Optimized control system for nitriding process gas and control method thereof

Abstract

The invention belongs to the technical field of nitriding furnace process control, and particularly relates to an optimal control system for nitriding process gas and a control method thereof. The optimization control system for the nitriding process gas comprises a control unit, a furnace pressure detection unit, a flow meter and an exhaust valve, the control unit is respectively connected with the furnace pressure detection unit, the flow meter and the exhaust valve; the furnace pressure detection unit is connected with the nitriding furnace; the flow meter is connected with a nitriding process gas inlet of the nitriding furnace; and the exhaust valve is connected with a waste gas outlet of the nitriding furnace. According to the optimal control system for the nitriding process gas, the control unit is connected with the furnace pressure detection unit, the flow meter and the exhaust valve, so that the furnace pressure in the nitriding furnace is maintained within the preset range, and waste of the nitriding process gas is reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of process control of nitriding furnace, and particularly relates to an optimized control system of nitriding process gas and a control method thereof. BACKGROUND

[0002] The main process raw material of gas nitriding is ammonia, and process raw materials also include carbon dioxide, methanol, kerosene, etc. if soft nitriding process is used. The exhaust gas emission of these process gases will cause great pollution to the environment, increase the concentration of PM2.5, and increase the nitrogen load of soil and water body due to ammonia deposition, resulting in ecological damage. The exhaust gas produces irritating odor, and high concentration will cause harm to the respiratory system and eyes of human body.

[0003] In the traditional nitriding process, constant furnace pressure control is used in the process, and the exhaust gas pipeline valve is in a constant open state under the action of the furnace pressure. The use amount of process gas is also in a relatively constant amount in each stage of the nitriding process, so that the gas exchange rate of the nitriding furnace is high, the use efficiency of the process gas is low, and the exhaust gas emission is large. SUMMARY

[0004] To solve the above problems, the application provides an optimized control system of nitriding process gas and a control method thereof. At least one aspect of the above technical problems is solved.

[0005] The application is realized by the following technical solutions:

[0006] In a first aspect, the application provides an optimized control system of nitriding process gas, which comprises a control unit, a furnace pressure detection unit, a flow meter and an exhaust valve.

[0007] The control unit is connected with the furnace pressure detection unit, the flow meter and the exhaust valve respectively.

[0008] The furnace pressure detection unit is connected with the nitriding furnace.

[0009] The flow meter is connected with the nitriding process gas inlet of the nitriding furnace.

[0010] The exhaust valve is connected with the exhaust gas outlet of the nitriding furnace.

[0011] In some possible implementation manners, the control unit comprises a furnace pressure control module and a flow control module.

[0012] The furnace pressure control module is connected with the furnace pressure detection unit, the flow control module and the exhaust valve respectively.

[0013] The flow control module is connected with the flow meter.

[0014] In some possible implementation manners, the furnace pressure detection unit comprises a pressure sensor.

[0015] In some possible implementation manners, the optimization control system further comprises a Kn value detection unit.

[0016] The control unit further comprises a Kn value control module.

[0017] The Kn value detection unit is connected with the nitriding furnace and the Kn value control module respectively.

[0018] The Kn value control module is connected with the flow control module.

[0019] In some possible implementation manners, the Kn value detection unit comprises a hydrogen probe and a nitrogen potential controller.

[0020] The hydrogen probe and the nitrogen potential controller are connected.

[0021] The nitrogen potential controller is connected with the control unit.

[0022] In the second aspect, the present application provides an optimization control method of an optimization control system of a nitriding process gas, comprising the following steps:

[0023] In the nitriding stage, the control unit controls the flow of the nitriding process gas and the on-off of the exhaust valve.

[0024] In some possible implementation manners, the control unit controls the flow of the nitriding process gas and the on-off of the exhaust valve comprises the following steps:

[0025] The control unit receives real-time furnace pressure and controls the flow of the nitriding process gas and the on-off of the exhaust valve according to the real-time furnace pressure.

[0026] In some possible implementation manners, the step of detecting real-time furnace pressure comprises:

[0027] The real-time furnace pressure is detected by using the furnace pressure detection unit.

[0028] In some possible implementation manners, the step of controlling the flow of the nitriding process gas and the on-off of the exhaust valve according to the real-time furnace pressure comprises:

[0029] The control unit compares the real-time furnace pressure with a preset furnace pressure range, and controls the flow of the nitriding process gas and the on-off of the exhaust valve according to the comparison result.

