JPS6147209B2 - - Google Patents
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- Publication number
- JPS6147209B2 JPS6147209B2 JP10239383A JP10239383A JPS6147209B2 JP S6147209 B2 JPS6147209 B2 JP S6147209B2 JP 10239383 A JP10239383 A JP 10239383A JP 10239383 A JP10239383 A JP 10239383A JP S6147209 B2 JPS6147209 B2 JP S6147209B2
- Authority
- JP
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- Prior art keywords
- grains
- steel
- heat treatment
- present
- temperature
- 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.)
- Expired
Links
- 229910000831 Steel Inorganic materials 0.000 claims description 43
- 239000010959 steel Substances 0.000 claims description 43
- 238000010438 heat treatment Methods 0.000 claims description 40
- 238000000034 method Methods 0.000 claims description 19
- 238000000137 annealing Methods 0.000 claims description 18
- 239000000463 material Substances 0.000 claims description 11
- 238000010791 quenching Methods 0.000 claims description 10
- 230000000171 quenching effect Effects 0.000 claims description 10
- 230000009466 transformation Effects 0.000 claims description 6
- 229910001563 bainite Inorganic materials 0.000 claims description 5
- 229910052804 chromium Inorganic materials 0.000 claims description 5
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 229910052750 molybdenum Inorganic materials 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 5
- 229910000734 martensite Inorganic materials 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- 238000005496 tempering Methods 0.000 claims description 4
- 238000003303 reheating Methods 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 2
- 230000000694 effects Effects 0.000 description 11
- 238000007670 refining Methods 0.000 description 8
- 239000000523 sample Substances 0.000 description 8
- 239000002245 particle Substances 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 229910052720 vanadium Inorganic materials 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 238000007796 conventional method Methods 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000002436 steel type Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 239000013078 crystal Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Description
本発明は極厚調質鋼の熱処理方法に係り、特に
針状組織を有する極厚鋼材の結晶粒を微細化し得
