JPS6353208A - Spheroidizing annealing method for alloy steel for machine structural use - Google Patents
Spheroidizing annealing method for alloy steel for machine structural useInfo
- Publication number
- JPS6353208A JPS6353208A JP19528686A JP19528686A JPS6353208A JP S6353208 A JPS6353208 A JP S6353208A JP 19528686 A JP19528686 A JP 19528686A JP 19528686 A JP19528686 A JP 19528686A JP S6353208 A JPS6353208 A JP S6353208A
- Authority
- JP
- Japan
- Prior art keywords
- less
- steel
- temperature
- pearlite transformation
- spheroidizing annealing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000137 annealing Methods 0.000 title claims abstract description 23
- 229910000851 Alloy steel Inorganic materials 0.000 title claims abstract description 10
- 238000000034 method Methods 0.000 title claims abstract description 10
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 46
- 230000009466 transformation Effects 0.000 claims abstract description 33
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 25
- 239000010959 steel Substances 0.000 claims abstract description 25
- 238000001816 cooling Methods 0.000 claims abstract description 17
- 238000010438 heat treatment Methods 0.000 claims abstract description 16
- 238000011282 treatment Methods 0.000 claims abstract description 11
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 8
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 7
- 229910052802 copper Inorganic materials 0.000 claims abstract description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract 2
- 229910052748 manganese Inorganic materials 0.000 claims description 6
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims 1
- 239000000203 mixture Substances 0.000 abstract description 6
- 230000001737 promoting effect Effects 0.000 abstract description 6
- 229910052719 titanium Inorganic materials 0.000 abstract description 2
- 229910052759 nickel Inorganic materials 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 17
- 239000000463 material Substances 0.000 description 10
- 230000014759 maintenance of location Effects 0.000 description 9
- 229910001566 austenite Inorganic materials 0.000 description 7
- 238000010273 cold forging Methods 0.000 description 7
- 238000010583 slow cooling Methods 0.000 description 7
- 229910001567 cementite Inorganic materials 0.000 description 6
- 239000011651 chromium Substances 0.000 description 6
- KSOKAHYVTMZFBJ-UHFFFAOYSA-N iron;methane Chemical compound C.[Fe].[Fe].[Fe] KSOKAHYVTMZFBJ-UHFFFAOYSA-N 0.000 description 6
- 238000010791 quenching Methods 0.000 description 4
- 230000000171 quenching effect Effects 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 238000005336 cracking Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000005496 tempering Methods 0.000 description 3
- 229910001563 bainite Inorganic materials 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000005098 hot rolling Methods 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- -1 AQN compound Chemical class 0.000 description 1
- 229910000954 Medium-carbon steel Inorganic materials 0.000 description 1
- 241000080590 Niso Species 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000012669 compression test Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 150000003606 tin compounds Chemical class 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は機械構造用合金鋼の球状化焼鈍法に係り、特に
冷間鍛造によって１例えばボルト、ナツトなどに加工さ
れる機械構造用合金鋼の軟質化を目的とする球状化焼鈍
法の改良に関するものである。[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a spheroidizing annealing method for alloy steel for machine structures, and particularly for alloy steels for machine structures that are processed into bolts, nuts, etc. by cold forging. The present invention relates to improvements in the spheroidizing annealing process aimed at softening.
［従来の技術］
従来１機械構造用合金鋼は、冷間鍛造に際し、その変形
抵抗を下げて冷間鍛造性の向上をはかるために、軟質化
処理が行われ、その手段の一つとしてセメンタイトの球
状化焼鈍処理が行われている。[Prior Art] Conventionally, alloy steel for machine structures is subjected to softening treatment during cold forging in order to lower its deformation resistance and improve cold forgeability, and one of the means for this is the use of cementite. Spheroidizing annealing treatment is performed.
この球状化焼鈍処理は、たとえば特開昭５９−１３６４
２１号公報などに見られるように、Ａ８点以上の温度に
加熱した後、１０℃／時程度の超徐冷で連続冷却するか
、あるいはＡ０点直下に３時間以上保定するという方法
で行われている。This spheroidizing annealing treatment is performed, for example, in Japanese Patent Application Laid-Open No. 59-1364.
As seen in Publication No. 21, etc., after heating to a temperature of A8 point or higher, it is continuously cooled by super slow cooling of about 10°C/hour, or maintained just below the A0 point for 3 hours or more. ing.
しかしながら、これでは処理時間が非常に長くなり工業
的に不利である。一方、焼鈍時間の短縮を目的として連
続冷却の冷却速度を速くしたり、あるいはＡ１点直下の
保定時間を短くするような試みを行うと、結果として強
度が増加し、いずれも軟質化の目的を達成できない。However, this requires a very long processing time, which is industrially disadvantageous. On the other hand, if attempts are made to increase the cooling rate of continuous cooling with the aim of shortening the annealing time, or to shorten the holding time just below the A1 point, the strength will increase as a result, and both of these methods will defeat the purpose of softening. Unachievable.
ところで、一般に球状化焼鈍材はフェライト。By the way, the spheroidizing annealed material is generally ferrite.
