TECHNICAL FIELD
[0001] A method for producing an oil temper treated wire for use in a coil spring or a valve
spring, used in an internal combustion engine, a torsion spring used in a clutch mechanism
for an automobile and the like.
BACKGROUND
[0002] There has been known such method for producing an oil temper wire according to the
EP-A-1 013 780. This document relates to a technique for producing a spring steel material, which
is called a rod, whereas the invention relates to a technique for producing an oil
tempered wire. The subject of the document belongs to steel makers and the inventive
method belongs to wire makers, which produce many kinds of spring products from the
spring steel rod, provided by the steel makers.
[0003] There has been known a further method for producing an oil temper wire for a coil
spring, the method comprising: using a wire material having a nonmetallic inclusion
controlled and carrying out an isothermal transformation heat treatment, applying
a lubrication film after acid washing, carrying out scalping or shaving, then carrying
out an isothermal transformation heat treatment, applying a lubrication film after
acid washing, carrying out wire-drawing processing, and finally applying an oil temper
treatment. In this case, the isothermal transformation heat treatment with a wire
material is often omitted since workability of a wire material is enhanced.
[0004] The conventional method for producing an oil temper wire which carries out the isothermal
transformation heat treatment after the scalping has been carried out includes: (a)
Since the wire material is heated to a degree in excess of a transformation temperature,
decarburization likely occurs; (b) since the isothermal transformation heat treatment
requires a traveling treatment with a strand, a dominant cause of producing a damage
caused by the traveling treatment and handling results; (c) in the isothermal transformation
heat treatment, a removal of an oxidized scale film produced during the heat treatment
and the lubrication film treatment after acid washing in order to wire-drawing processing
are necessary; and (d) an adhering state of the oxidized scale in the oil temper treatment
after wire-drawing is uneven due to unevenness of the lubrication film after acid
washing resulting in an evil of forming process of a coil spring (coiling).
[0005] In the
EP-A-0 656 427 a method is described in which a finished, i.e. a completely drawn wire, is explicitely
treated by a number of subsequent steps of a method, defined in that document. The
method step described in this document is different from the subject matter of the
invention. Method steps for carrying out annealing an atmosphere of a mixture of nitrogen
and oxgen of e.g. temperatures in the range of 500 to 650°C are not realized.
[0006] Finally a further document according to the
JP-A-630 728 32 discloses a method for producing oil temper wire in such a way that there will be
formed an oxide film on the surface of heated wire in an atmosphere of steam or in
an atmosphere of inert gas, such as nitrogen or argon, including steam. Namely the
method which is disclosed in this document is directed to forming an oxide film on
the surface of the wire.
DISCLOSURE OF THE INVENTION
[0007] In view of the aforementioned problem, it is an object of the invention to provide
a method for producing an oil temper wire, which improve quality, achieve reduction
in cost and simplify the steps after the scalping.
[0008] It is a further object of the invention to provide a method for producing an oil
temper wire which is free from decarburization of a wire material and free from a
damage or unevenness of scale on a surface layer after an oil temper treatment has
been carried out in order to facilitate the forming of a coil spring.
[0009] For solving the problems noted above the method for producing an oil temperature
according to the present invention comprises: firstly applying an isothermal transformation
heat treatment to the wire material having a non-metallic inclusion controlled, secondly
applying a lubrication film after acid washing, thirdly carrying out the scalping
followed by softening by annealing a work hardened layer produced on a surface layer
at the time of scalping, fourthly carrying out the wire drawing and finally carrying
out the oil temper treatment.
OPERATION OF THE INVENTION
[0010] The present inventor has found that in a method for producing an oil temper wire
using a coil spring, to carry out annealing after scalping or shaving of a wire material
having a nonmetallic inclusion controlled is effective for a thereafter wire drawing
process. That is, the method for producing an oil temper wire for use in a coil spring
resides in that a work hardened layer produced on a surface layer of a wire material
during scalping of a wire material is softened by annealing to thereby remove an drawback,
and after wire drawing an oil temper treatment is carried out.
[0011] Considering a wire drawing workability and a solid solution state of cementite caused
by austenite heating at the time of an oil temper treatment after wire drawing process,
an annealing temperature of a wire material is set to a temperature region from 500
to 650°C. For the atmosphere at the time of annealing, nitrogen or a mixture of nitrogen
and oxygen is used and the quantity of oxygen is preferably controlled. A control
is made such that an oxidized scale film produced by annealing of a wire material
is extremely thin and even. Thus it is possible to avoid the coventional lubrication
film treatment after acid washing for wire drawing process.
