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Here you will find useful information on current and commonly used concepts and terms associated with our products and technologies.

Anchor plate

An anchor plate consists of a steel plate, often in a standard size, with welded-on shear connectors, which is used to fasten steel components on concrete elements. The shear connectors are first welded on using the drawn arc stud welding method and then set in concrete such that, when installed, the smooth side of the steel plate faces outwards and is flush with the concrete This concrete-free surface can be used to weld on various steel components, such as mounting points for railings, cantilevers for balustrades and balconies, or even facade elements. But the main field of application lies in the construction of power stations, where the anchor plate has a whole range of uses.

Arc blow

Direct current is usually used for drawn arc stud welding. This supports the establishment of an even arc and usually leads to the desired result. However, direct current welding can have an unpleasant side effect:

the electromagnetic fields and their interaction at the tip of the electrode can cause turbulence that leads to air and welding gas entering the weld pool. The consequences can include oxidations, penetrations or pores that reduce the quality of the weld as well as joins with a stronger weld on one side. This phenomenon is referred to as “arc blow”, which only occurs when welding with arcs and presents a particular challenge for stud welds from a diameter of around 14 mm. This is because studs with larger diameters require longer welding times, which also makes arc blow more likely. A high level of expertise is necessary to prevent this phenomenon during arc welding. This fault has many causes. As a result, the measure to be taken to prevent arc blow needs to be decided on site.

Typical countermeasures are:

  • Move the connecting terminal on the workpiece
  • Create weld templates made of NF materials
  • Lift the welding cable
  • Implement compensating measures in edge welds
Auxiliary arc

In drawn arc stud welding, a small auxiliary arc is created when lifting the stud off the workpiece, which is superimposed immediately afterwards by the main arc. The auxiliary arc is merely tasked with emitting charge carrier and ionizing the arc path between the electrode (cathode) and workpiece (anode). Its arrival at the latter prepares the transfer of current.

→ see main arc

Bend test

A bend test in line with DIN EN ISO 7438 examines whether and under what bending stress the welding zone of a test specimen starts to tear. Ideally, the stud can be struck and bent with a hammer or bent with a pipe up to a determined bending angle defined in the standard without any visible weakening of the welding zone. While the bend test only helps to assess the applied welding method for that specific case, regular, random tests provide a reliable data pool and can protect against legal losses in case of disputes. This is a reliable standard method in destructive material testing, which requires a standardized test specimen.

Boiler stud

The boiler stud is a smooth pin comprised of highly heat-resistant steel that is used to mount boiler tube walls in the construction of power stations. It performs two functions in this respect: first, it enlarges the surface for greater thermal conductivity and, second, it serves as a joining element between the boiler tube wall and the sprayed on refractory concrete.

Break-off pin

The break-off pin is a smooth stud that is easily shortened at a predetermined breaking point after it is welded on and whose design guarantees a reliable, predictable final stud length. The break-off process is much more precise and also much faster than having to laboriously cut the stud to length with an angle grinder.

Typical applications are as follows:

  • Spacer
  • Positioning pin
  • Stop
  • Pivot point
  • Anti-slip element

Above all, its use as a spacer or positioning pin make this welding stud in extremely popular in the refractory construction of annealing furnaces. It can be used to precisely position insulating mats and panels before they are permanently fastened with other welding studs. The small diameter of these welding studs eliminates any issues with heat transfer while operating the annealing furnace.

Ceramic ferrule

Despite the speed of the stud welding process, the maximum duration of a welding process of 1.5 seconds is long enough for the inflowing oxygen from the ambient air to cause unwanted penetrations in the weld zone that negatively impact on the quality. To prevent this, the use of a ceramic ferrule has become standard practice. This is positioned above the weld zone to seal it. The metal vapor generated during the welding process is able to dissipate through gas vents and this prevents the atmosphere from reacting with the melt. The ferrule is struck off after the welding process. And this reveals another function of the ceramic ferrule. The melt pressed away when the stud is plunged in is formed into a defined weld bead. As a secondary function, the ceramic ferrule slows the cooling and protects the operator from radiation and spatter, as stud welding is a very intensive arc welding process.

→ see also shielding gas welding

Concave boiler stud

From the outside, the concave boiler stud looks like a regular smooth stud, the bottom of which has a conical inner bore, enabling it to be welded onto corroded and heavily worn boiler studs. The concave boiler stud is an essential service and maintenance tool in refractory construction where it helps to hold the insulation in position.

