WO2009078261A1 - 鋼板およびその製造方法 - Google Patents
鋼板およびその製造方法 Download PDFInfo
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- WO2009078261A1 WO2009078261A1 PCT/JP2008/071597 JP2008071597W WO2009078261A1 WO 2009078261 A1 WO2009078261 A1 WO 2009078261A1 JP 2008071597 W JP2008071597 W JP 2008071597W WO 2009078261 A1 WO2009078261 A1 WO 2009078261A1
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- Prior art keywords
- cementite
- graphite
- less
- ferrite
- steel
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Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0273—Final recrystallisation annealing
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/003—Cementite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/006—Graphite
Definitions
- the present invention relates to a steel plate suitable for applications such as automobile parts, and more particularly to a steel plate excellent in workability and hardenability and a method for producing the same.
- Patent Document 2 includes, in mass%, C: 0.10 to 0.45%, Si: 0.05 to 1.00%, ⁇ : 0 ⁇ 05 to 0.50%, Nb: 0.005 to 0 ⁇ 1%, ⁇ 1: 0.01 to 10.00%, ⁇ : 0 002 to 0.0103 ⁇ 4, B: 3 to 50ppm, Ca: 0.001 0.01% and Ni: 0 to 2.00%, the balance consists of Fe and impure impurities, in impurities P: 0.012% or less, S: a hot-rolled steel sheet is 0.008% or less, after 0.
- OX (N-B)% to 5.
- OX (N_B) % With the balance Fe and unavoidable impurities, P: 0.020% or less and S: 0.010% or less as impurities, ferrite, graphite and cementite
- P 0.020% or less
- S 0.010% or less as impurities
- ferrite, graphite and cementite A high carbon thin steel sheet having a work structure and good workability and a method for producing the same are disclosed.
- Patent Document 1 Japanese Patent Laid-Open No. 1-025946
- Patent Document 2 JP-A-7-258743
- Patent Document 3 Japanese Patent Laid-Open No. 4-202744 Disclosure of Invention
- Patent Document 2 is a technique for graphitizing 50% or more of the cementite in copper, and the component composition of copper disclosed in the Example of Patent Document 2 has a large amount of Si, 0. The amount exceeds 20%.
- the copper plates described in Patent Documents 1 to 3 are soft and have excellent bending workability and elongation properties in tensile tests, but depending on the heating conditions during the quenching of the steel sheet, the graph items may be cemented. May not be sufficiently dissolved, resulting in poor quenching.
- the steel sheets described in Patent Documents 1 to 3 are soft, they have a problem that they are not necessarily excellent in stretch flangeability, which is an index for hole expansion workability after punching.
- An object of the present invention is to provide a steel plate that is soft, has excellent workability, has excellent hardenability, has excellent stretch flangeability, and has excellent workability, and a method for producing the same.
- the present inventors have found that even in a high carbon steel, even when the Si content is very low, specifically 0.1% or less, the graph items and It was found that by controlling the distribution of cementite, good workability could be obtained without necessarily increasing the graphing rate, and good hardenability and stretch flangeability could be secured. That is, as a result of diligent research on the influence of the structure on the strength, hardenability and stretch flangeability of steel sheets containing 0.3 to 0.7 mass 3 ⁇ 4, the following was found. .
- the organization should include ferrites, graph items, and cementite.
- the total volume ratio of ferrite, graph items, and cementite in the entire organization should be 95% or more. It is effective to make the volume ratio of the graph items in the entire image 5% or more.
- the average particle size of graphite and cementite must be 5 / zm or less.
- Cooling conditions after hot rolling are extremely important for controlling the volume ratio of graphite and cementite present in ferrite grains.
- the total volume ratio of ferrite, graph item, and cementite is 95% or more, and the volume ratio of graph items (graph rate) in the entire graph item and cementite is 5% or more.
- Graphite and cementite The copper plate is characterized in that the average particle size of the copper is 5 ⁇ or less.
- the copper plate of the present invention further contains at least one selected from Ni: 3.0% or less, B: 0.005% or less, and Cu: 0.1% or less by mass%. Is preferred.
- the steel sheet of the present invention is a hot-rolled sheet obtained by hot rolling a steel having the above composition at a finishing temperature of 800 to 950 ° C, and the hot-rolled sheet after the hot rolling has an average of 50/3 or more. After cooling to a cooling stop temperature of 500 ° C or lower at a cooling rate, cutting is performed at a cutting temperature of 450 ° C or lower, and the hot-rolled sheet after the cutting is manufactured by a method of annealing at an annealing temperature of 720 or lower. it can.