[0012] A film of an oxidized scale caused by annealing prior to a wire drawing process of
a wire material may be subjected to descaling by means of a shot blast or the like.
The thickness of the oxidizedscale after the oil temper process becomes even and lubricating
property at the time of forming process (coiling) of a coil spring can be maintained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a photograph showing a surface crack of one wire material according to
the method for producing an oil temper wire according to the present invention; FIG.
2 is a photograph showing a solid solution state of one more material according to
the method for producing an oil temper wire; FIG. 3 is a schematic view representative
of an evaluation standard in a coil winding state of a wire material according to
the method for producing an oil temper wire; and FIG. 4 is a photograph showing a
decarburization state of a comparative wire material.
BEST MODE FOR CARRYING OUT THE INVENTION
[0014] The method for producing an oil temper wire according to the present invention is
characterized by softening by annealing a work hardened layer produced on the surface
of a wire during scalping or shawing of a wire material to thereby remove any drawbacks
thereby remove an evil, and after wire drawing is carried out carrying out an oil
temper treatment.
[Embodiment 1]
[0015] There were prepared wire materials A to G and H, as oil temper wires, in which an
alloy steel inclusion is controlled, comprising carbon 0.57% (hereinafter, % means
weight % unless otherwise particularly described clearly), silicone 1.45%, manganese
0.69%, phosphor 0.014%, sulfur 0.004%, chromium 0.67% and iron (the reminder) and
a comparative material H, these materials were subjected to an isothermal transformation
treatment, applying a lubrication film after acid washing, and scalping or shaving
of the surface. The scalping amount of a wire material is 0.3 mm in diameter (thickness
0.15 mm). Then, annealing of a wire material by batch was carried out in an atomosphere
of mixed nitrogen and oxigen. An annealing temperature of a wire material was varied
from 480 to 700°C to confirm workability of drawing of the wire materials A to G and
the comparative material H at respective annealing temperatures. The state of the
oxidized scale film after annealing of the wire material was extremely thin and even.
Further, the decarburization of the wire materials A to G in annealing was not recognized,
but the decarburization in the comparative material H was recognized, as shown in
FIG. 4.
[0016] Next, the oil temper treatment was carried out with respect to a wire material, which
is good in drawing wire process. The solid solution state (refer to FIG. 2) of cementite
at the time of oil temper treatment was confirmed. In the oil temper treatment, since
heating time is short, when the cementite is formed into sphere, the solid solution
of cementite is insufficient by heating and adequate strength is not obtained.
[0017] A relationship between the annealing temperature and the drawing wire workability
after the wire materials A to G in which an inclusion was controlled and the comparative
material H were subjected to the isothermal transformation treatment, application
of a lubrication film after acid washing, and scalping or shaving of the surface is
as follows:
Wire material A: At an annealing temperature of 450°C, a breakage occurred during
the drawing wire process, which was not practical.
Wire material B: At an annealing temperature of 480°C, the drawing wire process in
excess of 80% of reduction of area was accomplished, but crack-like crevices at right
angle to a fine wire axis occurred on the surface of the wire material, as shown in
FIG. 1.
Wire materials C to F: At an annealing temperature of 500 to 650°C, a crack-like crevice
at right angle to a fine wire axis was not recognized, and the cementite was not found
to be formed into sphere. By austenite heating after drawing wire process, the cementite
was sufficiently subjected to solid solution to obtain adequate strength. No unevenness
was recognized on the external appearance of the oxidized scale film after the oil
temper treatment.
Wire material G: In the annealing at a temperature of 700°C, formation of cementite
into sphere progresses, and the solid solution of spherical-cementite is insufficient
due to the austenite heating after the drawing wire process, failing to obtain the
adequate strength.
Comparative material H: Unevenness was recognized on the external appearance of the
oxidized scale film after the oil temper treatment. Evaluation circumstances of the
aforementioned wire materials A to G and comparative material H are summarized in
Table 1. The adequate annealing temperature is 500 to 650°C of the wire materials
C to F.
