JP2012210671A - Drill made of alloy steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drill formed of alloy steel and a surface coated drill formed of alloy steel each having excellent wear resistance in use over a long period.SOLUTION: Each of the drill formed of alloy steel and the surface coated drill formed of alloy steel has a tool base composed of alloy steel which contains 2.0-3.0 mass% of C, 3.0-6.0 mass% of Si, 9.0-15.0 mass% of Cr, 10.0-15.0 mass% of Co (preferably, C+Si+Cr+Co: 25.0-35.0 mass%), 9.0-11.0 mass% in the total of one or two of W and Mo, 1.5-2.5 mass% of V, and whose remaining part is composed Fe and inevitable impurities and which has resistance to high temperature temper softening.

Description

  The present invention relates to a drill that exhibits excellent wear resistance over a long period of use, and in particular, an alloy steel having excellent high-temperature tempering softening resistance even when the cutting edge is exposed to a temperature higher than the tempering temperature during high-speed cutting. The present invention relates to a drill made of an alloy steel that prevents a decrease in the hardness of the cutting edge and exhibits excellent machinability at high temperatures and a surface-coated alloy steel drill in which a hard coating layer is deposited on the surface of the tool base. .

  Alloy steels (JIS SKH, SKD, etc.), cemented carbide, cermet, cBN, diamond, etc. are known as materials for cutting tools. However, among the alloy steels for cutting tools, they have high wear resistance and toughness. High speed tool steel (JIS SKH) is frequently used because of its superiority.

  High-speed tool steel is a tool steel to which a large amount of alloying elements such as C, Cr, W, Mo, V, Co, etc. are added to improve hardness and wear resistance especially at high temperatures. There are two types of high-speed tool steel manufactured by the method and powder high-speed tool steel (also referred to as powder high speed) manufactured by the powder metallurgy method.

  In the case of the melting method, although it can be manufactured by a normal manufacturing method, the homogenization of the material due to segregation of coarse carbides tends to be a problem, while in the case of the powder metallurgy method, the manufacturing process is complicated and expensive. Although there are drawbacks, there is an advantage that even a material that is difficult to manufacture by a melting method can be manufactured and a uniform structure can be formed.

  The high-speed tool steel by the melting method is described in, for example, Patent Documents 1 to 5. According to Patent Document 1, a trace amount of rare earth elements is contained as a component in the steel, and the shape control of the eutectic carbide is performed. It is known to improve impact resistance and cutting performance by performing.

  Further, according to Patent Document 2, it is known to improve wear resistance by forming VC carbide in steel and to improve toughness by making the crystallization form of VC carbide fine and uniform. .

  Further, according to Patent Document 3, it is known that hot workability, toughness, impact resistance, and fatigue strength are improved by adjusting alloy components and their contents in steel.

  Moreover, according to Patent Document 4, the content of alloy components in steel, particularly C, Si, Cr, Mo, W, is adjusted, and C: 1.05 to 2.00%, Si: 0.3 to 2.0% (preferably Si: 0.3-1.0%), Cr: 3.0-5.0%, 0.4 ≦ 2Mo / (W + 2Mo) × Si ≦ 1.0 It is known that tempering hardness is high and toughness and wear resistance are improved by satisfying the above relationship.

  Further, according to Patent Document 5, the wear resistance, heat resistance, and seizure resistance are improved by forming fine carbides with high hardness in the steel, and further, the tool cutting edge is obtained by refining the cast structure. It is known to improve chipping resistance.

  About the powder high-speed tool steel (powder high speed) by the powder metallurgy method, for example, it is described in Patent Documents 6 and 7, and according to Patent Document 6, C is more than 1.5% and 2.6% or less. More than 6% and less than 13% Cr are contained, Si is 1.0% or less, and the (W + 2Mo) amount and (C-Ceq) value in the steel are regulated, and the value of Nb / V It is said that a powder high-speed tool steel having toughness and corrosion resistance and enhanced resistance to high-temperature tempering softening can be obtained by regulating the above.

  According to Patent Document 7, it is said that the wear resistance and toughness can be improved by adjusting the contents of the alloy components in the steel so as to satisfy a certain relationship.

