JP4853615B2 - Vacuum carburizing quality control method and vacuum carburizing furnace - Google Patents

Description

In the vacuum carburizing process, the present invention manages the carburizing depth of the workpiece, and obtains a desired carburizing depth, thereby reducing the variation in carburizing quality and making it uniform. The present invention relates to a method and a vacuum carburizing furnace.

Carburizing is a process of diffusing and penetrating carbon into the surface of a steel material. Usually, after carburizing, quenching is performed to harden the surface to produce a part composed of a highly wear-resistant surface and a tough core.

Examples of carburizing treatment include gas carburizing, plasma carburizing, and vacuum carburizing. Among these, the gas carburizing method is a method in which natural gas, propane, butane and the like are modified to produce a carburizing gas mainly composed of CO, and thereby carburizing a steel material. Since the gas carburizing method performs carburizing while controlling the atmosphere based on the carbon potential, the surface carbon concentration of the article to be treated can be stably controlled. For this reason, the gas carburizing method has the advantage that the reproducibility of the carburizing quality for the article to be processed is good. However, the gas carburizing method has problems such as a large amount of carburizing gas used, exhaust gas needs to be burned, and grain boundary oxidation occurs on the surface of the article to be processed.

On the other hand, the vacuum carburizing method is a kind of gas carburizing method, and is a gas carburizing method in which carburizing treatment is performed under reduced pressure (see, for example, Patent Documents 1 to 3 below). Hereinafter, in this specification, “gas carburizing” means a gas carburizing method performed under atmospheric pressure, and “vacuum carburizing” means a gas carburizing method performed under reduced pressure.

In vacuum carburization, the surface carbon concentration reaches the carbon solid solubility limit (Acm point) immediately after the start of carburization, and then the desired surface carbon concentration and carbon concentration distribution are managed by managing the carburizing gas input time (carburizing time) and diffusion time. Have gained. The carbon inflow depth (diffusion depth) in the product to be treated is controlled by the diffusion time for both gas carburizing and vacuum carburizing.

JP 2001-81543 A JP 2001-240954 A JP 2002-212702 A

In gas carburization, the atmosphere was controlled based on the carbon potential as described above. However, since the reaction forms differ between gas carburizing and vacuum carburizing, control of the atmosphere based on the carbon potential in gas carburizing is changed to vacuum carburizing. It is impossible to apply. For this reason, in vacuum carburizing, the carburizing quality (surface carburizing concentration, carburizing concentration distribution, surface hardness, effective hardened layer depth) is uniform for the products to be processed by controlling conditions such as carburizing / diffusion temperature, carburizing time, and gas input amount. I have tried to secure it.

However, in the case of vacuum carburizing according to the prior art, the carburizing quality cannot be controlled by the condition management as described above, and there is some variation in the carburizing quality between each operation batch, and the carburizing quality management is not sufficient. There was a problem of poor reproducibility. For this reason, conventionally, it has been necessary to verify the carburizing quality by a sampling test of the article to be processed after the carburizing process, and there is a problem that the management of the carburizing quality is complicated.

In view of the above-mentioned problems, the present invention can manage the carburizing quality by managing the carburizing depth to the product to be processed, improve the reproducibility by obtaining the desired carburizing depth, and vary the carburizing quality. An object of the present invention is to provide a vacuum carburizing quality control method and a vacuum carburizing furnace capable of ensuring the uniformity by reducing the amount and easily controlling the carburizing quality.

The first invention created to achieve the above object performs carburizing treatment on the article to be treated in a reduced pressure and heated state while supplying a carburizing gas composed of hydrocarbons into the treatment chamber in which the article to be treated is accommodated. This is a quality control method for vacuum carburizing, which detects a hydrogen partial pressure ratio with respect to the total pressure in a processing chamber during carburizing treatment, obtains a carbon inflow rate into a product to be processed based on a change in the hydrogen partial pressure ratio over time, and A quality control method for vacuum carburizing, characterized in that a carburizing depth of a product to be processed is obtained based on an inflow speed.

The second invention is characterized in that, in the first invention, when determining the carburization depth of the article to be processed based on the carbon inflow rate, the carburization depth is obtained based on the following equation. .
y = −b · Ci (t) · x + A
Where x is the depth from the surface of the article to be treated, y is the carbon concentration at the depth x, Ci (t) is the carbon inflow rate, -b is a coefficient for converting the carbon inflow rate into a carbon concentration gradient, and A is the target This is the surface carbon concentration during carburization of the treated product.

