U.S. patent application number 10/288598 was filed with the patent office on 2003-04-10 for semi-solid formed, low elongation aluminum alloy connecting rod.
Invention is credited to Bergsma, S. Craig.
Application Number | 20030066579 10/288598 |
Document ID | / |
Family ID | 25266325 |
Filed Date | 2003-04-10 |
United States Patent
Application |
20030066579 |
Kind Code |
A1 |
Bergsma, S. Craig |
April 10, 2003 |
Semi-solid formed, low elongation aluminum alloy connecting rod
Abstract
A method for forming a remateable cracked aluminum base alloy
connecting rod using a semi-solid aluminum alloy processing to
produce a connecting rod having a globular microstructure contained
in a lower melting eutectic with improved properties.
Inventors: |
Bergsma, S. Craig; (The
Dalles, OR) |
Correspondence
Address: |
ANDREW ALEXANDER & ASSOCIATES
3124 KIPP AVENUE
P.O. BOX 2038
LOWER BURRELL
PA
15068
US
|
Family ID: |
25266325 |
Appl. No.: |
10/288598 |
Filed: |
November 6, 2002 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10288598 |
Nov 6, 2002 |
|
|
|
09834189 |
Apr 13, 2001 |
|
|
|
Current U.S.
Class: |
148/549 ;
420/535 |
Current CPC
Class: |
B22D 17/007 20130101;
F16C 9/045 20130101; F16C 7/023 20130101; C22C 1/005 20130101; Y10T
74/2162 20150115; Y10T 74/2159 20150115; C22F 1/043 20130101 |
Class at
Publication: |
148/549 ;
420/535 |
International
Class: |
C22F 001/04 |
Claims
What is claimed is:
1. A method of forming a remateable cracked aluminum base alloy
connecting rod having a globular microstructure contained in a
lower melting eutectic matrix, the method comprising the steps of:
(a) providing a body of a semi-solid aluminum base alloy; (b)
providing a mold for a connecting rod, said mold defining a
connecting rod having a large bore therein for use as a large
bearing and a small bore for use as a small bearing, said bores
connected by an arm member; (c) injecting semi-solid aluminum base
alloy into said mold; (d) cooling said mold to solidify said
semi-solid aluminum base alloy to provide said connecting rod
having a globular microstructure contained in a lower melting
eutectic matrix; (e) aging said rod at a temperature of
200-400.degree. F. for a period of about 1 to 24 hours to provide
an aged rod having improved strength; and (f) fracturing a cap
portion along a fracture plane in a wall defining said large bore
to provide a cap portion having cracked surfaces which permit
substantially exactly rematching said cracked surfaces for securing
said large bearing to a bearing surface of an engine crank.
2. The method in accordance with claim 1 wherein said aged
connecting rod has an elongation not greater than 15%.
3. The method in accordance with claim 1 wherein said connecting
rod in the aged condition has an elongation in the range of 1 to
5%.
4. The method in accordance with claim 1 wherein said connecting
rod after solution heat treating, quenching and aging has a
globular microstructure contained in a lower melting eutectic
matrix.
5. The method in accordance with claim 1 including, prior to aging:
(a) solution beat treating said connecting rod at a temperature in
the range of 800.degree. to 1000.degree. F. for a period of 0.1 to
12 hours to provide a solution heat treated connecting rod; and (b)
quenching said solution heat treated rod to provide a quenched
connecting rod.
6. The method in accordance with claim 5 wherein said quenching is
a water quench.
7. The method in accordance with claim 1 wherein said aluminum
alloy is comprised of 4 to 7 wt. % Si, 0.55 to 1 wt. % Cu, 0.9 to 2
wt. % Mg, 0.1 to 1 wt. % Fe, 0.01 to 2 wt. % Ni, and 0.01 to 0.25
wt. % Ti, the balance aluminum, incidental elements and
impurities.
8. The method in accordance with claim 7 wherein Fe is maintained
in the range of 0.2 to 0.6 wt. %.
9. The method in accordance with claim 1 wherein said alloy is
comprised of 4.5 to 6 wt. % Si, 0.6 to 0.9 wt. % Cu, 1 to 1.5 wt. %
Mg, 0.2 to 0.6 wt. % Fe, 0.01 to 1.5 wt. % Ni and optionally one or
more of 0.1 to 7 wt. % Sn, 0.001 to 0.1 wt. % Be, 0.1 to 2 wt. %
Cd, 0.1 to 2 wt. % Pb and 0.01 to 2 wt. % Bi.
10. A method of forming a remateable cracked aluminum base alloy
connecting rod having improved strength, the method comprising the
steps of: (a) providing a body of a semi-solid aluminum base alloy
comprised of 4 to 7 wt. % Si, 0.55 to 1 wt. % Cu, 0.9 to 2 wt. %
Mg, 0.1 to 1 wt. % Fe, 0.2 to 2 wt. % Ni and 0.01 to 0.25 wt. % Ti,
optionally one of the following: 0.1 to 7 wt. % Sn, 0.001 to 0.1
wt. % Be, 0.1 to 2 wt. % Cd, 0.01 to 2 wt. % Pb and 0.01 to 2 wt. %
Bi; (b) providing a mold for a connecting rod, said mold defining a
connecting rod having a large bore therein for use as a large
bearing and a small bore for use as a small bearing, said bores
connected by an arm member; (c) injecting said semi-solid aluminum
base alloy into said mold; (d) cooling said mold to solidify said
semi-solid aluminum base alloy to provide said connecting rod
having a globular microstructure contained in a lower melting
eutectic matrix; (e) aging said rod to provide an aged rod having
improved strength and having an elongation of not greater than 6%
to promote fracturing; and (f) fracturing a cap portion along a
fracture plane in a wall defining said large bore to provide a cap
portion having cracked surfaces which permit substantially exactly
rematching said cracked surfaces for securing said large bearing to
a bearing surface of an engine crank.
