JP2001262203A - High hardness gas spray shot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an average hardness and a variability of the same level as a powder for high-speed tool steel, which is obtained by spraying (blasting) or tempering a dummy even while gas spraying is performed, that is, An object of the present invention is to provide a high-hardness gas spray shot having an average hardness of 850 HmV or more and a variation in hardness of 50 HmV or less in standard deviation for use in spraying such as shot peening. SOLUTION: In weight%, C: 0.9 to 3.5%, S
i: 0.02 to 1.00%, Mn: 0.40% or less, C
r: 2.0 to 6.0%, Mo: 8.0% or less, W: 5.
0 to 30.0%, V: 4.0 to 8.0%, and Co:
5.0 to 15.0%, with the balance having a component composition consisting of Fe and inevitable impurities, the average hardness of the gas spray as it is is 850 HmV or more, and the variation of the hardness is 50 HmV or less in standard deviation. A high-hardness gas spray shot characterized by being present.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-hardness gas spraying shot, and more particularly to a high-hardness gas spraying shot used for blasting such as shot peening and shot blasting.

[0002]

2. Description of the Related Art In a spraying process such as shot peening or shot blasting, a shot having a rounded shape without sharp corners and a grit having an irregular shape and a sharp corner are used. Among these shots, those having a powder particle size of usually 32 to 500 mesh (45 to 500 μm) and having a hardness equal to or higher than that of the metal to be impacted are used.

Conventionally, shots of high hardness used for spraying include commercially available powders for high-speed tool steel (C: 2%, Si:
0.3%, Mn: 0.3%, Cr: 4%, Mo: 8%,
W: 9%, V: 5.5%, Co: 12%, balance Fe) or a component of this high-speed tool steel powder (hereinafter referred to as “high-speed tool steel powder”) to increase strength and increase the strength. What changed the component in order to harden was used.
This component change was to achieve high alloying such as high C, high W, high Mo, etc., since plastic working was not performed to produce gas spray shots.

The high-speed tool steel powder and the powder whose composition has been changed are usually produced by spraying a molten state with a gas such as Ar or air. Its hardness is 500-750HmV (10
gf), not so high, and the strength and hardness varied greatly depending on the particle size of the powder. This is because it is in a quenched state, the amount of γ phase having low hardness in the powder increases, and the cooling rate increases as the particle size of the powder decreases,
This is because the amount of the γ phase having a low hardness in the powder increases.

[0005] Therefore, in the gas atomized high-speed tool steel powder produced by atomizing with the above-mentioned gas and the powder in which the components are changed, the hardness and the strength are increased, and the hardness and the hardness due to the difference in the shot particle size are increased. In order to eliminate the variation in the strength, a dummy is sprayed once to increase the hardness and strength by forming a work-induced martensite at the time of collision, or it is tempered at 500 to 600 ° C. to obtain a residual γ.
Is decomposed to have high hardness and high strength to achieve a maximum hardness of 8
At 50 HmV or more, the variation was small.

[0006]

However, the above-mentioned conventional gas-sprayed high-speed tool steel powder and powder obtained by changing these components need to be subjected to a dummy spraying or tempering once after gas-spraying. It was troublesome and costly. The present invention has an average hardness and a variance similar to those of the gas-sprayed high-speed tool steel powder which has been subjected to the once-sprayed or tempered gas-sprayed high-speed tool steel powder, that is, the average hardness is 850 HmV or more. It is an object of the present invention to provide a high-hardness gas spray shot used for spraying processing, which has a standard deviation of 50 HmV or less when measuring 20 points.

[0007]

Means for Solving the Problems To solve the above problems, the present inventors have reduced the cause of generation of a large amount of residual γ, which reduces the strength and hardness of gas-sprayed high-speed tool steel powder and the like, and reduce the residual γ. After various studies on methods and the like, it was found that the amount of γ was large in the center of the powder,
The reason for the large amount is that the central part is solidified later, so that C, Cr, Mo, W, etc. are concentrated in the molten steel in the central part by segregation, and the concentration of C, Cr, Mo, W, etc. The increase in the amount of M is, as expected by the following equation (3), that the significant decrease in the Ms point leads to the amount of residual γ. When a large amount of V is added, it is combined with C in the molten steel and is more stable than the high temperature. In addition, a large amount of VC carbide having high hardness is generated, and as a result, the hardness increases due to the VC carbide, and the Cs in the matrix decreases, the Ms point increases, and the γ content, which is low in hardness, decreases. Was obtained. Ms (° C, wt%) = 545-330 x C + 2 x Al + 7 x Co-14 x Cr-13 x Cu-23 x Mn-5 x Mo-4 x Nb-13 x Ni-7 x Si + 3 x Ti + 4 × V + 0 × W (Formula 3) The present invention has been made based on these findings.

