JP2000190007A - Plastic working method to manufacture seamless hollow body with bottom or seamless pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hollow body or pipe with specified outside diameter and wall thickness while reducing reheating time and preventing the danger of the bottom being broken through by using a mandrel with a spherical end when the hollow material pipe, wherein the bottom material integrally formed at the time of boring the hollow material pipe is reduced in thickness from the edge area toward the center, is punched. SOLUTION: A steel ingot or a continuous-cast steel is heated to the plastic working temperature, and with dies and a punching mandrel 2, rolling into a hollow material pipe is done so that the bottom is shaped into a truncated cone. With the dies, the material of a bottom portion 6' is reduced in thickness from the edge area toward the center and the bus line contour of the bottom portion 6' is brought into agreement with a hyperbolic binding string through the first approximation. Then the hollow material pipe is punched into the final size with a mandrel 17 on which a spherical end area 18 formed and one or more ring dies 7, and when necessary, the material is reheated between passes so that the bottom 6" is remained on the hollow material pipe or cut from the hollow material pipe. Thus, the seamless hollow body with a bottom or a seamless pipe of 200-1,450 mm outside diameter and 20-250 mm wall thickness can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an outer diameter of 200 to 1450 mm and a wall thickness of 20 to 1 described in the preamble of claim 1.
The invention relates to a plastic working method for producing a bottomed seamless hollow body or a seamless tube within a dimension range of 250 mm.

[0002]

2. Description of the Related Art Known punching and punching methods are described, for example, in Stahlroer-Huntbuch, 10th edition (October 1987), Vulcan Publishing, pages 138-140, and the booklet of seamless hollow bodies for h.
igh-pressure engineering.manufactured by pierce a
nd draw process, published February 1972). This method, developed by Heinrich Elhardt in 1899, is a method in which a steel ingot, which can now be made into a continuously cast billet, is heated to the plastic working temperature in a heating furnace and drilled after charging into the dies of a vertical drilling press. By means of a mandrel, it is rolled into a hollow shell whose bottom is shaped like a truncated cone. After projecting from the die, the hollow shell is extruded by forcing it through at least one, and usually a plurality, diameter reducing ring dies by a mandrel pressed into the hollow shell. Depending on the material and the number of passes, it may be necessary to provide a reheating unit between two consecutive passes. As can be seen from the schematic diagrams on pages 7 and 8 of the company booklet, the outer contour of the integrally rolled bottom conforms to a truncated cone. As a result, for example, after punching through a plurality of ring dies, a cross-sectional configuration in which the diameter of the hollow shell cylindrical portion substantially matches the diameter of the straight bottom surface integrally rolled on the front side is generated in the bottom region. There is. In such a situation, the mandrel pushed into the hollow shell breaks through the bottom in the next ring die,
Or it cannot be ruled out that the force is so high that the pressing force of the punching press is no longer sufficient to push the hollow shell through the next smaller ring die.

Conventionally, this situation has been addressed by removing the hollow shell from the stamping line and placing it under another forging press immediately before reaching this state. The forging press retained the bottom region. In other words, the thick shaft support was formed integrally. Since the hollow shell is strongly cooled during this operation, reheating for at least 60 minutes is required after this holding operation. The disadvantage of this procedure is, on the one hand, that the production is interrupted with a time loss and energy consumption resulting from a long reheating. On the other hand, there is a risk of forging defects, i.e. the risk that the central axis of the integrally forged bearing is no longer aligned with the central axis of the hollow shell. This then increases the eccentricity in the hollow shell, which in some cases may mean a defective part. However, in any case, the cost of the subsequent processing is considerably increased, which makes it difficult.

[0004]

It is an object of the present invention to provide a plastic working method of the type according to the preamble, in which the above-mentioned drawbacks are prevented.

[0005]

This object is achieved, starting from the premise, together with the features of the characterizing part of claim 1. According to the present invention, the bottom is integrally formed when the hollow shell is bored, and the material of the bottom is deviated from the edge region toward the center. A spherically shaped mandrel is used.
The bottom bus profile on the cross section corresponds to a first approximation to the hyperbolic knot. An advantage of the proposed treatment scheme is that the previously required intermediate step of bottom retention is eliminated and the reheating is reduced to a normal time of 20 minutes instead of the conventional 60 minutes. Furthermore, the risk of the bottom being torn or pierced is prevented. In this way, the productivity is considerably increased and a considerable amount of energy is saved. It has proven to be advantageous if the generatrix consists of a plurality of sections which alternately curve in a convex or concave manner, the radius of each curved section being at least 100 mm. Furthermore, it has been recognized that it is necessary that the ratio between the diameter of the bottom surface rolled on the front side and the diameter of the hollow shell cylindrical portion has a specific value. This ratio should be ≤0.5.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The main steps of a conventionally known punching and punching method are shown in the drawings in comparison with a novel plastic working method. The main steps of the known perforation punching method are shown in FIGS. 1 (a) to 1 (c). FIG. 1A shows a state in which a hollow shell 1 is formed by piercing with a piercing mandrel 2 and a die 3 arranged in a die holder 4. In order to extrude the rolled hollow shell 1, a knockout 5 is arranged in a concave portion below the die 3. A feature of this known method lies in the outer shape of the integrally rolled bottom 6. This shape conforms to a truncated cone in contour.

