The rod that creates the metal bead is called the “welding electrode.” Using an electrical current, the welding electrode can be used to make welding metal beads. The welding electrode is made of two different parts, namely:
- The actual metal
- The flux coating
The actual metal out of which the electrode is made can be any of the following: mild steel, stainless steel, cast iron, high-tensile steel, bronze, copper, or aluminum.
The actual metal is enveloped in a coating flux made of a mixture of cellulose. This coating gives the metal rods enough flexibility, hydrogen, and powder. It also comes with a mixture of Titania, Sodium, and Potassium. The purpose of the flux coating is to ensure that the electrical currents evenly flow when you are welding.
Metal Materials of a Welding Rod
Welding rods make use of different alloys made of various metals. There are three commonly used welding rods for joining various steel alloys. These three are the copper-coated mild steel alloy, the 3% nickel steel alloy, and the high carbon steel alloy. Nevertheless, there are myriads of materials used to create steel welding rods. Moreover, there are specific rods designed for specific metal like copper, aluminum, and other types of alloys. Here is a short description of the three most common types of welding rods:
1) Copper-coated Mild Steel Alloy
The copper-coated mild steel alloy is the most popular style of welding rods in the market today. It is commonly used for purposes of welding low carbon, steel, mild, and wrought iron. It may be the most common, but it is the less expensive one. Its copper coatings prevent rusting, and thus it protects the mild steel of the welding rod. This welding rod has a melting point of 2,714°F. Moreover, it does not require flux to weld. The flux, of course, is the substance that prevents oxidation and enhances the strength of the weld.
2) High Carbon Steel Alloy
The welding rod made of high carbon steel alloy is the second most commonly utilized welding rods around the world. This welding rod necessitates the use of flux when you are welding. Flux, of course, is the substance that prevents oxidation. Flux is essential in many welding processes. You can use high carbon steel for repairing and building things. It is also used in some bicycle manufacturing companies for building high carbon steel frames. This rod has a melting point of 2,462 °F.
3) 3% Nickel Steel Alloy
The 3 Percent Nickel Steel Alloy Rod combines carbon and iron in a single rod. This combination, together with a tinge of alloy materials is perfect for increased hardness. These alloy materials may be chromium, molybdenum, or nickel. This welding rod is more often used in welding camshafts, gears, and shafts of automobiles. It needs flux during welding. Moreover, it has a melting point of 2,642°F. This welding rod, of course, is resistant to corrosion and does not need copper coating.
Different Coatings for Welding Rods
The welding electrode’s coatings may have different mixtures of chemicals. These chemicals admixtures may have six to twelve chemicals. These ingredients include the following:
1. Cellulose – is a substance that provides a gaseous shield to the weld. It also comes with a reducing agent that produces the shield that surrounds the arc. The gaseous shield is produced when the cellulose disintegrates.
2. Metal Carbonates – is the ingredient added for adjusting the slag’s basicity and for providing the needed reducing atmosphere.
3. Titanium Dioxide – aids in forming a quick-freezing, highly fluid slag. It also provides the needed ionization for the welding arc.
4. Clays and Gums – aids in increasing the level of elasticity for the plastic coating materials that are extruded. It also aids in providing coating strength.
5. Ferromanganese and Ferrosilicon – aid in deoxidizing of the molten weld metal. It also helps in supplementing the silicon and manganese content of the weld metal that is deposited.
6. Calcium Fluoride – aids in providing shielding gas for protecting the arc. It also helps in adjusting the slag’s basicity as well as providing solubility and fluidity to the metal oxides.
7. Manganese or Iron Oxide – It helps in adjusting the fluidity of the slag. It also adjusts the properties of the slag. Moreover, it aids in stabilizing the arc.
8. Mineral Silicates – aids in providing slag while providing strength for the covering of the electrode. It also helps in alloying metals that include molybdenum, chromium, and nickel. Moreover, it provides to the deposited weld metal its alloy content.
9. Iron Powder – helps in increasing productivity by giving off extra metal for depositing in the metal weld.
Principal Welding Electrode Coating’s Types
There are myriads of types of electrode coatings. Yet, the principal welding electrode coating types used for mild steel include the following:
This electrode type comes with cellulosic material made of wood flour or low alloy electrodes that have been reprocessed. These low alloy electrodes come with 30% paper. Its gas shield carries hydrogen and carbon dioxide as its reducing agents. Moreover, the digging arc that it produces offers deep penetration. Its weld deposit is a bit rough. The spatter, however, has a higher level as compared to other electrodes.
As one of the early types of electrodes, it offers great mechanical properties. It is usually used in welding pipelines, utilizing a welding technique called downhill welding. You can use it with direct current using electrode positive or reverse polarity.
