Saturday, November 26, 2022

How to weld with MIG/MAG?

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One of the attractions of MIG/MAG welding (Arc Welding with Inert/Active Shielding Gas, respectively) is the ease of learning it. With a little instruction, virtually anyone can weld using MIG/MAG after a few hours of practice. In fact, the more you practice, the easier it will be and the better your welds will be. However, before we get too confident in our welds, it is convenient that we cut a cord What have we done to check the penetration and other features that will tell us if the weld is as strong as it looks.

The great advantage of the process MIG/MAG is that the gun welding it can be operated with one hand, allowing the other hand to be used to stabilize the primary hand and draw an even bead. Also the gun remains the same distance from the weld at all times, unlike in arc welding where the rod gets shorter and shorter. The MIG/MAG welding It also doesn’t require us to stop to change electrodes, so we can concentrate very well on what we’re doing.

To set up our team MIG/MAG and start welding efficiently, the first step is to read all the instructions and precautions included in the corresponding user manual. We recommend that you briefly review the components of a MIG/MAG welding equipment, in order to be clear about what we should do.

Once we are familiar with the components of our equipment and have chosen the type of gas and the type of wire to use, we will pay special attention to a series of key parameters that we must adjust to obtain a quality weld. These parameters are:

  • Amperage: controls heat input, weld size and penetration depth.
  • Arc voltage: controls the profile of the weld.
  • Wire feed speed: controls the welding intensity.
  • Wire diameter: It depends on its feed rate, the current intensity, the protective gas and the material to be welded.

We must also take into account the shielding gas flow rate (depends on the material and the wire used), the length of the free end of the wire and the welding speed.

The set-up of all these parameters is carried out following the manufacturer’s instructions and there are also tables in specialized welding manuals. In addition, constant practice teaches a lot. Once we have adjusted these parameters, we are ready to start the process. For it:

  1. We connect the nozzle selected and the nozzle to gun.
  2. We install the wire roll and regulate the wire feed speed.
  3. We press the trigger of the gun until approx. 6mm nozzle wire. If it protrudes more, we cut the excess with a pliers.
  4. We open the shielding gas cylinder and press the trigger of the gun again to purge the air from the hoses and adjust the flowmeter to the desired flow value.
  5. We graduate the voltage and the current of the team, according to type and thickness of metal to unite
  6. we bait the bow, using the scratch or scrape method. For extinguish the arc, we separate the gun from the metal or we release the trigger and press it again. If the wire sticks to the metal, we release the trigger and cut the wire with pliers.
  7. For lay down a cord, we must heat the metal forming an incandescent zone and then move the gun along the Council, maintaining a uniform speed to achieve a smooth and even weld.

Steps 1 and 2 are essential for the proper functioning of the equipment. It is very common that in MIG/MAG welding the operator forgets to change the nozzles and/or the wires and rollers from one weld to another, and this translates into poor quality of the welds obtained and damage to the equipment.

The wire feed speed it is also very important to get a good weld with the right heat and penetration. Speed ​​adjustment is not complicated. You simply have to listen to the sound that the equipment is making while a straight cord is deposited. If the speed is too fast, most of the wire coming out of the nozzle will be red hot and there will be a loud crackling sound. Therefore, gradually adjust the speed until you get a constant crackling sound.

Types of union or joint and types of welding

exist different types of Union Y different types of welding, completely independent of each other, which can be realized by MIG/MAG welding. They also vary the gun position, just like him displacement and the movements that it describes along the workpiece. Each variable responds to type and thickness of the metal to be welded, the nozzle and nozzle diameter, the distance from nozzle to workpiece and many other factors.

The table below summarizes the main types of joints and welds used in MIG/MAG. within the type of bevel weld (or chamfer or slot) the different types of bevel used are outlined (from top to bottom in the table): single, double, in “U”, in “V”, in “X”, in “J” and in square.

Types of weld joint

gun position

The most recommended is horizontal position or almost horizontal, since it allows a better control of the puddle, smooth and good looking beads can be obtained and optimizes the action of the shielding gas on the puddle. However, there are cases in which it is convenient to weld on parts inclined by 10 or 20 degrees. If so, the welding is done in descending. With this method, flatter seams are achieved and the welding speed is increased.

Gun offset and movement

In the MIG/MAG welding there are two ways of displacement of the gun:

  • To the left: the movement of the gun goes from right to left
  • To right: the movement of the gun goes from left to right

These variables depend on the material and the thickness of the part to be welded. For welding steel or similar metals the direction of welding is not relevant, but for welding aluminum the “left” method should be used.

The following table shows the characteristics and main applications of each displacement Y movement of the gun.

FEATURES AND MAIN APPLICATIONS OF DISPLACEMENT AND MOVEMENT

FEATURES AND MAIN APPLICATIONS OF DISPLACEMENT AND MOVEMENT

Once again, depending on the metal to be welded and the thickness, there are three filler metal transfer types, already listed opportunely:

  • Short Circuit Transfer: in this case the voltage and amperage are at their lowest value. This technique is used with small diameter wires to weld thin plates with root passes.
  • Globe transfer: the wire melts and the globules fall into the puddle. This technique is suitable for welding thick plates and filler layers.
  • Transfer by spray or spray: in this case the voltage and amperage are increased. The technique is used under inert gas and is suitable for welding stainless steel.

As seen, in MIG/MAG welding There are a large number of variables to take into account and experience will teach us to know them and manage them according to our needs, until we reach a good degree of perfection.

It is reasonable to assume that they may arise drawbacks not only during the welding process, but also weld defects obtained. In addition, we need to perform a simple MIG/MAG equipment maintenance To avoid many of these inconveniences and, it goes without saying, throughout the operation we will have to have protective gear appropriate and observe the corresponding security measures to prevent serious personal injury. In future articles we will detail all these topics.

It is time to choose, how to know which is the best model? Follow the recommendations of the experts in this technical article on MIG MAG welding

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