Study On The Method And Device For Rapid Detection Of Hydrogen Content In Aluminum Alloy Melt By Double Samples Density Difference Method

Aluminum alloy is widely used in vehicles,ships,aerospace and other fields due to its low density,high specific strength,excellent electrical conductivity and corrosion resistance.During the solidification of aluminum alloy,the solubility of hydrogen in the melt decreases greatly with the decrease of temperature.Some hydrogen is left in the casting because it is too late to precipitate,resulting in defects such as pores and shrinkage porosity,which reduces the strength of the casting and deteriorates the electrical conductivity.In industrial production,the hydrogen content of aluminum melt is not higher than 0.2 m L / 100 g,and it is required to be controlled below 0.1 m L / 100 g in aerospace and other fields.How to quickly detect the hydrogen content of aluminum alloy melt and take effective measures to remove hydrogen has always been a hot issue for foundry workers.In this paper,a new method for the determination of hydrogen content in aluminum alloy melt by double sample density difference is proposed.Gascontaining and non-porous samples are prepared simultaneously by using the same furnace melt.By controlling the pressure,temperature and holding time of the solidification chamber,the hydrogen in the gas-containing sample is fully precipitated,and the quenching ability of the thick-walled mold is used to suppress the hydrogen precipitation of the non-porous sample.The mass of the two samples in air and water was measured by a high-precision weighing system and the density was calculated.Finally,the hydrogen content of the measured melt was calculated according to the density difference of the two samples.A hydrogen measuring device based on double sample density difference method is constructed,which mainly includes sample preparation unit,weighing unit and computer measurement and control unit.The sample preparation unit and the weighing unit determine the accuracy of the detection device.The computer measurement and control unit are used for automatic control and data acquisition of the device.The sample preparation unit is composed of a double sample sampler,a thermal insulation layer of the sampler,a sample lifting platform,a solidification chamber of the gas-containing sample,an infrared temperature sensor of the solidification chamber,a pressure sensor of the solidification chamber,and a vacuum pump.The preparation of gas-containing and non-porous samples;the weighing unit is composed of a double-sample high-precision load sensor,a double-sample water tank,and a water tank lifting platform to complete the mass measurement of the double-sample in the air and water.The computer measurement and control unit are composed of 51 single-chip microcomputer minimum system,I / O interface circuit,LED display and keyboard.It completes the electric push rod lifting,vacuum pump start and stop,solenoid valve opening and closing control,solidification chamber temperature,pressure,double sample quality detection,double sample density difference and measured melt hydrogen content calculation.Under laboratory conditions,different hydrogen content aluminum alloys and different grades of aluminum alloys were used to test the detection device.The test results show that the detection time of the hydrogen content detection device for aluminum alloy melt based on the density difference method is not more than 130 s.The maximum absolute error of hydrogen measurement is 0.014 m L / 100 g Al,and the average absolute error is 0.008 m L / 100 g Al.The hydrogen measurement device is simple to operate.The detection accuracy and speed can meet the requirements of hydrogen content detection of aluminum alloy melt in casting factory or laboratory.