[0030] (1) When the real-time furnace pressure is higher than the upper limit of the preset furnace pressure, the control unit controls the exhaust valve to open the exhaust.

[0031] (2) when the real-time furnace pressure is within the preset furnace pressure range, the control unit controls the exhaust valve to be closed and controls the flow meter to reduce the flow rate of the nitriding process gas or to stop the nitriding process gas from entering;

[0032] (3) when the real-time furnace pressure is lower than the lower limit of the preset furnace pressure, the control unit controls the exhaust valve to be closed and controls the flow meter to increase the flow rate of the nitriding process gas.

[0033] In some possible implementations, a furnace pressure control module in the control unit is used to compare the real-time furnace pressure with the preset furnace pressure range.

[0034] In some possible implementations, the optimized control method further comprises the following steps:

[0035] In the nitriding stage, the control unit controls the proportion of ammonia and ammonia decomposition gas in the nitriding process gas: the control unit controls the flow meter to adjust the proportion of ammonia and ammonia decomposition gas in the nitriding process gas entering the nitriding furnace according to the real-time Kn value and the preset Kn value.

[0036] In some possible implementations, the step of controlling the flow meter to provide the proportion of ammonia and ammonia decomposition gas in the nitriding process gas comprises:

[0037] When the real-time Kn value is not within the preset Kn value range, the Kn value control module feeds back to the flow control module, and the flow control module controls the flow meter to increase or reduce the proportion of ammonia and ammonia decomposition gas entering the nitriding furnace.

[0038] In some possible implementations, the flow control module controls the flow meter to increase or reduce the proportion of ammonia and ammonia decomposition gas entering the nitriding furnace specifically as follows:

[0039] (1) when the real-time Kn value is higher than the upper limit of the preset Kn value, the Kn value control module feeds back to the flow control module, and the flow control module controls the flow meter to reduce the proportion of ammonia and ammonia decomposition gas entering the nitriding furnace;

[0040] (2) when the real-time Kn value is lower than the lower limit of the preset Kn value, the Kn value control module feeds back to the flow control module, and the flow control module controls the flow meter to increase the proportion of ammonia and ammonia decomposition gas entering the nitriding furnace.

[0041] In some possible implementations, the nitriding stage adopts a staged nitriding process, including a first nitriding stage, a second nitriding stage and a third nitriding stage.

[0042] In some possible implementations, the flow rate of the nitriding process gas is: the first nitriding stage > the second nitriding stage > the third nitriding stage. The total flow rate of the process gas is increased or reduced according to the Kn value, and the smaller the Kn value, the smaller the total flow rate of the process gas.

[0043] The nitriding process gas optimization control system and the control method thereof provided by the present application have at least the following beneficial technical effects compared with the prior art:

[0044] (1) The nitriding process gas optimization control system provided by the present application, the control unit is connected with the furnace pressure detection unit, the flow meter and the exhaust valve, so that the furnace pressure in the nitriding furnace is within the preset range, and the waste of the nitriding process gas is reduced.

[0045] (2) The nitriding process gas optimization control method provided by the present application, the control unit is used to control the flow rate of the nitriding process gas and the on-off of the exhaust valve according to the preset furnace pressure, so that the furnace pressure of the nitriding furnace is maintained within the preset range, the gas exchange rate of the nitriding process gas is reduced, the flow rate of the nitriding process gas is dynamically controlled, and finally the total amount of the nitriding process gas is reduced by more than 50% (the amount is 40%-50% of the traditional method). BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the drawings, and other drawings can be obtained by those skilled in the art without creative labor.

[0047] Figure 1 The structure schematic diagram of the nitriding process gas optimization control system in the embodiment of the present application is shown in the figure.

[0048] Figure 2 The structure schematic diagram of the nitriding process gas optimization control system in the embodiment of the present application is shown in the figure.

[0049] Figure 3 The optimization control flowchart of the nitriding process gas in the embodiment 1 of the present application is shown in the figure.

[0050] The figure mark explanation: 1-control unit, 2-furnace pressure detection unit, 3-flow meter, 4-exhaust valve, 5-nitriding furnace, 6-Kn value detection unit.

[0051] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the drawings. DETAILED DESCRIPTION

[0052] In order to make the objects, technical solutions and advantages of the present application clearer, the following describes and explains the present application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. Based on the embodiments provided by the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of the present application.

