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DCEP expands as Direct Current Electrode Positive whereas the electrodes are related to the positive terminal concerning the direct current. Only Direct Current has opted in this format of welding.

DCEN expands as Direct Current Electrode Negative whereas the electrodes are related to the negative terminal concerning the direct current. In this sequence of welding also, only direct current is used and no alternate current is preferred.

How DCEP is adopted in MIG Welding?

For Metal Inert Gas welding (MIG) generally, DCEP is preferred. Because negative electrodes offer increased melting for the prescribed level and grade of the current. So it is obvious to have reverse polarity options preferred in carrying out welding operations of MIG applications. In case if Direct Current Electrode Negative is used, it will end up in unstable welds with varying fluctuations in the resultant output. MIG welding can be carried out effectively with DCEP that uses natural gases without more flux.

How DCEN is preferred in TIG Welding?

Source: American Welding Society

DCEP vs. DCEN are generally defined as follows. DCEN is preferred in TIG welding wherein no cleaning process is required in this form as in case of positive electrode process. For this process, you need extended space for the use of tungsten electrodes and cooling purposes. Natural or straight polarity is preferred for easy welds and heat generated is converted into positive arcs that prevents the tungsten filament from overheating and makes the systems stabilized adequately. TIG Welding can be done using both direct current and alternate currents. Steel will be welded with Direct current and Aluminum will be preferred linked with alternate current.

Heat Distribution of DCEP and DCEN:

The first and foremost important point to be noted is that not all the electrodes available can be cast-off with all polarities for welding purposes. Electrodes should be adopted as per the specifications summarized in the ISO codebook of standards. The optimal selection of polarization also depends on the nature of the material incurred, its welding position, and the related design combinations of the material. By having all these things in mind we can arrive at needed polarity based on the specific run. The part of the welding track that is positive (entices electrons in the arc) is said to be an anode. The other part of the welding track that produces negative electrons in the arc is said to be a cathode. The positive anode and negative cathodes are employed in the welding process.

Welding Polarity effects on DCEP and DCEN in Arc Welding:

Main classifications and characteristics of DCEP vs. DCEN are described as follows.

Direct Current Electrode PositiveDirect Current Electrode Negative
Fusion is done in a proper and neat way because of the positive electrodes.Melting is highly insufficient as the electrodes are connected in negative terminal.
As the electrodes are highly positive deep penetration is enabled in the welding process.Because of the presence of negative electrodes penetration is moderate.
Amount of deposits in the filler material is extremely low.Amount of deposits in the filler material is higher.
Productivity is low for positive electrodes.Productivity is higher for negative electrodes.
Cleaning process is tedious and the result is heavily poor.Cleaning process here is so simple and good results are obtained.
Heat Affected Zones are higher.Heat Affected Zones are lower than expected.
Large distortion is produced.Distortion is less when compared to DCEP.

Straight Polarity effects in Direct Current Electrode Negative:

When Electrodes are connected in the negative terminal and the remaining power sources are linked to the positive terminal, the fall of electrons occurs. Heat source is liberated and it starts to flow towards the attached base plates. With the available potential difference, electrons are getting hastened between the negative electrodes and the attached base plates. As striking is enhanced, kinetic energy is developed and it is further converted into thermal energy in producing immense heat necessary for the continuation of the entire process.

Reverse Polarity effects in Direct Current Electrode Positive:

In this case, the base plates are connected to the negative terminal of the power end and the electrodes are directed to the positive terminal for heat generation. As a result, electrons get liberated from the base plates and start moving in the direction of the electrodes. The heat generated in the electrodes is slightly high when compared to the one generated in the base plates. For positive electrodes cleaning process is so easy and filler deposition is extremely low. By the heat generated the impurities and dust particles present in the base plates get cleared and the process is termed as Cleaning action. Thus by this cleaning action, contaminated particles present on the metal surface get cleared thoroughly.

Correspondences of DCEP and DCEN Polarities in Arc Welding:

  • Both DCEP and DCEN polarities can be held applicable for welding of two or more metallic components together with substantially different forms of positive results.
  • Primary and an essential source of heat is generated in both polarities and arc welding is made easy and simple. Finishing of the welded materials is smooth and good enough.
  • If alternate current is used for power supply the subsequent cycles of both the polarities are carried out in appropriate intervals and the cycle continues.
  • Thin metals can also be welded by using DCEP and DCEN polarities as melting temperature is sufficient enough in handling these working conditions.
  • As positive electrodes are deployed in the cleaning process filler materials are deposited in the metallic base plates at a smaller rate than the expected.

Why is DCEP currently used for GMAW?

Most of the gas metal arc welding (GMAW) applications preferably use DCEP polarity. By these conditions, a stable form of the arc is yielded with the smooth transfer of metals with comparatively low sprinkling. Deep penetration is inherited to have an appropriate finish in welds with a wide range of supply in electric currents. When DCEN is used concerning the direct current the resulting output would be of a very small size as resembling a droplet and the resulting finish would be uneven. By having proper wirings with appropriate connections welding process would become so simple and the use of alternate current will make the system stand stable even in fluctuating conditions. For GMAW power sources both direct and alternate currents are preferred with varying supplies.

