JPH04198462A - Carburizing device - Google Patents

Abstract

PURPOSE:To contrive reduction of carburization time and to discriminate accurate termination time of carburization by detecting temp. in the carburizing furnace at the time of carburization and carbon potential of carburizing atmosphere and measur ing carbon content in steel surface and effective carburized depth respectively. CONSTITUTION:The treating tray 14 mounted with treating articles 13 such as low carbon steel is provided in carburizing furnace 11 to introduce gaseous RX incorporating carbon monoxide and to heat it with heating element 15, and carburization of treating articles 13 is carried out. In this time, carbon potential and temp. in the furnace 11 are measured continuously by using a carbon sensor 16 and a temp. sensor 17, and this signal is sent to the central processing equipment CPU 18. CPU 18 calculates surface carbon content Cc of the treating articles 13 and available carburized depth Dc from inputted data and compares the previously set desired value of the surface carbon content CA with the desired available depth of carburization DA respectively When the results arrive to Cc>=CA and also Dc>=DA, the carburization is recognized to be completed. By this means, carburization treatment is accurately controlled in order to obtain desired surface carbon content and available carburized depth respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a carburizing device, and more particularly to a carburizing device that can accurately determine the end time of carburizing and shorten carburizing time.

[Conventional technology]

The carburizing method is a method in which low carbon steel, etc. is heated in a carburizing atmosphere containing C○ to infiltrate carbon from the surface of the steel and diffuse carbon into the steel. Depending on the state of the carburizing atmosphere, solid carburizing method , divided into liquid carburizing method or gas carburizing method.

The gas carburizing method uses a mixed gas (end gas or RX
gas, and hereinafter referred to as RX gas. ) in which the treated product is carburized.

The process mainly consists of a carburizing period in which a large amount of carbon infiltrates from the surface of the treated product, and a diffusion phase in which carbon penetrates deeply into the interior of the treated product, and quenching is usually performed as a step after the carburizing process. In the treatment conditions in this carburizing process, for example, as shown in FIG. Carbon potential (c, p,) indicating the carburizing ability of gas is set for each period. Normally, the carbon potential is 1.
1 to 1.4 (C of carbon steel in equilibrium with C atmosphere in carburizing furnace)
%), and the diffuser is set to a predetermined value within the range of 0.8 to 0.9 (C% of carbon steel in which the C atmosphere in the carburizing furnace is balanced).

[Problems to be Solved by the Invention] The surface hardness and hardening depth of a treated product after carburizing and quenching are mainly determined by the amount of carbon on the surface of the treated product and the effective carburization depth.

In the conventional carburizing process, processing conditions were determined from the carbon content of the treated product before carburizing, the target surface carbon content after carburizing, and the effective carburizing depth. It is assumed that the carbon potential and temperature are constant, ignoring the gaps, carbon potential fluctuations and temperature fluctuations during treatment, and the carburizing period and diffuser processing time are assumed to be constant. was set to a long time.

However, in reality, the temperature and carbon potential fluctuate in real time, and in particular, the actual fluctuations in carbon potential tend to be as shown in FIG.

As can be seen from FIG. 5, the carbon potential constantly repeats small fluctuations during both the carburizing stage and the diffuser, and large fluctuations occur during the transition period from the carburizing stage to the diffuser. However, such large fluctuations are not taken into account when setting the carburizing conditions, and therefore it is inevitable that differences will occur between the actual measured values and the target values for the surface carbon content and effective depth of the treated product after carburizing. The problem was that there was no. Moreover, as mentioned above, the processing time was set to be long, so
As the carburizing time becomes longer, the carburizing tends to be carried out excessively, resulting in additional costs, which is another problem.

Therefore, an object of the present invention is to provide a carburizing device that can achieve desired carburizing in a shorter time than the conventional technology by accurately controlling the target surface carbon content and effective carburizing depth. It is.

