JPH06207246A - Carbide dispersed maraging steel - Google Patents

Abstract

PURPOSE:To provide the material for a tool easy in machining and excellent in wear resistance. CONSTITUTION:Carbide dispersed maraging steel in which the total content of carbides consists of 19.9 to 25.5% Ti, 3.7 to 7% Mo and 5 to 6.8% C and the matrix contains 21 to 24% Co, 11 to 14% Ni and one or more kinds among 0.6 to 1% Al, Ti and Nb, and the balance Fe with inevitable impuritiets is prepd. In this way, the hardness is suitable before maraging so that machining can easily be executed, and the hardness is sufficiently increased after maraging, so that the steel can be applied for a tool material requiring excellent wear resistance or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high strength, high toughness maraging steel.

[0002]

2. Description of the Related Art Ni, C
Maraging steel that contains a large amount of o, etc. and precipitates intermetallic compounds by tempering is one that has toughness by utilizing the age-hardening property of an ultra-low carbon iron martensite alloy that forms a solid solution of substitutional alloying elements. It is widely used as a material for mechanical structures that requires high strength and toughness. Furthermore, recently, utilizing these characteristics, it is desired to use for a purpose other than the above applications, and for example, use as a material for a cold tool is under study.

[0003]

By the way, the materials for tools are required to have excellent wear resistance in the environment of use, and the maraging steel used for them is naturally required to have high wear resistance. To be done. However, the strengthening mechanism of maraging steel is to enhance the strength of the matrix by utilizing the precipitation hardening of the intermetallic compound as described above, and the intermetallic compound itself does not have high hardness, and the wear resistance is exceptional. It's not good. Therefore, maraging steel has insufficient wear resistance as a tool material, and this is a major factor that hinders its use as a tool material.

On the other hand, cemented carbides and cermets which have been put into practical use as materials for tools have particularly excellent wear resistance. However, these materials have very high hardness, making machining almost impossible,
There is a problem that the shape is restricted during sintering. The present invention has been made against the above circumstances.
By dispersing an appropriate amount of carbide in a maraging steel having an optimum composition, the hardness is set so that it can be machined before being age-hardened (for example, as-sintered or solution-treated). The purpose of the present invention is to sufficiently cure it by the subsequent aging treatment so that a predetermined hardness and wear resistance can be obtained. Here, if an example of mechanical properties desired as a tool steel is shown, the Vickers hardness before the age hardening treatment is 600 or less, the Vickers hardness after the age hardening treatment is 750 or more, and the three-point bending transverse strength is 150 kgf. / Mm ² or more.

[0005]

That is, the invention of the present application is
A carbide-dispersed maraging steel in which carbide is dispersed in a matrix, wherein the total amount (% by weight) of carbide is Ti
: 19.9 to 25.5%, Mo: 3.7 to 7%, C:
5 to 6.8%, the matrix is Co: 21 to
24%, Ni: 11-14% and 0.6-1% Al,
At least one of Ti and Nb is contained, and the balance is Fe and inevitable impurities. The carbide in the present invention consists of Ti carbide and Mo carbide, or composite carbides of these are mixed and dispersed in the matrix. The sum of these carbide components is specified above.

The method for producing the maraging steel of the present invention is not particularly limited, but generally, it is produced by mixing carbide particles and matrix particles and sintering them. As the carbide particles, the same carbide particles that are finally dispersed in the steel may be used, or the carbide particles may be added as carbide or metal particles by predicting the reaction during sintering. For example, Mo added as metal particles reacts with carbon to become Mo ₂ C, and also forms a composite carbide with Ti. This is Mo
Has a strong affinity for C and forms a solid solution carbide of Ti and Mo during sintering, so that a carbide morphology similar to the case of adding Mo ₂ C particles can be obtained. The maraging steel thus obtained is machined before the aging treatment and then subjected to the aging treatment, whereby a desired molded product can be obtained without being greatly restricted by the shape.

[0007]

According to the present invention, the hardness is such that it can be machined before the aging treatment, and in this state, it can be easily machined into a desired shape. Then, the age hardening treatment sufficiently increases the hardness to obtain desired mechanical properties. In addition, the appropriate carbides dispersed in the matrix can improve wear resistance without compromising machinability. Below, the reasons for limiting the components of the present invention will be explained together with specific actions.

(Carbide) Ti: 19.9 to 25.5% Ti forms spherical TiC having a very high hardness as a hard carbide. If Ti is less than 19.9%, the amount of carbide is too small to obtain sufficient hardness, and it becomes difficult to reach the target hardness of Hv750 after age hardening. On the other hand, if the upper limit is exceeded, the hardness before age hardening will be too high, exceeding the target value of Hv 600 or less and making machining difficult, so the above range is set.