A third invention is characterized in that, in the first invention, when the obtained carburizing depth reaches a desired carburizing depth, the supply of the carburizing gas into the processing chamber is stopped. It is.

A fourth aspect of the present invention is a furnace body having a processing chamber for storing a processed product and carburizing the processed product in a reduced pressure and heated state, and a carburizing gas supply means for supplying a carburizing gas composed of hydrocarbons to the processing chamber. And a hydrogen partial pressure ratio detection for detecting a hydrogen partial pressure ratio with respect to the total pressure in the processing chamber at the time of the carburizing process in a vacuum carburizing furnace having a gas exhaust means for exhausting the gas in the processing chamber and maintaining a predetermined reduced pressure state And an arithmetic processing means for performing a process of obtaining a carbon inflow rate into the article to be treated based on a time change of the hydrogen partial pressure ratio and obtaining an estimated value of a carburization depth of the article to be treated based on the carbon inflow rate. And a vacuum carburizing furnace characterized by comprising: an output means for displaying the carburizing depth of the workpiece obtained by the arithmetic processing means.

According to a fifth invention, in the fourth invention, the arithmetic processing means obtains a carburization depth based on the following equation.
y = −b · Ci (t) · x + A
Where x is the depth from the surface of the article to be treated, y is the carbon concentration at the depth x, Ci (t) is the carbon inflow rate, -b is a coefficient for converting the carbon inflow rate into a carbon concentration gradient, and A is the target This is the surface carbon concentration during carburization of the treated product.

A sixth invention further includes a carburizing gas control means for stopping the supply of the carburizing gas into the processing chamber when the obtained carburizing depth reaches a desired carburizing depth in the fourth invention. It is characterized by that.

In the present invention, the “hydrogen partial pressure ratio detecting means” means a device having a function for detecting the hydrogen partial pressure ratio with respect to the total pressure in the processing chamber during the carburizing process. Such a function can be achieved by combining a plurality of devices. It is a concept that includes what is achieved. In the embodiment, a combination of some of the functions of the hydrogen sensor, the vacuum gauge, and the arithmetic processing device corresponds to this.

The “arithmetic processing means” has a function of obtaining a carbon inflow amount to the article to be treated based on a time change of the hydrogen partial pressure ratio, and performing a process for obtaining an estimated value of the carburization depth of the article to be treated from the carbon inflow rate. It is a concept that includes what achieves such a function by using a part of the functions of the electronic computer. In the embodiment, the arithmetic processing device corresponds to this.

“Display” means to express the target information to the outside, including the concept of displaying by electromagnetic or magnetic method like a monitor, or displaying by tangible method by printing like a printer. It is.

The meaning of other terms will become apparent from the following description of this specification.

According to the first and fourth inventions described above, the hydrogen partial pressure ratio with respect to the total pressure in the processing chamber at the time of the carburizing process is detected, and the carbon inflow rate into the product to be processed is determined based on the change over time in the hydrogen partial pressure ratio. Since the carburization depth of the product to be processed is obtained based on the carbon inflow rate, the carburization quality based on the carburization depth can be managed. For this reason, it is not necessary to carry out a sampling test after carburizing treatment as in the prior art, and carburizing quality can be easily managed. As will be described in detail later, the carburization depth of carbon for the article to be treated can be obtained from the surface carbon concentration and the carbon concentration gradient of the article to be treated. Further, the carbon concentration gradient correlates with the time change of the carbon inflow amount, and the time change of the carbon inflow amount correlates with the time change of the hydrogen partial pressure ratio in the processing chamber. Therefore, the carburization depth of the product to be processed can be obtained (estimated) based on the change over time in the hydrogen partial pressure ratio in the processing chamber.

According to the second and fifth aspects of the invention, when the carburization depth of the product to be processed is estimated based on the carbon inflow rate, the calculation is based on a simple arithmetic expression y = −b · Ci (t) · x + A. Therefore, the carburization depth can be calculated easily and accurately. Specifically, x is the depth from the surface of the workpiece, y is the carbon concentration at the depth x, Ci (t) is the carbon inflow rate, -b is a coefficient for converting the carbon inflow rate into a carbon concentration gradient, Since A is the surface carbon concentration at the time of carburization of the article to be treated, the carburization depth x _C can be obtained by setting the carbon concentration y in the above formula to the base material carbon concentration y _{0 of the} article to be treated.

