JPH0463251A - sintered high speed steel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a high-strength sintered high-speed steel used for end mills, etc., which can obtain a hardness of HRC 72 or higher by ordinary quenching and tempering.

<Conventional technology> When high-speed steel is made using powder metallurgy, the carbide particles are finer and more uniform than in cast steel, resulting in improved toughness, forgeability, and
It has long been known that it has many advantages, such as excellent grindability. The present inventor's improvement research [powder and powder metallurgy, 35 (1988),
505, 36 (1989), 324 and 37 (1989)
1990), published a paper in 456], it has been applied to various tools and has received high praise.

Among the sintered high-speed steels used for end mills, VC and Ti have a relatively high hardness of HRC 70 or higher.
N-enriched high-alloy steel (for example, KF2 alloy KF261) is used, allowing for more efficient cutting than conventional end mills.

However, recently, there have been requests from users for higher efficiency, and materials with hardness of HRC 72 or higher are also required.

For example, JP-A-62-124259 and JP-A-62-
No. 124260, etc.

<Problem to be solved by the invention> However, these sintered high-speed steels with HRC 72 or higher [W]
(wt%) + 2 ×Mo (wt%)) is 18 to 4
0 (wt%) V amount is 1 to 24 (wt%), TiCN amount is 2 to 12 (wt%), and the total amount of these is 21 to 76
(wt%), which is too large. Furthermore, since there are more than 8 types of elements, it is insufficient to understand the relationship between these elements and tool performance based on experience with conventional high-speed steels and sintered high-speed steels or phase diagrams. It only discloses that it is easy to obtain, but does not show detailed properties such as strength and workability, and there are many cases where it is not practical as a tool. For example, when the amounts of W and Mo are large, it becomes difficult to control the shape, particle size, and distribution state of M and C, and the strength becomes unstable. In fact, commercially available W and M.

This kind of accident is observed in Enfu's sintered high-speed steel end mill (because we don't know how to solve it).

Also, [W (wt%) + 2 ×Mo (wt%)
) +V (wt%) +T i CN (wt%) When the total amount exceeds 44 (wt%), the annealing hardness becomes H
If it becomes RC52 or higher, the machinability deteriorates and its application as a tool is restricted.

As mentioned above, current high-hardness sintered high-speed steels tend to deteriorate in strength and workability, and are not considered for tools such as end mills, which have good workability but require high hardness and toughness. It is enough. Naturally, the relationship between each element and cutting performance is not understood in detail. Therefore, conventional sintered high-speed steels with HRC of 72 or higher do not have sufficient performance for use in end mills.

This invention was made with the aim of improving such conventional, immature technology, and we conducted a detailed study on each composition of sintered high-speed steel, which is hardened by compound additions, and specifically developed it as a material for end mills. The objective is to provide a sintered high-speed steel material that is superior to conventional high-hardness sintered high-speed steels.

<Means for solving the problem> The sintered high-speed steel according to the present invention has a hard phase grain size, type,
A detailed study of the relationship between the amount and cutting performance resulted in the following composition.

The particle size of the main hard phase is 5 μm or less, and the average is 1 to 3 μm. The particle size of the secondary hard phase is 5 μm
and the average particle size is 3 μm or less. The main hard phase is MC, and the secondary hard phases are M, C, and Ti.
It is CN. The amount of the hard phase is determined by the main components of the hard phase, W and M.
The relationship between o, V, and TiCN is W+2XM○+V+TiC
N is 38 to 44 (wt%). Within this range, the amounts of W, Mo, V, and T i CN are in the following range.

(2) is 6~IC) (wt%).

W and Mo are 18 to 30 (wt%) at W+2×Mo
So, in Mo/(W+2×Mo) within this range,
The maximum MO is 46 (wt%).

TiCN is 6 to IO (wt%), and regarding C and N of TiCN, C is 2 to 90 (wt%).

