JPH07224363A - High strength ferrous sintered alloy - Google Patents

Abstract

PURPOSE:To develop a high strength ferrous sintered alloy excellent in deflective strength and wear resistance by mixing the powder of a tool steel with specified amounts of Mo and Cr in a powdery state of an iron alloy together with graphite, subjecting it to compacting and executing sintering. CONSTITUTION:The powder of a tool steel having a compsn. contg., by weight, 11 to 13% Cr, 0.8 to 1.2% Mo, 0.2 to 0.5% V and 1.4 to 1.6% C, and the balance Fe is added to low Mo-contg. Fe-Mo contg. 1 to 2% Mo and the balance Fe, low Cr-contg. Fe-Cr contg. 1 to 2% Cr and the balance Fe or 20 to 75% of the powder of an iron alloy contg both Mo and Cr and 0.5 to 1.5% graphite powder respectively in a state of fine powder having <=75m average grain size, and mixing is executed. This mixed powder is subjected to compacting, is thereafter subjected to temporaly sintering, is furthermore repressed under 12 to 15ton/cm<2> pressure and is subsequently subjected to heat treatment at 850 to 1050 deg.C. The ferrous sintered alloy in which the alloy grain areas of Mo and Cr are bindingly dispersed into a tool steel grain area contg. fine metallic carbides of <=5mum via a dispersed phase can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength iron-based sintered alloy, which is a cam piece,
Not only used as a structural member that requires high strength for internal combustion engines such as camshafts, compressor rotors, and sprockets, but also as a structural member that requires high strength for other various types of drive devices that require high strength. The present invention relates to an iron-based sintered alloy used.

[0002]

2. Description of the Related Art Conventionally, an iron-based sintered alloy having excellent strength and wear resistance as described in JP-A-58-2902 is known, and this iron-based sintered alloy is used for an engine. It is used as various structural members such as cam pieces and journal pieces. This conventional iron-based sintered alloy is C:
1.5 to 3.5% by weight, Cr: 2.5 to 7.5% by weight,
Mo 3 wt% or less, Mn: 0.10-3 wt%, P:
It has a composition of 0.3 to 0.8% by weight and Si: 0.5 to 2.0% by weight, and the balance of Fe and unavoidable impurities, and fine carbides are uniformly dispersed.

This conventional iron-based sintered alloy has a C: 1.5-
3.5% by weight, Cr: 2.5 to 7.5% by weight, Mo: 3
% By weight, Mn: 0.10-3% by weight, P: 0.3-
After blending and mixing graphite powder with Fe-based alloy powder having a composition of 0.8 wt% and Si: 0.5 to 2.0 wt% and the balance of Fe and unavoidable impurities, 5
It was manufactured by press-molding at ˜7 ton / cm ² to obtain a green compact, which was liquid-phase sintered and then heat-treated.

[0004]

However, various components built in recent internal combustion engines and the like have been operated under more severe conditions than in the past as the performance and load of internal combustion engines have increased. Therefore, various parts such as the internal combustion engine are required to be made of high-strength structural members.
However, the above-mentioned conventional iron-based sintered alloys have not been sufficiently satisfactory in terms of strength even under severer conditions. The reason is that in the conventional iron-based sintered alloy, P is added to improve the sinterability, and the addition of P is
It has been found that the base material is embrittled and a large amount of coarse and elongated carbide is precipitated, and when such coarse and elongated carbide is precipitated, the transverse rupture strength is reduced.

[0005]