According to the third and sixth inventions, when the obtained carburization depth reaches the desired carburization depth, the supply of the carburizing gas to the processing chamber is stopped. You can get it. After the supply of the carburizing gas is stopped, the process proceeds to a diffusion process for diffusing the carbon carburized in the product to be processed inside the product to be processed, but the diffusion depth can be managed by the processing temperature and the processing time. For this reason, the reproducibility between different operation batches can be improved, and variation in carburizing quality can be reduced to ensure uniformity.

As described above, according to the present invention, the carburization quality can be managed by managing the carburization depth to the workpiece, the reproducibility is improved by obtaining the desired carburization depth, and the carburization quality varies. As a result, the uniformity can be ensured and the carburizing quality can be easily managed.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

First, the equipment configuration of a vacuum carburizing furnace for carrying out the quality control method for vacuum carburizing according to the present invention will be described.

FIG. 1 is a diagram showing a schematic configuration of a vacuum carburizing furnace 10 according to a first embodiment of the present invention. As shown in FIG. 1, the vacuum carburizing furnace 10 includes a furnace body 12 having a processing chamber 17 therein, a gas supply line 20, and a gas exhaust line 22. A heat insulating wall 14 is provided inside the furnace wall 16 of the furnace body 12. The processing chamber in which the product 1 is accommodated in the heat insulating wall 14 and carburized for the product 1 under reduced pressure and heating. 17 is formed. A heater 19 is installed in the processing chamber 17 so as to heat the heating chamber 17 and the workpiece 1 to a predetermined temperature.

The gas supply line 20 is connected to the heat insulating wall 14 and functions as “carburizing gas supply means” for supplying a carburizing gas made of hydrocarbon (for example, acetylene) into the processing chamber 17. The gas exhaust line 22 is connected to the heat insulating wall 14 and exhausts the gas in the processing chamber 17. Further, the gas exhaust line 22 is connected to a vacuum pump 24, and the gas exhaust line 22 and the vacuum pump 24 function as “gas exhaust means” for exhausting the gas in the processing chamber 17 and holding it in a predetermined reduced pressure state. To do.

Further, the vacuum carburizing furnace 10 includes a hydrogen sensor 30 that detects the hydrogen pressure in the processing chamber 17 during the carburizing process, a vacuum gauge 32 that detects the total pressure in the processing chamber 17 during the carburizing process, and various calculations and controls. An arithmetic processing unit 34 to perform, a display 36 for displaying an output from the arithmetic processing unit 34, and a printer 38 for printing the output from the arithmetic processing unit 34 are provided. The arithmetic processing unit 34 is connected with a keyboard 40 and a mouse 42 as input means.

The hydrogen sensor 30 can be composed of, for example, a quadrupole mass spectrometer, and the vacuum gauge 32 can be composed of, for example, a Baratron vacuum gauge. The hydrogen sensor 30 and the vacuum gauge 32 are connected to the arithmetic processing unit 34 and output the detected hydrogen partial pressure and total pressure in the processing chamber 17, and the output signals are input to the arithmetic processing unit 34. .

The arithmetic processing unit 34 includes at least a CPU and a memory and can execute various types of information processing / arithmetic / control, and can be configured by a personal computer or a dedicated electronic computer. Based on the hydrogen partial pressure from the hydrogen sensor 30 and the total pressure from the vacuum gauge 32, the arithmetic processing unit 34 in the present embodiment calculates and obtains a hydrogen partial pressure ratio with respect to the total pressure in the processing chamber 17 during the carburizing process. Process. As described above, in this embodiment, the hydrogen sensor 30, the vacuum gauge 32, and the arithmetic processing unit 34 serve as “hydrogen partial pressure ratio detecting means” that detects the hydrogen partial pressure ratio with respect to the total pressure in the processing chamber 17 during the carburizing process. Has achieved the function.

Moreover, in this embodiment, the arithmetic processing unit 34 calculates | requires the carbon inflow rate to the to-be-processed object 1 based on the time change of hydrogen partial pressure ratio, and the carburizing depth of the to-be-processed item 1 is calculated based on this carbon inflow rate. It functions as an “arithmetic processing means” for performing processing for obtaining an estimated value. A specific method for obtaining the carburization depth by the arithmetic processing unit 34 will be described later.

