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Forging and its classification

Forging is one of the two major components of forging (forging and stamping) by using a forging machine to apply pressure to a metal blank to plastically deform it to obtain a forging having a certain mechanical property, a certain shape and size. Through forging can eliminate defects such as as-cast looseness caused by metal in the smelting process, optimize the microstructure, and at the same time, the mechanical properties of the forgings are generally better than those of the same materials due to the preservation of the complete metal flow lines. Important parts in the relevant machinery with high load and severe working conditions, except for the use of rolled sheets, profiles or welded parts with simple shapes, forgings are often used.


There are many types of forging:

1. According to the forging temperature, it can be divided into hot forging, warm forging, and cold forging.

2. According to the forming mechanism, forging can be divided into free forging, die forging, rolling ring, special forging.

One (1) hot forging

The forging process performed above the metal recrystallization temperature is referred to as hot forging. Hot calcination, also known as hot die forging, has a severe flow of deformed metal during forging, and the contact time between the forging and the mold is longer. Therefore, the mold material is required to have high thermal stability, high-temperature strength and hardness, impact toughness, thermal fatigue resistance and wear resistance, and is easy to process. Hot forging dies for lighter workloads can be made from low alloy steel.

In addition to large and medium-sized free forgings using steel ingots as blanks, general forgings use various metal bars as blanks. Before the bar is forged, it is generally cut into the required size on the special unloading equipment. The common method of cutting is as follows:

Sawing

Sawing and cutting are often carried out on circular saws and bow saws and high speed band saws.

The circular saw is driven by a motor to drive the toothed saw blade to rotate slowly and move to cut the bar. The saw blade has a maximum diameter of 2m and the spawnable bar has a diameter of less than 750mm.

The bow saw is driven by a motor to drive the toothed saw blade to reciprocate and cut the bar. The bar material that can be sawed has a diameter of 100 mm or less. For bars with particularly small diameters, they can also be sawed in bundles.

The sawing feature is that the cut section is flat and accurate in size; however, the productivity is low, the kerf loss is lost, and the saw blade and the saw disc are also relatively large. The high-speed band saw is a more advanced cutting device with high production efficiency and regular blank shape.

Cutting

Shear blanking is generally carried out on a shearing machine, which can cut steel slabs having a diameter of 200 mm or less. When the steel billet is cold-cut, the sheared portion will generate a large stress and crack. Therefore, the high carbon steel, the alloy steel and the billet with a large cross-sectional size need to be preheated to 350-700 ° C before shearing; Steel billets with smaller cross-sections such as carbon steel and medium carbon steel can be cold cut.

The characteristic of the shearing machine is that the automatic feeding and discharging mechanism can be installed, the labor conditions of the workers are good, the production efficiency is high, the metal is saved, and the utilization rate of the materials is improved. However, the shear end face is not flat and slightly skewed, especially when the billet having a large diameter is cut in a hot state. Shears are commonly used in mass-produced die forging shops.

Shear blanking can also be carried out on equipment such as trimming presses, friction presses and the like.

Break off

The breaking of the blanking is carried out on a hydraulic press or a crank press. The pressure is transmitted to the material through the punch, causing the material to break along the prior incision. The principle is as shown. Before the breaking, the pre-cut is usually made by sawing or gas cutting. The purpose is to cause large stress concentration at the incision to ensure that the material does not cause large plastic deformation and affect the quality of the section when it is broken at a certain part.

The fracture is suitable for high carbon steel and high alloy steel with high hardness. For example, bearing steels such as GCr15, GCr15SiMn, GSiMnMo, and GSiMnV have a heating temperature of 300 to 400 °C.

Wheel cutting

Grinding wheel cutting is performed on a grinding wheel cutter. The grinding wheel cutting machine is driven by a motor to drive a thin grinding wheel (the thickness is generally less than 3 mm) to rotate at a high speed, and the billet is cut by manual or maneuvering to move it up and down. The grinding wheel cutter can cut metal blanks of any hardness up to 40mm in diameter.

The grinding wheel is characterized by high productivity and flat cutting section; however, the loss of the thin grinding wheel is large, the working conditions of the workers are poor, and good ventilation equipment is required.

