JPH0770711A - High rigidity composite material and production thereof - Google Patents

Abstract

PURPOSE:To produce a high rigidity composite material high in Young's module by dispersing dispersion particles into a matrix of a ferritic steel containing a specific quantity of aluminum and specifying a integrated degree of (111) plane in the vertical face to a fixed direction. CONSTITUTION:A composite powder is prepared by dispersing 0.2-5vol.% dispersion particles (of Y2O3 or the like and having 0.005-1mum average particle diameter) into the matrix of the ferritic steel containing >=3wt.% to <8wt.% Al and, if necessary, <=16wt.% Cr. Next, the composite powder is, after extruded at the extruding ratio of <=3, heat treated and secondarily recrystallized to make the integrated degree of (111) plane in the vertical face to the fixed direction >=30 times of that of an isotropic polycrystallive body in X-ray integrated intensity ratio. As a result, the high rigidity composite material having about 25000kgf/mm<2> Young's module is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly applied to automobiles, aircraft,
The present invention relates to a high-rigidity composite material used as a structural member requiring excellent rigidity for rockets, industrial machines, robots, and the like, and a method for manufacturing the same.

The high-rigidity composite material according to the present invention is used, for example, more specifically in crankshafts, piston pins, connecting rods, various valves mainly as engine parts of automobiles, and ball screws as mechanical parts. There is also a possibility of being used for parts of golf clubs and other shafts of golf clubs.

[0003]

2. Description of the Related Art In recent years, for example, as materials for automobiles, there is an increasing need for lightweight materials for improving fuel efficiency and damping materials for improving riding comfort. If a high-rigidity material is used to reduce the weight, the high-rigidity material has an advantage that the amount of strain such as bending can be absorbed and the shape of the component can be reduced. This is because the high-rigidity material has a property of absorbing strain.

On the other hand, even if a high rigidity material is used as the vibration damping material, it is possible to absorb vibration = strain by using a small amount of material. Therefore, as is clear from the future, expectations are growing for a high-rigidity material capable of absorbing a large amount of strain with a small shape in all structural members as well as automobile parts.

By the way, conventionally, the rigidity of a material has been improved by adding an alloying element or dispersing and compounding particles having a high Young's modulus. However, in the former case, in the Fe-based alloy, even if the Re element is added, only a Young's modulus improvement of at most about 21,000 to 22,000 kgf / mm ² can be obtained, and in the latter case, Ti
(C, N) 24,000 to 25,0 at the most even by dispersion compounding of particles etc.
The Young's modulus of 00 kgf / mm ² is only obtained as a practical material, and it is not sufficient in terms of ductility and toughness because it is necessary to add a large amount of particles.

On the other hand, for steel materials, a method of realizing high rigidity by aligning crystal orientations having a high Young's modulus in a specific direction by thermomechanical processing, that is, by integrating them, is adopted. That is, it is a material design and process design aiming at integration of the {111} planes of ferritic steel having a body-centered cubic lattice.

However, as disclosed in JP-A-56-23223 and JP-A-59-83721, in the past, after processing at a processing rate of 5 to 10% or more, 720 to 90
Even if the crystal orientation was accumulated in a certain direction by heat treatment such as tempering or winding at a temperature of 0 ℃ or less, the Young's modulus was only 23,000 to 24,000 kgf / mm ² at most.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to more generally propose a high rigidity material having high toughness, oxidation resistance and high strength, and a method for producing the same. is there. More specifically, an object of the present invention is to provide a highly rigid material having a Young's modulus of over 25,000 kgf / mm ² and a method for producing the same.

[0009]

Means for Solving the Problems The inventors of the present invention have made various investigations to achieve such an object. As a result, in the conventional method, the reason why only a slight improvement in Young's modulus can be obtained by the thermomechanical treatment method is as follows. {111} in ferritic steel
This is because the degree of surface integration is as small as 15 to 20 times as much as the X-ray integrated intensity ratio as compared with the isotropic polycrystal, and this is because the processing strain introduced in the processing step and its accumulation are small. Knew. Therefore, as a result of various studies to find a material system capable of imparting high working strain and a method of imparting the same, the following points were found and the present invention was completed.

