JP2002256381A - Free cutting tool steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide free cutting tool steel which has excellent free cutting property, and in which the anisotropy of mechanical properties in the cogging direction of the stock, particularly, in toughness is hard to occur. SOLUTION: The steel contains Ti and/or Zr so as to control the value of WTi+0.52 WZr to 0.03 to 3.5 mass% provided that the content of Ti is defined as WTi (mass%), and the content of Zr is defined as WZr (mass%). Further, at least one selected from S, Se and Te is contained so as to control the value of WS+0.4 WSe+0.25 WTe to 0.01 to 1.0 mass%, and also, so as to control the ratio of (WTi+0.52 WZr)/(WS+0.4 WSe+0.25 WTe) to 1 to 4 provided that the content of S is defined as WS (mass%), the content of Se is defined as WSe (mass%), and the content of Te is defined as WTe (mass%). Further, free cuttability impartion compound phases containing Ti and/or Zr as the main metallic element component, and essentially consisting of C and containing at least one selected from S, Se and Te as bonding components with the metalic element component are dispersedly formed in the structure in the range of 0.1 to 10% by area in the cross section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tool steel used as a material for tools and molds, and more particularly to tool steel having free-cutting properties.

[0002]

2. Description of the Related Art In many cases, molds and tools are made of an annealed steel material, and are subjected to roughing, quenching and tempering to a predetermined hardness and then finishing. Further, there is a case where a material which has been quenched and tempered to a predetermined hardness is directly processed into a mold and tools for the purpose of shortening a delivery time. this is,
Finally, it relates to the process sharing between a material supplier and a user who is a manufacturer of a mold or a tool for manufacturing a metal fitting or a tool. In other words, in the former, the material supplier supplies the steel material to the user in an annealed state, and the user performs roughing,
It takes the form of quenching and tempering and finishing.
In the latter case, the steel material is supplied in the form of a quenched and tempered material, while the user only shares the final processing. However, since the final processing does not pass through the rough processing, the processing amount itself is slightly increased.

[0003] In any of the above cases, machining is carried out mainly by removal such as cutting and grinding, but in the case of tool steel, hardness and toughness sufficient to overcome the work material are required. Therefore, it is not easy to machine the tool steel itself as compared with other iron-based materials. In particular, after quenching and tempering, processing becomes more difficult. In recent years, there has been a growing need to shorten the delivery time of molds and expand unmanned machining in order to reduce the manufacturing cost of molds and tools. To respond to this, machinability is higher than that of existing materials. Providing improved materials has been desired.

As elements for improving machinability of iron-based materials, S,
Pb, Se, Bi, Te, Ca and the like are known. Of these, Pb has been gradually shunned in recent years as concerns about environmental protection are increasing on a global scale, and the number of devices and parts that restrict its use is increasing. Therefore, a material using S or Te as a main component of the machinability improving element is considered as an alternative material. These mainly generate inclusions such as MnS and MnTe, and enhance the machinability and grindability by the stress concentration effect at the time of chip formation on the inclusions and the lubricating action between the tool and the chip.

[0005]

However, in steel materials using S or Te as a machinability improving element, MnS or MnTe
Although such inclusions improve the machinability, they have the disadvantage that they tend to elongate in the forging direction during rolling or forging, and tend to cause undesirable anisotropy in the mechanical properties of the material. Specifically, a direction perpendicular to the forging direction (hereinafter, referred to as a T direction)
As a result, the crack resistance is impaired. In addition, depending on the type of use of tools and dies, the direction in which the material is used must be taken into consideration.
This can easily lead to a decrease in the yield of material utilization.

An object of the present invention is to provide a free-cutting tool steel which has excellent machinability and hardly causes anisotropy in mechanical properties, particularly toughness, in the forging direction of a material.

[0007]

In order to solve the above-mentioned problems, a free-cutting tool steel according to the present invention has a capacity of 0.1%.
２．５2.5 wt% C, the Ti content is WTi (mass%), the Zr content is WZr (mass%), and WTi +
0.52WZr is 0.03-3.5% by mass,
WS + 0.4WSe + 0.25WT, containing Ti and / or Zr, with the S content as WS (mass%), the Se content as WSe (mass%), and the Te content as WTe (mass%)
e becomes 0.01 to 1.0% by mass, and (WTi +
0.52WZr) / (WS + 0.4WSe + 0.25WTe)
Is at least one of S, Se, and Te, and Ti and / or Zr is a main component of the metal element component, and C is a bonding component with the metal element component. Essentially, the free-cutting property-imparting compound phase containing at least one of S, Se and Te is dispersed and formed in the structure in the area ratio of 0.1 to 10% in the cross section. And In this specification, “main component” (also “mainly”) means a component having the highest weight content (including a phase as a concept) in a material or structure of interest. .

