Precipitation-hardening martensitic stainless steel for press plate, and solid solution treatment material and aging treatment material

Abstract

To provide a precipitation-hardening martensitic stainless steel and a solid solution treatment material and an aging treatment material thereof capable of realizing a press plate having high hardness and excellent flatness. The above-described problem is solved by a precipitation-hardening martensitic stainless steel for a press plate having a predetermined component composition, the component composition having MA defined by MA = [Ni] + 0.65 × [Mn] + 0.23 × [Si] + 0.62 × [Cr] + 0.25 × [Mo] + 0.35 × [Cu] + 30.6 × ([C] + [N]) - 16.5 being within a range of 1.0 to 4.5, and H defined by H = [Cu] + 0.6 × [Ni] + 1.8 × [Si] + 3.8 × [Ti] + 1.8 × [Nb] - 0.9 × [Mn] - 13.8 × ([C] + [N]) being in a range of 5.0 or greater. A solid solution treatment material has a two-phase structure of a martensite phase and a residual austenite phase, the residual austenite phase being in an amount of 0.2 to 8 vol%, and a hardness of less than 380 HV. The aging treatment material has a hardness of 450 HV or greater.

Description

TECHNICAL FIELD

[0001] The present invention relates to a precipitation-hardening martensitic stainless steel and a solid solution treatment material and an aging treatment material thereof capable of realizing a press plate having high hardness and excellent flatness.BACKGROUND ART

[0002] Precipitation-hardening martensitic stainless steels such as SUS630 that are capable of achieving high strength by precipitation of an ε-Cu phase through the addition of Cu are used for press plates used to manufacture multilayer printed wiring boards and other laminates by press forming.

[0003] For example, Patent Document 1 discloses a precipitation-hardening martensitic stainless steel that maintains high strength and toughness by controlling the ε-Cu phase as well as an Ni 16 Ti 6 Si 7 -based intermetallic compound phase (G phase) through the addition of Ti and Si so as to distribute these phases in crystal grains. In the G phase, that is, Ni 16 X 6 Si 7 , precipitated by aging heat treatment, not only Ti but also Fe, Mn, and Nb can be substituted for X. Thus, the component composition obtained by adjusting an amount of Nb, in particular, is clearly defined.

[0004] Further, Patent Document 2 discloses a manufacturing method of a press plate and a steel material thereof. The method includes subjecting an austenitic stainless steel having a high austenite ratio and containing 1.0 to 4.0 mass% of Si to aging treatment after necessary shape correction, and increasing a surface hardness to 430 HV or higher by strain aging. Here, Patent Document 2 points out that steel plates composed of hard stainless steel having a surface hardness of 400 HV or higher are difficult to sufficiently flatten through shape correction by temper rolling, a tension leveler, or the like, alone and, in a case in which martensitic stainless steel is used, flatness cannot be ensured in the quenching or tempering process, and an austenitic stainless steel having minimal martensite and a high austenite ratio should be used.PRIOR ART DOCUMENTSPatent Documents

[0005] Patent Document 1: Japanese Laid-Open Patent Application Publication No. 2021-134395 Patent Document 2: Japanese Laid-Open Patent Application Publication No. 2008-297601 DISCLOSURE OF THE INVENTIONProblem to be Solved by the Invention

[0006] Precipitation-hardening martensitic stainless steels such as SUS630 are solution-treated at 1000°C or higher and then aging-treated at a temperature around 500°C to obtain a predetermined hardness (strength). That is, a precipitation-hardening martensitic stainless steel for a press plate requires a hardness that allows shape correction after solid solution treatment on the one hand, and the capability of being increased in strength to a sufficient hardness by subsequent aging treatment on the other hand.

