5.2.4.2 Cold Forging Processes

There is a variety of cold forging processes currently in -use, either alone or in combination. Following is an overview of those used most often.

Forward Extrusion In the most common forward extrusion process, a billet is pushed through a container or die by means of a punch. The material flows in the same direction as the punch to provide various types of exit sections. The process is also used on hollow slugs to reduce wall thickness, and to manufacture cans with either cylindrical cavities or cavities with varying cross sections. It is used to produce solid shapes such as rounds, thread blanks, squares, rectangles, triangles, polygons and splines. Hollow shapes, including rounds, polygons and splines are also forward extruded. Figure 5-18 shows three types of forward extrusion.

Backward Extrusion In this process, the material flows in the opposite direction to the upper punch. The workpiece is formed either in the cavity formed between the punch and die, or in the cavity of the punch. Backward extrusion is used to produce circular inside and outside diameters, squares with rounded corners, multiple outside diameters and multiple inside diameters. Figure 5-19 shows three types of backward extrusion.

Side Extrusion In this process, the material flows lateral to the direction of the punch, generally in one direction. Two types of lateral extrusion are shown in Figure 5-20.

Upsetting In this process, material flows lateral to the direction of the punch in all directions, increasing the cross section of the stock. The term "heading" is often used interchangeably with upsetting. Sometimes a distinction is drawn, and "heading" (or "flanging") is used to describe upsetting at the end of the workpiece, and "gathering" to describe upsetting at locations other than the end. Headed shapes include T- and L-heads, ball heads, square heads and socket heads. Three types of upsetting operations are shown in Figure 5-21.

Ironing In this process, the wall thickness of hollow cans or tubes is reduced, as shown in Figure 5-22. The force is applied to the bottom of the preform by a relatively long punch. The process differs from forward extrusion in that the workpiece is in tension, whereas forward extrusion places the workpiece in compression.

Nosing Nosing is used to reduce the end of a backward extrusion, or its radius. The process is shown in Figure 5-23.

Radial Forging In this process, tools moving radially forge the workpiece to the desired shape, as shown in Figure 5-24. Radial forging can also be used to make solid parts, such as axles. Hollow parts, such as gun barrels, can be axially forged using a mandrel.

Bending Bending operations are often used to generate non-symmetrical shapes. The process is used to produce rod and bar shapes with and without heads, including J-, S, U-, W-, and Z-bends.

Combined Processes Many of the above processes can be combined to advantage in a single operation. For example, forward and backward extrusion are combined to produce shaft gears with either solid or cup heads, splined shafts and threaded shafts. Seven common process combinations are shown in Figure 5-25.

Process Sequence In almost all cases, cold forgings are made in several forming strokes. The number of strokes is determined by the formability of the alloy, die loading, press loading, press characteristics, and the opportunity to combine processes. If the formability limit is reached, the workpiece must be annealed in an intermediate stage before proceeding with the next operation. The application of surface coatings between processes may be necessary for some materials. The design of process sequence is therefore based on many years of experience by the process design engineer.

Process sequences for two cold forgings are shown in Figures 5-26 and 5-27. The process sequence for the bevel gear in the figure shows the progress in cold forming technology in recent years to produce very intricate shapes.


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There is a variety of cold forging processes currently in -use, either alone or in combination. Following is an overview of those used most often.

Forward Extrusion In the most common forward extrusion process, a billet is pushed through a container or die by means of a punch. The material flows in the same direction as the punch to provide various types of exit sections. The process is also used on hollow slugs to reduce wall thickness, and to manufacture cans with either cylindrical cavities or cavities with varying cross sections. It is used to produce solid shapes such as rounds, thread blanks, squares, rectangles, triangles, polygons and splines. Hollow shapes, including rounds, polygons and splines are also forward extruded. Figure 5-18 shows three types of forward extrusion.

Backward Extrusion In this process, the material flows in the opposite direction to the upper punch. The workpiece is formed either in the cavity formed between the punch and die, or in the cavity of the punch. Backward extrusion is used to produce circular inside and outside diameters, squares with rounded corners, multiple outside diameters and multiple inside diameters. Figure 5-19 shows three types of backward extrusion.

Side Extrusion In this process, the material flows lateral to the direction of the punch, generally in one direction. Two types of lateral extrusion are shown in Figure 5-20.

Upsetting In this process, material flows lateral to the direction of the punch in all directions, increasing the cross section of the stock. The term "heading" is often used interchangeably with upsetting. Sometimes a distinction is drawn, and "heading" (or "flanging") is used to describe upsetting at the end of the workpiece, and "gathering" to describe upsetting at locations other than the end. Headed shapes include T- and L-heads, ball heads, square heads and socket heads. Three types of upsetting operations are shown in Figure 5-21.

