The choice of aluminum and aluminum alloy welding wire is mainly based on the type of base metal, comprehensive consideration of the joint crack resistance, mechanical properties and corrosion resistance requirements. Sometimes when an item becomes a major contradiction, the choice of welding wire will focus on solving this major problem, taking into account other requirements. Under normal circumstances, the welding aluminum and aluminum alloys are made of welding wire of the same or similar composition as the parent material, so that good corrosion resistance can be obtained; however, when the heat-treated aluminum alloy has a large heat cracking tendency, the selected welding wire is mainly from the solution. With crack resistance, the composition of the welding wire is very different from that of the base metal.

Common defects (welding problems) and preventive measures

1, burn through

cause:

a, heat input is too large;

b. Improper processing of the bevel and excessive assembly clearance of the weldment;

c. When the solder joints are separated by a large distance during solid welding, a large amount of deformation occurs during the welding process.

Preventive measures:

a、Appropriately reduce the welding current, arc voltage, and increase the welding speed;

b, large blunt edge size, reduce the root gap;

c. Properly reduce the solder joint spacing when soldering.

2, stomata

cause:

a. There is oil, rust, dirt, scale, etc. on the base metal or welding wire;

b. Large air flow at the welding site is not conducive to gas protection;

c. The welding arc is too long to reduce the gas protection effect;

d, the distance between the nozzle and the workpiece is too large, the gas protection effect is reduced;

e. Improper selection of welding parameters;

f, the occurrence of pores at repeated arcing;

g, the purity of the shielding gas is low, and the gas protection effect is poor;

h, the ambient air humidity.

Preventive measures:

a. Carefully clean the wire, the surface of the weldment, oil, dirt, rust, scale, and oxide film before welding. Use a wire with a high deoxidizer content.

b, a reasonable choice of welding sites;

c. Reduce the arc length appropriately;

d, to maintain a reasonable distance between the nozzle and the weldment;

e. Try to choose a thicker wire and increase the blunt edge thickness of the workpiece. On the one hand, it can allow the use of high current, and on the other hand, it also reduces the proportion of wire in the weld metal. This is effective for reducing the porosity. ;

f, try not to repeat the arc in the same site, need to repeat the starting arc arc to be polished or scraped off; once the weld arc welding as long as possible, do not arbitrarily broken arc to reduce the amount of joints, in There must be a certain weld overlap area at the joint;

g, change protective gas;

h, check the size of the air flow;

i, preheating the parent material;

j. Check for leaks and damage to the airways.

k. Welding when the air humidity is low, or using a heating system.

3, arc instability

Cause: The power cable is connected, dirt, or windy.

Preventive measures:

a. Check all conductive parts and keep the surface clean;

b. Remove the dirt from the joint;

c. Try not to weld where the airflow is disturbed.

4, poor weld formation

cause:

a. Improper selection of welding specifications;

b. The torch angle is not correct;

c. Welders are not skilled in operation;

d, the contact hole diameter is too large;

e, welding wire, weldment and protective gas contains moisture.

Preventive measures:

a, repeated debugging to select the appropriate welding specification;

b. Maintain proper torch inclination;

c, select the appropriate contact nozzle 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. The groove is not properly machined and the equipment clearance is too small;

c, welding specification is too small;

d, welding current instability.

Preventive measures:

a, appropriately slow down the welding speed, lower the arc;

b, appropriate to 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, increase the voltage regulator power supply device

e. The fine welding wire helps to increase the penetration, and the thicker welding wire increases the amount of deposition. It should be chosen as appropriate.

6, not fused

cause:

a. The oxide film or rust on the welding area is not removed;

b. Insufficient heat input.

Preventive measures:

a. Clean the surface to be welded before welding

b. Increase welding current, arc voltage, and reduce welding speed;

c. U-joints are used for thick plates, but V-joints are generally not used.

7, crack

cause:

a. The structure design is unreasonable and the welds are too concentrated, resulting in excessive stress on the welded joints;

b. The molten pool is too large, overheated, and alloy elements are burned.

c. The arc pit at the end of the weld cools quickly;

d, the wire composition does not match the parent material;

e, the aspect ratio of the weld is too large.

Preventive measures:

a. Correctly design the welding structure, rationally arrange the weld, make the weld as far as possible avoid the stress concentration area, and reasonably select the welding sequence;

b, reduce the welding current or increase the welding speed;

c. The arc-removal operation should be correct. Add the arc-striking plate or use the current attenuation device to fill the arc pit;

d, the correct choice of wire.

8, slag inclusion

cause:

a. Incomplete cleaning before welding;

b, welding current is too large, leading to the local melting of the nozzle into the molten pool to form slag;

c, welding speed is too fast.

Preventive measures:

a. Strengthen the pre-weld cleaning work. In multi-pass welding, the same weld must be cleaned after each weld.

b, in the case of ensuring penetration, the appropriate reduction in welding current, high current welding do not press too low pressure;

c. Properly reduce the welding speed. Use a higher wire containing deoxidizer to increase the arc voltage.

9, undercut

cause:

a, welding current is too high, welding voltage is too high;

b. The welding speed is too fast and the filling is too small;

c, uneven welding torch swing.

Preventive measures:

a、Adjust welding current and arc voltage properly;

b. Appropriately increase wire feed speed or reduce welding speed;

c, strive to uniform welding torch.

10, weld pollution

cause:

a. Inappropriate protective gas coverage;

b. The wire is dirty;

c. The base material is dirty.

Preventive measures:

a. Check whether the air supply hose is leaky, whether there is ventilation, whether the gas nozzle is loose, and whether the protection gas is used correctly.

b. Whether the welding material is stored correctly;

c. Before using other mechanical cleaning, first remove the oil and grease substances;

d. Remove the oxide before using the stainless steel brush.

11. Bad wire feeding

   cause:

A, conductive mouth and welding wire ignition;

b, welding wire wear;

c, spray arc;

d, feed hose is too long or too tight;

e. Inappropriate or worn wire feed wheel;

f, welding material surface burr, scratches, dust and dirt more.

Preventive measures:

a. Reduce the tension of the wire feed roller and use the slow start system;

b. Inspect all welding wire contact surfaces and minimize metal-to-metal contact surfaces.

c. Check the condition of the contact nozzle and the situation of the wire feeding hose and check the condition of the wire feed wheel;

d. Check whether the diameter of the contact nozzle matches.

e, the use of wear-resistant materials to avoid the cutting process in the wire feeding;

f, check the wire disc wear condition;

g. Select the appropriate wire size, shape and suitable surface conditions;

h. Select welding materials with good surface quality.

12, bad arcing

cause:

a, bad grounding;

b, the size of the contact nozzle is not correct;

c. No protective gas.

Preventive measures:

a. Check whether all grounding conditions are good, use slow start or hot arc starting mode to facilitate arcing;

b. Check whether the air in the contact nozzle is blocked by metal material.

c. Use gas pre-cleaning function;

d, change the welding parameters.