Welding of tool steel - Bohler Uddeholm Africa

Welding of tool steel - Bohler Uddeholm Africa
Welding of tool steel
Welding of tool steel
1
Welding of tool steel
Content
Introduction ............................................ 3
General information on
welding of tool steel ............................... 3
Welding methods for tool steel .............. 4
The welding bay ..................................... 5
Filler-metal characteristics ...................... 6
Be careful as regards hydrogen! ............. 8
Elevated working temperature ............... 10
Welding procedure ................................. 11
Weld repair of
– hot work tool steel .............................. 13
– plastic mould steel .............................. 14
– cold work tool steel ............................. 15
This information is based on present state of knowledge and is
intended to provide general notes on our products and their
uses. It should not therefore be construed as a warranty of
specific properties of the products described or a warranty for
fitness for a particular purpose.
2
Welding of tool steel
Introduction
The weldability of steels with more than
0,2% carbon is usually considered to be
poor. Hence, tool steels with 0,3–2,5%
carbon are difficult to weld and many
steel suppliers will actually recommend
against welding. However, improved
quality of consumables, refined welding
equipment, developments in welding
technique and, not least, improvements
in tool steel quality have combined to
render tool welding as a realistic possibility, which can have considerable
economic consequences.
Hence, Uddeholm recognizes that
tool steels often need to be welded; this
is especially true for expensive tooling
like die-casting dies, large forging dies,
plastic moulds, carbody dies and blanking tools where repair and adjustment
via welding is highly cost-attractive in
comparison with the expense of producing new tooling.
General information on welding of
tool steel
Tool steels contain 0,3–2,5% carbon as
well as alloying elements such as
manganese, chromium, molybdenum,
tungsten, vanadium and nickel. The
main problem in welding tool steel
stems from its high hardenability. Welds
cool quickly once the heat source is
removed and the weld metal and part
of the heat-affected zone will harden.
This transformation generates stresses
because the weld is normally highly
constrained, with a concomitant risk for
cracking unless great care is exercised.
In what follows, a description is
given of the welding equipment, welding technique and weld consumables
that are required in order to weld tool
steel successfully. Of course, the skill
and experience of the welder is also a
vital ingredient in obtaining satisfactory
results. With sufficient care, it is possible
to achieve weld repairs or adjustments
which, in terms of tooling performance,
are hardly inferior to that of the base
steel.
Welding of tooling may be required
for anyone of the following reasons:
• Refurbishment and repair of cracked
or worn tooling
• Renovation of chipped or worn
cutting edges, e.g. on blanking tools
• Adjustment of machining errors in
tool making
• Design changes.
The welding bay.
3
Welding of tool steel
Welding methods
for tool steel
Power source
SHIELDED METAL-ARC WELDING
(SMAW OR MMA)
Principle
An electric arc generated by a DC or AC
power source is struck between a
coated, rod-like electrode and the workpiece (Fig. 1).
The electrodes consist of a central
wire core, which is usually low-carbon
steel, covered with a coating of pressed
powder (flux). The constitution of this
coating is complex and consists of iron
powder, powdered ferro-alloys, slag
formers and a suitable binder. The electrode is consumed under the action of
the arc during welding and drops of
molten metal are transferred to the
workpiece. Contamination by air during
the transfer of molten drops from electrode to workpiece and during solidification and cooling of the weld deposit
is inhibited partly by slag formed from
constituents in the electrode coating
and partly by gases created during
melting of the electrode.
The composition of the deposited
weld metal is controlled via the constitution of the electrode coating.
For MMA welding, it is possible to use
either an AC or DC power source.
However, whichever is used, the source
must provide a voltage and current
which is compatible with the electrode.
Normal arc voltages are:
• Normal recovery electrodes: 20–30 V
• High recovery electrodes: 30–50 V
Uddeholm welding consumables are
of normal-recovery type. A suitable
power source for these is a DC unit with
an open voltage of 70 V and which is
capable of delivering 250A/30 V at 35%
intermittence.
GAS TUNGSTEN-ARC WELDING
(GTAW OR TIG)
Principle
In MMA welding, the electrode rod from
which the arc is struck is consumed
during welding.
The electrode in TIG welding is made
of tungsten or tungsten alloy which has
a very high melting point (about
3300°C/6000°F) and is therefore not
consumed during the process (Fig. 2).
The arc is initially struck by subjecting
the electrode-workpiece gas to a highfrequency voltage. The resulting ioniza-
METHODS
Manual Metal-arc welding (MMA)
tion permits striking without the necessity for contact between electrode and
workpiece. The tungsten electrode is
always connected to the negative terminal of a DC power source because
this minimizes heat generation and
thereby any risk of melting the electrode. Current is conducted to the electrode via a contact inside the TIG-gun.
Any consumables which are required
during TIG-welding are fed obliquely
into the arc in the form of rod or wire.
