JPS63245332A - Manufacture of metallic short fiber - Google Patents

Abstract

PURPOSE:To produce such a metallic short fiber that has good physical properties and dimensional form in an inexpensive manner, by turning a low ductile columnar block, typical of brass, under the specified condition, utilizing the natural, and disruptively generating the acicular short fiber of a noncircular section. CONSTITUTION:In a casting ingot block 1 of low ductility such as brass, a thin layer 5 of the surface is continuously scraped up by a cutting edge 4 of a tool 3, and a rake angle theta, cutting speed and feed rate are all set under the specified condition. And the surface layer 5 is gathered 5 is gathered up to the specified quantity in the cutting edge 4, and when it is protuberant, a crack runs along an interface due to an interface due to an unstable phenomenon, and it is disruptively separated, thus such an acicular short fiber that its axis is orthogonal with the cutting direction and is formed into a noncircular section is generated, and it is continuously discharged out of a cutting face 7. In this case, infeed rate is accorded with fiber length L, and the rake angle theta should be set to about 0-40 deg.C, feed rate to about 0.05-0.3mm/rev., and cutting speed to about 86-276/min., respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing short metal fibers, particularly ultrafine short fibers suitable for use as a base material for composite materials.

In general, short metal fibers are called fibers.

There are various materials such as glass fiber, carbon fiber, and asbestos. Among these fibers, metal fibers are most suitable for friction materials such as brake linings and clutch plates, and structural composite materials such as filters, conductive FRP, electromagnetic shielding FRP, and noise shielding plates.

However, the metal fibers used for this type of application must be extremely fine, with a diameter of 100 microns or less and a length of 10 mm or less, and must also have good physical properties such as tensile strength as reinforcing fibers. Therefore, it is difficult to easily mass-produce them, and the manufacturing cost is extremely high, except for special products such as lead fibers, and it has not been possible to meet the wide-ranging demand described above.

That is, when producing ultrafine metal short fibers, generally a cast ingot is rolled to make a wire rod, this wire rod is drawn using a drawing die, etc., and this drawing and annealing are repeated many times to obtain the diameter as described above. The method used was to stretch it into fibers and then cut it at the end.This extremely time-consuming process and the need for large-scale equipment resulted in low productivity and very slow production. The cost was increasing.

Note that, as a method for manufacturing relatively long and thick metal fibers such as steel fibers for reinforcing concrete, there is a method of milling an ingot. However, this method involves intermittent machining by rotating a cutter with a plurality of cutting blades attached to its outer periphery, which poses a problem in terms of production speed. In addition, this method requires high accuracy from the machine and tools, and slight deviations in accuracy (for example, spindle runout, clearance between the arc and the inner diameter of the cutter, groove depth of the carbide tip, blade width, installation error, etc.) Since the run-out of the outer circumference of the cutting edge directly affects the dimensions and physical properties of the product, there is a problem in that it is difficult to mass-produce extremely thin and short fibers without variation, as described above.

The present invention was created through repeated research in view of the above-mentioned circumstances, and its purpose is to improve physical properties such as elastic modulus, abrasion resistance, electrical and thermal conductivity, wettability, and sinterability. An object of the present invention is to provide a method for mass-producing ultra-fine short metal fibers having dimensions and shapes extremely efficiently and inexpensively.

To achieve this objective, the present invention utilizes the natural cracks of the material by turning a columnar block with relatively low ductility, such as brass, under predetermined conditions, and produces acicular short fibers with a non-circular cross section. It is designed to divide and create.

That is, the present invention is characterized by using a columnar block made of a material with low ductility such as brass as a raw material to obtain short gold scrap fibers, and cutting this columnar block with a cut corresponding to the length of the fiber to be produced. amount and cutting speed of about 86~
276m/min, feed amount 0.05~0, 3mm
/rev, turning is carried out under the following conditions within the range of tool rake angle of about 0 to -40° to separate and create acicular short fibers with a non-circular cross section whose fiber axis is perpendicular to the cutting direction. A method for producing short metal fibers.

■When the tool rake angle is approximately 0 to -10', the lower limit of the feed rate is approximately 0.07 to 0.1 mm/r in the entire cutting speed range.
ev range and the closer the tool rake angle is to positive, the value gradually increases.

■If the tool rake angle exceeds approximately -10" and reaches approximately -20°,
Set the cutting speed below the upper limit and set the lower limit of the feed rate to approximately 0.
．． The value is set in the range of 0.05 to 0.07 mm/rev and gradually increases as the tool rake angle becomes more positive.

