Method and apparatus for sequentially and continuously determining concentrations of carbon, hydrogen, and nitrogen in molten steel, and method and apparatus for rapidly determining trace amounts of carbon in molten steel

• US 5,522,915 A
• Filed: 09/02/1994
• Issued: 06/04/1996
• Est. Priority Date: 09/03/1993
• Status: Expired due to Fees

• Current Assignee: Heraeus Electronite Japan Limited
• Original Assignee: Heraeus Electronite Japan Limited
• Inventors: Kosaka, Hiroaki, Ina, Masaki, Ogura, Toshihiro, Ono, Akihiro
• Primary Examiner(s): KASTLER, SCOTT R
• Application Number:
  US08/300,722
• Time in Patent Office: 641 Days
• Field of Search: 266/80, 266/79, 266/90, 266/99, 75/375, 75/376, 75/377, 75/384, 75/385, 75/386
• US Class Current: 75/385
• CPC Class Codes: G01N 33/0011 Sample conditioning preparing specimens for investigation G01N1/28
• CPC Class Codes: G01N 33/2025 Gaseous constituents
• CPC Class Codes: G01N 33/205 in liquid state, e.g. molten metals

Abstract

Disclosed herein is a method of sequentially and continuously determining the concentrations of carbon, hydrogen, and nitrogen in molten steel using a single apparatus. Disclosed also herein are a method and an apparatus for determining trace amounts of carbon in molten steel which are the specialized application of the principle used for the above-mentioned method.

Said method comprises bubbling through molten steel a carrier gas selected according to any specific element to be determined in molten steel, recovering the carrier gas containing the specific element, circulating or passing the recovered carrier gas through a gas circulating circuit so that the concentration of the specific element in the carrier gas reaches an approximate or complete equilibrium with the concentration of the specific element in molten steel, determining the concentration of the specific element by the means to determine the concentration of one or more specific elements, (and in the case of determination of several elements) discharging the carrier gas from the gas circulating circuit and repeating said steps with a renewed carrier gas to determine the remaining elements to be determined.

Claims

1. A method for determining sequentially and continuously the concentrations of carbon, hydrogen, and nitrogen in molten steel, said method comprising bubbling through molten steel an inert gas as a carrier gas selected according to any specific element to be determined among carbon, hydrogen, and nitrogen in molten steel, recovering the carrier gas containing the specific element through a gas supply-recover probe immersed in molten steel, circulating or passing the recovered carrier gas through a gas circulating circuit, performing the bubbling and recovery of the carrier gas once or several times so that the concentration of the specific element in the carrier gas reaches an approximate or complete equilibrium with the concentration of the specific element in molten steel, determining the concentration of the specific element by means to determine the concentration of one or more specific elements which is installed in said gas circulating circuit or in a gas circuit branching off from said gas circulating circuit, discharging the carrier gas from the gas circulating circuit to complete a series of steps for determining the concentration of the specific element, and repeating said steps with a renewed carrier gas to determine the remaining elements to be determined.

2. An apparatus for determining sequentially and continuously the concentrations of carbon, hydrogen, and nitrogen in molten steel, said apparatus comprising one or more than one source to supply an inert gas as a carrier gas according to the element to be determined;

a gas supply-recover probe consisting of a gas blowing tube with an open end and a gas recovery tube to recover the carrier gas through a porous part which is positioned in molten steel above the open end of the gas blowing tube;

a gas circulating circuit through which the carrier gas supplied from the carrier gas source is circulated compulsorily by a circulating pump through the gas supply-recover probe as many times as required or for a prescribed period of time;

a group of means to determine the concentration of a specific element including means to determine the concentration of carbon oxides, means to determine the concentration of hydrogen, and means to determine the concentration of nitrogen installed in the gas circulating circuit or in a gas circuit branching off from the gas circulating circuit;

a means to determine the concentrations of oxygen which is constructed integrally with or separately from the gas supply-recover probe; and

an arithmetic unit which receives the data of the concentrations of carbon oxides and oxygen from the means to determine the concentrations of carbon oxides and oxygen and calculates the concentration of carbon in molten steel from such data.

3. An apparatus for sequentially and continuously determining the concentrations of carbon, hydrogen, and nitrogen in molten steel as defined in claim 2, wherein the means to determine the concentration of a specific element is provided with a pretreatment unit to remove harmful components from the carrier gas.

4. An apparatus for sequentially and continuously determining the concentrations of carbon, hydrogen, and nitrogen in molten steel as defined in claim 2 or 3, wherein the means to determine the concentration of carbon oxides is an infrared gas analyzer, the means to determine the concentration of hydrogen is a semiconductor gas sensor, and the means to determine the concentration of nitrogen is a thermal conductivity detector.

5. A method for rapidly determining trace amounts of carbon in molten steel, said method comprising bubbling an inert gas as a carrier gas through molten steel with no deoxidation or slight deoxidation, thereby stirring molten steel and causing carbon and oxygen to react with each other at the interface between bubbles and molten steel to give carbon monoxide and carbon dioxide, recovering the carrier gas together with carbon monoxide and carbon dioxide, circulating or passing the recovered carrier gas through the gas circuit in which is installed a means to determine the concentration of carbon oxides, performing the steps of the bubbling and recovery of the carrier gas once or several times, thereby gradually increasing the concentrations of carbon monoxide and carbon dioxide in the carrier gas until they equilibrate with those of oxygen and carbon in molten steel, determining the concentrations of carbon monoxide and carbon dioxide in the carrier gas by the above-mentioned means to determine the concentrations of carbon oxides after the circulation has been carried out as many times as required or for a prescribed period of time, and estimating the concentration of carbon in molten steel from the relationship between the concentrations of carbon monoxide and carbon dioxide and the concentration of oxygen in molten steel.

6. An apparatus for rapidly determining trace amounts of carbon in molten steel, which comprises a source to supply an inert gas as a carrier gas;

a gas supply-recover probe consisting of a gas blowing tube with an open end and a gas recovery tube to recover the carrier gas through a porous part which is positioned in molten steel above the open end of the gas blowing tube;

a gas circulating circuit through which the carrier gas supplied from the carrier gas source is circulated compulsorily by a circulating pump through the gas supply-recover probe as many times as required or for a prescribed period of time, said gas circulating circuit being provided therein a means to determine the concentrations of carbon oxides;

a means to determine the concentrations of oxygen which is constructed integrally with or separately from the gas supply-recover probe; and

an arithmetic unit which receives the data of the concentrations of carbon oxides and oxygen from the means to determine the concentrations of carbon oxides and oxygen and calculates the concentration of carbon in molten steel from such data.