- the present invention is a.
- C 0.3 to 0.73 ⁇ 4, Si: 0.1% or less, Mn: less than 0.15%, P: 0.01% or less, S: 0.01% or less, A 1: 0 .05% or less, N: 0.005% or less, a composition comprising the balance Fe and inevitable impurities, having a structure including ferrite, graphite, and cementite, and accounting for the entire structure
- the total volume ratio of graph and graphite and cementite is 95% or more, the volume ratio of graphitems (graphite ratio) in the entire graphitem and cementite is 53 ⁇ 4 or more,
- a copper plate characterized in that the total volume ratio of graphite and cementite existing in ferrite grains occupying the whole is 153 ⁇ 4 or less.
- the steel sheet of the present invention may further contain at least one selected from the following in terms of mass%: Ni: 3.03 ⁇ 4 or less, B: 0.005% or less, Cu: 0.1% or less. preferable.
- the steel sheet of the present invention is a hot-rolled sheet obtained by hot-rolling steel having the above composition at a finishing temperature of 800 to 950 ° C, and the hot-rolled sheet after the hot-rolling is performed at 50 / s or more. After cooling to a cooling stop temperature of 600 ° C or less at an average cooling rate, cutting at a cutting temperature of 550 ° C or less, and annealing the hot-rolled sheet after the cutting at an annealing temperature of 720 ° C or less Can be manufactured.
- the steel sheet of the present invention it has become possible to produce a copper plate that is soft and has excellent workability and also has excellent hardenability.
- the steel sheet of the present invention can be easily manufactured at low cost because it only needs to control the components and the cooling conditions after hot rolling.
- the steel sheet of the present invention is soft and excellent in workability, so it is suitable for thickening processing of automobile drive system parts. Even if it is applied to parts with complicated shapes, it can process and weld multiple parts. This eliminates the need to improve the productivity of automobile parts and reduce costs.
- the steel sheet of the present invention does not suffer from quenching failure due to unmelted graph eye and cementite during heating at high frequency or the like.
- the steel sheet of the present invention it has become possible to produce a steel sheet that is soft and has excellent stretch flangeability and excellent workability.
- the steel sheet of the present invention can be easily produced at low cost because it is only necessary to control the components and the cooling conditions after hot rolling.
- the steel sheet of the present invention is soft and excellent in workability such as stretch flangeability, so it is suitable for thickening processing of automobile drive system parts. Even if it is applied to parts with complex shapes, it is not necessary to process or weld multiple parts, improving the productivity of automobile parts and reducing costs.
- FIG. 1 is a graph showing the relationship between cementite ⁇ , the average particle diameter d of graph items, and ⁇ .
- FIG. 2 is a graph showing the relationship between the cementite present in the ferrite grains, the volume ratio S of the graph items, and the average.
- C is an element that forms a graph item. If the amount of C is less than 0.3%, the hardness after quenching cannot be secured, and if it exceeds 0.7%, the copper plate becomes hard even if it is graphitized, and the workability decreases. Therefore, the C content is 0.3-0.7%.
- the Si content exceeds 0.1%, the ferrite becomes hard and the workability deteriorates. Therefore, the Si content is 0.1% or less, preferably 0.05% or less.
- Mn is 0.20% or less, preferably 0.10% or less.
- the P content is 0.01% or less, preferably 0.008% or less.
- the S content is 0.01% or less, preferably 0.007% or less.
- Al is an element that binds to solute N to form A1N, detoxifies the adverse effects of solute N, which has the effect of inhibiting graphite formation, and promotes graphite formation using A1N as a nucleus.
- the amount of A1 is preferably 0.003% or more, but if it exceeds 0.05%, the cleanliness of the steel decreases and the workability deteriorates, so the amount of A1 is 0.05% or less, preferably 0.04% or less. To do.
- the soot content is 0.0050%, preferably 0.0040% or less.
- the balance is Fe and inevitable impurities, but it is preferable that at least one selected from Ni: 3.0% or less, B: 0.005% or less, Cu: 0.1% or less is contained for the following reasons. .
- Ni is an element that promotes the formation of graphite and is also an element effective for improving hardenability. To obtain these effects, Ni is preferably contained in an amount of 0.1% or more, but the Ni content exceeds 3.0%. And the effect is saturated. For this reason, the Ni content is 3.0% or less, preferably 0 ⁇ 1 to 3 ⁇ 03 ⁇ 4, more preferably 0 ⁇ 3 to 1 ⁇ 0%.
