used for welding of galvanized steel metal core wire at full speed
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: 2017-01-04 17:58:24 591time to browse
galvanized steel surface with zinc oxide layer, so even very thin, also can achieve excellent corrosion resistance and high strength. however, these features for need welding galvanized steel, metal forming, is also a great challenge. for example, the easier the thinner galvanized steel material, welding wear if welding method with fault, the zinc oxide coating is also likely to cause weld defects.
many auto parts suppliers using 1.6 mm ~ 4 mm galvanized steel, manufacturing like motor shell frame, suspension, engine tray link parts, and even in other parts of the car using thinner galvanized steel material. in fact, in the car saw thin only 0.7 mm galvanized steel is also quite common.
the vast majority of manufacturers using three kinds of galvanized steel, hot dip plating, zinc and iron or electric galvanized. among them, the biggest challenge on welding hot dip galvanized steel material, but because of lower cost, is also the most common car industry application.
hot dip plating thickness of the material surface uneven, often in order to achieve consistent soldering effect, particularly challenging. after the zinc oxide polishing, even under the condition of high temperature (over 800 degrees fahrenheit), can also go beyond the melting point of zinc and other zinc chemistry challenge. strength of the surface of the zinc oxide can be used as the anode, provide material corrosion protective barrier.
the vast majority of manufacturers using gas metal arc welding (abbreviated as gmaw) technology in welding of galvanized steel, using pulse or constant voltage (abbreviated cv) solid welding wire. however, in pulse and cv during the welding process can be difficult to achieve perfect effect, with similar speed when the welding low carbon steel welding, on the galvanized steel is difficult to achieve consistent weld quality.
in the cv welding, arc length is shorter, so often produce "splash" this trouble problem. there is a bigger problem: the pore. under the current welding speed, it will directly affect the welding effect. and, on the hot dip galvanized steel sheet welding speed faster, the easier it is to freeze the molten pool. this particularly troublesome, for zinc evaporation temperature is much lower than steel. this kind of different evaporation temperature gas package will likely be fixed - somewhere in front of the weld solidification, the zinc vapor would have a chance to run out.
pore, a packet may vein, may also show across the entire welding material on the surface of the welding heads (commonly referred to as "pipe" or "bug"). although we can accept many pore hidden under the surface of the welding results, but because they may be in a straight line shape, working in a continuous cycle, it is possible to lead to welding of fracture.
in order to ensure the welding quality, at least should be greater than its diameter, the distance between each pore. on the weld length of 25 mm, the entire length of the pore diameter (combined) should not be more than 6.4 mm, between the pore diameter should not be more than 1.6 mm, welding in the area of pore is usually not more than 25%.
continue to seek technical solutions
in order to avoid pore, when the welding galvanized steel metal forming, often can directly reduce the welding speed, from the angle of quality is good, but for the production efficiency, limitations is too big. actually, can consider the existing pulse melting polar gas shielded arc welding and the metal wire together, instead of solid core wire method.
metal core wire is tubular - in metal sheath is full of metal powder, alloy and arc stabilizer. with solid core wire is opposite, metal core wire with high current density (under the equivalent current set), can improve the weld deposit rates. because the metal core welding wire is allowed at a rapid speed welding, so usually can be applied to the robot welding process.
recently, the metal core welding line appeared some new progress, especially those who perform the american welding society (abbreviated as aws) e70c - gs class standard of manufacturer, on hot dip galvanized steel sheet welding developed many new advantages. the welding line formula ingredients, to get them to respond to direct the butt welding between (dc pick up negative).
directly on the galvanized steel butt welding, can produce two obvious advantages:
soft arc penetration, helps to prevent burn through the thin material, improve the seepage situation (pictured);
pieces have sufficient arc evaporation galvanized coating. for zinc vapor enough time from the welding pool, try to reduce the possibility of welding surface and the lower part of the porosity.
metal core wire can also have the effect of stable arc, is helpful to improve the effect of the metal welding, minimize splash and clean up after welding.
control to freeze
the use of metal wire with pulsed gmaw waveform, also help to control the speed of the welding pool is frozen, make it easier for zinc vapor released out. in addition, the pulse gmaw process less heat than standard cv process need, help to avoid burning through.
when the welding of galvanized steel, the metal wire combined with a pulsed gmaw process and other benefits, such as:
mixer improved welding tee joint and go down;
pieces of metal welding using fine ball, can produce an arc, achieve good weld bridge function.
in pieces to welding of different thickness materials (from 1.2 mm to 4.0 mm);
welding ability in pieces in multiple locations.