[0053] Obviously, the following description is only some examples or embodiments of the present application, and for those of ordinary skill in the art, the present application can also be applied to other similar scenarios without creative efforts. In addition, it should be understood that although the efforts made during the development process can be complex and lengthy, for those of ordinary skill in the art related to the disclosed content of the present application, some designs, manufacturing or production changes based on the disclosed technical content of the present application are only routine technical means and should not be understood as insufficient disclosure of the present application.

[0054] However, there will be cases of omitting unnecessary detailed description. For example, there are cases of omitting detailed description of well-known matters, repeated description of actually identical structures. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the following description is provided to enable those skilled in the art to fully understand the present application and is not intended to limit the subject matter recited in the claims.

[0055] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0056] The term "nitriding process gas" refers to ammonia and ammonia decomposition gas.

[0057] The term "ammonia decomposition gas" refers to a mixed gas obtained after ammonia is cracked in a cracking furnace, containing nitrogen and hydrogen cracked from ammonia.

[0058] The term "Kn value" refers to the nitrogen potential Np value in GB / T 18177.

[0059]

Optimized control system of nitriding process gas

[0060] The first aspect of the embodiment of the present application provides an optimized control system of nitriding process gas, as shown in Figure 1 , which comprises a control unit, a furnace pressure detection unit, a flow meter and an exhaust valve. Figure 1 In the figure, 1 is the control unit, 2 is the furnace pressure detection unit, 3 is the flow meter, 4 is the exhaust valve, and 5 is the nitriding furnace.

[0061] The control unit is connected with the furnace pressure detection unit, the flow meter and the exhaust valve respectively;

[0062] The furnace pressure detection unit is connected with the nitriding furnace;

[0063] The flow meter is connected with the nitrogen process gas inlet of the nitriding furnace;

[0064] The exhaust valve is connected with the exhaust gas outlet of the nitriding furnace.

[0065] The optimization control system of the nitrogen process gas provided by the embodiment of the present application, the control unit receives the real-time furnace pressure feedback by the furnace pressure detection unit, compares the preset furnace pressure, controls the flow of the nitrogen process gas and the on-off of the exhaust valve through the control of the flow meter, realizes that the furnace pressure in the nitriding furnace is maintained in the preset range, and reduces the waste of the nitrogen process gas.

[0066] In some embodiments, the control unit comprises:

[0067] The furnace pressure control module and the flow control module;

[0068] The furnace pressure control module is connected with the furnace pressure detection unit, the flow control module and the exhaust valve respectively;

[0069] The flow control module is connected with the flow meter.

[0070] In the above control unit, the furnace pressure control module compares the real-time furnace pressure feedback by the furnace pressure detection unit with the preset furnace pressure, feeds back the comparison result of the furnace pressure to the flow control module, and the flow control module further controls the flow meter to control the flow of the nitrogen process gas into the nitriding furnace; the furnace pressure control module also controls the on-off of the exhaust valve according to the comparison result of the furnace pressure. The furnace pressure control module controls the flow of the nitrogen process gas and the on-off of the exhaust valve, so that the furnace pressure in the nitriding furnace is dynamically maintained in the preset range.

[0071] In some embodiments, the furnace pressure detection unit comprises a pressure sensor. In this case, the pressure sensor detects the furnace pressure in the nitriding furnace in real time and feeds back to the furnace pressure control module.

[0072] In some embodiments, the optimization control system of the nitrogen process gas further comprises a Kn value detection unit; the control unit further comprises a Kn value control module;

[0073] The Kn value detection unit is connected with the nitriding furnace and the Kn value control module respectively;

[0074] The Kn value control module is connected with the flow control module.

[0075] In this case, the Kn value detection unit detects the Kn value in the nitriding furnace in real time and feeds back to the Kn value control module in the control unit, the Kn value control module compares the real-time Kn value with the preset Kn value and feeds back the comparison result to the flow control module, and the flow control module in turn controls the flow meter to adjust the proportion of ammonia and ammonia decomposition gas in the nitriding process gas (into the nitriding furnace).

[0076] In some embodiments, the Kn value detection unit comprises a hydrogen probe and a nitrogen potential controller;

[0077] The hydrogen probe and the nitrogen potential controller are connected;

[0078] The nitrogen potential controller is connected with the control unit.