Flame cutting

Flame cutting is also called gas cutting. The principle is to use a gas cutter or a common welding torch to locally heat the steel to a melting temperature with an oxygen gas stream to gradually melt it. It is mainly used for large-section cutting of large billets and forgings (the thickness of the cutting section can reach more than 1500mm), and can also be used for trimming of large-scale die forgings produced in small batches.

Anode cutting

The principle is to cut metal materials by electro corrosion and electrochemical corrosion. The size of the material to be cut is 30 to 300 mm. Anode cutting is characterized by high productivity, low waste, and the ability to cut metal materials of any hardness with a clean profile. Warm forging is die forging that heats the mold to the forging temperature of the metal. The plasticity of the metal can be fully utilized to reduce the deformation resistance. Forging can be carried out with smaller tonnage equipment. Forming a workpiece with a complicated shape. It is mostly used for the processing of aluminum alloys, titanium alloys and other high-temperature alloy forgings which are difficult to deform during die forging and have a narrow deformation temperature range.

One (2) warm forging

Warm forging is die forging that heats the mold to the forging temperature of the metal. The plasticity of the metal can be fully utilized to reduce the deformation resistance. Forging can be carried out with smaller tonnage equipment. Forming a workpiece with a complicated shape. It is mostly used for the processing of aluminum alloys, titanium alloys and other high-temperature alloy forgings which are difficult to deform during die forging and have a narrow deformation temperature range. Warm forging is a forging process in which the metal is heated to near the recovery temperature or recrystallization temperature. The work hardening has different degrees of reduction during warm forging deformation, so the forging deformation force is lower than cold forging but larger than hot forging. Forgings have better precision, surface roughness, surface oxidation, decarburization, and mechanical properties than hot forgings, similar to cold forgings. It is also possible to forge high carbon steel and high alloy steel materials which are difficult to form by cold forging.

Generally speaking, small precision dies forgings of low carbon and low alloy steels with less complicated shapes can be formed by cold forging process; for medium and small-medium carbon steel precision die forgings with complicated shapes, cold forging method is difficult to solve the forming problem. Or simply using the cold forging process, the cost is too high, then warm forging can be used.


In general, the recrystallization temperature of steel is about 750 ° C. When forging at 700 ° C or higher, the deformation can be dynamically released due to the deformation energy, and the forming resistance is drastically reduced. When forging at 700-850 ° C, the scale of the forging is less. The surface decarburization phenomenon is mild, and the forging size changes little; when forging at 950 °C or above, although the forming force is smaller, the forging scale and surface decarburization are serious, and the forging size changes greatly. Therefore, forging in the range of 700-850 ° C can obtain forgings with better quality and precision.

Warm forging refers to the forging of steel forgings below the crystallization temperature and above normal temperature. The purpose of the warm forging process is to obtain precision forgings, which can improve the precision and quality of forgings without the large forming force of cold forging. The application of the warm forging process is closely related to the forging material, the size of the forging, and the complexity of the forging.

Warm forging is a kind of less non-cutting plastic forming process developed on the basis of cold forging. Its deformation temperature is generally considered to be in the temperature range above room temperature and below the recrystallization temperature. The current common temperature range of forging is generally 200 ° C to 850 ° C for ferrous metals and generally below room temperature to 350 ° C for nonferrous metals.

Warm forging has the advantages of cold forging and hot forging to a certain extent. Warm forging is because the metal is heated, the deformation force of the blank is smaller than that of cold forging, and the forming is easier than cold forging. The deformation amount larger than cold forging can be used, thereby reducing the number of processes, reducing the mold cost and equipment tonnage, and the die life is also colder. When forging is high. Compared with hot forging, due to low heating temperature, oxidation and decarburization, forgings have higher dimensional tolerances and lower surface roughness.