[0007] The present invention was made in view of circumstances such as described above, and an object thereof is to provide a precipitation-hardening martensitic stainless steel and a solid solution treatment material and an aging treatment material thereof capable of realizing a press plate having high hardness and excellent flatness.Means for Solving the Problem

[0008] A precipitation-hardening martensitic stainless steel for a press plate in the present invention has a component composition including, by mass%, C: 0.01 to 0.07 %, Si: 0.05 to 2.25 %, Mn: 0.5 to 5.0 %, Ni: 4.5 to 10.0 %, Cr: 10.0 to 17.0 %, Mo: 0.1 to 1.50 %, Cu: 0.30 to 5.0 %, Al: 0.001 to 0.100 %, N: 0.001 to 0.020 %, Ti: 0.15 to 0.55 %, Nb: 0.15 to 0.45 %, Co: 0.03 to 0.80 %, P: 0.04% or less, and S: 0.0020% or less, with the remainder consisting of Fe and inevitable impurities. The component composition has, given [M] as a mass% of element M, MA defined by being within a range of 1.0 to 4.5, and H defined by H = Cu + 0.6 × Ni + 1.8 × Si + 3.8 × Ti + 1.8 × Nb − 0.9 × Mn − 13.8 × C + N being in a range of 5.0 or greater.

[0009] According to such characteristics, through solid solution treatment and aging treatment, it is possible to provide a press plate having high hardness and excellent flatness.

[0010] Further, a solid solution treatment material of a precipitation-hardening martensitic stainless steel for a press plate according to the present invention has a two-phase structure of a martensite phase and a residual austenite phase, the residual austenite phase being in an amount of 0.2 to 8 vol%, a hardness of less than 380 HV, and a component composition including, by mass%, C: 0.01 to 0.07 %, Si: 0.05 to 2.25 %, Mn: 0.5 to 5.0 %, Ni: 4.5 to 10.0 %, Cr: 10.0 to 17.0 %, Mo: 0.1 to 1.50 %, Cu: 0.30 to 5.0 %, Al: 0.001 to 0.100 %, N: 0.001 to 0.020 %, Ti: 0.15 to 0.55 %, Nb: 0.15 to 0.45 %, Co: 0.03 to 0.80 %, P: 0.04% or less, and S: 0.0020% or less, with the remainder consisting of Fe and inevitable impurities. The component composition has, given [M] as a mass% of element M, H defined by H = Cu + 0.6 × Ni + 1.8 × Si + 3.8 × Ti + 1.8 × Nb − 0.9 × Mn − 13.8 × C + N being in a range of 5.0 or greater.

[0011] According to such characteristics, shape correction is easily achieved and high hardness is imparted through aging treatment, making it possible to provide a press plate with high hardness and excellent flatness.

[0012] In the invention described above, the component composition may have, given [M] as a mass% of element M, MA defined by being within a range of 1.0 to 4.5. According to such characteristics, shape correction is easily achieved and high hardness is imparted through aging treatment, making it possible to provide a press plate with high hardness and excellent flatness.

[0013] Further, an aging treatment material of a precipitation-hardening martensitic stainless steel for a press plate according to the present invention has a hardness of 450 HV or greater and a component composition including, by mass%, C: 0.01 to 0.07 %, Si: 0.05 to 2.25 %, Mn: 0.5 to 5.0 %, Ni: 4.5 to 10.0 %, Cr: 10.0 to 17.0 %, Mo: 0.1 to 1.50 %, Cu: 0.30 to 5.0 %, Al: 0.001 to 0.100 %, N: 0.001 to 0.020 %, Ti: 0.15 to 0.55 %, Nb: 0.15 to 0.45 %, Co: 0.03 to 0.80 %, P: 0.04% or less, and S: 0.0020% or less, with the remainder consisting of Fe and inevitable impurities. The component composition has, given [M] as a mass% of element M, MA defined by being within a range of 1.0 to 4.5.

[0014] According to such characteristics, it is possible to provide a press plate having high hardness and excellent flatness.

[0015] The component composition may have, given [M] as a mass% of element M, H defined by H = Cu + 0.6 × Ni + 1.8 × Si + 3.8 × Ti + 1.8 × Nb − 0.9 × Mn − 13.8 × C + N being in a range of 5.0 or greater. According to such characteristics, it is possible to provide a press plate having high hardness and excellent flatness.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Fig. 1 is a table of component compositions of steels used in tests. Fig. 2 is a table of test results. BEST MODE FOR CARRYING OUT THE INVENTION

[0017] As described above, a precipitation-hardening martensitic stainless steel for a press plate requires a relatively low hardness after solid solution treatment on the one hand, and the capability of obtaining a sufficient hardness by aging treatment on the other hand. The inventors conducted extensive studies on the effect of the addition of Co along with Nb on martensitic stainless steels having such a hardness, and found that the desired hardness can be obtained both after solid solution treatment and after aging treatment by adjusting the components of the steel so that an austenite phase remains after the solid solution treatment. The component composition of such a steel may be as follows.

