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TRANSCRIPT
Special engineering steels
EDELSTAHL WITTEN-KREFELD GMBH
Nitriding steels
NITRODURNITRODUR
NITRODUR
NITRODURNITRODUR
NITRODUR
3
Contents
Page 4 – 5 General
Page 6 – 7 Special features
Page 8 – 9 Steel portraits
Page 10 – 11 Application examples
Page 12 – 13 Steel production
Page 14 – 15 Steel processing
Page 16 Overview of grades and
chemical composition
Page 17 Forms supplied
Page 18 – 29 Material data sheets
Page 30 Sampling according to DIN EN 10085
Page 31 – 35 Nitriding and nitrocarburising
of steel components
Page 36 Temperature comparison
Page 37 Hardness comparison table
Page 38 List of photos
The use of special, high-perfor-
mance steel grades is essential
whenever machines and compo-
nents are exposed to high surface
stresses and dynamic loads.
If high surface hardness and
fatigue strength are required in
applications also involving high
temperatures, a product such as
our Nitrodur steel is the material
of choice.
Nitrodur is the name of our nitrid-
ing steel grades optimised for
use at elevated temperatures.
Different surface hardnesses and
hardening profiles can be set by
varying the nitriding parameters.
The advantage compared to the
surface hardening of standard
heat-treatable steel grades is the
lower distortion, as there are no
transformation processes during
cooling from the nitriding temper-
ature.
Our Nitrodur steel grades acquire
their high yield point, tensile and
fatigue strength (combined with
high toughness!) as a result of
hardening with tempering at
above 550 °C, but below the
microstructural transformation
temperature. The great strength
of our Nitrodur steel grades is
their optimum adaptation to the
respective intended application.
Depending on the cross-section
of the workpiece, optimum
quenching and tempering is en-
sured by selecting the appropri-
ate steel grade. The unusual
degree of purity and the homo-
geneity of the microstructure
guarantee uniform mechanical
properties, even where large
dimensions are involved.
Edelstahl Witten-Krefeld is in a
position to supply round billets of
up to approx. 750 mm diameter.
In this context, the strength and
toughness can be specifically
adjusted and combined to meet
the demands on the respective
component. Nitrodur steels offer
excellent hot formability. Their
cold formability and machinability
are dependent on the analysis
and the crystalline structure.
Nitrodur –
4
NITRODUR
Appropriate alloying and heat
treatment permit adjustment of
the material for optimum machin-
ability.
The top quality of Nitrodur is
achieved through high process
reliability and modern installations
for melting, secondary metallurgy,
vertical continuous casting, re-
melting, hot forming and heat
treatment, as well as through
advanced test facilities.
Edelstahl Witten-Krefeld is in a
position to offer you a tailor-made
nitriding steel for every applica-
tion and every component. Ask
our material specialists for ad-
vice.
Nitrodur – a speciality
from Edelstahl Witten-Krefeld
the right one for hot jobs
5
General
6
Spot-on analysis
The strength and toughness of
the base material are determined
by its chemical composition and
the heat treatment it undergoes.
Consequently, the required prop-
erties are already specifically
aimed for when melting the steel.
The facilities in Witten and
Krefeld enable us to achieve a
spot-on, reliably reproducible
chemical composition.
Specific hardenability
The hardenability of the material
can be specifically adapted to the
geometry of the respective com-
ponent by selecting the right
alloying elements. The most
important alloying elements for
nitriding steels are chromium,
nickel, aluminium, molybdenum
and vanadium. We offer not only
aluminium-alloyed nitriding steels,
but also aluminium-free grades.
Maximum purity
Extremely high purity is achieved
by secondary metallurgical treat-
ment and vertical continuous
casting, or also by remelting.
Undesirable non-metallic inclu-
sions are reduced to a minimum.
The homogeneity of our Nitrodur
steels cannot be beaten by any
other manufacturer of high-grade
steel.
High fatigue strength
In nitriding steels, the different
service properties required for the
individual components, such as
high strength under static and
dynamic stress, high toughness
and nitriding hardness, are set by
way of the chemical composition
and a sequence of heat treatment
operations. The nitriding treat-
ment increases wear resistance
and fatigue strength.
Nitrodur – specifically
7
Special features
Good machinability
The greater the number of com-
ponents to be manufactured, the
more important it is for the mate-
rial to have good machinability. In
other words: the cost-efficiency
of series production is already
partly determined when ordering
a specific steel grade.
Customised heat treatment
Depending on the envisaged
application and processing, we
can supply you with Nitrodur steel
grades in a wide variety of treated
conditions, e.g. with a defined
strength range.
Detailed technical information on
as-delivered conditions and pro-
cessing can be found starting on
Page 16.
adaptedto elevated temperatures
Nitrodur – steel grades
that get straight to the point
8
We’ve got the finest
Rolled or forged
Edelstahl Witten-Krefeld supplies
a wide variety of rolled and forged
products in different heat-treated
conditions, from bar steel, uni-
versal plate/flat dimensions and
semis, all the way to open-die
forgings.
Our partners in the steel trade
offer a wide selection of Nitrodur
grades in all standard sizes.
Unmachined or machined
Our strength is steel grades not
only in a variety of hot-formed
products, but also at various pro-
cessing stages. Our processing
operations range from rough-
machining and bright surfaces with
close tolerances, all the way to
ready-to-install components. Make
use of our extensive capabilities
and let us act as your “extended
workbench”.
Talk to our specialists about the
individual, tailor-made Nitrodur
solution you need.
NITRODUR
NITRODUR 14 CrMoV 5-9
NITRODUR 31 CrMo 12
NITRODUR 31 CrMoV 9
NITRODUR 34 CrAlNi 7
NITRODUR 41 CrAlMo 7
9
Steel portraits
specialitiesin stock for you
• NITRODUR 15 CrMoV 5-9Al-free nitriding steel with good high-temper-
ature strength, high fatigue strength and tem-
pering resistance, as well as optimum full
quenching and tempering.
Can be used as a nitriding, case-hardening or
heat-treatable steel. Particularly suitable for
quenched and tempered extrusion dies.
Suitable for welding by any method.
• NITRODUR 31 CrMo 12Al-free nitriding steel for relatively large
cross-sections, and also for higher nitriding
hardnesses as a result of its chemical com-
position. Suitable for gear wheels, cylinders,
drills, connecting rods, shafts, extruders,
guides, straightening rolls, thread gauges
with relatively large cross-sections.
• NITRODUR 31 CrMoV 9Al-free nitriding steel grade for relatively low
nitriding hardnesses and relatively great
nitriding depths. Suitable for gear wheels,
cylinders, drills, connecting rods, shafts,
extruders, guides, straightening rolls, thread
gauges.
• NITRODUR 34 CrAlNi 7Al-alloyed nitriding steel grade for large
cross-sections. Suitable for piston rods,
extruders, cylinders, gear wheels, rings.
• NITRODUR 41 CrAlMo 7Al-alloyed nitriding steel for medium cross-
sections. Suitable for connecting rods, small
extruders, valve stems.
• NITRODUR 34 CrAlMo 5Al-alloyed nitriding steel for high nitriding
hardnesses and small heat-treatment cross-
sections. Suitable for valve stems, super-
heated-steam fittings, cam plates, small gear
wheels, eccentrics.
34 CrAlMo 5 Talk to our
specialists for hot subjects
10
Nitrodur – hardness
Plastics processing
Cylinders and barrels, rams,
screws, injection nozzles and
other components are exposed to
great stress during injection
moulding, compression moulding
and extrusion. Consistently high
hardness must be retained, even
at elevated working temperatures,
in order to guarantee consistent
precision of the products to be
manufactured. Nitrodur offers just
that.
Gearbox construction
When made of Nitrodur, pinions,
toothed wheels and gear wheels
with external and internal gearing
offer greater operating reliability
and a longer service life in power
stations. Nitrodur steel grades are
also the perfect material if, after
heat treatment, the components
cannot be re-worked as a result of
their geometry or their small size.
Engine construction
For engines, such as racing-car
engines, which are exposed to
extreme stresses, particularly in
relation to temperature, it is advis-
able to use special Nitrodur steel
grades to manufacture crank-
shafts, connecting rods, piston
pins, cylinders, cylinder liners and
drive chains.