TABLE 1 Evaluation Results
Wire |
heat treatment |
|
|
drawing |
Mat'ls |
system |
temp. ato'phere °C |
decarb'tion |
thick'ns scale |
workability |
A |
annealing |
450 nitrogen |
O |
0 to 1 |
X |
B |
annealing |
480 nitrogen |
O |
0 to 2 |
Δ |
C |
annealing |
500 nitrogen |
O |
1 to 3 |
O |
D |
annealing |
550 nitrogen |
O |
1 to 3 |
O |
E |
annealing |
600 nitrogen |
O |
1 to 3 |
O |
F |
annealing |
650 nitrogen |
O |
2 to 5 |
O |
G |
annealing |
700 nitrogen |
O |
3 to 8 |
O |
H |
annealing |
500 redution |
Δ |
2 to 15 |
O |
Wire |
oil temper |
eddy current |
synthetic |
|
Mat'ls |
solid solusion state |
scale uneveness |
crack detection crack number |
evaluation |
|
A |
- |
- |
- |
X |
|
B |
- |
- |
- |
X |
|
C |
O |
O |
0 |
O |
|
D |
O |
O |
0 |
O |
|
E |
O |
O |
0 |
O |
|
F |
O |
O |
0 |
O |
|
G |
Δ |
- |
- |
X |
|
H |
O |
X |
7 |
X |
|
[0018] After the oil temper treatment, the inspection of cracks by eddy current crack detection
was conducted over the full length on the off line. In the wire materials C to F subjected
to the batch type annealing treatment, there is no number of cracks per coil (diameter:
6 mm, and length: 1500 m), whereas in the comparative material (which was subjected
to the isothermal transformation heat treatment after scalping), seven cracks per
coil were found.
[0019] In FIG. 3, A shows no scale-enevenness is present over the full length of the coil.
B shows several times of scale-unevenness are found in a few places within the coil.
C shows scores of rolls of scale-unevenness are found in one place within the coil.
D shows scale-unevenness in which B-C are combined.
TABLE 2 Evaluation items
Evaluation items |
evaluation standard |
Decarburization |
partial decarburization is not present |
Workability |
(a) degressive rate is not less than 80% |
|
(b) defect such as scratch is not present on the surface after peocessing |
solid solution state |
cementite is solid solution dispersed evenly |
scale unevenness |
A and B in scale-unevenness judgment standard are accepted |
[Embodiment 2]
[0020] A wire material, in which an alloy steel inclusion is controlled comprising carbon
0.65%, silicone 1.53%, manganese 0.69%, phosphor 0.007%, sulfur 0.008%, chromium 0.68%,
and iron (the reminder), which are different in component from Embodiment 1 was subjected
to an isothermal transformation treatment, applying a lubrication film after acid
washing, and scalping of a surface in diameter of 0.3 mm (thickness is 0.15 mm). The
scalping amount of a wire material is 0.3 mm in diameter (thickness 0.15 mm).
[0021] Then, annealing of a wire material by batch was carried out. The annealing temperature
was 500°C. The annealing treatment was carried out with respect to the wire material,
after which the wire was drawed to an adequate diameter, and then the oil temper treatment
was carried out. At this time, abnormality caused by the wire drawing process, the
short in strength in the oil temper treatment, and abnormality such as unevenness
of scale were not occurred.
[Embodiment 3]
[0022] As an oil temper wire used as a high fatigue strength material, a wire material,
in which an alloy steel inclusion is controlled comprising carbon 0.64%, silicone
1.43%, manganese 0.71%, phosphor 0.006%, sulfur 0.005%, chromium 1.48%, molybdenum
0.47%, vanadium 0.19% and iron (the reminder) was applied with a lubrication film
after acid washing, and scalping of a surface in diameter of 0.3 mm (thickness is
0.15 mm) was carried out. Then, the annealing treatment was carried out at 600°C with
respect to the wire material by the batch. Then, the wire drawing process was carried
out with respect to the wire material, after which the oil temper treatment was carried
out.
[0023] Also in the aforementioned high fatigue strength material, the abnormality caused
by the drawing wire process, the short in strength in the oil temper treatment, and
the abnormality such as unevenness of scale were not observed.
INDUSTRIAL APPLICABILITY
[0024] As described above, the method for producing an oil temper wire used for a valve
spring of the internal combustion engine, a coil spring of a clutch mechanism and
the like according to the present invention is useful in the point that no scratch
and unevenness of scale occur on the surface layer after the drawing wire process
and oil temper treatment, and forming of a coil spring is facilitated.
