Deformation temperature
The beginning of the steel recrystallization temperature is about 727 ℃, but commonly used 800 ℃ as a dividing line, higher than 800 ℃ is hot forging; between 300 ~ 800 ℃ is called warm forging or semi-hot forging.
Billet
According to the movement of blank, forging can be divided into free forging, upsetting, extrusion, die forging, closed forging, closed upsetting.
1, free forging. The use of impact force or pressure to the metal in the upper and lower two arrived iron (anvil) deformation between the required to obtain the forging, mainly hand forging and mechanical forging two.
2, forging. Die forging is divided into open-die forging and closed forging. Metal blank in a certain shape of the forging die pressure deformation obtained forging, can be divided into cold heading, roll forging, radial forging and extrusion and so on.
3, closed-die forging and closed upsetting As there is no flash, the material utilization is high. With a process or a few processes may be completed complex forging finishing. Because there is no flash, forging the force area is reduced, the required load is reduced. However, care should be taken not to completely limit the billet, in order to strictly control the volume of billet to control the relative position of forging die and forging measurements, and strive to reduce the wear of forging die.
Forging die
According to the movement of forging die, forging can be divided into swing rolling, swing swing forging, roll forging, wedge cross rolling, rolling ring and cross rolling and other methods. Pendulum rolling, swing swaging and rolling ring can also be used for precision forging processing. In order to improve the utilization of materials, roll forging and cross-rolling can be used as the elongated material before the process. Rotary forging, like free forging, is also locally formed and has the advantage that it can be formed in comparison to the forging dimensions when the forging force is small. The forging method, including free forging, extends from the vicinity of the die surface to the free surface during machining, so that it is difficult to ensure accuracy. Therefore, the movement direction and the swaging process of the forging die can be controlled by a computer, Of the forging force to obtain complex shape, high precision products, such as the production of many varieties, large size turbine blades and other forgings. Forging equipment, mold movement and freedom are inconsistent, according to the bottom dead center deformation characteristics, forging equipment can be divided into the following four forms:
1, the limited form of forging force: the hydraulic pressure direct drive slider hydraulic machine.
2, quasi-stroke limit mode: hydraulic crank-link mechanism of the hydraulic machine.
3, stroke limit mode: crank, connecting rod and wedge-driven mechanical slider slider press.
4, the energy limit mode: the use of spiral mechanism of the screw and friction press.
Heavy-duty hydraulic forging presses For high accuracy, care should be taken to prevent overloading at bottom dead center, control speed and mold position. Because these will be forging tolerance, shape accuracy and impact of die life. In addition, in order to maintain accuracy, should also pay attention to adjust the slide guide gap, to ensure stiffness, adjust the bottom dead center and the use of auxiliary transmission devices and other measures.
Slider
As well as vertical and horizontal movement of the slider (for slender pieces of forging, lubrication, cooling and high-speed production of forging parts), the use of compensation devices can be
Smooth forging the first large-scale disk-type products to increase the movement of other directions. In the above manner, the required forging force, process, material utilization, yield, dimensional tolerances and lubrication cooling are different, these factors also affect the level of automation factors.
2 Importance
Forging production machinery manufacturing industry is to provide mechanical parts rough one of the main processing methods. By forging, not only can the shape of mechanical parts, but also to improve the metal within the organization, improve the mechanical properties of metal and physical properties. Generally on the stress, demanding important mechanical parts, most of the forging production method of manufacturing. Such as turbine generator shaft, rotor, impeller, blade, retaining ring, large hydraulic press column, high pressure cylinder, rolling mill roll, internal combustion engine crankshaft, connecting rod, gears, bearings, and defense industry guns and other important parts are used forging produce.
Therefore, forging production is widely used in metallurgy, mining, automobiles, tractors, harvesting machinery, petroleum, chemical, 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 forging, forgings forging in the proportion of the total output, as well as forging equipment size and ownership and other indicators, to a certain extent, reflects a country's industrial level.
3 forging timber
Forging [2] The main materials used are various components of carbon steel and alloy steel, followed by aluminum, magnesium, copper, titanium and its alloys. The original state of the material bar, ingot, metal powder and liquid metal. The ratio of the cross-sectional area of the metal before deformation to the cross-sectional area after deformation is called the forging ratio. Proper selection of forging ratio, reasonable heating temperature and holding time, a reasonable initial forging temperature and final forging temperature, reasonable deformation and deformation speed to improve product quality and reduce costs have a great relationship.
General for small and medium-sized forgings are round or square bar as a blank. The grain structure and mechanical properties of the bar are uniform, good, the shape and size are accurate, the surface quality is good, and it is convenient for mass production. As long as the reasonable control of the heating temperature and deformation conditions, do not need large forging deformation of forging can be excellent performance.
The ingot is only used for large forgings. The ingot is a cast structure with a large columnar crystal and a loose center. So must be through the large plastic deformation, the columnar crystal broken into fine grains, the loose compaction, in order to obtain excellent metal structure and mechanical properties.