General mechanical engineering
Nitrodur steels grades are recom-
mended in mechanical engineer-
ing wherever reliable operation
and precision functioning at ele-
vated temperatures are indis-
pensable. For instance, in the pro-
duction of pump drive shafts, tim-
ing chains, pistons for hydraulic
controllers, screws and worm
gears, spindles, straightening rolls,
superheated-steam fittings, value
guides and valve seats.
11
Application examples
and precisionfor increased safety
Tool-making
When it comes to precision
mechanical parts and tools that
work at elevated operating tem-
peratures, Nitrodur guarantees the
unchanging geometry of the com-
ponents, such as sizing rolls, ring
gauges, thread gauges, limit plug
gauges, gear wheels and piston
rods. Nitrodur steel grades are
also particularly suitable materials
in cases where very small compo-
nents cannot be mechanically re-
worked after being heat-treated.
Machine tool manufacture
Nitrodur steel grades ensure a
long service life, reliable operation
and consistently high precision in
machine tools. For example, in
spindles and guide rails, grinding
and drilling machines, as well as
milling machines and lathes.
12
Our expertise in steel is Our own steel production in our
modern steelworks in Witten is
the basis for the purity and homo-
geneity of our heat-treatable
steels. Precisely defined proper-
ties are achieved by means of
exact alloying and process speci-
fications for melting, forming
and heat treatment. The steels
are melted in a 130 t electric arc
furnace.
The metallurgical precision work
is performed in a downstream
ladle furnace of the same size.
Depending on the steel grade and
the dimensions of the end prod-
uct, the steel melted in this way is
cast in ingots or continuous cast
blooms. Over 50 different mould
formats are available for ingot
casting, ranging from 600 kg to
160 t.
The continuous cast blooms are
manufactured in two strands on a
vertical continuous casting ma-
chine in a 475 x 340 mm format.
A remelting steelworks with two
electroslag remelting (ESR) fur-
naces and two vacuum arc re-
reactions, such as desulphurisa-
tion, and acting as an anti-oxidant
for the melting bath of the new
ingot. In addition, the slag has a
high capacity for absorbing non-
metallic inclusions, which means
that the remelted material is free
of coarse inclusions. The im-
provement in the microscopic
melting (VAR) furnaces is avail-
able in Krefeld for the production
of heat treatable steels involving
particularly stringent demands in
terms of homogeneity of their
microstructure and their purity.
Electroslag remelting
process
In the electroslag remelting
process (ESR), which works with
alternating current, a cast or
forged, self-consuming electrode
is immersed in a bath of molten
slag, which serves as an electrical
resistor.
The material to be remelted drips
from the end of the electrode
through the slag and forms the
new ingot in a water-cooled
mould below. The heat dissipa-
tion leads to directional solidifica-
tion in the direction of the longi-
tudinal ingot axis.
The remelting slag fulfils several
functions in this process. On the
one hand, it develops the neces-
sary process heat, while at the
same time supporting chemical
Scrap 130-t-electricarc furnace
Ladle degas-sing station(VD/VOD)
ca
Remelting facilities
ESR
VAR
I
EDELSTAHL WITTEN-KREFELD GMBH
THYSSEN KRUPP STAHL AG
Main production routes
Ladlefurnace
13
production something you can rely on
purity is attributable to desulphur-
isation and the resultant high
degree of sulphidic purity, and
also to a reduction in the size and
quantity of oxidic inclusions.
Nitrodur – reliable materials
thanks to reliable processes
Steel production
NITRODUR
Continuous bloomaster, 475 x 340 mm,
2 strands
Blooming/billet/large-sizebar rolling mill
Untreated
As-rolled
LSX 25
33 MN pressLSX 55
Long forging machines
As-forged
Finishingdepartments,rolling mills
Finishingdepartments,forging shops
Heattreatmentfacilities
Blooming-slabbing mill
Ingot casting
Machining
Products
Peelingmachines
• As-cast ingots As-continuously cast bloom material
• Open-die forgingsas-forged or machined
• Forged semis
• Forged round billets for tubemakingas-forged or peeled
• Forged bar steelas-forged or machined
• Machined tool steelforged or rolled
• Rolled semis
• Rolled tube roundsas-rolled or peeled
• Rolled bar steelas-rolled or machined
• Universal plate and flats
• Special products
Nitrodur –just
Vacuum arc remelting
process
The vacuum arc remelting (VAR)
process works with cast or
forged, self-consuming elec-
trodes in a vacuum.
Using an electric arc in a vacuum,
a melting bath is generated in a
copper crucible, which acts as
the opposite pole to the remelting
electrode and is connected to a
DC voltage source via current
contacts.
A new ingot is formed from the
liquefied electrode material drop
by drop in a continuous process.
In the VAR process, refinement of
the steel is brought about by the
reaction of the oxygen dissolved
in the steel with the carbon in the
molten material under the effect
of the vacuum. This results in the
best possible degree of micro-
scopic oxidic purity and freedom
from macroscopic inclusions. As
no desulphurisation takes place
during this remelting process, the
lowest possible sulphur content
has to be set prior to remelting, in
order also to meet the most strin-
gent demands on the degree of
sulphidic purity. Moreover, this
process guarantees the lowest
possible quantities of dissolved
gases in the steel and a homo-
geneous microstructure free of
segregation.
Hot forming and finishing
The blooming mill in Witten pro-
duces semi-finished products,
steel bars and universal plate/flat
dimensions. Two modern finishing
lines for checking the inner and
outer surface condition, as well
as the dimensions and identity,
are available for rolled and forged
products and steel bars. The
forge is equipped with a 33 MN
press, a GFM LSX 55 horizontal
long forging machine and a GFM
LSX 25 long forging machine.
14
Steel processing
nitriding steel, the way you need it
Machining
Edelstahl Witten-Krefeld offers
not only an optimum material in
various forms, but also pre-
machined and ready-to-install
parts. We put extensive consult-
ing know-how and modern ma-
Krefeld and Witten. Rotationally
symmetrical parts with a piece
weight of up to 20 tonnes are
manufactured in Krefeld on con-
ventional and modern CNC lathes
and grinding machines. The key
production fields are shafts, cylin-
ders and rolls for continuous
casting.
chining facilities at the disposal
of our customers.
After straightening, rolled or
forged bar steel and round billets
up to 300 mm diameter for tube-
making can be peeled, pressure
polished and chamfered in
15
1.8521
1.8515
1.8519
1.8550
1.8509
1.8507
0.13 –0.18
0.28 –0.35
0.27 –0.34
0.30 –0.37
0.38 –0.45
0.30 –0.37
1.20 –1.50
2.80 –3.30
2.30 –2.70
1.50 –1.80
1.50 –1.80
1.00 –1.30
0.80 –1.10
0.30 –0.50
0.15 –0.25
0.15 –0.25
0.20 –0.35
0.15 –0.25
0.20 –0.30
–
0.10 –0.20
–
–
–
–
–
–
0.85 –1.15
–
–
0.80 –1.10
0.40 –0.70
0.40 –0.70
0.40 –0.70
0.40 –0.70
0.40 –0.70
–
–
–
0.80 –1.20
0.80 –1.20
0.80 –1.20
≤ 0.40
≤ 0.40
≤ 0.40
≤ 0.40
≤ 0.40
≤ 0.40
≤ 0.025
≤ 0.025
≤ 0.025
≤ 0.025
≤ 0.025
≤ 0.025
≤ 0.030
≤ 0.035
≤ 0.035
≤ 0.035
≤ 0.035
≤ 0.035
16
Overview of gradesand chemical composition
Overview of grades Table 1
Chemical composition Table 2
Steel grade Chemical composition to DIN EN 10085, except1 (% by weight)
Code DIN EN Mate-name 10085 rial No. C Si Mn P max. S Al Cr Mo Ni V
Nitrodur 15 CrMoV 5-91
Nitrodur 31 CrMo12
Nitrodur 31 CrMoV 9
Nitrodur 34 CrAlNi 7
Nitrodur 41 CrAlMo 7
Nitrodur 34 CrAlMo 5
15CrMoV5-9
31CrMo12
31CrMoV9
34CrAlNi7
41CrAlMo7
34CrAlMo5
Grades Material No. Code name acc. Standardised into EN 10085
Page 18 – 19 Nitrodur 15 CrMoV 5-9 1.8521 15CrMoV5-9 DIN 17211
Page 20 – 21 Nitrodur 31 CrMo12 1.8515 31CrMo12 EN 10085
Page 22 – 23 Nitrodur 31 CrMoV 9 1.8519 31CrMoV9 EN 10085
Page 24 – 25 Nitrodur 34 CrAlNi 7 1.8550 34CrAlNi7 EN 10085
Page 26 – 27 Nitrodur 41 CrAlMo 7 1.8509 41CrAlMo7 EN 10085
Page 28 – 29 Nitrodur 34 CrAlMo 5 1.8507 34CrAlMo5 EN 10085
1) DIN 17211
17
NITRODUR
Forms supplied
55 – 250 mm dia.