Therefore, the present inventors have
From the above-mentioned viewpoints, as a result of conducting research to obtain an iron-based sintered alloy having more excellent strength and wear resistance than before without adding P, (a) Cr: 11 to 1
3% by weight, Mo: 0.8 to 1.2% by weight, V: 0.2 to
Mo: 1 to 2 wt% with respect to an alloy powder having a composition containing 0.5 wt% and C: 1.4 to 1.6 wt% with the balance being Fe and unavoidable impurities (hereinafter referred to as tool steel powder) %
A mixed powder containing an alloy powder (hereinafter referred to as a low Mo-Fe powder) having a composition containing Fe and the balance being Fe and unavoidable impurities, and (b) a tool steel powder, and a C
r: a mixed powder containing 1 to 2% by weight and the balance consisting of Fe and unavoidable impurities (hereinafter referred to as low Cr-Fe powder) and C powder, (c) tool steel powder , Mo: 1-2% by weight and Cr: 1-2
Alloy powder having a composition containing wt% and the balance being Fe and unavoidable impurities (hereinafter referred to as low Mo-Cr-Fe powder) and a mixed powder obtained by mixing C powder, respectively, are mixed and press-molded into a green compact. Mold and temperature this green compact:
Pre-sintered at 850 to 1050 ° C, 12 to 15 ton / c
When pressure is applied again at m ² and then heat treatment is performed at a temperature of 850 to 1050 ° C., (1) Cr: 11 to 13% by weight, M
o: 0.8 to 1.2% by weight, V: 0.2 to 0.5% by weight, C: 1.4 to 1.6% by weight, with the balance being Fe and inevitable impurities Alloy grain region in which fine carbide is dispersed (hereinafter referred to as tool steel alloy grain region), and alloy grain region having a composition containing Mo: 1 to 2 wt% and the balance consisting of Fe and unavoidable impurities (hereinafter, low Mo- Fe alloy grain area) is a high-strength iron-based sintered alloy having a structure in which it is bonded and dispersed through a diffusion phase, (2) Tool steel alloy grain area and Cr: 1 to 2 wt% and the balance is Fe. And an alloy grain region of a composition consisting of inevitable impurities (hereinafter, low Cr-F
e alloy grain area) is a high-strength iron-based sintered alloy having a structure in which it is bonded and dispersed through a diffusion phase, (3) Tool steel alloy grain area and Mo: 1-2 wt% and Cr: 1-2 A high-strength iron-based material having a structure in which an alloy grain region (hereinafter, referred to as a low Mo-Cr-Fe alloy grain region) having a composition containing wt% and the balance consisting of Fe and inevitable impurities is bonded and dispersed through a diffusion phase. Sintered alloys are obtained, and it has been found that the iron-based sintered alloys having these structures all have a higher transverse rupture strength than before, and the present invention was made based on such findings.

Tool steel powder, low Mo-Fe powder, low C as raw material powder for producing the high strength iron-based sintered alloy of the present invention
The component composition of each of the r-Fe powder and the low Mo-Cr-Fe powder is generally known, and the average particle size of each is preferably 75 μm or less.
More preferably, it is within the range of 75 μm.

20-75% by weight (preferably 40%) of each of low Mo-Fe powder, low Cr-Fe powder or low Mo-Cr-Fe powder with respect to the tool steel powder.
˜60% by weight) and C powder in a proportion of 0.5 to 1.5% by weight, and then mixed and press-molded to prepare a green compact, which is temporarily sintered. ~ 15 ton / cm ²
And pressurize again, and then heat treatment is performed at a temperature of 850 to 1050 ° C.

Compared with the tool steel powder, the low Mo-F
Since the e powder, the low Cr-Fe powder or the low Mo-Cr-Fe powder is easily deformed, the low Mo-Fe powder, the low Cr-Fe powder or the low Mo during compacting is formed.
The --Cr--Fe powder preferentially deforms, fills the voids, promotes the contact between the alloy powders, activates the contact portion, and promotes sintering without adding P. Further, 12 to 15 t
densification by re-pressurizing at a high pressure of on / cm ² ,
It is considered that an iron-based sintered alloy with high strength can be obtained.

The high-strength iron-based sintered alloy of the present invention produced as described above is, as mentioned above, dispersed by bonding the tool steel alloy grain region and the low Mo-Fe alloy grain region through the diffusion phase. Microstructure, tool steel alloy grain area and low Cr-Fe alloy grain area bonded and dispersed through diffusion phase, tool steel alloy grain area and low M
The o-Cr-Fe alloy grain region has a structure in which it is bonded and dispersed through a diffusion phase. On the other hand, the conventional iron-based sintered alloy has a macroscopically uniform structure. It is considered that the iron-based sintered alloy of the present invention and the conventional iron-based sintered alloy have a difference in transverse rupture force due to the difference in the structure.