In the above composition range, C, Ti, Zr,
By including S, Se and Te, Ti and / or Zr are mainly composed of a metal element component in the steel material structure, and C is essential as a binding component with the metal element component;
A free-cutting property imparting compound phase containing at least one of Se and Te is dispersed and formed. By forming this compound, good machinability can be imparted to the steel material. The present inventors have found that when performing processing such as cutting or grinding, when the material portion to be removed is cut off by processing, the finely dispersed granular free-cutting property imparting compound phase acts like a perforation. Then, as a result of promoting the formation of the cut surface, it is considered that the machinability is improved.

An important point is that such a free-machining property imparting compound phase does not extend in the forging direction even after rolling or forging, and maintains a granular state. As a result, unlike MnS or the like which is easily stretched in the forging direction, it is possible to significantly suppress the decrease in the toughness in the T direction. Further, the free-cutting tool steel of the present invention has good machinability not only in the annealed state but also in the quenched and tempered state, and in order to cope with the shortened delivery time, the quenched and tempered state. It becomes possible to cope with heavy machining.

[0010] As described above, the free-cutting property imparting compound phase must be dispersed and formed in the structure in an area ratio of 0.1 to 10% in the cross section. When the area ratio is less than 0.1%, the effect of improving machinability is poor, and when it exceeds 10%, toughness is reduced. The area ratio is more desirably 0.2 to 4%.
It is good to do. Further, in order to enhance the machinability improving effect, the size of the free-machining imparting compound phase observed in the polished cross-sectional structure (when the circumscribed parallel line is drawn while changing the position to the observed outline of the compound particle). , Expressed by the maximum interval between the circumscribed parallel lines) is preferably, for example, about 1 to 5 μm.

The free-cutting property imparting compound phase is, for example, a composition formula M ₄
Q ₂ C ₂ (where M is a metal element component containing Ti and / or Zr as a main component, and Q is at least one of S, Se and Te). Can be. This compound is particularly difficult to elongate in the forging direction, has good dispersibility in the structure, and has the effect of enhancing machinability without causing extreme anisotropy in the mechanical properties of the material. Are better. In addition, about the component M in the said compound, although Ti is essential, Zr may be contained, and when V is contained as an alloy component, at least one part is contained in the M component. It may be. Also, for the Q component, S, Se and T
e may contain only one kind, or two or more kinds. In addition, components M and Q
In both cases, the components other than those described above are contained as accessory components as long as the hard-stretchability-imparting compound phase should not have the poor stretchability and dispersibility that the free-machining property imparting compound phase should have. Do not hinder.

The identification of an M ₄ Q ₂ C ₂ compound in steel (hereinafter sometimes abbreviated as “TICS” in this specification) may be performed by X-ray diffraction (eg, diffractometer). Method) and electron beam probe microanalysis (EPM)
A) can be carried out by the method. For example, M ₄ Q ₂ C ₂
Whether or not the system compound exists can be confirmed by whether or not a peak of the corresponding compound appears in the measurement profile by the X-ray diffractometer method. The formation region of the compound in the structure is obtained by performing a surface analysis by EPMA on the cross-sectional structure of the steel material and comparing the two-dimensional mapping results of characteristic X-ray intensities of Ti, Zr, S, Se or C. Can be identified.

Hereinafter, the reasons for limiting the content range of each component in the tool steel of the present invention will be described. First, C is an essential element for ensuring wear resistance as tool steel, and in the present invention, it is also an essential element of the free-cutting property imparting compound phase. However, if the content is less than 0.1% by mass, sufficient hardness and wear resistance as tool steel cannot be secured. On the other hand, an excessive addition causes a decrease in toughness and hot strength, so the upper limit is made 2.5% by mass.

Ti and Zr are essential constituent elements of the free-machining imparting compound phase which plays a central role in the development of the machinability improving effect in the free-machining tool steel of the present invention. WTi + 0.52W
If Zr is less than 0.03% by mass, the amount of the compound phase imparting free machinability becomes insufficient, and a sufficient effect of improving machinability cannot be expected. On the other hand, when WTi + 0.52WZr is excessive, the machinability is rather lowered, so the upper limit is 3.5% by mass.
And

As in the above-described M ₄ Q ₂ C ₂ compound phase, the free-cutting property imparting compound phase has a substantially constant binding stoichiometric ratio of the binding component Q or C to the metal component M, It has been empirically found that the nature of the property imparting is governed by the formation area ratio of the compound. Therefore, it is often more convenient to use the atomic content than the weight content as the content of M or Q as a scale for estimating the amount of phase formation. In the present specification, the M component indicates an atomic relative content based on Ti, that is, an optimum content range in a form converted into a Ti weight of the same number of atoms. In addition, Q
The components show the relative content of atoms based on S, that is, the optimum content range in a form converted to S weight of the same number of atoms. For example, in the case of the M component, WZr is multiplied by the coefficient 0.52 in the above for this purpose, and when other subcomponents are contained, TiZ having the same number of atoms is used.
It is desirable that the total of the mass contents multiplied by a coefficient for converting into weight be 0.03 to 3.5% by mass.

