JP2004244717A - Method of producing steel for carburizing, and steel for carburizing obtained by the method - Google Patents
Method of producing steel for carburizing, and steel for carburizing obtained by the method Download PDFInfo
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- 238000005255 carburizing Methods 0.000 title claims abstract description 129
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 66
- 239000010959 steel Substances 0.000 title claims abstract description 66
- 238000000034 method Methods 0.000 title description 7
- 238000004519 manufacturing process Methods 0.000 claims abstract description 18
- 239000000463 material Substances 0.000 claims description 9
- 150000002910 rare earth metals Chemical class 0.000 abstract description 65
- 229910052761 rare earth metal Inorganic materials 0.000 abstract description 64
- 230000000694 effects Effects 0.000 description 15
- 239000013078 crystal Substances 0.000 description 13
- 239000002244 precipitate Substances 0.000 description 8
- 229910001566 austenite Inorganic materials 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 238000011156 evaluation Methods 0.000 description 3
- 238000005242 forging Methods 0.000 description 3
- 229910001339 C alloy Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000002436 steel type Substances 0.000 description 2
- 238000006557 surface reaction Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
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Abstract
Description
本発明は、浸炭用鋼の製造方法および当該方法により得られる浸炭用鋼材に関する。 The present invention relates to a method for producing carburizing steel and a steel material for carburizing obtained by the method.
従来の浸炭用鋼は、高熱浸炭時におけるオーステナイト結晶粒度の粗大化を抑制するために、Ｎｄを添加している（例えば、特許文献１参照。）。 Conventional carburizing steel contains Nd in order to suppress the austenite grain size from being coarsened during high-temperature carburizing (for example, see Patent Document 1).
また、結晶粒度の粗大化を防止するために、ＲＥＭ（希土類金属）を添加しているものもある（例えば、特許文献２参照。）。 In some cases, REM (rare earth metal) is added to prevent coarsening of the crystal grain size (for example, see Patent Document 2).
さらに、ＲＥＭの存在下において、浸炭を施すものもある（例えば、特許文献３参照。）。
しかし、特許文献１および特許文献２に記載の方法においては、浸炭速度の向上は、浸炭温度の上昇に因るものである。したがって、浸炭処理炉の耐久性、例えば、高熱による損傷などの問題を生じる虞がある。
However, in the methods described in Patent Literature 1 and
一方、特許文献３に記載の方法においては、ＲＥＭは、浸炭に対する触媒として機能しており、浸炭ガス中に添加される。したがって、ＲＥＭの所要量が大きくなる問題を有している。 On the other hand, in the method described in Patent Document 3, REM functions as a catalyst for carburizing and is added to carburizing gas. Therefore, there is a problem that the required amount of REM becomes large.
本発明は、上記従来技術に伴う課題を解決するためになされたものであり、浸炭速度を効率的に向上させることができる浸炭用鋼の製造方法および当該方法により得られる浸炭用鋼材を提供することを目的とする。 The present invention has been made in order to solve the problems associated with the above prior art, and provides a method for producing a carburizing steel capable of efficiently improving the carburizing speed, and a carburizing steel obtained by the method. The purpose is to:
上記目的を達成するための請求項１に記載の発明は、
重量％（以下同じ）でのＣ濃度が０．１〜０．３％である浸炭用鋼に、ＲＥＭを添加し、ＲＥＭ濃度を０．０１〜０．２５％に調整し、９３０〜１０５０℃の浸炭温度で、浸炭を施すことを特徴とする浸炭用鋼の製造方法である。
The invention according to claim 1 for achieving the above object,
REM is added to carburizing steel having a C concentration of 0.1 to 0.3% by weight (the same applies hereinafter), the REM concentration is adjusted to 0.01 to 0.25%, and 930 to 1050 ° C. A method for producing carburizing steel, characterized in that carburizing is performed at a carburizing temperature of.
上記目的を達成するための請求項９に記載の発明は、
請求項１〜８のいずれか１項に記載の浸炭用鋼の製造方法によって製造されたことを特徴とする浸炭用鋼材である。
The invention according to claim 9 for achieving the above object is as follows.
