the concept to combat wear and tear … technical information no. iii/2007 the concept to combat...

DILLIDURTECHNICAL INFORMATION NO. III /2007

THE CONCEPT TO COMBAT WEAR AND TEAR

DILLINGER HÜTTE GTS

eng_01-52_0848_dihd_dur.411 04.04.2007 13:05 Uhr Seite 1

April 2007


5A Longer Life for your Machinery

12The Manufacture of DILLIDUR

Melting the SteelShaping into Heavy Plate

Hardening

17The Material Properties of DILLIDUR

Hardness and StrengthToughness

Through Thickness HardeningHigh-Temperature Strength

20The Processing of DILLIDUR

Cold FormingHot Forming

Thermal CuttingWelding

MachiningNitriding

49Literature

50Index

CONTENTS


4

Figure 1: Excavator shovel made of DILLIDUR-V steels in the harsh conditions of open-cast mining(Illustration used with the kind permission of Schlüter Baumaschinen, Erwitte, Westphalia, Germany)


Quarries and mines, gravel pits,construction, iron and steel – inno other industries are valuablemachines and installationsliterally “worn out“ as much asthey are in these sectors.

Slide conveyors, chutes, silos,deflectors, steel plating, screenplates, cutting edges, dumptrucks, loading shovels etc. arecomponents which are expectedto provide a maximum of resis-tance to wear. Therefore, thequality and service life of themachines and their componentsis particularly dependent on thematerials they are made of.

We would like to introduce toyou a group of steels combining

requirements which used to bedifficult to reconcile, such ashigh wear resistance coupledwith a minimum use of materialand excellent processing prop-erties: the DILLIDUR steelsfrom DILLINGER HÜTTEGTS.

Renowned manufacturers ofconstruction machinery,conveyor systems and pro-cessing plants use them andplace their confidence in thedecades of experience thatDILLINGER HÜTTE GTShas in the production of wear-resistant steels.

The DILLIDUR concept wasdesigned for a variety of areas

of application. Therefore,DILLIDUR steels are availablein a wide range of hardness levels to cover each set of re-quirements: DILLIDUR 275 C,325 L, 400 V, 450 V and 500 V.

Information about the specialquality for pavement moulds(DILLIDUR 275 SFX) can befound in the correspondingdata sheet.

Our delivery program shows in which dimensions our DILLIDUR steels are normallydeliverable. In addition, specialdimensions are possible onrequest.

A LONGER LIFE FOR YOUR MACHINERY

5


The decision on which DILLI-DUR steel is most suitable de-pends on a precise knowledge ofthe conditions of use and theprocessing options.

In your analysis of cases ofwear, you should take intoaccount the many facets of tri-bological processes, whichmeans that a comprehensive

investigation of all componentsdirectly involved is necessary. Inthis investigation, the formerstandard DIN 50320 “Wear“will help. Such a “tribologicalsystem“ is illustrated in diagramform in Figure 2. Unlike theproperties of hardness, strengthetc., which can be regarded ascharacteristics of the material,wear from tribological loading

results from the interaction ofall parts of a technical structurethat are involved in the wearprocess, and can only bedescribed by “system-related“wear characteristics. It is thus a general principle that “wear is not a characteristic of thematerial, it is always a charac-teristic of the system!“

6

Figure 2: Structure of a general tribological system 1)

▼

Active body

Accompanyingsecondary

Passive body

Ambient medium(Environment)

1) Reproduced by permission of DIN Deutsches Institut für Normung e.V.The definitive version for the implementation of this standard is the edition bearing the most recent date of issue, obtainable from Beuth VerlagGmbH, 10772 Berlin, Germany. Translated by DILLINGER HÜTTE GTS. This translation has not been checked by DIN Deutsches Institutfür Normung e.V., Berlin.


As can be seen in Figure 2,there are generally four elementsinvolved in a wear process.These elements form the actualstructure of the tribological sys-tem, and they fundamentallyaffect the selection of a suitablewearing plate (passive body).

The following questions andexplanations are designed tohelp you to diagnose thisstructure, and then to select amaterial which is appropriate for the wear situation.

■ What kind of material(stones, silica, gravel, coal,sludge, flour, sugar etc.) actson the wear plate with whatseverity, or what is the natureof the active body (the itemwhich the metal plate comesinto contact with)?

■ What is the type of wearload (sliding, rolling, push-ing, flowing) and how highare the forces that affect thematerial (velocity, pressure,temperature, duration ofloading, etc.)?

■ Which accompanying secon-daries are also involved(water, oil, acid, air, abrasiveproducts etc.)?

■ In what kind of environmentdoes the wearing process takeplace (moist, saline, dry air,ambient temperature etc.)?

Depending on the cause ofwear, wear is subdivided intotypes of wear and wearmechanisms.

On the basis of the standardDIN 50320, which is officiallyno longer valid but neverthelessinstructive, Table 1 shows acompilation of the major typesof wear that could result for thedifferent tribological loads, withthe effective wear mechanismsmarked.

7


8

Table 1: Subdivision of the wear area, based on the former standard DIN 50320 1)

System structure Tribological cause of wear(Symbols)

Type of wear Acting mechanisms(singly or combined)

Adhesion Abrasion Surfacedestruction

Tribo-chemi-cal reactions

– Solids– Accompanying secondary (complete separa- tion of substances)– Solids

SlidingRollingImpact

Sliding Slide abrasion

Rolling Rolling wear

Oscillation Oscillation wear

ImpactAbrasive Impactwear

Abrasive slidingwear

Impact wear

Sliding

Sliding

Rolling

Impact

Three-bodyabrasive wear

Flowing Hydro-abrasivewear

Flowing Jet blastingwear

FlowingImpact

Impact wearOblique blasting wear

FlowingOscillating

Cavitation-erosion

Impact Erosion byimpingement

Flowing Liquid-erosion

Flowing Gas erosion

– Solids– Solids

(solid friction, boundary friction,mixed friction)

– Solids– Particles

– Solids– Solids and particles

– Solids– Particles– Liquid

– Solids– Particles (gas)

– Solids– Liquids

– Solids– Gas

Mainly active

Sometimes active

–

– –

–

– –

– –

– –

– – –

– – –



Types of wear mainly describethe kinetics and structure oftribological systems, and wearmechanisms result from theinteraction of materials andenergy between the active andpassive bodies, influenced by theaccompanying secondary andthe ambient medium. The fol-lowing distinctions are made 1) :

■ Adhesion: caused by localbonding of the contactsurfaces, e.g. “plucking“

■ Abrasion: score grooving ofthe material as a result ofabrasive loading

■ Surface destruction: fatigueand formation of cracks inthe surface as a result ofdynamic load, e.g. “pitting“

■ Tribo-chemical reaction:occurrence of reactionproducts due to tribologicalloading in chemical reactionwith the environment, e.g.“oxidation“.

Each of these mechanisms sol-licitates the material in a differ-ent way and requires a specificoptimisation of the individualmaterial characteristics, e.g.hardness to fight abrasionand/or toughness to fight sur-face erosion.

A knowledge of the structure of a tribological system servesas an aid to diagnose wear pro-cesses and to reduce them bysuitable means, if possible assoon as the design stage of amachine.

However, an exact prediction of wear processes and wear ratesis usually extremely difficultsince the number of facets ofthe process is almost unlimited.This means that, in spite of longexperience, it is usually onlypossible to provide reliable weardata by testing the material inpractical use.

