JPS5865516A - Corner projecting forming method by cold rolling of stainless steel - Google Patents

Abstract

PURPOSE:To form the outside radius of a bent part by bending to plate thickness or below, by continuously executing the first forming for bending to a prescribed angle, the second forming for bringing a material nearer to the tip of the bent part, and the third forming for corner projection. CONSTITUTION:By the first plural stage rolls of a tandem roll, the first forming for bending to a prescribed angle is executed. Subsequently, between a punch roll 1 having a prescribed angle on its roll forming surface, and a die roll which has opposed at a specified distance C left and right split rolls 6A, 6B of a die 11 having a prescribed air-gap space (d) against the puch roll surface, the second forming for bringing a material nearer the tip of the bent part. Subsequently, the third forming is executed continuously by the upper and lower corner projection rolls of the first stage.

Description

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

Light-weight shaped steel products produced by conventional cold roll forming have a larger outer radius at the bending part than those produced by hot rolling, and the outer radius was limited to about twice the plate thickness. . This is not limited to lightweight products, but when cold rolled,
This causes surface flaws, increases in internal stress, and stress corrosion. Furthermore, defects may appear over time. Also, depending on the usage conditions, for example, containers that use trace amounts of chlorine, sulfur, alkali or acids,
When applied to heat exchange tanks, heat pipes, piping, etc., stress corrosion cracking may occur in bent or formed parts.

Rather, defects may appear during or after processing. For this reason, depending on the purpose, the bottom shape may be made of high-grade stainless steel.

Either the shape or degree of processing is unavoidably made modest, or special measures are taken, such as incorporating a structural design into the structure to compensate for the shortcomings of stainless steel molded products. 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 significantly improves workability, economy, and efficiency while maintaining quality stability in the forming process. It is an object of the present invention to provide a method and an apparatus that can perform corner forming to a degree that could not be performed using conventional methods.

Next, the present invention will be explained in detail. In the non-invention, tandem roll molding is performed, and the first case and the second case are carried out. In the first case, the first formation is performed using the first multiple stages of tandem rolls, then the second formation is performed using the special rolls shown in Figure 2B, and then the first formation is performed as shown in Figure 2A. Perform a third forming with a roll to bring out the corners. In the second case #-i, as in the first case, the first molding is performed using the first plurality of rolls, and then the third molding is performed as in the first case. The first case is superior because the bending radius of the corner is made smaller than the plate thickness and the molding is sound without defects. In this case, the interval C is determined rationally. The distance 0 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,
By determining the amount of extra area for both longitudinal elongation and plate thickness increase, it is possible to prevent strain distribution, and by extension, surface flaws and uneven distribution of internal stress, and reduce potential stress corrosion cracking. In this way, the outer bending radius can be made less than the plate thickness, and the stone can be bent to ensure quality.

Next, one embodiment of the present invention will be described with reference to drawings and numerical values and relational values. FIG. 1 is a front sectional view showing the forming cross-sectional shape of 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
The figure is a partially enlarged front sectional view of the special forming roll for the second forming in the first case, and the figure of the fourth person is 70 shown in Tables 1 and 2.
A, Figure 4B is 70B, Figure 5 is 71B, 5th
Figure B is a partially enlarged front sectional view of each bent part of 71B', Figure 6 is a sketch of five wrinkles that occurred during molding,
Fig. 7A is the measured value of the outer radius R of the bending part in each series of experiments, Fig. 7B is the measured value of strain e1 in the longitudinal direction of each series of experiments, Fig. 7C is a machining strain 88 distribution diagram of each series of experiments,
Figure 1θ is a model of the plate deformation process.

Table 1 shows a method for forming a tandem roll according to an embodiment of the present invention.