る熱処理方法に関する。
一般に調質鋼の調質焼入れ時のオーステナイト
粒度（以下γ粒度と称する）は調質処理後の機械
的性質に極めて大きな影響を及ぼすものであつ
て、例えば良好な低温靭性を得るためにはγ粒は
細粒でなければならない。更に衝撃特性のばらつ
きが少なく安定して良好な靭性を確保するために
はγ粒が均一な細粒であることが必須要件であ
る。しかしながら均一な細粒を得る場合に部分的
もしくは全面的にマルテンサイトと下部ベイナイ
トより成る針状組織が存在することによつて悪い
影響をを与える。例えば針状組織と、フエライト
組織、パーライト組織、上部ベイナイト組織もし
くはこれらの混合組織より成るいわゆる塊状組織
が混在する場合には、再加熱時のγ粒は混粒にな
り易い。これは前組織が塊状組織の部位はオース
テナイト化で微細なγ粒を形成するのに対し、前
組織が針状組織の部位は細粒化が見られないから
である。
針状組織を有する鋼素材を細粒化する方法とし
て加熱速度を高める熱処理方法が公知である。し
かしながら極厚調質鋼においては加熱速度を大き
くすることができない。従つて極厚調質鋼であつ
て、前組織が針状組織の場合の従来の熱処理法
は、1000℃以下の焼ならしおよび焼入れを行つて
いるが、この方法では焼ならしおよび焼入れ処理
のオーステナイト化により細粒化されず、粗大な
γ粒を形成する結果となつている。かかる熱処理
方法によつては良好な靭性は期待できないのは当
然である。
本発明の目的は針状組織を有する極厚調質鋼の
上記従来の熱処理方法の欠点を克服し針状組織に
より形成されたγ粒の細粒化を図り、調質焼入れ
時のγ粒を均一かつ細粒化し得る極厚調質鋼の熱
処理方法を提供するにある。
本発明の要旨とするところは次の如くである。
すなわち、
重量比にて Ｃ：0.05〜0.40％
Si：0.02〜1.00％
Mn：0.30〜2.00％
Ni：0.05〜4.00％
Cr：0.10〜3.00％
Mo：0.01〜2.00％
を含有し、更に、Ｖ：0.10〜0.40％
Ｎ：0.0050〜0.0200％
を含み残部はFeおよび不可避的不純物より成る
鋼であつて、かつ部分的もしくは全面的にマルテ
ンサイトとベイナイトより成る針状組織を有する
極厚調質鋼の熱処理方法において、前記鋼素材を
1030〜1100℃の温度範囲で焼なまし処理した後、
再びAc3変態点〜1030℃の温度範囲に再加熱し焼
入れした後焼もどしして細粒化することを特徴と
する極厚調質鋼の熱処理方法である。
本発明者らは極厚調質鋼の熱処理に際し、加熱
速度が小さい場合に発生する粗大なγ粒を微細化
する方法について種々研究した結果、従来の1000
℃以下の焼ならしおよび焼入れ温度よりかなり高
い1030℃以上の高温に加熱することによりはじめ
て再結晶が見られ微細化することができることを
見出し本発明を完成したものであつて、本発明者
らの実験の詳細については後記することとする。
而して本発明の効果をより大ならしめるために、
使用調質鋼の化学成分を限定し、特にＶおよびＮ
の限定量を添加することにより高温熱処理におけ
るγ粒の成長を抑制することとした。本発明にお
ける使用調質鋼の化学組成の限定理由は次の如く
である。
Ｃ：
Ｃは焼入性を向上し極厚鋼材において針状組織
を得るためには少くとも0.05％のＣを必要とする
が、0.40％を越えると残留オーステナイトが存在
するようになる。残留オーステナイトが存在する
と針状組織の細粒化が緩慢となり本発明の細粒化
効果が弱まるので上限を0.40％とし、0.05〜0.40
％の範囲に限定した。
Si，Mn，Ni，Cr，Mo：
Si，Mn，Ni，Cr，Moはいずれも上記Ｃと同一
限定理由により上限および下限を定め、それぞれ
次の範囲に限定した。
Si ：0.02〜1.00％
Mn ：0.3〜2.00％
Ni ：0.05〜4.00％
Cr ：0.10〜3.00％
Mo ：0.01〜2.00％
Ｖ，Ｎ：
本発明において使用する極厚調質鋼には特に
Ｖ，Ｎを適量添加し、その添加量を限定したこと
は大きな特徴であつて、これらの元素の添加効果
ならびに限定理由は次の如くである。すなわち、
ＶとＮはVNを形成しγ粒の成長を抑制する効果
があり、その効果は1000℃以上の高温においても
有効に作用する。
而して本発明における熱処理温度の1030℃以上
の高温でγ粒粗大化の抑制効果を維持するために
はＶ：0.10％以上、Ｎ：0.0050％以上が必要であ
る。しかし一方使用する調質鋼の機械的性質の観
点から良好な靭性を確保するために上限を定める
必要があり、その上限をＶ：0.40％、Ｎ：0.0200
％とし、Ｖ：0.10〜0.40％、Ｎ：0.0050〜0.0200
％の範囲に限定した。
次に本発明による極厚調質鋼の熱処理条件の限
定理由について説明する。前組織が針状組織の調
質鋼と、前組織が塊状組織の調質鋼について本発
明者らの行つた加熱温度とγ粒度との関係につい
ての比較試験結果は第１図に示すとおりである。
第１図より明らかなとおり前組織が塊状の供試材
No.１においては約900℃で細粒化が見られるのに
対し、前組織が針状組織の供試材No.２の場合は、
これよりさらに高温の約1030℃以上で細粒化する
ことが認められ、1030℃以上では供試材No.１，No.