A carburizing steel material produced by the method for producing carburizing steel according to any one of claims 1 to 8.
上記のように構成した本発明は以下の効果を奏する。 The present invention configured as described above has the following effects.
請求項１に記載の発明によれば、鋼中のＲＥＭ濃度が０．０１〜０．２５％であるため、鋼の表面反応および内部拡散反応を促進させて浸炭速度を向上させるＲＥＭ効果が効率的に発揮される。また、浸炭温度が９３０〜１０５０℃であるため、ＲＥＭ効果が顕著となる。したがって、浸炭速度を効率的に向上させることができる浸炭用鋼の製造方法を提供することができる。 According to the first aspect of the present invention, since the REM concentration in the steel is 0.01 to 0.25%, the REM effect of promoting the surface reaction and the internal diffusion reaction of the steel to improve the carburizing rate is efficient. It is effectively exhibited. Further, since the carburizing temperature is 930 to 1050 ° C., the REM effect is remarkable. Therefore, it is possible to provide a method for producing carburizing steel capable of efficiently improving the carburizing speed.
請求項９に記載の発明によれば、浸炭速度を効率的に向上させることができる浸炭用鋼の製造方法よって得られる浸炭用鋼材を提供することができる。 According to the ninth aspect of the present invention, it is possible to provide a carburizing steel material obtained by a method for producing a carburizing steel capable of efficiently improving a carburizing speed.
以下、本発明の実施の形態を、図面を参照しつつ説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
図１および図２は、本発明の実施の形態に係る浸炭用鋼の一例を説明するための化学組成を示している図表、図３は、比較例に係る浸炭用鋼の一例を説明するための化学組成を示している図表である。 1 and 2 are tables showing chemical compositions for explaining an example of a carburizing steel according to an embodiment of the present invention, and FIG. 3 is a diagram for explaining an example of a carburizing steel according to a comparative example. 3 is a table showing the chemical composition of the present invention.
本発明の実施の形態に係る浸炭用鋼Ａ０１〜Ａ２５は、重量％（以下同じ）でのＣ濃度が０．１〜０．３％である肌焼き鋼、例えば、低炭素合金鋼（鋼種名：ＳＣｒ４２０）をベースとしている。なお、鋼中のＲＥＭ濃度は０．０４〜０．２４％、Ｎ濃度は０．０１０〜０．０１２％、Ａｌ濃度は０．００９〜０．０７０％、Ｎｂ濃度は０．００９〜０．０７１％、Ｔｉ濃度は０．００４〜０．０７０％となるように、各元素を添加して調整している。また、各元素の濃度は、最初から鋼自体に含有させる形態を適用することも可能である。 The carburizing steels A01 to A25 according to the embodiment of the present invention are case hardened steels having a C concentration of 0.1 to 0.3% by weight (the same applies hereinafter), for example, a low carbon alloy steel (steel type name). : SCr420). The REM concentration in the steel is 0.04-0.24%, the N concentration is 0.010-0.012%, the Al concentration is 0.009-0.070%, and the Nb concentration is 0.009-0. Each element is added and adjusted so that 071% and the Ti concentration become 0.004 to 0.070%. Further, the concentration of each element can be applied to a form in which the element is contained in the steel itself from the beginning.
比較例に係る浸炭用鋼Ｂ０１〜Ｂ０４も、低炭素合金鋼（鋼種名：ＳＣｒ４２０）をベースとしている。なお、浸炭用鋼Ｂ０１は、ＲＥＭの無添加鋼である。また、浸炭用鋼Ｂ０２〜Ｂ０４は、ＲＥＭ濃度が０．２６〜０．３０％であり、実施の形態に係る浸炭用鋼Ａ０１〜Ａ２５より多くのＲＥＭを添加している。 The carburizing steels B01 to B04 according to the comparative examples are also based on a low carbon alloy steel (steel type name: SCr420). The carburizing steel B01 is a REM-free steel. The carburizing steels B02 to B04 have a REM concentration of 0.26 to 0.30%, and contain more REM than the carburizing steels A01 to A25 according to the embodiment.
