Forging hammer

  The use of pneumatic or hydraulic transmission mechanism to make the falling part (piston, hammer rod, hammer head, anvil (or module), produce motion and accumulation of kinetic energy, in a very short time to impose on the forging, so that the plastic deformation energy, complete a variety of forging process of forging machinery called forging hammer. The hammer head strikes a fixed anvil base for anvil base hammer; The hammer with the upper and lower hammer heads against each other is a hammer without anvil.

  Forging hammer is one of the most widely used forging equipment. The forging hammer is a machine that produces kinetic energy to work the billet and plastic deformation by the heavy hammer falling or processing external force. Forging hammer is the most common, the oldest forging machinery, it has simple structure, flexible work, wide use, easy maintenance, suitable for free forging and die forging. But the vibration is larger and it is difficult to realize automatic production.

  Working principle: The use of steam, hydraulic and other transmission machinery to make the falling part (piston, hammer rod, drilling, module) produce motion and accumulate energy, the kinetic energy is applied to the forging, so that the forging obtains plastic deformation energy, in order to complete a variety of forging process.

  Features: The forging hammer is the main forging production equipment with simple structure and good process adaptability. Forging hammer is generally divided into air hammer (steam hammer), percussion hammer, electrohydraulic hammer, etc. Because the air hammer has the characteristics of large vibration and high noise, it is suitable for medium and small tonnage. Large tonnage forging hammer principle with counterhammer, hydraulic hammer and other equipment instead. According to the purpose of forging hammer can be divided into free forging hammer, die forging hammer, etc. [1]

  The forging hammer with a large anvil or movable hammer head as the supporting surface of the strike, in the working stroke, the hammer hitting speed instantly drops to zero, the work is impact, can produce a lot of striking force, usually cause a lot of vibration and noise.

The specification of the forging hammer is usually expressed by the mass of the falling part, but because it is energy limiting equipment, its exact performance parameter should be the hitting energy.

The forging process on the hammer is a striking process. The characteristics of the striking process can be analyzed by using the elastic positive impact theory in mechanics. It can be seen that the forging hammer is a kind of impact forming equipment, the main parts in the process of work to bear the impact load, and the vibration of the foundation and the surrounding environment, therefore, the study of the hammer strike process, analysis of the hammer strike efficiency and strike force is the hammer design and performance analysis, parts strength check and hammer vibration analysis of the foundation.

  The striking process of the forging hammer is divided into two stages.

  The first stage is the loading stage. At the beginning of the strike, the speed of the hammer is V1 and the speed of the anvil is V2=0. At this stage, the forging is formed as the anvil blocks (or dies) approach each other. At the end of the first stage, the hammer head and the anvil base reach the same sinking speed V, then the forging deformation is the largest, the anvil base and the foundation sink, and the kinetic energy of the falling parts is transformed into the plastic deformation energy of the forging, the elastic deformation energy of the hammer system and the kinetic energy of the system movement. For the hammer, the upper and lower hammer heads are close to each other, which can improve the stress of the steel belt when striking.

  The second stage is the unloading stage. The elastic deformation energy of the hammering system at the end of the first stage is released in the second stage, resulting in the reverse separation of the hammer and anvil or upper and lower hammer at the end of the impact, the velocity of which reaches U1 and U2 respectively, at which time the two begin to separate. The anvil base strikes the foundation at the initial speed of U2, resulting in serious ground impact vibration. The upper and lower hammer heads of the hammer without anvil base are piled up in the air, and there is basically no impact vibration on the ground.

  Forging hammer is a limited energy forging equipment, its main performance parameter is the falling part of the strike energy. However, the impact force it may produce should also have its measurement criteria to meet the needs of the strength check of the forging hammer parts, the determination of the pressure surface of the die and the correct selection and use of equipment.

There are many kinds of forging hammer, according to the striking characteristics, there are hammer and anvil hammer; According to the process use, there are free forging hammer, die forging hammer and sheet metal stamping hammer; The force acting on the falling part of the downward stroke is divided into single acting hammer and double acting hammer. When the single acting hammer works, the falling part is in free fall. Double acting hammer in the downward stroke, the falling part in addition to the action of gravity, but also by the action of compressed air or liquid pressure, so the impact energy is larger. Usually according to the driving form, the forging hammer is divided into the following four categories:

Steam air hammer

  With steam or compressed air from the power station as the working medium, through the slide valve distribution mechanism and cylinder drive down part of the reciprocating motion of the forging hammer called steam - air hammer. The working medium carries out various thermal processes in the working cylinder through the steam distribution mechanism of the slide valve, converting the thermal energy into the kinetic energy of the falling part of the forging hammer, so as to complete the deformation of the forging.

Air hammer

  The air hammer has a working cylinder and a compression cylinder, and the two cylinders are connected by a rotary valve. The working medium is compressed air, which only plays a flexible connection between the compression piston and the working piston. The motor drives the crank shaft to rotate through the deceleration mechanism, drives the compression piston to make up and down reciprocating motion, so that the compressed air enters the upper chamber or lower chamber of the working cylinder through the rotary valve, and drives the falling part to do downward movement to strike or return.

  Mechanical hammer

  Driven by a motor, by mechanical transmission to lift the hammer hammer, collectively referred to as the mechanical hammer. It is a kind of single acting drop hammer which mainly relies on gravity potential energy to achieve forging deformation. Depending on the connection, it is divided into splint hammer (or clamp rod hammer), spring hammer and chain hammer (or wire rope hammer).

