DUCTILE IRON DATA FOR DESIGN ENGINEERS

 

 

 

Home Page

SECTION VI.  MACHINABILITY

Introduction
Machinability
Effect of Microsturcture
Comparative Machinability
Hard Spots
Surface Finish
Coining
Manufacturability Considerations
Machining Recommendations
References

Introduction

To succeed in the fiercely competitive international markets for all finished products, from motorcycles to machine tools, manufacturers must offer the end user the best value - the highest ratio of quality to cost. In order to maximize quality while minimizing cost, designers have added manufacturability to the list of criteria that must be met by a successful design. This trend toward increasing importance of manufacturability has been confirmed by the results of a survey of 2500 design engineers conducted by the Ductile Iron Group. When asked to rank 19 materials selection criteria in order of importance, respondents placed both ease of machining and cost of manufacture in the top six. In modem manufacturing terminology, manufacturability is an attribute which indicates how economically a component can be produced to meet customer specifications. This concept embraces the traditional indicators of machinability - tool life, power requirements, and surface finish and accuracy - and adds other manufacturability criteria such as cycle times, yield, scrap, consistency, inventory requirements, compatibility with automated NC machining, and overall manufacturing cost.

The production of most finished metal products involves machining operations to produce the desired final shape. Castings offer the designer the lowest cost route for the production of complex shapes because they can be cast to near final shape, reducing both machining and materials costs. Near net shape casting technology and improved dimensional consistency offered by competent, modern foundries yield additional savings in manufacturing costs. Ductile Iron, with its excellent castability, offers the designer all the manufacturing advantages of castings plus the added benefits of a machinability: strength ratio that is superior to other cast irons and cast steels.

Back to Top

Machinability
Machinability is not an intrinsic property of a material, but rather the result of complex interactions between the workpiece and various cutting devices operated at different rates under different lubricating conditions. As a result, machinability is measured empirically, with results applicable only under similar conditions. Traditionally, machinability has been measured by determining the relationship between cutting speed and tool life because these factors directly influence machine tool productivity and machining costs. The increased use of disposable inserts has reduced tool life costs and this factor, along with a greater emphasis on quality, has increased the importance of surface finish and dimensional accuracy and consistency.

Back to Top

Effect of Microstructure
Machinability is determined by microstructure and hardness. The graphite particles in Gray, Malleable and Ductile Irons are responsible for the free-machining characteristics of these materials and their superior machinability when compared to steels. Within the cast irons, graphite morphology plays an important role in machinability, with the graphite flakes found in Gray Iron providing superior machining characteristics. While the graphite particles influence cutting force and surface finish, the matrix is the primary determinant of tool life.

Hardness is often used as an indicator of machinability because of the close relationship between hardness and microstructure. However, hardness gives an accurate representation of machinability only for similar microstructures. For example, a tempered martensite matrix will exhibit superior machinability to a pearlitic matrix of similar hardness. Figure 6.1 describes the relative machinability of ferrite and pearlite. The properties and machinabilities of these and other matrix components follow.

Ferrite is the softest matrix constituent in Ductile Iron and as a result exhibits the best machinability. While not as soft as the ferrite in steel, the ferrite in Ductile Iron gives superior machinability due to the effect of silicon, which decreases ferrite toughness, and the lubricating and chip-breaking effects of the graphite spheroids. Machinability increases with silicon content up to about 3% but decreases significantly with increasing silicon content above this level.

Pearlite, which consists of an intimate mixture of soft ferrite and hard lamellar iron carbide, is a common matrix component in all intermediate strength grades of Ductile Iron. The volume fraction of pearlite and the fineness of the lamellae determine the hardness and the machinability of Ductile Iron. Although machinability decreases with increasing pearlite content, pearlitic irons are considered to have the best combination of machinability and wear resistance. Figure 6.1 shows that pearlite fineness affects machinability and that the effect of hardness decreases as pearlite fineness increases.

Carbides are the hardest constituents in Ductile Iron and have the poorest machinability. When present as thin lamellae in pearlite they are easily sheared and are in their most machinable form. When present as massive or "free" carbide, both iron and alloy carbides cause a dramatic reduction in machinability (Figure 6.2).

