JPS5937740B2 - High wear resistance sintered high speed steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the wear resistance and cutting performance of sintered high speed steel.

Compared to the melting method, the powder metallurgy method allows steel products to contain various constituent elements in a wide range of proportions with relative ease.
Moreover, due to its manufacturing process, it is an advantageous method for manufacturing steel products that are difficult to process.

When this powder metallurgy method is applied to the production of high-speed steel, it is possible to uniformly disperse fine carbides and nitrides in the steel structure, giving it a high degree of cutting performance. It is possible to produce high-alloy high-speed steel, which has been difficult or impossible to produce from the viewpoints of hardness, grindability, toughness, etc.

For example, the 5KHIO type, which is a high-speed melting steel, contains as many as 5 ■, so it has poor grindability and cannot be practically applied to the manufacture of precision gear cutting tools such as hobs and pinion cutters. It has been confirmed that the adoption of powder metallurgy solves manufacturing problems and also has the effect of improving cutting performance due to improved toughness.

This 5KHIO type has the highest wear resistance among the high-speed melting steels currently in practical use, but by applying powder metallurgy, it can be made into a higher alloy without deteriorating toughness. It is believed that it is possible to further improve the wear resistance.

Therefore, in order to commercialize steel equivalent to 5KH class 10 by powder metallurgy, the present inventors conducted intensive research on the effects of various alloying elements on tool properties in order to further improve tool performance. We have discovered that this objective can be achieved by specifying the proportions of various alloying elements, including the W and Mo contents defined as , and have completed the present invention.

That is, in the present invention, C1.5 to 2.0%, Cr 3.
8-4.5%, Wll, 5-13.5%, Mo2.6
~5.8 section, V 4.2~5.2%, Co 4.2~5
．． 2%, including the balance iron and unavoidable impurities, the sum of twice the amount of W and Mo (W (%l + 2 Mo (%)
) is adjusted so that it is 18 to 23.5%, and if necessary, a certain amount of C and N are added to the above composition to form a component composition, which has a high degree of wear resistance and is superior to conventional This is a result of the successful commercialization of a powder high-speed steel that has significantly superior cutting performance, especially continuous cutting performance, compared to the 5KHIO type equivalent.

The reasons for limiting the components of the high-speed steel of the present invention will be explained below.

W is a fundamentally important element for obtaining performance as a high-speed steel, and combines with C, N and Fe to form MC, M6
While forming C-type carbides, MX, and M6X-type carbonitrides, the remaining part dissolves into the matrix, improving wear resistance, temper hardening, and high-temperature hardness, and greatly contributing to improving cutting performance.

Mo exhibits the same behavior and characteristics as W in high-speed steel, and it is said that the addition of 1% Mo has almost the same effect as the addition of 2% W.

Therefore, in the present invention, the sum of the W content and the value obtained by doubling the Mo content, W + 2 Mo (hereinafter referred to as "
The content of W and Mo is defined by "W equivalent").

The cutting performance of the tool can be evaluated by a continuous cutting test, an interrupted cutting test, etc., and as shown in the examples below, the continuous cutting performance improves significantly as the W equivalent weight increases.

The improvement in interrupted cutting performance is also remarkable.

In order to provide sufficient performance, the W equivalent is adjusted to be about 16 parts or more, preferably about 18 parts or more.

However, if it is added excessively, toughness will decrease due to excessive precipitation of carbides mainly composed of M6C, tool damage due to chipping will become dominant, and cutting performance will tend to decrease.

Therefore, the upper limit of the W equivalent is about 24%, and more preferably about 23.5% or less.

That is, the W equivalent is about 16-24%, preferably about 18-24%.
In Section 23.5, continuous cutting performance can be effectively improved without deteriorating toughness or interrupted cutting performance.

As mentioned above, the W and Mo contents are defined as the W equivalent based on their mutual relationship, but it is more preferable that the respective addition amounts be defined.

Since W is expensive, it is disadvantageous in terms of cost to add a large amount, but if the amount is less than about 1, the grain refining effect is small and it is difficult to obtain good toughness.

