Rod Ovens: What Are They and Do I Need One?

Those proficient at stick welding already possess expertise in temperature management, shielding gas, travel speed and more. You would expect no less from them in terms of equipment and materials prep. Stick welders should carefully maintain everything involved in the welding process. A rod oven is a good example.

What are rod ovens and do I need one? Rod ovens are heating devices that maintain electrodes at temperatures that prevent moisture absorption. They also “repair” compromised electrodes (those exposed to the atmosphere). Yes, you need a rod oven.

If you perform a lot of stick welding, you go through a lot of electrodes. You need a rod oven to protect your stock. If you don’t do a lot of stick welding, your electrodes sit around unused for a long time. You need a rod oven in that case as well.

Why Do I Need a Rod Oven?

In stick welding (SMAW), the most frequently used welding electrodes are coated with flux, which easily absorbs moisture from the air.  This flux coating burns and releases a shielding gas that protects the weld pool from contaminants such as hydrogen, nitrogen, oxygen and others. If these contaminants enter the weld pool they will cause defects such as cracking, sputtering and porosity (worm holes.)

These defects are substantial. They compromise the strength of the weld, cause aberrations in the appearance of the welds and pose a slightly elevated risk to the operator.

When you store rods improperly, you change the flux from a protective agent to one that actually introduces risk to the weld. For example, low-hydrogen 7018 rods work to block hydrogen from the weld pool. But if the rods have been exposed to the atmosphere, they will have absorbed moisture, and releases hydrogen to the weld pool. This moisture contamination is super-heated during the welding process, converts into steam and then bubbles up to the surface. This leaves an open pocket in the finished weld bead.

Therefore, to avoid working against yourself and to avoid producing welds that might not pass inspection, you need to store your electrodes properly in a rod oven.

 

Types of Rod Ovens

Rod ovens come in a range of sizes and heating capacities, based on the workflow and environment. The two basic types of rod ovens are holding ovens and rebake ovens. A holding oven provides moisture-free storage for electrodes and sometimes work metal. Moisture is eliminated from the oven through heat and tight seals.  A rebake oven provides all of the storage capabilities as the holding oven, but has the heating capacity to “rebake” electrodes that have been exposed to the elements for too long.

There are additional types of rod ovens, based on electrode type. Those include:

  • Welding Flux Storage and Rebake Oven. These ovens are the big boys of the rod oven category. They provide rapid heat-up and a no-nonsense environment that pushes moisture out of the picture and keeps it away.
  • Welding Electrode Rebake Oven. As we mentioned earlier, the coating on welding electrodes that help shield against hydrogen can also introduce it to the weld pool if exposed to the atmosphere. You can rehabilitate a compromised electrode by rebaking it in an oven like this.
  • Portable Welding Electrode Oven. You carry this with you in the field, sometimes to transport electrodes that have been rebaked. This is not itself a rebake oven, but more of a storage device. As the name implies, it is portable. This type of oven holds between five and 50 pounds of material.
  • Filler Rod Holding Oven. Consumables in TIG and MIG processes require moisture control as well. This type of oven tends to run larger, in order to hold wire spools used in the MIG welding process.

Using a Rod Oven – Storage

The main thing you don’t do with electrodes is open the seal of their package and then leave it lying around. According to specifications, the electrodes should immediately be transferred to a rod oven for storage once the seal is broken. You should take the term “immediately” at face value, even though you do have a little time before the electrode becomes compromised. Err on the side of caution.

It makes no difference if you store the rods horizontally, as on a shelf, or vertically, as in a small, upright portable oven. Ideally, the electrodes should not be piled on top of one another or scrunched together to the extent that air cannot easily flow around them.

Using a Rod Oven – Rebaking

The manufacturer generally posts rebaking information on the package. The process involves two basic factors – time and temperature. (Just like a cake in the oven!) If your oven has a high heating capacity, you can trim off some of the time. If the heating capacity is less than recommended, you can leave the rods in for a longer period of time, in most cases.

An electrode can be rebaked only once. Some welders will brag about rebaking electrodes multiple times, but they are asking for trouble down the road.

Old Welder’s Tales About Electrode Storage

The Internet ranks as the best source of information ever developed. It also ranks the best source for misinformation ever developed. The following list includes some bits of misleading, understated, overstated and completely false information:

Misleading

Dry storage for electrodes applies only to humid locales and environments. While some locales, such as the deep south and coastal areas tend to be more humid, any location can get humid. While you can get away with open-air storage of electrodes for non-structural applications, you won’t achieve the best possible weld.

The flux on perfectly dry, oven-stored electrodes breaks off too easily during the weld. True, it does break off more readily, but this is what you want. Remember, the decomposition of the flux during the arc is what keeps the hydrogen away from the weld pool.

False

You can tell from visual inspection that an electrode is good to use. Sure, if the flux shows signs of completely falling off the electrode you can assume it can’t be used, but other potential problems are not detectable by visual inspection.

