Forging Press Selection And Tonnage Calculation

Metal Working Machine for Sale!

Learn More About Our
Mechanical & Hydraulic Press Machine.

(Factory Directly Supply)
Strong After-sale Services and 3 years warranty!
Check It Out

Overview

Die forging hammer, screw press and hot die forging press are the three main forging equipment in the forging industry.

Although the respective technologies have been developed correspondingly for many years, they have different adaptabilities due to their respective performance characteristics!

Performance characteristics and selection of forging equipment

1 Die Forging Hammer

Die forging hammer

1.1 Performance characteristics

Die forging hammer is a forging equipment for the production of various die forgings under medium or large batch production conditions.

It can be used for multi-type die forging.

Because of its simple structure, high productivity, low cost and adaptability to the die forging process, it is a commonly used forging equipment.

The position of forging hammer in the modern forging industry depends on the following aspects:

  • Simple structure and low maintenance cost;
  • Easy to operate and flexible;
  • Die forging hammer can be used for multi-die forging, no need for pre-forging equipment, and with strong versatility;
  • Forming speed is fast, adaptability to different types of forgings;
  • Equipment investment is low (only 1/4 of the investment in hot forging presses).

The special advantage of the forging hammer is that the striking speed is fast, so the contact time of the mold is short, which is especially suitable for the occasion where high-speed deformation is required to fill the mold.

For example, forgings with thin ribbed plates, complex shapes and weight tolerance requirements.

Due to its fast and flexible operating characteristics, its adaptability is very strong, and some people call it “universal” equipment.

Therefore, it is especially suitable for the production of multiple varieties and small batches.

Forging hammer is the most cost-effective forming equipment.

1.2 How to select forging hammer

The maximum impact energy of the forging hammer is the most important parameter of the working capacity of the forging hammer. The selection of the required hammering impact energy can be referred to the following formula:

E=25(3.5~6.3)KFtotal

In the formula:

  • E—Strike energy required for forgings (J);
  • K—Steel type coefficient (0.9 for low carbon steel; 1 for medium carbon steel and low carbon alloy steel; 1.1 for medium carbon low alloy steel; 1.25 for high alloy structural steel);
  • Ftotal—Total deformation area of forging plan (including skin and flash) (㎝2)

When in batch production and require high productivity, the formula takes the upper limit value of 6.3, and the lower limit of 3.5 is used for the case where the final forging step can be performed and the productivity is not high.

2 Screw Press

Screw press

2.1 Performance characteristics

The screw press is suitable for die forging, upsetting, precision pressing, correction, trimming, bending processes.

However, the average eccentric load capacity of the screw press is much smaller than that of the hot forging press and the forging hammer.

Therefore, the screw press is not suitable for several processes in one heating (such as descaling, pre-forging and trimming).

Therefore, when using a screw press for final forging, additional equipment is required to complete the auxiliary process.

The process characteristics of the die forging of the screw press are determined by the performance of the equipment.

Since the screw press has the dual working characteristics of the die forging hammer and the hot forging press, namely:

  • Have a certain impact during the work process;
  • The stroke of the slider is not fixed; the device is equipped with an ejecting device;
  • The force received between the slider and the table during the formation of the forging is received by the frame structure of the press.

Therefore, the die forging of the screw press has the following characteristics:

  1. The screw press slider has a slow stroke speed and a slight impact and can be deformed multiple times in one groove. Therefore, it can provide large deformation energy for large deformation processes (such as upsetting and extrusion), and can also provide large deformation force for small deformation processes (such as precision pressing and embossing).
  2. Since the stroke of the slider is not fixed and the ejecting device is equipped, it is suitable for upsetting for flashless die forging and long rod forgings. For the extrusion and trimming process, a limit stroke device must be added to the mold.
  3. The screw press has poor ability to withstand the eccentric load, and is usually used for single-slot die forging. The blank is generally carried out on other auxiliary equipment. It is also possible to arrange two grooves in the case of a small eccentric force, such as press bending – final forging or upsetting – final forging.