Components other than the hard phase have a Cr content of 3 to 5 (wt%).

is 5 to 15 (svt%). The amount of carbon is [W (wt
%)+2×Mo(wt%)]X0.017+V(
wt%)×0, 22 + 0. 19 +TiC=
±0.25 (wt%) for the value given by Ny (wt%) x (XX0.2+0.05) (x+y=1)
) is within the range.

<Function> The inventors have already reported that it is advantageous to add carbides and nitrides to harden sintered high-speed steel (three papers mentioned above). Current sintered high-speed steels contain more than 8 types of elements through compound addition, but the composition of the alloy is M as a hard phase, carbides such as C1MC, and carbon/nitrides such as TiCN, and a Fe matrix as a soft phase. It can be simplified. M and C are mainly composed of W and Mo, and are also composed of Fe and the like. MC is mainly composed of V and W.
, Mo, etc. TiN and TiCN have a very small amount of W, Mo, and V in solid solution around their particles. (The discovery was reported in the third paper above). By the way, M2O exists as a eutectic melt under the sintering temperature, and crystallizes during the cooling process, but its particle size and shape are determined by the amount of W and Mo (W (wt%)
)+2XM.

(wt%)) is about 20 (wt%) or more, about 1μ
From fine particles of less than m to coarse particles of several tens of μm or more and tens of μm
This often results in abnormal particles such as tree-like mottling. This is because the amount of melt becomes locally excessive.
As W and Mo increase, this will naturally become more likely to occur. Here, if the amount of MC is determined appropriately in relation to cutting performance, the amount of M2O, particle size, etc. can be controlled by WSM, which is dissolved in the surrounding tissue of TiCN.

This becomes possible by controlling the amount of solid solution such as.

The reason for determining the amount of MC first is that MC is W, M up to the inside.
This is because o is dissolved in solid solution, which is disadvantageous (difficult to consider) for delicate control, but even if we first focus on hard particles other than MC, the same result will be obtained in the end. Based on this idea, I began research. First, as a method of obtaining hardness, we varied the total amount, type, and particle size of the hard phase, and studied the relationship with the overall performance of the end mill.Next, we studied the relationship between MC carbide and cutting performance. The present invention was completed by studying the relationship between MC+M6C and cutting performance, and finally by studying the amount of TiCN as M and C control and the relationship between TiCN and cutting performance.

In addition, for convenience's sake, MC is described as the main hard phase, and M2O and TiCN are described as the secondary hard phases.

The grain size of MC as the main hard phase must be 5 μm or less; if the grain size is coarser than 5 μm, the probability that it will act as a source of fracture increases and the strength becomes impractical. The average particle size of the MC of the main hard phase should be 1-3 μm.

If the particles are finer than 1 μm, the wear resistance will be poor.
becomes impractical. If the grain size is coarser than 3 μm, a region where carbides are segregated, which is the origin of fracture, is likely to occur, and the strength becomes impractical and the workability deteriorates, making it impractical.

The particle size of the secondary hard phases MaC and TiCN is less than 5 μm. If the grain size is coarser than 5 μm, the probability that it will become the origin of fracture increases and the strength becomes impractical. The average particle size of M, C and TiCN in the secondary hard phase is on average less than 3 μm. If it is larger than 3 μm, there is a high probability that it will cause a breakage, making it impractical.

The amount of the hard phase is determined by the main components of the hard phase: W, Mo, and VXTi.
The total amount of CN is W+ 2 ×Mo +V+T i CN is 38 to 44 (wt%). When it is less than 38 (wt%), the wear resistance becomes impractical, and when it is more than 44 (wt%), the annealing hardness becomes higher than HRC52, making it difficult to process and making it impractical in terms of workability.