11. The method in accordance with claim 10 wherein prior to aging,
said rod is: (a) solution heat treated at a temperature in the
range of 800.degree. to 1000.degree. F. for a period of 0.1 to 12
hours followed by quenching; and (b) quenched and solution heat
treated to provide a quenched connecting rod.
12. A method of forming a remateable cracked aluminum base alloy
connecting rod having improved strength, the method comprising the
steps of: (a) providing a body of a semi-solid aluminum base alloy
comprised of 4 to 7 wt. % Si, 0.55 to 1 wt. % Cu, 0.9 to 2 wt. %
Mg, 0.1 to 1 wt. % Fe, 0.01 to 2 wt. % Ni and 0.01 to 0.25 wt. %
Ti, optionally one of the following: 0.1 to 7 wt. % Sn, 0.001 to
0.1 wt. % Be, 0.1 to 2 wt. % Cd, 0.01 to 2 wt. % Pb and 0.01 to 2
wt. % Bi; (b) providing a mold for a connecting rod, said mold
defining a connecting rod having a large bore therein for use as a
large bearing and a small bore for use as a small bearing, said
bores connected by an arm member; (c) injecting said semi-solid
aluminum base alloy into said mold; (d) cooling said mold to
solidify said semi-solid aluminum base alloy to provide said
connecting rod having a globular microstructure contained in a
lower melting eutectic matrix.; (e) aging said rod to provide an
aged rod having improved strength and having an elongation of not
greater than 6% to promote fracturing; and (f) fracturing a cap
portion along a fracture plane in a wall defining said large bore
to provide a cap portion having cracked surfaces which permit
substantially exactly rematching said cracked surfaces for securing
said large bearing to a bearing surface of an engine crank.
13. The method in accordance with claim 12 wherein said rod is
solution heat treated and quenched prior to aging.
14. An aluminum base alloy suitable for forming in semi-solid
condition into a connecting rod having a globular microstructure
contained in a lower melting eutectic matrix and having a large
bore therein for use as a large bearing and a small bore for use as
a small bearing, the bores connected by an arm member to form said
connecting rod, the alloy comprised of 4 to 7 wt. % Si, 0.55 to 1
wt. % Cu, 0.9 to 2 wt. % Mg, 0.1 to 1 wt. % Fe, 0.01 to 2 wt. % Ni,
and 0.01 to 0.25 wt. % Ti, the balance aluminum, incidental
elements and impurities.
15. The alloy in accordance with claim 14 wherein said aluminum
alloy contains 0.2 to 0.6 wt. % Fe.
16. The alloy in accordance with claim 12 wherein said alloy is
comprised of 4.5 to 6 wt. % Si, 0.6 to 0.9 wt. % Cu, 1 to 1.5 wt. %
Mg, 0.2 to 0.6 wt. % Fe, 0.1 to 1.5 wt. % Ni and optionally one or
more of 0.1 to 7 wt. % Sn, 0.001 to 0.1 wt. % Be, 0.1 to 2 wt. %
Cd, 0.1 to 2 wt. % Pb and 0.01 to 2 wt. % Bi.
17. An aluminum base alloy comprised of 4 to 7 wt. % Si, 0.55 to 1
wt. % Cu, 0.9 to 2 wt. % Mg, 0.1 to 1 wt. % Fe, 0.01 to 2 wt. % Ni,
and 0.01 to 0.25 wt. % Ti, the balance aluminum, incidental
elements and impurities.
18. The alloy in accordance with claim 17 wherein said aluminum
alloy contains 0.2 to 0.6 wt. % Fe.
19. The alloy in accordance with claim 17 wherein said alloy is
comprised of 4.5 to 6 wt. % Si, 0.6 to 0.9 wt. % Cu, 1.0 to 1.5 wt.
% Mg, 0.2 to 0.6 wt. % Fe, 0.1 to 1.5 wt. % Ni and optionally one
or more of 0.1 to 7 wt. % Sn, 0.001 to 0.1 wt. % Be, 0.1 to 2 wt. %
Cd, 0.1 to 2 wt. % Pb and 0.01 to 2 wt. % Bi.
20. An aluminum base alloy connecting rod for an internal
combustion engine having a crank, said rod formed from a semi-solid
aluminum base alloy and having: (a) a globular microstructure
contained in a lower melting eutectic matrix; (b) a large bore
therein for use as a large bearing end and a small bore for use as
a small bearing, the bores connected by an arm member to form said
connecting rod; (c) a cap portion fractured along a fracture plane
in a wall defining said large bore; and (d) cracked surfaces
provided on opposite ends of said cap portion and a second portion
defining remainder of said large bore, said cap portion and said
remainder having cracked surfaces substantially exactly rematching
for securing said large bearing to a bearing surface of a
crank.
