JP6812948B2 - Carburizing method - Google Patents
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- 238000005255 carburizing Methods 0.000 title claims description 95
- 238000000034 method Methods 0.000 title claims description 51
- 238000011282 treatment Methods 0.000 claims description 71
- 238000009792 diffusion process Methods 0.000 claims description 70
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 30
- 229910052799 carbon Inorganic materials 0.000 claims description 30
- 229910000975 Carbon steel Inorganic materials 0.000 claims description 29
- 239000010962 carbon steel Substances 0.000 claims description 29
- 238000010438 heat treatment Methods 0.000 claims description 15
- 230000005496 eutectics Effects 0.000 claims description 11
- 238000010587 phase diagram Methods 0.000 claims description 5
- 239000007789 gas Substances 0.000 description 24
- 239000002994 raw material Substances 0.000 description 9
- 238000002360 preparation method Methods 0.000 description 7
- 238000002844 melting Methods 0.000 description 6
- 230000008018 melting Effects 0.000 description 6
- 238000004904 shortening Methods 0.000 description 5
- 230000007423 decrease Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 238000007865 diluting Methods 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 230000000630 rising effect Effects 0.000 description 3
- 239000007790 solid phase Substances 0.000 description 3
- 239000002344 surface layer Substances 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 229910017112 Fe—C Inorganic materials 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 239000004071 soot Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/20—Carburising
- C23C8/22—Carburising of ferrous surfaces
-
- 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
- C21D1/06—Surface hardening
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/80—After-treatment
Description
本発明は、浸炭方法に関する。 The present invention relates to a carburizing method.
従来、炭素鋼製の処理対象物に対する浸炭方法としては、例えば、雰囲気ガス浸炭方法、真空浸炭方法、大気圧直接浸炭方法などが知られている。雰囲気ガス浸炭方法では、大気圧下、変成炉にて生成された混合ガスと原料ガスとを用いて浸炭処理が行われる。真空浸炭方法では、減圧下、原料ガスのみを用いて浸炭処理が行われる。大気圧直接浸炭方法では、大気圧下、原料ガスと希釈ガスとを用いて浸炭処理が行われる。これら浸炭方法では、通常、浸炭工程後、処理対象物の表面に注入された炭素を処理対象物の内部へ拡散させるため、拡散処理が行われる。 Conventionally, as a carburizing method for a carbon steel object to be treated, for example, an atmospheric gas carburizing method, a vacuum carburizing method, an atmospheric pressure direct carburizing method and the like are known. In the atmospheric gas carburizing method, carburizing is performed using the mixed gas and the raw material gas generated in the transformation furnace under atmospheric pressure. In the vacuum carburizing method, the carburizing treatment is performed under reduced pressure using only the raw material gas. In the atmospheric pressure direct carburizing method, the carburizing treatment is performed using the raw material gas and the diluting gas under atmospheric pressure. In these carburizing methods, after the carburizing step, the carbon injected into the surface of the object to be treated is usually diffused into the inside of the object to be treated, so that the diffusion treatment is performed.
例えば、特許文献１には、所定時間の間、浸炭処理を行った後、処理温度を維持した状態で、浸炭された炭素を処理対象物の内部へ拡散させる拡散処理を行う浸炭方法が開示されている。 For example, Patent Document 1 discloses a carburizing method in which a carburizing treatment is performed for a predetermined time and then a diffusion treatment is performed in which the carburized carbon is diffused into the treatment object while maintaining the treatment temperature. ing.
