DIEVAR

UDDEHOLM DIEVAR

DIEVAR

REFERENCE STANDARD

ASSAB DF-2

ARNE

ASSAB DF-3

AISI

WNr.

JIS

O1

(1.2510)

(SKS 3)

O1

(1.2510)

(SKS 3)

ASSAB XW-5

SVERKER 3

D6 (D3)

(1.2436)

(SKD 2)

ASSAB XW-10

RIGOR

A2

1.2363

SKD 12

ASSAB XW-41

SVERKER 21

D2

1.2379

SKD 11

D2

1.2379

SKD 11

ASSAB XW-42 CARMO

CARMO

1.2358

CALMAX

CALMAX

1.2358

CALDIE

CALDIE

ASSAB 88

SLEIPNER

ASSAB PM 23 SUPERCLEAN

VANADIS 23 SUPERCLEAN

(M3:2)

1.3395

SKH 53

ASSAB PM 30 SUPERCLEAN

VANADIS 30 SUPERCLEAN

(M3:2 + Co)

1.3294

SKH 40

ASSAB PM 60 SUPERCLEAN

VANADIS 60 SUPERCLEAN

VANADIS 4 EXTRA SUPERCLEAN

VANADIS 4 EXTRA SUPERCLEAN

VANADIS 6 SUPERCLEAN

VANADIS 6 SUPERCLEAN

VANADIS 10 SUPERCLEAN

VANADIS 10 SUPERCLEAN

VANCRON 40 SUPERCLEAN

VANCRON 40 SUPERCLEAN

ELMAX SUPERCLEAN

ELMAX SUPERCLEAN

(1.3292)

ASSAB 518

P20

1.2311

ASSAB 618

P20 Mod.

1.2738

ASSAB 618 HH

P20 Mod.

1.2738

ASSAB 618 T

P20 Mod.

1.2738 Mod.

ASSAB 718 SUPREME

IMPAX SUPREME

P20 Mod.

1.2738

ASSAB 718 HH

IMPAX HH

P20 Mod.

1.2738

NIMAX

NIMAX

MIRRAX 40

MIRRAX 40

VIDAR 1 ESR

VIDAR 1 ESR

UNIMAX

UNIMAX

CORRAX

CORRAX

ASSAB 2083

420 Mod. H11

1.2343

SKD 6

420

1.2083

SUS 420J2

STAVAX ESR

STAVAX ESR

420 Mod.

1.2083 ESR

SUS 420J2

MIRRAX ESR

MIRRAX ESR

420 Mod.

POLMAX

POLMAX

RAMAX HH

RAMAX HH

ROYALLOY

ROYALLOY

420 F Mod.

PRODAX ASSAB MM40 ALVAR 14

ALVAR 14

ASSAB 2714 ASSAB 8407 2M

ORVAR 2M

ASSAB 8407 SUPREME

ORVAR SUPREME

DIEVAR

DIEVAR

HOTVAR

HOTVAR

QRO 90 SUPREME

QRO 90 SUPREME

1.2714

SKT 4

1.2714

SKT 4

H13

1.2344

SKD 61

H13 Premium

1.2344 ESR

SKD 61

4340

1.6582

SNCM8

ASSAB 709

4140

1.7225

SCM4

ASSAB 760

1050

1.1730

S50C

ASSAB 705

ASSAB is a trademark of ASSAB Pacific Pte Ltd. The information contained herein is based on our present state of knowledge and is intended to provide general notes on our products and their uses. It should not therefore be construed as a warranty of specific properties of the products described or a warranty for fitness for a particular purpose. Each user of ASSAB products is responsible for making its own determination as to the suitability of ASSAB products and services. Edition D140715

2

DIEVAR

DIEVAR Dievar is a hot work die steel specially developed by Uddeholm Tooling, our steel mill in Sweden, to provide the best possible performance. The chemical composition and the very latest in production technique make the property profile outstanding. Dievar possesses a combination of excellent toughness and very good hot strength, resulting in a superior hot work die steel that have excellent resistance to heat checking and gross cracking. Dievar is suitable for high demand hot work applications like die casting, extrusion and forging. The property profile also makes it a suitable choice in other applications such as plastic moulding (e.g., to solve chipping/ cracking) and High Performance Steel. Dievar offers the potential for significant improvements in die life, thereby improving the tooling economy.