Martensite is an extremely hard matrix phase produced by quenching Ductile Iron. It is too hard and brittle to be machined as quenched, but after tempering martensite is more machinable than pearlite of similar hardness.

Other structures such as acicular bainites and ferrite are produced by interrupted cooling in Ductile Irons with sufficient hardenability to suppress the formation of ferrite and pearlite. Acicular microstructures have a similar machinability to martensite tempered to the same hardness.

Back to Top

Comparative Machinability
Improved machinability is often one of the benefits gained when a steel component is replaced by a Ductile Iron casting. Machining Handbooks do not present an unambiguous indication of the improved machinability of Ductile Iron, and it is instructive to use practical examples whenever possible. Experience gained by General Motors during the machining of ferritized Ductile Iron blanks for the production of ADI hypoid pinion-and-ring gears revealed improvements in tool life ranging from 20% to over 900%, compared to the annealed, forged steel blanks (Table 6.1). In addition to improved tool life and reduced tool costs, the improved machinability led to significant increases in productivity. Both laboratory and shop trials at Fiat (Table 6.2) on the machining of differential bevel gears revealed that, compared to a forged 18CrMo4 steel, ferritic Ductile Iron could be machined faster with less tool wear, resulting in increased productivity and reduced costs.

Back to Top

Table 6.1 Tool life improvement resulting from the replacement of forged steel gear blanks by ferritic Ductile Iron.

Machining operation Tool-life improvement
%
Pinion blanking
- centre press
- drill
- rough lathes
- finish lathes
- grind
30
35
70
50
20
Rear-gear blanking
- bullard turning
- drilling
- reaming
200
20
20
Gleason machining
- pinion - roughing
- pinion - finishing
- ring - roughing
- ring - finishing
900
233
962
100

Back to Top

Table 6.2 Comparison of the machinability of a ferritic Ductile Iron and a forged 18CrMo4 steel.

    Ductile Iron Steel
Component Operation No. machined Wear, mm No. machined Wear, mm
Crown wheel Rough boring 250-300 0.5 - 0.7 80 - 100 1.5
Facing 250 0.2 100 0.4
Drilling, reaming and
tapping of bolt holes
1300 --- 500 ---
Rough tooth-cutting 1300 0.4 - 0.5 180 0.9 - 1.0
Finish tooth-cutting 1300 0.2 200 0.5
Bevel pinion Hoading of both ends 3200 --- 1600 ---
Turning of shank
and conical head
400 0.4 200 ---
Rough tooth-cutting 1300 0.4 - 0.5 200 0.9 - 1.0
Finish tooth-cutting 1300 0.2 200 0.4

Back to Top

Hard Spots
Isolated "hard spots" in castings can seriously degrade machining performance. These areas of significantly increased hardness usually consist of carbides caused by localized rapid cooling and excess levels of carbide forming elements. Undissolved inoculant, oxides (slag), refractories, dross and burned-on moulding sand can also produce hard spots that are detrimental to machinability. Most hard spots can be eliminated by the use of good foundry practice: minimum levels of carbide forming elements (including magnesium and cerium), good inoculation, minimum holding times, correct pouring temperatures, good pouring practices, hard, expansion-resistant molds and good gating practices, including the use of gating system filters. Unavoidable hard areas in complex castings caused by rapid, localized cooling can be eliminated by annealing or normalizing heat treatments.

Surface Finish
Ductile Iron can be machined to produce a very fine surface finish, with the degree of finish depending on the fineness of the grain structure and the finishing method. With grinding and honing, a surface finish of four microinches or less is possible. Table 6.3 summarizes the surface finishes that can be obtained with various machining operations and different grades of Ductile Iron.

Back to Top

Table 6.3 Surface finish in machined Ductile Irons.

