WO2011114342A2

WO2011114342A2 - A device with semi quantitative technique used to determine the hydrogen content in aluminum melts

Info

Publication number: WO2011114342A2
Application number: PCT/IN2010/000160
Authority: WO
Inventors: Priya Darshan Pant
Original assignee: Priya Darshan Pant
Priority date: 2010-03-18
Filing date: 2010-03-18
Publication date: 2011-09-22
Also published as: WO2011114342A3

Abstract

This invention is based on advanced semi quantitative technique which is crucial to analyze hydrogen content in aluminum melt. The main features of the system encompasses the Auto calibration, facility to plot calibration curves, facility to do re- standardization from time to time to get good accuracy on long-term basis, reduction of analysis time from 5 minutes to around 1 min, good extrapolation using mathematical algorithms, reduction of downtime between consecutive analyses by using a more powerful vacuum pump, fully microcontroller-based circuits, PC connectivity, Logging of last 1,000 analyses data, capacity for Incorporation of weighing balance in the machine to correct for sample weight, capacity for Incorporating temperature measurement of the sample to see the effect which temperature has on the output. Measurement accuracy is 0.01 ml/100g and measurement range is 0-0.99 cm/100g. It can work in the harsh environments of aluminium foundries up to 60 deg. C.

Description

TITLE OF INVENTION;

A Device with semi quantitative technique used to determine the hydrogen content in aluminum melts

Field of invention

This invention is based on advanced semi quantitative technique and appliance which is crucial for determine the hydrogen content in aluminum melt.

Prior Art

In the existing system as given in United States Patent 4878375 wherein, The device comprises an immersion probe (10) which is permeable to hydrogen and is made of melt-resistant sintered or calcined ceramic material connected, in a vacuum tight manner via a capillary tube (4), to a pressure gauge (2). The immersion probe (10) features at least two essentially plate-shaped diffusion membranes (7, 8) that in each case form a common interface (9). The capillary tube (4) as such communicates freely with the interface (9). The immersion probe (10) is preferably situated in a crucible featuring openings above the level of the probe (10); on dipping the crucible into the melt 12, the openings allow the melt (12) to flow in, permit equalization of the hydrogen content of the metal and, after removing the crucible from the melt (12), allow the melt to flow out leaving a residual amount that protects the probe (10). The measuring probe is robust, easily changed and features a short response time. In the existing system as given in United States Patent 4170139 wherein A sampling device for a quantitative determination of hydrogen in molten metal, which includes a material in which hydrogen is relatively non-diffusible during testing or readily soluble during sampling and a refractory vessel housing this material. This refractory vessel is sealed so as to maintain a vacuum or negative (reduced) pressure therein, and is provided with a thin-walled aspirating portion which is readily destroyed by an external pressure.

In the existing system as given in United States Patent 3683669 wherein An apparatus for determining the gas content of samples includes a vacuum furnace for heating the samples to be tested which is arranged within a protective housing having a closeable cover and which is connected to a pump within the housing provided for evacuating the furnace. The apparatus includes an indicator for analyzing the gases extracted from the samples, arranged with the furnace in the upper portion of the housing adjacent the cover. The cover is hinged and carries a pivotally mounted cover for the furnace which is located so that it will seat over the furnace closure rim and close it in a gas tight manner when the cover is closed. The cover also includes an opening which is aligned with the indicator so that the indicator readings can be viewed through the cove

In the existing system as given in United States Patent 7086274 wherein A method and apparatus for measuring the concentration of gas, such as hydrogen, in a liquid, such as molten aluminum, without requiring a bias or adjustment to compensate for variations in ambient conditions, such as humidity. A measurement system includes a probe connected to an analyzer with a housing enclosing a pump assembly. The measurement system may include a climate-controlled environment substantially devoid of ambient humidity and surrounding at least the pump assembly. A modified pump assembly includes at least one seal, at least one diaphragm and at least one gasket made from a material compatible with hydrogen and substantially unaffected by ambient humidity. A method of use is also disclosed.

In the existing system as given in European Patent EP0369725 Al wherein The invention provides a new method for the determination of the concentration of gas dissolved in a molten metal or metal matrix composite employing a new immersion head probe in apparatus employing the method. Such determinations are needed to facilitate removal of the gas, which can cause loss of desirable properties and/or bubbles in the solidified material and subsequent processing difficulties. This determination is particularly difficult with metals containing high concentrations of particulate additions, such as metal matrix composites, since it is necessary to avoid deposition of the particulates and consequent inaccurate readings. The method employs apparatus which circulates an inert carrier gas through the probe in gas exchange contact with the molten metal to entrain dissolved gas until an equilibrium mixture is obtained; the concentration of the dissolved gas in the mixture then is representative of its concentration in the molten metal. The head consists of a monolithic or integral body of a porous gas-permeable material of sufficient porosity, pore size and permeability to permit the necessary gas diffusion in a reasonable period of time. If the test is to be carried out in a stationary body of molten metal, the probe may be vibrated or the metal may be stirred.

