US2160610A - Metallurgical furnace - Google Patents

Description

i 1939- AIG. wrr'rme METALLURGICAL FURNACE Filed May ZO, 1938 57Sheets-Sheet 1 7'14!!!IIIIIIIIIIIIIIIIIIIIIII o .0 AU WW I INVENTOR. ALB/N Q W/TTl/VG? ATTORNEYJZ runnnlllilll May 30,1939. v I A. G. WITTING v fl a METALLURGICAL FURNACE Filed May 20. 1958 5 Sheets-Sheet 2 COLD WATER INLET DEA/N W EQ INVENTOR. 'ALE/N GT W/rr/NG. BY

ATTORNEYS May30,1939.- 1 I MWTTING 6 METALLURGICAL FURNACE Filed May 20, 1938 5 Sheets-Sheet 5 INVENTOR. ALE/N VV/TT/A/G.

TTOR NEY5 May 30, 1939.

A. G. WITTING 7 2,160,610

METALLURGICAL FURNACE Filed May 20, 1958 5 Sheets-Shet 4 {ATTORNEYS BY ALB/N May 30, 1939. I W, 2,160,610-

METALLURGICAL FURNACE Filed May E0, 1958 5 Sheets-Sheet 5- ALB/A/ G MT/NGZ ORNEYS Patented May 30, 1939 UNITED STATES.

PATENT OFFICE 6 Claims.

This invention relates to furnaces and more particularly to rail treatment furnaces. In rail treatment furnaces, particularly of the elongated roller bottom type adapted to heat-treat elonated steel articles such as rails, rods, bars and the like, the length of the furnace is adapted to enclose several such articles in end spaced relation and the width of the furnace is adapted to enclose several such articles in side spaced relation. In such furnaces it is customary to periodically feed several side spaced articles at a time into the furnace at the front end of the furnace, to advance each group of articles periodically within the furnace while feeding in the succeeding groups until the furnace is completely filled and to thereafter simultaneously discharge a group from the rear end of the furnace when feeding a group in the front end. It is customary also-to provide means to supply heat energy to the furnace over substantially the entire length, as for example, by means of gaseous or liquid fuel burners spaced alternately in opposite side walls of the furnace.

Due to the periodic openin'gof the furnace doors it is exceedingly difiicult to maintain the furnace section adjacent each .end at desired operating temperatures. It is also diflicult to exhaust gases of combustion from the furnace without disturbing the desired thermal condition in the furnace. Moreover, furnace structures heretofore proposed 5 have not been flexible as to heat treatment processes which may be practiced therein, moststructures being designed for one specific process and being incapable of ready conversion to another process. Another deleterious feature of prior art furnaces is that no provision is made for rapidly cooling down the furnace in the event of shutdown or during such cooling to protect the interior of the furnace from the deleterious effects of oxidation during the cooling period.

One of the objects of the present invention is to provide an elongated roller bottom furnace structure which is substantially free from the above noted deleterious features. Another object is to provide an elongated furnace structure in which the heating and gas exhaust'means cooperate in such manner that the thermal condition within the furnace from end to end is flexible.

and regulatable'within relatively wide limits. Still another object of this invention is to provide 50 means to exhaust gases from the interior of the furnace at either ,or both ends or to proportionately distribute the gases exhausted at either end and to further provide means co-operatively assembled with said exhaust means to exhaust said gases from one end only, when operation of the furnace is suspended, and to cool the exhausted gases and to feed the cooled gases into the opposite end under pressure greater than atmos-- pheric pressures thereby to accelerate the cooling of the furnace and to prevent the access of at- 5 mospheric gases to the furnace interior.

Other objects and advantages will be apparent as the invention is more fully disclosed.

In accordance with these objects, the furnace and associated means as hereinafter disclosed, has 10 been devised. Before disclosing the same, referenceshould be made to the accompanying drawings, wherein- Fig. 1 is a side elevational view partly in section of the furnace and associated means of the presl5 ent invention; Fig. 2 is a top plan view of the same also partly in section; Fig. 3 is an enlarged elevational view in section of the same; Fig. 4 is an enlarged cross-sectional view of the same; Fig. 5 is an enlarged plan of one of the associated means of the present invention; Fig. 6 is an enlarged section of the said associated means of Fig. 5; and Fig. 7 is a second enlarged section of the same means of Fig. 5.

