US3914973A

US3914973A - Method and apparatus for the preparation of round stock in strand form from steel or other metallic materials by hot forming

Info

Publication number: US3914973A
Application number: US492304A
Authority: US
Inventors: Heinz Koch; Bruno Kralowetz
Original assignee: Fried Krupp Huettenwerke AG
Current assignee: Fried Krupp Huettenwerke AG
Priority date: 1973-07-28
Filing date: 1974-07-26
Publication date: 1975-10-28
Anticipated expiration: 1992-10-28
Also published as: SU683606A3; DE2338391B2; DE2338391C3; JPS5071562A; FR2238539A1; AT325382B; FR2238539B1; DE2338391A1; JPS5415020B2; GB1440725A

Abstract

An improvement in a process for the manufacture of round stock in strand form to close tolerances from a steel or other metallic stock wherein said stock is hot forged into a rod, the improvement comprising hot forging said stock so that the rod has a cross section of a polygon with four n equal sides wherein n is 2, 3 or 4, and thereafter rolling said polygonal shaped rod while in the same heat to the round; an apparatus for carrying out such process comprising a pass-through hot forge equipped with a 4hammer to 8-hammer tool disposed about an imaginary centerline through which stock to be shaped is passed, and means for pressing said tools against said stock as it passes through such line, which apparatus further comprises a pair of rolls whose roll surface contour is generally round, which rolls are disposed coaxially of said imaginary line and no more than about 600 mm from said forge.

Description

United States Patent 1 1191 Koch et a]. Oct. 28, 1975 [5 METHOD AND APPARATUS FOR THE 2,101,959 12/1937 Schulz 72/235 PREPARATION OF ROUND STOCK IN 3,135,139 6/1964 Kralowetz 72/402 X STRAND FORM FROM STEEL OR OTHER ggg METALLIC MATERIALS BY HOT 3:625,043 12/1971 Neumann et a]. 72/228 x FORMING Inventors: Heinz Koch, Sprockhovel, Germany;

Bruno Kralowetz, Steyr, Austria Fried, Krupp Huttenwerke AG GFM Gesellschait fur Fertigungstechnik und Maschinenbau AG, Bochum, Germany Filed: July 26, 1974 App]. No.: 492,304

Assignee:

Foreign Application Priority Data July 28, 1973 Germany 2338391 US. Cl. 72/206; 72/235; 72/377 Int. Cl. B21B 15/00 Field of Search 72/206, 278, 234, 235, 72/377, 472, 285, 76, 402, 279, 374, 375; 29/3314, 33 S, 33 Q References Cited UNITED STATES PATENTS 2/1891 Williams 72/235 Primary Examiner-Milton S. Mehr Attorney, Agent, or FirmBurgess, Dinklage & Sprung 5 7] ABSTRACT carrying out such process comprising a pass-through hot forge equipped with a 4-ham'mer to S-hammer tool disposed about an imaginary centerline through which stock to be shaped is passed, and means for pressing said tools against said stock as it passes through such line, which apparatus further comprises a pair of rolls whose roll surface contour is generally round, which rolls are disposed coaxially of said imaginary line and no more than about 600 mm from said forge.

14 Claims, 3 Drawing Figures US. Patent Oct. 28, 1975 Sheet 10f2 3,914,973

U.S. Patent Oct.28, 1975 Sheet2of2 3,914,973

METHOD AND APPARATUS FOR THE PREPARATION OF ROUND STOCK IN STRAND FORM FROM STEEL OR OTHER METALLIC MATERIALS BY I'IOT FORMING BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a process and apparatus for the production of round stock in strand form to close tolerances from steel or other materials by hot forging through the use of pass-through forging. More particularly, this invention relates to a process for the manufacture of round stock having close tolerances by a hot forging process followed by a hot rolling process wherein-stock to be formed into round stock of close tolerances is initially formed into a polygonally shaped rod and thereafter, is subjected while in the same heat to a hot rolling process.

2. DISCUSSION OF THE PRIOR ART In the production of round stock is strand form, especially from steel, there has always been a need to keep the circular cross section of the hot-formed material within close tolerances throughout the length of the strand.