The pressed and sintered into the powder metallurgy preform, in the hot state without flash forging can be made of powder forgings. Forging powder close to the general density of forging parts, with good mechanical properties, and high precision, can reduce the subsequent cutting. Powder forging uniform internal organization, no segregation, can be used to manufacture small gears and other parts. But the price of the powder is much higher than the price of the general bar, in the production of the application subject to certain restrictions. , & Lt;
Forging, crystallizing, flowing, plastically deforming and shaping the liquid metal poured in the mold cavity to obtain the desired shape and properties of the forged piece under static pressure. Liquid metal die forging is between die-casting and die forging forming method, especially for the general difficult forging forming complex thin-walled parts.
Forging materials in addition to the usual materials, such as various components of carbon steel and alloy steel, followed by aluminum, magnesium, copper, titanium and its alloys, iron-based superalloys, nickel-based superalloys, cobalt-based superalloys Of the deformation alloy is also used forging or rolling to complete, but these alloys because of its relatively narrow plastic area, so the difficulty of forging will be relatively large, different materials, heating temperature, open forging temperature and final forging temperature has strict requirements.
4 process
Different forging methods have different processes, in which the process of hot forging the longest, the general order: forging blanks; forging billet heating; roll forging billet; die forging forming; trimming; punching; In the middle of inspection, test forging size and surface defects; forging heat treatment to eliminate forging stress, improve the metal cutting performance; clean up, mainly to remove the surface oxide; correction; inspection, general forgings to go through the appearance and hardness inspection, important forging To go through chemical composition analysis, mechanical properties, such as residual stress test and nondestructive testing.
5 forging characteristics
Compared with the casting, the metal after forging processing can improve its organizational structure and mechanical properties. After the deformation of the forging method of hot forging deformation of the metal deformation and recrystallization, the original coarse dendrites and columnar grains into smaller grain size, uniform size of the equiaxed recrystallization of the organization so that the original ingot of segregation, Loose, porosity, slag and other compaction and welding, the organization becomes more closely, and improve the plasticity of metal and mechanical properties. The mechanical properties of the castings are lower than those of the same forging. In addition, the forging process to ensure the continuity of the metal fiber, the forging of the fibrous tissue and forging consistent shape, metal flow line integrity, to ensure that the parts have good mechanical properties and long service life Precision die forging, cold extrusion , Warm extrusion and other processes forging, are castings can not match the forging is the metal is applied pressure, plastic deformation through the shape of the shape required or the appropriate compression force of the object. This force is typically achieved by using a hammer or pressure. The casting process creates a fine grain structure and improves the physical properties of the metal. In the actual use of components, a correct design allows the particle flow in the direction of the main pressure. Casting is a variety of casting method to obtain the metal forming objects, that is, the smelting of liquid metal, with casting, injection, inhalation or other casting method into the mold prepared in advance, after cooling by the sand, Processing, etc., to obtain a certain shape, size and performance of the object.
6 Precautions
Forging process should pay attention to the place
1. The forging process involves cutting the material into the desired dimensions, heating, forging, heat treatment, cleaning and inspection. In a small artificial forging, all these operations by a number of forging workers to get started and start in a small place. They are exposed to the same harmful environmental and occupational hazards; in large forging workshop, the harm varies with the workplace. WORKING CONDITIONS Although working conditions vary depending on the forging form, they share some common characteristics: moderate intensity of physical labor, dry and hot microclimate, noise and vibration, and air pollution by smoke.
2. Workers are also exposed to high temperature air and heat radiation, resulting in heat accumulation in the body, combined with calories of heat, will cause thermal imbalance and pathological changes. 8 hours of work will be the amount of sweat with the small gas environment, physical exertion and thermal adaptability vary between 1.5 to 5 liters, or even higher. In the smaller forging plant or away from the heat source, Beihashi two heat stress index is usually 55 ~ 95; but in large forging workshop, near the furnace or hammer down the working point may be as high as 150 ~ 190. Easily lead to lack of salt and heat cramps. In the cold season, exposure to changes in microclimate may contribute to its adaptability to some extent, but rapid and frequent changes may pose a health hazard.
Air Pollution: Air may contain soot, carbon monoxide, carbon dioxide, sulfur dioxide, or acrolein in the air, depending on the type of furnace fuel and impurities contained, as well as combustion efficiency, airflow and ventilation.
Noise and vibration: The forging hammer will inevitably produce low frequency noise and vibration, but may also have a certain high-frequency components, the sound pressure level between 95 to 115 decibels. Workers exposed to forging vibrations can cause temperamental and functional imbalances that reduce work ability and affect safety.
Risk factors
The Risk Factors and Main Causes of Forging Production
First, in forging production, prone to traumatic accidents, according to their causes can be divided into three types:
First, mechanical injury - a direct result of the machine, tool or workpiece scratching, bruising;
Second, burns;
Third, electrical injury.
