GB1569016A - Production of metal hexagonal bars - Google Patents

Description

(54) PRODUCTION OF METAL HEXAGONAL BARS (71) We, ZAKLADY HUTNICZO PRZETWORCZE METALI NIEZELAZ NYCH "HUTMEN", of 50-950 Wroclaw, Grabiszynska 241, Poland, an Enterprise organised and existing under the laws of Poland do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the production of metal hexagonal bars.

In accordance with the known methods, a hexagonal bar is obtained by hot extrustion or rolling usually followed by drawing operation to obtain a bar having suitable mechanical properties and required shape and dimensions. The hot extrusion process is used in the case of non-ferrous metals, particularly copper, copper alloys, aluminium and aluminium alloys, while hot rolling is used for ferrous alloys.

A hexagonal copper or copper alloy bar obtained by hot extrusion is prepared, for subsequent drawing operation by providing a point at one of its ends and by pickling it.

Extruded bars thus prepared are drawn in drawbenches, in drum-type drawing machines or in draw-straightening-cutter machines, and are then heated, straightened and cut at their ends. The drawing operation is performed by means of a drawing die whose forming walls in the entry section and in the deformation and sizing sections are flat. The dies used for hot extrusion in production of hexagonal bars are damageable due to high stresses occurring in the die corners. The extruded hexagonal bars are vulnerable to scars forming on their edges at the exit from the press and in transport.

In extrusion processes used in production of hexagonal bars the rectilinearity of side faces is not ensured over the whole length of the extruded bars. In drawing these bars the deformation of their edges takes place from guide rolls in a drawbench and the faces of the hexagon become additionally twisted.

The object of this invention is to obviate or mitigate the above drawbacks.

In accordance with one aspect of this invention, there is provided a drawing die for production of metal hexagonal bars, said drawing die having an entry zone, a deformation section, and a sizing section, each of the six side faces in the deformation section being straight longitudinally and convexly curbed transversely with the convexity diminishing from the entry zone to the sizing section, the angle between opposite side faces being within the range of 8" to 32", the angle between opposite edges being greater than the first mentioned angle and the tangent of the second-mentioned angle being greater than the product of the tangent of the first-mentioned angle and a factor 1.17.

In accordance with another aspect of this invention, there is provided a method for production of metal hexagonal bars, wherein a drawing die, as defined in the next preceding paragraph, is used to subject extruded material, which is round in cross-section, to a single drawing operation to yield a hexagonal bar, the diameter of the round bar introduced into the drawing die being minimally 1.09 of the dimension across flats of the finished hexagon.

The drawing operation can be effected in a drawbench, a drum-type drawing machine or in a draw-straightening-cutter machine.

Drawing of a round bar into a hexagonal bar eliminates the imperfections of the conventional process, improves the life of extruding dies because round dies are used, and improves the output, improving namely the weight ratio of finished bars to bars used in production.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 illustrates the die in plan; Fig. 2 illustrates the die in a section along the line A-A shown in Fig. 1; Fig. 3 illustrates the die in a section along the line B-B shown in Fig. 1; Fig. 4 illustrates the die in plan with the bar to be drawn inserted into the die; and Fig. 5 illustrates the die in a section along the C-C line shown in Fig. 4, showing the deformation zones of the die.

A round bar of diameter d is subjected to a drawing operation to obtain a hexagonal bar of "across flats" (A.F.) dimension s upon condition that the diameter d of the bar introduced to the die is minimally 1.09 of the dimensions of the hexagon, while for a hexagon with sharp edges in copper or copper alloy the diameter d is 1.15 to 1.5 of the dimensions of the hexagon. A round bar 1 of diameter d is drawn by means of a die 2, said die having a deformation section 3 and a sizing section 4. In the deformation section 3 of the die two forming zones of the hexagon can be distinguished. these zones being designated as zone I and zone II. In zone II the edges and side faces of the hexagon are formed. and in zone I only the side faces of this hexagon are formed.In the zone I the material of the drawn bar of diameter d is elongated and forced towards the corners of the die. the contact of the drawn material with six corners of the die taking place at the beginning of zone II. The finished hexagonal form of the drawn bar is obtained in the end part of zone II. Dimensional tolerance of the cross section of the bar and its rectilinearity are stabilised in the sizing zone III of the die.

Each of the six side faces of the deformation section 3 of the die, e.g. EFGH, is a surface of diminishing convexity along a centre line 5, this diminishing convexity being determined by points Rand T. The geometry of the drawing die is also determined by an angle 2 a confined between extensions of generating lines x-y and x'-y'. as well as by an angle 2a1 confined between the extensions of edges M-N and M'-N'.The angle 2axis greater than the angle 2a bv a value resulting from the dependence in which the tangent of angle a1 1 is greater than the product of the tangent of angle a and the factor 1.17, the difference between these two angles being preferably 3 to 18". The value of angle 2a depends on the type of drawn material and is confined within the range of 8" to 32". The length of the sizing zone is designated as a dimension c whose accepted minimum value is 0.3s, s being the A.F. dimension of the hexagon.