JP-A-1-165748 JP-A-7-228946 Japanese Patent Application Laid-Open No. 8-100239 JP 2000-144333 A Japanese Patent No. 2573951 JP-A-5-171373 JP 2001-294986 A

  Recent progress in cutting technology is remarkable, and in addition, there are strong demands for labor saving, energy saving, cost reduction and efficiency improvement in cutting, and accordingly, high speed cutting and high efficiency cutting are also required. When high-speed cutting is performed using an alloy steel drill made from the above-mentioned conventional alloy steel, the cutting blade is exposed to high heat during cutting, and the alloy steel is softened at high temperature. There was a problem that the hardness decreased, and as a result, the wear progressed and the tool life was shortened.

  Therefore, the present inventors do not cause high-temperature temper softening even when high-speed cutting with high heat generation is performed, and to provide a drill made of alloy steel and a surface-coated alloy steel with less hardness reduction, As a result of earnest research, the following findings were obtained.

  Conventional alloy steels, particularly high-speed tool steels, usually contain C, Si, Mn, Cr, W, Mo, V, Co, etc. as their alloy components. Of these alloy components, Si Is added mainly in anticipation of the action as a deoxidizer, and also has the effect of improving hardness, but if the Si content is too high, the toughness of the high-speed tool steel will be deteriorated. (For example, refer to Patent Document 4) Therefore, from the viewpoint of not adversely affecting the toughness, it was usually added within a range of at most 2%.

  The inventors pay attention to the contents and actions of the C component, Si component, Cr component, and Co component, and investigate the influence on the high-temperature temper softening characteristics when the content of each of these components is variously changed. As a result, when the content of the Si component in the steel is increased to 3.0 to 6.0%, and when a large amount of the C component, the Cr component and the Co component in the steel are added at the same time, the high temperature of the alloy steel. When the temper softening characteristics are greatly improved, and when the C component, Si component, Cr component and Co component are simultaneously added in large quantities, and the total content of C + Si + Cr + Co is regulated within a specific numerical range, it is further enhanced. It has been found that the high-temperature temper softening property is improved, and the hardness reduction is suppressed even when exposed to high temperatures.

  In addition, in this case, a large amount of Si refers to an amount far exceeding the amount added as a deoxidizer in ordinary alloy steel. For example, in the high-speed tool steels of Patent Documents 1 to 6 listed above. The Si content is 2% by mass at the maximum (in Patent Document 4, excessive addition exceeding 2% is said to cause a decrease in toughness due to segregation), and the content of Si is 3% by maximum. Also in Patent Document 7 to be obtained, the preferable upper limit value of the Si content is 1% (see paragraph 0022), and the present inventors added 3 mass% or more of Si, and at the same time, added C, Cr and Co. It was found that by adding a large amount, the high temperature temper softening property of the alloy steel was greatly improved to an extent that could not be expected from the prior art, and the drill tip made of this alloy steel had a cutting edge. Tempering It has been found that it has excellent high temperature tempering softening resistance even when exposed to high temperatures, and the hardness of the cutting edge is prevented, so it exhibits excellent wear resistance and toughness at high temperatures. .

This invention has been made based on the above findings,
“(1) In mass%, C: 2.0 to 3.0%, Si: 3.0 to 6.0%, Cr: 9.0 to 15.0%, Co: 10.0 to 15.0 %, W and Mo, one or two total: 9.0 to 11.0%, V: 1.5 to 2.5%, the balance being high temperature temper softening resistance consisting of Fe and inevitable impurities An alloy steel drill characterized by comprising alloy steel provided.

  (2) The total content of C, Si, Cr, and Co is 25.0 to 35.0%, and is made of an alloy steel having high-temperature temper softening resistance as described in (1) above. Alloy steel drill.

(3) A surface-coated alloy steel drill characterized in that the alloy steel having high-temperature temper softening resistance described in (1) or (2) is used as a base, and a hard coating layer is formed by vapor deposition on the surface of the base. "
It has the characteristics.

  The present invention will be described in detail below.

  First, the reasons for limiting the numerical values of the alloy component composition range of the alloy steel constituting the alloy steel drill of the present invention are as follows.

C: 2.0-3.0 mass% (in the following, mass% is simply indicated by%)
Part of C is hardened and solidifies in the matrix to strengthen the matrix, and part of it combines with W, Mo, Cr, and V to form carbides, and the hardness and wear resistance of the alloy steel. Improve sexiness.

  If the C content is less than 2.0%, not only the hardness and wear resistance can be expected to be improved, but also the high temperature temper softening property cannot be improved by the interaction with Si described later. Further, if the C content exceeds 3.0%, it becomes too hard and deterioration of toughness occurs, and the uniformity of the material cannot be ensured due to the formation of a non-uniform microstructure. Was determined to be 2.0 to 3.0%.

