Steel's ability to absorb hydrogen increases with temperature. Molten steel absorbs more than .0024% hydrogen, and at 2,600^oF, when the steel is austenitic, the hydrogen solubility is about .0001%. When the metallurgical structure is ferrite at 1,600^oF, the solubility of hydrogen falls to about .00025%, and at a normal 70^oF, .0002%. Because weld deposit hydrogen content from standard electrodes runs from .0001 to .002%, there is a significant risk of generating sufficient levels of hydrogen to supersaturate the molten weld from the core wire alone. The operator must reduce the available hydrogen in the coating for quality welds.

When steel is heated above it's critical temperature (the point of temperature where there is a transformation from one metallurgical phase to another phase) and fully austenitic is cooled slowly it converts to a hard brittle martensitic structure. Cooled rapidly enough the austenite will not transform into martensite. The retained austenite now changes very slowly to martensite at temperatures from 400^oF to room temperature. During the delayed transformation, the metal microcracks and fissures. If other stresses are present, cracking becomes aggravated and is easily detected. The defect may appear in the weld, at the weld interface, or in the parent metal, depending on how the hydrogen moves or where it becomes trapped.

Preventing hydrogen embrittlement is critical. Detecting a defect is difficult and frequently found only after the weld is put into service. Like cancer it grows and worsens with time. High strength steels, depending on high carbon content or low martensitic transformation properties, demand close watch for the possibilities of hydrogen absorption during welding. You cannot engineer or design the hydrogen from the weld. Heat drives out moisture, so turn on the heat.

Electrode drying ovens come in sizes holding from 15 to 1,100 lbs. and with temperature controls to 1000^oF. The smaller ovens are portable, making it easy and convenient for the shop or field.

If you suspect that your electrodes are wet, and don't have a makers recommendation, remove the electrodes from the container, heat to 800^oF in a drying oven (see back cover). Baking time depends on the electrode's moisture content.

There is some indication that baking at 1000^oF for 10 minutes is better than 800^oF for 4 hours, however, you are safer with the lower temperature and longer time. When you heat the electrodes to 1000^oF you risk breakdown of the coating which may prove more harmful than the presence of hydrogen.

If your electrodes are wet or were exposed to high moisture for a long period, bake at 800^oF depending on the weld quality needed. For meeting X-ray quality and high strength steel building code requirements, wet electrodes should be discarded.

Flux used for submerged arc welding is another source of hydrogen. Treat flux the same as electrode coatings, especially if high strength steel is to be submerged arc welded. Never reuse dirty or fused flux. If you know the flux contains moisture, heat to 800^oF for one hour, then store in a holding oven at 250^o to 300^oF. It is a good idea to put new flux in a holding oven for storage.

The electrode drying equipment is relatively inexpensive, and quality fabricators and welding operators would never think of leaving their ovens cold.

What Happens to Electrodes* Under Normal Shop Exposure Conditions?

Within two hours at 80% relative humidity, rods may contain up to 13 times the allowable moisture content for U.S. Government & Nuclear Specifications. Within 24 hours, the rods may test up to 26 times the 0.2% allowed. Phoenix DryRod Ovens hold electrodes well within specified limits.

Dry Flux, Too...Flux used for submerged arc welding is another source for hydrogen. It is a good idea to put flux in a holding oven for storage. Treat flux the same as electrode coatings, especially if high strength steel is to be welded.

* Including, to a lesser extent, "moisture resistant" electrodes.