パーライト組織となっている。従って強度を低下させる
ためには、組織の大半を占めるパーライトの強度を低下
させることが必要である。It has a perlite structure. Therefore, in order to reduce the strength, it is necessary to reduce the strength of pearlite, which occupies most of the structure.
一般にパーライトの強度は、セメンタイト間隔に反比例
する関係があるので、球状パーライト強度を低下させる
ことを考えると、そのためにはパーライトのセメンタイ
ト間間隔を粗くすることが必要になる。In general, the strength of pearlite is inversely proportional to the cementite spacing, so in order to reduce the strength of spherical pearlite, it is necessary to coarsen the spacing between cementites in pearlite.
しかるに、球状パーライトのセメンタイト間間隔は、オ
ーステナイトからパーライトが変態生成する温度で一義
的に決り、高い温度で変態するほど粗くなる。ところが
パーライト変態は、温度が高くなるほど進行が遅れ、終
了にきわめて長時間を要するようになる。However, the intercementite spacing of spherical pearlite is primarily determined by the temperature at which pearlite transforms from austenite, and becomes coarser as the transformation temperature increases. However, the higher the temperature, the slower the pearlite transformation progresses, and it takes an extremely long time to complete.
そこで本発明者らは、かかる従来の知見を種々解析して
、中炭素系機械構造用鋼についてその強度の支配因子を
検討した結果、Ａ１点近傍の温度域でのパーライト変態
を促進して、短時間の球状化焼鈍により鋼材の軟質化を
はかるための手段として、従来の鋼に含まれるＭｎの一
部をＣｒとおき変えるとともに、球状化焼鈍条件として
適正なるものを選択すればよいという知見を得て、先に
特願昭６０−１３６０７号により提案を行っている。Therefore, the present inventors analyzed various such conventional findings and examined the factors governing the strength of medium carbon steel for mechanical structural use. Knowledge that as a means of softening steel materials through short-time spheroidizing annealing, it is sufficient to replace part of the Mn contained in conventional steel with Cr and to select appropriate spheroidizing conditions. In response to this, the proposal was first made in Japanese Patent Application No. 13607-1983.
ところで、この製造手段は焼入性の低い低合金鋼の軟質
化という点では極めて優れているものの、Ｓ Ｃｒ、
Ｓ ＣＭ鋼のような焼入性の高い合金鋼の軟質化という
点ではまだ改良の余地があった。By the way, although this manufacturing method is extremely superior in terms of softening low alloy steel with low hardenability, S Cr,
There was still room for improvement in terms of softening alloy steels with high hardenability such as SCM steel.
［発明が解決しようとする問題点コ
本発明は上記のごとき実情に鑑みなされるものであって
、焼入性の高い合金鋼を短時間の球状化焼鈍で軟質化す
る方法を堤供することを目的とするものである。[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned circumstances, and aims to provide a method for softening highly hardenable alloy steel by short-time spheroidizing annealing. This is the purpose.
［問題点を解決するための手段 作用］即ち、本発明者
らは先に提案した技術をさらに改良し、Ｂを添加するこ
とによって軟質化の最大のポイントであるところの高温
でのパーライト変態を一層促進させるとともに、球状化
焼鈍条件として適正なものを選択することにより、焼入
性の高い合金鋼でも短時間で軟質化が可能であるという
全く新たな知見を得て本発明をなしたものである。[Means for Solving the Problems] That is, the present inventors have further improved the previously proposed technique, and by adding B, the pearlite transformation at high temperatures, which is the most important point in softening, has been improved. The present invention was made based on the completely new knowledge that even alloy steels with high hardenability can be softened in a short time by further promoting the spheroidizing annealing and selecting appropriate conditions for spheroidizing annealing. It is.
本発明は、以上の知見に基づいてなされたものであって
、その要旨とする所は、重量％でＣ： ０．１５〜０．
６５％、Ｓｉ： ０．１％未満。The present invention was made based on the above findings, and its gist is that C: 0.15-0.
65%, Si: less than 0.1%.
Ｍｎ：０．２〜０．５％、Ｂ ： ０．０００３−０．
０１％、Ｃｒ：０．９超〜１．８％、ＡＱ：０．０１−
０．１％を含有し、Ｐを０．０２％未満、Ｓを０゜０２
％未満と制限し、その他必要に応じて（Ａ）Ｎｉ：１％
以下、Ｍｏ：０．３％以下、Ｃｕ：１％以下の１種また
は２種以上、（Ｂ）Ｔｉ： ０．００２〜０．０５％、
Ｎｂ： ０．００５〜０．０５％、ｖ：０ 、、ＯＯ５
〜０．２％の１種または２種以上、の（Ａ）、（Ｂ）の
群の一方または両方を含有し。Mn: 0.2-0.5%, B: 0.0003-0.
01%, Cr: more than 0.9 to 1.8%, AQ: 0.01-
Contains 0.1%, P less than 0.02%, S 0°02
(A)Ni: 1% as necessary.
Below, Mo: 0.3% or less, Cu: 1% or less, one or more types, (B) Ti: 0.002 to 0.05%,
Nb: 0.005-0.05%, v:0, OO5
Contains ~0.2% of one or more of the groups (A) and (B).
残部は、Ｆｅおよび不可避不純物よりなる鋼について、
７４０超〜８５０℃に２０秒〜２時間加熱した後、（イ
）５℃／分以下の冷却速度でパーライト変態終了までの
温度範囲を徐冷するか、あるいは（ロ）６９０〜７４０
℃の範囲の温度に１５分〜３時間保定した後放冷するか
（イ）、（ロ）いずれかの球状化処理を実施することを
特徴とする機械構造用合金鋼の球状化焼鈍法にある。For steel, the remainder consists of Fe and unavoidable impurities.
After heating to over 740°C to 850°C for 20 seconds to 2 hours, (a) slowly cool the temperature range until the end of pearlite transformation at a cooling rate of 5°C/min or less, or (b) 690 to 740°C.
A spheroidizing annealing method for alloy steel for machine structural use, which comprises holding at a temperature in the range of °C for 15 minutes to 3 hours and then allowing it to cool, or performing either (a) or (b) spheroidizing treatment. be.
以下に本発明の詳細な説明する。The present invention will be explained in detail below.
まず最初に、本発明において軟質化とは、その焼鈍材の
引張強度を、炭素当Ｊ＋ｔ Ｃａｑ （Ｃａｑ＝ Ｃ＋
ＳＬ／２４＋Ｍｎ／６＋Ｃｒ１５＋Ｃｕ／１３＋Ｍ。First of all, in the present invention, softening refers to the tensile strength of the annealed material as J+t Caq (Caq= C+
SL/24+Mn/6+Cr15+Cu/13+M.
／４＋Ｎｉ／４０）によって規定される強度＝ ２０
＋ ５９ Ｃｅｑ （Ｋｇ／ａｍ”）以下とすることを
意味する。この強度式はＣａｑｉを０゜３〜１．３の範
囲内で求めたものであり、２０はフェライトとパーライ
トの強度に、また５９はＣｅｑ量即ちパーライト量にそ
れぞれ依存する項である。Ｃａｑ量によって決る同大の
値を強度が越える場合には球状化焼鈍により軟質化した
とは言えない。/4+Ni/40) = 20
+59 Ceq (Kg/am") or less. This strength formula is obtained by calculating Caqi within the range of 0°3 to 1.3, and 20 is the strength of ferrite and pearlite, and 59 is a term that depends on the amount of Ceq, that is, the amount of pearlite.If the strength exceeds the same value determined by the amount of Caq, it cannot be said that the material has been softened by spheroidizing annealing.
次に１本発明の対象とする鋼の成分限定理由についての
べる。Next, the reason for limiting the composition of steel, which is the object of the present invention, will be described.
まず、Ｃは冷間鍛造後の焼入れ焼戻し処理において製品
に所要の強度を付与するために必須の元素であるが、０
．１５％未満では所要の強度が得られず、一方０．６５
％を越えても焼入れ焼戻し後の強度はもはや増加しない
ので、０．１５〜０゜６５％の範囲に限定した。First, C is an essential element in order to impart the required strength to the product in the quenching and tempering treatment after cold forging, but 0
．． If it is less than 15%, the required strength cannot be obtained;
%, the strength after quenching and tempering will no longer increase, so it was limited to a range of 0.15 to 0.65%.
また、Ｓｉはその固容体硬化作用によって圧延材の強度
を高めるので、固容体硬化の影響を無視できるようにな
る０、１％未満に含有量を限定した。また、このように
ＳＬを下げても、焼入処理時に要求される焼入性は低下
しない。In addition, since Si increases the strength of the rolled material through its solid hardening effect, the content was limited to less than 0.1% so that the influence of solid hardening can be ignored. Further, even if the SL is lowered in this way, the hardenability required during hardening treatment does not decrease.
つぎに、ＭｎとＢに関してであるが、この含有量を前記
のように定めた点が本発明の最も重要な点である。Next, regarding Mn and B, the most important point of the present invention is that the contents are determined as described above.
即ち、例えば従来の代表的な機械構造用クロム鋼である
Ｓ Ｃｒ４３０鋼は
Ｃ： ０．２８〜０．３３％、Ｓｉ： ０．１５〜０．
３５％、Ｍｎ： ０．６０〜０．８５％、Ｃｒ： ０
．９０〜１．２０％を含むことが規定されているが、そ
のＭ ｎ Ｊｉｌを減らすことによって、Ｓ Ｃｒ４３
０鋼に比べ軟質化のポイントであるパーライト変態の終
了温度が高くなる。Ｍｎｉが減少しただけ焼入性は低下
するが、これはＢを添加することによって補う。さらに
、Ｂは徐冷域ではパーライト変態を抑制することはなく
、逆に固溶ＢがＢ化合物として析出することによりパー
ライト変態を促進させる効果がある。従って、Ｂを添加
した鋼を徐冷すると高温でのパーライト変態を短時間で
終了させることができる。なお通常、Ｂは焼入性を向上
させる元素として使用されているが、本発明ではＢを焼
鈍時のパーライト変態を促進させるためと冷間鍛造後の
熱処理時における焼入性向上の両方に利用するものであ
る。従って、このような鋼は５Ｃｒ４３０ｔ！ｌ！に比
べ高速で冷却しても同じ温度でパーライト変態させられ
る。また、この錆はＭｎ量を減らしてＢを添加すること
によりパーライト変態温度が高温側ヘシフトするので、
Ａ８点近傍の温度に保定した場合にも短時間でパーライ
ト変態を終了させることができる。That is, for example, S Cr430 steel, which is a typical conventional chromium steel for mechanical structures, has C: 0.28 to 0.33% and Si: 0.15 to 0.