Si: 3.0-6.0%
As in the case of ordinary alloy steel, Si acts as a deoxidizer.

  Further, in the present invention, in order to improve the high temperature temper softening property of the alloy steel, it is an important alloy component together with the C and Cr and Co described later.

  If the Si content is less than 3.0%, no contribution is seen in improving the softening resistance. On the other hand, if the Si content exceeds 6.0%, the toughness is greatly reduced. Set to 6.0%.

Cr: 9.0 to 15.0%
Cr secures the hardenability of the steel, improves the oxidation resistance during heat treatment, and, if added in a large amount simultaneously with Si, contributes to improving the softening properties, and therefore requires a Cr content of 9.0% or more, If the Cr content exceeds 15.0%, Cr carbide segregates, and not only the workability deteriorates but also the toughness significantly decreases. Therefore, the Cr addition amount is determined to be 9.0 to 15.0%. .

Co: 10.0-15.0%
Co needs to be contained in an amount of 10.0% or more in order to obtain a sufficient tempering hardness. However, if its content exceeds 15.0%, it precipitates in a single phase of Co and greatly increases the toughness. In order to reduce, Co content was defined as 10.0 to 15.0%.

  The present inventors conducted a detailed investigation on the relationship between the contents of the above-mentioned C, Si, Cr, Co, which are alloy components of alloy steel, the tempering temperature, and the high temperature hardness.

  In FIG. 1, an example of the high temperature hardness change (softening ratio (HRC hardness)) by tempering temperature (degreeC) about various steel is shown.

In FIG. 1, the contents of C, Si, Cr and Co in the steel are as follows.
Invention steel 1-A: 2.1% C, 4.0% Si, 12.4% Cr, 10.2% Co,
And C + Si + Cr + Co = 28.7%
Invention steel 2-A: 2.5% C, 4.0% Si, 9.2% Cr, 14.1% Co,
And C + Si + Cr + Co = 29.8%
Comparative steel 11-A: 2.1% C, 4.0% Si, 9.1% Cr, 4.7% Co,
Comparative steel 12-A: 3.0% C, 4.0% Si, 9.0% Cr, 4.6% Co,
Comparative steel 13-A: 2.5% C, 4.0% Si, 12.0% Cr, 4.3% Co,
Comparative steel 15-A: 1.0% C, 0.2% Si, 4.0% Cr, 7.3% Co,
Here, the comparative steel 15 is a conventional steel in which all of the C, Si, Cr, and Co contents are out of the composition range of the present invention, and the comparative steel 11 has the C content and the Si content. Although within the scope of the present invention, the Cr content and the Co content are outside the scope of the present invention, and the comparative steels 12 and 13 have the C content, the Si content and the Cr content within the scope of the present invention. However, the Co content is outside the scope of the present invention.

In Figure 1, a reference hardness at tempering temperature of 600 ° C. The _{(H 600),} tempering temperature T (° C.) (where, T ≧ 600) when the hardness at was _{H T,} decreases the hardness due to tempering temperature When the softening ratio (however, the softening ratio (%) = (H _T −H ₆₀₀ ) × 100 / H ₆₀₀ ), which is an index indicating the degree of the above, the comparative steel 11 having a high Si content is compared with the comparative steel 15. Comparative steels 12 and 13 having excellent softening resistance but simultaneously adding a large amount of Cr with Si have better tempering softening resistance than Comparative Steel 11, but simultaneously adding a large amount of Co together with Si and Cr. It can be seen that the inventive steels 1 and 2 have even more excellent temper softening resistance than the comparative steels 11 to 13 and 15.

  FIG. 2 shows the tempering temperature (° C.) − By the total content of C + Si + Cr + Co for the steel of the present invention satisfying the component compositions of claims 1 and 2 and the comparative steel having a component composition outside the scope of the present invention. As shown in FIG. 2, the steels according to the present invention 1, 5 and 9 have a total content of C + Si + Cr + Co in the range of 25.0 to 35.0% by mass. 2)), the change in tempering hardness due to high-temperature tempering is small and the amount of decrease in tempering hardness is small compared to the comparative steels 11, 12, and 13.

  From this, the C content is set to 2.0 to 3.0%, the Si content is increased to 3.0 to 6.0%, and the Cr content is set to 9.0 to 15.0. %, The high temperature temper softening resistance of the alloy steel of the present invention in which the Co content is 10.0 to 15.0% (more preferably, the total content of C + Si + Cr + Co is 25.0 to 35.0% by mass) is It turns out that it is very excellent.