[Means to solve the problem]

In order to achieve the above-mentioned object, the present invention monitors the temperature and carbon potential fluctuations in the carburizing furnace during the carburizing process, and calculates the carburizing period and diffuser phenomena by computer based on the monitored data. At the same time, the carbon distribution, surface carbon content, and effective carburizing depth of the treated product were calculated in real time and compared with the above data to determine whether carburization should continue or end. Therefore, the device of the present invention is a carburizing device that heats steel in a carburizing furnace in a carburizing atmosphere to permeate and diffuse carbon from the surface of the steel, thereby increasing the amount of carbon in the steel. ) a temperature sensor that detects the temperature inside the carburizing furnace, b) a carbon sensor that detects the carbon potential of the carburizing atmosphere, and -ζ ~ C) the temperature inside the carburizing furnace detected by the temperature sensor and the temperature detected by the carbon sensor The surface carbon content CC and effective carburizing depth DC of the steel during carburizing are calculated based on the carbon potential, and the calculated surface carbon NCC and effective carburizing depth DC are calculated based on the preset target surface carbon content CA and target. The gist of the present invention is a carburizing apparatus characterized by comprising an arithmetic processing means that compares each with an effective carburizing depth DA and determines that carburizing is completed when co≧CA and DC≧DA.

[For production]

RX gas or the like is introduced into the carburizing furnace of the carburizing apparatus and heated to maintain a carburizing atmosphere, and the processed product placed in the carburizing furnace is carburized. The carbon potential in the carburizing furnace is measured by a carbon sensor, and the temperature is measured by a temperature sensor, and each measured value is sent to the arithmetic processing means from time to time.

As carburization progresses, carbon infiltrates from the surface of the treated product and diffuses into the interior, but the greater the carbon potential of the carburizing atmosphere, the more carbon infiltrates and the amount of carbon on the surface of the treated product decreases. As the temperature increases, the rate of penetration and diffusion increases, and carburization progresses deep into the interior of the treated product. The arithmetic processing means calculates the carbon distribution of the treated product from the measured values of carbon potential and temperature sent from each of the sensors over time, and sets the target surface carbon content CC and effective carburization depth DC. Compare with carbon content CA and effective carburizing depth DA.

If co<CA or DC<DA, carburizing is continued, and when co≧CA and DC≧DA, it is determined that the carburizing has been achieved as intended, and the carburizing is terminated. This prevents excessive time from being spent on carburization and diffusion.

〔Effect of the invention〕

According to the carburizing apparatus according to the present invention, the progress state of carburization can be accurately grasped by attaching a carbon sensor and a temperature sensor and calculating the carbon distribution of the processed product over time based on the measured values thereof. I can do it. That is, even if the progress of carburization changes due to fluctuations in carbon potential and temperature, a transition in carbon distribution corresponding to the change can be obtained by calculation processing. Conversely, by controlling the carbon potential or temperature while monitoring the progress of carburization, it is also possible to induce the carbon distribution after carburization into an arbitrary form depending on the purpose.

In addition, since the continuation and completion of carburizing can be accurately determined, there is no need to set a long carburizing time as in the past.
It can also prevent excessive carburization. the result,
The cost of carburizing can also be minimized, and product properties can be made uniform and productivity can be improved.

〔Example〕

Next, one embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the carburizing apparatus of the present invention has a carburizing furnace 11 in which carburizing is performed and a control section 12 that controls carburizing. Processed products 13 such as low carbon steel are loaded onto a processing tray 14 and transported to a carburizing furnace 11.

Then, an RX gas containing CO is introduced into the carburizing furnace 11 and is heated by the heating elements 1 to 15 to maintain a carburizing atmosphere. Furthermore, the carbon potential is adjusted by appropriately introducing into this carburizing atmosphere a carbon enriched gas such as butane which increases the carbon potential, and air which lowers the carbon potential.

The control unit 12 includes a carbon sensor 16 and a temperature sensor 1.
7 and a central processing unit CPU18.

These carbon sensor 16 and temperature sensor 17 continuously measure the carbon potential and temperature within carburizing furnace 11, respectively, and send the measured values as signals to central processing unit CPU18. The central processing unit CPU 18 calculates the carbon diffusion phenomenon of the processed product, that is, the carbon distribution, at regular intervals from the sent measurement data. This carbon distribution is obtained by analyzing a diffusion equation (formula 0) known as Fick's second law, which takes into account the diffusion and movement of carbon in steel.

C: Concentration of carphone D: Diffusion coefficient X: Direction of temperature gradient Analysis methods include the finite element method, the difference method, etc.
In the case of the interior point finite difference method, analysis is performed using the following formula (■).

