JPH0791579B2 - Method for manufacturing case-hardening steel in which crystal grains do not coarsen during carburizing heat treatment - Google Patents

Method for manufacturing case-hardening steel in which crystal grains do not coarsen during carburizing heat treatment

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Publication number
JPH0791579B2
JPH0791579B2 JP3124001A JP12400191A JPH0791579B2 JP H0791579 B2 JPH0791579 B2 JP H0791579B2 JP 3124001 A JP3124001 A JP 3124001A JP 12400191 A JP12400191 A JP 12400191A JP H0791579 B2 JPH0791579 B2 JP H0791579B2
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JP
Japan
Prior art keywords
steel
heat treatment
deoxidation
alloy
carburizing heat
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 - Fee Related
Application number
JP3124001A
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Japanese (ja)
Other versions
JPH04350113A (en
Inventor
啓督 高田
善郎 子安
雄二 河内
Original Assignee
新日本製鐵株式会社
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Priority to JP3124001A priority Critical patent/JPH0791579B2/en
Publication of JPH04350113A publication Critical patent/JPH04350113A/en
Publication of JPH0791579B2 publication Critical patent/JPH0791579B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Description

【発明の詳細な説明】Detailed Description of the Invention
【0001】[0001]
【産業上の利用分野】本発明は、自動車、産業機械など
の機械部品に加工される鋼のうち、特に浸炭熱処理を施
されて部品となる鋼に関するものである。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to steel that is machined into machine parts such as automobiles and industrial machines, and in particular to steel that is carburized and heat treated to become parts.
【0002】[0002]
【従来の技術】肌焼鋼を素材として作られる自動車、産
業用機械部品は、熱間あるいは冷間で成形、切削された
後、通常920℃から930℃程度の炭素雰囲気中に加
熱し、長時間をかけて炭素を表面部に拡散させ、表面を
強化して使用されている。近年はコスト低減のため、高
温短時間にて浸炭熱処理を行うことが要求されている
が、高温での浸炭熱処理における問題点は異常な粗大粒
が発生することである。粗大粒は熱処理歪を増大させ、
歯車では使用時の騒音の原因となる。
2. Description of the Related Art Automobiles and industrial machine parts made of case-hardening steel are hot or cold-formed and cut, and then usually heated in a carbon atmosphere of about 920 ° C to 930 ° C for a long time. It is used by diffusing carbon over the surface over time to strengthen the surface. In recent years, in order to reduce the cost, it has been required to carry out a carburizing heat treatment at a high temperature in a short time, but a problem in the carburizing heat treatment at a high temperature is that abnormal coarse grains are generated. Coarse grains increase heat treatment strain,
Gears cause noise during use.
【0003】浸炭熱処理において粗大粒の発生を抑制す
るためには、鋼中に微細析出物を分散させることが有効
であることは良く知られており、例えば特開平2−85
342号公報には微細NbNを利用する方法が述べられ
ている。また、高温における結晶粒の粗大化防止効果を
高めるためには、分散する析出物粒子を微細化すること
が有効であり、特開昭63−162812号公報には鋳
造後の凝固速度を制御して鋼中のTiNを微細分散させ
る方法が示されている。
It is well known that it is effective to disperse fine precipitates in steel in order to suppress the generation of coarse grains in the carburizing heat treatment. For example, JP-A-2-85.
Japanese Patent No. 342 describes a method of using fine NbN. Further, in order to enhance the effect of preventing coarsening of crystal grains at high temperature, it is effective to make dispersed precipitate particles finer, and JP-A-63-162812 discloses that the solidification rate after casting is controlled. Method for finely dispersing TiN in steel.
【0004】[0004]
【発明が解決しようとする課題】これらの発明により、
高温で粗大粒が発生しにくい肌焼鋼が実用化されるよう
になってきてはいるが、加工条件によって高温浸炭熱処
理での粗大粒発生は防止しきれないのが実情である。本
発明は、酸化物による晶析出物の制御効果を利用し、よ
り一層効果的でかつ安定な粗大粒の発生防止を実現せし
め、高温における浸炭熱処理時に結晶粒が粗大化しない
肌焼鋼の製造方法を提供することを目的とするものであ
る。
With these inventions,
Although case-hardening steel that does not easily generate coarse grains at high temperatures has come into practical use, the fact that coarse grains cannot be prevented by high-temperature carburizing heat treatment cannot be prevented depending on the processing conditions. The present invention utilizes the control effect of crystal precipitates by oxides to realize a more effective and stable prevention of coarse grains, and the production of case-hardening steel in which the crystal grains do not coarsen during carburizing heat treatment at high temperature. It is intended to provide a method.
【0005】[0005]
【課題を解決するための手段】従来の技術に記載したよ
うに、浸炭熱処理時に生ずる結晶粒の粗大化を防止する
ためには、浸炭熱処理温度において安定な析出物あるい
は晶出物を微細分散させることが有効であるが、本発明
者らは、これまで浸炭熱処理時の粗大粒発生防止に利用
されることのなかったMnS粒子が、実は粗大粒発生防
止に有効であることを見出した。
As described in the prior art, in order to prevent the coarsening of crystal grains that occurs during the carburizing heat treatment, a stable precipitate or crystallized substance is finely dispersed at the carburizing heat treatment temperature. However, the present inventors have found that MnS particles that have not been used to prevent the generation of coarse particles during the carburizing heat treatment are actually effective for preventing the generation of coarse particles.
