US1765955A - Apparatus for annealing rolled-metal products - Google Patents

Description

Patented June 24, 1930 i UNITED lsikras (PATENT vor-'l-Ylca EDHUND von HAL'IITZ, OF GARY, INDIANA, AND FREDRIK WILLE, OF 'WILMETTE ILLINOIS, ASBIGNORS TO H. A. v.BIR'ASSIILR'I & COMPANY, OF CHICAGO, ILLINOIS, .A

CORPORATION OF ILLINOIS Humanes ron ANNEALING Roman-METAL PRODUCTS Application led January 5, 1927. Serial No. 159,072.4

This invention relates to a new method of annealing rolled metal products, such as,

sheets, strips, or wire, made of steel, copper or other metals which can be rolled or drawn.

In the manufacture ofsuch materials it is generally necessary to anncal the `rolled tops are set on the bottoms and sealed in sand. 'The seal is necessarily shallow, which often results in air being sucked into the interior of the box during the slow cooling process. These boxes are put into heating furnaces where they are brought up to the proper tcmvperature of annealing. They are generally held in these furnaces for a period of from twelve to twenty-four hours, and are then rcmoved from the furnaces and set to one side for cooling. The control of the temperature is more or less uncertain during this operation, owing to the large number of small units which have to be individually handled and which it is impossible to subject to exactly the same conditions.- The process also has the objection of requiring a great deal of labor and of space. The process is also wasteful of fuel, ue to the necessity of heating and cooling the great inert mass of thek annealing boxes. The equipment for box an nealing is large, cumbersome and expensive. The annealing boxes have only a. compara.

tively short life and they are expensive to replace. The loading of the boxes, their charging into the furnace, their heating, drawing and unloading, requires a long time and much labor. For even a moderate tonnage of box annealed wire or strip, the annealin equipment is very extensive.

. Furt ermore, whereas the annealing .process should be carried on in an absolutely reducing or neutral atmosphere so as to avoid oxidation, the drawing 1n of air causes oxidation of the annealed materials.l In the case of cold rolled or cold drawn materials this is particularly objectionable, as a product free from surface oxidation is desired. In the presentvmethod of using annealing boxes this cannot be prevented as in the heating of the box and of the charge therein the air entrapped under the cover expands and escapes through the sand seal, whereas when box and charge cool off, a partial vacuum is created and air is drawn in. While the original air contained in the box is not so detrimental to the surface of the metal, as the iron oxide which is formed is reduced again at the high annealing temperatures by the carbon contained in the metal, however, at the lower temperatures which are reached during the latter Aor cooling period of the annealing process, the temperature is not sufficient for the reaction between the air and the carbon, the aflinity of the oxygen for the iron being much greater at the lower temperatures than it is for carbon; conse uently, oxidation or scaling of the metal w ich takes place re- I mains as a defect on the material. This oxidation of the metal in the case of strip steel or wire not only scales the surface but also discolors it and changes a bright surface to one ranging from light straw to llight blue in color. While it is possible to prevent air from entering the annealing box during the cooling process by introducing generous quantities of reducing gases under the cover, this is an expensive process, diiiicult to execute. 4

`urthermore, for maximum grain refinement, high annealing temperaturesare required, and precautions against the material packed in the boxes welding together. are expensive. In fact, withbox annealin ahigher tem erature is liable to give just t e -opposite e ect tothat obtained with open annealing, viz. the grains in the annealed steel become lar e, its ductility is correspondingly less, and 1ts brittleness is greater, for the reason that the cooling of the steel in the boxes is l method of annealing hereinafter described, the coolling down from the critical temperature is fast and no o portunity is given to form large grains of errite. Another drawback of box annealing is the uneven temperature between the outer and inner portions in the case of annealing coils of wire or of strip, which with very careful work may be reduced to a difference of about 50 degrees Fahr., but which is still toogreat to produce a uniform material well annealed t roughout.

