JP2003027175A - Sintered alloy excellent in high temperature property and die for hot-formation using the alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintered alloy excellent in hardness at high temperature, oxidizing resistance, specular glossiness and degree of the sintering, suitable to particularly a die for hot-forming. SOLUTION: The sintering alloy is the alloy, in which M6-9 C or M6-9 (C, N) type multiple carbide (nitride) (M is metallic element) phase containing W, Si, Ni and/or Co exists besides WC (hard phase) and a combined phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered alloy having excellent sinterability, high-temperature hardness, and oxidation resistance, a hot-molding die using the same, and peripheral members thereof.

[0002]

2. Description of the Related Art In recent years, many glass or plastic products such as lenses and substrates for hard desks have come to be manufactured by hot forming these materials in order to omit complicated machining. ing. Ceramics, cemented carbide, etc. are used as the material of the mold used for such hot forming. For example, Japanese Patent Laid-Open No. 52-
45613 discloses silicon carbide and silicon nitride, and JP-B-62-51211 discloses a tungsten carbide based cemented carbide containing 3 to 10% by weight of cobalt. Further, there are some examples in which a W-based alloy or the like is used for a die peripheral member such as a holder for fixing the die.

[0003]

However, although ceramics are excellent in oxidation resistance, they are poor in toughness and inferior in grindability, so that there is a problem that it takes a long time for mirror-finishing. The cemented carbide is an alloy mainly containing WC as a hard phase and Co and / or Ni as a binder phase, but has problems such as a remarkable decrease in hardness at high temperatures and poor oxidation resistance. Although the W-based alloy has excellent oxidation resistance, it has low hardness and is poor in grindability, so that there is a problem that it takes a long time for precision processing.

[0004]

The present invention has been made to solve the above problems. That is, by adding Si to the cemented carbide and adjusting the amount of carbon (C) in the alloy to be lower than the stoichiometric composition, W, Si, Ni and / Or M containing Co
_The presence of a _{6 to 9} C-type double carbide (M is a metal element) phase makes the alloy excellent in hardness and oxidation resistance at high temperatures.

The reason why WC is the main hard phase is that WC has excellent mechanical properties, but its average particle size is 10 μm.
If it exceeds m, the transverse rupture strength is remarkably reduced, and if it is less than 0.4 μm, the high temperature hardness tends to be lowered.

[0006] Adding Si is M _6-9 C containing Si
This is because the double carbide phase of the mold improves the high temperature hardness and oxidation resistance of the alloy, and if the addition amount is less than 0.1%, its effect is small, and if it is added in excess of 10%, densification during sintering will occur. It will be difficult.

The reason for adding Ni and / or Co is to improve the sinterability. If the addition amount is less than 0.5%, the effect is small, and if it exceeds 15%, WC and M are added.
_{The 6-9} C-type double carbide phase becomes coarse and the strength is significantly reduced.

Part of W is a periodic table IVa, Va other than W.
And when substituted with one or more transition metals belonging to Group VIa, MC-type double carbide phases containing these transition metals are formed in the structure, whereby the oxidation resistance of the alloy is further improved and the hardness is increased. Although it has an effect of increasing, the sinterability decreases when the content exceeds 10%.

When a part of C is replaced with N, the above M _6-9
C and MC type double carbide phases are M _6-9 (C,
N) and M (C, N) type double carbonitride phases, which are preferable because they further improve the oxidation resistance of the alloy, but if they are replaced by more than 20%, the sinterability will decrease.

Even if a part of Ni and / or Co is replaced with Fe, it is effective in improving the sinterability. However, if the amount of substitution is large, the oxidation resistance deteriorates.
Alternatively, it is preferably 50% or less of the total amount of Co.

[0011]

EXAMPLES In order to produce the products of the present invention, W was used as a basic component.
Using C, SiC, W and Ni and / or Co powder,
A mixed powder is obtained by a conventional method except that the C content is lower than the stoichiometric composition determined by the mixing ratio of WC and SiC, and the mixture is pressed into a desired shape at about 1 to 5 t / cm ² . Next, the molded body is vacuum-sintered at 1350 to 1500 ° C. for 60 minutes, and then at 1350 ° C. for 60 minutes at 1000 atmospheric pressure Ar.
HIP processing is performed in the inside, and then the final shape is processed. Here, the W powder is added because M _{6 to 9} containing W, Si, Ni and / or Co by adjusting the C content to a low level.
This is for forming C-type double carbide. C
In order to adjust the amount, Si, WSi ₂ or the like may be added instead of SiC.

