JP3695935B2 - Fe-Si-C amorphous alloy and powder metallurgy member using the alloy - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a high-carbon iron-based amorphous alloy that can be amorphized and can uniformly disperse fine graphite in a metal structure by annealing from an amorphous state, and a powder metallurgy member using the powder alloy. "
[0002]
[Prior art]
At present, research on Fe-based amorphous alloys based on iron, which is most widely used as an industrial material and is the most important industrial material, has been actively conducted. However the current treatment, albeit reports of what part of that composition to Fe, Ri mostly iron der ingredients, for example, reports on high-carbon Fe-based amorphous alloy, such as steel or cast iron is not.
[0003]
On the other hand, it has been known from previous studies on amorphous that the smaller the critical cooling rate, the easier it becomes amorphous. In metallography, eutectic points, that is, two or more phases, coagulate and mix simultaneously at the same temperature. One of these points is considered to be a new organization. In other words, since the melting point is considerably reduced in the vicinity of the eutectic structure, the temperature difference between the melting point and the glass transition point becomes small, and this temperature region can be passed quickly, and as a result, it is said that it is easy to become amorphous. .
[0004]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to focus on the eutectic composition of cast iron, and the Fe-C-Si-based alloy composition occupying the majority of the iron content can be amorphized, and an iron-based amorphous in which fine graphite is generated inside The development of alloys is the first issue, and the development of powder metallurgical members with special properties made of such alloys or alloy powders and at least the surface of which is amorphized is used. It is to be an issue .
[0005]
[Means for Solving the Problems]
The present invention is a "weight%, C is from 2.0 to 7.0 wt%, B is from 0.2 to 3.0 wt%, Si is 1.0 to 2.5 wt%, the balance being F e And inevitable impurities, and fine graphite is formed in the metal structure.
[0006]
According to this, both are high carbon-containing iron-based alloy compositions including a eutectic composition, and when quenched at a rate capable of amorphization, the addition of B causes a hypoeutectic with less C content than the eutectic composition. precipitation of primary crystal austenite is inhibited in the case of the composition, or in the case of the C content is not multi hypereutectic than the eutectic composition is inhibited precipitation of graphite, in the case of eutectic composition it coagulates the The whole or at least the entire surface layer or a part of the surface layer is amorphized, and the amorphized portion exhibits a very high hardness.
[0007]
Amount of wherein B is 0. If 2 wt% or less without effective entirely too little amorphous 3. 0 for wt% or more without even precipitation of fine graphite annealed, F The e- B compound and cementite precipitate to form a very brittle and hard metal structure, and there is no industrial use. Accordingly, the present invention is the addition of B 0. 2 to 3. 0 wt% is employed.
[0008]
When the alloy of the present invention having the above composition is annealed, first, the structure relaxation occurs, and then nanocrystallization gradually starts. When annealing is further advanced, fine graphite having an average diameter of 1 to 2 μm (of course, there are also larger or smaller ones) precipitates uniformly on the entire metal structure as the crystal grows, and the remainder becomes a ferrite structure. It becomes softer and can be processed.
[0009]
When this is further heated, the fine graphite grows to form large spherical graphite. In particular, when the composition is a eutectic composition and its vicinity, it is likely to be amorphous due to the above-described reason. If you look at the Fe-C-based parallel state diagram, C;. 4 but 3 wt% where is the eutectic point, Fe-C-Si based parallel state diagram; if you look at (Si case of 2 wt.%), C;. 3 of 5 wt% where there is a eutectic point. Incidentally, the content of Si increases, the eutectic point is moved to the low-carbon side, S i;. 3 8 is eutectic point in the case of wt% C;. 3 0 wt% at the eutectic point It becomes.
[0010]
As described above, when “fine graphite is formed in the metal structure”, fine graphite is uniformly dispersed in the soft ferrite structure. For example, this fine graphite is impregnated with lubricating oil. Therefore, the load applied to the bearing surface is supported by the ferrite layer, and the lubricating oil is gradually released from the graphite layer that absorbs and holds the lubricating oil to the bearing surface to prevent wear of the bearing surface. I can do it.
[0011]
Claim 2 is characterized in that “the surface layer is amorphized” with respect to the amorphous structure of the alloy of claim 1, and since the entire surface layer or part thereof is amorphized, the surface hardness Not only improves the wear resistance, but also improves the corrosion resistance when the entire surface layer is amorphized, since there are no crystal grain boundaries.