- ⁇ is a useful element that combines with ⁇ to form ⁇ and acts as a core for graphite formation, and also an effective element for improving hardenability.
- 0.0005% It is preferable to contain the above, but if the amount of soot exceeds 0.005%, the effect is saturated. For this reason, the soot amount is 0.005% or less, preferably 0.0005 to 0.005%, more preferably 0.0010 to 0.0040%.
- Cu is an element that promotes the formation of graphite, and is also an element effective for improving hardenability. To obtain these effects, it is preferably contained in an amount of 0.01% or more, more preferably 0.02% or more. However, when the amount of Cu exceeds 0.1%, the effect is saturated. Therefore, the Cu content is 0.1% or less, and more preferably 0.07% or less.
- the structure should include ferrite, graphite, and cementite.
- the sum of the volume fractions of cementite must be 95% or more, and the graph item ratio in the graph items and the entire cementite must be 5% or more.
- the present invention also includes the case where the graph item rate is 100%, that is, when all cementites are converted into graph items, the same effect can be obtained. If the sum of the volume fractions of fillite, graphite, and cementite is less than 95%, that is, if the volume fraction of other phases exceeds 5%, the workability deteriorates. In addition, when the graph item rate is less than 5%, the workability deteriorates.
- the volume ratio of ferrite, graphite, and cementite was obtained as follows. In other words, after polishing the 1/4 position of the thickness cross section in the rolling direction of the copper plate, it corroded with nital, and with an optical microscope, observed 5 spots per field at a magnification of 400 times, 10 fields (50 places in total), These images are analyzed with Media Cybernetics image analysis software “Image Pro Plus ver. 4.0” to determine the area of ferrite, graphite, and cementite, and the percentage of the total observation area ( The area ratio was defined as the volume fraction of each of ferrite, graphite, and cementite.
- the ratio (area ratio) of the area (Sgr) of the graph item to the sum of the area (Sgr) of the graph item and the area (Scm) of the cementite (volume ratio of the graph item) ) That is, the graph item rate (3 ⁇ 4) can be expressed by the following equation.
- the average particle size of cementite and graphite needs to be 5 m or less. More preferably, it is as follows. The present inventors have made various studies in order to obtain excellent hardenability. An example of examination is shown below.
- the temperature range from finish rolling to the take-off temperature was changed within the range of average cooling rate from air cooling (5 ° C) to 200 ° C / s. Cooled down.
- the structure and hardenability were investigated as follows. In the same way as above, the thickness 1/4 position of the cross section in the rolling direction is polished.
- Figure 1 shows the relationship between the average particle diameter d of cementite and graphite and ⁇ ⁇ . It can be seen that when the average particle size d of cementite and graphite is less than ⁇ is less than 8, and excellent hardenability can be obtained.
- the inventors need to make the average particle size of cementite slag and graphite below to ensure excellent hardenability. It has been found that it is necessary to make it preferably 3 ⁇ or less.
- excellent hardenability can be obtained by specifying yarn and weave in this way is considered as follows. In other words, when the cementite or graphite average particle size is below, the cementite and graphite are almost completely dissolved during high-frequency heating, and the hardness after quenching can be made uniform.
- the manufacturing method of the steel plate of this invention is not limited to the following.
- Finishing temperature during hot rolling 800 ⁇ 950
- the temperature should be 800 to 950 ° C.
- Average cooling rate after hot rolling 50 ° C / s or more
- the steel sheet after hot rolling is immediately cooled at an average cooling rate of 50 / s or more to the cooling stop temperature described later.
- average cooling rate is less than 50 ° C / s
- ferrite grains tend to grow during cooling, and large ferrite grains are formed.
- graphite cementite is thought to be formed with ferrite grain boundaries and inclusions as nuclei, so if ferrite grains are large, graphite formed with grain boundaries as nuclei. And cementite becomes coarse and hardenability decreases.
- the average cooling rate is 50 ° C / s or more, the rolling strain introduced into the austenite by hot rolling tends to remain in the structure after the transformation, resulting in an increase in the dislocation density.
- the average cooling rate is 50 ° C / s or higher, preferably 80 ° C / s or higher.
- the upper limit of the average cooling rate is not particularly required, but is preferably 200 ° C./s or less in order to suppress the deterioration of the shape of the steel sheet and ensure the shape of the steel sheet.