  Type of Ductile Iron
60-40-18
152 BHN
80-55-06
223 BHN
100-70-03
265 BHN
120-90-02
302 BHN
Machining Operation Microinch µm Microinch µm Microinch µm Microinch µm
Turning, Carbide,
Roughing Depth with
soluble oil
60-80 1.52-2.03 55-80 1.40-2.03 60-100 1.52-2.54 60-100 1.52-2.54
Turning, Carbide,
Finishing Depth with
soluble oil
70-80 1.78-2.03 40-60 1.02-1.52 50-100 1.27-2.54 50-100 1.27-2.54
Face Milling, Carbide,
Roughing Depth with
and without face land
100-400 2.54-10.16 70-350 1.78-8.89 70-400 1.78-10.16 90-400 2.29-10.16
Face Milling, Carbide,
Finishing Depth
with face land
80-120 2.03-3.05 60-80 1.52-2.03 60-70 1.52-1.78 80-110 2.03-2.79
Surface Grinding,
Roughing
15-30 0.38-0.76 15-25 0.28-0.64 15-25 0..38-0.64 15-25 0.38-0.64
Surface Grinding,
Finishing
4-15 0.10-0.38 4-15 0.10-0.38 3-12 0.08-0.30 3-10 0.08-0.25
Cylindrical Grinding,
Roughing*
21 0.53 21 0.53 21 0.53 21 0.53
Cylindrical Grinding,
Finishing
4 0.10 4 0.10 4 0.10 4 0.10
Flat Lapping, Roughing* 12-20 0.30-0.51 12-20 0.30-0.51 12-20 0.30-0.51 12-20 0.30-0.51
Flat Lapping, Finishing 6-11 0.15-0.28 6-11 0.15-0.28 6-11 0.15-0.28 6-11 0.15-0.28
Cylindrical Lapping* 7-9 0.18-0.23 7-9 0.18-0.23 7-9 0.18-0.23 --- ---
Honing* 4-6 0.10-0.15 4-9 0.19-0.23 4-6 0.10-0.15 --- ---
Super Finishing* 5-11 0.13-0.28 --- --- 5-9 0.13-0.23 3-4 0.08-0.10

*Reference

Back to Top

Coining
Coining is a specialized operation that can be used to both deform a Ductile Iron casting to produce its final shape, and shear off ingates, feeder necks and parting line "flash". Due to the strength of Ductile Iron, the size of casting that can be coined and the degree of deformation produced are limited. However, for small, high production castings that have been cast to near final shape and require limited further dimensional control and ingate and feeder neck removal, coining is a highly cost-effective operation that can eliminate certain machining operations.

Manufacturability Considerations
The machinability of a casting is an important component in its overall manufacturability, but there are other important considerations. Machining allowance affects productivity, yield and machining costs. Compared to steel castings, Ductile Iron requires reduced machining allowance for similar section sizes. Increased consistency of casting dimensions resulting from high density molding, and reduced surface defects can permit further decreases in machining allowance. Consistency of casting dimension is critical to obtaining the performance offered by modem automated machining centers. Consultation between the designer and foundry, the incorporation of manufacturability criteria in the purchase specifications, and the selection of a competent Ductile Iron foundry as a source of consistent castings can significantly improve the manufacturability of the component and increase the value offered to the end user.

Machining Recommendations
Starting recommendations for the machining of Ductile Iron are summarized in Tables 6.4 - 6.8, obtained with permission from the Machining Data Handbook. For more complete data the reader should consult the first three references. Additional information on the machinability of Austempered Ductile Iron and Austenitic Ductile Iron can be found in Sections IV and Section V respectively.

Back to Top

Table 6.4 Starting recommendations for drilling Ductile Iron.

  Feedt: ipr or mm/rev  
Nominal Hole Diameter  
Material Hard-
ness
BHN
Condition Speed
fpm
m/min
1/16 in
1.5 min
1/8 in.
3 mm
1/4 in.
6 mm
1/2 in.
12 mm
3/4 in.
18 mm
1 in.
25mm
1-1/2 in.
35 mm
2 in.
50 mm
Tool
Material
Grade
AISI or C
ISO
DUCTILE CAST IRONS
Ferritic
ASTM A536; Grades
60-40-18. 65-45-12
SAE J434c: Grades
D4018. D4512
140
to
190
Annealed 85
115