[0079] In the above Kn value detection unit, the hydrogen probe detects the concentration of hydrogen in the ammonia decomposition gas in the process gas in the nitriding furnace in real time, feeds back to the nitrogen potential controller and calculates the real-time Kn value (ammonia decomposition rate) in the nitriding furnace, and then feeds back the real-time Kn value to the Kn value control module in the control unit.

[0080] In some specific embodiments, an optimized control system for nitriding process gas is provided, as shown in Figure 2 The control unit, the Kn value detection unit, the furnace pressure detection unit, the flow meter and the exhaust valve are connected. Figure 2 In some specific embodiments, an optimized control system for nitriding process gas is provided, as shown in

[0081] The control unit is connected with the Kn value detection unit, the furnace pressure detection unit, the flow meter and the exhaust valve respectively;

[0082] The Kn value detection unit is connected with the nitriding furnace;

[0083] The furnace pressure detection unit is connected with the nitriding furnace;

[0084] The flow meter is connected with the nitriding process gas inlet of the nitriding furnace;

[0085] The exhaust valve is connected with the exhaust gas outlet of the nitriding furnace.

[0086]

Optimized control method for nitriding process gas

[0087] The second aspect of the embodiment of the present application provides an optimized control method for the optimized control system for nitriding process gas as described above, comprising the following steps:

[0088] S10. In the nitriding stage, the control unit controls the flow of the nitriding process gas and the on-off of the exhaust valve.

[0089] The nitrogenation process gas optimization control method provided by the embodiment of the present application controls the flow rate of the nitrogenation process gas and the on-off of the exhaust valve according to the preset furnace pressure, so that the furnace pressure of the nitrogenation furnace is maintained within the preset range, thereby reducing the air exchange rate of the nitrogenation process gas and achieving dynamic control of the flow rate of the nitrogenation process gas. The optimization control method provided by the embodiment of the present application controls the furnace pressure in the nitrogenation furnace, so that the total consumption of the nitrogenation process gas is reduced by more than 50% (the consumption is 40%-50% of that of the conventional method), and the excessive waste of the nitrogenation process gas is reduced.

[0090] In some embodiments, in the step S10, the nitrogenation stage adopts a staged nitrogenation process, including a first nitrogenation stage, a second nitrogenation stage and a third nitrogenation stage.

[0091] In some embodiments, in the step S10, the flow rate of the nitrogenation process gas is: the first nitrogenation stage > the second nitrogenation stage > the third nitrogenation stage.

[0092] In some embodiments, in the step S10, the control unit controls the flow rate of the nitrogenation process gas and the on-off of the exhaust valve, including the following steps:

[0093] S101. The control unit receives the real-time furnace pressure and controls the flow rate of the nitrogenation process gas and the on-off of the exhaust valve according to the real-time furnace pressure.

[0094] In this case, during the nitrogenation stage, the control unit controls the furnace pressure in the nitrogenation furnace and the on-off of the exhaust valve according to the preset furnace pressure range, so that the furnace pressure is in a dynamic and regular change within the preset range; the exhaust valve is in a periodic (pulsed) on and off, that is, the exhaust valve no longer needs to be in a constant on state, thereby reducing the exhaust amount of the nitrogenation process gas (and the consumption of the nitrogenation process gas), and reducing environmental pollution.

[0095] In some embodiments, in the step S101, the step of detecting the real-time furnace pressure includes:

[0096] S1011. The furnace pressure detection unit is used to detect the furnace pressure of the nitrogenation furnace in real time.

[0097] In some embodiments, in the step S101, the step of controlling the flow rate of the nitrogenation process gas and the on-off of the exhaust valve according to the real-time furnace pressure includes:

[0098] S1012. The control unit compares the real-time furnace pressure with the preset furnace pressure range, and controls the flow rate of the nitrogenation process gas and the on-off of the exhaust valve according to the comparison result:

[0099] (1) When the real-time furnace pressure is higher than the upper limit of the preset furnace pressure, the control unit controls the exhaust valve to open the exhaust;

[0100] (2) When the real-time furnace pressure is within the preset furnace pressure range, the control unit controls the exhaust valve to be closed and controls the flow meter to reduce the flow rate of the nitriding process gas or to stop the nitriding process gas from entering;

[0101] (3) When the real-time furnace pressure is lower than the lower limit of the preset furnace pressure, the control unit controls the exhaust valve to be closed and controls the flow meter to increase the flow rate of the nitriding process gas.

