DE1552886A1 - Method of forging - Google Patents

Description

Patent attorneys

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IeI. 5 36 058ο P 15 52 886.6

: Federal Mogul Corporation August 7, 1969

Attorney's file 17 o92

Process of forging

The invention relates to a method for forging workpieces at medium temperatures, namely at temperatures between the usual hot forging and cold forming, wherein the workpieces are forged from semi-finished products such as bars or round profiles. In particular, relates to the new method the manufacture of bearing rings. During oxidation and scaling of the ferrous metals at normal ambient temperatures As the temperature progresses slowly, the tendency to scale increases with increasing temperature.

When hot forging steel, the material is initially heated to temperatures of 100 ° C and more. At these high levels Schmxedetemperaturen a significant scale formation and j significant decarburization occurs. As the tinder and the decarburized Surfaces have to be removed again, occurs with this type

; Process a waste material regardless of the one used for scale removal necessary operations required costs. Though

ι no scale formation occurs when workpieces are cold formed;

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At normal ambient temperature, however, the material has a • greater strength, so that it is much greater for deformation Forces are required. As a result, the cold forming must often be carried out in several steps, with the material only gradually takes on the desired shape. In addition, if the material is repeatedly deformed in several work steps, then this cold working increase the strength in such a way that between the successive cold working operations the material must be subjected to an annealing treatment.

The object on which the invention is based is therefore to be found therein see deforming the material at an average temperature that is high enough on the one hand to improve the strength of the material to facilitate deformation and on the other hand so low below the temperatures required for hot forging in which scale formation and decarburization occurs relatively quickly. According to the invention The process is thus carried out at a temperature below the temperatures usually required for hot forging, in which the material strength is significantly reduced, but prevents the formation of scale and decarburization is to enable the production of forgings with tight tolerances.

The described object is achieved by the features specified in claim 1. According to the invention there is thus a protective coating or a lubricant used at the middle temperature not evaporated or on the workpiece during forging

remains. The lubricant has minimal scaling and It results in decarburization and also reduces deformation necessary forces. In the method according to the invention can ! Bar or round profiles with minimal waste of material Find use, so that lower material costs for the workpieces can be applied. It is therefore advantageous that the Workpieces can be produced from rod or round profiles, a lubricant being used to reduce friction and to reduce the formation of scale and decarburization.

The strength of the scale formation depends on the temperature. Scale formation is much faster at higher temperatures than at low temperatures, as a result of which the extent of scale formation is kept as low as possible at higher temperatures by the material is only heated to this temperature for as short a time as possible. Another advantage of the method according to the invention is effective in that the workpieces can be deformed at high temperatures with as little scale formation as possible.

The method according to the invention is particularly used for manufacturing of annular workpieces such as bearing parts. The method according to the invention is used to produce ring-shaped parts particularly suitable in an advantageous manner. Bearing rings can be produced in a simple manner from rod or round profiles •will.

(In addition, the method according to the invention is taken into account.

igen that more than just one bearing ring together in one common

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j forging process can be forged. That way you can

ί the inner and outer rings are forged together. It will

but also considered to save material by that

! bearing rings are manufactured together, but not connected. In this way two inner and two outer rings can be forged together, or an outer ring for one bearing and an inner ring for another bearing, so that either the most advantageous use of the material is made or the manufacture of certain parts, which are in larger or larger sizes, is simplified smaller quantities than other parts should be used. The method according to the invention advantageously also permits such a production of bearing rings in which two or more rings are forged together, the individual rings being selected in such a way that the material consumption and the waste are possible . lent is low and / or the production of rings is facilitated, which are required in larger or smaller quantities.

ι With the method according to the invention, it is also possible at least ^ forging two rings together. By separating the rings from each other axially, they can be machined together, so that the number of machining steps is reduced, the time required for machining per bearing ring is reduced and thus the costs can be saved. In an advantageous manner, several bearing rings are thus forged coherently and then machined the bearing rings together in this still connected state.