26
35

.001
---

.025
---
.003



.075
.006



.15
.010



.25
.013



.33
.016



.40
.021



.055
.025



.065
M10
M7
M1
S2, S3
Ferritic-Pearlitic
ASTM A536: Grade
80-55-06
SAE J434c: Grade
D5506
190
to
225
As Cast 70


21
.001


.025
.003


.075
.006


.15
.010


.25
.013


.33
.016


.40
.021


.055
.025


.065
M10
M7
M1
S2, S3
  225
to
260
As Cast 50
15
.001
.025
.002
.050
.004
.102
.007
.18
.010
.25
.012
.30
.015
.40
.017
.45
T15, M42*
S9, S11*
Pearlitic-Martensitic
ASTM A536: Grade
100-70-03
SAE J434c: Grade D7003
240
to
300
Normalized
and
Tempered
45
14
.001
.025
.002
.050
.004
.102
.007
.18
.008
.20
.010
.25
.013
.33
.015
.40
T15, M42*
S9, S11*
Martensitic
ASTM A536: Grade
120-90-02
SAE J434c: Grade DQ&T
270
to
330
Quenched
and
Tempered
30
9
---
---
.001
.025
.002
.050
.004
.102
.005
.13
.006
.15
.007
.18
.008
.20
T15, M42*
S9, S11
  330
to
400
Quenched
and
Tempered
20
6
---
---
.001
.025
.002
.050
.004
.102
.005
.13
.006
.15
.007
.18
.009
.20
T15, M42*
S9, S11*
Austenitic (NI-RESIST)
ASTM A439: Types D-2,
D-2C, D-3A, D-5
ASTM A571: Type D-2M
120
to
200
Annealed 35
11
.001
.025
.002
.050
.005
.13
.007
.18
.010
.25
.012
.30
.015
.40
.018
.45
T15, M42*
S9, S11*
Austenitic
(NI-RESIST Ductile)
ASTM A439: Types
D-2B, D-3, D-4, D-5B
140
to
275
Annealed 25
8
.001
.025
.002
.050
.005
.13
.007
.18
.010
.25
.012
.30
.015
.40
.018
.45
T15, M42*
S9, S11*

Back to Top

Table 6.5 Starting recommendations for turning Ductile Iron with single point and box tools.

