TW200936785A - Cold-work die steel and die - Google Patents

Abstract

Disclosed is a cold-work die steel which comprises the following components (by mass): C: 0.5-0.7%, Si: 0.5-2.0%, Mn: 0.1-2.0%, Cr: 5-7%, Al: 0.01-1.0%, N: 0.003-0.025%, Cu: 0.25-1%, Ni: 0.25-1%, Mo: 0.5-3%, W: 2% or less (including 0%), and S: 0.1% or less (excluding 0%), with the remainder being iron and unavoidable impurities, and which fulfills the requirements represented by the following formulae (1) to (3): (1) [Cr] x [C]=4; (2) [Al]/[N]: 1-30; and (3) [Mo]+0.5 x [W]: 0.5-3.00% [wherein [ ] means the content (%) of each element].

Description

。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 。 Die steel for wearing, bending, twisting, trimming, etc.). @ [Prior Art] The mold used for the forming of steel sheets for automobiles and steel sheets for home appliances is required to improve the life of steel sheets in accordance with the increase in strength of steel sheets. In particular, in the steel sheet for automobiles, the environmental impact is considered, and the fuel cost of the automobile is increased. Therefore, the demand for high-strength steel sheets having a tensile strength of about 590 MPa or more is rapidly increasing, but the mold surface is damaged early and occurs. "Bite" (a phenomenon of burning together during press forming) causes a problem that the life of the mold is extremely lowered. The mold is generally produced by applying a hard Q film to the surface of the mold base material (steel steel). The steel for the mold of the base material is generally produced by annealing-cutting-quenching and tempering. In the present specification, the quenching treatment is specifically referred to as a solution treatment and a tempering treatment is referred to as an aging treatment. Mold steel (cold-worked sheet steel) up to now, high-carbon high-chromium alloy tool steel represented by JIS SKD1 1 and high-speed tool steel represented by JIS SKH51 with improved wear resistance. In these tool steels, hardness is mainly increased by precipitation hardening of Cr-based carbides and Mo, W, and V-based carbides. In addition, for the purpose of improving wear resistance and toughness, we use JIS SKH51's 200936785 low-alloy high-speed tool steel (usually called high-speed steel base material) which reduces the amount of alloying elements such as C, Mo, W, and V. . It is desirable to further improve the characteristics of steel for a mold, and various methods have been proposed (for example, Patent Documents 1 and 2). Patent Document 1 discloses the purpose of suppressing the dimensional change amount (variation) caused by the quenching and tempering treatment, particularly suppressing the expansion and deformation of the tempering, and increasing the hardness, and revealing the appropriate amount of Ni and A1. And adding a corresponding amount of Cu to the cold-worked sheet steel. Further, it is described that when the content of C and Cr is adjusted to finely disperse the carbide distribution in the structure, the bite resistance can be improved. Patent Document 2 discloses that even if it is quenched at a lower temperature than the prior high-speed steel base material, it is possible to ensure the same degree of properties (hardness and toughness) as the prior material, and to have a Cr state in a quenched state (state before heat treatment). The main M23C6 system carbide is a composition of 2 to 5 vol% of the composition, which consists of a V-based MC carbide after quenching and tempering, and a M〇C-based M6C-based carbide, which is a structure in which the precipitated structure is dispersed. Alloy tool steel. [Patent Document 1] JP-A-2004-169177 (Patent Document 2) The above-mentioned mold is generally manufactured by subjecting the surface of steel for a mold to a hard film treatment. This hard film treatment is now generally a TD process for forming a VC film by thermal diffusion, a CVD process mainly forming TiC, and a PVD process mainly for forming TiN. Here, the "TD process" is a method in which a steel material is immersed in a molten salt bath such as V to be used in a steel material. The reaction with V is carried out and the VC film of about 5 to 15 μm is diffused and penetrated to the surface of the substrate at a temperature of about 900 to 1030 ° C in -6-200936785. These hard film treatments are suitably employed depending on the mold user and the pressure manufacturer. Therefore, it is required to use a steel for a mold which can be well handled by any hard film treatment (i.e., forming a hard film having a long life). Further, in steel for molds, of course, good basic characteristics (e.g., hardness, toughness, etc.) are required. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a steel for cold working molds and a mold which can provide excellent basic characteristics (hardness and toughness, etc.) and can cope with various hard film treatments. That is, the present invention provides a mass%, C: 0 · 5 to 0.7%, S i : 0.5 to 2.0%, Μη: 0·1 to 2.0%, C r : 5 to 7 %, and A1: 0.0 1 to 1 0 %, N: 0.003 to 0.025%, C u : 0 · 2 5 〜1 %, N i : 0 · 2 5 〜1 %,

