U.S. patent application number 14/887423 was filed with the patent office on 2016-05-05 for aluminum bar and production method thereof.
The applicant listed for this patent is SHOWA DENKO K.K.. Invention is credited to Tomoya HAYAKAWA.
Application Number | 20160121381 14/887423 |
Document ID | / |
Family ID | 55851596 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160121381 |
Kind Code |
A1 |
HAYAKAWA; Tomoya |
May 5, 2016 |
ALUMINUM BAR AND PRODUCTION METHOD THEREOF
Abstract
A production method of an aluminum bar includes a surface
pressing step of pressing a surface of an aluminum bar with
pressure rollers. A pressing force of the pressure rollers in the
surface processing step is set within a range of 1.5 Fc to 4.0 Fc,
where, in a relationship between a pressing force of the pressure
rollers to the aluminum bar and a straightness of the aluminum bar,
when a boundary point at which a section where the straightness of
the aluminum bar improves as the pressing force of the pressure
rollers increases shifts to a section where the straightness does
not change as the pressing force of the pressure rollers increases
is a straightness saturation point, and the pressing force of the
pressure rollers at the straightness saturation point is "Fc".
Inventors: |
HAYAKAWA; Tomoya;
(Kitakata-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHOWA DENKO K.K. |
Tokyo |
|
JP |
|
|
Family ID: |
55851596 |
Appl. No.: |
14/887423 |
Filed: |
October 20, 2015 |
Current U.S.
Class: |
72/252.5 |
Current CPC
Class: |
B21B 13/023 20130101;
C22C 21/02 20130101; B21J 5/002 20130101; B21B 2003/001
20130101 |
International
Class: |
B21B 3/00 20060101
B21B003/00; C22C 21/02 20060101 C22C021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2014 |
JP |
2014-221296 |
Claims
1. A production method of an aluminum bar, comprising: a surface
pressing step of pressing a surface of an aluminum bar with
pressure rollers, wherein a pressing force of the pressure rollers
in the surface processing step is set within a range of 1.5 Fc to
4.0 Fc, where, in a relationship between a pressing force of the
pressure rollers to the aluminum bar and a straightness of the
aluminum bar, when a boundary point at which a section where the
straightness of the aluminum bar improves as the pressing force of
the pressure rollers increases shifts to a section where the
straightness does not change as the pressing force of the pressure
rollers increases is a straightness saturation point, and the
pressing force of the pressure rollers at the straightness
saturation point is "Fc".
2. The production method of an aluminum bar as recited in claim 1,
wherein a pair of straightening rolls are used as the pressure
rollers, and wherein a straightening step for straightening an
aluminum bar by passing the aluminum bar between the pair of
rotating straightening rolls is also used as the surface pressing
step.
3. The production method of an aluminum bar as recited in claim 1,
further comprising a peeling step of cutting and removing an outer
peripheral surface of the aluminum bar before performing the
surface pressing step.
4. The production method of an aluminum bar as recited in claim 1,
wherein the aluminum bar is an aluminum member to be used as a
forging blank.
5. An aluminum bar produced by the production method as recited in
claim 1, wherein, among two points set on a load curve showing a
relationship between a cutting level and a load length for a
contour curve on a surface of the aluminum bar, when two points in
which an interval of the load length becomes 60% of the entire
length of the load length are a pair of measuring points, a minimum
value of a slope of a straight line passing the pair of measuring
points is 0.5 or less.
Description
CROSS-REFERENCE TO THE RELATED APPLICATIONS
[0001] The present application claims priority to Japanese Patent
Application No. 2014-221296 filed on Oct. 30, 2014, the entire
disclosure of which is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Some embodiments of the present invention relate to a
production method of an aluminum bar in which a bar-shaped aluminum
material is pressed by pressure rollers and an aluminum bar
produced by the method. In this disclosure, the term "aluminum
(Al)" is used to include the meaning of aluminum alloys (Al
alloys).
[0004] 2. Description of the Related Art
[0005] The following description of related art sets forth the
inventor's knowledge of related art and certain problems therein
and should not be construed as an admission of knowledge in the
prior art.
[0006] A round bar-shaped aluminum bar which is used as a forging
blank is made of, for example, a continuously cast bar. In
producing a continuously cast bar, as described in Patent Document
1 (Japanese Unexamined Laid-open Patent Application Publication No.
2004-314176), a consistent production line is well known, in which
a continuously cast bar (bar-shaped member) obtained by casting is
sequentially subjected to a cutting step, a heat treatment step
(homogenization treatment step), a pre-straightening step (first
straightening step), a peeling step (surface cutting step), a
post-straightening step (second straightening step), and a visual
inspection step, and then packed and carried out.
[0007] In the consistent production line, the aluminum bar in which
the outer peripheral surface was removed in the peeling step is
straightened to correct the bend using straightening rolls as
described in the aforementioned Patent Document 1 or Patent
Document 2 (Japanese Patent No. 5211928) in a post-straightening
step to increase the inspection accuracy in the inspection step.
However, in the aforementioned production line, since the bar will
not be especially subjected to a surface treatment after the
peeling step, damage occurred after the peeling step remain. For
this reason, such damage may sometimes cause the following
inconveniences.
[0008] In the meantime, in the aforementioned production line for a
continuously cast bar, for example, a rolling conveyance system is
used to convey the aluminum bar between steps.
[0009] FIG. 6A is a side view showing a rolling conveyance device.
