CN102002663B - Vacuum carburization method - Google Patents
Vacuum carburization method Download PDFInfo
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- CN102002663B CN102002663B CN201010266292.5A CN201010266292A CN102002663B CN 102002663 B CN102002663 B CN 102002663B CN 201010266292 A CN201010266292 A CN 201010266292A CN 102002663 B CN102002663 B CN 102002663B
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Abstract
The invention provides a vacuum carburization method capable of preventing excessive spot-shaped carburization from being generated and also performing the high quality carburization of the article to be processed. The carburization gas is sprayed into a carburization chamber 3 under the atmosphere of decompressed gas to carburize the article 2 to be processed in the carburization chamber 3. The method comprises the following steps: a gas spraying amount determination step (S3), in which: the ratio (carburization gas utilization factor) of the gas consumption amount usable for the carburization of the article 2 to be processed to the carburization gas amount sprayed into the carburization chamber 3 is in the range of preventing excessive spot-shaped carburization from being generated; a gas spray period determination step (S4) of determining the gas spray time and the spray stop time, in which: the carbon concentration on the surface of the article 2 to be processed is kept less than the concentration upper limit value capable of preventing excessive spot-shaped carburization from being generated; a gas spray step (S5) of intermittently spraying the carburization gas of the gas spray amount determined by the step S3 based on the gas spray time and the spray stop time determined by the step S4.
Description
Technical field
The present invention relates to the vacuum carburization method that carries out carburizing for the object being treated in the carburizing chamber to being arranged at depressed gas atmosphere.
Background technology
Known have the vacuum carburization (referring to patent documentation 1) of for example, carrying out carburizing by spraying the carburizing gas such as propane flammable gas in the carburizing chamber to depressed gas atmosphere to being arranged on object being treated (parts of rigidity (Steel)) in this carburizing chamber.
Patent documentation 1 relates to vacuum carburization as above, and disclose with being arranged on composition that the atmosphere gas sensors such as the indoor oxygen sensor of carburizing carry out the carburizing gas in analytical gas atmosphere, according to this analytical results, the composition to the carburizing gas spraying thereafter etc. carries out the technology of feedback control simultaneously.Utilize this technology, can monitor the composition of the carburizing gas in atmosphere, thereby carry out feedback control, thus, can realize with high reproducibility and economy and carry out the carburizing of high-quality.
Prior art document:
Patent documentation 1: TOHKEMY 2002-212702 communique
Summary of the invention
The problem that invention will solve
But in patent documentation 1 there is following problems in disclosed method: there will be mottled over cargurization on the surface of object being treated.Described mottled over cargurization refers to: owing to having supplied with carburizing gas more than necessary amount in carburizing chamber, cause the excess carbon in carburizing gas to be deposited in the surface of object being treated and to form blackspot shape.Wherein, occur that the position of blackspot shape exists the defect of surface hardness reduction.
Describe for the reason that produces the problems referred to above in aforesaid method.According to the method described above: by using atmosphere gas sensor, the feedback control such as composition of the carburizing gas that is supplied to carburizing chamber can be become to suitable value.But, in reality, because the coal being produced by carburizing gas or tar cannot normally play a role atmosphere gas sensor, or, due to the carbon amount in the carburizing gas that utilizes atmosphere gas sensor to measure and the problem such as the inconsistent tolerance range reduction that causes feedback control of carbon amount that is supplied to object being treated.Its result, has caused to the generation of the situation of the carburizing gas more than indoor supply necessary amount of carburizing.
In addition, while supplying with carburizing gas more than necessary amount, except the problems referred to above, also there is the problem that can cause carburizing cycle stretch-out.In addition, also relate to for the atmosphere gas sensor that cannot normally play a role and the problem that the cost that causes while safeguarding increases such as exchange.
The present invention completes in view of above-mentioned technical problem, and object is to provide a kind of vacuum carburization method that can carry out to object being treated again high-quality carburizing in preventing mottled over cargurization generation.