Mo: 0.5 to 3 % and W: 2% or less (including 〇%), and S: 0 · 1 % or less (excluding 〇%), and the remaining part is iron and inevitable impurities for cold working die steel' The following (1) to (3) {[] means the content (%) of each element} (l) [Cr]x[C] S 4, 200936785 (2) [A1]/[N] : 1 ~ 30, (3) [Mo] + 〇.5x [W]: 0.5 to 3.00% of the cold working die steel. Moreover, it is preferable that the steel for cold working die further contains at least one of the following (a) to (c). (a) V: 0.5% or less (excluding 0%), (b) at least one element selected from the group consisting of Ti, Zr, Hf, Ta, and Nb is 0.5% or less (excluding 0%), and ( c) Co: 10% or less (excluding 〇%). The mold of the present invention is obtained by using any of the above-described steels for cold working molds. The steel for cold working die of the present invention is excellent in hardness and toughness because of the balance between the alloy component and the specified element as described above, and a hard film having a long life can be formed on the surface even if it is treated with a plurality of hard films. The mold obtained by using the above-described steel for cold working die is particularly preferably used as a molding die for a high-strength steel sheet having a tensile strength of about 590 MPa or more. [Embodiment] The present inventors have repeatedly reviewed the steel for cold working molds which can sufficiently cope with various hard film treatments in order to exhibit the basic characteristics such as hardness and toughness. As a result, it has been found that not only the content of various alloying elements is controlled within a specified range, but also the balance between the specified elements is appropriately controlled as shown in the above (1) to (3), and peeling of the TiN film can be prevented-8 - 200936785 'And improve hardness and toughness. Further, as a result, it has been found that even if a hard film treatment such as TD treatment, CVD treatment or PVD treatment is performed, a hard film having a long life can be formed on the surface thereof, and the present invention has been completed. Hereinafter, the warp and weft which achieve the present invention will be described. The inventors of the present invention first searched for the damage of the TiN film formed by the PVD treatment and the cause of occurrence of biting in the mold using the prior JIS SKD11 and the high-speed steel base block. φ Fig. 1(a) is an optical micrograph showing the state in which the surface of the mold on which the TiN film is formed by PVD treatment using JIS SKD1 1 as a steel for a mold. Fig. 1(b) also shows an optical micrograph of the base material of the mold before the application of the TiN film. In Fig. 1(b), the portion in which white is observed is a Cr-based carbide. Fig. 1 (c) and (d) are optical micrographs showing an enlarged portion of Fig. 1 (a). As shown in Fig. 1 (c) and (d), it is understood that in the region where the TiN film is peeled off, a hard coarse Cr-based carbide (mainly containing Cr and Fe, a carbide of about 1 to 50 μm or so) is precipitated on the surface. And cracks occur starting from the carbon φ compound. From the observation results of the above, the present inventors have found that the origin of the bite of the TiN film is the coarse Cr-based carbide described below, and if the formation of the carbide can be suppressed, the peeling of the TiN film can be prevented, and the mold can be improved. life.

In order to suppress the formation of coarse Cr-based carbides and to increase the life of the PVD-treated TiN film, it is preferable to reduce the amount of C and the amount of Cr in the steel. Therefore, when the amount of C is excessively lowered, it is difficult to form a sufficient thickness of the VC film or the TiC 200936785 film on the surface of the steel for the mold (base material) by TD treatment or CVD treatment. Therefore, in the present invention, the amount of c, the amount of Cr, and the product thereof (the above (1)) are appropriately controlled, so that coarse Cr-based carbides are not precipitated, and on the other hand, a sufficient thickness of the VC film can be secured. The TiC film is one of its characteristics. In the steel for a mold of the present invention, in order to increase the life of the PVD-treated TiN film, it is possible to suppress the formation of coarse Cr-based carbide. However, if Cr-based carbide is not formed, coarsening of crystal grains during quenching cannot be prevented, and excellent toughness after quenching cannot be ensured. Thus, the present invention is characterized in that fine A1N can be formed by precisely controlling the A1 amount, the N amount, and the balance thereof (the above (2)), and the excellent toughness is ensured after quenching. In the present specification, the term "excellent toughness" means that the single beam type impact enthalpy at the time of measurement by the method described in the examples of the examples below is 20 J or more. Further, the term "fine A1N" means a substance having an average particle diameter of about 5 μm or less. Further, since the steel for a mold of the present invention contains fine ruthenium, it is considered that the adhesion to the PVD-treated nitride-based film (for example, CrN and TiN) is improved as described above, and the steel for mold of the present invention is for suppressing the coarse Cr system. The formation of carbides is lower than that of the previous steel JIS SKD11, which reduces the amount of C and the amount of Cr. Therefore, in the present invention, the hardness caused by the decrease in the amount of C is reduced, and the alloy component (particularly Al, Cu, Ni, Mo, W) is actively added to compensate. In particular, the steel for a mold of the present invention particularly controls the above (2) to cause precipitation hardening of an Al-Ni-based intermetallic compound, and to control the secondary hardening of the above-mentioned (3) formation of carbides by using Mo and W and C to achieve high hardness. -10-200936785 In the present specification, the term "high hardness" means that the maximum hardness at the time of measurement by the method described in the column of the following examples is 650 HV or more. Hereinafter, the components in the steel of the present invention will be described in detail one by one. Further, the percentages in the present specification are based on masses unless otherwise specified. Also, all percentages defined by the mass, etc., are the same as defined for each weight. C : 0 · 5 ～ 0.7 % C is an element that ensures hardness and wear resistance and also helps to suppress HAZ softening. Further, when a carbide film such as VC or TiC is formed on the surface of the mold base material by the TD method or the CVD method, if the amount of C is low, there is a problem that the thickness of the film is reduced. Considering these circumstances, in order to effectively exert the above effects, the lower limit of the amount of C is 0.5%. The amount of C is preferably 0.55% or more. However, if the amount is excessive, coarse Cr-based carbides are formed, and the TiN film formed by PVD treatment is easily peeled off. Further, when the amount of C is excessive, the retained austenite is increased, and the aging treatment cannot be performed at a high temperature, and the desired hardness cannot be obtained. Further, if the amount of C is excessive, the toughness is adversely affected. Therefore, the upper limit of the amount of C is 0.7%. The amount of C is preferably 0.65% or less. S i : 0.5 ～2.0 %

