Title of Invention | MARTENSITE BASED STAINLESS STEEL SHEET FOR HEAT RESISTANT DISK BRAKE EXCHELLENT IN HARDENABILITY |
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Abstract | Disclosed is a martensitic stainless steel for heat-resistant disc brakes which is excellent in hardenability and can be easily quench hardened at relatively low temperatures while maintaining high heat resistance. This martensitic stainless steel for heat-resistant disc brakes is characterized by having a composition consisting of, in mass%, 0.05-0.10% of C, not less than 0.1% and not more than 1% of Si, 0.2-2.0% of Mn, not more than 0.04% of P, not more than 0.010% of S, 0.010-0.025% of N, 11-14% of Cr, 0.5-2% of Ni, 0.5-2% of Cu, 1-2% of Mo, 0.03-0.3% of Nb, not more than 0.01% of Al, not more than 0.1% of Ti and the balance of Fe and unavoidable impurities while satisfying that C + N is 0.06-0.1%. This martensitic stainless steel for heat-resistant disc brakes is also characterized in that ϝp obtained by the formula (1) below is not less than 80. ϝp = 420[%C] + 470[%N] + 23[%Ni] + 9[%Cu] + 7[%Mn] - 11.5[%Cr] - 11.5[%Si] -52[%Al] - 12[%Mo] - 47[%Nb] + 189 (1) |
Full Text | FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10, rule 13) " MARTENSITE BASED STAINLESS STEEL SHEET FOR HEAT RESISTANT DISK BRAKE EXCELLENT IN HARDENABILITY NIPPON STEEL & SUMIKIN STAINLESS STEEL CORPORATION of 2-2 Nihonbashi Hongokucho 3-chome, Chuo-ku, Tokyo 103-0021, Japan. The following specification particular!/ describes the invention and the manner in which it is to be performed. DECLARATION I, Masaki Honda , c/o Seiwa Patent & Law, Toranomon 37 Mori Bldg., 5-1, Toranomon 3-chome,. Minato-ku, Tokyo, Japan, hereby verify that I am the translator of the attached translation of International Application No. PCT/JP2006/317401 and that I believe the attached translation is a true and accurate translation of the same. This 13th day of February , 2008 NSSC-S804 DESCRIPTION MARTENSITE BASED STAINLESS STEEL SHEET FOR HEAT RESISTANT DISK BRAKE EXCELLENT IN HARDENABILITY TECHNICAL FIELD The present invention relates to steel sheet for a disk brake of a motorcycle, more particularly relates to martensite based stainless steel sheet excellent in heat resistance stably giving a hardness required for a brake as quenched from a relatively low temperature of less than 1000°C after being worked into a brake and being resistant to softening even when the disk temperature reaches as high as 650°C during use. BACKGROUND ART Steel sheet for a disk brake of a motorcycle requires wear resistance, rust resistance, toughness, and other characteristics. Wear resistance in general becomes greater the higher the hardness. On the other hand, if the hardness is too high, so-called brake squealing occurs between the brake and the pad, so the brake is required to have a hardness of 32 to 38 HRC (Rockwell hardness C scale). From these required characteristics, martensite based stainless steel sheet is used for motorcycle disk brake materials. In the past, SUS 420J2 was quenched and tempered to adjust it to the desired hardness for use for a brake, but in this case there was the problem that two heat treatment processes of quenching and tempering were required. As opposed to this, Japanese Patent Publication (A) No. 57-198249 discloses an invention relating to a steel composition able to stably give the desired hardness in a quenching temperature range broader than the conventional steel of SUS 420J2 and able to be used as quenched. This reduces the C and N and compensates for the resultant narrower austenite temperature range, that is, narrower quenching temperature range, by adding the austenite forming element Mn. Further, Japanese Patent Publication (A) No. 8-60309 discloses steel sheet for a motorcycle disk brake made of low Mn steel able to be used as quenched. This steel sheet lowers the Mn but 5 instead adds Ni and Cu having similar effects as austenite forming