JPH03268808A - Tool for plastic working of metal - Google Patents

Abstract

PURPOSE:To make a product superior in dimensional accuracy and appearance without generating burning flaw or slip by making a tool for plastic working with a number of small recesses on its smooth plane and making the diameter and depth of the size of each recess into a specified value respectively. CONSTITUTION:The tool 1 is provided with the recesses 3 of the diameter of 5-50mum and depth of 0.5-50mum on the smooth surface 2. These recesses 3 are provided on the whole of the surface of tool so that the total area of the recesses 3 becomes 5-50% to the surface area of the tool before recessing. When a metal is plastically worked with this tool, it is worked in a such state that a part of the material 4 is entered into these recesses 3. Thus, the coefficient of friction is increased and also lubricating oil in the recesses 3 is pressed out and extended on the smooth surface part 1. In this way, because burning flaw and slip are hard to generate even if it is plastic working at high speed and high working rate, the product is superior in dimensional accuracy and appearance.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a tool for plastic working of metal, and more specifically, it is resistant to seizure scratches and slips that occur during cold working or press working of metal. Regarding tools for plastic working.

(Prior Art) Rolls are used in cold rolling of metals, and plastic working tools such as punches are used in press working.

In cold rolling and press working, a problem that occurs when the processing amount or processing speed is increased is that the processed material has a poor appearance due to seizure defects. These seizure flaws occur because the lubricating oil film is thermally destroyed by the rise in material temperature associated with an increase in machining amount or machining speed, causing the tool and material to stick together, and the material is transferred to the tool surface. It is from.

In general, seizure flaws can be reduced by improving the lubrication conditions during plastic working. One possible method for this is to use a lubricating oil with high viscosity and a high oil film breakage temperature, but if this method is adopted for cold rolling, excessive lubrication occurs during acceleration and deceleration of the rolling speed, resulting in poor bonding between the rolls and the material. A problem arises in that slips occur between the two and the rolling cannot be performed stably.

The problem of slip in cold rolling can be improved by increasing the roll surface roughness. For example, JP-A-62-8950
When using a dull roll with a roughened roll surface as disclosed in Publication No. 5, slipping is less likely to occur.However, in the case of a dull roll, the lubricating oil film is broken at the roughened parts, resulting in seizure defects. In particular, when rolling with a high rolling reduction ratio, it is extremely easy to seize, and therefore rolling at high speed and under high pressure cannot be performed.

On the other hand, when a lubricating oil with high viscosity and high oil film breaking temperature is used in press processing, the friction coefficient of the temporary holding part decreases, and the flow of the lubricant into the forming part of the material becomes uneven.
Problems occur such as wrinkles appearing in the processed material and variations in wall thickness.

For this reason, it is possible to prevent seizure by coating the tool surface with Cr or Cr-based alloys or carbides such as TiC, WC, VC, etc., which are less likely to seize, or by changing the entire tool to a material that is less likely to seize, such as cemented carbide or ceramics. Attempts have been made to prevent scratches.

However, the coating layer of the former tool tends to peel off during plastic working at a high degree of processing, and it is difficult to uniformly coat a large tool with the metal or carbide described above. The latter type of tool is difficult to grind due to the high hardness and low toughness of the material that makes up the tool, and the resistance of the tool is also low, so if an impact is applied during use, the product may crack or may be severely damaged. JP-A-56-89302 discloses a method of controlling the surface roughness of a dull roll within a certain range to prevent it from seizing. According to this invention, for example, in copper strip rolling, the average surface roughness of the work roll is 0.2 to
It is stated that seizure flaws can be prevented if controlled within the range of 0.4 μm, but the surface roughness of rolls changes over time due to wear during use, so even with this roll, long-term Seizure scratches will occur if used for a period of time.

(Problems to be Solved by the Invention) The problem to be solved by the present invention is that when metal is subjected to plastic working such as cold rolling or press working, seizing defects and slipping occur over a long period of time even when processing is performed at high speed and with a large amount of processing. The object of the present invention is to provide a tool for plastic working that does not occur over time.

