KR20220002523A - Steel for hot stamping mold, hot stamping mold and manufacturing method thereof - Google Patents

Abstract

Provided are a steel for a mold capable of producing a mold for hot stamping having both high hardness and high thermal conductivity, a mold for hot stamping, and a manufacturing method thereof. In % by mass, C: 0.45 to 0.65%, Si: 0.1 to 0.6%, Mn: 0.1 to 0.3%, Cr: 2.5 to 6.0%, Mo: 1.2 to 2.6%, V: 0.4 to 0.8%, balance Fe and inevitable Steel for hot stamping with a component composition of red impurities. Also provided are a mold for hot stamping having the above component composition, and a method for manufacturing the same.

Description

Steel for hot stamping mold, hot stamping mold and manufacturing method thereof

The present invention relates to a steel for a mold for hot stamping, a mold for hot stamping, and a manufacturing method thereof.

Recently, for the purpose of reducing the weight of automobiles and improving collision safety, the need for ultra-high-strength steel sheets having a tensile strength exceeding 1 GPa is increasing. However, when a steel sheet having a tensile strength of 1.2 GPa or more is attempted to be formed by cold pressing, problems such as an increase in forming load, springback, and formability occur. Therefore, in recent years, hot stamping (also referred to as hot pressing or hot stamping) construction method is attracting attention. In the hot stamping method, the steel sheet is heated to an austenite temperature or higher, press-formed, and the mold is held at the bottom dead center and quenched by rapid cooling.

As an advantage of the hot stamping method, a molded article of an ultra-high tensile strength steel sheet having a tensile strength of about 1.5 GPa can be obtained by quenching by die quenching, which is quenched by a die. Moreover, the advantage of being excellent in moldability, such as a springback hardly occurring is also mentioned.

However, the hot stamp method has a problem of low productivity. That is, since it takes time to maintain the bottom dead center for die quenching, productivity is lowered. As a countermeasure, a mold with high thermal conductivity is required. This is because, in die quenching, the heat of the steel sheet is absorbed by the mold, but the higher the thermal conductivity of the mold, the shorter the time for maintaining the bottom dead center and the higher the productivity.

In addition, in the mold for hot stamping, high hardness is required in order to increase wear resistance.

Therefore, in the steel for a mold for hot stamping, it is required to have both high hardness and high thermal conductivity when it is used as a mold. Generally, it is necessary to increase the alloy amount of the steel for metal molds in order to obtain a high hardness mold, but there is a problem that the thermal conductivity of the mold decreases as the alloy amount increases, and hardness and thermal conductivity have a trade-off relationship. Then, the optimal component composition is examined by controlling the alloy amount. For example, in patent documents 1 - 3, the component composition of the steel for metal mold|die which has both hardness and thermal conductivity is proposed. In addition, Patent Document 4 also discloses a hot tool steel useful as a material for a mold used for hot pressing, die casting, hot forging, etc., and has excellent thermal conductivity and excellent wear resistance.

Japanese Patent Laid-Open No. 2017-43814 Japanese Patent Laid-Open No. 2017-53023 Japanese Patent Laid-Open No. 2018-24931 Japanese Patent No. 5744300 Publication

The steel for molds of Patent Documents 1 to 3 and the hot tool steel of Patent Document 4 are useful for hot stamping. However, considering the quenching and tempering properties of mold steel or hot tool steel, and that the working surface of the hot stamping mold is used after being nitridized, in the case of conventional mold steel or hot tool steel, hardness may be insufficient. Specifically, in recent years, high hardness of 52HRC or more has been requested as steel for hot stamping, but in Patent Documents 1 to 4, high hardness of 52HRC or more cannot be stably obtained.

An object of the present invention is to provide a steel for a mold that can produce a mold having both high hardness and high thermal conductivity suitable for a hot stamping method, a mold for hot stamping, and a manufacturing method thereof.

