US2890325A

US2890325A - Process for producing metal forgings

Info

Publication number: US2890325A
Application number: US638630A
Authority: US
Inventors: Havlik Jaroslav
Original assignee: Individual
Current assignee: Individual
Priority date: 1957-02-06
Filing date: 1957-02-06
Publication date: 1959-06-09
Anticipated expiration: 1976-06-09

Description

June 9, 1959 J. HAVLIK PROCESS FOR PRODUCING METAL FORGINGS 2 Sheets$heet 1 Filed Feb. 6, 1957 PRIMARY F E E DERS EL EC TRON/C CURRENT AND TIME CONTROL FIG. 7

lnventdr JAROSLAV HAVL/K ATTORNEY June 9, 1959 J. HAVLlK PROCESS FOR PRODUCING METAL FORGINGS 2 Sheets-Sheet 2 Filed Feb. 6, 1957 TRANSFORMER TRANSFORMER ELECTRON/C CURRENT AND FEEDERS TIME CONTROL FIG. 2

FIG. 2.

In ventor JAROSLAV HAV lK fijfi FIG. 7

ATTORNEY United States Patent 2,890,325 PROCESS FOR PRODUCING METAL FORGINGS Iaroslav Havlik, Preston, Ontario, Canada Application February 6, 1957, Serial No. 638,630

3 Claims. or. 219-152 The present invention relates to the production of forged metal parts using pulsations of electric current to heat the material and forging the softened metal part to the desiredshape in a die.

In the past, forgings have been produced by heating and hand hammering, or on a drop hammer, by split dies, and by upsetting, all of which have many disadvantages, i.e. several die stations are required, excessive flash and scale, poor dimensional control, etc.

One of the objects of this invention is to produce from sheared material forgings which are free of scale and flash, with excellent grain flow and metallurgical properties, and with a minimum wastage of material.

A further object is to produce dimensionally correct forgings having very close tolerance, thus minimizing or eliminating further machining by forging the material at the optimum degree of softness without the need of impact pressures. This also allows the forging equipment to be of comparatively light construction and extends the useful life of the dies.

A further object of this invention is automatically and Y continuously to produce forgings which are completely finished and ready to be heat treated, if required, and put into use.

Accordingly, the present invention resides in a process for producing metal forgings, the steps of applying a heating anvil to one end of a metal bar secured in a die,

subjecting said metal bar to pulsations of current to heat said metal barm, controlling the heat in said metal bar to soften the metal in the portion to be forged without softening the remaining portion, cooling the end of said metal bar to form a hardened portion, and applyinga forging anvil to said metal bar under increased pressure to force the heated metal into the die cavity.

I have found that precise electronic current and time control is an important factor in the exercise of this invention for the following reasons. It gives a very precise amount of heat input by pulsations. It allows heat to be introduced into the metal very quickly in waves and then provides precise waiting periods to allow .the heat to be distributed. It permits the forging end of the bar to cool and harden slightly in order that it may be firm enough to accept the pressure of the anvil and fill the die with the softened portion of the metal. It allows heat at both ends of the bar to be independently and accurately controlled to provide a similar forging at each end if required. It allows repeatedly accurate heating and soaking periods which provide ideal electrical forging conditions consistently to produce substantially identical forged parts. It allows for easy adjustment of the heating and soaking periods and gives such close control over the softening point of the material that it can be forged at the ideal degree of softness with a minimum of pressure resulting in ideal 1 forging conditions.

The manner in which I achieve the foregoing objects will be described and claimed in the specification Patented June 9, 1959 2 which follows, with reference to the accompanying drawings, in which:

Figure 1 is a schematic view showing one embodiment of my invention with a metal bar in the die ready to be forged; I

Figure 2 is a block diagram showing the arrangement of parts for controlling the heating to both ends of a metal bar;

Figure 3 is a side elevation of a heating anvil and rough sheared metal bar;

Figure 4 is a side elevation of the same heating anvil and metal bar after the rough sheared end has been,

corrected;

Figure 5 shows a die in cross-section with a hexagonal bar after the forging operation;

Figure 6 shows a die with a forging anvil extending thereinto, after the forging operation;

7 Figure 7 shows the heated bar in a die prior to the final forging action.

Like reference numerals refer to the same parts throughout the specification and drawings.

The following is a description of the apparatus shown in Figure 1 which is used to carry out the process of this invention.

A metal bar 10 is shown in forging position in a die 11, and is held in position by clamp 21. The die 11 ,may be mounted in a die holder 14 by means of adapter on anvil holder 21, and the whole assembly is mounted on a bracket 22, but insulated therefrom by insulation 23. Heating anvil 19 is water-cooled, as at 24, and is provided with an alloy tip 25 on its heating contact surface.