However, even if it exceeds about 14 parts, the effect will not improve much considering the amount added, and it will only lead to an undue increase in cost.

Therefore, it is preferable to adjust the amount of W to a range of about 1 to 14 fO.

Mo forms a carbide and exhibits the same characteristics as W as described above, and also has the effect of lowering the quenching temperature.

That is, although it is necessary to raise the quenching temperature in W-based high-speed steel, the addition of Mo lowers the temperature, which has the effect of suppressing the coarsening of crystal grains and carbides.

At the same W equivalent, the higher the amount of Mo, the higher the toughness, but if the amount added is less than about 2%, the effect is not sufficient and the amount of carbide itself tends to be insufficient.

However, even if the ratio exceeds about 10, the effect almost reaches saturation.

Therefore, the amount of Mo added is preferably about 2 to 10%.

Cr exists in the matrix and carbonitrides and improves hardenability, temper hardening, high-temperature hardness, and oxidation resistance during heat treatment, but if the amount is less than about 3 Cr, the effect is low. This is not sufficient; on the other hand, even if it exceeds about 5%, the effect increases slowly.

Therefore, Cr is about 3 to 5, preferably about 3.8 to 4.5
Added within the scope of the above.

When used in combination with W, Mo, V, etc., Co is effective in increasing the heat resistance of the matrix and improving high-temperature hardness, and is a necessary element especially when the purpose is to make tools for difficult-to-cut materials. .

In the steel of the present invention, if the modulus is less than about 0.1%, the effect is insufficient, so the modulus is about 0.1% or more, preferably about 4.2% or more.

However, even if it exceeds about 5.5%, there is no effect as generally said, so it should be about 5.5% or less, preferably about 5.2% or less.

(2) has the effect of improving toughness, increasing hardness by forming carbonitrides, and imparting wear resistance.

In the steel of the present invention, if the amount added is less than about 4%, the effect will not be sufficient; on the other hand, even if it exceeds about 6%, the effect will increase slowly; Approximately 4.
It is added in a range of 2 to 5.2 parts.

C dissolves into the matrix and contributes to strengthening it, and is especially necessary to combine with the above-mentioned W, Mo, Cr, etc. to form carbides or carbonitrides.

The amount added depends on the content of carbide and carbonitride forming elements, and in the steel of the present invention, it is added in an amount of about 1.2 to 2.2%, preferably about 1.5 to 2.0%. .

Note 1. C has properties similar to N, and both are interstitial solid solution atoms in steel and easily form stable compounds, and both play almost the same role.

For this reason, as will be described later, when a certain amount of N is added, it is desirable to add a condition defined by the value of C+H.

In addition to the above-mentioned components, the following elements can be added as necessary.

N, together with the aforementioned C, combines with W, Mo, V, etc. to form carbonitride, and plays an effective role in improving cutting performance.

For this purpose, it is desirable to add about 0.2% or more of N.

In this case, since N plays the same role as C, the value of the sum (C+H) with the C content is preferably specified for its addition amount.

If the value of C+H is less than about 1.4, the amount of carbonitride precipitated will be insufficient and it will be difficult to obtain sufficient wear resistance, while if it exceeds about 2.4, the amount of C and N in the matrix will be The concentration becomes too high,
Toughness deteriorates.

Therefore, the value of C+H is about 1.4-2.4%, preferably about 1.5-2.0%.

In addition, elements such as Si and Mn may be present within the range normally included in this type of high speed steel, for example Si about 0.4
% or less, and the Mn coefficient is approximately 0.4 or less.

In addition, S, P and other impurities are within normally permissible ranges, for example, S about 0.03% or less, P about 0.03% or less.
May exist in the following ranges.

Note that since AI combines with N to form AIN and reduces the effect of N, it is desirable to limit it to about 0.4% or less.