In view of such a reality, the present inventors have intensively researched, and as a result, have found a steel for a mold that is optimal for hot stamping by controlling the alloy amount. And, by using the steel for a mold, a mold for hot stamping capable of achieving high hardness and high thermal conductivity and a method for manufacturing the same have been found.

That is, in one embodiment of the present invention, in mass%, C: 0.45 to 0.65%, Si: 0.1 to 0.6%, Mn: 0.1 to 0.3%, Cr: 2.5 to 6.0%, Mo: 1.2 to 2.6%, V: It is a steel for a mold for hot stamping, characterized in that it has a component composition of 0.4 to 0.8%, the remainder Fe and unavoidable impurities.

Another embodiment of the present invention is, by mass%, C: 0.45 to 0.65%, Si: 0.1 to 0.6%, Mn: 0.1 to 0.3%, Cr: 2.5 to 6.0%, Mo: 1.2 to 2.6%, V: 0.4 It is a mold for hot stamping, characterized in that it has a component composition of ~0.8%, balance Fe and unavoidable impurities.

Preferably, the mold for hot stamping according to claim 2 is characterized in that the hardness is 45 HRC or more and the thermal conductivity (λ(W/(m·K))) satisfies the following formula (1).

λ≥-0.5H+53… Equation (1)

H: Rockwell hardness (HRC) of the mold

More preferably, the hardness is 52HRC or more. And at this time, more preferably, the thermal conductivity (λ) is 25 W/(m·K) or more.

It also preferably has a nitride layer on the working surface.

Another aspect of the present invention is a method for manufacturing a mold for hot stamping, wherein the steel for hot stamping is quenched and tempered at a quenching temperature of 1020 to 1080°C and a tempering temperature of 500 to 625°C.

Preferably, the tempering temperature is 540 ~ 600 ℃.

Preferably, after performing the quenching and tempering, it is characterized in that the work surface is further subjected to a nitriding treatment.

ADVANTAGE OF THE INVENTION According to this invention, the steel for metal mold|die optimal for hot stamping is obtained. Furthermore, by using this steel for a mold, it is possible to provide a mold for hot stamping having both high hardness and high thermal conductivity, and a method for manufacturing the same.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the hardness for each tempering temperature about an example of the metal mold|die produced by tempering at 500-650 degreeC after quenching the steel for metal mold|die of this invention example and a comparative example from 1030 degreeC.
2 is a view showing the thermal conductivity of an example of a mold produced by quenching the steel for a mold of the present invention example and a comparative example at 1030 ° C., and then tempering it to a hardness of 45HRC, 50HRC, and 55HRC.
3 is a view showing the softening resistance of an example of a mold prepared by quenching the steel for a mold of the present invention example and a comparative example from 1030° C. and then tempering it to a hardness of 55 HRC, when maintained at 600° C. FIG.

A feature of the present invention is that the high hardness and high thermal conductivity of the hot stamping mold are achieved at the same time when considering that the mold for hot stamping is produced by performing quenching and tempering on the steel for the mold, or when nitriding is performed on the working surface of the mold for hot stamping. It is at the point of finding out that there exists a component composition of the steel for metal mold|die which is optimal for doing this. In particular, it is at the point that it was discovered that there is a component composition of steel for a mold that is optimal for simultaneously achieving high hardness of 52HRC or more and high thermal conductivity of 25W/(m·K) or more. In addition, the point is that the best quenching and tempering conditions to achieve the high hardness and high thermal conductivity at the same time. Hereinafter, each component requirement of this invention is demonstrated.

The steel for a mold for hot stamping of the present invention, in mass% (hereinafter, simply expressed as "%"), C: 0.45 to 0.65%, Si: 0.1 to 0.6%, Mn: 0.1 to 0.3%, Cr: 2.5 -6.0%, Mo: 1.2-2.6%, V: 0.4-0.8%, the balance has a component composition of Fe and unavoidable impurities.

