US2213295A - Refining furnace - Google Patents

Description

Sept. 3, 1940. J. R. WYATT 2,213,295

REFINING FURNACE Filed April 12, 1938 4 Sheets-Sheet l INVENTOR JflMES E. WYIYTT BY funk-PW ATTORNEY p 1940- J. R. -WYATT 2,213,295

REFINING FURNACE Filed April 12, 193a 4 Sheets-Sheet 2 FIG. 2

INVENTOR JAMES F. WYATT BYYMTM ATTORNEY $ept.'3, 1940.

' REFINING FURNACE Filed April 12, 1938 4 Sheets-Sheet 3 FIG 5 INVENTOR JAMES A. WYfiTT BY? I ATTORNEY J. R. WYATT 2,213,295

P 1940- J. R. WYATT 2,213,295

REFINING FURNACE Filed April 12, 1938 4 Sheets-Sheet 4 J r J 5 I8 1 E5 00 -0O 0" l 24' 24' .l g

INVEN TOR.

Jfl/WE 5 R W Y/? 77 fMTM ATTORNEY.

Patented Sept. 3, 1940 UNITED STATES REFINING FURNACE James R. Wyatt, Camden,

Electric Furnace Corporation,

N. J., assignor to Ajax Philadelphia,

Pa., a corporation of Pennsylvania Application April 12, 1938, Serial No. 201,487

9 Claims.

This invention deals with a furnace for the melting, refining and holding of metal, and has to do with the construction, lining and maintenance of a lining in such a furnace.

An object of the invention is to provide clamping and restraining means in conjunction with-a furnace shell to prevent expansion of the refractory lining in certain directions and to control the expansion and contraction in other directiohs.

A further object is to maintain a positive pressure on .vital parts. of a refractory lining to prevent cracking of the lining due to expansion and contraction in normal use.

A further object is to provide a novel method for lining a furnace of the type described.

Other objects will appear in or be evident from the specification and the claims.

While the construction herein described is applicable to furnaces in general, and for both the high and low temperature fields, the particular application is for a Wyatt or submerged resistor type furnace for holding, melting and refining steel. The Wyatt type furnace is used universally for the commercial melting of the non-ferrous metals, and because of its inherent economy, low first cost, and excellent alloying characteristics has largely replaced otherfurnaces in its field. It has not heretofore been used for the commercial refining of steel.

The Wyatt type furnace consists of a melting chamber having a depending inductive loop. A transformer iron core' threads the loop and a primary winding on this core, connected with a source of low frequency alternating current induces energy into any metal which may fill the loop. The melting chamber and loop are molded in refractory, and this in turn is contained in an outside metal container, reinforced where necesy, ing mechanism, spouts,.vents and the like. A hole is maintained through the loop 'to admit the transformer core and primary winding, and the metal I case around ,the secondary inductive loop is insulated to" prevent stray eddy currents from heating the outside sh ell. V

" Obviously the furnace will not operate unless there is a conducting medium-in the furnace loop. Hence'it must be started by a high temperature-starting strip, or.by liquid metal. To

avoid undue stresses on starting, the refractory of the metal holding chamber and loop are usually preheated as by a torch beforeanv liquid metal.

is Poured into it.

When liquid metal or a resistor has been-placed and adapted with supporting devices, tiltin the loop and the power has been turned on, the furnace operates by transformer action. If the metal in the loop is liquid, the energy induced in it heats it, and the pinch and motor effects stir it, forcing the heated metal upward toward the furnace bath in the outside portions of the loop, and drawing colder metaldown from the bath in the inside portions of the loop. "In this way heat is transmitted from the loop into the main furnace chamber, and additional scrap may be m melted up to the capacity of the holding cham= ber.

The power drawn by a specific charge depends primarily upon its resistivity, the cross section of the secondary loop, and the voltage applied to 1155 the primary inductor or winding. This power is constant over a long period of time but may vary as the lining becomes old due to the building up and closing ofi of the loop cross section, or the cutting away and enlarging of this section. 2g When the cross section of the loop is diminished the power drawn from the line decreases, and vice versa. 7 Copper as a rule cuts the lining while brasses usually build it up.;

Due to the irregular shape of the lining used in the Wyatt type furnace, the inaccessibility and the proportions of the lower loop, together with the hole which must be left for the transformer iron core, the lining is particularly susceptible to thermal shock, and must be treated with the an greatest care. Over a long period of years those materials most useful for, and the procedure for melting, the non-ferrous metals have been carefully checked or worked out. The, practice has been more or less standardized. g5