The method of dealing with problems
The present invention relates to a kind of vacuum carburization method, the method is by spraying the vacuum carburization method that carburizing gas carries out carburizing to the object being treated being arranged in described carburizing chamber in the carburizing chamber to depressed gas atmosphere, the method comprises the steps: gas injection amount determining step: determine described gas injection amount, so that actual contribution is (following with respect to the ratio of gas injection amount that is injected into the described carburizing gas in described carburizing chamber in the gas consumption of the carburizing of described object being treated, be called " carburizing gas utilization ratio ") be included in and can suppress the scope that mottled over cargurization occurs, gas injection cycle determining step: determine gas injection time and gas injection stand-by time while spraying described carburizing gas, so that the surface carbon concentration of described object being treated remains on the state that is less than the upper limit of concentration value that can suppress mottled over cargurization generation, gas injection step: the carburizing gas that carrys out interrupted injection definite gas injection amount in above-mentioned gas emitted dose determining step according to gas injection time definite in above-mentioned gas injection cycle determining step and gas injection stand-by time.
The effect of invention
According to the present invention, can determine gas injection amount based on carburizing gas utilization ratio, can also determine gas injection time and gas injection stand-by time by the surface carbon concentration based on object being treated simultaneously.In addition can in the scope that can suppress mottled over cargurization generation, determine, each set(ting)value of these gas injection amounts, gas injection time and gas injection stand-by time.Thus, can in the generation that prevents mottled over cargurization, carry out the carburizing of high-quality to object being treated.
Brief description of the drawings
Fig. 1 is the formation picture of device that the vacuum carburization device relating in present embodiment is shown.
Fig. 2 is the schema that the steering logic of the vacuum carburization device relating in present embodiment is shown.
Fig. 3 is the correlationship figure that total surface area A and the gas injection amount V of object being treated are shown.
Fig. 4 (a) and (b) be the figure of the upper lower limit value for carburizing gas utilization ratio E is described.
Fig. 5 is the correlationship figure that the surface carbon concentration D of gas injection number of times T and object being treated is shown.
Fig. 6 (a) and (b) be the figure of the definite method for gas injection time of relating in present embodiment and gas injection stand-by time are described.
Fig. 7 is the figure that the temperature curve of the carburizing treatment relating in present embodiment is shown.
Fig. 8 (a) and (b) be the figure of the effect for the carburizing treatment relating in present embodiment is described.
Nomenclature
1 vacuum carburization device
2 object being treateds
3 vacuum carburization chambers (carburizing chamber)
4 carburizing gas are supplied with route
5 flow control valves
6 control device
Step S3 gas injection amount determining step
Step S4 gas injection cycle determining step
Step S5 gas injection step
The embodiment of invention
Below, by reference to the accompanying drawings embodiments of the present invention are described.
(formation of device)
Fig. 1 is the slightly pie graph of cylinder that the vacuum carburization device 1 relating in present embodiment is shown.In the formation of the vacuum carburization device 1 shown in Fig. 1, there is object being treated 2, vacuum carburization chamber 3, carburizing gas stream 4, flow control valve 5, control device 6.
Object being treated 2 is the parts as the rigidity of carburizing object.For example,, for the belt wheel (material JIS-SCr420H) of auto continuously variable transmission.Vacuum carburization chamber 3 is that inside is provided with object being treated 2, is used for, in the atmosphere of decompression, this object being treated 2 is implemented to the vacuum cementation furnace of vacuum carburization.Carburizing gas stream 4 is for being communicated with the gas flow path of carburizing gas supply source (without diagram) to the carburizing gas of vacuum carburization chamber 3.Flow control valve 5 is mounted in carburizing gas stream 4, be used for the gas flow of to the circulation carburizing gas in this stream 4, be injected into the switch-valve that the gas injection amount in vacuum carburization chamber 3 regulates.The switch motion of this flow control valve 5 is controlled by control device 6.Control device 6 is microcontrollers of the switch motion for controlling flow control valve 5.About Control the content, as hereinafter described.
According to formation as implied above, in the vacuum carburization device 1 relating in present embodiment, by the switch motion of flow control valve 5 being controlled by control device 6, adjust the gas injection amount being injected in vacuum carburization chamber 3, thereby the object being treated 2 being arranged in this carburizing chamber 3 is carried out to carburizing.
(steering logic)
Fig. 2 is the schema that the steering logic of the vacuum carburization device 1 relating in present embodiment is shown.The control device 6 of Fig. 1 is carried out the steering logic shown in Fig. 2 in cementation process.