２とも粒度差が少い整粒が得られた。すなわち、
前組織が塊状組織場合には再結晶は公知の如く
Ac1〜Ac3変態点の直上であるに対し、前組織が
針状組織の場合にはこれよりかなり高温の1030℃
以上であることが判明した。而してこの細粒化温
度は化学組成の如何に拘らず前組織が針状組織で
ある場合にほぼ一定である。従つて針状組織の調
質鋼の熱処理に際して細粒化を図るためには、焼
入れ処理以前に1030℃以上の高温焼なましが有効
であることが判明した。しかし焼なましに際し
1100℃を越す高温加熱においては、一旦細粒化し
たγ粒が粗大化するので加熱上限を1100℃とすべ
きであり、従つて本発明における熱処理において
は焼入れ、焼もどしの熱処理以前に高温焼なまし
を施すこととし、その有効な焼なましによつて針
状組織の粗大粒を分割破壊して細粒化するために
1030〜1100℃の温度範囲の加熱に限定した。
次に焼なまし処理後、この焼なましによつて得
た均一なγ粒を更に細粒化を図る目的で焼入れを
行なう。焼入れの温度範囲は前工程の焼なまし温
度より低いAc3変態点〜1030℃の範囲に限定し
た。この理由は焼なましで得た細粒化されたγ粒
を更に微細化するためには少くともAc3変態点よ
り高い温度に加熱して再結晶させる必要がある
が、前工程の焼なまし温度の下限1030℃よりも高
くないことが必要であるからである。この焼入れ
処理後、通常のAc1変態点以下の600〜700℃で焼
もどしを行なう。
次に本発明が効果的に適用されるのは針状組織
を有する極厚調質鋼材であるので針状組織を有す
る極厚調質鋼と限定した。その理由を第２図にて
示した焼鈍処理後のγ粒と昇温速度との関係図に
よつて説明する。すなわち、通常厚さの調質鋼供
試材No.１を従来法により950℃焼鈍を施すに当
り、昇温速度を100℃／hr以上に高めることによ
つて著しく結晶粒度を微細化することができる。
しかし、本発明により1050℃の高温焼鈍を実施す
る供試材No.２においては、昇温速度を高めても結
晶粒度の微細化効果は極めて少く、特に極厚調質
鋼の場合は昇温速度を高めることは事実上不可能
である。従つて昇温速度を高めることが可能の通
常厚さの調質鋼に対しては、供試材No.１の如く従
来の低温焼鈍で加熱速度を高めることによつて細
粒化が可能であるが、極厚材の場合はこの方法を
適用することができない。本発明法が効果を発揮
し得るのは従つて昇温速度の遅い極厚調質鋼の場
合である。
また組織が針状組織を有する場合に限定したの
は、塊状組織の細粒化に対しては従来法による低
温焼鈍の方が有効であるが、針状組織を含む場合
には従来法では不可能であり、本発明法によつて
始めて細粒化が可能となる。
上記理由により、本発明において使用する素材
としては、部分的もしくは全面的にマルテンサイ
トと下部ベイナイトより成る針状組織を有する極
厚調質鋼に限定した。
実施例
第１表にて示す化学成分を有するNo.１，２，
３，４の４鋼種の極厚調質鋼素材を1250℃に加熱
した後、200mm厚鋼板に熱間加工した後放冷し
た。
第１表にて示す供試鋼においてNo.１，２は本発
明鋼であるが、No.３はＮが過小であり、No.４はＶ
が過少である比較鋼である。
上記加工した200mm厚鋼板から200mm厚×500mm
幅×500mm長さの試料を採取し、それぞれ第２表
に示す熱処理を施した。
The present invention relates to a heat treatment method for extremely thick tempered steel, and more particularly to a heat treatment method capable of refining the crystal grains of extremely thick steel having an acicular structure. In general, the austenite grain size (hereinafter referred to as γ grain size) during temper quenching of heat-treated steel has a very large effect on the mechanical properties after heat treatment.For example, in order to obtain good low-temperature toughness, γ The grains must be fine-grained. Furthermore, in order to ensure stable and good toughness with little variation in impact properties, it is essential that the γ grains be uniform and fine grains. However, the presence of an acicular structure partially or entirely composed of martensite and lower bainite has an adverse effect on obtaining uniform fine grains. For example, when an acicular structure and a so-called massive structure consisting of a ferrite structure, a pearlite structure, an upper bainite structure, or a mixed structure thereof coexist, the γ grains during reheating tend to become mixed grains. This is because fine γ grains are formed by austenitization in areas where the previous structure is a blocky structure, whereas no grain refinement is observed in areas where the previous structure is acicular. A heat treatment method that increases the heating rate is known as a method for refining the grains of a steel material having an acicular structure. However, in extremely thick tempered steel, the heating rate cannot be increased. Therefore, the conventional heat treatment method for ultra-thick tempered steel with an acicular structure involves normalizing and quenching at 1000°C or less; Due to austenitization, the grains are not refined and coarse γ grains are formed. Naturally, good toughness cannot be expected by such heat treatment methods. The purpose of the present invention is to overcome the drawbacks of the above-mentioned conventional heat treatment methods for ultra-thick tempered steel having an acicular structure, to refine the γ grains formed by the acicular structure, and to reduce the γ grains during temper quenching. An object of the present invention is to provide a heat treatment method for extremely thick tempered steel that can make the grains uniform and fine. The gist of the present invention is as follows. That is, it contains C: 0.05-0.40% Si: 0.02-1.00% Mn: 0.30-2.00% Ni: 0.05-4.00% Cr: 0.10-3.00% Mo: 0.01-2.00%, and further contains V: 0.10 to 0.40% N: 0.0050 to 0.0200%, the remainder being Fe and unavoidable impurities, and having an acicular structure partially or entirely consisting of martensite and bainite. In the heat treatment method, the steel material is
