GB2114474A

GB2114474A - Forging steel blanks

Info

Publication number: GB2114474A
Application number: GB08204211A
Authority: GB
Inventors: Michael Knaggs; Donald Eric Wainman; Keith Brian Wilford
Original assignee: British Steel Corp
Current assignee: British Steel Corp
Priority date: 1982-02-12
Filing date: 1982-02-12
Publication date: 1983-08-24
Also published as: GB2114474B

Abstract

A method of manufacturing forged steel blanks from which combined web and pin crank throws can be produced comprises the steps of flattening a forged steel annulus, spreading the major sides of the flattened annulus over a mandrel to give a thickness equal to or approaching that required for the webs of the throw product, sectioning the flattened annulus to produce at least two substantially "U"-shaped workpieces and forging one or both of said workpieces to produce a blank or blanks having two substantially ovaloid webs separated by a pin.

Description

SPECIFICATION Manufacture of forged blanks This invention relates to the manufacture of forged steel blanks from which combined web and pin crank throws can be produced and to such throws produced from such blanks for use in, for example, marine diesel engines. Such throws conventionally comprise two substantially ovaloid webs joined by a pin.

Previously, the production of combined web and pin crankthrows by forging techniques has proved to be unduly expensive because of the considerable machining required and to the high yield losses occasioned in converting the original start material to the end product.

The present invention sets out to provide an improved method of manufacturing combined web and crank throws which alleviates these disadvantages.

According to the present invention in one aspect there is provided a method of manufacturing forged steel blanks from which combined web and pin crank throws can be produced, the method comprising the steps of flattening a forged steel annulus, spreading the major sides of the flattened annulus over a mandrel to give a thickness equal to or approaching that required for the webs of the throw product, sectioning the flattened annulus to produce at least two substantially "U"-shaped workpieces and forging one or both of said workpieces to produce a blank or blanks having two substantially ovaloid webs separated by a pin. The steel blank so formed may subsequently be machined to produce the required crank throw product.

The forged steel annulus may be produced by becking a hollow steel ingot. Preferably, spreading is effected by inserting a suitably shaped flat faced mandrel into the hollow flattened annulus and applying an external force to one or each major side of the flattened annulus by flat tooling. The ingot may either be cast as a hollow or may be hollowed by a punching technique. Two or more annuli may be cut from a single elongate ingot.

The or each "U"-shaped workpiece may be manipulated within tapered forging tools to form short and long tapers on the workpiece. The preformed workpieces may subsequently be rough shaped within horizontal or vertical dies.

According to the present invention in another aspect, there is provided a method of manufacturing a combined web and pin crank throw from a hollow steel ingot, said method comprising the sequential steps of becking an annulus from the ingot, flattening the becked annulus, spreading the major sides of the flattened annul us, splitting the flattened spread annulus to form at least two substantially 'U"shaped workpieces, and forming the workpieces to produce a combined web and pin crank throw comprising two substantially ovaloid webs joined by a pin.

The invention will now be described byway of example with reference to the accompanying diagrammatic drawings in which: Figure 1 illustrates a series of sequential steps A-L taken to produce a combined web and pin crank throw by one method in accordance with this invention; Figures 2 and 3 are respectively side and end views of a crank throw produced by the steps illustrated in Figure 1; and Figure 4 illustrates an alternative series of sequential steps A-M taken to produce a similar crank throw by another method in accordance with this invention.

As indicated by the sequential steps illustrated in Figure 1,a hollow steel ring 1 sectioned from a punched ingot is becked to form a steel annul us 2 of thickness approximating to the diameter of the pin of the final crank product, is flattened between flat plates 3, expanded by narrow tools 4 over a flat mandrel 5 and then cut along planes normal to and containing the axis of the annulusto produce two workpieces 6 of substantially "U"-shaped form.