21. An aluminum base alloy connecting rod in accordance with claim
20 wherein said rod has an elongation of not greater than 6%.
22. An aluminum base alloy connecting rod in accordance with claim
20 wherein said connecting rod in the aged condition has an
elongation in the range of 1 to 5%.
23. An aluminum base alloy connecting rod in accordance with claim
20 wherein said rod has a tensile strength in the range of 40 to 80
KSI, yield strength in the range of 30 to 75 KSI and an elongation
of 0.1 to 15%.
24. An aluminum base alloy connecting rod in accordance with claim
20 wherein said aluminum alloy is comprised of 4 to 7 wt. % Si,
0.55 to 1 wt. % Cu, 0.9 to 2 wt. % Mg, 0.1 to 1 wt. % Fe, 0.01 to 2
wt. % Ni, and 0.01 to 0.25 wt. % Ti, the balance aluminum,
incidental elements and impurities.
25. An aluminum base alloy connecting rod in accordance with claim
20 wherein Fe is maintained in the range of 0.2 to 0.6 wt. %.
26. An aluminum base alloy connecting rod in accordance with claim
20 wherein said alloy is comprised of 4.5 to 6 wt. % Si, 0.6 to 0.9
wt. % Cu, 1.0 to 1.5 wt. % Mg, 0.2 to 0.6 wt. % Fe, 0.1 to 1.5 wt.
% Ni and optionally one or more of 0.1 to 7 wt. % Sn, 0.001 to 0.1
wt. % Be, 0.1 to 2 wt. % Cd, 0.1 to 2 wt. % Pb and 0.01 to 2 wt. %
Bi.
27. An aluminum base alloy connecting rod in accordance with claim
20 wherein said globular microstructure has a grain size in the
range of 50 to 250 .mu.m.
28. An aluminum base alloy connecting rod for an internal
combustion engine having a crank, the rod formed from semi-solid
aluminum base alloy, the rod comprising: (a) 4 to 7 wt. % Si, 0.55
to 1 wt. % Cu, 0.9 to 2 wt. % Mg, 0.1 to 1 wt. % Fe, 0.01 to 2 wt.
% Ni, and 0.01 to 0.25 wt. % Ti, and optionally one or more of 0.1
to 7 wt. % Sn, 0.001 to 0.1 wt. % Be, 0.1 to 2 wt. % Cd, 0.1 to 2
wt. % Pb and 0.01 to 2 wt. % Bi, the balance aluminum, incidental
elements and impurities; (b) a globular microstructure contained in
a lower melting eutectic matrix; (c) a large bore therein for use
as a large bearing end and a small bore for use as a small bearing,
the bores connected by an arm member to form said connecting rod;
(e) a cap portion fracture along a fracture plane in a wall
defining said large bore; and (e) cracked surfaces provided on
opposite ends of said cap portion and a second portion defining
remainder of said large bore, said cap portion and said remainder
having cracked surfaces substantially exactly rematching for
securing said large bearing to a bearing surface of a crank.
29. A rod in accordance with claim 28 wherein said rod has an
elongation of not greater than 6%.
30. A rod in accordance with claim 28 wherein said connecting rod
in the aged condition has an elongation in the range of 1 to
5%.
31. A rod in accordance with claim 28 wherein said alloy is
comprised of 0.4.5 to 6 wt. % Si, 0.6 to 0.9 wt. % Cu, 1.0 to 1.5
wt. % Mg, 0.2 to 0.6 wt. % Fe, 0.1 to 1.5 wt. % Ni and optionally
one or more of 0.1 to 7 wt. % Sn, 0.001 to 0.1 wt. % Be, 0.1 to 2
wt. % Cd, 0.1 to 2 wt. % Pb and 0.01 to 2 wt. % Bi.
32. A rod in accordance with claim 28 wherein Fe is maintained in
the range of 0.2 to 0.6 wt. %.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a low elongation aluminum alloy
member and more particularly it relates to low elongation aluminum
alloy members formed in a semisolid condition into shaped aluminum
alloy members such as internal combustion engine connecting rods
and caps therefor. Further, the invention relates to the production
of connecting rods having split bearing assemblies and matched
mating surfaces at the large bore or circumferential opposite
ends.
[0002] Most aluminum alloys solidify to form a dendritic
microstructure. Such structure requires forces such as forging type
forces to shape the solidified alloy into a high strength member
suitable for use, for example, as a connecting rod in an internal
combustion engine. If the connecting rod is cast into shape without
further work then it usually has low strength and is not suitable
for many applications where strength is important. If the high
strength members are produced utilizing powder metallurgy
techniques, a green compact must be first formed and then the
compact sintered to form the desired part.
[0003] These techniques are used to form connecting rods for
internal combustion engines. The connecting rod has three parts,
namely, a small end or terminal portion with a small bearing hole,
a large end with a large bearing opening and a rod portion
connecting the small bearing to the large bearing. The connecting
rod is comprised of two members including a semi-circular end cap
which forms approximately half the large bearing opening. The end
cap is fastened to a mating surface formed as part of the
connecting rod. The small end is an integral part of the connecting
rod. The end cap is required to fit the connecting rod to the crank
of the internal combustion engine.
