FI119602B - Method of repair welding a steel strip used in a fiber web machine - Google Patents

Description

A method of repair welding a steel belt used in a fiber web machine

The present invention relates to a method for repair welding of a steel belt used in a fiber web machine, in which an endless metal belt arranged movably supported by guide rollers 5 is stopped.

The metal belts currently used in a fiber web machine are subjected to fatigue loads and corrosion stress in use. In addition, the metal belts are also subjected to strong abrasive forces, resulting in fatigue cracks on the metal belts 10. This is the case, for example, with a metal belt sling and a CondeBelt search. An attempt has been made to reduce the drawback associated with wear in the Applicant's own patent publication FI 117982, in which metal belt blanks are joined together by a friction welding process (joint composition is the same as the substrate) and by anti-slip solutions 15 such as heat treatment of joint between blanks.

Although this way the fatigue cracks in the metal belt can be reduced, it is desirable to provide a method for repairing the cracks faster and more cost-effectively. Today, the metal belt is used in applications where it heats up, for example, in contact between heated control rollers. In order to repair the metal belt, the machine must be stopped and then the metal belt must be cooled down. It is necessary to wait for cooling until it is possible to work in the space defined by the metal belt. At present, one workman is required in the space bounded by the metal belt to support the inside of the space defined by the metal belt while another worker performs a welding on the opposite side, so that the time spent cooling the metal belt cannot be avoided at present.

It is an object of the present invention to provide a method for achieving the above objectives.

2

To achieve the above objectives, the method of the present invention is characterized in that the welding point of the metal belt is stopped in the advancing direction of the metal belt against a surface of a guide roll, supported at least at position 5 to be welded

The invention according to the method achieves significant advantages over the present method of repair welding. First of all, the repair weld 10 can be practically performed without the cooling of the metal belt since there is no need to enter the space limited by the metal belt. This avoids the waiting time of even hours (Cooling Time), which also reduces the repair time to a fraction of what it was before. In addition, only one person is needed to perform the repair welding. A further advantage may be mentioned that on behalf of the weld root (Me-15 metal belt side, which abuts against the guide roller) becomes a straight flush with the inside of the metal belt surface, wherein the inner metal belt sanding (weld split) is usually required.

Preferred embodiments of the present invention are set forth in the appended claims.

The invention will now be described in more detail by way of example with reference to the accompanying drawings, in which: Figure 1 schematically illustrates an embodiment of an arrangement employing the method of the invention with a metal belt calender, and

Fig. 2 shows a partial magnification marked at II in Fig. 1.

Figures 1 and 2 thus show an embodiment of a metal belt calender 1 having an arrangement for applying the method according to the invention. A similar arrangement is disclosed in the applicant's own patent publication FI

3, 117982. Figure 1 shows three guide rollers 2 around which an endless metal belt 4 is arranged to rotate. The structural variants and the manufacture of the metal belt 4 are also disclosed in the aforementioned patent publication FI 117982 of the applicant.

5

The thermal roll is denoted by reference numeral 3. The material web W is arranged to pass between the first surface 4a of the metal belt 4 and the circumferential portion of the surface of the thermal roll 3.

The guide of the calender metal strap 4 is arranged to allow the welding point of the metal strap 4 to be guided and stopped in the advancing direction of the metal strap 4 by automatic (not shown) or manually against the guide roll 2, in this case the left roll 2.

Thus, the stationary welding point is supported by a guide roll 2 2 on its other surface 4b.

While moving the welding point in the above manner, an additional support 6, i.e. the root support for the weld, may be inserted between the metal belt 4 and the guide roller 2, if necessary. The export can be made from the edge of the metal belt 4, so that there is no need to enter the space 10 defined by the metal belt 20. The purpose of the root support 6 is to protect the guide roller 2 from the thermal loads caused by welding, which may adversely affect the surface quality of the roller 2. The material of the root support 6 may be any solid material which prevents or at least reduces the transfer of the heat load due to welding to the roll 2. In addition, the material 25 forms a flat surface. Such materials include, for example, copper in the form of a thin sheet or foil, or aluminum, for example, in the form of a thin sheet or foil.

Thereafter, the welding of the metal belt 4 may be performed on the opposite side of the second surface 4b of the metal belt 4 against the guide roll 30 2, i.e. the first side 4a of the metal belt 4. Repair welding is performed by any welding method suitable for the material of the metal belt 4 to be repaired, including laser welding, TIG welding, and friction welding (FSW welding). In Figs. 1-2, the apparatus employing the welding process is denoted by the reference numeral 5. The materials of the metal belt 4 are discussed in more detail in Applicant's Patent Publication FI 117982, so it is not necessary to go into more detail here.

Since the second surface 4b is tightly against the surface of the guide roller 2 or against an additional support 6 having a flat surface, the weld is just flat and flush with the other surface 4b. Thus, the metal belt 4 of the second side 10 of the grinding 4b is not required. grinding the weld point is required to make the guide roller 2 against the supported surface 4b on the opposite side with respect to the surface of a first surface 4a.

Because of the stresses in the material during welding, the stress relief annealing is performed after grinding. For this purpose, the welding point is moved into the free area between the guide rollers 2 or the free area between the guide roller 2 and the thermal roller 3, and the stress relieving annealing is otherwise carried out by a method known in the art.

The present invention is not to be limited to this metal belt calender application, but can be applied in many ways within the scope of the claimed claims.

Claims (6)

1. A method of repair welding of an adjusting strip (4) used in a fiber web machine (1), in which method one of endless metal strip (4) supported by guide rollers (2) is stopped, characterized in that the section of the metal strip (4), which shall be welded stopped in the running direction of the metal strip (4) towards the surface of any guide roller (2), the metal strip (4) supported in the running direction at least at the section to be welded to the guide roller (2), and that the repair welding of the metal strip (2) is carried out on the opposite side. the surface (4b) coming towards the guide roller (2). Method according to claim 1, characterized in that a thin additional support (6) is adapted between the surface (4b) of the metal strip (4) and the surface (4b) of the guide roller (2). 15 Method according to claim 2, characterized in that the material of the additional support (6) is preferably copper plate or foil or aluminum plate or foil. 20 Method according to any of the preceding claims 1-3, characterized in that for repair welding, at least one laser, TIG and / or friction welding method is used. Method according to any of the preceding claims 1-4, characterized in that, after the repair welding, the welding site is grinded from relative to the supporting surface (4b) on the opposite side (4) of the guide roller (2). Method according to any of the preceding claims 1-5, characterized in that after the repair welding, the welding site is moved to the free area between the control rollers (2) and the voltage annealing is performed.