JP5644093B2 - Manufacturing method of high strength members - Google Patents

Manufacturing method of high strength members Download PDF

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JP5644093B2
JP5644093B2 JP2009271984A JP2009271984A JP5644093B2 JP 5644093 B2 JP5644093 B2 JP 5644093B2 JP 2009271984 A JP2009271984 A JP 2009271984A JP 2009271984 A JP2009271984 A JP 2009271984A JP 5644093 B2 JP5644093 B2 JP 5644093B2
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勇樹 田路
勇樹 田路
高木 周作
周作 高木
長谷川 浩平
浩平 長谷川
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Jfeスチール株式会社
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本発明は、自動車骨格部材、補強部材等に好適な、遅れ破壊特性に優れる高強度部材の製造方法に関する。   The present invention relates to a method for producing a high-strength member that is suitable for automobile frame members, reinforcing members, etc. and has excellent delayed fracture characteristics.

近年、地球環境保全という観点から、自動車の燃費改善が要求されている。また、車両衝突時に乗員を保護する観点からは、自動車車体の安全性向上も要求されている。このため、燃費改善と安全性向上の両方を満足するべく、自動車車体の軽量化と強化の双方を図る検討が積極的に進められている。自動車車体の軽量化と強化を同時に満足させるには、部品素材を高強度化かつ薄肉化することが効果的であり、最近では引張強さTSが1180MPa以上の高張力薄鋼板が自動車骨格部材、補強部材等に使用され始めている。   In recent years, there has been a demand for improving fuel efficiency of automobiles from the viewpoint of global environmental conservation. Further, from the viewpoint of protecting occupants in the event of a vehicle collision, it is also required to improve the safety of the automobile body. For this reason, in order to satisfy both the fuel efficiency improvement and the safety improvement, studies for reducing the weight and strengthening of the automobile body are being actively promoted. In order to satisfy the weight reduction and strengthening of the automobile body at the same time, it is effective to increase the strength and thickness of the component material. Recently, a high-strength thin steel sheet having a tensile strength TS of 1180 MPa or more is an automobile skeleton member, It has begun to be used for reinforcing members.

しかしながら、非特許文献1に記載されているように、引張強さTSが1180MPa以上の高強度鋼板は、それよりも強度の低い鋼板に比べ、その使用中に、腐食に伴い侵入する水素に起因して、遅れ破壊が生じる可能性が高くなる。なお、それを表すページを図1として記載する。このため、引張強さTSが1180MPa以上の高強度鋼板の適用は、限定的なものとなっている。   However, as described in Non-Patent Document 1, a high-strength steel sheet having a tensile strength TS of 1180 MPa or more is caused by hydrogen that intrudes during corrosion compared to a steel sheet having a lower strength than that. Thus, the possibility of delayed fracture increases. In addition, the page showing it is described as FIG. For this reason, application of the high strength steel plate having a tensile strength TS of 1180 MPa or more is limited.

また、自動車骨格部材等の部材は、通常、プレス成形やロール成形といった成形加工を施して目的の形状に成形した後に使用されるが、非特許文献2に記載されているように、遅れ破壊特性は加工により劣化することが知られている。このため、加工後の遅れ破壊特性に優れる高強度部材が求められている。
さらに、自動車骨格部材等の部材は、通常、成形加工後、化成処理および電着塗装して使用される。このとき、化成処理、電着塗装中に侵入する水素により遅れ破壊が発生することが懸念される。化成処理、電着塗装は、実使用中の腐食環境に比べると遅れ破壊しにくい条件であるが、1320MPa以上に強度が高くなった場合には、よりマイルドな条件である、化成処理電着塗装中に遅れ破壊が発生する可能性があり、成形加工後、化成処理、電着塗装中に遅れ破壊しないことが必要である。
In addition, members such as automobile skeleton members are usually used after being molded into a desired shape by performing a molding process such as press molding or roll molding. However, as described in Non-Patent Document 2, delayed fracture characteristics are used. Is known to deteriorate with processing. For this reason, the high strength member which is excellent in the delayed fracture characteristic after a process is calculated | required.
Furthermore, members such as automobile skeleton members are usually used after forming and chemical conversion treatment and electrodeposition coating. At this time, there is a concern that delayed fracture may occur due to hydrogen entering during chemical conversion treatment and electrodeposition coating. Chemical conversion treatment and electrodeposition coating are conditions that are less likely to break later than in corrosive environments during actual use, but chemical conversion treatment electrodeposition coating is a milder condition when the strength becomes higher than 1320 MPa. There is a possibility that delayed fracture may occur, and it is necessary to prevent delayed fracture during chemical conversion treatment and electrodeposition coating after molding.

そして、遅れ破壊特性に優れる自動車部材用高強度薄鋼板の製造として、従来、特許文献1〜5に記載の技術がある。
特許文献1〜3では、CaやMg、Mo、Vなどの元素を添加することで、遅れ破壊特性を向上させている。また、特許文献4、5では、鋼組織を限定することで、遅れ破壊特性を向上させようとしている。
And conventionally, there exists a technique of patent documents 1-5 as manufacture of the high intensity | strength thin steel plate for motor vehicle members which is excellent in a delayed fracture characteristic.
In Patent Documents 1 to 3, delayed fracture characteristics are improved by adding elements such as Ca, Mg, Mo, and V. Patent Documents 4 and 5 attempt to improve delayed fracture characteristics by limiting the steel structure.

特開2003−166035号公報Japanese Patent Laid-Open No. 2003-166035 特開2004−359974号公報JP 2004-359974 A 特許第3406094号公報Japanese Patent No. 3406904 特許第3424619号公報Japanese Patent No. 3424619 特開2005−220440号公報JP 2005-220440 A

「遅れ破壊」(日刊工業新聞社、1989年8月31日発行)"Delayed Destruction" (Nikkan Kogyo Shimbun, August 31, 1989) 自動車技術会論文集、Vol.39、No.5、P.133Automobile Engineering Society Proceedings, Vol. 39, no. 5, P.I. 133

しかしながら、特許文献1〜3は、いずれも遅れ破壊特性を向上させるためにCaやMg、Mo、Vなどの特殊な元素の添加を必須としている。このため、鋼板製造コストが増大するという課題がある。また、特許文献4及び特許文献5は、鋼組織を限定する必要があり、通常の鋼に対する汎用的な遅れ破壊特性の改善には到っていない。
本発明は上記問題点を解決するためになされたものであり、素材となる鋼板の成分や組織に厳しい規制をすることなく、成形加工後の遅れ破壊特性に優れる高強度部材を提供することを課題としている。
However, Patent Documents 1 to 3 all require the addition of special elements such as Ca, Mg, Mo, and V in order to improve delayed fracture characteristics. For this reason, there exists a subject that the steel plate manufacturing cost increases. In addition, Patent Document 4 and Patent Document 5 need to limit the steel structure, and have not yet improved general-purpose delayed fracture characteristics with respect to ordinary steel.
The present invention has been made to solve the above problems, and provides a high-strength member having excellent delayed fracture characteristics after forming without restricting the components and structure of the steel sheet as a raw material. It is an issue.