Oxidation of the weld pool is prevented
by an inert-gas shroud which streams
from the TIG tun over the electrode and
weld.
Power source
TIG welding can be performed with a
regular MMA power source provided
this is complemented with a TIG control
unit. The gun should be water cooled
and be capable of handling a minimum
current of 250 A at 100% intermittence.
A gas lens is also a desirable feature in
order that the inert gas protection is as
efficient as possible. Welding is facilitated if the current can be increased
steplessly from zero to the optimum
level.
METHODS
TIG-Welding
Electrode holder
Power source
+Pole
– Pole
Shielding gas
Welding conv.
Welding rectifier
Workpiece
Cooling water
Tungsten
electrode
Molten pool
Slag
Welding torch
Power supply
– Pole
Electrode
Shielding gas
+ Pole
Workpiece
Weld
Fig. 1
4
Workpiece
Filler rod
Fig. 2
Weld
Welding
rect.
Welding of tool steel
The welding bay
In order to be able to effect satisfactory
welding work on tool steel, the following items of equipment are to be regarded as minimum requirements (over
and above the welding equipment).
DRY CABINET
The coated electrodes used for MMA
welding are strongly hygroscopic and
should not be allowed to come into
contact with anything other than dry air.
Otherwise, the weld will be contaminated with hydrogen (see later). Hence,
the welding bay should be equipped
with a dry cabinet for storage of electrodes. This should be thermostatically
controlled in the range 50–150°C (120–
300°F). The electrodes should be removed from their containers and lie
loose on racks.
For welding of tooling outside the
welding bay, it will also be found useful
to have a portable heated container in
which the electrodes can be carried.
PREHEATING EQUIPMENT
GRINDING MACHINES
Tool steels cannot be welded at room
temperature without considerable risk
for cracking and it is generally necessary to pre-heat the mould or die before
any welding can be attempted (see
later). While it is certainly possible to
weld tools successfully by preheating in
a furnace, the chances are that the
temperature will fall excessively prior to
completion of the work. Hence, it is
recommended that the tool be maintained at the correct temperature using
an electrical heating box supplied from
a current-regulated DC source. This
equipment also enables the tool to be
heated at a uniform and controlled rate.
For minor repairs and adjustments, it
is acceptable that the tool be preheated
using a propane torch. Hence, liquid
propane cylinders should be available in
the welding bay.
The following should be available:
• Disc grinder with minimum 180 Ø x
6 mm wheel (7 Ø x 0,25 inch) for
preparing the joint and grinding out
of any defects which may occur
during welding.
• Flat grinder capable of ≥25 000 rpm
for grinding of minor defects and of
the finished weld.
• If a welded mould is subsequently to
be polished or photo-etched, it may
be necessary to have a grinder capable of giving a sufficiently fine finish.
Electrical elements for
an insulated preheating box.
WORKBENCH
It is particularly important during critical
welding operations, of the type performed with tool steel, that the welder
enjoys a comfortable working position.
Hence, the workbench should be stable,
of the correct height a sufficiently level
that the work can be positioned securely and accurately. It is advantageous
if the workbench is rotatable and adjustable vertically, since both these
features facilitate the welding operation.
Dry cabinet for storage of electrodes.
5
Welding of tool steel
Filler-metal
characteristics
The chemical composition of a weld
deposit is determined by the composition of the consumable (filler metal), the
base steel composition and the extent
to which the base material is melted
during welding. The consumable
electrode or wire should mix easily with
the molten base steel giving a deposit
with:
• Uniform composition, hardness and
response to heat-treatment
• Freedom from non-metallic inclusions,
porosity or cracks
• Suitable properties for the tooling
application in question.
Since tool steel welds have high
hardness, they are particularly susceptible to cracking which may originate at
slag particles or pores. Hence, the
consumable used should be capable of
producing a high-quality weld. In a
similar vein, it is necessary that the
consumables be produced with very
tight analysis control in order that the
hardness as welded and the response to
heat treatment is reproducible from
batch to batch. High-quality filler metals
MMA welding consumables from Uddeholm.
6
are also essential if a mould is to be
polished or photo-etched after welding.
Uddeholm welding consumables meet
these requirements.
TIG filler rod is normally produced
from electro-slag remelted stock while
coated electrodes are of basic type,
which are far superior to rutile electrodes as regards weld cleanliness.
Another advantage with basis coated
electrodes over those of rutile type is
that the former give a much lower
hydrogen content in the weld metal.
In general, the consumable used for
welding tool steel should be similar in
composition to the base material. When
welding in the annealed condition, e.g.
if a mould or die has to be adjusted
while in the process of manufacture, it
is vital that the filler metal has the
same heat treatment characteristics as
the base steel, otherwise the welded
area in the finished tool will have different hardness. Large compositional
differences are also associated with an
increased cracking risk in connection
with hardening.
