• The E7018 welding rods I've been buying are now marked E7018 H4R. What does the H4R mean? Are these rods different than the E7018 rods I've used before? 
• Why is hydrogen a concern in welding?
• What is the maximum plate thickness which can be welded with Innershield® NR®-211-MP (E71T-11) wire? 
• What electrode can I use to join mild steel to stainless steel?
• What consumable should be used to weld cast iron?
• What consumable can be used to weld on SAE 4130 steel tubing?
• What consumable should be used for weathering steel? 
• What are you recommendations for welding AR400 plate? 
• What consumables are better for welding over rusty, dirty steel? 
• What flux-cored wires are better for welding on high sulfur steel? 
• What precautions should I take when welding T-1 steels? 
• Why are the Charpy impact values from my test welds lower than that printed on your Certificate of Conformance? 
• I'm using Outershield® 71M (E71T-1) flux-cored wire with 75Ar/25CO2. Why am I getting gas marks on the weld surface? 
• I'm welding with an Innershield FCAW-SS wire and occasionally get porosity. How can I eliminate this? 
• Can I use flux-cored wires (FCAW-GS or FCAW-SS) on a constant current (CC) stick welding power source? 
• Why is preheat sometimes required before welding? 
• How should preheat be measured? 
• What is interpass temperature?
• Do I need an oven to store low hydrogen electrodes?

1. The E7018 welding rods I've been buying are now marked E7018 H4R. What does the H4R mean? Are these rods different than the E7018 rods I've used before?

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 80ºF(26.7ºC) 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.

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2. Why is hydrogen a concern in welding?

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.

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3. What is the maximum plate thickness which can be welded with Innershield® NR®-211-MP (E71T-11) wire?

NR®-211-MP is restricted to welding these maximum plate thicknesses:

For thicker steels, look to Innershield® NR-212. It has similar welding characteristics to NR®-211-MP but is designed for use on materials up to 3/4" (19.1mm) thick.

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4. What electrode can I use to join mild steel to stainless steel?

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.

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5. What consumable should be used to weld cast iron?

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. Softweld® 99Ni and Softweld® 55Ni are the Lincoln Electric® electrodes designed for welding cast iron.

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6. What consumable can be used to weld on SAE 4130 steel tubing?

On light chrome-moly 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.

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7. What consumable should be used for weathering steel?

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 -C1, -C2, and -C3.

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8. What are you recommendations for welding AR400 plate?

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.
   

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9. What consumables are better for welding over rusty, dirty steel?

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: SuperArc® L-56
FCAW-GS: Outershield® 75
FCAW-SS: Innershield® NR-311
SAW: Lincolnweld® 761 and 780 fluxes

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10. What flux-cored wires are better for welding on high sulfur steel?

AWS D5.20-95 FCAW Specification states that E70T-4 and E70T-7 flux-cored 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.

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11. What precautions should I take when welding T-1 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.

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12. Why are the Charpy impact values from my test welds lower than that printed on your Certificate of Conformance?

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

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13. I'm using Outershield® 71M (E71T-1) flux-cored wire with 75Ar/25CO₂. Why am I getting gas marks on the weld surface?

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

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15. I'm welding with an Innershield FCAW-SS wire and occasionally get porosity. How can I eliminate this?

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.

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16. Can I use flux-cored wires (FCAW-GS or FCAW-SS) on a constant current (CC) stick welding power source?

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.

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17. Why is preheat sometimes required before welding?

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.

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18. How should preheat be measured?

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.

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19. What is interpass 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.

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20. Do I need an oven to store low hydrogen electrodes?

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 250º-300ºF (121º-149ºC).

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 650º-750ºF
E8018, E9018, E10018, E11018:	1 hour at 700º-800ºF

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 180º-220ºF 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.

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