Resistance welding electrode and process for making

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No. 08/975,022, filed Nov. 20, 1997, now U.S. Pat. No. 6,047,741.

BACKGROUND OF THE INVENTION

The present invention relates to welding electrodes, and to a process for forming same.

Resistance welding has long been used as a quick and effective method of joining metal members. The workpieces to be welded are placed in abutting relationship and a large electrical current is caused to flow through the workpieces by a pair of opposed electrodes that contact the workpieces on opposite sides of the weld point. The current causes the abutting surfaces of the workpieces to be heated sufficiently to effect the formation of a weld nugget. Typically, the electrodes apply significant pressure to the workpieces during welding. This facilitates the welding process by urging the material together and, also, reducing electrical resistance between each electrode tip and the adjacent workpiece material that it contacts.

Since welding is accomplished by resistance heating of the material being welded, it will be appreciated that the electrodes will also be heated substantially. It is important to have electrodes of high electrical conductivity in order to minimize the power loss in the electrode, and the resulting heating of the electrode.

Over time, the repeated heating and pressing operations involved in resistance welding cause breakdown, softening, mushrooming and other deformation of the electrodes. The current density of the current going through the workpieces drops. As this occurs, electrical current requirements for welding increase with the enlarged welding tip face contacting the workpiece material until ultimately, redressing or replacement of the electrode is required. Accordingly, it is also important to have an electrode which is capable of withstanding significant distorting force at the elevated temperatures which result from the welding process so as to minimize the number of times it becomes necessary to redress or replace the electrode within a given period of time.

It is known in the art to form resistance welding electrodes by combining a copper electrode body with an anneal resistant, high hardness insert. Typically, the insert performs much better than the copper material from which the electrode body is formed. However, the insert material is much more expensive than the copper used to form the electrode body.

The insert may be brazed onto the shank of the electrode. The brazing step is disadvantageous, however, as it adds an additional step to the electrode manufacturing process and, hence, increases the cost of the electrode. Furthermore, the brazing operation may anneal and soften the electrode body.

It is also known to force the insert into an electrode body via a press-fit operation. The steel being welded today is often galvanized or coated with a zinc or other, softer metal coating. As a result, resistance welding electrode may tend to stick to the coated metal. An electrode tip joined to an electrode body only by means of a press-fit may tend to pull out of the body as the electrode is retracted following resistance welding of coated materials, thus requiring replacement of the electrode.

Accordingly, there is a need for an improved resistance welding electrode which can be manufactured via an efficient and more cost effective process and, yet, is capable of performing in an acceptable manner.

SUMMARY OF THE INVENTION

This need is met by the present invention, whereby an improved resistance welding electrode, and a process for forming the same are provided. The process involves providing a billet having an inner cavity, inserting a dispersion strengthened copper insert into the billet and deforming the insert-containing billet via cold-working operations so as to lock the insert in place mechanically in the billet. The forming operations may be performed in a single step such that the electrode can be manufactured in an efficient and cost effective manner. Furthermore, because the insert is mechanically locked in place within the billet, it is unlikely that the normal amount of sticking that occurs during resistance welding of coated steel will pull the insert out of the billet. It is also noted that the billet is preferably formed from a CDA C10700 silver bearing copper which is a high conductivity material. Previously, it was generally thought that silver bearing copper should not be used in forming welding electrodes as it was believed that such material would anneal at the temperatures involved in resistance welding. However, by virtue of cooling water located in an inner cavity of the silver bearing copper main body portion and because the main body portion makes only limited, if any, contact with a workpiece, annealing of the main body portion is prevented.

According to a first aspect of the present invention, a process for forming a resistance welding electrode is presented. A billet formed from a high conductivity metal is provided. The billet includes a first portion having a first inner cavity being defined by a first wall and a first stop face. An insert is inserted into the first inner cavity of the billet with the insert having a first portion positioned substantially adjacent the first stop face. The insert is deformed such that an outer diameter of the first portion of the insert is increased, thereby mechanically locking the insert in place in the billet.

