MMA welding

MMA welding
(electrode welding)

1. Stick electrode welding process

The electric arc causes the melting of the base metal and the filler metal, achieving a transfer of molten metal by means of the so-called plasma column, which is nothing more than an ionized atmosphere caused by part of the surrounding air and by the gases from the melting of the slag elements of the electrode itself.

In addition, some metallic chemical elements can also be added to the flux to complement or enrich the new metal obtained in the weld bead, providing, in turn, part of the elements vaporized by the action of the temperature. All this is covered at all times by the molten slag that helps to complete the welding process, cooling and protecting the weld bead at all times.

2. Gala Gar has different types of equipment for electrode welding.

Transformers

Its basic function is to modify the current and voltage values of the network. This equipment consists of a magnetic core between two wires forming two coils, one primary and the other secondary.

These equipments are always of alternating current, and therefore lack polarity.

They are recommended for large thicknesses, but offer a slightly unstable electric arc.

Rectifiers

They consist of a transformer, to subsequently pass the current through an electrical element called diode and thus modifying the AC mains current in DC / DC working current, separating the polarity and choosing, at will, its connection.

Inverter Equipment

This is a welding or cutting device in which the output power is regulated by means of an electronic control system capable of converting the mains frequency of 50Hz to a signal with a frequency between 50 and 100KHz, thus obtaining a considerable reduction in the size of the equipment.

3. Special functions in electrode welding

HOT START

Intensity booster that assists the ignition by means of an electrical induction that facilitates the ignition of the electrode.

ARC FORCE

Control system that reads the welding voltage, regulating the arc force to reduce or increase the size of the fusion, thus keeping the electric arc more stable.

ANTI STICK

In case of contact, it prevents the electrode from sticking by reducing the current of the equipment.

4. TYPE OF ELECTRODES

GALA B50 Basic Electrodes E-7018-1

It is a type of basic electrode, high quality, contains a high content of manganese which makes it excellent for all those welding applications subjected to high resistance and dynamic loads, and where a deposited material of high performance of the welded assembly is required.

It offers an efficiency of 115% being suitable for all types of works in Engineering, Civil Works, Shipyards, Heavy Boilermaking, Bridge Cranes, Tanks, Heavy and Earthmoving Machinery, Mining, Carriages, Maintenance, etc…

Suitable for low alloy steels and steels with high carbon content.

Valid in all positions except vertical downward.

Recommended to dry at 300º approx. 2 hours.

Rutile electrodes GALA 46 E-6013

It is a type of electrode for universal use, with excellent weldability, suitable for generic works in carbon steels of any thickness, metal carpentry, locksmithery, boilermaking, etc.

Especially useful for welding in Vertical Down position where most of the Rutilos electrodes, do not have weldability, this on the contrary, can give the sensation of greater amount of projections, and a possible heating of the electrode to high intensities.

As with all types of electrodes, a logical maintenance of the product and a drying if necessary at temperatures above 150-250º approx. is recommended. 30-90 min.

Stainless steel electrodes GALA INOX E-316L-16

Rutile type stainless steel electrode for universal use with excellent weldability, low smoke and spatter. It can be used not only with stainless steels, but also with low alloy carbon steels and with chromium, nickel and molybdenum contents.

Suitable for generic works as well as for joints and/or repairs of extreme quality in applications such as: Tanks, Piping, Textile Industry, Chemical Industry, Paints, Water Treatment, Recycling Plants, Furnaces, etc.

The deposited metal, apart from having excellent mechanical properties, is unalterable and perfectly resistant to the attack of acids and corrosive elements even at temperatures above +400ºC.

It is important to remove any trace of moisture from your coating by drying up to 300º for 2 hours.

5. Execution of electrode welding

1. Electrode selection and drying.
2. Pre-cleaning and verification of the material to be welded.
3. Adjustment of welding equipment.
4. Intensity test on the adjustment plate.
5. Weld specimen in position.
6. Final cleaning.

5.1. Electrode selection and drying.

The electrode is selected according to the material to be welded and, depending on the type of electrode, it is advisable to pre-dry it in an oven.

Excessive moisture in the coating can lead to pores in the weld, and hydrogen from moisture can lead to cold cracking. Therefore, depending on the type of electrodes, it is necessary to pre-dry them in an oven or in a drying oven.

Which electrodes should be dried?

The basic electrodes must be dried before use whenever there are mechanical requirements of the metal provided and/or radiographic quality in the applications.

Electrodes for rutile-acid type stainless steels and all basic types can produce pores if they have not been stored under the proper conditions. By resecting the electrodes we will recover them for use.

Electrodes for carbon steels of the rutile and acid types do not normally need to be dried.

Cellulosic electrodes should not dry out.

Electrodes that are badly damaged by moisture will not give optimal results even after being dried. They should therefore be discarded.

5.2. Pre-cleaning and verification of the material to be welded.

We remove traces of rust, paint, etc. to avoid contamination of the test tube.

5.3. Adjustment of welding equipment.

Depending on the diameter and type of electrode, we will adjust the intensity of the equipment.

 

 

* Estimated values

 

We regulate the intensity, the higher the intensity the greater the penetration.

Adjust the intensity according to the welding position, in inner angle it will be 20% higher and in ascending 15% lower.

The arc length should be half of the electrode diameter. It is convenient to maintain the same arc length, avoiding oscillations in tension and intensity that generate an uneven penetration.

The travel speed should be adjusted so that the electric arc is slightly ahead of the molten pool.

5.4. Intensity test on the adjustment plate.

Pre-weld on a martyr plate to adjust the electric arc according to the welding position.

Proceed to make intensity adjustments and repeat the welding test until the desired setting is achieved.

5.5. Weld specimen in position.

Execute the welding of the specimens in the agreed positions.

5.6. Final cleaning.

Remove the remains of slag with the reinforced pickaxe and superficially clean the bead with the wire brush.

 

6. Electrode welding applications

Especially recommended for short welds:

1. repair and maintenance,
2. pipe manufacturing and installation,
3. as well as outdoor assembly works.

7. Conclusion

The main characteristics of the process are its simplicity and low price, which make it a practical and excellent procedure for construction works, metallic structures, maintenance and any type of conduction piping.

However, the stick welding process does not lend itself to automation or semi-automation; its application is essentially manual.