The display 36 outputs the carburizing depth obtained by the arithmetic processing unit 34 by image display. Further, the printer 38 outputs the carburized depth obtained by the arithmetic processing unit 34 by printing. Thus, in this embodiment, the display 36 or the printer 38 functions as an “output unit” that displays the carburization depth obtained by the arithmetic processing unit.

In the vacuum carburizing furnace 10 configured as described above, when the respective chambers are soaked with the processing chamber 17 containing the article 1 to be processed in a predetermined reduced pressure and heating state, the carburizing gas is supplied into the processing chamber 17 at a predetermined flow rate (for example, While being supplied at 20 L / min), it is evacuated by the vacuum pump 24, and the workpiece 1 is carburized for a predetermined time while maintaining a predetermined reduced pressure state. Thereafter, the supply of the carburizing gas is stopped, and the inside of the processing chamber 17 is evacuated by the vacuum pump 24 to return to the original vacuum degree, and the diffusion processing is performed.

Next, a specific method for calculating the estimated value of the carburization depth of the article to be processed from the time change of the hydrogen partial pressure ratio in the above-described arithmetic processing unit 34 will be described. Hereinafter, a case where acetylene (C ₂ H ₂ ) is used as the carburizing gas will be described.

The carburization depth of carbon for the article to be treated can be obtained from the surface carbon concentration and the carbon concentration gradient of the article to be treated. Further, since the carbon concentration gradient has a correlation with the time change of the carbon inflow amount (carbon inflow rate), the carbon concentration gradient can be derived from the carbon inflow rate if the correlation (correspondence) is known in advance. Furthermore, since the carbon inflow rate has a correlation with the time change of the hydrogen partial pressure ratio in the processing chamber during the carburizing process, the carbon inflow rate can be derived if the time change of the hydrogen partial pressure ratio is known. Therefore, the carburization depth of the product to be processed can be obtained (estimated) from the time change of the hydrogen partial pressure ratio in the processing chamber during the carburizing process.

Therefore, first, the arithmetic processing unit 34 performs a process of obtaining the carbon inflow rate from the time change of the hydrogen partial pressure ratio. Specifically, first, based on the following (1), the carbon amount ΣC (t) dissociated by the carburization reaction (C ₂ H ₂ → H ₂ + 2C) is determined from the hydrogen partial pressure ratio.
ΣC (t) = 2 · N · K (t) /22.4 L / mol (1)
However, N is an acetylene supply amount (L / min) and K (t) is a hydrogen partial pressure ratio.

Based on the following equation (2), the carbon inflow rate Ci (t) is obtained from the dissociated carbon amount ΣC (t).
Ci (t) = a · ΣC (t) (2)
However, a is a ratio (carburization contribution rate) which contributes to the carburization to a to-be-processed product among carbon dissociated by carburization reaction. a is experimentally determined in advance.

When the carbon inflow rate Ci (t) is obtained in this way, the arithmetic processing unit 34 performs processing for obtaining an estimated value of the carburization depth of the product to be processed based on the following equation (3).
y = −b · Ci (t) · x + A (3)
Where x is the depth from the surface of the article to be treated, y is the carbon concentration at the depth x, Ci (t) is the carbon inflow rate, -b is a coefficient for converting the carbon inflow rate into a carbon concentration gradient, and A is the target This is the surface carbon concentration during carburization of the treated product.

The calculation of the carburization depth based on the above equation (3) will be described in more detail. FIG. 2 is a diagram showing the relationship between the depth of the article to be treated and the carbon concentration during the carburizing process, where the x-axis is the depth from the surface of the article to be treated, and the y-axis is the carbon concentration. L1 in the figure is a straight line expressed by equation (3), y ₀ in the figure are the base material carbon concentration of the treated product. As shown in FIG. 2, the carbon concentration of the article to be processed decreases as the depth from the surface increases starting from the surface carbon concentration A (carbon concentration at x = 0), and the base material carbon concentration y at a certain depth. Matches ₀ . The depth at which the the base material carbon content y ₀ is a carburized depth to be determined. Therefore, the carburization depth x _C can be obtained by setting the carbon concentration y in the above formula (3) to the base material carbon concentration y _{0 of the} article to be processed.