Screw press die forging is also limited by unfavorable factors such as equipment tonnage, low working speed and blanking of auxiliary equipment. It is generally used for small and medium batch production of small and medium forgings.

2.2 Adaptability to other die forging press

The screw press works by striking energy.

Its working characteristics are similar to that of the die forging hammer. The stroke of the press slider is not fixed, and it can be allowed to return at any position before the lowest position. According to the required deformation work of the forging, the striking energy and the number of strikes can be controlled.

However, when the screw press is forged, the deformation resistance of the forging is balanced by the elastic deformation of the bed closure system. Its structural characteristics are similar to those of the hot forging press.

Therefore, it is a die forging device between the forging hammer and the hot forging press, which has a certain overload capacity.

The tonnage of the screw press must be adapted to its characteristics.

The average eccentric load capacity of the screw press is much smaller than that of the hot forging press and the CNC die forging hammer.

Therefore, the screw press is not suitable for multi-die forging, usually used for single-slot die forging.

Therefore, when using a screw press for final forging, additional equipment is required to complete the auxiliary process.

The screw press slider has a slower stroke speed and a lower frequency of operation, and can only perform a single strike deformation in a single groove.

In the single-shot deformation, the middle part of the blank is greatly deformed, and it is easy to flow to the horizontal direction, forming a large flashing edge, which makes the metal in the deep groove not easy to be filled, which is more likely to be folded than the hammer forging.

This is more prominent for forgings with complex cross-sectional shapes.

At the same time, compared with the CNC die forging hammer, the flexibility is poor and the die life is short. Therefore, it is suitable for forging a part with a relatively simple shape, low precision requirement, and large deformation energy.

The striking energy and striking beat of the screw press are usually determined by the operator based on the amount of deformation work required by the forging. The control performance is poor compared with the CNC die forging hammer, and the forging quality is unstable, making it difficult to automate.

It is usually suitable for small and medium batch production of small and medium forging parts.

2.3 How to select screw press

The calculation formula for selecting the tonnage of the screw press is as follows:

1)P= p/q=(64~73)F/q

In the formula:

  • P—Screw press tonnage (KN);
  • p—Deformation force required for die forging (KN);
  • F—Forged piece together with the projected area of the flash (㎝2)
  • (64~73)—The coefficient of complex forgings is 73, and the simple forgings is 64;
  • q—q is a deformation coefficient, which can be divided into stroke and deformation work in die forging of a screw press:

①Forgings require large deformation stroke, deformation and deformation work for die forging, q=0.9~1.1;

②Forgings require less deformation stroke and deformation work for die forging, q=1.3;

③Forgings only require a small deformation stroke, but require a large deformation force for precision pressing, q=1.6。

2)  P=(17.5~28)K·Ftotal(KN)

In the formula:

  • Ftotal—Total projected area of forgings together with flash (㎝2);
  • K—Steel type coefficient (0.9 for low carbon steel; 1 for medium carbon steel and low carbon alloy steel; 1.1 for medium carbon low alloy steel; 1.25 for high alloy structural steel);
  • (17.5~28)—The coefficient 28 is used for deformation difficulties (such as extrusion deformation, flash edge deformation, etc.) and high productivity. Otherwise, the coefficient is taken as 17.5.

The above formula is applicable to the tonnage calculation of equipment required for hammering 2 to 3 times of forming. If a hammer forming is required, it should be doubled according to the calculation.

3 Hot Die Forging Press

Hot Die Forging Press

3.1 Performance characteristics

The characteristics of die forging on hot forging presses are determined by the structural characteristics of the press itself.

It has the following characteristics:

  • The rigidity of the frame and crank linkage mechanism is large, the elastic deformation during operation is small, and the die forging can obtain the forgings with higher precision.
  • The slider has an additional guided nose-like structure, thereby increasing the guiding length of the slider and improving the guiding precision. Since the hot forging press has high guiding precision and adopts a combined die with a guiding device, it can forge a forging with higher precision. The groove of each step is made on a convenient insert and fastened to the universal formwork with fastening screws. The upper and lower molds do not produce a counterattack during work.
  • The working stroke of the press is fixed, and one step is completed in one stroke.
  • There is an automatic ejection device.