[0018] That is, a precipitation-hardening martensitic stainless steel for a press plate according to this example has a component composition including, by mass%, C: 0.01 to 0.07 %, Si: 0.05 to 2.25 %, Mn: 0.5 to 5.0 %, Ni: 4.5 to 10.0 %, Cr: 10.0 to 17.0 %, Mo: 0.1 to 1.50 %, Cu: 0.30 to 5.0 %, Al: 0.001 to 0.100 %, N: 0.001 to 0.020 %, Ti: 0.15 to 0.55 %, Nb: 0.15 to 0.45 %, Co: 0.03 to 0.80 %, P: 0.04% or less, and S: 0.0020% or less, and including Co along with Nb.

[0019] Furthermore, the component composition includes, given [M] as a mass% of element M, MA defined by being within a range of 1.0 to 4.5, and H defined by H = Cu + 0.6 × Ni + 1.8 × Si + 3.8 × Ti + 1.8 × Nb − 0.9 × Mn − 13.8 × C + N being in a range of 5.0 or greater.

[0020] Here, it was found that, in the component composition including just a small amount of Co along with Nb described above, a difference in hardness before and after aging treatment can be made sufficiently large and, moreover, the hardness before aging treatment, that is, after solid solution treatment, can be stabilized at a hardness that allows for shape correction. Co is a stabilizing element of the austenite phase, but the MA value described above serves as an indicator of the stabilization of the austenite phase with respect to this small amount of Co. With the MA value set within the range described above, an amount of residual austenite (residual γ-phase) after solid solution treatment can be kept at an appropriate level, a hardness after solid solution treatment can be made relatively low, and excellent flatness can be obtained by shape correction of the plate material. Incidentally, Co is included more in the ε-Cu phase than in the G phase relatively, affecting the precipitation form of the compound. The H value described above is an indicator of the hardness obtained after aging treatment, and a range of the H value is determined in consideration of the precipitation form of the compound with respect to this small addition of Co. With the H value set within the range described above, sufficient hardness can be obtained by aging treatment from a hardness that allows for shape correction. That is, the Co being contained in just a small amount increases a mechanical strength of a base material composed of the martensite phase, making it possible to maintain a high mechanical strength of the aging treatment material despite the austenite phase being caused to remain.

[0021] The material after solid solution treatment requires a two-phase structure of a martensite phase and a residual austenite phase, with the amount of the residual austenite phase being 0.2 to 8 % by vol%, and a hardness of less than 380 HV. To obtain such a solid solution treatment material, the MA value is within the range of 1.0 to 4.5 described above, preferably within a range of 1.2 to 3.5, and more preferably within a range of 1.4 to 2.5.

[0022] Further, as an aging treatment material, a hardness of 450 HV or greater is required. To obtain such an aging treatment material, the H value is in the range of 5.0 or greater described above, preferably within a range of 6.0 to 15.0, and more preferably within a range of 7.0 to 12.0. It should be noted that preferably an upper limit of the H value is set so as to prevent embrittlement of the steel material during manufacture.

[0023] It should be noted that a manufacturing method of the press plate in this example may be as follows. First, steel having the component composition described above is cast, hot-rolled, and then cold-rolled to obtain strip steel material having a predetermined thickness. The obtained strip steel material is solution-treated and martensitically transformed while causing a portion of the residual austenite phase to remain during the cooling thereof. In the solid solution treatment, for example, the material is retained at a predetermined temperature within a range of 1000 to 1150 °C and then cooled with water. Thereby, a solid solution treatment material of the precipitation-hardening martensitic stainless steel for a press plate can be obtained.

[0024] Next, the strip steel material that is a solid solution treatment material is corrected in shape. For shape correction, for example, a tension leveler can be suitably used. The hardness of the solid solution treatment material is less than 380 HV as described above, making it possible to make the burden on the manufacturing process for shape correction relatively small. For example, excellent flatness can be obtained by shape correction with a tension leveler alone.

