Stud welding

Arc stud welding ( short form: stud welding, Eng. Stud welding ) belongs to the arc welding process, it is similar to the thermo-compression welding in microelectronics ( a method of wire bonding ).

The aim of the stud welding is the permanent connection of pin-shaped elements (eg, threaded studs, pins, sockets, hooks, eyes ) with larger components (eg body panels, housings, radiators).

• 4.1 magnetic stud welding (SRM )
• 4.2 Pad welding with magnetically impelled ( rotating ) Arc - MARC

History

First experiments were carried out until 1918 by Ing Harold Martin in England in 1915. An attempt was made to simplify the tedious drilling and attaching bolts to ship bolts. The first industrial application was made in America around 1938. A welder in the U.S. Navy saw the difficulties of wooden planking of the steel decks of aircraft carriers. We solved the problem by stud welding. There were welded through the predrilled wood studs to the steel deck. The U.S. Navy saved by this new technology during the war, 50 million man-hours of work time. In 1945 the first patent for capacitor discharge welding ( capacitor discharge ). 1970 was established in the technical committee of the German Association for Welding Technology eV, the working group " stud welding ".

Principle

When stud welding an arc is struck between an end surface of the stud and the workpiece, both parts are stated locally melted and then added under low pressure. The arc stud welding is according to the type of arc ignition divided into drawn arc stud welding and stud welding with tip ignition. The two methods differ in the weld surface geometry of the bolt, the process flow of the device technology and partly in the area of ​​application. The so-called arc blow can have a disturbing effect as in other arc welding processes.

The most important standards for stud welding are:

• DIN EN ISO 14555 - Arc stud welding of metallic materials
• DIN EN ISO 13918 - Studs and ceramic ferrules for arc stud welding
• DVS 0901 - Arc stud welding
• DVS 0902 - arc drawn arc stud welding
• DVS 0903 - Arc stud welding with tip ignition
• DVS 0904 - Arc stud welding, notes for practice

The most important welding parameters for arc stud welding are at the drawn arc:

• Welding current
• Welding time
• Stroke ( arc length)
• Supernatant ( depth of immersion )

The most important welding parameters for arc stud welding are at the top of ignition:

• Charging voltage
• Capacity
• Welding time
• Gap
• Immersion speed / welding time

Different methods

Distinction on the type of ignition

Hubzündungsbolzenschweißen

Hubzündungsbolzenschweißen the arc is generated by current flow from the device by lifting the bolt.

Capacitor discharge stud welding

At the peak firing stud welding, the bolt on the side to be welded to a defined and tightly toleranced firing tip. The arc is ignited at this point. This firing tip melts explosion ( bang ) and evaporated to a small extent. The induction voltage which is produced by the opening of the circuit, ignites an electric arc, which is then detected in the whole bolt face. The strong but short heat development provides a geographically small puddle, but which is sufficient to connect the workpiece at the weld bolts permanently. Due to the low penetration depth due to the short sealing time, it is possible to relatively thin materials bolt ( 1,5 - 3 mm) to bring.

• The cleavage method: The bolt is moved to the component of a certain height ( gap ). The ignition of the arc is effected by contact of the firing tip to the component.
• Contact method: The bolt has at the beginning of the weld contact with the component. Otherwise the operation is the same as the splitting method.

Distinction according to the type of Schweißbadschutzes

• Stud welding with ceramic ferrule
• Stud welding with shielding gas
• Stud welding without weld pool

Distinction according to the energy source

• Stud welding with welding rectifier (transformer) or inverter power source
• Capacitor discharge stud welding

Distinction according to the welding time

• Kurzzeitbolzenschweißung (short -cycle )
• "Normal time" stud welding

Special procedures

Magnetic stud welding (SRM )

Stud welding in radially symmetrical magnetic field ( SRM - Studwelding in Radially Symmetrical Magnetic Field) follows on from the stud welding with drawn arc and inert gas. The arc is ignited in the center of the bolt at the center point. Starting from the center of the arc is rotated by an external magnetic field in a rotational movement. After thermal activation of the entire planar design bolt face creates a stabilized, the entire surface of the bolt cross section formed arc column. The weld is terminated as soon as a sufficient amount of melt was generated. Under low pressure in this case the melting of stud and the workpiece can be connected together. Due to the uniform incipient melting of the bolt and the base material through the magnetically stabilized arc welds are made possible at a ratio of 1/10 (thickness / diameter bolt ). The melt depth is only a few tenths of a millimeter. Negative impacts due to arc blow through unilateral ground terminal or mass accumulation can be compensated by the process throughout the stud welding process. Other benefits include a very small heat-affected zone in the base material (60 % reduced penetration into the base material ) no disabling weld and no spatter. Stud welding in horizontal or overhead position ( predicaments ) are facilitated by the magnetic field.

Pad welding with magnetically impelled ( rotating ) Arc - MARC

The abbreviation MARC stands for Magnetic Rotating Arc. Welding with magnetically impelled arc extends the field of application of stud welding. The method is similar to the Hubzündungsbolzenschweißen in sequence, but is carried out with a rotating arc. The MARC process is an extremely economical connection technology. The advantages of MBL (MBP ) welding (control of heat input for the sleeve- like components by a magnetically impelled arc ) are combined with those of the arc stud welding with drawn arc ( simple and inexpensive device technology, welding times in the range of milliseconds ). The possibility of displacement of the arc column by an external magnetic field is the basis of MARC method. The welding process is characterized by very short welding times, low heat input, low energy requirements, accurate final size and high cost. The rotation of the arc, and thus a concentrated and uniform energy input over the welding surface, is obtained by a separate magnetic field in the sealing gap. It allows low distortion and spatter-free welding of tubes and bolts up to 30 mm outer diameter, preferably of high alloyed stainless steel with flat welding surface to 5 mm workpiece thickness. There are gas-tight and pressure-tight welds on perforated and non- components possible.

Other possibilities for welding studs

• Resistance stud welding
• Reibbolzenschweißen
• Cold press stud welding