Similarly, S, Se and Te (Q component) are also essential constituent elements of the free-cutting property imparting compound phase. WS +
When 0.4WSe + 0.25WTe is less than 0.01% by mass,
The formation amount of the free-cutting property imparting compound phase becomes insufficient, and a sufficient machinability improving effect cannot be expected. On the other hand, WS + 0.4WS
If e + 0.25WTe is excessive, the toughness will decrease.
The upper limit is set to 1.0% by mass. In addition, about a Q component,
When other subcomponents are contained, the sum of the mass contents multiplied by a coefficient for converting to the S weight of the same number of atoms is 0.1%.
It is desirable that the content be 01 to 1.0% by mass.

The above-mentioned M ₄ Q _{2 is used} as a free-cutting property-imparting compound phase.
When the C ₂ compound phase is mainly formed, the weight ratio of M to Q when all M in the compound is Ti and Q is S is 3: 1. Therefore, ideally, M and Q should be added without excess or deficiency, that is, Ti / S =
(WTi + 0.52WZr) / (WS + 0.4WSe + 0.2
5WTe) is preferably 3. However, the effect of the present invention for improving the machinability without causing excessive toughness anisotropy is not limited to the case where the above value is 3, but can be sufficiently achieved even in the range of 1 to 4.

Next, the free-cutting tool steel of the present invention contains 2.0%
Mn of not more than mass%, Ni of not more than 2.5% by mass, Cr of not more than 17% by mass, Mo and / or W having not more than 12% by mass of Mo + 0.5W, and V of not more than 6% by mass, 15.0% by mass. % Or less selected from Co. Hereinafter, the reason will be described.

Mn: has the effect of improving hardenability and hardness. Further, since a compound effective for machinability is generated by coexistence with S or Se, it is effective to add the compound when machinability is particularly important. However, when a more remarkable effect is expected, the content is desirably 0.1% by mass or more. On the other hand, excessive formation of MnS causes excessive anisotropy of the toughness described above, so the upper limit is 2% by mass. Note that Mn is also useful as a deoxidizing element at the time of refining, and may be inevitably contained.

Ni: Effective for improving hardenability, strengthening the matrix, or improving corrosion resistance. When a more remarkable effect is expected, the content is desirably 0.1% by mass or more. On the other hand, if added excessively, the processability will decrease,
The upper limit is set to 2.5% by mass.

Cr: Forming carbides has the effect of strengthening the matrix, improving wear resistance, and improving hardenability. However, when a more remarkable effect is expected, the content is desirably 0.1% by mass or more. On the other hand, excessive addition causes addition of hardenability and hot strength.
It is set to 7.0% by mass.

Mo, W: It has the effect of forming a carbide to strengthen the matrix, improve wear resistance, and improve hardenability. Mo and W are elements having the same effect.
Is about twice the atomic weight of Mo, so Mo + 0.5W
(Of course, only one of them may be added, or both may be added together). However, when a more remarkable effect is expected, Mo + 0.5W is set to 0.1.
It is desirable that the content be not less than mass%. Excessive addition of Mo and / or W increases the amount of carbides and causes addition of toughness. Therefore, the upper limit of Mo + 0.5W is set to 12.0% by mass.

V: It forms carbides and has the effect of strengthening the matrix and improving the wear resistance. In addition, the formation of fine carbides is also effective for refining crystal grains and improving toughness. However, when a more remarkable effect is expected, the content is desirably 0.1% by mass or more. Note that V
May also be a forming component of the above-mentioned M ₄ Q ₂ C ₂ compound. On the other hand, if added excessively, the toughness is reduced, so the upper limit is set to 6.0% by mass.

Co: Effective for strengthening the matrix.
In order to obtain a more remarkable effect, it is preferable to contain 0.3% by mass or more. However, when added in excess,
Since the hot workability is reduced and the cost of raw materials is increased, the upper limit is set to 1.5% by mass.

Although the following elements can be positively added, they may be inevitably mixed in for reasons of the production method, and are shown below together with their allowable upper limits. Si: Used as a deoxidizing element during refining, and is often inevitably contained. On the other hand, the positive addition effect has an effect of increasing softening resistance and, when used in a hot die or a cutting tool, suppressing softening during holding at a high temperature. However, since toughness is improved by reducing the amount of Si, Si may be reduced as much as possible. In this case, deoxidation is performed with another element such as Al, Mn, and Ca. The upper limit is set to 2.0% by mass in consideration of a decrease in toughness due to an increase in the amount of Si.

