STEELS FOR MOULDS

Steels for moulds

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ContentsProduct Design ....................................... 4

Mould Design ......................................... 6

Mouldmaking ........................................ 10

Moulding ............................................... 14

Service ................................................... 17

Product Programme............................... 18

Mould steel selection ............................ 19

This information is based on our present state of knowledgeand is intended to provide general notes on our products andtheir uses. It should not therefore be construed as a warranty ofspecific properties of the products described or a warranty forfitness for a particular purpose.

Edition 5, 01.2004Ref. No. 040101

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The cost of the tool steel in amould usually represents only5–10% of the tool cost. And it

is an even smaller part of the total tool-ing cost.

The moulder knows this and he alsoknows that the cost of excessive mouldmaintenance, e.g. major repolishing,cleaning, replating and replacing ofworn or broken parts has to be takeninto account. And so do the costs ofproduction and down time. At worstthey may even cause overtime pay-ments, late-delivery penalties and lossof customer goodwill.

Put briefly, the moulder knows thathe has to solve the problem of maxi-mizing the life and performance of theproduction tool, e.g. the mould, toachieve the lowest possible total tool-ing cost per part produced.

He also knows from experience thatone of the major decisions is to specifythe best possible mould steel for thejob.

We at Uddeholm have developed arange of high quality mould steels sothat moulders can use the best possi-ble steels for their jobs.

In this brochure we present thesehigh quality steels. We also focus onimportant factors that contribute toeconomical production of plasticsmouldings.

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Product DesignWe at Uddeholm can help the productdesigner to ensure that the final mould-ing matches his original concept.

Our worldwide marketing organiza-tion is able to provide high qualitymould steels to meet every plasticsmoulding and extrusion requirement.

Our Technical Support will give com-petent technical advice and informationon the selection of the appropriatesteel, heat treatment and applicationtechniques.

THE IMPORTANT ROLEOF THE PRODUCT DESIGNER

When setting out to create a newmoulded part a product designer facesmany criteria that have to be satisfied.

Apart from its purely functional per-formance, the moulding is often re-quired to match high standards of finishand tolerance over a long productionrun.

Whether these requirements aresuccessfully met or not depends to alarge extent on good component de-sign, good mould design, good mould-making and the selection of the bestmould steel for the job.

CHOOSING THE BESTMOULD STEEL FOR THE JOB

The product designer is thus involved inlot of important decisions. Decisionsthat sooner or later will relate to themould steel selected. He has to askhimself questions such as:

How important is the surface finish?Does it need to be a mirror or opti-cal finish?(On page 10 you can see where wecan be of assistance in helping him toanswer these questions.)

Will the mould for the part be pat-terned by photoetching?Are there several patterned parts tobe matched, e.g. mouldings in a carinterior?(On page 13 you can see what Udde-holm has to offer in this field.)

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AVOID SHARP CORNERSAND STAY OUT OF TROUBLE!

Avoiding sharp corners and edgeswherever possible is one example ofhow an experienced product designercan improve mould life and mouldingproductivity.

Sharp corners in mouldings andtherefore in the mould are alwayspotential stress-raising points. Pointslikely to cause cracking and failure ofboth moulding and mould.

By increasing the radius of the cor-ners of moulded parts a product de-signer significantly improves the impactstrength of the mould.

The result is a stronger mould, muchbetter able to resist high locking andinjection pressures.

Effect of increasing radius on impact strength.(Steel type: AISI H13 at 46–47 HRC. Sample taken fromsurface, in the longitudinal direction.)

30

25

20

15

10

5

0,25 0,75 1,25 1,75 2,25 mm0,010 0,030 0,050 0,070 0,090 inch

Radius

Impact strengthKV

Will the moulding material be corro-sive, abrasive or both?(For further information on how wetackle these problems see page 19.)

How critical is it that the tolerancesare held within close limits?What quantities have to beproduced?(The answer is important since the pro-duction quantity will affect the degreeof wear resistance and other propertiesrequired in the mould material.)

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Mould DesignThe mould designer can significantlycontribute to optimum tooling economyby thinking standard, i.e. using standardsteel grades, standard steel sizes andstandard machined plates.

THE IMPORTANT ROLEOF THE MOULD DESIGNER

In seeking to produce the best possiblemould a mould designer faces severalcriteria that have to be satisfied.

Together with the mouldmaker heshares the heavy responsibility of pro-ducing a mould that gives reliable andeconomical production of the part con-ceived by the product designer.

He also endeavours to ensure thatthe mould can be constructed as easilyand economically as possible by themouldmaker.

Whether these requirements aresuccessfully met or not depends to alarge extent on specifying the bestmould steel and hardness for the mouldconcerned.

A clever mould designer can also adda valuable service to all concerned bythinking standard.

TAKE A SHORT CUT TOPRODUCTIVITY BY THINKINGSTANDARD!

Most mould designers are used to speci-fying a whole range of standard partssuch as guide pins and bushings, ejectorpins etc. Since these parts are availablequickly at competitive prices they helpthe mouldmaker save valuable time.