上記いずれの特許文献に記載の技術も、加工による遅れ破壊特性の劣化を考慮したものではない。そして、加工後の高強度部品の遅れ破壊の問題を抜本的に解決する技術は、未だ見出されていない。
そのような課題を解決するために、本発明のうち請求項1に記載した発明は、引張強さが1320MPa以上の鋼板を、目的の形状に成形した後に化成処理及び電着塗装を施す高強度部材の製造方法において、上記鋼板を上記目的の形状に、ホットプレスを除く加工方法で成形する成形工程と、上記成形工程で目的の形状に成形された鋼板を、100℃〜400℃の温度範囲で且つ1秒〜60分の熱処理時間で熱処理を施す熱処理工程と、上記熱処理工程で熱処理を施した鋼板に対し化成処理した後に電着塗装を施す塗装工程と、を備えることを特徴とするものである。
None of the techniques described in any of the above-mentioned patent documents considers the deterioration of delayed fracture characteristics due to processing. And the technique which fundamentally solves the problem of delayed fracture of the high-strength parts after processing has not yet been found.
In order to solve such problems, the invention described in claim 1 of the present invention has a high strength in which a steel sheet having a tensile strength of 1320 MPa or more is formed into a target shape and then subjected to chemical conversion treatment and electrodeposition coating. In the member manufacturing method, a forming step of forming the steel plate into the target shape by a processing method excluding hot pressing, and a steel plate formed into the target shape in the forming step in a temperature range of 100 ° C. to 400 ° C. And a coating process in which electrodeposition coating is performed after the chemical conversion treatment is performed on the steel plate that has been heat-treated in the heat treatment process. It is.

次に、請求項2に記載した発明は、請求項1に記載した構成に対し、上記熱処理工程での熱処理は、200℃〜400℃の温度範囲で且つ1秒〜10分の熱処理時間で熱処理を施すことを特徴とするものである。
次に、請求項3に記載した発明は、引張強さが1320MPa以上の鋼板を、目的の形状に成形した後に化成処理及び電着塗装を施す高強度部材の製造方法において、
上記成形を、100℃〜400℃の温度範囲で施すことを特徴とするものである。
Next, the invention described in claim 2 is the heat treatment in the temperature range of 200 ° C. to 400 ° C. and a heat treatment time of 1 second to 10 minutes with respect to the configuration described in claim 1. It is characterized by giving.
Next, the invention described in claim 3 is a method for producing a high-strength member in which a steel sheet having a tensile strength of 1320 MPa or more is formed into a target shape and then subjected to chemical conversion treatment and electrodeposition coating.
The molding is performed in a temperature range of 100 ° C to 400 ° C.

本発明によれば、引張強さが1320MPa以上の鋼板を、プレス成形やロール成形等の加工によって目的の形状に成形し塗装を施すことで製造される高強度部材について、鋼板を高強度部材に加工する際の処理を工夫することによって、遅れ破壊特性に優れる高強度部材を提供することが出来る。すなわち、引張強さが1320MPa以上の鋼板を製造する際に、必ずしも、遅れ破壊特性を向上させるための特殊な成分添加や、鋼組織の限定をする必要はない。   According to the present invention, a high-strength member manufactured by forming a steel sheet having a tensile strength of 1320 MPa or more into a desired shape by processing such as press molding or roll molding and coating the steel sheet into a high-strength member. By devising the processing at the time of processing, a high-strength member excellent in delayed fracture characteristics can be provided. That is, when producing a steel sheet having a tensile strength of 1320 MPa or more, it is not always necessary to add a special component for improving delayed fracture characteristics or limit the steel structure.

そして、本願発明によって得ることが出来る高強度部材は、高強度と遅れ破壊特性を兼ね備えており、自動車骨格部材、補強部材等の構造材として好適である。   The high-strength member that can be obtained by the present invention has both high strength and delayed fracture characteristics, and is suitable as a structural material such as an automobile frame member and a reinforcing member.

引張強度と遅れ破壊強さの関係を示す図である。It is a figure which shows the relationship between tensile strength and delayed fracture strength. 本発明に基づく第1実施形態に係る製造工程を説明する図である。It is a figure explaining the manufacturing process which concerns on 1st Embodiment based on this invention. 加工部と未加工部とにおける水素放出の違いを示す図である。It is a figure which shows the difference in hydrogen discharge | release in a process part and an unprocessed part. 実施例の遅れ破壊の試験方法を説明する図である。It is a figure explaining the test method of the delayed fracture of an Example. 本発明に基づく第2実施形態に係る製造工程を説明する図である。It is a figure explaining the manufacturing process which concerns on 2nd Embodiment based on this invention.

(第1実施形態)
次に、本発明の第1実施形態について図面を参照しつつ説明する。
図2は、本実施形態の高強度部材の製造工程を示した概要図である。
(製造方法)
図2中、符号1は、引張強さTSが1320MPa以上の鋼板を示す。この鋼板1の製造例は後述する。
(First embodiment)
Next, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 2 is a schematic view showing a manufacturing process of the high-strength member of the present embodiment.
(Production method)
In FIG. 2, the code | symbol 1 shows the steel plate whose tensile strength TS is 1320 Mpa or more. An example of manufacturing the steel sheet 1 will be described later.

本実施形態の高強度部材TWの製造方法では、成形工程A、熱処理工程B及び化成処理・電着塗装工程Cを順に実施して、目的とする高強度部材TWを製造する。
上記成形工程Aでは、引張強さTSが1320MPa以上の鋼板1のコイルから、所要の長さの鋼板1を切り出し(送り出し機及びシャーについては不図示)、その切り出した鋼板1からなるワークWKについてプレス成形を行って、使用目的の形状に成形する。なお、成形の加工方法は、プレス成形に限定されず、ロール成形などによっても良い。所望の形状にするために、曲げや絞りなどの加工を施す工程であれば良い。
In the manufacturing method of the high strength member TW of this embodiment, the forming process A, the heat treatment process B, and the chemical conversion treatment / electrodeposition coating process C are sequentially performed to manufacture the target high strength member TW.
In the forming step A, a steel plate 1 having a required length is cut out from the coil of the steel plate 1 having a tensile strength TS of 1320 MPa or more (the feeder and shear are not shown), and the work WK made of the cut out steel plate 1 is used. Press molding to form the desired shape. The forming method is not limited to press forming, and may be roll forming or the like. What is necessary is just the process of giving a process, such as bending and drawing, in order to make it a desired shape.

熱処理工程Bでは、成形を施したワークWKに対し、100℃〜400℃の温度範囲で且つ1秒〜60分の熱処理時間で熱処理を施す。
化成処理・電着塗装工程Cでは、成形工程Aで目的の形状に成形し且つ熱処理工程Bで上記条件で熱処理を施したワークWKに対して、化成処理した後に電着塗装を行うことで、塗装処理を行う。
これによって、目的形状に成形されると共に熱処理が施され且つ塗装された高強度部材TWが製造されることになる。
In the heat treatment step B, the formed workpiece WK is heat treated in a temperature range of 100 ° C. to 400 ° C. and a heat treatment time of 1 second to 60 minutes.
In the chemical conversion treatment / electrodeposition coating step C, the electrodeposition coating is performed after the chemical conversion treatment on the workpiece WK that has been formed into the target shape in the molding step A and heat-treated in the heat treatment step B under the above conditions. Apply paint.
As a result, a high-strength member TW that has been molded into a target shape, heat-treated, and painted is manufactured.

(作用効果)
本発明者らは、上述の課題を解決すべく鋭意研究した。
まず、C:0.10〜0.40質量%、Si:0.01〜3.0質量%、Mn:0.5〜3.0質量%を含有する種々の鋼を鋳造し、更に熱間圧延、冷間圧延、焼鈍を実施して引張強さTSが1320MPa以上の鋼板1を製造した。その後、その引張強さTSが1320MPa以上の鋼板1について、種々の条件で加工を施して高強度部材TWを製造し、その高強度部材TWの遅れ破壊特性を調査した。その結果、非特許文献2と同様に、加工歪量の増加により遅れ破壊特性が劣化することを確認した。
(Function and effect)
The present inventors have intensively studied to solve the above problems.
First, various steels containing C: 0.10 to 0.40% by mass, Si: 0.01 to 3.0% by mass, Mn: 0.5 to 3.0% by mass, and further hot Rolling, cold rolling, and annealing were performed to produce a steel plate 1 having a tensile strength TS of 1320 MPa or more. Then, about the steel plate 1 whose tensile strength TS is 1320 Mpa or more, it processed on various conditions, manufactured the high strength member TW, and investigated the delayed fracture characteristic of the high strength member TW. As a result, as in Non-Patent Document 2, it was confirmed that delayed fracture characteristics deteriorate due to an increase in the amount of processing strain.