[0004] Conventionally, the connecting rod was fabricated in two
parts comprised of the end cap and connecting rod. However,
considerable difficulty was experienced in precisely mating the end
cap to the connecting rod to form the large bearing opening. To
overcome the problem of matching the end cap to the mating surface,
the end cap is forged against or cracked from the large bearing
surface utilizing crack initiating indents to promote a cracking
plane to provide an exactly remateable end cap surface which is
employed in sintered powder or forged aluminum connecting rods. For
example, U.S. Pat. No. 5,566,449 discloses a connecting rod as a
shaft clamping member and includes a rod member and cap, each of
which has mating faces at circumferentially opposite ends of a
semi-circular recess and which are fastened to each other by bolts
by matching the opposed mating faces to each other to define a
crank pin hole by the two semi-circular recesses. The rod member
and the cap are forgings formed from an aluminum alloy and
simultaneously produced by forging powder preforms of the rod
member and cap in a cavity having the desired shape of the
connecting rod. After forging, the opposed mating faces have an
infinite number of recesses and projections which are formed from
the flow of the material during the forging and which are in a
matched and fitted relation to each other.
[0005] U.S. Pat. Nos. 5,353,500; 5,131,577; 5,109,605; 5,105,538;
4,993,134 and 4,936,163 disclose a method of making a connecting
rod for attachment to a bearing journal by separation of parts of
the connecting rod, including: (a) forging a powder metal sintered
preform to provide a one-piece connecting rod having an annular
wall defining a crank opening with a center axis and with stress
risers for establishing a cracking plane that extends across the
crank opening; (b) providing access for a compression coupling
across the cracking plane; (c) while at ambient conditions,
applying tension substantially uniformly across the cracking plane
to propogate fracture from the stress risers along the cracking
plane and thereby separate the connecting rod into a cap and body
with cracked surfaces; and (d) remating the cap and body by
applying a compression coupling through the access to draw the cap
and body together under guidance and with metal yielding pressure
to effect substantially an exact rematch of the cracked surfaces.
Control of the diametrical clearance between the bolt shanks and
the bolt openings, of the bolts used as the compression coupling,
promotes guidance needed to achieve such rematch. The cracking is
effected in an improved manner by use of continuous pulling apart
of the rod in a direction perpendicular to the cracking plane.
[0006] U.S. Pat. No. 4,860,419 discloses a method for making split
bearing connecting rods, including steps wherein previously clamped
body and cap portions are quickly forced apart longitudinally to
cause fracture separation of both pairs of integral legs in a
single motion while the cap and body are restrained from
substantial relative rotation by a clamp of a fracture separation
apparatus.
[0007] U.S. Pat. No. 4,569,109 discloses split bearing assemblies
having separable bearing caps for both single applications, such as
connecting rods, and multiple applications, such as engine
crankshaft supports, together with methods and apparatus for making
such assemblies by integrally forming the caps with the main body
and separating them by fracture separation. A two step separation
method is disclosed with bore starter notches and semicircular die
expanders that minimize split plane and bore distortion.
[0008] U.S. Pat. No. 5,051,232 discloses that the separation of two
or more forged powder metal components is facilitated by forming a
compacted and sintered powder metal preform with at least one slit
that separates the component pieces. An anti-bonding agent such as
graphite is introduced into the slit and the preform is then forged
to final shape. The anti-bonding agent prevents the complete
bonding of the powder metal pieces to each other thereby
facilitating separation of the pieces at the slit. This method is
particularly suited for the manufacture of piston connecting rod
assemblies of the type including a connecting rod and cap.
[0009] U.S. Pat. No. 5,722,036 discloses a manufacturing process of
a sintered connecting rod assembly comprising a first member with a
projection and a second member with a concavity in which the first
member and the second member are mated with each other by engaging
the projection with the concavity. A powdered raw material is
compacted into a first compact and a second compact for the first
and second members, wherein the projection of the first compact has
a width slightly larger than the width of the concavity of the
second compact. Then the projection of the first compact is engaged
with the concavity of the second compact to mate the first compact
with the second compact, thereby the projection and the concavity
are tightly pressed against each other. After sintering the mated
first and second compacts, they are forced to release the
projection from the concavity. The die for compacting the raw
material has a whole cavity and a removable core for dividing the
whole cavity into two cavities.
[0010] U.S. Pat. No. 3,994,054 discloses that the crankshaft
bearing cap of a connecting rod is formed from a forged rod blank
which includes an integral circular head having an internal bearing
surface and have integrally formed interconnecting lug portions.
The lug portions are provided with cracking openings aligned with
and parallel to a cracking plane. Each of the openings is provided
with a cracking notch or recess which extends downwardly from one
side of the head between twenty and fifty percent of the opening
length. The assembly is located on a lubricated supporting bed with
the unnotched face resting on the supporting surface.
Interconnected cracking pins with a suitable tapered configuration
are simultaneously forced into the cracking holes with an impact
type force. The tapered pins are interconnected to a common support
equalizing the cracking impact pressure as the pins are moved into
cracking openings. Each of the notches is formed with a V-shape
with an inclusive angle of forty-five degrees and a relatively
shallow depth of from 0.010 to 0.020 inches to define a sharp apex
in the cracking plane. Suitably sized and circumferentially spaced
radial lubrication holes in the cap provide improved lubrication
and simplify the manufacturing process. The lubrication holes are
spaced in accordance with the spacing of the needle roller bearings
such that only one roller bearing is in aligned overlying
relationship with each lubrication hole at any given instant.