Warm forging is mainly used for stainless steel, alloy steel, bearing steel and tool steel with high hardening or high deformation force during cold forging deformation; poor plasticity during cold deformation, easy to crack materials, such as aluminum alloy, copper alloy, etc.: cold state Materials that are difficult to process, but are heavily oxidized and inhaled in hot state, such as titanium, molybdenum, chromium, etc.: complex shape or in order to improve the overall mechanical properties of the product, it is not suitable for cold forging; the degree of deformation is large, or the part size is large, cold When the capacity of the forging equipment is insufficient.


Warm forging temperature selection

When selecting the warm forging temperature, the following influencing factors should generally be considered:

(1) Effect of temperature on material flow stress and plasticity

Temperatures with lower flow stress or temperatures exceeding larger flow stress are generally selected. For metals with a blue-brittle temperature zone, the temperature range should be avoided by selecting the warm forging temperature.

(2) Strong oxidation of steel

Generally, the oxidation of the steel is higher than 800 ° C, so the warm forging temperature should be lower than 800 ° C. It can be used to prevent the oxidation of the blank when it is heated by rapid heating or solid lubricant on the surface of the blank.

(3) Effect of warm forging temperature on product performance

As the warm forging temperature increases, the toughness and plasticity of the product increase, while the strength decreases. At a certain temperature, as the degree of deformation increases, the strength of the product increases and the plasticity decreases. When the mechanical properties of warm extruded steel are between 200 °C and 400 °C, the mechanical properties of the warm extruded product are similar to those of the cold extruded product at the same degree of deformation; and the mechanical properties of the warm extruded product at 400 °C to 800 °C The performance is 1.1 to 1.5 times that of the annealed product.

Warm forging application

(1) Stainless steel, alloy steel, bearing steel and tool steel with high hardening or high deformation resistance during cold forging.

(2) Materials with poor plasticity and easy cracking during cold forming, such as aluminum alloy LC4, copper alloy HPb59-1, and titanium alloy.

(3) Materials that are difficult to process in cold state, and that are heavily oxidized and hydrogen-absorbing during hot forming, such as titanium, molybdenum, and chromium.

(4) Parts with complex shapes and cold forging are not suitable.

(5) The degree of deformation is large, or the size of the parts is so large that the existing equipment capacity is insufficient during cold forging.

(6) To facilitate the organization of continuous production.

The warm forging forming is to complete the forming of the part under the condition that the deformation resistance is lowered and the plasticity is improved after the temperature of the metal material is raised, and the surface is not violently oxidized. The deformation temperature has an important influence on the plasticity of the metal. Most of the metals increase in plasticity with increasing temperature, but this increase does not increase nonlinearly. In some temperature ranges of the heating process, brittle zones often occur due to precipitation or phase change of excess phase, which reduces the plasticity of the metal. In general, when the temperature rises from the thermodynamic temperature to zero, three brittle zones may occur low temperature, medium-temperature, and high-temperature brittle zone.

One (3) cold forging

A general term for plastic processing such as cold die forging, cold extrusion, and cold heading. Cold forging is a forming process below the recrystallization temperature of the material and is forging at a temperature below the recovery temperature. Forging in the production of unheated blanks is called cold forging. Cold forging materials are mostly aluminum and some alloys, copper and some alloys, low carbon steel, medium carbon steel and low alloy structural steel with less deformation resistance and good plasticity at room temperature. Cold forgings have good surface quality and high dimensional accuracy, which can replace some cutting processes. Cold forging can strengthen the metal and increase the strength of the part.

Cold forging, also known as cold volume forming, is a manufacturing process and a processing method. It is basically the same as the cold stamping process. The cold forging process is also composed of three elements: materials, molds, and equipment. Only the materials in the stamping process are mainly sheets, and the materials in the cold forging process are mainly discs or wires.

Japan is called cold forging (referred to as cold forging), China is called cold shovel, and some screw factories also like to call it ahead.

Basic concepts

Cold forging refers to various volume forming performed below the recrystallization temperature of the metal. According to the theory of metallography, the recrystallization temperature of various metal materials is different;

The shape of cold-forged parts is becoming more and more complex, from the initial stepped shafts, screws, screws, nuts and conduits to parts with complex shapes.