【0006】また、鋼の脱酸時に生成する微細な酸化
物、あるいは鋼鋳造後の冷却時に晶析出する酸化物を、
MnSの晶析出核として最適に利用することにより、M
nSを鋼中に微細分散化できること、またその結果、粗
大粒発生の防止効果が大きくなることを発見して本発明
を完成した。本発明者らが表1に示した基本成分の鋼を
用いて、酸化物を利用した晶析出物の制御方法を鋭意研
究した結果、MnS粒子の大きさに及ぼすAl脱酸前の
溶存酸素量と脱酸Al量の影響について、図1に示した
ような結果を得た。図1は鋳造ままの10kg鋼塊におけ
る結果であり、同図から脱酸前の溶存酸素量が10〜1
60ppm であるとき、かつAl量が0.005%から
0.06%である時に比較的微細なMnSが晶析出して
いることが分かる。
Further, fine oxides produced during deoxidation of steel or oxides precipitated during cooling after casting of steel,
By optimally utilizing it as a crystal precipitation nucleus of MnS, M
The present invention has been completed by discovering that nS can be finely dispersed in steel and, as a result, the effect of preventing the formation of coarse particles becomes large. As a result of diligent studies by the inventors of the present invention on the control method of crystal precipitates using oxides, using the steels of the basic components shown in Table 1, the amount of dissolved oxygen before Al deoxidation that affects the size of MnS particles Regarding the effect of the deoxidized Al amount, the results shown in FIG. 1 were obtained. Figure 1 shows the results for an as-cast 10 kg steel ingot. From the figure, the amount of dissolved oxygen before deoxidation is 10 to 1
It can be seen that relatively fine MnS is crystallized when the content is 60 ppm and the Al content is 0.005% to 0.06%.
【0007】また、表1の基本成分の鋼を種々の脱酸条
件、鋳造後の冷却条件で溶製し、MnSの大きさを変え
たインゴットから試料を切出し、900℃で2時間焼準
した後、70%の冷間加工を加え、1000℃に1時間
加熱焼入れして旧オーステナイト組織を調べた。その結
果を図2に表す。図2よりMnSが微細なほど再加熱オ
ーステナイト組織の平均粒度が小さく、かつ粗大な粒が
発生し難くなることが分かる。
Further, steels having the basic components shown in Table 1 were melted under various deoxidizing conditions and cooling conditions after casting, samples were cut out from ingots having different MnS sizes, and normalized at 900 ° C. for 2 hours. After that, 70% cold working was added, and heating and quenching was performed at 1000 ° C. for 1 hour to examine the former austenite structure. The result is shown in FIG. It can be seen from FIG. 2 that the finer the MnS, the smaller the average grain size of the reheated austenite structure and the more difficult it is for coarse grains to occur.
【0008】[0008]
【表1】 [Table 1]
【0009】さらに、Ti、Zrの脱酸元素についても
同様の研究を積み重ねた結果、現用の鋼精錬、鋳造設備
で実現できる、晶析出物制御法を見出し、本発明を完成
させた。すなわち、本発明の要旨とするところは以下の
とおりである。 (1)重量%で C :0.10〜0.30%、Si:0.05〜0.5
0%、 Mn:0.30〜2.00%、S :0.02〜0.2
0%、 N :0.002〜0.020%、 および Al:0.005〜0.050%、Ti:0.005〜
0.030% の1種あるいは2種を含む鋼を製造する際、製鋼炉から
出鋼された粗溶鋼にC、Si、Mnの単体もしくは合金
の1種または2種以上を添加する脱酸処理、および/ま
たは真空脱ガス処理にて脱酸を行い、溶鋼中の溶存酸素
量を10〜150ppm とした後、Al、TiあるいはA
l合金、Ti合金の1種または2種で脱酸することを特
徴とする浸炭熱処理時に結晶粒が粗大化しない肌焼鋼の
製造方法。
Further, as a result of conducting similar research on the deoxidizing elements of Ti and Zr, the inventors have found a method for controlling crystal precipitates that can be realized by the current steel refining and casting equipment, and completed the present invention. That is, the gist of the present invention is as follows. (1) C: 0.10 to 0.30% by weight, Si: 0.05 to 0.5
0%, Mn: 0.30 to 2.00%, S: 0.02 to 0.2
0%, N: 0.002-0.020%, and Al: 0.005-0.050%, Ti: 0.005-
When producing 0.030% steel containing one or two kinds, deoxidation treatment by adding one or more kinds of C, Si, Mn simple substance or alloy to the crude molten steel discharged from the steelmaking furnace , And / or deoxidation by vacuum degassing treatment to adjust the dissolved oxygen amount in the molten steel to 10 to 150 ppm, and then Al, Ti or A
1. A method for manufacturing case-hardening steel, in which crystal grains do not coarsen during carburizing heat treatment, which is characterized by deoxidizing one or two of a 1-alloy and a Ti-alloy.