FIG. 1B shows a punching process using, for example, three ring dies 7 to 9. The last two ring dies 8, 9 each have a smaller diameter than each preceding ring die 7 or 8. A mandrel 10 is pushed into the hollow shell 1 to apply a required pushing force, and the mandrel presses the bottom 6 of the hollow shell 1.

FIG. 1B shows the situation after three dies have been passed, and the diameter 11 at the front of the bottom 6 is the hollow shell 1.
Substantially coincides with the diameter 12 of the cylindrical portion of. In this situation, there is a risk of the bottom tearing, especially in the edge region, which is indicated by the crack lines 13, 13 '. In order to avoid this crack, as shown in FIG. 1C, the bottom region of the hollow shell 1 is held by two saddles 15, 15 'of a free forging press (not shown). These saddles plastically work the bottom region into a kind of thick shaft support 16. The hollow shell 1 thus plastically worked can be pushed through another ring die after reheating.

2 (a) to 2 (c) show a new processing method, and the same parts are denoted by the same reference numerals. FIG.
(A) shows the perforation of the hollow shell, and the same perforation mandrel 2 as in FIG. 1 (a) is used. The contour of the bottom area of the die is newly constructed as described in more detail in FIG. The bottom 6 'formed integrally by the die has its material deviated from the edge region toward the center. The bus contour at the bottom 6 'corresponds to a first approximation to a hyperbolic knot. The hollow shell 1 'thus formed is pushed through the first ring die 7 for punching, whereby the hollow shell 1'
The mandrel 17 pushed into the end is formed with an end region 18 which is configured in a spherical shape.

FIG. 2C shows the result of the first punching partial process. A pre-rolled bottom shape 6 'is formed by the mandrel 17 into a spherical bottom 6 ". This bottom is particularly suitable for enabling punching with other ring dies without the disadvantages mentioned above. .

One half of the bottom area of the die 20 constructed in accordance with the present invention is shown in cross section in FIG. In this embodiment, the die has two convexly curved portions 2 whose bus contour in the bottom region is two.
1 and 22 and a concave curved portion 23 interposed therebetween. Both convex curved portions 21, 22
Has a radius R ₁ of at least 100 mm,
The radius R ₂ of the concave curved portion 23 can even occupy values up to 600 mm. The ratio between the diameter D ₂ of the cylindrical portion of the front side of the linear portion of diameter D ₁ and the die 20 is also important. This ratio should be ≤0.5.

FIG. 4 shows the possibility of producing a mandrel 24 whose end region is configured to be spherical. A spherical cap 26 is secured to the old end region 25 to make the remainder present on the mandrel available for the new method. The spherical cap 26 has a pin 27 which is
It has. Two bolts 2 that engage with this groove 28
9, 29 'are held by screws 30 and closure parts 31.

[Brief description of the drawings]

FIG. 1 (a) shows a perforation of a bottomed hollow shell by a known processing method. (B) shows a punching operation using three ring dies. (C) shows the retention of the bottom region.

FIG. 2 (a) shows drilling of a hollow shell with a bottom by a novel processing method. (B) shows the pushing of the mandrel with the spherical head into the hollow shell. (C) shows a punching operation.

FIG. 3 is a cross-sectional view of a die half of a punch press having a novel bus bar profile;

FIG. 4A is a longitudinal sectional view of a mandrel having a spherical end region. FIG. 4B is a cross-sectional view taken along the line AA in FIG.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B21K 21/14 B21K 21/14 (72) Inventor Theodor Schmitz Day 41515, Germany Femmbroich, Febel Strasse 10 (72) Inventor Hans-Jürgen Schrüssel Germany, Day 41542 Dormagen, Odirienstrasse 40 (72) Inventor Alexander Borovikou Germany, Day 16230 Grünthal, Bernauer Weg 5 (72) Inventor Holger Blei Germany, Day 10405 Berlin, Era-Kay-Strasse 38

Claims (4)

[Claims] An outer diameter of 200 to 1450 mm and a wall thickness of 20 to 1
A plastic working method for producing a bottomed seamless hollow body or a seamless tube within a dimension range of 250 mm, comprising heating a steel ingot or a continuously cast steel slab to a plastic working temperature, using a die and a perforated mandrel. The bottom is rolled into a hollow shell so as to form a frusto-conical shape, and subsequently punched to final dimensions by means of a mandrel and at least one ring die entering the hollow shell, and if necessary the material and the number of passes Reheating between two successive passes in response to and finally leaving the bottom member in the hollow shell or cutting from the hollow shell, wherein the bottom is formed integrally when piercing the hollow shell, A plastic working method characterized in that the bottom material is uneven in thickness from the edge region toward the center, and a mandrel having a spherical end at the time of punching the hollow shell manufactured in this way. 2. The plastic working method according to claim 1, wherein the bottom generatrix contour on the cross section is constituted by a plurality of portions which are alternately convexly or concavely curved. 3. The radius of each curved portion is at least 100 m
The plastic working method according to claim 2, wherein m is m. 4. The plastic working method according to claim 1, wherein the ratio of the diameter of the front-side straight bottom surface to the diameter of the hollow shell portion is 0.5 or less. .