Referring to the drawings, the present invention consists of an elongated furnace I, rectangular in section, provided with a roller bottom 2 and with means 3 to drive the said bottom to move. rails 4 disposed on said roller bottom 2 by feed table 5, lengthwise through the furnace from inlet end 6 to outlet end I and onto delivery table 8. The opposite side walls 9-9 of furnace l are provided with a plurality of fluid fuel burners l0 arranged in alternate sequence substantially as indicated, and means II is provided to supply each said burner I0 with a regulated mixture of fluid fuel (gaseous or liquid) and air, so that the heat energy output of each burner I!) may be adjusted to a desired amount for the purpose of heating the furnace section affected therebyto a desired temperature. The means per se, not being a part of the present invention, will not be further described.

Along the roof of furnace l,'I provide a plurality of fans l3 with associated means M for driving the said fans l3, whereby a downward circulation of the gases of combustion from burners Ill upon roller bottom 2 and rails 4 may be maintained. As may be noted roller bottom 2 is located in spaced relation to the usual refractory bottom 15 of furnace l providing a channel lengthwise of the furnace I for the circulation of the heated gases lengthwise of the furnace I. Adjacent each end of the furnace I and in the bottom I5 of the furnace, I provide gas outlet I6 and I1 leading ultimately to stack [8. In each flue l6il I provide damper means IS-l to regulate the amount of gases to be exhausted through each flue from furnace I into stack ll. The total draft of stack It to be divided by the fiues I6-Il is'regulated by means of damper 20.

Flues l6-I1" join together prior to passing through damper .20 into stack ill but after the gases pass through damper means 10-49.

This arrangement of flues and dampers enables me to regulate the amount of gasesdrawn from the furnace at each end and the capacity of each flue is adapted to take all the gases from the furnace or any portion of the gases as may. be desired. By so regulating the draft to each flue, I am enabled to regulate the temperature differential at each end of the furnace or the drop in temperature at each end incident to the feeding of relatively cold rails through the inletopening 6 and hot rails out of outlet opening 'I. In the practice of the rail treatment method described and claimed in Brunner Patent Re.

No. 19,884, dated March 10,1936, the rails are allowed to cool on a hot bed in freely moving air from the finishing rolling temperature down through the transformation temperaturefland to undergo transformation from austenite into ferritic structures other than martensite. The rails are then reheated to a temperature slightly above the so-called upper critical temperature (at which the ferritic structures transform into austenite again) and thereafter are allowed to cool normally or by regulated rates to atmospheric temperatures. This reheating and cooling in accordance with the Brunner method is for the purpose of refining the grain size of the ferritic *structure ultimately obtained, it being one of the various ways heretofore proposed to overcome the deleterious effects of internal stresses and strains and the development'of internal cracks and fissures incident to the said stresses and strains. The furnace of the present invention is adapted to accomplish the reheating of therails to above the upper critical temperature, preparatory to the second cooling step of the Brunner substantially identical heating and cooling conditions so that uniformity of product as to grain structure and physical characteristics be maintained as between the treated rails.

In the practice of the "Brunner method in the furnace of the present invention, aplurality of parallel spaced rails l forming a batch or group are fed endwiseinto the furnace from feed table through inlet opening 0 which opening is then closed to thevatmosphere. After a determinedtime interval the batch of rails is moved lengthwise within the furnace approximately a rail length and a second batch introduced within'the furnace. The length of the furnace is sufllcient to provide for the locating of a plurality (I or I) bf these said batches of rails in end to end delivery table 8.

In accordance with the Brunner method, the discharged batch should have a temperature approximating but above the upper critical temperature of the steel composition comprising the rail. This temperature varies somewhat with variations in steel composition, but in general -may-be saidto bein the range 660 to 685 C. Accordingly, the heating of the furnace by-burners I0 is regulated to maintain furnace temperatures within this range at the outlet opening I and through the greater portion of the length towards the inlet opening 6. The draft regulation in fiues 16-41 is adapted'to draw such a proportion of heated gases through fiue i 6 opening into the furnace bottom I5 adjacent the outlet opening I of furnace l as will insure the maintenance of a temperature within this range at the said outlet opening, the balance of the said gases being drawn off by flue ll opening into the furnace bottom i5 adjacent the inlet opening 6 of furnace l. r

