US2430477A

US2430477A - Method and apparatus for heating steel

Info

Publication number: US2430477A
Application number: US417973A
Authority: US
Inventors: William A Morton
Original assignee: Amsler Morton Co
Current assignee: Amsler Morton Co
Priority date: 1941-11-06
Filing date: 1941-11-06
Publication date: 1947-11-11
Anticipated expiration: 1964-11-11

Description

w. A. MoRToN `METHOD AND APPARATUSl FOR HEATING STEEL Nov. ll, 1947.

F1e d Nov. 6, 1941 2 Sheets-Sheet l a INVENTOR f BY t ATTORNEY NOV. l1, 1947. w, A, MOR-TON Y 2,430,477

METHOD AND APPARATUS FOR HEAT'VING STEEL Filed Nov. 6, 1941 2 Sheets-Sheet 2 l INVENTOR fmmf "1 ATTORNEY lParental Nov. 11, i947 I `William A. Morton, Mount Lebanon, Pa., assignor to` The Amsler-Morton Company, Pittsburgh, Pa., a corporation of Pennsylvania Application November 6, 1941, Serial'No. 417,973

' zz claims. (ci. ass- 39) This. invention relates generally to methods for heating steel and alloys and more particularly to such methods wherein articles of steel and steel alloys are heated as they are continuously moved through the furnace, and to heating furnaces foraccomplishing the s-ame. Y

A .continuous type heating furnace is employed in the steel industry to uniformly heat or reheat billets, ingots, blooms, slabs, rails and the like, which vary not only in size but in metallurgical characteristics. Thus each grade or analysis of steel or alloy must be heated to a predetermined temperature and at a predetermined rate to preserve the metallurgical characteristics and properly prepare it for rolling or performing other operations thereon.

In the present practice of heating high carbon and various other special steels it is usually customary to employ at least two independent furnaces to properly heat the articles before they can be worked in their heated state. The furnaces required. may be of the continuous ty'pe or the soaking pit type in and out or a. combination' of both. The use of two or more furnaces for properly heating the articles involves certain extra fuel, labor and equipment which this method will avoid. This method also avoids material losses and the waste which occurs if these steels are heated in conventional single compartment furnaces.

The principal object of this invention is the provision of a continuous heating furnace which a primary heating chamber, and a secondary heating chamber through which the articles to be `heated travel in succession.

Another object is the provision of a continuous furnace structure, the main heating chamber of which is divided transversely by a partition which Ais adjustable 'relative to the hearth l to admit the travel of different size articles from one section to the other.

Another object is the provision of a, continuous heating furnace having two heating chambers through which the articles being heated pass in succession and which are red independently of one another.

Another object is the provision for introducing and withdrawing the heating medium at both ends in the main heating chamber @of a continuous furnace and having an intermediate trans` verse wall which is adjustable vertically to divide the main furnace chamber into two independent chambers.

Another object is the provision of a transverse adjustable partition wall structure inv a continuous heating furnace having a seal withv the permanent Wall structure thereof.

Another object is the provision of a continuous heating furnace provided with a transversely disposed and vertically movable partition wall arranged when in one position to permit the furnace to operate as a single chambered furnace and when in another position to operate as a double chambered furnace wherein the temperatures are independently controlled and through which the articles pass in succession. l

The means for controlling the temperatures and regulating' furnace pressure, etc. are similar to those described in my copending application Serial Number 337,987, filed May 31, 1940, now Patent No. 2,329,211.

The furnace atmosphere adjacent the steel is composed of the products of combustion. The products of combustion being free of oxygen are caused to circulate in a protective blanket between the steel and the incomplete combustion cf the heating flames to protect the steel frornd 5 carburization. I' While the design` of these furnaces as tothe relative sizeV of the compartments is" generally lfixed by the quantity of steel to beheatedper hour, it is readily apparent that the rate of heating in the several compartments may be varied to some reasonable extent by varying the quantity of heat supplied, the temperaturei at which the heat is liberated, or both, Without departing from the intent of the design.

Other objects and advantages appear hereinafter in the following description and claims.

-In 'the accompanying drawings a practical embodiment illustrating the principles of this'invention is shown wherein;

Fig. 1 is a diagrammatic sectional view taken longitudinally of the furnace showing the parti- Fig. 3 is a vertical sectional view of the furnace showing the adjustable divisional wall..

