JPS5941451A - Anti-wear fe base sintered alloy having self-lubricity - Google Patents

Abstract

PURPOSE:To provide an Fe base sintered alloy having excellent anti-wear property and self-lubricity, obtained by uniformly dispersing a specific area ratio of free qraphite and CaF2 in a steel base material containing C, Si, Cr, P or/and B, CaF2 respectively in a predetermined ratio. CONSTITUTION:An Fe base sintered alloy contains, on the basis of wt% 2-8% C, 0.1-5% Si, 4-30% Cr, 0.02-5% P or/and B, 0.05-5% CaF2 and comprises the ramainder Fe and inevitable impurities. In this case, 2-30% in an area ratio of graphite and CaF2 are uniformly dispersed in said alloy base material. Because this Fe base sintered alloy has the above aforementioned characteristics, effect as mentioned hereinbelow is developed when said alloy used in praparing the movable valve mechanism member of an internal combustion engine especially applied with high surface pressure and poor in a lubricating state at the start of operation. That is, excellent capacity is stably developed over the extremely long period of time without damaging an opposed member.

Description

Detailed Description of the Invention This invention has excellent wear resistance and self-lubricating properties, and is particularly applicable to usage conditions where high surface pressure is applied and a sufficient lubrication state cannot be established at the start of operation. The present invention relates to an Fe-based sintered alloy suitable for use in the manufacture of exposed sliding members, such as sliding members of rocker arms in internal combustion engines, cams, valve seats, valve guides, and sleeves.

In recent years, as vehicles have become faster, more efficient, and more powerful, 1. The operating conditions of internal combustion engine valve train components, especially sliding components such as high surface pressure plates, valve guides, and sleeves, are becoming increasingly severe, for example, making it difficult to form a stable lubricating oil film. Yes, therefore,
There is a strong desire to develop a material that can withstand these harsh conditions of use.

However, at present, no material has yet been proposed that fully satisfies these requirements.

Therefore, from the above-mentioned viewpoint, the present inventors conducted research to find a material suitable for manufacturing sliding members that are exposed to usage conditions where the surface pressure is particularly high and the lubrication state is insufficient. As a result, the sliding member was ii% heavy and C: 2 to 8%.
, i3i: 0.1-5%, Cr: 4-30%, one or two of P and B: 0.02-5%, calcium fluoride (hereinafter referred to as CaF2): 0.05
~5%, and optionally Mo, W,
One or more of Nb, Ta, Ti and V: 0.1 to 10%, and Ni, Co
.

One or more of Cu and Mn: 0.1
~10% of either or both, with the remainder being li
When composed of an Fe-based sintered alloy having a composition consisting of '6 and unavoidable impurities, this Fe-based sintered alloy has excellent self-lubricity due to the free graphite and CaF uniformly dispersed in the base material, and Because the base material ensures excellent wear resistance, this sliding member can be used for an extremely long period of time without damaging the mating member, even under conditions of high blood pressure and insufficient lubrication. They obtained the knowledge that it exhibited excellent performance.

This invention was made based on the above knowledge, and the reason why the component composition range was limited as described above will be explained below.

(a) C The C component is solid-dissolved in the base material to strengthen it, and
In addition to combining with carbide-forming components such as carbon to improve the wear resistance of the alloy, the remaining C precipitates in the matrix as free graphite and improves the self-lubricating properties of the alloy. If the amount is less than 2%, the desired effect of improving the above-mentioned action cannot be obtained.On the other hand, if the amount of nitrate is added to 8% by 6M, the fluidity of the mixed powder becomes extremely poor during alloy production, making it difficult to form a green compact. Therefore, the content was set at 2 to 8%.

(b) The 5i Si component not only dissolves in the base material and strengthens it, but also generates a liquid phase during sintering to activate sintering and thereby densify the sintered body. It has the effect of promoting the precipitation of graphite, but if its content is less than 0.1%, the desired effect will not be obtained, while if it is contained in excess of 5%, the alloy will become significantly brittle. Therefore, its content was determined to be 0.1 to 5%.

