Practical application of MMA welding
Specifics of MMA welding
The greatest advantage of MMA welding is that it can be used in any field conditions, without regard for the grade of steel to be welded, the welding ratio or the specifics of the structure, which is why it is considered the most popular technique in the industry. By combining versatility and universality, it has gained a wide following. MMA has found applications in the shipbuilding and defence industries, construction, manufacturing and repair services, among others.
What is covered electrode welding?
Manual arc welding with a covered electrode is one way of joining structural components. The process focuses on melting the electrode by means of the heat of the arc of the molten electrode with the material to be welded. Evenly with the welding time, the electrode shortens, so the distance between the workpiece and the electrode is constantly changing. This process requires the welder to have special skills and a precise and skilful hand.
SMAV welding station
An extremely important element during the welding process turns out to be the workstation, which should be properly equipped. The most important elements are first of all: electrodes, a suitable welding machine, connecting cable, earth clamp and electrode holder. In addition, the welder should have a suitable protective apron, work shoes, gloves and a welding mask with filters to prevent the inhalation of escaping gases. In cases where welding takes place in a workshop, proper provision must also be made for fume extraction.
The most commonly chosen equipment is:
- welding generators;
- welding transformers;
- welding inverters;
- rectifier welding power supplies.
The basic electrodes used for MMA are divided into:
- (A), i.e. those with an acidic envelopeThe lagging consists of iron oxides and a large amount of deoxidisers. The sour lagging consists of iron oxides and a large quantity of deoxidisers. As long as there are no white efflorescences on these electrodes making welding difficult, they do not need to be dried.
- (B), i.e. those with an alkaline envelope, which are characterised by resistance to hot and cold fracture and high binder ductility. Fluorspar together with magnesium and calcium carbonates are contained in the above lagging. A disadvantage of alkaline lagged electrodes is that they must be dried before use.
- (C), those with cellulose laggingwhich are primarily used for welding in outdoor conditions (e.g. transmission pipelines). The cellulose cover consists of cellulose, deoxidisers and wood flour. These electrodes do not need to be dried before use, as they have their most favourable welding properties when the water content is about 3%.
- (R), i.e. those with rutile liningwhich are described as the most versatile in terms of their application. Their lagging consists of deoxidisers (ferrosilicon and ferro-manganese) and rutile. The resulting rutile weld has a smooth surface, while slag is removed from the surface with little effort. Normally, these electrodes do not need to be dried. This is only necessary if white efflorescence forms on the coating or if the arc glows unstably during welding.
There are also electrodes that combine the properties of the above-mentioned types (with lagging: rutile-base, rutile-cellulose or rutile-acid).
Application of covered electrode welding
- minor construction and repair work;
- welding of power station pipelines or other pipes;
- hobby use by novice DIY enthusiasts;
- use in small services or workshops;
- use in installation work;
- use in the shipbuilding industry;
- use on construction sites;
- welding under water, in areas with difficult access and in field conditions.
Optimisation of covered electrode welding
WeldEye, a system for the electronic management of the SMAV process.
The first manufacturing company to successfully launch an electronic MMA welding process management system in Poland is Base Group. This system prepares the welding process instruction after the welding technology qualification protocol has been passed by the welding engineers. In addition, it also supports the assignment of work to welders. The software is equipped with a function, which checks whether a given welder has the necessary qualifications needed to weld a specific structure, and if not, the programme will not allow the assignment of a contractual task to this welder.
It is a solution that is used from the first stage of planning the welding work, through coordinating the welding of the structure, to the final stage - project reporting..
The aforementioned software technology includes all stock Base Group welding machines. By connecting all devices to the server, the plant can monitor the parameters of all workplaces. The automatic recording of parameters makes it possible to control and follow the workflow of employees.
Strengths of the welding management system
- Continuous monitoring of compliance against the WPS;
- continuously monitoring the welding process of the structure;
- reduced time for preparing documentation;
- independence of report results;
- improved resource management;
- meeting customer expectations;
- elimination of quality errors.
Questions and answers
Can we weld MMA outdoors?
Yes, welding with covered electrodes is possible when working outdoors, including underwater, in areas with complex access and field conditions.
How to prepare for welding?
The most essential items in a welder's kit are first and foremost a suitable protective apron, work shoes, gloves and a welding mask with filters to prevent the inhalation of escaping gases.