■When the tool rake angle exceeds approximately -20" and reaches approximately -30°, the cutting speed should be approximately 158 m/min or less, and the feed rate should be adjusted to
When the cutting speed is at the lower limit, the feed rate is approximately 0.05 my+/rev or more, and when the cutting speed is approximately 158 m/min, the feed amount is approximately 0.05 m/rev.
~0.75mm/rev, the cutting speed is approximately 1 from the lower limit
Between 58 m/min, approx. 0 and 051 m/rev
Above, the faster the cutting speed and the more negative the tool rake angle, the smaller the value.

■When the tool rake angle is negative and exceeds about -30°, reduce the cutting speed to about 158 m/min or less, and reduce the feed rate to about 0.05 to 0°1 nu/re when the cutting speed is at the lower limit.
v, when the cutting speed is about 158 m/min, the feed rate is about o
, o5~0. Between 75 mm/rev and cutting speed of about 158 m/mj from the lower limit, about 01o5 between n
~0.1 mm/rev, the faster the cutting speed, the smaller the value.

The present invention will be explained below based on the accompanying drawings.

FIGS. 1 and 2 show an embodiment of the method for producing ultrafine short fibers according to the present invention. In producing the ultrafine short fibers, a columnar block 1 such as a cast ingot is used as a raw material. The columnar block 1 in this embodiment is suitably made of a material with low ductility such as brass, most preferably free-cutting brass.

Next, the end of the columnar block 1 in the axial direction is gripped by a holding means such as a chuck, and the columnar block 1 is rotated at a predetermined speed and number of rotations via this holding means, and the end face of the columnar block 1 is 2, the cutting edge 4 of the tool 3 is set to a predetermined depth of cut Q and a rake angle θ and brought into contact with each other, and a predetermined feed f is applied to the tool 3 in the block axis direction.

By doing this, the thin N5 on the surface of the metal block 1 is continuously scraped up by the cutting edge 4 of the tool 3.

At this time, if the rake angle, cutting speed, and feed rate of the tool are not set appropriately, the collected thin layer may flow out for a long time along the rake face, resulting in curved or curled flow chips. 6 In the present invention, the columnar block 1 is made of a material with relatively low ductility, typically brass, and the tool rake angle and cutting speed are determined as described later. and the feed rate are set to certain conditions. Therefore, like a rabbit, the surface layer of the columnar block is scraped up to a certain amount by the cutting edge 4, and when this rises, due to an unstable phenomenon, it cracks along the approximate interface between the scraped layer and the surface layer of the columnar block. enters.

The layers collected along the cracks are instantaneously broken and separated, creating needle-shaped short fibers 6 with fiber axes perpendicular to the cutting direction and non-circular cross sections, one each from the rake face 7. It is released continuously in an independent form.

FIG. 3 shows the short fiber 6 in an enlarged manner.

In addition, although FIG. 1 shows that the tool 3 is fed in the axial direction,
Alternatively, the feed may be perpendicular to the axis, that is, in the radial direction. In that case, it goes without saying that the feed and depth of cut will have an inverse relationship to that shown in FIG.

The present invention employs certain turning conditions in the production of short fibers, that is, basically, the depth of cut is made to match the length of the fiber to be produced, and the tool rake angle θ is
approximately 0 to -40°, feed amount f approximately 0.05 to 0.3 mn
/rev, and the cutting speed is approximately 86 to 276 m/min. If this condition is not met, chips will be serrated or flow-shaped, making it impossible to produce the desired short fibers industrially and stably.

First, the rake angle O is an important condition that affects the thickness, shape, and strength of the fiber, and it is preferable to make it as negative as possible. The reason why the upper limit of the rake angle is set to 0° is because when the rake angle is set to the positive side, the shaved layer easily flows along the rake face without being compressed, resulting in a flow type chip.

If the rake angle is increased to a negative value, the layer that has been scraped and is accumulating on the cutting edge will be compressed and deformed, promoting instability and making it easier to crack, so it is necessary to use thin and hard fibers. Moreover, at the same time, a rough surface 61 can be formed on the free surface of the short fiber 6 as shown in FIG.

The rough surface 61 has a funnel-like shape running along the fiber axis, thereby increasing the surface area and increasing the frictional resistance. However, if the rake angle is made extremely large, serrated chips tend to occur in areas where the feed is large, and when the feed is small, flow-shaped chips occur, making it impossible to produce fibers. Therefore, the negative upper limit of the rake angle should be -40°.