C: 0.45 to 0.65%

C is an element that improves the hardness of the mold by dissolving in the base material (matrix) by quenching. Moreover, it is an element which improves the hardness of a metal mold|die by forming a carbide|carbide with carbide-forming elements, such as Cr, Mo, and V, which are mentioned later. However, when there is too much C content, the toughness of a metal mold|die will fall due to coarsening of a primary carbide, etc. Therefore, C is set to 0.45 to 0.65%. Preferably it is 0.47% or more. More preferably, it is 0.49% or more. Moreover, Preferably it is 0.63 % or less. More preferably, it is 0.60% or less. More preferably, it is 0.58% or less.

Si: 0.1~0.6%

Si is used as a deoxidizer in the solvent process. And it is an element which dissolves in a base material and improves the hardness of a metal mold|die. However, when there is too much Si, the segregation tendency in steel becomes strong after melting, and the solidification structure also becomes coarse, and it leads to the fall of the toughness of a metal mold|die. And it is an element which reduces the thermal conductivity of the metal mold|die after quenching and tempering remarkably. Accordingly, Si is 0.1 to 0.6%. Preferably it is 0.14% or more. More preferably, it is 0.17 % or more. Moreover, Preferably it is 0.45 % or less, More preferably, it is 0.4 % or less. More preferably, it is 0.35% or less. Even more preferably, it is 0.3% or less.

·Mn: 0.1~0.3%

Mn is used as a deoxidizer or desulfurization agent in the solvent process. And it is an element contributing to the improvement of the toughness after hardening of a base material, hardenability, and hardening and tempering. However, when there is too much Mn, the thermal conductivity of a metal mold|die will fall remarkably. Therefore, Mn is set to 0.1 to 0.3%. A preferable lower limit of Mn is 0.15% or more. In addition, a preferable upper limit of Mn is 0.28% or less. A more preferable upper limit of Mn is 0.26% or less.

·Cr: 2.5~6.0%

Cr is an element that increases hardness by being dissolved in the substrate. Moreover, it is an element which raises hardness also by forming carbide|carbonized_material, It is an element which contributes to secondary hardening at the time of tempering similarly to Mo and V mentioned later. In particular, Cr is an element capable of increasing the tempering softening resistance (even if the tempering temperature is increased, the rate of decrease in hardness obtained by secondary hardening can be reduced) compared to Mo and V. Usually, in the case where the mold is adjusted to the working hardness by quenching and tempering the steel for the mold, in order to increase the thermal conductivity of the mold for hot stamping, it is effective to increase the tempering temperature. And, in the present invention, by setting the Cr content to 2.5% or more, even if the tempering temperature is increased (for example, exceeding 600°C), sufficient hardness such as 45HRC or more can be maintained, so that at the same time, the thermal conductivity is reduced You can also make it higher. And even if the tempering temperature is, for example, 540° C. or higher, a hardness of 52 HRC or higher can be achieved, and a mold for hot stamping having a thermal conductivity of 25 W/(m·K) or higher can be obtained. And, after maintaining the hardness, it is possible to obtain a mold for hot stamping, which has a thermal conductivity of 28 W/(m·K) or more, and further improved to 30 W/(m·K) or more. In addition, the said hardness and thermal conductivity are values when it measures at room temperature (room temperature).

In addition, since the nitriding properties of the steel for molds can be improved by increasing the Cr content, for example, the wear resistance (hardness of the working surface) of the mold can be improved by further nitriding the working surface of the mold after quenching and tempering. .

However, when there is too much content of Cr, it becomes difficult to make high the thermal conductivity of a metal mold|die by itself that the alloy amount of the steel for metal mold|die increases. Therefore, Cr is set to 2.5 to 6.0%. Preferably it is 2.8% or more. More preferably, it is 3.0 % or more. Moreover, Preferably it is 5.5 % or less, More preferably, it is 4.8 % or less, More preferably, it is less than 4.5 %. And, especially, when it is desired to emphasize the improvement of thermal conductivity, Cr can also be made into 4.0% or less or 3.5% or less.