Uddeholm welding consumable are
designed to be compatible with the
corresponding tool steel grades (QRO
90 WELD and QRO 90 TIG-WELD are
recommended for all Uddeholm hot
work steels) irrespective of whether
welding is carried out on annealed or
hardened-and-tempered base material.
Obviously, the weld metal of welded
tools will require different properties for
different applications.
For the three main application segments for tool steels (cold work, hot
work and plastic moulding), the important weld-metal properties are:
Cold Work
• Hardness
• Toughness
• Wear resistance
Hot Work
• Hardness
• Temper resistance
• Toughness
• Wear resistance
• Heat checking resistance
Plastic Moulding
• Hardness
• Wear resistance
• Polishability
• Photoetchability
These properties are discussed briefly
on following pages.
Welding of tool steel
HARDNESS
If the mould or die is welded in the
hardened and tempered condition, then
it is important that the weld exhibits the
same hardness as the base steel in the
as-welded condition. Such being the
case, small welds can be effected without the necessity of subsequently tempering the tool. All Uddeholm welding
consumables fulfil this requirement
(Fig. 3).
HV10
450
Surface
400
350
300
0
2
0,1
▲
4
▲
250
Weld metal
▲
▲
Heat
Base affected
zone
steel
▲
Fig. 3. Hardness profile across a weld
in IMPAX SUPREME (MMA welding using
IMPAX WELD electrodes).
6
8
10
0,2
0,3
0,4
Distance from surface
12
Note the uniform hardness
distribution, only marginally
higher than the base hardness,
and the very narrow heataffected zone with only a
modest hardness increase at
the fusion line.
mm
0,5 inch
TEMPER RESISTANCE
TOUGHNESS
HEAT-CHECKING RESISTANCE
If the mould or die is to be heat treated
after welding (base steel in annealed
condition), then the hardening and
tempering characteristics of the weld
metal should be similar to those of the
base steel so that the same hardness is
obtained in both (Fig. 4).
In spite of the fact that we are dealing
with that is essentially a casting, weld
metal in tool steel can be surprisingly
tough as a result of the rather fine
microstructure derived from a high rate
of solidification. In general, however, the
toughness will be improved by subsequent heat treatment. Hence, larger
weld repairs on a fully-hardened tool
should always be tempered after welding, even though the hardness of the
weld metal and base steel may be compatible in the as-welded condition.
For cold work steels, where very high
hardness is required, it will be advisable
to use a softer filler metal for the initial
layers and finish with a hard electrode
on the working surface of the tool. This
procedure will produce a tougher repair
than if the hard electrode had been
used throughout.
Welds in hot work tools will normally
heat-check faster than the base steel
because of poorer hot strength, temper
resistance or toughness (ductility).
However, if a consumable is used which
gives a weld metal with superior hot
strength and hot hardness, then the
heat-checking resistance can be equal
to or even better than the base steel.
QRO 90 WELD and TIG-WELD
produce welds which exhibit excellent
resistance to heat checking (Fig. 5).
HRC
Austenitizing temperature
1020°C (1870°F)
55
50
QRO 90
WELD
45
QRO 90
SUPREME
40
35
500
900
550
1000
600
650
700 °C
1100
1200
1300 °F
Tempering temperature
(holding time 2 x 2h)
Fig. 4. Comparison of tempering curves for
QRO 90 SUPREME and weld metal produced
by MMA welding with QRO 90 WELD
electrodes.
WEAR RESISTANCE
Just as with tool steel, the wear resistance of a weld metal increases with its
hardness and alloy content. Uddeholm
welding consumables are designed to
give weld metals with the same wear
resistance as the compatible base steel.
HRC
60
55
Austenitizing temperature
1020°C (1870°F)
ORVAR
SUPREME
50
QRO 90 WELD
45
40
35
30
100 200
200
400
300
400
500
600
°C
600 800 1000 1200°F
Holding time 2 x 1h
Fig. 5. QRO 90 WELD exhibits superior
temper resistance to premium H13 base steel
(ORVAR SUPREME).
7
Welding of tool steel
STAVAX WELD/TIG WELD and IMPAX WELD/
TIG WELD match their corresponding tool
steel grades exactly and give perfect results
after polishing or texturing of a welded mould.
8
s
trode
elec
oated
(Rutile)
C
(Basic)
la
rc
Flux-cored wire (CO2)
eta
The weld metal and the base steel must
also be similar in composition of a
welded surface of a plastic mould is to
be textured via photoetching. If not, the
response to etching will vary between
the weld and the base metal and this
will result in a witness mark on the
plastic component. Welds in IMPAX
SUPREME and STAVAX ESR with IMPAX
or STAVAX WELD (or TIG-WELD) will
normally not be discernible after photoetching, provided that the proper welding procedure is used.
Weld in tool steel have high hardness
and are, therefore, especially susceptible
to cold cracking derived from hydrogen
ingress during welding. In many cases,
hydrogen is generated as a result of
water vapour being adsorbed in the
hygro-scopic coating of MMA electrodes.
sm
PHOTOETCHABILITY
(TEXTURABILITY)
Be careful as
regards hydrogen!