次に、浸炭速度に対する浸炭温度およびＲＥＭ濃度の影響を説明する。 Next, the influence of the carburizing temperature and the REM concentration on the carburizing speed will be described.
使用した試料は、実施の形態および比較例に係る浸炭用鋼を溶製し、加熱し、圧延することで得られるφ２０ｍｍの線材である。当該線材は、浸炭温度を適宜変更し、３〜６時間の浸炭を施し、油冷した。 The sample used is a φ20 mm wire obtained by melting, heating, and rolling the carburizing steel according to the embodiment and the comparative example. The wire rod was appropriately carburized at appropriate temperatures, carburized for 3 to 6 hours, and oil-cooled.
実施の形態および比較例に係る浸炭用鋼は、ベースの鋼材が共通であり、ＲＥＭ以外の鋼材成分に大幅な差がないため、焼入性は同等であり、浸炭速度と浸炭深さとは対応していると見なせる。したがって、浸炭速度を浸炭深さによって評価している。なお、浸炭深さは、ビッカース硬さＨＶが５１２である鋼材の内部位置と、鋼材の表面との間の距離で定義される有効硬化深さである。 The carburizing steels according to the embodiment and the comparative example have the same base steel material, and there is no significant difference in steel material components other than REM, so that the hardenability is equivalent, and the carburizing speed and the carburizing depth correspond. Can be regarded as doing. Therefore, the carburizing speed is evaluated by the carburizing depth. The carburizing depth is an effective hardening depth defined by a distance between an inner position of a steel material having a Vickers hardness HV of 512 and a surface of the steel material.
図４は、浸炭温度を変更した場合におけるＲＥＭ濃度と浸炭深さとの関係を示しているグラフである。浸炭温度は、９３０℃、９９０℃、１０５０℃の３種類であり、ＲＥＭ濃度を、０．０２％の増分値で、０％から０．３％まで変更している。 FIG. 4 is a graph showing the relationship between the REM concentration and the carburizing depth when the carburizing temperature is changed. The carburizing temperatures are 930 ° C., 990 ° C., and 1050 ° C., and the REM concentration is changed from 0% to 0.3% in increments of 0.02%.
図に示されるように、ＲＥＭ濃度が０．０２％である場合においても、ＲＥＭ無添加の場合に比べて、浸炭深さ（浸炭速度）が顕著に向上している。また、ＲＥＭ濃度が０．０２〜０．３％においては、ＲＥＭ濃度の増加による影響は、顕著でなく、浸炭深さの増加効果が飽和する傾向が見られる。 As shown in the figure, even when the REM concentration is 0.02%, the carburizing depth (carburizing speed) is remarkably improved as compared with the case where no REM is added. Further, when the REM concentration is 0.02 to 0.3%, the effect of the increase in the REM concentration is not remarkable, and the effect of increasing the carburizing depth tends to be saturated.
したがって、ＲＥＭ濃度を０．０１〜０．２５％とする場合、鋼の表面反応および内部拡散反応を促進させて浸炭速度を向上させるＲＥＭ効果を、効率的に発揮させることが可能である。 Therefore, when the REM concentration is set to 0.01 to 0.25%, it is possible to efficiently exert the REM effect of promoting the surface reaction and the internal diffusion reaction of the steel to improve the carburizing rate.
図５は、ＲＥＭ濃度を変更した場合における浸炭温度と浸炭深さとの関係を示しているグラフである。ＲＥＭ濃度は、０％つまりＲＥＭ無添加、０．０２％、０．１％、０．２％の４種類であり、浸炭温度を、３０℃の増分値で、８７０℃から１０８０℃まで変更している。 FIG. 5 is a graph showing the relationship between carburizing temperature and carburizing depth when the REM concentration is changed. The REM concentrations are 0%, that is, no REM added, 0.02%, 0.1%, and 0.2%, and the carburizing temperature is changed from 870 ° C. to 1080 ° C. in increments of 30 ° C. ing.
