US2158063A - Method of cleaning sheet metal and the like - Google Patents

Description

May 16, 1939. 'w. ||A BRoADFlELD METHOD OF CLEANING SHEET METAL' ND THE LIK s sheets-sheet 1 Filed April 2s, 193e NVENTOR WARD HOI- T BRQADFIELD am M ATTORNEY May 16, 1939. w. BROADFIELD METHOD OFCLEANING SHEET METAL AND THE LIKE Filed Ap'ril 23, 1936 5 sheets-sheet 2 lug @p BYw ATTOREI@ May 16, 1939. w. H. BROADFIELD METHOD OF CLEANING SHEET METAL ANDl THE LIKE Filed April 25, 1956 3 Sheets-Sheet 3 WARD HoLT BRoADFll-:Lo BM ATTORN Y Patented May 16, 1939 UNITED STATES PATENT ol-FYlcav wal-a Emu nroadaeld, scandale, N. Y., assigner to The American Foundry Equipment Company, Mishawaka, Ind., a corporation of Dela- Application April 23, 1936, Serial No. 75,941

ZClaims.

'I'he invention relates to the cleaning oi' metal sheets, 'wire, castings and other metal shapes and, more particularly, to a continuous process for cleaning ferrous metal sheets direct from the rolling operation.

It is well known that sheet material, such as steel sheets, after being rolled from the hot ingot down to the desired gage, have an accumulation of scale and other undesirable matter as a result of the rolling operation. According to prior practices, this scale is removed by separately subjecting the sheet material to various cleaning operations, such as pickling, abrasive blasting, etc., to put the surface of the sheet into clean, smooth form suitable for further finishing operation, as for example, cold rolling, lacquering, enameling, or painting.

According to the present invention, the sheet material may be cleaned in a continuous process following the rolling operation. The sheet material, which-is delivered in strip form from the last pair of rolling rolls, may be turned to a plane convenientl for the subsequent cleaning operation. The strip is then' passed through a normalizing chamber where the strip is raised to the proper temperaturenecessary for normalizing the particular composition of the sheet. The strip is then led directly to a reaction chamber where the scale is acted upon by a suitable reagent, preferably gaseous, to change the composition of the scale to a form more easily removable. The strip is then led directly to an abrading chamber where it is subjected to a cleaning or scrubbing operationin which an inactive atmosphere may exist which will prevent further chemical change in the surface of the metal. 'I'he cleaning or scrubbing process may utilize any mechanical scraper, brusher, or air blast, but the sheet is preferably cleaned by a blast or stream of abrasive particles driven directly from an airless abrader of the type now on the market known as the Wheelabrator. After the sheet has been subjected to a sumcient amount of abrading action to give it the desired nish, it is thenl led directly to a cooling chamber where the sheet is subjected to a cooled inert or reducing atmosphere which preferably has no further chemical action on the sheet and which cools the sheet down to a. temperature sulciently low so that it will not oxidize or corrode in the ordinary open atmosphere.

Some of the advantages of the process are the elimination of the step o f storing and transferring the sheet material between the rollingand cleaning processes; the efficient chemical action of the gaseous treatment for changing the nature of the scale; the scrubbing or abradlng action by the airless abrasive projector in an inactive atmosphere; and the great reduction in cost and increase in efciency'in placing the sheet in nished form ready for transportation to the fabricator, all in a continuous process directly from the hot ingot.

The invention further consists in the new and novel features of operatipn and the new and original arrangements and combinations of steps in the process hereinafter described and more particularly set forth in the claims.

Although the novel features which are believed to be characteristic of this inventionwill be particularly pointed out in the claims -appended hereto, the invention itself, as to its objects and advantages, and the manner in which it may be carried out, may be better understood by referring tothe following description taken in connection with the accompanying drawings forming a part thereof, in which l Fig. 1 is a diagrammatic elevational view of one form of apparatus for carrying out the in plan view of the one form of vabrading chamber, being a horizon# y tal cross-section through the chamber;

Fig. 4 is a vertical longitudinal cross-section of Fig. 3; and y Fig. 5 represents a section on the line 5-5 of Fig. 4.

In the following description and in the claims, various details will be identified by specific names for convenience, but they are" intended to be as generic in their application as the art will permit.

Like reference characters denote likeparts in the several figures of, the drawings.

In the drawings accompanying and forming part of this specification, certain specic disclosure of the invention is made for purposes of explanation, but it will be understood that the details may be modified in various respects without departure from the broad aspect of the invention.

