US1989186A - Method of forming rolls - Google Patents

Description

Patented Jim.A ze, 11935 UNiTED STATES PATENT orFicE 1,989,188 Mn'rnon oF FonmNG nous .rm Hubert Louis Dennis, East orange, N. Lt. I

Application october s', 1932, serial No. 636,283

4 claims. (ci. asa-14m) This invention relates to improvements in methods of forming rolls from nitrided steelsand other alloys and the improved compositions and articles'prepared therefrom.

` monia. Such processes are inherently costly and tively high heats, Thus, it will be seen that, up-

Hitherto, it has been proposed to nitride aluminum bearing steels and-other alloy materials by exposing articles prepared therefrom to atmospheres of nitrogeneous compounds such as am? lacking in eillciency, due to the fact that penetration of the surface of the metal article by the nitrogen alloy, the so called nitride,

While the nitrides thus formed apparently exhibit an inhibiting effect on the nitrogen gas liberthat the iron nitride or other nitrides formed are very resistant to decomposition, even under relaon ,the formation of a stable surface layer of nitriderthe underlying unreacted metal 4is protected from the nitrogeniferous composition used,

and the surface or skin itself. immediately after' its formation, becomes a barrier or bar to the smooth continuance of the nitriding reaction. As

pointed out above, the attainment' of a nitrided case of substantially 1/64" in depth, 'requires about ninety hours heat treatment in a stream of ammonia.

Metallic articles having a nitrided case, are characterized V'by great surface hardness, ithe hardness of iron nitride approximating that of the heavy metal carbides, such as tungsten carbide.l Such hard surfaces are particularly dethe body of the roll, the skin does not have al slrable for use in rolls for rolling mills andV forl wearing parts generally, which are subjected to abrasive wear. However, owing to the thinness of the skin of nitride, as comparedto the bulk of 'backing or support `of sufficient strength to perlmt the article to be used to a great extent, comvmensurate with the capabilities ofthe nitride least, to the fact that the nitriding reaction results often-times in an uneven, pitted surface, occurring when carbide particles are present, and

also due to the fact of unevenness'in surface reaction, caused by oily nger marks formed or 5 imprinted, on the surface in the preliminary i handling of the roll or other article to be treated. Extreme care is therefore necessary to avoid any or all of'these defects, although certain of them may be inherent and not readily detectable save at great cost. f

It has now been found that the desirable characteristics of nitrided alloysmay be made use of and rendered available in a wide variety of articles and in most any thickness whatsoever. This improvement is accomplished by rst preparing the alloys to be nitrided, as such, according to the general principles laid down in my appli- -cation for improvements in Metallic nitrides and b methods and apparatus for preparing same, led A October 1, 1932, Serial Number 635,818 and to then further process them with particular modications, as will be hereinafter described with greater particularity to obtain nitridedmaterial. The so `prepared nitride alloys are formed or tamped in place in a suitable mold, and thereafter heated, preferably not above 875 F. or 900 F., to adesired forging or working temperature. The rough formed and heated articles are then forged, either in a press or by swaging, or by any other-well known manner, to the desired dimensions, and cooled. The resulting articles may be finish ground or machined to the desired nal dimensions, and the iinished product will be substantially shock proof and wear resistant, due to the fact thatl the actual wearing surface or s urfaces are formed or supported on materials of like physical characteristics. This uniformity of composition, and of physical characteristics, assures evenness of wear and uniform results in 40 operation. In addition, due to the speed with which the nitride alloys can be made and formed,

`according to the practices of the present invention and those of my invention above referred to, the cost of preparing a roll'ofanitride alloy is 455 appreciably less than that of forming a skin of nitride on a roll. In addition, the time involved becomes a matter of a few hours at the most, as compared witlrthe ninety hours or more required to form the/{relatively thin, inefficient, nitride skin according to prior methods.

Forming rolls, dies, and other machine parts, which are subjected to heavy wear, may thus be made rapidly, economically and in a superior and absolutely .uniformv manner, so as. to assure a 55 superior and entirely uniform productl orproducts which can be duplicated at will, and which will permit of desirable economies in all types of machine parts.