As shown in this figure, this rolling conveyance device is equipped
with a frame 1 inclining downward toward the conveyance direction,
and a plurality of round bar-shaped aluminum bars W set on the
frame 1 are contiguously rolled by their self-weights and
conveyed.
[0010] As shown in FIG. 6A, in such a rolling conveyance, in
theory, adjacent preceding and following bars W and W are in line
contact with each other along a line in the axial direction
(longitudinal direction). However, in reality, as shown in FIG. 6B
and FIG. 6C, they are not in line contact, but in point contact
with each other at a number of points along a line in the axial
direction depending on the respective bent states and/or respective
surface states of the bars W.
[0011] Here, as shown in FIG. 6B and FIG. 6C, when a contact point
to which the strongest force is acting among contact points of
adjacent preceding and following bars W and W is referred to as
"Wc", at the contact point Wc, the front side (preceding) bar W
moves upward and the rear side (following) bar W moves downward. In
other words, since the front (preceding) and rear (following) bars
W and W are moving in opposite directions at the contact point Wc,
a force is applied to the contact point Wc in the circumferential
direction. The force applied to the contact point Wc is not only
affected by the weight of one rear (following) side bar W, but also
is affected by the total weight of all bars W existing on the rear
side with respect to the contact point Wc, so it is a considerable
force. Specifically, when the total weight of bars W on the rear
side with respect to the contact point Wc is "m", the gravitational
acceleration is "g", and the force obtained when the inclination
angle of the frame 1 is ".theta." is "F", there is a correlation of
F=mgsin .theta.. This force F is applied to the contact point
Wc.
[0012] In this way, since a large force is acting on the contact
point Wc, when a surface of either one of the bars W and W
positioned adjacently at a position corresponding to the contact
point Wc has a protruding damage which occurred in a previous step,
the protruding damage cuts into the surface of the other bar W to
cause a scratch by the force in the circumferential direction,
resulting in new damage on the surface of the other bar W.
[0013] FIGS. 7A and 7B shows a typical example of scratch damage.
As shown in this figure, the scratch damage 2 is not a simple
spot-shaped scratch, but a scratch that spreads in a wide range in
a manner as to extend on the circumferential surface of the bar,
starting from a portion where the scratch occurred at the contact
point Wc. In detail, the damage 2 includes a concave part 21 formed
by gouging a part of the surface of the bar and a convex part 22
plastically deformed by moving the gouged part of the surface of
the bar. Further, for the outer diameter dimension of the damage 2,
generally, the average value of the height .alpha.2 is 50 .mu.m to
300 .mu.m, the average value of the starting point width .beta.2 is
100 .mu.m to 500 .mu.m, and the average value of the length
.gamma.2 is 20 .mu.m to 50 .mu.m.
[0014] Since the newly occurred damage 2 as mentioned above
includes a convex part 22, the convex part 22 becomes a starting
point of new damage on an adjacent bar W in contact with the bar W
having the convex part 22, which causes damage 2 on another
adjacent bar W in the same manner as described above. In this way,
the damage 2 is sequentially and continuously transferred to
another adjacent bar W. As a result, occurrence of damage 2 spread
endlessly on a number of bars W arranged on the frame 1.
[0015] On the other hand, in the case of using a bar W having
damage 2 on the surface as a forging blank, the damage 2 becomes a
starting point to cause a breakage at the time of forging, or
remains on the surface of a forging blank even after forging. Above
all, in cases where damage 2 having a certain depth remains, the
damage 2 may become a forging defect.
[0016] Particularly, as shown in FIG. 7, when there is damage 2
extending in the circumferential direction on the outer
circumferential surface of the forging blank, it is not preferable
in a forging process.
[0017] That is, in many cases, in order to improve dimensional
accuracy, a surface of a forging blank is subjected to a cutting
process after forging. With this cutting process, to assuredly
remove the damage, the cutting allowance (depth of the cutting
process) needs to be larger than the depth of the damage. However,
from the viewpoint of improving the material yield, reducing the
processing labor, etc., the cutting allowance is preferably as
small as possible. Further, the cutting allowance differs depending
on the portion of the forging blank. Further, in a portion where
the required dimensional accuracy is not strict, the forged
processed surface may be kept as it is without performing a cutting
process when the dimensional tolerance is permitted. In this way,
there exist uncut portions or almost uncut portions (hereinafter
collectively referred to as "non-cut portion(s)") in the forging
blank. On the other hand, in the case of the scratch damage 2 as
mentioned above, since the dimension .gamma.2 of the damage 2 in
the circumferential direction is long, there is an increased
possibility that a part of the damage 2 is present in the non-cut
portion. Therefore, it is not preferable since it is difficult to
assuredly cut and remove the damage 2 remaining on the forging
blank and there is an increased possibility that a poor appearance
may occur on the final product after cutting.
[0018] Further, in the damage 2 having such a convex part 22 as
described above, the convex part 22 is pressed and crushed at the
time of forging and a plastically deformed part may occur in a
manner as to cover the surface of the forging blank in a layer
form. The covering part in such a layer form is not preferable
since there is a risk that lap defects such as minute cracks may
occur.
[0019] The description herein of advantages and disadvantages of
various features, embodiments, methods, and apparatus disclosed in
other publications is in no way intended to limit the present
invention. For example, certain features of the preferred described
embodiments of the invention may be capable of overcoming certain
disadvantages and/or providing certain advantages, such as, e.g.,
disadvantages and/or advantages discussed herein, while retaining
some or all of the features, embodiments, methods, and apparatus
disclosed therein.
