JPS5928409B2 - Method of cold roll corner forming of stainless steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for edging a stainless steel sheet by cold roll forming.

Light-weight shaped steel products formed by conventional cold roll forming have a larger outer radius of the bent portion than those formed by hot rolling, and the outer radius has a limit of about twice the plate thickness dimension.

This is a similar limit not only for lightweight products but also for corner forming of various products using cold rolls or cold forming molds. In addition, if severe cold forming is performed,
This causes surface flaws, increases in internal stress, and stress corrosion cracking. Furthermore, defects may appear over time. Also, depending on the usage conditions, for example, stress corrosion cracking may occur in bent or formed parts when applied to containers, heat exchange tanks, heat pipes, piping, etc. that use trace amounts of chlorine, sulfur, alkalis, or acids. There is. Rather, defects may appear during or after processing. For this reason, depending on the application, it may be necessary to mold stainless steel with a high-grade composition, or unavoidably reduce the processed shape or degree of processing, or mold stainless steel into the structure to be incorporated. Special measures may be taken, such as incorporating structural designs to compensate for the product's deficiencies. All of these methods are complicated, and even if implemented, it cannot be said that concerns regarding quality or structure can be resolved. In view of these current circumstances, the present invention performs angular forming using cold rolls of stainless steel, and improves workability while maintaining quality stability in the forming.
The object of the present invention is to provide a method and apparatus that can significantly improve economy and efficiency, and can perform corner forming to a degree that could not be performed using conventional methods.

Next, an overview of the present invention will be explained.

The present invention involves tandem roll forming, and the first case and the second case are carried out. In the first case, the first forming is performed using the first multiple stages of tandem rolls, and then the second forming is performed using the special rolls shown in Fig. 2B.
A third forming is then carried out to provide angulation with rolls as shown in FIG. 2A. In the second case, as in the first case, the first molding is performed using the first multiple stages of rolls, and then, as in the first case, the third molding is performed. The first case is excellent in order to make the cornering radius smaller than the plate thickness and to perform sound forming without defects. In this case, the interval C is determined rationally. The distance C depends on the plate thickness, the tensile strength of the stainless steel, and the raw steel plate material. In the second case, it also depends on the shape of the final corrugated roll of the first forming. In both the second case and the first case, the excess area related to longitudinal elongation and plate thickness increase is determined to prevent strain distribution, and by extension, surface flaws and uneven distribution of internal stress. can reduce stress corrosion cracking. In this way, the outer bending radius can be made equal to or less than the plate thickness, and the bending can be performed with quality assurance. Next, one embodiment of the present invention will be described with reference to drawings and numerical values and relationship values.

FIG. 1 is a front sectional view showing a molded cross-sectional shape according to an embodiment of the present invention, FIG. 2A is a partially enlarged front sectional view of the cornering roll in the second case, and FIG. 2B is a front sectional view in the first case. A partially enlarged front cross-sectional view of the special forming roll for the second forming, FIG. 4A is for 70A shown in Tables 1 and 2, FIG. 4B is for 70B, FIG. 5A is for 71B, and FIG. 5B is for 71B'' is a partially enlarged front cross-sectional view of each bent part, Fig. 6 is a sketch of the wrinkles that occurred during molding, Fig. 7A is the measured value of the outer radius R of the bent part in each series of experiments, and Fig. 7B is a series of Strain εz% measurement value in the longitudinal direction of each experiment, Figure 7C is a relationship between distance from the edge and plate thickness strain for each series of experiments, Figure 7D is a relationship between σB, 5/εo and R, and Figure 8 Figures (1), (2
) and (3) are partially enlarged front views of the model in which the lower mold 11 approaches the upper mold 10 roll surface during material deformation, Figure 9 is a longitudinal strain distribution diagram of the plate, and Figure 10 is the deformation process of the plate. model. Table 1 shows a method for forming a tandem roll according to an embodiment of the present invention.