ここで、本発明者等は、加工により遅れ破壊特性が劣化する理由の一つとして、加工歪量の増加に伴い、侵入水素量が増加するためであると考えた。すなわち、加工により導入される転位がひずみ量と共に増加し、その転位が水素のトラップサイトになるためであると考えた。そこで、加工による水素侵入量の増加を抑制することができれば遅れ破壊特性の劣化を回避でき、加工後の遅れ破壊特性に優れると考え、種々検討を行った。その結果、加工後に100℃以上、好ましくは200℃以上の熱処理を施すことにより、侵入水素量が大きく低減され、それに伴い遅れ破壊特性が向上することを見出した。例えば、実験例の一例を図3に示す。この図3のように、未加工部分に比べ加工部分からの水素放出が多いことが分かる。すなわち加工により侵入水素量が増加していることが分かる。   Here, the present inventors considered that one of the reasons why the delayed fracture characteristics deteriorate due to machining is that the amount of invading hydrogen increases as the amount of processing strain increases. That is, it was considered that the dislocations introduced by processing increased with the amount of strain, and the dislocations became hydrogen trap sites. Therefore, various studies were conducted on the assumption that if the increase of the hydrogen penetration amount due to processing can be suppressed, the deterioration of delayed fracture characteristics can be avoided and the delayed fracture characteristics after processing are excellent. As a result, it has been found that by performing heat treatment at 100 ° C. or higher, preferably 200 ° C. or higher after processing, the amount of invading hydrogen is greatly reduced, and the delayed fracture characteristics are improved accordingly. For example, an example of an experimental example is shown in FIG. As shown in FIG. 3, it can be seen that more hydrogen is released from the processed portion than the unprocessed portion. That is, it can be seen that the amount of invading hydrogen is increased by processing.

また、自動車部品の製造工程を考慮すると、加工後、化成処理-電着塗装されて使用される場合は、引張強さTS1320MPa以上の超高強度鋼板では、実使用環境で腐食に伴い侵入する水素のみならず、化成処理-電着塗装時に侵入する水素によっても遅れ破壊する場合があり、化成処理-電着塗装中の遅れ破壊を回避するためには、加工後、化成処理-電着塗装前に100℃以上400℃以下で熱処理を施すことが有効であることを見出した。   Also, considering the manufacturing process of automobile parts, when used after being processed and subjected to chemical conversion treatment-electrodeposition coating, ultra high strength steel sheets with a tensile strength of TS1320 MPa or more are hydrogen that invades due to corrosion in the actual use environment. Not only chemical conversion treatment-hydrogen may intrude at the time of electrodeposition coating, but there may be delayed fracture. In order to avoid delayed fracture during chemical conversion treatment-electrodeposition coating, after processing, before chemical treatment-electrodeposition coating It has been found that it is effective to perform heat treatment at 100 ° C. or higher and 400 ° C. or lower.

そして、上述の高強度部材TWの製造方法において、化成処理・電着塗装工程Cの前に、上述の熱処理条件で熱処理を行うことで、耐遅れ破壊特性に優れる高強度部材TWを得ることが可能となる。
すなわち、鋼板1を高強度部材TWに加工する際の処理について工夫することによって、遅れ破壊特性に優れる高強度部材TWを提供することが出来る。つまり、引張強さTSが1320MPa以上の鋼板1を製造する際に、必ずしも、遅れ破壊特性を向上させるための特殊な成分添加や鋼組織の限定をする必要はない。
And in the manufacturing method of the above-mentioned high strength member TW, by performing heat treatment on the above-mentioned heat treatment conditions before chemical conversion treatment and electrodeposition coating process C, it is possible to obtain a high strength member TW having excellent delayed fracture resistance. It becomes possible.
That is, the high strength member TW which is excellent in delayed fracture characteristics can be provided by devising the processing when the steel plate 1 is processed into the high strength member TW. That is, when manufacturing the steel plate 1 having a tensile strength TS of 1320 MPa or more, it is not always necessary to add a special component or improve the steel structure for improving delayed fracture characteristics.

そして、本願発明により得られる高強度部材TWは、高強度と遅れ破壊特性を兼ね備えており、自動車骨格部材、補強部材等の構造材として好適な部材である。
ここで、加工後100℃以上の熱処理を施すことにより、水素の侵入が抑制され、遅れ破壊特性が改善される理由として、次のような理由が考えられる。すなわち、加工により導入された転位に対し、熱処理により固溶Cや固溶Nが固着し、水素の侵入サイトが減少したためであると考えられる。
The high-strength member TW obtained by the present invention has both high strength and delayed fracture characteristics, and is a member suitable as a structural material such as an automobile skeleton member and a reinforcing member.
Here, the following reasons can be considered as the reason why hydrogen penetration is suppressed and delayed fracture characteristics are improved by performing heat treatment at 100 ° C. or higher after processing. That is, it is considered that solute C or solute N was fixed by dislocation introduced by processing, and the hydrogen penetration sites were reduced.

(熱処理条件等について)
「熱処理温度について」
100℃未満では水素侵入抑制に要する時間が60分を越えて長時間となり、部材生産性が劣化する。このため、熱処理温度の下限値を100℃に設定した。
好ましくは150℃以上、より好ましくは200℃以上である。熱処理温度が高くなるにつれて、より短時間で侵入水素量を抑制可能となるからである。特に、200℃以上では、熱処理時間を10分程度以下とすることが可能となり、短時間の熱処理で十分な効果が得られることから、さらに好ましい。
(About heat treatment conditions)
About heat treatment temperature
If it is less than 100 ° C., the time required for suppressing hydrogen intrusion exceeds 60 minutes and becomes a long time, and the member productivity is deteriorated. For this reason, the lower limit of the heat treatment temperature was set to 100 ° C.
Preferably it is 150 degreeC or more, More preferably, it is 200 degreeC or more. This is because the amount of invading hydrogen can be suppressed in a shorter time as the heat treatment temperature increases. In particular, at 200 ° C. or higher, the heat treatment time can be reduced to about 10 minutes or less, and a sufficient effect can be obtained by a short heat treatment.

一方、400℃を超えると鋼板1の種類によっては強度が低下する場合がある。このため、熱処理温度の上限値を400℃とする。より好ましくは300℃以下である。
「熱処理時間について」
1秒未満では十分な水素侵入抑制の効果が得られない場合がある。このため、熱処理時間の下限値を1秒とした。水素侵入抑制の効果を十分得る為には、好ましくは30秒以上である。なお、この熱処理時間は、熱処理温度を高くするほど短くすることが出来る。
一方、60分を越えると生産性を阻害する。このため、熱処理時間の上限は60分とする。より好ましくは30分以下である。
On the other hand, when the temperature exceeds 400 ° C., the strength may decrease depending on the type of the steel plate 1. For this reason, the upper limit of heat processing temperature shall be 400 degreeC. More preferably, it is 300 degrees C or less.
“About heat treatment time”
If it is less than 1 second, there may be a case where sufficient effect of suppressing hydrogen intrusion cannot be obtained. For this reason, the lower limit of the heat treatment time is set to 1 second. In order to sufficiently obtain the effect of suppressing hydrogen intrusion, it is preferably 30 seconds or longer. This heat treatment time can be shortened as the heat treatment temperature is increased.
On the other hand, when it exceeds 60 minutes, productivity is inhibited. For this reason, the upper limit of the heat treatment time is 60 minutes. More preferably, it is 30 minutes or less.

