JP4687554B2 - Steel plate for quenched member, quenched member and method for producing the same - Google Patents
Steel plate for quenched member, quenched member and method for producing the same Download PDFInfo
- Publication number
- JP4687554B2 JP4687554B2 JP2006131703A JP2006131703A JP4687554B2 JP 4687554 B2 JP4687554 B2 JP 4687554B2 JP 2006131703 A JP2006131703 A JP 2006131703A JP 2006131703 A JP2006131703 A JP 2006131703A JP 4687554 B2 JP4687554 B2 JP 4687554B2
- Authority
- JP
- Japan
- Prior art keywords
- steel sheet
- steel
- less
- hot
- quenching
- 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.)
- Active
Links
Description
本発明は、自動車のボデー構造部品、足回り部品等を始めとする機械構造部品等に好適な、焼入れ部材用鋼板及びその製造方法ならびに焼入れ鋼板部材及びその製造方法に関する。 The present invention relates to a steel plate for a quenching member and a manufacturing method thereof, and a quenching steel plate member and a manufacturing method thereof, which are suitable for machine structural components such as automobile body structural parts and undercarriage parts.
近年、自動車の軽量化のため、鋼材の高強度化を図り、使用重量を減ずる努力が進んでいる。自動車に広く使用される薄鋼板においては、鋼板強度の増加に伴って、プレス成形性が低下し、複雑な形状を製造することが困難になってきている。具体的には、延性が低下し、加工度が高い部位で破断が生じる、スプリングバックや壁反りが大きくなり、寸法精度が劣化する、といった問題が発生する。従って、高強度、特に７８０ＭＰａ級以上の引張強さ（以下、ＴＳとも表記する）を有する鋼板を用いて、プレス成形により部品を製造することは容易ではない。 In recent years, in order to reduce the weight of automobiles, efforts have been made to increase the strength of steel materials and reduce the weight used. In thin steel plates widely used in automobiles, press formability decreases with increasing steel plate strength, making it difficult to manufacture complex shapes. Specifically, there are problems that ductility is reduced, fracture occurs at a high degree of processing, springback and wall warp increase, and dimensional accuracy deteriorates. Therefore, it is not easy to produce a part by press molding using a steel plate having high strength, particularly a tensile strength of 780 MPa class or higher (hereinafter also referred to as TS).
このような問題を解決するため、特許文献１には、強度が必要な車体の特定箇所について、高強度鋼板を使用するのではなく、当該箇所を局部的に加熱して焼入れ処理を施すことにより強度を向上させる方法が開示されている。特許文献２には、ＴＳ１６２０ＭＰａ以上となる焼入れ型超高強度電縫鋼管及びその製造方法が開示されている。
しかし、これら従来法では、ＴＳが１.８ＧＰａ以上の部材については、靭性を確保する技術開示が不十分である。
本発明の具体的課題は、急速加熱焼入れ後、靱性に優れた、ＴＳが１.８ＧＰａ以上の部材を比較的容易に製造することを可能にする、焼入れ部材用鋼板及びその製造方法、さらにそれらの鋼板を用いて製造される、焼入れ鋼板部材、ならびにその製造方法を提供することである。
However, in these conventional methods, technical disclosure for securing toughness is insufficient for members having a TS of 1.8 GPa or more.
A specific problem of the present invention is a steel plate for a quenched member and a method for producing the same, which makes it possible to relatively easily produce a member having high toughness after TS of 1.8 GPa after rapid heating and quenching. It is providing the hardening steel plate member manufactured using this steel plate, and its manufacturing method.
本発明者らは、例えば急速加熱焼入れ後のＴＳが１.８ＧＰａ以上の焼入れ部材の靱性を改善すべく鋭意検討を行った結果、鋼板の化学組成、鋼板部材の金属組織の調整、必要により鋼板の金属組織の調整、焼入れ時のヒートパターンの適正化により、靱性が大幅に改善されることを知見した。その知見に基づき完成させた本発明は、次の通りである。 As a result of intensive studies to improve the toughness of a quenched member having a TS of 1.8 GPa or more after rapid heating and quenching, for example, the inventors have adjusted the chemical composition of the steel plate, the metal structure of the steel plate member, and if necessary, It was found that the toughness was greatly improved by adjusting the metal structure of the steel and optimizing the heat pattern during quenching. The present invention completed based on the knowledge is as follows.
(1) 質量％で、Ｃ：０.２６〜０.４５％、Ｍｎ＋Ｃｒ：０.５〜３.０％、Ｎｂ：０.０１〜１.０％、及びＢ：０.０００１〜０.０１％を含有し、さらにＳｉ：１％以下、Ｎｉ：２％以下、Ｃｕ：１％以下、Ｖ：１％以下及びＡｌ：１％以下の１種又は２種以上を含有し、残部Ｆｅ及び不純物からなる化学組成を有する焼入れ部材用鋼板であって、前記焼入れ部材は、焼入れ処理を施すことにより得られる引張強さ１.８ＧＰａ以上の焼入れ部材であり、前記焼入れ処理は、５０℃／秒以上の平均加熱速度で(Ａｃ ３ 点＋４０℃)〜（Ａｃ ３ 点＋２００℃）の温度域に加熱し、前記温度域で１０秒間以下保持したのちに焼入れを施す焼入れ処理であることを特徴とする焼入れ部材用鋼板。 (1) By mass%, C: 0.26 to 0.45%, Mn + Cr: 0.5 to 3.0%, Nb: 0.01 to 1.0%, and B: 0.0001 to 0.01 1% or less, Ni: 2% or less, Cu: 1% or less, V: 1% or less, and Al: 1% or less, and the balance Fe and impurities a quenching member for steel that have a chemical composition consisting of, the hardened member is a strength of 1.8GPa or more quenching member tension obtained by applying a quenching treatment, wherein the quenching treatment is 50 ° C. Heating at a temperature range of (Ac 3 points + 40 ° C.) to (Ac 3 points + 200 ° C.) at an average heating rate of at least / sec and holding for 10 seconds or less in the temperature range, followed by quenching treatment. A steel plate for hardened members .
(2)前記化学組成が、Ｆｅの一部に代えて、質量％で、Ｍｏ：１.０％以下を含有する。
(3)前記化学組成が、Ｆｅの一部に代えて、下記式(1)を満たす量のＴｉを含有する。
３.４２Ｎ＋０.００１≦Ｔｉ≦３.４２Ｎ＋０.５・・・（１）
ここで、式中のＴｉ及びＮは鋼中の各元素の含有量（単位：質量％）を示す。
(2) The chemical composition contains, by mass%, Mo: 1.0% or less instead of part of Fe.
(3) The chemical composition contains Ti in an amount satisfying the following formula (1) instead of a part of Fe.
3.42N + 0.001 ≦ Ti ≦ 3.42N + 0.5 (1)
Here, Ti and N in a formula show content (unit: mass%) of each element in steel.
(4)前記化学組成が、Ｆｅの一部に代えて、質量％で、Ｃａ：０.００１〜０.００５％を含有する。
(5)前記化学組成が、不純物であるＰ、Ｓ及びＮの１種又は２種以上の含有量に関して、質量％で、Ｐ：０.００５％以下、Ｓ：０.００５％以下及びＮ：０.００２％以下の１条件又は２条件以上を満足する。
(4) The chemical composition contains Ca: 0.001 to 0.005% in mass% instead of part of Fe.
(5) With respect to the content of one or more of P, S, and N as impurities, the chemical composition is P: 0.005% or less, S: 0.005% or less, and N: Satisfy one condition or more than two conditions of 0.002% or less.
