US3435499A

US3435499A - Roll assembly

Info

Publication number: US3435499A
Application number: US692785A
Authority: US
Inventors: Selwyn R Rackoff; Martin J Dempsey
Original assignee: American Shear Knife Co
Current assignee: American Shear Knife Co
Priority date: 1967-12-22
Filing date: 1967-12-22
Publication date: 1969-04-01
Anticipated expiration: 1986-04-01

Description

April 1969 s. R. RACKOFF ETAL 3,435,499

ROLL AS 5 EMBLY Sheet of Filed Dec. 22, 1967 6.!25 ioo| 50o" RADIUS FIG.4

*1 IHO INVENTORS SELWYN R. RACKOF F MARTIN J.DEMPSEY A TTORNE Y April 1969 s. R. RACKOFF ETAL 3,435,499

ROLL AS SEMBLY Filed Dec. 22, 1967 Sheet 2 of 2 F IG.6

United States Patent 3,435,499 ROLL ASSEMBLY Selwyn R. Rackoif and Martin J. Dempsey, Bethel Park,

Pa., assignors to American Shear Knife Co., West Homestead, Pa, a corporation of Pennsylvania Filed Dec. 22, 1967, Ser. No. 692,785 Int. Cl. B21k 1/02; B21b 31/08; B2311 11/02 US, Cl. 29-425 8 Claims ABSTRACT OF THE DISCLOSURE A roll assembly including a tungsten-carbide roll insert on a mandrel having a flange engaged by a lateral surface of the roll. The engaging surface of the insert is roughened by adhered particles of tungsten carbide and the roller is compressed against the flange so that the particles bite into the flange. To reduce tensile stress on the tungsten-carbide insert the inside diameter of the insert and the outside diameter of the mandrel are made equal and the insert is mounted by cooling the mandrel and slipping the insert over the mandrel.

Background of the invention This invention relates to the art of reducing work by rolling and has particular relationship to the reduction of work by rolling with rolls of materials or metalloids of the tungsten-carbide type. The expression of the tungsten-carbide type as used in this application means primarily tungsten carbide (WC) and its alloys. It also means other hard metalloids such as titanium carbide, molybdenum carbide, tantalum carbide, niobium carbide and numerous others including borides, silicides, nitrides, and the like, and their alloys. For an elaborate list of these metalloids reference is made to Goetzel 2,581,252, particularly column 6, beginning line 16.

In the interest of concreteness this invention is discussed in this application with reference to the rolling or reduction of Billets to rod or rod to wire. The reduction of rod is carried out by oppositely engaging the reducing rolls of a pair of roll assemblies in reducing relationship with the rod while rotating the assemblies and advancing the rod.

Typically, steel is reduced to round wire of about .218" to .5625" diameter and the wire is delivered at the rate of 5000 to 10,000 feet per minute (typically 8500 f.p.m.) from a 25-stand system. In the high numbered stands (from the 17th) the roller assemblies rotate at about 1600 revolutions per minute. The reducing rolls particularly in the advanced assemblies are of the tungsten-carbide type. In each roll assembly including a roll of the tungsten carbide type, the roll is in the form of an annular insert and is mounted on a mandrel of steel, which is driven to produce the rolling operation. During the rolling tperation the roll insert is subjected to enormous stresses and it is necessary that rotation of the insert relative to the mandrel be prevented.

In accordance with prior-art practice the tungsten-carbide roll is provided with precisely dimensioned keys which are locked to suppress relative rotation of the roll and mandrel. In addition the inside diameter of the roll is dimensioned substantially smaller than the outside diameter of the mandrel (so that there will be no relative movement in use). A high failure-rate of rolls in these prior-art assemblies has been experienced. In addition these prior-art assemblies are difiicultand costly to produce because of the precise dimensioning of the keys in tungsten-carbide which is not readily worked. There is also a high-failure rate of the rolls during production so that the production shrinkage is high.

3,435,499 Patented Apr. 1, 1969 It is an object of this invention to overcome the above described disadvantages of the prior-art roll assemblies, and to produce assemblies which shall be producible at a relatively lower cost than prior-art assemblies and shall not fail at a high rate in the making or in use and also to provide a method of producing such assemblies.

Summary of the invention This invention arises from the realization that the high rate of failure of the rolls in prior-art assemblies, both when they are made and later, is caused by the keys and by the manner in which the assemblies are made. The keys are in effect notched regions and their very presence weakens the rolls. In addition the dimensioning of the inside diameter of the roll smaller than the outside diameter of the mandrel causes enormous tensional forces to be applied to the roll by the mandrel as it warms up during the making of the assembly and causes the roll to fail during making, or, in its weakened condition, shortly after the assembly is put into use. It is an object of this invention to provide an assembly in which the roll insert is a smooth annulus but the roll assembly is accomplished in such a way that the roll insert does not have a high rate of failure and does not, when in use, move relative to the mandrel.

In accordance with this invention a roll assembly is provided in which the roll is a smooth annulus but its lateral face or surface which engages the flange of the mandrel is roughened. The roughening is effected by securing or binding to this face a hard particled material, typically particles of the tungsten-carbide type mixed with a brazing material such as copper. Typically the particles are of -30 to +20 mesh, but they may be smaller, even a powder. To roughen a later face of a roll insert the particles of tungsten-carbide and brazing material are disposed on the surface and then the surface is raised to the sintering temperature of the carbide. This temperature exceeds the brazing temperature of the brazing material and the particles are joined to the surface both by sintering and brazing. Alternatively, the brazing material alone may serve to hold the particles on the surface.