「引張強さTSが1320MPa以上の鋼板1について」
本実施形態が前提とする素材としての鋼板1については、引張強さTSが1320MPa以上となるように製造されていれば良い。下記に鋼板1の組成例や製造方法について記載するが、本実施形態の高強度部材TWの製造方法は、素材となる鋼の組成や製造方法について、下記の内容に限定されるものではない。
“Regarding steel plate 1 having a tensile strength TS of 1320 MPa or more”
About the steel plate 1 as a raw material which this embodiment presupposes, it should just be manufactured so that tensile strength TS may be 1320 Mpa or more. Although the example of a composition and manufacturing method of the steel plate 1 are described below, the manufacturing method of the high strength member TW of this embodiment is not limited to the following content about the composition and manufacturing method of steel used as a raw material.

もっとも、引張強さTSとして1320MPa以上を確保するためには、Cは0.14質量%以上が好ましい。また、Cが0.5質量%を超えると靱性が低下する。このため、C量は0.14質量%以上0.5質量%以下が好ましい。
その他の元素の好ましい範囲は、次の通りである。
Si:3.0質量%以下、Mn:0.5〜3.0質量%、P:0.1質量%以下、S:0.01質量%以下、Al:0.01〜0.1質量%、N:0.02質量%以下、Ti:0.1質量%以下、Nb:0.1質量%以下、V:0.5質量%以下、Mo:0.5質量%以下、Cr:1質量%以下、B:0.005質量%以下、Cu:0.5質量%以下、Ni:0.5質量%以下、である。
However, in order to ensure 1320 MPa or more as the tensile strength TS, C is preferably 0.14% by mass or more. Moreover, when C exceeds 0.5 mass%, toughness will fall. For this reason, the amount of C is preferably 0.14% by mass or more and 0.5% by mass or less.
Preferred ranges of other elements are as follows.
Si: 3.0 mass% or less, Mn: 0.5-3.0 mass%, P: 0.1 mass% or less, S: 0.01 mass% or less, Al: 0.01-0.1 mass% N: 0.02 mass% or less, Ti: 0.1 mass% or less, Nb: 0.1 mass% or less, V: 0.5 mass% or less, Mo: 0.5 mass% or less, Cr: 1 mass %: B: 0.005 mass% or less, Cu: 0.5 mass% or less, Ni: 0.5 mass% or less.

上記以外の残部はFe及び不可避不純物とする。不可避的不純物としては、例えば、Sb、Sn、Zn、Co等が挙げられる。これらの不可避的不純物の含有量の許容範囲としては、Sb:0.01質量%以下、Sn:0.1質量%以下、Zn:0.01質量%以下、Co:0.1質量%以下の範囲である。またMg、Ca、Zr、REMについても通常の鋼組成の範囲内で含有しても、その効果は失われない。   The balance other than the above is Fe and inevitable impurities. Examples of inevitable impurities include Sb, Sn, Zn, and Co. As an allowable range of the content of these inevitable impurities, Sb: 0.01% by mass or less, Sn: 0.1% by mass or less, Zn: 0.01% by mass or less, Co: 0.1% by mass or less It is a range. Even if Mg, Ca, Zr, and REM are contained within the range of the normal steel composition, the effect is not lost.

なお、TiやNbなど、強固に炭化物や窒化物を形成する元素を添加する場合は、
Ti/48+Nb/93 < C/12+(N/14−Al/27)を満たすことが好ましい。Ti/48+Nb/93 ≧ C/12+(N/14−Al/27)となると、製造条件にもよるが、鋼板1製造後、加工前の状態で固溶CまたはNが全く無くなる場合があり、上述のような加工後の熱処理を施しても、水素侵入抑制の効果が得られない場合がある。
In addition, when adding an element that strongly forms carbide or nitride, such as Ti or Nb,
It is preferable to satisfy Ti / 48 + Nb / 93 <C / 12 + (N / 14−Al / 27). When Ti / 48 + Nb / 93 ≧ C / 12 + (N / 14−Al / 27), depending on the manufacturing conditions, there may be no solute C or N at all in the state before processing after manufacturing the steel plate 1, Even if the heat treatment after processing as described above is performed, the effect of suppressing hydrogen intrusion may not be obtained.

(素材となる鋼の製造方法について)
素材となる引張強さTSが1320MPa以上の鋼板1の製造方法の例について、説明する。なお、本実施形態の高強度部材TWの製造方法で使用する鋼板1の製造は、これに限定されるものではない。
(About the manufacturing method of steel used as material)
The example of the manufacturing method of the steel plate 1 whose tensile strength TS used as a raw material is 1320 Mpa or more is demonstrated. In addition, manufacture of the steel plate 1 used with the manufacturing method of the high strength member TW of this embodiment is not limited to this.

上述の化学成分範囲に調整された溶鋼から、連続鋳造または造塊でスラブを溶製し、その鋼スラブに、熱間圧延工程、冷間圧延工程、及び連続焼鈍工程を順次施す。
使用する鋼スラブは、成分のマクロ偏析を防止すべく連続鋳造法で製造することが好ましいが、造塊法、薄スラブ鋳造法によっても可能である。
熱間圧延工程について説明する。
From the molten steel adjusted to the above-mentioned chemical composition range, a slab is melted by continuous casting or ingot forming, and a hot rolling process, a cold rolling process, and a continuous annealing process are sequentially performed on the steel slab.
The steel slab to be used is preferably produced by a continuous casting method in order to prevent macro segregation of components, but can also be produced by an ingot-making method or a thin slab casting method.
A hot rolling process is demonstrated.

熱間圧延工程の好ましい条件は、まず、スラブ鋳造後、再加熱することなく若しくは1000℃以上に再加熱する。本実施形態では、スラブを製造したのち、いったん室温まで冷却し、その後再度加熱して圧延する。この従来法の代わりに、製造したスラブを冷却しないで、温片のままで加熱炉に装入する、あるいは保熱をおこなった後に、直ちに圧延する。あるいは鋳造後そのまま圧延する直送圧延・直接圧延などの省エネルギープロセスで行っても良い。いったん室温まで冷却し再加熱する場合、スラブ加熱温度は1000℃以上とするのが好ましい。上限は特に限定されないが、1300℃を超えると酸化重量の増加にともなうスケールロスが増大することなどから、1300℃以下とすることが好ましい。また、冷却しないで、温片のままで加熱炉に装入し再加熱する場合も、スラブ加熱温度は1000℃以上とするのが好ましい。   The preferable conditions for the hot rolling step are to first reheat to 1000 ° C. or higher without reheating after slab casting. In this embodiment, after manufacturing a slab, it is once cooled to room temperature, and then heated and rolled again. Instead of this conventional method, the manufactured slab is not cooled, but is charged as it is in a heating furnace, or is heated and then immediately rolled. Alternatively, it may be performed by an energy saving process such as direct feed rolling or direct rolling in which rolling is performed after casting. When it is once cooled to room temperature and reheated, the slab heating temperature is preferably 1000 ° C. or higher. The upper limit is not particularly limited, but if it exceeds 1300 ° C., the scale loss accompanying an increase in the oxidized weight increases, and therefore it is preferably 1300 ° C. or lower. Moreover, also when not heating and charging with a heating furnace with a warm piece and reheating, it is preferable that slab heating temperature shall be 1000 degreeC or more.

次いで、必要に応じて粗圧延を行った後、好ましくは仕上げ圧延温度:800℃以上で仕上げ圧延を行う。仕上げ圧延温度が800℃を下回ると、鋼板1の組織が不均一になり、加工性を劣化させる。よって、仕上げ圧延温度は800℃以上とするのが好ましい。上限は特に限定されないが、過度に高い温度で圧延するとスケール疵などの原因となるので、1000℃以下とすることが好ましい。
その後、700℃以下で巻き取る。700℃を超えると巻取り後に多量のスケールが生成し、冷間圧延前の酸洗の負荷が大きくなるため、700℃以下とするのが好ましい。
Next, after rough rolling as necessary, finish rolling is preferably performed at a finish rolling temperature of 800 ° C. or higher. When the finish rolling temperature is lower than 800 ° C., the structure of the steel sheet 1 becomes non-uniform and the workability is deteriorated. Therefore, the finish rolling temperature is preferably 800 ° C. or higher. The upper limit is not particularly limited, but if it is rolled at an excessively high temperature, scale wrinkles and the like are caused.
Then, it winds up at 700 degrees C or less. If it exceeds 700 ° C., a large amount of scale is generated after winding, and the load of pickling before cold rolling becomes large.