The temperatures in the furnace section next adjacent inlet opening 6 preferably should be as closely approximate the desired range (660-685 C.) as possible, which is exceedingly difllcult to obtain in practice because of the intermittent feeding of relatively cold rails into this end of the furnace. However, temperatures not over 60 to 100 C. lower than the average range desired may be maintained in this section by proper regulation of the heat energy input to this section and by care in feeding rails of relatively uniform and identical temperatures successively into the furnace. The preferred temperature of the rail prior to feeding into the furnace is within the range 500 C. to 700 C. although any temperature within the range 300 to 700 C..'may be briefly comprises means to shut off the fiues l0 and II from the stack I8 'and means to draw the gases of combustion remaining in the furnace after burners II! have been shut off) from one end of the furnace through one flue (l8) thence through a cooling means, andthence under pressures greater than atmospheric pressure back into the furnace to recirculate' the cooled gases therethrough. In this manner the interior of the furnace may be rapidly cooled by the cooled non-oxidizing gases of combustion to temper-v atures at which it is safe to expose the interior of the furnace to atmospheric gases.

As indicated in Fig. .5, 'I provide a by-p'ass conduit 2| between fiues I6 and II on the furnace side of damper means I! and I9 therein; and provide a blower fan means 22 to create the draft or pressure necessary to draw the gases from furnace I into flue I, through the 'by-pass conduit 2| through the cooling means 23 and thence through valve 24 into fiue l1 and back to the furnace.

Valve shut-01f means 24 is provided in conduit II to isolate fiues liand I! from each other during normal operation .of the furnace. When the furnace is shut down and dampers l0 and I9 are closed, valve shut-off means 24 is moved to open position before recirculation and cooling of furnace gases is initiated. 1

It is obvious from the brief descriptionof this means, that the specific means employed may be widely varied without departing from the broad inventive idea. In Figs. 6 and 7 I have illustrated in detail one arrangement that has proven satisfactory. Fig; 6 is a sectional view taken along plane 6-6 of Fig. 5 and Fig. 7 is a sectional view along plane 1-! of Fig. 5.

In the arrangement shown, cooling means 23 is a rectangular box with double walls at the smaller ends forming a chamber at each said end. A plurality of horizontal tubes 25 disposed interiorly of the box connect the two chambers together so that water may be supplied to one end chamber, pass through the tubes into the opposite chamber and drain from the said opposite chamber into a discharge pipe. The top and bottom of the box 23 is open in between the opposite end chambers and the by.- I

pass conduit 2| conducts gases from flue I 6 to the said open bottom. Fan means 22 closes the open top of the box and exhausts cooled gases from the box through mushroom valve 24 into flue I! when valve 24 is in open position, as indicated by arrows in Fig. 6.

I have shown dampers l9, l9 and 20 as hand operated slide dampers, counter-weighted for convenience in operation but other types and kinds of dampers effective to shut off flues l6 and H from the draft in stack l8 would be just as satisfactory for the purposes of the present invention.

The advantages of the furnace cooling means above described may be recognized by those skilled in the art. In general, the operating temperatures of the furnace approximate 1600 F.

rotating to prevent sagging or distortion incl-Q dent to the cooling. The normal cooling time to i this temperature where heat .loss by radiation only is relied on is '72 hours or more and in such cooling the contraction of the gases within the furnace inevitably causes an inrush of air with resultant oxidation of the metal rollers. It is estimated that by the time the furnace cools from 1600 F. to 800 F. the atmosphere within the furnace is at least air. This amount of oxygen in the furnace atmosphere is highly oxidizing.

In'cooling the furnace by the means hereinabove described, the time interval of cooling may be lowered. to from frto 6-hours by thermostatically controlling the rate of water flow through the cooling means to maintain a temperature in the returning gas of about 300 F. The fan means insures a substantially constant volume of gases at 300 F. temperature feeding into the furnace I at a positive pressure which prevents the leakage of air into the furnace during the cooling period. This eliminates entirely the deleterious effects of oxygen on the heated rollers during the cooling period and also shortensthe cooling period to a relatively small period as compared with the normal cooling period.

' Having broadly and specifically described the present invention it is apparent that many modifications and departures may be made therein without departing from the nature .and scope thereof and all such modifications and departures are contemplated as may fallwithin the scope of the accompanying claims.

What I claim is:

i. In combination with an elongated furnace provided with inlet and outlet openings adjacent each end of the furnace, and with means to heat the same with hot gaseous products of combustion, and with flue outlets at each end of the .furnace adjacent said inlet and outlet openings,

and with means to regulate the proportionate distribution of gases exhausted through each flue ,outlet, means to cool said furnace when' said heat supply means is shut or, said means comprising a cooling chamber and means to exhaust the hot gases of combustion remaining in the furnace from one'end of the furnace into said cooling chamber and to return the cooled gases to the opposite end of the furnace undera pressure at least sufficient to prevent the inflow of air through said inlet and outlet openings.

