JPS58181426A - Forming method of dieless plate utilizing thermal stress - Google Patents

Abstract

PURPOSE:To execute forming without using a die, by providing a heat cycle of local heating and cooling to a metallic plate from the surface and the reverse side. CONSTITUTION:Both end parts of a test piece 11 are supported on a heat resisting glass round rod 13 placed on a supporting base 12 with a lifter, having a heat resisting brick base, in a linear contact state so as to be freely movable without being restricted from the outside. Thermo-electromotive force of a CA thermocouple 18 spot-welded in the center of the reverse side of the test piece 11 repeats a heat cycle of heating and cooling by a prescribed number of times by controlling the opening and closing of a valve 20 of a water cooling pipe 16 by a heating and cooling waveform control device 19 connected to the thermocouple 18. In this regard, the number of times of the heat cycle, a heat cycle upper limit temperature, a heating speed and a holding time are selected suitably in accordance with a kind and plate thickness of a metallic plate material to be worked.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tieless plate forming method using thermal stress.

In press forming of non-manufacturing large structures and small and medium-sized products, etc., the total mold cost accounts for a large proportion of the additional J-cost. It is clear that there would be great advantages if these products could be molded without molds (tieless). However, there are few research reports on dieless molding of such products.

One of them is the linear heating plate bending method (Ishiyōjima/I).
¥1-Gyo Co., Ltd. Shipbuilding Department; Ships, Volume 29, No. 12)
(+956) pages 1037 to 1044).

This method uses an oxygen acetylene/no-ner as a heat source, moves this heat source over the surface of the steel plate at an appropriate speed in a straight line or in a curved line, and rapidly cools the area around the heated part using a water sprinkler. By doing so, a thermal strain difference is produced in the thickness direction of the steel plate, and the steel plate is bent toward the heating surface side using the heating line as a broken line.

For example, as shown in Fig. 1 Fal, when the linear heating wire is moved sequentially at regular intervals as shown by the arrow 2 on the surface of the steel plate 1, as shown in Fig. 1 ft)l, The steel plate is curved along the heating line along the dotted chain line 3 to the heating surface side to obtain an arc-shaped steel plate 4. However, in the case of this method, it is necessary to apply a certain amount of load (moment within the elastic range) to the steel plate before processing.

Another example is the transformation superplastic phenomenon, in which the metal material is press-formed under a low load while being subjected to daily waveform temperature cycles with the phase transformation point that appears during heating and cooling of the metal material as an intermediate temperature. There is a method of pressing a thin sheet metal material using the method (see Japanese Patent Publication No. 44132/1983).

Moreover, it is also stated that this method of forming can, in some cases, make it possible to perform such forming using only the material's own weight, without requiring the pre-loading claw of the die.

In other words, this addition method applies a triangular waveform heating/cooling cycle with the phase transformation point at an intermediate temperature to the entire thin sheet metal material to be processed, and at the same time uses only the lower die, and only the self-weight of the material is added. Dieless processing I--similar forming processing 1--is carried out under a load of .

The present invention differs from the conventional tieless forming process 1, as described in 1-1 below, in that it does not apply a IF in advance (it uses only the thermal stress generated during heating and cooling of the metal plate). The present invention aims to provide a method for performing tieless temporary forming.

The present inventors have discovered that ``plastic modification of metal plates 1. In the process of conducting various experiments and studies on the metal removal plate, we found that while the peripheral part of the metal plate was supported so that the metal plate could move freely without being restrained from the outside, the metal plate was dots on the surface,
At the same time as applying linear or curved intermittent heating cycles, a cooling cycle is applied during non-heating between the heating cycles to the position corresponding to the surface heating position marked +iif on the back side of the metal plate, and +1i1) the metal plate (Narrow and steep local temperature gradient repeats I7)
．． The inventors have discovered that the metal plate can be bent toward the heating surface around the surface heating portion without applying a load to the extent required in the prior art, and have arrived at the present invention.

Next, an outline of the liquid addition I' and the deformation behavior of the metal plate during the heating/cooling thermal cycle of the present invention will be explained with reference to FIG. Figure (a) shows the state before addition. 11 is a strip-shaped flat test piece, 14 is a high-frequency heating coil installed in the width direction at the center of the surface of the test piece 11. The piece 11 is heated linearly with a narrow width in the width direction.

FIG. The bending remains at the position shown by the solid line due to the thickness and rigidity of the piece, indicating that the test piece 11 is bent downward around the heating line. FIG. At that time, it is thought that this is because the heating wire portion of the test piece 11 receives compressive stress in the longitudinal direction of the plate, but as shown in the figure, the test piece 11 is bent in one direction by -1 around the surface heating wire. Become.

