US2695248A

US2695248A - Furnace conveyer element and manufacture thereof

Info

Publication number: US2695248A
Application number: US65384A
Authority: US
Inventors: Martin N Ornitz; Ray H English
Original assignee: Blaw Knox Co
Current assignee: Blaw Knox Co
Priority date: 1948-12-15
Filing date: 1948-12-15
Publication date: 1954-11-23
Anticipated expiration: 1971-11-23

Description

Nov. 23, 1954 M. N. ORNITZ EI'AL FURNACE CONVEYER ELEMENT AND MANUFACTURE THEREO Filed Dec. 15, 1948 IVNVENTORS N. ORNITZ & H. EN

MARTIN RAY cLligaw m mg,

United States Patent ()fi ice \I I PatenteiNov. 23,-.1954

ages of silicon and .iron are approximately 50% each; 2,695,248. 1 held to the range'betwecn 40% and" 60%.

FURNACE-CONVEYER ELEMENT 'AND' MANUFACTURETHEREOF Martin N Oi'nitz and Ray English; Pittsburgh; Pa,

assignors,b'y mesneassi'gnm'ents, to" Blaw-Knox Company; Pittsburgh, Pa}, a -corporatitim of- Delaware- ApplicationrDecember-IS; 194s; S'erialSNo. 65,384- 6 Claims cl; 117-45 This-invention relates to and the manufacture thereof.

thereby in the presence of-Lthe furnace atmosphere at temperatures above 1-200 F2, as, for example, inthe :annealing'ofsheets at about 1600 F., yetare ofrelatively simple construction and economical to manufacture.

Our invention is applicable .to furnace'conveyor elements and the manufacturethereofgeneralIy butfor purposes of explanation and *illustratiomthe"invention will be 'described'as embodied in a' furnaceconveyor roll and as practiced in'the manufacture'iof such a'roll; we shall describe the .st'ructureand' manufacture of 'a' roll for conveying sheets through an annealing furnace.

Those skilled in the art are aware. of the diffiCLllfieS encountered in. the useof metallic conveyor elements in heating furnaces. For example, conveyor rolls used in sheet annealing, furnaces tend to collect accretions of material from the sheets which dentithe sheets'passing thereover. The problem is .partieularlyacute in then-eat.- ment of high-silicon steels and othersteels.requiringhigh annealing temperatures. Thelphenomenon of. accretion formation is complex-and is' influencedtbyfthescomposion the surface of silicon carbide mserts when used-in the annealing-of high" silicon steels: Fnrthermore;.the provision and application of the refractory inserts entail substantial labor and expense; The-present invention is an improvement rendering refractory-inserts unnecessary. y

We provide a furnace conveyor element having an are not fully sat- The ferro-silico'n may be-applied .tov the conveyor fele ment body in any suitable wa We find it convenient to spray'the ferro-sil'icon onto the using any metalizing spray gun art. The thickness of the ferro-silicon coatingshould be between about .005" and about .030. To beadesirably effective the thickness of the coatingshould be not less than .005", while if the-thicknessof thecoating is increased materially beyond .030 thecoating is subject to spalling. Thecoatingis brittle-and iseffective when maintained within the thickness" limits indicated.

e prefer to apply the ferro-sili'con to the conveyorelement body in a thickness of about .015

The conveyor element body-With' the-ferro-silicon' applied to the surface thereof is slowlyheated to atem pera ture in the neighborhood of 1600 F. to

thermal expansion oft-he roll and the thermal expansion coating. and isheld at 1600" F. in an oxidizing atmosphere for a su-fiic'ient time. to form a stable oxide. Conveniently the heating maybe effected in stages at successively-higher temperatures until-ate perature of about 1600 F. is reached, at which temperature the roll is held for about twohours.

The heat treatment of the coating-converts it to a' large extent into a stable oxide and also bonds it to the roll surface by alloying, at the interface between theroll sur- The ratio of each of-iro'nand silicon in the coating'is in'the range'30-70%. The best results are obtainedwith about 50%f each of ironand silicon, within a tolerance of 10% either way, or Within the range of'40%-60%.

