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Aluminum alloy welding process parts common defects and prevent solutions

Aluminum welding common defects and solutions
When aluminum MIG welding, weld joints common weld defects are mainly poor, cracks, holes, burn, incomplete penetration, lack of fusion, slag and so on.
First, poor weld
Mainly in poor weld seam ripples pretty, not bright; weld bent not straight, varies in width, the joint too much; weld central projection, both sides of the flat or depressed; weld overflowing like.
1. Causes
1) improper selection of welding specifications; 2) the torch angle is not correct;
3) operating unskilled welders; 4) the contact tip aperture too;
5) the welding arc is not strictly aligned groove centers; 6) wire, weldment and protective gas contains moisture;
2. Preventive Measures
1) repeated testing to select appropriate welding specifications; 2) holding the gun right angle;
3) to strengthen welding skills training; 4) Select the appropriate contact tip diameter;
5) strive to make the welding arc and groove strictly; and 6) carefully clean before welding wire, welding pieces; to ensure the protection of the purity of the gas.
Second, crack
Aluminum and aluminum alloy weld cracks are generated in the weld metal crystallization process, known as thermal cracking, known as solidification cracking. In the form of longitudinal cracks, transverse cracks (often extend to the base metal), as well as the roots of the crack, crater cracks and so on. Cracks will reduce structural strength, or even cause a sudden destruction of the whole structure, and therefore is totally not allowed.
1. Causes
1) aspect ratio weld gap is too large; crater cooled fast 2) the end of the weld;
3) wire component and the base material does not match; 4) technique is incorrect.
2. Preventive Measures
1) an appropriate increase or decrease arc voltage welding current is reduced to widen the weld penetration depth;
2) properly fill the crater and attenuating measures to reduce the cooling rate;
3) to ensure reasonable match wire and the base material;
4) Select the appropriate welding parameters, welding sequence, an appropriate increase in welding speed, we need to preheat preheat the measures to be taken.
Third, the stomata
MIG welding of aluminum and aluminum alloys, the pores are the most common type of defect. To completely remove weld porosity is difficult, not only to minimize its content. According to their type, aluminum weld porosity major surface porosity, pore diffusion, partial stomatal density, single large pores, roots chain holes, cylindrical holes and other. It will not only reduce the porosity of the weld compactness, reduced bearing area of ​​the joint, but also the strength of the joint, the plastic lower, especially cold bend and impact toughness decreases more, must be prevented.
1. Causes
1) gas is bad, impure gas protection;
2) wire, solder member is contaminated;
3) the atmosphere of absolute humidity is too large;
4) an arc of instability, the arc is too long;
5) wire extension length is too long, the distance between the nozzle and the weldment is too large;
6) in the form of wire diameter and groove poor choice; 7) Repeat arcing, a few too many joints at the same site.
2. Preventive Measures
1) to ensure the gas quality, due to increase shielding gas flow, to exclude all of the air in the welding zone, to eliminate the gas nozzle spatter, the protective gas flow uniform, the air flow must have measures to prevent the weld zone, to prevent air intrusion pads, shielding gas flow rate too large, should be appropriate to reduce traffic proper;
2) Carefully clean up before welding wire, surface oil, dirt, rust, dirt and oxide film weldment, using wire containing higher Deoxidizer;
3) a reasonable choice of welding place;
4) appropriate to reduce the arc length;
5) to maintain a reasonable distance between the nozzle and the weldment;
6) Try to choose a thicker wire, while increasing the thickness of the workpiece blunt edge groove, one can permit allows the use of a large current, also makes the weld metal wire proportional decline, which reduce the porosity is effective;
7) Do not repeat the same site from the arc, the wife repeated arcing To arcing at grinding or scraping clean up; a weld once the welding arc to try longer, do not arbitrarily broken arc, in order to reduce the amount of joints , in the joints need to have some welds the overlapping area.
Fourth, burn
1. Causes
1) excessive heat input; improper 2) beveling, weldment assembly gap is too large;
3) tack welding pad spacing is too large, resulting in a large amount of deformation during the welding process; operating position is incorrect.
3. Preventive Measures
1) appropriate to reduce the welding current, arc voltage, welding speed;
2) increase the blunt edge size, reduced root gap;
3) tack welding when properly reduced spot pitch;
4) welding process, holding the gun position to the right, the operation to be skilled.
Fifth, the lack of penetration
1. Causes
1) the welding speed is too fast, the arc is too long;
2) beveling improper assembly gap is too small;
3) Welding technology lower operating position to grasp improper;
4) welding specification is too small;
5) the welding current unstable.
2. Preventive Measures
1) The appropriate welding speed slows down, down arc; 2) appropriate to reduce or increase the blunt edge clearance;
3) the torch angle to ensure maximum penetration welding, arc weld pool remains at the forefront, have the correct posture;
4) Increase welding current and arc voltage to guarantee adequate base material to obtain the amount of heat input;
5) increasing the power supply unit or avoid open peak.
Sixth, lack of fusion
1. Causes
1) oxide or rust welding parts are not cleaned; 2) heat input inadequate; inappropriate 3) welding technique.
2. Preventive Measures
1) Carefully clean the surface prior to welding to be welded at;
2) increase the welding current increase, the arc voltage, welding speed reducer small;
3) To use a little strip welding operation mode, the groove surface of a momentary stop, the wire in the forefront of the bath to improve welder technology.
Seven, slag
1. Causes
1) before welding is not completely clear;
2) the welding current is too large, resulting in electrical mouth partially melted to form a mixed slag bath;
3) the welding speed is too high.
2. Preventive Measures
1) to strengthen cleanup before welding, multi-pass welding, each weld together the same should be finished weld clean-up;
2) In the case of penetration assurance, appropriate to reduce the welding current, high current welding contact tip not kept too low;
3) appropriate to reduce speed, use of higher oxygen scavenger-containing wire, increase the arc voltage.

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