Ga
For plastic mould which need to be
polished after welding, it is essential
that the weld metal does not differ
greatly in composition or hardness from
the base steel. Otherwise, an outline of
the weld is visible after polishing which
will leave a witness mark on the plastic
part.
IMPAX SUPREME and STAVAX ESR
welded with IMPAX and STAVAX WELD
(or TIG-WELD) consumables, will in
conjunction with correct welding procedure, normally give welds which are to
all intents and purposes invisible after
polishing.
Amount of hydrogen available
POLISHABILITY
Very low
0
Low
Medium
High
5
10
20
Hydrogen concentration in ml/100 g of weld metal.
Fig. 6. Typical quantities of hydrogen available and weld metal
hydrogen contents for different welding processes and electrode types.
Welding of tool steel
The susceptibility of a weld to hydrogen cracking depends on:
• The microstructure of the weld metal
(different microstructures have
different hydrogen sensitivities)
• The hardness of the steel (the greater
the hardness, the higher the susceptibility)
• The stress level
• The amount of diffusible hydrogen
introduced in welding.
MICROSTRUCTURE/HARDNESS
The characteristic microstructures giving
high hardness in the heat-affected zone
and weld metal, i.e. martensite and
bainite, are particularly sensitive to
embrittlement by hydrogen. This
susceptibility is, albeit only marginally,
alleviated by tempering.
STRESS LEVEL
Stresses in welds arise from three
sources:
• Contraction during solidification of
the molten pool
• Temperature differences between
weld, heat-affected zone and base
steel
• Transformation stresses when the
weld and heat-affected zone harden
during cooling.
CONTENT OF DIFFUSIBLE
HYDROGEN
As regards the susceptibility of welds to
cold cracking, this is the factor that it is
easiest to do something about. By adhering to a number of simple precautions, the amount of hydrogen introduced during welding can be reduced
appreciably.
• Always store coated electrodes in a
heated storage cabinet or heated
container once the pack has been
opened (see earlier).
• Contamination on the surfaces of the
joint of the surrounding tool surface,
e.g. oil, rust or paint, is a source of
hydrogen. Hence, the surfaces of the
joint and of the tool in the vicinity of
the joint should be ground to bare
metal immediately prior to starting to
weld.
• If preheating is performed with a
propane burner, it should be remembered that this can cause moisture to
form on the tool surfaces not directly
impinged by the flame.
In general, the stress level in the
vicinity of the weld will reach the magnitude of the yield stress, which for
hardened tool steel is very high indeed.
It is very difficult to do anything about
this but the situation can be improved
somewhat via proper weld design,
(bead location and sequence of runs).
However, no measures to reduce stress
will help if the weld is seriously contaminated by hydrogen.
Heat treatment of a die-casting die after welding.
9
Welding of tool steel
Elevated working
temperature
The basic reason for welding tool steel
at elevated temperature derives from
the high hardenability and therefore
crack sensitivity of tool steel welds and
heat-affected zones. Welding of a cold
tool will cause rapid cooling of the weld
metal and heat-affected zone between
passes with resulting trans-formation to
brittle martensite and risk for cracking.
Cracks formed in the weld could well
propagate through the entire tool if this
is cold. Hence, the mould or die should
during welding be maintained at 50–
100°C (90–180°F) above the Ms-temperature (martensite-start temperature)
for the steel in question; note that,
strictly speaking, the critical temperature is the Ms of the weld metal, which
may not be the same as that of the
base metal.
In some instances, it may be that the
base steel is fully hardened and has
been tempered at a temperature below
the Ms-temperature. Hence, pre-heating
the tool for welding will cause a drop in
hardness. For example, most low-temperature tempered cold-work steels will
have to be pre-heated to a temperature
in excess of the tempering temperature,
which is usually ca. 200°C (400°F). The
hardness drop must be accepted in
order to perform a proper preheating
and mitigate the risk for cracking during welding.
During multi-run welding of a properly pre-heated tool, most of the weld
will remain austenitic under the entire
welding operation and will transform
slowly as the tool cools down. This
ensures a uniform hardness and microstructure over the whole weld in comparison with the situation where each
run transforms to martensite in between passes (quite apart from the risk
for cracking in the latter instance).
It will be clear from this discussion
that the entire welding operation
should be completed while the tool is
hot. Partially welding, letting the tool
cool down and then preheating later on
to finish the job is not to be recommended because there is considerable
risk that the tool will crack.
While it is feasible to pre-heat tools
in a furnace, there is the possibility that
the temperature is uneven (creates
stresses) and that it will drop excessively before welding is completed
(especially if the tool is small).
The best method of preheating and
maintaining the tool at the requisite
temperature during welding is to use an
insulated box with electrical elements in
the walls (see earlier).