But there is even more time andmoney to be saved. Time and cost sav-ings can be further improved by extend-ing this standard thinking to standardsteel sizes, machined plates and steelgrades.

In fact, by specifying readily availablesteel grades in standard sizes themouldmaker can ensure prompt deliver-ies while keeping initial machining costsand material losses to a minimum.

CHOOSING THE OPTIMUMMOULD STEEL FOR BEST TOOLINGAND PRODUCTION ECONOMY

The choice of steel grade and supplier isoften made at the design stage in orderto simplify and speed up the delivery ofthe mould. This means that the materialand parts can be ordered in good timeand that the work can be betterplanned.

This is not always a simple task. Inmany cases the choice of steel grade isa compromise between the wishes ofthe mouldmaker and the moulder.

The mouldmaker is primarily inter-ested in the machinability of the steel,its polishability, heat treatment andsurface treatment properties.

The moulder is looking for a mouldwith good wear and corrosion resist-ance, high compressive strength etc.

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MOST COMMONLY USEDMOULD STEELS

The steel types most commonly usedare:• prehardened mould and holder

steels• through-hardening mould steels• corrosion resistant mould steels

(For further information on these steeltypes and their properties see pages18–19.)

WHEN TO USE PREHARDENEDMOULD AND HOLDER STEELS?

These steels are mostly used for:• large moulds• moulds with low demands on

wear resistance• high strength holder plates

The steels are delivered in the hard-ened and tempered condition, usuallywithin the 270–350 Brinell range. Noheat treatment is necessary before themould is put into use.

The surface hardness can be in-creased in many cases by flameharden-ing or nitriding (see “Why Heat Treat-ment” on page 11).

Prehardened mould steels are gener-ally used for large moulds and formoulds with moderate production runs.

UDDEHOLM PREHARDENEDMOULD AND HOLDER STEELS

Impax Supreme (AISI P20 modified),which is refined by the vacuum degas-sing technique, offers good machinabil-ity and homogeneity, excellent polish-ability and consistent photoetchingproperties due to a low sulphur content.

Holdax (AISI 4140 modified), oftenrecommended for high strength holderblocks and large moulds with low re-quirements on polishability, offers excel-lent machinability enabling high metalremoval rates for deep forms and insertcavity recesses.

Both Impax Supreme and Holdax areprehardened steels with a deliveredhardness of 290–330 Brinell.

Ramax 2 (AISI 420 F modified) is apre-hardened, free-machining, stainlessholder steel. It has a delivery hardnessof approx. 340 Brinell and offers excel-lent machinability and corrosion resist-ance. It is also an ideal partner forStavax ESR, Stavax Supreme, Polmaxand Elmax.

WHEN TO USETHROUGH-HARDENED STEELS?

These steels are mostly used:• for long productions runs• to resist abrasion from certain

moulding materials• to counter high closing or injec-

tion pressures

The steels are delivered in the softannealed condition. They are usuallyrough-machined, stress-relieved, finish-machined, hardened and tempered tothe required hardness and then finish-ground and often polished or photo-etched.

Through-hardened steels, used forcavity and core inserts, are usuallyplaced in holder blocks of prehardenedsteels such as Holdax or Ramax 2.

By using through-hardened mouldor cavity inserts, e.g. in the range 48–60 Rockwell C, you’ll obtain better wearresistance, resistance to deformationand indentation and better polishability.

Better wear resistance is especiallyimportant when filled or reinforcedplastic materials are used. Resistance todeformation and indentation in thecavity, gate areas and parting lines helpsto maintain part quality.

Better polishability is important whenhigh surface finished are required on themoulded part.

UDDEHOLMTHROUGH-HARDENING STEELS

Stavax ESR (AISI 420 modified),Stavax Supreme, Polmax (AISI 420modified), Orvar Supreme (AISI H13improved) and Grane (AISI L6) are alltypical Uddeholm through-hardeningsteels.

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Plastic moulds can be affected bycorrosion in several ways:• Plastic materials can produce

corrosive by-products, e.g. PVC.• Corrosion leads to reduced cool-

ing efficiency when water chan-nels become corroded or com-pletely blocked.

• And, of course, condensationcaused by prolonged productionstoppages, humid operating orstorage conditions, often leads tocorrosion.

Calmax, Rigor (AISI A2) and Elmaxare other steels that we recommend formould with high wear resistance.

Vanadis 10, our powder-metallurgyhigh speed steel, is our most wear re-sistant steel.

WHEN TO USE CORROSIONRESISTANT MOULD STEELS?

If a mould is likely to be exposed to acorrosion risk, then a stainless steel isstrongly recommended.

The increased initial cost of this steelis often less than the cost involved in asingle repolishing or replating operationof a mould from conventional steel.

UDDEHOLM CORROSIONRESISTANT MOULD STEELS

Stavax ESR and Stavax Supreme, arecorrosion resistant mould steels offeringexcellent polishability combined withgood wear and indentation resistance.Stavax Supreme is developed to meetthe increased requirements on goodtoughness and through hardenability inlarger sections.