  Carbide Tool
Uncoated Coated
  High Speed Steel Tool Speed  
Material Hard-
ness
BHN
Con-
dition
Depth
of
Cut*
(in)
mm
Speed
fpm
m/min
Feed
ipr
mm/r
Tool
Material
AISI
ISO
Brazed
fpm
m/min
Index-
able
fpm
m/min
Feed
ipr
mm/r
Tool
Material
Grade
C
ISO
Speed
fpm
m/min
Feed
ipr
mm/r
Tool
Material
Grade
C
ISO
DUCTILE CAST
IRONS
Ferritic
ASTM A536;
Grades 60-40-18,
65-45-12
SAE J434c:
Grades
D4018, D4512
140
to
190
An-
nealed
.040
.150
.300
.625
1
4
8
16
200
150
125
100
60
46
38
30
.007
.015
.020
.030
.18
.40
.50
.75
M2, M3
M2, M3
M2, M3
M2, M3
S4, S5
S4, S5
S4, S5
S4, S5
700
550
450
360
215
170
135
110
775
600
500
400
235
185
150
120
.010
.020
.030
.040
.25
.50
.75
1.0
C-7
C-7
C-6
C-6
P10, M10
P10, M10
P20, M20
P30, M30
950
775
650
---
290
225
200
---
.010
.020
.030
---
.25
.50
.75
--
-
CC-7
CC-7
CC-6
---
CP10, CM10
CP10, CM10
CP20, CM20
---
Ferritic-Pearlitic
ASTM A536:
Grade
80-55-06
SAE J434c:
Grade
D5506
190
to
225
As Cast .040
.150
.300
.625
1
4
8
16
140
110
85
70
43
34
26
21
.007
.015
.020
.030
.18
.40
.50
.75
M2, M3
M2, M3
M2, M3
M2, M3
S4, S5
S4, S5
S4, S5
S4, S5
480
375
310
250
145
115
95
76
540
425
350
275
165
130
105
84
.010
.020
.030
.040
.25
.50
.75
1.0
C-7
C-7
C-6
C-6
P10, M10
P10, M10
P20, M20
P30, M30
700
550
450
---
215
170
135
---
.010
.020
.030
---
.25
.50
.75
---
CC-7
CC-7
CC-6
---
CP10, CM10
CP10, CM10
CP20, CM20
---
  225
to
260
As Cast .040
.150
.300
.625
1
4
8
16
100
75
60
50
30
23
18
15
.007
.015
.020
.030
.18
.40
.50
.75
T15, M42t
T15, M42t
T15, M42t
T15, M42t
S9, S11t
S9, S11t
S9, S11t
S9, S11t
320
250
200
160
100
76
60
49
360
280
230
185
110
85
70
56
.010
.020
.030
.040
.25
.50
.75
1.0
C-7
C-7
C-6
C-6
P10, M10
P10, M10
P20, M20
P30, M30
475
350
300
---
145
105
90
---
.010
.020
.030
---
.25
.50
.75
---
CC-7
CC-7
CC-6
---
CP10, CM10
CP10, CM10
CP20, CM20
---
Pearlitic-Martensitic
ASTM A536:
Grade
100-70-03
SAE J434c:
Grade D7003
240
to
300
Nor-
malized
and
Tempered
.040
.150
.300
.625
1
4
8
16
75
55
45
35
23
17
14
11
.005
.010
.015
020
.13
.25
.40
.50
T15, M42t
T15, M42t
T15, M42t
T15, M42t
S9, S11t
S9, S11t
S9, S11t
S9, S11t
260
220
160
130
79
67
49
40
300
230
190
150
90
79
58
46
.005
.010
.020
.030
.13
.25
.50
.75
C-8
C-7
C-6
C-6
P10, M10
P10, M10
P20, M20
P30, M30
400
300
250
---
120
90
76
---
.005
.010
.020
---
.13
.25
.50
---
CC-8
CC-7
CC-6
---
CP10, CM10
CP10, CM10
CP20, CM20
---
Martensitic
ASTM A536:
Grade
120-90-02
SAE J434c:
Grade DQ&T
270
to
330
Quenched
and
Tempered
.040
.150
.300
.625
1
4
8
16
50
40
30
---
15
12
9
---
.005
.010
.015
---
.13
.25
.40
---
T15, M42t
T15, M42t
T15, M42t
---
S9, S11t
S9, S11t
S9, S11t
---
175
130
110
---
53
40
34
---
200
150
125
---
60
46
38
---
.005
.010
.015
---
.13
.25
.40
---
C-8
C-7
C-7
---
P10, M10
P10, M10
P10, M10
---
250
200
150
---
76
60
46
---
.005
.010
.015
---
.13
.25
.40
---
CC-8
CC-7
CC-7
---
CP10, CM10
CP10, CM10
---
---
  330
to
400
Quenched
and
Tempered
.040
.150
.300
1
4
8
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
75
55
45
23
17
14
95
70
60
29
21
18
.003
.005
.010
.075
.13
.25
C-8
C-8
C-7
P10, M10
P10, M10
P10, M10
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
Austenitic
(NI-RESIST)
ASTM A439:
Types D-2,
D-2C, D-3A,
D-5 ASTM A571:
Type D-2M
120
to
200
Annealed .040
.150
.300
.625
1
4
8
16
70
60
50
35
21
18
15
11
.007
.015
.020
.030
.18
.40
.50
.75
T15, M24t
T15, M24t
T15, M24t
T15, M24t
S9, S11t
S9, S11t
S9, S11t
S9, S11t
225
160
125
100
69
49
38
30
250
175
140
115
76
53
43
35
.007
.015
.030
.040
.18
.40
.75
1.0
C-7
C-7
C-6
C-6
P10, M10
P10, M10
P20, M20
P20, M2O
325
225
175
---
100
69
53
---
.007
.015
.020
---
.18
.40
.50
---
CC-7
CC-7
CC-6
---
CP10, CM10
CP10, CM10
CP20, CM20
---

Back to Top

Table 6.6 Starting recommendations for turning Ductile Iron with ceramic tools.