Without limitation, the invention is illustrated below the drawing explained in more detail. Show it:

- If -

Fig. 1 shows a full rod round profile from which the workpieces according to of the invention are made »

FIG. 2 shows a blank separated from the round profile of FIG. 1

of a certain size,

• Fig. 3 shows the blank of Fig. 2 after shaping into the workpiece,

ι Fig. Ta another form of the separated from the round profile : Workpiece that is used for a modified method instead of the workpiece shown in Fig. 3,

FIG. K shows a diagram for the representation of the process steps carried out with the workpieces of FIGS. 3 and 3a,

FIG. 5 shows the cup-shaped shape after the heating according to FIG. 4 Workpieces of FIGS. 3 and 3a,

6 shows the cup-shaped workpiece from FIG. 5 after machining for the production of the inner and outer bearing ring,

Fig. 7 is a section through the inner and outer rings of the

Fig. 6 after separation, j

Fig. 8 the inner and outer rings after assembly in \

• I

j a warehouse.

In Fig. 1, a round profile Io is shown, from which the counter ·? Stands are produced according to the invention. In Fig. 2 is

Blank 12 shown, which has a certain volume of material and has been separated from the round profile. The blank 12 is then brought to the correct size by cold forming, so that it fits into the die of the next step in the process. In Fig. 3, the cylindrical full workpiece is designated by the reference number 14; The workpiece 14 is then in a process step indicated by the reference numeral 16 in FIG. 4, overlaid. The coating prevents oxidation or scale formation and the decarburization of the workpiece 14, which is relatively quick would occur at the high temperatures subsequently applied. It is desirable that this coating also act as a lubricant acts to reduce the forces required to deform workpiece 14. Because the blank at a temperature is heated, in which the material strength is significantly reduced is selected, the coating agents are selected so that they do not evaporate at this temperature or at least so evaporate slowly, so that the process steps can be carried out after the material has been heated, with the coating still adheres to the surface of the workpiece 14. In one embodiment of the invention, the workpiece 14 consists of Steel coated with manganese phosphate, which is used as a base for the application of a lubricant made from tungsten disulphide consists. After the application of the coating, the workpiece 14 is heated by induction or in some other way, whereupon the reference numeral 18 in Fig. 4 indicates. The workpiece 14 is brought to a high temperature, which is preferred Embodiment below the usual hot forging temperature lies and yet significantly above the ambient temperature, namely,

552886

so high that the material strength is essential. With steel Temperatures in the range between 700 and 87o ° are preferred.

For case-hardening and through-hardening steels that are used during manufacture of bearing rings are used, is the preferred one

high
Temperature 7oo C, because it / is below the hot forging temperature j, at which the formation of scale and decarburization is very favorable; and because a significant reduction in the strength of the material still occurs. In order to achieve a significant reduction in the strength of steel, the minimum temperature should be set at around 54o ° C. The workpiece 14 is heated to the desired temperature as quickly as possible. As a result, the material is only subjected to the increased temperatures for a very short time, so that the formation of scale is kept to a minimum even without the use of the protective coating. Understandably, however, the best results are achieved through the combination, that is to say through the use of the protective coating plus rapid heating, the formation of scale and decarburization being as low as possible and the frictional forces being minimal.

In the heated state, the workpiece 14 is inserted into the die 2o, which consists of two coaxial circular recesses 16 and 24, the recess 22 having a smaller diameter than the recess 24. An ejector die 26 is arranged at the bottom of the recess 22. The workpiece 14 is provided with a recess 15 which is of such a size that it serves to receive the front end 27 of the ejector die 26,

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so that the workpiece 14 is aligned in the recess. If the workpiece is seated in the recess, a punch 28 of a certain size engages the workpiece 14, which is heated in the Ztistand is, whereby the cup-shaped portion 3o during a single stroke is formed.

t.

The section 3o formed in this way consists of two annular ones Sections 32 and 34, the outside diameter of which corresponds to » knives of the recesses 22 and 24 correspond. The ring sections 32 and 34 are axially separated from each other and over the Web section 36 connected to one another. A flat web 38 is formed on the bottom of the narrower ring section 32. The front one The punch end 27 extends partially into the die so that the material flows both forward and backward to fill up the die. With this material displacement is obtained a flowing of the material, so that wrinkling is excluded. By moving the web 38 inwards in this way, very good flow characteristics are obtained. Furthermore For example, the minimum thickness of the web 38 can be reduced from the web thickness that would occur if the web were at the bottom himself comes to rest. In order to increase the service life of the die and to avoid excessive forces on the die it has been found that the web 38 should be limited in terms of its minimum thickness. For example, the one made of ball bearing steel manufactured part 3o with a diameter of 40 mm for the ring 22 with the smaller diameter of the web 38 have an average minimum thickness of about 3.2 mm.