Second, from the point of view of safety technology labor protection, forging workshop is characterized by:
1. Forging production is in the state of metal glow (such as low carbon steel forging temperature range of 1250 ~ 750 ℃), due to a large number of manual labor, carelessness may be burns.
2. Forging plant heating furnace and the hot ingot, blanks and forgings continue to emit a lot of radiant heat (forging at the end of forging, still has a very high temperature), workers are often exposed to heat radiation.
3. Forging plant heating furnace in the combustion process generated by the smoke into the air in the workshop, not only affect health, but also reduces the visibility of the workshop (for burning solid fuel heating furnace, the situation is even more serious), which may Causing industrial accidents.
4. Forging production equipment used in such as air hammer, steam hammer, friction presses, etc., are issued by the impact of work. Equipment to withstand this impact load, itself is easy to sudden damage (such as forging hammer piston rod suddenly broken), and cause serious injury accidents.
Presses (such as hydraulic press, crank hot die forging press, flat forging machine, precision press), such as shear, at work, although the impact of small, but the sudden damage to equipment and other situations occur, Often caught off guard, may also lead to work-related accidents.
5. Forging equipment in the work of the force is great, such as crank press, stretching and hydraulic press forging presses such equipment, although their working conditions are more stable, but the working parts of the force is very large , Such as China has manufactured and used 12000t forging hydraulic press. Is a common 100 ~ 150t press, the power is great enough. If the mold is installed or operated slightly incorrectly, most of the force is not acting on the workpiece, but on the part of the mold, tool, or device itself. In this way, some installation errors or improper operation of the tool, it may cause mechanical damage and other serious equipment or personal accident.
6. Forging tools and auxiliary tools, in particular, hand forging and free forging tools, clamps and other items are numerous, these tools are placed together on the workplace. In the work, the tool is replaced very frequently, the storage is often messy, which inevitably increase the difficulty of checking these tools, when forging a tool needed and often can not quickly find, sometimes "improvise" to use Similar tools, often resulting in work-related accidents.
7. As the noise and vibration of the equipment in the forging workshop, so that the workplace noisy ears, affecting the human hearing and nervous system, distracting attention, thus increasing the possibility of an accident.
Analysis of the causes of industrial accidents in the forging workshop
1. Where protection is required, the equipment lacks guards and safety devices.
2. The guards on the device are not perfect, or not in use.
3. Production equipment itself is defective or defective.
4. Damage to equipment or tools and improper working conditions.
5. Forging die and anvil faulty.
6. Workplace organization and management confusion.
7. Process operations and remedial work are inappropriate.
8. Personal protective equipment such as safety glasses are defective, work clothes and work shoes do not meet working conditions.
9. When several people work together, they do not coordinate with each other.
10. The lack of technical education and safety knowledge led to the adoption of incorrect steps and methods.
8 level analysis
China's forging industry is based on the introduction, digestion and absorption of foreign technology developed after years of technological development and transformation of the industry's leading technology, including process design, forging technology, heat treatment technology, machining technology, products Detection and other aspects have been greatly improved.
(1) process design
Advanced manufacturers commonly used thermal processing computer simulation technology, computer-aided process design and virtual technology to improve the level of process design and product manufacturing capabilities. Introduced and applied DATAFOR, GEMARC / AUTOFORGE, DEFORM, LARSTRAN / SHAPE and THERMOCAL simulation programs, computer design and thermal processing of the process control.
(2) forging technology
40MN and above hydraulic press most equipped with 100-400t.m main forging operation machine and 20-40t.m auxiliary operation machine, a considerable number of operating machines using computer control, forging process to achieve a comprehensive control of the forging accuracy can be forged Control in ± 3mm, forging the use of laser measurement of online measurement devices.
(3) heat treatment technology
The emphasis is on improving product quality, improving heat treatment efficiency, conserving energy and protecting the environment. Such as the use of computer-controlled heating furnace and heat treatment furnace heating process to control the burner to automatically adjust the combustion, adjust the furnace temperature, automatic ignition and heating parameter management; waste heat utilization, heat treatment furnace equipped with regenerative combustion chamber, etc .; with low pollution capacity and the ability to Effectively control the cooling of the polymer quenching oil tank, a variety of water-based quenching medium gradually replace the traditional quenching oil.
(4) machining technology
The proportion of CNC machine tools in the industry is gradually increasing. In some industries, there are processing centers equipped with proprietary processing machines, such as five-axis machining centers, blade processing machines, roll mills and roll lathes, depending on the type of products.
(5) quality assurance measures
Some domestic enterprises have been equipped with the latest detection instruments and test technology, computer-controlled data processing of modern automated ultrasonic flaw detection system, using a variety of special automatic ultrasonic flaw detection system to complete a variety of quality system certification. High-speed heavy-duty gear forging products, the key production technology has been overcome, and on this basis to achieve the industrial production. On the basis of introducing foreign advanced production technology and key equipment, China has been able to design and manufacture high-speed heavy-duty gear forging production equipment, which are close to the international advanced level, technology and equipment to enhance the domestic forging industry development of.