The step of deforming the insert may comprise containing a first section of the first portion of the billet by a forming element and then applying pressure to the billet so as to displace at least the first portion of the billet not contained by the forming element and the first portion of the insert thereby increasing the outer diameter of the first portion of the insert and mechanically locking it in the billet. The step of providing a billet may comprise providing a generally cylindrical cut-off portion of high conductivity metal, upsetting and forward extruding the cut-off portion so as to form the billet having the first portion and a second portion, and forming the first inner cavity in the first portion of the billet. The process may further comprise the step of forming a second inner cavity in the second portion of the billet. The step of forming the first inner cavity in the first portion of the billet and the step of forming a second inner cavity in the second portion of the billet may be performed substantially simultaneously. Preferably, the insert is formed from an internally oxidized copper-aluminum alloy or dispersion strengthened copper. The billet may be formed from a high conductivity copper or a silver bearing copper.

According to another aspect of the present invention, a process for forming a resistance welding electrode comprises providing a generally cylindrical cut-off portion of high conductivity metal. A billet is formed from the generally cylindrical cut-off portion having a first portion with a first inner cavity therein and a second portion with a second inner cavity therein. The first inner cavity is defined by a first wall and a first stop face. An insert is inserted into the first inner cavity of the billet. The insert includes a first portion positioned substantially adjacent the first stop face. A first section of the first portion of the billet and a second portion of the insert are contained via a forming element. Pressure is applied to the billet thereby increasing an outer diameter of a second section of the first portion of the billet and an outer diameter of the first portion of the insert so as to lock the insert in place mechanically in the billet, thereby forming the resistance welding electrode.

The step of containing a first section of the first portion of the billet and a second portion of the insert via a forming element may comprise the steps of positioning the first section of the first portion of the billet and the second portion of the insert in an inner cavity of the forming element, the forming element being part of a punch assembly. The inner cavity of the forming element includes an inner diameter substantially equal to an outer diameter of the first portion of the billet. The second section of the first portion of the billet is positioned in an inner cavity of a forming die, the forming die being part of a die assembly. The inner cavity of the forming die having an inner diameter substantially equal to an outer diameter of a second section of a first portion of the electrode. The die assembly includes a forming pin located axially within the second inner cavity and extending into the second inner cavity. The forming pin has an outer diameter substantially equal to an inner diameter of the second inner cavity of the billet. The step of applying pressure to the billet may comprise the step of applying pressure to the billet via a forming punch of the punch assembly to cause the outer diameter of the second section of the first portion of the billet to increase, the outer diameter of the first portion of the insert to increase and a length of the insert to decrease. The forming punch has an outer diameter substantially equal to the outer diameter of the first portion of the billet. The step of applying pressure to the billet via a forming punch may cause forward extrusion of the first portion of the billet over the forming pin thereby increasing a length of the second inner cavity into the first portion of the billet.

According to yet another aspect of the present invention, a process for forming a resistance welding electrode comprises providing a generally cylindrical cut-off portion of high conductivity metal. The cut-off portion is upset and forward extruded so as to form a billet having a first portion and a second portion. A first inner cavity is back extruded in the first portion of the billet with the first inner cavity being defined by a first wall and a first stop face. A second inner cavity is back extruded in the second portion of the billet. An insert is inserted into the first inner cavity of the billet. The insert includes a first portion positioned substantially adjacent the first stop face. A first section of the first portion of the billet and a second portion of the insert are contained via a forming element. Pressure is applied to the billet thereby increasing an outer diameter of a second section of the first portion of the billet and an outer diameter of the first portion of the insert so as to lock the insert in place mechanically in the billet. The first portion of the billet is forward extruded thereby extending the second cavity into the first portion of the billet. The second portion of the billet is contoured such that second portion of the billet has a predetermined shape. The steps of back extruding the first inner cavity and back extruding the second inner cavity may be performed substantially simultaneously. The steps of applying pressure to the billet and forward extruding the first portion of the billet may be performed substantially simultaneously.

According to a further aspect of the present invention, a resistance welding electrode comprises a main body formed from a high conductivity metal. The main body includes a first portion having a first inner cavity being defined by a first wall and a first stop face. An insert is provided in the first inner cavity. The insert includes a first portion which is substantially adjacent the first stop face. The first portion of the insert has a diameter greater than a diameter of the first inner cavity such that the insert is mechanically locked in place in the main body. The main body includes a substantially planar surface composed of a substantially planar surface of the first portion of the main body and a substantially planar surface of the second portion of the insert.

