Forging is one of the two components of forging (forging and stamping), which is a processing method that makes use of forging machinery to exert pressure on metal billets and produce plastic deformation to obtain forgings with certain mechanical properties, certain shape and size. Through forging can eliminate the defects such as loose cast state produced in the smelting process of metal, optimize the microstructure structure, at the same time because of the preservation of a complete metal streamline, the mechanical properties of the forging is generally better than the same material castings. [SCALE STEEL]Forgings are mostly used for the important parts with high load and severe working conditions in the relevant machinery, except for the simple plate, profile or welding parts that can be rolled.
Mainly used in automobiles, general machinery and so on
Wuxi turbine blade maximum impact force 35,500 tons of screw press
The initial recrystallization temperature of steel is about 727℃, but 800℃ is generally used as the dividing line, higher than 800℃ is hot forging; Between 300 and 800℃ is called warm forging or semi-hot forging, forging at room temperature is called cold forging.
Forgings used in most industries are hot forging. Warm forging and cold forging are mainly used in forging parts of automobiles and [SCALE STEEL]general machinery. Warm forging and cold forging can effectively save material.
As mentioned above, according to the forging temperature, it can be divided into hot forging, warm forging and cold forging.
According to the forming mechanism, forging can be divided into free forging, die forging, grinding ring and special forging.
1, free forging. It refers to the processing method of forging parts with simple universal tools, or directly applying external force to the blank between the upper and lower anvils of forging equipment, so that the blank can be deformed and the required geometric shape and internal quality can be obtained. The forging produced by free forging method is called free forging. Free forging is based on the [SCALE STEEL]production of small number of forgings, forging hammer, hydraulic press and other forging equipment to form the blank processing, obtain qualified forgings. The basic processes of free forging include upsetting, drawing, punching, cutting, bending, twisting, dislocation and forging. Free forging is all hot forging.
2, die forging. Die forging is divided into open die forging and closed die forging. The metal blank is deformed under pressure in the forging die chamber of a certain shape to obtain the forging. Die forging is generally used to produce small weight and large batch parts.
Die forging can be divided into hot die forging, warm forging and cold forging. Warm forging and cold forging are the future [SCALE STEEL]development direction of die forging and represent the level of forging technology.
According to the material, die forging can also be divided into black metal die forging, non-ferrous metal die forging and powder products forming. As the name implies, is that the materials are carbon steel and other ferrous metals, copper and aluminum and other non-ferrous metals and powder metallurgy materials.
Extrusion should be attributed [SCALE STEEL]to die forging, can be divided into heavy metal extrusion and light metal extrusion.
Closed die forging and closed upsetting forging are two advanced techniques of die forging. It is possible to finish complex forgings with one or more steps. Because there is no flying edge, the forgings force area is reduced, the required load is reduced. However, it should be noted that the blank can not be completely limited, so it is necessary to strictly control the volume of the blank, control the relative position of the forging die and measure the forgings, and try to reduce the wear of the forging die.
3, grinding ring. Grinding ring refers to the production of ring parts of different diameters through special equipment[SCALE STEEL] grinding ring machine, also used to produce car wheel hub, train wheels and other wheel parts.
4, special forging. Special forging includes roll forging, cross wedge rolling, radial forging, liquid die forging and other forging methods, which are more suitable for the production of some special shape parts.
For example, roll forging can be used as an effective preforming process to greatly reduce the subsequent forming pressure; Cross wedge rolling can produce steel balls, drive shafts and other parts; Radial forging can produce large gun barrel, step shaft and other forgings.
According to the motion mode of forging die, forging can be divided into swing forging, swing forging, roll forging, cross wedge rolling, ring rolling and cross rolling. Rotary forging, rotary forging and ring forging[SCALE STEEL] can also be processed by precision forging. In order to improve the utilization rate of materials, roll forging and cross rolling can be used as the prior process of slender materials. Rotary forging, like free forging, is also partially formed. Its advantage is that compared with the forging size, the forging force can also be formed under the condition of small. Including free forging, the way of forging and processing the materials from the mold surface near to the free surface extension, therefore, it is difficult to guarantee the accuracy, so will the movement direction of the forging die and spin blacksmith sequence with computer control, a lower forging force are available on complex shape, high precision products, such as the production of many varieties, large size of the turbine blade forgings.
The die movement and degree of freedom of forging equipment are inconsistent. According to the characteristics of deformation limitation of bottom dead point, forging equipment can be divided into the following four forms:
1, limited forging force form: oil pressure direct drive slider hydraulic press.
2. Quasi-stroke limit: hydraulic press driven by crank and connecting rod mechanism.
3, stroke limit mode: crank, connecting rod and wedge mechanism to drive the slider mechanical press.