In FIG. 1, the steel plate thickness t=1.21 m, the bending angle θ1=90 degrees, the equiangular sides a=b=35.6 m, and the two forming methods of forming A<5B in Table 1 are performed.

After passing the gap d between the upper roll 1 and the lower roll 11 with the first, second, and third three-stage rolls (Fig. 2A) in Table 1, A
Or do B molding. In case A, the fourth stage roll shown in FIG. 2B is not used. The forming process consists of an upper roll 1 and a lower roll 11 which are fixed to and rotated by a rotating pivot shaft 4. The shaft 4 has a common conduction, and the opposing split molds 5A and 5B of the lower roll 11 of the squaring roll are in close contact with each other. In the case of forming B, the opposing split molds 6A of the lower roll 11 of the cornering roll shown in FIG. 2B
and 6B are separated by a gap c, and the upper part of the space c communicates with the gap d between the upper and lower rolls 1 and 11. In the case of this example, which will be described later, c=6wr1n (thickness of plate to be formed t=1
．． 2). In other words, the size is five times the plate thickness. In addition to setting c to 67 m, 2, 4, 8, 1
We investigated the gap spatial distance spacing of 0 and 12 m, but no spatial effect was observed in the case of C = 2 WfL, and c = 1
In the case of 07rrm, it is recognized that it becomes excessive, and c is set to 4~
It was confirmed that a value of 8Fm is appropriate, and among these, c=6m is optimal in this example. In short, the gap c is about 3.4 to 7 times the plate thickness, preferably about 4.
A range of 0 to 5.5 times is appropriate. Each of the first stage stand, second stage stand, and third stage stand had a roll shaft diameter of 30 wrm, and the fourth stage stand and the fifth stage stand had a roll shaft diameter of 40 m.

No lubricant was used in the first to third stages, and machine oil +120 was used in the fourth and fifth stages. Molding speed is approximately 3
．． It is 6m/m.

The number of roll stages and molding speed are not limited to the above numbers. This can be arbitrarily selected depending on the material and dimensions of the steel plate used, but it is preferable that a plurality of stands be used for the first stage, that is, the first to third forming stages, and at least one stand for the second stage. Use plural. The steel plate width is shown in Table 2, the steel type is shown in Table 3, and the bending radius R is defined as R=L and L as shown in FIG.
(υ r value is the value of plate width strain/plate thickness strain in a tensile test (2) The longitudinal direction strain of the product is expressed by εz.

(3) The preload of the cornering roll is 3 tons f, and the distance d between the upper roll and lower roll is almost the same as the plate thickness during forming. The molding load was approximately 3.1 to 3.4 tons FO.As a result of carrying out the molding under the above conditions, the following was clearly confirmed.

(1) Regarding the shape: In the case of forming A in Table 2 TIA for each material shown in Table 3, that is, for a plate width of 71 wrm, there are surface wrinkles as shown in the sketch perspective view in Figure 6. , side A
and B, in the direction D perpendicular to the forming arrow direction C.

However, in the case of IOB and TIB, that is, B molding, such surface wrinkles do not occur. In order to achieve the purpose of the present invention, it is necessary to avoid excessive molding, where the amount of indentation of the material to be molded by the cornering roll is about 1.7 - as in the case of IIA, and to avoid excessive molding in the case of 70B and TIB. It is clearly shown that molding with an indentation amount of 0 is appropriate. (2) Regarding the outer radius R of the bent part: Regarding other examples excluding the defective IIA, SUS3O
4 case is shown in Figure 4A for TOA and Figure 4 for IOB.
An enlarged side sectional view of the actual product is shown in Fig. B, Fig. 5A for TIB, and Fig. 5B for TIB'.

