WO2005113842A1 - 熱間絞り成形品の製造方法 - Google Patents
熱間絞り成形品の製造方法 Download PDFInfo
- Publication number
- WO2005113842A1 WO2005113842A1 PCT/JP2005/009089 JP2005009089W WO2005113842A1 WO 2005113842 A1 WO2005113842 A1 WO 2005113842A1 JP 2005009089 W JP2005009089 W JP 2005009089W WO 2005113842 A1 WO2005113842 A1 WO 2005113842A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- blank
- oxide scale
- thickness
- molding
- hot
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/20—Deep-drawing
- B21D22/22—Deep-drawing with devices for holding the edge of the blanks
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
- B21D22/20—Deep-drawing
- B21D22/208—Deep-drawing by heating the blank or deep-drawing associated with heat treatment
-
- 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
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0478—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing involving a particular surface treatment
-
- 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
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
- C21D9/48—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals deep-drawing sheets
Definitions
- the present invention relates to a field of manufacturing a thin steel sheet molded product mainly applied to an automobile body, and to hot-draw by heating a steel sheet (blank) as a material thereof to a temperature higher than a ferrite + austenite temperature (Acl transformation point).
- the present invention relates to a method for producing a molded article by molding, and particularly to a method for producing a molded article capable of achieving good deep drawing without causing breakage or cracking during press molding.
- Japanese Patent Application Laid-Open No. 2002-102980 proposes a technique in which a metal material is heated to 850 to 1050 ° C and formed using a relatively low-temperature press die. ing. According to this technology, it is said that the formability of the metal material is improved and delayed fracture due to residual stress can be prevented. In particular, it is possible to obtain parts with high tensile strength, which was considered difficult to form using ordinary cold pressing methods, equivalent to that of high-strength steel sheets of 1470 MPa class, and good dimensional accuracy. Become.
- Fig. 1 is a schematic explanatory view showing a mold configuration for performing the hot forming (hereinafter, sometimes referred to as "hot stamping") as described above.
- Indicates die 3 indicates blank holder (wrinkle holder), 4 indicates steel plate (material), BHF indicates wrinkle holder force, rp indicates punch shoulder radius, rd indicates die shoulder radius, and CL indicates punch / die clearance.
- the passages la and 2a through which the cooling medium for example, water
- the cooling medium for example, water
- the hot stamp as described above is actually applied to the molding of parts having a relatively simple shape and not requiring wrinkle control.
- the above-mentioned problem occurs when the temperature is significantly reduced in the portion corresponding to the flange, so that its application has been limited (for example, Door impact beams, etc.).
- the oxide scale formed on the blank surface is preferably as thin as possible.
- the thickness of the oxide scale is controlled to be thin by setting the heating rate to 50 ° C./sec or more, and the subsequent chemical conversion treatment is improved. It is disclosed.
- Japanese Patent Application Laid-Open No. 2003-231915 discloses a technique to reduce the scale thickness of the steel sheet surface before press forming to 10 ⁇ m or less from the viewpoint of improving the hardenability of a low carbon steel blank. Has also been proposed.
- Patent document 1 JP 2002-102980 A
- Patent Document 2 JP-A-2002-18531
- Patent Document 3 JP 2003-231915 A
- the present invention has been made under such a circumstance, and an object of the present invention is to provide a good deep drawing method without causing breakage or cracking at the time of forming a metal plate by hot drawing. It is an object of the present invention to provide a method for producing a hot drawn product that can realize the above.
- the method for producing a hot drawn product of the present invention which has achieved the above object comprises the following steps: forming an oxide scale having a thickness of 15 / m or more on both surfaces of a metal plate; and The metal plate on which the oxide scale is formed is hot drawn using a punch and a die.
- the thickness of the oxide scale means an average thickness of one metal plate. It is more preferable that the thickness of the oxide scale is 50 ⁇ or more.
- the thickness of the oxide scale is defined by a value measured in a state where a target metal plate is heated in a heating furnace and then cooled to room temperature by natural cooling.
- the method of the present invention can be suitably applied to forming of a steel sheet. In this case, it is preferable to heat the steel sheet to 800 ° C. or more in the step of forming the oxide scale. Preferably, the step of hot drawing is performed at a temperature higher than the martensitic transformation start temperature of the steel sheet.
- the surface of the metal plate is By using a material on which an oxide scale is formed, it is possible to produce a molded product that can achieve good deep drawing without causing breakage or cracking during molding.
- FIG. 1 is a schematic explanatory view showing a configuration of a mold for performing hot forming.
- FIG. 2 is a perspective view schematically showing the external shape of a molded product that can be molded.
- FIG. 3 is a graph showing the relationship between the oxide scale thickness of a blank and the maximum forming load.
- FIG. 4 is a graph showing a cross-sectional hardness distribution in a portion corresponding to a punch of a molded product.
- the present inventors have studied from various angles the causes of the above-mentioned inconveniences in the prior art. As a result, the following was found.