elements. Recently, motorcycles are also being required to be reduced in weight. Reduction of the weight of the motorcycle brake disks is therefore being studied. In this case, the problem becomes the deformation of the disk due to softening of the disk material by the heat generated at the time of braking. To solve this, it is necessary to improve the heat resistance of the disk material. As one solution, there is improvement of the temper softening resistance. Japanese Patent Publication (A) No. 2001-220654 discloses a method of improvement of heat resistance by the addition of Nb and Mo. However, the effect of improvement of heat resistance is limited to 530°C. Further, Japanese Patent Publication (A) No. 2004-346425 discloses steel sheet resistant to temper softening even at a temperature over 600CC. Further, Japanese Patent Publication (A) No. 2005-133204 discloses a disk material having excellent heat resistance by quenching from a temperature over 1000°C. DISCLOSURE OF THE INVENTION However, rather than quenching from a temperature over 1000°C such as in the invention described in Japanese Patent Publication (A) No. 2005-133204, quenching from a low temperature range less than 1000°C is advantageous in terms of energy costs and production costs. However, assuming use as quenched, for example, even at a high temperature over 600°C, if attempting to improve the heat resistance by the addition of alloy for realizing a temper softening resistance effect etc., there is the problem that the hardness hardly rises with quenching from a relatively low temperature of 900°C to 1000°C or so, that is, the phenomenon easily occurs of the hardenability dropping. The invention described in Japanese Patent Publication (A) No. 2004-346425 does not make any suggestions at all regarding this problem. 5 Further, the invention described in Japanese Patent Publication (A) No. 2005-133204 is originally directed toward quenching from a high temperature. Therefore, the present invention has as its object the provision of martensite based stainless steel sheet for a heat resistant disk brake excellent in hardenability which is predicated on use as quenched, has a temper softening resistance effect even at a high temperature over 600°C and otherwise maintains a high heat resistance, and is easily hardened even with quenching from a relatively low temperature of about 900 to 1000°C. The present invention was made to solve the above problems and has as its gist the following. (1) Martensite based stainless steel sheet for heat resistant disk brake excellent in hardenability containing, by mass%, C: 0.05% to 0.10%, Si: 0.1% to 1%, Mn: 0.2% to 2.0%, P: 0.04% or less, S: 0.010% or less, N: 0.010% to 0.025%, Cr: 11% to 14%, Ni: 0.5% to 2%, Cu: 0.5% to 2%, Mo: 1% to 2%, Nb: 0.03% to 0.3%, Al: 0.01% or less, Ti: 0.1% or less, C and N satisfying C+N: 0.06% to 0.1%, and the balance of Fe and unavoidable impurities, yp expressed by the following (1) equation being 80 or more. yp=420[%C]+4 70[%N]+23[%Ni]+9[%Cu]+7[%Mn]-11.5[%Cr]-11.5[%Si]-52[%Al]-12[%Mo]-47[%Nb]+18 9...(l) BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the results of hardenability evaluation tests for high C low N steel and low C high N steel having the same total amounts of C and N. FIG. 2 shows the results of temper softening resistance evaluation tests for high C low N steel and low C high N steel having the same total amounts of C and N. BEST MODE FOR WORKING THE INVENTION The best mode for working the present invention and the limiting conditions will be explained in detail next. The inventors engaged in detailed studies on motorcycle disk brake materials able to be used as quenched. Among these, in the studies relating to the heat resistance, they focused on studies of improvement of the temper softening resistance. To improve the temper softening resistance, alloy elements such as Nb and Mo are added, but as a result it is hard to raise the hardness even with