ROLTEC SF



 

  


General

Roltec Sf is a chromium - molybdenum - vanadium alloyed cold tool steel.

Characteristics found in ROLTEC SF

High wear resistance

High compressive strength

High 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 1.4
Si
1.0
Mn 0.6
Cr 4.6
Mo
3.2
V
3.7
Standard Specification
None
Delivery
Condition
Soft annealed to approx
240HB
Colour Code
Blue / Green

   

 Applications

Roltec SF is suitable for medium and long run tooling where materials used are likely to result in mixed or abrasive wear and / or chipping / cracking and / or plastic deformation of the tool.

Examples:

  Cold rolls requiring very high wear resistance and resistance to cracking.
  Form rolls requiring a very high wear resistance and resistance to cracking.
  Knives.
  Engineering applications.
  Substrate for surface coating.



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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
7 650
0.276
-
-
Modulus of elasticity
MPa
Psi

215 000
31.2 x 106
196 000
28.4 x 106

185 000
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
-
-
11.4 x10-6
6.3x 10-6
12.1 x 10-6
6.7 x 10-6
Thermal conductivity
W/m º C
Btu in (ft²hº F)
-
-
25
174
27
188
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COMPRESSIVE STRENGTH
Hatdness HRC
CompressiveStrength Rc0,2(MPa)
50
1 550
55
2 100
60
2 550
62
2 750
64
2 950

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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.

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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).

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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
894
1
2
882
28
3
870
415
4
813
1030
5
690
2325
6
508
5215
7
421
7320
 
 

TempºC Time hours HardnHv10
800
23.3
835
750
0
289
700
2.7
327
650
7.4
468
600
14.2
824
350
5.8
835
300
4.8
536
250
17.8
579
200
15.2
824
 
Hardness and retained austenite as a function of aystenitizing temperature.10 minutes holding time at 1150ºC(2100ºF), else 30 minutes.

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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.Roltec 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 .240HB.

 TURNING
Cutting Data Parameters Turning With Carbide
Rough Turning Fine Turning
Cutting speed ,Vc
m/min
f.p.m
100-150
330-500
150-200
500-800
Feed,f
mm/rev
i.p.r
0,2-0,4
0,008-0,16
0,5-0,2
0,02-0,008
Depth of cut ap
mm
inch
2-4
0,08-0,16
0,5-2
0,02-0,08
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
10-12*
33-40
0,05-0,10
0,002-0,004
5-10
3/16-3/8
10-12*
33-40
0,10-0,20
0,004-0,008
10-15
3/8-5/8
10-12*
33-40
0,20-0,25
0,008-0,010
15-20
5/8-3/4
10-12*
33-40
0,25-0,30
0,010-0,012
*For coated HSS drill Vc 20-25 m/min.(66-83 f.p.m)

 

 Carbide drill
 
Type of drill
Cutting data parameters Indexable insert solid carbide Brazes Carbide¹
Cutting Speed (Vc)
m/min
f.p.m
10-130
330-430
50-60
165-200
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
90-100
300-330
100-120
330-400
Feed,fz
mm/tooth
inch/tooth
0,2-0,4
0,008-0,16
0,1-0,2
0,003-0,008
Depth of cut ap
mm
inch
2-4
0,08-0,16
-2
-0,08
Carbide designation
ISO
K20-P20
Coated Carbide*
K15-P15
Coated Carbide*

 * 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
40-50
130-165
80-110
260-360
5-8
17-26
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)  With coated HSS Vc =14-18 m/min.(40-60 f.p.m)
 ² )  Depending on radial depth of cut and cutter diameter.
 3)  Use a wear resistant Al2o3-coated Carbide

 BAND SAWING
For sawing of Roltec use a band with a coarse tooth pitch, but at least three teeth must br engaged in the work piece atthe same time.

 
HSS bi-metal band
 Carbide tipped band
Cutting speed
m/min
f.p.m
20-25
65-80
60-70
200-230
Down feed
mm/min
inch/min
6-8
0,2-0,3
20-22
0,8-0,9


 GRINDING

 Wheel recommendation

Type of grinding
Annealed condation
Hardened condition
Face grinding stright wheel
B151 R50 B3³
A46 Hv²
B151 R50 B3¹
A46 Gv²
Face grinding segments
A36Gv
A46GV
Cylindrical grinding
B151 R50 B3¹
A60KV²
B151 R50 B3¹
A60JV²
Internal grinding
B151 R75 B3¹
A60JV
B151 R75 B3¹
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 Roltec 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.