JPH1112602A - Powder with high young's modulus, and its sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder having high Young's modulus and high specific Young's modulus, capable of thining, compacting, and weight reduction when applied to machine structural parts such as automobile parts, and a sintered compact of the powder. SOLUTION: The powder has a composition which consists of, by weight, 1.0-4.5% C, <=2.0% Si, <=2.0% Mn, 3.0-20.0% Cr, one or more elements among <=25.0% Mo, <=15% V, and <=12% Ti in the range satisfying Mo+V+Ti>=10%, and the balance essentially Fe and in which the contents of W, Ta, and Co are controlled to <=2%, <=2%, and <=2%, respectively. The machine structural parts are constituted of a sintered compact of this powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder having a high Young's modulus and a high specific Young's modulus (Young's modulus / specific gravity) suitable for use in mechanical structural parts such as automobile parts, and a sintered body thereof.

[0002]

2. Description of the Related Art
Higher performance of automobiles has been realized by injecting as much fuel as possible and rotating the engine at high speed. On the other hand, however, the problem of environmental degradation due to large consumption of petroleum resources and exhaust gas has been left.

In order to achieve both high performance and low fuel consumption of the engine, it is extremely effective to reduce the mechanic loss (energy loss) as much as possible, for example, to reduce the weight of each part of the engine and reduce the inertia force. is there. Further, not only for automobiles but also for general mechanical structural parts, it is strongly required to reduce the weight. Al, M
The use of lightweight materials such as g and Ti is an effective means.

[0004] However, these lightweight materials cannot sufficiently achieve the purpose in sufficiently increasing the rigidity of mechanical parts such as automobile parts, thereby making the parts thinner and more compact.

[0005] Therefore, if a material having a high Young's modulus is used as a material used for a mechanical structural part, the part can be made thinner and smaller, and at the same time, the weight can be reduced.

[0006] In general, an ingot made of iron has a Young's modulus of 210G.
It is about Pa (gigapascal), and its value does not basically largely change even if heat treatment is performed. It is conceivable to increase the Young's modulus of iron-based ingots by precipitating carbides at the time of solidification. However, the Young's modulus obtained as a material itself is about 220 GPa, which naturally has a limit.

Although materials having a high Young's modulus, such as cemented carbide tool steels for cutting or wear resistance, are known, these materials contain a large amount of WC having a high specific gravity, thereby achieving a high Young's modulus of parts. Even if it can be done, the weight will increase with this, and when it is applied to a machine structural part such as an automobile part, it is not possible to sufficiently achieve the object of reducing the weight and reducing the mechanic loss.

[0008]

SUMMARY OF THE INVENTION The invention of the present application has been made to solve such a problem, and in particular, when applied to a machine structural part, it can be made sufficiently thinner, smaller and lighter. It is intended to provide a high Young's modulus powder and a sintered body thereof. In the invention of the present application, the powder composition is expressed as C: 1.0 to 4.% by weight.
5%, Si: ≤ 2.0%, Mn: ≤ 2.0%, Cr:
3.0 to 20.0%, one or more of Mo, V, Ti
o: ≦ 25.0%, V: ≦ 15%, Ti: ≦ 12%, M
o + V + Ti: ≧ 10%, the balance being substantially composed of Fe, W: ≦ 2%, Ta: ≦ 2%, and Co: ≦ 2% (Claim 1). The sintering is performed (claim 2).

[0009]

As described above, according to the present invention, the content of C in the powder is set to 1.0 to 4.5%, and Cr and M which form a carbide having a high Young's modulus and a small specific gravity together with C are provided.
o, V, and Ti in the amounts specified above.
When a mechanical structural component such as an automobile component is manufactured by sintering the powder of the present invention, it can be effectively reduced in thickness, size, and weight.

Although W and Ta also form carbides having a high Young's modulus, these carbides also have a high specific gravity and reduce the purpose of reducing the weight of parts. Therefore, in the present invention, each of these components is 2%. It is regulated as follows.

Next, the reasons for limiting each chemical component in the present invention will be described in detail. C: 1.0 to 4.5% C is necessary for carbide formation, and for this purpose, 1.0% or more is contained. However, if it is contained in a large amount exceeding 4.5%, the toughness decreases, so the content is made 4.5% or less. Preferably it is 1.5 to 4.0%.

Si: ≦ 2.0% Si is useful for strengthening the matrix, increasing the yield point, and preventing surface oxidation at high temperatures. However, if it is contained in a large amount exceeding 2.0%, the toughness is impaired. Preferably it is 0.2 to 1.0%.

Mn: ≦ 2.0% Mn contributes to the hardenability of steel, but is set to 2.0% or less because the amount of oxygen in the powder is increased. Preferably 0.2 to 1.0%
It is.

Cr: 3.0 to 20.0% Cr has a lower specific gravity than Fe, and is effective in lowering the specific gravity of the steel of the present invention, and combines with C together with Mo, V and Ti to form a double carbide. To at least 3.0%.
On the other hand, since the carbide mainly composed of Cr does not have a very large Young's modulus, even if it is excessively added, the contribution to the object of the present invention is small, so the upper limit is made 20.0%.