Hydraulic hammer

  Hydraulic hammer is hydraulic oil as the working medium, the use of hydraulic transmission to drive the hammer head to move up and down, to complete the forging process of forging equipment. Divided into gas - liquid and pure hydraulic drive two forms. The principle of gas-liquid driving is: before working, the first time to fill the air chamber with a quantitative high-pressure gas (nitrogen or compressed air). With the help of the change of lower chamber pressure, the quantitative closed gas is compressed and expanded repeatedly to do work, so that the hammer is lifted and quickly lowered for forging. Its working characteristics are: oil chamber inlet, hammer lift; The oil cavity is discharged, the hammer is lowered and the forging is formed. The characteristics of pure hydraulic die forging hammer are: hydraulic cylinder chamber usually pressure; The upper chamber is injected with oil, and the hammer quickly descends and is forged. The upper chamber is discharged and the hammer is lifted.

Hydraulic hammer has the advantages of high efficiency, energy saving and environmental protection, the use of hydraulic power head made of gas-hydraulic drive to reform high energy consumption steam and air free forging hammer and die forging hammer, there has been a great development in our country, especially the 8~12t hydraulic free forging hammer is made and put into use in the world, which is a product of Chinese independent intellectual property rights. A series of products with better performance of fast hydraulic forging hammer have been put in the market, and the products of reforming steam hammer with hydraulic power head made of pure hydraulic principle have also been put in the market.

The forging hammer is generally composed of a hammer head, anvil base and a frame. The anvil base and the foundation are provided with a cushion, and the whole forging hammer base is placed on the foundation. The hammer head strikes a fixed anvil base for anvil base hammer; The hammer with the upper and lower hammer heads against each other is a hammer without anvil. The specification of the forging hammer is usually expressed by the mass of the falling part, but because it is energy limiting equipment, its exact performance parameter should be the hitting energy.

There are many kinds of forging hammer, according to the striking characteristics, there are hammer and anvil hammer; According to the process use, there are free forging hammer, die forging hammer and sheet metal stamping hammer; The force acting on the falling part of the downward stroke is divided into single acting hammer and double acting hammer. When the single acting hammer works, the falling part is in free fall. Double acting hammer in the downward stroke, the falling part in addition to the action of gravity, but also by the action of compressed air or liquid pressure, so the impact energy is larger. According to the driving form, the forging hammer is divided into steam - air hammer, air hammer, mechanical hammer, hydraulic hammer.

  Because of its simple structure, strong applicability and easy maintenance, the forging hammer is widely used in forging factories, but the forging hammer will produce great vibration in the work and give great impact to the foundation, so it is necessary to build a large and strong foundation separately under the forging hammer. In addition, it is necessary to control the vibration value of the foundation within a certain range to avoid excessive vibration propagation. The normal use of other equipment and the safety of plant and personnel are affected. When the surrounding environment requires strict vibration, it is necessary to adopt advanced and effective vibration isolation technology. In FIG. 1, a) is the double-column free forging hammer and foundation, and b) is the die forging hammer and foundation, which are mainly composed of hammer frame, drop hammer, anvil block and foundation.

1. Nominal mass and actual weight of the falling part.

2, anvil and hammer weight.

3, the height of the anvil, the size of the bottom and the relative elevation of the top of the anvil to the floor of the workshop.

4. The size of the bottom of the hammer frame and the form, diameter, length and position of the anchor bolt.

5. The maximum speed or stroke of the falling part, the inner diameter of the cylinder, the maximum intake pressure or the maximum impact energy. 6. Center of gravity position of single-arm hammer frame.

(1) Before starting the forging hammer, it is necessary to carefully check whether the bolts, nuts and dowel of each fastening connection part are loose or broken, whether the anvil block, hammer head, hammer rod and inclined wedge are combined and whether there is a crack, find the problem, solve it in time, and check the lubricating oil supply.

(2) The control handle of the air hammer should be placed in the empty position, and the positioning pin should be inserted, and then it can be started, and empty operation for 3 to 5 minutes. The steam and air free forging hammer should eliminate the condensate in the cylinder before starting. Before working, the exhaust valve should be fully opened, and then the intake valve should be slightly opened. After the steam passes through the trachea system to preheat the air valve, the intake valve should be slowly opened, and the piston should go up and down several times.

(3) In winter, the hammer rod, hammer head and anvil block should be preheated, and the preheating temperature is 100 ~ 150℃.

(4) After the forging hammer starts, we should concentrate on it, according to the instructions of the palm fitter, operate according to the specified requirements, and pay attention to observation at any time. If irregular noise or cylinder head air leakage and other abnormal phenomena are found, the machine should be shut down immediately for maintenance.

(5) In the operation, avoid eccentric forging, air strike or blow low temperature, thin blank, at any time to clear the oxide skin on the lower anvil, so as not to splash out wounding or damage the anvil surface.

(6) The foot control mechanism is used. When measuring workpiece size or changing tools, the operator should leave the foot pedal to prevent misstepping.

(7) After the work is completed, the hammer should be put down smoothly, the intake and exhaust valves should be closed, the air hammer should open the switch, and the shift should be completed.

This entry is approved by the project of "Science Popularization China" science encyclopedia entry compilation and application.