JPH02111802A - Manufacture of green compact by using powder having super plastic function - Google Patents

Abstract

PURPOSE:To manufacture a precise green compact having high density by giving super plastic function in powder manufactured with water atomizing method and compacting this powder with a super plastic compacting mold. CONSTITUTION:Components of base alloy powder are designed so as to obtain the composition showing high strength and high toughness and this powder is manufactured, for example with the water atomizing method. For example, Fe-Cu alloy powder having the super plastic function is mixed with this base alloy powder and compacted in the super plastic expressing range of the Fe-Cu alloy. Then, as the temp. of condition of the super plastic deformation is low, the condition of the base alloy powder, in which the components are designed to the aimed strength and toughness and the structure is controlled, can be held as it is and the precise green compact is obtd. at high density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a technology for manufacturing high-density, precise molded sintered parts using powder having superplastic functionality.

[Conventional technology] Powder metallurgy technology has the following characteristics compared to the case of using bulk solid materials: ■ It improves the machining yield of the material and significantly reduces the cost required for machining; ■ It is less complex. It has the following advantages: 1. It is particularly advantageous for molding high-melting point metals.

Regarding the strength of sintered parts, especially toughness, density (relative density)
is the most effective parameter.

Therefore, when considering sintered parts, the first technical issue is how to manufacture a molded body with a high relative density in a light process.

Conventionally, methods for obtaining high relative density include high-temperature sintering using interdiffusion and liquid phase sintering.
sintering), activated sintering method (acti
There is a vated interring method, a high interpolation method, or a HIP method.

Among these methods, the sintering method processes the molded product at a high temperature of over 1,000°C in the case of steel powder, so (1) grain growth occurs; (2) individual atomized products have The excellent microstructure is destroyed.

(3) There are many problems inherent in high-temperature sintering, such as difficulty in controlling the microstructure (4) and (4) limitations in controlling the dimensions of molded products for high-temperature processing. .

On the other hand, the high-temperature forging method or the HIP method is an excellent method for obtaining a high-density molded product, but the cost of the mold is high, and the latter requires high-pressure gas atmosphere, making it difficult to run. High cost.

Furthermore, due to the high temperature, there is a problem similar to high-temperature two-component sintering.

[Problem to be solved by the invention] The compression molding process of powder at high temperature is 1III81/? This is thought to be caused by the degree of plasticity yTa of the powder f.

In general, the phenomenon of work hardening due to plastic f-shape is caused by the change J[
This is 1-+F-17 as a cohesion in which the motion resistance of the dislocations increases due to the phase n action between the dislocations formed inside the crystal as a result of a. The deformation resistance of powder to compression molding is also determined by the resistance to motion of dislocations.

A special case of high l-crystalline deformation is Tfl plastic deformation. Super □□□ properties are 2F+1 (precipitates) that are stable with respect to ζ grade when the material has an equiaxed fine grain structure.

This is a phenomenon in which abnormal ductility occurs under low stress at the temperature (relatively low temperature) and deformation rate specific to Amazara-1 when two phases (such as one phase when α and γ2 coexist) coexist.

Is there any material that has shown superplasticity so far? However, in the case of steel materials, abnormal large deformations due to ultra-r properties such as thermal shock and Knob are avoided before designing machines and structures, and therefore steel materials are As for the material, 5
'4 Partly because the superplastic phenomenon was understood from the perspective of how to prevent Tsunenobu's problems and how to deal with strength loss, there were few steel materials in the form of fine-grained superplastic alloys, and it was not possible to put them into practical use. There's nothing inside. Furthermore, there is no technology that utilizes the superplastic properties of the powder itself, and there are no reports that directly prove the superplastic behavior of the crystal grains of the powder itself.

The object of the present invention is to provide a new powder molding technology that applies this superplastic phenomenon.

[Means for Solving the Problems 1] The present invention is a powder metallurgy method that applies superplasticity, and takes a first-order method.

(a) Making a molded body using powder with superplastic function
1 Neutral compression molding.

(b) Powder produced by a water atomization method or the like is post-treated to impart superplastic functionality, and a molded body is produced using the powder by superplastic compression molding.

(cl) Fine powders such as metal carbides, metal nitrides, or fine ceramic powders are mixed and added to the H material which has a superplastic function, and molded by applying the wettability and superplastic flow of the five materials. Compression mold the body.

(d) An alloy powder whose components are designed to have high strength and high toughness is produced, a powder having a superplastic function is added and mixed with the alloy powder, and the added powder is compression molded in the superplastic expression region.

(e) Compression molding is performed using iron powder or alloyed copper powder whose composition is designed to have high strength and high toughness and plasticity as a binder, using superplastic powder other than iron-based alloy as a binder.

(f) Further, a diffusion annealing process is added after the molding process in (d) or (e) above.