Polmax is also a corrosion resistantmould steel specially developed to meetthe high demands on polishability fromproducers of such high-tech products asCDs, memory discs and lenses.

Elmax, finally, is a powder-metallurgymould steel with high wear and corro-sion resistance.

Corrax is a precipitation hardeningmould steel with un-matched corrosionresistance, easy heat treatment andgood weldability.

OTHER MATERIAL

Alumec is recommended for prototypemoulds and for short runs with lowdemands on strength and wear resist-ance.

Beryllium copper Moldmax HH andProtherm are used in moulds when highthermal conductivity is needed.

FINDING THE CORRECT WORKINGHARDNESS FOR THE MOULD

The chosen working hardness for themould and the heat treatment methodused to achieve it affect a lot of proper-ties. Properties such as toughness, com-pression strength, wear and corrosionresistance.

Generally it can be said that in-creased hardness results in better resist-ance against wear, pressure and identa-tion and that decreased hardness leadsto better toughness.

A normal working hardness for athrough-hardening steel is 48–60 Rock-well C. The optimum working hardnessused depends on the chosen steel, themould size, layout and shape of thecavities, the moulding process, plasticmaterial etc.

For recommended steel grades andworking hardness related to variousplastic materials and processes, seepage 19–20.

And for information on heat treatingplastic moulds ask for the Uddeholmpublication “Heat Treatment of ToolSteels”.

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IMPAX SUPREMECALMAXSTAVAX ESR/STAVAX SUPREMEPOLMAXORVAR SUPREMEGRANEELMAXCORRAX

HOLDAXRAMAX 2UHB 11FORMAX

MouldmakingA substantial part of the total toolingcost is that incurred in the making ofthe mould. It is therefore of great impor-tance that the mouldmaking processshould be as straight-forward as possi-ble.

THE IMPORTANT ROLEOF THE MOULDMAKER

A well equipped machine shop withcompetent and experienced personnel isan essential part of the mouldmakingprocess.

The significant investment that thisprocess represents is ultimately focusedon the mould material. An experiencedmouldmaker, therefore, places highdemands on his steel supplier and hisproduct when it comes to steel qualityand properties as well as steel finishand availability.

CHOOSING THEOPTIMUM MOULD STEEL

The mouldmaker is looking for a mouldsteel free from defects, easy to machineand polish, stable in heat treatment andsuitable in many cases for EDM and/orphotoetching.

WITHOUT DEFECTS

All material supplied by Uddeholm hasbeen subjected to various external andinternal inspection procedures includingultrasonic testing. This ensures that highand even quality standards are met.

GOOD MACHINABILITY GOODECONOMY

The cost of machining accounts forroughly 1/3 of the total cost of mouldmanufacture. So a good and uniformmachinability is of outmost importance.

Most of Uddeholms mould steels aresupplied in the fully annealed conditionenabling the best possible metal re-moval rates for the type of steel con-cerned.

The only exceptions are ImpaxSupreme (AISI P20 modified), Holdax(AISI 4140 modified) and Ramax 2 (AISI420F modified).

HOW IMPORTANT ISGOOD POLISHING?

Polishing sometimes accounts for up to30% of the total mould cost. Not sur-prisingly, since it is a very time consum-ing and expensive process.

The result obtained depends to alarge extent on the polishing techniquesand a few other factors. The cleanlinessof the steel, i.e. the type, distribution,quantity and size of non-metallic inclu-sions, the homogeneity of the steel, thehardness of the steel and, for hardenedsteel, how the heat treatment has beencarried out.

Non-metallic inclusions are reducedto a minimum if the steel is vacuum-degassed and/or Electro Slag Refined(ESR process) during production. ThisESR treatment results in improved ho-mogeneity and freedom from inclusionscompared to conventional steel produc-tion processes.

DON’T POLISH MORETHAN NECESSARY!

It is pointless to polish beyond a certainlevel de-pending on the heat treatmentprocess to be used.

IMPAX SUPREME, HOLDAX and RAMAX 2were tested in the prehardened condition.

A machinability comparison guide fora number of grades of Uddeholm steelsis shown below. The guide is based ontool wear tests.

Alumec has an excellent machinabil-ity i.e. high cutting speed which leads tolower mould cost and shorter deliverytime.

The table, to the right, shows thesmallest recommended grain size ofabrasive to be used in a surface prior tobeing hardened and tempered by vari-ous methods.

For further information ask for theUddeholm publication “Polishing of ToolSteel”.

Increasing machinability

▲

Holdersteels

Mouldsteels

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Surface finish prior to heat treatment

Cast Protec-Uddeholm Iron Salt tivegrade Vacuum Chips Bath Gas

STAVAX ESRSTAVAXSUPREMEPOLMAXORVARSUPREMECALMAXGRANERIGORELMAX

SVERKER 21 400 180 60 220–400grain grain or grain grain

coarser

400 180–200 180 220–400grain grain or grain grain

coarser orcoarser

WHY HEAT TREATMENT?

