JPH04300003A - Hole mold roll of pilger rolling mill - Google Patents

Abstract

PURPOSE:To improve the dimensional accuracy of tube without reducing efficiency in tube manufacturing by finding, from a formula, the diameter of the bottom part of a caliber channel in the sizing zone of the caliber which is formed into a hole mold roll. CONSTITUTION:In the sizing zone of the caliber formed in a pair of upper and lower hole mold rolls 1, 1 which are assembled in a roll stand with a prescribed gap, the diameter Dk of the bottom part K of the caliber channel excluding both sides of the side relief areas F, F is determined by the formula. In the formula, sigmar is a yield stress kg f/mm<2> at the time of work completion of the tube, E is Young's modulus kg f/mm<2> of a tube material, K is a constant within 0.6-1.4 range, and DF is a target outer diameter mm of the finished tube.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grooved roll for a Pilger rolling mill having an improved caliber shape in the sizing zone.

0002

BACKGROUND OF THE INVENTION In cold rolling of pipes using a Pilger rolling mill, as shown in FIG. The tube 2 then undergoes rolling between each caliber 3 of the slotted rolls 1, 1 and the mandrel 4 in turn. The terminal end LS of the rolling region is called a sizing zone, and is distinguished from the working zone LW on the starting end side. Each caliber 3 of the grooved rolls 1, 1 is
The sizing zone LS has the same shape in the circumferential direction.

It is well known that the caliber shape of the grooved rolls 1, 1 has a great influence on the quality of the rolled tube 2. Therefore, many improvements were made to the caliber shape of the working zone LW (Japanese Patent Laid-Open No. 59
-7408, JP-A-59-156504, etc.). However, there are almost no new proposals regarding the caliber shape of the sizing zone, which has no substantial rolling function, and the formula recommended by Mehr (Germany) is generally used. According to the formula recommended by Mehr, the caliber shape in the sizing zone is determined by the diameter DK of the bottom of the caliber groove excluding the side relief areas on both sides, and the target finished outer diameter DF of the tube.
designed to match.

0004

[Problems to be Solved by the Invention] However, in tube rolling by a Pilger rolling mill using such grooved rolls, there is a problem in that when the rolling speed is increased, the dimensional accuracy of the rolled tube decreases. Therefore, when attempting to manufacture a tube with high dimensional accuracy, the tube manufacturing efficiency is inevitably reduced, specifically, the feed rate is inevitably reduced.

An object of the present invention is to provide a grooved roll for a Pilger rolling mill that can manufacture tubes with high dimensional accuracy without reducing tube manufacturing efficiency.

[0006]

[Means for Solving the Problems] The grooved roll of the present invention has the following features:
In the caliber sizing zone formed on a pair of upper and lower hole-shaped rolls built into a roll stand with a predetermined gap, the diameter DK of the bottom of the caliber groove excluding the side relief areas on both sides is

[0007] However, σr: Yield stress at the end of pipe processing (kg
f/mm2) E: Young's modulus of pipe material (kgf/mm2) K
: constant DF within the range of 0.6 to 1.4 : finished target outer diameter of the tube (mm).

[0008]

[Operation] In order to achieve the above object, the present inventors focused on the caliber shape of the sizing zone, which was uniformly designed according to the formula recommended by Mehr. Figure 1 shows the caliber shape of the sizing zone. Hole roll 1
, 1 each have side relief areas F,
F and the caliber groove bottom K excluding the side relief areas F and F, and the sizing zone has the same shape over its entire area. The diameter DK of the caliber groove bottom K is conventionally the finished target outer diameter D of the tube.
F, which is smaller than the diameter 2R of the side relief regions F, F. B represents the center deviation amount of the side relief regions F, FX represents the side relief amount, and ΔG represents the roll gap amount.