上述した浸炭方法は、一般に、温度により制約を受けるため、一定以上の処理時間を必要とする。そのため、生産性向上等の観点から、処理時間の短縮化を図ることが望まれている。上述した浸炭方法では、処理対象物の表面に炭素を固溶、拡散させることから、浸炭処理温度、拡散処理温度を上げることによって処理時間の短縮化を図ることができる。しかしながら、処理温度が炭素鋼の共晶温度以上になると、処理対象物が融解するおそれがある。そのため、実生産上では、浸炭処理温度、拡散処理温度ともに、炭素鋼の共晶温度以下とされるのが通常である。また、拡散処理は、浸炭処理温度をそのまま維持した状態で行われるため、拡散処理時間の短縮化も難しい。 The above-mentioned carburizing method is generally restricted by temperature, and therefore requires a certain amount of processing time or more. Therefore, from the viewpoint of improving productivity and the like, it is desired to shorten the processing time. In the above-mentioned carburizing method, carbon is dissolved and diffused on the surface of the object to be treated, so that the treatment time can be shortened by raising the carburizing treatment temperature and the diffusion treatment temperature. However, if the treatment temperature exceeds the eutectic temperature of carbon steel, the object to be treated may melt. Therefore, in actual production, both the carburizing treatment temperature and the diffusion treatment temperature are usually set to be equal to or lower than the eutectic temperature of carbon steel. Further, since the diffusion treatment is performed while maintaining the carburizing treatment temperature as it is, it is difficult to shorten the diffusion treatment time.
本発明は、かかる課題に鑑みてなされたものであり、炭素鋼製の処理対象物の融解を抑制しつつ、処理時間の短縮化を図ることが可能な浸炭方法を提供しようとするものである。 The present invention has been made in view of the above problems, and an object of the present invention is to provide a carburizing method capable of shortening the processing time while suppressing melting of a carbon steel processing object. ..
本発明の一態様は、炭素鋼製の処理対象物を浸炭処理する浸炭工程と、上記浸炭工程にて上記処理対象物の表面に注入された炭素を上記処理対象物の内部へ拡散させる拡散処理を行う拡散工程と、を有する浸炭方法であって、
上記拡散工程において、
上記炭素の内部拡散によって上記処理対象物の表面炭素濃度が低下するのに従って、
浸炭処理温度超、かつ、上記炭素鋼の平衡状態図で、上記低下した表面炭素濃度のときのγＦｅに対する固相線温度未満の温度範囲内で、連続的または段階的に拡散処理温度を上昇させ、
上記拡散処理温度の最大値が、上記炭素鋼の共晶温度以上とされる、
浸炭方法にある。
One aspect of the present invention is a carburizing step of carburizing a carbon steel object to be treated, and a diffusion treatment of diffusing carbon injected into the surface of the object to be treated in the carburizing step into the inside of the object to be treated. Is a carburizing method having a diffusion step of
In the above diffusion step
As the internal diffusion of carbon reduces the surface carbon concentration of the object to be treated,
In the equilibrium phase diagram of the carbon steel above the carburizing treatment temperature, the diffusion treatment temperature is continuously or stepwise raised within the temperature range below the solidus temperature with respect to γFe at the time of the lowered surface carbon concentration. Let,
Maximum value of the diffusion process temperature, Ru is the eutectic temperature or more of the above carbon steel,
It is in the carburizing method.
拡散工程では、炭素の内部拡散によって処理対象物の表面炭素濃度が低下するのに従い、処理対象物の表層部の融点が上がる。上記浸炭方法では、この現象を利用し、炭素の内部拡散によって処理対象物の表面炭素濃度が低下するのに従って、上記特定の温度範囲内で拡散処理温度を上昇させる。そのため、上記浸炭方法によれば、炭素鋼製の処理対象物の融解を抑制しつつ、拡散処理時間の短縮による処理時間の短縮化を図ることができる。 In the diffusion step, the melting point of the surface layer of the object to be treated rises as the surface carbon concentration of the object to be treated decreases due to the internal diffusion of carbon. In the carburizing method, this phenomenon is utilized to raise the diffusion treatment temperature within the specific temperature range as the surface carbon concentration of the object to be treated decreases due to the internal diffusion of carbon. Therefore, according to the above-mentioned carburizing method, it is possible to shorten the treatment time by shortening the diffusion treatment time while suppressing the melting of the carbon steel treatment target.