In addition to the selection of material appropriate to the

causes of wear, you should takeinto account that design, operat-ing and process-related mea-sures can also help to achieve asignificant reduction to wear.

For example, changing thetransport velocity of bulk material in a chute system caninfluence the dumping para-meters, and thus the angle ofimpact into a charging hopper.This in turn changes the pro-portion of impact and abrasivewear, and thus possibly the rateof wear (operating measure).Similarly, however, it is alsopossible to change the angle of inclination of the charginghopper wall (design measure),which could also change the rate of wear.

Passive wear protection measureswhich lead to self-protection bythe abrasive material, e.g. by fix-ing steps (batons) to the wall ofthe charging hopper, can alsohelp to reduce component wear.

9



In addition to the wear-resistantcharacteristics of a steel such ashardness, ductility, resistanceagainst crack formation andpropagation, the following cri-teria for decision also play animportant role in selection:

■ Weldability■ Cold forming capacity■ Hot forming capacity■ Machinability■ Toughness■ Economic effectiveness

DILLIDUR steels offer you anideal compromise between highwear resistance and optimumworkability. This helps to savematerial and processing costs.

To make the selection of theright DILLIDUR steel easier,Table 2 compares the propertiesof the individual DILLIDURsteels. The details given applyfor plate thickness of less than25 mm and are merely intendedas a guide. However, the relative

ratio between the individualsteel qualities does not changesignificantly when the thicknessis changed.

A detailed explanation ofthose properties is given in thecorresponding sections of thisbrochure.

10

Table 2: Assistance in selecting the DILLIDUR grade most appropriate for your set of requirements

DILLIDUR 275 C 325 L 400 V 450 V 500 V

Wear resistance 1) +++ + ++ ++(+) +++

Weldability 0 + +++ ++ +

Cold forming capacity + ++ ++ ++ +

Hot forming capacity ++ ++ 0 0 0

Machinability ++ ++ ++ + 0

Toughness 0 + ++ +(+)

(+++ = very good, ++ = good, + = satisfactory, 0 = not advisable if this property is especially important.)

1) Mainly applies to abrasive wear (measured wear resistance under laboratory conditions)


Because of their special micro-structure and hardness, the wearresistance of DILLIDUR steelsis up to 5 times higher than thatof conventional steels (see Fig-ure 3).

Therefore, modern steels such as DILLIDUR offer designerspossibilities formerly difficult to achieve, enabling them forinstance to slim down theirdesigns and increase the wearresistance where it is necessary.

Similarly, it can be seen in Figure 3 that the adage: “Theharder the steel, the better itswear resistance“ has only lim-ited validity. This is due to met-allurgical differences in themicrostructure and applies gen-erally for all wear resistingsteels.

In examinations with the weartank method (abrasion with drygravel under laboratory condi-tions), the measured relative

wear resistance in relation to the structural steel S355J2+Nwas compared with the averagehardness of the tested materials.The conclusion was that anincrease in hardness only corre-late with increased wear resis-tance when comparisons are

made within a specific steelquality (C, L or V).

This can be explained by thefact that the hardness of a steelcan be achieved in different ways(see section “The Manufactureof DILLIDUR“, p. 12ff).

11

Figure 3: Relative durability of DILLIDUR steels by comparisonwith S355J2+N

600

500

400

300

200

100

0 100 200 300 400 500 600

Average hardness [HB]

Rel

ativ

e du

rabi

lity

vs.

S355

J2+

N [%

]

S355J2+N

275 C

400 V

500 V

325 L

450V


The high degree of hardness dis-played by DILLIDUR steels is not only achieved by selectivealloying, but also by special manu-facturing processes. After rolling,the heavy plates are hardened bycontrolled heat treatment. Allprocesses involved - steel produc-tion, shaping into heavy plate andhardening - are exactly combinedfor each steel melt, thus providingoptimum control of the materialmicrostructure and the best possi-ble characteristics.

Melting the Steel

After careful hot metal desulphur-ization, DILLIDUR steels are

produced by melting in a top-blowing basic oxygen process, thentreated by ladle metallurgy and,for usual plate dimensions, cast bycontinuous casting. For very thick,heavy plates, ingot casting is alsoavailable.

A low phosphorus and sulphurcontent are both prerequisites for high toughness. As a rule, thephosphorus content is below 0,020 % and the sulphur contentbelow 0,005 %. The required alloy content is exactly adjusted in the ladle as well, with a view to an optimum combination ofmechanical values and goodmachinability.

Particular attention is paid to thecarbon equivalent (CEV, PCM orCET), which goes up togetherwith the alloy content. Low car-bon equivalent values indicate agood weldability. However, a mini-mum of alloy elements, whichincreases with the plate thickness,is necessary to ensure sufficienthardening as a result of the finalheat treatment.

Indicative values of the carbonequivalent of DILLIDUR 275 C, 325 L, 400 V, 450 V and500 V are shown in Table 3.

THE MANUFACTURE OF DILLIDUR

12

Table 3: Carbon equivalent of DILLIDUR 275 C, 325 L, 400 V, 450 V and 500 V (indicative values)

DILLIDUR 275 C 325 L 400 V 450 V 500 V

Thickness [mm] 40 40 10 25 40 80 120 10 40 80 10 40 80

CEV 0.80 0.78 0.37 0.46 0.51 0.61 0.64 0.46 0.53 0.65 0.47 0.52 0.67

CET 0.66 0.44 0.28 0.31 0.33 0.35 0.36 0.33 0.36 0.39 0.36 0.37 0.42

PCM 0.62 0.37 0.23 0.25 0.27 0.30 0.31 0.29 0.32 0.35 0.34 0.35 0.39

Carbon equivalent:

CEV = C+Mn/6+(Cr+Mo+V)/5+(Cu+Ni)/15

CET = C+(Mn+Mo)/10+(Cr+Cu)/20+Ni/40

PCM = C+Si/30+(Mn+Cu+Cr)/20+Mo/15+Ni/60+V/10+5•B


13

Shaping into Heavy Plate

DILLINGER HÜTTE GTS has two of the most powerfulrolling stands in the world. Theslabs produced in the steel works are rolled there accordingto a rolling schedule preciselydefined and tuned to the respec-tive chemical composition of thesteel. Thanks to the high rolling

forces of up to 108,000 kN(11,000 metric tons), sufficientdeformation is achieved in thecore of the plate, even for largeplate thickness.

The microstructure is thenhighly suitable for the subse-quent hardening process andforms one of the prerequisitesfor the good homogeneity and

mechanical properties ofDILLIDUR steels. The repro-ducibility of the rolling processin terms of rolling temperature,rolling force and thicknessreduction ratio is ensured by accurate measurement andfast process control. These features are used to set the nar-row dimension tolerances.

Figure 4: The typical microstructure of DILLIDUR V steels magnified 500 times


14

Figure 5: An austenized DILLIDUR V plate enters the quenching device


15

Hardening

DILLIDUR 275 C is normal-ized and receives its hardnessmainly from its carbon content.The microstructure of this typeof steel is largely ferritic andpearlitic.

DILLIDUR 325 L is also nor-malized, but it receives its hard-ness from additional alloying,while the carbon content is keptlow to improve weldability.

The microstructure of this nor-malized steel is largely bainitic.