Here, according to the saturation value adjustment method, the surface carbon concentration A is said to shift to internal diffusion without further increasing the carbon concentration when the surface of the carburized material reaches the carbon solid solubility limit (Acm). Yes. However, it has been confirmed that the carbon concentration actually increases beyond the carbon solid solubility limit. Therefore, the surface carbon concentration A is Acm or Acm + α.

Thus, the carburization depth can be obtained based on the surface carbon concentration A and the carbon concentration gradient of the article to be processed. Since the surface carbon concentration A is Acm or Acm + α as described above, if the carbon concentration gradient ([−b · Ci (t)] in the above equation (3)) is known, the carburization depth can be obtained. it can. Therefore, a coefficient [−b] to be converted into a carbon concentration gradient for each carbon inflow rate Ci (t) is experimentally determined in advance. Specifically, the carbon inflow speed Ci (t) and the carburization depth at the speed are experimentally acquired as data for each speed. Then, from the slope of the straight line connecting the coordinates (x _C , y ₀ ) at each carburizing depth and the coordinates (0, Acm) at the surface carbon concentration A, and the carbon inflow velocity Ci (t) at that time, for each velocity. [-B] is determined.

Thus, the arithmetic processing unit 34 obtains an estimated value of the carburization depth of the article 1 to be processed from the time change of the hydrogen partial pressure ratio based on the above equations (1) to (3). For this reason, the memory of the arithmetic processing unit 34 stores an arithmetic program for obtaining an estimated value of the carburization depth of the article 1 to be processed from the time change of the hydrogen partial pressure ratio based on the above equations (1) to (3). ing. That is, this calculation program calculates the amount of carbon ΣC (t) dissociated by carburization reaction from the hydrogen partial pressure ratio based on the above equation (1), and the amount of dissociated carbon ΣC based on (2) above. A process for obtaining the carbon inflow rate Ci (t) from (t), a process for obtaining an estimated value of the carburization depth of the workpiece 1 from the carbon inflow rate Ci (t) based on the above (3), Is a program that causes a computer to execute.

According to the vacuum carburizing furnace 10 according to the first embodiment described above, hydrogen with respect to the total pressure in the processing chamber 17 during the carburizing process is performed by the hydrogen sensor 30, the vacuum gauge 32, and the arithmetic processing unit 34 that function as hydrogen partial pressure detecting means. Since the partial pressure ratio is detected, the estimated value of the carburizing depth is obtained by the arithmetic processing unit 34 functioning as arithmetic processing means, and the carburizing depth is displayed by the display 36 or the printer 38 functioning as output means. Based on the carburizing quality management. For this reason, it is not necessary to carry out a sampling test after carburizing treatment as in the prior art, and carburizing quality can be easily managed.

Further, according to the vacuum carburizing furnace 10 according to the first embodiment, when estimating the carburizing depth of the article 1 to be processed based on the carbon inflow rate, a simple calculation formula y = −b · Ci (t) · x + A Therefore, the carburization depth can be calculated easily and accurately.

Next, a second embodiment of the present invention will be described. FIG. 3 is a diagram showing a schematic configuration of the vacuum carburizing furnace 10 according to the second embodiment of the present invention. In the vacuum carburizing furnace 10 according to the present embodiment, a gas flow rate adjusting valve 26 is added to the vacuum carburizing furnace 10 according to the first embodiment described above, and the calculated carburizing depth is calculated by the arithmetic processing unit 34 to a desired carburizing depth. When this is reached, the gas flow rate control valve 26 is controlled so as to stop the supply of the carburizing gas into the processing chamber. A control program for performing such control is stored in the memory of the arithmetic processing unit. As described above, in the second embodiment, when the desired carburizing depth is reached by the gas flow rate adjusting valve 26 and the arithmetic processing unit 34, the supply of the carburizing gas into the processing chamber 17 is stopped. The function as "means" is achieved. Other device configurations are the same as those in the first embodiment described above.

According to the vacuum carburizing furnace 10 according to the second embodiment, when the determined carburizing depth reaches the desired carburizing depth, the supply of the carburizing gas into the processing chamber 17 is stopped. Can be obtained. After the supply of the carburizing gas is stopped, the process shifts to a diffusion process for diffusing the carbon carburized in the article to be processed 1 inside the article to be processed 1, but the diffusion depth can be managed by the processing temperature and the processing time. For this reason, the reproducibility between different operation batches can be improved, and variation in carburizing quality can be reduced to ensure uniformity.