quenching, i.e., there is the problem that the hardenability drops. The inventors engaged in detailed studies on this point and as a result discovered that by effectively combining C and Mo, it is possible to 15 secure the hardenability while achieving an improvement in the temper softening resistance. That is, they took note of the fact that the elements C and N essential for obtaining a predetermined hardness after quenching differ in effect on the drop in hardenability when increasing 20 the amounts of Nb, Mo, and other alloy elements added. FIG. 1 shows the results of evaluation of the hardenability of steels with the same amounts of C+N (0.08%) but differing in the ratios of C and N (Al steel, A2 steel, for specific compositions, see Table 1) . From this figure, it is learned that when the amount of N is large (A2 steel), if increasing the amount of alloy elements added, the hardenability falls, while if C is large (Al steel), even if increasing the amount of alloy elements added, the hardenability hardly falls. This effect was also found to remarkably appear when adding Mo. Further, regarding the heat resistance, when including a small amount of Nb, the inventors discovered that by limiting the Ti, the temper softening resistance 35 is improved. First, the limiting conditions relating to the different ingredients will be explained. C is an element essential for obtaining a predetermined hardness after quenching and is added in combination with N to obtain a predetermined hardness level. When adding alloy elements such as Nb and Mo like 5 in the present invention so as to improve the heat resistance, it is preferable to add more C than N. However, if adding over 0.10%, the hardness becomes too great and trouble such as brake squealing, degraded toughness, etc. occur, so 0.10% is made the upper limit. Further, if less than 0.05%, it is necessary to excessively add N to obtain hardness, so 0.05% is made the lower limit. N is an element useful for obtaining a predetermined hardness after quenching in the same way as C and is added together with C to obtain a predetermined hardness level. When adding alloy elements such as Nb and Mo like in the present invention so as to improve the heat resistance, it is preferable to add more C than N and reduce the amount of N. If adding it over 0.025%, a drop in the hardenability is invited, so this is made the upper limit. Further, making N less than 0.010% leads to an increase in the steelmaking costs, so 0.010% is made the lower limit. C+N is an amount directly related to the hardness after quenching. The greater the amount of addition, the harder. To avoid the problem of the drop in hardenability, which becomes an issue due to the large addition of alloy elements such as Nb and Mo so as to improve the heat resistance, this has to be limited to 0.06% to 0.1% so as to adjust the steel to satisfy the predetermined hardness level HRC32 to 38. Si is extremely powerful as a ferrite forming element and in this regard has to be suppressed. However, it is useful as a deoxidizing material. Accordingly, the suitable range is made 0.1% to 1%. If over 1%, the austenite forming element Ni, Cu, and Mn have to be excessively added, so this is not preferred, while if less than 0.1%, the deoxidizing effect becomes poor, so this is not preferred. Mn is an important austenite forming element. In the present invention, it must be added in an amount of 0.2% 5 or more along with Ni and Cu to secure an austenite phase and secure hardenability at a high temperature. If over 2.0%, deterioration of the rust resistance is seen, so 2% was made the upper limit. Mn differs from Ni and Cu in that it does not have the effect of improving the heat resistance, so when further improvement of the heat resistance is necessary, 1% or less is preferable. P is an ingredient unavoidably included in steel, but if included over 0.04%, the toughness falls, so 0.04% was made the upper limit. Cr is a basic element