First,, in step S1, set carburizing treatment temperature (S1) by control device 6.Wherein, control device 6 is based on setting the temperature of vacuum carburization chamber 3 by temperature sensor (without diagram) value or the value of being set by user etc. of measuring being arranged in vacuum carburization chamber 3.Details as hereinafter described.
Then, enter step S2, set the total surface area (S2) of object being treated 2 by control device 6.Wherein, the value of the total surface area of object being treated 2 is input in control device 6 by user, by control device 6, this input value is set as to the total surface area of object being treated 2.Details as hereinafter described.
Then, enter step S3, determine gas injection amount (S3) by control device 6.Wherein, the total surface area of the object being treated 2 of control device 6 based on setting in step S2 is determined gas injection amount.Details as hereinafter described.The value that it is pointed out that the gas injection amount that also can the total surface area based on object being treated 2 be calculated by user is input in control device 6, determines that by control device 6 this input value is as gas injection amount.In addition, user adjusts the aperture of flowrate control valve 5 according to determined gas injection amount.
Then, enter step S4, determine gas injection time and gas injection stand-by time (S4) by control device 6.Wherein, control device 6 was determined gas injection time and gas injection stand-by time.Details as hereinafter described.It should be noted that, also can each value of the gas injection time calculating and gas injection stand-by time be input in control device 6 by user, by control device 6, this input value is defined as to gas injection time and gas injection stand-by time.
Then,, in step S5, controlled the switch motion (S5) of flow control valve 5 based on gas injection amount and gas injection time by control device 6.Wherein, the gas injection amount based on definite in step S3 and in step S4 definite gas injection time and gas injection stand-by time control the switch motion of flow control valve 5.Details as hereinafter described.
By steering logic as implied above, the control device 6 shown in Fig. 1, the particularly switch motion based on controlled flow control valve 5 by step S3 and definite gas injection amount, gas injection time and the gas injection stand-by time of step S4.Thus, the carburizing gas that is injected into vacuum carburization chamber 3 is adjusted.Below, be elaborated for each step.
(about step S1)
To step, S1 is elaborated.In step S1, be the arbitrary temp of 1203K～1253K scope by the Temperature Setting of vacuum carburization chamber 3.Its reason is, the vacuum carburization device 1 relating in present embodiment is effective for the carburizing temperature within the scope of this.
(about step S2)
To step, S2 is elaborated.In step S2, user asks the value that calculates the total surface area that is arranged on the whole object being treateds 2 in vacuum carburization chamber 3, and this value is input in control device 6.The value of this total surface area is corresponding to the number of object being treated 2, shape and the value that can change.
(about step S3)
To step, S3 is elaborated.As mentioned above, in step S3, the total surface area of the object being treated 2 based on setting in step S2 is determined gas injection amount.For this reason, first the correlationship of the total surface area to object being treated 2 and gas emitted dose describes.
(correlationship of the total surface area of object being treated 2 and gas emitted dose)
Present inventor finds: the total surface area (unit: m that makes object being treated 2
2) be the gas injection amount (unit: NL/hr) of time per unit under A, standard state when the V, between the total surface area A of these object being treateds 2 and gas injection amount, there is correlationship as shown in Figure 3.
Fig. 3 is the figure of the correlationship of total surface area A for object being treated 2 is described and gas injection amount V.In Fig. 3, transverse axis represents that total surface area A, the longitudinal axis represent gas injection amount V.The numerical value representative of the each point of marking and drawing on Fig. 3 in addition, based on total surface area A corresponding to each point and gas injection amount V, utilize the numerical value of the carburizing gas utilization ratio E (unit: %) that following formula (1) calculates.Here, described carburizing gas utilization ratio E refers to: actual contribution in the total carbon (or gas consumption) of the carburizing of object being treated 2 with respect to the ratio (unit: %) of total carbon (or gas injection amount) of carburizing gas that is injected into vacuum carburization chamber 3.
[mathematical expression 1]
It should be noted that, in formula (1), F represents the flux values (unit: g/m of object being treated 2
2), T represents that carburizing gas injecting time (unit: hr), n represent that mole number (unit: mol), C represent carbon atom amount (unit: 12.01g/mol).