[0025] Finally, the steel plate is subjected to aging treatment to obtain the predetermined hardness. Aging treatment, for example, can be retained at 400 to 600 °C for 30 minutes to 10 hours. This makes it possible to set the hardness after aging treatment to 450 HV or greater as described above. Thus, the aging treatment material of the precipitation-hardening martensitic stainless steel for a press plate can be obtained.

[0026] As described above, a press plate with high hardness and excellent flatness can be obtained.[Testing of Solid Solution Treatment Material and Aging Treatment Material]

[0027] Next, results of preparing plate materials using a plurality of precipitation-hardening martensitic stainless steels and conducting tests on hardness and other properties will be described.

[0028] Using the steels having the component compositions shown in Examples 1 to 11 and Comparative Examples 1 to 8 in Fig. 1, 20-kg steel ingots were cast, hot-forged to obtain forged plates, and then cold-rolled to obtain steel plates having a 1.6-mm thickness. The obtained steel plates were solution-treated by being retained at 1050°C for 2.5 minutes and then cooled to obtain solid solution treatment materials. Furthermore, a portion of the solid solution treatment materials were corrected in shape and subjected to aging treatment to obtain aging treatment materials.

[0029] As shown in Fig. 2, the obtained solid solution treatment materials were measured for Vickers hardness (solid solution hardness) and for the amount of residual γ-phase. The amount of residual γ-phase was measured by electron backscatter diffraction (EBSD) using a field emission scanning electron microscope (FE-SEM; JEOL Ltd., JSM-7001F). Further, the flatness of each solid solution treatment material after shape correction was measured. The flatness was determined from a maximum distance between an upper surface of the steel plate and a lower surface of a ruler with the 2-m ruler applied from above the steel plate placed on a surface plate. The flatness was determined as "very good" and recorded as "v" when such a distance was 1 mm or less. Similarly, the flatness was determined as "good" and recorded as "g" when the distance was more than 1 mm and equal to or less than 3 mm, determined as "acceptable" and recorded as "a" when the distance was more than 3 mm and equal to or less than 5 mm, and determined as "poor" and recorded as "p" when the distance was more than 5 mm. Furthermore, the aging treatment materials were also measured for Vickers hardness (aging hardness).

[0030] As shown in the table, for the steels of Examples 1 to 11, the flatnesses of the solid solution treatment materials after shape correction were all "acceptable" or better, and the hardnesses of the aging treatment materials were 450 HV or greater. It should be noted that the MA values described above were within the range of 1.0 to 4.5, the H values were in the range of 5.0 or greater, the residual y amounts of the solid solution treatment materials were within the range of 0.2 to 8.0 vol%, and the hardnesses were 380 HV or less, with the exception of Example 1. In Example 1, the hardness of the solid solution treatment material was relatively high at 386 HV, but the flatness was "acceptable."

[0031] On the other hand, in Comparative Example 1, the Mn content was low compared with those of the examples, and the MA value was low. Further, in Comparative Example 2, the Ni content was low, and the MA value was low. Then, each of these had a low residual y amount and a "poor" flatness. Conceivably, the residual y amount being low caused the hardness of the solid solution treatment material to be relatively high and failure to improve the flatness even by shape correction.

[0032] In Comparative Example 3, the amount of each element in the component composition was about the same as in the examples, but the MA value was high and the H value was low. As a result, the hardness of the aging treatment material was low. Conceivably, the MA value being high increased the residual y amount and decreased the hardness of the solid solution treatment material excessively, which resulted in insufficient hardness in the aging treatment material. Further, the H value being low conceivably lowered the precipitation hardenability in the aging treatment, which conceivably led to failure to obtain sufficient hardness in the aging treatment material.

[0033] In Comparative Example 4, the amount of each element in the component composition was about the same as in the examples, but the H value was low. As a result, the hardness of the aging treatment material was low. Although the hardness of the solid solution treatment material was the same as in the examples, conceivably the precipitation hardenability in the aging treatment was low due to the low H value.

[0034] In Comparative Example 5, the content of Si was low. As a result, the hardness of the aging treatment material was low. Although the hardness was the same as in the examples at the time of the solid solution treatment material, conceivably sufficient hardness could not be obtained through the aging treatment due to the low Si content.