In addition, each measured value of all materials is shown in Fig. TA. TIB' is obtained by molding the molded TIB again using the same molding roll. R is TOA→TOB→TIB-? T.I.B.
′ is small in order. In other words, B molding is better than A molding.
It shows that the case of molding is good, and the case of adding the same molding again is even better. The R value is defined as TO/tl<T2/, where the thickness of the bent steel plate is TO, t2, t3 at the bending part, and tl is the thickness of the steel plate itself, as shown in the figure.
When the value of tl<T3/tl is large, R is small and side A
, 5B, and the area formed by the outside of the bent part is AO>A1
>A2>A2', which is small, is good.

In this way, it is easy to make the R value smaller than the plate thickness, and moreover, no defects occur in the material. The curved surface reveals good gloss and increases the effect of small radius. (3) Regarding the longitudinal strain εz: As shown in the measured values in FIG. 1B, all the strains extend in the longitudinal direction.

If the same molding method is used, the smaller the plate width, the smaller the elongation. For the same sheet width, B molding has less elongation than A molding.
To reduce longitudinal strain, this can be achieved by minimizing the plate width and using B forming. (4) Regarding the plate thickness strain εt: Among the test measured values, for those made of SUS3O4, the measured values are illustrated in Fig. TC, and the relationship between the distance from the edge of the steel plate and the strain %.

The radius of the bent part can be made smaller than the plate thickness, but there is a difference between forming B and A. The increase in plate thickness near edge 13 (FIG. 6) is remarkable. It also increases at bent corners (inner corners in the figure), but no cracking is observed. The inner corner plate thickness of molding B is larger than that of molding A. In addition, the thickness of the inner corner of the wider plate is often increased. S
A similar tendency is observed for materials other than US3O4. It was confirmed that when the internal bending radii of the corners were the same, reduction in plate thickness could be prevented by forming B. In the case of molding B, no abnormality was observed in the tendency for latent stress corrosion cracking to occur. (5) Difference in effectiveness due to different forming methods Forming A tries to force the material into the tip of the bent part using only the cornering roll, so the increased thickness and longitudinal elongation of the material near edge 13 cause the bended part to Since the material does not approach the tip, R does not become small.

On the other hand, in forming B, since the material is brought to the tip of the bent portion in advance before the cornering roll, the effect of increasing the plate thickness there is recognized, and R is also reduced. When the plate width is increased or when the plate width is large, the effect brought about by B forming increases. (6) Influence of materials As shown in Figure 7A, R is the smallest for SPCC and the largest for SUS3O4,
SUS43O and SUS444 are intermediate.

The longitudinal strain shown in FIG. 7B is far apart for SPCC, and other materials, namely stainless steel, exhibit a similar tendency to SPCC, but are approximately the same. 71 in Figure 7D
The relationship between tensile strength σB, longitudinal elongation, and R in case of B is shown. In order to correct the variation in the width of the blank plate, the amount ε indicating the elongation in the longitudinal direction is expressed as 5/εo. That is, 6Z/ε
O is the virtual elongation strain ε in the longitudinal direction when the product cross-sectional area becomes equal to the roll hole cross-sectional area.

The actual elongation strain is expressed as a ratio of 5. As σB increases, the amount of longitudinal elongation decreases and R increases. This indicates that as σB increases, the molding reaction force during molding increases, and the gap d between the upper and lower rolls (Fig. 2B) increases, resulting in insufficient molding. As shown at 71B' in Figure 6,
For materials with a large σB, a better effect can be brought about by performing angular roll forming again, and R can be made smaller than the plate thickness. Regarding r value and R,
No correlation could be found. (7) Deformation value of steel plate In the case of forming B, the material deformation model within the cornering roll will be studied for a steel plate of unit width as shown in FIG.

Assume that the roll surface is completely smooth. Tenthly, the process of deformation of the plate is shown. The deformation value is the overhang height Y in FIG. and the changing amount ΔY between the surface of the lower roll 11 and the material overhang shown in FIG. 8 (1) → (2) → (3) σ
= 6Y/YO, and in the case of close contact, set it to 100#).
The black dots in FIG. 10 indicate contact with the roll.
When the top roll tip and the material are not in contact and σ is 60%, the vertical load W and the plate edge pushing load T are almost equal, but after this, w increases rapidly.

