JPS58126963A - Powdered high speed steel - Google Patents

Abstract

PURPOSE:To obtain a powdered high speed steel with remarkably enhanced wear resistance and strength by rapidly cooling a steel contg. MC type carbide of one or more among V, Nb and Ti by a powder metallurgical means to distribute the carbide at high density. CONSTITUTION:A steel contg. by weight, 1.8-3.3% C, 3.5-5% Cr, 7-11% W, 3-5% Mo, 7-10% Co, 0.1-0.6% Si, 0.1-0.6% Mn and 8-11% one or more among V, Nb and Ti and further contg. MC type carbide of one or more among V, Nb and Ti is melted and rapidly cooled by a powder metallurgical means to form a fine structure contg. the MC type carbide having <=2mum average grain size distributed at high density of <=2mum intervals. The MC type carbide is contained by 30-45% by area.

Description

Detailed Description of the Invention The present invention provides an MC type carbide that prevents coarsening of the structure, maintains high toughness, and exhibits high hardness by distributing MC type carbide in high-speed steel at high density. This invention relates to powder high-speed steel that has high wear resistance due to high density.

In recent years, the properties required of high-speed steel have become more severe, and it has become necessary to have the different properties of high toughness and high wear resistance. Under these conditions, many developments have been made in the production of high-speed steel by powder metallurgy techniques. When processed by powder metallurgy, the structure becomes fine and uniform, making hot working easier, and the toughness, grindability, cutting performance, etc. are also improved compared to high-speed steel made by conventional melting methods. Furthermore,
By using powder metallurgy techniques, it is now possible to produce high-speed steel with components that cannot be produced by melting methods. However, even under such circumstances, it is possible to obtain high-speed steel that has both extremely high wear resistance and high toughness, which are required for tools for interrupted cutting such as hobs and pinions. In particular,
From this perspective, the present inventors have developed an alloy composition that has been extremely difficult to manufacture due to costs arising from plastic working problems and the problem of reduced toughness due to iM alloying. As a result of repeated detailed research and experiments on and tissues,
By adjusting the amount and distribution of MC-type carbides in high-speed steel to a certain range, it is possible to prevent coarsening of the structure, maintain high toughness, and provide high wear resistance. We have discovered a high-speed steel that can be plastically worked, and have completed the present invention.

When high-speed steel is used as a cutting tool, it is usually quenched and tempered to strengthen the base material, and the remaining carbides provide wear resistance. In this case, the toughness of high-speed steel when it is rolled into a product, i.e. in service condition, is determined mainly by the roughness of the structure, the distribution of reinforcing dust and carbides in the matrix, that is, the size and shape of carbides, and the distance between carbides. I knew it was a mistake. In order to have high toughness, the structure must be fine and the carbides must be fine and uniformly distributed, and preferably have a round shape when rolled. Yet another condition is
As is generally known, the narrower the spacing between the carbides, the better the strength will be.Also, wear resistance is determined by the amount of carbide remaining.
In this case, the type of carbide is a major condition. In the case of high-speed steel, when it is exposed to a product, that is, in the state of use, M and C are large. In general, the elements that stably form MC type carbides in high-speed steel are represented by V, Nb, and Ti. However, MC-type carbides containing V, Nb, and Ti are found in steel and hardly change during heat treatment within the range of general heat treatment, and once MQ-type carbides are formed, they retain their shape and position. Next, we focused on the fact that %C6 or nMaCMC type carbides in steel hardly penetrate into the base material or precipitate during heat treatment, and hardly cause secondary coarsening. Furthermore, it was found that MC type carbides can be easily distributed finely, uniformly, and with high density by using a powder metallurgy method that uses a powder with an extremely fine structure by rapid cooling. These are the roots of the present invention.

That is, the present invention includes an MC-type carbide containing one of V, N'b, and Ti or two of these types.
When molded carbide is made into a product, it has an average particle size of 2 μm or less.
The MC type carbides are manufactured using raw material high speed steel powder with a fine structure by rapid cooling using a powder metallurgy method so that the distance between the MC type carbides is distributed at high density with an interval of 2 μm or less. The present invention provides a powdered high-speed steel characterized by the following. The powder high speed steel according to the present invention has improved wear resistance due to stable MC type carbides being distributed finely and uniformly in the steel at high density, strength increaser due to shortening of the distance between carbides, And stable maintenance of high toughness is obtained by maintaining fineness of the base material.
These effects cannot be obtained by conventional melting methods because they cannot be manufactured due to the segregation and coarsening of carbides.

