JPS60114555A - Sintered iron alloy and manufacture - Google Patents

Abstract

PURPOSE:To improve the strength and toughness by sintering prescribed percentages of Mo, Ni, Cr, Mn, Cu, C and Fe. CONSTITUTION:An alloy consisting of, by weight, two or more among 0.2-1% Mo, 0.2-2% Ni, 0.2-2% Cr and 0.2-0.7% Mn and the balance Fe is refined and powdered. This alloy powder is mixed with 1.5-4% Cu powder and 0.2- 0.6% C powder, and the powdery mixture is press-molded and sintered to obtain a sintered iron alloy having bainite as the principal structure. The sintered iron alloy has superior strength and toughness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present research relates to a high-strength and high-toughness iron-based sintered alloy and a method for producing the same.

In addition, there are methods for manufacturing iron-based sintered alloys with high strength and toughness, such as increasing the density and alloying by repressing resintering method, sinter forging method, etc., and changing the structure by further heat treatment. , these methods have a tensile strength of 7 Q Irg/tut
A sintered alloy of about 100% or more can be obtained. However, these methods require Lq complex steps and are expensive (the energy required for production is also greater than that of the conventional laminate method).

On the other hand, a sintered alloy with high surface strength and toughness can be produced by mixing iron powder with copper powder and graphite or boron powder, or by mixing copper powder with iron powder and graphite or phosphorus powder, and by just normal forming and sintering. However, the maximum tensile strength of the product obtained by this method is about 65 kg/mm.

Therefore, the present invention provides an iron-based sintered alloy that has a tensile strength of about 65 JT9/mX or more and has excellent toughness, and that processes this sintered alloy by re-ffM re-sintering, high-temperature sintering, and sintering. To provide a method for manufacturing by normal forming and sintering at a forming pressure of about 4 ton/c+J to 7 ton/cJ and a sintering temperature of about 1100° C. to 1160° C. without using means such as forging or heat treatment. The purpose is to

That is, the first iron-based sintered alloy provided by the present invention contains molybdenum (MO) 0.2% to 1.0% and nickel/L/(Nl) 0.2% to 2.0% as the first flammable component. 0%, chromium (
Cr) o, z% ~ 2.096, manganese (Mn) 0.2
Contains at least 2 yuzu of ~0.7%, and copper (Cu) of approximately 1.5%~4.0% as the second fire component,
This first sintered alloy is produced by high-temperature sintering by using a mixed powder obtained by mixing powder of the second pyrotechnic component with a low alloy powder containing the first pyrotechnic component and the remainder being substantially iron. , it can be manufactured by the above-mentioned normal molding and sintering without using any means such as heat treatment.

Further, the second iron-based sintered alloy provided by the present invention includes the same first sintered alloy and second sintered alloy as the first sintered alloy,
In addition to this, the WI tertiary component color is boron (B) 0.01%
~0.296, Molybdenum (MO) 0.1% ~
2.0%! J N (P) 0.1 96~0
．． 5%, the remainder is substantially made of iron, and has a structure mainly composed of bainite.

The second sintered alloy is produced by using a mixed powder obtained by mixing the second and third pyrotechnic components with a low-alloy powder that contains the first pyrotechnic component and the remainder is substantially iron. It can be manufactured by conventional molding and sintering.

Next, details of the present invention will be explained using the following examples in comparison with a conventional example.

lol example 1゜ The following three types of mixed powders were prepared.

(a) Fe-1,9% N'i -0,5% Mn alloy powder with 2% Cu powder, graphite powder'ii 0.5%
Added 0.8% zinc stearate as a lubricant
A mixture.

(b) Fe-1,040r-o, 23%MO-0.
654Mn alloy powder with 296% Cu powder and 0% graphite powder
．． 5% mixed and further added 0 zinc stearate as a lubricant.
．． 8% mixture.

These mixed powders were molded with a crushing force of 5 tons/c++f and then sintered at 1150° C. for 30 minutes to obtain a first sintered body of the present invention.