（実施形態１）
実施形態１の浸炭方法について、図１、図２を用いて説明する。本実施形態の浸炭方法は、図１に示されるように、浸炭工程と、拡散工程とを有している。浸炭工程は、炭素鋼製の処理対象物を浸炭処理する工程である。拡散工程は、浸炭工程にて処理対象物の表面に注入された炭素を処理対象物の内部へ拡散させる拡散処理を行う工程である。
(Embodiment 1)
The carburizing method of the first embodiment will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the carburizing method of the present embodiment includes a carburizing step and a diffusion step. The carburizing step is a step of carburizing a carbon steel object to be treated. The diffusion step is a step of performing a diffusion treatment in which carbon injected into the surface of the object to be treated in the carburizing step is diffused into the inside of the object to be treated.
浸炭工程および拡散工程は、具体的には、真空浸炭方法、または、大気圧直接浸炭方法における浸炭工程および拡散工程とすることができる。真空浸炭方法では、減圧下、原料ガスのみを用いて浸炭処理がなされる。また、大気圧直接浸炭方法では、大気圧下、原料ガスと希釈ガスとを用いて浸炭処理がなされる。雰囲気ガス浸炭方法は、雰囲気を維持するために浸炭処理温度、拡散処理温度を向上させることが難しい。これに対し、真空浸炭方法、大気圧直接浸炭方法は、雰囲気ガス浸炭方法に比べ、浸炭処理温度、拡散処理温度を向上させやすい。そのため、上記構成によれば、処理時間の短縮化を図りやすくなる。 Specifically, the carburizing step and the diffusion step can be a carburizing step and a diffusion step in a vacuum carburizing method or an atmospheric pressure direct carburizing method. In the vacuum carburizing method, the carburizing treatment is performed under reduced pressure using only the raw material gas. Further, in the atmospheric pressure direct carburizing method, the carburizing treatment is performed using the raw material gas and the diluting gas under the atmospheric pressure. In the atmospheric gas carburizing method, it is difficult to improve the carburizing treatment temperature and the diffusion treatment temperature in order to maintain the atmosphere. On the other hand, the vacuum carburizing method and the atmospheric pressure direct carburizing method tend to improve the carburizing treatment temperature and the diffusion treatment temperature as compared with the atmospheric gas carburizing method. Therefore, according to the above configuration, it becomes easy to shorten the processing time.
真空浸炭方法、大気圧直接浸炭方法で用いられる原料ガスとしては、例えば、ＣＨ４、Ｃ２Ｈ２、Ｃ３Ｈ８、Ｃ４Ｈ１０等の炭化水素ガスなどが挙げられる。大気圧直接浸炭方法で用いられる希釈ガスとしては、Ｎ２等が挙げられる。なお、上記希釈ガスは、原料ガスを爆発圧以下にする、スス発生を抑制する、原料ガスを処理対象物まで供給する流量を確保するなどの役割を有する。 Examples of the raw material gas used in the vacuum carburizing method and the atmospheric pressure direct carburizing method include hydrocarbon gases such as CH 4 , C 2 H 2 , C 3 H 8 , and C 4 H 10 . Examples of the diluting gas used in the atmospheric pressure direct carburizing method include N 2 and the like. The diluted gas has a role of lowering the raw material gas to the explosive pressure or less, suppressing soot generation, and securing a flow rate for supplying the raw material gas to the object to be processed.
浸炭工程における浸炭温度の下限は、例えば、オーステナイト形成温度などの観点から、好ましくは、Ａ３線温度℃以上とすることができる。浸炭工程における浸炭温度の上限は、原料ガスの分解が生じないように、処理対象物を構成する炭素鋼の共晶温度未満の温度から選択すればよい。浸炭工程における浸炭温度の上限は、好ましくは、１１００℃以下、より好ましくは、１０５０℃以下とすることができる。なお、浸炭工程を実施する前の昇温工程では、例えば、ヒータ加熱などによって処理対象物を昇温することができる。 The lower limit of the carburizing temperature in the carburizing step can be preferably A3 line temperature ° C. or higher from the viewpoint of, for example, the austenite formation temperature. The upper limit of the carburizing temperature in the carburizing step may be selected from temperatures lower than the eutectic temperature of the carbon steel constituting the object to be treated so that the raw material gas does not decompose. The upper limit of the carburizing temperature in the carburizing step is preferably 1100 ° C. or lower, more preferably 1050 ° C. or lower. In the temperature raising step before the carburizing step is carried out, the temperature of the object to be treated can be raised by, for example, heating with a heater.
