JP2006068797A - Hot pressing method for high strength steel sheet having excellent resistance to hydrogen embrittlement - Google Patents
Hot pressing method for high strength steel sheet having excellent resistance to hydrogen embrittlement Download PDFInfo
- Publication number
- JP2006068797A JP2006068797A JP2004257862A JP2004257862A JP2006068797A JP 2006068797 A JP2006068797 A JP 2006068797A JP 2004257862 A JP2004257862 A JP 2004257862A JP 2004257862 A JP2004257862 A JP 2004257862A JP 2006068797 A JP2006068797 A JP 2006068797A
- Authority
- JP
- Japan
- Prior art keywords
- hydrogen
- steel sheet
- hydrogen embrittlement
- hot pressing
- high strength
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Shaping Metal By Deep-Drawing, Or The Like (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
本発明は、自動車の足回り・衝突安全用補強部材等に使用される高強度鋼板のホットプレス成形方法を提供するものである。 The present invention provides a hot press forming method of a high-strength steel plate used for an automobile underbody / collision safety reinforcing member and the like.
近年、地球環境問題を発端とした自動車の低燃費化に対する要求、および衝突安全性向上等の観点から、鋼板特に自動車用鋼板に対する高強度化の要望が強い。しかし、一般に高強度化は加工性、成形性の低下、さらに製品製造時および使用時の水素の侵入による水素脆化起因の遅れ破壊が懸念され、高強度、高成形性、耐水素脆化特性を備える鋼板が要望されている。高強度かつ高成形性に対する一つの解決手段としては、残留オーステナイトのマルテンサイト変態を利用したＴＲＩＰ（ＴＲａｎｓｆｏｒｍａｔｉｏｎ Ｉｎｄｕｃｅｄ Ｐｌａｓｔｉｃｉｔｙ）鋼があり、近年用途が拡大しつつある。 In recent years, there has been a strong demand for higher strength of steel plates, particularly steel plates for automobiles, from the viewpoints of reducing fuel consumption of automobiles due to global environmental problems and improving collision safety. In general, however, high strength is associated with a decline in workability and moldability, as well as delayed fracture due to hydrogen embrittlement due to hydrogen penetration during product manufacture and use. High strength, high moldability, and hydrogen embrittlement resistance There is a need for a steel plate comprising: One solution to high strength and high formability is TRIP (Transformation Induced Plasticity) steel using martensitic transformation of retained austenite, and its use is expanding in recent years.
しかしこの鋼により、成形性の優れた１０００ＭＰａ級の高強度鋼板を製造することは可能であるが、更に高強度、例えば１５００ＭＰａというような超高強度鋼で成形性を確保することは困難である上、ＴＲＩＰ鋼の加工では、部材加工時に残留オーステナイトがマルテンサイトに変態することによる遅れ破壊特性の劣化が懸念される。そこで、高強度、高成形性、及び耐水脆化特性を備えた部材の製造法として最近注目を浴びているのがホットプレスである。これは鋼板を８００℃以上の高温に加熱した状態で成形することにより、高強度鋼板の成形性の問題を無くし、成型後の冷却により所望の材質を得るというものである。 However, with this steel, it is possible to produce a 1000 MPa class high strength steel plate with excellent formability, but it is difficult to secure formability with ultra-high strength steel such as a higher strength, for example 1500 MPa. Moreover, in the processing of TRIP steel, there is a concern about the deterioration of delayed fracture characteristics due to the transformation of retained austenite into martensite during member processing. Therefore, hot press is recently attracting attention as a method for producing a member having high strength, high formability, and water embrittlement resistance. This is to form a steel sheet heated to a high temperature of 800 ° C. or higher, thereby eliminating the problem of formability of the high-strength steel sheet and obtaining a desired material by cooling after forming.