SUMMARY OF THE INVENTION
[0020] The disclosed embodiments of this disclosure have been
developed in view of the above-mentioned and/or other problems in
the related art. The disclosed embodiments of this disclosure can
significantly improve upon existing methods and/or apparatuses.
[0021] Some embodiments of the present invention were made in view
of the aforementioned problems, and aim to provide a production
method of an aluminum bar capable of preventing occurrence of
damage by a surface pressing process using pressure rollers, and
also aim to provide an aluminum bar produced by the method.
[0022] The other purposes and advantages of some embodiments of the
present invention will be made apparent from the following
preferred embodiments.
[0023] To achieve the aforementioned purposes, the inventors
diligently made an effort to repeatedly conduct thorough
experiments and research regarding a relationship between a
correction process (surface pressing process) using straightening
rolls and a surface condition of an aluminum bar.
[0024] As a result, by adding specific configurations to the
surface pressing process, a configuration in which occurrence of
detrimental damage can be prevented and no transfer of the damage
due to rolling and carrying is recognized was discovered, and the
present invention was completed.
[0025] That is, some embodiments of the present invention have the
following structure.
[0026] [1] A production method of an aluminum bar, comprising:
[0027] a surface pressing step of pressing a surface of an aluminum
bar with pressure rollers,
[0028] wherein a pressing force of the pressure rollers in the
surface processing step is set within a range of 1.5 Fc to 4.0
Fc,
[0029] where, in a relationship between a pressing force of the
pressure rollers to the aluminum bar and a straightness of the
aluminum bar, when a boundary point at which a section where the
straightness of the aluminum bar improves as the pressing force of
the pressure rollers increases shifts to a section where the
straightness does not change as the pressing force of the pressure
rollers increases is a straightness saturation point, and the
pressing force of the pressure rollers at the straightness
saturation point is "Fc".
[0030] [2] The production method of an aluminum bar as recited in
the aforementioned Item [1],
[0031] wherein a pair of straightening rolls are used as the
pressure rollers, and
[0032] wherein a straightening step for straightening an aluminum
bar by passing the aluminum bar between the pair of rotating
straightening rolls is also used as the surface pressing step.
[0033] [3] The production method of an aluminum bar as recited in
the aforementioned Item [1] or [2], further comprising a peeling
step of cutting and removing an outer peripheral surface of the
aluminum bar before performing the surface pressing step.
[0034] [4] The production method of an aluminum bar as recited in
any one of the aforementioned Items [1] to [3], wherein the
aluminum bar is an aluminum member to be used as a forging
blank.
[0035] [5] An aluminum bar produced by the production method as
recited in any one of the aforementioned Items [1] to [4], wherein,
among two points set on a load curve showing a relationship between
a cutting level and a load length for a contour curve on a surface
of the aluminum bar, when two points in which an interval of the
load length becomes 60% of the entire length of the load length are
a pair of measuring points, a minimum value of a slope of a
straight line passing the pair of measuring points is 0.5 or
less.
[0036] According to the production method of an aluminum bar as
recited in the aforementioned Item [1], since a surface pressing
treatment is performed by setting a pressing force to the surface
of the aluminum bar within a specific range, the surface of the
aluminum bar becomes in a good state, and damage can be prevented
from occurring on the surface, and problems such as deformation of
the aluminum bar and occurrence of roll transfer marks can also be
assuredly prevented.
[0037] According to the production method of an aluminum bar as
recited in the aforementioned Item [2], the surface of the aluminum
bar can be finished in a good state by the straightening step for
straightening.
[0038] According to the production method of an aluminum bar as
recited in the aforementioned Item [3], the surface of the aluminum
bar can be maintained in a good state after cutting the surface of
the aluminum bar.
[0039] According to the production method of an aluminum bar as
recited in the aforementioned Item [4], a high quality forged
product can be assuredly obtained.
[0040] According to the aluminum bar as recited in the
aforementioned Item [5], the aluminum bar can have a good surface
condition, and can be suitably used as a forging blank, etc.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] Embodiments of the present invention are shown by way of
example, and not limitation, in the accompanying figures.
[0042] FIG. 1A is a plane view showing a roll straightening machine
used for a production method of an aluminum bar according to an
embodiment of the present invention.
[0043] FIG. 1B is a side view showing the roll straightening
machine according to the embodiment of the present invention.
[0044] FIG. 2 is a graph showing a relationship between a
straightening rolling force and a surface profile, etc.
[0045] FIG. 3 is a graph showing a load curve for explaining the
surface profile according to the embodiment.
[0046] FIG. 4 is a graph showing a load curve of an aluminum bar of
Example 1.
[0047] FIG. 5 is a graph showing a load curve of an aluminum bar of
Comparative Example 1.
[0048] FIG. 6A is a side view showing a rolling conveyance device
according to a related art.
[0049] FIG. 6B is a cross-sectional view showing adjacent aluminum
bars on the rolling conveyance device according to the related
art.
[0050] FIG. 6C is an enlarged cross-sectional view showing contour
lines of the adjacent bars at a contact point thereof on the
rolling conveyance device.
[0051] FIGS. 7A and 7B show damage and its periphery, the damage
being formed on a surface of an aluminum bar, wherein FIG. 7A is a
plane view thereof and FIG. 7B is a cross-sectional view
thereof.
EMBODIMENT FOR CARRYING OUT THE INVENTION
[0052] In the following paragraphs, some embodiments of the present
invention will be described by way of example and not limitation.
It should be understood based on this disclosure that various other
modifications can be made by those in the art based on these
illustrated embodiments.