[0012]
Claim 3 is a “powder metallurgy member” using an alloy according to the present invention, wherein the amorphous alloy powder is kneaded with a vanida powder such as soft iron, or is formed into a predetermined shape only with the amorphous alloy powder. When sintering after pressure compression molding, fine graphite is precipitated in the amorphized powder during the sintering process. When this fine graphite is impregnated with lubricating oil, a good oil-free bearing can be obtained, and when it is used as it is, the fine graphite exhibits a vibration absorbing ability, and thus functions as a vibration absorbing member.
[0013]
Claim 4 is a powder metallurgy member characterized in that “at least the surface layer of the alloy powder described in claim 3 is amorphized”, and has no remarkable grain resistance as described above, since there is no crystal grain boundary. Improved.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. As described above, the alloy according to the present invention is an Fe-Si-C-based alloy that can be made amorphous by adding B. The alloy is wt% and C is 2.0 to 7.0 wt%. B is 0.2 to 3.0% by weight, Si is 1.0 to 2.5% by weight, and the balance is composed of Fe and inevitable impurities.
[0015]
In the above composition, the cast iron composition (the chemical composition of cast iron is not strictly defined, the main composition is C, Si, Mn, P, S, and the above-mentioned alloy cast iron, etc., for its intended use. For example, if necessary, Ni, Cr, Mo, V, Cu, Ti, etc. are added as gray cast iron (FC10, FC15, FC20, FC25, FC30, based on tensile strength) as a representative cast iron composition. Represented by FC35).
[0016]
Moreover, silicon iron or calcium silicate powder is inoculated into this to promote graphitization, and the shape of graphite is spheroidized (spheroidized graphite cast iron = FCD37, FCD40, FCD45, FCD50, FCD60, FCD70, FCD80, etc.) ), Worm-like or pseudo-piece-shaped (for example, mehernite cast iron = material type is represented by GE, GD, GC, GB, GA, GM, GS, GSH, GSF, and the structure is GGS, GSH) , GSF is spheroidal graphite, others are worm-like graphite uniformly distributed in uniform dense pearlite structure that does not contain free cementite and ferrite, various alloy elements (Ni, Cr, Mo, Ti, V , Cu, etc.) alloy cast iron << high strength alloy cast iron (for example, acicular) with mechanical properties, corrosion resistance and other properties that cannot be obtained with ordinary cast iron Iron), wear resistance cast iron, acid resistance cast iron "and the like.
[0017]
Generally, cast iron is used in the hypoeutectic to eutectic region, so C; 2.8-3.4 wt%, but when used in the hypereutectic region, C; up to 7. 0% by weight is employed. When the C content is 7.0% by weight or more, the solidified structure becomes cementite and cannot withstand industrial use . The other components are Si; 1.4 to 2.5% by weight, Mn; 0.4 to 1.0% by weight, P; 0.3 to 0.8% by weight, S; For applications such as the alloy cast iron, for example, Ni: 1.0 to 1.0% by weight, Cr: 0.2 to 0.6% by weight, Mo; 0.1 to 1.6% by weight as necessary. V: 0.1 to 1.0% by weight; Cu; 0.1 to 1.0% by weight; Ti; 0.01 to 0.05% by weight.
[0018]
In the cast iron composition, C is 2.8 to 4.4% by weight (the maximum content of C when used in the hypereutectic region is 7.0% by weight), and Si is 1.0. -2.5 wt%, B is 0.2-3.0 wt%, of which eutectic composition is preferred for the reasons described above. In the above composition, the addition of B is too small in the case of 0.2% by weight or less and does not exhibit the effect of amorphization at all. In the case of 3.0% by weight or more, fine graphite does not precipitate even when annealed. Cementite and Fe-B compounds are precipitated and are very hard and brittle, so they cannot be used for industrial applications.
[0019]
All of the cast iron compositions have a wide range of eutectic compositions including eutectic compositions. When quenched at a rate capable of becoming amorphous, the addition of B inhibits the precipitation of primary austenite or graphite and solidifies as it is. The entire surface or at least the entire surface portion or a part thereof becomes amorphous and exhibits a very high hardness. (In the case of a cast iron composition, the non-amorphous part has a predetermined composition according to the phase diagram or Maurer's structure diagram.)
[0020]
Then, when this amorphous material is annealed (for example, annealed at a temperature of A1 point or higher (generally about A1 point + 50 ° C.) (ie, slowly cooled)), atoms easily move and the structure is relaxed. Further heating produces nanocrystals. When heating is continued, graphite precipitates and crystallizes. The graphite at this stage is fine and has an average diameter of 1 to 2 μm, and appears uniformly dispersed throughout the ferrite structure. The annealing structure is soft enough to be machined easily. When this is further heated, crystal growth occurs, and graphite agglomerates, generating large spherical graphite. (See Figure 1)
[0021]
If the alloy that has been annealed and graphitized is remelted and then rapidly cooled, it becomes amorphous again. In remelting, the entire sample is naturally melted, but only the surface layer may be heated and melted, for example, by laser or high-frequency heating. The cooling method is sufficient as long as a cooling rate sufficient for amorphization is obtained, and any method such as oil cooling, water cooling, and air cooling may be used.