Fig. 7 shows the differences in
hardness distribution across welds
which were made on tools preheated in
a furnace and in an insulated box. It is
clear that the tool preheated in a
furnace shows a considerably greater
scatter in hardness than that preheated
in an insulated box.
HV10
600
Fusion line
Weld metal
Parent
metal
(460)
500
400
0
0
1
2
0,1
3
4
5
0,2
6
7
8 mm
0,3 inch
Preheating temperature 350°C (660°F) in furnace
Preheating temperature 350°C (660°F) in insulated box
Fig. 7. Hardness distribution across welds using QRO 90 WELD
where preheating has been performed in a furnace and in an
insulated box.
Preheating in an insulated box.
10
Welding of tool steel
Welding procedure
Even with the very best of equipment
and properly designed consumables,
tool steel can not be welded successfully unless considerable care is exercised in joint preparation, in the actual welding operation, and i performing proper heat treatment after
welding.
JOINT PREPARATION
The importance of careful joint preparation can not be over-emphasized.
Cracks should be ground out so that the
joint slope at an angle of at least 30° to
the vertical. The width of the joint bottom should be at least 1 mm (0.04 inch)
greater than the maximum electrode
diameter which will be used.
Erosion or heat-checking damage on
hot work tools should be ground down
to sound steel.
The tool surfaces in the immediate
vicinity of the intended weld and the
surfaces of the joint itself must all be
ground down to clean metal. Prior to
starting welding, the ground areas
should be checked with penetrant to
make sure all defects have been removed. The tool should be welded immediately joint preparation is finished,
because otherwise there is risk for contamination of the joint surfaces with
dust, dirt or moisture.
Joint preparation
✗ ✗
BUILDING UP THE WELD
First of all, the joint surfaces are clad in
using an appropriate number of runs.
This initial layer should be made with a
small diameter MMA electrode (3,25
mm – 1/8 inch – Ø max.) or via TIG
welding (max. current 120 A).
The second layer is made with the
same electrode diameter and current as
the first in order that the heat-affected
zone is not too extensive. The idea here
is that any hard, brittle microstructures,
which may form in the base-material
heat-affected zone of the first layer, will
be tempered by the heat from the second layer and the propensity to cracking
will thereby be reduced. The remainder
of the joint bode can be welded with a
higher current and larger-diameter
electrodes.
The final runs should be built up well
above the surface of the tool. Even
small welds should comprise a minimum of two runs. Grind off the last
runs.
During welding, the arc should be
short and the beads deposited in distinct runs. The electrode should be angled at 90° to the joint sides so as to
minimize undercut. In addition, the
electrode should be held at an angle of
75–80°C to the direction of forward
movement.
Pass sequence
Wrong!
1. Initial cladding
Right!
2. Second layer
3. Filling up
The arc should be struck in the joint
and not on any tool surfaces which are
not being welded. The sore form striking
the arc is likely location for crack initiation. In order to avoid pores, the starting
sore should be melted up completely at
the beginning of welding. If a restart is
made with a partly-used MMA electrode, the tip should be cleaned free
from slag; this assists striking the arc at
the same time as a potential source of
porosity is eliminated.
In building up edges or corners, both
time and consumables can be saved by
using a piece of copper plate or graphite as support for the weld metal
(Fig. 8). Using such support also means
that the molten pool i hotter which
reduces the risk for pore formation (low
currents need to be used when building
up sharp edges or corners).
Electrode
Workpiece
Space for slag
Copperplate
Fig. 8. A copper plate as support for the weld
when building up corners.
If copper or graphite support is used,
an extra 1,5 mm (0,06 inch) must be
allowed between the support and the
required weld surface because the slag
takes up a certain amount of space
(MMA welding).
For repair or adjustment of expensive
tooling, e.g. plastic mould with a polished or textured cavity, it is essential
that there is good contact between the
return cable and the tool. Poor contact
gives problems with secondary arcing
and the expensive surface can be damaged by arcing sores. Such tools should
be placed on a copper plate which provides for the best possible contact. The
copper plate must be preheated along
with the tool.
11
Welding of tool steel
The completed weld(s) should be
carefully cleaned and inspected prior to
allowing the tool to cool down. Any
defect, such as arcing sores or undercut,
should be dealt with immediately. Before the tool has cooled, the surface of
the weld should be ground down
almost to the level of the surrounding
tool before any further processing.
Moulds where welded areas have to
be polished or photo-etched should
have the final runs made using TIGwelding, which is less likely to give
pores or inclusions in the weld metal.
HEAT TREATMENT AFTER WELDING
Depending on the initial condition of
the tool, the following heat treatments
may be performed following welding:
• Tempering
• Soft annealing, then hardening
+ tempering as usual
• Stress relieving.
Soft annealing
Tools which are welded to accommodate design changes or machining errors during toolmaking, and which are
in soft-annealed condition, will need to
be heat treated after welding. Since the
weld metal will have hardened during
cooling following welding, it is highly
desirable to soft anneal the weld prior
to hardening and tempering of the tool.
