Die Steel Handbook

SOMERS FORGE LIMITED

HOT WORK DIE & MOULD STEELS2 kg to 36 tonnes

Quality is remembered long after price is forgotten!

SOMERS SOLIDISED DIE & MOULD STEELS

Hot Work Die & Mould Steels 2kg to 36 tonnes

In service, die blocks have severe workingstresses imposed upon them and often oper‐ate under a triaxial stress condition. SomersForge has developed a specialised forgingtechnique whereby the the mechanical prop‐erties of the heat treated die block can betterwithstand the normal shock loading charac‐teristics of the metal forming process.

Solidised grain flow is highly beneficial to dielife. To achieve best results, the mechanicalproperties of the heat treated die block mustbe balanced between those present in thelongitudinal plane and those existing in thetransverse axis.

For example, if a die block is direct forged bysimply “drawing out”, whilst the longitudinalproperties are satisfactory, the transverseductility and notch strength are greatly im‐paired. Upset forging minimises the loss oftransverse toughness. Lengths of die steelscan be supplied from our specially processedbars held in our Steelstock Divisions in theUSA and UK.

You must agree that it pays to useSomers Solidised Steels.

Page 3 Somers Solidised™ Die and Mould Steels

Page 4‐5 Supply Conditions and Related Specifications

Page 7 Wear Resistance and Relative Toughnesss

Page 8‐9 Die Steel Selection Chart

Page 10‐11 Machinability

Page 14 No. 5 Electem

Page 15 Somdie andSomtherm

Page 16 Thermodie

Page 17 Hydie

Page 18 Bestem

Page 19 VWMC

Page 20‐21 VMC andHytuf

Page 22 Somplas 30

Page 23 Supamold

Page 24‐25 Fracture and Notch Toughness

Page 26 Thermal Fatigue Resistance

Page 27 Hot Tensile Properties

Page 28‐29 Hardness Conversion Table

Page 31 Stress, Metric and Temperature Conversion Tables

CONTENTS ™

Solidised

Hardness Letter

Trade NameThis indicates the type of steel used.

Production NumberA complete record is kept of all die blocks.

Page 4 Page 5

SUPPLY CONDITIONS ANDRELATED SPECIFICATIONS

Die Steel Selection Nearest Related Specifications

French German American Japanese

No. 5 Electem 55NDCV07‐03 1.2713

Somdie 55NDCV07‐05 1.2714 SKT4

Thermodie 55NDCV08

Hydie 1.2307

Bestem

VWMC Z38CDWV05 1.2606 H12

VMC Z37CDV5 1.2344 H13 SKD61

Hytuf 1.2344 H13

Somers Supermold P20

Somplas 30 1.5864 3335

An essential function of any hot work diesteel is its capacity to retain sufficient hard‐ness at the normal elevated working temper‐atures. When considering the workingcharacteristics of a die steel the user willoften base the selection of die block hard‐ness upon the type of equipment to be used,i.e. hammer or press.

The selected hardness of the block is invari‐ably the subject of compromise. High hard‐ness is best for resisting wear, but this canlead to premature cracking, whilst if thehardness of the die block is too low it willrapidly erode under working conditions andlack thermal stability.

Additional factors to be considered in the se‐lection of a die steel must include the com‐plexity of the impression, chemicalcomposition of the forging stock and thenumber of forgings to be produced. The fol‐lowing pages of this brochure assist in the se‐lection procedure, taking into account theparameters previously mentioned. Startingfrom page 8, the choice of material or rangeof materials can be made. Technical and typi‐cal composition details for the chosen mate‐rial follow from page 14. If you requirefurther in‐depth technical information do nothesitate to contact our Technical Departmentand discuss your needs.

Die blocks can be supplied black or roughmachined, dovetails sawn or finished and inthe annealed, normalised or hardened andtempered conditions. See pages 28‐29 forhardness conversion table.

Supply Condition

The grain flow is normally parallel to thelength dimension but the block can be crossforged on request, i.e. with grain flow inwidth dimension.

Grain Flow

Markings on Somers Forge Die Block

Trade MarkThe arms of the trade mark indicate the di‐rection of the grain flow.