As a comparative material, a mixed powder (d) was prepared by mixing Fe powder with 20% of Cu powder and 14% of graphite powder, and further mixed with 0.896% of zinc stearate as a lubricant, and was molded and sintered under the same conditions as above. did.

FIG. 1 shows the tensile strength and elongation of the sintered bodies obtained as described above plotted against the density of the sintered body. In the figure, a, b.

(corresponds to the inside). Density and tensile strength are approximately 201"
9/knock 2 shows high value 'CC oshi, only 7.0 Q
/ c, J density at 90 Trt) / mm”
It has reached a high level of strength. Furthermore, the elongation was t7, which was comparable to that of the conventional product.

Implementation 1xl 2 t(No 3□1chi□fY powder is interfering with trade.

Light)' The amount of graphite powder mixed in the mixed powder (a) of Example 1 was 0.
．． 2': Transformed between Yy and 07%, and F
l t5) powder mixed with Q and 1%.

(a)' - B in the mixed powder of (a)< is mixed with 0.1% P in place of B.

(B Doten Example 14 + Mixed Powder (1)) 1.1.21
) The powder mixture amount was varied between 0.2% - 〇, 7%, and tAo was 0.9%r,! 4 go.

(L))//- (1) In place of MO in any of the mixed a powders, 0.1% of B was added.

(c) F'e-0,24% Ni, -0,21%Cr
-0,3096M0-0.40%Mn alloy powder with Cu
A mixture of 2% powder, 0.2% to 0.7% graphite powder, 0.8% zinc stearate as a lubricant, and 0.9% Mo.

(C) B in place of MO in the mixed powder of (0) above
A mixture of O and 1%.

A mixture of these six types was molded at a pressure of 5 tons/crl and then sintered at 1150°C for 30 minutes to produce a second sintered body of the present invention. FIG. 2 shows the relationship between the tensile strength and elongation of the sintered body and the amount of mixed graphite.

Although the trends differ slightly depending on the mixed powder used, in all cases, the tensile strength shows a peak with the addition of 0.496 to 0.5% graphite, and the peak value is 70ky/mt in all cases.
It far exceeds n2.

The elongation tends to increase as the amount of mixed graphite decreases in all cases, and shows a high value exceeding 1% at the amount of graphite where the tensile strength peaks. Among them, (a)' is an extremely strong alloy with a tensile strength of lOOkg/mx' or more and an elongation of 2%.

In addition, the molding pressure in the above example was 5 tons/c++t
However, if we take this into account, the tensile strength also improves, for example, if it is 6 on/cJ, then in Figure 2, if the tensile strength is relatively low, the graphite amount a' is 0.296, and the graphite amount is 0.296.
Even in the case of 3% C, the tensile strength is 65 kg/square or more.

FIG. 3 shows the tensile strength and elongation plotted against the density when the amount of B mixed in the alloy yarn (a) was varied. The amount of B is 0.06% for al and 0.08% for a.
LS, as is 0.04%.

Note that a is B-free (same as a in FIG. 1).

As explained earlier, the sintered body of the present invention indicated by a in FIGS. 1 and 3 has a tensile strength of 20% higher than that of the conventional product.
hy/mtn” is high, but as known from Figure 3, B
When only 0.06% of (al) is mixed, the tensile strength further improves by approximately 2Q try/m♂, and the sintered body density increases to approximately 7.
Q/c++! The tensile strength is l 201+y
/ mtn” and the elongation reaches 2%.

FIG. 4 shows the relationship between the amount of Cu and the tensile strength and elongation of the sintered body. In the figure, a4 is the mixed powder (a) used in Example 1, b4 is the mixed powder (b), and a4 is the mixed powder (a) used in Example 2.
Regarding a), the results of varying the amount of JtCu are shown. In both cases, the molding pressure is 5 ton/crl,
The sintering conditions were 1150°C and 130 minutes. In either case, the strength is maximum at Cuff of 12% to 3%.