In the accompanying. drawings we .have'illustrate'd a presentpreferred method of practicing the invention andhave shownv a present preferredzform of furnace conveyor element preparedin' accordancetherewith in which.

Figure 1 is av perspectiveview of a furnace conveyor roll shown as having its"work=enga'ging surface sprayed with ferro-silicon;

Figure 2 is a diagrammatic fragmentary cross-sectional view to enlarged scale through. the body'of the roll;!

Figure 3 is. a diagrammatic and fragmentary plan view of a lower portion ofa sheetsteel annealing, fur' nace having roll's' therein'of'the kind illustrated in Figures land 2; said planviewbeing-taken generally alonglineiIII-III of Figure 4; and

Figure 4.-is. a diagrammatic and fragmentary view in elevation of the furna'ceportion shownin Figure 3taken generally along li'ne IV--IV thereof.

Referring now more The roll comprises a body or Work-engaging portion 3, necks 4 and conical portions 5 joining the necks to the roll body. The roll may be a steel or alloy roll of known composition. There is provided means for spraying finely divided ferro-silicon onto the roll body 3, such means being shown diagrammatically in Figure l as a metalizing gun 6 by which the finely divided ferro-silicon is melted and applied. Preferably the roll is rotated and the gun traversed along the roll until the roll body 3 is covered to the thickness desired.

The rolls 2 may be rotatably mounted by their journals 4 in bearings 8 set just outside refractory walls 9 of an annealing furnace 10.

The roll body is covered with ferro-silicon to a depth approximating .015". Preferably the ferro-silicon contains 50% iron and 50% silicon. The roll with the ferro-silicon thereon may then be heated slowly to a temperature of about 1600 F., taking several hours to reach that temperature, to bond the coating to the roll without spalling, and the temperature of the roll may then be held at 1600 F. for about two hours in air to oxidize the silicon. The coated and treated roll is cooled in the furnace; the cooling may take about eight hours. By this treatment the coating is alloyed to the roll face and there is formed a very stable ferrous silicate saturated with iron and silicon with excess iron and silicon probably also present. Each of iron and silicon is present in the coating in the range 3070%.

Figure 2 shows the roll body at 3 and the coating at 7. Due to the extreme thinness of the coating it is diificult to illustrate, but Figure 2 is intended to indicate in more or less diagrammatic fashion the ferrous silicate coating and the bonding of the coating to the roll body.

When conveyor elements other than rolls are made the process employed is generally the same, the coating being applied to the surface portion or portions of the conveyor element normally coming in contact with the work during operation of the furnace.

While we have shown and described a present preferred embodiment of the invention and have illustrated a present preferred method of practicing the same, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

We claim:

1. A method of making a furnace conveyor element comprising depositing ferro-silicon containing between about 40% and about 60% by weight of silicon onto the surface of a metal conveyor element body to form thereon a coating of ferro-silicon having a thickness between about .005" and about .030", gradually heating the surface of the metal conveyor element body and the coating of ferro-silicon thereon to raise them slowly to a temperature in the neighborhood of 1600 F. to bond the ferro-silicon to the body and holding the same in the presence of oxygen at the said temperature in the neighborhood of 1600 F. to oxidize the ferro-silicon to a ferrous silicate compound, whereby in the use of such conveyor element the formation of accretions thereon may be avoided.

2. A method of making a furnace conveyor roll comprising depositing ferro-silicon containing about 50% by weight of silicon onto the peripheral surface of a metal roll body to form thereon a coating of ferro-silicon having a thickness of about .01 gradually heating the surface of the roll and the coating of ferro-silicon thereon to raise them to a temperature in the neighborhood of 1600 F. to bond the ferro-silicon to the roll body and holding the same in the presence of oxygen at the said temperature in the neighborhood of 1600" F. to oxidize the ferro-silicon to a ferrous silicate compound, whereby in the use of such conveyor element the formation of accretions thereon may be avoided.