The soft annealing cycle used is that
recommended for the base steel. The
welded area can then be machined and
the tool may be finished and heat
treated as usual. However, even if the
tool can be finished by merely grinding
the weld, soft annealing is first recommended in order to mitigate cracking
during heat treatment.
Tempering
Fully-hardened tools which are repair
welded should if possible be tempered
after welding.
Tempering improves the toughness
of the weld metal and is particularly
important when the welded area is
highly stressed in service (e.g. cold work
and hot work tooling).
The tempering temperature should
be chosen that the hardness of weld
metal and base steel are compatible. An
exception to this rule is when the weld
metal exhibits appreciably improved
temper resistance over the base material (e.g. ORVAR SUPREME welded with
QRO 90 WELD); in this case, the weld
should be tempered at the highest possible temperature concomitant with the
base steel retaining its hardness (typically 20°C/40°F under the previous
tempering temperature).
Product brochures for Uddeholm
welding consumables and tool steels
give tempering curves from which the
tempering conditions for welded tools
can be ascertained.
Very small repairs need not be
tempered after welding; however, this
should be done if at all possible.
12
Stress relieving
Stress relieving is sometimes carried out
after welding in order to reduce residual
stresses. For very large or highly-constrained welds, this is an important precaution. If the weld is to be tempered or
soft annealed, then stress relieving is
not normally necessary. However, prehardened tool steel, e.g. IMPAX
SUPREME welded with IMPAX WELD
or IMPAX TIG-WELD, should be stress
relieved after welding since no other
heat treatment is normally performed.
The stress relieving temperature
must be chosen such that neither the
base steel nor the welded area soften
extensively during the operation. If
IMPAX SUPREME is to be machined
after welding, it is absolutely essential
that the mould is stress relieved in order
that adequate dimensional stability is
achieved.
Very small weld repairs or adjustments will normally not require a stress
relieving treatment.
Further information
Information concerning heat treatment
of the tool subsequent to welding can
be obtained from the brochures for the
welding consumable and/or the tool
steel in question.
Welding of tool steel
The following tables give details
concerning weld repair or adjustment of
tooling made from Uddeholm tool steel
grades for hot work, plastic moulding
and cold work applications.
WELD REPAIR OF HOT WORK TOOL STEEL
Uddeholm
tool steel
Condition
Welding
method
Consumables
Preheating
temperature
Hardness
as welded
Heat
treatment
Soft annealed
MMA
(SMAW)
QRO 90 WELD
Min.
325°C (620°F)
50–55 HRC
Soft annealing
ORVAR SUPREME/
ORVAR 2
Microdized
Soft annealed
MMA
(SMAW)
QRO 90 WELD
Min.
325°C (620°F)
50–55 HRC
Soft annealing
QRO 90 SUPREME
Soft annealed
MMA
(SMAW)
QRO 90 WELD
Min.
325°C (620°F)
50–55 HRC
Soft annealing
DIEVAR
Soft annealed
MMA
(SMAW)
QRO 90 WELD
Min
325°C (620°F)
50–55 HRC
Soft annealing
ALVAR 14
Prehardened
MMA
(SMAW)
UTP 73G4
ESAB OK 83.28
225–275°C
(430–520°F)
340–390 HB
340–390 HB
None
Hardened
MMA
(SMAW)
QRO 90 WELD
Min.
325°C (620°F)
50–55 HRC
Tempering
ORVAR SUPREME/
ORVAR 2
Microdized
Hardened
MMA
(SMAW)
QRO 90 WELD
Min.
325°C (620°F)
50–55 HRC
Tempering
QRO 90 SUPREME
Hardened
MMA
(SMAW)
QRO 90 WELD
Min.
325°C (620°F)
50–55 HRC
Tempering
DIEVAR
Hardened
MMA
(SMAW)
QRO 90 WELD
Min
325°C (620°F)
50–55 HRC
Tempering
Uddeholm
tool steel
Condition
Welding
method
Consumables
Preheating
temperature
Hardness
as welded
Heat
treatment
Soft annealed
TIG
(GTAW)
QRO 90 TIG-WELD
Min.
325°C (620°F)
50–55 HRC
Soft annealing
ORVAR SUPREME/
ORVAR 2
Microdized
Soft annealed
TIG
(GTAW)
QRO 90 TIG-WELD
Min.
325°C (620°F)
50–55 HRC
Soft annealing
QRO 90 SUPREME
Soft annealed
TIG
(GTAW)
QRO 90 TIG-WELD
Min.
325°C (620°F)
50–55 HRC
Soft annealing
DIEVAR
Soft annealed
TIG
(GTAW)
QRO 90 TIG-WELD
DIEVAR TIG-WELD
Min
325°C (620°F)
50–55 HRC
Soft annealing
Prehardened
TIG
(GTAW)
UTPA 73G4
ESAB OK
Tigrod 13.22
225–275°C
(430–520°F)
340–390 HB
340–390 HB
None
Hardened
TIG
(GTAW)
QRO 90 TIG-WELD
Min.