Si can be used as an acid-removing element in steel making, and is an element that contributes to improvement in hardness and ensuring machinability. Further, Si is a temper softening which suppresses the block body and can be used for suppressing HAZ softening. In order to effectively perform such effects, the lower limit of the amount of Si is 〇·5%. However, if the amount is excessive, the initiality is lowered. Further, the segregation becomes large, and the density after heat treatment becomes large. Therefore, the upper limit of the amount of Si -11 - 200936785 is 2.0%. The amount of Si is preferably 1.0% or more, more preferably 1.2% or more, and most preferably 1.85% or less. Μη: 0.1 ～2.0% Μη is an element that can be used to ensure hardenability. However, if the amount is excessive, the retained austenite increases. Therefore, in addition to the inability to perform high-temperature aging treatment and the inability to obtain desired hardness, the toughness is also lowered. Considering these circumstances, the amount of Μη is determined as the above range. The amount of Μη is preferably 0.15% or more, preferably 1% or less, more preferably 〇·5 % or less, still more preferably 0.35% or less. I 〇 C r : 5 ～ 7 %

Cr is a useful element for ensuring a given hardness. More specifically, when the amount of Cr is too small, the hardenability is insufficient and a part of bainite is formed, so that the hardness is lowered, and the wear resistance cannot be ensured. Moreover, Cr is also a useful element for ensuring the uranium resistance of the mold. Thus, the lower amount of Cr is limited to 5%. The amount of Cr is preferably 5.5% or more. However, if the amount is excessive, a large amount of coarse Cr-based carbide is formed, and the TiN film formed by the PVD treatment becomes easily peeled off. Further, if the amount of Cr is excessive, the shrinkage after the heat treatment lowers the durability of the hard film. Further, if the amount of Cr is excessive, the toughness is adversely affected. Thus, the upper limit of the amount of Cr is 7%. The amount of Cr is preferably 6.5% or less. A1 : 〇.〇1 ～1 ·0% A1 can also be used as a deacidifying agent, and it is also possible to increase the hardness by precipitation precipitation strengthening of an Al_Ni-based intermetallic compound such as Ni3A丨 and an element which contributes to suppression of HAZ softening. . Further, A1 is an important element which forms an A1N precipitate together with N, prevents coarsening of crystal grains during quenching, and achieves excellent enthalpy. Considering these circumstances, the lower limit of A1 is limited to 〇.〇1%. The amount of A1 is preferably 0.02% or more, more preferably 0.03% or more, compared with -12-200936785. In addition, in the field of tool steel, in order to improve the quality of the intermediary, it is generally possible to reduce the amount of A1 as much as possible. However, in the present invention, in order to increase the hardness of the steel for the mold, it is preferred to suppress the softening of the HAZ and to prevent the coarsening of the crystal grains, A1 is actively added. The positive addition of A1 in the present invention is one of the most significant differences compared to the prior art. On the other hand, if the amount of A1 is excessive, the segregation is increased in addition to the decrease in toughness, and the density after heat treatment is increased. Therefore, the upper limit of the amount of A1 is limited to 1 · 〇 %. The amount of A1 is preferably 0.8% or less. N: 0.003 to 0.025% N is an important element for forming an A1N precipitate together with A1 and preventing coarsening of the crystal grains at the time of quenching to achieve excellent toughness. In order to achieve excellent toughness, the lower limit of the amount of N is 0.03 3 %. However, if the amount is excessive, it will reduce the toughness. The upper limit of the amount of N is then limited to 0.025%. The amount of N is preferably 0.004% or more and 0.020% or less.