Table 1 Forming method @ Figure 1 Steel plate thickness t = 1.2U1 Bending angle θ1 = 90 degrees,
The equilateral side of the chevron is a = 4 = 35.5 &l, and the two molding methods A and B shown in Table 1 are performed. 1 of Table 1. Second. A third three-stage roll (FIG. 2A) passes through the gap d between the upper roll 1 and the lower roll 11, and after forming, enter or B forming is performed. In case A, the fourth stage roll shown in FIG. 28 is not used. The forming process consists of an upper roll 1 and a lower roll 11 that are fixed to and rotated by a rotating pivot shaft 4. The shaft 4 has a common conduction, and the lower roll 11 of the squaring roll has opposing splits W5A and 58.
#i Close contact. In the case of forming B, the opposing split molds 6A and 6B of the lower roll 11 of the cornering roll shown in FIG. 2B are as follows:
With an interval C between the gap spaces, 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=(3) The preload of the cornering roll is 3 tons f1 The distance d between the upper roll and the lower roll is almost the same as the thickness of the plate during forming.

The molding load was about 3.1 to 3.4 tons f0.As a result of carrying out the molding under the above conditions, the following was clearly confirmed.

(1) About the shape: In the case of forming A for the 71 people in Table 2 for each material shown in Table 3, that is, the board width 71 & 1B, the surface is as shown in the sketch perspective view in Figure 6. My side A
and B, in a direction perpendicular to the forming arrow direction C. However, in the case of 70B and 71B1, that is, B molding, such surface wrinkles do not occur. this is,
In order to achieve the object of the present invention, the amount of indentation of the material to be formed by the edging roll, such as in the case of 71N, is approximately 1.
It is clearly shown that it is appropriate to avoid excessive molding with 71LI1 and mold with 0 indentation amount as in the case of 70B and 71B.

(2) Regarding the outer radius R of the bent part: Honyoshi 71A
Regarding other embodiments except for 5U84B, 'yt
An enlarged side sectional view of the actual product is shown in FIG. 5A for B and FIG. 5B for 71B'. Figure 7A also shows the measured values for all materials. 71B' is obtained by molding the molded 71B again using the same molding roll. R is 70A → 7
They are small in the order of 0B→71B→71B'. That is,
This shows that molding B is better than molding A, and even better when the same molding is repeated.

The R value is 1. The thickness of the bent steel plate is s 1 at the bent part as shown in the figure.
@＋! ! If e1m is the thickness of the steel plate itself, and tl is the thickness of the steel plate itself, then % '6/11<"It @ <"If the value of II is large, R is small, and the extension line of sides N and B and the outside of the bending part are It is preferable that the area formed by ka > AI > AI >Am' is small. 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 bending surface reveals a good light beam and increases the effect of small radius.

(3) Regarding longitudinal strain ε8: As shown in the measured values in Fig. 7B, each strain is elongated by one length 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. This can be achieved by minimizing the plate width and using B forming to reduce longitudinal strain.

(4) Regarding the plate thickness strain of 6t: Among the test measured values, for those made of 8US 304, the measured values are illustrated in FIG. 7C, and the relationship between the distance from the edge of the steel plate and the strain coefficient.

The R1 of the bent part can be made smaller than the plate thickness, but the molding B and A are different. 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.

A similar tendency is observed for materials other than SUS 304.

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) Differential forming A#i due to the difference in forming method, in which the material is pushed into the tip of the bent part using only the cornering roll, and due to the increase in the thickness of the material near edge 13 and the elongation in the longitudinal direction, the bending Since the material does not reach the tip of the part, it is not possible to turn R.