Any sealed container will provide sufficient moisture abatement for electrodes. Everything revolves around the codes for the various products. There is no one-size-fits-all storage solution. Some electrodes, like 6010, tolerate more moisture than 7018, and in fact do not do as well if stored under conditions more suited for 7018. Codes may also vary by application. Military and high-stress structural codes demand greater compliance with moisture tolerances.

IFFY 

If the electrodes ship in a hermetically sealed package, you can reclose the package without compromising the remaining electrodes. In low-stress applications, this might serve as an acceptable practice, but the fact remains that opening the package introduces the contents to the atmosphere.

True, But Do You Really Want to Do This?

You can’t tell by looking at a weld whether the electrode was compromised by moisture. The porosity that occurs with moisture-affected electrodes defies detection by the unaided eye. However, x-ray inspection and destructive testing reveal the issue. If the base metal or weld material exceeds 80,000 PSI yield strength, the moisture could lead to weld cracking and a failed inspection.

Moisture Resistant, Low Hydrogen Electrodes

While they by no means give you an excuse for sloppy electrode storage practices, low-hydrogen electrodes provide a little more forgiveness where moisture is an issue. The deciding factor concerns the type of metal being used. Thick metal or metal that has a tendency to crack make good candidates for low hydrogen electrodes.

When applied to the arc, stick electrodes provide a path for electricity within its metallic core and a shielding gas that releases when the flux burns. The composition of the flux makes it a protector against moisture, but when the electrode is stored improperly, it can actually induce moisture into the weld.

Low-moisture electrodes combat this by providing high-deposition properties. Where porosity is likely, these electrodes produce greater fill material. The weld is therefore tougher, stronger and more apt to pass x-ray inspection.

Identifying Low Hydrogen Electrodes

Some low hydrogen stick electrodes have a “1” suffix in the AWS classification. This simply indicates that the electrode meets the requirements for improved toughness.

Others may have an “R” designation. These electrodes have been physically tested for moisture resistance. Electrodes were removed from their water-tight retail packages and exposed to 80 percent relative humidity at 80 degrees Fahrenheit for nine hours and then tested for moisture. To qualify for the “R” designation, the electrodes must show moisture content less than 0.4 weight percent.

Less prevalent is the optional hydrogen diffusible factor. This designation includes H4, H8 and H16. The “H” and the number that follows indicates the milliliters of diffusible hydrogen per 100 grams of weld material.

Techniques That Combat Moisture

Proper storage of electrodes always gives you a head start against moisture-related problems. Proper welding techniques provide an additional level of security. Remember that the unaided eye cannot see the issues with porosity and cracking, so dedication to the technique becomes a discipline that must be learned and adhered to.

Keep it Close

Make your arcs short and sweet. Long arcs spell trouble for the process by increasing the gap between the electrode and the base metal. The shielding gas becomes thinner and more subject to dispersal by air currents. This in turn causes the consumable to melt prematurely and not create enough slag to fill all the gaps in the weld.

Amp It Right

Setting the correct amperage is crucial at all times, but especially so when working in a moisture-critical environment. Setting the amperage too high causes the flux to burn off too soon and too thoroughly, therefore dissipating the gas shield. Also, don’t set the hot start control too high, as it tends to create too long of an arc, and the problems of premature coating melt arise.

The rule of thumb for setting amperage in a low-hydrogen process is for every quarter-inch of metal thickness (0.25), give 250 amps. Simply convert all fractions to decimals, and multiply by 1,000.

Ease the Electrode Out of The Weld Puddle

In some applications, you want to work fast. This is not one of them. When you scramble eggs, you want a lot of sloshing and churning to add air to the mix, which produces fluffier scrambled eggs. But don’t do that with your weld puddle. You don’t want a fluffy weld.

Slowly pull the electrode out of the weld puddle, maintaining a five to 10 degree angle, with the elevated part in the direction of travel. Too great of an angle will cause a “fingernail” of weld material floating on top of the weld puddle, rather than blended in with it.

When performing the second pass, use either the weave method or stringer pattern, taking care to create a finished bead no larger than 3/4s of an inch.

Plan Your Restarts

The stick electrode will only allow a few inches of weld before it runs out – or comes close. You have to get a new stick and restart, but you don’t want this to be arbitrary, because restarts can be tricky. As the electrode nears its end, many welders try to get the most out of it, and start moving too fast to cover more ground.

This can result in too long of an arc and gaps.

For the best technique, don’t worry about where the weld will end. Worry more about where the next weld will begin. Ideally, start the next weld 1/4 to 1/2 inch above the previous weld and work back to the previous weld. Then, at the point where you started the new weld, move forward over new territory at the same pace and speed.

If you reach a convenient stopping point and the electrode isn’t all used up, disconnect the electrode from the stinger and while it’s still hot, rub it on a hard surface – the welding table, if available. Scratch off just enough coating to expose the core wire. Do not bang the electrode to knock the crusty crud off the tip. It can crack the coating at places other than the tip, and create gaps in the gas coverage.

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