Stud Welding Operations
All stud welding works, should be carried out in line with a current WPS & WPQR and conducted in a safe and professional manner at all times.
The Stud welding hand tool locates the weld or shear studs to the required positions, it is also used to control the amount of lift and plunge during the installation process. The hand tool is connected to the welding converter by the weld and control cable, the converter/ rectifier changes mains input power to a weld current to fix the stud or shear connector.
This process is a drawn arc process and stud types used are formed in a special way to assist with the welding process, studs over 6mm in diameter will have a flux ball inserted to assist with the initiation of arc and help the weld become fluid, it also serves to deoxidise the molten material and aid in reducing porosity and produce a full penetration weld. The ceramic ferrule used in this process contains the weld arc and heat within it.
To ensure that the shear stud and parent material are adequately fused giving full penetration.
There are a number of specifications and practices that can be used to help and guide you with the stud welding processes The BCSA code of practice for metal decking and shear stud welding and EN ISO 14555:2014 Both are good guides to use
Thru Deck stud welding can be successfully achieved only when the upper flanges of the steel to be welded are unpainted and relatively clean. The upper surfaces should be free from weldable primer, galvanising, excessive rust, mill scale or dirt on it that could interfere with the welding operation.
Stud welding cannot take place through reinforcement bar or mesh due to the risk of the welding equipment short-circuiting against the reinforcement
Welding should take place as soon as possible after the decking has been laid, this will help prevent dirt, moisture and other contaminants building up between the decking and the top flange thus ensuring good weld quality
A complete welding circuit needs to be created, so it is important to ensure that all beams to be welded are interconnected and adequately bolted together. A continuous earth loop needs to be provided through the steel frame to within 10 meters of the welding converter.
Welding Conditions should be considered as no stud welding should be carried out in inclement weather, when water cannot be kept from laying on the deck or beams to be welded. It should also not be carried out when the temperature is below freezing
ALL stud welding should be carried our utilising the correct PPE and air fed respirators supplied.
None use of issued PPE may result in disciplinary action being taken.
Testing of shear studs for thru deck welding
Thru Deck stud welding should only be carried out in the PA position (Down hand position only)
For drawn arc stud welding with ceramic ferrule and shielding gas and short-cycle drawn arc stud welding. Visual examination is used for assessing the following as appropriate for the application
a) The uniformity of the shape, the size and the colour of the surface of the weld collar (guidance values for drawn arc stud welding with ceramic ferrule are given in ISO 13918)
b) Location, length and angle of the stud after welding
The ring test serves as a production test for shear connectors. Principally subject to static loads in building constructions. The ring test is only permitted for studs welded under the qualification in accordance with BS EN ISO 14555:2014 10.3.2
The head of a shear connector is tapped with a hammer with a weight of 0.9kg to 2kg
The angle of swing shall be between 20⁰ and 30⁰ and shall be allowed to free fall
The execution and the assessment of the ring test needs sufficient experience.
This test serves as a simple test for checking the chosen parameters.
A minimum of 5% or 2 studs per beam shall be tested to an angle of 30⁰.
In this test the weld is subjected to bending in an undefined manner. If arc blow or any other visible imperfection is suspected or witnessed then the stud shall be bent in a manner such that the area to be examined is in the tension zone.
Shear connectors that have been bent shall not be straightened, if the bending angle does not exceed 30⁰, the shear capacity is not significantly reduced.
During the installation of shear connectors, the above production surveillance tests shall be carried out, some additional testing maybe required depending on the contract requirements or specification used.
The installer MUST keep a record of all the tests completed