• · Ί552886

If you wanted the metal thickness of the web 38 to be less than about 3.2 mm even at the high temperatures of the workpiece 14 reduce, this results in extremely high compressive forces. This above-average thickness changes with arrival ! Turning of different materials and according to the size of the j parts. In the following, the mirimal Specify thickness for all combinations of materials and dimensions. Suffice it to say that with This phenomenon is to be expected, so that now the average person skilled in the art himself can determine the minimum thickness for different combinations. It is also essential that the material volume of the workpiece 14 or 14a not by more than lo% than the recess given by the die shape. If the volume exceeds the permitted lo%, then occur on the Die too high forces. Therefore, the volume of the workpiece 14 or 14a should be kept under control.

As already mentioned, the cup section 3o is made into a single one Stroke of the punch 28 made. In the case of cold heading, this would require several strokes, plus the annealing treatment and of the coating processes if one wants to produce such a cup-shaped part 3o from the workpiece 14. According to the invention,

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even with larger or other parts, in which more! than a stroke is required, the material can in general! j are kept at the mean temperature for as long as ■

which is sufficient to be able to carry out several strokes without rewarming. Of course, there is no annealing treatment j required in between. The number of strokes in the middle '

The temperature would then still be lower than the number of strokes in cold forging, which also involves multiple annealing of the workpiece must be interposed. On the other hand, however, the shape denoted by the reference numeral 3o can through a single blow can be obtained from conventional hot forging, where "the material is heated to about 100 ° C. In this case, however, considerable scaling occurs, so that greater Amount of material must be used to obtain the same dimensions after removing the scale.

Depending on the necessity and desire, the heating can be carried out before the workpiece 14 is produced. A rewarming is not required since the next stroke shown in Fig. 5 can be performed before the material temperature noticeably decreases. Instead of the preformed workpiece 14, the workpiece 14a of FIG. 3a can also be used. The workpiece IUa can be separated from a round profile, which has a diameter which is approximately equal to the diameter of the narrower die recess 22. The workpiece 14a is then automatically inserted correctly in the die. It is then not necessary that the workpiece is the right size is brought so that it can be used immediately after being separated from the round profile.

With the connected ring sections 32 and 34, the piece 3o processed as a unit. Should the ring 32 be the inner cage ring of a ball bearing and the ring 34 be the outer cage ring form a ball bearing, the cup-shaped part 3o;

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brought into the form shown in FIG. The web 38 has been removed. In FIG. 6, the same reference numerals are used as in FIG. 5, but with the addition "a". The milled or turned cup-shaped part 3oa is then connected to its larger ring section 3Ua with the turned inner raceway Ho

see, while the smaller ring portion 32a on its outer surface j has career U 2. After finishing the processing. can the rings 32a and 34a by severing the connection I Web 36a are separated from each other. After the removal of the web 36a, the ring 3Ua forms one with the large diameter

outer cage ring and the ring 32a with the smaller diameter .; an inner cage ring, as shown in Fig. 7, which is then assembled into the ball bearing U6 by inserting several balls UU will.

While the method of the invention has been illustrated in the manufacture of ball bearing retainer rings, the method is also in the manufacture of other types of bearings, for example roller bearings, tapered roller bearings or other types of roller bearings Advantage usable.

In the process, the inner and outer cages can be either can be finished separately or together. Since the

drive very precise tolerances are obtained, the rings 32a and 3Ua also only need to be partially machined, i.e. for ; Manufacture of the raceways, inclined surfaces, etc. For some bearing ; constructions, the turning of the raceways can be dispensed with at all. The parts are now ready for hardening and grinding before

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they are assembled in the manner shown in FIG. Instead of that one produces inner and outer cages for the same ball bearing, inner and outer cages can also be used for different ones Ball bearings are forged together and finished at the same time. Also can have two outer rings or two inner rings for different ones Rolling bearings are forged together and machined.

According to Fig. 5, the rings 32 and 34 are in the axial direction of each other separated by the web section 36. It has been shown that the simple workpieces 14 and 14a can be used wherein the cup-shaped part 3o in a single process or in the case of large dimensions in the smallest possible number of process steps can be produced, which in any case less than with cold forming and. By this special arrangement he. if the material also has good flow characteristics, like this that the parts are forged without wrinkles or cracks. In addition, the spaced apart rings 32 and 34 the double machining of the two rings is very beneficial. For example, if the two rings were to sit inside each other, then this is Double processing impossible. However, with this arrangement of the rings, the loss of material required by the web 36 would be dispensed with Therefore, in some cases, forging such interlocking rings may be desirable.