Material Hardness
BHN
Condition Depth
of cut
in
mm
Speed
fpm
m/min
Feed
ipr
mm/rev
Type of
Ceramic*
DUCTILE CAST IRONS
Ferritic
ASTM A536: Grades 60-40-18, 65-45-12
SAE J434c: Grades D4018, D4512
140
to
190
Annealed .040
.150
.300
1
4
8
1200
1000
750
365
305
230
.010
.015
.025
.25
.40
.65
HPC
HPC
HPC
HPC
HPC
HPC
Ferritic-Pearlitic
ASTM A536: Grade 80-55-06
SAE J434c: Grade D5506
190
to
225
As Cast .040
.150
.300
1
4
8
1100
900
650
335
275
200
.010
.015
.020
.25
.40
.50
HPC
HPC
HPC

HPC
HPC
HPC
  225
to
260
As Cast .040
.150
.300
1
4
8
900
700
550
275
215
170
.005
.010
.015
.13
.25
.40
HPC
HPC
HPC
HPC
HPC
HPC
Pearlitic-Martensitic
ASTM A536: Grade 100-70-03
240
to
300
Normalized and
Tempered
.040
.150
.300
1
4
8
800
600
450
245
185
135
.005
.010
.015
.13
.25
.40
HPC
HPC
HPC
HPC
HPC
HPC
Martensitic
ASTM A536: Grade 120-90-02
SAE J434c: Grade DQ&T
270
to
330
Quenched and
Tempered
.040
.150
.300
1
4
8
750
550
400
230
170
120
.004
.008
.012
.102
.20
.30
HPC
HPC
HPC
HPC
HPC
HPC
  330
to
400

Quenched and
Tempered

.040
.150
.300
1
4
8
600
450
350
185
135
105
.003
.006
.009
.075
.15
.23
HPC
HPC
HPC
HPC
HPC
HPC
Austenitic (NI-RESIST Ductile)
ASTM A439: Types D-2, D-2C, D-3A, D-5
ASTM A571: Type D-2M
120
to
200

Annealed

.040
.150
.300
1
4
8
1000
700
450
305
215
135
.005
.010
.015
.13
.25
.40
HPC
HPC
HPC
HPC
HPC
HPC

Back to Top

Table 6.7 Starting recommendations for face milling Ductile Iron.

  Carbide Tool
Uncoated Coated
  High Speed Steel Tool Speed  
Material Hard-
ness
BHN
Condition Depth
of
Cut*
(in)
mm
Speed
fpm
m/min
Feed
ipr
mm/r
Tool
Material
AISI
ISO
Brazed
fpm
m/min
Index-
able
fpm
m/min
Feed
ipr
mm/r
Tool
Material
Grade
C
ISO
Speed
fpm
m/min
Feed
ipr
mm/r
Tool
Material
Grade
C
ISO
DUCTILE CAST
IRONS
Ferritic
ASTM A536;
Grades
60-40-18. 65-45-12
SAE J434c: Grades
D4018. D4512
140
to
190
Annealed .040
.150
.300
1
4
8