しかし、大気中での加熱を伴うため、表面に酸化物が生成してこれを後工程で除去する必要がある。これを改善したものが特開２０００−３８６４０号公報（特許文献１）に開示された発明であり、０．１５〜０．５ｍｏｌ％の炭素を含有する鋼板にアルミめっきして加熱時の酸化抑制を図っている。これにより、高温に加熱時の表面酸化を低減することは可能となった。しかし、ホットプレスにより製造した部材は、９８０ＭＰａを超える強度において高い成形性を確保するために、高温から成型と同時に焼き入れを行い、ミクロ組織は６０％以上の体積率のマルテンサイト相を有する。 However, since it involves heating in the atmosphere, an oxide is generated on the surface and needs to be removed in a later step. What improved this is the invention disclosed in Japanese Patent Application Laid-Open No. 2000-38640 (Patent Document 1), which suppresses oxidation during heating by aluminizing a steel sheet containing 0.15-0.5 mol% of carbon. I am trying. This makes it possible to reduce surface oxidation during heating to a high temperature. However, a member manufactured by hot pressing is quenched simultaneously with molding from a high temperature in order to ensure high moldability at a strength exceeding 980 MPa, and the microstructure has a martensite phase with a volume ratio of 60% or more.
このため、特に強度の高い９８０ＭＰａを超える部材では水素脆化起因による遅れ破壊が懸念される。水素侵入経路は様々なケースが考えられるが、その１つとしてプレス直前の昇温の際に鋼材中に侵入する事が考えられる。ホットプレス工法により製造される部材は、成形後にトリムやピアッシングといった切断加工を行うことがある。また、これらの加工を行わない場合、直ちに部材として組み込まれる場合もある。したがって、プレス前の焼鈍時に鋼材に侵入した水素と、プレス後の加工や組付けにより導入される応力に起因し、自動車用部品の耐水素脆化特性が劣化する恐れがある。 For this reason, there is a concern about delayed fracture due to hydrogen embrittlement in a member having a particularly high strength exceeding 980 MPa. There are various cases for the hydrogen intrusion route. One of them is to enter the steel material at the time of temperature rise immediately before pressing. A member manufactured by a hot press method may be subjected to a cutting process such as trimming or piercing after molding. Moreover, when these processes are not performed, it may be immediately incorporated as a member. Therefore, there is a risk that the hydrogen embrittlement resistance of automotive parts may deteriorate due to hydrogen that has entered the steel during annealing before pressing and stress introduced by processing or assembly after pressing.
本発明は９８０ＭＰａ以上の引張強度を有する鋼板をホットプレス成形する際に、耐水素脆化特性を改善した成形方法を提供することを目的とする。 An object of the present invention is to provide a forming method with improved hydrogen embrittlement resistance when hot press forming a steel sheet having a tensile strength of 980 MPa or more.
本発明者らは、上記のような課題を克服するために、引張強度９８０ＭＰａ以上を有する鋼板をホットプレス工法により製造した成形品の、熱処理雰囲気の違いによる耐水素脆化特性の変化を詳細に検討した結果、耐水素脆化特性を向上させる手段として、ホットプレス前の熱処理雰囲気を工夫する事が有効である事を見出した。
本発明は、上記知見に基づいて完成されたもので、その要旨とするところは以下の通りである。
In order to overcome the above-mentioned problems, the inventors have made detailed changes in the resistance to hydrogen embrittlement due to the difference in heat treatment atmosphere of a molded product produced by hot pressing a steel sheet having a tensile strength of 980 MPa or more. As a result of the examination, it was found that devising the heat treatment atmosphere before hot pressing is effective as a means for improving the hydrogen embrittlement resistance.
The present invention has been completed based on the above findings, and the gist thereof is as follows.
（１）９８０ＭＰａ以上の引張強度を有する鋼板をホットプレスする際に、ホットプレス前の焼鈍炉の露点を−１００℃以上３０℃未満とした不活性ガス雰囲気で鋼板を６５０〜１０００℃に加熱した後、プレス成形することを特徴とする耐水素脆化特性に優れた高強度鋼板のホットプレス成形方法。
（２）さらに、ホットプレス前の焼鈍炉の水素濃度を５ｍｏｌ％以下とすることを特徴とする前記（１）に記載の耐水素脆化特性に優れた高強度鋼板のホットプレス成形方法にある。
(1) When hot-pressing a steel sheet having a tensile strength of 980 MPa or more, the steel sheet was heated to 650-1000 ° C. in an inert gas atmosphere in which the dew point of the annealing furnace before hot pressing was −100 ° C. or more and less than 30 ° C. Thereafter, a hot press forming method of a high strength steel sheet having excellent hydrogen embrittlement resistance, characterized by press forming.
