U.S. patent number 3,615,927 [Application Number 04/675,437] was granted by the patent office on 1971-10-26 for method for heat treating metallic articles.
This patent grant is currently assigned to C. I. Hayes Inc.. Invention is credited to Carl G. Paulson.
United States Patent |
3,615,927 |
Paulson |
October 26, 1971 |
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.
Inventors: |
Paulson; Carl G. (West
Kingston, RI) |
Assignee: |
C. I. Hayes Inc. (Cranston,
RI)
|
Family
ID: |
24710492 |
Appl.
No.: |
04/675,437 |
Filed: |
October 16, 1967 |
Current U.S.
Class: |
148/640;
148/587 |
Current CPC
Class: |
C21D
9/22 (20130101); C21D 1/70 (20130101) |
Current International
Class: |
C21D
1/70 (20060101); C21D 9/22 (20060101); C21D
1/68 (20060101); C21d 001/70 () |
Field of
Search: |
;148/148,149,16,20.3,143,144,145,146,147,13.1,14 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Dean; Richard O.
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.
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.
* * * * *