The typical process of the spline shaft is: positively pressing the rod portion - the middle portion of the upset - the squeeze spline;

The main process of the spline sleeve is: anti-squeezing the cup-shaped part - the bottom part is made into a ring-shaped part - the sleeve is being squeezed.

The cold extrusion technology of cylindrical gears has also been successfully used in production. In addition to ferrous metals, cold extrusion applications of copper alloys, magnesium alloys, and aluminum alloy materials are becoming more widespread.

Application range

The rapid development of the current automobile industry, motorcycle industry and machine tool industry has provided the driving force for the development of the traditional technology of cold forging. For example, the total national output of motorcycles in China in 1999 was 11.26 million. According to preliminary estimates in 2000, the total demand for automobiles in China will reach 3.3 million by 2005, including 1.3 to 1.4 million cars. The demand for forgings in the automotive industry is above 500,000 to 600,000 tons. Although the cold forging technology started in China is not too late, the development speed is far from the developed countries. So far, the weight of cold forgings on cars produced in China is less than 20kg, which is equivalent to half of the developed countries. The potential is great. Strengthening the development and application of cold forging technology is an urgent task for China.

Process

Cold precision forging is a (near) net forming process. The parts formed by this method have high strength and precision, and the surface quality is good. At present, the total amount of cold forgings used in a foreign ordinary car is 40~45kg, and the total amount of tooth-shaped parts is more than 10kg. The weight of the cold-forged gear can reach more than 1kg and the tooth profile can reach 7th.

Continuous process innovation has promoted the development of cold extrusion technology. Since the 1980s, precision forging experts at home and abroad have begun to apply split forging theory to the cold forging of spur gears and helical gears. The main principle of split forging is to create a split or split channel for the material in the forming portion of the blank or mold. During the forging process, while the material fills the cavity, part of the material flows to the split or split channel. The application of the split forging technology has enabled the production of high-precision gears to be small and without cutting to quickly reach the industrial scale. For extrusions with a length to diameter ratio of 5, such as piston pins, a wide axial splitting of the axial residual mass can be used for cold extrusion once, and the stability of the punch is good; for flat spur gears Forming, cold extrusion of the product can also be achieved with radial residual blocks.

The occlusion forging is a one-way or opposite-direction extrusion of the metal in one or two punches in the closed die to obtain a near-net-shape precision forging without flash. Some car precision parts such as planetary and semi-axle gears, star sleeves, cross bearings, etc., if the cutting method is used, not only the material utilization rate is very low (average less than 40%), but also the labor and the production cost are extremely high. Foreign countries use occlusion forging technology to produce these net forgings, eliminating most of the cutting processing, and the cost is greatly reduced. [1]

skills requirement

Cold forging technology has higher forming precision than warm forging and hot forging and has unique advantages in the field of precision forming. The application of the cold forging process improves the internal smoothness, dimensional accuracy, surface strength, prolongs the life of the barrel, improves the firing accuracy of the gun, and facilitates the processing of the cone barrel, which can reduce the quality. The cold forging process was first proposed by Steyr. Later, many countries in the world used Steyr's cold forging machine to process the barrel.

The development of cold forging technology is mainly to develop high value-added products and reduce production costs. At the same time, it is constantly infiltrating or replacing it in the fields of cutting, powder metallurgy, casting, hot forging, sheet forming, etc. The combination of processes constitutes a composite process. Hot forging-cold forging composite plastic forming technology is a new precision metal forming process combining hot forging and cold forging. It makes full use of the advantages of hot forging and cold forging: good metal plasticity in a hot state, flow stress Low, so the main deformation process is done with hot forging; the cold forgings have high precision, so the important dimensions of the parts are finally formed by cold forging. Hot forging-cold forging composite plastic forming technology appeared in the 1980s and has been used more and more widely since the 1990s. Parts manufactured with this technology have achieved good results with improved precision and reduced cost.

Process

Cold precision forging is a (near) net forming process. The parts formed by this method have high strength and precision, and the surface quality is good. At present, the total amount of cold forgings used in a foreign ordinary car is 40~45kg, and the total amount of tooth-shaped parts is more than 10kg. The weight of the cold-forged gear can reach more than 1kg and the tooth profile can reach 7th.

