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Rod and Wire Drawing Techniques

Rod and wire drawing involves reducing the diameter of a rod or wire by pulling it through a constricting die. The process uses compression forces from the reaction between the metal and die to cause plastic flow. Drawing can be used to produce rods and wires to high dimensional accuracy. The maximum reduction per pass depends on whether the material is perfectly plastic or strain-hardening, but is generally around 63% for perfectly plastic materials. Die pressure is calculated based on the flow stress of the material at different diameters along the die.

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Adil Azeem
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103 views12 pages

Rod and Wire Drawing Techniques

Rod and wire drawing involves reducing the diameter of a rod or wire by pulling it through a constricting die. The process uses compression forces from the reaction between the metal and die to cause plastic flow. Drawing can be used to produce rods and wires to high dimensional accuracy. The maximum reduction per pass depends on whether the material is perfectly plastic or strain-hardening, but is generally around 63% for perfectly plastic materials. Die pressure is calculated based on the flow stress of the material at different diameters along the die.

Uploaded by

Adil Azeem
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Wire drawing

2
Rod and Wire Drawing
Introduction
Rod and Wire drawing involves reducing the diameter of a rod or wire by
passing through a converging die.
The plastic flow is caused by compression force, arising fromthe reaction of
the metal with the die
Rod and wire drawing are usually carried out at room temperature, except
for large deformation, which leads to considerable rise in temperature during
drawing.
Same principals for drawing bars, rods, and wire but
equipment is different in sizes depending on products.
Tube Drawing Operations
Fig : Examples of tube-drawing operations, with and without internal mandrel. Note
that a variety of diameters and wall thickness can be produced from the same
initial tube stock (which had been made by other processes).
3
Die Design
Characteristic features of a typical die design for drawing
Terminology of a typical die
used for drawing round rod
or wire.
Tungsten-carbide die insert in a steel casing.
Diamond dies, used in drawing thin
wire, are encased in a similar manner.
4
5
Rod and Wire Drawing
Rod and Wire drawing can be used as finishing process to produce a rode or wire of
high dimensional accuracy.
Similar to extrusion except that the rod (bar) is under tension in drawing, but
extrusion is under compression (pull material through die instead of pushing it in
extrusion).
5
6
Rods: relatively larger diameter products.
Wires: small diameter products < 5 mm diameter.
Rod and Wire Drawing
6
7
Mechanics of rod and wire drawing
Reduction ratio (reduction in area), r
0
f 0
A
A A
r

=
=
0
f
A
A
1 r 1
A
A
0
f
=
r 1
1
Ln
L
L
Ln
A
A
Ln
0
f
f
0

= = = c
(Tensile)
7
8
Mechanics of rod and wire drawing
Ideal deformation (homogeneous and
frictionless deformation
|
.
|

\
|

=
|
|
.
|

\
|
=
r 1
1
Ln . Y
A
A
Ln . Y
f
0
d
o
|
.
|

\
|

=
|
|
.
|

\
|
=
r 1
1
Ln . Y
A
A
Ln . Y
f
f
0
f d
o
(For perfectly plastic material)
(For strain hardening material)
f d d
A . F o =
f d d
L . F W =
8
9
For perfectly plastic material
To avoid failure of the rod o
d
Y.
Maximum reduction is point where o
d
= Y
63 . 0 r 1
r 1
1
Ln
Y
r 1
1
Ln . Y
d
= =
|
.
|

\
|

=
|
.
|

\
|

= o
Maximum reduction per pass = 0.63
Calculation of the maximum reduction per pass
9
10
Calculation of the maximum reduction per pass
For strain hardening material
To avoid failure of the rod o
d
Y
f
Maximum reduction is point where o
d
= Y
f
Maximum reduction per pass ,
f f d
Y
r 1
1
Ln . Y =
|
.
|

\
|

= o
) 1 n ( 1 n
n
n
e 1 r e
r 1
1
1 n
r 1
1
Ln K
r 1
1
Ln .
1 n
K
+ +
= =
|
.
|

\
|

+ =
|
.
|

\
|

=
|
.
|

\
|

|
|
.
|

\
|
+
c
c
) 1 n (
e 1 r
+
=
11
Calculation of the maximum reduction per pass
For strain hardening material
To avoid failure of the rod o
d
Y
f
Maximum reduction is point where o
d
= Y
f
Maximum reduction per pass ,
f f d
Y
r 1
1
Ln . Y =
|
.
|

\
|

= o
) 1 n ( 1 n
n
n
e 1 r e
r 1
1
1 n
r 1
1
Ln K
r 1
1
Ln .
1 n
K
+ +
= =
|
.
|

\
|

+ =
|
.
|

\
|

=
|
.
|

\
|

|
|
.
|

\
|
+
c
c
) 1 n (
e 1 r
+
=
11
12
Die pressure
o =
f
Y P
The die pressure P at any diameter along the die contact length can be
obtained as follows
Where is the tensile stress in the deformation zone in any diameter (at the die exit =

d
),
Y
f
is the flow stress of the material at any diameter
12

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