次に、冷間圧延工程について説明する。
熱間圧延により得られた熱延板に冷間圧延工程を施す。冷間圧延工程では、熱延板に冷間圧延を施し冷延板とする。冷間圧延条件は、所望の寸法形状の冷延板とすることができればよく、特に限定されないが、表面の平坦度や組織の均一性の観点から、圧下率20%以上とすることが好ましい。なお、冷間圧延前には、通常行われている酸洗を施せばよいが、熱延板表面のスケールが極めて薄い場合には直接冷間圧延を施してもよい。
Next, the cold rolling process will be described.
A cold rolling process is performed on the hot-rolled sheet obtained by hot rolling. In the cold rolling process, the hot rolled sheet is cold rolled to form a cold rolled sheet. The cold rolling condition is not particularly limited as long as it can be a cold-rolled sheet having a desired dimension and shape. However, the rolling reduction is preferably 20% or more from the viewpoint of the flatness of the surface and the uniformity of the structure. In addition, what is necessary is just to perform the pickling currently performed before cold rolling, but when the scale of a hot-rolled sheet surface is very thin, you may perform cold rolling directly.

次いで、冷間圧延によって得られた冷延板に連続焼鈍工程を施す。
連続焼鈍工程では、冷延板に焼鈍を施し冷延焼鈍板とする。焼鈍は、連続焼鈍ラインで行うことが好ましい。連続焼鈍工程では、750℃以上900℃以下の温度域に加熱保持することが好ましい。加熱保持温度が750℃未満では十分に再結晶が起こらず、加工性が低下する場合がある。一方、900℃を超えた場合には組織が粗大化し、強度加工性バランスが低下する。このため、加熱保持温度は750℃以上900℃以下が好ましい。また、加熱保持時間は、生産性の観点から600秒以下が好ましい。加熱保持時間の下限は、鋼板1の均一性の観点から60秒以上であることが好ましい。さらに好ましくは120秒以上である。次いで、平均冷却速度10℃/秒以上で300℃以下まで急冷することが好ましい。冷却速度が10℃/秒未満では、十分な強度を得るために合金元素を多量に添加する必要がありコストアップにつながる。さらに、急冷後そのまま、または室温まで冷却後に、100〜450℃で保持することが好ましい。また、その保持時間は3分〜30分であることが好ましい。
Next, a continuous annealing process is performed on the cold-rolled sheet obtained by cold rolling.
In the continuous annealing step, the cold-rolled sheet is annealed to form a cold-rolled annealed sheet. Annealing is preferably performed in a continuous annealing line. In the continuous annealing step, it is preferable to heat and hold in a temperature range of 750 ° C. to 900 ° C. When the heating and holding temperature is less than 750 ° C., recrystallization does not occur sufficiently, and workability may be reduced. On the other hand, when the temperature exceeds 900 ° C., the structure becomes coarse and the strength workability balance decreases. For this reason, the heating and holding temperature is preferably 750 ° C. or higher and 900 ° C. or lower. The heating and holding time is preferably 600 seconds or less from the viewpoint of productivity. The lower limit of the heating and holding time is preferably 60 seconds or more from the viewpoint of the uniformity of the steel sheet 1. More preferably, it is 120 seconds or more. Next, it is preferable to rapidly cool to 300 ° C. or less at an average cooling rate of 10 ° C./second or more. If the cooling rate is less than 10 ° C./second, it is necessary to add a large amount of alloy elements in order to obtain sufficient strength, leading to an increase in cost. Furthermore, it is preferable to hold at 100 to 450 ° C. as it is after rapid cooling or after cooling to room temperature. Further, the holding time is preferably 3 minutes to 30 minutes.

ここで、上記説明では、素材となる鋼板1として冷延鋼板を例示した。ただし、本実施形態の高強度部材TWの製造方法が前提とする、素材としての鋼板1は、冷延鋼板に限定されない。溶融亜鉛メッキ鋼板や電気亜鉛メッキ鋼板、熱延鋼板など、引張強さTSが1320MPa以上のあらゆる高強度鋼板1に適用可能である。
さらに、鋼板1製造後、耐食性改善のためにNi等を付着させるなど、表面改質処理を施してあっても、本発明の効果は問題なく得ることが出来る。また、鋼板1の製造後、形状矯正、表面粗度等の調整のために、伸び率5%以下の調質圧延を施してあってもよい。
Here, in the said description, the cold rolled steel plate was illustrated as the steel plate 1 used as a raw material. However, the steel plate 1 as a raw material on which the manufacturing method of the high-strength member TW of the present embodiment is based is not limited to a cold-rolled steel plate. The present invention can be applied to all high-strength steel plates 1 having a tensile strength TS of 1320 MPa or more, such as hot-dip galvanized steel plates, electrogalvanized steel plates, and hot-rolled steel plates.
Furthermore, the effect of the present invention can be obtained without problems even if a surface modification treatment such as attaching Ni or the like to improve corrosion resistance after the production of the steel sheet 1 is performed. Further, after the production of the steel sheet 1, temper rolling with an elongation of 5% or less may be performed for shape correction, adjustment of surface roughness and the like.

(変形例その他)
(1)本実施形態での高強度部材TWは、構造材として好適であり、また、自動車用途に限定されない。自動車用の高強度部材以外の家電および建築など、高強度および耐遅れ破壊特性が必要とされる分野においても好適である。
(Modifications and others)
(1) The high-strength member TW in the present embodiment is suitable as a structural material, and is not limited to automotive applications. It is also suitable in fields where high strength and delayed fracture resistance are required, such as home appliances and buildings other than high strength members for automobiles.

(2)本実施形態では、塗装前のワークWK全体を上述の条件で熱処理を行った。図3のように、少なくとも加工を施した部分に対して熱処理を施せば良い。従って、加工が複雑でない場合などにあっては、所定以上の曲げなどを施した部分だけに対して熱処理を施しても良い。 (2) In the present embodiment, the entire workpiece WK before coating is heat-treated under the above-described conditions. As shown in FIG. 3, heat treatment may be performed on at least a processed portion. Therefore, when the processing is not complicated, heat treatment may be performed only on a portion that has undergone bending or the like beyond a predetermined level.

(実施例1)
次に、第1実施形態に係る実施例について説明する。
この実施例で使用した鋼板1は、次のようにして製造した。
すなわち、表1に示す化学組成の鋼スラブを連続鋳造により製造し、1250℃に再加熱後、仕上げ圧延温度:約850℃、巻取り温度:約600℃で、板厚3.0mmまで熱間圧延を行った。
Example 1
Next, examples according to the first embodiment will be described.
The steel plate 1 used in this example was manufactured as follows.
That is, a steel slab having the chemical composition shown in Table 1 was manufactured by continuous casting, reheated to 1250 ° C., then finished rolling temperature: about 850 ° C., coiling temperature: about 600 ° C., and hot to a plate thickness of 3.0 mm. Rolled.

さらに酸洗後、冷間圧延を施して、板厚1.6mmの冷延板とし、次いで820℃〜900℃に300秒間加熱均熱し、550〜750℃まで徐冷(平均冷却速度:10℃/秒)の後、室温まで水冷し、150〜250℃で10分間焼戻し処理を施した。その後、伸び率:0.2%の調質圧延を施した。
そして、上述のようにして製造した鋼板1を用いて、引張強度、遅れ破壊特性を調査した。
各試験方法の詳細は以下の通りである。
Further, after pickling, cold rolling is performed to obtain a cold-rolled sheet having a thickness of 1.6 mm, followed by heating and soaking at 820 to 900 ° C. for 300 seconds, and then gradually cooling to 550 to 750 ° C. (average cooling rate: 10 ° C. After cooling to room temperature, a tempering treatment was performed at 150 to 250 ° C. for 10 minutes. Thereafter, temper rolling was performed at an elongation of 0.2%.
And the tensile strength and the delayed fracture characteristic were investigated using the steel plate 1 manufactured as mentioned above.
Details of each test method are as follows.

