KR910009972B1 - Carbide-dispersed type fe-base sintered alloy excellent in wear resistance - Google Patents

Abstract

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Description

Carbide-dispersed Fe Base Binder with Excellent Wear Resistance

The present invention is excellent when used as a rocking arm tip or a valve lifter sliding part of a heat-resistant engine, for example, a heat-resistant engine that uses liquefied natural gas (LPG) as a fuel. The present invention relates to a carbide dispersed Fe-based small bond alloy exhibiting wear resistance.

In general, carbides, P-components or B-components are added to the sliding members of heat-resistant engines using LPG fuel to liquid-phase sinter to high density, and carbides containing (Fe, Cr) ₇ C ₃ or the like are dispersed in the matrix. Dispersed Fe gas bonds are used.

However, when LPG is used as fuel in the sliding member of an internal combustion engine, the condition of lubrication is poor and oil film breakage is easy. Therefore, the use conditions are extremely harsh. When the dispersion ratio is high, the metal volume bonds with the mating member in conjunction with the 30% by volume point, and in some cases, there is a problem such as a scarf wear of about 0.5mm in depth or a significant damage to the cam member as the mating member. It is.

Herein, the present inventors have developed a suitable material as a sliding member of an internal combustion engine using LPG as a fuel, in view of the above-mentioned aspect. 10 to 40%, Mo 2 to 25%, Co or Ni, 0.1 to 15% of one or two species, containing (a) W 0.1 to 10%, (b) Ti, Zr, Hf, V , At least one of Nb and Ta, at least 0.1 to 5%, at least 0.1 to 5%, at least one of (a) and (b), or a composition containing the remainder as Fe and an unavoidable impurity, 71 vol% The carbide-dispersed Fe-based low-alloyed alloy having a structure in which the above carbides are dispersed and the theoretical density ratio of 97% or more is almost completely filled by the carbides, and thus has a structure where the exposed metal is less exposed. Since there is no metal adhesion between them, the lubrication state is bad, and even if there is an oil break, scarf abrasion occurs. And show excellent wear resistance and low relative aggressiveness, and furthermore obtain the knowledge that since the holes have a high density is also formed to be suppressed anti-pitching wear.

The present invention is based on the above knowledge, and the reason why the composition composition, the dispersion ratio of carbides, and the theoretical density ratio are limited as described above will be explained below.

(a) C

The C component is partially dissolved in the matrix to reinforce it, and the rest forms a complex carbide with Cr, Mo, and Fe to improve abrasion resistance and adhesion resistance, but when the content is less than 4%, it is dispersed in the matrix. If the ratio of carbide is less than 71% by volume, the desired abrasion and adhesion resistance cannot be secured. If the content exceeds 6.5%, free carbon is formed and the alloy strength is lowered. Therefore, the content is 4 to 6.5%. Decide

(b) Cr

The Cr component has a function of partially solid solution at the base to improve their heat resistance and corrosion resistance, and to form a complex carbide having low relative aggressiveness as described above to improve the abrasion resistance of the alloy, but if the content is less than 10%, the action is desired. If the effect is not obtained and the content exceeds 40%, the alloy strength is lowered, so the content is set to 10 to 40%.

(c) Mo

The Mo component has a function of inhibiting coarsening at the time of sintering of the formed carbides, in addition to partially solidifying and strengthening the matrix, but when the content is less than 2%, the desired effect cannot be obtained. If the content exceeds 25%, the strength is lowered, so the content is set to 2 to 25%.

(d) Co, Ni

These components have the effect of increasing the alloy strength by solid solution in the matrix, but if the added amount is less than 0.1%, the desired strength improvement effect cannot be obtained. Since this is only increased, the addition amount thereof is set at 0.1 to 15%.

(e) W

Part of W is used to strengthen the base and reinforce it, and it is also employed in double carbides dispersed in the body to increase the hardness of this carbide, thereby improving the wear resistance. Therefore, it is necessary when the counter member is composed of a hard material. If the content is less than 0.1%, the desired abrasion resistance improvement effect cannot be obtained. On the other hand, if the content exceeds 1%, the above-mentioned action is saturated, and a further wear resistance improvement effect cannot be obtained. Set in%.

(f) Ti, Zr, Hf, V, Nb and Ta

These components mainly contain Fe, Cr, Mo, and C, and in addition to the formation of carbides, they also form carbides alone to further enhance the hardness of the alloy, so that they may be included as necessary, especially when high hardness is required. If the content is less than 0.1%, the desired hardness improvement effect cannot be obtained. On the other hand, if the content is more than 5%, the single carbide of these components has a high relative aggressiveness, which leads to significant wear of the mating member, so that the content is 0.1 to 5%. Decide on

(g) carbide

The alloy of the present invention fills almost all of the matrix with carbides as described above, thus suppressing the occurrence of metal adhesion with the counterpart member and thus excellent wear resistance and extremely low relative resistance even under severe conditions in internal combustion engines using LPG fuel. It has the characteristic of showing aggressiveness, but the electrical property cannot be secured when the dispersion ratio is less than 71 vol%, so the dispersion ratio of carbide is set to 71 vol% or more.

In addition, the alloy of the present invention may be composed of only carbide, i.e., 100% by volume of carbide, and the dispersion ratio of the carbide can be freely adjusted by component composition or heat treatment.