The purpose of heat treating a finishedtool is to obtain suitable mechanicalproperties. Properties such as hardness,toughness and strength. But there aresome problems associated with heattreatment. Problems like distortion anddimensional changes have to be solved.

Smallest recommended grain size of abrasiveto be used prior to hardening and tempering.

SOLVING THE DISTORTION PROBLEM

The tool should be stress-relieved afterrough-machining in order to minimizedistortion problems. In this way thestresses induced by the machining-operations are relieved. And any distor-tion is then rectified in the final machin-ing.

When using through-hardeningsteels at maximum hardness levels,however, the requirement for minimumdistortion may have to be sacrificed. Thereason is that higher hardening tem-peratures and rapid quenching rates arenecessary. This is especially the casewhen heavy sections are involved.

The safest way of avoiding distortionis to use a prehardened steel such asImpax Supreme—a steel for which noadditional heat treatment is required.

Flame hardening of parting surfacescan locally increase surface hardness toapprox. 55 Rockwell C.

HOW TO DEAL WITHDIMENSIONAL CHANGES

It is true that some dimensionalchanges are inevitable during harden-ing. But it is also possible to limit andcontrol these changes to a certain ex-tent. For instance by slow, uniform heat-ing to the austenitizing temperature, byusing a temperature that is not too highand a suitable quenching medium.

Stavax ESR, Stavax Supreme, Calmax,Grane, Orvar Supreme, Polmax, Elmaxand Rigor can all be air hardened whendimensional stability is important.

Corrax needs only an aging processat 500–600°C (930–1110°F) and noquenching. This means that no distor-tion will occure, only an linear and ho-mogenous shrinkage in the order of0,1%. Since it is totally predictable it iseasy to compensate for this shrinkageby adding stock before the heat treat-ment.

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Graphite electrode in dielectric medium.

TAKE THE SHORT CUTTO PRODUCTIVITY!

Purchasing steel in a prefinished form isa smart way of releasing toolmakingcapacity for the more skilled machiningoperations. Many grades of steel areobtainable in a number of forms andfinishes. And many of them have beenpremachined to a greater or lesser de-gree.

Uddeholm tool steels are available asmachined bar and as fine machinedmould steel.

It is always possible to find a suitablestock size for the work in hand and thusreduce the amount of unnecessary andexpensive machining.

In all cases a plus machining allow-ance is made on all sizes to allow forfinal finishing to a standard dimension.

MACHINED BAR

By using machined bar as startingmaterial a tool-maker gets considerablebenefits which have an effect on thetotal cost of the steel.• Less material by weight can be pur-

chased, which means that waste isconsiderable reduced.

• No machining costs for removal ofthe decarburized surface layers areinvolved.

• And the manufacturing time is short-ened, which makes planning simplerand calculations more accurate.

MACHINED STEEL PLATES

Machining costs can be reduced alreadyat the design state. One way of doingthis is to construct a tool from machinedsteel plates, i.e. ground to specificdimensions on all sides.

Uddeholm Service Centers areequipped with a full line of processingmachinery, including grinders, cut-offsaws and other equipment.

ELECTRICAL DISCHARGEMACHINING (EDM)

When spark eroding cavities, one or twoimportant points should be noted inorder to obtain satisfactory results.During the operation the surface layer

WIRE EDM’ING

This process makes it easy to cut com-plicated shapes from hardened steelblocks. However, hardened steels alwayscontain stresses and when large vol-umes of steel are removed in a singleoperation, distortion may be caused oreven cracking. These difficulties can bereduced by conventionally machiningthe work piece before heat treatment toa shape near the final form. This allows

of the steel is rehardened and conse-quently in a brittle state. This may resultin cracking and shortened tool life. Toavoid this problem the following pre-cautions should be taken

• Finish the EDM operation by finesparking, i.e. using low currentand high frequency.

• The affected surface layer shouldbe removed by polishing or ston-ing.

• If the spark eroded surface tex-ture is to be used in the finishedmould it should be retempered ata temperature ≈ 25°C below thatused previously.

• If the spark eroded surface is tobe textured by photoetching it isimportant that all of the surfacelayer affected is carefully re-moved by stoning etc.

For further information see the Udde-holm publication “Electrical DischargeMachining of Tool Steels”.

the work piece to adjust to the finalshape and stress pattern during heattreatment.

WHY THE PHOTOETCHING PROCESSHAS BECOME SO POPULAR

Plastic mouldings with a textured sur-face have become increasingly popular.And texturing by photoetching is fre-quently used as a finish on mouldingtools instead of polishing.

The photoetching process givesthe product an attractive, easily heldsurface, relatively insensitive to minorscratches and damage.

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UDDEHOLM MOULD STEELSSUITABLE FOR PHOTOETCHING

Impax Supreme (AISI P20 modified)pre-hardened mould steel and OrvarSupreme (AISI H13 improved) through-hardened steel yield particularly goodand consistent results due to their verylow sulphur contents.

Stavax ESR, Stavax Supreme, Elmax,Corrax and Polmax can easily be photo-etched to the required pattern but willrequire a slightly different etching tech-nique, because of their corrosion resist-ance.

