KÖCO as a supplier in composite construction
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KÖCO has taken an active part in the development of composite construction from the very beginning.
As early as in the mid-sixties, KÖCO was already producing millions of shear connectors and also welding them on. Shear connectors are manufactured on multistage presses, forging the head and end face in several cold-forging steps. In comparison with hot-forging, this increases the strength and the yield point; however, the doubly killed steel with a low carbon content, which is specially suited for this purpose, still has sufficient ultimate elongation of at least 15%. Cold forging provides high precision in dimensions as weil as a clean surface, which in turn ensures the good conductivity required for stud welding.

Dimensions of shear connectors (AII measurements are given in mm.)
Stud diameter d1 Head diameter d2 Min. length Lmin Max.length Lmax
10
 19 50 200
13
25 50 400

16

32 50 525
19 32 75 525
22 35 75 525
25 40 75 525
Shear connectors are almost exclusively welded on by drawn arc stud welding (No.783 according to lSO 4063). By this process, a drawn arc with high current melts the end of the stud and the work-piece surface below it within a very short time. The strength of the current applied -up to 2500 A -must be calculated in relation to the stud diameter. At the end of welding time, the stud is driven by a spring to plunge into the melt, and the current is cut off. The resulting connection over the whole surface has a strength exceeding that of the materials in both the stud and the work-piece.
Figure 17: Drawn arc stud welding with a ceramic ferrule shielding the welding pool
 
Cost-effective welding of shear connectors in large quantities within a short period of time places high demands on welding equipment. The following features make KÖCO equipment first choice for any stud welding tasks:
1 Electronic control of current during welding, which means that the most important parameter is kept stable regardless of mains voltage fluctuations or heating up of the power source;
2 Ignition of the arc via a pilot current with simultaneous testing for sufficient electric conductivity;
3 Hot plunging of the stud into the welding pool, to prevent lack of fusion in the weld;
4 Welding cable diameters of up to 120 mm2 allow greater distances between power source and operator, with a low levelof heat generation;
5 Predetermined settings for all electric and mechanical parameters provide security for the operator;
6 In case of any malfunctions, KÖCO power sources can diagnose the cause and thus contribute to
having the malfunction quickly remedied;
7 Manufacturing in accordance with all relevant norms (CE) and safety standards certified by TÜV (GS).