US3423975A

US3423975A - Method of hot-extruding metals which require a low rate of deformation

Info

Publication number: US3423975A
Application number: US543426A
Authority: US
Inventors: Andre Collinet
Original assignee: Cefilac SA
Current assignee: Cefilac SA
Priority date: 1965-04-22
Filing date: 1966-04-18
Publication date: 1969-01-28
Anticipated expiration: 1986-01-28
Also published as: FR1443987A; GB1147945A

Description

Jan. 28, 1969 A. COLLINET Y 3,423,975

METHOD OF HOT-EXTRUDING METALS W H H REQUIRE A LOW 10 RATE OF DEFORMATLON Filed April 18, 1966 PRIOR ART IV I 7 INVENTOR. Alva/Q5 COLL/IVE?- A 2 Y a mi M KM 14AM United States Patent 14,174 US. C]. 7242 5 Claims Int. Cl. B21b 45/02; B21c 23/00 ABSTRACT OF THE DISCLOSURE A method for hot-extruding metals and alloys thatrequire a low rate of deformation in a fiat-faced die and container by providing the billet to be extruded with a frustoconical leading portion and inserting prior to extrusion thereof, a solid deformable lubricant in an amount to substantially fill the annular space defined by the frustoconical portion of the billet, the face of the die and the container, and then extruding said billet.

In the known practice for hot-extruding steels, a flat extrusion die or plate is used, and the front face of the billet has a straight and thereby a planar section which may be joined to its lateral surface by a toroidal surface. The mass of lubricant required for the entire extrusion is then placed as close as possible to the die. This lubricant is generally vitreous and is in a solid deformable form at room temperature before the start of the operation. FIG- URE 1 relates to this known method and in its upper part illustrates an axial section of a billet I placed in a container 7 with a die 4 before the start of the extrusion and in its lower part, it illustrates the same billet during the extrusion.

At the start of the extrusion, the metal flow assumes an outline which is substantially that of the initial shape of the billet, and progressive heating of the lubricant 2 assures a continuous supply of the lubricant which is viscous and has the appropriate thickness.

This method is satisfactory for extruding carbon steels and low and medium alloy steels, but it includes the deformation of the metal over a very short distance immediately in front of the bearing land of the die 4. Further, this billet must be extruded within a few seconds to prevent its cooling whereby these two factors combine to generate very high speeds or rates of deformation in the mass of the metal. However, certain alloys contains a high proportion of alloy elements which are described as super-refractory, such as super-refractory stainless steels, nickel alloys, and molybdenum, tungsten and their alloys, and these cannot withstand high speeds of deformation without deterioration. Hereinafter, they are referred to as very resistant metals or alloys.

The reduction in cross-section of the metal over a short distance includes a pronounced deformation of the glove-finger type of its successive sections, and consequently the formation at the rear end of a deep axial tubular cavity.

To increase the deformation distance, conical dies are employed and the front face of the billet is shaped so as to plug the entry to the die. FIGURE 2 relates to this known method and in its upper part illustrates an axial section of the billet I placed in position in a container 7 before the start of the operation, and in its lower part shows the same billet during its extrusion. Prior to the extrusion, the mass of the generally glass-like lubricant 2 required for the whole extrusion is placed in position around the lateral surface of the billet, where it immediately acquires the appropriate temperature and viscosity to lubricate the metal during the extrusion operation.

At the beginning of the extrusion, the flow of metal assumes the precise shape defined by the entry 3 to the die 4 and it entrains a film of lubricant of appropriate thickness to ensure continuous lubrication of the die, even if the extrusion is very fast. This method is satisfactory for the extrusion of the very resistant metals and alloys, but it has certain problems, including difficulty in the production of the dies and high costs in their fabrication, for the shape is complex. Also, the application of a layer of glass on the billet is an operation whose results are sometimes unsatisfactory, and only glasses which possess appropriate viscosity over a wide range of temperatures are used.

This invention avoids the problems encountered in hot extrusion of the very resistant metals and alloys and provides a deformation distance of noteworthy length for the metal. It relates to a method for extruding the very resistant metals and alloys in solid or hollow sections and even in complex sections, and comprises using a fiat die with a billet whose front portion is a frustoconical body of revolution. The method includes filling the annular space formed between the surfaces of the die and the billet with a generally gass-like lubricant, having a solid deformable form such as agglomerated glass powder, fibreglass and multi-cellular glass.