POINTS TO BE OBSERVEDWHEN PHOTOETCHING

The results obtained by photoetching donot entirely depend on the processtechnique and the selected mould mate-rial. The way in which the tool has beentreated during manufacture is also ofgreat importance. Therefore, the follow-ing points should be observed:

• If a number of moulding insertsare included in a tool and theseare to be etched with the samepattern, the mould material andthe rolling direction should be thesame for these parts (preferablyfrom the same bar or block).

• Complete the machining opera-tion by stress-relieving, followedby finish-machining.

• There is generally no advantagein using finer abrasives than220 grain on a surface that is tobe photoetched.

• Spark eroded surfaces shouldalways be ground or polishedotherwise rehardened surfacelayers from the spark erosion willcause a poor etching result.

• Flamehardening should beavoided prior to photoetching.

• In some cases a welded tool canbe photoetched provided that thesame material is used in the weldas in the tool itself. In such casesthe welded area should be indi-cated to the photoetcher.

• If a tool is to be nitrided this mustbe done after photoetching.

• The surface area of a mould cavityis greatly increased by texturing,which may cause ejection prob-lems. Early consultation with thephotoetching specialist is recom-mended to determine the opti-mum draft angle for the shapeand pattern concerned.

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MouldingBy specifying Uddeholm material, themoulder can take an important steptowards getting a reliable and produc-tive tool.

THE DEMANDS OFTHE MANUFACTURER OF PLASTICMOULDINGS

The manufacturer expects his mould tobe delivered on time. And he expects itto produce a certain quantity of compo-nents at a specified quality level and atlowest possible cost.

The manufacturer’s essential de-mands are:

• A reliable mould delivery date,implying the ready availability ofsuitable mould materials.

• A reliable mould performance interms of a uniform, high rate ofproduction, uniform quality ofmouldings, long mould life andlow mould maintenance costs.

• Availability of replacement mate-rials and components.

All these demands can be summa-rized as tool reliability.

TOOL RELIABILITY

Tool reliability depends on such factorsas the ready availability of suitablemould material and components, theperformance of the mould steel and theinterchangeability of mould compo-nents.

AVAILABILITY OF MOULD STEELS

The ready availability is determined bylocal stocks, reliable delivery service andcomprehensive product and size range.

LOCAL STOCKS

The location of stock is important ifgood delivery service is to be main-tained.

With our worldwide marketingorganization we place great emphasison matching our stock size programmeand our stock levels to the local needsof each individual market.

To us competent technical adviceand printed material on the selection,heat treatment and application ofmould materials, EDM, polishing andsurface texturing of tool steel are veryim-portant aspects of our service.

MOULD STEEL PERFORMANCEAND TOOL RELIABILITY

The performance of the mould steel hasa decisive influence on the reliability ofthe tool. Mould cavity and insert materi-

RELIABLE DELIVERY SERVICE

Our widespread network of Uddeholmwarehouses and our complete range ofproducts form the basis for our deliveryservice.

Each of our stock locations has awell established distribution system.

COMPREHENSIVE PRODUCT RANGE

To sum it up, we are able to offer a widerange of mould and holder steels.

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als are therefore selected according tothe types of plastics to be moulded,length of production run, mouldingprocess used and the nature of theproduct.

The performance of the mould steeldepends on wear resistance, compres-sive strength, corrosion resistance, ther-mal conductivity and toughness.

We have concentrated our mouldsteel programme on a few steel grades,each suited to specific applications. This

assures not only ready availability butalso gives the mouldmaker and themoulder an opportunity to becomemore readily familiar with the character-istics of each steel (e.g. machinability,heat treatment response etc.) and per-formance.

WEAR RESISTANCE

The level of wear resistance demandedwill depend on the type of resins to beused, the filling agent, amount of addi-tives, length of production run, toler-ances etc.

Mould steels cover a wide range ofwear resistance and compressivestrength. In principle, they fall into twocategories: prehardened mould steelsfor moderate demands, e.g. ImpaxSupreme, Holdax and Ramax 2 andthrough-hardening mould steels forsevere demands, e.g. Stavax ESR, StavaxSupreme, Polmax, Corrax, Orvar Sup-reme, Elmax, Calmax and Grane.

Prehardened mould steels can besurface treated to obtain greater wearresistance, for instance, by nitriding.However, through-hardened steels givethe best combination of wear resistanceand compressive strength.

The wear resistance of fully hardenedsteels can be further improved by sur-face treatment or surface coating, suchas nitriding, hard chromium plating etc.

Such surface treatments are prefer-ably applied only after the mould hasbeen fully approved, since further ma-chining can be difficult.

It should be noted that the corrosionresistance of Stavax ESR, Stavax Sup-reme, Polmax, Corrax and Elmax isreduced by nitriding.

The powder metallurgy grades,Elmax, Vanadis 4, Vanadis 6 and Vanadis10, are extremely wear-resistant. Theyare recommended for small moulds,inserts and cores subjected to abrasivewear.