35%, Mn: 0.60-0.85%, Cr: 0
．． Although it is specified that S Cr43 contains 90 to 1.20%, by reducing its M n Jil
Compared to zero steel, the end temperature of pearlite transformation, which is the point of softening, is higher. Hardenability decreases as Mni decreases, but this is compensated for by adding B. Furthermore, B does not suppress pearlite transformation in the slow cooling region, but on the contrary, solid solution B precipitates as a B compound, thereby having the effect of promoting pearlite transformation. Therefore, when steel to which B is added is slowly cooled, pearlite transformation at high temperatures can be completed in a short time. Generally, B is used as an element to improve hardenability, but in the present invention, B is used both to promote pearlite transformation during annealing and to improve hardenability during heat treatment after cold forging. It is something to do. Therefore, such steel is 5Cr430t! l! Even if it is cooled at a higher speed than that of , it can undergo pearlite transformation at the same temperature. In addition, this rust can be prevented by reducing the amount of Mn and adding B, as the pearlite transformation temperature shifts to the higher temperature side.
Even when the temperature is maintained at around point A8, the pearlite transformation can be completed in a short time.
ここで、ＭｎとＢの添加量を上記のように限定したのは
以下の理由による。Here, the reason why the amounts of Mn and B added are limited as described above is as follows.
高温域のパーライト変態を短時間で終了させるためには
、できるだけＭｎを減らした方がよいが。In order to complete the pearlite transformation in the high temperature range in a short time, it is better to reduce Mn as much as possible.
Ｍｎが０．２％未満では鋼中のＳを十分に固定すること
ができず、熱間脆性をおさえることができない、一方、
Ｍｎが０．５％を越えるとＢが添加されていても高温で
のパーライト変態を短時間に終了させることができない
ので、Ｍｎ量を０．２〜０゜５％に限定した。If Mn is less than 0.2%, S in the steel cannot be sufficiently fixed and hot embrittlement cannot be suppressed;
If Mn exceeds 0.5%, pearlite transformation at high temperature cannot be completed in a short time even if B is added, so the Mn amount was limited to 0.2 to 0.5%.
Ｂは、徐冷域でのパーライト変態を促進させ且つ冷間鍛
造後の熱処理の焼入性を著しく高め強度を向上させるの
に有効であるが、０．０００３％未満ではその効果が上
がらず、一方Ｃ）、０１％を越えると冷間鍛造性を劣化
させるので、０．０００３〜０．０１％に限定した。B is effective in promoting pearlite transformation in the slow cooling region and significantly increasing the hardenability in heat treatment after cold forging and improving strength, but if it is less than 0.0003%, the effect will not increase, while C ), if it exceeds 0.01%, cold forgeability deteriorates, so it is limited to 0.0003 to 0.01%.
また、Ｃｒは焼入性を高め、強度、靭性を向上させるの
に有効であるが、０．９％以下ではその効果が不十分で
あり本発明の目的とするところの焼入性の高い鋼となら
ない、一方、１．８％を越えると鋼の焼入性が高まりす
ぎてパーライト変態終了温度が低下し軟質材とならない
ので、０．９超〜１．８％に限定した。In addition, although Cr is effective in increasing hardenability and improving strength and toughness, if it is less than 0.9%, the effect is insufficient and the purpose of the present invention is to improve the hardenability of the steel. On the other hand, if it exceeds 1.8%, the hardenability of the steel will increase too much, the temperature at which pearlite transformation ends will drop, and the material will not be soft, so it is limited to more than 0.9 to 1.8%.
Ａ Ｑは冷間鍛造後の焼入れ処理時のオーステナイト粒
度の粗大化を防止するためとＮをＡＱＮ化合物として固
定しＢの焼入性効果を確保するために必要な元素である
が、０．０１％未満ではその効果がなく、一方０．１％
を試えると上記の効果が飽和する上、むしろ冷間鍛造性
を劣化させるので、０．０１〜０．１％に限定した。A Q is an element necessary to prevent coarsening of austenite grain size during quenching treatment after cold forging, and to fix N as an AQN compound to ensure the hardenability effect of B, but 0.01 Less than % has no effect, while 0.1%
If tried, the above effect would be saturated and the cold forgeability would actually deteriorate, so it was limited to 0.01 to 0.1%.
Ｐ、Ｓはいずれも冷間鍛造性に有害な元素である。いず
れも０．０２％を越えると悪影響が顕著になるので、こ
れ未満に限定した。Both P and S are elements harmful to cold forgeability. In either case, if it exceeds 0.02%, the adverse effects become significant, so the content was limited to less than this.
