What are Stick Electrodes?
(also known as welding electrodes, welding rods, weld rods)
Welding electrodes are metal wires with baked on chemical coatings. The rod is used to sustain the welding arc and to provide the filler metal required for the joint to be welded. The coating protects the metal from damage, stabilizes the arc, and improves the weld. The diameter of the wire, less the coating, determines the size of the welding rod. This is expressed in fractions of an inch such as 3/32", 1/8", or 5/32." The smaller the diameter means it requires less current and it deposits a smaller amount of filler metal.
The type of base metal being welded, the welding process and machine, and other conditions determines the type of welding electrode used. For example, low carbon or "mild steel" requires a mild steel welding rod. Welding cast iron, aluminum or brass requires different welding rods and equipment.
The flux coating on the electrodes determines how it will act during the actual welding process. Some of the coating burns and the burnt flux forms smoke and acts as a shield around the welding "pool," to protect it from that air around it. Part of the flux melts and mixes with the wire and then floats the impurities to the surface. These impurities are known as "slag." A finished weld would be brittle and weak if not for the flux. When the welded joint is cooled, the slag can be removed. A chipping hammer and wire brush are used to clean and examine the weld.
The metal-arc welding electrodes may be grouped as bare electrodes, light coated electrodes, and shielded arc or heavy coated electrodes. The type used depends on the specific properties required that include: corrosion resistance, ductility, high tensile strength, the type of base metal to be welded; and the position of the weld that is flat, horizontal, vertical, or overhead.
The American Welding Society's (AWS) classification number series has been adopted by the welding industry. The electrode identification example below is for a steel arc-welding rod labeled E6010:
- "E" indicates "electrode" for electric arc welding
- The first two (or three in some cases) digits (60) indicate tensile strength in thousands of pounds per square inch
- The third (or fourth in some cases) digit (1) indicates the position of the weld. An "O" indicates that this classification is not used; "1" is for all positions; "2" is for flat and horizontal positions only; 3 is for flat position only
- The last two digits together (10) indicate the type of coating and the type of power supply required, 10 organic coating and DC current with reverse polarity.
- Therefore, a welding rod numbered E6010 indicates "E" an manual arc-welding electrode with (60) a minimum strength of 60,000 psi., that can be used (1) in all positions and (10) DC reverse polarity is required.
Welding Rods and the Damaging Effects of Moisture
Welding electrodes must be kept dry. Moisture destroys the desirable characteristics of the coating and may cause excessive spattering and lead to the formation of cracks and weakness in the welded area. Electrodes exposed to humid air for more than a few hours should be preheated before use and when in doubt as to how long they were exposed they should be re-dried by heating in a suitable oven. After they have dried, they should be stored in a holding oven or moisture proof container.
Low-hydrogen welding rods are the backbone of structural welding. Known as "low-hy" to welders in the field, this versatile electrode is manufactured to contain less than 0.6% of moisture in the covering and is required by currently acceptable welding standards and procedures to be stored in an environment that maintains factory quality dryness. Its low hydrogen content ensures a smooth, strong weld that is very ductile, making it the welding rod of choice for structural welding jobs.
Low hydrogen 7018 particularly does not tolerate moisture and must be kept dry before use. If not, when welding it will allow for pitting and porosity (worm holes) which are weld defects. This happens when moisture gets in the flux coating and allows hydrogen to adversely affect the weld pool. 7018 rods that haven't been dried properly may make a good looking weld at first but they will be subject to longitudinal cracking either right after welding, or later on. Longitudinal cracking is where a crack starts and follows the length of the weld.
It is well known that prior to beginning a structural welding job that low-hydrogen electrodes must be conditioned properly to avoid damaging defects in the welds. One of the ways utilized to protect the low-hydrogen coating is to double coat using a titania layer to help avoid defects when low hydrogen deposits are required. But problems such as porosity, hydrogen embrittlement, lack of fusion and cracking can result if standard low hydrogen rods are not stored according to the manufacturer's specifications.