- Cooling stop temperature for cooling after hot rolling 500 ° C or less
- the cooling stop temperature When the minimum temperature that needs to be cooled at the cooling rate as described above, that is, the cooling stop temperature, exceeds 500 ° C, proeutectoid ferrite is generated during cooling until scraping, and coarse parlite is generated. When it is generated and annealed after scraping, the cementite becomes coarse and the hardenability deteriorates, so the temperature is set to 500 ° C or lower, preferably 470 ° C or lower.
- the lower limit of the cooling stop temperature does not need to be specified, but is preferably 200 ° C. or higher in order to secure the shape of the steel sheet.
- the hot-rolled sheet is cooled immediately after cooling, but at that time, if the milling temperature exceeds 450 ° C, coarse pearlite is generated, and the cementite and graphite become coarse during annealing, resulting in hardenability. Decreases. Therefore, the coiling temperature should be 450 ° C or less. In order to sufficiently obtain the cooling effect after! ⁇ -Rolling as described above, it is preferable that the cutting temperature is lower than the cooling stop temperature. Also, since the shape of the hot-rolled sheet is likely to deteriorate, the cutting temperature is preferably 200 ° C or higher.
- Annealing temperature 720 ° C or less After removing scales by pickling, etc., the hot rolled sheet of cocoon removal is annealed in order to promote spheroidization and graphiteization of cementite and to make it softer. At that time, if the annealing temperature exceeds 720, coarse pearlite is generated during cooling, resulting in a decrease in hardenability. Further, if the annealing temperature is less than 600 ° C, the annealing time becomes extremely long, so the annealing temperature is preferably 600 ° C or higher.
- the annealing time is not particularly limited. However, the annealing time should be 8 hours or longer in order to form graphite, and the ferrite grains may be excessively coarsened, resulting in reduced ductility. It is preferable to set it to lOOhr or less.
- a converter or an electric furnace can be used to melt the steel of the present invention.
- the steel melted in this way is made into slabs by ingot-bundling or continuous forging.
- Stebs are usually hot-rolled (reheated) and then hot-rolled.
- direct feed rolling in which heat is maintained for the purpose of suppressing the temperature drop may be applied as it is.
- the slab heating temperature is preferably 1280 ° C or lower in order to avoid deterioration of the surface state due to scale. Hot rolling can be performed only by finish rolling, omitting rough rolling.
- the material to be rolled may be heated by a heating means such as a sheet heater during hot rolling.
- the thickness of the hot-rolled sheet is not particularly limited as long as the production conditions of the present invention can be maintained, but 1.0 to 10.0 mm is preferable.
- the annealed steel sheet can be temper-rolled as necessary. Examples are given in Example 1.
- the total volume ratio of cementite and glassite present in the ferrite particles must be 15% or less. More preferably, it is 10% or less.
- the present inventors conducted various studies in order to obtain excellent stretch flangeability. An example of the study is shown below. C: 0.55%, Si: 0.01%, Mn: 0.13, P: 0.003%, S: 0.0006%, A1: 0.005%, ⁇ : 00018%, Ni: 0.
- the structure and stretch flangeability were investigated as follows.
- the thickness 1/4 position of the cross section in the rolling direction is polished.
- the cross-section is observed at 5 locations, with 10 magnifications at a magnification of 400 at each location (total 50 views) with an optical microscope.
- the cementite ⁇ and graphite existing on the ferrite grain boundary and the cementite and graph item existing in the ferrite grain are identified, and the cementite existing on the ferrite grain boundary is identified. And the area occupied by the graph item.
- the area of the single cementite grain or the entire graphite grain is determined by Measured as the area occupied by cementite grains or graphite grains existing on the grain boundaries, and the area of cementite grains or graphite grains that do not have a portion present on the ferrite grain boundaries The area occupied by cementite grains or graphite grains present in the grains was measured.
- Stretch flangeability Specimen for hole expansion test (100 X 100 was sampled and punched using a punching tool with a punch diameter of 10 mm and a die diameter of 11.6 (clearance: 20% thickness) at the center of the specimen. After that, the punched hole was pushed up with a cylindrical flat bottom punch (diameter 50 1) and shoulder R 8mm) to expand the hole, and the hole diameter d was measured when a through-thickness crack occurred at the hole edge. Then, the hole expansion rate 1 (%) was calculated from the following formula, and the same test was performed 6 times to obtain the average (%).