There is a great similarity between the cellulose-sodium and this electrode. This similarity lies in its arc action, penetration, and weld results. However, it contains more sodium. Since sodium aids in the arc’s ionization, it makes the electrode suitable for alternating current. When using electrodes—E6011 and E6010—you can add a bit of iron powder to aid in stabilizing the arc. It will also enhance the rate of deposition.
The higher the titanium dioxide or rutile content of an electrode, the more it is appreciated and liked by welders. The good thing about this type of electrode is that its coating exhibits a quiet arc. It also brings in an easy-to-control slag. Moreover, it exhibits less spatter. Plus, it produces a smoother surface. The penetration is less as compared to the cellulose types. It also offers a deposition rate that is quite high. Its low arc voltage is also likable. Besides, you can use it with direct or alternating current with straight polarity or negative electrode.
This coating is quite like that of the rutile-sodium electrode. Yet, its main difference is it makes use of potassium for providing arc ionization. It is more suited for alternating current. Nevertheless, you can use it with direct current. Its running arc is smooth and quiet.
5) EXXX4—Rutile-iron Powder
Though quite similar to rutile coatings, it distinguishes itself from the former because it contains added iron powder. It is electrode EXX24 if it contains 25% to 40% of iron. But if it has 50% iron, then, it is the EXX24 electrode. You can use the one with the lower iron percentage for all positions, while you can only use the one with the higher percentage in a flat position and horizontal fillet welding purposes. The rate of deposition, of course, increases depending on the iron powder’s amount in the coating.
6) EXXX5—Low Hydrogen-sodium
Its coating contains a high level of calcium fluoride or calcium carbonate. It is referred to as lime ferritic and low hydrogen. It is also referred to as basic type electrodes. This type of electrode coating doesn’t use clays, asbestos, cellulose, and other minerals that combine with water. This is done to ensure that it has the least possible content of hydrogen.
EXXX5 has weld properties that are superior. It also provides the highest level of ductility of deposits. Its medium arc offers moderate penetration likewise. Moreover, it provides a medium deposition rate; yet, you should utilize special welding techniques to best use this electrode. Besides, you should store this electrode in a highly controlled storage. You should also use this type of electrode with electrode positive using direct current.
7) EXXX6—Low Hydrogen-potassium
Similar to that of the low hydrogen-sodium, saved for the fact that it contains potassium instead of sodium, this electrode carries smoother arc action. Its penetration, however, is similar to that of the low hydrogen-sodium. You can use this electrode with both alternating current and direct current. If the coating contains 35% to 40% of iron powder, then, it is grouped as an EXX18.
8) EXX28—Low Hydrogen-iron Powder
This electrode is quite the same with the EXX28, saved for the fact that it has 50% iron powder or more in its coating. You can only use this in a flat position. Its rate of deposition is, of course, higher than that of the EXX18. This low hydrogen type of electrode is used for stainless steel welding and different types of alloys.
9) EXX20—Iron oxide-sodium
This coating type provides high-speed deposition and offers medium penetration. It also exhibits a low level of spatter. Plus, it produces a smooth finish. Moreover, you can use this electrode only when doing horizontal fillet welds or flat-position welding. You can use this electrode with a direct or alternating current.
10) EXX27–Iron-oxide-iron power
This one is almost the same as the iron oxide-sodium. Yet, it has 50% iron or more. With its greater iron powder content, its deposition rate is also increased. You can use this electrode with either direct or alternating current of whatever polarity.
Do Electrode Defects Affect the Welding Results?
As a welder, you will notice that if there are elements that have accidentally combined with the electrode coatings, they may affect the arc stability. Thus, the uniformity and the composition of the coatings are crucial in controlling the arc stability. One example of which is the presence of phosphorus or sulfur in the electrode that may exceed .04%. Such presence will impair the weld because such amount is transferred to the molten metal from the electrode. Phosphorus, for example, produces grain growth and brittleness. Sulfur breaks up the solidity of the weld. This, in turn, causes hot shortness and brittleness likewise.
It is also important to note that electrodes vary in its deposition rate depending on the composition of its coatings. Those with the highest deposition rates, for example, are those electrodes with iron power.
Welding is an art and a science. It is an art when you have perfected the different techniques involved in welding. It is also a science when you study the different ingredients, including the elements and compounds used in welding. The welding rod, of course, is an essential component of a welding machine. Its main ingredients are iron and cellulose. Lastly, the coatings of the electrode are crucial in the determination of the results of welding.
Aside from the abovementioned coating types of electrodes, you will still find other types of electrode coatings that are not included in the abovementioned list. Many of such coatings feature a combination of the abovementioned elements. These other types of coatings are used for specific applications such as welding non-ferrous metals, hard surfacing, and cast-iron welding.