required for securing the rust resistance required by a motorcycle disk brake material. If the content is less than 11%, a sufficient rust resistance cannot be obtained. Further, Cr is a ferrite forming element, so if added over 14%, the temperature range of austenite phase formation is narrowed, a ferrite phase not transforming to the martensite phase in the quenching temperature range is formed, and the hardness after quenching can no longer be satisfied. Accordingly, the amount of addition of Cr is made 11% to 14%. Ni is an austenite forming element like Mn and is an element effective for securing the austenite phase and securing hardenability at a high temperature. Further, to contribute to improvement of the temper softening resistance, 0.5% or more is added. If added over 2%, a drop in toughness is invited, so 2% is made the upper limit. Cu, like Mn and Ni, is an element effect for securing an austenite phase and securing hardenability. Cu is effective in suppressing softening of the disk due to the brake braking heat. In the case where the disk braking heat will become high such as applications for large motorcycles etc., 0.5% or more is added. However, if added over 2%, the toughness deteriorates, so the upper limit was made 2%. Al is extremely useful as a deoxidizing agent, but is liable to cause deterioration of the rust resistance, 5 so is suppressed as much as possible in the present invention. Accordingly, 0.01% is made the upper limit. S is an ingredient unavoidably included in steel, but in the present invention, if included over 0.010%, CaS easily is formed, so 0.01% is made the upper limit. Further, making S less than 0.001% invites an extreme increase in the steelmaking cost, so 0.001% is preferably made the lower limit. Mo is an extremely important element in the present invention. By adding a suitable amount of Mo, the temper softening resistance is remarkably improved and the hardenability is also improved. The mechanism for improvement of the temper softening resistance is still not clear, but in the case of 0.05% or more of C, the effect of improvement is remarkable, so it is believed that the precipitation and coarsening of Cr carbides are suppressed, dislocation can be suppressed even at a high temperature, and the temper softening resistance can be improved. Further, regarding the mechanism for improvement of the hardenability as well, it is conjectured that this is caused by suppression of precipitation of Cr carbides and thereby securing solid solution C. On the other hand, in the prior art, the combination of C and Mo was never focused on, so the effect of improvement on the hardenability could not be discovered. However, if less than 1%, the effect is not obtained, so Mo has to be added in ah amount of 1% or more. Further, addition of Mo over 2% degrades the toughness, so the upper limit of Mo is made 2%. Nb is also an extremely important element in the present invention. By adding a suitable amount of Nb, the temper softening resistance is remarkably improved. This mechanism is still not clear, but it is believed that Nb is closely correlated to N, suppresses precipitation and coarsening of Cr oxides, and suppresses dislocation so as to improve the temper softening resistance. In the present invention, N is suppressed, but it is still 5 included to a certain extent, so the effect of improvement of the tempering resistance by Nb is sufficiently effective. However, Nb easily bonds with N and precipitates in the form of NbN. If precipitated in this form, there is no strengthening function, the solution strengthening effect of N is reduced, and further the hardenability is reduced, so excess addition must be avoided. For this reason, to improve the temper softening resistance, 0.03% or more has to be added. On the other hand, addition over 0.3% invites deterioration of the hardenability, so the upper limit was made 0.3%. Ti is an element which should be restricted in the present