Referring nog,l to the drawings', and 'more particularly to Figs. l and 2'. the last pair 'of rolling rolls is denoted by I0. The sheet material, indicated by 9, emerges from these rolls at the usual temperature and with the desired gage and width. From the last pair of rolling rolls Il, the strip 9 is delivered directly to a set ofrturning rolls II and I2 which turn or rotate the strip to any plane most suitable for the subsequent cleaning operation. If desired, the strip may be supported by a series of rollers I3 located between the sets of turning rolls II and I2.

A vertical plane for treatment after leaving rolls IU has been shown for purposes of illustration as being desirable for the subsequent treating operation, but it will be understood that other planes may also be used, as, for example, planes at a slight angle from the vertical or horizontal or otherwise, depending upon the nature of the sheet and the use to which the product is to be put. Furthermore, if necessary, the plane of the strip may be changed between any subsequent steps.

From the turning rolls I2, the strip is led to a normalizing furnace I4 where it is subjected to the required temperature for normalizing, and relieving the strains in the metal. This temperature will depend upon the composition of the metal and upon the use to which the metal product is to be put. 'I'he normalizing furnace may be of any suitable form, but is preferably of the muffle type in which the hot gases supplying the heat are not permitted to come into contact with the strip, or of the electric type. If desired, the atmosphere of the space occupied by the sheet may be filled with some inert or reducing gases which do not increase the oxidation of the metal. The length of the normalizing furnace and the speed of the sheet therethrough will be arranged to subject the sheet to the necessary normalizing temperature for the desired length of time to complete the normalizing process.

The' metal is 'then directly led to a reaction or chemical treating chamber I5 in which it is sub'- jected to a special chemical treatment, preferably in the form'of gases for converting the scale into a form more easily removable. Any suitable gas may be used. which will have the desired effect on the scale. For example, any gas containing hydrogen in the proper proportion may be used. Suitable mixtures of hydrogen or steam with oxygen and nitrogen may be used. The scale ordinarily found on sheet material from the rolling operations is the black oxide of iron and the chemical reagent may change this oxide into a hydro-oxide of iron which can be removed from the metal more easily than if not` so treated. The reagent chamber I5 may be provided with suitable circulatory pipes I6 and II for keeping the reagent in proper condition. Here again, the length of the reagent chamber will be suiiicient for obtaining the necessary chemical action with the speed of travel of the metal. The temperature of the strip, while passing through the reagent chamber, will be less than that of its temperature in the normalizing furnace. For example, the temperature of the strip while in the reagent chamber may be, say, 1200 centigrade, as a maximum.

The metal is then led to the abrading chamber I8 where it is subjected to the cleansing action of a blast or spray of abrasive in an inert or reducing atmosphere. This atmosphere may be of any gas so long as it has no detrimental chemical effect on the strip at the elevated temperature of the strip. This gas may be one of the so-called inert gases, such as nitrogen, or it may be one of the reducing gases, such as carbon monoxide.

As the strip travels through the abrading chamber I8, it may be subjected to al thorough cleaning action simultaneouslyfon A,both sides.

This cleaning action may be obtained by any of the well-known cleaning and scrubbing apparatus, such as Wire brushes, Scrapers, high pressure abrasive blast, etc., but the cleaning is preferably done with the so-called airless Wheelabrator manufactured by the American Foundry Equipment Company. 'I'his device consists of a motor-driven wheel having a series of rotating impeller blades to the center of which is fed a stream of abrasive particles, such as sand, metallic grit, or metallic shot. The rotation of the impeller blades at suitable speed delivers this abrasive in a swiftly moving, efcient column of abrasive particles, thoroughly cleaning the strip. By the proper arrangement of Wheelabrator speed and type of abrasive, any desired cleaning action may be obtained from a rough scouring action to a fine polishing action. For a more complete disclosure of the Wheelabrator, attention is called to Patent No. 1,953,566, issued April 3, 1934, in the name of Louis D. Peik.

While, as above stated, the mechanical cleaning and abrading apparatus may be of any desired type, when Wheelabrators are used, the mechanical arrangement may be somewhat as illustrated in Figs. 3 to 5, it being understood that these figures are given only for purposes of illustration and are merely diagrammatic.

Referring to Figs. 3 to 5 inclusive, the abrading chamber I8 may have a trough-like bottom I9 for collecting the spent abrasive dropping from the strip 9. A series of Wheelabrators, indicated by 20, may be arranged in the side walls of the chamber I8. In the form shown the Wheelabrators are arranged in two horizontal rows, but the number of rows will depend upon the practical considerations, such as the Width' of the strip. These Wheelabrators may be arranged on opposite sides of the strip 9 to clean the surface thereof simultaneously, the patterns of the blast being somewhat as indicated diagrammatically in Fig. 5.