Sharp-edged50 – 160 mm square
DIN 1014
DIN 7527
DIN 1013
> 200 mm dia. standard in-company tolerance, closertolerance on request
Subject topurchaseorder
Special:*)≤ +100/-0
Flat:Width: 80 – 510 mmThickness: 25 – 160 mmWidth/thickness ratio 10:1 max
Width: 25 – 160 mm
Thickness:80 – 550 mm
65 – 750 mm dia.
265 – 650 mm square
flat: on request
50 – 320 mm square,rising in 1 mm incre-ments
52 – 400 mm dia.
52 – 300 mm dia.
DIN 1017up to 150 mm width and 60 mm thickness;over 150 mm widthstandard in-company toler-ance
Tolerance on request
≤ 210 mm +/- 2%> 210 mm +/- 3%of edge length
Special:*)≤ 100 mm +/- 1%
of edge length
> 100 mm – 210 mm
+/- 1.5% of edge length
ISA Tol. 11 or comparabletolerance
ISA Tol. 11 or comparabletolerance
ISA-Tol. 8 or comparable tolerance
≤ 80 mm: 4.0 mm/m
> 80 mm: 2.5 mm/m
4.0 – 10 m,other lengthson request
Lengths as a function ofdimensionsand heat-treatmentcondition on request
3 - 10 m, onrequest 30 mmax. as afunction ofdia. andmax. bardead weightof 7 t
Hot-sawn or hot abra-sive-cut
Special:*)Cold-sawn,cold abrasive-cut
Hot abrasive-cut or cold-sawn
Special:*)Cold abrasive-cut
≤ 210 mm square:hot-sawn or hot abra-sive-cut
> 210 mm square:hot-sheared
Special:*)Cold abrasive-cut, cold-sawn
Hot-sawn/hotabrasive-cut
Special:*)Cold-sawn/abrasive-cut
Dimensions 50- 105 mm withround chamfer30° or 45°,chamfer widthapprox. 5 -12mm, otherwidths by ar-rangement
Rough-peeled finishavailable for 52 -240 mm
Max. permissiblesurface defectdepths:
Round: 1% max. ofdia. + 0.05 mm
Square: 1% max. ofedge length
Flat: 1.5% max. ofwidth, 2.0% max. ofthickness
Special:*)Smaller surfacedefect depth onrequest
Special:*)
- Rough-peeled- Turned- Milled
Edge radius:
≤ 210 mm - 12-18%of edge length
> 210 mm: withoutdefined edge radius
Max. perm. surfacedefect depth:
≤ 140 mm sq.0.3 mm max.
> 140 - 200 mm sq.0.6 mm max.
> 200 mm sq.visible defects elimi-nated
Technically crack-freecondition e.g. eddy-current tested orcomparable tech-nique, defined depthof roughness andsuitable packaging byspecial arrangement
< 1000 mm2:4.0 mm/m
> 1000 mm2:2.5 mm/m
Special:*)Speciallystraightened
Standard: 6 mm/m
Special:*)4 mm/m
As-peeledstraightness ≤ 2 mm/m, 1 mm/m orcloser as afunction ofdimensions on request
Untreated
Cold-shear-able
Cold-sawable
Normalized
Treated toferrite-pearlitestructure
Treated tohardnessrange
Soft-annealed
Spheroidize-annealed
Stress-relieved
Quenchedand tempered
Bar steeland roundbillets fortubemakingrolled
Sheet barsrolled withbulbous nar-row face
Bar steeland semis forged
Semisrolled
Bright steel
peeled
peeled andpolished
*) Special finishes subject to further inquiry (partly dependent on quality, dimensions and condition)
ground 52 – 100 mm dia.
Semis:as-forgedstraightness
Bar steel:to DIN withinthe tolerancelimit
3 – 8 m
Surface finishAs-suppliedcondition
End condition
Lengths/weightsStraightnessLengthsDia. or edge length
TolerancesProduct Dimensions
on requestAs-castingots/c.c.blooms Open-dieforgings
Forgings forged toshape on request(drawing)
18
C
0.13 – 0.18
Si
≤0.40
Mn
0.80 – 1.10
P
≤0.025
S
≤0.030
Cr
1.20 – 1.50
Mo
0.80 – 1.10
V
0.20 – 0.30
NITRODUR® 15 CrMoV 5-9
Material No.
1.8521
Code
15CrMoV5-9
Typical analysis in %acc. to DIN 17211
To DIN 17211
To DIN 17211
Material No.Code
Chemicalcomposition
Mechanical properties in differenttreatment conditions
Heat treatmentdiameter
in mmØ
0.2% proofstress
(Rp 0.2) min.N/mm2
Tensile strengthin N/mm2
Rm
Elongation atfracture in %
Amin.
Reduction ofarea at fracture
in % Zmin.
Notch impact energy(ISO-V)in J Av
min.
≤ 100
100 < d ≤ 250
750
700
900 – 1100
850 – 1050
10
12
–
–
30
35
Quenched and tempered QT
Hardness in differenttreatment conditions
Treated forshearing S
HB
max. 255
Soft annealedA
HB
max. 248
Nitrided,surface hardness
HV1
approx. 800
Soft annealing
680 – 740
Hardening
940 – 980
Quenching medium
Oil/polymer or water
Tempering
600 – 700
Nitriding
500 – 580
Heat treatment
To DIN 17211Temperatures in °C
From -191to +16
9.1
20100
11.1
20200
12.1
20300
12.9
20400
13.5
20500
13.9
Thermal expansion
Coefficient of linear thermalexpansion α 10-6 K-1
Temperature in °C
ApplicationsAl-free nitriding steel with good high-temperature strength, high fatigue strength and tempering resistance, as wellas optimum full quenching and tempering. Can be used as a nitriding, case-hardening or heat-treatable steel.Particularly suitable for quenched and tempered extrusion dies. Suitable for welding by any method.
19
NITRODUR® 15 CrMoV 5-9
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
100 101 102
100 101 102 103 104
100 101 102 103 104 105 106
HV 10 427
353
337 337 336 325 322 269292
236
278
Ac3
Ac1
A
MS
M
F
10
90
205 50 60 75
B
363 353393
250
500
750
1000
1250
1500
1750
2000
500 550 600 650 700 7500
800
200
175
150
0
125
100
75
50
25
100,0
87,5
75,0
62,5
50,0
37,5
25,0
12,5
0,0450
Rm
Rp0,2
Z
A5
Av
Tempering diagram High-temperature strength diagram
Time-temperature-transformation diagram(continuous)
1200
100 200 300 400 500 600 700RT
1000
800
600
400
200
90
80
70
60
30
20
10
200
175
150
125
100
75
Rm
Rp0,2
Z
A5
ISO-V
DVM
Elo
ngat
ion
at f
ract
ure
A5
and
red
uctio
n o
f ar
ea
at f
ract
ure
Z in
%
Not
ch im
pac
t en
ergy
Av
in J
(IS
O-V
)
0.2%
pro
of s
tres
s R
p0.