図に示されるように、浸炭温度が９３０℃未満である場合、浸炭深さ（浸炭速度）に対する顕著な影響が見られない。一方、浸炭温度が９３０〜１０５０℃の範囲にある場合、ＲＥＭ濃度の増加に伴って、浸炭深さが増加している。 As shown in the figure, when the carburizing temperature is lower than 930 ° C., no remarkable influence on the carburizing depth (carburizing speed) is observed. On the other hand, when the carburizing temperature is in the range of 930 to 1050 ° C., the carburizing depth increases as the REM concentration increases.
しかし、浸炭温度が１０５０℃を越える場合、浸炭深さに対するＲＥＭ濃度の影響は飽和する傾向が見られ、ＲＥＭ無添加の場合との差が縮小している。また、ＲＥＭ濃度が０．０２〜０．２％においては、ＲＥＭ濃度の増加による影響は、顕著でない。 However, when the carburizing temperature exceeds 1050 ° C., the effect of the REM concentration on the carburizing depth tends to be saturated, and the difference from the case where no REM is added is reduced. Further, when the REM concentration is 0.02 to 0.2%, the influence of the increase in the REM concentration is not significant.
そのため、浸炭温度を９３０〜１０５０℃とする場合、浸炭速度を向上させるＲＥＭ効果を顕著に発揮させることが可能である。なお、浸炭温度が１０５０℃を越えないことは、浸炭処理炉における高熱による損傷などの耐久性に関する問題を生じ難い点で好ましい。 Therefore, when the carburizing temperature is 930 to 1050 ° C., the REM effect for improving the carburizing speed can be remarkably exhibited. In addition, it is preferable that the carburizing temperature does not exceed 1050 ° C. since a problem relating to durability such as damage due to high heat in the carburizing furnace hardly occurs.
以上のように、Ｃ濃度が０．１〜０．３％である浸炭用鋼に、ＲＥＭを添加し、ＲＥＭ濃度を０．０１〜０．２５％に調整し、９３０〜１０５０℃の浸炭温度で、浸炭を施すことによって、浸炭速度を効率的に向上させることができる。 As described above, REM is added to the carburizing steel having a C concentration of 0.1 to 0.3%, the REM concentration is adjusted to 0.01 to 0.25%, and the carburizing temperature of 930 to 1050 ° C. Thus, by carburizing, the carburizing speed can be efficiently improved.
したがって、浸炭速度を効率的に向上させることができる浸炭用鋼の製造方法を提供することができる。また、浸炭速度を効率的に向上させることができる浸炭用鋼の製造方法よって得られる浸炭用鋼材を提供することができる。 Therefore, it is possible to provide a method for producing carburizing steel capable of efficiently improving the carburizing speed. Further, it is possible to provide a carburizing steel material obtained by a method for producing a carburizing steel capable of efficiently improving a carburizing speed.
次に、Ａｌ濃度、ＲＥＭ濃度および浸炭温度の関係を説明する。 Next, the relationship among Al concentration, REM concentration and carburizing temperature will be described.
図６は、浸炭温度を変更した場合におけるＲＥＭおよびＡｌ濃度とオーステナイト結晶粒度との関係を示している図表である。 FIG. 6 is a chart showing the relationship between REM and Al concentration and austenite grain size when the carburizing temperature is changed.
浸炭温度は、９６０℃、９９０℃、１０２０℃、１０５０℃の４種類である。ＲＥＭ濃度は、０％、０．１％、０．２％の３種類である。Ａｌ濃度は、０．０１％、０．０３％、０．０５％、０．０７％の４種類である。なお、結晶粒度が６．０以上である場合を、良好（符号○で表示）であると評価し、６．０未満である場合を、不良（符号×で表示）であると評価した。 There are four types of carburizing temperatures: 960 ° C, 990 ° C, 1020 ° C, and 1050 ° C. There are three types of REM concentrations: 0%, 0.1%, and 0.2%. There are four types of Al concentrations: 0.01%, 0.03%, 0.05%, and 0.07%. In addition, when the crystal grain size was 6.0 or more, it was evaluated as good (indicated by the symbol ○), and when it was less than 6.0, it was evaluated as poor (indicated by the symbol x).