上記(1)〜(5)のいずれかに記載の焼入れ部材用鋼板は、下記(6)〜(9)のいずれかの形態をとることができる。
(6)体積率で５０％以上のフェライトを含有する鋼組織を有し、引張強さが７８０ＭＰａ以下である機械特性を有する熱間圧延鋼板である。
The steel sheet for quenched member according to any one of the above (1) to (5) can take any of the following forms (6) to (9).
(6) A hot rolled steel sheet having a steel structure containing 50% or more of ferrite by volume and having mechanical properties of a tensile strength of 780 MPa or less.
(7)体積率で５０％以上のフェライトを含有する鋼組織を有し、引張強さが７８０〜１１８０ＭＰａである機械特性を有する、冷間圧延ままの冷間圧延鋼板である。
(8)体積率で５０％以上のフェライトを含有する鋼組織を有し、引張強さが７８０ＭＰａ以下である機械特性を有する、冷間圧延後に焼鈍が施された冷間圧延鋼板である。
(7) A cold-rolled steel sheet as cold-rolled, having a steel structure containing 50% or more of ferrite by volume and having mechanical properties of a tensile strength of 780 to 1180 MPa.
(8) A cold-rolled steel sheet having a steel structure containing 50% or more of ferrite by volume and having a mechanical property of a tensile strength of 780 MPa or less, which has been annealed after cold rolling.
(9)平均粒径が０.０１〜５.０μｍのセメンタイトが０.１個／μｍ2以上の密度で分散したフェライトからなる鋼組織を有し、引張強さが７８０ＭＰａ以下である機械特性を有する、冷間圧延後に焼鈍が施された冷間圧延鋼板である。 (9) Mechanical properties having a steel structure made of ferrite in which cementite having an average particle size of 0.01 to 5.0 μm is dispersed at a density of 0.1 piece / μm 2 or more and having a tensile strength of 780 MPa or less. A cold-rolled steel sheet that has been annealed after cold rolling.
(10)上記(1)〜(5)のいずれかに記載の化学組成を有する鋼塊又は鋼片を１０５０〜１３００℃としたのちに熱間圧延を施し、８００〜９５０℃で熱間圧延を完了し、５００〜７００℃で巻取ることを特徴とする、上記(6)に記載の焼入れ部材用鋼板の製造方法。 (10) Hot rolling is performed after setting the steel ingot or steel slab having the chemical composition according to any one of (1) to (5) above to 1050 to 1300 ° C, and hot rolling is performed at 800 to 950 ° C. The method for producing a steel plate for a quenched member according to (6), which is completed and wound at 500 to 700 ° C.
(11)上記(1)〜(5)のいずれかに記載の化学組成を有する鋼塊又は鋼片を１０５０〜１３００℃としたのちに熱間圧延を施し、８００〜９５０℃で熱間圧延を完了し、５００〜７００℃で巻取ることにより熱間圧延鋼板とし、前記熱間圧延鋼板に脱スケール処理と冷間圧延とを施すことを特徴とする、上記(7)に記載の焼入れ部材用鋼板の製造方法。 (11) Hot rolling is performed after setting the steel ingot or steel slab having the chemical composition according to any one of (1) to (5) above to 1050 to 1300 ° C, and hot rolling is performed at 800 to 950 ° C. It is completed, and it is made into a hot-rolled steel sheet by winding at 500 to 700 ° C., and subjected to descaling and cold rolling on the hot-rolled steel sheet, for the quenched member according to (7) above A method of manufacturing a steel sheet.
(12)上記(1)〜(5)のいずれかに記載の化学組成を有する鋼塊又は鋼片を１０５０〜１３００℃としたのちに熱間圧延を施し、８００〜９５０℃で熱間圧延を完了し、５００〜７００℃で巻取ることにより熱間圧延鋼板とし、前記熱間圧延鋼板に脱スケール処理と冷間圧延とを施し、次いで（ＡＣ１点＋１０℃）〜ＡＣ３点の温度域に１０秒間以上保持したのちに１〜１００℃／秒の平均冷却速度で３００〜５００℃の温度域まで冷却し、さらに３００〜５００℃の温度域に３０秒間〜１０分間保持し、その後に１〜１０℃／秒の平均冷却速度で室温まで冷却することを特徴とする、上記(8)に記載の焼入れ部材用鋼板の製造方法。 (12) Hot rolling is performed after setting the steel ingot or steel slab having the chemical composition according to any one of (1) to (5) above to 1050 to 1300 ° C, and hot rolling is performed at 800 to 950 ° C. Completion and winding at 500 to 700 ° C. to obtain a hot rolled steel sheet, descaling and cold rolling to the hot rolled steel sheet, and then the temperature range of (AC 1 point + 10 ° C.) to AC 3 point For 10 seconds or more, and then cooled to a temperature range of 300 to 500 ° C. at an average cooling rate of 1 to 100 ° C./second, and further maintained at a temperature range of 300 to 500 ° C. for 30 seconds to 10 minutes, and then 1 The method for producing a steel sheet for quenched member according to (8) above, wherein the steel sheet is cooled to room temperature at an average cooling rate of 10 ° C / second.
(13)上記(1)〜(5)のいずれかに記載の化学組成を有する鋼塊又は鋼片を１０５０〜１３００℃としたのちに熱間圧延を施し、８００〜９５０℃で熱間圧延を完了し、５００〜７００℃で巻取ることにより熱間圧延鋼板とし、前記熱間圧延鋼板に脱スケール処理と冷間圧延とを施し、次いで（ＡＣ１点−１００℃）〜（ＡＣ１点＋３０℃）の温度域に１〜２４時間保持したのちに１〜１００℃／時の平均冷却速度で室温まで冷却することを特徴とする、上記(9)に記載の焼入れ部材用鋼板の製造方法。 (13) Hot rolling is performed after setting the steel ingot or steel slab having the chemical composition according to any one of (1) to (5) above to 1050 to 1300 ° C, and hot rolling is performed at 800 to 950 ° C. It completes and it winds at 500-700 degreeC, it is set as a hot-rolled steel plate, The descaling process and cold rolling are given to the said hot-rolled steel plate, and then ( AC1 point-100 degreeC)-( AC1 point + 30) The method for producing a steel sheet for a quenched member according to (9) above, wherein the steel sheet is cooled to room temperature at an average cooling rate of 1 to 100 ° C./hour after being held in a temperature range of 1 ° C. for 1 to 24 hours.
(14)上記(1)〜(5)のいずれかに記載の化学組成を有し、その鋼組織が、旧オーステナイト平均粒径が２０μｍ以下であるマルテンサイトにより構成され、かつ引張強さが１.８ＧＰａ以上であり、さらに平均粒径が１〜２００ｎｍのＮｂ系炭化物を５０個／μｍ2以上含有することを特徴とする、焼入れ鋼板部材。 (14) The chemical composition according to any one of (1) to (5) above, wherein the steel structure is composed of martensite having a prior austenite average particle size of 20 μm or less, and a tensile strength of 1 Quenched steel sheet member characterized by containing 50 Nb / μm 2 or more of Nb-based carbide having an average particle size of 1 to 200 nm of 0.8 GPa or more.
(15)上記(1)〜(9)のいずれかに記載の鋼板を、５０℃／秒以上の平均加熱速度で(Ａｃ３点＋４０℃)〜（Ａｃ３点＋２００℃）の温度域に加熱し、前記温度域で１０秒間以下保持したのち、２００℃／秒以上の平均冷却速度でＭｓ点以下の温度域まで冷却することを特徴とする、上記(14)に記載の焼入れ鋼板部材の製造方法。 (15) Heating the steel sheet according to any one of (1) to (9) above to a temperature range of (Ac 3 points + 40 ° C.) to (Ac 3 points + 200 ° C.) at an average heating rate of 50 ° C./second or more. And maintaining the temperature range for 10 seconds or less, and then cooling to a temperature range below the Ms point at an average cooling rate of 200 ° C./second or more, wherein the quenched steel sheet member according to (14) is manufactured. Method.