The high hardness ofDILLIDUR V steels is achievednot only through systematicalloying, it is also the result ofa special manufacturing process.After rolling, the heavy platesare heated to austenitizingtemperature and then cooleddown with water in a specialquenching device. A fast-run-ning water film over the top and

bottom surface of the plateensures extremely high coolingrates. This leads to a fine-grained,hard microstructure. Continu-ous and steady cooling results in a homogeneous hardness,basis of a high wear resistance.

The typical hardened microstruc-ture of a DILLIDUR V steel isshown in Figure 4 on page 13.

Figure 5 shows an insight into the quenching device.


16

Figure 6: Charging hopper of a crushing plant, walls made of DILLIDUR 400 V


Hardness and Strength

The hardness level of DILLIDURsteels far surpasses that of con-ventional steel.

Table 4 shows indicative valuesfor hardness, yield strength,tensile strength, elongation atrupture and toughness.

In spite of their high tensileproperties, DILLIDUR steelsare not intended for security

relevant components. For thispurpose high strength steelsDILLIMAX are available.

Toughness

In spite of their high hardness,DILLIDUR steels have suffi-ciently good toughness for theirusual field of application. Theimpact toughness is highest forthe low-carbon DILLIDUR Vsteels with a martensitic micro-structure, and the toughness

level decreases gradually withincreasing carbon content.Therefore, the impact toughnessof DILLIDUR L is lower(bainitic microstructure) andthat of DILLIDUR C is lowbecause of the high carbon content. Even in wear resistingsteels, the toughness underimpact load or surface erodingimpact wear may be decisive,e.g. in ventilation systems or in truck dumping bodies (see Figure 21, p. 38).

THE MATERIAL PROPERTIES OF DILLIDUR

17

Table 4: Indicative values for hardness, yield strength, tensile strength, elongation at rupture andtoughness for plate thickness below 25 mm

DILLIDUR 275 C 325 L 400 V 450 V 500 V

Hardness [HB] 1) 275 320 400 450 500

Yield point Y.P. [MPa] 650 650 800 950 1100

Tensile strength U.T.S. [MPa] 950 1000 1200 1400 1600

Elongation A [%] 2) 9 15 12 11 9

Impact toughness [J] 3) 10 20 45 35 25

1) Average surface hardness2) Round tensile test specimen, transverse3) Charpy-V specimens, longitudinal at - 20 °C


Through-Thickness Hardening

To achieve outstanding mechan-ical properties, in this case ahigh hardness value in the coreof the plate and homogeneousmicrostructure, it is necessary in addition to the extremly high cooling rates and very low amount of non-metallicsubstances and hydrogen, toprovide a precisely tunedamount of alloying elements.

Chromium, molybdenum, man-ganese, vanadium and boron are particularly suitable for fullhardening. The chemical com-position of the DILLIDURsteels is designed to ensure that the reduction of hardnesstowards the core of the plate isas low as possible, taking intoaccount the necessary limitationof the carbon equivalent for thesake of weldability.

A high hardness penetrationprevents wear from taking placetoo quickly from the surface tothe core of the plate.

High-Temperature Strength

Wear processes which are activeat elevated temperatures re-quire good high-temperaturestrength properties of thematerials used. Even at hightemperatures, the protectionagainst wear has to be as goodas possible to ensure long service life.

The „air hardeners“ DILLIDUR Cand L can be used in permanentoperation up to a temperatureof 400 °C. On the basis of hottensile tests for various platethickness values, Figure 7 shows that DILLIDUR 325 Lstill has a strength of 630 MPaat this temperature.

18

Figure 7: Effect of temperature on the yield and tensile strength ofDILLIDUR 325 L (auxiliary data, plate thickness = 20 mm)

1200

0 100

Temperature [°C]

500400200 300

Y.S

. and

T.S

. [M

Pa]

600

1100

1000

900

800

700

600

500

400

300

200

Y.S.T.S.


Because of their special heattreatment, DILLIDUR V steelscannot be used permanently attemperatures above 200 °C - 250 °C without losing hardnessand strength.

By means of hot tensile tests for various plate thickness val-ues, Figures 8 and 9 show thetypical effect of temperature onthe mechanical properties ofDILLIDUR 400 V and DILLIDUR 500 V.

19

Figure 8: Effect of temperature on the yield and tensile strength ofDILLIDUR 400 V (auxiliary data, plate thickness = 20 mm)

Figure 9: Effect of temperature on the yield and tensile strength ofDILLIDUR 500 V (auxiliary data, plate thickness = 20 mm)

1200

0 100

Temperature [°C]

500400200 300

Y.S

. and

T.S

. [M

Pa]

600

1100

1000

900

800

700

600

500

400

1300

Y.S.T.S.

200

300

0 100

Temperature [°C]

500400200 300

Y.S

. and

T.S

. [M

Pa]

600200

600

800

1000

1200

1400

1600

1800

Y.S.T.S.

400


DILLIDUR steels are wellsuited for processing in spite oftheir high degree of hardness.Nevertheless, certain processingguidelines apply to DILLIDURsteels. The user should ensurethat his design, construction andprocessing methods are alignedwith the material, correspond tothe state-of-the-art that the fab-ricator has to comply with andare suitable for the intended use.

The following pages explain anumber of fundamental princi-ples and provide practical pro-cessing hints for DILLIDUR.

Cold Forming

DILLIDUR steels are wellsuited for cold forming bybending in spite of their highhardness and strength. It mustbe taken into account that theforce needed to form a givenplate thickness increases withthe yield strength of the steel.The elastic spring-back effectalso increases. In order to avoidthe risk of cracking from theedges, flame cut or shearededges should be grounded in thearea that is to be cold formed.It is also advisable to round theplate edge slightly on the out-side of the bend coming undertension stress during bending.Because of the relatively highcarbon content, the flame cut ofDILLIDUR 275 C is very hard(approx. 600 HB) and brittle.

That’s why the flame cut areashould be worked off by about3 mm for the cold forming.

Because of the different heattreatment conditions, therequired minimum bendingradius is not the same for DILLIDUR C, L and V steels(see Table 5) In addition, theminimum required bendingradius and die opening forbending perpendicular to therolling direction are lower thanfor bending parallel to it,which is due to the deformationprocess during rolling. The following minimum values forthe bending radius can be usedas a guide for DILLIDURsteels, assuming that the form-ing speed does not exceed 10 %expansion of the outer fibre per second.

THE PROCESSING OF DILLIDUR

20


21

Table 5: Minimum bending radius and die opening for cold forming of DILLIDUR steels

DILLIDUR 275 C 325 L 400 V 450 V 500 V

Position of perp. parallel perp. parallel perp. parallel perp. parallel perp. parallelbending line torolling direction

Bending radius 6 t 8 t 5 t 6 t 3 t 4 t 5 t 6 t 7 t 9 t

Die opening 14 t 18 t 14 t 16 t 10 t 12 t 14 t 16 t 16 t 20 t

Hot forming possible possible - - -

Bending angle < 90°, t = plate thickness, forming time > 2 sec (< 10 % expansion of outer fibre per second)

W

t

r

F


22

Figure 10: Continuous ship unloader in the harbour of DILLINGER HÜTTE GTS


Hot Forming

By hot forming we generallyunderstand forming at tempera-tures at which a metallurgicalalteration can be expected.For DILLIDUR 275 C andDILLIDUR 325 L this is thestress-relieving temperature(approx. 580 °C). For DILLIDUR V steels, because of the special hardening process,this limit is significantly lower(approx. 250 °C).

