The selection of aluminum and aluminum alloy welding wire is mainly based on the type of base metal, and the requirements for joint crack resistance, mechanical properties and corrosion resistance are comprehensively considered. Sometimes when a certain item becomes the main contradiction, the selection of welding wire should focus on solving this main contradiction, taking into account other requirements
In general, welding wires with the same or similar grades as the parent metal are used for welding aluminum and aluminum alloys, so that better corrosion resistance can be obtained; but when welding heat-treated aluminum alloys with a high tendency to hot cracking, the selection of welding wires is mainly from the solution Starting with crack resistance, the composition of the welding wire is very different from the base metal.
Common defects (welding problems) and preventive measures
1. Burn through
cause:
a. Excessive heat input;
b. Improper groove processing and excessive assembly clearance of weldments;
c. The distance between the solder joints is too large during spot welding, which will cause a large amount of deformation during the welding process.
Preventive measures:
a. Appropriately reduce the welding current and arc voltage, and increase the welding speed;
b. Large blunt edge size reduces root gap;
c. Appropriately reduce the spacing of solder joints during spot welding.
2. Stomata
cause:
a. There is oil, rust, dirt, dirt, etc. on the base metal or welding wire;
b. The air flow in the welding site is large, which is not conducive to gas protection;
c. The welding arc is too long, which reduces the effect of gas protection;
d. The distance between the nozzle and the workpiece is too large, and the gas protection effect is reduced;
e. Improper selection of welding parameters;
f. Air holes are generated at the place where the arc is repeated;
g. The purity of the protective gas is low, and the gas protection effect is poor;
h. The ambient air humidity is high.
Preventive measures:
a. Carefully clean the oil, dirt, rust, scale and oxide film on the surface of welding wire and weldment before welding, and use welding wire with higher deoxidizer content;
b. Reasonable selection of welding places;
c. Appropriately reduce the arc length;
d. Keep a reasonable distance between the nozzle and the weldment;
e. Try to choose a thicker welding wire, and increase the blunt edge thickness of the workpiece groove. On the one hand, it can allow the use of large currents. On the other hand, it can also reduce the proportion of welding wire in the weld metal, which is beneficial to reduce Porosity is proven;
f. Try not to repeat arc strikes at the same position. When repeated arc strikes are required, the arc strike point should be polished or scraped off; once a weld seam has arc strike, try to weld as long as possible, and do not break the arc at will to reduce the amount of joints. There needs to be a certain overlapping area of the weld seam at the joint;
g. Change the protective gas;
h. Check the size of the airflow;
i. Preheating base metal;
j. Check whether there is air leakage and damage to the trachea;
k. Weld when the air humidity is low, or use a heating system.
3. The arc is unstable
cause:
Power cord connection, dirt, or wind.
Preventive measures:
a. Check all conductive parts and keep the surface clean;
b. Remove the dirt from the joint;
c. Try not to weld in places that can cause airflow disturbance.
4. Poor weld formation
cause:
a. Improper selection of welding specifications;
b. The angle of the welding torch is incorrect;
c. Welders are not skilled in operation;
d. The aperture of the contact tip is too large;
e. Welding wire, welding parts and shielding gas contain moisture.
Preventive measures:
a. Repeated debugging to select the appropriate welding specification;
b. Maintain an appropriate inclination angle of the welding torch;
c. Select the appropriate contact tip aperture;
d. Carefully clean the welding wire and weldment before welding to ensure the purity of the gas.
5. Incomplete penetration
cause:
a. The welding speed is too fast and the arc is too long;
b. Improper groove processing and too small equipment clearance;
c. The welding specification is too small;
d. The welding current is unstable.
Preventive measures:
a. Appropriately slow down the welding speed and lower the arc;
b. Appropriately reduce the blunt edge or increase the root gap;
c. Increase the welding current and arc voltage to ensure sufficient heat input energy for the base metal;
d. Add a stabilized power supply device
e. Thin welding wire helps to increase the penetration depth, and thick welding wire increases the deposition amount, so it should be selected as appropriate.
6. Not fused
cause:
a. The oxide film or rust on the welding part is not cleaned;
b. Insufficient heat input.
Preventive measures:
a. Clean the surface to be welded before welding
b. Increase the welding current and arc voltage, and reduce the welding speed;
c. U-shaped joints are used for thick plates, but V-shaped joints are generally not used.
7. Crack
cause:
a. The structural design is unreasonable, and the welds are too concentrated, resulting in excessive restraint stress of the welded joints;
b. The molten pool is too large, overheated, and the alloying elements are burned;
c. The arc crater at the end of the weld is cooled quickly;
d. The welding wire composition does not match the base metal;
e. The depth-to-width ratio of the weld is too large.
Preventive measures:
a. Correctly design the welding structure, arrange the welds reasonably, make the welds avoid the stress concentration area as far as possible, and choose the welding sequence reasonably;
b. Reduce the welding current or increase the welding speed appropriately;
c. The arc crater operation must be correct, adding an arc strike plate or using a current attenuation device to fill up the arc crater;
d. Correct selection of welding wire.
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8. Slag inclusion
cause:
a. Incomplete cleaning before welding;
b. Excessive welding current causes the contact tip to partially melt and mix into the molten pool to form slag inclusions;
c. The welding speed is too fast.
Preventive measures:
a. Strengthen the cleaning work before welding. During multi-pass welding, the weld seam cleaning must also be carried out after each welding pass;
b. In the case of ensuring penetration, reduce the welding current appropriately, and do not press the contact tip too low when welding with high current;
c. Properly reduce the welding speed, use welding wire with higher deoxidizer content, and increase the arc voltage.
9. Undercut
cause:
a. The welding current is too large and the welding voltage is too high;
b. The welding speed is too fast and the filling wire is too little;
c. The torch swings unevenly.
Preventive measures:
a. Properly adjust the welding current and arc voltage;
b. Appropriately increase the wire feeding speed or reduce the welding speed;
c. Make every effort to swing the torch evenly.
10. Weld pollution
cause:
a. Improper protective gas coverage;
b. The welding wire is not clean;
c. The base material is unclean.
Preventive measures:
a. Check whether the air supply hose is leaking, whether there is draft, whether the gas nozzle is loose, and whether the protective gas is used correctly;
b. Whether the welding materials are stored correctly;
c. Remove oil and grease before using other mechanical cleaning methods;
d. Remove the oxide before using a stainless steel brush.
11. Poor wire feeding
cause:
A. The contact tip and the welding wire are ignited;
b. Welding wire wear;
c. Spray arc;
d. The wire feeding hose is too long or too tight;
e. The wire feed wheel is improper or worn;
f. There are many burrs, scratches, dust and dirt on the surface of welding materials.
Preventive measures:
a. Reduce the tension of the wire feed roller and use the slow start system;
b. Check the contact surface of all welding wires and minimize the metal-to-metal contact surface;
c. Check the condition of the contact tip and the wire feeding hose, and check the condition of the wire feeding wheel;
d. Check whether the diameter of the contact tip matches;
e. Use wear-resistant materials to avoid truncation during wire feeding;
f. Check the wear condition of the wire reel;
g. Select the appropriate size, shape and surface condition of the wire feed wheel;
h. Select welding materials with better surface quality.
12. Poor arc starting
cause:
a. Poor grounding;
b. The size of the contact tip is wrong;
c. There is no protective gas.
Preventive measures:
a. Check whether all grounding conditions are good, and use slow start or hot arc starting to facilitate arc starting;
b. Check whether the inner space of the contact tip is blocked by metal materials;
c. Use the gas pre-cleaning function;
d. Change the welding parameters.
Post time: Jun-21-2023
