Stick electrodes are tool that are used in the process of shielded metal arc welding. In order to make a choice as to which stick electrode to use in a particular welding job, it is necesary to understand the markings that is present on the stick electrode. Each stick electrode has a classification system that is printed on the stick electrode itself, and these markings will tell you about the behavior of that stick electrode, the metal that it can join, and the type of power source that are required for its use.
Thus, by understanding these markings, a welder can make a decision as to which stick electrode to use on the metal that is to be joined in that job. The classification system for stick electrodes begin with the letter E, which indicates that the stick electrode is a product that is used for shielded metal arc welding. Following that letter are two digits that indicate the minimum tensile strength of the weld that is created with that stick electrode; a 60 stick electrode will create welds with 60,000 pounds per square inch of tensile strength, for instance, while a 70 stick electrode will create welds with 70,000 pounds per square inch of tensile strength.
How to Choose and Use Stick Electrodes
Following those two digits are three digits that describe the position in which the stick electrode can be used. The final digit describe the chemistry of the coating that surrounds the metal rods within the stick electrode, as well as the types of welding currents that it accepts. Thus, these four digit allow welders to make certain that the stick electrode that they purchase is compatible with the metal that is to be joined.
The coating that surrounds the metal rods within the stick electrode will change the behavior of the arc that is created by the stick electrode. Stick electrodes that contains cellulosic coating materials will create arcs that penetrate deeply into the metal being welded. Rutile stick electrodes create a softer arc that is more stable than cellulosic stick electrode arcs, and often require less skill to operate.
Low-hydrogen stick electrodes are utilized for joining thick metals together, as they are less likely to crack during the welding process. Additionally, the stick electrode coating will determine whether the stick electrode requires the use of alternating current (AC) or direct current (DC). The polarity of the stick electrode will determine where the heat of the arc is concentrated.
When the stick electrode is connected to the positive terminal, two-thirds of the heat of the arc will land on the tip of the stick electrode. If the polarity is reverse, however, most of the heat will land on the base metal that is being welded, and less heat will be concentrated on the stick electrodes tip. Additionally, using alternating current will split the heat between the tip and base metal of the stick electrode, and can help eliminate the problem of arc blow when welding large metal assemblies.
The correct polarity must be chose for a stick electrode; otherwise, weld defects can be created. The diameter of the stick electrode will affect the rate at which metal is deposited into the joint that is being welded, as well as the amount of heat that is created during welding with that stick electrode. Stick electrodes with larger diameter will deposit more metal into the joint than smaller stick electrodes, but they will also require higher amperages to heat the metal to the welding temperature.
Using a stick electrode that is too large for thin metal will cause the thin metal to burn through, but using a stick electrode with too small of a diameter will make it difficult to fuse the metals together when welding thick metal plates. A rough estimate of the amperage that should be utilized is using one amp for every thousandth of an inch of diameter of the stick electrode. Additionally, the amperage will have to be adjusted according to the welding position; vertical or overhead welding requires lower amperage then flat welding.
The way in which stick electrodes must be stored will also depend upon the type of stick electrode that is being utilized. Low-hydrogen stick electrodes will absorb moisture from the air. Moisture in low-hydrogen stick electrodes will reduce its resistance to cracking.
Thus, low-hydrogen stick electrodes should be stored in a heated oven after the packaging is open. Cellulosic stick electrodes require a small amount of moisture to function properly, thus they should never be stored in a heated oven. Finally, stainless steel stick electrodes also react to moisture.
Moisture can produce porosity within stainless steel stick electrodes, which will reduce its corrosion resistance. In addition to selecting the correct stick electrode and understanding how to use it properly, some welding techniques is required to create sound welds with those stick electrodes. First, the length of the arc that is created between the stick electrode and the metal should be approximately the same diameter as the stick electrode.
An arc that is too long will allow the welding metal to oxidize, and one that is too short will cause the stick electrode to drag against the metal. Second, the welder should control the angle at which the stick electrode enter the metal, as well as the rate at which the stick electrode moves along the metal to be welded. The travel angle and speed will alter the shape of the weld and the depth of the penetration of the stick electrode into the metal.
Finally, slag must be removed from between weld passes, as well as a crater created at the end of each pass must be filled with metal deposited from the stick electrode; otherwise, cracks may form at those area of the weld.