In the present invention, the bending angle ((1) is assumed to be as shown in Figure fcl.

The present invention will be explained in detail below using experimental examples.

(The sample material is a 5IOC rolled polished steel plate with a thickness of 1)? and 3
mm, and its chemical composition is shown in Figure 3 for humans. Test pieces were cut from these materials and had a width of 5 mm.
, is machined to a length of I/IOmm.

(2) Experimental method Figure 4 is a schematic diagram of the experimental equipment used in this experiment.
al is 11:, a top view, and (in the figure) is a side view.

In the figure, 11 is a test piece, and its both ends are placed on a support stand 121- with a lifter equipped with a heat-resistant pressure stand.
It is supported in line contact with the bent heat-resistant glass round rod I; 31- so that it can move freely without being restrained from the outside.

Reference numeral 14 denotes a U-shaped water-cooled high-frequency heating coil (tube diameter 5 mm, 1 center) installed in the center of the surface of the test piece 11 at right angles to the longitudinal direction and close to the test piece 11 (with a spacing of about 0.7 mm). The test specimen 11 is heated in a straight line in its width direction (with a heating axis of 2 to 3 mm) by the high frequency heating coil 14. ).

Reference numeral 16 denotes a water-cooling tube, and water-cools the position corresponding to the surface linear heating line iif on the back surface of the test piece 11 using water 17 ejected from the intermediate tube.

To control the temperature of the test piece 11, the thermoelectromotive force of the CA thermocouple 18 spot-welded to the center of the back surface of the test piece 11 is transferred to the thermocouple 18.
At the same time, the control device 19 controls the water cooling pipe 1.
0 to 90 by controlling the opening and closing of the valve 20 of 6.
Thermal cycles of heating and cooling were repeated a predetermined number of times at an arbitrary heating rate between deg/sec. I did it 20 times.

(3) Experimental results (31) Effect of thermal Y cycle number Figure 5 shows the bending angle (α) and the number of repeated thermal cycles (N).
shows the relationship between The figure shows the thermal cycle upper limit maintained! o! Every time(
Among the heating conditions that can obtain a relatively large bending angle, the heating rate (Ilr) is
, holding time (n, 'r,), and H-thickness (1) are different, and the relationship between the bending angle and the number of thermal cycles is shown from the same figure. It can be seen that there is a proportional relationship between them.

That is, under any conditions, as the number of thermal cycles increases, the bending angle also increases.

(32) Effect of heating rate It is thought that the heating and cooling conditions have a significant effect on the bending angle. FIG. 6 shows the relationship between the bending angle (α) and the heating rate (Hr) at constant holding times (H, T,) for thermal cycles 1-11. The degree A (Th) is shown as a parameter. As shown in the same figure, it can be seen that the higher the temperature (Th) is, the better the bending is. Then, thermal cycle 1-limit holding 1jIA degrees (Th
) A clear maximum value appears when Th is 950'C compared to the case of 750'C. In other words, it can be seen that optimal molding conditions exist.

(3, 3) Influence of holding time The rate of phase transformation is roughly proportional to the heating rate, and holding time also affects the progress of transformation, so there should be a close relationship between the two, and this point I researched about it.

FIG. 7 shows the relationship between the bending angle (a) and the holding time (H, T,) under the condition of "thermal cycle" where the eye holding temperature (Th) is constant, using the acceleration (Hr) as a parameter.

The maximum bending angle is obtained at a heating rate of (H,T,)-5 seconds. This is Hr == 40.8Q deg
A similar tendency was observed at any heating rate of /see.

The reason why the bending angle becomes smaller when the holding time is longer is because the heating line width of the test piece widens and the effect of heating on deformation decreases based on the increase in L of the test piece. It seems to be.

(34) Effect of Plate Thickness The effect of the change in plate thickness on test piece J-method on tie-less bending is shown in FIGS. 8 and 9. Figure 8 shows thermal cycle 1 - limited hold l! degree (Th) = 950
The relationship between the bending angle (α) and the heating rate (If T, ) under a constant strip A'I of a holding time (H, T, )-5 sec at ℃, with the plate j-no(+) as a parameter. It is.

In addition, Figure 9 shows thermal cycle 1-limit holding temperature (q”h)=
415 (I C1 heating rate (Ilr) = 40 d
The relationship between the bending angle (a) and the holding time (11, T,) under constant conditions of egA; ec is expressed as /Jζ with 'tM thickness (1) as a parameter.