Next, as the feed f is decreased, the fiber cross-sectional area tends to become smaller, and the smaller the feed and the more negative the rake angle, the thinner the short fibers can be. However, if the feed rate is too small, the longitudinal side edges of each fiber will tend to connect when they leave the cutting edge 4, resulting in a flowing chip. Should be set to a range. According to the studies carried out by the present inventors, even if the rake angle is within the above conditions, a minimum feed of about 0.05 mm/rev is required. The upper limit of feed is approximately 0.3 mm/rev in view of the fiber thickness.

Next, the cutting speed V affects productivity, and the faster the cutting speed, the greater the number of fibers produced. But on the other hand,
The faster the cutting speed, the narrower the fiber generation area. This is thought to be because the increasing speed increases the breaking strain of the material, making it difficult to separate the chips. According to the implementation by the present inventors, the rake angle is 0 to -40°, the feed is 0, 05 nun
/rev or higher, the productivity and error is approximately 86 to 276 m.
/min was found to be within a practical range.

Note that the rake angle θ also affects the cross-sectional shape of the fiber, and as the rake angle becomes more negative under constant conditions of cutting speed and feed, the width of the upper base decreases and the width of the lower base increases. Therefore, by setting the rake angle, it is possible to manufacture anything from a trapezoidal shape to a triangular shape. Further, the length of the short fibers 6 corresponds to the cutting depth of the tool 3 in the axial direction as shown in FIG. 1, and corresponds to the cutting width in the radial direction. Therefore, by adjusting them, it is possible to manufacture anything from relatively long to extremely short.

The above-mentioned basic conditions are the basic conditions, but in order to stably produce the desired short fiber without variation, within the framework of the above-mentioned basic conditions, the following relationship between the tool rake angle, cutting speed, and feed amount is required. should be set to .

Under these conditions, desired short fibers can be produced with high efficiency and good yield.

■When the tool rake angle is approximately 0 to -10°, the lower limit of the feed rate should be approximately 0.07 to 0, in the entire cutting speed range.
/rev and the value gradually increases as the tool rake angle becomes more positive.

■If the tool rake angle exceeds about -100 and reaches about -20",
Set the cutting speed below the upper limit and set the lower limit of the feed rate to approximately 0.
, 05 to 0,07 mn/rev, and the value gradually increases as the tool rake angle becomes more positive.

■If the tool rake angle exceeds about -20° and reaches about -30°,
The cutting speed was set to about 158 m/+nin or less, and the feed rate was set to about 0.0 mm at the lower limit of the cutting speed. When the cutting speed is approximately 158 m/win and the feed rate is approximately 0,
05~0, 75mm/rev, cutting speed is between about 158 m/min from the lower limit, about 0.051 m/r
ev or more, the faster the cutting speed and the more negative the tool rake angle, the smaller the value.

■When the tool rake angle is negative and exceeds about -30°, reduce the cutting speed to about 158 m/win or less and reduce the feed rate.
When the cutting speed is at the lower limit, it is approximately 0.05~0゜1 nvn/
r6y, when the cutting speed is about 158 m/min, the feed rate is between about 0.05 and 0.75 mm/rev, and when the cutting speed is between the lower limit and about 158 m/min.

The higher the cutting speed is, the smaller the value is set between approximately 0.05 and 0.1 nm/rev.

Next, examples of the present invention will be shown.

■As a columnar block, a free-cutting brass rod with an outer diameter of 60 mm (
Pb: 2.98%, Fe: 0.23%, Fe+Sn:
0.30%, balance Zn, tensile strength 38.4 glare/rm
m”, elongation 23.6%, reduction of area 25.2%), and a Class 2 carbide throw-a-wi tip (12.7nn+
Using a cutting tool with a mouth x 4.8mmt) attached to a holder,
Average cutting speed 86-276 m/min, feed 0.
021~0.306+nm/rev, rake angle 10'
, O', -10°, -20', -30', -4
0' and a cutting miller of 5 mm, ultrafine short fibers were produced by the method shown in FIGS. 1 and 2.

(2) The influence of turning conditions on short fiber production at this time is shown in Fig. 4. In FIG. 4, the desired ultrafine short fibers were obtained in the area surrounded by diagonal lines. In FIG. 4, the portions surrounded by solid lines on the right side of each cutting speed display represent fiber generation. From the results shown in Fig. 4, as mentioned earlier, the cutting speed is approximately 86 to 276 m/min, and the rake metal is O to -4.
0°, feed rate 0.05~0.3++m/rev, and the cutting speed, rake angle, and feed amount meet the above ■~
It can be seen that it is necessary to have the following relationship.

