JPH0784638B2 - Especially hard corrosion resistant alloy with excellent mirror finish - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hard corrosion-resistant alloy, and more particularly to a Fe-based hard corrosion-resistant alloy suitable for resin molding die materials such as optical disks and plastic lenses, which has excellent mirror-finishing properties. It is a thing.

(Prior art and problems to be solved) In recent years, with the spread of optical discs and plastic lenses, etc., resin molding with excellent mirror-like finish to obtain smooth and glossy surfaces at the same time as molding these from resin The need for mold materials is increasing rapidly.

Conventionally, as a mold material for this type of mirror finish, 13
Cr martensitic stainless steel, maraging steel, etc. are used.

However, in the case of the former 13Cr martensitic stainless steel, since it contains C, dimensional changes are likely to occur during heat treatment when manufacturing the mold, and when resin molding is performed using the manufactured mold, the surface of the mold becomes rough. Carbide, which is a precipitation phase, is transferred to the resin, and there is a problem that mirror finish is poor.

Therefore, in order to solve this problem, a method of coating the surface of the manufactured mold with TiN by the CVD method has been attempted, but in this method, distortion occurs at the boundary between the base material and the coating layer. There is a problem that the coating layer is peeled off, and further, the cost of coating treatment is high and the cost is high.

On the other hand, in the case of the latter maraging steel, since the manufactured mold does not contain carbides, it has an advantage in terms of mirror finish, but the hardness is not sufficient and it was heated. There is a problem that the corrosion resistance to the corrosive gas generated from the resin is insufficient.

As described above, it is difficult to say that any of the above-mentioned mold materials is a material having sufficient required properties such as mirror finish, corrosion resistance, etc., or a special surface treatment is required, and there is a problem in manufacturing cost. .

The present invention eliminates the above-mentioned drawbacks of the prior art, does not require surface treatment such as coating treatment, has excellent mirror-finishing properties without containing coarse precipitation phases such as carbides on the surface, and is also hard and corrosion resistant. The object is to provide a superior new alloy.

(Means for Solving Problems) In order to achieve the above-mentioned object, the present inventor cannot secure mirror finish by a conventional hardening mechanism by precipitation of carbides (cementite, chrome carbide, etc.) unless coating treatment is performed. In view of this, a new mechanism different from the conventional age-hardening type has led to intensive studies to develop an alloy having sufficient hardness and corrosion resistance, and as a result, the alloy can be hardened by clustering Mo, and The present invention has been made by finding an age-hardening Fe-based alloy that can have both excellent mirror finish and corrosion resistance.

That is, in the present invention, Mo and Al are the points c shown in FIG.
(Mo10%, Al8%), d (Mo8%, Al%), e (Mo8%, A
l50%), f (Mo22%, Al50%), g (Mo22%, Al8%)
The present invention is directed to a hard corrosion-resistant alloy having particularly excellent mirror-finishing properties, characterized in that it is contained in a region surrounded by a line connecting in succession with the balance being substantially Fe.

The present invention will be described in more detail below.

First, the action of each component in the alloy of the present invention will be described. Needless to say, each component exerts its unique action within an appropriate amount range described below.

Mo is the most important component to utilize the hardening mechanism by clustering in the present invention, and the atoms of Mo gather together to form a cluster by aging after liquefaction treatment. And the average spacing is so fine that the alloy can be hardened by the periodic lattice strain due to the clusters. This mechanism, as illustrated in FIG. 2, arranges Mo atoms collectively on the iron (Fe) lattice plane to create a periodic lattice strain. For example, for every 10 Fe atoms, At the lattice plane, a large number of Mo atom aggregates are formed. To obtain this effect,
At least 8% or more Mo is required. However, if it exceeds 22%, the alloy becomes brittle, which is not preferable. This is because, generally, an element having a body-centered cubic crystal structure has a ductility-brittleness temperature, and in the case of Mo, the elongation is 0% at 24 ° C. or less, and in the case of the alloy of the present invention, the Mo content is locally increased. It is considered that the above brittleness appears when Mo is excessively added to form an aggregate. Further, Mo is an element that significantly improves the corrosion resistance to reducing acids such as hydrochloric acid.

Al has a function of promoting the formation of Mo clusters. Fe
-In the binary Mo system, if 20% or more of Mo is not added, hardening due to Mo cluster formation does not occur. However, according to the research by the present inventors, the addition of Al promotes the formation of Mo clusters, and Mo It became clear that it could be reduced to%. As described above, it is desirable that Mo has a low concentration from the viewpoint of toughness of the alloy, but since addition of Al makes it possible to reduce the concentration of Mo, Al is effective in terms of strength of the alloy. It can be called an additive element.

Further, Al is an element that improves the corrosion resistance against an oxidizing acid such as nitric acid, and significantly improves the oxidation resistance in the atmosphere. 8% or more of Al is required to improve corrosion resistance, while 50
%, The brittle intermetallic compound ζ phase precipitates, so the amount of Al added is in the range of 8 to 50%.

By the action of the elements as described above, it was found that it is necessary to regulate and adjust Mo and Al in the Fe-based alloy of the present invention so as to belong to the shaded area shown in FIG.

That is, FIG. 1 shows the relationship between the amount of Mo, which is the main component of the curing mechanism (horizontal axis), and the amount of Al, which is the component that accelerates curing (vertical axis). In the figure, area A (hatched area)
Is c (10%, 8%), d (8%, 25%), e (8%,
50%), f (22%, 50%), and g (22%, 8%) are surrounded by a line that sequentially connects the points, which indicates that the composition is within the scope of the present invention. If the amount of components in this region A, it can be hardened to 550 or more in Vickers hardness (mHv) by aging. In particular, in the region A, Al is 22 to 34% and 34
In the range of up to 50%, the matrix phase forms ordered lattices of Fe ₃ Al and FeAl by aging, so that age hardening becomes more remarkable.