In Figure 9, σ is approximately 99.50! ) of the steel plate in the Z direction (
The distribution of strain 5 (in the direction perpendicular to the plane of the paper) is shown. The calculated value in this example is 2.7% for the extra area of the material relative to the roll hole shape, but it is due to elongation in the longitudinal direction and increase in thickness rather than the forming flow of the steel plate to the tip of the bending part. It was confirmed that there is a tendency for this to occur.

Regarding one embodiment, as already explained, the present invention reduces the bending radius R, performs cold roll cornering to form a chevron bend, and forms a product that does not have defects such as surface wrinkle deformation due to processing. Forming is performed using multiple stages of tandem rolls, followed by at least one stage of cornering rolls, and at least one pass to avoid defects that could potentially cause stress corrosion inside the bent part. And, more preferably, a plurality of stages of cornering rolls and a plurality of re-passes were performed to obtain the cornering, and very good results were obtained.

This type of forming allows the outer radius of the bent portion to be less than the plate thickness and does not cause any damage. Moreover, stress corrosion cracking does not pose a practical problem. As already explained,
The method and apparatus for squaring stainless steel according to the present invention produces bent outer sections with extremely small bend radii.

Therefore, even if the conventional technology is subject to various restrictions, the present invention can eliminate the restrictions to some extent. In addition, the light reflection at the bent part shows a uniform gloss due to the small radius. Due to these advantages, it can be expected to be applied to many applications and bring about great effects.

[Brief explanation of the drawing]

Fig. 1 is a front view of the shape of one embodiment, Fig. 2A is a partially enlarged front view of the cornering roll of the upper die in close contact with the lower die, Fig. 2B is a partially enlarged front sectional view of the special roll, and Fig. 3 The figure is a cross-sectional front view of one product; Figures 4A, 4B, 5A, and 5B are partially enlarged front sectional views of an exemplary bent portion; Figure 6 is a sketch perspective view of wrinkles; Figure JA is the radius measurement value, Figure 7B is the longitudinal strain measurement value, Figure 7C is the relationship between distance from the edge and strain, Figure 7D is the relationship between strain and bending radius, and Figure 8 is part of the deformed model. An enlarged front view, Fig. 9 is a strain distribution diagram in the longitudinal direction, and Fig. 10 is a model of the plate deformation process. A, B...bent side, θbi...angle, A, b...side length, t la TO? t1 la T2? T3ll thickness) RFRlFR
2...Radius, C, d...Gap space, AO, Al, A
2, A2″...Area, 1...Upper roll, 11...
- Lower die roll, 5A, 5B, 6A, 6BI... divided lower die roll, 2A, 2B, 3A, 3B... upper die support part, 4... roll center drive shaft.

Claims (1)

[Claims] 1. For bending and forming stainless steel sheet shaped steel,
In the gap between the upper and lower rolls at the front of the dandem roll, the flat steel plate surface is first formed at a predetermined angle in the gap between the upper and lower roll mold holes, and then the predetermined angle is applied to the mold surface. The material is brought to the tip of the bending part between the upper mold roll attached and the lower mold roll, which is provided with a left and right split mold of the lower mold facing each other with a certain distance between the upper mold roll surface and the lower mold with a predetermined gap interval. A method for cold roll squaring of stainless steel, characterized in that a second forming is carried out, and then a third forming is carried out successively using at least one stage of upper and lower squaring rolls. 2. The stainless steel according to claim 1, in which the bending by the third forming is repeated using upper and lower rolls in multiple stages, each stage having the same shape, so that the bending radius is smaller than the thickness of the raw steel plate. method of cold roll corner forming. 3. Cold roll angulation of stainless steel according to claim 1, wherein the distance between the opposing surfaces of the left and right split molds of the lower mold roll in the second forming is 3.4 times or more the plate thickness. Method of molding.