Pulses of electric current are supplied to the heating anvil through a transformer 26 in conjunction with an electronic current and time control 27 which is supplied by primary feeders as shown in Figure 1. Current is supplied from the transformer secondary to electrode 40 in the heating anvil 19 and the brushes 16, and passes through the metal bar 10 which completes the circuit between the alloy tip 25 and the brushes 16.

The electronic current and time control 27 is adjustable to regulate the number of pulses of current applied to the heating anvil and the length of the soaking periods, to provide optimum forging conditions.

In the embodiment, in Figure 2, separate controls are shown for both ends of a bar 10, in which

transformers

26a, 26b are controlled by electronic current and time control 2.7 to feed current to the ends of bar 10 through

heating anvils

19a, 19b and

brushes

16a, 16b, respectivel In the practice of this invention, a sheared bar 10 which may have a rough or uneven end surface, as shown in Figure 3, is fed into die 11 and is clamped in position by clamp 12, with the end of the bar to be forged extending beyond the die for engagement with the heating anvil 19 and forging anvil 20. The brushes 16 are in contact with the metal bar 10 ready to complete the electrical circuit through the metal bar 10 when the heating anvil is brought into contact therewith.

The heating anvil 19 is brought into contact with the end of the metal bar 10 and pressure is applied, followed by an application of heat by passing electronically controlled current pulsations through the bar. softens the rough sheared end of the bar 10 which is straightened by the face of the heating anvil 19 so as to provide a good electrical contact.

The heat v The current then is turned off for a precise electronically controlled period to allow the heat to soak through the metal, followed by further periods of heating and soaking until the bar is heated to desired temperature consistently throughout the area of the bar to be forged. The duration and number of the heating and soaking periods will depend upon the characteristics and size of the bar. Therefore, it is not intended to limit the scope of the invention in this respect.

During the last soaking period, heat travels to the farthest portion of the bar to be forged. Also, the end of the bar cools and hardens slightly so that it is firm enough to take the pressure of the forging anvil which follows. This feature is very important in the operation of the invention, for Without it the end of the bar softens and tends to bend or distort, falling into contact with the side of the die, and resulting in loss of material, flashing and an inferior forging in the finished product.

The feature of the hardened portion of the bar 10 is illustrated in Figures 5 and 6, in which the hardened end is identified by the numeral 30. In Figure 5, the finished forging is shown with the hardened end 30 approximately flush 'with the face of the die 11. This result is obtained when a forging anvil is used Whose forging surface is larger than the die opening. Figure 6 illustrates the resulting forging where a forging anvil is used having a forging surface slightly smaller than the die opening. In operation, the arrangement of Figure 6 produces a finished forging which is superior to the forging using the arrangement of Figure 5.

Following the last soaking period with the metal in the bar at the ideal heat for forging, the heating anvil 19 is removed from the bar end, the forging anvil is brought into contact with the hardened end 30 and applies increased pressure to force the hot softened metal into the die cavity 31.

The pressure of the forging anvil 20 is removed, the clamps 12 and brushes 16 are released and the finished forging is ejected from the die 11 completely finished, free of scale and flash, with excellent grain flow and very close tolerances.

The process is completely automatic, including feeding the rought sheared bars into the apparatus ready to be forged and ejecting the finished forging, onto a storage or cooling rack. Therefore it is apparent that the process is readily adaptable for use in large scale production to produce forgings continuously and automatically.

Referring now to the electrical circuit, it is pointed out that the direction of heat flow in the metal bar 10 may be controlled by varying the water cooling in the heating anvil 19 and the brush holders 17. Also, of course, the type of resistance offered by the material and the contact area of the heating anvil 19 and brushes 16 will determine the heat flow.

Precautions have been taken to prevent welding of the die 11 and brush holders 17 by inserting a suitable insula tion 18 therebetween.

A- further important feature to be observed in carrying out the present invention with a closed die is to ensure that proper clearance is provided in the die' 11 to prevent the metal bar 10 from contacting the die 11 and welding thermally due to contact when the bar 10 swells under pressure during the heating period. In the case of a split die, of course, the dies could be left open when the current is on to prevent such welding.

Using a one inch bar of steel (MS. 3414) to be forged for a length of approximately three inches, the following times and values were used. Time is based on cycles (60 cycles per second).

1. Initial pressure 1900 to 2000 pounds p.s.i.

for 100 cycles.

2. Heating period 1900 to 2000 pounds p.s.i. for 200 cycles applied in pulses 55,000 to 75,000 amps.

3. Heat distribution 1900 to 2000 pounds p.s.i.

for 140 cycles.

