H4R is an optional supplementary designator, as defined in AWS A5.1-91
(Specification for shielded metal arc welding electrodes). Basically, the
number after the "H" tells you the hydrogen level and the "R" means it's
moisture resistant.
"H4" identifies electrodes meeting the requirements of 4ml average
diffusible hydrogen content in 100g of deposited weld metal when tested
in the "as-received" condition.
"R" identifies electrodes passing the absorbed moisture test after exposure
to an environment of 80؛F(26.7؛C) and 80% relative humidity for a period
of not less than 9 hours.
The H4R suffix is basically just additional information printed on the rod,
and does not necessarily mean a change in an electrode previously marked
E7018.
Hydrogen contributes to delayed weld and/or heat affected zone cracking.
Hydrogen combined with high residual stresses and crack-sensitive steel
may result in cracking hours or days after the welding has been completed.
High strength steels, thick sections, and heavily restrained parts are more
susceptible to hydrogen cracking. On these materials, we recommend
using a low hydrogen process and consumable, and following proper
preheat, interpass, and postheat procedures. Also, it is important to keep
the weld joint free of oil, rust, paint, and moisture as they are sources of
hydrogen.
NR-211MP is restricted to welding these maximum plate thicknesses:
Wire diameter Maximum plate thickness
.035"(0.9mm) 5/16"(8mm)
.045"(1.1mm) 5/16"(8mm)
.068"(1.7mm) 1/2"(13mm)
5/64"(2.0mm) 1/2"(13mm)
3/32"(2.4mm) 1/2"(13mm)
For thicker steels, consumables without thickness limitations are
recommended. NR-212 has similar welding characteristics to NR-211MP
without a thickness limitation.
Electrode selection is determined from the base metal chemistries and the
percent weld admixture. The electrode should produce a weld deposit with
a small amount of ferrite (3-5 FN) needed to prevent cracking. When the
chemistries are not known, our Blue Max 2100 electrode, which produces
a high ferrite number, is commonly used.
Cast irons are alloys which typically have over 2% carbon plus 1-3% silicon and are difficult to weld. Electrodes with a high percentage of
nickel are commonly used to repair cast iron. Nickel is very ductile,
making it a good choice to weld on cast iron, which is very brittle. Soft
weld 99Ni and Soft weld 55Ni are the Lincoln Electric electrodes
designed for welding cast iron.
On light chrome-molly tubing, mild steel electrodes are commonly used.
There is enough pickup of alloy from the base material to give the
required tensile strength in the as-welded condition. On multiple pass
welds, Cro-Mo alloy electrodes are usually specified.
Core Ten (A242 & A588) steels are weathering steels commonly used for
outdoor structures. These steels have a higher resistance to atmospheric
corrosion than typical mild steels. Often, welds on these steels are
specified for similar corrosion resistance and color match.
On single pass welds, mild steel electrodes are commonly used. There is
usually enough pickup from the base metal to obtain a good color match.
On multiple pass welds, low-alloy electrodes are commonly used to obtain
a good color match and similar corrosion resistance. The electrodes
commonly specified include those with the suffixes -B1, -B2, -C1, -C2,
and -C3.
AR400 is a quench and tempered steel and may be difficult to weld due its
high strength and hardenability. The base steel around the weld rapidly
heats and cools during welding, resulting in a heat affected zone (HAZ)
with high hardness. Any hydrogen in the weld metal may diffuse into
HAZ and may cause hydrogen embrittlement, resulting in delayed
underbead or toe cracks outside of the weld. To minimize heat affected
zone cracking:
1. Use a low hydrogen consumable with an -H4 or -H2
designation.
2. Preheat to slow the cooling rate. Note that excessive
preheat may anneal the base material.
3. Slow cool. More time at elevated temperatures allows the
dissolved hydrogen to escape.
4. Peen the weld beads to minimize residual weld stresses.
5. Use the lowest strength filler metal meeting design
requirements. If making fillet welds, the weld can be oversized to
give the specified strength
6. Minimize weld restraint.
Steel should be cleaned of any oil, grease, paint, and rust before using any
arc welding process. However, if complete cleaning cannot be performed,
consumables that form a slag, have deeper penetration, are slower
freezing, or have higher Silicon and Manganese are recommended for
dirty steels. These consumables include:
SMAW: Fleetweld 5P+
GMAW: L-56, MC-710
FCAW-GS: Outershield 75
FCAW-SS: Innershield NR-311
SAW: 761, 780 fluxes
AWS D5.20-95 FCAW Specification states that E70T-4 and E70T-7 fluxcored
wires are designed with a slag system to produce welds very low in
sulfur and resistant to hot cracking. Corresponding Lincoln products are
Innershield NS-3M and NR-311 self-shielded flux-cored wires. Also our
E70T-5, Outershield 75-H gas-shielded flux-cored wire is also a better
choice for welding on high sulfur steels.
