US1859803A - Apparatus for continuous treatment of sheet steel - Google Patents

Description

May 24, 1932- D. M. SHANAFELT ET Al. 1,859,803

APPARATUS FOR CONTINUOUS TREATMENT OF' SHEET STEEL Filed Aug. 3, 1929 4 Sheets-Sheet l May 2 4, 1932; D. M. sHANAFi-:LT ET AL 1,859,803

APPARATUS FOR CONTINUOUS TREATMENT OF SHEET STEEL Filed Aug. 5, 1929l 4 Sheets-Sheet 2 ATTORNEY May 24, 1932. 4 D. M. SHANAFELT E`T- AL t 1,859,803

APPARATUS FOR CONTINUOUS TREATMENT OF SHEET STEEL Filed Aug. 43, 1929 4 Sheets-Sheet 5 INVENTORS BY MW )6.7M @Mfg/JM,

ATTORNEY May 24, 1932. 1,859,803

APPARATUS FOR CONTINUOUS TREATMENT OE SHEET STEEL D. M. SHANAFE-LT ET AL Filed Aug. 5, 1929 4 Sheets-Sheet 4 INVENTORS @www /v fsf MMM

"y MJATTORNEY Patented May 24, 1932 UNITEDgs'rATEs vlasrlezlai* OFFICE.

DONALD'M. SEANAELT, 0F LAKEWOOD, GEOBJGAE B. NISBET, OF OLEVELAND, V.AND

OF LAKEWOOD, OHIO, ASSIGNOBS TO THE OTIS' ALBERT E. SHONKWILEB,

COMPANYfOF CLEVELAND, OHIO, A GORPOBATION F OHIO APPARATUS FOB-CONTINUOUS TREATMENT 0F SHEET STEEL Application fled August 3, 1929. Serial No. 383,318..

This invention relates to heat treatment and finishing of steel sheets and the like, and more particularly to an apparatus for producing commercial sheetsv of the required degrec of hardness and ductility at a very reduced cost.

Heretofore in the production of commercial sheets the practice'has been to pass the sheets through a furnace in which the steel is heated to a temperature above the critical range, then slowly cooled to a temperature somewhat below the scaling temperature, and then placed in stacks and cooled in the open air to air temperature.

The next step has .been to pass the sheets through a picklingbath, cold roll them, and then'again place them in stacks in a box annealing furnace. In this last furnace they nal heat treatment was given by very slowly heating and slowly cooling a large stack of material in a single mass. Such a process has proven very expensive, not only due to the numerous times-the sheets must be handled, butalso due to the great amount of time consumed. Furthermore, numerous handlings of the sheets between the various steps damaged and scratched the surfaces of a large number sothat an additional rolling and extra' pickling is often necessary.

Again," due to the'size of the mass treated in the box annealing furnace, great heat is required to penetrate the inner sheets m a reasonable time, and quitel generally the outer edge of all the sheets tend to heat too quickly while the inner portions of such a stack are not heated suicientl Uniform-- ity of the nished sheets coul be obtained4 only by a processso slow that instead of taking the required time, it was' considered better practice to heat more quickly, even at the sacrifice of several sheets in each stack. i

In the pickling process much of the corrosive action of the bath is utilized in removing scale or rust and mechanicall irregularities resulting from handling of the sheets. Furthermore, after the sheets are pickled sufciently,fthey must be washed to prevent further corrosive action of the bath. If exposed to the air when wet, there is a tendenc for them to rust, losing much of the bene t of thepickling. The same is true if they are left to the open air for an appreciable length of time. Again, exposure to the atmosphere allowed other foreign matter to drop on the sheets so that if rolled or subjected to heat without being treated, this foreign matter .tended to imbed in or fuse onto the sheets or otherwise mar the surface.

It is one of the objects of our invention to reduce the expense of present methods, yet to produce commercial sheets of the required surface finish, and other characteristics, in

a very much shorter time.

