Electric heating – Metal heating – By arc
Patent
1991-12-13
1996-04-16
Shaw, Clifford C.
Electric heating
Metal heating
By arc
B23K 909
Patent
active
055084931
DESCRIPTION:
BRIEF SUMMARY
FIELD OF ART
The present invention relates to a method and apparatus for pulse MAG arc welding which can obtain a welding bead having a regular waveform appearance or showing an appropriate cross-sectional shape
BACKGROUND OF THE ART
In the recent years, aluminum and aluminum alloy (referred to an aluminum herein after) have been used widely for interior materials of buildings, various vehicles and transportation machines. Welded joints of these aluminum used in the above fields form directly an outside appearance and hence are required to have a beautiful appearance of the welding beads in addition to a sufficient mechanical strength. As an arc welding method showing a beautiful appearance of welding beads, a widely used method is a TIG arc welding method having a filler wire added thereto. The welded joint obtained with a TIG arc welding having the filler wire added thereto (referred to a TIG filler arc welding method hereinafter) shows a bead appearance in regular wave form (referred to a scale bead hereinafter) as shown in FIG. 1. The welding bead according to the TIG filler arc welding method has an appearance more beautiful than that of the MIG arc welding method.
The TIG arc welding method is lower in the welding speed than that of MIG arc welding method which melts the consumable electrode and is in a lower production efficiency. Therefore, various proposals have been conducted to a method in which the MIG arc welding method could be able to achieve the welding bead appearance near to the scale bead due to the TIG arc welding method having the filler wire added thereto.
The prior art 1 is a MIG arc welding method disclosed in the Japanese Patent Publication (examined) Syo 46-650 and is to change alternatively the arc spray amount between the high value and the low value. In order to actually execute this method, the electric power supplied to the arc is alternatively changed between the relatively high value and relatively low value (for example 3:2).
FIG. 2 shows a block diagram of an electric source for use in this welding method. FIG. 3 is a graph showing a V-I characteristic between an output current (horizontal axis) and an output voltage (vertical axis) (referred to V-I characteristic hereinafter) and an arc characteristic. With reference to FIG. 2, a reference numeral 101 denotes an output circuit for welding electric source; a reference numeral 102, a resistor for switching the V-I characteristic of the output circuit for welding electric circuit 101; a reference numeral 103, a contact for shortcircuiting and opening the resistor 101; and a reference numeral 104, a timer for switching periodically the contact 103. A reference numeral 1 denotes a consumable electrode wire (referred to a consumable electrode hereinafter) transferred to a welding material 2 through an electric supplying tip 4 at a predetermined speed by a wire supplying motor WM. An arc 3 is generated between the consumable electrode 1 and the welding material 2 and is 10 to weld the welding material 2.
FIG. 3 shows a V-I characteristic AA applied between the consumable electrode 1 and the welding material 2 when the resistor 102 is connected to the output circuit, a V-I characteristic BB when the resistor 102 is short circuited and an arc characteristic at arc lengths of L1 to L3 shown by dotted lines L1 to L3. It is assumed that an operation point is a crossing point A of a solid line AA and a dotted line L1 of FIG. 3 when the consumable electrode 1 is transferred at predetermined value of wire supplying speed WF1. At this time, a welding electric current is in I1 and an arc voltage is in V1.
There are three methods for switching the above electric power.
(1) A first method is to switch an output voltage supplied across the consumable electrode 1 and the welding material 2. For example, in FIG. 3, when the V-I characteristic is switched from AA to BB, the welding electric current I1 does not change but the operation point moves usually to B point of the V-I characteristic curve BB because the wire supplying speed and the
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Yamamoto, et al., "The development of welding current control systems for spatter reduction", Welding International, vol. 4, No. 5, 1990.
Pfeiffer, G., "Investigations into the arc and spatter behavior of pulsed MAG welding", Welding International, vol. 4, No. 11, 1990.
Doi Toshimitsu
Harada Shoji
Matsumoto Ichiro
Nakai Hiroshi
Nakamata Toshiaki
Daihen Corporation
Shaw Clifford C.
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