JPH01252701A - High alloy steel powder for powder metallurgy having excellent compressibility and formability - Google Patents

Abstract

PURPOSE:To obtain alloy steel powder for powder metallurgy having high Co and excellent compressibility and formability and being suitable to raw material for heat resistant sintered alloy steel by mixing the specific composition of high Co alloy steel powder and alloy steel powder having high Mo and W contents. CONSTITUTION:By mixing water atomizing powder of the alloy steel composing of 10-36wt.% Co, 0.2-20wt.% Ni+Cu, <=0.15wt.% Mo+1/2 W and the balance Fe with impurities of C, Si, Mn, P, S, O, etc., and water atomizing powder of the alloy steel composing of 0.2-19wt.% Mo+1/2 W. <=2wt.% Co+Ni+Cu and the balance Fe with little content of impurities, the mixed powder of the alloy steel having composition composing of 3-25wt.% Co, 0.2-10wt.% Ni+Cu, 0.2-15wt.% Mo+1/2 W and the balance Fe with little content of impurities is manufactured. The mixed powder is the alloy steel powder for powder metallurgy having excellent compressibility and formability, and it has excellent characteristic as the raw material for the heat resistant sintered alloy steel.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a high-alloy steel powder containing cobalt gold, which is used when manufacturing heat-resistant sintered alloy parts etc. by a powder metallurgy method. It has improved moldability.

<Prior Art> Sintered alloy steel is widely used in automobile parts and the like, and recently the number of parts with high alloy compositions has also increased. Heat-resistant parts are used in important applications, such as exhaust-side valve seat rings for automobile engines.

These heat-resistant parts often use Co as an alloying element, for example, 6.5% (weight %, hereinafter pJ) Co
The raw material is alloy steel powder containing In order to improve heat resistance, it is often necessary to add a larger amount of Co. A sintered alloy steel containing =25% Co is being considered. When the Co content exceeds 7%, the steel powder particles in conventional pre-alloyed steel powders become hard, resulting in deterioration in the compressibility and formability of the copper powder, which poses a major problem in the manufacture of parts. On the other hand, if parts are manufactured using the so-called mixed powder method by mixing iron powder and powder of an alloying element, such as Co powder, it is possible to achieve uniform diffusion alloying during wall sintering without any problems in compressibility of the powder. ,Co
If such a fine powder is used, the flowability of the powder is poor, the moldability is extremely deteriorated, and the problem arises that the green compact frequently has missing parts.

In order to solve these problems, a method called the master alloy method in which a Fe-Co alloy with a higher Co content is mixed with pure iron powder etc. has been considered, and a similar technology was developed in the Japanese Patent Publication No. 61-3.
As also seen in No. 6043, there has been no master alloy method with an excellent composition including additive elements other than Co.

By the way, the element used in heat-resistant alloy steel, which is an ingot material, is C.
o, Cr+ st, Mo, V, etc. However, in the case of powder metallurgy, if difficult-to-reducible oxides are formed in the process up to sintering, they will not be reduced and will deteriorate the quality of the parts, so easily reducible elements are Co, Ni+No, etc. are preferred and often used. Here, part of Ni is equal weight of Cu, and M
A part of o can be replaced with twice the weight of W. Currently, the composition often considered for sintered steel is C.
o: 3-25%, Ni: 0.2-10%.

Mo: 0.2 to 15%. When Cu or W is included, Ni can be replaced with Ni+Cu (representing the sum of Ni content and Cu content, the same applies hereinafter), and
1) o can be replaced with Mo+%W (representing the sum of Mo content and W content A, the same applies hereinafter).

<Problems to be Solved by the Invention> In view of these circumstances, the present invention provides an alloy containing alloying elements in such a composition range, with a Co content ranging from 3 to 25%, and having excellent compressibility and formability. It provides steel powder.

<Means for solving tlM> In the present invention, Co: 10 to 36%, Ni+C
u: 0.2-20%, Mo+! '4w: 0
．． Alloy steel powder with a composition range containing 15% or less and the balance consisting of Fe and unavoidable impurities, and Mo + % W:
0.2-19%, Co+Ni+Cu: 2% or less, and the balance is Fe and unavoidable impurities.Pure iron powder for powder metallurgy can also be mixed if necessary. Its average composition is co=3~25%, N
i+Cu: 0.2-10%, M.

+1/2W: Q, in the range of 2 to 15%, the remainder being Fe
This is a high-alloy steel powder for powder metallurgy that has excellent compressibility and formability, and is characterized by consisting of unavoidable impurities. However, Ni+Cu is the sum of Ni and Cu content, Mo+1/
2W is the sum of Mo content and half of ~V content, Co+
Ni+cu is the phase representation of the content of Co, Ni and Cu, respectively.

For Kusaku Hereinafter, the basis of the limited scope of the present invention will be explained in detail.