【0010】(2)重量%で C :0.10〜0.30%、Si:0.05〜0.5
0%、 Mn:0.30〜2.00%、S :0.02〜0.2
0%、 N :0.002〜0.020%、および Cr:0.20〜2.00%、Mo:0.10〜0.5
0%、 Ni:0.30〜4.00%の1種以上、および Al:0.005〜0.050%、Ti:0.005〜
0.030% の1種あるいは2種を含む鋼を製造する際、製鋼炉から
出鋼された粗溶鋼にC、Si、Mnの単体もしくは合金
の1種または2種以上を添加する脱酸処理、および/ま
たは真空脱ガス処理にて脱酸を行い、溶鋼中の溶存酸素
量を10〜150ppm とした後、Al、TiあるいはA
l合金、Ti合金の1種または2種で脱酸することを特
徴とする浸炭熱処理時に結晶粒が粗大化しない肌焼鋼の
製造方法。
(2) C: 0.10 to 0.30% by weight, Si: 0.05 to 0.5
0%, Mn: 0.30 to 2.00%, S: 0.02 to 0.2
0%, N: 0.002-0.020%, and Cr: 0.20-2.00%, Mo: 0.10-0.5.
0%, one or more of Ni: 0.30 to 4.00%, and Al: 0.005 to 0.050%, Ti: 0.005.
When producing 0.030% steel containing one or two kinds, deoxidation treatment by adding one or more kinds of C, Si, Mn simple substance or alloy to the crude molten steel discharged from the steelmaking furnace , And / or deoxidation by vacuum degassing treatment to adjust the dissolved oxygen amount in the molten steel to 10 to 150 ppm, and then Al, Ti or A
1. A method for manufacturing case-hardening steel, in which crystal grains do not coarsen during carburizing heat treatment, which is characterized by deoxidizing one or two of a 1-alloy and a Ti-alloy.
【0011】(3)前項(1)または(2)の成分に加
えて、重量%でZr:0.010〜0.070%、C
e:0.010〜0.070%、Hf:0.010〜
0.070%、の1種あるいは2種以上を含む鋼を製造
する際、製鋼炉から出鋼された粗溶鋼にC、Si、Mn
の単体もしくは合金の1種または2種以上を添加する脱
酸処理、および/または真空脱ガス処理にて脱酸を行
い、溶鋼中の溶存酸素量を10〜150ppm とした後、
Al、Tiの1種または2種とZr、Ce、Hfの1種
あるいは2種以上の単体もしくは合金で複合脱酸するこ
とを特徴とする浸炭熱処理時に結晶粒が粗大化しない肌
焼鋼の製造方法。
(3) In addition to the above-mentioned component (1) or (2), Zr: 0.010 to 0.070% by weight, C
e: 0.010 to 0.070%, Hf: 0.010
When producing steel containing 0.070% of one or more, C, Si and Mn were added to the crude molten steel discharged from the steelmaking furnace.
After deoxidizing by adding one or more of the above simple substance or alloy, and / or vacuum degassing, the dissolved oxygen content in the molten steel is adjusted to 10 to 150 ppm,
Manufacture of case-hardening steel that does not coarsen crystal grains during carburizing heat treatment, which is characterized by complex deoxidizing one or more of Al and Ti and one or more of Zr, Ce, and Hf, or alloys. Method.
【0012】(4)前項(1)、(2)または(3)の
方法に加え、鋳造後凝固点から1000℃までの平均冷
却速度を20℃/分以上とすることを特徴とする浸炭熱
処理時に結晶粒が粗大化しない肌焼鋼の製造方法。以下
に、本発明の成分、条件の限定理由について述べる。 C:Cは脱酸剤として溶鋼中の溶存酸素量を調整するの
に有効な元素であり、またCは鋼の強化元素であるが、
0.10%未満では鋼の強度を向上させるのに不足であ
り、0.30%を越えると鋼の靱性を低下させる。
(4) In addition to the method described in (1), (2) or (3) above, during carburizing heat treatment characterized in that the average cooling rate from the freezing point after casting to 1000 ° C. is 20 ° C./min or more. A method for manufacturing case-hardening steel in which crystal grains do not coarsen. The reasons for limiting the components and conditions of the present invention will be described below. C: C is an element effective as a deoxidizer for adjusting the amount of dissolved oxygen in molten steel, and C is a strengthening element of steel,
If it is less than 0.10%, it is insufficient to improve the strength of the steel, and if it exceeds 0.30%, the toughness of the steel is lowered.
【0013】SiおよびMn:本発明のSi、Mnは弱
脱酸元素として溶鋼中の酸素量を制御する。すなわち、
Alで最終脱酸する前の酸素量の制御に有効である。ま
た、Si、Mnの酸化物はSiとMnの複合酸化物とし
て、あるいはAlとSi、AlとMnの複合酸化物とし
て鋼中に微細分散し、MnSの晶析出核となる。MnS
の晶析出核としての酸化物をつくるため、Siは0.0
5%以上、Mnは0.30%以上が必要である。Si、
Mnは鋼の固溶強化元素であるが、Siは0.50%を
越えて添加した場合、浸炭熱処理時に粒界酸化層ができ
やすく、最終部品となった時の疲労特性を劣化させる。
またMnは2.00%を越えて添加した場合、靱性を著
しく低下させる。
Si and Mn: Si and Mn of the present invention control the amount of oxygen in molten steel as a weak deoxidizing element. That is,
It is effective for controlling the amount of oxygen before the final deoxidation with Al. Further, the oxides of Si and Mn are finely dispersed in the steel as a complex oxide of Si and Mn, or a complex oxide of Al and Si, and Al and Mn to form MnS crystal precipitation nuclei. MnS
To form an oxide as a crystal precipitation nucleus of
5% or more and Mn must be 0.30% or more. Si,
Mn is a solid solution strengthening element of steel, but when Si is added in an amount of more than 0.50%, a grain boundary oxide layer is easily formed during the carburizing heat treatment, which deteriorates the fatigue properties of the final part.