Pinning of dislocations by dispersed particles is effective for introducing processing strain, and in a material system containing such dispersed particles, sufficient strain can be imparted by hot extrusion molding with an extrusion ratio of 3 or more, for example. To be seen.

The composite material in which the dislocations pinned by the dispersed particles are introduced as described above is then subjected to a heat treatment at a high temperature of, for example, 1300 ° C. to cause a rapid secondary recrystallization and a {111} plane in the processing direction. Remarkably accumulated.

The present invention is a composite material in which dispersed particles are dispersed in a matrix of ferritic steel containing Al: more than 3% by weight and 8% by weight or less, and optionally Cr: 16% by weight or less. A high-rigidity composite material characterized in that the degree of integration of {111} planes in a certain direction is 30 times or more in X-ray integrated intensity ratio as compared with an isotropic polycrystal.

As described above, {111} in a certain direction
The degree of integration of planes is 30 in X-ray integrated intensity ratio compared to isotropic polycrystals.
There are various means for doubling or more, but the following method can be considered as a practical means. In addition, "constant direction" means
It means any one direction, and in the present invention, at least that direction may satisfy the above relationship.
Generally, in the case of extrusion, the "constant direction" is the extrusion direction.

That is, it is a method of subjecting the composite powder in which the particles are dispersed to a strong work forming with an extrusion ratio of 3 or more and then performing a secondary recrystallization heat treatment. Preferably, such a composite powder used is one produced by a mechanical alloying method.

Therefore, from another aspect, the present invention relates to a method for producing a high-rigidity composite material, which comprises subjecting at least a particle-dispersed composite powder having a ferritic steel composition as a whole to a molding process and then heat-treating the composite powder. Processing includes at least extrusion molding with an extrusion ratio of 3 or more, and the heat treatment is secondary recrystallization heat treatment, Al: more than 3% by weight and 8% by weight or less, and optionally Cr: 16% by weight or less Is a method for producing a high-rigidity composite material in which dispersed particles are dispersed in a matrix of ferritic steel.

[0016]

Next, the reason why the steel composition and manufacturing conditions are limited as described above in the present invention will be explained. In the present invention, the matrix of the composite material is constituted by the ferritic steel having the crystal structure of the body-centered cubic lattice, which has the highest Young's modulus <111 as confirmed by the iron single crystal.
In the> direction, the value is almost 2 for ferritic iron.
This is because it is 9,000 kgf / mm ² .

The matrix phase in the present invention is Al: 3.
A ferrite phase containing more than 8% by weight and less than 16% by weight of Cr, if desired. The reason why Al: exceeds 3% by weight is not only for the purpose of addition as a ferrite-forming element, but also for imparting oxidation resistance and improving strength.

Al: not more than 8% by weight, when Al exceeds 8% by weight, not only is the toughness deteriorated, but
For example, when the dispersed particles such as Y ₂ O ₃ and Al ₂ O ₃ react with Al and the dispersed particles grow and become coarse, during the secondary recrystallization heat treatment {11
This is because the degree of integration of the 1} plane is insufficient and a high Young's modulus is not exhibited particularly in the case of Al ₂ O ₃ . In addition, a decrease in strength is recognized.

Further, when Al exceeds 8% by weight, when hard facing for the purpose of improving the wear resistance of the surface is required by surface treatment or the like, carburizing and quenching for that purpose is substantially impossible. It becomes possible, and a problem arises when the application to a crankshaft for automobiles, a piston pin, etc. is considered.
The reason for this is that since the ferrite phase is stabilized due to the large amount of Al, it becomes difficult to form martensite by carburization.

The matrix phase in the present invention is mainly composed of a ferrite phase exhibiting a high Young's modulus, but other phases such as an austenite phase and a martensite phase have a Young's modulus of 25,000 kgf / mm ^2. Of course, a multi-phase structure may be used as long as it does not fall below. There is no problem if the other phase is about 5% (volume%) or less.