325°C (620°F)
50–55 HRC
Tempering
ORVAR SUPREME/
ORVAR 2
Microdized
Hardened
TIG
(GTAW)
QRO 90 TIG-WELD
Min.
325°C (620°F)
50–55 HRC
Tempering
QRO 90 SUPREME
Hardened
TIG
(GTAW)
QRO 90 TIG-WELD
Min.
325°C (620°F)
50–55 HRC
Tempering
DIEVAR
Hardened
TIG
(GTAW)
QRO 90 TIG-WELD
DIEVAR TIG-WELD
Min
325°C (620°F)
50–55 HRC
Tempering
VIDAR SUPREME
VIDAR SUPREME
VIDAR SUPREME
ALVAR 14
VIDAR SUPREME
Remarks
Heat treatment
See product information brochure for
parent steel.
Stress relieve large
repairs.
10–20°C (20–40°F)
below the original
tempering temperature.
Remarks
Heat treatment
See product information brochure for
parent steel.
Stress relieve large
repairs.
10–20°C (20–40°F)
below the original
tempering temperature.
13
Welding of tool steel
WELD REPAIR OF PLASTIC MOULD STEEL
Uddeholm
tool steel
Consumables
Preheating
temperature
STAVAX WELD
200–250°C
(390–480°F)
Hardened
MMA
(SMAW)
STAVAX WELD
200–250°C
(390–480°F)
54–56 HRC
Tempering
Prehardened
MMA
(SMAW)
IMPAX WELD
200–250°C
(390–480°F)
320–350 HB
None
Hardened
MMA
(SMAW)
UTP 73G2
UTP 67S
225–275°C
(430–520°F)
RAMAX S
Prehardened
MMA
(SMAW)
STAVAX WELD
200–250°C
(390–480°F)
HOLDAX
Prehardened
MMA
(SMAW)
IMPAX WELD
150–200°C
(300–390°F)
ELMAX
Hardened
MMA
(SMAW)
Inconel 625 type
UTP 701
250–300°C
(480–570°F)
STAVAX ESR
STAVAX ESR
IMPAX SUPREME
GRANE
Condition
Welding
method
Soft annealed
MMA
(SMAW)
Hardness
as welded
54–56 HRC
Heat
treatment
Soft annealing
Remarks
Heat treatment
See product brochure
for parent steel.
Tempering temp.
200–250°C
(390–480°F)
Stress relieve large
repairs.
Tempering
Tempering temp.
200–250°C
(390–480°F)
54–56 HRC
Tempering
Tempering temp.
590–630°C
(1090–1170°F)
320–350 HB
None
55–58 HRC
280 HB
approx. 56 HRC
(initial plus
finishing layers
respectively)
Stress relieve large
repairs.
Tempering at
200°C (390°F)
Welding of ELMAX
should generally be
avoided, due to the
risk for cracking.
See product brochure
CALMAX
Soft annealed
MMA
(SMAW)
CALMAX/CARMO WELD
200–250°C
(390–480°F)
59–62 HRC
Soft annealing
CALMAX
Hardened
MMA
(SMAW)
CALMAX/CARMO WELD
180–250°C
(360–480°F)
59–62 HRC
Tempering
Contact your local
Uddeholm office.
Uddeholm
tool steel
Condition
Welding
method
Consumables
Preheating
temperature
Hardness
as welded
Heat
treatment
Remarks
Soft annealed
TIG
(GTAW)
STAVAX TIG-WELD
200–250°C
(390–480°F)
Hardened
TIG
(GTAW)
STAVAX TIG-WELD
200–250°C
(390–480°F)
54–56 HRC
Tempering
Prehardened
TIG
(GTAW)
IMPAX TIG-WELD
200–250°C
(390–480°F)
320–350 HB
None
Hardened
TIG
(GTAW)
UTPA 73G2
UTPA 67S
225–275°C
(430–520°F)
RAMAX S
Prehardened
TIG
(GTAW)
STAVAX TIG-WELD
200–250°C
(390–480°F)
HOLDAX
Prehardened
TIG
(GTAW)
IMPAX TIG-WELD
150–200°C
(300–390°F)
Hardened
TIG
(GTAW)
CALMAX
Soft annealed
CALMAX
CORRAX
STAVAX ESR
STAVAX ESR
IMPAX SUPREME
GRANE
ELMAX
CORRAX
14
54–56 HRC
Soft annealing
Heat treatment
See product brochure
for parent steel.
Tempering temp.
200–250°C
(390–480°F)
Stress relieve large
repairs.
Tempering
Tempering temp.
200–250°C
(390–480°F)
54–56 HRC
Tempering
Tempering temp.