Each hard phase is controlled by adjusting the composition below. First, V is strongly related to the formation of MC, and as a result of a detailed study, it was found that 6 to 10 (wt%) is preferable. If it is less than 6 (wt%), the amount of MC is too small,
Surface area also decreases and wear resistance decreases. 10 (wt%)
If the amount is larger, segregation of carbides, which is the origin of fracture, is likely to occur and the strength is likely to be lowered, making it impractical. The required amounts of M and C are determined in relation to this MC amount. W
And Mo is set to 18 to 30 (wt%) in W+2XMO. When the amount is less than 18 (wt%), W is solid-dissolved in MC,
Since the amount of Mo is large, the amount of M2O produced is too small, making it difficult to increase the hardness, and if it is higher than 30 (wt%), it becomes too easy to cause abnormal grain growth of M2O, which cannot be controlled even with the next maximum amount of TiCN. , the probability of low intensity increases. In addition,
The composition ratio of W and Mo is 46 (wt%) at maximum.

If Mo is more than 46 (wt%), the high-temperature hardness deteriorates, making it impractical.

TiCN is preferably 6 to 10 (wt%). 6 (wt%
), the strength becomes impractical due to insufficient control of M and C. Furthermore, cutting performance deteriorates, making it impractical. If it is more than 10 (wt%), it is advantageous for controlling M and C, but it is not practical because the workability after annealing and heat treatment deteriorates. C in TiCN
The amount ratio of and N is changed depending on the amount of W and MO.
If the amount of W and Mo is large, increase C up to 90 (wt%) LM
, C is controlled, but the advantage of nitride (formation of surrounding tissue) is lost, so it is controlled up to 90 (wt%). When the amounts of W and Mo are small, the amount of C can be reduced to 2 (wt%). If it is less than 2 (wt%), the amount of W and Mo solidly dissolved in the surrounding tissues will be too small, making it impossible to control M and C, so 2 (wt%) is the upper limit.

Regarding the soft phase, we focus on Cr, Co, Fe, and C to bring out the performance of the hard phase.

Most of the Cr is dissolved in the matrix, and the content may be 3 to 5 (wt%), which is the same as in ordinary high-speed steel.

If it is less than 3 (wt%), hardenability and corrosion resistance will decrease. If the amount exceeds 5 (wt%), precipitation of Cr carbides may occur, reducing the strength of the matrix, or M
It produces abnormal phases such as 2C. Co is 5-15 (wt%
) is better. If it is less than 5 (wt%), the hardenability decreases,
Hardness becomes impractical. If it exceeds 15 (wt%), the strength decreases and becomes impractical. The amount of carbon is (W (wt%)
)+2×Mo (wt%))Xo, 017 +V (
wt%) ×0.22+0.19+T icx N,
(wt%) x (XxO,2+0.05) (However, x+y=1) ±0.25 (wt%)
is within the range of This formula is a formula that adds the carbon content required by TiCN to the carbon content required by the carbide and matrix. If it is less than 0.25 (wt%) with respect to the amount given by the formula, the hardness will not reach HRC 72 or higher even at the practical upper limit temperature of 1280°C (at temperatures above 1280°C, the commonly used salt bath method) (The heat treatment furnace deteriorates rapidly, and the matrix strength of the alloy also decreases.) If the amount exceeds 0.25 (wt%) relative to the amount given by the formula, a large amount of residual austenite will be generated during quenching, and it will not be possible to convert it to martensite unless the tempering temperature is increased, making it impossible to obtain the necessary strength and hardness. .

<Example> It has been found that the alloy of the present invention has almost the same excellent properties when using either co-reduced powder or water atomized powder as the starting material powder, so in this example, compared to the reduced powder of 5KH57 WC, MO□C1Cr5 C! , V.C.
Various types of sintered high-speed steel were made by adding predetermined amounts of , Co, and TiCN, and their mechanical properties were investigated. End mills were also made and their workability and cutting performance were investigated.

Cold - View - Above table! Composition of sample (LX) Appropriate amounts of Cr3C2, VC, Co, and TiCN were added, wet milled using a ball mill for 72 hours, dried, molded, vacuum sintered (0.5 Torr), then 11
It was made by HIP treatment (1500 atm, Ar atmosphere) at 50°C for 1hr. 5m at 1240°C if required
After holding for 1n, it was oil quenched and tempered at 500°C to 620°C to obtain a JIS test piece of 24 x 8 x 4 mm. Here, TiCN is TiCo, 0IN0.99. In this case, an alloy with the same characteristics can also be obtained by using TiN and removing nitrogen sufficiently during sintering by maintaining a vacuum to form TiCN.