That is, in the high hardness gas spray shot of the present invention, the component composition is C: 0.9 to 3.5%, and Si:
0.02-1.00%, Mn: 0.40% or less, Cr:
2.0 to 6.0%, Mo: 8.0% or less, W: 5.0 to 2.0%
30.0%, V: 4.0 to 8.0%, and Co: 5.0
-15.0%, with the balance being Fe and unavoidable impurities, with an average hardness of 850 as a gas spray.
HmV (HmV at 10 gf, same in the present invention) or more, and the hardness variation is set to 50 HmV or less as a standard deviation at the time of measuring 20 points.

Further, in the high hardness gas spray shot of the present invention, the component composition is C: 0.9 to 3.5%, and Si:
0.02-1.00%, Mn: 0.40% or less, Cr:
2.0 to 6.0%, Mo: 8.0% or less, W: 5.0 to 2.0%
30.0%, V: 4.0 to 8.0%, and Co: 5.0
To 15.0%, with the balance being Fe and unavoidable impurities. When ΔC and ΔC are represented by the following formulas (1) and (2), V / Weq. ≧ 0.
30 and 0 ≧ ΔC ≧ −0.2 are satisfied, the average hardness of the gas spray is 850 HmV or more, and the variation of the hardness is 50 HmV or less as a standard deviation at the time of measuring 20 points. Formula: Weq. = 2 × Mo + W (Formula 1) ΔC = C− (0.06 × Cr + 0.063 × Mo + 0.033 × W + 0.2 × V) (Formula 2)

In the high-hardness gas spraying shot of the present invention, the V content is set to 6.0 to 8.0%.

[0011]

Next, the reasons for limiting the component composition and hardness of the high-hardness gas spray shot of the present invention as described above will be described. C: 0.9 to 3.5% C particularly combines with V to form a VC carbide, thereby contributing to high hardness and remaining in the matrix at the time of quenching at the time of melting and solidification. Since it contributes to high hardness by martensitization, it is an element contained for that purpose. 0.9% to get these effects,
Preferably, the content should be 1.5% or more.
If it exceeds 5%, preferably 2.5%, the Ms point decreases,
Since an increase in hardness cannot be expected due to an increase in residual γ,
The content range is set to 0.9 to 3.5%. The preferred range is 1.5-2.5%.

Si: 0.02 to 1.00% Si acts as a deoxidizing agent during smelting and is effective for controlling the amount and type of carbides during solidification. It is. To obtain these effects, it is necessary to contain 0.02%, preferably 0.15% or more, but 1.00%, preferably 0.1%.
If it exceeds 50%, stable and coarse M ₆ C carbides form a net-like solidified structure and become a starting point of powder destruction generated during spraying. Therefore, the content range is set to 0.02 to 1.00%. The preferred range is 0.15 to 0.50%.

Mn: 0.40% or less Mn acts as a deoxidizing agent at the time of melting, and is an element to be contained therein. However, lowering the Ms point prevents high hardness by martensitization. Because it does.
Its content is made 0.40%, preferably 0.3% or less.

Cr: 2.0-6.0% Cr is an element to be contained because, when quenched from the molten state, it dissolves in the matrix to improve the strength. To obtain this effect, it is necessary to contain 2.0%, preferably 3.0% or more, but if it exceeds 6.0%, preferably 5.0%, other carbides (MC, M
_{Since a} Cr-based carbide having a lower hardness than that of 6C) is formed, the content range is set to 2.0 to 6.0%. A preferred range is 3.0 to 5.0%.

Mo: 8.0% or less Mo is an element contained for forming stable and high-hardness M ₆ C carbides and increasing the hardness of gas spray shots. However, when the content exceeds 8.0%, preferably 5.0%, the crystallization temperature at the time of solidification is lowered to increase the amount of solid solution such as MoC in the matrix, and the residual γ content in the powder is increased. To soften by increasing the
The content is 8.0% or less, preferably 5.0%.

