EP0404496A1 - Wärmebehandlung von Metallen - Google Patents

Wärmebehandlung von Metallen Download PDF

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Publication number
EP0404496A1
EP0404496A1 EP90306645A EP90306645A EP0404496A1 EP 0404496 A1 EP0404496 A1 EP 0404496A1 EP 90306645 A EP90306645 A EP 90306645A EP 90306645 A EP90306645 A EP 90306645A EP 0404496 A1 EP0404496 A1 EP 0404496A1
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EP
European Patent Office
Prior art keywords
nitrogen
annealing
furnace
hydrogen
gas mixture
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP90306645A
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English (en)
French (fr)
Inventor
Robert Franks
Paul Francis Stratton
Colin John Precious
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BOC Group Ltd
Original Assignee
BOC Group Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BOC Group Ltd filed Critical BOC Group Ltd
Publication of EP0404496A1 publication Critical patent/EP0404496A1/de
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/02—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working in inert or controlled atmosphere or vacuum
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • C21D1/763—Adjusting the composition of the atmosphere using a catalyst

Definitions

  • This invention relates to the heat treatment of metals.
  • metals which are less readily oxidisable than iron.
  • metals include cobalt, nickel, lead, copper, palladium, silver and gold, alloys of such metals, and alloys of mercury.
  • nitrogen may be used to form an atmosphere that is inert for the purposes of annealing.
  • the nitrogen may be supplied from a source of nitrogen which has been separated from air by distillation at cryogenic temperatures and need only contain parts per million of reactive impurities such as oxygen.
  • Such nitrogen can be used in a heat treatment shop as the atmosphere for a range of different heat treatments.
  • non-cryogenic methods are able to be used to produce a nitrogen product containing in the order of 1% by volume of oxygen more cheaply than cryogenic methods may be used to separate nitrogen from air, provided the cost of transporting the cryogenically produced nitrogen to its site of use is taken into consideration.
  • the fact that the non-cryogenically produced nitrogen contains in the order of 1% of oxygen as an impurity is not a drawback.
  • a suitable annealing atmosphere may be produced by mixing hydrogen with the non-cryogenically produced nitrogen, in for example the annealing of copper, which takes place at temperatures of 400 to 800 C, the reaction between hydrogen and oxygen proceeds sufficiently slowly at temperatures in at least the lower part of this temperature range for there to be a substantial risk that oxidation of the copper will still take place notwithstanding the addition of a stoichiometric excess of hydrogen to the atmosphere.
  • a method of annealing an article of a metal less oxidisable than iron comprising the steps of subjecting the article to an annealing temperature in a heat treatment furnace, separating nitrogen from air at the site of the annealing furnace to produce a gas mixture containing at least 95% by volume of nitrogen and a minor proportion of oxygen impurity, catalytically reacting the oxygen impurity with a stoichiometric excess of hydrogen to form water vapour, and passing the resulting gas mixture comprising nitrogen, water vapour and unreacted hydrogen into the furnace to create an annealing atmosphere.
  • the invention also provides apparatus for annealing an article of a metal less oxidisable than iron comprising an annealing furnace, means for separating a gas mixture comprising at least 95% by volume of nitrogen and oxygen impurity from air, and a catalytic reactor for catalytically reacting the oxygen impurity with a stoichiometric excess of hydrogen to form a gas mixture comprising nitrogen, water vapour and unreacted hydrogen, wherein said reactor has an outlet in communication with the annealing furnace so as to enable a suitable annealing atmosphere to be created in the furnace.
  • the method and apparatus according to the invention are particularly suited for the bright annealing of the metals less oxidisable than iron.
  • the nitrogen product contains 0.5-3% by volume of oxygen upstream of its catalytic reaction with hydrogen.
  • suitable annealing conditions can be maintained provided that the ratio of the partial pressures of hydrogen to water vapour in the annealing atmosphere does not fall below 1 x 10- 6 .
  • the catalytic reaction preferably takes place over a platinum or palladium catalyst.
  • a platinum or palladium catalyst Alternatively, copper or nickel catalysts may be used.
  • the catalyst is typically heated by the reaction between hydrogen and oxygen to a temperature of up to 200 C.
  • FIG. 1 of the drawings there is shown a plant 2 for separating nitrogen from air by pressure-swing adsorption. Suitable plants and apparatus for this purpose are for example disclosed in Patent Specifications 2073043A and UK 2195097A.
  • the resulting nitrogen typically contains from 0.5 to 3% by volume of oxygen impurity.
  • the nitrogen stream is passed through a catalytic reactor 4 in which its oxygen impurity is reacted with a small stoichiometric excess of hydrogen over a palladium or platinum catalyst at a reaction temperature.
  • the resulting gas mixture comprises nitrogen, hydrogen and water vapour.