(引張強度の試験)
上記冷延鋼板1から、長軸を圧延方向に直交する方向としたJIS5号引張試験片を採取し、JIS Z 2241の規定に準拠して引張試験を行った。その引張試験により得られた引張強度(TS/MPa)の結果を、表2に示す。
(Tensile strength test)
From the cold-rolled steel sheet 1, a JIS No. 5 tensile test piece having a major axis in a direction perpendicular to the rolling direction was sampled, and a tensile test was performed in accordance with the provisions of JIS Z 2241. Table 2 shows the results of the tensile strength (TS / MPa) obtained by the tensile test.

更に、加工後の熱処理を模擬して、圧下率5%の圧延を施した後、塗装前に、表2に示す熱処理を施し、その後、引張試験を行い、引張強度(TS’/MPa)を測定した。
そして、加工及び熱処理による強度変化として、処理前後の引張強度差ΔTS(=TS’−TS)を求めた。この引張強度差ΔTSが、ゼロ以上の場合(強度低下が無い場合)を○、負の場合(強度低下する場合)を×として、その結果を表2に示す。
Furthermore, after simulating the heat treatment after processing and rolling at a reduction rate of 5%, before coating, the heat treatment shown in Table 2 is performed, and then a tensile test is performed to determine the tensile strength (TS ′ / MPa). It was measured.
And the tensile strength difference (DELTA) TS (= TS'-TS) before and behind a process was calculated | required as a strength change by a process and heat processing. Table 2 shows the results when the tensile strength difference ΔTS is greater than or equal to zero (when there is no strength reduction) and when it is negative (when the strength is reduced) as x.

(遅れ破壊特性の試験)
加工後の遅れ破壊特性の試験は、まず、上記冷延鋼板1から、図4(a)に示すような、長手を圧延方向に平行にして採取した100mm×30mmの試験片Hを用意する。そして、その試験片Hに対し、加工ひずみ量を変化させるため、表2に記載する種々の曲げ半径でU曲げ加工をした後、スプリングバック分をボルトで締付けることによって応力負荷する(図4(b)、(c))。
(Delayed fracture test)
For the test of delayed fracture characteristics after processing, first, a test piece H of 100 mm × 30 mm sampled from the cold-rolled steel sheet 1 with the length parallel to the rolling direction as shown in FIG. And in order to change the amount of processing distortion with respect to the test piece H, after carrying out U bending process with the various bending radii described in Table 2, it stress-loads by tightening a spring back part with a volt | bolt (FIG. 4 ( b), (c)).

次に、そのまま、または50〜410℃で熱処理を施し、更に、以下に示す条件で化成処理、電着塗装を実施し、化成処理、電着塗装中に破壊しなかった場合を○、破壊した場合を×とした。また、化成処理−電着塗装の試験片曲げ加工部の鋼中拡散性水素量を、昇温分析法(昇温速度200℃/h)により分析した。なお、拡散性水素は200℃以下で放出される水素量とした。遅れ破壊の有無、拡散性水素量を表2に示す。   Next, heat treatment was performed as it is or at 50 to 410 ° C., and further, chemical conversion treatment and electrodeposition coating were performed under the conditions shown below, and the case where it did not break during chemical conversion treatment and electrodeposition coating was broken. The case was marked with x. In addition, the amount of diffusible hydrogen in the steel in the test specimen bending portion of chemical conversion treatment-electrodeposition coating was analyzed by a temperature rising analysis method (temperature rising rate 200 ° C./h). The diffusible hydrogen was the amount of hydrogen released at 200 ° C. or lower. Table 2 shows the presence or absence of delayed fracture and the amount of diffusible hydrogen.

化成処理条件
市販の化成処理薬剤(日本パーカライジング株式会社製、パルボンドPB−L3020)を用いて浴温43℃、処理時間120秒で行った。
電着塗装条件
化成処理後の鋼板に市販の電着塗料(関西ペイント社製、GT−10HT)を用い塗膜厚が20〜25μmになるように電着塗装を施した。
Chemical conversion treatment conditions Commercially available chemical conversion chemicals (manufactured by Nippon Parkerizing Co., Ltd., Palbond PB-L3020) were used at a bath temperature of 43 ° C. for a treatment time of 120 seconds.
Electrodeposition conditions Electrodeposition coating was applied to the steel sheet after chemical conversion treatment using a commercially available electrodeposition paint (manufactured by Kansai Paint Co., Ltd., GT-10HT) so that the coating thickness was 20 to 25 μm.

表2から分かるように、加工後に熱処理を施すことで、化成処理−電着塗装中の侵入水素量が低下している。すなわち、本発明例は、いずれも破壊が発生しておらず、遅れ破壊特性に優れている。一方、加工後に熱処理を施していない、または熱処理温度が低い、実施例No.1、2、8、10は化成処理−電着塗装中に破壊が発生している。また、熱処理温度が本発明の上限を超えている実施例No.7では、化成処理−電着塗装中に破壊が発生しておらず、遅れ破壊特性には優れているが、加工および熱処理後の強度が元の強度に比べて低下してしまっている。   As can be seen from Table 2, the amount of intrusion hydrogen during chemical conversion treatment-electrodeposition coating is reduced by performing heat treatment after processing. That is, none of the examples of the present invention is broken and has excellent delayed fracture characteristics. On the other hand, no heat treatment was performed after processing, or the heat treatment temperature was low. Nos. 1, 2, 8, and 10 are broken during chemical conversion treatment-electrodeposition coating. Moreover, Example No. in which the heat treatment temperature exceeds the upper limit of the present invention. In No. 7, no breakage occurred during the chemical conversion treatment-electrodeposition coating, and the delayed fracture characteristics were excellent, but the strength after processing and heat treatment was lower than the original strength.

「第2実施形態」
次に、第2実施形態について図面を参照して説明する。なお、上記実施形態と同様な構成等については同一の符号を付して説明する。
本実施形態の高強度部材TWの製造方法は、基本的に、上記第1実施形態の製造方法と同様である。ただし、図2に示す工程のうち、熱処理工程Bを省略し、代わりに成形工程における成形を100℃〜400℃の温度範囲で行う点が異なる。その他は、上記第1実施形態で説明した内容と同じである。
“Second Embodiment”
Next, a second embodiment will be described with reference to the drawings. In addition, about the structure similar to the said embodiment, the same code | symbol is attached | subjected and demonstrated.
The manufacturing method of the high strength member TW of the present embodiment is basically the same as the manufacturing method of the first embodiment. However, in the process shown in FIG. 2, the heat treatment process B is omitted, and the molding in the molding process is performed in the temperature range of 100 ° C. to 400 ° C. instead. Others are the same as those described in the first embodiment.

すなわち、本実施形態の高強度部材TWの製造方法では、図5に示すように、成形工程A、及び化成処理・電着塗装工程Cを順に実施して、目的とする高強度部材TWを製造する。
上記成形工程Aでは、引張強さTSが1320MPa以上の鋼板1のコイルから、所要の長さの鋼板1を切り出し、その切り出した鋼板1からなるワークWKについて、100℃〜400℃の温度範囲でプレス成形を行って、使用目的の形状に成形する。なお、成形の加工方法は、プレス成形に限定されず、ロール成形などによっても良い。所望の形状にするために、曲げや絞りなどの加工を施す工程であれば良い。
That is, in the manufacturing method of the high-strength member TW of this embodiment, as shown in FIG. 5, the forming process A and the chemical conversion treatment / electrodeposition coating process C are sequentially performed to manufacture the target high-strength member TW. To do.
In the forming step A, the steel plate 1 having a required length is cut out from the coil of the steel plate 1 having a tensile strength TS of 1320 MPa or more, and the workpiece WK made of the cut out steel plate 1 is in a temperature range of 100 ° C. to 400 ° C. Press molding to form the desired shape. The forming method is not limited to press forming, and may be roll forming or the like. What is necessary is just the process of giving a process, such as bending and drawing, in order to make it a desired shape.

