C/C..C/V

By Lawrence (*****)

Date 03-03-2010 12:08

Hey Steve

Typically SAW is a CV process.

The pro's would be that SAW works with CV

The Con's would be the SAW won't work with CC

By js55

Date 03-03-2010 12:55

If I may, SAW works very well with CC. But it is generally reserved for bigger wires. I usually use about 1/8 to 5/32 as the cutoff point for switching from CV to CC. The old Lincoln NA-3's allowed you to switch back and forth in about 2 minutes with the flip of a switch and reversing the face plate. When they went to the NA-5 they eliminated the CC option.
A shop I worked in had been using CC for years with the NA-3's on 3/32 and it worked ok. I switched em to CV and after they got over freekin out about the amp needle jumpin around they settled in and preferred it.
We'd switch back on jumbo stuff.

By Lawrence (*****)

Date 03-03-2010 13:33

Well there ya go.

I stand corrected.

A good thing about the fourm is that there are posters like js55 to make sure you get the most accurate information.

Thanks js

By CHGuilford (****)

Date 03-03-2010 17:26

Check the applicable welding code. I might be mistaken (haven't checked lately) but I thought D1.5 requires SAW to be run as CV.

By js55

Date 03-03-2010 18:09

Chet,
That wouldn't surprise me. D1.1 has CV only on GMAW/FCAW prequals.

By OBEWAN

Date 03-03-2010 17:59

I seem to remember some of the old Linde controls also had a switch on the wire feeder circuit board for CC/CV. I have not seen one since 1983 so I have long since forgotten the applications.

By SWP

Date 03-03-2010 19:18

I ran several automated pulsed GMAW units in high production auto parts manufacturing, and originally the systems were setup for CC, but I changed over to CV. CC was thought to be a wise choice since as the contact tip wears or if tip to work distance changes, the current remains constant, and this should be best to maintain consistent penetration. However, with tip wear on CC, the voltage and arc length tend to increase, and this was more of a problem for my welds which required a very tight arc length. So by switching to CV, voltage and arc length remain constant through the tip wear of several hundred weld cycles, and the reduction in current with tip wear was not an issue.

Maybe you can apply this logic to SAW?

By 357max

Date 03-05-2010 00:26

CC the amperage is limited to set value; the voltage can go high as the open circuit voltage. Voltage is controlled by the wire feed speed. More wire (shorter arc length), less volts - less wire (longer arc length), more volts.
The CV/CP the voltage is limited to set value; the amperage is controlled by the wire feed speed. More wire, more amperage - less wire, less amperage.
Voltage controls the height and width of the weld deposit; amperage controls the penetration/has the most affect on penetration. In SAW, voltage is a big factor in slag release also. Some GMAW CV machines 38 - 45 volts is the maximum output. SAW CV machines 60-65 volts, CC voltage could be 80 - 95 OCV. Big diameter wire, higher voltages.

By js55

Date 03-05-2010 13:34

You won't see much difference at 1/8" wire. And the advantage you will find is that bead control and arc stability will be increased with CC on the larger wires. I read once why but the reason escapes me at this age. The most noticable points wiil be cross overs, bead starts, and side wall beads where instabilites can be exaggerrated. I think it has to do with the arc density relationship.
Lawrence, Allan, Henry, or Stephen might be far beter at explaining this than I.

By ssbn727 (*****)

Date 03-05-2010 18:30 Edited 03-05-2010 18:34

I have to respectfully disagree with you Jeff... I think you did an excellent job of explaining it IMHO! ;)

However, I would be honored to add what I found in my copy of the AWS Welding Handbook, Ninth Edition, "Welding Processes" Volume 2, Part 1. I would strongly recommend to Steve E. to have a look @ Chapter 6 on Submerged Arc Welding in this book which has some really good information, knowledge, and very sound welding advice regarding the recent advances in Submerged Arc Welding (SAW) which @ one time or another during it's infancy in the late 1920's was sometimes called: "Under Powder Welding" or "Smothered Arc welding" also.

This is from page 258. Chapter 6: POWER SOURCES

"The power source for a submerged arc welding system is of major importance and should be carefully selected. Submerged arc welding is typically a high-current process wth a high duty cycle, thus a power source capable of providing high amperage @ 100% duty cycle is recommended. Two general types of power sources are suitable. Direct current power sources, which may be transformer rectifiers, motor or engine generators, (and most recently - inverters) provide a constant voltage (CV), constant current (CC), or a selectable constant voltage/constant current output. Alternating current power sources (generally transformer types with notable exceptions such as the recently advanced AC/DC Power Wave 1000 SD Square wave inverter based power source: http://content.lincolnelectric.com/pdfs/products/literature/e9181.pdf ) can provide either a constant current or a constant voltage square wave output.

