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The welding electrode can be greatly improved, the welding depth is high, the welding wire is melting fast, the production efficiency is quite high, such as the large thickness aluminum plate manufacturing structure, the use of MIG melting electrode welding for double-sided welding Butt welding, full thickness of the penetration, easy to get high-quality weld.
First, the nature of aluminum
1. Thermal conductivity, heat capacity (about 3 to 4 times the steel).
2. Linear expansion coefficient (about 2 times the steel).
3. Low melting point (660 ℃) The alloy is lower (aluminum alloy series is 595 ℃, aluminum and zinc series is 475 ℃).
4. Liquid and solid colorless changes.
5. Aluminum alloy in the manganese, magnesium, zinc and so easy to evaporate at high temperatures.
6. High conductivity, especially in the resistance welding, the power needs of welding steel than high.
7. At room temperature, the surface and the air to form a layer of dense oxide film (AI2O3), the melting point of 2050 ℃, the oxide film can absorb a lot of water, and the formation of pores, easily lead to slag, (due to the proportion of oxide film and aluminum close)
8. Hydrogen in the liquid and solid solution ratio of aluminum is about 20 (so if the hydrogen content in the welding atmosphere is too high will easily produce pores) so in the gas metal arc welding, the weld cooling rate too fast, hydrogen is not easy And the stomatal tendency is less than that of the gas metal arc welding when the tungsten gas is arc welded.
Second, welding materials
Most of the aluminum material can be welded with gas metal arc welding or tungsten gas arc welding, different welding materials used as follows:
Pure aluminum wire 301
Aluminum and manganese alloy wire 321
Aluminum-magnesium alloy wire 331
Al - Si alloy wire
According to the welding workpiece material grades, use the same wire material grades for welding, you can get excellent welding quality
Third, the preparation before welding:
1. Work parts clean, welding parts must be polished to remove the oxide film, can be installed with grinding wheel or stainless steel wire wheel grinding edge of the welding site, about 10 ~ 15mm range, until the smooth metal so far.
2. To ensure wire stability, reduce wire resistance, welding is a key issue of stability.
① welding wire than the use of polytetrafluoroethylene nylon hose, so that smooth wire feed, and a certain degree of wear resistance.
② The wire feeder adopts the double drive wheel to feed the wire, and the wire tube must be arranged (the front drive wheel and the Torch joint). The center of the tube is aligned with the wire feed wheel, and the cutting point is fixed on the wire feed wheel. Can overcome the phenomenon of wire bending).
③ using U-shaped wire to send wire, a little pressure can be.
④ automatic welding machine, should use the straight gun, to reduce the welding gun R angle wire resistance.
⑤ As the aluminum wire conductivity is good, the use of welding wire 1.2mm should use 1.6mm conductive Tsui, (with chromium zirconium copper conductive Tsui).
⑥ protective gas using inert gas argon, in order to protect the effect is good, should be pure argon 99.99% gas, can also be used mixed gas protection.
A. Argon + (1 ~ 3)% carbon dioxide, can simplify the wire and weldment surface cleaning, and no pores, strength and plastic good weld, weld appearance smooth and smooth.
B. Argon + 2% oxygen, especially for the removal of pores.
Fourth, welding specifications:
1. DC reverse polarity connection, that is, the workpiece then "a" pole, welding gun then "ten" pole, cathode crushing area.
2. Can choose a lower arc voltage, the use of "sub-jet transition" welding, welding process issued a slight "flap" sound, this time the welding process is stable, weld deep penetration, weld appearance.
3. Welding thicker parts can also be used "jet transition" welding
Wire diameter 1.2mm, welding current 250 ~ 280A,
Arc voltage 22 ~ 24V, gas flow: 25 ~ 28 liters / min
4. According to the different thickness of the workpiece specific welding specifications as shown in Table:
Different thickness of the workpiece selection of different wire diameter, air flow is also different, that is, the thicker the board, the greater the wire diameter, the higher the welding efficiency, the greater the gas flow.
Note: should be configured 50 liters / sub-flow meter when the thickness of 10mm or more should consider grinding with a grinder V-groove, groove depth of about 3 ~ 4mm can be welded
Fifth, welding operation technology:
1. The length of the lead wire is 10 ~ 15mm from the workpiece, and the arc welding is carried out at the welding spot
2. Left welding method, from left to right welding, welding gun and the workpiece after the angle of 70 ~ 80 ° to keep the distance, keep the angle, uniform speed welding.
3. Vertical welding can be under the welding method and the upper welding method.
4. Aluminum welding speed faster, when the gas flow is impure or the flow of small welds and black hair on both sides of the black phenomenon, this time should increase the gas flow, or slow down the welding speed, the weld when the silver-white, And on both sides have a bright gas protection line.
5. Workpiece welding should be carried out before the ventilation treatment.
6. Welding gun hose bending, welding, the bending diameter should be> 1.5 m to keep the hose smooth wire.
7. Welding parts shall not blow the wind when the wind is too large, should be added to the plate for welding.
8. Feeder should always move the different types of welding position, to keep the wire smooth.
9. Welding should be carried out before the standard debugging, simulation process board can be used, accurate debugging, before welding.
10. After the work is completed every day, should be closed cylinder machine and shutdown, the remaining aluminum wire application plastic bag wrap, to prevent oxidation.
11. The nozzle should be cleaned for a certain period of time, remove the splash adhesion, keep the ventilation smooth
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