One of the common methods of production is hot rolling. Where the dimensional accuracy requirements are stringent, it is necessary that the hot rolling be followed by operations such as recalibration, paring and drawing for the purpose of perfecting the material in the hot or cold state. Cold drawing can produce especially close tolerances, but it is expensive and requires heavy investment in equipment. In particular, it requires high tooling costs, which increase constantly as the resistance of the material to shaping increases. The

paring or rolled round stock requires a considerable in- "vestment in equipment and has an inherently poor output. Rerolling is not so disadvantageous in regard to installation cost, but there results poorer precision, poorer surface quality and greater expense the roll dressing shop. 1

The circumstances are similar in production-of round material onpass-through forging machines, although the surface is more irregular than it is in. all the processes mentioned above.

The idea of paring forged round stock was objectionable on account of the above-mentioned disadvantages of the great loss of material involved. The objection to was precluded by the fact that pass-through draw forg- -ing is an intermittent method of procedure whereas rolling is commonly a continuous one, so that forming the material in both machines in the same heat and at the same time was out of the question.

This invention is directed to providing a method by tolerances, with good surface quality, and which process will be applicable to a wide variety of materials,

, and which can be performed by an apparatus whose installation cost is low, whose floor space requirements are small and whose operating costs are low.

SUMMARY OF THE INVENTION The problems of providing a process in which stock can be formed into round stock of close tolerances without high installation costs, high operating costs or excess floor space requirements is answered by an improved process for the manufacture of round stock in strand form to close tolerances from steel or other metallic stock wherein said stock is hot-forged or swagged into a rod. The improved process is characterized in that the stock is hot forged so that the resultant rod has a cross section of a polygon with four n equal sides, wherein n is 2, 3 or 4, and the polygonally shaped rod is thereafter rolled to the round.

Theprocess is generally conducted utilizing an apparatus comprising a pass-through hot forge equipped with a 4-hammer to S-hammer tool disposed about an imaginary centerline through which stock to be shaped is passed. The apparatus is provided with means for pressing the tools against the stock as it passes through said line. According to the invention, the apparatus is improved by at least one pair of rolls whose roll surface contour is generally round, the pair of rolls being disposed coaxially of said imaginary line and no more than about 600 mm from said forge.

According to the invention, round material in strand form can be manufactured to especially close tolerancesusing the swagging or forging process by forging the metal to bars whose cross section is a regular octagon, dodecagon or hexadecagon and, at the same heat and at the same speed, rolling the forged bars to calibrated rounds. In the operation of the invention, the starting temperature in the forging operation is so selected that the material, by gaining heat from the forging, is at the hot rolling temperature commonly used for the particular type of material employed at the beginning of the finish rolling operation, By this method,

bars are produced whose diameter can range from 8 to 200 mm. The .process is conducted generally by using a known forging apparatus which will form the stock into a cross section having equal sides such as an octagon, dodecagon and hexagon. Thereafter, the polygonally shaped rod is subjected to a rolling process using hydraulically driven rolls. In the case of thin material, particularly in the case of stock whose diameter is to be 30 mm or less,

' heat imparted to the stock as it passes through the forge. The stock generally continuously passes through the forge and thence, through the driven rolls. The first roll is disposed no more than about 600 mm from the exit of the forge.

4 which round stock can be prepared to especially close For good quality it is important for the material to be freed of scale immediately prior to the forging. For this purpose, a mechanical scale breaking process followed by high pressure water blasting can be disposed before the entrance to the forge so that the material is free of scale and secondary scale formation is inhibited.

The rolling speed of the rolls employed during the finish rolling operation, of course, depends upon the output of the forging machine. Generally speaking, the modern forging machines operate with a rod output at the rate of about 16 to 25 meters per minute. Thus, the finish rolling process and the forging process operate coterminously on the stock so that the process is a continuous treatment of the stock at the same speed.

