EP0798057A1 - Calibration of the shoulder roll of an Assel mill - Google Patents

Abstract

The rolling mill has at least three inclined rollers at 120 degrees to each other. Each roller has an approach part in front of the shoulder, a trailing part behind it. The continuous transitional section from approach to trailing part is determined by three tangential radii, which merge into the sections. The central transitional radius (R2) is larger than the approach radius (R1), and smaller than the trailing radius (R3). Transitional and trailing radii have the same direction of curvature, and all radii are described by the shoulder height (Hs) of the Assel roller. Shoulder height is calculated from blank diameter and the ratio of hollow block diameter and hollow block wall.

Description

The invention relates to a calibration of the shoulder rolls of an Assel cross-rolling mill for the hot rolling of tube blanks from pre-punched hollow bodies over a mandrel, with three rolls offset by 120 ° relative to one another and inclined with respect to the rolling axis and pivoted to the rolling axis, each with an inlet part arranged upstream of the shoulder, one of the Shoulder downstream discharge part, as well as continuous transitions between the parts of each shoulder roller.

Shoulder rolls of the type described in the introduction work on the principle of cross rolling over mandrel bars. Assel rolls serve to stretch a relatively thick-walled hollow body in a relatively short forming zone, in which a reduction in wall thickness is carried out. The shoulder rollers of the Assel mill consist essentially of an inlet part, which is usually formed from an inlet cone with a slight inclination, the work part with the work shoulder and the smoothing part or the outlet part. The inlet cone or the inlet part has the task of grasping the billet, rotating it and pulling it onto the mandrel rod with a constant feed.

The work part, also called the work shoulder or shoulder part, adjoins the inlet part, a step-like change in the roller diameter, the step height of which depends on the material to be processed. The higher the shoulder or the step, the greater the material stress. The purpose of the shoulder is to carry out a large reduction in wall thickness within a relatively narrow range in order to have a favorable influence on the dimensional stability of the thick-walled one Use the front tube to distribute tangential and axially directed changes in shape.

The subsequent outlet part has the purpose of partially detaching the tube from the mandrel bar and smoothing the surface of the tube.

In conventional calibrations of shoulder rollers, the caliber contour of the inlet part, working part and smoothing part is composed of straight line elements which are connected to one another with continuous transitions in the form of an arc. A roll calibration is known in which two small radii merge tangentially into one another and into the inlet and outlet parts.

The disadvantage of this shoulder geometry is due to an unfavorable degree of stretch distribution in the forming zone. In FIG. 2, the degree of stretch distribution over the area of the forming zone is shown logarithmically in a diagram. You can see a sharp rise in the curve, then a sharp drop and then an increase followed by a sharp drop in the curve. This curve is to be interpreted as an unfavorable flow condition in the forming zone. The known solution limits the feed efficiency and the d / s ratio of the billet due to these flow conditions.

On the basis of the known prior art and the disadvantages described, it is the object of the present invention to optimize the degree of stretching in the region of the roll which is critical in terms of forming technology, and at the same time to obtain an improved smoothing effect.

$${\text{R}}_{\text{2}}{\text{∼ 1,9-2,1 · H}}_{\text{s}}$$

$${\text{R}}_{\text{3}}{\text{∼ 12 - 21 · H}}_{\text{s}}$$

und wobei für die Berechnung der Schulterhöhe H_s aus dem Luppendurchmesser D_L und dem Verhältnis Hohlblockdurchmesser / Hohlblockwand [D_H/S_H] gilt: $${\text{H}}_{\text{s max}}\text{=}\frac{{\text{D}}_{\text{L}}}{{\text{D}}_{\text{H}}{\text{/S}}_{\text{H}}}{\text{- (0,02D}}_{\text{L}}\text{+ 1,0)}$$

To achieve the object, a calibration of the shoulder rolls of a woodlead inclined rolling mill is proposed according to the invention, which is characterized in that the transition from the inlet part to the outlet part is determined by three radii which merge tangentially into one another and into the inlet and outlet part, the mean radius of which is greater than the transition radius R ₂ than the input radius R ₁ and smoother than the output radius R ₃ and whose transition radius R ₂ and output radius R _{3 have the} same directions of curvature, the radii R _{1-3 being described} by the shoulder height H _{s of} the woodlayer as follows: $${\text{R}}_{\text{1}}{\text{∼ 0.7-0.9H}}_{\text{s}}$$

$${\text{R}}_{\text{2nd}}{\text{∼ 1.9-2.1 · H}}_{\text{s}}$$

$${\text{R}}_{\text{3rd}}{\text{∼ 12 - 21H}}_{\text{s}}$$

and the following applies to the calculation of the shoulder height H _s from the bowl diameter D _L and the ratio of the hollow block diameter / hollow block wall [D _H / S _H ]: $${\text{H}}_{\text{s max}}\text{=}\frac{{\text{D}}_{\text{L}}}{{\text{D}}_{\text{H}}{\text{/ S}}_{\text{H}}}{\text{- (0.02D}}_{\text{L}}\text{+ 1.0)}$$

