Written by Ed Craig
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STEELS. HIGH CARBON - CHROMINUM,
COLD WORK TOOL STEELS.
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Steels. AISI / SAE D2 / D3 / D4 / D5 / D6 / D7
UNS T3040X - ASTM A681
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Steels. Air or oil hardened. Hardness 54 - 61 HRC (D7 to 66 HRC)
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Steels. Carbon 1.4 - 2.5% / Chrome 11-13.5% / Mo 1% / V 1.4 -4%
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Steels. About 50% machinability of (W) steels annealed.
W steels = 100% machinability.
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Steels. Unmachinable when hardened.
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Steels. Grinding can cause expansion and cracking.
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Steels. None deforming yet highly stressed and low impacts.
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Steels subject to thermal cracking near stress raisers.
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Steels Annealing temperature 1650F
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Steels Hardened in air temp 1850F
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Steels Tempering temp 900F, hold temper minimum
3-4 hrs after welding..
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Steels weld pre-post heat 900F
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Steels Interpass max temp 800F
| D2 |
Germany - Din 1.2379
UK - BD2
Carbon 1.6% max.
Mn 0.6 / Si0.6 / Cr13 / Ni 0.3
Mo1.2 / Co 1 / V 1.1. |
| D3 | France
- Z200 C 12
UK - BD3
Germany - DIN 1.2080
Japan - SKD 1
|
 What is Brittleness?:The
ease at which the weld or metal will break or crack without appreciable deformation.
When a metal gets harder it becomes more brittle. Preheat, inter-pass temp controls
and post heat all are designed to reduce the potential for brittleness.
GENERAL
CONSIDERATIONS FOR WELDING TOOL STEELS:
Ensure
base metals are clean avoid tool marks.
Remove all sharp edges and tight corners in weld areas.
Use
Dye pen to check for surface cracks.
Majority of tool steels will be weld repaired in the Hardened condition
A
hardness test will determine if steel is hard or annealed.
To
weld massive tool parts with large amounts of weld "anneal first"
Steels
in the annealed condition metal can be removed with an oxy acet/fuel torch.
Steels
in the hardened condition use grinding/carbon arc rather than oxy fuel or plasma
to remove metal.
Discoloration
glazing of steel while grinding indicates damage.
Preheating
before grinding or oxy cutting prevents damage.
ALL
TOOL STEELS MUST BE PRE HEATED BEFORE WELDING.
Pre
heat prevents cracking, distortion stresses and shrinking.
Annealed
or hardened steels the steel must be pre heated.
If
base metal hardened yet not tempered anneal temper first.
Preheat
hardened steels don't exceed temper temperature.
Hardened
steels if temper unknown >25mm use 300 to 400F preheat.
Annealed
steels, preheat at maximum pre heat recommendation.
If
steels are quenched and tempered to match tool steel properties, the
electrode
selection and heat treatment recommendations critical.
What is Hardness? The
resistance of the metal or the weld to penetration. Hardness is related to the
strength of the metal. A good way to test the effectiveness of the weld procedure
after the weld and heat treatment is complete, test the hardness of weld and
the base metal surrounding the weld.
With
all tool steels the first weld consideration should be does the weld require the
same hardness as the base.
Is the metal to be welded in the annealed or hardened condition.
Use
lowest possible weld current, (smallest electrode diamaeter)
No
weaves use stringer beads.
Peen
each weld after completion,
Ensure
parts are clean.
Avoid
excess joint restraints.
 What is Ductility? The
amount that a metal or weld will deform without breaking. Measured
on welds by the % of elongation in a 2 inch 51 mm test piece. An E71T-1 flux cored
electrode should result in a minimum of 20% elongation. An E70S--6 MIG weld should
produce approx 22%.
TOOL
STEELS AND SMAW ELECTRODE DATA.
SMAW
Electrodes most versatile weld process for tool steels.
Electrode
3/32 2.5mm amperage 50 to 80 amps DCSP
Electrode
1/8 3.2.5mm amperage 70 to 115 amps DCSP
Electrode
5/32 4mm amperage 100 to 150 amps DCSP
Most
tool and die SMAW electrodes use AC-DC Positive.
Flux
cored good for welds which benefit from high weld depositions.
GTAW,
TIG good for small precise welds.
- Don't
use oxy fuel to weld.
- Ask.
Is the weld for joining or does the weld require a
specific mechanical property
( hardness or machinability)?
- Use
smallest electrodes possible.
- Peen
each weld bead.
- Avoid
arc strikes.
- Consider
run on plates.
- Avoid
craters.
- Try
to use stringers rather than weaves.
- If
possible for the firsts pass (butter pass) consider the E312 electrode except
for water hardened steels.
- For
water hardened steels use E11018 instead of E312 for butter pass.
- When
using E312 use only one layer to avoid shrink cracks.
- If
excessive hardness not required in weld use E312 then an E9018-6 or E11018-
FOR
LARGE COMPONENTS THAT REQUIRE BOTH STRENGTH AND HARDNESS
- First
use E312 followed by E11018-G followed by the tool steel.