3. A conveyor element for a metal heat-treating furnace or the like, comprising, in combination, a metallic conveyor element body, a coating on the surface of said body to engage work and to inhibit accretions, said coating consisting essentially of ferrous silicate saturated with iron and silicon, the weight of silicon in said coating relative to the combined weights of iron and silicon being between about 30% and about 70%, said ferrous silicate being a deposit of iron and silicon on said surface of said body which has been oxidized in place, said coating further having a thickness of not less than about 0.005

inches, said coating still further being firmly adherent to said surface of said body and having a smooth outer suriacg extending over the work-supporting area of said 4. A conveyor element for a metal heat-treating furnace or the like operative at about 1200 F. or above, comprising, in combination, a metal conveyor element body, a coating bonded to the surface of said body to engage work and to in bit accretions, said coating consisting essentially of ferrous silicate saturated with iron and silicon, said ferrous silicate being formed by depositing and oxidizing ferro-silicon on said surface of said body to form a firmly adherent coating in situ, the weight of silicon in said ferrous silicate relative to the combined weights of iron and silicon therein being between about 30% and about said coating having a smooth outer surface extending over at least the work-supporting sur face portion of said body, said coating further having a thickness of not less than about 0.005 inch.

5. A conveyor roll for a metal heat-treating furnace or the like operative at about 1200" F. or above, comprising, in combination, a roll body of steel or alloy, a coating adhering to the surface of said body to engage ferrous Work and inhibit accretions, said coating consisting essentially of ferrous silicate saturated with iron and SlllCOIl said ferrous silicate being formed by depositing ferro-sllicon on said surface of said body and oxidizing said ferro-silicon in place, the weight of silicon in said ferrous silicate relative to the combined weights of iron and silicon therein being between about 30% and about 7 0%, said coating having a smooth outer surface extending over at least the work-supporting portion of said surface of said body to a thickness of at least about 0.005 inch, said coating being firmly bonded to said surface of said body at the interface between said coating and said surface.

6. method of making a furnace conveyor element comprising depositing ferro-silicon containing about 30% to about 70% by weight of silicon onto the surface of a metal conveyor element body to form therein a coating of ferro-silicon having a thickness between about .005 inch and about .030 inch, gradually heating the surface ofthe metal conveyor body and the coating of ferros1licon thereon to raise them slowly to a temperature in the neighborhood of 1600 F. to bond the ferro-silicon to the body, and holding the same in the presence of oxygen at the said temperature in the neighborhood of 1600 F. to oxidize the ferro-silicon to a ferrous silicate compound, whereby in the use of such conveyor element the formation of accretions thereon is inhibited.

References Cited in the file of this patent Rawdon: Protective Metal Coatings (1928), The

Chemical Catalogue Company, Inc., New York, New York.

Claims

1. A METHOD OF MAKING A FURNACE CONVEYOR ELEMENT COMPRISING DEPOSITING FERRO-SILICON CONTAINING BETWEEN ABOUT 40% AND ABOUT 60% BY WEIGHT OF SILICON ONTO THE SURFACE OF A METAL CONVEYOR ELEMENT BODY TO FORM THEREON A COATING OF FERRO-SILICON HAVING A THICKNESS BETWEEN ABOUT .005" AND ABOUT .030", GRADUALLY HEATING THE SURFACE OF THE METAL CONVEYOR ELEMENT BODY AND THE COATING OF FERR-SILICON THEREON TO RAISE THEM SLOWLY TO A TEMPERATURE IN THE NEIGHBORHOOD OF 1600* F. TO BOND THE FERRO-SILICON TO THE BODY AND HOLDING THE SAME IN THE PRESENCE OF OXYGEN AT THE SAID TEMPERATURE IN THE NEIGHBORHOOD OF 1600* F. TO OXIDIZE THE FERRO-SILICON TO A FERROUS SILICATE COMPOUND, WHEREBY IN THE USE OF SUCH CONVEYOR ELEMENT THE FORMATION OF ACCRETIONS THEREON MAY BE AVOIDED.