Since the high-strength iron-based sintered alloy of the present invention is solid-phase sintered, it has a structure in which alloy grain regions having substantially the same average grain diameter as the raw material powder are bonded and dispersed through the diffusion phase. Also, the average grain size of the alloy grain region which is bonded and dispersed in the structure through the diffusion phase is preferably 75 μm or less.
More preferably, it is in the range of ~ 75 µm.

Further, the carbide dispersed in the tool steel alloy grain region base material is preferably fine and circular with a size of 5 μm or less, and its aspect ratio is preferably 2 or less.

[0012]

EXAMPLES Tool steel powders, low Mo-Fe powders, low Cr-Fe powders, and low Ms each having an average particle size within the range of 1 to 100 μm and having the composition shown in Table 1 as raw material powders
Prepare o-Cr-Fe powder and C powder respectively,
Further Fe-5Cr-1Mo-2Cu-1Si-0.5
Mn-0.5P-2.5C powder was prepared.

Example 1 Tool steel powder, low Mo-Fe powder and C powder were blended in the proportions shown in Table 1 and mixed well, and the resulting mixed powder was pressurized at a pressure of 6 ton / cm ² and a length of 10 mm. × width: 10m
m × length: compacted into a shape having dimensions of 55 mm,
The obtained powder compact was pre-sintered under the conditions shown in Table 1 in a vacuum atmosphere at a temperature of 1000 ° C., then repressurized at the high pressure shown in Table 1, and then the conditions shown in Table 1. Was heat-treated in order to produce iron-based sintered alloys 1 to 8 of the present invention.

[0014]

[Table 1]

The structures of these iron-based sintered alloys 1 to 8 of the present invention are observed with a metallurgical microscope, and the average grain size of the alloy grain region and the tool steel alloy grain region which are bonded and dispersed through the diffusion phase in the structure. The average particle size of the carbide dispersed in the matrix and its aspect ratio were measured, and the results are shown in Table 2.

Further, the iron-based sintered alloys 1 to 8 of the present invention were subjected to a three-point bending bending test, and the results are also shown in Table 2.

Next, the iron-based sintered alloys 1 to 8 of the present invention are used as test pieces for performing a block-on-ring type wear test.
Consisting of: vertical: 10 mm, horizontal: 10 mm, length: 55 mm
The block with the dimensions of
As an on-ring type wear test partner material, SCM435
Consisting of: outer diameter: 40 mm, inner diameter: 30 mm, thickness: 15
A ring having a size of mm was prepared. After using the above block and ring so that the block is in contact with the ring and applying refrigerating machine oil as a lubricating oil around the ring, a load of 20 kg is applied to the block 1 and the ring requires high strength: A block-on-ring type wear test was conducted in which the ring was rotated at 3.5 m / sec and the amount of wear of the ring at a load time of 120 minutes was measured. The measured values of the amount of wear are shown in Table 2.

[0018]

[Table 2]

Example 2 Tool steel powder, low Cr-Fe powder and C powder were mixed in the proportions shown in Table 5 and mixed well, and the resulting mixed powder was pressurized at a pressure of 6 ton / cm ² and a length of 10 mm. × width: 10m
m × length: compacted into a shape having dimensions of 55 mm,
The obtained powder compact was pre-sintered at a temperature of 1000 ° C. in a vacuum atmosphere under the conditions shown in Table 3, repressurized at the high pressure shown in Table 3, and then the conditions shown in Table 3. Heat treatment was carried out to prepare iron-based sintered alloys 9 to 16 of the present invention.

[0020]

[Table 3]

The structures of these iron-based sintered alloys 9 to 16 of the present invention were observed with a metallurgical microscope, and the average grain size of the alloy grain regions bonded and dispersed through the diffusion phase in the structure and the tool steel alloy grain region. The average particle size of the carbide dispersed in the matrix and its aspect ratio were measured, and the results are shown in Table 4.

Further, according to the present invention, iron-based sintered alloys 9 to 16-3
A point bending bending test was conducted, and the results are also shown in Table 4 below.
Further, in the same manner as in Example 1, the iron-based sintered alloy 9 of the present invention
Block-on-ring type wear tests were conducted on Nos. 16 to 16 and the measured values of the amount of wear of the blocks are shown in Table 4.