4. Energy limit: Screw and friction press with screw mechanism.
In order to obtain high accuracy, care should be taken to prevent overload at the bottom dead point, control speed and mold position. Because these will have an impact on forging tolerance, shape accuracy and die life. [SCALE STEEL] In addition, in order to maintain accuracy, attention should also be paid to adjusting the slideway gap, ensure stiffness, adjust the bottom dead point and use of auxiliary transmission device and other measures.
There are vertical and horizontal movement of the slider (used for slender forging, lubrication cooling and high-speed production of parts forging), the use of compensation device can increase the movement of other [SCALE STEEL]directions. The required forging force, process, material utilization, yield, dimensional tolerance and lubrication cooling methods are also factors that affect the level of automation.
The forging materials are mainly carbon steel and alloy steel, followed by aluminum, magnesium, copper, titanium and their alloys. The original state of the material is bar, ingot, metal powder and liquid metal. The ratio of the cross-sectional area of a metal before and after deformation is called the forging ratio. Correct selection of forging ratio, reasonable heating temperature and holding time, reasonable initial forging temperature and final forging temperature, reasonable amount [SCALE STEEL]of deformation and deformation speed have great influence on improving product quality and reducing cost.
General small and medium forgings are round or square bars as billets. The bars have uniform grain structure and good mechanical properties, accurate shape and size, good surface quality, convenient for mass production. As long as the heating temperature and deformation conditions are controlled reasonably, good forgings can be forged without large forging deformation.
Ingot is only used for large forgings. The ingot is an as-cast structure with large columnar crystals and loose centers. Therefore, the columnar crystals must be broken into fine grains through large plastic[SCALE STEEL] deformation, and loose compaction can obtain excellent metal structure and mechanical properties.
Powder forging can be made from pre - made powder metallurgy preforms after pressing and firing under hot state by die forging without flapping. Forgings powder is close to the density of ordinary die forgings, with good mechanical properties and high precision, which can reduce subsequent cutting. Powder forgings with uniform internal structure and no segregation can be used to manufacture small gears and other workpiece. However, the price of powder is much higher than that of ordinary [SCALE STEEL]bar, so its application in production is limited.
The desired shape and properties of die forgings can be obtained by applying static pressure to the liquid metal pouring in the die chamber to make it solidify, crystallize, flow, plastic deformation and form under the action of pressure. Liquid metal die forging is a forming method between die casting and die forging, especially suitable for complex thin-walled parts which are difficult to be formed by ordinary die forging.
Forging materials in addition to the usual materials, such as various composition of carbon steel and alloy steel, followed by [SCALE STEEL]aluminum, magnesium, copper, titanium and its alloys, high temperature iron base alloy, nickel base superalloy, cobalt-based superalloy deformation of the alloy also USES forging or rolling way, only the alloy due to its plastic zone is relatively narrow, so the forging difficulty will be relatively large, Different materials heating temperature, open forging temperature and final forging temperature have strict requirements.
1. Aircraft forgings
2, diesel engine forgings
4. Weapon forgings
5, mine forgings
6, nuclear power forgings
7, petrochemical forgings
The Process Flow
Different forging methods have different processes, among which the hot die forging process is the longest, the general [SCALE STEEL]order is: forging blank blanking; Forging billet heating; Roll forging billet preparation; Die forging; Trimming; Punching; Correction; Intermediate inspection, inspection forgings size and surface defects; Heat treatment of forgings to eliminate forging stress and improve metal cutting performance; Cleaning, mainly to remove the surface oxide skin; Correction; Inspection, general forgings to go through the appearance and hardness inspection, important forgings also through chemical composition analysis, mechanical properties, residual stress and other tests and non-destructive testing.
Characteristics of Forgings
Compared with castings, the microstructure and mechanical properties of metal can be improved after forging. Casting[SCALE STEEL] organization after forging method of thermal deformation due to metal deformation and recrystallization, make original bulky dendrite and columnar grain to grain is fine and uniform axial recrystallization organization, make the ingot in the original segregation, porosity, porosity, slag compaction and welded, such as its organization become more closely, plasticity and mechanical properties of the metal.
The mechanical properties of castings are lower than those of forgings of the same material. In addition, forging processing can ensure the continuity of the metal fiber organization, so that the fiber organization of the forgings and the shape of the forgings remain consistent, the metal streamline is complete, can ensure that the parts have good mechanical properties and long service life. The forgings produced by precision die forging, cold extrusion, warm extrusion and other processes are incomparable to castings
Forgings are objects in which [SCALE STEEL]metal is subjected to pressure and plastic deformation to form the desired shape or the appropriate compression force. This force is typically achieved by the use of a hammer or pressure. The forging process builds fine grain structures and improves the physical properties of the metal. In the practical use of parts, a correct design can make the particle flow in the direction of the main pressure. Casting is a metal molding object obtained by a variety of casting methods, that is, the smelted liquid metal, with pouring, injection, inhalation or other casting methods into the pre-prepared casting, after cooling by falling sand, cleaning and post-processing, obtained with a certain shape, size and performance of the object.