Fig. 4 is a view similar to Fig. 3 showing the partition wall in a raised position. A

Referring to the drawings, the furnace illustrated is provided with a continuous hearth g I II extending from the charge end II to the discharge end I2. The first portion of the hearth comprises a. series of parallel water cooled skids I3 extending longtudinally 'of the hearth from the charging end II. The outermost skids I3 are supported on the vertically and longitudinally disposed walls I4, whereas the intermediate skids are supported by the ordinary piers I5. The skids I3 extend to the solid monolithic hearth section ,I6 which extends to the discharge end I2 of the furnace.

The charging end II of the furnace is provided with a suitable door I1 whichwhen elevated permits the entry of transversely disposed steel articles I8. These articles move into and through the furnace in the conventional manner by means of a pusher, not shown. Suitable doors I9 are provided for closing oppositely disposed openings 20 in the side walls 2I at the discharge end I2 of the furnace through which the steel articles I8 are ejected. A pusher bar, not shown, is operated by the motor driven pinch roll 22 and engages the ends vof a steel article, shoving it longitudinally through the opening 20 onto the motor driven discharge roll 23 which delivers the heated independent-

heating chambers

23 and 21. This partition wall is preferably constructed to have a U-shaped cross section as indicated in Fig. 1 so that it may be properly cooled. This wall is built up of refractory blocks supportedv by the transversely disposed metal bridge structure 23 which extends beyond the side walls 2| of the furnace structure and is arrangedto be supported at its ends by the hydraulic jack structures 33. Thus by actuating the hydraulic jack structures the partition wall 24 may be raised or lowered to any suitable height relative to the plane of the hearth III of` the furnace. The refractory material on the ends of the wall 24 may extend into a recess 3| in the side walls 2l as illustrated in Figs. 1 and 2, thus forming a labyrinth seal between the

furnace chambers

26 and 21. The lroof 32 of the furnace may be sealed with the adjustable partition wall 24 by means of the depending anges 33 which are integral with the partition wall and extend into the sand filled troughs 34 lying transversely across the roof on each side of the /U-shapedpartition wall. The depending ange 33 and the troughs 34 are of sumcient depth to permit vertical adjustment of the wall 24 without breaking the seal when the wall is raised to its uppermost position as illustrated in Fig. 4.

Again the bridge structure and the refractory material of the partition wall 24 may extend through the side walls 2l and the roof 32 as shown in Fig. 4 and be sealed therewith by the application of mud and nrebrlck 23 in the gap formed in the side walls and between the roof, after the partition wall 24 has been adjusted to the proper elevation with respect to the hearth Ill.

The furnace chamber 26 is divided into upper and lower independent chambers 3i and 36 by I the skid /supporting walls I4 and the continuous series of steel articles I3 lying on the hearth. The upper chamber 35, is nred by means of a row of burners 31 placed in the rear wall 38 of the furnace above the hearth. The flames issuing from these burners travel out over the steel articles and parallel therewith toward the partition wall 24 and reverse, as indicated by arrows in Fig. 1, flowing back over and immediately above the steel articles to the charging end II of the furnace, passing through the preheating chamber 40 from whence the products are discharged through the nues 4I leading to the common passageway 42, and thence through the passageway 43 to the recuperator or stack as the case may be.

The lower. chamber 36 is fired by a row of burners 44 in the lower wall 45. The flames issuing from these burners travel, as indicated by arrows in Fig. 1, toward the intermediate wall 46, and then reverse, traveling immediately adjacent the under side of the steel articles to the lower portion of the preheating chamber 40 and are discharged through the vertically disposed flues 41 which lead into the common passageway 42,

The chamber 21 at the discharge end of the furnace is rheated'by the burners 50 in the end wall 5I. The llames from these burners travel horizontally through the chamber 21 toward the partition wall 24 substantially parallel with the steel articles and are then redirected back over the steel to the discharge openings 52 and are then carried through the flues 53 to the common passageway 54. 'I'he products of combustion at this end of the furnace may be carried through the passageway 55 to the passageways 43 and thence tothe stack, or they may be transferred by other passageways not shown to suitable heat exchange apparatus. The temperature and operation of the furnace may be controlled by the temperature of the products of combustion measured in the flues immediately after the gases have passed over the steel or by y means of a thermal responsive element in the bottom of the partition wall 24 where it is not affected by the direct heat of the flames.