W: 5.0 to 30.0% W is an element to be contained because it forms a stable M ₆ C carbide similarly to Mo and increases the hardness of a gas spray shot. Forming the required amount of M ₆ C carbides,
In order to obtain the effect of increasing the hardness of the gas spray shot, it is necessary to contain 5.0%, preferably 10% or more, but if it is contained 30%, preferably 20% or more, WC is formed as a primary crystal during melting. System carbides, which make spraying from the nozzle difficult.
0.0%. The preferred range is 10.0 to 20.0%
It is.

V: 4.0-8.0% V forms a VC carbide which is stable up to a high temperature and has a higher hardness than other carbides, improves the hardness of the gas spray shot, and increases the matrix. It is an element to be contained for the purpose of making the amount of C therein suitable for producing martensite. 4.0 to get those effects
%, Preferably 6.0% or more,
If it exceeds 8.0%, VC carbides are crystallized from a high temperature and a nozzle used for producing a gas spray shot is blocked, so the content range is set to 4.0 to 8.0%. A preferred range is 6.0 to 8.0%.

Co: 5.0 to 15.0% Co does not form carbides and intermetallic compounds even in high-C steel, but forms a solid solution with the matrix to improve the hardness of the matrix. is there. In order to obtain these effects, it is necessary to contain 5.0%, preferably 8.0% or more, but 15.0%, preferably 1%.
If the content exceeds 2.0%, the effect is saturated and the cost increases, so the content range is set to 5.0 to 15.0%. The preferred range is 8.0 to 12.0%.

In the present invention, P: 0.050% or less, S: 0.030% or less, Cu:
0.25% or less, Ni: 0.25% or less, Al: 0.1
% Or less is acceptable.

V / Weq. ≧ 0.30 V / Weq. Is 0.3 or more, the type of carbide contained in the structure at the time of rapid solidification becomes a carbide centering on high-hardness VC, which contributes to the improvement of the overall hardness, so that V / Weq. Is set to 0.3 or more. An index represented by 0 ≧ ΔC ≧ −0.2 ΔC is an index indicating the amount of C remaining in the matrix. When the index is 0 or more, the amount of C in the matrix is large, and the amount of residual γ is increased. become,
On the other hand, when the value is less than -0.2, the amount of C in the matrix becomes insufficient, and it becomes difficult to secure the hardness of martensite in the rapidly cooled structure. Therefore, the amount of ΔC is made -0.2 or more and 0 or less.

The average hardness of the gas spray shot as it is sprayed is 850 HmV or more. The shot must have an average hardness of 850 HmV or more in order to spray a workpiece having high hardness, that is, most alloys. And its average hardness is 850 HmV or more. Standard deviation of hardness variation of gas spray shot: 50H
If the shot has a large variation in hardness and a large number of shots with low hardness, a predetermined effect is not obtained in the addition of blowing, so the standard deviation is set to 50 HmV or less.

Next, a method for producing a high-hardness gas spray shot used in the spraying process of the present invention will be described. The high hardness gas spray shot of the present invention is a method similar to the conventional high-speed tool steel powder of gas spray, for example, molten steel completely melted at 1500 ° C. or more by an induction furnace is allowed to flow down from a nozzle provided at the bottom of the furnace, It can be manufactured by blowing gas such as Ar gas onto the molten steel.

[0023]

Embodiments of the present invention will be described below. Example After steel having the composition shown in Table 1 below was melted in an induction furnace,
The molten steel at 1500 ° C. is caused to flow down from a nozzle provided at the bottom of the furnace, and the molten steel is blown with Ar gas to thereby reduce the temperature of the molten steel to 50 ° C.
kg gas spray shots were produced. This was classified using a 32 mesh sieve.

The γ content and hardness of the classified gas spray shots of 32 mesh or less were measured by the following methods. Table 2 below shows the γ content, the average hardness of 20 pieces, and the standard deviation. Method for measuring γ content α-200, α-211 and γ-22 by powder X-ray method
It measured using the integrated intensity ratio of 0 and (gamma) -311. Hardness Measurement Method The hardness was measured using a micro Vickers hardness tester under a load of 10 gf.