以」−が本発明の対象とする鋼の基本成分であるが、本
発明においてｌよ、さらにこの鋼に（Ａ）Ｎｉ： １％
以下、Ｍｏ：０．３％以下、Ｃｕ：１％以下の１種また
は２種以上、
ＣＢ）Ｔｉ： ０．００２〜０．０５％、Ｎｂ： ０．
００５〜０．０５％、Ｖ：０．００５〜０．２％の１種
または２種以上
の（Ａ）、（Ｂ）の群の一方または両方を含有せしめる
こともできる。These are the basic components of the steel that is the object of the present invention, but in the present invention, (A) Ni: 1% is added to this steel.
Below, Mo: 0.3% or less, Cu: 1% or less, CB) Ti: 0.002 to 0.05%, Nb: 0.
005 to 0.05% and V: 0.005 to 0.2% of one or more of the groups (A) and (B).
まず、（Ａ）群のＮｉは靭性を向上させるとともに焼入
性を大きくして強度を上げるために添加されるが、１％
を越えると焼入性が大きくなり過ぎて冷間鍛造性が悪く
なるのでこれを上限とした。First, Ni in group (A) is added to improve toughness and increase hardenability to increase strength.
If this value is exceeded, the hardenability becomes too large and the cold forgeability deteriorates, so this was set as the upper limit.
Ｍｏは焼入れ性を向上させ、強い焼戻し軟化抵抗を与え
る元素であるが、０．３％を越えても添加量に見合うだ
けの効果が期待できないのでこれを上限とした。Mo is an element that improves hardenability and provides strong temper softening resistance, but even if it exceeds 0.3%, an effect commensurate with the amount added cannot be expected, so this was set as the upper limit.
Ｃｕ＋ＪＮｉと同様に靭性と焼入性を向上させるが。Like Cu+JNi, it improves toughness and hardenability.
１％を越えるとその効果は飽和するのでこれを上限とし
た。If it exceeds 1%, the effect will be saturated, so this was set as the upper limit.
一方、（Ｂ）群のＴｉ、Ｎｂ、Ｖはいずれも熱間圧延後
のオーステナイト結晶粒を微細化させ焼鈍時の高温域で
のパーライト変態の促進を目的に添加される。On the other hand, Ti, Nb, and V in group (B) are all added for the purpose of refining austenite crystal grains after hot rolling and promoting pearlite transformation in a high temperature range during annealing.
ＴｉはＮと結合してＴｉＮ化合物を形成し、熱間圧延後
のオーステナイト結晶粒の粗大化を防止する。また、Ｔ
ｉとＢは組合せて添加する方が効果的で、ＴｉはＡＱと
共にＮを固定してＢのパーライト変態を促進させる効果
と冷間鍛造後の焼入性効果を十分に発揮させるために添
加される。Ｔｉは０．００２％未満ではＮを固定する効
果が不十分であり、一方０．０５％を越えると冷間鍛造
性及び靭性に有害な粗大なＴ ｉ ＮあるいはＴｉＣが
生成するので、０．００２〜０．０５％に制限した。Ti combines with N to form a TiN compound, which prevents austenite crystal grains from becoming coarser after hot rolling. Also, T
It is more effective to add i and B in combination, and Ti is added together with AQ to fix N and promote the pearlite transformation of B, and to fully exhibit the hardenability effect after cold forging. Ru. If Ti is less than 0.002%, the effect of fixing N is insufficient, while if it exceeds 0.05%, coarse TiN or TiC that is harmful to cold forgeability and toughness will be generated. It was limited to 0.002% to 0.05%.
Ｎｂ、Ｖはいずれも圧延後のオーステナイト粒度を微細
化させて、焼鈍時のパーライト変態を促進することを目
的に添加するが、それぞれ０．００５％未満では微細効
果が期待できず、一方Ｎｂが０．０５％、■が０．２％
をそれぞれ越えるとＮｂ、 ｖの粗大な炭窒化物が析出
して靭性及び冷間鍛造性を劣化させるので、Ｎｂは０．
００５〜０゜０５％、またＶは０．００５〜０．２％ニ
ソれぞれ限定した。Both Nb and V are added for the purpose of refining the austenite grain size after rolling and promoting pearlite transformation during annealing, but if each is less than 0.005%, no finer effect can be expected; 0.05%, 0.2%
If Nb and v are exceeded, coarse carbonitrides of Nb and V will precipitate, deteriorating toughness and cold forgeability.
0.005 to 0.05%, and V was limited to 0.005 to 0.2% niso.
次に、本発明においては、軟質化処理のための球状化焼
鈍条件として、７４０超〜８５０℃に２０秒〜２時間加
熱した後、（イ）５℃／分の冷却速度でパーライト変態
が終了するまでの温度範囲を徐冷するか、あるいは（ロ
）６９０〜７４０℃の範囲の温度に１５分〜３時間保定
した後放冷するかの（イ）、（ロ）のうちいずれかの処
理を施すのであって、（イ）、（ロ）いずれの手段によ
っても高温域でのパーライト変態を短時間に終了せしめ
、且つ引張強度を２０ ＋ ５９ Ｃｅｑ（ｋｇ／ｍｍ
”）以下とすることが可能である。Next, in the present invention, as the spheroidizing annealing conditions for softening treatment, after heating to over 740 to 850 °C for 20 seconds to 2 hours, (a) pearlite transformation is completed at a cooling rate of 5 °C/min. Either of (a) or (b): slow cooling in the temperature range until the temperature reaches By applying (a) and (b), pearlite transformation in a high temperature range can be completed in a short time, and the tensile strength can be reduced to 20 + 59 Ceq (kg/mm).