4. Heating period 1900 to 2000 pounds p.s.i. for 200 cycles applied pulses 55,000 to 75,000 amps.

5. Heat distribution Current off for cycles.

6. Forging Forging anvil applied for 60,000 to 90,000 pounds p.s.i. instantaneous pressure with the metal at 2300" F. (approx.)

It should be observed that the foregoing values are given by Way only of example and it is not intended to limit the scope of the invention to the particular temperature and time ranges given. Each type of material may be treated in accordance with the present process by determining the proper temperature and time controls required for such material.

The embodiment described and illustrated thus far has been based on the use of a closed die. It will be apparent, however, that the process is equally applicable to any type of forging operation to produce a finished article of excellent quality.

It has been observed that variations in the heating and soaking periods, as well as in the current and voltage values, will vary the resulting product However, the preceding example of an application of the process to a specific type of material will be useful in obtaining an understanding of the values of current and voltage and the duration of the heating and distribution periods.

In the operation of this process, high heats are generated in the brushes 16 and heating anvil 19, thus requiring cooling of these parts. My preferred method of water cooling is to form the electrode 40 with an internal water channel 24 with a Water return 24 in communication with a water line to a source of supply. The brush holders 17 are provided with a plurality of conventional water channels 43 in communication with a source of water supply.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. In a process for producing metal forgings, the steps of mounting a metal bar to be forged with at least a portion thereof in a die, applying a controlled substantially constant initial contact pressure to the metal bar, heating the portion of the metal bar within the die to forging temperature, by applying a substantially constant amperage to the metal bar throughout the heating period, controlling the distribution of heat throughout the area of the metal bar to be forged by regulated periods of heating interrupted by regulated soaking periods during which the heat diffuses throughout the area of the metal bar to be forged, cooling one portion of the metal bar for a controlled forge delay period to form a hardened portion, applying pressure to the hardened portion of the metal bar to thicken the metal bar through a portion of its length extending into the die, and when the metal has reached forging temperature applying a controlled substantially constant forging pressure to the hardened portion to forge the portion of the metal bar within the die, the duration and intensity of the initial contact pressure, the heating functions and the forging pressure being accurately controlled to distribute the correct amount of heat throughout the area of the metal bar to be forged, and at the correct temperature to cause the metal to flow and be forged within the die.

2. In a process for producing metal forgings, the steps comprising mounting a metal bar to be forged with at least a portion thereof in a die constituting one electrode and in contact with another electrode, applying a controlled substantially constant initial contact pressure to the metal bar to establish the best possible electrical contact between the electrodes and the metal bar, heating the portion of the metal bar within the die to forging temperature by applying a substantially constant amperage to the metal bar throughout the heating period while maintaining the pressure throughout the said heating period, controlling the distribution of heat throughout the area of the metal bar to be forged by regulated periods of heating interrupted by regulated periods of soaking, cooling one portion of the metal bar to form a hardened portion, and when the metal has reached forging temperature applying a controlled substantially constant forging pressure to forge the portion of the metal bar within the die.

3. In the process set forth in claim 2, wherein the cooling step of the portion of the metal bar is for a controlled forge delay period.

References Cited in the file of this patent UNITED STATES PATENTS 1,259,275 Murray Mar. 12, 1918 2,231,695 Vedder Feb. 11, 1941 2,366,756 Spencer Jan. 9, 1945 2,400,472 Strickland May 14, 1946 2,581,774 Stone et al Ian. 8, 1952 2,790,067 Riley et a1 Apr. 23, 1957

Claims

1. IN A PROCESS FOR PRODUCING METAL FORGINGS, THE STEPS OF MOUNTING A METAL BAR TO BE FORGED WITH AT LEAST A PORTON THEREOF IN A DIE, APPLYING A CONTROLLED SUBSTANTIALLY CONSTANT INITIAL CONTACT PRESSURE TO THE METAL BAR, HEATING THE PORTION OF THE METAL BAR WITHIN THE DIE TO FORGING TEMPERATURE, BY APPLYING A SUBSTANTIALLY CONSTANT AMPERAGE TO THE METAL BAR THROUGHOUT THE HEATING PERIOD, CONTROLLING THE DISTRIBUTION OF HEAT THROUGHOUT THE AREA OF THE METAL BAR TO BE FORGED BY REGULATED PERIODS OF HEATING INTERRUPTED BY REGULATED SOAKING PERIODS DURING WHICH THE HEAT DIFFUSES THROUGHOUT THE AREA OF THE METAL BAR TO BE FORGED, COOLING ONE PORTION OF THE METAL BAR FOR A CONTROLLED FORGE DELAY PERIOD TO FORM A HARDENED PORTION, APPLYING PRESSURE TO THE HARDENED PORTION OF THE METAL BAR TO THICKEN THE METAL BAR THROUGH A PORTION OF ITS LENGTH