<Means for solving tan) A tool with a smooth surface will cause slippage, whereas a tool with a rough surface will cause seizure flaws. This is because, as mentioned above, in the case of a tool with a smooth surface, there will be excessive lubrication and the g! ! ! This is because the coefficient decreases, and in the case of tools with rough surfaces, the oil film is broken at the protrusions, resulting in insufficient lubrication and an excessively high coefficient of friction. Therefore, if the coefficient of friction can be adjusted appropriately, it is thought that seizure defects and slips will not occur.

The present inventors have discovered that by improving the surface condition of the tool, it is possible to plastically process metal with an appropriate coefficient of friction.

The gist of the present invention is a plastic working tool having a smooth surface with a large number of small depressions, each of the depressions having a diameter of 5 to 50 μm and a depth of 0.5 to 5 μm. and the total area of these depressions is 5 to 50% of the area of the tool surface before the depressions are formed.

The total area of the depressions means the total area of the projected areas of the respective depressions. Typical examples of the above-mentioned plastic working tools include cold rolling rolls, press working dies and punches, and tube rolling mandrels.

(effect) The present invention will be explained in detail below.

FIG. 1 is a partially enlarged sectional view showing the surface part of the tool according to the present invention, and FIG. 2 is a partially enlarged sectional view showing the contact state between the tool and the material when the material is plastically worked with the tool of the present invention. It is an enlarged sectional view.

As shown in the figure, the tool 1 of the present invention has a smooth surface 2, for example, a smooth surface with a maximum height (Rwax) of 2 μm or less,
A depression 3 with a diameter of 5 to 50 μm and a depth of 0.5 to 5 μm is formed. The depressions 3 are formed over the entire surface of the tool so that the total area of the depressions 3 is 5 to 50% of the surface area of the tool before enrichment. Therefore, when metal is plastically worked with this tool, a part of the material 4 is worked into the depression 3 as shown in FIG. As a result, the Wl friction coefficient increases, and the lubricating oil in the depression 3 is pushed out and spreads to the smooth surface part 1. Since the surface part of the lubricating oil spread to the surface part 1 is smooth, no oil film breakage occurs. The number of depressions 3 is kept constant so that the lubricating oil does not spread to the smooth surface 1 in excess or insufficient, and the coefficient of friction does not increase excessively due to material entering. In other words, the total area of the recesses is provided within a certain range relative to the area of the tool surface before enrichment, so that seizure and slipping do not occur.

In the present invention, the size of the depression and the total area of the depression are defined as described above for the following reasons.

That is, even if the total area of the dents is in the range of 5 to 50% of the area of the tool surface before making the dents, the diameter of each dent is smaller than 5 μm or the depth is shallower than 0.5 μm. In this case, there is less material entering each depression, and not only is it impossible to expect the wear coefficient to increase until slippage is prevented, but the amount of lubricating oil that spreads from the depression to the smooth surface is also small, which reduces the plasticity of low-speed, high-speed machining. This is because seizure flaws occur during machining, and if the diameter of the recess exceeds 50 μm or the depth exceeds 5 μm, the amount of material that enters each recess increases, and the coefficient of friction becomes too high, causing seizure. This is because not only is it more likely to occur, the material that has entered will be scraped off by the smooth surface and become abrasion powder, causing stains, indentation scratches, etc. on the surface of the workpiece.

On the other hand, each depression has a diameter of 5 to 50 μm and a depth of 0.5 to 5 μm.
Even in the μm range, if the total area of the recesses is less than 5% of the area of the tool surface before enrichment, the friction coefficient will decrease because the number of recesses is small and the total amount of material entering is small. The rise is low and slips and shape defects are more likely to occur. In addition, if the total area of dents exceeds 50%, the number of dents becomes too large and the proportion of smooth surface area decreases, resulting in an excessive increase in the coefficient of friction due to the penetration of material, resulting in seizure defects. It becomes easier.

The depressions can be formed on the tool surface by etching, stamping, electrical discharge machining, frust machining, or other methods, but the best method for continuously forming fine richness is to use a laser beam. In the case of a laser beam, the enrichment can be formed by irradiating the tool surface with the beam to form a crater, and then removing the protrusions on the edge of the crater by grinding or polishing. In addition, the dents created by the laser beam are smooth and do not cause burn-in.
When making depressions using these methods, it is best to make the depressions in a continuous streak or grid pattern so that the lubricating oil does not leak out and create oil pits on the tool surface. .