Continuous process innovation has promoted the development of cold extrusion technology. Since the 1980s, precision forging experts at home and abroad have begun to apply split forging theory to the cold forging of spur gears and helical gears. The main principle of split forging is to create a split or split channel for the material in the forming portion of the blank or mold. During the forging process, while the material fills the cavity, part of the material flows to the split or split channel. The application of the split forging technology has enabled the production of high-precision gears to be small and without cutting to quickly reach the industrial scale. For extrusions with a length to diameter ratio of 5, such as piston pins, a wide axial splitting of the axial residual mass can be used for cold extrusion once, and the stability of the punch is good; for flat spur gears Forming, cold extrusion of the product can also be achieved with radial residual blocks.

The occlusion forging is a one-way or opposite-direction extrusion of the metal in one or two punches in the closed die to obtain a near-net-shape precision forging without flash. Some car precision parts such as planetary and semi-axle gears, star sleeves, cross bearings, etc., if the cutting method is used, not only the material utilization rate is very low (average less than 40%), but also the labor and the production cost are extremely high. Foreign countries use occlusion forging technology to produce these net forgings, eliminating most of the cutting processing, and the cost is greatly reduced.

SKills requirement

Cold forging technology has higher forming precision than warm forging and hot forging and has unique advantages in the field of precision farming. The application of the cold forging process improves the internal smoothness, dimensional accuracy, surface strength, prolongs the life of the barrel, improves the firing accuracy of the gun, and facilitates the processing of the cone barrel, which can reduce the quality. The cold forging process was first proposed by Steyr. Later, many countries in the world used Steyr's cold forging machine to process the barrel.

The development of cold forging technology is mainly to develop high value-added products and reduce production costs. At the same time, it is constantly infiltrating or replacing it in the fields of cutting, powder metallurgy, casting, hot forging, sheet forming, etc. The combination of processes constitutes a composite process. Hot forging-cold forging composite plastic forming technology is a new precision metal forming process combining hot forging and cold forging. It makes full use of the advantages of hot forging and cold forging: good metal plasticity in a hot state, flow stress Low, so the main deformation process is done with hot forging; the cold forgings have high precision, so the important dimensions of the parts are finally formed by cold forging. Hot forging-cold forging composite plastic forming technology appeared in the 1980s and has been used more and more widely since the 1990s. Parts manufactured with this technology have achieved good results with improved precision and reduced cost.

Process disadvantage

High material requirements; not suitable for small processing; high mold requirements.


Two (1) free forging

Free forging is a processing method that uses impact force or pressure to freely deform metal in all directions between the upper and lower anvil surfaces without any limitation to obtain a desired shape and size and certain mechanical properties, referred to as free forging.

The tools and equipment used for free forging are simple, versatile and low cost. Compared with cast blanks, free forging eliminates defects such as shrinkage, shrinkage, and porosity, resulting in higher mechanical properties of the blank. Forgings are simple in shape and flexible in operation. Therefore, it is of particular importance in the manufacture of heavy machinery and important parts.

Application field

Free forging is to control the shape and size of the forging by manual operation. Therefore, the forging has low precision, large machining allowance, high labor intensity, and low productivity, so it is mainly used in single-piece and small-batch production.


classification

Free forging is divided into manual free forging and machine free forging.

Manual free forging has low production efficiency and high labor intensity and is only used for repairing or production of simple, small and small-batch forgings.

In modern industrial production, free forging of machines has become the main method of forging production, and it plays a particularly important role in the manufacture of heavy machinery. The shape and size of the forged parts produced are primarily determined by the skill level of the operator.

Major equipment

Free forging equipment is divided into two categories: forging hammer and hydraulic press. Forging hammers used in production include air hammers and steam-air hammers. Some plants also use spring hammers, plywood hammers, lever hammers and wire hammers with simple structure and low investment [1]. The hydraulic press deforms the billet by the static pressure generated by the liquid and is the only way to produce large forgings.

Basic process

The basic processes of free forging include upsetting, lengthening, punching, bending, twisting, misalignment, cutting and forging.