The situation occurred of the mottled over cargurization of present inventor to each point on Fig. 3 checks.Result shows: at the each point (E=4.6%, 6.7%, 11.3%, 12.1%) of marking and drawing with "×", in vacuum carburization chamber 3, supplied with carburizing gas more than necessary amount, mottled over cargurization has occurred.On the other hand, at the each point (E=25.4%, 32.3%) of marking and drawing with " △ ",, to the carburizing gas of supplying with necessary amount in vacuum carburization chamber 3, not there is not carburizing deficiency.Wherein, at the each point (E=16.4%, 16.6%, 17.0%, 17.1%) of marking and drawing with "○", supply with the carburizing gas of appropriate amount, carried out suitable carburizing.
Straight line L1 shown in Fig. 3 and L2 represent the critical of these "×", " △ ", "○".Straight line L1 is the straight line that represents E=15%.On the other hand, L2 is the straight line that represents E=25%.That is, when the total surface area A in satisfied 15%≤E≤25% and gas injection amount V, meet the "○" of Fig. 3, can carry out suitable carburizing.Lower value 15% and higher limit 25% in conjunction with Fig. 4 to this carburizing gas utilization ratio E are specifically described.Fig. 4 is the figure of the upper lower limit value for carburizing gas utilization ratio E is described.
(about the lower value 15% of carburizing gas utilization ratio E)
Fig. 4 (a) is the figure of the lower value 15% for carburizing gas utilization ratio E is described.In Fig. 4 (a), transverse axis represents that carburizing gas utilization ratio E, the longitudinal axis represent mottled over cargurization occurred level.Here, described mottled over cargurization occurred level, is the index that characterizes the occurrence degree of mottled over cargurization.In the present embodiment, be defined as follows for mottled over cargurization occurred level: when mottled over cargurization occurred level is 1 when above, represent to have occurred mottled over cargurization; In the time that mottled over cargurization occurred level is 0, represents mottled over cargurization does not occur, but carried out suitable carburizing.
Particularly, the representative of the mottled over cargurization occurred level (3) shown in the longitudinal axis of Fig. 4 (a): have 5 with upper part, mottled over cargurization to occur, and each happening part is aterrimus.In addition, mottled over cargurization occurred level (2) representative: mottled over cargurization has occurred at more than having 1 and 5 positions of less than, and each happening part is aterrimus.In addition mottled over cargurization occurred level (1) representative: mottled over cargurization has occurred at more than having 1 and 5 positions of less than, and each happening part is light/dark balance (grey).In addition, mottled over cargurization occurred level (0) representative: mottled over cargurization does not occur, but carried out suitable carburizing.
Based on this, from this Fig. 4 (a): carburizing gas utilization ratio E lower than 15% scope in, mottled over cargurization occurred level reduces stage by stage; And within carburizing gas utilization ratio E is greater than 15% scope, mottled over cargurization occurred level has the tendency of trend 0.The above-mentioned reason that mottled over cargurization occurs in lower than 15% scope at carburizing gas utilization ratio E is: within the scope of this, exist a large amount of (being greater than 85%) unemployed carburizing gas.
Thus, can think that the lower value of the carburizing gas utilization ratio E that can carry out suitable carburizing is 15%.It is pointed out that in Fig. 4 (a), represent that carburizing gas utilization ratio E can be by acquisitions such as minimum 2 multiplication lower than the dotted line of the relation of the carburizing gas utilization ratio E in 15% scope and mottled over cargurization occurred level.
(about the higher limit 25% of carburizing gas utilization ratio E)
Fig. 4 (b) is the figure of the higher limit 25% for carburizing gas utilization ratio E is described.In Fig. 4 (b), transverse axis represents that carburizing utilization ratio E, the longitudinal axis represent carburized depth deviation.Here, described carburized depth deviation, is the index (for example mm of unit) that characterizes the carburized depth extent of deviation in object being treated 2.
Present inventor finds: between carburizing gas utilization ratio E and carburized depth deviation, have the correlationship shown in Fig. 4 (b),, between carburizing gas utilization ratio E and carburized depth deviation, there is following relation: when carburizing gas utilization ratio E is less than 25%, carburized depth deviation is steady state value (being 0.03 here); When carburizing gas utilization ratio E is greater than 25%, carburized depth deviation increases pro rata with carburizing gas utilization ratio E.
