Cyanfrinising as a pre-welding operation: methods and execution of the processing
Why make a Crimping?
It is the most important process in the preparation of the subsequent welding process.
It is used in the mechanical and energy sector and consists of eliminating the edges of the workpieces or sheets in the area where they are joined in order to make the welding bath between the workpieces penetrate as far as possible. V-shaped chamfers are produced in K-shaped and X-shaped and Y-shaped chamfers as required. Their function is the preparation for the welding of shoulders for structures in carpentry, viroles or sealed pipes, especially in the boiler sector on tanks and sometimes also on stainless steel alloys.
The result is considered perfect when subjecting the welded piece to mechanical tests, the results of tensile strength and breaking strength are better in the welded area.
The different types of chianfrinatura
The crimping is achieved by two different methods and with different results, so choices must be made according to the type of material used and the mechanical characteristics that will have to overcome the welding.
The first method, which is also the cheapest and fastest one, is flame cutting, which in Tecnos we perform using a bevel plasma torch managed by a numerical control on a 3750×28000 cutting plane. This rotating at 360° and tilting up to 45° on sheet thicknesses even of 60mm, allows to remove large quantities of material in a short time with an accuracy of +/- 1 or 2mm.
For higher thicknesses we use a wheeled machine with two oxyfuel torches with the possibility of tilting at will. Also in this case a trolley on rails, positioned parallel to the area to be chianfrinated, with two oxyfuel torches for thicknesses up to 400mm, allows in a single pass to realize an X bevel with inclinations over 45° and a glossy, flat and without marks.
The second method consists of chamfering or crimping by mechanical machining.
Then by means of a machine tool or, in our case, by means of a wheeled milling machine, this is turned around the perimeter of the workpiece to be chipped to obtain the chamfers necessary for the subsequent welding.
The process is much longer and more expensive, since small material removal operations are possible and several passes on the same edge are necessary.
Why and when to use this method?
When the material to be welded is a special alloy that should not be heat treated because it could then generate cracks or brittleness at the same weld, or when the chamfer is very small and the use of a large cutting machine involves operating costs that can not be amortized.
The machines used in Tecnos to make chamfers and bevels are divided into two categories according to finish, precision and the possibility of using a thermal cut that would chemically alter the cut surface.
THERMAL CUT CHAMBERS: these are the most economical and fastest ones, they allow to remove large quantities of material in a single pass with tolerances of +/-1-2mm. We use for these chamfers machines with bevel plasma torches of size 3700×28000 up to a thickness of 70mm or both fixed and mobile oxyfuel cutting machines with unlimited working range and thickness up to 400mm.
MILLING CHAMBERS: these are those obtained with the help of chip removal machines, either fixed with a working field of 12000×5000 or wheeled for small bevels of max. 40mm x 45°.