First, the Co1) of the 1st m powder is set to 10 to 36%. This is because, as shown in the examples below, when the final composition is set to -, the compressibility and formability of the mixed alloy steel powder are optimal. It has been selected in order to Given the final composition, 1) 1
) If the Co content of the powder is less than 10%, the blending ratio of the second W4 powder, which is softer than the first 81 powder, will inevitably be smaller, resulting in poor overall compressibility and moldability. On the other hand, Co is 3
If it exceeds 6%, the 1st m powder itself becomes too hard,
This also causes deterioration in compressibility and moldability. A suitable range is 10-36%.

The amount of Ni+Cu in the first steel powder is 0.2 to 20%.

! The lower limit of li+cul is automatically determined to ensure the lower limit amount of Ni+Cu in the final sintered material. The upper limit is
Like Co, it is defined as a range that improves compressibility and moldability.

It is basically desirable that the cuprous powder does not contain Mo or W. This is based on the findings of the inventors' studies and is an important point of the present invention. That is, M
O and W do not significantly impair compressibility or formability even when alloyed with iron powder, but when Co, Nl, or Cu coexist, their deterioration is markedly significant due to the synergistic effect. It will become.

In the examples described later, the appropriate range will be specifically shown as data, but the upper limit amount of Mo+y2W in the first steel powder is 0.15%.
It is. If this value is exceeded, the compressibility and moldability will be significantly reduced.

In the present invention, as described above, the content of Mo and W in the first steel powder is limited as much as possible, and the second copper powder is made to contain Mo and W. Second
Mo-1-zW in the steel powder is 0.2 to 19%.

This lower limit is necessarily established in order to ensure a lower limit amount of the final composition. Similar to Co and N++Cu of the first steel powder, the upper limit is given as a condition for not deteriorating the compressibility and formability of the mixed alloy steel powder as a whole. These are supported by specific data in Examples described below.

The second steel powder basically does not contain Co, Ni, and Cu for the same reason as the reason for limiting Mo and W in the first il powder. However, Co+Ni+Cu is 2%
Up to this point, it is acceptable because the negative effects are small.

The second form of the present invention includes, in addition to the first tR powder and the second steel powder,
This is a case where pure iron powder for powder metallurgy is further mixed. The advantage in this case is that the first Iil powder and the second Iil powder have a limited composition range.
1) Mixed alloy steel powder with various final compositions can be obtained by mixing powder with pure iron powder.

This pure iron powder for powder metallurgy can be obtained by an atomization method or by reduction of oxide scale.

Further, it is not necessary that the first steel powder and the second steel powder are each one type of steel powder, and two or more types of copper powder may be mixed and used within the respective composition ranges. A final steel powder can be obtained by blending one steel powder consisting of two types of steel powder and the second copper powder consisting of three types of copper powder.

The scope of the present invention also includes mixed powders in which stainless steel powder, graphite powder commonly used in powder metallurgy, and lubricants such as zinc stearate and stearic acid are added to these alloy steel mixed powders.

<Example> The ropes used in the examples were all made by pulverizing molten steel with a predetermined composition by water atomization, and heating it at 980°C in H2 gas for 30 minutes.
A final reduction of 1 minute was applied and used as a -80# particle size. All of the copper powders contained C: 0.002 to 0.002 as impurities.
016%, Si: 0.01-0.03%.

Mn: 0.05-0.32%, P: 0.
003-0.029%.

S: 0.006-0.026%, o:o, os~0
．． It contained 23%.

The pure iron powder used as the third powder in the method of the present invention was similarly used as -80# after water atomization and final reduction. Impurities are: C: 0.003%, 'Si: 0.01%, M
n: 0.06%l P: 0.008%, S:
It was 0.010%, o:o, o'y%.

Pre-alloyed steel powder for comparison was also procured using the same manufacturing method. In addition, in a comparative example using the conventional mixed powder method, the same atomized powder as above was used as the pure iron powder, Ni had an average particle size of 7 μm, Cu had an average particle size of 13 μm, Co had an average particle size of 5 μm, and Mo had an average particle size of 10
Single metal powders μ and W each having an average particle size of 9 μm were mixed with the above pure iron powder.

Table 1 shows the compositions of the steel powder of the example and the copper powder of the comparative example.

These copper powders contain 0.8% zinc stearate and graphite FA.
(average particle size 19μ) 0.5% and molding pressure 7t/
cj, diameter 1). 3ms, height 1). 3+m (71) was formed into a cylindrical shape, and the compressibility was evaluated based on the density of the green compact, and the formability was evaluated based on the Rattler value. The results are summarized in Table 2 together with the composition of the steel powder after blending.

Comparative example 1. Examples 1-4. Comparative Examples 2 to 4 are cases in which the final composition is Co %, Ni: 1.4%, and Mo: 1.4%. Figure 1 summarizes and shows these results.
When the Co content in one powder is in the range of 10 to 36%, the compressibility is good (high green density) and the formability is excellent (low Rattler value) compared to the conventional Brialloy method. Furthermore, compared to the mixed powder method, the moldability is significantly improved.

Examples 5 and 6. Comparative Examples 5 to 7 have a final composition of C.