1−−−−−−−−−−−−−−−−−−=−■c'j
+at:H'le□□yu1. oh. , Oh, engineering. . C'
j: Bji? Il t+4:oi:t6i element,). 9AVj ・Volume Cjl of i element ・Time of adjacent element j of i element 16. C%Sfj ・Contact area D between j element and j element
・Diffusion coefficient of C in steel (at carburizing diffusion temperature) l-
・Distance between i element and j element j C, P, , surface carbon potential R ・Surface mass transfer resistance The carbon distribution of the treated product obtained by such calculations draws a curve as shown in Figure 2, for example. .

Point A in this figure indicates the amount of surface carbon of the treated product.

Further, the distance at the minimum amount of carbon (0.4% in the example shown in the drawing) that can exhibit the desired effect of carburization is defined as the effective carburization depth, and is indicated by point B in the drawing.

The target surface carbon content and effective carburizing depth are input into the central processing unit CPU 18 in advance.

After the carburization progresses, when the actual surface carbon content and effective carburization depth are determined from the carbon potential and temperature measurement data as described above, the central processing unit CPU 18 further manually calculates the surface carbon content and effective carburization depth in advance. Compare each target value. Then, when the actual value matches the target value or the actual value exceeds the target value, it is determined that carburization is completed. Based on this judgment, a processing I-ray transport signal is immediately sent to the carburizing furnace, and the processed product is transferred to the next process, the quenching process.

Next, the operation of the control section 12 will be explained based on the flowchart shown in FIG.

First, in step 31, the initial carbon content CC (%) before carburizing, the target surface carbon content CA (%) after carburizing, and the effective carburizing depth DA (mm) of the product to be carburized are input. Then, a carburizing start signal is sent to start carburizing. Simultaneously with the start of carburizing, a timer is started in step 32 and the measurement interval Δt is input. Subsequently, in step 33, it is determined whether the time t+ΔL has elapsed, and after the time has also elapsed, the process proceeds to step 34. In step 34, a diffusion program is executed based on the carbon potentials C, P and temperature measurement data sent in advance from the carbon sensor 16 and temperature sensor 17, respectively, and the initial carbon NCo before carburization inputted in advance. In this program, the above formula ■,
Calculate the amount of surface carbon after carburization of the treated product CC (
%) and the effective carburization depth D, (mm). In step 35, this surface carbon amount CC is compared with the target surface carbon amount CA input in advance, and CC≧C
If A, the process proceeds to step 36, and if CC<CA, the process returns to step 33 to continue carburizing. Step 36: Similar to step 35, the effective carburizing depth obtained in step 34 is determined. and the target effective carburizing depth DA entered in advance.
I'm comparing it with. If ≧DA, proceed to step 37,
, <DA, the process returns to step 33 to continue carburizing.

In this way, CC≧CA. If ≧D, it is determined that carburizing is completed, and a transition signal to the next process, that is, a quenching process, is sent to the processing tray 14 in step 37. Quenching hardens the carburized area of the treated product,
A steel material with a hard surface and a tenacious interior can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing one embodiment of the present invention, Fig. 2 is a graph showing the carbon distribution after carburizing the treated product, Fig. 3 is a flowchart for explaining carburization control, Fig. 4 The figure is a graph for explaining the temperature conditions in the carburizing process, and FIG. 5 is a graph for explaining the fluctuation of carbon potential in the carburizing process. 11...Carburizing furnace 12...Control unit 13...Processed product 14...Processing tray 15...Heat element 16...Carbon sensor 17...Temperature sensor 18...Central processing unit

Claims (1)

[Scope of Claims] A carburizing device that heats steel in a carburizing furnace in a carburizing atmosphere to permeate and diffuse carbon from the surface of the steel to increase the amount of carbon in the steel, comprising: a) carburizing; a) a temperature sensor that detects the temperature inside the furnace; b) a carbon sensor that detects the carbon potential of the carburizing atmosphere; and c) based on the temperature inside the carburizing furnace detected by the temperature sensor and the carbon potential detected by the carbon sensor. Calculate the surface carbon amount C_C and effective carburizing depth D_C of the steel during carburizing, and calculate the calculated surface carbon amount C
_C and effective carburizing depth D_C are compared with a preset target surface carbon amount C_A and target effective carburizing depth D_A, respectively, and when C_C≧C_A and D_C≧D_A, a calculation processing means determines that carburization is completed. A carburizing device characterized by comprising: