JPH08103831A - Punching method for titanium alloy plate material - Google Patents

Abstract

PURPOSE: To provide a punching method, for a plate material of titanium alloy, which is capable of preventing punching defects such as cracks and chips generating in corner parts. CONSTITUTION: Assuming (d) (μm) as a crystal grain size of a titanium alloy plate material, (t) (mm) as its plate thickness and R (mm) as the radius of curvature of a corner part in punching, the punching method for the titanium alloy plate material is such that punching is performed under the conditions in which (d) is 7μm or larger and also satisfies the following equation: R/t>=0.20×1n(d)+0.1... formula.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for punching a titanium alloy sheet material.

[0002]

2. Description of the Related Art Generally, titanium alloys are lightweight, have high strength, and have excellent corrosion resistance, but their cold workability is poor. When punching, if the plate thickness exceeds 1 mm, the surface cracks as the plate thickness increases. The frequency of occurrence of cracks and cracks is high. Especially at the corners, the frequency of cracks and chips becomes more remarkable due to the peculiarity of the stress state around the corners.

Although this is not a direct solution to the problem of punching workability of titanium alloys, it is disclosed in JP-A-1-177.
Japanese Patent Publication No. 906 proposes a method for cutting a titanium alloy using the same shear stress as in the punching process. This is a method in which a notch is provided at the cutting position of the material, and shear stress is concentrated at the notch portion during cutting to facilitate cutting, and defects such as burrs and inclinations occurring on the cut surface are reduced. In addition, technical literature “Plasticity and processing” (vol. 15, No. 6)
4, 1964), a method of stamping a carbon steel sheet is presented, and the radius of curvature R of the corner portion is set to 0.3 of the steel sheet thickness.
It is described that the punching failure at the corner can be solved by increasing the amount to 1 time or more.

[0004]

However, in the method described in Japanese Patent Laid-Open No. 177906/1990, the number of steps for forming a notch increases and the cost increases, and in order to accurately apply shear stress to the notch forming portion. Requires high-precision positioning technology. In particular, when punching a complicated shape, the cost is greatly increased and the productivity is significantly reduced. In addition, the above-mentioned technical literature "Plasticity and processing"
Although the method described in (1) gives effective guidelines for steel materials and aluminum materials, it cannot be applied as it is to titanium materials, which are inferior in cold workability to these materials.

The present invention has been made to solve the above problems, and a punching method for a titanium alloy sheet material capable of preventing a punching defect such as a crack or a chip occurring at a corner portion without using any special means. The purpose is to provide.

[0006]

Means for Solving the Problems The above-mentioned problems are as follows: the crystal grain size of a titanium alloy plate is d (μm), the plate thickness is t (mm),
A method of punching a titanium alloy plate material, characterized in that when the radius of curvature of the corner portion in the punching process is R (mm), the punching process is performed under the condition that d is 7 μm or less and the formula (1) is satisfied. Will be solved by. R / t ≧ 0.20 × ln (d) +0.1 (1)

[0007]

FUNCTION The cracking during punching is basically a problem related to the ductility of the material. Therefore, it is inferred that there is some relation with the structure of the material, especially the crystal grain size. Further, as described above, in the case of steel materials, it is effective to make the ratio of the curvature radius of the corner portion to the plate thickness of the steel sheet more than a certain value against the punching failure of the corner portion. The ratio of the radius to the plate thickness may affect punching workability. Therefore, as shown below, the punching workability was examined by consciously changing the crystal grain size d and the plate thickness t of the titanium alloy and the radius of curvature R of the punching corner portion.

Ti-4.5Al-3V-2Fe-2Mo
A system α + β type titanium alloy was melted, and hot-rolled sheets having various crystal grain sizes d were prepared by changing the hot-rolling conditions and the heat treatment temperature after hot-rolling. From these hot-rolled sheets, samples having different sheet thickness t were prepared by machining in the range of 1 mm or more. Then, a 100 mm × 100 mm blank plate was cut out and punched using a 60 mm × 60 mm square die having various corner Rs. Then, the corners of the punched pieces were observed to determine the presence or absence of cracks or chips.

As a result, in the sample having the crystal grain size d exceeding 7 μm, cracks and chips were recognized irrespective of the plate thickness t and the radius R of the corner portion of the die. FIG. 1 shows the relationship between R / t, d and the presence or absence of cracks or chips in a sample having a crystal grain size d of 7 μm or less. Crystal grain size d is 7 μm
In the following cases, if R, t, and d are adjusted so as to satisfy the expression (1), the occurrence of cracks and chips can be suppressed.

[0010]

[Example] Ti-4.5Al-3V-2Fe-2Mo type and Ti-6Al-4V type α + β type titanium alloys were melted and the hot rolling conditions and the heat treatment temperature after hot rolling were set as shown in Table 1. Instead, a hot-rolled sheet having a crystal grain size d of 2 to 10 μm was prepared. The thickness of these hot-rolled sheets was machined to 1.
A 100 mm × 100 mm blank plate was cut out at 5, 3.2, and 5.0 mm, and the corner portion R was 0.3, 0.6, 1.
Punching was performed using a 60 mm × 60 mm square die that was changed to 5, 3.0 mm. The size of the punch is adjusted so that the gap between the punch and the die is 12.5% of the plate thickness. Then, the corners of the punched pieces were observed to determine the presence or absence of cracks or chips.

[0011]

[Table 1]

FIG. 2 shows the relationship between R / t and d in the Ti-4.5Al-3V-2Fe-2Mo system and FIG. 3 in the Ti-6Al-4V system and the presence or absence of cracks and chips. The crystal grain size d in any of the component system samples
Is 7 μm or less and satisfies the expression (1), R, t,
If d is adjusted, cracks and chips can be prevented from occurring.

[0013]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, there is provided a method of punching a titanium alloy sheet material capable of preventing a punching defect such as a crack or a chip occurring at a corner portion without using any special means. Can be provided.

[Brief description of drawings]

FIG. 1 shows R in a sample having a crystal grain size d of 7 μm or less.
It is a figure showing the relationship between / t and d and the presence or absence of a crack or chipping.

FIG. 2 is a diagram showing a relationship between R / t and d and presence / absence of cracking or chipping in a Ti-4.5Al-3V-2Fe-2Mo type α + β type titanium alloy plate material.

FIG. 3 is a diagram showing a relationship between R / t and d in a Ti-6Al-4V type α + β type titanium alloy plate material and the presence or absence of cracking or chipping.

Claims (1)

[Claims] 1. The crystal grain size of a titanium alloy sheet is d (μ
m), the plate thickness is t (mm), and the radius of curvature of the corner portion in the punching process is R (mm), the punching process is performed under the condition that d is 7 μm or less and the formula (1) is satisfied. A method for punching a titanium alloy sheet, characterized by: R / t ≧ 0.20 × ln (d) +0.1 (1)