ここで、本実施形態の浸炭方法では、拡散工程において、炭素の内部拡散によって処理対象物の表面炭素濃度が低下するのに従い、連続的または段階的に拡散処理温度を上昇させる。この際、拡散処理温度は、浸炭処理温度を超える温度とされる。これは、浸炭処理温度を超える温度とすることにより、拡散処理速度を向上させ、全体の処理速度を向上させるためである。また、拡散処理温度は、図２に例示されるような、処理対象物を構成する炭素鋼の平衡状態図（Ｆｅ−Ｃ系状態図）で、上記低下した表面炭素濃度のときのγＦｅに対する固相線ＪＱ温度未満の温度とされる。つまり、図２に示すように、拡散中の表面炭素濃度のときにおける拡散処理温度は、拡散中の表面炭素濃度ＣｄのときにγＦｅに対する固相線ＪＱと交わる点Ｄの温度Ｔｄ未満の温度とされる。これは、拡散によって低下した表面炭素濃度のときに、γＦｅに対する固相線ＪＱ温度を超えるような急激な昇温が実施されると、炭素鋼製の処理対象物の融解が生じるためである。このように浸炭工程および拡散工程を実施する本実施形態の浸炭方法によれば、炭素鋼製の処理対象物の融解を抑制しつつ、拡散処理時間の短縮による処理時間の短縮化を図ることができる。 Here, in the carburizing method of the present embodiment, in the diffusion step, the diffusion treatment temperature is continuously or stepwise raised as the surface carbon concentration of the object to be treated decreases due to the internal diffusion of carbon. At this time, the diffusion treatment temperature is set to a temperature exceeding the carburizing treatment temperature. This is because the diffusion treatment speed is improved and the overall treatment speed is improved by setting the temperature to exceed the carburizing treatment temperature. Further, the diffusion treatment temperature is shown in the equilibrium state diagram (Fe-C system state diagram) of the carbon steel constituting the object to be treated, as illustrated in FIG. The temperature is lower than the phase diagram JQ temperature. That is, as shown in FIG. 2, the diffusion treatment temperature at the surface carbon concentration during diffusion is the temperature lower than the temperature Td at the point D where the solid phase line JQ with respect to γFe intersects at the surface carbon concentration Cd during diffusion. Will be done. This is because when the surface carbon concentration is lowered by diffusion and a rapid temperature rise exceeding the solid phase line JQ temperature with respect to γFe is performed, the carbon steel object to be treated is melted. According to the carburizing method of the present embodiment in which the carburizing step and the diffusion step are carried out in this way, it is possible to shorten the treatment time by shortening the diffusion treatment time while suppressing the melting of the carbon steel treatment object. it can.
なお、処理対象物を構成する炭素鋼の平衡状態図は、炭素鋼の材質によって決定される。また、図２において、Ｊは、包晶反応点、Ｔｐは、包晶温度、Ｑは、γＦｅの炭素固溶最大点、Ｅは、共晶点、Ｔｅは、共晶温度、Ｓは、共析点、Ｔｓは、共析温度である。 The equilibrium phase diagram of the carbon steel constituting the object to be treated is determined by the material of the carbon steel. Further, in FIG. 2, J is the peritectic reaction point, Tp is the peritectic temperature, Q is the maximum carbon solid solution point of γFe, E is the eutectic point, Te is the eutectic temperature, and S is the eutectic temperature. The analysis point and Ts are eutectoid temperatures.