The novel features and advantages of the present invention, as intimated hereinabove, will be described more in detail with particular reference to the drawing, although it will be understood that it is not intended to be limited to the matter herein disclosed, except as such limitations are imposed by the appended claims.

In the drawing, like numerals refer to similar parts throughout the several views, of which Fig. 1 is a. vertical section of a mold for forming a roll with the several parts in place;

Fig. 2 is a transverse vertical section of a roll ina forging press;

Fig. 3 is a vertical elevation, partly in section of a nished roll;

Fig. 4 is a longitudinal section through a roll, as made according to prior processes;

Fig. 5 is an enlarged vertical section of a portion of the surface of the prior art roll, taken on lines 5-5 of Fig. 4.

Referring now more particularly 4to the drawing, a shaft or core is mounted on a base or support 11, which is provided with a central depression or well 12, and, if desired, with a centering pin 13. A casing or sheathing 14 of seamless tubing, of iron, steel, or any other desired material, isl mounted on the support 11 and uniformly spaced from the shaft or core 10.

'Ihe shaft 10 may be provided with serrations 15, cr a coating of any suitable metal, such as copper,'brass, or the like. The member 14 conalloy is assured. When a desired amount of this material is rammed up in a mold, it will be obvious that the article formed. therefrom will be uniform in its physical characteristics, as well as being uniform in chemical com sition. In addition, the material so formed partake of the nature of true iron and steel alloys in that they remain forgeable and may be readily hot worked according to well known methods, Iand may be cold worked, although, of course, to a considerably less degree than hot worked. v

The composite article is heated to a forging temperature of about 875 F., in the presence of a reducing gas, and is vforged or swaged to a desired shape, as indicated in Fig. 2. Any well known type of forging or swaging apparatus may be used such as one shown in Fig. 2, wherein the anvil 30 is provided with a removable swaging block 31, with which cooperates a hammer 32, provided with a removable face or,a head 33, configured to the anvilface 31. After the member 201has been reduced to the desired dimensions, the sheath 14 is removed in any well known manner, as by grinding or machining, and the surface is finish ground to give a nished roll, as shown' in Fig. 3. Where'the nitride composition 20 is -applied to the core without vusing; a sheathing, the swaging or forging may desirably take place in a reducing atmosphere to prevent oxidation of the surface. However, if the surface is oxidized, the coating may be removed by a nish grindin or machining.

The uniformity of performance of the surfaces of the members 20, as formed by the methods of the present invention, and the desirable stitutes a mold or form in which a nitride com- /results obtained, are strikingly illustrated' by composition 20 is rammed up into with the shaft or core 10.

This nitride composition may comprise a steel or iron base material, which may have been subjected, while in particle form, to an atmosphere of a nitrifying agent, such as ammonia, in an apparatus and according tothe method set forth and claimed in my application for Improved method and apparatus for making powdered metals, Serial Number 627,548, led August 5, 1932. The nitride alloy so formed may be ball milled to a suitable flneness to insure uniformity of composition and density, as well as to promote packing of the samev when rammed or pressed up in suitable molds.

While the nitride alloys are preferably prein powdered form by the method recited above, the novel concepts of the present invention also comprehend the preparation of the same by reacting metal chips, grindings and flnely divided rtions in an atmosphere of ammonia, andw e heated to a desired temperature of the order of 875 F., or above, while subjecting the materials to attrition. This may be accomplished by placing the materials in a tumble mill, provided with rods, balls or other devices, which mill may be disposed in an induction furnace or heatedin any desired manner, and which is also pronitride alloy will be uniform in com vided with a current of ammonia gas or other nitrogeneous material adapted to react with the metal contained therein, to nitrify the same, all as 635,818, led October 1, l1932.