(g) Molding using a powder in which the densification rate ρ of the powder is in the formula, D has a value close to the grain boundary self-diffusion coefficient of the powder, and n = 0.35 to 1.0. Compression mold the body.

However, ρ: Densification rate of powder ε: Strain rate during compression molding 2: Material constant ρ: Relative density P^: Added stress E It consists of information on superplastic forming methods using knowledge and its properties.

In this case, if the raw material powder (5 particles) itself has a superplastic function, the superplastic function is used to mold. An alloy powder exhibiting superplasticity is mixed with six metal powders or alloy powders that do not have a superplastic function, and molded using the superplastic function of the mixed and added superplastic powder. A non-iron-based superplastic powder is used as a binder for iron powder or alloy steel powder, and solid phase bonding is performed by utilizing its superplastic function.

As described above, the following advantages can be obtained by molding using a powder having a superplastic function.

(b) The pressure required for molding is reduced, reducing the cost of molds.

C) Plastic flow becomes Newtonian viscous flow (Newt, oni)
Since it is close to a viscous flow, the pressure transmission function is improved and more delicate precision molding is possible.

The superplastic behavior of powder will be explained in detail below.

In general, the deformation stress (0) of a superplastic material is determined by the strain rate (temperature,
It is expressed as m > 0.3.

Note that m≦0.25 for the RB material.

FIGS. 1 to 5 show the relationship between the densification rate ρ, that is, the strain rate ε, of various materials and the effective compressive stress of zero.

Figure 1 shows water atomized 1.2% C steel powder, Figure 2 shows water atomized 2.0% C steel (this steel is superplastic even in bulk), Figure 3 shows 2.0% C-0, 5% M low ■, 5% C
r-0.02%Mo steel, Figure 4 shows 1.5%-Ni-1,
It is a graph of 0% P alloy steel. Note that FIG. 5 is a graph of reduced pure iron powder.

Figures 1 to 4 all show m = 0.4 to 0.33 (1
/ m = 2.5 to 3.0), indicating that the steel powders in Figs. 1 to 4 are compression-molded by superplasticity. The stress index m of reduced pure iron powder in Figure 5 is 0.
．． 25 (1/m = 4.0) and has no superplasticity. Although not shown in the figure, steel powder with a composition that exhibits superplasticity in the bulk material, for example, steel powder with H3LA steel composition, copper powder of high-speed composition steel Fe-(10-20)%Mn steel powder Fe-4%Ni -3%Mo -1,6%Ti steel powder Fe
-50% Cu steel, steel powder alloy powder, N1 alloy powder, Sn alloy powder, etc. all exhibited superplastic behavior during the hot compression molding process. From the above, it can be seen that materials that exhibit superplasticity in bulk also exhibit superplasticity in powder form.

Also, from the results shown in Figures 1 to 4, the densification of the powder...
... (2) However, ρ, powder enrichment rate ε, strain rate in the compression mold are 2. Material constant ρ: relative enrichment PA - added stress E, Young's modulus n in case of superplastic powder is 1.0 ~ 3.0 D=Dgb: Lattice self-diffusion coefficient rr'i (has activation energy for grain boundary diffusion) For powders that do not exhibit superplasticity, n: 3.0 to 5.0 D=DL: Lattice self-diffusion It is described by the coefficient ((has the activation energy of δ ion diffusion).

That is, in Equation (2) of -F, the activation energy for deformation during the compression process of the target powder is close to that of grain boundary diffusion, and the stress index Rn is in the range of 1.0 to 3.0. is a superplastic powder.

Next, a molding method using superplastic metal powder and alloy powder will be described in detail.

First, a case will be described in which a raw material powder having superplastic function is used. In this case, compression molding can be done as is, but as an advanced application, hard fine powder (har
There is a dispersion strengthening method using d fine powder 6 In other words, WC, T
i By mixing fine powders such as C, Cr carbides, N compounds, Nb compounds, or fine ceramic powders and molding them using the wettability of superplasticity, it is possible to disperse these hard fine powders in the matrix. It is possible to strengthen the dispersion by using hard fine powder.

Next, a method of superplastic compression molding by mixing an alloy powder having a superplastic function with an alloy powder will be described. A master alloy powder is designed to have a composition that exhibits high strength and high toughness, and is prepared by, for example, a water atomization method. For example, FeCu alloy powder having a superplastic function is mixed with the Konoke alloy powder, and compression molding is performed in the superplasticity expression region of the Fe-C14 alloy. Since the temperature under superplastic deformation conditions is low, the state of the bamboo alloy powder, which is designed for M minutes and whose structure is controlled with the aim of strength and toughness, is preserved as it is. Furthermore
Diffusion annealing may also be performed at relatively low temperatures, in which case greater densification is achieved.