Another object is to produce-sheets of suchl smooth finish which are very'l uniform in grain structure. By our process precisely the-desired grain structure may be accurately controlled andthe required drawabilty freedom from splits, cracks, lamnations and the like is obtained, and the product may have a smooth surface finish, meeting the most exacting commercial requirements.

In the drawings-'- Fig. 1 is a diagrammatic longitudinal section of a furnace adapted for carrying out our process;

Fig. 2 is a graph lcurve illustrating the temperatures of the various portions of the furnace in Fig. 1,- as indicated in vertical alignment with Fig. 1;

Figs. 3 and 4 are respective continuations of the furnace andthe graph shown in Figs. 1 and 2 respectively;

Figs. 5 and 6 are enlarged illustrations in the nature of a longitudinal section of such a furnace embodymg means for continuous normalizing, pickling, rolling and annealing;

Fig. 7 is an enlar ed section through the apparatus shown in the line 7f-7 Fig. 8 isl an enlarged section through a portion of the apparatus taken on a plane indicated by the line 8-8 ofFg. 6;

Fig. 9 is a section through the portion of the furnace shown in Figs. 1 and 5, as indicated by the line 9 9.

- Fig. 10 is a section through a portionnf the and furnace shown along line 10-10 of Fig. 6,

5 and 6 taken along Fig. 11 is a detail horizontal section taken as indicated by the line 11--11 of Figs. 5 and 9.

Referring more in detail to the drawings, `our arrangement, as illustrated in Figs. l and 3, comprises a continuous ,furnace having 'c a primary heating zone 1, a quickquenching zone 2, a secondary heating and tempering Zone 3 and a slow cooling zone 4. The furnace is here shown as provided with the usual conveying rollers 5 mounted on water cooled shafts 6. The quick quenching zone is separated from the adjoining portions by means of exible baflies suoli as chains 7, and is provided with cooling means, such for instance, as cool air or water pipes 8 in the upper portion.

This zone lowers the temperature of the sheets and yet allows the passage of gas through it from adjacent compartments. An open water tank 9 in this section through the quick quenching zone vfurnishes additional means for reducing the temperature therein.

It should be noted in this connection that the various zones intercommunicate. preferable to cause a non-oxidizing atmos- I phere to be retained in them, for the purpose of the prevention of scale or rust upon the sheets. Such an arrangement is particularly shown/ and described in our previous applicationfiled June 22, 1929, Serial No. 372,812.

An additional precaution in preventing the accumulation of scale and foreign matter on the sheets, due to such accumulation-on the conveyors, may be taken by adding suitable Scrapers, bearing against the rolls in the hottest zones, as indicatedat 20 in Fig. 5.

The sheets enter the furnace, shown in Figs. 1 and 3, at the right, at air temperature or relatively cool, and pass into the compartment 1, wherein the temperature is raised toa degree above the critical range for the particular steel being treated, usually about 17 50 to 1800o Fahrenheit. As discussed and illustrated in the above cited application, at

such temperature the granular structure. of the steel becomes veryfine and regular.

While in this condition the sheet passes annealing temperature, for instance, to about.

1200o F. It is then kept constantly at the desired temperature for a relatively long pe-- riod of time, during which the grains grow or increase in size, yet retain their regularity and relative positions, so that the required This isv softness, 'ductility andl drawability is ob- Thereafter the sheet is passed into a long,

iiiuch slower cooling compartment 4 and gradually cooled therein to a temperature at which it may be exposed to the open air, without further change, for instance, at a blue heat, or about 400 or 500. Because of the exposure of the sheets over their entire area to the heat during this reheating and cooling, the annealing action is very uniform throughout and the time required to treat them is but a few minutes as compared to the large number of hours required in box annealing. Thus we may dispense with blue or box annealin and assure a controlled uniform treatment o each sheet. A

The heating of the sheets may be Very quick, as compared to raising the temperature of the large mass of stacked sheets as in box annealing alone.

The desired conditions may be exactly controlled. There are no difhculties from oxidation because the sheets are at all times enveloped ifi a neutral atmosphere of the products of combustion, which pass from the heating zones throughout the length of the furnace.

