DURO for Cold WorkSpecial Steels for Precise Die and Mold
RFor Cold WorkHigh Toughness Grades

DURO-F1
DURO-F3
DURO-F7High Wear Resistance Grade DURO-SPDURO-Created by NACHI’s original technology
Steels with superior balance of toughness and wear
resistance for precise die and mold
• DURO series, special steels for precise die and mold, are high quality and high grade materials
which are made by NACHI’s original technology of steel manufacturing and refining.
• They have less non-metallic inclusion and segregation that can cause fractures. Also shows
superior performance because of great control of carbide quantity and size.

: DURODURO-F1
DURO-F3
Matrix HSSToughness•DURO for Cold Work has two
type grades, High Toughness
Grades are DURO-F1, F3, F7,High Wear Resistance Grade is
DURO-SP.
•Each grade has a different
balance of toughness andwear resistance, so whatever
the application, there is a
DURO grade available.

GoodProperties of DURO for Cold WorkDURO-F7
FAX38
DURO-SP

M2
HM35

PM HSS

D2

Conventional HSS*Toughness=Resistance for crack initiation + Resistance for crack propagation

GoodWear Resistance

Typical Nachi Steel Grades
Classification

High Speed Steels(HSS)

Conventional HSS

SKH9D

Die and Punch
Plus Punch

HM42FAX SeriesPunch

ICS22

Die for Eye Glasses

MDS9

Mold for Rubber

MCR1

Die and Punch

DURO-F1, 3, 7, SP

Cold Work Die and Punch

DURO-F1, N1

Hot Work Die and Punch

Plastic Mold Steel with Corrosion
Resistance and Mirror Finish

PROVA-400

Plastic Mold

Corrosion and Wear Resistance
Alloy Steel

NPR1

Injection Molding Machine Parts

Die and Mold Steel for Cold Work

Steel for Precise Die and Mold
(DURO Series)
FM ALLOY

Application

HSU2C

Powder Metallugical HSSAlloy Tool Steels

Grade1

FM ALLOY isDURO isa brand name for NACHI’s newest material
products. Made from NACHI’s own technology tobe high performance alloys with finemicrostructure control.

named from the Latin word which means “hard”
or “endure”. A description for our tough materials
to be used for die and mold.

Benefits of DURO
• DURO is made by a highly purified procedure, to have high toughness and fatigue strength
because of very little non-metallic inclusions.
• Quantity and size of carbides in DURO microstructure are controlled to have a superior balanceof toughness and wear resistance.
Classification

GradeHardness

Strong Points

DURO-F1

HRC 54-60

Has the highest toughness in all die and mold materials
that get HRC60.

DURO-F3

HRC 57-62

Is a medium grade between F1 and F7, has goodtoughness and wear resistance.

DURO-F7

HRC 59-65

Has high hardness of HRC65, and still shows hightoughness.

DURO-SP

HRC 60-67

Has higher wear resistance than PM HSS, and stillshows good toughness.

High toughness die and mold steel

High Toughness
Matrix HSSWell balance steel

High wear resistance steelHigh WearResistanceSuper high wear resistance steel

HSS*DURO-F1 is also good for hot work, please reference NACHI catalog “DURO for Hot Work”.

Microstructure
DURO-F1

DURO-F3

DURO-F7

PM HSS

Conventional HSS

Die and Mold Steel for
Cold WorkDURO-SP*Nital etching
× 500

2

DURO Series have thebest balance forquantity and size ofcarbides in each grade
and a uniform
microstructure withminor segregation.

Features of DURO-F Series,
High Toughness Steels
Mechanical Properties

High bending fracture strength

Superior Charpy impact resistance

Charpy Impact Resistance (J/cm2)

Bending Fracture Strength (GPa)6.0
DURO-F1

5.5
DURO-F3

5.0
4.5

DURO-F7

4.0
M2

3.5
D2

3.0
2.5
2.0
565860626466

68160
140120

DURO-F1

100
DURO-F3806040

M2

D2

DURO-F7

200565860626466

68

Hardness (HRC)

Hardness (HRC)

DURO-F Series show high bending fracture strength inhardness range HRC 56-65.

DURO-F Series show superior charpy impact
resistance in hardness range HRC 56-65.

Grindability of DURO-F Series

Better grindability than other materialGround Ratio= (weight loss of a sample)/(weight loss of a wheel)
D2=100

Good160

Surface Grinder Machine
Wheel: WA60K
Feed: 60m/min
Depth: 0.05 mm
RPM: 2000 min-1

150

Ground Ratio

140130120110
1009080
DURO-F1

DURO-F3

DURO-F7

M2

D2

Grindability of DURO-F Series is better than M2
and D2.