195
150
115
59
46
35
.010
.014
.018
.25
.36
.45
M2, M7
M2, M7
M2, M7
S4, S2
S4, S2
S4, S2
665
500
350
205
150
105
730
550
430
225
170
130
.010
.015
.020
.25
.40
.50
C-6
C-6
C-6
M20, P20
M30, P30
M40, P40
1100
715
560
335
220
170
.008
.012
.016
.20
.30
.40
CC-6
CC-6
CC-6
CP20, CM20
CM30, CP30
CM40, CP40
Ferritic-Pearlitic
ASTM A536:
Grade 80-55-06
SAE J434c: Grade
D5506
190
to
225
As Cast .040
.150
.300
1
4
8
145
110
85
44
34
26
.008
.012
.016
.20
.30
.40
M2, M7
M2, M7
M2, M7
S4, S2
S4, S2
S4, S2
465
350
245
140
105
75
510
385
300
155
115
90
.008
.012
.016
.20
.30
.40
C-6
C-6
C-6
M20, P20
M30, P30
M40, P40
765
500
400
235
150
120
.008
.012
.015
.20
.30
.40
CC-6
CC-6
CC-6
CM20, CP20
CM30, CP30
CM40, CP40
  225
to
260
As Cast .040
.150
.300
1
4
8
115
90
70
35
27
21
.008
.012
.016
.20
.30
.40
M2, M7
M2, M7
M2, M7
S4, S2
S4, S2
S4, S2
400
310
210
120
95
64
440
330
255
135
100
78
.007
.010
.014
.18
.25
.36
C-6
C-6
C-6
M20, P20
M30, P30
M40, P40
650
425
325
200
130
100
.007
.010
.014
.18
.25
.36
CC-6
CC-6
CC-6
CM20, CP20
CM30, CP30
CM40, CP40
Pearlitic-Martensitic
ASTM A536:
Grade
100-70-03
SAE J434c:
Grade D7003
240
to
300
Normalized
and
Tempered
.040
.150
.300
1
4
8
85
65
50
26
20
15
.006
.010
.014
.15
.25
.36
M2, M7
M2, M7
M2, M7
S4, S2
S4, S2
S4, S2
320
240
170
100
73
52
350
265
205
105
81
62
.006
.008
.010
.15
.20
.25
C-6
C-6
C-6
M20, P20
M30, P30
M40, P40
525
350
275
160
105
84
.005
.007
.009
.13
.18
.23
CC-6
CC-6
CC-6
CM20, CP20
CM30, CP30
CM40, CP40
Martensitic
ASTM A536:
Grade
120-90-02
SAE J434c:
Grade DQ&T
270
to
330
Quenched
and
Tempered
.040
.150
.300
.1
4
8
45
35
25
14
11
8
.006
.010
.014
.15
.25
.36
T15, M24t
T15, M24t
T15, M24t
S9, S11t
S9, S11t
S9, S11t
190
140
100
58
43
30
210
155
120
64
47
37
.006
.008
.010
.15
.20
.25
C-6
C-6
C-6
M20, P20
M30, P30
M40, P40
315
200
150
95
60
46-
.005
.007
.009
.13
.18
.23
CC-6
CC-6
CC-6
CM20, CP20
CM30, CP30
CM40, CP40
  330
to
400
Quenched
and
Tempered
.040
.150
.300
1
4
8
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
90
70
50
27
21
15
100
80
60
30
24
18
.004
.006
.008
.102
.15
.20
C-6
C-6
C-6
M20, P20
M30, P30
M40, P40
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
---
Austenitic
(NI-RESIST)
ASTM A439:
Types D-2,
D-2C, D-3A, D-5
ASTM A571:
Type D-2M
120
to
200
Annealed .040
.150
.300
1
4
8
40
25
20
12
8
6
.008
.012
.016
.20
.30
.40
T15, M24t
T15, M24t
T15, M24t
S9, S11t
S9, S11t
S9, S11t
175
100
70
53
30
21
195
110
85
59
34
26
.008
.012
.016
.20
.30
.40
C-6
C-6
C-6
M20, P20
M30, P30
M40, P40
290
140
110
88
43
34
.008
.012
.016
.20
.30
.40
CC-6
CC-6
CC-6
CM20, CP20
CM30, CP30
CM40, CP40
Austenitic
(NI-RESIST
Ductile)
ASTM A439:
Types
D-2B, D-3,
D-4, D-5B
140
to
275
Annealed .040
.150
.300
1
4
8
30
20
15
9
6
5
.006
.010
.014
.15
.25
.36
T15, M24t
T15, M24t
T15, M24t
S9, S11t
S9, S11t
S9, S11t
120
80
60
37
24
18
135
90
70
41
27
21
.007
.010
.014
.18
.25
.36
C-6
C-6
C-6
M20, P20
M30, P30
M40, P40
200
115
90
60
35
30
.007
.010
.014
.18
.25
.36
CC-6
CC-6
CC-6
CM20, CP20
CM30, CP30
CM40, CP40

Back to Top

Table 6.8 Starting recommendations for slab milling Ductile Iron.