2an
d t
ensi
le s
tren
gth
Rm
in N
/mm
2
Pre-treatment: 980 °C, 30 min./airHardening: 980 °C, 30 min./oilHeat treatment cross-section: 60 mm dia.
Tempering temperature in °C (tempering time: 2 hours)
Test temperature in °C
No
tch
imp
act
ener
gy
E
long
atio
n
R
educ
tion
of
0
.2%
pro
of
stre
ss R
p0.
2an
d
Av
in J
at
fra
ctur
e
are
a at
fra
ctur
e
te
nsile
str
eng
th R
m in
N/m
m2
A5
in %
Z in
%
Tem
per
atur
e in
°C
Hardnessvalues
Time in s
Time in min
Time in h
20
NITRODUR® 31 CrMo 12
acc. to DIN EN 10085Typical analysis in %
To DIN EN 10085
To DIN EN 10085
Material No.Code
Chemicalcomposition
Mechanical properties in differenttreatment conditions
Hardness in differenttreatment conditions
Treated forshearing S
HB
max. 255
Soft annealedA
HB
max. 248
Nitrided,surface hardness
HV1
approx. 800
Soft annealing
650 – 700
Hardening
870 – 930
Quenching medium
Oil/polymer or water
Tempering
580 – 700
Nitriding
480 – 570
Heat treatment
To DIN EN 10085Temperatures in °C
From -191to +16
9.1
20100
11.1
20200
12.1
20300
12.9
20400
13.5
20500
13.9
Thermal expansion
Coefficient of linear thermalexpansion α 10-6 K-1
Temperature in °C
ApplicationsAl-free nitriding steel for relatively large cross-sections, and also for higher nitriding hardnesses as a result of itschemical composition. Suitable for gear wheels, cylinders, drills, connecting rods, shafts, extruders, guides,straightening rolls, thread gauges with relatively large cross-sections.
C
0.28 – 0.35
Si
≤0.40
Mn
0.40 – 0.70
P
≤0.025
S
≤0.035
Cr
2.80 – 3.30
Mo
0.30 – 0.50
Material No.
1.8515
Code
31CrMo12
Heat treatmentdiameter
in mmØ
0.2% proofstress
(Rp 0.2) min.N/mm2
Tensile strengthin N/mm2
Rm
Elongation atfracture in %
Amin.
Reduction ofarea at fracture
in % Zmin.
Notch impact energy(ISO-V)in J Av
min.
16 ≤ d ≤ 240
40 < d ≤ 100
100 < d ≤ 160
160 < d ≤ 250
835
785
735
675
1030 – 1230
1980 – 1180
930 – 1130
880 – 1080
10
11
12
12
–
–
–
–
25
30
30
30
Quenched and tempered QT
21
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
100 101 102
100 101 102 103 104
100 101 102 103 104 105 106
HV 10
548530 525 498 493 421 397 394
327337
330 238
Ac3
Ac1
A
MS
M
P
105
9515
11
5
92
3
40
3
8235
B
97 98 94 62
3
200
600
400
800
1000
1200
1400
1600
1800
2000
100 200 300 400 500 6000
700
200
180
160
140
120
0
100
80
60
40
20
100
90
80
70
60
50
40
30
20
10
0
Rm
Rp0,2
Z
Av
A5
Time-temperature-transformation diagram(continuous)
1200
100 200 300 400 500 600 700RT
1000
800
600
400
200
90
80
70
60
30
20
10
200
175
150
125
100
75
Rm
Rp0,2
Z
A5
ISO-V
DVM
NITRODUR® 31 CrMo 12Tempering diagram High-temperature strength diagram
Pre-treatment: 920 °C, 30 min./airHardening: 900 °C, 30 min./oilHeat treatment cross-section: 15 mm dia.
Tempering temperature in °C (tempering time: 2 hours)
0.2%
pro
of s
tres
s R
p0.
2an
d t
ensi
le s
tren
gth
Rm
in N
/mm
2
Not
ch im
pac
t en
ergy
Av
in J
(IS
O-V
)
Elo
ngat
ion
at f
ract
ure
A5
and
red
uctio
n o
f ar
ea
at fr
actu
re Z
in %
Test temperature in °C
Tem
per
atur
e in
°C
Hardnessvalues
Time in s
Time in h
No
tch
imp
act
ener
gy
E
long
atio
n
R
educ
tion
of
0
.2%
pro
of
stre
ss R
p0.
2an
d
Av
in J
at
fra
ctur
e
are
a at
fra
ctur
e
te
nsile
str
eng
th R
m in
N/m
m2
A5
in %
Z in
%
Time in min
22
NITRODUR® 31 CrMoV 9
acc. to DIN EN 10085Typical analysis in %
Material No.Code
Chemicalcomposition
Mechanical properties in differenttreatment conditions
Hardness in differenttreatment conditions
Treated forshearing S
HB
max. 255
Soft annealedA
HB
max. 248
Nitrided,surface hardness
HV1
approx. 800
Soft annealing
680 – 720
Hardening
870 – 930
Quenching medium
Oil/polymer or water
Tempering
580 – 700
Nitriding
480 – 570
Heat treatment
To DIN EN 10085Temperatures in °C
From -191to +16
9.1
20100
11.1
20200
12.1
20300
12.9
20400
13.5
20500
13.9
Thermal expansion
Coefficient of linear thermalexpansion α 10-6 K-1
Temperature in °C
ApplicationsAl-free nitriding steel grade for relatively low nitriding hardnesses and relatively great nitriding depths. Suitable forgear wheels, cylinders, drills, connecting rods, shafts, extruders, guides, straightening rolls, thread gauges.
C
0.27 – 0.34
Si
≤0.40
Mn
0.40 – 0.70
P
≤0.025
S
≤0.035
Cr
2.30 – 2.70
Mo
0.15 – 0.25
V
0.10 – 0.20
Material No.
1.8519
Code
31CrMoV9
Heat treatmentdiameter
in mmØ
0.2% proofstress
(Rp 0.2) min.N/mm2
Tensile strengthin N/mm2
Rm
Elongation atfracture in %
Amin.
Reduction ofarea at fracture
in % Zmin.
Notch impact energy(ISO-V)in J Av
min.
16 ≤ d ≤ 240
40 < d ≤ 100
100 < d ≤ 160
160 < d ≤ 250
900
800
700
650
1100 – 1300
1000 – 1200
1900 – 1100
1850 – 1050
19
10
11
12
–
–
–
–
25
30
35
40
Quenched and tempered QT
To DIN EN 10085
To DIN EN 10085
23
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
100 101 102
100 101 102 103 104
100 101 102 103 104 105 106
HV 10 478496 481 493 428 404 390 351374351 264 186
Ac3
Ac1
A
MS
M
F
1005060
340 30
B
97
70
177 170
172
100 100 100100
60
P
70 70
30 30
7030
200
600
400
800
1000
1200
1400
1600
1800
2000
100 200 300 400 500 6000
700
200
180
160
140
120
0
100
80
60
40
20
100
90
80
70
60
50
40
30
20
10
0
Rm
Rp0,2
Z
Av
A5
Time-temperature-transformation diagram(continuous)
1200
100 200 300 400 500 600 700RT
1000
800
600
400
200
90
80
70
60
30
20
10
200
175
150
125
100
75
Rm
Rp0,2
Z
A5
ISO-V
DVM
NITRODUR® 31 CrMoV 9Tempering diagram High-temperature strength diagram
Pre-treatment: 890 °C, 30 min./airHardening: 870 °C, 30 min./oilHeat treatment cross-section: 15 mm dia.
Tempering temperature in °C (tempering time: 2 hours)
0.2%
pro
of s
tres
s R
p0.
2an
d t
ensi
le s
tren
gth
Rm
in N
/mm
2
Not
ch im
pac
t en
ergy
Av
in J
(IS
O-V
)
Elo
ngat
ion
at f
ract
ure
A5
and
red
uctio
n o
f ar
ea
at f
ract
ure
Z in
%
Test temperature in °C
Tem
per
atur
e in
°C
Hardnessvalues
Time in s
Time in min
Time in h
No
tch
imp
act
ener
gy
E
long
atio
n
R
educ
tion
of
0
.2%
pro
of
stre
ss R
p0.