[0102] In some embodiments, in the step S1012, the furnace pressure control module in the control unit is used to compare the real-time furnace pressure with the preset furnace pressure range.

[0103] In some embodiments, the optimization control method of the optimization control system of the nitriding process gas further comprises the following steps:

[0104] S20. In the nitriding stage, the control unit controls the ratio of ammonia gas and ammonia decomposition gas in the nitriding process gas.

[0105] In this case, the control unit controls the exhaust valve and the Kn value in a dual manner: in the nitriding stage, within the preset furnace pressure range, the ratio of ammonia gas and ammonia decomposition gas in the nitriding process gas is adjusted to maintain the Kn value in the nitriding furnace within the preset range; when the preset Kn value is low (generally in the third nitriding stage, i.e. the diffusion stage), the ammonia gas flow rate can be reduced to increase the ammonia decomposition rate, so that the flow rate of ammonia decomposition gas can also be reduced accordingly. Under the dual control of the control unit on the exhaust valve and the Kn value, the total flow rate of the nitriding process gas (ammonia gas and ammonia decomposition gas) in the nitriding stage is ultimately reduced.

[0106] In some embodiments, in the step S20, the control unit controls the ratio of ammonia gas and ammonia decomposition gas in the nitriding process gas comprises the following steps:

[0107] S201. The control unit controls the ratio of ammonia gas and ammonia decomposition gas in the nitriding process gas entering the nitriding furnace according to the real-time Kn value and the preset Kn value.

[0108] In some embodiments, in the step S201, the detection of the real-time Kn value comprises the step of: the Kn potential control instrument calculates the real-time Kn value according to the hydrogen concentration detected by the hydrogen probe.

[0109] In some embodiments, in the step S201, the step of controlling the flow meter to provide the ratio of ammonia gas and ammonia decomposition gas in the nitriding process gas comprises:

[0110] S2011. When the real-time Kn value is not within the preset Kn value range, the Kn value control module feeds back to the flow control module, and the flow control module controls the flow meter to adjust the ratio of ammonia gas and ammonia decomposition gas in the nitriding process gas entering the nitriding furnace.

[0111] In some embodiments, in the step S2011 above, the flow control module controls the flow meter to adjust the proportion of ammonia gas and ammonia decomposition gas in the nitriding process gas entering the nitriding furnace, specifically:

[0112] (1) When the real-time Kn value is higher than the preset upper limit of Kn value, the Kn value control module feeds back to the flow control module, and the flow control module controls the flow meter to reduce the proportion of ammonia gas and ammonia decomposition gas entering the nitriding furnace.

[0113] (2) When the real-time Kn value is lower than the preset lower limit of Kn value, the Kn value control module feeds back to the flow control module, and the flow control module controls the flow meter to increase the proportion of ammonia gas and ammonia decomposition gas entering the nitriding furnace.

[0114] The following will be further described in combination with specific embodiments.

[0115] For convenience of description, in the following examples and comparative examples, the steel material 42CrMoA is used for nitriding, and the nitriding process requirements are: the layer depth requirement of 42CrMoA nitriding is ≥0.30mm, and the nitriding hardness requirement is 580HV-750HV.

[0116] In the following examples and comparative examples, the effective heating area of the nitriding furnace is Φ2.5m×2m.

[0117] In the following examples and comparative examples, a hierarchical nitriding process is used, the temperature of the first nitriding stage is 500℃, the temperature of the second nitriding stage is 510℃, and the temperature of the third nitriding stage is 510℃.

[0118] Figure 3 In the following examples and comparative examples, the nitrogen gas purging and temperature rising before the nitriding stage and the cooling after the nitriding stage are conventional operations in the art, and are only an example of the embodiments of the present application.

[0119] Example 1

[0120] Example 1 provides an optimization control system for nitriding process gas, which is composed of a control unit, a pressure sensor, a flow meter and an exhaust valve.

[0121] The control unit is connected with the pressure sensor, the flow meter and the exhaust valve respectively.

[0122] The pressure sensor is connected with the nitriding furnace.

[0123] The flow meter is connected with the nitriding process gas inlet of the nitriding furnace.

[0124] The exhaust valve is connected with the exhaust gas outlet of the nitriding furnace.

[0125] Among them, the control unit is composed of a furnace pressure control module and a flow control module.

[0126] The furnace pressure control module is connected with the pressure sensor, the flow control module and the exhaust valve respectively.

[0127] The flow control module is connected with the flow meter.