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 the 7th figure, the minimum R is %5pao, and SUS
304 up to %SUS 430 and 5US444
is in between. The longitudinal strain shown in FIG. 7B is separated by 5POO, and other materials, namely stainless steel, show the same tendency as 5POO, but are approximately the same. FIG. 7D shows the general relationship between tensile strength σB and longitudinal elongation in the case of 71B. In order to correct the variation in the width of the blank plate, the amount ′ε indicating the elongation in the longitudinal direction is tz 7g @
Indicated by

That is, s M x/g. is the virtual elongation strain ε in the longitudinal direction when the product cross-sectional area is equal to the roll hole cross-sectional area. The actual elongation strain relative to C8 is expressed as a ratio of C8. As σB increases, the amount of longitudinal elongation decreases and R increases. This is because as σB increases, the molding reaction force during molding increases,
An increase in the gap d (FIG. 2B) between the upper and lower rolls indicates that the molding is not sufficiently formed. As shown in 71B' in Fig. 6, for materials with a large σB, a better effect can be brought about by performing corner roll forming again, and R can be made smaller than the plate thickness. I can do it.

No correlation could be observed between the r value and R.

(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. Take the th σ=”/Yo,
For close contact, set it to 100 inches. 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<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
shows the distribution of strain C8 in two directions (direction perpendicular to the plane of the paper) of the steel plate at approximately 99.5%.

The excess area of the material relative to the roll hole shape is calculated to be approximately 2.7 inches in the case of this example, but it is due to the elongation in the longitudinal direction and the plate 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 to increase.

As already explained with regard to one embodiment, the present invention reduces the bending radius R, performs cold roll cornering to form a chevron, and forms a product that does not cause defects such as surface wrinkle deformation due to processing. In addition, in order to prevent defects that could potentially cause stress corrosion inside the bent part, forming with multiple stages of tandem rolls and then forming with at least one stage of squaring rolls in 1 ii [, at least 1 pass i] is performed. This shaping and, more preferably, multiple re-passes with multiple stages of cornering rolls for cornering have yielded very good results. 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 previously described, the method and apparatus for squaring stainless steel according to the present invention forms 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 that it will be applied to many applications and even the thick table effect will be improved.

[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, Fig. 3 is a sectional front view of one product, and Fig. 4A. , FIG. 4B, FIG. 5A, and FIG. 5B are partially enlarged front cross-sectional views of an illustrative bent part, FIG. 6 is a sketch perspective view of generated wrinkles, FIG. 7A is a radius measurement value, and FIG. 7B is a longitudinal strain. Measured values, Figure 7C is a diagram of the relationship between distance from the edge and strain, Figure 7D is a diagram of the relationship between strain and bending radius, Figure 8 is a partially enlarged front view of the deformed model, and Figure 9 is the strain in the longitudinal direction. The distribution map, Figure 10, is a model of the plate deformation process. In, B Bending side θl Angle 4.4 Side length t* '(1s 11 t t, I t= Thickness R
, R1, - radius c + ' 1% J [space 'O
*A1 w A, -A11 Area 1 Upper mold roll
ll Lower mold rolls 5A, 5B, 6A, 6B
Split lower roll 2 people, 2B, 3A, 3B Upper mold support part 4 Roll center drive shaft Special punch Applicant Nippon Metal Industries Co., Ltd. Agent Patent attorney Nishi Naka - -7

Claims (1)

[Scope of Claims] l In order to bend and form a stainless steel plate shaped steel, a flat steel plate surface is deformed within a gap between a plurality of upper and lower rolls at the front of a dandem roll in a predetermined manner within a gap between upper and lower roll mold holes. First molding is performed at an angle, and then an upper mold roll with a predetermined angle on the mold surface and a left-right split mold of a lower mold with a predetermined gap distance from the upper mold roll surface are placed at a certain distance. A second forming process is performed in which the material is brought to the tip of the bent part between the lower mold rolls provided facing each other, and then a third forming process is performed continuously using at least one stage of cornering upper and lower rolls. A method of cold roll corner forming of stainless steel. 2. The first aspect of claim 1, in which bending by third forming is repeated using upper and lower rolls in multiple stages, each stage having the same two shapes, so that the bending radius is smaller than the thickness of the raw steel plate.
The method for cold roll squaring of stainless steel as described in . 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.