It will be noted that the rows of burners 31,

44 and 5U supplying the

chambers

35, 36 and 21,*-

respectively, are arranged to produce heating flame substantially horiz`ontal and parallel to the steel articles I8 lying on the hearth and they are spaced farther from the plane of the hearth than from the roof or the floor of the furnace. The reason for this arrangement is to provide flames that travel outwardly from the burners in a path substantially parallel with the steel articles until the velocity of the flames are reduced to such an extent that the draft created by the independent discharge openings of each chamber redirects the path of movement of the products of combustion of the flame, causing it to travel in a reverse direction parallel and adjacent to the steel articles being heated.

The combustion is substantially complete in each of the flames before the path of the flame is redirected by the draft eifect. The hottest or initial portion of the flames do not directlyl impinge on the steel articles being heated and the inert products of combustion, which travel intermediate of the steel and the initial llame, thus blanket the steel on its return path of movement to the flues. In this' manner the atmosphere surrounding the steel articles may .be controlled to prevent localized overheating, excess oxidation and decarburization of the steel. The hottest portion of the heating flames is along the initial gree of temperature.

. 5 path oi the iiame propagation and the heat is diffused in passing through the `blanketing layer to the steel.

andere'` Thus the steel is heated by radiation from the initial portion of the llame and by convection from the products of combustion which blanket the steel while passing back through the combastion chamber. The radiant heat reflected from ne roof and the walls must also pass through the blanketing layer of the products of combustion in traveling to the steel. Thus the direct and reflected radiant heat energy is diffused as it passes through the products of combustion blanketing the steel, thereby uniformly heating the steel, Control of the discharge of these products of combustion is obtained in the nues 4i and 41 by the adjustable dampers 56 and the fiues 53 by thev adjustable dampers 51. A stack damper 58 is provided in the passageway 43 for regulating thetotal discharge of the products of combustion.

Thus the three

combustion chambers

21, 35

and 36 are independently red by the

burners

50, 31 and 44 respectively. These burners are each provided with an independent automatic temperature combustion control which regulates the air-gas ratio, the rate of combustion, and the temperature of each chamber independently of each other. Ordinarily the

combustion chambers

35 and 36 are regulated to provide the same air. gas ratio, thereby exposing the upper and the lower sides of the steel articles to the same de- The removal of the vwaste gases from any one of the three combustion chambers in no way affects the removal of the 3 waste gases in any other of the combustion chambers as the partition wall 24 is adjusted relative to the steel article I8 to prevent the flow of gases to either side thereof and the vertical skid supporting walls I4 prevent commingling of the gases between the

combustion chambers

35 and 36. The furnace pressure controll may be operated by the stack damper 58 to maintain the common pressure throughout the entire furnace. Thus the desired rate of heating may be produced in each combustion chamber without affecting the rate of heating in an adjacent combustion chamber.'

High carbon and various special steels may thus be slowly heated to approximately 1600 F. as they pass through the combustion chamber 26. After the steel passes under the partition wall 24 it is subjected to the heating flames in the Combustion chamber 21 which raises the temperature of this steel to approximately 1900 F. or 2300 F. at a comparatively rapid rate. In heating the high carbon and special alloy steels in this manner and by blanketing them with the products vof combustion of the heating name, decarburization of the steel is reduced to a minimum, thereby greatly increasing the percentage of the steel that is available for rolling or other hot working' operations and withoutmaterially changing the metallurgical characteristics of the steel due to the heating process. This is a material ,advantage of this invention and in conventional furnaces it is not practical to set up two distinct temperature cycles in which the heat l from one combustion chamber is distributed or controlled independently of the other.

`Under certain conditions it may be necessary to use only the combustion chamber 21 for heating the material. Thus all of the heating takes place in this chamber, and the chambers 35 and 3B are shut down. However the operation ofthe alloy steels.

furnace in this manner would only be desirable I under specific circumstances wherein the desired heating could be obtained n a. short ltime by very high temperature. The size of the steel article and its metallurgical characteristics are of course of prime consideration andv determine whether or not the furnace may be 'operated in this way. l Again the partition wall 24 may be raised, thus combining the

chambers

26 and 21 in a large single combustion chamber 25. Under these conditions the furnace would be operated by the independent controls to function in the manner of the present type ofv continuous heating furnace of this character. -Thus the continuous furnace comprising this invention may be operated to advantage of this invention in the heat treating process of lthe present high carbon and special This advantage can only be obtained by segregating and independently controlling each of the three combustion systems within the

chambers

21, and 36 and results in less decarburization of the high carbon steels and alloys.

By operating the hydraulic jack structures 30 ered without shutting vdown the furnace, and if this wall is not within the furnace the seal'between the walls and the roof for the furnace may be quickly made by the application of clay with amud gun.