2. In an elongated furnace having inlet and .outlet openings in opposite ends, means to supply hot gases of combustion to said furnace to heat the same, and means to exhaust said gases from opposite ends adjacent said inlet and outlet open.- ings, said means including separate exhaust flues leading to a stack with damper means in each said flue to proportionately distribute thestack draft to said flues, means to facilitate the cooling of said furnace and to prevent the inflow of air through said'inlet and outletopenings when said heat supply means is 'shut off, said means comprising a cooling .chamber, and fan means to exhaust the hot gases of combustion from one end' of said furnace through said flue adjacent the said end into said cooling chamber and thence under pressure back to the other end of the furnace through the other said flue.

3. In combination with'an elongated. furnace having inlet and outlet openings in opposite ends, exhaust flues adjacent each said opening, damper means to regulate the flow of gases in each said flue, and means to supply hot gases of-combustion'to the furnace to heat the same, means to facilitate the cooling of said furnace and to prevent the inflow of air through said inlet and outlet openings during the cooling of said furnace when the said heat supply means is shut off, said means comprising a gas cooling means, a by-pass conduit communicating with each said exhaust flue on the furnace side of said dampermeans,-an

exhaust fan located in said conduit towithdraw gases from one end of said furnace through the said flue adjacent said end and to feed the same under pressure through said gas cooling means into said other flue and back to the other the furnace.

4. In combination, an elongated furnace having inlet and outlet openings in opposite ends, means to supply hot gases of combustion at spaced intervals over substantially the entire length of the furnace, means to convey articles to be treated through the furnace, a stack, a gas exhaust flue opening'into one end of said furnace adjacent the inlet opening and communicating with said stack, a second gas exhaust flue opening into the opposite end of the furnace adjacent the outlet openingand communicating with the said stack, damper means to regulate the stack draft, damper means in each said flue to regulate the proportionate distribution of said stack draft in each said flue, and means to cool said furnace when the said heat supply means is shut off, said means including a by-pass conduit connecting the two said flues at a point intermediate the flue dampers and the-furnace, a gas cooling means located in said by-pass conduit, and fan means to exhaust gases from the furnace through one said flue into said gas cooling means and thence into the other said flue and back to the said furnace under a pressure at least sufllcient to prevent the inflow of air into the furnace through the said inlet and outlet openings.

, 5. A rail treating furnace comprising an elongated refractory lined chamber rectangular in cross-section having a. width adapted to enclose a plurality of side spaced rails and a length adapted to enclose a plurality of end spaced rails, inlet and outlet openings in opposite ends of the chamber adapted to permit the entry and exit of rails endwise into and out of said chamber, movabl closure members for said end openings, a roller bottom in said chamber adapted to impart endwise motion to rails located thereon so as to conduct the rails from the inlet to the outlet opening of the chamber, means to supply hot gases of combustion to said chamber at spaced intervals along substantially the entire length of the chamber, means to exhaust said gases from each end of the chamber, said means including means to regulate the relative proportions of said gases exhausted at each said end, and means to cool the interior of the furnace when the said heating means is shut off, said means including means to exhaust the hot gases of combustion then in the furnace from one end of the furnace, means to cool said gases, and means to return the cooled gases to the opposite end of the furnace under a pressure at least sufllcient to prevent the inflow of air through the inlet and outlet openings.

6. A rail treating furnace comprising an elongated refractory lined chamber rectangular in cross-section having a width adapted to enclose a plurality of side spaced rails and a length adapted to enclose a plurality of end spaced rails,

inlet and outlet openings in opposite ends of the chamber adapted to permit the entry and exit of rails endwise into and out of said chamber, movabl closure members for said end openings, a roller bottom in said chamber adapted to impart endwise motion. to rails located thereon so as to conduct the rails from the inlet to the outlet opening of the chamber, means to supply hot gases of combustion to said chamber at spaced intervals along substantially the entire length of the chamber, means to exhaust said gases from each end of the chamber, said means including means to regulate the relative proportions of said gases exhausted at each said end, and means to cool the interior of the furnace when the said heating means is shut off, said means including means to close off said exhaust means, means to draw all the gases from one end of the chamber, means to cool said gases,'means to return the cooled gases for recirculation through the said chamber and means to regulate the temperature and pressure of said cooled gases to provide a positive pressure within the furnace effective to prevent the inflow of air into said furnace through said inlet and outlet openings.

ALBIN G. WIT'I'ING.

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