After annealing treatment in the temperature range of 1030~1100℃,
This is a heat treatment method for extremely thick tempered steel, which is characterized by reheating and quenching to a temperature range from the Ac 3 transformation point to 1030°C, followed by tempering to refine the grains. The present inventors conducted various research on methods for refining coarse γ grains that occur when the heating rate is low during heat treatment of extra-thick tempered steel.
The present inventors have completed the present invention by discovering that recrystallization can be observed and refinement can be achieved only by heating to a high temperature of 1030°C or higher, which is considerably higher than the normalizing and quenching temperatures of below 30°C. The details of the experiment will be described later.
Therefore, in order to further enhance the effects of the present invention,
The chemical composition of the tempered steel used is limited, especially V and N.
It was decided to suppress the growth of γ grains during high-temperature heat treatment by adding a limited amount of . The reason for limiting the chemical composition of the tempered steel used in the present invention is as follows. C: At least 0.05% of C is required to improve hardenability and obtain an acicular structure in extremely thick steel materials, but if it exceeds 0.40%, retained austenite will be present. If retained austenite exists, the grain refining of the acicular structure becomes slow and the grain refining effect of the present invention is weakened, so the upper limit is set at 0.40% and 0.05 to 0.40%.
% range. Si, Mn, Ni, Cr, Mo: Upper and lower limits for Si, Mn, Ni, Cr, and Mo were determined for the same reason as for C above, and were limited to the following ranges. Si: 0.02 to 1.00% Mn: 0.3 to 2.00% Ni: 0.05 to 4.00% Cr: 0.10 to 3.00% Mo: 0.01 to 2.00% V, N: The extra-thick tempered steel used in the present invention especially contains V and N. Adding appropriate amounts of these elements and limiting the amount of addition is a major feature, and the effects of adding these elements and the reason for the limitation are as follows. That is,
V and N form VN and have the effect of suppressing the growth of γ grains, and this effect is effective even at high temperatures of 1000° C. or higher. In order to maintain the effect of suppressing γ grain coarsening at the heat treatment temperature of 1030° C. or higher in the present invention, V: 0.10% or more and N: 0.0050% or more are required. However, from the viewpoint of the mechanical properties of the tempered steel used, it is necessary to set upper limits to ensure good toughness, and the upper limits are V: 0.40%, N: 0.0200.
%, V: 0.10~0.40%, N: 0.0050~0.0200
% range. Next, the reasons for limiting the heat treatment conditions for extra-thick tempered steel according to the present invention will be explained. The results of a comparative test on the relationship between heating temperature and γ grain size conducted by the present inventors on tempered steel with a pre-acicular structure and heat-treated steel with a block-like pre-structure are shown in Figure 1. be.
As is clear from Figure 1, the sample material has a lumpy front structure.