The present invention is intended to increase the rigidity by utilizing the characteristics of ferritic steels, and is not particularly limited as long as it has the above-mentioned composition, but generally has the following steel composition: Is desirable.

Mn: 1.0% or less, Ni: 5.0% or less, Mo: 2.
5% or less, W: 5.0% or less, Nb: 3.0% or less, Ti: 2.0
% Or less, V: 2.0% or less, Si: 0.5% or less, P: 0.1%
S: 0.1% or less, Cr: 16.0% or less, Oxygen: 0.2% or less excluding oxygen contained in oxide, N: 0.2% or less excluding N contained in nitride, C: Carbide Except for the C content, 0.2% or less is the balance of iron. (All percentages are% by weight.) These elements do not necessarily need to contain all of them, but Ni, Mo, W, Nb, Ti,
Regarding V, it is desirable to add one kind or two or more kinds. That is, the addition of a small amount of C and Mn improves the strength,
Addition is effective in improving toughness.

Addition of Mo and W up to 2.5% and 5.0%, respectively, is effective for improving strength by solid solution strengthening, but if it exceeds this, embrittlement occurs due to intergranular precipitation of intermetallic compounds such as σ phase. Sometimes.

The addition of small amounts of Nb, Ti and V stabilizes C as a carbide, stabilizes the ferrite phase, and has the effect of improving strength by precipitation strengthening. But each
Addition of 3.0%, 2.0%, or more than 2.0% may cause embrittlement due to carbide precipitation on grain boundaries.

Further, Si, P, and S are acceptable as long as the impurities are 0.5% or less, 0.1% or less, and 0.1% or less, respectively. If it exceeds this value, the toughness is lowered due to precipitation at grain boundaries and the like. When oxygen and nitrogen are contained in a small amount of 0.2% or less, the strength is improved, but if the contents are exceeded, the toughness may decrease.

Addition of Cr up to 16% is effective for improving corrosion resistance. However, if it exceeds 16% by weight Cr, embrittlement may occur due to precipitation of carbides, intermetallic compounds, etc. at grain boundaries during heat treatment and the like. Furthermore, hard facing for the purpose of improving the wear resistance of the surface by surface treatment etc.
When it is necessary, carburizing and quenching for that purpose becomes substantially impossible, and a problem arises when application to a crankshaft, piston pin, etc. for automobiles is considered. The reason for this is that since the ferrite phase is stabilized due to the large amount of Cr, it becomes difficult to form martensite by carburization.

As described above, according to the present invention, in order to increase the rigidity of the material, in the ferritic steel, the {111} plane can be highly integrated in the plane perpendicular to one direction. is important. The integration of {111} planes in ferritic steel becomes easier as the amount of accumulated strain = dislocation becomes larger. Therefore, the strain = dislocation applied in the processing step is pinned by the dispersed particles to increase the amount of accumulation.

Here, as the dispersed particles, an oxide,
There are carbides, nitrides, borides, and even intermetallic compounds, and their average particle size is preferably 0.005 to 0.1 μm.
m, and the compounding ratio thereof is 0.2 to 5% (volume%).

That is, the kind, shape, size, and amount of the dispersed particles are not particularly limited, but preferably, they are thermally stable and effectively dislocation pinned. Also, in order to secure ductility and toughness as a practical material, it is preferable to limit the amount to a small amount. Average grain size that does not re-dissolve in ferritic steel as a base component even at high temperatures of 1200 ° C or higher.
Borides of 1 μm or less and 3% by volume or less, oxide particles of easily oxidizable metal elements (eg, Al, Ti, Y, etc.), and nitride particles are desirable.

The ferritic steel containing such dispersed particles is
Strain is accumulated by performing hot extrusion molding at about 1000 to 1200 ° C. Of course, it is needless to say that the strain imparted by warm and cold working is also good. The processing ratio in the strong work forming is set to an extrusion ratio of 3 or more, but if it is smaller than this, sufficient dislocations may not be introduced.

