Introduction of Free Forging Products
Free forging is to use impact force or pressure to make the metal deform freely in all directions between the upper and lower anvil surfaces, it is a method of processing forgings with required shape and size and certain mechanical properties by any restriction.
The basic purpose of free forging is to obtain the required shape, size and internal quality of forgings economically. The types of forgings are large and medium-sized forgings. Small forgings are mainly formed with rolling materials, large forgings (especially important parts) and special steels to improve internal quality. Ingot is the main material. After forging, coarse grains are broken, non-metallic inclusions and heterogeneous particles are dispersed, internal defects are forged, the density is high, streamline distribution is reasonable, and comprehensive mechanical properties are greatly improved.
Common defects in ingots are segregation, inclusions, bubbles, shrinkage, porosity, cracks, etc.
Free forging equipment can be divided into hammer and hydraulic press. The forging hammers used in production are air hammer and steam-air hammer. Some factories also use spring hammer, splint hammer, lever hammer and steel wire hammer with simple structure and low investment. The forging hammer is deformed by impact force, and the equipment specification is expressed by the weight of the falling part. The tonnage of air hammer is small, only 0.5-10 kN, which is used for forging forgings less than 100 kg. The tonnage of steam-air hammer is larger, which can reach 10-50 KN and forge forgings less than 1500kg. Hydraulic press is the only way to produce large forgings, which deforms the billet by static pressure generated by liquid. Hydraulic press is the main equipment for forging large forgings because of its high pressure, up to 5000-15000kN.
Characteristics of Free Forging
Advantage:
1. The equipment has good versatility, simple tools and great flexibility.
2. It can be forged as small as less than 1 kg and as large as several hundred tons of large forgings, and the structure of large forgings is compact and the mechanical properties are good. Free forging is mainly used for single piece and small batch production, and is the only way to produce large and super large forgings.
Disadvantages:
1. The forgings have simple shape, large machining allowance and low precision.
2. Free forging has high technical requirements, low productivity and high labor intensity.
Advantage:
1. The equipment has good versatility, simple tools and great flexibility.
2. It can be forged as small as less than 1 kg and as large as several hundred tons of large forgings, and the structure of large forgings is compact and the mechanical properties are good. Free forging is mainly used for single piece and small batch production, and is the only way to produce large and super large forgings.
Disadvantages:
1. The forgings have simple shape, large machining allowance and low precision.
2. Free forging has high technical requirements, low productivity and high labor intensity.
Free forging process
Free forging process includes basic process, auxiliary process and dressing process.
The basic processes include upsetting, drawing, punching, reaming, bending, torsion, offset, cutting and forging. Auxiliary process is to cooperate with basic process to pre-deform billet, such as chamfering of ingot, pre-pressing clamp handle and indentation by stages.
The dressing process is arranged after the basic process to dress the size and shape of forgings.
Free forging process includes basic process, auxiliary process and dressing process.
The basic processes include upsetting, drawing, punching, reaming, bending, torsion, offset, cutting and forging. Auxiliary process is to cooperate with basic process to pre-deform billet, such as chamfering of ingot, pre-pressing clamp handle and indentation by stages.
The dressing process is arranged after the basic process to dress the size and shape of forgings.
Compared with other processing methods, free forging has the following characteristics：
Improve structure and mechanical properties of metals
After forging, the structure and properties of metal materials have been improved and improved. Forging and pressing can eliminate the defects of gas holes, shrinkage holes and dendrites in ingots. Due to the plastic deformation and recrystallization of metals, coarse grains can be refined and dense metal structures can be obtained, thus improving the mechanical properties of metals. In the design of parts, the impact resistance of parts can be improved if the direction of force and the direction of fiber structure are chosen correctly.
High material utilization rate
Metal plastic forming mainly relies on the relative position of the structure of the metal to rearrange, without the need to remove the metal.
Higher productivity
Forging process is usually carried out by means of press and die. For example, the efficiency of processing hexagonal screw with multi-station cold heading process is more than 400 times higher than that of cutting with bar material.
The metal materials used in forging should have good plasticity so that plastic deformation can be produced without fracture under the action of external force. Among the commonly used metal materials, cast iron is a brittle material with poor plasticity and can not be used for forging. Copper, aluminum and their alloys in steel and non-ferrous metals can be processed under cold or hot pressure.
It is not suitable to synthesize parts with complex shapes. Forging is formed in solid state. Compared with casting, the flow of metal is limited. Generally, heating and other technological measures are needed to achieve this. It is difficult to manufacture parts or blanks with complex shape, especially with complex inner cavity.
Improve structure and mechanical properties of metals
After forging, the structure and properties of metal materials have been improved and improved. Forging and pressing can eliminate the defects of gas holes, shrinkage holes and dendrites in ingots. Due to the plastic deformation and recrystallization of metals, coarse grains can be refined and dense metal structures can be obtained, thus improving the mechanical properties of metals. In the design of parts, the impact resistance of parts can be improved if the direction of force and the direction of fiber structure are chosen correctly.
High material utilization rate
Metal plastic forming mainly relies on the relative position of the structure of the metal to rearrange, without the need to remove the metal.
Higher productivity
Forging process is usually carried out by means of press and die. For example, the efficiency of processing hexagonal screw with multi-station cold heading process is more than 400 times higher than that of cutting with bar material.
The metal materials used in forging should have good plasticity so that plastic deformation can be produced without fracture under the action of external force. Among the commonly used metal materials, cast iron is a brittle material with poor plasticity and can not be used for forging. Copper, aluminum and their alloys in steel and non-ferrous metals can be processed under cold or hot pressure.
It is not suitable to synthesize parts with complex shapes. Forging is formed in solid state. Compared with casting, the flow of metal is limited. Generally, heating and other technological measures are needed to achieve this. It is difficult to manufacture parts or blanks with complex shape, especially with complex inner cavity.
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