Preferably, the diameter of a first section of the first portion of the main body is less than the diameter of a second section of the first portion of the main body. The first section of the first portion of the main body terminates at the substantially planar surface. The main body may further include a second inner cavity provided in a second portion of the main body which is adapted to be supplied with a cooling fluid during a resistance welding process. Preferably, the insert is formed from an internally oxidized copper-aluminum alloy or dispersion strengthened copper. The main body may be formed from a high conductivity copper or a silver bearing copper.

Accordingly, it is an object of the present invention to provide an improved low cost resistance welding electrode and process for forming same. It is further an object of the present invention to provide a resistance welding electrode having a dispersion strengthened copper insert which is mechanically locked in position within a main body formed from a high conductivity metal. Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-6A

illustrate various manufacturing steps for manufacturing a resistance welding electrode according to the present invention;

FIGS. 1B-6B

are cross-sectional views of the electrode after each of the manufacturing steps illustrated in

FIGS. 1A-6A

;

FIG. 7

is a side view of the electrode manufactured according to the present invention; and

FIG. 8

is a top view of the electrode of FIG.

7

.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to

FIGS. 1A-6A

, a press

10

is provided having a stationary bed portion

12

and a ram portion

14

which is caused to move back and forth relative to the bed portion

12

by a conventional drive apparatus (not shown). The bed and ram portions

12

and

14

include respectively first and second electrode forming tooling

16

and

18

, which are provided at first, second, third, fourth and fifth forming stations

20

,

40

,

60

,

80

and

100

. Referring specifically to

FIG. 1A

, positioned adjacent to the first forming station

40

is a conventional cutting station

120

. A roll of substantially solid wire stock

122

having a predetermined diameter is fed to the cutting station

120

where it is cut into discrete, generally cylindrical cut-off portions

124

, one of which is shown in FIG.

1

B. The cut-off portions

124

are used in forming resistance welding electrodes

180

, one of which is shown in

FIGS. 6B

,

7

and

8

. The wire stock

122

is fed through a quill

126

and cut to a predetermined length by a cutter

128

thereby forming the cut-off portions

124

. Conventional work transfer fingers

130

(shown schematically in the drawings) move each of the discrete cut-off portions

124

from the cutting station

120

to the first forming station

20

and from the first forming station

20

through the remaining forming stations

40

,

60

,

80

and

100

.

Referring now to

FIG. 2A

, the cut-off portion

124

is then transferred to the first forming station

20

where the cut-off portion

124

is transformed into a billet

140

shown in FIG.

2

B. The billet

140

includes a nose or first portion

142

having a first outer diameter D

B1

, a stem or second portion

144

having a second outer diameter D

B2

and an intermediate tapered portion

146

. The first forming station

20

includes a first forming die assembly

22

and a first forming punch

24

. The first die assembly

22

includes a first forming die

26

and a second forming die

28

which are fixedly coupled to the bed portion

12

and, hence, are stationary. The first die

26

includes a first inner cavity

26

A having an inner diameter substantially equal to the first outer diameter D

B1

. The second die

28

includes a second inner cavity

30

having a first section

30

A having an inner diameter substantially equal to the first outer diameter D

B1

, a second section

30

B having a tapered diameter corresponding to the tapered portion

146

, and a third section

30

C having an inner diameter substantially equal to the second outer diameter D

B2

.

The first punch

24

is fixedly coupled to and moves with the ram portion

14

. The first punch

24

has an outer diameter substantially equal to the first outer diameter D

B1

. As the ram portion

14

is driven towards the bed portion

12

, the first punch

24

engages the cut-off portion

124

held adjacent to the first die

26

via the pair of the work transfer fingers

130

and inserts the cut-off portion

124

into the first inner cavity

26

A of the first die

26

and into the first section

30

A of the second inner cavity

30

of the second die

28

. The first punch

24

then applies sufficient pressure to the cut-off portion

124

to effect forward extrusion and upsetting of the cut-off portion

124

such that the billet

140

is formed. The cut-off portion

124

is upset since the first diameter D

B1

of the first portion of the billet

140

is greater than the diameter of the cut-off portion

124

. The cut-off portion

124

is forward extruded as the cutoff portion

124

is forced through the third section

30

A which has an inner diameter less than the diameter of the cut-off portion

124

. The first die assembly

22

includes an ejection pin

32

which ejects the billet

140

from the first and second dies

26

,

28

and into the work transfer fingers

130

after the cut-off portion

124

has been forward extruded and upset

The billet

140

is then transferred to the second forming station

40

shown in FIG.