3

DIEVAR

General Dievar is a high performance chromium-molybdenumvanadium alloyed hot work tool steel which offers a very good resistance to heat checking, gross cracking, hot wear and plastic deformation. Dievar is characterised by:

DIE CASTING

Excellent toughness and ductility in all directions Good temper resistance Good high-temperature strength Excellent hardenability Good dimensional stability throughout heat treatment and coating operations

Type

Cr-Mo-V alloyed hot work tool steel

Standard specification

None

Delivery condition

Soft annealed to approx. 160 HB

Colour code

Yellow / Grey

Part

Aluminium / Magnesium alloys

Dies

44-50 HRC

EXTRUSION

Dievar is a premium hot work tool steel developed by Uddeholm. It is manufactured utilising the very latest in production and refining techniques. The Dievar development has yielded a die steel with the ultimate resistance to heat checking, gross cracking, hot wear and plastic deformation. The unique properties profile of Dievar makes it the best choice for die casting, forging and extrusion.

Applications Heat checking is one of the most common failure mechanisms, e.g., in die casting and nowadays also in forging applications. Dievar’s superior ductility yields the highest possible level of heat checking resistance. With Dievar’s outstanding toughness and hardenability, its resistance to heat checking will be further improved. If gross cracking is not a factor, then a higher working hardness can be utilised (+2 HRC).

Part

Copper alloys

Aluminium / Magnesium alloys

Dies

-

46-52 HRC

46-52 HRC

44-52 HRC

Liners, dummy blocks, stems

HOT FORGING

Regardless of the dominant failure mechanism (e.g., heat checking, gross cracking, hot wear or plastic deformation), Dievar offers the potential for significant improvements in die life as well as tooling economy. Part

Dievar is the material of choice for the high demand die casting, forging and extrusion industries.

4

Inserts

Steel / Aluminium 44-52 HRC

DIEVAR

Properties The reported properties are representative of samples which have been taken from the centre of a 610 x 203 mm bar. Unless otherwise indicated, all specimens were hardened at 1025°C, quenched in oil and tempered 2 + 2 hours at 615°C to 45±1 HRC. PHYSICAL PROPERTIES

Charpy V-notch impact toughness at elevated temperatures Short transverse direction.

Hardened and tempered to 44 - 46 HRC. Temperature

At a hardness of approximately 45 HRC, the minimum average unnotched impact ductility is 300 J in the short transverse direction.

20°C

Impact energy, J

400°C

140

600°C

120 Density kg/m3 Modulus of elasticity MPa

7800

7700

7600

210 000

180 000

145 000

45 HRC 100 80 47 HRC 60

Coefficient of thermal expansion per °C from 20°C

-

13.3 x 10 -6

12.7 x 10 -6

40 20

Thermal conductivity W/m °C

-

31

50 HRC

32 50

100 150

200 250 300 350 400 450°C Testing temperature

MECHANICAL PROPERTIES Temper resistance

Approximate tensile properties at room temperature, tested in the short transverse direction. Hardness

The specimens have been hardened and tempered to 45 HRC, and then held at different temperatures from 1 to 100 hours.