It will be seen that, due to the nitrifying of substantially innitely small particles of4 etal, the sition'and not restricted to a surface casing, skin or coatintimate contact;

parison with the structures shown in Figs. 4 and 5. In Fig.'4, there is disclosed a longitudinal section of a roll 40, having shaft portions 4l, 42 formed integral therewith, although, of course, the shaft may be a continuous member with a body or roll portion shrunk thereon. The roll may be provided with a nitrided surface 50, which, as indicated hereinabove, may attain a depth of about 1/64" after ninety hours heating in anv atmosphere of ammonia and at a temperature of about 875 F. The skin or surface 50 isv possessed of a markedly different chemical composition from that of the underlying material `ofl the body 40. 'I'his difference in composition is accompanied by differences in physical characteristics, among which, for the purposes -of the discussion, l ncunced. IIfhe iron nitride of the skin 50 has a hardness, approximately 110 Scleroscope (Shore) of the order of that of tungsten carbide, vanadium carbide, tantalum carbide agg/other like compounds of the heavy metals. e body tion 40, however, is relatively so/ft, even if e of so called high speed steel, which may attain a maximum hardness, in some grades, of about 100 Scleroscope (Shore).

When e roll or other article is subjected, during use, to uneven pressures, pittings or depressions 51 may be formed' therein due to the compression of the underlying portions 43 of the metal body. The skin is fractured or ruptured,

. set forth in my application, Serial Number/jas indicated at 52., and the surface of the roll is damaged, requiring refinishing. This refinishing is a costly procedure, as the skin can not be built .up, but must be ground or machined off and the roll again subjected to a nitriding operation. If the roll is required tohave certain standard diing. By suitable reduction of the particles to a mensions, a surface of the body material-will desired ilneness, complete homogeneityl of the have to be built up thereon, as by welding or 76 hat of hardness is most proaceaiee been disclosed as the preferred embodiment oi the present invention, it will, of course, be ap- .invention may be applied to the surfacing and/or formation of wear resisting articles generally, including slide faces, guides, wristguides, wearing surfaces or bearings for locomotives and -other heavy machinery, roller bearings, forming members and 'facings for the same for use in metal bending either inpsheet metal work or boiler plate work. ,In fact, the applications of the principles and products' of the present invention are limited to no small degree by the machines now in use in industry.

It will now be appreciated that there has been f provided an improved methodof forming rolls While certain novel features of the invention' have been disclosed and are pointed out in the 'annexed claims. it will be understand that vari-f ous omissions, substitutions and changes maybe 40 made by these skilled m the art without depart'- ing from the spirit of the invention. What is claimed is:

l l.. The method of forming rolls for metal rolling machines and the like, and having wor surfaces of a tough, hard alloy of iron nitride in solid solution in iron', comprising forming a confo mold chamber, inserting a nitrided alloy cosition, in discrete form, in the .so formed mold, rg up the nitride composition to a desired degree, heating the mold-and contained nitride to a. swaging heat, hammer wormng the heated composite to desired dimensions; and thereafter cooling the roll and removing the sheath.

2. In the formation of rolls, wearing parts" and the like for heavy machinery, the improvements comprising forming 'a tubular, metallic mold member of the. general shape of the article to he formed, filling the 'mold with a discrete iron nitride composition, compressing the same in the mold, thereafter heating the mold and contained nitride to a hot working temperature of the order of 875 F., but below the utemperature of decomposition of the nitride, hot working the so heated composite to secure a desired nal shape, and thereafter removing the sheath or mold member.

3. The method of forming rolls for metal working machines and the/like and having working surfaces of a tough, hard alloy of iron nitride in solid solution in iron, comprising inserting a shaft member in a conformed tubular sheath and cen-'- trally thereof, insertingan alloy comprisingiron nitride in solid solution in iron and in discrete form in-place between said sheath and said core, compressing the said alloy to a desired density, heating .the composite sheathed valloy roll in a suitable furnace and to a temperature not exceeding the decomposition .temperature of the alloy material, thereafter pressure working the said sheathed article to a desired nished shape. and removing the sheath from the formed alloy article. l

4. The method of forming rolls for metal rolling machines and the like, and having working surfaces of a tough, hard alloy of iron nitride iny solid solution in iron, comprising forming a conformed mold chamber, inserting a nitridcd ironbase alloy composition in iinely divided form m the smd mold, ramming up the nitride composition to a desireddegree, heating the mold and contained nitride to a forging temperature of the order of about 875 F., er-working the soheated composite to desired dimensions and thereafter cooling the roll and removing the sheath.

` iIEAN HUBERT LOUIS DE BATS.

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