Cu : 0.25 〜1 %

Cu is an essential element for improving hardness by precipitation strengthening of ε-Cu, and also contributes to suppression of HAZ softening. However, if the amount is excessive, the toughness is lowered and forging cracks are likely to occur. The upper amount of Cu is then limited to 1%. The amount of C u is preferably 0·30% or more and 0.8% or less. N i : 〇 · 2 5 〜1 %

Ni is an essential element for improving the hardness by precipitation strengthening of an Al-Ni-based intermetallic compound such as Ni3Al, and also contributes to suppression of HAZ softening. Further, Ni is used for the purpose of suppressing the hot brittleness of -13-200936785 caused by excessive addition of Cu, and also preventing cracking during forging. However, if the amount is excessive, the amount of austenite remaining increases and the temperature is not aged at a high temperature and the hardness cannot be ensured to expand after the heat treatment. Further, if the amount of Ni is excessive, the toughness also decreases. Consider this case' The amount of Ni is set in the above range. The amount of Ni is preferably 0.30% or more and 0.8% or less.

Mo : 0.5 to 3% and W : 2% or less (including 0%)

Both Mo and W are elements which form a Ni3Mo-based intermetallic compound in addition to the formation of the M6C-type carbide and contribute to precipitation strengthening. However, if these amounts are excessive, the above-mentioned carbides and the like are excessively produced. In addition to the decrease in toughness, the density after heat treatment is increased. Then, the amount of Mo and the amount of W are set in the above range. In the present invention, 'Mo is an essential component, and W is a selective element, but both may be used. A preferred lower limit of the amount of W is 0.02%. The amount of Mo is preferably 7%7% or more and 2.5% or less. The amount of W is preferably 0.05% or more and 1.5% or less. S : 0.1% or less (excluding 〇%) S is an element that can be used to ensure the machinability. From the viewpoint of ensuring the machinability, S is preferably 0.002% or more, and more preferably 0.004% or more. However, if the amount is excessive, a weld crack occurs. The upper limit of the amount of S is then limited to 0.1%. The amount of S is preferably 0.07% or less', more preferably 0.05% or less, still more preferably 0.025% or less. Further, in the present invention, it is necessary to satisfy the following requirements (1) to (3) {[] means the content (%) of each element}. (l) [Cr]x [C]^ 4 The above (1) is set for the purpose of suppressing the formation of coarse Cr-based carbides 200936785. When [Cr]x[C] is more than 4', coarse Cr-based carbides are formed and the TiN film is easily peeled off. In addition, if the product exceeds 4', the durability of the hard film is reduced, and the density after heat treatment is increased. [Cr]x[C] is preferably 3.8 or less, and more preferably 3.7 or less. Further, the lower limit is preferably small from the viewpoint of suppressing the formation of coarse Cr-based carbides and suppressing the deformation after heat treatment. However, if the addition of Cr and C is also considered to make the above effects work effectively, it is preferably about 〇 8. φ (2) [A1] / [N] : 1 to 30 The above (2) is set for forming fine A1N and ensuring toughness after quenching. Even if [A1]/[N] is too small or too large, it is difficult to obtain fine A1N precipitates, and excellent toughness cannot be ensured. Therefore, it is important to precisely control its balance. It is preferable that [A1]/[N] is 2 or more and 20 or less. (3) [Mo] + 0.5x[W] : 0.5 to 3.00%