As is clear from the above description, according to the present invention, the carburizing quality can be managed by managing the carburizing depth to the workpiece, the reproducibility can be improved by obtaining the desired carburizing depth, and the carburizing An excellent effect is obtained that the uniformity of quality can be ensured by reducing the variation in quality, and the carburizing quality can be easily managed.

In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.

It is a figure which shows schematic structure of the vacuum carburizing furnace by 1st Embodiment of this invention. It is a figure which shows the relationship between the depth of the to-be-processed goods at the time of a carburizing process, and carbon concentration. It is a figure which shows schematic structure of the vacuum carburizing furnace by 2nd Embodiment of this invention.

Explanation of symbols

1 Processed Product 10 Vacuum Carburizing Furnace 12 Furnace Body 14 Heat Insulating Wall 16 Furnace Wall 17 Processed Chamber 20 Gas Supply Line 22 Gas Exhaust Line 24 Vacuum Pump 26 Gas Flow Control Valve 30 Hydrogen Sensor 32 Vacuum Gauge 34 Processing Unit 36 Display 38 Printer 40 Keyboard 42 Mouse

Claims (4)

A quality control method for vacuum carburizing in which carburizing treatment is performed on the article to be treated in a reduced pressure and heated state while supplying a carburizing gas composed of hydrocarbons into a processing chamber in which the article to be treated is accommodated.
Detects the hydrogen partial pressure ratio with respect to the total pressure in the processing chamber during carburizing,
By utilizing the correlation between the carbon flux rate into time ratio water oxygen partial change and a workpiece, the carbon flux rate based from formulas (1) and (2) the time change of the pressure ratio water oxygen partial Seeking
A quality control method for vacuum carburizing, characterized in that, when the carburization depth of a product to be treated is determined based on the carbon inflow rate, the carburization depth is determined based on Equation (3) .
ΣC (t) = 2 · N · K (t) /22.4L/mol (1)
Ci (t) = a · ΣC (t) (2)
y = −b · Ci (t) · x + A (3)
N: Acetylene supply amount (L / min)
K (t): Hydrogen partial pressure ratio
a: Ratio of carbon dissociated by carburization reaction that contributes to carburization of the product to be treated (carburization contribution rate)
x: Depth from the surface of the workpiece
y: carbon concentration at depth x
Ci (t): Carbon inflow rate
A: Surface carbon concentration during carburization of the product to be treated
-B: The carbon inflow rate Ci (t) and the carburization depth at that rate are experimentally acquired as data for each speed, and the coordinates (x _C , y ₀ ) and the surface carbon concentration A at each carburization depth are obtained . Coefficient for converting the carbon inflow rate obtained from the slope of the straight line connecting coordinates (0, A) and the carbon inflow rate Ci (t) at that time into a carbon concentration gradient A furnace body having a processing chamber for containing the product to be processed and carburizing the product to be processed in a reduced pressure and heated state, a carburizing gas supply means for supplying a carburizing gas composed of hydrocarbons to the processing chamber, In a vacuum carburizing furnace provided with a gas exhaust means for exhausting gas and maintaining a predetermined reduced pressure state,
A hydrogen partial pressure ratio detecting means for detecting a hydrogen partial pressure ratio with respect to the total pressure in the processing chamber at the time of carburizing;
By utilizing the correlation between the change in the hydrogen partial pressure ratio over time and the carbon inflow rate into the article to be processed, the equation (1) and the expression (2) are applied to the article to be processed based on the change in the hydrogen partial pressure ratio over time. An arithmetic processing means for obtaining a carbon inflow rate of the material, and performing a process for obtaining an estimated value of a carburization depth of the article to be processed based on the carbon inflow rate;
Output means for displaying the carburized depth of the workpiece obtained by the arithmetic processing means,
The said vacuum processing means calculates | requires carburizing depth based on Formula (3), The vacuum carburizing furnace characterized by the above-mentioned.
ΣC (t) = 2 · N · K (t) /22.4L/mol (1)
Ci (t) = a · ΣC (t) (2)
y = −b · Ci (t) · x + A (3)
N: Acetylene supply amount (L / min)
K (t): Hydrogen partial pressure ratio