”) It is possible to do the following.
まず、加熱温度を７４０℃超以上に限定したのは、７４
０℃以下の温度ではセメンタイトが十分にオーステナイ
トへ溶は込まないので、その後の冷却で球状パーライト
に変態させられないで、目標とする軟質化度が得られな
いためである。一方。First, the heating temperature was limited to over 740°C.
This is because cementite does not fully melt into austenite at temperatures below 0° C., so it is not transformed into spherical pearlite by subsequent cooling, and the target degree of softening cannot be obtained. on the other hand.
加熱温度が８５０”Ｃを越えると、オーステナイトから
球状パーライトではなく層状パーライトが変態生成して
目標の軟質化度が得られないので８５０℃を上限とした
。なお、好ましい加熱温度範囲は７５０℃〜７９０℃で
ある。If the heating temperature exceeds 850"C, the austenite transforms into layered pearlite instead of spherical pearlite, making it impossible to obtain the target degree of softening. Therefore, the upper limit was set at 850"C.The preferred heating temperature range is 750"C~ The temperature is 790°C.
加熱時間を２０秒〜２時間に限定したのも同じ理由で、
２０秒未満ではセメンタイトの溶は込みが不十分なため
、又２時間を越えると、球状パーライトを変態生成させ
られないためである。For the same reason, we limited the heating time to 20 seconds to 2 hours.
This is because if the time is less than 20 seconds, the dissolution of cementite is insufficient, and if it is more than 2 hours, spherical pearlite cannot be transformed.
次に、上記のごとき条件で加熱後、（イ）連続冷却によ
り徐冷を行う場合は、その冷却速度が５℃／分を越える
と、球状パーライトの変態態度が下がりすぎて層状の低
温変態パーライトもしくはベイナイトが生成して軟質化
できないのでこれを上限とした。軟質化の点からは、冷
却速度は小さい方がいいが、設備上、生産性上の実用的
な面を考慮すると、０．２〜ｂ
化と生産性を両立させる望ましい冷却速度範囲である。Next, after heating under the above conditions, (a) if slow cooling is performed by continuous cooling, if the cooling rate exceeds 5°C/min, the transformation behavior of spherical pearlite will drop too much, resulting in layered low-temperature transformed pearlite. Otherwise, bainite is generated and it cannot be softened, so this is set as the upper limit. From the point of view of softening, the lower the cooling rate is, the better; however, considering the practical aspects of equipment and productivity, the cooling rate range is preferably within the range of 0.2-b and achieving both productivity.
徐冷停止温度は、パーライト変態終了前に徐冷を停止す
るとその後の放冷過程で強度の高い低温パーライトもし
くはベイナイトが生成して硬くなるので、パーライト変
態終了温度とした。パーライト変態終了温度は鋼種、冷
却速度によって変るが、本発明の対象とする成分系の鋼
では、約６６０〜６９０℃である。The slow cooling stop temperature was set as the pearlite transformation finish temperature because if slow cooling is stopped before the end of pearlite transformation, high-strength low-temperature pearlite or bainite will be generated and hardened in the subsequent cooling process. The end temperature of pearlite transformation varies depending on the steel type and the cooling rate, but is approximately 660 to 690°C in the steel of the composition targeted by the present invention.
一方、（ロ）保定を行う場合、保定温度の上限を７４０
℃に限定したのは、７４０℃を越えると球状パーライト
変態を終了させるのに５時間以上を要し実用的でないた
めである。しかし、６９０℃より下ではセメンタイト間
隔が細かくなって。On the other hand, (b) When performing retention, the upper limit of the retention temperature is 740℃.
The temperature was limited to 740°C because it would take more than 5 hours to complete the spherical pearlite transformation, which is not practical. However, below 690℃, the cementite spacing becomes finer.
目標の軟質化度が得られない、また、保定時間は１５分
未満ではパーライト変態が終了せず、目標の軟質化に到
達しないので１５分保定を下限とした。一方３時間を越
えて保定しても軟質化はもはや進行しないので３時間を
上限とした。保定後は放冷を行うものであるが、これは
前記保定によってパーライト変態が完了するので、その
後徐冷する必要がないからである。 ”
以下、実施例により本発明の効果をさらに具体的に説明
する。The target degree of softening cannot be obtained, and if the retention time is less than 15 minutes, the pearlite transformation will not be completed and the target softening will not be achieved, so the retention time of 15 minutes was set as the lower limit. On the other hand, since softening no longer progresses even if held for more than 3 hours, the upper limit was set at 3 hours. After the retention, the material is left to cool. This is because the pearlite transformation is completed by the retention, so there is no need for subsequent gradual cooling. ” Hereinafter, the effects of the present invention will be explained in more detail with reference to Examples.
［実施例］
第１表に供試材の化学組成ならびに通常の熱間圧延で１
１φＩに仕上げた後の冷却条件等を示す。[Example] Table 1 shows the chemical composition of the sample material and the
The cooling conditions etc. after finishing to 1φI are shown.