Lengthen

Also referred to as extension, it is a forging process that reduces the cross-sectional area of the blank and increases the length. Long length is often used for forging rods and shaft parts. There are two main methods for lengthening:

1. Pull up on the flat anvil.

2. Pull up on the mandrel.

In forging, the mandrel is inserted into the punched blank and then elongated as a solid blank. When pulling out, it is generally not a single pull. First, the blank is drawn into a hexagonal shape. After being forged to the required length, the chamfer is rounded and the mandrel is taken out. In order to facilitate the removal of the mandrel, the working part of the mandrel should have a slope of about 1:100. This lengthening method can increase the length of the hollow billet, reduce the wall thickness, and the inner diameter is constant and is often used for forging sleeve type long hollow forgings.

Upsetting

A forging process that reduces the height of the blank and increases the cross-sectional area. The upsetting process is mainly used for forging gear blanks and round cake forgings. The upsetting process can effectively improve the blank structure and reduce the anisotropy of mechanical properties. Repeated upsetting and lengthening can improve the morphology and distribution of carbides in high alloy tool steels.

There are three main forms of upsetting:

1, completely upright. Full upsetting is to place the blank vertically on the anvil surface, and under the hammering of the upper anvil, the billet is made to have a reduced height and a plastic deformation with an increased cross-sectional area.

2, the end is thick. After the billet is heated, one end is placed in a leaky disk or a tire mold to limit the plastic deformation of this portion, and then the other end of the billet is hammered to be formed into an upset shape. The upsetting method of the leaky tray is mostly used for small batch production; the method of upsetting the tire mold is mostly used for mass production. Under single-piece production conditions, the portion that requires upsetting may be locally heated, or after heating, the portion that does not require upsetting will be chilled in water and then upset.

3, the middle is thick. This method is used for forging a forging having a large intermediate section and a small cross-section at both ends, for example, a gear blank having a boss on both sides is forged by this method. Before the billet is thickened, the two ends of the billet are first drawn, and then the billet is erected in the middle of the two drain pans to be hammered to make the middle portion of the billet upset.

punching

It is a forging process in which a through-hole or a hole is not punched through the bad material. There are two main methods for punching:

1, double-sided punching method. When punching the blank to a depth of 2/3 to 3/4, the punch is taken out, the blank is turned over, and the punch is used to align the position from the reverse side, and the hole is punched out.

2, single-sided punching method. A blank having a small thickness can be punched by one side. When punching, the blank is placed on the backing ring, and the large end of the slightly tapered punch is aligned with the punching position, and the blank is driven by hammering until the hole penetrates.

bending

A forging process in which a certain tool mold bends a billet into a predetermined shape is called bending.

There are two common bending methods:

1. Forging hammer compression bending method. One end of the blank is pressed by the upper and lower anvils, and the other end is pulled by a sledgehammer or bent by a crane.

2. Die bending method. Bending in the mat allows for a small forging that is more accurate in shape and size.

Cutting

[Cutting] refers to a forging process in which the billet is divided into portions or partially cut, or a part is cut off from the outside of the billet, or a part is cut out from the inside.

Misplaced

[Shifting] refers to a forging process in which a portion of a blank is staggered in parallel with respect to another portion, but still maintains a parallel axis, and is often used for forging crankshaft parts. When the shift is made, the blank is partially cut, and then the impact force or pressure of equal size, opposite method, and perpendicular to the axis is applied on both sides of the slit to make the blank shift.

Forging.

[Forging] is a forging process in which the billet is heated in the furnace to a high temperature and then hammered to make the two are combined in a solid-state. Forging methods include lap joints, butt joints, snap joints, and the like. The joint strength after forging can reach 70% to 80% of the strength of the material to be joined.

[Twist] is a forging process in which a part of the wool is rotated by a certain angle about its axis with respect to another part. This process is often used to forge multiple crankshafts and to correct certain forgings. When the small billet has a small twist angle, a hammering method can be used.

defect

crack

It may be caused by the poor quality of the blank, insufficient heating, too low forging temperature, improper forging of the forging and incorrect forging method.

