Argon Arc Welding: Principles, Characteristics, and Classification
This is what you want to “argon arc welding” operating skills knowledge detailed, good collection! Discover the principles, characteristics, and classification of argon arc welding, including preparation before welding and manipulation techniques. This welding method produces high-quality welds with minimal stress and deformation.
The principle of argon arc welding
Argon arc welding is the use of argon gas as a protective medium of an arc welding method. Argon gas is an inert gas, it is neither a chemical reaction with the metal to be welded metal oxidation, nor dissolved in liquid metal. Therefore, welding defects can be avoided and high-quality welds can be obtained.
In argon arc welding, the ionization potential of argon gas is high, so it is difficult to start the arc, so it is often used to generate high-frequency high-voltage electricity to start the arc. Due to the low heat dissipation capacity of argon, and thus once ignited, it can be more stable combustion.
The characteristics of the argon arc
(1) high quality of the weld, because argon is an inert gas, does not react chemically with the metal, alloying elements will not be burned, and argon does not melt in the metal, the welding process is basically the process of melting and crystallization of metal, therefore, the protection is better than the fruit, can obtain a more pure and high-quality weld
(2) welding deformation stress is small, because the arc by the argon gas flow compression and cooling effect, the arc heat concentration, and argon arc temperature is very high, so the heat-affected zone is small, so the welding stress and deformation is small, specially made for thin welding and pipe bottoming welding.
(3) Welding a wide range, almost all metal materials can be welded, especially suitable for welding the chemical composition of active metals and alloys.
The classification of argon arc welding
Argon arc welding according to the different electrode materials can be divided into tungsten argon arc welding (not melting pole) and melting pole argon arc welding. Its method of operation can be divided into manual, semi-automatic, and automatic argon arc welding. The power source can be divided into DC tig-arc welding, AC tig-arc welding, and pulse tig-arc welding.
Fourth, the preparation before welding
(1) read the welding process card, understand the material of the welded workpiece, the required equipment, tools, and related process parameters, including the selection of the correct welding machine, (such as welding aluminum alloy need to use AC welding machine), the correct choice of tungsten electrode and gas flow, first of all, from the welding process card to know the size of the welding current and other process parameters. Then choose the tungsten electrode (generally speaking, the diameter of 2.4mm is used more, and its current should range from 150A-250A, with the exception of aluminum). Then according to the diameter of the tungsten electrode to choose how big the nozzle is, the tungsten electrode diameter 2.5-3.5 times is the internal diameter of the nozzle D = (2.5-3.5) dw where D said nozzle diameter (mm), dw said tungsten electrode diameter (mm). Finally, according to the inner diameter of the nozzle selection of gas flow, the nozzle inner diameter of 0.8-1.2 times is the flow of gas. q = (0.8-1.2) D, where Q indicates the gas flow (L / min) tungsten pole Shen out the length must not exceed the diameter of its nozzle inner diameter, otherwise it is easy to produce air holes.
(2) Check whether the welding machine, gas supply system, water supply system, and grounding are intact.
(3) Check whether the workpiece is qualified:
1. whether there is oil, rust, and other dirt (the weld must be clean and dry within 20mm)
2. Whether the bevel angle, gap, and blunt edge are appropriate. Bevel angle, gap, then had a large welding volume, easy to produce weld tumor. The bevel angle is small, small gap, the blunt edge thick is easy to produce not fused, and welding is impermeable. Generally speaking, the bevel angle is 30-32 degrees, the gap is 0-4mm, and the blunt edge is 0-1mm.
3. The wrong side should not be too large, generally within 1mm.
4. Positioning welding length, points to meet the requirements, positioning welding itself to be free of defects.
5, argon arc welding manipulation: argon arc is a left and right-handed simultaneous action of the operation, and our usual life of the left hand to draw a circle right hand to draw the same square, so it is recommended that at the beginning of learning argon arc welding personnel for similar training, to learn argon arc welding has some help.
(1) wire feed: divided into internal and external filler wires.
External filler wire can be used for priming and filling, is a larger current, its wire head in the bevel front, left-hand pinch wire, constantly sent into the molten pool for welding, and its bevel gap requirements are small or no gap.