次に、本発明において、各範囲に限定した理由について説明する。以後の説明で合金元素についての「％」は「質量％」を表す。
本発明における素地鋼板としての鋼板の化学組成については、以下のように規定する。
Next, the reason why the present invention is limited to each range will be described. In the following description, “%” for alloy elements represents “mass%”.
About the chemical composition of the steel plate as a base steel plate in this invention, it prescribes | regulates as follows.
Ｃ：０.２５〜０.４５％
Ｃは、鋼板の焼入れ性を高め、かつ焼入れ後強度を主に決定する非常に重要な元素である。特に、焼入れ後強度でＴＳ１.８ＧＰａ以上を確保するためには、Ｃ含有量を少なくとも０.２５％とする必要がある。一方で、Ｃ含有量が０.４５％を超えると、焼入れ後の強度が高くなりすぎるため、靱性劣化が著しくなる。望ましいＣ含有量は０.２８〜０.３３％である。
C: 0.25 to 0.45%
C is a very important element that enhances the hardenability of the steel sheet and mainly determines the strength after quenching. In particular, in order to ensure TS1.8 GPa or more in the strength after quenching, the C content needs to be at least 0.25%. On the other hand, if the C content exceeds 0.45%, the strength after quenching becomes too high, and the toughness deterioration becomes significant. A desirable C content is 0.28 to 0.33%.
Ｍｎ＋Ｃｒ：０.５〜３.０％
Ｍｎ及びＣｒは、鋼板の焼入れ性を高め、かつ焼入れ後強度を安定して確保するために、非常に効果のある元素である。しかし、Ｍｎ及びＣｒの合計含有量（以下、「（Ｍｎ＋Ｃｒ）含有量」ともいう。）が０.５％未満ではその効果は十分ではなく、一方で（Ｍｎ＋Ｃｒ）含有量が３.０％を超えるとその効果は飽和し、逆に安定した強度確保が困難となる。望ましい（Ｍｎ＋Ｃｒ）含有量は０.８〜２.０％である。
Mn + Cr: 0.5 to 3.0%
Mn and Cr are very effective elements in order to enhance the hardenability of the steel sheet and to ensure a stable strength after quenching. However, if the total content of Mn and Cr (hereinafter also referred to as “(Mn + Cr) content”) is less than 0.5%, the effect is not sufficient, while the (Mn + Cr) content is 3.0%. If it exceeds, the effect will be saturated, and it will be difficult to secure stable strength. Desirable (Mn + Cr) content is 0.8 to 2.0%.
Ｎｂ：０.０１〜１.０％
Ｎｂは、鋼板をＡｃ3点以上に加熱したときに、再結晶を抑制しかつ微細な炭化物を形成してオーステナイト粒を細粒にするため、靱性を大きく改善する効果を有する。このため、Ｎｂ含有量を０.０１％以上とする。一方で、Ｎｂ含有量が１.０％超になると、その効果は飽和し、いたずらにコスト増を招く。望ましいＮｂ含有量は０.０２〜０.１５％、さらに望ましくは０.０４〜０.１％である。
Nb: 0.01 to 1.0%
Nb has the effect of greatly improving toughness because it suppresses recrystallization and forms fine carbides to make austenite grains fine when the steel sheet is heated to Ac 3 point or higher. For this reason, Nb content shall be 0.01% or more. On the other hand, when the Nb content exceeds 1.0%, the effect is saturated, and the cost is unnecessarily increased. A desirable Nb content is 0.02 to 0.15%, and more desirably 0.04 to 0.1%.
Ｂ：０.０００１〜０.０１％
Ｂは、鋼板の焼入れ性を高め、かつ焼入れ後強度の安定確保効果をさらに高めるのに有効である。また、粒界に偏析して粒界強度を高め、靱性を向上させる点でも重要な元素である。さらに、加熱時のオーステナイト粒成長抑制効果も高い。このため、Ｂ含有量を０.０００１％以上とする。一方で、Ｂ含有量が０.０１％を超えるとその効果は飽和し、かつコスト増を招く。望ましいＢ含有量は０.００１０〜０.００３０％である。
B: 0.0001-0.01%
B is effective in enhancing the hardenability of the steel sheet and further enhancing the effect of ensuring the stability of the strength after quenching. It is also an important element in that it segregates at grain boundaries to increase grain boundary strength and improve toughness. Furthermore, the austenite grain growth inhibitory effect at the time of a heating is also high. For this reason, the B content is set to 0.0001% or more. On the other hand, when the B content exceeds 0.01%, the effect is saturated and the cost is increased. A desirable B content is 0.0001 to 0.0030%.
Ｓｉ：１％以下、Ｎｉ：２％以下、Ｃｕ：１％以下、Ｖ：１％以下、Ａｌ：１％以下
これらの元素は、鋼板の焼入れ性を高めかつ焼入れ後強度の安定確保に効果のある元素である。しかし、上限値以上に含有させてもその効果は小さく、かついたずらにコスト増を招くため、各合金元素の含有量は上述の範囲とする。
Si: 1% or less, Ni: 2% or less, Cu: 1% or less, V: 1% or less, Al: 1% or less These elements are effective in enhancing the hardenability of the steel sheet and ensuring stable strength after quenching. It is an element. However, since the effect is small even if it contains more than an upper limit, and it causes a cost increase unnecessarily, the content of each alloy element is set to the above range.
Ｍｏ：１.０％以下
Ｍｏは、任意添加元素であり、鋼板をＡｃ3点以上に加熱したときに、微細な炭化物を形成してオーステナイト粒を細粒にするため、靱性を大きく改善する効果を有する。しかしＭｏ含有量が１.０％超になると、その効果は飽和し、いたずらにコスト増を招く。より望ましいＭｏ含有量は０.０１〜０.２％であり、さらに望ましくは０.０４〜０.１５％である。
Mo: 1.0% or less Mo is an optional additive element. When the steel sheet is heated to Ac 3 point or higher, fine carbides are formed and the austenite grains are made finer, so that the toughness is greatly improved. Have However, when the Mo content exceeds 1.0%, the effect is saturated and the cost is increased unnecessarily. The more preferable Mo content is 0.01 to 0.2%, and still more preferably 0.04 to 0.15%.
３.４２Ｎ＋０.００１≦Ｔｉ≦３.４２Ｎ＋０.５
Ｔｉは、任意添加元素であり、鋼板をＡｃ3点以上に加熱したときに、再結晶を抑制し微細な炭化物を形成してオーステナイト粒を細粒にするため、靱性を大きく改善する効果を有する。かかる効果を確実に得るためにＴｉ含有量を（３.４２Ｎ＋０.００１）％以上とすることが好ましい。一方で、Ｔｉ含有量が（３.４２Ｎ＋０.５）％超になると、その効果は飽和し、いたずらにコスト増を招く。より望ましいＴｉ含有量は３.４２Ｎ＋０.０ ２≦Ｔｉ≦３.４２Ｎ＋０.０８である。
3.42N + 0.001 ≦ Ti ≦ 3.42N + 0.5
Ti is an optional additive element, and has the effect of greatly improving toughness because it suppresses recrystallization and forms fine carbides to make austenite grains fine when the steel sheet is heated to Ac 3 points or more. . In order to reliably obtain such an effect, the Ti content is preferably set to (3.42N + 0.001)% or more. On the other hand, when the Ti content exceeds (3.42N + 0.5)%, the effect is saturated and the cost is unnecessarily increased. A more desirable Ti content is 3.42N + 0.02 ≦ Ti ≦ 3.42N + 0.08.