The front face of the billet is formed into a frustoconical body of revolution whose small base 5 substantially fits into the section of the product to be produced, and whose large base 6 and small base circles are rounded off toroidally, for example, with a radius of 20 mm. The angle at the base of the frustoconical body is preferably between 30 and 60.

FIGURE 3 relates to the method of the invention and in its upper part illustrates an axial section of the billet 1 placed in position in a container 7 prior to the start of the extrusion, and in its lower part shows the same billet during the extrusion. To perform the extrusion'and before insertion of the =billet into the container 7, a volume of vitreous lubricant is placed in position in the container against the die. This volume exceeds slightly, after compression, the volume of metal removed from the cylindrical billet to form its front extremity. It is advantageous to make this volume of lubricant of several rings of agglomerated glass powder 2a having the same diameter as the billet and pierced in such manner as to leave the aperture of the die largely unobstructed.

When the billet is compressed before the extrusion, the front of the billet advances its conical portion into the mass of the glass and compresses it into the angle formed in the front of the container with the die. By flowing towards the different parts of the die aperture, the metal creates the most suitable junction surfaces in the mass of glass between its conical form and the die aperture. Over a substantial part of its surface, the flat die is thus separated from the billet by a substantial thickness of insulating lubricant, which limits its heating and thereby enhances its life.

To avoid losses of the very resistant metal or alloy from machining the conical front portion, the method also comprises retaining a flat front surface of the billet, which may or may not be joined to the lateral surface by a toroidal surface. To this front face is afiixed, connected or placed a frustoconical element of carbon steel delimited at the front as specified herein, and delimited at the rear as required for the front face of the billet. The metal flow is the same, and some of the losses of the very resistant metal or alloy which is frequently expensive is avoided.

EXAMPLE In production of 38 x 38 x 10 mm., from a nickel alloy containing 16% Mo, 15.5% Cr, 5% Fe, 4% W, 2.5% Co, 1% Mn, 1% Si, 0.08% C, the balance being Ni, the cylindrical billets were employed and they had an overall length of 270 mm., a diameter of 120 mm., Whose front extremity had simply been turned to frustoconical shape with a base angle of 45, with a small base of a diameter of 30 mm., and with a radius of 15 mm. along each base circle.

The extrusion press had a force of 1,500 tons and was equipped with a 126 mm. diameter container which terminated in a flat die and a die-holder. Before each extrusion, 3 pierced discs of agglomerated glass powder 122 mm. in diameter and 20 mm. in thickness were placed in appropriate direction against the die. The first disc had an L-shaped bore in dimensions of 60x60x30 mm. The second disc had a circular bore 70 mm. in diameter and the third disc had a circular bore 90 mm. in diameter.

The extrusion was controlled so as to leave a plug of a thickness of mm. This rendered it possible to obtain sections free of cracks and imperfections, and free of any tubular cavity at their rear ends.

While I have shown and described preferred embodiments of my invention, it may be otherwise embodied within the scope of the appended claims.

I claim:

1. A method of hot-extruding metals and alloys that require a low rate of deformation in a container and flatfaced die, comprising:

(A) forming a substantially frustoconical leading portion on a billet to be extruded;

(B) placing adjacent the flat face of the die a lubricant in a solid deformable state when cold and in an amount to substantially fill the area defined by the container, the die face and the frustoconical portion when the leading end of the billet is adjacent the die;

(C) inserting the billet heated to extrusion temperature into said container; and,

(D) extruding the billet through the die.

2. The method of claim 1 wherein said billet is so formed that the frustoconical surface of said leading portion is disposed at an angle of substantially between and relative to the central longitudinal axis of said billet.

3. The method of claim 1 wherein said lubricant comprises discs of agglomerated glass powder pierced centrally thereof to substantially surround the aperture of said die.

4. The method of claim 1 wherein said billet is so formed that the frustoconical surface of said leading portion is disposed at an angle of substantially between 30 and 60 relative to the central longitudinal axis of said billet and wherein said lubricant comprise discs of agglomerated glass powder pierced centrally thereof to substantially surround the aperture of said die.

5. The method of claim 1 wherein said amount of said lubricant is at least that volume of metal removed from said billet in formation of said frustoconical portion.

References Cited UNITED STATES PATENTS 2,806,596 9/1957 Dodds et al. 72-42 2,946,437 7/1960 Edgecombe 72-253 3,059,769 10/1962 Frost 72-42 3,072,251 1/1963 Sauve 72-42 3,255,621 6/1966 Ohsol 72-42 CHARLES W. LANHAM, Primary Examiner.

E. M. COMBS, Assistant Examiner.

US. Cl. X.R. 72 2s3, 41