The nfcMc-type carbide-all-carbide powder high-speed steel with uniform and high density obtained by the present invention exhibits the above-mentioned more favorable properties, dramatically improves the chipping resistance and wear resistance of cutting tools, and improves the tool life. became significantly longer.

To explain in detail, the particle size and carbide spacing of MC type carbides,
Focusing on the fact that MC-type carbides are hardly involved in general heat treatment, we developed conditions for stable microstructure. stipulated to obtain.

MC type carbide generally has a diameter of 0.2 in powder high speed steel.
Force ζ distributed in the range of ~4 μm When the average grain size exceeds 2 μm, the extraction and grinding properties deteriorate, and precision tools such as hobs and binions become extremely difficult to maintain dimensions and shape, which is economically disadvantageous. Is the spacing between 1hMe type carbides reduced by 2μmg on average?
When the MC type carbides are present, coarsening of the Mi weave is prevented, and the spacing between the carbides becomes narrower, making it possible to maintain high toughness. However, if the distance between the MC type carbides exceeds 2 μm'4 on average, the effect of maintaining toughness due to increased density of the carbides decreases, so the distance between the carbides was set to 2 μm or less on average. Next, the elements that form MC type carbides in high-speed steel and are commercially available at low cost are V, Nb, and Ti. However, when using elements other than these, the sintering conditions and The various conditions become complicated and impractical. Therefore, MC type carbide is V, N
l), Ti carbide or two or more of these
It is limited to use as a component.

Preferably, the area occupation rate of the MC type carbide is
If the average grain size of the MC type carbide is less than 2 μmJ-1 and the area occupation rate is less than 30%, the material to be cut will deteriorate the wear resistance of the substrate during cutting. . Therefore, in order to obtain the effect of improving wear resistance by increasing the density of MC type carbide, the area occupation rate of MC type carbide must be 30% or more.

When the area occupancy exceeds 45 inches, hot plastic working such as forging and rolling becomes impossible, and sufficiently forged powdered high-speed steel cannot be obtained, and the scope of use is limited, making economical practical application impossible. Since this would be difficult, the upper limit was set at 45 inches. Furthermore, MC
As mentioned above, when the area occupation rate of type carbide is 30% or more, fc
Even if elements that form MC type carbides other than V, Nb, and Ti are added, there is almost no effect over the above three elements,
More preferably, the powder high speed steel has a meaning.
The main component is Ol,s~3. a%, Ors,
s ~ s, o%, W7. O-1], o%.

MC3.0~5.0chi, 007.0~10.0chi; one type of V, Nb, Ti or two of these
The sum of types or more is 80 to 11.0% and the remainder ij Si0.
It is preferable that the content is 1 to 0.6%, Mno, t to 0.6%, Fe, and impurity Th. To explain in detail, C;
C is an indispensable element that not only dissolves in solid solution in the matrix and contributes to strengthening, but also combines with V, Nb, and Ti that form the entire MC type carbide, and serves as a matrix for high hardness carbides with high wear resistance. If the content is less than 1.88%, it will not be possible to obtain the necessary hardness and it will be impossible to distribute the MC type carbide in a high density, so it must be at least 1.8%. No. In addition, as will be described later, when looking at the relationship with the amount of alloying elements that form MC type carbides, 3.3% is necessary. However, if it exceeds 3.3%, hot working becomes impossible and , the sintering conditions also shorten the processing range and become impractical, so the upper limit of the amount of C added was specified as 33. Enter n
Some of it dissolves in the base material and strengthens the base material, improving hardness and heat resistance at high temperatures, but some remains and becomes MC.
It is an important component that supports the wear resistance of type carbides. If W is less than 7.0, the reinforcement of the base material will not be satisfactory and the strength and heat resistance of the base material will be insufficient. However, 11.0L
If it exceeds ib'z, it will have a more effective effect than that of a sore, and it will be economically expensive. However, when actually used as a cutting tool, the addition of MO has a greater effect on improving the hardenability of high-speed steel than strengthening the base material, and is effective in maintaining heat treatment hardness. It is. Therefore, it is not necessary to add a large amount of MO, and the lower limit is set at 3.0%, which shows the effect of improving hardenability, and the upper limit is set at 5.0% in consideration of economic efficiency. Effect of solid solution in all forming components'
*m'h, it is preferable to strengthen the base material and give heat resistance, or if it is added more than necessary, it will make the high speed steel brittle and reduce hot workability, so it is preferable to add more than 10.0 h. It's not right. However, unless it is deeper than 7.0ch, JMo and Or
Because the strength of the substrate due to the synergistic effect with
For C carbide type powder high speed steel, it is necessary to add 7.0.1 or more.