Mo: 1.2~2.6%

Mo, like Cr, is an element that increases hardness by dissolution in the substrate, and also increases hardness by forming carbides, and is an element contributing to secondary hardening at the time of tempering. Moreover, it is also an element which improves hardenability. However, when there is too much Mo amount, the thermal conductivity of a metal mold|die will become low by itself that the alloy amount of the steel for metal mold|die increases. Therefore, Mo is 1.2 to 2.6%. Preferably it is 1.5% or more. More preferably, it is 1.7% or more. More preferably, it is 1.9% or more. Moreover, Preferably it is 2.5 % or less. More preferably, it is 2.3% or less. More preferably, it is 2.1% or less.

V: 0.4 to 0.8%

Like Cr, V is an element that increases hardness even by forming carbides, and is an element that contributes to secondary hardening at the time of tempering. However, when there is too much V amount, the thermal conductivity of a metal mold|die will become low by itself that the alloy amount of the steel for metal mold|die increases. Therefore, V is set to 0.4 to 0.8%. Preferably it is 0.5% or more. Moreover, Preferably it is 0.75 % or less, More preferably, it is 0.65 % or less, More preferably, it is 0.6 % or less.

Remaining Fe and unavoidable impurities

Considering that when the alloy amount of the steel for a mold increases, the thermal conductivity of the mold decreases, it is preferable that the remainder other than the element species substantially consists of Fe. However, elemental species not specified here (e.g., elemental species such as P, S, Cu, Al, Ca, Mg, O (oxygen), N (nitrogen), etc.) may inevitably remain in the steel. elements, and it is permissible to include these elements as impurities. At this time, when P is too large, it segregates at the prior austenite grain boundary during heat treatment such as tempering, and the toughness of the mold deteriorates. Therefore, it is preferable to regulate P to 0.05% or less. More preferably, it regulates to 0.03% or less. And when there is too much S, when crushing a steel ingot, etc., hot workability will deteriorate. Therefore, it is preferable to regulate S to 0.01% or less. More preferably, it is regulated to 0.008% or less.

In addition, although Ni is useful as an element species that contributes to the improvement of the toughness of the mold, it is preferable to suppress the content of Ni to a low level from the viewpoint of suppressing a decrease in the thermal conductivity of the mold due to an increase in the alloy amount of the steel for the mold. . In addition, as the upper limit of regulation of the amount of Ni, preferably 0.25% is allowed.

By performing quenching and tempering on the steel for a mold having the above component composition, the mold for hot stamping of the present invention having excellent hardness and thermal conductivity can be obtained. The hardness of the mold for hot stamping of the present invention is a value measured at room temperature (room temperature), and it is easy to achieve sufficient hardness, for example, 45 HRC or higher. And, by adjusting the tempering temperature, the hardness of the mold can be preferably set to 52 HRC or more, and excellent wear resistance can be provided to the mold during use. The hardness of the mold is more preferably 53 HRC or higher, and still more preferably 55 HRC or higher.

In addition, in this invention, it is not required to prescribe|regulate the upper limit of the hardness of a metal mold|die. However, in the case of steel for a mold having the above component composition, it is realistic that the secondary hardening peak hardness (approximately in the range of 500 to 600 ° C. tempering temperature) is about 60 HRC. And, with respect to the upper limit of this hardness, it is preferable to set it as 58 HRC or less from the point which can make the tempering temperature high exceeding the said peak hardness (that is, the point which can make thermal conductivity high).

And, after adjusting the hardness of the mold to 45HRC or more by performing quenching and tempering on the steel for a mold having the above component composition, the thermal conductivity (λ(W/(m·K)) that satisfies the following formula (1) is obtained characterized by having

λ≥-0.5H+53… Equation (1)

Here, H in Equation (1) is the Rockwell hardness (HRC) of the mold. For example, when the hardness of the mold of the present embodiment is 45 HRC, the thermal conductivity is 30.5 W/(m·K) or more. In addition, when the hardness of the mold is 52HRC, the thermal conductivity is 27W/(m·K) or more. And, Preferably, it is "λ≧-0.5H+54". In addition, this thermal conductivity is the value measured at room temperature (room temperature).