[0053] An aluminum bar to be produced using a production method
according to an embodiment of the present invention is used as a
material to be forged (which is referred to as "forging blank" in
this disclosure). The material of the aluminum bar of this
embodiment is not especially limited as long as it is made of pure
aluminum or aluminum alloy. Among other things, an aluminum alloy
of hypereutectic Si (Si content rate of 12 to 18 wt %) which is an
especially hard-to-cut material, or an aluminum alloy which is low
in so-called "0-material" (i.e., annealed aluminum material)
hardness in which damage easily occurs, e.g., 1000 series, 3000
series, 5000 series, 6000 series JIS alloy number aluminum alloys,
can be suitably used.
[0054] The production method of this embodiment is equipped with a
consistent production line for producing a continuously cast bar.
The production line includes a casting step for obtaining a
continuously cast bar, a cutting step for cutting the continuously
cast bar, a heat treatment step (homogenization treatment step) for
subjecting the cut continuously cast bar to a heat treatment, a
pre-straightening step (first straightening step) for straightening
the heat-treated continuously cast bar, a peeling step for cutting
and removing the surface of the pre-straightened continuously cast
bar, a post-straightening step (second straightening step) for
correcting the bend of the continuously cast bar in which the
surface is in contact, a visual inspection step for inspecting the
post-straightened continuously cast bar, and a packing step for
packing the inspected continuously cast bar.
[0055] The peeling step in this embodiment is performed for the
purpose of removing the inverse segregation layer on the surface.
The peeling step is a process to cut about 1 mm to 3 mm of the
surface of the bar, and it can be performed using a peeling device,
a lathe device, etc. In this embodiment, it is preferable that the
surface roughness (Ra) of the aluminum bar is adjusted to 5 .mu.m
or less with this peeling step.
[0056] In this embodiment, the post-straightening step is performed
after the peeling step, but the post-straightening step has a
specific configuration.
[0057] FIG. 1A and FIG. 1B show a roll straightening machine 5 used
in the post-straightening step. As shown in both the figures, the
roll straightening machine 5 is equipped with a pair of upper and
lower straightening rolls (which is also called "correction rolls"
(pressure rollers) 51 and 52 capable of sandwiching an aluminum bar
W. The pair of straightening rolls 51 and 52 is arranged so as to
intersect in a planar view (see FIG. 1A).
[0058] The upper straightening roll (roller) 51 has a drum-shape in
which the circumferential surface curves in a concave shape. The
lower straightening roll (roller) 52 has a drum-shape in which the
circumferential surface bends in a convex shape.
[0059] To process an aluminum bar W using this roll straightening
machine 5, at least one of the pair of straightening rolls 51 and
52 is rotated by a driving mechanism (not illustrated), and by
introducing the aluminum bar W between the pair of straightening
rolls 51 and 52, the aluminum bar W is carried in the conveyance
direction (left direction in FIG. 1A) while rotating. At the time
of the conveyance, the surface pressing process is performed since
the surface of the aluminum bar W is pressed by the pair of
straightening rolls 51 and 52, and at the same time, the bend is
corrected to improve the straightness.
[0060] The distance between the pair of straightening rolls 51 and
52 (roll distance) is configured to be adjustable, and is adjusted
according to the outer diameter dimension of the aluminum bar W,
etc.
[0061] Further, in a planar view (see FIG. 1A), the angle (roll
angle) R.beta. of the rotational axis of the upper straightening
roll 51 and the angle (roll angle) R.alpha. of the rotational axis
of the lower roll 52 with respect to the conveyance axis of the
aluminum bar W are configured to be adjustable. With this
adjustment, the contact distance of each of the straightening rolls
51 and 52 and the aluminum bar W can be adjusted. Furthermore, by
adjusting the contact distance in this way, the surface pressing
process can be performed efficiently even when the cross-section of
the aluminum bar W is not a perfect circle.
[0062] In this embodiment, the rolling force (rolling load) of the
straightening rolls 51 and 52 against the aluminum bar W can be
adjusted by the roll distance (roll position) and the roll angles
R.alpha. and R.beta.. Furthermore, the pressing force (processing
degree) of the straightening rolls 51 and 52 to the aluminum bar W
is based on the aforementioned rolling force (rolling load) and the
rotation number of the straightening rolls 51 and 52, and
therefore, the terms "pressing force" and "rolling force" are not
used as a synonym.
[0063] The inventors have found the fact or configuration that, in
the post-straightening step in the aforementioned series of
production line, by setting the pressing force (processing degree)
of the straightening rolls 51 and 52 within a specific range, the
bend can be corrected and the surface of the aluminum bar W can be
adjusted to a good state, which in turn can prevent occurrence of
detrimental damage. Hereinafter, the specific configuration will be
explained.
[0064] FIG. 2 is a graph showing the relationship between the
straightness (degree of correction), the surface profile and the
deformation amount of the outer diameter/length (deformation amount
of the outer diameter/length) of the aluminum bar W and the
straightening rolling force (rolling load) in the
post-straightening step. In this graph, the vertical axis shows the
straightness, the surface profile and the deformation amount of the
outer diameter/length, and the values become better toward the
bottom side. The horizontal axis shows the straightening rolling
force and becomes larger toward the right side. Furthermore, for
the curved lines in this graph, the alternate long and short dash
line shows the straightness, the solid line shows the surface
profile, and the short dashed line shows the deformation amount of
the outer diameter/length. Further, the value of the rolling force
in this graph is shown as a ratio when the rolling force at a
later-described roundness saturation point is "1".