- Figure 2 shows the relationship between the cementite and graphite volume fraction S present in the ferrite grains and the average ⁇ . It can be seen that when the volume fraction S of cementite and graphite present in the ferrite grains is 15% or less, an average of 603 ⁇ 4 or more is obtained, and excellent stretch flangeability is obtained.
- the inventors have found that the total body of cementite and graphite present in the ferrite grains is necessary to secure excellent stretch flangeability. It has been found that the volume fraction needs to be 15% or less, more preferably 10% or less.
- the reason why good stretch flangeability can be obtained by defining the structure in this way is considered as follows. In other words, if there is a large amount of cementite or graphite in the ferrite grains, fine cracks are likely to occur at the interface between the cementite and graphite during the punching process. From Propagation 'Combination, easy to lead to cracks through the plate thickness.
- the manufacturing method of the steel plate of this invention is not limited to the following.
- Finishing temperature during hot rolling 800-950 ° C
- finishing temperature during hot rolling is less than 800, the rolling load increases remarkably, and if it exceeds 950 ° C, the scale to be produced becomes thick and the pickling property decreases, and a decarburized layer is formed on the surface of the copper plate. Since it may occur, it should be 800-950.
- Average cooling rate after hot rolling 50 ° C / s or more
- the average cooling rate should be 50 ° C / s or higher, preferably 80 ⁇ or higher.
- the upper limit of the average cooling rate need not be specified, but is preferably set to 200 ° C./s or less in order to suppress the deterioration of the shape of the steel plate and ensure the shape of the steel plate.
- Cooling stop temperature for cooling after hot rolling 600 ° C or less
- the cooling stop temperature When the minimum temperature that needs to be cooled by the cooling rate as described above, that is, the cooling stop temperature, exceeds 600 ° C, proeutectoid light is generated during cooling up to the removal, and pallet light is generated.
- the temperature should be 600 ° C or lower, preferably 550 ° C or lower.
- the lower limit of the cooling stop temperature does not need to be specified, but is preferably 200 or more in order to ensure the shape of the steel sheet.
- the hot-rolled sheet is cooled immediately after cooling, but if the coiling temperature exceeds 550 ° C, no. One line is formed, and the cementite present in the ferrite grains increases during annealing, and the stretch flangeability decreases. Therefore, the trapping temperature is 550 and below.
- the winding temperature is preferably lower than the cooling stop temperature.
- the securing temperature is preferably 200 ° C. or higher, and more preferably 450 ° C. or higher, in securing the shape of the steel plate.
- Annealing temperature 720 ° C or less
- the hot-rolled sheet after scraping is subjected to annealing to remove the scale by pickling, etc., and to promote spheroidization and graphiteization of cementite and softening.
- annealing temperature exceeds 720 ° C, pearlite is generated during cooling and the stretch flangeability is deteriorated.
- the annealing temperature is less than 600 ° C, the cementite and graphite present in the ferrite grains increase and the stretch flangeability tends to deteriorate, so the annealing temperature should be 600 ° C or higher. It is preferable.
- the annealing time does not need to be particularly limited, but it can be 8 hours or longer in order to form graphite and reduce cementite in the ferrite grains to reduce graphite. Since the grains may become excessively coarse and the ductility may be lowered, it is preferable to set it to lOOhr or less.
- a converter or an electric furnace can be used to melt the steel of the present invention.
- the steel melted in this way is made into slabs by ingot-bundling or continuous forging.
- Slabs are usually heated (reheated) and then hot rolled.
- the rolling is carried out as it is or for the purpose of suppressing the temperature drop. Good.
- the slab heating temperature is preferably 1280 ° C or lower in order to avoid deterioration of the surface state due to scale. Hot rolling can be performed only by finish rolling, omitting rough rolling.
- the material to be rolled may be heated by a heating means such as a sheet bar heater during hot rolling.
- the thickness of the hot-rolled sheet is not particularly limited as long as the production conditions of the present invention can be maintained, but 1.0 to 10.0 mm is preferable. Hot-rolled sheet is pickled
- Example 2 After removing the surface scale by shot blasting, etc., it is annealed by hot rolling.
- the annealed steel sheet can be temper-rolled as necessary. Examples are given in Example 2.