Al: Used as a deoxidizing element during refining,
Often unavoidable. In addition, as a positive addition effect, the formation of AlN can contribute to the refinement of crystal grains and, consequently, the improvement of strength or toughness. However, an excessive content causes a decrease in toughness, so the upper limit is set to 0.1% by mass.

N: Element unavoidably mixed in the production of steel. On the other hand, a nitride is formed with Ti, Al, V, etc.
Since it is effective in refining crystal grains, it may be added positively in some cases. However, in the present invention, if added excessively, a large amount of TiN is formed, and the amount of the free-machining property imparting compound phase such as the M ₄ Q ₂ C ₂ phase is reduced.
% By mass.

Further, the free-cutting tool steel of the present invention can contain the following elements as necessary. Ca: ≦ 0.05% by mass It is an element effective for improving hot workability. In addition, sulfides and oxides are formed, which is effective in improving machinability. However, even if it is added excessively, these effects are saturated, so that the upper limit of the content is 0.050% by mass.

Pb: ≦ 0.2% by mass, Bi: ≦ 0.2% by mass Both are dispersed in steel and have an effect of enhancing machinability.
However, if added excessively, the hot workability decreases,
The upper limit is set to 0.2% by mass. Further, in order to obtain a remarkable effect, it is desirable to add 0.02% by mass or more in each case.

B: ≦ 0.010% by mass It is an element effective for improving hardenability. However, if added excessively, hot workability and toughness decrease, so the upper limit is made 0.010% by mass. In order to obtain a remarkable effect, it is desirable to add 0.001% by mass or more.

Nb (% by mass) +0.5 Ta (% by mass):
≦ 0.05% by mass All form fine carbides, and are effective for refining crystal grains and improving toughness. Note that Ta has an atomic weight about twice as large as Nb, and is defined as Nb + 0.5Ta (only one of Nb and Ta may be added, or may be co-added). In addition, since the effect is saturated even if it is added excessively, the upper limit of Nb + 0.5Ta is set to 0.05% by mass. To obtain a remarkable effect, Nb + 0.5Ta
Is desirably 0.005% by mass or more.

Rare earth metal element (REM): ≤0.50
It has the effect of fixing impurities such as mass% O and P, increasing the cleanliness of the matrix, and improving the toughness. If a large amount is added, ground flaws occur, so the upper limit is made 0.50% by mass. Note that RE
As M, it is easy to handle mainly using an element having low radioactivity, and from this viewpoint, Sc,
Y, La, Ce, Pr, Nd, Sm, Eu, Gd, T
It is effective to use one or more selected from b, Dy, Ho, Er, Tm, Yb and Lu. In particular, it is desirable to use light rare earth elements, particularly La or Ce, from the viewpoints of more remarkable manifestation of the above effects and cost.
However, a trace amount of a radioactive rare earth element (for example, Th or U) inevitably remaining in the rare earth separation process or the like may be contained. In addition, non-separable rare earths such as misch metal and dymium can be used from the viewpoint of reducing raw material costs.

The free-cutting tool steel of the present invention is formed by dispersing and forming the above-mentioned free-cutting imparting compound phase in the structure based on various conventional steels used as tool steel. Thus, good machinability can be imparted to the base tool steel without significantly impairing the performance thereof. Hereinafter, a specific example will be described.

Containing 0.1 to 0.6% by mass of C;
Mo and / or W in which the total of Mn of 0% by mass or less, Ni of 1.0% by mass or less, Cr of 3% by mass or less, and Mo + 0.5W is 1.0% by mass or less, 0.5% by mass or less A composition containing at least one selected from V and 1% by mass or less of Co. A steel material having this composition is not required to have high hardness and heat resistance, and is suitable for use in which complicated cutting for forming a cavity or the like is required to be easy, such as a material for a plastic molding die. Representative examples of the base composition include JIS: S55C and AISI: P20.

C is contained in an amount of 0.2 to 0.6% by mass.
3 to 7% by mass of Cr as an essential component, Mn of 2.0% by mass or less, Ni of 2.5% by mass or less, Mo and / or W in which the total of Mo + 0.5W is 4.0% by mass or less; A composition containing at least one element selected from V at 2% by mass or less and Co at 5.0% by mass or less. This corresponds to a material whose high-temperature strength has been improved by blending a certain amount of Cr in addition to the above composition, and for example, a material for a hot die (for example, a hot press die, a hot forging die, It is effective to use it as a die casting mold, a hot extrusion molding mold, or the like.
As representative examples of the base composition, JIS: SKD6, SK
D8, SKD61, Cr-Mo steel (for example, 5 mass% Cr
-3% by mass Mo).