a: Ratio of carbon dissociated by carburization reaction that contributes to carburization of the product to be treated (carburization contribution rate)
x: Depth from the surface of the workpiece
y: carbon concentration at depth x
Ci (t): Carbon inflow rate
A: Surface carbon concentration during carburization of the product to be treated
-B: Carbon inflow rate Ci (t) and carburization depth at that rate are experimentally acquired as data for each speed, and the coordinates (x _C , y ₀ ) and surface carbon concentration A at each carburization depth are obtained . Coefficient for converting the carbon inflow rate obtained from the slope of the straight line connecting coordinates (0, A) and the carbon inflow rate Ci (t) at that time into a carbon concentration gradient A quality control device for vacuum carburizing in a vacuum carburizing furnace that performs carburizing treatment of the article to be treated in a reduced pressure and heated state while supplying a carburizing gas comprising hydrocarbon into a processing chamber in which the article to be treated is accommodated,
Based on the hydrogen partial pressure ratio with respect to the total pressure in the processing chamber detected by the hydrogen partial pressure ratio detection means during the carburizing process, use the correlation between the time variation of the hydrogen partial pressure ratio and the carbon inflow rate into the workpiece. Thus, when the carbon inflow rate is obtained based on the time variation of the hydrogen partial pressure ratio from the equations (1) and (2), and the carburization depth of the article to be treated is obtained based on the carbon inflow rate, the equation (3) The quality control device for vacuum carburizing is characterized by comprising arithmetic processing means for determining the carburizing depth based on the above .
ΣC (t) = 2 · N · K (t) /22.4L/mol (1)
Ci (t) = a · ΣC (t) (2)
y = −b · Ci (t) · x + A (3)
N: Acetylene supply amount (L / min)
K (t): Hydrogen partial pressure ratio
a: Ratio of carbon dissociated by carburization reaction that contributes to carburization of the product to be treated (carburization contribution rate)
x: Depth from the surface of the workpiece
y: carbon concentration at depth x
Ci (t): Carbon inflow rate
A: Surface carbon concentration during carburization of the product to be treated
-B: Carbon inflow rate Ci (t) and carburization depth at that rate are experimentally acquired as data for each speed, and the coordinates (x _C , y ₀ ) and surface carbon concentration A at each carburization depth are obtained . Coefficient for converting the carbon inflow rate obtained from the slope of the straight line connecting coordinates (0, A) and the carbon inflow rate Ci (t) at that time into a carbon concentration gradient A quality control program for vacuum carburizing in a computer that controls a vacuum carburizing furnace that performs carburizing treatment of the article to be treated in a reduced pressure and heated state while supplying a carburizing gas consisting of hydrocarbons into the processing chamber in which the article to be treated is accommodated. There,
Based on the hydrogen partial pressure ratio with respect to the total pressure in the processing chamber detected by the hydrogen partial pressure ratio detection means during the carburizing process, use the correlation between the time variation of the hydrogen partial pressure ratio and the carbon inflow rate into the workpiece. Thus, when the carbon inflow rate is obtained based on the time variation of the hydrogen partial pressure ratio from the equations (1) and (2), and the carburization depth of the article to be treated is obtained based on the carbon inflow rate, the equation (3) ) To cause the computer to function as a means for obtaining the carburization depth based on the above).
ΣC (t) = 2 · N · K (t) /22.4L/mol (1)
Ci (t) = a · ΣC (t) (2)
y = −b · Ci (t) · x + A (3)
N: Acetylene supply amount (L / min)
K (t): Hydrogen partial pressure ratio
a: Ratio of carbon dissociated by carburization reaction that contributes to carburization of the product to be treated (carburization contribution rate)
x: Depth from the surface of the workpiece
y: carbon concentration at depth x
Ci (t): Carbon inflow rate
A: Surface carbon concentration during carburization of the product to be treated
-B: The carbon inflow velocity Ci (t) and the carburization depth at the velocity are experimentally acquired as data for each velocity, and the coordinates (x _C , Y ₀ ) And the coordinate (0, A) of the surface carbon concentration A and the coefficient for converting the carbon inflow rate obtained from the carbon inflow rate Ci (t) at that time into a carbon concentration gradient

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