From both figures, it can be seen that the plate bends well due to the small force due to the plate thickness. ,
However, it has become clear that the behavior is almost the same even if the plate thickness is different.

Figure 10 shows the holding time (H,'I
The relationship between the bending angle (cz) and heating rate (I(r) under the conditions of
Fig. 11 shows thermal cycle 1 when the plate thickness is 3 mm.
The relationship between the bending angle (α) and the holding time (11, T,) under the condition of -950°C is expressed as the heating rate (
'r''h) is shown as a parameter. From both figures, it can be seen that the same tendency as in the case where the plate thickness is 2 mm is observed.

(': 3, 5) Thermal cycle 1 - Influence of limit holding temperature Figure 12 shows the holding time (H, T) - 10 when the plate thickness is 2 mm.
sec. Bending angle (a) under constant conditions and thermal cycle 1
- The relationship between the holding temperature (Th) and the heating rate () - 1r
) is shown as a parameter. As is clear from the figure, each curve has a heating effect at Th = 400°C.
Even after repeated cooling, almost no bending occurs. but,
In the case of 750° C. and 950 t corresponding to the transformation temperature section, that is, in a thermal cycle in which heating and cooling pass through the AI transformation point, A;1 transformation point, a large bending angle was obtained. This fact shows that there is a relationship between bending deformation due to thermal stress and phase transformation.

(36) Properties of bent parts The cross-sectional structures of the bent parts of the same mild steel plates as the test specimens, which were opened in a V-shape (α-20'), and those subjected to the dieless plate bending of the material and the present invention, were examined. (corrosion with nital liquid) is shown in Figure 13. Figure tc+ shows VQIJ bending (a
= 20°), but the structure shown in Figure (C
Addition of 1) 1: +'+: No clear tissue change was observed compared to the tissue of i. Figure (al) shows the structure of dieless plate bending (Th = 950°C), which shows a remarkable tendency for crystal refinement compared to that of Figure td) processed + iif. In this structure, A transformation of the pearlite part and subsequent austenitization to ferrite area is recognized. In addition, dieless plate bending (Th = 750℃) shown in the figure)
This refinement was not observed in the microstructure.

FIG. 14 is a diagram showing the distribution of microhardness (Hv = 200 g) in the bent cross section. From the figure, dieless plate bending causes a 1-increase in hardness due to the refinement of the structure, which is comparable to or greater than the 1-increase in hardness due to the force u I hardening in V-shaped opening. In other words, the bending portion can be expected to be strengthened.

In the following, we have explained the case where the present invention is applied to a mild steel plate that has a phase transformation point, but the present invention has the same effect on an austenitic stainless steel plate that does not have a phase transformation point! j, it is something that can be obtained.

An example thereof is shown in FIG. The figure shows plate thickness -2m
For the SUS 304 stainless steel specimen of m,
Bending angle (α) under the conditions of heating rate (Hr) -40 deg/sec and holding time (H, T,) -5 sec
These are the results of determining the relationship between and thermal cycle-1 limit holding temperature (Th). The figure shows that in this case as well, the results are almost the same as in the case of the mild steel plate shown in FIG. 12, but it is shown that SUS, which has poor thermal conductivity compared to mild steel, bends better.

Even metal materials with good thermal conductivity, such as copper plates, can be bent by appropriately selecting the thermal cycle.

In addition, the heating method may be infrared heating, laser heating, etc. other than high-frequency induction heating, and the cooling method may be air cooling or oil cooling instead of water cooling.

As is clear from the above explanation, dieless plate forming is possible by applying heat particles for local heating and cooling to a metal plate from the front and back sides, and the effect of this method on the bending angle is , a linear law holds true for the number of thermal cycles, and in order to obtain the desired bending angle, the number of thermal cycles, thermal cycle-1 limit temperature, heating rate, and holding time must be adjusted according to the type of liquid processed metal sheet material, It may be selected appropriately depending on the plate thickness.