Ｃａ：０.００１〜０.００５％
Ｃａは、任意添加元素であり、鋼中の介在物を微細化し、焼入れ後の靱性を向上させる効果を有する。かかる効果を確実に得るためにＣａ含有量を０.００１％以上とすることが好ましい。一方、Ｃａ含有量が０.００５％を超えるとその効果は飽和する。より望ましいＣａ含有量は０.００２〜０.００４％である。
Ca: 0.001 to 0.005%
Ca is an optional additive element, and has the effect of reducing the inclusions in the steel and improving the toughness after quenching. In order to ensure such an effect, the Ca content is preferably 0.001% or more. On the other hand, when the Ca content exceeds 0.005%, the effect is saturated. A more desirable Ca content is 0.002 to 0.004%.
Ｐ：０.００５％以下
Ｐは、焼入れ後の靱性を大きく劣化させる元素であるため、０.００５％以下とすることが好ましい。より望ましくは０.００３％以下である。
P: 0.005% or less Since P is an element that greatly deteriorates the toughness after quenching, it is preferably 0.005% or less. More desirably, it is 0.003% or less.
Ｓ：０.００５％以下
Ｓは、焼入れ後の靱性を大きく劣化させる元素であるため、０.００５％以下とすることが好ましい。より望ましくは０.００３％以下である。
S: 0.005% or less Since S is an element that greatly deteriorates the toughness after quenching, it is preferably 0.005% or less. More desirably, it is 0.003% or less.
Ｎ：０.００２％以下
Ｎは、鋼中にて介在物を形成し、焼入れ後の靱性を劣化させる元素であるため、０.００２％以下とすることが好ましい。より望ましくは０.００１％以下である。
N: 0.002% or less N is an element that forms inclusions in the steel and deteriorates the toughness after quenching, and therefore is preferably 0.002% or less. More desirably, it is 0.001% or less.
熱間圧延
上述した化学組成を有する鋼塊又は鋼片を、１０５０〜１３００℃としたのちに熱間圧延を施し、８００〜９５０℃で熱間圧延を完了し、５００〜７００℃で巻取りを行う。
Hot rolling The steel ingot or steel slab having the above-described chemical composition is subjected to hot rolling after being set to 1050 to 1300 ° C, hot rolling is completed at 800 to 950 ° C, and winding is performed at 500 to 700 ° C. Do.
鋼塊又は鋼片を１０５０〜１３００℃とするのは、加工性を劣化させる非金属介在物を十分に固溶させる必要があるためである。このような効果は、上述組成の本発明鋼板に対して、１０５０℃以上とすることで認められるが、１３００℃超としても効果が飽和するだけでなく、スケールロスが増加する。このため、熱間圧延に供する鋼塊又は鋼片の温度を１０５０℃〜１３００℃とする。望ましくは１０５０〜１２５０℃、さらに望ましくは１０５０〜１２００℃である。なお、熱間圧延に供する鋼塊又は鋼片の温度が１０５０〜１３００℃であればよく、１０５０℃未満となった鋼塊又は鋼片を加熱して１０５０〜１３００℃とする場合のみならず、連続鋳造後の鋼塊又は分塊圧延後の鋼片を１０５０℃未満に低下させることなく熱間圧延に供する場合も含まれる。 The reason why the steel ingot or the steel slab is set to 1050 to 1300 ° C. is because it is necessary to sufficiently dissolve nonmetallic inclusions that deteriorate the workability. Although such an effect is recognized by setting it as 1050 degreeC or more with respect to this invention steel plate of the above-mentioned composition, not only an effect will be saturated even if it exceeds 1300 degreeC, but a scale loss will increase. For this reason, the temperature of the steel ingot or steel slab used for hot rolling shall be 1050 degreeC-1300 degreeC. Preferably it is 1050-1250 degreeC, More preferably, it is 1050-1200 degreeC. In addition, the temperature of the steel ingot or steel slab used for hot rolling should just be 1050-1300 degreeC, and not only when heating the steel ingot or steel piece which became less than 1050 degreeC to 1050-1300 degreeC, The case where the steel ingot after continuous casting or the steel slab after partial rolling is subjected to hot rolling without being lowered to less than 1050 ° C. is also included.
熱間圧延完了温度については、Ａｒ３点未満にならないようにする必要がある。これはＡｒ３点未満で圧延を施すと加工フェライトが残存し、延性が大幅に劣化するためである。上述した化学組成の本発明鋼板では８００℃以上とすれば、これらの問題は生じない。一方、仕上げ圧延完了温度が９５０℃超になるとスケール噛み込み等の表面欠陥を生じる場合がある。したがって、熱間圧延完了温度を８００〜９５０℃とする。 The hot rolling completion temperature needs to be less than Ar 3 points. This is because when the rolling is performed at less than the Ar 3 point, the processed ferrite remains and the ductility is significantly deteriorated. In the steel plate of the present invention having the chemical composition described above, these problems do not occur if the temperature is set to 800 ° C. or higher. On the other hand, when the finish rolling completion temperature exceeds 950 ° C., surface defects such as scale biting may occur. Accordingly, the hot rolling completion temperature is set to 800 to 950 ° C.
巻取り温度については、その温度が低すぎると、パーライト、ベイナイト、マルテンサイトといった低温変態組織が多く生成し、フェライト組織が減少するため、鋼板強度が高くなってしまう。そのため下限温度を５００℃とする。一方、巻取り温度が高すぎると、酸化スケールが厚くなり、脱スケール処理が困難となるため、上限温度を７００℃とする。望ましくは５５０〜６５０℃である。 As for the coiling temperature, if the temperature is too low, many low temperature transformation structures such as pearlite, bainite and martensite are generated and the ferrite structure is decreased, so that the steel sheet strength is increased. Therefore, the lower limit temperature is set to 500 ° C. On the other hand, if the coiling temperature is too high, the oxide scale becomes thick and the descaling process becomes difficult, so the upper limit temperature is set to 700 ° C. Preferably it is 550-650 degreeC.
このようにして得られる熱間圧延鋼板は、鋼板を所望形状の部材へ加工する際の加工性確保の観点より、体積率で５０％以上のフェライトを含有する組織とし、ＴＳが７８０ＭＰａ以下とすることが好ましい。残部の組織には、パーライト、ベイナイト、マルテンサイト、又は残留オーステナイトのうち１種又は２種以上含まれていてもよい。なおフェライトには、セメンタイトといったＦｅ系炭化物やＴｉ系、Ｎｂ系、Ｍｏ系、Ｃｒ系、Ｖ系、Ｍｎ系炭化物が含まれていてもよい。また、鋼板強度については、より低強度のほうが望ましいが、コスト面や強度調整のしやすさといった点より、下限強度は５９０ＭＰａ程度とするのが望ましく、さらに望ましくは６９０ＭＰａ程度である。熱間圧延後は、通常は、酸洗、ショットブラスト、研削等の処理により、表面に生成したスケールの除去を行う。 The hot-rolled steel sheet thus obtained has a structure containing 50% or more ferrite by volume and TS of 780 MPa or less from the viewpoint of securing workability when processing the steel sheet into a member having a desired shape. It is preferable. The remaining structure may contain one or more of pearlite, bainite, martensite, or retained austenite. The ferrite may contain Fe-based carbides such as cementite, Ti-based, Nb-based, Mo-based, Cr-based, V-based, and Mn-based carbides. The steel plate strength is preferably lower, but the lower limit strength is preferably about 590 MPa, and more preferably about 690 MPa from the viewpoint of cost and ease of strength adjustment. After hot rolling, the scale generated on the surface is usually removed by treatments such as pickling, shot blasting, and grinding.