Since the yield strength of thesteel decreases with increasingtemperature, it may still be bene-ficial for DILLIDUR 275 C and DILLIDUR 325 L to carryout the forming process at hightemperature in case of narrowbending radius and thick plates.The required forming forcedecreases in proportion to thetemperature.

DILLIDUR 275 C: As the steelreaches its hardness by air cool-ing after normalization, hotforming is always possible with-out a loss of hardness if thesteel is then normalized again orif an equivalent temperaturecontrol is maintained during hotforming. The temperature for

normalization is 880 to 950 °C.Without subsequent normaliz-ing, the steel can be heated toabout 600 °C without significantloss of hardness. Figure 11shows the general change in thehardness and strength values forDILLIDUR 275 C in relation to the tempering temperature.

23

Figure 11: DILLIDUR 275 C: Effect of the tempering tempera-ture on tensile strength, yield strength and hardness after thecooling down to the room temperature (auxiliary data)

Tensile strengthYield strengthHardnessMinimum hardness

0 100

Tempering temperature [°C]

500400200 300

Har

dnes

s [H

B] o

r R

m r

esp.

Rp

0,2

[MP

a]

6000

100

200

300

400

500

600

700

800

900

1000


DILLIDUR 325 L: As the steelreaches its hardness by aircooling after normalizing, hotforming is always possible with-out a loss of hardness if thesteel is then normalized againor if an equivalent temperaturecontrol is maintained duringhot forming.

The temperature for normaliza-tion is 900 to 950 °C.

Without subsequent heat treat-ment, the steel can be heated upto about 600 °C without signifi-cant loss of hardness. The gen-eral change of hardness andstrength with the tempering tem-perature are shown in Figure 12.

24

Figure 12: DILLIDUR 325 L: Effect of the tempering tempera-ture on tensile strength, yield strength and hardness after thecooling down to the room temperature (auxiliary data)

Tensile strengthYield strengthHardnessMinimum hardness

0 100


500400200 300

Har

dnes

s [H

B] o

r R

m r

esp.

Rp

0,2

[MP

a]

6000

200

400

600

800

1000

1200


DILLIDUR 400 V/500 V: Asthe steel reaches its hardness byaccelerated cooling from theaustenitizing temperature, hotforming without a loss of hard-ness is only possible if the work-piece is then hardened again.

Due to the different heat treat-ment equipment of the process-ing factory and the geometry ofthe component, the cooling rate achieved is generally slowerand the hardness lower than forplate manufacturing.

The original hardness andthrough-thickness hardeningproduced in the mill can generally not be reached again.Additionally there is a risk ofdistortion. For componentswhich must be quenched duringprocessing, the chemical com-position can be adjusted accord-ingly in consultation withDILLINGER HÜTTE GTS.

Figures 13 and 14 show the gen-eral change of tensile strength,yield strength and hardness val-ues for DILLIDUR 400 V and 500 V in relation to the tempering temperature.

25

Figure 13: DILLIDUR 400 V: Effect of the tempering tempera-ture on tensile strength, yield strength and hardness after thecooling down to the room temperature (auxiliary data)

0 100


500400200 300

Har

dnes

s [H

B] o

r R

m r

esp.

Rp

0,2

[MP

a]

6000

Tensile strengthYield strengthHardnessNominal hardness

200

400

600

800

1000

1200

1400

1600


If hot forming of DILLIDUR Vsteels is necessary, it should asfar as possible be carried out ata temperature between 880 and950 °C.

During the subsequent harden-ing, a quick heat dissipationmust be ensured and the for-mation of insulating layers ofvapour avoided, in order toreach sufficient hardening acrossthe thickness of the component.

26

Figure 14: DILLIDUR 500 V: Effect of the tempering tempera-ture on tensile strength, yield strength and hardness after thecooling down to the room temperature (auxiliary data)

0 100


500400200 300

Har

dnes

s [H

B] o

r R

m r

esp.

Rp

0,2

[MP

a]

6000

Tensile strengthYield strengthHardnessNominal hardness

200

400

600

800

1000

1200

1400

1600

1800


Thermal Cutting

Flame cutting, plasma arccutting or laser cutting ofDILLIDUR L and V steels ispossible without any difficulty ifcarried out correctly and as longas appropriate tools in goodworking condition, suitable forthe respective job are available.As different manufacturershave developed a variety oftools, you should note therespective settings and adviceprescribed by the manufacturerin the cutting tables (nozzleselection, gas pressure, workingmethods, speed etc.).

The surface condition of theplates also has a marked influ-ence on the flame cuttingconditions and the cut facequality that can be achieved.Where high demands are placedon the cut face quality, it is nec-

essary to clean the top of theworkpiece around the cut fromscale, rust, paint and any otherimpurities.

Oxycutting: In this flame cuttingmethod, the steel is heated toinflammation point with a gasand oxygen flame and thenburned in a cutting oxygen jet.In this process, only an extre-mely narrow zone (< 1 mm) next to the cutting edge is heatedto hardening temperature (austenized), and because of theextremely high flow of heat intothe surrounding cold material,it is transformed into a hardenedstructure. This heat dischargecan reach the cooling speed ofquenching in water. The sur-rounding areas are tempered.We also speak of the so-calledheat-affected zone (HAZ). Theextreme differences in tempera-ture can lead to stress and,

under unfavourable conditions,to hardness cracking. Withincreasing thickness and alloy-ing content, flame cutting ofDILLIDUR steels requiresmore care than conventionalconstructional steels.

Flame cutting must be carriedout at a temperature high enoughto avoid cracking.

The cooling speed is therebyreduced so that the austenizedzone is not hardened so stronglyand the shrinking stress is signif-icantly reduced. The minimumpreheating temperatures given in the table 6 have proved to beappropriate for oxyacetylenecutting.

Re-entering angles should beflame cut with a radius, in orderto reduce the notch effect.

27

Table 6: Minimum preheating temperatures for flame cutting of DILLIDUR steels

Plate thickness [mm] < 10 < 20 < 30 < 50 < 60 < 100

DILLIDUR 275 C 150 °C 150 °C 175 °C 225 °C 225 °C 225 °C

DILLIDUR 325 L 15 °C 75 °C 100 °C 120 °C – –

DILLIDUR 400 V 1) 15 °C 15 °C 15 °C 75 °C 100 °C 100 °C



1) Max. heating temperature < 250 °C, for short periods 300 °C


If the cutting edges are coldformed in further processing, forexample by bending, the zonehardened by flame cutting shouldbe removed for all DILLIDURsteels by grinding in the area tobe formed (see section „Coldforming“, p. 20).

Figure 15 shows the typical hard-ness profile in the heat affectedzone (HAZ) of the flame cuttingedge of a DILLIDUR 325 Lplate. The hardness values arecomparable to those obtainedafter water quenching. But thishardness quickly drops down tothe original hardness of theworkpiece.

28

Figure 15: Hardening of DILLIDUR 325 L at the flame cuttingedge after oxycutting (auxiliary data, plate thickness: 15 mm)

0

Distance from the flame cutting edge [mm]

Har

dnes

s [H

V5]

150

Midthickness3 mm subsurface

0,5 1,0 1,5 2,0 2,5 3,0 4 6 7 85

200

250

300

350

400

450

500

550

600


For DILLIDUR V steels, theflame cutting edge reaches thehardness of the original water-hardened material again. Inbetween is a small softenedzone, which is rather wider near the surface because ofthe spreading of the heatingflame (see Figures 16 and 17).