Be described as follows.In the time that carburizing gas utilization ratio E is less than 25%, supply with the carburizing gas that only can fully be full of whole vacuum carburization chamber 3 inner amounts.Thus, can in object being treated 2, not produce the deviation of carburized depth, and carburized depth deviation is steady state value.On the other hand, in the time that carburizing gas utilization ratio E is greater than 25%, there is no to supply with the carburizing gas that only can fully be full of whole vacuum carburization chamber 3 inner amounts.Thus, can be in object being treated 2 occur through the part of suitable carburizing with without the part of carburizing etc., thereby produce carburized depth deviation.Present inventor finds: represent that the generation of above-mentioned carburized depth deviation and the critical carburizing gas utilization ratio E not producing are 25%.
From situation described above, can think that the higher limit of the carburizing gas utilization ratio E that can carry out suitable carburizing is 25%.It is pointed out that line and carburized depth deviation that the dotted line shown in Fig. 4 (b) is steady state value (being 0.03) by carburized depth deviation combine with the line of the proportional increase of carburizing gas utilization ratio E here.
(gas injection method for determination of amount in step S3)
Above, be illustrated for the upper lower limit value of the surface-area A of object being treated 2 and the correlationship of gas emitted dose V and carburizing gas utilization ratio E.In view of foregoing, in step S3, the surface-area A of the object being treated 2 of control device 6 based on setting in step S2, is defined as gas injection amount V the value of utilizing following formula (2) and formula (3) to calculate.Wherein, formula (2) is derived by formula (1).
[mathematical expression 2]
[mathematical expression 3]
15≤E≤25 (3)
As mentioned above, by determining gas injection amount V so that carburizing gas utilization ratio E is included in the scope shown in formula (3), can suppress due to the generation of having supplied with carburizing gas more than necessary amount to vacuum carburization chamber 3 and cause mottled over cargurization.Thus, can also shorten the cycle of carburizing.In addition, can suppress because superfluous carburizing gas generation thermolysis generates coal, tar, thereby can seek to reduce the maintenance cost causing due to the generation of coal, tar.
(about step S4)
To step, S4 is elaborated.As mentioned above, in step S4, determine gas injection time and gas injection stand-by time.According to present embodiment, in the case of the correlationship of surface carbon concentration of considering closely above-mentioned gas injecting time and gas injection stand-by time and object being treated 2, determine the value of two key elements.Here first this correlationship is described.
(relation between gas injection time and gas injection stand-by time and the surface carbon concentration of object being treated 2)
Present inventor finds: while making surface carbon concentration (unit: %) that gas injection number of times (unit: number of times) is T, object being treated 2 for D, between these gas injection number of times T and surface carbon concentration D, there is correlationship as shown in Figure 5, here, described gas injection number of times is using the injection stand-by time in the gas injection time in tens of seconds and tens of seconds as gas injection number of times a pair of and while being defined as the injecting times of 1 time.
Fig. 5 shows the figure of the correlationship of the surface carbon concentration D of gas injection number of times T and object being treated 2.In Fig. 5, transverse axis represents that gas injection number of times T, the longitudinal axis represent the surface carbon concentration D of object being treated 2.Whether the symbology of the each point of marking and drawing on Fig. 5 in addition, there is the situation of mottled over cargurization at each point.It should be noted that, the correlationship shown in this Fig. 5 is to be the correlationship that 1223K, internal pressure are 950Pa, observed value when changing gas injection number of times T and quenching obtains from the carburizing treatment temperature by making vacuum carburization chamber 3.
The situation occurred of the mottled over cargurization of present inventor to each point on Fig. 5 checks.Result shows: at the each point (D > 1.40%) of marking and drawing with "×", mottled over cargurization occurs.On the other hand, at the each point (D < 1.40%) with " △ " mapping, there is not mottled over cargurization.In addition, before surface carbon concentration D reaches D=1.40% during, along with gas injection number of times T increases the surface carbon concentration D rising that is in line, and once exceed D=1.40%, surface carbon concentration D reaches capacity, thereby mottled over cargurization occurs.