2an
d
Av
in J
at
fra
ctur
e
are
a at
fra
ctur
e
te
nsile
str
eng
th R
m in
N/m
m2
A5
in %
Z in
%
24
NITRODUR® 34 CrAINi 7
acc. to DIN EN 10085Typical analysis in %
Material No.Code
Chemicalcomposition
Mechanical properties in differenttreatment conditions
Hardness in differenttreatment conditions
Treated forshearing S
HB
max. 255
Soft annealedA
HB
max. 248
Nitrided,surface hardness
HV1
approx. 950
Soft annealing
650 – 700
Hardening
870 – 930
Quenching medium
Oil/polymer or water
Tempering
580 – 700
Nitriding
480 – 570
Heat treatment
To DIN EN 10085Temperatures in °C
From -191to +16
9.1
20100
11.1
20200
12.1
20300
12.9
20400
13.5
20500
13.9
Thermal expansion
Coefficient of linear thermalexpansion α 10-6 K-1
Temperature in °C
ApplicationsAl-alloyed nitriding steel grade for large cross-sections. Suitable for piston rods, extruders, cylinders, gear wheels,rings.
C
0.30 – 0.37
Si
≤0.40
Mn
0.40 – 0.70
P
≤0.025
S
≤0.035
AI
0.80 – 1.20
Cr
1.50 – 1.80
Mo
0.15 – 0.25
Ni
0.85 – 1.15
Material No.
1.8550
Code
34CrAINi7
Heat treatmentdiameter
in mmØ
0.2% proofstress
(Rp 0.2) min.N/mm2
Tensile strengthin N/mm2
Rm
Elongation atfracture in %
Amin.
Reduction ofarea at fracture
in % Zmin.
Notch impact energy(ISO-V)in J Av
min.
16 ≤ d ≤ 240
40 < d ≤ 100
100 < d ≤ 160
160 < d ≤ 250
680
650
600
600
1900 – 1100
1850 – 1050
1800 – 1000
1800 – 1000
10
12
13
13
–
–
–
–
30
30
35
35
Quenched and tempered QT
To DIN EN 10085
To DIN EN 10085
25
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
100 101 102
100 101 102 103 104
100 101 102 103 104 105 106
HV 10 534
566
543 505 368383
442
333 293
Ac3
Ac1A
MS
F
305
2
3 1540
B
95
233
219
348
1580
9060
P
50
361 240
9080
4050 50
50 50 50
200
600
400
800
1000
1200
1400
1600
1800
2000
100 200 300 400 500 6000
700
200
180
160
140
120
0
100
80
60
40
20
100
90
80
70
60
50
40
30
20
10
0
Rm
Rp0,2
Z
Av
A5
Time-temperature-transformation diagram(continuous)
1200
100 200 300 400 500 600 700RT
1000
800
600
400
200
90
80
70
60
30
20
10
200
175
150
125
100
75
Rm
Rp0,2
Z
A5
ISO-V
DVM
NITRODUR® 34 CrAINi 7Tempering diagram High-temperature strength diagram
Pre-treatment: 920 °C, 30 min./airHardening: 900 °C, 30 min./oilHeat treatment cross-section: 15 mm dia.
Tempering temperature in °C (tempering time: 2 hours)
0.2%
pro
of s
tres
s R
p0.
2an
d t
ensi
le s
tren
gth
Rm
in N
/mm
2
Not
ch im
pac
t en
ergy
Av
in J
(IS
O-V
)
Elo
ngat
ion
at f
ract
ure
A5
and
red
uctio
n o
f ar
ea
at f
ract
ure
Z in
%
Test temperature in °C
Tem
per
atur
e in
°C
Hardnessvalues
Time in s
Time in min
Time in h
No
tch
imp
act
ener
gy
E
long
atio
n
R
educ
tion
of
0
.2%
pro
of
stre
ss R
p0.
2an
d
Av
in J
at
fra
ctur
e
are
a at
fra
ctur
e
te
nsile
str
eng
th R
m in
N/m
m2
A5
in %
Z in
%
26
NITRODUR® 41 CrAIMo 7
acc. to DIN EN 10085Typical analysis in %
Material No.Code
Chemicalcomposition
Mechanical properties in differenttreatment conditions
Hardness in differenttreatment conditions
Treated forshearing S
HB
max. 255
Soft annealedA
HB
max. 248
Nitrided,surface hardness
HV1
approx. 950
Soft annealing
650 – 700
Hardening
870 – 930
Quenching medium
Oil/polymer or water
Tempering
580 – 700
Nitriding
480 – 570
Heat treatment
To DIN EN 10085Temperatures in °C
From -191to +16
9.1
20100
11.1
20200
12.1
20300
12.9
20400
13.5
20500
13.9
Thermal expansion
Coefficient of linear thermalexpansion α 10-6 K-1
Temperature in °C
ApplicationsAl-alloyed nitriding steel for medium cross-sections. Suitable for connecting rods, small extruders, valve stems.
C
0.38 – 0.45
Si
≤0.40
Mn
0.40 – 0.70
P
≤0.025
S
≤0.035
AI
0.80 – 1.20
Cr
1.50 – 1.80
Mo
0.20 – 0.35
Material No.
1.8509
Code
41CrAIMo7
Heat treatmentdiameter
in mmØ
0.2% proofstress
(Rp 0.2) min.N/mm2
Tensile strengthin N/mm2
Rm
Elongation atfracture in %
Amin.
Reduction ofarea at fracture
in % Zmin.
Notch impact energy(ISO-V)in J Av
min.
16 ≤ d ≤ 240
40 < d ≤ 100
100 < d ≤ 160
160 < d ≤ 250
750
720
670
625
1950 – 1150
1900 – 1100
1850 – 1050
1800 – 1000
11
13
14
15
–
–
–
–
25
25
30
30
Quenched and tempered QT
To DIN EN 10085
To DIN EN 10085
27
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
100 101 102
100 101 102 103 104
100 101 102 103 104 105 106
HV 10 613 599 595 409483
590
339 244
Ac3
Ac1
A
MS
F
103
3 15
B
95
223 206375
55
8540
P25
92
3030
75 70
M
70
30
~
~
~~
200
600
400
800
1000
1200
1400
1600
1800
2000
100 200 300 400 500 6000
700
200
180
160
140
120
0
100
80
60
40
20
100
90
80
70
60
50
40
30
20
10
0
Rm
Rp0,2
Z
A5
Av
Time-temperature-transformation diagram(continuous)
1200
100 200 300 400 500 600 700RT
1000
800
600
400
200
90
80
70
60
30
20
10
175
150
125
100
75
50
50
Rm
Rp0,2
Z
A5
ISO-V
DVM
NITRODUR® 41 CrAIMo 7Tempering diagram High-temperature strength diagram
Pre-treatment: 930 °C, 30 min./airHardening: 910 °C, 30 min./oilHeat treatment cross-section: 15 mm dia.
Tempering temperature in °C (tempering time: 2 hours)
0.2%
pro
of s
tres
s R
p0.
2an
d t
ensi
le s
tren
gth
Rm
in N
/mm
2
Not
ch im
pac
t en
ergy
Av
in J
(IS
O-V
)
Elo
ngat
ion
at f
ract
ure
A5
and
red
uctio
n o
f ar
ea
at f
ract
ure
Z in
%
Test temperature in °C
Tem
per
atur
e in
°C
Hardnessvalues
Time in s
Time in min
Time in h
No
tch
imp
act
ener
gy
E
long
atio
n
R
educ
tion
of
0
.2%
pro
of
stre
ss R
p0.
