WO2016184668A1

WO2016184668A1 - Method and welding device for drawn arc welding

Info

Publication number: WO2016184668A1
Application number: PCT/EP2016/059743
Authority: WO
Inventors: Hermann Krippl; Tuba BASKAYA
Original assignee: Bayerische Motoren Werke Aktiengesellschaft
Priority date: 2015-05-20
Filing date: 2016-05-02
Publication date: 2016-11-24
Also published as: DE102015209203B4; DE102015209203A1

Abstract

The invention relates to a method for drawn arc welding using direct current, in which a welded part (100) is welded to a workpiece (200) at a joint (300), wherein initially in a pre-current phase during a pre-current period (t_V), an arc is formed between the welded part (100) and the workpiece (200) by means of a pre-current (I_V), and in a subsequent main current phase, the pre-current (I_V) is increased to a main current (I_H) for a main current period (t_H). The workpiece is operated as an anode and the pre-current period (t_V) and/or the amount of the pre-current (I_V) is adjusted such that the workpiece (200) is heated during the pre-current phase in the area of the joint (300) at least up to plastic deformability. Furthermore, a device for carrying out the method is described.

Description

description

The invention relates to a method for direct-current arc welding according to the preamble of patent claim 1 and to a welding device for carrying out the method.

In the case of lift-and-strike welding, a welded part, e.g. a bolt, welded to a workpiece at a joint. For this purpose, the welding part at the joint on the

Workpiece attached. In a first phase, the

Vorstromphase, a low bias current is switched on, which flows through the welding part and the workpiece. The

Welded part is up to a predetermined distance from

Workpiece removed. This leads to the formation of a weak arc. This is followed by the

Main current phase in which the bias current is increased to a main current (welding current). The resulting

Welding arc requires at least partially

On fusion of the materials of welding part and workpiece. To end the process, the welding part is lowered onto the workpiece or immersed in the workpiece by a small distance and the current is switched off. The melted materials cool.

When Hubzündungschweißen with DC, the

Flow direction of the stream during the process not changed.

The direct current welding with DC is an unstable and difficult to control process, especially when welding aluminum-containing workpieces or

Weldments. It often comes to spattering by explosion of the melt or to strength problems due to blowing effect or insufficient penetration into the workpiece. To improve the quality of welding

Stroke welding with direct current is from the

Publication DE 10 2012 107 702 AI known, the

Mainstream phase already begin while the welding part is still moved away from the workpiece. This is intended to be

Emigration of the arc can be prevented and a

uniform melting can be achieved.

Object of the present invention is to provide a method for DC-DC welding, with which the quality of the welded joint can be further improved, and a welding apparatus for performing the

Procedure. The object of the invention is achieved by a method according to claim 1 and an apparatus according to claim 7.

According to the invention, the workpiece is operated as an anode and the amount of the bias current and the duration of the pre-current phase are selected so that the workpiece during the

Vorstromphase in the joining area heated at least to plastic deformability. In experiments, this procedure has shown that by a larger

Energy input in the Vorstromphase especially the

Heat input on the workpiece side can be increased, whereby the quality of the welded joint is increased.

While in conventional methods, the Vorstromphase is only used to form the arc, now during the Vorstromphase a significant heating of the

Workpiece in the joint sought. For this purpose, a higher pre-flow and a longer pre-flow time is used compared to the conventional pre-flow phase. Due to the higher energy input into the base material, the welding result results in a deeper penetration with a better joining zone between

Realized welding part and workpiece. Surprisingly, it has been shown that the tendency to spatter is significantly reduced. The reason for this is assumed to be improved surface cleaning due to the stronger or longer-lasting pre-arc. The method according to the invention therefore provides for increasing the amount of the pre-flow and / or the duration of the pre-flow phase compared with the known lift-and-strike welding methods. As a result, in the Vorstromphase the

Energy input increased, so in the subsequent

Hauptstrom- or welding phase of the main stream can be reduced. Advantageously, this results in a reduced melting of the weldment and a quieter melt and reduced bead ejection. The method has proved to be particularly effective when a significant proportion of the introduced electrical energy is introduced within the pre-current phase.

As a result, the base material is better melted at the same time reduced melting of the weldment. Thus, in one embodiment, at least 30% of the

electrical energy in the pre-flow phase are introduced, preferably at least 50%, and more preferably

at least 60%. The introduced energy EGES is determined according to equation 1.

wherein, in simplified terms, the energy E _v introduced in the pre-flow period as the product of pre-flow Iv,

Arc voltage Uv in the Vorstromphase and Vorstromzeit tv gives (equation 2), and the introduced in the main flow period energy E _H as the product of the main current I _H ,

Arc voltage UH in the main current phase and

Main current time t _H (equation 3).