(2) Further, in the hot press forming method of a high strength steel sheet having excellent hydrogen embrittlement resistance as described in (1) above, the hydrogen concentration of the annealing furnace before hot pressing is 5 mol% or less. .
本発明により、ホットプレス工法を用いた鋼材で課題であった、プレス直後の初期拡散性水素による耐水素脆化特性の劣化を回避する事ができる。 According to the present invention, it is possible to avoid the deterioration of the hydrogen embrittlement resistance due to the initial diffusible hydrogen immediately after pressing, which was a problem in the steel material using the hot press method.
一般に水素脆化は引張強度で９８０ＭＰａ以上の鋼材において懸念される。水素脆化に対する主な影響因子として、鋼材の強度、鋼材中の拡散性水素量、鋼材に負荷される応力が挙げられる。ここで、拡散性水素とは室温でも拡散可能な水素を指し、これが水素脆化の起因であると言われている。ホットプレス工法により高強度自動車部材を製造する際、プレス直前の焼鈍雰囲気から鋼材中に水素が侵入し、成形冷却後もその水素が鋼材中に留まる事で、初期拡散性水素濃度が増加し耐水素脆化特性が劣化する事が懸念される。 In general, hydrogen embrittlement is a concern in steel materials having a tensile strength of 980 MPa or more. The main influencing factors for hydrogen embrittlement include the strength of steel, the amount of diffusible hydrogen in the steel, and the stress applied to the steel. Here, diffusible hydrogen refers to hydrogen that can diffuse even at room temperature, which is said to be the cause of hydrogen embrittlement. When manufacturing high-strength automotive parts by the hot press method, hydrogen penetrates into the steel material from the annealing atmosphere immediately before pressing, and the hydrogen remains in the steel material after forming cooling, increasing the initial diffusible hydrogen concentration and increasing resistance. There is a concern that the hydrogen embrittlement characteristics deteriorate.
そこで、プレス直前の焼鈍雰囲気を工夫する事で、初期侵入拡散性水素濃度を減少させ、耐水素脆化特性を向上させる事に成功した。
すなわち、焼鈍炉内の露点を−１００℃以上３０℃未満とした不活性ガス雰囲気で鋼板を６５０〜１０００℃に加熱し、さらに必要に応じ焼鈍炉内の水素濃度を５ｍｏｌ％以下とする事により耐水素脆化特性が向上する。
Therefore, by devising the annealing atmosphere immediately before pressing, we succeeded in reducing the initial interstitial diffusible hydrogen concentration and improving the hydrogen embrittlement resistance.
That is, by heating the steel plate to 650 to 1000 ° C. in an inert gas atmosphere with a dew point in the annealing furnace of −100 ° C. or more and less than 30 ° C., and further adjusting the hydrogen concentration in the annealing furnace to 5 mol% or less as necessary. Improves hydrogen embrittlement resistance.
以下に本発明を更に詳細に説明する。
まず、本発明における加工範囲の限定理由について説明する。
焼鈍炉内から鋼材中に侵入する水素の源と考えられるのは、炉内の水分および水素である。したがって、焼鈍炉内の雰囲気を低露点とし、更に必要に応じ低水素濃度として、不活性ガス雰囲気で焼鈍する事で鋼材中に侵入する拡散性水素濃度を低減する事ができる。
The present invention is described in further detail below.
First, the reason for limiting the processing range in the present invention will be described.
It is the moisture and hydrogen in the furnace that are considered to be sources of hydrogen that penetrates into the steel from the annealing furnace. Therefore, by setting the atmosphere in the annealing furnace to a low dew point and further reducing the hydrogen concentration as necessary, annealing in an inert gas atmosphere can reduce the concentration of diffusible hydrogen entering the steel material.