[0023]

[Table 4]

Example 3 Tool steel powder, low Mo-Cr-Fe powder and C powder were blended in the proportions shown in Table 9 and mixed well, and the resulting mixed powder was vertically mixed at a pressure of 6 ton / cm ^2. : 10 mm x width:
After compacting into a shape having a size of 10 mm × length: 55 mm, the compacted compact thus obtained was pre-sintered at a temperature of 1000 ° C. in a vacuum atmosphere under the conditions shown in Table 5, and then Table 5
Was re-pressurized at the high pressure shown in Table 1 and then heat treated under the conditions shown in Table 5 to produce the iron-based sintered alloys 17 to 23 of the present invention.

[0025]

[Table 5]

The structures of these iron-based sintered alloys 17 to 23 of the present invention were observed with a metallurgical microscope, and the average grain size of the alloy grain regions bonded and dispersed through the diffusion phase in the texture and the tool steel alloy grain region. The average particle size of the carbide dispersed in the matrix and its aspect ratio were measured, and the results are shown in Table 6.

Further, the iron-based sintered alloys 17 to 23 of the present invention were subjected to a three-point bending bending test and a block-on-ring type abrasion test in the same manner as in Example 1 to measure the bending strength and the wear amount. The results are shown in Table 6.

Conventional Example 1 On the other hand, for comparison, Fe-5Cr-1Mo-2Cu-
1Si-0.5Mn-0.5P-2.5C powder was made into a green compact under the same conditions as in Example 1, and the green compact was sintered at 1170 ° C. in a vacuum atmosphere. Heat treatment under the conditions shown in 6 to produce a conventional iron-based sintered alloy 1,
A three-point bending bending test and a block-on-ring type abrasion test were performed in the same manner as in Example 1 to measure the bending strength and the amount of abrasion, and the results are shown in Table 6.

[0029]

[Table 6]

[0030]

From the results shown in Tables 1 to 6, the iron-based sintered alloys 1 to 23 of the present invention have almost the same wear resistance as compared with the conventional iron-based sintered alloys. It can be seen that the transverse rupture strength is much better. Therefore, the iron-based sintered alloy of the present invention is excellent in both transverse rupture strength and wear resistance, so that it can be sufficiently applied as a structural member of a high-power internal combustion engine and, in practical use, has excellent performance. By exerting it for a long period of time, it has an excellent industrial effect.

Claims (4)

[Claims] 1. Cr: 11 to 13% by weight, Mo: 0.8
~ 1.2 wt%, V: 0.2-0.5 wt%, C: 1.
An alloy grain region in which fine carbides are dispersed in a base material having a composition of 4 to 1.6% by weight and the balance of Fe and unavoidable impurities, and Mo: 1 to 2% by weight and the balance of Fe and unavoidable impurities A high-strength iron-based sintered alloy, characterized in that the alloy grain region of the composition is composed of a structure that is bonded and dispersed through a diffusion phase. 2. Cr: 11 to 13% by weight, Mo: 0.8
~ 1.2 wt%, V: 0.2-0.5 wt%, C: 1.
An alloy grain area in which fine carbides are dispersed in a base material having a composition of 4 to 1.6% by weight and the balance of Fe and unavoidable impurities, and Cr: 1 to 2% by weight of the balance of Fe and unavoidable impurities A high-strength iron-based sintered alloy, characterized in that the alloy grain region of the composition is composed of a structure that is bonded and dispersed through a diffusion phase. 3. Cr: 11 to 13% by weight, Mo: 0.8
~ 1.2 wt%, V: 0.2-0.5 wt%, C: 1.
An alloy grain area in which fine carbides are dispersed in a base material having a composition of 4 to 1.6% by weight and the balance of Fe and inevitable impurities, and Mo: 1 to 2% by weight and Cr: 1 to 2% by weight A high-strength iron-based sintered alloy, characterized in that an alloy grain region having a composition in which the balance is Fe and unavoidable impurities has a structure in which it is bonded and dispersed through a diffusion phase. 4. The high-strength iron-based sintered alloy according to claim 1, wherein the alloy grain region has an average grain size of 75 μm or less, preferably 40 to 75 μm.