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Welding - The DIY Guide > MMA Tutorial > MMA Electrode Classification

MMA Electrode Classification

Some rods perform best when used downhand. Some also perform well out of position ie vertical upwards, overhead, vertical downwards, horizontal. The AWS classification (ie E6013 or E7018) doesn't really cater for this, however, the ISO standard does. This page decodes the classification used for the more common rod types.

AWS Standard

Rods are commonly known by their AWS (American Welding Society) name, so it's a useful standard to decode. We'll use E7018 rods as an example:

E

Electrode

E just means the electrode is for MMA welding and has a flux coating.
70

Tensile Strength (in ksi)

The minimum tensile strength measured in kilo-pounds(force) per square inch. In our example 70ksi would be 70,000psi pounds(force) per square inch, or 480N/mm2.
1

Welding Positions

1 All Positions
2 Flat and horizontal positions
8

Flux Coating and Current

Note the last 2 digits are used together to describe the flux coating.

0 High cellulose sodium (Cellulosic) DC+
1 High cellulose potassium AC or DC+ or DC-
2 High titania sodium (Rutile) AC or DC-
3 High titania potassium (Rutile) AC or DC+
4 Iron powder titania (Rutile) AC or DC- or DC+
5 Low hydrogen sodium DC+
6 Low hydrogen potassium (Basic) AC or DC+
7 Iron powder iron oxide AC or DC+ or DC-
8 Iron powder low hydrogen (Basic) AC or DC+

If the second last number (representing the welding position is 2 the classification changes a little. From the last 2 digits:

20 High iron oxide AC or DC+ or DC-
22 High iron oxide AC or DC-

 

1SO 2560 Standard

The European coding system has recently been amended and is now an International Standard 1SO 2560 which is basically the same as EN499.

The ISO standard gives you more information especially the last two digits signifying the operation characteristics. But it doesn't roll off the tongue quite so easily as the AWS classification.

In the ISO standard E7018 rods are known as E46 4 B 32 H5

E

Electrode

E just means the electrode is for MMA welding and has a flux coating.
46

Yield Strength (in N/mm2)

Multiply this number by 10 for the minimum yield strength in N/mm2. In our example 46 will represent a minimum yield strength of 460N/mm2

This is not directly equivalent to the tensile strength in the AWS standard. Yield Strength is where the metal starts to deform plastically (when it doesn't spring back to it's original form after the load is released). Tensile Strength is when the metal breaks.

  Yield Strength (N/mm2) Tensile Strength (N/mm2)
35
>355
440-570
38
>380
470-600
42
>420
500-640
46
>460
530-680
50
>500
560-720
4

Minimum Impact Temperature at 46J

This represents the temperature at which the weld material becomes brittle.

A +20°C 4 -40°C
O 0°C 5 -50°C
2 -20°C 6 -60°C
3 -30°C Z Other

So 6 represents -60 degrees C.

Chemical Composition

There is an additional field included here for some specialist rods and represents the percentage of Manganese (Mn), Nickel (Ni) and Molybdenum (Mo) in the filler metal.

  %Mn %Ni %Mo
-
2.0
-
-
Mo
1.4
-
0.3-0.6
MnMo
> 1.4-2.0
-
0.3-0.6
1Ni
1.4
0.6-1.2
-
2Ni
1.4
1.8-2.6
-
3Ni
1.4
> 2.6-3.8
-
Mn1Ni
> 1.4-2.0
0.6-0.12
-
1NiMo
1.4
0.8-1.2
0.3-0.6
Z
Other

1NiMo may be used for some of the lower strength grades of Weldox. Otherwise these alloyed grades are normally used for welding mild steel that has been "improved" for applications such as offshore work.
B

Rod Flux Coating

A Acid
A type of rutile characterised by very smooth arc but with minimal penetration and prone to moisture pick up. good on very thin sheet		 RC Rutile Cellulosic (E6013)
Most rutiles contain some cellulose to improve the penetration, otherwise the same as R.
C Cellulosic (E6010)
An organic coating containing Cellulose with good penetration, high deposition, and easily removed slag, but high hydrogen content.		 RA Rutile Acid
Hybrid between Acid type and full Rutile. Rarely used, if ever.
R Rutile (E6013)
 In welding rod coatings it provides slag cover, arc stability (it ionizes easily) and helps the fast freeze ability of positional rods.
 RB Rutile Basic
Another hybrid. a rutile with better mechaicals but lose some of their ease of welding characteristic. Some of the glassy slag low hydrogen rods could be classed as RB or maybe BR.
RR Rutile thick coated (E7024)
Rutile rods with the addition of iron powder which increases deposition rate. Normally only used on the flat.		 B Basic (E7018 or E7016)
These chemically basic (alkali) coatings contain calcium carbonate or calcium fluoride. They are normally used for Low Hydrogen rods.
3

Current Type and Recovery

'Recovery' is the weight of weld metal deposited in the weld relative to the weight of the core wire. Over 100% means that the weld will weigh more than the weight of the core wire. In other words the coating contains iron powder (or in some rods other alloys).

  Recovery Current Type
1 <105 AC + DC
2 DC Only
3 105-125 AC + DC
4 DC Only
5 125-160 AC + DC
6 DC Only
7 >160 AC + DC
8 DC Only
2

Welding Positions

1 All positions
2 All positions except vertical down
3 Flat. For fillet welds they can also be used in horizontal and vertical positions.
4 Flat butt and fillet welds
5 Vertical Down
H5

Hydrogen content

Further information at the end (used in low Hydrogen rods) gives the Hydrogen content in ml/100g.

H5 5ml/100g maximum
H10 10ml/100g maximum
H15 15ml/100g maximum
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Common Faults

Flat Joints

Fillet Joints

Buying an Arc Welder

Types of Arc Welder

Electrode Classification

Welding Different Steels
Weld Testing
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