There are no special restrictions in producing the powdered high-speed steel according to the present invention (according to a conventional method, raw steel powder (e.g., water atomized steel powder) containing predetermined alloying elements is filled into a mild steel capsule, and the necessary In that case, after blending the ferroalloy powder to the desired composition and deaerating it, compression mold it into a steel ingot using, for example, a hot e-static press. It is also possible to perform nitriding treatment as follows.

), and then heat treatment of quenching and tempering can be performed on the obtained steel ingot (compression molded sintered crystal).

Next, the cutting performance of the high speed steel of the present invention will be specifically explained with reference to Examples.

Except for Example C, test cutting tools with various component compositions were produced by adding a predetermined amount of graphite to alloy steel powder (atomized powder) containing a predetermined amount of alloy components, and manufactured according to the usual method of powder metallurgy.
Continuous cutting and interrupted cutting tests (using a Chang-Roku Zneuve lathe) were conducted using a cutting tool (bite), and the cutting performance of each was compared.

In addition, each sample material was quenched and tempered (maintained in the austenite region for 3 minutes, then quenched.

Tempering holding time 1.5 Hrs Number of tempering 3 times)
was applied.

Table 1 shows the chemical composition and heat treatment temperature of the sample materials, and Table 2 shows the cutting test conditions.

In Table 1, sample materials/16.2, 3, 4, 5 and 8 are A
Composition of l5I T15 (equivalent to JIS SKH 10 type) (However, flat 8 contains N), same //66 and 7 are A
It has a composition of l5I T15 system, among which sample material A
, 2, 3, 4, 7 and 8 belong to the steel of the present invention, and the others are comparative materials.

As a means of evaluating the cutting performance in the cutting test, the V-T curve (complete life) was used in the continuous test, and the wear amount of the cutting edge after 3000 impacts was used in the intermittent test.

The above test results are shown in FIGS. 1 to 4.

FIGS. 1 and 2 are the results of continuous cutting tests, and represent the cutting speeds for cutting life times of 60 minutes and 5 minutes, respectively.

Figures 3 and 4 show the degree of wear of the tool cutting edge in the intermittent test, with the former representing the crater width and the latter representing the crater depth.

In each figure, the numbers indicate the sample materials listed in Table 1.

As shown in the continuous cutting test results in Figures 1 and 2, the continuous cutting performance improves as the W equivalent increases, especially the W
Materials of the present invention having an equivalent weight of about 16 or more (sample materials A2, 3
, 4, 7) is the comparative material (Al.

6) is much better than 6).

Moreover, when N is added, even better performance is shown at the same -W equivalent (sample material A8).

- In terms of force and interrupted cutting performance, the inventive material was also superior to the comparative material (
It is recognized that this is superior to the sample material/l61).

Comparative material layer 5, which has a W equivalent of more than about 24%, exhibits almost the same cutting performance as the present invention material, but has a high W equivalent (
The material is inferior to the material of the present invention in that it contains an unnecessarily large amount of expensive alloying elements), is expensive, and has a tendency for craters to significantly deteriorate the interrupted cutting performance.

As described above, the powder high speed steel according to the present invention has good toughness and high wear resistance, and has a high level of wear resistance compared to conventional melting 5KHI.
This guarantees extremely excellent cutting performance that surpasses that of type O.

[Brief explanation of the drawings] Figures 1 and 2 are graphs showing continuous cutting performance, and Figure 3 is a graph showing continuous cutting performance.
FIG. 4 and FIG. 4 are graphs showing interrupted cutting performance.

Claims (1)

[Claims] I C1.5-2.0%, Cr3.8-4.5%, W
ll, 5-13.5%, Mo 2.6-5.8%, V
4.2-5.2%, Co4.2-5.2%, balance iron and unavoidable impurities, sum of twice the amount of W and Mo (
W (%) + 2M. A highly wear-resistant sintered high-speed steel with excellent continuous cutting performance, characterized in that (@) is 18 to 23.5%. 2. The high speed steel according to item 1 above, containing 2% or more. 3 The total of C content and N content (C+N) is 1.4~
2.4% of the high speed steel of item 1 above. 4. The high speed steel according to item 3 above, wherein the value of C+N is 1.5 to 2.0%.