2an
d
Av
in J
at
fra
ctur
e
are
a at
fra
ctur
e
te
nsile
str
eng
th R
m in
N/m
m2
A5
in %
Z in
%
28
NITRODUR® 34 CrAIMo 5
acc. to DIN EN 10085Typical analysis in %
Material No.Code
Chemicalcomposition
Mechanical properties in differenttreatment conditions
Hardness in differenttreatment conditions
Treated forshearing S
HB
max. 255
Soft annealedA
HB
max. 248
Nitrided,surface hardness
HV1
approx. 950
Soft annealing
650 – 700
Hardening
870 – 930
Quenching medium
Oil/polymer or water
Tempering
580 – 700
Nitriding
480 – 570
Heat treatment
To DIN EN 10085Temperatures in °C
From -191to +16
9.1
20100
11.1
20200
12.1
20300
12.9
20400
13.5
20500
13.9
Thermal expansion
Coefficient of linear thermalexpansion α 10-6 K-1
Temperature in °C
ApplicationsAl-alloyed nitriding steel for high nitriding hardnesses and small heat-treatment cross-sections. Suitable for valvestems, superheated-steam fittings, cam plates, small gear wheels, eccentrics.
C
0.30 – 0.37
Si
≤0.40
Mn
0.40 – 0.70
P
≤0.025
S
≤0.035
AI
0.80 – 1.20
Cr
1.00 – 1.30
Mo
0.15 – 0.25
Material No.
1.8507
Code
34CrAIMo5
Heat treatmentdiameter
in mmØ
0.2% proofstress
(Rp 0.2) min.N/mm2
Tensile strengthin N/mm2
Rm
Elongation atfracture in %
Amin.
Reduction ofarea at fracture
in % Zmin.
Notch impact energy(ISO-V)in J Av
min.
16 ≤ d ≤ 240
40 < d ≤ 100
600
600
1800 – 1000
1800 – 1000
14
14
–
–
35
35
Quenched and tempered QT
To DIN EN 10085
To DIN EN 10085
29
200
600
400
800
1000
1200
1400
1600
1800
2000
100 200 300 400 500 6000
700
200
180
160
140
120
0
100
80
60
40
20
100
90
80
70
60
50
40
30
20
10
0
Rm
Rp0,2
Z
Av
A5
1200
100 200 300 400 500 600 700RT
1000
800
600
400
200
90
80
70
60
30
20
10
200
175
150
125
100
75
Rm
Rp0,2
Z
A5
ISO-V
DVM
NITRODUR® 34 CrAIMo 5Tempering diagram High-temperature strength diagram
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
100 101 102
100 101 102 103 104
100 101 102 103 104 105 106
HV 10
472
490 460 383 345
318
293
287 265
260 229 192
Ac3
Ac1
A
MS
M
F
7
10
5
30
15 50
179
174
1744560
6575 80
80
B
1010 50
45 5050
50 P50
50
Time-temperature-transformation diagram(continuous)
Pre-treatment: 950 °C, 30 min./airHardening: 930 °C, 30 min./oilHeat treatment cross-section: 15 mm dia.
Tempering temperature in °C (tempering time: 2 hours)
0.2%
pro
of s
tres
s R
p0.
2an
d t
ensi
le s
tren
gth
Rm
in N
/mm
2
Not
ch im
pac
t en
ergy
Av
in J
(IS
O-V
)
Elo
ngat
ion
at f
ract
ure
A5
and
red
uctio
n o
f ar
ea
at f
ract
ure
Z in
%
Test temperature in °C
Tem
per
atur
e in
°C
Hardnessvalues
Time in s
Time in min
Time in h
No
tch
imp
act
ener
gy
E
long
atio
n
R
educ
tion
of
0
.2%
pro
of
stre
ss R
p0.
2an
d
Av
in J
at
fra
ctur
e
are
a at
fra
ctur
e
te
nsile
str
eng
th R
m in
N/m
m2
A5
in %
Z in
%
30
Samplingaccording to DIN EN 10085
Sampling of bar steel and wire rod
d up to 25 mm 1) d over 25 mm a up to 25 mm 1)
b ≥ aa over 25 mmb ≥ a
Round sections Square and rectangular sections
Tensile specimen notched bar impact specimen
For thin products (d or b ≤ 25 mm) the specimen should,as far as possible, consist of an unmachined part of the bar.
With products having a round section, the longitudinal axle of the notchshould be generally in the direction of a diameter.
With products having rectangular sections, the longitudinal axle of the notchmust be at right angles to the wider roll surface.
d
d
d
12.5
d
12.5
12.5
a
b
12.5
a
b
12.5
a
b
12.5
12,5
b
a
12.5
2) 3) 3)
1)
2)
3)
The values given for the mechani-
cal properties in the material data
sheets apply to samples in the
“quenched and tempered” heat-
treated condition, taken in accor-
dance with DIN EN 10085.
31
Technical information
The surfaces of steel components
are subject to a wide variety of
stresses, such as wear, rolling and
bending stresses. In such cases,
it makes sense to increase the re-
sistance to such stresses on the
surface of the component by way
of appropriate hardening.
Nitriding and nitrocarburising are
two hardening processes with
particularly low distortion. In con-
trast to flame, induction and case
hardening, where the increase in
hardness is achieved by micro-
structural transformation of the
steel, low treatment temperatures
are sufficient for nitriding and ni-
trocarburising.
Temperatures of 490 to 530 °C are
customary for nitriding, while ni-
trocarburising is performed at
temperatures of 550 to 580 °C.
The two processes differ in that
nitrogen alone is used for nitrid-
ing, whereas nitrocarburising in-
volves a simultaneous combina-
tion of nitrogen and carbon.
Nitriding and nitrocarburisingof steel components
The aim of nitriding is to form a
diffusion layer (precipitation layer)
with a material-dependent nitrid-
ing depth of up to 0.9 mm. The
prerequisite for successful nitrid-
ing is the use of alloyed steel
grades containing nitride-forming
elements (Al, Cr, V, Mo, Mn). Only
in this way is it possible for so-
called alloy nitrides to form, which
in turn create high residual com-
pression stresses in the case.
The achievable surface hardness
is dependent not only on the ni-
triding temperature and the
amount of nitrogen available, but
particularly also on the quantity of
nitride-forming elements and the
strength of the components in
quenched and tempered condi-
tion. The higher the content of
these elements, the higher the
surface hardness after nitriding.
Aluminium is a particularly effec-
tive element when it comes to in-
creasing hardness by nitriding.
For instance, surface hardnesses
of approx. 1000 HV can be
achieved in a steel grade contain-
ing 1% aluminium. In steel grades
that contain no aluminium, but
roughly 1% chromium, the achiev-
able surface hardness is in the re-
gion of 600 HV. In order to obtain
a surface hardness of approx.
1000 HV in chrome steels, the
chromium content has to be in-
creased to approx. 5%. The differ-
ent effects of the alloying ele-
ments is clearly illustrated by
hardness profiles, such as shown
in Figs. 1 and 2 (Page 32) for com-
parable nitriding parameters.
The top diagram applies to a
31 CrMoV 9 steel and the bottom
diagram to a 34 CrAlNi 7 steel.
The carbon content of the steels
to be nitrided should not exceed
0.5%, as most nitride-forming ele-
ments also form carbides and sta-
ble carbides only allow limited
binding of nitrogen.
32
Gas-nitrided
500°C 10 to 20h
500°C 36h
500°C 84h
Hardness profiles of NITRODUR 31 CrMoV 9 steel after different nitriding times Fig. 1
Surface hardness to DIN EN 10085
1200
1000
800
600
400
200
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8
Distance from the surface in mm
HV
0,5
Hardness profiles of NITRODUR 34 CrAlNi 7 steel after different nitriding times Fig. 2
Surface hardness to DIN EN 10085
1200
1000
800
600
400
200
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8
Distance from the surface in mm
HV
0,5
Gas-nitrided
500°C 10 to 20h
500°C 36h
500°C 84h
Distance from the surface in mm
Distance from the surface in mm
Surface hardness to DIN EN 10085
Surface hardness to DIN EN 10085
33
Technical information
Consequently, nitriding results in
increasingly high surface hard-
nesses at increasing strengths in
Q+T condition, as the carbides
present are less stable.
Nitriding treatment can be carried
out in gas or plasma. Ammonia
gas (NH3) is used as the nitrogen
source in gas nitriding.
It dissociates at the surface of the
steel, which acts as a catalyst.
The nitrogen, which is then pres-
ent in atomic form, diffuses into
the steel surface and combines
with the iron there to form iron ni-
tride (Fe2-3 N, Fe4 N). The nitrogen
diffuses further into the material in
the course of treatment, leading
to the formation of the alloy ni-
trides.