(h) theoretical density ratio

As described above, when the dispersion ratio of carbides is 71 vol% or more, a decrease in alloy strength is inevitable, and this tendency is further promoted when the theoretical density ratio is less than 97%, so that fracture or pitching wear is likely to occur. The density ratio is set to 97% or more.

EXAMPLE

Next, the Fe-based sintered alloy of the present invention will be specifically described by way of examples.

As the raw material powder, either Fe powder having an average particle diameter of 10 μm, Fe-30% Cr-8% Mo-3% C-0.5% alloy powder, and Fe-55% Cr alloy powder, similarly Fe-15 having an average particle diameter of 6 μm % Cr-15% Mo-5% Ni-4% C alloy powder and Fe-10% Cr-5% Mo-5% W-1% Nb-3% C alloy powder, Mo powder with 2 μm as well, W powder , Co powder and Ni powder, TiC powder, ZrC powder, HfC powder, VC powder, NbC powder, and TaC powder, which have 1.5μm as well, graphite powder of -350 mesh, and these raw powders After mixing to the indicated composition, mixed under normal conditions, press molding at a pressure of 5 to 7 Ton / Cm ² , and then at a predetermined temperature within a range of 1100 to 1200 ° C. in a vacuum of 5 × 10 ⁻² Torr. Sintering was carried out for 1 hour holding conditions, and then slowly cooled in a range of 1000 to 600 ° C. over 3 to 5 hours to perform precipitation treatment. It was also prepared having a carbide dispersion ratio and the theoretical density ratio of the invention Fe charged coupled gold 1 to 14 and Comparative Fe-based sintered alloys 1 to 4 shown in the first table, respectively.

The comparative Fe-based small bonds 1 do not contain Co or Ni, and the comparative Fe-based small bonds 2 to 4 have any of the component content carbide dispersion ratios and the theoretical density ratios (see Table 1). It is outside the scope of the invention.

Next, the Fe-based small-sintered alloys 1 to 14 and comparative Fe-based small-sintered alloys 1 to 4 of the present invention were cast and deposited on a rocker arm sliding surface made of Al during die casting.

The wear test was performed under the conditions of and the maximum wear depth was measured.

The results are shown in the first table.

In the first table, the maximum wear depth of the cam member as the mating member is indicated.

From the results shown in Table 1, Fe-based small-alloy alloys 1 to 14 of the present invention were poorly lubricated, and even when used under conditions of LPG fuel use, where the oil film was easily disconnected, and under high load conditions, the occurrence of scarf wear and pitching wear did not occur. It shows excellent wear resistance, low wear of the mating member, and extremely low relative aggression. However, as shown in Comparative Fe Base Sintering Alloys 1 to 4, the component content of any of the constituent components deviates from the range of the present invention to the lower side. It was clear that the performance and the wear resistance were deteriorated to increase the relative aggression, which was accelerated further when the theoretical density ratio was lowered.

[Table 1]

As described above, the Fe base sintered alloy of the present invention has excellent abrasion resistance and remarkably low relative aggression, and for example, LPG fuel is used by internal combustion engine as a sliding member requiring high lubrication characteristics such as rocker arm chips and valve lifter sliding parts. In this case, excellent performance is achieved over a long period.

Claims (4)

Contains 4 to 6.5% of C, 10 to 40% of Cr, 2 to 25% of Mo, 0.1 to 15% of one or two species of Co Ni, and is composed of the remaining Fe and unavoidable impurities (% by weight), 71 vol% Carbide-dispersed Fe-based Fe-based alloy having excellent abrasion resistance, characterized in that the carbide is dispersed at a ratio of more than 97% and the theoretical density ratio is greater than 97%. It contains 4 to 6.5% of C, 10 to 40% of Cr, 2 to 25% of Mo, 0.1 to 15% of one kind or one of Co and Ni, and again contains 0.1 to 10% of W and is composed of remaining Fe and unavoidable impurities. (Abnormal weight%), a structure in which carbides are dispersed at a ratio of 71 vol% or more, and 97% or more have a theoretical density ratio, and the carbide dispersed Fe-based small base alloy having excellent abrasion resistance. C 4 to 6.5%, Cr 10 to 40%, Mo 2 to 25%, Co or Ni, or 1 to 2 kinds 0.1 to 15%, and again one of Ti, Zr, Hf, V, Nb and Ta or A composition containing at least two kinds of 0.1 to 5% and consisting of the remaining Fe and unavoidable impurities (ideal weight%), a structure in which carbides are dispersed at a ratio of 71 volume% or more, and a theoretical density ratio of 97% or more; Carbide-dispersed Fe base alloy with excellent wear resistance. 4 to 6.5% of C, 10 to 40% of Cr, 2 to 25% of Mo, 0.1 to 15% of one or two of Co and Ni, and 0.1 to 10% of W, Ti, Zr, Hf, V, One or two or more of Nb and Ta, containing 0.1 to 5% of the composition, the composition consisting of the remaining Fe and unavoidable impurities (% by weight), a structure in which carbides are dispersed at a ratio of 71% by volume or more, and a theoretical density ratio of 97% or more A carbide-dispersed Fe base alloy having excellent abrasion resistance, characterized by having.