C is contained in an amount of 0.3 to 1.8% by mass, and the total of Cr of 4% by mass or less, Mn of 2.0% by mass or less, Ni of 2.5% by mass or less, and Mo + 0.5W is 2. Mo and / or W to be 5% by mass or less, V and 1% by mass or less.
A composition containing at least one member selected from Co of 0% by mass or less. This material is equivalent to a material with higher hardness due to its high carbon composition, and is used for cold mold materials (cold press dies, press punches, punches, dies, etc.) and cutting tool materials (knives,
Suitable for use as razor, saw blade, etc.), and material for impact-resistant tools (eg, chisel, punch, etc.). As representative examples of the base composition, JIS: SK3, SKS4, SK
S51 can be exemplified.

Containing 0.5 to 2.5% by mass of C,
17% by mass of Cr as an essential component, 2.0% by mass or less of Mn, 1.0% by mass or less of Ni, Mo + 0.5W and the total of Mo and / or W become 1.5% by mass or less, 1% by mass % Of V and 1.0% by mass or less of Co
Composition containing more than one species. A steel type with improved wear resistance and hardenability due to the inclusion of Cr in the high carbon region, suitable for use as a material for cold dies (cold press dies, press punches, punch dies, dies, etc.) ing. Representative examples of the base composition include JIS: SKD1, SKD11, and SK.
D12, Cr tool steel (for example, 8 mass% Cr) and the like can be exemplified.

C is contained in an amount of 0.5 to 2.0% by mass,
Mo and / or W as an essential component having a total of 7% by mass of Cr and Mo + 0.5W of 4 to 12% by mass or less, V as an essential component of 0.5 to 6.0% by mass, 2.0% by mass or less of Mn, 1.0% by mass or less of Ni
And a composition containing at least 3 kinds selected from 15.0% by mass or less of Co. The base composition corresponds to high speed tool steel (so-called high speed steel). Well-known fields of application of high-speed tool steels, eg materials for cutting tools (drills, end mills, cutting tools, indexable inserts, etc.), materials for cold dies (cold press dies, press punches, punches, dies, etc.) Or, it is suitable for use as a material for a hot die (a hot press die, a hot forging die, a hot extrusion molding die, etc.). In addition, high-speed tool steel secures abrasion resistance by crystallized carbides and further strengthens by precipitation of carbides in the matrix (iron-based substrate). In the present specification, a steel material in which only carbide is precipitated and strengthened to the same degree as ordinary high-speed tool steel is treated as belonging to high-speed tool steel (so-called matrix high-speed steel).

[0039]

EXAMPLES The following experiments were performed to confirm the effects of the present invention. (Example 1) As an alloy having a composition corresponding to the above, Table 2
And various alloys shown in Table 3 (the classification of the base composition is shown in the remarks column of Table 4) were melted and cast in the form of 150 kg ingot in a vacuum induction furnace. The ingot obtained is 12
Hot forging at 00 ° C, thickness 60mm, width 65
mm. The obtained steel slab was kept at 870 ° C. for 5 hours and then annealed by cooling at 15 ° C./h.

From the annealed steel pieces, a Charpy impact test piece (No. 3 test piece (having a so-called 2 mm U notch) specified in JIS: Z2202) material and a machinability test material (dimensions: height 55 mm) , A rectangular parallelepiped shape having a width of 60 mm and a length of 200 mm). In addition, the Charpy impact test specimen was produced as one set of two types, a T-direction specimen having a notch direction parallel to the forging direction of hot forging, and an L-direction specimen having the same vertical direction. In addition, one of the above-mentioned machinability test piece materials was used, and the surface thereof was finish-processed to obtain an annealed machinability test piece.

Next, one of the Charpy impact test specimen material and the machinability test specimen material was subjected to normalizing or quenching and tempering treatment under a constant condition for each base composition shown in Table 1, and the surface was further finished. This was processed into a final Charpy impact test specimen and a quenched and tempered test piece (normalized only for those having a base composition of S55C) as a machinability test specimen. Also, using the machinability test specimen material among them, the Rockwell C scale hardness (S) was determined by the method specified in JIS: Z2245.
For 55C only, Shore hardness specified in JIS: Z2246) was measured.

[0042]

[Table 1]

Then, using a Charpy impact test piece,
When the Charpy impact test specified in IS: Z2242 is performed, and the test is performed on both a T-direction test piece whose notch direction is parallel to the forging direction and an L-direction test piece that is also vertical, the T Assuming that the Charpy impact value obtained for the directional test piece is IT and the Charpy impact value obtained for the L direction test piece is IL, IT / IL (T
/ L). In addition, annealed machinability test pieces (S
A) and a quenched and tempered machinability test specimen (HT) were used to conduct a machinability test under the following conditions. That is,
For both the annealed material and the quenched and tempered material, the machinability is determined by cutting with a carbide end mill, measuring the cutting length until the flank wear width becomes 0.3 mm, and evaluating the machinability. In addition, a result is relatively displayed with the cutting length of the conventional steel being 100.
The test conditions were as follows: The cutting width was 1 m with a single-edge carbide end mill.
m, the cutting depth was 3 mm, the cutting speed was 50 m / min, the feed rate of the workpiece was 0.05 mm / blade, and the cutting was performed by wet cutting using cutting oil.

