JPH05247608A - Powdery high speed steel - Google Patents

Abstract

PURPOSE:To improve the hardness of powdery high speed steel without deteriorating its toughness by incorporating the carbides or nitrides of Ta, Nb and Ti into powdery high speed steel. CONSTITUTION:Powdery high speed steel is incorporated with >=two kinds among the carbides or nitrides of Ta, Nb and Ti. At this time, the weight ratio of TaC/NbC is preferably regulated to the range of 1/10 to 10/1. Furthermore, Tac/(NbC+TiC) is preferably regulated to the range of 1/10 to 10/1. Moreover, the total solid soln. of the three kinds including TaC is preferably contd. by 0.5wt.%. The objective powdery high speed steel is obtd., prior to the compacting of the base metal powder, by adding>=two kinds among the carbides or nitrides of Ta, Nb and Ti in a powdery state, mixing them, thereafter once subjecting the mixture to primary compacting by a hot press and subsequently executing sintering and hot hydrostatic compacting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder high speed steel as a material for wear resistant tools such as rolling rolls and forging tools, and cutting tools such as drills.

[0002]

2. Description of the Related Art High-speed steel (high speed steel) used for wear-resistant tools such as rolling rolls and forging tools, and cutting tools such as drills contains iron as a main component in order to improve hardness and wear resistance. , Various kinds of hard elements such as molybdenum (Mo) and vanadium (V) are contained.

This high-speed steel includes so-called molten high-speed steel that is formed by melting raw materials once and so-called powder high-speed steel (powder high-speed steel) formed by powder metallurgy. Compared with HSS, it has no segregation of hard carbides and is superior in toughness and hardness.

Here, as a method of producing a base metal powder which is a raw material of powder high speed steel, a gas atomizing method,
Water atomization method, oxide reduction method, etc. are known. Among them, the powder obtained by the gas atomization method has a high content of powder oxygen in recent years because the content of oxygen is the most harmful when used as a tool in its composition. It has become the mainstream in the production of raw materials for speed steel, and the following method is available as a method for producing powder high speed steel using this gas atomized powder.

First, a method of filling a raw material powder into a capsule, hot or cold isostatic pressing, and then forging / rolling, removing the capsule to obtain a tool, and Japanese Patent Application No. No. 2-87730, there is a method in which the raw material powder is temporarily solidified by hot pressing, and thereafter, sintering and hot isostatic pressing are performed.

[0006]

However, in any of the above methods, there is a problem that grain strength grows when the hard phase, which once became the liquid phase at the solidification stage, solidifies, and the alloy strength decreases. there were.

Also, regarding the elements added to the raw material powder for the purpose of improving the hardness of the alloy, if too large an amount is added, the alloy toughness is deteriorated, and so there is a limit to improving the hardness.

An object of the present invention is to solve the above problems and to provide a powder high speed steel capable of improving hardness without lowering the toughness of the alloy.

[0009]

Means for Solving the Problems The inventors of the present invention have made earnest studies and, by incorporating two or more kinds of carbides or nitrides of Ta, Nb and Ti in powder high speed steel,
At the stage of sintering and solidification of the raw material powder, the hard phase does not undergo grain growth, so that the toughness does not decrease, and further, the toughness at high temperature is excellent, and it has been found that the powder high speed steel has improved hardness. ..

As a method for producing the powder high-speed steel of the present invention, Ta, Nb, and T are formed before the powder high-speed powder (base metal powder) obtained by the spraying method after being once melted is solidified.
i) two or more carbides or nitrides of i are added in a powder state and mixed, and then these raw material powders are once primary solidified by hot pressing, followed by sintering and hot isostatic pressing. Get steel.

The powder high speed steel containing two kinds of TaC and NbC of the present invention has an optimum value in the composition range, and TaC / NbC (weight ratio) is within the range of 1/10 to 10/1. If TiC is added, TaC / (NbC + TiC) (weight ratio) is 1/10.
It is preferably within the range of 10/1.