  • the heat treatment furnace 6 which may be of a batch or continuous kind in which an article made of copper or an alloy of copper such as bronze, copper-nickel, or brass containing up to 15% by weight of zinc, is annealed by immersion in an annealing atmosphere at a temperature of 400 ⁇ -800 ⁇ C for a period of time typically in the order of 10 minutes to 2 hours.
  • an annealing atmosphere at a temperature of 400 ⁇ -800 ⁇ C for a period of time typically in the order of 10 minutes to 2 hours.
  • a conventional continuous mesh belt furnace 10 having an inlet zone 12, 1 metre in length, a hot or heated zone 14, 5.67 metres in length, and a cooling zone 16, 6.86 metres in length.
  • the furnace 10 is provided at its respective ends with baffles 18 or the like to impede the ingress of air from outside the furnace into its interior.
  • the hot zone 14 and the cooling zone 16 have respectively inlets 20 and 22 for gas.
  • the inlets 20 and 22 are each alternatively able to be placed in communication for source 24 of gas mixture comprising hydrogen, water vapour and nitrogen.
  • the source 24 comprises a plant 26 for separating nitrogen from air by pressure swing adsorption, and a catalytic reactor 28 for reacting oxygen impurity in the nitrogen with hydrogen.
  • a commercially available catalyst comprising palladium supported on alumina is used. Typically, the catalyst is heated by the reaction between hydrogen and oxygen and the gas mixture leaves the reactor 28 at a temperature in the range of 50 to 150 C.
  • a gas mixture comprising nitrogen, water vapour and hydrogen from the catalytic reactor 28 is passed into the furnace 10 through either or both the inlets 20 and 22.
  • the hot zone 14 is heated to a chosen temperature typically in the range 500 to 800° C. Copper work to be bright annealed is loaded onto the belt (not shown) of the furnace and the belt is then advanced slowly through the furnace at a speed such that the work typically has a residence time in the furnace of from 30 minutes to 1 hour. As the work passes through the hot zone 14 so it is raised approximately to the temperature of the hot zone 14. On leaving the hot zone 14 the work passes into the cooling zone 16 in which it is cooled by contact with the relatively cold atmosphere therein. Typically, the work is at a temperature between ambient and 50° C when it leaves the furnace 10. By employing an atmosphere in accordance with the invention, it can be ensured that bright annealed work leaves the furnace 10.
  • Table 1 shows the results of comparative experiments in which various different proportions of hydrogen were mixed with nitrogen from a PSA plant (0.5% oxygen impurity) and the resulting mixture passed into the furnace without a catalytic reaction between hydrogen and oxygen being performed. It was a feature of the furnace used that entry to the hot zone was by way of a muffle made of an alloy with high nickel and chrome content which had the property of acting as a getter for free oxygen. Accordingly, it was found that substantially all the oxygen entering the furnace with the gas mixture was removed therefrom. It was therefore possible to obtain bright work (at 750. C) even when the oxygen level was nominally in excess of the stoichiometric requirement for reaction with hydrogen. Results are given in Table 1 for the oxygen concentration, hydrogen concentration and dew point in both the hot zone 14 and the cooling zone 16 of the furnace 10 at the different hydrogen levels.
  • Table 2 relate to a set of experiments similar to those of Table 1 save that the mixture of nitrogen, oxygen and hydrogen was reacted in the catalytic reactor 28 upstream of being admitted to the hot zone of the furnace through the inlet 20.
  • Table 3 and 4 are respectively comparable to those set out in Tables 1 and 2 with the exception that the gas mixture is not introduced directly into the hot zone 14 through the inlet 20. Rather, it is introduced directly into the cooling zone 16 through the inlet 22.
  • Table 3 shows experiments in which the gas mixture by-passed the catalytic reactor 28, whereas Table 4 relates to experiments in which the catalytic reactor was used.
  • the low dew points obtained in the experiments illustrated by Table 3 indicate that when the gas mixture is supplied directly to the cooling zone, a failure to react the oxygen with at least a stoichiometric quantity of hydrogen in the catalytic reactor 28 will tend to result in work that is not bright even if the hot zone is ooerated at a temperature as high as 750 C.
  • Oxygen concentrations were measured using an oxygen probe.
  • the temperature of the gas from the hot zone at the sampling point was 750° C: the temperature of the gas from the cooling zone at the sampling point was 200°C. Most results are shown in Millivolts (mV).
  • the actual oxygen concentration can be calculated using the formula

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Catalysts (AREA)
  • Gas Separation By Absorption (AREA)
EP90306645A 1989-06-22 1990-06-19 Wärmebehandlung von Metallen Withdrawn EP0404496A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8914366 1989-06-22
GB898914366A GB8914366D0 (en) 1989-06-22 1989-06-22 Heat treatment of metals

Publications (1)

Publication Number Publication Date
EP0404496A1 true EP0404496A1 (de) 1990-12-27

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ID=10658890

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90306645A Withdrawn EP0404496A1 (de) 1989-06-22 1990-06-19 Wärmebehandlung von Metallen

Country Status (7)