invention. If adding Ti, it precipitates in the form of coarse TiN (C also dissolves), so not only is there no strengthening function, but also the solid solution N and the solid solution C end up be reduced, so the hardenability and heat resistance are reduced. Further, if adding a slight amount of Nb to improve the temper softening resistance like in the present invention, the effect becomes particularly remarkable. For this reason, the amount of Ti has to be made 0.1% or less. When there is a great need for heat resistance, this is preferably further reduced to 0.05% or less. Further, the elements referred to here have to be adjusted in this range of ingredients so that the gamma potential yp expressed by the following equation (1) is 80 or more in order to enable stable quenching in the temperature range of 900 to 1100°C. This is because if yp is less than 80, even with quenching, ferrite phases will remain in some cases and the predetermined hardness level will sometimes not be reached. yp=420[%C]+4 70[%N]+23[%Ni]+9[%Cu]+7[%Mn]-11.5[%Cr]- 11.5[%Si]-52[%Al]-12[%Mo]-47[%Nb]+18 9... (1) Regarding the quenching temperature, too high a temperature leads to an increase in the production time and an increase in the costs, so the quenching is preferably performed from 900°C to 1000°C. Even if quenched from this temperature range, the steel of the present invention satisfies the predetermined hardness range. "yp" is an indicator of the stability in the high temperature range. The above equation (1) is taken from "Etude des transformations isothermes dans les aciers inoxydabile semi-ferritiques a 17% de chrome", Memoires Scientifiques Rev. Metallurgy LXIII, N°7/8, 1966. Next, the method of production will be explained in detail. Slabs (or ingots etc.) comprised of the above compositions of ingredients may be hot rolled to hot rolled sheets of a thickness of 2 to 8 mm or so, then annealed and softened and then pickled to obtain the final product steel sheets. It is also possible to forego the pickling and use shot blasting to finish the materials. These steel sheets are worked into disk shapes in the process of production of the brake disks, then heated and quenched at 900 to 1000°C, then polished on their two surfaces to obtain brake disks. EXAMPLES (Example 1) Steel slabs of thicknesses of 200 mm having the chemical ingredients shown in Table 1 were hot rolled to obtain 6 mm thick hot rolled sheets. Further, they were heated to 850°C and gradually cooled for softening annealing. Hardenability evaluation test pieces were taken from these steel sheets. The remainders were held at 950°C or at 1000°C for 10 minutes, then water cooled for quenching treatment. Table 1 (mass%) Steel C Si Mn P S Cr Ni Cu Mo Nb Al Ti N C+N TP Remarks Al 0.06 0.3 0.3 0.03 0.005 12.5 1 1.5 1.5 0.1 0.007 0.01 0.02 0.08 92 Inv. ex. A2 0.02 0.3 0.3 0.03 0.005 12.5 1 1.5 1.5 0.1 0.007 0.01 0.06 0.08 94 ex. The hardenability was evaluated by holding a sheet at 850°C to 1100°C in temperature for 10 minutes, then water cooling it and measuring the quenched material for hardness by a Rockwell hardness test (HRC) based on JIS Z 2245. An HRC of 32 to 38 is satisfactory. Various test pieces were taken from the quenched steel sheets and used for evaluation tests. The temper softening characteristics were evaluated by tempering at 550°C to 650°C for 1 hour, then performing a Rockwell test in the same way as the hardness test of the quenched material. A hardness after tempering not falling below HRC30 is the passing standard. Further, a rust resistance test was conducted by #240 polishing the two sides of a test piece, conducting a saltwater spray test (based on JIS Z 2371) for 240 hours, and examining the extent of rusting. No rusting was deemed as passing and rusting as failing. FIG. 1 shows the results of the hardenability evaluation tests. The same C+N and high C Al steel satisfies the predetermined range of HRC32 to 38 and exhibits a substantially