Ironing In this process, the wall thickness of hollow cans or tubes is reduced, as shown in Figure 5-22. The force is applied to the bottom of the preform by a relatively long punch. The process differs from forward extrusion in that the workpiece is in tension, whereas forward extrusion places the workpiece in compression.

Nosing Nosing is used to reduce the end of a backward extrusion, or its radius. The process is shown in Figure 5-23.

Radial Forging In this process, tools moving radially forge the workpiece to the desired shape, as shown in Figure 5-24. Radial forging can also be used to make solid parts, such as axles. Hollow parts, such as gun barrels, can be axially forged using a mandrel.

Bending Bending operations are often used to generate non-symmetrical shapes. The process is used to produce rod and bar shapes with and without heads, including J-, S, U-, W-, and Z-bends.

Combined Processes Many of the above processes can be combined to advantage in a single operation. For example, forward and backward extrusion are combined to produce shaft gears with either solid or cup heads, splined shafts and threaded shafts. Seven common process combinations are shown in Figure 5-25.

Process Sequence In almost all cases, cold forgings are made in several forming strokes. The number of strokes is determined by the formability of the alloy, die loading, press loading, press characteristics, and the opportunity to combine processes. If the formability limit is reached, the workpiece must be annealed in an intermediate stage before proceeding with the next operation. The application of surface coatings between processes may be necessary for some materials. The design of process sequence is therefore based on many years of experience by the process design engineer.

Process sequences for two cold forgings are shown in Figures 5-26 and 5-27. The process sequence for the bevel gear in the figure shows the progress in cold forming technology in recent years to produce very intricate shapes.


Return to Table of Contents

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There is a variety of cold forging processes currently in -use, either alone or in combination. Following is an overview of those used most often.

Forward Extrusion In the most common forward extrusion process, a billet is pushed through a container or die by means of a punch. The material flows in the same direction as the punch to provide various types of exit sections. The process is also used on hollow slugs to reduce wall thickness, and to manufacture cans with either cylindrical cavities or cavities with varying cross sections. It is used to produce solid shapes such as rounds, thread blanks, squares, rectangles, triangles, polygons and splines. Hollow shapes, including rounds, polygons and splines are also forward extruded. Figure 5-18 shows three types of forward extrusion.

Backward Extrusion In this process, the material flows in the opposite direction to the upper punch. The workpiece is formed either in the cavity formed between the punch and die, or in the cavity of the punch. Backward extrusion is used to produce circular inside and outside diameters, squares with rounded corners, multiple outside diameters and multiple inside diameters. Figure 5-19 shows three types of backward extrusion.

Side Extrusion In this process, the material flows lateral to the direction of the punch, generally in one direction. Two types of lateral extrusion are shown in Figure 5-20.

Upsetting In this process, material flows lateral to the direction of the punch in all directions, increasing the cross section of the stock. The term "heading" is often used interchangeably with upsetting. Sometimes a distinction is drawn, and "heading" (or "flanging") is used to describe upsetting at the end of the workpiece, and "gathering" to describe upsetting at locations other than the end. Headed shapes include T- and L-heads, ball heads, square heads and socket heads. Three types of upsetting operations are shown in Figure 5-21.

Ironing In this process, the wall thickness of hollow cans or tubes is reduced, as shown in Figure 5-22. The force is applied to the bottom of the preform by a relatively long punch. The process differs from forward extrusion in that the workpiece is in tension, whereas forward extrusion places the workpiece in compression.

Nosing Nosing is used to reduce the end of a backward extrusion, or its radius. The process is shown in Figure 5-23.

Radial Forging In this process, tools moving radially forge the workpiece to the desired shape, as shown in Figure 5-24. Radial forging can also be used to make solid parts, such as axles. Hollow parts, such as gun barrels, can be axially forged using a mandrel.

Bending Bending operations are often used to generate non-symmetrical shapes. The process is used to produce rod and bar shapes with and without heads, including J-, S, U-, W-, and Z-bends.

Combined Processes Many of the above processes can be combined to advantage in a single operation. For example, forward and backward extrusion are combined to produce shaft gears with either solid or cup heads, splined shafts and threaded shafts. Seven common process combinations are shown in Figure 5-25.

Process Sequence In almost all cases, cold forgings are made in several forming strokes. The number of strokes is determined by the formability of the alloy, die loading, press loading, press characteristics, and the opportunity to combine processes. If the formability limit is reached, the workpiece must be annealed in an intermediate stage before proceeding with the next operation. The application of surface coatings between processes may be necessary for some materials. The design of process sequence is therefore based on many years of experience by the process design engineer.

Process sequences for two cold forgings are shown in Figures 5-26 and 5-27. The process sequence for the bevel gear in the figure shows the progress in cold forming technology in recent years to produce very intricate shapes.


Return to Table of Contents

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