Each workpiece 6 is subsequently manipulated by open tooling to achieve the various functions identified in stages F to L inclusive of Figure 1; thus, the workpiece ends are squared, the web thickness set, the short and long tapers formed, the web thickness reforged, the pin formed and the web finally reforged.

More specifically, to produce the crankthrow illustrated in Figures 2 and 3 having substantially ovaloid webs 8 joined by a pin 9, a steel ring of 2040 mm diameter and 639 mm thickness is becked to a wall thickness of 576 mm and flattened leaving a central spacing of 225 mm. The flat faced mandrel 5 is then inserted between the major sides of the flattened ring and narrow spreading tools applied to the ring material above and below the mandrel to elongate the same. The mandrel and tools are progressively moved along the expanding major sides until a thickness equal to or approaching that required by the web of final product is achieved. The flattened expanded ring is then sectioned to give pairs of workpieces of web thickness approximately to 576 mm and a width equivalent to the diameter of the webs of the crank throw product.

Each workpiece is subsequently forged using plate tools 10 having flat and tapered surfaces, the latter being employed to impart long and short tapers to the workpiece as and where required.

Machining may be further reduced by forging the pin shape with a notched insert such as shown in Figure 1 K. Such an insert reduces deformation of the webs when shaping the pin.

In the alternative production route indicated in Figure 4, vertical die forging is empioyed to forge the required blank from the cut 'U'-shaped workpiece 6.

In this Figure, steps E to M sequentially illustrate the formation of tapers of the two faces of the blank, followed by vertical die forging within a die bolster 14 to form the desired crank shaping.

1. A method of manufacturing forged steel blanks from which combined web and pin crank throws can be produced, the method comprising the

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Manufacture of forged blanks This invention relates to the manufacture of forged steel blanks from which combined web and pin crank throws can be produced and to such throws produced from such blanks for use in, for example, marine diesel engines. Such throws conventionally comprise two substantially ovaloid webs joined by a pin. Previously, the production of combined web and pin crankthrows by forging techniques has proved to be unduly expensive because of the considerable machining required and to the high yield losses occasioned in converting the original start material to the end product. The present invention sets out to provide an improved method of manufacturing combined web and crank throws which alleviates these disadvantages. According to the present invention in one aspect there is provided a method of manufacturing forged steel blanks from which combined web and pin crank throws can be produced, the method comprising the steps of flattening a forged steel annulus, spreading the major sides of the flattened annulus over a mandrel to give a thickness equal to or approaching that required for the webs of the throw product, sectioning the flattened annulus to produce at least two substantially "U"-shaped workpieces and forging one or both of said workpieces to produce a blank or blanks having two substantially ovaloid webs separated by a pin. The steel blank so formed may subsequently be machined to produce the required crank throw product. The forged steel annulus may be produced by becking a hollow steel ingot. Preferably, spreading is effected by inserting a suitably shaped flat faced mandrel into the hollow flattened annulus and applying an external force to one or each major side of the flattened annulus by flat tooling. The ingot may either be cast as a hollow or may be hollowed by a punching technique. Two or more annuli may be cut from a single elongate ingot. The or each "U"-shaped workpiece may be manipulated within tapered forging tools to form short and long tapers on the workpiece. The preformed workpieces may subsequently be rough shaped within horizontal or vertical dies. According to the present invention in another aspect, there is provided a method of manufacturing a combined web and pin crank throw from a hollow steel ingot, said method comprising the sequential steps of becking an annulus from the ingot, flattening the becked annulus, spreading the major sides of the flattened annul us, splitting the flattened spread annulus to form at least two substantially 'U"shaped workpieces, and forming the workpieces to produce a combined web and pin crank throw comprising two substantially ovaloid webs joined by a pin. The invention will now be described byway of example with reference to the accompanying diagrammatic drawings in which: Figure 1 illustrates a series of sequential steps A-L taken to produce a combined web and pin crank throw by one method in accordance with this invention; Figures 2 and 3 are respectively side and end views of a crank throw produced by the steps illustrated in Figure 1; and Figure 4 illustrates an alternative series of sequential steps A-M taken to produce a similar crank throw by another method in accordance with this invention. As indicated by the sequential steps illustrated in Figure 1,a hollow steel ring 1 sectioned from a punched ingot is becked to form a steel annul us 2 of thickness approximating to the diameter of the pin of the final crank product, is flattened between flat plates 3, expanded by narrow tools 4 over a flat mandrel 5 and then cut along planes normal to and containing the axis of the annulusto produce two workpieces 6 of substantially "U"-shaped form. Each workpiece 6 is subsequently manipulated by open tooling to achieve the various functions identified in stages F to L inclusive of Figure 1; thus, the workpiece ends are squared, the web thickness set, the short and long tapers formed, the web thickness reforged, the pin formed and the web finally reforged. More specifically, to produce the crankthrow illustrated in Figures 2 and 3 having substantially ovaloid webs 8 joined by a pin 9, a steel ring of 2040 mm diameter and 639 mm thickness is becked to a wall thickness of 576 mm and flattened leaving a central spacing of 225 mm. The flat faced mandrel 5 is then inserted between the major sides of the flattened ring and narrow spreading tools applied to the ring material above and below the mandrel to elongate the same. The mandrel and tools are progressively moved along the expanding major sides until a thickness equal to or approaching that required by the web of final product is achieved. The flattened expanded ring is then sectioned to give pairs of workpieces of web thickness approximately to 576 mm and a width equivalent to the diameter of the webs of the crank throw product. Each workpiece is subsequently forged using plate tools 10 having flat and tapered surfaces, the latter being employed to impart long and short tapers to the workpiece as and where required. Machining may be further reduced by forging the pin shape with a notched insert such as shown in Figure 1 K. Such an insert reduces deformation of the webs when shaping the pin. In the alternative production route indicated in Figure 4, vertical die forging is empioyed to forge the required blank from the cut 'U'-shaped workpiece 6. In this Figure, steps E to M sequentially illustrate the formation of tapers of the two faces of the blank, followed by vertical die forging within a die bolster 14 to form the desired crank shaping. CLAIMS