constant hardness in the temperature range from the quenching temperature 900°C to 1100°C, but the high N A2 steel reaches the predetermined range just barely at 950CC but even if raising the quenching temperature, has a low peak hardness compared with the Al steel. It is learned that the Al steel is better in hardenability. FIG. 2 shows the results of evaluation of the temper softening resistance. The present invention example Al steel has a hardness of HRC30 or more and exhibits an excellent heat resistance even with tempering at 650°C for 1 hour. The comparative example A2 steel also exhibits a 5 considerably excellent heat resistance, but the initial hardness is low and due in part to this the HRC30 falls at 600°C or more. The results of the rust resistance test were that both steels passed. From the above, it is clear that the present invention steels are excellent in heat resistance and excellent in hardenability. (Example 2) Steel slabs of 200 mm thicknesses having the chemical ingredients shown in Table 2 were melted, then hot rolled to obtain hot rolled sheets of thicknesses of 6 mm. Further, these were heated to 850°C and gradually cooled for softening annealing. These steel sheets were held at 900°C, 950°C, and 1000°C for 10 minutes, then water cooled for quenching. Various test pieces were taken from the quenched steel sheets and used for evaluation tests. The temper softening characteristics were evaluated by tempering at 600°C and 650°C for 1 hour, then performing a Rockwell hardness test (HRC) based on JIS Z 2245. An HRC of 32 to 38 is passing. A hardness after tempering not falling below HRC30 is the passing standard. Further, a rust resistance test was conducted by #240 polishing the two sides of a test piece, conducting a saltwater spray test (based on JIS Z 2371) for 240 hours, and examining the extent of rusting. No rusting was deemed as passing and rusting as failing. The results are shown in Table 3. The Bl steel to the B5 steel were comprised of 12.5Cr-1.2Ni-lCu with changed amounts of Mo. The Bl steel was insufficient in hardenability and low in heat resistance as well. This is believed to be because since the Mo is low, precipitation of carbides is not sufficiently suppressed. The B2 steel to the B4 steel are steels of the present invention and are sufficient in both of hardenability and heat resistance. The B5 steel has a large Mo content, so is sufficient in hardenability and heat resistance, but becomes low in toughness and is liable to crack in use, so is not preferred. The CI steel to the C5 steel are changed in ingredients other than Mo. The CI steel and the C2 steel are both steels of the present invention and are sufficient in hardenability and heat resistance. The low C+N C3 steel is insufficient in hardness even in the state with sufficient quenching. Further, the low yp C4 steel is insufficient in hardenability, low in hardness after quenching, and therefore did not pass. Further, the high Ti C5 steel has an HRC after tempering of 30 or less and does not pass in heat resistance. Note that all of the steels used for the tests passed in rust resistance. It is believed that this is due to the large content of elements such as Ni, Cu, and Mo improving the rust resistance. From the above, it is clear that the steels of the present invention are excellent in heat resistance and excellent in hardenability and are suitable as materials for disk brakes. Table 2 (mass*) Steel C Si Mn P S Cr Ni Cu Mo Nb Al Ti N C+N YP Remarks Bl 0.07 0.3 0.2 0.03 0.005 12.5 1.2 1 0.7 0.15 0.006 0.02 0.01 0.08 98 Conip. ex. B2 0.07 0.3 0.3 0.03 0.005 12.3 1.2 1 1.2 0.15 0.006 0.03 0.01 0.08 95 Inv. ex. B3 0.07 0.2 0.4 0.03 0.005 12.3 1.2 1 1.5 0.15 0.006 0.02 0.01 0.08 93 Inv. ex. B4 0.07 0.2 0.5 0.03 0.005 12.3 1.2 1 1.8 0.15 0.006 0.02 0.01 0.08 90 Inv. ex. B5 0.07 0.2 0.6 0.03 0.005 12.3 1.2 1 2.5 0.15 0.006 0.02 0.01 0.08 83 Comp. ex. CI 0.06 0.3 0.5 0.02 0.001 13.5 1.2 1.5 1.2 0.1 0.006 0.02 