For supplying the Wheelabrators 20 with abrasive, elevators 22 are provided, located at the bottoms of the troughs I9. These bucket elevators 2 2 supply reservoirs 26' located above the chamber I8 from which supply pipes, indicated in general by 28, extend to the intake funnels 21 of the several Wheelabrator units and through which the abrasive flows by gravity.

For maintaining the proper atmospherewithin the abrading chamber I8, circulatory pipes 3,0 and 3| are provided. It will be understood that the abrading chamber I8 is otherwise approximately gas-tight so that the proper atmosphere is maintained. The Wheelabrators suck in a small amount of gas at the funnels 21 with the abrasive so, as illustrated, the intakes to the Wheelabrators are located within caps or covers 36 communicating with the chamber I8. These caps 36 are removable so that the Wheelabrators may be removed from the chamber in servicing, as necessary, Without tying up the cleaning operation.

It will be understood that the size of the individual Wheelabrators, their number and their disposition, and the length of the cleaning chamber will depend upon actual conditions in practice, the arrangement being such to obtain the desired cleaning effect.

From the abrading chamber I8 the strip 9 is led directly to the cooling chamber 32 where the strip is subjected to the cooling effects of an inactive gas. This gas, like the gas in the abrading chamber, may be of any material so long as it has no harmful effect on the strip. It may be one of the so-called inert gases, such as nitrogen or one of the reducing gases, such as carbon monoxide. For maintaining the gas in proper condition, a circulatory system is provided including a heat exchanger 33 and a blower 34 for continually circulating the gas through the cooling chamber 32 in the direction indicated by the arrows. This gas will be cooled by the heat exchanger to such a degree that the metal 9, as it emerges into the atmosphere, will be at a sufciently low temperature to be safe from any atmospheric oxidation.

From the chamber 32,- the sheet 9 may be pulled by rolls 3'I whence it may be given any desired subsequent treatment, as, for example, cold rolling, or the surface may be coated, such as by enameling, lacquering or painting, or the strip may be cut up into commercial sizes or rolled into rolls as desired.

As the strip 9 passes from one chamber to another, it will be understood that suitable sealing devices, indicated diagrammatically by 35, will be provided for preventing contamination of the atmosphere in the chambers. These sealing devices may comprise suitable spring-pressed members having packing or padding capable of withstanding the high temperature, pressing against the strip as it passes through from one chamber to another. Furthermore, supporting rollers 38 under the strip and guiding rollers 39 on the side faces of the strip may be provided at suitable intervals along the paths of the strip.

If desired, while in the reagent chamber I5 and in the abrading chamber I8, the strip may be vibrated edgewise to further assist in the removal of the dirt and scale. Also suitable arrangement will be made for removing the broken abrasive from the abrading chamber I 8 and for removing the dust. Furthermore, instead of a strip of sheet metal, the product treated may be wire, pipe, tubing, or any other continuous material. The products may also be individual castings or other metal shapes in which case a conveyor will be provided to carry the individual articles through the several treating chambers.

Thus, a process for cleaning a metal strip and other articles has been described which is relatively simple and yet eillcient. The direct cleaning treatment directly following the rolling treatment in the case of sheet metal eliminates all storage and transfer of the strip material between these operations and the continuous linear process permits the steps to becarried out with a minimum amount of time and with aminimum consumption of energy, having all of the advantages of any continuous linear treatment. The normalizing temperature insures proper 'conditioning of the metal and the chemical treatment by the geaseous reagent assists in removing the dirt `and scale without having a deleterious effect on the metal. 'I'he abrading apparatus serves to nish the removal of this dirt and scale, which has been started by the chemical treatment, and the cooling chamber places the metal at a safe low temperature so that no further oxidation or corrosion can take place when the strip is delivered into the ordinary atmosphere of a room. The airless Wheelabrato'r is especially advantageous in that it permits cleaning by a. blasting action with the exclusion of atmospheric air which would cause harmful oxidizing action on the hot metal strip.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The 'method of cleaning ferrous metal which has been raised to an elevated temperature from a previousoperation, which'comprises directing a stream of abrasive particles without atmospheric air on said metal, while at said elevated `temperature within a closed chamber while maini WARD noLirl BaoADFmm.

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