heat treatment thereof, the shank portions 46 of each drill is embedded in a metallic insert, the flute portions extending above the block and being directly exposed to the high temperatures generated in the heat-treating chamber 13.

In preparing for the heat treating of the drill blanks or any other metallic article that is to be heat treated in the furnace 10, it is first desirable to condition the ceramic fiber block 30 so as to render it inert, thereby preventing decarborization of the metallic articles supported therein. The ceramic fiber block is cleansed by placing it in the furnace chamber and bringing the temperature of the heating chamber 13 up to normal operating temperatures. The impurities in the ceramic fiber block are thus removed, and the block is rendered substantially inert for all practical purposes.

After the ceramic fiber block has been preconditioned, the drill blanks are placed therein by locating the shanks 46 of the drill blanks in the inserts 50. The openings in the block 30 and the length of the inserts 50 are such that the shanks of the drills are effectively insulated, whereas the flute portions 44 are exposed and extend above the upper surface of the ceramic fiber block 30. With the ceramic fiber block 30 located in the basket 28 and the basket disposed on the tray 26, the tray is pushed into the heating chamber 13 to the position as illustrated in FIG. 1. The heat treatment operation is then carried out, wherein the flute portions 44 of the drill blanks are brought up to the austenitizing temperature so as to provide for bright hardening thereof. After the heating cycle is completed, the door 16 is opened and the tray 26 is then pushed by a hand or cylinder operated push rod from the heating chamber 14 through the the duct 17 and into the cooling chamber 19. This operation is quickly carried out, and the fan 20 is then operated to circulate the conditioning atmosphere entering into the cooling chamber 19 through the inlet 22. By rapidly circulating the atmosphere in the cooling chamber 19 the metallic articles are cooled quickly enough so that sufficient heat is removed therefrom to prevent their shank portions 46 from reaching the austenitizing or hardening temperature.

It is seen that the process by which the metallic articles are heated and cooled in the apparatus of the subject invention, the flute portions 44 of the articles are bright hardened while the lower shank portions 46 thereof are maintained relatively soft so that they may be marked for identification by stamping the drill size and other identifying indicia thereon. The forced atmosphere recirculation in the cooling chamber wherein the atmosphere is moved over and around the drill blanks removes the heat therefrom in the shortest possible time and since the heating cycle is controlled such that the flute portions are heated just sufficiently to be brought up to the austenitizing temperature, the supporting ceramic fiber block and the metal inserts are thus only partially heated to this temperature. This being the case, the shank portions 46 of the drill blanks are also only partially heated to the austenitizing temperature; and when the block 30 with the drill blanks therein are moved in the cooling chamber, the heat is removed therefrom quickly enough to prevent the shanks of the drills from reaching the hardening temperature. Marking of the drill shanks for identification by stamping is then carried out without any additional procedures necessary, since the drill shanks are still soft enough to permit ready marking thereon.

Although the present invention has been described in connection with the heat treatment of metallic articles, such as drills, it is also understood that other metallic articles can be heat treated in a similar manner, particularly when it is desired to maintain a portion of the articles in a relatively soft condition for marking. It is also understood that the articles may be disposed other than in a vertical position as long as a portion thereof is protected in the ceramic fiber block.

While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.

Claims

What is claimed is:

1. In a method of heat treating a metallic article, wherein the article includes a first portion and a second portion that is integrally joined to said first portion, comprising the steps of placing a metallic insert within a holder that has insulating characteristics, locating said article in said metallic insert as mounted in said article holder such that the first portion of the article is embedded in said insert in insulated relation and the second portion thereof is exposed, placing said holder with the article mounted in the insert therein in a furnace heating chamber, heating said article for a predetermined period of time that enables the exposed second portion of said article to reach the austenitizing temperature without the embedded first portion reaching the same temperature, removing the article holder and article therein from said heating chamber to a cooling chamber, and quickly quenching said article in said cooling chamber, whereby said second portion of said article is hardened while the first portion is prevented from being hardened.

2. In a method as set forth in claim 1, wherein the step of quickly quenching said article comprises circulating an atmosphere through said cooling chamber thereby rapidly cooling the second portion of the article and removing heat from the surrounding area to prevent the first portion from reaching the austenitizing temperature.

3. In a method as set forth in claim 2, comprising the further step of conditioning said article holder by preheating it in said furnace heating chamber, prior to the heat-treating operation to remove impurities and to thereby render said article holder inert for preventing decarburization of said article during the heat-treating operation.

4. In a method as set forth in claim 3, comprising the further step of controlling the temperature of said furnace during the heat-treating operation in the range of 1,450.degree.-2,350.degree. F.