The reason why the high-temperature tempering softening resistance is improved in the present invention has not yet been fully elucidated. However, in a temperature range of 600 to 700 ° C., Si contained in a large amount in the steel forms cementite. It is considered that Cr dissolved in cementite continuously forms carbides, thereby delaying cementite aggregation and coarsening and delaying softening of the matrix during tempering.
In addition, the simultaneous addition of Si and Cr forms an intermetallic compound of Si and Cr in the matrix, and the tempering secondary hardening peak moves to the high temperature side, and the softening start point during tempering is on the high temperature side. It is done.
It is presumed that the high temperature temper softening resistance is greatly improved by these effects.

Total of one or two of W and Mo: 9.0 to 11.0%
W forms MC-type and M ₆ C-type carbides, and a part thereof dissolves in the matrix to improve wear resistance and high-temperature temper softening resistance. However, when the W content is excessive, , Leading to coarsening of carbides and toughness.

Mo, like W, forms MC-type and M ₆ C-type carbides to improve wear resistance and high-temperature temper softening resistance and improve toughness, but when the Mo content becomes excessive The crystal grains become coarse and brittle, and decarburization is likely to occur during heat treatment.

  Therefore, in order to improve wear resistance and high temperature temper softening resistance, the total of one or two of W and Mo needs to be 9.0% or more, but the total amount is 11.0%. If it exceeds 1, the carbides become coarse and the toughness is lowered due to the coarsening of crystal grains. Therefore, the content of one or two of W and Mo is 9.0 to 11.0%. It was determined.

V: 1.5-2.5%
V is a strong carbide-forming element, and when combined with C, forms fine MC-type carbides, and is effective in improving wear resistance. Further, V has a crystal grain refining action, prevents a decrease in toughness due to crystal grain coarsening, and increases high-temperature temper softening resistance. In order to exert such an effect, it is necessary to contain 1.5% or more, but if it is contained excessively, grindability is impaired, so the upper limit was set to 2.5%.

Mn: 1.0% or less In the present invention, since Si contains a large amount and acts as a deoxidizing agent, it is not always necessary to add Mn that acts as a deoxidizing agent like Si, but Mn is quenched. Since there is also a property improving effect, it can be added within a range of 1.0% or less.

  As described above, the alloy steel of the present invention is in mass%, C: 2.0 to 3.0%, Si: 3.0 to 6.0%, Cr: 9.0 to 15.0%, Co: 10.0 to 15.0% (preferably, the total content of C, Si, Cr and Co is 25.0 to 35.0%), the total of one or two of W and Mo: 9 0.0 to 11.0%, V: 1.5 to 2.5%, and the balance is made of Fe. As described above, it is allowed to contain 1.0% or less of Mn, and as an inevitable impurity The alloy steel of the present invention is allowed to contain P, S, N, Ni, Nb, Cu, As, Sb, etc. within a range that does not affect the high temperature temper softening resistance.

Moreover, when the high temperature temper softening resistance of the alloy steel of the present invention was quantified by experiment, the softening ratio (%) at 600 to 700 ° C.
Softening ratio (%) = (H _T −H ₆₀₀ ) × 100 / H ₆₀₀
In the alloy steel of the present invention, it was confirmed that the softening ratio (%) was in the range of 0 to 10%.

Here, the softening percentage, as a reference hardness at tempering temperature of 600 ° C. The _{(H 600),} tempering temperature T (° C.) (where, 600 ≦ T ≦ 700) The hardness at was _{H T} This is an index indicating the degree of hardness reduction due to tempering temperature.

  Further, in the present invention, a person skilled in the art such as a composite nitride layer of Al and Ti, a composite nitride layer of Al, Ti and Si, a composite nitride layer of Al and Cr, etc. on the surface of a drill made of alloy steel as a base. Can be used as a surface-coated alloy steel drill by vapor deposition of a well-known hard coating layer.

  The surface-coated alloy steel drill on which the hard coating layer is formed by vapor deposition is further improved in heat resistance and wear resistance, and exhibits further excellent machinability under high-temperature cutting conditions.