[0128] The embodiment provides an optimization control method of the optimization control system of the nitriding process gas in the embodiment, and the steps are as follows:

[0129] E1. The preset furnace pressure range is 10mbar-20mbar;

[0130] The preset Kn value is that the Kn value of the first nitriding stage is 6±0.5, the Kn value of the second nitriding stage is 2±0.2, and the Kn value of the third nitriding stage is 1±0.1.

[0131] E2. The control unit controls the real-time furnace pressure: the pressure sensor detects the real-time furnace pressure and feeds back to the furnace pressure control module in the control unit:

[0132] When the real-time furnace pressure is higher than 20mbar, the furnace pressure control module automatically controls the exhaust valve to open the exhaust;

[0133] When the real-time furnace pressure is about 15mbar, the furnace pressure control module automatically controls the exhaust valve to stop the exhaust;

[0134] When the real-time furnace pressure is lower than 10mbar, the furnace pressure control module feeds back to the flow control module, and the flow control module automatically controls the flow meter to input the process gas into the nitriding furnace;

[0135] The furnace pressure control module, the flow control module and the exhaust valve cooperate, so that the furnace pressure in the nitriding furnace is dynamically maintained at 10mbar-20mbar, in the preset furnace pressure range, the lower the real-time furnace pressure, the greater the process gas flow, and the higher the real-time furnace pressure, the smaller the process gas flow.

[0136] Embodiment 2

[0137] Embodiment 2 provides an optimization control system of a nitriding process gas, and the structure is basically same as that of embodiment 1, except that the optimization control system is further provided with a Kn value detection unit.

[0138] The control unit is further provided with a Kn value control module.

[0139] The Kn value detection unit is connected with the nitriding furnace and the Kn value control module respectively.

[0140] The Kn value detection unit is composed of a hydrogen probe and a nitrogen potential control instrument.

[0141] The hydrogen probe and the nitrogen potential control instrument are connected.

[0142] The nitrogen potential control instrument is connected with the control unit.

[0143] The embodiment also provides an optimization control method of the optimization control system of the nitriding process gas of the embodiment, which has the same steps as those of the embodiment 1, except that the control unit further controls the real-time Kn value.

[0144] The step of controlling the real-time Kn value by the control unit is as follows: as shown in the figure, the hydrogen probe detects the hydrogen concentration in the nitriding furnace in real time, the Kn value is calculated by the nitrogen potential controller according to the hydrogen concentration, and is fed back to the Kn value control module, which compares the real-time Kn value with the preset Kn value: Figure 3

[0145] (1) In the first nitriding stage, when the real-time Kn value is not in 6±0.5, the Kn value control module feeds back to the flow control module to control the flow meter to adjust the ratio of ammonia gas and ammonia decomposition gas in the process gas, so as to dynamically maintain it in 6±0.5. Among them, the ratio of ammonia gas and ammonia decomposition gas is about 3.6 on average. Process gas consumption: ammonia gas flow is about 3.6m 3 / h, and the consumption is about 36m 3 ; ammonia decomposition gas flow is about 1.0m 3 / h, and the consumption is about 10m 3 .

[0146] (2) In the second nitriding stage, when the real-time Kn value is not in 2±0.2, the Kn value control module feeds back to the flow control module to control the flow meter to adjust the ratio of ammonia gas and ammonia decomposition gas in the process gas, so as to dynamically maintain it in 2±0.2. Among them, the ratio of ammonia gas and ammonia decomposition gas is about 2.0 on average. Process gas consumption: ammonia gas flow is about 2.2m 3 / h, and the consumption is about 33m 3 ; ammonia decomposition gas flow is about 1.1m 3 / h, and the consumption is about 16.5m 3 .

[0147] (3) In the third nitriding stage, when the real-time Kn value is not in 1±0.1, the Kn value control module feeds back to the flow control module to control the flow meter to adjust the ratio of ammonia gas and ammonia decomposition gas in the process gas, so as to dynamically maintain it in 1±0.1. Among them, the ratio of ammonia gas and ammonia decomposition gas is about 1.2 on average. Process gas consumption: ammonia gas flow is about 1.5m 3 / h, and the consumption is about 30m 3 ; ammonia decomposition gas flow is about 1.25m 3 / h, and the consumption is about 25m 3 .

