JPS6350114B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for efficiently rolling a composite steel plate with excellent joint strength. Composite steel plates (hereinafter referred to as clad steel plates) manufactured by stacking and rolling different materials are used in various fields, but recently there has been a demand for clad steel plates with excellent joint strength. Conventionally, one of the manufacturing methods for clad steel sheets is to insert an insert material such as nickel foil between the mating surfaces of the base material and the mating material, whose mating surfaces have been cleaned, to overlap them, to weld and fix the periphery, and to remove the mating surface. There is a so-called hot welding rolling method in which a laminated slab is produced by removing air between the slabs, and this slab is hot rolled. FIG. 1 is a diagram showing an asymmetric rolling method, which is one of the hot welding and rolling methods. (a) shows the slab used for asymmetric rolling, and (b) shows the rolling state. 1 is base material, 2 is laminate material, 3
is the welded part. The slab used in this method is one in which a base material 1 and a laminate material 2 are stacked on top of each other and their peripheral edges are welded and fixed. After heating, such a slab is rolled into a predetermined size by a rolling mill 4. However, the base material 1 and the laminate material 2 have different elongation rates due to their different coefficients of linear expansion, and the base material 1 and the laminate material 2, which are in contact with the upper and lower rolls, separate from each other as they move along the rolls. There is a drawback that force acts in the direction of (in the direction of the arrow in the figure) and peeling may occur if the welding at the peripheral edge is not sufficient. As a method for eliminating such drawbacks, there is a target rolling method which is the same hot welding rolling method. FIG. 2 is a diagram showing the target rolling method. (c) is a slab used in this target rolling method, and (d) shows the state of rolling. The slab used in this method is base material 1
Two more laminated materials 2 and 2 are stacked together with a release material 5 interposed between the laminates 2 and 2', and their peripheral edges are welded and fixed to produce a slab, and this slab is heated. It is manufactured by separating the mating materials 2 and 2' after rolling them to a predetermined size using a post-rolling mill 4. In this method, the peeling force between the base material and the laminate is canceled out, resulting in a crucified steel plate with good bonding strength. However, this method
Since the four sheets of laminate materials 2 and 2' are stacked, the thickness of the slab increases and is limited by the thickness that can be rolled by a rolling mill. Furthermore, since the welded area becomes wider, the number of man-hours required for welding increases, resulting in higher costs. This invention has been made to address the above-mentioned drawbacks, and its gist is to overlap a base material and a laminate material, fix their peripheral edges by welding, and then add a dummy material to cover the top surface of the laminate material. The method is characterized in that a slab formed by overlapping and partially welding the dummy materials to the peripheral edge of the base material is hot-rolled, and the dummy material is removed after rolling. That is, the slab used for asymmetric rolling is covered with a dummy material and rolled. The following will be explained based on the drawings. FIG. 3 is a diagram showing the rolling method of the present invention. (e) shows the slab used in this invention, and (f) shows the state of rolling. The slab used in this invention is first made by inserting an insert material such as nickel foil between the mating surfaces of the base material 1 and the mating material 2, whose mating surfaces have been cleaned by grinding or the like, overlapping them, welding and fixing the peripheral edges, and then mating. Air is removed between the surfaces. Next, a dummy material 6 covering the upper surface of the laminated material 2 is overlapped and partial welding 7 is performed on the peripheral edge of the base material 1 to form a slab. Such a slab is heated and then hot rolled, and after rolling, the dummy material 6 is removed to obtain a clad steel plate. FIG. 4 is a plan view of a slab used in this invention.
6 is a dummy material, and 7 is a partial weld. During rolling, the dummy material 6 absorbs the peeling force between the base material and the laminate material to increase the bonding strength, and also keeps the welded part at the peripheral edge warm to prevent the welded part from becoming brittle due to rapid cooling. Also, it is preferable that this dummy material 6 covers the laminate material 2 until the end of rolling and does not peel off from the base material 1, but if it can be held without peeling until about 5 to 6 passes when the base material 1 and the laminate material 2 are completely crimped together. good. Therefore, the welding between the dummy material 6 and the base material 1 is from 2 to 2 per side.
It is sufficient to perform partial welding at three locations with a length of 50 to 100 mm. Further, the thickness of the dummy material 5 is preferably 10 to 20 mm. If it is less than 10 mm, there is a risk of melting during heating, and if the desired welding strength is to be obtained, the welded part needs to be long, so a thickness of 10 mm or more is preferable. However, if the thickness exceeds 20 mm, workability deteriorates, so it is preferable to use a steel plate with a thickness of 10 to 20 mm as the dummy material. Next, examples will be described. JIS G3101--SS41 as base material, JIS G4303,
A clad steel plate made of SUS309L stainless steel was rolled according to the present invention. The components of the base material and the laminate material are shown in Table 1, and the dimensions of the base material, the laminate material, and the dummy material are shown in Table 2.

【table】

[Table] The mating surfaces of the base material and cladding material shown in Tables 1 and 2 were ground and cleaned, then nickel foil was placed between the mating surfaces and overlapped, and the periphery was fixed by welding, leaving an air vent hole. did. The remaining air was removed from the air vent hole using a vacuum pump, and the hole was closed by welding.
Next, a 20 mm thick dummy carbon steel plate covering the top surface of the laminate was overlapped and partially welded to the periphery of the base metal. As shown in Figure 4, the slab was manufactured with two welds on each side and a weld length of 70 mm. This slab was heated to 1250° C. and then hot rolled to a thickness of 8 mm (base material 6 mm, laminated material 2 mm). During rolling, a crack occurred in one welded part of the dummy material, but there was no problem with rolling. After rolling, the dummy material was removed, and the bonding state of the obtained clad steel plate was investigated using ultrasonic waves. As a result, a clad steel plate with excellent bonding strength and no bonding defects was obtained. As described above, the rolling method of the present invention solves the peeling force that occurs during conventional asymmetric rolling by using a dummy material, and can obtain a crud steel plate with excellent joint strength. In addition, unlike conventional target rolling, the thickness of the slab does not increase, so workability is good. Furthermore, the dummy material of the present invention has many effects such as keeping the welded part warm so that the welding strength does not decrease.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the non-target rolling method, FIG. 2 is a diagram showing the target rolling method, FIG. 3 is a diagram showing the rolling method of the present invention, and FIG. 4 is a plan view of a slab used in the present invention. . In the figure, 1... Base metal, 2... Laminated material, 3... Welded part, 4
...Rolled material, 5...Peeling material, 6...Dummy material, 7...Partial welding.

Claims (1)

[Claims] 1 Layer the base metal and cladding material whose mating surfaces have been cleaned, and weld and fix the periphery. Then, overlap the dummy material that covers the top surface of the laminate material, and partially weld the laminate material to the periphery of the base material.The resulting slab is heated. A method for rolling a composite steel sheet, comprising rolling the dummy material during rolling and removing the dummy material after rolling.