JPS5931429B2 - Overlay repair method for down coiler unit roller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for overlay repair of a unit roller of a down coiler.

A down coiler for winding a strip in a hot rolling line is roughly constructed as shown in FIG. unit roller to press the strip uniformly and wrap it tightly around the mandrel; G is the apron guide;
s is a piston-cylinder mechanism for opening the apron guide after the initial winding of the strip.

The role of the down coiler is extremely important; it not only winds up the hot rolled strip, but also ultimately determines the quality of the strip. Quality abnormalities that occur during strip winding of a down coiler are called coiler defects, and typical examples include:
There are so-called top marks, scratches, ridges, meandering, bead marks, etc. Most of these problems, other than the bead marks, can be solved by modifying the side guide in front of the pinch roll or the unit frame. Therefore, among the coiler defects, the unresolved one is the bead mark described below, and solving this problem has been an issue for the time being. The unit roller of the down coiler is provided to ensure that the strip that is wound around the mandrel completely adheres to the mandrel and to eliminate looseness between the strips to obtain the best coil shape. properties and abrasion resistance are required.

In order to provide the above properties, the conventional roller base material is SCH
-3H, and the surface is overlaid with 13C1 SUS, but the bead joints (where the beads overlap, see Figure 2) become a deteriorated layer and are prone to corrosive wear. As the weld progresses, a spiral corrosion groove is formed on the surface of the roller body along the welding direction. This corrosion groove is transferred to the strip, resulting in a coiler defect in the strip called a bead mark. Figure 2 is an explanatory diagram of the bead joining part, B is the bead, F is the melting part,
H is an altered layer. Originally, overlay welding is different from casting, where the entire product is formed as one piece at the same time.In contrast, overlay welding involves continuously repeating local melting using arc heat to solidify the deposited metal to create a bead, and then overlap the beads. However, since this is a method of forming the entire bead, as each bead solidifies, dendrites (dendritic crystals) develop respectively, but the direction of these dendrites is in the direction of solidification at the end of the local molten pool.

Therefore, the dendrites grow in different directions near the boundaries (bonds) between each bead, and the bonds of each bead form a kind of arm opening. Therefore, the layer near the bond, including the bond, is non-uniform in metallographic structure, has unstable mechanical properties, and generally contains microscopic notch defects. As mentioned above, unit rollers manufactured or refurbished by overlay welding undergo highly periodic (spiral) corrosive wear between the beads on the body surface during use, resulting in bead marks on the strip. Not only that, but also the life of the roller is shortened due to partial wear of the roller. Therefore, there was a need to solve the problem of bead marks from both the viewpoints of strip quality and roller repair costs. When repairing the unit roller of a down coiler, the present invention changes the deteriorated layer formed at the bead joint of overlay welding to a uniform structure,
This invention provides a method for repairing unit rollers that solves the problem of bead mark generation described above.

In the method of the present invention, when repairing a unit roller of a down coiler, first, a first layer is built up in a spiral shape on the body of the unit roller, rough-processed, and then a strip-shaped electrode is used on this built-up layer. After the second layer is built up in the axial direction of the roll body, the first layer is ground down and the soil is processed, and will be described below with reference to the drawings based on an example.

FIG. 3 is an explanatory diagram of the method of the present invention, showing a cross section of a unit roller.

In the figure, R is a roller, and 1 indicates the final finishing dimension of the repair. In the method of the present invention, an intermediate rough machining dimension 2 having a radius larger than the final finishing machining dimension 1 is set in advance, and beads are first superimposed in a spiral shape along the circumference of the body of the roller up to just above the intermediate rough machining dimension 2. Make the first layer of meat. The difference between the first final finish machining dimension 1 and the intermediate rough machining dimension 2 is 2 to 31 seconds in radius. (In the figure, 3 is the build-up welding part of the first layer.) Next, the build-up of the first layer is cut (rough machining) to intermediate rough machining dimensions, and further, the build-up of the first layer is cut (rough processing). As a second layer on top, a strip electrode automatic overlay welding device is used to deposit the first layer parallel to the roller axis.
Overlay welding is performed over the entire surface of the layer. The build-up of the second layer is performed in one pass or in two passes. (In the figure, 4 is the overlay welding part of the second layer.) After overlaying the two layers mentioned above, finishing is performed by cutting down the first layer to the final finishing dimension of 1, and the roller repair is completed. do. According to one embodiment of unit roller repair, the dimension (radius) of the worn roller to be repaired is 345 m, and the final finishing dimension is 35.
0mm, intermediate rough processing dimension 3521'', second layer overlay welding dimension 360mm.

According to the two-layer build-up described above, the deteriorated layer of the spiral bead joint generated by the first build-up is recrystallized by the welding heat generated during welding of the second layer in the roller axis direction. At the same time, since the roller is subdivided in the axial direction, the structure of the deteriorated layer at the bead joining portion becomes uniform, and if the build-up amount of the second layer is completely removed, a roller with a uniform structure is regenerated. The reason why a strip electrode is used for overlay welding of the second layer is as follows.
Remaining overlay welding layers in the direction of the roller axis may cause uneven wear of the roller (polygonal wear), and must be completely removed as extra welding during finishing. This is because welding has a much shallower penetration than other methods and is optimal for forming the layer to be cut and finished. The rollers repaired by the method of the present invention described above have uniform wear due to the uniform structure, and therefore no bead marks occur in actual operation, contributing to improving the quality of the strip and extending the life of the roller. It has been significantly extended.

The method of the present invention can be applied not only to repairs but also to the production of new unit rollers.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of a down coiler, FIG. 2 is an explanatory diagram of a bead joining part, and FIG. 3 is an explanatory diagram of the repair method of the present invention, showing a cross section of a unit roller. M: Mandrel, R: Unit roller, G: Apron guide. S: Piston/cylinder mechanism, B: Bead,
H゛: Altered layer, F: Penetration part, 1: Final finishing dimension, 2: Intermediate rough machining dimension, 3. 1st layer overlay welding part, 4
Overlay welding part of the second layer.

Claims (1)

[Claims] 1. When overlaying and finishing the unit roller body, the first layer is overlaid in a spiral shape and rough processing is performed, and the second layer is applied on the first layer in the axial direction of the roll body using a strip electrode. A method for repairing overlay of a down coiler unit roller, characterized in that after overlaying, finishing is performed by cutting down to the first layer.