The threshold concentration of carbon will be defined as the generation of above-mentioned mottled over cargurization and the critical surface carbon concentration D (D=1.40% here) that do not produce.This threshold concentration is consistent with the maximum solid solution concentration that experiment obtains.And the value of this threshold concentration changes according to the carburizing treatment temperature of vacuum carburization chamber 3 is different.
In the example shown in Fig. 5, so that it remains on the state that is less than this threshold concentration (, being 1.40%) here, can stop the generation of mottled over cargurization by control surface carbon concentration D.That is, can think, this threshold concentration is to suppress the higher limit of the surface carbon concentration D of mottled over cargurization generation.
(definite method of gas injection time and gas injection stand-by time in step S4)
In view of foregoing, in step S4, determine gas injection time and gas injection stand-by time by control device 6, so that surface carbon concentration D remains on the state that is less than threshold concentration.Utilize Fig. 6 to be specifically described.Fig. 6 is the figure of the definite method for gas injection time of relating in present embodiment and gas injection stand-by time are described.
Fig. 6 (a) is the figure of the gas injection pattern for present embodiment is described.The conventional rheological parameters' change with time of the surface carbon concentration D of solid line L3 in Fig. 6 (a) representative in the time that gas injection starts to stop gas injection when reaching capacity concentration because of surface carbon concentration D.On the other hand, the dotted line L4 in Fig. 6 (a) represents the rheological parameters' change with time of the surface carbon concentration D being caused by the gas injection pattern of present embodiment.
As shown in the solid line L3 in Fig. 6 (a), after the moment, T0 started gas injection, at the reach capacity moment T1 of concentration of surface carbon concentration D, gas injection stops.Thus, after this moment, reduce to the shape that is in line of surface carbon concentration D before moment T2.This be due to, the surperficial carbon that is deposited in object being treated 2 diffuses to the inside of object being treated 2.Afterwards, taking this moment T2 as transition point, the time dependent reduction degree of surface carbon concentration D reduces.This be due to, slow up to the diffusion of inner carbon from the surface of object being treated 2.
In the vacuum carburization device 1 of present embodiment, in view of the trend of the conventional rheological parameters' change with time of surface carbon concentration D as above, gas injection is after the moment, T0 started, stop gas injection at the reach capacity moment T1 of concentration of surface carbon concentration D, as shown in the dotted line L4 in Fig. 6 (a).Thereafter, in the time of the T2 reaching as transition point, jet flow stream again.Then,, at the reach capacity moment T3 of concentration of surface carbon concentration D, again stop gas injection.Then, in the time of the T4 reaching as transition point, jet flow stream again.As mentioned above, while reaching capacity concentration taking surface carbon concentration D, as the upper limit, carry out intermittently and repeat to spray and the interrupted injection that stops spraying.
Fig. 6 (b) shows the figure of the specific examples of the gas injection pattern of present embodiment.In Fig. 6 (b), show the rheological parameters' change with time of gas injection amount V and the rheological parameters' change with time of surface carbon concentration D.
As shown in Fig. 6 (b), gas injection, after starting elapsed time t0 from the moment 0, stops gas injection (being equivalent in Fig. 6 (a) from moment T0 to T1) in the time that surface carbon concentration D reaches capacity concentration.Thereafter, at the constant time ts of process, after surface carbon concentration D has passed through linearity decline, jet flow stream (being equivalent in Fig. 6 (a) from moment T1 to T2) again.Then,, through constant time tp, when surface carbon concentration D reaches capacity concentration, again stop gas injection (being equivalent in Fig. 6 (a) from moment T2 to T3).Then, at the constant time ts of process, after surface carbon concentration D has passed through linearity decline, jet flow stream (being equivalent in Fig. 6 (a) from moment T3 to T4) again., while reaching capacity concentration taking surface carbon concentration D, as the upper limit, carry out intermittently and repeat to spray and the interrupted injection that stops spraying.It is pointed out that the gas injection amount V shown in Fig. 6 (b) is gas injection amount definite in step S3.
As mentioned above, in step S4, control device 6 is determined gas injection time and gas injection stand-by time on the basis of rheological parameters' change with time of considering surface carbon concentration D, so that surface carbon concentration D remains on the state that is less than threshold concentration.Thus, surface carbon concentration D not only can be remained on below threshold concentration, can also suppress the generation of mottled over cargurization simultaneously.