44 HRC

48 HRC

52 HRC

Tensile strength, Rm

1480 MPa

1640 MPa

1900 MPa

Yield strength, RP0.2

1210 MPa

1380 MPa

1560 MPa

Elongation, A 5

13 %

13 %

12.5 %

Reduction of area, Z

55 %

55 %

52 %

Hardness, HRC 50 500°C 45 550°C 40

35

Approximate tensile properties at elevated temperatures

600°C 30

Short transverse direction, 45±1 HRC. A5, Z % 100

Rm, Rp0.2 MPa 2000 Z

1800

90

25 0.1

650°C

1

10

100

Time, h

80

1600

70

1400 Rm

1200

60 50

1000 800

40

Rp0.2

30

600

20

400 200

10

A5 100

200 300 400 500 Testing temperature

600

700ºC

5

DIEVAR

Heat treatment SOFT ANNEALING

QUENCHING

Protect the steel and heat through to 850°C. Then cool in the furnace at 10°C per hour to 650°C, then freely in air.

As a general rule, quench rates should be as rapid as possible. Accelerated quench rates are required to optimise tool properties specifically with regards to toughness and resistance to gross cracking. However, risk of excessive distortion and cracking must be considered.

STRESS RELIEVING

The quenching media should be capable of creating a fully hardened microstructure. Different quench rates for Dievar are defined by the CCT graph as shown in page 7.

After rough machining, the tool should be heated through to 650°C, holding time 2 hours. Cool slowly to 500°C, then freely in air.

High speed gas/circulating atmosphere Vacuum (high speed gas with sufficient positive pressure). An interrupted quench at 320–450°C is recommended for distortion control, or when quench cracking is a concern. Martempering bath, salt bath or fluidised bed at 450–550°C Martempering bath, salt bath or fluidised bed at approx. 180–200°C Warm oil, approx. 80°C

HARDENING Preheating temperature: 600–900°C. Normally a minimum of two preheats, the first in the 600–650°C range, and the second in the 820–850°C range. When three preheats are used, the second is carried out at 820°C, and the third at 900°C. Austenitising temperature: 1000–1030°C

Temperature °C

Soaking time minutes

Hardness before tempering

1000

30

52±2 HRC

1025

30

55±2 HRC

Note: Temper the tool as soon as its temperature reaches 50–70°C.

TEMPERING Choose the tempering temperature according to the hardness required by reference to the tempering graph below. Temper at least three times for die casting dies, and two times for forging and extrusion tools. The tool should be cooled to room temperature between the tempers. The minimum holding time at tempering temperature is 2 hours.

Soaking time = time at hardening temperature after the tool is fully heated through.

Tempering in the range of 500–550°C is normally not recommended, and it will result in a lower toughness.

Protect the tool against decarburisation and oxidation during austenitising.

Tempering graph Hardness, HRC 60

Hardness, grain size and retained austenite as functions of austenitising temperature Grain size ASTM Hardness, HRC 10 60 8

58

6

56

1000°C

Retained austenite

1010

1020

1030

1040 1050°C

Austenitising temperture

6

Temper

45

54

50 990 1000

50

Grain size

Hardness

52

Austenitising temperature 1025°C

55 Retained austenite %

Retained austenite, %

40

6

4

35

4

2

30

0

25

Retained austenite

100

200

300

400

2

500

Tempering temperature (2 + 2h)

600

700°C

DIEVAR

Effect of tempering temperature on room temperature Charpy V-notch impact energy

DIMENSIONAL CHANGES DURING HARDENING AND TEMPERING

Short transverse direction.

During hardening and tempering, the tool is exposed to both thermal and transformation stresses. These stresses will result in distortion. Insufficient levels of machine stock may result in slower than recommended quench rates during heat treatment. To reduce the level of distortion, a stress relief is always recommended bewteen rough and semi-finish machining, prior to hardening.

Impact strength 60

Hardness HRC 60

50

50

40

40 Temper brittleness zone

30

30

20

20

10

10 200

300

400

500

600

For a stress relieved Dievar tool, a minimum machining allowance of 0.3% is recommended to correct for distortion during heat treatment with a rapid quench.