[0011] U.S. Pat. No. 4,693,139 discloses that the bearing half and
bearing cap are integrally connected together by bolts, chamfers
are made in the peripheral portions of the bearing half and the
bearing cap facing their broken and divided surfaces. Such chamfers
are made before the dividing of the larger diameter end portion and
thus cause the breaking and dividing operation to be
facilitated.
[0012] U.S. Pat. No. 4,836,044 discloses that a multi-piece
connecting rod has the large eye end formed with a yoke receiving a
bearing bracket supported on an angled wedge surface by an angled
counter surface of a wedge. The wedge is carried by a pin-like bolt
between legs of the yoke and includes a threaded portion engaged by
the bolt for tightening the angled wedge surfaces to clamp the
bearing bracket in position.
[0013] U.S. Pat. No. 5,594,187 discloses an apertured connecting
rod having a stress riser crease formed in one side thrust surface
made by forging a powder metal sintered preform with a V-shaped
notch mold formed in a side face whereby the spaced surfaces
defining the V-shaped notch are folded inwardly toward one another
during forging to create a deep crease without any substantial
width.
[0014] In spite of these disclosures, there is still a great need
for an aluminum alloy based connecting rod having improved
properties and fractured mating surfaces to provide exactly
remateable end cap surfaces which can be fastened to form the large
bearing opening in the connecting rod.
SUMMARY OF THE INVENTION
[0015] It is an object of the invention to provide an improved
aluminum base alloy connecting rod for an internal combustion
engine.
[0016] It is another object of the invention to provide an aluminum
base alloy for fabricating into articles such as connecting
rods.
[0017] It is still another object of the invention to provide an
aluminum base alloy for semi-solid forming into articles or members
such as connecting rods.
[0018] Yet it is another object of the invention to provide a
method for semi-solid forming an aluminum base alloy into
connecting rods for internal combustion engines.
[0019] These and other objects will become apparent from a reading
of the specification and claims appended hereto.
[0020] In accordance with these objects, there is provided a method
of forming a remateable cracked aluminum base alloy connecting rod
having improved strength. The method comprises the steps of
providing a body of a semi-solid aluminum base alloy and a mold for
a connecting rod, the mold defining a connecting rod having a large
bore therein for use as a large bearing and a small bore for use as
a small bearing, the bores connected by an arm member. The
semi-solid aluminum base alloy is injected into the mold and cooled
to solidify the semi-solid aluminum base alloy to provide the
connecting rod having a globular microstructure in a lower melting
eutectic matrix. The rod is aged or optionally solution heat
treated in a temperature range of 800.degree.-1000.degree. F. for a
period of 0.1 to 12 hours. Then the rod can be quenched and aged in
a temperature range of 200-400.degree. F. for a period of about
1-24 hours to provide an aged rod having improved strength. The rod
may be aged to a T5 condition without the solution heat treatment.
A cap portion is fractured along a fracture plane in a wall
defining the large bore to provide a cap portion having cracked
surfaces which permit substantially exactly rematching the cracked
surfaces for securing the large bearing to a bearing surface of an
engine crank. The invention also includes a semi-solid formed
connecting rod having a globular microstructure contained in a
lower melting eutectic phase.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a flow chart showing steps in the process of the
invention.
[0022] FIG. 2 is a plan view of an aluminum base alloy connecting
rod manufactured in accordance with the process of the
invention.
[0023] FIG. 3 is a plan view showing the large end portion of the
connecting rod after fracturing a cap portion from the large bore
to provide substantially identical remateable surfaces.
[0024] FIG. 4 is a plan view showing the large end portion of the
connecting rod showing the cap portion bolted to the connecting rod
after being fractured across the fracture plane.
[0025] FIG. 5 is a plan view of a large bore illustrating the use
of shell bearing when the cap portion is reconnected to the
connecting rod.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Referring now to FIG. 1, there is shown a flow chart
illustrating steps which may be used in the invention. In FIG. 1,
it will be seen that a body of semi-solid aluminum base alloy is
provided for forming into a connecting rod. The semi-solid aluminum
base alloy may be provided from a billet or sections of a billet
which has been stirred during solidification or solidified in
accordance with certain procedures to obtain the required globular
grain structure. The sections of billet which are sufficient in
size to provide one connecting rod are reheated to the semi-solid
state required for forming into the connecting rod. This method is
described in my U.S. Pat. Nos. 5,968,292; 5,846,350 and 5,571,346
incorporated herein by reference, as if specifically set forth.
[0027] The body of semi-solid aluminum alloy may be provided by
another method. That is, a large body of molten aluminum base alloy
is provided in sufficient quantity to produce a number of
connecting rods. In this process, the body of suitable aluminum
base alloy is cooled to a temperature where the semi-solid
condition is obtained. Quantities of the semi-solid aluminum alloy
are discharged therefrom for forming into the connecting rods. This
process is described in U.S. Pat. No. 6,165,411, for example.