When Mn is added in excess of 2.00%, the toughness is significantly reduced.
【0014】なお、Si、MnはAl、Ti、Zrによ
る脱酸の前と後のいずれに添加しても十分な量の複合酸
化物をつくり、MnS、TiN等の晶析出核として働
く。 Cr:Crは強度の向上のために添加される元素であ
り、0.20%未満では強度の向上のために十分ではな
く、また2.00%を越えて添加した場合、靱性を低下
させる。
It should be noted that Si and Mn form a sufficient amount of complex oxide whether added before or after deoxidation with Al, Ti or Zr, and act as crystal precipitation nuclei for MnS, TiN and the like. Cr: Cr is an element added for improving the strength. If it is less than 0.20%, it is not sufficient for improving the strength, and if it exceeds 2.00%, the toughness is lowered.
【0015】S:浸炭熱処理時の粗大粒発生を防止する
のに十分な量の微細MnSを晶析出させるためSは0.
02%以上が必要である。しかし、0.20%を越える
Sは多量の硫化物をつくるため、機械的性質に大きな異
方性をもたらすので、これを限定する。 N:Nは微細なAl、Ti窒化物を析出させ、高温にお
ける結晶粒粗大化防止効果を高める効果があるが、0.
002%未満のN量では十分な粗大粒発生防止効果が期
待できず、また0.020%を越えた場合、結晶粒の粗
大化は防止されるが靱性が低下する。
S: S is 0. to crystallize fine MnS in an amount sufficient to prevent the generation of coarse grains during the carburizing heat treatment.
02% or more is required. However, S exceeding 0.20% forms a large amount of sulfides, which brings about great anisotropy in mechanical properties, and is therefore limited. N: N has the effect of precipitating fine Al and Ti nitrides and enhancing the effect of preventing crystal grain coarsening at high temperatures.
If the N content is less than 002%, a sufficient effect of preventing coarse grains cannot be expected, and if it exceeds 0.020%, coarsening of crystal grains is prevented, but toughness decreases.
【0016】Mo:強度、靱性の向上、あるいは粒界酸
化層の低減にMoは有効である。0.10%未満ではこ
の効果が不十分であり、また0.50%を越えて添加し
た場合、かえって靱性が低下する。 Ni:NiもMo同様に強度と靱性を向上させる元素で
ある。また、疲労強度を向上させる効果もある。Niは
0.30%未満では効果が小さく、4.00%超ではコ
ストが高くなりすぎる。
Mo: Mo is effective for improving strength and toughness or reducing the grain boundary oxide layer. If it is less than 0.10%, this effect is insufficient, and if it exceeds 0.50%, the toughness is rather deteriorated. Ni: Ni is an element that improves strength and toughness like Mo. It also has the effect of improving fatigue strength. If Ni is less than 0.30%, the effect is small, and if it exceeds 4.00%, the cost becomes too high.
【0017】Al、TiおよびZr:Al、Tiおよび
Zrは、鋼中に酸化物として微細分散し、浸炭熱処理時
の粗大粒発生防止に有効な微細MnS粒子の晶析出核と
なる。また、窒化物として析出して同じく浸炭熱処理時
の粗大粒発生を防止する。Al、Ti、Zr添加前の溶
鋼段階における溶存酸素量が150ppm 以下で、かつA
l、TiおよびZr量範囲がそれぞれ、0.005〜
0.060%、0.005〜0.060%、0.010
〜0.070%において、MnS粒子が微細分散する。
0.005%未満のAl、Ti、あるいは0.010%
未満のZr添加では晶析出核となる酸化物が不足し、ま
た0.06%を越えたAl、Ti、0.07%を越えた
Zrを添加すると、酸化物上にMnSが微細に晶析出し
にくくなる。
Al, Ti and Zr: Al, Ti and Zr are finely dispersed in the steel as oxides and serve as crystal precipitation nuclei of fine MnS particles which are effective in preventing the generation of coarse grains during carburizing heat treatment. In addition, it also prevents precipitation of coarse particles during the carburizing heat treatment by precipitation as a nitride. The dissolved oxygen content in the molten steel stage before addition of Al, Ti, and Zr is 150 ppm or less, and A
l, Ti and Zr content ranges of 0.005 to
0.060%, 0.005-0.060%, 0.010
At 0.070%, MnS particles are finely dispersed.
Al, Ti less than 0.005%, or 0.010%
If Zr is added in an amount of less than less than 0%, the oxide serving as a crystal precipitation nucleus will be insufficient, and if more than 0.06% of Al and Ti and more than 0.07% of Zr are added, MnS will be finely crystallized on the oxide. Hard to do.
