QUALITY.

DESCRIPTION

The present invention concerns a welding system, particularly but not exclusively suited to weld steel straps.

The present invention also concerns a method for controlling the welding quality, particularly but not exclusively indicated for TIG welding.

As is known, TIG welds are made with non consumable electrodes and can be carried out with or without weld material. In the first case we talk about braze welding, while in the second case we talk about autogenous welding.

In TIG welds it is possible to notice defects like porosity, no melting or formation of cracks.

In particular, the incomplete melting or the perforation of the material affect the quality of the joint. The Japanese patent JP2005007451 solved this problem through the immersion of the end of an optical fibre, contained in a protective tube, in the area where the welding operation is carried out, while the quality of the weld is controlled by means of synchrotron radiation based on the molecular agitation of the weld pool particles. First of all, this type of check is a destructive test, as the measurement of temperature in the welding area is carried out in the weld pool area.

Furthermore, the type of check proposed by this patent measures the temperature in the weld pool area based on the thermal agitation of the X-ray particles. The object of the present invention is to provide a welding system that is capable of controlling the quality of the weld through a non-destructive test and at the same time makes it possible to compare the measured values with reference values.

A further object of the invention is to provide a welding system that makes it possible to eliminate the impurities produced during the welding operation, in such a way as to avoid affecting the reading of the values adopted for checking the quality of the successive welds.

The objects described above are achieved by the present invention concerning a welding system whose main characteristics are in accordance with the contents of the first claim. The objects described above are achieved by the present invention concerning also a welding method in accordance with the contents of claim 12. Advantageously, the welding system constructed according to the present invention makes it possible to obtain specific values regarding the welding quality by means of a measurement carried out from a remote position.

Still advantageously, the welding system constructed according to the present invention makes it possible to obtain specific values regarding the welding quality by means of light-sensitive sensors that capture the light produced by the material's melting point and measure the luminosity produced in that point. The objects and advantages described above will be highlighted in greater detail in the description of a preferred embodiment of the invention that is supplied as an indicative, non-limiting example with reference to the enclosed drawings, wherein:

- Figure 1 shows a cross section of a detail of the welding system constructed according to the present invention;

- Figure 2 is an axonometric view of the plate shown in Figure 1 ;

- Figure 3 is an axonometric view of the plate shown in Figure 2 connected to light-sensitive sensors and to a PLC.

According to the invention, the welding system comprises: - a frame supporting a current generator (not shown in the figures);

- one or more welding electrodes 1 , visible in Figure 1 , connected to the generator.

As shown in the detail of Figure 1 , the material to be welded is positioned below the electrodes 1. In this case, the situation is as shown in Figure 1 , which illustrates two superimposed steel straps 2.

As shown in Figure 1 , these straps are superimposed and then interposed between the electrodes 1 and a copper-clad plate 3 resting on the object 4 around which the straps 2 will be applied.

When it is necessary to make a weld, the tips 1a of the electrodes 1 are arranged coaxial with the cavities 5 of the plate 3 and then the electric arc is generated.

Figures 1 and 2 show that the cavities 5 are provided with a bottom 5a, while their upper opening 5b, arranged on the opposite side with respect to the bottom 5a, is directed towards the electrodes 1. During the welding operation, the light produced by the melting point is captured by optical fibres 6 arranged along first lateral channels 7, created on the plate 3 and communicating with the cavities 5.

Once the welding operation has been carried out and the welded material has been removed, air is blown into second channels 8 by means of blowing devices (not illustrated in the figure), in order to eliminate the impurities produced during the welding operation.

It should be noted that, as shown in Figure 2, the second channels 8 are constituted by a first vertical section 8a connected to a second horizontal section 8b that is coplanar with and incident on the first channels 7. Blowing air into the second channels 8 means allowing foreign matter to be eliminated and thus ensuring a correct reading of the data relating to the welding quality.

The light-sensitive sensors 9 detect the luminosity of the melting point produced inside the cavity 5 and transfer the measured data to a PLC 10, to which they are connected.

The PLC 10 compares the values received from the light-sensitive sensors 9 with standard reference values that depend on the type of material used for the straps 2.

Consequently, each type of material used for the straps will correspond to a different luminosity range.

The light-sensitive sensors 9 are of known type and their spectrum activity is included between 400 and 700 nanometers.

It is important to underline that, in accordance with the present invention, the light-sensitive sensors 9 are arranged in a remote position with respect to the point where the welding operation is carried out and therefore this type of measurement, differently from those adopted by the known technique, destroys neither the sensors nor the optical fibres.

Once the luminosity data are transferred to the PLC 10, they are compared with standard reference values, so that it is possible to check the quality of the weld that has just been carried out.

It may happen, in fact, that the luminosity is too low, which means that the weld pool of the straps 2 has penetrated only the upper strap and not the lower one.

In this case, this means that the lower strap has not been welded.

It may also happen, on the other hand, that the luminosity is too high, which means that the straps 2 are perforated and therefore cannot be used any longer, thus putting at risk the resistance of the weld.

In the case of steel straps, the luminosity of the melting point produced during the welding operation must be included between a minimum and a maximum reference value, specific for the type of steel and the strap used. The above clearly shows that the welding system and the method for checking the welding quality that are the subjects of the invention achieve all the set objects.

In particular, they achieve the object to check the welding quality by means of a non-destructive test, thanks to measurements made with light-sensitive sensors 12 arranged in a remote position with respect to the weld pool area. The welding system and the control method carried out according to the present invention can be subjected to modifications that must all be considered protected by the present patent, provided that they fall within the scope of the following claims. Where technical features mentioned in any claim are followed by reference signs, those reference sings have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.