[0148] ​The control unit automatically adjusts the process gas flow according to the Kn value of each nitriding stage. The larger the Kn value, the larger the process gas flow. The smaller the Kn value, the smaller the process gas flow. In this way, the second and third nitriding stages belong to the nitriding diffusion stage, and the Kn value is smaller, and the process gas consumption is also smaller than the first stage (nitriding strong penetration stage).

[0149] Comparative Example 1

[0150] Comparative Example 1 provides a control system for nitriding process gas, which is composed of a flow control module, a Kn value control module, a Kn value detection unit and a flow meter;

[0151] The Kn value control module is connected with the Kn value detection unit and the flow control module respectively;

[0152] The flow control module is connected with the flow meter.

[0153] The Kn value detection unit is composed of a hydrogen probe and a nitrogen potential controller;

[0154] The hydrogen probe and the nitrogen potential controller are connected;

[0155] The nitrogen potential controller is connected with the Kn value control module.

[0156] The control method of the control system for nitriding process gas of the comparative example is provided, and the steps are as follows:

[0157] Under the condition of constant furnace pressure and open exhaust valve, the Kn value is controlled as follows: the total flow of process gas ammonia and ammonia decomposition gas is relatively constant in each stage of nitriding:

[0158] D1. The preset furnace pressure is 15 mbar, the preset Kn value of the first nitriding stage is 6±0.5, the preset Kn value of the second nitriding stage is 2±0.2, and the Kn value of the third nitriding stage is 1±0.1.

[0159] D2. In the first nitriding stage, the Kn value detection unit monitors the real-time Kn value in the nitriding furnace in real time and feeds back to the flow control module. When the Kn value is not 6±0.5, the flow control module controls the flow meter to adjust the proportion of ammonia and ammonia decomposition gas in the process gas, so that it is dynamically maintained at 6±0.5. The second and third nitriding stages are controlled in the same way.

[0160] Wherein,

[0161] In the first nitriding stage, the proportion of ammonia and ammonia decomposition gas is about 4.0. The process gas consumption: the average ammonia flow is about 5.8 m 3 / h, the consumption is about 58 m 3 ; The average ammonia decomposition rate flow is about 1.5 m 3 / h, the consumption is about 10 m3 .

[0162] In the second nitriding stage, the ratio of ammonia gas to ammonia decomposition gas is about 1.4. The process gas consumption is: the ammonia gas flow is about 4.0 m 3 / h, and the consumption is about 60 m 3 ; the ammonia decomposition rate flow is about 2.9 m 3 / h, and the consumption is about 43.5 m 3 .

[0163] In the third nitriding stage, the ratio of ammonia gas to ammonia decomposition gas is about 1.0. The process gas consumption is: the ammonia gas flow is about 3.6 m 3 / h, and the consumption is about 72 m 3 ; the ammonia decomposition gas flow is about 3.6 m 3 / h, and the consumption is about 72 m 3 .

[0164] In order to verify the progressiveness of the optimization control system of the nitriding process gas and the control method thereof provided by the embodiment of the present application, the ammonia decomposition rate, the penetration depth, the surface hardness and the total consumption of the process gas in the nitriding stage are detected in the example 2 and the comparative example 1, and the results are shown in Table 1.

[0165] Table 1

[0166]

[0167] From the above table and the accompanying drawings, at least the following conclusions can be drawn:

[0168] (1) The optimization control method provided by the embodiment of the present application controls the on-off of the exhaust valve periodically (pulsed) by dynamically controlling the furnace pressure of the nitriding furnace. The optimization control method provided by the embodiment links the process gas flow with the furnace pressure, and the process gas flow is simultaneously associated with the control of the Kn value (ammonia decomposition rate). When the Kn value is reduced (in the third nitriding stage), the ammonia gas flow is reduced, thereby increasing the ammonia decomposition rate in the nitriding furnace, and further reducing the ammonia decomposition gas flow, so that the process gas flow forms a stable and regular variable control.

[0169] (2) Under the same nitriding stage conditions, the total consumption of the process gas used in the example 2 is as low as 150.5 m 3 , which is much lower than that of the comparative example 1 (315.5 m 3 ) using the traditional nitriding process control method, and the total consumption of the process gas is 47.7% of that of the comparative example. It can be seen that the optimization control method provided by the embodiment of the present application greatly reduces the consumption of the nitriding process gas and reduces unnecessary waste.

[0170] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exerting the same effects within the scope of the technical solution of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications that can be thought of by those skilled in the art to the embodiments or by combining part of the constituent elements of the embodiments are also included in the scope of the present application without departing from the gist of the present application.