In other areas, that is, in areas where the rake angle is extremely negative and the feed is large, the chips will be serrated, and if the rake angle is too large or the feed is too small, the chips will be flow-type chips, producing the desired short fibers. It's difficult.

(2) A study of the relationship between the cross-sectional area of short fibers and turning conditions under the above-mentioned appropriate conditions is as shown in FIGS. 5 and 6.

FIG. 5 shows the relationship between feed and cross-sectional area, and it can be seen that the smaller the feed, the smaller the cross-sectional area, but in the region where the feed is large, the cutting speed and rake angle affect the cross-sectional area. Figure 6 shows the relationship between rake angle and cross-sectional area.

(2) Furthermore, Fig. 7 shows the results of examining the fiber productivity at the upper and lower limits of the cutting speed, and it can be seen that the productivity is highest when the feed is reduced and the cutting speed is increased. Number of short fibers produced by rotary shear force and flat milling Q
is Q = Z-N (2 = number of teeth, N = cutter rotation speed),
In actual production equipment, cutter diameter is 300φ, z=5
0, N''210 (V=200m/m1n), and therefore Q=approximately 10,000 lines/min.

The present invention was able to produce approximately 2,000,000 pieces/mjn even with experimental equipment, which shows that it is possible to achieve a remarkable productivity improvement of approximately 2.0 times that of the conventional method.

According to the present invention as described above, short fibers having physical properties suitable for a base material for composite materials, ultrafine dimensions and a large surface area can be produced in large quantities without variation, and can be produced at low cost with a low degree of processing. It can be manufactured directly from raw materials, and the machines and tools are simple, so it can be provided at a cost that is not much different from that of raw materials.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an example of the method for producing short metal fibers according to the present invention, FIG. 2 is an enlarged cross-sectional view showing the fiber production mechanism, and FIG. 3 is a partial view of the short metal fibers obtained by the present invention. An enlarged perspective view, FIG. 4 is a graph showing the relationship between manufacturing conditions and short fiber production area in the present invention, FIG. 5 is a graph showing the relationship between feed and cross-sectional area, and FIG. 6 is a graph showing the relationship between rake angle and cross-sectional area. Graph showing,
FIG. 7 is a graph showing short fiber productivity according to the present invention. 1... Columnar block, 3... Tool, 6... Short fiber,
O...Tool rake angle, f...Feed, ■...Cutting speed.

Claims (1)

[Claims] To obtain short metal fibers, a columnar block made of a material with low ductility such as brass is used as a raw material, and the columnar block is cut at a cutting depth corresponding to the length of the fiber to be produced and at a cutting speed of approximately 86-276m/min, feed rate approximately 0.05-0
．． Turning was performed under the following conditions within the range of 03 mm/rev and tool rake angle of approximately 0 to -40° to separate and create acicular short fibers with a non-circular cross section whose fiber axis was perpendicular to the cutting direction. Characteristic manufacturing method of short metal fibers. (1) When the tool rake angle is approximately 0 to -10°, the lower limit of the feed rate is approximately 0.07 to 0.1 mm in the entire cutting speed range.
/rev and the value gradually increases as the tool rake angle becomes more positive. (2) When the tool rake angle exceeds about -10° and reaches about -20°, the cutting speed should be lower than the upper limit, the lower limit of the feed rate should be in the range of about 0.05 to 0.07 mm/rev, and the tool rake angle should be lower than the upper limit. The closer the angle is to positive, the more gradually the value is taken. (3) When the tool rake angle is more than about -20° and up to about -30°, the cutting speed should be about 158 m/min or less, and the feed rate should be about 0.05 mm/rev or more when the cutting speed is at the lower limit, and the cutting speed should be about 0.05 mm/rev or more when the cutting speed is at the lower limit. At approximately 158m/min, the feed amount should be approximately 0.05~
Between 0.75mm/rev, the cutting speed is approximately 15% from the lower limit.
Between 8 m/min and approximately 0.05 mm/rev or more, the faster the cutting speed and the more negative the tool rake angle, the smaller the value. (4) When the tool rake angle is negative and exceeds about -30°, reduce the cutting speed to about 158 m/min or less and reduce the feed rate.
The cutting speed is approximately 0.05 to 0.1 mm/rev at the lower limit,
When the cutting speed is approximately 158 m/min, the feed rate is approximately 0.05
~0.75mm/rev, the cutting speed is approximately 1 from the lower limit
Between 58m/min, approximately 0.05~0.1mm/r
ev, the faster the cutting speed is, the smaller the value is taken.