図に示されるように、浸炭温度の上昇に伴って、結晶粒度の粗大化が引き起こされる傾向が見られる。一方、Ａｌ濃度の増加によって、結晶粒度の粗大化が抑制されている。 As shown in the figure, there is a tendency that as the carburizing temperature rises, the crystal grain size becomes coarse. On the other hand, the increase in the Al concentration suppresses the coarsening of the crystal grain size.
また、評価が良好と不良との境界に位置するＡｌ濃度［Ａｌ］は、９６０〜１０５０℃の温度域においては、浸炭温度Ｔ（℃）とＲＥＭ濃度［ＲＥＭ］とを含んでいる関係式（［Ａｌ］＝（Ｔ−９４０）／１０００−０．０３５×［ＲＥＭ］）で表すことが可能である。 In addition, the Al concentration [Al] located at the boundary between good and poor evaluations is a relational expression including the carburizing temperature T (° C) and the REM concentration [REM] in a temperature range of 960 to 1050 ° C. [Al] = (T-940) /1000-0.035× [REM].
なお、Ｎ濃度は、０．０１％未満である場合、析出物生成の効果が顕著ではなく、０．０３％を越える場合、鍛造や熱間加工時において割れが発生しやすくなる。Ａｌ濃度は、０．０１％未満である場合、析出物生成の効果が顕著でなく、０．０５％を越える場合、析出するＡｌＮの粗大化により、結晶粒の微細化に対する寄与が低減、つまり結晶粒の粗大化防止効果が低下する。 When the N concentration is less than 0.01%, the effect of forming precipitates is not remarkable, and when it exceeds 0.03%, cracks are likely to occur during forging or hot working. If the Al concentration is less than 0.01%, the effect of the formation of precipitates is not remarkable, and if it exceeds 0.05%, the contribution to the refinement of the crystal grains is reduced due to the coarsening of the precipitated AlN. The effect of preventing crystal grains from being coarsened is reduced.
したがって、浸炭温度が９６０℃以上である上記温度域にある場合、結晶粒度の粗大化を確実に抑制するためには、Ｎ濃度は、０．０１〜０．０３％であり、Ａｌ濃度は、０．０１〜０．０５％であることが好ましく、また、関係式（［Ａｌ］≧（Ｔ−９４０）／１０００−０．０３５×［ＲＥＭ］）を満足することがさらに好ましい。 Therefore, when the carburizing temperature is in the above temperature range of 960 ° C. or higher, the N concentration is 0.01 to 0.03% and the Al concentration is It is preferably 0.01 to 0.05%, and more preferably the relational expression ([Al] ≧ (T-940) /1000-0.035× [REM]) is satisfied.
次に、Ｎｂ濃度、ＲＥＭ濃度および浸炭温度の関係を説明する。 Next, the relationship among the Nb concentration, the REM concentration, and the carburizing temperature will be described.
図７は、浸炭温度を変更した場合におけるＲＥＭおよびＮｂ濃度とオーステナイト結晶粒度との関係を示している図表である。なお、Ａｌ濃度代わりとして、Ｎｂ濃度が適用されている点を除けば、図６の場合と同様の条件である。 FIG. 7 is a table showing the relationship between REM and Nb concentrations and austenite grain size when the carburizing temperature is changed. The conditions are the same as those in FIG. 6 except that the Nb concentration is applied instead of the Al concentration.
図に示されるように、浸炭温度の上昇に伴って、結晶粒度の粗大化が引き起こされる傾向が見られる。一方、Ｎｂ濃度の増加によって、結晶粒度の粗大化が抑制されている。 As shown in the figure, there is a tendency that as the carburizing temperature rises, the crystal grain size becomes coarse. On the other hand, the increase in the Nb concentration suppresses the coarsening of the crystal grain size.