[0035] Comparative Example 6 contained almost no Co, but the content and the MA value in other component compositions were substantially identical to those in Example 7. Comparative Example 6, despite having almost the same solid solution hardness as in Example 7 as well, had a lower value in aging hardness. That is, it was found that the Co content in Example 7 was an amount having almost no effect on the solid solution hardness, but significantly contributed to the aging hardness. Relationships between Comparative Example 7 and Example 11, and between Comparative Example 8 and Example 2 are also similar.

[0036] Thus, with the steels of Examples 1 to 11, it is possible to impart relatively low hardness to the solid solution treatment material so as to obtain excellent flatness by shape correction and impart high hardness to the aging treatment material. That is, it is possible to obtain a precipitation-hardening martensitic stainless steel and a solid solution treatment material and an aging treatment material thereof capable of realizing a press plate having high hardness and excellent flatness.

[0037] The ranges of the component compositions of the steel of the present invention, including Examples 1 to 11, are defined as follows.

[0038] C is an element that stabilizes the austenite phase while contributing to a rise in mechanical strength through solid solution treatment, suppresses the generation of δ ferrite at high temperatures, and increases the residual austenite phase after solid solution treatment. Therefore, excessive content reduces the precipitation hardenability by the aging treatment. Considering these factors, C is within a range of 0.01 to 0.07 %, preferably within a range of 0.02 to 0.06 %, and more preferably within a range of 0.03 to 0.05 % by mass%.

[0039] Si is added for deoxidization and is an important element for generating the G phase and obtaining mechanical strength through aging treatment. On the other hand, Si is a ferritizer, and excessive content leads to an increase in a δ-ferrite phase, which deteriorates hot workability. Considering these factors, Si is within a range of 0.05 to 2.25 %, preferably within a range of 1.05 to 2.05 %, and more preferably within a range of 1.35 to 1.85 % by mass%.

[0040] Mn is an element that stabilizes the austenite phase and contributes to the generation of residual austenite while suppressing the generation of the δ-ferrite phase. On the other hand, excessive content causes a significant amount of the austenite phase to remain, which reduces the mechanical strength after aging treatment. Considering these factors, Mn is within a range of 0.5 to 5.0 %, preferably within a range of 0.6 to 4.0 %, and more preferably within a range of 0.8 to 3.0 % by mass%.

[0041] Ni is an element that stabilizes the austenite phase, and is an important element that contributes to the generation of residual austenite while suppressing the generation of the δ-ferrite phase, and further generates the G phase and contributes to a rise in mechanical strength through aging treatment. On the other hand, excessive content causes a significant amount of the austenite phase to remain, which reduces the mechanical strength after aging treatment. Considering these factors, Ni is within a range of 4.5 to 10.0 %, preferably within a range of 5.5 to 9.0 %, and more preferably within a range of 6.5 to 8.0 % by mass%.

[0042] Cr is an element required to ensure corrosion resistance as a stainless steel and also contributes to the generation of residual austenite. On the other hand, excessive content causes generation of the δ-ferrite phase, resulting in a decrease in hot workability. Considering these factors, Cr is within a range of 10.0 to 17.0 %, preferably within a range of 12.0 to 16.0 %, and more preferably within a range of 13.0 to 15.0 % by mass%.

[0043] Mo is an element required to ensure corrosion resistance as a stainless steel and also contributes to the generation of residual austenite. On the other hand, excessive content causes generation of the δ-ferrite phase, resulting in a decrease in hot workability. Considering these factors, Mo is within a range of 0.1 to 1.50 %, preferably within a range of 0.6 to 1.20 %, and more preferably within a range of 0.7 to 1.00 % by mass%.

[0044] Cu is an element that stabilizes the austenite phase, and is an important element that contributes to the generation of residual austenite while suppressing the generation of the δ-ferrite phase, and further generates the ε-Cu phase and contributes to a rise in mechanical strength through aging treatment. On the other hand, excessive content causes a significant amount of the austenite phase to remain, which reduces the mechanical strength after aging treatment. Considering these factors, Cu is within a range of 0.30 to 5.0 %, preferably within a range of 0.40 to 3.0 %, and more preferably within a range of 0.50 to 1.5 % by mass%.