Since the steel for a mold of the present invention satisfies the relationship of formula (1) by quenching and tempering, even at the time of tempering hardness in the high hardness range (for example, 52 HRC or more), where the decrease in thermal conductivity was a problem, 25 W/(m · K) or higher thermal conductivity can be maintained. When the hardness of the mold is 52HRC or more, the preferable thermal conductivity is 28W/(m·K) or more. A more preferable thermal conductivity is 30 W/(m·K) or more. And, at the time of tempering hardness in the low hardness range (for example, less than 52HRC), it is also possible to achieve thermal conductivity of 30W/(m·K) or more, and that is, when it is hardness around 45HRC, thermal conductivity of 32W/(m·K) or more is also possible to achieve. Thereby, high thermal conductivity can be maintained in the mold in use for a hot stamping method (for example, 100-400 degreeC).

Such thermal conductivity can be easily achieved by increasing the tempering temperature in addition to the component composition of the steel for a mold. For example, it is possible to adjust the thermal conductivity to 30 W/(m·K) or more by making the tempering temperature higher than the temperature at which the peak hardness is obtained.

In the case of the present invention, it is not necessary to specify the upper limit of the thermal conductivity of the mold. However, considering that the hardness of the mold decreases as the tempering temperature is increased (for example, by adjusting the temperature to exceed 600°C), the thermal conductivity is 50 W/(m) when the hardness of the mold is less than 45 HRC. ·K), it is when the hardness of 45 HRC or more is maintained, and it is realistic that it is approximately 50 W/(m·K). Preferably, it is 47 W/(m*K) or less. More preferably, it is 45 W/(m*K) or less. And, when the mold is maintaining the hardness of 52HRC or more, it is realistic that the upper limit of the thermal conductivity is approximately 40W/(m·K). Preferably it is 38 W/(m*K) or less. More preferably, it is 35 W/(m*K) or less. And, from the upper limit of these thermal conductivity, the relationship between the above-mentioned thermal conductivity (λ(W/ (m·K)) and Rockwell hardness (H (HRC)) is roughly expressed in Equation (2) of “λ≤-0.5H+70” It is realistic that the relationship is preferably "λ≤-0.5H+66", and more preferably "λ≤-0.5H+61".

The mold for hot stamping of the present invention preferably has a nitride layer on its working surface.

As described above, the mold for hot stamping of the present invention has both high hardness and high thermal conductivity. In addition, the wear resistance (hardness of the working surface) of the mold can be further improved when the working surface of the mold further has a nitride layer. In addition, the working surface is the surface of the metal mold|die in contact with the steel plate in hot stamping.

The method for manufacturing a mold for hot stamping of the present invention is to perform quenching and tempering on the steel for a mold.

When quenching and tempering the steel for a mold having the above component composition, the quenching temperature varies depending on the target hardness and the like, but may be, for example, approximately 1020 to 1080°C. Preferably it is 1050 degrees C or less.

In addition, sufficient hardness of 45 HRC or more can be maintained by tempering the steel for metal molds that has been quenched at this quenching temperature, for example, at a tempering temperature of 500 to 625°C. The quenching temperature and tempering temperature at this time can be selected so that the hardness and thermal conductivity of the mold after quenching and tempering satisfy the relationship of Formula (1) described above.

And, even by tempering at high temperature, it is effective to maintain sufficient mold hardness and increase the thermal conductivity of the mold, for example, at a tempering temperature of 540 ° C. or higher, hardness of 52 HRC or higher can be achieved. , a mold having a thermal conductivity of 25 W/(m·K) or more can be obtained. At this time, in maintaining the hardness of 52HRC or more, the upper limit of the tempering temperature is preferably about 600 ℃. More preferably, it is 595 degrees C or less. More preferably, it is 590 degrees C or less.