3

A. The second forming station

40

includes a second forming die assembly

42

and a second forming punch

44

. The second die assembly

42

includes a third forming die

46

and a fourth forming die

48

which are slidably coupled to the bed portion

12

. The third die

46

includes a third inner cavity

46

A having an inner diameter substantially equal to the first diameter D

B1

. The fourth die

48

includes a fourth inner cavity

50

having a first section

50

A having an inner diameter substantially equal to the first diameter D

B1

and a second section

50

B having an inner diameter substantially to the second diameter D

B2

. The second die assembly

42

includes a forming pin

52

which is fixedly coupled to the bed portion

12

and extends into the fourth inner cavity

50

. The forming pin

52

has an outer diameter substantially equal to an inner diameter of a second inner cavity

148

in the second portion

144

of the billet

140

, see FIG.

3

B. The third and fourth dies

46

,

48

slide about the forming pin

52

and are biased towards the ram portion

14

via a pair of springs

54

.

The second punch

44

is fixedly coupled to the ram portion

14

and moves with the same. The second punch

44

includes a first portion

44

A having an outer diameter substantially equal to the first diameter D

B1

and a second portion

44

B having an outer diameter substantially equal to an inner diameter of a first inner cavity

150

in the first portion

142

of the billet

140

, see FIG.

3

B. The first inner cavity

150

is defined by a first wall

150

A and a first stop face

150

B. As the ram portion

14

is driven towards the bed portion

12

, the second punch

44

engages the billet

140

held adjacent to the third die

46

via the pair of the work transfer fingers

130

and inserts the billet

140

into the second die assembly

40

. The second portion

144

of the billet

140

is contained in the second section

50

B of the fourth inner cavity

50

of the fourth die

48

while the first portion of the billet

140

is contained in the third inner cavity

46

A of the third die

46

. The intermediate portion

146

of the billet

140

is positioned within the first section

50

A of the fourth inner cavity

50

of the fourth die

50

. The second punch

44

applies sufficient pressure to the first portion

142

of the billet

140

so as to form the first inner cavity

150

through back extrusion. The second punch

44

continues to apply sufficient pressure against the billet

140

thereby causing the third and fourth dies

46

to slide towards and around the forming pin

52

. The second inner cavity

148

is thus formed through back extrusion as the second portion

148

of the billet

140

is driven over the forming pin

52

.

In the illustrated embodiment, the first inner cavity

150

is smaller than the second inner cavity

148

such that the amount of force required to form the first inner cavity

150

is less than the amount of force required to form the second inner cavity

148

. Accordingly, the first inner cavity

150

may be formed prior to sliding the third and fourth dies

46

,

48

for formation of the second inner cavity

148

. As the first and second inner cavities

150

,

148

are formed, the lengths of the first and second portions

142

,

144

increase as the extruded material is displayed around the second portion

46

A of the second punch

46

and the forming pin

52

. Further, the intermediate portion

146

is displaced into the first portion

142

of the billet

140

. The second die assembly

42

further includes an ejection sleeve

56

positioned about the forming pin

52

and is movable relative to the pin

52

. The ejection sleeve

56

ejects the billet

140

from the dies

46

and

48

and into the work transfer fingers

130

after the first and second cavities

150

,

148

have been formed.

The billet

140

is then transferred to the third forming station

60

shown in FIG.

4

A. The third forming station

60

includes a third forming die assembly

62

and a third forming punch assembly

64

. The third die assembly

62

includes a fifth forming die

66

and a pressure pin

68

which are fixedly coupled to the bed

12

and, hence, are stationary. The fifth die

66

includes a fifth inner cavity

66

A having a inner diameter substantially equal to second outer diameter D

B2

of the second portion

144

of the billet

140

. The pressure pin

68

has an outer diameter substantially equal to the inner diameter of the second inner cavity

148

.