In No. 1, grain refinement is observed at approximately 900°C, whereas in the case of sample No. 2, whose previous structure is an acicular structure,
At temperatures even higher than this, about 1030°C or higher, grain refinement is observed, and at temperatures above 1030°C, sample materials No. 1 and No.
In both cases, sized particles with little difference in particle size were obtained. That is,
If the previous structure is a blocky structure, recrystallization is carried out as is well known.
This is just above the Ac 1 to Ac 3 transformation point, whereas if the previous structure is an acicular structure, the temperature is much higher than this, 1030℃.
It turns out that this is all. Regardless of the chemical composition, this grain refinement temperature is approximately constant when the previous structure is an acicular structure. Therefore, it has been found that high-temperature annealing at 1030° C. or higher is effective before quenching in order to make the grains finer during heat treatment of tempered steel with an acicular structure. However, during annealing
In high-temperature heating exceeding 1100°C, the γ grains that have been refined once become coarse, so the upper limit of heating should be 1100°C. In order to divide and destroy the coarse grains of the acicular structure and make them fine grains by effective annealing.
Heating was limited to a temperature range of 1030-1100°C. Next, after annealing, the uniform γ grains obtained by this annealing are quenched in order to further refine the grains. The temperature range for quenching was limited to the Ac 3 transformation point to 1030°C, which is lower than the annealing temperature in the previous step. The reason for this is that in order to further refine the refined γ grains obtained by annealing, it is necessary to heat them to a temperature higher than the Ac 3 transformation point and recrystallize them, but the annealing process in the previous step This is because it is necessary that the temperature is not higher than the lower limit of 1030°C. After this hardening treatment, tempering is performed at 600 to 700°C, which is below the normal Ac 1 transformation point. Next, since the present invention is effectively applied to extremely thick tempered steel having an acicular structure, the present invention is limited to extremely thick tempered steel having an acicular structure. The reason for this will be explained with reference to the relationship between the γ grains after annealing treatment and the temperature increase rate shown in FIG. 2. In other words, when annealing tempered steel sample No. 1 of normal thickness at 950°C using the conventional method, the grain size was significantly refined by increasing the heating rate to 100°C/hr or more. I can do it.
However, in sample No. 2, which is annealed at a high temperature of 1050°C according to the present invention, the effect of refining the grain size is extremely small even if the heating rate is increased, especially in the case of extra-thick tempered steel. It is virtually impossible to increase speed. Therefore, for tempered steel of normal thickness, for which it is possible to increase the heating rate, it is possible to refine the grains by increasing the heating rate with conventional low-temperature annealing, as in test material No. 1. However, this method cannot be applied to extremely thick materials. Therefore, the method of the present invention is effective in the case of extremely thick tempered steel whose temperature rise rate is slow. In addition, when the structure has an acicular structure, low-temperature annealing using the conventional method is more effective for refining the lumpy structure, but when the structure contains an acicular structure, the conventional method is not effective. It is possible, and the method of the present invention makes it possible to make the particles finer. For the above reasons, the material used in the present invention is limited to extremely thick tempered steel having an acicular structure partially or entirely composed of martensite and lower bainite. Example No. 1, 2, having the chemical components shown in Table 1
Extra-thick tempered steel materials of four steel types 3 and 4 were heated to 1250°C, hot worked into 200mm thick steel plates, and then left to cool. Among the test steels shown in Table 1, Nos. 1 and 2 are inventive steels, but No. 3 has too little N, and No. 4 has too little V.
This is a comparative steel with too little. 200mm thick x 500mm from the 200mm thick steel plate processed above
Samples with a width of 500 mm and a length of 500 mm were taken, and each sample was subjected to the heat treatment shown in Table 2.