Specifically, hydrogen can adversely affect a weld and some steels under a variety of conditions. The primary source for the presence of hydrogen is moisture in the electrode coating picked up through exposure to the atmosphere. For this reason with any welding job proper storage, handling and treatment of low hydrogen electrodes is critical to prevent a defective weld. This is especially important in the construction and erection of multiple story buildings which rely for their support and inner structure on welded steel beams.
A defective weld can result in the collapse of a building or during subsequent inspection rejection of the weld. This requires rebuilding a portion of the metal inner structure of a skyscraper or other building sometimes at a cost of many millions of dollars.
Welding electrodes are manufactured to be within acceptable moisture limits consistent with the type of covering and strength of the weld metal to be used with the electrode. They are then packaged in a container which has been designed to provide the degree of moisture protection considered necessary by the industry for the type of covering involved. A common mistake is opening the container from the wrong end, or tossing them around which can crack the low hydrogen coating on the welding rods rendering them useless.
With any welding job It is very important to maintain your rods or electrodes within a temperature range of 100°F and 300°F. This temperature range has been determined by the welding industry to be adequate to prevent atmospheric moisture from entering the welding rod coating and subsequently entering the weld during the welding process.
In particular, maintaining low-hydrogen electrodes in a dry, consistently heated environment is a must. Ask any welding professional and they will recommend that low-hydrogen electrodes be stored in a rod oven. Any other rudimentary method such as utilizing an old refrigerator or microwave with a 100 watt light bulb is laughable and is in no way acceptable for today's welding professional.
Stick Welding Process Intro
SMAW (Shielded Metal Arc Welding) is often called stick welding. It is one of the most popular welding processes used today. Its popularity is due to the versatility of the process and the simplicity and low cost of the equipment and operation. SMAW is commonly used with such materials as mild steel, cast iron, and stainless steel.
How Stick Welding Works
Stick welding is a manual arc welding process. It requires a consumable electrode that is coated in flux to lay the weld, and an electric current is used to create an electric arc between the electrode and the metals that are being welded together. The electric current may be either an alternating current or a direct current from a welding power supply.
While the weld is being laid, the electrode’s flux coating disintegrates. This produces vapors that provide a shielding gas and a layer of slag. Both the gas and slag protect the weld pool from atmospheric contamination. The flux also serves to add scavengers, deoxidizers, and alloying elements to the weld metal.
You can find flux-coated electrodes in a variety of diameters and lengths. Typically, when choosing an electrode, you want to match the electrode properties to the base materials. Flux-coated electrode types include bronze, aluminum bronze, mild steel, stainless steel, and nickel.
Common Uses of Stick Welding
SMAW is so popular throughout the world that it dominates other welding processes in the repair and maintenance industry. It also continues to be widely used in industrial fabrication and the construction of steel structures, although flux-cored arc welding is gaining in popularity in these areas.
Other Traits of Stick Welding
Other characteristics of Shielded Metal Arc Welding include:
- It provides all position flexibility
- It is not very sensitive to wind and drafts
- The quality and appearance of the weld vary according to the skill of the operator
- It is usually capable of producing four types of welded joints: the butt joint, lap joint, T-joint, and fillet weld
Selecting the Right Electrode for Basic Stick Welding
It really isn’t difficult to select the right electrode for basic stick welding. In fact, electrode selection is pretty straight forward, if you just remember a few facts about the rods.
Facts to remember include:
- When choosing an electrode for use with basic stick welding equipment, take into consideration the type of welding job to be done and the material to be welded. Typically, but not always, you’ll want to use an electrode that has a core composition similar to or identical to the base material.*
- There are three different groups of electrodes used in stick welding – “fast-fill” electrodes are designed to melt quickly so the welding speed can be maximized; “fast-freeze” electrodes are made to solidify quickly for welding in all positions without the weld pool shifting significantly before it solidifies; “fill-freeze” or “fast-follow” electrodes are intermediate rods.
