How to Quickly Distinguish Acidic Electrode From Alkaline Electrode?

Welding rod

The common electrodes are J422 and J507, of which 422 is acid electrode and 507 is alkaline electrode.

According to the alkalinity classification of slag after welding, welding rods can be divided into acid welding rods and alkaline welding rods.

Related reading: How to Choose the Right Welding Rod?

How to distinguish acid electrode from alkaline electrode more quickly?

We can know whether the welding rod is using DC welding machine or AC welding machine from the welding rod grade.

From the welding rod grade, we can also see whether the welding rod is acidic or alkaline.

J422 series of welding rods include J421, J422, J423, J424, J425, J426 and J427;

J507 series of welding rods include J501, J502, J503, J504, J505, J506 and J507.

Carbon steel series welding rods are these kinds.

Look at the last digit of the welding rod grade. The last digit of the grade indicates the specific meaning:

Last digit of welding rod gradeCoating typeCurrent type
0The type of coating is not specifiedApplicable current type is not specified
1Titanium oxide coatingAC, DC
2Titanium calcium coatingAC, DC
3Ilmenite type coatingAC, DC
4Iron oxide type coatingAC, DC
5High cellulose coatingAC, DC
6Low hydrogen potassium type drug skinAC, DC
7Low sodium hydrogen type drug skinADC
8Graphite coatingAC, DC
9Base coatingDC

We can see from it that the third digit of the grade also indicates the type of drug coating.

Electrodes containing a large amount of acid oxides (TiO2, SiO2, etc.) in the coating are called acid electrodes.

Among them, the electrodes of titanium oxide type coating, titanium calcium type coating, ilmenite type coating, iron oxide type coating and high cellulose type coating are all acid electrodes, that is, those whose third digit number is 1, 2, 3, 4 and 5 are acid electrodes, and DC welding and AC welding machines can also be used.

Acid electrode can be used for both AC and DC, with good welding process performance, arc and small spatter, good slag fluidity, easy deslagging, and beautiful weld appearance.

Because the coating contains more silicate, iron oxide, titanium oxide, etc., the oxidation is strong, but the mechanical properties of the weld, especially the impact toughness, are poor.

It is suitable for the welding of general low carbon steel and low alloy structural steel with low strength.

It is the most widely used electrode.

Alkaline electrodes contain a large amount of alkaline oxides (Cao, Na2O, etc.) in the coating.

The electrode mainly relies on the decomposition of CO2 from carbonate (such as CaCO3 in marble) as the protective gas, and CaF2 in fluorite combines with H to synthesize hydrogen fluoride HF at high temperature, thus reducing the hydrogen content in the weld, so the alkaline electrode is also called low hydrogen electrode.

Therefore, the electrodes with low hydrogen potassium type and low hydrogen sodium type coating are alkaline electrodes, and the third place of electrode grade is 5 and 6.

Because the J506 coating is added with arc stabilizer, the electrode is easy to start the arc and maintain the stable combustion of the arc during the welding process, so the 506 electrode can be used for both AC and DC, and the J507 electrode can be welded only by using DC reverse connection.

Comparison of characteristics of acid electrode and alkaline electrode:

1. The components of acid electrode coating have strong oxidizability;

However, the oxidizability of the coating components of alkaline electrode is weak.

2. The acid electrode is not sensitive to pores caused by water and rust.

The electrode is baked at 75~150 ℃ for 1H before use;

The alkaline electrode is sensitive to pores caused by water and rust.

The electrode is baked at 350~400 ℃ for 1~2H before use.

3. The arc of acid electrode is stable, and AC or DC welding can be used;

However, the alkaline electrode, which contains fluoride in the coating and worsens the arc stability, must be welded with DC. Only when the arc stabilizer is added to the coating, can it be used for both AC and DC.

4. The welding current of acid electrode is large;

The welding current of alkaline electrode is smaller, which is about 10% smaller than that of acid electrode of the same specification.

5. Acid electrode should be operated with long arc;

The alkaline electrode should be operated with short arc, otherwise it is easy to cause pores.

6. The transition effect of alloy elements of acid electrode is poor;

The alkaline electrode has good alloy element transition effect.

7. The weld of acid electrode is well formed and the penetration is shallow;

However, the alkaline electrode has good weld formation, easy to pile up, and slightly deeper penetration.

8. The slag structure of acid electrode is glassy;

The slag structure of alkaline electrode is crystalline.

9. It is convenient for acid electrode to deslag;

However, it is difficult to deslag the first layer in the groove of alkaline electrode, and it is easy to deslag the subsequent layers.

10. The impact performance of acid electrode weld at normal and low temperature is general;

However, the alkaline electrode weld has higher impact properties at normal and low temperature.

11. Acid electrode has poor crack resistance;

The alkaline electrode has good crack resistance.

12. The hydrogen content in the weld of acid electrode is high, which is easy to produce “white spots” and affect the plasticity;

However, the hydrogen content in the weld of alkaline electrode is low.

13. Less smoke and dust during acid electrode welding;

However, there is more smoke and dust during alkaline electrode welding.

Comparison table of differences between acid electrode and alkaline electrode

CategoryAcid electrodeAlkaline electrode
Typical gradeExx03Exx15
typeTitanium calcium typeLow hydrogen type
Power SupplyAC / DC dual purposeDC reverse connection
electric arcGood stabilityPoor stability
slagGood liquidityGood liquidity
Appearance moldinggoodrough
Weld beadModerate penetrationHigh weld bead
Toxic gaslessmany
Impurity sensitivitylowhigh
Groove cleaning requirementslowhigh
stomalessEasy to produce
Hydrogen contentMoreless
Oxide inclusionmanyless
desulphurizing abilitydifferencestrong
Mechanical properties of metalsPoorgood
Crack resistancePoorgood
Slag state during weldingA layer of black-and-white mucus that is about 2-3mm higher than the molten ironA layer of dark red mucus with a thickness of about 1mm, which is not too churning, and soon solidifies
Molten iron state during weldingConstantly fluctuatingRelatively calm
Best stateMake the molten slag cover about 2/3 of the molten poolMake the molten slag cover the molten pool about 2/5
Welding status descriptionThe fluctuation indicates that the gas in molten iron can be fully dischargedNot calm means that the welding rod is not dry or there is too much dirt on the surface or the arc is too long
Transitional formLarge drop transition or short-circuit transitionFine particle transition

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