Further, the surface of the Charpy impact test specimen after the test was mirror-polished, and then subjected to SEM observation and EPM.
An A-plane analysis was performed to determine the formation area ratio of TICS. When the structure of TICS was examined by X-ray diffraction, it was found that the above-mentioned M ₄ Q ₂ C ₂ compound phase was mainly used. Table 4 shows the above results.

[0045]

[Table 2]

[0046]

[Table 3]

[0047]

[Table 4]

As is clear from these results, among alloys having the same base composition, those satisfying the composition of the present invention can be obtained in any state of annealing and quenching and tempering (or normalizing). The machinability is excellent, the difference between the Charpy impact values in the T direction and the L direction is small, and it can be seen that the anisotropy is improved.

(Example 2) As alloys having the above compositions, various alloys shown in Tables 5 and 6 (the classification of base compositions are shown in the remarks column of Table 7) were melted in the same manner as in Example 1. Made and cast. The obtained ingot was made into a steel piece by hot forging under the same conditions as in Example 1 and further subjected to an annealing treatment. From the annealed steel pieces, the same Charpy impact test material and the machinability test material as in Example 1 were cut out. In addition, one of the above machinability test specimen materials
The surface was finished and used to obtain an annealed machinability test piece. Next, one of the Charpy impact test material and the machinability test material was subjected to a quenching and tempering treatment under a certain condition for each base composition shown in Table 1, and the surface was further processed to obtain a final Charpy material. An impact test piece and a quenched and tempered machinability test piece were used. Then, as in the first embodiment,
Rockwell C scale hardness measurement, Charpy impact test and machinability test were performed. In addition, the surface of the Charpy impact test specimen after the test was mirror-polished, and SEM observation and EPMA surface analysis were performed on the surface to determine the formation area ratio of TICS. When the structure of TICS was examined by X-ray diffraction, it was found that the above-mentioned M ₄ Q ₂ C ₂ compound phase was mainly used. Table 7 shows the above results.

[0050]

[Table 5]

[0051]

[Table 6]

[0052]

[Table 7]

As is clear from the results, alloys having the same base composition and satisfying the composition of the present invention have excellent machinability in both annealing and quenching and tempering conditions. Further, the difference between the Charpy impact values in the T direction and the L direction is small, and it can be seen that the anisotropy is improved.

(Example 3) As alloys corresponding to the above, various alloys shown in Tables 8 and 9 (the classification of the base composition is shown in the remarks column of Table 10) were melted in the same manner as in Example 1. Made and cast. The obtained ingot was made into a steel piece by hot forging under the same conditions as in Example 1 and further subjected to an annealing treatment. From the annealed steel specimen, a Charpy impact test specimen material (same as in Example 1 except that a test specimen having a 10 mm R notch was used instead of the No. 3 test specimen) and a machinability test specimen material were cut out. In addition, one of the above-mentioned machinability test piece materials was used, and the surface thereof was finish-processed to obtain an annealed machinability test piece. Next, one of the Charpy impact test material and the machinability test material was subjected to a quenching and tempering treatment under a certain condition for each base composition shown in Table 1, and the surface was further processed to obtain a final Charpy material. An impact test piece and a quenched and tempered machinability test piece were used. And
Rockwell C scale hardness measurement, as in Example 1,
A Charpy impact test and a machinability test were performed. Also,
After the surface of the Charpy impact test specimen after the test is mirror-polished, SEM observation and EPMA surface analysis are performed on the surface, and the TI
The formation area ratio of CS was determined. The structure of TICS is X
Examination by line diffraction revealed that the above-mentioned M ₄ Q ₂ C ₂ compound phase was mainly contained. Table 10 shows the above results.

[0055]

[Table 8]

[0056]

[Table 9]

[0057]

[Table 10]

As is clear from these results, alloys having the same base composition and satisfying the composition of the present invention have excellent machinability in both annealing and quenching and tempering conditions. Further, the difference between the Charpy impact values in the T direction and the L direction is small, and it can be seen that the anisotropy is improved.

