JPH048484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method of producing a wear-resistant surface using a high density energy source such as a laser beam.

In general, ferrite-based spheroidal graphite cast iron or compact vermiform cast iron (hereinafter simply referred to as CV cast iron) has a ductility comparable to that of steel, but on the other hand, it has the disadvantage of poor wear resistance due to its low hardness. Conventionally, heat treatment such as induction hardening is used to surround the ferrite base or the spheroidal graphite in spheroidal graphite cast iron or CV cast iron containing some pearlite with a martensitic structure, bainite structure, or sorbite structure (hereinafter, such a structure is used). The structure is called an annular second phase) to improve plastic flow resistance and wear resistance.

However, with conventional heat treatment methods, it is difficult to obtain a stable annular second phase due to large variations in heating temperature. There were drawbacks such as the properties of the base material deteriorated, such as inhibition of the properties of the base material.

This invention was made with the aim of improving such drawbacks, and by irradiating ferrite-based or partially pearlite-based spheroidal graphite cast iron or CV cast iron with a high-density energy source such as a laser beam or an electron beam, stable The present invention provides a method for producing a wear-resistant surface using a high-density energy source in which an annular second phase is easily obtained, thereby providing a wear-resistant surface without compromising ductility or impact resistance. .

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. The base material 1 on which the wear-resistant surface is to be formed is made of ferrite-based or ferrite-based spheroidal graphite cast iron and CV cast iron containing a portion of pearlite. ,
When the surface of this base material 1 was irradiated with a high-density energy source 2 consisting of a CO ₂ gas laser beam, a structure having an annular second phase was formed at an energy density in the range of 2 J/s·cm ² to 200 J/s·cm ² . generated on the surface of base material 1. Also, the energy density is 1J/s・cm ² ~150J/
When the same high-density energy source 2 was irradiated twice or more in the range of s·cm ² , it was also possible to generate an annular second phase on the surface of the base material 1 .

Note that the energy density of the high-density energy source is
If it is ^less than 2J/s・cm2, the surface temperature will not rise enough, and the diffusion of carbon into the ferrite layer will be insufficient, resulting in α
, and the cyclic second phase is no longer generated; on the other hand,
Since a region of 200 J/s·cm ² or more is a chilling region due to surface melting, an energy density range of 2 to 200 J/s·cm ² is an optimal annular second phase generation region.

Furthermore, it was confirmed that a similar annular second phase was generated even if an electron beam was used as the high-density energy source 2 instead of a laser beam and irradiated in the same energy density range as above.

Next, microscopic photographs (×200) of the tissues before and after irradiation with the high-density energy source 2 were taken and compared, and the results were as shown in FIGS. 2a, b and 3 a, b. In other words, Figure 2a shows the microstructure of spheroidal graphite cast iron before irradiation with a high-density energy source, and Figure 2b shows the microstructure after irradiation.The spheroidal graphite is often surrounded by an annular second phase. Recognize. In addition, Figure 3a shows the state before irradiation with the high-density energy source.
The microstructure of CV cast iron, and Figure 3b shows the microstructure after irradiation, clearly showing the formation of the annular second phase in the case of CV cast iron as well. Note that in all of these photographs, the upper side is the surface of the base material 1.

Next, in order to confirm the wear resistance of the wear-resistant surface on which the annular second phase was generated by the heat treatment, a wear test was conducted using a friction and wear tester shown in FIG.

For comparison, we also report the results of a similar wear test conducted on a conventional SCSiMn ₂ material subjected to induction hardening. For the test, the base material 1 heat-treated with the high-density energy source 2 and the conventional product (shown in Figure 5) subjected to induction hardening were attached to the mounting socket 5 of the testing machine and rotated at a circumferential speed of 0.5 m/sec. Press the sample disk 6 with a surface pressure of 350 kg/cm ² to
Wear was measured.

Reference numeral 7 denotes a pressure gauge for monitoring surface pressure, which is connected to a guide shaft 8 connected to the mounting socket 5 via a load cell 9 for measuring load movement and a coupling 10.

In addition, LBc-3 was used as the mating material (sample disk 6).

The results of a 12-hour wear test using the above method are shown in the 4th test.
As shown in the figure. As is clear from this figure, it can be seen that the wear resistance has been significantly improved compared to conventional products that have been induction hardened.

Further, o in FIG. 4 shows the wear resistance when the base material 1 is not heat treated, and the effect of the heat treatment is even clearer.

As described in detail above, this invention irradiates spheroidal graphite cast iron or CV cast iron with a ferrite base or a ferrite base containing some pearlite with a high-density energy source to generate an annular second phase around the spheroidal graphite. Therefore, the wear resistance of the base material surface is significantly improved by the annular second phase, and since the annular second phase is generated only near the surface of the base material, the rolled material of the base material is and impact resistance are less likely to be impaired. In addition, since the high-density energy source is irradiated only on the surface of the base material, thermal distortion is less likely to occur in the base material, which eliminates the need for work such as strain relief and makes grinding easier. Therefore, the man-hours required for grinding work etc. can be significantly reduced.
Moreover, unlike high-frequency heat treatment, there is no need to pour cooling water, so there is almost no surface roughening due to oxidation, etc., and therefore no rework is required after treatment.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the method of the present invention, FIGS. 2 a, b and 3 a, b are micrographs of spheroidal graphite cast iron and CV cast iron before and after treatment,
FIG. 4 is a diagram showing the results of the abrasion test, and FIG. 5 is an explanatory diagram of the friction and wear tester. 1 is the base material and 2 is the high-density energy source.

Claims (1)

[Claims] 1. An energy density of 2 to 200 J/s cm by a laser or an electron beam is applied to the surface of the base material 1, which is made of a ferrite base of spheroidal graphite cast iron and compact vermilion cast iron (CV cast iron), or a ferrite base containing some pearlite. ^2. A method for producing a wear-resistant surface using a high-density energy source, the method comprising: irradiating the base material 1 with a high-density energy source 2 to generate an annular second phase of martensitic structure on the surface of the base material 1.