[0045] Al is added for deoxidization and is an effective element for stably containing Nb and Ti, which are readily oxidized, resulting in a low adding yield in molten metal. On the other hand, Al increases the martensitic transformation initiation temperature (Ms point), and therefore excessive content inhibits the generation of residual austenite. Further, excessive content causes an increase in the δ-ferrite phase, deteriorating hot workability. Considering these factors, Al is within a range of 0.001 to 0.100 %, preferably within a range of 0.002 to 0.060 %, and more preferably within a range of 0.002 to 0.020 % by mass%.

[0046] N is an element that stabilizes the austenite phase and contributes to the generation of residual austenite while suppressing the generation of the δ-ferrite phase. On the other hand, excessive content causes a significant amount of the austenite phase to remain, which reduces the mechanical strength after aging treatment. Further, excessive content forms nitrides, mainly with Ti, generating a fracture origin of the press plate. Furthermore, excessive content may change the Ms point and cause slab cracking. Considering these factors, N is within a range of 0.001 to 0.020 %, preferably within a range of 0.002 to 0.015 %, and more preferably within a range of 0.003 to 0.010 % by mass%.

[0047] Ti is an important element that generates the G phase through aging treatment, and contributes to a rise in mechanical strength. On the other hand, excessive content causes generation of the δ-ferrite phase, resulting in a decrease in hot workability. Further, excessive content may change the Ms point and cause slab cracking. Considering these factors, Ti is within a range of 0.15 to 0.55 %, preferably within a range of 0.20 to 0.50 %, and more preferably within a range of 0.25 to 0.45 % by mass%.

[0048] Nb is an important element that generates the G phase through aging treatment, and contributes to a rise in mechanical strength. On the other hand, excessive content causes generation of the δ-ferrite phase, resulting in a decrease in hot workability. Further, excessive content may change the Ms point and cause slab cracking. Considering these factors, Nb is within a range of 0.15 to 0.45 %, preferably within a range of 0.20 to 0.40 %, and more preferably within a range of 0.25 to 0.35 % by mass%.

[0049] Co stabilizes the passivation film to increase corrosion resistance as a stainless steel and, as a stabilizing element of the austenite phase, lowers the Ms point and affects the generation of residual austenite. Further, Co increases the mechanical strength of the base material (matrix) by improving quenching performance, thereby ensuring the mechanical strength of the aging treatment material. On the other hand, excessive content causes excessive generation of the residual austenite in the solid solution treatment, making it no longer possible to obtain sufficient hardness even through the aging treatment, and reduces toughness. It should be noted that, after the aging treatment, in the plate materials fabricated from the steel in Examples 1 to 11 described above, it was observed that Co was included abundantly in the ε-Cu phase and contained minimally in the G phase. This revealed that Co affects the precipitation forms of the ε-Cu phase and the G phase. Considering these factors, Co is within a range of 0.03 to 0.80 %, preferably within a range of 0.05 to 0.50 %, and more preferably within a range of 0.06 to 0.30 % by mass%.

[0050] P is an element inevitably mixed in steel and is segregated at crystal grain boundaries and concentrated in the final solidification area during casting, which promotes solidification cracking and also results in a decrease in hot workability. Therefore, the content is desirably reduced to the extent possible, but excessive refining increases manufacturing costs. Considering these factors, P is 0.04% or less, preferably 0.030% or less, and more preferably 0.025% or less by mass%.

[0051] S is an element inevitably mixed in steel and forms compounds with Mn, which become inclusions that reduce corrosion resistance. Furthermore, S segregates at grain boundaries and decreases hot workability. Therefore, the content is desirably reduced to the extent possible, but excessive refining increases manufacturing costs. Considering these factors, S is 0.0020% or less, preferably 0.0015% or less, and more preferably 0.0010% or less by mass%.

[0052] The above are representative examples of the present invention and modifications based thereon. However, the present invention is not necessarily limited to these examples, and one skilled in the art can find various alternative examples and modifications without departing from the gist of the present invention or the appended claims.

[0053] In summary an embodiment can be described as follows: To provide a precipitation-hardening martensitic stainless steel and a solid solution treatment material and an aging treatment material thereof capable of realizing a press plate having high hardness and excellent flatness.