Generally, in order to improve the strength of a sintered body, it is necessary to take into consideration three factors: (1) strengthening of interparticle bonds, (2) improvement of density, and (3) strengthening of the matrix inside the particles. Most conventional high-strength sintered bodies have focused on elements (1) and (2) among these elements. However, (18(
There is a limit to the strength that can be achieved with only the element 2). For this reason, recently, efforts have been made to mix M≦metal alloy components in iron powder, diffuse the alloy components into the interior of the iron powder through high-temperature sintering, and then perform heat treatment to satisfy element (3). There is a tendency.

However, this method of performing high-temperature sintering and heat treatment is extremely disadvantageous compared to normal sintering methods in terms of energy and productivity. In this way, in a mixture using pure iron powder, it is difficult to equalize the substitutional alloying elements (!j3, ψW).

・1 (The invention provides an iron-based sintered body that has a strong bainite as its main structure and has high product strength and resistance. When producing the sintered body, pre-alloyed powder is used. In addition to the fact that it is easy to homogenize the alloy components due to the wood quality, alloy powder has e-fail crystal grains compared to pure iron powder, so the diffusion of mixed Cu is much faster than that in pure iron powder. Coupled with the phenomenon of high speed, a uniform bainite structure can be formed even inside the particles during the cooling process after sintering, and the above (3)
) It has now become possible to fully satisfy the above requirements only by so-called ordinary sintering. Especially MOo, 2% ~ 2.096
, Ni 0.296-2.0%, Cr 0.2%-2.
0%, Mno, 24~O,'7% (in addition to U, graphite, B, lφO, P
Adding TeE'e -B-C, Fe-Mo-C,
A low melting point liquid phase mainly composed of Fe-P-C yarns is generated,
This promotes densification during sintering, making it possible to obtain a high-density sintered body. Since liquid AI4 sintering is used in this way, there is no need for high-temperature sintering.
Sufficient strength can be obtained by sintering at 100°C to 1160°C. Moreover, residual pores in the structure are made spherical by liquid phase sintering, and the strength of the interparticle bonds is also good. In particular, the effect when B is added is remarkable.

Next, regarding the content of each component, each component (M
o, Cr, , Ni, Mn) are determined by the above-mentioned reinforcement elements (
In order to satisfy 3), this is the minimum amount required to make bainite the main structure during cooling after sintering, and each upper limit is a limit that does not extremely reduce the compressibility of the alloy powder.

Further, the amount of Cu added is shown in FIG. 4, and as mentioned above, the strength is maximum at about 2% to 3%.

If it is less than 1.5%, the reinforcement of the bonded part of the particles will be insufficient, and if it exceeds 4%, the toughness and dimensional accuracy will decrease, so 1.5% to 4% is suitable. Graphite amount is 0.2%
If it is less than 0.6%, martensite will be the main structure, and if it exceeds 0.6%, martensite will be the main structure.
．． It needs to be in the range of 2% to 0.6%. 0.4%～
0.596 is optimal as seen in FIG.

Regarding the liquid phase forming components B, Mo, and P, as described above, B: 0.01% to 0.2%, MO:O,
1% to 2.0%, P:O, 1% to 0.596 are suitable sb, the lower limit of these is the minimum amount for densification of the structure during sintering, and the upper limit is the residual liquid This was determined in view of the decrease in toughness and dimensional accuracy associated with an increase in phase components.

Figure 5 shows a conventional sintered alloy using the mixed powder in Example 1, and Figure 6 shows an optical microscope assembly of the sintered alloy of the present invention using mixed powder in Example 2. This is a photograph showing the conventional material having a pearlite structure, whereas the present alloy has a uniform bainite structure.

Note that although a higher sintering temperature is advantageous for improving the strength of the sintered body, increasing the sintering temperature is not preferable from the viewpoint of energy saving and productivity. In the present invention, 1100°C to 1160°C
A high-strength sintered body can be obtained at the normal sintering temperature.