In the present invention, it is desirable that the powder high speed steel contains 0.5% by weight or more of the total solid solution of three kinds of carbides including TaC.

[0013]

[Function] A powdered high-speed powder made of a material containing Fe as a main component is mixed with two or more kinds of carbides or nitrides of Ta, Nb, and Ti, and mixed and subjected to primary solidification by hot pressing, followed by sintering and hot-static treatment. Hydroforming is performed to obtain the powder high speed steel of the present invention.

The above Ta, Nb and Ti contained in the alloy
The carbides or nitrides have the effect of improving the hardness of the alloy. Further, the hard phase in the alloy becomes a liquid phase during sintering during production, and when the liquid phase solidifies, the Ta, N
Carbides or nitrides of b and Ti are stable substances,
The size of the structure becomes fine without grain growth, and it is possible to prevent deterioration of the toughness of the obtained alloy as much as possible.

Incidentally, TaC, N, which is a carbide of the above element,
Comparing bC and TiC, the higher hardness is TiC>
The order is NbC> TaC, and it is the order of TaC, NbC, and TiC that makes grain growth difficult.

Therefore, when two or more of these elements are contained, there is an optimum value. For example, when TaC and NbC are contained, if the TaC / NbC (weight ratio) is less than 1/10, the structure grows grains. Alloy toughness decreases and TaC /
If NbC is 10/1 or more, the hardness will decrease.
However, if TaC / NbC is in the range of 1/10 to 10/1, hardness can be improved while preventing deterioration of alloy toughness.

When three kinds of TaC, NbC and TiC are contained, TaC / (NbC + TiC) is 1/10 to 1
Within the range of 0/1, hardness and toughness can be improved in a more balanced manner.

Further, if TaC is contained, the three kinds of carbides containing TaC have the effect of completely melting and forming a single-phase crystal in the entire region, so that three kinds of carbides containing TaC in the powder high-speed steel. At least 0.5 wt% solid solution
If the content is at least%, the composition of the obtained alloy will be stable.
Further, TaC is thermally stable and can delay the reaction with the material to be processed and the progress of oxidation even under use conditions at high temperature, and has the effect of improving the life of the tool.

[0019]

Embodiments of the present invention will be described below.

After powdered HSS powder (base material powder) having the composition shown in Table 1 was mixed with powders of carbides or nitrides of Ta, Nb and Ti shown in Table 1 by dry mixing (Sample Nos. 1 to 10). Then, it was filled in a carbon mold and subjected to primary solidification by hot press molding in an N ₂ gas atmosphere.

Thereafter, sintering and HIP are carried out in the same furnace to obtain a powder high speed steel, and the hardness of the obtained material,
The transverse rupture strength was measured and the results are shown in Table 2.

Further, in the same process, a powder high-speed steel was obtained by the same process without mixing powders of carbides or nitrides of Ta, Nb, Ti, and Ta, outside the scope of the present invention. Hardness and transverse rupture strength were measured (Sample Nos. 11 to 16) using a comparative example in which powdered high-speed steel obtained by mixing Nb and Ti carbides by the same method.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

As described above, according to the present invention, since Ta, Nb, and Ti exist in a stable carbide or nitride state in the powder high-speed steel without grain growth, the alloy toughness decreases. Without doing so, it is possible to obtain a powder high-speed steel whose hardness is improved more than before.

Claims (4)

[Claims] 1. A powder high-speed steel characterized by containing two or more kinds of carbides or nitrides of Ta, Nb, and Ti. 2. The high-speed powder steel according to claim 1,
Powder high-speed steel characterized in that TaC / NbC (weight ratio) is in the range of 1/10 to 10/1. 3. The powdered high speed steel according to claim 1, wherein
TaC / (NbC + TiC) (weight ratio) is 1/10 to 1
Powder high speed steel characterized by being in the range of 0/1. 4. The powder high speed steel according to claim 1, wherein
0.5% by weight of total solid solution of three kinds of carbides including TaC
Powder high speed steel containing the above.