It has long been desired to utilize the electromagnetic efiect of the induction furnace for the refining of steel, but until the recent development was completed the results fell short of that desired. The are type furnace has some stirring 4Q effect, but is basically unwieldy, and there is danger of carbon contamination from the graph= ite electrodes. The low frequency coreless induction furnace is inefiiclent, and when sumcient power is applied to melt a charge the electro- 43 magnetic turbulence is entirely too great. The

high frequency coreless induction furnace, while ideal in operation, requires expensive equipment for changing the line frequency to the desired higher frequency. -It is believed that the sub- 5 merged resistor or Wyatt type furnace, adapted as herein described, may prove to be one of the best so far produced for the steel refining field. Five figures have been used toiiiustrate applicants invention."

Figure 4 is a detail drawing of the lower rear portion of the furnace shell of Figures 1 to 3,

' showing the location of various spring members used to keep the lining in compression.

Figure 5 is a detail drawing of the lower left side portion of the furnace shell of Figures'l to 3 showing the location-of various spring members used to keep the lining in compression.

applicant found that the main difllculty in using the Wyatt :type furnace for steel melting or holding lay in the fact that, with the higher temperatures required, the refractory would expand and contract in use, opening up cracks through which the metal would flow, causing ultimate rupture and failure of the lining. To offset this he tried different materials and lining methods, finally solving the problem by" properly clamping or restraining the refractory in a resilient manner, whereby the expansion and contraction could be followed, in substantially all directions, to prevent any cracks from forming.

Specifically, applicant has adapted his furnace so that no vertical movement of the refractory lining will take place at the point where the upper and lower sections of the furnace meet, and so that, .with this part held rigid, the upper and lower parts will be held in compression with respect thereto atall times. He has also arranged means whereby the furnace may be originally lined against a non-resilient backing,

- or whereby the resilient backing may be adjusted from time to time to maintain a given pressure at a given point as the furnacei's operated.

In the figures, like numerals represent like parts.

Referring to Figures 1 to 3, inclusive, l repre-- sents the cover or upper portion of the main holding chamber of the furhace, 2 represents in compression at all strategic points. For instance, in the particular example shown, the roof or upper portion I, of the furnace proper, comprises 4 separate castings each provided with external flanges l4 and internal flanges IS. The external flanges form seats whereby the four parts may be bolted together to form a generally hemispherically shaped double arch top, and

where the top as a whole may be bolted to the lower or charge holding portion, 2, of the furnace. The internal flange l5 forms a retaining member around the entire lower portion of the dome against which the refractory lining of the dome 1 A third layer of refractory I1, is then placed in the actual melting and holding chamber, 3 represents the upper portion of the loop assembly,

and 4 representsthev lower portion of the loop assembly. These parts rest on the usual supporting structure-5, and are-tiltable about an axis through the pouringspout 6 by means of hydraulic pistons I.

Referring more particularly to Figures 2 and 3, an iron core 8, having a primary winding 9, 0 its upper horizontal leg, passes through the uppe: portion of the loop assembly 8' and threads the loop l0. When the primary is energized from an alternating current source It Figure 3), current is induced in metal l2 in the secondary loop l0,

eifecting a heating of the metal, and a circulation denotedby arrows I3, in the loop and main holding portion of the furnace. Applicant has greatly enlarged the main holding" portion, 2, of the furnace to accommodate the largertonnage melts desired in steel refining. over the average nonferrous metal charges, and contemplates furnaces having a capacity of many. tons of steel.

In designing the furnace here described, applicant has taken the usual care to design the shell and lining with the least number of sharp breaks in contour possible, andin addition he has designed expansion devices to hold the lining the shell, rammed hard and dried. Applicant has used mixtures of aluminum silicate or magnesia with success for this inner lining, moistening same with water before using. The rammed lining is preferably air hardened for 24 hours and then baked hard. After the refractory lining has been prepared as stated, then the bolts holding the parts together are removed, one side at a time, the metal spacing strip is removed, and the parts are again bolted together with adjustable spring compression bolts l8. When the whole assembly is complete the adjustable bolts are drawn up to a definite compression. While applicant has described one specific lining it will be understood that the lining is not a part of this.

invention and that any suitable lining may be used.