Mo and W are elements which contribute to precipitation strengthening as described above, and the above (3) is mainly set by a parameter Q type which ensures hardness improvement by such precipitation strengthening. Further, by suppressing these parameters, HAZ softening can be favorably suppressed. In order to effectively exert such effects, the lower limit of the above (3) is made 0.5%. However, if the amount of Mo and the amount of W are excessive, the carbide is excessively added, and in addition to the decrease in toughness, the density after heat treatment becomes large. Therefore, the upper limit of the above (3) is limited to 3.00%. The lower limit of the above (3) is preferably 1.0%, more preferably 1.2%, and the upper limit thereof is preferably 2.8%. Further, in the above (3), the coefficient (0.5) of [W] is determined by considering that the atomic weight of Mo is about 1/2 of W, and the basic component in the steel of the present invention is as described above, and the residual portion is iron- 15-200936785 and the inevitable impurities. The unavoidable impurities include, for example, an element which is inevitably mixed in the production process, and specifically, p, hydrazine or the like can be exemplified. The amount of P is preferably about 0.05% or less, more preferably 0·〇3% or less. The amount of ruthenium is preferably about 0.005% or less, more preferably 0.003 1⁄4 or less, and still more preferably 0.002% or less. Further, in the present invention, for the purpose of improving other characteristics, the following optional components may be contained. V: 0.5% or less (excluding 0%) V is an element which is effective in suppressing HAZ softening except that carbides such as VC are formed to contribute to the improvement of hardness. Further, when the diffusion hardening layer is formed by nitriding treatment of gas nitriding, salt bath nitriding, plasma nitriding or the like on the surface of the base material, it is an element which effectively increases the surface hardness and increases the depth of the hardened layer. In order to effectively perform such effects, it is preferred to add about 0.05% or more of the V amount. However, if the amount is excessive, the amount of solid solution C is lowered, and the toughness is lowered in addition to the decrease in the hardness of the mother phase martensite structure. Therefore, when V is contained, the upper limit thereof is 0.5%, preferably 0.4% or less, more preferably 0.3% or less. At least one element selected from the group consisting of Ti, Zr, Hf, Ta, and Nb is 0.5% or less in total (excluding 0%). These elements are all nitride-forming elements, contributing to the fineness of the nitride and A1N. As a result of the dispersion, an element which prevents coarsening of crystal grains and contributes to improvement of toughness is obtained. In order to effectively exhibit such an effect, it is preferable to contain about 0.01% or more of Ti, 0.02% or more of Zr, 0.04% or more of Hf, 0.04% or more of Ta, and 0.02% or more of Nb. However, if these amounts are excessive, the amount of solid solution C decreases and the hardness of the martensite body decreases. Therefore, the total amount of the above elements is preferably 0.5%. The total amount of the above elements is preferably 0.4% or less below 200936785, more preferably 0.3% or less. The above elements may be contained alone or in combination of two or more. C 〇 : 1 0 % or less (excluding 0 %)

Co is an element which raises the Ms point and effectively reduces the residual austenite, thus increasing the hardness. In order to effectively exert the above effects, it is preferred that the amount of Co be about 1% or more. However, if the amount is excessive, the cost will increase, so the upper limit is preferably 10%. The amount of C is preferably less than 5.5%. 0 The present invention also encompasses a mold obtained by using the steel for a mold described above. The method for producing the mold is not particularly limited, and for example, after the steel is melted and then hot forged, it is annealed (for example, after being held at about 700 ° C for 7 hours, it is averaged at about 17 ° C / hour. After cooling the furnace to about 400 ° C, it is cooled and softened, and then rough-processed into a specified shape by cutting or the like, and then melted at a temperature of about 950 to 11 50 ° C. A method of aging treatment at about 400 to 53 ° C to impart a desired hardness. The present invention will be more specifically described by the following examples, but the present invention is not limited by the following examples, and may be appropriately modified and carried out within the scope of the above-mentioned spirit and scope. The technical scope of the invention.

Using the various steel types described in Table 1, a 150 kg ingot was melted in a vacuum induction melting furnace, and then heated at about 900 to ll5 ° C, and forged into a plate of 40 mm Tx 75 mm W x about 2000 mmL, and thereafter, about 60 pieces. °C -17- 200936785 / hour average cooling rate for cold. After cooling to a temperature of 100 ° C or lower, it was heated again to a temperature of about 850 ° C and was quenched (annealed) at an average cooling rate of about 50 ° C / hour. Using the respective annealed materials obtained by the above treatment, the following tests (1) to (3) were carried out. (1) Hardness test (measurement of maximum hardness) A test piece having a size of 20 mm Tx 20 mm Wx 15 mmL was cut out from the annealed material described above, and used as a test piece for measuring hardness, and subjected to the following heat treatment. Solution treatment (quenching treatment): heating at about 1 020 to 1 03 ° C for 120 minutes - air cooling - aging treatment (tempering treatment): holding at about 400 to 560 ° C for about 3 hours - cooling as described above, The hardness at the time of changing the tempering temperature in the range of about 400 to 560 ° C was measured by a Vicus hardness meter (AVK of AKASHI Co., Ltd., load: 5 kg), and the maximum hardness (HV) was investigated. In the present embodiment, the maximum hardness was 650 HV & The results are shown in Table 2. (2) Toughness test (measurement of single beam impact enthalpy) For the above annealed material, the following heat treatment was applied. Solution treatment (quenching treatment): heating at about 1020~1 030 °C for 120 minutes - air cooling - aging treatment (tempering treatment): holding at about 400~560 °C for about 3 hours - air cooling or cooling, followed by As shown in Fig. 2, a test piece having a V-notch portion of 1 OmmR was cut out to prepare a test piece for measuring toughness (charpy impact test piece). -18- 200936785 This test piece was used to carry out the charpy impact test' and the absorption energy at room temperature (charpy impact enthalpy) was measured. The charpy impact test piece is collected for every three pieces, that is, the average enthalpy is the charty impact 値. In the present embodiment, the one with a single beam impact enthalpy of 20 J or more was evaluated as "excellent toughness". The results are shown in Table 2. (3) Evaluation of characteristics of hard film φ (3-1) Formation of hard film A test piece having a size of 4 mmtx Φ 50 mm was cut out from the above-mentioned annealed material, and subjected to the same heat treatment as the toughness test to make a hard film. Test piece for evaluation of characteristics. This test piece was subjected to TD treatment, CVD treatment, and PVD treatment under normal conditions to form a VC film, a TiC film, and a TiN film on the surface. (3-2) Determination of film thickness of hard film