590–630°C
(1090–1170°F)
320–350 HB
None
UTPA 701
250–300°C
(480–570°F)
~56 HRC
Tempering at
200°C (390°F)
Welding of ELMAX
should generally be
avoided, due to the
risk for cracking.
TIG
(GTAW)
CALMAX/
CARMO TIG-WELD
200–250°C
(390–480°F)
58–61 HRC
Soft annealing
See product brochure
Hardened
TIG
(GTAW)
CALMAX/
CARMO TIG-WELD
180–250°C
(360–480°F)
58–61 HRC
Tempering
Solution treated
TIG
(GTAW)
CORRAX TIG-WELD
None
30–35 HRC
Ageing
Aged
TIG
(GTAW)
30–35 HRC
Depending
on hardness
CORRAX TIG-WELD
None
55–58 HRC
Stress relieve large
repairs.
Contact your local
Uddeholm office.
See produc brochure
CORRAX TIG-WELD
Welding of tool steel
WELD REPAIR OF COLD WORK TOOL STEEL
Uddeholm
tool steel
Condition
Welding
method
Consumables
Preheating
temperature
Hardness
as welded
ARNE
Hardened
MMA
(SMAW)
AWS E312
200–250°C
(390–480°F)
300 HB
Prehardened
MMA
(SMAW)
FERMO
ESAB OK 84.52
200–250°C
(390–480°F)
UTP 67S
Heat
treatment
Remarks
53–54 HRC
55–58 HRC
Tempering
Initial layers welded with
soft weld metal.
Hardened
MMA
(SMAW)
Castolin 2
200–250°C
(390–480°F)
54–60 HRC
VIKING
Hardened
MMA
(SMAW)
Castolin N 102
200–250°C
(390–480°F)
54–60 HRC
Choose consumable for
finishing layers which
gives suitable hardness.
SVERKER 21
Hardened
MMA
(SMAW)
200–250°C
(390–480°F)
SVERKER 3
Hardened
MMA
(SMAW)
Inconel 625 type
UTP 67S
Castolin 2
Castolin 6
200–250°C
(390–480°F)
280 HB
55–58 HRC
56–60 HRC
59–61 HRC
For FERMO and CARMO,
small repairs
can be made with tool at
ambient temperature.
VANADIS 4
Hardened
MMA
(SMAW)
Inconel 625 type
Castolin 6
200–250°C
(390–480°F)
280 HB
59–61 HRC
AWS E312
UTP 69
Castolin 6
250°C (480°F)
300 HB
60–64 HRC
59–61 HRC
Tempering
Hardened
MMA
(SMAW)
Prehardened
MMA
(SMAW)
CALMAX/CARMO WELD
200–250°C
(390–480°F)
59–62 HRC
Tempering
RIGOR
SLEIPNER
CARMO
MMA
(SMAW)
CALMAX
Tempering
Tempering
See “Weld repair of plastic mould steel”
Note: Consumables with high carbon content are generally not recommended for MMA welding because of the cracking risk
Uddeholm
tool steel
Condition
Welding
method
Consumables
Preheating
temperature
Hardness
as welded
ARNE
Hardened
TIG
(GTAW)
AWS ER 312
200–250°C
(390–480°F)
300 HB
Prehardened
TIG
(GTAW)
FERMO
UTPA 67S
200–250°C
(390–480°F)
UTPA 73G2
Hardened
TIG
(GTAW)
VIKING
Hardened
TIG
(GTAW)
SVERKER 21
Hardened
TIG
(GTAW)
Hardened
TIG
(GTAW)
Inconel 625 type
UTPA 73G2
UTPA 67S
UTPA 696
Castotig 5
Hardened
TIG
(GTAW)
Inconel 625 type
UTPA 73G2
UTPA 696
Castotig 5
Hardened
TIG
(GTAW)
Prehardened
TIG
(GTAW)
RIGOR
SVERKER 3
VANADIS 4
SLEIPNER
CARMO
CALMAX
TIG
(GTAW
Castotig 5
200–250°C
(390–480°F)
Heat
treatment
55–58 HRC
53–56 HRC
Tempering
Initial layers welded with
soft weld metal.
60–64 HRC
Choose consumable for
finishing layers which
gives suitable hardness.
200–250°C
(390–480°F)
200–250°C
(390–480°F)
280 HB
53–56 HRC
55–58 HRC
60–64 HRC
60–64 HRC
200–250°C
(390–480°F)
280 HB
53–56 HRC
60–64 HRC
60–64 HRC
AWS ER 312
UTPA 696
Castotig 5
Tempering
250°C (480°F)
300 HB
60–64 HRC
60–64 HRC
CALMAX/CARMO
TIG-WELD
200–250°C
(390–480°F)
58–61 HRC
Tempering
200–250°C
(390–480°F)
Remarks
Tempering
For FERMO and CARMO,
small repairs can be
made with tool at
ambient temperature.
Castotig 5 should not be
used for more than 4
layers (cracking risk).
Tempering
See “Weld repair of plastic mould steel”
15
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