WEARTECH SF



 

  


General

WeartecSF is a chromium - molybdenum - vanadium alloyed tool steel.

Characteristics found in WEARTEC

Excellent abrasive wear resistance

High compressive strength

Good toughness

Good dimensional stability at heat treatment   and in    service.

Very good through - hardening properties.

Very good resistance to tempering back.

Good WEDM properties.

Good surface treatment properties.

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Typical Analysis %
C 2.8
Si 0.8
Mn 0.7
Cr 7.0
Mo
2,3
V
8.9
Standard Specification
None
Delivery
Condition
Soft annealed to approx
270HB
Colour Code
Yellow/Orange

   
 

 Applications

 Weartec Sf   is suitable for medium run to long run tooling where the work  materials used are likely to result in abrasive wear and / or plastic deformation  of the tool.

 Examples:

  Cold rolls requiring very high wear resistance
  Forming rolls requiring a very high wear.
  Knives.
  Dies for tile and brick pressing
  Granulation screws.



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Properties

PHYSICAL DATA

Hardened and tempered to 62 HRC.

Temparature
20º C
(70º F)
200º C
(390º F)
400º C
(750º F)
Density, Kg/m³
Ibs/in³
7 340
0,264
-
-
Modulus of elasticity
MPa
Psi

212 000
30.8 x 106
199 000
28.8 x 106

191 000
27.70 x 106
Specific heat
J/kg º C
Btu/Ib º F

460
0,11
-
-
Coeffcient of thermal expansion per
º C form 20º C
º F from 68º F
-
-
10.8 x10-6
6.0 x 10-6
11.6 x 10-6
6.4 x 10-6
Thermal conductivity
W/m º C
Btu in (ft²hº F)
-
-
17
118
20
132
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COMPRESSIVE STRENGTH
Hatdness HRC
CompressiveStrength Rc0,2(MPa)
50
1 550
55
2 050
60
2 450
62
2 600
64
2 800

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 IMPACT STRENGTH
 Approximate room temperature impact strength at different tempering  temperatures.
 Specimen size : 7 x 10 x 55 mm(0,27 x 0,4 x 2.2") unnotched.
 Hardened for 30 minutes , except at 1150º C(2100º F) where 10 minutes is  used.Quenched in air. Tempered 2 x 2 hrs.

 Relative chipping resistance for AISID2 ,PM 23, WEARTEC,Roltec and PM23 at  60HRC.High value indicates good ductility.High temperature tempered condition.

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 WEAR RESISTANCE
 Relative abrsive wear resistance for Weartec,Roltec,PM 23 and AISI D 2 at  60HRC.A high value indicates good wear resistance.high temperature tempered  condition.



 HEAT TREATMENT RECOMMENDATIONS
 Soft Annealing
 Protect the steel and heat through to 900°C(1650°F).Then cool in the furnace  at 10°C(20°F)per hour to 650°C(1200°F), then freely in air.

 Stress Relieving
 After rough machining the tool should be heated through to 650°C(1200°F),  holding time 2 hours.Cool slowly to 500°C(930°F),then freely in air.

 Hardening
 Preheating in two stages:600-650°C(1100-1200°F)and 900-0°C(1650- 1740°F)
 Austenitizing temperature : 950-1150°C(1740 - 2100°F), normally  1020°C(187°F).
 Holding time: 30 min for <=1120°C(2050°F),
 10minutes for> 1120°C(2050°F).
 Protect the part against decarburization and oxidation during hardening.




Effect of testing temperature on impact energy.
Charpy-V specimens, longitudinal and short transverse direction.Approximate values for specimens fromØ25mm(4.9")bar.

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 Quenching Media

   High speed gas / circulating atmosphere.
  Vacuumfurnace (high speed gas with sufficient overpressure).
  Martempering bath ,salt bath or fluidized bed at 500-550ºC(930-1020ºF)
  Martempering bath at 200 -350ºC (390-660ºF)

Note: Temper the tool as soon as its temperature reaches 50-70ºC(120-160ºF).
Harness and retained austenite as a function of austenitizing temperature.
10 minutes holding at 1150ºC(2100ºF), else 30 minutes.

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  Tempering

 Choose the tempering temperature according to the hardness required by reference to    the tempering graphs below. Temper at least twice with intermediate cooling to room  temperature.The lowest tempering temperature which should be used without deep cooling is 525ºC
 (980ºF) and with sub-zero tretment 500ºC(930ºF).The minimum holding time at  temperature is 2 hours.For a hardening temperature of>=1100ºC (2010ºF).Weartec SF  should be sub-zero cooled and / or high temperature tempered three times in order to  reduce the amount of retained austenite.