"Giant heavy duty forging operation equipment" has been successfully developed and accepted by experts, filling the gap in the field of large forging manipulator technology equipment in China.
This project belongs to the[SCALE STEEL] national 863 Program advanced manufacturing subject, undertaken by China First Heavy Machinery Co., LTD. Through hard work, it has successfully developed the first 4000KNM forging manipulator in China, and has completely independent intellectual property rights. The 4000KNM forging manipulator has been put into production of large forgings after a successful thermal test, and has completed the precision forging of 11 types of more than 30 kinds of forgings.
In the field of large forging manipulator technology, China has been monopolized by foreign countries for a long time, [SCALE STEEL]and is in urgent need of large heavy duty forging equipment with independent intellectual property rights. The successful development of 4000KNM forging manipulator will greatly improve the manufacturing quality and environmental protection of large forging products in China, and can significantly reduce the cost and shorten the cycle. It is an important symbol of the technical transformation and upgrading of large forging capacity in China's large casting and forging industry, and will play an important role in nuclear power, shipbuilding, aerospace and other fields in the future.
Risk factors and main reasons of forging production
I. In forging production, traumatic accidents are prone to occur, which can be divided into three kinds according to their causes:
First, mechanical injury -- [SCALE STEEL]directly caused by the machine, tool or workpiece scratch, bruise;
Third, electrical contact injury.
Two, from the point of view of safety and technical labor protection, the characteristics of the forging workshop are:
1. Forging production is carried out in the state of hot metal (such as low carbon steel forging temperature range between 1250~750℃), because of a lot of manual labor, a little careless may occur burns.
2. The heating furnace in the forging shop and the hot ingot, blanks and forgings constantly emit large amounts of radiant heat (forgings still have a very high temperature at the end of forging), and the workers are often harmed by thermal radiation.
3. The smoke and dust from the heating furnaces of the forging workshop discharged into the air of the workshop during [SCALE STEEL]the combustion process, which not only affects the health, but also reduces the visibility of the workshop (for the heating furnaces burning solid fuel, the situation is more serious), thus may also cause industrial accidents.
4. The equipment used in forging production, such as air hammer, steam hammer, friction press, etc., work out of the impact force. When the equipment is under the impact load, it is easy to be damaged suddenly (such as the sudden break of the piston rod of the forging hammer), and cause serious injury accidents.
Press (such as hydraulic press, crank hot die forging press, flat forging press, fine press) shearing machine, in the work, although the impact is small, but the sudden damage of equipment and other situations also happen, the operator is often caught off guard, may also lead to industrial accidents.
5. Forging equipment in the work of the force is very large, such as crank press, tensile forging press and hydraulic press[SCALE STEEL] such forging equipment, their working conditions are more stable, but its working parts of the force is very large, such as China has been manufactured and used 12000T forging hydraulic press. Is the common 100~ 150T press, the force is enough. If the mold is installed or operated incorrectly, most of the force is not on the workpiece, but on the mold, tool, or parts of the equipment itself. In this way, some errors in installation and adjustment or improper[SCALE STEEL] tool operation may cause damage to parts and other serious equipment or personal accidents.
6. There is a wide variety of tools and auxiliary tools for forging, especially hand and free forging tools, clamps, etc., which are kept together at the work place. In the work, the replacement of tools is very frequent, and the storage is often messy, which inevitably increases the difficulty of checking these tools. When a certain tool is needed in forging and often can not be found quickly, sometimes the use of similar tools will "make do", which often leads to industrial accidents.
7. Because of the noise and vibration of the equipment in the forging workshop, the working place is extremely noisy, which affects people's hearing and nervous system and distracts their attention, thus increasing the possibility of accidents.
Analysis of Causes of Work-Related Accidents in Forging Workshops
1. Areas requiring [SCALE STEEL]protection and equipment lack protection and safety devices.
2. Inadequate or unused protection on equipment.
3. The production equipment itself is defective or defective.
4. Damaged equipment or tools and improper working conditions.
5. The forging die and anvil are defective.
6. Confusion in workplace organization and management.
7. Improper operation of process and auxiliary work of repair.
8. Personal protective equipment such as protective glasses are defective, work clothes and work shoes do not meet working conditions.
9. When several people work together on an assignment, they don't coordinate well with each other.
10. Lack of technical education and safety knowledge leads to incorrect procedures and methods.
Matters Needing Attention
The Forging Process Should be Noted
1. The forging process includes cutting the material to the required size, heating, forging, heat treatment, cleaning and inspection. In small hand forging, all these operations are carried out by a number of hands and hands in a small space. Exposure to the same hazardous environment and [SCALE STEEL]occupational hazards; In a large forging shop, the harm varies with the job position.