The proportions of the compartments shown by way of illustration are satisfactory for passing the sheets at a rate of one foot in about two seconds. Of course numerous variations may be made in the length of the various compartments if different speeds and conibustion zone temperatures are used. 'As set forth in the application above cited, the use of the non-oxidizing atmosphere and scraper-s commercial sheets and also permits a more uniform heat in the upper and lower surfaces of each sheet. A sheet which has been ca1e fully rolled before and well protected until placed in the furnace will be found to be iii good condition for commercial use when the above operations have' been performed.

Thesesheets however must necessarily bc treated if they are for use iii exposed positions requiring fine surface finishing, such as the p exterior of automobile bodies, for example.

They are however perfectly satisfactory for such uses as concealed or rough finish surfaces, such as frame parts, oil pans, storage shelf, metal furniture and the like.

It will be seen however that the use of the process thus far described actually produces finished sheets which have all the desired characteristics for reasonably smooth surfaces, .exact conditions of grain structure and drawability. .Further treatment may be given them as by pickling and a cold rolling operation, which very slightly reduces the gauge and finishes the surface without noticeably altering the grain structure, lengthening the 55 low throng? sheet for example only from V2 to 1 inch in one hundred inches.

By a process using the annealing and normalizing apparatus and system, described in 5 the above designated a plication, the sheets 'to be finished require t e open annealing or normalizing in such a furnace, ollofWe by pickling, and then either a dry c old rolling or, if the sheets require, a wet cold rolling. lf the dry cold rolling is used, they may'be immediately box annealed, which as stated requires many hours, in fact' several days, and again requires the finishing cold roll pass. is, water used.l on the mill, they must again be pickled to remove the rust or results of oxidation occurring immediately, then box 4 annealed and iinish cold rolled as before.

It will be noted that the several days time required for cold rolling is eliminated by the method described, and also by the method employing additional steps vwhich we will now describe, and by which the sheets are normalized, quenched, pickled, washed and cold rolled, and then annealed while controlling the grain growth, and thereafter slowly cooled and finally surface finished or roller leveled. Thus we are enabled to produce, inone `continuous operation, finished sheets for the most exactin requirements and all during a comparative y few minutes of time, eliminating all of the handling necessar to the present intermediate steps and the al box annealing 'or final roller levelling or -separate cold roll pass.

The apparatus for carrying out all of these steps in one continuous process is best understood by reference to Fig. 5 and 6. As here shown, we employ a primary heating zone 11, uickcooling or quenching zone 12, reheating zone 13, in the order named, said zones corresponding respectively to the zones 1, 2 and 3 ofFig. 1. These comprise the present normalizing system as described in the application above referred to. As stated, the vsheets thusv treated v'must be cleaned, pickled, cold rolled and again annealed, and all of this is accomplished by the subsequent continuous stepsas follows:

Upon leaving the chamber 13, the sheets are subjected to a washing operation in which of course the are entire y cooled in the chamber 14, w ile passing over rollers, water being sprayed upon them from above and bepipes '25 and 26, shownas cona common water. sup 1y pi e 30,

` netted wit as indicated in Fig. 7. A suita le ba e.27

e defines one end wall of thisl chamber, the

baille being omitted in Fig. 7 for clearness. 'A drainage opening, as indicated at 28 is provided to carry of the water from this chamber. The sets of conve rollers in this chamber are arrange at Y, different heights, forming an incline to permit drainage of the sheets. Further. drainageyis eflf the sheets are wet cold rolled, that eign matter ected by maintaining the sheets sloping downwardly as they leave the washing chamber. The sheets then pass onto a chain or like conveyor 35 in the pickling chamber 15, shown as arranged to contain a suitable pickle bath through which the sheets are passedwhile carried onthis conveyor. The length of this chamber is such as to permit the proper corrosive action of the pickling liquid, thoroughly cleaning the sheets. They are again passed along a downwardly and an upwardly sloping series of rollers in .another washing chamber 16, also provided. with spray pipes 25 and 26, and closed by a baffle wall 29. Here again lsurplus water may flow to a drainage opening as indicated.