Mo: ≦ 25.0% Mo is an element useful for forming carbides and increasing Young's modulus. However, if the content exceeds 25.0%, powder production becomes difficult, so the upper limit is set to 25.0%.

V: ≤15% V is a useful element for forming carbide having a small specific gravity and increasing the Young's modulus. However, if the content exceeds 15%, the powder production becomes difficult, so the upper limit is set to 15%.

Ti: ≦ 12% Ti forms a carbide having a small specific gravity, and is a useful element for increasing the Young's modulus. However, if it is contained in a large amount exceeding 12%, powder production becomes difficult, so the upper limit is made. 12%.

Mo + V + Ti: ≧ 10% In the present invention, it is essential to contain at least one of Mo, V, and Ti. In addition, it is necessary to add a total of 10% or more of the content in order to increase the Young's modulus of the powder or the sintered body to a predetermined Young's modulus or more.

W: ≦ 2% Ta: ≦ 2% These W and Ta easily form carbides, but their specific gravities exceed 10 g / cm ^3, which lowers the specific Young's modulus (Young's modulus / specific gravity). . Therefore, in the present invention, these are set to 2% or less, respectively, so that they are not substantially contained.

Co: ≦ 2% Co is an element that strengthens the matrix, but has a higher specific gravity than Fe, and lowers the specific Young's modulus similarly to W and Ta described above.
Therefore, in the present invention, Co is set to 2% or less so as not to be substantially contained.

[0021]

Next, embodiments of the present invention will be described in detail. <Example 1> A raw material was melted in a 2 kg high-frequency induction furnace in a vacuum, and then the production of powder having the composition shown in Table 1 was attempted by Ar gas spraying. As a result, when V exceeds 15% N
o. No. 3, Ti exceeding 12%. 4, Mo is 25.
No. exceeding 0% In No. 6, the pouring nozzle was blocked during the spraying, and powder could not be produced.

[0022]

[Table 1]

Example 2 A raw material was melted in a 2 kg high-frequency induction furnace in a vacuum, and powder having the composition shown in Table 2 was produced by Ar gas spraying. The powder was classified into -42 mesh, and the classified powder was set to an outer diameter of 30 mm and a length of 10 mm.
A 0 mm mild steel bottomed cylindrical container was filled, EB-welded, vacuum degassed and sealed.

Subsequently, HIP treatment was performed under a hydrostatic pressure of 1000 kgf / cm ² and a condition of 1200 ° C. × 1 hr. Then, after the HIP treatment, heating was performed at 870 ° C. × 2 hr, and spheroidizing annealing was performed by slow cooling. From the obtained HIP body, a test piece having a width of 8 mm, a thickness of 2 mm, and a length of 60 mm was cut out and subjected to heating at 1100 ° C. × 3 min → quenching of oil cooling, followed by repeating 580 ° C. × 1 hr → air cooling three times. After tempering, the surface of the test piece was polished.
The Young's modulus of the test piece was measured by a transverse vibration resonance method, and the density was measured by a water immersion method. Table 2 shows the results.

[0025]

[Table 2]

From the results shown in Table 2, the sample of the present invention had a high Young's modulus and a specific Young's modulus, and the case of the prototype piston pin had a large weight reduction. Note that the target values of the Young's modulus and the specific Young's modulus are, respectively, Young's modulus of 260 GPa or more,
The specific Young's modulus is 34 or more. The weight reduction rate was determined by the ratio of specific Young's modulus of invention steel (comparative steel) / specific Young's modulus of structural steel.

The results in Table 2 are examples of the case where the powder is HIP-treated and sintered. In the present invention, a sufficient effect was recognized even when the powder was sintered by ordinary powder metallurgy. .

Although the embodiment of the present invention has been described in detail above, this is merely an example, and the present invention can be carried out in various modified forms without departing from the gist thereof.

Claims (2)

[Claims] C: 1.0 to 4.5% by weight% Si: ≤ 2.0% Mn: ≤ 2.0% Cr: 3.0 to 20.0% At least one of Mo, V and Ti Mo: ≦ 25.0% V: ≦ 15% Ti: ≦ 12% Mo + V + Ti: ≧ 10%, the balance substantially consisting of Fe, and W: ≦ 2
%, Ta: ≦ 2%, Co: ≦ 2%. A high Young's modulus powder. 2. C: 1.0 to 4.5% by weight% Si: ≤ 2.0% Mn: ≤ 2.0% Cr: 3.0 to 20.0% At least one of Mo, V and Ti Mo: ≦ 25.0% V: ≦ 15% Ti: ≦ 12% Mo + V + Ti: ≧ 10%, the balance being substantially composed of Fe and W: ≦ 2%,
A high Young's modulus powder sintered body obtained by sintering a powder regulated to Ta: ≦ 2% and Co: ≦ 2%.