End depression and axial crack

It may be that the inside of the billet is not hot during forging or the entire section of the billet is not forged, and the deformation is only caused on the surface of the billet.

fold

It may be caused by the fact that the billet is fed at a level less than the one-sided reduction.

Two (2) die forging

Die forging refers to a forging method in which a blank is molded by mold on a special die forging device to obtain a forged piece. The forgings produced by this method are accurate in size, small in machining allowance, and relatively complicated in structure and high in productivity.

A process for forging a metal blank by a forging die on a die forging hammer or a press. The die forging process has high production efficiency, low labor intensity, accurate size, small machining allowance, and forging forgings with complex shapes; suitable for mass production. However, the cost of the mold is high, and special die forging equipment is required, which is not suitable for single or small batch production.

1 The shape of the forging can be complicated due to the flow of the mold guiding metal.

2 The forging flow line inside the forging is distributed according to the contour of the forging, which improves the mechanical properties and service life of the part.

3 Easy to operate, easy to mechanize, and high productivity.

classification

According to different equipment, die forging is divided into hammer forging, crank press forging, flat forging die forging, friction press [2] die forging and so on. The equipment used for hammer forging is a die forging hammer, usually, an air die forging hammer. For a complex forged piece, it is initially formed in a blank cavity and then forged in a forging cavity. According to the forging structure classification: the forging die has a burr groove for accommodating excess metal, which is called open die forging; on the contrary, the forging die does not have a burr groove for accommodating excess metal, which is called closed die forging. Directly formed from the original blank, it is called single die boring. For forgings with complex shapes, it is required to be pre-formed in several steps on the same forging die, which is called multi-die boring. Precision dies forging is developed on the basis of die forging. It can forge parts with complex shapes and high dimensional accuracy, such as bevel gears, blades, and aerospace parts.

preparation

The forging die for die forging consists of two upper and lower modules, the die is the working part of the forging die, and the upper and lower die are each half. The dovetail and wedge are fixed on the anvil and the workbench, and the lock or guidepost is guided to prevent the upper and lower modules from being misaligned. The metal blank is deformed in the shape of the mold.

The steps of die forging are blanking pre-forging and final forging. The die of the final forging die is determined by the size and shape of the forging, plus the margin and deviation. Die forging is generally divided into open die forging and closed die forging: the open die forging die has a burr groove around it, the excess metal flows into the groove after forming, and finally the burr is cut off; the closed die forging has only a small at the end. Raw edges, if the blank is accurate, it can also be free of burrs.


Research on Die Forging Process of HXN5 Connecting Rod

The HXN5 locomotive is a high-power diesel locomotive developed by a locomotive company and the United States GE Company. The connecting rod, which is one of the key parts of the diesel engine, is imported and expensive. In 2012, the company introduced the PZS series 22,000-ton electric screw press produced by the German Miller-Wanjiadun Company and localized the HXN5 locomotive diesel engine connecting rod.

The connecting rod is made of 42Cr Mo A alloy steel. The forgings are long shaft parts with an I-shaped cross-section. The shape and shaft are not machined after die forging so that the tight link surface structure can be obtained and the surface of the connecting rod can be improved. The strength and the roughing process of the connecting rod can be omitted, the process flow of the connecting rod is simplified, and the production cost is reduced, which puts high requirements on the die forging process of the connecting rod.

1 HXN5 connecting rod forging process analysis

The connecting rod die forgings belong to the long rod type special forgings, the shaft is relatively simple, the small end of the forging has a height drop, the angle between the big end and the shaft axis is large, and the weight of the big end has a large difference, in order to make the material use more economical and reasonable, The blank should be made before forging to make the link member easier to form during forging.

2 HNX5 connecting rod forging process design

According to the characteristics of die forgings, the key problems to be solved in the whole die forging process are: 1 to carry out the reasonable material division to form a blank suitable for die forging; 2 to properly set the strike point and strike energy when die forging on a 22,000-ton electric screw press.

The mold is the most direct factor affecting the dimensional accuracy of the die forging. According to the structural design of the forging, the forging die of the connecting rod is determined, and the horizontal and vertical square closed locking buckle is adopted to reduce the misalignment. The mold was selected from 5Cr Ni-Mo, the heat treatment hardness was HRC44~48, the mold roughness was 1.6, and the remaining 3.2.