(c) Cr The Cr component has the effect of forming a solid solution in the base material, strengthening it, and forming Cr carbide with high hardness as described above to improve the wear resistance of the alloy. Content: 4%
If the content is less than 30%, it will not be possible to secure the desired excellent wear resistance, while if the content exceeds 30%, the alloy will become brittle and the aggressiveness of the alloy will also increase. , its content was determined to be 4 to 30%.

(d) P and B These components have the effect of forming a solid solution in the base material and strengthening it, increasing its hardness and improving the wear resistance of the alloy, and also suppressing the liquid phase during sintering. When the content is less than 0.02%, the desired effect cannot be obtained. On the other hand, if the content exceeds 5%, the toughness of the alloy will be significantly impaired, so the content was set at 0.02 to 5%.

(e) CaF2 CaF, a component, has the effect of dispersing itself into the substrate and improving self-lubricating properties, and also has the effect of contributing to the spheroidization and stabilization of precipitated free graphite, but when its content is 0 .0
If it is less than 5%, the desired effect cannot be obtained;
If the content exceeds 0.05% to 5%, the alloy becomes brittle, so the content was set at 0.05 to 5%.

(fi Mo , W , Nb , Ta tTt and ■ These components have a solid solution in the base material to strengthen it, and also combine with C to form carbide, thereby improving the wear resistance of the alloy. (hereinafter, these components are collectively referred to as wear resistance improving components), so they are included as necessary especially when even higher wear resistance is required, but if the content is 0.1 If the content is less than 10%, the desired effect of improving wear resistance cannot be obtained, whereas if the content exceeds 10%, the damage to the mating member becomes significant. Therefore, the content was set at 0.1 to 10%.

(g) Nit Co T Cu + and Mn These components have the effect of solid-dissolving in the base material and further improving the alloy strength (hereinafter collectively referred to as strength improving components), so they are particularly effective for high strength. It is included as needed when required, but if its content is less than 0.1%, the desired strength improvement effect cannot be obtained, while if it is contained in excess of 10%, a further improvement effect will not be obtained. Since this does not occur, the content was determined to be 0.1 to 10% in consideration of economic efficiency.

The Fe-based sintered alloy of the present invention preferably has a theoretical density ratio of 90% or more, because if the theoretical density ratio is less than 90%, the strength of the base material will be low and large pores will be present. This is because the notch effect of these holes makes the base more likely to be destroyed and pitting wear is more likely to occur.

Next, the Fe-based sintered alloy of the present invention will be specifically explained using Examples.

Examples of raw material powders include scale-like Kurofune powder with a particle size of -200 mesh and atomized Fe-
Cr alloy powder tCr: 12.5% content), same 10
0mesh high carbon Fe-Cr alloy powder (Cr:60
% content), the same 200 mesh Fe-Si alloy powder (Si: 17% content), the same 350 mesh Fe
-2 alloy powder (P: 17% content), same 250 m
esh Fe-2 alloy powder (P: 25.7% content), same 200 mesh Fe-B alloy powder (B: 20%)
), same 200 mesh CaF, powder, same 350 mesh MO grain powder, same 200 mesh Fe-Nb alloy powder (Nb: 15% content), same 20
0 mesh Fe-V alloy powder (contains 0% V near)
, Ta powder, W powder, Ti powder, all with an average particle size of 5 μm.
Powder, Ni powder, CO powder, and Mn powder, particle size -2
00 mesh Cu powder, the same 100 mesh atomized Fe-Cr-Mn-Ta alloy powder (Cr:
14.0%, Mn: 1.1%, Ta: 4.3
% containing) and Fe powder of the same 100 mesh were prepared, these raw material powders were blended into the composition shown in Table 1, 0.5% of zinc stearate was added as a lubricant, and a V-type mixer was used. After mixing at
/(Mold into a green compact at a pressure of 7, then this green compact,
Sintering is carried out in a vacuum at a predetermined temperature within the temperature range of 1050 to 1200°C for 60 minutes, and immediately after sintering,
By performing forced cooling quenching at a temperature of 00℃,
Fe of the present invention having substantially the same component composition as the blended composition
Base sintered alloys 1 to 33 and comparative Fe-based sintered alloys 1 to 9 were manufactured, respectively. Comparative Fe-based sintered alloys 1 to 9 each have a composition in which the content of one of the constituent components (marked with * in Table 1) is outside the scope of this invention. It is.