One embodiment of the present invention resides in the apparatus for forging and rolling the stock into a 1nd having close tolerances. This apparatus is comsed of a combination of a pass-through forging maine and a rolling machine cooperating therewith. For practice of the invention, it is necessary that differt forming tools be in a fixed relationship to one anier, so that the forming can be performed simultaously in the forging machine and in the rolling maine that is disposed thereafter. The distance between forging tools and the first rolls must be kept small, d this is limited by the structural possibilities. The iximum distance should not exceed 500 to 600 mm.

BRIEF DESCRIPTION OF DRAWINGS The invention can be more readily understood and preciated when reference is made to the accompanyg drawings in which:

FIG. 1 is a sectional side elevation of the apparatus liCh forges and hot rolls stock 1 into a round having me tolerances;

FIG. 2 is a view showing the formation of'the stock into a polygonally shaped rod through the use of four -.ir of tools, said shaping process being conducted in e forge; and

FIG. 3 is a view similar to FIG. 2 showing the actua- )n of the rolls on the stock 1 during the rolling pro- DESCRIPTION OF SPECIFIC EMBODIMENTS The present process, it should be understood, can .ape, through the use of the apparatus shown in the :companying drawings and described herein, stock to round stock. By such term It is meant that the :neral overall, ultimate cross sectional configuration the material is basically round, i.e., it has a circular 'oss section. However, by a suitable choice of rolls aving interior configurations, the process can be con- Jcted so as to provide round stock which can have iread-like projections extending lengthwise of the rand or spirally about the same or transversely of the (is of the strand. Obviously, by the use of such rolls 1e surface can be altered somewhat to show scoring nes, perforations and the like. The term round .ock is to be considered as encompassing all of such )rms, whether smooth round stock or round stock aving perforations or indentations.

Referring to the drawings, a descaling system 2 is disosed immediately prior to the entrance to the forge. tock l is caused to pass through'the nip of two pairs f sequentially disposed rollers. Thereafter, it passes no the forge. The forge can be any forging apparatus )r forming the stock into polygonally shaped rods havig equal sides, such as an apparatus having 8 hamiers, for example, of which 4 hammers strike or press 1e stock at the same time. Preferably, the forging mahine will be one of the type made by GFM Gesellshaft fiir Fertigungstechnik und Maschinenbau AG. 'lachines of this type are shown in German Offen- :gungsschriften Pat. No. 1,915,656; 1,930,747; ,003,130 and 2,024,248. They are also shown in the 'rospectus of such firm, GFM Durchlaufschiiedemaschinen", Models SD, SDQ and SDR. The dislosure in the above-mentioned Offenlegungsschriften .nd the prospectus of GFM Gesellschaft fiir Fertigungtechnik und Maschinenbau AG is hereby incorporated lerein by reference.

The reduction of a metal product to form a taper uch as a rod or tube can be carried out by a swagging process. Examples of swagging are forging, squeezing or hammering. In forging the metal is plastically deformed, usually hot, into desired shapes with compressive force, with or without dies. 5 A suitable apparatus is shown in FIG. 2 in which a set of 8 hammers is employed. The 4 hammers marked 3 strike the bar or stock 1 at the same time while the 4 hammers marked 3' are at their top dead center. A set of this kind is appropriate for the forging of hexadecagonal bars, which is preferred in accordance with the invention, if the face of each hammer confronting the bar has a saddle shape represented by solid lines. If the hammers have a flat face instead of the saddle, as represented by dotted lines, the set of 8 hammers will be used for the forging of octagonal bars. A set of hammers for use in the forging of dodecagonal bars can best consist of 6 hammers with saddles or 12 hammers with flat striking faces.

Referring to FIG. 1, the descaling system 2 is shown to be immediately followed by the forging system in which 2 of the 8 forging hammers 3 can be seen. Following the forging apparatus, within a maximum distance of 500 to 600 mm from the forging tools, there are disposed three pairs of rolls 4, 5 and 6 in cassettes 7 each of which rolls is driven by a hydraulic drive maintained in the cassette. The hydraulic drive is not shown. In FIG. 3, there is shown in detail the manner by which the pairs of rolls 4, 5 and 6 engage the rod 1 to form it into a round. While the apparatus is shown as utilizing three sequentially disposed pair of rolls 4, 5 and 6, the apparatus can contain more or less than three pair of rolls.