雰囲気中の露点の下限値を−１００℃とした理由は、自動車用部材を製造するような大きな焼鈍炉において連続的に鋼板を処理する際、完全に炉外からの大気の侵入を防ぐ事は難しく、また−１００℃より低い温度で連続的に操業する事はコスト的にも困難である事から下限を−１００℃とした。また、上限値を３０℃未満とした理由は、露点が３０℃以上では鋼材中に多量に水素が侵入し耐水素脆化特性が劣化するからである。 The reason why the lower limit of the dew point in the atmosphere is set to −100 ° C. is that when the steel plate is continuously processed in a large annealing furnace for manufacturing automobile parts, it is possible to completely prevent the intrusion of air from outside the furnace. It is difficult, and since it is difficult to operate continuously at a temperature lower than -100 ° C, the lower limit is set to -100 ° C. Moreover, the reason why the upper limit is less than 30 ° C. is that when the dew point is 30 ° C. or more, a large amount of hydrogen enters the steel material and the hydrogen embrittlement resistance deteriorates.
炉内の雰囲気は水素を含まない不活性ガスであれば構わない。ただし不活性ガスとしては産業的には窒素またはアルゴンを体積分率で８０％以上使用する事がコストに見合うガス成分として有望であり、これらのガス雰囲気からは鋼材中に水素が侵入しない。残部ガス成分として、酸素、二酸化炭素、ネオン、ヘリウム、メタン、クリプトン、一酸化炭素、キセノンの１種又は２種以上を含有しても良い。 The atmosphere in the furnace may be any inert gas that does not contain hydrogen. However, industrial use of nitrogen or argon as a volume fraction of 80% or more is promising as a gas component commensurate with cost, and hydrogen does not enter the steel from these gas atmospheres. As the remaining gas component, one or more of oxygen, carbon dioxide, neon, helium, methane, krypton, carbon monoxide, and xenon may be contained.
加熱温度はプレス工程において十分な成形性を得るために６５０℃以上とし、表面の酸化やミクロ組織中のγ粒の粗大化を防ぐために１０００℃以下とする。
また、炉内ガス雰囲気中の水素濃度の上限値を５ｍｏｌ％以下とした理由は、５ｍｏｌ％超の炉内水素濃度では鋼材中に多量の水素が侵入し耐水素脆化特性が劣化するからである。また、下限値に関しては炉内雰囲気が無水素である事が最も望ましい事から０ｍｏｌ％を含むものであり、特に規定しない。
The heating temperature is set to 650 ° C. or higher in order to obtain sufficient moldability in the pressing step, and is set to 1000 ° C. or lower in order to prevent surface oxidation and coarsening of γ grains in the microstructure.
The reason why the upper limit of the hydrogen concentration in the furnace gas atmosphere is set to 5 mol% or less is that when the furnace hydrogen concentration exceeds 5 mol%, a large amount of hydrogen enters the steel material and the hydrogen embrittlement resistance deteriorates. is there. Further, regarding the lower limit value, 0 mol% is included because it is most desirable that the atmosphere in the furnace is hydrogen-free, and is not particularly specified.
次に、実施例で本発明をより詳細に説明する。
表１に示すように９８０ＭＰａ以上の引張強度を有する厚さ１．６ｍｍの鋼板を３種類用意した。ホットプレス後の引張強度はそれぞれ１０５５ＭＰａ、１２１３ＭＰａ、１５６６ＭＰａである。炉内の露点および雰囲気を制御できる焼鈍炉を用い、成形焼き入れ後の耐水素脆化特性を評価した。耐水素脆化特性の評価方法は、１００ｍｍ×３０ｍｍの短冊試験片を９４０℃に加熱後、曲げ加工半径１０ｍｍにてＵ曲げ加工後そのまま室温の金型にて焼入れを行い所定の強度とした。この試験片に対し速やかに６０ｋｇｆ／ｍｍ2 および９０ｋｇｆ／ｍｍ2 の応力を付加し、室温にて１ヶ月間放置したときの割れ発生時間を評価した。炉内の露点を４０℃、０℃、−４０℃の３水準とし、ガス雰囲気は窒素に対し水素を０ｍｏｌ％、４ｍｏｌ％、１０ｍｏｌ％の３水準にて変化させた条件にて評価した。
Next, an Example demonstrates this invention in detail.