[0065] Focusing on the straightness (degree of correction) as shown
by the alternate long and short dashed line in FIG. 2, the
numerical value of the straightness gradually decreases and the
straightness gradually improves in a section where the rolling
force is from "0" to "1". However, in a section in which the
rolling force is more than "1" ("1" to "5"), the straightness does
not change and is constant although the rolling force is
increasing. In this embodiment, a boundary point where the
straightness transfers from a section in which the straightness
decreases (changes) to a section in which the straightness is
constant (does not change) will be referred to as "roundness
saturation point (straightening degree saturation point)". Here, a
section after the roundness saturation point (roundness saturation
range) is a section in which the roundness shows little change even
when the rolling force increases, for example, a section in which
the deformation amount of the roundness is 0.2 mm or less per meter
(mm/m or less).
[0066] Next, focusing on the deformation amount of the outer
diameter/length as shown by the short dashed line in FIG. 2, the
deformation amount of the outer diameter/length gradually increases
along with the increase in the rolling force. When the rolling
force is set in a section in which the rolling force is from "4" to
"5" (overstraightening range), the aluminum bar becomes in an
overstraightened state, which causes occurrence of a detrimental
transfer mark on the aluminum bar W by the straightening rolls 51
and 52, a detrimental deformation, such as elongation of the bar W
due to the reduction of the outer diameter thereof. In other words,
when the rolling force is "4" or less, occurrence of a detrimental
transfer mark, a deformation, etc., can be controlled.
[0067] Under these conditions, in a typical straightening step, it
is common to adjust the rolling force by the straightening rolls to
around "1" for the purpose of prevention of overstraightening,
alleviation of labor, improvement of work productivity, reduction
of load on a workpiece, etc.
[0068] However, the inventors were not satisfied with the
conditions, and repeated detailed experiments and research. As a
result, the inventors found that, with an innovative configuration
that the rolling force of the straightening rolls 51 and 52 is set
to be significantly larger than around "1", the surface of the
aluminum bar W can be pressed and processed to have a good surface
profile (good state) and occurrence of damage can be effectively
prevented while preventing occurrence of a roll transfer mark and a
deformation of the aluminum bar W.
[0069] In this embodiment, the surface profile is defined by a load
curve parameter tan(P.theta.min) which is obtained based on the
load curve of the surface of the aluminum bar W after the
straightening. The details will be explained later. In this
embodiment, in the aluminum bar W in which the surface profile is
adjusted so as to fall within a predetermined range, the state of
the surface becomes good and occurrence of damage can be
prevented.
[0070] In the graph of FIG. 2, focusing on the surface profile
shown by the solid line, in a section in which the rolling force is
from "0" to "around 1.8", the surface profile gradually decreases,
i.e., improves. However, in a section in which the rolling force is
larger than "around 1.8", the surface profile does not change and
is constant although the rolling force is increasing. In this
embodiment, the boundary point where the surface profile transfers
from a section in which the surface profile decreases to a section
in which the surface profile is constant as the rolling force
increases will be referred to as the "surface profile saturation
point". Further, according to the graph in FIG. 2, at the time when
the rolling force is "1.5", the surface profile is at the upper
limit in a suitable range, and when the rolling force is "1.5" or
more, the surface profile is in a good range (section).
[0071] According to the aforementioned results, when the rolling
force is "1.5" or more, a good surface profile can be obtained and
occurrence of damage can be effectively prevented. Further, when
the rolling force is "4.0" or less, a detrimental transfer mark, a
deformation, etc., by the straightening rolls can be suppressed.
Therefore, in this embodiment, in the straightening step, the
rolling force of the straightening rolls needs to be set to
1.5.times."1" to 4.0.times."1", with reference to the rolling force
"1" at the straightness saturation point (straightening degree
saturation point).
[0072] Here, the section in which the rolling force is
1.5.times."1" to 4.0.times."1" is also referred to as a
semi-overstraightened range, and as explaining repeatedly, an
aluminum bar having a good surface state can be obtained by
performing a straightening process (surface pressing process) with
a rolling force in such a range.
[0073] Specifically, as will be explained in the following
Examples, in the case of a 4000 series aluminum alloy bar having a
diameter of .phi.25 mm, the roundness saturation point becomes "1"
when the rolling force of the straightening rolls is 0.5 ton
(0.5.times.10.sup.3.times.9.80 N), it becomes a
semi-overstraightened range in a section where the rolling force is
0.75 ton (0.75.times.10.sup.3.times.9.80 N) to 2.0 ton
(2.0.times.10.sup.3.times.9.80 N). When the rolling force is set in
this range, an aluminum bar having a good surface profile can be
obtained. Further, in a section where the rolling force exceeds 2.0
ton (2.0.times.10.sup.3.times.9.80 N), it becomes an
overstraightening range. When the rolling force is set within this
range, a detrimental deformation may occur due to occurrence of
stretching in the aluminum bar or reduction of the diameter of the
bar, and/or a detrimental roll transfer mark may occur on the
aluminum bar.
[0074] In this embodiment, the surface profile is determined by the
pressing force (processing degree) applied to the surface of the
aluminum bar W. As explained above, the pressing force is affected
not only by the rolling force (rolling load and roller angle) of
the straightening rolls, but also by the number of rotations per
unit time of the straightening rolls. However, since the pressing
force and the rolling force are correlated, a relational expression
of the pressing force and the surface profile can be derived based
on the relational expression of the rolling force and the surface
profile.