(Example 1) A laser beam was used on the surface of a cold rolling roll having a diameter of 250 mm and a surface roughness of Rwax 2 μm or less to change the size and area ratio as shown in Table 1 by the following method. I became rich.

[How to find wealth]

A laser beam with an output of 400 to 1200 W, with a number of teeth of 20
After irradiating the rotating roll surface with a chipper of 0 to 1000 intermittently and creating a crater, the edge of the crater is ground with a grindstone containing abrasive grains of #400 to 1200 or a puff. Wealth was created in The depth and diameter of the depression were adjusted by this polishing.

Note that the roll rotation speed and chopper rotation speed are determined by a=(roll rotation speed x roll diameter x π)/[number of chopper teeth x chopper rotation speed], where a is the pitch of the crater roll in the circumferential direction. a was adjusted by controlling the rotational speed of the roll and chopper, and the pitch of the craters in the roll axis direction was adjusted by the feed rate of the laser beam.

A roll with a rich surface obtained by the above method, a laser dull roll that is not polished after making a crater with a laser beam, and a ground finish roll are used to make oil and fat 3.
0% 10 tallow fatty acid octyl ester 30% 10 mineral oil 30%
Using a 3% emulsion of rolling oil with a viscosity of 35 cs and 150°C, which mainly consists of
), rolling speed 500m/m111, reduction rate 5-45%
Cold rolled. Table 1 also shows the results of examining the rolling reduction ratio at which seizure occurred and the presence or absence of slip.

(Hereinafter, blank space) As shown in Table 1, seizure occurred with the as-ground roll of Seed 15 and the laser dull roll of NCL16 at a low rolling reduction ratio, but the rolling roll of the present invention of Nchl-48 On the other hand, even with rolls with depressions as in the comparative example of floors 9 to 14, the size and area ratio of the depressions are not the same. If the rolling reduction ratio is outside the range specified in the invention, the rolling reduction ratio at which seizure occurs will be low or slip will occur.

(Example 2) Indentations with different sizes and area ratios as shown in Table 2 were made using a laser beam on the surface of a punch with an outer diameter of 100 mm and a surface roughness of Rmaxo of 5 μ■ in the same manner as in Example 1. Wearing.

Using the punch with this depression and the punch with the ground finish, the thickness was 0.6++n and the diameter was 200cm- under the conditions shown below.
10 low carbon steel plates (TS: 33 kgf/sn+) and 10 hard aluminum plates (TS: 38 kgf/am'') were each continuously deep drawn.

[Deep drawing processing conditions] Apply machine oil (oil) with a viscosity of 48 cs t at 40°C to the material surface, set the punch speed to 2 m/s, change the clearance between the punch and die, and set the ironing rate to [1]. -(thickness after processing/thickness of material)] was set to 10 to 40%, and deep drawing was performed into a cup shape with a depth of loo+wm.

Table 2 also shows the results of examining the ironing rate at the time when seizure occurred and the wall thickness variation rate of the processed material.

(Hereinafter, blank space) Table 2 shows that the punch of the present invention has a higher ironing rate at which seizure occurs than the conventional punch, and can be processed at a high ironing rate. Additionally, the product has little variation in wall thickness.

(Effects of the invention) As shown in the examples, when the tool of the present invention is used, seizing defects and slips are less likely to occur even in high-speed, high-density plastic working, so the product has excellent dimensional accuracy and Excellent appearance characteristics.

[Brief explanation of drawings]

Fig. 1 is a partially enlarged sectional view showing the surface portion of the tool according to the present invention, and Fig. 2 is a partially enlarged sectional view showing the contact state between the tool and the material when the material is plastically worked with the tool of the present invention. It is an enlarged sectional view. 1: Tool, 2: Smooth surface, 3: Hollow, 4: Workpiece material

Claims (1)

[Claims] A plastic working tool having a smooth surface with a large number of small depressions, each of which has a diameter of 5.
~50 μm and a depth of 0.5 to 5 μm, and the total area of these depressions is 5 to 50% of the area of the tool surface before making the depression.