As shown in Table 1, three types of 1.6 mm thick steel plates having a tensile strength of 980 MPa or more were prepared. The tensile strength after hot pressing is 1055 MPa, 1213 MPa, and 1566 MPa, respectively. Using an annealing furnace that can control the dew point and atmosphere in the furnace, the hydrogen embrittlement resistance after forming and quenching was evaluated. The evaluation method of the hydrogen embrittlement resistance was such that a 100 mm × 30 mm strip test piece was heated to 940 ° C., U-bent with a bending radius of 10 mm, and then quenched with a mold at room temperature to obtain a predetermined strength. For this specimen was added quickly stress of 60 kgf / mm 2 and 90 kgf / mm 2, it was evaluated cracking time when left for one month at room temperature. The dew point in the furnace was set at three levels of 40 ° C., 0 ° C., and −40 ° C., and the gas atmosphere was evaluated under the conditions in which hydrogen was changed at three levels of 0 mol%, 4 mol%, and 10 mol% with respect to nitrogen.
上記検討の結果、低露点かつ低水素濃度の際に割れが発生しなかった。したがって、加工端部の耐水素脆化特性の向上には露点を−１００℃以上３０℃未満かつ炉内の水素濃度を５ｍｏｌ％以下にする事で、成形焼き入れ後の耐水素脆化特性を向上する事ができる。
特許出願人 新日本製鐵株式会社
代理人 弁理士 椎名 彊 他１
As a result of the above examination, cracks did not occur at a low dew point and a low hydrogen concentration. Therefore, to improve the hydrogen embrittlement resistance at the machining end, the debris point is -100 ° C. or higher and lower than 30 ° C. and the hydrogen concentration in the furnace is 5 mol% or less. You can improve.
Patent applicant: Nippon Steel Corporation
Attorney Attorney Shiina and others 1
Claims (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004257862A JP2006068797A (en) | 2004-09-06 | 2004-09-06 | Hot pressing method for high strength steel sheet having excellent resistance to hydrogen embrittlement |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004257862A JP2006068797A (en) | 2004-09-06 | 2004-09-06 | Hot pressing method for high strength steel sheet having excellent resistance to hydrogen embrittlement |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2006068797A true JP2006068797A (en) | 2006-03-16 |
Family
ID=36149937
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2004257862A Pending JP2006068797A (en) | 2004-09-06 | 2004-09-06 | Hot pressing method for high strength steel sheet having excellent resistance to hydrogen embrittlement |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2006068797A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104159681A (en) * | 2012-03-06 | 2014-11-19 | 杰富意钢铁株式会社 | Warm press forming method and automobile frame component |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02200737A (en) * | 1989-01-31 | 1990-08-09 | Kawasaki Steel Corp | Manufacture of low iron loss grain-oriented silicon steel sheet free from deterioration of properties caused by stress relieving annealing |
| JP2003126920A (en) * | 2001-10-23 | 2003-05-08 | Sumitomo Metal Ind Ltd | Hot press processing method |
| JP2003213336A (en) * | 2002-01-18 | 2003-07-30 | Hitachi Metals Ltd | Method of producing sheet metal for shadow mask having excellent etching uniformity |
| JP2003253338A (en) * | 2002-02-27 | 2003-09-10 | Hitachi Metals Ltd | Process for manufacturing alloy thin sheet for lead frame showing excellent rust resistance |
| JP2003266123A (en) * | 2002-03-12 | 2003-09-24 | Jfe Steel Kk | Method of forming high tensile strength steel sheet |
| JP2004058082A (en) * | 2002-07-26 | 2004-02-26 | Aisin Takaoka Ltd | Method for producing tailored blank press formed article |
| JP2006051543A (en) * | 2004-07-15 | 2006-02-23 | Nippon Steel Corp | Hot press method for high strength automotive member made of cold rolled or hot rolled steel sheet, or al-based plated or zn-based plated steel sheet, and hot pressed parts |
-
2004
- 2004-09-06 JP JP2004257862A patent/JP2006068797A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02200737A (en) * | 1989-01-31 | 1990-08-09 | Kawasaki Steel Corp | Manufacture of low iron loss grain-oriented silicon steel sheet free from deterioration of properties caused by stress relieving annealing |