WEAR RESISTANCE OF DIE STEELS FORDROP FORGING

The wear resistance of a die steel depends upon the volume fraction of stable carbides pres‐ent in the heat treated structure. The main elements which confer high wear resistance areMolybdenum, Tungsten and Vanadium.

A good indication of the wear resistance of a given die steel may be obtained by calculating awear resistance factor ‘F’ from the following formula:

F = 54X + 4SWhere X = Mo + W/2 + 3VAnd S = Mn + Si + Ni + Cr + Co

The wear resistance factor ‘F’ of Somers Forging die steels is shown below:

Wear Resistance

VMC

VWMC

BESTEM

HYDIE

THERMODIE

SOMDIE

ELECTEM

0 50 100 12525 75Wear Resistance Factor F

Page 8

SELECTION OF A HOT WORK DIE STEEL

Page 10

MACHINABILITY

DEPO HC2012

3 axis horizontal machine tool, built to pro‐duce very high metal removal rates on rough‐ing operations.When blocking up Die Blocks we typically usea pentagon style face mill to the followingdata: • Cutter Diameter – 66 mm• Surface Speed – 160m/min • Spindle Speed – 774 rpm• Feedrate – 1000 mm/min• Depth of Cut – 8 mm• Axial Cut – 40 mm• Metal Removal Rate – 320 cm3/min

After the blocking up process is complete,rough machining of a 3 dimensional cavity iscommenced, typically a button style cutter isused to the following data:• Cutter Diameter – 66 mm• Surface Speed – 160 m/min • Spindle Speed – 774 rpm• Feedrate – 2000 mm/min• Depth of Cut – 3 mm• Axial Cut – 40 mm• Metal Removal Rate – 300 cm3/min

Using these 2 cutters we are able to block upand rough out a complex work piece in a veryshort time.

DEPO VF4525

5 axis vertical machine tool, built to providegreat flexibility with no limitations to the sizeof the work piece required for machining.The benefits of this machine are:• Complete processing on one machine

from roughing ‐ all the way to the finishingtouches.

• The CNC programmable head makes effi‐cient milling of even the smallest radii atgreat depths possible with high precision& finish quality in the shortest time this inturn can eliminate or reduce the need forspark erosion and benching.

• The ability to accurately machine under‐cuts and angled holes to a very high accu‐racy with ease.

• The flexibility to clamp a work piece andmachine more than one side in oneclamping operation.

Somers Forge currently have 2 Depo CNC machine tools built to the higheststandard on the market with the capability to produce a finished mould ordie to a maximum capacity of 4.5m x 2.5m.

Having these two machines provides SomersForge with the ability to dedicate the 3 axishorizontal machine tool to heavy roughingand the 5 axis vertical machine to carry onfurther operations such as semi finishing andfinishing, also, operations requiring 3+2 axismachining. This ensures we utilize both ma‐chines to their maximum capabilities.Using our high spec machine tools in con‐junction with the latest cad/cam softwareand cutting tools on the market enablesSomers Forge to produce complex work‐pieces in the shortest possible lead timeachieving great accuracy, aiming to provide amould or die without any additional fitting orbenching operations.

Page 14

550

450

350

400 500 600 700750 930 1110 1290

Brin

ell H

ardn

ess N

umbe

r

°C°F

This tempering graph indicates the approxi‐mate range of hardness expected followingheat treatment. The upper and lower limitsare indicated but hardness may vary, beingdependent on bulk of material, chemicalanalysis, soaking time and temperature dur‐ing hardening and subsequent temperingtime.

Tempering CurveSomdie and Somtherm

SOMDIE

• This die steel is recommended where ad‐ditional toughness is required in a generalpurpose die block.

• Oil quenched and double tempered.

Typical analysis % C 0.55Si 0.30Mn 0.85Ni 1.60Cr 1.20Mo 0.50V 0.10

• Can be supplied to a maximum hardnessof 477 BHN depending on the size of blockand impression depth.

• Recommended pre‐heat temperature200°C (392°F) min.

A Superior Ni‐Cr‐Mo‐VGeneral Purpose Die Steel

SOMTHERM

• Developed for additional toughness andhardenability.