"-.We have invented a new method which prevents oxidation of the steel or other metals durin the annealin process, which provides etter control o the temperature during the annealing process and a more uniform application thereof to the metal, and whlch greatly reduces the labor and fuel cost of the annealing process and requires much less space in its operation.A

Our invention will be better understood by referring to the attached drawing showing a preferred method of-applying our invention.v On the drawing is shown a vertlcal cross-section of a contmuous annealing furnace, in which 1 is a piece of strip steel or rolled or drawn wire fed in over theroller 2, into a seal box or chamber 3. The materlal is carried around a roller 4, and up through a vertical riser chamber 5, Which preferably is equipped with radiating ribs 6 on 1ts inner surface. The seal chamber 3 and the vertical riser chamber 5 are filled with a sealing material, such as charcoal or sand, or a mixture of both, or other material which -will prevent the access of, air. This material fulfills the purposes of pre-heating the metal, and the charcoal at the same tune acts as a reducing agent in respect to the air which might be carried into the apparatus with the steel. The sealing chamber 3 is heated by a combustion chamber 7 with gas, oil lor other convenient fuel, the waste gases of which pass upward and around the riser chamber 5 through jacketed space 8 and out through stack 8, the heat from the waste gases being transmitted through the walls of the same and through the radiating fins into the sealing material which surrounds the sheet, strip or wire which is to be annealed. v

From chamber y5 the strip or wire passes through an annealing furnace comprising a communicatingseries of vertical annealing chambers, as 10, 10a, 10b, 10c and 10, being guided through the same over rollers 9, 9F, 9b, 9, 9d and 9. These chambers are preferably heated electrically by heating elements,

as 11, 11a, 11b, lic, 11d, 11e, 11f, 11S, 11h, but they can also be heated by other means, the heat being preferably radiated from vertical partition walls when other than electric heaters are used; in the case of electric heaters these in themselves form the partitions. At

the annealing chambers, preferably at the bottom of the last one, is another seal box 13 filled with sand or other sealing material,

through which the strip of metal, or strand of Wire, is carried over roller 14 into a cooler 15, which may be a sectional pipe or box, preferably made of copper or other metal of high heat conductivity, having radiating ribs 16 on its outside surface, to facilitate quick cooling. .Rollers 17, 17n located at the top and bottom of this box carry the material down through a similar section 15a of the cooler into seal box 18 lle'd with oil or water, or other sealing liquid or solid, as may be required to give the best finish to the material. We have found that oil at a moderate temperature is particularly effective in preventingtoxidation of annealed material.

While the apparatus as described presents the simplest form to carry out our invention, many variations may be used. For instance another method is to carry the strip or wire parallel to the electric heater elements or heated partition walls, and centrally between them, b feeding it over pairs of rollers instead of singles at the top and bottom of the chambers.

To start the operation, the strip or wire is fed over the rollers in the furnace, which can readily be done by hand, the lids 12 being removed and the sealing boxes being empty. When the first ieee, which may or may not be of the-.same kind that is to be annealed, has been pulled through so that its ends protrude from opposite ends of the furnace, the strip or Wire to be annealed is welded on to it by spot welding at the feed side of the furnace. It can also be fastened on by other means, and in case of wire it' can be hooked onto the perforated feeder strip. The seal boxes are then filled, the heat is turned on, and the strip or wire is slowly moving through the annealing furnace by any suitable power operated means capable of speed regulation, at a rate of speed which can be accurately calculated to carry through the annealing process exactly to the theoretical requirement. The temperature is carefully controlled by pyrometers inserted atl various points of the annealing chambers. vIf the pyrometers indicate too high or-too low a temperature, the speed is increased or decreased, which effects an immediate change.

the result being much quicker than that of lincreasmg or decreasing the heat, which can be done as a secondary remedy. When almost the entire length of la stri of wire or v coil to be annealed has been fedinto the furnace, the next -piece is Welded or fastened onto the'end ofthe iirst' one, and so on, so that the annealing operation may go on contmuously from the time it hasbeen tirst started without any interruption yof the process. Changes can be made from wide strips to narrow strips without stoppage of the operation, o'r even from heavy wire to light wire, and as amatter of fact from one materialto another, 1f such an occaslon should arise, provldlng only that the same can be welded or fastened together mechanically.

It Will be readily seen that this method of annealing guarantees the presence at all times of a neutral or reducing atmosphere. At the very start of the operation, the original air contained in the chamber is quickly expanded by heating, and displaced by the evolution of carbon monoxide gases from the charcoal contained in the seal box and the annealing chamber; during the process this lis aug` terial in a vertical position suspended freely and not in contact with any surface except that of the rollers, which are driven' and therefore present no friction surface. Thereby damage to the surface of the material is Jrevented. The material -in the seal box is ne sand and charcoal,thecharcoalbeingsoft, and the fine sand having an effect of polishing the material. There is no opportunity anywherev in this operation for the material' to become scratched, which is one of the important features of this invention, much of the good material being destroyed in the box annealing` process through scratches.