【0018】Ce、Hf:比重の大きなCe、Hfを添
加して、Al、Tiとの酸化物とすると、酸化物の凝集
浮上が防止され、晶析出物の大きさ、数の分布が鋳造時
間に影響されにくくなる。この効果を期待するには0.
010%以上が必要であるが、0.070%を越える添
加はコストがかかることからこれを限定する。本発明に
おいて重要な点の一つは晶析出核として適当な酸化物を
微細分散させることである。しかるに、酸化物を形成す
る強脱酸元素を、150ppm を越える溶存酸素を含む粗
溶鋼に添加した場合には、酸化物は粗大化し、また晶析
出核となりにくくなる。また、溶鋼中の溶存酸素量が1
0ppm 未満では必要とする酸化物が十分形成されない。
よって、始めにC、Si合金、Mn合金の1種または2
種以上を添加する脱酸処理、および/または真空脱ガス
処理にて脱酸を行い、溶鋼中の溶存酸素量を10〜15
0ppm とした後、Al、Ti、ZrあるいはAl合金、
Ti合金、Zr合金の1種または2種以上で最終脱酸す
るのが適当である。
Ce, Hf: When Ce and Hf having a large specific gravity are added to form an oxide with Al and Ti, the flocculation and floating of the oxide are prevented, and the distribution of the size and number of crystal precipitates depends on the casting time. Less susceptible to. To expect this effect 0.
010% or more is required, but the addition of more than 0.070% is costly, so this is limited. One of the important points in the present invention is to finely disperse a suitable oxide as crystal precipitation nuclei. However, when a strong deoxidizing element that forms an oxide is added to the crude molten steel containing dissolved oxygen in excess of 150 ppm, the oxide becomes coarse and is less likely to become a crystal precipitation nucleus. Also, the amount of dissolved oxygen in molten steel is 1
If it is less than 0 ppm, the required oxide is not sufficiently formed.
Therefore, first, one or two of C, Si alloy, and Mn alloy is used.
Deoxidation treatment is performed by adding at least one species and / or vacuum degassing treatment, and the amount of dissolved oxygen in molten steel is set to 10 to 15
After adjusting to 0ppm, Al, Ti, Zr or Al alloy,
It is suitable to perform final deoxidation with one or more of Ti alloy and Zr alloy.
【0019】C、Si、Mnの単体もしくは合金の1種
または2種以上を添加する脱酸処理、および真空脱ガス
処理による脱酸は、ともに溶存酸素量の調整が目的であ
り、順番はこれを限定しない。また、その他の成分は溶
存酸素量にはほとんど影響しないので、添加の時期を限
定しない。また、鋳造後凝固点から1000℃までの平
均冷却速度を20℃/分以上とすることにより、凝固
中、あるいは凝固後に晶析出するMnS、TiNは微細
化され、浸炭熱処理時の粗大粒発生防止効果は一層高め
られる。
Deoxidation treatment by adding one or more of C, Si and Mn alone or alloys, and deoxidation by vacuum degassing treatment are for the purpose of adjusting the amount of dissolved oxygen. Does not limit Moreover, since the other components have almost no effect on the dissolved oxygen amount, the timing of addition is not limited. Further, by setting the average cooling rate from the freezing point after casting to 1000 ° C. to 20 ° C./min or more, MnS and TiN that are crystallized during solidification or after solidification are refined, and the effect of preventing the formation of coarse grains during carburizing heat treatment is achieved. Is further enhanced.
【0020】本発明の方法は、強化のためさらにNbを
添加した鋼、被削性向上のためにCa、Bi、Pbを添
加した鋼、その他防錆、耐塩性向上等の目的で特許請求
の範囲に記載されていない元素を添加した鋼についても
有効な方法である。以下に実施例を説明する。
In the method of the present invention, a steel to which Nb is further added for strengthening, a steel to which Ca, Bi and Pb are added for improving machinability, and other purposes such as rust prevention and salt resistance improvement are claimed. It is also an effective method for steel containing elements not listed in the range. Examples will be described below.
【0021】[0021]
【実施例】実施例1 真空溶解炉にて20kgの粗溶鋼を溶解し、表2に示した
成分に調整した後、表3に示したようにAl、Ti、Z
r脱酸前の酸素量を変えて脱酸を行い鋼塊に鋳造した。
鋳造後凝固点から1000℃までの平均冷却速度は30
℃/分 となるような鋳型を使用した。冷却後の鋼塊を
1200℃に加熱して直径30mmの棒鋼に成形し、これ
を試験素材とした。
EXAMPLES Example 1 After melting 20 kg of crude molten steel in a vacuum melting furnace and adjusting the components shown in Table 2, as shown in Table 3, Al, Ti, Z
r Deoxidation was performed by changing the amount of oxygen before deoxidation, and cast into a steel ingot.
The average cooling rate from the freezing point to 1000 ° C after casting is 30
A mold was used such that the temperature was ° C / min. The cooled steel ingot was heated to 1200 ° C. and formed into a steel bar having a diameter of 30 mm, which was used as a test material.