1. 'I'heprocess of heating steel and steel-alloy billets, ingots and other shapes which comprises causingV the same to travel uninterruptedly through two separate heating zones, thermally isolating the heating zones by firing and withdrawing all of the products of combustion from each heating zone independently, slowly heting :sisA

i independently.

the steel in the rst zone to a predetermined temperature. heating the steel in the second zone to a higher predetermined temperature and at a faster rate, and .independently controlling the temperature of the respective zones.

V2. The process of heating steel and steel-alloy billets, ingots and other shapes which comprises causing the same to travel uninterruptedly through two separate and independently heated zones, and heating the same both from above and below in the rst zone and from above in the second zone. thermally isolating the heating zones by firing and withdrawing all of the products of combustion from each part of each heating zone 3. The process of heating steel and steel-alloy billets, ingots and othershapes which comprises causing theV same to travel uninterruptedly through two separate and independent heating zones substantially thermally isolated from one another, heating the same both from above and below in the rst zone to a temperature below the steel is raised to the final desired temperature.

4. In a heating furnace for the purposes departiijn wall interposed between said chambers,

andfxneans to adjust thek wall to provide an opening of predetermined fixed height relative to the hearth to pass a selected size of steel articles from one chamber to the other. y

5. In a heating furnace for the purposes described, the combination of two heating chambers arranged lin sequence, means for causing the articles to be heated to travel in the form of a substantially continuous row or rows through said chambers in sequence, means for individually controlling the temperature in each of said zones, separate means for withdrawing the products of vcombustion from each chamber, a depending partition wall interposed between the chambers,

and means for raising and lowering said wall to Y different xed elevations to cause the selected size of articles being heated to seal the opening between the chambers.

6. In a heating furnace for the purposes described, the combination of two heating chambers arranged in sequence, means for causing the articles to travelv uninterruptedly through the chambers in sequence, independently controlled means for heating each of said chambers, separate means for withdrawing the products of combustion from each chamber, a depending partltion wall interposed between said chambers. means for raising and lowering said wall to different fixed elevations to cause the selected size of articles being heated to seal the opening between the chambers, means for heating the articles from aboveand below in the first chamber, and means for heating the articles from above in the second chamber.

7. In a heating furnace for the purposes del scribed. the combination of two heating chambers arranged in sequence, means for causing the articles to be heated to travel in the form of a substantially continuous row .through s'aid chambers in sequence, means for individually controllling the temperature in each of'said zones, separate means for withdrawing the products of combustion from each chamber, a depending partition wall interposed between the chambers, means for raising andlowering said wall to different fixedl elevations to cause the selected size of articles beingvheated to seal the opening be, tween the chambers, means for heating the articles from above arid below in the first chamber, and means for heating the articles fromabove in the second chamber.

8. In a continuous heating furnace for the purposes described, the combination with two heating chambers arranged in sequence, of a communicating aperture between the chambers and at the bottom of the chambers for the passage of the materials from one chamber to the other chamber, and means. to adjust the aperture to floor level thereof, independent heating means above and below the floor level of the said chamber, a communicating aperture between the chambers and at the floor level of the chambers for the passage of the materials from one chamber to the other chamber, and means to adjust the aperture to provide a fixed. height that is substantially sealed by the material selected to pass from one chamber to the other, independent heating means for the second chamber, and independent exhaust means for each chamber remote of said aperture.

10. In a continuous heating furnace for the purposes described, the combination with two heating chambers arranged in sequence, of a charging opening at the end of the first chamber at the floor level thereofy independent heating means above and below the floor level of the said chamber, a communicating aperture between the chambers and at the oor level of the chambers for the passage of the materials from one chamber to the other chamber, and means to adjust the aperture to provide a fixed height that is substantially, sealed by the material selected to pass from one chamber to the other, independent heating'means i for the second chamber, independent exhaust means for each chamber, and a discharging opening at the extreme opposite end of the second heating chamber at the floor level thereof, said exhaust means being adjacent the charging and discharging openings respectively.

11. In a continuous heating furnace. a depending partition means interposed in the furnace to divide Iit into separate heating chambers, means for independently heating the said chambersand independently discharging the products of cornbustion therefrom, and means for varying the height of the partitionv to provide a fixed aperture to permit the passage of materials of different thickness beneath the partition whereby substantial atmospheric isolation is maintained between the chambers.