なお、素材となる鋼板1の組成や製造方法などについては、上記第1実施形態と同様である。
上記化成処理・電着塗装工程Cでは、成形工程Aで所定の温間状態で目的の形状に成形したワークWKに対し、化成処理した後に電着塗装を行うことで、塗装処理を行う。
これによって、目的形状に成形されると共に熱処理が施され且つ塗装された高強度部材TWが製造されることになる。
In addition, about the composition of the steel plate 1 used as a raw material, a manufacturing method, etc., it is the same as that of the said 1st Embodiment.
In the chemical conversion treatment / electrodeposition coating step C, the workpiece WK formed into a target shape in a predetermined warm state in the molding step A is subjected to a chemical conversion treatment and then an electrodeposition coating to perform the coating treatment.
As a result, a high-strength member TW that has been molded into a target shape, heat-treated, and painted is manufactured.

(作用効果など)
本発明者らは、第1実施形態のように加工後に100℃〜400℃で熱処理を施す代わりに、100℃〜400℃の温間で成形の加工を施すことにより、同様の効果が得られることを見出した。すなわち、加工を鋼板温度が100℃以上、好ましくは200℃以上の温度となる条件で施すことにより、侵入水素量が大きく低減され、それに伴い遅れ破壊特性が向上することを見出した。
(Effects etc.)
The present inventors can obtain the same effect by performing the forming process at a temperature of 100 ° C. to 400 ° C. instead of performing the heat treatment at 100 ° C. to 400 ° C. after the processing as in the first embodiment. I found out. That is, it has been found that by performing the processing under conditions where the steel sheet temperature is 100 ° C. or higher, preferably 200 ° C. or higher, the amount of invading hydrogen is greatly reduced, and the delayed fracture characteristics are improved accordingly.

また、自動車部品の製造工程を考慮すると、加工後、化成処理-電着塗装されて使用される場合は、引張強さTS1320MPa以上の超高強度鋼板では、実使用環境で腐食に伴い侵入する水素のみならず、化成処理-電着塗装時に侵入する水素によっても遅れ破壊する場合があり、化成処理-電着塗装中の遅れ破壊を回避するためには、100℃以上400℃以下で加工することが有効であることを見出した。そして、上述の高強度部材TWの製造方法において、温間で加工することで、耐遅れ破壊特性に優れる高強度部材TWを得ることが可能となる。   Also, considering the manufacturing process of automobile parts, when used after being processed and subjected to chemical conversion treatment-electrodeposition coating, ultra high strength steel sheets with a tensile strength of TS1320 MPa or more are hydrogen that invades due to corrosion in the actual use environment. Not only chemical conversion treatment-Electrodeposition coating may cause delayed fracture due to hydrogen intruding, and in order to avoid delayed fracture during chemical conversion treatment-electrodeposition coating, process at 100 ° C or more and 400 ° C or less. Was found to be effective. And in the manufacturing method of the above-mentioned high intensity | strength member TW, it becomes possible to obtain the high intensity | strength member TW which is excellent in a delayed fracture resistance by processing warmly.

すなわち、鋼板1を目的の形状に加工する際の鋼板温度について工夫することによって、遅れ破壊特性に優れる高強度部材TWを提供することが出来る。そして、引張強さTSが1320MPa以上の鋼板1を製造する際に、必ずしも、遅れ破壊特性を向上させるための特殊な成分添加や鋼組織の限定をする必要はない。
以上により、第2実施形態の製造方法により得られる高強度部材TWは、高強度と遅れ破壊特性を兼ね備えており、自動車骨格部材、補強部材等の構造材として好適な部材である。
That is, the high strength member TW which is excellent in delayed fracture characteristics can be provided by devising the steel plate temperature when processing the steel plate 1 into a desired shape. And when manufacturing the steel plate 1 whose tensile strength TS is 1320 MPa or more, it is not always necessary to add a special component or improve the steel structure to improve delayed fracture characteristics.
As described above, the high-strength member TW obtained by the manufacturing method of the second embodiment has both high strength and delayed fracture characteristics, and is a suitable member as a structural material such as an automobile skeleton member and a reinforcing member.

また、上述のような温間加工とすることにより、第1実施形態に比べて少ない工程数で、耐遅れ破壊特性に優れる高強度部材TWを、より効率よく製造することが可能である。   In addition, by performing the warm processing as described above, it is possible to more efficiently manufacture the high-strength member TW having excellent delayed fracture resistance with a smaller number of processes than in the first embodiment.

(温度条件などについて)
加工時の鋼板温度は、100℃未満では十分な水素侵入抑制効果が得られないため、下限値を100℃に設定した。加工温度が高くなるにつれて、水素侵入抑制効果が高まることから、好ましくは150℃以上、より好ましくは200℃以上である。一方、400℃を越えると、鋼板1の種類によっては強度が低下する場合がある。このため、熱処理温度の上限値を400℃とする、より好ましくは300℃以下である。
(About temperature conditions)
When the steel plate temperature during processing is less than 100 ° C., a sufficient hydrogen penetration suppressing effect cannot be obtained, so the lower limit value was set to 100 ° C. Since the effect of suppressing hydrogen penetration increases as the processing temperature increases, it is preferably 150 ° C. or higher, more preferably 200 ° C. or higher. On the other hand, when the temperature exceeds 400 ° C., the strength may decrease depending on the type of the steel plate 1. For this reason, the upper limit of heat processing temperature shall be 400 degreeC, More preferably, it is 300 degrees C or less.

また、加工時のひずみ速度は、遅いほど水素侵入抑制の効果が顕著に得られるが、通常のプレス加工のひずみ速度(0.1〜10/秒程度)で十分な効果が得られる。これは、第1実施形態のように加工後熱処理を施す場合は、固溶Cや固溶Nが転位まで拡散する必要があるが、第2実施形態のように温間で加工した場合には、加工中に転位が移動する際に固溶Cや固溶Nが転位に引きずられるため、より短時間であるにもかかわらず、固溶Cや固溶Nが転位に固着し、水素侵入抑制効果が得られたものと考えられる。好ましくは10/秒以下、より好ましくは1/秒以下である。   Further, the slower the strain rate during processing, the more remarkable the effect of suppressing hydrogen intrusion. However, a sufficient effect can be obtained at a normal strain rate (about 0.1 to 10 / second) of press working. This is because when the post-processing heat treatment is performed as in the first embodiment, the solid solution C or the solid solution N needs to diffuse to the dislocation, but when the processing is warm as in the second embodiment. In addition, since the solid solution C and solid solution N are dragged by the dislocation when the dislocation moves during processing, the solid solution C and solid solution N are fixed to the dislocation even though the time is shorter, and hydrogen penetration is suppressed. It is thought that the effect was obtained. Preferably it is 10 / second or less, more preferably 1 / second or less.