COMPRESSIVE STRENGTH

The compressive strength required isdetermined by the plastic mouldingprocess, the injection and closing pres-sures and the tolerances of the finishedmoulding. During moulding compressive

forces are concentrated on the partingfaces of the tool.

Local hardening, e.g. flameharden-ing, can give the required increase incompressive strength when prehard-ened steels are used.

CORROSION RESISTANCE

The moulding surfaces should not dete-riorate during production if you want toproduce plastic mouldings at a high andconstant rate of production and at auniform level. Corrosion with a conse-quent threat to production efficiencycan be experienced in several ways.• Certain types of plastics can emit

corrosive by-products during pro-duction. An example is the hydro-chloric acid produced from PVC.This effect can be minimized bynot exceeding the recommendedmoulding temperature for thismaterial, usually about 160°C(320°F).

• The cooling medium can be corro-sive. This can result in a loss ofcooling efficiency or even in thetotal blockage of the coolingchannels.

• Productions in a humid or corro-sive atmosphere or prolongedstorage may cause surface dam-age by water, condensation andeventually rust in the cavitieswith loss of surface finish on theproducts.

All the problems mentioned abovecreate a demand for insert and holdermaterials with some degree of resist-ance to corrosion. Corrax which has thebest corrosion resistance is used where-ver corrosion is the main problem, i.e.processing corrosive plastics. Stavax ESRand Stavax Supreme are corrosion re-sistant mould steels with high cleanli-ness, Polmax can meet the highest de-mands on polishability combined withcorrosion resistance. Elmax is combiningthe corrosion resistance with wear re-sistance and Ramax 2 is a corrosionresistant holder steel with very goodmachinability. By using Ramax 2 for theholders the stainless properties areextended to the full mould.

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THERMAL CONDUCTIVITY

The rate of production of a mouldingtool depends mostly on the ability ofthe mould to transfer the heat from themoulded plastic to the cooling medium.

In a highly alloyed steel the coeffi-cient of thermal conductivity is reducedto some degree compared to a lowalloyed steel. However, investigationsclearly indicate that it is the plastic inthe moulded part that dominates theheat flux in a mould due to its very lowthermal conductivity compared to steel.

However, good corrosion resistanceis of much greater importance whenaiming for a high and uniform produc-tion rate. This has a beneficial effect onthe resultant heat transfer properties inthe cooling channels. The use of a stain-less mould steel such as Stavax ESR orStavax Supreme is often the answer.

When mould materials with goodcorrosion resistance, combined withvery high thermal conductivity are re-quired, we can supply several grades ofcopper mould alloys.

Moldmax HH and Moldmax XL arehigh-strength grades with high thermalconductivity, good corrosion and wearresistance and good polishability.

Protherm is a moderate strengthgrade that offers even higher thermalconductivity for maximum heat transfereffect.

TOUGHNESS

Development of cracks is the worstthing that can happen to a mould.

Complicated cavities, small radii,sharp corners, thin walls and severechanges of section are commonplacetoday. Toughness is therefore one of themost important properties a mould steelshould possess.

The fracture toughness of a materialis a measure of its capacity to withstandcrack propagation from stress raiserswhen subjected to tensile stresses. Inpractice these stress raisers occur assurface defects from machining opera-tions, incipient fatigue cracks, inclusionsor as faulty structure due to improperheat treatment.

We are fully aware of the importanceof toughness. We utilize state of the artmetallurgical technology to give themould steel optimum toughness. Byutilizing such techniques as vacuumdegassing, special refining processesand electro-slag remelting, the tough-ness properties of all our steels are thehighest currently available. This im-proved toughness is evident not only atthe surface but also in the center of thesteel.

INTERCHANGEABILITYOF STEEL AND COMPONENTS

By thinking standard a mould designercan make a significant contribution tokeeping mould maintenance costs to aminimum.

By selecting readily available steelgrades, standard sizes and stock compo-nents from the outset he can help tominimize the time and cost of putting amould back into service. Furthermore,the use of identical material and partsmade to close tolerances will ensurethat the tool performance will remainunchanged.

By using standard parts and compo-nents wherever possible in the moulddesign the ease and speed of repair andmaintenance will be significantly in-creased.

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COMPLETE LOCAL STOCKS

From our long experience serving theplastic mould industry we have becomefamiliar with the sizes, grades andtolerances most frequently used.

We have stocked these in strategi-cally located Service Centers.

OUTSTANDING TECHNICAL SERVICE

Our staff of metallurgists and fieldspecialists can help you with materialselection at the design stage and laterwith recommendations on heat treat-ment, grinding and machining.

Printed material on the selection, heat treatmentand application of mould materials, EDM,

polishing and surface texturing of tool steelare very important aspects

of our service.

WELDING CONSUMABLES

To ensure successful repair welding it isof outmost importance to exactly matchthe consumables to the mould steel.Especially if the welded surface is to bephotoetched or polished.

We offer welding consumables forImpax Supreme, Stavax ESR andCalmax. They are available as TIG-wireor as coated electrodes for MMA weld-ing.

