US3556493A - Method and apparatus for heat-treating of workpieces - Google Patents

Method and apparatus for heat-treating of workpieces Download PDF

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Publication number
US3556493A
US3556493A US804063A US3556493DA US3556493A US 3556493 A US3556493 A US 3556493A US 804063 A US804063 A US 804063A US 3556493D A US3556493D A US 3556493DA US 3556493 A US3556493 A US 3556493A
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United States
Prior art keywords
chamber
workpiece
workpieces
streams
spirals
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Expired - Lifetime
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US804063A
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English (en)
Inventor
Ruediger Knaak
Richard Sitte
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KOPPER WISTRA OFENBAU GES MIT
KOPPER-WISTRA-OFENBAU GESELLSCHAFT MIT
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KOPPER WISTRA OFENBAU GES MIT
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Priority claimed from DE19681608325 external-priority patent/DE1608325A1/de
Application filed by KOPPER WISTRA OFENBAU GES MIT filed Critical KOPPER WISTRA OFENBAU GES MIT
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    • 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
    • C21D1/767—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material with forced gas circulation; Reheating thereof

Definitions

  • the present invention relates generally to the heat-treating of workpieces, and more particularly to a method of heattreating workpieces in an industrial furnace.
  • the method of the invention also relates toan apparatus'for carrying out the method.
  • the workpieces In the heat-treating of workpieces in continuously operating industrial furnaces, the workpieces generally require a very well defined specific volume of space within the heat-treating chamber. This is different from batch-type furnaces because there workpieces of different sizes and different quantities of workpieces are usually present in different batches, whereas in continuously operating furnaces, workpieces of a given series have identical dimensions and the quantity of workpieces in the heat-treating chamber at any given time is usually unvarying. Accordingly, in continuous furnaces of this type the available volume within the heat-treating chamber, that is the volume in which the hot gases may move, remains substantially unchanged at all times.
  • Both types of solu tions suffer from some disadvantages.
  • the so-called lateral burners which are arranged in the sidewalls bounding the chamber fail to provide for uniform heating of the workpieces across the width of the chamber, that is transversely of the direction of movement of the workpieces.
  • the reason for this is that the conventional burners have relatively low issue speeds, that is speed at which combustion gases issue from the burner and enter into the heat-treating chamber, so that the rate of admixture of the combusted gases with the ambient atmosphere prevailing in the treating chamber is slow with the result that heat radiation onto the workpiece is uneven.
  • a further disadvantage is the fact that combustion in large measure takes place only after the combustion gases have entered into the heat-treating chamber; this results in the development of flame jets which further intensify the unevenness of heating of the workpieces.
  • these problems have been so pronounced that in the past two decades there has been a decided movement away from the use of lateral burner arrangements.
  • Ceiling burners on the other hand, require special mounting arrangements and are usable only in the ceiling, that is the upper wall bounding the heat-treating chamber. Furthermore,
  • a more particular object of the present invention is to provide a method of heat-treating workpieces in continuously operating industrial furnaces.
  • a further object of the invention is to provide such a method which will result in more even and quicker treating of the workpieces.
  • Yet a further object of the invention is to provide an apparatus for carrying out the method. 7
  • one feature of our invention resides in the provision of a method of heat-treating workpieces in an industrial furnace provided with a horizontally elongated treating chamber having an. upper and a lower wall.
  • a workpiece to be treated is advanced through the chamber in a path intermediate the walls, and streams of substantially fully combusted combustion gases are introduced into the chamber at speeds in excess of 50 m./sec.
  • the streams of combustion gases are so oriented as to form intermediate the workpiece and at least one of the top and bottom walls a pair of laterally adjacent gas spirals each of which has an axis coincident with the direction of elongation of the treating chamber and a rotary component of movement about its respective axis in direction towards the associated gas spiral.
  • the main concept of the invention to so orient the incoming streams of combustion gases that the combustion gases are forced into a spiral movement about an axis or axes coincident with the direction of advancement of the workpieces, that is the direction of elongation of the heattreating chamber.
  • the kinetic energy of the streams of combustion gases is not allowed to become dissipated, but rather is retained to a significant extent with the result that the constant spiral movement of the streams of combustion gases effects constant circulation and turnover of the entire ambient atmosphere and eliminates the accumulation of stagnant gas in so-called dead corners, a phenomenon which evidently results in inadequate heat radiation from such areas and therefore inadequate heat-treating of workpiece portions'which are exposed to gases in such areas.
  • FIG. I is a diagrammatic vertical transverse section illustrating a furnace for carrying out our invention, according to one embodiment
  • FIG. 2 is a view similar to FIG. I but illustrating a further embodiment of the invention.
  • FIG. 3 is a view similar to FIG. 1 but illustrating yet an additional embodiment of the invention.
  • reference numeral I identifies the lateral walls
  • reference numeral 1a identifies the top and bottom walls which together bound the heat-treating chamber 1b of a continuously operating industrial furnace. It is not believed necessary to discuss further details concerning the general construction of such a furnace because this is conventional and forms no part of the invention.
  • guide means 4 are provided located substantially midway between the top and bottom walls Ia and extending in what is the direction of elongation of the. heatrtreating chamber, that is intermediate the (nonillustrated) inlet and outlet thereof.
  • the guide means 4 may be constructed as water-cooled tubular guides.
  • the workpiece or workpieces 3 are advanced resting on the guide means 4.
  • FIG. I there is a space between the upper side of the workpiece 3 and the top wall In and a further space between the lower side of the workpiece 3 and the bottom wall la.
  • the sidewalls I are provided with lateral burners 2 which are so arranged as to reject streams of combustion gases into the interior of the heat-treating chamber lb in the direction of the respectively indicated arrows.