Tempering Graph-without sub-zero treatment


 
 
 CCT-graph
 Austenitizing temperature 1025ºC(1875ºF).holding time 30 minutes.

cooling curveNo Hardness HV 10 T800-500
(Sec)
1
933
1
2
907
37
3
882
140
4
882
630
5
824
1241
6
734
2325
7
613
5215
8
620
7320
9
336
19400
 
 

TempºC Time hours HardnHv10
775
8.1
279
750
4.3
302
700
66.0
309
650
39.0
383
400
18.7
894
350
18.9
882
300
63.0
642
250
6.6
792
200
22.7
813
 
 

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SUB- ZERO TREATMENT
Pieces requiring maximum dimensional stability in service can be sub-zero treated as follows:

Immediately after quenching the piece should be sub-zero treated to -70ºC to-80ºC (-95-110ºF),soaking time 1-3 hours, followed by tempering .

Sub- zero treatment will give a hardness increase of ~1 HRC .Avoid intricate shapes as there will be risk of cracking .

For the highest demands on dimensional stability , sub-zero cooling in liquid nitrogen is recommended after quenching and after each tempering
Dimensional Changes

The dimensional changes have been measured after austenitizing and tempering.

Austenitizing:1025ºc(1875ºf)/30minutes,cooling vacuum furnace at 1,1ºC/s(1,8ºF/s)between 800ºC(1470ºF) and 500ºC(930ºF)

Tempering: 2 x2 hrs at various temperatures.

Specimen size : 100 x 100 x 100 mm (3.9" x 3.9" x 3.9" )

Dimensional changes in length, width and thickness after hardening and tempering
 
 

 SURFACE TREATMENTS

 Some cold work tool steels are given a surface treatment in order to reduce friction and increase wear  resistance .The most commenly used treatments are nitriding and surface coating with wear resistant layers  produced via PVD or CVD.

 The high hardness and toughness together with a good dimenional stability makes Weartec ideal as a  substrate  for various surface coatings.


 NITRIDING

 Nitriding gives a hard surface layer that is resistant to wear and erosion.WEARTEC is normally high  temperature tempered at around 525ºC(980ºF).This means that the nitriding temperature used should not  exceed 500-525ºC(930-980ºF).Ion nitriding at a temperature below the tempering temperature used is  prefered.
 The surface hardness after nitriding is approximately 1150HV0.2kg.The thickness of the layer should be chosen  to suit the application in question.

Process
 Time
Depth
mm
inch
Gas nitriding at 510ºC(950ºF) 10hrs 0,15 0,0059
Plasma nitriding at 480ºC(895ºF) 10hrs
30hrs 		0,10
0,20 		0,0039
0,0079

 PVD
 Physical vapour deposition ,PVD, is a method of applying a wear - resistant coating at temperatures between  200-500ºc(390-930ºF) .

 CVD

 Chemical vapour deposition , CVD, is used for applying wear- resistant surface coatings at a temperature of  around 1000ºc(1830ºF).It is recommended that the tools should be seperately hardened and tempered in vacuum furnace  after surface treatment.
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 MACHINABILITY

Relative machinability and grindability for Weartec , Roltec, AIS D2 and PM 23 .A high value indicates good machinability and grindability.

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 MACHINING RECOMMENDATIONS
 The cutting data below are to be considered as guiding values which must be adapted to existing local  conditions.
 Conditions: Soft annealed to approx .270HB.

 TURNING
Cutting Data Parameters Turning With Carbide
Rough Turning Fine Turning
Cutting speed ,Vc
m/min
f.p.m
80-100
260-330
100-120
330-395
Feed,f
mm/rev
i.p.r
0,2-0,4
0,008-0,16
0,1-0,2
0,004-0,008
Depth of cut ap
mm
inch
2-4
0,08-0,16
1-2
0,04-0,08
Carbide designation
ISO
K20*,P20
K15,P15
* Use a wear resistant Al2o3-coated Carbide

