U.S. patent number 3,798,954 [Application Number 05/200,002] was granted by the patent office on 1974-03-26 for method and apparatus for producing metal tubes by extrusion of a hollow billet.
This patent grant is currently assigned to Kobe Steel Company Ltd.. Invention is credited to Akira Asari.
United States Patent |
3,798,954 |
Asari |
March 26, 1974 |
METHOD AND APPARATUS FOR PRODUCING METAL TUBES BY EXTRUSION OF A
HOLLOW BILLET
Abstract
Metal tubes are produced by extruding a hollow billet through an
annular die opening defined by a die and a movable rod-shaped
mandrel having a larger length than the tube to be produced, and by
feeding the mandrel rod through the die together with the tube as
it is being formed so that the tube as produced has the mandrel rod
disposed therein along its entire length, whereby damage to the
inner surface of the tube caused by scratching due to relative
movement of the mandrel therewith is avoided and tubes having
improved inner surface characteristics are obtained.
Inventors: |
Asari; Akira (Osaka,
JA) |
Assignee: |
Kobe Steel Company Ltd. (Kobe,
JA)
|
Family
ID: |
14343236 |
Appl.
No.: |
05/200,002 |
Filed: |
November 18, 1971 |
Foreign Application Priority Data
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Nov 19, 1970 [JA] |
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45-103030 |
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Current U.S.
Class: |
72/255; 72/265;
72/370.03 |
Current CPC
Class: |
B21C
23/085 (20130101) |
Current International
Class: |
B21C
23/02 (20060101); B21C 23/08 (20060101); B21c
023/00 () |
Field of
Search: |
;72/255,265,370,264,266 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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370,627 |
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Apr 1932 |
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GB |
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395,906 |
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Jul 1933 |
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GB |
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Primary Examiner: Herbst; Richard J.
Assistant Examiner: Rogers; Robert M.
Attorney, Agent or Firm: Oblon, Fisher, Spivak, McClelland
& Maier
Claims
What is claimed as new and desired to be secured by letters patent
of the united states is:
1. A method of producing metal tubes by extruding a hollow billet
through a die with the cooperation of a mandrel, comprising the
steps of:
preparing a hollow billet having a central through opening of
predetermined dimensions;
applying an external compression force to said hollow billet in an
axial direction thereof across its annular cross-section for
extruding said hollow billet through an annular die opening defined
by a die and a rod-shaped mandrel having a greater length than that
desired for a tube being produced;
feeding said mandrel rod through said die with said tube being
extruded so that substantially no relative motion occurs between
said tube and said mandrel rod;
cutting the rear end of the tube from the remaining billet by
shearing in the axial direction of said tube as said billet is
being extruded through said die; and
removing said mandrel rod from the said tube after said tube has
been completely extruded.
2. A method according to claim 1, further comprising:
charging said hollow billet in a cylindrical chamber axially
connected to said die opening; and
moving said hollow billet with respect to the wall of said
cylindrical chamber as a whole while applying said external
compression force as the extrusion proceeds.
3. A method according to claim 1, further comprising:
charging said hollow billet in a cylindrical chamber axially
connected to said die opening
maintaining said hollow billet substantially stationary with
respect to the wall of said cylindrical chamber as a whole while
applying said external compression force as the extrusion
proceeds.
4. An apparatus for producing metal tubes by extruding a hollow
billet through a die with a cooperating mandrel, comprising:
a die having an opening therein;
a billet container having a cylindrical chamber for receiving a
hollow billet;
means for supporting said billet container and said die so that
said die opening and said cylindrical chamber are axially
connected;
a rod-shaped mandrel of greater length than that desired of a tube
to be produced being movably supported for movement in an axial
direction through said billet chamber and said die opening for
defining an annular opening between said die and said mandrel;
means for applying an axial compression force to a billet in said
cylindrical chamber for extruding said billet through said annular
opening and moving said rod-shaped mandrel therethrough with said
tube being extruded; and
a shear mandrel being movable within said means for applying an
axial compression force to said billet for applying a shearing
force to an inner peripheral portion of said hollow billet in said
cylindrical billet chamber as the same is being extruded through
said annular opening.
5. An apparatus according to claim 4, wherein said die and said
billet container are firmly connected together and said compression
force applying means is an actuator having an annular stem
receivable in said cylindrical billet chamber.
