JPS61139640A - Graphite particle dispersion type wear resistant cast iron and its manufacture - Google Patents

Abstract

PURPOSE:To obtain advantageously case iron in which fine particles of graphite are dispersed uniformly by higher content than in conventional cast iron by molten metal method, by supplying graphite particles of prescribed particle diameter and quantity on the midway of flowing down of molten cast iron, mixing and solidifying them. CONSTITUTION:The molten cast iron 1 melted by melting method is allowed to flow out from bottom of a crucible 2 by pulling up a stopper 3. Just thereunder, graphite particles having <=250mu diameter are supplied by 1-20wt%. quantity to cast iron from a particles supplying apparatus 7. Inert gas is blown in spray state to the flow of molten metal and particles from a jetting nozzle 4 through a reducing valve 6 from a supplying apparatus 5, to mix both uniformly. The material is cast in a mold 8 immediately, cooled rapidly and solidified to obtain cast iron i which the aimed graphite particles are dispersed uniformly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to wear-resistant cast iron with dispersed graphite particles and a method for producing the same.

BACKGROUND OF THE INVENTION Conventionally, cast iron has been widely used in bearings, pistons, cylinders, brake materials, and other parts where sliding wear is a problem. In this case, the greater the amount of graphite that acts as a solid lubricant or oil reservoir, the better the wear resistance will be, but the amount of graphite that exists in cast iron obtained by ordinary melting methods is limited by the equilibrium phase diagram. If the composition is higher than the eutectic point of 4.3% by weight of carbon leaves, it is difficult to distribute the silencing particles uniformly, and the graphite tends to become coarse, resulting in a marked decline in mechanical properties. Therefore, cast iron uniformly containing a large amount of graphite above the eutectic point has not been manufactured.

On the other hand, it is possible to manufacture such materials using the powder metallurgy method, but this method is expensive because it produces raw metal powder, requires multiple steps to manufacture, and cannot produce large products. Therefore, something like this had not been made before.

OBJECTS OF THE INVENTION The object of the present invention is to provide a cast iron in which fine graphite particles are uniformly dispersed, and a method for manufacturing the same by a molten metal method.

Structure of the Invention As a result of intensive research to achieve the above object, the present inventors found that fine graphite particles (particle size 25
(0 μm or less) and blowing an inert gas onto the flow of the molten metal and graphite particles to form a spray, the fine graphite particles are uniformly dispersed in the molten cast iron. It has been found that by directly casting this into a mold and rapidly solidifying it, it is easier to obtain cast iron in which more graphite fine particles are dispersed evenly than in conventional cast iron. The present invention was completed based on this knowledge.

The gist of the present invention is as follows: l) A wear-resistant cast iron with graphite particles dispersed in it, which is made by uniformly dispersing 1 to 20% by weight of graphite particles with a grain size of 250 fine or less in cast iron.

2) While the molten cast iron is flowing down, graphite particles with a particle size of 25Q μm or less are supplied to the cast iron in an amount of 1 to 20 times the weight, and an inert gas is blown into the flow of the molten metal and graphite particles. A method for producing wear-resistant cast iron with dispersed graphite particles, which is characterized by mixing the two in a spray form, casting directly into a mold, and rapidly solidifying the graphite particles.

It is in.

The particle size of graphite particles to be uniformly dispersed in the present invention is 250
It is necessary that the particles be micrometers or less, with an average particle size of 2
A thickness of about 5 to 125 μm is preferable. The larger the graphite particles to be dispersed, the easier the dispersion, but if the particle size is 250
If it exceeds μm, the improvement in wear resistance will not be significant. If the dispersed amount of graphite particles is less than 1% by weight of cast iron, the improvement in wear resistance will be small, and if it exceeds 20% by weight, the amount of dispersed graphite particles will be less than 1% by weight, and if it exceeds 20% by weight, If the area ratio of graphite appearing on the worn surface exceeds 50%, the continuity of the substrate will decrease.
The mechanical strength of the worn surface decreases significantly, making it unusable.

The manufacturing method will be explained based on the drawings. FIG. 1 shows an embodiment thereof.

Molten cast iron 1 melted by a melting method is caused to flow out from the bottom of a crucible 2 by pulling up a stopper 3. Graphite particles are supplied directly below the molten metal from a particle supply device 7, and an inert gas is sprayed onto the flow of the molten metal and graphite particles using a gas spray nozzle 4 to form a mist and mix the two. 5 is an inert gas supply device, and 6 is a pressure reducing valve.

This mixture is immediately cast into a mold 8 and rapidly solidified. In this case, rapid cooling is required to solidify the dispersed graphite particles before they aggregate and float.

There are no particular restrictions on the cast iron before graphite particles are dispersed therein, but since it is necessary to rapidly cool it, it is desirable that the cast iron has a composition that does not easily generate chill.

Example Using an alumina crucible, gray cast iron (
After melting (equivalent to FC25) and raising the temperature to 1350 tl', the molten metal is allowed to flow down from the outlet at the bottom of the crucible,
Graphite particles having an average particle diameter of 90 μm were supplied therein in the amount shown in Table 1, and argon gas (10%) was sprayed from a gas spray nozzle installed at the bottom to mix the two. This was immediately cast into a cold mold (made of cast iron) to obtain graphite particle dispersed cast iron. In this case, the amount of graphite dispersed was controlled by the feed rate of graphite particles to obtain cast irons A and B having different amounts of graphite dispersed.

Samples were cut out from these A and B and subjected to an abrasion test.

The results were as shown in Table 1.

Table 1 (Rotor): 555C1 contact pressure crab
30 to 17° sliding speed: 1. '05 +T//S
, sliding distance: 10b, lubricating oil: paraffin system As is clear from these results, conventional gray cast iron (Fe
Compared to No. 12), the cast iron of the present invention had less wear, indicating that the wear resistance was significantly improved.

Effects of the Invention As described above, according to the present invention, a graphite particle dispersion material can be efficiently produced from molten metal using inexpensive cast iron and graphite particles with simple equipment, so it is very advantageous in terms of cost. Furthermore, when the cast iron of the present invention is used for sliding parts, the amount of wear is significantly reduced compared to conventional cast iron, which not only extends the life of the sliding material but also reduces replacement costs.

In addition, since the cast iron of the present invention contains a large amount of graphite, which is effective in reducing the rate of internal energy loss, it has even higher damping properties than cast iron used as a secondary material, making it an effective vibration damping material. Use 1: Molten cast iron 2 Niru pot 3: Stopper 4 = Gas spray nozzle 5: Inert gas supply device 6: Pressure reducing valve 7: Particle supply device 8: Mold Patent applicant Ryu Kawa, Director of the Metals Materials Technology Research Institute, Science and Technology Agency −

Claims (1)

[Scope of Claims] 1) A wear-resistant cast iron with graphite particles dispersed therein, in which 1 to 20% by weight of graphite particles having a particle size of 250 μm or less are uniformly dispersed. 2) While the molten cast iron is flowing down, graphite particles with a particle size of 250 μm or less are supplied in an amount of 1 to 20% by weight relative to the cast iron, and an inert gas is blown onto the flow of the molten metal and graphite particles to form a spray. A method for producing wear-resistant cast iron with dispersed graphite particles, which is characterized by mixing, casting directly into a mold, and rapidly solidifying.