Table 2 First, five types of sintered high-speed steel shown in Table 1 were prepared at 5KH.
WC, Mo□C1 (b) to (e) to the reduced powder of 57 composition
The current temperature is 124υ℃.

W (wt%) of samples (a) to (e) + 2 ×Mo
(wt%) and W(wt%) + 2 × Mo (w
t%) +V (wt%) +TiCN (wt%) are shown in Table 2 together with mechanical properties such as transverse rupture strength test (JISB4104) results.

As can be seen from the table, this sample has almost the same basic mechanical properties, with a constant hardness of HRC72 and a transverse rupture strength of 180 kgf/m2 or more. The amount, type, and particle size of the hard phase are given characteristics so that the relationship between processability, cutting characteristics, and composition (hard phase) can be understood. Here, the hard phases of samples (a) to (e) are as shown in FIG. The characteristics of each sample will be described. For comparison, sample (a) does not contain TiCN and has high hardness. In contrast to sample (a), samples (b) and (c) are enriched with MC and TicN and have high hardness. Sample (d) is T
Although iCN is enriched, the carbide is only made into fine particles and is not enriched, and the increased amount of secondary hardening caused by making the carbide into fine particles results in high hardness. By comparing with other samples, the required amount of carbide enrichment (W+2×Mo and V amount), the upper limit amount of TiCN, the effect of secondary hardening, etc. can be determined. Sample (e
) is MaC(W+2×M
o) is enriched. By comparing with samples (b) and (C), the effect of M2O and the necessary amounts of W and Mo can be understood.

Next, end mills were actually manufactured using the above samples (a) to (e), and their workability and cutting characteristics were investigated. The size of the end mill at this time was 10 mm in diameter and two blades, and the shape of the cutting edge was the same as that of a conventional end mill using high-grade powdered high-speed steel.

The processability of samples (a) to (e) is summarized in Table 3.

Sample (a) has the poorest workability. From this, Ti
It can be seen that the workability is determined regardless of the presence or absence of CN. In the case of sample (a), it was found as a result of examining the machined surface that the amount of hard phase was too large, leading to deterioration in workability. Sample (c) has poorer workability than sample (e).

This is because there are too many MC and TiCN. Sample (d
) had a small amount of MC and hard phase, but had a large amount of TiCN, which resulted in poor workability. Therefore, sample (b) and sample (e) were excellent in processability, and the appropriate state of the hard phase for processability was found.

Experiment 2 Next, the results of the cutting test are shown. Work material is 550C1SKD
There were three types: 61 and 5KDII. Table 4 shows the cutting conditions.
Shown below. This makes it more efficient than ordinary high-speed steel. Table 5 shows the results of the cutting test. Regarding the cutting performance of 850C, sample (d) is the best, followed by samples (c) and (e).
The order was This indicates that when the cutting force is relatively low and the cutting speed is high, a material with fine carbides and a large amount of TiCN is preferable. It can also be seen that the amount of hard phase may be small. In cutting 5KD61, sample (c) was the best, followed by sample (e). From this, 5KD61
The cutting contains TiCN and the amount of hard phase is about 4° (wt%
) is good. There seems to be little relationship with other factors. In 5KDII cutting, when there are many hard phases,
It is preferable to include TiCN.

According to the observation results of the cutting edge, coarse particles (approximately 3 μm) seemed to have better wear resistance than fine particles.

Table 4 Cutting conditions "rUH75" is a sulfurized oil-based cutting oil (manufactured by Yushiro Chemical Industry Co., Ltd.) Table 5 Cutting test results (cutting length: m) It was set as the point when

The life span was defined as the point in time when the width of the second outer periphery of wear reached 0.2 mm.

From the above, it was found that samples (c) and (e) had excellent cutting performance.

Next, sample (c) was prepared under higher efficiency conditions (cutting speed 1600 rpm, feed rate 192 mm/min, 5 mm x 10 mm groove cutting, dry method) using only 5KD61 (HRC41) as the work material. and (e) were compared.