- Try
to provide a minimum of 3 layers of tool steel weld to a minimum depth of 3mm.
- If
the repairs are on annealed steels remember the electrode selected must respond
to heat treatment after weld.
- The weld hardness
will depend on the preheat/interpass temperatures plus weld procedures.
- The
weld hardness will depend on the chemistry of the selected electrode along with
the base metal dilution.
- The weld hardness will
depend on the post heat treatment and cooling rate time.
- To
join components, and prevent cracks preheat and deposit ductile electrodes.
- To
prevent cracks, limit carbon pickup in first pass, (use low current narrow stringer
beads) also if possible stress relieve.
- To minimize
the potential for underbead cracks, preheat and limit heat input during the
weld.
- To
prevent underbead cracks provide uniform cooling, with immediate stress relief.
- Fast
heating or concentrated heating can cause cracks.
What is Toughness:
The ability of the metal or weld sample at a predetermined temperature to withstand
a shock.The test for toughness measures the impact of a pendulum
on a notched
specimen. You may see that the required impact properties for the metal or
weld are 20ft-lbf @ -20 F (27 j @ -29C) reheat
at maximum pre heat recommendation.
TOOL
STEELS, PRE HEAT BASICS
M-T-H-D2
Pre heat 900F (482C)
- All other tool
steels preheat at 350F (176C)
- Preheat
"slowly" The higher the alloy content the slower the preheat.
- Preheat,
the more complex the part shape the slower the preheat.
- Preheat.
High alloy steels avoid oxy fuel use ovens or electric.
- Preheat.
Use insulation around part to retain heat.
- Preheat.
Maintain preheat during welds, don't exceed preheat temp.
The
"yield and tensile strength". The
stress that can be applied to a base metal or weld without "permanent deformation"
of the metal. The "tensile strength". The ultimate tensile strength,
the maximum tensile strength that the metal or weld can with stand before "failure
TOOL
STEELS AND PRACTICES TO AVOID CRACKING.
Annealed
steels preheat, for the weld stress relieve, machine harden temper.
Hardened steels, pre heat, weld temper then grind finish.
DECARBURIZATION
= LOSS OF CARBON CAUSES SURFACE SOFTENING.
Coating
surface with Borax prevents decarburization.
TEMPERING FOLLOW AFTER QUENCHING TO REDUCE HARDENING
STRESSES.
High
temper provides more toughness with less hardness.
Tempering
at low end provides max hardness (max wear) with less toughness.
Tempering
above Temper range reduces toughness.
For
large repairs on hardened steels use the electrode temper requirements.
Welding
on hardened steels not tempered cracking will occur.
Brittleness:
The ease at which the weld or metal will break or crack without appreciable deformation.
When a metal gets harder it becomes more brittle. Preheat, inter-pass temp controls
and post heat all are designed to reduce the potential for brittleness.
STRESS
RELIEVING (SR) BASIC GUIDELINES: STRESS
RELIEF - CONTROLLED HEATING & COOLING TO REDUCE STRESS. STRESS
RELIEF MACHINED PARTS FOR DIMENSIONAL STABILITY. STRESS
RELIEF SLOW HEATING AND COOLING REQUIRED CONFIRM
WITH CODE SPECIFICAIONS FOR STRESS RELIEF REQUIREMENTS.
Fatigue:
The ability of a metal or weld to withstand repeated loads. Fatigue failures occur
at stress levels less than the metal or weld yield strength. Some things that
can influence fatigue failure:
FCAW
or SMAW slag inclusions. Lack
of weld penetration. Excess
weld heat, typically from multi-pass welds without inter-pass temp controls. Items
to a part that adds restraint while welding. Items
added to a part that can concentrate stresses in a specific location. Incorrect
selection of filler metal, weld too weak or weld too strong.