Material Hardness
BHN
Condition Depth
of cut
in
mm
Speed
fpm
m/min
Feed/
Tooth
in mm
HSS Tool
Material
AISI
ISO
DUCTILE CAST IRONS
Ferritic
ASTM A536: Grades 60-40-18, 65-45-12
SAE J434c: Grades D4018, D4512
140
to
190
Annealed .040
.150
.300
1
4
8
190
145
115
58
44
35
.010
.012
.014
.25
.30
.36
M2, M7


S4, S2

Ferritic-Pearlitic
ASTM A536: Grade 80-55-06
SAE J434c: Grade D5506
190
to
225
As Cast .040
.150
.300
1
4
8
125
95
75
38
29
23
.008
.010
.012
.20
.25
.30
M2, M7


S4, S2

  225
to
260
As Cast .040
.150
.300
1
4
8
110
85
65
34
26
20
.006
.008
.010
.15
.20
.25
M2, M7


S4, S2

Pearlitic-Martensitic
ASTM A536: Grade 100-70-03
SAE J434c: Grade 7003
240
to
300
Normalized and
Tempered
.040
.150
.300
1
4
8
80
60
45
24
18
14
.006
.008
.010
.15
.20
.25
M2, M7


S4, S2

Martensitic
ASTM A536: Grade 120-90-02
SAE J434c: Grade DQ&T
270
to
330
Quenched and
Tempered
.040
.150
.300
1
4
8
40
30
20
12
9
6
.005
.006
.007
.13
.15
.18
M2, M7


S4, S2

Austenitic (NI-RESIST Ductile)
ASTM A439: Types D-2, D-2C, D-3A,
D-5
ASTM A571: Type D-2M
330
to
400
Quenched and
Tempered
.040
.150
.300
1
4
8
35
20
15
11
6
5
.005
.007
.009
.13
.18
.23
M2, M7


S4, S2

Austenitic (NI-RESIST Ductile)
ASTM A439: Types D-2B,
D-3, D-4, D-5B
120
to
200
Annealed .040
.150
.300
1
4
8
25
15
10
8
5
3
.005
.007
.009
.13
.18
.23
M2, M7


S4, S2

Back to Top

REFERENCES

The Iron Castings Handbook, Iron Castings Society, Inc., 1981,

Machining Data Handbook, 3rd edition. Metcut Research Associates, Inc., Cincinnati, OH, 1980.

Metals Handbook, Vol. 16, 9th Edition, American Society for Metals, Metals Park, OH, 1967.

N. M. Lottridge and R. B. Grindahl, "Nodular Iron Hypoid Gears." Proceedings, SAE Conference on Fatigue, Dearborn, USA, 14-16 April, 1982. Society of Automotive Engineers, Warrendale PA, pp. 213-218.

S. Corso, "Development of bainitic nodular iron for the construction of speed gears for the car industry." EEC Commission Report
Eur 8639.

M. Field and J. F. Kahles, "Factors Influencing Surface Finish in Turning and Milling of Gray and Ductile Irons," Society of Manufacturing Engineers, Dearborn, MI, 1971.

A. F. Ackenhausen and M. Field, "Determination and Analysis of Costs in N/C and Conventional Machining," SME Technical Paper, 1970.

"Machining Ductile Irons," International Nickel Co. Inc., New York, NY.

S. I. Karsay, Ductile Iron II, Quebec Iron and Titanium Corporation, 1972.

Machinery's Handbook, Industrial Press, 21st edition, New York, NY, 1979.

Tay-Forth Sales Limited, Private Communication, Stirlingshire, England, 1989.

K. B. Palmer, "The machinability of gray, nodular and compacted graphite irons compared by means of drilling tests," BCIRA Journal, January, 1983.

P. S. Cowen, "Coining Ductile Iron," Gray & Ductile Iron News, May, 1966.

Back to Top