また、評価が良好と不良との境界に位置するＮｂ濃度［Ｎｂ］は、９６０〜１０５０℃の温度域においては、浸炭温度Ｔ（℃）とＲＥＭ濃度［ＲＥＭ］とを含んでいる関係式（［Ｎｂ］＝（Ｔ−９４０）／３０００−０．０２５×［ＲＥＭ］）で表すことが可能である。 In addition, the Nb concentration [Nb] located at the boundary between good and bad evaluations is a relational expression including the carburizing temperature T (° C.) and the REM concentration [REM] in a temperature range of 960 to 1050 ° C. [Nb] = (T-940) /3000−0.025× [REM].
さらに、Ｎｂ濃度は、０．０１％未満である場合、析出物生成の効果が顕著でなく、０．０５％を越える場合、析出物が凝集するため、結晶粒の微細化に対する寄与が低下するとともに、冷間鍛造性の悪化を引き起こす。なお、Ｎ濃度は、上述のように、０．０１％未満である場合、析出物生成の効果が顕著ではなく、０．０３％を越える場合、鍛造や熱間加工時において割れが発生しやすくなる。 Further, when the Nb concentration is less than 0.01%, the effect of forming precipitates is not remarkable, and when it exceeds 0.05%, the precipitates are aggregated, so that the contribution to the refinement of crystal grains is reduced. At the same time, cold forgeability is deteriorated. As described above, when the N concentration is less than 0.01%, the effect of forming precipitates is not remarkable, and when it exceeds 0.03%, cracks are likely to occur during forging or hot working. Become.
したがって、浸炭温度が９６０℃以上である上記温度域にある場合、結晶粒度の粗大化を確実に抑制するためには、Ｎ濃度は、０．０１〜０．０３％であり、Ｎｂ濃度は、０．０１〜０．０５％であることが好ましく、また、関係式（［Ｎｂ］≧（Ｔ−９４０）／３０００−０．０２５×［ＲＥＭ］）を満足することがさらに好ましい。 Therefore, when the carburizing temperature is in the above temperature range of 960 ° C. or higher, the N concentration is 0.01 to 0.03% and the Nb concentration is in order to surely suppress the coarsening of the crystal grain size. It is preferably 0.01 to 0.05%, and more preferably the relational expression ([Nb] ≧ (T−940) /3000−0.025× [REM]) is satisfied.
次に、Ｔｉ濃度、ＲＥＭ濃度および浸炭温度の関係を説明する。 Next, the relationship between the Ti concentration, the REM concentration, and the carburizing temperature will be described.
図８は、浸炭温度を変更した場合におけるＲＥＭおよびＴｉ濃度とオーステナイト結晶粒度との関係を示している図表である。なお、Ａｌ濃度代わりとして、Ｔｉ濃度が適用されている点を除けば、図６の場合と同様の条件である。 FIG. 8 is a chart showing the relationship between REM and Ti concentration and austenite grain size when the carburizing temperature is changed. The conditions are the same as those in FIG. 6 except that the Ti concentration is applied instead of the Al concentration.
図に示されるように、浸炭温度の上昇に伴って、結晶粒度の粗大化が引き起こされる傾向が見られる。一方、Ｔｉ濃度の増加によって、結晶粒度の粗大化が抑制されている。 As shown in the figure, there is a tendency that as the carburizing temperature rises, the crystal grain size becomes coarse. On the other hand, the increase in the Ti concentration suppresses the coarsening of the crystal grain size.
また、評価が良好と不良との境界に位置するＴｉ濃度［Ｔｉ］は、９６０〜１０５０℃の温度域においては、浸炭温度Ｔ（℃）とＲＥＭ濃度［ＲＥＭ］とを含んでいる関係式（［Ｔｉ］＝［（Ｔ−９４０）／３６００−０．０２０×［ＲＥＭ］）で表すことが可能である。 In addition, the Ti concentration [Ti] located at the boundary between good and bad evaluations includes a carburizing temperature T (° C.) and a REM concentration [REM] in a temperature range of 960 to 1050 ° C. [Ti] = [(T−940) /3600−0.020× [REM]).