なお、鋼板を加熱する方法については、加工時に鋼板が所定の温度になっていればよく、特に規定しない。加熱炉などで鋼板を加熱し、炉から取り出して鋼板が所定の温度範囲の間に加工する方法でも、所定温度雰囲気下で保持中に加工する方法でも、構わない。
ここで、第2実施形態と第1実施形態とを併用しても構わない。すなわち、温間加工後に、そのまままたは一旦冷却後、100〜400℃で熱処理を施すと、更に効果が高まるのは勿論である。
In addition, about the method of heating a steel plate, the steel plate should just be predetermined temperature at the time of a process, and it does not prescribe | regulate in particular. A method of heating a steel plate in a heating furnace and taking out from the furnace and processing the steel plate during a predetermined temperature range or a method of processing while holding in a predetermined temperature atmosphere may be used.
Here, you may use together 2nd Embodiment and 1st Embodiment. That is, if the heat treatment is performed at 100 to 400 ° C. as it is or after being cooled after the warm working, it is a matter of course that the effect is further enhanced.

(実施例2)
次に、第2実施形態に係る実施例について説明する。
この実施例においても、上述の第1実施形態の実施例で説明したものと同じ条件で製造した鋼板1を試験片として使用した。
そして、上記試験片に対し、温間成形を模擬して、表3に示す条件で伸び率5%の温間引張変形を行い、除荷後空冷し、その後、室温で引張試験を行い、引張強度(TS’/MPa)を測定した。そして、温間変形による強度変化として、処理前後の引張強度差△TS(=TS’−TS)を求めた。この引張強度差△TSが、ゼロ以上の場合(強度低下が無い場合)を○、負の場合(強度低下する場合)を×として、その結果を表3に示す。
(Example 2)
Next, examples according to the second embodiment will be described.
Also in this example, the steel plate 1 manufactured under the same conditions as those described in the example of the first embodiment was used as a test piece.
The test piece was subjected to warm forming under the conditions shown in Table 3 under the conditions shown in Table 3, subjected to warm tensile deformation after unloading, then air-cooled, and then subjected to a tensile test at room temperature. The strength (TS ′ / MPa) was measured. And the tensile strength difference (DELTA) TS (= TS'-TS) before and behind a process was calculated | required as an intensity | strength change by warm deformation. The results are shown in Table 3 when the tensile strength difference ΔTS is zero or more (when there is no strength reduction) and when it is negative (when the strength decreases) x.

(遅れ破壊特性の試験)
加工後の遅れ破壊特性の試験は、まず、上記冷延鋼板1から、図4(a)に示すような、長手を圧延方向に平行にして採取した100mm×30mmの試験片Hを用意する。
その試験片Hに対し、50℃〜410℃の温度範囲で曲げ加工を施し、更に、以下に示す条件で、化成処理、電着塗装を施した。そして、化成処理、電着塗装中に破壊しなかった場合を○、破壊した場合を×とした。また、化成処理−電着塗装後の試験片曲げ加工部の鋼中拡散性水素量を、上記同様に昇温分析法により分析した。遅れ破壊の有無、拡散性水素量を表3に示す。
(Delayed fracture test)
For the test of delayed fracture characteristics after processing, first, a test piece H of 100 mm × 30 mm sampled from the cold-rolled steel sheet 1 with the length parallel to the rolling direction as shown in FIG.
The test piece H was bent in a temperature range of 50 ° C. to 410 ° C., and further subjected to chemical conversion treatment and electrodeposition coating under the following conditions. And the case where it did not destroy during chemical conversion treatment and electrodeposition coating was set as (circle), and the case where it destroyed was set as x. Moreover, the amount of diffusible hydrogen in the steel in the test piece bending part after chemical conversion treatment-electrodeposition coating was analyzed by the temperature rising analysis method as described above. Table 3 shows the presence or absence of delayed fracture and the amount of diffusible hydrogen.

化成処理条件
市販の化成処理薬剤(日本パーカライジング株式会社製、パルボンドPB−L3020)を用いて浴温43℃、処理時間120秒で行った。
電着塗装条件
化成処理後の鋼板に市販の電着塗料(関西ペイント社製、GT−10HT)を用い塗膜厚が20〜25μmになるように電着塗装を施した。
Chemical conversion treatment conditions Commercially available chemical conversion chemicals (manufactured by Nippon Parkerizing Co., Ltd., Palbond PB-L3020) were used at a bath temperature of 43 ° C. for a treatment time of 120 seconds.
Electrodeposition conditions Electrodeposition coating was applied to the steel sheet after chemical conversion treatment using a commercially available electrodeposition paint (manufactured by Kansai Paint Co., Ltd., GT-10HT) so that the coating thickness was 20 to 25 μm.

表3から分かるように、本願発明の温度に設定した温間で加工を施すことで、化成処理一電着塗装中の侵入水素量が低下している。すなわち、本発明例は、いずれも破壊が発生しておらず、遅れ破壊特性に優れている。   As can be seen from Table 3, the amount of intrusion hydrogen during chemical conversion treatment and one electrodeposition coating is reduced by processing at the temperature set to the temperature of the present invention. That is, none of the examples of the present invention is broken and has excellent delayed fracture characteristics.

一方、室温または加工温度が低い、実施例No.12、13、21、23では化成処理−電着塗装中に破壊が発生している。また、加工温度が本発明の上限を超えている実施例No.20では、化成処理−電着塗装中に破壊が発生しておらず、遅れ破壊特性には優れているが、加工後の強度が元の強度に比べて低下してしまっている。   On the other hand, Example No. with low room temperature or processing temperature. In 12, 13, 21, and 23, destruction occurred during chemical conversion treatment-electrodeposition coating. In addition, Example No. in which the processing temperature exceeds the upper limit of the present invention. In No. 20, no breakage occurred during the chemical conversion treatment-electrodeposition coating, and the delayed fracture characteristics were excellent, but the strength after processing was lower than the original strength.

1 鋼板
A 成形工程
B 熱処理工程
C 化成処理・電着塗装工程
TW 高強度部材
WK ワーク
1 Steel plate A Forming process B Heat treatment process C Chemical conversion treatment and electrodeposition coating process TW High-strength member WK Workpiece

Claims (3)

引張強さが1320MPa以上の鋼板を、目的の形状に成形した後に化成処理及び電着塗装を施す高強度部材の製造方法において、
上記鋼板を上記目的の形状に、ホットプレスを除く加工方法で成形する成形工程と、
上記成形工程で目的の形状に成形された鋼板を、100℃〜400℃の温度範囲で且つ1秒〜60分の熱処理時間で熱処理を施す熱処理工程と、
上記熱処理工程で熱処理を施した鋼板に対し化成処理した後に電着塗装を施す塗装工程と、を備えることを特徴とする高強度部材の製造方法。
In a method for producing a high-strength member in which a steel sheet having a tensile strength of 1320 MPa or more is formed into a desired shape and then subjected to chemical conversion treatment and electrodeposition coating,
A forming step of forming the steel sheet into the target shape by a processing method other than hot pressing,
A heat treatment step of subjecting the steel sheet formed into the target shape in the forming step to a heat treatment in a temperature range of 100 ° C. to 400 ° C. and a heat treatment time of 1 second to 60 minutes;
A high-strength member manufacturing method comprising: a coating step of subjecting the steel plate subjected to the heat treatment in the heat treatment step to a chemical conversion treatment followed by an electrodeposition coating.
上記熱処理工程での熱処理は、200℃〜400℃の温度範囲で且つ1秒〜10分の熱処理時間で熱処理を施すことを特徴とする請求項1に記載した高強度部材の製造方法。   The method for producing a high-strength member according to claim 1, wherein the heat treatment in the heat treatment step is performed in a temperature range of 200 ° C to 400 ° C and a heat treatment time of 1 second to 10 minutes. 引張強さが1320MPa以上の鋼板を、目的の形状に成形した後に化成処理及び電着塗装を施す高強度部材の製造方法において、
上記成形を、100℃〜400℃の温度範囲で施すことを特徴とする高強度部材の製造方法。
In a method for producing a high-strength member in which a steel sheet having a tensile strength of 1320 MPa or more is formed into a desired shape and then subjected to chemical conversion treatment and electrodeposition coating,
A method for producing a high-strength member, wherein the molding is performed in a temperature range of 100 ° C to 400 ° C.
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