(Example 4) As alloys corresponding to the above, various alloys shown in Tables 11 and 12 (the classification of the base composition is shown in the remarks column of Table 13) were melted in the same manner as in Example 1. Made and cast. The obtained ingot was made into a steel piece by hot forging under the same conditions as in Example 1, and further subjected to an annealing treatment. From the annealed steel specimen, a Charpy impact test specimen material (10 mmR
(Same as Example 1 except that the test piece had a notch)
And a machinability test piece material were cut out. In addition, one of the above-mentioned machinability test piece materials was used, and the surface thereof was finish-processed to obtain an annealed machinability test piece. Next, one of the Charpy impact test specimen material and the machinability test specimen material is shown in Table 1.
The quenching and tempering treatment was performed under certain conditions for each base composition shown in Table 2 and the surface was further finished to obtain a final Charpy impact test specimen and a quenched and tempered machinability test specimen. Then, in the same manner as in Example 1, a Rockwell C scale hardness measurement, a Charpy impact test, and a machinability test were performed. Further, the surface of the Charpy impact test specimen after the test was mirror-polished, and SEM observation and EPMA surface analysis were performed on the surface to obtain the TICS formation area ratio. In addition, when the structure of TICS was examined by X-ray diffraction, the above-mentioned M ₄ Q ₂
C ₂ compound phase was found to be the initiative. Table 13 shows the above results.

[0060]

[Table 11]

[0061]

[Table 12]

[0062]

[Table 13]

As is clear from these results, alloys having the same base composition and satisfying the composition of the present invention have excellent machinability in both annealing and quenching and tempering conditions. Further, the difference between the Charpy impact values in the T direction and the L direction is small, and it can be seen that the anisotropy is improved.

(Example 5) As alloys having the above compositions, various alloys shown in Tables 14 and 15 (the classification of the base composition is shown in the remarks column of Table 16) were melted in the same manner as in Example 1. Made and cast. The obtained ingot was made into a steel piece by hot forging under the same conditions as in Example 1, and further subjected to an annealing treatment. From the annealed steel piece, a bending test piece material (dimensions: 3 mm × 5 mm × 35 mm) and a machinability test piece material as in Example 1 were cut out.
The bending test piece material is a set of a test piece (L-direction test piece) whose forging / stretching direction is matched in the longitudinal direction and a test piece (T-direction test piece) which is also matched in the thickness direction. We are making. In addition, one of the above-mentioned machinability test piece materials was used, and the surface thereof was finish-processed to obtain an annealed machinability test piece.
Next, one of the bending test piece material and the machinability test piece material is
Quenching and tempering treatment was performed under certain conditions for each base composition shown in Table 1, and the surface was further finished to obtain a final bending test piece and a quench and temper machinability test piece. Then, in the same manner as in Example 1, a Rockwell C scale hardness measurement and a machinability test were performed. On the other hand, using a bending test piece, a 3-point bending bending test with a span length of 30 mm was performed.
Assuming that the bending force obtained for the directional test piece is PT and the bending force obtained for the L-direction test piece is PL, PT / PL (T
/ L). Further, the surface of the bending test piece after the test was mirror-polished, and SEM observation and EPMA surface analysis were performed on the surface to determine the formation area ratio of TICS. Note that TI
When the structure of CS was examined by X-ray diffraction, the aforementioned M
It was found that the ₄ Q ₂ C ₂ compound phase was mainly used. Table 16 shows the above results.

[0065]

[Table 14]

[0066]

[Table 15]

[0067]

[Table 16]

As is evident from the results, alloys having the same base composition and satisfying the composition of the present invention have excellent machinability in both annealing and quenching and tempering conditions. Further, the difference between the Charpy impact values in the T direction and the L direction is small, and it can be seen that the anisotropy is improved.

 ──────────────────────────────────────────────────の Continuing from the front page (71) Applicant 000003713 Daido Steel Co., Ltd. 1-11-18 Nishiki, Naka-ku, Nagoya City, Aichi Prefecture (72) Inventor Kiyohito Ishida 3-5-20 Uesugi, Aoba-ku, Sendai City, Miyagi Prefecture (72) Inventor Katsunari Oikawa 4-1-34 Nishifunako, Shibata-machi, Shibata-gun, Miyagi Prefecture (72) Inventor Toshimitsu Fujii 2--30 Datodo-cho, Minami-ku, Nagoya-shi, Aichi, Japan Daido Special Steel Co., Ltd. ) Inventor Yuki Matsuda 2-30 Daido-cho, Minami-ku, Nagoya City, Aichi Prefecture Inside the Technology Development Laboratory of Daido Special Steel Co., Ltd. (72) Inventor Kozo Ozaki 2-30 Daido-cho, Minami-ku, Nagoya City, Aichi Prefecture Daido Special Steel Corporation Inside the Technology Development Laboratory (72) Inventor Seiji Kurata 2-30 Daido-cho, Minami-ku, Nagoya City, Aichi Prefecture Inside the Technology Development Laboratory, Daido Steel Co., Ltd.