700°C

Tempering temperature (2h + 2h)

CCT graph Austenitising temperature 1025°C. Holding time 30 minutes. °C 1100

Austenitising temperature 1025ºC Holding time 30 minutes

1000

AC1 = 890ºC

900

f

AC1 = 820ºC

Carbides

800

s

Pearlite

700 600 500

Cooling Hardness Curve No. HV 10

400 300

1 2 3 4 5 6 7 8 9

Bainite

MS

200

Mf

Martensite

100 1

1

3

2

10

100 1

4

1000 10

1.5

6

10 000

10

8

7

100 000

100

1000

1 0.2

5

1.5 15 280 1248 3205 5200 10400 20800 41600

Seconds Minutes

10 90

9

681 627 620 592 566 488 468 464 405

T800-500 (sec)

600

100 Hours Air cooling of bars, Ømm

7

DIEVAR

Machining recommendations The cutting data below are to be considered as guiding values and as starting points for developing your own best practice.

MILLING Face and square shoulder milling

Condition: Soft annealed condition ~160 HB TURNING

Cutting data parameters

Rough turning

Fine turning

Fine turning

150 - 200

Feed (f) mm/r

0.2 - 0.4

0.05 - 0.2

0.05 - 0.3

2-4

0.5 - 2

0.5 - 2

P20 - P30 Coated carbide

P10 Coated carbide or cermet

-

Carbide designation ISO †

Turning with HSS†

Turning with cabide

Cutting speed (vc) m/min

Depth of cut (ap) mm

Milling with carbide

Cutting data parameters

200 - 250

Rough milling

Fine milling

Cutting speed (vc) m/min

130 - 180

180 - 220

Feed (f z) mm/tooth

0.2 - 0.4

0.1 - 0.2

2-4

≤2

P20 - P40 Coated carbide

P10 Coated carbide or cermet

15 - 20 Depth of cut (ap) mm Carbide designation ISO

End milling

High speed steel

Type of milling Cutting data parameters

Solid carbide

Carbide indexable insert

High speed steel

130 - 170

120 - 160

25 - 301

Feed (f) mm/tooth

0.03 - 0.202

0.08 - 0.202

0.05 - 0.352

Carbide designation ISO

-

P20 - P30

-

DRILLING High speed steel twist drill Drill diameter mm

Cutting speed (vc) m/min

Feed (f) mm/r

≤5

15 - 20 *

0.05 - 0.15

5 - 10

15 - 20 *

0.15 - 0.20

10 - 15

15 - 20 *

0.20 - 0.25

15 - 20

15 - 20 *

0.25 - 0.35

Cutting speed (vc) m/min

1

For coated HSS end mill, vc~ 45–50 m/min

* For coated HSS drill, vc~ 35–40 m/min

GRINDING Wheel recommendation

Carbide drill

Type of grinding

Type of drill Cutting data parameters

Cutting speed (vc) m/min Feed (f) mm/r 1 2

Indexable insert

Solid carbide

180 - 220

120 - 150

60 - 90

0.05 - 0.252

0.10 - 0.252

0.15 - 0.252

Drill with replaceable or brazed carbide tip Depending on drill diameter

8

Brazed carbide1

Grinding wheel designation

Face grinding straight wheel

A 46 HV

Face grinding segments

A 24 GV

Cylindrical grinding

A 46 LV

Internal grinding

A 46 JV

Profile grinding

A 100 LV

DIEVAR

Machining recommendations The cutting data below are to be considered as guiding values and as starting points for developing your own best practice.