Φ A 2000-times photograph of each of the hard films (VC, TiC, and TiN films) formed as described above was photographed by a scanning electron microscope (SEM), and the film thickness was measured at any five places. The average enthalpy of measurement of enthalpy at five points was regarded as the film thickness (μπι) of each hard film. In the present embodiment, the film thickness of the VC film and the TiC film was 7. 〇μηι or more was regarded as acceptable. The results are shown in Table 2. (3-3) Measurement of peeling critical load of hard film The peeling critical load of each hard film (VC, TiC, and TiN film) was measured by a Pinon Disc test. In detail, the front end of the R half-19-200936785 diameter 200μιη diamond indenter, load increase speed: 100N / min and head movement speed: l〇mm / min conditions, pressure hard film and move, will initially The load (N) at which the film peeling occurred was determined as the peeling critical load. In the present embodiment, the peeling critical load of each hard skin is 20 N or more, which is considered to be acceptable. The results are shown in Table 2. ❹

-20- 200936785 [1撇] Ϊ-NFS miscellaneous ikK-¥ls Discussion, %_«i

i>< S113. «—»o CM r— Οί Μ C^l Ο) (Ο Ο) CD 0> 03 (£>σ> ο co 7 c〇Oi c〇σ> ΙΟ σ> CO 〇ϊ (Ο σ > ο I—1 |Η· (Ο 03⁄4 05 σ> σ! CO 05 <Ό 05 s> o tH σ> 1 σ> 03⁄4 v-* ο ο Ο Ο ο ooo ο ο ο ο ο ο ο ο ooo CO o ο ol—l 3.85 48. 53 73. 72 73. 57 0.53 ι.ιο 1 3.03 1 6.06 13.41 18, 79 15. 38 28· 06 54. 12 I 6.06 6.83 1 6.06 I 1 6.06 1 6.79 6.67 I 6.06 I Oi <£> CO ΙΟ I 6.06 I L6J7 I 1 6.06 I o to ID to σ £ ιό 3.85 X sa 1 18.03 inch CQ 00 ΙΛ ιη inch ιη 啼U3 inch CO m LO but CO ιο CO ΙΩ守Tt ίο ιη 00 U? ΙΛ ΙΛ 00 ΙΟ CO ιο inch CO CV3 tA VO inch 00 1A inch CO in CO LO CO LO CO 3.46 00 CO CO co CO CO CO CO CO CO CO CO C0 ς〇C〇CO CO CO CO Other 1 o Λ 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 Ti : 0. 04 1 ο 'έ Η ο ώ 2Μ d 0, CJ LO c§ 1 ! 1 1 1 1 Ti: 0.25, Nb: 0.3 1 ΪΛ CM gos CN4 CO 00 OJ CO σ> CSJ 00 C>J ο 00 00 o 03⁄4 CnJ 00 o 00 Ν > OJ 00 OJ ο 1 00 CM ο 00 CS1 σ> 00 CM ο CM 00 CS3 00 CM 〇> 00 o 03⁄4 CM 00 DJ § 00 oi :0.29 〇ο O ο ο ο ο oo oo ο ο ο ο ooooooo O LO gso CO ο CO »-H o U3 Ο 21 ο ο LO Ο 〇 o in ooo 10. 