The tensional forces which disrupt the roll inserts of prior-art assemblies is, in the practice of this invention, reduced by dimensioning the inside diameter of the insert and the outside diameter of the mandrel substantially equal. The mandrel is then cooled and the roll insert slipped over it and compressed by a pressure exerting tons of force. A nut is then screwed onto the mandrel. The nut engages the remaining face of the insert and has grooves which are engaged by a spanner wrench and the wrench is turned to exert additional compressive force on the insert. The mandrel is then provided with additional grooves coextensive with the grooves in the nut to provide a keyway which serves in the use of the assembly.

The mandrel, nut and insert are coordinated in strength. The mandrel and nut are hardened typically, to 50 to 55 Rockwell-C hardness. The grooves in the mandrel may be cut out in various ways but are typically cut out by abrasive sawing.

Brief description of the drawings For a better understanding of this invention, both as to its organization and as to its method of operation, together with additional objects and advantages thereof, reference is made to the following description, taken in connection with the accompanying drawings, in which:

FIGURE 1 is a plan view of a roll assembly constituting an embodiment of this invention;

FIG. 2 is a view in section taken along line IIII of FIG. 1;

FIG. 3 is a plan view of the roll insert of the assembly shown in FIG. 1;

FIG. 4 is a view in section taken along line IV-IV of FIG. 3;

FIG. 5 is a fragmental view enlarged showing the relationship between the roll and the flange and the roughening interposed between the roll and flange; and

FIGS. 6 and 7 are views showing typical dimensions of the mandrel, and insert included, not with any intention of limiting this invention in any way, but with the purpose of aiding those skilled in the art to practice this invention.

Description preferred embodiment The apparatus shown in the drawings includes a roll assembly A having a mandrel M, a roll insert R of the tungsten-carbide type and a nut N. The roll insert is held tightly, against relative rotation under the high stresses, between the nut N and the flange F of the mandrel M. An aspect of this invention resides in the prevention of relative rotation by the provision in the surface S of the carbide roll R, which engages the flange F, of a rough surface which bites into the surface of the flange F. It is not obvious that a surface of tungsten carbide, a very hard material, can be roughened so that it will hold under the high stresses to which the roll is subjected. But operation has shown that the assembly according to this invention does hold. The roughened surface S may typically be provided as follows:

A mixture of copper powder or particles (or other brazing material) and tungsten-carbide powder or particles is deposited on the surface of the presintered roll to be roughened. The roll is then heated to the tungsten-carbide sintering temperature which is higher than the brazing temperature for the copper. The tungsten carbide is brazed and sintered to the roll. In the sintering the cobalt of the roll material fuses to the tungsten-carbide particles so that the particles become part of the roll surface. The tungsten carbide powder consists of small tetrahedra T (FIG. which are sintered to the roll insert surface on their bases with their sharp apices outwardly.

The mandrel M is composed of very hard tool steel. The outer diameter of the mandrel is dimensioned precisely (typically within :0001 inch) equal to the inside diameter of the roll insert (compare FIGS. 6 and 7). The mandrel M is cooled to about 150 F. and the roll R is then slipped over the mandrel M. The roll R is then compressed onto the mandrel by applying about 160 tons force or higher (typically 300 tons) to the roll. The

nut N is then screwed on and tightened by engaging a t long spanner wrench in the grooves G (see FIGS. 1 and 2). Substantial compressive force is applied between the surfaces, S, of the roll R and flange F in this way. The portion of the mandrel M bounded by the grooves G is then sawed out by an abrasive saw and the slot through the grooves G and the adjacent portion of the mandrel M serves as a key slot in which a driving key K engages in the use of the apparatus. Movement of the nut N relative 4: to the mandrel M is thus prevented. The equal dimensioning of the mandrel outside diameter and the roll inside diameter reduces the tensile stress to which the roll is subject during subsequent use, when the roll temperature at the work may be as high as 1600 F. to 2000 F., so

that the roll failures are minimized.

What is claimed is:

1. A roll assembly including a cylindrical mandrel having a flange and a roll insert of the tungsten-carbide type on said mandrel, said insert having a lateral surface, means connected to said insert for holding said lateral surface in firm engagement with said flange, said lateral surface being roughened so that it bites into said flange and is held against rotation by said flange, the roughening on the lateral surface being a mixture of particles of the tungsten carbide type and of a brazing material.

2. The assembly of claim 1 wherein the brazing material is copper.

3. The assembly of claim 1 wherein the particles of thetungsten-carbide type are adhered to the lateral surface.

4. A roll assembly including a cylindrical mandrel, a flange of metal on said mandrel, a roll insert of the tungsten-carbide type on said mandrel, said insert having a lateral surface, means engaging said insert for forcing said lateral surface into firm engagement with said flange, and adhesive means interposed between said lateral surface and said flange, said adhesive means being of a type which is capable of biting into the material of said flange and when actuated by said forcing means so biting into said flange and effectively holding said insert against rotation on said mandrel.

5. The assembly of claim 4 wherein the adhesive means is a roughening on the lateral surface and the lateral surface is forced into engagement with the flange under high compressive pressure so that the roughening eflectively bites into the flange.

6. The assembly of claim 4 including a key through the forcing means and the mandrel for preventing rotation of the forcing means relative to the mandrel.

7. The assembly of claim 4 wherein the adhesive means consists of particles of the tungsten carbide type sintered to the lateral surface.

8. The assembly of claim 4 wherein the flange is composed of hardened alloy steel and the adhesive means is composed of particles of the tungsten-carbide type capable of biting into the flange when the lateral surface is held in firm engagement with the flange.

References Cited UNITED STATES PATENTS BILLY I. WILHITE, Primary Examiner.

- US. Cl. X.R. 29148.4, 447