In the formula recommended by Mehr, no special consideration is given to the caliber groove bottom dimension of the sizing zone in order to obtain a tube with high dimensional accuracy. In order to manufacture high dimensional precision tubes without reducing the feed rate, the caliber groove bottom dimension of this sizing zone becomes important, and the inventors have found that it is necessary to take into account the elastic recovery of the tube. This became clear from the survey. That is, in plastic working of metal, elastic recovery of strain exists after the working is completed. This elastic recovery exists even when a tube is cold rolled using a Pilger rolling mill. For example, for tubes with high dimensional accuracy that require an ellipticity of 0.5% or less, this amount of elastic recovery is It is difficult to obtain the desired dimensional accuracy of the tube unless it is folded into the caliber dimensions, especially the caliber groove bottom dimensions of the sizing zone. Figure 2 shows the elastic recovery of the tube in the Pilger rolling mill. If the outer diameter of the tube during processing, that is, during roll load, is D1, then the outer diameter of the tube during unloading is D2 (>D1). The elastic recovery amount ΔD (D2-D1) is expressed by equation 1, which is proportional to the outer diameter D1 of the pipe being processed, and for general metals, it is 0.3 to 0 of the outer diameter D1 of the pipe being processed. This amounted to .7%.

0010

[Formula 1]

FIG. 3 shows the results of an actual investigation of the elastic recovery of tubes in a Pilger rolling mill. The rolling mill used was a 25 VMR manufactured by Demagmaer, and the test material was Zircaloy 2 (ASTM B353 R60802). The Young's modulus of this material is 10,000 kgf/mm2, and the yield stress after processing with a reduction in area of 75% is 60 kg.
f/mm2. The pass schedule is ■Outside diameter 20
mm x wall thickness 2mm → outer diameter 12mm x wall thickness 0.8mm, ■
Outer diameter 17mm x wall thickness 1.7mm → outer diameter 11mm x wall thickness 0
．． 7mm, ■Outer diameter 14mm x wall thickness 1.2mm → Outer diameter 9m
There were three types: m x wall thickness 0.5 mm. Since the outer diameter of the tube during processing cannot be directly measured, it was determined from the roll gap amount ΔG and the caliber groove bottom diameter DK of the sizing zone, which had been measured in advance. The results in FIG. 3 correspond to Equation 1.

The grooved roll of the present invention takes into consideration the elastic recovery amount ΔD of the tube as a correction value for the caliber groove bottom diameter DK of the sizing zone, and the tube after rolling has the following characteristics:
It suppresses the reduction in dimensional accuracy due to elastic recovery and improves its roundness. In addition, the caliber groove bottom diameter DK of the sizing zone in the grooved roll of the present invention is:
It is theoretically correct when K = 1, but even if K changes slightly, it can be accommodated by adjusting the roll gap amount ΔG, and due to the influence of significantly changing the roll gap amount ΔG from the standard setting value. Considering the two points of deterioration of roundness, the range was set to 0.6≦K≦1.4.

[0013]

[Examples] Examples of the present invention will be described below. Said ■～
In the tube rolling of (2), the caliber groove bottom diameter DK in the sizing zone of the grooved roll was changed within the range of the present invention. Table 1 shows the results of measuring the amount of outer diameter ellipse of the tubes manufactured before and after the change. With conventional slotted rolls, as the tube feed rate increases, the roundness decreases. In the grooved roll of the present invention, sufficient roundness is ensured even if the tube feed amount is increased. In addition, in the comparative example in which K is outside the range of the present invention, the roundness is better than the conventional example, but it is worse than the example of the present invention.

[0014]

[Table 1]

[0015]

Effects of the Invention As is clear from the above description, the grooved roll of the Pilger rolling mill of the present invention can manufacture pipes with high dimensional accuracy without reducing pipe manufacturing efficiency, and improves product quality and productivity. It has a great effect on improving sexual performance.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the shape of caliber grooves in the sizing zone of a grooved roll.

FIG. 2 is a schematic diagram showing elastic recovery of a tube in a Pilger rolling mill.

FIG. 3 is a chart showing the results of an investigation of elastic recovery of a tube.

FIG. 4 is a schematic diagram showing an overview of tube rolling using a Pilger rolling mill.

[Explanation of symbols] 1. Groove roll 2 pipe 3 Caliber 4 Mandrel

Claims (1)

[Claims] Claim 1: In the sizing zone of a caliber formed on a pair of upper and lower grooved rolls installed in a roll stand with a predetermined gap, the diameter DK of the bottom of the caliber groove excluding the side relief areas on both sides is defined as σr: pipe Yield stress at the end of machining (kgf
/mm2) E: Young's modulus of pipe material (kgf/mm2) K
: Constant DF within the range of 0.6 to 1.4 : Finished target outer diameter of pipe (mm) A grooved roll for a Pilger rolling mill.