【0022】浸炭熱処理時の組織を再現するため、この
試験素材を直径10mm、高さ15mmの円柱試料とし、冷
間で50%圧下した後、950℃から1100℃に1時
間再加熱、焼入し、旧オーステナイト結晶粒を観察し
た。粗大粒の発生結果を表3に示す。ここで粗大粒の発
生とは、マトリクスの平均粒径の3倍以上の径を有する
粒の出現を表わす。
In order to reproduce the structure at the time of carburizing heat treatment, this test material was used as a cylindrical sample having a diameter of 10 mm and a height of 15 mm, cold-pressed by 50%, and then reheated from 950 ° C to 1100 ° C for 1 hour and quenched. Then, the old austenite crystal grains were observed. Table 3 shows the results of generation of coarse particles. Here, the occurrence of coarse particles means the appearance of particles having a diameter three times or more the average particle diameter of the matrix.
【0023】表3より、Al、TiあるいはZr脱酸前
の酸素量が10〜150ppm である時に1000℃の高
温浸炭熱処理時に粗大粒が発生しないことが明らかであ
る。
From Table 3, it is clear that coarse particles are not generated during the high temperature carburizing heat treatment at 1000 ° C. when the oxygen content before deoxidation of Al, Ti or Zr is 10 to 150 ppm.
【0024】[0024]
【表2】 [Table 2]
【0025】[0025]
【表3】 [Table 3]
【0026】実施例2 溶解炉にて20kgの粗溶鋼を溶解した後、C、Si、M
nあるいは真空脱ガス処理にて予備脱酸し、他の成分を
調整して溶存酸素量を100ppm 以下とした後、脱酸剤
であるAl、Ti、Zrの添加量を変えた脱酸を行い、
表4〜6に示した成分の鋼塊を鋳造した。鋳造後凝固点
から1000℃までの平均冷却速度は30℃/分 とな
るような鋳型を使用した。冷却後の鋼塊を1200℃に
加熱して直径30mmの棒鋼に成形し、これを試験素材と
した。
Example 2 After melting 20 kg of crude molten steel in a melting furnace, C, Si, M
n or vacuum degassing to pre-deoxidize and adjust other components to adjust the dissolved oxygen content to 100ppm or less, then deoxidize by changing the addition amount of Al, Ti, Zr ,
Steel ingots having the components shown in Tables 4 to 6 were cast. A mold was used such that the average cooling rate from the solidification point to 1000 ° C after casting was 30 ° C / min. The cooled steel ingot was heated to 1200 ° C. and formed into a steel bar having a diameter of 30 mm, which was used as a test material.
【0027】この試験素材を750℃に8時間加熱空冷
する焼準し後、直径10mm、高さ15mmの円柱試料と
し、冷間で50%圧下した。続いて浸炭熱処理の再現の
ため1000℃に1時間再加熱、焼入し、粗大粒の発生
を調べた。この結果を表6に示した。表6に示したよう
に、本発明の成分の鋼は1000℃浸炭の再現実験にお
いて粗大粒が発生しない。
This test material was heat-air-cooled at 750 ° C. for 8 hours, air-cooled, and then made into a cylindrical sample having a diameter of 10 mm and a height of 15 mm, which was cold-rolled by 50%. Subsequently, in order to reproduce the carburizing heat treatment, reheating to 1000 ° C. for 1 hour and quenching were performed, and generation of coarse particles was examined. The results are shown in Table 6. As shown in Table 6, the steel of the component of the present invention does not generate coarse grains in the 1000 ° C. carburization reproduction experiment.
【0028】表6において比較鋼No. 25の鋼には粗大
粒が発生していないが、Nの限定理由で述べたように
0.025%のNを添加した場合には粗大粒が発生しな
くても靱性が低下する。
Coarse grains are not generated in the steel of Comparative Steel No. 25 in Table 6, but coarse grains are generated when 0.025% of N is added as described in the reason for limiting N. Even without it, the toughness decreases.
【0029】[0029]
【表4】 [Table 4]
【0030】[0030]
【表5】 [Table 5]
【0031】[0031]
【表6】 [Table 6]
【0032】実施例3 100ton の粗溶鋼を酸素転炉にて精錬した後、Si合
金、Mn合金を添加し、真空脱ガス装置にて溶存酸素量
を表7に示したように100ppm 以下とし、他の合金元
素を添加した後、Tiにて最終脱酸を行った。No. 33
の鋼は鋳造断面大きさが350×560mmの連続鋳造機
で鋳造し、最終的に直径100mmの棒鋼に圧延した(圧
下比25.0)。No. 34の鋼は鋳造断面大きさが16
2×162mmの連続鋳造機で鋳造し、最終的に直径37
mmの棒鋼に圧延した(圧下比24.4)。No. 33、3
4の鋳造時の凝固点から1000℃までの平均冷却速度
は、それぞれ10℃/分 、52℃/分 であった。No.