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Abstract
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Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1020137005432A KR20130035276A (ko) | 2007-12-19 | 2008-11-20 | 강판 및 그 제조 방법 |
CN2008801214570A CN101903547B (zh) | 2007-12-19 | 2008-11-20 | 钢板及其制造方法 |
EP08861016.7A EP2246450B1 (en) | 2007-12-19 | 2008-11-20 | Steel sheets and process for manufacturing the same |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2007326869A JP5157417B2 (ja) | 2007-12-19 | 2007-12-19 | 鋼板およびその製造方法 |
JP2007-326868 | 2007-12-19 | ||
JP2007-326869 | 2007-12-19 | ||
JP2007326868A JP5157416B2 (ja) | 2007-12-19 | 2007-12-19 | 鋼板およびその製造方法 |
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WO2009078261A1 true WO2009078261A1 (ja) | 2009-06-25 |
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PCT/JP2008/071597 WO2009078261A1 (ja) | 2007-12-19 | 2008-11-20 | 鋼板およびその製造方法 |
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EP (1) | EP2246450B1 (ja) |
KR (2) | KR20100076073A (ja) |
CN (1) | CN101903547B (ja) |
WO (1) | WO2009078261A1 (ja) |
Cited By (1)
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CN101906597A (zh) * | 2010-08-14 | 2010-12-08 | 武汉钢铁(集团)公司 | 一种环保型高性能石墨化易切削钢 |
Families Citing this family (6)
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JP5594226B2 (ja) * | 2011-05-18 | 2014-09-24 | Jfeスチール株式会社 | 高炭素薄鋼板およびその製造方法 |
JP5338873B2 (ja) * | 2011-08-05 | 2013-11-13 | Jfeスチール株式会社 | 引張強度440MPa以上の加工性に優れた高強度溶融亜鉛めっき鋼板およびその製造方法 |
IN2014KN01254A (ja) | 2012-01-05 | 2015-10-16 | Jfe Steel Corp | |
JP6479538B2 (ja) * | 2015-03-31 | 2019-03-06 | 株式会社神戸製鋼所 | 機械構造部品用鋼線 |
CN106048179B (zh) * | 2016-07-15 | 2017-09-15 | 北京科技大学 | 一种石墨化热轧钢板的制备方法 |
CN113862609B (zh) * | 2021-09-03 | 2022-05-27 | 北京科技大学 | 利用渗碳、表面石墨化提高中低碳钢工件耐磨减摩的方法 |
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JPH02107742A (ja) * | 1988-10-14 | 1990-04-19 | Kawasaki Steel Corp | 加工性、焼入性に優れた鋼材 |
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2008
- 2008-11-20 KR KR1020107013257A patent/KR20100076073A/ko active Search and Examination
- 2008-11-20 WO PCT/JP2008/071597 patent/WO2009078261A1/ja active Application Filing
- 2008-11-20 EP EP08861016.7A patent/EP2246450B1/en not_active Not-in-force
- 2008-11-20 CN CN2008801214570A patent/CN101903547B/zh not_active Expired - Fee Related
- 2008-11-20 KR KR1020137005432A patent/KR20130035276A/ko not_active Application Discontinuation
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JPH02107742A (ja) * | 1988-10-14 | 1990-04-19 | Kawasaki Steel Corp | 加工性、焼入性に優れた鋼材 |
JPH04124216A (ja) * | 1990-09-12 | 1992-04-24 | Sumitomo Metal Ind Ltd | 成形性の良好な高炭素薄鋼板の製造方法 |
JPH04202744A (ja) | 1990-11-30 | 1992-07-23 | Sumitomo Metal Ind Ltd | 成形性の良好な高炭素薄鋼板とその製造方法 |
JPH0913142A (ja) * | 1991-01-17 | 1997-01-14 | Kawasaki Steel Corp | 曲げ加工性及び熱処理性に優れた黒鉛析出熱間圧延鋼 板ならびにその製造方法 |
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JPH07258743A (ja) | 1994-03-18 | 1995-10-09 | Sumitomo Metal Ind Ltd | 加工性に優れた中炭素鋼板の製造方法 |
JP2007039796A (ja) * | 2005-06-29 | 2007-02-15 | Jfe Steel Kk | 高炭素熱延鋼板およびその製造方法 |
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CN101906597A (zh) * | 2010-08-14 | 2010-12-08 | 武汉钢铁(集团)公司 | 一种环保型高性能石墨化易切削钢 |
Also Published As
Publication number | Publication date |
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EP2246450A4 (en) | 2012-01-25 |
EP2246450A1 (en) | 2010-11-03 |
EP2246450B1 (en) | 2013-09-04 |
KR20130035276A (ko) | 2013-04-08 |
CN101903547B (zh) | 2012-05-23 |
CN101903547A (zh) | 2010-12-01 |
KR20100076073A (ko) | 2010-07-05 |
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