1. A method of manufacturing forged steel blanks from which combined web and pin crank throws can be produced, the method comprising the steps of flattening a forged steel annulus, spreading the major sides of the flattened annulus over a mandrel to give a thickness equal to or approaching that required for the webs of the throw product, sectioning the flattened annul us to produce at least two substantially "U"-shaped workpieces and forging one or both of said workpieces to produce a blank or blanks having two substantially ovaloid webs separated by a pin.

2. A method as claimed in Claim 1 wherein the forged steel annulus is produced by becking a hollow steel ingot.

3. A method as claimed in Claim 1 or Claim 2 wherein spreading is effected by inserting a suitably shaped flat faced mandrel into the hollow flattened annulus and applying an external force to one or each major side of the flattened annulus by flat tooling.

4. A method as claimed in any one of Claims 1 to 3 wherein the ingot is hollowed by a punching technique.

5. A method as claimed in any one of the preceeding claims wherein the or each "U"-shaped workpiece is mainipulated within tapered forging tools to form short and long tapers on the workpiece.

6. A method as claimed in Claim 5 wherein the preformed workpieces are subsequently rough shaped within horizontal or vertical dies.

7. A method of manufacturing a combined web and pin crankthrowfrom a hollow steel ingot, said method comprising the sequential steps of becking an annulus from the ingot, flattening the becked annulus, spreading the major sides of the flattened annulus, splitting the flattened spread annulus to form at least two substantially "U"-shaped workpieces, and forming the workpieces to produce a combined web and pin crank throw comprising two substantially ovaloid webs joined by a pin.

8. A combined web and crank throw blank manufactured by a method as claimed in any one of the preceeding claims.

9. A method of manufacturing forged steel blanks substantially as herein described with reference to Figures 1 to 3 or Figure 4 of the accompanying drawings.