The third punch assembly

64

includes a first support element

69

, a second support element

70

, a third punch

72

and an insert supply mechanism

74

. The first support element

69

includes an inner cavity

69

A having a inner diameter substantially equal to the first outer diameter D

B1

of the first portion

142

of the billet

140

. The second support element

70

includes an inner cavity

70

A having a inner diameter substantially equal to the inner diameter of the first inner cavity

150

. The first and second support elements

69

,

70

are slidably coupled to the ram portion

104

through a support block

75

. The third punch

72

has an outer diameter substantially equal to the inner diameter of the first inner cavity

150

. The third punch

72

is slidably coupled to the ram portion

14

. The third punch

72

slides through an inner cavity

75

A of the support block

75

as the support block

75

engages the third die assembly

62

. The third punch

72

is biased towards the bed portion

12

via a spring

76

. The insert supply mechanism

74

supplies dispersion strengthened copper inserts

160

one at a time into the path of movement of the third punch

72

such that the third punch

72

inserts a copper insert

160

into the first inner cavity

150

of the billet

140

as shown in FIG.

4

B. The insert supply mechanism

74

comprises a supply conduit

162

having a plurality of inserts

160

therein. The inserts

160

are fed to the conduit

162

via a feed device (not shown). The conduit

162

extends through a bore

75

B in the support block

75

and is fixedly connected to the support block

75

so as to move with the same. A distal end

162

A of the conduit

162

terminates at an insert receiving channel

164

in the support block

75

such that the conduit

162

supplies inserts

160

to the channel

164

.

The supply mechanism

74

further includes a reciprocating pin

166

which extends into the channel

164

. A spring

168

biases the pin

166

toward an outer surface

164

A of the channel

164

away from the conduit

162

. The supply mechanism

74

includes a plunger

170

positioned in a plunger channel

172

within the support block

75

and connected to the channel

164

. The plunger

170

includes a beveled surface

170

A which engages a corresponding beveled surface

166

A on the pin

166

. The spring

168

biases the pin

166

toward the plunger

170

such that the beveled surface

166

A engages the beveled surface

170

A on the plunger

170

forcing the plunger

170

up from the plunger channel

172

. The plunger

170

includes a surface

170

B which extends above an upper surface

75

C of the support block

75

when the punch assembly

64

is in a first position separated from the die assembly

62

. Upon upward movement of the punch assembly

64

, the plunger

170

moves downward, engaging the pin

166

through the interaction of the beveled surfaces

166

A,

170

A such that the pin

166

is moved inward against the force of the spring

168

. As the pin

166

moves inward, it pushes an insert

160

located in the channel

164

in a direction toward the path of movement of the pin

72

.

FIG. 4A

shows the punch assembly

64

in a second position with the pin

166

extending through the channel

164

covering the conduit

162

. Upon separation of the punch assembly

64

from the die assembly

62

, the plunger

172

is pushed upwards from the plunger channel

172

as the spring

168

pushes against the pin

166

. Once the pin

166

extends away from the conduit

162

, another insert

160

is forced into the channel

164

.

As the ram portion

14

moves toward the bed portion

12

, the punch assembly

64

engages the billet

140

held adjacent to the fifth die

66

via the pair of the work transfer fingers

130

. The second portion

144

is pushed into fifth die

66

with the second inner cavity

148

being supported by the pressure pin

68

. The billet

140

is pushed into the inner cavity

69

A of the first support element

69

. The surface

170

B of the plunger

170

engages die assembly

62

pushing the pin

166

inward such that an insert

160

is pushed into the inner cavity

75

A of the support block

75

. With the insert

160

in the inner cavity

75

A, the support block

75

slides about the pin

72

with the insert

160

being pushed into the first inner cavity

150

of the first portion

142

of the billet

140

. The spring

76

provides sufficient force so as to press fit the insert

160

into the first inner cavity

150

. The insert

160

includes a first portion

160

A which is positioned substantially adjacent to the first stop face

150

B of the first cavity

150

. The billet

140

includes a substantially planar surface

140

A comprised of a substantially planar surface

142

A of the first portion

142

of the billet

140

and a substantially planar surface

160

C of a second portion

160

B of the insert

160

. The first portion

142

of the billet

140

includes a first section

142

B extending from the planar surface

142

A to a first end of the first portion

160

A of the insert

160

and a second section

142

C extending from the first end of the first portion

160

A of the insert

160

to the second portion

144

of the billet

140

.