同表中試験番号Ｎｏ、４．６．１０−１５．２１−２４
．２８が本発明例で、その他は比較例である。これらの
材料を用いて、引張試験はＪＩＳＩ４Ａ号試験片で行い
、冷鍛性の評価は０ 、５ ｍｍ深さのＶノツチを付け
た１０φｍｍＸ１５ｍｍの試験片で据込率４０％の圧縮
試験を行った時の割れの発生の有無で求め、○印は割れ
が発生がしなかったこと、Ｘ印は割れが発生したことを
示す、これらの試験結果を第１表に併記する。Test number No. 4.6.10-15.21-24 in the same table
．． No. 28 is an example of the present invention, and the others are comparative examples. Using these materials, tensile tests were performed using JISI No. 4A test pieces, and cold forgeability evaluation was performed using 10φmm x 15mm test pieces with a V-notch of 0 and 5 mm depth and a compression test with an upsetting rate of 40%. The test results are determined based on the presence or absence of cracking when the test piece is heated, and the ○ mark indicates that no cracking occurred, and the X mark indicates that cracking occurred.These test results are also listed in Table 1.
同表に見られるように、本発明例はいずれも圧延材にお
いて引張強度２０ ＋５９ Ｃｅｑ （ｋｇ／＋ｉｍ”
）を十分に下まわり、満足すべき軟質化度が得られてい
る。また、冷間鍛造性と焼入れ焼戻し処理後の靭性も申
し分ない。As seen in the table, all of the examples of the present invention have a tensile strength of 20 +59 Ceq (kg/+im") in the rolled material.
), and a satisfactory degree of softening was obtained. It also has excellent cold forgeability and toughness after quenching and tempering.
これに対して、比較例であるＮｏ、３．８，９゜２５．
２６．２７はいずれも焼鈍条件が不適切なために軟質化
されなかった例である。即ち、Ｎｏ。On the other hand, the comparative example No. 3.8, 9°25.
No. 26 and No. 27 are both examples in which softening was not achieved due to inappropriate annealing conditions. That is, No.
３は加熱後の冷却速度が速すぎたために、セメンタイト
間隔が細かくなって、またＮｏ、８は加熱源底が高すぎ
たために層状パーライト変態が生成して、いずれも軟質
化されなかった。さらに、Ｎｏ、９は保定温度が高すぎ
、Ｎｏ、２５は加熱時間が短かすぎ、Ｎｏ、２６は保定
時間が短かすぎ、Ｎｏ、２７は保定温度が低すぎるため
に、いずれも目標強度を下回ることができなかった。。In No. 3, the cooling rate after heating was too fast, so the cementite spacing became fine, and in No. 8, the bottom of the heating source was too high, resulting in layered pearlite transformation, and neither softened. Furthermore, No. 9 has a too high retention temperature, No. 25 has too short a heating time, No. 26 has a too short retention time, and No. 27 has a retention temperature too low, so all of them have the target strength. could not be lower than that. .
一方、比較例であるＮｏ、１．．２，５，７．１６−２
０は、鋼材組成が不適切な例で、 Ｎｏ、 １はＣｒ、
Ｎｏ、、２はＭｎ、Ｎｏ、５はＳｉの含有是がそれぞれ
多すぎろために軟質化されていない。また、Ｎｏ、７は
１１．Ｎｏ、１９はＶ、Ｎｏ、２０は゛［ｉの含有址が
それぞれ多すぎるために軟質化は達成されているものの
冷間ｔ８造性が悪い例である。On the other hand, No. 1, which is a comparative example. ．． 2,5,7.16-2
0 is an example where the steel material composition is inappropriate, No. 1 is Cr,
Nos. 2 and 2 contain too much Mn, and Nos. 5 and 5 contain too much Si, so they are not softened. Also, No. 7 is 11. No. 19 is an example of V, and No. 20 is an example in which the amount of "[i" contained is too large, so although softening has been achieved, the cold t8 formability is poor.
さらに、Ｎｏ、１８はＳｉとＭｎの含有址が多すぎるた
めに強度が高く、しかもＮｂｉが多すぎるために冷間鍛
造性も悪い、Ｎｏ、２５．２６はそれぞれｐ、ｓｍが多
すぎて冷間鍛造性に問題があった例である。Furthermore, No. 18 has high strength because it contains too much Si and Mn, and has poor cold forgeability because it contains too much Nbi. No. 25.26 has too much p and sm, so This is an example where there was a problem with forgeability.
［発明の効果］
以上の実施例からも明らかなごとく、本発明は鋼材組成
と球状化焼鈍条件とを適９ｊに選択することによって、
機械構造用高合金鋼の球状化焼鈍時間の短縮と軟質化の
確保、冷間鍛造性の確保を両立させることを可能にした
ものであり、産業上の効果は極めて顕著なものがある。[Effect of the invention] As is clear from the above examples, the present invention achieves the following effects by appropriately selecting the steel composition and the spheroidizing annealing conditions
This has made it possible to reduce the spheroidizing annealing time of high-alloy steel for machine structures, ensure softening, and ensure cold forgeability, and the industrial effects are extremely significant.