DILLIDUR V steels should notbe heated above 250 °C for long periods, since they wouldotherwise lose much of theirhardness.

Therefore, for flame cuttingparts which are unable todissipate heat quickly enoughsuch as small components,screen plates, lamellae, cutterblades etc., additional coolingshould be provided instead ofpreheating.

This can be achieved, for exam-ple, by flame cutting in a waterbath with the plate to be flamecut 2/3 immersed in the water sothat the heat can be rapidly dis-sipated via the water. In thiscase, the resulting shrinkageforce is much smaller, so thatthere is little risk of crackingbecause of the narrow heat-affected zone (HAZ). A furtheradvantage is the tighter dimen-sionional tolerance that can beachieved with this flame cuttingmethod.

29

Figure 16: Hardening of DILLIDUR 400 V at the flame cuttingedge after oxycutting (auxiliary data, plate thickness: 20-30 mm)and example of the flame cutting HAZ on plate edge (micrograph)

Figure 17: Hardening of DILLIDUR 500 V at the flame cuttingedge after oxycutting (auxiliary data, plate thickness: 20-30 mm)

0


Har

dnes

s [H

V5]

1500.5 1.0 1.5 2.0 2.5 3.0 4 6 7 85

200

250

300

350

400

450


9 10 11 12

Midthickness

3 mmsubsurface

0


Har

dnes

s [H

V5]

2500.5 1.0 1.5 2.0 2.5 3.0 4 6 7 85

300

350

400

450

500

550


9 10 11 12


Laser and plasma cutting: Themajor advantages of laser andplasma cutting lie in the highercutting performance and thenarrower heat-affected zone,along with minimum heat input.With both cutting processes it ispossible to cut even the smallestparts, lamellae and screen plateswith low distortion and withoutloss of hardness (see Figure 18).With these methods it is alsopossible to dispense with pre-heating.

A perfect surface of the plates isa fundamental precondition forlaser cutting because the laserbeam must be concentratedwithout reflection loss andabsorbed without disturbanceon the so-called focus on thesurface of the plate.

If required, all DILLIDURsteels can be supplied shot-blasted and coated especially forthis purpose. The achievable cut-ting performance depends to a

great extent on the laser powerand the plate thickness to becut. With a plate thickness of10 mm and a laser energy of2-3 kW, cutting speeds of up to2000 mm/min are possible.

With suitable surface treatment,e.g. the use of an emulsion, itmay even be possible to improvethis performance.

30

Figure 18: Laser-cut screen plate made of DILLIDUR 400 V, plate thickness 12 mm


Unlike laser cutting, plasmacutting is also suitable for platethickness above 30 mm. How-ever, the heat affected zone issomewhat wider. Figure 19shows the typical effect of thedifferent cutting methods on theheat affected zone of a hard-ened, wear resisting steel.

Water jet cutting: This method is particularly suitable forcutting of DILLIDUR steelsbecause there are no thermaleffects which may inducechanges in the material andimpair the properties of thecomponent. However, the cut-ting speed is rather slower.

31

Figure 19: Typical effect of different flame cutting processes onthe heat affected zone of a hardened, wear resisting steel

0

Distance from the cutting edge [mm]

Har

dnes

s [H

V10

]

250

300

350

400

450

500

550

1 2 3 4 5 6 7

LaserPlasmaOxycutting


32

Figure 20: Welded excavator shovel made of DILLIDUR V plates(Illustration used with the kind permission of Schlüter Baumaschinen, Erwitte, Westphalia, Germany)


33

Welding

Weldability: With increasingalloying contents, the process-ing, and especially the heat con-trol during welding, requiresspecial care.

As long as the general rules ofwelding technology (EN 1011,see section “Literature“, p. 49)and the following instructionsare observed, DILLIDUR 400 Vand 450 V are very suitable forwelding with normal weldingtechniques: submerged arc,manual arc and gas shieldedmetal arc welding.

On the contrary, the welding of DILLIDUR 275 C is moredifficult because of the relativelyhigh carbon content. Otherbonding types, e.g. bolting,are preferable.

DILLINGER HÜTTE GTSpoints out that the followingrecommendations on weldingare purely for information.

The wide variety of weldingconditions, the construction andthe consumables used have asignificant effect on the qualityof the welded joints. As therespective operating and

processing conditions are notknown, it is not possible toguarantee in advance themechanical properties of theweld or the lack of defects in thewelds. But practical experienceshows that good results areobtained if suitable weldingconditions are maintained.

Preparation of the weld seam:The weld seam can be preparedby machining or by thermalcutting. At the beginning of thewelding process, the seam mustbe bright, dry and free fromflame cutting slag, rust, scale,paint and any other impurities.


Weld fillers and consumables:Weld fillers must be selected inaccordance with the require-ments for the mechanicalproperties.

In most cases it is sufficient, forfillet welds and butt joints thatare not subject to full stress, touse a “soft“ weld filler with alow strength and hardness (yieldstrength ≤ 355 MPa). However,this is only practical if the weldscan be designed to be in areasthat are subject to less wear, sothat the wear of the weld doesnot have a negative effect on theservice life of the component.

Table 7 shows an overview ofsuitable “soft“ weld fillers. Theroot seam should in any case be

“soft“ welded so that it can fullyabsorb any tension which arises.

For welds subject to extremewear, we recommend that thefinal pass should be carried outwith special hard facing elec-trodes. For such applications,Table 8 shows an overview ofsuitable “hard“ weld fillers. Youshould take into account that ahigh degree of hardness in theweld increases the risk of coldcracking.

In manual arc welding, basic-coated rod electrodes are alwaysused because of the risk of cracks.Basic-coated rod electrodes havetwo outstanding properties: thetoughness of the weld metal ishigher and their hydrogen intro-

duction, at approx. 5 ml/100gweld metal is lower than for anyother types of coating (approx.10 to 15 ml/100g weld metal).The risk of cold cracking istherefore lower. It is essentialthat redrying and storage arecarried out according to theinstructions of the consumablemanufacturer because basiccoatings absorb air humidity.

Where austenitic electrodes orelectrodes on a nickel basis areused, it is sometimes possible todispense with preheating. Butthe use of such electrodes is gen-erally only advisable for smallseam cross-sections because ofthe higher costs.