33、34の棒鋼から直径20mmの試料を切出し、12
00℃にて50%の熱間加工を加えた。その後900℃
で1時間焼準し、放冷したものを供試材とし、950℃
から1100℃に1時間加熱、焼入れして旧オーステナ
イト結晶粒を調べた。その結果、表7中に示したよう
に、本発明(3)を示した方法、すなわちNo. 34の鋼
の粗大粒発生温度は、No. 33の鋼より高温であること
が分かる。
Example 3 After refining 100 tons of crude molten steel in an oxygen converter, Si alloy and Mn alloy were added, and the amount of dissolved oxygen was set to 100 ppm or less as shown in Table 7 by a vacuum degassing apparatus. After adding other alloying elements, final deoxidation was performed with Ti. No. 33
Steel was cast by a continuous casting machine having a casting cross-sectional size of 350 × 560 mm, and finally rolled into a steel bar having a diameter of 100 mm (reduction ratio 25.0). No. 34 steel has a casting cross section size of 16
It is cast on a 2 x 162 mm continuous casting machine and finally has a diameter of 37.
It was rolled into a steel bar of mm (reduction ratio: 24.4). No. 33, 3
The average cooling rates from the freezing point to 1000 ° C during casting of No. 4 were 10 ° C / min and 52 ° C / min, respectively. No.
Samples with a diameter of 20 mm were cut out from steel bars 33 and 34, and 12
50% hot working was added at 00 ° C. Then 900 ° C
Normalized for 1 hour at room temperature and allowed to cool, then used as the test material at 950 ° C
To 1100 ° C. for 1 hour and quenched to examine old austenite crystal grains. As a result, as shown in Table 7, it is understood that the method showing the invention (3), that is, the coarse grain generation temperature of the No. 34 steel is higher than that of the No. 33 steel.
【0033】[0033]
【表7】 [Table 7]
【0034】[0034]
【発明の効果】以上述べたように、本発明の方法によっ
て製造された鋼は、高温における浸炭熱処理時に結晶粒
が粗大化せず、高温短時間での浸炭熱処理が可能であ
る。
As described above, in the steel produced by the method of the present invention, the crystal grains do not become coarse during the carburizing heat treatment at high temperature, and the carburizing heat treatment can be performed at high temperature in a short time.
【図面の簡単な説明】[Brief description of drawings]
【図1】鋳造ままの10kg鋼塊中のMnS円相当直径
(観察されたMnSの面積を円に置き換えた場合の円の
直径)に及ぼすAl脱酸前の溶存酸素量と脱酸Al量の
影響を示す図である。
Figure 1: MnS circle equivalent diameter in as-cast 10kg steel ingot
It is a figure which shows the influence of the dissolved oxygen amount before Al deoxidation and the amount of deoxidized Al on (the diameter of the circle at the time of replacing the observed area of MnS with a circle).
【図2】鋳片中のMnS粒子の円相当直径と、同鋳片を
70%冷間加工した後、1000℃に1時間再加熱した
場合のオーステナイト結晶粒度との関係を示す図であ
る。
FIG. 2 is a diagram showing a relationship between a circle-equivalent diameter of MnS particles in a slab and austenite grain size when the slab is cold-worked by 70% and then reheated to 1000 ° C. for 1 hour.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.6 識別記号 庁内整理番号 FI 技術表示箇所 C22C 38/00 301 N 38/14 ─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. 6 Identification code Internal reference number FI technical display location C22C 38/00 301 N 38/14

Claims (4)

    【特許請求の範囲】[Claims]
  1. 【請求項1】 重量%で C :0.10〜0.30%、Si:0.05〜0.5
    0%、 Mn:0.30〜2.00%、S :0.02〜0.2
    0%、 N :0.002〜0.020%、 および Al:0.005〜0.050%、Ti:0.005〜
    0.030% の1種あるいは2種を含む鋼を製造する際、製鋼炉から
    出鋼された粗溶鋼にC、Si、Mnの単体もしくは合金
    の1種または2種以上を添加する脱酸処理、および/ま
    たは真空脱ガス処理にて脱酸を行い、溶鋼中の溶存酸素
    量を10〜150ppm とした後、Al、TiあるいはA
    l合金、Ti合金の1種または2種で脱酸することを特
    徴とする浸炭熱処理時に結晶粒が粗大化しない肌焼鋼の
    製造方法。
    1. C: 0.10 to 0.30% by weight, Si: 0.05 to 0.5
    0%, Mn: 0.30 to 2.00%, S: 0.02 to 0.2
    0%, N: 0.002-0.020%, and Al: 0.005-0.050%, Ti: 0.005-
    When producing 0.030% steel containing one or two kinds, deoxidation treatment by adding one or more kinds of C, Si, Mn simple substance or alloy to the crude molten steel discharged from the steelmaking furnace , And / or deoxidation by vacuum degassing treatment to adjust the dissolved oxygen amount in the molten steel to 10 to 150 ppm, and then Al, Ti or A
    1. A method for manufacturing case-hardening steel, in which crystal grains do not coarsen during carburizing heat treatment, which is characterized by deoxidizing one or two of a 1-alloy and a Ti-alloy.