[0022]
The alloy material according to the present invention can be used in a block, or a ribbon having a thickness of about 0.01 to 0.5 mm formed by a single roll method, and an average particle size of 5 to 20 μm by a spray impact fine powder production apparatus. It is used in the form of powders of various particle sizes, wire rods or rods having a diameter of about 0.01 to 2 mm by a twin roll method or an underwater spinning method.
[0023]
In the case of a block having a diameter of 2 mm or more, since the internal cooling rate is generally insufficient, the inside becomes a structure in which graphite is precipitated in ferrite, but the surface layer is made amorphous because the cooling rate is sufficient. To do. The cooling may be any of air cooling, water cooling, and oil cooling as long as the cooling rate is sufficient. The ribbon and the wire or rod are made amorphous to the center because the cooling rate is sufficient even in the center. The hardness of the amorphous surface is harder than Fe ₃ C and exhibits excellent wear resistance. In addition, when the entire surface is amorphized, there is no crystal grain boundary like a crystalline metal, so that the corrosion resistance peculiar to amorphous is shown.
[0024]
(Example) Fe: 92.6% by weight, C: 3.5% by weight, Si: 2.7% by weight, P: 0.1% by weight, Mn: 0.07% by weight, B: (a ) 0 wt%, (b) 0.2 wt%, (c) 0.5 wt%, (d) 1.0 wt%, (e) 2.0 wt%, (f) 3.0 wt%, (g) A cast iron ribbon (thickness: 0.1 mm) is prepared by a single roll method by adding 4.0% by weight and used as a sample (a) to examine amorphization, which is further annealed at 1150K and graphite. The precipitation state of was investigated. Sample (a) in which the amount of B added was 0% by weight did not become amorphous and large graphite precipitated from the beginning. Samples (b) to (g) having B addition amounts of 0.2 wt% to 4.0 wt% were made amorphous by rapid cooling.
[0025]
When this was annealed at 1150 K, the smaller the amount of B added, the larger the amount of graphite precipitated, and the larger the amount of B added, the smaller the amount of graphite precipitated. In the 4.0 wt% sample (g), cementite and Fe It became a -B compound, and precipitation of graphite was hardly seen. The precipitated graphite was fine with an average particle size of 1 to 2 μm, was uniformly dispersed in the ferrite structure, and agglomerated and coarsened with the progress of annealing. This tendency is the same even when C is changed. In the case of an Fe-C alloy, the same effect is observed at 2.0 to 7.0% by weight. In the Fe-Si-C alloy, C is 2 Similar effects were observed at 0.0 to 7.0 wt% and Si at 1.0 to 2.5 wt%. When the amount of C is large, it is preferable that the amount of B is large. In the above case, the balance is Fe and inevitable impurities.
[0026]
In addition, Fe; 92.6% by weight, C; 3.5% by weight, Si; 2.7% by weight, P: 0.1% by weight, Mn: 0.07% by weight, B: 1.3% by weight %, The hardness of the arc-melted master alloy (non-amorphous state) was Hv 423, but the amorphous part was examined and the hardness of the amorphous part was examined. Shows high hardness. When this was annealed at 1000 ° C. to precipitate graphite, it softened with Hv 312 and showed almost the same hardness as the mother alloy. The tendency was the same even when C was changed.
[0027]
FIG. 1 shows the annealing of the amorphized cast iron ribbon in the example, which is based on the crystallization behavior analysis method. The horizontal axis represents the annealing temperature, and the vertical axis represents DSC mJ / S. In this graph, a structure relaxation peak is reached at 558.6K, followed by a nanocrystallization peak at 782.4K. Thereafter, precipitation of graphite starts around 900K, and ferrite formation of the metal structure proceeds. Graphite precipitation is completed at around 1050 K, and thereafter graphite agglomeration and crystal grain growth occur.
[0028]
Next, product examples using the alloy of the present invention will be described. FIG. 2 shows a cylindrical member (1) used for a bearing, for example, and FIG. 2 (a) shows a pressure-compression-molded powder of the alloy of the present invention. The powder is sufficiently fine and the whole is amorphous. When this is annealed, fine graphite (2) is precipitated through the structure relaxation as described above, and by impregnating this with a lubricating oil, for example, an excellent bearing can be obtained. Further, when the annealed member is used as it is, the fine graphite (2) (12) exhibits a vibration absorbing ability, and thus functions as a vibration absorbing member for a musical instrument or an acoustic device, for example.
