JPH0120929B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing torsion defects when roll forming corrugated sheets such as keystone plates and deck plates.

When a corrugated sheet 1 as shown in FIG. 1 is cold roll formed, torsional defects as shown in FIG. 2 occur after forming. In order to prevent such twisting, measures such as making the clearance of the forming rolls uniform in the width direction, or adjusting the upper and lower transmission shafts of the forming machine so that they are parallel, are taken to prevent the molded product from forming. This ensures uniform deformation in the width direction.

However, no matter how perfectly such countermeasures are taken, torsional defects cannot be completely eliminated because they are caused by residual stress caused by forming the steel plate into a predetermined corrugation itself. To explain the mechanism of generation of such residual stress, when a corrugated sheet 1 having the shape shown in Fig. 1 is roll-formed, the central ridge A is usually formed, and then the ridges B on both sides are formed. Even if the number of peaks and valleys is larger, molding is performed sequentially from the center to the outside. When forming the first mountain A, the plate width of the flat plate parts on both sides of mountain A is wide, so the width of the flat plate part on both sides of mountain A is very large due to the width shifting resistance of the material on both sides and the friction between the plate and the roll. directional tension acts and shrinks in the longitudinal direction. This shrinkage increases as the number of peaks and valleys increases.
The wider the material board is, the larger it is.

As a result, as shown in FIG. 1, the residual stress in the longitudinal direction becomes tension in the width direction near the central portion a in the width direction, and compression in the width direction at both left and right sides b to balance this stress. In this way, when the distribution of residual stress becomes compressive on both sides with tension in between, twisting occurs and a more stable state is attempted. This is the mechanism by which torsional defects occur. That is, when the widthwise distribution of residual stress in the longitudinal direction becomes compressive on both sides with tension interposed, a torsional defect occurs. If such a torsion defect exists, it poses problems in transportation of the product, in construction when using the molded product, and in terms of the aesthetic appearance of the product.

The present invention has been proposed in view of the above circumstances, and its purpose is to provide a method for preventing torsion defects by which torsion defects can be eliminated.

The defect prevention method according to the present invention includes rolling and rolling a part or all of the initially formed peaks or valleys where tensile residual stress occurs in the forming/longitudinal direction after forming, depending on the amount of shrinkage in the forming/longitudinal direction. By stretching and molding in the longitudinal direction, the distribution of longitudinal residual stress in the width direction is made uniform, thereby eliminating torsional defects.

The present invention will be described below based on illustrated embodiments. In this embodiment, X=50 as shown in FIG.
mm, Y=70mm, W=450mm, H=30mm, plate thickness 0.6mm
This is a case where a cold-rolled steel sheet 1 is formed using a 12-stage roll stand, and a torsion defect correction stand 2 is installed at the final stage, and the forming method according to the present invention is performed here.

This straightening stand 2 has an upper roll 3 and a lower roll 4 that form a hole shape corresponding to the final shape of the steel plate 1. Protrusions 5 are formed on the rolls 3 and 4 corresponding to the central peak A of the steel plate 1, and the protrusion 5 gives longitudinal elongation to the peak A. As shown in FIG.
It may be provided so that the upper surface corner portions 1b of the valley A' located on both sides of the mountain A are rolled down, or the lower surface center portion 1c and the valley A' as shown in FIG.
It may be provided so as to press down the center portion 1d of the upper surface of A'. In such a configuration, the applied longitudinal elongation can be freely changed by changing the gap between the upper roll 3 and the lower roll 4.

Figure 7 shows the effect of preventing torsional defects by the above-mentioned forming method, where the horizontal axis shows the actual reduction rate determined from the material plate thickness and the plate thickness after forming, and the vertical axis shows the unit of torsional defects. The experimental points are plotted by measuring the twist angle per length. In this graph, white circles indicate the case where l ₁ =10 mm in FIG. 5, and black circles indicate the case where l ₂ =35 mm in FIG. 6. As is clear from this graph, without the correction stand 2, the torsional defect was 8.7 deg/m, but the
This problem is resolved with an actual reduction rate of 0.3%.

Considering the above experimental results, the same effect can be obtained even if all the parts where tensile residual stress occurs, including the hypotenuse of mountain A, are stretched in the longitudinal direction by rolling, and if the rolling reduction rate is appropriate, all the parts where tensile residual stress is There is no need to press down, and the same straightening effect can be obtained even by partially elongating in the longitudinal direction.

Next, as shown in FIGS. 8 and 9, a large number of coining protrusions 6 are provided on the outer peripheral surface of the lower roll 4 at equal intervals in the circumferential direction, and a coining groove 7 is formed on the lower surface of the center of the crest A. The material is formed to provide elongation in the longitudinal direction. This coining groove 7 is E=3mm, F=35mm, P=15
mm. Further, the depth of the coining groove 7 can be adjusted by adjusting the gap between the rolls 3 and 4, as in the previous example.

FIG. 10 shows the effect of preventing torsional defects by such coining grooves, with the depth of the coining grooves plotted on the horizontal axis, and it can be seen that torsional defects are eliminated when the coining depth is about 0.15 mm or more. It goes without saying that in the case of such a coining groove, the portion where tensile residual stress occurs may also be coined at the same time. Further, the coined shape may be any shape as long as it provides elongation in the longitudinal direction.

In the above embodiments, a correction stand was added in addition to the original molding stand to remove torsional defects, but it can also be incorporated into the molding process.

Note that the straightening stand 2 requires a considerably large rolling force and a large mill rigidity. Therefore, if necessary, an appropriate backup roll may be used.

As described above, according to the present invention, it is possible to eliminate torsional defects in roll-formed products, which have hitherto been intractable, with a relatively simple structure.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a corrugated plate, Fig. 2 is a perspective view showing a state in which torsion occurs, Fig. 3 is a cross-sectional view showing an example of the corrugated plate, and Fig. 4 is a front view showing a correction stand according to the present invention. 5 and 6 are front views showing examples of roll shapes of similar stands, FIG. 7 is a graph showing the effect of preventing torsional defects by the above-mentioned rolls, and FIG. 8 is a side view showing examples of other roll shapes. 9 is a perspective view showing the coining groove, and FIG. 10 is a graph showing the effect of preventing twisting defects by the roll of FIG. 8. 1...Corrugated plate (steel plate), 2...Correcting stand, 3
...Top roll, 4...Bottom roll, 5...Protrusion,
6...protrusion, 7...coin groove.

Claims (1)

[Claims] 1 In the roll forming of a plate material in which a plurality of peaks and valleys with a uniform cross section are continuous in the width direction, the first formed peak or valley where tensile residual stress occurs in the longitudinal direction after forming. A method for preventing torsion defects in roll forming, characterized by forming a part or all of a valley portion by forming/stretching in the longitudinal direction according to the amount of shrinkage in the forming/longitudinal direction.