- the blank (steel) is heated in a non-oxidizing atmosphere under a force S, and the oxide scale thickness of the blank during forming is in a very thin state (about 10 ⁇ m or less). If holding down is required, the temperature of the flange-equivalent portion will decrease significantly. As a result, it was thought that the inflow resistance of the part corresponding to the flange increased, and it became difficult to perform deep drawing while suppressing the occurrence of wrinkles in the part corresponding to the flange.
- the present inventors have further studied under the idea that good formability can be realized by eliminating such inconveniences.
- the thickness of the oxide scale on the blank surface is intentionally increased, and an oxide scale film is interposed between the die and the flange, which is sandwiched between the blank holder. It was found that it was possible to have both.
- a temperature drop during molding at a portion corresponding to the flange is suppressed (insulation effect), and at the same time, it functions as a solid lubricant, and the breaking limit at the punch shoulder is reduced. They have found that they can be improved and completed the present invention.
- the thickness of the oxide scale is required. Must be at least 15 / im.
- the thickness of the oxide scale is preferably set to 50 zm or more. However, if the thickness is too large, the thickness of the product becomes thin due to descaling after molding. Therefore, it is preferable to keep the thickness within an allowable range ( For example, about 100 zm or less).
- the heating temperature may be 950 ° C in air and the heating time may be 5 minutes or more.
- the mechanism by which the blank can easily flow into the mold can be inferred as follows.
- a blank having an oxide scale on the surface comes into contact with the mold (particularly a part of the steel sheet sandwiched between the die 2 and the blank holder 3 in Fig. 1)
- the surface temperature drops sharply and the thermal shock
- the oxide scale destructively peels off.
- the oxide scale is destructively peeled off by the stress generated by the difference in the expansion coefficient between the oxide scale and steel.
- the peeled scale serves as a solid lubricant.
- a normal steel sheet for example, a 980 MPa class cold-rolled steel sheet, a steel sheet for strengthening hardening, etc.
- the surface thereof is subjected to plating treatment [Zn Plating (Zn plating, Zn_Ni plating, etc.), Ni plating, Co plating, etc.].
- the oxide scale formed on the surface thereof is preferably mainly composed of iron oxide, but when a plated steel sheet is used, the elements constituting the oxide scale plating layer are preferably Oxide as the main component is acceptable. Even when oxide scale is formed on the surface of such a plating layer, the thickness of the oxide scale Is effective if it is 15 ⁇ m or more (preferably 50 ⁇ m or more).
- the atmosphere at the time of heating the blank may be an oxidizing atmosphere (for example, in the air).
- the thickness of the oxide scale can be controlled by adjusting the holding time in the atmosphere.
- the blank heating temperature before molding is preferably at least the Ac 1 transformation point (the temperature at which two phases of ferrite and austenite exist) when strength is required after molding.
- the heating time required to reach the specified thickness of the scale is within the practical range. It is desirable to adjust as follows. Specifically, heating at about 600 ° C takes a long time to achieve a scale thickness of 15 ⁇ m or more, so it is desirable to heat the material to at least the two-phase region (above the Acl transformation point). It is more preferable to heat to 800 ° C or more.
- the blank temperature at the start of molding is based on the martensitic transformation start temperature (Ms point: 450 ° C, for example) of the material. It is also preferable to set the temperature higher. If the molding start temperature is lower than the Ms point, martensite is generated and the material strength increases, which may make molding difficult.
- Ms point 450 ° C, for example
- the present invention by forming an oxide scale on the blank surface, good hot formability can be ensured.
- the force scale is thickened, the heat insulating effect of the scale is more exerted.
- the blank temperature decreases.
- the area of contact with the punch is responsible for the force that flows the blank into the mold.
- the strength of the (corresponding part) remains soft. For this reason, the strength of the punch-equivalent portion may be lower than the deformation resistance of the flange-equivalent portion, which may result in good molding.
- a cooling method prior to the molding air is partially blown, or the punch is divided and the punch at a specific part is blown before the molding. For example, a method such as contacting with a hook may be considered.
- the term "hot” refers to a temperature region equal to or higher than the Acl transformation point of a material, since it is necessary to perform quenching by quenching with a mold after forming in hot forming. become.
- the lower limit of the thickness of the oxide scale is defined by a value measured in a state where the blank is heated in a heating furnace and then naturally cooled to room temperature. This is for the following reasons.
- the thickness of the oxide scale at the moment of press forming is essentially a problem.
- the invention is defined based on the thickness of the oxide scale measured when the blank is at room temperature by natural cooling, as a value corresponding to the thickness of the oxide scale at the moment of press forming.
- the thickness of the oxide scale at the moment of press forming and the thickness of the oxide scale measured at room temperature by natural cooling are not exactly located.
- the blank heated in the heating furnace is transported to the press machine (working place) in a state where it is naturally cooled and cooled to the hot working temperature.
- the scale thickness after cooling is considered to have a corresponding relationship with the oxide scale thickness at the moment of processing. That is, there is no need to consider uncertain factors such as scale peeling due to rapid cooling.
- the lower limit of the thickness of the oxide scale in the present invention is not affected by the thickness of the metal plate to be processed.
- the heating time is 3 to 5 minutes (of which the time maintained at 900 ° C is about several tens of seconds), and the oxide scale thickness at that time is about 11 ⁇ m.