00141 C0 ο ο 2 ο 10.00141 inch ο CO ο inch*•4 ο ιο ο 2 ο CO vH o inch o CO o Oo oo o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o tH oo o 00 r-^ 00 ο 2 ο 00 ο <Ji rH 00 ο 00 ο 00 σ> r-1 2 ο 00 o 00 o 00 o 00 o O) o 2 o oo 00 o 0.019 oo ο o Ο ο ο ο 〇 oooo ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο S ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο o 2 gossoo ο o ο ο ο ο 〇oooo ο ο ο ο ο ο ο ooooooo s si w CO 〇> ΙΟ 05 ι/> CD σ> ΙΑ (33⁄4 ΙΛ Oi o to <73 <〇σ&gt LO 〇> LX3 〇ϊ ΙΑ Ο) LO σ> ο LO σ> (Ο σ> ο U? σ> co 03⁄4 ιο σ> ud σ> (D Oi o 1 o LO o § o 00 03⁄4 04 CO Oi LO ⁄ ο ο ο ο ο ο ο ο ο σ> C-3 ο <J) C4 s 沄00 inch rH Oi C^4 s 〇) 0,30 ! 0.29 1 o ο ο ο ο ο Ο ooo ο ο ο ο ο ο ο ο oo oooooo 5 g § CO o CO % ? η ο σ» Another o Another 00 CS3 σ> CVJ Another C0 Another σ> CM ο Another ο gt> CNJ Another 7 CNJ ο Another sso Another o O) CJ 0. 30 1 o ο ο ο ο ο Ooo ο ο ο ο ο ο oooooo 00 CD ο 00 inch § ο 1^ inch ΙΛ 1ί> 思ο ιο to ο CO ο U9 (D «-Η 1Γ9 (Λ CO 2 o points σ) ο ίΤ3 CO *—4 S U7 <β ΙΑ (Ο ο eg CO ^4 Ι 1 LO (Ο •Η <〇»»Η CO CO «Η IA 1 iH (A <D 1 52 om CO o cq (O o inch to o LO co 0. 0260 I o ο ο O ο Ο ο ο ο 〇〇 ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο ο Oo oo oo oo oo o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o o LO & U U U U U U U U U U U U U U U U 1 σ> cS (O σϊ 15. 95 1 IA σ> co 〇> io σ> 5.97 1 οο inch LO ΙΑ Ι3 ΙΩ ΙΩ in ΙΟ ιη in ΙΛ in in U) in Lf) IA inch S 00 Οϊ LA CM CM Oj inch CO 兮CQ inch inch CO inch inch inch ο rH CVJ inch C>J ο CO inch ο Μ 呀 CO inch CNJ inch ο inch CO inch 0 01 Cs3 inch CO inch cvj 兮CO 兮0.42 0.43 1 d ο ο ο Ο ο ο Ο 〇 oo Ο ο ο ο ο ο oo oooooo CO in CQ 〇g CM CO in co ο r—1 g Γ·^ gsg LC τ-^ S τ-4 SS fH g S tH 1-Η tH s CNJ s — ss 4 s ιΉ 1.02 1 〇05 ί-Η in ca § 00 U) 00 ΙΑ Ο) ΙΑ 00 tA § oo Oi u> o οο if> 0D ΙΑ 00 ΙΛ S 00 ΙΩ g Oi to 00 ΙΛ S ο 00 ΙΛ ο 05 00 LD s 00 in 05 LO § σ> LA 0.60 1 0. 58 1 ο o ο Ο Ο Ο O o O ο ο ο ο ο ο ο ο ooooooo CS3 CO inch LT3 CO οο 05 o CM CO 21 ΙΟ 2 00 os S C0 CQ CVI CO CSI inch ca LA C·) (D CSJ oo eg 〇> CSI CO -21 200936785 [Table 2]