It is pointed out that the time t0 shown in Fig. 6 (b), ts, tp can determine by time from moment T0 to T1 in the rheological parameters' change with time trend of the surface carbon concentration D shown in Fig. 6 (a), the time from moment T1 to T2, time from moment T2 to T3 are carried out to experiment measuring.Be that 1223K, internal pressure are under 950Pa, the threshold concentration condition that is 1.40% in the carburizing treatment temperature of the vacuum carburization chamber 3 such such as this specific examples, be expressed as: t0≤180s, ts≤300s, tp≤120s (unit: second, s).In addition,, according to the difference of effective cured layer (ECD) of object being treated 2, multiplicity (ts+tp) is variable value.
(about step S5)
To step, S5 is elaborated.In step S5, the gas injection amount based on definite in step S3 and in step S4 definite gas injection time and gas injection stand-by time the switch motion of flow control valve 5 is controlled.
Fig. 7 shows the temperature profile of the carburizing treatment relating in present embodiment.As shown in Figure 7, used the treating processes of the vacuum carburization of the vacuum carburization device 1 of present embodiment to be divided into temperature raising period, carburizing cycle, diffusion period and quenching phase.Wherein, relevant temperature raising period, diffusion period and quenching phase, due to identical with traditional treatment process, thereby in this description will be omitted.In the carburizing cycle shown in Fig. 7, according to the gas injection pattern being illustrated in Fig. 6 (b), the switch motion of flow control valve 5 is controlled.
(effect of the carburizing treatment of present embodiment)
Fig. 8 is the figure that utilizes the effect of the carburizing treatment that the vacuum carburization device 1 of present embodiment carries out for explanation.In Fig. 8 (a), the rheological parameters' change with time of the surface carbon concentration D while showing the vacuum carburization method that adopts the vacuum carburization device 1 based on present embodiment.On the other hand, in Fig. 8 (b), the rheological parameters' change with time of the surface carbon concentration D while showing the vacuum carburization method that adopts the vacuum carburization device based on traditional.
As shown in Fig. 8 (a), while adopting the vacuum carburization method of the vacuum carburization device 1 based on present embodiment, surface carbon concentration D can remain on the state lower than threshold concentration (being 1.40%) here.Thus, in the generation that prevents mottled over cargurization, can also carry out the carburizing of high-quality to object being treated 2.
(brief summary)
As mentioned above, according to present embodiment, can be in determining gas injection amount V based on carburizing gas utilization ratio E, the surface carbon concentration D based on object being treated determines gas injection time and gas injection stand-by time.And, can determine each set(ting)value of above-mentioned gas emitted dose, gas injection time and gas injection stand-by time, to realize the inhibition of the generation to mottled over cargurization.Thus, in preventing that mottled over cargurization from occurring, can also carry out to object being treated 2 carburizing (effect of the invention of recording in claim 1) of high-quality.
In addition according to present embodiment, be that the total surface area of E (%), described object being treated 2 is A (m making described carburizing gas utilization ratio,
2), flux values is F (g/m
2), carburizing gas injecting time is that T (hr), mole number are that n (mol), carbon atom amount are the gas injection amount of time per unit under C (=12.01g/mol), standard state while being V (NL/hr), determines gas injection amount V so that it meets above-mentioned formula (2).Thus, can consider on the basis of the total surface area A of object being treated 2 and the correlationship of gas emitted dose V, in preventing that mottled over cargurization from occurring, can also carry out to object being treated 2 carburizing (effect of the invention of recording in claim 2) of high-quality.
In addition, according to present embodiment, can determine gas injection amount V, so that carburizing gas utilization ratio E is included in the scope shown in formula (3).Thus, can be on the basis of correlationship of considering carburizing gas utilization ratio E and mottled over cargurization or occur with carburized depth deviation, in preventing that mottled over cargurization from occurring, can also carry out to object being treated 2 carburizing (effect of the invention of recording in claim 3) of high-quality.
In addition,, according to present embodiment, in gas injection cycle determining step (the step S4 in Fig. 2), determine gas injection time and the gas injection stand-by time of carburizing gas, so that surface carbon concentration D remains on the state that is less than maximum solid solution concentration.Thus, can be on the basis of correlationship of generation of considering maximum solid solution concentration and mottled over cargurization, in preventing that mottled over cargurization from occurring, can also carry out to object being treated 2 carburizing (effect of the invention of recording in claim 4) of high-quality.