Country Link
EP (1) EP0404496A1 (de)
JP (1) JPH03166343A (de)
KR (1) KR910001073A (de)
AU (1) AU621230B2 (de)
CA (1) CA2019565A1 (de)
GB (1) GB8914366D0 (de)
ZA (1) ZA904677B (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5284526A (en) * 1992-12-22 1994-02-08 Air Products And Chemicals, Inc. Integrated process for producing atmospheres suitable for heat treating from non-cryogenically generated nitrogen
US5290480A (en) * 1992-12-22 1994-03-01 Air Products And Chemicals, Inc. Process for producing furnace atmospheres by deoxygenating non-cryogenically generated nitrogen with dissociated ammonia
US5320818A (en) * 1992-12-22 1994-06-14 Air Products And Chemicals, Inc. Deoxygenation of non-cryogenically produced nitrogen with a hydrocarbon
EP0603799A2 (de) * 1992-12-22 1994-06-29 Air Products And Chemicals, Inc. Verfahren zum Herstellen von Wärmebehandlungsatmosphären
US5401339A (en) * 1994-02-10 1995-03-28 Air Products And Chemicals, Inc. Atmospheres for decarburize annealing steels

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100432697B1 (ko) * 1997-01-31 2004-09-07 동양매직 주식회사 식기 세척기와 그 제어 방법

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3535074A (en) * 1965-10-29 1970-10-20 Hitachi Ltd Method and apparatus for purifying crude inert gases
FR2306936A1 (fr) * 1975-04-11 1976-11-05 Azote & Prod Chim Procede et dispositif de generation d'une atmosphere reductrice pour installation de traitement thermique
US4398971A (en) * 1981-12-31 1983-08-16 Aga Aktiebolag Method of heating, holding or heat treatment of metal material
EP0266745A2 (de) * 1986-11-03 1988-05-11 Air Products And Chemicals, Inc. Verfahren zur Trennung der Komponenten eines Gasstroms
JPS63310915A (ja) * 1987-06-10 1988-12-19 Daido Steel Co Ltd 連続式熱処理炉の操業方法
FR2639250A1 (de) * 1988-11-24 1990-05-25 Air Liquide
FR2639252A1 (de) * 1988-11-24 1990-05-25 Air Liquide

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3535074A (en) * 1965-10-29 1970-10-20 Hitachi Ltd Method and apparatus for purifying crude inert gases
FR2306936A1 (fr) * 1975-04-11 1976-11-05 Azote & Prod Chim Procede et dispositif de generation d'une atmosphere reductrice pour installation de traitement thermique
US4398971A (en) * 1981-12-31 1983-08-16 Aga Aktiebolag Method of heating, holding or heat treatment of metal material
EP0266745A2 (de) * 1986-11-03 1988-05-11 Air Products And Chemicals, Inc. Verfahren zur Trennung der Komponenten eines Gasstroms
JPS63310915A (ja) * 1987-06-10 1988-12-19 Daido Steel Co Ltd 連続式熱処理炉の操業方法
FR2639250A1 (de) * 1988-11-24 1990-05-25 Air Liquide
FR2639252A1 (de) * 1988-11-24 1990-05-25 Air Liquide

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
ADVANCED MATERIALS & PROCESSES, vol. 134, no. 3, September 1988, pages 100,102,104,107, Metals Park, Ohio, US; W.C. QUANTZ: "Stealing nitrogen from the air" *
PATENT ABSTRACTS OF JAPAN, vol. 13, no. 156 (C-585)[3504], 14th April 1989; & JP-A-63 310 915 (DAIDO STEEL CO., LTD) 19-12-1988 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5284526A (en) * 1992-12-22 1994-02-08 Air Products And Chemicals, Inc. Integrated process for producing atmospheres suitable for heat treating from non-cryogenically generated nitrogen
US5290480A (en) * 1992-12-22 1994-03-01 Air Products And Chemicals, Inc. Process for producing furnace atmospheres by deoxygenating non-cryogenically generated nitrogen with dissociated ammonia
US5320818A (en) * 1992-12-22 1994-06-14 Air Products And Chemicals, Inc. Deoxygenation of non-cryogenically produced nitrogen with a hydrocarbon
EP0603799A2 (de) * 1992-12-22 1994-06-29 Air Products And Chemicals, Inc. Verfahren zum Herstellen von Wärmebehandlungsatmosphären
EP0603799A3 (de) * 1992-12-22 1994-10-05 Air Prod & Chem Verfahren zum Herstellen von Wärmebehandlungsatmosphären.
US5417774A (en) * 1992-12-22 1995-05-23 Air Products And Chemicals, Inc. Heat treating atmospheres
US5401339A (en) * 1994-02-10 1995-03-28 Air Products And Chemicals, Inc. Atmospheres for decarburize annealing steels

Also Published As

Publication number Publication date
JPH03166343A (ja) 1991-07-18
ZA904677B (en) 1991-08-28
AU621230B2 (en) 1992-03-05
AU5759290A (en) 1991-01-03
CA2019565A1 (en) 1990-12-22
GB8914366D0 (en) 1989-08-09
KR910001073A (ko) 1991-01-30

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