Object of the invention

The classical method of Sieverts has been widely used for the determination of the solubility of gases in solids. The amount of hydrogen absorbed by a degassed metal sample of known mass is determined by the difference of the volumes of hydrogen and an inert gas necessary to attain the same equilibrium pressure at a given temperature. The very low solubility of hydrogen in aluminum causes errors. Since a small difference between two relatively large volumes has to be determined. Therefore, large samples are used, which slow down the kinetics of the process. Carefully degassed samples are needed; the hydrogen uptake is retarded by the oxide layer covering the sample surface. The difference between the thermal properties of the inert gas used and those of hydrogen and the hydrogen loss due to permeation of hydrogen through the wall of the absorption bulb are also to be considered. Since the lifetime of the absorption bulbs used is also limited, the determination of the solubility as a function of temperature and composition becomes extremely time-consuming. In another known process a circulating stream of nitrogen is introduced into the melt. When equilibrium saturation is reached, the hydrogen concentration is measured via a thermal conductivity cell. The high cost of the probes, which are susceptible to malfunctioning, and the need for trained personnel to operate them, limit the extent to which the instrument can be used in rough operating conditions.

In another known hot-extraction method, samples that have been carefully prepared by machining are degassed in an inert gas stream either in the solid state at 500°-600° C. or after melting in vacuum. The process is labor intensive and therefore is expensive and can only be performed under laboratory conditions. The method is not suitable for magnesium-containing alloys because of getter effects and decomposition of hydride and hydrate.

This system is very advanced to other system for measuring the hydrogen content in molten aluminum because it has Auto calibration, it has facility to plot calibration curves, it has facility to do re-standardization from time to time to get good accuracy on long-term basis, it has a reduction of analysis time from 5 minutes to around 1 min, it has good extrapolation using mathematical algorithms, it has reduction of downtime between consecutive analyses by using a more powerful vacuum pump, it is fully microcontroller-based circuits,PC connectivity, it is Logging of last 1 ,000 analyses data, it has capacity for Incorporation of weighing balance in the machine to correct for sample weight, it has capacity for Incorporating temperature measurement of the sample to see the effect which temperature has on the output, ,Output in ppm as well as in percentage terms.

Statement of the invention

This invention is based on advanced method semi quantitative technique, which is used for determine the hydrogen in aluminum, melts. It is very time consuming method, it has facility to do re-standardization from time to time to get good accuracy on long-term basis, it uses more powerful vacuum pump, it has capacity for Incorporation of weighing balance in the machine to correct for sample Weight, and it has capacity for incorporating temperature measurement of the sample. Measurement accuracy is 0.01 ml/1 OOg and measurement range is 0-0.99 cm/lOOg. Detail Description of Invention

During molten aluminum processing, the most significant dissolved gas is hydrogen, which is created when aluminum reacts with moisture to form aluminum oxide and hydrogen. The solubility of hydrogen in the liquid aluminum is much higher than that in solid aluminum, so dissolved hydrogen can direct to porosity during solidification. A small amount of molten aluminum alloy sample is allowed to solidify under controlled reduced pressure and the gas content is estimated or determined by observing the solidification performance of the sample or by density measurement or porosity investigation of the solidified specimen. To produce sound castings, molten aluminum must often be degassed to remove hydrogen. The efficiency of these degassing processes can be improved using real-time measurement of the hydrogen content during the process.

This system is very advanced to other systems for measuring the hydrogen content in molten aluminum because it has auto-calibration, it has facility to plot calibration curves, it has facility to do re-standardization from time to time to get good accuracy on long-term basis, it has a reduction of analysis time from 5 minutes to around 1 min, it has good extrapolation using mathematical algorithms, it has reduction of downtime between consecutive analyses by using a more powerful vacuum pump, it is fully microcontroller-based circuits, has PC connectivity, it has Logging of last 1.000 analyses data, it has capacity for Incorporation of weighing balance in the machine to correct for sample weight, it has capacity for Incorporating temperature measurement of the sample to see the effect which temperature has on the output, ,Output in ppifi as well as in percentage terms. Measurement accuracy is O.Olml/lOOg and measurement range is 0-0.99 cm/lOOg. It can work in the harsh environments of aluminium foundries up to 60 deg. C.

Claims

I/We Claims;

1. An advanced semi quantitative technique and appliance used to determine the hydrogen content in aluminum melt.

2. An advanced semi quantitative technique and appliance comprises Auto calibration, mathematical algorithms, powerful vacuum pump, fully microcontroller-based circuits

3. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said Auto calibration.

4. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said facility to plot calibration curves

5. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said facility to do re-standardization from time to time to get good accuracy on long-term basis.

6. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said reduction of analysis time from 5 minutes to around 1 min.

7. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said good extrapolation using mathematical algorithms

8. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said reduction of downtime between consecutive analyses by using a more powerful vacuum pump.

9. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said fully microcontroller-based circuits.

10. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said PC connectivity.

11. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said logging of last 1,000 analyses data.

12. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said capacity for Incorporation of weighing balance in the machine to correct for sample weight.

13. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said, capacity for incorporating temperature measurement of the sample to see the effect which temperature has on the output.

14. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said Measurement accuracy is O.Olml/lOOg and measurement range is 0-0.99 cm/lOOg.

15. An advanced semi quantitative technique and appliance as claimed in claim 1 wherein said it can work in the harsh environments of aluminium foundries up to 60 deg. C.