The lower half of the furnace melting chamber 2 and the upper and lower parts of the loop assembly 3 and 4 respectively are then lined as one shell. The lower part of the metal melting and holding chamber 2 is made as arigid shell, and to this is bolted the upper half of the loop assembly 3. The lower half of the loop assembly 4 is then bolted to the upper part 3 at the flanged section I9, 20 and to the depending arm 2|, on the front of the furnace. While the furnace is being lined the joints at I9, 20 and 2| are made rigid, fixed spacers being used between the flanges I8 and 20, but on operation this joint is made adjustably resilient. Within the lower holding portion 2, at either side, are false or auxiliary side members 22. These are held inwardly from the sides of the main shell by rigid bolts during the" lining operation, and then during operation, are resiliently clamped by springs 23, and bolts 24, to obtain a deflnite pressure on the refractory lining.

The part of the shell around the upper portion of the loop assembly 3 is tapered on all four sides, the horizontal sectional opening in the shell being less at the top than at the bottom. This is shown most clearly in Figures 4 and 5. In addiill refractory,

'aei aaes to the outer shell casing byother bolts or by welding.

The sides of the bottom portion 6, oi the loop assembly are supplied with auxiliary members 2?, and the back with an auxiliary 28. These are lined and operated exactly as are the corresponding parts in section 3, just described. The front of this part of the shell, as in the section 33, is rigid at all times with respect to the back and sides, but is adapted to slide along the rollers 29 on the depending supports ll from section 3. Section 4 is clamped against these rollers by bolts 36 which permit no movement away from the rollers, but which because of slotted bolt holes 3i do permit movement along the rollers. A movement of almost an inch has been allowed in this direction, while a movement oi the order of /3 inch has been allowed elsewhere.

The lower part of the furnace, constituting the lower or main holding portion 2, the upper loop assembly lined. in much the same manner as the dome or cover. In the case cited, the same materials are used. The outside or auxiliary shell or retaining members are first lined with a double layer of sllocel or other suitable insulating brick. This brick work is formed around the opening 8 left for the transformer core, and a pro-formed transite or asbestos cylinder 32 is then slipped into place as a mold or backing for the rammed refractory. The loop it is made in the usual manner. A hollow wood form is placed in position around the asbestos or transite cylinder and it, a mixture of aluminum silicate or magnesia, slightly dampened with water is rammed in hard between it and the cylinder, and between it and the outer brick lining. The lining, thus made, is allowed to air dry for about 24 hours and then is baked out, usually a gas flame.

The wooden form for the loop is burned out, leaving the refractory loop channel. Depending on the use the furnace is put to and the preference of the operator any other suitable lining may be used, and no claim is made in this application for the particular lining described.

Before operation the springs l8 and 23, all over the'furnace shell, are brought to bear on the resilient joints and plates, and are adjusted to the proper pressure. Applicant has found a pressure of the order of 500 pounds effective. The

, bolts holding these parts are then backed on and the lining is thereafter maintained in selective compression.

On use, the lining is preheated to nearly 280W- F. and molten steel is poured into the loop. The power is turned on and the metal in the loop is heated and circulated into the upper part of the furnace where cold scrap melted down as required.

During operation or after shut-downs the springs may be released or the springs and/or bolts tightened, as desired, to follow up any natural expansion or contraction of the lining.

An inspection of the drawings will show that applicants method of restraining the refractory expansion and contraction leaves no place where the lining can develop damaging strains. The tapered portion 3 prevents movement of the lining upwardly at this position. The loop proper is held rigidly against the solid front oi the furnace at this. point, and the resilient back and sides. tend to hold it against this solid front at all times. Any pressure in a downward direction is opposed by the springs operating around the flanges l9 and 2c, and the solid front, with the and the lower loop assembly 3, are

may be added and.

3 rollers 29, permits movement along the rollers but not away therefrom. No shearing force can be exerted therefore on the lower loop at this joint, and as in the upper loop portion, the resilient plates at the back and sides tend to hold the lining in compression against the onerigid side.

The lining in the main holding portion, 2, of the furnace, can push only outwardly and up. It is held in the outward direction by the resilient plates 32, and in the upward direction by the resilient flange B5 of the dome.