• Recommended for medium to long termdie runs.

• Normally supplied oil quenched and dou‐ble tempered.


• Can be supplied to a maximum hardnessof 477 BHN depending on the size of blockand impression depth.


High Grade Die SteelNi‐Cr‐Mo Die Steel

• Recommended as the standard die blocksteel.

• Water / oil quenched tempered die steel.


• Normally supplied in the OH&T conditionto a hardness range specified by the cus‐tomer.

• Supplied annealed for hardening and tem‐pering after sinking of impression by thecustomer, or hardened and tempered tosuit customer requirements.



550

450

350

250400 500 600 700750 930 1110 1290

°C°F

Brin

ell H

ardn

ess N

umbe

r

No. 5 ELECTEM

Tempering Curve No.5 Electem

HYDIE

Page 16

THERMODIE

• Recommended for all types of hot workapplications including long‐run dies, in‐serts, gripping dies, rolls, punches, stemsand liners for aluminium extrusionprocesses.

Typical analysis % C 0.55Si 0.55Mn 0.60Ni 2.00Cr 0.90Mo 0.75

• Supplied hardened and tempered or an‐nealed.



Hot Work Die and Insert Steel• Recommended for use as a general pur‐

pose die steel on hammers or as press in‐serts.

Typical analysis % C 0.37Mn 0.60Ni 0.30Cr 3.00Mo 0.80V 0.20

• This die steel offers extremely good wearresistance and retains a good hardness atelevated temperatures.

• Supplied hardened and double temperedor annealed.

• Can be nitrided.• Recommended pre‐heat temperature

200°C (392°F).

Special Die and Insert Steel

450

400

350

300

600

550

500

0 100 200 30033 212 390 570

°C°F

500 600 700930 1110 1290

400750

Brin

ell H

ardn

ess N

umbe

r

550

450

350

500 600 700930 1110 1290

Brin

ell H

ardn

ess N

umbe

r

400750

°C°F

Tempering Curve Thermodie


Tempering Curve Hydie

VWMC

Page 18

BESTEM

• Hot work die steel suitable for mechanicalforging press inserts and upset forging ma‐chine dies and punches.

• Precipitation hardening die steel.• Supplied hardened to 341 / 388 BHN for

immediate us or annealed to 302 BHNmax.

• To harden, air cool from 1000 – 1020°C(1832 – 1870°F) followed by tempering.Owing to precipitation effects, temperingincreases the hardness at approximately570°C (1060°F) beyond which the hard‐ness falls rapidly. Please consult our tech‐nical department for the optimumtempering temperature for the desiredhardness. It should be emphasised that upto this limit tempering has the reverse ef‐fect to that of normal steel becauseBestem is relatively soft as quenched andincreases in hardness as the temperingtemperature is raised.

• The time for tempering is also a factor, atleast 1 hour per 25mm (1”) of thicknessmust be allowed.


This temperature graph indicated the approx‐imate range of hardness expected followingheat treatment. The upper and lower limitsare indicated but hardness may vary, beingdependent on bulk of material, chemicalanalysis, soaking time and temperature dur‐ing hardening and subsequent temperingtime.

Nickel‐Molybdenum‐Chromium Die Steel• Recommended for dies, inserts, punches

etc. with mechanical and friction screwpresses, also horizontal upsetters. Applica‐tions in hot brass pressing and forginghigh nickel alloys.

Typical analysis % C 0.34Si 1.00Mn 0.29W 1.50Cr 5.00Mo 1.50V 0.50

• This steel is normally supplied in the an‐nealed condition to 241 BHN max.

• To harden, pre‐heat to 850°C (1560°F)then heat quickly to 1030 – 1050°C (1886– 1922°F) but do not unduly soak, cool inair. Large sections should be oil quenchedor martempered.

• Tempering to follow immediately afterhardening for 1 hour per 25mm (1”) ofthickness. Double temper to suit require‐ments.

• A second tempering should only be car‐ried out after the block has cooled to am‐bient temperature and is recommendedwhere maximum toughness and resist‐ance to heat checking is desired.

• Tempering in a controlled atmosphere willbe found advantageous.