While We have described a method particularly adapted for annealing and heat treating strip steel and wire, it will be understood that the same process can be carried out by a different design of apparatus, by employing various heating means, and other means of sealing, transporting and cooling the material Without deviating from this invention. Also while this process has been particularly developed to tr/eat steel products, it is equally applicable to other metals which require annealing or heat treating.

It should be understood that the term strip is used in the claims in a generic sense,

to comprehend any elongated flexible form in which the materlal to be treated may be fashioned, whether it be in the form of a thin fiat band,such as is ordinaril termed a strip, or in the form of wire, or o links connected in'the'form of a chain, &'c. l

In addition to the aforesaid process our invention includes also the apparatus illustrated and described.

What we claim as our invention and desire to secure by Letter Patent, is-

1. In a device o the class described, the combination of a heating furnace and an annealing chamber comprising a continuous zigzag passageway in which the passes are disposed substantially vertically, the passes in the furnace being separated by walls adapted to give oil' heat to the material between them, and the passes in the annealing chamber being separated by walls adapted to dissipate heat, a U-shaped seal between the furnace and the annealing chamber filled.

with granular material and having a circular guide over which the strip to be treated is trained, an entrance seal of granular material for the furnace, and a liquid seal for he exit of the strip from the annealing cham- 2. In a device of the class described,'the combination of a heating chamber comprising a zigzag passagewayconsisting of substantially vertical passes, and an annealing chamber comprising substantially vertical passes', heat supplying walls for the vertical f passes in the furnace, and heat dissipating Walls for the passes inthe annealing chamber, and a granular U-shaped seal separating the passes of the furnace from the passes of the annealing chamber.

3. In a furnace of the class described, a heating chamber comprising side and end walls, granular material disposed in the bottom of the chamber, a U-shaped outlet from the chamber filled with granular material, a zigzag passageway comprising substantially vertical passes disposed Within the chamber, said passes being separated by heat supplying walls contained Within the chamber, removable cover means for the passes of the chamber, means for heating the incoming stri a of-material comprising a substantially U-s aped passageway filled with granular material anfhcontaining a guide in the bottom of the U, and heating means for heating said granular material.

4. In a device of the class described, a zigzag passageway comprising a plurality of passes, means for training a continuous strip through the passageway, means for sealing off one part of the passageway from the remainder,'means for heating the passes in said one part, and means for cooling the passes of the remainder, and a liquid outlet seal for the last pass.

5. In a device of the class described, a cooling chamber comprising a pluralit of substantially vertical passes, each pass eing delined by a tubular heat radlatlng wall, and

a roller at the junction of each pair of asses' for conducting a metal strand throug said passes out of contact with the wall thereof.

6. An annealing chamber comprising an inverted U-shaped passageway having a roller at the upper end of the passageway for guiding a strip to be annealed, the wa ls of the passageway being defined by metallic heat rad1at1ng members, a U-shaped granular in- 1ct seal for the introduction of a heated metallic strip, and a, U-shaped liquid outlet seal `-for withdrawing the strip from the annealin chamber. M g. Ina device of the class described, the

combination of a closed heating chamber comprising a generally zig-zag passageway conslsting of substantially vertical passes,

heat supplying walls forming parts of the passes, rollers at the junctions of the passes for forwarding a metal strand to be treated out of contact with the walls of the passes and an annealing chamber comprising substantially vertical passes, said latter chamber comprising heat dissipatlng walls and having strand forwarding rollers for forwarding the metal strand out of contact with the walls, and a granular U-shaped seal separating the passes of the furnace from the passes of the annealing chamber, there being removable portions at the upper end of the heating chamber and at the upper end of the annealing chamber to facilitate training of the metal strand over the rollers.

8. In combination, an annealing chamber havin an entrance chamber provided with a seal o charcoal and providing a zigzag passageway having an outlet seal of granular material, means yfor passing a metal strip through said entrance seal, said passageway and outlet seal and maintaining the strip out of contact with, the walls of said chamber, and means for heating said entrance chamber for bringingthe strip to an annealing temperature. Y

9. In combination, an annealing chamber havin" an entrance chamber provided with a seal o? charcoal and providing a zig-zag pasc sageway having an outlet seal, a cooling chamber having walls for dissipating heat, an exit seal for the cooling chamber, means for passing a metal strip through said entrance seal, said passageway, said outlet seal v and cooling chamber, while maintaining the stripfout of cont-act with the walls of said cham-bers, and means forpheating -said entrance chamber to bring the strip to an an# nealing temperature.

EDMUND voN MALTITZ.

FREDRIK WILLE.

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