3.2 Adaptability to other die forging equipment:

The hot die forging press has a certain stroke and a slow speed.

The blank can perform the predetermined deformation in one stroke.

Therefore, in the deformation, the middle portion of the billet is greatly deformed and easily flows to the horizontal direction, forming a large flash, which causes the metal in the deep groove to be not easily filled.

At the same time, folding is more likely to occur than hammering, which is more prominent for forgings with complex cross-sectional shapes.

In order to smoothly forge such forgings on a press, it is necessary to use a blanking step to bring the blank close to the shape of the forging, thus requiring the proper design of the die forging step.

The die forging hammer has a large number of strokes per minute, and can control the weight of the hammer according to the requirements of the deformation of the blank.

It is convenient to operate the forgings, such as lengthening and rolling.

It is difficult to carry out the long-rolling and rolling process of the hot forging press.

Therefore, for a long rod type blank having a large difference in cross-section, it is necessary to perform blanking by means of other equipment such as air hammer, roll forging machine, flat forging machine when stretching and rolling.

When hammering the upper ends, the oxide scale on the surface of the blank is relatively easy to be blown off, and the die forging on the hot forging press is difficult, especially the oxide scale on the upper and lower ends of the blank is easily pressed into the surface of the forging.

Therefore, electrical heating and other less oxidation-free heating methods must be used.

Since the hot forging press adopts a combined die with a guiding device, the groove of each step is made on a convenient insert, and the size of the insert die is much smaller than that of the hammer, thereby effectively saving the mold material.

Moreover, the manufacture, use and repair of the insert mold are also much more convenient.

3.3 How to select hot die forging press

The determination of the tonnage of the hot forging press is determined based on the maximum deformation resistance at the end of the forging.

The forging pressure P can be calculated according to the following empirical formula:

P=(64~73)KF

In the formula:

  • F—Projection area of forgings including flash bridges (cm2);
  • K—Steel type coefficient (0.9 for low carbon steel; 1 for medium carbon steel and low carbon alloy steel; 1.1 for medium carbon low alloy steel; 1.25 for high alloy structural steel);

For forgings with a simple shape, large round surface, thick and low ribs, and thick wall, the complex coefficient takes a small value, and vice versa.

Performance comparison table of three die forging press

Item

Steam hammer Screw press Crank press

Die forging hammer

Strike speed(m/s) 4~7 0.6~0.8 0.3~0.7 4~6
Cold strike time (ms) 2~3 30~60 30~60 2~3
Forming time (ms) 5~15 30~150 80~120 5~15
Strike frequency 80~100 6~15 40~80 80~110
Flexibility Good Bad Bad Good
Investment ratio 1 1~2 4 2
Adaptability Multi-variety small batch Single part in large quantities Single part in large quantities Multi-variety small batch
Structure complexity Simplest Average Most complicated Simple
Automation degree Bad Bad Good Good
Forging principle Multiple hammer forming One impact forming Static pressure forming Multiple hammer forming
Working accuracy Bad Bad High High
Comparison of energy consumption 15 2~3 3 1

Equivalent relationship of three die forging equipment

When forgings selecting forging equipment with similar capabilities, the conversion relationship between the forging equipment capacity is: 25KJ die forging hammer (1 ton double-acting hammer), equivalent to 10000KN hot forging press, equivalent to 3500 ~ 4000KN screw press.

1 thought on “Forging Press Selection And Tonnage Calculation”

Leave a Comment

Your email address will not be published. Required fields are marked *

Stay Updated
close-link
Metal Working Machine for Sale!

Learn More About Our
Mechanical & Hydraulic Press Machine.

(Factory Directly Supply)
Strong After-sale Services and 3 years warranty!
Check It Out
Get FREE quote for metalworking machines
Get Free Quote
close-image

Mechanical & hydraulic press for sale.
3-Years Warranty

close-link
error: Content is protected !!