[0028] The semi-solid state is desirable because it is more easily
formed into a shaped member. When a cast body is heated to a
sufficient temperature, it transforms from a dendritic
microstructure to a globular or spheroidal phase contained in a
lower melting eutectic matrix and generally retains the same shape
as the cast body. After transformation, the body is provided in a
state resembling a thixotropic state which permits ease of forming
by use of smaller forces than would be required for making a
forging.
[0029] Referring again to FIG. 1, it will be seen that after having
obtained the semisolid body of an aluminum base alloy, a mold the
shape of the desired connecting rod is provided. The semi-solid
aluminum base alloy is injected into the mold and the mold is
cooled or permitted to cool to provide a solidified connecting rod.
Equipment for injecting semi-solid aluminum alloy into the mold on
a continuous basis is illustrated in U.S. Pat. No. 6,165,411,
incorporated herein by reference.
[0030] After the connecting rod is formed and removed from the
mold, it may be solution heat treated for purposes of solutionizing
soluble constituents such as magnesium, copper and silicon in a
controlled temperature range for a given period of time, depending
on the alloy. After such heat treating, the connecting rod is
quenched preferably in water and artificially aged for a period of
time to improve strength. The connecting may be aged to a T5
condition without the solution heat treatment Thereafter, a cap is
fractured along a fracture plane in a wall defining a bore suitable
as a bearing surface in the large end to provide a remateable cap
having substantially identical rematchable surfaces. The cap is
used to secure the large end bearing of the connecting rod to a
bearing surface of an engine crank, as further described
herein.
[0031] Metal alloys which can be formed into connecting rods by the
semi-solid process include iron base, titanium base, magnesium
base, and aluminum base alloys. That is, any metal alloy that can
be provided in a semi-solid condition can be formed into the
connecting rod.
[0032] Suitable aluminum alloys that can be cast and formed in
accordance with the invention include hypoeutectic and
hypereutectic alloys having high levels of silicon. In hypoeutectic
alloys, for example, the alloy can comprise from about 2.5 to 11
wt. % silicon with preferred amounts being about 5.0 to 7.5.
[0033] In addition, the alloy can contain magnesium and titanium,
incidental elements and impurities. Magnesium can range from about
0.2 to 2 wt. %, preferably 0.3 to 1.5 wt. %, the remainder
aluminum, incidental elements and impurities. The amount of
titanium is the conventional amount used with such alloys. The
amount of titanium is normally less than 0.2 wt. % and preferably
in the range of 0.01 to 0.2 wt. % as titanium only, with typical
ranges being in the range of 0.05 to 0.15 wt. % and preferably 0.10
to 0.15 wt. %. In some of these casting alloys, copper can range
from 0.2 to 5 wt. % for the AlCu alloys of the AA2XX series
aluminum alloys. In the AA5XX series alloys (AlMg) where silicon is
maintained low, e.g., less than 2.5 wt. %, magnesium can range from
2 to 10.6 wt. %. Further, in AA7XX (AlZnMg) series alloys,
magnesium can range from about 0.2 to 2.4 wt. %, and zinc can range
from about 2 to 8 wt. %. The ranges for AA2XX, AA3XX, AA4XX, AA5XX,
AA7XX and AA8XX are provided in the "Registration Record of
Aluminum Association Alloy Designations and Chemical Composition
Limits for Aluminum Alloys in the Form of Castings and Ingot",
revised February 1999, and are incorporated herein by
reference.
[0034] Typically, the AA2XX series comprises aluminum and about 3.5
to 11 wt. % Cu and smaller amounts of elements including manganese,
magnesium, silicon and nickel, depending on the alloy, all included
herein by reference as if specifically set forth. AA206, for
example, includes 4.2 to 5 wt. % Cu, 0.2 to 0.5 wt. % Mn, 0.15 to
0.35 wt. % Mg, 0.15 to 0.3 wt. % Ti, the balance comprising
aluminum incidental elements and impurities. The AA4XX series
comprises aluminum and about 3 to 13 wt. % Si with only minor
amounts of iron, copper and manganese, for example. AA443.0
comprises 4.5 to 6.0 wt. % Si, max. 0.8 wt. % Fe, max. 0.6 wt. %
Cu, max. 0.5 wt. % Mn, max. 0.05 wt. % Mn, max. 0.05 wt. % Mg, max.
0.25 wt. % Cr, max. 0.5 wt. % Zn and max. 0.25 wt. % Ti, the
remainder comprising aluminum. The AA8XX series comprises aluminum,
silicon, copper, magnesium, nickel and tin. The AA8XX can comprise
aluminum, 5.5 to 7 wt. % Sn, 0.3 to 1.5 wt. % Ni, 0.7 to 4 wt. %
cu. Some of the alloys are low in silicon, e.g., max. 0.7 wt. % Si.
AA850.0 comprises 0.7 wt. % max. Si and Fe each, 0.7 to 1.3 wt. %
Cu, 0.1 wt. % max. Mn and Mg, 0.7 to 1.3 wt. % Ni, 5.5 to 7 wt. %
Sn and max. 0.2 wt. % Ti, remainder aluminum and incidental
elements and impurities.
[0035] Typical of such alloys are Aluminum Association alloys AA356
and AA357, the compositions of which are incorporated herein by
reference.