[0054] The above-described problem is solved by a precipitation-hardening martensitic stainless steel for a press plate having a predetermined component composition, the component composition having MA defined by MA = Ni + 0.65 × Mn + 0.23 × Si + 0.62 × Cr + 0.25 × Mo + 0.35 × Cu + 30.6 × (C + N) - 16.5 being within a range of 1.0 to 4.5, and H defined by H = Cu + 0.6 × Ni + 1.4 × Si + 3.8 × Ti + 1.8 × Nb - 0.9 × Mn - 13.8 × (C + N) being in a range of 5.0 or greater. A solid solution treatment material has a two-phase structure of a martensite phase and a residual austenite phase, the residual austenite phase being in an amount of 0.2 to 8 vol%, and a hardness of less than 380 HV. The aging treatment material has a hardness of 450 HV or greater.

Claims

1. A precipitation-hardening martensitic stainless steel for a press plate, the precipitation-hardening martensitic stainless steel comprising: a component composition including, by mass%, C: 0.01 to 0.07 %, Si: 0.05 to 2.25 %, Mn: 0.5 to 5.0 %, Ni: 4.5 to 10.0 %, Cr: 10.0 to 17.0 %, Mo: 0.1 to 1.50 %, Cu: 0.30 to 5.0 %, Al: 0.001 to 0.100 %, N: 0.001 to 0.020 %, Ti: 0.15 to 0.55 %, Nb: 0.15 to 0.45 %, Co: 0.03 to 0.80 %, P: 0.04% or less, and S: 0.0020% or less, with the remainder consisting of Fe and inevitable impurities, and the component composition having, given [M] as a mass% of element M, MA defined by being within a range of 1.0 to 4.5, and H defined by H = Cu + 0.6 × Ni + 1.8 × Si + 3.8 × Ti + 1.8 × Nb − 0.9 × Mn − 13.8 × C + N being in a range of 5.0 or greater.

2. A solid solution treatment material of a precipitation-hardening martensitic stainless steel for a press plate, the solid solution treatment material comprising: a two-phase structure of a martensite phase and a residual austenite phase, the residual austenite phase being in an amount of 0.2 to 8 vol%, a hardness of less than 380 HV, and a component composition including, by mass%, C: 0.01 to 0.07 %, Si: 0.05 to 2.25 %, Mn: 0.5 to 5.0 %, Ni: 4.5 to 10.0 %, Cr: 10.0 to 17.0 %, Mo: 0.1 to 1.50 %, Cu: 0.30 to 5.0 %, Al: 0.001 to 0.100 %, N: 0.001 to 0.020 %, Ti: 0.15 to 0.55 %, Nb: 0.15 to 0.45 %, Co: 0.03 to 0.80 %, P: 0.04% or less, and S: 0.0020% or less, with the remainder consisting of Fe and inevitable impurities, and the component composition having, given [M] as a mass% of element M, H defined by H = Cu + 0.6 × Ni + 1.8 × Si + 3.8 × Ti + 1.8 × Nb − 0.9 × Mn − 13.8 × C + N being in a range of 5.0 or greater.

3. The solid solution treatment material of a precipitation-hardening martensitic stainless steel for a press plate according to claim 2, wherein the component composition has, given [M] as a mass% of element M, MA defined by being within a range of 1.0 to 4.5.

4. An aging treatment material of a precipitation-hardening martensitic stainless steel for a press plate, the aging treatment material comprising: a hardness of 450 HV or greater and a component composition including, by mass%, C: 0.01 to 0.07 %, Si: 0.05 to 2.25 %, Mn: 0.5 to 5.0 %, Ni: 4.5 to 10.0 %, Cr: 10.0 to 17.0 %, Mo: 0.1 to 1.50 %, Cu: 0.30 to 5.0 %, Al: 0.001 to 0.100 %, N: 0.001 to 0.020 %, Ti: 0.15 to 0.55 %, Nb: 0.15 to 0.45 %, Co: 0.03 to 0.80 %, P: 0.04% or less, and S: 0.0020% or less, with the remainder consisting of Fe and inevitable impurities, and the component composition having, given [M] as a mass% of element M, MA defined by being within a range of 1.0 to 4.5.

5. The aging treatment material of a precipitation-hardening martensitic stainless steel for a press plate according to claim 4, wherein the component composition has, given [M] as a mass% of element M, H defined by H = Cu + 0.6 × Ni + 1.8 × Si + 3.8 × Ti + 1.8 × Nb − 0.9 × Mn − 13.8 × C + N being in a range of 5.0 or greater.

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