Further, even if HIP, CIP, rolling and forging are performed before the extrusion, if the extrusion is finally performed at an extrusion ratio of 3 or more, a sufficient processing strain is imparted. Furthermore, after extrusion processing,
Even if HIP, rolling, forging, etc. are performed, there is no problem as long as the processing strain due to extrusion is sufficiently imparted.

More preferably, in the step of dispersing the particles, a mechanical alloying method is used which is capable of uniformly finely dispersing while subjecting to strong working in the cold. Here, the mechanical alloying method (MA) is a method of using a ball mill or the like to forcefully mix the powders in a cold manner and repeatedly perform rolling, forging, and pressure bonding.

The composite material thus hard-worked and molded is then subjected to a secondary recrystallization heat treatment at a high temperature. The heat treatment conditions at that time are the kind of matrix and dispersed particles,
It depends on the number, amount, size, etc., but preferably from 1100
A secondary recrystallization heat treatment is performed at 1400 ° C for 0.5 to 2 hours.

The secondary recrystallization heat treatment is {111}.
This is a heat treatment performed to align the planes with the plane perpendicular to the specific direction. In other words, as long as such an object can be achieved, the heat treatment is not limited to the specific condition.

In the composite material thus obtained, the degree of integration of {111} planes in a plane perpendicular to a certain direction is X.
The linear integrated intensity ratio is 30 times or more that of the isotropic polycrystal, but if this is less than 30 times, the Young's modulus targeted by the present invention is 25,000.
It is not possible to obtain a highly rigid material with a weight above kgf / mm ² .

As one of the criteria for judging that the X-ray integrated intensity ratio is 30 times or more, the X-ray integrated intensity of the {222} plane in the plane perpendicular to the fixed direction and the {11}
The ratio of the 0} plane to the X-ray integrated intensity is 0.10 or more.

Here, these points will be further described. In general, a material having a fine structure in which lattice strain is introduced by strong processing such as extrusion and rolling is subjected to heat treatment to start primary recrystallization with the lattice strain energy as a driving force and to be embedded in crystal grains with extremely few lattice defects. To be done. The material that has undergone the primary recrystallization is further heat-treated for a long time or at a high temperature, and then the coarsening of the primary recrystallized grains is started by using the grain boundary energy as a driving force, resulting in an extremely coarse secondary recrystallized grain structure. To form.

In the case of the present invention, the <110> extruded texture changes into a <111> secondary recrystallized texture in the course of this series of recrystallization phenomena, and accordingly, the Young's modulus is about 22,0.
It will be improved from 00kgf / mm ² to about 29,000kgf / mm ² .

In the present invention, for example, 0.2% by volume Y ₂ O ₃
In the as-extruded material, a very fine crystal grain structure with lattice strain introduced was formed in the as-extruded state.
When a heat treatment of 1200 ° C. × 1 hr is applied, coarsening of crystal grains and formation of <111> texture occur as a result of the secondary recrystallization phenomenon, and the Young's modulus in the extrusion direction is improved to 28,000 kgf / mm ² .

The heat treatment conditions for the secondary recrystallization differ depending on the amount of dispersed particles and processing conditions, and therefore cannot be determined unconditionally. For example, if the extrusion conditions are 1050 ° C and the extrusion ratio is 10, 1200 ° C is the secondary recrystallization temperature when 0.2% by volume Y ₂ O _{3 is} added, but 1300 ° C is the secondary recrystallization temperature when 0.5% by volume Y ₂ O _{3 is} added. It becomes temperature. This is because the dispersed particles act as an inhibitor that prevents grain boundary migration in the recrystallization process, and the more dispersed particles, the greater the effect.

When the amount of dispersed particles is fixed at 0.5% by volume of Y ₂ O ₃ , the lower the extrusion temperature and the higher the extrusion ratio, the lower the recrystallization temperature. This is because recrystallization starts at a lower temperature when the introduced lattice strain energy is higher.