本実施形態の浸炭方法において、拡散処理温度の最大値は、処理対象物を構成する炭素鋼の共晶温度以上とされる。但し、拡散処理温度の最大値は、上述したように、γＦｅに対する固相線温度を超えないように選択される。この構成によれば、炭素鋼の共晶温度以上の高い温度で拡散処理がなされる。また、この構成によれば、炭素鋼の包晶温度近くまで拡散処理温度の高温化を図ることが可能となる。そのため、この構成によれば、拡散処理時間の短縮による処理時間の短縮化を図りやすくなる。 In carburizing method of this embodiment, the maximum value of the diffusion process temperature, Ru is the eutectic temperature or more carbon steel constituting the processing object. However, as described above, the maximum value of the diffusion treatment temperature is selected so as not to exceed the solid phase temperature with respect to γFe. According to this configuration, the diffusion treatment is performed at a temperature higher than the eutectic temperature of carbon steel. Further, according to this configuration, it is possible to raise the diffusion treatment temperature to near the peritectic temperature of carbon steel. Therefore, according to this configuration, it becomes easy to shorten the processing time by shortening the diffusion processing time.
本実施形態の浸炭方法において、拡散処理温度は、昇温速度を制御することによって制御することができる。この構成によれば、連続的または段階的に拡散処理温度を上昇させやすい。そのため、この構成によれば、上述した作用効果を確実なものとすることができる。 In the carburizing method of the present embodiment, the diffusion treatment temperature can be controlled by controlling the rate of temperature rise. According to this configuration, it is easy to raise the diffusion treatment temperature continuously or stepwise. Therefore, according to this configuration, the above-mentioned action and effect can be ensured.
本実施形態の浸炭方法において、拡散処理温度は、高周波加熱によって上昇させることができる。この構成によれば、ヒータ加熱に比べ、所定の拡散処理温度まで迅速に昇温することができ、また、昇温速度の制御もしやすい。そのため、この構成によれば、拡散処理時間の短縮による処理時間の短縮化を図りやすくなる。 In the carburizing method of the present embodiment, the diffusion treatment temperature can be raised by high frequency heating. According to this configuration, the temperature can be raised to a predetermined diffusion treatment temperature more quickly than the heater heating, and the rate of temperature rise can be easily controlled. Therefore, according to this configuration, it becomes easy to shorten the processing time by shortening the diffusion processing time.
本実施形態の浸炭方法の使用時には、上述した拡散工程の後、処理対象物を焼入れする焼入工程を経ることにより、処理対象物の表層に硬化層を形成することができる。なお、焼入条件等については、公知の条件を適用することが可能である。 When the carburizing method of the present embodiment is used, a hardened layer can be formed on the surface layer of the object to be treated by undergoing a quenching step of quenching the object to be treated after the diffusion step described above. As for the quenching conditions and the like, known conditions can be applied.
（実験例）
＜試料１の作製＞
Ｃ：０．１５質量％、Ｓｉ：０．２質量％、Ｍｎ：０．７５質量％、Ｃｒ：１．０５質量％、Ｍｏ：０．２質量％を含有し、残部がＦｅおよび不可避不純物よりなる炭素鋼から構成される処理対象物を準備した。なお、上記炭素鋼における共晶温度は、１１４３℃である。また、上記炭素鋼における包晶温度は、１４８５℃である。
(Experimental example)
<Preparation of sample 1>
Contains C: 0.15% by mass, Si: 0.2% by mass, Mn: 0.75% by mass, Cr: 1.05% by mass, Mo: 0.2% by mass, and the balance is from Fe and unavoidable impurities. A treatment object composed of carbon steel was prepared. The eutectic temperature of the carbon steel is 1143 ° C. The peritectic temperature of the carbon steel is 1485 ° C.
準備した処理対象物を、以下の浸炭処理条件で浸炭処理した。
−浸炭処理条件−
雰囲気圧力：大気圧
ガス種：Ｎ２ガス（９９体積％）＋Ｃ２Ｈ２ガス（１体積％）
熱処理条件：１０５０℃まで昇温後、２５０秒間保持
The prepared object to be treated was carburized under the following carburizing treatment conditions.