The steel for a mold of the present invention is adjusted to a mold for hot stamping having a predetermined hardness by quenching and tempering. In the meantime, the steel for the mold is adjusted to the shape of the mold for hot stamping by various machining processes such as cutting or drilling. The timing of this machining can be performed in the low hardness state (namely, annealing state) before quenching and tempering. And in this case, you may perform finishing processing after quenching and tempering. In addition, depending on the case, you may perform the said machining process in the pre-hardened state after all of the said finishing processings are quenched and tempered.

In the method for manufacturing a mold for hot stamping of the present invention, preferably, the working surface of the mold after the quenching and tempering is further subjected to nitriding treatment.

As described above, by performing quenching and tempering on the steel for a mold having the above component composition, for example, a mold having a hardness of 45 HRC or more and a thermal conductivity satisfying the formula (1) can be obtained. And, since the steel for a mold having the above component composition also has excellent nitriding properties, by further nitriding the working surface of the mold after this quenching and tempering, the wear resistance (hardness of the working surface) of the mold can be improved. At this time, as the conditions for the nitridation treatment, for example, those of various known nitriding treatments such as gas nitriding treatment and salt bath nitriding treatment can be applied.

(Example 1)

The 10 kg steel ingot which has the component composition of Table 1 was melted. And, after heating this steel ingot to 1160 degreeC and hammer forging, it stood to cool, 870 degreeC annealing process was performed to the steel material after this standing-to-cool, and No. of this invention example. Steels of 1 to 8, and Comparative Example No. Crafted 9-11 steels.

<Evaluation of temper hardness>

No. The steel for metal mold|die of 1-11 was quenched by the quenching temperature of 1030 degreeC. At this time, the cooling conditions were assuming the cooling rate when the steel for molds such as the present invention steel and the comparative steel is the size of the actual hot stamping mold, and the half cooling time was 40 minutes (the half cooling time is from the quenching temperature ( Quenching temperature + room temperature) is the time required for cooling to a temperature of /2). And the tempering by the tempering temperature of 500-650 degreeC was performed to the steel for metal mold|die after this quenching. Tempering was performed twice, and was maintained at each temperature for 2 hours. The tempering temperature was set to 7 conditions of every 25 degreeC. And, No. For each of 1 to 11, the Rockwell hardness (C scale) at room temperature of the center was measured for each tempering temperature. The results are shown in FIG. 1 .

Inventive example No. 1-8 maintained a tempering hardness of 45 HRC or greater over the entire tempering temperature of 500-625 °C. And, in particular, approximately 52HRC or more was obtained in the range of the tempering temperature of 540-600 degreeC in any one. Moreover, even if it raised the tempering temperature to more than 600 degreeC which becomes effective in raising the thermal conductivity of a metal mold|die, the tempering hardness of 45 HRC or more was achieved in general.

On the other hand, the comparative example No. In the tempering temperature range of 9°C and 500-600°C, the tempering hardness of 45HRC or more was maintained, but the No. 10, when the tempering temperature was 575°C, the tempering hardness was already lower than 45 HRC. No. No. 11 had a tempering hardness of 45 HRC or higher in a tempering temperature range of 500 to 625°C, but a hardness of 50 HRC or higher was not obtained.

<Evaluation of thermal conductivity>

Based on the results of the above <Evaluation of temper hardness>, No. The thermal conductivity at the time of tempering hardness of 45HRC, 50HRC, and 55HRC about 1-6 and 9 was measured. As for the measurement method, first, the metal mold|die was processed into the disk-shaped test piece of diameter 10mm x thickness 2mm, and the thermal diffusivity and specific heat of this test piece were measured by the laser flash method. And the thermal conductivity in room temperature was computed from following formula (3) using the value of this measured thermal diffusivity and specific heat. The results are shown in FIG. 2 .