3

Heat Treatment of DURO-F Series

Heat treatment condition
GradeRequirement

Aus. [˚C (˚F)]

Temp. [˚C (˚F)]

Hardness (HRC)

For toughness

1100 (2012)

580 × 2 (1076)

56.0Standard1120 (2048)

560 × 2 (1040)58.0

For wear1160 (2120)

560 × 2 (1040)

59.5

For toughness

1100 (2012)

580 × 2 (1076)

59.0Standard1140 (2084)

580 × 2 (1076)

60.0

For wear1160 (2120)

560 × 2 (1040)

61.5

For toughness1120 (2048)

600 × 2 (1112)

60.0Standard

1120 (2048)

580 × 2 (1076)

62.5

For wear1180 (2156)

560 × 2 (1040)

65.0

DURO-F1

DURO-F3

DURO-F7*Thickness of sample: 50 mm, vacuum furnace + pressure gas quenching (about 4 bar)
*Hardness may vary depending on material size and method, condition or facilities of heat treatment.

Hardness chart
DURO-F360625958

Aus.Temp. (˚C)

57

1160
1140
1120
1100
1080

565554500520540560580

600

Tempering Temperature (˚C)

DURO-F1 can be used in range
HRC 54-60.
To get HRC 60 it is suggested touse a salt bath furnace.

620

DURO-F766
65
Aus.Temp. (˚C)

611180
1160

60
5958

1140

57

1120
1100

56500

520

540560580

600

Tempering Temperature (˚C)

DURO-F3 can be used in range
HRC 57-62.
If hardness under HRC 57 isnecessary, DURO-F1 isrecommended.

4Hardness (HRC)

63

Hardness (HRC)

Hardness (HRC)

DURO-F1
61

Aus.Temp. (˚C)

646311801160

62611140

601120
1100

59620

58500

520

540

560

580

600

Tempering Temperature (˚C)

DURO-F7 can be used in range
HRC59-65.

620

Features of DURO-SP,High Wear Resistance Steel
Mechanical Properties
Superior wear resistance
5Matrix HSS(59HRC)OGOSHI’s test
Rotor: SCM435
Distance: 200 m
Final load: 6.3 kg

Wear Ratio ×10 –4(mm3/kgf•m)

4
PM HSS(65HRC)

32M2(62HRC)

1
DURO-SP(65HRC)

00.0

Good

0.5

1.0

1.5

2.0

2.5

Friction Speed (m/s)

3.0

3.5

Harder Situation

4.0

DURO-Sp shows superior wear resistancecompared not only to matrix HSS but
conventional HSS and even PM HSS.

Minimal loss of strength with rough surface◆Charpy impact resistance
Charpy Impact Resistance (J/cm2)◆Bending fracture strength

Bending Fracture
Strength (GPa)65
Worse surface
roughness

43

DURO-SP21

PM HSS

1023Strokes of die performance (x104)

60
50
40
Worse surface
roughness

3020

DURO-SP

10PM HSS0012

3

Strokes of die performance (x104)

DURO-SP shows less surface roughness andstrength decreases because of better wear
resistance than PM HSS.

DURO-SP shows less charpy impact resistancedecrease than PM HSS.
*Generally strength of materials decreases by notch effect as surface
roughness of the materials become worse.

*Generally strength of materials decreases by notch effect as surface
roughness of the materials become worse.

■Applications
GradeApplication

Life comparison

DURO-F1

Blanking punch

5 times longer than other matrix HSS

DURO-F3

Forming roll2 times longer than other cold work die steel

DURO-F7

Forming rack

1.5 times longer than other matrix HSS

Fine-blanking punch

4 times longer than other matrix HSS

Flow forming mandrel

5 times longer than other matrix HSS

Injection die

8 times longer than other matrix HSS

DURO-SP

5

Heat treatment of DURO-SP
Heat treatment condition
GradeRequirement

Aus. [˚C (˚F)]

Temp. [˚C (˚F)]

Hardness (HRC)

For toughness1120 (2048)

600 × 3 (1112)

61.0Standard

1160 (2120)

580 × 3 (1076)

64.0

For hardness andwear resistance

1200 (2192)

560 × 3 (1040)

66.0

DURO-SP*Thickness of sample: 50 mm, vacuum furnace + pressure gas quenching (about 4 bar)
*Hardness may vary depending on material size and method, condition or facilities of heat treatment.

Hardness of DURO-SP• The best heat treatment of DURO-SP differs depending on applications.
• For fine blanking around HRC 64 is a standard hardness.
• For flow forming mandrel HRC 60-62 is common and for some cold work forming punchs over HRC 67
could be a good choice.

Hardness chart6867Hardness (HRC)

6665
64

Aus. Temp. (˚C)

63

1200
1180
1160
1140

62611120
1100

60
59500

520

540560580

600

DURO-SP can be used in range HRC 60-67.
HRC 62-64 is normally recommended.

620

Tempering Temperature (˚C)

■Sample choices of steel grade for applications
Current Grade
PM HSS
M2
Matrix HSS
D2
H13

Recommendation

Life Factor

DURO-F1

DURO-F3

◎

○◎

◎

○○◎
◎

◎

DURO-F7

DURO-SP◎

Wear, Micro chipping
Chipping, Fracture
Wear, Micro chipping
Chipping, Fracture
Wear, Micro chipping
Chipping, Fracture
Wear, Micro chipping
Chipping, Fracture
Wear, Micro chipping

◎
○○○

◎◎○
◎ : Best ○ : Good

6

S4303E
2008.01.X-ABE-ABE