Claims (15)

[Claims] 1. The composition contains 0.1 to 2.5% by mass of C, has a Ti content of WTi (mass%), and a Zr content of WZr.
(Mass%) Ti and / or Zr is contained so that WTi + 0.52WZr becomes 0.03-3.5 mass%, the S content is WS (mass%), and the Se content is WSe (Mass%) and the content of Te as WTe (mass%), WS + 0.4WSe + 0.25WTe is 0.01 to 1.0 mass%, and (WTi + 0.52WZr) / (WS + 0.4WSe + 0.2
5WTe) contains at least one of S, Se, and Te so that 1 to 4, and Ti and / or Zr as a main component of the metal element component, and as a binding component with the metal element component, C is essential, and the free-cutting property-imparting compound phase containing at least one of S, Se, and Te has an area ratio of 0.1 in cross section.
A free-cutting tool steel, wherein the tool steel is dispersedly formed in a structure in the range of 10% to 10%. 2. The free-machining property imparting compound phase has a composition formula of M ₄
Q ₂ C ₂ (where M is a metal element component mainly composed of Ti and / or Zr, and Q is at least one of S, Se and Te). Item 4. A free-cutting tool steel according to item 1. 3. Mn of 2.0% by mass or less, 2.5% by mass.
The following Ni, Cr and Mo + 0.5W of 17% by mass or less, Mo and / or W in which 12% by mass or less, and 6% by mass.
The free-cutting tool steel according to claim 1, comprising one or more selected from the following V, 15.0 mass% or less of Co. 4. 4. The method according to claim 1, wherein the Si content is 2.0% by mass or less, the Al content is 0.1% by mass, and the N content is 0.040% by mass or less. Free-cutting tool steel. 5. Ca, not more than 0.0050% by mass, 0.2
Pb by mass or less, Bi by 0.2 mass% or less, and Nb +
The method according to any one of claims 1 to 4, comprising 0.5% by mass or less of Nb and / or Ta, and 0.50% by mass or less of one or more rare earth metal elements. Free-cutting tool steel. 6. An alloy containing 0.1 to 0.6% by mass of C; Mn of 2.0% by mass or less; Ni of 1.0% by mass or less;
Mo and / or W in which the total of Cr and Mo + 0.5W of not more than 1.0% by mass is 1.0% by mass or less, and V of not more than 0.5% by mass.
The free-cutting tool steel according to any one of claims 1 to 5, further comprising at least one selected from Co and 1.0% by mass or less. 7. The free-cutting tool steel according to claim 6, which is used as a material for a plastic molding die. 8. An alloy containing 0.2 to 0.6% by mass of C, 0.3 to 7% by mass of Cr as an essential component, Mn of 2.0% by mass or less, and Ni of 2.5% by mass or less. , Mo + 0.5
Mo and / or W in which the total of W is 4.0% by mass or less,
The composition according to any one of claims 1 to 5, further comprising at least one element selected from V at 2% by mass or less and Co at 5.0% by mass or less.
Free-cutting tool steel according to the item. 9. The free-cutting tool steel according to claim 8, which is used as a material for a hot mold. 10. An alloy containing 0.3 to 1.8% by mass of C, 4% by mass or less of Cr, 2.0% by mass or less of Mn, 2.5% by mass or less.
At least one element selected from the group consisting of Mo and / or W in which the total of Ni and Mo + 0.5W of not more than 2.5% by mass is 2.5% by mass or less, V of 1% by mass or less, and Co of 1.0% by mass or less. The free-cutting tool steel according to any one of claims 1 to 5. 11. The free-cutting tool steel according to claim 10, which is used as a material for a cold mold, a material for a cutting tool, or a material for an impact-resistant tool. 12. An alloy containing 0.5 to 2.5% by mass of C, 4 to 17% by mass of Cr as an essential component, 2.0% by mass.
The following Mn, 1.0 mass% or less Ni, Mo + 0.5W
Mo and / or W in which the total of
The free-cutting tool steel according to any one of claims 1 to 5, further comprising at least one member selected from the group consisting of V and 1.0% by mass. 13. The free-cutting tool steel according to claim 12, which is used as a material for a cold mold. 14. Cr and Mo + 0.5 W as essential components containing 0.5 to 2.0% by mass of C, and 3 to 7% by mass.
As an essential component, the total of which is 4 to 12% by mass or less.
o and / or W, V as an essential component of 0.5 to 6.0% by mass, selected from Mn of 2.0% by mass or less, Ni of 1.0% by mass or less, and Co of 15.0% by mass or less. The free-cutting tool steel according to any one of claims 1 to 5, which contains three or more kinds. 15. The free-cutting tool steel according to claim 14, which is used as a material for a cutting tool, a material for a cold mold, or a material for a hot mold.