MILLING Face and square shoulder milling

Condition: Hardened and tempered to 45±1 HRC TURNING Cutting data parameters

Turning with carbide Rough turning

Fine turning

Cutting speed (vc) m/min

40 - 60

70 - 90

Feed (f) mm/r

0.2 - 0.4

0.05 - 0.2

1-2

0.5 - 1

Depth of cut (ap) mm Carbide designation ISO

Milling with carbide

Cutting data parameters

P20 - P30 Coated carbide

Rough milling

Fine milling

Cutting speed (vc) m/min

50 - 90

90 - 130

Feed (f z) mm/tooth

0.2 - 0.4

0.1 - 0.2

2-4

≤2

P20 - P40 Coated carbide

P10 Coated carbide or cermet

Depth of cut (ap) mm Carbide designation ISO

P10 Coated carbide or cermet

End milling Type of milling Cutting data parameters

DRILLING

Solid carbide

Carbide indexable insert

High speed steel TiCN coated

60 - 80

70 - 90

5 - 10

Feed (f) mm/tooth

0.03 - 0.201

0.08 - 0.201

0.05 - 0.351

Carbide designation ISO

-

P10 - P20

-

High speed steel twist drill (TiCN coated) Drill diameter mm

Cutting speed (vc) m/min

Feed (f) mm/r

≤5

4-6

0.05 - 0.10

5 - 10

4-6

0.10 - 0.15

10 - 15

4-6

0.15 - 0.20

15 - 20

4-6

0.20 - 0.30

Cutting speed (vc) m/min

1

Depending on radial depth of cut and cutter diameter

GRINDING Wheel recommendation

Carbide drill

Type of grinding

Type of drill Cutting data parameters

Cutting speed (vc) m/min Feed (f) mm/r 1 2

Indexable insert

Solid carbide

Brazed carbide1

60 - 80

60 - 80

40 - 50

0.05 - 0.252

0.10 - 0.252

0.15 - 0.252

Grinding wheel designation

Face grinding straight wheel

A 46 HV

Face grinding segments

A 36 GV

Cylindrical grinding

A 60 KV

Internal grinding

A 60 IV

Profile grinding

A 120 JV

Drill with replaceable or brazed carbide tip Depending on drill diameter

9

DIEVAR

Surface treatment NITRIDING AND NITROCARBURISING

Depth of nitriding

Nitriding and nitrocarburising result in a hard surface layer which has the potential to improve resistance to wear and soldering, as well as resistance to premature heat checking. Dievar can be nitrided using gas or plasma. It can also be nitrocarburised via gas or salt bath process. The nitriding and nitrocarburising temperature should be at least 25–50°C below the highest previous tempering temperature, depending upon the process time and temperature. Otherwise, a permanent loss of core hardness, strength, and/or dimensional tolerances may be experienced. During nitriding and nitrocarburising, a brittle compound layer, known as the white layer, may be generated. The white layer is very brittle and may result in cracking or spalling when exposed to heavy mechanical or thermal loads. As a general rule, the white layer formation must be avoided.

Process

Surface hardness

HV0.2

Depth* mm

Gas nitriding at 510°C

10 30

1100 1100

0.16 0.22

Plasma nitriding at 480°C

10

1100

0.15

2

1100

0.13

1

1100

0.08

Nitrocarburising – in gas at 580°C – in salt bath at 580°C *

Time h

Depth of case = distance from surface where hardness is 50 HV0.2 over base hardness

Electrical discharge machining Following the EDM process, the applicable die surfaces are covered with a resolidified layer (white layer) and a rehardened and untempered layer, both of which are very brittle and hence detrimental to die performance. If EDM is used, the white layer must be completely removed by grinding or stoning. After finish machining, the tool should be given an additional temper at approx. 25°C below the highest previous tempering temperature.

Nitriding in ammonia gas at 510°C, or plasma nitriding at 480°C, both result in a surface hardness of approx. 1100 HV0.2 . In general, plasma nitriding is the preferred method because of better control over nitrogen potential. However, careful gas nitriding can give perfectly acceptable results. The surface hardness after nitrocarburising in either gas or salt bath at 580°C is approx. 1100 HV0.2 .