冷間圧延
上述の熱間圧延された鋼板に、冷間圧延を施して冷間圧延ままの鋼板として使用する場合には、鋼板を所望形状の部材へ加工する際の成形性確保の観点より、体積率で５０％以上のフェライトを含有する組織とし、ＴＳを１１８０ＭＰａ以下とすることが好ましい。鋼板強度については、より低強度のほうが望ましいが、コスト面や強度調整のしやすさといった点より、ＴＳを７８０ＭＰａ以上とすることが好ましい。より望ましくは、ＴＳ：７８０〜１１００ＭＰａ、さらに望ましくはＴＳ：７８０〜１０５０ＭＰａである。また冷間圧延時の圧下率は、３０〜８０％とするのが望ましく、より望ましくは４０〜７０％である。
Cold Rolling When using the steel sheet that has been cold-rolled and subjected to cold rolling as described above, from the viewpoint of securing formability when processing the steel sheet into a member having a desired shape, It is preferable to use a structure containing 50% or more by volume of ferrite and TS to 1180 MPa or less. Regarding the steel plate strength, lower strength is desirable, but TS is preferably set to 780 MPa or more from the viewpoint of cost and ease of strength adjustment. More preferably, it is TS: 780-1100MPa, More preferably, it is TS: 780-1050MPa. The rolling reduction during cold rolling is desirably 30 to 80%, and more desirably 40 to 70%.
焼鈍方法
上述の冷間圧延された鋼板に、連続焼鈍を施す場合には、（ＡＣ１点＋１０℃）以上、ＡＣ３点以下に加熱し、その温度域で１０秒間以上保時したのち、1〜１００℃／秒の平均冷却速度で３００〜５００℃の温度域まで冷却し、さらに３００〜５００℃の温度域に３０秒間から１０分間以上保持し、その後に１〜１０℃／秒の平均冷却速度で室温まで冷却する。
The annealing process of cold rolled steel sheets described above, when subjected to continuous annealing, (A C1 point + 10 ° C.) or higher, and heated below C3 points A, After intersubunit at that temperature range for more than 10 seconds, 1 Cool to a temperature range of 300 to 500 ° C. at an average cooling rate of ˜100 ° C./second, and hold at a temperature range of 300 to 500 ° C. for 30 seconds to 10 minutes or more, and then average cooling of 1 to 10 ° C./second Cool to room temperature at speed.
（ＡＣ１点＋１０℃）以上、ＡＣ３点以下に加熱するのは、（ＡＣ１点＋１０℃）より低い温度では、再結晶が十分に進行せず、鋼板強度が高くなりやすいという問題があり、一方、ＡＣ３点より高い温度では、オーステナイト単相化に起因して、冷却中に低温変態相が生成しやすく、鋼板強度が高くなりやすいという問題があるためである。保持時間１０秒間以上としたのは、保持時間が１０秒間より短くなると、置換型元素であるＭｎ等の偏析が残り、焼鈍板の組織が不均一となるためである。なお、長時間加熱はいたずらにコスト増を招くため、保持時間は３００秒間以下とするのが望ましい。なお、焼鈍雰囲気は非酸化性雰囲気（たとえば９８体積％Ｎ２＋２体積％Ｈ２）とすることが好ましい。 Heating to ( AC1 point + 10 ° C) or more and AC3 point or less has a problem that recrystallization does not proceed sufficiently at a temperature lower than ( AC1 point + 10 ° C), and the steel sheet strength tends to increase. On the other hand, at a temperature higher than the AC3 point, due to the austenite single phase, there is a problem that a low temperature transformation phase is likely to be generated during cooling, and the strength of the steel sheet tends to be high. The reason why the holding time is 10 seconds or more is that when the holding time is shorter than 10 seconds, segregation of substitutional elements such as Mn remains and the structure of the annealed plate becomes non-uniform. In addition, since long-time heating unnecessarily increases the cost, the holding time is desirably 300 seconds or less. The annealing atmosphere is preferably a non-oxidizing atmosphere (for example, 98 volume% N 2 +2 volume% H 2 ).
平均冷却速度を１〜１００℃／秒としたのは、冷却が速すぎると、低温変態相が多く生成し、フェライトが減少して鋼板強度が高くなりすぎてしまうという問題があり、一方冷却が遅すぎると、生産効率が落ちてしまうという問題があるためである。望ましくは１〜２０℃／秒であり、さらに望ましくは１〜１０℃／秒である。また冷却停止温度域を３００〜５００℃としたのは、低温変態相の生成をできるだけ抑制するためである。より望ましくは、３５０〜５００℃、さらに望ましくは４００〜４５０℃である。また冷却停止温度域で３０秒間〜１０分間保持するのは、未変態オーステナイトのフェライト変態を促進するためである。より望ましい保持時間は３０秒間〜５分間、さらに望ましくは３０秒間〜３分間である。 The average cooling rate of 1 to 100 ° C./second is that if the cooling is too fast, a lot of low-temperature transformation phases are generated, and the ferrite is reduced and the steel sheet strength becomes too high. This is because if it is too slow, there is a problem in that the production efficiency falls. It is desirably 1 to 20 ° C./second, and more desirably 1 to 10 ° C./second. The reason why the cooling stop temperature range is set to 300 to 500 ° C. is to suppress the generation of the low temperature transformation phase as much as possible. More preferably, it is 350-500 degreeC, More preferably, it is 400-450 degreeC. The reason why the temperature is maintained for 30 seconds to 10 minutes in the cooling stop temperature range is to promote the ferrite transformation of untransformed austenite. A more desirable holding time is 30 seconds to 5 minutes, and further desirably 30 seconds to 3 minutes.
このようにして得られる冷間圧延後に連続焼鈍が施された冷間圧延鋼板は、鋼板を所望形状の部材へ加工する際の成形性確保の観点より、体積率で５０％以上のフェライトを含有する組織とし、ＴＳを７８０ＭＰａ以下とすることが好ましい。より低強度のほうが望ましいが、コスト面や強度調整のしやすさといった点より、下限強度は４４０ＭＰａ程度とするのが望ましい。 The cold-rolled steel sheet subjected to continuous annealing after cold rolling thus obtained contains 50% or more ferrite by volume from the viewpoint of ensuring formability when processing the steel sheet into a member having a desired shape. It is preferable that the TS be 780 MPa or less. Although lower strength is desirable, the lower limit strength is desirably about 440 MPa from the viewpoints of cost and ease of strength adjustment.
上述の冷間圧延された鋼板に、箱焼鈍を施す場合には、（ＡＣ１点−１００℃）以上（ＡＣ１点＋３０℃）以下の温度域に１〜２４時間保持したのち、１〜１００℃／時の平均冷却速度で室温まで冷却する。 The cold rolled steel sheet described above, when subjected to box annealing, after holding for 1 to 24 hours in the following temperature range (A C1 point -100 ° C.) or higher (A C1 point + 30 ° C.), 1 to 100 Cool to room temperature at an average cooling rate of ° C / hour.
