JPH0137471B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wear-resistant sintered alloy that can be sintered and joined to cast iron or steel, and a method for producing the same.

Conventionally, various methods have been known for locally joining a material with excellent wear resistance only to a portion of a base material where wear resistance is required for economical or strength reasons. Those methods and drawbacks are discussed below.

(a) Brazing method using silver solder, brass brazing, etc. The soldering material, especially the soldering material used in silver soldering, is expensive and difficult to automate, making mass production expensive. It also has an adverse effect on wear-resistant materials and substrates due to heating.

(b) Self-fusing alloy joining method The deformation during self-fusing increases the machining allowance, which increases costs.

(c) Thermal spraying method using Mo, W, etc. PV value (product of surface pressure P applied to the sliding surface and sliding speed V) for sliding parts between the Rocker arm and the cam, etc.
There is a lot of wear in areas with high levels of friction, making them difficult to use. In addition, material yield is poor and costs are high.

(d) Plating method for Cr, Ni-P plating, etc. The usage conditions (PV value, lubrication, etc.) are limited, and it cannot be used under severe conditions where the oil film breaks (such as the sliding part between the rocker arm and cam).

In addition, as long as the bonding method is not limited to wear-resistant materials, powder metallurgy is known as another joining method. Those methods and drawbacks are discussed below.

(a) A method of joining using dimensional changes during sintering This method uses expansion or contraction during sintering to join, so it cannot be joined on flat parts.

(b) A method of compressing and sintering the compacted powder onto a base material during compaction Since sufficient strength cannot be obtained unless the powder compact is compacted by compaction, the shape of the base material is limited.

(c) Method of joining at the same time as sintering using a copper-based infiltrant or brazing material To complete the bonding, a sufficient amount of infiltrating material or brazing material is required to fill the pores of the green compact. . As a result, the area occupied by the infiltration material or the brazing material increases with respect to the sliding surface, and it cannot be used in areas with a high PV value because seizure is likely to occur.

The above are conventional joining methods, but there are other methods such as welding a wear-resistant material to a base material by welding such as projection welding. material is generally
Because it is made of carbide-forming elements such as Mo, Cr, W, V, Ti, and Nb, and materials with good hardenability (containing Ni, Cu, Cr, and Mo, and with a large amount of C), cracks may occur in the weld. There is a problem in that it is easy to occur.

On the other hand, when sintering and bonding, the heating temperature during sintering and bonding must be 1120°C or less, as a limiting condition due to the iron-based base material. The reason for this is that, with the exception of special steels, the eutectic temperature of cast iron is approximately 1150°C, so the safe temperature at which deformation does not occur industrially is at most 1120°C. In addition, in the case of steel, if the heating temperature is too high, the crystal grains will coarsen, resulting in
Impact strength and fatigue strength are significantly reduced, so
This is because the heating temperature needs to be kept below 1100°C.

Therefore, the present applicant first developed a wear-resistant sintered alloy that eliminates the drawbacks of the above-mentioned conventional technology and also satisfies the limited conditions (heating temperature conditions) during sintering and joining to the above-mentioned iron-based base material. is proposed. That is,
In this proposal, Fe−(5~30%) Mo−(2.5%
~5.0%) C alloy powder and Fe− (3.0~7.0%) P−
We propose a wear-resistant sintered alloy obtained by mixing C (0.5 to 2.5%) with alloy powder, compacting, and sintering. However, this proposal has a very large PV value and is intended to be used in parts with insufficient lubrication (e.g. piston rings, apex seals of rotary piston engines, etc.), so it has a hard phase (carbide phase). ) As a result of increasing the proportion of
In addition to being small (less than ^cm2 ), Fe−Mo−
Both the C alloy powder and the Fe-P-C alloy powder have high hardness and hardly undergo plastic deformation during compaction, so they have the disadvantage that the strength of the compact is insufficient.

The present invention is a further improvement of the above-mentioned proposal in order to eliminate such drawbacks, and it ensures the strength of the green compact, reduces the amount of hard phase (hardened layer), and imparts toughness. Furthermore, it is an object of the present invention to provide a wear-resistant sintered alloy that can be sintered and bonded to iron-based substrates at low temperatures, and a method for manufacturing the same, which has a reduced number of pores.

That is, the wear-resistant sintered alloy of the present invention is
Mo3.0~6.5wt%, P0.5~1.5wt%, C1.0~3.0
% by weight, and 2.0 to 7.0% by weight of Cr alone or a combination of Cr and at least one of Ni and Mn, with the remainder being Fe.

In addition, the method for producing a wear-resistant sintered alloy of the present invention involves mixing Fe-Mo-P-C alloy powder and Fe-Cr-based or Fe-Cr-Ni-based stainless steel powder with a fine particle size of 150 mesh or less. The method is characterized in that it is mixed into a powder, compacted, and sintered at a temperature of 1000 to 1120°C.

