Manual Tungsten Inert Gas Welding by The Rules

1. Preparatory work
(1) be familiar with the pattern and process planning, master of the location, size and requirements of the welding, a reasonable choice of welding method and order.
(2) clean up the workplace, aids and protective equipment.
(3) Check the equipment. The adjusting mechanism on the welder, wire, cable and grounding is good; handle insulation is good, the ground wire and the workpiece connection is reliable; by sea, air, road is smooth; high frequency or pulsed arc initiation and stability whether good.
(4) Check the workpiece. Slag, dirt, grease, sand and other objects may not exist in the groove weld both sides of the 20mm range, not oil, rust, welding wire for degreasing rust.
(5) do not place in the outlet or forced ventilation welding.
(6) According to the process documentation and product design requirements, the correct choice of welding wire.

2. Security technology
(1) the wearing of personal protective equipment, work in well-ventilated environment, the workplace to prevent humid and filled with water, is strictly prohibited stacked flammable liquids.
(2) of the workpiece must be reliably grounded when welding with DC power, attention to reducing the operating time of the high-frequency electric arc to cut off the high frequency power supply.
(3) welding must use compressed air to the water in the entire waterway system blowing, in order to avoid frozen pipes.
(4) grinding tungsten to wear gloves and masks.

3. Process parameter selection
Gas tungsten arc welding process parameters are mainly the type and polarity of the welding current, welding current, tungsten diameter and shape of the ends to protect the gas flow.
(1) Welding current type and size generally select the current type of workpiece material. The size of the welding current is the most important parameters to determine the weld penetration depth, it is mainly based on workpiece material, thickness, joint type, welding position to choose, and sometimes also consider the factors of welders technical level (manual welding).
(2) The shape of the tungsten diameter and ends tungsten electrode diameter according to the welding current size of the current polarity selection (see Table 3-14).
Tungsten extreme head shape is an important process parameters. According to the type of welding current is used, the choice of a different shape of the ends, as shown in Figure 3-11 shows, the state-of-the-art point of view. The size of the tungsten allowable current, arc starting and arc stability, Table 3-15 lists the recommended current range of state-of-the-art size tungsten different.
(3) gas flow rate and nozzle diameter welding quality depends largely on the protective effect of argon. Under certain conditions, the gas flow rate and nozzle diameter of one of the best range, at this time, gas protection is best, effective protected areas. Table 3-16 shows the welding current and nozzle diameter, gas flow relationship.
Argon protective effect of the assessment is mainly based on the color of the weld surface. Welding the protective effect of surface color and gas are shown in Table 3-17.

4. Operating techniques
TIG operating techniques, including arc, filler wire welding, the closing arc process.
(1) arc
① short circuit arc method (contact arc method), tungsten, weldments instantaneous short-circuit, immediately a little mention, the arc between the weldment and tungsten;
② frequency arc method, the use of high-frequency arc starter ordinary frequency alternating current (220V or 380V, 50Hz) to convert the high-frequency (150 ~ a 260kHz), high pressure (2000 ~ 3000V), the argon gas breakdown ionizing , in order to ignite the arc.
(2) closing arc
(1) increase the welding speed method, welding torch, welding will be terminated gradually increase the speed of mobile;
(2) current decay welding termination, stop the filler wire welding current is gradually reduced, so that the molten pool size is shrinking, the last power outage, the welding gun or torch to stop walking.
(3) filler wire welding with filler wire must wait before they can fill in the parent metal melted fully added in order to avoid lack of fusion, filling the position to fill the bath cutting-edge site, and wire to recover, try not to immediately out of the argon gas protected areas.

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