Eq. 2: Ev = Iv * U _v * tv

Eq. 3: E _H = LH * U _H * t _H Depending on the materials used and component dimensions are different process parameters to achieve the

desired effect necessary. Pre-flow and pre-flow time are chosen in particular so that, although there is a significant heating in the workpiece, but not yet to a melting at the weldment. This takes place only in the following main flow or welding phase, including the

Main current or the main current time are selected accordingly.

Experiments have shown that a weld of particularly high quality can be achieved if the Vorstromzeitraum or Vorstromzeit in one embodiment at least seven times the duration of the main flow period or the

Main current time, preferably eight to 10 times the duration. In addition, it is advantageous if, in this embodiment, the amounts of pre-flow and main flow are selected such that the ratio of pre-flow to main flow is in a range of 0.3 to 0.5, preferably in a range of 0.35 to 0, 45th

To terminate the process, the welding part is lowered onto the workpiece and the welding current is switched off. To increase the process stability of the welding current is switched off in one embodiment, as soon as a ground contact between the welding part and the workpiece is produced.

A further reduction of welding spatters as well as a higher strength of the welded connection can be achieved in one

Design can be achieved, in which the immersion, ie the lowering of the welding part on or in the workpiece, at a reduced speed of 0.11 m / s or less and preferably from 0.1 m / s or less.

The method described above is suitable

in particular for the application of T-bolts and threaded bolts (with external or internal thread), preferably with a diameter in the range of 3 mm to 9 mm. However, other types of bolts, such as ball pins, etc., and bolts of other dimensions can also be applied to a workpiece by this method.

The method is particularly suitable for welding bolts on thin sheets having a thickness in the range of 0.5 mm to 3 mm. The process achieves special advantages when welding aluminum-containing workpieces or

Welded parts and in the welding of workpieces, which are provided with an anti-corrosion layer, e.g. zinc or aluminum coated sheets. Here is through the

prolonged Vorstromphase achieved a good surface cleaning. However, the method is not limited to the aforementioned workpieces and weldments.

In other words, compared with one

conventional welding process with lift ignition, an increase in the bias current and the Vorstromzeit while reducing the main flow. In addition, the

Reduces immersion speed, whereby the melt stably impacts the base material. By the novel process with novel welding

Characteristic result in the following advantages. The base material is better melted, at the same time the bolt is not so much melted, resulting in a high connection strength. By the low

Immersion speed keeps the melt quiet until it reaches the

Connection is coming. Thus, spatter is minimized and the melt is not over-expelled. This results in a higher lower head size and very low spatter formation, bead formation and a very high strength tensile test or Scherzugbelastung in the assembly. A welding device according to the invention for carrying out the method described above has a conventional holder for receiving a welding part. Furthermore, the welding device has a DC power source and a control and regulating device, by means of a direct current between the welding part (cathode) and a workpiece (anode) can be applied, to form an arc between the welding part and the workpiece. The control and regulating device is suitable for carrying out the method described above, for example, the

Parameters Vorstrom, Vorstromzeit, main stream, main stream time, immersion speed, immersion delay in the control and regulating device in the required value range

adjustable or stored as a characteristic.

Further advantageous embodiments of the invention will become apparent from the dependent claims.

The above-described characteristics, features and advantages of this invention as well as the manner in which they are achieved will become clearer and more clearly understood

Related to the following description of

Embodiments. If the term "may" is used in this application, these are both

technical possibility as well as the actual

technical implementation.

Hereinafter, embodiments of the hand

explained in the accompanying drawings. Show:

1 shows a characteristic for the exemplary representation of

Process parameters according to an embodiment of the invention,

Figure 2 is a schematic representation of a

welding device according to the invention for

Hubzündungsschweißen. Figure 1 shows a characteristic of a DC stud welding process according to an embodiment of the invention. It was a T-bolt with 5 mm diameter on a workpiece in the form of a hot-dip galvanized aluminum sheet (DX54D Z100) with a thickness of 0, 7 mm to 0, 8 mm

applied. In Figure 1, the course of the current I, the resulting voltage U and the Abhubbewegung s of the welding bolt over time for the embodiment shown. The dashed auxiliary lines along the time axis t each indicate time intervals of 30 milliseconds. The

scale dashed guides in y direction, depending on

Reference value in increments of 100 A, 10 V or 1 millimeter.

At the beginning of the process, after contacting the bolt with the workpiece surface, a bias current Iv of 100 A was switched on for a pre-current period t _v of 0.1 s (100 milliseconds). The bolt was raised 1.4 mm from the workpiece at a speed of 0.127 m / s. After expiration of the pre-current time tv, the current was increased to a welding or main current I _H of 270 A for a welding time tu

(Main flow period) of 0.012 s (12 milliseconds).