As already mentioned, the formation of scale and decarburization is prevented, by applying a protective layer before the workpiece 14 is heated to the forging temperature. Of course occurs always a scale formation and decarburization with a warm steel

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a, but the extent of scale formation and decarburization, generally grows with the rise in temperature. Therefore, the choice of protective layer depends at least in part on temperature to which the workpiece is to be heated and the cooling time. According to the invention it is provided that the heating ' made by induction heat or in some other rapid manner is, where the deformation should follow immediately, j such that the workpiece is the high temperature only for a short time

Has a period of time. That is why the protective layer has been selected Ϊ

that it does not completely evaporate in the period between heating and forging after top drawing. Alternatively, the workpiece can be heated in a protected atmosphere in which no scale formation and decarburization occurs. It is also desirable that a lubricant is provided for the die and workpiece 14. Therefore, a top layer can be selected that has both lubricant properties and prevents scale formation. The above-mentioned coating made of manganese phosphate tungsten j disulphide fulfills both requirements. Instead of applying a lubricant to the workpiece 14, one can also use
the / contact with the workpiece IH die parts with standing

Cover j- with the lubricant.

When machining steel, it is essential that some steels,! for example, high-carbon steels, when the air cools down

harden after heating to the critical temperature. Will • If these materials are hardened in this way, it is necessary to subject them to a spheroidizing annealing process,

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ORIGINAL

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J to make the subsequent finishing easier. The temperature \ door, at which this occurs in the material is usually j called the critical temperature. With the invention that will
The workpiece is heated to a temperature below this critical temperature of the material for the subsequent annealing process
to avoid.

"9 0 9T82 / 0232"

Claims (9)

JS Pah Dr. Federal Mogul Corporation August 7, 1969 Attorney's file 17 o92 Claims .1. Method of forming an article of ferrous metal by Deforming a workpiece, characterized in that the workpiece has an inhibitor of scale formation and decarburization Oberzug is provided, which is used in the j deformation temperature neither volatilizes nor decomposes, the workpiece is heated to a predetermined temperature in the range of approx. 54o to 87o C, at which the strength properties of the material are much lower than at room temperature, but which are below the critical temperature of the material, at which air hardening takes place, and then the workpiece is deformed, with the temperature up to Completion of deformation is maintained. 2. The method according to claim 1, characterized in that in the deformation of a workpiece made of roller bearing steel, the workpiece is heated to a temperature of about 700 ° C. 90988 2/023 2 ORIGINAL INSPEC 3. The method according to claim 1, characterized in that the
The workpiece is provided with a top coat having lubricant properties prior to deformation. 4. The method according to claim 1 to 3 for deforming a pair of bearing rings of a solid profile in the form of a pane, characterized in that the pane after the protective layer has been applied and heating to the predetermined temperature at this Tem- ι temperature is brought into a die, in which it is deformed into an annular part comprising a pair of separable ring | section which form the pair of bearing rings. I. 5. The method according to any one of claims 1 to 3 for forming a cup-shaped part from a solid profile in the form of a Scheib ^, characterized in that the disc after application of the, protective layer and heating to said predetermined temperature | placed in a die and formed into a cup-shaped part
is deformed, being in a predetermined position inside the! cup-shaped part of a bridge is left standing by a I average thickness that is not below the predetermined Minimum thickness at which the deformation forces are excessive | increase. 6. The method according to claim 1 to 3, for the formation of rolling bearing rings from a solid profile in the form of a disc, characterized
characterized in that after applying the protective layer and
Heat the disc to the predetermined temperature in a
Form comprising a pair of axially separated cavities - 2 909882/02 3 2 INSPECTED having, introduced and deformed, wherein a cup-shaped part with a pair of axially separated ring parts, the are connected to one another by an intermediate web, is formed, which has a bottom web of a thickness not below the predetermined Minimum thickness at which the deformation forces increase excessively. 7. The method according to claim 6, characterized in that in the Ring parts Races are incorporated as long as the parts are still connected. 8. The method according to any one of the preceding claims, characterized in that the workpiece at the starry Temperature is deformed using a minimum number of blows, with no processing steps being switched on between the blows. 9. The method according to any one of the preceding claims, characterized in that the workpiece is a flat disc a thickness is used that it is narrower Recess of a die provided with two coaxially arranged recesses leads automatically. 90988 2/0232 Blank page