Claims (2)
１％未満、 Ｍｎ：０．２〜０．５％、 Ｂ：０．０００３〜０．０１％、 Ｃｒ：０．９超〜１．８％、 Ａｌ：０．０１〜０．１％、 を含有し、Ｐを０．０２％未満、Ｓを０．０２％未満と
制限し、残部はＦｅおよび不可避不純物よりなる鋼につ
いて、７４０超〜８５０℃に２０秒〜２時間加熱した後
、（イ）５℃／分以下の冷却速度でパーライト変態終了
までの温度範囲を徐冷するか、あるいは（ロ）６９０〜
７４０℃の範囲の温度に１５分〜３時間保定した後放冷
するか、（イ）、（ロ）いずれかの球状化処理を実施す
ることを特徴とする機械構造用合金鋼の球状化焼鈍法。(1) C: 0.15-0.65%, Si: 0.
less than 1%, Mn: 0.2-0.5%, B: 0.0003-0.01%, Cr: more than 0.9-1.8%, Al: 0.01-0.1%, For steels containing P and S of less than 0.02% and S of less than 0.02%, with the remainder consisting of Fe and unavoidable impurities, after heating to over 740°C to 850°C for 20 seconds to 2 hours, (I) ) Slowly cool the temperature range until the end of pearlite transformation at a cooling rate of 5°C/min or less, or (b) 690~
Spheroidizing annealing of alloy steel for machine structures, characterized in that the temperature is maintained at a temperature in the range of 740°C for 15 minutes to 3 hours and then allowed to cool, or the spheroidizing treatment of either (a) or (b) is performed. Law.
制限し、更に （Ａ）Ｎｉ：１％以下、Ｍｏ：０．３％以下、Ｃｕ：１
％以下の１種または２種以上、 （Ｂ）Ｔｉ：０．００２〜０．０５％、Ｎｂ：０．００
５〜０．０５％、Ｖ：０．００５〜０．２％の１種また
は２種以上、 の（Ａ）、（Ｂ）の群の一方または両方を含有し、残部
はＦｅおよび不可避不純物よりなる鋼について、７４０
超〜８５０℃に２０秒〜２時間加熱した後、（イ）５℃
／分以下の冷却速度でパーライト変態終了までの温度範
囲を徐冷するか、あるいは（ロ）６９０〜７４０℃の範
囲の温度に１５分〜３時間保定した後放冷するか、（イ
）、（ロ）いずれかの球状化処理を実施することを特徴
とする機械構造用合金鋼の球状化焼鈍法(2) C: 0.15-0.65% by weight. Si: less than 0.1%, Mn: 0.2-0.5%, B: 0.0003-0.01%, Cr: more than 0.9-1.8%, Al: 0.01-0. 1%, P is limited to less than 0.02%, S is limited to less than 0.02%, and (A) Ni: 1% or less, Mo: 0.3% or less, Cu: 1
% or less, (B) Ti: 0.002 to 0.05%, Nb: 0.00
5 to 0.05%, V: 0.005 to 0.2%, one or more of the groups (A) and (B), and the remainder is Fe and unavoidable impurities. About Naru Steel, 740
After heating to ultra-850℃ for 20 seconds to 2 hours, (a) 5℃
Either slowly cool the temperature range until the end of pearlite transformation at a cooling rate of /min or less, or (b) maintain the temperature in the range of 690 to 740°C for 15 minutes to 3 hours and then let it cool. (b) A spheroidizing annealing method for machine structural alloy steel, which is characterized by carrying out any of the spheroidizing treatments.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19528686A JPS6353208A (en) | 1986-08-22 | 1986-08-22 | Spheroidizing annealing method for alloy steel for machine structural use |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19528686A JPS6353208A (en) | 1986-08-22 | 1986-08-22 | Spheroidizing annealing method for alloy steel for machine structural use |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS6353208A true JPS6353208A (en) | 1988-03-07 |
Family
ID=16338629
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP19528686A Pending JPS6353208A (en) | 1986-08-22 | 1986-08-22 | Spheroidizing annealing method for alloy steel for machine structural use |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6353208A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008088448A (en) * | 2006-09-29 | 2008-04-17 | Sanyo Special Steel Co Ltd | Method for annealing low-carbon steel containing cr |
| CN107587069A (en) * | 2017-08-25 | 2018-01-16 | 武汉钢铁有限公司 | A kind of high-intensity high-tenacity bolt steel and production method |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61174321A (en) * | 1985-01-29 | 1986-08-06 | Nippon Steel Corp | Spheroidizing annealing method of machine structural steel |
-
1986
- 1986-08-22 JP JP19528686A patent/JPS6353208A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61174321A (en) * | 1985-01-29 | 1986-08-06 | Nippon Steel Corp | Spheroidizing annealing method of machine structural steel |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008088448A (en) * | 2006-09-29 | 2008-04-17 | Sanyo Special Steel Co Ltd | Method for annealing low-carbon steel containing cr |
| CN107587069A (en) * | 2017-08-25 | 2018-01-16 | 武汉钢铁有限公司 | A kind of high-intensity high-tenacity bolt steel and production method |
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