JPS5823582B2 - Ironing test equipment for thin steel plates - Google Patents

Description

[Detailed description of the invention] The present invention relates to a testing device for testing thin steel sheets.

When testing the formability of thin steel sheets for drawing, practical tests such as the Erichsen test, conical cup test, or drawing limit test, and strength tests targeting so-called forming characteristics such as n value and r value are generally conducted. However, all of the above tests were unsuitable for detecting defects in the layer immediately below the surface of the material under test.

However, in the case of actual drawing of thin steel sheets, there are cases where the amount of drawing is small but the amount of ironing is large, and in these cases, apart from the so-called formability and forming characteristics, the surface Cleanliness of the layer immediately below is strongly required.

The present invention improves the cleanliness of the layer directly below the surface of the material to be tested by relimiting the drawing state that requires a relatively large amount of squeezing for the material under test, so that the amount of squeezing can be adjusted as desired. The purpose of the present invention is to provide a testing device for testing thin steel sheets, which makes it possible to perform evaluations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of the thin steel plate ironing test apparatus of the present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a cross-sectional front view of a press die for simple drawing to explain the drawing that is commonly performed.
1 is a die, 2 is a punch, and 3 is a presser plate.

As is clear from Fig. 1, blank (sheet metal material) 4
Apply pressing force H between die 1 and presser foot 3 and hold.
The punch 2 is pressed down with a pressing force P to draw and finish the product into a cylindrical product with a bottom. Especially when performing deep drawing, or by narrowing the gap between the die 1 and the punch 2, a precise drawing finish is performed. In this case, the shoulder 5 of the die 1 (curved surface with radius dr) is usually used to squeeze the blank 1, and in order to cope with such a case, the die 1 and the presser plate 3 are In order to prevent the occurrence of wrinkles, meshing uneven grooves (beads) are provided opposite to each other.

When a product undergoes drawing processing that involves ironing, a crack as shown in Figure 5 may appear near the ironing surface due to a defect (such as foreign matter contamination) in the layer immediately below the surface of the thin steel sheet. This induces fatal defects such as "(I)", "1 bulge" (Ii), and "Crack" (buttons (defects become stronger in the order of (I) - @button).

In order to determine the limit of the ironing amount (combination of the radius dr of the ironing surface and the tensile force) for a certain lot of thin steel sheets, the present invention reproduces a predetermined ironing process state on sampled test materials. This is a testing device designed to inspect the occurrence of the above-mentioned fatal defects.

FIGS. 2 and 3 are a front view and a side view, respectively, showing an embodiment of the thin steel sheet ironing test apparatus of the present invention, and 6 is a test machine frame, which connects the base 7, the upper board 8, and the four parts. It is configured into a cylindrical shape by the bolt 9 for use.

Reference numerals 10 and 10' denote a pair of upper and lower clamping jig pieces, and a mating bead 16 for gripping the end of the test material 15 is provided at the joint between the two, and the upper clamping jig piece 10 is fixed to the upper board 8, and the lower clamping jig piece 10' is attached to a hydraulic cylinder device 11 installed on the base 7 and is arranged to move forward and backward relative to the upper fixed clamping jig piece 10. It is being

Reference numeral 12 denotes a wringing jig, which is detachably attached to the upper panel 8 of the testing machine frame 6 via bolts 13.

The shaking jig 12 is equipped with a shoulder for shaking made of a curved surface with a predetermined radius dr, and a large number of shaking jigs 12 with various radii dr are prepared in advance and replaced as needed to conduct the required shaking test. It is set up so that it can be done.

Reference numeral 14 denotes a chuck, which chucks the other end of the material to be tested 15 whose ends are gripped by a pair of clamping jig pieces 10 and 10', and holds the material to be tested 15 at the shoulder portion of the above-mentioned squeezing jig 12. Bend it approximately at right angles along the curved surface and pull it (
Arrow) It is provided so that it can move in a straight line.

The thin steel plate ironing tester of the present invention having the structure described above is equipped with an ironing jig 12 having a rounding curved surface suitable for actual drawing, and a pair of clamping jigs for gripping the ends of the test material 15. The gripping strength of the tool pieces 10, 10' can be adjusted by adjusting the pressure of the hydraulic cylinder device 11, thereby making it possible to arbitrarily set the tensile force on the test material 15. This makes it possible to reproduce the drawing conditions involved.

The chart shown in FIG. 4 shows that the ironing test was carried out using the ironing test apparatus of the present invention on each test material sampled from lots A, B, and C (using the same ironing jig and adjusting the tensile force). This figure shows the relationship between the amount of ironing and defects occurring on the surface of the ironing part of the test material.

The horizontal axis shows the elongation (645%) between the 50 mm measurement marks (G, L,) on the test material and the corresponding tensile force (kp/ff1
), the vertical axis shows the small defect → dog judgment, i.e. I (neck), ■
This indicates the determination (by visual inspection, magnetic particle inspection, etc.) of the occurrence of (blister) and ■ (cracking).

; Now, if we assume that the defect I (incision) is the maximum allowable defect, the diagram in Figure 4 shows the results for each lot of A, B, and C for the actual drawing process reproduced in the above test. The limits of the amount of ironing for thin steel sheets were set at 2.5%, 6.3%, and 14.6%, respectively (measurement mark interval (G)).

This indicates that it is sufficient to set the value to iL, ) elongation % relative to 50 mm.

Further, 17 (indicated by chain lines) in FIGS. 2 and 3 is a removable plate-shaped protrusion protruding below the base plate 7, and this plate-shaped protrusion 1
7 is held by the lower chuck of a general tensile tester, and the tensile end of the test material 1 is gripped by the upper chuck. It is also possible to operate a Shigoki testing machine.

[Brief explanation of drawings]

i Fig. 1 is a cross-sectional front view of an embodiment of a conventional drawing press mold, and Figs. 2 and 3 are a front view and a side view, respectively, showing an embodiment of the thin steel plate ironing test device of the present invention. It is. Figure 4 is a chart showing the relationship between the amount of ironing and the defects that occur on the surface of the ironed part of the test material, and Figure 5 is the name of the defects that occur on the surface of the ironed part of the thin steel plate. An explanatory drawing to show the following, a brief explanation of the drawing below. 1: Dice, 2: Punch, 3: Presser plate, 4 blanks,
5: Shoulder of die 1, 6: Testing machine frame, 57 = base, 8
: Upper panel, 9: Connection bolt, 10° 10' pair of upper and lower clamping jig pieces, 11: Hydraulic cylinder device, 12: Shigoki jig, 13: Screwing jig 12 is installed with bolts, 14:
Chuck, 15: Test material, 16: Clamping jig piece 10,1
0' meshing bead 9 - 17: plate-like protrusion.

Claims (1)

[Claims] 1 Equipped with an interlocking bead for gripping the end of the test material
A pair of clamping jigs are arranged on the testing machine frame so that one clamping jig piece can move forward and backward relative to the other fixed clamping jig piece using a hydraulic cylinder device, and the pair of clamping jigs are A stripping jig with a predetermined stripping curved surface for stripping the material to be tested is detachably attached to the front of the stripping jig, and a chuck provided to grip the other end of the material to be tested is attached to the striping curved surface of the stripping jig mentioned above. 1. An ironing test device for a thin steel plate, characterized in that the test material is bent approximately at right angles along the line and is provided so as to be able to move linearly in the direction of tension.