It will be seen therefore that applicant has devised a lining which is restrained against movement in certain critical directions and is free to expand in any other direction, and that the various compression forces follow each expansion and corresponding contraction in such manner that voids cannot form and that strains cannot result to rupture the lining. In the particular form of applicant's invention shown in the figures metal is charged through a charging door at the rear'of the furnace. An opening 3-3 is provided at the top of the unit for the'escape or entry of gases or for other purposes. I

Applicant is aware that linings have been made heretofore, utilizing some compression means, but he does not believe that any such previous at tempts have been or are successful in the type furnace with which he has been working. Applicant has built and operated these furnaces, utilizing all the skill and knowledge known to the art, but has not until his present invention been able to adapt a lining of the class described for commercial refining of steel. While he is most interested in protecting his invention as it applies to' the Wyatt type furnace he realizes that there are other furnaces in which itmaykhave value, and he therefore desires to protect by United States Letters Patent, all that is claimed.

I claim:

1.121 a furnace for holding liquid metal, a hearth, 8. depending inductor loop opening into said hearth, only rigid refractory material around and forming said hearth and loop, a shell substantially surrounding said refractory material and plates between said shell and said lining adjustably resiliently spaced from said shell and cooperating with said shell to hold said lining in adjustably resilient compression over substantially its whole external surface.

2. a furnace for holding liquid metal, hearth, 2. depending inductor loop opening said hearth, a rigid refractory material around and forming said and loop, an external shell portion surrounding said refractory. a portion of suhsta cone shape at the upper part 61 the loop, a resiliently at= tached portion lower part of the loop whereby the refractory the loop is held in compression against J e cone poron, resilient and said shell on all shell spaced therefrom by additional spring.

means in conjunction with the aforesaid iii means mmntg the in said to shell in a state of adjustably resilient compression over substantially its whole external area. 4. In a melting furnace of the submerged resistor type an outer shell comprising hearth and upper and lower submerged loop portions, trunnions attached to the sides thereof and supports therefor, Spring and bolt means resiliently clamping the lower loop portion to the upper loop and hearth portion and auxiliary shell members within said loop portions resiliently spaced from three sides thereof, the shell section at the upper part of the loop section being smaller than at lower sections whereby a refractory lining in said loop portion may be held against vertical movement upward from this point and whereby movement in any other direction may be controlled.

5. In a melting furnace of the submerged resistor type, a hearth portion, trunnions attached to the side members of said hearth portion and supports therefor, a loop section depending therefrom, a metallic shell surrounding the sides and bottom of said loop section, said shell having a smaller section at the top than elsewhere and having one rigid side and other resilient sides and bottom whereby a refractory lining in said shell may be kept in compression'over its entire surface area.

6. In a melting furnace of the submerged resistor type, a hearth portion, trunnions attached to the sidemembers of said hearth portion and supports therefor, a refractory lined loop section depending therefrom, a metallic shell comprising upper and lower portions surrounding the sides and bottom of the refractory of said loop section said upper portion having a top opening of restricted section as compared with lower sections, having one rigid side, other resilient sides, and depending guide and bearing arms for the lower portion of said shell,.a lower portion of said shell comprising a rigid other resilient sides, the whole lower portion being resiliently clamped to said upper portion, bearing on and being movable along said depending guide and bearing arms whereby the refractory lining in said loop section may be held in a desired state of controlled compression.

7. In a furnace of the submerged resistor type a hearth portion, trunnions attached to the side side and bottom and members of said hearth portion and supports therefor, a metallic refractory lined shell depending from said hearth portion forming a channel or submerged resistor loop and comprising upper and lower sections, the upper portion of the upper section having a mouth of smaller section as compared to other sections, and resilient clamping means between the two sections whereby the refractory lining in said loop section may be held in a desired state of controlled compression.

8. In a furnace of the submerged resistor type a hearth portion, trunnions attached to the side members of said hearth portion and supports therefor, a metallic refractory lined shell depending from said hearth portion forming a channel or submerged resistor loop and upper and lower sections resiliently clamped together,

a depending arm rigidly fastened to said upper section forming a guide and bearing for said tions surrounding said lining and depending from said hearth portion, said shell having an upper side inclined toward and a lower side substantially parallel to the plane of said loop and in rigid contact with said lining, the lower side being divided from but resiliently clamped to said upper side, guide means comprising an arm rigidly attached to the upper side member but slidably bolted to the lower side member allowing linear movement between the twodirectly toward and away from each other in a. direction parallel to the plane of the loop, other side members within said shell resiliently spaced therefrom but in rigid contact with said lining, the upper members inclined toward the plane of the loop at their-upper extremities.

JAM RWYATT.

Images