In a subsequent chamber the rollers are shown positioned to move the sheets upwardly, allowing drainage, and are presented to one or more pairs (two being shown) of cold rollers 40. These veryslightly reduce the. thiclmess of the sheet without materially altering the grain structure, but producing almost exactly the desired finished gauge. The sheets pass from these cold rollers to the long annealing chamber 18, where heating burners 19 raise the temperature of the sheets to an annealing temperature, preferably of about 1200o F., and. maintain this temperature, for a sufficient length of time to cause exactly the desired grain growth.

Passing beyond the' zone of the burners, the sheets are allowed to very slowly coolstill within the neutral atmosphere of the products of combustion to a temperature at which they are completely free from danger of scaling, due to exposure of the air, preferably somewhat below 400, although 500 or 600 ares'atisfactory. This is substan tially as described above and indicated by the graph'curves Aon the charts Figs. 2 and 4. Here they are passed through the levelling or flattening rolls 50, which merely fiatten and smooth the surfaces of the completely finished sheet. Subsequent cooling of the sheets is permitted in the open air, either sin ly or in stacks, as desired.

ue to the protection of the sheets throughout the" length of the furnace and the freedom of the rollers from scale, due to the Scrapers indicated at 20 onthe rollers in the hotzones, thfsheets are protected from forrom above-and below, intermediate treatment of washing, pickling,

.washing and subsequent rolling being while the sheets are still kept clean and free from foreign matter, the final resultant product is a very uniform sheet meeting the most exactin commercial requirements.

. Re erence may be had to an application, directed to construction and arrangement of said roller Scrapers 20, filed lg Messrs. Shonkwiler and Macklin, Serial o. 372,812, filed June 22, 1929. By the use of these Scrapers, rider sheets may be eliminated, and when and the sheets are of the thinner gauges two or more sheets may be superimposed While passing through the furnace. The time for passing the sheets through the furnace being at a preferred speed of approximately'one foot in two seconds, We may accomplish this complete treatment in the series of steps described in about thirty to forty minutes, depending on variations due to changes of conditions: v

Thus in about one half an hour a sheet may be completely treated, whereas the time now required for the corresponding steps, particularly due to the box annealing, time consumed in frequent handling, Waiting for cooling between the steps, is actually quite a number of days.

We claim:

l. An apparatus for treating sheet steel comprising a heat treating furnace, a pickling bath and a Washing bath,and means for continuously passing the 'sheet steel through said furnace and baths in the order named, said furnace and baths being closed to exclude outside atmosphere and communieating with each other, and means for heating said furnace and for maintaining therein and in said baths a non-oxidizing atmosphere. ,i

2. An apparatusfor treating sheet steel comprising a heat treating furnace, a pickling bath, a Washing bath and levelling rolls arranged in succession in the order named, said baths and rolls being enclosed to eX- clude outside atmosphere and said furnace being substantially sealed to exclude outside atmosphere, and said enclosures communicating With each other and With said furnace, and means for continuously progressing the sheet steel through said furnace, baths and rolls in the order named, Aand means for .heating said furnace and for maintaining a non-oxidizing atmosphere in said furnace and all 'of said enclosures.

3. An apparatus for treating sheet steel comprising two heat treating furnaces substantially sealed along their respective lengths to exclude outside atmosphere, and means for continuously progressing the sheet steel along a given path extending through said furnaces, said furnaces being. spaced apart from each other relative to the pat-h of travel of the steel, a pickling bath and a .Washing bath arranged along said path of travel in the order named and intermediate the furnaces, said baths being 'enclosed to exclude outside atmosphere, and said enclo- .sures communicating with each other and withV said furnaces and means for heating said furnaces and for maintaining therein and in said enclosuresa non-oxidizing atmosphere. l

4. The combination With a furnace for treating sheet steel and means for continuously progressing the steell therethrough and along a given path, of a pickling bath and Washing bath arranged in the order named along said path of travel, and means enclosing the baths sealed to exclude outside atmosphere therefrom, said means communi-

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