Cr: Cr is added to improve the hardenability and corrosion resistance of high-speed steel, but its effect is minimal at 35% or less. In addition, in the case of high-01 high-MO carbide-type high-speed steel as in the present invention, hardenability tends to be lower than that of high-speed steel with a viscous composition, so in order to obtain sufficient base hardness, 3.5% It is preferable to add more than 5.0%, but since adding more than 5.0% will result in unfavorable performance such as a decrease in impact resistance, the upper limit was set at 50% ◇ V, Nb, Ti MO coal making ( 1(/!, V, Nb
, Ti(r) carbide are representative examples, but for these carbides to be effective in the present invention, it is necessary to add 8.0% or more even as a component of iron, and less than 8.0% is necessary. , it is not possible to maintain the area occupancy of the carbide sufficient to maintain high wear resistance, and the effect of increasing the density of the MC type carbide cannot be obtained.

However, if MC-type carbide is produced in an unnecessarily large amount, the hot plastic workability will be significantly deteriorated, and furthermore, embrittlement will occur due to insufficient base material, so it is not preferable to add more than ut, o%. Therefore, O8i, Mn, which is limited to 80 to 11.0% even in the mixed addition state of two or more types of sono or nico, to the MO type carbide forming component;
The content was set at 0.1 to 0.6%, which is the range generally included as an i and MnH deoxidizing agent.

The high-speed steel of the present invention is manufactured by a powder metallurgy method, and the manufacturing conditions are characterized by using raw material high-speed steel powder with a microstructure for rapid cooling, and MC type carbide. There are no special restrictions other than selecting sintering conditions that do not cause the average grain size to exceed 2 μmf. That is, after annealing the atomized powder in a vacuum or atmosphere, it is compacted using a machine or OIP (cold isostatic press).
Vacuum or atmosphere sintering (sintering temperature below 1200°C, preferably 1150 to 1180°C, a temperature range in which MC type carbides do not become coarse) hot working to obtain powdered high speed steel with desired dimensions and shape. Conventional Techniques and Conditions 1.91 Manufacturing 60.6.1 Next, the present invention will be specifically explained with reference to Examples.

Example Water atomized high-speed steel powder (particle size: 60 mesh fine grains) was used as a starting material, annealed in H2 atmosphere, compacted in OIP, sintered in vacuum, and then 1150-1 in H2 atmosphere.
Table 1: Chemical component composition of the sample materials (Table 1: Chemical composition of the sample materials) lol
(t%) These test materials were heat-treated under the conditions shown in Table 2 to obtain powdered high-speed steel tools. The rupture strength, grindability, interrupted cutting properties, etc. were compared. In addition, sample material A1 is a comparison material corresponding to 5KH57, 42, and 5KHIQ, and 5KH57, 42, and 5KHIQ are comparative materials. Kara & 9 casings are invented materials.

Tables 3 and 4 show the results of measuring the properties of each of the above-mentioned test materials. However, the grindability is the value obtained by grinding sKug by the melting method under specified conditions, and is compared with the value 7'<100'i+, and the average carbide distance (from carbide to carbide 1
The average carbide particle size and average carbide area occupation rate are the average values of values measured in 5 fields at 5,000 times magnification. 'E7'c anti-cutting edge, Table 2 Heat treatment conditions Table 3 Properties (1) Table 4 Properties (2) Measurement conditions for wear resistance, grindability and cutting performance are as follows. .