Thermal conductivity (λ(W/ (m·K)))=ρ·α·C _p … Equation (3)

(ρ: room temperature density, α: thermal diffusivity, C _p : specific heat)

From the result of FIG. 2, No. which is an example of this invention. 1 to 6, in all hardnesses of 45HRC, 50HRC, and 55HRC, the thermal conductivity satisfies the formula of λ≥-0.5H+53, and even when the hardness is increased to 52HRC, high thermal conductivity of 30W/(m·K) or more was found to be holding. Moreover, also in the high hardness of hardness 55HRC, it had the high thermal conductivity of 25 W/(m*K) or more.

On the other hand, the comparative example No. In 9, when the low hardness of 45HRC and 50HRC is adjusted, the thermal conductivity is small (the expression of λ≥-0.5H+53 is not satisfied), and even if the hardness is raised to 52HRC, λ≥-0.5H+53 is satisfied I knew it didn't.

For the samples of No, 7, and 8, the thermal conductivity when tempering hardness was 52HRC was measured. For the measurement method, the above-mentioned No. It is the same as the times of 1 to 6 and 9. As a result, No. The thermal conductivity of 7 is 31W/(m·K), No. It was confirmed that the thermal conductivity of 8 was 37 W/(m·K) and high thermal conductivity of 30 W/(m·K) or more even with a hardness of 52 HRC.

<Evaluation of softening resistance>

Since the mold in the hot stamping method is used at a high temperature, the softening resistance of the steel for the mold becomes important. So, this invention example No. 1 to 6 and Comparative Example No. 9 was kept at 600° C. in a state in which it was tempered at 55 HRC, and the change in hardness was measured. The results are shown in FIG. 3 . Inventive example No. In 1-6, since the tempering temperature could be made high, even after holding|maintenance for 4 hours, the hardness of 50 HRC or more was maintained. On the other hand, Comparative Example No. In 9, since the tempering temperature was low, the hardness after holding|maintenance for 4 hours was less than 50 HRC. And after this, as the holding time increased, the difference in hardness between the inventive steel and the comparative steel increased. In the steel of the present invention, the softening resistance is large, and it is effective in the hot stamping method.

Claims (9)

In % by mass, C: 0.45 to 0.65%, Si: 0.1 to 0.6%, Mn: 0.1 to 0.3%, Cr: 2.5 to 6.0%, Mo: 1.2 to 2.6%, V: 0.4 to 0.8%, balance Fe and inevitable Steel for a mold for hot stamping, characterized in that it has a component composition of red impurities. In % by mass, C: 0.45 to 0.65%, Si: 0.1 to 0.6%, Mn: 0.1 to 0.3%, Cr: 2.5 to 6.0%, Mo: 1.2 to 2.6%, V: 0.4 to 0.8%, balance Fe and inevitable A mold for hot stamping, characterized in that it has a component composition of red impurities. 3. The method of claim 2,
A mold for hot stamping, characterized in that the hardness is 45 HRC or more, and the thermal conductivity (λ(W/(m·K))) satisfies the following formula (1).
λ≥-0.5H+53… Equation (1)
H: Rockwell hardness (HRC) of the mold 4. The method of claim 3,
A mold for hot stamping, characterized in that the hardness is 52HRC or higher. 5. The method of claim 4,
A mold for hot stamping, characterized in that the thermal conductivity (λ) is 25 W/(m·K) or more. 6. The method according to any one of claims 2 to 5,
A mold for hot stamping, characterized in that it has a nitride layer on the working surface. A method for manufacturing a mold for hot stamping, wherein the steel for a mold for hot stamping according to claim 1 is quenched and tempered at a quenching temperature of 1020 to 1080°C and a tempering temperature of 500 to 625°C. 8. The method of claim 7,
The method of manufacturing a mold for hot stamping, characterized in that the tempering temperature is 540 ~ 600 ℃. 9. The method according to claim 7 or 8,
A method of manufacturing a mold for hot stamping, characterized in that after performing the quenching and tempering, a nitriding treatment is further performed on the working surface.

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