• Where maximum abrasion resistance is re‐quired nitriding is recommended.

• Recommended pre‐heat temperature150 – 350°C (302 – 662°F).


Special Hot Work Steel

Tempering Curve Bestem Tempering Curve VWMC

Page 20

VMC & HYTUF

Tempering Curve VMC and Hytuf


• Recommended for die inserts on mechani‐cal friction screw presses and horizontalforging machines, additionally for use inaluminium die casting, extrusionprocesses and plastic moulds.

Typical analysis % C 0.37Si 1.00Mn 0.50Cr 5.00Mo 1.50V 1.00


• Somers premium grade H13.• Manufactured by special clean steel melt‐

ing route, with very low sulphur levels toachieve maximum toughness in service.

• Recommended for die inserts, extrusiontools, plastic moulds and die casting in‐serts and cores.

• It is particularly suitable for severe duties.

Typical analysis % C 0.37Si 1.00Cr 5.30Mo 1.40V 1.00


Cr‐Mo‐V Hot Work Die Steel A Superior Hot Work Tool Steel Heat Treatment

These steels can be supplied in the hardened and tempered condition but they are normallysupplied annealed to 241 BHN max. Further treatment by the customer after die sinkingwould be as follows.

Annealing

Heat slowly to 820 – 850°C (1510 – 1560°F). Cool in furnace at not more than 10°C (50°F) perhour to 600 – 650°C (1110 – 1200°F). Should this cooling rate be exceeded the furnace tem‐perature should be held at 720°C (1330°F) for 4 – 6 hours prior to further cooling.

Stress Relieving

Where dies have been heavily machined it is advisable to stabilise at 650°C (1200°F) in orderto relieve stresses prior to further machining and hardening and tempering operations.

Hardening

The use of a protective furnace atmosphere (vacuum furnace) is required to prevent exces‐sive oxidisation and carburisation or decarburisation during austenitising, which could affectthe properties of the steel.

Oil or grease should also be removed from the die surface. Pre‐heat to 820 – 850°C (1510 –1560°F) then heat quickly to 1000 – 1050°C (1830 – 1920°F) but do not soak unduly. Cool invacuum or air.

Tempering

Temper immediately after hardening for 1 hour per 25mm (1”) of thickness. Double temperto suit requirements. The second tempering should only be carried out after the block hascooled to ambient temperature and is recommended where Nitriding

The surface can be hardened by gaseous or plasma process to give approximately 950 to1100 Vickers hardness number. Nitriding cycles of between 10 – 30 hours are normally em‐ployed or the shorter Tufftriding process can be used.

VMC (H13) HYTUF

SUPAMOLD

Page 22

SOMPLAS 30

• Recommended for all types of plasticmoulds.

Typical analysis % C 0.32Mn 0.500Ni 4.25Cr 1.25Mo 0.30

• A high grade steel suitable for both pres‐sure and injection plastic moulds.

• Specially recommended when high polishis required.

• An air hardened steel with minimum dis‐tortion.

• Easily machinable in the annealed state.• Further treatment by customer after die

sinking as follows:

Hardening

Equalise at 620°C (1150°F), then heat quicklyto 820°C (1510°F), soaking up to one hourper 25mm (1”) of minimum dimension, coolin air or oil quench.

Tempering

To follow immediately after hardening for 1hour per 25mm (1” of thickness).

Tempering curve Somplas 30


High Finish Plastic Mould Steel (835 M30 Type)• Recommended for plastic moulds and zinc

die‐casting dies.

Typical analysis % C 0.35Mn 0.80Si 0.30Cr 1.50Mo 0.40

• Supplied in the pre‐hardened condition atapproximately 300 BHN.

• Readily machinable and can be polished toa mirror finish.

• Suitable for photo‐etching or texturing.

Tempering Curve Somers Supamold


Special Plastic Mould Steel (AISI P20 Type)

Page 24

FRACTURE & NOTCH TOUGHNESS CURVES

Fracture Toughness Notch ToughnessCharpy impact valves are a measure of the resistance to brittle fracture under shockloadingconditions. Pre‐heating is important for optimum toughness.