[0075] That is, when the pressing force by the straightening rolls
at the straightness saturation point is "Fc", in the straightening
step, by setting the pressing force by the straightening rolls
within a range of 1.5.times."Fc" to 4.0.times."Fc", an aluminum bar
having a good surface profile can be obtained, which enables to
prevent occurrence of damage, and also enables to assuredly prevent
occurrence of inconvenience such as a detrimental roll transfer
mark, a deformation of the outer diameter, etc.
[0076] For example, as shown by the symbols in parentheses in FIG.
2, when the pressing force is set to "Fb" and "Fa", which are,
respectively, two times and four times the straightness saturation
point "Fc", an aluminum bar having a good surface profile can be
obtained. When the pressing force is set to "Fd" which is five
times the straightness saturation point "Fc", it becomes difficult
to obtain an aluminum bar having a good surface profile.
[0077] As a specific example, for a cylinder shaped aluminum bar
having a diameter (outer diameter) of .phi.23 mm, when the roll
angles R.alpha. and R.beta. of the straightening rolls 51 and 52
are set to 13.degree. to 15.degree., by adjusting the roll distance
in accordance with the aluminum bar and setting the roll rotational
number to 600 rpm to 1,200 rpm, the pressing force can be set so as
to fall within the straightness saturation range (correction degree
saturation range) which is a section beyond the straightness
saturation point (correction degree saturation point) Fc. Further,
when the pressing force is increased by narrowing the roll distance
and/or reducing both the roll angles R.alpha. and R.beta., it can
be adjusted to the semi-overstraightened range (suitable range),
which enables to obtain an aluminum bar having a good surface
profile (1.5.times.Fc or more).
[0078] As described above, in this embodiment, by setting the
pressing force within the aforementioned specific range to perform
the post-correction step, even when surface treated aluminum bars W
are rolled and carried by a rolling conveyance device as shown in
FIG. 6A, damage can be prevented from being occurred on the
surface, and an inconvenience such as transferring of damage
between aluminum bars W can be assuredly prevented. For example, in
an aluminum bar W obtained by this embodiment, the number of
detrimental damage per 1 m length becomes 0.1 pieces
(pieces/m).
[0079] In this embodiment, the aluminum bar W will be used as a
forging blank through an inspection step and a binding and packing
step after performing a post-straightening step. For example, after
subjecting the aluminum bar as a forging blank to a cutting step, a
preliminary heating step and a lubricant treatment step, the
forging blank is introduced into a mold in a forging device in the
forging step and molded to produce a predetermined forging
blank.
[0080] A forging blank obtained as mentioned above can prevent
occurrence of damage on the surface, and also can prevent
occurrence of a plastically deformed part in which a convex shaped
damage is crushed into a layer shape so as to be covering, which in
turn can prevent occurrence of a lap defect such as a minute crack.
Therefore, a high quality forged product can be assuredly
obtained.
[0081] FIG. 3 is a graph showing a load curve for explaining a
surface profile according to this embodiment.
[0082] This curve line in this graph is a load curve (bearing
curve) on a surface of an aluminum bar after straightening (after
pressing), and is stipulated in JIS B0671. In this graph, the
vertical axis shows a cutting level (%) to a contour curve of a
surface shape, and the horizontal axis shows a load length rate (%)
of the contour curve. Specifically, the horizontal axis is a ratio
of a load length of a contour curve element to an evaluation length
(entire length of the load length) of each cutting level. Further,
the cutting level and the load length may be denoted with a unit of
length such as .mu.m, etc.
[0083] In this embodiment, among two points on the load curve, two
points (for example, "A1, A1", "A2, A2", etc.) in which the
interval of the load length (difference in the load length) is 60%
of the length of the entire length (100%) of the evaluation load
length (evaluation length) are referred to as "pair of measurement
points". The minimum value of the slope (tangent of the straight
line and the horizontal axis (X axis)) of the straight line (line
segment A1-A1, line segment A2-A2, etc.) passing through the pair
of measurement points is defined as "surface profile (load curve
parameter)". In other words, the angle value of a secant (line
segment A1-A1, line segment A2-A2, etc.) passing through two points
("A1, A1", "A2, A2", etc.) on the load curve in which the interval
of the load length is 60% of the entire length (100%) of the load
length is referred to as "P .theta.". And among the slopes of
secants "tan(P .theta.)", the slope of the secant having the least
steep slope "tan(P.theta.min)" is defined as "surface profile (load
curve parameter)".
[0084] Specifically, in the graph of FIG. 3, among the straight
lines (secants) passing through the pair of measurement points, the
inclination angle "P.theta.min" of the line segment A1-A1 is the
smallest, and the slope of the line segment A1-A1
"tan(P.theta.min)" becomes the surface profile (load curve
parameter) of the aluminum bar.
[0085] In this embodiment, when the load curve parameter
tan(P.theta.min) is 0.5 or less, the surface state of the surface
profile becomes good and occurrence of damage can be prevented.
Further, when the load curve parameter tan(P.theta.min) exceeds
0.5, the surface state of the surface profile becomes insufficient,
and damage may occur.
[0086] Therefore, in this embodiment, in the aforementioned
post-straightening step, by setting the pressing force by the
straightening rolls to a range of 1.5 Fc to 4.0 Fc as described, an
aluminum bar having a good surface profile in which the load curve
parameter tan(P.theta.min) is 0.5 or less can be produced.