| TYPICAL
STRESS RELIEF SOAK TIME
ONE HOUR PER INCH OF THICKNESS | SR
HEAT & COOL RATE PER HOUR 400oF 204oC DIVIDE THICKER PART |
PARTS
OF DIFFERENT THICKNESSES
SR MAX TEMP DIFFERENCE 75oF 24oC | STRESS
RELIEF CARBON STEELS 1100oF 593oC
TO 1250oF 677oC |
STRESS RELIEF
CARBON 0.5% Mo
1100oF 593oC TO 1250oF 677oC | SR
1% CHROME 0.5% Mo
1150oF 621oC TO 1325oF 718oC |
SR 1.25
% CHROME 0.5% Mo
1150oF 621oC TO 1325oF 718oC | SR
2% CHROME 0.5% Mo
1150oF 621oC TO 1325oF 718oC |
SR 2.25
% CHROME 1% Mo
1200oF 649oC TO 1375oF 746oC | SR
5% CHROME 0.5% Mo
1200oF 649oC TO 1375oF 746oC |
SR 7% CHROME
0.5% Mo
1300oF 704oC TO 1400oF 760oC | SR
9% CHROME 1% Mo
1300oF 704oC TO 1400oF 760oC | SR
12% CHROME 410 STEEL
1550oF 843oC TO 1600oF 871oC | SR
16% CHROME 430 STEEL
1400oF 760oC TO 1500oF 815oC |
SR 9% NICKEL
1025oF 552oC TO 1085oF 585oC | FOR
300 SERIES STAINLESS SR WILL
RESULT IN CARBIDE PRECIPITATION |
WITH
LOW CARBON 300 SERIES
MAX SR 1050oF 566oC | SR
400 SERIES CLAD STAINLESS
1100oF 593oC TO 1350oF 732oC |
SR
CLAD MONEL INCONEL Cu NICKEL
1150oF 621oC TO 1200oF 649oC | STRESS
RELIEF MAGNESIUM AZ31B 0
500oF 260oC 15 MIN | STRESS
RELIEF MAGNESIUM AZ31B
H24 300oF 149oC 60 MIN |
HK31A H24 550oF 288oC
30 MIN
HM21A T8-T81 700oF 371oC 30 MIN
|
MAGNESIUM
WITH MORE THAN 1.5%
ALUMINUM STRESS RELIEF | MAGNESIUM
CAST ALLOYS AM100A
500oF 260oC 60 MIN | AZ-63A
81A 91C & 92A
500oF 260oC 60 MIN | |
| | | | |
If
steels are quenched and tempered to match properties electrode
selection and
heat treatment recommendations critical.
HARDNESS
CONVERSION FOR CARBON AND LOW ALLOY STEELS.
1000 psi = ksi x 6.894 = MPa
| Steel
0.15 Carbon Tensile 60- 65 ksi 413 448 MPa
Hardness Br 132 | HRC
43 Br 400 Tensile 201 ksi 1385 MPa
HRC 44 Br 409 Tensile 208 ksi 1434 MPa |
Steel
0.3 Carbon Tensile 85 ksi 568 MPa
Hardness Br 172 | HRC
45 Br 421 Tensile 215 ksi 1482 MPa
HRC 46 Br 432 Tensile 222 ksi 1530 MPa |
Steel
0.5 Carbon Tensile 100 ksi 689 MPa
Hardness Br 219 | HRC
47 Br 443 Tensile 229 ksi 1578 MPa
HRC 48 Br 455 Tensile 237 ksi 1634 MPa |
HRC
20 Br 228 Tensile 111 ksi 765 MPa
HRC 21 Br 233 Tensile 113 ksi 779 MPa | HRC
50 Br 481 Tensile 255 ksi 1758 MPa
HRC 52 Br 512 Tensile 273 ksi 1882 MPa |
HRC
23 Br 243 Tensile 117 ksi 806 MPa
HRC 24 Br 247 Tensile 120 ksi 827 MPa | HRC
54 Br 543 Tensile 292 ksi 2013 MPa
HRC 56 Br 577 Tensile 313 ksi 2158 MPa |
HRC
25 Br 253 Tensile 122 ksi 841 MPa
HRC 26 Br 258 Tensile 125 ksi 861 MPa | HRC
58 Br 615 | HRC
27 Br 264 Tensile 128 ksi 882 MPa
HRC 28 Br 271 Tensile 132 ksi 910 MPa | |
HRC
29 Br 279 Tensile 132 ksi 910 MPa
HRC 30 Br 286 Tensile 138 ksi 951 MPa | |
HRC
31 Br 294 Tensile 142 ksi 979 MPa
HRC 32 Br 301 Tensile 145 ksi 999 MPa | |
HRC
33 Br 311 Tensile 149 ksi 1027 MPa
HRC 34 Br 319 Tensile 153 ksi 1054 MPa | |
HRC
35 Br 327 Tensile 157 ksi 1082 MPa
HRC 36 Br 336 Tensile 162 ksi 1116 MPa |
| HRC
37 Br 344 Tensile 167 ksi 1151 MPa
HRC 38 Br 353 Tensile 171 ksi 1179 MPa | |
HRC
39 Br 362 Tensile 176 ksi 1213 MPa
HRC 40 Br 371 Tensile 181 ksi 1247 MPa | |
HRC
41 Br 381 Tensile 188 ksi 1296 MPa
HRC 42 Br 390 Tensile 194 ksi 1337 MPa | |
DECARBURIZATION
= LOSS OF CARBON CAUSES SURFACE SOFTENING. Coating
surface with Borax prevents decarburization.
ANNEAL
HEAT ABOVE CRITICAL TEMP THEN COOL 50F (10C) PER HR TO TEMPER.
STRESS
RELIEVE BELOW CRITICAL TEMP. TYPICAL 1100-1300F (700C) WITH SLOW COOL.
Don't stress relieve a weld on hardened steel.
TEMPERING
FOLLOW AFTER QUENCHING TO REDUCE HARDENING STRESSES. High
temper provides more toughness with less hardness. Tempering
at low end provides max hardness (max wear) with less toughness. Tempering
above Temper range reduces toughness. With
hardened steel let steel cool to 150F (65c) then temper. For
large repairs on hardened steels use the electrode temper requirements. Welding
on hardened steels not tempered cracking will occur.
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