-Carburizing conditions-
Atmospheric pressure: Atmospheric pressure Gas type: N 2 gas (99% by volume) + C 2 H 2 gas (1% by volume)
Heat treatment conditions: Hold for 250 seconds after heating to 1050 ° C
上記浸炭処理後の処理対象物を、以下の拡散処理条件で拡散処理した。
−拡散処理条件−
雰囲気圧力：大気圧
ガス種：Ｎ２ガス
熱処理条件：昇温速度１１℃/秒にて１０５０℃から１２７５℃まで昇温後、２６秒
間保持
The object to be treated after the carburizing treatment was diffused under the following diffusion treatment conditions.
-Diffusion processing conditions-
Atmospheric pressure: Atmospheric pressure Gas type: N 2 gas Heat treatment conditions: 26 seconds after raising the temperature from 1050 ° C to 1275 ° C at a heating rate of 11 ° C / sec.
Hold between
上記拡散処理後の処理対象物を、水冷にて焼入処理した。 The object to be treated after the diffusion treatment was quenched by water cooling.
以上により、試料１を作製した。なお、本例の浸炭方法は、大気圧直接浸炭方法である。また、試料１の作製時における浸炭処理後の処理対象物における表面炭素濃度は、１．５５質量％であった。図３に、試料１の作製時における浸炭処理後の処理対象物表面から深さ方向への距離と、炭素濃度との関係を示す。また、図４に、試料１の作製時における熱処理パターンを示す。なお、試料１の作製では、昇温速度を制御することにより、炭素の内部拡散によって処理対象物の表面炭素濃度が低下するのに従って、浸炭処理温度超、かつ、炭素鋼の平衡状態図で、低下した表面炭素濃度のときのγＦｅに対する固相線温度未満の温度範囲内で、連続的に拡散処理温度を上昇させている。 As described above, Sample 1 was prepared. The carburizing method of this example is an atmospheric pressure direct carburizing method. The surface carbon concentration in the object to be treated after the carburizing treatment at the time of preparing the sample 1 was 1.55% by mass. FIG. 3 shows the relationship between the distance in the depth direction from the surface of the object to be treated after the carburizing treatment at the time of preparing the sample 1 and the carbon concentration. Further, FIG. 4 shows a heat treatment pattern at the time of preparing the sample 1. In the preparation of sample 1, as the surface carbon concentration of the object to be treated decreases due to the internal diffusion of carbon by controlling the temperature rise rate, the carburizing treatment temperature is exceeded and the carbon steel equilibrium state diagram is shown. The diffusion treatment temperature is continuously raised within a temperature range lower than the solidus line temperature with respect to γFe when the surface carbon concentration is lowered.
金属顕微鏡にて、試料１の表面に垂直な断面を観察したところ（図５（ａ）の線Ｌの位置）、図５（ｂ）に示されるように、処理対象物の溶解は確認されなかった。なお、この結果から、試料１の浸炭方法によれば、炭素鋼製の処理対象物の融解を抑制しつつ、処理時間の短縮化を図ることができるといえる。 When the cross section perpendicular to the surface of the sample 1 was observed with a metallurgical microscope (position of line L in FIG. 5 (a)), as shown in FIG. 5 (b), dissolution of the object to be treated was not confirmed. It was. From this result, it can be said that according to the carburizing method of Sample 1, the treatment time can be shortened while suppressing the melting of the carbon steel treatment target.