In plasma nitriding, the compo-
nents to be treated are loaded
into a vacuum retort that is fed
with a mixture of nitrogen and hy-
drogen as the treatment gas. A
plasma is ignited by applying a
constant or pulsating direct volt-
age (300 to 800 V) between the
components, which act as the
cathode, and the retort, which
serves as the anode. The ionised
nitrogen molecules hit the surface
of the components with high ki-
netic energy, are split into nitrogen
atoms and trigger the nitriding
process, which then takes place
via the diffusion processes de-
scribed. As atoms are also de-
tached from the surface at the
same time, this process also per-
mits the nitriding of corrosion-re-
sistant steel grades by way of de-
struction of the passive chromium
oxide layer.
The aim of nitrocarburising is to
form a largely monophase ε-com-
pound layer (Fe2-3 N), which is sta-
bilised by the addition of carbon
to the treatment cycle. This layer
possesses high hardness, as well
as good sliding, wear and anti-
corrosion properties. Its thickness
is usually approx. 10 to 20 µm.
The precipitation layer below it
has a material-dependent depth
of approx. 0.2 to 0.4 mm. This
method is particularly suitable for
plain steels, which cannot be ni-
trided owing to the absence of ni-
tride-forming elements. Nitrocar-
burising can be performed in a
salt bath (Tenifer treatment), in
gas or in plasma. This process
should not be used when aiming
for relatively great depths of nitra-
tion, as high nitrogen concentra-
tions are required and lengthy
treatment times would otherwise
involve a risk of embrittlement of
the nitrided layer.
34
Hardness testing
Nitrided layers should be tested
using the hardness test according
to Vickers. A test load of 5 daN
has proven successful (HV 5).
Higher test loads falsify the re-
sults, as the hardness of the core
has a major influence on the test
results.
When testing nitrocarburised lay-
ers, a test load of 1 daN (HV 1)
has become generally accepted
for material testing. The exact
hardness of the compound layer
can only be measured by micro-
hardness testing.
The depth of nitration is deter-
mined on the cross-section by
low-load hardness testing with
the HV 0.5 test load in accor-
dance with DIN 50190, Part 3.
Fatigue strength
Nitriding generates residual com-
pression stresses in the case, re-
sulting in increased fatigue
strength. Precise information as to
the degree of improvement, e.g. in
the fatigue test under reversed
bending stresses, cannot be
given, as the result is influenced
by a host of factors. By way of ap-
proximation, it can be assumed
that the fatigue strength in ni-
trided condition is approx. 30%
higher than in quenched and tem-
pered condition.
As a special safety precaution
during nitriding and during the
subsequent loading of nitrided
workpieces in operation, it should
be pointed out that there must be
no defects in the brittle nitrided
layer, which can be damaged by
even slight impact loads. Surface
defects lead to a notch effect,
which eliminates the advantages
of the nitriding process and has a
negative effect on the service life
of the workpiece. Bearing this in
mind, it is advisable to use ni-
trided surfaces primarily in cases
of severe wear, but on surfaces
which should not be exposed to
any impact-type stresses, if at all
possible.
Corrosion resistance of
nitrided components
The corrosion resistance of the
iron nitride layer is greater than
that of the nitrided steel in its
original condition. However, in or-
der to exploit this effect to the full,
this layer must be free of pores,
as discontinuities in the formation
Advantages of the methods de-
scribed:
• Wear-resistant surfaces
• High fatigue strength
• Good sliding properties
• High temperature resistance
• Low distortion
• Good corrosion resistance
(nitrocarburising)
The methods have the following
disadvantages:
• Relatively low hardening
depth
• Occasionally long treatment
times
• Sensitivity to shock loads
35
Technical information
C ≤ 0.45 ± 0.02
Si ≤ 0.40 + 0.03
Mn ≤ 0.80 ± 0.04
P ≤ 0.025 + 0.005
S ≤ 0.035 + 0.005
Al ≥ 0.80 ≤ 1.20 ± 0.10
Cr ≥ 1.00 ≤ 2.00 ± 0.05> 2.00 ≤ 3.50 ± 0.10
Mo ≤ 0.30 ± 0.03> 0.30 ≤ 1.00 ± 0.04
Ni ≤ 1.15 ± 0.05
Sn ≤ 0.030 + 0.005
V ≤ 0.25 + 0.021 ± means that, for a given melt, either the upper or the lower limit of the range given for theladle analysis in Table 2 may be exceeded, but not both at once.
Maximum permissiblecontent in the ladle analysis
% by weight
Deviation from limit1 of the check analysis from the defined ladle analysis
to DIN EN 10085
Permissible deviations between check analysis and ladle analysis Table 3
Element
of the nitride layer and in the con-
centration profile again reduce the
degree of additional corrosion re-
sistance. This applies to the nitrid-
ing steels described in this
brochure. However, in the possi-
ble event of nitriding chromium-
containing stainless materials –
with 13 or 17% Cr – the corrosion
resistance must be expected to
decline after nitriding in compari-
son with that of the base material.
Temperature Comparison
Chart
°C °F K °C °F K °C °F K
–273.15 –459.67 0.00 380.00 716.00 653.15 910.00 1670.00 1183.15
–270.00 –454.00 3.15 390.00 743.00 663.15 920.00 1688.00 1193.15
–200.00 –328.00 73.15 400.00 752.00 673.15 930.00 1706.00 1203.15
–150.00 –238.00 123.15 410.00 770.00 683.15 940.00 1724.00 1213.15
–100.00 –148.00 173.15 420.00 788.00 693.15 950.00 1742.00 1223.15
– 90.00 –130.00 183.15 430.00 806.00 703.15 960.00 1760.00 1233.15
– 80.00 –112.00 193.15 440.00 824.00 713.15 970.00 1778.00 1243.15
– 70.00 – 94.00 203.15 450.00 842.00 723.15 980.00 1796.00 1253.15
– 60.00 – 76.00 213.15 460.00 860.00 733.15 990.00 1814.00 1263.15
– 50.00 – 58.00 223.15 470.00 878.00 743.15 1000.00 1832.00 1273.15
– 40.00 – 40.00 233.15 480.00 896.00 753.15 1010.00 1850.00 1283.15
– 30.00 – 22.00 243.15 490.00 914.00 763.15 1020.00 1868.00 1393.15
– 20.00 – 4.00 253.15 500.00 932.00 773.15 1030.00 1886.00 1303.15
– 17.78 0.00 255.37 510.00 950.00 783.15 1040.00 1904.00 1313.15
– 10.00 14.00 263.15 520.00 968.00 793.15 1050.00 1922.00 1323.15
0.00 32.00 273.15 530.00 986.00 803.15 1060.00 1940.00 1333.15
10.00 50.00 283.15 540.00 1004.00 813.15 1070.00 1958.00 1343.15
20.00 68.00 293.15 550.00 1022.00 823.15 1080.00 1976.00 1353.15
30.00 86.00 303.15 560.00 1040.00 833.15 1090.00 1994.00 1363.15