Its advantages are high productivity and easy-to-master operation skills because of the high current and small gap. The disadvantage is that it is easy to produce unfused and undesirable reverse side forming because the operator cannot see the blunt side melting and the reverse side residual height if it is used for bottoming.
The inner filler wire can only be used for bottoming welding, which is to use the left thumb, index finger, or middle finger with the wire feeding action, the pinky and ring finger to hold the wire to control the direction, the wire is close to the inner blunt edge of the bevel, melting with the blunt edge for welding, requiring the bevel gap to be larger than the wire diameter, and the wire can be bent into an arc if it is a plate.
Its advantages because the wire is on the opposite side of the bevel, you can clearly see the blunt edge and the melting of the wire, and the afterglow of the eye can also see the reverse residual height, so the weld is well fused, and the reverse residual height and unfused can be well controlled. The disadvantage is that the operation is difficult, requiring welders to have more skilled operating skills, because the gap is large, so there is a corresponding increase in the amount of welding, the gap is large so the current is low, and the efficiency of work is slower than the external filler wire.
(2) transport welding handle, divided into shaking handle and mop.
Shaking the welding nozzle is slightly pressed on the top of the weld, the arm shakes substantially for welding. Its advantages are because of the welding nozzle pressure on the weld, the welding handle in the running process is very stable, so the weld protection, good quality, the appearance of forming very beautiful, high product qualification rate, especially the welding back welding is very convenient, welding stainless steel, can get a very beautiful appearance of the color. The disadvantage is that it is difficult to learn, because of the arm shaking amplitude, so it is impossible to apply welding at the obstacle.
Mopping is the welding nozzle gently leaning or not leaning on the top of the weld, the right pinky or ring finger is also leaning or not leaning on the workpiece, and the arms swing is small, dragging the welding handle for welding. The advantage is easy to learn, and good adaptability, the disadvantage is that the shape and quality are not as good as the shaking handle, especially the back welding no shaking handle convenient welding, welding stainless steel is difficult to get the ideal color and shape.
(3) arc: the arc is generally introduced using the arc inducer (high-frequency oscillator or high-frequency pulse generator), the tungsten electrode and the weld does not contact the ignition arc, there is no arc inducer when using contact arc (more for site installation, especially high-altitude installation), available copper or graphite on the bevel of the weld to induce the arc, but this method is more troublesome, the use of less, generally with a light scratch of welding wire, so that the weld and tungsten electrode directly short-circuit and quickly disconnected and The arc is ignited.
(4) welding: after the arc ignition to the beginning of the weld preheat the place for 3-5 seconds and the formation of the molten pool after the start of wire feeding. When welding, the angle of the welding wire welding gun is to be appropriate, and wire feeding is to be uniform. Welding gun to move forward smoothly, swing left and right is a little slower on both sides, slightly faster in the middle. To pay close attention to changes in the molten pool, the molten pool becomes larger, the weld becomes wider or appears concave, to speed up the welding speed or re-adjust the welding current. When the molten pool is not fused well and the wire feed has the feeling of not being sent, to reduce the welding speed or increase the welding current, if it is bottoming welding gaze attention should be focused on the two sides of the bevel at the blunt edge, the afterglow of the corner of the eye in the opposite side of the seam, pay attention to the remaining high changes.
(5) arc: If the direct arc is easy to produce shrinkage holes, if the arc inducer torch to intermittent arc or adjusts to the appropriate arc current slow arc, such as no arc inducer welding machine is slow to lead the arc to the side of the bevel, do not produce shrinkage holes, such as shrinkage holes to be polished clean before welding.
If the arc is at the joint, the joint should be polished first into a bevel, to be fully melted at the joint, and then forward welding 10-20mm and then slowly close the arc, so as not to produce shrinkage holes. In production often see the joint is not polished into a bevel, directly lengthening the joint welding time for the joint, which is a very bad habit, so that the joint is easy to produce concave, the joint is not fused and the reverse side of the disconnect affects the formation of beautiful, such as high alloy materials are also easy to produce cracks.
After welding check the appearance of qualified, people go to turn off the power and gas.
Pipe welding technology is said to be able to weld into this level of experience for at least ten years, this technology must be convinced thick plate and steel welding process why argon arc welding priming? Senior welder welding knowledge 28 questions and answers to solve.