＜試料１Ｃの作製＞
拡散処理条件における熱処理条件の昇温速度１６℃/秒とした点、拡散工程における保持時間を２９秒とした点以外は、試料１の作製と同様にして、試料１Ｃを作製した。なお、本例において、拡散工程における保持時間を、試料１の作製の場合よりも長くした理由は、高速で昇温した分、拡散時間を要するためである。図６に、試料１Ｃの作製時における熱処理パターンを示す。なお、試料１Ｃの作製では、拡散処理工程にて意図的に過度な急速昇温を行うことにより、拡散処理温度を、炭素鋼の平衡状態図で、炭素の内部拡散によって低下した表面炭素濃度のときのγＦｅに対する固相線温度を上回る温度とした。
<Preparation of sample 1C>
Sample 1C was prepared in the same manner as that of Sample 1 except that the temperature rising rate of the heat treatment conditions under the diffusion treatment conditions was 16 ° C./sec and the holding time in the diffusion step was 29 seconds. In this example, the reason why the holding time in the diffusion step is longer than that in the case of preparing the sample 1 is that the diffusion time is required because the temperature is raised at a high speed. FIG. 6 shows a heat treatment pattern at the time of preparation of sample 1C. In the preparation of sample 1C, the diffusion treatment temperature was set to the surface carbon concentration lowered by the internal diffusion of carbon in the phase diagram of carbon steel by intentionally excessively rapidly raising the temperature in the diffusion treatment step. The temperature was set to be higher than the solidus temperature of γFe.
金属顕微鏡にて、試料１Ｃの表面に垂直な断面を観察したところ（図７（ａ）の線Ｌの位置）、図７（ｂ）に示されるように、処理対象物の表層部に溶解部Ｍが確認された。この結果から、試料１Ｃの浸炭方法では、処理時間の短縮化を図ることができても、炭素鋼製の処理対象物の融解を抑制することが困難であるといえる。 When the cross section perpendicular to the surface of the sample 1C was observed with a metallurgical microscope (position of line L in FIG. 7 (a)), as shown in FIG. 7 (b), a dissolved portion was formed on the surface layer of the object to be treated. M was confirmed. From this result, it can be said that it is difficult to suppress the melting of the carbon steel treatment object by the carburizing method of sample 1C, even if the treatment time can be shortened.
本発明は、上記各実施形態、各実験例に限定されるものではなく、その要旨を逸脱しない範囲において種々の変更が可能である。例えば、上記実験例では、昇温速度を制御することにより、上述した特定の温度範囲内で連続的に拡散処理温度を上昇させたが、他にも、昇温速度を制御することにより、上述した特定の温度範囲内で段階的に拡散処理温度を上昇させることも可能である。 The present invention is not limited to each of the above-described embodiments and experimental examples, and various modifications can be made without departing from the gist thereof. For example, in the above experimental example, the diffusion treatment temperature was continuously raised within the above-mentioned specific temperature range by controlling the temperature rising rate, but in addition, by controlling the temperature rising rate, the above-mentioned It is also possible to raise the diffusion treatment temperature stepwise within a specific temperature range.
Claims (4)
上記拡散工程において、
上記炭素の内部拡散によって上記処理対象物の表面炭素濃度が低下するのに従って、
浸炭処理温度超、かつ、上記炭素鋼の平衡状態図で、上記低下した表面炭素濃度のときのγＦｅに対する固相線温度未満の温度範囲内で、連続的または段階的に拡散処理温度を上昇させ、
上記拡散処理温度の最大値が、上記炭素鋼の共晶温度以上とされる、
浸炭方法。 A carburizing step of carburizing a carbon steel object to be treated and a diffusion step of diffusing carbon injected into the surface of the object to be treated in the carburizing step into the inside of the object to be treated. It is a carburizing method that has
In the above diffusion step
As the internal diffusion of carbon reduces the surface carbon concentration of the object to be treated,
In the equilibrium phase diagram of the carbon steel above the carburizing treatment temperature, the diffusion treatment temperature is continuously or stepwise raised within the temperature range below the solidus temperature with respect to γFe at the time of the lowered surface carbon concentration. Let,
Maximum value of the diffusion process temperature, Ru is the eutectic temperature or more of the above carbon steel,
Carburizing method.
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| PCT/JP2018/035314 WO2019087619A1 (en) | 2017-10-30 | 2018-09-25 | Carburization method |
| CN201880069859.4A CN111315914A (en) | 2017-10-30 | 2018-09-25 | Carburizing method |
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