  • the burners 2 are of the high-speed type which ejects the combustion gases, when in full operation, with an outlet speed of more than 50 m./sec.; the burners 2 are further so constructed that the combustion gases are at least substantially fully combusted before they enter into the heat-treating chamber lb.
  • Burners such as the ones identified with reference numeral 2 in FIG. 1 are well known to those skilled in the art and are therefore not described in detail. Their construction does not, in itself, constitute a part of the present invention.
  • the burners 2 are arranged in pairs with the burners of each pair being transversely aligned in the opposite lateral walls 1, and with the combustion gases issuing from the respective burners having such an orientation that they form spirals or coils 5 of which in the illustrated embodiment of one pair is located in the space above and one pair is located in the space below the workpiece 3.
  • the construction of the furnace may be such that only a space exists above the workpiece, or that a space exists only below the workpiece. In this case there would then of course be only one pair of the spirals 5.
  • the spirals are shown to have longitudinal axes which extend in the direction of elongation of the chamber lb, that is in the direction of advancement of the workpiece 3.
  • the combustion gases rotate in such a manner that the gases in each spiral rotate towards the other spiral of the pair, that is after the combustion gases issue from the respective burners they rotate towards the middle of the chamber and then reverse direction to rotate back towards the sidewall 1 from which they have just issued.
  • a component not only of rotary movement as illustrated by the arrows, but also a component of longitudinal movement which is not shown but which is largest where the component of rotary movement is smallest, that is at the core or center of the spirals 5 and in the space below the workpiece 3 in the area between the guide members 4.
  • FIG. 2 which is basically similar to that of FIG. 1 and wherein like elements are identified with like reference numerals, we have shown a construction wherein workpieces may be advanced through the heat-treating chamber on two or more vertically spaced and superimposed levels.
  • the manner in which this is accomplished is the same as in FIG. I, that is the workpieces 3 advance on guide members 4.
  • FIG. 1 it is immaterial what means are utilized for advancing the workpieces 3 because such means are entirely conventional and form no part of the invention.
  • FIG. 2 we provide additional high-speed burners 6 associated with the respective lateral walls 1 and transversely aligned, as before. They are arranged approximately midway between the upper and lower limits of the space existing' between the upperand lower workpieces and, when in operation, produce two further superimposed pairs of combustion gas spirals, of which the spirals of the upper pair are identified with reference numeral 5a and those of the lower pair with reference numeral 5b. It should be noted, however, that their rotational component is reversed with respect to the rotational component of the spirals 5.
  • the advantages of this construction are the same as discussed above with respect to FIG. 1 except that in the embodiment of FIG. 2, two workpieces, or two layers of workpieces, may be treated simultaneously. Of course, it is possible to further expand the construction of FIG. 2 by providing additional layers of workpieces and additional ones of the burners 6.
  • the type of furnace with which our present invention is utilized may differ.
  • the arrangement of the burners 2as opposed to the burners 6 of FIG. 2 is advantageously such that they eject their streams of combustion gas into the upper third of the volume of space above the workpieces and into the lower third of the volume of space below the workpieces, as illustrated in FIG. 1.
  • FIG. 3 it will be seen that this is largely the same as the one of FIG. 1 from which it differs only in the provision of partition walls 7 which extend from the respective top and bottom walls 10 into the chamber lb towards but short of the guide means 4 so as to subdivide the upper space above the workpieces 3 and the lower space below the workpieces 3 in the manner illustrated in FIG. 3.
  • the purpose of these partition walls 7, which extend in the direction of elongation of the heat-treating chamber Ib and therefore in the direction of movement of the workpieces 3, is to enhance, particularly in furnaces having relatively small distance between the lateral walls 1 thereof, the direction reversal of the incoming streams of combustion gases to thereby facilitate their guidance in a sense forming the gas spirals 5.
  • a method of heat-treating workpieces in an industrial furnace provided with a horizontally elongated treating chamber having an upper and a lower wall comprising the steps of advancing a workpiece to be treated through said chamber in a path intermediate said walls; and introducing streams of substantially fully combusted combustion gases into said chamber at spaced locations at speeds in excess of 50 m./sec. and with orientation that said gas streams impinge upon one another and form intennediate said workpiece and at least one of said top and bottom walls a pair of laterally adjacent gas spirals each of which has an axis coincident with the direction of elongation of said treating chamber and a rotary component of movement about its respective axis in direction towards the associated gas spiral.
  • a method as defined in claim 2 further comprising the step of advancing an additional workpiece through said chamber in an additional path vertically spaced from the firstmentioned path; and introducing into said chamber additional streams of said gases at speeds in excess of 50 mJsec. and with such orientation as to fonn in the space between said paths two additional superposed pairs of laterally adjacent gas spirals similar to the first-mentioned pairs of gas spirals.
  • An industrial furnace for heat-treating workpieces comprising wall means defining a horizontally elongated treating chamber having transversely spaced sidewalls and vertically spaced top and bottom walls; guide means extending longitudinally of said chamber in a plane intermediate said top and bottom walls for guiding a workpiece for advancement through said chamber; and burner means includingpairs of burners provided in said sidewalls transversely aligned for ejecting streams of substantially fully combusted combustion gases into said chamber at speeds in excess of 50 m./sec.
  • said burner means comprising further pairs of burners provided in said sidewalls transversely aligned and operative for ejecting further streams of said combustion gases at said speeds into a further space" between said workpiece and the other of said top and bottom walls whereby to provide in said further space a further pair of laterally adjacent gas spirals similar to the first-mentioned pair.
  • said guide means comrising first and second guide instrumentalities for guiding the irst-mentioned workpiece and an additional workpiece in two vertically superposed spaced planes; and said burner means including additional pairs of burners provided in said sidewalls transversely aligned and operative for ejecting into the space between said workpieces two additional superposed pairs of laterally adjacent gas spirals similar to the firstmentioned pairs of gas spirals.