6. An apparatus according to claim 4 wherein said die is movably
received in said cylindrical billet chamber and said billet
container is axially movable by said axial compression force.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the production of metal tubes
and more particularly to a method and apparatus for producing metal
tubes by extruding a hollow billet through a die and a cooperating
mandrel.
2. Description of the Prior Art
The production of metal tubes by extruding a hollow billet through
a die and a cooperating mandrel, wherein the die and the mandrel
define an annular die opening through which the hollow billet is
extruded to be formed into a tube having a cross-section
corresponding to the annular die opening, is well known.
Conventionally, however, the mandrel which forms the inside surface
of the tube moves relatively over the inside surface thereof as the
tube is being formed by extrusion in such a scraping manner that
the life of the mandrel is shortened due to frictional wear
thereof. In addition, the finished condition of the inside surface
of the tube is relatively poor because of scratches and other
faults produced by the relative sliding with friction between the
inside surface of the tube and the mandrel.
These scratches and other faults generally degrade the quality of
the tubes and, in some cases, become a serious obstacle to the
tubes being satisfactorily used for accomplishing the tasks being
imposed thereon. For example, fuel encasing tubes designed for use
in atomic reactors are required to be perfectly free from even
minute scratches and similar related defects.
In order to avoid these disadvantages of former methods of
extruding metal tubes, one common practice is to supply a lubricant
to the boundary of the billet and the mandrel, with the lubricant
being selected from any one of a number of suitable materials
according to the material from which the billet is constructed,
such as, for example, glass powder for billets which are made of
steel or titanium, zirconium or aluminum alloys.
However, even with the use of a lubricant, as described above, it
is very difficult to completely avoid the generation of scratches
or other faults on the inside surface of tubes being formed in this
manner, especially in the case of tubes of hard metals such as
stainless steel, titanium or zirconium alloys, and the like.
Therefore, in the production of such metal tubes by this
conventional extrusion process, manufacturers have been compelled
to maintain very strict control and supervision during the
procedure in order to provide tubes having satisfactory inside
surface conditions.
Furthermore, when a lubricant is used in the extrusion process,
relatively complicated methods and devices are required for
applying the lubricant to the boundary of the hollow billet and the
mandrel, as well as for removing the layer of the lubricant
remaining on the inside surface of the tubes being produced,
especially when glass powder is used as the lubricant. These
complicated procedures and the complex apparatus associated
therewith which are tied in with the use of a lubricant adversely
affect the productivity of an extrusion plant and thereby increase
the cost of the products. Thus, while it has heretofore been
possible to successfully produce metal tubes of the character
described having adequate inner surface qualities, the methods
which have necessarily been resorted to have not been altogether
satisfactory for various reasons.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to
provide a method and apparatus for producing metal tubes by
extruding hollow billets through a die opening with the cooperation
of a mandrel, wherein, however, the generation of scratches or
other faults on the inside surface of the tube being formed due to
relative frictional sliding motion between the tube and the mandrel
is effectively avoided.
Another object of the present invention is to provide a method of
producing metal tubes by extruding a hollow billet through a die
with the help of a cooperating mandrel, which is not complex and
does not require strict control, yet is capable of producing such
tubes having inner surface characteristics of improved quality.
Still another object of the present invention is to provide an
apparatus for practicing the method described immediately
hereinbefore.
The foregoing and other objects are attained, according to one
aspect of this invention, by an improved method of producing metal
tubes comprising the steps of preparing a hollow billet having a
central through opening of predetermined dimensions, extruding the
hollow billet through an annular die opening defined by a die and a
movable rod-shaped mandrel having a length greater than that of the
tube being produced, feeding the mandrel rod through the die in
accordance with the extrusion of the tube, and removing the mandrel
rod from the tube after the tube has been completely extruded.
According to this invention, since the mandrel which cooperates
with the die to define an annular opening through which a tube is
extruded from a hollow billet is a rod of a greater length than the
tube being produced and is fed through the die together with the
tube as it is extruded from the die, such that the tube is always
accompanied by the mandrel rod, substantially no relative sliding
occurs between the inside surface of the tube and the mandrel over
the whole length of the tube, and thereby scratches or other faults
on the inside surface of the tube due to such relative sliding or
friction between the tube and the mandrel are substantially
avoided. Thus, tubes produced by the method of this invention have
a very high quality of inside surface characteristics.