[0087] In this embodiment, a continuously cast bar is used as an
aluminum bar, but in the present invention, bars other than
continuously cast bars can be used. For example, in the present
invention, an extruded bar obtained by extruding a cast billet can
also be used.
[0088] Further, in the aforementioned embodiment, a case in which a
pressing step is also used as a straightening step was explained,
but it is not limited to that. In the present invention, a surface
pressing step can be performed separately from the straightening
step (post-straightening step).
EXAMPLES
[0089] An Al--Si--Cu--Mg alloy (Si: 11%, Cu: 4.5%, Mg: 0.7%, and
the balance being Al and inevitable impurities) was subjected to
continuous casting to obtain a cylinder shaped aluminum alloy
continuously cast bar having a diameter of 30 mm.
[0090] The surface of the aluminum alloy continuously cast bar was
removed by a cutting process to prepare a cut (unstraightened)
aluminum alloy bar (aluminum bar).
TABLE-US-00001 TABLE 1 Surface Surface Pressing State Process Load
Curve Effect of Damage Diameter/Length Processing Pressing Pressing
Parameter Occurrence Dimensional Change performed Point Force *1
tan(P.theta.min) Prevention Forging Defect Straightness Roll
Transfer Mark Ex. 1 Yes Fa 4 0.42 .smallcircle. .smallcircle.
.smallcircle. .smallcircle. Ex. 2 Yes Fb 2 0.38 .smallcircle.
.smallcircle. .smallcircle. .smallcircle. Com. Ex. 1 No -- -- 0.7 x
x .DELTA. .smallcircle. Com. Ex. 2 Yes Fc 1 0.61 .DELTA. .DELTA.
.smallcircle. .smallcircle. Com. Ex. 3 Yes Fd 5 0.43 .smallcircle.
.smallcircle. .smallcircle. x *1: The pressing force is shown as a
ratio when the saturation point of the straightness is 1.
Example 1
[0091] The aforementioned cut aluminum alloy bar was subjected to a
surface pressing process (straightening process) using a roll
straightening machine similar to the machine shown in FIG. 1A and
FIG. 1B to obtain an aluminum alloy bar of Example 1. For the
conditions of the straightening process, the roll angles R.alpha.
and R.beta. (see FIG. 1A) were set to 14.degree. (degrees) and
14.degree. (degrees), the rolling load was set to 2.0 ton
(2.0.times.10.sup.3.times.9.80 N), and the roll rotational number
was set to 1,200 rpm.
[0092] Further in Table 1, the pressing force corresponding to the
rolling load is shown as a ratio when the straightness saturation
point (straightening degree saturation point) at the rolling load
of 0.5 ton (0.5.times.10.sup.3.times.9.80 N) is "1". Furthermore,
the pressing points "Fa" to "Fd" in Table 1 show that they
correspond to the pressing points "Fa" to "Fd" in the graph of FIG.
2, and Example 1 corresponds to the pressing point "Fa" in the
graph of FIG. 2.
[0093] Further, when the load curve of the surface of the aluminum
bar in Example 1 was measured, it was a load curve as shown in FIG.
4. Furthermore, when the abovementioned load curve parameter
(surface profile) tan(P.theta.min) was determined from the load
curve, it was 0.42.
[0094] Further, as shown in Table 1, for the aluminum of Example 1,
each of the "effect of damage occurrence prevention", the "forging
defect", the "straightness", the "outer diameter/length dimensional
change/roll transfer mark" was evaluated.
[0095] The evaluation of the effect of damage occurrence prevention
(degree of damage occurrence) for the aluminum bar of Example 1 was
performed based on the number of occurrences of damage per 1 m of
length. That is, it was ".smallcircle. (Good)" when it was less
than 0.10/m, ".DELTA. (somewhat poor)" when it was 0.10/m or more
and less than 1.0/m, and "x (poor)" when it was 1.0/m or more.
[0096] The evaluation of the straightness of the aluminum bar of
Example 1 was performed based on the displacement (mm) of the axial
center per 1 m of length. That is, it was ".smallcircle.(good)"
when the displacement was less than 0.7 mm/m, ".DELTA.(somewhat
poor)" when it was 0.7 mm/m or more and less than 1.0 mm/m, and
"x(poor)" when it was 1.0 mm/m or more.
[0097] In the evaluation for the outer diameter.cndot.length
dimensional change/roll transfer marks for the aluminum bar in
Example 1, when the deformation ratio of the length measurement was
0.2% or less, the amount of deformation of the outer diameter was
0.05 mm or less, and there were no spiral shaped unevenness
(transfer marks) from the straightening rolls, it was evaluated as
".smallcircle.(Good)". Further, when the deformation ratio of the
length measurement exceeded 0.2%, the amount of deformation of the
outer diameter exceeded 0.05 mm, and there were spiral shaped
unevenness (transfer marks) from the straightening rolls, it was
evaluated as "x(defective)".
[0098] In the evaluation of the forging defect, the aluminum bar of
Example 1 was cut into predetermined lengths to obtain forging
blanks, and the evaluation was performed based on the rate of
occurrence of forging defects on the forged product (forging blank)
obtained by upsetting (forging) the forging blank. That is, it was
".smallcircle.(Good)" when the rate of occurrence was less than 1%,
".DELTA.(Somewhat poor)" when it was 1% or more and less than 5%,
and "x(Poor)" when it was more than 5%.
[0099] As shown in Table 1, in the aluminum bar of Example 1, all
evaluations were ".smallcircle.(Good)".