Claims

1. An optimized control system for nitriding process gases, characterized in that, Includes control unit, furnace pressure detection unit, flow meter and exhaust valve; The control unit is connected to the furnace pressure detection unit, the flow meter, and the exhaust valve, respectively. The furnace pressure detection unit is connected to the nitriding furnace; The flow meter is connected to the nitriding process gas inlet of the nitriding furnace; The exhaust valve is connected to the exhaust gas outlet of the nitriding furnace.

2. The optimized control system for nitriding process gas according to claim 1, characterized in that, The control unit includes: a furnace pressure control module and a flow control module; The furnace pressure control module is connected to the furnace pressure detection unit, the flow control module, and the exhaust valve, respectively. The flow control module is connected to the flow meter.

3. The optimized control system for nitriding process gases according to claim 1 or 2, characterized in that, The furnace pressure detection unit includes a pressure sensor.

4. The optimized control system for nitriding process gas according to any one of claims 1 to 3, characterized in that, The optimization control system also includes a Kn value detection unit; The control unit also includes a Kn value control module; The Kn value detection unit is connected to the nitriding furnace and the Kn value control module, respectively. The Kn value control module is connected to the flow control module.

5. The optimized control system for nitriding process gas according to claim 4, characterized in that, The Kn value detection unit includes a hydrogen probe and a nitrogen potential controller; The hydrogen probe is connected to the nitrogen potential controller; The nitrogen potential controller is connected to the control unit.

6. An optimization control method for an optimized control system of nitriding process gas as described in any one of claims 1 to 5, characterized in that, Includes the following steps: During the nitriding stage, the control unit controls the flow rate of the nitriding process gas and the opening and closing of the exhaust valve.

7. The optimized control method for the optimized control system of nitriding process gas according to claim 6, characterized in that, The control unit controls the flow rate of the nitriding process gas and the on / off state of the exhaust valve, including the following steps: The control unit receives real-time furnace pressure and controls the flow rate of the nitriding process gas and the opening and closing of the exhaust valve based on the real-time furnace pressure.

8. The optimized control method for the optimized control system of nitriding process gas according to claim 7, characterized in that, It satisfies at least one of the following characteristics a to c: a. The step of detecting real-time furnace pressure includes: The real-time furnace pressure is detected using the furnace pressure detection unit. b. The step of controlling the flow rate of the nitriding process gas and the on / off state of the exhaust valve based on the real-time furnace pressure includes: the control unit compares the real-time furnace pressure with a preset furnace pressure range, and controls the flow rate of the nitriding process gas and the on / off state of the exhaust valve based on the comparison result. (1) When the real-time furnace pressure is higher than the preset furnace pressure upper limit, the control unit controls the exhaust valve to open and exhaust; (2) When the real-time furnace pressure is within the preset furnace pressure range, the control unit controls the exhaust valve to close and controls the flow meter to reduce the flow rate of the nitriding process gas or stop the nitriding process gas from entering; (3) When the real-time furnace pressure is lower than the preset furnace pressure lower limit, the control unit controls the exhaust valve to be closed and controls the flow meter to increase the flow rate of the nitriding process gas; c. The furnace pressure in the control unit is compared with the preset furnace pressure range using the furnace pressure control module.

9. The optimization control method for the optimization control system of nitriding process gas according to any one of claims 6 to 8, characterized in that, The optimized control method further includes the following steps: During the nitriding stage, the control unit controls the ratio of ammonia and ammonia decomposition gas in the nitriding process gas: the control unit controls the flow meter to adjust the ratio of ammonia and ammonia decomposition gas in the nitriding process gas entering the nitriding furnace according to the real-time Kn value and the preset Kn value.

10. The optimized control method for the optimized control system of nitriding process gas according to claim 9, characterized in that, It satisfies at least one of the following characteristics a to b: a. The step of controlling the flow meter to provide the flow ratio of ammonia and ammonia decomposition gas in the nitriding process gas includes: when the real-time Kn value is not within the preset Kn value range, the Kn value control module feeds back to the flow control module, and the flow control module controls the flow meter to increase or decrease the ratio of ammonia and ammonia decomposition gas entering the nitriding furnace; b. The nitriding stage adopts a graded nitriding process, including a first nitriding stage, a second nitriding stage, and a third nitriding stage.

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