Since relative sliding between the tube and the mandrel is
prevented, the extrusion is performed more smoothly and with less
power than heretofore required for the conventional extrusion
processes. Furthermore, the mandrel is relieved from severe
frictional sliding under relatively high temperatures over the
inside surface of the tube being formed, so that the life of the
mandrel rod is substantially longer than previous mandrels employed
in the prior devices and techniques.
By employing a number of the mandrel rods in cooperation with an
extrusion press, it is possible to construct a circuit for the
extrusion processes through which the mandrel rods are circulated,
wherein the extrusion press can be operated essentially at its
highest rate with no regard to the problems usually concerning
operators of apparatus operating under the former processes, such
as withdrawing, cooling or changing of the mandrels. Thus, it is
possible with the present invention to obtain a high productivity
in the extrusion plant.
Furthermore, since it is not necessary either to supply or remove
lubricant as required in the former practice, the extrusion plant
for carrying out the process according to this invention is very
simplified and can readily be automated, to thereby further improve
the productivity of the plant.
BRIEF DESCRIPTION OF THE DRAWINGS
Various other objects, features and attendant advantages of the
present invention will be more fully appreciated as the same
becomes better understood from the following detailed description
when considered in connection with the accompanying drawings,
wherein like reference characters designate like or corresponding
parts throughout the several views, and in which:
FIG. 1 is a plan view schematically showing the layout of a tube
extrusion plant for practicing the method of this invention;
FIG. 2 is a longitudinal section of essential parts of an extrusion
press for practicing the method of this invention;
FIG. 3 is a longitudinal section of another embodiment of an
extrusion press; FIGS. 4, 5 and 6 show the die portion of the
extrusion press shown in FIG. 2, respectively in three different
phases of the extrusion process; and
FIG. 7 shows a tube just extruded according to the method of this
invention, having a mandrel rod still disposed therein.
DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Referring now to the drawings, and more particularly to FIG. 1,
there is shown an example of a layout of a tube extrusion plant
designed for practicing the method of this invention, wherein a
billet extrusion press 1 as explained in detail hereinbelow is
provided for extruding a tube 2 therefrom in the state in which a
mandrel rod is yet disposed therein onto a runout table 3. The
tubes placed on the table 3 are then transferred to a cooling table
4, where they may be cooled for a sufficient period of time to
attain a required temperature without regard to the operation cycle
of the extrusion press 1. Next, the cooled tubes 2 are fed to a
mandrel stripper 5 of the push-bench or reeler type, which itself
is known in the art.
The strippers 5 of the character described are conventionally used
to draw out a core or other rod-like element from a tubular
element, and generally accomplish their purposes without any
difficulty and without causing scratches or other faults on the
inside surface of the tubular element. The stripper of the reeler
type, which employs pairs of cooperating skewed rollers, especially
can be favorably employed for the present purpose of drawing the
mandrel rod out from the extruded tube, by arranging a number of
pairs of cooperating skewed rollers corresponding to the length of
the tube.
After the mandrel rods have been removed, the tubes 2 are
transferred from the mandrel stripper 5 to a suitable product
storing station, not shown, while the mandrel rods are returned to
a mandrel feed table 6, where they are further cooled and prepared
for their next use in the extrusion process.
In the layout drawing schematically shown in FIG. 1, other
equipment related to the billet extrusion press 1 are shown, such
as billet heating furnaces 7, 8, 9, 10 and 11, a transfer device 12
for charging billets into the billet heating furnaces and another
transfer device 13 for discharging the billets from the furnaces
and feeding them to the billet extrusion press 1. A water pump 14
is provided for cooling the extruded tubes, mandrels and other
equipment. Other parts of the plant which are shown include a water
storage tank 15, a compressor 16, compressed air accumulators 17, a
main stop valve 18, control valves 19, a low pressure tank 20, oil
hydraulic units 21, a control room 22 and motors 23.
The manner of extruding the tubes from the billet at the billet
extrusion press 1 is shown in the subsequent figures of the
drawings. FIGS. 2 and 3, for example, show the state of different
embodiments of extrusion presses wherein the extrusion of the tube
has been initiated and is in progress.