To complete the process, the bolt was lowered and slightly lowered into the plate at a speed of 100 mm / s.

Compared with the process parameters of a conventional method of Hubzündungschweißen this

Material combination, the Vorstromzeit tv was extended. Thus, the pre-flow phase lasts more than eight times as long as the subsequent welding phase. Furthermore, the amount of the bias current I _{V was} increased and the main current IH reduced.

Vorstrom l _v and main current I _H are at this Embodiment in a ratio of 0.37.

At the same time, the dipping speed was reduced.

Table 1 shows a comparison of

Control parameters according to embodiment and

conventional method:

Table 1:

In Figure 1 it can be seen that during the welding only slight fluctuations in the course of the current and the voltage occur. The extended pre-flow phase with higher pre-flow and reduced main flow creates a quiet melt with reduced bead ejection. Slowly lowering the weldment to the workpiece at the end of the process further reduces spattering.

The method can be implemented by simple means in a plant for Hubzündungschweißen. FIG. 2 shows a schematic representation of the essential components of a lift-and-lift welding system for carrying out the invention

inventive method. The welding device 10 has a holder 20 for receiving and holding a welding part 100 in the form of a bolt. Opposite the bolt 100, a workpiece 200 is arranged, on which the bolt 100 is to be welded at a joint 300. The

Welding apparatus 10 further comprises a DC power source 30, which by means of lines 32, 34 a Welding circuit is formed with the bolt 100 as a cathode and the workpiece 200 as an anode. A control and regulating device 40 is connected via electrical lines 42, 44 in the device 10, and formed so that the for the

above-described method necessary welding and process parameters can be implemented. In particular, the control and regulating device 40 via a not

illustrated interface for entering the desired

Parameters may be formed or it may be e.g. one or more corresponding characteristics in the control and

Regulating device 40 deposited.

The embodiments are not to scale and are not restrictive. Modifications in the context of expert action are possible.

LIST OF REFERENCE NUMBERS

10 welding device

20 bracket

30 DC power source

32, 34 lines

40 control device

42, 44 lines

100 welding part

200 workpiece

300 joints

I electricity

Iv Vorstrom

IH Hauptström

s lift distance

tv Vorstromzeit (raum)

t _H main current time (room)

U voltage

Claims

claims

1. A DC spark plug welding method in which a welding part (100) is welded to a workpiece (200) at a joint (300),

wherein initially in a Vorstromphase via a

Vorstromzeitraum (t _v ) by means of a bias current (I) a

Arc between the welding part (100) and the workpiece (200) is formed and in a subsequent

Main current phase, the bias current (I _v ) is increased to a main current (I _H ) for a main current period (tH),

characterized in that

the workpiece is operated as an anode and the

Vorstromzeitraum (tv) and / or the amount of the bias current (I) are set so that the workpiece (200) during the Vorstromphase in the region of the joint (300) is heated at least until plastic deformability.

2. Hubzündungschweißverfahren according to claim 1, wherein at least 30%, preferably at least 50% and more preferably at least 60% of the introduced

electrical energy is introduced in the Vorstromphase.

3. Hubzündungschweißverfahren according to claim 1 or 2, wherein

the Vorstromzeitraum (tv) has at least seven times the duration of the main power period (tH), preferably eight to 10 times the duration and

the amount of the bias current (I _v ) and the amount of the main current (I _H ) are chosen to have a ratio of bias current to main current in a range of 0.3 to 0.5 and preferably in a range of 0.35 to 0.45.

4. Hubzündungschweißverfahren according to any one of the preceding claims, in which

to terminate the process, the welding part (100) is lowered onto or into the workpiece (200) and the main flow (I _H ) is switched off as soon as a ground contact between

Welded part (100) and workpiece (200) is produced.

5. Hubzundungsschweißverfahren according to any one of the preceding claims, in which

to terminate the process, the welding member (100) is lowered onto or into the workpiece (200) at a rate of 0.11 m / s or less, preferably 0.1 m / s or less.

6. The method according to any one of the preceding claims, wherein the welding part (100) is a bolt and with a thin sheet, in particular a galvanized aluminum sheet is welded.

7. Welding device for connecting a welding part (100) and a workpiece (200) at a joint (300) by means of lift-arc welding with

a holder (20) for receiving the welding part (100), a DC power source (30) and

a control and regulating device (40) by means of a direct current (Iv, IH) between the welding part (100) and the workpiece (200) can be applied to form a

Arc, characterized in that the control and regulating device (40) is suitable for carrying out the method according to one of the preceding claims.