0.02 0.08 90 Inv. ex. C2 0.06 0.5 0.3 0.02 0.001 11.5 0.9 1 1.2 0.1 0.007 0.02 0.02 0.08 98 Inv. ex. C3 0.04 0.5 1 0.02 0.001 13 1.2 1.5 1.2 0.1 0.006 0.03 0.01 0.05 84 Comp. ex. C4 0.05 0.5 0.7 0.02 0.001 13.5 1.2 1 1.5 0.1 0.006 0.03 0.02 0.07 77 Comp. ex. C5 0.06 0.5 0.7 0.02 O.OOl 13.5 1.2 1 1.2 0.1 0.006 0.11 0.02 0.08 85 Comp. ex. Table 3 Steel Quenchingtemperature(°C) Hardnessafterquenching(HRC) Tempersofteningresistance(HRC) Rust resistance Other Remarks 600°C 650°C Bl 900 31 27 24 Good Comp. ex. 950 33 29 27 Good 1000 35 32 29 Good B2 900 35 33 30 Good Inv. ex. 950 37 34 32 Good 1000 37 34 32 Good B3 900 35 33 30 Good Inv. ex. 950 37 34 32 Good 1000 37 34 32 Good B4 900 35 33 30 Good Inv. ex. 950 37 34 32 Good 1000 37 34 32 Good B5 900 35 33 30 Good Yield strength degraded Comp. ex. 950 37 34 32 Good 1000 38 34 32 Good CI 900 35 33 30 Good Inv. ex. 950 37 34 32 Good 1000 37 34 32 Good C2 900 35 33 30 Good Inv. ex. 950 37 34 32 Good 1000 37 34 32 Good C3 900 28 24 20 Good Comp. ex. 950 31 26 24 Good 1000 31 32 29 Good C4 900 31 27 24 Good Comp. ex. 950 33 29 27 Good 1000 35 32 29 Good C5 900 34 27 24 Good Comp. ex. 950 35 27 25 Good 1000 35 29 27 Good INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide martensite based stainless steel sheet for heat resistant motorcycle disk brakes used as quenched, the martensite based stainless steel sheet for heat resistant motorcycle disk brakes giving a hardness of 32 to 38 HRC, excellent in hardenability, and having a temper softening resistance effect even at a high temperature over 600°C even if quenched in a relatively low quenching temperature range of 900 to 1000°C, and therefore it is possible not only for the manufacturer, but also the party using the steel sheet to obtain tremendous benefits. WE CLAIMS CLAIMS 1. Martensite based stainless steel sheet for heat resistant disk brake excellent in hardenability containing, by mass%, C: 0.05% to 0.10%, Si: 0.1% to 1%, Mn: 0.2% to 2.0%, P: 0.04% or less, S: 0.010% or less, N: 0.010% to 0.025%, Cr: 11% to 14%, Ni: 0.5% to 2%, Cu: 0.5% to 2%, Mo: 1% to 2%, Nb: 0.03% to 0.3%, Al: 0.01% or less, Ti: 0.1% or less, C and N satisfying C+N: 0.06% to 0.1%, and the balance of Fe and unavoidable impurities, yp expressed by the following (1) equation being 80 or more. yp=420[%C]+470[%N]+23[%Ni]+9[%Cu]+7[%Mn]-11.5[%Cr]-11.5[%Si]-52[%Al]-12[%Mo]-47[%Nb]+18 9... (1) ABSTRACT The present invention provides martensite-based stainless steel for heat resistant disk brakes 5 maintaining a high heat resistance, easy to harden at a relative low temperature, and excellent in hardenability, characterized by containing, by massl, C: 0.05 to 0.10%, Si: 0.1%' to 1%, Mn: 0.2 to 2.0%, P: 0.04% or less, S: 0.010% or less, N: 0.010 to 0.025%, Cr: 11 to 14%, Ni: 10 0.5 to 2%, Cu: 0.5 to 2%, Mo: 1 to 2%, Nb: 0.03 to 0.3%, Al: 0.01% or less, Ti: 0.1% or less, C+N satisfying 0.06 to 0.1%, and a balance of Fe and unavoidable impurities, yp of the following (1) equation being 80 or more. yp=420[%C]+4 70[%N]+23[%Ni]+9[%Cu]+7[%Mn]-11.5[%Cr]-11.5[%Si]-52[%Al]-12[%Mo]-4 7[%Nb]+18 9... (1) |
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Patent Number | 258644 | |||||||||
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Indian Patent Application Number | 412/MUMNP/2008 | |||||||||
PG Journal Number | 05/2014 | |||||||||
Publication Date | 31-Jan-2014 | |||||||||
Grant Date | 27-Jan-2014 | |||||||||
Date of Filing | 05-Mar-2008 | |||||||||
Name of Patentee | NIPPON STEEL & SUMIKIN STAINLESS STEEL CORPORATION | |||||||||
Applicant Address | 2-2, NIHONBASHI HONGOKUCHO 3-CHOME, CHUO-KU, TOKYO 103-0021, | |||||||||
Inventors:
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PCT International Classification Number | C22C38/00,C21D9/00 | |||||||||
PCT International Application Number | PCT/JP2006/317401 | |||||||||
PCT International Filing date | 2006-08-29 | |||||||||
PCT Conventions:
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