JPH0195824A - Method for draw-forming - Google Patents

Abstract

PURPOSE:To upgrade the appearance quality of a product by cooling a contact surface between a die and a blank when a metal sheet blank is drawn by the die and a punch. CONSTITUTION:When a metal sheet blank is worked into a cup shape in cooperation between the punch and the die, cooling water, mist of aqueous emulsion lubricant or cooling air is sprayed to the die in use from a spray nozzle, etc., provided on the end of the punch. Besides, cooling holes are provided in the die to circulate refrigerant and to cool the working contact surface between the die and blank. Hereby, the temperature of the die in the drawing operation is prevented from rising, all the parts are lubricated and the deterioration of surface quality, such as occurrence of black clouds, etc., on the product is prevented. Accordingly, the appearance quality of the product is upgraded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for forming a metal sheet blank into a cup-shaped body by drawing it in cooperation with a punch and a die.

(Prior art) Draw-formed cans (so-called DI cans or one-piece cans) used for beer cans, carbonated beverage cans, etc. are made by drawing a circular blank of aluminum alloy thin plate or tin-plated steel plate. It is manufactured by forming a cup-shaped body (without a flange) and then subjecting the cup-shaped body to reproofing and multi-stage ironing.

After washing and drying, the above DI cans are printed on the outside, but when printed with relatively light ink, dark vertical streaks (black streaks) appear.
may appear to be floating, spoiling the appearance and damaging the product value. This phenomenon occurs when an aluminum alloy thin plate is used as a blank, and the drawing process requires high-speed production (for example, 1
It has been found that this phenomenon is likely to occur when the process is carried out at a rate of 70 cans/min or more.

This is presumably because such high-speed production has not been implemented in the industry in the past, but as far as the inventors are aware, no effective measures against the above phenomenon have been proposed.

(Problems to be Solved by the Invention) The present invention is characterized in that the blank is made of an aluminum alloy thin plate.
To provide a drawing method for a metal thin plate blank that does not cause black streaks on printed DI cans, which are products, even when this blank is drawn at high speed.

Another object of the present invention is to provide a drawing method for a thin metal sheet blank that improves the critical drawing ratio and is less likely to cause cup breakage.

(Means for Solving the Problems) The method for drawing a thin metal sheet blank of the present invention is a method for drawing a thin metal sheet blank into a cup-shaped body by cooperation of a punch and a die, the method comprising: It is characterized by cooling the surface that comes into contact with the blank during drawing.

The die can be cooled by spraying a mist of cooling water or water emulsion lubricant (preferably with a high water content), or cooling air (for example, at a temperature below 0°C) from a spray nozzle provided at the hole opening at the tip of the punch. temperature) onto the face of the die during the period between each drawing operation (during which the blank is fed), or by providing cooling holes in the die and allowing the coolant to flow through the cooling holes. etc. are exemplified.

(Function) It has been found that the black streaks on the DI can correspond to the streak-like rough surface portions present on the outer surface of the squeezed cup-shaped body. Due to the significant temperature rise of the die due to processing heat and frictional heat during high-speed production, the viscosity of the lubricating oil (usually applied to the surface of the blank) has decreased, or the quality of the lubricating oil has deteriorated, resulting in deterioration of the lubricating performance. Easy to occur. As a result, oil-depleted portions tend to occur on the contact surface between the die and the blank, and it is thought that the above-mentioned rough surface portions occur in these oil-depleted portions.

By cooling at least the surface of the die that comes into contact with the blank during drawing processing, the temperature rise of the die is suppressed.
Therefore, since there are no oil-depleted areas, the occurrence of black streaks is prevented.

Furthermore, since there are no oil-draining areas, the frictional resistance between the blank and the die is reduced, and as a result, the limit drawing ratio is improved, and breakage during cup forming becomes less likely to occur.

(Example) A die made of cemented carbide with a cavity inner diameter of 88 mm, a radius of curvature of the curvature portion between the cavity surface and the upper surface of the die of 3.0 mm, and a punch made of cemented carbide were used. , coated with emulsion lubricant (emulsified oil such as water, mineral oil, interfacial agent, etc.), 0.35 mm thick, 14 mm in diameter.
5mm circular aluminum alloy thin plate blank (JIS
3004) is drawn to have an outer diameter of 88 mm and an average height of 40 mm.
A cup-shaped body of wm was formed. The processing speed was 180 pieces per minute.

At this time, the punch has a guide hole that extends along the axis, and pressurized air and a mother tube (air pressure 1, 0 kl) passing through the guide hole are used as punches.
? /cm 2, the air temperature is room temperature) and a spray nozzle formed by the confluence of the cooling liquid and the mother pipe are used at the open end of the guide hole, and the cooling liquid is sprayed from the spray nozzle, 20
A mist of water at ℃ was sprayed onto the top surface of the die and the circumferential surface of the cavity. The nozzle itself is always open, but is closed by the blank during drawing. During the upward movement of the punch, the ejection of mist containing pressurized air facilitates the extraction of the squeezed cup-shaped body. The amount of coolant used is 2
It was 017 minutes.

The above cup-shaped body was placed in a DI can forming machine and subjected to three-stage ironing process using a recalibration seam to form a DI can having an outer diameter of 66 m1, a height of 130 cm, and an average wall thickness of 0.13 mm. After degreasing, washing, and drying these DI cans, a vinyl coating film was formed on the inner surface and a yellow polyester ink printing film was formed on the outer surface using a conventional method, but there were no black streaks on the outer surface of any of the DI cans. I couldn't see it.

For comparison, a printed DI can was produced in the same manner as described above, except that no coolant was supplied to the coolant pipe. No black streaks were observed in the DI cans produced from cup-shaped bodies up to about 150 cans after the start of the drawing process, but black streaks were found in DI cans produced from cup-shaped bodies drawn after that. DI cans corresponding to cup-shaped bodies that had elapsed after the start of drawing were markedly black streaked.

(Effects of the Invention) The drawing method of the present invention has the effect that even if the blank is made of an aluminum alloy thin plate and the blank is subjected to high-speed drawing, no black streaks will appear on the printed DI can, which is the product. .

Furthermore, there is an effect that the limit drawing ratio is improved.

Claims (1)

[Claims] (1) A method for drawing a thin metal blank into a cup-shaped body by cooperation of a punch and a die, characterized in that at least the surface of the die that comes into contact with the blank during drawing is cooled. drawing method.