Table 1 shows the composition of the alloy of the present invention and the comparative alloy. Inventive alloy No. Nos. 1 to 4 are alloys in which the binder phase metal is Ni and the amount of Si is changed. 5-
8 is a transition metal belonging to groups IVa, Va and VIa of the periodic table other than W, with Ni as the binder phase metal and part of W as 1
Type or alloys substituted with two or more types, No. 9 to 13 are
An alloy in which Ni was used as the binder phase metal and a part of the carbide was replaced with nitride, No. 14 is an alloy with Co as the binder phase metal, N
o. 15 is an alloy in which the binder phase metal is Ni and Co, N
o. Comparative alloy Nos. 16 and 17 are Ni and alloys in which Ni and Co are partially replaced with Fe. Reference numerals 1 and 2 are so-called binderless cemented carbides containing no binder phase metal,
No. 3 and 4 are _M6-9C by adjusting the amount of C in the alloy to be higher.
-Type cemented carbide that prevents formation of double carbide phase, N
o. Reference numerals 5 and 6 are general cemented carbides for wear resistant tools that do not contain Si. In the table, the C content and WC in the alloy after sintering
The average particle size is also shown.

[0013]

[Table 1]

Structures of the alloys of the present invention and comparative alloys having the compositions shown in Table 1, the transverse rupture strength, the hardness, the oxidation resistance (increased amount of oxidation), and the mold push pin (outer diameter 30 mm) made of these alloys.
Table 2 shows the results of examining the change in the surface roughness of the push pin pressing surface by press molding a glass lens using. The hardness is measured by Micro Vickers hardness (load 9.8N),
In the oxidation weight increase test, a test piece of 10 × 10 × 5 mm was mirror-finished, heated at 800 ° C. for 30 minutes in the atmosphere, and calculated from the weight change.

The glass lens molding test was conducted as follows. First, the flint type optical glass is made into a spherical shape and placed in the cavity of a cemented carbide mold. next,
Heat molding in a vacuum or nitrogen atmosphere. The condition is
After heating to 600 ° C at a heating rate of 10K / min and holding at a molding pressure of 1MPa for 5 minutes, up to 400 ° C 5K / min
And then cooled at a rate of 20 K / min or more and opened to the atmosphere at 300 ° C. The molding as described above was repeated up to 100 times, and the surface roughness of the push pin pressing surface was measured after molding 10 times and 100 times.

[0016]

[Table 2]

The alloy of the present invention is superior in oxidation resistance to the comparative alloys 1 and 2, and has a lower transverse rupture strength than the comparative alloys 3 to 6, but has a high high temperature (600 ° C.) hardness. It can be seen that the amount of increase in oxidation is small and the heat resistance and the oxidation resistance are excellent. Further, the push pin pressing surface of the alloy of the present invention in the glass forming test is superior in surface roughness before the test as compared with the comparative alloy, and deterioration of the surface roughness is observed to some extent in the coarse grain alloy having a WC grain size of 5 to 10 μm. However, it can be seen that it is less likely to deteriorate and wear less than that of the comparative alloy.

From these results, the fine grain alloy is less likely to deteriorate the push pin surface roughness at the contact surface with the glass, and is excellent in oxidation resistance. Although the surface roughness is slightly deteriorated by contact, it is excellent in oxidation resistance, and generally, the coarse grain alloy has a larger thermal conductivity than the fine grain alloy, and therefore is suitable for the die peripheral member. It can be seen that it is extremely excellent as a material for a hot-molding die such as glass and its peripheral members.

[0019]

As described above, the sintered alloy according to the present invention has excellent heat resistance and oxidation resistance, is less likely to be worn in a practical test as a hot forming die, and has an industrial utility value. Is high.

Claims (6)

[Claims] 1. Mass ratio (hereinafter, the same), W: 65-9
6.4%, Si: 0.1-10%, C: 3-10%, N
i and / or Co: 0.5 to 15%, and tungsten carbide and M having a composition of inevitable impurities and having an average grain size of 0.5 to 10 μm as a hard phase in the structure.
_6-9 A sintered alloy containing a C-type double carbide (M is a metal element) phase. 2. Periodic table I excluding W is 10% or less of W
The sintered alloy according to claim 1, which is substituted with one kind or two or more kinds of transition metals belonging to the Va, Va and VIa groups. 3. A method in which 20% or less of C is replaced by N.
The sintered alloy according to. 4. Periodic table IV excluding W up to 10% of W
The sintered alloy according to claim 1, wherein at least one of transition metals belonging to the groups a, Va and VIa is substituted, and 20% or less of C is substituted with N. 5. A total amount of Ni and / or Co of 50.
The sintered alloy according to any one of claims 1 to 4, wherein not more than% is replaced by Fe. 6. A hot-molding die and its peripheral member using the sintered alloy according to claim 1.