Mo: 3.7-7% When only the above TiC is dispersed in the maraging steel, the wettability between the TiC and the matrix is poor and the pores tend to remain. Therefore, by adding Mo as it is or in the form of Mo ₂ C, a solid solution carbide is formed with Ti to improve the wettability, and a normal alloy in which pores hardly remain can be obtained. If this Mo is less than 3.7%, the improvement of wettability is insufficient. If the wettability is poor, the diffusion rate will be low, so that solid solution carbides of Ti and Mo will not be sufficiently formed, and fine Ti carbides and Mo carbides will individually be formed, respectively, and these will be mixed in the matrix. . For this reason, the hardness becomes unnecessarily high, and it becomes difficult to perform machining before aging.
Therefore, the content of Mo is set to the above range. C: 5 to 6.8% C is contained in an amount necessary for carbide formation of Ti and Mo.

(Matrix) Co: 21-24%, Ni: 11-14% The above elements and Fe are important elements that determine the properties of the matrix phase, and the Co-Ni-Fe ternary system is the basic element. It becomes the composition. With an appropriate composition ratio of Co, Ni and Fe, it has a hardness that can be machined before aging treatment (as-sintered or solution-treated), and after heat treatment it exhibits optimum age-hardenability. Become. In the present invention, the optimum composition is found to be 35% Co-20% Ni-45% Fe, and based on this composition ratio, the hardness before aging treatment and the hardness and transverse rupture strength after aging treatment are considered. Then, the proper range of each element was defined.

One or more of Al, Ti and Nb: 0.6 to 0.6
One or more kinds are added in order to make 1% age hardening remarkable.
If the addition amount is less than the lower limit, there is no effect, and if it exceeds the upper limit, the toughness after age hardening decreases, so the above range was made. In addition to the above elements, unavoidable impurities are contained. For example, in addition to the amount of carbon specified by the carbide, carbon is contained as an impurity in the matrix.

[0012]

[Examples] With the compounding ratio (% by weight) shown in Table 1, TiC powder (particle size 1-2 μm), Mo ₂ C powder (average particle size about 3 μm)
m), Co powder (average particle size of about 1.5 μm), Ni powder (3 to 7 μm), Fe powder (4 to 6 μm), Al powder (average particle size of about 10 μm), Ti powder (44 μm or less) The powders were blended and mixed with 2-propanol as a solvent in a wet ball mill for 24 hours. This mixed powder was filled and sealed in a rubber mold having a space of 15 (t) × 30 (w) × 150 (L) mm, and CIP molding was performed at a pressure of 1500 kgf / cm ² . This CIP body is put under vacuum 142
Vacuum sintering was performed by heating at 0 ° C. for 6 hours. Then
The obtained sintered body (test material) was subjected to solution treatment at 850 ° C. for 4 hours, and further subjected to aging treatment at 500 ° C. for 6 hours.

The above test materials were subjected to a three-point bending test while measuring the Vickers hardness after sintering and the Vickers hardness after the aging treatment. The results are shown in Table 2. As is clear from the table, the hardness of the steel of the present invention after sintering is Hv 600 or less, which is a hardness that enables machining. The hardness after aging treatment is Hv7.
It is 50 or more, and sufficient hardness is obtained. In addition, a sufficiently high transverse rupture strength is also shown in the three-point bending test. On the other hand, the comparative steels outside the scope of the present invention are No. In Nos. 5 and 6, the hardness after the aging treatment was sufficient, but the hardness after sintering was too high and the machining was difficult.
In addition, comparative steel No. In No. 7, the hardness after sintering is such that it can be machined, but the hardness is insufficient even after the aging treatment. All of these comparative steels are inferior to the invention steels in the transverse rupture strength.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

As described above, the carbide-dispersed maraging steel of the present invention is a carbide-dispersed maraging steel in which carbide is dispersed in a matrix, and the total amount (% by weight) of carbide is Ti: 19.9 to 25.5
%, Mo: 3.7-7%, C: 5-6.8%,
The matrix is Co: 21-24%, Ni: 11-1
4% and 0.6 to 1% of one or more of Al, Ti or Nb, and the balance Fe and unavoidable impurities, so that it is easy to machine before aging treatment. It can be used for shape materials. Since the hardness is sufficiently increased after the aging treatment, it can be applied to a tool material or the like which requires excellent wear resistance.

Claims (1)

[Claims] 1. A carbide-dispersed maraging steel in which carbide is dispersed in a matrix, wherein the total amount (% by weight) of carbide is Ti: 19.9 to 25.5%, Mo: 3.7.
.About.7%, C: 5 to 6.8%, and the matrix is
Co: 21-24%, Ni: 11-14%, 0.6-
Carbide-dispersed maraging steel containing 1% of Al, Ti or Nb, and a balance of Fe and inevitable impurities.