40.00 104.00 313.15 570.00 1058.00 843.15 1100.00 2012.00 1373.15
50.00 122.00 323.15 580.00 1076.00 853.15 1110.00 2030.00 1383.15
60.00 140.00 333.15 590.00 1094.00 863.15 1120.00 2048.00 1393.15
70.00 158.00 343.15 600.00 1112.00 873.15 1130.00 2066.00 1403.15
80.00 176.00 353.15 610.00 1130.00 883.15 1140.00 2084.00 1413.15
90.00 194.00 363.15 620.00 1148.00 893.15 1150.00 2102.00 1423.15
100.00 212.00 373.15 630.00 1166.00 903.15 1160.00 2120.00 1433.15
110.00 230.00 383.15 640.00 1184.00 913.15 1170.00 2138.00 1443.15
120.00 248.00 393.15 650.00 1202.00 923.15 1180.00 2156.00 1453.15
130.00 266.00 403.15 660.00 1220.00 933.15 1190.00 2174.00 1463.15
140.00 284.00 413.15 670.00 1238.00 943.15 1200.00 2192.00 1473.15
150.00 302.00 423.15 680.00 1256.00 953.15 1210.00 2210.00 1483.15
160.00 320.00 433.15 690.00 1274.00 963.15 1220.00 2228.00 1493.15
170.00 338.00 443.15 700.00 1292.00 973.15 1230.00 2246.00 1503.15
180.00 356.00 453.15 710.00 1310.00 983.15 1240.00 2264.00 1513.15
190.00 374.00 463.15 720.00 1328.00 993.15 1250.00 2282.00 1523.15
200.00 392.00 473.15 730.00 1346.00 1003.15 1260.00 2300.00 1533.15
210.00 410.00 483.15 740.00 1364.00 1013.15 1270.00 2318.00 1543.15
220.00 428.00 493.15 750.00 1382.00 1023.15 1280.00 2336.00 1553.15
230.00 446.00 503.15 760.00 1400.00 1033.15 1290.00 2354.00 1563.15
240.00 464.00 513.15 770.00 1418.00 1043.15 1300.00 2372.00 1573.15
250.00 482.00 523.15 780.00 1436.00 1053.15 1310.00 2390.00 1583.15
260.00 500.00 533.15 790.00 1454.00 1063.15 1320.00 2408.00 1593.15
270.00 518.00 543.15 800.00 1472.00 1073.15 1330.00 2426.00 1603.15
280.00 536.00 553.15 810.00 1490.00 1083.15 1340.00 2444.00 1613.15
290.00 554.00 563.15 820.00 1508.00 1093.15 1350.00 2462.00 1623.15
300.00 572.00 573.15 830.00 1526.00 1103.15 1360.00 2480.00 1633.15
310.00 590.00 583.15 840.00 1544.00 1113.15 1370.00 2498.00 1643.15
320.00 608.00 593.15 850.00 1562.00 1123.15 1380.00 2516.00 1653.15
330.00 626.00 603.15 860.00 1580.00 1133.15 1390.00 2234.00 1663.15
340.00 644.00 613.15 870.00 1598.00 1143.15 1400.00 2552.00 1673.15
350.00 662.00 623.15 880.00 1616.00 1153.15 1500.00 2732.00 1783.15
360.00 680.00 633.15 890.00 1634.00 1163.15 2000.00 3632.00 2273.15
370.00 698.00 643.15 900.00 1652.00 1173.15 2500.00 4532.00 2773.15
°C °F K
X = Particular K X– 273 9/5 (X–273) + 32 X
measured °C X 9/5 X + 32 X + 273
temperature °F 5/9 (X–32) X 5/9 (X–32) + 273
36
37
Technical information
Hardness comparison table
Tensile strength, Brinell, Vickers and Rockwell hardness
Tensilestrength
RmN/mm2
Ball inden-tation mm
d HB
Brinell hardness Vickershardness
HV
Rockwell hardness
HRB HRC HR 30 N
255 6.63 76.0 80 – – –270 6.45 80.7 85 41.0 – –285 6.30 85.5 90 48.0 – –305 6.16 90.2 95 52.0 – –320 6.01 95.0 100 56.2 – –335 5.90 99.8 105 – – –350 5.75 105 110 62.3 – –370 5.65 109 115 – – –385 5.54 114 120 66.7 – –400 5.43 119 125 – – –415 5.33 124 130 71.2 – –430 5.26 128 135 – – –450 5.16 133 140 75.0 – –465 5.08 138 145 – – –480 4.99 143 150 78.7 – –495 4.93 147 155 – – –510 4.85 152 160 81.7 – –530 4.79 156 165 – – –545 4.71 162 170 85.0 – –560 4.66 166 175 – – –575 4.59 171 180 87.1 – –595 4.53 176 185 – – –610 4.47 181 190 89.5 – –625 4.43 185 195 – – –640 4.37 190 200 91.5 – –660 4.32 195 205 92.5 – –675 4.27 199 210 93.5 – –690 4.22 204 215 94.0 – –705 4.18 209 220 95.0 – –720 4.13 214 225 96.0 – –740 4.08 219 230 96.7 – –755 4.05 223 235 – – –770 4.01 228 240 98.1 20.3 41.7785 3.97 233 245 – 21.3 42.5800 3.92 238 250 99.5 22.2 43.4820 3.89 242 255 – 23.1 44.2835 3.86 247 260 (101) 24.0 45.0850 3.82 252 265 – 24.8 45.7865 3.78 257 270 (102) 25.6 46.4880 3.75 261 275 – 26.4 47.2900 3.72 266 280 (104) 27.1 47.8915 3.69 271 285 – 27.8 48.4930 3.66 276 290 (105) 28.5 49.0950 3.63 280 295 – 29.2 49.7965 3.60 285 300 – 29.8 50.2995 3.54 295 310 – 31.0 51.3
1030 3.49 304 320 – 32.2 52.31060 3.43 314 330 – 33.3 53.61095 3.39 323 340 – 34.4 54.41125 3.34 333 350 – 35.5 55.41155 3.29 342 360 – 36.6 56.41190 3.25 352 370 – 37.7 57.41220 3.21 361 380 – 38.8 58.41255 3.17 371 390 – 39.8 59.31290 3.13 380 400 – 40.8 60.21320 3.09 390 410 – 41.8 61.11350 3.06 399 420 – 42.7 61.91385 3.02 409 430 – 43.6 62.71420 2.99 418 440 – 44.5 63.51455 2.95 428 450 – 45.3 64.31485 2.92 437 460 – 46.1 64.91520 2.89 447 470 – 46.9 65.71555 2.86 (456) 480 – 47.7 66.41595 2.83 (466) 490 – 48.4 67.11630 2.81 (475) 500 – 49.1 67.71665 2.78 (485) 510 – 49.8 68.31700 2.75 (494) 520 – 50.5 69.01740 2.73 (504) 530 – 51.1 69.51775 2.70 (513) 540 – 51.7 70.01810 2.68 (523) 550 – 52.3 70.51845 2.66 (532) 560 – 53.0 71.21880 2.63 (542) 570 – 53.6 71.71920 2.60 (551) 580 – 54.1 72.11955 2.59 (561) 590 – 54.7 72.71995 2.57 (570) 600 – 55.2 73.2
Tensilestrength
RmN/mm2
Ballindentation
mm d HB
Brinell hardness Vickershardness
HV
Rockwell hardness
HRB HRC HR 30 N
2030 2.54 (580) 610 – 55.7 73.72070 2.52 (589) 620 – 56.3 74.22105 2.51 (599) 630 – 56.8 74.62145 2.49 (608) 640 – 57.3 75.12180 2.47 (618) 650 – 57.8 75.5
– – – 660 – 58.3 75.9– – – 670 – 58.8 76.4– – – 680 – 59.2 76.8– – – 690 – 59.7 77.2– – – 700 – 60.1 77.6– – – 720 – 61.0 78.4– – – 740 – 61.8 79.1– – – 760 – 62.5 79.7– – – 780 – 63.3 80.4– – – 800 – 64.0 81.1– – – 820 – 64.7 81.7– – – 840 – 65.3 82.2– – – 860 – 65.9 82.7– – – 880 – 66.4 83.1– – – 900 – 67.0 83.6– – – 920 – 67.5 84.0– – – 940 – 68.0 84.4
Tensile strength N/mm2 Rm
Brinell hardness1) Diameter of the d1) Calculated from: ball indentation in mm
HB = 0.95 · HV
(0.102 F/D2 = 30) Hardness HBD = 10 value =
Vickers hardness Diamond pyramid HVTest forces ≥ 50 N
Rockwell hardness Ball 1.588 mm (1/16“) HRBTotal test force = 98 N
Diamond cone HRCTotal test force = 1471 N
Diamond coneTotal test force = 294 N HR 30 N
0.102 · 2 Fπ D (D – √D2 – d2)
Conversions of hardness values using this conversion table are only approximate.See DIN 50 150, December 1976.
38
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39
General note (liability)
All statements regarding the properties
of utilisation of the materials or products
mentioned are for the purposes of
description only. Guarantees regarding
the existence of certain properties or a
certain utilisation are only ever valid if
agreed upon in writing.
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Nitriding steels
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