12. In a longitudinally extending continuous heating furnace adapted for the controlled heating of special steels moved along its longitudinal 4 axis, a depending partition member interposed provide a fixed height that is substantially sea-led by the material selected to Apass from one chamber to the other, independent heating means for each chamber, and independentl exhaust means for each chamber.

across the longitudinal axis of the furnace and spaced above the hearth of the furnace for the passage of steel units therebeneath, means for moving the partition member vertically to provide clearance for steel units of different height, separate heating chambers formed in the furnace by the said member, separate means for withdrawing the products of combustion from each chamber, and a seal means across the top of the furnace which remains effective during any vertical adjustment of the said member. Y

13. In a furnace for heating high carbon steels and the like which comprises a continuous furnace having heating zones substantially isolated atmospherically from each other when the furnace is operating, means for moving the steel from one zone to the other while maintaining such isolation, individual outlet ilues connected to the several heating zones, separate heating means and controls for regulating the temperature of each of the zones whereby the steel is slowly heated to the critical or recalescence point in the first zone and rapidly heated tothe final desired temperature in the final zone.

14. A method of heating high carbon and alloy steels which comprises the steps of preheating the steel in a zone of low thermal potential, passing the steel into a second zone of higher thermal potential, slowly adding most of the sensible heat 9 to be finally contained in the steel in the second zone, and sharply accelerating the rate of heating the steel bypassing it through a third zone of higher thermal potential wherein the final `de l sired temperature is attained.l

- 15. The process of heating steel and steel alloy -billets and the nlike which comprises the steps of causing the same to travel uninterruptedly along l a common hearth through separately flame heated and exhausted furnace chambers, heating the steel in the first chamber to a predetermined temperature, sharply accelerating the` heating to the finaldesired temperature in the second chamber, and discharging the steel at the end of the second chamber. y 16. The process of claim 15 which also includesV the step of initially heating the steel in a preheating chamber connected withthe ilrst chamber.

17. 'I'he process of claim 15 which also includes the step of heating the steel both from above I 21. 4In -a continuous steel heating furnace, .the

combination of a furnace chamber, a hearth extending through the furnace chamber from the charging end to the discharge end to support the steel moving continuously therethrough, a movable transverse wallv dividing the furnacechamber into a long heating chamber adjacent the charging end and-a relatively short isolated heatling chamber adjacent the discharge end, means and below in the first chamber and from above 4 i in the second chamber.

18. The process of claim 15 which also includes the step of protecting the steel in both chambers from the direct action of the ilames of combustion by passing waste gases between the steel and the heating flames. l

19. The process of claim 15 which also includes the step of slowly heating the steel in the first chamber for a materially longer period of time than the accelerated vheating in the secon chamber.

20. In a continuous steel heating furnace, the

' combination of a furnace chamber, a common hearth extending through the furnace chamber from the charging to the discharge end to support the steel moving continuously therethrough, a movable transverse wall dividing the furnace chamber into two heating'chambers, independent ame heating and exhaust means for each heat,- ing chamber, means to adjust the wall to different flxed heights relative to the hearth for the pas-Y sage of -varied sizes of steel articles, and means to seal the wail at a fixed height to pass a selected size of steel articles from one heating chamber to the other.

to adjust the wall to diierent xed heights relative' to the hearth for the passage of varied sizes of steel articles. and independent llame heating and exhaust means for each heating chamber.

V22. In a continuous steel furnace, the combina- 4tion of a furnace chamber, a hearth extending through the chamber from the charging end to the discharge end to support the steel moving continuously therethrough, a vertically adjustable transverse wall sealed with the walls and roof of the furnace chamber to divide the latter longi tudinally, upper andlower heating chambers extending from the charging end to the movable wall, an upper heating chamber extending from the movable wall to the discharge and separate heating and exhaust means for each of said heating chambers adjacent the furnace `WILLIAMaisfnjnvroN. REFERENCES CITED of the movable wall.

` The following references are of record in the me of this patent:

35 Number UNITED STATES PATENTS l Date SfiaSSl-net -Ju"- Mar.Y 14,1939

ends remote Certicato of Correction Patent No. 2,430,477. November 11, 1947. WILLIAM A. MORTON It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Column 6, lines 68 and 69, claim 3, strike out the words substantially thermally isolated from one another; line 72, same claim, after zone and before the comma insert thermally isolating the heating zones by jr'lng and uthdrawlng all of the products of combustion from each part of each heating zone independently; and that the said Letters Patent should be read with these gili'rections therein that the same may conform to the record of the case in the Patent Signed and sealed this 10th day of February, A. D. 1948.

THOMAS F. MURPHY,

Assistant 0ommz'aszoner of Patents.