  2. 【請求項2】 重量%で C :0.10〜0.30%、Si:0.05〜0.5
    0%、 Mn:0.30〜2.00%、S :0.02〜0.2
    0%、 N :0.002〜0.020%、および Cr:0.20〜2.00%、Mo:0.10〜0.5
    0%、 Ni:0.30〜4.00%の1種以上、および Al:0.005〜0.050%、Ti:0.005〜
    0.030% の1種あるいは2種を含む鋼を製造する際、製鋼炉から
    出鋼された粗溶鋼にC、Si、Mnの単体もしくは合金
    の1種または2種以上を添加する脱酸処理、および/ま
    たは真空脱ガス処理にて脱酸を行い、溶鋼中の溶存酸素
    量を10〜150ppm とした後、Al、TiあるいはA
    l合金、Ti合金の1種または2種で脱酸することを特
    徴とする浸炭熱処理時に結晶粒が粗大化しない肌焼鋼の
    製造方法。
    2. C: 0.10 to 0.30% by weight, Si: 0.05 to 0.5
    0%, Mn: 0.30 to 2.00%, S: 0.02 to 0.2
    0%, N: 0.002-0.020%, and Cr: 0.20-2.00%, Mo: 0.10-0.5.
    0%, one or more of Ni: 0.30 to 4.00%, and Al: 0.005 to 0.050%, Ti: 0.005.
    When producing 0.030% steel containing one or two kinds, deoxidation treatment by adding one or more kinds of C, Si, Mn simple substance or alloy to the crude molten steel discharged from the steelmaking furnace , And / or deoxidation by vacuum degassing treatment to adjust the dissolved oxygen amount in the molten steel to 10 to 150 ppm, and then Al, Ti or A
    1. A method for manufacturing case-hardening steel, in which crystal grains do not coarsen during carburizing heat treatment, which is characterized by deoxidizing one or two of a 1-alloy and a Ti-alloy.
  3. 【請求項3】 請求項1または2の成分に加えて、重量
    %でZr:0.010〜0.070%、Ce:0.01
    0〜0.070%、Hf:0.010〜0.070%の
    1種あるいは2種以上を含む鋼を製造する際、製鋼炉か
    ら出鋼された粗溶鋼にC、Si、Mnの単体もしくは合
    金の1種または2種以上を添加する脱酸処理、および/
    または真空脱ガス処理にて脱酸を行い、溶鋼中の溶存酸
    素量を10〜150ppm とした後、Al、Tiの1種ま
    たは2種とZr、Ce、Hfの1種あるいは2種以上の
    単体もしくは合金で複合脱酸することを特徴とする浸炭
    熱処理時に結晶粒が粗大化しない肌焼鋼の製造方法。
    3. In addition to the component of claim 1 or 2, Zr: 0.010 to 0.070% by weight, Ce: 0.01
    When producing a steel containing one or more of 0 to 0.070% and Hf: 0.010 to 0.070%, C, Si, or Mn alone or in the crude molten steel discharged from the steelmaking furnace Deoxidation treatment by adding one or more alloys, and / or
    Alternatively, deoxidation is performed by vacuum degassing treatment to adjust the dissolved oxygen content in the molten steel to 10 to 150 ppm, and then one or more of Al and Ti and one or more of Zr, Ce, and Hf alone. Alternatively, a method of manufacturing case-hardening steel in which crystal grains do not coarsen during carburizing heat treatment, which is characterized by complex deoxidation with an alloy.
  4. 【請求項4】 請求項1、2または3の方法に加え、鋳
    造後凝固点から1000℃までの平均冷却速度を20℃
    /分以上とすることを特徴とする浸炭熱処理時に結晶粒
    が粗大化しない肌焼鋼の製造方法。
    4. The method according to claim 1, 2 or 3, wherein the average cooling rate from the freezing point after casting to 1000 ° C. is 20 ° C.
    / Min or more, a method for producing case-hardening steel in which crystal grains do not coarsen during carburizing heat treatment.
JP3124001A 1991-05-28 1991-05-28 Method for manufacturing case-hardening steel in which crystal grains do not coarsen during carburizing heat treatment Expired - Fee Related JPH0791579B2 (en)

Priority Applications (1)

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JPH0791579B2 true JPH0791579B2 (en) 1995-10-04

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2989766B2 (en) * 1995-12-25 1999-12-13 株式会社神戸製鋼所 Case hardened steel with excellent fatigue properties and machinability
WO2001073139A2 (en) * 2000-03-27 2001-10-04 Newland Bart G Compositions and two-stage methods for the deoxidation of molten steel
JP2005163181A (en) * 2004-11-22 2005-06-23 Sanyo Special Steel Co Ltd Carburizing heat treatment method of case-hardening boron steel having excellent crystal grain size characteristic
JP5098486B2 (en) * 2007-07-25 2012-12-12 新日鐵住金株式会社 Manufacturing method of carburized parts
JP5241185B2 (en) * 2007-09-21 2013-07-17 山陽特殊製鋼株式会社 Steel manufacturing method with excellent rolling fatigue life
JP5454620B2 (en) * 2012-05-31 2014-03-26 新日鐵住金株式会社 Steel for carburized parts with excellent grain size prevention properties

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6154844A (en) * 1984-08-27 1986-03-19 Matsushita Electric Ind Co Ltd Small-sized motor
JPS63162812A (en) * 1986-12-26 1988-07-06 Nippon Steel Corp Manufacture of case-hardening steel

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6154844A (en) * 1984-08-27 1986-03-19 Matsushita Electric Ind Co Ltd Small-sized motor
JPS63162812A (en) * 1986-12-26 1988-07-06 Nippon Steel Corp Manufacture of case-hardening steel

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