In the billet extrusion press shown in FIG. 2, the reference
numeral 30 generally designates a die assembly composed of a die 31
and a die packer 32 being housed in a die holder 33 and directly
abutting on a press platen 34 having a central opening 35 through
which an extruded tube 36 is fed out. Adjacent the die holder 33
there is provided a billet container 37 defining a billet chamber
38 in which is charged a hollow billet 39 being preformed to
present a central opening which is adapted to allow penetration of
a mandrel rod 40 therethrough. The billet container 37 is supported
by a container holder 41, which in turn is supported by one end of
a pair of press columns 42 mounted on the platen 34. The columns 42
guide a cross head 43 having a stem portion 44 extending therefrom
to be received in the billet chamber 38 for applying a compression
force to the billet 39 charged therein through a disk 45. The
central portion of the crosshead 43 is constituted as a
piston-cylinder assembly including a movable element 46 presenting
a shear mandrel 47 at its forward end and a piston 48 at its rear
portion, which is disposed in a cylinder chamber 49 formed in the
crosshead 43 for driving the movable element 46 with respect to the
crosshead. Along the axis of the movable element 46, there is
formed a through opening 50 adapted to allow feeding of the mandrel
rod 40 therethrough. The crosshead 43 is movable along the columns
42 by rams 51 being actuated by supplying pressure to cylinders 52,
and can be retracted to open the billet chamber 38 for charging a
billet therein or moved forward to apply a compression force to the
billet charged in the billet chamber. Reference numeral 53
designates a series of mandrel transfer rollers which carry the
mandrel rod 40 and feed it according to the progress of the
extrusion process.
The billet extrusion press shown in FIG. 3 is almost identical with
the press shown in FIG. 2, except that in the press shown in FIG.
3, the billet container 37 is carried by the crosshead 43 through
the container holder 41, which in this case is integrally formed as
a part of the crosshead 43, and the die 31 is supported by a stem
portion 54 projecting from the platen 34 in a manner that it is
receivable in the forward end of the billet chamber 38.
The difference in the extruding operations of the presses shown in
FIGS. 2 and 3 is that in the former press, the billet 39 is slid
within the billet container 37 as the extrusion proceeds, while in
the latter press, the billet 39 is kept substantially unmoved with
respect to the billet container 37, and the die 31 is slid over the
wall of the billet chamber 38.
FIGS. 4 to 6 show the starting, intermediate and ending conditions,
respectively, of an extrusion process being carried out with the
press shown in FIG. 2.
In the beginning, the billet 39 is charged in the billet chamber 38
with the crosshead 43 first being sufficiently retracted to open
the chamber 38, and then the disk 45 is engaged and the crosshead
43 is moved forward to advance the disk 45 to be in close
contracting relation with the billet. In this condition, the shear
mandrel 47 is so retracted with respect to the stem portion 44 of
the crosshead that it applies no shearing force to the billet.
Next, the mandrel rod 40 is fed through the opening 50 of the
movable element 46 in the crosshead 43 and the central opening of
the billet 39 until the forward end thereof just penetrates the
opening in the die assembly 30, to attain the starting position
shown in FIG. 4.
Now the cylinders 52 are actuated to advance the crosshead 43 and
apply a compression force to the billet 39, whereby the billet is
extruded through the annular opening defined by the die assembly 30
and the mandrel rod 40 to form the tube 36. As the tube 36 is being
formed and fed out through the die opening, the mandrel rod 40
accompanies the tube 36 with no substantial sliding motion
occurring therebetween, and it also is fed out of the die opening
as shown in FIG. 5, or FIGS. 2 and 3, wherein the annular die
opening at each instant is provided by the die inner periphery and
each corresponding portion of the mandrel rod.
When a predetermined length of the tube has been extruded, the
cylinder 49 in the cross head 43 is actuated to advance the shear
mandrel 47 with respect to the stem portion 44 and into the die
opening, as shown in FIG. 6, whereby the end of the tube 36 is cut
off from the remaining billet 39 which is disposed as a
discard.
As a result of the extrusion process described above, there is
obtained a tube 36 having the mandrel rod 40 extending throughout
the entire length thereof, as shown in FIG. 7. These tubes,
including the mandrel rods, are cooled and supplied to the mandrel
stripper as described above and are relieved of the mandrels
without being caused any substantial fault on the inside surface
thereof.
Obviously many modifications and variations of the present
invention are possible in light of the above teachings. It is to be
understood, therefore, that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
* * * * *