Furthermore, it is clear that more complex curved surface processing is possible by the dieless forming of the present invention by applying point-like, straight-line, or curved local thermal cycles to a plurality of predetermined locations of the plate material.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the conventional linear hot plate bending method 1, Fig. 2 is a schematic explanatory diagram of the deformation behavior of a test piece in the present invention, and Fig. 3 is an explanatory diagram of the deformation behavior of a test piece in the present invention.
The figure shows the chemical composition of the SI○C rolled polished steel plate used in the experiments of the present invention, Figure 4 is a schematic diagram showing the experimental equipment using the high-frequency induction heating method used in the experiments of the present invention, and Figures 5 to 5 FIG. 15 is a diagram showing experimental results for supporting the present invention. In the figure, 11. Test piece 12. Support stand with lifter 13. Heat-resistant glass bar 14. High frequency heating coil 15. High frequency power supply 16. Water cooling pipe 17. Spouting water.
18... CA thermocouple 19 - Heating/cooling waveform control device 20... Valve attorney Junnosuke Nakamura 1 Figure 3 Figure 1-4 Figure 1-2 Heating (C) Water pump N Sai 5 Figure 6181 Heating rate HY (deg/5ec) 1? 7 PJl 1-8 Illustration 0 Heat 2 degrees )-b (deg/c; ec)'! F9 figure spear 10 figure power nh goods ) 1r (deg/5ec) Volume 13 figure) F11 figure age 12 figure Josui I shadow attendant star degree Th ('C) L14 figure 1υη )! Figure 15 Procedural Amendment (Method) August 26, 1980 t11 Commissioner of the Licensed Agency Mr. + Relationship Patent applicant name: Osamu Katsuyo Kobayashi Subject of Hitosode+li: Brief description of drawings in the specification and attached drawings. Contents of amendment 1: 1 shown on page 11, line 15 of the specification. Between j and 1-Fig. (C)-1, 1-Fig.
h-950℃ and 750℃ Toshita Mono, I”21 (C)
i1 Shows the structure of a product subjected to normal ■ mold opening processing. Add j. 2. Figure 5 on page 14, lines 8 to 9 of the specification. -1 to 1 Figure 5 shows the thermal cycle upper limit holding temperature (Th) constant at 950°C and the heating rate (l
Figure 6 shows the relationship between the bending angle (α) and the number of thermal cycles (N) when the holding time (Il, T, ), and plate thickness (t) are different. ”,
) is kept constant at 5 seconds, and the thermal cycle upper limit holding temperature (Th
) when changing the bending angle (α) and heating rate (llr)
Figure 7 shows the relationship between the thermal cycle upper limit holding temperature (T
Bending angle (α) and holding time (Il, i” when heating rate (llr) is varied while holding h ) constant at 950 °C
), Figure 8 shows the thermal cycle upper limit f+Aj
+, S temperature ('l”h) = 950℃, holding time -
53 (A diagram showing the relationship between the bending angle (α) and the heating rate (Ilr) when the IC is kept constant.
llr) -4[1dcg/'iC(,
A diagram showing the relationship between the bending angle ((t) and holding time (II, T, ) when the plate thickness (+) is changed. The 10th section is the plate thickness (+).
+, ) -3nun, retention time (Il, T, )
Figure 11 shows the relationship between the bending angle (α) and the heating rate (llr) when the thermal cycle upper limit holding temperature (1″h) is changed at −5 sec, and the thermal cycle upper limit holding temperature is −3 mm. (TI+) -950℃, heating rate (
Bending angle (α) and holding time (Ilr) when changing
Figure 12 shows the relationship between Il, 'l'', ), and the plate thickness is -2 mm, and the holding time (Il, T, ) -19 sec.
Figure 1 shows the relationship between the bending angle (α) and the thermal cycle upper limit holding temperature (Th) when the heating rate (mountain) is changed.
Figure 6 shows the microscopic structure of the dieless bending process of the present invention (Figures 1 and 1)), and the conventional dieless bending process (Figure () and Figure C). Figure 14 shows the microhardness distribution of the bending section γlIS of dieless plate bent material and V-7], 1 bending and pressing 4'A.
, r ST, JS 304 stainless steel plate: Heating rate (llr) -43 dcg/sec, holding time (+1. It is a figure showing a relationship. Correct to l. 6. Figure 16 attached to the specification is corrected to match the drawing attached to this document. t13 ((11) (C) (b) C(J) 0tpt Yushuo

Claims (1)

[Claims] 1. Applying intermittent heating cycles in the form of dots, straight lines, or curves to the surface of a metal plate supported so that it can move freely without being restrained from the outside, and at the same time A cooling cycle is applied to a position corresponding to the surface heating position on the back side of the plate during the non-heating period between the heating cycles, and a local temperature gradient is repeatedly applied between the front and back surfaces of the metal plate. A dieless plate forming method using thermal stress, characterized in that the metal plate is bent toward the surface side of the metal plate around the surface heating position. 2. In the method for forming a tieless plate using thermal stress according to claim 1, a metal plate having a predetermined curved surface is formed by sequentially moving the heating and cooling positions of the metal plate in a predetermined direction at a predetermined interval. A method for forming dieless plates using thermal stress, which features scales.