Application of fracture mechanics at elevated temperature has shown that steels with im‐proved wear resistance need not necessarily be more prone to premature fracture.

Testing of two die steels has shown the difference if their fracture toughness, and the superi‐ority of the more wear resistant material when die pre‐heating temperatures are maintainedwithin specific limits.

No. 5 ElectemIdeal

Die WorkingTemperature

HydieIdeal

Die WorkingTemperature

HOT TENSILE PROPERTIES OF SELECTEDDIE STEELS

Page 26

THERMAL FATIGUE RESISTANCE CURVES

ElectemHardness at Room Temperature

VWMCHardness at Room Temperature

SomdieHardness at Room Temperature

VMCHardness at Room Temperature

Thermal Fatigue Resistance Curves

The development of cyclic thermal fatigue cracking is one of the causes of reduced die life.Cracks of a shallow nature, resulting from thermal fatigue, often do not significantly affect theperformance of a die and many thousands of forgings may be produced long after surfacecracks have been introduced. Cracks resulting from mechanical fatigue, and thermal fatiguecracks, extended by hot metal being forced into the crack opening, can often extend beyondeconomical limits of re‐machining or may propagate in a rapid manner, resulting in the com‐plete breakage of a die block.

Graph ‘A’ shows the growth of thermal fatigue cracks in die steels subjected to repetitiveheating and cooling cycles shown in Graph ‘B’.

363 / 388 BHN

Temperature of test °C 300 400 500

Tensile strength, ton/in² 72.0 59.9 51.2

Proof stress, ton/in²0.2% 55.5 47.8 40.60.1% 52.8 44.8 37.40.05% 50.0 41.6 34.20.02% 46.6 37.4 30.2

Limit of proportionality, ton/in² 40.0 29.0 18.9

Elongation % on 5.65 √A 16.5 18.5 20.1

Reduction of area % 47.2 64.0 75.2

51 / 52 Rockwell ‘C’ = 495 / 514 BHN

Temperature of test °C 400 500 600

Tensile strength, ton/in² 92.0 78.0 53.9

Proof stress, ton/in²0.2% 77.2 63.7 41.30.1% 70.2 56.8 36.40.05% 61.6 49.6 31.40.02% 49.7 39.7 26.0

Limit of probability, ton / in² 27.2 23.8 16.0

46 / 47 Rockwell ‘C’ = 429 / 444 BHN

Temperature of test °C 400 500

Tensile strength, ton/in² 78.5 65.8

Proof stress, ton/in² 0.2% 65.0 54.9 0.1% 60.8 48.9 0.05% 55.2 42.2 0.02% 49.4 34.9

363 / 388 BHN

Temperature of test °CR.T. 200 300 400

Yield stress, ton / in²76.0 – – –

Proof stress, ton / in²– 68.0 65.6 61.6

Tensile strength, ton / in²80.0 78.5 77.2 68.0

Elongation % on 5.65 √A15.0 13.2 15.0 17.0

Reduction of area %54.4 51.0 57.6 69.6

Graph BGraph A

Page 28

HARDNESS CONVERSION TABLE SHOWING STANDARD HARDNESS RANGES OF HEAT TREATED DIE BLOCKS

Page 30

STRESS CONVERSION TABLE METRIC CONVERSION TABLE TEMPERATURE CONVERSION TABLE

Somers Forge Ltd.Haywood Forge, Prospect Road

Halesowen, West MidlandsB62 8DZ, ENGLAND

Tel: (+44) 0121 585 5959Fax: (+44) 0121 585 6699

Email: [email protected] Sales: [email protected]

Web: www.somersforge.com

Somers SteelstockHaywood Forge, Prospect Road

Halesowen, West MidlandsB62 8DZ, ENGLAND

Tel: (+44) 0121 585 5959Fax: (+44) 0121 585 2929

Email: [email protected]: www.somersforge.com

Somers Steel (USA)6221 Commerce Drive

Westland, MichiganMI 48185‐7630, USA

Tel: 734‐729‐3700Toll free in USA: (1) 800‐854‐2927

Fax: 734‐729‐4130Email: [email protected]

A FOLKES HOLDING COMPANY

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Die Steel Handbook

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