  The alloy steel drill and surface-coated alloy steel drill of the present invention increase the Si addition amount, the Cr addition amount, and the Co addition amount, particularly with C as the alloy component being 2.0 to 3.0%. The Si content is 3.0 to 6.0%, the Cr content is 9.0 to 15.0%, the Co content is 10.0 to 15.0% (preferably C, Si, Cr and Co). Therefore, even when tempering is performed in a temperature range of 600 to 700 ° C., it exhibits excellent high-temperature tempering softening resistance, so that it is exposed to high temperatures. Even under high-speed cutting conditions, since the cutting edge is not softened (decrease in hardness), excellent cutting performance can be exhibited over a long period of use.

It is a graph which shows the relationship between tempering temperature (degreeC) and a softening ratio (%) at the time of performing tempering. It is a graph which shows the influence of the total content of C, Si, Cr, and Co on the relationship between the tempering temperature (° C.) and the tempering hardness (HRC) of the steel of the present invention and the comparative steel.

  The invention is illustrated below by means of examples.

  A powder having a predetermined component composition produced by a nitrogen gas atomization method is filled into a capsule and degassed, and then subjected to HIP treatment (hot isostatic pressing) at a temperature of 1150 ° C. and a pressure of 100 MPa to obtain the component composition shown in Table 1. The powder alloy steels 1 to 10 of the present invention (hereinafter referred to as the present invention steels 1 to 10) were produced.

  Similarly, powder alloy steels 11 to 15 of comparative examples (hereinafter referred to as comparative steels 11 to 15) having component compositions that depart from the present invention were produced.

  Similarly, Table 1 shows component compositions of comparative steels 11 to 15.

上記本発明鋼１〜１０について、表２に示す条件で熱処理を行い、本発明鋼１−Ａ〜１−Ｄ，本発明鋼２−Ａ〜２−Ｄ，本発明鋼３−Ａ、３−Ｂ，本発明鋼４−Ａ、４−Ｂ，本発明鋼５−Ａ、５−Ｂ，本発明鋼６−Ａ、６−Ｂ，本発明鋼７−Ａ、７−Ｂ，本発明鋼８−Ａ、８−Ｂ，本発明鋼９−Ａ、９−Ｂ，本発明鋼１０−Ａ、１０−Ｂを作製した。

About the said invention steel 1-10, it heat-processes on the conditions shown in Table 2, this invention steel 1-A to 1-D, this invention steel 2-A to 2-D, this invention steel 3-A, 3- B, Invention Steel 4-A, 4-B, Invention Steel 5-A, 5-B, Invention Steel 6-A, 6-B, Invention Steel 7-A, 7-B, Invention Steel 8 -A, 8-B, Invention steels 9-A, 9-B, Invention steels 10-A, 10-B were produced.

  Similarly, the comparative steels 11 to 15 were also heat-treated under the conditions shown in Table 3, and the comparative steels 11-A to 11-D, the comparative steels 12-A to 12-D, the comparative steels 13-A and 13-B were used. Comparative steels 14-A and 14-B and comparative steels 15-A and 15-B were produced.

  That is, after performing austenitizing treatment under conditions of 850 to 950 ° C. × 60 to 90 minutes, quenching is performed by holding at 1130 to 1180 ° C. for 30 minutes, then holding at 600 to 700 ° C. for 1 hour, and the number of times of return is 3 Tempering was performed.

For each, the hardness is measured by measuring the quenching hardness, the hardness at 600 ° C. (H ₆₀₀ ), and the hardness at a predetermined tempering temperature T (H _T ) with a Rockwell hardness meter (both are average values of five points). And the softening ratio (%) from the hardness value (= (H _T −H ₆₀₀ ) × 100 / H ₆₀₀ )
Was calculated.

  These values are shown in Tables 2 and 3.

  In addition, about this invention steel 1-A, this invention steel 2-A, comparative steel 11-A, comparative steel 12-A, comparative steel 13-A, and comparative steel 15-A, the relationship between tempering temperature and a softening ratio is shown. This is shown in FIG.

表２、表３および図１から明らかなように、６００〜７００℃という高温焼戻しが行われた場合でも、本発明鋼１〜１０は、すぐれた焼戻し硬さ（ＨＲＣは５０以上）を有するとともに、比較鋼１１〜１５に比してすぐれた高温焼戻し軟化抵抗性を示し、例えば、焼戻し温度７００℃における軟化割合（％）は最大でも−１０％（例えば、本発明鋼１−Ｄ，３−Ｂ，５−Ｂ，１０−Ｂ）であった。

As is apparent from Tables 2 and 3 and FIG. 1, even when high temperature tempering of 600 to 700 ° C. is performed, the steels 1 to 10 of the present invention have excellent tempering hardness (HRC is 50 or more). And high temperature tempering softening resistance compared to comparative steels 11 to 15, for example, the softening ratio (%) at tempering temperature of 700 ° C. is −10% at the maximum (for example, steels of the present invention 1-D, 3- B, 5-B, 10-B).