 Drilling
 High speed steel twist drill

Drill diameter
Cutting Speed(Vc)
Feed (f)
mm
inch
m/min
f.p.m
mm/r
i.p.r
-5
-3/16
6-8
20-26
0.05-0.10
0.002-0.004
5-10
3/16-3/8
6-8
20-26
0.10-0.20
0.004-0.008
10-15
3/8-5/8
6-8
20-26
0.20-0.25
0.008-0.010
15-20
5/8-3/4
6-8
20-26
0.25-0.30
0.010-0.012

 

 Carbide drill
 
Type of drill
Cutting data parameters Indexable insert solid carbide Brazes Carbide¹
Cutting Speed (Vc)
m/min
f.p.m
70-90
230-300
40-60
130-200
30-40
100-130
Feed (f)
m/r
i.p.r

0.05-0.15²

0.002-0.006²
0.10-0.25²
0.004-0.010²
0.15-0.25²
0.006-0.01²

 ¹) Drill with internal cooling channels and brazed carbide tip
 ²) Depending on drill diameter.

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 Milling
 Face and square shoulder milling.

Cutting Data Parameters Milling With Carbide
Rough Milling Fine Milling
Cutting speed ,Vc
m/min
f.p.m
40-60
130-200
60-80
200-260
Feed,fz
mm/tooth
inch/tooth
0,2-0,4
0,008-0,16
0,1-0,2
0,004-0,008
Depth of cut ap
mm
inch
2-4
0,08-0,16
-2
-0,08
Carbide designation
ISO
K20-P20*
K15-P15*

 * Use a wear resistant Al2o3-coated Carbide

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 End milling

 
Type of milling
Cutting data Parameters Solid carbide Carbide indexable insert
High speed steel
Cutting Speed(Vc)
     m/mm
     f.p.m
20-30
65-100
30-50
100-165
10-14
30-45
Feed (fz)
     mm/tooth
     inch/tooth
0.03-0.2¹
0.001-0.008¹
0.08-0.2¹
0.003-0.008¹
0.05-0.35¹
0.002-0.014¹
Carbide designation
     ISo
     US
-
K15²
-
 ¹)  Depending on radial depth of cut and cutter diameter.
 ² )  Use a wear resistant Al2o3-coated Carbide
 3)  With coated HSS.

 BAND SAWING
 For sawing of WEARTEC a carbide tipped band is recommended.the tooth pitch should be coarse but at least  three teeth must be engaged in the work piece at the same time.

 
Carbide tipped band
Cutting speed
m/min
f.p.m
40-50
130-165
Down feed
mm/min
inch/min
10-15
0.4-0.6


 GRINDING

 Wheel recommendation

Type of grinding
Annealed condation
Hardened condition
Face grinding stright wheel
B151 R50B3³
A46 Hv²
B151 R50B3¹
A46 Gv²
Face grinding segments
A36Gv
A46GV
Cylindrical grinding
B151 R50B3¹
A60KV²
B151 R50B3¹
A60JV²
Internal grinding
B151 R75B3¹
A60JV
B151 R75B3¹
A60IV
Profile grinding
B126 R100 B6¹
A 100JV²
B126 R100 B6¹
A 100IV²
1)The first choise is a CBN - wheel for this operation
2) Preferable a wheel type containing sintered AI2O3(Seeded gel)

 Electrical Discharge Machining,EDM

 If EDM is performed in the hardened and tempered condition,finish with "fine-sparking",i.e. low current , high  frequency.For optional performance EDM'd surface should be ground/ polished and the tool retempered a  approx.25ºC(50ºF) lower than the original tempering temperature.

 When EDM'ing larger sizes or complicated shapes WEARTEC should be tempered at high temperatures  >=525ºC(980ºF)

 Relative comparision of Uddeholm tool steel

 MATERIAL PROPERTIES AND RESISTANCE TO FAILURE MECHANISMS

   
Resistance to
Fatigue cracking resistance
 
uddeholm grade
Hardness/
Resistance to plastic
deformation
Machinability
Grindability
Dimension
Stability
Abrasive wear
Adhesive wear
Ductility/
resistance to
chipping
Toughness/
gross cracking
  Roltec
 
 
 
 
 
 
 
 
  Weartec
 
 
 
 
 
 
 
 
  AISI D2
 
 
 
 
 
 
 
 
  PM 23
 
 
 
 
 
 
 
 




 Further Information

 Please contact your local uddeholm office for further information on the selection, heat treatment, application  and availability of Uddeholm tool steels.
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Böhler Uddeholm Group company © 2007 ASSAB SRIPAD STEELS LTD.All Rights Reserved.