As a result, sample (c) had a cutting length of 3.3 m, sample (e)
However, sample (e) was superior at a cutting length of 6.5 m (life is determined when the second wear on the outer periphery reaches 0.4 mm). When we observed the state of wear on the cutting edge, we found that sample (C) had minute chips compared to sample (e).
), which resulted in a shorter lifespan. This indicates that materials with higher strength are advantageous under harsher cutting conditions. From the above, sample (e) had the best machinability and cutting performance, but sample (e) seemed to be unstable in terms of strength because M and C tended to change depending on the amount of alloy carbon. Furthermore, since it is desired that the SKD material has better cutting performance than 850C, it was decided to further fine-tune the amount of carbides and nitrides.

Experiment 4 Regarding sample (e), the composition of MC and TiCN was finely adjusted, especially for the purpose of controlling the structure of M and C, as shown in Table 6.
Shown below. Table 7 shows the characteristics.

Although the amount and particle size of the hard phase were the same, the amounts for each type were different in relation to the particle size control of M6C. Sample (f
) - (i) TiCN uses TtCo, sNO, and S to make MaC more stable. That is, sample (i) differs from sample (e) only in the amounts of C and N in TiCN.

Sample (f) has more TiCN than sample (e).
An attempt is made to stabilize the shapes of M and C by adjusting the amounts of W and Mo dissolved in the surrounding tissue. Sample (g)
attempts to stabilize the shape of MaC by increasing the amount of MC compared to sample (e).

In sample (h), MC and TiCN are decreased compared to sample (e), M and C are increased, and the precipitation amount is appropriate and stable. As a result, the stability of M and C was in the order of sample (h) = (i) ≧ (f) ≧ (g) > (e). Sample (h) has hardness and transverse rupture strength that are similar to sample (h).
It is advantageous in terms of processability as it is lower than e).

In addition, when comparing the high temperature hardness of samples (f) to (e), sample (h) was the best.
Regarding e), we decided to make an end mill and compare it.

Real-μ-2 The workability of sample (h) was slightly better than that of sample (e).

As shown in Table 8, the cutting test results showed that sample (h) was superior.

That is, it was shown that an excellent sintered high-speed steel can be obtained by focusing on M and C and adjusting each hard phase.

As a result of examining the cutting edge of the end mill, focusing on the particle size of carbide and TiCN, it was found that if it contains coarse particles larger than 5 μm or if the average particle size is larger than 3 μm, the workability and cutting characteristics deteriorate.

Effects> Since the sintered high-speed steel according to the present invention has the contents as described above, it is most suitable for use in tools that require high hardness, especially end mills.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the amounts of each component in the hard phase of samples (a) to (e) according to Examples of the present invention. Figure sample procedure amendment (voluntary) August 1990

Claims (1)

[Claims] The particle size of MC in the main hard phase is 5 μm or less and its average particle size is 1 to 3 μm, and the particle size of M, C, and TiCN in the secondary hard phase is 5 μm or less and its average particle size is 3 μm.
m or less, and the amount of the main and secondary hard phases is W+2×Mo+V+TiC
38 to 44 wt% of N, within this range,
The amounts of W, Mo, V, and TiCN are as follows: W+2Mo: 18 to 30 wt% [However, Mo/(W+2×Mo) is up to 46 wt%] V: 6 to 10 wt% TiCN: 6 to 10 wt% % [However, regarding C and N in TiCN, C is 2 to 90 wt%] In addition, the amounts of components other than the hard phase are as follows: Cr: 3 to 5 wt% Co: 5 to 15 wt% Furthermore, The amount of carbon is (W+2×Mo)×0.017+V×0.22+0.1
9+TiC_xN_y×(X×0.2+0.05);(
However, ±0.25wt for the value given by x+y=1)
%, with the remainder consisting of Fe but less than 2 wt% of Mn, Si, and Ni.
and sintered high-speed steel with unavoidable impurities.