Nextweld: The Future of WeldingDavid Koutz, The Lincoln Electric Co.
This evening we will discuss several of the electric welding processes, and then look at how the Nextweld program of Lincoln Electric has made vast improvements to many of the techniques.
Probably the best know form of electric welding is SMAW (Shielded Metal Arc Welding). In this process a rod of consumable weld metal is coated with flux. As melting occurs the flux protects the metal from the atmosphere by deoxidizing and forming a protective gas. The method is usually done with a robust constant current power source. Advantages of SMAW are low cost, portability, and it works in all positions.
A method which has the highest deposition rate is SAW (Submerged Arc Welding. Continuous wire consumable electrode metal is protected when melted by external shielding flux. Electrode size up to .125" is possibly with this method. A limitation is the dependency on gravity to hold flux (thus weld positions are restricted). Up to 1500 amps of current has been used in highest deposition applications of this welding method.
GTAW (Gas Tungsten Arc Welding) [also called TIG]. This is a welding method which emphasized control. Constant current DC is the most common power source. The method used a non-consumable tungsten alloy electrode and an external shielding gas of Argon, Helium or a mix. Welding rod can be used for filler metal but is not always necessary. The method is excellent for thin metal welding and has not sparks or crackle associated with the welding. Grinding for post weld clean-up can be eliminated. Disadvantages of GTAW are the fact that it is very slow with low deposition rate. It is not portable due to bottled gas requirements, and it requires very clean bas metal surfaces. Control of the process can be enhanced by using polarity to control penetration. Higher positive polarity accomplishes more cleaning while higher negative polarity produces deeper penetration. Later we will see how new waveform control electronics takes advantage of this principle.
GMAW (Gas Metal Arc Welding) is also known as "MIG". It is very useful for high productivity production as the consumable electrode comes in long wire coils permitting long runs. In this respect is it similar to SAW. Since the wire is transformed to droplets which must fall into the weldment, it is a gravity sensitive process and not useful for all positions. There are many forms of metal transfer associated with GMAW welding.
A newer process similar to GMAW is Pulsed Spray. This process allows deposition at many angles including fully inverted.
Nextweld is a term used by Lincoln Electric to include many of the "next generation" developments and improvements to the electric welding process. Many of these are in the form of waveform control technology which allows much better control of the welding process. Another Nextweld development is in the Ethernet or wireless communications being integrated into welder power sources to provide realtime monitoring and statistics about weld production to a desktop of supervisory station.
In the area of waveform control one method is Surface Tension Transfer (STT). This prevents weld spatter. It is particularly suited for the GMAW root welds on pipe where lack of penetration and poor sidewall fusion are eliminated. Initially a uniform molten ball is produced in the electrode tip which is allowed to short out to the puddle. Current is monetarily reduced to allow this ball to wet into the puddle. Next a precision ramped pinch current is applied which constricts the remaining contact with the electrode. Electronics detect this constriction and cut back current just before breakoff, eliminating spatter. A low current level is then used to reestablish the arc followed by peak current which is tailed down to form the next ball.
Another waveform control for GMAW is called Pulse-on-Pulse. This is particularly suited to aluminum and even very thin aluminum welding. The waveform is controlled to oscillate between high and low energy pulses. The high energy pulse promotes longer arc and cleaning of the aluminum. The low energy pulse allows the weld puddle to cool and promotes good penetration. In recent years virtually all production electric aluminum welding has gone to pulse-on-pulse because of the obstacles it overcomes.
A waveform control innovation for SAW is called "AC/DC". With AC/DC the current can be controlled as to for a specific duration of positive current followed by a balanced or unbalanced amount and duration of negative current. Adjustment of dials can maximize penetration (DC positive cycle) and also deposition rate (DC Negative). Extremely high deposition is achieved with unsurpassed quality.
Networking welding units allows both real time monitoring of all parameters, as well as building a detailed welding history.