The present invention will be described in detail below. The wear-resistant sintered alloy according to the present invention can be sintered and bonded to a ferrous base material such as cast iron or steel at a temperature below the limiting condition (approximately 1120°C). Therefore, the composition range of Fe is 3.0 to 6.5% by weight of Mo, 0.5 to 1.5% by weight of P, and
C1.0 to 3.0% by weight, Cr alone or Cr plus Ni,
The total content of at least one kind of Mn is 2.0 to 7.0% by weight. Depending on this range of ingredients,
The strength of the compact is ensured, the amount of hard phase is reduced, toughness is imparted by Ni, Cr, and Mn, the impact strength is increased to 0.1 to 0.8 Kg・m/ ^cm2 , and there are fewer pores. It is what it is.

Regarding the reasons for limiting the range of components of the wear-resistant sintered alloy, firstly, Mo contributes to strengthening the base and forming a hard phase, and
It combines with Fe and C to lower the melting point. If the component range is less than 3.0% by weight, the amount of precipitated hard phase is small, and the amount of liquid phase is also small, so the density does not increase, and as a result, wear resistance decreases and bonding is impossible. On the other hand, when it exceeds 6.5% by weight, the above effects are saturated and
On the contrary, it becomes brittle because the amount of liquid phase becomes too large. Therefore, it is set in the range of 3.0 to 6.5% by weight.

Further, P combines with Fe and C to form a phosphorus eutectic, which serves to improve wear resistance and lower the melting point. Therefore, the component range is
If it is less than 0.5% by weight, the above effects are very small;
If it exceeds 1.5% by weight, the phosphorus eutectic will crystallize into a net shape, significantly reducing toughness, so the content is set in the range of 0.5 to 1.5% by weight.

Furthermore, C combines with Fe, Mo, and P to strengthen the matrix and form a hard phase, and also forms a low melting point, which is useful for increasing density and bonding with iron-based base materials. Therefore, if the component range is less than 1.0% by weight, the effect will be small, and if it exceeds 3.0% by weight, the hard phase will crystallize in a net shape and the crystal grains will become coarse, resulting in a significant decrease in toughness. Therefore, it is set in the range of 1.0 to 3.0% by weight.

Further, Cr, Ni, and Mn are useful for strengthening the matrix, particularly improving toughness, and for this purpose, at least one of Cr, Ni, and Mn is required in an amount of 2.0 to 7.0% by weight.
However, since the powders of Fe-Cr series or Fe-Cr-Ni series stainless steel described below both contain Cr, the powder content of Cr alone or in combination with at least one of Ni and Mn is 2.0 to 7.0. Weight% is required. In addition, if it is less than 2.0% by weight, the above effects will be small;
Moreover, if it exceeds 7.0% by weight, the above effects will be saturated and it is not economically necessary.

In addition, the method for manufacturing a wear-resistant sintered alloy according to the present invention uses Fe-Mo-P-C alloy powder as a bonding metal, and combines this with Fe-Cr-based or Fe-Cr-Ni-based stainless steel powder. This is done by sintering the skeleton metal. Furthermore, both of the above powders are powders with a fine particle size of 150 mesh or less, and these two powders are mixed, this mixed powder is compacted, and 1000
By sintering at a temperature of ~1120°C, a wear-resistant sintered alloy having the above-mentioned composition range can be obtained.

Here, the above Fe-Mo-P-C alloy powder and Fe-
The reason for using Cr-based or Fe-Cr-Ni-based stainless steel powder is simply to add iron powder, chromium, molybdenum, manganese, phosphorus, etc. to the above-mentioned range of the wear-resistant sintered alloy of the present invention. When ferroalloy powder and graphite powder are mixed, compacted, and sintered, large pores (more than 200μ) are generated when the liquid phase appears, which hinders the increase in density and causes crystal grains and This is because the coarsening of carbides reduces strength and wear resistance, and these phenomena do not occur when powders such as those of the present invention are used.

In particular, as the Fe-Mo-P-C alloy powder of the skeleton metal, Mo5 to 15% by weight, P1.5 to 3.0% by weight,
Preferably, the composition ranges from 3.0 to 4.5% by weight of C and the balance being Fe. That is, among these components, Mo
is useful for strengthening the base after sintering, forming a hard phase by combining with Fe and C, increasing density in liquid phase crystallization due to Fe-Mo-C eutectic, and bonding with iron-based base materials. If it is less than 5% by weight, the above effect will be small, and if it exceeds 15% by weight, the amount of liquid phase will be too large and it will become brittle, so a range of 5 to 15% by weight is preferable. In addition, P helps form a phosphorus eutectic by combining with Fe and C, and if it is less than 1.5% by weight, the effect is small, and if it exceeds 3.0% by weight, the phosphorus eutectic crystallizes in a net shape, improving toughness. as it significantly reduces
A range of 1.5 to 3.0% by weight is preferred. Furthermore, C is
It combines with Fe, Mo, and P to help strengthen the base and form a hard phase, and also forms a low melting point phase that helps increase density and bond with iron-based substrates. If less than 3.0% by weight, Its effect is less, 4.5
If it exceeds % by weight, the hard phase will crystallize into a net shape and the crystal grains will become coarser, significantly reducing toughness.
A range of 3.0 to 4.5% by weight is preferred.