[0025]

[Table 1]

[0026]

[Table 2]

According to the results in Table 2, the example of the present invention shows that the residual γ
The amount was 36-76%, the average hardness was 850-945 HmV and the standard deviation was 9-40 HmV. Among the inventive examples, inventive example 3 had a relatively high C / V content and a large V / Weq., And thus had an average hardness of 945 Hm.
V showed the highest hardness, and the standard deviation was 9 HmV, which was the minimum. In addition, among the inventive examples, inventive example 7 had a large residual γ content of 76%, so that despite the large C and V contents, the average hardness was not so high as 880 HmV,
Further, the standard deviation was 40 HmV, which was the largest among the examples of the present invention.

On the other hand, according to the present invention, C, V and C
Comparative Example 1 having a low o content and a low ΔC and V / Weq. had a slightly large residual γ content of 58%, an average hardness of 727 HmV of 86% or less of the present invention, and a standard deviation of that of the present invention. It was 74 HmV of 185% or more. Further, Comparative Example 2 having a lower W / V content, a lower V / Weq. And a higher Mo content than the present invention has a residual γ content of 80%
612Hm having an average hardness of 72% or less of the examples of the present invention.
V, 151 HmV whose standard deviation is 378% or more of the present invention.
Met.

Comparative Example 3 having only V / Weq. Smaller than that of the present invention has the highest residual γ content of 90%, 731 HmV having an average hardness of 86% or less of the present invention, and a standard deviation of that of the present invention. It was 115 HmV of 288% or more. Further, the content of W, V and Co is smaller than that of the present invention, and V / Weq.
Comparative Example 4 having a small residual γ content was not as large as 55%, but had a small C content and a small content of V and the like.
4HmV, 60H with standard deviation of 150% or more of the present invention example
mV. Comparative Example 5, which contained only less Co than the present invention, had a residual γ content of as low as 52%, an average hardness of 842 HmV of 99% or less of the present invention, and a standard deviation equivalent to that of the present invention. .

Comparative Example 6, which has a smaller V / Weq. Than the present invention, has a large residual γ content of 77%, an average hardness of 784 HmV of 92% or less of the present invention, and a standard deviation of 1% of the present invention.
It was 78 HmV of 95% or more. As described above, the comparative example has an average hardness of 842 Hm lower than that of the present invention.
V or less, and the standard deviation was larger than that of the present invention except for Comparative Example 5 in which only the Co content was low.

[0031]

The high hardness gas spray shot used in the spraying process according to the present invention has an average hardness of 850 HmV or more even when gas is sprayed, and a variation of hardness of 50 HmV or less in standard deviation, even when the gas is sprayed. This is an excellent effect.

Claims (3)

[Claims] C .: 0.9 to 1% by weight (the same applies hereinafter)
3.5%, Si: 0.02 to 1.00%, Mn: 0.4
0% or less, Cr: 2.0 to 6.0%, Mo: 8.0% or less, W: 5.0 to 30.0%, V: 4.0 to 8.0%, and Co: 5.0 １５15.0%, the balance being a component composition consisting of Fe and unavoidable impurities, the average hardness as gas spray is 850HmV or more, and the variation of hardness is 50HmV or less in standard deviation. Characterized high hardness gas spray shot. 2. C: 0.9-3.5%, Si: 0.02
1.00%, Mn: 0.40% or less, Cr: 2.0-
6.0%, Mo: 8.0% or less, W: 5.0 to 30.0
%, V: 4.0 to 8.0%, and Co: 5.0 to 15.
0%, with the balance being the composition of Fe and unavoidable impurities. When ΔC and ΔC are represented by the following formulas (1) and (2), V / Weq. ≧ 0.3
High hardness gas spraying characterized by satisfying the conditions of 0 and 0 ≧ ΔC ≧ −0.2, and having an average hardness of gas spray of 850 HmV or more, and a standard deviation of 50 HmV or less in standard deviation. shot. Formula: Weq. = 2 × Mo + W (Formula 1) ΔC = C− (0.06 × Cr + 0.063 × Mo + 0.033 × W + 0.2 × V) (Formula 2) 3. The high-hardness gas spraying shot according to claim 1, wherein the content of V is 6.0 to 8.0%.