: 8%, Ni: 6%, Mo: 2%. As shown in FIG. 2, the amount of Ni in the first steel powder is 0.2, which is within the range of the present invention.
It can be seen that when the content is 20%, excellent moldability and compressibility are obtained.

Example 7.8. Comparative Example 8.9 has a final composition of Co: 10%
, Ni: 3%, Mai 1%. As shown in FIG. 3, excellent compressibility and moldability can be obtained by suppressing the Mol in the first m product to 0.15% or less.

Example 9.10. Comparative Example 10.1) has a final composition of C.

This is a case of Ni: 4%, Mo: 8%. As shown in Figure 4, Mail in cupric powder is 0.2 to 19%.
If so, a product with excellent compressibility and moldability can be obtained.

Examples 1) to 13. Comparative Examples 12 to 15 have a final composition of C
This is a case where o: 22%, Ni: 9.5%, and Mo: 2.5%.

As shown in FIG. 5, Go + Ni + in the second steel powder
When the amount of Cu is kept within 2%, the overall properties of compressibility and moldability are improved compared to the conventional Brialloy method and mixed powder method.

Example 14.15. Comparative Examples 16 and 17 have a final composition of C
o: 8%, Ni: 1.5%, Cu: 0.5%, M
o: 1.5%.

This is a case of W: 2%. As is clear from Table 2, N
Even when a portion of i is replaced with Cu and a portion of Mo is rinsed with W, the method of the present invention provides better compressibility and moldability than the conventional method. In Example 15, as the third powder, 20 pure iron powder
%, but this also shows very excellent properties.

Example 16. Comparative Examples 18 and 19 have a final composition of Co:3
%, Cur: 1%, W: 2%. As can be seen from Table 2, even when the amount of Co is low, the effect of the method of the present invention can be fully seen.

Example 17 and Example 18 have the final composition of Example 14.
, 15. Similar to Comparative Example 16.17, the final composition was Co:
8%, Ni: 1.5%, Cu: 0.5%, Mo:
1.5%, W: 2%, but this is a case where the first W4 powder and the second steel powder are plural. In all cases, the effects of the present invention have been achieved.

Example 19. Comparative Example 20.21 has a final composition of Co:4
．． 5%, Ni: 1.5%, Mo: 14.5%, which is a case where the -〇 content is high. By controlling the Mo content of the second tlA powder to within 19%, high compressibility and moldability can be obtained.

<Effects of the Invention> As shown in the examples above, according to the present invention, compressibility and formability are superior to conventional ones not only in high Co1) compositions of 7% or more but also in Go&[l compositions of 3% or more. Significant improvement over Brialloy method and mixed powder method, Co: 3-25%,
Ni+Cu: 0.2-10%, Mo+1/
It is clear that for final compositions of 2 W: 0.2-15% very useful alloyed steel powders are provided.

[Brief explanation of the drawing]

Figures 1 to 5 respectively show the amount of Go in the first steel powder;
Ni amount in the 1st w4 powder, hO amount in the tm material, 2nd W1
This figure shows the influence of the amount of Mail in the fourth powder and the amount of Co+Ni+Cu in the second steel powder on the compressibility and formability of the mixed alloy steel powder. Patent Applicant: Kawasaki Steel Corporation Figure 1 M A Law Figure 2 M3 Master Alloy Method Figure 4 Figure 5 A Law

Claims (2)

[Claims] (1) Alloy steel powder with a composition range containing Co: 10 to 36%, Ni + Cu: 0.2 to 20%, Mo + 1/2W: 0.15% or less, and the balance consisting of Fe and inevitable impurities, in terms of weight percentage. , Mo+1/2W: 0.2-19% Co+Ni+Cu: A mixed powder with an alloy steel powder having a composition range of 2% or less, with the balance consisting of Fe and unavoidable impurities, with an average composition of Co: 3-25% Ni+Cu :0.2~10% Mo+1/2:0.2~15% High alloy steel powder for powder metallurgy with excellent compressibility and formability, with the balance consisting of Fe and inevitable impurities. . However, Ni+Cu is the sum of the content of Ni and Cu, Mo+1
/2W is the sum of the Mo content and half of the W content, Co+
Ni+Cu is the sum of the contents of Co, Ni and Cu. (2) Alloy steel powder with a composition range containing Co: 10 to 36%, Ni + Cu: 0.2 to 20%, Mo + 1/2W: 0.15% or less, and the balance consisting of Fe and unavoidable impurities, in weight proportions. , Mo+1/2W: 0.2-19% Co+Ni+Cu: 2% or less, the balance is Fe and unavoidable impurities, and the average composition is a mixed powder with alloy steel powder and pure iron powder for powder metallurgy. Co: 3-25% Ni+Cu: 0.2-10% Mo+1/2W: 0.2-15%, with the balance consisting of Fe and inevitable impurities. Excellent compressibility and moldability. High alloy steel powder for powder metallurgy. However, Ni+Cu is the sum of the content of Ni and Cu, Mo+1
/2W is the sum of the Mo content and half of the W content, Co+
Ni+Cu is the sum of the contents of Co, Ni and Cu.