- Know what the electrode numbers represent. The first two or three numbers indicate what the tensile strength of a weld will be. For instance, if the rod number is 6011, there will be a minimum of 60,000 pounds of tensile strength per square inch of weld. If the number begins with 70 (i.e. 7018), the tensile strength per square inch of weld will be a minimum of 70,000 pounds.
- The last two digits of the rod number refer to the flux on the rod. The higher the number, the higher the shielding and the more flux or metal is deposited.
- A 6011 electrode is good for general maintenance. When repairing steel machinery, this particular rod will be sufficient. The 6011 electrode can be used in all welding positions, works well on dirtier metals, and can tolerate a joint that is less than perfect.
Commonly used rods for welding steel include:
- 6010 and 6011 rods – work great on dirtier metals, penetrate deeply , and work well in all positions
- 6013 – works well in all positions; doesn’t work as well on dirtier metals; penetrates only mildly
- 7018 – mild penetration; will work in any position; best used on clean metals
- 7024 – mild penetration; works best in a flat position and on clean metals
*Note: Although generally the composition of the electrode core is similar to or identical to the base material, this is not always the case. Keep in mind that even a slight difference in alloy composition can greatly affect the properties of the weld. Nevertheless, sometimes, using an electrode with a core composition that is significantly different from the base metal is desirable.
Stick Welding Techniques
Shielded metal arc welding (SMAW) is a versatile welding process that can be performed in any position. Welding in the flat position is always preferable. However, some projects, such as machine repair, require welding in a vertical, horizontal, or overhead position.
There are a couple of techniques that may be used for striking the arc, and there are several techniques that may be used for depositing the weld metal. Although a welder may develop a preference for a certain technique, the technique used may depend upon the particular job to be done.
Striking the Arc
There are two basic methods for striking the arc in stick welding. The first method is called the “scratching technique.” This method is similar to striking a match. The striking end of the electrode is dragged across the worksite to get the arc going. Once contact is made, the electrode is withdrawn to prevent it from being welded to the work piece. If, by chance, the electrode does weld itself to the work, a quick twist of the wrist can free the rod.
A second method for striking the arc is called the “tapping method.” When using this technique, the electrode is brought straight down to make contact with the work piece. Then the electrode is immediately pulled away from the work to a point where the arc has reached the desired length.
It takes practice to accurately determine the proper arc length. The proper arc length depends upon the electrode used. The arc should be kept as short as possible while the edge of the electrode scrapes the work piece with each movement. An easy guide for determining proper arc length is to listen to the sound of the arc. When it is at the proper length, there will be a sharp, crackling sound. The appearance of the deposited weld bead is another indication of whether the arc length is accurate.
Welding techniques may vary with the particular electrode used as well as the welding job to be done. The type of metal to be welded and the welding position may help determine which welding technique will be used.
Common welding methods used with an E6011 electrode include:
- Circular pattern created by moving the electrode in a circular motion.
- Whipping pattern achieved by moving the rod in a back and forth motion.
- Weaving pattern for wider welds created by using a side to side motion.
When using low-hydrogen electrodes, circular motions work well. You can also just hold the rod steady and let it fill the gap. Because low-hydrogen electrodes are high in flux, a whipping motion could cause the flux to get trapped in the weld, creating a problem called slag inclusion. So, avoid using the whipping motion with this type of rod.
When welding thinner metals, a whipping motion is desirable, because this motion prevents the electrode from burning a hole in the metal. A circular or whipping motion works well when working with slightly thick metals. The weaving pattern is preferable for working with thick metals.
Practice, Practice, Practice
Developing welding skills takes practice. It is important to practice striking the arc, holding the arc, and depositing the weld metal. Most likely, the first few tries will fall quite short of the desired results. However, the more you practice your techniques, the easier they will become, and the better your results should be.
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