34


35

Table 7: “Soft“ weld fillers and consumables for welding of DILLIDUR steels

Manual arc welding

Designation Standard Manufacturer

Tenacito DIN EN 499 E 42 6 B 42 H5 – AWS A 5.1 E 7018 OERLIKON

Phoenix 120 K DIN EN 499 E 42 5 B 32 H5 – AWS A 5.1 E 7018 THYSSEN

Fox EV 50 DIN EN 499 E 42 4 B 42 H5 – AWS A 5.1 E 7018 BOEHLER

OK 48.00 DIN EN 499 E 38 2 B 42 H5 – AWS A 5.1 E 7018 ESAB

Gas shielded metal are welding


Fluxofil 30 DIN EN 758 T 42 2 B C 3 – AWS A 5.20 E 70 T-5 OERLIKON

Fluxofil 31 DIN EN 758 T 42 4 B C 3 – AWS A 5.20 E 70 T-5 OERLIKON

Union K 52 DIN EN 440 G 42 A C G3 Si1 – AWS A 5.18 ER 70 S-6 THYSSEN

OK Autrod 12.51 DIN EN 440 G 42 5 M G3 Si1 – AWS A 5.18 ER 70 S-6 ESAB

Submerged are welding


OE S2 DIN 756 S2 – AWS A 5.17 EM 12 OERLIKON

Union S2 DIN 756 S2 – AWS A 5.17 EM 12 THYSSEN

OK Autrod 12.20 DIN 756 S2 – AWS A 5.17 EM 12 ESAB

EMS 2 DIN 756 S2 – AWS A 5.17 EM 12 BOEHLER

To combine with fluoride-alkaline powders, TYPE FB according to DIN EN 760, e.g. A FB 1 55 AC


36

Table 8: “Hard“ weld fillers and consumables for welding of DILLIDUR steels

Manual arc welding


Tenacito 80 DIN EN 757 E 69 4 Mn2NiCrMo B H5 – AWS A 5.5 E 11018-G OERLIKON

Tenacito 100 DIN EN 757 E 89 2 Mn2Ni1CrMo B H5 – AWS A 5.5 E 12018-G OERLIKON

SH Ni2 K 90 DIN EN 757 E 55 5 2 NiMo B – AWS A 5.5 E 10018-M THYSSEN

SH Ni2 K 130 DIN EN 757 E 89 2 Mn2Ni1CrMoB – AWS A 5.5 E 12018-M THYSSEN

Gas shielded metal arc welding


Union NiMoCr AWS A 5.28 ER 100 S-1 THYSSEN

Fluxofil 41 DIN EN 758 T 50 6 1NiMo B C(M) 3 – AWS A 5.29 E 90 T5-G OERLIKON

Fluxofil 42 AWS A 5.29 E 110 T5 K4 OERLIKON

Submerged arc welding


Union S3 Mo DIN EN 756 S3Mo – AWSA 5.23 EA 4 THYSSEN

Union S3 NiMoCr AWSA 5.23 ~ EM2 THYSSEN

Fluxocord 41 AWSA 5.23 F9A8-EC-G OERLIKON

Fluxocord 42 AWSA 5.23 F11 A8-EC-F5 OERLIKON

to combine with fluoride-alkaline powders, type FB according to DIN EN 760, e.g. A FB 1 55 AC


Prevention of cold cracking:Like all hardened wear resistantsteels, DILLIDUR steels canunder unfavourable conditionsalso tend to form cold cracks in the hardened structure at the weld.

Given that the cracks appearonly several hours after welding,checking for cracks should bemade 48 hours after welding atthe earliest.

But cold cracking can be avoi-ded if suitable precautions areadopted during welding, andespecially if two factors whichfavour cracking are excluded:hydrogen in the weld metal andintrinsic constraint. A thirdfactor, hardening in the heat-affected zone of DILLIDURsteels, can only be controlled toa limited extent because of thehigher alloy content of the basematerial and the weld fillers,depending on the steel type.Inclusion of hydrogen atoms at

the grain boundaries of the weldmetal structure and on thefusion line are the main causesof cracking. The hydrogenenters the weld through moistweld fillers, films of moisture on the weld edges or the atmos-phere surrounding the arc. Thehydrogen entry must be reducedby selecting suitable weld fillers,keeping them dry in storage andespecially by warming up thecomponent to be welded or theweld area.

The higher temperature leads to a delay in the cooling of theweld after welding, which meansthat the hydrogen has more timeto diffuse out. This process mainlytakes place in the temperaturerange between 300 and 100 °C.

Heat control not only refers to the heating of the seam at the beginning of the weldingprocess, it also refers to ad-herence to a certain minimumtemperature throughout the

whole welding process (interpasstemperature). In gas shieldedmetal arc welding, only compar-atively small amounts of hydro-gen are introduced to the weldmetal (< 2 ml/100 g), so that pre-heating can often be dispensedfor the DILLIDUR 400 V and450 V series when using weldingwires of a lower strength.

Because of the generally higherenergy input per unit length thatis used for submerged arc weld-ing, the danger of cold crackingis reduced here by comparisonwith manual metal arc weldingas long as the powder is redriedand stored in accordance withits manufacturer's instructions.

Experience shows that sub-merged arc welding should beused only for DILLIDUR 400 V.If the heat input per unit lengthis higher than 2.5 kJ/mm, thegiven preheating temperaturescan generally be reduced byabout 30 °C.

37


38

Figure 21: Welded truck dumping body made of DILLIDUR 400 V, plate thickness 10 mm


39

Preheating temperatures forwelding of DILLIDUR steels areshown in Figures 22 to 25. Theyshow the recommended mini-mum preheating temperatures inrelation to the plate thickness,and thus the carbon equivalentCET and the hydrogen contentof the fused weld filler.

At the beginning of the weldingprocess, the whole length of theseam shall have reached the pre-heating temperature. A zone of

about 100 mm width (or at least4 times the plate thickness) onboth sides of the weld shall havereached the preheating tem-perature as well. For multiplelayer welding, you must alsoadhere to the preheating temper-ature as a minimum interpasstemperature.

The danger that cracks mayoccur in welded joints as a resultof residual stresses is particu-larly high when the seam volumeis only partly filled. Therefore,cooling below the prescribedinterpass temperature must beavoided during the whole wel-ding process. In the interest oflower residual stresses, harsh

cross-sectional transitions andconcentrations of welds must beavoided. Also make sure that thecomponents to be welded form agood fit and that the welds arefree from notches as far as pos-sible. An advantageous weldsequence can also reduce theresidual stresses.

In principle, the weld sequenceshould be selected to ensure thatthe individual components canshrink freely for as long aspossible.

Root welds and tack weldsshould be sufficiently thick tak-ing into account the minimumpreheating temperature.

The plate thickness does notrefer to the combined platethickness. The criterion isalways the thickest plate in the construction to be welded.


40

Figure 22: DILLIDUR 325 L: recommended preheating tempera-tures in relation to the plate thickness and hydrogen content ofthe fused weld filler

0

Hyd

roge

n co

nten

t [m

l/10

0 g]

010 20 30 40 50

2

4

6

8

10

Heat input2.0 kJ/mm

200°C

150°C

100°C

75°C

50°C

Hydrogen content HDM according to ISO 3690

Plate thickness [mm]


41

Figure 23: DILLIDUR 400 V: recommended preheating tempera-tures in relation to the plate thickness and hydrogen content ofthe fused weld filler

0

Hyd

roge

n co

nten

t [m

l/10

0 g]

025 50 75 100

2

4

6

8

10

50°C

25°C

100°C

125°C

150°C

175°C


Heat input1.5 kJ/mm



42

Figure 24: DILLIDUR 450 V: recommended preheating tempera-ture in relation to the plate thickness and hydrogen content ofthe fused weld filler

0

Hyd

roge

n co

nten

t [m

l/10

0 g]

025 50 75 100

2

4

6

8

10

200°C

150°C

150°C

75°C

25°C

100°C

Heat input1.5 kJ/mm




43

Figure 25: DILLIDUR 500 V: recommended preheating tempera-tures in relation to the plate thickness and hydrogen content ofthe fused weld filler

200°C

200°C

175°C

150°C

100°C

50°CHyd

roge

n co

nten

t [m

l/10

0 g]


Heat input1.5 kJ/mm

00

25 50 75 100

2

4

6

8

10



Hard facing: Components whichare subject to extreme local wearload can be additionally pro-tected by hard facing throughweld overlay. Application ofwelded wear protection layers ispossible for all DILLIDURsteels.