1. A method for producing an oil temper treated wire, comprising the following steps:
carrying out wire drawing and
carrying out scalping,
characterised in that,
firstly: applying an isothermal transformation heat treatment to the wire material
having a non-metallic inclusion controlled,
secondly: applying a lubrication film after acid washing,
thirdly:carrying out the scalping, after which softening a work hardened layer produced
on a surface layer at the time of scalping by annealing,
fourthly: carrying out the wire drawing and finally: carrying out the oil temper treatment.
2. The method for producing oil temper wire according to claim 1, wherein an annealing
temperature is set to 500 to 600°C.
3. The method for producing an oil temper wire according to claim 1, wherein in said
annealing step, the in-furnace atmosphere is nitrogen in order to suppress an oxidized
scale film.
4. The method for producing an oil temper wire according to claim 1, wherein in said
annealing step, the in-furnace atmosphere is a mixture of nitrogen and oxygen in order
to suppress an oxidized scale film and a quantity of oxygen is controlled.
5. The method for producing an oil temper wire according to claim 1, wherein said wire
material is Si-Cr steel.
1. Verfahren zur Herstellung eines mit Öl härtebehandelten Drahtes, umfassend die folgenden
Schritte:
Ausführen des Ziehens des Drahtes und
Ausführen des Entfernens der Oberflächenhaut,
dadurch gekennzeichnet,
daß zunächst eine isothermische Transformationswärmebehandlung des Drahtmaterials durchgeführt
wird, das eine nichtmetallische gelenkte Einlagerung aufweist,
daß danach ein Schmierstoffilm nach dem Säurewaschen aufgebracht wird,
daß anschließend das Entfernen der Oberflächenhaut nach dem Enthärten einer gehärteten
Schicht ausgeführt wird, die auf einer Oberflächenschicht im Augenblick ihres Entfernens
durch Glühen erzeugt wird,
daß danach das Ziehen des Drahtes ausgeführt wird und
daß schließlich die Ölhärtebehandlung ausgeführt wird.
2. Verfahren zur Erzeugung eines mit Öl härtebehandelten Drahtes nach Anspruch 1, bei
dem die Glühtemperatur bei 500 bis 600°C liegt.
3. Verfahren zur Erzeugung eines mit Öl härtebehandelten Drahtes nach Anspruch 1, bei
dem der Glühschritt in der Ofenatmosphäre Stickstoff ist, um einen oxidierten Hautfilm
zu unterdrücken.
4. Verfahren zur Erzeugung eines mit Öl härtebehandelten Drahtes nach Anspruch 1, bei
dem der Glühschritt in der Ofenatmosphäre aus einem Gemisch aus Stickstoff und Sauerstoff
besteht, um einen oxidierten Hautfilm zu unterdrücken, wobei eine bestimmte Menge
von Stickstoff gesteuert wird.
5. Verfahren zur Erzeugung eines mit Öl härtebehandelten Drahtes nach Anspruch 1, bei
dem das Drahtmaterial Si-Cr-Stahl ist.
1. Un procédé de fabrication d'un fil traité par trempe à l'huile comprenant les étapes
:
- d'étirage du fil
- d'écroutage,
caractérisé en ce que
- premièrement: on procède au traitement thermique de transformation isotherme du
matériau d'un fil comportant une inclusion non métallique contrôlée,
- deuxièmement: on applique un film de lubrification après lavage à l'acide,
- troisièmement: on procède à l'écroutage, après quoi on ramollit une couche écrouie
produite sur une couche de surface au moment de l'écroutage par recuit,
- quatrièmement: on procède à l'étirage du fil,
- et enfin: on effectue le traitement de trempe à l'huile.
2. Le procédé de fabrication d'un fil traité par trempe à l'huile selon la revendication
1, dans lequel la température de recuit est fixée entre 500 et 600°C.
3. Le procédé de fabrication d'un fil traité par trempe à l'huile selon la revendication
1, dans lequel, dans ladite étape de recuit, l'atmosphère du four est formée d'azote
afin d'éviter la formation d'un film de calamine oxydée.
4. Le procédé de fabrication d'un fil traité par trempe à l'huile selon la revendication
1, dans lequel, dans ladite étape de recuit, l'atmosphère du four est formée d'un
mélange d'azote et d'oxygène afin d'éviter la formation d'un film de calamine oxydée
et la quantité d'oxygène présente est contrôlée.
5. Le procédé de fabrication d'un fil traité par trempe à l'huile selon la revendication
1, dans lequel ledit matériau métallique est en acier au Cr-Si.