10

DIEVAR

Welding

Further information

Welding of die components can be performed, with acceptable results, as long as proper precautions are taken during the preparation of the joint, the filler material selection, the preheating of the die, the controlled cooling of the die and the post weld heat treatment processes. The following guidelines summarise the most important welding process parameters. Welding method

TIG

MMA

Working temp.1

325 - 375ºC

325 - 375ºC

Filler material

QRO 90 TIG-WELD DIEVAR TIG-WELD

QRO 90 WELD

475°C

475°C

Maximum interpass temp.2 Cooling rate Hardness after welding

For further information, i.e., steel selection, heat treatment, application and availability, please contact our ASSAB office nearest to you.

20 - 40ºC/h for the first 2 to 3 hours and then freely in air

50 - 55 HRC

50 - 55 HRC

Heat treatment after welding

1 2

Hardened condition

Temper at 25°C below the original tempering temperature.

Soft annealed condition

Soft anneal the material at 850°C in protected atmosphere. Then cool in the furnace at 10°C per hour to 600°C, then freely in air.

Preheating temperature must be established throughout the die and must be maintained for the entire welding process, to prevent weld cracking The temperature of the tool in the weld area immediately before the second and subsequent pass of a multiple pass weld. When exceeded, there is a risk of distortion of the tool or soft zones around the weld.

11

DIEVAR

Relative comparison of ASSAB hot work die steels QUALITATIVE COMPARISON OF CRITICAL DIE STEEL PROPERTIES ASSAB grade

Temper resistance

Hot yield strength

Creep strength

Coefficient of thermal expansion

Heat conductivity

Ductility

ALVAR 14 ASSAB 8407 2M ASSAB 8407 SUPREME DIEVAR HOTVAR QRO 90 SUPREME

QUALITATIVE COMPARISON OF RESISTANCE TO DIFFERENT DIE FAILURES ASSAB grade ALVAR 14 ASSAB 8407 2M ASSAB 8407 SUPREME DIEVAR HOTVAR QRO 90 SUPREME

12

Heat checking

Gross cracking

Hot wear / Erosion

Plastic deformation

Corrosion (Al)

DIEVAR

13

DIEVAR

Case study RESISTANCE TO HEAT CHECKING Product : Automotive housing Work material : A380 Aluminium alloy Work temp. : 690°C Tooling size : 406 x 508 x 508 mm Die material : Premium H13 at 44-46 HRC vs DIEVAR 46-48 HRC Background : Severe heat checking begins on Premium H13 at approximately 20,000 shots. The customer wanted better die life.

Premium H13

DIEVAR

Comparison of Premium H13 and DIEVAR after 42,000 shots.

Premium H13

14

DIEVAR

DIEVAR

Ningbo ASSAB Tooling Technology (Ningbo) Co., Ltd. Tel : +86 574 8680 7188 Fax: +86 574 8680 7166 [email protected]

Cikarang* PT. ASSAB Steels Indonesia Tel : +62 21 461 1314 Fax: +62 21 461 1306/ +62 21 461 1309 [email protected]

MALAYSIA Kuala Lumpur - Head Office ASSAB Steels (Malaysia) Sdn. Bhd. Tel : +60 3 6189 0022 Fax: +60 3 6189 0044/55 [email protected]

Tel : +62 21 5316 0720-1

Jiangxi* ASSAB Tooling (Dong Guan) Co, Ltd., Jiangxi Branch Tel : +86 769 2289 7888 Fax : +86 769 2289 9312 [email protected]

15

Choosing the right steel is of vital importance. ASSAB engineers and metallurgists are always ready to assist you in your choice of the optimum steel grade and the best treatment for each application. ASSAB not only supplies steel products with superior quality, we offer state-of-the-art machining, heat treatment and surface treatment services to enhance steel properties to meet your requirement in the shortest lead time. Using holistic approach as a one-stop solution provider, we are more than just another tool steel supplier. ASSAB and Uddeholm are present on every continent. This ensures you that high-quality tool steels and local support are available wherever you are. Together we secure our position as the world's leading supplier of tooling materials. For more information, please visit www.assab.com