(1) Transverse rupture strength 1] Test piece; 5 to 10 B , compared.

l) Mating material; 80M44s (HRf:!40)2]
Friction degree i 2.86 m7BeQ3) Final load i
12.6'p7 Friction distance i 400m (3) Grindability 1) Test piece; 20mX5+uX20MJI two grinding stones i WA l0K 3] Grinding speed i 1170 m/m1n5] Spring constant; 4) Cutting performance Using a horizontal milling machine (aML) y, intermittent cutting tests were conducted on cutting high-hardness materials at low speeds (low-speed cutting) and cutting tests on low-hardness materials at high speeds (high-speed cutting). However, in the case of low-speed cutting, the flank wear amount was evaluated after cutting 195 m under the required conditions, and in the case of high-speed cutting, the evaluation was performed based on the cutting length at the end of the complete life. Also in the case of pi) shape io ,0ilO,8,
6°, 200. O' Te common mouth A) @, fast cutting B) high cutting speed;
28.1m/min Speed i 77.4m/min
n feed 0;0.09yuI//r8V feed;0. □rxx/r61V cutting depth: lOga
Depth of cut 11-0m cutting oil, H82 cutting oil; H
82 Work material; 5KDIICI (H320) Cutting material i
550c (HE2oo) From the above results, the present invention material (I
Comparing the comparative materials (41, 42) to No. 63 to No. 9), they showed high performance in interrupted cutting at both low and high speeds. In other words, in wear resistance tests using high-hardness materials at low speeds, 5K, which is currently known as the most wear-resistant high-speed steel, was tested.
It has significantly higher wear resistance than HIQ, indicating that it is an excellent high speed steel. In addition, in high-speed cutting when testing impact resistance, it was found that about 3
It is clearly recognized that the steel of the present invention has extremely high performance in interrupted cutting.
Ru. Further, the transverse rupture strength hardly decreases even though 80 to 11.0% of MC type carbide forming elements are added, indicating that high toughness is maintained. In addition, the specific wear amount shows a significant improvement in wear resistance due to the high density of MC type carbide, which supports the high performance of the steel of the present invention in interrupted cutting. : Despite the area occupation rate of MC type carbide, which has remarkable grindability, it can be manufactured economically even with precision cutting tools such as 1p1 bob and pinion due to its miniaturization. It is shown that.

(The melted material of 5KH57 lowers the grindability by about 130%.) In other words, it is clear that the steel of the present invention has a much faster grindability than 5KH57 and 5KHIQ.

Some of the above-mentioned characteristics are illustrated in FIGS. 1 and 2 to clarify the significance of the present invention. The curves shown in Fig. 1 show the relationship between the area occupation rate of the MO-type compound and (■) the specific wear amount, and (■) the relationship with the cutting length at full life 1 in high-speed cutting. Although this shows a remarkable improvement in wear resistance and a sudden increase in the cutting length, at the upper limit of the present invention, there is little possibility of further development. Furthermore, Fig. 2 plots the relationship between flank wear amount and MO type compound area occupation rate when cutting 195 m at low speed, but this is essentially the same as Fig. 1. shows meaning.

[Brief explanation of the drawing]

Figure 1 B is a graph showing the relationship between the area occupation rate of MO type carbide and specific wear amount. Figure 2 is a graph showing the relationship between the flank wear amount and the area occupation rate of MO type carbide during low speed cutting. be. Representative Patent Attorney Junji Kawauchi

Claims (1)

[Scope of Claims] (II) Contains an MC type carbide containing two or more types of V, Nb, and Ti as components, and the MC type carbide has an average particle size of 2 μm or less when incorporated into a product. using raw material high-speed steel powder that has a fine structure by rapid cooling using a powder metallurgy method so that the MC type carbides are densely distributed at intervals of 2 μm or less between each other. Powdered high-speed steel (2) characterized in that the area occupation rate of the MC type carbide is 30 to 45 cm when added to a product.Claim 1.V. High speed steel.(The power mentioned above is powder high speed@, so the principal component force C1 is the weight% of the powder.
, 8-3. a%, Or3.5-5.0%, w7. Q+l
1.09J, MO3.0-5.0%, Co7.0~
I Q, Ochi; one type of V, Nb, Ti, or the sum of two or more types of these tl is 8.0 to 11. o
Si 0.1-0.6%9Mno1~o6φ
1. Powdered high-speed steel according to claim 1 or 2, which is made from 100% Fe or 100% Fe. (4) The powder high speed steel is powder compacted and heated
1.Claim No. 1 in which plastic working is possible. rJ, the powder high speed steel according to item 2 or 3.