Cylindrical pin

The cylindrical pin is a smooth stud used to precisely position components without permanently fixing them. It merely holds the component in position until it has been fastened using other fasteners. The smooth surface supports the gliding of components in any wall thickness, as smooth cylindrical studs prevent components from catching, as can occur for threaded studs with external thread.

Drawn arc stud welding

Stud welding with an ionized arc works with the brief application of a high DC voltage. When the welding process is triggered, a low current is activated, the stud is raised off the workpiece and an arc skips across. This arc melts the contact points of both materials and the welding stud is then pressed on. When the welding stud comes into contact with the workpiece, the arc disappears and the voltage is switched off. The weld pool cools and hardens. Fusion is complete.

In stud welding with a ceramic ferrule, the welding stud has a small aluminum ball at the bottom. This burns within milliseconds as soon as the welding current is switched on. This converts the oxygen present at the welding site completely into chemically neutral aluminum oxide, which prevents unwanted oxidations at the weld.

Hardness test

The hardness test is used to check the resistance of a stud weld in terms of strength and toughness, and assesses the hardness profile of the weld zones. The calculation of characteristic values (hardness values) enables the assessment of a stud weld for a technically relevant component, which requires official acceptance as part of general quality assurance. During the hardness test, an indenter with a defined dimension and defined load is pushed into the weld zone to be tested. The hardness is determined by measuring the size of the imprint left by the indenter and the associated test force.

Insulation pin

The insulation pin is a single- or double-sided pointed needle that can be used to attach insulation packs of highly effective insulating materials in incinerators. The insulation packs are simply pinned onto the pointed ends of the insulation pins. In shipbuilding, the insulation pin is used to attach insulation during interior finishing.

Internal threaded stud

The internal threaded stud is a smooth pin with internal thread. It is used wherever components with an external thread are to be screw mounted into a welding stud. The smooth outer surface makes the internal threaded stud particularly easy to install and its internal thread enables the use of countersunk-head and flat-head screws. This allows components to be installed without a protruding thread to create a smooth surface.

Main arc

The main arc performs two tasks when using the drawn arc method:

first, it releases the energy required to fuse the stud and the workpiece and, second, it deoxidizes the resulting weld pool.

Pilot arc

→ see auxiliary arc

Shear connector

The shear connector is a steel pin with a head that is used to permanently join steel components and concrete. Shear connectors are welded onto a component after which the stud side is surrounded with formwork and encased in concrete.

The protruding head establishes the positive-locking connection between the component and the concrete. Special corrosion protection for the shear connector is not necessary as, once it is encased in concrete, the studs are well-protected against corrosion.

Shielding gas welding

Despite the speed of the stud welding process, the maximum duration of a welding process of 1.5 seconds is long enough for the inflowing oxygen from the ambient air to cause unwanted penetrations in the weld zone that negatively impact on the quality. Besides welding with a ceramic ferrule, welding with shielding gas is another suitable measure to further optimize the level of deoxidation and prevent the described penetrations. In shielding gas welding, a bell jar is placed over the weld zone during the welding process and then filled with shielding gas. This prevents the atmosphere from reacting with the melt.

Welding with shielding gas is less intensive than welding with a ceramic ferrule, and is primarily used for stud diameters up to 12mm.

→ see also ceramic ferrule

Stud welding gun

The stud welding gun is a standard tool in metalworking and, together with a connected stud welding machine, is designed to mate cylindrical pins on metal surfaces (stud welding). A safe and ergonomic design that is easy to use makes it ideal for every skill level and allows studs to be welded on wherever large and bulky components cannot be clamped into a machine tool.

Stud welding inverter

The welding inverter is a complex, high-quality welding current source with a compact design, extremely light weight, and which also enables the precise control of the voltage and frequency of the welding current. In addition, various comfort functions support the user in their work, such as with the automatic adjustment of the welding parameters after entering the sheet thickness, material, and desired welding method. This makes it a transportable universal solution for almost all welding methods and enables professional joining, even for beginners.

Stud welding machine

The stud welding machine acts as a welding current source and, together with a stud welding gun, is designed to mate cylindrical studs on metal surfaces (stud welding). Due to the diversity of products, welding studs ranging from a few millimeters through to two centimeters in diameter may need to be processed in consistent quality. The smallest machines are ideal for manual workstations or for hard-to-reach points on construction sites. The largest machines are predominantly designed for power and speed.