However, in the region B, the amount of Mo is small and the amount of Al is also small, so that the clusters are not sufficiently formed and the hardness mHv is 550.
If less than, the alloy will not harden.

On the other hand, in area C, each point a (20%, 0%), b (15%,
1%), c (10%, 8%) or more than the amount indicated by the line
When Mo and Al are added, clusters are formed and hardened, but since Al is small, corrosion resistance is poor and oxidation resistance in the air is deteriorated.

Further, in the region D, a brittle intermetallic compound ζ phase is precipitated due to excessive Al, so that the region is very brittle, and in the region E, brittleness appears due to excessive Mo and the toughness is poor, and therefore, any of them cannot be used as a practical material. .

Next, the production of the Fe-based alloy having the above chemical composition will be described.

When the amount of Al is 8-25%, after melting, casting, homogenizing annealing, hot working such as hot rolling to manufacture the material, and then subjecting it to solution treatment, the desired size is obtained. It is desirable to perform plastic working on shaped products. In that case, plastic working is easy in the solution heat treated state, and thereafter, it is hardened by aging, so there is no hindrance to the forming work. On the other hand, the amount of Al is 25-50
%, Regularization of Fe atoms and Al atoms occurs from around 1000 ° C., and hot workability deteriorates. Therefore, the amount of Al is 25 ~
In the case of 50%, powder (atomized powder) is produced from the molten state using the atomizing method, and this is molded into the final shape by hot isostatic pressing (HIP), and then subjected to solution treatment and aging treatment. Then, a hard sintered alloy having fine crystal grains can be obtained. Even if the amount of Al is 8 to 25%, it can be produced by the same process, and the sintering of atomized powder can be effectively applied in terms of making the crystal grain size finer.

Since the alloy of the present invention is structurally hardened in a state not containing a coarse precipitation phase, when used as a mold material, the surface roughness
Achieving 0.003 μmRa and excellent mirror finish. Therefore, it is possible to manufacture a mold that exhibits high performance in resin molding of optical disks and the like. Further, the alloy of the present invention is applicable not only to mold materials but also to various members such as cylinders and screws of plastic injection molding machines by utilizing its characteristics.

Next, examples of the present invention will be described.

(Example) An alloy having the chemical composition (at%) shown in Table 1 was melted and cast, and the obtained ingot was subjected to homogenization annealing at 1250 ° C for 5 hours, and then at a temperature of 1250 to 1000 ° C. Was hot-rolled.

After hot rolling, solution treatment was performed at 1250 ° C for 20 minutes, and then aging treatment was performed at 500 ° C for 7 hours to obtain a match. In addition, the alloy described as “HIP” in the remarks column of Table 1 is an atomized powder of the alloy, which is HIP under the conditions of 1250 ° C., 1000 atmospheric pressure, and 3 hours.
After the treatment, the heat treatment is applied.

The age hardness (mHv) was measured for each match and the corrosion resistance and oxidation resistance were examined. The results are also shown in Table 1. In the corrosion resistance test, the sample was immersed in a 5% HCl solution at 50 ° C. for 24 hours, and the corrosion weight loss was measured to evaluate the corrosion resistance. Regarding the oxidation resistance, after being put in a furnace at 400 ° C for 8 hours, those having a metallic luster after being put are described as "Yes", those having a metallic luster due to the formation of an oxide film are described as "No", The oxidation resistance was evaluated.

As is clear from Table 1, the alloys of the present invention No. 11 to No. 18
All have sufficient hardness and have good corrosion resistance and oxidation resistance.

On the other hand, Comparative Alloys No. 3 to No. 10 have hardness, corrosion resistance,
There is a problem in either oxidation resistance or toughness.

That is, since No. 3 to No. 6 are the component compositions belonging to the region B in FIG. 1, the hardening is insufficient. No.7 and No.8
Since it belongs to the region C of FIG. 1 and is hardened, it has a small amount of Al, so it does not have oxidation resistance and has a problem in the molten resin molding operation at high temperature when used as a mold material. .

No. 9 and No. 10 are areas D and E in Fig. 1, respectively.
In this example, there is a problem in toughness. That is, when the Weibull coefficient was obtained by performing four 4-point bending tests for each sample, it was confirmed that No. 9 and No. 10 both had very small values, and that there was a problem in practical use.

Next, the same test was performed for conventional alloy No. 1 (13Cr stainless steel) and No. 2 (maraging steel).
As shown in the table, all have problems in corrosion resistance,
In the case of 13Cr stainless steel, there is a problem that the carbide is transferred to the resin as described above.

(Effects of the Invention) As described in detail above, according to the present invention, since a proper amount of Mo and Al are added to the Fe-based alloy and a new hardening mechanism different from the conventional one is used, a coarse precipitation phase is formed. It is possible to provide an alloy that is hardened without containing it, has an excellent mirror-finishing property, and has excellent corrosion resistance. It is particularly suitable for resin molding die materials such as optical disks and plastic lenses.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the amount of Mo (horizontal axis) and the amount of Al (vertical axis) in the alloy of the present invention, and FIG. 2 is an explanatory diagram showing Mo clusters formed on the lattice plane of Fe atoms. is there.

Claims (1)

[Claims] 1. Mo and Al are first in atomic% (hereinafter the same).
Each point c (Mo10%, Al8%), d (Mo8%, Al25) shown in the figure
%), E (Mo8%, Al50%), f (Mo22%, Al50%),
g (Mo22%, Al8%) so that it is contained in the area surrounded by the line connecting in sequence, and the balance is substantially Fe, which is a hard corrosion-resistant alloy with particularly excellent mirror finish.