【表】【table】
【表】
第２表に示す如く、試料Ｂの焼なまし条件は本
発明の限定要件を満足しないもので、その他の試
料Ａ，Ｃ，Ｄ，Ｅについてはいずれも同一の本発
明の限定要件で熱処理した。
上記各試料Ａ，Ｂ，Ｃ，Ｄ，Ｅについて熱処理
後のγ粒度を比較した結果は第３図に示すとおり
である。すなわち、本発明による限定化学成分を
有する鋼種No.１であつても、本発明の熱処理要件
を満足しない試料ＢはJIS粒度No.が3.3〜6.5と粗
大であり、かつ粗大粒と細粒の差が著しく大き
い。また、本発明による熱処理要件を満足して
も、使用鋼種が限定外のNo.３，No.４を使用した試
料Ｄ，Ｅも粒度No.がそれぞれ3.4〜5.2、3.3〜5.3
と粗大であるのに対し、使用鋼の化学成分および
熱処理条件が、いずれも本発明の限定要件を満足
する試料ＡおよびＣにおいてはJIS粒度No.が5.4〜
6.5と極めて細粒であり、かつその粒度が均一で
あることが判明した。
次に、これら各試料について調質処理後引張試
験および衝撃試験を施し、それぞれの機械的性質[Table] As shown in Table 2, the annealing conditions of sample B do not satisfy the limiting requirements of the present invention, and the other samples A, C, D, and E all have the same limiting requirements of the present invention. heat treated. The results of comparing the γ grain sizes after heat treatment for each of the above samples A, B, C, D, and E are shown in FIG. That is, even though it is steel type No. 1 having the limited chemical composition according to the present invention, sample B, which does not satisfy the heat treatment requirements of the present invention, has a coarse JIS grain size No. of 3.3 to 6.5, and has a large difference between coarse grains and fine grains. The difference is significantly large. In addition, even if the heat treatment requirements according to the present invention are satisfied, samples D and E using steel types outside the limits, No. 3 and No. 4, have grain size numbers of 3.4 to 5.2 and 3.3 to 5.3, respectively.
On the other hand, in samples A and C, in which the chemical composition of the steel used and the heat treatment conditions both satisfy the limiting requirements of the present invention, the JIS grain size No. is 5.4 to 5.4.
It was found that the particles were extremely fine with a particle size of 6.5, and the particle size was uniform. Next, each of these samples was subjected to a tensile test and an impact test after heat treatment, and their mechanical properties were determined.
【表】
を測定した結果は第３表に示すとおりである。第
３表より明らかな如く、比較例試料Ｂ，Ｄ，Ｅ，
は本発明例試料Ａ，Ｃに比し降伏応力（Y.S.）、
引張強さ（T.S.）においてやや劣るほか、伸び
（El）、断面収縮率（R.A.）においてもやや劣る
ものの明確な差異が認められないが、衝撃特性の
吸収エネルギーvE20および遷移温度（F.A.T.T.
）において著しく劣ることを示している。これに
対し、本発明例の試料ＡおよびＣは引張特性がす
ぐれているばかりでなく、特に衝撃特性が比較例
に比し著しくすぐれており、かつそのばらつきも
少く靭性がきわめて良好である。これは第３図に
て示したγ粒度の微細化により招来されたもので
ある。
上記実施例より明らかな如く、本発明は針状組
織を一部もしくは全面に有する極厚調質鋼素材の
調質においては、従来1000℃以下の低温で焼なま
し、焼入れを行つているので結晶粒の微細化がで
きず、従つて靭性のすぐれた熱処理ができなかつ
たに鑑み、本発明は焼入れ、焼もどし処理の前処
理として1030〜1100℃の温度範囲で焼なまし処理
を行ない、かつ鋼成分を限定し、特にＶ，Ｎの適
量を添加することによつて本発明の効果を十分発
揮できるような新規な熱処理方法によつたので細
粒整粒化することができ、すぐれた衝撃靭性を安
定して得ることができる効果を収めることがで
き、針状組織を含む極厚調質鋼素材の機械的性質
の改善に大なる寄与をすることができた。[Table] The results of the measurements are shown in Table 3. As is clear from Table 3, comparative samples B, D, E,
is the yield stress (YS) compared to samples A and C of the present invention,
In addition to being slightly inferior in tensile strength (TS), elongation (El) and area shrinkage rate (RA) are also slightly inferior, but no clear difference is observed.