In the present invention, the degree of integration of the high-rigidity material in a certain direction, that is, the {111} plane or the {110} plane in the extrusion direction, is an isotropic (random) polycrystal (for example, a packing ratio). It is described by the X-ray integrated intensity ratio to a reduced iron powder sample of 65% and a density of 5.1 g / cm ³ ) as a standard sample).

To obtain the X-ray integrated intensity ratio, for example, the X-ray integrated intensities of the peaks of the {110} plane and the {222} plane in the extruding direction of ferritic steel are measured, and I ₁₁₀ and I, respectively.
₂₂₂ , similarly, a standard sample is also measured and designated as I ⁰ ₁₁₀ and I ⁰ ₂₂₂ , respectively. At this time, the integrated intensity ratio of the {110} plane is I ₁₁₀ / I ⁰ ₁₁₀ , and the integrated intensity ratio of the {222} plane is I.
It is represented by ₂₂₂ / I ⁰ ₂₂₂ . Thus, in the present invention, the Young's modulus is over 25,000 kgf / mm ² , most of which is 28,000 kgf / mm 2.
A highly rigid material with ^two or more is provided.

[0044]

EXAMPLES The effects of the present invention will be described in detail below with reference to examples.

Y ₂ O ₃ particles having an average crystal grain size of about 0.02 μm,
And 0.02, 0.06, 0.10 μm Al ₂ O ₃ particles, and 0.02 μm TiC, AlN, TiB ₂ , BN particles and electrolytic iron powder (average particle size about 100 μm), C (graphite) powder (about 3 μm) ,
Mn powder (about 10 μm), Ni powder (about 100 μm), Cr powder (about 40 μm)
μm), Al powder (about 60 μm), Mo powder (about 3 μm), W powder
(About 2 μm), Nb powder (about 50 μm), Ti powder (about 10 μm), V
Using powder (about 20 μm) and Fe-4Al alloy powder (gas atomized powder, about 30 μm), mechanical alloying method (MA) was carried out with an attrition type ball mill to prepare a composite powder. The mixing ratio of each powder was set to be the composition of ferritic steel as a whole.

Then, using these composite powders, under various conditions such as extrusion, HIP + extrusion, HIP + forging + extrusion, CIP + forging + extrusion, extrusion + forging, extrusion + rolling, etc. After heating at 1450 ° C. for 1 hour, air-cooled heat treatment was performed.

Tables 1 and 2 are for the case where the matrix is ferritic steel containing 4% Al, and Tables 3 and 4 are 0-10%.
This is the case where Al-containing ferritic steel and the third additive element are included therein. Here, in Nos. 8, 9, 10, and 11, Fe-4Al alloy gas atomized powder was used as the matrix raw material powder, and other than that, the compounded powder of the element powder was used as the raw material powder.

The degree of integration of {111} planes in the working direction of the material thus obtained, Young's modulus, Charpy impact value and tensile strength were measured, and the oxidation resistance was also investigated. Regarding the oxidation resistance, an exposure test was conducted for 200 hours in an air atmosphere at 600 ° C., and the degree of surface oxidation was visually judged, and the oxidation resistance was classified into three grades: good, good and poor. These results are collectively shown in Tables 1 to 4 together with comparative examples.

The influence of the amount of dispersed particles is No. 2, which is an example of the present invention,
3, 4 and No. 1 which is a comparative example. When there are no dispersed particles, secondary recrystallization hardly occurs, the {111} plane is not integrated, and the Young's modulus does not increase. It can be seen that dispersed particles are essential. When the amount of dispersed particles increases, the optimum secondary recrystallization temperature increases, but the {111} planes are integrated and a high Young's modulus is exhibited.