[0029]
In this case, since the fine graphite (2) is precipitated in a dispersed state, the graphite (2) is distributed throughout the conventional growth type oil-impregnated bearing (1 ') shown in FIG. 2 (c). The large flake graphite (2 ′) precipitated vertically and horizontally does not work as a defect such as a crack, and the lubricity can be improved, but the strength is not lowered. Therefore, it can be used sufficiently even in places where heavy loads are applied. On the other hand, in the case of FIG. 2 (c), the flake graphite (2 ′) becomes a defect as described above and causes a decrease in strength, and is not suitable for a portion where a heavy load is applied.
[0030]
FIG. 3 shows the case of the plate member (10). When the amorphous plate member (10a) is used as it is, it is used for wear resistance or corrosion resistance. (FIG. 3 (a1)) (FIG. 3 (b)) shows the case where the nanocrystal (11) is crystallized by annealing this, and this plate-like member is indicated by (10b). When further annealed to precipitate fine graphite (12) in the ferrite crystal (13) in a uniformly dispersed state, it is used as a member (10c) like a sliding plate as described above. (Figure 3 (c))
[0031]
Also, the laser beam is applied to all or necessary portions of the surface of such a member (10c) or a plate-like material (10d) (12a) obtained by further annealing and agglomerating graphite (12a). Then, when only the irradiated part is melted and quenched, the quenched layer (14) becomes amorphous. Thereby, it is possible to obtain a member (10e) in which only the irradiated portion is in an amorphous state. (FIG. 3 (e)) Only the surface layer can be melted by high-frequency induction heating or the like in addition to laser irradiation. In the case of the plate member (10), it is manufactured by a method such as casting, powder metallurgy, single roll method or twin roll method, and in the case of the cylindrical member (1), it is manufactured by powder metallurgy.
[0032]
The alloy powder used in the powder metallurgy is melted at the same time as the atomization method or by spraying molten liquid droplets onto an umbrella-shaped rotating roll, and at the same time, cooled at a speed equal to or higher than the critical cooling rate. A fine amorphous alloy powder is obtained.
[0033]
【The invention's effect】
According to the alloy of the present invention, by adding 0.2 to 3.0% by weight of B, it can be brought into an amorphous state when rapidly cooled, and by annealing this, fine graphite is precipitated in the ferrite structure. For example, a good oil-free bearing, a sliding plate, or a vibration absorbing member can be obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing a state change when an alloy of the present invention is annealed. FIG. 2 is a perspective view when the alloy of the present invention is formed into a cylindrical shape. FIG. 1 (a) is a case where the surface is an amorphous layer. (B) is a state where the amorphous surface layer is crystallized and fine graphite is deposited at the same time, and (c) is a conventional flake graphite next-morrow type oil-impregnated bearing.
FIG. 3 is a perspective view when the alloy of the present invention is used as a plate member, (a1) is a plate member in the whole or amorphous state, and (a2) is a plate member formed by solidifying the alloy powder of the present invention. (b) is a state where the plate member of (a1) is annealed to crystallize nanocrystals, (c) is a state where further annealing is performed to finely disperse fine graphite in the ferrite crystal, (d) When this is further annealed to grow graphite and ferrite crystals, (e) is melted by irradiating the surface of the member of (d) with a laser, and when this molten layer is rapidly cooled to an amorphous layer, (f) is a case where this is further annealed to decompose the amorphous layer and cause fine graphite to disperse and crystallize in the ferrite layer.
[Explanation of symbols]
(1)… Cylindrical member
(2) (12) ... fine graphite
(10) Plate member
(10a) ... Amorphized plate member
(10b) ... Plate-shaped member crystallized from nanocrystals
(10c): A plate-like member in which fine graphite is annealed and precipitated in a ferrite crystal in a uniformly dispersed state
(10d): Plate member when graphite is further aggregated and coarsened by annealing
(10e)… A plate-like member in which only the irradiated part is in an amorphous state
(10f) ... Plate-shaped member where necessary parts are made amorphous
(10a1) ... Powder metallurgy member

Claims (4)

C is 2.0 to 7.0% by weight, B is 0.2 to 3.0% by weight, Si is 1.0 to 2.5% by weight, and the balance is Fe and inevitable impurities. An Fe-Si-C-based amorphous alloy, characterized in that fine graphite having an average particle size of 1 to 2 [ mu] m is formed in a metal structure.   An Fe-Si-C amorphous alloy characterized in that at least the surface layer of the alloy according to claim 1 is amorphized.   A powder metallurgy member formed of the alloy powder according to claim 1.   A powder metallurgy member, wherein at least a surface layer of the alloy powder according to claim 3 is amorphized.

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