Free forging is a plastic processing method that uses the pressure of the upper and lower anvils of the forging equipment to forge the metal blank into various shapes. During free forging, only part of the metal surface is restricted by the tool, and the rest is a free surface.
Free forging can be divided into three categories: manual free forging, hammer free forging, and hydraulic press free forging. Its advantages are: strong applicability, great flexibility, short production cycle, and it is the only production method for extra-large forgings; its disadvantages are: low forging precision, large machining allowance, low productivity, high labor intensity, and it can only be used for single-piece small-batch production.
Process of free forging
Basic process:
The process that can significantly change the shape and size of the blank is also the main deformation process in the free forging process.
1) Upsetting: a process that reduces the height of the blank and increases the cross-sectional area
2) Drawing: a process that reduces the cross-sectional area of the blank and increases the length
3) Punching: a process that forges a through hole or a semi-through hole on the blank
4) Hole expansion: a process that reduces the wall thickness of the hollow blank and increases its outer diameter
5) Mandrel drawing: a process that reduces the wall thickness of the hollow blank and increases its length
6) Bending: the process of bending the blank into a specified shape
7) Rounding: the auxiliary process of eliminating the drum shape of the cylindrical blank after upsetting and making its shape more regular
8) Displacement: the auxiliary process of offsetting one part of the blank relative to another part, but still keeping the axis parallel
9) Twisting: the auxiliary process of rotating one part of the blank relative to another part around the same axis
10) Cutting: the auxiliary process of cutting or partially separating the blank
11) Forging: the process of forging and welding two pieces of blanks into one after heating them to a high temperature
Auxiliary process:
The process of pre-deforming the blank before entering the basic process, such as ingot chamfering and neck chamfering, pre-pressing clamp handle, stepped shaft forging indentation and other processes
Finishing process:
The process used to refine the size and shape of the forging to fully meet the requirements of the forging drawing, such as drum rounding and cross-section rounding after upsetting, flattening of convex, concave and uneven and indented surfaces, flattening of end faces, bending straightening after drawing and correction after forging inclination, etc.
Classification of free forging
Block type
The horizontal dimension of the forging is larger than the height dimension, or the two are similar, such as discs, impellers, alloy steel gears, modules, hammer heads, etc. The basic process used is upsetting
Hollow type
Forgings have a central through hole, generally forgings with equal wall thickness on the circumference, and can have step changes in the axial direction. Such as various circular rings, gear circles, bearing rings and various cylinders (special-shaped cylinders), cylinder bodies, hollow shafts, etc. The basic processes used are: upsetting, punching, expanding holes or mandrel drawing, etc.
Axle type
Forgings are solid shafts, and the axial dimension is much larger than the cross-sectional dimension. They can be straight shafts or stepped shafts, such as drive shafts, axles, rollers, columns, tie rods, etc., or they can be rods with rectangular, square, I-shaped or other cross-sectional shapes, such as connecting rods, rockers, levers, push rods, etc. The basic processes for forging shaft forgings include drawing, or upsetting + drawing
Crankshafts
Forgings are solid long shafts. Not only do the cross-sectional shape and area of the forgings change along the axis, but the axis also bends in multiple directions, including various forms of crankshafts, such as single-turn crankshafts and multi-turn crankshafts. The basic processes for forging crankshaft forgings include drawing, shifting and twisting, etc.
Bending
Forgings have a curved axis, generally one bend or multiple bends. Along the curved axis, the cross section can be a uniform cross section or a variable cross section. The bend can be symmetrical or asymmetrical. The basic processes for forging this type of forgings include drawing and bending
Complex shape
This type of forgings is a forging of other shapes other than the above five types of forgings, or it can be a complex forging composed of the characteristics of the above five types of forgings, such as valve bodies, fork rods, lifting ring bodies, cross shafts, etc. Since this type of forging is difficult to forge and requires more auxiliary tools, the forging process should be reasonably selected during forging to ensure the smooth formation of the forgings.
Post time: Jun-12-2025