Working conditions Although working conditions vary with different forging forms, they have certain common characteristics: moderate intensity of physical labor, dry and hot microclimate environment, noise and vibration, air pollution by smoke.
2. Workers are exposed to high temperature air and heat radiation at the same time, resulting in the accumulation of heat in the body. Heat combined with metabolic heat will cause heat dissipation disorders and pathological changes. The amount of perspiration for an 8-hour labor will vary depending on the low-gas environment, physical exertion, and thermal fitness generally between 1.5 and 5 liters or more. In a small forging shop or far from the heat source, the Behard heat stress index is usually 55~95. However, in large forging workshops, the working point near the heating furnace or drop hammer machine may be as high as 150~190. Salt deficiency and heat cramps. [SCALE STEEL] In the cold season, exposure to microclimate changes may promote adaptation to some extent, but rapid and too frequent changes may pose health hazards.
Air pollution: The air in the workplace may contain soot, carbon monoxide, carbon dioxide, sulfur dioxide, or acrolein, depending on the type of furnace fuel and impurities, combustion efficiency, airflow and ventilation.
Noise and vibration: The TYPE forging hammer will inevitably produce low frequency noise and vibration, but may also have certain high frequency components, and its sound pressure level is between 95 and 115 db. Exposure of workers to forging vibrations may cause temperamental and functional disorders that reduce work ability and affect safety.
The Level of Analysis
China's forging industry is developed on the basis of introducing, digesting and absorbing foreign technology. After years of [SCALE STEEL]technological development and transformation, the technological level of leading enterprises in the industry has been greatly improved, including process design, forging technology, heat treatment technology, machining technology, product testing and other aspects.
(1) Process design
Advanced manufacturers generally use computer simulation technology, computer aided process design and virtual technology to improve the process design level and product manufacturing capacity. DATAFOR, GEMARC/AUTOFORGE, DEFORM, LARSTRAN/SHAPE and THERMOCAL were introduced and applied to realize the process control of computer design and hot working.
(2) Forging technology
Most of the hydraulic presses of 40MN and above are equipped with 100-400t. M main forging manipulator and 20-40t. M auxiliary manipulator. A considerable number of manipulators are controlled by computer to realize the comprehensive control of forging process, so that the forging accuracy can be controlled within ±3mm.
(3) Heat treatment technology
The key point is to improve product quality, improve heat treatment efficiency, save energy and protect environment. Such as the use of computer control heating furnace and heat treatment furnace heating process, control burner to achieve automatic regulation of combustion, furnace temperature adjustment, automatic ignition and heating parameters management; Waste heat utilization, heat treatment furnace equipped with regenerative combustion chamber, etc. The polymer quenching oil [SCALE STEEL]tank with low pollution capacity and effective cooling control is adopted. Various water-based quenching media gradually replace the traditional quenching oil.
(4) Machining technology
The proportion of CNC machine tools in the industry has gradually increased, some enterprises in the industry have processing centers, according to different types of products equipped with proprietary processing machinery, such as five-axis processing centers, blade processing machines, roller mills, roller lathes and so on.
(5) Quality assurance measures
Some domestic enterprises have been equipped with the latest testing instruments and testing technology, the use of computer control data processing of modern automatic ultrasonic testing system, using a variety of special automatic ultrasonic testing system, to complete the certification of various [SCALE STEEL]quality systems. The key production technology of high speed and heavy duty gear forgings has been continuously conquered and industrialization has been realized on this basis. On the basis of introducing advanced production technology and key equipment from abroad, China has been able to design and manufacture production equipment for high-speed and heavy-duty gear forgings by itself, which has approached the international advanced level. The improvement of technology and equipment level has strongly promoted the development of domestic forging industry.
Forging production is one of the main processing methods to provide the blank of mechanical parts in the machinery manufacturing industry. Through forging, not only can get the shape of mechanical parts, but also can improve the internal structure of metal, improve the mechanical and physical properties of metal. Generally, the important mechanical parts with high stress and high requirements are made by forging production method. Such as turbine generator shaft, rotor, impeller, blade, protection ring, large hydraulic press column, high pressure cylinder, rolling mill roll, internal [SCALE STEEL]combustion engine crankshaft, connecting rod, gear, bearing, as well as national defense industry artillery and other important parts, are produced by forging. 
Therefore, forging production is widely used in metallurgy, mining, automobile, tractor, harvesting machinery, petroleum, chemical industry, aviation, aerospace, weapons and other industrial sectors, is in daily life, forging production also has an important position.
In a sense, the annual output of forgings, the proportion of die forgings in the total output of forgings, the size and ownership [SCALE STEEL]of forging equipment and other indicators, to a certain extent, reflect the industrial level of a country.