Next, the resulting Fe-based sintered alloys 1 to 3 of the present invention
3 and comparative Fe-based sintered alloys 1 to 9, the theoretical density ratio, maximum hardness (Vickers hardness of the substrate), and transverse rupture strength were measured, and a chip piece suitable for the butt surface of the rocker arm of an automobile engine was measured. Cut it out, cast it in when rocker arm is cast, and insert the resulting rocker arm into a 4-cylinder OHC engine. Oil used: Diamond 2.
A wear resistance test was conducted under the conditions of 0W (trade name), rotation speed: 850 r, pom, operating time = 200 hours, and the depth of wear on the butt surface of the rocker arm and the cam, which is a mating member, was measured. These measurement results are also shown in Table 1.

From the results shown in Table 1, the Fe-based sintered alloys 1 to 1 of the present invention
No. 33 had excellent wear resistance and self-lubricating properties, so the amount of wear on the butt surface of the rocker arm and the mating cam was extremely small, and the worn surfaces were also extremely smooth.

On the other hand, as seen in Comparative Fe-based Sintered Alloys 1 to 9, if the content of any of the constituent components falls outside the scope of the present invention, the desired wear resistance and self-lubrication properties may be lost. As a result, at least one of the two members has more wear paths, and moreover, scuffing and pitting are observed on the wear surface.

As mentioned above, the Fe-based sintered alloy of the present invention has excellent wear resistance and self-lubricating properties, so it can be used particularly in valve train systems of internal combustion engines that are subject to high blood pressure and are poorly lubricated at the start of operation. When used in the manufacture of parts, it has industrially useful properties such as exhibiting excellent performance stably over an extremely long period of time without causing much damage to the other parts.

Applicant: Mitsubishi Metals Corporation Agent: Kazuo Tomita and 1 other person

Claims (1)

[Claims] (11C: 2-8%, Si: 0.1-5%, Cr:
4-30%, one or two of P and B: 0.
Calcium fluoride: Contains 0.05 to 5%, with the remainder consisting of Fe and unavoidable impurities (weight%), and has a free area ratio of 2 to 30% in the matrix. A self-lubricating wear-resistant 1i'e-based sintered alloy characterized by having a structure in which graphite and calcium fluoride are uniformly dispersed. (2) C: 2-8%, Si: 0.1-5%, Cr:
4-30%, one or two of P and B = 0
．． 02-5%, calcium fluoride: 0.05-5%, and further contains MO + W + Nb, Ta, T
One or more of i and v20.1-1
0% and the remainder is Fe and unavoidable impurities (weight%), and the area ratio in the base material is 2 to 30%.
Wear-resistant F with self-lubricating properties characterized by a structure in which % free graphite and calcium fluoride are uniformly dispersed
e-based sintered alloy. (3) C: 2-8%, Si: 0.1-5%, Cr
: 4-30%, one or both of P and B 0.02-5%, calcium fluoride: 0.05-5%
and further contains 0.1 to 10% of one or more of Ni, Co, Cu, and Mn, with the remainder consisting of pe and unavoidable impurities (wt%). and a wear-resistant Fe-based sintered alloy having self-lubricating properties, characterized in that it has a structure in which free graphite and calcium fluoride are uniformly dispersed in an area ratio of 2 to 30%. (4) C: 2-8%, Si: 0.1-5%, Cr
: 4-30%, one or two of P and B: 0.02-5%, calcium fluoride: 0.05-5%
Contains Mo, W, Nb, Ta,
One or more of Ti and ■: 0.1
~10% and Ni. Contains 0.1 to 10% of one or more of Co, Cu, and Mn, with the remainder consisting of Fe and unavoidable impurities (in weight percent), and has an area in the base material. A wear-resistant Fe-based sintered alloy having self-lubricating properties, characterized by having a structure in which free graphite and calcium fluoride are uniformly dispersed in a ratio of 2 to 30%.