Continuous Detection Method For Hydrogen Content Of Aluminum Alloy Melt Based On Inert Gas Circulation

The hydrogen content of the aluminum alloy melt has an important impact on the quality of aluminum alloy castings.Quickly detecting the hydrogen content in the melt before pouring and taking effective hydrogen removal measures are of great significance to improve product quality,reduce scrap rates and reduce production costs.With the continuous progress of metallurgical casting technology,new requirements have been set for the frequency,speed,and accuracy of hydrogen content detection in aluminum alloy melts.The research of online continuous hydrogen measurement technology has been put on the agenda.The inert gas cycle method is by far one of the most mature methods for detecting the hydrogen content of aluminum alloy melts.The disadvantage is that the detection time is a bit long and continuous on-line detection is not possible.In this paper,by improving the structure of key components such as the sampler,barometric balance unit,and hydrogen concentration sensor in the inert gas circulation circuit,a device capable of quickly,accurately,and continuously detecting the hydrogen content of the aluminum alloy melt was developed.The function of the inert gas circulation loop is to continuously provide the inert gas with a constant pressure to the melt,recover the mixed gas carrying hydrogen and provide an accurate signal of the hydrogen concentration of the mixed gas to the computer measurement and control unit.When the hydrogen content of the melt is at a low level,it can Automatically reduce the hydrogen concentration of the mixed gas in the loop to achieve continuous detection.The improved inert gas circulation circuit is mainly composed of an inert gas bottle,a miniature circulation pump,a permanent sampler,a hydrogen concentration sensor TCS208 F,a K-type thermocouple,an air pressure sensor,an electromagnetic directional valve,an electric push rod and a cylinder.The TCS208 F sensor is a high-precision thermal conductivity gas sensor,which can significantly improve the hydrogen concentration sensing speed and detection accuracy.The permanent sampler adopts the technology of porous blow head and automatic detection of meilt depth,which can not only improve the melt hydrogen diffusion speed,but also eliminate the influence of the air in the sampler to the greatest extent,thereby further reducing the detection time;the combination of electric push rods,cylinders and air pressure sensors constitutes the gas circulation loop pressure balance and automatic control of hydrogen concentration,making it possible to continuously detect the hydrogen content of the aluminum alloy melt online.This article also completed the design of a computer measurement and control unit for real-time collection and processing of information parameters such as the action control of inert gas circulation unit and gas pressure,hydrogen concentration and solution temperature.The hardware part is mainly composed of computer,ADAM-4117 module,ADAM-4050 module,ADAM-4520 serial converter and relay.ADAM-4117 module is connected to the sensor to complete the analog input;ADAM-4050 module controls the actions of related components in the loop through the relay;ADAM-4520 is used to implement the function of a computer to control multiple modules.All software of the measurement and control unit is written in Microsoft Visual Basic 6.0,including the main program and several subprograms.The TCS208 F sensor was calibrated by mixing a certain proportion of mixed gas with argon and hydrogen.Simulation tests were performed on the inert gas circulation loop with different proportions of mixed gas.It was proved that the inert gas circulation loop can meet the constant loop pressure and the hydrogen concentration of the circulating gas.Requirements for automatic adjustment.Under laboratory conditions,the inert gas circulation circuit developed in this paper was tested by using the configured aluminum alloy melt.The comparison between the test results and the test data of the decompression solidification hydrogen tester shows that the aluminum alloy melt hydrogen measurement device developed in this paper The detection time is less than 2min,and the difference between the detection results is in the range of 0.009(ml/100g).The precision is high and the repeatability is good,which can meet the actual production needs.