Furthermore, the above Fe-Mo-P-C alloy powder and
The reason for using Fe-Cr or Fe-Cr-Ni stainless steel powder with a fine particle size of 150 mesh or less is that if the particle size is larger than 150 mesh, a liquid phase will appear during sintering. In the process of shrinking and increasing density, the large powder particles cause a bridging phenomenon, leaving large pores and ultimately preventing the density from increasing.
Furthermore, if larger particles are present in the Fe-Mo-P-C alloy powder, large pores will be created in the areas where the large particles were present when a liquid phase appears during sintering. Therefore, it is necessary to keep it below 150 meters.

Also, if you do not use only alloy powder containing Ni, Cr, and Mn in advance, the hardness of the powder particles will increase and they will not deform plastically, resulting in a decrease in the strength of the compact and the liquid in the alloy powder. This is because the melting point of the part where the phase is generated rises and exceeds 1120°C, which is the limit condition for the heating temperature during sintering and joining.

Next, to explain examples of the present invention, SUS410 powder with a particle size of 150 mesh or less and a particle size of 150 mesh or less with Mo10.5% by weight and P2.4
After blending and mixing an alloy powder of 3.6% by weight, C3.6% by weight, and the balance being Fe, graphite powder, and a lubricant, and compacting this mixed powder at a compression pressure of 5t/ ^cm2 , the S45C base placed on a material and placed in a hydrogen atmosphere.
By holding at a temperature of 1080℃ for 20 minutes and sintering, 5.25% by weight of Mo, 1.2% by weight of P,
A composite material was obtained in which a wear-resistant sintered alloy having a composition of 2.05% by weight of C, 6.75% by weight of Cr, and the remainder Fe was sintered and joined. This sintered alloy has a density of 7.53 g/cm ² and a hardness of H _RC 58, and photographs of its internal structure and of the joint are shown in FIGS. 1 and 2. A photograph of the internal structure of the sintered alloy shown in Fig. 1 (×
200), white parts indicate carbides and gray parts indicate fine carbides. In addition, in the structure photograph (×400) of the joint shown in FIG. 2, the white part shows the sintered material, and the black part shows the S45C base material.

Next, the above composite material was processed into the shape of a rocker arm (an example of the present invention), and this rocker arm was combined with a cast iron camshaft with a chilled cam part, and a wear resistance test was conducted at a rotation speed of 700 r.pm.
2000rpm and under test conditions using degraded oil as the oil, and the results were compared to a conventional example (chilled product made of the same material as the camshaft, alloyed cast iron with 0.45% Cr added to FC25). Figures 3 and 4 show a comparison with the Rocker arm.

Figure 3 shows the degree of wear on the part surface of the rocker arm. In the conventional example, the amount of wear increased as the operating time progressed, especially at high rotational speeds (2000 r.p.
In contrast, in the example of the present invention, the amount of wear remains small over the course of operation time, and is almost constant regardless of the number of rotations. It can be seen that it has wear resistance.

Further, FIG. 4 shows the degree of wear of the cam portion of the camshaft, and both the example of the present invention and the conventional example show almost the same wear tendency. In other words, it can be seen that the sintered alloy of the present invention has excellent wear resistance and does not damage the mating member.

As explained above, the wear-resistant sintered alloy of the present invention not only has excellent wear resistance, but also ensures green compact strength, reduces the amount of hard phase, and
It is possible to provide a sintered alloy that can be sintered and joined to cast iron or steel at low temperatures while imparting toughness and reducing pores.

Further, according to the manufacturing method of the present invention, a wear-resistant sintered alloy that exhibits the above effects can be effectively obtained.

[Brief explanation of drawings]

The drawings illustrate embodiments of the present invention, and FIG. 1 is a photograph of the internal structure of the wear-resistant sintered alloy according to the present invention, FIG. 2 is a photograph of the structure of the joint, and FIG.
4 and 4 are test result diagrams showing the degree of wear of the rocker arm pad surface and the cam portion of the camshaft, respectively, comparing the example of the present invention and the conventional example.

Claims (1)

[Claims] 1 Mo3.0-6.5% by weight, P0.5-1.5% by weight, C1.0
~3.0% by weight, and Cr alone or Cr plus Ni,
A wear-resistant sintered alloy comprising a total of 2.0 to 7.0% by weight of at least one type of Mn, with the balance being Fe. 2 Fe-Mo-P-C alloy powder and Fe-Cr-based or Fe-Cr-Ni-based stainless steel powder are mixed into powder with a fine particle size of 150 mesh or less, and this mixed powder is compacted. , Mo3.0~6.5wt%, P0.5 by sintering at a temperature of 1000~1120℃
A wear-resistant sintered alloy comprising ~1.5% by weight, 1.0-3.0% by weight of C, and 2.0-7.0% by weight of Cr alone or a combination of Cr and at least one of Ni and Mn, with the balance being Fe. A method for manufacturing a wear-resistant sintered alloy, characterized by manufacturing.