[0036] In the hypoeutectic type aluminum-silicon alloys, a
particularly suitable aluminum alloy comprises 2 to 9 wt. % Si, 0.3
to 1.7 wt. % Mg, 0.3 to 1.2 wt. % Cu, 0.1 to 1.2 wt. % Fe,
optionally 0.01 to 2.0 wt. % Ni, 0.01 to 0.35 wt. % Cr, max. 0.2
wt. % Ti, max. 0.3 wt. % V, the balance aluminum, incidental
elements and impurities. A preferred composition comprises 2.1 to
6.5 wt. % Si, 0.35 to 1.45 wt. % Mg and 0.35 to 1.2 wt. % Cu. This
preferred composition has the advantage that it has a wide melting
range. Typically, the alloy has a solidus temperature of about
554.degree. C. and liquidus temperature of about 638.degree. C.
[0037] In the hypereutectic type aluminum alloys, particularly
suitable alloys are the AA390 type alloys as set forth by the
Aluminum Association, noted above, and incorporated herein by
reference. The hypereutectic aluminum alloy can comprise 11 to 30
wt. % Si, 0.4 to 5 wt. % Cu, 0.45 to 1.3 wt. % Mg, max. 1.5 wt. %
Fe, max. 0.6 wt. % Mn, max. 2.5 wt. % Ni, up to 0.3 wt. % Sn and up
to 0.3 wt. % Ti. Preferably, the alloy comprises 13 to 25 wt. % Si,
4 to 5 wt. % Cu and 0.4 to 0.7 wt. % Mg.
[0038] While the invention is particularly suitable for alloys as
noted, the invention can be applied to any aluminum alloy that can
be thermally transformed from a microstructure, e.g., dendritic
structure, to a globular phase. Such aluminum alloys can include
Aluminum Association Alloys 2XXX, 4XXX, 5XXX, 6XXX and 7XXX series
incorporated herein by reference.
[0039] In the AA4XXX series wrought alloys, for example, AA4011
comprises 6.5 to 7.5 wt. % Si, 0.45 to 0.7 wt. % Mg, 0.04 to 0.2
wt. % Ti, max. 0.2 wt. % Fe and Cu, max. 0.1 wt. % Mn, 0.04 to 0.07
wt. % Be, the remainder aluminum, incidental elements and
impurities. In the AA5XXX series alloys, magnesium is one of the
main alloying elements, with smaller amounts of other elements,
depending on the alloy. For example, AA5356 comprises 4.5 to 5.5
wt. % Mg, 0.05 to 0.2 wt. % Mn, 0.05 to 0.2 wt. % Cr, 0.06 to 0.2
wt. % Ti, with max. limitations on Si, Fe, Cu and Zn.
[0040] The preferred grain refiner is a Ti/B combination.
Typically, the Ti/B grain refiner is provided in a relationship of
5% Ti and 1% B. Preferably, Ti is provided in the alloys in the
range of 0.01 to 0.05 wt. % Ti, with a typical amount being about
0.02 wt. % Ti. The Ti/B grain refiner results in more uniform grain
size throughout the body of metal, and further it reduces the grain
size approximately 10 to 30%.
[0041] Connecting rods in accordance with the invention can be used
with or without shell-bearing sleeves in the large end bore. If
shell-bearing sleeves are not used, then the alloy should comprise
additional elements. For example, an aluminum alloy in accordance
with the invention can comprise 4 to 7 wt. % Si, 0.55 to 1 wt. %
Cu, 0.9 to 2 wt. % Mg, 0.1 to 1 wt. % Fe, 0.01 to 2 wt. % Ni, 0.01
to 0.25 wt. % Ti, and optionally one or more of 0.1 to 7 wt. % Sn,
0.001 to 0.2 wt. % Be, 0 to 2 wt. % Cd, 0.01 to 2 wt. % Pb and 0.01
to 2 wt. % Bi, the balance aluminum, incidental elements and
impurities. In a preferred embodiment, Fe is maintained in the
range of 0.1 to 0.6 wt. % and preferably 0.2 to 0.5 wt. % to favor
low elongation properties. A preferred alloy comprises 4.5 to 6.0
wt. % Si, 0.6 to 0.9 wt. % Cu, 1.0 to 1.5 wt. % Mg, 0.2 to 0.4 wt.
% Fe, 0.01 or 0.1 to 1.5 wt. % Ni and optionally Sn, Be, Cd, Pb or
Bi as noted above. Thus, when this alloy is cast into a connecting
rod in accordance with the invention, the elongation can be as high
as 15% but should be less than 8% and preferably less than 5%.
Typically, the elongation should be maintained in the range of 1 to
5%. Normally, the use of 0.2 to 0.6 wt. % Fe produces an elongation
in the range of 1 to 5%. Typically, the connecting rod can have a
grain size in the range of 50 to 250 .mu.m. The ranges set forth in
this application are meant to include all the numbers within the
range as if specifically set forth.
[0042] If the semi-solid body of aluminum alloy is produced from
billet as noted, the billet is preferably cast as described in my
U.S. Pat. No. 5,968,292 and also described in U.S. Pat. Nos.
4,693,298; 4,598,763; and 4,693,298, incorporated herein by
reference.