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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)
  • Tunnel Furnaces (AREA)
  • Combustion Of Fluid Fuel (AREA)
US804063A 1968-03-02 1969-03-03 Method and apparatus for heat-treating of workpieces Expired - Lifetime US3556493A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19681608325 DE1608325A1 (de) 1968-03-02 1968-03-02 Industrieofenbeheizung

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US3556493A true US3556493A (en) 1971-01-19

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US (1) US3556493A (zh)
JP (1) JPS4920687B1 (zh)
FR (1) FR1579996A (zh)
GB (1) GB1190908A (zh)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3969069A (en) * 1973-04-14 1976-07-13 Koppers-Wistra-Ofenbau Gesellschaft Mit Beschrankter Haftung Burner systems for ovens and methods of operating such systems
US4792301A (en) * 1985-04-01 1988-12-20 Daiming Pan Method and furnace apparatus for continuously heating steel blanks
US5954498A (en) * 1998-02-26 1999-09-21 American Air Liquide, Inc. Oxidizing oxygen-fuel burner firing for reducing NOx emissions from high temperature furnaces

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3174735A (en) * 1963-03-13 1965-03-23 Bickley Furnaces Inc Furnace with burner means
US3208740A (en) * 1961-01-06 1965-09-28 Midland Ross Corp Heating apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3208740A (en) * 1961-01-06 1965-09-28 Midland Ross Corp Heating apparatus
US3174735A (en) * 1963-03-13 1965-03-23 Bickley Furnaces Inc Furnace with burner means

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3969069A (en) * 1973-04-14 1976-07-13 Koppers-Wistra-Ofenbau Gesellschaft Mit Beschrankter Haftung Burner systems for ovens and methods of operating such systems
US4792301A (en) * 1985-04-01 1988-12-20 Daiming Pan Method and furnace apparatus for continuously heating steel blanks
US5954498A (en) * 1998-02-26 1999-09-21 American Air Liquide, Inc. Oxidizing oxygen-fuel burner firing for reducing NOx emissions from high temperature furnaces

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Publication number Publication date
GB1190908A (en) 1970-05-06
JPS4920687B1 (zh) 1974-05-27
FR1579996A (zh) 1969-08-29

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