) is significantly inferior. On the other hand, Samples A and C of the invention examples not only have excellent tensile properties, but especially impact properties, which are significantly superior to those of the comparative examples, and have very good toughness with little variation. This is caused by the refinement of the γ grain size shown in FIG. As is clear from the above examples, in the present invention, annealing and quenching are conventionally performed at a low temperature of 1000°C or less when refining an extremely thick tempered steel material that has an acicular structure partially or entirely. In view of the fact that crystal grains could not be refined and therefore heat treatment with excellent toughness could not be performed, the present invention performs annealing treatment at a temperature range of 1030 to 1100 ° C. as a pretreatment for quenching and tempering treatment, In addition, by limiting the steel components and in particular adding appropriate amounts of V and N, a new heat treatment method was used that fully exhibited the effects of the present invention, making it possible to achieve finer grain size. We were able to achieve the effect of stably obtaining impact toughness, and made a significant contribution to improving the mechanical properties of ultra-thick tempered steel materials containing acicular structures.
第１図は本発明者らの実験により得た塊状組織
鋼No.１と針状組織鋼No.２との焼なまし加熱温度と
γ粒度No.との関係を示す線図、第２図は950℃焼
鈍の従来法による供試材No.１と、1050℃焼鈍の本
発明法による供試材No.２との加熱時の昇温速度と
γ粒度No.との関係を示す線図、第３図は本発明の
実施例における本発明例試料ＡおよびＣと、比較
例の試料Ｂ，Ｄ，Ｅの熱処理後のγ粒度No.を対比
する線図である。
Fig. 1 is a diagram showing the relationship between annealing heating temperature and γ grain size No. of blocky structure steel No. 1 and needle structure steel No. 2 obtained through experiments by the present inventors, and Fig. 2 is a diagram showing the relationship between the temperature increase rate during heating and the γ grain size No. of specimen No. 1 annealed at 950°C by the conventional method and specimen No. 2 annealed at 1050°C by the method of the present invention. , FIG. 3 is a diagram comparing the γ grain size numbers after heat treatment of samples A and C of the present invention in the examples of the present invention and samples B, D, and E of comparative examples.
Claims (1)
鋼であつて、かつ部分的もしくは全面的にマルテ
ンサイトとベイナイトより成る針状組織を有する
極厚調質鋼の熱処理方法において、前記鋼素材を
1030〜1100℃の温度範囲で焼なまし処理した後、
再びAc3変態点〜1030℃の温度範囲に再加熱し焼
入れた後焼もどしして細粒化することを特徴とす
る極厚調質鋼の熱処理方法。[Claims] 1 Contains C: 0.05-0.40% Si: 0.02-1.00% Mn: 0.30-2.00% Ni: 0.05-4.00% Cr: 0.10-3.00% Mo: 0.01-2.00% , further contains V: 0.10 to 0.40%, N: 0.0050 to 0.0200%, and the remainder is Fe and unavoidable impurities, and is an extremely thick steel having an acicular structure partially or entirely composed of martensite and bainite. In the heat treatment method for tempered steel, the steel material is
After annealing treatment in the temperature range of 1030~1100℃,
A heat treatment method for extremely thick annealed steel, characterized by reheating and quenching to a temperature range from the Ac 3 transformation point to 1030°C, followed by tempering to refine the grains.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10239383A JPS59229412A (en) | 1983-06-08 | 1983-06-08 | Heat treating method of extra-thick tempered steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10239383A JPS59229412A (en) | 1983-06-08 | 1983-06-08 | Heat treating method of extra-thick tempered steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS59229412A JPS59229412A (en) | 1984-12-22 |
| JPS6147209B2 true JPS6147209B2 (en) | 1986-10-17 |
Family
ID=14326198
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10239383A Granted JPS59229412A (en) | 1983-06-08 | 1983-06-08 | Heat treating method of extra-thick tempered steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS59229412A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20150344997A1 (en) * | 2012-12-20 | 2015-12-03 | Sandvik Intellectual Property Ab | Bainitic steel for rock drilling component |
-
1983
- 1983-06-08 JP JP10239383A patent/JPS59229412A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20150344997A1 (en) * | 2012-12-20 | 2015-12-03 | Sandvik Intellectual Property Ab | Bainitic steel for rock drilling component |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS59229412A (en) | 1984-12-22 |
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