Corrax consumables are available asTIG-wire only.

The same consistent quality steel,the same dependable technical service,available to you worldwide.Only from Uddeholm!

ONE SOURCE FOR ALL YOURTOOL STEEL NEEDS

Cold work tool steel including precisionground flat stock, drill rod and hollowbar, plastic mould steel, die casting diesteel and hot work steel.

Polishing mould steel

CORRAXA stainless precipitation hardening steel

IMPAX SUPREME

Prehardened mould steel

Steels for moulds

18

Mould steels

IMPAX SUPREME(AISI P20, modified)

CALMAXGRANE

STAVAX ESR/SUPREME(420, modified)

POLMAX(420, modified)

CORRAX

ORVAR SUPREME(H13, improved)

RIGOR(A2)

ELMAXVANADIS 4VANADIS 6VANADIS 10

Holder steels

HOLDAX(AISI 4130/35, modified)

RAMAX 2(420F, modified)

Aluminium

ALUMEC

Copper alloys

MOLDMAX HHMOLDMAX XL

Beryllium copper alloy

PROTHERM

A prehardened Ni-Cr-Mo steel, supplied at 290–330 Brinell, with excellent polishing and photo-etching properties. Suitable for a wide range of injection moulds, blow-moulds, extrusion dies.

A steel recommended for injection-, compression- and transfer-moulds requiring good wearresistance and compressive strength.

A through-hardening stainless mould steel with good corrosion resistance and very goodpolishability.

A through-hardening stainless mould steel with good corrosion resistance and extremely goodpolishability.

A precipitation hardening steel with exceptionally good corrosion resistance, easy heattreatment and good weldability.

A versatile through-hardening 5% Cr mould and die steel with good wear resistance andpolishability.

A through-hardening steel, recommended for very long production runs of smaller, complicatedmouldings.

Powder metallurgically produced mould steels characterized by very good dimension stability,good polishability and wear resistance. Elmax is corrosion resistant, Vanadis 4 has the highesttoughness and Vanadis 10 the best wear resistance. Recommended for long production runs ofsmaller and complicated shapes and/or abrasive plastics.

A prehardened steel with very good machinability and high tensile strength.

A prehardened stainless holder steel with excellent machinability, high tensile strength and goodcorrosion resistance.

A high strength Al-alloy supplied at ~160 HB. Recommended for prototype moulds and for shortruns with low demands on strength and wear resistance.

High strength copper mould alloys with high thermal conductivity. For applications like pinchoffs and neck rings for blow moulds, cores and inserts in injection moulds and injection nozzlesand manifolds for hot runner systems.

A high conductivity beryllium copper mould alloy. For applications requiring very high thermalconductivity but with moderate strength demands.

Product Programme

SuppliedAnalysis % hardness

Uddeholm grade C Si Mn Cr Ni Mo V S Brinell

Mould steelsIMPAX SUPREME 0,37 0,3 1,4 2,0 1,0 0,2 – <0,01 ~310CALMAX 0,6 0,35 0,8 4,5 – 0,5 0,2 – 200GRANE 0,55 0,3 0,5 1,0 3,0 0,3 – – ~230ORVAR SUPREME 0,39 1,0 0,4 5,2 – 1,4 0,9 – 180STAVAX ESR 0,38 0,9 0,5 13,6 – – 0,3 – 215STAVAX SUPREME Cr-Ni-Mo-V alloyed 250POLMAX 0,38 0,9 0,5 13,6 – – 0,3 – 215CORRAX 0,03 0,3 0,3 12,0 9,2 1,4 – Al 1,6 ~320RIGOR 1,0 0,2 0,8 5,3 – 1,1 0,2 – 215ELMAX 1,7 0,8 0,3 18,0 – 1,0 3,0 – ~240VANADIS 4 1,5 1,0 0,4 8,0 – 1,5 4,0 – 230VANADIS 6 2,1 1,0 0,4 6,8 – 1,5 5,4 – 255VANADIS 10 2,9 0,5 0,5 8,0 – 1,5 9,8 – 275

Holder steelsHOLDAX 0,4 0,4 1,5 1,9 – 0,2 – 0,07 ~310RAMAX 2 Cr-Ni-Mo-V-S alloyed ~340

Chemical composition

Steels for moulds

19

HardnessProcess/Material Steel grade HRC (HB)

Injection Thermoplasticsmoulding – Prehardened mould steel ALUMEC (~160)

IMPAX SUPREME 33 (~310)

– Through-hardened mould steel CALMAX 45–58GRANE 45–56ORVAR SUPREME 45–52STAVAX ESR/SUPREME 45–52POLMAX 45–52CORRAX 36–50ELMAX, VANADIS 4 58–60VANADIS 6 60–64

Thermoset plastics CALMAX 52–58GRANE 52–56RIGOR, ELMAX, VAN. 4 58–60VANADIS 6 60–64

Compressions/ Thermoset plastics CALMAX 52–58Transfer GRANE 52–56moulding STAVAX ESR/SUPREME 45–52