Direct Current Constant Voltage Power Sources

Direct-current constant voltage power sources are available in both transformer rectifier and motor generator models (Also offered as inverters such as the Power wave 1000 SD Square wave output power source). They range in output from 400 amperes (A) to 1500A. The lower amperage power sources may also be used for gas metal arc (GMAW) and flux cored arc welding (FCAW). These power sources are used for semi-automatic submerged arc welding at currents ranging from about 300 A to 600 A with electrode diameters of 1.6, 2.0, and 2.4 millimeters (1/16th of an inch, 5/64", and 3/32"). Automated and mechanized welding require currents ranging from 300 A to over 1000 A, with electrode diameters generally ranging from 2.0 mm to 6.4 mm (5/64" to 1/4"). Applications for direct current(CV) welding over 1000 A are limited, however, because severe arc blow - the deflection of the arc from it's normal path - may occur at these high currents.

A constant voltage power source is self regulating: the wire feed speed and wire diameter control the arc current and the power source controls the arc voltage. Once the arc length is established by the voltage adjustment, any changes in arc length caused by welding conditions are automatically compensated for by an increase or decrease in current. This, in turn, increases the strip or wire burn off rate and the arc is returned to it's original setting. Constant voltage power sources are intended for use with constant-speed wire feeders (Very Important point when comparing DC-CV output to DC-CC output variables.). Because voltage or current sensing is not required to maintain a stable arc, very simple wire feed speed controls that assure constant wire feed can be used. Constant voltage DC power sources are the most commonly used power sources for submerged arc welding and are the best choices for the welding of stainless steel, high speed welding of thin steel, and all cladding applications, and for use with flux cored wire. This power source can also be used for carbon arc cutting and gouging (CAC-A).

Direct Current Constant Current Power Sources

Direct current constant current power sources are available in both transformer-rectifier and motor generator models (as well as the hybrid AC/DC Power wave CV/CC inverter power sources being offered by both Licoln and ESAB as well as other manufacturers also) with rated outputs of up 1500 A (Some Mfg's offer even higher amperage output).
Some constant current DC power sources can also be used for (GTAW) gas tungsten arc welding, (SMAW) shielded metal arc welding, (CAC-A) and air carbon arc cutting and gouging. With the exception of the high speed welding of thin steel, constant current DC power sources can be used for the same range of applications as constant voltage DC power sources.

Constant current power sources are not self-regulating, so they must be used with a voltage sensing variable wire feed speed control. This type of control adjusts the wire feed speed in response to changes in arc voltage. The voltage is monitored to maintain a constant arc length. With this system, the arc voltage is dependent on the wire feed speed and the wire diameter. The power source controls the arc current. Because voltage-sensing variable wire feed speed controls are more complex, they are also more expensive than the simple constant wire feed speed controls that can be used with constant voltage systems.

Combination Power Sources

Some power sources used for submerged arc welding can be switched between constant voltage and constant current modes. Power sources rated at up to 1500 A are available, but machines rated at 650 A or less are much more in common. The value of these power sources is in their versitility, as they can also be used for SMAW, GTAW, GMAW, FCAW, CAC-A and arc stud welding.

Alternating Current Power Sources

The power sources used for AC submerged arc welding are most commonly transformers. Power sources rated for 800 A to 1500 A @ 100% duty cycle are available. If higher amperages are required, these machines can be connected in parallel. Conventional AC power sources are the constant-current type. The output voltage of these machines approximates a sine wave... The output of these machines drops to zero with each polarity reversal, so a high open-circuit voltage (greater than 80 volts) is require to ensure reignition of the arc. Even at that high open circuit voltage, arc reignition problems are sometimes encountered with fully basic fluxes that are not designed for alternating current. Because these power osurces are the consant current type, the speed controls must be the voltage sensing, variable wire feed type.

With constant voltage square wave AC power sources, the output current and the output voltage approximate a square wave. Because polarity reversals are instantaneous with square wave power sources, arc reignition problems are not as severe as those encountered with conventional AC power sources. Hence, some of the fluxes that do not work with conventional AC power sources can be used with square wave sources. Relatively simple constant wire feed speed controls can be used with square wave power sources because they provide constant voltage. The most common uses of AC power for submerged arc welding are high current applications, multiple wire applications, narrow groove welding, and applications in which arc blow is a problem."

There's more, but I'll end it here for now and pick up on it later because I've got to get this errand out of the way before 3PM! ;)

Respectfully,
Henry

By js55

Date 03-05-2010 19:29

I am particularly fond of Chapter 6 in the Ninth Edition of the Welding handbook.