さらに、Ｔｉ濃度は、０．０１％未満である場合、析出物生成の効果が顕著でなく、０．０５％を越える場合、析出物が凝集するため、結晶粒の微細化に対する寄与が低下するとともに、冷間鍛造性の悪化を引き起こす。なお、Ｎ濃度は、上述のように、０．０１％未満である場合、析出物生成の効果が顕著ではなく、０．０３％を越える場合、鍛造や熱間加工時において割れが発生しやすくなる。 Further, when the Ti concentration is less than 0.01%, the effect of forming precipitates is not remarkable, and when the Ti concentration is more than 0.05%, the precipitates are aggregated, so that the contribution to the refinement of crystal grains is reduced. At the same time, cold forgeability is deteriorated. As described above, when the N concentration is less than 0.01%, the effect of forming precipitates is not remarkable, and when it exceeds 0.03%, cracks are likely to occur during forging or hot working. Become.
したがって、浸炭温度が９６０℃以上である上記温度域にある場合、結晶粒度の粗大化を確実に抑制するためには、Ｎ濃度は、０．０１〜０．０３％であり、Ｔｉ濃度は、０．０１〜０．０５％であることが好ましく、また、関係式（［Ｔｉ］≧（Ｔ−９４０）／３６００−０．０２０×［ＲＥＭ］）を満足することがさらに好ましい。 Therefore, when the carburizing temperature is in the above temperature range of 960 ° C. or higher, the N concentration is 0.01 to 0.03% and the Ti concentration is It is preferably 0.01 to 0.05%, and more preferably the relational expression ([Ti] ≧ (T−940) /3600−0.020× [REM]) is satisfied.
Claims (9)
［Ａｌ］≧（Ｔ−９４０）／１０００−０．０３５×［ＲＥＭ］
の関係を満足することを特徴とする請求項２に記載の浸炭用鋼の製造方法。 The Al concentration [Al] and the REM concentration [REM] in the steel, which is weight%, and the carburizing temperature T (° C.)
[Al] ≧ (T-940) /1000-0.035× [REM]
The method for producing carburizing steel according to claim 2, wherein the following relationship is satisfied.
［Ｎｂ］≧（Ｔ−９４０）／３０００−０．０２５×［ＲＥＭ］
の関係を満足することを特徴とする請求項４に記載の浸炭用鋼の製造方法。 The Nb concentration [Nb] and the REM concentration [REM] in the steel, which are weight%, and the carburizing temperature T (° C.)
[Nb] ≧ (T-940) /3000−0.025× [REM]
The method for producing carburizing steel according to claim 4, wherein the following relationship is satisfied.
［Ｔｉ］≧（Ｔ−９４０）／３６００−０．０２０×［ＲＥＭ］
の関係を満足することを特徴とする請求項６に記載の浸炭用鋼の製造方法。 The Ti concentration [Ti] and the REM concentration [REM] in the steel, which are weight%, and the carburizing temperature T (° C.)
[Ti] ≧ (T-940) /3600-0.020× [REM]
7. The method for producing carburizing steel according to claim 6, wherein the following relationship is satisfied.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007113071A (en) * | 2005-10-20 | 2007-05-10 | Kobe Steel Ltd | Case hardening steel having excellent rolling fatigue property and crystal grain coarsening prevention property |
| CN102154613A (en) * | 2011-03-11 | 2011-08-17 | 蚌埠市钰诚五金工贸有限公司 | Rare earth carburizing process using rolling furnace to treat screws |
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2003
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007113071A (en) * | 2005-10-20 | 2007-05-10 | Kobe Steel Ltd | Case hardening steel having excellent rolling fatigue property and crystal grain coarsening prevention property |
| CN102154613A (en) * | 2011-03-11 | 2011-08-17 | 蚌埠市钰诚五金工贸有限公司 | Rare earth carburizing process using rolling furnace to treat screws |
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