In laying pipe lines, long sections of pipe are joined together at spaced circular joints having a defined cross-sectional profile with an interior portion defining a small gap with a width and height of approximately 1/16 inch which is about 1.5 to 2.0 mm. To join the next section to the pipe line, the gap in the joint is first filled by a molten metal using an electric arc welding process. The joining together of the pipe sections at the gap is achieved by laying a molten bead in the gap. This procedure melts the metal defining the gap and combines it with the melted metal of an advancing electrode, as the electrode is moved circumferentially around the joint. This process is referred to as the root pass. After the root pass or bead is laid to fill the gap of the adjacent pipe sections completely around the circumference of the joint, the rest of the joint is filled by several successive molten metal beads. An important aspect of a pipe welding process is the laying of the root pass or bead by a stick electrode moving circumferentially downwardly from the top to the bottom of the pipe on both sides of the cylindrical pipe sections. A stick electrode developed for the root pass has a length of about 14 inches and is consumed as the root pass progressively joins the two sections of pipe. After about 12 inches of stick electrode has been consumed, the welder must load another stick electrode in the electrode holder, start the power supply and continue progression around the circumference of the pipe joint. When the electrode has been consumed, the time and labor required to start the next electrode is substantial; therefore, it is desirable to weld the two pipe sections together using a minimum number of electrodes. This can be accomplished by a stick electrode which joins the spaced gap between the sections over a greater run out distance for consumption of the single electrode. Thus, a stick electrode having greater run out during root pass welding is desirable. The greater run out of an electrode decreases the number of electrodes used for the root pass welding.
Manufacturers of stick electrodes developed for the root pass welding formulate the electrode and extruded covering on the electrode to maximize the run out distance. Run out is determined by the chemical and physical characteristics of the stick electrode and can be effected by such characteristics as arc force, wetting of the weld bead, surface tension of the weld bead, slag interference to name a few. Manufacturers tend to claim that its stick electrode designed for the root pass welding has a superior run out. However, undocumented claims of high run out are not helpful to a pipe welder when judging the quality and advisability of selecting particular types of stick electrodes for root pass welding available from diverse manufacturers. There is no repeatable procedure to evaluate the run out of a stick electrode for root pass welding so that the run out can be compared to the cost of the electrode for economical selection of a particular stick electrode. This is the dilemma to which the present invention is directed.
USPTO Backgrounds
USPTO Backgrounds