Next, a case will be described in which compression molding is performed using iron powder or alloy steel powder whose composition is designed to have high strength and high toughness and plasticity as a binder, and a superplastic powder other than an iron-based alloy as a binder. In this case as well, the temperature of the superplastic deformation condition is low, similar to the method of mixing alloyed steel powder with superplasticity with alloy powder and forming it into superplasticity. will be saved as is. Furthermore, by diffusion annealing with low l crystal, the - layer can be made denser.

[Example 1 Example 1 Pre-compression materials were manufactured using water atomized 1.6% C steel powder and commercial reduced pure iron powder, each having a relative density of 60% at room temperature, and these were h 7H degree 650
FIG. 6 shows the change in relative density when compressed under a load of 400 kg f/crn'. In this case, while the reduced pure iron powder is compressed to a relative density of only about 80%, it was possible to achieve a relative density of 100% of the water atomized 1.6% C steel powder.

In this case, the activation energy for the 1.6% C steel powder type is about 170 kJ/mo+, which is equal to the value of grain boundary diffusion of iron, and the stress index n = 2. 5
The activation energy for deformation of reduced pure iron powder was 260 kJ/mol, which was equal to the value of iron lattice diffusion, and n = 4.0.

Example 2 Figure 7 shows water atomized steel powder A (C = 1.5% by weight, 5% by weight).
i=0.3% by weight, Mn=0.5fftm%, Cr=1
．． 5fffffi%, M o = 0.02 Ichikawa%, m
= 2.5 and water atomized steel powder B (C2O11
mu%, 5i=0.3ffiu%, Mn=0.1 Ichikawa%
, Cr=0°5 layer%, m=4.0) at temperature 7
At 00°C, strain rate IQ/s from load 0 to 1.5 tons
The change in relative density with respect to compression load when compressed by EC was reduced.

It has been shown that steel powder A exhibiting superplasticity easily reaches a high density compared to steel powder B. Note that the activation energy Q for deformation of steel powder A was +80 kJ/mol, which was close to the value of grain boundary diffusion of iron, and n = 2.5. In contrast,
Steel powder B has Q=275kJ/mo1. n=4.0.

[Effect of the invention 1 The temperature of conventional sintering is 700 to 900°C, and the punch pressure at that time is 100 to 150 kg/rnrr? (1
0-15j/crrr'). 600~700°C
In this case, it becomes 20t/c. On the other hand, in the case of superplastic compression, molding can be performed at 700℃, 2t/c or less,
The molding load is 115 or less.

In addition, the quality of one product also decreases by more than 100°C. Therefore, the running cost and manufacturing cost of the die are reduced, and the plastic flow becomes close to Newtonian flow, resulting in a high pressure transmission function, making it possible to perform fine precision molding that was impossible with conventional methods. Ta.

[Brief explanation of the drawing]

Figures 1 to 5 are graphs showing the relationship between strain rate and compression load during compression molding of various powders, Figure 6 is a graph showing changes in relative density, and Figure 7 is a graph showing the relationship between load and relative density. This is a graph. ρ・Relative density (ratio of green compact density to bulk density) DL=Lattice self-diffusion coefficient Dgb: Grain boundary self-diffusion coefficient pA・Additional load E: Young’s modulus ρ=Relative density change rate

Claims (1)

[Scope of Claims] 1. A method for manufacturing a compression molded body, in which the molded body is manufactured by superplastic compression molding using powder having a superplastic function. 2. A method for producing a molded body, in which a powder produced by a water atomization method or the like is post-treated to impart a superplastic function, and a molded body is produced using the powder by superplastic compression molding. 3 Add fine powders such as metal carbides and metal nitrides or fine ceramic powders to a mother powder with superplastic function, and apply the wettability and superplastic flow of the mother powder to form a molded body. A method for manufacturing a molded body by compression molding. 4. Manufacture alloy powder whose composition is designed to have high strength and high toughness,
A method for manufacturing a molded body, which comprises adding and mixing a powder having a superplastic function to the alloy powder, and compression molding the mixed powder in a region where the added powder exhibits superplasticity. 5. The method according to claim 4, wherein the mother powder is iron powder or alloyed steel powder whose composition has been designed to have plasticity that exhibits high strength and high toughness, and compression molding is performed using superplastic powder other than iron-based alloy as a binder. 6 Claim 4: A diffusion annealing process is added after compression molding.
or the method described in 5. 7 The densification rate of the powder ■ is expressed by the formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ where D has a value close to the grain boundary self-diffusion coefficient of the powder, and n = 0.35 to 1.0. A method for producing a molded body, comprising compression molding the molded body using a powder showing the following. However, ■: Powder densification rate K_2: Material constant ρ: Relative density P_A: Added stress E: Young's modulus