Example 2
[0100] For a cut aluminum bar, the rolling load was set to 1.0 ton
(1.0.times.10.sup.3.times.9.80 N) (the pressing point corresponds
to Fb of FIG. 2), and other than that, a surface pressing process
(straightening process) was performed under the same pressing
process conditions as the aforementioned Example 1 to obtain an
aluminum bar of Example 2. The load curve parameter
tan(P.theta.min) of the aluminum bar was 0.38.
[0101] Furthermore, as shown in Table 1, also for the aluminum bar
of Example 2, all evaluations were good after performing the same
evaluations as above.
Comparative Example 1
[0102] A cut aluminum bar was used as it was as the aluminum bar of
Comparative Example 1 without performing a straightening process
(surface pressing process). When the load curve of the aluminum bar
was measured, the load curve was as shown in FIG. 5. Furthermore,
when the abovementioned load curve parameter (surface profile)
tan(P.theta.min) was determined from the load curve, it was
0.70.
[0103] Further, as shown in Table 1, the same evaluations as
described above were performed for Comparative Example 2, but good
evaluations could not obtained for the evaluations of the effect of
damage occurrence prevention, the forging defect, and the
straightness.
Comparative Example 2
[0104] For a cut aluminum bar, the rolling load was set to 0.5 ton
(0.5.times.10.sup.3.times.9.80 N) (the pressing point corresponds
to Fc of FIG. 2), and other than that, a straightening process was
performed under similar pressing process conditions as the
aforementioned Example 1 to obtain the aluminum bar of Comparative
Example 2. The load curve parameter tan(P.theta.min) of the
aluminum bar was 0.61.
[0105] Further, as shown in Table 1, the same evaluations as
described above were performed for the aluminum bar of Comparative
Example 2, but good evaluations could not be obtained for the
evaluations of the effect of damage occurrence prevention and the
forging defect.
Comparative Example 3
[0106] For a cut aluminum bar, the roll angles R.alpha. and R.beta.
were set to 15.degree. (degrees) and 13.degree. (degrees) and the
rolling load was set to 2.5 ton (2.5.times.10.sup.3.times.9.80 N)
(the pressing point corresponds to Fd of FIG. 2), and other than
that, a straightening process was performed under similar pressing
process conditions as the aforementioned Example 1 to obtain the
aluminum bar of Comparative Example 3. The load curve parameter
tan(P.theta.min) of the aluminum bar was 0.43.
[0107] Further, as shown in Table 1, the same evaluations as
described above were performed for the aluminum bar of Comparative
Example 3, but good evaluations could not be obtained for the
evaluations of the outer diameter/length dimensional
deformation/roll transfer marks.
<Comprehensive Evaluation>
[0108] When Example 1 and Comparative Example 1 were compared, in
Comparative Example 1 in which a roll straightening (straightening
process) was not performed, the load curve parameter
tan(P.theta.min) exceeded 0.50, and sufficient effect of damage
occurrence prevention, etc., could not be obtained. On the other
hand, in Example 1 in which the load curve parameter tan
(P.theta.min) was 0.50 or less, sufficient effect of damage
occurrence prevention, etc., was obtained.
[0109] In Comparative Example 2, roll straightening was performed,
but since the pressing force was less than the predetermined value
(1.5.times.Fc) and was small, the load curve parameter
tan(P.theta.min) exceeded 0.50, and sufficient effect of damage
occurrence prevention, etc., could not be obtained.
[0110] In Comparative Example 3, since the pressing force exceeded
the predetermined value (4.0.times.Fc) and was large,
overstraightening occurred, making the outer diameter/length
dimensional deformation amount large, and occurrence of spiral
shaped detrimental unevenness (transfer marks) from the rolls was
recognized.
[0111] When Examples and Comparative Examples were compared, when
the pressing force was 1.5.times.Fc or more, the load curve
parameter tan(P.theta.min) was 0.50 or less, and good evaluations
were obtained for the effect of damage occurrence prevention,
forging defect, and straightness. When the pressing force was
4.0.times.Fc or less, overstraightening did not occur, and good
evaluations were obtained for the outer diameter/length dimensional
deformation/roll transfer marks.
[0112] The terms and descriptions used herein are used only for
explanatory purposes and the present invention is not limited to
them. The present invention allows various design-changes falling
within the claimed scope of the present invention unless it
deviates from the spirits of the invention.
INDUSTRIAL APPLICABILITY
[0113] The method of producing an aluminum bar of the present
invention can be used, for example, when producing an aluminum bar
which is used as a forging blank.
[0114] It should be understood that the terms and expressions used
herein are used for explanation and have no intention to be used to
construe in a limited manner, do not eliminate any equivalents of
features shown and mentioned herein, and allow various
modifications falling within the claimed scope of the present
invention.
[0115] While the present invention may be embodied in many
different forms, a number of illustrative embodiments are described
herein with the understanding that the present disclosure is to be
considered as providing examples of the principles of the invention
and such examples are not intended to limit the invention to
preferred embodiments described herein and/or illustrated
herein.
[0116] While illustrative embodiments of the invention have been
described herein, the present invention is not limited to the
various preferred embodiments described herein, but includes any
and all embodiments having equivalent elements, modifications,
omissions, combinations (e.g., of aspects across various
embodiments), adaptations and/or alterations as would be
appreciated by those in the art based on the present disclosure.
The limitations in the claims are to be interpreted broadly based
on the language employed in the claims and not limited to examples
described in the present specification or during the prosecution of
the application, which examples are to be construed as
non-exclusive.
* * * * *