ORVAR SUPREME 45–52ELMAX, VANADIS 4 58–60VANADIS 6 60–64

Blow moulding General ALUMEC (~160)IMPAX SUP. 33 (~310)

PVC STAVAX ESR/SUPREME 45–52RAMAX 2 37 (~340)CORRAX 36–50

Extrusion General IMPAX SUPREME 33 (~310)

PVC STAVAX ESR/SUPREME 45–52RAMAX 2 37 (~340)CORRAX 36–50

Holder material 1. High strength, prehardened, free-machining HOLDAX 33 (~310)

2. As 1, plus corrosion resistance for low- maintenance production runs. Also for “hygenic” operating conditions. No plating required. RAMAX 2 37 (~340)

Mould steel selectionGeneral recommendations

Normal hardnessHRC (HB) (~310) 58 56 52 52 52 52 46 58 60 58 62 (~310) (~340)Wear resistance 3 8 7 7 7 7 7 5 9 9 9 10 3 4Toughness 9 5 5 6 5 6 5 7 4 3 5 4 7 7Compressive strength 4 8 7 7 7 7 7 6 9 9 9 10 4 5Corrosion resistance 2 3 3 3 9 9 9 10 7 2 2 2 2 8Machinability 5** 8 8 9 8 8 8 3 3 4 3 4 7** 6**Polishability 8 8 8 8 9 9 10 8 8 7 8 8 4 4Weldability 6 4 4 4 4 4 4 6 2 2 2 2 6 5Nitriding ability 6 8 6 10 – – – – – 8 8 8 5 –Photoetchbility 9 8* 8 8* 8* 8* 8* 8* 8* 5 8 5 3 4

RAM

AX 2

HOLD

AXProperty

CALM

AX

RIG

OR

ELM

AX

STAV

AXES

R

CORR

AX

POLM

AX

ORV

ARSU

PREM

E*Special process required **Tested in delivery condition

GRA

NE

VAN

ADIS

6

IMPA

XSU

PREM

E

VAN

ADIS

4

Properties

The properties of the main mould and holder steel grades have beenrated from 1–10, where 10 is the highest rating. Such comparisonsmust be considered as approximate, but can be a useful guide to steelselection.

Note: It is not possible to make valid “total comparisons” betweensteel grades by adding their respective “points”—it is only intendedthat individual properties be compared.

STAV

AXSU

PREM

E

Steels for moulds

20

Special requirement Hardnessor demand Steel grade HRC (HB)

Large mould size For automotive components, including panels, bumpers, ALUMEC (~160)fascias, etc. IMPAX SUPREME 33 (~310)

CORRAX 36–46STAVAX SUPREME 36–50ORVAR SUPREME 36–50

As above, with low demands on surface finish HOLDAX 33 (~310)RAMAX 2 37 (~340)

High surface For moulding optical/medical parts, clear covers/panels STAVAX ESR/SUPREME 45–52POLMAX 45–52

finish ELMAX, VANADIS 4 58–60ORVAR SUPREME 45–52

Complex shapes 1. For large automobile/household components IMPAX SUPREME 33 (~310)CORRAX 34–46STAVAX SUPREME 36–52

2. For small parts with low wear demands IMPAX SUPREME 33 (~310)CORRAX 34–46

3. For small parts with high wear demands, e.g. electrical/ RIGOR 60–62 electronic mouldings CALMAX 52–58

ORVAR SUPREME 50–52STAVAX ESR/SUPREME 50–52ELMAX, VANADIS 4 58–60VANADIS 6 60–62

Abrasive Reinforced/filled moulding materials; engineering resins RIGOR 58–62moulding materials CALMAX 52–58

ORVAR SUPREME 50–52STAVAX ESR/SUPREME 50–52VANADIS 4, ELMAX 58–60VANADIS 6 60–64

Long production For thermoplastic parts, including disposable cutlery, STAVAX ESR/SUPREME 45–52runs containers and packaging VANADIS 4, ELMAX 58–60

VANADIS 6 60–64CALMAX 45–58GRANE 52–56ORVAR SUPREME 45–52

Corrosion 1. For corrosive moulding materials, including PVC STAVAX ESR/SUPREME 45–52resistance 2. For humid moulding/mould storage conditions ELMAX 58–60

3. General resistance to surface staining/rusting RAMAX 2 37 (~340)4. Resistance to corrosion of cooling channels CORRAX 34–50

Photoetching 1. Prehardened steel IMPAX SUPREME 33 (~310)

2. Through-hardened steel GRANE 45–56ORVAR SUPREME 45–52STAVAX ESR/SUPREME 45–52VANADIS 4, ELMAX 58–60VANADIS 6 60–64

High thermal For injection and blow moulds, cores and inserts; MOLDMAX HH 40conductivity parts for hot runner systems. MOLDMAX XL 30

PROTHERM (~190)

MOLDMAX® and PROTHERM® are registered trademarks of Brush Wellman Inc., Cleveland, Ohio.

Special recommendations

Steels for moulds

21