On the other hand, the comparative steels 11 to 15 are inferior in high-temperature temper softening resistance as compared with the inventive steels 1 to 10, for example, the softening ratio (%) at a tempering temperature of 700 ° C.
Are -34% (Comparative Steel 14-B) and -26% (Comparative Steel 15-B), and cannot be said to have sufficient high-temperature temper softening resistance.

  Next, the present invention steels 1 to 10 having the composition shown in Table 1 prepared as described above are used as a raw material, and the diameter x length of the groove forming portion is 6 mm x 56 mm and the twist angle is 30 degrees by grinding. The present invention alloy steel drills (hereinafter referred to as the present invention drills) 1 to 10 having a two-blade shape were manufactured, respectively.

  Similarly, the comparative example drills 11-15 were produced also about the comparative example steels 11-15.

Next, a hard coating layer made of (Al _0.6 , Ti _0.4 ) N and having a layer thickness of 5 μm is deposited on each of the above-described drills 1 to 10 and comparative drills 11 to 15 by arc ion plating. By forming, drills 1-10 of the present invention alloy steel (referred to as this invention coated drill) and 11-15 drills made as a comparative example alloy (referred to as comparative example covered drill) were produced.

  Next, using the inventive coated drills 1 to 10 and comparative example coated drills 11 to 15 on which the hard coating layer was formed by vapor deposition, a wet high speed drilling cutting test was performed under the following conditions to evaluate the cutting performance.

Work material-plane: 100 mm x 250 mm, thickness: 16 mm JIS / S50C plate material,
Cutting speed: 60 m / min. ,
Feed: 0.22 mm / rev,
Hole depth: 16 mm,
Wet high-speed drilling test of carbon steel under the conditions (normal cutting speed is 30 m / min.).
In the wet high-speed drilling test (using a water-soluble cutting oil), the cutting length up to the tool life was measured.
The results are shown in Table 4.

表４に示す結果から、本発明被覆ドリル１〜１０は切削加工時の高温にさらされても、切刃部の高温焼戻し軟化抵抗性が高いことから、軟化（硬度低下）による摩耗進行は抑制され、また、欠損等の異常損傷を生じることもなく、正常な摩耗形態をとり、本発明被覆ドリル１〜１０では切削長は１２０ｍ以上であり、すぐれた切削性能を示した。

From the results shown in Table 4, the coated drills 1 to 10 of the present invention have high resistance to high-temperature tempering and softening at the cutting edge portion even when exposed to high temperatures during cutting, so that the progress of wear due to softening (decrease in hardness) is suppressed. Moreover, it took a normal wear form without causing abnormal damage such as defects, and the coated drills 1 to 10 of the present invention had a cutting length of 120 m or more, and showed excellent cutting performance.

  On the other hand, since the comparative example coated drills 11 to 15 have lower softening resistance than the coated drills 1 to 10 of the present invention, the progress of wear due to the decrease in hardness is promoted, the cutting length is less than 120 m, and the short service life is achieved. Met.

  As described above, the alloy steel drill of the present invention, the surface-coated alloy steel drill has excellent high-temperature tempering softening resistance, and as a result of preventing hardness reduction of the blade edge, under cutting conditions that generate high heat, Since it exhibits excellent cutting performance and wear resistance, and has a long life, it can be said that the industrial benefits are very large.

Claims (3)

  In mass%, C: 2.0 to 3.0%, Si: 3.0 to 6.0%, Cr: 9.0 to 15.0%, Co: 10.0 to 15.0%, W and Sum of one or two of Mo: 9.0 to 11.0%, V: 1.5 to 2.5%, the balance is an alloy steel having high temperature temper softening resistance composed of Fe and inevitable impurities Alloy steel drill characterized by comprising.   The total content of C, Si, Cr and Co is 25.0 to 35.0%. The alloy steel drill comprising the alloy steel having high temperature temper softening resistance according to claim 1. .   A drill made of surface-coated alloy steel, characterized in that the alloy steel having high-temperature temper softening resistance according to claim 1 or 2 is used as a base, and a hard coating layer is formed by vapor deposition on the surface of the base.

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