Preferably, the finishing rolls have at least three pairs of rolls, each of which is offset 90 from the other. It is also desirable for the rolling stands to be inclined 45 from the horizontal, as shown in FIG. 3. The working roll diameter should be as small as possible in relation to the cross section of the material to be rolled. As a rule it will be between 280 and 450 mm, according to the thickness of the material to be rolled.

It is additionally advantageous for the cross sectional reduction during the rolling, which will be between 2 and 8% according to the thickness of the material being rolled, to roll the stock down to its final thickness utilizing three successive pairs of rolls, the cross sectional reduction being reduced by the three successive pair of rolls according to the ratio 50:30:20 with the maximum reduction (50) being provided by the first roll, i.e., the roll closest to the forge, and the least reduction being provided by the last roll.

Particularly advantageous is the use of a hydraulic drive for each of the three pair of rolls. Individual hydraulic driving of the roll pairs has the special advantage that this kind of drive easily adapts itself to the speed of the material going through the forging section without any investment in control systems. Electrical devices can be used, but these normally require high investment in controls.

The descaling system represents a desirable addition to the process and it is desirably one which permits the mechanical breaking of the scale followed by a blasting with a high pressure water jet.

I In order to more fully illustrate the nature of the invention and the manner of practicing the same, the following Example is presented:

EXAMPLE In an apparatus of the kind shown in FIG. 1 and having a continuous forging section with a set of 8 hammers as shown in FIG. 2 each hammer having a saddle to enable forging of regular sixteen-sided bars with equal sides a square bar with a side length of 80 mm consisting of a steel according to SAE 4340: 0.40 C;0.72 Mn; 0.28 Si; 1.82 Ni; 0.90 Cr; 0.28 Mo and heated to 1,060C, was forged to a sixteen-sided bar with a diagonal length of 51.4 mm and immediately rolled in the rolling section according to FIG. 1 into a round bar having a diameter of 48 mm.

The spacing between the end of the forging section and the rolling section was 500 mm. As shown in FIG. 1 the forging and rolling procedure are performed simultaneously as soon as the top of the bar 1 had entered the rolls 4.

The temperature of the bar coming out of the forging section was 1,090C and after rolling the temperature of the round bar was 1,060 C. The tolerance of the round bar was 10.1 mm. The delivery speed at the rolling section was 24 m per minute.

The invention as above described offers considerable advantages. It permits rapid and precise adaptation of the various characteristics of the material being worked, especially where both the characteristics and dimensions change frequently. It permits the precise maintenance of uniform shape and temperatures as an aid in achieving high quality. It is especially suitable for materials having a particularly high resistance to hot forming operations. The resultant surface quality is very good and dimensional accuracy is equal or virtually equal to that of bright steel and substantially higher than that of rolled steel which has been calibrated hot.

The output is incomparably higher than in the case of pared steel. Secondary scaling is very slight on account of the brevity of the shaping operation.

Working from the hexadecagonal to the round results in a good distribution of material and excellent filling out of the final caliber. Outstanding results are also achieved by working from the dodecagon or the octagon.

Additionally, the space requirement for the apparatus is quite small. Installation costs are incomparably smaller than those of other systems of the type described above. It can serve economically even for small production runs, and if greater capacity is needed, it can easily be achieved, step by step, by the installation of additional similar units.

The concept of the invention, which in itself is a i broad one, has been explained above as a combination of forging to hexadecagonal shape with a calibration rolling to the round. Although this is by far the most preferred embodiment, one can, by modifying the tools in the forging part, forge the stock to an octagonal or dodecagonal shape. This is done simply by the appropriate choice of hammers and the appropriate choice of hammer shapes as described above. These tools themselves are known in the metal forging art.

Materials which can be formed into round stock of close tolerance include non-alloy steel, alloy and highgrade alloy steel, light metals, heavy metals and special materials which are forgeable. The initial stock can have a square, round or flat cross section.