Stud welding (standard)

Stud welding technology is quick and easy to learn, and is also a very safe technology if appropriate training is provided and attention is paid to potential hazard sources. The objective is to weld cylindrical steel pins, either with or without a thread, onto metal surfaces. Threaded studs allow attachments to simply be screw mounted and removed again as necessary. By contrast, threadless studs are used to produce a permanent rivet or weld connection, or as guide studs without a permanent connection.

This requires a stud welding machine, a connecting cable, and a welding gun as well as standard safety goggles and heat-resistant gloves. Beginners should start with practice welds.

The user connects the stud welding gun to the base machine with the connecting cable. They then insert the welding stud in the gun. An additional adapter may be required in some cases when working with particularly slim studs. The user adjusts the welding current and welding time on the welding machine. The base material to which the welding stud is to be attached must be bright, clean, and free of grease and rust. Once the stud, gun, and surface have been prepared and the earth cable attached to the base material, the gun is positioned at right angles. It is especially important that the operator holds the machine level, as it is virtually impossible to subsequently correct a slanted stud. The user is supported by an adjustable guide attached on the front. When flicking the switch on the gun, a large current flows through the stud and into the base material. This generates a high-temperature arc at the contact point that causes both elements to melt. The liquid metals of the base material and welding stud mix together and immediately solidify as soon as the welding current is interrupted. This creates the solid weld. The welding gun can now be removed and is ready for the next weld. The weld then lightly cleaned to complete the process.

Stud welding works in the following steps:

  • Clean the welding element
  • Insert the welding stud
  • Adjust the welding parameters on the machine and gun
  • Position the welding gun
  • Trigger the welding current
  • Remove the welding gun

Typical applications of stud welding are:

  • Steel construction and structural engineering (as fastening points for cladding, formwork, and insulation material; in bridge construction as joining studs)
  • Construction of power stations (as fastening points for all kinds of attachments)
  • Vehicle construction (for guiding body components and as grounding points)
  • Plant construction and mechanical engineering (as fastening points for cladding, flange fasteners, and attachments)
  • Refractory construction (as fastening points for insulation packs in annealing furnaces and combustion chambers)
  • Shipbuilding (universal application)
Tensile test

The tensile test in line with DIN EN ISO 6892-1 determines the tensile strength and yield strength of a component. Two key pieces of information for assessing quality. The specimen is stressed such that it initially buckles and then breaks. While the result of a tensile test merely provides an indication of the quality of the specimen, it allows indirect conclusions to be drawn as to the behavior of the finished component in its installed state. Consistent sampling allows potential deviations from the defined tolerances to be identified early on.

Threaded stud

The threaded stud is a cylindrical pin with metric thread. It is suitable for screw-mounting removable components, such as cladding, formwork, insulation, or the like with the advantage that assembly and repair are both made easier.

Through-deck welding

This welding technology is used in building/composite construction.

In through-deck welding, shear connectors are welded through galvanized trapezoidal plates onto steel girders and all components are joined together.

The resulting combination of composite girder and composite decking provides a range of installation options on the underside for suspended ceilings as well as air conditioning and electrical equipment, and also saves a great deal of time compared to conventional formwork. Through-deck welding is particularly popular in the Anglo-Saxon countries due to the use of uncoated girders as well as the prevalence of the size 19 shear connector, which is easier to machine than the size 22 shear connector traditionally preferred in Germany for composite construction.

Visual inspection

The quality of a stud weld connection can be negatively affected by external influences. An unnoticed draft, moisture, and impurities at the weld point as well as an insufficient power supply all impact the welding process. In addition, careless calibration or parameter configuration errors can have a significant adverse impact on the quality of the stud weld A trained eye and, where necessary, a magnifying glass are all that are needed to detect external defects.

Typical error patterns in stud welds are:

  • slanted studs
  • blowholes
  • penetrations
  • pores
Weld time

The weld time is the time from which the arc is ignited until the molten surfaces of the stud and workpiece meet.

Welding stud

Welding studs are the consumables in stud welding. They need to be geometrically correct for the specific task and, above all, be technically suitable for drawn arc or capacitor discharge welding. The stud material is precisely adapted to the specific application to ensure the best results and protect the equipment.


The Y-anchor is used to quickly and efficiently fasten light and fibrous insulation materials, such as fiberglass, mineral wool, or wood insulation boards.

In this role, the anchor has established itself in the following applications in particular:

  • Steel construction and structural engineering
  • Refractory construction

Its wave-shaped surface acts as a retainer that facilitates secure attachment, even when working with thick-walled insulation packs in refractory construction.