No·Maximum mt charpy Street hardy m) __M Hard fine 鼸 屎 load (10) HV j VC-TD TiC-CVD TiN - PVD VC-TD TiC-CVD TiN - PVD 1 690 10 7.8 6.7 5.1 27 22 17 2 720 13 7.5 7.9 5.0 23 23 18 3 685 22 4.3 4.3 5.1 12 10 33 4 7Ϊ0 17 6.5 6.2 4.9 18 15 32 5 700 15 7.5 7.3 5.0 24 25 31 6 710 30 7.4 7.5 5.0 27 26 32 7 715 35 7.3 7.5 。 。 。 。 。 。 。 。 。 。 29 13 745 18 7.4 7.4 4.9 II 28 28 30 14 726 21 7.3 7.7 5.0 23 24 32 15 719 22 7.5 7.6 5.0 26 23 3〇16 721 23 7.9 7.5 5.1 25 26 30 17 730 22 7.4 7.5 5.0 20 ' 21 31 18 722 15 7.8 7.5 5.0 28 — 29 3〇19 709 40 7.3 7.3 5.1 21 22 33 2Ό ]| /11 41 7.5 7.6 5.0 22 — 21 30 21 | 708 39 7.5 7.4 4.9 20 22 31 22 ΥΙΟ 28 7.6 7.8 5.0 20 22 32 23 724 35 7.5 7.3 4.9 24 24 30 24 729 17 7.3 7.7 5.1 25 26 33 25 730 16 7.9 7.5 5.0 26 25 28 26 728 17 7.5 7.6 5.1 24 23 31 27 648 2 0 7.4 7.5 5.0 29 30 30 28 741 7.3 7.6 5.1 21 22 32 29 718 7.6 7.8 5.0 28 29 30 30 600 B 7.7 7.9 5.1 24 25 31 61 n (U 16 1 7.5 7.5 5.1 24 24 30 As shown in Tables 1 and 2 As a result, steel Nos. 6-12 and 14-23 satisfying the requirements of the present invention are (maximum) hardness, toughness (single beam impact enthalpy), film thickness of VC or TiC film, and hard film (vc film, The peeling critical load of the TiC film and the TiN film was all good. In contrast, steels No. 1 to 5, 13, and 24 to 31 which do not satisfy any of the requirements of the present invention have the following disadvantages. Steel No. 1 and 2 are the amount of C and the amount of Cr, and any of [Cr]x [C] is excessive. Because the system is a coarse Cr-based carbide, the peeling threshold of the TiN film is -22-200936785. . Further, since the amount of C and Cr is excessive, the toughness is also 〇. Steel Nos. 3 and 4 have a small amount of C, so that the films of the Vc and TiC films are sufficient. The result is that the peeling critical load of these films is lowered. Steel No. 5 has a small amount of A1 and a small amount of [A1]/[N], so the toughness is sufficient. The steel Νο·13 has a large amount of A1, and the [A1]/[N] is large, so the toughness is sufficient. Steel No. 24 has an excessive amount of Si, and steel N〇.25 because the amount of Μη is over-steel No _26 is Cu and the amount of Ni is excessive. Therefore, the toughness is insufficient. Steel No. 27 has a small amount of Mo, and [M 〇]+〇5x[w] is small and not enough. Steel Ν〇·28 is [Mo] + 0.5x[w], so the hardness is not enough. Filling steel No.29 is the excess of the selected element v, so the toughness is not enough 〇❹ Steel No. 30 is the selection element Ti and Nb The total amount of the mixture is more than 'there is a decrease in the amount of solid solution C, and as a result, the hardness is insufficient. Steel N 〇 · 3 1 is an excess of N, so the toughness is not sufficient. While the invention has been described in detail with reference to the specific embodiments, various modifications and Further, the present application is filed on Nov. 13, 2007, the entire disclosure of which is hereby incorporated by reference. In addition, all references cited herein are in the form of all types of reduction, and the thickness is not insufficient, and is not enough. A sufficient 0.5% of the hair of the present invention is -23-200936785. Industrial Applicability The steel for cold working mold of the present invention has a balance between the alloy composition and the specified element as described above, so that the hardness and toughness are excellent, and even A variety of hard film treatments can also form a hard film with a long life on the surface. The mold obtained by using the steel for cold working die is particularly suitable for use as a molding die for a high-strength steel sheet having a tensile strength of about 590 MPa or more. [FIG. 1] FIG. 1(a) shows the use of JIS SKD11. An optical micrograph of the surface of the mold on which the TiN film is formed by PVD treatment as a mold steel, and FIG. 1(b) is an optical micrograph of the mold base material before the application of the TiN film, FIG. 1 (c) And (d) are optical microscope photographs that enlarge a part of Fig. 1(a). Fig. 2 is a schematic view showing the shape of a single-shot (Charpy) impact test piece used in the embodiment. -twenty four-

Claims (1)

200936785 X. Patent application scope 1. A steel for cold working die, containing mass%, C: 0.5 〇. 7 %, S i : 0 · 5 ～2.0 %, Μ η : 0 · 1 〜 2 · 〇% , C r : 5 〜 7 %, A1 : 0 · 0 1 〜1 · 〇%, φ N: 0.003 〜0.025 %, C u : 0 · 2 5 〜1 %, N i : 0.2 5 〜1 %, Μ 〇: 0 · 5~3 °/. And W: 2% or less (including 0%), and S: 0 · 1% or less (excluding 〇%), and the remaining part is iron and inevitable impurities, the steel for cold working mold satisfies the following (1)~ (3) {[] means the content of each element (%)} (l) [Cr]x[C] $ 4, ❹ (2) [A1]/[N] : 1 〜30, and (3) [Mo] + 0.5x[W]: 0.5 to 3.00% of the requirements. 2. The steel for cold working die according to the first aspect of the patent application, wherein the steel for cold working die further contains at least one of the following (a) to (c), (a) V : 0.5% or less (excluding 〇%) (b) At least one element selected from the group consisting of Ti, Zr, Hf, Ta, and Nb is 0.5% or less (excluding 〇%), and -25-200936785 (c) Co: 10% or less (excluding 0%). 3. A mold for use in a steel for cold working die as in the first or second aspect of the patent application. -26-