The proposed geometry of the forming zone changes the characteristic of the curve for the degree of stretch distribution significantly. With flow conditions in the forming zone favored at the same time and a smoothing effect in the outlet of the shoulder area, the feed efficiency increases. This is equivalent to an increase in the performance of an Assel mill that is equipped with the calibration of the rolls according to the invention. Tests have shown that the feed efficiency has risen from 0.7 to 0.9 today to 1.48 to 1.68. Due to the optimized forming conditions, taking into account today's theoretical calculation of the run-out speed of the billet from the Assel roller, the feed efficiency can be greater than 1. The tolerances both in the thick-walled and in the thin-walled dimensional range can be improved by the proposal of the invention; the risk of triangulation is reduced by reducing the axial resistance, so that an improved product is to be expected overall.

Fig. 1

eine erfindungsgemäße Walzenkalibrierung mit drei ineinander übergehenden Radien,

Fig. 2

in einem Digramm die Charakteristik herkömmlicher Schultergeometrie und

Fig. 3

ein Diagramm der Charakteristik einer erfindungsgemäßen Asselschultergeometrie.

An embodiment of the invention is shown in the drawing and is described below. It shows:

Fig. 1

a roll calibration according to the invention with three merging radii,

Fig. 2

the characteristics of conventional shoulder geometry and

Fig. 3

a diagram of the characteristics of a woodlouse shoulder geometry according to the invention.

In the drawing figure 1, the deformation part of a woodleaf is shown in the shoulder area. The run-in area is designated E, the run-out area is A. Starting from the run-in part E, the roller with the entry radius R ₁ of 6 mm is curved and merges tangentially into the transition radius R ₂ of 15 mm, the center of the radius of which corresponds to the center of the radius of the entry radius R ₁ opposite side. On the same side of the curve is the center point of the exit radius R ₃ of 100 mm, which merges tangentially into the transition radius R ₂ . This results in a contour of the woodleaf shoulder, which is characterized by a steeply increasing input radius and an output radius that approaches 0, with a transition radius. The choice of these radii results in a high degree of stretch in the first third of the forming zone at the beginning of the forming process, while in the last two thirds there is a continuously decreasing degree of stretching which approaches 0. As a result, the aspect ratios in the forming zone are evened out and an improved smoothing effect occurs in the outlet. The diagram according to FIG. 3 clearly shows that the drop in the curve characterizing the stretching in the shoulder region of the roll, which occurs during a calibration according to the prior art, is omitted; the curve falls flat, which is synonymous with a uniformly and gently decreasing stretching.

Claims (1)

Calibration of the shoulder rolls of an Assel cross-rolling mill for hot rolling thin-walled tube blanks from pre-perforated hollow bodies over a mandrel, with at least three rolls offset by 120 ° relative to each other, inclined with respect to the rolling axis and pivoted to the rolling axis, each with an inlet part upstream of the shoulder and one downstream of the shoulder Discharge part, as well as continuous transitions between the parts of each shoulder roller,
that the transition from the inlet part to the outlet part is determined by three radially merging into one another and into the inlet and outlet part, the mean radius of which as the transition radius R _{2 is} greater than the input radius R ₁ and smaller than the output radius R ₃ and the transition radius R ₂ and Output radius R _{3 have the} same directions of curvature, the radii R _1-3 being described as follows by the shoulder height H _{s of} the woodlouse roller: $${\text{R}}_{\text{1}}{\text{∼ 0.7-0.9H}}_{\text{s}}$$

$${\text{R}}_{\text{2nd}}{\text{∼ 1.9-2.1 · H}}_{\text{s}}$$

$${\text{R}}_{\text{3rd}}{\text{∼ 12 - 21H}}_{\text{s}}$$

and the following applies to the calculation of the shoulder height H _s from the bowl diameter D _L and the ratio of the hollow block diameter / hollow block wall [D _H / S _H ]: $${\text{H}}_{\text{s max}}\text{=}\frac{{\text{D}}_{\text{L}}}{{\text{D}}_{\text{H}}{\text{/ S}}_{\text{H}}}{\text{- (0.02D}}_{\text{L}}\text{+ 1.0)}$$

Images