保持温度が（ＡＣ１点−１００℃）より低い場合では、鋼板強度が十分に低下しないという問題があり、一方、（ＡＣ１点＋３０℃）より高い温度では、セメンタイトの再固溶−逆変態が進行し過ぎ、その後の冷却過程で低温変態相が生成し、鋼板強度が高くなりやすいという問題があるので、（ＡＣ１点−１００℃）以上（ＡＣ１点＋３０℃）以下の温度域とする。 When the holding temperature is lower than ( AC1 point−100 ° C.), there is a problem that the strength of the steel sheet is not sufficiently lowered. On the other hand, when the holding temperature is higher than ( AC1 point + 30 ° C.), the re-solution-reverse transformation of cementite. there proceeds excessively, to generate the low-temperature transformation phase in the subsequent cooling process, there is a problem that strength of the steel sheet tends to increase, and the temperature range below (a C1 point -100 ° C.) or higher (a C1 point + 30 ° C.) To do.
また、保持時間については、１時間未満では鋼板強度の低下が十分ではなく、一方、２４時間を超えても効果は飽和し、いたずらにエネルギーの浪費を招くので、１〜２４時間とする。また焼鈍後の冷却過程では、冷却速度が速いと低温変態相が生成するため、できるだけ遅いほうが好ましい。しかし遅すぎると処理効率の低下をいたずらに招くだけであるため、冷却速度は１〜１００℃／時とする。望ましくは１〜５０℃／時である。 The holding time is set to 1 to 24 hours because the steel plate strength is not sufficiently lowered when the holding time is less than 1 hour, and the effect is saturated and energy is wasted even if it exceeds 24 hours. Further, in the cooling process after annealing, a low-temperature transformation phase is generated when the cooling rate is high, so that it is preferable to be as slow as possible. However, if it is too slow, it will only cause a decrease in the processing efficiency. Therefore, the cooling rate is 1 to 100 ° C./hour. 1 to 50 ° C./hour is desirable.
なお、焼鈍処理時の炉内雰囲気は、窒素ガスの混入が少なく、露点ができるだけ低い、水素を９５容積％以上含むガスであるほうが好ましい。
このようにして得られる冷間圧延後に箱焼鈍が施された冷間圧延鋼板は、鋼板を所望形状の部材へ加工する際の成形性確保の観点より、体積率で５０％以上のフェライトを含有する組織とし、ＴＳを５９０ＭＰａ以下とすることが好ましい。より低強度のほうが望ましいが、コスト面や強度調整のしやすさといった点より、下限強度は４４０ＭＰａ程度とするのが望ましい。また、平均粒径０.０１〜５.０μｍのセメンタイトが０.１個／μｍ2以上の密度で分散したフェライト組織とすることが好ましい。
Note that the atmosphere in the furnace during the annealing treatment is preferably a gas containing 95% by volume or more of hydrogen with little nitrogen gas mixing and the lowest dew point.
The cold-rolled steel sheet subjected to box annealing after cold rolling thus obtained contains 50% or more ferrite by volume from the viewpoint of securing formability when processing the steel sheet into a member having a desired shape. It is preferable that TS be 590 MPa or less. Although lower strength is desirable, the lower limit strength is desirably about 440 MPa from the viewpoints of cost and ease of strength adjustment. Further, it is preferable to have a ferrite structure in which cementite having an average particle diameter of 0.01 to 5.0 μm is dispersed at a density of 0.1 / μm 2 or more.
鋼板組織を、平均粒径０.０１〜５.０μｍであるセメンタイトが０.１個／μｍ2以上の密度で分散したフェライト組織とするのは、焼入れ前の加熱時に、ピン止め効果を利用して、オーステナイト粒を細粒にするためである。セメンタイトの平均粒径及び密度が下限値未満では、加熱時に速やかに溶解するため、その効果が十分に発揮されない。一方、セメンタイトの平均粒径及び密度が上限値を超えると、セメンタイトが焼入れ前の加熱時に未溶解炭化物として残存し、部材の靭性劣化や延性劣化を招くので、上述の範囲とする。より望ましい平均粒径は、０.０１〜４.０μｍ、さらに望ましくは０.０１〜３.０μｍである。セメンタイトの密度は、単位面積当たりの個数で、望ましくは、０.１５個／μｍ2以上、さらに望ましくは０.２個／μｍ2以上である。 The steel structure is a ferrite structure in which cementite having an average particle size of 0.01 to 5.0 μm is dispersed at a density of 0.1 piece / μm 2 or more because of the pinning effect during heating before quenching. This is to make the austenite grains fine. When the average particle diameter and density of cementite are less than the lower limit, the effect is not sufficiently exhibited because the cementite dissolves rapidly during heating. On the other hand, when the average particle diameter and density of cementite exceed the upper limit values, cementite remains as undissolved carbide during heating before quenching and causes toughness deterioration and ductility deterioration of the member. A more preferable average particle diameter is 0.01 to 4.0 μm, and more preferably 0.01 to 3.0 μm. The density of cementite is preferably the number per unit area, preferably 0.15 pieces / μm 2 or more, more preferably 0.2 pieces / μm 2 or more.
本発明の焼入れ鋼板部材は、ＴＳが１.８ＧＰａ以上の強度下で靱性を確保するために、旧オーステナイト平均粒径が２０μｍ以下であり、かつ平均粒径が１〜２００ｎｍのＮｂ系炭化物を５０個／μｍ2以上含有するマルテンサイト組織とする。旧オーステナイト平均粒径は、望ましくは１５μｍ以下、より望ましくは１０μｍ以下、さらに望ましくは５μm以下である。またＮｂ系炭化物の平均粒径は、望ましくは１〜１５０ｎｍ、さらに望ましくは１〜１００ｎｍである。Ｎｂ系炭化物の密度は、単位面積当たりの個数で、望ましくは１００個／μｍ2以上、さらに望ましくは１５０個／μｍ2以上である。旧オーステナイト平均粒径、Ｎｂ系炭化物の平均粒径及び単位面積当たりの個数は、次に説明するように、焼入れ前の加熱条件に依存して変化する。 In order to ensure toughness under the strength of TS of 1.8 GPa or more, the quenched steel sheet member of the present invention is made of 50 Nb carbide having a prior austenite average particle diameter of 20 μm or less and an average particle diameter of 1 to 200 nm. Martensite structure containing 1 piece / μm 2 or more. The prior austenite average particle diameter is desirably 15 μm or less, more desirably 10 μm or less, and still more desirably 5 μm or less. The average particle size of the Nb carbide is preferably 1 to 150 nm, and more preferably 1 to 100 nm. The density of the Nb-based carbide is preferably 100 / μm 2 or more, more preferably 150 / μm 2 or more, per unit area. The prior austenite average particle diameter, the average particle diameter of the Nb-based carbide, and the number per unit area vary depending on the heating conditions before quenching, as will be described below.
本発明によれば、上記鋼板に対して焼入れを行うが、そのときの焼入れ前の好適な加熱条件は次の通りである。
焼入れ工程においては、目的とする強度と靱性を得るために、焼入れに供する鋼板を、（Ａｃ3点＋４０℃）以上（Ａｃ3点＋２００℃）以下の温度域に５０℃／秒以上の平均加熱速度で加熱し、その温度域で１０秒間以下の時間保持することが好ましい。保持温度の下限は、一旦オーステナイト単相として目的とする強度を得るのと、靭性を確保するためである。一方、保持温度の上限及び加熱速度の下限は、焼入れ後の旧オーステナイト粒径を２０μｍ以下、Ｎｂ系炭化物の平均粒径及び単位面積当たりの個数を上述の範囲として、ＴＳが１.８ＧＰａ以上の強度下で靱性をより確実に確保するためである。より望ましい保持温度は、（Ａｃ3点＋８０℃）以上、（Ａｃ3点＋１８０℃）以下、より望ましい加熱速度は１００℃／秒以上である。冷却速度については、マルテンサイト組織にするために、上部臨界冷却速度以上で冷却すればよく、水冷や油冷により２００℃／秒以上とすれば、本発明鋼板では十分である。
According to the present invention, the steel sheet is quenched, and suitable heating conditions before quenching are as follows.