| JP2003126920A (en) * | 2001-10-23 | 2003-05-08 | Sumitomo Metal Ind Ltd | Hot press processing method |
| JP2003213336A (en) * | 2002-01-18 | 2003-07-30 | Hitachi Metals Ltd | Method of producing sheet metal for shadow mask having excellent etching uniformity |
| JP2003253338A (en) * | 2002-02-27 | 2003-09-10 | Hitachi Metals Ltd | Process for manufacturing alloy thin sheet for lead frame showing excellent rust resistance |
| JP2003266123A (en) * | 2002-03-12 | 2003-09-24 | Jfe Steel Kk | Method of forming high tensile strength steel sheet |
| JP2004058082A (en) * | 2002-07-26 | 2004-02-26 | Aisin Takaoka Ltd | Method for producing tailored blank press formed article |
| JP2006051543A (en) * | 2004-07-15 | 2006-02-23 | Nippon Steel Corp | Hot press method for high strength automotive member made of cold rolled or hot rolled steel sheet, or al-based plated or zn-based plated steel sheet, and hot pressed parts |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104159681A (en) * | 2012-03-06 | 2014-11-19 | 杰富意钢铁株式会社 | Warm press forming method and automobile frame component |
| CN104159681B (en) * | 2012-03-06 | 2016-02-24 | 杰富意钢铁株式会社 | Warm briquetting process and automobile skeleton part |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN110678569B (en) | High-strength steel sheet and method for producing same | |
| KR101682868B1 (en) | Method for producing hot-pressed steel member | |
| KR102144194B1 (en) | Method of manufacturing hot stamping parts | |
| KR101833655B1 (en) | Hot-pressed steel sheet member, production method for same, and steel sheet for hot pressing | |
| KR20190071755A (en) | High-strength cold-rolled steel having a tensile strength of 1500 MPa or more and excellent moldability and a manufacturing method thereof | |
| EP2589674A1 (en) | Ultrahigh-strength cold-rolled steel sheet with excellent ductility and delayed-fracture resistance, and process for producing same | |
| KR101881234B1 (en) | Hot-pressed steel sheet member, production method for same, and hot-press steel sheet | |
| JP2017186647A (en) | High-strength steel sheet and method for producing the same | |
| JP2006316338A (en) | Method for producing product made of stainless steel, and the product made of stainless steel | |
| KR20180001590A (en) | Steel sheet for hot forming | |
| JP2005205477A (en) | Hot-press-forming method with excellent productivity and automotive member | |
| JP2006212663A (en) | Method for producing member made of hot-pressed high strength steel having excellent formability | |
| JP2017214648A (en) | High strength steel sheet and manufacturing method therefor | |
| JP2006070346A (en) | Steel sheet for hot press having excellent hydrogen embrittlement resistance, automobile member and production method therefor | |
| JP2006104546A (en) | High strength automobile member and hot pressing method | |
| KR20150121229A (en) | Method for producing an ultra high strength material with high elongation | |
| CN103993147A (en) | Cold rolled steel plate and preparation method thereof | |
| JP2007291464A (en) | High-strength steel material and its production method | |
| WO2018025674A1 (en) | High-strength steel plate and manufacturing method thereof | |
| JP6003837B2 (en) | Manufacturing method of high strength pressed parts | |
| JPWO2019131099A1 (en) | Hot rolled steel sheet and method for producing the same | |
| KR102209555B1 (en) | Hot rolled and annealed steel sheet having low strength-deviation, formed member, and manufacturing method of therefor | |
| JP5405325B2 (en) | Differential gear and manufacturing method thereof | |
| JP2006130519A (en) | Method for manufacturing hot-pressed high strength steel member with low residual stress | |
| JP2006068797A (en) | Hot pressing method for high strength steel sheet having excellent resistance to hydrogen embrittlement |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20061113 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20090205 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20100202 |
|
| A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20100330 |