WHAT WE CLAIM IS: 1. A drawing die for production of metal hexagonal bars, said drawing die having an entry zone, a deformation section, and a sizing section, each of the six side faces in the deformation section being straight longitudinally and convexly curved transversely with the convexity diminishing from the entry zone to the sizing section, the angle between opposite side faces being within the range of 8" to 32", the angle between opposite edges being greater than the first-mentioned angle and the tangent of the second-mentioned angle being greater than the product of the tangent of the first-mentioned angle and a factor 1.17.

2. A drawing die according to claim 1, wherein the difference between the two angles is within the range of 3 to 18".

3. A drawing die for production of metal hexagonal bars, substantially as hereinbefore described with reference to the accompanying drawings.

4. A method for production of metal hexagonal bars, wherein a drawing die according to any one of claims 1 to 3 is used to subject extruded material, which is round in cross-section, to a single drawing operation to yield a hexagonal bar, the minimum diameter of the round bar introduced into the drawing die being 1.09 of the dimension across flats of the finished hexagon.

5. A method according to claim 4, wherein, with copper or copper alloy bars, the diameter of the round bar is 1.15 to 1.5 of the A.F. dimension of the finished hexagonal bar. - -

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. Fig. 1 illustrates the die in plan; Fig. 2 illustrates the die in a section along the line A-A shown in Fig. 1; Fig. 3 illustrates the die in a section along the line B-B shown in Fig. 1; Fig. 4 illustrates the die in plan with the bar to be drawn inserted into the die; and Fig. 5 illustrates the die in a section along the C-C line shown in Fig. 4, showing the deformation zones of the die. A round bar of diameter d is subjected to a drawing operation to obtain a hexagonal bar of "across flats" (A.F.) dimension s upon condition that the diameter d of the bar introduced to the die is minimally 1.09 of the dimensions of the hexagon, while for a hexagon with sharp edges in copper or copper alloy the diameter d is 1.15 to 1.5 of the dimensions of the hexagon. A round bar 1 of diameter d is drawn by means of a die 2, said die having a deformation section 3 and a sizing section 4. In the deformation section 3 of the die two forming zones of the hexagon can be distinguished. these zones being designated as zone I and zone II. In zone II the edges and side faces of the hexagon are formed. and in zone I only the side faces of this hexagon are formed.In the zone I the material of the drawn bar of diameter d is elongated and forced towards the corners of the die. the contact of the drawn material with six corners of the die taking place at the beginning of zone II. The finished hexagonal form of the drawn bar is obtained in the end part of zone II. Dimensional tolerance of the cross section of the bar and its rectilinearity are stabilised in the sizing zone III of the die. Each of the six side faces of the deformation section 3 of the die, e.g. EFGH, is a surface of diminishing convexity along a centre line 5, this diminishing convexity being determined by points Rand T. The geometry of the drawing die is also determined by an angle 2 a confined between extensions of generating lines x-y and x'-y'. as well as by an angle 2a1 confined between the extensions of edges M-N and M'-N'.The angle 2axis greater than the angle 2a bv a value resulting from the dependence in which the tangent of angle a1 1 is greater than the product of the tangent of angle a and the factor 1.17, the difference between these two angles being preferably 3 to 18". The value of angle 2a depends on the type of drawn material and is confined within the range of 8" to 32". The length of the sizing zone is designated as a dimension c whose accepted minimum value is 0.3s, s being the A.F. dimension of the hexagon. WHAT WE CLAIM IS:

1. A drawing die for production of metal hexagonal bars, said drawing die having an entry zone, a deformation section, and a sizing section, each of the six side faces in the deformation section being straight longitudinally and convexly curved transversely with the convexity diminishing from the entry zone to the sizing section, the angle between opposite side faces being within the range of 8" to 32", the angle between opposite edges being greater than the first-mentioned angle and the tangent of the second-mentioned angle being greater than the product of the tangent of the first-mentioned angle and a factor 1.17.

2. A drawing die according to claim 1, wherein the difference between the two angles is within the range of 3 to 18".

3. A drawing die for production of metal hexagonal bars, substantially as hereinbefore described with reference to the accompanying drawings.

4. A method for production of metal hexagonal bars, wherein a drawing die according to any one of claims 1 to 3 is used to subject extruded material, which is round in cross-section, to a single drawing operation to yield a hexagonal bar, the minimum diameter of the round bar introduced into the drawing die being 1.09 of the dimension across flats of the finished hexagon.

5. A method according to claim 4, wherein, with copper or copper alloy bars, the diameter of the round bar is 1.15 to 1.5 of the A.F. dimension of the finished hexagonal bar. - -