Uses of Shielded Metal Arc Welding:

  • Shielded Metal Arc Welding (SMAW) is the normally preferred welding method which is a manual process that uses a consumable electrode for the processing strategy.
  • At the saturated melting point, the electrode starts melting and the weld area is protected from the external gases present in the natural atmosphere.
  • It is one of the simplest and affordable forms of welding that can be preferred by almost every individual.
  • The decomposition of electrodes is prevented by this form of welding and a protective shield is formed to save the arc from the resulting chemical reaction.
  • Ferrous metals and other related structures can be joined easily using SMAW.
  • Quality of SMAW is tested by using nondestructive testing methods and high strength is assured.
  • Stainless steel materials, Cast iron, and other non-ferrous alloys can also be treated without flaws.

What is Weld Sputtering?

Sputtering is the process by which microscopic particles present in the solid substance gets ejected from the lower surface after a bombardment has happened inside the material by the presence of natural gas or fume. The process usually takes place in an open and fresh airy environment free from pollution. When the direct electrical current changes with actual little resistance the material becomes very conductive. Take gold as an example as it is one of the widely used conductive materials present on the earth. It is widely used everywhere and it cannot be used as a welding instrument as it may lose its grade and it is costly of course.

In general Copper, aluminum, and other related metals are widely used in the welding process because they do possess a good balance between the price and conductivity. Among all the metals copper still does the best job by conducting good electricity all the time. Precisely, there is a static amount of resistance inherited in the properties of all the material and those are not sufficient enough in interfering with the metallic properties inside the material. Circuit resistance has few problems such as failure in premature equipment, less count in productivity, and finally defects in welding.

Watch Video: Know More About Sputtering

Determination of Polarity by the presence of Metallic Electrodes:

  1. Base metal present in the material should be placed in a flat position and the surface should be of a clean one free from impurities.
  2. Amperage value should be set ranging from 130 to 145 degrees for the respective electrodes.
  3. Polarity ranges must be set adjusted for having enough reference value. Study the arc generated and its respective length is measured.
  4. Sound of the resultant arc is studied carefully for polarity check. Incorrect range in polarity is to be ascertained.
  5. Extinguishing features of the normal arc and bead is studied concerning the metallic electrodes.
  6. The process is repeated multiple times to recognize and check the unevenness in the polarity.

How Polarity Affects Electrode Performance in Arc Welding?

Welding is done positive current electrodes (Reverse Polarity) results in deeper penetration whereas electrodes with negative (straight polarity) result in the benefit of earlier melting and quicker deposition rate at increased speed. A variety of shielding gases is used in the welding process to obtain smoother and leveled finishing. Though, if the power spring distributes alternate current (AC) then both circumstances occur one after the other. Changes occur in every single second and it depends on the emerging frequency of the current supply. Take an example wherein for 60Hz AC power supply both the polarities will occur for a minimum of 60 times in a second.

Influence of Polarity in the extended life of Electrodes:

In general, reverse polarity surges the filler deposition rate when the electrode is made of consumable type and grade. Polarity has extended influence in the life of non-consumable electrodes as in the case of TIG welding. Through reverse polarity, too much heat is generated more rapidly to the tip of the electrode. When the process of welding is carried out continuously with the available non-consumable electrodes, it starts melting down mechanically and large bubbles of molten metal will format the tip of the electrodes. In some cases, the resultant droplet deposits on the weld surface lead to the presence of flaws. Sometimes it gets retained on the electrode tip that is swept away by the grinding process before starting the new and next welding operation. Both the cases result in forfeiture of the electrode materials and the life of non-consumable electrodes diminishes concerning reverse polarity.

Stick Welding Stainless Steel Polarity:

For Stick Welding, Direct current is preferred and that is the most commonly adopted option. Because stainless steel alloys possess chromium level which is less than 10% of the original content. Base classes of stainless steel are available and they are grouped under specific categories. Three different classes of stainless steels are generally grouped and those are as follows.

  • Austenitic Stainless Steel – These are the non-magnetic stainless steels possessing increased chromium and nickel levels and the carbon consumption is comparatively low. This form of stainless steel is highly resistant to corrosion and the grades given are higher. This type of steel is a widely used form of stainless steel and it is affordable.
  • Martensitic Stainless Steel–These types of steels also hold the same components as of normal austenitic steels. Because of its high oxidation resistance, it possesses increased strength even at very low temperatures. The creep resistance of such materials is high at moderate and preeminent temperatures.
  • Ferric Stainless Steel–As the name itself says the steel is magnetic one possessing more than 15% of chromium and low carbon level. The material is strong enough in withstanding heavy rust. Though corrosion resistance is low when compared to other forms of steel the quality is far better than the other subsequent forms.