The influence of heat treatment conditions was investigated by changing the temperature from 1100 ° C to 1450 ° C. As already mentioned, generally 11
00 to 1400 ° C. × 0.5 to 2 hours is sufficient, but in the case of this example, as shown in Inventive Example No. 5 and Comparative Examples No. 23 and 24,
It can be seen that even if the heat treatment temperature is low or high, secondary recrystallization does not occur and the optimum temperature exists at about 1200 to 1400 ° C. Of course, this optimum secondary recrystallization temperature differs depending on the composition component, dispersed particle type, diameter, and amount.

Comparative Example No. 1, Invention Example Nos. 3, 5, 8, 9,
As is clear from 10 and 11, the presence of fine dispersed particles is essential for achieving high rigidity. When finely dispersed particles are present, they are all secondarily recrystallized by heat treatment to form {111}
The degree of surface accumulation is 30 times or more, but in the absence of dispersed particles, secondary recrystallization does not occur under any heat treatment conditions.
Therefore, the {111} plane was hardly integrated.

The influence of the processing conditions of the present invention example No. 5, 12, 13,
15, 16, 17, 18, 19, 20, 21 and Comparative Example No. 14 are shown. As is clear from this, the extrusion step is necessary, and the lower the temperature and the higher the extrusion ratio, the more likely secondary recrystallization will occur. Further, unless the extrusion ratio is 3 or more, the integration of {111} faces by secondary recrystallization is insufficient and the Young's modulus is insufficient.

Finally, as to the influence of the components, as shown in Tables 3 and 4, if the matrix is essentially a ferrite phase, a high Young's modulus can be obtained, but the ferrite as shown in No. 43 can be obtained. Even in a matrix having a mixed phase structure of austenite and austenite, a Young's modulus of 25,000 kgf / mm ² or more may be obtained.

Regarding the influence of the amount of Al, Comparative Example No. 25, which does not contain Al, has a poor oxidation resistance, whereas in the invention examples of 3% Al or more, excellent or good oxidation resistance is obtained. Have. Regarding the strength, in Comparative Example No. 25 containing no Al and Comparative Example No. 28 containing 10% Al, the tensile strengths are 63 kgf / mm ² and 68 kgf / mm ² , respectively, while 3 to 8 In the invention examples of% Al, all are 90 kgf / mm
High strength of ² or more can be obtained.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

[Table 4]

[0059]

According to the present invention, a large amount of processing strain can be imparted, and the degree of integration of {111} planes can be remarkably improved.
As a result, it becomes possible to manufacture high-rigidity materials with a Young's modulus of over 25,000 kgf / mm ² , and can be applied to various spring materials, various shaft materials, and various structural parts such as automobiles that require vibration absorption. Not only that, its high rigidity material also has excellent oxidation resistance and strength.

Claims (5)

[Claims] 1. A composite material in which dispersed particles are dispersed in a matrix of ferritic steel containing Al: more than 3% by weight and 8% by weight or less, and the degree of integration of {111} planes in a plane perpendicular to a certain direction. The high-rigidity composite material is characterized in that the X-ray integrated intensity ratio is 30 times or more that of the isotropic polycrystal. 2. A composite material in which dispersed particles are dispersed in a matrix of ferritic steel containing Al: more than 3% by weight and 8% by weight or less, wherein X-rays of {222} plane in a plane perpendicular to a certain direction. A high-rigidity composite material, characterized in that the ratio of the integrated intensity to the X-ray integrated intensity of the {110} plane is 0.10 or more. 3. The ferritic steel is less than 16 wt% Cr
The high-rigidity composite material according to claim 1, further comprising: 4. A method for producing a high-rigidity composite material, which comprises subjecting a composite powder in which particles having a ferritic steel composition are dispersed as a whole to a molding process, and then subjecting the composite powder to a heat treatment, wherein the molding process is at least an extrusion ratio of 3 or more. The method for producing a high-rigidity composite material according to any one of claims 1 to 3, wherein the heat treatment is a secondary recrystallization heat treatment including molding. 5. The method for producing a high-rigidity composite material according to claim 4, wherein the composite powder is obtained by dispersing the particles by a mechanical alloying method.