Iron-based sintered alloys are increasingly used in various fields such as vehicles and office equipment. In particular, it is widely used as automobile parts such as clutches and gears, and the parts used are required to be small and thin, and also to withstand high loads and are required to be strong. If the current sintered alloy has a pearlite structure as its main structure, it can be made denser by Ashion sintering, etc.
When changing the structure, heat treatments such as quenching and tempering are used to increase strength.

The present invention provides a sintered alloy with crystal strength and crystal toughness mainly composed of bainite, which is stronger than pearlite. The object of the present invention is to provide a manufacturing method that allows manufacturing without performing post-curing heat treatment, thereby meeting the above-mentioned current demands.

[Brief explanation of the drawing]

Figure 1 shows the tensile strength of the sintered alloy of the present invention and comparative materials.
Figure 2 is a diagram showing the relationship between elongation and density, Figure 2 is a diagram showing the relationship between tensile strength, elongation, and graphite content of the sintered alloy of the present invention, Figure 3 is a diagram showing the relationship between the tensile strength and elongation of the sintered alloy of the present invention, and Figure 3 is a diagram showing the relationship between the boron-containing ii'i□ sintered alloy of the present invention. Figure 4 shows the relationship between tensile strength, elongation, and density of the sintered alloy of the present invention; Figure 5 shows the relationship between the tensile strength and elongation of the sintered alloy of the present invention; Figure 5 shows the relationship between the tensile strength and elongation of the conventional sintered alloy. A photograph showing the mirror structure of the metal alloy (100
0x), 61st image 1 is a photograph (1000x) showing the optical microstructure of the glue of the present invention, ``L-Imakine optical microscope''.

Claims (6)

[Claims] (1) Molybdenum 0.2% by weight (hereinafter referred to as %) ~
1.0%, Nickel/l/0.2%~2. OtA, chromium 0.2%~2.0%, manganese 0.2%~O,'?
At least two of 96 and copper 1.5% to 4.096
A high-strength, high-toughness iron-based sintered alloy having a bainite-based structure, containing 0.2% to 0.6% of graphite, and the remainder substantially consisting of iron. (2) Molybdenum 0.2% to 1.0%, nickel 0.2
%~2.0%, chromium 0.2%~2.0%, manganese 0
．． 2% to 0.7% of at least two types of alloy powder, the balance being substantially iron, copper powder 1.5% to 4.0% and graphite powder 0.2% to 0.64 i A method for producing a high-strength, high-toughness iron-based sintered alloy, which comprises pressurizing and sintering a mixed powder mixture. (3) The method for producing a high-strength, high-toughness iron-based sintered alloy according to claim 2, wherein the sintering is carried out at a temperature range of 1.1 LOO''c to 1160°C. (4) Molybdenum 0.2% to 1.0%, nickel, +v
At least two of the following: 0.296-2.0%, chromium 0.2%-2.0%, manganese 0.2%-0.7%, copper 1.596-4.0% and graphite 0.2% to 0.6%, further boron 0.0196 to 0.2%, molybdenum 0.1%
A high-strength, high-toughness iron-based sintered material whose main structure is bainite, containing at least la Combined gold. (5) Molybdenum 0.2% to 1.0%, nickel 0.
Alloy powder containing at least two of 2% to 2.0%, chromium 0.2% to 2.0%, and manganese 0.2% to 0.7%, with the remainder being substantially iron. , copper powder 1.5%~4
．． 0% and graphite powder 0.2% to 0.6%, and further contains powder containing at least one of boron, molybdenum and phosphorus as a liquid phase forming component, converted into the amount of boron, molybdenum and phosphorus. Boron 0.01% ~ 0.296,
Molybdenum 0.196-2.0%, phosphorus 0.1%-0.
A method for producing a high-strength, high-toughness iron-based sintered alloy, which comprises pressurizing and sintering a 5% mixed powder. (6) The above sintering was carried out at a temperature of 1100°C to 1160°C.
A method for manufacturing a high-strength, high-toughness iron-based sintered alloy according to claim 5, which is carried out in a 11'L area.