It must be taken into accountthat weld overlay changes theoriginal properties of the platewithin the heat affected zone,especially for DILLIDUR Vsteels.

When the weld layer has beenworn away, the softened basicmaterial may then wear fasterthan was to be expected for thematerial in its original condi-tion, so that in the long-termthis wear protection may pro-duce inferior results if the cappass is not replaced in time. Forinformation about suitable weldfillers for hard facing, we recom-

mend that you consult the re-spective manufacturers.

Machining

DILLIDUR steels are very wellsuited for machining in spite oftheir high strength and hard-ness. However, some basic rulesmust be observed when machin-ing these hardened steels. Vibra-tions should be avoided. It istherefore advisable to work on amachine that is as rigid as possi-ble and to keep the gap betweenthe workpiece and the machine(support) to a minimum. Simi-larly, it is advisable to fix theworkpiece firmly to the work-bench.

Depending on the type ofmachining work, sufficientcooling should be ensured. Aninterruption of the coolantsupply or insufficient coolantsand lubricants can lead to over-

heating of the cutting edge,which can lead to increased wearof the cutting edge and, in ex-treme cases, to breakage of thetool. Please note the relevantinformation given by the toolmanufacturer. To minimizemaintenance costs and increasethe service life of the tools, theyshould regularly be checked forwear (wear band) and ground.

The recommendations given inthe following tables for the selec-tion of tools and the machiningof DILLIDUR steels are guide-lines which may lead to differentresults for different machines.The validity of these recommen-dations should be checked bythe processing specialist on site.Detailed information aboutmachining and tool selectioncan be obtained by consultingtool manufacturers or DILLIN-GER HÜTTE GTS.

44


Drilling: DILLIDUR steels arewell suited for drilling in spite oftheir high hardness. Suitabletools are cobalt-alloyed HSStwist drills, twist drills withbrazed carbide cuttings, solidcarbide twist drills (with internalcooling where appropriate) and

drills with indexable inserts. Forstable drills, the feed rate shouldbe set rather higher when machi-ning begins to ensure that thetool engages firmly. This helpsto reduce vibrations. Before thedrill is completely through thematerial, feed should be inter-

rupted briefly. This reduces thetension on the machine and thetool and avoids breaking of thecutting edges. Details on theselection of tools, cutting speedsand feed rates can be found inTable 9.

45

Table 9: Recommendations for drilling DILLIDUR 325 L, 400 V, 450 V and 500 V

DILLIDUR Tool type Cutting speed Feed f [mm/rev.](Cutting material) Vc [m /min] depending on diameter

5 – 15 mm 20 – 30 mm 30 – 40 mm

325 L Twist drill with brazed carbide cutting 8 – 12 0.02 – 0.12 0.10 – 0.20 0.15 – 0.25or solid carbide twist drill 1)

Drill with indexable inserts 2) 80 – 90 0.06 – 0.075 0.10 – 0.11 0.11 – 0.12

400 V Solid carbide heavy 35 – 50 withoutduty drill (TIN) 1) internal cooling 0.06 – 0.16 0.18 – 0.25 –

40 – 70 withinternal cooling

Cobalt-alloyed HSS-twist drill 2) 8 – 10 0.05 – 0.16 0.20 – 0.25 –

Drill with indexable inserts 2) 60 – 70 – 0.10 – 0.12 0.12

450 V Solid carbide heavy 35 – 50 withoutduty drill (TIN) 1) internal cooling 0.06 – 0.16 0.18 – 0.25 –



Drill with indexable inserts 2) 50 – 60 – 0.10 – 0.12 0.11

500 V Solid carbide heavy 35 – 50 without 0.06 – 0.16 0.18 – 0.25 –duty drill (TIN) 1) internal cooling



Drill with indexable inserts 2) 40 – 50 – 0.10 0.10

1) Results with tools from Fette GmbH, Schwarzenbek, Germany Coolant / lubricant: emulsion2) Results with tools from Ferrotec, Bielefeld, Germany


Countersinking: Cylindrical andconical countersinking can bestbe made in hardened plates ifthe tool has a pilot. This pre-vents vibrations. The use ofthree-edged countersinkers canalso contribute to a reduction ofvibrations. Recommendationsfor cutting speed and forwardfeed are given in Table 10.

Tapping: Screw threads can gen-erally be tapped by machine.Information on the selection oftools, cutting speeds and speedscan be found in Table 11.

Sawing: When using a band sawto saw DILLIDUR steels, werecommend grinding the flamecutting edge 1-2 mm deep in thearea to be sawn and sawing thesmallest cross-section. In prac-tice, cobalt-alloyed or carbide-tipped saw blades have provedthemselves there. We recom-mend a cutting speed of about18 m/min with good cooling.

46

Table 10: Recommendations for countersinking DILLIDUR 325 L, 400 V, 450 V and 500 V

DILLIDUR Tool type Cutting speed Feed f [mm/rev.] (Cutting material) Vc [m /min] depending on diameter

15 – 30 mm 30 – 60 mm

325 L Countersinker made of 30 – 40

0.10 – 0.15 0.15 – 0.25400 V solid carbide or with reversible 30 – 40450 V carbide tips1) 20 – 30500 V 10 – 201) Results with tools from Fette GmbH, Schwarzenbek, Germany and from Ferrotec, Bielefeld, Germany Coolant/lubricant: emulsion

Table 11: Recommendations for tapping DILLIDUR V steels

DILLIDUR Tool type Cutting speed Speed n [rpm] (Cutting material) Vc [m /min] depending on diameter

M10 M16 M20 M30 M42

400 VManual or machine tap 1.5 – 3.5 50 – 120 40 – 80 30 – 60 20 – 40 15 – 30450 VHSS-Co 1)

500 V1) Results with tools from Ferrotec, Bielefeld, Germany Coolant/lubricant: emulsion


Milling: DILLIDUR steels canbe processed with tools made ofhigh-speed steel (HSS, TiN,TiCN-coated) and with toolsequipped with indexable inserts.Please note that flame cut edgesmay show significantly higherhardness values than the rest ofthe material. Therefore, the firstcut should be at least 2 mmdeep, i.e. should go far enoughbelow the heat affected zone.To mill DILLIDUR V steels, itis advisable to use round inserts.

Experience has shown that thisgeometry is superior to a planarface milling geometry (i.e. with a45° angle of incidence). The use of indexable inserts with abroad cutting edge chamfer also minimizes wear. Instead of cooling with emulsion, drymachining is recommended inthis case. But the use of com-pressed air or minimal quantitylubrication can lead to furtherimprovements in the service life.Indexable inserts are sensitive

to vibrations. Therefore, allpossible measures must beadopted to reduce vibrations,e.g. firm clamping of the work-piece. If large surfaces need tobe processed, it is advisable tomachine the plate alternately onboth sides, as this enables dis-tortion of the workpiece to beavoided. Recommendations forthe cutting speed and feed ratefor face and edge milling aregiven in Tables 12 and 13.