We claim:

1. In a process for the manufacture of round stock in strand form to close tolerances from steel or other metallic stock wherein said stock is hot forged into a rod, the improvement which comprises hot forging said stock so that the rod has a cross section of a polygon with four n equal sides, wherein n is 2, 3 or 4, thereafter rolling said polygonally shaped rod while in the same heat to the round by passing the same through the nip of opposed driven rolls.

2. A process according to claim 1 wherein the rolling to the round is performed by passing the rod through a pair of opposed rolls whose surface contour is generally round and rolling said rolls on the surface of said rod.

3. A process according to claim 2 wherein there are a series of at least three sequentially disposed roll pairs.

4. A process according to claim 2 wherein said rolls have a roll speed of 1 to 1.5% higher than the speed at which the rod emerges from the hot forging.

5. A process according to claim 3 wherein said roll pairs are offset from one another by 6. A process according to claim 3 wherein three pair of rolls are employed and the rod is rolled so that the cross sectional reduction is divided among the three successive pairs of rolls according to the ratio 50:30:20 from the first pair of rolls to the last.

7. A process according to claim 3 wherein the rolls are inclined 45 from the horizontal.

8. In an apparatus for the manufacture of round stock in strand form to close tolerances from steel or other materials comprising a pass-through hot forge equipped with a 4-hammer to S-hammer tool disposed about an imaginary centerline through which stock to be shaped is passed and means for pressing said tools against stock passed along said line, the improvement which comprises at least one pair of driven rolls whose roll surface contour is generally round disposed coaxially of said imaginary line and no more than about 600 mm from said forge, and means for rolling said rolls on stock passed along said imaginary line.

9. An apparatus according to claim 8 wherein said rolls have hydraulic means for rolling the same about the surface of stock which has passed through said forge.

10. An apparatus according to claim 8 wherein at least three pair of rolls are employed, all of which are provided with hydraulic means to drive said rolls.

11. An apparatus according to claim 10 wherein the pairs of rolls are offset from one another by 90.

12. An apparatus according to claim 10 wherein the roll pairs are inclined 45 from the horizontal.

13. An apparatus according to claim 10 wherein a dehigh pressure water jet systems.

Claims

1. IN A PROCESS FOR THE MANUFACTURE OF ROUND STOCK IN STAND FORM TO CLOSE TOLERANCES FROM STEEL OR OTHER METALLIC STOCK WHEREIN SAID STOCK IS HOT FORGED INTO A ROD, THE IMPROVEMENT WHICH COMPRISES HOT FORGING SAID STOCK SO THAT THE ROD HAS A CROSS SECTION OF A POLYGON WITH FOUR N EQUAL SIDES, WHEREIN N IS 2, 3 OR 4, THEREAFTER ROLLING SAID POLYGONALLY SHAPED ROD WHILE IN THE SAME HEAT TO THE ROUND BY PASSING THE SAME THROUGH THE NIP OF OPPOSED DRIVEN ROLLS.

5. A process according to claim 3 wherein said roll pairs are offset from one another by 90*.

6. A process according to claim 3 wherein three pair of rolls are employed and the rod is rolled so that the cross sectional reduction is divided among the three successive pairs of rolls according to the ratIo 50:30:20 from the first pair of rolls to the last.

7. A process according to claim 3 wherein the rolls are inclined 45* from the horizontal.

8. In an apparatus for the manufacture of round stock in strand form to close tolerances from steel or other materials comprising a pass-through hot forge equipped with a 4-hammer to 8-hammer tool disposed about an imaginary centerline through which stock to be shaped is passed and means for pressing said tools against stock passed along said line, the improvement which comprises at least one pair of driven rolls whose roll surface contour is generally round disposed coaxially of said imaginary line and no more than about 600 mm from said forge, and means for rolling said rolls on stock passed along said imaginary line.

11. An apparatus according to claim 10 wherein the pairs of rolls are offset from one another by 90*.

12. An apparatus according to claim 10 wherein the roll pairs are inclined 45* from the horizontal.

13. An apparatus according to claim 10 wherein a descaling apparatus is connected to the pass-through hot forge at the input side.

14. An apparatus according to claim 13 wherein said descaling apparatus consists of scale breaking rolls and high pressure water jet systems.