Nitriding Temperature Sensing With Equal-Potential Thermocouple Sheath
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Solution Overview
Problem
Conventional nitriding apparatuses face challenges in accurately measuring the temperature of metal objects during the nitriding process, leading to excessive temperature increases and the formation of compound layers, which deteriorate treatment efficiency.
Innovation Solution
A nitriding apparatus with a thermocouple wire and a metal sheath thermocouple system that sets the object and sheath to an identical potential, allowing accurate temperature measurement and control, preventing excessive temperature rises and compound layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a radiation thermometer is used to measure temperature of the metal member in the vacuum chamber, then temperature measurement is possible without direct contact, but measurement accuracy is poor due to temperature changes of the thermometer itself and focal position fluctuations
Solution Approach 1:
A thermocouple wire is introduced as an intermediary measurement device that directly contacts the metal member to be treated. The thermocouple wire provides accurate temperature measurements by being in direct thermal contact with the workpiece, eliminating the issues of radiation thermometer drift and focal position fluctuations. The thermocouple signal is then used to control the heater power supply.
Solution Approach 2:
The radiation thermometer system (optical/electromagnetic measurement) is replaced with a thermocouple-based measurement system. This substitution provides more reliable and accurate temperature measurements suitable for the nitriding process control, as thermocouples directly measure the temperature at the workpiece surface without being affected by vacuum chamber conditions or optical alignment issues.
2Productivity
If temperature measurement is not accurately controlled, then the nitriding process can proceed without additional measurement devices, but excessive temperature increase causes compound layer formation requiring polishing
Solution Approach 1:
A feedback control system is established where the thermocouple wire continuously monitors the temperature of the metal member during nitriding. The thermocouple signal is fed to a power supply control unit that adjusts the heater power in real-time to maintain the temperature within the optimal range (300-650°C), preventing compound layer formation and eliminating the need for subsequent polishing operations.
Solution Approach 2:
Temperature measurement and control are implemented at the beginning of the nitriding process using the thermocouple wire. By establishing accurate temperature monitoring before treatment starts, the system can prevent compound layer formation from occurring in the first place, rather than requiring corrective polishing after the fact.
3Measurement precision
If a thermocouple wire is placed directly adjacent to the object to be treated for accurate measurement, then temperature control improves, but the thermocouple wire may be affected by plasma discharge
Solution Approach 1:
The thermocouple wire serves as an intermediary measurement device that is electrically isolated from the plasma discharge environment. By positioning the thermocouple wire in the vacuum chamber adjacent to the workpiece but electrically isolated, it can accurately measure temperature without being directly exposed to harmful plasma effects, while still providing the necessary temperature data for process control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enables precise temperature control and measurement, preventing compound layer formation and enhancing the efficiency of the nitriding process by maintaining stable temperatures, thus improving the treatment outcome.
Implementation Method 1
at least one thermocouple wire that is disposed in the internal space, being adjacent to the at least one object to be treated and has a temperature measuring section
Implementation Method 2
a plasma source that generates plasma in the internal space, and has a cathode disposed in the internal space and an anode disposed facing the cathode to generate nitrogen ions from at least the nitrogen
Implementation Method 3
at least one heater disposed in the internal space to heat the object to be treated
Implementation Method 4
a power supply for an object to be treated that applies predetermined voltage to the at least one object to be treated and the at least one accommodating member to set the at least one object to be treated and the at least one accommodating member to an identical potential on a negative side
Data Source
AI summary
Provided are a nitriding apparatus and a method of nitriding, which are capable of suppressing generation of a compound layer by accurately measuring temperature of an object to be treated by nitriding. A nitriding apparatus includes a chamber, a gas supplying unit, a support, a plasma source, a heater, a thermocouple wire including a temperature measuring section, an accommodating member, a power supply for an object to be treated, and a treatment condition control unit. The accommodating member internally accommodates the thermocouple wire to cover the temperature measuring section, while being insulated from the thermocouple wire. The power supply for an object to be treated applies a predetermined voltage to an object to be treated and the housing member so that the object to be treated and the accommodating member are set to an identical potential on the negative side.