In the quenching process, in order to obtain the intended strength and toughness, the steel sheet to be quenched is heated to an average temperature of 50 ° C./second or more in a temperature range of (Ac 3 points + 40 ° C.) to (Ac 3 points + 200 ° C.). It is preferable to heat at a speed and hold for 10 seconds or less in that temperature range. The lower limit of the holding temperature is to obtain the intended strength once as an austenite single phase and to secure toughness. On the other hand, the upper limit of the holding temperature and the lower limit of the heating rate are as follows. This is to ensure the toughness more reliably under the strength. A more desirable holding temperature is (Ac 3 point + 80 ° C.) or more and (Ac 3 point + 180 ° C.) or less, and a more desirable heating rate is 100 ° C./second or more. As for the cooling rate, in order to obtain a martensite structure, it is sufficient to cool at an upper critical cooling rate or higher, and if it is set to 200 ° C./second or higher by water cooling or oil cooling, the steel sheet of the present invention is sufficient.
本発明の好適な加熱方法としては、急速加熱及び急速冷却を達成する方法であれば、どのような方法を採用してもよい。例えば、高周波加熱焼入れ法や通電加熱焼入れ法等が挙げられる。 As a suitable heating method of the present invention, any method may be adopted as long as rapid heating and rapid cooling are achieved. For example, an induction heating quenching method or an electric heating quenching method can be used.
また、本発明の焼入れ部材用鋼板及び焼入れ鋼板部材は、耐食性付与等を目的として鋼板表面にめっき被膜を備えることができる。めっき被膜としては、Ｚｎ系めっき、Ａｌ系めっき等が挙げられる。 Moreover, the steel plate for hardened members and the hardened steel plate member of the present invention can be provided with a plating film on the steel plate surface for the purpose of imparting corrosion resistance and the like. Examples of the plating film include Zn-based plating and Al-based plating.
以下に本発明の実施例について説明する。
表１に示す化学組成を有する鋼板（板厚：１.４ｍｍ）を素地鋼板とした。これらの鋼板は、実験室にて溶製したスラブを、表２に示す条件で加熱後、熱間圧延し、その後、一部の鋼板について冷間圧延又は冷間圧延後に焼鈍処理を施して製造した鋼板である。なお、連続焼鈍における加熱温度からの１次冷却の平均冷却速度を１０℃／秒、室温までの２次冷却の平均冷却速度を５℃／秒、箱焼鈍後における冷却速度を２０℃／時とした。
Examples of the present invention will be described below.
A steel plate (plate thickness: 1.4 mm) having the chemical composition shown in Table 1 was used as the base steel plate. These steel plates are manufactured by subjecting a slab melted in the laboratory to hot rolling after heating under the conditions shown in Table 2, and then subjecting some of the steel plates to an annealing treatment after cold rolling or cold rolling. Steel plate. The average cooling rate of primary cooling from the heating temperature in continuous annealing is 10 ° C./second, the average cooling rate of secondary cooling to room temperature is 5 ° C./second, and the cooling rate after box annealing is 20 ° C./hour. did.
上述の鋼板から、１.４ｔ×１５ｗ×２００Ｌのサイズの試験片を切断して採取し、表３に記載の加熱条件にて通電加熱した後、直ちに水冷することで焼入れた。焼入れた部位から各種試験片を採取し、断面組織観察、切断法による旧オーステナイト粒径測定、引張試験（ＪＩＳ１３号Ｂ試験片）、シャルピー衝撃試験、析出物粒径測定及び密度測定に供した。試験結果も表３に示す。 A test piece having a size of 1.4 t × 15 w × 200 L was cut and collected from the steel plate described above, energized and heated under the heating conditions shown in Table 3, and then immediately quenched with water. Various test pieces were collected from the quenched part, and subjected to cross-sectional structure observation, old austenite particle size measurement by cutting method, tensile test (JIS No. 13 B test piece), Charpy impact test, precipitate particle size measurement and density measurement. The test results are also shown in Table 3.
各相の組織分率は、断面の光学顕微鏡観察画像又は電子顕微鏡観察画像より、画像解析を行って算出した。
析出物粒径と密度の測定は、電子顕微鏡のレプリカ法を採用し、各試料につき倍率１０万倍で５視野を撮影し、円換算粒径で算出した後、析出物の全個数を測定し、その個数を撮影視野の面積で割り、規格化することにより密度を算出した。
The tissue fraction of each phase was calculated by performing image analysis from an optical microscope observation image or an electron microscope observation image of the cross section.
The particle size and density of the precipitates were measured using the electron microscope replica method, taking five fields of view for each sample at a magnification of 100,000, calculating the circularly converted particle size, and then measuring the total number of precipitates. The number was divided by the area of the field of view and normalized to calculate the density.
各鋼種のＡｃ１点及びＡｃ3点は、上述の加熱時に、試験片の熱膨張変化の測定により求めた。
シャルピー衝撃試験については、焼き入れた後の１.４ｔの鋼板を１.２ｔに研削したのち、４枚積層してネジ止めした後、Ｖノッチ試験片を作製し、シャルピー衝撃試験に供した。靱性評価としては、０℃での衝撃値が３０Ｊ／ｃｍ2以上となる場合に合格として○とした。それに達しないのは「×」とした。
The Ac 1 point and Ac 3 point of each steel type were determined by measuring the change in thermal expansion of the test piece during the heating described above.
For the Charpy impact test, after quenching the 1.4t steel plate after grinding to 1.2t, four sheets were stacked and screwed, and then a V-notch test piece was prepared and subjected to the Charpy impact test. As the toughness evaluation, a pass was marked when the impact value at 0 ° C. was 30 J / cm 2 or more. If it did not reach that, it was marked “x”.
なお、強度が目標強度に達しなかった試験片については一部試験を省略した。 In addition, some tests were abbreviate | omitted about the test piece which intensity | strength did not reach target intensity.
本発明例である鋼種Ｎｏ.１および３〜１３は、ＴＳが１.８ＧＰａ以上で、かつ靱性値も良好であることがわかる。一方、比較例である鋼種Ｎｏ.１４は、強度が低く、鋼種Ｎｏ.１５及び１６は、本発明範囲を満足しないため、靱性値が不芳である。 It can be seen that steel types No. 1 and 3 to 13 which are examples of the present invention have a TS of 1.8 GPa or more and a good toughness value. On the other hand, steel type No. 14 which is a comparative example has low strength, and steel types No. 15 and 16 do not satisfy the scope of the present invention, and thus the toughness value is unsatisfactory.
Claims (15)
前記焼入れ部材は、焼入れ処理を施すことにより得られる引張強さ１.８ＧＰａ以上の焼入れ部材であり、
前記焼入れ処理は、５０℃／秒以上の平均加熱速度で(Ａｃ ３ 点＋４０℃)〜（Ａｃ ３ 点＋２００℃）の温度域に加熱し、前記温度域で１０秒間以下保持したのちに焼入れを施す焼入れ処理であることを特徴とする焼入れ部材用鋼板。 By mass%, C: 0.26 ~0.45%, Mn + Cr: 0.5~3.0%, Nb: 0.01~1.0%, and B: containing from 0.0001 to 0.01% In addition, Si: 1% or less, Ni: 2% or less, Cu: 1% or less, V: 1% or less, and Al: 1% or less. a quenching member for steel that having a composition,
The quenching member is a quenching member having a tensile strength of 1.8 GPa or more obtained by performing a quenching treatment,
The quenching treatment is performed by heating to a temperature range of (Ac 3 points + 40 ° C.) to (Ac 3 points + 200 ° C.) at an average heating rate of 50 ° C./second or more, and holding for 10 seconds or less in the temperature range. A steel sheet for quenching members, which is a quenching treatment to be performed .