The third die assembly

62

further includes an ejection sleeve

78

positioned about the pressure pin

68

and is movable relative to the pin

68

. The ejection sleeve

78

in conjunction with the pin

72

ejects the billet

140

from the die

66

and support element

69

, respectively, and into the work transfer fingers

130

after the insert

160

is positioned in the billet

140

. As the punch assembly

64

is removed from the die assembly

62

, the pin

72

is extended further in a direction toward the die assembly

62

so as to eject the billet

140

from the punch assembly

64

.

From the third forming station

60

, the billet

140

is moved to the fourth forming station

80

where it is deformed so as to lock the insert

160

in place mechanically and form a resistance welding electrode

180

, one of which is shown in FIG.

5

B. The electrode

180

includes a nose or first portion

182

and a stem or second portion

184

which correspond to the first and second portions

142

,

144

of the billet

140

, respectively. Further, the first portion

182

of the electrode

180

includes a first section

182

B and a second section

182

C which correspond to the first and second sections

142

B,

142

C of the first portion

142

of the billet

140

. The first portion

182

of the electrode

180

also includes a substantially planar surface

182

A which corresponds to the substantially planar surface

142

A of the first portion

142

of the billet

140

. The electrode

180

includes a substantially planar surface

180

A corresponding to the substantially planar surface

140

A of the billet

140

. The billet

140

is also referred to herein as the main body of the electrode

180

.

The fourth forming station

80

comprises a fourth forming die assembly

82

and a fourth forming punch assembly

84

. The fourth die assembly

82

includes a sixth die

86

, a seventh die

88

and an extrusion pin

90

. The sixth die

86

includes a seventh inner cavity

86

A having an inner diameter substantially equal to an outer diameter D

E1

of the second section

182

B of the first portion

182

of the electrode

180

. The seventh die

88

includes a seventh inner cavity

88

A having an inner diameter substantially equal to the outer diameter of the second portion

144

of the billet

140

. The extrusion pin

90

has an outer diameter substantially equal to the inner diameter of the second inner cavity

148

. The extrusion pin

90

is fixedly coupled to the bed portion

12

and extends through the inner cavity

88

A. The sixth and seventh dies

86

,

88

are slidably coupled to the bed portion

12

and slide about the extrusion pin

90

.

The fourth punch assembly

84

includes a forming element

92

and a forming punch

94

which are fixedly coupled to the ram portion

14

and move with the same. The forming element

92

includes an inner cavity

92

A having an inner diameter substantially equal to the outer diameter of the first portion

142

of the billet

140

, and specifically, substantially equal to the outer diameter of the first section

142

B of the first portion

142

of the billet

140

. The punch

94

has an outer diameter substantially equal to the outer diameter of the first section

142

B of the first portion

142

of the billet

140

. As the ram portion

14

moves toward the bed portion

12

, the punch assembly

84

engages the billet

140

held adjacent to the sixth die

86

via the pair of the work transfer fingers

130

. The second portion

144

of the billet

140

is pushed through the sixth die

86

until it engages the seventh die

88

. The first section

142

B of the first portion

142

of the billet

140

is contained within the forming element

92

.

The ram portion

14

continues to move towards the bed portion

12

with the second portion

144

of the billet supported by the seventh die

88

and the extrusion punch

90

. The first section

142

B of the first portion

142

of the billet

140

as well as the second portion

160

B of the insert

160

are contained and supported by the forming element

92

and the punch

94

. The punch

94

is driven with an appropriate amount of force to cause the sixth and seventh dies

86

,

88

to slide about the extrusion pin

90

, thereby displacing material from the second section

142

C of the first portion

142

of the billet

140

and the first portion

162

A of the insert

162

outwards. The outer diameter of the second section

142

C and the outer diameter of the first portion

162

A of the insert

162

increase, thereby mechanically locking the insert

162

into the billet

140

. The length of the insert

160

also decreases in the process. In other words, the displacement of material causes the first portion

160

A of the insert

160

to swell outward and to compress longitudinally, thereby locking it into place as the outer diameter of the first portion

160

A is greater than the outer diameter of the second portion

160

B. Further, the second cavity

144

is forward extruded into the first portion

142

of the billet

140

. With the billet

140

deformed and the insert