Above, be the explanation of carrying out for one embodiment of the present invention, but shown in above-mentioned embodiment be one of Application Example of the present invention, technical scope of the present invention is not limited to the concrete formation of above-mentioned embodiment.
For example, in the explanation of above-mentioned steps S3, illustrated, can carry out suitable carburizing when adopting while meeting the total surface area A of 15%≤E≤25% and gas injection amount V, but be not limited to this kind of situation.For example, also allow the error of existence ± 2% left and right.Its reason is, according to performance of flow control valve 5, control device 6 etc., following situation may occur: actual ejection may not be the steady state value setting to the gas injection amount of the carburizing gas in vacuum carburization chamber 3.
In addition, in the explanation of above-mentioned steps S4, illustrated, determine gas injection time and gas injection stand-by time so that surface carbon concentration D remains on the state that is less than threshold concentration.The value of threshold concentration, described here can change according to the carburizing treatment temperature of vacuum carburization chamber 3.Therefore, also the threshold concentration when can be in advance obtaining carburizing treatment temperature and change for every kind of temperature by experimental measurement etc., then ask calculation can make surface carbon concentration D remain on gas injection time and the gas injection stand-by time of the state that is less than threshold concentration for every kind of temperature.Now, in step S4, can set most suitable gas injection time and gas injection stand-by time according to the carburizing treatment temperature of setting in step S1.
In addition, in the explanation of above-mentioned steps S3 and S4, illustrated, control device 6 is determined gas injection time and gas injection stand-by time after definite gas injection amount again, but is not limited to this situation.As long as can make carburizing gas utilization ratio E be included in can to suppress in scope that mottled over cargurization occurs and the surface carbon concentration D of object being treated 2 be remained on be less than to suppress the state of the upper limit of concentration value that mottled over cargurization occurs determining of gas injection amount, gas injection time and gas injection stand-by time, the processing of above-mentioned steps S3 and S4 can front and back backward be carried out, and also can carry out simultaneously.
Claims (1)
1. a vacuum carburization method, the method is by spraying the vacuum carburization method that carburizing gas carries out carburizing to the object being treated being arranged in described carburizing chamber in the carburizing chamber to depressed gas atmosphere, wherein, carburizing gas described in interrupted injection, makes the total surface area A (m of carburizing gas utilization ratio E (%), described object being treated
2), flux values F (g/m
2), the gas injection amount V (NL/hr) of time per unit meets following formula under mole number n (mol), the carbon atom amount C (=12.01g/mol) of the carbon atom of carburizing gas injecting time T (hr), described carburizing gas, standard state:
Described carburizing gas utilization ratio is actual contribution in the gas consumption of the carburizing of described object being treated with respect to the ratio that is injected into the described gas injection amount in described carburizing chamber,
Determine gas injection time and the gas injection stand-by time of described carburizing gas, so that the surface carbon concentration of described object being treated keeps being less than the state of maximum solid solution concentration,
Described carburizing gas utilization ratio E meets following formula:
15≤E≤25。
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| JP6412436B2 (en) * | 2015-02-13 | 2018-10-24 | ジヤトコ株式会社 | Vacuum carburizing method and vacuum carburizing apparatus |
| JP6497208B2 (en) * | 2015-05-19 | 2019-04-10 | 大同特殊鋼株式会社 | Manufacturing method of high-concentration carburized steel |
| JP6849520B2 (en) * | 2017-04-28 | 2021-03-24 | 光洋サーモシステム株式会社 | Manufacturing method of steel parts and carburizing furnace |
| JP7086481B2 (en) * | 2018-12-14 | 2022-06-20 | ジヤトコ株式会社 | Continuous carburizing furnace |
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| JP2005350729A (en) * | 2004-06-10 | 2005-12-22 | Ishikawajima Harima Heavy Ind Co Ltd | Vacuum carburization method |
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| JP2005350729A (en) * | 2004-06-10 | 2005-12-22 | Ishikawajima Harima Heavy Ind Co Ltd | Vacuum carburization method |
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