- various oxide scale thicknesses were realized by appropriately employing a heating time longer than the normal heating time.
- a heating time of 15 minutes (of which the time maintained at 900 ° C was about 10 minutes) was required to obtain an oxide scale thickness of 50 xm.
- the thickness of the oxide scale at this time is obtained by measuring the cross-sectional thickness when the blank is taken out of the heating furnace and left to cool as it is.
- the thickness of the oxide scale was measured by cutting out a part of the part corresponding to the position between the die 2 and the blank holder 3 at the time of molding, and measuring the maximum at three places (one side only) in a 400-fold microscope field of view. The thickness was measured and averaged.
- the chemical composition and the mechanical properties of the steel sheet are as follows.
- the Acl transformation point of this steel sheet is 725 ° C, and the Ac3 transformation point is 850 ° C.
- the wrinkle holding force was 3 tons, and a paste-like solid lubricant with a heat-resistant temperature of 1000 ° C was used as a lubricant and applied to the mold.
- a mechanical press was used, and molding was performed immediately after removing the blank from the heating furnace. That is, in the present embodiment, the heating originally required for performing the hot working is appropriately lengthened in order to make the oxide scale thicker.
- the molding speed at this time was 40 cycles Z minutes, the mold was stopped at the bottom dead center for 20 seconds, and a quenching operation was performed.
- Other press molding conditions are as follows.
- Punch shoulder radius rp 5mm
- Punch-die clearance CL [1. 32/2 + 1.4 (steel plate thickness)] mm
- FIG. 2 schematically shows the appearance of the molded article that could be molded.
- the molding start temperature in this test was determined by heating a blank with a thermocouple having the same plate thickness in the same manner as during molding and measuring the natural cooling curve in advance, and determining the heating temperature during actual molding. It was estimated based on the curve from the time taken to take out of the furnace and start molding.
Abstract
Description
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Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2004-151753 | 2004-05-21 | ||
JP2004151753A JP2005329448A (ja) | 2004-05-21 | 2004-05-21 | 熱間絞り成形品の製造方法 |
Publications (1)
Publication Number | Publication Date |
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WO2005113842A1 true WO2005113842A1 (ja) | 2005-12-01 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/JP2005/009089 WO2005113842A1 (ja) | 2004-05-21 | 2005-05-18 | 熱間絞り成形品の製造方法 |
Country Status (2)
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JP (1) | JP2005329448A (ja) |
WO (1) | WO2005113842A1 (ja) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2010179317A (ja) * | 2009-02-03 | 2010-08-19 | Toyota Motor Corp | 熱間プレス成形方法及び装置 |
EP2623225A4 (en) * | 2010-09-30 | 2016-09-07 | Kobe Steel Ltd | METHOD OF MANUFACTURING A PRESSING ARTICLE |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4681492B2 (ja) * | 2006-04-07 | 2011-05-11 | 新日本製鐵株式会社 | 鋼板熱間プレス方法及びプレス成形品 |
PL2290133T3 (pl) * | 2009-08-25 | 2012-09-28 | Thyssenkrupp Steel Europe Ag | Sposób wytwarzania elementu stalowego z antykorozyjną powłoką metalową i element stalowy |
KR101171450B1 (ko) * | 2009-12-29 | 2012-08-06 | 주식회사 포스코 | 도금 강재의 열간 프레스 성형방법 및 이를 이용한 열간 프레스 성형품 |
ES2586555T3 (es) * | 2011-09-01 | 2016-10-17 | Kabushiki Kaisha Kobe Seiko Sho | Pieza moldeada estampada en caliente y método de fabricación de la misma |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2002018531A (ja) * | 2000-07-06 | 2002-01-22 | Sumitomo Metal Ind Ltd | 金属板の熱間プレス成形方法 |
JP2003231915A (ja) * | 2002-02-08 | 2003-08-19 | Jfe Steel Kk | プレス焼入れ方法 |
JP2003266131A (ja) * | 2002-03-13 | 2003-09-24 | Nippon Steel Corp | 高温プレス方法 |
-
2004
- 2004-05-21 JP JP2004151753A patent/JP2005329448A/ja active Pending
-
2005
- 2005-05-18 WO PCT/JP2005/009089 patent/WO2005113842A1/ja active Application Filing
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2002018531A (ja) * | 2000-07-06 | 2002-01-22 | Sumitomo Metal Ind Ltd | 金属板の熱間プレス成形方法 |
JP2003231915A (ja) * | 2002-02-08 | 2003-08-19 | Jfe Steel Kk | プレス焼入れ方法 |
JP2003266131A (ja) * | 2002-03-13 | 2003-09-24 | Nippon Steel Corp | 高温プレス方法 |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2010179317A (ja) * | 2009-02-03 | 2010-08-19 | Toyota Motor Corp | 熱間プレス成形方法及び装置 |
EP2623225A4 (en) * | 2010-09-30 | 2016-09-07 | Kobe Steel Ltd | METHOD OF MANUFACTURING A PRESSING ARTICLE |
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JP2005329448A (ja) | 2005-12-02 |
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