[0043] A connecting rod 2 in accordance with the invention is shown
in FIG. 2. Connecting rod 2 comprises a large end 4 having a bore 6
defined by wall 8. Further, large end 4 comprises a cap portion 10
having shoulders 12. Shoulders 12 are provided for drilling and
tapping to provide openings 14 (shown in outline form) for bolts to
secure cap portion 10 to arm member 16 after cap portion 10 is
removed by fracturing. Crevices or notches 20 in wall 22 are
provided for purposes of providing a fracture plain A-A across bore
6. Connecting rod 2 further comprises arm member 16 which extends
from lower portion 24 (below fracture plain A-A) to small end 30
comprising small bore 32 suitable for a wrist pin and bearing
utilized for securing to a piston of an internal combustion
engine.
[0044] It will be noted that crevices or notches 20 may be formed
in large end 4 when the rod is cast or the crevices or notches may
be machined in after casting. Further, crevices or notches 20 are
illustrative and can take away form in wall 8.
[0045] After aging, e.g., to a T5 condition, solution heat
treating, quenching and aging, holes or openings 14 may be drilled
and the portion of bore 14 in wall 8 below fracture plane A-A
tapped or threaded to receive bolts to secure cap portion 10 after
fracturing. Further, after solution heat treating, quenching and
aging, cap portion 10 is fractured across fracture plane A-A to
separate cap portion 10 from arm or member 16, as shown in FIG. 3.
Fracturing is facilitated by the globular microstructure and
provides for improved remateable surfaces 40 and 42 which are
substantially exactly remateable having complementary peaks and
recesses which permit the refastening of cap portion 10 to arm
member 16 by bolts to provide the position or relationship of cap
portion 10 to arm member 16 substantially the same as before
fracturing. FIG. 4 shows cap portion 10 and arm member 16
reassembly and fastened together using bolts 50.
[0046] While it is preferred to fracture cap portion 10 after
solution heat treating, quenching and aging, cap portion 10 may be
fractured before solution heat treating or intermediate any of the
steps of solution heat treating, quenching and aging. Further, with
reference to the alloys referred to herein, it is preferred to
adjust the alloy composition to favor fracturing. That is, it is
preferred to use alloy compositions having low elongation
properties to favor fracturing.
[0047] Fracturing of cap portion 10 can be made to occur in any
manner that provides remateable surfaces 40 and 42. Apparatus and
procedures for fracturing cap portion 10 across fracture plane A-A
are disclosed in U.S. Pat. Nos. 5,105,538; 4,936,163; 4,860,419;
and 4,569,109.
[0048] Connecting rods fabricated in accordance with the present
invention are preferably solution heat treated to dissolve soluble
elements such as magnesium and silicon which unite to form
Mg.sub.2Si, for example, to improve tensile properties. The
solution heat treatment is preferably accomplished in a temperature
range of 800.degree.-1080.degree. F., typically
850.degree.-1000.degree. F. or 1050.degree. F. The time at
temperature for solution heat treatment purposes can range from 0.1
to 12 hours. However, solution heat treatment should be controlled
so as to avoid substantial loss of the globular grain structure and
the redevelopment of the dendritic structure. After solution heat
treatment, the connecting rods are rapidly quenched using cold
water, for example, to prevent or minimize uncontrolled
precipitation of the strengthening phases. Quench rates of at least
50.degree. F. per second may be used.
[0049] After the connecting rods are quenched, they may be subject
to aging treatments to improve strength. Thus, the connecting rods
can be subject to underaging or overaging treatments including
natural aging. The aging treatment may include multiple aging
steps, including two or three aging steps. In two or more aging
steps, the first step may include aging at a relatively high
temperature followed by a lower temperature. Or, the first step may
be relatively low followed by a relatively high aging step. In
three-step aging, high and low combination aging steps may be
employed. In single-step aging, the quenched connecting rod is held
at a temperature in the range of 200.degree.-450.degree. F.,
preferably 300.degree.-400.degree. F. for a period sufficient to
increase strength. Times for aging at these temperatures can range
from 1 to 24 hours and typically 8 to 24 hours.
[0050] Connecting rods in accordance with the invention have
improved tensile strength compared to the same alloy provided by
conventional casting. That is, fabricating a connecting rod as
described with respect to the invention can improve the tensile
strength by 50 to 100%, depending on the alloy used. For example,
tensile strengths of 40 to 50 KSI and yield strengths of 35 to 48
KSI are attainable. Comparable strengths the same alloy provided by
conventional casting ranges from 20 to 35 KSI.
[0051] The globular microstructure of the connecting rod in
accordance with the invention can be used have a hardness of about
75 to 125 Vickers DPH hardness and the lower melting eutectic
matrix can have a hardness of 100 to 175 Vickers DPH hardness.
[0052] It should be noted that connecting rods fabricated in
accordance with the invention be used with or without shell-bearing
sleeves. If used without shell-bearing sleeves, then the large end
bore defined by wall 8 is machined to the required size or diameter
for use with an engine crank. Shell bearing sleeves 52 are shown in
FIG. 5 which is a partial view of the connecting rod showing the
large end bore. Typically, shell-bearing sleeves 52 are
semi-circular and extend from one fracture surface to the opposite
fracture surface and are anchored in the bore to prevent turning
during rotation of the crank.
[0053] While the invention has been described in terms of preferred
embodiments, the claims appended hereto are intended to encompass
other embodiments which fall within the spirit of the
invention.
* * * * *