３.４２Ｎ＋０.００１≦Ｔｉ≦３.４２Ｎ＋０.５・・・（１）
ここで、式中のＴｉ及びＮは鋼中の各元素の含有量（単位：質量％）を示す。 The steel sheet for quenched members according to claim 1 or 2, wherein the chemical composition contains Ti in an amount satisfying the following formula (1) instead of a part of Fe.
3.42N + 0.001 ≦ Ti ≦ 3.42N + 0.5 (1)
Here, Ti and N in a formula show content (unit: mass%) of each element in steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2006131703A JP4687554B2 (en) | 2006-05-10 | 2006-05-10 | Steel plate for quenched member, quenched member and method for producing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2006131703A JP4687554B2 (en) | 2006-05-10 | 2006-05-10 | Steel plate for quenched member, quenched member and method for producing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2007302937A JP2007302937A (en) | 2007-11-22 |
| JP4687554B2 true JP4687554B2 (en) | 2011-05-25 |
Family
ID=38837113
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2006131703A Active JP4687554B2 (en) | 2006-05-10 | 2006-05-10 | Steel plate for quenched member, quenched member and method for producing the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4687554B2 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4699341B2 (en) * | 2006-11-17 | 2011-06-08 | 株式会社神戸製鋼所 | High strength hot forged non-tempered steel parts with excellent fatigue limit ratio |
| JP4699342B2 (en) * | 2006-11-17 | 2011-06-08 | 株式会社神戸製鋼所 | High strength non-tempered steel for cold forging with excellent fatigue limit ratio |
| JP5353642B2 (en) * | 2009-11-06 | 2013-11-27 | 新日鐵住金株式会社 | Steel plate for heat treatment and manufacturing method thereof |
| JP2015157972A (en) * | 2014-02-21 | 2015-09-03 | 日新製鋼株式会社 | Steel sheet for electric heating molding |
| JP6390572B2 (en) * | 2015-09-29 | 2018-09-19 | Ｊｆｅスチール株式会社 | Cold-rolled steel sheet, plated steel sheet, and production method thereof |
| JP7302756B1 (en) | 2021-09-22 | 2023-07-04 | Ｊｆｅスチール株式会社 | Steel plate for hot press, manufacturing method thereof, hot press member and manufacturing method thereof |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0770695A (en) * | 1993-08-31 | 1995-03-14 | Sumitomo Metal Ind Ltd | Steel for machine structure excellent in delayed fracture resistance |
| JP2004323944A (en) * | 2003-04-25 | 2004-11-18 | Sumitomo Metal Ind Ltd | Hot dip galvanized steel sheet for quenching, its production method, and its use |
| JP2005350776A (en) * | 2001-02-07 | 2005-12-22 | Jfe Steel Kk | Thin steel sheet having excellent toughness after quenching and its production method |
| JP2006152427A (en) * | 2004-10-29 | 2006-06-15 | Sumitomo Metal Ind Ltd | Hot-pressed steel sheet member, manufacturing method therefor and steel sheet to be hot-pressed |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6431928A (en) * | 1987-07-27 | 1989-02-02 | Kawasaki Steel Co | Manufacture of wear-resistant steel stock by direct hardening |
-
2006
- 2006-05-10 JP JP2006131703A patent/JP4687554B2/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0770695A (en) * | 1993-08-31 | 1995-03-14 | Sumitomo Metal Ind Ltd | Steel for machine structure excellent in delayed fracture resistance |
| JP2005350776A (en) * | 2001-02-07 | 2005-12-22 | Jfe Steel Kk | Thin steel sheet having excellent toughness after quenching and its production method |
| JP2004323944A (en) * | 2003-04-25 | 2004-11-18 | Sumitomo Metal Ind Ltd | Hot dip galvanized steel sheet for quenching, its production method, and its use |
| JP2006152427A (en) * | 2004-10-29 | 2006-06-15 | Sumitomo Metal Ind Ltd | Hot-pressed steel sheet member, manufacturing method therefor and steel sheet to be hot-pressed |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2007302937A (en) | 2007-11-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP5344454B2 (en) | Steel for warm working, warm working method using the steel, and steel and steel parts obtained thereby | |
| JP6237962B1 (en) | High strength steel plate and manufacturing method thereof | |
| JP5464302B2 (en) | Cold-rolled steel sheet and manufacturing method thereof | |
| JP6583588B2 (en) | Carburizing steel sheet and method for manufacturing carburizing steel sheet | |
| JP5387073B2 (en) | Steel plate for hot pressing, method for manufacturing the same, and method for manufacturing steel plate member for hot pressing | |
| US20120312433A1 (en) | High-strength steel sheet excellent in workability and cold brittleness resistance, and manufacturing method thereof | |
| WO2014185405A1 (en) | Hot-rolled steel sheet and production method therefor | |
| JPWO2010137317A1 (en) | High-strength steel sheet, hot-dip galvanized steel sheet, alloyed hot-dip galvanized steel sheet having excellent fatigue characteristics and elongation and impact characteristics, and methods for producing them | |
| JP6583587B2 (en) | Carburizing steel sheet and method for manufacturing carburizing steel sheet | |
| WO2020213179A1 (en) | Steel sheet and method for manufacturing same, and molded article | |
| JP2021509438A (en) | Hot-rolled steel sheets, steel pipes, members with excellent impact resistance and their manufacturing methods | |
| WO2013094130A1 (en) | High-strength steel sheet and process for producing same | |
| CN111511945A (en) | High-strength cold-rolled steel sheet and method for producing same | |
| JP2004359973A (en) | High strength steel sheet having excellent delayed fracture resistance, and its production method | |
| JPWO2021079756A1 (en) | High-strength steel plate and its manufacturing method | |
| JP4687554B2 (en) | Steel plate for quenched member, quenched member and method for producing the same | |
| JP7350057B2 (en) | hot stamp molded body | |
| JP7010418B1 (en) | High-strength hot-rolled steel sheet and its manufacturing method | |
| JP7366121B2 (en) | Steel plate for hot stamping | |
| JP6690792B1 (en) | Steel sheet, method of manufacturing the same, and molded body | |
| TWI665310B (en) | Carburizing steel sheet and manufacturing method of carburizing steel sheet | |
| JP7006849B1 (en) | Steel sheets, members and their manufacturing methods | |
| JP5825204B2 (en) | Cold rolled steel sheet | |
| JP3952714B2 (en) | Hot-rolled steel sheet having excellent toughness after quenching and manufacturing method thereof | |
| JP4178940B2 (en) | High-strength steel sheet with excellent secondary work brittleness resistance and method for producing the same |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20080624 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20100726 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20100810 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20101007 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20110118 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20110131 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 4687554 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20140225 Year of fee payment: 3 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20140225 Year of fee payment: 3 |
|
| S111 | Request for change of ownership or part of ownership |
Free format text: JAPANESE INTERMEDIATE CODE: R313111 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20140225 Year of fee payment: 3 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| S533 | Written request for registration of change of name |
Free format text: JAPANESE INTERMEDIATE CODE: R313533 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |