With the development and progress of technology, aluminum and its alloys are gradually replacing steel in many important fields, such as automobiles, high-speed rail, aircraft, ships, etc. Due to the obvious characteristics of aluminum and its alloys, aluminum and aluminum alloys will encounter many problems during welding and other processing, which also increases the overall ability requirements of our welding operators. Therefore, in order to better solve the common problems encountered by aluminum and aluminum alloys in welding processing, the editor has made a simple summary. Please let us know if there are any incomplete places.
Generally, welding aluminum and aluminum alloys use welding wires with the same or similar grades as the parent material, which can achieve better corrosion resistance; but when welding heat-treated aluminum alloys with a high tendency to thermal cracking, the selection of welding wires is mainly based on crack resistance. At this time, the composition of the welding wire is very different from that of the parent material.
Common defects (welding problems) and preventive measures
1. Burn-through
Causes:
a. Excessive heat input;
b. Improper groove processing, too large assembly gap of welded parts;
c. Too large spacing between welds during spot welding, resulting in large deformation during welding.
Preventive measures:
a. Appropriately reduce welding current and arc voltage, and increase welding speed;
b. Large blunt edge size, reduce root gap;
c. Appropriately reduce the spacing between welds during spot welding.
2. Porosity
Causes:
a. Oil, rust, dirt, and scale on the base material or welding wire;
b. Large air flow in the welding site is not conducive to gas protection;
c. The welding arc is too long, which reduces the gas protection effect;
d. The distance between the nozzle and the workpiece is too large, which reduces the gas protection effect;
e. Improper selection of welding parameters;
f. Porosity is generated at repeated arcing;
g. The purity of the protective gas is low and the gas protection effect is poor;
h. The humidity of the surrounding air is high.
Preventive measures:
a. Before welding, carefully clean the oil, dirt, rust, scale and oxide film on the surface of the welding wire and weldment, and use welding wire with a high deoxidizer content;
b. Choose a reasonable welding site;
c. Appropriately reduce the arc length;
d. Maintain a reasonable distance range 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 current, WeChat public account: Welding King, on the other hand, it also reduces the proportion of welding wire in the weld metal, which is effective in reducing porosity;
f. Try not to repeatedly start the arc at the same part. If you need to repeat the arc, grind or scrape the arc starting point; once a weld is started, try to weld it longer and do not break the arc at will to reduce the number of joints. There needs to be a certain weld overlap area at the joint;
g. Change the protective gas;
h. Check the airflow size;
i. Preheat the base material;
j. Check for air leakage and air pipe damage;
k. Weld when the air humidity is low, or use a heating system.
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3. Unstable arc
Causes:
Power cord connection, dirt or wind.
Preventive measures:
a. Check all conductive parts and keep the surface clean;
b. Remove dirt from the joints;
c. Try not to weld in places that can cause airflow turbulence.
4. Poor weld formation
Causes:
a. Improper selection of welding specifications;
b. Incorrect welding gun angle;
c. Unskilled welder;
d. Too large conductive nozzle aperture;
e. Water in welding wire, weldment and shielding gas.
Preventive measures:
a. Repeatedly debug and select appropriate welding specifications;
b. Maintain appropriate welding gun inclination;
c. Select appropriate conductive nozzle aperture;
d. Carefully clean welding wire and weldment before welding to ensure gas purity.
5. Incomplete penetration
Causes:
a. Welding speed is too fast and the arc is too long;
b. Improper groove processing and too small equipment gap;
c. Welding specification is too small;
d. Unstable welding current.
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 parent material;
d. Add a voltage-stabilized power supply device
e. Fine welding wire helps to increase the depth of penetration, and thick welding wire increases the amount of deposition, so it should be selected as appropriate.
6. Lack of fusion
Causes:
a. Oxide film or rust on the welding part is not cleaned up;
b. Insufficient heat input.
Preventive measures:
a. Clean the surface of the weld before welding
b. Increase welding current and arc voltage, and reduce welding speed;
c. For thick plates, use U-type joints, and generally do not use V-type joints.
7. Cracks
Causes:
a. Unreasonable structural design, too concentrated welds, resulting in excessive restraint stress in the weld joint;
b. The molten pool is too large, overheated, and the alloy elements are burned out;
c. The arc pit at the end of the weld cools quickly;
d. The composition of the welding wire does not match the base material;
e. The depth-to-width ratio of the weld is too large.
Preventive measures:
a. Correctly design the welding structure, arrange the welds reasonably, avoid the stress concentration area as much as possible, and choose the welding sequence reasonably;
b. Reduce the welding current or increase the welding speed appropriately;
c. Correctly operate the arc closure, add an arc starter plate or use a current attenuation device to fill the arc pit;
d. Select the welding wire correctly.
8. Slag inclusion
Causes:
a. Incomplete cleaning before welding;
b. Excessive welding current causes the conductive nozzle 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. When welding multiple passes, the welds should also be cleaned after each pass;
b. While ensuring full penetration, appropriately reduce the welding current. Do not press the conductive nozzle too low when welding with high current;
c. Appropriately reduce the welding speed, use welding wire with a higher deoxidizer content, and increase the arc voltage.
9. Undercut
Causes:
a. Welding current is too large and welding voltage is too high;
b. Welding speed is too fast and wire is too little;
c. Welding gun swings unevenly.
Preventive measures:
a. Properly adjust welding current and arc voltage;
b. Appropriately increase wire feeding speed or reduce welding speed;
c. Strive to make welding gun swing evenly.
10. Weld contamination
Causes:
a. Improper shielding gas coverage;
b. Unclean welding wire;
c. Unclean parent material.
Preventive measures:
a. Check whether the air hose is leaking, whether there is ventilation, whether the air nozzle is loose, and whether the shielding gas is used correctly;
b. Whether the welding material is stored correctly;
c. Before using other mechanical cleaning, remove oil and grease substances;
d. Remove oxides before using stainless steel brushes.
11. Poor wire feeding
Causes:
A. Sparking between the conductive nozzle and the welding wire;
b. Wear of welding wire;
c. Arc spraying;
d. The wire feeding hose is too long or too tight;
e. The wire feeding wheel is inappropriate or worn;
f. There are many burrs, scratches, dust and dirt on the surface of the welding material.
Preventive measures:
a. Reduce the tension of the wire feed wheel and use a slow start system;
b. Check all wire contact surfaces and minimize metal-to-metal contact surfaces;
c. Check the condition of the conductive nozzle and the wire feeding hose, and check the condition of the wire feeding wheel;
d. Check whether the diameter of the conductive nozzle matches;
e. Use wear-resistant materials to avoid truncation during wire feeding;
f. Check the wear of the wire reel;
g. Select the appropriate wire feed wheel size, shape and surface condition;
h. Select welding materials with good surface quality.
12. Poor arc starting
Causes:
a. Poor grounding;
b. Incorrect conductive nozzle size;
c. No shielding 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 space inside the conductive nozzle is blocked by metal materials;
c. Use gas pre-cleaning function;
d. Change welding parameters.
Post time: Dec-02-2024