T-1 is a quenched and tempered steel. Welding quenched & tempered
steels may be difficult due its high strength and hardenability. The base
steel around the weld is rapidly being heated and cooled during welding,
resulting in a heat affected zone (HAZ) with high hardness. Hydrogen in
the weld metal may diffuse into HAZ and cause hydrogen embrittlement,
resulting in delayed underbead or toe cracking outside of the weld. To
minimize heat affected zone cracking:
1. Use a low hydrogen consumable, like a -H4 or -H2.
2. Preheat. This slows the cooling rate. Note that excessive
preheat may anneal the base material.
3. Slow cool. More time at elevated temperatures allows the
dissolved hydrogen to escape.
4. Peen the weld beads to minimize residual weld stresses.
5. Use the lowest strength filler metal meeting design
requirements. If making fillet welds, the weld can be oversized to
give the specified strength
6. Minimize weld restraint.
The test results on our Certificate of Conformance were obtained from
welding an AWS filler metal test plate. Any change in welding procedure
will affect Charpy impact values. Below are common practices for
welding test plates when Charpy impact specimens are required:
1. Controlled heat input
2. Controlled preheat and interpass temperature
3. Even number of passes per layer
4. Build-up cap pass to maximum allowed in specification
The fast freezing rutile slag on an E71T-1 Outershield wire gives it
excellent out-of-position characteristics, but can also trap gases under the
slag as the weld solidifies, resulting in gas marks. Gas marks are more
commonly observed welding at high procedures under a high Argon blend
shielding gas. Gas marking and/or can be minimized by:
1. Switching to 100% CO2 shielding gas
2. Lowering the welding procedure
3. Cleaning the weld joint of paint, rust, and moisture
4. Minimize any wind disturbance
5. Cleaning spatter from inside gas nozzle
6. Increasing the shielding gas flow rate
First, make sure the steel is clean. Vaporization of contaminants on the
base metal such as moisture, rust, oil, and paint may cause porosity.
Second, this can be commonly caused by excessive voltage or too short a
stickout (the length of wire from the end of the contact tip to the
workpiece). Make sure these are within our recommended parameters.
Also, reducing the travel speed also helps minimize porosity.
Our flux-cored wires are designed to operate on constant voltage (CV) DC
machines. If used on a constant current (CC) machine, any small changes
in electrical stickout(length of the wire from the end of the contact tip to
workpiece) will produce large voltage fluctuations, resulting in stubbing
and porosity. Therefore, using flux-cored wires on CC is not
recommended.
Preheating the steel to be welded slows the cooling rate in the weld area.
This may be necessary to avoid cracking of the weld metal or heat affected
zone. The need for preheat increases with steel thickness, weld restraint,
the carbon/alloy content of the steel, and the diffusible hydrogen of the
weld metal. Preheat is commonly applied with fuel gas torches or
electrical resistance heaters.
AWS D1.1 Structural Steel Welding Code, Section 5.6 states: Preheat and
all subsequent minimum interpass temperatures shall be maintained during
the welding operation for a distance at least equal to the thickness of the
thickest welded part, but not less than 3 in. [75mm] in all directions from
the point of welding.
In general, when preheat is specified, the entire part should be thoroughly
heated so the minimum temperature found anywhere on that part will meet
or exceed the specified preheat temperature.
Interpass temperature refers to the temperature of the steel just prior to the
depositing of an additional weld pass. It is identical to preheat, except that
preheating is performed prior to any welding.
When a minimum interpass temperature is specified, welding should not
be performed when the base plate is below this temperature. The steel
must be heated back up before welding continues.
A maximum interpass temperature may be specified to prevent
deterioration of the weld metal and heat affected zone properties. In this
case, the steel must be below this temperature before welding continues.
All low-hydrogen consumables must be dry to perform properly.
Unopened Lincoln hermetically sealed containers provide excellent
protection in good storage conditions. Once cans are opened, they should
be stored in a cabinet at 250؛300-؛F (121؛149-؛C).
When the electrodes are exposed to the air, they will pickup moisture and
should be redried. Electrodes exposed to the air for less than 1 week with
no direct contact with water should be redried as follows:
E7018: 1 hour at 650؛750-؛F
E8018, E9018, E10018, E11018: 1 hour at 700؛800-؛F
If the electrodes come in direct contact with water or have been exposed to
high humidity, they should be predried for 1-2 hours at 180؛220-؛F first
before following the above redrying procedure.
Standard EXX18 electrodes should be supplied to welders twice per shift.
Low hydrogen electrodes with the suffix "MR" have a moisture resistant
coating and may be left out up to 9 hours or as specified by code
requirements.