Flange forging closed die forging process and mold

As a pipe joint, flange parts are widely used in construction, chemical, water supply and drainage, petroleum, fire protection, plumbing, shipbuilding, and other fields because of their flexibility in disassembly and assembly. The closed die forging process is used to precisely form small and medium-sized flange parts, which can save materials and good forgings. In mass production, it shows the advantages of “finer, cleaner and more economical”.

A flange part for chemical pipelines for conveying low-pressure gas in 1Cr18Ni9 stainless steel. After a comprehensive analysis of product structure, quality requirements, production batch and forming characteristics, it is proposed to form the flange by closed die forging process. Forgings, to obtain better economic and social benefits and enhance the market competitiveness of enterprises.

1 process analysis

Flange parts drawing, the flange part diameter is up to Φ140mm, the full height is 55mm, the central aperture is Φ50mm, the calculated part volume is 287950mm3, the mass is 2.25kg. For example, the Φ145mm×60mm bar material is directly cut and processed, and the material utilization rate is only 29.1%, and the processing amount is large. Due to the large production volume, in order to reduce the production cost, it is a good manufacturing process to use the die forging blank + cutting process for the part. Taking into account the small size of the parts, the closed die forging process can be used to precisely form the flange forgings on the common forging press friction screw press, which can further reduce the production cost.

The production process of the flange member is: blanking → blank cleaning → heating → closed die forging → punching and skinning → pre-heat treatment → mechanical processing → final heat treatment.

2 Develop the closed die forging process

Develop forging drawings

8 Φ14 holes uniformly distributed on the flange and 6mm×4mm of the lower end annular sealing groove. Due to the small size, it can not be forged, filled with the remaining block, and obtained in the laser cutting process; in order to reflect the advantages of closed die forging technology, reduce The machining allowance is formed by swaging the boss with a lower end portion of 5 mm. The parting surface is taken on the upper surface of the flange. After considering the machining allowance, forging tolerance, and punching, the cold forging drawing is shown in Fig. 2 is drawn, and the volume is calculated to be 371951 mm3.

Based on the dimensions of the cold forging drawings, the shrinkage rate is added to form a hot forging drawing for equipment tonnage calculation, forging design and manufacturing.

3 mold working principle

The mold base of the closed mold of the flange forging adopts the standard mold base of the 1600t friction screw press, the lower mold 2 and the tailgate 7, the inclined surface pressure plate 5, are assembled by the inclined surface with the inclination of 15°, and are bent by the inclined surface pressing plate. The head wedge is engaged with the bevel groove of the lower die holder 6 (the inclination is 10°), and the lower die is fixed to the lower die holder by tightening the screw 4.

Sidewall panels 9 and screws 10 are used for lateral fastening and adjustment of the lower mold. The upper mold 1 and the upper mold base are fixed in the same manner as above. The upper and lower mold bases are respectively bolted to the slider and the work surface of the press. The guidepost and the guide sleeve are guide and positioning devices that guide the center of the upper and lower molds to align. In the case of closed die forging, the blank is placed in the lower mold, and the upper mold is pressed against the press slider to apply pressure to the blank, and the blank is filled with the mold cavity by the indentation, and the upper mold and the lower mold are used. At the right time, the blank just fills the mold cavity. The die forging is ejected by the ejector pin 8 and the forging process is finished.

Two (3) grinding rings.

Rolling ring refers to the production of ring-shaped parts of different diameters by special equipment grinding machine, and also used to produce wheel-shaped parts such as automobile wheels and train wheels.

Two (4) special forging.

Special forging includes roll forging, cross wedge rolling, radial forging, liquid forging, and other forging methods, which are more suitable for the production of parts with special shapes.


DESHENGRUI Machinery is a professional CNC manufacturing and Sheet metal fabrication company, including CNC machining services, CNC Turning service, CNC milling services, CNC drilling services, laser cutting services, stamping services, Die casting service, iron casting service and Steel Forging service.

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