47

Table 12: Recommendations for face milling DILLIDUR V steels

DILLIDUR Tool type Cutting speed Feed per tooth(Cutting type) Vc [m /min] fz [mm]

400 V Profile milling cutter / (FC 220N) 1) 130 – 150 0.10 – 0.12Facing cutter / (HC-P20+TiN)



1) Results with tools from Fette GmbH, Schwarzenbek, Germany(TwinCut profile milling cutter: d = 125 mm, number of teeth: z = 8) Coolant/lubricant: none

Table 13: Recommendations for edge milling DILLIDUR V steels

DILLIDUR Tool type Cutting speed Feed per tooth(Cutting type) Vc [m /min] fz [mm]

400 V Roughing cutter/ (FC 220N) 1) 145 – 155 0.13 – 0.15(HC-P20+TiN)

450 V Roughing cutter/ (FC 220N) 1) 100 – 140 0.15 – 0.17(HC-P20+TiN)

500 V Roughing cutter / (FC 220N) 1)

(HC-P20+TiN) 85 – 95 0.17 – 0.19

1) Results with tools from Fette GmbH, Schwarzenbek, Germany(TwinCut roughing cutter: d = 63 mm, number of teeth: z = 3) Coolant/lubricant: none


Nitriding

To increase the wear resistancenear the surface, it can be advis-able for special applications tocarry out additional nitriding ofDILLIDUR steels, for examplefor moulds or pressure rams.

During nitriding, the hardness isincreased by the diffusion ofnitrogen into the surface of theworkpiece, which leads to theformation of hard nitrides.

Depending on the process, nitrid-ing is carried out at tempera-tures between 500 and 600 °C.

DILLIDUR L and V steels areparticularly suitable for nitridingdue to their content of nitride-forming elements such as alu-minium, silicon, chromium, nio-bium, titanium and vanadium.For instance, gas nitriding ofDILLIDUR 325 L makes it pos-sible to achieve a surface hard-

ness of up to 920 HV and anitride hardening depth of up to0.7 mm at 340 HV (see Figure 26).Due to a tempering effect, thehardness in the core of the platedrops to the level of the minimumhardness in delivery condition.

For the selection of the mostappropriate DILLIDUR steel (including the quality DILLIDUR NT that was devel-oped specifically for nitriding),please contact DILLINGERHÜTTE GTS.

48

Figure 26: Typical hardness profile after gas nitriding ofDILLIDUR 325 L, nitriding duration approx. 80 hours,nitriding temperature 530 °C

0.0

Depth of hardening [mm]

Har

dnes

s [H

V5]

0

100

200

300

400

500

600

700

800

900

1000

0.2 0.4 0.6 0.8 1.0 1.2 1.4

minimum hardness in delivery condition


Additional reading for the section“A Longer Life for yourMachinery“

Uetz U.: Abrasion und Erosion,Carl Hanser Verlag, 1986, S. 2-25

Zum Gahr K. H.: Entwicklungund Einsatz verschleißfesterWerkstoffe. Materialwissen-schaft und Werkstofftechnik 19(1988), S. 223-230

DIN 50 320 (1979): Verschleiß.Beuth Verlag GmbH, Berlin,(withdrawn)

DIN 50 321 (1979): Verschleiß-Meßgrößen. Beuth VerlagGmbH, Berlin (withdrawn)

GfT Arbeitsblatt 7:Tribologie – Definitionen,Begriffe, Prüfung. Gesellschaftfür Tribologie e.V., Moers, 2002

Additional reading for the section“The Fabrication Properties ofDILLIDUR“

Stahl Merkblatt 252: Thermi-sches Schneiden von Stahl.Stahl-Informations-Zentrum,Düsseldorf, 1985

Hermann F. D.: ThermischesSchneiden - Die schweißtechni-sche Praxis. DVS-Berichte Band13. DVS-Verlag, Düsseldorf,1979

EN 1011 (Part 1: 05/2002,Part 2: 01/2001): Recommen-dations for welding of metallicmaterials, CEN

Uwer D. et al: Schweißen mo-derner hochfester Baustähle.Stahl u. Eisen 112 (1992) 4,S. 29-35

Stahl Merkblatt 381: Schweißenunlegierter und niedriglegierterBaustähle. Stahl-Informations-Zentrum, Düsseldorf, 1989

ISO 3690 (2000): Welding andallied processes – Determinationof hydrogen content in ferriticsteel arc weld metal. IIW

Stahl Merkblatt 447: Nitrierenund Nitrocarburieren. Stahl-Informations-Zentrum, Düssel-dorf, 1983

LITERATURE

49


INDEX

50

Bending radius ............................................................................. 20fCarbon equivalent ................................................................. 12, 39ffChemical analysis.......................................................................... 12Cold forming.......................................................................... 10, 20fCountersinking ............................................................................. 46Die opening ................................................................................. 20fDrilling ......................................................................................... 45Elongation .................................................................................... 17 Flame cutting, oxyacetylene ........................................................ 27ffGas shielded metal arc welding ................................................... 33ffHard facing ................................................................................... 44 Hardness..................................................................................... 15ffHardening ..................................................................................... 15Heat affected zone (HAZ) ..................................................... 27ff, 31Heat input per unit length ..................................................... 37, 40ffHigh-temperature strength .......................................................... 18ffHot forming .......................................................................... 10, 23ffHydrogen content ....................................................................... 37ffImpact toughness .......................................................................... 17Laser cutting ................................................................................. 30Machining............................................................................. 10, 44ffManual arc welding .................................................................... 33ffMicrostructure......................................................................... 13, 15Milling .......................................................................................... 47Minimum preheating temperature ..........................................27, 39ffNitriding ....................................................................................... 48Plasma arc cutting........................................................................ 30fResidual stresses............................................................................ 39Sawing .......................................................................................... 46Submerged arc welding ............................................................... 33ffSusceptibilty to cold cracking ..................................................... 37ffTapping......................................................................................... 46Tempering................................................................................... 23ffTensile strength........................................................................... 17ffThrough thickness hardening ........................................................ 18Toughness................................................................................ 10, 17Tribological system ....................................................................... 6ffWater jet cutting............................................................................ 31Water quenching.................................................................... 15ff, 26Wear types and mechanisms.......................................................... 7ffWeldability ............................................................................ 10, 33ffWeld fillers and consumables....................................................... 33ffYield strength ............................................................................. 17ff


SALES ORGANISATIONS

51

GermanyVertriebsgesellschaftDillinger Hütte GTS Postfach 10492770043 StuttgartTel: +49 7 11 61 46-300Fax: +49 7 11 61 46-221

FranceDILLING-GTS Ventes5, rue Luigi Cherubini93212 La Plaine Saint Denis CedexTel: +33 1 71 92 16 74Fax: +33 1 71 92 17 98

For your local representativeplease contact our coordinationoffice in DillingenTel: +49 68 31 47 23 85Fax: +49 68 31 47 99 24 72


52

AG der Dillinger Hüttenwerke

P. O. Box 1580D-66748 Dillingen/SaarTel: +49 68 31 47-21 46Fax: +49 68 31 47-30 89

e-mail: [email protected]://www.dillinger.de

General note (liability):Any information given aboutthe characteristics or possibleuse of materials and productsonly constitutes a description.Any assurances concerning theexistence of specific propertiesor suitability for a specific pur-pose always require a specialwritten agreement.

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AUSTRIA

SEANORTH

LONDON

NETHER-LANDS

BELGIUM


Tec

hnis

che

Info

rmat

ion

DIL

LID

UR

E/0

7K

DV


the concept to combat wear and tear … technical information no. iii/2007 the concept to combat...

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